Toro Groundsmaster 7210, Руководство по обслуживанию

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Lift Circuit (Raise)
A single-section gear pump is directly coupled to the transmission which is driven
by the engine. This gear pump supplies hydraulic flow for raising and lowering the
cutting deck (or implement). The pump takes its suction from the hydraulic tank.
During the conditions of not raising or lowering the cutting deck (or implement),
flow from the gear pump is bypassed by the lift-control manifold directly to the oil
cooler and then to the transmission. The flow then returns to the hydraulic tank.
Note: To raise the cutting deck, the engine must be in running condition.
Electrical Lift Control
The lift-control manifold is equipped with the 2 solenoid valves for electrical
control of the lift circuit. A deck lift/lower switch on the right side traction lever is
used to raise the cutting deck (or implement).
When the top of the lift/lower switch is pressed (momentary position), both the
solenoid valves (A/S1 and B/S2) in the deck lift manifold are energized to cause
the valves to shift. The energized solenoid valve B/S1 prevents the gear pump
flow from bypassing the lift cylinder. The energized solenoid valve A/S1 allows
the hydraulic flow from the gear pump to the cylinder head of the lift cylinder. The
lift cylinder extends, causing the cutting deck to raise. The fluid displaced from
the rod end of the lift cylinder is routed to the oil cooler, transmission, and then to
the hydraulic tank. An orifice in the manifold controls the extending speed of the
lift cylinder while raising the cutting deck.
The load on the lift cylinder causes the lift circuit pressure to increase. If the lift
circuit pressure reaches the implement relief valve pressure 20,700 kPa (3,000
psi), the relief valve in the gear pump shifts to allow the pump flow to return to
the hydraulic tank. This condition occurs in both the raise and lower modes.
When the top of the lift/lower switch is released, both the solenoid valves (A/S1
and B/S2) in the deck lift manifold are de-energized. The de-energized solenoid
valve B/S2 allows the gear pump flow to bypass the lift cylinder, returning to
the oil cooler, transmission, and then to the hydraulic tank. The de-energized
solenoid valve A/S1 prevents the hydraulic flow to and from the lift cylinder to
keep the cutting deck in the raised position.
Hydraulic System: Hydraulic Schematics Page 4–18 Groundsmaster 7210
16222SL Rev C