Foldable display device

An electronic device comprising:

• a housing including a first housing structure and a second housing structure,
• wherein the first housing structure includes a first surface and a second surface that is opposite to the first surface,
• wherein the second housing structure includes a third surface and a fourth surface that is opposite to the third surface, and
• wherein the first housing structure and the second housing structure are foldable with respect to each other, and the third surface faces the first surface in a folded state and the first surface and the third surface face the same direction in an unfolded state;
• a hinge structure connecting a first peripheral part of the first housing structure to a second peripheral part of the second housing structure;
• and
• a flexible display layer extending across at least a portion of the first surface and at least a portion of the third surface and being foldable in the first peripheral part and the second peripheral part or an adjacent area of the first peripheral part and the second peripheral part,
• wherein the hinge structure includes:
• a first shaft including a first saw-toothed spur gear that rotates about a first axis that is parallel to the first surface;
• a second shaft including a second saw-toothed spur gear that rotates about a second axis that is parallel to the first axis;
• a third saw-toothed spur gear engaged with the first saw-toothed spur gear to be rotatable;
• a fourth saw-toothed spur gear engaged with the second saw-toothed spur gear and the third saw-toothed spur gear to be rotatable;
• a first guide structure fixed to the first housing structure and including a first curved opening having a first saw-toothed inner spur gear that is engaged with the first saw-toothed spur gear and is not engaged with the second saw-toothed spur gear, the third saw-toothed spur gear, and the fourth saw-toothed spur gear, and configured to rotate about a first imaginary axis that is parallel to the first axis;
• and
• a second guide structure fixed to the second housing structure and including a second curved opening having a second saw-toothed inner spur gear that is engaged with the second saw-toothed spur gear and is not engaged with the first saw-toothed spur gear, the third saw-toothed spur gear, and the fourth saw-toothed spur gear, and configured to rotate about a second imaginary axis that is parallel to the first axis and offset from the first imaginary axis.