Ball Screw Preload Sensing With Thermal Strain Separation
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Solution Overview
Problem
Preload detectable screw devices face issues with heat generation affecting sensor output, leading to reduced accuracy in preload detection.
Innovation Solution
Incorporating axial and circumferential strain sensors on the nut member to differentiate between preload-induced and heat-induced strains, allowing for accurate preload detection and reduced heat influence on sensor output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an axial strain sensor is placed between two nuts to detect preload, then preload detection capability is improved, but heat generated by the screw device adversely affects sensor output accuracy
Solution Approach 1:
The strain detection is segmented into two independent components: axial strain sensors detect preload-induced strain, while circumferential strain sensors detect heat-induced strain. By separating the detection of these two different strain types into independent sensor systems, the patent enables differential measurement to eliminate heat interference from the preload detection signal.
Solution Approach 2:
The circumferential strain sensors act as an intermediary measurement system that detects the heat-induced strain component. This intermediary measurement allows the system to calculate and subtract the heat influence from the total strain measurement, thereby isolating the preload signal and improving detection accuracy.
2Device complexity
If only axial strain sensors are used to detect preload, then the device structure is simple, but heat-induced strain cannot be differentiated from preload-induced strain
Solution Approach 1:
The patent transitions from one-dimensional axial strain measurement to two-dimensional strain measurement by adding circumferential strain detection. This dimensional expansion allows the system to capture strain information in multiple directions, enabling the differentiation between axial preload strain and thermal expansion strain through comparative analysis.
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
Enhances sensor output accuracy by distinguishing between preload and heat-induced strains, effectively reducing the impact of heat on detection and enabling precise preload measurement.
Implementation Method 1
strain that causes the outer surface of the nut member to contract in the axial direction... occur on the surface of the nut member due to the preload of the screw device
Implementation Method 2
strain that causes the outer surface of the nut member to expand in the circumferential direction... occur on the surface of the nut member due to the preload of the screw device
Implementation Method 3
the screw device generates heat by use thereof
Implementation Method 4
strain that causes the outer surface of the nut member to expand in the axial direction... occur on the surface of the nut member due to the heat generated by the screw device
Data Source
AI summary
A preload detectable screw device is provided which can detect preload with accuracy and can reduce the influence of generated heat on the output of a sensor. A screw device (1) includes a screw shaft (2), a nut member (3), a plurality of rolling elements (7, 8), at least one axial strain sensor (24) (B, D) that is attached to a surface of the nut member (3) and detects strain in an axial direction on the nut member (3), and at least one circumferential strain sensor (24) (A, C) that is attached to the surface of the nut member (3) and detects strain in a circumferential direction on the nut member (3). Preload of the screw device (1) is detected on the basis of outputs of the axial strain sensor (24) (B, D) and the circumferential strain sensor (24) (A, C).