312F and 313F Excavator Machine Systems Engine Control Caterpillar


Engine Control
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312F and 313F Excavator Machine Systems [M0065824]
ELECTRICAL AND STARTING SYSTEM
CONTROL GP-SPEED
312F and 313F Excavator Machine Systems Engine Control
1.1. Engine Speed Control
2.1. Self-Diagnostic Function
3.1. Automatic Engine Speed Control (AEC)
4.1. One-Touch Low Idle
5.2. Using the One-Touch Low Idle Feature
6.2. Release of the One-Touch Low Idle
7.1. Engine Speed Protection
8.2. Engine Idle Shutdown
9.2. Pump Torque Control
10.3. Integrated Engine and Pump Power Management Control
11.3. Antistall Function
12.2. Boom Down Engine Speed Control
13.2. Automatic Travel Speed Change Function
14.2. Keep Alive Circuit

Engine Speed Control



Illustration 1g02623964
(1) Machine ECM
(2) Operator Monitor
(3) Engine speed dial
(4) Engine ECM

Machine ECM (1) receives the engine speed dial (3) signal from the soft switch panel. The machine ECM then transmits the desired engine speed to the engine ECM. The position of the engine speed dial is indicated on operator monitor (2). The machine ECM, engine ECM, and soft switch panel ECM communicates these signals via the CAN data link.

Engine speed dial (3) is a 10-position switch. The selected position is displayed on operator monitor (2). The desired engine speed for each dial position can be changed in Cat ET. The hydraulic torque settings for each dial position can be changed in Cat ET or through the monitor.

Note: The actual engine RPM and torque output will vary, depending on the setting of the power mode that is selected. The standard mode and economy mode will change to high hydraulic power mode during travel.

Table 1
Corresponding Engine RPM and Torque Output for Each Engine Speed Dial Position (No Load Condition) 
Engine Speed Dial Position  High Hydraulic Power Mode  Standard Power Mode 
Engine RPM Torque Output (%)  Engine RPM  Torque Output (%) 
1000  20.0  1000  20.0 
1100  48.0  1100  48.0 
1200  62.0  1200  62.0 
1250  75.0  1250  75.0 
1280  84.0  1280  84.0 
1320  84.0  1320  84.0 
1350  84.0  1350  84.0 
1400  84.0  1400  84.0 
1450  90.0  1450  90.0 
10  1500  100.0  1500  100.0 

Table 2
Corresponding Engine RPM and Torque Output for Each Engine Speed Dial Position (No Load Condition) 
Engine Speed Dial Position  Economy Mode 
Engine RPM Torque Output (%) 
1000  20.0 
1100  48.0 
1200  62.0 
1250  72.0 
1280  72.0 
1320  72.0 
1350  77.0 
1380  77.0 
1400  77.0 
10  1450  80.1 

Self-Diagnostic Function

Machine ECM (4) is a self-diagnostic component. The machine ECM monitors the inputs and the outputs. The machine ECM monitors the system problems that can occur and system warnings that are generated during the operation of the machine. The machine ECM will display a system warning that is generated, or a problem that has been detected, via the self-diagnostic function on operator monitor (2).

Note: A log file is kept for the warnings. The log file contains the time and the number of occurrences of each warning.

Automatic Engine Speed Control (AEC)



Illustration 2g02776096
(1) Machine ECM
(2) Operator Monitor
(4) Engine ECM
(5) Switch Panel
(6) Pump 1 Pressure Sensor
(7) Pump 2 Pressure Sensor
(8) Implement Pressure Switch

The Automatic Engine Speed Control (AEC) automatically reduces engine RPM when the machine is inactive. The AEC system is designed to reduce fuel consumption and noise. Lower engine speeds can also increase engine life.

The AEC system will be inoperable while the backup switch of the electronic controller system is in the MAN position.

The engine rpm will recover automatically to the setting of the engine speed dial when any hydraulic function is activated. The AEC system operates in three modes. Refer to Table 3 for a description of each mode.

Hydraulic demand is detected by either the implement pressure switch, the travel pressure switch, or the pump discharge pressure sensors.

Note: Input components related to the tool control system can detect hydraulic demand as well.



Illustration 3g02624857
Automatic Engine Speed Control (AEC) Selection Switch

The Automatic Engine Speed Control switch is activated when the engine start switch is turned to the ON position. The indicator lamp will turn on. When you press the AEC switch, the function of the AEC switch changes from ON to OFF. The operator can choose from three possible modes for automatic engine speed control. Refer to Table 3 for more details.



