Fiat Kobelco EX355 Tier2, Technical Manual

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T2-1-8 EX355
CONTROL SYSTEM
PUMP CONTROL
Speed Sensing Control
Purpose : To control the pump driving torque in re-
sponse to the load variations on the engine or the
output of the hydraulic pumps to utilize the engine
output more efficiently. (This avoids engine stalling
under bad conditions such as operating at high alti-
tudes).
Operation : The target engine speed is selected by
setting the engine speed with the engine control dial.
The MC receives the signals from the target engine
speed, and actual engine running speed from the N
sensor and the signal of pump delivery pressure
sensor.
After processing these data, the MC sends out control
signals to the solenoid valve unit (SD). According to
the control signals from the MC, the solenoid valve
unit (SD) supplies pilot oil pressure to the pump
regulators to control the pump flow rate.
When poor quality fuel is used or if the machine is
operated at high altitudes, the engine output torque
may decrease, causing the engine to run slower than
the target speed. As the MC in the speed sensing
control system instructs the solenoid valve unit (SD)
to reduce the pump flow rate, the pump drive torque
is reduced. Thereby, engine speed reduction or en-
gine stall is avoided.
(Refer to the Pump Device Group in the COMPO-
NENT OPERATION sextion).
NOTE: Pump control has speed sensing controls
down by MC, and also has controls down by pump
control valve inside the control valve. (Refer to the
Pump Device and Control Valve group in the COM-
PONENT OPERATION section).
Engine control dial
ENGINE
N sensor
S D
REG
REG
SM0110
MC
SD
Solenoid Valve
unit