Ball Screw Preload Loss Detection Using Vibration Thresholds
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Solution Overview
Problem
Existing methods for detecting abnormalities in ball screws, such as preload decrease due to wear, are inadequate as they require prior calculations and comparison with normal product signals, and fail to detect decreased preload effectively.
Innovation Solution
A method involving vibration measurement, calculation of vibration values in a specific frequency band, and abnormality detection based on threshold comparison with initial operation reference values, allowing for the detection of decreased preload without requiring specific specifications or prior calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If vibration measurement and frequency analysis are performed to detect ball screw abnormalities, then detection capability is improved, but device complexity and calculation requirements increase
Solution Approach 1:
The patent extracts only the necessary vibration signal processing steps (measurement and threshold comparison) while eliminating complex frequency analysis, shaft rotation frequency calculations, and ball-passing signal conversions. This extraction reduces calculation complexity while maintaining essential detection capability.
Solution Approach 2:
Instead of calculating complex frequency characteristics and comparing with reference values, the patent inverts the approach by directly measuring vibration acceleration and comparing with a simple threshold value. This inversion simplifies the detection process while maintaining effectiveness.
2Measurement precision
If comparison with normal product vibration signals is performed to detect abnormalities, then detection accuracy is improved, but measurement and data acquisition requirements increase
Solution Approach 1:
The patent extracts only the essential detection function by using a fixed threshold value instead of requiring acquisition and comparison with normal product vibration signals. This eliminates the need for reference signal storage and complex comparison processing.
Solution Approach 2:
The patent uses a simple, fixed threshold value that does not require ongoing acquisition or updates, replacing the need for continuous reference signal acquisition and storage. This simplifies the system while maintaining detection capability.
3Measurement precision
If complex frequency analysis and signal conversion are performed to detect preload vanishing, then detection capability is improved, but calculation time and processing requirements increase
Solution Approach 1:
The patent extracts only the essential vibration measurement and threshold comparison steps, eliminating time-consuming frequency analysis, shaft rotation frequency calculations, and ball-passing signal conversions. This reduces processing time while maintaining detection capability.
Solution Approach 2:
Instead of performing complex signal conversions and frequency analyses, the patent inverts the approach by directly comparing raw vibration acceleration measurements with a threshold, significantly reducing calculation time while maintaining detection effectiveness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable detection of decreased preload in ball screws by monitoring vibration values in a specific frequency band, ensuring detection of wear-induced preload loss without the need for special devices or prior calculations, suitable for various applications like machine tools and production equipment.
Implementation Method 1
a vibration measurement step of measuring vibration during operation of the ball screw
Data Source
Figure 1
Figure 2~3
AI summary
To provide a method for detecting a decrease in a preload applied to a ball screw and a linear motion drive device including a ball screw and capable of detecting decreased preload. A linear motion drive device including a ball screw (9), a linear motion table (1) driven by the ball screw (9) to move linearly, and an abnormality detection device (11) configured to detect a decrease in a preload applied to the ball screw (9). The abnormality detection device (11) includes a vibration sensor (10) configured to measure vibration during operation of the ball screw (9), a calculation processing unit (12) configured to acquire a vibration value of a vibration signal in a specific frequency band among vibration signals measured by the vibration sensor (10), and an abnormality detection unit (13) configured to determine that a decrease in the preload has occurred in the ball screw (9) when the vibration value is less than a previously determined threshold with respect to a reference value, the reference value being a vibration value in an initial stage of the operation of the ball screw or during a normal operation of the ball screw.