Illustration 4g06019117
One-Touch Low Idle Switch
(9) One-Touch Low Idle Switch (RH Joystick)

Activate the manual low idle in order to reduce the engine speed to approximately 1100 rpm. Pressing the switch again will allow the engine speed to return to the original setting of the engine speed dial.

The manual low idle allows the operator to reduce the rpm without touching the engine speed dial. This action is useful when the operator wants to reduce the engine speed to talk to someone or while the operator is waiting for a truck.

Operation of the automatic engine speed control depends on the position of the AEC switch and of the switch for manual low idle. The engine rpm will recover automatically to the setting of the engine speed dial when any hydraulic function is activated.

Table 3
AEC Mode  Position of AEC Switch  Setting of Engine Speed Dial  Position of Manual Low Idle Switch  Description of Mode 
First stage  OFF  3 to 10  OFF  The electronic controller automatically reduces engine speed by 100 rpm after there has been no hydraulic demand for approximately 5 seconds. 
Second stage  ON  3 to 10  OFF  The AEC system in the electronic controller will automatically reduce the engine rpm to approximately 1100 rpm after there has been no hydraulic demand for approximately 5 seconds. 
Manual low Idle  ON or OFF  3 to 10  ON  The engine speed is reduced to approximately 1100 rpm. 

One-Touch Low Idle



Illustration 5g03034623
(1) Machine ECM
(2) Monitor
(4) Engine ECM
(5) Switch Panel
(6) Pump 1 Pressure Sensor
(7) Pump 2 Pressure Sensor
(8) Implement Pressure Switch
(9) One-Touch Low Idle Switch (RH Joystick)

When one-touch low idle switch (10) is pressed, and the machine is not under load (all levers and pedals in the neutral position), the engine RPM can be set lower than the RPM set by the AEC "Stage 2" setting. When normal operations resume, the engine RPM will return to match the Engine Speed Dial 2 setting.

The operational condition of the machine is detected by the implement pressure switches of the joystick and the travel switch of the travel pedal .

Using the One-Touch Low Idle Feature

The one-touch low idle feature will activate during all "stopped" conditions of the implement, swing, travel, and tools. However, when the "One-Touch Low Idle" switch is pressed, the control will lower the engine speed. The speed is reduced to a speed dial setting of 2 or approximately 1100 rpm. This control overrides the AEC.

Release of the One-Touch Low Idle

The one-touch low idle switch will be released when any of the following conditions occur:

  • The one-touch low idle switch is pressed again.

  • The implement swing pressure sensor is set to the ON position.

  • A travel pressure switch is set to the ON position.

  • A pressure switch that is related to a tool is set to the ON position.

  • An increase in pump pressure sensed by the pump pressure sensors.

The engine RPM is different after the switch has been released. The different speed will depend on the conditions of the release.

  1. The engine RPM matches the engine speed dial setting when the one-touch low idle feature is released by operating an implement or tool.

  2. The engine RPM is set by the AEC when the one-touch low idle switch is used to release the one-touch low idle function. The engine RPM will be affected by the following conditions:

    1. When the AEC "Stage 1" is selected, engine RPM will be set to the AEC "Stage 1" setting. That setting is approximately 100 RPM lower than the current setting of the engine speed dial RPM.

    2. When the AEC "Stage 2" is selected, engine RPM will be set to the AEC "Stage 1" setting. That setting is approximately 1100 RPM.

    3. Engine RPM matches the RPM of current engine speed dial settings, when engine RPM is lower than the AEC "Stage 2" setting. The setting of this RPM is not based on a setting of the AEC function.

Engine Speed Protection

Engine Idle Shutdown



Illustration 6g03034656
(1) Machine ECM
(2) Monitor
(4) Engine ECM
(6) Pump 1 Pressure Sensor
(7) Pump 2 Pressure Sensor
(8) Implement Pressure Switch
(9) One-Touch Low Idle Switch
(10) Key Switch
(11) Hydraulic Lock Solenoid

The Engine Idle Shutdown function stops the engine automatically when the machine has been idle for longer than the set time. Before the engine stops, a warning message will be displayed on the Messenger.

