LQ400
Service Manual
Operating Principles
2.1 PRINTER MECHANISM OPERATION
This
section
describes the printer mechanism and explains how it works.
2.1.1 Printing Mechanism
The printing mechanism is composed of the
prirdhead,
ink ribbon, and ribbon mask.
The
printhead
is a 24pin head for impact dot printing. Each wire has own drive coil, which causes the wire to
move in and out of the
printhead
to print each dot.
The four steps below describe how these
driving wires work.
1.
2.
3.
4.
A drive signal transmitted from the control arcuit to the
printhead
drive arcuit is converted to
the proper
printhead
driving voltage, which energizes a corresponding coil. The energized coil
then causes the iron core to become magnetized.
The magnetic force draws the actuating plate toward the core, and the dot wire, which is
connected to the core, rushes toward the platen.
When the dot wire impacts the platen, pressing against the ribbon and paper, it prints a dot.
When the driving voltage stops energizing the coil, the magnetic force from the iron core
vanishes. The actuating plate returns to its original position
(the
position before coil was
energized) with spring action. The dot wire also returns to its original position.
This is the sequence used to print a single dot.
The mechanism is equipped with a built-in thermistor for head temperature detection. The
temperature detected by the thermistor is converted to an electric signal and fed back to the control
circuit.
Wire Resettin S rin
r
Stopper
Dot Wire
77
.
Yn7YY2
\
Actuating Spring
Figure 2-1.
Printhead Operation Principles
Rev.A
2-1
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