Traction Circuit - Toro Reelmaster 5010- H Service Manual

Traction Circuit

The hydraulic traction circuit consists of a variable dis-
placement piston pump (P3) connected in a closed loop,
parallel circuit to two (2) orbital roller vane wheel motors.
The piston (traction) pump input shaft is rotated by a
drive shaft connected to the motor/generator shaft that
is driven by the engine flywheel.
Traction circuit pressure (forward and reverse) can be
measured at test ports located in the hydraulic tubes
that connect the front wheel motors.
NOTE: In high load traction situations, the 48 VDC mo-
tor/generator may automatically assist the engine to
maintain piston (traction) pump input speed.
Forward Direction (Fig. 11)
Pushing the top of the traction pedal angles the piston
(traction) pump swash plate to create a flow of oil. This
oil flow is directed to the wheel motors via hydraulic
hoses and tubes to drive the wheels in the forward direc-
tion. Forward traction pressure is limited to 3625 PSI
(250 bar) by the forward traction relief valve (R3) located
in the piston (traction) pump.
Oil flowing from the wheel motors returns to the variable
displacement pump and is continuously pumped
through the traction circuit as long as the traction pedal
is pushed.
The angle of the swash plate determines pump flow and
ultimately traction speed. When the traction pedal is de-
pressed a small amount, a small swash plate rotation re-
sults in low pump output and lower traction speed. When
the traction pedal is depressed fully, the pump swash
plate rotates fully to provide maximum pump output and
traction speed.
Gear pump section (P2) supplies oil flow for the steering
circuit and also provides a constant supply of charge oil
to the closed loop traction circuit. This charge oil pro-
vides lubrication for traction circuit components and also
replenishes traction circuit oil that is lost due to internal
leakage in the traction circuit.
The hydraulic reservoir provides fluid for the gear pump
(P2) through the suction hose. Charge pump flow is di-
rected to the low pressure side of the closed loop trac-
tion circuit. Charge pressure is limited by the charge
relief valve (R5) located in the piston (traction) pump.
The charge relief pressure is 200 PSI (14 bar).
The piston pump (P3) includes a flushing valve that
bleeds off a small amount of hydraulic fluid for cooling
of the closed loop traction circuit. The charge system re-
plenishes oil that is bled from the traction circuit by the
flushing valve.
Reelmaster 5010- H
Reverse Direction
The traction circuit operates essentially the same in re-
verse as it does in the forward direction. However, the
flow through the circuit is reversed. Pushing the bottom
of the traction pedal rotates the piston (traction) pump
swash plate to create a flow of oil. This oil is directed to
the wheel motors to drive the wheels in the reverse
direction. Reverse traction pressure is limited to 3625
PSI (250 bar) by the reverse traction relief valve (R4) lo-
cated in the piston (traction) pump.
Oil flowing from the wheel motors returns to the piston
(traction) pump and is continuously pumped through the
closed loop traction circuit as long as the traction pedal
is pushed.
The charge circuit and flushing valve function the same
in reverse as they do in the forward direction.
TM
CrossTrax AWD (Optional)
On machines equipped with the optional CrossTrax
AWD kit, four (4) wheel motors are used (Fig. 12). Piston
(traction) pump flow is directed to the front tires and the
opposite rear tires to maximize traction. To reduce tire
scuffing when turning, traction system pressure is
equalized in the AWD manifold with an orifice and a bi-
directional relief valve. Check valves in the AWD man-
ifold allow the rear wheel motors to over run during tight
turns.
CrossTrax TM AWD Hydraulic Schematic
Page 4 - 13
G5
Figure 12
Hydraulic System
TM