Abstract:
The present invention relates to a hybrid-type device for inflating vehicle safety equipment with gas chamber for acceptance of compressed gases and at least two charges for the production of gas. The inflation devices is distinguished in that the two charges each have a mass of at least 5% of the mass of the compressed gas so that each charge can substantially increase the temperature of the gas and in that they are each arranged outside the gas chamber, on different sides thereof They can thus be ignited simply and precisely at predetermined without reciprocal impact.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a hybrid-type device for inflating vehicle safety equipment with a gas chamber for acceptance of compressed gases and at least two charges for the production of gas. 
     Such hybrid-type inflating devices, in which the inflation of the corresponding device is achieved, for one thing by a pressurized gas, and for another by a gas produced by igniting a gas-producing pyrotechnic charge, is known for example, from U.S. Pat. No. 3,758,131 or DE-OS 23 00 577. The minimum of two gas-producing charges can be ignited independently or sequentially. In this manner, the inflation process can be adapted to various parameters such as, for example, the weight of the occupants, the distance of the occupants from the safety equipment, the temperature, the force of the impact and similar. A time delay between the actuation of the various charges causes a gentler but also longer-lasting inflation of the safety equipment. 
     With known hybrid type inflation devices, it was difficult, however, to ignite the charges precisely at the predetermined times and to achieve the desired inflation characteristics. For example, there was a risk that the second charge would ignite unintentionally, for example as a result of an electric arc or electric leakage or through a transfer of heat from the first gas charge ignited. 
     The interaction of the two charges is a particular problem when these gas charges are of larger sizes. On the other hand, it is desirable for larger charges to be used to achieve a corresponding volume of gas to inflate the safety equipment and to achieve the desired inflation characteristics. 
     Proposals have already been made to not use electric ignition to ignite the gas-producing charges, to avoid electric wires in the gas chamber and to prevent electric arcs or leakage losses. But this makes it difficult to activate the charges independently at times to be defined. 
     SUMMARY OF THE INVENTION 
     The present invention therefore relates to creating an improved inflation device of the type cited at the beginning that avoids the known disadvantages in the state of the art. In particular, an inflation device is created in which the gas-producing charges produce a sufficient quantity of gas and can be ignited simply, independently of each other, at different times. 
     According to the invention, this task is solved by an inflation device of the type cited at the beginning in that the two charges each have a mass of at least 5% of the mass of the compressed gas and are each arranged outside the gas chamber on different sides thereof 
     The charges are therefore distances from each other and separated from the compressed gas in the gas chamber. There is no direct interaction between the charges upon ignition. In particular, thermal transfer from the charge ignited first to the second charge is prevented. Despite this, the two charges are sufficiently large. In particular, they are dimensioned such that each charge can cause a significant rise in temperature of the compressed gas in the gas chamber to influence the inflation process thereby. The charges can be ignited simply with an electric ignition initiator with no fear of a disruptive discharge or leakage losses. In particular, the two charges can be positioned at opposite ends of the gas chamber. 
     According to an advantageous development of the invention, pyrotechnic charges are used that produce carbon monoxide or other combustible gases. To oxidize these gases, the compressed inert gas stored in the gas chamber can be mixed with approximately 10%-20% oxygen (O 2 ). An advantageous inflation characteristic can thus be achieved by mixing the gases produced by the pyrotechnic charges with the compressed gas stored in the gas chamber. 
     The inflation device can work without material that are broken down, in particular, by pyrolysis and thus produce gas. The pyrotechnic charges are sufficiently large to produce the corresponding gas volumes by themselves. By mixing the gases produced by the pyrotechnic charges with the inert gas stored in the gas chamber, a substantial increase in the temperature of the inert gas can be achieved, to influence the inflation process accordingly. 
     According to a preferred embodiment of the invention, the gas chamber is formed essentially cylindrically and the charge is situated on the face opposite thereto. This prevents an undesirable reciprocal impact from the ignitable gas charges. 
