Roof air bag apparatus for vehicle

1. A roof air bag apparatus for a vehicle, the roof air bag apparatus comprising:

a front air bag cushion and a rear air bag cushion respectively mounted on a roof of the vehicle in a folded state, and configured to be unfolded between a front passenger and a rear passenger by receiving pressures of air bag gases;

an upper plate and a lower plate which are coupled to connect an upper end of the front air bag cushion and an upper end of the rear air bag cushion and a lower end of the front air bag cushion and a lower end of the rear air bag cushion to each other, respectively;

an air bag housing in which the front air bag cushion and the rear air bag cushion are accommodated in the folded state; and

an air bag cover configured to simultaneously cover the front air bag cushion and the rear air bag cushion accommodated in the air bag housing, wherein a front tear line and a rear tear line each torn by unfolding pressures of the front air bag cushion and the rear air bag cushion are formed on the air bag cover,

wherein bolts sequentially penetrate through the air bag cover, the lower plate, the upper plate, and the air bag housing, and are then fastened to a roof cross panel coupled to a roof panel, such that the roof air bag apparatus is fixedly installed on the roof of the vehicle, and

wherein when the front passenger and the rear passenger are seated so as to face to each other in the vehicle and an accident occurs, the unfolded front air bag cushion is configured to contact and protect the front passenger, and the unfolded rear air bag cushion is configured to contact and protect the rear passenger.

2. The roof air bag apparatus of claim 1 , wherein the front air bag cushion and the rear air bag cushion are unfolded at a same time.

3. The roof air bag apparatus of claim 1 , further comprising: a front inflator and a rear inflator configured to respectively generate the air bag gases supplied to the front air bag cushion and the rear air bag cushion,

wherein the front inflator and the rear inflator are fixedly mounted on the roof of the vehicle and are configured to be connected to the front air bag cushion and the rear air bag cushion through a front hose and a rear hose, respectively.

4. The roof air bag apparatus of claim 3 , further comprising:

a front tether coupled to the front air bag cushion and configured to maintain a shape of the front air bag cushion when the front air bag cushion is unfolded; and

a rear tether coupled to the rear air bag cushion and configured to maintain a shape of the rear air bag cushion when the rear air bag cushion is unfolded.

5. The roof air bag apparatus of claim 4 , wherein the front tether and the rear tether are tethers formed of a fabric material.

6. The roof air bag apparatus of claim 1 , wherein the upper and lower ends of the front air bag cushion and the rear air bag cushion are configured to be connected to each other.

7. The roof air bag apparatus of claim 1 , wherein bolt holes through which the bolts penetrate are formed in the upper plate and the lower plate, respectively,

a diameter of the bolt holes formed in the upper plate is greater than a diameter of a screw portion of the bolts and is less than a diameter of a head portion of the bolts, and

a diameter of the bolt holes formed in the lower plate is greater than the diameter of the head portion of the bolts.

8. The roof air bag apparatus of claim 1 , further comprising:

a front leg protecting portion configured to be unfolded and extend downwardly from the lower end of the front air bag cushion and a rear leg protecting portion configured to be unfolded and extend downwardly from the lower end of the rear air bag cushion, in a state in which the front air bag cushion and the rear air bag cushion are unfolded,

wherein the front leg protecting portion and the rear leg protecting portion are unfolded into a space between knees of the front passenger and the rear passenger to protect the knees and shins of the front and rear passengers.

9. The roof air bag apparatus of claim 1 , wherein when a front inflator and a rear inflator are exploded or ignited due to an accident in a state in which the front air bag cushion and the rear air bag cushion are folded and accommodated in the air bag housing, and thus the air bag gases are generated, the front air bag cushion and the rear air bag cushion are unfolded by pressures of the air bag gases, the front tear line and the rear tear line of the air bag cover start to be torn by unfolding pressures of the front air bag cushion and the rear air bag cushion, and at a same time, the lower plate is separated while falling from the bolts;

when the lower plate falls from the bolts, the lower end of the front air bag cushion, the lower end of the rear air bag cushion, and the lower plate are unfolded into a space between the front passenger and the rear passenger by self-weights of the front air bag cushion, the rear air bag cushion, and the lower plate; and

the front passenger and the rear passenger are protected by coming into contact with the unfolded front air bag cushion and rear air bag cushion, respectively.

10. The roof air bag apparatus of claim 9 , wherein when the front passenger is in contact with the unfolded front air bag cushion, the front air bag cushion is configured to absorb an impact force while an outer shape of the front air bag cushion is changed, and a phenomenon in which the rear air bag cushion is pushed to a rear at which the rear passenger exists does not occur.

11. The roof air bag apparatus of claim 9 , wherein when the rear passenger is in contact with the unfolded rear air bag cushion, the rear air bag cushion is configured to absorb an impact force while an outer shape of the rear air bag cushion is changed, and a phenomenon in which the front air bag cushion is pushed to a front at which the front passenger exists does not occur.

12. The roof air bag apparatus of claim 1 , wherein the bolts fastened to the roof cross panel become cushion hinge portions of the unfolded front air bag cushion and rear air bag cushion, and

when the front passenger is in contact with the front air bag cushion or the rear passenger is in contact with the rear air bag cushion at a time of collision of the vehicle, the front air bag cushion and the rear air bag cushion are configured to absorb collision energy while rotating around the cushion hinge portions, such that tension of upper end portions is reduced.