Dynamic Balancing Valve - Stiga Park 2WD Workshop Manual

WORKSHOP MANUAL Chapter EDITION Page
PARK 4 - Hydraulic system 2018 9
The engine drives the charge pump (1) and the main pump (2) with a constant speed. The
charge pump is feeding the main pump. The oil, fed into the main pump during operation, is
a replacement for the leak oil from the front and rear axle drives (A and B).
The charge pump sucs its oil from the rear axle drive volume and through the filter (5). The
rear axle drive is supplied with oil from the oil container (4).
The oil flow and the flow direction through the main pump (2) - front hydraulic motor (9)
- rear hydraulic motor (7) is controlled by the speed pedal, mechanical connected to the
main pump (2) in the rear axle drive (A). The main pump pressure is depending on the
power requirements at the wheel axles and is limited by the engine power.
The motors are connected in serie with the front motor (9) first, when driving forwards.
This means, due to the leakage in the front motor, that the machine under normal condi-
tions drives on the front wheels only. When the front wheels begin to slip (rotate with 1-4%
higher speed than the rear wheels) also the rear wheels start to drive and the slipping is
avoided.
This fact is not noticed by the operator, since the machine is driven with its four wheels
after demand.

Dynamic balancing valve.

The hydraulic circuit is equipped with a dynamic balancing valve for the correct balancing
of the circuit. When the machine is stationary, the dynamic balancing valve is open and al-
lows the hydraulic steering to rotate smoothly.
While when the machine starts to move forward, the dynamic balancing valve closes auto-
matically, the front drive axle starts to transmit and then a few moments later, the rear drive
axle also starts to transmit. The rotation of the hydraulic steering remains fluid.
The time that passes between the engagement of the front axle and the rear axle is not
normally perceived by the user.