JPS6358190A - Iron detector - Google Patents

Abstract

PURPOSE:To accurately measure a distance in a direction perpendicular to the surface of an object to be detected and enable the eccentricity of a rotating body or the vibration of a magnetic body to be measured by laying a saturable coil in parallel to a flat detecting surface in a nonmagnetic material container having the flat detecting surface. CONSTITUTION:A saturable coil 2 is laid in parallel to a flat detecting surface in a nonmagnetic material container 1 having the flat detecting surface and two permanent magnets A and B magnetized in reverse directions to each other are provided on substantially the same plane as the coil 2 and in directions perpendicular to the detecting surface while sandwiching the coil 2, composing a detecting head. The coil 2 responds to a magnetic field in an X-axis direction but no to magnetic fields in Y- and Z-axis directions. The magnetic field in the X-axis direction applied to the coil 2 by the magnet pieces A and B changes in accordance with the position of the coil 2 on a Z-axis. When the coil 2 is in a midpoint between the magnet pieces A and B in the Z-axis direction, an X-axis direction magnetic field applied to the coil 2 is equal to zero. However, when the coil 2 is deviated from the coil 2 is equal to zero. However, when the coil 2 is deviated from the midpoint, a positive or negative magnetic field is applied to the coil 2 in the X-axis direction. When an iron plate 3 to be detected approaches the flat detecting surface, a change in the magnetic field applied to the coil 2 is detected by a magnetic detector and outputted as a change in a voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an iron detection device that detects the approach of a magnetic object such as iron.

[Summary of the invention]

The present invention detects the approach of a magnetic object in a non-contact and highly sensitive manner by using a detection head that has a saturable coil between two permanent magnets placed at a distance in a non-magnetic container. It was made so that it could be done.

[Conventional technology]

Conventionally, there are the following methods for detecting magnetic objects.

(a) One that uses a metal detector that utilizes high-frequency eddy current loss.

A detector that uses a semiconductor sensor such as a Hall element or magnetoresistive element biased by a permanent magnet.

(c) A magnetic sensor that combines a saturable coil, a high-frequency oscillator, and a detector.

[Problem that the invention seeks to solve]

However, these conventional techniques have the following drawbacks.

Method (a) can be used to detect metal magnetic materials such as iron, but the detection distance is small and it is difficult to quantitatively and accurately detect the distance.

Method (b) allows the detector to be made smaller, but requires a strong bias magnetic field and the distance between the detector and the magnetic object is 0.1 mm!
Since they are used close to J, the range of use is limited and it is difficult to use for machine tools and industrial machinery.

Method (c) has a highly sensitive magnetic sensor that senses weak magnetic fields, so it can detect small magnet pieces from a distance of several millimeters or more, and is often used in industrial machinery, but is limited to the detection of magnetic fields or magnets. However, it is not used to detect magnetic objects that do not produce magnetic flux, such as pieces of iron.

[Failure to solve the problem]

The present invention includes a detection head in which a saturable coil is placed parallel to the detection plane in a non-magnetic container having a detection plane, and two permanent magnets are provided with the saturable coil sandwiched in substantially the same plane as the saturable coil. and a magnetic detection circuit that converts changes in the magnetic field applied to the saturable coil into changes in voltage.

〔Example〕

FIG. 1 is a side sectional view showing an example of a detection head that can be used in the present invention, and FIG. 2 is a top view of the same detection head. In these figures, (1) is a metal or plastic non-magnetic container, (2) is a saturable coil, (21) is its core, A and B are magnet pieces with a rectangular cross section, and (3) is a magnetic field to be detected. Indicates an object (e.g. a steel plate). Magnet pieces A and B are fixed to the container (1) at regular intervals and are magnetized in opposite directions in the thickness direction. That is, when viewed from the detection surface side, if the magnet piece A is, for example, a north pole, the magnet piece B is a south pole.

On almost the same plane as these magnet pieces A and B, in between them,
Fix the saturable coil (2) for magnetic flux detection. In the diagram,
The X, Y, and Z axes are shown for convenience of explanation.

Magnet pieces A and B, for example, width 10 mm, length 14 mm,
Plastic magnets with a thickness of 2 mm are used, and are pasted at intervals of 10 mm into a container (1) made of non-magnetic stainless steel (SO8-304) with a thickness of 1 mm, for example. The saturable coil (2) is made by winding two windings in opposite directions around a permalloy (saturable) core (2,) with a hole of, for example, 5 mm in length, 3 mm in width, and 100 microns in thickness. It is.

