GAS GENERATOR FOR A VEHICLE OCCUPANT SAFETY SYSTEM, AIRBAG MODULE AND VEHICLE OCCUPANT SAFETY SYSTEM COMPRISING A GAS GENERATOR OF THIS TYPE, AND PRODUCTION METHOD

Abstract

The invention relates to a gas generator (10) for a vehicle occupant safety system comprising an outer casing (20) and a filter structure (30) for purifying and/or cooling gas released inside the outer casing (20), wherein the filter structure (30) is integrated in the outer casing (20). The invention further relates to an airbag module and a vehicle occupant safety system comprising said gas generator as well as to a manufacturing method.

Claims

1. A gas generator (10) for a vehicle occupant safety system comprising an outer casing (20) and a filter structure (30) for purifying and/or cooling a gas released inside the outer casing (20), wherein the filter structure (30) is integrated in the outer casing (20).

2. The gas generator (10) especially according to claim 1, wherein at least one gas generator component, especially an outer casing (20) and/or an ignition unit (40) and/or a filter structure (30) of the gas generator (10), is manufactured by a 3-D printing method, especially a 3-D screen printing method.

3. The gas generator (10) according to claim 1, wherein the filter structure (30) includes channels (21), especially mazelike or meandering channels (2) extending through the outer casing (20).

4. The gas generator (10) according to claim 1, wherein the filter structure (30) is formed integrally with the outer casing (20).

5. The gas generator (10) according to claim 1, wherein the outer casing (20) has a cylindrical and/or polygonal circumferential wall (22) in which the filter structure (30) is formed.

6. The gas generator (10) according to claim 5, wherein the circumferential wall (22) includes oppositely arranged plate elements (23) having a planar outer surface (25) and a ribbed inner surface (31), wherein the ribbed inner surfaces (31) are facing each other.

7. The gas generator (10) according to claim 6, wherein the circumferential wall (22) has land elements (24) with two-sided rib structure (32) which are arranged between the ribbed inner surfaces (31) of the plate elements (32).

8. The gas generator (10) according to claim 7, wherein the land elements (24) are arranged offset in the circumferential direction relative to the plate elements (23) and extend through gas outlet openings (26) of the circumferential wall (22).

9. The gas generator (10) according to claim 7, wherein, the rib structure (32) of the land elements (24) engages rack-like in the ribbed inner surfaces (31) of the plate elements (23) such that released gas may flow around individual ribs (33) of the land elements (24) and of the plate elements (23).

10. The gas generator (10) according to claim 5, wherein the outer casing (20) includes plural ring segments (27) which are coaxially superimposed to form the circumferential wall (22).

11. The gas generator (10), especially according to claim 1, comprising an outer casing (20) having gas outlet openings (26) which are closed by a tamping (28), wherein the tamping (28) is formed integrally with the outer casing (20).

12. The gas generator (10) according to claim 11, wherein the tamping (23) is formed by an area of reduced wall thickness of the circumferential wall (22).

13. The gas generator (10) according to claim 1, wherein a retaining flange (29) which is formed integrally with the outer casing (20) and is manufactured especially integrally with the outer casing (20) by the 3-D printing method.

14. An airbag module, comprising a gas generator (10) according to claim 1.

15. A vehicle occupant safety system comprising a gas generator (10) and/or an airbag module according to claim 1.

16. A method of manufacturing a gas generator component, especially a gas generator (10) and/or an airbag module, preferably according to claim 1, in which the gas generator component, especially an outer casing (20) and/or an ignition unit (40) of a gas generator (10), is composed in layers by means of a 3-D printing method.

17. The method according to claim 16, wherein the 3-D printing method is a 3-D screen printing method.

18. The method according to claim 16, wherein the screen printing method comprises: providing a screen print mask (52); applying a printable suspension of a material powder to the screen print mask (52), wherein the suspension is applied especially under pressure; and heating the printable suspension for melting the material powder.

19. The method according to claim 18, wherein the screen print mask (52) is produced automatically based on a computer model.

20. The method according to claim 16, wherein at least two material powders different from each other are applied to the screen print mask (52) such that two components of the gas generator component including materials different from each other are manufactured in a joint process step.

