JP2004168309A - Gas generator for airbag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas generator for an airbag enabling reversibly controlling the inner pressure of a combustion chamber, and capable of stably burning gas generating agent having high pressure dependence. <P>SOLUTION: The gas generators 31, 61 for the airbag comprises the combustion chambers 40, 23 burning the stored gas generating agent 7 to generate gas, and increasing the pressure of the generated gas; gas holes 33, 25 provided on walls of the combustion chambers 40, 23 for discharging the gas; and a pressure controlling means for controlling the inner pressure of the combustion chambers 40, 23. The pressure controlling means has the gas holes 33, 25 having specified areas that keep opening. By the pressure controlling means, the opening areas of the gas holes 33, 25 are increased from the specified area with increase in the inner pressure P, and the opening areas of the gas holes 33, 25 are decreased toward the specified areas with decrease in the inner pressure P. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a gas generator for an airbag that protects an occupant from an impact, and more particularly to a gas generator capable of reversibly controlling the internal pressure of a gas generating agent combustion chamber.

  This type of gas generator for air bags has conventionally used an azide-based gas generating agent. For this reason, slag (combustion residue) is generated during combustion of the gas generating agent, and a gas filter is required to remove the slag, resulting in an increase in the weight and shape of the gas generator. Therefore, a non-azide-based new gas generating agent which hardly generates slag, such as a triaminoguanidine-based or tetrazole-based gas, has been developed, and a gas generator using this new gas generating agent has also been developed. A specific example of a gas generator using the new gas generating agent will be described with reference to FIGS. 9 and 10 which are sectional views. FIG. 9 shows a passenger seat gas generator. In FIG. 9, a passenger seat gas generator 1 has a housing 2 formed by fitting lid members 2b and 2c to both ends of a long cylindrical member 2a having a gas hole 8 opened on the peripheral surface. A cylindrical core housing 6 having a gas hole 9 formed on the peripheral surface thereof is provided concentrically inside the housing 2, and a gas generating agent 7 is accommodated therein. The core housing 6 constitutes a combustion chamber for the gas generating agent 7. At one end of the nuclear housing 6, a transfer agent 12 and a squib 11 are arranged in order in a storage portion 5 protruding from the center of the lid member 2c, adjacent to the gas generating agent 7, and these are ignited. 3. Reference numeral 13 is a lead wire for connecting the squib 11 to a collision detection unit (not shown). In the passenger seat gas generator 1, when a collision occurs, the squib 11 is energized and heated by the collision detection unit and ignites. The ignition charges the transfer charge 12 and ignites the gas generating agent 7. When the gas generating agent 7 burns, a high-temperature gas is generated, and the generated gas is pressurized by the presence of the combustion chamber 6, flows out of the gas holes 9 into the space 14 between the combustion chamber 6 and the housing 2, is diffused and decompressed. After being cooled, it is released from the gas holes 8 of the housing 2 and supplied to an airbag (not shown).

  FIG. 10 shows a gas generator for the driver's seat. In FIG. 10, the passenger seat gas generator 21 differs from the passenger seat gas generator 21 in FIG. 9 in that the housing 22 has a short cylindrical shape and a mounting flange 24 is provided on the outer periphery. The main differences are the same. That is, a cylindrical ignition device storage chamber 26 and a cylindrical core housing 23 are concentrically arranged in a short cylindrical housing 22, and the ignition device 3 including the transfer charge 12 and the squib 11 is disposed in the storage chamber 26. The gas generating agents 7 are stored in the housings 23, respectively. The storage chamber 26, the nuclear housing 23, and the housing 22 are provided with gas holes 27, 25, and 24, respectively. The operation of the driver seat gas generator 21 is the same as that of the passenger seat gas generator 1 shown in FIG. 9, and a description thereof will be omitted.