The number of turns is, for example, 100 times. Saturable coil (2)
Insert the core (
21) is fixed so as to be parallel to both magnet pieces, the saturable coil (2) is sensitive to the magnetic field in the X-axis direction, but hardly sensitive to the magnetic fields in the Y- and Z-axis directions.

The X-direction magnetic field applied to the saturable coil (2) by the magnet pieces A and B changes depending on the position of the saturable coil (2) on the Z-axis. 2 saturable coils (2)
When it is at the center of magnet pieces A and B in the direction (this time is Z=
Let it be O. ), the X-direction magnetic field applied to the saturable coil (2) is O, but if it deviates from the center, a positive or negative magnetic field will be applied in the X-direction.

FIG. 3 is a diagram illustrating the effect on the magnetic field when the iron plate (3) approaches the detection head. When the saturable coil (2) is placed at the position Z=O as shown in the figure and the magnetic field in the X direction due to only the magnet pieces A and B is measured on the Z axis, the result is a curve I in FIG. 4.

Therefore, by slightly shifting the position of the saturable coil (2) along two axes - H, a positive or negative bias magnetic field can be applied to the saturable coil (2). Next, consider the case where the iron plate (3) is placed at a distance pd from the front surface of the magnet piece. In this case, when the iron plate (3) is sufficiently large compared to the magnet pieces, the magnetic field of the magnet pieces A and H is replaced by mirrors @A', B
It is equal to the magnetic field when there are magnet pieces of the same strength as A and B at position '. At this time, the X-direction magnetic field on the Z-axis becomes like curve H in FIG. 4. In other words, the curve I is shifted to the left by approximately 2d.

FIG. 4 is a curve diagram showing changes in the X-direction magnetic field applied to the saturable coil (2) due to the approach of the iron plate. Curve I in the same figure
As for and ■, I have already mentioned it. Since the saturable coil (2) is located approximately at Z-0, the X-direction magnetic field represented by the point P on the curve 2 is applied to the saturable coil (2). Therefore, it represents the autumn situation in which the X-direction magnetic field applied to the saturable coil (2) changes when the distance d is changed.

FIG. 5 is a circuit diagram showing an example of a magnetic detection circuit used in combination with the detection head. The saturable coil (2) is a saturable coil of the detection head, and Ll and L2 indicate its windings. The OSC is a high frequency (for example, 50 kHz) pulse oscillator, and its output is a pulse train of the same polarity (for example, a pulse width of 1 μS). R is series resistance, Dl and D2
is a diode, r and r2 are output resistances, and C4, C2, and C3 are capacitors. The windings and L2 generate magnetic fluxes in opposite directions due to high frequency e-irrus, and the saturable coil (2
), an output voltage is generated at the output terminals (4) and t (5) at both ends of the capacitor C3. For example, if the X-direction magnetic field is in the range of ±50 Gauss, an output voltage of ±6 V is produced linearly, and at ±100 Gauss, it is saturated to produce an output voltage of ±10 V.

FIG. 6 is a characteristic curve diagram showing changes in the output of the magnetic detection circuit when the iron plate (3) approaches in two directions.

Curve A is for the case where no bias magnetic field is applied to the saturable coil (2) and therefore no bias voltage is applied to the detection circuit output.The output voltage (negative direction voltage in the figure) is 0 when there is no iron plate. It increases as the iron plate approaches, and decreases again as the distance d becomes smaller. If the X-direction magnetic field applied to the saturable coil (2) is too large, the core (2,) will become saturated and the output will be limited to IOV. Therefore, curve A is saturated where the output is large. Curve B is +
This shows the characteristics when a bias magnetic field equivalent to 6V is applied, and the saturation at the maximum output portion is alleviated and the output voltage width is widened. In other words, by applying a bias magnetic field,
The operating range of the magnetic detection circuit can be expanded. The iron plate used to measure the above output characteristics was 30 mm wide and 50 mm long.
It was a soft iron plate with a thickness of 0.2 mm. Even if the iron plate was made larger or thicker, there was no difference in the detection circuit output. Also, the strength of the magnetic field leaking to the detection surface of the detection head during measurement was 180 Gauss, but as shown in Figure 6, a large output voltage was obtained even with a relatively weak leakage magnetic field even at large intervals. Ta. By increasing the dimensions and spacing of the magnet pieces A and B, or by increasing the strength of each magnet piece, the -layer detectable distance can be increased.

