Vehicular door device

1. A vehicular door device comprising:

a first link arm and a second link arm that include a first rotary coupling point with respect to a vehicle body and a second rotary coupling point with respect to a door of a vehicle;

a door-side engagement portion provided on a closed-side end portion of the door that opens and closes a door opening of the vehicle, based on an operation of a link mechanism formed of the first link arm and the second link arm;

a vehicle body-side engagement portion provided on a closed-side end portion of the door opening to and from which the closed-side end portion of the door is brought closer and away, based on an opening-closing operation of the door; and

an expansion mechanism provided in at least any of the first link arm and the second link arm, and configured to change a length between the first rotary coupling point and the second rotary coupling point, wherein

one of the door-side engagement portion and the vehicle body-side engagement portion includes a shaft-shaped engagement portion extending in an up-down direction of the vehicle,

another of the door-side engagement portion and the vehicle body-side engagement portion includes a guide groove that includes a pair of side wall portions facing each other in a vehicle width direction and extends in an opening-closing operation direction of the door, and,

in an opening-closing operation position near a full closed position of the door where the door-side engagement portion and the vehicle body-side engagement portion engage with each other, the shaft-shaped engagement portion is disposed in the guide groove, and the shaft-shaped engagement portion is also relatively displaced along an extending direction of the guide groove while a change in length between the first rotary coupling point and the second rotary coupling point, based on an operation of the expansion mechanism, is accompanied, and thus the door is configured to perform an opening-closing operation.

2. The vehicular door device according to claim 1 , wherein

the door-side engagement portion includes the guide groove, and the vehicle body-side engagement portion includes the shaft-shaped engagement portion.

3. The vehicular door device according to claim 1 , wherein

the door-side engagement portion includes the shaft-shaped engagement portion, and the vehicle body-side engagement portion includes the guide groove.

4. The vehicular door device according to claim 1 , wherein

the guide groove is formed between two engagement claws that extend in the opening-closing operation direction of the door and are aligned in the vehicle width direction.

5. The vehicular door device according to claim 1 , wherein

the shaft-shaped engagement portion is rotatably supported.

6. The vehicular door device according to claim 1 , wherein

the first link arm includes the second rotary coupling point coupled to the door in a position closer to a center of gravity of the door than the second link arm, and

the expansion mechanism is provided only in the second link arm.

7. The vehicular door device according to claim 6 , wherein

the second link arm includes the second rotary coupling point coupled to the door in a position closer to the closed-side end portion of the door than the first link arm, and

the expansion mechanism includes a biasing member that provides a tensile force in a direction of reducing a length between the first rotary coupling point and the second rotary coupling point.

8. The vehicular door device according to claim 1 , further comprising:

a driving arm that includes a third rotary coupling point in a position between the first rotary coupling point and the second rotary coupling point, and is coupled to at least any of the first link arm and the second link arm; and

an actuator that drives the link mechanism by providing a driving force to the driving arm and rotating the driving arm.