JPH1026878A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the ratio of toner to carrier and to form a uniform image by providing a partition dividing into a developing chamber and a stirring chamber between stirring screws and making the upper opening part of the partition large at a position corresponding to a detecting sensor in the longitudinal direction of a developing sleeve. SOLUTION: The partition 6 provided between the stirring screws 11 and 12 divides into the developing chamber 13 equipped with a developer compressing member 1 keeping the electrostatic charge amount of two- component developer uniform, the developing sleeve 3 carrying and supplying the developer to a developing nip, the developer detecting sensor 7 detecting the mixing ratio of the toner to the carrier in the developer and the stirring screw 11, and the stirring chamber 14 equipped with the stirring screw 12. The partition 6 is notched at the position corresponding to the sensor 7 and the height of the upper opening part of the partition 6 is made large in the longitudinal direction of the sleeve 3. Thus, the fluctuation of the carrying amount of the developer is restrained, and the pressure of the developer applied to the sensor 7 is kept constant, so that output from the sensor 7 becomes stable.

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 printer.

[0002]

2. Description of the Related Art FIG. 6 shows a laser printer having four photosensitive drums. This printer has image forming means around a photosensitive drum, and is provided with four image forming stations corresponding to colors, and toner images formed on the photosensitive drum formed at each image forming station. But,
The image is transferred onto a transfer material conveyed by a belt-shaped moving body that moves opposite to the photosensitive drum, and a color image is formed.

That is, magenta, cyan, yellow, and black stations Pm, Pc, Py, and Pk include:
Each photosensitive drum 4 rotates in the direction of an arrow (clockwise).
(4M, 4C, 4Y, 4K) are arranged. Around the photosensitive drums 4M, 4C, 4Y, and 4K, a corona charger 16 (16M, 16C, 16Y, 16K) and a scanning optical device 17 (17M, 17C, 17K) as an optical scanning unit are provided.
Y, 17K) developing device 9 (9M, 9C, 9Y, 9K),
The cleaning device 18 (18M, 18C, 18
(Y, 18K).

Further, the transfer section 6 constituting one of the image forming means includes a transfer belt 19a and a transfer charger 19 for each drum commonly used in each image forming station.
(19M, 19C, 19Y, 19K), and the formation of a full-color image is achieved by sequentially transferring toner images of the respective colors formed on the photosensitive drum onto a transfer material P supported on a transfer belt 19a. Achieved by The transfer material P is supplied from the paper feed cassette 20, the transfer material P having completed the transfer process is separated, and discharged to the tray 22 via the fixing device 21.

[0005] The scanning optical devices 17M, 17C, 17
Y and 17K are a laser light source which is a light source (not shown);
A rotating polygon mirror that scans the laser beam from the laser light source, an fΘ lens that focuses the scanning beam on a generatrix on the surface of the photosensitive drum, and a reflection mirror that redirects the light beam;
A beam detecting device for detecting a specific position of the scanning beam.

The developing device 9 (9M, 9C, 9Y, 9K) will be described. As shown in FIG. 7, the developing device 9 disposed opposite to the photosensitive drum 4 includes a developing container 8 and a developer carrier. Of the developer, a developer return member 1 for regulating the developer pool 5, and a blade 2 as a developer height control member. The inside of the developing device 9 is divided into a developing chamber (first chamber) 13 and a stirring chamber (second chamber) 14 by a partition 6 extending in the vertical direction.
Is open. Developing room 13 and stirring room 1
4, a two-component developer containing a non-magnetic toner and a magnetic carrier is stored in the present embodiment, and the excess developer in the developing chamber 13 is stored in the stirring chamber 14 side. The developing chamber 13 and the stirring chamber 14 are respectively provided with screw-type first and second developer stirring / transporting means 11 and 12.
Is arranged. The first stirring screw 11 stirs and conveys the developer in the developing chamber 13, and the second stirring screw 12 stirs this toner from a toner replenishing tank (not shown) under the control of the developer concentration controller. The toner supplied to the upstream side of the screw 12 and the developer already in the stirring chamber 14 are stirred and conveyed to make the toner concentration uniform. In the partition 6, a developer passage (not shown) that connects the developing chamber 13 and the stirring chamber 14 to each other is formed at the front and rear ends in FIG. 5, and the stirring screws 11 and 12 are formed. The developer in the developing chamber 13 whose toner concentration has been reduced due to the consumption of toner by the development due to the conveyance force moves from the other passage into the stirring chamber 14.

The developing chamber 13 of the developing device 9 has an opening at a position corresponding to a developing area facing the photosensitive drum 4, and the developing sleeve 3 is exposed partially at the opening.
Are rotatably arranged. The developing sleeve 3 is made of a non-magnetic material, rotates in a direction indicated by an arrow in a developing operation, and has a magnet (magnet roller) 10 as a magnetic field generating means fixed therein. The developing sleeve 3
The layer of the two-component developer whose layer thickness is regulated by the blade 2 is carried and conveyed, and the developer is supplied to the photosensitive drum 4 in a development area facing the photosensitive drum 4 to develop a latent image. In order to improve the development efficiency, that is, the rate at which toner is applied to the latent image, a power supply 15 applies, for example, a development bias voltage in which an AC voltage is superimposed on a DC voltage to the development sleeve 3.

