e a plurality of oil guide parts 424 are formed in a zigzag pattern on the shoe surface 421 each oil guide part 424 has a pair of guide walls 424 a that are inner wall faces on the front side of the indentation 422 and a wall pair converging portion 424 b where the pair of guide walls 424 a converge to each other as shown in fig9 the configurations of various parts of these oil guide parts 424 are the same as those of the first embodiment next a modification of the fourth embodiment will be described with reference to fig1 the difference between the fourth embodiment shown in fig9 and the modification shown in fig1 is that the concavity and convexity on the shoe surface 421 are inverted more specifically the indentations 422 in the fourth embodiment are replaced with protrusions 423 in the modification shown in fig1 each oil guide part 424 u2032 has a pair of guide walls 424 a a wall pair converging portion 424 b where the pair of guide walls 424 a converge to each other and a pair of second guide walls 424 c the pair of guide walls 424 a are the outer wall faces on the rear side of the two protrusions 423 adjacent each other in the shoe width direction while the second guide walls 424 c are the outer wall faces on the front side of the protrusion 423 that follows after the aforementioned two protrusions 423 in this modification the pair of guide walls 424 a do not connect.