CH628460A5 - Ferromagnetic changeover device - Google Patents

Description

The present invention relates to a ferromagnetic tilting device according to the preamble of independent patent claim 1.

US Pat. No. 3,820,090 describes a ferromagnetic wire which has a core and a jacket section with different magnetic properties. As set forth in U.S. Patent No. 3,892,118, such a wire is e.g. obtained by applying cyclic torsional stress on the wire, thereby stretching the wire around its circumference. For this purpose, the wire is subjected to torsion alternating clockwise and counterclockwise and at the same time subjected to an axial pull. The result is a wire which, it can be assumed, due to a relatively harder sheath and a relatively softer core, has the property that after previous magnetization, the sheath can pull the magnetically softer core.

If the wire is magnetized and then exposed to an external, rising, magnetic field parallel to the axis of the wire, a threshold value is reached where the external field suddenly pulls the core and thus quickly reverses the magnetization of the core. In an induction coil wound around the wire, a pulse is generated in the core as a result of the rapid change in the direction of flow. The reversal of the nuclear magnetization results as a result of the external field intensity when it exceeds a threshold value and is essentially independent of the speed. This means that the level of the output pulse is only slightly dependent on the rate of change of the applied field if it exceeds the threshold value. This must be compared to the more common pulse generator circuitry based on soft magnetic materials, the hysteresis of which is continuous. The

Output pulse amplitude (and inverse the pulse width) of this latter class of arrangements is substantially proportional to the rate of change of the field over time when it exceeds the coercive force.

In a similar manner there is a reversal of the nuclear magnetization and a reverse pulse is generated in the induction coil when the external magnetic field decreases and falls below a second threshold value. Again, the output pulse is essentially independent of the rate at which the field is decreasing, and all that is needed is that the switching threshold be exceeded or undershot.

The size of the output pulse is extremely important for the value of the wire and the range of commercial applications. This is because the larger the pulse, the less wire is required in electronic circuit arrangements in order to distinguish the noise from the pulse supplied by the induction coil. However, the larger the impulse, the better information that is triggered or ascertained by the impulse can be repeated.

Accordingly, an object of the invention is that described above. To improve the tilting device in such a way that the pulses generated when passing through threshold values of an external magnetic field have a better signal / noise ratio and a larger peak amplitude. sen.

According to the invention, this is achieved according to the features in the characterizing part of independent patent claim 1. In said patent No. 3 820 090 the wire was made from a commercially available wire e.g. with a diameter of V4 mm diameter and made in an alloy of 48% iron and 52% nickel.

For this purpose, in the process for producing the tilting device according to Patent No. 3 892 118, it was provided to use a wire of a fine-grained iron / nickel alloy with a diameter of 0.25 mm. A piece of this 1 m long wire was extended by 4 cm. The elongated wire was held under tension by means of two clamping tools and turned clockwise and counterclockwise up to 0.4 turns per centimeter length of the wire about its longitudinal axis. Thus, clamping tools for a length of one meter of wire were completely turned 40 times in one direction and then 40 times in the other direction. This clockwise and then counterclockwise rotation was repeated ten to fifteen times. The clamping tools were held in a machine that maintains a constant pull of 450 g when the wire is twisted. Following this procedure, the tension is reduced and the one meter long wire is cut into any desired lengths (usually 1-3 cm long) for use in the various switch and pulse generator applications developed for this wire.

Some variations in tensile force, number of revolutions per meter, and number of cycles of clockwise and counter-clockwise rotation are desirable as a function of the wire diameter, the chemical composition of the wire, and the field of application.

A comparison of the known tilting device and the newly proposed tilting device showed the important improvement that in the new arrangement without an external field, there is no automatic tilting from the state in which the jacket and core have the same directional magnetization to the state with the magnetization directed in the opposite direction.

In addition, asymmetrical tilting can be observed with the new arrangement, i.e. that the induced pulse caused by tilting the magnetization of the nucleus

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of the cladding in one direction is different from the momentum that is generated when the magnetization of the core tilts upside down. In particular, if the core tilts from the reversed state to the synchronous state, the pulse is significantly greater than the pulse which is generated when the core is tilted from the synchronous state to the reversed state.

The switching from the reverse state to the synchronous state thus occurs with a large change in the magnetic flux and therefore with a large output pulse from the induction coil. It has also been shown that the new tilting device is relatively insensitive to environmental conditions, including most of the surrounding magnetic fields, and can therefore be particularly useful for timing, proximity detection and coding.