21. The method according to claim 20, wherein the different material powders are a metal powder for manufacturing electrically conductive components, and a quartz sand powder or plastic powder for manufacturing an insulation member (41).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Hereinafter the invention shall be illustrated in detail by way of exemplary configurations with reference to the enclosed schematic drawings, in which:

[0038] FIG. 1a is a perspective view of an outer casing of a gas generator according to the invention in accordance with a preferred embodiment;

[0039] FIG. 1b is a detailed view of the outer casing according to FIG. 1;

[0040] FIG. 2 is another perspective view of the outer casing according to FIG. 1, wherein the internal structure of the outer casing is visible;

[0041] FIG. 3 is a detailed view of the outer casing according to FIG. 2;

[0042] FIG. 4 is a cross-sectional view of a gas generator according to the invention in accordance with another preferred embodiment, wherein the gas outlet openings in an outer casing of the gas generator are closed by a tamping formed integrally with the outer casing;

[0043] FIG. 5 is a detailed view of the gas generator according to FIG. 4;

[0044] FIG. 6 is a perspective view of an outer casing of a gas generator according to the invention in accordance with another preferred embodiment, wherein a retaining flange formed integrally with the outer casing is provided;

[0045] FIG. 7 is a bottom view of the outer casing according to FIG. 6;

[0046] FIG. 8 is a cross-sectional view of an ignition unit of a gas generator according to a preferred embodiment, wherein the ignition unit is manufactured by a 3-D printing method; and

[0047] FIG. 9 is a representation of the manufacturing method according to the invention in accordance with a preferred embodiment.

DESCRIPTION

[0048] FIG. 1a shows a perspective view of an outer casing 20 for a gas generator, especially for a pyrotechnical gas generator, 10. The outer casing 20 supports an integrated filter structure 30 which filter structure 30 is suited for cooling and/or purifying gas released inside the outer casing 20 when it flows out of the pyrotechnical gas generator 10. Specifically, slag or particles can be deposited and, resp., filtered out of the gas by the filter structure 30.

[0049] Concretely speaking, FIG. 1a illustrates a cylindrical circumferential wall 22 of the outer casing 20. In general, further wall elements may be formed integrally with the circumferential wall 22 so as to form the outer casing 20. The outer casing 20 may further have a bottom 34 and/or a cover 35, for example, with each of the bottom 34 and the cover 35 covering and, resp., closing an axial end face of the cylindrical circumferential wall 22. An example of a completely closed outer casing 20 is shown in FIG. 4.

[0050] The filter structure 30 is formed by plural channels 21 extending through the circumferential wall 22. The channels are formed to be substantially mazelike or meandering so that the gas flowing through the circumferential wall 22 covers a relatively large distance. The course of the gas flow is exemplified in FIG. 1b by respective arrows.

[0051] The channels 21 are confined by meshing ribs 33 which are arranged in different components of the circumferential wall 22. The circumferential wall 22 includes plural plate elements 23 extending over the outer periphery of the circumferential wall 22. The plate elements 23 are curved so that in total a smooth cylindrical outer circumferential surface of the circumferential wall 22 is formed. On their inner surface 31 the plate elements 23 include ribs 33. Each of the ribs 33 has a substantially rectangular cross-sectional profile and extends over the entire height of the plate element 23. Opposed to the outer plate elements 23, inner plate elements 23 are provided which are curved in the opposite direction in contrast to the outer plate elements 23. Especially, the inner plate elements 23 have a planar outer surface 25 which is curved so that in total a cylindrical inner circumferential surface of the circumferential wall 22 is resulting. On their inner surface 31, the inner plate elements 23 equally comprise ribs 33. The inner and outer plate elements 23 are arranged relative to each other such that the ribs 33 thereof are facing each other. In particular, the ribs 33 are aligned with each other. This applies especially in the radial direction related to the center of the circumferential wall 22.

[0052] Between the plate elements 23, especially between the inner surfaces 31 thereof, land elements 24 are further integrated in the circumferential wall 22. The land elements 24 include a two-sided rib structure 32. The rib structure 32 is formed complementary to the arrangement of the ribs 33 of the plate elements 23. The ribs 33 of the plate elements 23 thus engage in the rib structure 32. The engagement of the ribs 33 in the rib structure 32 is selected so that a gap is formed between the rib structure 32 and the engaging ribs 33. The gap preferably has a constant width and forms a flow channel and, resp., the channel 21 for the flow of gas. Both the ribs 33 and the rib structure 32 extend over the entire height of the circumferential wall 22 and over the entire height of a ring segment 27 of the circumferential wall 22.

[0053] The circumferential wall 22 may be composed of plural ring segments 27 that are superimposed and are tightly interconnected. The ring segments 27 may be integrally interconnected. In other words, the circumferential wall 22 may be formed in one piece. In any case, between individual ring segments 27 separation trays in the form of ring plates 36 are provided for subdividing the channels 21 in the longitudinal direction of the circumferential wall 22. In FIG. 1a a ring plate 36 closing the circumferential wall 22 is shown. Such ring plates 36 are preferably arranged and, resp., formed also between the individual ring segments 27.

