Hybrid inflator

A hybrid inflator has flame-transferring holes 118 which allow outflow of a booster gas, and first communication holes 125 which allow outflow of a combustion gas are arranged in the same position in the longitudinal direction of the hybrid inflator to render smooth outflow of the booster gas and the combustion gas.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an inflating-type safety system of motor vehicles, and more particularly to a hybrid inflator capable of inflating an air bag rapidly and unfailingly and an air bag system using the same inflator.

2. Description of Related Art

With the development of an inflator for an inflating-type safety system of motor vehicles, a hybrid inflator using both a pressurized gas and a solid gas generating agent is attracting attention. A main design requirement for a hybrid inflator is that the inflator inflates an air bag by a predetermined amount in a predetermined time so that the air bag is effectively activated. Various proposals concerning a structure to meet the requirement have heretofore been made (for example, as referred in JP-A8-282427). In order to secure safety of an occupant, it is important for such a hybrid inflator to inflate the air bag unfailingly.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a hybrid inflator which is highly reliable when used for an air bag system and an air bag system using the same inflator.

The present invention may be employed in a single type, an inflator provided with one gas generating chamber, as well as a dual type, an inflator provided with two gas generating chambers.

The present invention provides, as a means for solving a problem, a hybrid inflator for an inflating-type safety system of a vehicle provided with an airbag, comprising an inflator housing, a gas generator accommodated in the inflator housing, and an ignition means chamber provided with ignition means connected to the gas generator, a pressurized medium containing an inert gas charged inside the inflator housing, whereinan outer shell of the gas generator is constituted by a gas generator housing, the gas generator housing includes a charge-transferring chamber formed inside a cylindrical charge-transferring chamber housing provided longitudinally in an extension of the ignition means and a gas generating chamber defined by the charge-transferring chamber housing and the gas generator housing and stores gas generating means;the charge-transferring chamber housing has a plurality of flame-transferring holes provided at intervals in the longitudinal direction to make the charge-transferring chamber and the gas generating chamber communicate with each other, and the gas generating chamber has a plurality of communication holes communicating the interior of inflator housing; andat least some of a plurality of the flame-transferring holes and the communication holes are arranged not to face each other opposingly in the longitudinal direction.

If some or all of the flame-transferring holes and the communication holes are arranged not to face each other opposingly in the longitudinal direction of the hybrid inflator in the above manner, a booster gas flowing from the charge-transferring chamber moves the longer distance and may contact with more gas generating means as compared with a case where all of the flame-transferring holes and the communication holes are arranged to face each other oppositely, and thereby the gas generating means can be burnt more uniformly.

The present invention provides, as other means for solving a problem, a hybrid inflator for an inflating-type safety system of a vehicle provided with an air bag, comprising an inflator housing, a gas generator accommodated in the inflator housing, and an ignition means chamber provided with ignition means connected to the gas generator, a pressurized medium containing an inert gas charged inside the inflator housing, whereinan outer shell of the gas generator is constituted by a gas generator housing, the gas generator housing includes a charge-transferring chamber formed inside a cylindrical charge-transferring chamber housing provided longitudinally in an extension of one ignition means, and a first gas generating chamber and a second gas generating chamber defined by the charge-transferring chamber housing and the gas generator housing and store gas generating means respectively;the charge-transferring chamber housing has a plurality of flame-transferring holes provided at intervals in the longitudinal direction to make the charge-transferring chamber and the first gas generating chamber communicate with each other, and the first gas generating chamber and the second gas generating chamber are provided with a plurality of first communication holes and a plurality of second communication holes which communicate the interior of inflator housing respectively; andat least some of a plurality of the flame-transferring holes and the first communication holes are arranged not to face each other opposingly in the longitudinal direction.

Thus, if the flame-transferring holes and the first communication holes are arranged not to face each other opposingly in the longitudinal direction of the hybrid inflator, the gas generating means can be burnt uniformly in the same manner as above.

Moreover, in a hybrid inflator of the present invention, in order to burn the gas generating agent more uniformly as mentioned above, it is preferable that at least some of a plurality of the flame-transferring holes and the communication holes or a plurality of flame-transferring holes and the first communication holes are arranged not to face each other opposingly in the longitudinal direction of the hybrid inflator as well as in the widthwise direction.

Moreover, in a hybrid inflator of the present invention, in order to burn the gas generating agent more uniformly in the above manner, it is preferable that the plurality of flame-transferring holes and the plurality of communication holes or the first communication holes are provided evenly along the longitudinal direction of the gas generating chamber or the first gas generating chamber.

Moreover, in the hybrid inflator of the present invention, in order to burn the gas generating agent more uniformly as mentioned above, it is preferable that a plurality of the flame-transferring holes and the communication holes, or a plurality of the flame-transferring holes and the first communication holes are arranged at equal intervals.

Further, the hybrid inflator of the present invention may be structured such that respective distances in the longitudinal direction of the first gas generating chamber and the second gas generating chamber are adjusted by a first retainer disposed on one end of the gas generator housing and a second retainer disposed on the other end, that is between the first gas generating chamber and the second gas generating chamber.

