Air damped crash sensor and construction method thereof

• US 5,804,783 A
• Filed: 06/07/1995
• Issued: 09/08/1998
• Est. Priority Date: 06/07/1995
• Status: Expired due to Fees

• Current Assignee: American Vehicular Sciences LLC (Acacia Research Corporation)
• Original Assignee: Automotive Technologies International Incorporated
• Inventors: Breed, David S.
• Primary Examiner(s): Donovan, Lincoln
• Assistant Examiner(s): Friedhofer, Michael A.
• Application Number:
  US08/476,881
• Time in Patent Office: 1,189 Days
• Field of Search: 200/61.45 R-61.45 M, 200/61.46, 200/61.47, 200/61.48, 200/61.49, 200/61.5, 200/61.51, 200/61.52, 200/61.53, 29/592, 29/592.1, 29/622, 29/837, 29/854-856, 439/604, 439/874, 439/894
• US Class Current: 200/61.45R
• CPC Class Codes: H01H 35/142 Damping means to avoid unwanted response

Abstract

An air damped crash sensor including a thin planar hinged inertial sensing mass which rotates within a sealed housing with a small clearance between the edges of the mass and the walls of the housing so as to create a restriction to the flow of a gas from one side of the sensing mass to the other side as the sensing mass rotates in response to accelerations during a crash of an automobile. The flow of gas within the sealed housing is designed to be in the inertial regime such that the damping force on the mass is proportional to the velocity of the mass squared and thus affected by the gas density but not temperature. The sensor may include (i) a thin hinge which is insert molded into the sensing mass and sensor body through a unique two step molding process whereby the hinge, typically made of plastic, is supported so that it does not deform, (ii) gas storage reservoirs placed to the side of the main cavity, (iii) a biasing contact designed so that it remains in contact with the sensing mass during the crash, and (iv) optionally an integral connector. With these elements, the sensor is ideally suited for sensing side impacts for the purpose of deploying a side impact passenger protection device.

Claims

1. In a vehicle having a deployable passive restraint device, a sensor for detecting that said vehicle is experiencing a crash requiring deployment of said passive restraint device comprising:

(a) a housing having an inboard end, an outboard en and a main cavity within, said main cavity being defined by side walls;

(b) an inboard cover for closing said inboard end of said housing;

(c) an outboard cover for closing said outboard end of said housing;

(d) a mass disposed within said main cavity and rotatable relative to said housing from a first at rest position where said mass is adjacent to said inboard cover of said housing to a second triggering position, closer to said outboard end of said housing, in response to accelerations of said housing, a space being defined between said inboard cover and said mass on a first side of said mass, said mass in cooperation with said main cavity side walls forming a clearance there between, said clearance creating a restriction to flow of a fluid between the space on the first side of said mass closer to said inboard cover and a space on a second side of said mass closer to said outboard cover;

(e) a hinge insert molded into said mass and said housing permitting said mass to rotate within said main cavity;

(f) means defining at least one fluid storage cavity within said housing in fluid communication with said space between said inboard cover and said mass on said first side of said mass, said at least one fluid storage cavity being arranged at a location other than between said mass and said inboard cover;

(g) an integral connector;

(h) a first contact means attached to said housing and coupled to said integral connector, extending within said main cavity and engaging and applying a force to said mass holding said mass at said first at rest position prior to a crash, said first contact means movable with said mass from said first at rest position to said second triggering position;

(i) means to prevent said first contact means from disengaging with said mass during an acceleration of 250 G'"'"'s for 0.002 seconds; and

(j) a second contact means attached to said housing, extending within said main cavity and positioned to be engaged by said first contact means when said mass moves to said second triggering position to deploy the passive restraint device, said second contact means being coupled to said integral connector;

wherein, as said mass rotates relative to said housing in response to accelerations of said housing, a pressure difference is created between the space on the first side of said mass and the space on the second side of said mass which is gradually reduced by the flow of fluid through said clearance into the space between said mass and said inboard cover and from said at least one fluid storage cavity into the space between said mass and said inboard cover without passing through said clearance to thereby retard the motion of said mass.

