Patent ID: 8714584

Claim:
A side airbag apparatus comprising an airbag, wherein the airbag has a lumbar-region-protecting inflatable portion, an upstream inflatable portion, and a downstream inflatable portion, which are inflated by inflation gas, the lumbar-region-protecting inflatable portion is deployed and inflated at a side of the lumbar region of an occupant seated on a vehicle seat, the upstream inflatable portion is adjacent to an upper side of the lumbar-region-protecting inflatable portion via a communication passage and is deployed and inflated at an internal pressure lower than that of the lumbar-region-protecting inflatable portion, the downstream inflatable portion is adjacent to a front side of the upstream inflatable portion via a planar partitioning member and is deployed and inflated by inflation gas that has passed through the upstream inflatable portion, at least one of the upstream inflatable portion and the downstream inflatable portion is a thorax-protecting inflatable portion, which is deployed and inflated at a side of the thorax of the occupant, a check valve that restricts outflow of inflation gas from the lumbar-region-protecting inflatable portion to the upstream inflatable portion is provided in the communication passage, a pressure regulation valve that has an opening and a pair of valve body elements is provided in the partitioning member, the valve body elements are arranged to be brought into contact with each other by being pushed by inflation gas in the upstream inflatable portion which is not receiving external force from the occupant, thereby restricting flow of inflation gas at the opening, and the valve body elements are arranged to be flexed and separated from each other by the external force received by the upstream inflatable portion which restrains the occupant, thereby permitting flow of inflation gas at the opening.