Patent ID: 7547043

Claim:
A passenger protection device for a vehicle, comprising: an airbag configured to expand and inflate in a passenger protection region, wherein said airbag includes a recessed region that alleviates restraint pressure at a time of restraining a passenger at a middle region of the airbag when the airbag is expanding and inflating, so as to restrain said passenger regardless of a difference in physical build of the passenger on a vehicle seat; an inflator for supplying gas for expansion and inflation of said airbag; a seatbelt mounted to the vehicle seat; a seatbelt sensor configured to detect tension information relating to a tension acting on said seatbelt without using a seat weight sensor; and a control device configured to determine whether or not a directly seated object on the vehicle seat is a passenger or a child seat based on said tension information from said seatbelt sensor, wherein in the event that a determination is made that said directly seated object is a passenger the control device is configured to control said inflator in a first gas supplying mode such that the recessed region of said airbag expands and inflates with a restraining pressure that is alleviated in relation to said passenger, while in the event that a determination is made that said directly seated object is a child seat, the control device is configured to control said inflator in a second gas supplying mode so as to suppress effects of the restraining pressure of said airbag in relation to the passenger in the child seat; wherein based on a transition over time of said tension information detected by said seatbelt sensor, said control device is configured to determine that said directly seated object is a passenger when the tension fluctuates over time, and on the other hand the control device is configured to determine that said directly seated object is a child seat when the tension stays generally constant over time.