[0054] It is further evident from FIG. 1a that the circumferential wall 22 has plural window-like gas outlet openings 26. The gas outlet openings 26 are preferably formed in the plate elements 23 and provided between the plate elements 23, respectively. In general, the gas outlet openings 26 extend completely through the circumferential wall 22. For preventing direct gas flow through the gas outlet openings 26 the land elements 24 having the rib structure 32 are arranged offset relative to the plate elements 23 so that the land elements 24 close the gas outlet openings 26 and, resp., extend through the gas outlet openings 26. In this way, the outflowing gas is forced to meander through the channels 21 before it leaves the outer casing 20 and the gas generator 10 through the gas outlet openings 26.

[0055] In FIG. 2 another perspective view of the outer casing 20 is shown, with the upper ring plate 36 being removed. The filter structure 30 formed by plural meandering channels 21 is clearly visible. It is especially visible that the circumferential wall 22 has plural plate elements 23 which land elements 24 extending there between. Each of the plate elements 23 and the land elements 24 comprise ribs 33 and, resp., a rib structure 32 which are in mesh and thus form the channels 21.

[0056] FIG. 3 illustrates a detailed view of the outer casing 20 according to FIG. 2, likewise in perspective representation. It is clearly visible in FIG. 3 that the land elements 24 extend transversely through the gas outlet openings 26 and thus block a direct outflow path for the gas. Rather, the outflowing gas is forced to flow through the meandering channels 21. Due to the larger surface provided in this way which is passed by the gas an especially good heat exchange is obtained. Accordingly, the gas is cooled. In addition, the meandering channels 21 cause filtering of particles and/or slag from the gas so that finally purified and cooled gas flows out of the gas outlet openings 26.

[0057] FIG. 4 illustrates a cross-sectional view of a gas generator 10 comprising an outer casing 20. The outer casing 20 includes a circumferential wall 22 as well as a cover 35 and a bottom 34. In the bottom 34 an ignition unit 40 is integrated or injected. The ignition unit 40 includes an igniter 42 comprising electric contact pins 43. The electric contact pins 43 project from the outer casing and are sheathed by an insulation member 41. The igniter 42 is embedded along with the contact pins 43 especially in a plastic base 56. The igniter 42 is embedded along with the contact pins 43 preferably by injecting plastic material around the igniter 42 and the contact pins 43. During injection at the same time the ignition unit 40 is connected to the outer casing 20, especially by form fit.

[0058] The igniter 42 extends into an ignition chamber 44 in which an ignition charge may be arranged. The ignition chamber 44 is separated from a combustion chamber 46 by an inner casing 45. The combustion chamber 46 is formed substantially by the interior of the outer casing 20. A filter structure 30 may be disposed in the combustion chamber 46. In the representation according to FIG. 4, the filter structure 30 is formed separately from the outer casing 20. It is also possible to integrate the filter structure 30 into the outer casing 20, as is shown in FIGS. 1a to 3, for example.

[0059] Preferably in the combustion chamber 46 a propellant is arranged which is indicated by individual pellets 47 in FIG. 4. For triggering the gas generator an electric signal is transmitted to the igniter 42 which then ignites an ignition charge disposed in the Ignition chamber 44. A gas is formed which passes via ignition chamber openings 48 arranged in the inner casing 45 into the combustion chamber 46. There the propellant is ignited and further gas is generated which is filtered by the filter structure 30 and now acts on the outer casing 20 under pressure.

[0060] In order to discharge the gas generated in the gas generator 10, for example to an airbag, the outer casing 20 further includes gas outlet openings 26. The gas outlet openings 26 are preferably configured in the circumferential wall 22. The gas outlet openings 28 are initially closed by a tamping 28 so as to protect the propellant disposed in the combustion chamber 46 against moisture or other environmental influences. In order to release the gas it is useful to remove or eliminate the tamping 28. Usually this is done by destroying the tamping 28.