     On the first side of the gas chamber, on which the first of the charges is situated, a gas chamber opening is preferably provided that leads to the safety equipment and is initially sealed with a corresponding seal. The compressed gas is therefore completely separated from the charges. 
     In a development of the invention, the charges are contained in separate charge chambers that each have a charge chamber opening. These charge chamber openings are initially sealed with corresponding seals. Expediently, each of the charges can be brought into a flow connection with the gas chamber and the compressed gas stored therein. This can be arranged by opening the corresponding openings, i.e., the gas chamber openings and/or the charge chamber openings. 
     Various methods can be provided to open the seals for the gas chamber opening and/or the charge chamber openings. For example, they can be activated from outside. According to a preferred embodiment of the invention, however, the seals are self-controlled, i.e., they are designed to be activated by the resultant gas pressure after ignition of the charges. Preferably, the seals for the gas chamber opening are designed such that they are opened by the expanding gas after ignition of any one of the charges. By ignition of at least one of the two charges, the resultant charge gas flows through and the compressed gas stored in the gas chamber flows out. The seals for the charge chamber opening are designed such that they are opened exclusively by the related charge, i.e., by the expanding gas after ignition of the corresponding charge. The ignition of the other charge preferably does not impact the seal for the other charge chamber. 
     In a development of the invention, to open the seal for the gas chamber opening, i.e., the opening through which the compressed gas in the gas chamber can exit, a piston can be provided that, in its initial state, sits in a related cylinder and that is impinged upon by the expanding gas from one of the charges after ignition thereof, and this, in such manner that the piston is moved through the gas chamber opening. Here the piston opens the seal that had initially kept the gas chamber opening closed. Expediently, the piston can be impinged upon by one of the gas-producing charges situated on the side of the gas chamber opening. 
     According to a preferred embodiment of the invention, the piston-cylinder device has a plug that is assigned to the charge, that is situated in the corresponding charge chamber opening and that seals the same, fluid-tight, in its initial state. If the gas-producing charge situated in the corresponding charge chamber is ignited, the resultant gas pressure in the charge chamber acts on the plug through the opening of the gas chamber, releases it from the charge chamber opening and drives it through the gas chamber opening. The seals on the gas chamber opening are thus opened. 
     The seals for the gas chamber opening preferably have a sealing washer made of a suitable matter, that is fitted over the gas chamber opening and covers it. The contact pressure that activates the seal is preferably applied by the gas pressure inside the gas chamber; the sealing washer is pressured into the gas chamber wall by the compressed gas, into which wall the gas chamber opening is built. In a development of the invention, the seals on the piston are supported, and the central section of the sealing washer can lie on the ends of the plug sealing the charge chamber opening. 
     An advantageous embodiment of the invention consists in the piston being situated, in its initial position, such that the cross-section of the gas chamber opening is reduced and, in its extended position, it frees the cross-section of the gas chamber opening. Various discharge speeds can be achieved for the gas exiting from the gas chamber. In the initial piston position, the gas chamber opening—with the seals open—has an annular cross-section that is enlarged when the piston is removed. 
     Preferably, the piston can lie with its end in the plane of the gas chamber opening. In particular, the head section of the piston has a larger diameter than that of the related cylinder and a smaller diameter that the gas chamber opening. The above-cited achievement of varying opening cross-sections for the gas chamber opening facilitates this. 
     In a development of the invention, the gases exiting the gas chamber do not expand directly into the safety equipment. A joint discharge chamber can be provided that can be brought into flow connection with the gas chamber as well as the charge chambers, directly or indirectly. All exiting gases first expand in the discharge chamber and from it through a discharge opening into the safety equipment. 
     Advantageously, the discharge chamber is located between the gas chambers and one of the discharge chambers and can be brought into flow connection with both of these, directly; in particular, the discharge chamber is situated coaxially to the longitudinal axis of the gas chamber, like a sandwich between it and one discharge chamber. The other charge on the opposite side of the gas chamber can be brought indirectly into flow connection with the discharge chamber. The gas produced by this charge first flows through the corresponding charge chamber opening to the gas chambers, from them into the discharge chamber and from there into the safety equipment. The different connections of the various chambers to the discharge opening permits multi-faceted, precise adaptation of the inflation characteristics to the parameters mentioned at the beginning. 
