JPS63118777A - Toner concentration controlling method - Google Patents

Abstract

PURPOSE:To attain proper toner feeding to developer with a simple constitution by forming an aperture between 1st and 2nd rooms and setting up the interface between the developer and the toner approximately to an aperture position. CONSTITUTION:While being stirred by the rotation of a developing sleeve 3 and a stirrer 7, the developer D is carried under a partition 6, reached to the stirrer 7 and then circulated through the upper side of the partition 6. A magnetic shielding plate can be used for the partition 6. The developer D is sufficiently stirred by said circulation and sufficiently electrostatically charged toner T can be supplied to a developing area 10. Since the wall of an upstream side aperture part 5 forms an aperture wall 2a extruding from a downstream side wall about the circulation flow of the developer D, the developer D can be completely prevented from being uselessly dispersed into the 2nd room 2 by gravity and the magnetic force of a permanent magnet 4. When toner T in the developer D is consumed, the interface between the developer D and the toner T is dropped and the toner T is entered into the 1st room 1 through an aperture part 5 to execute proper toner feeding.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a developing device for an image forming apparatus, and in particular, it performs development using a two-component developer of magnetic carrier and toner. The present invention relates to a toner density control method in which toner is replenished and development is performed.

[Background of the invention]

A developing device that performs development using a two-component developer generally consists of a developing sleeve, an agitating section, and a portion of toner. The image carrier is transported to a developing area facing the image carrier, and the electrostatic latent image on the image carrier is developed. After the toner is consumed by development, the developer adheres to the circumferential surface of the developing sleeve, is conveyed, and circulates to the stirring section.

2I! The conditions for good development with a 1-minute developer require that the content ratio of toner in the developer (toner concentration) be maintained within a certain range, and the magnetization of the developer in the stirring section must be detected. The toner density is indirectly detected by developing a standard latent image formed on a photoreceptor and measuring its reflection density.

The method of detecting toner concentration by measuring the density of a developed standard latent image is indirect and does not necessarily indicate the toner ratio in the developer.

Furthermore, toner concentration measurement by detecting the magnetization of the developer has a problem in that the detection results are unstable.

Further, in the developing device, consumed toner is replenished from a portion of the toner based on the measurement results of toner density, but this inevitably complicates the toner supply mechanism and its control.

[Problem that the invention seeks to solve]

Developing methods using two-component developers are classified into three types: large and large.

(a) Two-component magnetic brush development method This is a conventional and common development method in which a brush-shaped developer is formed by magnetic force on the circumferential surface of the developing sleeve at a location facing the photoconductor, and the brush of this developer is This is a developing method in which the photoreceptor is brought into sliding contact with the photoreceptor bearing the latent image.

(b) Two-component non-contact development method Patent No. 111N 181362/1983, JP-A-60/1983
In the developing method disclosed in Publication No. 176069 etc.,
This is a developing method in which a thin layer of developer is formed on the circumferential surface of the developing tube, and the development is performed without contacting the photoreceptor.

(c) Pseudo two-component development method For example, in the development method described in Japanese Patent Application Laid-Open No. 60-42768, only toner is attached to and conveyed to the development sleeve and developed in the development area facing the photoreceptor with the latent image. This is a developing method designed to

Regarding the toner concentration in the developer in the stirring section, among the above, (b) and (c) have a particularly large tolerance compared to (a), and are not maintained within such a strict concentration range (both are good and good). It is clear that a good development can be achieved, and (
In the case of a), the toner density range can also be expanded by making the carrier microscopic.

The present invention is a developing device in which the toner concentration in the stirring section is controlled without using toner concentration detection means and toner replenishment means based on various conventional studies, and in particular, the above (b). (c) It is an object of the present invention to provide a toner concentration control method that is suitable for a developing method, does not require complicated control, and allows toner replenishment with a simple structure.

[Means for solving problems]

The above-mentioned object is comprised of a first chamber containing a two-part developer consisting of a magnetic carrier and toner and forming a circulation system by a developing sleeve that rotates while applying a magnetic field, and a second chamber containing toner; Along with having an opening between the rooms,
This is achieved by a toner concentration control method characterized in that the toner is supplied in a layered manner on the developer, and the interface between the developer and the toner is set near the opening position.

