SE429075B - MAGNETIC WIRE DEVICE AND WAY TO MAKE A SUIT - Google Patents

Description

vsosozzen sensing coil around the wire will generate a pulse due to the rapid change in flow direction in the core. The reversal of the nuclear magnetization occurs depending on the intensity of the external magnetic field, when this exceeds a threshold value, and is essentially speed insensitive, ie. the magnitude of the output pulse is only insignificantly dependent on the rate of change of the applied field as it passes through the threshold value.

This is in contrast to more conventional pulse generating couplings, which are based on soft magnetic materials, the hysteresis loops of which are continuous. The amplitude of the output pulse and the inverted value of the pulse width at this lateral array of devices are substantially proportional to the time change rate of the field as it passes through the coercive force. In the same way, a reversed changeover occurs in nuclear magnetization and a reversed pulse is generated in the sensing coil, when the outer magnetic field decreases past a second threshold value. Again, the output pulse is essentially independent of the rate at which the magnetic field decreases and all that is required is that the switching threshold be passed. g The size of the output pulse is of critical importance in determining the dimensions of the wire and in determining the area of application within which the wire can be commercially questioned.

The larger the pulse, the less complicated electronic circuits required, which are coordinated with the sensing coil, to distinguish the pulse from background noise. The greater the amplitude of the pulse, the more it will be possible to repeat each initial state, which must be triggered or registered under the influence of the pulse.

Accordingly, the invention is mainly based on the task of developing a switching device of the type described above, which reacts to an external magnetic threshold field and generates a pulse with a particularly advantageous signal-to-noise ratio and high peak amplitude.

The above-mentioned patents describe a magnetic device with two magnetic states, namely an inverted state, in which core and shell have mutually opposite directions of magnetization, and a transition state, in which core and shell have the same direction of magnetization. According to U.S. Pat. No. 3,820,090, the wire is a commercially available wire which, according to one embodiment, has a diameter of 0.25 mm and is made of an alloy consisting of H8% iron and 52% nickel. When applying the method described in patent specification 3,892,118, a wire of a fine-grained non-ferrous alloy with a diameter of e.g. 0.25 mm. A piece of this wire with a length of 1 m is extended H cm, the extended wire being kept under tension between two clamping mandrels such as chucks and rotated counterclockwise and clockwise at a speed of 0.1 μm per cm of wire. With regard to the wire length of 1 m, the chucks H0 rotate complete orbital turns in one direction and then ÄO complete orbital turns in the other direction. This clockwise and counterclockwise rotation is repeated 10 to 15 times. The chucks are mounted in a machine, which maintains a constant tension of H50 g during rotation. After this processing, the tension is removed and the wire is cut to desired lengths, usually about 1 to 3 cm each, for use with various switching and pulse generating devices developed for this wire. Variations with respect to voltage, number of revolutions per m and number of periods of clockwise and counterclockwise rotation are desirable depending on the wire diameter, wire alloy and device at which the wire is to be used.

It has been found in the present case that a particularly suitable chemical composition for producing a wire having these conversion properties is a wire consisting of an alloy of iron, cobalt and vanadium. In one embodiment, the wire consists of 52% cobalt, 10% vanadium and the remainder iron. Vanadium seems to improve the coercive curve / evening without reducing the form child, which is required for cold processing. Furthermore, a particularly suitable production method has been developed for processing the wire consisting of cobalt, iron and vanadium, so that the wire is given a fast changeover effect and thus in a sensing coil produces a strong output pulse, which can be repeated and is uniform. A wire with a diameter of approx. 0.25 mm and a length of approx. 30 cm is subjected to sufficient tension so that it is straightened without stretching or stretching. Thereafter, the wire is subjected to torsional deformation in combination with elongation, whereby the torsional deformation takes place alternately in the clockwise and counterclockwise direction and gives rise to the required cold working of the wire. The sohemat of the deformation is asymmetric, ie. the number of revolutions used in each direction is not the same. At the end of the cold working process, the wire is subjected to aging heat treatment by allowing a strong current pulse to pass through it.

The result is a switching device which, in contrast to the device known from the above-mentioned patents, has the characteristic property that in the absence of an external field it will not automatically change from the state in which the core and jacket have the same direction of magnetization (transition state ) to the state in which the core and shell have opposite directions of magnetization (reversed state). The resulting changeover device further has asymmetric changeover characteristics, i.e. the induced pulse, when the direction of magnetization of the nucleus changes in a first direction relative to the mantle, is different in relation to the induced pulse, when the nucleus changes in a second direction relative to the mantle. In other words, when the device transitions from the reversed state to the transition state, the induced pulse is considerably stronger than the pulse which induces when the device transitions from the transition state to the reversed state. The magnetic changeover device transitions from inverted state to transition state with high flow change rate and thus generates a strong output pulse from a sensing coil. The guess is comparatively insensitive to environmental conditions, e.g. the majority of surrounding magnetic fields, and is therefore useful for time control, proximity detection and coding.

