JPS59114559A - Developing device - Google Patents

Abstract

PURPOSE:To form a toner film of a uniform thickness, by mixing and using newly supplied toner with toner already supplied to a developing process by recycling from the previous process. CONSTITUTION:Fresh toner 8 supplied into a hopper 9 from a toner supply port 9a is uniformly stirred with an agitator 10 and supplied to the peripheral surface of a supply roller 11 and the supplied toner 8 is carried to the distributing section of the 1st doctor blade 13 as the supply roller 11 rotates. The fresh toner 8 held by the magnetic force of magnets 12 installed to the inner peripheral surface of the roller 11 is passed through a regulation space D, where the feeding quantity of toner is regulated and subjecting ear cutting, and forms a toner film 8a of a uniform thickness. At the same time, the fresh toner 8 is electrostatically charged by friction and charge is added to each toner particle. The toner film 8a is carried to the distributing section of the 1st scraper 14. The scraper 14 scrapes off the toner film 8a and the scraped off toner accumulates near the scraper 14 at the upstream side, and thus, a toner accumulation S is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device using a -component developer, and more particularly, it is applied to image forming devices such as copying machines, facsimile machines, printers, etc. using electrophotographic copying methods. The present invention relates to a developing device that can be used.

Prior Art In general, developing devices using -component magnetic toner include:
A so-called touchdown type developing device shown in FIG. 1 is well known. In FIG. 1, a cylindrical developing roller 2 is rotatably supported and rotated in the direction of the arrow. An appropriate amount of toner 1 is replenished from a hopper 3 onto the circumferential surface of the developing roller 2, and a doctor blade 4 disposed on the downstream side of the hopper 3 in the rotating direction of the developing roller 2 forms a layer of toner 1. The thickness is regulated and the layer is made thinner, and at the same time it is triboelectrically charged. The thin layer of toner to which the necessary charge has been applied is then conveyed as the developing roller 2 rotates to the developing section where it comes into contact with the dielectric belt 5 on whose surface an electrostatic latent image is formed. The electrostatic latent image is transferred to the dielectric belt 5 side due to electrostatic attraction or the like, and the electrostatic latent image becomes a visible image. At this time, the unused layer of toner is scraped off by the scraper 6 and returned to the toner reservoir 4a on the upstream side of the doctor blade 4 through the window 6a of the scraper 6 by the scraper roll 7. In such a developing device, the fresh toner 1a supplied from the toner supply port 3a contains positively or negatively charged particles and uncharged particles, and the charged state thereof is not uniform. And fresh toner 1a like this
is supplied directly to the surface of the developing roller 2, or the toner accumulates in the toner pool 4a.
A thin toner layer is formed together with the toner 1b that has been replenished and has already been subjected to development several times, but because the charged states of the two are different, the density and surface potential of the thin toner layer that is formed changes, resulting in non-uniformity. Become. When development is performed using such a thin toner layer, image quality defects such as changes in density, unevenness, and background stains occur in the resulting image.

Purpose The present invention has been made in view of the above points, and is capable of forming a thin toner layer suitable for development with uniform charging potential, adhesion density, and layer thickness, thereby eliminating density unevenness, background stains, etc. It is an object of the present invention to provide a developing device that can exhibit a good developing effect and can obtain high image quality without the occurrence of.

Configuration Specific embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 2 is a schematic diagram showing a developing device using the one-component magnetic toner of the present invention. In FIG. 2, reference numeral 9 denotes a hopper that stores fresh monocomponent magnetic toner 8 replenished from a replenishment port 9a. An agitator 10 for stirring the fresh toner 8 is rotatably disposed at the gradually contracting tip of the hopper 9, and a supply port 9b for the fresh toner 8 is formed at the tip.

A replenishment roller 11 serving as a first toner feeding means is rotatably disposed at the supply port 9b with a passage area in the vicinity thereof. This replenishment roller 11 is formed into a cylindrical shape, and inside thereof, an appropriate number of magnets 12 forming a plurality of pairs of N and S poles are arranged approximately evenly along the inner peripheral surface of the replenishment roller 11. has been done. A first doctor blade 13 is provided on the downstream side of the supply port 9b in the rotational direction of the supply roller 11.
- The replenishing roller 11 is spaced apart from and substantially perpendicular to the surface of the replenishing roller 11, and an open-side gap is formed between the tip end surface of the replenishing roller 11 and the surface of the replenishing roller 11 to regulate the layer thickness of the toner. A suitable dimension of this regulation gap is about 0.3±0.2ml1, and the fresh toner 8 supplied onto the replenishment roller 11 is subjected to a so-called spike cutting process to break the chain state, and the replenishment roller 11 A thin toner layer 8a is formed on the surface of the toner. A scraper 14 is disposed on the circumferential surface of the replenishment roller 11 on the side substantially opposite to the first doctor blade 13, with its tip end in contact with the surface of the replenishment roller 11.

This scraper 14 forcibly scrapes and removes the thin toner layer 8a formed on the circumferential surface of the replenishment roller 11 and conveyed as the roller rotates, and causes the toner thin layer 8a to stay near the upstream side of the scraper 14. A reservoir S is formed.

