GB1604112A - Generator for delivering an electrical signal - Google Patents

Description

(54) A GENERATOR FOR DELIVERING AN ELECTRICAL SIGNAL (71) We, ROBERT BOSH GmbH, a German company of Postfach 50, 7000 Stuttgart 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to a generator for deriving an electrical signal upon the remagnetization of a ferromagnetic wire associated with a coil.

Such a generator is already known in which, before its use, the wire is subject to an exPensive mechanical treatment.

(Periodical "Electronics" of 10 July 1975 pages 100 to 105). With such a wire, which is generally called a Wiegand-wire, the domains of a polycrystalline material are polarised in one direction by a magnetic field.

After removing the magnetic field, the domains persist in the said polarised condition. If a magnetic field is then applied to the Wiegand-wire in the reverse direction, then the domains change their direction of polarisation suddenly when a definite magnetic field strength is exceeded. Due to this reversal of direction, a sharp needle pulse is generated in a receiving coil, the level of which is only determined by the reversal velocity in the domains of the Wiegand-wire.

When using generators, for example in motor vehicles, numerous symmetrical voltage pulses are required. When symmetrical voltage pulses have to be generated with the descnbed Wiegand-wire, then the pulses produced by the known devices are of very low amplitude. However, since during their application to motor vehicles and also to many other purposes, interference signals frequenty occur, which can trigger switching errors, the important thing is that the output signals reach a predetermined minimum amplitude. With the generators known today, only output signals of relatively low amplitude can be produced so that the use of such generators for many purposes is rejected.

The present invention provides a signal generating assembly comprising a generator device and means for subjecting the device to an external magnetic field, said device comprising a ferromagnetic wire maintained under a constant tensile and/or torsional stress, the wire being polarized in one direction and provided with a pick-off coil, and said means for subjecting the device to an external magnetic field being arranged to subject the generator device to a magnetic field in a direction to change the direction of polarisation of the wire whereby to cause a signal to be generated in the pick-off coil.

Using a preferred embodiment of the present invention, output signals of very high amplitude can be produced. Thus, the generator can be used even in many cases in which great problems with the interference voltages occur, for example the use of the generator in motor vehicles is thus immediately possible. Other operating power semiconductors such as transistors, thyristors can be controlled directly by the hlgh signals.

Moreover, the output signals have a substantially shorter pulse duration and a complicated treatment of the wire before putting it into service can be omitted. Finally, there is no critical dependence of the signal amplitude on the field strength applied.

It is of particular advantage that the generators are able to be manufactured in a continuous process so that the production is simple and cheap.

In order that the present invention be more readily understood embodiments thereof will now be described by way of example with reference to the accompanying drawings, in which: Figure I shows a magnetization curve in which the magnetic induction B is plotted against the magnetic field strength H; and Figures 2 to 5 are examples of various types of fixing of a wire in a coil former.

A magnetization curve is illustrated Figure 1. In this magnetization curve, the magnetic induction in a suitable material under tensile and/or torsional stress is plotted against the effective field strength. The path of the magnetization curve depends on a number of elemental magnetic procedures. In the demagnetized state, a ferromagnetic crystal is divided by so-called Bloch-walls into Weiss regions or domains the spontaneous magnetization of which lies in various directions so that the average magnetization of the entire crystal is equal to zero. By applying an external magnetic field, a parallel position of the spontaneous magnetization of all the Weiss regions in the field direction is enforced with an increasing field strength. In so doing, in the steep region of the curves plotted in Figure 1, all volume regions tilt with their magnetization direction into more preferable positions. In so doing, there exist so-called Barkhausen jumps. These are discontinuous variations in the magnetic induction. These Barkhausen jumps can achieve substantially double the level of the saturation induction when a wire 10 according to the embodiments illustrated in Figures 2 to 4 is subject to a tensile stress or a torsional stress or a tensile and torsional stress. Thus, the remagnetization is initiated on reaching a threshold in the field strength Hs of a re-magnetizing magnetic field. Thus, the re-magnetizing velocity does not depend on the speed of the field strength variation and is thus independent of frequency. The remagnetization generates a voltage signal in a coil 11, for example wound around the wire, which can lie in the region of greater than 10 volts and the pulse width of which lies in the region of a few microseconds. Moreover, the re-magnetization signal always occurs as a symmetrical voltage pulse.

Thus, if a wire 10, which is maintained under tensile and/or torsional stress in the coil former 12, is subject to a remagnetization then this re-magnetization step is characterised by an electrical signal which can be taken from the coil 11. The re-magnetization step can be triggered, for example, by variation in displacement or angle of a component arranged relatively to the wire 10 and the coil 11 (for example a magnet, deflector plate, a diaphragm, a segment). In that manner, displacement generators, angle generators, or even speed and reference marker generators can be produced, for example, in a simple manner.

How the wire 10 can be held inside the coil former 12 under tensile and/or torsional stress is shown in individual different examples in Figures 2 to 5. In Figure 2, a small glass tube 12 is provided as a coil former for the coil 11 and in which the wire 10 is stuck with the aid of an adhesive indicated at 13 under tensile and/or torsional stress. The hardened adhesive 13 retains the wire 10 in the small glass tube 12 permanently under the necessary tensile and/or torsional stress.

