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e-STUDIO3511/4511 DEVELOPER UNIT 12 - 4 November 2003 © TOSHIBA TEC
12
12.5 Black Developer Unit
12.5.1 Functions
a. Black developer material
The developer material consists of the carrier and toner. The carrier is made of electrically con-
ductive ferrites which is 30-100 µm and the toner is made of the resin particle which is 5-20 µm.
Since the developer material deteriorates after a long time use, periodic replacements are needed.
b. Mixer unit
The carrier and toner are frictionized each other when the developer material is stirred. Then the
carrier is positively charged (+) and the toner is negatively charged (–), and the toner is adhered
by the electrostatic force.
c. Developer sleeve (Magnetic roller)
These aluminum rollers have magnets inside. The developer material is pulled by these magnets
to form a magnetic brush. The magnets are fixed at their position so only the sleeve rotates. By
this rotation, the developer material is transported to the developer sleeve. Then the magnetic
brush formed at the developer sleeve sweeps over the drum surface and thus development is
performed.
d. Doctor blade
The doctor blade controls the amount of the developer material from the transport sleeve so that
the magnetic brush of the developer material can contact with the drum surface properly.
e. Black auto-toner sensor
To print out a precise image, the proportion (toner density ratio) of the carrier and the toner in the
developer material needs to be always constant. The magnetic bridge circuit in the auto-toner
sensor detects the toner ratio in the developer material. This sensor supplies the toner from the
toner cartridge.