JPS5922686Y2 - Proximity switch using magnetically sensitive wire - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a proximity switch that uses a magnetically sensitive wire to detect the proximity of a magnetic substance.

Various types of proximity switches have been devised in the past, and a typical proximity switch is a pickup coil that is energized with a high-frequency current, and an AC bridge that detects a change in the impedance of the pickup coil when a magnetic object approaches the pickup coil. It had a circuit and a comparator etc. that derived or cut off the output depending on the level of the signal derived from the AC bridge circuit.

Therefore, the comparator circuit is relatively complicated, and since it includes an AC bridge circuit, it has the drawbacks of being large in weight, shape, and cost.

The present invention has been devised to overcome the drawbacks of the conventional proximity switches mentioned above.

Here, the magnetically sensitive wire is made of a composition of iron, nickel, cobalt, etc., and has a diameter of 0.3 mm and a length of 10 to 3 mm.
It is a wire shaped to about 0 mm, and includes, for example, a bar made of a general magnetic material, a wire, a Wiegand wire, etc.

In general, magnetic materials have a hysteresis loop characteristic related to "magnetic field strength - magnetic flux", and the internal magnetic pole reverses at the rising point when the loop is reversed and the falling point when returning, so that the wound coil Derive an electromotive voltage pulse.

In particular, Wiegand wire has extremely good properties.

A Wiegand wire is a wire whose internal coercive force has been changed by applying strain to the wire itself through a predetermined operation.

The internal magnetic pole structure of the Wiegand wire is formed into a double magnetic pole with a layer with a high coercive force and a layer with a low coercive force on the surface and inside, and by applying an external magnetic field to the magnetic poles at both ends of the wire, It has a configuration that allows forcible reversal.

The magnetic pole of the above Wiegand wire is reversed by applying an external magnetic field in an appropriate direction, but the magnetic pole does not return only by removing the external magnetic field. It is necessary to apply a magnetic field in the direction.

That is, in order to frequently reverse and return the magnetic pole of the Wiegand wire, it is necessary to apply an alternating magnetic flux to the Wiegand wire.

Furthermore, Wiegand wire has unique characteristics as shown in the characteristic diagram of FIG.

In FIG. 10, the upper half A1 shows hysteresis loop characteristics related to "magnetic field strength - magnetic flux density", and the lower half A2 shows the magnetic flux waveform and electromotive force characteristics, and both are shown in relation to each other.

In this case, the electromotive voltage refers to the electromotive voltage generated in the coil wound around the Wiegand wire.

In the hysteresis loop characteristic diagram section A1 of FIG. 10, the horizontal axis H indicates the strength of the magnetic field, and the vertical axis B indicates the magnetic flux density.

In addition, in the magnetic flux waveform and electromotive voltage characteristics diagram section A2 of FIG. are shown respectively.

According to this, the Wiegand wire has an initial setting time T1
, when a strong magnetic field is applied in a predetermined direction to the internal magnetic pole structure with the larger coercive force, for example, when the initial setting magnetic flux waveform X1 is applied, the hysteresis loop becomes the loop characteristic shown by the solid line, and the above initial setting It has the property of retaining the strength of the magnetic field internally.

Therefore, at time T2 after the initial setting, when the Wiegand wire is given an alternating magnetic flux X2 with a weaker magnetic field than the initial setting magnetic flux waveform X1, it passes through L3 shown by the dotted line when the hysteresis loop returns, but as described above, the initial The strength of the magnetic field at the time of setting is retained internally.

Thus, the Wiegand wire causes the wound coil to derive a relatively large positive voltage pulse at the rising point L1 when the magnetic pole in the hysteresis loop reverses, but at the falling point L2 when the magnetic pole returns. Only an extremely small negative voltage is derived.

The present invention provides a novel proximity switch that utilizes a magnetically sensitive wire having the various unique properties described above.

Hereinafter, a preferred embodiment of a proximity switch using a magnetically sensitive wire according to the present invention (hereinafter referred to as "proximity switch according to the present invention") will be described in detail based on FIGS. 1 to 9.

FIG. 1 shows a preferred first embodiment of the proximity switch according to the present invention, and 2 is a magnetic pole piece.

The magnetic pole piece 2 is approximately U-shaped, a coil 3 is wound around its center, and a detection space 4 is formed at the tip of the magnetic pole piece 2 through which a magnetic substance to be detected can pass.

