Initiator for gas generator of vehicle safety device

Abstract

The initiator (10) for a gas generator of a vehicle safety device includes a cup (12) defining an interior, a primary pyrotechnic material (14) disposed within a primary combustion chamber (44) within the interior of the cup (12), and a pair of electrical pins (40) in initiating communication with the primary pyrotechnic material (14) through a bridgewire (42). The bridgewire (42) is in initiating contact with the primary pyrotechnic material (14) at a first end (14A) of the primary pyrotechnic material (14). The primary pyrotechnic material (14) is consolidated within the primary combustion chamber (44) to include a recess (46) at a second end (14B) of the primary pyrotechnic material (14), the second end (14B) being opposite the first end (14A).

Description

[Technical field]

[0001] The present disclosure relates generally to initiators for gas generators for vehicle safety devices such as inflatable airbags and pretensioned seat belts, etc. More specifically, the present disclosure relates to initiators for gas generators having a primary pyrotechnic material consolidated to include a central depression. [Background technology]

[0002] This section provides background information related to the present disclosure, which is not necessarily prior art.

[0003] Inflatable occupant restraint systems, including airbags, are typically included on motor vehicles for passive occupant protection. Airbags used for frontal impact protection are generally installed in the vehicle steering wheel for the driver and behind the vehicle instrument panel for other front seat occupants. In addition to frontal impact protection, inflatable restraint devices are used for occupant protection from side impacts. For example, side curtain airbags are typically mounted along the roof rails of the vehicle and deploy in a downward direction to provide an energy absorbing structure between the occupant's head and upper torso and the vehicle cabin components. Side airbags may also be mounted in the vehicle seats.

[0004] Inflator devices are employed to generate or supply inflation gas for inflating an inflatable airbag in the event of a crash. Inflator devices for such applications often include a gas generant material stored within a housing of the inflator device. The gas generant material is activated by an initiator when a sensor in the vehicle senses an accident condition (e.g., measures abnormal deceleration). Activation of the gas generant material triggers inflation of the airbag with the generated gas within milliseconds. The inflated airbag protects the vehicle occupant from the forces of the impact. Initiators are also used for seat belt pretensioning.

[0005] The initiator may typically have a first or primary pyrotechnic material and a second or secondary pyrotechnic material. The primary pyrotechnic material is activated by an electrical signal, which in turn ignites the secondary pyrotechnic material. Heat from the combustion of the secondary pyrotechnic material ignites a gas generating material in the inflator device to generate inflation gas for the airbag. Summary of the Invention [Problem to be solved by the invention]

[0006] Although known initiators for occupant restraint systems have generally been found to be suitable for their intended uses, there remains a continuing need for improvements in the related art.

[0007] This section provides a summary of the disclosure and is not an exhaustive disclosure of the entire scope or all of the features of the disclosure.

[0008] One general object of the present teachings is to provide an initiator for a gas generator of a vehicle safety device having a compacted primary pyrotechnic material with a more predictable density profile.

[0009] According to one particular aspect, the present teachings provide an initiator for a gas generator of a vehicle safety device, the initiator including a cup defining an interior, a primary pyrotechnic material disposed within a primary combustion chamber within the interior of the cup, and a pair of electrical pins in initiating communication with the primary pyrotechnic material through a bridgewire. The bridgewire is in initiating contact with the primary pyrotechnic material at a first end of the primary pyrotechnic material. The primary pyrotechnic material is consolidated within the primary combustion chamber to include a recess at a second end of the primary pyrotechnic material, the second end being opposite the first end.

[0010] According to another particular aspect, the present teachings provide an initiator for a gas generator of a vehicle safety device, the initiator including a cup defining an interior, a primary combustion chamber within the interior of the cup, a primary pyrotechnic material disposed within the primary combustion chamber, and a pair of electrical pins in initiating communication with the primary pyrotechnic material through a bridgewire. The bridgewire is in initiating contact with the primary pyrotechnic material at a first axial end of the primary pyrotechnic material. The primary pyrotechnic material is axially consolidated within the primary combustion chamber to include a first density at a radially inner portion of the primary pyrotechnic material and a second density at a radially outer portion of the primary pyrotechnic material. The first density is at least as great as the second density.

[0011] According to yet another particular aspect, the present teachings provide an initiator for a gas generator of a vehicle safety device, the initiator comprising: a cup defining an interior, a primary combustion chamber including a primary pyrotechnic material, a secondary combustion chamber including a secondary pyrotechnic material, and a pair of electrical pins in initiating communication with the primary pyrotechnic material through a bridgewire. The bridgewire is in initiating contact with the primary pyrotechnic material at a first axial end of the primary pyrotechnic material. The primary pyrotechnic material is consolidated within the primary combustion chamber to include a recess at a second axial end of the primary pyrotechnic material opposite the first axial end.

