Gas generator

A gas generator includes, a housing having a defining a first combustion chamber, an ignition chamber cup, defining an ignition chamber, and a combustion chamber cup, defining a second combustion chamber, being aligned at a distance in a radial direction, a first communication hole communicating the ignition chamber with the first combustion chamber being provided in a circumferential wall portion of the ignition chamber cup, a second communication hole communicating the second combustion chamber with the first combustion chamber being provided in a circumferential wall portion of the combustion chamber cup, a cup-shaped cover member covering the combustion chamber cup and closing the second communication hole, a disk-shaped retainer retaining a gas generating agent, being provided with a first opening for fitting the ignition chamber cup and a second opening for fitting the combustion chamber cup, an annular gap being formed between the second opening and the cover member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a gas generator for use in a restraining device of a vehicle and the like.

2. Description of Related Art

In a gas generator that uses a solid gas generating agent, a gas generating agent of various shapes such as granular, a pellet form and a disk shape is used. The surface area of a gas generating agent increases when the agent is powdered due to external vibration or shock, which affects the output of the gas generator. Thus, fixing means for the gas generating agent is needed in order to block movement of the gas generating agent in the combustion chamber.

In JP-A No. 2002-503584, an igniter cup56and a generant cup84are aligned in the radial direction in a housing construction12. A second gas generant material86and an initiating device90are accommodated in a second chamber82in the generant cup84. A plurality of gas exit orifices104are formed on a sidewall100of the generant cup84, and an outer side wall of the cylindrical sidewall100including the gas exit orifices104is covered with a cylindrical pressure sensitive insulator barrier material106.

As shown inFIG. 1, a first gas generant material36in a first chamber34is retained by a retainer50, and the retainer50further presses a part of the pressure sensitive insulator barrier material106. Since the other portions of the pressure sensitive insulator barrier material106are sandwiched with the igniter cup56and the generant cup84, it is impossible to expand and deform in the direction of the igniter cup56, and it is difficult for the gas exit orifices104of the generant cup84which face the igniter cup56to open. In addition, since the retainer50abuts against an upper surface of a filter42, an charging amount into the first chamber34is restricted, so in some cases, the function of retaining the gas generant cannot be sufficiently yielded depending on an amount of the first gas generant36.

SUMMARY OF THE INVENTION

The present invention provides a gas generator including:

a housing (11) formed by a diffuser shell (12) having a gas discharge port (14) and a closure shell (13), a first combustion chamber (31) defined in the housing (11) and a first gas generating agent (33) charged in the first combustion chamber,

in the first combustion chamber (31), an ignition chamber cup (32) defining an ignition chamber (30) and a second combustion chamber cup (41) defining a second combustion chamber (40) being aligned at a distance in the radial direction,

a first igniter (21) being accommodated in the ignition chamber (30) inside the ignition chamber cup (32), a first communication hole (34), for causing communication with the first combustion chamber (31) at the time of actuation, being provided in a circumferential wall portion (32c) of the ignition chamber cup (32),

a second igniter (25) and a second gas generating agent (43) being accommodated in the second combustion chamber (40) inside the second combustion chamber cup (41), a second communication hole (42), for causing communication with the first combustion chamber (31) at the time of activation, being provided in a circumferential wall portion (41c) of the second combustion chamber cup (41),

a cup-shaped cover member (50) covering the second combustion chamber cup (41) and closing the second communication hole (42),

a disk-shaped retainer (60), for retaining the first gas generating agent (33), being disposed in the housing (11) and provided with a first opening (62) and a second opening (63),

the disk-shaped retainer (60) being mounted by fitting the ignition chamber cup (32) through the first opening (62) and putting the second combustion chamber cup (41) through the second opening (63), and an annular gap (70) being formed between the second opening (63) and the cover member (50) covering the second combustion chamber cup (41).

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a gas generator including a retainer for retaining a gas generating agent in a first combustion chamber, and a cover member for closing a communication hole for causing the second combustion chamber and the first combustion chamber to be in communication. And the present invention provides a gas generator which can be operated smoothly because, during actuation, the retainer and the cover member do not interfere with each other and the first combustion chamber and the second combustion chamber are mutually associated.

