EP0467055B1 - Receiving coil for the programmable fuse of a projectile - Google Patents

Abstract

In order to improve the inductive transmission of pulses from a transmitter coil to a receiver coil of a projectile fuze, an insert formed of a steel band is mounted between a coil and a coil core formed of aluminum. This insert shields the coil against eddy current fields.

Description

The invention relates to a receiving coil for a programmable projectile detonator with a coil core on which there is a winding. A projectile fuse of the type mentioned is known from EP-A-0 300 255.

A programmable projectile detonator, e.g. According to EP-A-0 300 255, contains a device for setting a counter for triggering the detonator, in particular a time fuse, in the projectile after it has been fired, the counter being inductive from a transmitter coil fastened in front of the barrel of a weapon via the receiver coil located in the projectile is set with a device for measuring the muzzle velocity of the projectile in order to set the counter for triggering the time fuse as a function of the muzzle velocity, the receiving coil being wound on a coil former.

In order to be able to set the timer with the desired accuracy, it is necessary to transfer at least 12 bits from the transmitter coil to the receiver coil. At a muzzle velocity of, for example, more than 1200 m / sec, the receiving coil of the projectile passes through the transmitting coil attached to the weapon barrel muzzle in a relatively short time, so that there is only little time available for transmitting the information from the transmitting coil to the receiving coil. High frequencies are therefore necessary to transmit the information.

• a) die induzierte Spannung bei einem Aluminiumkern wesentlich kleiner als bei einem Eisenkern;
• b) die positiven und negativen Amplituden der induzierten Spannung sind bei einem Aluminiumkern asymmetrisch und nicht entgegengesetzt gleich gross.

It has now been shown that with a coil core made of steel, this information can be transmitted from the transmitter coil to the receiver coil, but this leads to an undesirable increase in the detonator weight. To do that To reduce the weight of the detonator in the projectile, the coil core can be made of aluminum

• a) the induced voltage in an aluminum core is significantly lower than in an iron core;
• b) the positive and negative amplitudes of the induced voltage in an aluminum core are asymmetrical and not opposite in size.

In order to avoid these disadvantages, an insert is arranged between the coil core and the coil winding, which shields the winding against eddy current fields. A thin, 0.05 mm thick steel strip is preferably inserted between a coil winding made of copper and a coil core made of aluminum. This steel strip dampens the magnetic fields of the transmitter coil so strongly that almost no eddy currents are generated in the aluminum coil core. Eddy currents also form in the steel strip, but these are considerably smaller due to the greater eddy current resistance R (fe) of the iron.

• a) Infolge der ferroelektrischen Eigenschaften des Stahlbandes werden die magnetischen Kraftlinien geringfügig verdichtet.
• b) Die auf den Zylinder aus Stahlband auftretenden magnetischen Feldlinien induzieren in demselben Wirbelströme. Diese schirmen den darunterliegenden Aluminium-Spulenträger so ab, dass sich innerhalb desselben nahezu keine Wirbelströme ausbilden.

The steel strip insert has two different functions:

• a) Due to the ferroelectric properties of the steel strip, the magnetic lines of force are slightly compressed.
• b) The magnetic field lines appearing on the cylinder made of steel strip induce eddy currents in the same. These shield the aluminum coil carrier underneath in such a way that almost no eddy currents form within it.

• a) Die Ausgangsspannung der Empfangsspule steigt bei gleichem Programmierstrom der Sendespule deutlich an.
• b) Die positiven und negativen Amplituden sind gleich gross.
• c) Mit einer dünnen, einseitig isolierten Stahlfolie mit mehreren Windungen können die Wirbelströme noch mehr reduziert werden.

If the steel strip is dimensioned correctly, the receiving coil according to the invention behaves like a coil on a coil core made of steel. That means:

• a) The output voltage of the receiver coil increases significantly with the same programming current of the transmitter coil.
• b) The positive and negative amplitudes are the same.
• c) The eddy currents can be reduced even more with a thin, one-sided insulated steel foil with several turns.

Fig.1

einen Längsschnitt durch eine Rohrmündung mit einer Einrichtung zum Messen der Mündungsgeschwindigkeit und mit einer Sendespule zum Übertragen von Informationen auf ein Geschoss, das aus der Rohrmündung austritt;

Fig.2

einen Längsschnitt durch ein Geschoss gemäss einem zweiten Ausführungsbeispiel;

Fig.3

einen vergrösserten Längsschnitt durch den Zünder gemäss Fig.2 zur Verdeutlichung der erfindungsgemässen Einlage.

