JP3264765B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for an image forming apparatus such as a copying machine and a facsimile.

[0002]

2. Description of the Related Art Conventionally, in an image forming process, as a developer used to visualize an electrostatic latent image on a photosensitive member,
A so-called 2 comprising carrier particles as a magnetic substance and toner particles as a colored resin adhered to the carrier particles in a triboelectric manner.
Component developers are widely used. Such a two-component developer forms a magnetic brush on the developing sleeve, and a visible image is formed by rubbing the electrostatic latent image on the photoconductor with the magnetic brush.

When development is performed using such a two-component developer, the toner portion of the developer is consumed each time the development is repeated, so that the ratio of the developer to the carrier decreases, and as a result, the ratio of the formed image is reduced. The concentration decreases. Therefore, an amount of fresh toner corresponding to the consumption amount is appropriately supplied to the developer.

On the other hand, carrier particles also have various problems. That is, if the image forming process is repeated and the carrier particles are used repeatedly each time, the surface of the particles is worn or the toner adheres and accumulates on the surface, so that the triboelectric charging characteristics of the carrier are deteriorated. When the characteristics deteriorate, the carrier and the toner are mixed and agitated, and the toner is adhered to the latent image by rubbing a magnetic brush formed on the developing sleeve with the developer against the electrostatic latent image on the photosensitive member. Disturbance occurs in the process of visualizing.

[0005] Therefore, in order to maintain image quality, not only the toner but also the carrier needs to be replaced according to the degree of use, and the replacement work is performed. This work requires time, Disposal of the deteriorated developer is complicated and workability is poor.

If the above operation is performed as a total replacement of the developer, the developer cannot be replaced until the life of the developer is reached, and the density of the formed image cannot be maintained constant.

Therefore, it is required to replace the toner at intervals at which the density does not substantially decrease. However, it is inefficient if the replacement is performed manually, and if the entire amount is replaced each time, the usable toner in the developer is used. Wastes are too much waste.

For example, Japanese Patent Application Laid-Open No. 53-22747 discloses a developing device in which a new two-component developer is supplied to a developing device, a stored developer is discharged on the other side, and toner is separately supplied. It has been proposed to exchange the developer while controlling the concentration of the developer therein to maintain the developing ability.

However, if a developer supply device is separately provided for supplying a carrier in addition to the toner replenishment, problems such as an increase in size, complexity, and cost of the device are caused.

[0010]

SUMMARY OF THE INVENTION Therefore, Japanese Patent Laid-Open Publication No.
No. 7683, a developer replenishing container and a waste reservoir are supplied so that a replenishing developer in which carrier particles are mixed in advance is supplied to a developing device, and the developer overflowed in the developing device can be removed. A developing device having the same is disclosed.

When the developer is replaced by using a so-called premix agent in which a carrier is previously mixed with the replenishment toner, for example, the premix agent is reduced when the toner concentration in the developer is reduced by the toner concentration detecting means. Therefore, the ratio of the toner particles to the carrier particles in the premix agent is considerably larger than the ratio of the toner particles to the carrier particles in the developing device. By such adjustment, the developer concentration in the developing device can be maintained.

However, when the deteriorated developer is discharged in the overflow mode, there are the following problems.

That is, the ratio of the carrier to the toner in the developing device is adjusted to, for example, 97: 3, and the toner is consumed by repeating the image forming process, and the ratio is 98: 2.
Let's say At that stage, the developer concentration in the developing device has decreased, and the amount of the developer has also decreased. Then, a toner supply instruction is issued, and the ratio of the carrier and the toner becomes 2
The premix at 0:80 is replenished, the density is adjusted, and the stored developer amount is restored. Only after the reduced storage amount recovers, the stored developer is discharged,
That is, the developer is discharged in a state where the ratio of the toner to be used for image formation is relatively high. That is, if the developer is not discharged at the stage where the toner concentration is the lowest, and the developer is discharged only at the stage where the toner concentration is relatively high, more toner is discharged, and waste is increased. . In order to minimize wasteful discharge of effective toner, it is preferable to discharge the developer at a time when the toner concentration is low. However, in the conventional configuration, it is difficult to discharge the developer from a stage where the toner concentration is low. is there.

In view of the above-mentioned problems, the present invention relates to a premix type toner supply and discharge of a deteriorated developer.
When the toner concentration is low, the developer is actively discharged, and when the concentration is high, the discharge is suppressed.If necessary, the discharge amount of the developer is controlled, and the unnecessary amount of toner to be used for image formation is controlled. An object of the present invention is to provide a developing device capable of reducing waste.

