JPH083683B2 - Development device - Google Patents

Description

The present invention relates to a developing device including a toner concentration of a developer including toner and magnetic particles, and a developer amount detecting means for detecting the toner amount.

[Conventional technology]

Form a latent image such as an electrostatic latent image or a potential latent image on the latent image holder,
Various principles and systems have been proposed and put into practical use as devices for developing the latent image to directly or indirectly (transfer) an image-formed product.

In particular, in a developing device for developing a latent image carrier surface by carrying a two-component developer of toner and magnetic particles on a developer carrying member,
The one that detects the concentration of the developer is often used.

In the case of a developing device that uses a two-component developer consisting of toner and magnetic particles, only toner is consumed for development, so the toner concentration of the developer will gradually decrease as it is, and the image density of the formed image will decrease. Will result in a decrease. In order to always keep the toner concentration of the developer proper regardless of the toner consumption, prompt detection of the current toner concentration of the developer, timely and appropriate replenishment of the toner component based on the detected value,
It is necessary to rapidly and uniformly disperse the replenishment toner into the entire developer and to quickly convey the developer to the toner concentration detecting section.

Therefore, this type of developing device includes a means for detecting the toner concentration of the developer in the developer storage portion, a means for bringing the developer in the developer storage portion into a stirring / conveying state, a replenishment toner storage portion, and a reinforcing toner storage portion. A means for conveying the toner to the developer accommodating portion is provided, and the degree of decrease in the toner concentration of the developer in the developer accommodating portion with time is detected by the above toner concentration detection concentration, and the detection information is input to the control circuit, When the decrease in toner concentration reaches a predetermined allowable lower limit, the replenishment toner conveying means is operated to introduce a part of the toner in the replenishment toner storage portion into the developer storage portion. The replenishment toner is rapidly mixed and dispersed throughout the developer in the developer storage portion by the developer stirring / conveying means, and the toner concentration of the developer is raised to a predetermined level by replenishing the toner. When it is detected in step 3, the operation of the replenishment toner conveying means is stopped, whereby the toner concentration of the developer is automatically managed and controlled to a predetermined substantially constant value.

Therefore, one of the requirements for performing the reliable and highly accurate toner concentration management control is the precision and reliability of the toner concentration detecting means. As the toner concentration detecting means, an optical detection method utilizing the reflected light amount of the developer,
Magnetic detection methods that utilize magnetic permeability are known, but for example, when the stirring and mixing of the developer is insufficient in the toner concentration detection section, or when there is a depletion layer or the like and the density is temporally uniform. If not, the toner concentration management control system malfunctions in the above detection method.

In particular, the developer amount is to be detected in close proximity to the carrying area of a developer carrying body (hereinafter referred to as a sleeve) which carries the developer for developing the latent image carrying body. However, in this case, the developer adheres to the sleeve surface or magnetic carrier particles in the sleeve surface area, so that a stable developer flow cannot be formed in the detection area. Therefore, conventionally, the detectability of the developer amount is low, and particularly in the case of detecting the developer concentration, a large amount of erroneous information is included in the detection result, which is a big problem.

〔Purpose〕

In view of the above problems, it is an object of the present invention to provide a developing device that can accurately detect the amount of developer, especially the developer concentration.

(Summary of the Invention) According to the present invention for achieving the above object, a carrier path for carrying a magnetic developer, a transparent member provided in the carrier path, and a developer concentration optically detected through the transparent member. A developing device comprising: a detecting unit; and a magnetic field forming member provided so as to face the transparent member, wherein the developer passing cross-sectional area of the transparent member is reduced.

〔Example〕

An embodiment of a developing device in an electrophotographic apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic front view of an example of the developing device according to the present invention, FIG. 2 is a cross-sectional view of the developing device of FIG. 1, and FIG. 3 is an enlarged explanatory view of the detection area of FIG.