Embodiments of the invention are explained below with reference to the drawing. Show it:

Fig. 1 is an enlarged schematic representation in elevation and a side elevation of a ferromagnetic tilting device according to the invention, the magnetization of the jacket and the core are shown in the reverse state, in which the jacket and core are magnetized in opposite directions;

FIG. 2 shows a schematic illustration of a magnetic coil for applying an external field to the ferromagnetic tilting device according to FIG. 1 and an induction coil for the purpose of emitting an output pulse due to the tilting of the magnetic field in the wire;

3 shows a graphical representation of the asymmetrical switching mode when tilting; Fig. 3 is the result of a test which was carried out with an arrangement according to Fig. 2; Fig. 3 shows the external trip field, the hysteresis loop and the output pulse obtained;

Fig. 4 is a graphical representation of the symmetrical switching mode when tilting and the external trigger field, the hysteresis loop and the received output pulse and

Fig. 5 is a perspective schematic representation of the technique for treating a wire to achieve the mode of operation according to this invention.

The wire according to the patents mentioned in the introduction is used in sections between 1 and 3 cm. When these are magnetized, each section has two magnetic states. When tipping between these two states, at least a portion of the magnetic flux tilts in direction, so that an induction coil wrapped around the wire generates a pulse. The speed at which the magnetic direction changes when the magnetic state in the wire changes is so great that the electrical pulse generated by the induction coil is a distinguishable, sharp and thus usable pulse with a duration of approximately 20 us. The tilting of the state is the result of an external magnetic field with its own field direction with either an increasing magnetic field strength that rises above a first threshold value or a decreasing magnetic field strength that falls below a second threshold value. The tilting in the wire is therefore dependent on a threshold value of a magnetic field that acts on it. As a result, the level of the output pulse is not dependent on the speed at which the external, triggering, magnetic field increases or decreases, this is at least the case up to very high rates of change. The use of this wire to produce this distinctive, extremely sharp output pulse has further advantages in that the process proceeds without any electrical input signal or current. Thus, external permanent magnets can be used as the source of the triggering magnetic field, and all that is needed is that the position between the bistable magnetic wire and the external permanent magnets is changed to increase the magnetic field above the first threshold and / or cause the decrease in the external field below the second threshold. Even if the triggering magnetic field is generated with an electric current by a coil around the wire, as shown in Fig. 2, no other electrical input is required for the switching device.

This bistable magnetic wire is believed to operate because of a close physical relationship between a magnetically harder cladding zone and a magnetically softer core zone. This physical relationship is the result of the fact that both the sheath and the core are elements of an otherwise homogeneous wire. The relationships through which this new phenomenon works are still being examined today.

An arrangement 10 of a magnetic wire according to the present invention is shown in FIG. 1 and comprises a cold-hardened, magnetic material consisting of cobalt, iron and vanadium. The magnetic wire section has a generally circular cross-section, preferably a precise circular cross-section, or at least as close as possible to this circular cross-section, as is reasonably available. Wire sections approximately 0.25 mm in diameter and 1-3 cm in length have been found useful.

The wire is treated as indicated below to produce a one-piece magnetic wire section 10 having a relatively "soft" core 11 with a relatively low magnetic coercive force and a relatively "hard" sheath 12 with a relatively high magnetic coercive force.

The term “coercive force” is used here in the traditional sense to indicate the intensity of the external magnetic field which is necessary in order to bring the magnetized test specimen made of ferromagnetic material to zero.

In Fig. 1, the relatively "soft" core 11 is magnetically anisotropic to the preferred axis of magnetization, which is essentially parallel to the axis of the wire. The relatively “hard” sheath 12 is also magnetically anisotropic with respect to a preferred axis of magnetization, which brings self-magnetization essentially parallel to the axis of the wire. The direction of the magnetization of the core 11 is largely a function of the action of the magnetic field of the cladding and any externally applied magnetic field. In the state shown in FIG. 1, the self-magnetization of the jacket 12 is reversed to the self-magnetization of the core 11. This state is referred to here as the state directed in the opposite direction. In this oppositely directed state, an interface 13 defines the connection between core 11 and sheath 12. This interface 13 is shown in FIG. 1 as a cylindrically shaped surface 13, although it is assumed that the interface appears more as a complex magnetic transition zone in the wire .

It has been found that impulses can be obtained from wires made of cobalt, iron and vanadium and which are at least an order of magnitude larger than the impulses obtained with an iron / nickel alloy described in the above-mentioned patents is.

