DE20302629U1 - Gas generator comprises has first and/or second section of housing designed so that in event of relative movement of housing sections in relation to one another a minimum value of variable flow passage is maintained - Google Patents

Abstract

The gas generator comprises a housing (20) with a first (22) and a second section (24), one or both of which have spacing means (44) which are designed so that in the event of relative movement of the housing sections in relation to one another a minimum value of the variable flow passage is maintained. An overflow opening formed by the two housing sections is completely closed before the activating of the propellant and opens after its activation, whereby the whole fluid flow is through the overflow opening.

Description

Gas generator

The invention relates to a gas generator with a housing and fuel introduced into the housing, wherein the fuel releases a pressurized fluid after activation, and wherein the housing has a first and a second housing part which are movable relative to one another under pressure and form an overflow opening with a pressure-dependent variable flow cross-section.

Such a gas generator is described, for example, in US 5,951,040. Gas generators of this type are used in vehicle occupant restraint systems, for example to inflate airbags or activate belt tensioners. If a sensor determines that unusual acceleration values are present or if it detects an accident, a propellant charge is ignited, releasing a fluid under pressure. The housing of the gas generator is deformable depending on the pressure of the released fluid, with the housing parts moving against each other depending on the pressure of the fluid and releasing an overflow opening. Essentially the entire fluid flow flows through the overflow opening. The flow cross-section of the overflow opening increases as the pressure of the fluid increases.

The invention has the task of optimizing the outflow behavior of such a gas generator and in particular of preventing blockage of the fluid flow. This is achieved in a gas generator of the type mentioned at the beginning by

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This is achieved by the first and/or the second housing part having spacing means, the spacing means being designed such that when the housing parts move relative to one another, a minimum value of the variable flow cross-section is maintained. In other words, this means that the two housing parts, which lie gas-tight against one another when the gas generator is at rest, are deformed after the gas generator is activated so that the overflow opening is opened. The spacing means guarantee that the fluid flows out of the gas generator because they prevent the overflow opening from being closed again and the fluid flow being blocked as a result of further deformation of the housing parts. This also enables a mechanically weaker design of the housing because after the gas generator is activated, a flow cross-section of the overflow opening that is sufficiently large for the generated fluid to escape is maintained, even if the housing parts are pressed against one another by the high pressure in the gas generator.

If the first and second housing parts are constructed essentially radially symmetrically, this is particularly advantageous since the pressure of the released fluid can then act evenly on the housing parts and thus an overload of individual housing sections is avoided.

Preferably, the first and the second housing part form a substantially annular overflow opening, since in this case a uniform outflow of the released fluid from the gas generator into the vehicle occupant restraint system is possible.

It is also particularly advantageous if the first and second housing parts form a common first contact area before the fuel is activated, with the common first contact area additionally secured with an adhesive connection. The adhesive connection guarantees an even higher gas-tightness of the gas generator housing when at rest. This prevents the penetration of moisture or other substances that have an adverse effect on the function of the gas generator.

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In a preferred embodiment, the spacing means are designed as beads. These can be incorporated into the housing parts in a particularly simple manner and also ensure further stiffening of the component. The fluid produced can then exit the housing through sections of the overflow opening formed in the area between the beads. The first housing part can be a cover that closes off the second housing part, for example a combustion chamber wall. The beads are then preferably arranged in an area of the cover that is adjacent to the first contact area between the cover and the second housing part.

A further preferred embodiment is one in which the spacing means are designed as grooves or are ribs on the first and/or second housing part. The grooves can be produced in a simple and cost-effective manner by milling on one of the housing parts, the ribs can be very easily connected to one of the housing parts, e.g. by welding, or in another way.

15 can be molded.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings, in which:

- Figure 1 shows a gas generator according to the invention;

- Figure 2 is a sectional view of a housing of a gas generator according to the

State of the art;

- Figure 3 shows a sectional view of the housing of the gas generator of Figure 1 with the gas generator activated in a first embodiment of the invention;

- Figure 4 is a plan view of the gas generator of the first embodiment;

- Figure 5 is a perspective view of the housing of the gas generator of the

first embodiment;

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- Figure 6 is a perspective view of a second embodiment of the housing of the gas generator;

- Figure 7 is a sectional view of the second embodiment of the housing of the gas generator;

- Figure 8 is a perspective view of a third embodiment of the housing of the gas generator; and

- Figure 9 is a sectional view of the third embodiment of the gas generator housing.

The figures show a gas generator 10 which in terms of structure and function essentially corresponds to the gas generator described in US 5,951,040.

