Komatsu 75001, Руководство по ремонту

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SEN03834-01
10-920
14
WA250, 250PZ-6
920 Electrical system, Part 2
Electrical system (HST controller system)
Fan reverse rotation function
q
As the fan reverse rotation switch is pressed for cleaning of the radiator core, the cooling fan reverse
rotation solenoid valve of the cooling fan motor is activated, reverse rotating the fan.
1. Fan manual reverse rotation function
The operator can select the desired fan rotation direction by pressing the fan reverse rotation switch to
"MANUAL" for 0.5 seconds or longer.
As long as switching of the fan rotation direction is taking place, the pilot lamps of the machine monitor
keeps blinking to inform the operator that the switching is underway. And when the fan rotation is
reversed responding to the high engine speed, high coolant or oil temperature, this lamp also keeps on
blinking until the preparation for switching is completed.
As the fan rotation switching condition is met, this function sends the accelerator opening ratio-restrict-
ing signal to the engine controller so that the engine speed may not reach 1,200 rpm or above while the
switching is underway. Above control, however, is not applicable when the HST oil temperature is 30
°
C
or above.
The pilot lamp of the machine monitor keeps on blinking as long as the reverse rotation of the fan is con-
tinued.
The fan rotation is switched from "forward" to "reverse" as every condition in the following table is met.
The fan rotation is switched from "reverse" to "forward" if any of the following conditions is met.
*1: The engine speed-related requirement (1,200 rpm) is exempted when the HST oil temperature is
30
°
C or above.
2. Overheat prevention function
If overheat in the coolant temperature, HST oil temperature or boost air temperature was recognized
while the fan was rotating reverse, the reverse rotation is forcibly stopped and the forward rotation is
turned on in order to increase the air flow to the radiator.
3. Fan speed during reverse rotation
While the reverse fan rotation is continued, this function sets the fan speed to the maximum by cutting
off the command current (sets the command current to 0 mA) to the fan motor flow rate control EPC
valve.
Setting the fan speed to the maximum increases air flow to the radiator core maximum, making the
cleaning work easier.
Condition 1 The fan reverse rotation switch was set to "MANUAL" for 0.5 seconds or longer.
Condition 2
(*1)
Engine speed over 500 rpm and below 1,200 rpm.
[above is required to prevent generation of peak pressure in the process of switching the direction.]
Condition 3
Coolant temperature is below 90°C.
[above is required to prevent overheating.]
Condition 4
HST oil temperature is below 95°C.
[above is required to prevent overheating.]
Condition 5
Boost air temperature is below 70°C.
[above is required to prevent overheating.]
Condition 6
30 seconds minimum have elapsed since the engine is started (since the engine speed reached 500
rpm or above).
[above is required to secure the oil to be supplied to the brake accumulator.]
Condition 1
(*1)
While the fan is rotating reverse, the fan reverse switch was again set to "MANUAL" and the engine
speed went to below 1,200 rpm.
Condition 2
(*1)
After the fan rotated in the reverse direction for 10 minutes, the engine speed went to less than 1,200
rpm.
Condition 3 The engine has stopped.