The developing device 9 holds the developer supplied to the surface of the developing sleeve 3 by the stirring screws 11 and 12 in the state of a magnetic brush by the magnetic force of the magnet roller 10, and holds the developer in the developing sleeve. The developer is conveyed to a portion (developing portion) facing the photosensitive drum 4 based on the rotation of the photosensitive drum 3, and the developer returning member 1 and the blade 2 cut off the magnetic brush to reduce the amount of the developer conveyed to the developing area. Maintain properly. More specifically, the magnet roller 10 of such a conventional developing device has a five-pole configuration, and the developer stirred by the developing chamber stirring screw 11 has a magnetic force of a transport magnetic pole (pumping pole) S2 for pumping. And is conveyed to the developer pool 5 by the rotation of the developing sleeve 3. The amount of the developer is regulated by the developer return member 11, and is sufficiently constrained by a transfer magnetic pole (cut pole) N2 having a certain or more magnetic flux density in order to constrain the stable developer. Conveyed while forming. Next, the magnetic brush is cut off by a blade, that is, a spike height restricting member 2, so that the amount of developer becomes appropriate,
Conveyed by. Further, at the developing pole N1, the developing sleeve 3 is connected via a bias power supply 15 provided on the image forming apparatus main body side.
Is applied with a bias voltage in which a direct current and / or an alternating electric field is superimposed on the photosensitive drum 4.
To the electrostatic latent image side, and the electrostatic latent image is visualized as a toner image. At this time, in forming a high quality image, it is essential to stabilize the charge amount of the developer. For this reason, the stirring screws 11 and 12 and the developer pool 5
As a result, the amount of charge is stabilized by the friction between the carrier and the toner.

[0009]

In the developing device having the above-described structure, as shown in FIG. 8, the developer in the portion A on the downstream side of the stirring screw 11 in the direction of transport of the developer tends to stay.

For this reason, the compression of the developer in the portion corresponding to the portion A of the compression section 5 in a state where the developer is compressed is likely to fluctuate.

It is preferable that the density detecting sensor detects the toner at a place where the toner ratio is small to secure the developed image density.

From this viewpoint, the position of the concentration detecting sensor is preferably located downstream in the conveying direction of the stirring screw 11.

Therefore, when a concentration detection sensor is arranged at a position corresponding to the downstream side of the stirring screw 11 in the transport direction,
As described above, since the compression state of the developer in this portion is apt to fluctuate, the detection output of the density detection sensor becomes unstable.

[0014]

According to the present invention, there is provided a developer carrier for carrying a two-component developer having a toner and a carrier, and a toner and a carrier of the developer on the developer carrier. A first chamber having a detection sensor for detecting the mixing ratio of the toner, a first stirring and conveying member for stirring and conveying the developer, and a second chamber for developing the toner replenished with the second stirring and conveying member. In a developing device divided into two chambers by a partition member provided between the first and second stirring and conveying members, the height of the open portion above the partition member is such that the position of the detection sensor is large in the longitudinal direction of the developer carrier. It is characterized by the following.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

The developing apparatus of the present invention is applicable to the image forming apparatus shown in FIG. 6, and the description of the image forming apparatus will be omitted from the above description.

FIGS. 1 and 2 are views showing a developing device according to an embodiment of the present invention. FIG. 1 is a developed view and FIG. 2 is a sectional view.

(First Embodiment) A developer compressing member 1 for applying a constant pressure to a two-component developer having a toner and a carrier to keep the charge amount of the developer uniform, A developing sleeve for carrying the developer and supplying it to the developing nip; 11, a screw as a first stirring and conveying member for stirring and conveying the developer in the developing chamber; and 12, a screw as a second stirring and conveying member for the stirring chamber. Reference numeral 6 denotes a partition for separating the developing chamber from the stirring chamber, and reference numeral 7 denotes a detection sensor for optically detecting the mixing ratio of the toner and the carrier of the developer.

Now, the developer stirred and transported in the direction of the arrow shown in FIG. 1 is uniformly distributed.

The developing device is driven by a driving device (not shown), and the stirring and conveying screws 11, 12 and the developing sleeve 3 rotate in synchronization. As a result, the developer is transported in the direction indicated by the arrow. The developing material stirred in the stirring chamber is conveyed, and is transferred from the stirring chamber to the developing chamber at a portion B ′ where the partition wall is broken. Further, the developer
While being conveyed through the developing chamber by the stirring screw, it is drawn up by the developing sleeve, receives a constant pressure by the compressing member 1, passes through the developing nip N shown in FIG. It is taken in and stirred by the stirring screw 11. The developer conveyed in the developing chamber while consuming (developing) the toner is detected by the developer concentration detection sensor 7 and fed back to a replenishing device (not shown) to supply the toner to the stirring chamber. Is performed.

The position of the density detecting sensor 7 is on the side where the toner ratio is small on the downstream side in the conveying direction of the stirring and conveying screw.

