PURPOSE: To prevent damage of a brake by constituting a pressurized fluid motor so as to be automatically set in a small capacity state, when the brake is in an operation state, in an assembly of the pressurized fluid motor with multiple cubic capacities and a brake associated therewith.

CONSTITUTION: In an assembly having a pressurized fluid motor 1 and a brake 2 equipped with multiple disks 50, 51, the pressurized fluid motor 1 is provided with an inner fluid distributing valve 19 having a plane distributing surface 20 and a cylindrical slide drawer 29 placed at two specific positions for selecting volume. The fluid distributing valve 19 is provided in an adhesion state in relation to the rotation with a cam 5 around an axial line 12 by a catch/notch assembly 65. The slide drawer 29 is provided so that it is slid receiving three forces, thrust from a spring 63, fluid pressure in a chamber 59, and fluid pressure in a chamber 58, and is exchanged between a first state for setting the pressurized fluid motor 1 to a large application capacity and a second state for setting it to a small application capacity.