Inflator, method of manufacturing the same and module including said inflator
10960846 ยท 2021-03-30
Assignee
Inventors
- Sebastian Bierwirth (Rechtmehring, DE)
- Achim Hofmann (Tuessling, DE)
- Hans-Peter Neumayer (Ampfing, DE)
- Dieter Spitzenberger (Kraiburg, DE)
- Franz Fuerstenberger (Taufkirchen, DE)
- Hannes Nuiding (Muehldorf Am Inn, DE)
- Dieter Leier (Haag, DE)
- Georg Schoenhuber (Oberneukirchen, DE)
- Joerg Friedrich (Munich, DE)
Cpc classification
B60R21/2644
PERFORMING OPERATIONS; TRANSPORTING
B60R21/264
PERFORMING OPERATIONS; TRANSPORTING
F42B3/04
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
B01D2279/10
PERFORMING OPERATIONS; TRANSPORTING
B01D39/12
PERFORMING OPERATIONS; TRANSPORTING
International classification
Abstract
An inflator as well as a method of manufacturing an inflator, a module including an inflator and an airbag module. In an inflator, especially for a protective device in a vehicle, comprising plural components a sealant is applied in the area of abutting components, especially a sealant which adheres to both abutting components.
Claims
1. An inflator for a protective device in a vehicle, comprising: a housing comprising a combustion chamber filled at least partially with a pyrotechnic material; at least one igniter actuatable to ignite the pyrotechnic material; one or more overflow orifices through which the pyrotechnic material in the combustion chamber is ignited in response to actuation of the igniter, wherein the overflow orifices are movable relative to the igniter in response to actuating the igniter; a cap that defines an intermediate chamber and separates the intermediate chamber from the combustion chamber, wherein the overflow orifices extend through a wall of the cap, the intermediate chamber contains a boosting charge positioned adjacent the igniter, and the igniter is configured to ignite the boosting charge, the cap being configured to move in response to igniting the booster charge; and a base that fixes the igniter to the housing, wherein the cap includes an open end fitted onto the base.
2. The inflator recited in claim 1, wherein the cap and base are configured to position the overflow orifices at an upper edge of the base when the cap is pressed onto the base.
3. An inflator according to claim 1, wherein the cap is press-fitted onto the base, the cap being movable on the base in response to activating the igniter.
4. An inflator according to claim 1, further comprising an elastic component positioned adjacent a closed end of the cap, opposite the open end of the cap.
5. An inflator according to claim 4, wherein the elastic component is configured to support the cap prior to activation of the igniter and to be compressed by the cap when the cap moves in response to actuation of the igniter.
6. An inflator according to claim 4, wherein the elastic component comprises a mesh filter material.
7. An inflator according to claim 4, wherein the elastic component comprises a recess into which the cap projects.
8. An inflator according to claim 4, wherein the elastic component is positioned adjacent a closed end of the cap and an inside of an end face of the inflator.
9. The inflator recited in claim 8, wherein the end face of the inflator comprises a bulge that provides space into which the cap can move axially.
10. An inflator according to claim 1, wherein the base is formed by injection-molding around the igniter and fixes the igniter to the inflator.
11. An inflator according to claim 1, wherein the cap forms the only partition between the intermediate chamber and the combustion chamber.
12. An inflator according to claim 1, wherein the housing comprises an orifice that extends through the housing, the base comprising a molded material that extends through the orifice and at least partially surrounds the igniter to support the igniter on the housing, the base comprising an end portion that extends into the housing, wherein the cap is pressed onto the end portion of the base so that a sidewall of the cap engages the end portion and is secured to the base.
13. An inflator according to claim 12, wherein the housing comprises a recess and the orifice is positioned in the recess, wherein the recess comprises a sidewall with a radially outward bulge that is filled with the molded material of the base, which helps secure the base and the igniter in the recess.
14. An inflator according to claim 13, wherein the recess further comprises a convex projection in the form of a circumferential bead that extends around the edge of the orifice and adjacent the bulge, wherein the molded material of the base surrounds the bead.
15. An inflator according to claim 1, wherein the cap is configured to direct combustion products from the intermediate chamber through the overflow orifices along radial paths outward from the cap into the gas-generating material in the combustion chamber, wherein the movement of the cap along the end portion of the base in response to actuation of the igniter causes the overflow orifices to also move axially so that the radial paths of the combustion products move axially with the cap.