The present invention provides the following preferably embodiments (2), (3) and (4):

(2) a gas generator according to the above shown invention, wherein

the cover member has a cut (55) formed on an opening (52) thereof, and the cut is formed on a surface that is opposite to a surface where the cover member abuts against the second communication hole, that is, the cut being formed on a surface of the cover member being opposite side to the second communication hole;

(3) a gas generator according to the above shown invention, wherein

the disk-shaped retainer includes a first annular wall (64) formed at a periphery of the first opening, and an inner circumferential surface of the first annular wall is fixed by being in press-contact with an outer surface of the circumferential wall portion of the ignition chamber cup; and

(4) a gas generator according to the above shown invention, wherein

the disk-shaped retainer includes the first annular wall formed at a periphery of the first opening, and an inner circumferential surface of the first annular wall is fixed by being in press-contact with an outer surface of the circumferential wall portion of the ignition chamber cup, and

the first annular wall is formed to extend to a diffuser shell side and so that an inner diameter thereof becomes smaller toward the diffuser shell side, and further includes notches (170) formed in a circumferential direction at intervals.

The gas generator of the present invention includes the retainer for retaining and blocking movement of the first gas generating agent charged in the first combustion chamber, and the cover member for covering the second communication hole formed on the second combustion chamber (the second combustion chamber cup).

Further in the gas generator of the present invention, during activation, when the second gas generating agent in the second combustion chamber is burnt, the cover member, enclosing the second combustion chamber (the second combustion chamber cup) from the outside, deforms outwardly in the axial direction, and thereby the second communication hole which has been closed by the cover member is opened, and as a result, causing the second combustion chamber and the first combustion chamber in communication with each other.

Moreover, the deformation of the cover member during the operation of the gas generator is achieved smoothly because of:

(I) a gap being formed between the ignition chamber cup and the second combustion chamber cup; and

(II) a gap being formed between the cover member covering the second combustion chamber cup and the second opening of the retainer.

In order to further facilitate the deformation of the above cover member in the gas generator of the present invention, a cut may be formed at the opening of the cover member. By using such a cover member, since the cover member cleaves at the cut, the second communication hole is opened and the gas discharge path is easily released. Thus, the discharge of combustion gas from the second combustion chamber can be performed smoothly.

Preferably, the retainer used in the present invention is of a structure where it can be press-fitted to the ignition chamber cup. With such a press-fitting structure, the assembling operation can be simplified since the retainer can be fixed by simply being fitted to the igniter cup.

Preferably, the cover member, used in the present invention, has an enlarged-diameter portion in which the opening thereof expands outward, in order to be easily fitted to the second combustion chamber cup.

With the gas generator of the present invention, movement of the first gas generating agent in the first combustion chamber is blocked before actuation due to function of the retainer.

Further, during actuation, the second gas generating agent in the second combustion chamber is not ignited and burnt due to function of the cover member even when combustion gas is generated in the first combustion chamber. And since the retainer and the cover member mutually interact without interference, the second communication hole is opened when the second gas generating agent in the second combustion chamber is ignited and burnt, and combustion gas can be smoothly discharged from the second combustion chamber.

Moreover, the height of mounting the retainer can be adjusted based on the amount of the gas generating agent charged in the first combustion chamber.

Embodiment of the Invention

The gas generator of the present invention will be explained with reference to the drawings.FIG. 1is a cross-sectional view of the gas generator using the retainer of the present invention, andFIG. 2is a cross-sectional view in the radial direction of the gas generator inFIG. 1(some members are not shown to facilitate understanding).

In a gas generator10ofFIG. 1, a diffuser shell12and a closure shell13are welded at a bonding part15to form a housing11as an outer container.

A plurality of gas discharge ports14are provided on the circumferential surface of the diffuser shell12, and the gas discharge ports14are closed from the inside with a seal tape16made of aluminum or the like.

Two holes are provided at the bottom surface of the closure shell13, and each of two holes are eccentrically formed with respect to the central axis X of the housing11outwardly in the radial direction.