Reference numeral 1 denotes the above-mentioned magnetic sensing wire, around which the detection coil 5 is wound.

The magnetically sensitive wire 1 is arranged between the leakage flux generating protrusions 2', 2' so as to respond to the leakage magnetic flux from the leakage flux generating protrusions 2' formed on the magnetic pole piece 2.

Reference numeral 26 denotes an oscillation source, which is constructed from a commercial power source to supply an alternating current to the coil 3.

Reference numeral 7 denotes a pulse detection device, which has a circuit configuration as shown in FIG.

The pulse detection device indicated by 7 in FIG.
．． 71, Zener diodes 72, 73, and resistors 74.
75, 76, 77, and a capacitor 78.

The magnetic sensing wire 1, magnetic pole piece 2, coil 3, detection coil 5
, and the pulse detection device 7 are molded into the case 8.

27 is a variable resistor for adjusting the amount of current flowing to the coil 3.

The first preferred embodiment of the proximity switch according to the present invention has the above-described structure and operates as follows.

When the switch 10 is turned on, the commercial power supply serving as the oscillation source 26 supplies an alternating current to the coil 3.

As a result, the coil 3 generates an alternating magnetic flux to excite the magnetic pole piece 2.

Therefore, when there is no magnetic substance to be detected in the detection space 4 formed at the end of the magnetic pole piece 2, all of the alternating magnetic flux generated from the coil 3 is transferred to the leakage magnetic flux generating peak formed at the magnetic pole piece 2. It is applied to the magnetically sensitive wire 1 from the portion 2'.

The magnetic pole of the magnetically sensitive wire 1 then repeats reversal or return in response to the alternating magnetic flux.

Therefore, a pulse current having the waveform shown in FIG. 9 is derived from the detection coil 5.

At this time, the pulse detection device indicated by 7 in FIG. 5 operates as follows.

When the transistor 70 is OFF, the capacitor 78 is charged from the DC power supply 9 via the switch 10 and the resistor 75 over a certain period of time.

However, since the transistor 70 is turned on every time a pulse current is derived from the detection coil 5, the charge stored in the capacitor 78 is discharged almost instantaneously every time the transistor 70 is turned on.

Here, the period of the pulse current derived from the detection coil 5 is approximately constant, and when the pulse current is derived from the detection coil 5, the transistor 71 is turned off.
To prevent NL, resistor 75 and capacitor 78
It is sufficient to set the time constant determined by the above to be slightly longer than the cycle of the pulse current derived from the detection coil 5.

Therefore, under the conditions set in this way, the detection coil 5
When the pulse current is derived from transistor 7
1 remains in the OFF state, and an H level output is derived from the collector of the transistor 71.

Now, when a magnetic body to be detected, for example, shown as 11 in FIG.
It will now be given to 1.

As a result, the amount of magnetic flux applied from the leakage magnetic flux generating protrusion 2' of the magnetic pole piece 2 to the magnetically sensitive wire 1 decreases, and the magnetic pole of the magnetically sensitive wire 5 no longer inverts or returns.

Therefore, no pulse current is derived from the detection coil 5.

As a result, transistor 70 is no longer turned on, and the charging voltage of capacitor 78 rises, turning transistor 71 on.

As a result, an L level output is derived from the collector of the transistor 71.

Set the determined time constant sufficiently small.

In FIG. 5, 8 is a case, 2 is a magnetic pole piece, and 12 is a conduit that is arranged in the detection space 4 of the magnetic pole piece 2 and serves as a passage for the magnetic substance 11 to be detected.

The waveform shown in FIG. 9g shows the time during which the magnetic body 11 to be detected passes through the detection space 4, and the waveform shown in FIG. 9f shows the output derived from the detection coil 5. .

Further, the waveform shown in FIG. 9 shows the change in the voltage charged to the capacitor 78, and the waveform shown in FIG. 9i shows the output derived from the transistor 71.

In the first embodiment of the proximity switch according to the present invention, a commercial power source is used as the oscillation source 26, so a special oscillator is not required, and the switch can be manufactured in a small size and light weight.

Furthermore, the variable resistor 27 can be built into the case 8.