  By the way, the burning speed of the gas generating agent increases according to the pressure during burning. For this reason, in FIG. 9, the gas generating agent 7 is burned in the combustion chamber 6, and the opening area of the gas hole is set to a predetermined value so that the pressure of the generated gas can be kept high. However, since the above-mentioned new gas generating agent has a particularly high pressure dependency, if the opening area is fixed as described above, the pressure (internal pressure) in the combustion chamber 6 due to the combustion of the gas generating agent 7 and the internal pressure increase The gas generating agent 7 may explosively burn due to the circulation effect with the increase in the burning speed. For this reason, there has been a problem that means for stably burning the gas generating agent 7 is separately required.

  In this case, rather than aiming at the new gas generating agent as described above, the purpose of eliminating the influence of the environmental temperature of the airbag device is to suppress the rise in the internal pressure of the combustion chamber in the gas hole of the combustion chamber. There has been proposed a gas generator capable of suppressing the burning rate of a gas generating agent by providing a means for performing the method (see Japanese Patent Application Laid-Open No. 2-74442). However, the means for suppressing the internal pressure rise of this gas generator is irreversible, and once the opening area of the gas hole is increased, it cannot be reduced again. The internal pressure cannot be raised.

JP-A-2-74442

  The present invention has been made in view of such problems of the related art, and an object of the present invention is to make it possible to control the internal pressure of the combustion chamber reversibly, and to reduce the pressure dependency. An object of the present invention is to provide a gas generator for an airbag which can stably burn a high gas generating agent.

Means and effects for solving the problem

The gas generator for an air bag according to the present invention includes combustion chambers 40 and 23 for generating gas by burning the stored gas generating agent 7 and increasing the pressure of the generated gas, and the combustion chamber 40 for discharging the gas. , 23 provided with gas holes 33, 25 provided on the walls of the gas holes 33, 25, and pressure control means for controlling the internal pressure of the combustion chambers 40, 23 provided in the gas holes 33, 25. In the pressure vessels 31 and 61, the pressure control means increases or decreases or opens or closes a predetermined area while the gas holes 33 and 25 are kept open. The opening area of each of the gas holes 33, 25 increases from the predetermined area, and the opening area of the gas holes 33, 25 decreases toward the predetermined area as the internal pressure P decreases.
Preferably, the pressure control means is a pressure control member provided in the gas hole 25 and having both a function of detecting an internal pressure and a function of opening and closing the gas hole.
The pressure control member includes a heat-resistant elastic plate disposed in the gas hole 25, a small hole 65 provided in the heat-resistant elastic plate, and a bending elastic deformation formed around the small hole 65. Those having a possible section 63a are preferred.

According to the above configuration, when the internal pressure of the combustion chamber increases, the opening area of the gas hole increases, and the increase in the internal pressure can be suppressed to suppress the combustion speed of the gas generating agent. On the other hand, when the internal pressure of the combustion chamber decreases, the opening area of the gas hole decreases, and the decrease in the internal pressure is suppressed to suppress the decrease in the combustion rate of the gas generating agent. Therefore, the gas generating agent can be stably burned.
Further, since the generated gas is completely released from the predetermined area while being opened, it is possible to prevent the internal pressure from remaining in the combustion chamber due to the pressurization of the pressure control means after the gas generating agent combustion is completed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a first embodiment will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view showing the configuration and operation of the gas generator for an air bag of the present invention, FIG. 2 is a graph showing the change over time of the internal pressure of the combustion chamber, FIG. FIG. 4 is a sectional view showing a modification of the urging means, and FIG. 5 is a sectional view showing a modification of the first container. In FIG. 1, portions having the same functions as in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted.

  First, the configuration will be described with reference to FIG. This embodiment shows an example of application to a passenger seat gas generator. 1 is substantially different from FIG. 9 in that the combustion chamber 40 is composed of first and second containers 34 and 35 which are relatively movable, and a compression spring 37 is provided on the bottom surface of the second container 35 which is movable. Is arranged. That is, the housing 2 is formed by screwing the lid member 2c to the cylindrical member 2a having the bottom 2b integrally, and the gas hole 8 is opened in the peripheral surface. At the center of the lid member 2c, a storage portion 5 of the ignition device 3 including the transfer charge 12 and the squib 11 is provided so as to protrude. A combustion chamber (nuclear housing) 40 for accommodating the gas generating agent 7 includes a cylindrical first container 34 protruding from the cover member 2c concentrically with the housing 2 and a slidable inner portion inside the first container 34. It is composed of a bottomed cylindrical second container 35 to be inserted, and a sliding hole 35b is provided at the center of the bottom 35a of the second container 35. A center pole 36 into which the sliding hole 35b is slidably fitted is projected from the center of the bottom 2b of the housing 2. The center pole 36 is for assisting the sliding of the second container 35. An appropriate number of compression springs 37 for urging the second container 35 upward in the drawing are interposed between the bottom 35a of the second container and the bottom 2b of the housing. The sliding portion between the first container 34 and the second container 35 is provided with an appropriate sealing means for preventing gas leakage as needed.

