Abstract: A two-stage speed change mechanism for a swash plate hydraulic motor, in which a swash plate is moved even during the revolution of the swash type hydraulic motor, thereby making it possible to vary the exclusion volume. An accommodating bore for accommodating a fixing pin is formed on a side wall of a housing. Piston for shifting the swash plate is provided, and control valves 14,15 and 16 each including a pilot line 14, a spool 15 and a compression spring 16 are installed for the actuation of the swash plate shifting piston 3. Thus the exclusion volume can be safely varied even during the rotating of the hydraulic motor.

Abstract: A variable displacement mechanism for a swash plate hydraulic pump or motor, in which a swash plate, a swash plate guiding wall, a tilting control piston, and a swash plate tilting guiding and swash plate rotation preventing pin are included for varying the requiring flow rate (volumetric displacement) per revolution without the rotation of the swash plate even during the tilting of the swash plate angle and during the rotation of the hydraulic pump or motor. The periphery of the swash plate is spherical for smoothing the tilting of the swash plate, and a securing pin accommodating slot is formed on the lower portion of the swash plate. Further, there are provided a securing pin for preventing rotation of the swash plate, and a bore formed on the bottom of a front cover for installing the securing pin.