JPS5849009B2 - Demagnetizing device - Google Patents

Description

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

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 device is often used to set 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 Ia and 1b to which a DC power supply voltage ED is applied to generate magnetic flux ψ1, and an iron core 2 forming a magnetic circuit.

The demagnetizing device shown in FIG. 2 includes a solenoid 1a to which alternating current power supply voltage EA is applied to generate alternating magnetic fluxes φ1 and 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.

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

In Figure 1, the DC power supply voltage ED is
When applied to , the current ■ is limited by the combined DC resistance of solenoids Ia and 1b.

flows. The combined number of turns of solenoids la and 1b is TM, t
Letting Rm be the composite magnetic resistance of the magnetic circuit, the magnetic flux φ1 is given by the following equation 1.

? It is well known that an electromagnetic field forming magnetic pole N-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 the AC power supply voltage EA is applied to the solenoid 1a, a current 2 limited by the impedance of the 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 polarity 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 drawbacks of the conventional ones as described above, and it detects the degree of magnetization of the magnetic material using a magnetic sensing element, compares it with a reference value, and detects the degree of magnetization of the magnetic material. It is an object of the present invention to provide a demagnetizing device that can set the strength of magnetization 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, and 4 is a semiconductor element whose main electrode is connected to the supply path to the excitation stage 1, which in this embodiment is a transistor 4a. .

Reference numeral 6 denotes a Hall element 6a and a conversion circuit 6b, which are magnetic sensing means.
7 is a comparison circuit, 8 is a starting switch, and 10 is a switching control circuit (hereinafter simply referred to as control circuit 10) connected to the control electrode (base) of transistor 4a to perform an integral operation.

). The control circuit 10 is composed of a flip-flop (hereinafter simply referred to as FF) 10a, a transistor 10b, a capacitor 10c, and resistors 10d and 10e.

Further, the reset terminal of F-F 10a is connected to the output of comparator circuit 7.

Next, the operation of the demagnetizing device with this configuration is shown in Figures 4 and 5a.
This will be explained with reference to the waveform diagram of each part shown in ``-f''.

The waveforms a to f in FIG. 5 are the waveforms applied to the points a to f in FIG. 3.

That is, when the DC power supply voltage E shown in FIG. 5a is applied to the semiconductor element 4 shown in FIG. 3, and the starting switch 8 shown in FIG. As shown in FIG. 5B, the voltage changes from EV to V, and the transistor 10b becomes cut-off, and as a result, the capacitor 10c is turned off via the resistor 10d as shown in FIG. 5C.
It will be charged like this.

Since the charging voltage Eca of the capacitor 10c is applied to the base of the transistor 4a, the emitter voltage ED of the transistor 4a is also applied to the capacitor 10 as shown in FIG.
It increases in the same way as the charging voltage Eca of c.

Now, assuming that the DC resistance of the solenoid 1a connected to the semiconductor element 4 is R, the output current ID of the semiconductor element 4 is as follows, as is clear from the above embodiments.

Here is the output voltage of semiconductor element 4 Therefore, the current given to the solenoid 1a by the above equation is ■.

flows, and a magnetic flux φ3 is generated by the sononoid 1a in proportion to the waveform of ED shown in FIG. 5d.

Therefore, a permanent magnet 3 that is demagnetized in a direction opposite to the magnetic pole of the magnetic field of the solenoid 1a is placed, and a Hall element 6a inserted into the magnetic flux B in the magnetic field of the permanent magnet 3 is arranged as shown in FIG. , when a constant current ■o is passed through one surface, a voltage VH of the following equation is generated from the remaining surface.

Here, K is a constant constant by the Hall element and is the product sensitivity.

The voltage generated by the single Hall element 6a is amplified to an appropriate voltage by the conversion circuit 6b, and this amplified voltage E is obtained.

becomes the waveform shown in FIG. 5e, and the input of the comparator circuit 7
It is applied to one of the terminals.

A reference voltage ER, which is a DC voltage divided by a variable resistor Rp, is applied to the other input terminal of the comparison circuit 7.

Immediately before the control circuit 10 is activated, the output voltage E of the conversion circuit 6b is as shown in FIG. 5e.

is smaller than the reference voltage ER, but when the magnetic flux φ3 generated in the solenoid 1a by the semiconductor element 4 increases, the permanent magnet 3 is demagnetized, the magnetic flux φ2 decreases, the output voltage of the Hall element 6a decreases, and the reference voltage ER increases. becomes larger.

