JP2008209240A - Method of sensing magnetic substance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a position of a magnetic substance, if peak magnetic field strength of a magnetic substance to be detected exceeds the upper limit of detectable magnetic field strength of a magnetic sensor. <P>SOLUTION: A paired magnetic sensor comprising two magnetic sensors provided in the same predetermined direction at a predetermined interval is used, this paired sensor or the magnetic substance is driven to travel in a predetermined direction, and a position where detection outputs from both magnetic sensors are substantially equal to each other is detected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for detecting the position of a magnetic body.

It is known to detect the position of a magnetic material by scanning a magnetic sensor. For example, when a catheter is inserted from the patient's mouth or nose into the stomach through the esophagus, a magnetic material is attached to the tip of the catheter, and during the insertion, the magnetic sensor is moved along the surface of the human body to position the magnetic material. It is known to detect. (For example, Patent Documents 1 and 2)
Japanese Patent Application Laid-Open No. 2004-215992 Japanese National Patent Publication No. 9-503054

  As shown in FIG. 1, with respect to the magnetized magnetic body A, the distribution of absolute values of the vertical component strength of the magnetic field along the path of a predetermined height has a mountain shape with the position directly above the magnetic body as a vertex. In order to detect the position of the magnetic body with a magnetic sensor, conventionally, the peak position of the peak of the magnetic field distribution is detected.

In FIG. 1, Hh represents the upper limit value that can be detected by the magnetic sensor (the boundary value at which the sensor element is magnetically saturated). When the magnetization of the magnetic material is strong and the peak magnetic field strength exceeds the detectable upper limit value, The conventional method cannot detect the position of the magnetic material.
In the manufacturing process of food and clothing, inspection for removing iron-based magnetic foreign matters such as mechanical debris is required. However, the above-mentioned peak magnetic field strength differs depending on the size of the foreign material, magnetic susceptibility (magnetized by stress or geomagnetism), etc. Beyond that, the foreign object cannot be detected, and it is difficult to guarantee the reliability of the inspection satisfactorily.

  An object of the present invention is to provide a method that enables detection of the position of a magnetic substance even when the peak magnetic field intensity of the magnetic substance to be detected exceeds the upper limit magnetic field intensity that can be detected by a magnetic sensor.

The method for detecting a magnetic material according to claim 1 is a method for detecting the position of the magnetic material by causing the magnetic sensor to travel with respect to the magnetic material to be detected or against the magnetic material to be detected. As the sensor, a magnetic sensor having two magnetic sensors arranged in a predetermined same direction at a predetermined interval is used, and the magnetic sensor or the magnetic body is moved in the predetermined direction so that both magnetic sensors It is characterized in that a position where detection outputs are substantially equal is detected.
In the magnetic body detection method according to the second aspect, the magnetic sensor is caused to travel to the detected magnetic body or to the detected magnetic body, and a magnetic field greater than or equal to a detectable upper limit value acts during the traveling. In this case, the position of the magnetic material is detected, and a magnetic sensor in which two magnetic sensors are arranged in a predetermined same direction at a predetermined interval is used as the magnetic sensor. Alternatively, the magnetic body is caused to travel in the predetermined direction to detect a position where detection outputs of both magnetic sensors are substantially equal.
According to a third aspect of the present invention, there is provided the magnetic body detection method according to the first or second aspect, wherein the magnetic sensor is a magnetic sensor that detects an absolute value of the magnetic field strength.
According to a fourth aspect of the present invention, there is provided the magnetic body detection method according to any one of the first to third aspects, wherein a gradient magnetic field detection sensor is used as the magnetic sensor.