  A step portion 38 is provided on the inner periphery of the first container 34, and the open end of the second container 35 contacts the step portion 38 as shown in the figure. Therefore, the second container 35 can be moved by the stroke S from the illustrated initial position to the limit position where the bottom 35a contacts the bottom 2b of the housing. Then, the second container 35 is pressed downward in the drawing by the internal pressure P of the combustion chamber 40 and moves to a position where it is balanced with the urging force of the compression spring 37 upward in the drawing. That is, the second container 35 moves downward in the drawing according to the internal pressure. The gas holes 33 of the first container are provided with a large number of small holes in four rows, for example, as shown in the figure, and the gas holes (first gas holes) 33a of the first row are The other three rows of gas holes (second gas holes) 33b to 33d are provided at a predetermined interval d within the distance of the stroke S of the second container 35 from the step portion 38. . Therefore, the gas holes 33a in the first row remain open irrespective of the movement of the second container 35, but the gas holes 33b to 33d in the second to fourth rows are in the initial state as shown in FIG. As it moves from the position in the direction a, the portion blocked by the second container 35 decreases and its opening area increases, and conversely, the portion blocked by the second container 35 increases as it moves in the direction b. The opening area is reduced. Therefore, the opening area is increased up to four times the initial size.

  Incidentally, the degree to which the gas generator 31 self-suppresses the internal pressure P is determined by the increase rate of the opening area of the gas holes 33b to 33d with respect to the increase of the internal pressure P, and the relationship between the internal pressure P and the increase rate of the opening area is as described above. Of the compression spring 37, and the shape and arrangement of the gas holes 33b to 33d. Therefore, these are appropriately set in accordance with the degree to which the internal pressure P is to be suppressed. The compression spring 37 may be pressurized, and the arrangement of the gas holes 33 may be a lattice shape, a staggered shape, or a random shape in addition to the row shape as shown.

  Next, the operation of the gas generator 31 having such a configuration will be described with reference to FIG. In FIG. 1, in the initial state, the second container 35 is at the position shown in the figure, and the gas holes 33 are only open in the first row 33a. Next, when the gas generating agent 7 is ignited by the ignition device 3 and combustion starts, the internal pressure P of the combustion chamber 40 increases, and the second container 35 moves in the a direction against the urging force of the compression spring 37. I do. Then, for example, if it moves by the distance L (the position indicated by the two-dot chain line), the gas holes 33b in the second row are opened. As a result, the total opening area of the gas holes 33 increases twice as much as the initial time, and the internal pressure P decreases. Therefore, the second container 35 is located at a position near this where the opening area and the internal pressure P are balanced. Thus, the increase in the internal pressure P is suppressed, and the increase in the burning speed of the gas generating agent 7 is suppressed. Then, when the internal pressure further increases, the second container 35 moves in the direction a accordingly, the opening area of the gas hole 33 further increases, and the increase in the burning speed of the gas generating agent 7 is suppressed. When the internal pressure P decreases toward the end of the combustion of the gas generating agent 7 and the internal pressure P decreases, the second container 35 moves in the direction b, the opening area of the gas hole 33 decreases, and the decrease in the internal pressure P is stopped. The decrease in the combustion speed of 7 is suppressed. When the combustion of the gas generating agent 7 is completed, the second container 35 returns to the illustrated initial position. In this case, since the gas holes 33a in the first row are opened, there is no possibility that the gas pressure remains in the combustion chamber 40 even if the compression spring 37 is pressurized.

