Patent Application
20120118193
The present invention relates to a gas generator, particularly to an improvement of an electric-ignition-type gas generator suitable for actuating a seatbelt pretensioner.
Cars and other vehicles are usually equipped with seatbelts, airbags and other safety devices for protecting the driver and passengers from the impact at the time of a crash. In the case of a seatbelt safety device, for example, the seatbelt winding-retraction device is additionally provided with a rapid winding-retraction means, and the driver and passengers are reliably protected from the impact at the time of a crash by activating this rapid winding-retraction means at the time of an accident or other emergency so as to instantaneously retract the seatbelts. As the aforesaid rapid winding-retraction means ones have recently been widely adopted that are equipped with a mechanism for rapidly retracting the seatbelt by using an electric ignitor that is activated by the impact at the time of a crash to instantaneously drive a cylinder piston or a rotor by utilizing the pressure of combustion gas when gunpowder or the like is made to burn instantly. The wide adoption of rapid winding-retraction means equipped with such mechanisms has been accompanied by the development of many gas generators for use therein.
[Patent Document 1]
A gas generator B is first provided with a holder 1A constituting a base. The holder 1A is formed of aluminum, and a connector insertion hole 11 is formed on the side attached to the vehicle body while a pedestal 12 for forming an ignitor unit is formed on the reverse side of the place where the connector insertion hole 11 is formed. The pedestal 12 comprises an outer peripheral portion having a flat boundary surface and a spacer insertion hole of circularly indented shape, and the center region of the spacer insertion hole is formed with a rectangular through-hole communicating with the connector insertion hole 11. Further, a resin spacer 13 provided with a pair of pin insertion holes 131 opening toward the connector insertion hole 11 is inserted into the spacer insertion hole and the rectangular through-hole of the pedestal 12. A plug assembly 2A equipped with a pair of electrode pins 21A serving as an electric signal input section is mounted on top of this spacer 13 and the outer peripheral portion of the pedestal 12 so as to sandwich a gasket 14 serving as a sealing material. Moreover, a peripheral wall 121 for ignitor unit attachment that is used to fix the ignitor unit is provided along the outer edge of the pedestal 12, and a peripheral wall 122 for case attachment that is used to fix a case charged internally with ignitor composition, gas generating agent and the like is further provided along the outer periphery of the peripheral wall for ignitor unit attachment.
The plug assembly 2A is equipped with a plug comprising a ring 22A made of metal and having a cylindrical side surface, the pair of electrode pins 21A that pass through this ring 22A, and an insulator 23 for fixing the pair of electrode pins 21A to the ring 22A. Note that the insulator 23 is constituted of glass, ceramic or other such insulator.
The ring 22A has a crimp margin at the portion mounted on the flat border surface of the pedestal 12 so that it is fixed by swaging the peripheral wall 121 for ignitor unit attachment of the holder 1A. The electrode pins 21A are electrically conductive members manifesting a cylindrical shape of finer diameter than the pin insertion holes 131 and extend in parallel with each other. On the side of insertion into the pin insertion holes 131, the electrode pins 21A pass through the insulator 23 and project a long distance, and project only slightly on the opposite side. And a resin sleeve 24 and a disk-shaped board 25 made of composite plastic are disposed on the ring 22A on this side where the electrode pins 21A project slightly. A resistor 26 composed of a thin film of nichrome alloy is provided on at least one side of the board 25 as a heating element. A primary charge 27 is placed on this resistor 26 and a coating 27a is additionally placed thereover.
Further, a hollow circular cylinder-shaped cylindrical body 28 is provided on the plug assembly 2A to cover the outer surfaces of the ring 22A and sleeve 24. Since the cylindrical body 28 is fixed by swaging the peripheral wall 121 of the holder 1A in the state fitted over the ring 22A, it is, like the ring 22A, formed along the lower edge with a crimp margin.
And the plug assembly 2A is fixed to the holder 1A by bending and crimping the upper edge portion of the peripheral wall 121 for ignitor unit attachments. Since the gasket 14 is press-fitted between the outer peripheral portion of the pedestal 12 and the lower edge of the ring 22A during this crimping, air-tightness is established between the holder 1A and the plug assembly 2A.
