Airbag deployment rate sensor with spool brake

• US 20040155445A1
• Filed: 02/06/2003
• Published: 08/12/2004
• Est. Priority Date: 02/06/2003
• Status: Active Grant

• Current Assignee: Key Safety Systems, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Original Assignee: Key Safety Systems, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Inventors: Husby, Harald Snorre
• Granted Patent: US 6,793,243 B2
• Time in Patent Office: Days
• US Class Current: 280/743.2
• CPC Class Codes: B60R 2021/01218 control of expansion speed
• CPC Class Codes: B60R 21/01504 detecting bag displacement

Abstract

An airbag deployment rate sensor employs a tape or string that is wound on a spool and connected to the fabric of an airbag cushion so that as the airbag deploys, tape or string is pulled from the spool causing it to rotate. A brake is applied to the spool to prevent the buildup of momentum and so the tape and the spool will come to a rapid stop when the tape is no longer being withdrawn from the spool because the portion of the airbag to which the tape is connected has collided with an object. A sensor is positioned to detect rotation of the spool and so to monitor the rate at which tape or string is being withdrawn.

Claims

1. An airbag device a motor vehicle comprising:

an airbag housing;

an airbag cushion mounted to the airbag housing, and defining a bag interior surface;

a cartridge mounted fixed with respect to the airbag housing and containing a quantity of line stored within the cartridge and wound about a spool, the spool being mounted for rotation about an axis within the cartridge, the line passing through the cartridge and extending through an outlet and being attached to the interior surface of the airbag cushion; and

a sensor positioned within the cartridge for detecting the string or tape being withdrawn from the cartridge, by detecting rotation of the spool.

2. The airbag device of claim 1 further comprising:

a brake shoe mounted within the cartridge; and

a spring positioned between a portion of the cartridge and a portion of the brake shoe, to bias the brake shoe to frictionally engage the spool.

3. The airbag device of claim 2 wherein the the spool has an upper flange joined by a cylindrical surface to a lower flange, and wherein the quantity of line is wound about the cylindrical surface, and wherein the brake shoe is biased axially downwardly against the upper flange.

4. The airbag device of claim 2 wherein the the spool has an upper flange joined by a cylindrical surface to a lower flange, and wherein the quantity of line is wound about the cylindrical surface, and wherein the brake shoe is biased axially upwardly against the lower flange.

5. The airbag device of claim 2 wherein the the spool has an upper flange joined by a cylindrical surface to a lower flange, and wherein the quantity of line is wound about the cylindrical surface, and wherein the brake shoe is biased radially inwardly against at least one of the upper flange and lower flange.

6. The airbag device of claim 1 wherein the spool has an innermost cylindrical surface, and rotates about a shaft which is formed in at least two parts which are biased radially outwardly to frictionally engage the innermost cylindrical surface.

7. The airbag device of claim 1 wherein the spool is mounted for rotation about a stub shaft, and further comprising a coil spring mounted between the stub shaft and the spool to resist rotation of the spool.

8. The airbag device of claim 7 wherein the cartridge is comprised of a housing further comprising a ratchet and pawl mechanism positioned between the spool and a portion of the housing so that the coil spring is prevented from rewinding the quantity of line about the spool.

9. The airbag device of claim 1 wherein the spool has an upper side and a lower side, and the sensor is a light source mounted in the cartridge above said upper side and a light sensitive detector in the cartridge below the lower side, so that rotation of the spool causes a variation in the amount of light transmitted from the light source to the light sensor.

10. The airbag device of claim 1 further comprising a magnet mounted to the spool, and wherein the sensor is a magnetic flux sensor that detects the motion of the magnet when the spool rotates.

11. The airbag device of claim 1 further comprising a light source positioned in the cartridge to shine light on the spool, and a light sensor positioned to receive light reflected from the spool, wherein the spool does not reflect light uniformly, so that rotation of the spool can be detected by the variation in reflected light detected by the light sensor.

