JPS5821809B2 - Demagnetizing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a demagnetizing device that demagnetizes a magnetic quantity that has already been magnetized.

This type of device is a permanent magnet used for braking of an induction disk overcurrent relay, an induction disk voltage relay, an induction disk integrated wattmeter, etc., or a permanent magnet of a movable ring voltmeter or ammeter. This is a device that is often used when setting magnetization to a constant value.

Conventionally, a demagnetizing device as shown in FIG. 1 or 2 has been proposed as this type of demagnetizing device.

The demagnetizing device shown in FIG. 1 includes solenoids 1a and 1b to which a DC power supply voltage ED is applied to generate a magnetic flux φ1, and an iron core 2 forming a magnetic I-magnetic circuit.

Further, the demagnetizing device shown in FIG. 2 generates an alternating magnetic flux φ1. It consists of a solenoid 1a that generates φ3.

Reference numeral 3 denotes a permanent magnet, which is magnetized to a predetermined magnetization level or higher, and is finally magnetized to a desired amount of magnetization by a demagnetizing device 2.

Next, the operation of these demagnetizing devices will be explained.

In Figure 1, the DC power supply voltage ED is
When applied to solenoid 1a, 1b, the combined DC current is controlled by resistance.

flows. If the combined number of turns of the solenoids 1a and 1b is T, and the combined magnetic resistance of the magnetic circuit is Rm, then the magnetic flux φ1 is given by the following equation (1).

Furthermore, it is well known that an electromagnetic field that becomes magnetic poles N and S is generated at the end face of the iron core.

Now, when the permanent magnet 3 that requires demagnetization is brought close to the electromagnetic field with the magnetic pole of the permanent magnet opposite to the magnetic pole of the electromagnetic field, the permanent magnet will be demagnetized.

In FIG. 2, when AC power supply voltage EA is applied to solenoid 1a, a current flow limited by the impedance of solenoid 1a flows.

When the number of turns of the solenoid 1a is Ta, and the magnetic resistance of the magnetic circuit is Ra, an alternating magnetic flux φ3 is given by the following equation (2), and an alternating electromagnetic field is generated at the end face of the solenoid 1a.

Similarly to the above, when the permanent magnet 3 that requires demagnetization is brought vertically close to the solenoid 1a as shown in Figure 2, the permanent magnet will be demagnetized when the alternating electromagnetic field is opposite to the magnetism of the permanent magnet. .

However, since conventional demagnetizing devices are configured as described above, even if it is necessary to demagnetize the permanent magnet to a desired magnetic field strength, it is difficult to manage the distance to bring the permanent magnet close to the demagnetizing device. Another disadvantage is that it is impossible to know whether the desired magnetic field strength is achieved unless the strength of the demagnetized permanent magnet is measured again.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional ones.The degree of magnetization of a magnetic material is detected using a magnetic sensing element, and this is set as a reference value.

It is an object of the present invention to provide a demagnetizing device that can set the magnetization strength of the magnetic material to any desired value.

An embodiment of the present invention will be described below with reference to the drawings.

Hereinafter, the same reference numerals as in FIGS. 1 and 2 indicate the same or corresponding parts, and the explanation of the reference numerals will be omitted as appropriate.

In Fig. 3, 3 is a permanent magnet that is demagnetized to a desired value;
4 is a current control circuit; 4a is a current control circuit;

4a1 is the movable part of the slider 4a, 4b is the motor that drives this movable part 4a1, 5 is a current cutoff circuit that stops power supply to the solenoid 1a, and 5a is the b contact of the electromagnetic switch of the current cutoff circuit 5. , 5b is the attachment of the electromagnetic switch of the current interrupting circuit 5.

6 is a magnetic flux detection circuit, 6a is a Hall element which is a magnetic sensing means, 6b is a conversion circuit, and 7 is a comparison circuit.

8 is a start switch for the current control circuit.

Next, the operation of this demagnetizing device will be explained with reference to waveform diagrams of various parts shown in FIGS. 4 and 5 a to 5 e.

In FIG. 5 a = e, the horizontal axis represents time t, and the vertical axis represents physical quantities such as voltage, current, and magnetic quantity.

The AC power supply voltage shown in FIG. 5a is applied to the current control circuit 4 shown in FIG. 3, and then the starting switch 8 of the current control circuit shown in FIG.
When the motor 4b in the current control circuit 4 is closed, the motor 4b in the current control circuit 4 starts moving, and the movable part 4a of the mechanically connected slide duck 4a
l also starts moving at the same time.

