Edition
Manual
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2008-10-23 Workshop Manual, Stiga Titan 4 Hydraulic system
8
Drive description
The charge pump (6) and the main pump (7) are integrated into one unit together with the
external hydraulics pump. The pump unit is integrated to the engine.
The engine drives the the hydraulic pump unit with a constant speed. The charge pump (6)
is feeding the main pump (7) with 2,5 bar through the non-return valves (13 and 14). This
pressure is limited by a pressure valve (integrated in the pump, and not shown). The
pressure valve is factory set and not adjustable. The oil, fed into the main pump during
operation, is a replacement for the leak oil from the wheel motors (A and B) and the main
pump (2). Such the charge pump always ensures a pressure of 2,5 bar at the main pump
suction side.
The charge pump sucs its oil direct from the oil tank (T).
The oil flow and the flow direction through the main pump (7) and the wheel motors (1, 2,
3, and 4) - is controlled by the drive pedal, mechanical connected to the main pump (7).
The main pump pressure is depending on the power requirements at the wheels and is
limited by the engine power.
Leak oil
The wheel motors and the hydraulic pump have a small oil leakage (1-4%), which
increases with increased power requirement (increased pressure). The leakage oil is
collected inside the unit housings and forwarded to the collector block back to the oil tank
through the leak flow lines (17). The charge pump (6) compensates for this leakage.
Drive priority
The motors on the same shaft are connected in parallel, after that, the front wheel motors
are are connected in serie with the rear wheel motors first, when driving forwards. This
means, due to the leakage in the rear motor, that the machine under normal conditions
drives on the rear wheels only. When the rear wheels begin to slip (rotate with 1-4% higher
speed than the front wheels) also the front 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.
Shunt line (differential)
The above discussions include a shunt line (12), connected between the front motor
connection lines (10 and 11). This shunt line allow all wheels to rotate with different speeds.
This is neccesary during rotating the steering wheel.
