DE102007025876A1 - Fuse for e.g. pyrotechnic actuator i.e. belt-taut, in vehicle safety system, has insulation layer and conductive layer provided with recesses that forms spark gap between conductive layers and conductive regions - Google Patents

Abstract

The fuse has a base with two electrically conductive regions (2, 3) that are insulated against each other with an insulator (1). An insulation layer (10) covers one of the electrically regions. An electrical conductive layer (12) electrically contacts the conductive regions. The insulation layer and the electrically conductive layer are provided with recesses (13), which forms a spark gap between the layer (12) and the regions. The electrically conductive layer is provided with a surface protection.

Description

The The present invention relates to an igniter for ignition of pyrotechnic active substances with the characteristics of the generic term of claim 1.

The igniters discussed here are commonly used for Ignition of gas generators, z. B. in airbags, for pyrotechnic actuators (belt tensioners) in vehicle safety systems, but also for the ignition of explosive charges, rocket engines, in aircraft and the like. Especially in the field of vehicle safety systems are the requirements for the reliability of such detonators especially high. For example, you can expect that to be one Igniter in an airbag of a motor vehicle for 20 years or more is mounted. There he is temperature fluctuations, Environmental influences and the stress of operation of the motor vehicle suspended. In a collision, however, it is expected that the detonator the gas generator of the airbag with an extremely low failure probability reliably ignites. But also in the various other applications becomes the permanent reliability of such a detonator expected. So it is necessary that the pyrotechnic active mass not by induced voltages, static electricity or interference signals on the lines is triggered. Such unintentional triggering can cause serious bodily harm of persons and cause material damage.

The first igniter for pyrotechnic active compositions, in particular Airbags have an approximately rotationally symmetric base, the in the middle carries an electrode, that of a gas-tight Glass mass is surrounded. The glass mass in turn is of a metallic Surround ring, which is electrically connected to the second electrode is. Between the centric electrode and the outer one Ring is a corrosion resistant over the glass insulation layer Strained wire, for example, a platinum wire with a diameter of 20 microns. This wire is in direct contact with a primary pyrotechnic ignition compound. The entire structure is provided with a metal jacket and helium-tight welded. This detonator is in turn immediately with the active mass in connection. The airbag is the detonator in contact with the gas generator. The airbag is ignited by a current pulse of about 1.8 A through the two electrodes. The current flows through the platinum wire, which is a thermal Plasma developed. This ignites the primary active mass in the detonator, which causes the metal sheathing to burst. The developing hot gas then ignites the pyrotechnic active mass, the gas generator.

Since the use of detonators for pyrotechnic active compositions in a variety of applications has recently been greatly increased, it is desirable not to supply the electrical ignition energy in full on the supply lines. There are therefore developed detonators that can be used instead of the platinum wire in an otherwise same structure. Such an ignition element is in the German patent DE 19756603 C1 shown.

at this detonator becomes on a silicon carrier a Semiconductor layer is generated, which serves as a first capacitor electrode. Then a dielectric layer is applied, which in turn is covered by a semiconductor layer. She forms a second Capacitor electrode and in the region of a tapered cross-section a resistance ignition element. The ignition element constructed in this way becomes in the region of the first semiconductor layer and on the Widerstandszündelement contacted. This results in a structure with a storage capacitor for storing the ignition energy and a Widerstandszündelement in series on a common silicon carrier. In this Build up the ignition energy is completely or at least partially stored in the capacitor, on the silicon carrier is trained. The ignition energy can be relatively low, because the Widerstandszündelement of the semiconductor material is constructed and requires a lower ignition energy, as a conventional wire.

The the former embodiment is in the triggering relatively slow and requires a high ignition energy. The second embodiment is in the development of the ignition pulse fast but expensive to manufacture and mechanical sensitive, which makes handling difficult during subsequent assembly power.

outgoing from this prior art, it is an object of the present invention an igniter for igniting pyrotechnic active compounds create that is to manufacture with less effort and the fast and is mechanically insensitive.