     To achieve various inflation characteristics, the charges are preferably different. In particular, they are of different sizes, i.e., the gas volume produced upon ignition and the resultant pressure are different from the individual charges. The mass of the two charges can come to approximately 5% to 20% of the mass of the gas stored in the gas chamber, while preferably one of the charges has a mass of about 5%-10%, and the other charge has a mass of about 10%-20% of the mass of the compressed gas. Furthermore, the charges can be of different chemical compositions; in particular, they can have different ignition or expansion speeds. 
     To adapt the inflation characteristics to the corresponding environmental and accident parameters, according to an advantageous embodiment of the invention, a control device is provided to control the charges that predetermines the ignition sequences of the charges. The inflation device can therefore be operated accordingly in different inflation modes. 
     In a first inflation mode, only the first of the charges is ignited by the control device. The second charge is not ignited; the related charge chamber remains sealed. In a second inflation mode, the second charge is ignited, while the first is not. This means that the plug sealing the charge chamber opening belonging to the first charge remains in its initial position, so that the gases exiting from the gas chamber must flow through the cross-section of the gas chamber opening, reduced by the plug cross-section. In the first inflation mode, on the other hand, the plug is driven out so that a larger gas chamber opening section is available and the gas can exit correspondingly faster. 
     In a third inflation mode, the two charges are ignited. A larger volume of gas accordingly flows into the safety equipment. Preferably, the two charges are ignited sequentially with a time delay. 
    
    
     BACKGROUND OF THE INVENTION 
     These and other characteristics can be derived from the following description and related drawings, in addition to the claims, and are explained in greater detail based on a preferred embodiment of the invention. The drawings show: 
     FIG. 1 a longitudinal section through an inflation device according to a preferred embodiment of the invention, where the device is shown in its initial state, 
     FIG. 2 a sectional view of the inflation device similar to FIG. 1, where the device is shown after ignition of a first gas-producing charge on the left side according to FIG. 2, where the gas-producing charge on the right side according to FIG. 2 has not been ignited, and 
     FIG. 3 is a sectional view similar to the above Figures, where the inflation device is shown after ignition of the second gas-producing charge on the right side according to FIG. 3, where the first gas-producing charge on the left side is not ignited. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The inflation device according to FIG. 1 has, as the central component, an essentially spherical gas chamber  1  that is delimited by a housing and a circumferential wall  2  as well as a first end wall  3  and a second end wall  4 . The circumferential wall  2  is connected fluid-tight, particularly welded, to the end walls  3  or  4 . Pressurized compressed gas is stored in the gas chamber  1 , which gas can be released to a vehicle safety device, particularly an airbag, not shown in greater detail, as will be described below. 
     At the first end, i.e., on the left end of the gas chamber  1  according to FIG. 1, is a discharge chamber  5  that is essentially cylindrical and is situated coaxially to the longitudinal axis of gas chamber  1 . The discharge chamber  5  is delimited from the gas chamber  1  by the first end wall  3  that, to this extent, forms a separating wall between the discharge chamber  5  and the gas chamber  1 . In a circumferential wall  6  radially delimiting the discharge chamber  5 , a discharge opening  7  is provided that is pointed radially outward and that forms a connection with the safety equipment. 
     In the first end wall  3  separating the discharge chamber  5  and the gas chamber  1  from each other, a recess is provided in the center that is known hereinafter as the gas chamber opening  8 . The gas chamber  1  can be brought into flow connection with the discharge chamber  5  through the gas chamber opening  8 , i.e., the gas in gas chamber  1  can flow through the gas chamber opening  8  into the discharge chamber  5  and from there to the safety equipment, as described below. 