[0061] In gas generators known so far from practice the tamping 28 is formed by a film applied to the gas outlet openings 26. The film ruptures under the influence of the gas pressure and thus releases the gas outlet openings 26. In the embodiment according to FIGS. 4 and 5, with FIG. 5 showing a detailed view of the gas outlet opening 26, it is provided, on the other hand, to form the tamping 28 integrally with the circumferential wall 22. The gas outlet opening 26 and, resp., the tamping 28 are preferably formed by an area of the circumferential wall 22 having a reduced wall thickness. In the area of the gas outlet opening 26 the circumferential wall 22 thus has a strongly reduced wall thickness, with the wall thickness in the area of the gas outlet opening 26 being dimensioned so that the circumferential wall 22 ruptures in the area of the gas outlet opening 26 as soon as the gas in the combustion chamber 46 generates a sufficiently high pressure. In other words, the tamping 28 is formed by the circumferential wall 22 itself, wherein in the area of the gas outlet opening 26 the circumferential wall 22 has a wall thickness that is smaller than outside the gas outlet opening 26. Especially the circumferential wall 22 has a pressure-stable wall thickness outside the gas outlet opening 26 and has a pressure-sensitive wall thickness inside the gas outlet opening 26.

[0062] The outer casing 20 of the gas generator 10 may be integrally formed, as exemplified in FIG. 4. Alternatively, it is possible to design the outer casing 20 in several parts, especially in two parts. An upper part 37 of the outer casing may comprise the circumferential wall 22 and the cover 35 and a lower part 38 may form the bottom 34. FIG. 6 illustrates an embodiment of an upper part 37 of an outer casing 20. The upper part 37 comprises a circumferential wall 22 including gas outlet openings 26 and a cover 35. The gas outlet openings 26 may be closed by a tamping 28 integrated in the circumferential wall 22. The tamping 28 may be formed especially integrally with the circumferential wall 22, as shown in FIGS. 4 and 5. It may be further provided that the outer casing 20, especially the circumferential wall 22, has an integrated filter structure 30 analogously to the embodiment according to FIGS. 1a to 3.

[0063] The upper part 37 according to FIG. 6 further comprises a retaining flange 29 which is annularly connected to the circumferential wall 22. The retaining flange 29 extends radially outwardly related to the longitudinal axis of the circumferential wall 22. In total, the upper part 37 of the outer casing 20 is hat-shaped and has a hat-shaped cross-sectional profile, respectively. The retaining flange 29 serves for mounting the outer casing 20 and, resp., the gas generator 10 in an airbag module.

[0064] FIG. 7 illustrates a bottom view of the upper part 37 according to FIG. 6. It is visible that the upper part 37 has plural notches 39 in the retaining flange 29. The notches 39 are substantially V-shaped and are spread irregularly along the periphery of the retaining flange 29. The notches 39 serve for aligning the upper part 37 and, resp., the entire gas generator 10 during mounting. This ensures that the gas generator 10 can be assembled at the correct orientation. Furthermore, the retaining flange 19 has a slotted hole 4 which serves for screw-fixing the gas generator 10, for example.

[0065] In FIG. 8 a cross-sectional view of an ignition unit 40 is illustrated which may constitute a gas generator 10 in connection with any one of the outer casings 20 according to FIGS. 1a to 7. In particular, FIG. 8 shows an igniter 42 of the ignition unit 40. The igniter 42 has two contact pins 43 embedded in an insulation member 41. The insulation member 41 may comprise plural elements. Specifically, the insulation member 41 may have a plastic base 56 which surrounds the entire igniter 42. In addition, the insulation member 41 may comprise a pressure glazing 57 disposed between the individual contact pins 43 and a metal ring 48 so as to electrically insulate the contact pins 43 and the metal ring 58 against each other. Preferably one of the contact pins 43 is directly connected to the metal ring 58, with the metal ring 58 being insulated against the other contact pin 43 by the pressure glazing 57. Nevertheless, an electric connection between the metal ring 58 and a contact pin 43 is provided by means of a bridge wire 59 which glows upon activation and thus ignites a pyrotechnical charge 11 disposed beneath a first cap 12. A second cap 13 extends over the first cap 12 at a distance from the first cap 12. The clearance between the first cap 12 and the second cap 13 may be formed by the ignition chamber 44 and correspondingly may accommodate an ignition charge.

[0066] In FIG. 9 a preferred manufacturing method for the outer casing 20 of a gas generator 10 is schematically shown. The preferred manufacturing method is a 3-D printing method which enables especially simple and quick manufacture of even complex structures.

[0067] The 3-D printing method preferably is a 3-D screen printing method. The starting material for the 3-D printing method is a material powder provided preferably as a suspension. The suspension on the one hand comprises the material powder and on the other hand a binder, wherein the binder may be present in liquid form. By mixing the binder with the material powder a suspension is formed which is applied via a mask to a substrate and, resp., an already printed layer located there beneath. The material powder used may be both a metal powder and a plastic powder. Other material powders are possible, If is especially imaginable to use quartz sand powder to finally manufacture a 3-D printed part from glass.

