Sensor system for a fuse

Abstract

The invention relates to a sensor system for installation in a fuse for a projectile, comprising at least one antenna element, wherein the antenna elements are arranged on a surface that is arranged at an angle α of between 85° and 95° relative to the centre line C-C of the fuse. The invention further relates to a fuse and a projectile equipped with a fuse.

Description

[0001] SENSOR SYSTEM FOR A FUSE

[0002] TECHNICAL FIELD

[0003] The present invention relates to a sensor system for installation in a fuse for a projectile, comprising at least one antenna element, wherein the antenna elements are arranged on a surface that is arranged at an angle a between 85° and 95° relative to the centre line C-C of the fuse. The invention further relates to a fuse and a projectile equipped with a fuse.

[0004] BACKGROUND OF THE INVENTION, PROBLEM AREA AND KNOWN TECHNOLOGY

[0005] Projectiles designed to cause damage to a target object can use various systems or technical solutions to improve their ability to achieve their objective. For example, the projectile can be equipped with various sensors to detect the target object and detonate with fragments to achieve a larger area of effect. Furthermore, the projectile can be equipped with various means of steering the projectile, such as fins, which can enable the projectile to steer towards the target object. To improve the ability of the projectile to strike the target, the projectile can be equipped with a sensor system, such as a proximity fuse. Proximity fuses can use sensors operating in optical wavelength ranges or sensors adapted for electromagnetic radiation in lower frequency ranges, such as in the micro wave range.

[0006] Patent document US 11,923,604 B2 describes a missile equipped with a radar device comprising a number of antennas arranged radially around a rotatable nose cone to create a directional antenna lobe. The patent document does not show that the antenna elements are arranged to direct the antenna lobe in the axial direction of the projectile, directly in the direction of travel of the projectile.

[0007] The solution to the above problem and additional problems with the solution are described below. THE INVENTION AND ITS PURPOSE

[0008] One purpose of the present invention is to solve the problems identified above.

[0009] The invention consists of a sensor system for installation in a fuse for a projectile, comprising at least one antenna element where the antenna elements are arranged on a surface that is arranged at an angle a between 85° and 95°° relative to the centre line C-C of the fuse, and that the surface is arranged at the tip of the fuse, which is the point on the fuse that is arranged at the distal end of the projectile, where the diameter D of the ogive is the surface area, and where the diameter D of the surface in a preferred embodiment is in the range of 5% to 20% of the diameter of the projectile.

[0010] According to further aspects of a sensor system according to the invention, the following applies:

[0011] th at the surface is concave or convex.

[0012] th at the surface is flat and arranged at an angle a that is 90° relative to the centre line C-C of the fuse.

[0013] th at the diameter D of the surface in an even more preferred embodiment is in the range of 8% to 12% of the diameter of the projectile.

[0014] th at the antenna elements consist of two antennas, a transmitting antenna and a receiving antenna.

[0015] th at the antenna elements are waveguide antennas arranged into a waveguide.

[0016] th at at least one microstrip is arranged in each waveguide. Other transitions between the printed circuit board and the waveguide are also conceivable.

[0017] th at the antennas are advantageously arranged to transmit and receive electromagnetic signals in the frequency range between 30 GHz and 300 GHz.

[0018] th at the antennas are even more advantageously arranged to transmit and receive electromagnetic signals in the frequency range between 60 GHz and 110 GHz. The invention further comprises a fuse wherein a sensor system is arranged in the fus and a processor unit is arranged to a detonator, wherein the detonator is initiated when a target object is detected by the sensor system.

[0019] According to further aspects of a fuse according to the invention, the following applies:

[0020] th at the fuse further comprises a strike sensor.

[0021] The invention further comprises a projectile comprising an explosive part and a fuse comprising a sensor system arranged in the projectile.

[0022] According to further aspects of a projectile according to the invention, the following applies:

[0023] th at the centre line of the fuse is identical to the centre line C-C of the projectile. FIGURE LIST

[0024] The invention will be described in more detail below with reference to the accompanying figures, where:

[0025] Fig. 1 shows a radiation pattern for a projectile equipped with a sensor system according to one embodiment of the invention.