A preferred composition of the wire of this invention is one in which the cobalt content is between 45-55%, the iron content is between 30-50% and the vanadium content is between 4 and 14%. A commercially available alloy with cobalt, iron and vanadium, which is suitable for practicing the present invention, can be obtained from Wilbur B. Driver Co., Inc. under the brand name "Vicalloy". 0.25mm diameter wires that worked cleanly

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ren have been used to manufacture magnet assemblies in accordance with the present invention. Vicalloy wire has a nominal composition of around 52% cobalt, around 10% vanadium and the rest iron with certain minor admixtures that contain manganese and silicone in amounts that are slightly below half a percent.

First treatment regimen

A 30 cm long wire with a diameter of V4 mm from Vicalloy is used; A preferred treatment scheme for cold forming includes the following steps:

1. The wire is stretched to its full length. 5, the length of the wire is held in place by clamping means 42 and 44. The wire is pulled enough by a spring reel 46 to pull the wire 40 such that there are no bends in it without the wire being elongated. The wire 40 is then subjected to a single cycle of torsional stress comprising approximately 64 counterclockwise rotations followed by approximately 48 clockwise rotations. The tension is maintained during all torsion stress steps.

2. The wire is then subjected to 17V2 cycles of V2 rotations in each direction. In particular, 8 V2 rotations in the counterclockwise direction are followed by 8V2 rotations in the clockwise direction, resulting in a single cycle. Such cycles are repeated 17 times, and then this step is completed with 8V2 turns counter-clockwise. During this second step, which normally takes 10-15 seconds, the 30 cm long wire is continuously extended. The amount of the renewal is between one and two percent.

3. The end of the process consists of a further series of 8V2 turns, this time with an even number of cycles and without further stretching, but while maintaining the tensile force on the wire. The number of cycles according to the second step is carried out three or four times during this step. It has been found that around 60 cycles give good results.

The wire is then cut into suitable sections, for example 1-3 cm in length.

The above-described scheme for cold hardening a wire alloyed with iron, cobalt and vanadium gave certain desirable results. To determine these desired results, it was also found that variations in the above scheme still result in a wire that has the tilting effect.

Second treatment regimen

A second method has been found to manufacture this Vical-loy wire for applications where maximum stability over a longer period of time is less important. A 30 cm long wire with a V4 mm diameter is also used.

1. The wire is pulled out to its full length. The voltage applied keeps the wire straight along its full length without lengthening it. The wire is then subjected to a single torsional stress with 14 turns in a counterclockwise direction, followed by 12 turns in a clockwise direction.

2. The wire is now subjected to 120 cycles of 12 turns in each direction; i.e. 12 counterclockwise turns followed by 12 clockwise turns form a cycle. This cycle is repeated 120 times. During this second process step, the wire is continuously stretched simultaneously with the torsional stress. This stretching slowly and continuously extends the 30 cm long wire by about 3 mm.

3. The final cold hardening process step consists of a further 20 cycles of 12 turns counter-clockwise and 12 turns clockwise without further lengthening the wire, but with constant tensile force, so that the lengthening obtained in step 2 is maintained.

The wire is then cut into sections of the desired length, e.g. Cut 1-3 cm.

The alloys used in both cold hardening processes are essentially the same. They are originally annealed so that the starting material is uniform and in order to obtain a suitable flexibility of the material for the cold forming. The annealing should be done to a point where the grain structure is approximately 10,000 grains per square millimeter (or more). This fine grain helps to ensure the required flexibility.

It was found that a fourth step is important in both methods. This step consists of a heat treatment. In the initial experiments, heating up to 320 ° C was carried out for eight hours. However, it has been found that the result is satisfactory when working at 300 ° C. for four hours, which also has the advantage that the production of the wire is accelerated. A heat treatment in which a current of 5.6 A is passed through the 0.25 mm wire for 120 ms seems to be promising at the moment. The heat treatment gives a noticeable improvement in the output pulse. Perhaps more importantly, this heat treatment reduces the risk that the properties of the wire will not change during use as a wire in a high temperature environment. This fourth step of the post-curing treatment leads to aging, which leads to better stability in use.

Wire testing and results

Fig. 2 schematically shows the test device used to determine the output pulse that can be obtained when a vanadium / cobalt / iron wire according to the invention is used and compared with the iron / nickel wire according to the cited patents . A current from the network is supplied to the transformer 20 at 50 Hz in order to feed the magnetic coil 22. A portion of the wire 10 is centrally located inside the solenoid 22 and an induction coil 24 is wrapped around the wire 10. A current through the windings of the solenoid 22 creates an axial magnetic field in the center of the solenoid 22.