The invention is described in more detail below with reference to the accompanying drawing, in which Fig. 1 schematically shows a longitudinal view and an end view of a ferromagnetic wire according to the invention and illustrates the magnetization of the shell and the core in the reversed state, in which the shell and the core are magnetized in opposite directions; Fig. 2 schematically shows a magnetic coil drive device for supplying an outer field to the magnetic wire shown in Fig. 1 and a sensing coil for generating an output pulse in response to a change in the magnetic state of the wire, Fig. 3 is a diagram for illustrating asymmetrical adjustment , this diagram shows the external drive field, in the vacsozz-4 hysteresis loop and the generated pulses, Fig. 4 a diagram for illustrating symmetrical adjustment together with the external drive field, the hysteresis loop and the pulses, and Fig. 5 a perspective view to prove the principle of processing of magnetic wire for the manufacture of the device according to the invention.

The wire described in the above-mentioned patents was used in segments with a length of about 1 to 3 cm. Each magnetization segment assumes two magnetic states during magnetization, at least a part of the flow changing direction when switching between these two magnetic states, so that a sensing coil wound around the wire will generate a pulse.

The speed at which the flow changes when the wire changes state is so high that the electrical pulse generated in the sensing coil is a pronounced, sharp pulse with a duration of about 20 microseconds. The state change takes place depending on an external magnetic field with a suitable direction, which either increases in magnetic field strength to above a first threshold value or decreases in field strength to below a second threshold value.

The adjustment of the wire is thus dependent on a magnetic threshold field to which the wire is exposed. As a result, the magnitude of the pulse is not appreciably velocity sensitive in that it is only insignificantly affected by the velocity at which the external triggering magnetic field increases or decreases. This is the case at least up to very high field change rates.

Using the wire to generate this output pulse also has the advantage that the process takes place without a requirement for any supplied electrical signal or current. Therefore, external permanent magnets can be used as the source of the triggering magnetic field and all that is required is that the gap between the bistable magnetic wire and the outer permanent magnets be changed to achieve the increase of the outer field above the first threshold value and / or the decrease of the outer field below the second threshold. Even in the cases where the triggering magnetic field is generated by electric current through a coil around the wire as in Fig. 2, no other electrical inputs are required on the switching device. It is believed that this bistable magnetic wire operates as described due to the intimate physical relationship between a magnetically harder sheath zone and a magnetically softer core zone. This connection is due to the fact that both the sheath and the core form parts of an otherwise homogeneous thread {The mechanism by which this new phenomenon arises is still being explored.

Fig. 1 shows an embodiment of a magnetic wire 10 according to the invention, which consists of cold-processed magnetic material, composed of cobalt, iron and vanadium. The magnetic wire segment has a substantially non-circular cross-section and preferably completely round cross-section or so around cross-section, which can reasonably be produced. Wire segments with a diameter of about 0.25 mm and a length of 1 to 3 if have been found to be usable.

The wire is machined as described below to achieve a single unit magnetic wire element 10 having a comparatively "soft" core II with comparatively low magnetic coercive force and a comparatively "hard" sheath 12 with comparatively high magnetic coercive force.

The term coercive force is used in the present case in its traditional sense to indicate the magnitude of the external magnetic field required to bring the residual magnetization or remanence of the magnetized sample of ferromagnetic material to 0.

The comparatively soft core 11 shown in Fig. 1 is magnetically anisotropic and has a preference magnetizing axis which is substantially parallel to the axis of the trees. The comparatively hard sheath 12 is also magnetically anisotropic and has a preference magnetizing axis, which gives rise to a remnant which is substantially parallel to the axis of the trees. The direction of magnetization of the core II is for the most part a function of the interaction between the magnetic field of the jacket and the external magnetic field which is applied. In the condition shown in Fig. 1, the remanence of the core 11 has the opposite direction to the remanence of the jacket 12. This state is referred to in the present case as an inverted state, in which a domain boundary layer 13 determines the boundary between the core 11 and the jacket 12. This boundary layer 13 is shown in Fig. 1 as a cylindrical boundary wall 13, but it may be considered that the boundary layer acts as a rather complicated magnetic transition zone in the thread. It has been found that pulses can be generated by means of wire composed of cobalt, iron and vanadium which is at least an order of magnitude larger than the pulses generated by the wire of nickel-iron alloy proposed in the above-mentioned patents. .