[Effect]

Basically, the present invention is based on the fact that although the toner is consumed in the developer, the magnetic carrier in the developer is not consumed, and the change in toner concentration corresponds to the change in the amount of developer. It is something.

That is, the developing device includes a first chamber that forms a circulation system that generates a conveying force by magnetic force and rotation of the developing sleeve, and conveys and circulates the developer in the stirring section to the developing area, and a first chamber that accommodates the toner. It is connected to the second chamber by an opening, and is set so that the interface between the developer and the toner having an appropriate toner concentration is located approximately at the opening position.

Toner concentration control is such that when the toner concentration decreases and the developer level decreases, toner is automatically supplied by its own weight, the amount of developer in the f:tSl chamber with the circulation system increases, and the toner supply is reduced. It is done by stopping.

In order for this toner supply/stop to work effectively, it is preferable that the following conditions are satisfied.

(1) The interface between the developer and toner is stable, and there is no agitation between the developer and toner near the interface, especially on the side of the toner storage chamber, and there is no developer in the second chamber that stores the toner. Does not spread.

(2) The interface position between the developer and toner is sensitive to the toner concentration of the developer.

The following means are effective in preventing the developer from spreading into the second chamber containing the toner (1).

(1-1)) Since magnetic carriers have a higher density (heavier) than carriers, for example, Fig. 14 (a) (b)
), the opening 5 is located above the first chamber 1 containing the developer. Note that the above-mentioned interface is set at a substantially open position, and the relationship between the toner concentration to be set and the open position is maintained.

(1-2) For example, as shown in FIG. 4(, ), a magnetic force is applied to prevent the developer from spreading from the opening 5 into the second chamber 2 containing the toner T. The magnetic field may be applied to the permanent magnet 4 provided inside the developing sleeve 3, and the direction of the magnetic field at the opening 5 may be vertical or horizontal.

(1-3) For example, the opening 5 has a shape as shown in FIG. 4(b), and the developer circulating in the direction of the arrow projects out.
The configuration is such that the developer is prevented from flowing into the second chamber 2 containing the toner T through the opening 5 by the fif opening wall 2a.

The following means are effective in making the interface position in (2) highly sensitive to the toner concentration of the developer.

(2-1) For example, as shown in Figure 5, in order to prevent agitation and conveyance of the development simultaneous 1D from occurring at the interface between the developer scraper and the toner T, and to make toner replenishment sensitive, the interface position is cut off. It is provided in the opening 5 whose area is reduced.

(2-2) The concern that reducing the cross-sectional area of the opening 5 described above may cause the developer scraper to become clogged and prevent toner replenishment can be resolved by making the developer spikes stand up using magnetic force. This can be resolved by applying a repulsive magnetic field to encourage high virtue.

Such a repulsive magnetic field is effective in preventing clogging of the developer. In particular, the developer is easily clogged in the developer regulating portion by the regulating plate 13, and the circulation of the developer is likely to be disrupted.
FIGS. 1 to 3 show the structure of a repulsive magnetic field when the developer is also used to scrape off the developer from the sleeve or to prevent the developer from remaining on the regulating portion. In the following embodiments, the magnet in the developing sleeve is fixed, but the magnet is not limited to this, and a rotating magnet can also be used. The direction of rotation may be the same as or opposite to that of the sleeve.

〔Example〕

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

(Embodiment 1) FIG. 1 is a cross-sectional view of a main part of an embodiment of the present invention, in which numeral 1 houses a developer tank, stirs the developer D, and transports charged toner T to a development area 10. The first room to be, 2 is f
jSt, a second chamber is provided above the chamber 1 and contains the toner T; 3 is a developing sleeve made of a non-magnetic or weakly magnetic material such as stainless steel or aluminum; and 4 is the developing sleeve which rotates in the direction indicated by the arrow; A permanent magnet is provided inside the sleeve 3 and has a plurality of magnetic poles in the circumferential direction; 5 is an opening located between the first chamber 1 and the second chamber 2 and connects the two chambers; 2a is an opening that connects the two chambers; An opening wall 6 is located on the upstream side of the sink where developing scrapers circulate, which will be described later, and protrudes from the opposite wall to the Ptt 12 room 2 side, and is made of a non-magnetic material and is installed approximately in the center of mi room 1. A partition plate 7 is provided near both sides of the developing sleeve 3, and a stirrer 8 rotates in the direction of the arrow.
1 is an agitator for stirring the toner T; 9 is a casing; 12 is an image carrier carrying an electrostatic latent image on its surface to be developed by this developing device; and 10 is a developing area where the development is performed.