[0026] Fig. 2 shows a cross-sectional view of a fuse comprising a waveguide according to one embodiment of the invention.

[0027] Fig. 3 shows a front view of a fuse according to one embodiment of the invention.

[0028] Fig. 4 shows a side view of a fuse according to one embodiment of the invention.

[0029] Fig. 5 shows a block diagram of a sensor system according to one embodiment of the invention.

[0030] Fig. 6 shows a block diagram of a sensor system according to an alternative embodiment of the invention.

[0031] DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention discloses a new and alternative design of a sensor system for fuse or fuze, which are a type of ignition tube, for projectile devices, also known as grenades. A launching device, also referred to as a cannon, howitzer, or gun, such as a medium-calibre gun, is intended to fire a projectile by means of a propellant. Preferably, a propellant, such as gunpowder, is initiated in a part of the cannon, often a sleeve or chamber specially adapted for this purpose. Ignition occurs through the ignition of the propellant, for example with a primer or a detonator in an ammunition unit, which is initiated by impact. Other methods of igniting the propellant include laser or electrical energy. The propellant burns at high speed and generates a large amount of gas, which creates gas pressure in the chamber that drives the projectile out of the barrel of the firing device. The propellant is designed to generate as constant a pressure as possible on the projectile throughout the entire barrel, as the projectile moves through the barrel, creating a high velocity for the projectile as it leaves the muzzle. Projectiles, such as various types of grenades, in most cases include some form of warhead and some form of fuse that initiates the warhead. Fuses can be of various types, with impact fuses commonly used for projectiles intended to detonate on contact with an object, time fuses for projectiles intended to detonate at a predetermined time, and proximity fuses for projectiles intended to detonate when an object comes within a certain distance of the projectile. Proximity fuses are primarily used in the defence against aircraft, while time fuses and impact fuses can be used in the defence against a large number of different objects. It is advantageous to combine different types of fuse functions in the same fuse, so that if a fuse with a proximity fuse function does not detect any object, the projectile detonates after a certain time, etc.

[0033] Proximity fuses have traditionally used electromagnetic radiation in frequencies between a few tens of kHz up to a few hundred kHz, but radar technology, which uses higher frequency electromagnetic radiation, can also be used. Radar is equipment and technology for detection and distance determination using radio waves. Radar primarily uses shortwave radio waves, i.e. electromagnetic radiation, to identify the distance and possibly the position and direction of travel of various objects located at a distance from the radar transmitter. A signal is sent out, reflected off the object and detected by the transmitter; the same antenna structure is primarily used to transmit and receive the radar signal.

[0034] The warhead preferably comprises some form of explosive and some form of splinterproducing casing that encloses the explosive. Furthermore, various forms of guidance devices, such as fins, can be arranged either in the fuse or in a separate subcomponent.

[0035] In order to stabilize the projectiles after they have left the barrel, the projectiles are preferably designed with rotation or fins. In the case where the projectiles are designed with rotation, the projectiles are said to be rotationally stabilized, and in the case where the projectiles are designed with fins, the projectiles are said to be fin-stabilized. Fin-stabilized projectiles should not have rotation or should have very low rotation when they leave the barrel.

[0036] To achieve rotation of the projectiles, grooves are often arranged in the barrel to which the projectile connects during the ejection process. Rifling means that the barrel of a firearm is equipped with spiral-shaped grooves. The opposite is a smoothbore barrel. When the rifling engages the projectile during firing, it rotates along its longitudinal axis. The rotation prevents minor irregularities or damage to the projectile from causing a deviation. Rotation is also necessary for an oblong (torpedo-shaped) projectile to maintain its direction after leaving the barrel and not start tumbling around; this is referred to as the projectile being rotationally stabilized. Only round (spherical) projectiles or fin-stabilized projectiles can be fired from smoothbore weapons. An elongated projectile without fins will tumble when it leaves the muzzle.

