Tilting-pad-type journal bearing

1. A tilting-pad-type journal bearing comprising:

a rotary shaft;

a plurality of tilting pads that support the rotary shaft in a radial direction;

a housing that accommodates the plurality of tilting pads inside;

a fixing structure that fixes a circumferential relative position with respect to the housing while allowing the tilting pads to swing;

an oil inlet that supplies lubricating oil between the tilting pads and the rotary shaft; and

side plates provided on both sides of the housing in a rotational-axis direction, wherein

among the plurality of tilt pads, a tilting pad provided in at least a lowest position with a loading direction as a downward direction, and a tilting pad provided adjacent on the rotational upstream side of the tilting pad provided in the lowest position, have a concave part at both side ends of the sliding surface in the rotational-axis direction, the concave portion formed by a first down step part from a sliding surface facing the rotary shaft and a second down step part from the sliding surface and a third down step part, wherein the first down step part makes a down step facing toward a rotational downstream side and the second down step part makes a down step from a center side of the tilt pad in the rotational-axis direction facing toward a rotational-axis direction side end, and

in the concave part, a side of the tilting pad in the rotational-axis direction is opened toward the inside of the housing.

2. The tilting-pad-type journal bearing according to claim 1 ,

wherein in the concave part, the end side of the tilting pad on the rotational downstream side is opened toward the inside of the housing.

3. The tilting-pad-type journal bearing according to claim 2 ,

wherein the first step down part is formed to have a height larger than half of a difference between a radius of the sliding surface and a radius of the rotary shaft.

4. The tilting-pad-type journal bearing according to claim 2 ,

wherein a ratio between an outer peripheral surface width and a sliding surface width on the end side of the tilting pad on the rotational downstream side is 0.7.

5. The tilting-pad-type journal bearing according to claim 2 ,

wherein the first step down part is formed on the rotationally downstream side from a center of the tilting pad in the circumferential direction.

6. The tilting-pad-type journal bearing according to claim 2 ,

wherein the oil inlet includes at least three oil inlets that are provided in the tilting pad along the rotational-axis direction.

7. The tilting-pad-type journal bearing according to claim 2 ,

wherein an exit of the oil inlet is opened in a part of the sliding surface of the tilting pad on the rotational upstream side, and

wherein a gap between the side plate and the rotary shaft is 2 mm or larger.

8. The tilting-pad-type journal bearing according to claim 7 ,

wherein an opening is provided in a radial position of the side plate facing a gap between the housing and an outer peripheral surface of the tilting pad provided in the lowest position, and

wherein the gap between the side plate and the rotary shaft in a circumferential position of the tilting pad provided in the lowest position facing the side end in the rotational-axis direction is formed to be wider than other circumferential positions.

9. The tilting-pad-type journal bearing according to claim 2 ,

wherein an exit of the oil inlet is opened in an inner peripheral surface of the housing, and

wherein a gap between the side plate and the rotary shaft is 1 mm or smaller, and the side plate and the rotary shaft are in a non-contact state.

10. The tilting-pad-type journal bearing according to claim 9 ,

wherein an opening is provided in a radial position of the side plate facing a gap between the housing and the tilting pad provided in a lowest position, and

wherein the gap between the side plate and the rotary shaft in a circumferential position of the tilting pad provided in the lowest position facing the side end in the rotational-axis direction is formed to be wider than the other circumferential positions.

11. The tilting-pad-type journal bearing according to claim 2 ,

wherein the concave part further comprises a fourth down step part and a fifth down step part forming a concave part with a stepped configuration.