Toro 41188, Service Manual

Page: 59 / 353

Multi Pro 1750 Hydraulic System Page 4 − 11
Steering Circuit
A single section gear pump supplies hydraulic flow to the
steering control valve, steering cylinder and spray boom
lift cylinders. The gear pump is directly coupled to the
engine and takes its suction from the transaxle. When
the ignition is switched to the ON position, the hydraulics
enable valve is energized, allowing hydraulic fluid flow
from the gear pump to the remainder of the hydraulic
system. When the ignition is switched to the OFF posi-
tion, the hydraulics enable valve closes and decreases
the time required for the engine and gear pump to stop
turning.
Hydraulic circuit pressure is limited to 1000 PSI (69 bar)
by a relief valve located in the gear pump. Hydraulic flow
and pressure to the steering control valve can be moni-
tored at the outlet of the gear pump.
With the steering wheel in the neutral position and the
engine running, gear pump flow enters the steering con-
trol valve and goes through the steering control spool
valve, by−passing the control valve rotary meter and
steering cylinder. Flow leaves the control valve and is
routed to the spray boom lift control manifold, to the oil
filter and returns to the transaxle.
Making a Left Turn
When a left turn is made with the engine running, the
turning of the steering wheel positions the spool valve so
that flow goes through the bottom of the spool. Flow en-
tering the steering control valve from the gear pump
goes through the rotary meter and out the L port. Pres-
sure extends the steering cylinder trunnion for a left turn.
The rotary meter ensures that the oil flow to the cylinder
is proportional to the amount of the turning on the steer-
ing wheel. Fluid leaving the cylinder flows back through
the steering control spool valve, then to the oil filter and
returns to the transaxle.
The steering control valve returns to the neutral position
when turning is completed.
Making a Right Turn
When a right turn is made with the engine running, the
turning of the steering wheel positions the spool valve so
that flow goes through the top of the spool. Flow entering
the steering control valve from the gear pump goes
through the rotary meter and out the R port. Pressure re-
tracts the steering cylinder trunnion for a right turn. The
rotary meter ensures that the oil flow to the cylinder is
proportional to the amount of the turning on the steering
wheel. Fluid leaving the cylinder flows back through the
steering control spool valve, then to the oil filter and re-
turns to the transaxle.
The steering control valve returns to the neutral position
when turning is completed.
Hydraulic
System