DE20104042U1 - Gas generator with a valve - Google Patents

Description

PRINCE & PARTNERS

GbR

PATENT ATTORNEYS Manzingerweg 7

EUROPEAN PATENT ATTORNEYS D-81241 Munich

EUROPEANTRADEMARKATTORNEYS Tel. +49 89 89 69 80

March 8, 2001

TRW Airbag Systems GmbH & Co. KG

Wernher-von-Braun-Strasse 1
D-84544 Aschau am Inn

Our reference: T 9585 DK

Kl/da/se

Gas generator with a valve

The invention relates to a gas generator with a fluid container and a valve with a movable element, wherein the position of the movable element can influence a fluid flow when the fluid flows out of the fluid container when the gas generator is activated.

The speed at which a gas bag unfolds and its hardness when inflated are influenced by the total amount and the temporal distribution of the fluid flowing into the gas bag. In order to avoid injuries to a vehicle occupant, it is desirable to adapt these parameters to the position of a vehicle occupant in the vehicle, for example. This is particularly important if the occupant is not in an optimal position (out-of-position).

It is known to equip a gas generator with a valve in which the fluid flow is controlled by electromagnets. The use of electrorheological or magnetorheological fluids in such valves is also known. In a purely pyrotechnic or compressed gas generator, for example, the valve is usually located at the

Outlet opening. There are also generators filled with liquid fuel, where the valve controls the amount of fuel injected into a combustion chamber. The disadvantage of these designs is the large installation space and the high weight of the valve mechanism. Another disadvantage is the high electrical energy requirement to operate the valve, which requires high currents or high voltages. This requires a complex power supply for the valve. In addition, conventional valves have relatively long switching times, which are caused by their mass inertia and the rise times of current and voltage.

The object of the invention is to create a gas generator with a compact, lightweight valve. In addition, the electrical energy requirement for the valve mechanism should be reduced compared to the prior art.

This is achieved in a gas generator of this type in that the valve contains at least one micro-ignition field with several igniters, in which igniters can be ignited independently of one another and in which the pressure generated when one or more igniters are ignited moves the movable element. The gas pressure generated when one or more igniters in the micro-ignition field are ignited exerts an impulse on the movable element, changing its position, which in turn influences the fluid flow, i.e. its strength can be changed. In this way, for example, the inflation behavior of a gas bag can be controlled. The energy for operating the valve comes mainly from the pyrotechnic combustion taking place in the individual igniters. Electrical energy is only required to ignite the igniters. The individual igniters can preferably be ignited by electrical pulses with low voltage and current, so that the electrical energy required to operate the valve is very low. In addition, micro-ignition fields make it possible to achieve very short switching times. Micro-ignition panels can be made very small, and above all very flat, and can be easily combined with known gas generators. Because of the low electrical energy required to trigger them, inexpensive electronic switches can also be used.

Preferably, a micro-igniter field is used, as presented in the article "Digital MicroPropulsion" by David H. Lewis et al. (12* IEEE International Micro Electro Mechanical Systems Conference, January 17 to 21, 1999). For such a micro-igniter field, a wafer is provided with recesses in the sub-millimeter range, which are filled with a gas-generating material and individually contacted. The igniters produced in this way can be ignited either individually or in freely definable groups. A micro-igniter field can contain up to 10,000 individual igniters. The intended application area for such micro-igniter fields is to stabilize micro spaceships weighing a few kilograms in a predetermined position or to carry out small orbital corrections.

The fluid can be generated in the gas generator from solid, liquid and/or gaseous gas-generating materials, whereby the gas generation is possible by combustion or by heating, e.g. of liquid gas.

The movable element of the valve of the gas generator according to the invention can preferably be moved into a position in which the valve is open and into a position in which the valve is closed. The valve is preferably either fully open or fully closed. The construction of such a valve is simple, stable and known. A specific outflow rate can be set by selecting the frequency and number of ignitions of igniters of a microigniter field (which corresponds to the frequency of the movements of the movable element into the open or closed position) according to the desired fluid flow. Optionally, a quasi-stationary fluid flow can be achieved.