In the present invention, it is preferable that the first and second retainers comprise a combination of a larger-diameter cylinder having one end surface closed and the other end face open, a smaller-diameter cylinder which is formed integrally with the larger-diameter cylinder to project towards the inside and the opening portion of the larger-diameter cylinder and has both end surfaces open, and an annular member provided between the larger-diameter cylinder and the smaller-diameter cylinder.

In the first and second retainers, the annular member provided between the larger-diameter cylinder and the smaller-diameter cylinder may be formed integrally with the closed end surface to project towards the opening portion or can be formed separately and arranged.

Further, in the first and second retainers, a height of the side wall of the larger-diameter cylinder is the highest and a height of the annular projecting member is the lowest.

In the present invention, preferably, the first retainer is arranged such that the closed end surface is positioned in the first gas generating chamber side and the second retainer is arranged such that the opening portion is positioned in the first gas generating chamber side.

When the first and second retainers are arranged in this manner, the first gas generating chamber lies between the closed end surface of the first retainer and the opening portion of the second retainer. With such an arrangement, a combustion gas generated in the gas generating chamber is prevented from entering the second gas generating chamber due to function of the second retainer. Furthermore, since the annular member exists on the opening portion of the second retainer, the gas generating means is prevented from entering the opening portion of the second retainer. If the annular member does not exist, combustion of the gas generating means which enters the opening portion of the second retainer may be delayed or movement of combustion gas may be blocked.

Also, the hybrid inflator of the present invention is structured such that a spare communication hole is provided in a wall surface of the gas generator housing where the gas generating chamber, or the first gas generating chamber and the second gas generating chamber do not exist, penetrating the wall surface.

Here, the “spare communication hole” does not function as a communication hole which is a passage of the pressurized medium and a combustion gas at normal activation, but functions as a communication hole, serving as a spare passage for discharging the pressurized medium and a combustion gas out of the inflator, only when there occurs the below-specified trouble at activation.

The gas generator housing provided with the communication holes or the first and second communication holes is not fixed by welding or the like, but it is mounted in a state such that one end thereof is fitted into a boss fixed to the inflator housing. Thereby, there may occur a trouble (the specified trouble) such that the gas generating housing moves in the longitudinal direction, due to the impact of activation, to block the passage for the pressurized medium and a combustion gas. In such a case, a normal activation of the hybrid inflator can be retrieved by the spare communication hole serving as another passage for the pressurized medium and a combustion gas.

Also in the hybrid inflator, a boss is disposed on one end of the hybrid inflator, the ignition means is disposed in an ignition means chamber formed inside the boss, the charge-transferring means adapted to be ignited and burnt by the ignition means is disposed inside the charge-transferring chamber housing, and one end of the charge-transferring chamber housing is fixed to the boss.

Furthermore, such a structure can be employed that one end of the charge-transferring chamber housing is provided with a skirt portion expanding in the radial direction, the charge-transferring means is inserted into the skirt portion, and the periphery of the skirt portion is crimped from the outside by an annular projecting portion integrated with the boss, or one end of the charge-transferring chamber housing has a bent portion bent outwardly in the radial direction, the charge-transferring means is inserted into one end formed with the bent portion in the charge-transferring chamber housing, and the periphery of the bent portion is crimped from the outside by the annular projecting portion integrated with the boss.

By employing such a structure, the charge-transferring means and the charge-transferring chamber housing are adhered and fixed to each other integrally, and thereby, a high-temperature booster gas (flame), generated by the charge-transferring means ignited and burnt due to activation of the ignition means, is prevented from leaking so that the gas generating means may be burnt smoothly.

Moreover, such a structure is preferably employed that the skirt portion and the annular projecting portion, or the bent portion and the annular projecting portion are brought into contact with each other to adhere closer by a force against a force applied in the longitudinal direction of the hybrid inflator.

During combustion of the charge-transfer means, a large force is applied to the charge-transferring chamber housing in the longitudinal direction of the hybrid inflator, and, by securing adhesion against that force, preferably by realizing surface-contact between the skirt portion and the annular projecting portion, or the bent portion and the annular projecting portion, leakage preventing action of a booster gas generated by actuation of the ignition means is further improved. If the skirt portion and the annular projecting portion, or the bent portion and the annular projecting portion are in spot-contact with each other, when a large force is applied in the longitudinal direction of the inflator, a clearance is generated between the skirt portion and the annular projecting portion, or the bent portion and the annular projecting portion, which may result in leakage of a booster gas.

Also, the present invention provides, as other means for solving the above problem, a hybrid inflator for an inflating-type safety system of a vehicle provided with an air bag, comprising an inflator housing, a gas generator accommodated in the inflator housing, and an ignition means chamber provided with ignition means connected to the gas generator, a pressurized medium containing an inert gas charged inside the inflator housing, whereinan outer shell of the gas generator is constituted by a gas generator housing, the gas generator housing includes a charge-transferring chamber formed inside a cylindrical charge-transferring chamber housing provided longitudinally in an extension of one ignition means, and a first gas generating chamber and a second gas generating chamber defined by the charge-transferring chamber housing and the gas generator housing and store gas generating means respectively;respective distances in the longitudinal direction of the first gas generating chamber and the second gas generating chamber are adjusted by a first retainer disposed on one end and a second retainer disposed on the other end, that is between the first gas generating chamber and the second gas generating chamber; andthe first and second retainers comprise a combination of a larger-diameter cylinder having one end surface closed and the other end surface open, a smaller-diameter cylinder formed integrally with the larger-diameter cylinder to project towards the inside and the opening portion of the larger-diameter cylinder and has both end faces open, and an annular member provided between the larger-diameter cylinder and the smaller-diameter cylinder.

