Ricoh A156 - ID Correction for the; SP Pattern

• V
SG
is measured at the start of every copy run.
• V
SP
is detected at the end of a copy run if 10 or more copies have been
made since V
SP
was last measured. The transfer belt must be released
to measure V
SP
, so it cannot be checked during a copy run.
1.3.3 ID Correction for the V
SP
Pattern
Background
Developer consists of carrier particles (ferrite and resin) and toner particles
(resin and carbon). The positive triboelectric charge on the toner is caused
by friction between the carrier and toner particles. However, the chargeability
of carrier decreases with time. Therefore, if the toner weight ratio in the
developer is the same, the amount of positive triboelectric charge for one
particle of toner decreases. This is because the number of toner particles
which surround one carrier particle is the same, but the chargeability of one
particle of carrier is less than before.
If the development potential, that is, the difference of voltage between the
development roller and the drum for the V
SP
pattern is the same, more toner
particles are attracted to the V
SP
pattern, because one particle of toner has
less positive charge than before. (More toner particles are required to
balance the charge of the V
SP
pattern.)
If the ID sensor were to check the V
SP
pattern’s reflectivity under this
condition, the V
SP
pattern would be darker than before. The CPU would then
incorrectly conclude that the toner weight ratio in the developer is too high
even though the ratio actually remains the same. The CPU would then
decrease the toner clutch on time, leading to a low percentage of toner in the
developer by weight as the copy count rises.
If uncontrolled, this would cause some side effects, such as low image
density or developer adhering to the copy. To prevent these side effects, ID
correction is done when the V
SP
pattern is made.
12345678 9101112
13
14 15
29
30
31
V
SP
Detection
V
SG
Detection
V
SP
Detection
1st Series of Copies
(8 copies)
3rd Series of
Copies (17
copies)
2nd Series
of Copies
(5 copies)
V
SG
Detection
V
SG
Detection
V
SG
Detection
V
SP
Detection
A156/A160/A162 2-12 STM