[0012] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. [Brief description of the drawings]

[0013] The drawings described herein are only for purposes of illustrating selected embodiments rather than all possible implementations and are not intended to limit the scope of the present disclosure.

[0014] [Figure 1] FIG. 1 is a side view of an initiator for a gas generator of a vehicle occupant restraint system in accordance with the present teachings. [Diagram 2]FIG. 2 is another side of an initiator for a gas generator according to the present teachings, where the initiator is shown rotated 90 degrees about its axis and the initiator's insulation resistance cover is shown removed for illustrative purposes. [Diagram 3] FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. [Figure 4] FIG. 4 is a simplified cross-sectional view of a portion of an initiator prior to compaction of the primary pyrotechnic material of the initiator by the ram. [Diagram 5] FIG. 5 is a simplified cross-sectional view similar to FIG. 4 illustrating a portion of the initiator after compaction of the primary pyrotechnic material of the initiator by the ram. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] One or more exemplary embodiments will now be described more fully with reference to the accompanying drawings. One or more exemplary embodiments are provided to fully convey the scope of the present disclosure to those skilled in the art. Many specific details, such as examples of specific components, devices, and methods, are described to provide a thorough understanding of the embodiments of the present disclosure. It is apparent to those skilled in the art that specific details need not be employed, and that the exemplary embodiments should not be construed to limit the scope of the present disclosure. Well-known processes, well-known device structures, and well-known technologies are not described in detail herein.

[0016] The phrases "connected," "coupled," and "in communication with" refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, fluid, and thermal interaction. Two components may be coupled to one another even if the two components are not in direct contact with one another. The term "adjacent" refers to things being in physical proximity to one another, but these things may not necessarily be in direct contact. The phrase "fluid communication" refers to two features that are connected such that fluid in one feature can pass into the other feature. As used herein, "exemplary" means serving as a typical or representative example or instance, and does not necessarily mean special or preferred.

[0017] Referring to the drawings, an initiator for a gas generator of a vehicle safety device in accordance with the present teachings is illustrated and generally identified by the reference numeral 10. The initiator 10 may be part of an automobile passenger restraint system that includes, for example, a gas generator and an inflatable airbag (not specifically shown). The exemplary inflator or pyrotechnic inflator 10 shown in the drawings is particularly adapted for a driver's side front airbag of the passenger restraint system. However, it will be understood that the initiator 10 described herein may be readily adapted for use with other airbags or seat belt pretensioners.

[0018] The initiator 10 is generally illustrated as including a cup or case 12, a first or primary pyrotechnic material 14, and a second or secondary pyrotechnic material 16. The primary and secondary pyrotechnic materials 14, 16 are disposed or stored within an interior 18 of the cup 12. The cup 12 may include a cylindrical sidewall 20 and a circular base. The cylindrical sidewall 20 extends between a closed end 22 and an open end 24 along an axis A of the initiator 10. The cup 12 may be formed from a metal and may be formed by cold striking. In one specific example, the cup 12 may be formed by stamping a sheet of nickeled steel, such as DC04 or DC06, and may have a thickness of 0.3 to 0.6 mm.

[0019] Although not illustrated, it will be understood that the cup 12 may be formed to include multiple weakened zones that preferably open in response to pressure from within the cup 12 generated by the combustion of the secondary pyrotechnic material 16. In one application, the side wall 20 may include four weakened zones evenly distributed about the axis A.

[0020] In the illustrated embodiment, the primary pyrotechnic material 14 is different from the secondary pyrotechnic material 16. The primary pyrotechnic material 14 may be separated from the secondary pyrotechnic material 16 by a separation member within the interior 18 of the cup 12. The primary pyrotechnic material 14 may be in the form of a slurry or in the form of a powder. The secondary pyrotechnic material 16 may be a granular material, including but not limited to a boron-based material. It will be understood that the particular pyrotechnic materials 14 and 16 are outside the scope of the present teachings and may be selected from a variety of pyrotechnic materials known in the art.

[0021] The initiator 10 of the present teachings may further include an adapter or base member 30. The adapter 30 functions to house the first pyrotechnic material 14 and to provide an interface between the cup 12 and the separation member 28. The adapter 30 may be formed from stainless steel or other suitable material. One suitable material is type 304L stainless steel. The adapter 30 has a cylindrical shape and includes a stepped configuration having a first or lower portion 32 and a second or upper portion 34. The first portion 32 has a first diameter and the second portion 34 has a second, smaller diameter.

