Pilot-Actuated Sizes 10 And 16 Servo Solenoid Valves - Siemens SINUMERIK 840D Description Of Functions

A Hydraulics
A.1 Servo solenoid valves
A.1.3

Pilot-actuated sizes 10 and 16 servo solenoid valves

Mechanical
construction
Inlet and outlet of
hydraulic fluid
Positions
Valve amplifier
A-244
SINUMERIK 840D/SIMODRIVE 611 digital Descr. of Functions HLA Module (FBHLA) – 04.00 Edition
In order to control higher flow rates, the principle of pilot control has been ap-
plied.
A directional servo solenoid valve of size 10 or 16 with corresponding control
edges on the valve spool functions as the main stage. Like the piston rod of a
cylinder, this stage is hydraulically clamped and positioned by a size 6 pilot
valve (see Section A.1.2).
The position of the main spool is scanned by another position sensor and the
corresponding actual value applied to a second, subordinate position control
loop.
The control fluid can be inlet and outlet either internally via ports P and T or, as
often the case in practice, externally via additional ports x and y. Plugs are used
to convert the assembly to the desired method.
Pilot-actuated servo solenoid valves have only the three stepless-transition
positions.
They do not have the 4th fail-safe position. If the supply voltage is discon-
nected, the spring force of the main spool causes the valve to assume an indif-
ferent mid-position.
The integrated valve amplifier is mounted on the pilot valve assembly and con-
tains both position control loops. A cable is used to connect the position sensor
on the main stage to the amplifier.
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