Epson U375 - TM B/W Dot-matrix Printer, Technical Manual

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2-3
■
Print head unit movement
When the carriage motor set drives the carriage motor gear
so that it rotates in the direction of the
➮
, the rotational force
is transferred first to the belt drive pulley and then to the
belt, and the carriage subset (which holds the print head
unit) mounted on the belt moves in the direction of the
➮
.
When the carriage motor gear rotates in the direction of the
➡
, the carriage subset moves in the direction of the
➡
.
Figure 2-7. Print Head Unit Movement
■
Wire movement for printing a single dot
1. When the prescribed pulse is supplied to the drive coil,
the iron core is magnetized and the moving plate is
pulled in the direction of
➡
A. At this point, because the
wire is pressed onto the moving plate by the force from
the wire return spring, the wire receives the force from
the moving plate and is pushed out towards the platen
set (in the direction of
➡
B).
2. When the wire that is pushed out strikes the platen set
through the ink ribbon and the paper, one dot is printed.
3. When the current supplied to the drive coil stops, the
wire and the moving plate are returned to their normal
positions by the force of the wire return spring and the
moving plate spring.
Figure 2-8. Wire Movement
■
Printing operations involved in forming
one character
Forming a character (5 x 9 dot matrix)
The carriage motor phase switching signal serves as a
reference signal for powering the print solenoids in accor-
dance with the carriage movement, to form a character.
One rotation step of the carriage motor (7.5
°
) moves the
print head unit by approximately 0.317 mm (0.012").
For example, to form the character "2", print solenoids 2
and 7 are first powered in sync with the carriage motor
phase switching signal. Next, one dot timing delay Tn+
1
is
introduced, and print solenoids 1, 6, and 7 are powered. By
continuing in this way, the character "2" is formed.
Figure 2-9. Print Timing Chart
CONFIDENTIAL