In the first and second retainers, the annular member provided between the larger-diameter cylinder and the smaller-diameter cylinder can be formed integrally with a closed end surface to project towards an opening portion or can be formed separately and arranged.

Moreover, in these first and second retainers, a height of a side wall of the larger-diameter cylinder may be the highest and a height of the annular projecting member may be the lowest.

In the present invention, in order to obtain the above described operation, it is preferable that the first retainer is arranged such that a closed end surface thereof is positioned in the first gas generating chamber side and the second retainer is arranged such that an opening portion thereof is positioned in the first gas generating chamber side.

Also, the present invention provides a hybrid inflator for an inflating-type safety system of a vehicle provided with an airbag, comprising an inflator housing, a gas generator accommodated in the inflator housing, and an ignition means chamber provided with ignition means connected to the gas generator, a pressurized medium containing an inert gas charged in the inflator housing, whereinan outer shell of the gas generator is constituted by a gas generator housing, the gas generator housing includes a charge-transferring chamber formed inside a cylindrical charge-transferring chamber housing provided longitudinally in: an extension of one ignition means, and at least one gas generating chamber defined by the charge-transferring chamber housing and the gas generator housing and store a gas generating means; anda spare communication hole is provided in a wall surface of the gas generator housing where the gas generating chamber is not provided to penetrate the wall surface.

Here, the “spare communication hole” is as described as the above and has the same functions as the above.

Also, the present invention provides a hybrid inflator for an inflating-type safety system of a vehicle provided with an airbag, comprising an inflator housing, a gas generator accommodated in the inflator housing, and an ignition means chamber provided with ignition means connected to the gas generator, a pressurized medium containing an inert gas charged in the inflator housing, whereinan outer shell of the gas generator is constituted by a gas generator housing, the gas generator housing includes a charge-transferring chamber formed inside a cylindrical charge-transferring chamber housing provided longitudinally in an extension of one ignition means, and at least one gas generating chamber defined by the charge-transferring chamber housing and the gas generator housing and store a gas generating means;a boss is disposed in one end of the hybrid inflator, the ignition means is disposed in the ignition means chamber formed inside the boss, and charge-transferring means adapted to be ignited and burnt by the ignition means is disposed in the charge-transferring chamber housing; andone end of the charge-transferring chamber housing has a skirt portion expanding in the radial direction, the charge-transferring means is inserted into the skirt portion, and the periphery of the skirt portion is crimped from the outside by an annular projecting portion integrated with the boss, or one end of the charge-transferring chamber housing has a bent portion bent outwardly in the radial direction, the charge-transferring means is inserted into one end formed with the bent portion in the charge-transferring chamber housing, and the periphery of the bent portion is crimped from the outside by the annular projecting portion integrated with the boss.

By employing such a structure, the charge-transferring means and the charge-transferring chamber housing are adhered and fixed to each other integrally as described above, a high temperature booster gas (flame) generated by the charge-transferring means ignited and burnt due to activation of the ignition means is prevented from leaking so that the gas generating means may be burnt smoothly.

In the hybrid inflator of the present invention, as described below, the gas generating agent (gas generating means) accommodated in the gas generating chamber, or first and second gas generating agents (gas generating means) accommodated in the first and second gas generating chambers, respectively, may be determined in relation with composition of the pressurized medium charged in the inflator housing. In this invention, the gas generating agent used in a single type inflator and the gas generating agent used in a dual type inflator are the same, so that the gas generating agent used in the dual type inflator will be described below.

The pressurized medium used in the hybrid inflator of the present invention consisting essentially of an inert gas such as argon, helium (nitrogen is also included in the inert gas in the present invention), etc., and it may contain oxygen as required. Argon works to promote the thermal expansion of the pressurized medium. It is preferable to contain helium in the pressurized medium since the leakage of the pressurized medium can be detected easily for the purpose of preventing distribution of the imperfect products. Also, oxygen works to convert carbon monoxide or hydrogen generated due to the combustion of the gas generating agent serving as the gas generating means into carbon dioxide or water steam. A charging pressure (=pressure in the inflator housing) of the pressurized medium is preferably 10,000 to 70,000 kpa, and more preferably 30,000 to 60,000 kPa. Incidentally, the pressurized medium may contain oxygen or it may not contain oxygen. When the pressurized medium contains oxygen, the content of oxygen is preferably at most 30 mol %.

As the first and second gas generating agents stored respectively in the first and second gas generating chambers, a gun propellant may be used for example. As the gun propellant, a single-base gun propellant, a double-base gun propellant, and a triple-base gun propellant may be used. In addition to those gun propellants, it is possible to use a gun propellant obtained by mixing a secondary explosive, a bonding agent, a plasticizer and a stabilizer and the like, and molding the resultant mixture to a desired shape.

