PM-201 Cold Planer Machine Systems Caterpillar

Location of Components (Steering System)

Usage:

Electrical Components

Circuit Breaker Panel

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Illustration 1	g01231971
Under the Right Side of the Instrument Panel (1) Circuit breaker "CB2"

Note: The rear steering solenoids are located on the rear manifold. For additional information about the rear manifold, refer to the auxiliary hydraulic system in this module.

The circuit breaker panel is located in a compartment under the instrument panel. Decals near each circuit breaker identify the function of the circuit breaker. Circuit breaker "CB2" (1) is the only circuit breaker which is part of the steering system.

Circuit breaker "CB2" (1) receives power when the main power relay is energized.

In the steering system, circuit breaker "CB2" distributes power to the following locations:

Contact "A" of the steering mode sensor
Contact "A" of the front track position sensor
Contact "A" of the rear track position sensor
Terminal "1" of the machine ECM

Machine ECM

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Illustration 2	g01231972
Under the Right Side of the Instrument Panel (2) Machine ECM (3) LED display (4) Forty pin connector

Machine ECM (2) is a model MPC-10. This unit is located inside the compartment, under the right side of the instrument panel. The machine ECM has single 40 pin connector (4). The 40 pin connector receives input signals from sensors around the machine which monitor current operating conditions. System software compares the gathered input to information already stored in the machine ECM's memory. The software evaluates the current conditions. The software then generates an output signal which controls the rear steering of the machine within set parameters.

The machine ECM has a self-diagnostic capability which assists in troubleshooting. The unit operates in one of three modes: mode 0, mode 1 and mode 2. Mode 0 is the operate mode. Mode 1 is the service mode. Mode 2 is the calibration mode.

The right side of LED display (3) on machine ECM (2) contains three indicators. The top indicator is the fault present indicator. The red fault present indicator illuminates when the machine ECM detects a fault in one of the input or output signals. The middle indicator is the calibrate mode indicator. The yellow calibrate mode indicator illuminates when the machine ECM is in mode 2. The bottom indicator is the power indicator. The green power indicator illuminates when the machine ECM receives electrical power.

When power is provided to machine ECM (2), the unit performs a self test. During the test, the number 888 flashes in LED display (3), and all three indicators illuminate. This is followed by the software version number, then " -0-". The "-0-" indicates that the machine ECM is in mode 0. After the self test is complete, if no faults are present, the LED displays the letter "P" followed by two dashes. The "P" followed by the two dashes remains on the LED until the power source is removed, or until the machine ECM mode is changed.

Note: If the machine ECM is faulty, the fault present indicator will flash, but the LED will not display a fault.

Machine ECM Connector

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Illustration 3	g01231973

This illustration shows the 40 pin connector of the machine ECM. Input to the machine ECM are indicated by arrows which point toward the connector. Outputs from the machine ECM are indicated by arrows which point away from the connector. The machine ECM receives power at terminal "1". The unit is grounded at terminal "2".

The control functions of the machine ECM system can be divided into the following five groups:

Propel control
Load control
Steering control
Rotor control
Water spray control

In order to control the rear steering system, the machine ECM gathers input from the following components:

Front track position sensor (terminal "3")
Rear track position sensor (terminal "4")
Rear service door switch (terminal "16" and terminal "17")
Rear steering switches (terminal "21" and terminal "24")
Steering mode sensor (terminal "29")

The software analyzes the input and determines whether an output signal should be sent to the left steering solenoid (terminal "33") or to the right steering solenoid (terminal "34").

Steering Mode Sensor

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Illustration 4	g01231974
Under the Instrument Panel (5) Detent block (6) Steering mode sensor

Steering mode sensor (6) is located under the instrument panel. The instrument panel can be tilted in order to access this component.

The steering mode switch that is on the instrument panel is connected to detent block (5). The detent block provides positive stops for each of the positions of the steering mode switch. The output shaft of the detent block controls steering mode sensor (6) .

Contact "A" of steering mode sensor (6) receives power from circuit breaker "CB2" (1). Contact "B" of the sensor is grounded at terminal "39" of machine ECM (2). Contact "C" of the steering mode sensor provides a pulse width modulated signal to terminal "29" of the machine ECM. The machine ECM analyzes the duty cycle of the input signal from the sensor in order to determine the desired steering mode. The duty cycle increases as the steering mode switch is rotated clockwise.

Front Steering Position Sensor

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Illustration 5	g01231975
Front Right Side of Machine (7) Front steering sensor (8) Spring loaded rod (9) Bolt

Front steering position sensor (7) is located on the right front leg tower. The rear steering position sensor (not shown) is located on the right rear leg tower. A cover must be removed in order to access each steering position sensor.

Front steering sensor (7) and rear steering sensor (not shown) are identical. The sensors are pulse width modulated sensors. Spring loaded rod (8) is attached to each sensor. The rod follows bolt (9) which is attached to the steering knuckle. The position of the rod determines the duty cycle of the steering position sensor.

Contact "A" of front steering sensor (7) receives power from circuit breaker "CB2" (1). Contact "B" of the sensor is grounded at terminal "39" of machine ECM (2). Contact "C" of the front steering sensor provides a pulse width modulated signal to terminal "3" of the machine ECM. The machine ECM analyzes the duty cycle of the input signal from the sensor in order to determine the position of the front track. The duty cycle increases as the sensor is rotated from the full left position to the full right position.

Contact "A" of the rear steering sensor (not shown) receives power from circuit breaker "CB2" (1). Contact "B" of the sensor is grounded at terminal "39" of machine ECM (2). Contact "C" of the rear steering sensor provides a pulse width modulated signal to terminal "4" of the machine ECM. The machine ECM analyzes the duty cycle of the input signal from the sensor in order to determine the position of the rear track. The duty cycle increases as the sensor is rotated from the full left position to the full right position.

Note: Calibration of the steering sensors is critical for the steering system to operate properly. Both the front steering sensor and the rear sensor are calibrated in the following positions: straight travel position, full right position and full left position. A properly calibrated straight travel position is especially critical while the machine is being operated in a straight cut. Improperly calibrated sensors may cause the rotor to crowd in to one side of the cut. This effect is known as "dog tracking". If dog tracking occurs, the crowded side of the cut will appear shiny, and that side of the rotor will show increased wear.

Location of Hydraulic Components

Base of Steering Wheel

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Illustration 6	g01232074
Base of Steering Wheel (10) Steering wheel control unit

Steering control unit (10) is located at the base of each steering wheel. The compartment under each steering wheel provides access to the steering control unit.

Filtered oil from the auxiliary pump flows to steering control unit (10). The steering control unit consists of a steering control spool and a metering pump. The steering control spool is a sleeve type rotary valve which is spring centered. The metering pump is a gerotor pump. The control spool governs the direction of the turn. The metering pump controls the rate of the turn.

Steering Unit Relief Valves

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Illustration 7	g01232075
Compartment Under the Right Steering Wheel (11) Relief valve block (12) Relief valve (rod end) (13) Relief valve (head end)

The front steering circuit contains single relief valve block (11). This block contains two relief valves. The compartment under the right steering wheel provides access to the relief valves.

The line to the rod end of the front steering cylinder and the line to the head end of the front steering cylinder each contain a relief valve. Relief valve (12) in the line to the rod end of the steering cylinder opens at 18630 kPa (2700 psi). Relief valve (13) in the line to the head end of the steering cylinder opens at 13800 kPa (2000 psi).

The difference in relief valve settings is due to the difference in the effective area between the rod end of the cylinder and the head end of the cylinder. This difference ensures that the maximum steering force is equal in both directions.