Method of inspecting magnetic carburization in a non-permeable material and probe therefore

• US 5,128,613 A
• Filed: 11/01/1991
• Issued: 07/07/1992
• Est. Priority Date: 02/25/1985
• Status: Expired due to Fees

• Current Assignee: Kubota Corporation
• Original Assignee: Kubota Corporation
• Inventors: Takahashi, Makoto
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): EDMONDS, WARREN
• Application Number:
  US07/785,197
• Time in Patent Office: 249 Days
• Field of Search: 324/207.12, 324/207.13, 324/207.20, 324/209, 324/219, 324/220, 324/221, 324/225-229, 324/232-243, 324/251, 324/252, 324/260, 324/262, 307/309, 332/32 R, 332/32 H
• US Class Current: 324/235
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: G01N 27/72 by investigating magnetic variables

Abstract

A probe comprises a magnet and a Hall element which are provided in a magnetically impermeable case. The Hall element is disposed at the midportion between the two poles of the magnet in parallel with the lines of magnetic force. The presence of a carburized portion in the member to be inspected and the depth of carburization are detected by passing d.c. current across the Hall element and detecting the Hall effect electromotive force produced between the two ends of the element which are opposed in a direction perpendicular to the direction of flow of the current.

Claims

1. An apparatus for detecting carburization in an object to be inspected comprising a substantially magnetically non-permeable material comprising:

a probe comprising;

a casing made of a non-magnetic test material,

a magnet positioned in the casing and emitting lines of magnetic force toward an inspection side of the casing, the poles of said magnet pointing in a direction parallel to said inspection side,

a first Hall element placed in the casing between the magnet and the inspection side of the casing and being disposed in a field of and parallel to the lines of magnetic force,

a second Hall element being disposed at the midportion between the two magnetic poles of the magnet to intersect the lines of magnetic force so as to detect a decrease of the density of magnetic flux through the second Hall element when the magnet approaches a carburized portion in said magnetically non-permeable material;

wherein each of the first and second Hall elements has a pair of terminals connectable to a current source for passing d.c. current therethrough and another pair of terminals connectable to a measuring device for detecting a Hall electromotive force, and wherein during inspection of said object the first Hall element remains unchanged and the second Hall element emanates a high output signal in its normal state, whereas the first Hall element emanates an output signal by detecting an inclination of the lines of magnetic force, said inclination being caused by a disturbance of the magnetic flux toward a carburized portion in said magnetically non-permeable material and the second Hall element decreases said high output signal when the probe is passed over a carburized portion in the magnetically non-permeable material.

2. An apparatus as defined in claim 1 wherein said probe further comprises a third Hall element disposed symmetrically with the second Hall element with respect to the magnet, and a dummy piece approximately equivalent in magnetic permeability to said substantially magnetically non-permeable material is disposed oppositely to the third Hall element and approximately symmetrically with the position of the object to be inspected relative to the second Hall element, wherein the Hall electromotive forces of the second Hall element and the third Hall element are offset to detect the carburized portion in said magnetically non-permeable material.

3. An apparatus for detecting carburization in an object to be inspected comprising a substantially magnetically non-permeable material comprising:

a probe comprising;

a casing made of a non-magnetic material,

a magnet positioned in the casing and emitting lines of magnetic force toward an inspection side of the casing, the poles of said magnet pointing in a direction parallel to said inspection side,

a Hall element positioned in the casing between the magnet and the inspection side of the casing and being disposed in a field of and parallel to the lines of magnetic force,

the Hall elements containing a pair of terminals connectable to a current source for passing d.c. current therethrough and another pair of terminals connectable to a measuring device for detecting a Hall electromotive force;

wherein during inspection of said object the Hall element remains unchanged in the field of lines of magnetic force in its normal state, but the Hall element emanates an output signal when it detects an inclination of the lines of magnetic force, said inclination being caused by a disturbance of the magnetic flux toward a carburized portion of the magnetically non-permeable material.

4. An apparatus for detecting carburization in an object to be inspected comprising a substantially magnetically non-permeable material comprising:

a probe comprising;

a casing made of non-magnetic test material, a magnet positioned in the casing and emitting lines of magnetic force toward an inspection side of the casing, the poles of said magnet pointing in a direction parallel to said inspection side,

a first Hall element disposed at the midportion between the two magnetic poles of the magnet to intersect the lines of magnetic force so as to detect a decrease of the density of the magnetic flux through the first Hall element when the magnet approaches a carburized portion, said decrease being the result of a disturbance of the magnetic flux caused by the carburized portion,

a second Hall element positioned symmetrically with the first Hall element with respect to the magnet to intersect lines of magnetic force emitted toward a side of the casing opposite to the inspection side, and

a dummy piece approximately equivalent in magnetic permeability to said magnetically non-permeable material, the dummy piece being positioned at a position opposite the inspection side of the casing adjacent to the second Hall element, the first and second Hall elements having a pair of terminals connectable to a cuurent source for passing d.c. current therethrough and another pair of terminals connectable to a measuring device for detecting a Hall electromotive force;

wherein the Hall electromotive forces of the first Hall element and the second Hall element are offset to detect a carburized portion in said magnetically non-permeable material.

5. A method for detecting carburization in a substantially magnetically non-permeable material comprising the steps of:

creating lines of magnetic force by a magnet;

positioning the magnet in a fixed position close to a Hall element so that said Hall element is disposed parallel to the lines of magnetic force and the lines of magnetic force pass tangentially along the Hall element without intersecting the Hall element;

passing the magnet and the Hall element over the substantially magnetically non-permeable material to be inspected for carburization, wherein the Hall element is disposed between the magnet and the magnetically non-permeable material being inspected, thereby causing lines of magnetic force to pass through the material; and

generating a signal by the Hall element when the line of magnetic force intersect a carburized portion of the magnetically non-permeable material thereby causing the lines of magnetic force to incline and to intersect the Hall element.