[0037] FUNCTION DESCRIPTION

[0038] A launching device is designed to fire projectiles with a propellant charge. The propellant charge, which may be gunpowder, for example, is ignited and generates high pressure that drives the projectile out of a barrel. The projectile may be designed as a casing filled with a propellant charge, referred to as an ammunition unit, where the projectile designed as a casing is attached or loaded into the launching device.

[0039] Alternatively, the projectile can be arranged separately in the barrel by means of a process known as rifling, whereby a belt surrounding the projectile is deformed in relation to the rifling arranged in the barrel, which holds the projectile in the barrel. The propellant charge is arranged in what is often referred to as a chamber in which the propellant charge is burned, generating gases, powder gases, which cause the projectile to move in the barrel. Preferably, a continuous / constant pressure is created in the chamber, which also fills the barrel with pressurised gas behind the projectile as it moves towards the muzzle. Preferably, projectiles with a calibre in the range of 20-105 mm are designed as cartridge ammunition, while for larger calibres, the projectile is preferably not cartridge-loaded. However, larger calibres are also sometimes cartridge-loaded.

[0040] Fig. 1 shows a radiation pattern 110 for projectile 100, including a sensor system with two forward-facing antennas arranged in the nose of the projectile. A single antenna can also be arranged to function as both a transmitting and receiving antenna. Furthermore, several antennas can be arranged if technically possible. In the case where an antenna array can be arranged, control of the radiation pattern is made possible. By obtaining a forward-facing antenna lobe, targets can be more easily detected at longer distances, which results in improved effectiveness in the target. Preferably, the antenna lobe is forward-facing and arranged so that objects within the effective range of the projectile can be detected, which is why the antenna lobe needs a certain width to be able to detect target objects.

[0041] Fig. 2 shows a fuse 200 with a circular flat surface 230 arranged at the front of the projectile 100, which is equipped with two antennas 232, 234. Antenna 232, which is a transmitter antenna, is fed by a waveguide 242, and waveguide 242 is fed by a microstrip 252. Antenna 234, which is a receiver antenna, is arranged to a waveguide 244, received electromagnetic radiation is conducted in the waveguide 244 to a microstrip 254 that receives electromagnetic radiation. Microstrip 252 is connected to a transmitter that is preferably semiconductor-based, and similarly, microstrip 254 is connected to a receiver that is preferably semiconductor-based. The number of antennas, or antenna elements, can be varied from one antenna that can be used as both a receiving antenna and a transmitting antenna up to a number of antennas that can be arranged on the flat surface 230 and can thus be varied depending on the diameter of the projectile and thus the size of the flat surface 230, which is preferably about 10% of the diameter, calibre, of the projectile. A waveguide is a device for transporting electromagnetic waves. The wave propagation in an electromagnetic waveguide occurs in different modes, which are divided into Transverse Electric (TE), Transverse Magnetic (TM) and Transverse Electromagnetic waves (TEM), which are not considered to be present in the waveguide described. In microwave technology, waveguides usually refer to a closed metallic hollow structure, as opposed to other transmission lines such as coaxial cables or transmission lines. TE and TM electromagnetic waves propagate in a closed metallic hollow structure provided that the frequency of the electromagnetic wave exceeds a lower cut-off frequency. This is determined by the geometry of the waveguide cross-section. Waves with a lower frequency than the cut-off frequency are attenuated in the waveguide. The waveguide is usually empty (i.e. vacuum or air) but can also consist of a dielectric material.