2. The invention in accordance with claim 1, wherein said housing comprises a substantially circular peripheral wall, said at least one fluid storage cavity being arranged between said side walls defining said main cavity and said circular peripheral wall of said housing.

3. In a vehicle having a deployable passive restraint device, a sensor for detecting that said vehicle is experiencing a crash comprising:

(a) a housing having an inboard end, an outboard end and a main cavity within, said main cavity being defined by side walls;

(b) an inboard cover for closing said inboard end of said housing;

(c) an outboard cover for closing said outboard end of said housing;

(d) a mass disposed within said main cavity and rotatable relative to said housing from a first at rest position where said mass is adjacent to said inboard cover to a second triggering position, closer to said outboard end of said housing, in response to accelerations of said housing, a space being defined between said inboard cover and said mass on a first side of said mass, said mass in cooperation with said main cavity side walls forming a clearance there between, said clearance creating a restriction to flow of a fluid between the space on the fist side of said mass closer to said inboard cover and a space on a second side of said mass closer to said outboard cover;

(e) a hinge attached to said mass and to said housing permitting said mass to rotate within said main cavity;

(f) means defining at least one fluid storage cavity within said housing outside of, adjacent to and in fluid communication with said space between said inboard cover and said mass on the first side of said mass, said at least one fluid storage cavity being situated at a location other than between said mass and said inboard cover; and

(g) mass movement detection means for detecting that said mass has moved to said second triggering position to initiate deployment of the passive restraint device;

wherein, as said mass rotates relative to said housing in response to accelerations of said housing, a pressure difference is created between the space on the first side of said mass and the space on the second side of said mass which is gradually reduced by the flow of fluid through said clearance into the space between said mass and said inboard cover and from said at least one fluid storage cavity into the space between said mass and said inboard cover without passing through said clearance to thereby dampen the motion of said mass.

4. The invention in accordance with claim 3 wherein said housing and said mass are made from plastic and said hinge is made from a plastic having a higher melting point than the plastic used for said housing and said mass.

5. The invention in accordance with claim 4 wherein said plastic hinge is made from Polyvinylidene Flouride.

6. The invention in accordance with claim 4 wherein said mass is substantially rectangular and includes reinforcing ribs.

7. The invention in accordance with claim 3 wherein said main cavity is substantially rectangular and defined by four of said side walls, and wherein said mass is attached to a first one of said side walls by said hinge and a second one of said side walls opposite said first side wall has a substantially planar form.

8. The invention in accordance with claim 3 further comprising control means for controlling displacement of said mass between said first at rest position and said second triggering position, said control means comprising a permanent deformation of said inboard cover.

9. The invention in accordance with claim 3 further comprising an integral connector coupled to said mass movement detection means.

10. The invention in accordance with claim 3, wherein said housing comprises a substantially circular peripheral wall, said at least one fluid storage cavity being arranged between said side walls defining said main cavity and said circular peripheral wall of said housing.

11. A method for molding a housing and sensing mass assembly for a crash sensor having a housing, said housing having a cavity therein and a sensing mass disposed within said cavity and rotatable relative to said housing, a hinge having a first portion within said sensing mass, a second portion between said sensing mass and said housing and a third portion within said housing, comprising the following steps:

(a) place said hinge into a mold adjacent a support member, said support member supporting one side of said first and said third portions of said hinge, and said mold having a housing cavity and a sensing mass cavity;

(b) close said mold and inject liquid plastic therein though a first injection port to fill said housing and sensing mass cavities, thereby substantially forming said housing and said sensing mass;

(c) remove said support member exposing a surface of said hinge at said first and said third portions and creating a cavity within said mold adjacent said hinge;

(d) inject liquid plastic into said mold though a second injection port, said plastic filling said cavity adjacent said first and third portions of said hinge thereby encapsulating said first portion of said hinge within said sensing mass and said third portion of said hinge within said housing; and

(e) remove said housing and sensing mass assembly from said mold.