Further, the gas generator B is provided with a case 3A surrounding the ignitor unit comprising the holder 1A and the plug assembly 2A. The case 3A is an aluminum shaped part configured as a cylinder having a bottom that comprises an open portion having a thickness and inside diameter of a scale that can be fitted into a grooved portion of the holder 1A formed inside the peripheral wall 122 for case attachment and a bottom portion 3Ab radially formed with grooves so that it can be readily opened by the pressure of combustion gas. The open portion of the case 3A is formed with a peripheral edge portion 3Aa by fold-machining, and the peripheral wall 122 for case attachment of the holder 1A crimps the peripheral edge portion 3Aa to fix the case 3A in a state covering the upper side of the holder 1A. Moreover, the inside of the case 3A is charged internally with a prescribed amount of ignitor composition 31 and gas generating agent 32.
And in the gas generator B, when the impact at the time of a crash is applied to the electrode pins 21A as an electric signal, the resistor 26 between the pair of electrode pins 21A produces heat, and this heat ignites the primary charge 27, whereupon the ignitor composition 31 and the gas generating agent 32 are immediately inflamed. And then the combustion gas of the gas generating agent 32 breaks through the bottom portion 3Ab of the case 3A and discharges to the exterior, whereby the rapid winding-retraction means of the seatbelt is instantaneously activated by the pressure of the combustion gas.
Here, as with other vehicle parts, the need for cost reduction has risen also with regard to gas generators, and efforts are continuing at development worksites toward replacing expensive metal components with ones made of plastic and other synthetic resins. A challenge faced in this is how to give the parts replaced with synthetic resin ones the strength to withstand the pressure of the combustion gas while still maintaining the arrangement for rapidly retracting the seatbelt by efficiently releasing the combustion gas pressure from the bottom portion 3Ab so as to instantaneously drive a cylinder piston or a rotor. For example, in the case where the ring 22A and the insulator 23 in the gas generator B of
[Patent Document 2]
On the other hand, Japanese Unexamined Patent Publication No. 2001-21293 (Patent Document 2), for example, teaches an invention wherein, with regard to the aforesaid plug, everything other than the electrode pins is replaced with synthetic resin, while the electrode pins are bent midway to expand the area of the electrode pins so as to maintain strength capable of withstanding the pressure of the combustion gas. The formation of the electrode pin bent portions can be expected to have an effect whereby the obstruction corresponding to the plug and its electrode pins do not disengage from the insertion hole provided on the vehicle body side.
[Patent Document 3]
Further, Japanese Unexamined Patent Publication No. 2004-114826 (Patent Document 3), for example, teaches a gas generator wherein the connector insertion hole provided in the holder is shaped like a pin-hole and used solely as a location for inserting the electrode pins, and the pair of electrode pins are twisted and provided integrally inside the holder 6. With this configuration, the twisted electrode pins are structured to catch in the direction of electrode pin extraction on a hole provided in a reinforcing member, so that the likelihood of the electrode pins flying outside the gas generator can be reduced.
Patent Document 1: Japanese Unexamined Patent Publication No. 2003-205823
Patent Document 2: Japanese Unexamined Patent Publication No. 2001-21293
Patent Document 3: Japanese Unexamined Patent Publication No. 2004-114826
However, the primer device or squib set forth in Patent Document 2 unavoidably requires electrode pin yield to be lowered in order to obtain the desired bending. Further, if it is one in which the electrode pins are merely bent, it involves such problems as that under application of the combustion gas pressure they are apt to fly into the vehicle body from the connector insertion hole side while being twisted. Further, the gas generator set forth in Patent Document 3, particularly the ones equipped with the electrode pins disclosed in
Thus, in the conventional gas generator, replacement of expensive metal parts with plastic or other synthetic resin ones gives rise to structural issues such as ensuring required strength, with the result that inability to respond adequately to cost reduction demands became a problem.
Further, since the gas generator uses an electric primer, one challenge in the process of replacing conventional metal parts with insulative synthetic resin has been the constant need to configure the gas generator so as not to experience malfunction upon exposure to static electricity or the like.
The present invention, which is proposed in light of the foregoing circumstances, has as it object to provide a gas generator wherein the constituent members of the plug other than the electrode pins are replaced with synthetic resin and which ensures strength of the plug assembly so that the electrode pins do not fly out from the connector insertion hole side, while enabling fabrication at good yield, thus making it possible to thoroughly meet the need for cost reduction, and also making it possible to prevent malfunction caused by static electricity or the like.
