Linde H 50 D, Service Training

Page: 251 / 282

Service Training
Section 4.9
Page 25
12.05
NOMINAL VALUE TRANSMITTER
The nominal value transmitter (5) is adjusted, via a hydraulic modulator (4), in accordance with the pedal
position and the actuation of the operating hydraulics. This adjustment changes the nominal value transmitter
(5) into a proportional electrical signal.
A conductive plastic potentiometer is built into the nominal value transmitter (5) with an electrically active
adjustment range of 44 °. The potentiometer is splash-proof and designed for the environmental require-
ments for vehicles in terms of temperature, vibration acceleration and corrosion protection.
The input value delivered from the nominal value transmitter (5) is adapted to the nominal value processing
(6).
ACTUAL VALUE TRANSMITTER
The actual value transmitter (3) detects the engine speed inductively via the starter ring gear. This induces
an a.c. voltage in it, with a frequency proportional to the speed. The speed sensor is a proven component
in vehicle technology.
In the speed signal processing, the a.c. voltage delivered from the actual value transmitter (3) is changed
into a d.c. voltage proportional to the speed.
TARGET VALUE / ACTUAL VALUE COMPARISON
At the nominal value / actual value comparison point (8), the nominal value received from the pedal position
is compared with the engine speed measured by the actual value transmitter (3). In accordance with the
regulating difference, the speed regulator (11) changes the setting of the throttle valve, via the modulator
(12). Thus the nominal value (speed) set is kept constant, irrespective of the engine load. In addition, the
two stop positions of the throttle valve are indicated via the magnet current capture of the PID regulator (9).
PID REGULATOR
The nominal value and actual value are compared and the difference is transmitted to the PID regulator (9).
The PID regulator (9) has a proportional, differential and integral element.
OUTPUT STAGE
The output stage (10) amplifies the output signal of the PID regulator (9) so that the operating magnet (12)
can be activated. A pulse-pause-controlled, clocked output stage is operated in this way.
The current of the operating magnet (12) is detected on a measuring resistor in the control system and is
recoupled to the output stage (10). In this way, the stability of the regulating circuit is improved.
For detection of the throttle valve stop positions (fully open or fully shut), the current flowing via the operating
magnet is measured. When the power and thereby also the direction of the magnet axis change in proportion
to the current, the PID regulator (9) recognises the position of the throttle valve and its end positions from
the current.
MODULATOR
The modulator (12) is a proportional magnet with a built-in return spring. By raising the magnet current, the
throttle valve is opened and the return spring is tensed, by means of a rod assembly. In the event of a power
failure or a break in the cables, the throttle valve is shut by the return force of the spring.