FIG. 2 shows a second preferred embodiment of the proximity switch according to the present invention, which differs from the proximity switch described in the first embodiment in that the oscillation source 6 is built into the case 8.

The alternating current derived from the oscillation source 6 has a waveform as shown in FIG. 9a, for example, and a desired oscillation frequency can be derived.

The second embodiment of the proximity switch according to the present invention has the above-described configuration.

Since its operation is the same as that explained in the first embodiment, the explanation will be omitted.

If the numbers used in FIG. 2 are the same as the numbers used in FIG. 1, they are the same.

However, in the second embodiment of the proximity switch according to the present invention, since the frequency of the alternating current derived from the oscillation source 6 can be varied, for example, while increasing the frequency of the alternating current derived from the oscillation source 6, By setting the time constant determined in step 78 small, it is possible to detect the magnetic body 11 even when it passes through the detection space 4 at high speed.

Next, a third embodiment of the proximity switch according to the present invention will be described based on FIG.

The third embodiment of the proximity switch according to the present invention differs from the proximity switch described in the second embodiment in that the current applied to the coil 3 has an intermittent waveform as shown in FIG. 9C. A magnet 13 is provided to constitute an oscillation source 6' and to apply a magnetic flux in the opposite direction to the magnetic flux generated from the coil 3 to the magnetic pole piece 2.

Here, the magnetomotive force generated from the coil 3 is set so as to cancel the magnetic flux applied to the magnetic pole piece 2 by the magnet 13 and to excite the magnetic pole piece 2 with magnetic flux in the opposite direction to that of the magnet 13.

The third embodiment of the proximity switch according to the present invention has the above-described configuration.

Since its operation is the same as that of the proximity switch described in the first embodiment, the explanation will be omitted.

Next, a fourth embodiment of the proximity switch according to the present invention will be described based on FIG. 4.

The fourth embodiment of the proximity switch according to the present invention differs from the proximity switch described in the second embodiment in that the coil wound around the magnetic pole piece 2 is differentially wound with two coils 3/, 3/
two differentially wound coils 3/,
3 // is alternately supplied with currents having the waveforms shown in FIG.
The reason lies in the fact that the

The fourth embodiment of the proximity switch according to the present invention has the above-described configuration.

Since its operation is the same as that of the proximity switch explained in the first embodiment, the explanation will be omitted.

The oscillation sources 6', 6'' shown in the third and fourth embodiments of the proximity switch according to the present invention can be constructed, for example, from a general multivibrator circuit.

The proximity switch according to the present invention has a screw 14 as shown in FIG.
It can be applied as a limit switch that detects the position of the movable body 15 that moves forward and backward by the rotation of the body.

In FIG. 6, 2 is a magnetic pole piece, 8 is a case, 16 is a proximity switch according to the present invention, and 17 is a magnetic substance to be detected.

The proximity switch according to the present invention can be applied as a liquid level gauge shown in FIG.

In FIG. 7, 16 is a proximity switch according to the present invention, 2 is a magnetic pole piece, 8 is a case, 18 is a magnetic substance to be detected, 19 is a float, 20 is a guide shaft, 21 is a container, and 22 is a liquid.

The proximity switch according to the present invention can be applied as a rotation detector as shown in FIG.

In FIG. 8, reference numeral 23 denotes a rotary plate, which has cutout spaces 24 at equal intervals and rotates with the rotation of the drive shaft 25.

2 is a magnetic pole piece, 8 is a case, and 16 is a proximity switch according to the present invention.

Since the proximity switch according to the present invention has the above-described structure and operation, it produces the following effects.

A detection coil is wound around a magnetically sensitive wire whose magnetic pole has the property of rapidly reversing or returning due to fluctuations in the external magnetic field, and alternating magnetic flux, which is leakage magnetic flux, is applied to the magnetically sensitive wire in accordance with the approach and separation of the magnetic body to be approached. Since the detecting coil is provided with a means to do this, the detection coil can derive a pulse current when the magnetic substance to be detected is separated from the detection coil, and can stop the derivation of the pulse current when the magnetic substance to be detected approaches.

Therefore, it is possible to simply configure a pulse detection device that detects the presence or absence of a pulse current derived from the detection coil.

Therefore, compared to conventional proximity switches, it is smaller, lighter, and can be produced at lower cost.