Since this embodiment 1 is constructed as described above, the developer material is agitated by the rotation of the developing sleeve 3 and the rotation of the agitator 7! One point FAI' on the bottom of the partition @, 6 while being p
It is transported in the direction of the arrow shown by l, and after reaching the agitator 7 on the left side in the figure, it passes above the partition plate 6 and circulates. A magnetic shield plate can also be used as the partition plate 6. This circulation ensures that the developer mixture is sufficiently agitated (
The charged toner T can be supplied to the development area 10. The wall of the opening 5 on the upstream side with respect to this circulating flow of developer is formed with the opening wall 2a that protrudes from the wall on the downstream side, so that the development uniformity is achieved by the combination of gravity and the magnetic force of the permanent magnet 4. It is possible to completely prevent the ID from being mischievously spread to the second room. When the toner T in the developer tank is consumed, the interface between the developer tank and the toner T lowers, the toner T enters the first chamber 1 through the opening 5, and appropriate toner replenishment is performed.

In this way, it is possible to obtain a developing device with a simple structure that can perform agitation of the developer layer and appropriate toner replenishment.

70% by weight of fine 7elite particles dispersed in the resin as carrier particles, the average particle size is 60μ, and the magnetization is 30eIIIu/g.
, using magnetic particles subjected to thermal spheroidization treatment with a resistivity of ion'ΩCa+ or higher, and toner particles with an average particle diameter of 5 μm.
1 of non-magnetic particles were used to carry out development using the apparatus shown in FIG. 1 under conditions such that the ratio of toner particles in the developer solution in the first chamber was 10% by weight relative to the carrier particles.

At this time, a non-magnetic metal plate was used for the regulation plate 13. The average charge amount of the toner was 30 μc/y.

The conditions for the image carrier 12 in this case were that it was an OPC photoreceptor, its peripheral speed was 180 mm/see, the highest potential of the electrostatic image formed on the image carrier 12 was -500V, and the lowest potential was -100V. The diameter of the sleeve 3 is also 301 N, however, the number of times is 150 r, p, w, and the maximum magnetic flux density of the magnetic pole facing the developing area 10 of the magnet body 4 is 120 (l us, developing area 10
The thickness of the developer layer consisting of carrier and toner before entering the sleeve 3 is 0.6xms.The bias voltage applied to the sleeve 3 is a DC voltage component of -200V and an AC voltage component of 2KH2,4QO.
It was set to V. In this embodiment, the gap between the sleeve 3 and the image carrier 12 is 0.4 wm, and the developer layer on the sleeve 3 is in contact with the surface of the image carrier 12.

The image was developed under the above conditions, transferred to plain paper by corona discharge, and fixed by a heat roller fixing device with a surface temperature of 140°C. The resulting image on the recording paper was free from edge effects and fog. The image was very clear and had a high density, and although 50,000 sheets of recording paper were subsequently obtained, it was possible to obtain an image that remained stable and unchanged from beginning to end.

(Embodiment 2) FIGS. 2a and 2b are sectional views of main parts of another embodiment of the present invention, and each reference numeral represents the same or corresponding part as in FIG. 1.

In this second embodiment, in particular, the cross-sectional area of the opening 5 is made small to increase the sensitivity to changes in the toner concentration of the developer. As shown in the figure, the magnetic poles of the permanent magnet 4 are magnetized so that the same magnetic poles are adjacent to each other on the side of the opening 5 to form a repulsive magnetic field and prevent the phenomenon of developer clogging in the opening 5. It is.

Also in this second embodiment, the partition plate 6 is the first part! !
The developer is placed near the center of the container 1, so that the developer can be circulated and agitated sufficiently. A magnetic shield plate can also be used as the partition plate 6.