[0015]

SUMMARY OF THE INVENTION According to the present invention, there is provided an apparatus main body having a developing means for visualizing a latent image formed on a surface of an image carrier, and a developing apparatus connected to the apparatus main body, In a developing device having a replenishing container containing a premix agent composed of magnetic particles and a coloring material, and a collecting container connected to the device main body and collecting a developer discharged from the main body, the device main body and the collecting container A shutter for changing the area of the discharge opening that connects the image forming apparatus, a means for detecting the toner concentration in the apparatus main body is provided, and the area of the discharge opening is adjusted by the shutter based on the detection result. It is solved by controlling.

[0016]

When the area of the discharge opening is changed, the shutter is preferably moved up and down so as to close in order from the lower part of the opening.

It is preferable that the shutter is disposed at a position farthest from the premixing agent replenishing position or at a central region in the longitudinal direction of the apparatus main body.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment based on the drawings.

In FIG. 1, which shows the overall structure of an image forming apparatus equipped with a developing device according to the present invention, the surface of a photoreceptor 1 is uniformly charged by a charger 2, and an electrostatic latent image is formed by light irradiation 3 by an optical system. Is formed on the surface. Next, when the electrostatic latent image passes the position facing the developing device 4, the latent image is visualized by toner adhesion, and is superimposed on the recording paper conveyed from the paper feed cassette 8 at a proper timing. Vessel 5
Is used to transfer the toner image onto the recording paper. The recording paper on which the toner image has been transferred is separated from the photoconductor 1 by the separator 6,
The sheet is sent to the fixing device 7 by the conveyor belt. The transferred toner image is fixed on the recording paper by passing through the fixing device 7, and the recording paper is sent to the waste paper unit 9. On the other hand, the photoreceptor 1 after the transfer process has the residual toner removed by the cleaning device, and the residual charge on the photoreceptor 1 is eliminated by a static eliminator (not shown).

In this series of image forming processes, in the developing device 4 containing a dry two-component developer of a carrier and a toner having a toner content of 2 to 3% by weight, the development stored in the casing The agent is charged while being stirred by the transport paddle 11, and is pumped up by the developing sleeve 10 containing a magnet to form a magnetic brush. The amount and height of the magnetic brush held by the developing sleeve 10 are regulated by the doctor blade 19. Thereafter, the magnetic brush is conveyed to a developing area where the surface of the developing sleeve 10 and the surface of the photoconductor 1 are closest to each other, and the frictionally charged toner is attracted to the electrostatic latent image on the photoconductor 1 charged to the opposite polarity. , And development is performed. Doctor blade 19
The developer scraped off by the above is subjected to so-called lateral stirring in the axial direction of the sleeve by the separator 12, and falls onto the paddle 11.

When the toner is consumed by the developing process, the fresh toner in the toner bottle 13 stirred by the agitator 15 is supplied to the developing device 4 in small amounts as needed by the rotation of the supply roller 14. Toner bottle 13
It also contains carrier particles, and the carrier and the fresh toner constitute a premix agent. The ratio of the toner particles to the carrier particles in the premix is slightly larger than the ratio of the toner particles to the carrier particles in the developing device.

When the premix is supplied to replenish the consumed toner in this manner, the carrier does not run out, so that the level of the developer in the developing unit 4 gradually increases, and eventually a part of the stored developer is discharged to the outlet. 16 overflows the developing device 4. The overflowed developer is collected in a developer collecting device 17.

In this way, a new carrier is supplied little by little, and the developer in the developing device 4 is discharged little by little, so that the deterioration of the developer in the developing device 4 is prevented, and the image forming apparatus main body is removed. There is no need to perform a special carrier exchange until the end of the life. If the capacity of the recovery unit 17 can accommodate all the amount of developer to be recovered before the end of the life of the main body, the recovery operation of the deteriorated developer becomes unnecessary.

As can be understood from FIG. 2 showing the developing casing from the rear side of the machine main body, the developer outlet 21 has a frame, and the shutter 2 capable of covering the frame.
2 is slidably mounted. The shutter 2
2 is a gear 25 having a common shaft with a drive motor (not shown).
And the rack gear 23 via the intermediate gear 24. For example, the shutter 22 slides on the frame of the discharge port 21 via the gears 24 and 25 by the rotation of a drive motor that is a stepping motor that can rotate forward and reverse, and the sliding area reduces the opening area of the discharge port 21. Change. The control of the drive motor is performed in accordance with the detection result of a toner density detection unit (not shown). Reference numeral 26 denotes a drive gear train for the developing sleeve 10 and the stirring paddle 11.

