Apparatus and method for determining the profile of the tread of a tire

• US 5,485,406 A
• Filed: 07/26/1993
• Issued: 01/16/1996
• Est. Priority Date: 01/31/1990
• Status: Expired due to Term

• Current Assignee: Sumitomo Rubber Industries Limited
• Original Assignee: Sumitomo Rubber Industries Limited
• Inventors: Asano, Kazuo, Wada, Yasuo
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): Assouad, Patrick J.
• Application Number:
  US08/096,837
• Time in Patent Office: 904 Days
• Field of Search: 73/146, 73/146.2, 356/3, 356/376, 356/377, 33/551, 33/554, 364/560, 364/562
• US Class Current: 702/167
• CPC Class Codes: G01B 11/22 for measuring depth
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01B 11/255 for measuring radius of curvature measuring diameter G01B11/08
• CPC Class Codes: G01M 17/027 using light, e.g. infrared, ultraviolet or holographic techniques

Abstract

The invention provides an apparatus, and a method, for detecting the tread profile of a tire mounted about an X-axis comprising a non-contact Y detection means movable in parallel to the X-axis for measuring the distance at a right angle between such means and the peripheral surface of the tread profile in the direction of the Y-axis, X detection means for detecting the position of the Y detection means along the direction of the X-axis, data memory means for storing X and Y data pairs obtained by both such detection means, and radius calculating means for calculating the radius of the article from the X and Y data stored in the data memory means. The radius calculating means includes division means for dividing the X and Y data for a plurality of portions of the tread profile based on predetermined reference values for the tread profile of the tire being measured and arithmetic means for determining the radii of the respective portions each from the corresponding data divided by the division means, the arithmetic means determining the circle equation of: x² +y² +ax+by+c=0, from the X and Y data to calculate the radius of the tread profile, the coefficients a, b and c of the circle equation being determined by least square approximation.

Claims

1. An apparatus for determining the profile of a tire tread with distinctive determinations of radii of a crown portion and shoulder portions comprising:

a mounting means for mounting the tire about an X axis such that the tire axis is parallel to the X axis;

a non-contact type Y axis distance measuring means for measuring a Y axis distance from the tire profile thereto and movable along the X axis, the Y axis distance measured being kept as Y data;

an X axis distance measuring means for measuring an X axis position of the Y axis distance measuring means, the X axis distance being kept as X data, each value of the X data being paired with one value of the Y data;

a radius calculating means for calculating a radius of at least part of the tire profile based on the paired X data and Y data, said radius calculating means including a sorting means for classifying pairs of the X data and Y data into data classified in point of local portions of the crown portion and shoulder portions of the tire with application of reference data for the tire, and an arithmetic means for determining radii of the respective tire portions by use of the classified data;

wherein

said reference data represents data prestored for reference to x axis regions of shoulder portions and the crown portion defining the tire profile, on a basis that a tire equator line is zero on the X axis as datum point,

said sorting means includes an end determination means for determining X data on two distal ends of the tire profile by detecting the two X data which exceed predetermined Y data,

a center determination means for determining a center point from the X data on two distal ends,

means for correcting the measured data with the reference data based so that the measured data as a whole is converted to be based on the datum point for the reference data, and for classifying the measured X and Y data pairs into data classified in point of the crown portion and of the shoulder portions by comparison with reference data on the crown portion and the two shoulder portions; and

said arithmetic means comprises calculation resources for calculating the radii of the crown portion and the shoulder portions, respectively, with use of the classified data.

2. The apparatus of claim 1 wherein the Y distance measuring means is a laser sensor movable in the direction of the X axis.

3. The apparatus of claim 1 wherein the X axis of the Y distance measuring means is provided by means of a feed screw engaging the Y measuring means and disposed parallel to the X axis and provided with a rotary encoder for detecting rotation of the feed screw to give the X data.

4. The apparatus according to claim 1 wherein the data memory means and the radius calculating means are a computer.

5. The apparatus of claim 1 further comprising tire rotation means provided to rotate the tire about its X axis, R detection means provided to detect the angle of rotation of the tire and output an R angle data, the data memory means storing said R angle data and radial runout (RRO) calculation means to determine the radial runout of the tire from the Y and R data in the data memory means.

6. A method of determining the profile of a tire tread with distinctive determinations of radii of a crown portions and shoulder portions comprising the steps of:

a. mounting the tire to a measuring apparatus with the tire axis being in parallel to an X axis;

b. inputting reference data on the tire to be measured into a data memory means, said reference data, based on a tire equator line set at a zero X axis point, including standard X axis lengths of the crown portion and shoulder portions of the profile for the tire to be measured,

c. measuring a Y axis distance from a Y axis distance detection means of the measuring apparatus to the tire profile to keep a measurement as Y data;

d. measuring an X axis position of the Y axis distance detection means corresponding to the Y data measurement and keeping such a measurement as X data;

e. repeating the steps c and d while moving the Y axis distance detection means along the X axis;

f. determining X axis data on two distal ends of the tire profile by finding the two X data which exceed predetermined Y data,

g. determining a center point from the X axis data on the two distal ends,

h. correcting the measured data on the center point with the reference data on the equator line as a new datum point so that the measured data as a whole is converted to be based on the new datum point, and classifying the measured data comprising X and Y data pairs now converted into data classified in point of the crown portion and on the shoulder portions with reference to the reference data; and

i. calculating radii of the crown portion and the shoulder portions, respectively, with use of the classified data.

7. The method of claim 6 wherein the X and Y data are divided into groups for the crown portion and the shoulder portions of the tire, respectively.

8. The method of claim 7 wherein the division of the X and Y data is carried out by determining the opposite end values of X data stored in the data memory means for which tire distance Y data exists, determining the mid-point between the opposite end X data values and comparing the X data based on the mid-point with reference values of the crown portion and reference of the shoulder portions which have been entered in advance.

9. The method of claim 6 wherein the tire is rotated about its X axis and the R angle data corresponding to particular X and Y values are calculated to determine the radial runout of the tire with respect to the X axis.