Figure 1 shows the gas generator 10 with a central igniter chamber 12, in which two igniters 14 are arranged. Alternatively, the igniter chamber 12 can also have just one igniter. The igniter chamber 12 is enclosed by an inner wall 15 in which there are channels 16, only one of which is shown here. The channels 16 establish a connection between the igniter chamber 12 and an outer chamber 18. The igniter chamber 12 and the outer chamber 18 contain fuel (not shown). The inner wall 15 is connected to an igniter flange 19 in which the igniters 14 are fastened. The igniters 14 and the chambers 12, 18 are enclosed by a multi-part housing 20.

The housing 20 is essentially constructed from three housing parts 22, 24, 26.

The first bell-shaped housing part 22 comprises a cover section 28, a wall section 30 circumferentially delimiting the generator with gas outlet openings 32 and a flange section 34, which can be used to attach the gas generator to a generator carrier (not shown). In the transition area between the cover section 28 and the wall section 30 of the first housing part 22, beads 44 are formed as spacer elements, which extend into the

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extend into the interior of the housing. In a variant (not shown), the beads 44 can also be formed on the outside.

The second housing part 24 is essentially a cylindrical ring that circumferentially delimits the chamber 18. At its end facing the first housing part, it forms an end section 36 that rests against the cover section 28 in a first contact area 38. In addition, the connection between the end section 36 and the cover section 28 is secured by an adhesive connection. Between the wall section of the first housing part 22 and the second housing part 24 there is an outflow area 39 through which a fluid connection is established from the chambers 12, 18 to the gas outlet openings 32.

The third housing part 26 also has a cylindrical wall section 40 and a base section 42. The wall section 40 of the third housing part is arranged between the wall section 30 of the first housing part and the second housing part 24, the base section 42 forms part of the underside of the gas generator 10 and receives the igniter flange 19 with the igniters 14.

In Figure 2, the housing 20 of a gas generator according to the prior art with the housing parts 22, 24, 26 is shown enlarged in two different positions (position I = dashed, position II = solid), the meaning of which is explained below.

Figure 3 shows an enlarged section of the housing 20 with the three housing parts 22, 24, 26. The position of the end section 36 of the second housing part 24 corresponds here to that of position II in Figure 2. The end section 36, however, only partially rests against the beads 44 on the cover section 28, forming second contact areas 38'. Between the second contact areas 38', an overflow opening 46 with opening sections 46a is formed, via which the outer chamber 18 and the outflow area 39 are in fluid communication, as symbolized by the arrow A.

In the variant (not shown) of the outwardly formed beads 44, contact between the

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End section 36 and the cover section 28. The overflow opening 46 with the opening sections 46a, via which the outer chamber 18 and the outflow region 39 are in fluid communication, is formed between the second contact regions 38'.

The formation of the beads 44 is shown in detail in Figures 4 and 5.

A bead 44 (see Figure 5) is arranged in the transition region between the cover section 28 and the wall section 30 of the first housing part 22 between two gas outlet openings 32.

The following describes how the gas generator works.

In Figure 2, the starting positions I of the housing parts 22, 24, 26 of the inactive gas generator are shown in dashed lines. When one or two of the igniters 14 are ignited, the pressure in the igniter chamber 12 increases greatly and the cover section 28 of the first housing part 22 is raised via mechanical transmission means (not shown), whereby the adhesive connection is released (see Figure 2, item II). At the same time, released gas flows through the channels 16 into the outer chamber 18. Due to the high pressure in the outer chamber 18, the second housing part 24 and in particular the end section 36 can be displaced radially outwards into the transition area between the cover section 28 and the wall section 30 if the wall thickness is too small; the position reached after this displacement is marked II in Figure 2. In gas generators according to the prior art (Figure 2), after activation of the gas generator, the overflow opening between the first housing part 22 and the second housing part 24 can become blocked and the gas can be prevented from escaping from the gas generator.

In the gas generator according to the invention, as can be seen in Figure ¹ 3, the end section 36 of the second housing part 24 is also displaced into the transition area between the cover section 28 and the wall section 30 after the activation of the gas generator; however, due to the formation of the beads 44, the end section 36 only rests partially against the cover section 28 and

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ensures that a minimum value of a flow cross-section is maintained. This ensures that gas released from the outer chamber 18 can pass through the overflow opening 46 in the direction of arrow A into the outflow area 39 in order to then be able to leave the gas generator via the gas outlet openings 32 and flow into an airbag or into another vehicle occupant protection device (not shown).