12. A crash sensor for a vehicle having a deployable passive restraint device, said sensor comprising:

(a) a housing having a front end, a rear end and a main cavity within, said main cavity having side walls;

(b) a front end cover for closing said front end of said housing;

(c) a rear end cover for closing said rear end of said housing;

(d) a mass disposed within said main cavity and rotatable relative to said housing from a first at rest position where said mass is adjacent to said rear end cover to a second triggering position, closer to said front end of said housing, in response to accelerations of said housing, a space being defined between said front end cover and said mass on a first side of said mass, said mass in cooperation with said main cavity side walls forming a clearance there between, said clearance creating a restriction to flow of a fluid between the space on the first side of said mass closer to said inboard cover and a space on a second side of said mass closer to said outboard cover;

(e) a hinge means attached to said mass and to said housing permitting said mass to rotate within said main cavity;

(f) a first contact means attached to said housing, extending within said main cavity and engaging and applying a force to said mass holding said mass at said first at rest position prior to a crash, said first contact means movable with said mass from said first at rest position to said second triggering position;

(g) disengagement prevention means for preventing said first contact means from disengaging with said mass during an acceleration of 250 G'"'"'s for 0.002 seconds, said disengagement prevention means comprising said first contact means being attached to said mass; and

(h) a second contact means attached to said housing, extending within said main cavity and positioned to be engaged by said first contact means when said mass moves to said second triggering position to deploy the passive restraint device.

13. The invention in accordance with claim 12 wherein said first contact means comprise a cantilevered beam contact.

14. The invention in accordance with claim 13 wherein said cantilevered beam contact has a circular cross section.

15. The invention in accordance with claim 13 wherein said cantilevered beam contact has a rectangular cross section.

16. The invention in accordance with claim 12, further comprising means defining at least one fluid storage cavity within said housing outside of, adjacent to and in fluid communication with said space between said inboard cover and said mass on the first side of said mass, said at least one fluid storage cavity being situated at a location other than between said mass and said inboard cover.

17. The invention in accordance with claim 12, wherein said housing comprises a substantially circular peripheral wall, said at least one fluid storage cavity being arranged between said side walls defining said main cavity and said circular peripheral wall of said housing.

18. The invention in accordance with claim 12, wherein said disengagement prevention means comprise a catch arranged on said mass and cooperating with said first contact to fixedly secure said first contact in connection with said mass.

19. A combination of an integral connector and an electrical device having a housing including an aperture extending between an interior of the electrical device housing and an exterior of the electrical device housing, said integral connector being at least partially situated within said aperture and comprising:

(a) at least two electrical conductors;

(b) a contact holder for holding said at least two electrical connectors in a position within an interior of the electrical device housing, a clearance being defined between said at least two electrical connectors and said contact holder;

(c) a connector housing spaced from said contact holder for retaining said at least two electrical connectors, a clearance being defined between said at least two electrical connectors and said connector housing, said contact holder, said connector housing and the electrical device defining a mold cavity in the aperture of the electrical device housing in which the portion of said at least two electrical connectors between said contact holder and said connector housing is situated, said clearances being of sufficient size permitting gas but not sealant to flow out of said cavity;

(d) a sealant which is flowable prior to injection into said cavity and which solidifies after injection into said cavity;

(e) at least one injection hole in the electrical device housing extending into connection with said cavity for enabling injection of said sealant into said cavity; and

whereby, as said sealant is injected into said cavity through said at least one injection hole, air within said cavity is displaced and forced to flow out of said cavity through said clearances between said at least two electrical conductors and said contact holder and said connector housing permitting said cavity to completely fill with said sealant and thereby seal the electrical device from the ambient atmosphere.

20. The invention in accordance with claim 19 wherein said sealant is polyurethane.