[0022] The adapter 30 is at least partially disposed within the cup 12. As shown, the adapter 30 is completely or substantially completely disposed within the cup 12. The adapter 30 is sized to be received within the open end 24 of the cup 12. The cylindrical sidewall 20 of the cup 12 may be attached to the adapter 30 around its outer periphery. In the illustrated embodiment, a first portion 32 of the adapter 30 may be welded to the cup 12.

[0023] The first portion 32 of the adapter 30 defines a central opening 36 that receives an igniter 38. The igniter 38 conventionally includes a pair of electrical connectors or pins 40 and a bridgewire 42. The pair of electrical pins 40 react to initiate communication with the first pyrotechnic material 14 through the bridgewire 42. In this regard, electrical current delivered to the pins 40 functions to melt the bridgewire 42 and ignite the first pyrotechnic material 14.

[0024] The second portion 34 of the adapter 30 defines a central cavity or primary combustion chamber 44. As shown, the cavity or primary combustion chamber 44 is defined by a cylindrical sidewall of the second portion 34 of the adapter 30. The primary combustion chamber 44 contains the primary pyrotechnic material 14. The primary combustion chamber 44 has an open end that is closed by a separator member 28. In the illustrated embodiment, the separator member 28 can seal the primary pyrotechnic material 14 from the secondary pyrotechnic material 16, such that the primary and secondary pyrotechnic materials 14 and 16 are completely sealed from one another, meaning that the primary and secondary materials 14 and 16 are completely sealed from one another.

[0025] The primary pyrotechnic material 14 is in initiating contact with the bridgewire 42. As shown particularly in the cross-sectional view of FIG. 3, the primary pyrotechnic material 14 is in initiating contact with the bridgewire 42 at a lower or first end of the primary combustion chamber 44. In this manner, a first end or first axial end 14A of the primary pyrotechnic material 14 is in initiating contact with the bridgewire 42. As will be discussed further below, the primary pyrotechnic material 14 is consolidated within the primary combustion chamber 44 to include a depression or recess 46 at a second end or second axial end 14B of the primary pyrotechnic material 14 opposite the first end 14A.

[0026] The initiator 10 of the present teachings is shown further including an insulation resistance or static cover 48 and an elastomeric overmolding or overmolded member 50. It will be understood that these elements 48 and 50 are conventional as far as the present invention is concerned. Briefly, the overmolding member 50 may be an injection molded form of glass filled nylon 6 material. The static cover 48 may be constructed from nylon 6 or other plastic materials.

[0027] 4 and 5, a portion of the initiator 10 is shown in operative association with a ram 52 for compacting the primary pyrotechnic material 14 within the primary combustion chamber 44. In FIG. 4, the ram 52 is shown prior to compaction of the primary pyrotechnic material 14. In FIG. 5, the ram 52 is shown after compaction of the primary pyrotechnic material 14 within the primary combustion chamber 44.

[0028] The ram 52 has a male shape to define a dome-shaped recess 46. In other applications within the scope of the present teachings, the recess 46 may have a frustoconical shape or other shape. As illustrated, the second axial end 14B of the primary pyrotechnic material 14 includes a central recess or recess axially aligned with at least a portion of the bridgewire 42. The recess 46 of the primary pyrotechnic material 14 is radially spaced from a sidewall defining the primary combustion chamber 44. In this regard, a toroidal shaped surface or portion is radially disposed between the recess 46 and the sidewall of the primary combustion chamber 44. This radial spacing of the recess 46 from the sidewall of the chamber 44 avoids build-up at the boundary defined by the sidewall that may otherwise prevent sufficient consolidation of the primary pyrotechnic material 14 to achieve optimal performance of the initiator 10. The first pyrotechnic material 14 is axially consolidated within the primary combustion chamber 44 to include a first density at a radially inner portion of the primary pyrotechnic material 14 and a second density at a radially outer portion of the primary pyrotechnic material 14, the first density being at least as great as the second density.

[0029] The diameter of the primary pyrotechnic material 14 and the depth of the recess 46 at the second end 14B of the primary pyrotechnic material 14 can vary as a function of the axial length of the primary pyrotechnic material 14 at the cylindrical sidewall of the primary pyrotechnic chamber 44. As shown in FIG. 5, for example, the maximum diameter of the recess 46 can be greater than the radial dimension of the recess from the cylindrical sidewall of the primary pyrotechnic chamber 44.

