169Service Manual – SC5000 30 - Solution System
EcoFlex Option
Machines that have the EcoFlex option have on-board detergent mixing using a pump-driven detergent
injection system. The detergent is stored in the removable detergent tank below the operator’s seat, which
has a suction hose from the detergent pump. The detergent pump draws the liquid from the detergent tank
and injects it into the solution line before the solution solenoid. The ow rate of the detergent is controlled by
the Main Machine Controller using PWM.
The detergent pump uses a solenoid-driven
diaphragm with one-way check valves. As
the solenoid oscillates in and out, it drives
a exible diaphragm that draws uid in
during the retraction stroke, and drives uid
out during the compression/extended stroke.
The check valves allow uid to enter only
though the inlet port, and exit only through
the outlet port.
Unlike an AC solenoid that moves its
plunger the same direction regardless of the
electrical polarity, a DC solenoid changes
its direction of travel depending on the
electrical polarity of the coil. Even though
the EcoFlex pump uses a DC solenoid, it still
contains a mechanical return spring to return the plunger to its relaxed (extended) state when no power is
present.
In the forward-bias direction, with positive-to-positive and negative-to-negative, as shown above; the
solenoid plunger retracts away from the diaphragm. This results in a suction at the inlet port, and uid is
drawn into the cavity caused by the diaphragm.
If voltage is simply removed at this point, the return spring will passively push the plunger forward, and
the spring pressure will push the uid out of the outlet port. However, if the solenoid is reverse-biased with
positive-to-negative and negative-to-positive, the plunger is actively pushed forward with a greater force
than what the spring alone can impart. Because this is the compression stroke of the diaphragm, the pump
can pump faster/harder against any resistance of the outlet tubing. This active-return also permits the pump
to operate at a higher PWM frequency for higher ow rates.
Pulse Train
The actual pulse train to the solenoid consists of a long
duration Off signal, followed by a rapid Positive voltage,
followed immediately by a rapid Negative voltage, and back
to the long duration Off. Because the pulse train is a rapid
off/plus/minus/off, the polarity of the pump’s connection is
still important to proper operation. If polarity was reversed
(off/minus/plus/off), the initial pulse would have no effect on
the plunger position, because it is already in the extended
(relaxed) position due to the return spring.
Therefore, reversing the polarity of the pump wires will not
show any outward sign of an error, but the volume of the
detergent may be slightly diminished from normal.
Outlet
Inlet
Pos
Neg
Diaphragm
Solenoid
+12V
-12V
RetractedRetracted
0V
Extended
ExtendedExtended
Extended
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