JP3513564B2 - Roundness measurement method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roundness measuring method for rotating a measurement object to measure the roundness.

[0002]

2. Description of the Related Art Conventionally, as a method for measuring the roundness,
A system called a polar coordinate system is known. This is a method of rotating a measurement object and detecting a variation in the distance between the rotation center and the circumference by a detector to obtain the roundness. That is, as shown in FIG. 5, first, the measurement object W is rotatably supported, and a detector 2 for detecting displacement in the radius r direction is provided on the peripheral surface of the measurement object W. Next, rotate the measurement object W,
Detection value Y (θk) of the detector 2 at each rotation angle
The geometric perfect circular curve M, which is a sine curve, is obtained by the method of least squares from ... (FIG. 6). Here, when the measured object W is a perfect circle and has no distortion (perfect circle error), the detected value Y
(Θk) ... Exists on the geometric perfect circular curve M. Therefore, the maximum value of the difference Ek between the value Y (θk) on the perfect circular curve M and the measured value Yk, which is obtained for each rotation angle θk, is the roundness.

In such a polar coordinate system, the so-called diameter method (two-point method) or V-block method (3
Compared to the method of obtaining the roundness from the variation of the chord length such as the point method), it has the following advantages. That is, a measurement object W that cannot be measured by the diameter method, for example, as shown by the solid line in FIG. 7, has a cross-sectional shape that is not a perfect circle, but the diameter during rotation is always the same as a perfect circle (broken line). Is also effective, and even if the cross-sectional shape of the measured object is polygonal,
Stable detection sensitivity can be secured with the same device. That is, V
Unlike the block method, there is no complexity of having to select V blocks having different angles according to the cross-sectional shape of the measurement object.

[0004]

However, in such a conventional method, when the axis of the object to be measured is horizontal, gravity acts on the object to be measured, so that the position of the center of gravity changes. There is a problem that the change in the deflection due to the reflection is reflected in the actual measurement value, resulting in an error in the measurement result.
On the other hand, in a factory, in order to convey a long object having a relatively large weight on a line, it is common to convey the article in a lying state. For accurate measurement, it is unavoidable that the articles conveyed to the inspection line are once erected for the reasons described above. Therefore, it is also a factor that hinders automation of the inspection line.

The present invention has been made in view of the above conventional problems, and is a perfect circle capable of measuring an accurate roundness irrespective of the direction of the axis of the object to be measured at the time of measurement. The purpose is to provide a measuring method.

[0006]

In order to solve the above-mentioned problems, according to the present invention, the object to be measured is rotated, and the displacements in the directions in which they are located on a straight line passing through the center of rotation and are separated from each other are on the positive side. Displacement at the same measurement point on the circumference of the measured object is detected for each predetermined rotation angle by two detectors whose displacements are equal to, and the two detection values at the same measurement point are summed and then averaged. , The geometric perfect circular curve is obtained from the calculated value by the method of least squares, the difference between the value on the geometric perfect circular curve and the value after the calculation at the same rotation angle is obtained, and the maximum value thereof is obtained. The difference from the minimum value is set as the roundness. Further, when the axis of the measured object is horizontal, it is preferable that the two detectors are located on a perpendicular line passing through the rotation center.

[0007]

In the above method, for example, when the measurement object is rotated with its axis being horizontal, the two detected values include the eccentricity between the axis of the measurement object and the rotation center, and the distortion (true value) of the measurement object. (Circle error), each component of the deflection due to the change of the position of the center of gravity of the measured object is included. Here, the displacement amounts due to the eccentricity and the strain included in the two detected values are always the same,
Also, the deflection due to the change of the center of gravity of the measured object is 1
The direction is reversed at a cycle of 80 °. Therefore, 2
Two detection values are summed and then averaged to obtain 2
The flexure component is removed from the one detected value. Therefore, the roundness obtained based on the value after the above calculation and the geometric roundness curve obtained by the least square method from the value is not affected by the deflection due to the change of the center of gravity of the object to be measured.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. That is, FIG. 1 is a schematic plan view showing the method of the present invention, in which a long measuring object W is set between spindles 1 and 1 facing each other in a state where the axis thereof is substantially horizontal. Further, to the left and right of the object to be measured W, there are two positions which are located on a straight line passing through the center of rotation O of the spindles 1, 1, that is, the center of rotation of the object to be measured W, and whose displacement in the direction in which they are separated from each other is the positive side displacement. Detectors 2 and 2 are set. It should be noted that the rotation center O of the spindles 1 and 1 and the axis of the measured object W are not always coincident with each other, and in the following description, they are not coincident with each other.

In the measurement, first, the spindle 1,
1. Rotate the object to be measured W by 1, and rotate at a predetermined rotation angle (θk)
Each time, the displacement in the radial direction at the same measurement point on the circumference of the measured object W is detected by the left and right detectors 2, 2. That is, the displacements of the same measurement point are 2
Detect times. Next, the two detection values at the same measurement point are summed and then averaged. That is, the detector 2 on the right side
Is the detection value of R (θk), and the detection value of the left detector 2 is L
If (θk), the calculated value is (R (θk) + L (θ
k)) / 2.

