TWO-LAYER COIL STRUCTURE

Japanese Patent JP2023077947

A

To provide a two-layer coil structure having high torsional rigidity and suppressing an occurrence of kink due to rotational resistance.SOLUTION: A torque coil (a two-layer coil structure) is so configured that a winding direction of an inner coil 11 and a winding direction of an outer coil 12 are opposite to each other, and when the torque coil is twisted in a circumferential direction thereof and in a direction of expanding a diameter of the inner coil 11, a variation in the diameter of the outer coil 12 becomes larger than a variation in the diameter of the inner coil 11. When the length of 1596 mm is defined as one unit in each of the inner coil 11 and the outer coil 12, a variation d1 in the diameter of the inner coil 11 when the inner coil 11 is twisted 360° in a circumferential direction thereof and in the direction of expanding the diameter of the inner coil 11 and a variation d2 in the diameter of the outer coil 12 when the outer coil 12 is twisted 360° in a circumferential direction thereof and in a direction of contracting the diameter of the outer coil 12 with respect to the length of the one unit, satisfy the following relation: -4.5