These Task is performed by a detonator with the characteristics of the claim 1 solved.

Because one insulation layer covers at least one of the electrically conductive regions, and one electrically conductive layer is electrically contacted with the other of the two conductive regions, and because the insulation layer and the electrically conductive layer are provided with recesses which form a spark gap between the layer and form the second region, a spark gap can be generated within the layer structure, which has a defined, very short length and which is mechanically protected within the layer structure. There is no two-sided electrically contacted ignition bridge required, which significantly reduces the probability of failure even under heavy mechanical stress against Brückenzündern.

If the electrically conductive layer with a surface protection is provided, the resistance value is improved.

A Manufacturing with known manufacturing devices is made possible when the socket is rotationally symmetric with a surface and a lateral surface is formed and that the conductive layer the socket electrically contacted on its lateral surface. Due to the large, peripheral contact is also This electrical connection is very robust.

A favorable plasma development and ignition assisting hot particles emerge when the electrically conductive Layer contains a metal selected from the group which comprises Au, Pt, Cu, Ti, Zr, Hf and Al.

The upper, the charge-facing layer is additionally activated, when the electrically conductive layer at least partially is hydrogenated.

It is preferred if the recesses with a pyrotechnic effective Mass are filled.

following becomes an embodiment of the present invention described with reference to the drawing. Show it:

1 a pedestal for a detonator according to the invention;

2 : the socket off 1 with the functional layers arranged thereon; such as

3 : a prefabricated detonator with the structure according to 2 ,

The 1 shows a known base for a pyrotechnic igniter. The base is constructed rotationally symmetrical overall, wherein an annular insulating body 1 made of glass from an outer, conductive metallic ring 2 is surrounded. The insulation body 1 carries an electrode in the middle 3 , The insulation body 1 with the surrounding ring 2 and the embedded electrode 3 is gas-tight and at his in 1 top surface 4 ground substantially flat. At the bottom, the surface 4 Opposite, the ring wears 2 a pin 6 for electrical contact. Also the centrically arranged electrode 3 carries a corresponding pin 7 ,

The in 1 described socket corresponds to the state of the art.

The 2 shows the socket 1 with a layer structure arranged thereon. An insulation layer resting directly on the base 10 is made of aluminum oxide, for example, in the thin-film process. The layer is initially also in the region of the centrally arranged electrode 3 applied continuously.

After that, a second layer 12 applied as a metallic or at least conductive layer. The layer 12 overlaps laterally in the outer edge region of the ring 2 the insulation layer 10 and thereby provides in the edge region an electrical contact with the ring 2 ago. In the middle of the surface 4 is the layer 12 by means of the insulation layer 10 from the electrode 3 spaced and electrically isolated.

With a material-removing process, preferably laser ablation, are now recesses 13 from the top of the layer 12 in the area of the electrode 3 introduced the layer 12 and the insulating layer 10 push through. In the recesses are then the conductive electrode 3 and the likewise conductive layer 12 at a distance from that of preferably about 0.5 to 10 microns of the layer thickness of the insulating layer 10 is determined without, however, is a high insulating material in between. So it creates a spark gap that generates a spark and thus a usable ignition pulse when exposed to a sufficient voltage.

In a further embodiment, the recesses are provided 13 To fill with a primary pyrotechnic active mass, which is used as a charge for the ignition of further active masses at a greater distance from the recesses 13 can serve.

The 3 Finally, shows a ready-made igniter with the layer structure 2 , The base carries one in its outer area on the ring 2 fixed cap 15 , the surrounding gas-tight with the ring 2 is welded. Inside the cap 15 is a pyrotechnic active material 7 arranged, which amplifies the electrically generated ignition pulse by chemical reaction in a conventional manner.

The manufacture of the igniter so far described is preferably carried out on the basis of in 1 illustrated socket. This base is on its outside, so the cylindrical Mantelflä che of the ring 2 held, wherein the holder at least the lateral surface, but possibly also a part of the surface 4 covers. The surface 4 can then be prepared with a plasma cleaning, after which the insulation layer 10 can be applied in a thin-film process. The layer thickness is in the range of 0.2 .mu.m to 100 .mu.m, preferably between 0.5 .mu.m and 10 .mu.m.