In FIG. 3, a change (a) in R (θk) and a change (b) in L (θk) are drawn with a circle P having the radius of the object W as a reference. FIG. 4 similarly shows the calculated value (R (θk) + L (θ
k)) ÷ 2 changes.

Here, the two detection values of the left and right detectors 2 and 2 include the eccentricity between the axis of the object to be measured and the center of rotation, the distortion (roundness error) of the object to be measured, and the position of the center of gravity of the object to be measured W. Each component of deflection due to change is included. On the other hand, the amount of displacement caused by the eccentricity and the strain included in the two detected values is always the same, and the deflection due to the change of the position of the center of gravity of the measured object is reversed in the direction with a cycle of 180 °.
Therefore, if the eccentricity component is A, the distortion component is α, and the deflection component is β, the detection value R (θk) can be expressed by A + α + β, and the detection value L (θk) can be expressed by A + α−β, and the calculated value (R (Θk) + L (θk)) / 2 can be expressed as A + α. That is, the deflection component (β) due to the change of the position of the center of gravity of the measurement object W is removed by the above calculation.

Similar to the polar coordinate system method already described with reference to FIGS. 5 and 6, a geometric perfect circle curve is obtained by the least square method based on the above calculated values, and the geometric true curve at the same rotation angle is obtained. The difference α (corresponding to Ek in FIG. 6) between the value on the circular curve and the calculated value is obtained, and the difference (αmax−αmin) between the maximum value (αmax) and the minimum value (αmin) is defined as the roundness. To do.

That is, in the method of the present invention, after removing the deflection component (β) due to the change of the center of gravity of the object W from the detection values of the left and right detectors 2 and 2, the true circle is obtained by the polar coordinate system method. To find the degree, as mentioned above,
Even if the axis of the object to be measured W is in a substantially horizontal state at the time of measurement, it is possible to measure the roundness that is not affected by the change in deflection due to the change in the position of the center of gravity of the object to be measured W. Therefore, the roundness can be accurately measured regardless of the direction of the object to be measured, and as a result, the roundness inspection line can be easily automated in the factory.

In this embodiment, the case where the two detectors 2 and 2 are arranged in the horizontal direction has been described.
When the axis of the object to be measured W is extended in a substantially horizontal direction as in the present embodiment, if the two detectors 2 and 2 are arranged in the vertical direction, the deflection components of the detection values of both detectors will be described. Since (β) becomes large, more accurate roundness can be obtained as compared with the case where the detectors 2 and 2 are arranged in the horizontal direction.

Further, according to the measuring method of the present invention, the roundness can be measured even when the axis of the object to be measured W is extended in the vertical direction at the time of measurement. Further, since the method of the present invention is a method of finding the roundness by detecting the variation in the distance on the circumference of the rotation center O of the measurement object W as a result, the roundness shown in FIG. It is possible to measure the roundness of a measurement object W having a constant diameter like a perfect circle without any trouble.

[0016]

As described above, according to the present invention, it is possible to obtain the roundness which is not affected by the change in the deflection due to the change of the position of the center of gravity of the object to be measured. The roundness can be measured more accurately regardless of the direction of the heart. As a result, the roundness inspection line can be easily automated in the factory.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a measuring method according to an embodiment of the present invention.

FIG. 2 is a schematic side view of the embodiment.

3A and 3B are diagrams showing changes in the detected value at the time of measurement, wherein FIG. 3A shows a change in the detected value at the right detector, and FIG. 3B shows a change in the detected value at the left detector. It is a figure.

FIG. 4 is a diagram showing changes in calculated values.

FIG. 5 is a schematic diagram showing a polar coordinate system measuring method.

FIG. 6 is an explanatory diagram of a homopolar coordinate system method.

FIG. 7 is a diagram showing an example of a measured object in which the diameter when rotated is constant like a perfect circle.

[Explanation of symbols]

1 spindle 2 detector W measurement object O rotation center

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Claims (2)

(57) [Claims] 1. A measuring object is rotated on a circumference of the measuring object by two detectors which are located on a straight line passing through the center of rotation and whose displacement in a direction in which they are separated from each other are positive displacements. The displacement at the same measurement point is detected for each predetermined rotation angle, the two detection values at the same measurement point are summed, then averaged, and the geometric perfect circular curve is obtained from the calculated value by the least square method. , A perfect circle, wherein the difference between the value on the geometrically perfect circular curve and the value after the calculation at the same rotation angle is obtained, and the difference between the maximum value and the minimum value is the roundness. Degree measuring method. 2. The roundness measuring method according to claim 1, wherein the two detectors are located on a perpendicular line passing through the center of rotation when the axis of the object to be measured is horizontal.