At this time, the output of the comparison circuit 7, which was 1 and O, now outputs EV as shown in FIG. 5f.

This voltage causes the flip-flop 10a of the control circuit 10 to
is reset, a voltage is applied to the base of the transistor 10b of the control circuit 10, the transistor 10b is turned on, and the charging voltage of the capacitor 10c also becomes zero as shown in FIG. 5C.

Therefore, ■ flows to solenoid 1a.

becomes zero, 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 ■ 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 VH according to the above-mentioned equation 3.

A differential amplification circuit (conversion circuit 6b) made up of an operational amplifier 6b6 and resistors 6b2 to 6b5 can amplify the voltage 1 of the Hall element 6a to an appropriate voltage Vout using the following four equations.

? The value of the drag resistor 6b3 = the value of the resistor 6b5 RB - the value of the resistor 6b2 = the value of the resistor 6b4 As shown in FIG. 7, the comparison circuit 7 is composed of transistors 7T1 to 7T3 and fixed resistors 7R1 to 7R4. There is.

In the above configuration, when the voltage ER and the comparison voltage input terminal input KEC are applied to the reference voltage input terminal REF of the comparison circuit 70, if ER<Eo, the transistor 7T2 is turned on, the transistor 7T1 is cut off, and the collector of the transistor 7T1 is turned on. The voltage becomes P, so the transistor 7T3 is turned off, and the output voltage Vout becomes V.

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 potential of the transistor 7T1 decreases, and the transistor 7T
The dotted line ■3 can flow from transistor 7T than 3.
3 is turned on, and the output terminal Vout becomes almost P voltage.

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

Hey, in the above embodiment, the capacitor 1 is used as the control circuit 10.
0c and a resistor 10d, the output of the conversion circuit 6b can be made into a smooth waveform as shown in FIG. 5e by utilizing the charging characteristics of the capacitor 10c. For example, compared to a method in which the resistance value of the slider is changed using a mechanical structure, this method has the advantage of achieving smooth demagnetization with a simple arrangement.

Further, in the above embodiment, the DC power supply voltage is applied to the semiconductor element 4, but the AC power supply voltage may be applied to a DC conversion circuit to convert the AC power supply voltage into a DC power supply voltage, and then apply this to the semiconductor element 4.

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

In FIG. 8, 3 is a permanent magnet to be demagnetized, and 4 is a semiconductor element, which in this embodiment is a bidirectional thyristor 4b.

10 is a phase control circuit (hereinafter simply referred to as control circuit 10), which includes a flip-flop 10a, an integrating circuit 10f, a synthesis circuit 10g, a waveform shaping circuit 10h, and a gate circuit 10i.
It consists of

What about the gate circuit 10i? The power is connected to the gate of the bidirectional thyristor 4b, and the waveform shaping circuit 10h is composed of a comparison circuit, a differentiation circuit, and the like.

Next, the operation of this demagnetizing device will be explained with reference to the waveform diagram of each part shown in FIG.

An AC power supply voltage shown in FIG. 9a is applied to the semiconductor element 4 shown in FIG. 8.

Next, when the starting switch 8 shown in FIG. 8 is closed, the flip-flop 10a of the control circuit 10 is set as shown in FIG. 9b, and the output becomes EV.

The integrator circuit 10f of the control circuit 10 uses the set signal (see FIG. 9b) of the flip-flop 10a to operate as shown in FIG.
As shown in the figure, the positive and negative integral outputs C, , C
2 is sent to the synthesis circuit 10g.

On the other hand, since the AC power supply voltage is supplied to the combining circuit 10g, the output C1 of the integrating circuit 10f, as shown in FIG.
Intersection points d0 to d5 with C2 are obtained.

Only these intersection points d1 to d are output by the waveform shaping circuit 10h as shown in FIG. 9e.

Since the magnitude of this output is unique, the output is sent to the gate circuit 10i, normalized to an appropriate size, and applied to the bidirectional thyristor 4a of the semiconductor element 4 (
(see FIG. 9f),...Since the alternating current voltage of FIG. 9a is applied to the semiconductor element 4K, the current of FIG. 9g is .

flows to solenoid 1a.

The solenoid 1a generates an alternating magnetic flux φ3 using this current.