A particularly suitable composition of the wire according to the invention is a proportion of cobalt from about 45 to 55%, a proportion of iron from about 30 to 50% and a proportion of vanadium between about 4 and 14%. An alloy of cobalt, iron and vanadium, which has been found to be suitable for the practice of the invention, is commercially available under the name Vicalloy. A wire of this material is nominally composed of about 52% cobalt, about 10% vanadium and the remainder mainly iron with certain minor constituents such as manganese and silicon in amounts slightly less than half a% each.

According to a first machining scheme, a wire made of Vicalloy with a length of 30 cm and a diameter of 0.25 mm is used, while a particularly suitable cold machining process comprises the following steps. First, stretch the thread to its full length.

According to Fig. 5, the length of wire 40 is attached to chucks 42 and 44.

Sufficient tension is applied to the wire by a spring-loaded roller 46 to hold the wire 40 in its unbent or straightened condition without extending the wire. Thereafter, the wire 40 is subjected to a single period of torsional deformation, comprising about 64 turns counterclockwise, followed by about 48 turns clockwise. The tension is maintained during all rotational deformation processes. Thereafter, the wire is subjected to 17 and a half periods of 8 and a half turns in each direction. 8 and a half turns counterclockwise, followed by 8 and a half turns clockwise is applied and forms a period. The period is repeated 17 times and then this second step ends with 8 and a half turns counterclockwise. During this second step, which normally lasts about 10 to 15 seconds, the 30 cm long thread is extended continuously slowly, the size of the extension being between 1 and 2%. The last moment during the cold working consists of another series of 8 and a half turns, this time for an even number of periods, without the wire being stretched further but its tension being maintained. During the second step, 3 to 4 times the number of periods were used. About 60 periods have been found to yield good results. The wire is then cut into reversible segments with a length of e.g. 1 to 3 cm. The above-described scheme for cold working a wire of an alloy of iron, cobalt and vanadium has been found to give certain desired results. In determining these results, it has also been found that variations in this scheme result in a thread which still exhibits a conversion effect.

A second machining scheme, which has been found to be particularly useful with respect to this Vicalloy wire in cases where maximum time stability is not essential, comprises the following steps, using a wire having a diameter of 0.25 mm and a length of 30 cm. . First, the wire is stretched to its full length, whereby the tension keeps the wire stretched for its entire length without extending the wire. Thereafter, the wire is subjected to a single period of torsional deformation, comprising three turns counterclockwise, followed by 12 turns clockwise. Then the wire is subjected to 120 periods of 12 turns in each direction. This means 12 revolutions counterclockwise, followed by 12 revolutions clockwise, which forms a period, which is repeated 120 times. During this second step in the cold working process, the wire is stretched continuously under the influence of the torsional deformation.

During this second step, the 30 cm long thread is extended slowly and continuously by approx. 3 mm. The last step in the cold machining process consists of a further series of 20 periods of 12 turns counterclockwise and 12 turns clockwise without the wire being further extended but kept under tension, so that the extension achieved during the second step is maintained. The wire is then cut to desired lengths.

The alloy used during the two cold working processes described is essentially the same. From the beginning, the alloy is heat-treated to ensure a uniform starting material and to ensure suitable formability for cold working.

The wire is preferably heat-treated initially to a point where the grain structure is approximately 10,000 grains or more per mm 2. This fine grain size helps to ensure the required formability.

A fourth work step has been found to be significant in connection with the two cold working processes described and comprises heat treatment. During the earlier experimental stages, this heat treatment took place at about 320 ° C for about 8 hours, but it has been found satisfactory to carry out the heat treatment for U hours at about 300 ° C, which shortens the time for processing the trees. It is currently particularly suitable to carry out the heat treatment by feeding a current with a value of 5.6 amps through the wire for 120 milliseconds. As a result of the heat treatment, there is a noticeable improvement in the output pulse and in addition the risk is reduced that the properties of the trees will change during operation, when it is exposed to high temperatures.

As a result of the fourth operation, an aging is achieved, which results in stable operation.