Pump Torque Control



Illustration 7g06019129
(1) Machine ECM
(2) Monitor
(5) Switch Panel
(6) Pump 1 Pressure Sensor
(7) Pump 2 Pressure Sensor
(12) Travel Pressure Switch
(13) Negative Flow Control 1 Pressure Sensor
(14) Negative Flow Control 2 Pressure Sensor
(15) Power Shift Pressure PRV

The pump regulators are controlled by the electronic control system. The machine ECM continually monitors various inputs. The machine ECM sends a pulse width modulated (PWM) driver to the proportional reducing valve on the pump regulators. Proportional reducing valve controls the output flow of the pump by changing the hydraulic signal pressure that flows to the actuator piston in the pump regulators.

The machine ECM controls the PWM driver sent to the PRV and determines the required pump flow based off the following inputs.

Desired engine speed - Determined by the engine speed dial.

Actual engine speed - Determined by the engine speed pickup.

Drive pump delivery pressure - The drive pump delivery pressure is measured by the drive pump pressure sensor located on the main control valve.

Idler pump delivery pressure - The Idler pump delivery pressure is measured by the idler pump pressure sensor located on the main control valve.

Negative flow control pressure - Determined by the drive pump pressure sensor and the idler pump pressure sensor.

Integrated Engine and Pump Power Management Control

The integrated engine and pump power management control is a suite of software programs loaded into the engine ECM and machine ECM. This power management control performs the function of coordinating hydraulic power demands with engine power production. The machine ECM monitors the position of the joystick which corresponds to operator requests for hydraulic power. The machine ECM communicates with the engine ECM to control the flow of fuel to the injectors in coordination with changes in power demands from the various machine systems. The engine output power is matched to the sum of all power loads to ideally provide zero engine speed acceleration or deceleration. The steady-state control output can be attained nearly instantaneously using the CAN Datalink connection between the machine ECM and engine ECM.

Antistall Function

The output of the engine will decrease when inferior fuel is used to operate the machine or when the machine is operated at high altitudes. When the engine output decreases, the engine speed will drop during operation.

When the engine speed is decreased by more than 250 rpm below the rpm for a “no load” condition at a given "Engine Speed Dial" setting, the power shift pressure is increased in order to reduce the load on the pump.

Boom Down Engine Speed Control

The boom down engine speed limits the speed of the engine when the boom is moving down. This function improves the overall fuel efficiency of the machine. The engine speed is reduced to a value that is less than the setting of the engine speed dial.

The boom lowering operation is detected by the boom lowering pilot pressure sensor and the negative flow control pressure.

When boom lowering is operated only, the engine speed is reduced according to the machine ECM parameters. When boom lowering is operated with other actuators, the engine speed is reduced according to the flow limitation pressure (NFC) sensors.

Automatic Travel Speed Change Function



Illustration 8g06019130
(1) Machine ECM
(5) Switch Panel
(6) Pump 1 Pressure Sensor
(16) Travel Speed Solenoid


Illustration 9g02627402
The location of the switch that is used to control the travel speed of the machine.

There are two modes of travel for the machine. The modes are "Tortoise" and "Rabbit". The control for the travel speed is located on the touch pad that is located to the right of the operator. The panel includes an indicator in order to display the speed function that is active. When the main pump pressure is low, the travel speed is automatically increased to high speed. When the main pump pressure is high and the selected travel speed is high, the travel speed is automatically switched to low speed. When the travel speed is set to Tortoise, the travel speed is fixed at the low speed (no change).

Keep Alive Circuit



Illustration 10g06025378
Schematic of the keep alive circuit

The keep alive circuit isolates the battery power from the rest of the system to ensure completion of the purge cycle.

The DEF Dosing Control Unit (DCU) communicates with the Engine ECM through the CAN C data link. The DCU monitors and controls the injection of the DEF into the exhaust stream.

When the disconnect switch is closed, the negative side of the battery is grounded and machine electrical power is available. The Engine ECM supplies power to the DCU power relay, which closes and transfers power to the keep alive relay. When the keep alive relay and normally close relay are closed, an alternate ground path is provided for the negative side of the battery.

When the disconnect switch is opened before the purge cycle is complete, the alternate ground path provided by the keep alive relay and normally close relay allows the auxiliary circuit to complete the electrical path to ground, and the DEF purge cycle continues.

When the key switch is turned to the On position, the normally close relay opens. When the normally close relay is opened, the circuit does not provide an alternate ground path for the negative side of the battery.

When the purge cycle is complete the DCU sends a signal to the Engine ECM, which de-energizes the DCU power relay. With the DCU power relay open, the auxiliary circuit is open and power is removed.

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