The type of fixing according to Figure 2 is especially suitable for a continuous method of production of the generator. In one especially preferable production method, the wire 10 is first of all drawn through an adhesive bath and is then drawn into the small glass tube 12. Thereafter, the wire 10 is tensioned and/or torsioned and the adhesive 13 is then hardened, for example by heating the entire generator. Thus, the wire 10 remains in a tensioned and/or torsioned condition.

In Figure 3, the wire 10 is sealed in the interior of the coil former 12 with the aid of a sealing compound 14. Thereby, the wire 10 which is tensioned and/or torsioned before the sealing in, remains in this condition.

A further possible method of fixing the wire 10 in the coil former 12 is illustrated in Figure 4. In this instance, the wire 10 is attached to a mechanical tensioning device 15 which is mounted at both ends of the wire 10. The tensioned and/or torsioned wire 10 can be maintained in this condition with the aid of the said mechanical tensioning device 15 after it has been drawn into the coil former 12.

In Figure 5, the wire 10 is sealed in the small glass tube 12 at its ends. Thereby, the wire 10 which is tensioned and/or torsioned before being sealed in remains in this condition.

The generator arrangement illustrated in the embodiments according to Figures 2 to 5, has a length of substantially a few millimetres up to some centimetres. Due to this small dimensioning, the generator is extraordinarily versatile in its application and can also be easily mounted in positions which are not easily accessible. In the embodiments according to Figures 2 to 5, the wire 10 is arranged inside the coil 11.

However, it is of course possible to arrange the tensioned and/or torsioned wire outside the coil 11. The fields of application of the described generator extend to displacement generators, positional generators, velocity generators, contactless switches, for example in motor vehicle ignition distributors, alarm systems, memory elements, map readers, magnetic cards, pulse generators and the like.

With the described generator arrangements, it is a question of non-contacting generators and thus generators requiring no maintenance.

When the wire 10 is arranged under tensile and/or torsional stress in the interior of the coil 11 the diameter of the outermost coil layer is not greater than 10 times the diameter of the wire.

WHAT WE CLAIM IS: 1. A signal generating assembly comprising a generator device and means for subjecting the device to an external magnetic field, said device comprising a ferromagnetic wire maintained under a constant tensile and/or torsional stress, the wire being polarised in one direction and provided with a pick-off coil, and said means for subjecting the device to an external magnetic field being arranged to subject the generator device to a magnetic field in a direction to change the direction of polarisation of wire whereby to cause a signal to be generated in the pick-off coil.

2. An assembly according to claim 1 characterised in that the wire is stuck in a tensioned and/or torsioned condition in a tube associated with the coil and especially serving as a coil former.

3. An assembly according to claim 1 characterised in that the wire is sealed in a tensioned and/or torsioned condition in a tube associated with the coil and serving as a coil former.

4. An assembly according to claim 1 characterised in that the wire is sealed in a tensioned and/or torsioned condition in a tube of glass associated with the coil and serving as a coil former.

5. An assembly according to claim 1 characterised in that the wire is retained in a tensioned and/or torsioned condition in a tube associated with the coil, serving as a coil former, with the aid of a mechanical tensioning device.

6. An assembly according to any one of claims 1 to 5 characterised in that the wire is arranged in the interior of the coil.

7. An assembly according to claim 6 characterised in that, when a wire is arranged under tensile and/or torsional stress in the interior of the coil the diameter of the outermost coil layer is not greater than 10 times the diameter of the wire.

8. A method of producing a generator assembly according to claim 2 characterised in that the wire is drawn through adhesive and is then drawn into the tube, that the wire is thereafter tensioned and/or twisted and that finally the adhesive is hardened and the wire is retained in its tensioned and/or torsioned position thereby.

9. A generator assembly substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. tensile and/or torsional stress in the interior of the coil 11 the diameter of the outermost coil layer is not greater than 10 times the diameter of the wire. WHAT WE CLAIM IS:

1. A signal generating assembly comprising a generator device and means for subjecting the device to an external magnetic field, said device comprising a ferromagnetic wire maintained under a constant tensile and/or torsional stress, the wire being polarised in one direction and provided with a pick-off coil, and said means for subjecting the device to an external magnetic field being arranged to subject the generator device to a magnetic field in a direction to change the direction of polarisation of wire whereby to cause a signal to be generated in the pick-off coil.

2. An assembly according to claim 1 characterised in that the wire is stuck in a tensioned and/or torsioned condition in a tube associated with the coil and especially serving as a coil former.

3. An assembly according to claim 1 characterised in that the wire is sealed in a tensioned and/or torsioned condition in a tube associated with the coil and serving as a coil former.

4. An assembly according to claim 1 characterised in that the wire is sealed in a tensioned and/or torsioned condition in a tube of glass associated with the coil and serving as a coil former.

5. An assembly according to claim 1 characterised in that the wire is retained in a tensioned and/or torsioned condition in a tube associated with the coil, serving as a coil former, with the aid of a mechanical tensioning device.

6. An assembly according to any one of claims 1 to 5 characterised in that the wire is arranged in the interior of the coil.

7. An assembly according to claim 6 characterised in that, when a wire is arranged under tensile and/or torsional stress in the interior of the coil the diameter of the outermost coil layer is not greater than 10 times the diameter of the wire.

8. A method of producing a generator assembly according to claim 2 characterised in that the wire is drawn through adhesive and is then drawn into the tube, that the wire is thereafter tensioned and/or twisted and that finally the adhesive is hardened and the wire is retained in its tensioned and/or torsioned position thereby.

9. A generator assembly substantially as hereinbefore described with reference to the accompanying drawing.