It has been found that the most pronounced output pulse is obtained from the vanadium / cobalt / iron wire when the wire is tilted asymmetrically. As a result of the circuit according to FIG. 2, it was found that the excitation field H, which acts on the wire 10, can be represented by the curve 32 in FIG. 3. The diode 28 passes the full positive half-wave of the 50 Hz alternating current, and the resistor 26 is set such that only a greatly reduced negative half-wave is conducted so that the excitation field acting on the wire 10 has a positive peak of 11 940 A / m (= 150 Örsted) and a negative peak of only about 1592 A / m (= 20 Örsted). The resistor 30 is only a current limiter resistor.

The hysteresis loop for the wire 10 according to the invention with this excitation is shown by curve 34 in FIG. 3. Fig. 3 is the representation as it would be seen on the screen of an Oszillo scope. The interruptions (Wiegand jumps) in curve 34, which are referred to as “reverse tilt” and “synchronous tilt”, appear as a pale line on the oscilloscope because the rate of change of the flux (or magnetization B) through the core 10 is very rapid in front

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goes when the strength of the outer field H exceeds the associated threshold. The larger gap in curve 34 is referred to as "synchronous tilt". This state appears when the external longitudinal magnetic field H removes the longitudinal magnetization of the core from the opposite direction (Fig. 1), i.e. the nuclear magnetization is reversed to the direction of magnetization of the jacket 12, tilts into the rectified state in which the nuclear magnetization has the same direction as the magnetization of the jacket. During the reverse tilt, the magnetic field H tilts the core from the rectified state to the opposite direction. As shown in FIG. 3, the pulse C which is induced in the coil 24 when tilting from the inverse state to the synchronous state is much larger than the pulse R which is induced by the tilting from the synchronous state to the reverse state. The pulse C in the synchronous tilt is approximately ten times as large as the pulse R in the reverse tilt.

When using a wire section of 3 cm in length for the wire 10 and with an induction coil 24 with 925 turns of wire with a diameter of 0.15 mm, the output of the coil 24 being guided to a load with 1000 ohms, an output pulse C can be obtained , which is greater than 1.5 V and has a width of about 20 as at half the amplitude. In contrast, the pulse R has a height of 125 mV and a width of at least 60 / is. Thus, under these conditions, pulse C has an amplitude which is twelve times that of pulse R. Against an open loop, a pulse C with more than 2 V could be obtained.

Surprisingly, with an excitation field H with 11 940 A / m in the negative direction, as well as with a field H with 11 940 A / m in the positive direction, pulses 40 could be generated which were the same but had a reversed polarity (FIG. 4). In the particular embodiment, as described above, the pulses 40 had an amplitude of approximately 550 mV and a width of approximately 40 fx at half the amplitude.

Thus, the two tilting pulses are the same in the case of symmetrical tilting and have a substantially smaller amplitude than in the case of synchronous tilting, where the pulse C with optimal asymmetrical tilting is significantly larger than the pulse R obtained in the case of reverse tilting. This state is shown in FIG. 4. The same arrangement as in FIG. 2 is used here, with the exception that the diode 28 and the resistor 26 have been omitted, so that a full, sinusoidal excitation field 36 on the wire 10 as an external field H with a strength between plus 11 940 A. / m and minus 11 940 A / m. The result is hysteresis curve 37.

If the field H is positive, the jacket 12 and the core 11 are magnetized in the positive direction, this is represented by the upper right corner of the hysteresis curve 37. This can be seen as a positive synchronous state. If the external field H decreases, the magnetization B also decreases, up to a relatively weak, negative field strength of minus 955 A / m (= 12 Örsted), where the core 11 changes its magnetization direction from positive to negative. Thus, the device 10 tilts from a synchronous state to a reverse state. This creates the interruption 37a in the curve 37 and gives an output pulse of approximately 550 mV with a width of f sharp via the induction coil 24. If the magnetic field H becomes stronger in the negative direction, a point is reached where the magnetization of the jacket tilts and causes a small interruption 37b in the hysteresis curve 37 and thus a small output pulse 42. The core and the jacket are thus in a negative synchronous state. The field H comes to a negative peak and then decreases by becoming less negative. When the field H becomes a little positive (955 A / m), the core 13 tilts from the negative direction to the positive direction, represented by the break 37c. This results in a further output pulse 40 which is 550 mV high and 40 ^ s wide. This is a flip from a negative synchronous state to a reverse state. The field H becomes more positive until a point is reached, which is represented by the small interruption 37d, where the jacket changes its direction of magnetization and generates a small output pulse 42, at which the device 10 tilts into the positive synchronous state.

