Canon DR-9080C Service Manual page 42

CHAPTER 2 FUNCTIONS & OPERATION
5 Skew Correction Mechanism
The skew correction (deskew) uses the front
registration sensors and the registration rollers.
Skew is detected by the front registration sensor
and then is corrected by the registration rollers.
Fig. 2-309 shows the arrangement of the front
registration sensors and Fig. 2-310 shows the
skew correction mechanism.
As shown in Fig. 2-309, the front registration
sensors consist of the left sensor (L) and the right
sensor (R), and are mounted in front of the
registration roller. If no skewing occurs, there is
no difference in the timing for both sensors
detecting the document.
document is skewed, one of the sensors detects
the document earlier and there is a difference in
the timing of detecting the document. As the
skew amount is increased, the difference is also
increased. The difference affects the time of the
skew correction performed by the registration
roller, and an increased difference will prolong
the skew correction time.
The time taken from the time both sensors
detect the document
registration roller begins to rotate is the time
required for the skew correction.
As shown in Fig. 2-310, the skew correction
is performed at the registration roller area. When
the feed roller feeds the document in the feeding
direction, either the right or left front end of the
document runs into the registration roller. Since
the registration roller remains stopped, the
document is turned on the fore-end of the
document run into the registration roller so that
the skew is corrected. (Refer to Fig. 2-310-a)
2 - 18
However, if the
together untill the
COPYRIGHT © 2003 CANON ELECTRONICS INC.
When the skew correction is performed after
both sensors detect the document together, the
registration roller begins to rotate and the
document is fed without being skewed. (Refer to
2-310-b)
Registration roller
Front
registration
L sensor
Feed direction
Fig. 2-309
Registration roller (stopped)
a.
Feed direction
Document
Registration roller (rotating)
b.
Fig. 2-310
CANON DR-6080/9080C REV.0 SEPT. 2003
Front
registration
R sensor
Document
Turns
this way