12. The airbag device of claim 1 further comprising a magnet mounted in the cartridge and a magnetic flux sensor mounted opposite the magnet with the spool positioned therebetween, and mounted to the spool there is at least one magnetic shunt, so that rotation of the spool causes the magnetic shunt to pass between the magnet and the magnetic flux sensor.

13. An airbag device for a motor vehicle comprising:

an airbag housing;

an airbag cushion mounted to the airbag housing, and having portions defining a bag interior surface;

a spool mounted for rotation on the airbag housing;

a string or tape wound about the spool and having a first end attached to the bag interior surface, so that as the airbag cushion is inflated, a portion of the string or tape is withdrawn from the spool, thereby causing the spool to rotate and so unwind the string or tape from the spool;

a brake, and a biasing member mounted with respect to the brake to bias the brake into frictional engagement with the spool, so that when the string or tape is no longer being withdrawn from the spool, the spool will stop rotating; and

a sensor fixedly mounted with respect to the airbag housing to detect rotation of the spool.

14. The airbag device of claim 13 further comprising a means for applying a braking force to the spool to overcome the momentum of the spool.

15. The airbag device of claim 13 wherein the means for applying a braking force to the spool comprises:

a braking shoe; and

a biasing member which biases the braking shoe into frictional engagement with a portion of the spool.

16. The airbag device of claim 13 wherein the spool has an innermost cylindrical surface, and rotates about a shaft which is formed in at least two parts that are biased radially outwardly to engage the innermost cylindrical surface frictionally.

17. The airbag device of claim 13 wherein the spool is mounted for rotation about a shaft, and further comprising a coil spring mounted between the shaft and the spool to resist rotation of the spool.

18. The airbag device of claim 13 wherein the spool has an upper side and a lower side, and the sensor is a light source mounted above said upper side and a light sensitive detector mounted below the lower side, so that rotation of the spool causes a variation in the amount of light transmitted from the light source to the light sensor.

19. The airbag device of claim 13 further comprising a magnet mounted to the spool, and wherein the sensor is a magnetic flux sensor that detects the motion of the magnet when the spool rotates.

20. The airbag device of claim 13 further comprising a light source positioned to shine light on the spool, and a light sensor positioned to receive light reflected from the spool, wherein the spool does not reflect light uniformly so that rotation of the spool can be detected by variation in reflected light detected by the light sensor.

21. The airbag device of claim 13 wherein the spool has an upper side and a lower side, and a magnet is mounted above said upper side and the sensor is a magnetic flux sensor mounted below the lower side, and the spool has at least one magnetic shunt mounted thereto so that rotation of the spool causes a variation in the amount of magnetic flux transmitted to the magnetic flux sensor.

22. An airbag device for a motor vehicle comprising:

an airbag housing;

an airbag cushion mounted to the airbag housing, and defining a bag interior surface;

a spool mounted for rotation on the airbag housing;

a string wound about the spool having a first end attached to the bag interior surface, so that as the airbag cushion is inflated, a portion of the string is withdrawn from the spool, thereby causing the spool to rotate and so unwind the string from the spool;

a coil spring having a first end fixedly mounted with respect to the airbag housing and a second end mounted to the spool to rotate with the spool, the coil spring opposing the rotation of the spool, and so opposing the portion of the string being withdrawn from the spool; and

a sensor fixedly mounted with respect to the airbag housing to detect rotation of the spool.

23. The airbag device of claim 22 further comprising a pawl and ratchet mechanism positioned between the spool and a structure fixed with respect to the airbag housing so as to prevent the spring from causing the spool to rotate to wind string on to the spool.

24. The airbag device of claim 23 wherein the spool has a first flange, and a second flange and a cylindrical surface extending between the first flange and the second flange on which the string is wound, and wherein the first flange has portions forming the ratchet, and a biasing member mounted to the structure fixed with respect to the airbag housing, forming the pawl which engages the portions forming the ratchet.

25. The airbag device of claim 22 further comprising a magnet mounted to the spool, and wherein the sensor is a magnetic flux sensor that detects motion of the magnet when the spool rotates.