Platen Gap Adjustment Mechanism - Epson DFX-8000 Service Manual

REV.-A

2.1.3 Platen Gap Adjustment Mechanism

The printer mechanism has an automatic platen gap adjustment function that ensures an optimum gap
(between the platen and printhead) by measuring the thickness of the paper.
Figure 2-4 shows the platen gap adjustment mechanism.
The carriage guide shaft supporting the front of the carriage has an elliptical section. The rotation of
the platen gap motor is transmitted to the carriage guide shaft through the gears. Counterclockwise
from the left side).
An encoder plate with equally-pitched slits is mounted coaxially with the rotor of the platen gap motor.
When the motor rotates, the platen gap sensor (photo coupler) detects it and outputs pulses. Each pulse
corresponds to 0.015 mm (horizontal distance), and the detection range is O to 0.7 mm.
Motor Specifications
Type
Supply voltage
Winding
resistance
Drive frequency
Excitation system
Gap
Platen
Gear
\
Platen Gap+
-
I r a n s t e r b e a r U
Platen Gap
Motor
Figure 2-4. Platen Gap Adjustment Mechanism
Table 2-4. Platen Gap Motor/Sensor Specifications
4-phase 48-pole PM-type
stepping motor
36.5 t 1 VDC
250 & 18 ohms/phase
(at 25"C)
2 8 5
2-2 phase excitation
Guide Shaft
Encorder Plate
' \
Platen Gap Sensor
Detector
output
Supply voltage
Phase difference
2-6
Sensor Specifications
Photo interrupter
2-channel rectangular
pulse (TTL level)
5 VDC
Approx. 45°
(