JPS61210976A - Remaining magnetism measuring instrument - Google Patents

Abstract

PURPOSE:To correctly measure a remaining magnetism of a steel plate by performing a subtraction from an integrating value of an output of a magnetizer for a magnetization saturating a magnetizing direction in two reverse directions an integrating value for a cycle integer times as long as a cycle of an external magnetism of this output in the steel plate. CONSTITUTION:A steel plate 11 is carried in a direction of X by a roller 12. A vertical magnetic field is applied to a surface of the steel plate 11 by a direct current magnetizer 13 and by a magnetism detecter 15, a strength of the vertical magnetic field is measured on the surface of the steel plate 11. A rotating position of the roller 12 is detected 16, a synchronizing signal of an external magnetic field is outputted. By receiving the synchronizing signal from the rotating position detector 16, a current changeover device 17 reverses a direction of the current fed to the magnetizer 13 every cycle (tn) integer times as long as a cycle tau. An integrator 21 receives a cycle signal from the detector 16, integrates an output of an inspector 15 every cycle (tn), and outputs the integrating value to a subtracter 22. The subtracter 22 subtracts the integrating value Y2 from the subtracting value Y1 obtained from the integrator 21 and the subtracted value is outputted to a display device 23 and displayed as a remaining magnetism of the steel plate 11.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a residual magnetism measuring device that continuously measures the residual magnetism of a cold rolled steel plate or the like after magnetically saturating the cold rolled steel plate or the like.

<Prior Art> Hardness, which is an indicator of the strength of cold-rolled steel, is generally related to the strength of residual magnetism after magnetic saturation.

Conventionally, there is a residual magnetism measuring device as shown in FIG. 3 (see Japanese Patent Application Laid-open No. 102148/1983). This residual magnetism measuring device magnetically saturates a running steel plate 1 with a DC magnetizer 2 having a positive magnetic pole (N pole) and a negative magnetic pole (S pole) spaced apart in the running direction X of the steel plate 1. The strength of the residual magnetism of the steel plate 1 is measured by the magnetic detector 3 at a position where there is no magnetic influence from the magnetizer 2, that is, at a position where the magnetic influence is minimal.

<Problems to be Solved by the Invention> By the way, in the above-mentioned conventional residual magnetism measuring device, the measured value of the magnetic detector 3 is Yo, and the residual magnetism of the steel plate I is Hro.
, the above measured value Y, where CI is the external magnetism which is a substantially constant value such as earth's magnetism, Ct is the magnetism from a peripheral device (not shown), and 03 is the offset amount specific to the magnetic detector 3. is, Yo = Hro+C++Ct+Ca +・+
(It becomes D.

From this (+) equation, in order to accurately determine the residual magnetism Hro, it is necessary to keep the external magnetism C,,C, and the offset amount C1 constant, and to measure this value in advance. I understand. That is, in the past, the magnetic detector 3
must be measured in a place where the external magnetism C,,C, is always constant, and the offset amount C of the magnetic detector 3
There is a problem in that zero point adjustment is required to eliminate 1. In other words, the external magnetism C1 from peripheral devices often fluctuates periodically, but in the past, in this case, the S/N ratio (signal/noise ratio) deteriorates and accurate measurement of residual magnetism is not possible. It disappears.

Therefore, the purpose of this invention is to be able to accurately measure the residual magnetism of a steel plate even when external magnetism fluctuates periodically.
Moreover, it is possible to eliminate the need for zero point adjustment of the offset amount of the magnetic detector before measurement.

<Means for Solving the Problems> In order to achieve the above object, the residual magnetism measuring device of the present invention includes a magnetizer that magnetically saturates a steel plate in two opposite directions, and a magnetizer that magnetically saturates a steel plate in two opposite directions. A magnetic detector detects the magnetic strength near the steel plate when the steel plate is magnetically saturated in two directions, and a magnetic detector detects the magnetic strength when the steel plate is magnetically saturated in one direction. an integral value of the output of the above-mentioned magnetic detector over a period that is an integral multiple of the period of the external magnetism;
subtraction means for subtracting the output of the magnetic detector which detects the magnetic strength when the steel plate is magnetically saturated in the other direction with an integral value over a period that is an integral multiple of the period of the external magnetism; The present invention is characterized in that the output of the subtraction means is measured as residual magnetism of the steel plate.

<Effect> The integral value of the output of the magnetic detector when the steel plate is magnetically saturated in one direction by the magnetizer is Yl, and the integral value of the output of the magnetic detector when the steel plate is magnetically saturated in the other direction. Letting Y be...(3).

