| |
| Illustration 1 | g06118928 |
|
(1) Machine ECM
(2) Engine speed dial (3) Switch panel (4) Idler pump pressure sensor (5) Drive pump pressure sensor (6) Pressure sensor (boom cylinder head end) (7) Left travel pressure sensor (8) Right travel pressure sensor (9) Straight travel pressure sensor (10) Implement pressure sensor (11) One-touch low idle switch (12) Battery (13) Fuse panel (14) Engine start switch (15) Monitor (16) Travel alarm (17) Fine swing solenoid valve (attachment) (18) Negative flow control PRV (drive pump) (19) Negative flow control PRV (idler pump) (20) Boom regeneration proportional reducing valve (21) Swing priority solenoid valve (22) Power shift solenoid valve (23) Hydraulic lockout solenoid (24) Swing brake solenoid valve (25) Travel speed solenoid valve (26) Straight travel solenoid valve (27) Heavy lift solenoid valve (attachment) (28) Pressure sensor (boom down control) (29) Pressure sensor (swing control) (30) Pressure sensor for the drive pump (negative flow control) (31) Pressure sensor for the idler pump (negative flow control) (32) Viscous clutch (33) Fan speed sensor (34) Engine (35) Main pumps (36) Engine speed pickup (37) Engine ECM | |
| |
| Illustration 2 | g01963756 |
|
View from the top of the cab (1) Machine ECM | |
| |
| Illustration 3 | g02141605 |
| (15) Monitor | |
The electronic control system consists of monitor (15) and the machine ECM (1) that is located in the cab. The electronic control system controls the engine speed and the pumps through the machine ECM.
Machine ECM (1) receives input signals from various components on the machine. The machine ECM continuously monitors the input signals to control the output flow rate of the main pumps, engine speed, and various components of the machine hydraulic systems.
The machine ECM has the following three major functions.
- The electronic control system controls the output flow rate of the main pumps. The machine ECM sends an electrical signal to the power shift solenoid that is based on engine speed and the position of the engine speed dial. This action allows the main pumps to supply the optimum output that matches the hydraulic load to the machine and the engine speed. When a large load is placed on the machine, the system allows the pumps to destroke. The system utilizes the available maximum engine horsepower.
- The electronic control system controls the engine speed. This function is called Automatic Engine Speed Control (AEC). When there is a small load condition or no load condition, the system automatically decreases the engine speed. The AEC system is designed to reduce fuel consumption and noise.
- The electronic control system controls various components of the machine hydraulic systems. The machine ECM sends output signals to the swing brake solenoid valve, the travel speed solenoid valve, and the straight travel solenoid.
Reference: For more information concerning the operation of the electronic control system, refer to Systems Operation/Testing and Adjusting, "Machine Electronic Control System".
The machine ECM receives input signals from various pressure sensors and pressure switches on the machine. The machine ECM monitors the input signals to control various functions of the hydraulic system.
Drive pump pressure sensor and idler pump pressure sensor
Drive pump and idler pump pressure sensors measure the pump discharge pressure. The pressure sensors send a pulse width modulated signal (PWM) input to the machine ECM. The pressure information is used for pump control and travel speed change.
Boom cylinder head end pressure sensor
Boom cylinder head end pressure sensor measures the hydraulic pressure on the head end of the boom cylinder. The pressure sensors send a pulse width modulated signal (PWM) input to the machine ECM. The pressure information is used for boom regeneration control.
Pressure sensor for boom down control
Pressure sensor for boom down control measures the pilot oil pressure during a boom DOWN function. The pressure sensor for boom down control sends an analog voltage input to the machine ECM. The machine ECM uses the pressure information to reduce engine speed and pump flow during a boom down function. Also, whenever the pilot pressure exceeds
Pressure sensors for negative flow control
Pressure sensor for the drive pump and pressure sensor for the idler pump measures the negative flow control pressure to the drive pump and the idler pump regulators. The pressure sensors send a pulse width modulated signal (PWM) input to the machine ECM. The machine ECM uses the pressure information for pump flow limitation.
Pressure sensor for swing control
Pressure sensor for swing control measures the pilot oil pressure during a swing function. The pressure sensor sends an analog voltage input to the machine ECM. The machine ECM uses the pressure information to control swing priority solenoid valve (21). Whenever the pilot pressure exceeds
Pressure sensor for swing control is also used to prevent oil loss over the crossover relief valve at the start of a swing function. The swing operation is detected with swing pilot pressure sensor (29). The swing load pressure is detected with the idler pump pressure sensor (4). The main pump flow is reduced when the idler pump pressure sensor is higher than the crossover relief valve pressure setting determined by the machine ECM. The machine ECM sends a PWM signal to the negative flow control PRV (19) to destroke the idler pump.
The machine ECM also reduces the idler pump flow during inching operation. Swing inching is detected by the pressure sensor for swing control. This function is only activated when no other implements are being operated.
When the joysticks are moved from the NEUTRAL position for a boom UP, stick IN, stick OUT, bucket IN, or a bucket OUT operation, pilot oil is directed to the implement pressure sensor. The implement pressure sensor sends an electrical signal to the machine ECM corresponding to the demand initiated by the operator. The signal information is used to control engine speed and pump control. Also, an electrical signal from the machine ECM energizes swing brake solenoid valve (24) to release the swing parking brake.
Note: The implement pressure sensor does not detect a boom lower or a swing operation.
Left travel pressure sensor and right travel pressure sensor
The left travel pressure sensor and right travel pressure sensor detects travel operation. The travel pressure sensors each send an input signal to the machine ECM. The machine ECM uses the sensor information to control the engine speed and pump control.
Proportional Reducing Valves (PRV's)
The boom regeneration PRV is used to control the amount of regeneration oil in the boom circuit. The machine ECM receives an input signal from pressure sensor for boom down control (28) and boom cylinder head end pressure sensor (6).
When the boom cylinder head end pressure is high and the pressure sensor for boom down control detects pilot pressure, the boom regeneration PRV remains de-activated. Pilot oil is then directed through the boom regeneration PRV and to the boom regeneration valve allowing regeneration.
When the boom cylinder head end pressure is low and the pressure sensor for boom down control detects pilot pressure, the boom regeneration PRV begins to receive a PMW signal from the machine ECM. The machine ECM begins to increase current flow which decreases the amount of pilot oil supplied to the boom regeneration valve. The boom regeneration circuit is then disabled.
Negative flow control PRV for the drive pump and negative flow control PRV for the idler pump
The negative flow control PRV's are used to control the main pump output flow. The machine ECM receives inputs from various pressure sensors and pressure switches. The machine ECM also receives inputs from the throttle dial position and the engine speed.
The machine ECM uses a PWM signal to vary the current that is sent to the negative flow control PRV. An increase in current causes an increase in hydraulic pressure which is then sent to the pump regulators. This increase in pressure to the pump regulators causes the main hydraulic pumps to destroke, decreasing the flow. The amount of pump destroke is determined by the machine ECM.
A decrease in current to the negative flow control PRV causes a decrease in hydraulic pressure to the pump regulators. This decrease of pressure to the pump regulators causes the main hydraulic pumps to upstroke, increasing the flow.
To prevent valve spool sticking due to thermal shock, the machine is equipped with a warm-up power derate mode. When either the drive pump or idler pump pressure remains above
When the drive pump and idler pump pressure drops below