ELECTRONIC CONTROL SYSTEM
TOTAL SYSTEM DIAGRAM
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD ELECTRONIC CONTROL SYSTEM
1. Engine and Pump control function
Function
• The operator can set the work mode switch on the monitor panel to mode A, E, or B (or L) and select proper engine torque and pump absorp-tion torque according to the type of work.
• The engine throttle and pump controller detects the speed of the engine governor set with the fuel control dial and the actual engine speed and con-trols them so that the pump will absorb all the torque at each output point of the engine, accord-ing to the pump absorption torque set in each mode.
: The L mode is on the multi-monitor specification machine only.
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD ELECTRONIC CONTROL SYSTEM
1) Control method in each mode Mode A, Mode E
• Matching point in mode A: Rated speed
• If the pump load increases and the pressure ris-es, the engine speed lowers.
At this time, the controller lowers the pump dis-charge so that the engine speed will be near the full output point. If the pressure lowers, the con-troller increases the pump discharge so that the engine speed will be near the full output point.
By repeating these operations, the controller constantly uses the engine near the full output point.
Mode A 246.3 kW/1,850 rpm {331 HP/1,850 rpm}
Mode E 213.3. kW/1,720 rpm {286 HP/1,720 rpm}
Mode B / (Mode L)
• At this time, the controller keeps the pump ab-sorption torque along the constant horsepower curve and lower the engine horsepower by the composite control of the engine and pump.
By this method, the engine is used in the low fuel consumption area.
: The L mode is on the multi-monitor specification machine only.
Mode Mode B Mode L
Partial output point 82% 61%
Mode B 194.9 kW/1,730 rpm
{261 HP / 1,730 rpm}
Mode L 150.8 kW/1,250 rpm
{202 HP / 1,250 rpm}
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD ELECTRONIC CONTROL SYSTEM
2) Function to control pump during travel
• When the travel is operated in A operation, or E or B working mode, the working mode stays as it is, and the pump absorption torque and engine speed rise to A travel mode.
• If the machine travels in mode L, the working mode and engine speed do not change, but the pump absorption torque is increased.
: The L mode is on the multi-monitor specification machine only.
3) Function to control when emergency pump drive switch is turned ON
• Even if the controller or a sensor has a trouble, the functions of the machine can be secured with pump absorption torque almost equivalent to mode E by turning on emergency pump drive switch (10).
In this case, a constant current flows from the battery to the EPC valve for PC and the oil pres-sure is sensed by only the EPC valve for PC.
2. Pump/Valve control function
Function
• The machine is matched to various types of work properly with the 2-stage relief function to in-crease the digging force, etc.
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD ELECTRONIC CONTROL SYSTEM
1) LS control function
• The change point (LS set differential pressure) of the pump discharge in the LS valve is changed by changing the output pressure from the LS-EPC valve to the LS valve according to the oper-ating condition of the actuator.
• By this operation, the start-up time of the pump discharge is optimized and the composite opera-tion and fine control performance is improved.
2) Cut-off function
• When the cut-off function is turned on, the PC-EPC current is increased to near the maximum value.
• By this operation, the flow rate in the relief state is lowered to reduce fuel consumption.
• Operating condition for turning on cut-off function
The cut-off function does not work, however, while the machine is travelling in mode A or the arm crane operation width swing lock switch is turned on.
1) 2-stage relief function
• The relief pressure in the normal work is 34.8 MPa {355 kg/cm2}. If the 2-stage relief function is turned on, however, the relief pressure rises to about 37.2 MPa {380 kg/cm2}.
By this operation, the hydraulic force is increased further.
• Operating condition for turning on 2-stage relief function
: The L mode is on the multi-monitor specification machine only.
Condition
• The average value of the front and rear pressure sensors is above 27.9 MPa {285 kg/cm2} and the one-touch power maximizing function is not turned on
Condition Relief
pres-sure
• Condition
• During travel
• When swing lock switch is turned on
• When boom is lowered
• When one-touch power maximizing function is turned on
• When L mode is operated
34.8 MPa {355 kg/cm2}
37.2 MPa {380 kg/cm2}
3. One-touch power maximizing/machine push-up function
Function
• Power can be increased for a certain time by op-erating the left knob switch.
• When the machine push-up switch is operated, the boom pushing force is increased.
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD ELECTRONIC CONTROL SYSTEM
1) One-touch power maximizing function
• When the operator needs more digging force to dig up a large rock, etc., if the left knob switch is pressed, the hydraulic force is increased about 7% to increase the digging force.
• If the left knob switch is turned on in working mode “A” or “E”, each function is set automatical-ly as shown below.
2) Machine push-up function
• Operate switch (1) to increase the boom pushing force when digging ditches or holes on hard ground.
Working
mode Engine/Pump control 2-stage relief function Operation time Software cut-off function A, E Matching at rated
output point
34.8 MPa {355 kg/cm2} 37.2 MPa {380 kg/cm2}
Automatically reset at
8.5 sec Cancel
Switch 2-stage safety valve function
OFF
Setting of safety valve at boom cylinder
14.7 MPa {150 kg/cm2}
ON
Setting of safety valve at boom cylinder
28.4 MPa {290 kg/cm2}
4. Auto-deceleration function
Function
• If the all control levers are set in NEUTRAL while waiting for a dump truck or work, the engine speed is lowered to the medium level automati-cally to reduce the fuel consumption and noise.
• If any lever is operated, the engine speed rises to the set level instantly.
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD ELECTRONIC CONTROL SYSTEM
Operation