Lift/Lower - Toyota 7BPUE15 Service Manual

Section 9. Theory of Operation
The lift button commands the carriage to lift.
When the lift button is pressed, the lift/lower
proportional solenoid valve (normally open)
stays open while the lift contactor closes. After
the contactor closes and the lift pump motor
turns on, the proportional solenoid valve ramps
closed which forces hydraulic fluid into the
cylinders and increases lift speed. The
proportional solenoid valve provides a smooth
transition between zero speed lift and full speed
lift and back to zero speed lift. When the lift
button is released, the proportional solenoid
opens and the lift contactor opens turning off
the lift pump motor. During lift, the load
holding solenoid valve remains closed
.
(de-energized)
The microprocessor on the steer/tractor
manager verifies the lift contactor remains
closed when commanded closed, and open
when commanded open. If either condition is
not met, the steer/tractor manager generates a
fault code.
See Figure 9-9 on page 9-36. (The electrical
schematic legend is on page 9-2.)
1. As the control handle lift switch is closed,
a digital ground is applied to JPC13-6 on
the carriage manager.
2. The carriage manager sends a lift
command message to the steer/tractor
manager over the transmit/receive lines.
3. The steer/tractor manager provides the
negative potential for the lift pump
contactor coil (JPT12- 18) and the pump
contactor coil is energized. The lift pump
contactor LED (IL6-5) on the steer/tractor
manager indicates the pump contactor coil
driver is energized. See Figure 9-8 on
page 9-35.
4. When the lift pump contactor coil is
energized, the lift pump contactor tips
close supplying B+ to the lift pump motor.
5. The steer/tractor manager provides the
negative potential for the lift/lower
Toyota Orderpicker Model 7BPUE 15 Service Manual
proportional solenoid valve coil a t
LED
ramp closed (this valve is normally open).
See Figure 9-8 on page 9-35.
6. The lift pump/motor assembly is now
running and supplying hydraulic pressure
and flow to the lift cylinders.
See Figure 9- 10.
00700-CL222-05, 1 5 March 2005