The present invention relates to an apparatus for storing a fluid under pressure, and, more particularly, to a membrane for an apparatus that stores a fluid for actuating a vehicle occupant protection device.
An inflator for actuating a vehicle occupant protection device can include a quantity of a stored fluid (e.g., stored gas) and a combustible material stored in an inflator housing. An igniter is actuatable to ignite the combustible material. As the combustible material burns, the combustion products heat the stored gas. The heated stored gas and the combustion products form an inflation fluid for actuating the vehicle occupant protection device.
The inflator housing can include a rupturable membrane that opens to discharge the inflation fluid from the housing. Discharge of the inflation fluid from the inflator actuates (e.g., inflates) the vehicle occupant protection device. The membrane can open when the inflation fluid in the housing reaches a predetermined pressure and/or temperature.
The rupturable membrane can be a burst disc that is formed from an alloy. One example of an alloy that can be used to form a burst disc for an inflator is INCONEL 625, which is commercially available from Special Metals Corporation (New Hartford, N.Y.). INCONEL 625 consists essentially of, by weight, up to about 5% iron, about 20% to about 23% chromium, about 8% to about 10% molybdenum, about 3.15% to about 4.15% combined niobium and tantalum, up to about 0.5% manganese, up to about 0.5% silicon, up to about 0.4% aluminum, up to about 0.4% titanium, up to about 0.1% carbon, up to about 0.015% sulfur, up to about 0.015% phosphorous, up to about 0.02% nitrogen, up to about 0.3% copper, and the balance nickel.
The present invention relates to an apparatus for actuating a vehicle occupant protection device. The apparatus comprises a housing having a chamber containing a fluid at a first pressure. An outflow opening is provided in the housing through which the fluid can flow from the housing to actuate the vehicle occupant protection device. A membrane having a first temperature closes the opening. The membrane includes a surface extending across the opening. The surface includes a plurality of indentations concentrically arranged relative to a center of the surface. Each indentation can have a substantially polygonal shape and be separated from each other indentation on the surface of the membrane.
The indentations can promote rupturing of the membrane when the membrane reaches an elevated temperature and/or the fluid reaches an elevated pressure. In an aspect of the invention, the indentations can have an average depth. The average depth can be about 1% to about 10% of a thickness of the membrane.
Another aspect of the invention relates to an apparatus that comprises a housing, which contains a fluid at a first pressure. A portion of the housing comprises a nickel-based alloy having a hardening index at temperatures of about 900° C. to about 1200° C. defined by:
σ=κεn
In an aspect of the invention, the microstructure of the nickel-based alloy can be substantially free of sigma phase and mu phase at temperatures above about 900° C.
In another aspect of the invention, the nickel-based alloy can comprise, by weight, at least about 50 nickel, at least about 20% chromium, up to about 3% molybdenum, and at least about 10% tungsten.
In a further aspect of the invention, the nickel-based alloy can comprise, by weight, up to about 5% cobalt, up to about 0.3% iron, about 20% to about 24% chromium, about 1% to about 3% molybdenum, about 13% to about 15% tungsten, about 0.3% to about 1% manganese, about 0.25 to about 0.75% silicon, about 0.2% to about 0.5% aluminum, about 0.05% to about 0.15% carbon, up to about 0.015% sulfur, up to about 0.03% phosphorous, and the balance substantially nickel.
In yet another aspect of the invention, the nickel-based alloy can consist essentially of, by weight, up to about 5% cobalt, up to about 0.3% iron, about 20% to about 24% chromium, about 1% to about 3% molybdenum, about 13% to about 15% tungsten, about 0.3% to about 1% manganese, about 0.25 to about 0.75% silicon, about 0.2% to about 0.5% aluminum, about 0.05% to about 0.15% carbon, up to about 0.015% sulfur, up to about 0.03% phosphorous, up to about 0.25% residual elements, and the balance nickel.
The foregoing and other features of the invention will become more apparent to one skilled in the art upon consideration of the following description of the invention and the accompanying drawings in which:
The present invention relates to a membrane that can be used to close an outflow opening of a housing. The membrane can have a first temperature. The housing can include a chamber that contains a stored fluid and the membrane can maintain the stored fluid in the chamber at a first pressure. When the pressure of the stored fluid increases to an elevated pressure (e.g., about 24 MPa to about 100 MPa) and/or the membrane reaches an elevated temperature (e.g., at least about 900° C.), the membrane plastically deforms and then ruptures to form an opening through which the stored fluid can flow. The membrane readily forms an opening in a controlled manner when the housing is exposed to ambient temperatures down to −35° C.
