Mode of operation of clutch adjuster valve -N255
The clutch actuator valve -N255 acts as a proportional valve
regulating the volumetric flow to the clutch slave cylinder with release
bearing. The piston in the clutch slave cylinder attempts to keep the cylinder
chamber empty based on a spring force.
Characteristics of the left side curve:
B = Volumetric flow/oil flow in l/min
A = Current consumption in A
The valve N255 operates with two chambers and three
-1- = Oil sump/tank
-2- = Clutch slave cylinder
-3- = Pressure accumulator
When no power is connected to the valve, the hydraulic fluid
flows out of the clutch slave cylinder back into the tank and the clutch is
fully open (hydraulic ports 1 and 2 connected).
As soon as the valve current reaches the rising slope of the
curve, a proportional oil flows into the clutch slave cylinder.
The piston in the clutch slave cylinder begins to close the
clutch (hydraulic ports 2 and 3 connected). When the current is reduced to the
low-level plateau (hydraulic port 2 not connected) the piston remains at the
position it has reached in the clutch slave cylinder. A further reduction in
current causes a proportional oil flow to flow out of the clutch slave cylinder
again when the falling slope is reached, and the clutch begins to open.
Risk of injury from highly pressurised
A Depressurise hydraulic system; see Workshop