Section 9. Theory of Operation Toyota Orderpicker Model 7BPUE 15 Service Manual

Travel Travel General

When the potentiometer voltage increases or decreases from the neutral deadband, the steer/tractor manager sends a travel request for direction (TF/FORWARD or FF/REVERSE) and speed (TRAVEL REQ) to the traction power amplifier. The voltage from the steer/tractor manager is directly related to the speed request. As the input request changes, the travel request voltage to the traction power amplifier mirrors the change.

When a change in direction is requested, the steer/tractor manager changes the direction request to the traction power amplifier and changes the speed request output (TRAVEL REQ) to reflect the requested plugging strength.

Movin Directional/Speed 7Contro

See the schematic in Figure 9 - 5 on page 9 - 24. (The electrical schematic legend is on page 9 - 2.)

NOTE: The current flowing through the drive motor armature and field windings are controlled independently of each other by the traction power amplifier.

1. When the throttle is moved to the forward position (tractor - first), the wiper in the variable resistor (VR-1) is moved so that the voltage output decreases. The carriage manager, sensing this decrease in voltage, sends a communication message over the transmit line to the tractor manager. The tractor manager interprets this as a request for travel in the forward direction and causes the following to occur:

NOTE: For clarity and simplification, only circuits directly related to vehicle travel will be traced on the remaining operation of the travel system diagram. All are with respect to (WRT)TP4 (B-).

2. The TF/FORWARD line to the traction power amplifier is activated (driven to about 19VDC).This is the input to the traction power amplifier which will determine the drive motor field polarity to enable travel in the forward direction.

3. The traction power amplifier will then drive its internal field control transistors to turn the drive motor in the correct direction.

4. Simultaneously an analog voltage, which represents and is proportional to the throttle command, is outputted from the steer tractor manager and sent to the traction power amplifier. This voltage (TRAVEL REQ) ranges from 0 to about +4.25 VDC depending on throttle input WRT TRAVEL REF. Based on this, the TPA will control the strength of the field and armature to obtain the proper travel speed in the appropriate amount of time. The higher the voltage the faster the TPA will make the truck travel.

NOTE: Travel speed is limited until the operator requests steering and the steer/tractor manager detects the request.

5. The TRAVEL REQ voltage is used by the traction power amplifier to drive the armature and field transistors to meet the throttle request. The armature transistor is, in effect, connecting terminal M- to B(in varying amounts) allowing current to flow through the drive motor armature. The traction power amplifier will also drive its internal field transistors which, in turn, will control the amount and direction of flow through the drive motor field winding. When a plug is requested, the steer/tractor manager changes the direction request to the traction power amplifier and changes the speed request output (TRAVEL REQ) to reflect the requested plugging strength. Current now flows from B+ through:

FU3

Drive motor armature

M-

B- (TP4)

To battery negative

6. During operation, the traction power amplifier monitors for:

Armature current*

Field current*

M- shorted to B-*

Battery under/over voltage: Less than +16 volts cuts down the output from the TPA and limits travel speed. Greater than +45 volts places the controller in a shut down condition

Under/over temperature: Over temperature of the traction power amplifier is 85 C (185 F) and above. Overheating is unusual, but can occur if the traction power amplifier is installed incorrectly or overloaded. At over temperature, the drive current limit is linearly decreased from full set current limit down to zero. Plugging current is not reduced by any thermal conditions to allow full plugging strength at all times. When the traction amplifier is operating at less than -25 C (- 13 F), the current limit is cut back resulting in reduced travel speed and acceleration.

"Disables PC contactor through PC DRniTE line. When the PC DRniTE line goes to 5 volts the PC opens and the STM tells the CM to display a code 2,2