Here, C1 is the strength of the external magnetic field that can be considered to be almost constant, including geomagnetism, etc., C1 is the strength of the external magnetic field that changes periodically,
C8 is the offset amount of the magnetic detector that can be considered constant during the measurement period, Hr+ is the strength of the residual magnetism of the steel plate when the steel plate is magnetically saturated in one direction, and Hrt is the strength of the residual magnetism of the steel plate when the steel plate is magnetically saturated in the other direction. The strength of the residual magnetism of the steel plate in the state, t
n is the integration period, Δt is the time difference at the start of measurement in both states of magnetic saturation in two opposite directions, and the integration period tn is an integral multiple (1) of the period (τ) of the external magnetic field C1.
(including times).

On the other hand, the saturated residual magnetism Hr+ in two opposite directions of the steel plate
The strength of Hrt and Hrt are determined by the known magnetic characteristic curve of steel plate,
Their absolute values are equal and their signs are opposite.

(Hr, =-Hro therefore, becomes.

Also, the period of Ct(t) is τ, and the integration period tn=n・
Since τ (n: integer), it follows.

Therefore, equation (3) is becomes.

When the integral value Yt of equation (6) is subtracted from the integral value Y1 of equation (2) by the subtraction means, the following is obtained: y=y, -yt (7).

In this way, the output of the subtraction means is as shown in equation (7),
It is the product of the residual magnetism Hr+ of the steel plate and the integration period tn, that is, it is proportional only to the residual magnetism Hr, excluding the extraneous magnetism c,, ct(t) and the offset amount C3 of the magnetic detector. Become something. Therefore, if the output Y of the subtraction means is corrected by the integration period tn,
The residual magnetism of the steel plate is accurately detected without being affected by the external magnetism c + , Ct(t) and the offset amount C1 of the magnetic detector.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

As shown in FIG. 1, a steel plate 11 whose residual magnetism is to be measured is conveyed by rollers 12 in the direction of arrow X. A DC magnetizer 13 is disposed facing the surface of the steel plate 11, and two poles (N pole, S pole) of the DC magnetizer 13 are connected to the steel plate II.
The wire plates 11 are spaced apart from each other in the conveying direction so as to apply a vertical magnetic field to the surface of the steel plate 11. The DC magnetizer 13 has enough strength to magnetically saturate the steel plate II. Further, a magnetic detector 15 is provided between the steel plate 11 toward the center of the roller 12, and the magnetic detector 15 is arranged perpendicularly to the surface of the steel plate 11, so that the magnetic field in the direction perpendicular to the surface of the steel plate 11 is detected. I try to measure strength. In this arrangement, the magnetic detector 15 is not magnetically influenced by the DC magnetizer 13. Since the steel plate II is in contact with the roller 12, the steel plate l! The distance between the magnetic detector 15 and the magnetic detector 15 is kept constant. That is, the roller 12 has the function of moving the steel plate 11 and keeping the distance between the steel plate 11 and the magnetic detector 15 constant. Further, the roller 12 has a non-uniform distribution of residual magnetism and is a source of periodic external magnetism Ct(t) with a period τ. (The source of periodic external magnetism is often generated from a rotating body with uneven distribution of residual magnetism.) On the other hand, the rotational position (rotation angle) of the roller 12 is detected by the rotational position detector 16. The rotational position detector 16 outputs a synchronizing signal for the external magnetic field ctQ).

In response to the synchronization signal from the rotational position detector 16, the current switch 17 reverses the direction of the current supplied to the DC magnetizer 13 every period tn that is an integral multiple of the period τ. Therefore, the steel plate 11 is magnetically saturated in the opposite direction every period tn. A constant current is supplied to the current switching device 17 from a DC power supply 18 .

On the other hand, the integrator 21 receives the synchronization signal from the rotational position detector 16, integrates the output of the magnetic detector 15 every period tn, and sends the integrated value to the subtracter 22, which is a subtracting means. do. Two consecutive outputs Y+ of the integrator 21,
Yt is the above-mentioned (2).

Exactly the same as equations (3) and (6), it becomes. In addition, C+, Ct, G3, Hr
The meanings of +, Hr t, and Δt are (2), (3),
This is the same as equation (6).

The subtracter 22 calculates the integral value Y obtained from the integrator 21 from the integral value Y! This subtracted value Y=YI Yt=
2tn-Hrl is output to the display 23.

The display 23 displays this subtracted value 2 tn-Hrl (the multiplication value of the integration period tn and the residual magnetism Hr+ of the steel plate 11) as the residual magnetism of the steel plate.

