Land vehicles – Wheeled – Attachment
Reexamination Certificate
2003-02-06
2004-09-21
Dickson, Paul N. (Department: 3616)
Land vehicles
Wheeled
Attachment
C280S743200
Reexamination Certificate
active
06793243
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to airbags and sensors used to control airbag deployment in general and to sensors which monitor the actual deployment sequence in particular.
BACKGROUND OF THE INVENTION
Airbags were originally developed as a passive restraint system, but are known to work best in combination with seatbelts and other safety systems. Although airbags contribute to the overall safety of occupants of an automobile, they can present a danger to an occupant who is positioned too close to an airbag when it deploys. This condition, where the occupant is positioned so that airbag deployment might be dangerous, is referred to as the occupant being “out of position.” Various systems have been developed to detect an “out of position” occupant. Sensor systems designed to detect the occupant's position often require constant monitoring so that in the event of a crash the occupant's position is known. Sensor systems designed to detect the position of the occupant have been proposed based on ultrasound, optical, or capacitance sensors. Constant monitoring of sensors, which may have high data rates, requires the design of algorithms which can reduce sensor data to a single condition or a limited number of data conditions which can be used in an airbag deployment decision logic to prevent airbag deployment or for a duel stage airbag to select the level of deployment. Maintaining data integrity between the non-crash positional data, and positional data needed during airbag deployment is complicated by the noisy environment produced by a crash. Dealing with data integrity issues requires increased processor capabilities and algorithm development, which also requires additional testing.
Prior art approaches attempt to determine, based on various sensors, the distance between the airbag and a vehicle occupant before the airbag is deployed. In many instances, the vehicle occupant will not be too close to the airbag at the time the decision to deploy the airbag is made, but, because of the rate at which the occupant is approaching the airbag, the occupant will be too close when the airbag is actually deploying. To handle these situations, more sophisticated sensors and algorithms are needed to attempt to predict the occupant's position when the airbag is actually deployed or nearly completely deployed. The ideal airbag deployment system functions so that the airbag deploys fully or nearly fully before the occupant engages the airbag. Existing systems inhibit airbag deployment when, based on various sensors and algorithms, it is determined that, because of the position of the vehicle occupant, the bag is more likely to harm than to benefit the occupant. Successfully creating a sensor and algorithm system is complicated because there is usually very little delay between the decision to deploy and the actual deployment. Rapid airbag deployment is desirable because the maximum benefit from an airbag is achieved by early deployment. However, more time before deployment maximizes the information available for determining whether deployment is necessary. The desire to maximize effective deployment of the airbag while minimizing unnecessary deployment creates a tension between waiting for more information and deploying immediately. Therefore, once sufficient information is available, deployment typically follows nearly immediately.
Therefore, a system which employs occupant position sensors and algorithms must be able to supply at all times an indication of whether airbag deployment should be inhibited so that the inhibit decision can be applied whenever the airbag deployment decision occurs. This means the sensors and algorithms used to develop the occupant position inhibit signal cannot be optimized to deal with a specific time frame in which the actual deployment decision is made. The end result is that such algorithms may be less accurate than desired because they must predict events relatively far in the future—perhaps tens of milliseconds. One known type of sensor shown in European Patent application EP 0990567A1 employs a plurality of tapes which extend between the front of the airbag cushion and a dispensing cartridge mounted on the airbag housing. Tape extraction sensors within the cartridge monitor markings on the tape to determine the rate at which tape is being withdrawn from the cartridge. The tape extraction sensors detect airbag impact with an occupant by a decrease in airbag velocity as measured by the rate of tape withdrawal from the cartridge. Improvements are needed to the known tape cartridges to improve the functionality and reliability of the tape type bag deployment monitoring sensors.
SUMMARY OF THE INVENTION
The airbag deployment rate sensor of this invention employs a tape or string which 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 that 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. This provides a measure of the movement of the portion of the airbag to which the tape or string is attached. A braking force is applied to the spool by biasing a shoe against a peripheral rim of the spool, or by biasing a shoe against an upper or lower surface of the spool. In yet another embodiment, the stub shaft about which the spool is mounted is split and biased to supply a braking force against the innermost bearing surface that is engaged with the stub shaft. Rotation rates may be monitored by passing a beam of light through one or more axial openings in the disk of the spool. Alternatively, one or more small magnets may be mounted to rotate with the spool, the magnets being detected by a magnetic flux sensor such as a Hall effect sensor, a GMR sensor, or a reed switch. In another alternative embodiment, a magnet may be positioned above the rotating spool, and the spool may contain magnetic shield elements that pass over a magnetic flux sensor positioned beneath the magnet. If a magnet is mounted on the spool, a simple wire positioned near the spool will experience an induced current. Finally, a spring motor type spring may be positioned between a central stub shaft and the tape or string containing spool to act as a brake.
It is a feature of the present invention to provide a means for detecting when a portion of an airbag cushion impacts an object.
It is another feature of the present invention to detect the rate at which a portion of an airbag cushion is deploying by monitoring the speed of rotation of a spool from which a tape or string which is attached to the portion of the airbag is withdrawn.
It is a further feature of the present invention to provide a sensor for determining the deployment rate of a portion of an airbag cushion that does not require an encoded tape or string.
It is a yet further feature of the present invention to provide a tape or string dispenser which can be used with a wide variety of sensors to detect the rate at which tape or string is drawn from the dispenser.
Further features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5762367 (1998-06-01), Wolanin
patent: 6129379 (2000-10-01), Specht
patent: 6250677 (2001-06-01), Fujimura
patent: 6315323 (2001-11-01), Pack, Jr.
patent: 6328335 (2001-12-01), Mueller
patent: 6371517 (2002-04-01), Webber et al.
patent: 6425603 (2002-07-01), Eschbach
patent: 6511094 (2003-01-01), Thomas et al.
patent: 6709010 (2004-03-01), Dominissini et al.
patent: 6746045 (2004-06-01), Short et al.
patent: 2004/0090053 (2004-05-01), White et al.
patent: 2004/0094941 (2004-05-01), Waid et al.
patent: 0812741
Dickson Paul N.
Drayer Lonnie
Key Safety Systems, Inc.
Rosenberg Laura B
Steinnon Patrick
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