(1) In order to achieve the aforesaid object, in a first invention of the present application, a gas generator comprising, a primer member including a mount portion for mounting a primary charge and at least two electrode pins projecting from a bottom surface of the mount portion and igniting the primary charge based on an electric signal passed through the electrode pins, a case charged with a gas generating agent for generating combustion gas upon ignition by the primer member, a holder having a pedestal including a single opening portion through which the plural electrode pins are inserted, the pedestal supporting the primer member, and on which the bottom surface of the mount portion is placed with the electrode pins inserted through the opening portion, having a mounting section for fitting a peripheral edge portion of the case, and having the case fitted thereover, wherein the primer member is configured so that the mount portion is formed of synthetic resin, the electrode pins are equipped midway with flange portions, and the flange portions are integrally formed in a state embedded inside the mount portion.
(2) In a second invention of the present application, in the gas generator of the aforesaid configuration the opening portion of the holder is formed in rectangular shape, and the flange portions of the electrode pins are given a larger diameter than short sides of the opening portion.
(3) In a third invention of the present application, it is required, for example, that, at locations of the same height in the horizontal direction, the flange portions of the individual electrode pins of the gas generator of the aforesaid configuration have an outer periphery of each flange portion out of contact with the outer periphery of the other electrode pin or the outer edge of the other flange portion.
(4) In the third invention of the present application in a gas generator, in addition to the aforesaid configuration, a minimum distance between the electrode pins and a periphery of the opening portion of the holder through which the electrode pins are inserted is 0.6 mm or less.
The gas generator of the present invention is configured so that the mount portion of the primer member is formed of synthetic resin, the flange portions are provided midway of the electrode pins, and these flange portions are integrally formed in a state embedded inside the mount portion. Owing to this configuration, expensive metal parts and glass, ceramic or other such insulators can be replaced with ones made of synthetic resin. Further, since the whole of the primer member is prevented from flying out from the connector insertion hole side upon softening of the mount portion exposed to high temperature, electrode pins expanded in surface area are fabricated using the high-yield method of providing the flange portions midway of the pins. Therefore, the present invention can thoroughly meet the need for cost reduction.
In addition, with regard to such a gas generator, the opening portion of the holder is formed in rectangular shape and the flange portions are given a larger diameter than the short sides of this opening portion, so that the electrode pins can be easily inserted through with no contact or interference with the holder, without any particular increase in the number of processes. Further, in the case where the gas generator is heated to a high temperature by exposure to a high temperature from the outside, the electrode pins can be prevented from disengaging from the connector insertion hole side even if the pressure of the combustion gas acts on the electrode pins in the softened state of the synthetic resin, because the flange portions of the electrode pins catch on the opening portion of the holder. In particular, if the sum of the sector angles formed by the outer peripheral portions of the flange portions of the electrode pins located outside the rectangular opening portion of the holder in the axial direction and the electrode pins is configured to be 180 degrees or greater, the flange portions catch adequately on the holder. By this configuration, the tendency of the electrode pins to fly out from the connector insertion hole side owing to the pressure of the combustion gas can be effectively avoided, and a high level of electrode pin fabrication yield can be maintained. In other words, it becomes possible to provide a gas generator that adequately satisfies the need for cost reduction while further preventing the electrode pins from flying out from the connector insertion hole side.
Further, the flange portions of the individual electrode pins are configured so that the outer periphery of each flange portion is out of contact with the outer periphery of the other electrode pin or the outer edge of the other flange portion, so that the integral formation of the primer member can be performed with better yield. And, for example, the primer member can be fabricated with still better yield by using identically shaped ones for the respective electrode pins.
Moreover, the minimum distance between the electrode pins and the periphery of the opening portion of the holder through which these electrode pins are inserted is preferably made 0.6 mm or less. This configuration enables suitable discharge to the holder when static electricity is applied, making it possible to prevent malfunctions caused by static electricity and also contribute to quality improvement.
