To perform a horse power control without ussizing a spring to energize a spool by providing a first stepped part wherein a first piston forms a pressure receiving surface of a variable pump and a second stepped part wherein a second piston forms a pressure receiving surface for reducing a horse power.
A first stepped part is provided to have a first piston 32 forming a pressure receiving surface 34 for a variable pump and a second stepped part is provided to have a second piston 33 forming a pressure receiving surface 36 for reducing a horse power. Discharge pressure of an auxiliary pump 14 is exerted on a pressure receiving surface 36 for reducing a horse power of the second piston 33 and simultaneously the self pressure of a hydraulic pump 2 is exerted on the pressure receiving surface 34 for a variable pump of the first piston 32. The second piston 33 and the first piston 32 are moved against the force of a spring 26 to energize the spool 25 of a regulator 31. This constitution controls desired horse power reduction by shifting the spool 25 without increasing the size of the spring 26 and needing an proportional pressure reducing solenoid valve.
GOTO YASUHARU
YUASA KAZUMASA
