Airbag unit

A method of inflating an airbag by use of an airbag unit for protecting people in a vehicle from a lateral collision exerted to the vehicle, said method comprising the steps of:

• inputting an acceleration signal from an acceleration sensor for detecting an acceleration applied to a vehicle as a result of said collision, and converting the acceleration signal fed from said acceleration sensor to a speed signal by an acceleration-to-speed converter;
• determining the type of collision based on the value of the converted speed signal by a crash state judging circuit;
• outputting said determined collision type to respective first to fourth threshold generating means for generating respective first to fourth thresholds based on said determined collision type;
• wherein when said speed signal has one of a positive or negative value,
• comparing the threshold from said first threshold generating means and said acceleration signal fed from said acceleration sensor by use of a first comparing means, and outputting a first crash signal when said acceleration signal exceeds said threshold;
• comparing the threshold from said second threshold generating means and said speed signal fed from said acceleration-to-speed converting means by use of a second comparing means, and outputting a second crash signal when said speed signal exceeds said threshold;
• and
• outputting an inflation signal for inflating an airbag when said first crash signal from said first comparing means and said second crash signal from said second comparing means are both output,
• and wherein when said speed signal has the other one of a positive or negative value,
• comparing the threshold from said third threshold generating means and said acceleration signal fed from said acceleration sensor by use of a third comparing means, and outputting a third crash signal when said acceleration signal exceeds said threshold;
• comparing the threshold from said fourth threshold generating means and said speed signal fed from said acceleration-to-speed converting means by use of a fourth comparing means,
• and outputting a fourth crash signal when said speed signal exceeds said threshold;
• and
• outputting an inflation signal for inflating an airbag when said third crash signal from said third comparing means and a said fourth crash signal from said fourth comparing means are both output.

An airbag actuation circuit for actuating a particular airbag in a vehicle in accordance with a direction of collision of said vehicle, comprising:

• first and second airbags, respectively mounted at left and right sides of said vehicle;
• a lateral acceleration sensor for detecting an acceleration and a direction of said acceleration applied to said vehicle as a result of a collision, and producing an acceleration signal having a magnitude corresponding to the magnitude of said acceleration, and a positive or negative value corresponding to the direction of the acceleration;
• and
• means responsive to said acceleration signal for actuating either said first airbag or said second airbag as a function of the positive or negative value of said acceleration signal.