Measuring and testing – Toothed gear
Reexamination Certificate
1998-06-29
2001-01-09
Noori, Max (Department: 2855)
Measuring and testing
Toothed gear
C073S635000, C073S862322
Reexamination Certificate
active
06170326
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to systems for testing electrical and mechanical energy transfer systems that exhibit vibratory and other responses to electrical or mechanical input energy, and more particularly, to an arrangement that isolates a mechanical or electrical system under test and produces signals and data corresponding to a plurality of operating characteristics of the system under test in response to the input energy.
2. Description of the Related Art
Noise testing of gears to date has been attempted by methods that rigidly mount the gear or axle assemblies in one or more planes. Some other previous attempts chose to have one of the rigidly mounted planes resonate at a frequency sympathetic to gear noise. None of these methods, or any other rigidly mounted test system has been successful. This is due to the lack of repeatability of the previous systems, largely as a result of interacting resonances, and external background noise that is transferred through the rigid mounting system. This is especially true in a production test environment.
These deficiencies in the prior art are most evident in the axle industry. At this time, the only widely accepted way of measuring gear noise is to acquire an assembled axle and install it in a test car. A specially trained individual then drives the car over its typical operating range while carefully listening for axle gear noise. The individual rates the quality of axle gear noise on a scale that is typically 0 to 10. Ten is usually a perfect axle, i.e. one that has no gear noise. This method is made difficult by:
1 The lack of available trained noise rating individuals
2 The cost of test cars.
3 The lack of quality roads or test tracks on which to perform a repeatable and accurate test.
4 The time required for each test.
5 The subjectivity that humans bring into the rating system
Typically less than a dozen axles can be tested by a major manufacturer in one shift due to all of the above complications. This low number is not statistically valid when it is considered that most manufacturers make thousands of axles each day. Even with all of the above problems, human testers in cars are the only widely accepted method of axle testing in the industry due to the lack of a better more reliable testing method. This lack of a scientific basis for rating axles and gear systems is made worse when the reader considers that modern cars are extremely quiet, and are evolving to become more quite. This market direction increases the pressure on axle and other gear manufacturers to make their products quieter. There is a need for a system that offers gear and axle manufacturers a repeatable, reliable, accurate and practical way of measuring gear noise in production or laboratory environments.
It is, therefore, an object of this invention to provide a system for testing an energy transfer system, such as a vehicle axle, quickly and inexpensively, and achieving repeatable results.
SUMMARY OF THE INVENTION
The foregoing and other objects are achieved by this invention which provides, in a first method aspect thereof, a method of signal analysis for processing information from a gear system under test. This further method aspect includes the steps of:
driving the gear system under test by application of a rotatory input;
producing a first signal responsive to the torque applied to the gear system under test;
producing first digital data responsive to a first correlation between the first signal and time;
measuring peaks in said first digital data to determine whether the peaks exceeds a predetermined threshold magnitude; and
first subjecting those of the peaks that exceed the predetermined threshold magnitude to harmonic analysis.
In a specific illustrative embodiment of the invention of this further method aspect, there is provided the further step of comparing the result of the harmonic analysis of the step of first subjecting against gear tooth harmonics to determine whether the peaks constitute an anomaly. Such an anomaly is a bump or a nick on a tooth of the gear system under test.
In a highly advantageous embodiment of the invention wherein improved results are obtained, there are provided the further steps of:
producing a second signal responsive to a noise produced by the gear system under test in response to the step of driving;
producing a second digital data responsive to a second correlation between the second signal and time;
identifying peaks in the second digital data that are simultaneous with peaks in said first digital data;
measuring the simultaneous peaks in the second digital data to determine whether they exceed a second predetermined threshold magnitude; and
second subjecting those of the simultaneous peaks in the second digital data that exceed the second predetermined threshold magnitude to harmonic analysis.
In a further embodiment of the invention, there is provided the step of applying a load to the gear system under test. Preferably, there is provided the further step of controlling the loading applied to the gear system under test, and such control can be responsive to the second signal.
As is the case in the embodiment where only the torque signal is subjected to harmonic analysis, there is additionally provided in this embodiment the further step of comparing the result of the harmonic analysis of the steps of first subjecting and second subjecting against gear tooth harmonics to determine whether the simultaneous peaks constitute an anomaly. Thus, in this embodiment, the torque and the noise signals are subjected to harmonic analysis. It is desired in an embodiment of the invention that is used to test gear systems, to determine whether the anomaly is a bump or a nick on a tooth of the gear system under test. In a further step of calculating, the severity of the anomaly determined in the step of comparing is determined.
In a still further embodiment of this method aspect, there are provided the further steps of:
establishing predetermined harmonic criteria; and
determining whether the results of the analysis in the step of subjecting conforms to the predetermined harmonic criterial of the step of establishing.
In accordance with a still further method aspect of the invention, there is provided a method of signal analysis for processing information from a gear system under test for determining the presence of bumps or nicks therein. In this still further method aspect, there are provided the steps of:
driving the gear system under test by application of a rotatory input;
producing a first signal responsive to the torque applied the gear system under test;
producing a second signal responsive to a noise produced by the gear system under test in response to the step of driving;
producing first digital data responsive to a first correlation between the first signal and time;
producing a second digital data responsive to a second correlation between the second signal and time;
identifying simultaneous peaks in the first and second digital data;
measuring the simultaneous peaks in the first and second digital data to determine whether they exceed a predetermined threshold magnitude; and
subjecting those of the simultaneous peaks that exceed the predetermined threshold magnitude to harmonic analysis.
The further method aspect of the invention can be performed exclusively with the torque signal, in certain embodiments of the invention.
In one embodiment of this method aspect, there is provided the further step of comparing the result of the harmonic analysis of the step of subjecting against gear tooth harmonics to determine whether the simultaneous peaks constitute an anomaly. In a further embodiment, there is provided the further step of calculating the severity of the anomaly of the step of comparing.
In accordance with a yet further method aspect of the invention, there is provided a method of testing a gear assembly of the type having an input and an output, the method having the steps of:
installing the gear assembly on a mounting arrangement that resilientl
Juranitch James C.
Lewis Eric J.
Theisz Lawrence C.
Noori Max
Rohm & Monsanto, P.L.C.
Veri-Tek Inc.
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