Pitch arrangement evaluation system of tread pattern of pneumati

Details Pitch arrangement evaluation system of tread pattern of pneumati Pitch arrangement evaluation system of tread pattern of pneumati

1997-06-12

1999-11-02

Dombroske, George

Measuring and testing

Tire, tread or roadway

Tire inflation testing installation

1522092, G01M 1702, B60C 1103

Patent

active

059748729

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a method of simulating and evaluating a pattern noise of a pitch arrangement of a tread pattern formed on the tread surface of a pneumatic tire. More particularly, this invention relates to an evaluation method of a tread pattern pitch arrangement of a pneumatic tire which makes it possible to bring an evaluation result of a low pattern noise by a noise simulation method into conformity with a feeling evaluation result by an actual car test.


BACKGROUND ART

It is generally known that the pattern noise resulting from the tread pattern formed on the tread surface of a pneumatic tire can be reduced by somehow devising the pitch arrangement of the tread pattern. It is known also that the pattern noise can be reduced particularly by achieving a certain specific cycle arrangement or a random arrangement by employing three or more kinds of pitches (pitch lengths).
Recently, simulation has been carried out to evaluate in advance whether or not the pattern noise can be reduced, when a tread pattern having a new pitch arrangement is designed.
A pitch variation method is one of the well known noise simulation methods for evaluating the noise by simulation.
This pitch variation method comprises the steps of determining an amplitude waveform of the noise resulting from the tread pattern of one circumference of the tire from each data of a pitch arrangement, transforming the amplitude waveform to a Fourier series not having limitation to the pitch arrangement method, avoiding those spectrum waveforms in which the amplitude of a specific frequency exhibits an excessive peak among the spectrum waveforms, regarding the spectrum waveforms which are dispersed into a large number of sideband waves having lower levels, as superior, and evaluating them as a pitch arrangement having a low pattern noise.
However, when the pneumatic tires which are evaluated as having a low noise pattern by the evaluation method described above are fitted actually to a car and a feeling test of the pattern noise is carried out by a driver, the evaluation often results in that the tires do not have a low pattern noise.
Though various other evaluation methods have been studied so far, a pitch arrangement evaluation method whose simulation result always coincides with the actual car test has not yet been developed, and a satisfactory simulation evaluation method has been desired earnestly.
It is therefore an object of the present invention to provide an evaluation method of a tread pattern pitch arrangement of a pneumatic tire which can always bring the simulation evaluation result of a low pattern noise resulting from the pitch arrangement into conformity with the actual measurement result.


DISCLOSURE OF THE INVENTION

To accomplish the object described above, the present invention provides an evaluation method of a pitch arrangement of a tread pattern of a pneumatic tire having a tread pattern divided by a large number of grooves disposed on the tread surface at a predetermined pitch in at least a tire circumferential direction and having at least three different kinds of pitch lengths, characterized in that an amplitude waveform corresponding to the frequency of noise resulting from the pitch arrangement of one circumference of the tire is determined by a noise simulation method, a correlation coefficient R expressed by the formula below, between the amplitude waveform and a quartic expression f(x)=ax.sup.4 +bx.sup.3 +cx.sup.2 +dx+e (where f(x) is a noise amplitude and x is the frequency) obtained by the regression of the amplitude waveform is determined, and whether or not the pitch arrangement obtained by the noise simulation method is a pitch arrangement of a low pattern noise is evaluated from the value of the correlational coefficient R: ##EQU1##
The inventors of the present invention have studied in detail the tread patterns and the pattern noises of pneumatic tires having various pitch arrangements through various trials and errors, and have discovered that the correlation between the amplitude

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