JPH0651634A - Developing device - Google Patents

Abstract

PURPOSE:To miniaturize a device and simultaneously, to obtain an excellent image without the nonuniformity of density by uniformizing the distributions of a developer in a stirring room and a toner concentration, in a developing device provided roughly in parallel in the width direction of a formed image, having two stirring rooms communicated at both end parts, and circulatingly carrying the developer in these stirring rooms. CONSTITUTION:Two stirring rooms 5 and 6 are vertically arranged side by side and besides an auger 8 carrying the developer, another auger 9 which is in the upper side of the auger 8 and carries the developer in the direction opposite to the auger 8 is provided in the stirring room 6 of the lower side. Thus, a large amount of the developer is prevented from being biasedly heaped in the vicinity of a part where the developer is transferred from the lower stirring room 6 to the upper stirring room 5 and an almost uniform developer distribution can be maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device which is used in an image forming apparatus such as an electrophotographic copying machine or a printer and which visualizes toner by adhering the toner to an electrostatic latent image. And a developing device using the two-component developer.

[0002]

2. Description of the Related Art In recent years, in image forming apparatuses such as electrophotographic copying machines, there has been a strong demand for downsizing of the apparatus body in order to achieve space saving. The demand for miniaturization is great.

FIG. 4 is a schematic view showing an example of a conventionally known developing device using a two-component developer. In this developing device, a first auger 107 and a second auger 108, which convey a two-component developer while stirring, are arranged side by side in the lateral direction behind a developing roll 103 (developer carrying member) to form a first auger. The developer is supplied to the developer carrier by 107. However, in such a developing device, the first auger 107 and the second auger 108 are arranged substantially horizontally, so that it is necessary to secure a dimension equal to or larger than the sum of the diameters of the two augers in the lateral direction in the device. The disadvantage is that the device becomes laterally larger.

To solve this problem, FIG. 5 or FIG.
The developing device as shown in FIG. FIG. 5 is a schematic configuration diagram showing a developing device disclosed in Japanese Patent Publication No. 3-16026. This developing device includes a developing roll 113 provided inside a housing 112 containing a developer so as to face the electrostatic latent image holding member 101, and the developing roll 113.
A first auger 117 and a second auger 1 which are arranged substantially parallel to each other and which convey the developer in mutually opposite directions.
18 and a blender 119 for equalizing the distribution of the developer.

The first auger 117 and the second auger 118 are partitioned by a partition wall 111 so that the developer is circulated in the first agitating chamber 115 and the second agitating chamber 116 which communicate with each other at both ends. It is to be transported. Further, the second auger 118 is located at a position facing the developing roll so that the developer can be supplied to the surface of the developing roll.

The developer agitated by the first auger 117 and the second auger 118 is the second auger 1
18 is supplied to the surface of the developing roller 113, and is conveyed by the rotation of the developing roller 113, and the electrostatic latent image carrier 10 is conveyed.
1 is used for development in the development area opposite to 1. On the other hand, the developer that has not contributed to the development is again collected in the second stirring chamber 116 and stirred by the second auger 118. In such a developing device, the first auger 117 and the second auger 118 are installed vertically in the developing device. Therefore, by devising the size and arrangement position of the blender 119, the developing device This has the advantage that the lateral dimension of can be reduced.

On the other hand, FIG. 6 is a schematic structural view showing another example of a developing device in which two augers are vertically arranged. This developing device includes a first stirring chamber 125 provided with a first auger 127 that conveys the developer in a certain direction at a position where the developer can be supplied to the developing roll 123, and below the first stirring chamber 125. The first auger 127 and a second stirring chamber 126 having a second auger 128 that conveys the developer in the opposite direction. The first stirring chamber 125 and the second stirring chamber 126 are partitioned by a partition wall 121,
The two ends communicate with each other, and the developer is supplied to these two stirring chambers 1
It is conveyed so as to circulate in 25 and 126.

The first auger 127 is used to develop the developing roll 1.
The developer supplied to 23 is provided for development at a position facing the electrostatic latent image holding member 101 by the rotation of the developing roller 123, and the developer not contributing to the development is again stored in the second stirring chamber 126. And is stirred by the second auger 128. In such a developing device as well, the first auger 127 and the second auger 128 are installed vertically in the developing device as in the developing device shown in FIG. Can be made smaller.