As shown in FIG. 1, the magnetic field intensity distribution of the magnetic substance to be detected along a path separated by a predetermined height with respect to the magnetic substance to be detected is H (x), and each magnetic sensor S ₁ , S of the magnetic sensor is used. the detectable limit of _{2 H h,} the lower limit value to _{H L.} When the antimagnetic sensor Se travels along the above-described path and the center point o of the antimagnetic sensor Se reaches directly above the detected magnetic body A as shown in FIG. 2, the magnetic sensors S ₁ , S _The magnetic field intensity at which ₂ is magnetized becomes hc and hd, and hc = hd is established from the left-right symmetry with respect to the vertical line nn ′ of the magnetic field intensity distribution. Therefore, the position of the magnetic body A can be detected from the position where the detection outputs of the magnetic sensors S ₁ and S ₂ are equal.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, A indicates a magnetized magnetic body, and the magnetization direction is a vertical direction. H (x) represents the distribution of the magnetic field strength of the magnetic body A in the vertical direction along a horizontal path with a predetermined height from the magnetic body. Se is an anti-magnetic sensor, and two magnetic sensors S ₁ and S ₂ are arranged at a distance L. The upper limit magnetic field intensity detectable by each magnetic sensor is indicated by H _h , and the lower limit magnetic field intensity is indicated. Indicated by _HL . The distance L between the two magnetic sensors S ₁ and S ₂ satisfies L _h <L <L _L with respect to the distance L _h between p and p and the distance L _L between p ′ and p ′ in FIG. It is set as follows.

In order to detect the position of the magnetic material according to the present invention, the anti-magnetic sensor is run along the above-described path and the magnetic sensors S ₁ and S ₂ are both oriented in the vertical direction. In FIG. 2, (A) → (B) → (C) → (D) indicates the time-dependent position of the magnetic sensor Se.
In (b) of FIG. 2, the magnetic sensor S ₁ pair magnetic sensor generates a detection output to the magnetic field strength ha, the magnetic sensor S ₂ generates a detection output to the magnetic field strength hc. ha ≠ hc. In (b), the magnetic sensor S ₁ pair magnetic sensor generates a detection output to the magnetic field strength hb, the magnetic sensor S ₂ generates a saturation detection output for the upper limit Hh. hb ≠ Hh. In (c), the magnetic sensor S ₁ of the magnetic sensor generates a detection output for the magnetic field strength hc, and the magnetic sensor S ₂ generates a detection output for the magnetic field strength hd. In (d), the magnetic sensor S ₁ pair magnetic sensor generates a detection output to the magnetic field strength hd, the magnetic sensor S ₂ generates a detection output to the magnetic field strength he. hd ≠ he.
In (c), when the center point o of the antimagnetic sensor Se is located immediately above the detected magnetic body A, hc = hd is established from the left-right symmetry with respect to the vertical line nn ′ of the magnetic field strength distribution. Therefore, the position of the magnetic body A can be detected from the position where the detection outputs of the magnetic sensors S ₁ and S ₂ are equal.

In contrast to (c) in FIG. 2, when the center point o of the magnetic sensor Se deviates by ΔL from the position directly above the magnetic body A as shown in FIG. 3, the magnetic field intensity hc of each of the magnetic sensors S ₁ and S ₂ , A difference Δh occurs in hd and a difference ΔE _out occurs in the detection output. However, if the difference ΔE _out is within a predetermined minute value, ΔL can be suppressed sufficiently small, and both magnetism of the magnetic sensor can be reduced. The position of the magnetic material can be detected with sufficient accuracy even from the position of the magnetic sensor where the difference in detection output between the sensors is within a predetermined minute value.

In the above example, the magnetization direction of the magnetic material is the vertical direction, but the magnetization direction of the magnetic material is usually given by the vector synthesis direction of the vertical direction and the horizontal direction.
FIG. 4A shows the distribution of the magnetic field strength in the vertical direction along a path having a predetermined height with respect to the magnetic body of the magnetic body having the horizontal magnetization direction, and the position of the magnetic body A is the center of symmetry. It is point symmetric. However, the absolute value intensity distribution with respect to the magnetic field intensity is symmetrical with respect to the vertical line passing through the magnetic material, as shown in FIG. In FIG. 4B, H _h indicates the upper limit magnetic field intensity that can be detected by each magnetic sensor, and H _L indicates the lower limit magnetic field intensity.
In order to detect the position of the magnetic material whose magnetization direction is the horizontal direction, a magnetic sensor that detects the absolute value of the magnetic field strength is used for each magnetic sensor, and the distance between both magnetic sensors of the magnetic sensor is set to L _h < L <L is set so as to satisfy _L , and the position of the magnetic body is detected in the same manner as described above.

