Centering mechanism

1. A centering mechanism that centers an inner member located inside in a radial direction, with respect to an outer member arranged to surround the inner member in a circumferential direction, the inner member comprising an upper inner member and a lower inner member, the outer member comprising an upper outer member and a lower outer member, the centering mechanism comprising:

a vertical-direction positioning unit which is provided on an inner circumferential surface located at the upper-end side part of the lower outer member,

the vertical-direction positioning unit positions the inner member in a vertical direction in a non-stepwise manner by moving the vertical-direction positioning unit in the horizontal direction.

2. A centering mechanism according to claim 1 , wherein,

the vertical-direction positioning unit includes an oblique member on which the inner member is placed and which extends obliquely with respect to a horizontal direction,

wherein the oblique member is moved in the horizontal direction to perform the positioning in the vertical direction.

3. A centering mechanism according to claim 2 , wherein an angle formed by a horizontal plane and an upper face of the oblique member, on which the inner member is placed, is equal to or larger than a friction angle of the inner member.

4. A centering mechanism according to claim 3 , wherein a low-pressure-side end face of the inner member and a high-pressure-side end face of the outer member are structured to be always in contact.

5. A rotary machine comprising the centering mechanism according to claim 1 .