JPH02116875A - Developing device - Google Patents

Abstract

PURPOSE:To supplement toner to a developer properly by providing an opening position for the border surface of the developer between a 1st chamber which contains the developer and has a developing sleeve rotating while a magnetic field is made to operate and a 2nd chamber which contains toner. CONSTITUTION:A partition plate 22 partitions the 1st chamber 11 constituting a circulation system which conveys and circulates the developer at an agitation part upward to a development area through the rotation of a developing sleeve 13 with a magnetic force and the 2nd chamber 12 which contains the toner. Then they are linked with each other through the partial opening part 5 of the partition plate and the border surface of the developer with proper toner concentration is set nearby and below the opening position of the partition plate 22. When the toner concentration decreases and the capacity of the developer decreases, the border surface of the circulated developer moves down or back and toner is supplied to the part; and the supply of the toner is stopped when the border surface of the developer moves up or forth. Consequently, the toner is supplied to the developer properly.

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 developing device that supplies toner and performs development.

[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. It is transported to a development area facing the image carrier, and develops the electrostatic latent image on the image carrier. After the toner is consumed by development, the developer adheres to the circumferential surface of the developing sleeve and is conveyed. and circulates to the stirring section.

The conditions for good development with a two-component developer are that the content ratio of toner in the developer (toner concentration) must 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]

Development methods using two-component developers are roughly classified into the following three types.

(a) Two-component magnetic brush development method This is a conventional and common development method in which a brush-shaped developer spike is formed by magnetic force at a location facing the photoreceptor on the circumferential surface of the developing sleeve. 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 JP-A-59-181362, JP-A-60-176
This is a developing method disclosed in Japanese Patent No. 069, etc., in which a thin layer of developer is formed on the circumferential surface of a developing sleeve, and the developing method is performed without contacting the photoreceptor.

(c) One-component non-contact developing method using a two-component developer For example, in the developing method described in Japanese Patent Application Laid-Open No. 60-42768, only toner is placed on the developing area facing the photoreceptor having a latent image on the developing sleeve. This is a developing method in which the film is attached to and transported to the surface of the film and developed.

Regarding the toner concentration in the developer in the stirring section, (b) and (c) above have a particularly large tolerance compared to (a), and even if the concentration is not maintained within a very strict range, it can still be maintained in a good condition. It is clear that development will take place. Also (a
), the allowable toner concentration range can be expanded by making the carrier particles 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 the toner concentration detection means that have been studied in various ways in the past. It is an object of the present invention to provide a developing device that is suitable for the developing methods b) and (c), does not require complicated control, and has a simple structure for toner replenishment.

[Failure to solve the problem]

The above object includes: a first chamber containing a two-component developer consisting of a magnetic carrier and toner and forming a circulation system for the developing sleeve and the developer; a second chamber containing the toner; a partition member having an opening between the chambers, toner is supplied in a layered manner on the developer, and an interface between the developer and the toner is set near the opening position, and the interface between the developer and the toner is set near the opening position; This is achieved by a developing device characterized in that it is provided with a shielding plate that can be opened only in one direction.

[Effect]

The present invention was basically made by focusing on the fact that although the toner is consumed in the developer, the magnetic carrier in the developer is not, and that changes in toner concentration correspond to changes in the amount of developer. It is.

That is, the developing device has 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 from the bottom to the top of the developing area. , separated from the second chamber containing toner by a partition plate, communicated by a partial opening in the partition plate, and having an appropriate toner concentration; the developer interface is located at the opening position of the partition plate. It is set so that it is near the bottom. The developer having a low toner concentration used for development is mainly supplied to the lower opening position of the partition member. Toner concentration control is achieved by reducing the toner concentration and developer capacity, causing the surface of the circulating developer to drop or retreat, and toner being supplied to that area.
When the amount of developer in the first chamber with the circulation system increases and the developer interface rises or advances, the developer interface located at the opening of the partition plate stays at the opening of the partition member, and the supply of toner stops. carried out by.

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

(1) The interface of the circulating developer is stable, and the developer and toner are not stirred near the interface, especially on the side of the second chamber, which is the toner storage chamber, and inside the second chamber that stores the toner. The developer will not diffuse. Or toner is the first
do not spread unrestricted within the room.

(2) The opening position of the partition member is configured to be sensitive to changes in developer capacity.

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

(1-1) Since the magnetic carrier has a higher density (heavier) than the toner, for example, as shown in the cross-sectional view of FIG.
It is located above the room 11.

(1-2) For example, as shown in FIG. 2(a), a magnetic force is applied to prevent the developer from spreading from the opening 15 into the second chamber 12 containing the toner T. For example, a permanent magnet 14 provided inside the developing sleeve 13
There is no problem even if it is due to Note that it is preferable that the direction of the magnetic field in the opening 15 be horizontal rather than vertical because the interface of the developer is uniformly formed in the opening. For this purpose, the permanent magnet 14 is fixed and placed at the position shown in the figure.
, an S pole is provided.