16. An inflator according to claim 1, wherein the cap is configured to move axially in response to the igniter igniting the boosting charge in the intermediate chamber.
17. An inflator according to claim 1, wherein the housing comprises a diffuser and a closing member, the closing member comprising a recess having an annular portion surrounding the orifice, wherein the base at least partially fills the recess.
18. An inflator according to claim 1, wherein the base leaves a portion of the igniter exposed to the boosting charge in the intermediate chamber.
19. An inflator according to claim 1, wherein the cap comprises a protective film that covers and closes the overflow orifices prior to actuation of the igniter.
20. An airbag module comprising: an inflator according to claim 1, wherein the inflator comprises an external housing having a peripheral flange; an airbag having an inlet orifice defined by an orifice edge; and a clamping element connectable with the flange for clamping the orifice edge of the airbag between the clamping element and the flange.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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(14) The closing member 18 includes a circumferential upright edge 20 which is adjacent to the inside of the circumferential wall 16 of the diffuser 14 and is fixedly connected to the same by way of a weld 22. The weld 22 preferably extends along the entire contact surface between the closing shell 18 and the diffuser 14 and to the outside of the inflator 10, where it fills a groove existing between the closing member 18 and the diffuser 14. For connecting the diffuser 14 and the closing member 18 a laser welding method can be used, for instance.
(15) At the closing member side end, the circumferential wall 16 of the diffuser 14 is bent outwardly so that a planar flange 24 being horizontally circumferential along the inflator 10 is formed.
(16) The closing member 18 has a central orifice 26 which serves for receiving a pre-fabricated igniter 28. The closing member 18 has a recess 34 including an annular portion 30 toward the central orifice 26. The recess 34 is sort of an inversion of the external housing. This area of the inflator 10 is illustrated in detail in
(17) The igniter 28 is enclosed by a base 32 connecting the igniter 28 also to the closing member 18 and especially to the edge of the orifice 26 and the annular portion 30.
(18) The base 32 consists of plastic material and is injection-molded after introducing the igniter 28 into the orifice 26. During injection-molding the plastic material encloses both the major part of the igniter 28 and the edge of the orifice 26 and also completely fills the recess 34 formed by the annular portion 30 at the outside of the inflator 10 with the exception of an outwardly directed igniter plug receipt 38 into which the contact pins for an electric contacting of the igniter 28 protrude. The igniter 38 is simultaneously embedded in the base 32 during injection molding. The orifice 26 is completely closed by the base 32 and the igniter 28 and the recess 34 is so-to-speak lined by the base.
(19) In this case the igniter 28 is enclosed by the base 32 so far that merely its upper side as well as a short upper portion of an igniter cap 36 are left open.
(20) The igniter 28 preferably is a separate pre-fabricated component. The igniter cap 36 is either part of the pre-fabricated igniter 28 or a separate component placed onto the igniter 28.
(21) The igniter cap 36 in this example consists of plastic material, namely of a plastic material similar to that of the base 32, preferably of an identical plastic material. A standard material having a share of glass fiber is preferably used, wherein the glass fiber share may be, for instance, 30% by weight. The use of a similar or identical plastic material entails the fact that during injection-molding the igniter cap 36 melts completely or partly with the base 32 and in this way a tight and non-detachable connection is formed.
(22) The recess 34 can also be formed at a separate part of the inflator 10 which is connected to the external housing 12, especially to the closing member 18.
(23) At the outside of the recess 34 a circumferential indentation is formed between the closing member 18 and the base 32, which indentation is filled with a sealant 42, in this case in the form of an acrylate adhesive.
(24) The sealant 42 is selected such that it adheres both to the metal of the closing shell 18 and to the plastic material of the base 32. The sealant 42 is applied from outside after injection molding of the base 32 and is located completely outside the external housing 12 of the inflator 10 and completely in the circumferential indentation.
(25) The sealant 42 is applied in liquid or pasty form and is hardened by UV light. It has high flexibility also at low temperatures of up to 40 C. It features low viscosity so that it is easy to process, has good wetting properties both for metallic and for plastic surfaces and adheres both to metal and to plastic material.
