Importance

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Abstract

An apparatus for controlling hydraulic pumps for a construction machine wherein the construction machine includes first and second hydraulic pumps adapted to be driven by an engine and hydraulic actuators hydraulically connected to the first and second hydraulic pumps via first and second actuating valves is disclosed. A controlling section calculates extra horse powers .DELTA.HP.sub.1 and .DELTA.HP.sub.2 based on reference allowable absorptive horse powers set relative to the first and second hydraulic pumps and actual absorptive horse powers (HP.sub.01) and (HP.sub.02) derived from the first and second hydraulic pumps. In addition, the controlling section calculates allowable discharge capacities (V.sub.1P) and (V.sub.2P) based on the number (N) of revolutions of the engines, pressures (P.sub.1) and (P.sub.2) of hydraulic oils discharged from the first and second hydraulic pumps, the extra horse powers .DELTA.HP.sub.1 and .DELTA.HP.sub.2 and allowable discharge capacities (V.sub.1P) and (V.sub.2P). Then, the controlling section selects a smaller one of a target discharge capacity and the allowable discharge capacity (V.sub.1P) and a smaller one of another target discharge capacity and the allowable discharge capacity (V.sub.2P) as minimum target discharge capacities (V.sub.1) and (V.sub.2). Thereafter, the controlling section controls swash plate angles of the first and second hydraulic pumps such that the minimum target discharge capacities (V.sub.1) and (V.sub.2) are correctly set corresponding to the first and second hydraulic pumps. Consequently, absorptive horse powers to be derived from the first and second hydraulic pumps can properly be controlled while a sum of the reference allowable absorptive horse powers is kept constant.

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First Claim