Patent ID: 7438310

Claim:
A knee protecting airbag device adapted to be mounted below a steering column in front of a driver seat, the device comprising: an airbag folded and housed in a case in front of knees of a driver; and an inflator for supplying inflation gas to the airbag, wherein the airbag protrudes from the case when fed with the inflation gas supplied from the inflator, and expands and inflates upwardly along a lower face of a column cover of the steering column protecting obliquely rearward and upwardly from an instrument panel and covers the lower face of the column cover from a lower end area of the lower face projecting from the instrument panel to an upper end of the column cover for protecting the knees of the driver, the airbag includes a vehicle body side deployed toward the column cover and a passenger side wall deployed toward the driver seat, respectively, at complete inflation of the airbag, the airbag further includes a plurality of tethers internal to the airbag for connecting the vehicle body side wall and the passenger side wall, the airbag is inflated into such a plate shape as to cover the lower face of the column cover and the instrument panel positioned at left and right sides of the column cover, the tethers are disposed at a central area of the airbag in the lateral direction of the airbag, the tethers reducing a thickness of the central area positioned at the lower face of the column cover whereas thickness of areas of the airbag at left and right sides of the central area positioned out of the column cover toward the leftward and rightward directions increases such that the passenger side wall becomes generally flat when the airbag is completely inflated along the lower face of the column cover, and the airbag is constructed to complete inflation at 15 to 20 milliseconds after the inflator is activated and to have an internal pressure of 50 KPa or more at 70 milliseconds after the start of inflow of the inflating gas while retaining the thickness at complete inflation.