(26) The sealant has at least one of the following properties:
(27) Breaking strength according to ISO 527 [MPa] 2-4, esp. 3;
(28) Elongation at break according to ISO 527 [%] 200-400, esp. 30040;
(29) Viscosity at 23 C. according to Brookfield Sp/U and 3/100 [mPas] 400-800, esp. 60080;
(30) Glass transition temperature (rheometer) [ C.] 10-30, esp. 204;
(31) Thermal expansion coefficient at 30-140 C. [ppm/K] 150-350, esp. 26030;
(32) Density at 23 C. [g/cm3] 0.6-1.5, esp. 1.00.1;
(33) Water absorption according to ISO 62, 24 h at 23 C. [%] 0.9-1.7, esp. 1.30.2.
(34) A dye, preferably a fluorescent dye, is added to the sealant 42. This permits simple control whether the sealing bead has been completely applied and the recess is completely filled with the sealant 42. When irradiated with UV light, it can be easily recognized due to the fluorescent dye at which position the sealant 42 is provided. If a non-fluorescent dye is used, for the same a color other than for the base 32 and the closing member 18 is chosen so that it can be recognized by way of the color whether the sealing bead is complete and circumferential.
(35) This can be checked using a camera.
(36) Prior to mounting into an airbag module, the contact pins 40 of the inflator 10 are connected via a short-circuit bridge 44. The igniter plug receipt 38, the base 32 and the sealant 42 are covered in this state by a laminate film 46 and are protected against environmental influences in this way.
(37) The wall forming the recess 34 is arc-shaped in portions in the radial direction r (cf.
(38) It is also possible to form the bulge 48 in circumferential direction intermittently and to provide only one or more separate bulges 48 along the circumference of the recess 34. The extension of the wall is shown in broken lines in
(39) In the section shown in
(40) Apart from the annular portion 30, the recess 34 includes a bottom portion 50 which is connected to the annular portion 30 toward the interior of the inflator 10. The bottom portion 50 also forms the edge of the orifice 26. At the bottom portion 50 an annularly circumferential projection 52 is formed at the edge of the orifice 26 toward the outside of the inflator (provided with reference numerals only in
(41) Both the groove 54 and the projection 52 are enclosed by liquid plastic material when the base 32 is injection-molded so that a fast and tight connection to the base 32 is formed which also withstands temperature variations and constitutes an additional support during and after solidification of the plastic material. Also the groove 54 is shown with reference numeral in
(42) Inside the external housing 12 an annular, thus substantially toroidal combustion chamber 56 is formed (cf.
(43) Toward the central axis A of the inflator 10, the combustion chamber 56 is confined by a cap 60 enclosing the igniter 28 and the portion of the base 32 located inside the inflator 10 as well as in addition a free space in the form of an intermediate chamber 62. The intermediate chamber 62 is filled with a boosting charge of known pyrotechnic gas-generating material 64.
(44) The cap 60 (cf.
(45) The upper portion of the combustion chamber 56 in
(46) The elastic component 70 has a central recess 72 into which the cap protrudes up to a step and whose upper end portion is somewhat smaller than the diameter of the cap 60 in order to counter the movement of the cap 60 by a defined moving resistance.
(47) In this case the cap 60 constitutes the only partition wall between the intermediate chamber 62 and the combustion chamber 56. It is possible that the inside of the cap 60 is lined with a protective film 74 closing the overflow orifices 66 prior to activation of the inflator 10, wherein the protective film 74 is destroyed upon ignition of the igniter 28.
(48) In the state before activation shown in
(49) A filter 76 is arranged in the combustion chamber 56 which in this case is ring-shaped, substantially cylindrical and extends in parallel to the circumferential wall 16 of the diffuser 14 at a small radial distance from the same.
(50) The filter 76 extends over the entire height of the inflator 10 and extends from the closing member 18 to the end face of the diffuser 14. The filter 76 is formed of a wire mesh including wires of different thickness.
(51) In the circumferential wall 16 of the diffuser 14 plural, in this example twelve, discharge orifices 78 are formed which are uniformly spaced along the circumference of the diffuser 14 and are arranged at an axial height. The filter 76 separates the discharge orifices 78 from the combustion chamber 56 so that the filter 76 is located upstream of the discharge orifices 78.
(52) The filter 76 is pressed into the external housing 12 with axial pretension.
(53) The filter 76 includes two axial ends 80, 82 at least one end of which is bent outwardly. In this case the bent portion forms the lower axial end 80 and the bending extends straight. In the bent portion the filter 76 has the same thickness as it has also in a central portion which is adjacent to the bent portion.