The secondary explosive may include hexahydrotrinitrotriazine (RDX), cyclotetramethylene tetranitramine (HMX), pentaerithritol tetranitrate (PETN), and triaminoguanidine nitrate (TAGN). For example, when a gas generating agent using RDX as a secondary explosive is burned in an oxygen-absent atmosphere under a pressure of 20,670 kPa and at a combustion temperature of 3348 K, a formed gas in a combustion gas comprises 33 mol % of nitrogen, 25 mol % of carbon monoxide, 23 mol % of vapor, 8 mol % of carbon dioxide and other gas components.

A preferable ratio of the secondary explosive to the bonding agent, plasticizer and stabilizer is about 50 to 90 wt. % of secondary explosive to about 10 to 50 wt. % of bonding agent, plasticizer and stabilizer in all.

In some cases, the gas generating agent of the above-described composition is not smoothly burnt under normal pressure. However, when the interior thereof is maintained at a high pressure in advance like the hybrid inflator of the present invention, the gas generating agents may be burnt stably and smoothly.

In addition, the first gas generating agent accommodated in the first gas generating chamber and the second gas generating agent accommodated in the second gas generating chamber may be obtained, for example, in such manner that one including fuel and oxidizing agent, or one including fuel, oxidizing agent, and slag-forming agent is mixed with bonding agent, if required, to be molded into a desired shape. If such a gas generating agent is used, a gas generated due to combustion of such an agent may be used for developing the air bag together with the pressurized medium. Especially, when the gas generating agent including the slag-forming agent is used, an amount of mist discharged from the inflator may be largely reduced.

Preferably, the fuel may be one or more materials selected from a group consisting of guanidine derivatives such as nitroguanidine (NQ), guanidine nitrite (GN), guanidine carbonate, amino nitroguanicine, amino guanidine nitrite, amino guanidine carbonate, diamino guanidine nitrite, diamino guanidine carbonate, and triamino guanidine nitrite but, not limited thereto. Further, as the fuel, at least one selected from tetrazole, tetrazole derivatives and the like may be also used.

As oxidizer, one or more materials selected from a group comprising strontium nitrate, potassium nitrate, ammonium nitrate, potassium perchlorate, copper oxide, ferrous oxide, basic copper nitrate may be used. Preferable composition amount of oxidizer is 10 to 80 parts by weight, and more preferably, 20 to 50 parts by weight with respect to 100 parts by weight of fuel.

Preferably, the slag-forming agent may be one or more materials selected from a group consisting of acid clay, talc, bentonite, diatomaceous earth, kaolin, silica, alumina, sodium silicate, silicon nitride, silicon carbide, hydrotalsite, and a mixture thereof. Preferable composition amount of slag-forming agent is 0 to 50 parts by weight, and more preferably, 1 to 10 parts by weight with respect to 100 parts by weight of fuel.

Preferably, the bonding agent may be one or more materials selected from a group consisting of sodium salt of sodium carboxymethylcellulose, hydroxyethyl cellulose, starch, polyvinyl alcohol, guar gum, microcrystal cellulose, polyacrylamide, and calcium stearate.

Preferable composition amount of the bonding agent is 0 to 30 parts by weight, and more preferably, 3 to 10 parts by weight with respect to 100 parts by weight of fuel. Preferably, the fuel may be one or more selected from guanidine derivative such as nitroguanidine (NQ), guanidine nitite (GN), guanidine carbonate, amino nitroguanidine, amino guanidine nitrite, amino guanidine carbonate, diaminoguanidine nitrite, diamino guanidine carbonate, and triamino guanidine nitrite. As fuel one or two or more materials selected from a group comprising tetrazole and tetrazole derivative may be used.

The present invention provides an air bag system comprising activation signal-outputting means including an impact sensor and a control unit, and a module case in which the above-described hybrid inflator and an air bag are accommodated.

Since one of the characteristics of the dual type hybrid inflator of the present invention is in the arrangement of the flame-transferring holes and the first communication holes, the structure and arrangement of the first and second retainers, the existence of the spare communication hole, the mounting method of the charge-transferring chamber housing and so on, malfunctioning of the hybrid inflator at activation is avoided owing to these functions. Even in a single type hybrid inflator, the same functions may be obtained. Accordingly, when the present invention is applied to an air bag system, an air bag may be inflated rapidly and unfailingly.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention will be explained in detail as follows with reference to the drawings showing embodiments of the invention.FIG. 1is a longitudinal sectional view of one embodiment of a dual type hybrid inflator100,FIG. 2is a widthwise sectional view of a first gas generating chamber shown inFIG. 1, FIG.3(a) is a perspective view of a retainer used in the embodiment shown inFIG. 1, and FIG.3(b) is a sectional view of the retainer shown in FIG.1.

