| (19) |
 |
|
(11) |
EP 0 542 276 A3 |
| (12) |
EUROPEAN PATENT APPLICATION |
| (88) |
Date of publication A3: |
|
22.09.1993 Bulletin 1993/38 |
| (43) |
Date of publication A2: |
|
19.05.1993 Bulletin 1993/20 |
| (22) |
Date of filing: 12.11.1992 |
|
| (51) |
International Patent Classification (IPC)5: G03G 15/08 |
|
| (84) |
Designated Contracting States: |
|
DE FR GB |
| (30) |
Priority: |
15.11.1991 JP 300025/91
|
| (71) |
Applicant: SHARP KABUSHIKI KAISHA |
|
Osaka-shi
Osaka-fu (JP) |
|
| (72) |
Inventors: |
|
- Kato, Keiji
1-303, Ohmiya-cho 4-chome,Nara-shi,
Nara (JP)
- Uchida, Katsuzo
Ikoma-gun,
Nara (JP)
- Imai, Yasuo
Kita-Katsuragigun,
Nara (JP)
- Andou, Yukinori
Nara-shi,
Nara (JP)
- Sugito, Takashi
Tenri-shi,
Nara (JP)
|
| (74) |
Representative: TER MEER - MÜLLER - STEINMEISTER & PARTNER |
|
Mauerkircherstrasse 45
81679 München
81679 München (DE) |
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| |
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(57) There is provided a developing unit having the function to decide freshness/oldness
of a developer by using a toner sensor. Toner concentration of the developer is detected
by the toner sensor and when an output voltage of the toner sensor is higher than
a reference voltage by a constant value or more, the developer is determined to be
fresh and based on this result, a main motor is driven to rotate rollers in a developing
tank, thus stirring the developer. On the other hand, when the developer is determined
not to be fresh, not only the main motor but also a toner motor is rotated for toner
replenishment so as to adjust the toner concentration.