At this time, since the movable part 4al of the slide duck 4a is driven at a substantially constant speed, the output of the current cutoff circuit 5 gradually increases from zero as shown in FIG.

Now, assuming that the impedance of solenoid 1a in Fig. 3 is an ideal coil and there is no resistor, solenoid 1a
It is well known that the current flowing through the capacitor lags 90° behind that shown in FIG.

Therefore, the alternating magnetic flux φ3 generated by the solenoid is shown in Figure 5C.
becomes.

By the way, as shown in FIG. 4, the Hall element 6a inserted into the magnetic flux B in the air gap of the permanent magnet 3 shown in FIG. 3 receives a constant current I on one surface.

When , the voltage expressed by the following equation (3) is generated from the remaining surface.

■H2K・Io-B ・・・・・・・・・
(3) Here, K is a constant determined by the Hall element and is expressed as the practical product sensitivity in m/mA-KG.

(G is Gauss) The voltage generated by the Hall element 6a is converted into an appropriate output voltage by the conversion circuit 6b, as shown in E of FIG. 5d.

is applied to the input terminal of the comparator circuit 7.

On the other hand, a reference voltage E8, which is a DC voltage divided by a variable resistor Rp, is applied to the other terminal of the comparator circuit 7, as shown in FIG.

Therefore, immediately before the current control circuit 4 is activated, the output voltage E of the magnetic flux detection circuit is as shown in FIG. 5d.

>Reference voltage E11. However, when the magnetic flux φ3 generated in the solenoid 1a by the current control circuit 4 increases, the permanent magnet 3 is demagnetized, the magnetic flux φ2 decreases, the output voltage of the magnetic flux detection circuit 6 decreases, and the reference voltage E□ becomes higher. growing.

At this time, the output of the comparator circuit 7 has been zero until now, but it outputs <E(V) as shown in FIG. 5e.

This voltage causes the coil 5 of the electromagnetic switch of the current cutoff circuit 5 to
b is energized and opens the b contact 5a.

Therefore, after this point, the input voltage of the solenoid coil 1a becomes 0 [■] as shown in Fig. 5, and the magnetic flux φ3
also becomes zero, and the demagnetization of the permanent magnet 3 is completed.

Next, specific details of the magnetic flux detection circuit 6 are explained according to FIG.
Further, specific details of the comparator circuit 7 will be explained according to FIG.

The magnetic flux detection circuit 6 shown in FIG. 6 consists of a Hall element 6a and a conversion circuit 6b, and this conversion circuit 6b has a variable resistance 6.
b1, fixed resistors 6b2 to 6b5, an operational amplifier 6b6, and the like.

P and N indicate DC plus and minus power supply voltage terminals.

In the above configuration, the current I is limited by the variable resistor 6bl in the Hall element 6a.

When energized and the Hall element 6a is placed in the magnetic flux B, the Hall element 6a generates a voltage ■□ according to the above-mentioned equation (3).

A differential amplification circuit (conversion circuit 6b) made of an operational amplifier 6b6 and resistors 6b2 to 6b5 converts the voltage VH of the Hall element 6a.
can be amplified to an appropriate voltage Vout using the following equation (4).

A Voul=--VH"-K°(4) B However, RA=value of resistor 6b3=value of resistor 6b5 RB-value of resistor 6b2-value of resistor 6b4 Regarding the comparison circuit 7, as shown in FIG. It is composed of transistors 7T1 to 7T3 and fixed resistors 7R1 to 7R4.

With the above configuration, a voltage EfL1 is applied to the reference voltage input terminal REF of the comparison circuit 7, and E is applied to the comparison voltage input terminal input.

is applied, E-PL<E. Then, the transistor 7T2 is turned on, the transistor 7T1 is cut off, and the collector voltage of the transistor 7T1 becomes P. Therefore, the transistor 7T3 is turned off, and the output voltage Vout
becomes O.

Next, when ER,>Eo, the transistor 7T1 is turned on and the transistor 7T2 is cut off.

By turning on this transistor 7T1, the collector voltage of the transistor 7T1 decreases, and the transistor 7T
Transistor 7T allows the dotted line 18 to flow from 3.
3 is turned on, and the output terminal Vout becomes approximately P voltage.

By configuring as described above, the magnetic flux detection circuit 6 and the comparison circuit 7 can be easily obtained.

In the above embodiment, since the solenoid 1a is excited with alternating current, there is no need to consider the polarity when demagnetizing the permanent magnet 3, which is advantageous in terms of work.

In the above embodiment, the current control circuit 4 includes a slider 4a.
The current control circuit 4 is shown as having a motor 4b and a motor 4b.
, a sliding resistance may be provided in place of the sliding duck 4a.

