Table of Contents
Advertisement
4/14
Bosch Rexroth AG
Function, sectional diagram
4WS2EM...VH1...-100
Valves of this type are electrically operated, 2-stage servo
directional control valves with a mounting hole configuration
to ISO 4401-05-05-0-05. They are predominantly employed
for closed-loop position, force and speed control.
These valves consist of an electro-mechanical converter
(torque motor) (1), a hydraulic amplifier (flapper nozzle princi-
ple) (2) and a control spool (3) in a sleeve (2nd stage), which
is connected to the torque motor via a mechanical feedback.
An electrical input signal at the coils (4) of the torque motor
causes a permanent magnet to generate a force that acts on
the armature (5) and, acting by means of a torque tube (6),
this force generates a torque. This torque then moves the
flapper plate (7) - which is connected to the torque tube (6) by
a rod - out of its central position between the two control ori-
fices (8), resulting in a pressure drop at the end faces of the
control spool. This pressure drop causes the position of the
spool to change, so that the pressure port is connected to one
consumer port and, at the same time, the other consumer
port is connected to the return port. In this special version
"100" the valve is trimmed about 10% from P → B and A → T.
Type 4WS2EM...VH1...-100
Hydraulics
T
A
4WS2EM...VH1...-100
The control spool is connected to the flapper plate or the
torque motor by a feedback spring (mechanical feedback) (9).
The position of the spool continues to change until the return
torque through the feedback spring and the electro-magnet-
ic torque of the torque motor reach a state of equilibrium, and
the pressure drop at the flapper nozzle system becomes zero.
In this way, the stroke of the control spool and thus the flow of
the servo valve are closed-loop-controlled proportionately to
the electrical input signal. At the same time, it should be noted
that the flow is dependent on the valve pressure drop.
External trigger electronics (order separately)
The valve is actuated by external trigger electronics (a servo
amplifier), which amplifies an analog input signal (setpoint) so
that the controlled-current output signal is capable of driving
the servo valve.
T1
P
B
RA 29583-VH1-100-B1
1
4
5
6
2
7
8
9
3
Advertisement
Table of Contents
