Hydraulics
Bosch Rexroth AG
RE 29926/10.06 VT 3006
3
/8
Functional Description
(Continuation)
By switching the relay K5 or through an external bridge the
ramp time is set to its minimum value (approx. 30 ms).
The output signal of the ramp generator [4] runs parallel to the
summator [6] and the step function generator [5]. The step
function generator produces a polarity-dependent constant
step signal with the command value voltages which is added
to the output signal of the ramp generator. This step function
causes the rapid travelling across the overlapping area of the
valve spool.
A positive command value signal at the input of the amplifier
controls the output stage for solenoid „B“, a negative com-
mand value signal the output stage for solenoid „A“. If the com-
mand value signal is smaller than ± % (step function still inef-
fective) a pilot current of 20 mA flows through both solenoids.
The actual values of the currents through the two solenoids
can be measured separately at the test points „I
A
“ (soleno-
id „A“) and „I
B
“ (solenoid „B“). Here a current of 800 mA cor-
responds to a voltage of 800 mV.
LED „H“ lights up when the system is powered up.
LED „H2“ („Ready for operation“) lights up to indicate troub-
le-free operation as long as:
– the internal power supply (±9 V) is functioning properly
– there is no short-circuit in the solenoid lines
In the event of a fault, both output stages are immediately de-
energized and the signal „Ready for operation“ is cancelled.
Once the fault has been cleared, the amplifier card is immedia-
tely operable and LED „H2“ lights up again.
)
= Reference potential for the command values to 5
is M0 (measuring zero)
[ ]
= Allocation in block circuit diagram page 4