Fig. 2 schematically shows an examination device for determining the pulses which can be obtained by using the wire consisting of ænadine, cobalt and iron according to the invention in comparison with the nickel-iron wire described in the above-mentioned patents. A mains voltage is applied to a transformer 20 for supplying an alternating voltage to a magnetic coil 22. A segment of the wire 10 is centrally located inside the coil 22, while a sensing coil 24 is wound around the wire 10. Current through the winding in the magnetic coil 22 produces an axial magnetic field in the middle of the coil 22. It has been found that the most pronounced pulses from the wire consisting of vanadium, cobalt and iron are obtained when the wire is adjusted asymmetrically. By means of the coupling shown in Fig. 2, an exciting field H is obtained, to which the wire 10 is exposed and which is represented by the curve 32 in Fig. 3. The diode 28 in Fig. 2 transmits the entire positive half period in the alternating voltage, while the resistor 26 is set to transmit a significantly reduced negative half-period, so that the exciting field to which the wire 10 is exposed has a positive peak at 150 Oe and a negative peak at only about 20 Oe. Resistor 30 is a current limiting resistor.

The hysteresis loop of the wire 10 according to the invention, when magnetized in this way, is indicated by the curve BU in Fig. 3, Fig. 5 being shown substantially in the form in which it would appear on an oscilloscope screen. The interruptions, the so-called Wiegand bobs, in curve 34, which are denoted by reversed core changeover and transition core changeover, appear on the oscilloscope screen only as weak lines, since the rate of change of the flow or magnetization B through the core 10 is very high, when the field strength of the outer field H exceeds the corresponding threshold value. The larger interruption in the curve BH is denoted by the transition of the core-core, whereby this state occurs when the externally applied longitudinal magnetic field H reverses the longitudinal magnetization of the core from the reversed state shown in Fig. 1, in which the magnetization of the core has the opposite direction to the magnetization of the jacket 12, to the transition state, where the core and the jacket have the same direction of magnetization. During reversed core conversion, the core is switched by the magnetic field H from the transition state to the reversed state. As shown in Fig. 3, the pulse C, which. is induced in the coil 24 upon conversion from reversed state to transition state, considerably larger than the pulse R, which is induced upon conversion from transition state to reversed state. Pulse C, which is induced during transition core conversion, has about ten times as much amplitude as the pulse R. induced during reversed core conversion.

When using a wire 10 of length 3 about and a sensing coil 2ü with 925 turns of a wire with a diameter of about 0.4 mm, while the output signal from the coil 2Ä is applied to a load with the resistance 1000 ohms, the amplitude of the pulse C 1 exceeds 5 volts and the pulse has a width of about 20 microseconds at half the amplitude. Pulse R, on the other hand, has comparable values of 125 millivolts and a width of at least 60 microseconds. In this case, the pulse C thus has 12 times as much amplitude as the pulse R. Without load, a pulse C with an amplitude of more than 2 volts can be obtained. g When the external drive field produces a negative field H with a field strength of 150 Oe and in addition a positive field H with a field strength of 150 Oe, two pulses 40 are generated which are equal to each other and have opposite polarity according to Fig. Ä. These two pulses H0 each have a amplitude of about 550 millivolts and a width of about .H0 microseconds at half amplitude. When the changeover is symmetrical risk, the two generated pulses OO are equal to each other and have considerably less value than the pulse C obtained at the optimum asymmetric changeover, and considerably larger in size than the pulse R obtained at the optimum asymmetric drive. This situation is illustrated in Fig. H. If exactly the same coupling is used as that shown in Fig. 2 except that the diode 28 and the resistor 26 are excluded, the wire 10 n '7805023-4 ll is subjected to a completely sinusoidal excitation field 56 to form an outer field 2 with a field strength, which varies from plus 150 Oe to minus 150 Oe. The result is the hysteresis curve 37.

At maximum positive field H, both the jacket 12 and the core 11 are magnetized in a positive direction, which is represented by the upper right corner of the hysteresis curve 37, which can be judged to be a positive transition state. As the outer field H decreases, the excitation B will decrease, until the core ll at a comparatively small negative field H of about minus 12 Oe changes its excitation direction from positive to negative.

The device 10 thus transitions from a transition state to a reversed state. As a result, an interruption 37a occurs in the curve 37 and an output pulse is emitted from the sensing coil 27 with an amplitude of approximately 550 millivolts and a width of 40 microseconds. When the excitation H continues to increase in the negative direction, a point is reached where the excitation direction of the jacket changes, so that a small interruption 37b arises in the hysteresis curve 57 and a small output pulse H2 is generated. The core and mantle are now in a negative transition state. Field H 'changes to a negative peak and then becomes less negative. here the field H becomes slightly positive (about 12 Oe), the core 12 changes direction in the positive direction, which is represented by the interrupt 37c. This produces an additional output pulse 40, which has a charge of 550 millivolts and a width of H0 microseconds.