[0030] In one particular embodiment, the primary combustion chamber may have a diameter of 3.6 mm and the primary pyrotechnic material 14 may have a weight of 43 mg. The primary pyrotechnic material 14 may be compacted to have an axial length of 1.32 mm. The dome-shaped recess 46 may be hemispherical and have a diameter of 0.609 mm. The toroidal shaped surface between the radial recess 46 and the sidewall of the chamber 44 may have a radial dimension of 0.508 mm.

[0031] In use, an electrical current is delivered to pin 40 of igniter 38 to both test and activate initiator 10. For purposes of testing initiator 10, an electrical test signal is delivered to pin 10 of igniter 38. The electrical test signal may have a first amperage. In one example, the first amperage may be approximately 0.4 amp. The present teachings provide a sufficiently compacted primary pyrotechnic material 14 in close proximity to bridgewire 42 such that heat generated in bridgewire 42 can be dissipated by primary pyrotechnic material 14 without actuating primary pyrotechnic material 14.

[0032] When an impact event is sensed, an electrical ignition signal is delivered to pin 40 of ignition device 38. The electrical ignition signal may have a second amperage. The second amperage is greater than the first amperage of the electrical test signal. In one example, the second amperage may be approximately 1.75 amp. The current of the electrical ignition signal melts bridge wire 42, which then ignites primary pyrotechnic material 14. Ignition of primary pyrotechnic material 14 creates pressure within chamber 44 of adapter 30, which opens a weakened zone (not shown) of separation member 28. Heat from ignition of primary pyrotechnic material 14 is exhausted through the open weakened zone, igniting secondary pyrotechnic material 16. Pressure from combustion of secondary pyrotechnic material 16 opens weakened zone 26 of cup 12.

[0033] While specific embodiments and applications of the present disclosure have been illustrated and described, it will be understood that the invention is not limited to the precise configuration and components disclosed herein. Various modifications, changes and variations which will be apparent to those skilled in the art can be made in the arrangement, operation and details of the methods and systems of the present disclosure without departing from the spirit and scope of the present disclosure.

Claims

1. An initiator 10 for a gas generator of a vehicle safety device, comprising: a cup 12 defining an interior; a primary pyrotechnic material 14 disposed within a primary combustion chamber 44 within the interior of the cup 12; a pair of electrical pins 40 in initiation communication with the primary pyrotechnic material 14 through a bridgewire 42, the bridgewire 42 being in initiation contact with the primary pyrotechnic material 14 at a first end 14A of the primary pyrotechnic material 14; the primary pyrotechnic material (14) is consolidated within the primary combustion chamber (44) to include a recess (46) at a second end (14B) of the primary pyrotechnic material (14), the second end (14B) being opposite the first end (14A).

2. The initiator (10) of claim 1, wherein the recess (46) at the second end (14B) of the primary pyrotechnic material (14) is axially aligned with at least a portion of the bridgewire (42).

3. The initiator (10) of claim 1, wherein the recess (46) at the second end (14B) of the primary pyrotechnic material (14) is dome-shaped.

4. 3. The initiator (10) of claim 2, wherein the recess (46) at the second end (14B) of the primary pyrotechnic material (14) is centrally located in the primary combustion chamber (44).

5. 2. The initiator (10) of claim 1, wherein the recess (46) at the second end (14B) of the primary pyrotechnic material (14) is radially spaced from a sidewall of the primary combustion chamber (44).

6. 6. The initiator (10) of claim 5, wherein the second end (14B) of the primary pyrotechnic material (14) includes a toroidal shaped portion radially disposed between the recess (46) and the sidewall of the primary combustion chamber (44).

7. 2. The initiator (10) of claim 1, wherein the maximum diameter of said recess (46) is greater than the radial distance of said recess (46) from a cylindrical sidewall defining said primary pyrotechnic chamber (44).

8. 2. The initiator 10 of claim 1, wherein the primary pyrotechnic material 14 is sufficiently compressed in a region adjacent the bridgewire 42 to absorb heat generated from an electrical test signal having a first amperage delivered to the electrical pins 40 without combusting, and to combust in response to an electrical test signal having a second amperage, the second amperage being greater than the first amperage.

9. 2. The initiator of claim 1, wherein the primary pyrotechnic material is axially consolidated in the primary combustion chamber to include a first density at a radially inner portion of the primary pyrotechnic material and a second density at a radially outer portion of the primary pyrotechnic material, the first density being at least as great as the second density.

10. a secondary pyrotechnic material (16) separated from the primary pyrotechnic material (14); The initiator (10) of claim 1 further characterized by a secondary combustion chamber in which combustion of the primary pyrotechnic material (14) in turn activates the secondary pyrotechnic material (16).

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