The controller also performs the following functions in addition to normal operation. For each of the following functions, use the keys on the monitor panel to make selections. The monitor will send this information to the controller. Then, the controller will activate the relays or the solenoids in order to perform the function.
Travel Speed
The "TRAVEL SPEED" key is used to select one of the following two travel speeds:
- HIGH
- LOW
When the "HIGH" travel speed is selected, the controller will activate the travel speed solenoid. This activation will cause the travel speed to increase according to the travel load. Selecting the "LOW" travel speed will deactivate the travel speed solenoid. This action will cause the travel speed to decrease.
The travel speed solenoid is energized and the rabbit indicator illuminates under the following conditions:
- The output pressure of the pump is less than or equal to 20600 kPa (2988 psi) for 0.4 seconds or more.
This energizes the travel speed solenoid in order to keep the travel speed HIGH.
The travel speed solenoid is not energized but the rabbit indicator illuminates under the following conditions:
- The output pressure of the pump is greater than 20600 kPa (2988 psi) for 0.4 seconds or more.
This does not energize the travel speed solenoid in order to keep the travel speed LOW.
For more information, see the following topics:
- Hydraulic System Systems Operation, "Trenching Operation"
- Hydraulic System Systems Operation, "Leveling Operation"
- Hydraulic System Systems Operation, "Pilot Circuit"
- Hydraulic System Systems Operation, "Travel Control"
Backup System
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| Illustration 1 | g00662823 |
(1) Backup switch (2) Speed change switch | |
The controller has a backup system in order to prevent uncontrolled operation of the pump and/or engine. When the backup switch (1) is placed in the manual position, the following conditions result:
- The proportional reducing valve is disconnected from the drive circuit of the proportional reducing valve. Then, the reducing valve is driven by a constant current that is adjusted by the backup resistor. The power shift pressure is kept constant and pump output is in the standard mode.
- The monitor does not display any information. The controller and the monitor are not receiving power.
- The engine speed can be controlled by the speed change switch (2). The engine speed will be increased, if the speed change switch is placed in the rabbit position. The engine speed will be decreased, if the switch is placed in the tortoise position. The switch returns to the neutral position when the switch is released.
- The swing parking brake is released. However, the parking brake is engaged when the primary pilot pressure is reduced to near zero by placing the hydraulic activation control lever to the lock position or by stopping the engine.
Prevention Of High Speed Start Of The Engine
In a conventional excavator, the engine will start in high speed with the engine speed dial in a high position (10) after the engine has been stopped. The following information will describe the actions that are designed in order to prevent a high speed start.
When the engine key start switch is placed in the OFF position, the governor actuator will stop. The governor lever is maintained in the identical position. The engine will restart at a RPM of 1300 or 1000 rpm, if the engine is stopped and the second stage of the AEC is operating. The engine will also restart at a RPM of 1300 or 1000 rpm, if the engine is stopped and the low idle switch is in the ON position. This function is designed to keep the governor actuator in position when the operation is terminated. Any of the following conditions can cause the termination:
- A control lever or a pedal is operated.
- A implement/swing switchis activated.
- A travel switch is activated.
- A boom raise pressure switch is activated.
- The engine speed dial is operated.
- The AEC switch is operated.
- The power mode switch is operated.
Then, the engine speed will correspond to the position of the engine speed dial. Operation of the low idle switch will also terminate this function. However, the engine speed is 1000 rpm even if the position of the engine speed dial is greater than 2.
The engine will restart at a high speed, if the governor actuator is held in a high speed position before stopping the engine. The speed of the engine will decrease to 1300 rpm. The speed is automatically decreased 3 seconds after the starting of the engine. The second stage of the AEC must be in the ON position.
Preventing Over Speed During Low Engine Oil Pressure
This function is designed to prevent the engine from starting at a high speed during a condition of low oil pressure. After the engine oil filter is replaced, a long time may be required before the engine oil pressure will reach the specified level. The turbocharger may be damaged, if the engine runs at the speed dial position of 10. The following information describes this function.
