METHOD AND APPARATUS FOR MEASURING CONCENTRICITY

• US 3,866,829 A
• Filed: 06/14/1973
• Issued: 02/18/1975
• Est. Priority Date: 06/14/1973
• Status: Expired due to Term

• Current Assignee: Masahiro Akahane, Mitsuru Egawa, Tomohiro Sanada
• Original Assignee: Masahiro Akahane, Mitsuru Egawa, Tomohiro Sanada
• Inventors: Egawa, Mitsuru, Akahane, Masahiro, Sanada, Tomohiro
• Primary Examiner(s): Morrison, Malcolm A.
• Assistant Examiner(s): Smith, Jerry
• Application Number:
  US05/369,889
• Time in Patent Office: 614 Days
• Field of Search: 235/151.3,151.32 33/174Q 73/65,459,462,464
• US Class Current: 702/168
• CPC Class Codes: G01B 7/312 for measuring eccentricity, i.e. lateral shift between two parallel axes
• CPC Class Codes: G06G 7/64 for non-electric machines, e.g. turbine

Abstract

A method and apparatus for measuring and recording the concentricity of a cylindrical workpiece relative to a reference axis comprising steps of setting the workpiece on a measuring table, measuring predetermined reference circumferences of the workpiece so as to obtain from the measured values a correction value for correcting the inclination between the rotation axis of the measuring apparatus and the reference axis of the workpiece, subsequently measuring a predetermined circumference of the workpiece to be evaluated, and in accordance with the measured value thus obtained and said correction value, effecting measurement of the concentricity of both axes.

Claims

1. In the method of measuring the concentricity of a workpiece, said workpiece being positioned with a reference axis of the workpiece inclined relative to an axis of rotation of a measuring system, where the least squares circles computed from the measured contour of the workpiece is a measurement circle, the improved steps resulting in an ascertainment of the coordinates of a measurement circle comprising:

obtaining first signals representing the central coordinates of two reference circles defined relative to the workpiece;

obtaining second signals representing the distance between the reference circles and the measurement circle;

computing the coordinates of a reference point of the measurement circle where said reference point is the point of intersection of the line connecting the centers of said two reference circles and the plane of said measurement circle, from said first and second signals, thereby ascertaining the coordinates of the center position of the measurement circle.

2. In the improved method for measuring the concentricity of a workpiece as set forth in claim 1, wherein said first signals representing the central coordinates of two reference circles are electrical signals (xe, xd) and (ye, yd) associated with the central coordinates of said two reference circles of the workpiece, said coordinates being represented by the integral values obtained during one rotation of the workpiece from sine and cosine components of the signals associated with the contours of said two reference circles;

wherein the step of ascertaining the coordinates of the center position of the measurement circle is performed by electrical computing means utilizing as inputs said electrical signals and utilizing resistance values determined in proportion to the referenced circles and to the distances, represented by L1 and L2, between the reference circles and the measurement circle, and wherein said corrected coordinates of said center position are represented by L2/L1 (xe-xd) + xd and L2/L1 (ye-yd) + yd.

3. In the improved method for measuring the concentricity of a workpiece as set forth in claim 1, wherein the step of computing the corrected coordinates of a center point of a measurement circle is performed by electrical computing means;

wherein said first signals are first electrical signals;

wherein said first electrical signals indicate the coordinates of the centers of two reference circles;

wherein said coordinates of the centers of two reference circles are expressed by integral values of sine and cosine components of the contours of said two reference circles over one revolution of said workpiece; and

wherein said second electrical signals indicate the distances between said two reference circles and the measurement circle of said workpiece.

4. A system for measuring the concentricity of a workpiece comprising:

detector means which rotates relative to the workpiece for generating signals associated with the contour of the workpiece;

first sine and cosine potentiOmeter means, which rotate synchronously with said detector means, for producing sine and cosine signal components of the signals generated by said detector means;

integrator means for integrating, over one rotation of the detector at each detecting position, the output signals of said potentiometer means;

x-axis and y-axis correction computing circuit means for computing the coordinates of a reference point, utilizing the output signals of said integrator means for each of two reference circles and also utilizing electrical signals representing the distances between the reference circles and the measurement circle;

second sine and cosine potentiometer means, which rotate synchronously with said detector means, for producing sine and cosine components of the outputs of said x-axis and y-axis correction computing circuit means;

adding circuit means for summing the outputs of said second sine and cosine potentiometer means; and

recorder means for drawing, accordingly to the output of said adding circuit means, the least squares circle of the measurement circle having the center which has been corrected with respect to inclination.

5. A system for measuring the concentricity of a workpiece comprising:

detector means which rotates relative to the workpiece for generating signals associated with the contour of the workpiece;

first sine and cosine potentiometer means, which rotate synchronously with said detector means, for producing said sine and cosine signal components of the signals generated by said detector means;

integrator means for integrating, over one rotation of the detector at each detecting position, the output signals of said potentiometer means;

x-axis and y-axis correcting computing circuit means for computing the coordinates of a reference point utilizing the output signals of said integrator means for each of two reference circles and also utilizing electrical signals representing the distances between the reference circles and the measurement circle;

second sine and cosine potentiometer means, which rotate synchronously with said detector means, for producing sine and cosine components of the output of said x-axis and y-axis correction computing component circuit means;

adding circuit means for summing the output of said second sine and cosine potentiometer means;

peak-to-peak circuit means for producing a difference between the maximum and minimum values of the signal used for drawing, according to the output of said adding circuit means, the least squares circle of the measurement circle having the center that has been corrected with respect to inclination; and

display device means for displaying half of said difference as the concentricity according to the output of said peak-to-peak circuit means.