If the excitation H becomes sufficiently negative and also sufficiently positive so that the jacket tilts according to FIG. 4, the core tilts whenever the arrangement tilts from the synchronous state to the reverse state. In contrast, if the excitation H is limited in one direction so that the magnetization of the cladding does not tip over, as shown in FIG. 3, asymmetrical switching results in that the core tilts into the reverse state when the arrangement changes from the synchronous state to the Reverse state tilts, and vice versa, the core tilts to the synchronous state when the arrangement tilts from the reverse state to the synchronous state. Tilting from the reverse state to the synchronous state produces a larger output pulse than tilting from the synchronous state to the reverse state, because the former is generated at a greater rate of change than the latter.

In the embodiments described above, it is necessary for the excitation field H to change its direction so that the magnetization direction tilts in the core. Only switching off the excitation field H does not result in a reversal of the magnetization of the core 11. This need to reverse the excitation field in order to tilt the nuclear magnetization remains the same in any case, regardless of whether the tilting process is asymmetrical according to FIG. 3 or symmetrical according to FIG. 4 expires.

In contrast, it has been found with nickel / iron wires according to the patents mentioned that the arrangement automatically tilts from a synchronous state to a reverse state when the field of excitation is removed. In addition, it can be stated that the greatest output pulse when using iron / cobalt / vanadium wires according to this invention is approximately 10 times as large as that with a nickel / iron wire as described in the cited patents, and could be obtained under the same load conditions and with the same induction coil 24.

Fig. 5 shows a schematic arrangement for the cold deformation of the wire. A length of a wire 40 of, for example, 30 cm is drawn off from a reel 46 pretensioned by a spring. The tension is maintained on wire 40 to keep it straight. The wire 40 is guided through the clamping device 40 to the clamping device 44. The jigs 40, 44 are then tightened to hold the wire in place. A cyclic torsional stress on the wire 40 is then brought about by alternating rotation of the pinion 48 on the rack 50. The extension of the wire 40 is brought about by slow rotation of the cam disk 56, which rests on a disk 58 on the clamping device 42. The cam disk 56 is rotated by a motor drive 60.

Although the embodiments have been described for a particular wire length and a single wire diameter, the invention does not include anything that would limit the wire to these particular dimensions. A wide range of wire section lengths and diameters are conceivable which can be used as a tilting arrangement according to the invention, and the limits of these ranges have not yet been determined. However, it is now believed that the possible

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3 could require an undetermined minimum length of the wire section 10 to obtain the tilting effect according to FIG. 3. In particular, in order to maintain the magnetism of the core in the synchronized state without an external field H, it would be conceivable that the wire section 10 would have to be larger than a certain length. It is believed that if that

Tilting from a synchronous state to a reverse state happens automatically due to the switching off of the external field H, the height of the synchronous tilting C of the core (when tilting from the reverse state to the synchronous state) should not be 5 as high in terms of the amplitude.

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Claims (5)

628 460 1. Ferromagnetic tilting device with two stable states, characterized by a wire with a core section (11) and a jacket section (12), which can be magnetized differently, such that the core section and the jacket section either have the same state of magnetization with the same magnetization direction of the core section and the jacket section or have a reversed state with different magnetization directions of the core section and the jacket section, that the coercive force in the core section is sufficiently large so that the magnetization of the jacket section in the synchronous state cannot tilt the core section into the reversed state, but that an external magnetic field is required in the synchronized state, to tilt the core section into the reverse state, the tilting from the reverse state to the synchronous state taking place more quickly than vice versa. 2. Device according to claim 1, characterized in that the wire consists of a single alloy consisting of vanadium, cobalt and iron. 2nd PATENT CLAIMS 3. Device according to claim 2, characterized in that the proportions of iron and cobalt together make up a weight percentage of over 80% in the alloy. 4. Device according to claim 2, characterized in that the alloy approximates 45-55% cobalt, 30-50% iron and 4-14% vanadium in each case at least Contains 100% compound. 5. The device according to claim 2, characterized in that the alloy contains at least approximately 52% cobalt, 10% vanadium and the rest consists essentially of iron.