  Next, the effect of the pressure control means will be described with reference to the graph of FIG. FIG. 2 shows the change over time of the internal pressure of the combustion chamber when a new gas generating agent is used. In FIG. 2, a curve 60 indicates a case where the pressure control unit is not provided, a curve 61 indicates a case where the pressure control unit of the present embodiment is provided, and a curve 62 indicates a case where the irreversible pressure control unit described in the related art is provided. Is shown. In the case where the pressure control means is not provided, the curve 60 has a steep peak as shown in the figure. However, when the pressure control means of the present embodiment is provided, the rise of the internal pressure is suppressed when the curve rises, In addition, since the decrease in the internal pressure is suppressed at the time of falling, the curve has a flat portion 61a. In the case where the conventional irreversible pressure control means 62 is provided, the point 62 is the same as that of this embodiment in that the rise of the internal pressure is suppressed when the curve rises, but the increased opening area cannot be reduced. Therefore, it is not possible to suppress a decrease in internal pressure at the time of falling, and the number of flat portions is reduced. The size of the flat portion 61a can be set to a desired size by changing the rate of increase in the opening area of the gas hole with respect to the increase in the internal pressure P, as described above.

  FIG. 3 shows a modification of the gas holes provided in the first container. That is, instead of the gas holes 33 in which a number of small holes arranged in the circumferential direction in FIG. 1 are arranged in four rows in the axial direction, rectangular gas holes 43 extending in the axial direction as shown in FIG. Singly or plurally in the circumferential direction. In this way, the opening area of the gas hole 43 can be continuously changed with respect to the movement of the second container 35 in FIG. As a result, the internal pressure of the combustion chamber 40 can be adjusted smoothly. Further, when one or more trapezoidal gas holes 53 extending in the axial direction as shown in FIG. 3B are provided in the circumferential direction, the opening area of the gas holes 53 becomes more abrupt as the second container 35 moves. Can be changed to As a result, a change in the internal pressure of the combustion chamber can be further suppressed, and the flat portion 61a in FIG. 2 can be enlarged.

  FIG. 4 shows a modification of the urging means of the second container. 4A is different from FIG. 1 in that the center pole 36 is removed and a cylindrical rubber member 46 is provided instead of the compression spring 37 as an urging means. Even with such a configuration, the same effect as in the case of FIG. 1 can be obtained, and the configuration can be simplified. 4 (b) is different from FIG. 1 in that the center pole 36 is removed and a single compression spring 47 is provided instead of the plurality of compression springs 37 as urging means. By doing so, the configuration can be simplified as compared with the case of FIG.

  FIG. 5 shows a modification of the first container. 5 is different from FIG. 1 in that the peripheral wall 55a of the first container 55 extends to the bottom of the housing 2 and has a bottom 55b at its end, and the bottom 55b has a center pole 56 for the second container 35, The point is that a compression spring 37 is provided. With this configuration, the space 70 between the second container bottom and the first container bottom 55b becomes airtight, and the air in the space 70 acts as an air spring against the movement of the second container. it can. As a result, the configuration of the compression spring 37 can be simplified, such as downsizing.

  Next, a second embodiment will be described with reference to FIGS. This embodiment is an embodiment in which a configuration in which pressure control means having both an internal pressure detection function and a gas hole opening / closing function is applied to a gas generator for a driver's seat. 6 is a sectional view of the gas generator for the driver's seat of the present invention, FIG. 7 is a sectional view taken along the arrow A in FIG. 6, and FIG. 8 is a sectional view taken along the line BB in FIG. In FIG. 7, portions having the same functions as those in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. 7 differs from FIG. 10 in that a pressure control member 62 is provided outside the gas holes 25 of the combustion chamber 23. The pressure control member 62 is an annular member made of a heat-resistant elastic plate material such as stainless steel. As shown in FIG. 7, the pressure control member 62 is arranged at predetermined intervals corresponding to the gas holes 25 in FIG. A cut 63 is provided in the cross, and a small hole 65 is provided in the center of the cut 63. As shown in FIGS. 7 and 8, the cut 63 has a size corresponding to the diameter of the gas hole 25. When the section 63a receives the internal pressure P from the combustion chamber 23, the section 63a bends outward from the base 64, and the opening area 66 at the center increases. Then, the degree of bending depends on the magnitude of the internal pressure P due to the bending elasticity. The small holes 65 are for preventing the gas pressure from remaining inside the combustion chamber 23 after the combustion of the gas generating agent 7 is completed due to the presence of the section 63a.

