Lubricating apparatus for rotating shaft

1. A rotating-shaft lubricating apparatus comprising:

a rotating shaft disposed horizontally;

a supporting wall adapted to rotatably support an end portion of the rotating shaft in an axial direction, with a bearing interposed therebetween;

an oil chamber surrounded by the supporting wall and an end surface of the rotating shaft in the axial direction;

an oil passage opened to the oil chamber through the end surface of the rotating shaft, the oil passage extending in the axial direction within the rotating shaft and communicating with at least one lubricating portion in an outer peripheral surface of the rotating shaft;

an oil intake portion for receiving oil from outside the oil chamber and for supplying the oil to the oil chamber; and

a plurality of guide ribs protruding from the supporting wall toward the end portion of the rotating shaft within the oil chamber,

wherein the plurality of guide ribs includes a first guide rib extending from a radially-outer portion of the oil chamber toward a center portion coincident with an opening of the oil passage, and a second guide rib adjacent to and spaced apart from the first guide rib, the first guide rib and the second guide rib being configured and arranged to form at least two oil flow paths from the radially-outer portion of the oil chamber toward the center portion between the first guide rib and the second guide rib and extending along the plurality of guide ribs.

2. The rotating-shaft lubricating apparatus according to claim 1 , wherein the guide ribs are configured such that oil having been pressurized by a centrifugal force from the rotating shaft flows toward the center portion through the respective oil flow paths, and such that at least two or more oil flows flowing opposite to each other impinge upon each other at the center portion so as to press against each other in any of the at least two oil flow paths.

3. The rotating-shaft lubricating apparatus according to claim 1 , wherein the plurality of the guide ribs are formed integrally with the supporting wall.

4. The rotating-shaft lubricating apparatus according to claim 1 , wherein the plurality of the guide ribs are formed as members separated from the supporting wall.

5. The rotating-shaft lubricating apparatus according to claim 1 , wherein:

the first guide rib is formed to have a substantially-U shape, the first guide rib having a bottom portion surrounding the center portion at its lower side, and having opposite side portions extending upwardly from opposite ends of the bottom portion when viewed in the axial direction of the rotating shaft,

the second guide rib is formed to have a substantially-I shape extending from the radially-outer portion toward the center portion and protruding between the opposite side portions of the first guide rib having the substantially-U shape, and

the first guide rib and the second guide rib are configured such that the at least two oil flow paths are formed between opposite side surfaces of the second guide rib having the substantially-I shape and the opposite side portions of the first guide rib having the substantially-U shape.

6. The rotating-shaft lubricating apparatus according to claim 1 , wherein:

the first guide rib is shaped to extend downwardly in a substantially-straight-line from an upper portion of an inner peripheral wall surface and to reach a vicinity of a first end of the center portion in a horizontal direction,

the second guide rib is shaped to extend upwardly in a substantially-straight-line from a lower portion of the inner peripheral wall surface and to reach a vicinity of a second end of the center portion in the horizontal direction, and

the at least two oil flow paths are formed respectively along surfaces of the guide ribs which face the center portion.

7. The rotating-shaft lubricating apparatus according to claim 1 , wherein:

the first guide rib comprises a pair of first main guide ribs which extend in the radial direction from outer peripheral ends of the center portion to reach the inner peripheral wall surface, the first main guide ribs being placed to have a phase difference of 180 degrees therebetween about a center of the center portion, and

the second guide rib comprising a pair of second sub guide ribs which are provided at a substantially-center portion of the oil chamber at positions substantially parallel with the main guide ribs, and

the respective oil flow paths are formed along side surfaces of the respective first main guide ribs.

8. The rotating-shaft lubricating apparatus according to claim 1 , wherein:

the plurality of the guide ribs comprises four guide ribs including the first guide rib and the second guide rib, the four guide ribs being formed to have a substantially-sectorial shape when viewed in the axial direction of the rotating shaft, and

the four guide ribs form the at least two oil flow paths intersecting with each other in a substantially-cross shape at the center portion.

9. The rotating-shaft lubricating apparatus according to claim 1 , wherein:

the rotating shaft comprises a speed-change shaft which is one of a plurality of rotating shafts in a gear-type transmission, and

a plurality of speed-change gears are rotatably supported on the speed-change shaft with a needle bearing interposed therebetween.