Engine speed and work mode control
In control system, we can have 10-step engine speed and 5 work-modes.
By rotating engine speed control switch, Engine rpm and work-mode is set at the same time. You can see
the specification at the next page.
This function allows the operator to select the engine speed and work mode according to working condition
and to optimise the machine performance and fuel efficiency.
Principle is simple. Excavator converts the mechanical power from engine to hydraulic power using
hydraulic pump. So engine power should be bigger than pump consuming power. If not, engine could be
stall or stop.
The V-ECU always receives the current engine speed from the E-ECU . It balances engine horsepower and
pump consuming power by changing output current to power-shift valve. Power-shift valve is kind of
proportional valve using PWM signal. By controlling power-shift valve, we can change the swash plate
angle and finally change pump flow rate. So system can keep pump torque maintain lower than engine
torque at the selected engine speed.
(1) In I (Idle)& F (Fine) mode, current is fixed at specified value regardless of engine load condition. That
means engine output is bigger enough compared to pump input power.
In P (Power max.), H (Heavy duty), G (General) mode,
(2) If engine is not loaded, it uses the specified current value at each engine speed.
(3) When engine is loaded, VECU increase the current of power-shift valve to decrease the consuming
power of pump.
Picture text:
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