A working space is advantageously provided adjacent to the movable element and the micro-ignition field, so that the gas generated by the micro-ignition field first flows into the working space before it hits the movable element in order to achieve a more uniform load on the movable element.

In the work area, e.g. through the micro-ignition field

The gas produced can preferably flow out to the environment via outflow channels that are in flow connection with the working chamber. These outflow channels can either be always open or only open to the environment when the movable element is in certain positions.

In a preferred embodiment of the invention, the microigniter field contains about 50 to 1500 microigniters and, more preferably, about 10 to 100 microigniters. With this number of microigniters, a sufficiently high number of ignitions can be carried out for the average size that can be used in a gas generator (preferably a diameter of a few centimeters) in order to control the fluid flow as desired.

In a preferred embodiment of the invention, the movable element is a membrane. A membrane is characterized by its low weight, which allows rapid movement with a low required impulse or gas pressure. In addition, membrane valves are based on a known technology, are reliable, small and can be used in any installation position.

In another preferred embodiment of the invention, the movable element is a rigid body with two opposite ends, the body having a passage opening between the ends. In addition, two micro-ignition fields are provided, each of which adjoins its own working space into which the gas released when an igniter of the respective micro-ignition field is ignited can flow. The rigid body adjoins a random working space at each of its ends and is moved by the ignition of at least one igniter of one micro-ignition field into a position in which the passage opening allows the fluid flow to pass, while when at least one igniter of the other micro-ignition field is ignited, the rigid body is moved into a position in which the fluid flow is interrupted by the rigid body. The rigid body is preferably a slide.

A particular advantage of using two opposing micro-ignition fields is that the

The restoring force from the open to the closed position of the valve is applied by the other micro-ignition field. This results in precise control, since the forces acting on the moving element are precisely known.

In other advantageous developments of the invention, the restoring force can be applied to the movable means by an elastic means or by the fluid flow itself. If a membrane is used, the elastic means is the membrane itself.

In this case, the impulses from the micro-ignition field are only necessary to open or close the valve; the respective counter movement takes place without using the micro-ignition field, which means that a second micro-ignition field is not required and the total number of igniters required is kept small.

A locking device can be provided which holds the movable element in a position adjusted by the ignition of igniters of the micro-igniter field. The locking device is preferably designed in such a way that the impulse when igniters of the micro-igniter field are ignited releases the locking so that the movable element can move. By using a locking device, the dependence of e.g. a slide valve on the installation position can be reduced.

In a further advantageous embodiment of the invention, the rigid body has a passage opening and can be displaced between a first end position and a second end position, wherein fluid can flow out of the fluid container when the rigid body is in the second end position, while the passage is closed by an adjacent wall when the rigid body is in the first end position, so that the fluid flow is interrupted.

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

- Figures 1 a,b a valve of a gas generator according to the invention

according to a first embodiment in the open and closed state in section;

- Figures 2 a,b show a valve of a gas generator according to the invention according to a second embodiment in closed and open state in section;

- Figures 3 a,b show a valve of a gas generator according to the invention according to a third embodiment in open and closed state in section; and

- Figure 4 shows an assembly with a gas generator according to the invention in a schematic representation.

In all figures, identical or functionally identical components are provided with the same reference symbols.

A valve 10 according to a first embodiment of a gas generator 12 (Figure 4) is shown in Figure 1a in the open state and in Figure 1b in the closed state. The valve 10 has a membrane 14 as a movable element. The membrane 14 is arranged between an outflow opening 16 of a fluid container 18, which provides the gas required to inflate a gas bag, and a micro-ignition field 20. The membrane 14 is held in a membrane holder 22. The membrane holder 22 has an annular, concave section in which the membrane, which has an approximately hemispherical shape, rests with its edge region. A working space 24 is formed between the freely suspended central region of the membrane 14 and the micro-ignition field 20.