Further, the current control circuit 4 and the current cutoff circuit 5 may be formed as an integrated circuit.

Furthermore, although the solenoid 1a shown in FIG. 3 has an air core, the solenoid ia and ib may be wound around an iron core 2 as shown in FIG.

Next, another embodiment of the present invention will be described with reference to FIGS. 8 and 9.

In this embodiment, alternating current from an alternating current power source Ea is once converted to direct current via a direct current conversion circuit 9, and then converted into direct current by a current control circuit 4.
It is configured to supply

The other parts have almost the same configuration as the previous embodiment.

The operation of the device having such a configuration will be explained with reference to FIG. 9. The waveforms of each part will be as shown in FIG.

That is, when the AC voltage shown in FIG. 9a is applied to the DC conversion circuit 9, the output of the DC conversion circuit 9 has the waveform shown in FIG.

Next, the starting switch 8 of the current control circuit shown in FIG. When moving from point A to point B, the value of variable resistor 4a changes from infinity to zero ohms.

At this time, if the DC resistance 1 of the solenoid 1a is S ohm, the current I flowing through the solenoid 1a falls within the range of current values given by the following equation.

D ID1=-=0 0 D ID2-- Here, (1) is the minimum current, and ID2 is the maximum current.

Now, when a current flows through the solenoid 1a in the direction shown in FIG. 8, a magnetic flux φ3 is generated as shown in FIG. 8, as in the previous embodiment.

The permanent magnet 3 is placed in the direction in which demagnetization is desired so that the magnetic pole is opposite to the magnetic pole of the magnetic flux φ3 (in FIG. 8), and the Hall element 6a is inserted into the magnetic flux φ2 in the gap of the permanent magnet 3.

In this embodiment, the AC power supply voltage Ea is used to generate the DC voltage ED using a direct-to-current conversion circuit, but the DC power supply voltage may be used instead of the AC power supply voltage and the DC conversion circuit may be omitted.

Further, the current control circuit and the current cutoff circuit may be integrated into one circuit.

Furthermore, although the solenoid 1a in FIG. 3 has an air core, the solenoids 1a and 1b may be wound around an iron core 2 as shown in FIG.

In that case, there is an advantage that various losses do not occur in the iron core 2 compared to the AC excitation method.

As described above, according to the present invention, the magnetic flux of a magnetized magnetic body that requires demagnetization is detected using a magnetically sensitive means, and the strength of the magnetic flux to be demagnetized is gradually increased from zero. Furthermore, the comparator circuit is configured to compare the magnetic flux of the magnetic material with a reference value and automatically cut off the demagnetizing magnetic flux, making it possible to easily maintain the strength of the magnetic flux of the magnetic material at a constant value and to achieve high accuracy. There are benefits to be gained.

[Brief explanation of the drawing]

1 and 2 are block diagrams of a conventional demagnetizing device, and FIG. 3 is a block diagram showing an embodiment of a demagnetizing device according to the present invention.
Figure 4 is a diagram showing the principle of the Hall element, Figures 5a-e are operational waveform diagrams of each part shown in Figure 3, Figure 6 is a circuit diagram showing details of the magnetic flux detection circuit, and Figure 7 is a diagram showing the details of the magnetic flux detection circuit. FIG. 8 is a block diagram showing another embodiment of the demagnetizing device according to the present invention, and FIGS. 9 a - f are operation waveform diagrams of each part of the circuit shown in FIG. be. In the figure, EA is an AC power supply, E is a DC power supply, 1 is an excitation means, 3 is a permanent magnet, 4 is a DC control circuit, 5 is a current cutoff circuit, 6 is a magnetic flux detection circuit, γ is a comparison circuit, and 8 is for starting. It's a switch. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A device for demagnetizing a pre-magnetized magnetic body to a predetermined value by demagnetizing it to a predetermined value; an excitation means for generating a magnetic field, connected between the excitation means and the power supply,
It has a current control circuit that gradually increases the strength of the demagnetizing magnetic field from zero by controlling the amount of power supplied to the excitation means, and a magnetic sensing means arranged to respond to the amount of magnetization of the magnetic body. death,
A detection circuit that detects the amount of magnetization of the magnetic body by detecting the output of this magnetic sensing means, a comparison circuit that compares the detected value of this detection circuit with a reference value, and a detection circuit that responds to the comparison result of this comparison circuit. A demagnetizing device comprising a current cutoff circuit for stopping power supply to the excitation means. 2. The demagnetizing device according to claim 1, wherein the current control circuit comprises a slider and a motor that drives the movable part of the slider in response to a start signal.