Platen Gap (Pg) /Parallelism Adjustment Mechanism; Carriage Home Position (Hp) Detection; Paper Feeding Mechanism - Epson PH890 Service Manual

EPSON Stylus Photo 890/1290

2.1.2.2 Platen Gap (PG) /Parallelism Adjustment Mechanism

The PG adjust lever is attached to the left end of the carriage guide shaft. When the
carriage guide shaft, which has an eccentricity, rotates as the adjustment lever moves, it
narrows or widens the distance (=PG: from 1.2 mm to 2.1 mm). This mechanism
enables the user to print with a correct PG according to print result or other conditions
such as paper curl.
Also, the parallelism adjustment bushings are attached to the right and left ends of the
carriage guide shaft. They are used to set the carriage guide shaft parallel with a platen.
Table 2-5.
Platen Gap Adjust Lever Setting
Lever Position
Front (0)
Rear (+)

2.1.2.3 Carriage Home Position (HP) Detection

Unlike previous Epson ink jet printers, the carriage home position is detected with the
drive current from the CR motor and speed/position signal from the linear encoder.
OPERATING PRINCIPLES
Table 2-6.
PG adjustment value
0 mm (=PG is 1.2 mm)
+ 0.9 mm (=PG is 2.1 mm)

2.1.3 Paper Feeding Mechanism

The paper feeding mechanism transports paper loaded from ASF using the PF rollers
and paper eject rollers. A new type of DC motor is used as the PF motor. See the table
below for the PF motor specifications.
Table 2-7.
Item
Motor type
Drive voltage
Coil Resistance
Inductance
Control method
Stepping motor that is used in other printers as the PF motor controls paper feed by the
open loop system. On the other hand, this printer controls paper feeding mechanism
with the closed loop system by employing the DC motor and rotary encoder for more
accurate paper feeding. Therefore, a rotary encoder attached to the left end of the PR
roller shaft controls paper feed amount. For detailed information, see Section "PF
motor driver circuit".
Drive from the PF motor is sent to the PF rollers and paper eject rollers as described
below.
o
Drive transmission to the PF rollers:
→
PF motor pinion gear
o
Drive transmission to the eject rollers:
→
PF motor pinion gear
→
gear (28) Paper eject rollers
Overview
PF Motor Specifications
Table 2-8.
Description
DC Motor with Brush
+42V +/- 5% (Applied to the driver)
29.2ohm +/- 25%
30.0mH +/- 25%
Constant current chopping drive
→
Spur gear (76) PF rollers
→
Spur gear (76) Combination gear (13.5, 308)
Revision B
→
Spur
38