Folding seat

1. A vehicle seat comprising:

a backrest;

a seat part; and

a seat part substructure, the seat part substructure being mounted such that it can swivel about a first swivel axis arranged in a width direction of the seat in order to move the seat part substructure together with the seat part from a sitting position into an upright position, wherein a lower region of the backrest with respect to a height direction of the seat and at least one of a rear region of the seat part and of the seat part substructure with respect to a longitudinal direction of the seat are interconnected in the sitting position by at least one releasable connection means and are not interconnected in the upright position, wherein the first swivel axis is fixed in a rotational manner to the seat part substructure, wherein the at least one releasable connection means is connected to the seat part, and wherein the seat part with the at least one releasable connection means is moveable with respect to the seat part substructure at least in the longitudinal direction of the seat.

2. The vehicle seat according to claim 1 , wherein during a movement of the seat part with respect to the seat part substructure, the lower region of the backrest is connected to at least one of the seat part and to the seat part substructure by the at least one releasable connection means while retaining the sitting position.

3. The vehicle seat according to claim 1 , wherein the at least one releasable connection means is configured as a hook element.

4. The vehicle seat according to claim 3 , wherein the hook element comprises at least one of an angle plate and is arched.

5. The vehicle seat according to claim 4 , wherein the angle plate has on the upwardly directed region an arched portion, a C-shaped portion or a portion which is formed forwards with respect to the longitudinal direction of the seat.

6. The vehicle seat according to claim 1 , wherein the at least one releasable connection means is arranged on the rear region of the seat part.

7. The vehicle seat according to claim 1 , wherein the backrest is flexible at least in the lower region thereof at least in the longitudinal direction of the seat.

8. The vehicle seat according to claim 1 , wherein the backrest and the seat part substructure are connected to a seat frame.

9. The vehicle seat according to claim 8 , wherein the backrest is suspended on the seat frame such that it can swivel about a second swivel axis extending in the width direction of the seat.

10. The vehicle seat according to claim 8 , wherein the seat part substructure has at least one end stop in its rear region and the seat frame has at least one cross strut which extends in the width direction of the seat and on which the at least one end stop rests in the sitting position to hold the seat part substructure in the sitting position.

11. The vehicle seat according to claim 10 , wherein the at least one cross strut is adjustable at least in the height direction of the seat and has at least one recess to prevent contact between the cross strut and the at least one releasable connection means during a swiveling movement of the seat part substructure.

12. The vehicle seat according to claim 10 , wherein the at least one cross strut is adjustable at least in the height direction of the seat.

13. The vehicle seat according to claim 10 , wherein the at least one cross strut has at least one recess to prevent contact between the cross strut and the at least one ret connection means during a swiveling movement of the seat part and structure.

14. A vehicle seat comprising:

a backrest;

a seat part; and

a seat part substructure, the seat part substructure being mounted such that it can swivel about a first swivel axis arranged in a width direction of the seat in order to move the seat part substructure together with the seat part from a sitting position into an upright position, wherein a lower region of the backrest with respect to a height direction of the seat and at least one of a rear region of the seat part and of the seat part substructure with respect to a longitudinal direction of the seat are interconnected in the sitting position by at least one releasable connection means and are not interconnected in the upright position, wherein the backrest and the seat part substructure are connected to a seat frame, and wherein the seat part substructure has at least one end stop in its rear region and the seat frame has at least one cross strut which extends in the width direction of the seat and on which the at least one end stop rests in the sitting position to hold the seat part substructure in the sitting position,

wherein the at least one cross strut is adjustable at least in the height direction of the seat and has at least one recess to prevent contact between the cross strut and the at least one releasable connection means during a swiveling movement of the seat part sub structure.

15. A vehicle seat comprising:

a backrest;

a seat part; and

a seat part substructure, the seat part substructure being mounted such that it can swivel about a first swivel axis arranged in a width direction of the seat in order to move the seat part substructure together with the seat part from a sitting position into an upright position, wherein a lower region of the backrest with respect to a height direction of the seat and at least one of a rear region of the seat part and of the seat part substructure with respect to a longitudinal direction of the seat are interconnected in the sitting position by at least one releasable connection means and are not interconnected in the upright position, wherein the backrest and the seat part substructure are connected to a seat frame, and wherein the seat part substructure has at least one end stop in its rear region and the seat frame has at least one cross strut which extends in the width direction of the seat and on which the at least one end stop rests in the sitting position to hold the seat part substructure in the sitting position,

wherein the at least one cross strut is adjustable at least in the height direction.