A second embodiment of the invention is shown in Figures 6 and 7. The second housing part 24 here has grooves 48 on an outer wall 47 in the region of the end section 36.

In the resting state before the gas generator is activated, the end section 36 rests on the cover section 28 in a gas-tight connection (compare position I in Figure 2). With regard to the function of the gas generator, reference is made to the explanations for the first embodiment until the end section 36 of the second housing part 24 is moved into the transition area between the cover section 28 and the wall section 30 (position II in Figure 2). Due to the grooves 48, in the second embodiment the end section 36 in position II only rests on the cover section 28 in the second contact areas 38'. Released gas can pass from the outer chamber 18 through the overflow opening 46 in the direction of arrow A into the outflow area 39 and then reaches the gas outlet openings 32 of the gas generator.

In the third embodiment shown in Figures 8 and 9, short, spaced-apart ribs 50 are formed on the outer wall 47 of the second housing part 24 in the region of the end section 36. Alternatively, the ribs can also be formed as insert components in the transition region between the cover section and the wall section of the first housing part.

In this embodiment, too, the end section 36 rests in a gas-tight connection on the cover section 28 in the resting state before the activation of the gas generator (see position I in Figure 2). With regard to the function in the initial phase after the activation of the gas generator, reference is also made to the

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Description of the first embodiment. In the third embodiment, after activation of the gas generator, the end section 36 rests with the ribs 50 in the second contact areas 38' on the transition area between the cover section 28 and the wall section 30. The open areas between the ribs 50 allow gas from the outer chamber 18 to safely reach the gas outlet openings 32 through the overflow opening 46 in the direction of arrow A via the outflow area 39.

Claims (12)

1. Gas generator ( 10 ) with
a housing ( 20 ) and fuel introduced into the housing,
wherein the fuel releases a pressurized fluid upon activation,
and wherein the housing ( 20 ) has a first ( 22 ) and a second housing part ( 24 ) which are movable relative to one another under pressure and form an overflow opening ( 46 ) with a pressure-dependent variable flow cross-section,
characterized in that the first ( 22 ) and/or the second housing part ( 24 ) have spacing means ( 44 , 48 , 50 ), wherein the spacing means ( 44 , 48 , 50 ) are designed such that in the event of relative movement of the housing parts ( 22 , 24 ) to one another, a minimum value of the variable flow cross-section is maintained. 2. Gas generator according to claim 1, characterized in that the overflow opening ( 46 ) is completely closed before activation of the fuel and is opened after activation of the fuel, wherein substantially the entire fluid flow flows through the overflow opening ( 46 ). 3. Gas generator according to claim 1 or 2, characterized in that the first ( 22 ) and the second housing part ( 24 ) are constructed substantially radially symmetrically. 4. Gas generator according to one of the preceding claims, characterized in that the first ( 22 ) and the second housing part ( 24 ) form a substantially annular overflow opening ( 46 ) after the activation of the fuel. 5. Gas generator according to one of the preceding claims, characterized in that the overflow opening ( 46 ) has several opening sections ( 46a ) separated from one another. 6. Gas generator according to one of the preceding claims, characterized in that the spacing means ( 44 , 48 , 50 ) are beads ( 44 ). 7. Gas generator according to one of claims 1 to 5, characterized in that the spacing means ( 44 , 48 , 50 ) are grooves ( 48 ). 8. Gas generator according to one of claims 1 to 5, characterized in that the spacing means ( 44 , 48 , 50 ) are ribs ( 50 ) formed on the first ( 22 ) and/or second ( 24 ) housing part. 9. Gas generator according to one of the preceding claims, characterized in that the first ( 22 ) and the second housing part ( 24 ) form a common first contact region ( 38 ) before activation of the fuel, the common first contact region ( 38 ) being secured with an adhesive connection, and that the first ( 22 ) and the second housing part ( 24 ) form a plurality of common second contact regions ( 38 ') after activation of the fuel. 10. Gas generator according to one of the preceding claims, characterized in that the first housing part ( 22 ) has a cover section ( 28 ) and a wall section ( 30 ) and the spacing means ( 44 , 48 , 50 ) are arranged in the transition region between the cover section and the wall section. 11. Gas generator according to one of the preceding claims, characterized in that the second housing part ( 24 ) forms a combustion chamber wall. 12. Gas generator according to claim 11, characterized in that the spacing means ( 44 , 48 , 50 ) are arranged at an end portion ( 36 ) of the combustion chamber wall.