[0042] Waveguides are primarily used to transport high-power signals in feed networks to, for example, transmitter antennas. It is common for a waveguide to be terminated with a horn antenna in cases where the electromagnetic signal in the waveguide is intended to be transmitted. The waveguide can also be terminated with an aperture, without a horn shape, and still functions as a transmitter antenna. In the present invention, termination with an aperture is a preferred embodiment. By not arranging a horn antenna as the termination of the waveguide, a physically smaller antenna can be arranged. The most common special cases of metallic waveguides are rectangular and circular waveguides, which come in a number of standard sizes depending on the frequency range. In a rectangular waveguide, it is normally desirable that only a so-called fundamental mode, TE10, be active. If several modes are active in the waveguide, dispersion is caused as the modes transport information at different group velocities. In practice, a standard waveguide is therefore selected for the frequency in question with dimensions such that only the fundamental mode is active. A microstrip is a type of electrical transmission line that can be manufactured using several different manufacturing techniques, where a conductor is separated from a ground plane by a dielectric layer called a substrate. A microstrip can be arranged on a printed circuit board (PCB) comprising a conductor, such as aluminium, arranged with a dielectric layer, such as silicon or other dielectric material. Unlike waveguides, a microstrip can handle lower power and has higher losses. As radio electronics are primarily developed for arrangement on printed circuit boards, it is common for high-frequency signals to be wired and thus primarily transmitted using a microstrip. In cases where a waveguide antenna is suitable as a transmitting antenna, a transition must be arranged between the microstrip and the waveguide to ensure good electromagnetic coupling between the microstrip and the waveguide. Such a microstrip-wave guide transition is preferably arranged in one embodiment of the invention. In a preferred embodiment, the wave guide is arranged with a dielectric material to improve the aerodynamic performance of the projectile.

[0043] Fig. 3 shows a fuse 200 in a front view comprising a circular flat surface 230 arranged with two antennas 232, 234. The number of antennas or antenna elements can be varied but is preferably between 1 and 12 antennas. In the case shown, the antenna is a waveguide antenna with an aperture opening, which is directed in the forward direction of the projectile, which means that the radiation pattern of the antenna, the antenna lobe, can be directed directly forward. In the case where an antenna array comprising several antennas can be arranged on the flat surface 230, an embodiment comprising phase control can be realised. If phase shifters are arranged in the feed network, the antenna structure can function as a phase-controlled antenna. By arranging a phase-controlled antenna, the radiation pattern of the antenna can be adjusted, and the antenna lobe can be directed in different directions to change the performance of the antenna structure.

[0044] Fig. 4 shows a fuse 200 comprising a nose cone 210 in which an antenna structure is arranged in the surface of the fuse or behind a protective layer arranged on the nose cone 210. The fuse is circularly symmetrical for connection, preferably with a threaded joint 220, in the nose of a projectile. The igniter shown in Fig. 4 is of the proximity fuse type and is arranged with a sensor system comprising an antenna structure. Proximity fuses are preferably used for projectiles fired at air targets but can also be used against ground targets and can detect target objects close to the projectile during the flight of the projectile in the trajectory of the projectile. The most common type of proximity fuses is radar-based proximity fuses. These emit a continuous or pulsed radio signal after launch. When the projectile with proximity fuse approaches the ground or a flying object, part of the transmitted signal is reflected and picked up by a receiver in the proximity fuse, the receiving antenna may be the same as the transmitting antenna. Due to the movement of the grenade, the reflected signal has a slightly higher frequency than the transmitted signal, which is known as the Doppler effect. The difference between the transmitted signal and the received signal creates interference, and the resulting signal is detected and triggers the proximity fuse when it reaches a predetermined value. Since the proximity fuse detects signal strength and does not directly measure distance, the burst height is affected by whether the ground reflects poorly, for example dry ground, in relation to for example, wet ground. On some proximity fuses, it is therefore possible to adjust the sensitivity before firing. When a target object is detected, the proximity fuse can initiate an explosive charge arranged in the projectile, which creates a weapon effect, such as shrapnel, that can act on the target object. The sensitivity of the proximity fuse is adapted to the ability of the warhead to cause damage to the target object. Shrapnel is preferably dispersed radially from the projectile but can be adjusted based on the proximity fuse, the warhead, the ejection device and the capacity and performance of the target object. The fuse has an axial spread in the longitudinal axis A of the fuse and is rotationally symmetrical in the rotational axis B of the fuse. The fuse has a circularly symmetrical tapered, conically tapering surface around the fuse. The circumference of the fuse decreases in the longitudinal direction A of the fuse. The fuse ends with a completely flat surface 230 consisting of a circular surface at the tip of the fuse with a diameter D. The circular flat surface 230 preferably has a diameter of approximately 10% of the calibre of the projectile, i.e. 10% of the diameter of the projectile at its widest point. For a 40 mm projectile, D is therefore approximately 4 mm. Under certain conditions, it is aerodynamically advantageous for a projectile to have a completely flat surface 230. The flat surface is preferably arranged perpendicular to the centre line C-C of the projectile or at an angle between 85 degrees and 95 degrees from the centre line C-C so that the angle a is between 85 and 95 degrees.