An embodiment of the device containing the receiving coil according to the invention is described in detail below with reference to the accompanying drawing. It shows:

Fig. 1

a longitudinal section through a pipe muzzle with a device for measuring the muzzle velocity and with a transmitter coil for transmitting information to a projectile that emerges from the pipe muzzle;

Fig. 2

a longitudinal section through a projectile according to a second embodiment;

Fig. 3

an enlarged longitudinal section through the igniter according to Figure 2 to illustrate the insert according to the invention.

1, the weapon barrel muzzle 10 is surrounded by a three-part cage 11, 12, 13, which projects beyond the weapon barrel muzzle 10. In the middle part 12 of the cage there is a first measuring coil 14 and in the front part 13 of the cage there is a second measuring coil 15 and a transmitting coil 16. The attachment of the three-part cage 11, 12, 13 to the weapon barrel muzzle 10 and Connection of the three parts to one another is assumed to be known and is neither shown nor described here. Lines 17 and 18 are provided for the electrical supply of the two measuring coils 14 and 15. A number of soft iron rods 19 are inserted in the three-part cage 11, 12, 13 to shield the entire measuring system from interference from magnetic fields, of which only two are visible in FIG. The transmitter coil 16 consists of a single turn 20 and a coil body 21. A projectile 22 flies in the direction of arrow A through the device for measuring the initial speed and for transmitting information, ie through the two measuring coils 14 and 15 and through the transmitter coil 16 . The transmitter coil consists of a single turn 20 and is relatively narrow. In order to determine the initial or muzzle velocity of the projectile 22, the time t which the projectile 22 needs to travel from the coil 14 to the coil 15 is measured. The speed V _o = a / t results from the distance a between these two coils 14, 15 and this time t. Taking this muzzle velocity of the projectile 22 into account, the time until the projectile 22 reaches the target can be calculated. A timer 24 located in the projectile 22 can thus be set or "temped" so that the projectile 22 is ignited in the area of the target. This time, which the projectile 22 needs to reach the destination when it exits the pipe mouth 10, is transmitted in digital form from the transmitter coil 16 to a receiver coil 25 in the projectile. As usual, the transmission is inductive. To set the timer 24 with the desired accuracy, at least twelve pulses should be transmitted from the transmitter coil 16 to the receiver coil 25. Since, as already mentioned, the projectile 22 flies through the transmitting coil 16 at a speed of approximately 1,200 meters per second, it is necessary to transmit the twelve pulses at a relatively high frequency at the right time. The right time to send the impulses is with the help of determined front measuring coil 15 of the device for measuring the muzzle velocity. As soon as the projectile 22 has flown through the coil 15, the information can be transmitted from the transmitter coil 16 to the receiver coil 25. The pulses pass from the receiving coil 25 through a filter 29 to a counter 32 which is connected to the timer 24.

According to FIG. 2, a so-called ground igniter 40 is screwed into the rear end of a projectile 41 via a thread 42. The individual organs of the detonator are located inside a detonator housing 43, which also acts as a coil core 43 and, together with a winding 23, forms the receiving coil 25 already mentioned. An insulation layer 44 protects the coil against damage from the hot propellant gases. The structure of the detonator is assumed to be known and is not described in more detail here.

According to FIG. 3, an insert 45, preferably a steel strip, for example made of ferroelectric material with high permeability, is located between the winding 23 made of copper wire and the coil core 43 made of aluminum between the winding 23 and a thickness of 0.05 mm is sufficient to shield the winding 23 against an eddy current field.

Instead of the thin steel strip, a much thicker insert 45 made of insulating material can be used, provided there is enough space. A similar effect is achieved by the distance formed between the copper wire and the aluminum core.

Claims (5)

1. Receiving coil (25) for a programmable projectile fuse (24, 40) comprising a coil core (43) with a winding (23) thereon, characterised in that the coil core (43) is of aluminium, and that an insert (45) which protects the winding (23) from eddy current fields is arranged between coil core (43) and winding (23).
2. Receiving coil according to claim 1, characterised in that a steel band is used as insert (45).
3. Receiving coil according to claim 2, characte rised in that the steel band is made of ferro-electrical material of high permeability.
4. Receiving coil according to claim 3, characte rised in that the steel band is made of a singlesidedly insulated steel foil with a plurality of windings.
5. Receiving coil according to claim 1, characte rised in that an electrical insulating material is used as insert (45).

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