JP2001175063A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device for surely and thoroughly bringing developer into contact with the detection surface of a toner concentration sensor and accurately detecting the toner concentration, even in a small-sized developing device. SOLUTION: The developing device is provided with a developer stirring spiral member which is arranged in a developer carrying path so as to extend along the developer carrying path, and the toner concentration sensor which is arranged on the midway of the developer carrying path, and as for the diameter of the spiral member, the diameter near the detection surface of the toner concentration sensor is made smaller than the diameter of other part of the spiral member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a printer,
The present invention relates to a developing device used in an electrophotographic image forming apparatus such as a facsimile machine.

[0002]

2. Description of the Related Art A developing device used in an electrophotographic image forming apparatus is provided with a toner density sensor for detecting a toner density (ratio of toner to developer). In order to accurately detect the toner density by the toner density sensor, it is necessary to bring the developer into contact with the detection surface of the toner density sensor.

[0003] In recent years, with the space saving and miniaturization of machines, the size of developing devices has been reduced. In particular, the downsizing of the developing device in the color machine is remarkable. In such a small-sized developing device, there is a problem that the developer capacity is small, it is difficult to ensure sufficient contact of the developer with the detection surface of the toner density sensor, and it is difficult to accurately detect the toner density. There is.

[0004]

SUMMARY OF THE INVENTION According to the present invention, even in a small developing device, sufficient contact of the developer with the detection surface of the toner density sensor can be ensured, and the toner density can be accurately detected. It is an object of the present invention to provide a developing device.

[0005]

A developing device according to the present invention is provided with a spiral member for stirring the developer extending along the developer conveying passage in the developer conveying passage. A developing device in which a toner concentration sensor is provided in the developing device, wherein a means for increasing the amount of developer near the detection surface of the toner concentration sensor in the developer conveying passage is provided more than in other portions. .

Specifically, for example, the spiral diameter of the spiral member near the detection surface of the toner density sensor is smaller than the spiral diameter of the other parts.

Specifically, for example, the spiral pitch of the spiral member near the detection surface of the toner density sensor is shorter than the spiral pitch of the other portions.

Specifically, for example, an obstacle wall that hinders the ability to transport the developer is provided downstream of the detection surface of the toner concentration sensor in the developer transport path.

[0009]

Embodiments of the present invention will be described below.

[1] Description of First Embodiment

FIGS. 1 and 2 show a developing device used in an electrophotographic copying machine. The developing device 1 includes a developing housing 11 having an opening facing the photosensitive drum 2. The photosensitive drum 2 is driven to rotate in the direction of arrow A.

The developing housing 11 contains a two-component developer composed of a non-magnetic toner and a magnetic carrier. An upper chamber 12 and a lower chamber 13 are provided in the developing housing 11. The upper chamber 12 and the lower chamber 13 communicate with each other at both left and right ends. In the upper chamber (developer conveying passage) 12, a first spiral member 14 for stirring the developer is rotatably provided. The first spiral member 14 is driven to rotate in the direction of arrow B.

First spiral member 1 in lower chamber 13
A second spiral member 15 for stirring the developer is rotatably provided directly below the position 4. The second spiral member 15 is driven to rotate in the direction of arrow C. A developing sleeve 16 is rotatably provided near the opening in the lower chamber 13. A plurality of magnets (not shown) for attracting the developer with magnets are fixed in the developing sleeve 16 so as not to rotate. The developing sleeve 16 is driven to rotate in the direction of arrow D by a driving device (not shown).

In the developing housing 11, a cutting board 17 for regulating the height of a magnetic brush formed on the surface of the developing sleeve 16 is disposed at a position close to the developing sleeve 16.

In the right end communication portion between the upper chamber 12 and the lower chamber 13, the developer conveyed by the second spiral member 15 to the right end of the lower chamber 13 is conveyed to the right end of the upper chamber 12. A magnet roller 18 is provided.

The first spiral member 14, the second spiral member 15, the developing sleeve 16, and the magnet roller 1
Numeral 8 is connected by a power transmission mechanism constituted by a plurality of gears, and is integrally driven to rotate.

At the center of the width of the upper chamber 12, a toner density sensor 20 is provided. The detection surface 21 of the toner density sensor 20 faces the inside of the upper chamber 12. Detection surface 2 of toner density sensor 20 in first spiral member 14
The spiral diameter of the portion near one is formed smaller than the spiral diameter of the other portion.