[0045] Fig. 5 shows a block diagram for a sensor system 1000 comprising a Control unit 1010 that controls the functionality of the components included in the sensor system 1000. A Waveform generator 1020 consists, for example, of an oscillator that generates the carrier frequency used by the sensor system to transmit the signal from the sensor system 1000 emanating from the proximity fuse. The Waveform generator 1020 may be arranged to generate a certain predetermined frequency, but in an alternative embodiment it may be controlled by the Control unit 1010 to change the carrier frequency. However, the frequency change must take place within the bandwidth of the Antenna structure 1060. A Transmitter 1030 can amplify the carrier signal from the Waveform generator 1020 and possibly modulate the signal or otherwise affect the signal to be transmitted from the Antenna structure 1060. The signal from the Transmitter 1030 can pass through a Duplexer 1050. A duplexer is an electrical device that enables two-way communication over a single path, for example by isolating a Transmitter 1030 from a Receiver 1040 and enabling the Transmitter 1030 and Receiver 1040 to use the same Antenna structure 1060. After a pulse or continuous signal has been transmitted from the Antenna structure 1060 from the Transmitter 1030, a reflected pulse, for example reflected from a target object, can be received by the Antenna structure 1060 and forwarded to the Receiver 1040. The signal received by the Receiver 1040 can, for example, be filtered in various ways before the signal is forwarded, in signal-processed form or as the originally received signal, to a Processor unit 1070 which calculates the received signal and, based on predetermined criteria, the Processor unit 1070 can determine whether the received signal represents a target object being within the range of the proximity fuse, and thus the effective range of the warhead. If the Processor unit 1070 determines that a target object is within the effective range, the proximity fuse initiates a detonator which initiates the warhead, whereupon the effect, for example in the form of splinters or preformed fragments, such as balls, such as carbide balls, is dispersed from the effector towards the target object.

[0046] Fig. 6 shows a block diagram of a sensor system 1100 comprising a Control unit 1010 that controls the functionality of the components included in the Sensor system 1100. A Waveform generator 1020 consists, for example, of an oscillator that generates the carrier frequency used by the sensor system to transmit the signal from the sensor system 1000 emanating from the proximity fuse. The Waveform generator 1020 may be arranged to generate a certain predetermined frequency, but in an alternative embodiment may be controlled by the Control unit 1010 to change the carrier frequency. However, the frequency change must occur within the bandwidth of the Transmitter antenna structure 1150. A Transmitter 1030 can amplify the carrier signal from the Waveform generator 1020 and possibly modulate the signal or otherwise affect the signal to be transmitted from the Transmitter antenna structure 1150. After a pulse or continuous signal has been transmitted from the Transmitter antenna structure 1150 from the Transmitter 1030, a reflected pulse, for example reflected from a target object, can be received by the Receiver antenna structure 1160 and forwarded to the Receiver 1040. The signal received by the Receiver 1040 can, for example, be filtered in various ways before the signal is forwarded, in signal -processed form or as the originally received signal, to a Processor unit 1070 that calculates the received signal and, based on predetermined criteria, the Processor unit 1070 can determine whether the received signal represents a target object being within the range of the proximity fuse, and thus the effective range of the warhead. If the Processor unit 1070 determines that a target object is within the effective range, the proximity fuse initiates a detonator which initiates the warhead, whereupon the warhead, for example in the form of shrapnel or preformed fragments, such as balls, such as carbide balls, is dispersed from the warhead towards the target object.

[0047] EXAMPLE OF IMPLEMENTATION

[0048] Examples of calibres of the projectiles are 20-155 mm. With a sabot projectile, it is possible, for a given barrel diameter, to fire all calibres between the largest calibre allowed by the barrel and all calibres below this largest calibre.