For example, 970 g of a carrier is placed in a developing device.
r, when 30 gr of toner is present, the toner density is 3%. At this stage, it is assumed that the developer does not leak from the outlet 21. The image forming process is repeated, the toner is reduced to 10 gr, the toner density detecting means detects a decrease in toner density (toner density is about 1%), and when a toner replenishment signal is issued, the premix agent is supplied from the toner bottle to the replenishing port 27. And supplied to the developing device. Assuming that the ratio of the toner and the carrier in the premix agent is 1: 1 and that the premix agent of 20 gr is supplied into the developing device without changing the opening area of the discharge port 21, the discharge of the developer is started. At this stage, the toner concentration in the developing unit is 2%, and the supply of the premix agent must be continued while the discharge of the stored developer is continued until the toner concentration returns to 3%. As a result, the amount of toner that is discarded without being used is unnecessarily increased. In the present invention, when the toner density detecting unit detects a decrease in the density, the toner replenishment signal is issued, and at the same time, the drive motor for the shutter 22 is rotated to increase the opening area of the discharge port 21. For example, if the outlet 21 is rapidly expanded so as to reduce the storage development amount to 960 gr, the toner amount is 9.6 gr in the remaining storage amount because the toner concentration is 1%. When the drive motor is immediately rotated in the reverse direction to return the shutter 22 to the original position, the premix agent can be supplied in an amount of 40 gr (20 gr of toner). As a result, 1 g of toner is discharged as the toner concentration is restored.
r, and wasteful disposal can be minimized.

Without moving the shutter as described above,
When the toner concentration is low, it is possible to control the discharge of the developer to be large, and to reduce the discharge amount as the concentration increases. Also, in order to prevent the freshly replenished premix from being discharged immediately, the replenishing port 27 is required.
And the discharge port 21 are separated from each other, but the developer discharge port 31 may be located substantially at the center of the developing unit as shown in FIG. Accordingly, when the developing unit is inclined in the longitudinal direction, it is possible to prevent the developer from being discharged more than necessary or conversely from being discharged. In short, the present invention is not limited to the above embodiments in detail, and it goes without saying that many improvements and modifications can be made without departing from the scope of the invention.

[0028]

According to the present invention, there is provided a shutter for changing the area of the discharge opening connecting the apparatus main body and the collection container, and further provided with means for detecting the toner concentration in the apparatus main body, Based on the detection result, the shutter is controlled so as to adjust the area of the discharge opening. Therefore, when the toner concentration is low, the developer is actively discharged, and when the concentration is high, the discharge is refrained and used for image formation. Unnecessary disposal of toner to be performed can be reduced.

[0029]

[Brief description of the drawings]

FIG. 1 is a schematic end view of an image forming apparatus provided with a developing device of the present invention.

FIG. 2 is a perspective view of a schematic configuration of a developing casing as viewed from a rear side of a machine main body.

FIG. 3 is a perspective view of another configuration.

[Explanation of symbols]

 21 Developer Outlet 22 Shutter 23 Shutter Side Gear 24, 25 Gear 26 Drive Gear Train 27 Toner Supply Port

Continued on the front page (72) Inventor Yasufumi Nakazato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Sou 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company (72) Inventor Yoshiko Ishii 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. Inside Ricoh Company (72) Inventor Nobuto Yokokawa 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Company, Ltd. (72) Inventor Masako Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (56) References JP-A-5-289506 (JP, A) JP-A-4-66984 (JP, A) Actual opening Sho 62-35369 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 13/08-13/095 G03G 15/08-15/095

Claims (4)

(57) [Claims] 1. An apparatus main body having a developing means for visualizing a latent image formed on the surface of an image carrier, and a premix agent connected to the apparatus main body and comprising a magnetic particle and a coloring material. A developing container having a supply container connected to the main body of the apparatus and a collecting container connected to the main body of the apparatus for collecting the developer discharged from the main body. A developing device comprising a shutter, means for detecting the toner concentration in the apparatus main body, and controlling the shutter to adjust the area of the discharge opening based on the detection result. 2. The developing device according to claim 1, wherein when the area of the discharge opening is changed, the shutter moves up and down so as to close in order from a lower part of the opening. 3. The developing device according to claim 1, wherein the shutter is provided at a position farthest from a premix agent supply position. 4. The developing device according to claim 1, wherein the shutter is provided in a central region in a longitudinal direction of the apparatus main body.