Hitachi ZW180 Technical Manual page 60

Torque Decrease Control
Purpose: To utilize engine output power by changing
pump delivery flow rate in response to in-
crease or decrease of the engine speed due
to traveling load effectively.
Operation:
1. When the accelerator pedal is depressed, MC
calculates the target engine speed.
2. MC calculates the pump maximum displacement
angle most suitable to each time, by using the
target engine speed and the signals from the
main pump delivery pressure sensor, torque
converter input speed sensor and torque con-
verter output speed sensor, and transmits the
signal to the pump torque control solenoid valve.
3. The pump torque control solenoid valve transmits
pilot pressure according to the signal to the main
pump regulator, and controls the pump delivery
flow rate.
4. If load applied to the engine becomes large and
decreases the actual engine speed below the
target speed, the pump displacement angle is
decreased and delivery flow rate is decreased.
Thus, operation of the vehicle body is improved.
5. MC calculates the actual engine speed by re-
ceiving the signal from the torque converter input
speed sensor.
SYSTEM / Control System
T2-1-18
Q
Flow
Rate
NOTE: In case the accelerator pedal becomes
abnormal, the backup control of the accel-
erator pedal control fixes the engine speed
-1
at 1100 min
NOTE: In case the signal from either the main
pump delivery pressure sensor, torque
converter input speed sensor or torque
converter output speed sensor is not
transmitted to MC, MC does not make
torque reduction control, MC makes pump
control by only the standard torque control.
NOTE: In case the pump torque control solenoid
valve becomes abnormal, neither standard
torque control nor torque decrease control
is made.
P-Q Line
Pressure
.
P