In this way, this residual magnetism measuring device is a magnetic detector in each state where the steel plate 11 is magnetically saturated in the opposite direction! The integral value Y,,Y! of the external magnetic field CzQ) of the output of 5 over a period tn that is an integral multiple of the period τ. , and from this integral value Y1, the integral value Y,
Subtract the external magnetic C+.

Since the effects of Ct(t) and the offset amount C1 of the magnetic detector 15 are eliminated, residual magnetism can be detected accurately.
Moreover, zero point adjustment of the magnetic detector 15 is not required.

FIG. 2 shows another embodiment. In this embodiment, the different parts of the steel plate 11 are magnetically saturated in opposite directions on the assumption that the magnetically saturated residual magnetism is the same even in different parts of the steel plate 11 in the embodiment shown in FIG. While we are looking for residual magnetism, the synchronized rollers 12a, 12b, 12
Steel plate 1 transported by c! The same portion A of the steel plate 11 is magnetically saturated in the opposite direction so that the residual magnetism of each portion of the steel plate 11 can be accurately measured. That is, in this embodiment, a current switching device is not required, and the DC magnetizer 13a dedicated to the N pole connected to the DC power source 18 magnetically saturates the portion A of the steel plate 11 in one direction, while the DC magnetizer 13a dedicated to the S pole At 13b, the portion A of the steel plate 11 is magnetically saturated in the opposite direction. Then, using magnetic detectors 15a and 15b with the same characteristics, a portion A of the steel plate 2 is magnetically saturated in one direction by one magnetic detector 15a.
Detects residual magnetism. Next, the part A of the steel plate 11 is magnetically saturated in the other direction by the synchronization signal from the rotational position detector 16, and when passing through the location where the magnetic detector +5b is located, the magnetic detector 15b detects the position of the steel plate +1. Part A
Detects residual magnetism. Integrator 2. Ia and 21b integrate the output over a period that is an integral multiple of the period τ of the external magnetism Ct(t) when the magnetic detectors 15a and 15b are respectively detecting the residual magnetism of the same portion A. The subtracter 22 subtracts the output 'Yt of the integrator 21b from the output Y1 of the integrator 21a, and displays the subtracted value Y=Y, -Y on the display 23. Since the subtraction is performed in this way, the external magnetic field c,,cy(t
) is eliminated, and the residual magnetism of portion A of the steel plate 11 is accurately measured. Moreover, since the magnetic detectors 15a and 15b have the same characteristics, the effect of the offset amount is reduced by the above-mentioned subtraction, and the necessity of offset adjustment is reduced.

<Effects of the Invention> As is clear from the above, according to the present invention, even if the value of the external magnetism is not constant, when its change is periodic, the residual magnetism of the steel plate can be used to reduce the S/N ratio. Accurate measurements can be made without Furthermore, the residual magnetism of the steel plate can be accurately measured without separately measuring the value of external magnetism. Further, the residual magnetism of the steel plate can be measured without adjusting the zero point of the magnetic detector, without requiring a zero point adjusting circuit, or with reducing the necessity of zero point adjustment.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the invention, FIG. 2 is a block diagram of another embodiment of the invention, and FIG. 3 is a block diagram of a conventional example. 11 =-・Steel plate,! 2. 12a, l 2b,
12c.-Roller, 13. 13a, l 3b
-・DC magnetizer! 5゜15a, 15b...Magnetic detector, 21.21a, 21b...Integrator, 22...
・Subtractor, 23...Display device. Patent applicant Kawasaki Steel Corporation Haka 1 representative agent
Patent attorneys Aohaku Ao and 2 others Figure 1 × Middle =

Claims (1)

[Claims] (1) A residual magnetism measuring device that continuously measures the strength of residual magnetism in a steel plate after magnetically saturating the steel plate, the magnetizer magnetically saturating the steel plate in two opposite directions. and a magnetic detector that detects the strength of magnetism near the steel plate when the steel plate is magnetically saturated in two opposite directions, and a magnetic detector that detects the strength of magnetism near the steel plate when the steel plate is magnetically saturated in one direction an integral value of the output of the magnetic detector detecting the magnetic strength over a period that is an integral multiple of the period of the external magnetic field;
subtraction means for subtracting the output of the magnetic detector which detects the magnetic strength when the steel plate is magnetically saturated in the other direction with an integral value over a period that is an integral multiple of the period of the external magnetism; A residual magnetism measuring device, characterized in that the output of the subtraction means is measured as residual magnetism of a steel plate.