Hydraulic motor

In a hydraulically operated rotary machine of the type incorporating therein a nutating bevel gear transmission train, said machine comprising a casing member, a shaft member journalled in said casing member, main bearing means interposed between said casing member and said shaft member such that one of said members is stationary while the other member is rotary or vice versa, a low pressure port and a high pressure port formed in said stationary member, a nutating member disposed for nutation in said casing member in coaxial relationship with said shaft member and including a first bevel gear and a second bevel gear, said first bevel gear being in mesh with a bevel gear mounted on said casing member, said second bevel gear being in mesh with a bevel gear carried by said shaft member and having a different number of teeth from that of the bevel gear carried by said shaft member, and a valve unit disposed within said casing member and including a plurality of pistons each of which is slidably disposed in said machine for reciprocal movement in the longitudinal direction of said casing member and functioning as a spool of a three-way valve, the pistons having free ends extending out of said valve unit and abutting against said nutating member, whereby the reciprocal movement of each of said pistons and the nutation of said nutating member operates such that a space behind the end of said piston remote from said free end thereof varies in volume, said hydraulic machine further comprising a swash plate having an inclined end face and being mounted by means of thrust and radial bearing means within said casing member for rotation in coaxial relationship with said shaft member, spherical surface bearing means with a spherical bearing surface mounted within said casing member in coaxial relationship with said shaft, between said pistons and said swash plate, said nutating member being carried by said spherical bearing means such that the center of the nutation of said nutating member coincides with the center of radius of the spherical bearing surface of said spherical bearing, and thrust bearing means interposed between said nutating member and said inclined end face of said swash plate, with said thrust bearing means being mounted on said nutating member.