II-144
WSM Minor Change II Service Engineering Section
e. New auto idling (AI) control system
(1)Purpose
When you interrupt a job and set the control lever to neutral, the engine will come to the automatic idling
rpm in 4 seconds. This helps save energy and keep quiet.
(2)Auto idle function mechanism
1. The auto idle type machines are equipped with the electrical devices that are shown in the accompa-
nying AI function layout.
(1) Meter panel (AI system lamp)
(2) AI motor
(3) Pull cable
(4) Acceleration sensor
(5) AI pressure switch
(6) Governor sensor
(7) Engine speed sensor
2. To enable the auto idle function, first turn on the AI switch.
3. When you operate the machine, the AI pressure switch detects the primary pressure of the hydraulic
pilot system and opens the contact. The signal is then sent to the CPU of the controller.
The AI pressure switch is attached on the control valve. This switch is of normally closed type (the
contact is usually kept closed).
4. The acceleration sensor is attached on the support of the accelerator knob. The knob position is
detected in terms of turning angle by a potentiometer, and the signal is sent to the controller CPU.
5. The governor sensor and the engine speed sensor are installed on the engine governor. The gover-
nor position signal is sent to the controller CPU.
6. The controller CPU processes the above information and feeds a current command to the AI motor
so that the engine governor should run at maximum speed.
7. Receiving the command, the AI motor starts and controls for the engine governor, through the pull
cable, to reach maximum rpm. This leads to the maximum engine speed.
8. When all the hydraulic actuators are at neutral, the AI pressure switch gets normally closed and
sends the signal to the controller CPU.
9. The CPU of the controller then feeds a current command to the AI motor so that the engine governor
should run idle. In this way, the engine will also set itself to the idling speed.
The CPU will get idling, too, 4 seconds after receiving the pressure switch signal.
Trouble cases
Electrical system:
If the AI switch or its coupler is out of position or if the harness is broken, the circuit gets open (contact
off). In other words, the microcomputer judges that the hydraulic actuator is running, and the auto idle
function fails.
Hydraulic system:
If a trouble occurs in the hydraulic system, there is no pressure rise often. In other words, the AI pressure
switch gets normally closed, and the microcomputer judges that the hydraulic system is not running,
namely, the control lever is at neutral. (Even by moving the control lever, the initial; engine speed cannot
be resumed.)
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