| 摘要 |
When a mode selection command selects an economy mode, a mode selector 700 e is turned on and outputs an engine revolution speed modification value DeltaN 0 (DeltaN 1 =DeltaN 0 ) computed by an engine-revolution-speed modification value computing section 700 d. A subtracter 700 f subtracts the engine revolution speed modification value DeltaN 1 from a rated target revolution speed Nmax, thereby computing a target engine revolution speed NR 2 . The computing section 700 d computes the engine revolution speed modification value DeltaN 0 depending on a pump delivery pressure mean value Pm. In a table stored in a memory, the relationship between Pm and DeltaN 0 is set such that when Pm is not higher than PA near a midpoint pressure, DeltaN 0 is 0 and when Pm exceeds PA, DeltaN 0 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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