Epson Perfection 4870 Photo, Service Manual

Page: 22 / 87

Perfection 4870 Photo Revision A
OPERATING PRINCIPLES Engine Operation Outline 22
2.1.2 Moving Mechanism operation
2.1.2.1 Carriage Moving Mechanism operation
The image data of a document are scanned in the combination of the main scanning
direction (one line: CCD Sensor) and sub scanning direction (multiple lines: Carriage
Unit movement).
(Refer to figure 2-4.)
The line type color CCD Sensor can only scan the data of one line in the main scanning
direction (in parallel with the Carriage Unit) at one time. To scan the data of the second
and latter lines in the sub scanning direction, the Carriage Unit having a built-in CCD
Sensor is moved by CR drive. The scanned data are sent to the Control Board. The
scanning of Line n data and the processing of Line n-1 image data are performed
consecutively at the same time.
Figure 2-4. Carriage Movement
The Carriage Unit slides along the guide rail in the sub scanning direction. To perform
this sliding operation, the CR (Carriage) Motor transmits its drive power to the CR
Timing Belt, which is fixed to the Carriage Unit, via the Drive Pulley and Deceleration
Gear. The image data scanning start position is determined by the CR HP Sensor
located on the Control Board. A stepping motor used as the CR Motor is driven under
open loop control.
(Refer to figure 2-5.)
Figure 2-5. Carriage Operation
Main
scanning
1 pixel
Document
Second line
First line
Scanner Head
(Carriage)
Sub scanning (by Carriage movement)
Carriage Unit
CR HP Sensor
Driven Pulley
CR Timing Belt
Front
Rear
Drive Pulley
Deceleration Gear
CR Motor