Up to now, the present invention has been described for detecting the distance d in two directions between the detection surface of the detection head and the iron plate.
can be kept constant and the end of the iron piece moving in the KY-axis direction parallel to the detection surface can be detected.

As shown in Figure 7, an iron plate (e.g. 30mm wide, 5mm long
0 mm, thickness 0.2 mm) is moved in the Y direction while keeping the distance d from the detection head constant, an output voltage as shown in FIG. 8 is obtained. As shown in this figure, a large output is generated almost linearly with respect to the displacement of the edge of the iron plate, so it can be used as an edge position detector.

FIG. 9 is a top view showing another example of a detection head that can be used in the present invention, and FIG. 1O is a circuit diagram showing an example of a switching circuit used in combination with this detection head. The arrangement relationship between the magnet pieces A, B and the saturable coil (2) in the detection head of FIG. 9 is the same as in the detection head of FIGS. 1 and 2,
The difference is that the saturable coil (2) is a single winding wound around a ■-shaped core. In FIG. 10, Ql and C2 are transistors, and (6) and (7) are output terminals. When the iron piece approaches, the voltage at the zero point changes, and this can be used to cause the transistors Q1 + C2 to perform an on/off switching action. In curve B of Fig. 6, the voltage slope at a distance of 3 mm reaches 4 V/1 mm, which is a change of 4' mV for a displacement of 1 μm, so it is a non-contact and highly accurate limit (repeatability of 1 μm).・
Can be used for switches.

In the above description, the object to be detected is an iron plate or an iron piece, but the object is not limited to these, and any object with high magnetic permeability such as a ferrite or cast iron structure can be detected.

〔Effect of the invention〕

The present invention has the following various remarkable effects.

(a) The distance 9 in the direction perpendicular to the surface of the object to be detected can be measured almost linearly and accurately over a range of 0 to 10 mm or more.

(b) A non-contact, highly accurate limit switch can be obtained by combining the detection circuit output with a switching circuit that turns on and off at a constant voltage.

(c) If the detection head is placed at a distance of several millimeters from the surface of the iron roll, the amount of eccentricity during roll rotation can be measured. Since waveforms occur repeatedly in a rotating body, O offset is not a problem, and eccentricity of 1 μm or less can be measured by increasing the output and amplifying it.

(d) Vibrations of magnetic materials can be measured. The response speed of this detection device is over 4 kHz, and it can accurately measure vibrations ranging from small amplitudes of several micrometers to large amplitudes of several millimeters.

(e) The end position of the iron plate where the belt falls continuously can be detected.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing an example of a detection head that can be used in the present invention, Fig. 2 is a top view of the detection head, Fig. 3 is a diagram illustrating the influence on the magnetic field due to the approach of a steel plate, and Fig. 4 is a curve diagram showing changes in the X-direction magnetic field applied to the saturable coil as the iron plate approaches, Figure 5 is a circuit diagram showing an example of a magnetic detection circuit used in combination with a detection head, and Figure 6 is a curve diagram showing changes in the X-direction magnetic field applied to the saturable coil as the iron plate approaches. Figure 7 is a curve diagram showing the output change of the magnetic detection circuit according to
Figure 8 is a curve diagram showing output changes due to displacement of the iron plate in the Y direction, Figure 9 is a top view showing another example of the detection head, and Figure 10 is a combination with the same detection head. FIG. 2 is a circuit diagram showing an example of a switching circuit used in the present invention. cl, c2. c3) , (osc,r,,Ql,Q2
)...Magnetic detection circuit, (3)...Iron plate (magnetic object)
.

Claims (1)

[Claims] A saturable coil is placed parallel to the detection plane in a non-magnetic container having a detection plane, and the saturable coil is sandwiched in substantially the same plane as the saturable coil, so that the saturable coil is placed in parallel to the detection plane. The detection head includes two permanent magnets magnetized in opposite directions in a perpendicular direction, and a magnetic detection circuit that converts a change in the magnetic field applied to the saturable coil into a change in voltage, An iron detection device characterized by producing a linear voltage change when a magnetic object approaches.