(54) In the shown example the filter 76 extends in S-shape viewed in an axial section. At the upper axial end 82, too, a slight bending is provided which extends toward the center of the inflator 10, however (indicated on the left half in
(55) At the filter 76 the radially innermost contacting position of the outwardly bent lower axial end 80 is located radially further outward than the radially outermost contacting position of the inwardly bent axial end 82 so that the end-face contact surfaces are laterally completely offset.
(56) The bent portion at the lower axial end 80 is adjacent to a corner formed by the housing of the inflator 10. In this case the housing part is formed by the closing member 18 and the lower axial end 80 of the filter 76 is adjacent to the transition from a bottom plate of the closing member 18 to the upwardly bent edge 20 of the same.
(57) At the upper axial end 82 the filter 76 is tapered, as is visible especially on the right side of
(58) This shaping permits to deform the material during axial pressing into the inflator such that no bypass is formed for particles possibly occurring during combustion of the pyrotechnic material 58.
(59) The pyrotechnic material 58 in the combustion chamber 56 is surrounded with metal on all sides, i.e. the combustion chamber wall composed of several parts consists throughout of the same material. The combustion chamber 56 is enclosed by the elastic filler 70, the filter 76, the cap 60 and the closing member 80. As stated before, all these components preferably consist of the same metal, preferred of the same steel.
(60) The discharge orifices 78 are closed prior to activation of the inflator 10 by a tamping 84 in the form of a tamping film. The tamping 84 is disposed circumferentially at the inside of the circumferential wall 16 of the diffuser 14 at the height of the discharge orifices 78 and covers all discharge orifices 78. The height of tamping 84 is approximately four times the diameter of the discharge orifices 78 in this case.
(61) The lower end of the tamping 84, viz. the end facing the closing member 18, is arranged at a distance from the weld 22 which connects the diffuser 14 to the closing member 18. The distance a from the weld 22, or in this case equivalent to the end of the upper edge 20 of the closing member 18, in the shown case amounts to approx. 5.5 mm and preferably ranges from 3 to 7 mm (cf.
(62) The external housing 12 of the inflator 10 has a relatively thin wall thickness which in the example shown here nowhere is more than 2 mm. In particular, the wall thickness of the diffuser is 1.5 mm and that of the closing member is 1.9 mm. These wall thicknesses are sufficient to withstand a combustion chamber pressure of 300 bars upon activation of the inflator 10.
(63) The diffuser 14 and the closing member 18 are connected only through the weld 22 so that said weld 22 forms the only connection between the components of the external housing 12 defining the strength. Preferably a tension rod is not provided.
(64) In this case, the ratio of the maximum combustion chamber pressure to the wall thickness preferably is between 150 and 220 bars/mm.
(65) The ratio of the entire discharge area of the inflator 10, viz. the sum of the areas of all discharge orifices 78, to the wall thickness is more than 30, especially more than 34 mm, in this case.
(66) The ratio of the diameter D of the diffuser, measured by the diameter of the circumferential wall 16, to the minimum wall thickness of the external housing is preferably less than 50 and preferably ranges from 35 to 45. The flange 24 is not taken into account when determining the diameter.
(67) The inflator 10 has substantially the shape of a flat cylinder, the ratio of the diameter D to the maximum axial height H being approx. 1.80.2, preferably 1.80.1.
(68) The flange 24 at the outer circumference of the diffuser 14 is planar but unsymmetrical (cf.
(69) In the present example three notches are spaced along the circumference of the flange 24 as mounting positioning means 86, namely at different angular distances. The angles between the notches amount, for instance, to 115 and 148 or to 93 and 109 in a different example.
(70) As an additional or alternative mounting positioning means an orifice 88 is formed as oblong hole in the flange 84. This orifice 88 is the only orifice provided in the flange 84.
(71) As a matter of course, also more or fewer notches 86 or projections instead of the notches or other suitable mounting positioning means 86 can be provided.
(72) When mounting the inflator 10 into a module, for instance an airbag module 90 shown in
(73) The orifice 88 in the flange 24 serves for defining the mounting position of an airbag 96 (indicated in
(74) The oblong hole 88 moreover can also be used for manufacturing the inflator. In particular, in different manufacturing steps the correct position of the diffuser (flange) with respect to other inflator components can be ensured by a pin in the tool head which is adapted to be engaged with the oblong hole, e.g. for orientation of the igniter pins.