One of the above holes is mounted with a first igniter21fixed to a first igniter collar22, and the other hole is mounted with a second igniter25fixed to a second igniter collar26.

A cylindrical filter18is disposed inside the housing11, and a cylindrical gap17is provided between the outer circumferential surface of the filter18, and the gas discharge port14and the seal tape16.

A first combustion chamber31is defined inside the filter18, and a first gas generating agent33is charged therein.

Further in the first combustion chamber31, an ignition chamber cup32and a second combustion chamber cup41are arranged adjacently at a distance in the radial direction.

The ignition chamber cup32includes an opening32a, a top plate32b, and a circumferential wall portion32c, and the cup32is fitted to the first igniter collar22from the opening32aside so as to cover the first igniter21. The ignition chamber cup32is disposed so that the central axis X1thereof is eccentric with respect to the central axis X of the housing11outwardly in the radial direction.

The circumferential wall portion32cof the ignition chamber cup32has a constant outer diameter from the top plate32bto the opening32a, and a plurality of first communication holes34are formed therein. The plurality of first communication holes34are closed with a seal member (not shown) prior to actuation of the gas generator10, and are opened after actuation of the gas generator10and causes the first combustion chamber31and an ignition chamber30to be in communication with each other.

As shown inFIG. 2, the first communication holes34are formed in the circumferential wall portion32cat a position where a large amount of the first gas generating agent33exists (a position where the distance from the cylindrical filter18is large).

The inside of the ignition chamber cup32becomes the ignition chamber30, and a known enhancer or a gas generating agent is filled, as the transfer charge35, in the space excluding the first igniter21of the ignition chamber30.

The second combustion chamber cup41includes an opening41a, a top plate41b, and a circumferential wall portion41c, and the cup41is fitted to the second igniter collar26from the opening41aside so as to cover the second igniter25. The second combustion chamber cup41is disposed so that the central axis X2is eccentric with respect to the central axis X of the housing11outwardly in the radial direction.

The circumferential wall portion41cof the second combustion chamber cup41has a constant outer diameter from the top plate41bto the opening41a, and two second communication holes42are formed therein.

As shown inFIG. 2, the two second communication holes42(42a,42b) are formed, in the circumferential wall portion41cat a position where a large amount of the first gas generating agent33exists (a position where the distance from the cylindrical filter18is large). Note that, since the second communication holes42can be formed at different height positions, more than two (for example, a total of four to ten) holes may be formed as a whole.

The two second communication holes42(42a,42b) are formed at symmetrical positions relative to the line Y connecting the central axis X1of the ignition chamber cup32and the central axis X2of the second combustion chamber cup41. Note that the line Y also coincides with the line connecting the intermediate point of the second communication holes42a,42b, and the central axis X2.

The angle (α1) formed by the line Y and the line connecting the central axis X2and the center of the second communication hole42a, and the angle (α2) formed by the line Y and the line connecting the central axis X2and the center of the second communication hole42bare the same, and they can be set to be within the range of α1=α2=15 to 45°.

The inside of the second combustion chamber cup41is a second combustion chamber40, and a known second gas generating agent43is charged therein.

A cup-shaped cover member50covers the second combustion chamber cup41from the top plate41bside.

The cup-shaped cover member50includes, as shown inFIG. 1andFIG. 3(a perspective view of the cover member50), a bottom portion51, an opening52, and a circumferential surface portion53, and the top plate41bof the second combustion chamber cup41and the bottom portion51of the cover member50abut against each other. The cover member50is made of iron having a thickness of 0.4 mm, and a part of the bottom portion51, including the center part thereof, may be opened.

The second communication holes42(42a,42b) of the second combustion chamber cup41are covered with the cover member50from the outside, and the circumferential wall portion41cof the second combustion chamber cup41and the circumferential surface portion53of the cover member50are in close contact with each other.

The cover member50has an enlarged-diameter portion54with an enlarged outer diameter formed in the circumferential surface portion53in the vicinity of the opening52, and a triangular cut55is further formed in the enlarged-diameter portion54.

