318F Excavator Machine Systems Electronic Control (Travel System) Caterpillar


Electronic Control (Travel System)
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1.1. Electronic Control Module (ECM)
2.1. Pin Locations
3.1. Inputs
4.2. Sensors
5.3. Low Pressure Sensors
6.3. Negative Flow Control Pressure Sensors
7.3. High Pressure Sensors
8.3. Drive Pump Pressure Sensor and Idler Pump Pressure Sensor
9.2. Switches
10.3. Pressure Switch
11.3. Left Travel Pressure Switch and Right Travel Pressure Switch
12.1. Outputs
13.2. On/Off Solenoids
14.3. Travel Speed Solenoid
15.3. Hydraulic Lock Solenoid
16.4. High Pressure Change Solenoid
17.2. Proportional Reducing Solenoid Valve
18.3. Power Shift Pressure PRV
19.3. Negative Flow Control 1 Limit PRV and Negative Flow Control 2 Limit PRV
20.1. Data Link
21.2. Cat Data Link
22.2. CAN Data Link
23.1. Travel Alarm

Electronic Control Module (ECM)



Illustration 1g02612416
Machine ECM
(1) Controller
(2) J1 Connector
(3) J2 Connector


Illustration 2g02613001
Connectors of Machine ECM
(2) J1 Connector
(3) J2 Connector

The output from the Machine ECM is based on input information from the sensors. The output commands are based on the software programmed into the control module. After the Machine ECM receives the input information, the ECM sends a corresponding response to the outputs. The inputs and outputs of the ECM are connected to the machine harness by two 54-pin connectors (J1 and J2). The inputs and outputs to the ECM can be viewed through the AVSpare Electronic Technician (Cat ET). Input and output information can also be viewed using the Operator Monitor.

The ECM also communicates with sensors and other control modules via the CAN Data Link. The data link is bi-directional, allowing the Machine ECM to both receive and send information with the Engine ECM. The Machine ECM also communicates to input and output components that are directly connected to the Switch Panel. The Switch Panel is used to link input and output components to the Machine ECM via the CAN Data Link.

Note: Only the complete ECM is serviced (no lower levels components). The ECM must be replaced if the ECM is damaged. Replace the ECM if a failure is diagnosed.

Pin Locations

The Cat Data Link is used to provide a connection for the service tool for troubleshooting, testing, and calibrations. The data link is bidirectional. The data link allows the ECM to receive information. The data link also allows the ECM to send information.

Table 1
Machine ECM Connector J1 Contact Descriptions(1) 
No.  Type  Pin Description 
Power  +Battery 
Ground  Ground 
25  Output  Travel Speed Change Solenoid 
27  Power  Power Supply for Sensor (8V) 
29  Input  Left Travel Pressure Switch 
30  Input  Right Travel Pressure Switch 
48  Input  Negative Flow Control 1 Pressure Sensor 
49  Input  Negative Flow Control 2 Pressure Sensor 
53  Input  Drive Pump Pressure Sensor 
54  Input  Idler Pump Pressure Sensor 
(1) Contacts that are not listed are not used.

Table 2
Machine ECM Connector J2 Contact Descriptions(1) 
No.  Type  Pin Description 
Output  Power Shift Pressure EPRV 
21  Ground  PRV Return 
22  Ground  PRV Return 
27  Input  Hydraulic Lock Cancel Switch 
28  Output  High Pressure Change Solenoid 
43  Output  Negative Flow Control 2 Limit EPRV 
47  Input/Output  CAN (J1939) Data Link + 
48  Input/Output  CAN (J1939) Data Link - 
50  Input/Output  Machine CAN Data Link + 
51  Input/Output  Machine CAN Data Link - 
53  Output  Negative Flow Control 1 Limit EPRV 


Illustration 3g02655338
Underside of Soft Switch Panel

Table 3
Switch Panel Connector J3 Contact Descriptions(1) 
No.  Type  Pin Description 
Power  +Battery 
Ground  Ground 
12  Output  Travel Alarm 

Inputs

The inputs describe the status of the machine systems. Two types of inputs exist. The inputs can be either a switch type or a sensor type. Switches provide an open, a ground, or a + battery signal to the inputs of the controller. Sensors (frequency, PWM, or voltage) provide a changing signal to the sensor inputs of the controller. The controller will recognize the following types of sensor signals:

Frequency - The sensor will produce an AC signal (sine wave or square wave) that varies in frequency (Hz) as the condition changes.

Pulse Width Modulated - The sensor produces a digital signal and varies the duty cycle as the condition changes. The frequency of the signal will remain constant.

In some cases the operator is provided a manual switch that can be used to change a condition of the machine.

Sensors

Low Pressure Sensors



Illustration 4g02263393

Note: The values in Table 4 are for bench testing only. Values may not represent parameters for machine systems specifications.

Table 4
Operating pressure  10 MPa 
Supply Voltage  +7V ~ +14V 
Output signal  500 ± 100 Hz (PWM) 
Output range  5% ~ 95% 

Negative Flow Control Pressure Sensors

The negative flow control (NFC) pressure sensors for the drive pump and idler pump are inputs to the machine ECM. The machine ECM uses this pressure information to determine the hydraulic demand requested by the operator. The machine ECM then sends a PWM driver to the NFC solenoids to control the pump flow rate.

The NFC pressure sensors are located on the top on the main control valve in the end plate.

For more information on the NFC pressure sensors, refer to Systems Operation, "Negative Flow Control System".

High Pressure Sensors



Illustration 5g02263513

Note: The values in Table 5 are for bench testing only. Values may not represent parameters for machine systems specifications.