(75) The airbag 96 likewise has an orifice at the orifice edge 100 (not shown) which is made to match with the orifice 88 in the flange in order to correctly position the airbag 96. The orifice 88 does not serve as screwing orifice and constitutes the only orifice at the orifice edge 100 of the airbag 96. This means that the airbag 96 is clamped between the flange 24 and the holding element 92 by fastening means, usually stud bolts, which are located outside the flange 24. Thus the flange surface is optimized.
(76) For fastening the airbag module 90 the holding element 92 includes fastening bolts 102, four of them in the shown example, through which the airbag module 90 can be connected to a vehicle (not shown). The fastening bolts 102 are adjacent to the outer circumference of the flange 24 but offside the area of the mounting positioning means 86.
(77) The flange 24 is circumferential and planar.
(78) It forms an annular clamping surface for the airbag 96, wherein the width B of the flange (the transition radius between the planar flange portion and the circumferential wall of the diffuser 14) is between 5 and 12%, preferably between 8 and 11% of the maximum diameter D of the external housing 12.
(79) The width B of the clamping surface in the radial direction r ranges from 5 to 8.5, preferably from 5.5 to 7.5 mm (cf.
(80) At the holding element 92 opposed to the clamping surface a clamping portion 104 is defined at the flange 24 (cf.
(81)
(82) The upper end of the igniter in
(83) In the contacting area 140 located in the vicinity of the orifice 120 or the edge 122 between the plastic base 116 and the first component 112, the latter is provided with an adhesive film 142 which was applied already before injection-molding the plastic base 116. The adhesive film 142 only covers a portion of the injection-molded area of the first component 112. The adhesive film 142 is fully circumferential around the edge 122, however.
(84) The adhesive film 142 is a pre-fabricated component and consists of a plastic film 144 and an adhesive layer 146 directly and evenly applied thereto (cf.
(85) The material used for the plastic film 144 in this example is the same material as used for the plastic base 116. It is also possible, however, to use a different material which is suited for establishing a tight connection with the material of the plastic base 116. This can be a thermoplastic elastomer, for instance.
(86) The adhesive film 142 serves as a bonding bridge between the plastic base 116 and the first component 112.
(87) Deviating from the illustrated configuration, the surface of the adhesive film 142 can also extend over the entire injection-molded portion of the component 112 or project from the same, as a matter of course. It is also possible to provide an appropriate adhesive film also between the second component 114 and the plastic base 116.
(88) The inflator 110 is manufactured as follows: To start with, the first component 112 (the inflator housing) as well as the second component 114 (the igniter) are provided and the first component 112 is provided with the adhesive film 124 in the later connecting area of the components (corresponding to the contacting area 140) by gluing one or more appropriately cut pieces of the adhesive film 142 with the adhesive layer 146 onto the corresponding positions of the first component 112, in this case on both sides in the area of the edge 122.
(89) The adhesive of the adhesive layer 146 can be activated or hardened already now by the pressure during gluing. Alternatively, it is activated or hardened by heating, which is effectuated e.g. during injection-molding by the heat influence of the liquid plastic material.
(90) After the adhesive film 142 was glued onto the first component 112, the second component 114 is positioned relative to the first component 112, and both components 112, 114 are jointly surrounded by injection-molded forming the plastic base 116, wherein both components 112, 114 are embedded at least partly in the plastic base 116.
(91) During injection-molding the material of the plastic film 144 combines with the injected plastic material by the fact that a surface layer of the plastic film 144 melts in a connecting zone 148 with the plastic base 116. As an alternative, in the connecting zone 148 also a chemical reaction can take place between the material of the plastic film 144 and that of the plastic base 116, which reaction tightly and non-detachably interconnects the plastic film 144 and the plastic base.
(92) The adhesive layer 146 forms a bonding bridge between the first component 112 and the plastic base 116, the bonding bridge being resilient and/or plastically deformable so that tensions and shear forces occurring due to different thermal expansion coefficients of the different materials are compensated. The adhesive layer 146 also acts as a packing between the first component 112 and the plastic base 116.
(93) All described features can be combined with or exchanged for one another at the discretion of those skilled in the art.