As shown inFIG. 1, an inflator housing102comprises a cylindrical pressure-resisting container, and its inner space103is filled with a pressurized medium and maintained at a high pressure. The pressurized medium is usually charged from a small hole107formed in a boss145connected to one end of the inflator housing102, and the small hole107is closed with a seal pin109after the pressurized medium has been charged. The inflator housing102may be formed to have a shape such that the outer shape thereof except for a portion in the vicinity of the end portion in the diffuser108side has a uniform diameter (even shape without constriction or the like).

An outer shell of a gas generator108is formed by a gas generator housing105, one end of which is fitted into a boss145. The gas generator108includes, therein, a charge-transferring chamber110, and a first gas generating chamber120and a second gas generating chamber130surrounding the charge-transferring chamber110and disposed adjacent to each other in series in the longitudinal direction of the inflator housing102.

The charge-transferring chamber110comprises a cylindrical charge-transferring chamber housing111, and is connected to a first igniting initiator117through a booster cup116, in which a booster agent (transfer charge)112serving as charge-transferring means is charged and a first communication passage closed by a first rupturable plate119serving as first closing means. The charge-transferring chamber110is in communication with the first gas generating chamber120through flame-transferring holes118.

The first gas generating chamber120surrounds the charge-transferring chamber110, and is defined by the gas generator housing105, the charge-transferring chamber housing111, a first retainer126, and a second retainer136. A required amount of a first gas generating agent124, serving as gas generating means, is accommodated in the first gas generating chamber120. The first gas generating chamber120and the inflator housing102communicate each other through a plurality of first communication holes125. A diameter of a plurality of first communication holes125is adjusted such that the first gas generating agent124does not pass through the holes125into the first gas generating chamber120.

As shown inFIG. 1, a plurality of the flame-transferring holes118and a plurality of the first communication holes125are arranged in part not to face each other opposingly in the longitudinal direction of the inflator housing102. If the flame-transferring holes118and the first communication holes125are arranged in this manner, the first gas generating agent124may be burnt uniformly for the following reason.

If the flame-transferring holes118and the first communication holes125are arranged in part not to face each other opposingly, a flow of a high temperature-booster gas, generated due to combustion of the booster agent118to flow out of the charge-transferring holes, passes the longer distance to flow out of the first communication holes125after contacting with the first gas generating agent124, compared with a case such that the flame-transferring holes118and the first communication holes125are arranged to face each other opposingly. For this reason, all the first gas generating agent may be burnt uniformly. Furthermore, inFIG. 1, since some of the flame-transferring holes118and the first communication holes125are arranged to face each other opposingly, the gas flow is never blocked because of the other holes which do not face each other opposingly.

Meanwhile, if all flame-transferring holes118face opposingly the first communication holes125, a booster gas which flows out of the flame-transferring holes118passes the shortest distance from the flame-transferring hole118and the first communication hole125so that the first gas generating agent124, positioned on an imaginary line connecting the flame-transferring hole118and the first communication hole125may be burnt but the first gas generating agent124which is not positioned on said imaginary line may be burnt at a delayed timing.

Moreover, as shown inFIG. 2, it is preferable that the plurality of the flame-transferring holes118and the plurality of the communication holes125are arranged not to face each other opposingly in the widthwise direction (radial direction). With such an arrangement, the booster gas flows, as shown in arrows, so that the first gas generating agent124may uniformly be burnt.

Also, in order to burn the first gas generating agent124uniformly, it is preferable that the plurality of flame-transferring holes118and the plurality of communication holes125are provided evenly along the longitudinal direction of the first gas generating chamber120.

Further, it is preferable that the plurality of flame-transferring holes118and the plurality of first communication holes125are arranged at equal intervals, respectively.

A second gas generating chamber130is defined by the gas generator housing105, the charge-transferring chamber housing111, the second retainer136, and the boss145(and a second rupturable plate139). The second gas generating chamber130includes, therein, a required amount of second generating agent134serving as second gas generating means. The second gas generating chamber130and the inflator housing102communicate with each other through a plurality of communication holes135having diameters adjusted in the above-described manner.

The volumes of the first gas generating chamber120and the second gas generating chamber130are determined by the first retainer126and the second retainer136. As the second retainer136, one having the structure shown in FIGS.3(a) and3(b) is preferably employed. Also, in view of reducing manufacturing steps, the first retainer126and the second retainer136may be the same.

Each of the first retainer126and the second retainer136comprises a larger-diameter cylinder201having one end closed and the other end open, a smaller-diameter cylinder202having both ends open and formed integrally with the larger-diameter cylinder201to project towards the inside and the open end of the larger-diameter cylinder201, and an annular member203provided between the larger-diameter cylinder201and the smaller-diameter cylinder202and integrated with the closed end to be projected.

The annular member203is for preventing the first gas generating agent124from entering the opening portion of the second retainer136. Therefore, as long as the annular member203has such a function, it is not particularly limited this structure and an annular member formed separately may be fitted.

As shown inFIG. 1, the first retainer126and the second retainer136are engaged by inserting the charge-transferring chamber housing111into a through-hole portion of the smaller-diameter cylinder202, so that an outer wall surface of the larger-diameter cylinder201make contact with an inner wall surface of the gas generator housing105, and that an outer wall surface of the smaller-diameter cylinder202makes contact with an outer wall surface of the charge-transferring chamber housing111.