In an aspect of the invention, the housing can be part of an inflator of a vehicle occupant protection apparatus and be used for actuating a vehicle occupant protection device.
An inflator 14 is associated with the vehicle occupant protection device 12. The inflator 14 can be actuatable to direct fluid to the vehicle occupant protection device 12 to actuate (e.g., inflate) the vehicle occupant protection device 12.
The apparatus 10 also includes a sensor 16, such as a crash sensor. The crash sensor 16 is a known device that senses a vehicle condition, such as vehicle deceleration, indicative of a collision. When the crash sensor 16 senses a vehicle condition for which actuation of the vehicle occupant protection device is desired, the crash sensor 16 either transmits a signal or causes a signal to be transmitted to actuate the inflator 14. The inflator 14 actuates the vehicle occupant protection device to help protect a vehicle occupant from a forceful impact with parts of the vehicle.
An example of a container 24 in accordance with the present invention has an elongated generally annular wall 50 that extends along a central axis 52 between an end wall 54 and a circular open end 56 of the container 24, which is closed by the end cap 26. The container 24 can be formed from a metal that is typically used in pressure vessel formation. Such metals can include, for example, a stainless steel (e.g.,SS316), a low-carbon high strength steel (e.g., AISI 1513) as well as aluminum and/or an aluminum-based alloy (e.g., 6061 aluminum alloy). The container 24 formed from the metal will have a structural integrity that is substantially higher than the structural integrity of the membrane 44. Thus, when the inflator 20 is at an elevated pressure and/or elevated temperature, the membrane 44 will rupture prior to the container 24 rupturing.
The fluid 32 stored under pressure in the storage chamber 30 can comprise a fluid 32 that is typically used to inflate an inflatable vehicle occupant protection device, such as an air bag. For example, the fluid can comprise at least one inert gas, such as helium, nitrogen, and/or argon. The stored fluid can also include an oxidizer gas and/or a combustible fuel gas. The oxidizer gas can comprise, for example, oxygen. The fuel gas can comprise, for example, hydrogen, nitrous oxide, and/or methane.
The pressure at which the fluid is stored in the container (i.e., the first pressure) depends upon such factors as the volume of the inflatable vehicle occupant protection device 12 to be inflated, the time available for inflation, the inflation pressure desired, and the volume of the chamber 30 storing the gas. In an aspect of the invention, the fluid 32 can be stored at a pressure of about 12.5 MPa to about 55 MPa (e.g., about 20 MPa to about 27 MPa).
An end portion of the housing 20 supports a combustion chamber housing 57 and an actuatable pyrotechnic igniter 58. The combustion chamber housing 57 is aligned with the axis 52 and extends within the diffuser 48. The combustion chamber housing 57 includes a combustion chamber 60 that contains a readily ignitable gas generating material, such as a nitramine-based gas generating material, a guanidine-based gas generating material, and/or a nitroguanidine-based gas generating material. Other gas generating materials can also be used.
The igniter 58 contains an ignitable material (e.g., BKNO3) (not shown) and functions to ignite the gas generating material in the combustion chamber 60. The igniter 58 is connected in an electrical circuit 62 that include a power source 64 (e.g., battery and/or capacitor) and a normally open switch 66. The switch 66 can be part of the crash sensor 16.
When the crash sensor 16 senses a vehicle condition for which actuation of the vehicle occupant protection device is desired, the switch 66 can close and the igniter is actuated electrically. The igniter 58 then ignites the gas generating material. Hot gas produced through deflagration of the gas generating material flows from the combustion chamber 60 and against the membrane to increase the temperature of the membrane from a first temperature (e.g., 25° C.) to an elevated temperature (e.g., at least about 900° C.). When the increasing membrane temperature reaches the elevated temperature, the membrane 44 plastically deforms in a controlled manner and ruptures (
Referring also to
The central potion 102 has a first surface 110 and a spaced apart substantially parallel second surface 112. The first surface 110 and the second surface 112 extend radially from a center 120 of the membrane 44, which is aligned with the axis 52. When the membrane 44 is fastened to the membrane holder 70, as shown in
In accordance with an aspect of invention, the central portion 102 includes a plurality of indentations 130 that promote opening of the membrane 44 when the membrane 44 reaches an elevated temperature (e.g., at about 900° C.) and/or the pressure in the chamber 30 reaches an elevated pressure (e.g., about 24 MPa to about 100 MPa). The indentations create preset strains in the membrane 44 that promote deformation of the membrane 44 during increase in temperature of the membrane to the elevated temperature and/or increase of the fluid pressure to an elevated pressure and potentially form nominal fracture points that at least partially define the opening area (or rupture area) of the membrane 44.
