| 摘要 |
When a mode selection command selects an economy mode, a mode selector 700e is turned on and outputs an engine revolution speed modification value DeltaN0 (DeltaN1=DeltaN0) computed by an engine-revolution-speed modification value computing section 700d. A subtracter 700f subtracts the engine revolution speed modification value DeltaN1 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 DeltaN0 depending on a pump delivery pressure mean value Pm. In a table stored in a memory, the relationship between Pm and DeltaN0 is set such that when Pm is not higher than PA near a midpoint pressure, DeltaN0 is 0 and when Pm exceeds PA, DeltaN0 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.
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