Kyocera FS C5020N - Color LED Printer Service Manual page 151

(2) Touch down developing method
Touchdown development system is a development system having the best of both mono-component system and dual
component system. Dual component developer which is a powder of mixture of toner and carrier powder is continuously
agitated by mixer screws A and B in the toner hopper in the developer unit. The toner and carrier powder are adsorbed to
each other by means of electrostatic charge developed by the friction when they are stirred. The developing magnet roller
is comprised of a magnet and a sleeve which revolves coaxially with the magnet. The developer powder forms 'brushes' of
toner and carrier on the magnet sleeve along the magnetic field centering the magnet. The 'brushes' are truncated to a
constant length of height (approximately 0.5 to 0.55 millimeters) as they pass under the doctor blade. The developing
magnet roller lies along the developing sleeve at the distance of 0.40 millimeters. As the developing magnet roller
revolves, the brushes formed at pole N1 sweep the developing sleeve and the toner is transferred to the developing
sleeve as it is attracted by the difference in potential between them. The toner on the developing sleeve is approximately
70 micrometer in thickness. The developing sleeve is located 0.23 millimeter from the drum. The toner is transferred to the
drum by means of the DC/AC bias applied to the developing sleeve.
Mixer screw A
Developing
magnet roller
S
Magnetic
brush
Developer unit
Toner hopper
Toner
Carrier
Mixer screw B
Developing
magnet roller
S
N
Developing
sleeve
Doctor blade
LED print head
N3
S2
N2
S1 N1
Developing
sleeve
Developing
sleeve
Figure 2-1-13
: 0.50 to 0.55 mm
: 0.40 mm
: 0.23 mm
Main charger
Drum
Drum
70 µm
2F3/2F4
2-1-9