Section Vi. Hydraulic System - Bolens DuraTrac DGT 1800 Service Manual

Section VI. HYDRAULIC SYSTEM
5100 SERIES
TRACTOR
PAGE 6-1 Rev. 3/92
PRINCIPLES OF OPERATION
The hydraulic system Is made up
of seven major components.
These are: the hydrostatic
transmission charge pump, power
steering control valve, power
steering cylinder, attachment lift
valve, attachment lift cylinder, filter
and all external lines and hoses.
The source of the fluid flow Is a
roller type charge pump mounted
on the hydrostatic package, which
Is driven by the engine. This
charge pump provides hydraulic
pressure. The fluid reservoir Is the
transmission and final drive
housing. All flow Is first routed
through the power steering control
valve.
POWER STEERING CIRCUIT
The power steering control valve is a
rotary valve
w~h
a buiH-in 'hand
pump', which allows manual steering
if
hydraulic power is lost. A function
of this-valve is to give priortty flow to
the the power steering circu~ (See
Fig. 6-1 Power steering valve flow
schematic). When the steering is in
the neutral position, no fluid flow to
the steering cylinder is required. In
this position, all fluid flowing to the
steering valve through the 'IN' port,
immediately flows out through the
'AUX' port, and to the attachment lift
valve. Also while in this position, the
valve isolates the 'RH' and 'LH' work
ports which are connected to the
steering cylinder, so the steering
linkage remains in a fixed position.
When the steering wheel is turned,
the valve is rotated to allow flow to be
diverted to one side of the steering
cylinder, and to allow return from the
opposite side. When the steering
wheel is turned in the opposite
direction, the valve is indexed so the
fluid flow is reversed, resulting in
cylinder movement in the opposite
Fig. 6·1
POWER STEERING VALVE FLOW SCHEMATIC
NO TURN
LEFT TURN
Priority fluid flows along solid
line--Volume will vary
depending on speed of rotation
of steering wheel--Remaining
pump oulput flows In the palh
of the dotted line to
1111.
RIGHT TURN