Further, the first chamber 1 and the #2 chamber 2 are configured to be horizontally lined up left and right, and the toner T is supplied above the opening 5 by the stirrer rod 8. The toner T pumped up and replenished by the stirrer rod 8 is replenished through the opening 5 in an amount corresponding to the amount of developer reduced by the toner jff cost. In particular, in Figure 2, the developer interface is not formed in the Pt51 chamber but only between the first and second chambers, so the fifth
As already explained using the figure, since changes in developer level due to changes in toner concentration are largely reflected, development y! is preferable in this embodiment. The tra can be made into a flat shape, and an image forming apparatus equipped with this developing device can be made smaller. In particular, there are multiple developing parts on the peripheral edge of the photoreceptor drum.
In a color image forming apparatus in which the color image forming apparatus is provided with a color image forming apparatus, it is extremely effective to provide the present detector as shown in the second embodiment in order to make the color image forming apparatus more compact.

In this way, it is possible to obtain a developing device with a simple structure that can appropriately replenish and stir toner in the developer.

The carrier particles are resin-coated spherical ferrite particles with an average particle diameter of 30 μm, the magnetization is 50 emu/g, and the resistivity is 1014 Ω CR or more. The toner particles are non-magnetic particles with an average particle size of 5 μm. Then, development was carried out using the apparatus shown in FIG. 2 under conditions such that the ratio of toner particles in the developer solution in the first chamber was 15% by weight relative to the 177 particles of the developer. At this time, non-magnetic metal was used for the regulating plate 12. The average charge amount of the toner was 20 μc/y.

The conditions for the image carrier 12 in this case were that it was an OPC photoreceptor, its peripheral speed was 180 iz/sea, the highest potential of the electrostatic image formed on the image carrier 12 was -500V%, and the lowest potential was -1100V. The diameter of the sleeve 31 is also 2011. However, the number of rotations is 150 r, p, m, and the maximum magnetic flux density of the magnetic pole facing the developing area 10 of the magnet body 4 is 1200 glass, forming a horizontal magnetic field in the developing area. The center part is 800 Gauss, the thickness of the developer layer consisting of carrier and toner before entering the development zone 10 is 0.4 mm, and the bias voltage applied to the sleeve 3 is DC voltage component -200V and AC voltage component 2 llz. .

It was set to 1ooov. In this embodiment, the gap between the sleeve 3 and the image carrier 12 is 0.7zz, and the developer layer on the sleeve 3 is not in contact with the surface of the image carrier 12.

After developing under the above conditions, the image was transferred to a sheet of paper using corona discharge, and then passed through a heat roller fixing device with a surface temperature of 140°C to fix it. The image was extremely clear, free of dark spots, and of high density.Even after 50,000 sheets of recording paper were subsequently obtained, it was possible to obtain an image that remained stable and unchanged from beginning to end.

(Embodiment 3) FIG. ftS3 is a sectional view of a main part of still another embodiment of the present invention, and each reference numeral except 6a and 11 represents the same or equivalent part as in FIG. 1. 6a is a shield partition plate made of a magnetic material and has a magnetic shielding effect, and a region 11 indicated by a broken line indicates the effective range of the magnetic field of the permanent magnet 4, and is shielded by the above-mentioned Nhrdeich cut plate 6a. The magnetic field does not reach the area of the shield partition plate 6a opposite to the sleeve 4 or the entire second room 2, but acts on the area 11 below the opening 5. Therefore, the magnetic carrier is attracted by the magnetic force and does not enter the second chamber 2 and combine with the toner T.

The mi section IM1 in which the developer is accommodated and stirred is provided along one side of the developing sleeve 3, as shown in FIG. The Pt52 chambers 2 containing the toner T are slightly higher than the first chamber 1, but are arranged substantially horizontally, and the opening 5 is located below the first chamber 1. In this third embodiment as well, the developer layer is moved by the rotation of the developing sleeve 3 in the direction of the arrow and the rotation of the agitator 7, and is circulated in the direction of the arrow of the dashed-dotted line by installing the shield partition plate 6a. An effective stirring action takes place.

The wall 2b of the opening 5 prevents the developer shavings from flowing into the second chamber 2 with respect to the circulation of the developer reservoir, and together with the deterrent force due to the magnetic force of the magnetic field range 11, the wall 2b of the developer reservoir prevents developer scraps from flowing into the second chamber 2. Diffusion into room 2 is reliably prevented. Furthermore, since the opening 5 is formed to have a small cross-sectional area, it is highly sensitive to changes in the toner concentration of the developer. As shown in the figure, the magnetic poles of the permanent magnet 4 are magnetized to generate a repulsive magnetic field, which, together with the action of the shield partition plate 6a, acts to keep the developer at the bottom and prevents the developer from clogging. It is designed to prevent the phenomenon from occurring.

