EPSON FX-890/2190 Revision B
Operating Principles Overview 45
2.1.1 Printer Mechanism
This printer mechanism consists of Printhead, Paper feed mechanism, Carriage
movement mechanism, Tractor feed mechanism, Platen gap adjustment mechanism,
Ribbon feed mechanism, PF motor, CR motor, detectors, and so on.
2.1.1.1 Printhead
The printhead prints data from the control board on paper using the ink ribbon. The
printhead is mounted on the carriage unit.
Printing method: Impact dot matrix printing
Number of dot wires: 18
Diameter of dot wire: φ0.29 mm
Dot wire arrangement:
Figure 2-3. Dot Wire Arrangement
2.1.1.2 Paper Feed Mechanism
The paper feed mechanism picks up paper and transports it to the printhead, then ejects
the paper step by step or continuously driven by the PF motor. PF motor drives the
paper feed mechanism gears and the platen roller. The top of form and paper out
condition are detected by the front and rear PE detectors, respectively.
2.1.1.3 Carriage Movement Mechanism
The carriage movement mechanism carries the carriage unit left and right along the CR
guide shaft and mechanism frame, and stops it at any position for printing. It is driven
by torque sent from the CR motor via the timing belt. Home position is detected by the
HP (home position) detector at power on and at CR motor phase change.
2.1.1.4 Tractor Feed Mechanism
The tractor feed mechanism feeds continuous paper to the printhead and ejects it.
Torque from the PF motor is transferred to the tractor unit via the release mechanism in
the paper feed mechanism. The release lever in the release mechanism switches torque
from the PF motor between cut sheet feeding and continuous paper feeding. This
printer is equipped with several tractor feeding methods (front / rear push tractor
feeding, front / rear push & pull tractor feeding and front / rear pull tractor feeding),
which is selected according to the tractor unit setting positions and the lever positions.
The tractor detector detects the release lever setting position, for cut sheet feeding or
continuous paper feeding.
2.1.1.5 Platen Gap Adjustment Mechanism
The platen gap (the gap between the platen and the printhead) adjustment mechanism
consists of the CR guide shaft, parallelism adjustment bushing, PG adjust lever and PG
detector. The PG adjust lever is attached to the left side of the CR guide shaft. The
bushing is attached to the left frame. Since the CR guide shaft is eccentric, the
printhead approaches or recedes from the platen roller as the PG lever turns forward or
backward. The PG detector detects the PG lever position. If the lever is set to a position
between “2” and “6”, the printer is in the copy mode.
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