SAME SILVER 90 - Hydrostatic steering; General information; Hydraulic directional control valve; steering cylinders (single acting)

hydraulic directional control valve
p/n 290.6310.4/10
type of valve OSPC 80 OR open centre with feedback control
relief valve setting (bar)
150
clearance between spool and sleeve (mm) 0.03
turns of steering wheel before road wheels respond
- engine running 0° - 2°
- engine at standstill 0° - 6°
steering cylinders (single acting)
working stroke of piston rod (mm) 171
rod diameter (mm) 2WD 42
4WD 50
pushing force (kN) 2WD 13,6
4WD 19
steering wheel turns to full lock 2.17
tightening torques
valve cover securing screws (Nm / kgm) 29 / 3
cylinder securing bolt (Nm / kgm) 155 /16
controls
hydrostatic steering
Hydrostatic steering
no. 290.6310.4/10 Danfoss type
General information
There in no direct mechanical connection between the wheels and the steering wheel and therefore no vibration can
reach the driver.
Turning the steering wheel operates a rotary distributor connected to an oil flow control shutter permitting the pressure
oil to be directed to the hydraulic cylinder in the amount necessary to provide the desired steering action.
The steering system is an open-centre reactive type: the user can directly feel the steering response on the steering
wheel and perform a prompt correction of the driving direction.
In addition, the remarkable wheel caster angle will help increase the wheel self-centering effect as the wheels will
automatically get in a straight line when the steering wheel is released.
The hydraulic circuit is fully independent. The oil drawn from the gearbox flows first through a high-delivery filter before
being routed under pressure to the distributor by a pump constantly in mesh driven by the engine and fitted on gearbox
left-hand side.
Two powerful single-acting cylinders, connected to the front wheel hubs, ensure the thrust necessary to steering under
any working conditions.
Oil returning from the power steering unit is cooled by a radiator in the engine compartment and then directed to the
unit piloting the electrohydraulic controls and sole function to lubricate the gearbox.
Moreover this system offers the advantage that the tractor can be driven also in the event of either a pump failure or
an engine stop. A valve within the distributor will allow the oil to be drawn from the discharge circuit through the oil
control shutter, whenever a pressure drop occurs in the pump delivery circuit.
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