Sliding door structure

1. A sliding door structure of a vehicle in which a front door and a rear door both are sliding doors, the sliding door structure comprising:

a front door and a rear door;

lower arms respectively extending from lower parts of the front door and the rear door toward a vehicle body of the vehicle; and

lower rails, attached on an upper part of a side sill of the vehicle body, for guiding lower rollers attached on ends of the lower arms,

wherein: on the side sill, there is attached a reinforcing bracket having a wall surface facing an outside of the vehicle body;

the reinforcing bracket includes a front support surface and a rear support surface which are inclined with respect to a front-rear direction of the vehicle body, at both ends in the front-rear direction;

the front support surface and the rear support surface are formed so that a direction orthogonal to the front support surface and a direction orthogonal to the rear support surface intersect each other inside the vehicle body:

the front support surface and the rear support surface of the reinforcing bracket are provided with a front engagement hole and a rear engagement hole as engaged portions, respectively; and

the lower arm of the front door and the lower arm of the rear door are each provided with an engaging portion that engages with each of the engaged portions when the front door and the rear door are fully closed.

2. The sliding door structure according to claim 1 , wherein:

there is provided a striker that fits a latch mechanism when the front door fully closes, in a vicinity of a substantially central portion in a front-rear direction of the reinforcing bracket, the latch mechanism being provided on the front door; and

a flange portion of the reinforcing bracket and the striker are jointly fastened and fixed to the side sill via a bolt.

3. The sliding door structure according to claim 1 , wherein:

there is provided a striker that fits a latch mechanism when the front door fully closes, in a vicinity of a substantially central portion in a front-rear direction of the reinforcing bracket, the latch mechanism being provided on the front door; and

a vertical wall portion of the reinforcing bracket is placed on a vehicle inner side of the striker.

4. The sliding door structure according to claim 1 , wherein:

the lower rails each have a lower rail bracket extending toward the reinforcing bracket; and

the lower rail bracket is provided with a cushioning member, and the cushioning member comes into contact with a base portion of each engaging portion when the front door and the rear door fully close.

5. The sliding door structure according to claim 4 , wherein the lower rail bracket is fixed to the reinforcing bracket.

6. The sliding door structure according to claim 1 , wherein:

base end parts of the lower arms of the front door and the rear door are each provided with a sliding door bracket and a female member connecting the sliding door bracket and the lower arm; and

a reinforcing member is attached on an upper surface of the reinforcing bracket, the reinforcing member including a stepped portion into which a support portion of the female member is inserted.

7. A sliding door structure of a vehicle in which a front door and a rear door both are sliding doors, the sliding door structure comprising:

a front door and a rear door;

lower arms respectively extending from lower parts of the front door and the rear door toward a vehicle body of the vehicle; and

lower rails, attached on an upper part of a side sill of the vehicle body, for guiding lower rollers attached on ends of the lower arms,

wherein: on the side sill, there is attached a reinforcing bracket having a wall surface facing an outside of the vehicle body;

the wall surface of the reinforcing bracket is provided with engaged portions on a front side and a rear side, respectively;

the lower arm of the front door and the lower arm of the rear door are each provided with an engaging portion that engages with each of the engaged portions when the front door and the rear door are fully closed;

there is provided a striker that fits a latch mechanism when the front door fully closes, in a vicinity of a substantially central portion in a front-rear direction of the reinforcing bracket, the latch mechanism being provided on the front door; and

a flange portion of the reinforcing bracket and the striker are jointly fastened and fixed to the side sill via bolts.

8. A sliding door structure of a vehicle in which a front door and a rear door both are sliding doors, the sliding door structure comprising:

a front door and a rear door;

lower arms respectively extending from lower parts of the front door and the rear door toward a vehicle body of the vehicle; and

lower rails, attached on an upper part of a side sill of the vehicle body, for guiding lower rollers attached on ends of the lower arms,

wherein: on the side sill, there is attached a reinforcing bracket having a wall surface facing an outside of the vehicle body;

the wall surface of the reinforcing bracket is provided with engaged portions on a front side and a rear side, respectively;

the lower arm of the front door and the lower arm of the rear door are each provided with an engaging portion that engages with each of the engaged portions when the front door and the rear door are fully closed;

there is provided a striker that fits a latch mechanism when the front door fully closes, in a vicinity of a substantially central portion in a front-rear direction of the reinforcing bracket, the latch mechanism being provided on the front door; and

a vertical wall portion of the reinforcing bracket is placed on a vehicle inner side of the striker.