Apparatus for controlling hydraulic pumps for construction machine

An apparatus for controlling hydraulic pumps for a construction machines wherein said construction machine includes first and second hydraulic pumps adapted to be driven by an engine and hydraulic actuators hydraulically connected to said first and second hydraulic pumps via first and second actuating valves, wherein said apparatus comprises;

• engine revolution number detecting means for detecting the number (N) of revolutions of said engine,
• pressure detecting means for detecting pressures (P.sub.1) and (P.sub.2) of hydraulic oils discharged from said first and second hydraulic pumps,
• horse power setting means for presetting reference allowable absorptive horse powers relative to said first and second hydraulic pumps,
• target discharge capacity commanding means for commanding target discharge quantities (V.sub.1L) and (V.sub.2L) corresponding to quantities of actuations of said first and second actuating valves,
• absorptive horse power calculating means for calculating actual absorptive horse powers (HP.sub.01) and (HP.sub.02) derived from said first and second hydraulic pumps,
• extra horse power calculating means for calculating extra horse powers (.DELTA.HP.sub.1) and (.DELTA.HP.sub.2) based on said reference allowable absorptive horse powers and said actual absorptive horse powers (HP.sub.01) and (HP.sub.02), said extra horse powers (.DELTA.HP.sub.1) and (.DELTA.HP.sub.2) failing to be absorbed by said first and second hydraulic pumps,
• means for calculating allowable discharge capacities (V.sub.1P) and (V.sub.2P) based on said engine revolution number (N), said discharge pressure (P.sub.1) and (P.sub.2), said extra horse powers (.DELTA.HP.sub.1) and (.DELTA.HP.sub.2) and said reference allowable horse powers relative to said first and second hydraulic pumps,
• means for selecting a smaller one of said target discharge capacity (V.sub.1L) and said allowable discharge capacity (V.sub.1P) and a smaller one of said target discharge capacity (V.sub.2L) and said allowable discharge capacity (V.sub.2P) as minimum target discharge capacities (V.sub.1) and (V.sub.2), and
• swash plate controlling means for controlling swash plate angles of said first and second hydraulic pumps such that the capacities of hydraulic oils discharged from said first and second hydraulic pumps coincide with said minimum target discharge capacities (V.sub.1) and (V.sub.2).