Hydraulic Motor; Control Unit - Husqvarna PT26D Workshop Manual

Hydraulic motor

The hydraulic motor is an inverted gear
motor. The valve disc and gearwheel unit are
located on two levels in the motor. Between
these is a partition wall with drilled holes,
where the oil can flow when they are not cov-
ered by the oscillating rotor. When driving in
one direction, the incoming oil is piped to the
gearwheel unit, which is provided a certain
rotation and power by the oil, via the valve
disc's outer track. The oil is then piped back
via the valve disc and its inner track out
through the output port.

Control unit

The control unit consists of a rotating valve
and a rotating oil gauge. When the operator
turns the wheels, the hydraulic oil is piped
from the control unit via the rotating valve
and the rotating oil gauge to the cylinder port
L(Left) or R(Right), depending on which way
the operator turns the steering wheel. The
rotating oil gauge measures the oil flow to the
control unit in proportion to the steering angle
on the wheels. It is possible to steer the
machine even if there is a breakdown in the
hydraulic pump.
In the control unit is an excess flow valve,
which limits the system pressure to approx.
12 MPa (120 bar).
The control unit, which has a type of excess
pressure function, provides the option in
neutral to let the flow go from port P through
the unit and on to port E. The control unit
always prioritises control function and in case
of excess pressure, the control unit permits
the oil to be piped to port E. At full lock all
flow is led through the excess flow valve and
the flow to port E is stopped.
DESIGN AND FUNCTION
Valve disc
Gearwheel unit
Control unit
Control unit, diagram
1. Outer track
2. Inner track
8043-211
3. Hole to valve disc
4. Roller
5. Rotor
8043-210
8043-116
8043-237
45
English-