Epson DFX-8500 Service Manual page 55

DFX-8500


Carriage mechanism:
The carriage mechanism moves the printhead along the platen. The carriage motor drives the carriage. The
printhead is attached to the carriage. The carriage encoder sensor detects the carriage motor speed and
carriage position. The carriage motor is closed-loop controlled. Because the carriage motor is driven at a
very high speed, it has an isolation resistance sensor to detect abnormal resistance. The sensor detects an
error if the resistance is less than 2.2 kΩ. (See "Carriage Motor Drive Circuit" on page 2-26.)


Interlock switch:
When the top cover is opened, the interlock switch cuts the drive voltage to the carriage motor to slow down
the carriage speed and prevent accidents. This is necessary because the carriage ordinarily moves at
dangerous speed. A control circuit decelerates the carriage motor. (See "Carriage Motor Drive Circuit" on
page 2-26.) Printing resumes when the top cover is closed.


Auto platen gap adjustment mechanism:
The printer mechanism has an automatic platen gap adjustment function that measures paper thickness and
adjusts the gap between the platen and printhead accordingly. The printer mechanism adjusts the platen gap
by moving the carriage (and printhead) either forward or backward. The front and rear carriage guide shafts
that hold the carriage are eccentrically mounted; the carriage moves as the platen gap motor rotates the
shafts. The platen gap sensor transmits the amount of movement to the control circuit.


Ribbon feed mechanism:
The printer's ribbon cartridge contains an endless ribbon. The ribbon feed mechanism moves the ribbon so
that there is always fresh ribbon in front of the pins. The ribbon feed motor drives the ribbon feed
mechanism.
Platen Gap Motor
Platen Gap Home
Position Sensor
2-2
Rear Carriage Guide Shaft
Carriage Timing Belt
Ribbon Feed
Motor
Figure 2-2. Printer Mechanism Operation (1)
Interlock Switch
Printhead
Carriage Encoder Belt
Carriage Sensor
Carriage
Motor