Workshop Manual

SYSTEM / Control System
T2-1-12
Engine Torque Control
Purpose: Improving fuel consumption rate by
changing the torque curve in response to
input signals from the work mode selector
switch, shift switch, and vehicle speed
sensor
Operation:
1. When the signal of the selected work mode is
transmitted to the MC, it detects signals from the
main pump delivery pressure switch, shift switch,
torque converter input speed sensor, and torque
converter output speed sensor.
2. MC has programmed torque curves to be
selected in response to the combination of work
mode, speed shift, torque converter speed ratio,
and pump delivery pressure, and outputs to the
ECM the selection command signal most suitable
to each time.
• When the light mode (L) is selected, Torque
Curve 4 or 3 is primarily used, which is
advantageous in making much of low fuel
consumption at light-load work.
• When normal mode (N) is selected, Torque Curve
3 or 2 is primarily used, which is advantageous in
making much of production as well as low fuel
consumption.
• When the power mode (P) is selected, Torque
Curve 1 or 2 is primarily used, which is
advantageous in making much of production
mainly as well as low fuel consumption slightly.
3. ECM controls torque curves in response to the
inputted torque curve selection command signal.
NOTE: In case the signal from the work mode
selector switch is not transmitted to the MC,
back-up control of fixing the work mode to
the normal mode is made.
NOTE: In case the signal from the torque converter
input speed sensor or the torque converter
output sensor is not transmitted to the MC,
engine torque control is made by setting
the vehicle speed at the back-up speed.
NOTE: In case the signal from the shift switch is
not transmitted to the MC, back-up control
of fixing to Torque Curve 2 is made.
NOTE: Each mode switch of the mode selector
switch is supplied with respectively different
voltages from the monitor unit, and when
the switch selects a mode, the MC judges
which mode has been selected by the input
voltage.
NOTE: Shift switch has two switches, and the
combination of their ON varies depending
on each speed shift. Controller judges
which speed shift has been selected by the
combination of the two input signals.
Engine
Torque
Engine
Speed
1
2
3
4
Conceptual Diagram of
Engine Torque Curve