In this developing device, reference numeral 1 denotes a developing container, which is partitioned by a partition wall into a toner storage portion D and a developer storage portion C for storing a two-component developer having toner and magnetic particles. The toner stored in the toner storage portion D and the developer in the developer storage portion C are omitted in the drawing. The developer accommodating portion C is partitioned by the partition wall 7 into a developer agitating portion and a developer supplying portion to the developer carrying member 2. This partition wall 7 is the developer carrying member 2
It also serves as a scraping member for scraping off the developer above. The toner stored in the toner storage portion D is replenished from the toner replenishing port 5 into the developer storage portion C when the toner conveying member 6 is rotationally driven.

Reference numeral 2 denotes a developer carrying member disposed in the developer accommodating portion C, which is composed of a developing sleeve 21 made of a non-magnetic material containing a magnet roll 22. The magnetized position of the netroll 22 is shown. The magnet roll 22 has both ends fixedly supported and does not rotate, and the developing sleeve 21 on the outer side thereof is rotationally driven around the magnet roll 22 at a predetermined peripheral speed in the arrow direction.

Numerals 3 and 4 are screws arranged substantially parallel to the developing sleeve 2 as a developer agitating / conveying means, and inside the developer accommodating portion where the developing sleeve exists (a region corresponding to the developing carrying region) and the longitudinal direction of the developing sleeve. It is provided over the developer agitation / conveyance area A, which is arranged on the extension and deviates from the carrying area. These screens 3 and 4 are rotationally driven so as to stir and convey the developer (new toner and toner collected from the sleeve surface, carrier) under the container in the upward direction shown in the figure, and the screen is rotated. Conveyor tube with
The developer is delivered through a common opening 32 of 31,30. The developer conveyed by the screen 3 is supplied from the developer supply port 9 toward the developing sleeve 2. The cross-sectional area S1 perpendicular to the carrying direction of the carrying section A as the second carrying means is smaller than the cross-sectional area S perpendicular to the carrying direction of the carrying section C as the first carrying means. Therefore, in the developer stirring / conveying area A, there is no depletion layer of the developer, and the developer is rapidly conveyed. With such a configuration, the replenishment toner is uniformly dispersed and mixed in the transport area A, and the transport of a predetermined amount of the developer is stably ensured. Therefore, by arranging the toner concentration detecting means B in the developer stirring / conveying area A, the developer is rapidly conveyed to the toner concentration detecting section, which is necessary for controlling the toner concentration, and the proper developer in the detecting section. The conditions of the agitated / mixed state and the predetermined amount of developer necessary for detection in the detection unit and the uniformity of the density thereof are satisfied.

The embodiment of the present invention has a structure as shown in FIG. 5 which is effective even for those which do not have such a preferable structure. That is, a magnet M as a magnetic field generating means for forming a substantially immovable layer 17 of magnetic particles (carrier or magnetic toner) is provided in the detection area. The substantially immovable layer is a layer that is partially changed by the magnetic particles but hardly changes in volume in the detection region. As a result, the developer passage cross-sectional area 11 in the detection area can be made smaller than the developer passage cross-sectional area 12 on the upstream side of the detection area (see FIG. 6), the amount of developer passing can be stabilized, and the detection surface can be surely secured. It also has the effect of cleaning with a developer.

The magnets are preferably arranged so as to face the detection surface, but they may be arranged around them.

The poles of the magnets M are preferably arranged so that the lines of magnetic force are orthogonal to the developer conveying direction, and the lines of magnetic force are preferably arranged substantially perpendicular to the toner concentration detecting portion. Since the magnetic particles form a chain-like brush along the lines of magnetic force, by arranging the magnet so that it is almost perpendicular to the direction of the detection unit, the passage near the toner concentration detection unit becomes the narrowest, The agent carrying force becomes the largest in the toner concentration detecting section, and the cleaning effect of the detecting section becomes optimum accordingly. Further, when a plurality of magnets are arranged, it is desirable that the repulsive poles are arranged adjacent to each other so that the lines of magnetic force are directed toward the detecting portion, as shown in FIG. By arranging the repulsive poles next to each other,
Since the magnetic flux density of the magnetic lines of force in the direction of the detector increases, the cross-sectional area of the immovable layer 17 is substantially larger than that in the case where different poles are arranged next to each other (see FIG. 7), and a better effect is obtained. . Further, as compared with the case where the different poles are arranged next to each other, the substantially immovable layer 17 of the magnetic particles is replaced with particles in an appropriate state, and a good effect can be obtained with respect to the clogging of the developer in the developer transport passage near the detection portion. Was given.