6. A system for measuring the concentricity of a workpiece comprising:

detector means which rotates relative to the workpiece for generating signals associated with the contour of the workpiece;

first channel means for producing a direct current component correction value by integrating during one rotation of said detector means the detection signal generated by said detector means at the workpiece contour whose circumference is to be measured for concentricity;

second and third channel means, comprising first sine and cosine potentiometer means, which rotate synchronously with said detector means, for producing sine and cosine components of the signal from said detector means;

integrator means for integrating the outputs of said potentiometer means over one rotation of the detector means at each reference circle detecting position;

x-axis and y-axis correction computing circuit means for computing the coordinates of a referenced point utilizing the output signals of said integrator means for each of two reference circles and utilizing electrical signals representing the distances between the reference circles and the measurement circle;

second sine and cosine potentiometer means, which rotate synchronously with said detector means, for producing sine and cosine components of the outputs of said x-axis and y-axis correction computing circuit means;

adding circuit means for summing the outputs of said first channel means, said second sine potentiometer means and said second cosine potentiometer means;

subtracting circuit means for subtracting the adding circuit means output from the detector means output; and

recorder means for drawing, according to the output of said subtracting circuit means, a profile curve having the corrected center of the measurement circle.

7. A system for measuring the concentricity of a workpiece comprising:

detector means which rotates relative to the workpiece for generating signals associated with the contour of the workpiece;

first channel means for producing a direct current component correction value by integrating during one rotation of said detector means the detection signal of the circumference to be measured for concentricity;

second and third channel means comprising first sine and cosine potentiometer means, which rotate synchronously with said detector means, for producing sine and cosine components of the signal from said detector means;

integrator means for integrating the outputs of said potentiometer means over one rotation of the detector means at each reference circle detecting position;

x-axis and y-axis correction computing circuit means for computing the coordinates of a reference point utilizing the output signals of said integrator means for each of two reference circles and utilizing electrical signals representing the distances between the reference circles and the measurement circle;

second sine and cosine potentiometer means which rotate synchronously with said detector means, for producing sine and cosine components of the outputs of said x-axis and y-axis correction computing circuit means;

adding circuit means for summing the outputs of said first channel means, said second sine potentiometer means and said second cosine potentiometer means;

subtracting circuit means for subtracting the adding circuit means output from the detector means output;

peak-to-peak circuit means for producing a difference between the maximum and minimum values of the signal used for drawing, according to the output of said subtracting circuit means, a profile curve having the corrected center of the measurement circle; and

a display means for displaying half of said difference as the concentricity according to the output of said peak-to-peak circuit means.

8. A method for measuring the concentricity of a workpiece, about an axis of rotation of the workpiece, comprising the steps of:

a. establishing a three axis orthogonal reference coordinate measurement system wherein one of the three axes is designated as the axis of rotation of the workpiece;

b. positioning the workpiece within the three axis orthogonal reference coordinate system with the axis of rotation of the workpiece coincidental with said designated one of the three axes of the orthogonal reference coordinate system;

c. establishing first and second reference circles, said circles being oriented with their centers coincident with the axis of rotation of the workpiece and being oriented such that the planes of said circles are orthogonal to the axis of rotation of the workpiece;

d. establishing a reference axis for the workpiece, said reference axis being non-coincidental with any of the three axes of the orthogonal reference coordinate measurement system;

e. measuring the contour of the workpiece as it rotates about its axis of rotation, said contour defining a measurement circle and said contour being measured in a plane perpendicular to the axis of rotation of the workpiece;

f. projecting the two points defined by the intersection of the reference axis with the planes of tHe reference circles onto the plane defined by the two axes, other than the axis of rotation, of the orthogonal reference coordinate measurement system, to define two planar points;

g. ascertaining a straight line connecting said two planar points, said straight line being the projection of said reference axis on said plane defined by the two axes which are other than the axis of rotation, of the orthogonal reference coordinate system;

h. computing a least square circle from said measurement of the contour of the workpiece, said least squares circle being in a plane perpendicular to the axis of rotation of the workpiece;

i. projecting the point defined by the intersection of said least squares circle and the axis of rotation of the workpiece onto the plane defined by the two axes other than the axis of rotation of the orthogonal reference coordinate system, to define a first circle center point;

j. projecting the center point of the least squares circle onto the plane defined by the two axes other than the axis of rotation of the orthogonal reference coordinate system, to define a second circle center point;

k. transforming the first circle center point in the plane defined by the two axes other than the axis of rotation of the orthogonal reference coordinate system, to the point of intersection of said two axes;

l. transforming the second circle center point in the plane defined by the two axes, other than the axis of rotation, of the orthogonal reference coordinate system to a new, corrected second circle center point position such that the spatial orientation of the second circle center point to the first circle center point remains the same as before the transformation of the two circle center points;

m. constructing two said least squares circles with centers at said first and second circle center points;

n. assertaining the relationship as would result by drawing a straight line connecting said first and second circle center points and passing through said two least squares circles;

o. and obtaining the concentricity of the workpiece as the ratio of the shortest length of said straight line contained between the two least squares circles, to the diameter of said least square circle.

9. The method of claim 8 wherein steps e through o inclusive are performed by electronic circuit means.