  The operation of the gas generator 61 will be described with reference to FIG. In FIG. 8, when the gas generating agent 7 starts burning and the internal pressure P of the combustion chamber 23 rises, the section 63a bends outward c and bends to a position corresponding to the internal pressure P (for example, a two-dot chain line position). Then, since the opening area 66 of the gas hole 25 increases, the increase in the internal pressure P is suppressed. Then, when the combustion of the gas generating agent 7 ends and the internal pressure P falls, the section 63a returns to the inside d, the opening area 66 of the gas hole 25 decreases, and the decrease in the internal pressure P is stopped. As a result, a flat pressure curve similar to that of FIG. 2 can be obtained with a simple configuration, and the gas generating agent can be stably burned. The flatness of the pressure curve (corresponding to 61a in FIG. 2) can be set to a desired value by changing the bending elasticity of the section 63. The bending elasticity of the section 63 can be set to a desired value by selecting a material thickness, a material, and the like.

  In the above-described first embodiment, the case where the present invention is applied to a gas generator for a passenger seat is described, and in the second embodiment, the case where the present invention is applied to a gas generator for a driver seat is described. The present invention in the embodiment can be similarly applied to a gas generator for a driver's seat, and the present invention in the second embodiment can be similarly applied to a gas generator for a passenger seat. Further, in the above-described embodiment, the case where the present invention is applied to a gas generator using a new gas generating agent having a high pressure dependency has been described. However, the same applies to a gas generator using a conventional gas generating agent. Can be.

It is a longitudinal section showing composition and operation of a gas generator for airbags of the present invention. It is a graph which shows the relationship between the internal pressure of a combustion chamber, and time. It is a figure which shows the modification of a gas hole shape. It is sectional drawing which shows the modification of an urging means. It is sectional drawing which shows the modification of a 1st container. It is sectional drawing of the gas generator for driver's seats of this invention. FIG. 7 is a view taken in the direction of arrow A in FIG. It is BB sectional drawing of FIG. It is a longitudinal section of the conventional gas generator for airbags for a passenger's seat. It is a longitudinal section of the conventional gas generator for airbags for a driver's seat.

Explanation of reference numerals

P Internal pressure 7 Gas generating agent 31 Gas generator for passenger seat (Gas generator for airbag)
33 gas hole 33a gas hole (first gas hole)
33b to 33d gas holes (second gas holes)
34 first container (pressure control means)
35 Second container (pressure control means)
37 compression spring (pressure control means, biasing means)
40 Combustion chamber 62 Pressure control member 63 Cut (pressure control means)
63a section 64 small hole

Claims (3)

  Combustion chambers 40 and 23 that generate gas by burning the stored gas generating agent 7 and pressurize the generated gas, and gas holes 33 and 23 provided in the walls of the combustion chambers 40 and 23 to release the gas. 25, and a pressure control means provided in the gas holes 33, 25 for controlling the internal pressure of the combustion chambers 40, 23. The pressure control means increases or decreases the internal pressure P and increases or decreases the opening area of the gas holes 33 and 25 from the predetermined area. The gas generator for an airbag, wherein the opening area of the gas holes 33, 25 decreases toward the predetermined area as the internal pressure P decreases.   2. The gas generator for an air bag according to claim 1, wherein the pressure control means is a pressure control member provided in the gas hole 25 and having both an internal pressure detection function and a gas hole opening / closing function. 3. The pressure control member includes a heat-resistant elastic plate material provided in the gas hole 25, a small hole 65 provided in the heat-resistant elastic plate material, and a bending elastic deformation formed around the small hole 65. 3. The gas generator for an airbag according to claim 2, comprising a section 63a.

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