An embodiment of the present invention is explained below based on the drawings. Note that portions the same as or corresponding to the conventional gas generator shown in
As shown in
The ring 22 serving as the mount portion is made of synthetic resin, more specifically of an insulating resin, and can be constituted, for example, as a composite material obtained by incorporating carbon fiber, a silica such as fused silica or crystalline silica, alumina, silicon nitride, aluminum nitride, boron nitride, titanium oxide, glass fiber or other reinforcing agent, antistatic agent and like additives into a resin such as polybutylene terephthalate (PBT) or polyphenylene sulfide (PPS). When the softening point of the synthetic resin is low, the flame retardancy and high-temperature strength of the ring 22 can be suitably adjusted by regulating the composition ratios of the additives incorporated in the synthetic resin.
Note that the primary charge 27 is mounted on the ring 22 via a cup-shaped sleeve 24 and a board 25. In other words, as noted earlier, the primary charge 27 is mounted on the board 25 placed inside the sleeve 24 on the bottom surface thereof, and a resistor 26 is provided as a heating element on at least one surface of the board 25. The primary charge 27 is placed on this resistor 26 and a coating 27a is additionally placed thereover. Further, the holder 1 is formed with an opening portion 1a for inserting the electrode pins 21, a pedestal 12 for supporting the plug assembly 2 on the bottom surface of the ring 22, and the peripheral wall 122 for case attachment serving as a mounting section for fitting the peripheral edge portion 3Aa at the lower end of the case.
Particularly, as shown in
In the following, the individual components of the gas generator A according to the present invention are explained while comparing the embodiment of the present invention shown in
First, the holder 1 of the gas generator A according to the present invention is formed of aluminum or zinc as heretofore, but unlike in the conventional gas generator B of
Further, in the present invention, differently from the ring 22A and insulator 23 of the conventional gas generator B, the ring 22 of the plug assembly 2 is made of a resin such the polybutylene terephthalate or polyphenylene sulfide set out above or of a highly insulative composite material. Therefore, as shown in
In addition, as shown in
Further, the electrode pins 21 and flange portions 21a are made of the same metal material, and from the viewpoint of strength, an iron alloy such as iron-nickel alloy is preferably used.
Note that the case 3 used in the present invention can be one configured the same as in the conventional gas generator B.
Here, as shown in
Thus, in the gas generator A according to the present invention, the metal ring 22A and the glass, ceramic or other such insulator 23 of the conventional gas generator B are integrally constituted of synthetic resin or highly insulative composite material, whereby cost reduction can be achieved. In addition, since the flange portions 21a are provided midway of the electrode pins 21 and these flange portions 21a are constituted to be integrally formed in a state embedded inside the ring 22, the problem caused by constituting the ring 22 of synthetic resin can be overcome. Specifically, when the ring 22 softens, it is possible to overcome the problem of the electrode pins 21 flying outside from the connector insertion hole 11 side owing to the pressure of the combustion gas. Further, the flange portions 21a are disk-shaped and the structure therefore makes application of twisting force to the electrode pins 21 less likely than in the aforesaid Patent Documents 2 and 3, so that the electrode pins 21 are resistant to flying out from the connector insertion hole 11 side. In addition, advantage can be taken of ring 22 cost reduction because the flange portions 21a are easy to fabricate owing to their disk-like shape, thus making it possible to fabricate the electrode pins 21 with good yield. Further, the flange portions 21a are given a larger diameter than the short sides of the rectangular opening portion 1a of the holder 1, and in addition, the sum of the sector angles R formed by the outer peripheral portions 21r located outside the opening portion 1a of the holder 1 in the axial direction and the electrode pins 21 is made 180 degrees. Owing to this configuration, the electrode pins 21 can be more reliably prevented from flying out from the connector insertion hole 11 side owing to the pressure of the combustion gas, while taking advantage of the good yield in the fabrication of the electrode pins 21. Further, the pair of electrode pins 21 are both given the same shape, thereby enabling the plug assembly 2 to be fabricated with good yield, while establishing a prescribed interval between the flange portions 21a of the pair of electrode pins 21 so that the outer periphery of each does not contact the outer periphery of the other.
