M313C, M315C, M316C, M318C, M318C MH, M322C and M322C MH Excavators Electronic System Travel Activation Function Caterpillar

Illustration 1	g01150701
Travel activation function block diagram

Illustration 2	g01150716
ECM connections for components involved for the travel activation function for machines in the following serial number ranges: BDR1-2000, BDM1-2000, BDX1-2000, BCZ1-2000, BDK1-2000, BDY1-2000 and BEB1-2000.

Illustration 3	g01150719
ECM connections for components involved for the travel activation function for machines in the following serial number ranges: BDR2001-UP, BDM2001-UP, BDX2001-UP, BCZ2001-UP, BDK2001-UP, BDY2001-UP, BEB2001-UP, H2A1-UP, H2B1-UP, H2C1-UP, H2D1-UP, H2E1-UP, H2F1-UP and H2G1-UP.

The ECM can enable or disable the travel function by controlling the state of the proportional solenoid for the travel pilot hydraulic circuit. In order for the ECM to enable the travel function, the following conditions must be met:

• The parking brake is OFF.

• The left armrest is DOWN.

• The signal from the transmission pilot pressure sensor (transmission clutch) indicates that the hydraulic pressure is within the correct range.

• The service brake pedal is unlocked. The machine ECM monitors the state of the service brake pedal limit switch in order to determine if the service brake pedal is depressed.

When above conditions are correct and a travel command is initiated by pressing the travel pedal, the ECM will energize the travel activation / travel pilot pressure solenoid.

If any of the required conditions change, the ECM will disable the travel activation / travel pilot pressure solenoid. If a diagnostic code becomes active for the armrest position switch, the brake pedal limit switch or the transmission pressure sensor, the ECM will disable the travel activation / travel pilot pressure solenoid.

Travel Pedal Operation

Machines that are equipped with the travel activation solenoid (see illustration for S/N's) are fitted with a limit switch that indicates an actuated / not actuated signal to the ECM in order to indicate the direction of travel. Machines that are equipped with the travel pilot pressure solenoid (see illustration for S/N's) are equipped with a position sensor on the travel pedal. The operation of this sensor is detailed in the following text.

Illustration 4	g01151695
Pedal position sensor block diagram

Illustration 5	g01151754
Pedal position sensor schematic

The travel pedal is mechanically connected to the pilot hydraulic system. When the pedal is depressed, this mechanical connection actuates the pilot valve in order to enable travel. The travel pedal position sensor sends an analogue signal to the ECM. The ECM interprets this voltage signal as a specific pedal position. The ECM uses this information along with information from other sensors and system parameters to determine the output current for the travel motor swash plate angle limit solenoid. This solenoid will control the output of the travel motor. The position sensor allows the speed of the machine to be varied within the select speed range according to the position of the travel pedal.

Position Sensor Auto-Calibration And Operation

The analog position signal that is sent to the ECM is calibrated automatically by the ECM every time that the key switch is turned to the ON position. An allowable "zero position" for the pedal is set as a default in the ECM based on where the pedal is expected to be at rest, when there is not pressure of any kind on the pedal. When the rear section of the pedal is completely depressed, the ECM will interpret the signal received as a maximum reverse travel direction command or -100%. When the forward section of the pedal is completely depressed, the ECM will interpret the signal received as a maximum forward travel direction command or +100%. The ECM will interpret the first 20% of pedal travel in either the forward or the backward direction as a 0% command. The ECM will interpret 80% of pedal travel in either direction as a 100% command, consequently, the ECM sees 80% pedal travel in either direction as either a -100% or +100% command. The analogue voltage values for these three positions are shown in Table 1.

When the key switch is turned to the ON position, the ECM reads the voltage signal from the sensor. If this voltage is within the allowable zero range, then that voltage will become the zero position for the duration of the key switch ON cycle. If the voltage is not within the allowable zero position range, then the ECM will assume that the pedal is pressed and will use the last known zero position voltage for the current zero position voltage.

During machine operation, as the travel pedal is depressed further in either direction, the voltage signal to the ECM will result in an increased current output to the travel motor swash plate angle limit solenoid when the other conditions are correct. This will cause increased travel speed for the machine.