Method and apparatus for testing fluid pressure in a sealed vessel

An air bag diagnostic apparatus for use in an air bag restraint system including a crash sensor connected to a controller for providing a signal upon the occurrence of a vehicle crash condition, a pressurized fluid bottle, a squib connected to the fluid bottle and electrically connected to the controller, and an air bag connected to the fluid bottle, the controller actuating the squib upon the occurrence of a crash condition to pierce a seal on the fluid bottle and let the pressurized fluid in the bottle inflate the air bag, the diagnostic apparatus comprising:

• transducer means operatively coupled to said fluid bottle for, when energized, transferring energy to pressurized fluid in said fluid bottle, said energy establishing oscillations of the pressurized fluid in the fluid bottle;
• receiver means operatively coupled to said fluid bottle for providing a received electrical signal having a frequency value indicative of the oscillation frequency of the pressurized fluid in said fluid bottle;
• receiver circuit means operatively connected to said receiver means for providing a fluid resonating signal having a frequency indicative of the natural frequency of the oscillating pressurized fluid in the fluid bottle, the natural frequency being indicative of the fluid pressure in said fluid bottle;
• drive circuit means operatively connected to said receiver circuit means and to said transducer means for initially driving said transducer means with a square wave energy pulse signal and subsequently driving said transducer means with an oscillating energy wave having a frequency equal to said natural frequency of said pressurized fluid in said fluid bottle;
• monitoring means for monitoring the natural frequency of the fluid in said fluid bottle and determining the fluid pressure of the fluid in the fluid bottle in response to the sensed natural frequency;
• and
• means for providing an indication to the vehicle operator if the determined fluid pressure in the fluid bottle is less than a predetermined value.

An apparatus for sensing pressure in a sealed vessel, said apparatus comprising:

• transducer means operatively coupled to said vessel for, when energized, transferring a square wave energy pulse to pressurized fluid in said vessel, said transferred square wave energy pulse establishing oscillations of the pressurized fluid in the vessel including a frequency value equal to the natural frequency of the pressurized fluid;
• receiver means operatively coupled to said vessel for providing a received electrical signal having a frequency value indicative of the natural frequency of the pressurized fluid in said vessel;
• and
• receiver circuit means operatively connected to said receiver means for providing a fluid resonating signal having a frequency equal to the natural frequency of the oscillating pressurized fluid in the vessel, the natural frequency being indicative of the fluid pressure in said vessel, said receiver circuit means including filtering means connected to said receiver means for removing frequency components from said received electrical signal that result from oscillations of the vessel itself.

A method for sensing pressure in a vessel, said method comprising the steps of:

• transferring energy to pressurized fluid in the vessel, said transferred energy establishing oscillations of the pressurized fluid in the vessel;
• receiving a signal from the vessel having a frequency value indicative of the oscillation frequency of the pressurized fluid in said vessel including the natural frequency of the pressurized fluid in said vessel;
• providing a fluid resonating signal having a frequency equal to the natural frequency of the oscillating pressurized fluid in the vessel, the natural frequency being indicative of the fluid pressure in said vessel;
• initially providing a square wave energy pulse signal to said vessel;
• and
• subsequently providing an oscillating energy wave having a frequency equal to said natural frequency of said pressurized fluid in the vessel.

A method for determining the functionality of an air bag restraint system including a crash sensor connected to a controller for providing a signal upon the occurrence of a vehicle crash condition, a pressurized fluid bottle, a squib connected to the fluid bottle and electrically connected to the controller, and an air bag connected to the fluid bottle, the controller actuating the squib upon the occurrence of a crash condition to pierce a seal on the fluid bottle and let the pressurized fluid in the bottle inflate the air bag, the method comprising the steps of:

• transferring energy to pressurized fluid in said vessel from a transducer means, said transferred energy establishing oscillations of the pressurized fluid in the fluid bottle;
• providing a received electrical signal having a frequency value indicative of the oscillation frequency of the pressurized fluid in said fluid bottle including the natural frequency of the pressurized fluid in the vessel;
• providing a fluid resonating signal having a frequency equal to of the natural frequency of the oscillating pressurized fluid in the vessel, the natural frequency being indicative of the fluid pressure in said fluid bottle;
• initially providing a square wave energy pulse signal to the fluid bottle;
• subsequently providing an oscillating energy wave to the fluid bottle having a frequency equal to said natural frequency of said pressurized fluid in said fluid bottle;
• monitoring the natural frequency of the fluid in said fluid bottle;
• determining the fluid pressure of the fluid in the fluid bottle in response to the sensed natural frequency;
• and
• providing an indication to the vehicle operator if the determined fluid pressure in the fluid bottle is less than a predetermined value.

A method for sensing pressure in a vessel, said method comprising the steps of:

• transferring a square wave energy pulse to pressurized fluid in the vessel, said transferred energy establishing oscillations of the pressurized fluid in the vessel including a frequency value equal to the natural frequency of the pressurized fluid;
• receiving a signal from the vessel having a frequency value indicative of the oscillation frequency of the pressurized fluid in said vessel including the natural frequency of the pressurized fluid in said vessel;
• filtering the signal received from the vessel to remove frequency components that result from oscillations of the vessel itself;
• and
• providing a fluid resonating signal in response to the filtered received signal having a frequency equal to the natural frequency of the oscillating pressurized fluid in the vessel, the natural frequency being indicative of the fluid pressure in said vessel.