  In the present invention, an absolute magnetic field detection sensor is used as each magnetic sensor of the magnetic sensor. As the absolute magnetic field detection sensor, the detected magnetic field-detection output characteristic of the sensor is bilaterally symmetrical as shown in FIG. 5 (a), and the output characteristic capable of discriminating polarity as shown in FIG. A sensor that fully rectifies the output of the sensor can be used.

  A magnetic field sensor that outputs a difference between outputs of both magnetic sensors arranged at a predetermined distance L as a detection amount is used as the magnetic sensor, and the position of the magnetic body is detected from the position where the detection amount is 0. it can.

  The distance L depends on the magnetization intensity of the magnetic substance to be detected and the detectable upper limit magnetic field intensity of each magnetic sensor, and is determined by experiments. Usually, it is set from the range of 0.5 to 5 times the height of the above-mentioned route. The distance can be adjusted, and can be adjusted according to the height of the detection path.

In the above example, the magnetic field strength detected by the magnetic sensor is the vertical magnetic field strength, but the horizontal magnetic field strength may be detected.
In the present invention, a magnetic impedance effect sensor, MR sensor, fluxgate sensor or the like can be used as the magnetic sensor.

  In the above example, the antimagnetic sensor is running. For example, when inspecting whether or not a magnetic foreign object is contained in a component conveyed by the conveyor, the antimagnetic sensor is fixed and this antimagnetic Parts can be run directly below or directly above the sensor.

  In carrying out the present invention, the present invention can also be carried out after magnetizing the magnetic substance to be detected in the vertical direction or the horizontal direction by a magnetizer.

3 is a drawing showing a magnetic field strength distribution of a magnetic body and a magnetic field sensor in the magnetic body detection method according to the present invention. It is drawing which shows the movement state of the antimagnetic sensor in the detection method of the magnetic body which concerns on this invention. 3 is a drawing used to show the position detection accuracy in the magnetic body detection method according to the present invention. 4 is a diagram for illustrating a magnetic body detection method according to the present invention when the magnetization direction of the magnetic body is a horizontal direction. It is drawing which shows the to-be-detected magnetic field-detection output characteristic of the absolute magnetic field detection sensor used by this invention.

Explanation of symbols

Se Magnetic sensor S ₁ Magnetic sensor S ₂ Magnetic sensor L Interval between magnetic sensors S ₁ and S ₂ H _h Detectable upper limit magnetic field intensity H _L Detectable lower limit magnetic field intensity A Magnetic body

Claims (4)

A method of detecting the position of a magnetic body by moving the magnetic sensor with respect to the magnetic body to be detected or the magnetic sensor with respect to the magnetic body to be detected. A pair of magnetic sensors arranged in the same direction is used, and the magnetic sensor or the magnetic body is moved in the predetermined direction to detect a position where the detection outputs of both magnetic sensors are substantially equal. A method for detecting a magnetic material. When the magnetic sensor is run against the magnetic substance to be detected or to the magnetic substance to be detected, and the magnetic sensor is detected to detect the position of the magnetic substance when a magnetic field exceeding the detectable upper limit value is applied to the magnetic sensor during the running. The magnetic sensor is a magnetic sensor in which two magnetic sensors are arranged in a predetermined direction at a predetermined interval, and the magnetic sensor or the magnetic body is placed in the predetermined direction. A method of detecting a magnetic material, characterized by detecting a position where the detection outputs of both magnetic sensors are substantially equal by running. 3. The method of detecting a magnetic material according to claim 1, wherein the magnetic sensor is an absolute magnetic field detection sensor for detecting an absolute value of the magnetic field strength. 4. The magnetic substance detection method according to claim 1, wherein a gradient magnetic field detection sensor is used as the magnetic sensor.

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