Table 5
Operating Pressure  50 MPa 
Supply Voltage  +7V ~ +14V 
Output Signal  500 ± 100 Hz (PWM) 
Output Range  5% ~ 95% 

Drive Pump Pressure Sensor and Idler Pump Pressure Sensor

The drive pump pressure sensor and idler pump pressure sensors are inputs to the machine ECM. The drive pump and idler pump pressure sensors are located on the main control valve. The drive pump pressure sensor monitors the pressure of the drive pump oil in the front half of the main control valve high-pressure passages. The idler pump pressure sensor monitors the idler pump oil pressure in the rear half of the main control valve high-pressure passages.

The pressure sensors send a pulse width modulated (PWM) input to the machine ECM. This pressure information is used for pump control and travel speed.

Switches

Pressure Switch



Illustration 6g02332474

Note: The values in Table 6 are for bench testing only. Values may not represent parameters for machine systems specifications.

Table 6
Activation Pressure  490 ± 49 kPa (71 ± 7 psi) 
Deactivation Pressure  294 kPa (43 psi) MIN 
Rating  + 12V ~ +32V
0.01 Amp to 1 Amp 
Pressure Range  0 to 10 MPa 

Left Travel Pressure Switch and Right Travel Pressure Switch

The left travel pressure switch and right travel pressure switch detects a travel operation. The travel pressure switches send an input signal to the machine ECM. The machine ECM uses the switch information to control the engine speed and pump control.

Outputs

The ECM responds to decisions by sending electrical signals to the outputs. The outputs can create an action or the outputs can provide information to the operator or the service technician.

On/Off Solenoids



Illustration 7g01158530

Note: The values in Table 7 are for bench testing only. Values may not represent parameters for machine systems specifications.

Table 7
Rated Voltage  24 VDC 
Coil Resistance  41.5 ± 2.0Ω (T=20° C) 

Travel Speed Solenoid

The travel speed solenoid is an output of the Machine ECM. When the travel speed solenoid is active, the machine can travel at high speed. The travel speed solenoid is active when the travel speed mode switch is set to "RABBIT (high)" mode. The travel speed also depends on the delivery pressure of the main pump. If the delivery pressure of the main pump is high, the travel speed solenoid is de-energized. When the delivery pressure of the main pump is low, the travel speed solenoid is energized.

Hydraulic Lock Solenoid

The hydraulic lock solenoid is an output of the Machine ECM. The hydraulic lock solenoid is energized in order to enable the primary hydraulic pressure. The hydraulic lock solenoid is de-energized in order to disable the primary hydraulic pressure.

This solenoid is activated while the key switch is in the ON position and the hydraulic lock lever is in the UNLOCK position.

The high-pressure change solenoid is an output of the Machine ECM. The high-pressure change solenoid is energized in order to increase the main hydraulic system pressure. The Machine ECM energizes the solenoid during a boom UP operation when the head end cylinder pressure is high or a travel operation only.

Proportional Reducing Solenoid Valve



Illustration 8g02703776

Note: The values in Table 8 are for bench testing only. Values may not represent parameters for machine systems specifications.

Table 8
Current Range  0 mA ~ 700 mA 
Coil Resistance  15.0 ± 0.7Ω (T=20° C) 

Power Shift Pressure PRV

The power shift pressure PRV is used to destroke the main pump under load to maintain engine speed. The main functions of the PRV, in conjunction with, the monitoring system, are listed below:

  • The PRV manages the transfer to engine power into hydraulic power as needed.

  • The system control the output of the pump according to the workload, improving fuel efficiency.

Negative Flow Control 1 Limit PRV and Negative Flow Control 2 Limit PRV

Two proportional reducing valves for negative flow control are used to control the amount of NFC signal to the pump regulators. The machine ECM receives various input signals to control the flow limitation from the main hydraulic pumps. When the NFC valves are energized by the machine ECM, pilot oil pressure is directed to the main hydraulic pump regulators from the pilot manifold. The pilot oil pressure causes the hydraulic pumps to destroke which reduces hydraulic oil flow.

Data Link

Cat Data Link

The Cat Data Link is an input/output of the ECM. The data link uses the connector for the service port in order to communicate with the AVSpare Electronic Technician. A data link connection is provided for the product link.

Note: The control for the product link provides a global positioning system for the machine.

The data link is bidirectional. The bidirectional link allows the ECM to input information and output information. The data link consists of the following parts: internal ECM circuits, the related harness wiring, the service tool connector and the connector for the product link. The Cat Data Link connects to the ECM at contact J2-16 (wire 892-BR(Brown)) and contact J2-25 (wire 893-GN(Green)).

  • The ECM receives commands from the Cat ET in order to change the operating modes. The Cat ET will read the service codes that are stored in the memory of the ECM. The Cat ET will clear the service codes that are stored in the memory of the ECM.

  • The ECM sends the input and the output information to the AVSpare ET.

CAN Data Link

A Controller Area Network (CAN) Data Link allows communication between the Machine ECM, Engine ECM, and the input and output devices of the switch panel. The CAN Data Link allows for bi-directional electronic signals to be passed among the controllers and the switch panel. The data link allows the Machine ECM to be connected to sensors and actuators connected to the switch panel. The Machine ECM can also use the data link to communicate engine speed and/or torque requirements to the Engine ECM.

Travel Alarm

The travel alarm SOUNDS in order to alert the area that the machine is moving. The travel alarm is activated by the machine ECM whenever the travel levers/pedals are moved.

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