Gas damped crash sensor

• US 4,900,880 A
• Filed: 02/21/1989
• Issued: 02/13/1990
• Est. Priority Date: 08/15/1988
• Status: Expired due to Term

• Current Assignee: Key Safety Systems, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Original Assignee: Automotive Technologies International Incorporated
• Inventors: Breed, David S.
• Primary Examiner(s): Scott, J. R.
• Application Number:
  US07/313,630
• Time in Patent Office: 357 Days
• Field of Search: 73/492, 102/262, 280/731, 280/734, 280/735, 335/205, 200/61.45 R, 200/61.45 M, 200/61.53, 200/82 E
• US Class Current: 200/61.45M
• CPC Class Codes: H01H 35/142 Damping means to avoid unwanted response

Abstract

Conventional ball-in-tube, gas-damped, crash sensors utilize a gold plated ball to bridge two contacts. When the ball senses acceleration (deceleration) in the longitudinal direction of a cylinder of sufficient magnitude and duration, it moves to where it bridges the contacts, completing the electrical circuit and initiating deployment of a safety restraint system. The contact duration of this type of sensor is significantly affected by bouncing of the contacts after being hit by the sensing mass and by the accelerations in directions perpendicular to the axis of the tube. This sometimes results in no triggering, or late triggering, of the sensor. A switch activated by magnetic flux is combined with this type of gas-damped sensor to provide a solid and reliable contact duration and ensure the correct functioning of the sensor. The level of biasing force for crash zone crash sensors of this type has been increased to avoid late firing problems on marginal crashes.

Claims

1. A crash sensor comprising:

(a) a tubular passage;

(b) a magnetically permeable sensing mass, arranged to move in said passage between a first location and a second location;

(c) a magnet for biasing said sensing mass toward said first location in said passage;

(d) first and second electrical contacts arranged to come in contact with each other when said sensing mass is moved to said second location, both said first and said second contacts being constructed of magnetically permeable material;

(e) means for concentrating magnetic flux from said magnet through said first and second contacts in response to the presence of said sensing mass at said second lcoation, such that said contacts are mutually attracted to each other and tend to remain in contact once closed as long as said flux is present.

2. The crash sensor in accordance with claim 1, wherein a tight clearance is provided between said sensing mass and said tubular passage, and wherein said passage is substantially closed at least at one end to the flow of fluid, thereby requiring fluid in said passage to pass through said tight clearance when said mass moves from said first location to said second location.

3. The crash sensor in accordance with claim 1, wherein said first and second contacts are enclosed in glass.

4. The crash sensor in accordance with claim 1, wherein said flux concentration means includes a magnetically permeable member to channel magnetic flux from said sensing mass at said second location in said passage to said first and second contacts.

5. The crash sensor in accordance with claim 1, wherein said sensing mass is a ball.

6. The crash sensor in accordance with claim 1, wherein said first and second contacts are normally open and in close proximity to each other, and wherein said flux concentrating means operates to close said first and second contacts when said sensing mass is moved to said second location.

7. A crash sensor adapted for locations in the crush zone of a motor vehicle for detecting motor vehicle crashes comprising:

(a) a tubular passage;

(b) a sensing mass arranged to move in said passage between a first location and a second location;

(c) means to dampen the motion of said sensing mass in said passage;

(d) means for biasing said sensing mass toward said first location in said passage with an average force of more than 5 G'"'"'s; and

(e) means for closing an electrical circuit when said sensing mass moves to said second location in said passage.

8. The crash sensor in accordance with claim 7, wherein said biasing means provides an average biasing force magnitude in the range of within 5 to 10 G'"'"'s within the moving range of said sensing mass in said passage.

9. A sensor for detecting a motor vehicle crash comprising:

(a) a tubular passage;

(b) a sensing mass arranged to move in said passage in response to a vehicle crash, there being a tight clearance between said sensing mass and said passage such that the movement of said sensing mass with respect to said passage is damped by gas flow;

(c) a flexible first electrical contact;

(d) a second more rigid electrical contact in proximity to said first contact;

(e) means responsive to the movement of said sensing mass with respect to said passage for displacing said first contact toward said second contact causing said first and second contact to close an electrical circuit during a crash;

(f) means for biasing said sensing mass so as to maintain said first and second contacts in open relationship in the absence of a vehicle crash.

10. The crash sensor in accordance with claim 9, wherein said first contact is normally in contact with said sensing mass and said biasing means includes said first contact.

11. The crash sensor in accordance with claim 9, wherein said sensing mass is a ball.

12. The crash sensor in accordance with claim 9, wherein the movement of said sensing mass with respect to said passage is damped by the gas flow through said tight clearance between said sensing mass and said passage.

13. The crash sensor in accordance with claim 9, wherein said means for biasing said sensing mass applies an average force in the range of within 5 to 10 G'"'"'s when said sensing mass is in any position within said passage.