MTZ 1220.1, Operator'S Manual

Page: 109 / 244

MTZ 1220.1/1220.3 Section D. Construction and Operation
D61
Hydrostatic steering control
The hydrostatic steering control
(HSC) is intended for controlling the turn-
ing of the steerable wheels and reducing
the force to be applied to the steering
wheel for turning the tractor. The steering
wheel and the steerable wheels are con-
nected hydraulic by oil pipelines and high-
pressure hoses which connect the dosing
pump mounted in the tractor’s cabin on
the steering column and differential hy-
draulic cylinder which is installed in the
steering linkage of the front driving axle.
The hydraulic circuit of HSC of the trac-
tors MTZ-1220.1/1220.3 is given on Fig.
Д
-40.
During turning of the steering
wheel the dosing pump (2) (Fig. Д -40)
gives the steering hydraulic cylinder (1)
the oil volume which is proportional to the
turning value of the steering wheel. When
the steering wheel is not rotated the dos-
ing pump locks in the oil volume in the
hydraulic cylinder. It achieves stability of
the direction of movement of the chassis
through road or soil variations. At the
normal working conditions when the feed
pump (3) ensures necessary flow and oil
pressure, maximal force on the steering
does not exceed 30 N.
If oil flow from the dosing pump is
too small or is out (for example, in case of
failures of the diesel engine, dosing pump
or break of the oil supply pipeline), the
dosing pump works as a handl pump in
the steering control system. The steering
wheel force which is applied by the op-
erator for wheels turning at the hand con-
trol is very much increasing, sometimes
till 600 N.
When the diesel engine is running
oil from the feed pump (3) (Fig.
Д
-40) (the
steering wheel does not rotate) comes to
the dosing pump (2) and is delivered to
the oil tank (5) through the filter (4) in the
oil tank. As you rotate the steering wheel,
the spool of the dosing pump (the spool is
connected to the steering wheel) displac-
es, ensuring oil supply into one of the
cavities of the hydraulic cylinder of the
turn 1 in the volume that corresponds to
the turning angle of steering wheel.
When the diesel engine is not running
and you rotate the steering wheel left or
right the dosing pump is acting as a
pump, supplying oil into the correspond-
ing cavity of the hydraulic cylinder of the
turn und ensuring the turning of the direc-
tive wheels.