In particular, if a commercial power source is used as the oscillation source, there is no need to build a special oscillator into the case, making it possible to provide a smaller, lighter, and less expensive device.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a first embodiment of a proximity switch according to the present invention, FIG. 2 is a partial cross-sectional view of a second embodiment of a proximity switch according to the present invention, and FIG. 3 is a partial cross-sectional view of a second embodiment of a proximity switch according to the present invention. FIG. 4 is a partial sectional view of a third embodiment of the proximity switch, FIG. 4 is a partial sectional view of the fourth embodiment of the proximity switch according to the present invention, and FIG. An electric circuit diagram of the detection device, FIG. 6 is a front view of an embodiment in which the proximity switch according to the present invention is applied as a limit switch, and FIG. 7 shows an embodiment in which the proximity switch according to the present invention is applied as a liquid level detection device. A sectional view, FIG. 8 is a front view showing an embodiment in which the proximity switch according to the present invention is applied as a rotation detector, and FIG. 9 a
and FIG. 9C is a waveform diagram showing an example of the current waveform applied to the coil 3, FIGS. 9S and 9F are pulse waveform diagrams derived from the detection coil wound around the magnetically sensitive wire, Figures 9d and 9e are current waveform diagrams energized to the coils 3' and 3'', respectively; Figure 9g is a diagram showing the time it takes for the magnetic substance to be detected to pass through the detection space; is capacitor 7
8, FIG. 9i is an output waveform diagram derived from the transistor 71, and FIG. 10 is a characteristic diagram of a Wiegand wire. 1...Magnetic sensitive wire, 2...Magnetic pole piece, 2
'...Leakage magnetic flux generating protrusion, 3, 3', 3''
......Coil, 4...Detection space, 5...
...Detection coil, 6, 26...Oscillation source, 7
...Pulse detection device, 8...Case,
9...DC power supply, 10...Switch,
11.17.18...Magnetic substance to be detected, 12...
... Conduit, 13 ... Magnet, 14 ...
...Screw, 15...Movable body, 16...
... Proximity switch according to the present invention, 19 ... Float, 20 ... Guide shaft, 21 ... Container, 22 ... Liquid, 23 ... ...Rotating plate, 2
4... Notch, 25... Drive shaft, 27.
...Variable resistance.

Claims (6)

[Scope of utility model registration request] (1) magnetic pole pieces arranged to face each other so as to form a detection space through which the magnetic substance to be detected can pass; excitation means for applying alternating magnetic flux to the magnetic pole pieces; and an oscillation source that operates the excitation means; A magnetically sensitive wire whose magnetic pole has the property of rapidly changing due to fluctuations in an external magnetic field and responds to the amount of alternating magnetic flux leaking from the magnetic pole piece, and a magnetically sensitive wire that is wound around the magnetically sensitive wire to detect changes in the magnetic pole of the magnetically sensitive wire. a detection coil that derives a pulse output; and a pulse detection device that responds to the pulse output derived from the detection coil and detects whether the pulse output is continuously derived from the detection coil and derives the output. A proximity switch using a magnetically sensitive wire, characterized by comprising: (2) Proximity using a magnetically sensitive wire according to claim 1 of the utility model registration claim, characterized in that the magnetic pole piece is formed with a leakage flux generating protrusion for imparting leakage magnetic flux to the magnetically sensitive wire. switch. (3) A proximity switch using a magneto-sensitive wire according to claim 1, wherein the excitation means is constituted by a coil wound around a magnetic pole piece and to which an alternating current is applied. (4) The excitation means includes a magnet arranged close to the magnetic pole piece to excite the magnetic pole piece, and a magnet wound around the magnetic pole piece to generate a magnetic flux in the opposite direction to the magnetic flux generated from the magnet and magnetized by the magnet. A proximity switch using a magneto-sensitive wire according to claim 1, characterized in that the switch comprises a coil that is intermittently energized to magnetize the magnetic pole piece to a reverse magnetic pole. (5) The magneto-sensitive wire according to claim 1, wherein the excitation means is constituted by a differential coil wound around the magnetic pole pieces so as to be alternately energized and to excite the magnetic pole pieces with alternating magnetic flux. Proximity switch using. (6) A proximity switch using a magneto-sensitive wire according to claim 3, wherein the oscillation source is constituted by a commercial power source that supplies an alternating current to a coil wound around a magnetic pole piece.