In addition, in the gas generator A according to the present invention, the minimum distance D between the electrode pins 21 and the periphery of the opening portion 1a of the holder 1 through which the electrode pins 21 are inserted is not particularly limited insofar as insulation from the holder 1 is ensured. However, from the viewpoint of establishing both insulation property of up to around 500 V and dischargeability to the holder 1 of static electricity of around 25,000 V, it is preferably made 0.1 mm to 0.6 mm or less, for example, 0.5 mm. By establishing the aforesaid minimum distance D in the aforesaid range, passage to the holder of the current of the electric signal applied to the electrode pins 21 can be avoided, and when static electricity is applied, it can be suitably discharged to the holder 1 to prevent malfunction owing to static electricity.
Further, according to the present invention, the spacer 13 and insulator 23 required by the conventional gas generator B become unnecessary to enable a cutback in the number of parts and thereby make it possible to realize cost reduction.
Therefore, in the present invention, the ring 22 can be replaced with one made of synthetic resin and the electrode pins 21 and plug assembly 2 can be fabricated with good yield, thereby making it possible to thoroughly meet the need for cost reduction, and, in addition, a gas generator A can be provided that is capable of preventing malfunction owing to static electricity.
Although an embodiment of the present invention is set forth in the foregoing, the present invention is not limited to the aforesaid embodiment. And it is possible in the present invention to make various design changes in the shape and the like of the gas generator of the present invention insofar as they do not depart from the matters set out in the scope of claims.
Further, it goes without saying that as the materials and the like used in the individual constituents of the gas generator of the present invention can be used publicly-known or well-known raw materials insofar as they do not depart from the matters set out in the scope of claims.
Therefore, in the gas generator of the present invention, preferred embodiments are obtained in all modes provided that the flange portions of the electrode pins are larger in diameter than the short sides of the opening portion of the holder and the sum of the sector angles formed by the outer peripheral portions located outside the opening portion of the holder in the axial direction and the electrode pins is made 180 degrees or greater. For example, the outer shape of the flange portions of the electrode pins can be configured in polygonal shapes like triangular, rectangular or trapezoidal, or in elliptical and other desired non-circular shapes. Further, even if the outer shapes of the flange portions of the electrode pins differ from each other, it is possible to reliably prevent the electrode pins from flying out from the connector insertion hole side owing to the pressure of the combustion gas insofar as the aforesaid conditions regarding the sector angles is satisfied.
Further, if the minimum distance between the electrode pins and the periphery of the opening portion of the holder through which these electrode pins are inserted is made 0.6 mm or less, any static electricity that should be applied can be suitably discharged to the holder to make it possible to prevent malfunction owing to static electricity, which is still more preferable. Note that in the present invention, electrode pins can be used whose sectional shape is other than circular, such as elliptical or polygonal.
The scope of the right in the present invention also extends to a configuration wherein the height location of the flange portions is differed in level in order to make the flange portions of the electrode pins mutually non-contacting and large in diameter. However, a pair of electrode pins constituted to be non-contacting at the same height level in the horizontal direction come to be electrode pins of the same shape, which is a preferable embodiment because it enables the primer member to be fabricated with still better yield.
Note that since synthetic resin is charged between each electrode pin or its flange portion and the other electrode pin or the other flange portion, the minimum distance therebetween is not particularly limited insofar as they do not contact each other, and insulation property can be adequately established at a clearance of around 0.5 mm. Therefore, the distance between the electrode pins is decided with the pitch of the insertion holes of the connector used as the main condition.
Further, in the aforesaid embodiment, the number of electrode pins is defined as two so as to improve the yield of the electrode pins. However, the plug assembly can be constituted using three or more electrode pins provided that they are properly inserted in the connector insertion hole and the minimum distance from the opening portion of the holder satisfies the aforesaid relationship.
As explained above, the gas generator having the configuration of the present invention makes it possible to replace expensive metal parts and glass, ceramic or other such insulators with ones made of synthetic resin and enables production by a very high yield production method, thus making it possible to thoroughly satisfy the need for cost reduction.
Further, when the pressure of combustion gas acts on the electrode pins with the synthetic resin parts in a state softened by exposure to high temperature from the outside, disengagement of the electrode pins from the connector insertion hole side can be effectively prevented in the case of the gas generator of the present invention.
Being additionally configured to prevent malfunction owing to static electricity, the gas generator of the present invention has high reliability compared to conventional gas generators.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-176244 | Jul 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/054158 | 3/5/2010 | WO | 00 | 1/27/2012 |