The shape of the magnet is not particularly limited, but it is desirable that the magnet have an area equal to or larger than the area of the detection portion, and that the magnetic flux density is several hundred gauss or more. However, if the magnetic force is too strong, the transport passage will be blocked by the magnetic particles, so it is necessary to consider the shape of the transport passage, the transport force of the transport member, and the like.

 An example of the toner concentration detecting means B is shown in FIG.

Reference numeral 10 is a lamp, 11 and 12 are sensors for detecting the amount of light reflected by the developer and the amount of direct light of the lamp, respectively, and the housing of B is made of a light-shielding member. Reference numeral 13 is a transparent member that transmits the light from the lamp 10 and the reflected light from the developer. The amount of light 14 and 15 entering each sensor is converted into a voltage by a predetermined circuit. Sensor 11,1
If the voltage due to 2 is Vb and Vc, respectively, and the developer is of a predetermined concentration, and the circuit is adjusted so that Vb = Vc, Vb will increase / decrease as the toner concentration increases / decreases, and Vc will always remain constant. Therefore, the toner concentration of the developer can be controlled to a predetermined value by repeating the operations of toner supply off when VbVc and toner supply ON when Vb <Vc.

The polar structure of the developer carrying member and the rotating direction are not limited to those in the above-described embodiment.

The shape of the stirring / conveying area on the sleeve longitudinal extension is
The invention is not limited to the above embodiment.

The mounting position of the toner concentration detecting means is not limited to the above-mentioned embodiment, and the detecting method is the same, and a magnetic method or the like may be used.

As described above, since the developer flow can be controlled substantially stably, the responsiveness of the remaining developer amount detection can be further improved, and the most difficult detection of the developer concentration can be accurately detected without malfunction. The importance of inventing is high.

According to the above-described embodiment, since the screw is provided in the developer amount detection area, the stirring and mixing state of the developer is good, and there is no depletion layer of the developer, and the temporal uniformity of the density is maintained. The toner density management control was carried out with high reliability and high accuracy, and a stable high-quality image-formed product could be obtained.

In the above-mentioned embodiment, the area S of the conveying path for moving the developer in the longitudinal direction of the sleeve as the first conveying means is approximated to the range substantially surrounded by the peripheral members. The cross-sectional area of In the above example, the screws of the first conveying means and the second conveying means are integrated with the same pitch and the same number of turns, but they may be separate bodies.

〔The invention's effect〕

According to the present invention, since a substantially immovable layer can be formed in the detection area and the amount of developer can be detected accurately and stably,
Developability can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration front view of an example of the developing device of the present invention, FIG. 2 is a cross-sectional side view of the example of the developing device of FIG. 1, and FIG. 3 is an enlarged configuration diagram of an example of the toner density detection unit of FIG. 4, FIG. 4 is an explanatory view of the main part of another embodiment of the present invention, FIG. 5 is a perspective view of FIG. 2, FIG. 6 is a sectional view of the detection area of FIG. 5, and FIG. 7 is of FIG. It is a detection area sectional view. 2 is a developing sleeve as a developer carrying member, 3 and 4 are screens as developer agitating and conveying means, S and S1 are cross-sectional areas,
B is a toner concentration detecting member.

Claims (1)

[Claims] 1. A transport path for transporting a magnetic developer, a transparent member provided in the transport path, a detection means for optically detecting the developer concentration through the transparent member, and a transparent member facing the transparent member. And a magnetic field forming member provided on the transparent member, and the developer passing cross-sectional area of the transparent member is reduced.