The indentations 130 can be provided in at least the first surface 110 or the second surface 112 of the central portion 102 of the membrane 44 in a substantially annular pattern to ensure that the area of the opening formed after rupture of the membrane 44 is at least about 25% of the area of the outflow opening 42. The annular pattern of indentations 130 also ensures that the membrane 44 adequately opens when the inflator 20 is actuated at colder temperatures, such as less than 0° C., (e.g., about −35° C.). At colder temperatures, the pressure and, hence, the load provided by the fluid 32 can be substantially lower and may potentially affect the size of the opening in the membrane 44.
In an aspect of the invention, the indentations 130 are concentrically arranged in the second surface 112 relative to the center 120 of the membrane 44 so that after rupture of the membrane 44, as shown in
Referring again to
Although
The minimum depth of each indentation 130 can be that depth that is sufficient to promote opening of the membrane 44. The maximum depth of each indentation 44 can be a depth that allows the membrane to sustain an increased fluid pressure when the inflator 20 is heated to a temperature of about 95° C. to about 105° C., without being actuated. By way of example, the average depth of each indentation 130 can be about 1% to about 15% of the thickness of the membrane 44 (e.g., about 5% to about 10% of the thickness of the membrane 44). By way of example, for a membrane 44 that has an average thickness of about 0.175 mm, the depth of the indentation (and the reduction in the thickness of the membrane) can be about 0.00175 mm to about 0.026 mm. This depth will vary depending on the particular metal used to form the membrane 44.
Referring to
The membrane 44 can be stamped with the indenter 202 at a pressure sufficient to form the indentations 130. The stamping pressure can depend on the particular metal used to form the membrane 44 as well as the desired depth of the indentations 130.
In accordance with an aspect of the invention, the membrane 44 can formed from any metal that can be readily indented with an indenter to provide indentations, welded to the membrane holder, as well as exhibits at least some plastic deformation prior to rupture. Such metals can include, for example, nickel-based alloys, such as corrosion-resistant nickel-based alloys. By “nickel-based” alloy, it is meant alloys that include at least about 50, by weight, nickel (e.g., at least about 55%, by weight, nickel).
One example of a nickel-based alloy that can be used in accordance with the invention is a corrosion-resistant nickel-chromium-molybdenum-niobium alloy that can comprise, for example up to about 22% by weight chromium and up to about 9% by weight molybdenum. Examples of nickel-chromium-molybdenum-niobium alloys include Haynes 625, which is commercially available from Haynes International, Kokomo, IN, Krupp VDM NiCr22Mo9Nb, which is commercially available from Krupp VDM GmbH, Werdohl, Germany, and UNS N06625 (i.e., “Unified Numbering System for Metals and Alloys” N06625).
Haynes 625 comprises, by weight, about 62% nickel, about 1% cobalt, about 5% iron, about 21% chromium, about 9% molybdenum, about 3.7% combined niobium and tantalum, about 0.5% manganese, about 0.5% silicon, about 0.4% aluminum, about 0.4% titanium, and about 0.1% carbon.
Krupp VDM NiCr22Mo9Nb comprises, by weight, about 62.92% nickel, about 3.15% iron, about 21.05% chromium, about 8.6% molybdenum, about 3.35% combined niobium and tantalum, about 0.14% manganese, about 0.15% silicon, about 0.13% aluminum, about 0.2% titanium, about 0.08% carbon, about 0.0005% sulfur and about 0.007% phosphorous.
UNS N06625 comprises, by weight, up to about 1% cobalt, up to about 5% iron, about 20% to about 23% chromium, about 8% to about 10% molybdenum, about 3.15% to about 4.15% combined niobium and tantalum, up to about 0.5% manganese, up to about 0.5% silicon, up to about 0.4% aluminum, up to about 0.4% titanium, up to about 0.1% carbon, up to about 0.015% sulfur, up to about 0.015% phosphorous, up to about 0.02% nitrogen, and up to about 0.30% copper.
Another example of a nickel-based alloy that can be used to form the membrane is UNS N07718. UNS N07718 comprises, by weight, about 50 to about 55% nickel, up to about 1% cobalt, about 17% to about 21% chromium, about 2.8% to about 3.3% molybdenum, about 4.75% to about 5.5% combined niobium and tantalum, up to about 0.35% manganese, up to about 0.35% silicon, about 0.2% to about 0.8% aluminum, about 0.65% to about 1.15% titanium, up to about 0.08% carbon, up to about 0.015 sulfur, up to about 0.015% phosphorous, up to about 0.006% boron, and up to about 0.30% copper.