Carrier particles coated with a tree layer of spherical ferrite have an average particle diameter of 70 μ11, magnetization of 40 emu/g, and resistivity of 1.
Using spherical magnetic particles with a resistance of 0 Ωc1 or more, and using non-magnetic particles with an average particle size of 5 μm as toner particles, the ratio of toner particles removed by development in the first chamber to carrier particles is determined by the apparatus shown in Fig. 3. On the other hand, development was carried out under conditions where the contrast ratio was 20%. At this time, a magnetic plate was used as the regulating plate 13, and the closest distance from the image carrier 12 to the regulating plate B was set to 0.4 am. The average emperor of toner 1! The amount was 10 μC/g. As a result, the carrier is a regulating plate 1 made of a magnetic material.
3, and only the toner layer was formed on the sleeve. In this case, the conditions of the image carrier 12 are OP.
C photoconductor, its IM speed is 60xz/5ee1 image carrier 1
The highest potential of the electrostatic image formed in 2 was -500V, and the lowest potential was -toov.The diameter of sleeve 3 was also 20mz.
However, the rotation speed is 70 r, p), and the maximum magnetic flux density of the magnetic pole facing the developing area 10 of the magnet body 4 is 1200 mm, forming a horizontal magnetic field in the developing area. The thickness of the developer layer before entering the developing area 10 is 0.1 mm.
, the bias voltage applied to the sleeve 3 is a DC voltage component -
200V, AC voltage component 2 K11z, 500V. The purpose of the horizontal magnetic field in this case is to cause the ears of carriers to lie down so that the carriers do not come into contact with the photoreceptor when there are carriers that have passed through the regulating plate 13. In this embodiment, the gap between the sleeve 3 and the image carrier 12 is 0.3 zm, and the developer layer on the sleeve 3 is not in contact with the surface of the image carrier 1. Development is carried out under the above conditions. The image is transferred onto plain paper using corona discharge, and then fixed through a heat roller fixing device with a surface temperature of 140°C.The resulting image on the recording paper is extremely clear and has no edge effects or fog, and is highly dense. 50,000 sheets of recording paper were subsequently obtained, and images remained stable and unchanged from beginning to end.

〔Effect of the invention〕

As described above, in the toner density control method of the present invention, the first chamber accommodates the developer and forms a purple ring system with a rotating developing sleeve while applying a magnetic field, and the toner is accommodated! Since the #2 chamber has an opening approximately between the two chambers and the interface between the developer and the toner is approximately set at the opening position, no complicated control is required. This has the excellent effect of providing an inexpensive developing device that has an extremely simple structure and can appropriately replenish toner to the developer.

[Brief explanation of the drawing]

1 to 3 are sectional views of essential parts of an embodiment of the present invention, and FIGS. 4(a), 4(b), and 5 are sectional views for explaining the basic operation of the present invention. In the figure, 1...first room, 2...second room, 2a
...Protruding opening wall, 3...Developing sleeve, 4
...Permanent magnet, 5...Opening, 6...
Partition plate, 6a...Shield partition plate, 7...
- Stirrer, 8... Stirring rod, 9... Casing, 10... Development area, 11... Magnetic field range, 12... Image carrier, 13... Regulating plate,
D: Developer, T: Toner. Applicant Konishiroku Photo Industry Co., Ltd. Figure 1 Figure 2-8 13 Figure 3 Figure 2-b

Claims (5)

[Claims] (1) Consisting of a first chamber containing a two-component developer consisting of a magnetic carrier and toner and forming a circulatory system by a developing sleeve that rotates while applying a magnetic field, and a second chamber containing toner; 1. A toner concentration control method, comprising: having an opening between the chambers, supplying toner in a layered manner on a developer, and setting an interface between the developer and the toner near the opening position. (2) The toner density control method according to claim 1, wherein a partition plate is provided in the first chamber, and the moving direction of the developer is different on both sides of the partition plate. (3) The toner concentration control method according to claim 2, wherein the partition plate includes a stirring member rotating in the same direction as the moving direction of the developer at the end of the partition plate. (4) The toner density control method according to claim 1, wherein a magnetic field that attracts the developing sleeve acts on the opening. (5) The toner concentration control method according to claim 1, wherein a repulsive magnetic field acts in the vicinity of the developer regulating section.