The first retainer126and the second retainer136are mounted in a state such that they are fitted to the charge-transferring chamber housing111. In order to secure stability at a time of mounting, it is preferable that the height of the side wall of the larger-diameter cylinder201is higher than that of the smaller-diameter cylinder201. The annular member203has such a height that the gas generating agent124cannot enter the inside.

The first retainer126is arranged such that the closed end surface is positioned in the first gas generating chamber120side, and the second retainer136is arranged such that the opening portion is positioned on the first gas generating chamber120side.

With such an arrangement, when the first gas generating agent124is burnt and a pressure inside the first gas generating chamber120increases, the second retainer136is inflated to be spread outwardly so that the outer wall surface of the larger-diameter cylinder201presses the inner wall surface of the gas generator housing105to obtain closer contact therebetween, and also the outer wall surface of the smaller-diameter cylinder202presses the outer wall surface of the charge-transferring chamber housing111to obtain closer contact therebetween. As a result, the combustion gas in the first gas generating chamber120is prevented from leaking into the second gas generating chamber130. Moreover, the other surface205of the annular member of the first retainer126is also pressed and at the same time, the larger-diameter cylinder201and the smaller-diameter cylinder202are spread apart, and thereby, the combustion gas is prevented from leaking into the space177.

The second gas generating chamber130is connected to a second igniting initiator140through a second communication passage closed by a second rupturable plate139serving as second closing means. Incidentally, in the second gas generating chamber130, a plurality of second communication holes135are formed in the opposite side of the second igniting initiator140in the widthwise direction (a radial direction).

Since the first igniting initiator117(the first ignition means chamber115) and the charge-transferring chamber110are arranged on the center axis (shown in the dotted line inFIG. 1) extending in the longitudinal direction of the inflator housing102, the second igniting initiator140is arranged eccentrically with respect to the center axis.

An amount of the second gas generating agent134may be equal to or more than or less than an amount of the first gas generating agent124. Also, a shape and composition of the second gas generating agent134may be the same as or different from the first gas generating agent124.

As mentioned above, the charge-transferring chamber110communicates with the first gas generating chamber120, the first gas generating chamber120communicates with the inflator housing102, and further, the second gas generating chamber130communicates with the inflator housing102, and thereby, the charge-transferring chamber110, the first gas generating chamber120, and the second gas generating chamber130are all maintained in a high pressure, namely they are maintained in the same pressure as that of the interior (inner space103) of the inflator housing102.

The first gas generating chamber120and the second gas generating chamber130are arranged in series and adjacent to each other along the longitudinal direction of the inflator housing102. By arranging them in series, even when two gas generating chambers are provided, the entire size of the hybrid inflator can be made compact and increase in weight thereof can be suppressed.

In the first gas generating chamber120and the second gas generating chamber130, passages, through which gases respectively generated by combustion of the first gas generating agent124and the second gas generating agent134flow into the inflator housing102, are independent from each other. That is, a combustion gas generated in the first gas generating chamber120flows from the first communication holes125into the inflator housing102, and the combustion gas generated in the second gas generating chamber130flows from the second communication holes135into the inflator housing102.

Also, in the first gas generating chamber120and the second gas generating chamber130, when a gas generated in the first gas generating chamber120flows as a gas flow from the first communication holes125of the inflow path to a diffuser port182inside the inflator housing102, the second communication hole135of an inflow path of the second gas generating chamber130is positioned in a direction opposite to the first communication hole125, which is the inflow path of the first gas generating chamber120, in view of the gas flow.

By arranging the first gas generating chamber120and the second gas generating chamber130in this manner, the combustion in the first gas generating chamber120does not affect the second gas generating chamber130. Such an arrangement is effective especially in such a case that oxygen is not contained in the pressurized medium because combustion in the first gas generating chamber120does not affect the second gas generating chamber130. Incidentally, the arrangement order of the first gas generating chamber120and the second gas generating chamber130may be reversed.

An ignition means chamber114formed in the boss145includes a first ignition means chamber115and a second ignition means chamber141. The first ignition means chamber accommodates the first igniting initiator117therein and the second ignition means chamber141accommodates the second igniting initiator140. The first and second ignition means chambers may be arranged in parallel and adjacent to each other in the widthwise direction of the inflator housing102.

The first igniting initiator117and the second igniting initiator140are mounted to the boss145through an initiator collar143, and the boss145is fixed to the inflator housing102at a joining portion146by welding or the like.

As shown in FIG.1andFIG. 4, a partially enlarged view ofFIG. 1, one end of the charge-transferring chamber housing111has a skirt portion133expanded in the radial direction, and a buster cup116is inserted into the skirt portion133. Then, by a annular projecting portion131of the skirt portion133integrated with the boss145, a periphery of the skirt portion133is crimped from the outside, and by a surface-contact between an inner surface131aof the annular projecting portion131and an outer surface of the skirt portion133, these surfaces make contact with each other closely.