     On the side of the discharge chamber  5  opposite to the gas chamber  1 , is a first discharge chamber  9  that is also essentially cylindrical and is arranged coaxially to the longitudinal axis of the gas chamber  1  or the discharge chamber  5 . A first gas-producing charge  10  is placed in the charge chamber  9 , which charge  10  can be ignited by means of a first detonator  11 , preferably electric. The detonator  11  is placed in a recess in an exterior wall  12  which delimits the charge chamber  9  from the exterior end of the inflation device. Radially, the charge chamber  9  is delimited from the circumferential wall  6 , which simultaneously delimits discharge chamber  5  radially as well. Between the discharge chamber  5  and the charge chamber  9 , a separating wall  13  is provided that has a passage recess that serves as the charge chamber opening  14  and—in the unsealed state—connects the first charge chamber  9  with the discharge chamber  5 . The separating wall  13  is connected fluid-tight at its exterior circumference with the circumferential wall  6 . Here, connectors are provided that are designed axially such that they fail when a predetermined pressure is achieved in the first charge chamber  9  after ignition of the corresponding charge  10 , and the separating wall  13  can be pressed into the discharge chamber  5  by means of gas pressure in the charge chamber  9 . A flange connection  14  is provided as the connector here, which has an exterior flange formed in one piece with the separating wall, projecting radially outward at the exterior circumference of the separating wall, and an interior flange projecting inward radially from the circumferential wall  6 . The interior wall is formed from a bead on circumferential wall  6 , formed by pressing on the originally cylindrical circumferential wall  6 . The exterior flange at the separating wall can be deformed in an axial direction, which separating wall  13  can fail upon the corresponding pressure in the charge chamber  9  without the circumferential wall  6  expanding radially and without the risk of crack formation. The described failure of separating wall  13  serves to prevent explosion of the device in the case of excessively fast expansion or detonation speeds for charge  10 , for example as a result of greater exterior thermal effects, as in the case of a fire. Here the connection of separating wall  13  with circumferential wall  6  is also designed to be weaker than the connection of the exterior wall  12  with the circumferential wall  6  so that the exterior wall  12  cannot, in any event, be exploded away from it. In the case of normal detonation of charge  10  in accordance with the regulations, the connection of the separating wall  13  withstands the pressure arising in charge chamber  9 . 
     The first charge chamber opening  14  is formed as a cylinder toward the discharge chamber  5 . As FIG. 1 shows, a cylinder section  16  is attached to the side of the separating wall  13  facing the discharge chamber  5  and is connected fluid-tight therewith. The first charge chamber opening  9  therefore has a cylindrical cross-section from the first charge chamber  9 ; connected thereto is a expanding section of a sphere, and a second cylinder section is connected thereto, which second cylinder section corresponds essentially in diameter to the first cylinder section. The first charge chamber opening  14  is sealed with a plug  17  that serves as a piston and is thrust into the cylinder section, facing the discharge chamber  5 , of the charge chamber opening  14 . The plug  17  has an essentially cylindrical head section  18  projecting over the charge chamber opening  14 , which head section, on the one hand, reaches to the end of the tube or the cylinder section  16  and on the other, its end extends in the plane of the gas chamber opening  8 , or more precisely, in approximately the plane in which the edge of the gas chamber opening  9 , facing the gas chamber  1 , lies. 
     The diameter d 18  of the head section  18  is larger than the outside diameter d 16  of the tube or cylindrical section  16 , while the diameter of the head section  18  is smaller than the diameter d 8  of the gas chamber opening  8 . Based on these differences in diameter, varying flow cross-sections can be created for the gas chamber opening  8 . As long as the plug  17  is in its initial position, i.e., in its position sealing the charge chamber opening  14 , the available cross-section of the gas chamber opening  8  is circular, and the full cross-section area of the gas chamber opening  8  is reduced by the cross-section area of the head section  18  of the plug  17 . As soon as the plug  17  is removed, however, the cross-section area of the gas chamber opening  8 , reduced by the cross-section of the cylinder  16 , is available. The gas then flows accordingly more rapidly out of the gas chamber  1 , i.e., the volume flowing through the gas chamber opening  18  is greater. This therefore results in a variable inflation characteristic. 