Further, the developer conveyed in the developing chamber is transferred from the developing chamber to the stirring chamber in the portion A 'where the partition 6 is cut off. In addition, toner is supplied to the replenishing port T by a replenishing device (not shown) by a signal obtained by the developer concentration detecting sensor 7, and the developer is conveyed in the conveying chamber by the conveying screw 12, and the concentration of the developer decreases at the A ′ portion. They merge and are agitated and transported by the transport screw 12.

The developer in the developing chamber is pumped by a fixed magnet 10 in the developing sleeve, is conveyed on the developing sleeve by the rotation of the developing sleeve 3, and receives a constant pressure by the developer compressing member 1. At this time, since the developer is regulated by the developing blade 2, when the amount of the developer to be pumped is large, the time interposed in the compression unit 5 becomes longer,
The deterioration of the developer proceeds. Therefore, the upper portion of the partition 6 is opened to release the pressure so that the developer does not accumulate in a certain amount or more.

However, in order to reduce the size of the developing device, the center of the shafts of the two stirring screws is not at a horizontal position and the developing chamber side is lowered. Is difficult to transfer, and the developer tends to stay in the developing chamber. Then, when the fluctuation of the amount of the developer transported in the developing chamber was measured, the result as shown in FIG. 3 was obtained. It can be seen that the agent conveying force has dropped at the portion A 'at the most downstream of the developing chamber. The position of α shown in the figure corresponds to the position of the developer concentration detection sensor. Is a variation in the amount of developer transported when the upper part of the partition 6 is uniformly opened in the thrust direction. In the present embodiment, the partition 6 is opened by about 5 to 15 mm as shown in FIG.

As shown in FIG. 4, the developer is
A difference occurs in the detection signal due to the pressure applied to the developer, causing a deviation from the initial developer concentration, which is a factor of causing a change in image density. Further, since the pressure applied to the developer locally increases, the image density at a position corresponding to the portion is reduced. However, by cutting the partition wall 6 as in the present embodiment, fluctuations in the amount of developer transported can be suppressed, and fluctuations in image density can be reduced by keeping the pressure of the developer applied to the developer detection sensor 7 constant. And a uniform image can be obtained. In addition, as for the cut-off amount of the partition 6, 10-30% of the height of the partition was favorable. Below that, the stagnation of the developer is not eliminated, and if the opening is given more, the developer flows out of the opening into the stirring chamber, so that the circulation of the developer is broken and the developer concentration becomes uniform. You can not get the sex.

(Second Embodiment) In the first embodiment, the opening of the upper part is made larger than that of the upstream side at the cut-out parts A "to C of the partition 6 in FIG. Fig. 3 shows the variation in the amount of developer transported by the partition wall shape in the present embodiment, and Fig. 5 shows the present embodiment. By appropriately adjusting the opening width of the partition wall, the circulation can be further solidified.

In this embodiment, the opening width of the portion C is 3 mm,
The opening width of A ″ was set at 15 mm, but it differs depending on the developer capacity, the screw pitch, and the number of rotations.

Thus, by cutting the partition wall 6 as in the present embodiment, fluctuations in the amount of developer conveyed can be suppressed, and the pressure of the developer applied to the developer detecting sensor 7 can be kept constant, thereby changing the image density. Can be reduced, and a uniform image can be obtained.

[0029]

As described above, according to the present invention, the ratio of toner to carrier can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a development view of a developing device showing one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the developing device according to the first embodiment viewed from the other surface.

FIG. 3 is a diagram illustrating a change in a developer conveyance amount.

FIG. 4 is a diagram showing a change in output due to pressure applied to a concentration detection sensor.

FIG. 5 is a partially enlarged view showing a second embodiment.

FIG. 6 is a configuration diagram of an image forming apparatus.

FIG. 7 is a cross-sectional view of a conventional developing device.

FIG. 8 is a configuration diagram of the conventional developing device viewed from the other surface.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developer compressing member 2 developer regulating blade 3 developing sleeve 4 photosensitive drum 5 developer reservoir 6 partition 7 developer concentration detection sensor 11, 12 conveyance stirring screw

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Oki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shigeru Matsuzaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Fumitake Hirobe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor ▲ Toshinobu Yoshikawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Kunihiko Kitayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (3)

[Claims] 1. A developer carrier for carrying a two-component developer having a toner and a carrier, a detection sensor for detecting a mixture ratio of the toner and the carrier of the developer on the developer carrier, and a developing device. A first chamber having a first stirring and conveying member for stirring and conveying the agent, and a second chamber having a second stirring and conveying member for supplying and developing toner between the first and second stirring and conveying members. In the developing device, the height of the opening above the partition member is such that the position of the detection sensor is large in the longitudinal direction of the developer carrier. 2. The sensor according to claim 1, wherein the detection sensor is provided on a downstream side of the first stirring and conveying member in a developer conveyance direction, and a height of the opening is larger on a downstream side from the detection sensor than on an upstream side from the detection sensor. The developing device according to claim 1. 3. The ratio of the height difference of the opening to the height of the partition member is 30% or less.
Or 2 developing device.