groove for accommodating the protrusion 375 a is formed in an outer portion of an end portion of the inner tube 380 so that the elastic tube layer 372 is firmly fixed to the inner tube 380 fig7 is a perspective view illustrating the direction conversion tube 330 according to an embodiment of the present invention as illustrated in fig7 the direction conversion tube 330 has a form of a tube having a circular cross section in which three opening portions are formed one of the opening portions is a fluid discharging opening portion formed at the fluid outlet 383 front end side and the two other opening portions are a fluid inlet opening portion and a third inlet opening portion formed at the fluid inlet 381 back end side an x axis of fig7 corresponds to a central axis of the direction conversion tube 330 and along a circumferential direction centered about the x axis and with respect to a y axis as a reference line the fluid discharging opening portion is disposed in a range from 0 to 45 degrees and the fluid inlet opening portion is disposed in a range from 0 to u2212 45 degrees and the third inlet opening portion is disposed in a range from 45 to 90 degrees when the hydraulic power unit 300 a jets a fluid toward the hydraulic power unit 300 b as denoted by a thick arrow in fig2 the direction conversion tube 330 maintains a state as illustrated in fig7 to change a rotational direction of the output axis 110 of the hydraulic engine 100 the direction conversion tube 330 is.