[0009]

However, in the developing device as shown in FIGS. 5 and 6, when the developer is conveyed in a circulating manner by the first auger and the second auger, the developer is lowered downward. The developer may not be smoothly transferred from a certain stirring chamber to the upper stirring chamber, and the developer may be deposited in the vicinity of the end of the lower stirring chamber. As described above, when a large amount of the developer is deposited on the rear portion of the developing roll (on the side opposite to the portion facing the electrostatic latent image holding member), the stirring becomes insufficient at that portion, and the toner density after passing through the developing area is reduced. The low developer is supplied again to the developing roll and is conveyed to the developing area again. Therefore, there is a problem in that the toner concentration in the developer on the surface of the developing roll becomes non-uniform in the axial direction of the developing roll, and uneven density tends to occur in the image.

For example, the flow of the developer which causes the above-mentioned problems in the developing device shown in FIG. 6 will be described by modeling as a block diagram shown in FIG. In an ideal developer flow in this developing device, as shown by the solid line, the developer separated from the developing roll is transported in the second stirring chamber and transferred to the first stirring chamber (communication part). Pass through, first
And is supplied to the developing roll. In addition, the developer not supplied to the developing roll is the second
Then, it is returned to the second stirring chamber via the transfer section to the stirring chamber.

However, when the developer stays in the vicinity of the transfer section (communication section) from the second stirring chamber to the first stirring chamber, the developer having a reduced toner concentration passes through the developing area in the vicinity of the transfer section. There is a case where there is a developer flow in which the toner is transported to the developing area again without being collected in the second stirring chamber. As shown in FIG. 6, when the developer is deposited in the second stirring chamber 126 near the surface of the developing roll 123 (at the position indicated by reference symbol G), the developer collected from the developing area is again deposited on the surface of the developing roll. The toner adheres and is conveyed to the developing area by the rotation of the developing roller 123, and the developer flow shown by the broken line in FIG. 7 is obtained. However, in the other regions in the axial direction of the developing roll, the developer flow is as shown by the solid line, which causes a phenomenon that the toner concentration of the developer on the developing roll becomes uneven.

FIG. 8 shows the toner density on the developing roll after the continuous development of 10 solid black images using the developing device shown in FIG. The toner concentration on the back side, which is in the vicinity of the developer transfer portion from the second stirring chamber 126 to the first stirring chamber 125, is lower than the toner concentrations on the front side and the center side.
Therefore, density unevenness easily occurs in the image during development.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a downsized developing device, in which the amount of the developer in the axial direction of the developer carrier in the stirring chamber is controlled. It is an object of the present invention to provide a developing device capable of obtaining a good image without unevenness in density by making the distribution and the distribution of toner density uniform.

[0014]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a developer carrier provided to face an electrostatic latent image carrier, and an axial direction of the developer carrier. A first stirring chamber provided with a first auger for transporting the developer along the first stirring chamber, and the first stirring chamber is provided substantially parallel to the first stirring chamber and communicates with the first stirring chamber at both ends. In a developing device having a first auger and a second stirring chamber provided with a second auger that conveys a developer in the opposite direction,
The second stirring chamber is provided substantially directly below the first stirring chamber, and the developer is conveyed above the second auger in the second stirring chamber in a direction opposite to the second auger. It shall be equipped with 3 augers.

The third auger is located above the second auger and retains the developer accumulated in the vicinity of the developer transfer section (communication section) from the second stirring chamber to the first stirring chamber. As long as it can be conveyed in the direction opposite to the second auger, its arrangement position, size, etc. can be set appropriately. Further, the rotation direction of each auger can be appropriately set according to the arrangement and structure of each auger. The communication part (transfer part) between the first stirring chamber and the second stirring chamber is arranged outside the both ends of the developer adhering region on the developer carrier in the developing device. desirable.

[0016]