The wall of the outflow opening 16 of the fluid container 18 projects into the hemispherical space formed by the membrane 14, wherein the membrane 14 is spaced from the edge of the outflow opening 16.

In the membrane holder 22, an outflow channel 26 is also formed, which connects the working chamber 24 with the environment and the ambient pressure. Otherwise, the working chamber 24 is sealed by the micro-ignition field 20 as well as the membrane 14 and the membrane holder 22.

• ft · · · ■

-7-completed.

The micro-igniter field 20 has a plurality of individual pyrotechnic igniters 28, wherein the number of igniters is preferably 50 to 1500 per micro-igniter field and particularly preferably 10 to 100 micro-igniters per micro-igniter field.

Preferably, each of the individual igniters 28 of the micro-igniter field 20 can be electrically ignited separately. It is also advantageous if certain groups of igniters 28, e.g. in certain patterns, can be ignited together in order to achieve a uniform pressure and impulse distribution as well as an adjustable force development on the movable element.

The igniters 28 are preferably individually contacted (not shown). The micro-igniter field 20 can be connected via electrical lines 21, for example to a controller 30 (Figure 4), via which it is supplied with ignition signals for the independent ignition of individual igniters or individual igniter groups. The controller 30 can be identical to a controller via which the gas generator 12 is activated in the event of an accident.

In the open state of the valve 10, which is shown in Figure 1a, there is a free space between the edge surrounding the outlet opening 16 and the membrane 14 through which the fluid shown by arrows can flow. The fluid can be a gas or a liquid (e.g. liquefied gas). The membrane 14 is relaxed so that the valve is open in the normal state.

When igniters 28 are ignited, gas is generated in the working chamber 24 (shown schematically) and a pressure is built up which acts on the membrane 14 and moves it in the direction of the edge surrounding the outflow opening 16 so that the outflow opening 16 is closed. The movable element 14 is thereby moved into a closed valve position in which the fluid is prevented from escaping and the fluid flow is interrupted.

The inherent elasticity of the simultaneously as an elastic means for :··. :··· .·*. .··. .: .··.: .··.: .··. : : ..·

-8th-

The return force of the diaphragm 14 used for resetting and the fluid pressure on the diaphragm 14 cause a return force by which the diaphragm 14 is moved back to its starting position so that the valve opens automatically after a short time. A quasi-stationary fluid flow of the desired strength can be set by selecting the frequency of the ignitions of individual igniters 28 or igniter groups accordingly.

Depending on the design of the micro-igniter field 20, the fluid container 18 and the membrane 14, one igniter 28 may be sufficient to completely or partially close the valve or any group of igniters 28 may be ignited to achieve this purpose.

An advantage of the valve 10 shown in Figures 1a and 1b is that its installation position is independent of direction, since the movement of the membrane 14 is only influenced by the micro-ignition field 10, the inherent elasticity of the membrane 14 and the fluid pressure.

In a second embodiment of the invention, the valve is designed as a slide valve 100. Here, two opposing micro-ignition fields 20 are provided, each of which is connected to a controller 30 via lines 21.

Each of the micro-ignition fields 20 borders on a working chamber 24, which in turn is in flow connection with a slider holder 102. A slider 104 can move in the slider frame 102. The working chambers 24 and the slider holder 102 are formed in a holder 106. The slider holder 102 and each working chamber 24 are separated from one another by a stop 108 for the slider 104, so that two defined end positions are provided for the slider 104. The holder 106 has a central opening 110. The slider 104 has a passage opening 112 between its ends, slightly offset from the center. Outflow channels 26 in the holder 106 and the slide 104 form a flow connection from the working spaces 24 to the environment when the slide 104 is in one of its end positions in order to prevent the outflow of gas generated by the micro-ignition field 20 and in the respective working space 24

to allow the air to circulate.

If one or more igniters 28 of one of the two micro-igniter fields 20 are ignited, the gas pressure acts on one end of the slide 104 and moves it to its stop 108 on the opposite micro-igniter field 20. In one end position (Figure 2b), the opening 110 in the holder 106 is aligned with the passage opening 112 in the slide 104, and fluid can flow from the fluid container 18 arranged above the opening 110 through the valve. In the second end position (Figure 2a), the passage opening 112 is covered by the slide holder 102, so that the valve is closed.

