Rolling Device Lubrication Diagnosis Using Impedance and Phase Angle

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Solution Overview

Problem

Existing methods for diagnosing the lubrication state in rolling devices require numerous parameters that are difficult to set uniquely, leading to high calculation loads and complexity.

Innovation Solution

A method involving the application of an AC voltage to an electric circuit comprising rolling elements and peripheral members, measuring impedance and phase angle, and using simplified formulas to derive an evaluation value for lubrication state diagnosis, including formulas such as 1/R = l * kn * cos(θ) and 1/C = -kn * l * ω * sin(θ), where R and C represent resistance and reactance at one contact point per rolling element.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the method in Patent Literature 1 is used to calculate lubricating film thickness and metal contact ratio, then the lubrication state can be diagnosed, but many parameters are required and it is difficult to uniquely set them, increasing device complexity and ease of operation issues

Engineering Contradiction:
Improvelubrication state diagnosis accuracyVSAvoidcalculation parameter complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential parameters (impedance and phase angle) needed for lubrication state diagnosis, eliminating the need for numerous difficult-to-set parameters from the related art. By focusing on these two key measurable quantities, the method achieves accurate diagnosis while significantly reducing parameter complexity and setting difficulty.

Inventive Principle:
Principle #2Taking out (Extraction)

2Measurement precision

If the method in Patent Literature 1 is used to calculate lubricating film thickness and metal contact ratio, then the lubrication state can be diagnosed, but many parameters are required, increasing the processing load and time consumption

Engineering Contradiction:
Improvelubrication state diagnosis accuracyVSAvoiddiagnosis efficiency
Core Design Contradiction:
Measurement precisionVSProductivity

Solution Approach 1:

The patent extracts and uses only the essential parameters (impedance and phase angle) for lubrication state diagnosis, eliminating the need to process numerous other parameters. This extraction approach significantly reduces calculation load and processing time while maintaining diagnosis accuracy, thereby improving overall diagnostic efficiency and productivity.

Inventive Principle:
Principle #2Taking out (Extraction)

3Ease of operation

If simplified diagnosis methods are used, then the processing load is reduced and ease of operation is improved, but measurement precision may be compromised

Engineering Contradiction:
Improvediagnosis method simplicityVSAvoidlubrication state diagnosis accuracy
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The patent changes the measurement parameters from complex multi-parameter calculations to direct measurement of impedance and phase angle. This parameter transformation enables a simplified diagnostic method that is easier to operate while maintaining high measurement precision, as these two parameters directly reflect the lubrication state without requiring complex computations or additional parameter settings.

Inventive Principle:
Principle #35Parameter changes

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

This approach allows for simpler and more efficient lubrication state diagnosis by reducing processing load and enabling real-time diagnosis without requiring complex parameter settings, particularly in conditions where parameters like dielectric constant or rotational speed are unknown.

Implementation Method 1

measuring an impedance and a phase angle of the electric circuit when the AC voltage is applied

Methodology Applied
Scientific EffectElectrical Impedance: Electrical Resistance

Implementation Method 2

measuring an impedance and a phase angle of the electric circuit when the AC voltage is applied

Methodology Applied
Scientific EffectCapacitance: Capacitance

Data Source

PatentEP4597066A1Rolling device diagnosing method, diagnosing device, and program
Publication Date: 2025.08.06 NSK LTD
  • EP4597066A1 patent drawingFigure 1
  • EP4597066A1 patent drawingFigure 2
  • EP4597066A1 patent drawingFigure 3

AI summary

This method for diagnosing a rolling device in which rolling elements and peripheral members are lubricated using a lubricant includes: applying an alternating-current voltage to an electric circuit comprising the rolling elements and the peripheral members; measuring an impedance and a phase angle of the electric circuit when the alternating-current voltage is applied; deriving an evaluation value representing a lubrication state inside the rolling device, using a calculation formula defined by the measured impedance and phase angle, an angular frequency of the alternating-current voltage, the number of rolling elements in the rolling device, and the number of contact points; and using the evaluation value to diagnose the lubrication state of the rolling device.