[0068] The manufacturing method starts with manufacturing a mixture of material powder and binder. The suspension of material powder and binder then is applied in layers by means of screen print. In this way, spatial structures are formed. Finally, the printed component part is subjected to heat treatment.

[0069] The material powders used preferably are metal powders, wherein especially stainless steels, copper, titanium, hard metals and generally light metals and sintered metals may be used.

[0070] In the preferred three-dimensional screen printing method, the screen print mask 52 is preferably produced directly from a CAD model 53 which CAD model 53 is produced at a CAD computer 50. A printable compound of binder and material powder is applied to the screen print mask 52 with the aid of a scraper 54 under the influence of pressure. Preferably the corresponding screen print system has a suspension reservoir 51 from which the suspension of material powder and binder can be directly taken. By repeated application of individual screen print layers, with different screen print masks 52 where appropriate, a spatial structure is produced. Said spatial structure may form the outer casing 20 of the gas generator 10, for example.

[0071] Especially the outer casing 20 may have an integrated filter structure 30, as is exemplified in FIGS. 1a to 3. It is also possible that, alternatively or additionally, the outer casing 20 includes a circumferential wall 22 comprising a tamping 28 integrated in one piece (FIGS. 4 and 5).

[0072] Moreover, the three-dimensional structure produced in screen printing may constitute an upper part 37 of an outer casing 20 having an integrally formed retaining flange 29. Finally, it is also possible to produce a three-dimensional structure forming an ignition unit 40 by screen printing. For the ignition unit 30 especially different material powders and different suspensions of material powder and binder may be used so as to simultaneously manufacture both the metal structures which are electrically conducting and the insulation member 41. Both the metal ring 58 and the contact pins 43 and the pressure glazing 57 can be manufactured by the 3-D screen printing method. The screen printing method may thus be carried out simultaneously with plural materials, for example metal and glass. In this case the pressure glazing 57 is not a pure pressure glazing but a 3-D manufactured glass member.

[0073] After composing the spatial structure in layers by screen printing a heat treatment by means of a heat source 55 is carried out so as to harden and, resp., structurally stabilize the outer casing 20 and/or a pole member comprising the metal ring 58, the (pressure) glazing 57 and the contact pins 43, for example.

[0074] In general, it is referred to the fact that the 3-D printing method described here, especially the three-dimensional screen printing method, can be used for manufacturing the outer casing 20 according to FIGS. 1 to 7 and for manufacturing the ignition unit according to FIG. 8. In particular, the embodiment according to FIGS. 1a to 3, but also the embodiment according to FIGS. 4 and 5, are disclosed in the present application even separately from the manufacturing method. In other words, the outer casing 20 according to FIGS. 1a to 3 can be manufactured both conventionally, for instance by a machining method and/or a casting method, and by means of the 3-D screen printing method. This applies mutatis mutandis to the outer casing 20 according to FIGS. 4 and 5 which is manufactured, on the one hand, by machining and/or casting, but preferably by the 3-D screen printing method which is equally described within the scope of the application.

LIST OF REFERENCE NUMERALS

[0075] 10 gas generator

[0076] 11 pyrotechnical charge

[0077] 12 first cap

[0078] 13 second cap

[0079] 20 outer casing

[0080] 21 channel

[0081] 22 circumferential wall

[0082] 23 plate element

[0083] 24 land element

[0084] 25 outer surface

[0085] 26 gas outlet opening

[0086] 27 ring segment

[0087] 28 tamping

[0088] 29 retaining flange

[0089] 30 filter structure

[0090] 31 inner surface

[0091] 32 rib structure

[0092] 33 rib

[0093] 34 bottom

[0094] 35 cover

[0095] 36 ring plate

[0096] 37 upper part

[0097] 38 lower part

[0098] 39 notch

[0099] 40 ignition unit

[0100] 41 insulation member

[0101] 42 igniter

[0102] 43 contact pin

[0103] 44 ignition chamber

[0104] 45 inner casing

[0105] 46 combustion chamber

[0106] 47 pellet

[0107] 48 ignition chamber opening

[0108] 49 slotted hole

[0109] 50 CAD computer

[0110] 51 suspension reservoir

[0111] 52 screen print mask

[0112] 53 CAD model

[0113] 54 scraper

[0114] 55 heat source

[0115] 56 plastic base

[0116] 57 pressure glazing

[0117] 58 metal ring

[0118] 59 bridge wire