US 5,861,681 AGranted

Occupant crash protection device for a vehicle

AssigneeKansei Corporation

InventorsTakashi Nakano, Tamotsu Tominaga

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Abstract

An occupant crash protection device for a vehicle has: a current limiting circuit which receives a supply of a trigger signal generated when it is judged that a significant accident happens, and which controls a squib firing current to have a constant amount; a squib; and a mechanical acceleration switch, the current limiting circuit, the squib, and the acceleration switch being connected in series between terminals of a direct current power source. In the device, the current limiting circuit has: a first n-channel field effect transistor which is connected in series to the squib; a second n-channel field effect transistor which is connected in parallel to the first n-channel field effect transistor and which receives a minute amount of a current obtained by shunting the squib firing current which is to flow through the first n-channel field effect transistor; and bias control means for, in synchronization with the squib firing current, comparing the amount of the current flowing through the second n-channel field effect transistor with a reference amount, and controlling a gate voltage so that the amount of the current flowing through the first n-channel field effect transistor has an amount proportional to the reference amount.

Claims4

Dependent claims

An occupant crash protection device for a vehicle, comprising:

an acceleration sensor for detecting a crash of the vehicle to output a deceleration signal
a microcomputer for judging that an accident happens according to the deceleration signal outputted from said acceleration sensor and for outputting a trigger signal when judging that the accident happens;
a current limiting circuit which receives a trigger signal generated from said microcomputer when said microcomputer judges that the accident happens, for controlling a squib firing current to be a constant value;
a squib;
an acceleration switch;
and
a direct current power source having two terminals between which said current limiting circuit, said squib and said acceleration switch are connected in series;
wherein said current limiting circuit comprises:
a first n-channel field effect transistor which is connected in series to said squib;
a second n-channel field effect transistor which is connected in parallel to said first n-channel field effect transistor and which receives a minute amount of a current obtained by shunting the squib firing current that flows through said first n-channel field effect transistor;
and
bias control means for, in synchronization with the squib firing current, comparing the amount of the current flowing through said second n-channel field effect transistor with a reference value to control a gate voltage so that the amount of the current flowing through said first n-channel field effect transistor has an amount proportional to the reference value.

9 more elements

Dependencies are inferred from the claim text.