Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2000-04-14
2001-05-08
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C280S801100, C024S303000
Reexamination Certificate
active
06230088
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to assemblies in which seat belt buckles cooperate with sensors used to determine when and how vehicle occupant protection devices should be deployed.
BACKGROUND OF THE INVENTION
Airbags were developed to protect occupants of cars during vehicle crashes. Originally airbags were viewed as an alternative to seat belts, because they are passive devices which do not require the cooperation of the vehicle's occupants to be effective. However, experience has shown that airbags should be considered an adjunct to seat belts. When used properly, airbags can in certain crash situations reduce injuries to occupants. An airbag is a gas-filled bag that is rapidly deployed in the event of a vehicle crash. When appropriate sensors determine that a crash situation has occurred, the airbag is rapidly inflated to create an impact cushion between an occupant of a vehicle and the structure of the vehicle. Consideration is also being given to the design of airbags that better position the vehicle occupant to withstand crash-induced accelerations.
An airbag system is made up of two basic functional components: an airbag module, including the means for deploying the airbag; and the sensors and circuitry which determine whether the airbag should be deployed.
Recently sensors have been developed to determine the weight imposed on the front seat. The value of the determined weight may then be used as input into the system logic that determines whether or not an airbag should be deployed. Furthermore, the value of the determined weight may be used as input into system logic which determines or whether the mode of deployment should be modified in airbag systems which are capable of varying the deployment sequence to accommodate varying circumstances. In some cases, however, these weight sensors can be confused by loads imposed by the compression of the seat resulting from installing a child's car seat and tensioning the seat belt to hold the child seat into place.
One proposed solution is to place a device on each child seat that can be detected by a sensor and thus used to determine the presence of a child seat. However, this approach relies on gaining cooperation of all manufacturers of child car seats and would take many years before all old child car seats have been replaced with child car seats containing the needed sensor.
What is needed is a device comprising a seat belt buckle and a sensor that can provide data for determining whether a child's seat is positioned in the front passenger seat of an automobile.
Pretensioners are used to take up the slack in a seat belt in the event of a crash. However, if there is no significant slack in a seat belt because the user has drawn the seat belt exceptionally tightly around him or has already taken up the slack by his forward movement as a result of a crash it may not be desirable to activate the pretensioner. What is needed is a device comprising a seat belt buckle and a sensor that can provide data for determining whether it is necessary to activate a pretensioner associated with the seat belt system.
SUMMARY OF THE INVENTION
The devices according to the present invention include a sensor that measures seat belt tension. Seat belt tension is by itself indicative of the presence of a child car seat because proper installation of a car seat involves tightening the car seat belt as tight as possible to snugly hold the car seat in place. Thus a passenger will be uncomfortable with much less seat belt tension than a child seat will normally be installed with. When used in combination with a seat occupant weight sensor the assembly of a seat belt buckle and seat belt tension sensor allows direct determination of the actual weight of the seat occupant corrected for any loads imposed by a tensioned seat belt. In this way the weight of the seat occupant can be used with greater confidence to decide when and how an airbag should be deployed.
The seat belt tension sensor used in the assembly of this invention preferably employs a magnetic field sensor, preferably a magneto-resistive sensor of the Giant Magneto-Resistive (GMR) type. The sensor is attached to an anchor bracket or to a cable that is a part of a seat belt pretensioner. In one embodiment a loop portion of a base plate of a seat belt buckle passes through an opening in the sensor while the sensor is secured to a cable that is part of the pretensioner. A magnet positioned on a sliding carriage is biased away from a sensing element by springs. The loop extends around the carriage, and tension from the seat belt causes the carriage with the magnet to be drawn against the springs toward the magnetic field sensor.
The magnetic field sensor measures the magnetic field present at the sensor and a microprocessor determines belt tension based on the known spring constants and the strength of the measured magnetic field that is a function of displacement of the magnet. Thus the sensed magnetic field is directly proportional to carriage displacement, carriage displacement is proportional to spring compression force based on a spring constant, and belt tension is equal to the determined compression force of the springs.
There is provided in accordance with the present invention to provide a vehicle occupant protection device deployment system that incorporates seat belt tension as one factor used by the system deployment logic.
Further features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.
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Breed Automotive Technology Inc.
Drayer Lonnie
Nguyen Tan
LandOfFree
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