When a large force is applied to the charge-transferring chamber housing111in the direction of the arrow (in the longitudinal direction) at an activation of the hybrid inflator100, the skirt portion133is also moved in the direction of the arrow (see FIG.4), and the outer surface133athereof is pressed against the inner surface131aof the annular projecting portion, namely, a force against a force in the direction of the arrow (the longitudinal direction) is applied to the outer surface133aof the skirt portion by the inner surface131aof the annular projecting portion, and thereby, a contact between the contacting surfaces is further enhanced. Therefore, the booster gas generated in the charge-transferring chamber110is prevented from leaking into the first igniting initiator117side.

Next, a structure for preventing a booster gas from leaking according to a different embodiment from that shown in FIG.4will be explained with reference to FIG.5. As shown inFIG. 5, one end of a charge-transferring chamber housing111is bent outwardly in the radial direction to form a bent portion133′, and a booster cup116is inserted into the bent portion133′. Then, the periphery of the bent portion133′ is crimped from the outside by an annular projecting portion131′ integrated with the boss145, and an inner surface131a′ of the annular projecting portion131′ and an outer surface133a′ of the bent portion133′ are brought in surface-contact with each other, thereby achieving a closer contact between contacting areas. Even in the embodiment shown inFIG. 5, a booster gas generated in the charge-transferring chamber110may be prevented from leaking into the first igniting initiator117side according to the same action as FIG.4.

An adapter170is connected in extension of the charge-transferring chamber110, and a projectile175having the illustrated shape for rupturing a main rupturable plate178upon actuation is mounted through an O-ring172to an opening portion where the charge-transferring chamber110and the adapter170communicate each other, straddling the charge-transferring chamber110and the adapter170. A top end of the projectile175is positioned in an inner space176of the adapter170. The inner space176and inner space103of the inflator housing102communicate with each other exclusively through a plurality of gas inflow holes166provided on a surface of the adapter170opposing an inner surface of the housing105. Since a gas flow path105ais defined by the inner surface of the housing105and the outer surface of the adapter170, the pressurized medium in the inner space103necessarily flows in the gas inflow holes166through the gas flow path105aat the time of activation.

A spare communication hole155which communicates with the inner space103is provided in a wall surface of the gas generator housing105where the first gas generating chamber120and the second gas generating chamber130do not exist. The spare communication hole155serves as a spare path for discharging the pressurized medium and a combustion gas out of the hybrid inflator100.

The diffuser180is connected to one end of the inflator housing102. The diffuser180is fixed at a connecting portion181by welding. The main rupturable plate178of the main closing means for blocking a flow path to a diffuser port182of the pressurized medium before actuation is disposed on one end of the diffuser180, opposing the projectile175. Therefore, before actuation, a gas inflow space150and the inner space103of the inflator housing102are completely separated and isolated from each other by the main rupturable plate178and a flow of the pressurized medium is, therefore, blocked.

On the other end of the diffuser180, a plurality of diffuser ports182for introducing the pressurized medium to the air bag and a diffuser screen186for removing fine particles are provided. A stud bolt190for connecting the inflator to the air bag module is fixed to the outer surface of the diffuser180.

In the hybrid inflator100, it is preferable that the above-described constituent elements are arranged symmetrically in the widthwise direction with respect to the center axis (shown as the dotted line in FIG.1), but some or all of the constituent elements may be arranged eccentrically with respect to the center axis.

In the hybrid inflator of the present invention, the arrangement of the first and second gas generating chambers may be changed appropriately as described below.

For example, the first gas generating chamber120and the second gas generating chamber130may be arranged on both ends of the inflator housing102, respectively, to face each other inside the housing. In this case, the pressurized medium is charged into the space between the first gas generating chamber120and the second gas generating chamber130.

Further, for example, in the inflator housing102, the first gas generating chamber120(or the second gas generating chamber130) may surround the charge-transferring chamber110, and the second gas generating chamber130(or the first gas generating chamber120) may surround the first gas generating chamber120.

Next, a single type hybrid inflator100will be explained with reference to FIG.6. The single type hybrid inflator has the same structure and operation as those in the dual type hybrid inflator100shown inFIG. 1except that the single type hybrid inflator includes only one gas generating chamber (corresponding to the first gas generating chamber inFIG. 1) and only one ignition means corresponding thereto. InFIG. 6, the same reference numerals as those shown inFIG. 1have the same meanings, but, as the retainer126, a retainer in a different shape from that inFIG. 1is used.

The air bag system of the present invention is provided with activation signal-outputting means including an impact sensor and a control unit, and a module case in which the hybrid inflator100and the air bag are accommodated. The hybrid inflator100is connected to the activation single-outputting means (the impact sensor and the control unit) at the first igniting initiator117and the second igniting initiator140, and it is connected and fixed inside the module case attached with the air bag by screwing the stud bolt190. In the air bag system thus structured, an amount of gas generation is adjusted according to the degree of impact by properly setting the activation signal-outputting conditions in the activation signal-outputting means, so that an inflating speed of the air bag may be adjusted.

Next, an operation of the hybrid inflator100will be explained with reference toFIGS. 1to4.

