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Machine General Information | |
The propel control system contains an electrical portion, a hydraulic portion, and a mechanical portion. The electrical portion is made up of electronic control modules (ECMs) and input and output devices. The hydraulic and mechanical portions of the propel system differ slightly depending upon the undercarriage configuration.
The hydraulic portion of the propel control system consists of two closed-circuit hydrostatic drive loops. In each hydrostatic drive loop, the ECMs on the machine control a variable-displacement propel pump.
Each propels pump drives a two-speed propel motor. Each motor drives a single speed planetary final drive. The final drives transfer power from the propel motors to the wheels.
The planetary final drives have spring-applied, hydraulically released parking brakes. The auxiliary hydraulic pump supplies oil to release the brakes. The ECMs on the machine control the engagement of the parking brake and the shifting of the machine.
The electronic control system monitors the machine and monitors engine operating conditions. The ECMs on the machine, the screed, and the engine communicate through controller area network (CAN) lines.
The control system determines if an output signal should be sent to the pump solenoids. During normal operation, the propel system is controlled through closed-loop logic. The system prevents the machine from moving under the following conditions:
- The propel lever is out of the NEUTRAL position when the machine is started.
- The parking brake status is set to "engaged"
- The propel lever is in theNEUTRAL
- The propel speed dial status is set to "0", and the propel mode status is set to "pave", "maneuver", or "travel".
- The decelerator pedal (optional) is fully depressed.
- A fault is detected in a circuit to any of the following components: propel solenoid, propel lever, steering sensor, or parking brake solenoid.
- The machine is in a runaway condition, in a rollback condition, or uncommanded machine movement has been detected.
The electronic control system is also programmed with underspeed control logic. The underspeed control logic automatically adjusts the machine speed during low engine speed conditions to prevent the engine from stalling.
The machine can be equipped with an optional front-wheel assist system. This feature can power the front wheels only while the machine is operating in the pave mode. The front-wheel assist system provides added traction when the machine is pushing trucks or working on soft base.
The front-wheel assist system can be either four-wheel drive or all-wheel drive. In the four-wheel drive system, two of the front wheels are equipped with hydraulic motors. In the all-wheel drive system, each front wheel is equipped with a hydraulic motor.