The valve 100 does not experience any restoring force due to the fluid pressure, but is moved between its two end positions by ignition of igniters 28 of the two micro-igniter fields 20 into the other end position.

A locking device can be provided, which consists, for example, of two spring bolts 114 that hold the slide 104 in its respective end position. The force for releasing the locking device is preferably selected to be high enough that the slide 104 cannot be moved by slight vibrations of the gas generator 12 or by gravity, but naturally low enough that the impulse on the slide 104 generated by the ignition of one or more igniters 28 of the micro-igniter field 20 is sufficient to overcome the locking force. The preferred installation position of the valve 100 is horizontal, but this installation position can also be deviated from when a locking device is used.

A third embodiment of the invention is shown in Figures 3a and 3b. The valve 200 has a micro-igniter field 20 which is arranged in a holder 202 in such a way that a working space 24 is formed above the micro-igniter field 20. In the holder 202, a guide 204 is formed centrally above the igniter field 20, which has a stop 206 at the transition to the working space 24, but is in flow connection with the working space 24. A bolt 208 can be moved in the guide 204. Above the holder 202, but at a distance from the holder 202, the edge of the

- 10-

The outflow opening 16 of the fluid container 18 is arranged such that the guide 204 and the outflow opening 16 are aligned with one another.

A second guide 210 for the bolt 208 is formed in the edge of the outflow opening 16. A stop 212 is formed on the upper edge of the second guide 210. The bolt projects into the second guide 210 and can be moved between the first stop 206 and the second stop 212 into two end positions, whereby it is always guided in both guides 204, 210.

The bolt 208 has a passage opening 214 with a T-shaped cross section at its upper end facing the fluid container 18, with an open outlet of the passage opening 214 extending into the outflow opening 16. The other outlets of the passage opening 214 open into the intermediate space 216 between the holder 202 and the edge of the outflow opening 16 when the bolt is in its first, lower end position at the stop 206.

In the normal position, the valve 200 is open, the bolt 208 rests on the stop 206 of the guide 204, and fluid can flow out of the fluid container 18 through the passage opening 214 into the gap 216 between the holder 202 and the fluid container 18 (arrows).

By igniting one or more igniters 28 of the micro-igniter field 20 (shown schematically in Figure 3b), the bolt 208 is moved in the direction of the fluid container 18 so that it reaches its second, upper end position in which the bolt 208 rests against the stop 212. The guide 210 and the passage opening 214 are designed such that the passage opening 214 is now closed by the edges of the outflow opening 16 or the guide 210 and the fluid flow is interrupted.

The return of the bolt 208 to its first, lower end position is effected by the fluid pressure and by gravity, so that after a short time the valve 200 opens again and the fluid can flow out again.

The holder 202 has an outflow channel 26 which is connected to the

Guide 204 is in flow connection, wherein the outflow channel 26 is arranged such that the channel is open when the bolt 208 is in its second, upper end position, and closed when the bolt 208 is in the first, lower end position.
5

In this embodiment, an additional locking device and/or an elastic means, e.g. in the form of a spring 220, for resetting the bolt is also conceivable.

In all embodiments, the fluid container 18 is preferably closed by a suitable known means, such as another membrane, before activation of the gas generator.

The energy to trigger the igniters can also be found near the

Micro-ignition field 20, e.g. on a small capacitor,

stored, or the energy can be taken from an autonomous energy source.

The micro-ignition field 20 can also be arranged in front of a one-time valve, e.g. in the form of a grid with closed fields that are individually destroyed by igniters. This releases more or fewer fields through which fluid can flow out.

It is also conceivable to provide micro-igniter fields 20 for igniting one or more pyrotechnic charges. If many igniters are activated immediately, the charge(s) will burn more quickly than if fewer igniters are activated.