It will suffice as long as the cut55is formed in the enlarged-diameter portion54on the surface that is opposite to the surface of the cover member50abutting against the second communication holes42a,42b, but as shown inFIG. 3, it may be formed in the enlarged-diameter portion54at a position that is farthest from both second communication holes42a,42b(a position where the line Y and the cover member50intersect one another inFIG. 2). The circumferential surface portion53may also be formed with a score (a fragile part)56extending as an extension of the apex of the cut55.

Note that, when a cut55is formed in the cover member50, in order to prevent the cover member50, covering the second combustion chamber cup41, from rotating and changing the position of the cut55, the foregoing rotation may be prevented by causing the bottom portion51of the cover member50to be in press-contact with the ceiling surface of the housing11, or by forming convex and concave portions on the top plate41bof the second combustion chamber cup41.

In the first combustion chamber31, a retainer60for preventing the movement of the first gas generating agent35is disposed.

The retainer60includes, as shown inFIG. 4, a base portion61, a first opening62for inserting the ignition chamber cup32, and a second opening63for inserting the second combustion chamber cup41.

Moreover, a first annular wall64protruding toward the diffuser shell12ofFIG. 1is formed on the circumferential edge of the first opening62, and a second annular wall65protruding toward the diffuser shell12ofFIG. 1is formed on the circumferential edge of the base portion61. The height of the first annular wall64is higher than the second annular wall65.

The ignition chamber cup32is fitted into the first opening62of the retainer60, and the second combustion chamber cup41(a cover member50) is put through the second opening63of the retainer60.

Since the inner diameter of the first annular wall64of the first opening62is adjusted to be slightly smaller than the outer diameter of the circumferential wall portion32cof the ignition chamber cup32, the first annular wall64is in press-contact with the circumferential wall portion32c(abuts in a pressed state). As a result of causing the first annular wall64and the circumferential wall portion32cto be in a press-contact state, the overall retainer60is fixed in the first combustion chamber31.

The inner diameter of the second opening63is adjusted to be larger than the outer diameter of the cover member50covering the second combustion chamber cup41, and an annular gap70is formed between the inner circumferential edge of the second opening63and the circumferential surface portion53of the cover member50.

The second annular wall65of the retainer60is arranged so as to be spaced from the inner circumferential surface of the filter18with a gap of a size that the first gas generating agent33is not allowed to pass through. The second annular wall65may abut against the inner circumferential surface of the filter18.

Next, operation of the gas generator10shown inFIG. 1will be explained. Note that, with the first igniter21and the second igniter25, there are cases where only the first igniter21is actuated, where the first igniter21is actuated first and the second igniter25is actuated later, and where the first igniter21and the second igniter25are simultaneously actuated, according to a degree of the shock at the time of collision. The following is a case where the first igniter21is actuated first and the second igniter25is actuated later.

Before actuation, movement of the first gas generating agent33inside the first combustion chamber31is blocked due to function of the retainer60.

When an automobile collides and is subject to shock, the first igniter21is actuated and ignited upon receiving an actuation signal from a control unit, and ignites and combusts the transfer charge35inside the ignition chamber30.

The combustion product (high temperature gas, flames and the like) passes through the first communication hole34and enters the first combustion chamber31, ignite and combust the first gas generating agent33, and thereby generates combustion gas.

Here, the second communication hole42formed on the second combustion chamber cup41is closed by the cover member50, and the second gas generating agent43inside the second combustion chamber40is not ignited and combusted by the above combustion gas (in the state shown in (a) ofFIG. 5).

The combustion gas generated from the first gas generating agent33in the first combustion chamber31passes through the filter18and is filtered and cooled, and thereafter breaks the seal tape16and is discharged from the gas discharge port14.

The second igniter25is actuated and ignited later, behind the first igniter21, and the second gas generating agent43in the second combustion chamber40is ignited and combusted, and combustion gas is thereby generated.

The circumferential surface portion53of the cover member50closing the second communication holes42(42a,42b) is pushed toward the outward radial direction by this combustion gas and deformed, and since tensile stress works on the cut55shown inFIG. 3, the circumferential surface portion53can be easily cleaved therefrom (in the state shown in (b) ofFIG. 5).