[0049] The antenna structure is connected to the electronics of the projectile, including a receiver, transmitter or transceiver. The antenna structure can also be used for communication. Examples of communication that can be exchanged with the projectile include control information to the projectile, position information from the projectile, method of action to the projectile, sensor information from the projectile, and other information relevant to improving current, subsequent or preceding projectiles to achieve the desired effect on one or more target objects. Suitable adjustments in terms of the operating frequency of the antenna are determined by the antenna principle and size limitations related to the arrangement of the antenna on the projectile.

[0050] The antenna structure can be arranged cast in a casting compound, for example epoxy, resin or silicone. Where the casting compound does not affect, or has limited effect on, the electromagnetic performance of the antenna structure. The casting compound protects the antenna from external influences, for example from gunpowder gases, which can act on the antenna during the launch phase. The antenna elements may be waveguide antennas or other types of antennas.

[0051] ALTERNATIVE DESIGNS

[0052] The invention is not limited to the embodiments specifically shown, but may be varied in various ways within the scope of the patent claims.

[0053] It is understood, for example, that the number, size, material and shape of the elements and details included in the projectiles are adapted to the barrel, projectile and projectile assemblies and other design features currently available.

[0054] Projectiles may, for example, be designed for explosive action, fragmentation action, incendiary action, therm obaric action, firefighting, training projectiles, flares, smoke charges, electromagnetic action, electromagnetic interference or other loads and functions.

Claims

PATENT CLAIMS1. Sensor system, for installation in a fuse for a projectile, comprising at least one antenna element c h a r a c t e r i s e d i n that the antenna elements are arranged on a surface (230) arranged at an angle a between 85° and 95° relative to the centre line C-C of the fuse, and that the surface (230) is arranged in the tip of the fuse, which constitutes the point on the fuse arranged in the distal end position of the projectile, where the diameter D of the ogive is constituted by the surface that constitutes the surface (230) where the diameter D of the surface (230) in a preferred embodiment is in the range of 5% to 20% of the diameter of the projectile.

2. Sensor system according to claim 1, c h a r a c t e r i s e d i n that the surface (230) is concave or convex.

3. Sensor system according to claim 1, c h a r a c t e r i s e d i n that the surface (230) is flat and arranged at an angle a of 90° relative to the centre line C-C of the ignition tube.

4. Sensor system according to any of the above requirements,c h a r a c t e r i s e d i n that the diameter D of the surface (230) in an even more preferred embodiment is in the range of 8% to 12% of the diameter of the projectile.

5. Sensor system according to any of the above requirements,c h a r a c t e r i s e d i n that the antenna elements consist of two antennas, a transmitting antenna (232) and a receiving antenna (234).

6. A sensor system according to any of the above requirements,c h a r a c t e r i s e d i n that the antenna elements (232, 234) are waveguide antennas arranged in a waveguide (242, 244).

7. Sensor system according to requirement 6, c h a r a c t e r i s e d i n that at least one microstrip (252, 254) is arranged in each waveguide (242, 244).

8. Sensor system according to any of the above requirements, c h a r a c t e r i s e d i n that the antennas are advantageously arranged to transmit and receive electromagnetic signals in the frequency range between 30 GHz and 300 GHz.

9. Sensor system according to any of the above requirements,c h a r a c t e r i s e d i n that the antennas are even more advantageously arranged to transmit and receive electromagnetic signals in the frequency range between 60 GHz and 110 GHz.

10. A fuse c h a r a c t e r i s e d i n that a sensor system according to any of claims 1 - 9 is arranged in a fuse and in which a processor unit is arranged to a detonator, the detonator being initiated when a target object is detected by the sensor system.

11. A fuse according to claim 10, c h a r a c t e r i s e d i n that the fuse further comprises a strike sensor.

12. Projectile (100) comprising an explosive part c h a r a c t e r i s e d i n that a fuse according to claim 10 is arranged in the projectile.

13. Projectile (100) according to claim 12, c h a r a c t e r i s e d i n that the centre line of the fuse is identical to the centre line C-C of the projectile.

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