(1-3) As shown in FIG. 2(c), the shape of the partition member tip 22a is such that the developer circulating in the direction of the arrow is inclined so that it returns to the first chamber by the protruding partition member 22. Second part 1 that accommodates toner T from opening 15
It has a shape structure that prevents developer from flowing into i12.

(1-4) Partition member 22 further adjacent to the second room side
A protrusion may be provided at the end of the opening s15 to reliably prevent the developer from flowing into the second chamber accommodating the toner T.

(1-5) The upper surface of the inner wall of the first chamber 11 is sloped to ensure that the interface between the developer and the toner is formed below the opening. This prevents developer from flowing back into the second chamber 12.

(1-6) Furthermore, when the developing device is removed from the main body of the image forming apparatus, by attaching a shielding plate to the opening that can be rotated only toward the first chamber 11 to open the opening. The structure is such that the developer can be prevented from flowing back into the second chamber 12 even if the developing device is overturned.

On the other hand, the following means is effective in making the interface position (2) highly sensitive to the toner concentration of the developer.

(2-1) For example, as shown in FIG. 2(a), in order to make toner supply sensitive, the partition member 22 is installed higher than the stirring plate 17, and the cross-sectional area of the interface is made small; 15.

(2-2) The concern that reducing the cross-sectional area of the opening 15 may cause the developer to become clogged and prevent toner replenishment can be avoided by making the developer spikes stand up using magnetic force. Furthermore, this problem can be solved by applying a repulsive magnetic field to make the ears stand taller.

Such a repulsive magnetic field is also effective in preventing developer clogging. In particular, the developer regulating portion formed by the regulating plate 23 is easily clogged with developer, and the circulation of the developer is likely to be disrupted.

In FIG. 2(a), the permanent magnet 14 is fixed and the opening 15 is
The magnetic field is horizontal to the developer sleeve 1.
When the regulation plate 2 is also used to scrape off the developer attached to the plate 3.
3 shows the configuration of a repulsive magnetic field for preventing clogging. In the embodiment described later, the magnet in the developing sleeve 13 is fixed, but the present invention is not limited to this, and a structure in which the permanent magnet 14 rotates in addition to the sleeve rotation can also be used.

When a permanent magnet rotates, it has four magnets with alternating north and south poles.
400 to 2 per minute using magnetic rolls with 16 to 16 poles
Use at 000 rpm. The direction of rotation may be the same as or opposite to that of the sleeve.

In FIG. 2(b), an elastic plate 8A such as a rubber plate, a resin plate such as Mylar, or a phosphor bronze plate is provided at the tip of the stirring member 18 to more effectively pump up the toner T in the chamber 2 and open the opening. 15.

〔Example〕

An embodiment of the present invention is shown in FIG.

FIG. 1(a) is a sectional view of essential parts of an embodiment of the developing device of the present invention, in which 11 houses a developer, stirs the developer, and conveys the charged toner T to the development area E. A first room 12 is provided adjacent to the first room 11,
A second chamber 13 containing the toner T is made of a non-magnetic or weakly magnetic material such as stainless steel or aluminum, and a developing sleeve 14 rotates in the direction indicated by the arrow. 15 is an opening that is located between the first chamber 11 and the second chamber 12 and connects the two chambers, and 22a is a partition that corresponds to the circulating flow of developer, which will be described later. The distal end of the member 22, 16, is connected to the second chamber 1 connected to the opening 15.
This is a shielding plate whose upper part is attached to the outer wall surface of No. 2.

The shielding plate 16 is a highly elastic plate-like member made of an extremely thin metal plate, etc., and always closes the opening 15 by its elasticity. Therefore, even if the developing device is overturned while being handled as a single unit, the developer will naturally flow into the second chamber M12.
The elasticity of the shielding plate 16 can also prevent inadvertent inflow into the first room 11 from the shielding plate 16.

Reference numeral 17 denotes a rotating elliptical stirring plate provided near the developing sleeve 13, and 18 a pair of stirring members for stirring the toner T, which rotate in the direction of the arrow.

Of the pair of stirring members 18 described above, the one installed on the first chamber 11 side has a configuration particularly as shown in FIG. 1(c).

That is, the stirring member 18 has an elastic plate 18A provided at its tip divided into two parts and attached only to both end portions of the stirring member 18, and an elastic plate 18A that overlaps the elastic plate 18A.
A separate mylar plate 18B is provided.

The mylar plate 18B has a length such that its tip slightly protrudes from the elastic plate 18A, and is separate from the elastic plate 18A except for the adhesive surface at the upper end.

When the stirring member 18 rotates in the direction of the arrow, the elastic plate 1
8A and Mylar plate 18B are combined as shown in FIG. The shielding plate 16 is pressed and bent to open the opening 15 as shown in FIG. 1(b).

Next, the toner T pumped up from the following Mylar plate 18B is transported to the first chamber 11 through the open opening 15, and the toner T is replenished.