This means a transition from the negative transition state to a reversed state. The field H continues to become further positive until a point is reached, which is represented by the short interruption 37d, where the jacket changes its magnetization direction and a small output pulse H2 is generated, while the device 10 returns to its positive transition state. When the applied magnetization H becomes sufficiently negative as well as sufficiently positive for the changeover of the jacket according to Fig. U, the changeover of the core takes place constantly, when the device changes from its transition state to its reversed state. On the other hand, when the magnetization H is limited in one direction, so that the magnetization direction of the jacket does not change as in Fig. 5, there is asymmetrical adjustment in that the reverse core changeover is present, when the device changes from its transition state to its reversed state, and a transition core. , when the device switches from its reversed state to its transition state. The transition from a reversed state to a transition state gives rise to a larger pulse than is the case with the transition from a transition state to a reversed state, since the former occurs at a greater speed than the latter. In the embodiments described above, the excitation field H must change its direction in order to change the excitation direction of the core. Simply removing the drive field H completely will not result in reversing the magnetization of the core II.

This necessity for reversing the drive field in order to change the magnetization of the core applies whether the changeover is asymmetrical in Fig. 3 or symmetrical according to Fig. 4. In contrast, the embodiments proposed in the above-mentioned patents automatically change from a transition state to a reversed state, when the excitation field is removed.

Furthermore, in contrast to the known proposals, the maximum pulse which can be achieved by using the wire according to the invention is almost ten times as large as can be achieved with the known devices under similar load conditions and with the same sensing coil 24.

Fig. 5 schematically shows a mechanism for cold processing of the wire. A thread 40 of length e.g. 50 cm is pulled from a spring-loaded roller 46. The wire 40 is then kept under tension, so that it becomes straight. The wire H0 is fed through the chuck 42 to the chuck RH, whereby the hooks 42, ÄH are then tightened to hold the wire in place. Periodic rotational deformation of the trees HO is then performed by alternately rotating the gear 48 along the rod 50. The rod 50 moves back and forth, since it is eccentrically mounted on the plate 52, which is driven by a motor Sä. Elongation of the wire 40 is accomplished by slowly rotating the cam 56, which abuts a portion 58 of the chuck H2. The cam 56 is rotated by a motor 60.

Claims (3)

A magnetic wire device in the form of a single unit with a magnetic sheath and a magnetic core part, which parts have remanence after being subjected to a magnetic field, the sheath part having considerably greater coercive force than the core part and these parts has substantially the same chemical alloy composition, while the device is arranged to assume an inverted state, in which the parts have the opposite direction of magnetization, and a transition state, in which the parts have the same direction of magnetization, the two parts in the inverted state being separated from each other only by means of a magnetic boundary layer, characterized in that the core part has such a coercive force that the magnetization of the jacket part in the transition state is insufficient to switch the device to the reversed state. Device according to claim 1, characterized by an external field for converting the device to the reversed state, when it is in the transition state. Device according to claim 1 or 2, characterized in that it is switchable from the reversed state to the transition state considerably faster than in the opposite direction. A. A device according to claim 1, 2 or 5, characterized in that the alloy is composed of a comparatively large weight fraction of iron, a comparatively large weight fraction of cobalt and a comparatively small weight fraction of vanadium and that the proportions of iron and cobalt together constitute over 80 weight percent of the alloy. Device according to claim U, characterized in that the alloy consists of between H5% and 55% cobalt, between 30% and 50% iron and between A% and lä% vanadium. Device according to claim H or 5, characterized in that the alloy consists of about 52% cobalt and 10% vanadium, while the remainder is mainly iron. A method of manufacturing a device according to one or more of claims 1 to 6, characterized in that a predetermined length of wire is kept under tension, the wire mainly consisting of an alloy of iron, cobalt and vanadium, that the wire is subjected to at least one period of asymmetric rotational deformation, the residual rotational deformation in one direction being greater than in the other direction and the magnitude of the deformation amounts to about two revolutions per centimeter, and that the wire is subjected to symmetrical periodic rotational deformation, this symmetrical deformation is generally less than one revolution per centimeter and the number of symmetrical periods is considerably greater than the number of periods of asymmetrical deformation. 8. A method according to claim 7, characterized in that the wire is extended at almost between one and two percent during one of the deformation processes. 9. A method according to claim 7 or 8, characterized in that the wire is heat treated after it has been subjected to the symmetrical torsional deformation. 10. A method according to any one of claims 7 - 9, characterized in that the material in the wire, when kept under tension, has an average grain size of about 10,000 grains per mm2.