The Hall element 6a inserted into the magnetic flux B within the magnetic field of the permanent magnet 3, which is demagnetized within the alternating magnetic flux of the solenoid 1a, generates a predetermined voltage 1, and this generated voltage is converted into an appropriate output voltage by the conversion circuit 6. Enlarged E in Figure 9h.

The signal is applied to the input terminal of the comparison circuit I.

A reference voltage ER, which is a DC voltage divided by a variable resistor RP, is applied to the other input terminal of the comparison circuit 7.

Just before the semiconductor element 4 starts up, the output voltage equation of the magnetic flux detection circuit is higher than the reference voltage as shown in FIG. The magnetized magnetic flux φ2 decreases, the output voltage of the Hall element 6a decreases, and the reference voltage ERo increases.

At this time, the output of the comparison circuit 7, which was V at the current time, outputs EV as shown in FIG. 9i.

This voltage resets the 9-rip flop 10a and makes the integral output zero.

Therefore, the gate circuit 10i also closes the gate and the semiconductor element 4
■ Output current.

becomes zero, the magnetic flux φ3 also becomes zero, and the demagnetization of the permanent magnet 30 is completed.

In this 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 simplifies the work.

In the above embodiment, a bidirectional silicon element was used as the semiconductor element 4, but a semiconductor element such as a silicon element or a transistor may be used instead.

Furthermore, although the phase control circuit is constructed of the flip-flop 10a, the synthesis circuit 10g, the integration circuit 10f, the waveform shaping circuit 10h, and the gate circuit 10i, it may be constructed using a comparison circuit instead of the synthesis circuit 10g.

Furthermore, a display circuit may be provided at the output of the magnetic flux detection circuit 6 so that the state of demagnetization can be seen.

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, the amount of demagnetization is gradually increased from zero, and further comparison is made. Since the circuit is configured to compare the magnetic flux of the magnetic body with a reference value and control demagnetization, there is an effect that the degree of magnetization of the magnetic body can be easily and precisely maintained at a constant level.

[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 shows the principle of the Hall element. Figures 5 a - f 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. Figure 7 is a comparison. FIG. 8 is a block diagram showing another embodiment of the demagnetizing device according to the present invention, and FIGS. 9 a to 9 i are operation waveform diagrams of each part of the circuit shown in FIG. 8. . 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 semiconductor element, 6 is a magnetic flux detection circuit, 6a is a Hall element, 6b is a converter circuit, and 7 is a comparison 8 is a starting switch, 10 is a control circuit, C is a capacitor, and R is a resistor. Note that the same reference numerals in the figures indicate the same or corresponding 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, a semiconductor element having a main electrode connected between the excitation means and the power source, and a signal applied to a control electrode of the semiconductor element to control the strength of the magnetic field generated by the excitation means; A control circuit for controlling the amount of power supplied to the excitation means so as to gradually increase from zero, a magnetically sensitive means arranged to respond to the amount of magnetization of the magnetic body, and an output of the magnetically sensitive means. A detection circuit that detects the amount of magnetization of the magnetic material by detecting a button, and a detection value of this detection circuit is compared with a reference value,
A demagnetizing device comprising a comparison circuit that supplies a signal to the control circuit to stop power supply to the excitation means when the detected value reaches a reference value. 2. The detection circuit has a Hall element as a magnetic sensing means,
The demagnetizing device according to claim 1, further comprising a conversion circuit for amplifying the output of the Hall element. 3. The control circuit consists of a logic circuit that receives the output of the comparison circuit and the start signal as input, and an integration circuit provided on the output side of this logic circuit, and the output of this integration circuit is led to the control electrode of the semiconductor element. 3. A demagnetizing device according to claim 1, wherein the demagnetizing device is configured such that the demagnetizing device is configured to 4. The control circuit includes a logic circuit that receives the output of the comparison circuit and the start signal as input, an integration circuit provided on the output side of this logic circuit, and a synthesis circuit that synthesizes the output of the power supply and the output of the integration circuit. and a waveform shaping circuit that sends out a timing signal that provides the conduction timing of the semiconductor element based on the synthesis result of this synthesis circuit, and a waveform shaping circuit that controls the output surface of a predetermined midpoint value based on the output from this waveform shaping circuit. 3. The demagnetizing device according to claim 1, further comprising a gate circuit that provides a conduction control signal to the electrode.