After replenishing the toner T, the stirring member 18 is moved again to the elastic plate 1.
8A and Mylar plate 18B are combined to stir the toner T, while the shielding plate 16 is restored to its flat state and the opening 1
Close 5.

Reference numeral 19 denotes a casing of the developing device, and in the present invention, it is used to prevent the developer from spreading into the second chamber 12 and to ensure that an interface between the developer and the developer is formed at the opening 15. A slope 19a toward the step opening 15 is provided on the upper surface of the inner wall of the first chamber 11. This inclination forms a stable developer interface below the opening even when the developing device is inclined. Reference numeral 30 denotes an image carrier that bears on its surface an electrostatic latent image developed by this developing device, and E denotes a development area where the development is performed.

Since this embodiment is constructed as described above, the developer layer is stirred and circulated by the rotation of the developing sleeve 13 and the rotation of the elliptical stirring plate 17. Through this circulation, the developer can supply the charged toner T to the development area E. At the opening 15 on the upstream side of the circulating flow of the developer, a developer layer is formed by the magnetic force from the developing sleeve. That is, gravity and permanent magnet 1
Combined with the magnetic force of No. 4, it completely prevents the developer from spreading into the second chamber 12 and forms an interface with the toner. When the toner T in the developer is consumed,
The developer interface recedes, and the toner T enters the first chamber 11 through the opening 15 due to the operation of the stirring member 18 described above, 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.

The width of the opening 15 is set to 1/3 of the width of the first portion 1ull in the axial direction of the developing sleeve 13, and is narrowed to an area where an interface between the toner T and the developer can be formed, and the developer is The structure is designed so that large fluctuations in the amount of

The carrier particles are thermally spheronized magnetic particles with an average particle diameter of 60 μm, magnetization of 30 amu/g, and resistivity of 10"0 cm or more, which are made by dispersing 70% by weight of fine ferrite in a resin. Using non-magnetic particles with a particle size of 5 μm, development was carried out using the apparatus shown in FIG. 1 under conditions such that the toner particle ratio in the developer in the first chamber 11 was 10% by weight with respect to the developer. At this time, a magnetic metal plate was used as the regulating plate 23. The average charge amount of the toner was 7 μc/g.

The conditions for the image carrier 30 in this case were that it was an OPC photoreceptor, its peripheral speed was 90 mm/sec, the highest potential of the electrostatic image formed on the image carrier 30 was -500V, and the lowest potential was -1100V.

The diameter of the sleeve 13 is also 30 mm, but its rotation speed is 75.
r.

p, m, The maximum magnetic flux density of the magnetic pole facing the development area E of the magnet body 14 is 900 Gauss, and the other 800 Gauss, and the thickness of the developer layer consisting of carrier and toner before entering the development area E is 0. .4 mm, and the bias voltage applied to the sleeve 13 has a DC voltage component of -200V and an AC voltage component of 2KHz.

It was set to 800v. In this embodiment, the gap between the sleeve 13 and the image carrier 30 is 0.6 mm, and two
The component developer layer is in contact with the surface of the image carrier 30.

The image was developed under the above conditions, transferred to plain paper by corona discharge, and fixed by passing it through a heat roller fixing device with a surface temperature of 140°C. The resulting image on the recording paper has no edge effect or It was extremely clear with no fog and had a high density, and even though 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.

〔Effect of the invention〕

As explained above, in the toner concentration control method of the present invention, there is a first chamber that accommodates developer and forms a circulation system with a rotating developing sleeve while applying a magnetic field, and a second chamber that accommodates toner. It consists of a chamber and a partition member between the chambers, and the interface of the developer is set to have the opening position, so that the developer can be accessed with an extremely simple structure that does not require complicated control. This provides an excellent effect of providing an inexpensive developing device in which toner can be replenished appropriately.

[Brief explanation of the drawing]

FIG. 1 is a sectional view and a diagram of a main part of a developing device of the present invention, and FIG. 2 is a sectional view and a diagram of a main part of a conventional developing device. 11...First room 12...Second room 13
...Developing sleeve 14...Permanent magnet 15...
Opening 16... Shielding plate I7... Elliptical stirring plate 18... Stirring member 18A... Elastic plate
18B...: Mylar board 19...Casing
19a... Inclined 22... Partition member 23...
・Regulation plate 30...Image carrier Fig. 1 (i

Claims (3)

[Claims] (1) A developing sleeve that has a two-component developer consisting of a magnetic carrier and toner and rotates while applying a magnetic field, a first chamber that forms a circulation system for the developer, and a second chamber that has toner.
and a partition member having an opening between the chambers, toner is supplied in a layered manner on the developer, and an interface between the developer and the toner is set near the opening position, A developing device characterized in that a shielding plate that can be opened only in one direction is provided near the opening. (2) The developing device according to claim 1, wherein the shielding plate is opened by operation of a stirring member provided in the second chamber. (3) The developing device according to claim 1 or 2, wherein the inner wall of the first chamber has an upper portion thereof inclined toward the opening.