In the developing device having the above-described structure, the second stirring chamber is provided almost immediately below the first stirring chamber, and the second stirring chamber is provided above the second stirring chamber in the second stirring chamber. Since the third auger that conveys the developer in the opposite direction is provided, when the developer in the second stirring chamber is conveyed by the second auger and carried into the first stirring chamber, The developer staying in the vicinity of the transfer portion from the stirring chamber to the first stirring chamber is conveyed by the third auger in the direction opposite to the second auger. Therefore, it becomes possible to keep the developer in the second stirring chamber substantially evenly in the axial direction of the second auger.
These developers are again conveyed in a predetermined direction by the second auger and carried into the first stirring chamber. Therefore, the developer having a lowered toner concentration is not supplied to the developer carrier from the second stirring chamber, and the developer having a sufficient toner concentration and a uniform toner concentration is supplied to the developer carrier. . As a result, it becomes possible to form an image having a uniform density in the axial direction of the developer carrying member.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing a developing device which is an embodiment of the present invention. The developing device 2 is provided so as to face the electrostatic latent image holding member 1 capable of holding an electrostatic latent image due to a difference in charging potential, and a two-component developer including a non-magnetic toner and a magnetic carrier is provided. In the housing 12 to accommodate,
A developing roll (developer carrying member) 3 that magnetically adsorbs a two-component developer to form a magnetic brush on the surface, and a developer regulating member 4 that regulates the amount of the developer adsorbed on the developing roll 3. , A first stirring chamber 5 provided with a first auger 7 that conveys a developer along the axial direction of the developing roll 3, and a first stirring chamber 5 and a partition 13 which are located immediately below the first stirring chamber 5. And a second stirring chamber 6 with two augers 8. Furthermore, in the second stirring chamber 6, a third auger 9 is provided between the second auger 8 and the developing roll 3 above the second auger 8.

The developing roll 3 has a rotatable cylindrical sleeve arranged around the outer circumference of a magnetic roll whose position is immovable and contains a plurality of magnets. The two-component developer is magnetically attracted to the developing roll 3. The magnetic brush can be formed by using the magnetic brush and the developer can be conveyed by rotating the cylindrical sleeve. The first auger 7 and the second auger 8 are arranged substantially parallel to each other in the vertical direction and can rotate to stir the developer and convey the developer in the axial direction. It is set to do. Further, the first auger 7 is arranged substantially parallel to the developing roll 3 so as to face the developing roll 3, and rotates in the direction of arrow A shown in FIG. 1 to supply the two-component developer to the developing roll 3. By rotating the second auger 8 in the direction of arrow B shown in FIG. 1, a large amount of developer is deposited on the side opposite to the developing roll 3, and the toner collected from the developing roll 3 is formed. Is designed to facilitate stirring.

The third auger 9 is arranged substantially parallel to the second auger 8 adjacent thereto, and its rotation direction is set in the direction of arrow C shown in the figure, and the second auger 8 is set. The developer is conveyed in the opposite direction. The first stirring chamber 5 and the second stirring chamber 6 are separated from each other by a partition wall 13
And is communicated at both ends, and the developer is conveyed so as to circulate in both stirring chambers 5 and 6 as the first auger 7 and the second auger 8 rotate. . Further, the communication portion (developer transfer portion) is arranged inside the housing 12 so as to be located outside both end portions in the axial direction of the developing roll 3.

In such a developing device, the flow of the developer is as follows. FIG. 2 is an explanatory view showing a developer flow of the developing device, in which the developer collected from the surface of the developing roll 3 into the second stirring chamber 6 after passing through the developing area is shown by the second auger 8 in the figure. It is conveyed in the direction of the arrow D shown in. The transported developer passes through the transfer section (communication section) 11 from the second stirring chamber 6 to the first stirring chamber 5 and is carried into the first stirring chamber 5; Since the chamber 5 is above the second stirring chamber, the transport amount of the second auger 8 may exceed the transport amount to the first stirring chamber 5, and the developer may stay near the transport unit 11. The retained developer is conveyed by the third auger 9 in the second stirring chamber 6 in the direction opposite to the second auger 8 (the direction of arrow E shown in the drawing). This developer is mixed with the developer collected from the developing roll 3, and is again conveyed by the second auger 8 in the direction opposite to the third auger (the direction of arrow D shown in the drawing). As a result, the developer in the second stirring chamber 6 is sufficiently stirred and the accumulated amount is equalized in the axial direction of the developing roll. Therefore, the developer is not partially excessively accumulated, and the developer having a low toner concentration is not supplied from the second stirring chamber 6 to the developing roll 3.

In the first stirring chamber 5, the first auger 7
Is in the opposite direction to the second auger 8 (arrow F shown in the figure).
The developer is smoothly carried into the first stirring chamber 5 from the second stirring chamber 6 by rotating so as to convey the developer in the direction (1). In the first stirring chamber 5, the developer is conveyed to the developing roll 3 by the rotation of the first auger 7, and the developer not supplied to the developing roll 3 is supplied to the developing roll 3. It is carried into the second stirring chamber 6 through the transfer unit (communication unit) 10 from the first stirring chamber to the second stirring chamber.