Claims (15)

1. Gas generator with a fluid container ( 18 ) and a valve ( 10 ; 100 ; 200 ) with a movable element ( 14 ; 104 ; 208 ), wherein the position of the movable element ( 14 ; 104 ; 208 ) can influence a fluid flow when the fluid flows out of the fluid container ( 18 ) when the gas generator ( 12 ) is activated, characterized in that the valve ( 10 ; 100 ; 200 ) contains at least one micro-ignition field ( 20 ) with a plurality of igniters ( 28 ), in which igniters ( 28 ) can be ignited independently of one another and wherein the pressure caused when one or more igniters ( 28 ) are ignited moves the movable element ( 14 ; 104 , 208 ). 2. Gas generator according to claim 1, characterized in that the movable element ( 14 ; 104 ; 208 ) can be moved into a position in which the valve ( 10 ; 100 ; 200 ) is opened and into a position in which the valve ( 10 ; 100 ; 200 ) is closed. 3. Gas generator according to one of the preceding claims, characterized in that a working space ( 24 ) is provided, to which the movable element ( 14 ; 104 ; 208 ) and a micro-ignition field ( 20 ) adjoin. 4. Gas generator according to one of the preceding claims, characterized in that the micro-igniter field ( 20 ) contains about 50-1500 igniters ( 28 ). 5. Gas generator according to one of the preceding claims, characterized in that the micro-igniter field ( 20 ) contains about 10-100 igniters ( 28 ). 6. Gas generator according to one of the preceding claims, characterized in that the movable element is a membrane ( 14 ). 7. Gas generator according to one of claims 1 to 5, characterized in that the movable element is a rigid body ( 104 ; 208 ). 8. Gas generator according to claim 7, characterized in that the movable element is a slide ( 104 ). 9. Gas generator according to one of the preceding claims, characterized in that two micro-ignition fields ( 20 ) are provided. 10. Gas generator according to claim 9, characterized in that the two micro-igniter fields ( 20 ) are arranged so that they act on the movable element ( 104 ) from opposite directions when igniters ( 28 ) are ignited. 11. Gas generator according to claim 10, characterized in that the movable element is a rigid body ( 104 ) with two opposite ends, the body ( 104 ) having a passage opening ( 112 ) between the ends, that each of the two micro-igniter fields ( 20 ) adjoins its own working space ( 24 ) into which the gas released when an igniter ( 28 ) of the respective micro-igniter field ( 20 ) is ignited can flow, the rigid body ( 104 ) adjoins a disordered working space ( 24 ) with each of its ends and the ignition of at least one igniter ( 28 ) of the one micro-igniter field ( 20 ) moves the rigid body ( 104 ) into a position in which the passage opening ( 112 ) allows the fluid flow to pass, while when at least one igniter ( 28 ) of the other micro-ignition field ( 20 ) the rigid body ( 104 ) is moved into a position in which the fluid flow through the rigid body ( 104 ) is interrupted. 12. Gas generator according to claim 7, characterized in that the rigid body ( 208 ) has a passage opening ( 214 ) and can be moved between a first end position and a second end position, wherein fluid can flow out of the fluid container ( 18 ) via the passage opening ( 214 ) when the rigid body ( 208 ) is in the second end position, while the passage opening ( 214 ) is closed by an adjacent wall when the rigid body ( 208 ) is in the first end position, so that the fluid flow is interrupted. 13. Gas generator according to one of the preceding claims, characterized in that an elastic means is provided which acts on the movable means opposite to the direction of movement caused by the ignition of the igniter(s) ( 28 ) of the micro-igniter field ( 20 ). 14. Gas generator according to one of the preceding claims, characterized in that the fluid flow exerts pressure on the movable means ( 14 ; 208 ) opposite to the direction of movement caused by the ignition of the igniter(s) ( 28 ) of the microigniter array ( 20 ). 15. Gas generator according to one of the preceding claims, characterized in that the working chamber ( 24 ) has an outflow channel ( 26 ) through which gas present in the working chamber ( 24 ) can flow out.