Device and Method for Inspecting for Flaw on Surface of Work

• US 20080033664A1
• Filed: 08/25/2005
• Published: 02/07/2008
• Est. Priority Date: 09/03/2004
• Status: Active Grant

• Current Assignee: Komatsu Ltd.
• Original Assignee: Komatsu Machinery Corporation (Komatsu Ltd.)
• Inventors: Yamanoto, Makoto, Yoshimoto, Akihiro
• Granted Patent: US 7,499,813 B2
• Time in Patent Office: Days
• US Class Current: 702/36
• CPC Class Codes: G01B 5/285 for controlling eveness
• CPC Class Codes: G01N 19/08 Detecting presence of flaws or irregularities

Abstract

A device for inspecting for minute flaws upon the outer surface of journal or pin portions of a crank shaft comprises a main device 12 and a control device 14. The main device 12 brings a gauge head 56, which can freely move forwards and backwards along a Y axis direction, into contact with an inspection region 16A of the the crank shaft 16 while rotating the crank shaft 16 around a rotational axis 16C, measures the surface position of the inspection region 16A for each of rotational angles, and obtains surface portion waveform data corresponding to rotational angle. The gauge head 56 has an oscillation function, and always contacts against the inspection region 16A during rotation. The control device 14 extracts high frequency waveform components from the obtained waveform data, and detects flaws on the inspection region based on the high frequency waveform components.

Claims

1. A flaw inspection device which inspects for presence of a flaw on a surface of a workpiece, comprising:

a surface position measurement means which, while rotating said workpiece around a predetermined rotational axis, measures a surface position of an inspection region of said workpiece in a direction perpendicular to said rotational axis, for each of rotational angles;

a surface waveform acquisition means which receives an output signal of said surface position measurement means, and acquires surface waveform data which specifies said surface position with respect to each of the rotational angles;

a high frequency waveform extraction means which extracts, from said surface waveform data, high frequency waveform data which has a frequency higher than a predetermined frequency, or high frequency waveform data which specifies a change of a position within an angular range smaller than a predetermined angle; and

a flaw decision means which decides upon the presence of the flaw at said inspection region, based upon said high frequency waveform data which has been extracted.

2. The flaw inspection device described in claim 1, wherein:

said surface position measurement means comprises a gauge head which contacts against a surface of the inspection region upon said workpiece, and said gauge head, along with shifting freely along a first direction which is orthogonal to the rotational axis of said workpiece, is also biased in the direction towards said workpiece, so as continuously to contact against the inspection region of said workpiece while said workpiece is rotated; and

said surface position measurement means measures the surface position of said inspection region for each of the rotational angles, by measuring a position of said gauge head for each of the rotational angles while said workpiece is rotated.

3. The flaw inspection device described in claim 2, wherein the contacting surface of said gauge head to said inspection region has a predetermined length in a second direction which is orthogonal to the shifting direction of said gauge head and to a direction of said rotational axis of said workpiece, and said predetermined length is equal to or greater than a stroke length of said inspection region in said second direction when said workpiece rotates.

4. The flaw inspection device described in claim 2, wherein the contacting surface of said gauge head to said inspection region is a flat plane which has been processed to an accuracy equal to or greater than that of the surface of said inspection region, and moreover has a width in the direction of said rotational axis which almost corresponds to a width of said inspection region in the direction of said rotational axis.

5. The flaw inspection device described in claim 2, wherein the contacting surface of said gauge head to said inspection region has a width in the direction of said rotational axis which almost corresponds to a minimum width among widths of straight line portions of said inspection regions in the direction of said rotational axis.

6. The flaw inspection device described in claim 2, wherein said gauge head can swing within a predetermined angular range around, as a center, a rotational axis in a second direction which is orthogonal to a direction of said rotational axis of said workpiece and to said shift direction of said gauge head.

7. The flaw inspection device described in claim 1, wherein, based upon said high frequency waveform data, said flaw decision means calculates a rate of change with respect to the rotational angle of the surface position of said inspection region, and detects a flawing in said inspection region by comparing said rate of the change which has been calculated with a threshold value set in advance.

8. The flaw inspection device described in claim 1, wherein, based upon said high frequency waveform data, said flaw decision means obtains a height or a width of portions at which the surface position of said inspection region changes with respect to the rotational angle, and detects a flaw in said inspection region by comparing said height or width with a threshold value set in advance.

9. The flaw inspection device described in claim 1, wherein said surface position measurement means comprises a plurality of contour measurement units whose relative positions with respect to said workpiece are variable, and said contour measurement units simultaneously measure surface positions of different inspection regions upon the same workpiece independently.

10. A flaw inspection device which inspects for presence of a flaw on a surface of a workpiece, comprising:

a surface position measurement device which, while rotating said workpiece around a predetermined rotational axis, measures a surface position of an inspection region of said workpiece in a direction perpendicular to said rotational axis, for each of the rotational angles; and

a control device which is connected to said surface position measurement device;

wherein said control device;

receives an output signal of said surface position measurement means;

acquires surface waveform data which specifies said surface position with respect to each of rotational angles;

extracts, from said surface waveform data which has been acquired, high frequency waveform data which has a frequency higher than a predetermined frequency, or high frequency waveform data which specifies a change of a position within an angular range smaller than a predetermined angle; and

decides upon the presence or absence of a flaw at said inspection region, based upon said high frequency waveform data which has been extracted.

11. A flaw inspection method which inspects for presence of a flaw on a surface of a workpiece, comprising:

a step of measuring a surface position of an inspection region of said workpiece in a direction perpendicular to a predetermined rotational axis, for each of rotational angles around said rotational axis;

a step of acquiring, from said surface position for each of the rotational angles which has been measured, surface waveform data which specifies a waveform of said surface position with respect to each of the rotational angles;

a step of extracting, from said surface waveform data, high frequency waveform data which has a frequency higher than a predetermined frequency, or high frequency waveform data which specifies a change of a position within an angular range smaller than a predetermined angle; and

a step of deciding upon the presence of a flaw at said inspection region, based upon said high frequency waveform data which has been extracted.