Before the hybrid inflator100is activated, the pressurized medium charged in the inflator housing102under a high pressure is also contained in the first gas generating chamber120and the second gas generating chamber130which are in communication with the interior of the inflator housing102through the first communication holes125and the second communication holes135respectively. Further, the pressurized medium is also contained in the charge-transferring chamber110through the flame-transferring holes118, being maintained at the same high pressure. Also, since the projectile175is mounted to straddle the inner space176and the charge-transferring chamber110maintained at the same pressure, malfunction of the hybrid inflator100is avoided.

When a vehicle collides, the first igniting initiator117is ignited by the activation signal-outputting means to rupture the first rupturable plate119, and then ignites and burns the booster112, thereby generating a high-temperature booster gas.

When the internal pressure in the charge-transferring chamber110increases by generation of the booster gas, the projectile175pushed by the pressure is moved such that the main rupturable plate178is ruptured by a sharp top end of the projectile. At this time, a portion of the booster gas flows into the gas inflow space150due to rupturing of the main rupturable plate178. Incidentally, since the skirt portion133and the annular projecting portion131are brought in surface-contact with each other to resist the pressure at activation, the booster gas is prevented from leaking into the first igniting initiator117side.

Most part of the booster gas flows into the first gas generating chamber120from the flame-transferring holes118to ignite and burn the first gas generating agent124, and a required amount (corresponding to the amount of the first gas generating agent124) of high-temperature combustion gas is generated. At this time, the flame-transferring holes118and the first communication holes125are arranged in part not to face each other in the longitudinal direction of the hybrid inflator and also are all arranged not to face each other in the widthwise direction thereof, so that the first gas generating agent124may be burnt uniformly. Also, since the pressurized medium flows into the first gas generating chamber120to maintain the interior thereof at a high pressure, the combustion of the first gas generating agent124is stable. Incidentally, at the time of combustion of the first gas generating agent, the second gas generating agent134is never ignited and burnt due to function of the first retainer126. Further, the arrangement of the first communication holes125of the first gas generating chamber120and the second communication holes135of the second gas generating chamber130also serves to prevent the second gas generating agent134from being ignited and burnt due to the combustion of the first gas generating agent124.

Thereafter, the combustion gas generated in the first gas generating chamber120flows into the inner space103through the first communication holes125, and the pressurized medium pressed by this combustion gas flows into the gas inflow space150through the ruptured main rupturable plate178. The pressurized medium flowing into the gas inflow space150in this manner is further ejected from the diffuser port182through the diffuser screen186to inflate the air bag mounted to the air bag module.

Further, the second igniting initiator140is ignited by the activation signal-outputting means simultaneously when or slightly after (about 10 to 40 ms) the first igniting initiator134is activated, and the second rupturable plate139is ruptured, and the second gas generating agent134is ignited and burnt, thereby generating the required amount (an amount corresponding to the charged amount of the second gas generating agent134) of a high-temperature combustion gas. At this time, since the second gas generating chamber130has been charged with the pressurized medium and maintained in a high pressure, the combustion of the second gas generating agent134is stable.

Also, as shown inFIG. 1, since the second igniting initiator140is separated from the second communication holes135and oriented in a different direction therefrom in the radial direction, the second gas generating agent134in the second gas generating chamber130is burnt uniformly. For example, if the second communication holes135are arranged in the vicinity of the second igniting initiator140, the second gas generating agent134close to the second communication holes135is burnt smoothly, but the second gas generating agent134positioned far from the second communication holes134may be hardly burnt in some cases.

The high-temperature combustion gas generated by combustion of the second gas generating agent134flows in the inner space103through the second communication holes135to increase the pressure, and the pushed remaining pressurized medium flows into the gas inflow space150through the ruptured main rupturable plate178and is ejected from the diffuser port182to further inflate the air bag.

Incidentally, since the gas generator housing105is fitted into the boss145to be mounted, there is a possibility such that it is moved in the longitudinal direction opposite to the boss145by increase of pressure due to the combustion of the first gas generating agent124and the second gas generating agent134so that the tip end106of the gas generator housing105may collide the inflator housing102. If the gas generator housing105collides, a passage from the inner space103to the gas flow passage105aand the gas inflow hole166is blocked so that a flow passage of the pressurized medium and a combustion gas towards the outside is blocked. However, with the spare communication hole155, even in case of the above collision of the gas generator housing105, the passage to the gas flow passage105aand the gas inflow hole166is secured because the spare communication holes155are positioned to face oppositely the gas inflow holes166in the longitudinal direction and/or in the widthwise direction.

In the above-described hybrid inflator, by generating the combustion gas in two stages, an inflating action of an air bag at the time of a vehicle collision may be prevented from being delayed by the function of the first gas generating chamber120, and the pressurized medium in the inflator housing102may be discharged completely by the function of the second gas generating chamber130, thereby inflating the air bag immediately up to a satisfying safety level.

Since two gas generating chambers are provided, this hybrid inflator may also be adapted to an embodiment in which a combustion gas is generated only in the first gas generating chamber120, an embodiment in which combustion gases are generated in the first and second gas generating chambers120and130simultaneously, and an embodiment in which an interval between the times of generating respective combustion gases in the first gas generating chamber120and the second gas generating chamber130may be adjusted optionally.