The developer is conveyed while being stirred in the upper chamber 12 from the right end in FIG. 2 to the left by the first spiral member 14, and is transferred to the lower chamber 13 by the left end communication portion of the upper chamber 12 and the lower chamber 13. Conveyed. Lower room 13
The developer transported to the upper chamber 12 and the lower chamber 13 is sent to the right end communication part of the upper chamber 12 and the lower chamber 13 while being stirred by the second spiral member 15 from the left end in FIG.

The developer sent to the right end communication portion between the upper chamber 12 and the lower chamber 13 is conveyed to the upper chamber 12 by the magnet roller 18. That is, the developer is circulated between the upper chamber 12 and the lower chamber 13 and is agitated in this process.

In this developing device, the first spiral member 1
4, the spiral diameter of the portion near the detection surface 21 of the toner density sensor 20 is formed smaller than the spiral diameter of the other portions. The transport capacity decreases. For this reason, the toner concentration sensor 20 in the upper chamber 12
In the vicinity of the detection surface 21, the amount of developer present increases,
Sufficient contact of the developer with the detection surface 21 of the toner density sensor 20 is ensured. As a result, the toner density sensor 20
, The detection accuracy of the toner density is improved.

[2] Description of Second Embodiment

FIG. 3 shows a second embodiment.
3, the same reference numerals are given to the corresponding portions in FIGS. 1 and 2.

In the second embodiment, the spiral diameter of the first spiral member 14 is uniform, but the spiral pitch of the first spiral member 14 near the detection surface 21 of the toner density sensor 20 is different from that of the other spiral members. Is formed shorter than the spiral pitch.

Since the spiral pitch in the vicinity of the detection surface 21 of the toner density sensor 20 in the first spiral member 14 is formed shorter than the spiral pitch in the other portions, the detection surface of the toner density sensor 20 in the upper chamber 12 is formed. In the portion near 21, the developer carrying capacity is reduced. For this reason, the detection surface 21 of the toner density sensor 20 in the upper chamber 12
In the vicinity, the amount of the developer increases, and sufficient contact of the developer with the detection surface 21 of the toner density sensor 20 is ensured. As a result, the accuracy of toner concentration detection by the toner concentration sensor 20 is improved.

[3] Description of Third Embodiment

FIGS. 4 and 5 show a third embodiment. 4, the same reference numerals are given to the corresponding parts in FIGS. 1 and 2.

In the third embodiment, the spiral diameter and the spiral pitch of the first spiral member 14 are uniform.

An obstruction wall 30 is provided on the first spiral member 14 downstream of the detection surface 21 of the toner density sensor 20 for hindering the ability to transport the developer. For this reason,
In the vicinity of the detection surface 21 of the toner concentration sensor 20 in the upper chamber 12, the amount of developer increases, and sufficient contact of the developer with the detection surface 21 of the toner concentration sensor 20 is ensured. As a result, the accuracy of toner concentration detection by the toner concentration sensor 20 is improved.

[0029]

According to the present invention, even in a small developing device, sufficient contact of the developer with the detection surface of the toner density sensor can be ensured, and the toner density can be accurately detected. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a developing device.

FIG. 2 is an arrow view along the line II-II in FIG.

FIG. 3 is a diagram illustrating another example of the developing device and corresponding to FIG. 2;

FIG. 4 is a view corresponding to FIG. 2 and showing still another example of the developing device.

FIG. 5 is an enlarged sectional view taken along line VV of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Developing device 11 Developing housing 12 Upper chamber 14 1st spiral member 20 Toner density sensor 21 Detection surface 30 Obstacle wall

Claims (4)

[Claims] A developing device provided with a spiral member for stirring the developer extending along the developer conveying passage in the developer conveying passage, and a toner concentration sensor provided at an intermediate position of the developer conveying passage. 3. The developing device according to claim 1, further comprising means for increasing the amount of the developer near the detection surface of the toner concentration sensor in the developer transport passage to be larger than other portions. 2. The developing device according to claim 1, wherein a spiral diameter of a portion around the detection surface of the toner concentration sensor in the developer stirring spiral member extending along the developer conveying passage is smaller than the spiral diameter of other portions. The developing device according to claim 1, wherein: 3. The developing device according to claim 1, wherein a spiral pitch of a portion of the spiral member near a detection surface of the toner density sensor is shorter than a spiral pitch of another portion. 4. The developing device according to claim 1, wherein an obstacle wall that hinders the ability to transport the developer is provided downstream of the detection surface of the toner density sensor in the developer transport path.