The engine speed will be limited to the position of 5, if the engine oil pressure switch is open. The engine speed will also be limited to the position of 5, if the governor actuator was held in the high speed position before the stopping of the engine. The engine will start at the speed of the 5 position.
This function is designed to keep the governor actuator in position when the operation is terminated. Any of the following conditions can cause the termination:
- A control lever or a pedal is operated.
- A implement/swing switchis activated.
- A travel switch is activated.
- A boom raise pressure switch is activated.
- The engine speed dial is operated.
- The AEC switch is operated.
- The power mode switch is operated.
Then, the engine speed will correspond to the position of the engine speed dial. Operation of the low idle switch will also terminate this function. However, the engine speed is 1000 rpm even if the position of the engine speed dial is greater than 2.
The engine will restart at a high speed, if the governor actuator is held in a high speed position before stopping the engine. The speed of the engine will decrease to 1300 rpm. The speed is automatically decreased 3 seconds after the starting of the engine. The second stage of the AEC must be in the ON position.
Swing Lock System
The swing parking brake is immediately released after any of the following control lever operations.
- Boom
- Stick
- Bucket
- Swing
- Attachment
The swing parking brake is engaged 6.5 seconds after all the control levers return to the neutral position. The swing parking brake is not released while the hydraulic activation control lever is placed to the locked position. The swing parking brake is released by turning the fine swing switch to the ON position, if the fine swing attachment is installed.
Overcurrent Cutoff
In the controller, the overcurrent cutoff prevents the flow of current due to a short circuit in the output circuit. This function activates on all of the output circuits of the actuator. Each circuit has a different value for current.
Reverse Voltage Supply Protection Circuit
The protection circuit for possible reverse voltage supply is designed to protect the internal circuits of the engine and pump controller against reverse voltage. The reverse voltage could be caused by an incorrect battery connection.
Overvoltage Cutoff
The overvoltage cutoff activates the transistor in the controller under the following condition:
- The power supply to the controller is greater than 43 volts or equal to 43 volts.
The overvoltage cutoff is designed to prevent damage to the controller.
Watch Dog Timer
The watch dog timer (WDT) monitors the function of the controller's central processing unit (CPU). If a problem occurs in the CPU, the WDT sends a reset signal to the CPU. If the problem persists, the alert indicators for the controller will illuminate. The machine can continue operation by using the backup system. Refer to "Backup System".
Speed Control for the Cooling Fan
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| Illustration 2 | g00820079 |
Flow Chart of the Fan Speed Control | |
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| Illustration 3 | g00820080 |
Schematic of the Fan Speed Control | |
Sensors respond to the following temperatures:
- The engine coolant temperature
- The hydraulic oil temperature
- The temperature of the air in the air intake manifold on the engine
The engine ECM sends the temperatures to the engine and pump controller. The engine and pump controller receives the hydraulic oil temperature directly. The engine and pump controller calculates the fan speed from the information about the temperatures. The fan speed is sent from the engine and pump controller to the engine ECM through the Cat Data Link. The engine ECM sends the electric current to the fan speed control solenoid on the regulator for the fan. The speed of the fan varies from approximately 570 RPM to 1320 RPM. When each temperature is lower than the desired temperature, the speed of the fan is lowered. When each temperature is higher than the desired temperature, the speed of the fan is increased. The engine ECM varies the speed of the fan until the desired temperature is achieved.
For more information, refer to Testing and Adjusting, " 345 B Series II Fan Motor Speed (Radiator Cooling) - Test and Adjust".
Hydraulic Tank Air Pressure
If the air pressure in the hydraulic tank is decreased, a vacuum may occur on the suction side of the pump. When the air pressure in the hydraulic tank is decreased, the indicator for the hydraulic tank air pressure illuminates. The indicator is located on the right console in the cab.
In order to prevent a vacuum in the hydraulic tank, the controller automatically regulates the following items:engine speed and pump flow. If a vacuum exists, the maximum engine speed is 1800 RPM. Pump flow is reduced. In order to increase the air pressure that is in the hydraulic tank, move any control lever. The engine turbocharger supplies the air pressure to the hydraulic tank.