In accordance with another aspect of the invention, the metal used to form the membrane 44 can comprise a nickel-based alloy that exhibits nearly perfect plastic behavior at temperatures to which the membrane 44 is subjected after actuation of the inflator 20. These temperature can be at least about 900° C. (e.g., about 900° C. to about 1200° C.) depending on the combustion temperature of the gas generating material employed in the inflator 20. By “nearly perfect plastic behavior”, it is meant that at the elevated temperature (e.g., about 900° C. to about 1200° C.) the nickel-based alloy's ultimate tensile strength is essentially the same (or nearly the same) as its yield strength. Nearly perfect plastic behavior at temperatures of about 900° C. to about 1200° C. can also be defined in accordance with Ramberg-Osgood's model, which has the following general equation:
σ=κεn
A membrane 44 formed from a nickel-based alloy exhibiting nearly perfect plastic deformation at temperatures of at least about 900° C. can more readily open in a controlled manner to a desired opening size (e.g., greater than about 25% of the outflow opening area) and produce fewer fragments and/or particles upon rupture. Additionally, a membrane 44 formed from a nickel-based alloy exhibiting nearly perfect plastic deformation at temperatures of at least about 900° C. can be formed without indentations 130 and still open to the desired opening size.
An example of a nickel-based alloy that exhibits nearly perfect plastic deformation at temperatures of at least about 900° C. is UNS 06230 (e.g., Inconel 230). UNS 06230 is a nickel-chromium-molybdenum-tungsten alloy that comprises, by weight, at least about 50 nickel, at least about 20% chromium, up to about 3% molybdenum, and at least about 10% tungsten. UNS 06230 is commercially available from Special Metal Corporation (New Hartford, N.Y.) as Inconel 230. Inconel 230 has a nominal composition that comprises, by weight, up to about 5% cobalt, up to about 0.3% iron, about 20% to about 24% chromium, about 1% to about 3% molybdenum, about 13% to about 15% tungsten, about 0.3% to about 1% manganese, about 0.25 to about 0.75% silicon, about 0.2% to about 0.5% aluminum, about 0.05% to about 0.15% carbon, up to about 0.015% sulfur, up to about 0.03% phosphorous, and the balance substantially nickel.
In an aspect of the invention, the nickel-based alloy exhibiting nearly perfect plastic behavior can consist essentially of, by weight, up to about 5% cobalt, up to about 0.3% iron, about 20% to about 24% chromium, about 1% to about 3% molybdenum, about 13% to about 15% tungsten, about 0.3% to about 1% manganese, about 0.25 to about 0.75% silicon, about 0.2% to about 0.5% aluminum, about 0.05% to about 0.15% carbon, up to about 0.015% sulfur, up to about 0.03% phosphorous, up to about 0.25% residual elements, and the balance nickel. By residual elements, it is meant the combined weight of additional elements including, for example, boron, niobium, lanthanum, tantalum, and nitrogen.
Inconel 230 has a high tungsten content compared to other nickel-based alloys used to form the membrane. The high tungsten content improves the alloys resistance to pitting and crevice corrosion. Inconel 230 also has a fully austenitic microstructure. By virtue of the Inconel 230's carbon content, the microstructure contains quantities of secondary carbide particles (e.g., M6C and M23C6) that contribute substantially to the alloy's strength. The microstructure of Inconel 230 does not exhibit sigma phase (i.e., nickel-chromium-molybdenum precipitation), mu phase (i.e., nickel-iron-molybdenum precipitation) or other deleterious phase formation at high temperatures (e.g., at least about 900° C.).
As shown in
The nearly perfect plastic behavior exhibited by Inconel 230 compared to Inconel 625 is also shown in
From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Examples of changes include changes in the inflator construction. For example, the combustion chamber can be provided in the chamber 30 used to store the gas 32. Thus, upon actuation of the inflator, the deflgration gas increases the pressure of the stored gas 31 in the chamber to an elevated pressure (e.g., about 24 MPa to about 100 Mpa) that can cause the membrane to rupture. Additionally, the inflator can have a construction similar to the inflator construction in U.S. Pat. Nos. 5,348,344 and 5,786,543, which are herein incorporated by reference in their entirety. The inflators in these patents include a fuel gas (e.g., H2) and an oxidizer gas (O2) instead of solid gas generating material, as described with respect to the present invention. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.