Hitachi ZW180 Technical Manual page 72

Automatic Speed Shift Control
Purpose: To shift the speed automatically with three
kinds of timing selection of automatic speed
shift change
Operation:
1. If either of 1-4L, 2-4N and 1-4H of the travel mode
switch is selected, MC is supplied with votage
according to the selected mode.
Mode Auto 1-4L
Output
2 V
Voltage
2. MC starts the selected automatic speed shift pro-
gram.
•
The vehicle starts with speed 2 in auto 1-4L control,
and it automatically be shifted down to speed 1 if
travel load is too high. In this mode, the vehicle shifts
at early timing during low engine speed.
•
The vehicle starts with speed 2 in auto 2-4N control.
In this mode, the vehicle shifts at higher engine
speed than auto 1-4L control.
•
The vehicle starts with speed 2 in auto 1-4H control,
and it automatically be shifted down to speed 1 if
travel load is too high. In this mode, the vehicle shifts
at higher engine speed than auto 1-4L control.
NOTE: Even if a mode of 1-4L, 2-4N, or 1-4H is
selected, the vehicle starts with speed 1 if
the shift switch is selected.
3. The shift switch is a rotary type and has two
switches inside. When a speed shift is selected
among speed 1 through speed 4, the selected
shift signal is transmitted to MC according to the
combination of ON in the shift switch.
Speed
Speed Shift
Internal Switch
1
Internal Switch
2
SYSTEM / Control System
Auto 2-4N Auto 1-4H
3 V
Speed Speed
1 2 3
ON
ON
4. MC transmits the signal to the speed shift solenoid
valve in response to the output value each time of
the torque converter input speed sensor, torque
converter output speed sensor, vehicle speed
sensor and accelerater pedal sensor. MC eventu-
ally makes speed shift control until the selected
speed shift.
NOTE: Each shift position specifies necessary ve-
4 V
NOTE: In case the travel mode switch becomes out
NOTE: In case a malfunction occurs in either so-
NOTE: In case a malfunction occurs in the vehicle
Speed
4
ON
ON
NOTE: The speed shift selected by the shift
T2-1-30
hicle speed and accelerator pedal output
value that allows shifting change to its posi-
tion. The setting parameter is programmed
in MC. Thus, when the travel mode switch
is set in auto 1-4L and the shift switch is set
in speed 3, the vehicle starts with speed 2,
and then shifts up speed 3 according to the
acceleration of the vehicle speed. On the
other hand, when the shift switch is
changed from speed 3 to speed 1 while
traveling, the vehicle shifts down to speed 2
automatically, and then shifts down speed 1
if the vehicle speed reduces in the range of
speed 1.
of order, MC makes speed shift control in
the manual traveling mode.
lenoid valve of speed 1, speed 3, or speed
4, the vehicle speed fixed is at speed 2. In
case a malfunction occurs in either of the
forward clutch solenoid valve, reverse
clutch solenoid valve, or speed 2 solenoid
valve, only the abnormal one cannot be
used.
speed sensor, the vehicle speed is detected
by using the transmission middle shaft
sensor, which may have large margin error.
In case a malfunction occurs in both vehicle
speed sensor and the transmission middle
shaft sensor, the vehicle speed is fixed at
speed 2.
switch is the highest speed shift.