     The gas chamber opening  8  is initially sealed. A sealing washer  19  made of a suitable material serves as the seal; it is located on the first end wall  3 , on the side of the gas chamber  1 , and covers the gas chamber opening  8 . The sealing washer  19  is situated on the plug  17 ; it lies on the end of the head section  18 . It is pressed into the first end wall  3  by the gas pressure in the gas chamber  1 , so that the pressure force necessary for sealing is present. The section of the first end wall  3  surrounding the gas chamber opening  8  is preferably designed as a flat sealing section. 
       20  designates a guide in the discharge chamber  5  that supports the separating wall  13  at the first end wall  3 . The guide  20  is placed symmetrically to the longitudinal axis of the discharge chamber  5 . It sits on a shoulder-shaped projection of the separating wall  13 , on its side facing the discharge chamber  5  (See FIG.  1 ). Pierced openings are designed in the guide  20 , through which the gas can flow. Furthermore, the guide  20  has a theoretical deformation section that permits axial creasing of the guide  20 . 
       21  indicates a porous gas-permeable structure that is formed as a collar and designed as a mesh (see FIG.  1 ). It is situated in such manner that the gas exiting from discharge opening  7  flows through it. 
     On the side of the gas chamber  2  opposite the discharge chamber  5  and the first charge  10 , is a second gas-producing charge  22  that is enclosed in a second charge chamber  23 , analogous to the first charge  10 . The charge chamber  23  is delimited, in the direction of gas chamber  1 , by a second end wall  4  that forms, to this extent, a separating wall between the gas chamber  1  and the second charge chamber  23 . Furthermore, the second charge chamber  23  is delimited by a circumferential wall  24  and an exterior wall  25 , which forms the end of the whole cylinder-shaped inflation device. The second end wall  4  is made in one piece with the circumferential wall  24  and forms a sort of basin on its floor; the exterior wall  25  is thrust into this similarly to the exterior wall  12  of the open side of the circumferential wall  24  and is connected therewith by means of fluid-tight connectors, particularly a flange connection. As FIG. 1 shows, the circumferential wall  24  is pressed in from the outside, in the form of an annular circumferential groove in exterior wall  25 , in the style of a flange. 
     The second charge  22  can be ignited similarly to the first charge  10 , by an electric second detonator  26  that is placed in a corresponding central recess in the second exterior wall  25  (see FIG.  1 ). 
     The second charge  22  is smaller than the first charge  10 , i.e., the gas volume produced by the second charge  10  is smaller than that on the side of gas chamber  1  facing the first charge  10 . Furthermore, the second charge  22  is of a different chemical composition; its speed of ignition or expansion is different from that of the first charge  10 . 
     For certain embodiments, a pyrotechnic charge can be used that produces carbon monoxide (CO) or other combustible gases. To oxidize these gases, the inert gas stored in gas chamber  1  is mixed with approximately 10%- 20 % oxygen (O 2 ). For example, according to a preferred embodiment, 12-16 g of powder is used in the first charge  10  and about 5-7 g of powder in the second charge  22 . In gas chamber  1 , about 100-120 g of cold compressed gas can be stored. 
     As FIG. 1 shows, two recesses are created in the second end wall  4  that separates the second charge chamber  23  from the gas chamber  1 . A filler opening  27  serves to fill the gas chamber  1  with gas and is sealed with a suitable filler seal  28 . 
     Furthermore, a second charge chamber opening  29  is provided that serves as the flow connection between the second charge chamber opening  23  and the gas chamber  1 . The charge chamber opening  29  is initially sealed with a suitable seal. As FIG. 1 shows, a sealing washer  30  made of suitable material, covering the charge chamber opening  29 , is provided on the side of the second and wall  3  facing the gas chamber  1 . The section of the end wall  4  surrounding the second charge chamber opening  29  is designed as a flat sealing section. The sealing washer  30  is fastened to the end wall  4  in this section. 
