Specifications

TORQUE MOTOR
➣ Charged permanent magnets polarize the polepieces.
➣ DC current in coils causes increased force in diagonally
opposite air gaps.
➣ Magnetic charge level sets magnitude of decentering force
gradient on armature.
HYDRAULIC AMPLIFIER
➣ Armature and flapper rigidly joined and supported by thin-wall
flexure sleeve.
➣ Fluid continuously flows from pressure P
S
, through both inlet
orifices, past nozzles into flapper chamber, through drain orifice
to tank T.
➣ Rotary motion of armature/flapper throttles flow through one
nozzle or the other.
➣ This diverts flow to one end of the spool.
Æ
Spool at Null
Feedback Spring
Spool
Bushing
Spool Dispaced to Left
P
s
T
TP
s
A
B
P
s
T
TP
s
A
B
T
P
S
P
S
ARMATURE
FLEXURE
SLEEVE
FLAPPER
INLET
ORIFICE
Permanent
Magnet
Flux
Permanent
Magnet
Attractive
Force
Coil Flux
Torque to
Rotate
Armature
N
S
N
S
N
S
➤
➤
➤
➤
N
N
S
S
Upper
Polepiece
Permanent
Magnet
Armature
Coil
N
S
Lower
Polepiece
NOZZLE FLAPPER SERVOVALVE OPERATION
VALVE SPOOL
➣ Spool slides in bushing (sleeve) or directly in body bore.
➣ Bushing contains rectangular holes (slots) or annular grooves
that connect to supply pressure P
S
and tank T.
➣ At “null” spool is centered in bushing; spool lobes (lands) just
cover P
S
and T openings.
➣ Spool motion to either side of null allows fluid to flow from P
S
to one control port and from other control port to T.
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