Nondestructive testing of gears

• US 4,872,337 A
• Filed: 01/29/1988
• Issued: 10/10/1989
• Est. Priority Date: 01/29/1988
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Inventors: Watts, Robert J., Rice, David A., Neun, John A.
• Primary Examiner(s): YASICH, DANIEL
• Application Number:
  US07/150,114
• Time in Patent Office: 620 Days
• Field of Search: 73/162, 73/593, 364/575, 364/424.1, 74/856
• US Class Current: 73/162
• CPC Class Codes: F16H 57/00 General details of gearing of screw-and-nut gearing F16H25/00; of fluid gearing F16H39/00 - F16H43/00
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence
• CPC Class Codes: G01M 13/021 Gearings
• CPC Class Codes: G01M 13/028 Acoustic or vibration analysis

Abstract

A gear evaluation system which includes means for measuring gear rotational speed and gear case vibrational displacement associated with gear mesh action. A signal is displacement associated with gear mesh action. A signal is developed that represents the time series average signal synchronized to the relevant gear shaft speed. This signal is passed through a bandpass filter set to pass a signal at the gear mesh frequency (for the particular gear under evaluation). After rectification the output signal provides information relating to average vibrational levels associated with gear mesh action and deviations from the average levels.

Claims

1. A method of determining the acceptability of a first gear in a set of rotatable gears within a case of a given automotive transmission, the first gear being meshed with a second gear in the set, the method comprising:

(a) producing a synchronizer signal once per a period corresponding to one or more complete revolutions of the first gear;

(b) using a vibration sensor to output an analog electrical signal corresponding to vibrations of the gear case, the sensor generating an analog signal for a plurality of said periods;

(c) averaging together the analog signals from the periods to form a composite signal whose duration is a single period and whose form is that of a wave having peaks and valleys;

(d) selecting points within the single period and then determining absolute values of the amplitude of the composite signal at the selected points, and then calculating the root mean square of the selected absolute values;

(e) repeating steps a) through d) for each gear in the set of rotatable gears, and then averaging the root mean squares found for each repetition of these steps, thereby deriving a normalization factor for the given transmission;

(f) band pass filtering the composite signal to obtain a plurality of component signals corresponding to the first, second and one or more subsequent harmonics of the composite signal, the components signals having a wave form with evenly spaced peaks and valleys disposed along a reference line;

(g) for each component signal, determining the individual absolute values of the amplitude of peaks or valleys and then ascertaining the average value for the absolute values so determined;

(h) for each component signal, determining the the statistical standard deviation for the amount by which the absolute values deviate from the average value;

(i) for each component signal, deriving a first and second weighting factor, each weighting factor based upon the harmonic of the component signal, the gear ratio between the first and second gears, the rotational speed of a gear shaft upon which the first gear is mounted, the gear type of the first gear, and the position of the first gear relative to others gears in the gear train;

(j) using the average values for the absolute values derived in step g, the statistical standard deviations from step h, the normalization factor from step e, and the weighting factors from step i to calculate a first fault characterization parameter;

(k) comparing the first fault characterization parameter to a selected fault characterization parameter for gears similar to the first gear in transmission similar to the given transmission.

2. A gear evaluation system comprising means for producing a first electrical input signal representing gear rotational speed;

means for producing a second input signal representing gear case surface velocity caused at least partly by gear tooth mesh action;

time series averaging means for receiving the input signals and creating therefrom a first output signal synchronized to shaft speed of a shaft rotating the gear;

means for receiving the first output signal and segregating therefrom a plurality of wave-like signals having alternated peaks and valleys and having frequencies which are integral multiples of gear mesh frequency for the gear, the wave-like signals being at least mainly determined by the gear case surface velocity caused by meshing action of the gear;

signal processing means for recording the wave-like signals, determining individual amplitudes of the peaks of the wave-like signals, averaging the amplitudes, and determining average deviation of the individual amplitudes from an averaged amplitude, assigning empirical weighting factors to averaged amplitudes and to average deviations, and then summing together numerical values of averaged amplitudes with numerical values of average deviations.

3. The system of claim 2 wherein the time series averaging means includes a means for sampling a second input signal at a frequency that is at least twice the gear mesh frequency for the gear.

4. The system of claim 3 wherein the step of determining individual amplitudes of the peaks in the wave-like signals is comprised of full wave rectification of the wave-like signals and then determination of the amplitude values of resultant wave-like signals caused by the full wave rectification.