     The second charge chamber opening  29  can be designed smaller in cross-section than the first charge chamber opening  14 . The first charge chamber opening  14  can, in turn, be designed smaller in cross-section than the discharge opening  7 . 
     The inflation device can be operated in three different inflation modes, with different ignition sequences. To control the gas-producing charges  10  and  22 , a control device (not shown in the drawing) is provided, with which the two charges  10  and  22  can be controlled and ignited independently of each other. 
     In a first inflation mode, only the first gas-producing charge  10  is ignited, while the second gas-producing charge  22  remains unignited. The resultant method of operation is shown in FIG.  2 . After ignition of the first gas-producing charge  10 , gas pressure builds up in the first charge chamber  10 , the resultant gas expands into the first gas chamber opening  8  and impinges upon the plug  17  with a corresponding force: the cylinder section  16 , together with the plug  17 , is pressed in the direction of the gas chamber  1  until the cylinder section  16  reaches the stop  31 , which is formed of a interior flange projecting radially inward on guide  20  and an exterior flange on cylinder  16 , projecting radially outward. This movement is supported by the conically-expanding section of the charge chamber opening  14 , and the expanding gas also presses on the end of the cylinder section  16 , projecting in this section, as shown in FIGS. 1 and 2. 
     As soon as the cylinder section  16  reaches the stop  31 , the gas from the first gas-producing charge  10 , continuing to expand, presses the plug  17  out of the cylinder section  16  so that the charge chamber opening  14  is opened by means of the hollow cylinder section  16  and the gas expanding from the first charge chamber  9  can expand into the discharge chamber  5  or the gas chamber  1 . 
     Through the movement of the plug  17  through the gas chamber opening  8 , the sealing washer  19  is removed and the gas chamber opening  8  is opened. Accordingly, the compressed gas can expand from the gas chamber  1  through the gas chamber opening  8  into the discharge chamber  5  and from there through the discharge opening  7  to the safety equipment. The gas exiting from the first charge chamber  9  can likewise flow through the discharge chamber  5  and its discharge opening  7 . The second charge chamber  23  remains sealed and the second charge  22  does not produce any gas. 
     In a second inflation mode, in contrast to this, only the second gas-producing charge  22  is ignited, while the first gas-producing charge  10  remains unignited. The resultant method of action is shown in FIG.  3 . Through the ignition of the second charge, the gas pressure builds up correspondingly in the second charge chamber  23  and presses of the sealing washer  30  so that the second charge chamber opening  29  is opened. The gas resulting from the second charge  22  can expand into gas chamber  1 . This increases the gas pressure in gas chamber  1  such that subsequently the gas chamber opening  8  is also opened. The sealing washer  19  is pressed upon by the increase in the gas chamber pressure. The gases in gas chamber  1  expand through the gas chamber opening  8  into the discharge chamber  5  and from there flow through the discharge opening  7  to the safety device. In the second inflation mode, another inflation characteristic arises. For one thing, the available cross-section area of the gas chamber opening  8  is smaller since the plug  17  with its head section  18  blocks a part of the gas chamber opening  8 . The head section  18  here blocks a larger portion of the gas chamber opening  8  than the cylinder section  16  that is thrust into the gas chamber opening  8  in the first inflation mode. For another, a smaller volume of gas is released by the second charge  22  so that overall the gas volume producing the inflation of the safety device is smaller. 
     In a third inflation mode, both the first gas-producing charge  10  and the second gas-producing charge  22  is ignited. Preferably, the two charges are ignited with a predetermined delay. Depending on the inflation characteristics desired, the first charge  10  or the second charge  22  can be ignited first. A repeated increase in pressure in the safety device can be achieved through the subsequent ignition of the other charge, and furthermore, the pressure available can be maintained over a longer period.