Paper Feed Mechanism - Epson Stylus COLOR 800 Service Manual

2.2.4 Paper Feed Mechanism

This printer is equipped with the PF motor which is used to feed paper only to improve feeding speed. The
drive from the Pump motor is used to load paper at the ASF and the drive from the PF roller is
independently used to feed paper only. The paper feed mechanism is classified to 2 parts; the paper feed
part having the PF roller for the main assembly, and the paper eject part having the Paper eject roller for
the main assembly. The PF roller is coated with the powdery material, which is used to improve the paper
feed accuracy. The PF motor located at the rear left part of the printer mechanism transmits the torque via
the Combination gear (14, 31.5) and Gear (70) to the PF roller assembly to feed paper loaded.
The torque is then transmitted from the Gear (17) on the Paper feed roller assembly to the Paper eject
roller via the Gear (19) to eject paper. The torque is transmitted in the following order:
‰Paper feed part
1) PF motor pinion gear
‰Paper Eject part
1) PF motor pinion gear
assembly) 5) Gear 19 (Front paper guide assembly )
eject assembly)
This printer uses a 4-phases/96-pole/HB type pulse motor which is controlled by the bipolar constant
voltage system for the PF motor. The current control signal for each phase and phase control signal
output from the IC2 gate array E05B33CB are converted into the PF motor control signal by the IC16
bipolar driver UDN2917EB to control the PF motor. Since the power switch of this printer is wired to the
secondary circuitry, the voltage remains the constant level until the loaded paper is ejected after the printer
power is turned off. Table 2-4 and Table 2-5 show the PF motor specification and PF motor drive
frequency, respectively.
Item
Motor type
Drive voltage
Coil resistance
Inductance
Drive frequency
Excitation mode
Minimum step
Feeding
Mode speed-
(inch/s)
Normal feed 5
Fast feed 6
Slow feed 2.5
At loading 3
Micro adjust 1 1.25
Micro adjust 2 0.55
Note) Drive frequency and pulse interval are reduced to 2-2 phase.
Rev. A
2) Combination gear 14, 31.5
2) Combination gear 14, 31.5
Figure 2-5. Paper Feed Mechanism
Table 2-4. PF Motor Specification
4-phases / 96-pole / HB type pulse motor
42 VDC 5% (The voltage applied to the driver)
7.8 10% (at 25 C per 1 phase)
14 mH 20% (1 KHz, 1 Vrms)
400 ~ 4320 Hz
Bipolar drive
1/120 inch / pulse (2-2 phase drive)
Table 2-5. PF Motor Drive Terms
Drive Pulse
Frequency interval-
(Hz) (us)
3600 278
4320 231
1800 556
22160 463
900 1111
400 2500
3) Gear 70
3) Gear 70 4) Gear 17 (PF roller
6) Paper eject roller assembly (Front paper
Description
Acceleration step
for each phase
W1-2 2-2 1-2
50
60
20
30
2
Operating Principles
4) PF roller assembly
Deceleration step
for each phase
W1-2 2-2 1-2
50
60
20
30
2
2-5