Now the holder of the base with the insulation layer deposited thereon 10 that the electrode 3 preferably completely covered, at least partially removed, so that the insulating layer 10 surrounding metallic area of the ring 2 is free. It may, as in the 2 shown around an annular outer area of the surface 4 act. It can also be a surface 4 adjacent portion of the outer surface of the ring 2 be.

The next process step is a renewed cleaning of the now exposed and newly formed surface, preferably also in the plasma cleaning process. This will be the previously covered metallic surface of the ring 2 and the insulation layer 10 cleaned. Thereafter, in the same setting, the metal layer 12 deposited. This metal layer may also have a thickness of 1 .mu.m to 100 .mu.m. Currently, a coating of aluminum, copper, gold or platinum is preferred. An alternative embodiment provides a coating of titanium or tungsten.

In the coating, which takes place in the PVD method, a continuous conductive layer is formed on the surface of the insulation layer 10 , Next results in an electrical connection between the ring 2 as an outer conductive base part and the layer 12 but not with the electrode 3 as an inner conductive base part.

Of the Layer construction can except in the thin-film process also be done in a thick-film process, for example by printing.

The recesses 13 are now made as described above. Depending on the application, you can choose almost anything, just by the dimensions of the electrode 3 have limited diameter of about 20 microns to 1 mm. The recesses in the insulating layer 10 can also be made in other ways than by laser ablation. Thus, mechanical processing methods are known with which the material can be removed with sufficient precision. For example, a drilling technique can be used. The remaining packing, which in the 3 is also known from the prior art.

For ignition can now be a voltage pulse to the electrodes 6 and 7 be created. The tension leaves between the metallic layer 12 and the electrode 3 generate an electric field strength, which certainly auscht to sparks. This occurs within the recesses 13 a plasma, so that arise here for the ignition of a pyrotechnic active mass required conditions.

In handling during or after production of the igniter so far described is extremely robust, since in addition to the layer structure virtually no electrical contact is required. There are no exposed components. The igniter has an almost completely smooth, closed surface before being assembled. If particularly high mechanical loads are to be expected, the metallic layer can 12 also be made of a material that can be cured. Then this layer can 12 nitrated, for example, in a final manufacturing step. The resulting surface of titanium nitride, for example, will then have a hardness that will largely preclude damage even when the primers are packaged in bulk in a bag and loosely handled. Even in the prefabricated state, which in the 2 is illustrated, the ignition element is then free-flowing, without mechanical damage would be feared.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19756603 C1 [0004]

Claims (6)

Igniter for pyrotechnic active compositions with a base, the two electrically conductive areas ( 2 . 3 ), the areas ( 2 . 3 ) with an isolator ( 1 ) are insulated from each other, characterized in that an insulating layer ( 10 ) at least one of the electrically conductive regions ( 2 . 3 ), wherein an electrically conductive layer ( 12 ) with the other area ( 2 . 3 ) is electrically contacted, and wherein the insulating layer ( 10 ) and the electrically conductive layer ( 12 ) with recesses ( 13 ), which provide a spark gap between the layer ( 12 ) and the second area ( 2 . 3 ) form. Igniter according to Claim 1, characterized in that the electrically conductive layer ( 12 ) is provided with a surface protection. Igniter according to one of the preceding claims, characterized in that the base is rotationally symmetrical with an upper surface ( 4 ) and a lateral surface is formed and that the conductive layer ( 12 ) electrically contacted the base on its lateral surface. Igniter according to one of the preceding claims, characterized in that the electrically conductive layer ( 12 ) contains a metal selected from the group comprising Au, Pt, Cu, Ti, Zr, Hf and Al. Igniter according to one of the preceding claims, characterized in that the electrically conductive layer ( 12 ) is at least partially hydrogenated. Igniter according to one of the preceding claims, characterized in that the recesses with a pyrotechnic effective mass are filled.