In-seat airbag device

1. An in-seat airbag device comprising an airbag main body having a front-rear chamber that, due to gas jetted from an inflator that operates due to a collision of a vehicle being detected or predicted, expands past a side of a head of a passenger toward a seat front side and is disposed at the side of the head of the passenger, and a distal end chamber that expands from a seat front side end portion of the front-rear chamber toward a seat width direction inner side and is disposed at a seat front side of a face of the passenger,

wherein the airbag main body and a seatback frame are connected by a force limiter mechanism that moves the airbag main body toward a seat front side when a load, which is toward a seat front side and is applied to the airbag main body, exceeds a predetermined threshold value at a time of head restraining when the head of the passenger is restrained.

2. The in-seat airbag device of claim 1 , wherein the force limiter mechanism has:

a movable member including a supply pipe supplying gas jetted-out from the inflator to the airbag main body that is attached to an upper end portion of the movable member, the movable member being supported at the seatback frame such that a lower end portion thereof can rotate with a seat width direction being an axial direction; and

an energy absorbing portion that is provided between the seatback frame and the supply pipe or the movable member, and that, when the load exceeds the predetermined threshold value, permits rotation of the movable member toward a seat front side while absorbing energy.

3. The in-seat airbag device of claim 1 , wherein the force limiter mechanism has:

a supply pipe connected to an inflator that is fixed to the seatback frame, and supplying the gas, which is jetted-out from the inflator, to the airbag main body;

a tube that has excess length, accommodates the supply pipe at an interior thereof, and connects the inflator and the airbag main body;

a reaction force plate provided at a seat rear side end portion of the airbag main body; and

an energy absorbing portion that is provided between the reaction force plate and the seatback frame, and that, when the load exceeds the predetermined threshold value, permits movement of the reaction force plate toward a seat front side while absorbing energy.

4. The in-seat airbag device of claim 2 , wherein the force limiter mechanism is structured so as to not operate at a load toward a seat front side at a time of inflation/expansion of the airbag main body.

5. The in-seat airbag device of claim 4 , wherein:

the energy absorbing portion includes a plate that absorbs energy by plastically deforming, and

a thickness of one deformation region of the plate is set to be thicker than a thickness of other deformation regions of the plate, such that the plate can withstand the load toward the seat front side at the time of inflation/expansion of the airbag main body.

6. The in-seat airbag device of claim 4 , wherein the force limiter mechanism is structured to include an actuator that operates the force limiter mechanism at a time when the load exceeds the predetermined threshold value.

7. The in-seat airbag device of claim 3 , wherein the force limiter mechanism is structured so as to not operate at a load toward a seat front side at a time of inflation/expansion of the airbag main body.

8. The in-seat airbag device of claim 7 , wherein:

the energy absorbing portion includes a plate that absorbs energy by plastically deforming, and

a thickness of one deformation region of the plate is set to be thicker than a thickness of other deformation regions of the plate, such that the plate can withstand the load toward the seat front side at the time of inflation/expansion of the airbag main body.

9. The in-seat airbag device of claim 7 , wherein the force limiter mechanism is structured to include an actuator that operates the force limiter mechanism at a time when the load exceeds the predetermined threshold value.