jcb JS70, Service Manual

Page: 77 / 385

4 - 2
Basic Operation of Engine Control
Starter Switch OFF
When the starter switch is OFF, there is no voltage,
either from the ACC voltage (24V) from the starter switch
or the 24V from the fuse box entering into the motor
driver.
The throttle motor loses retaining force and stops until
the spring force of the coil spring on the throttle link
section resets itself.
Starter Switch ON
When the starter switch is ON, there is voltage from the
ACC, from the starter switch to the motor driver.
The 24V from the fuse box enters into the motor driver.
The potentiometer signal showing the throttle switch
and the motor angle in the throttle motor enters into the
motor driver. The required rotating position is compared
with the motor angle.
To provide an equal voltage between the throttle switch
voltage and the motor angle voltage, a pulse is sent
from the motor driver to the throttle motor and the motor
is rotated at the correct speed. Under remaining status,
the voltage enters into the coil A-A1 or A-B1 or B-A1 or
B-B1 of the throttle motor.
Revolution increase, Maximum revolution
When the throttle switch moves clockwise the voltage rises.
Since this produces a different voltage to the Potentiometer
voltage, a pulse is sent until an equal voltage is reached.
When the throttle switch moves fully clockwise (maximum
engine speed), the throttle motor moves until the limit switch
on the full side is operated.
Engine Stop
When the starter switch is off, the ACC line signal of the
motor driver is cut . The motor sends a pulse to the throttle
motor which rotates clockwise until the switch on the stop
side is engaged.
The governor lever is moved to the stop side to stop the
engine. The stop solenoid moves the fuel cut lever to the
stop side to cut the fuel flow.
Section C Electrics
9803/6020
Section C
4 - 2
Issue 1
Engine Control
288330
A
Left Switch Panel
B
Starter Switch
C
One Touch Idle Switch
D
Fuse Box
E
Engine Stop Relay
F
Stop Solenoid
G
Emergency Stop
H
Right Switch Panel
J
Starter Switch Input
K
Engine Stop
L
L Mode
M
Engine Stop Input
R
Throttle Switch
A
R
B
C
D
E
F
G
H
J
K
L
M
When the CN12 starter switch input on the right side of the
switch panel is OFF, the engine stop line inside the switch
panel is earthed, so that the engine stop relay is operated and
the stop solenoid is isolated (Fuel cut).
There is a timer on the engine stop line of the switch panel
which takes 5 seconds to work.