Patent attributes
When a mode selection command selects an economy mode, a mode selector 700e is turned on and outputs an engine revolution speed modification value ΔN0 (ΔN1=ΔN0) computed by an engine-revolution-speed modification value computing section 700d. A subtracter 700f subtracts the engine revolution speed modification value ΔN1 from a rated target revolution speed Nmax, thereby computing a target engine revolution speed NR2. The computing section 700d computes the engine revolution speed modification value ΔN0 depending on a pump delivery pressure mean value Pm. In a table stored in a memory, the relationship between Pm and ΔN0 is set such that when Pm is not higher than PA near a midpoint pressure, ΔN0 is 0 and when Pm exceeds PA, ΔN0 is increased with an increase of Pm. Thus, the revolution speed of a prime mover is reduced by mode selection so as to improve fuel economy.
