Printer Mechanism Operating Principles; Carriage Mechanism - Epson Stylus COLOR 900 Service Manual

EPSON Stylus COLOR 900/900N

2.2 Printer Mechanism Operating Principles

2.2.1 Carriage Mechanism

The carriage mechanism includes several major components:
T
carriage home position (CRHP) sensor
T
linear encoder
T
ink cartridge sensors
2.2.1.1 CRHP Sensor
The CRHP (Carriage Home Position) sensor lets the printer keep track
of the carriage position. It checks the carraige position at the following
times:
T
When power is turned on or off
T
When a head cleaning operation, including initial ink charge, is
performed
T
When the printer returns to ready status because it has finished
a print job or has received no data for more than one second
The CRHP sensor's drive voltage is 5.0 V ± 5%. Its output signal
specifications are as shown in the table below:
Table 2-1. CRHP Sensor Specifications
CR Position
CR in home position
CR away from home position
If this sensor should become defective, the carriage cannot be detected
when it returns to home position. In this case, the printer cuts off power
to the CR motor and shows a fatal error.
Sensor output
0.7 VDC or less
2.4 VDC or more
2.2.1.2 Linear Encoder
The EPSON Stylus COLOR 900/900N uses a linear encoder to obtain
even carriage movement and accurate print timing. The linear encoder
reads bands on the encoder belt, and IC2 interprets the signals from the
encoder. This enables the printer to produce the appropriate printhead
drive frequency and to control the carriage. Table 2-2 gives the linear
encoder specifications:
Table 2-2. Linear Encoder Specifications
Item
±
Drive voltage 5 VDC 5%
Output
Phase A/B 2-channel digital output (TTL level)
waveform
Minimum step 1/180 inch (spacing of the bands on the encoder belt)
Response
20 KHz
frequency
Beside detecting the carriage position, the encoder also serves to
detect paper jams. If the pulses from the encoder do not reach specified
levels during printing, the printer assumes that paper has jammed,
stops printing, and displays the paper jam error.
During power-on initialization, the printer checks the status of the
encoder sensor before performing the CR home position check. If the
encoder is defective, the printer generates a fatal error immediately
after power on.
Chapter 2 Operating Principles
Specifications
34