In this way, the first stirring chamber 5 and the second stirring chamber 5
The developer conveyed in the stirring chamber 6 of each of the augers 7, 8,
The toner is agitated by the rotation of 9, and a desired charge is imparted by frictional electrification between the non-magnetic toner and the magnetic carrier. The developer, which is sufficiently charged and supplied from the first auger 7 to the developing roll 3, is magnetically adsorbed on the surface of the developing roll 3 to form a magnetic brush of the developer. At this time, the developer is sufficiently stirred and the toner concentration is uniform in the axial direction of the developing roll 3. The amount of the developer of the magnetic brush of the developer is regulated by the developer regulating member 4, and the developing roll 3
By the rotation of the surface, it is conveyed to the developing area facing the electrostatic latent image holder 1.

In the developing area, a voltage is applied between the developing roll 3 and the electrostatic latent image carrier 1 to form a desired electric field, and the magnetic brush rubs the surface of the electrostatic latent image carrier 1. As a result, the non-magnetic toner is attached to the electrostatic latent image and development is performed. On the other hand, the toner and the magnetic carrier remaining on the surface of the developing roll 3 after the development are released from the surface of the developing roll 3 at the position where the repulsive magnetic pole is arranged in the developing roll 3 due to the rotation of the surface of the developing roll 3, Stirring chamber 6
Will be recovered in. The collected developer is transported in the second stirring chamber 6 and the first stirring chamber 5 as described above.

After continuously developing ten solid black images by using such a developing device, the toner density of the developer on the developing roll was measured. As shown in FIG. It was confirmed that the toner concentration was almost uniform at any position in. Further, it was confirmed that the average toner concentration at this time is very close to the toner concentration of the entire developer housed in the developing device, and the efficiency of exchanging the old developer and the new developer is high. Therefore, it is possible to obtain the performance in which the image density is not uneven even when the copying is continuously performed. Also, the lateral dimension of the developing device can be set to about 100 mm from the axial center of the electrostatic latent image holding member (Φ84), and a very small developing device can be provided.

[0025]

As described above, in the developing device of the present invention, the second stirring chamber is provided almost directly below the first stirring chamber,
The main body of the apparatus can be downsized, and at the same time, the third auger that conveys the developer in the opposite direction to the auger is provided above the second auger in the second stirring chamber. The distribution of the developer contained in the stirring chamber can be made uniform in the axial direction of the developer carrier. Therefore, a developer having a uniform toner concentration can be supplied onto the developer carrying member, and stable development can be performed without unevenness in image density.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a developing device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a flow of a developer in the developing device of the above embodiment.

FIG. 3 is a diagram showing a result of measuring a toner concentration of a developer on a developing roll in the developing device of the embodiment.

FIG. 4 is a schematic sectional view showing an example of a conventional developing device.

FIG. 5 is a schematic cross-sectional view showing an example of a conventional developing device in which two stirring chambers are arranged vertically.

FIG. 6 is a schematic cross-sectional view showing another example of a conventional developing device in which two stirring chambers are arranged vertically.

7 is a block diagram showing a flow of a developer in the developing device shown in FIG.

8 is a diagram showing a result of measuring a toner concentration of a developer on a developing roll in the developing device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrostatic latent image holder 2 Developing device 3 Developer carrier 4 Developer regulating member 5 1st stirring chamber 6 2nd stirring chamber 7 1st auger 8 2nd auger 9 3rd auger 10 1st Transfer portion from the stirring chamber to the second stirring chamber 11 Transfer portion from the second stirring chamber to the first stirring chamber 12 Housing 13 Partition wall

Front page continued (72) Inventor Masa Ishikawa 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd.Ebina business office (72) Inventor Toshikazu Tameda, 2274 Hongo, Ebina city, Kanagawa Fuji Xerox Co., Ltd.Ebina business office (72 ) Inventor Shinichi Kuramoto 2274 Hongo, Ebina City, Kanagawa Fuji Xerox Co., Ltd.Ebina Business Office (72) Inventor Masanori Kato 2274 Hongo, Ebina City, Kanagawa Fuji Xerox Co., Ltd.Ebina Business Office (72) Inventor Nitta Tatsuya 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (1)

[Claims] 1. A first carrier provided with a developer carrier provided to face the electrostatic latent image carrier, and a first auger for transporting the developer along an axial direction of the developer carrier. An agitating chamber and a second auger which is provided substantially parallel to the first agitating chamber and communicates with the first agitating chamber at both ends and conveys the developer in a direction opposite to the first auger. Second
A second stirring chamber is provided substantially directly below the first stirring chamber, and the second auger is provided above the second auger in the second stirring chamber. And a third auger that conveys the developer in the opposite direction.