Here, since an annular gap70is formed between the second opening63of the retainer60and the cover member50(the circumferential surface portion53), and a gap is also formed between the ignition chamber cup32and the second combustion chamber cup41, the cleavage caused by the deformation of the cover member50is not inhibited.

Consequently, a space80(refer to (b) ofFIG. 5) serving as the gas passage is formed between the second combustion chamber cup41and the cover member50. The gas passes through the gap80and flows toward the closure shell13(in the downward direction inFIG. 1), and then reaches the first combustion chamber31. Accordingly, the combustion gas is cooled while flowing in contact with the second combustion chamber cup41and the cover member50, and meantime the combustion residue contained in the gas is trapped, so that the amount of combustion residue is reduced until the gas reaches the filter18.

Since the retainer60is mounted by press-fitting the first annular wall64to the circumferential wall portion32cof the igniter cup32, the press-fitting depth (the height position in the axial direction) can be adjusted based on the charged amount of the first gas generating agent33. Thus, a gas generator with a broad output performance can be provided with a single component (a single retainer60).

Note that the retainer60of the present invention can be used in a gas generator including a filter18for partitioning the first combustion chamber31as shown inFIG. 1. Further the retainer60of the present invention can also be used in a gas generator in which the combustion chamber is defined by a cylindrical ring member in substitute for the filter18.

A retainer160according to another embodiment will be explained with reference toFIG. 6.FIG. 6, in (a), is a perspective view, andFIG. 6, in (b), is a partial cross-sectional view.

The retainer160is different in part from the retainer60shown inFIG. 4, but is used as shown inFIG. 1, which is the same as the retainer60shown inFIG. 4.

The retainer160includes, as shown in (a) ofFIG. 6, a base portion161, a first opening162for inserting the ignition chamber cup32, and a second opening163for inserting the second combustion chamber cup41.

Further, a first annular wall164protruding toward the diffuser shell12ofFIG. 1is formed on the circumferential edge of the first opening162, and a second annular wall165protruding toward the diffuser shell12ofFIG. 1is formed on the circumferential edge of the base part161. The height of the first annular wall164is higher than the second annular wall165.

The inner diameter of the first annular wall164becomes smaller toward the diffuser shell12(toward the opposite side of the base161) (φA<φB) as shown in (b) ofFIG. 6.

Unlike the retainer60ofFIG. 4, a plurality of V-shaped notches170are formed at equal intervals on the first annular wall164in the circumferential direction. The width of the notches170become greater toward the diffuser shell12(toward the opposite side of the base161).

By changing the inner diameter of the first annular wall164and providing the notches170as described above, the first annular wall164has elasticity, and the insertion of the ignition chamber cup32to the first opening162is thereby facilitated.

An embodiment of assembling the gas generator10shown inFIG. 1will be explained.

The first igniter21fixed to the first igniter collar22and the second igniter25fixed to the second igniter collar are fixed to the two holes of the closure shell13respectively.

Then, the ignition chamber cup32(charged with the transfer charge35) is fitted and fixed to the first igniter collar22, and the second combustion chamber cup41(charged with the second gas generating agent43) is fitted and fixed to the second igniter collar26.

Next, the cover member50is put to cover the second combustion chamber cup41. Note that, in the previous process, the second combustion chamber cup41covered with the cover member50may be fitted to the second igniter collar26.

Then, after disposing the cylindrical filter18, the first gas generating agent33is charged.

Next, the retainer60is mounted by press-fitting the first opening62to the ignition chamber cup32and putting the second combustion chamber cup41through the second opening63. Here, by press-fitting the first annular wall64to the ignition chamber cup32, the first annular wall64and the ignition chamber cup32are caused to be in a press-contact state. The retainer60can be fixed with only the above process, and the position of the filter18is decided with the second annular wall65of the retainer60.

Subsequently, the diffuser shell12is placed and the bonding part15is welded for integration.

With the gas generator10of the present invention, the retainer60can be mounted simply by press-fitting the first annular wall64to the ignition chamber cup32. Thus, it is no longer necessary to adjust the mounting state of the retainer and other members, and the operation can thereby be simplified enormously.