The developing roller 15 as a second toner feeding means, which is formed in a cylindrical shape similarly to the replenishing port 511, is rotated with a part of its circumferential surface passing through the area of the toner reservoir S. In this example, the gap at the closest portion of both rows 511.15 is 2 to 6IIll.
The developing roller 15 is arranged so that about Il is secured, and the developing roller 15 is rotated in the counterclockwise direction of the arrow. This developing roller 15
A conductive silicone rubber 15a having a specific resistance value of 1050·Cll1 or less is adhered to the circumferential surface of the roller, and a plurality of magnets 16 are disposed inside the rubber, similar to the replenishment roller 11.

The developing roller 15 passing through this toner pool S
A second doctor blade 17, which regulates the toner layer thickness and forms a thin toner layer, is disposed at the surface outlet portion P with its tip pressed against the surface of the developing roller 15 with a predetermined pressure. Therefore, the toner 8' that has already been developed and recycled upstream of the second doctor blade 17 is retained in approximately the same region as the toner pool S of the fresh toner 8, and here The toner 8- is mixed.

On the downstream side of the second doctor blade 17 in the rotational direction of the developing roller 15, an endless dielectric belt 18 is rotatably disposed so as to be able to move in the same direction and come into contact with the surface of the developing roller 15. ing.

While being driven at a constant speed, the dielectric belt 18 is uniformly charged with a predetermined polarity on its surface to form an electrostatic latent image, and then reaches the point where it comes into contact with the developing roller 15. When the toner thin layer formed on the surface of the developing roller 15 is supplied, the electrostatic latent image is visualized.

Further, on the downstream side of the above-mentioned developing section on the circumferential surface of the developing roller 15, a second scraper 19 is provided with a tip end of the developing roller 15.
The toner 8' is disposed in contact with the developing roller 15, and scrapes off the toner 8' remaining on the surface of the developing roller 15 without being subjected to development. A scraper roller 20 is rotatably disposed near the upstream side of the second scraper 19 where the scraped toner 8' stays, and the scraper roller 20 removes the scraped toner from the peripheral surface of the developing roller 15. The toner 8' is returned to the toner reservoir S on the upstream side of the second doctor blade 17.

Next, the operation of this embodiment configured as described above will be explained below.

First, the fresh toner 8 supplied into the hopper 9 from the toner supply port 9a is uniformly agitated by the rotating agitator 10 and replenished onto the circumferential surface of the replenishment roller 11. As the roller 11 rotates, it is conveyed to the location where the first doctor blade 13 is provided. The fresh toner 8 carried by the magnetic force of the magnet 12 disposed inside the circumferential surface of the replenishment roller 11 is forced to pass through the regulation gap and is regulated to a predetermined layer thickness, and the chain state is eliminated. After undergoing the cutting process, a thin toner layer 8a having a uniform thickness is formed. Also, at this time, each toner particle is triboelectrically charged and an electric charge is imparted to each toner particle. The formed thin toner layer 8a is conveyed as the replenishment roller 11 rotates to a portion where the first scraper 14 is provided, where it is scraped off from the surface of the replenishment roller 11 by the first scraper 14 and remains near the upstream side thereof. A toner pool S is formed.

The area where this toner pool S is formed is located at the second doctor blade 1 disposed on the surface of the developing roller 15 as described above.
This area almost coincides with the area where the toner 8' whose drive is regulated at step 7 stays, and therefore, in this toner pool S, the toner 8- that has already been subjected to the development process and the fresh toner that has been newly replenished. 8 are mixed. In addition, if the two types of toner 8, 8' removed from both rollers 11.15 accumulate too much in the toner reservoir S, they are recycled into the hopper 9 as shown by the white arrows and marks in the figure, and are recycled again. It is replenished onto the circumferential surface of the replenishment roller 11 and undergoes a series of processes similar to those described above. In this way, instead of directly replenishing the fresh toner 8 to the developing roller 15 as in the prior art, first,
Only the fresh toner 8 is subjected to preliminary layer thickness regulation and frictional charging processing using the first doctor blade 13 to alleviate variations in electric charge and density originally held by the fresh toner 8, and then developed in a toner reservoir S. By mixing the toner 8' that has been used in the process, variations in the charging state of the toner particles before the layer thickness is regulated by the second doctor blade 17 are eliminated.

As described above, the mixed toner 8'' whose charging state has been made uniform is conveyed to the outlet portion P of the toner reservoir S as the developing roller 15 rotates, and is subjected to the layer thickness regulating action of the second doctor blade 17 here. The tip of the second doctor blade 17 is in contact with the surface of the developing roller 15, but since the silicone rubber 15a is coated on the circumferential surface of the developing roller 15, the toner is completely absorbed by the elastic effect of the silicone rubber 15a. The flow of toner 8'' is not blocked, and toner 8'' is forced to pass through at a predetermined rate, forming an extremely thin toner layer. A certain amount of electrical charge is applied.

In this way, a thin toner layer 8''a suitable for development with uniform toner adhesion density and surface potential is formed on the circumferential surface of the developing roller 15, and as the developing roller rotates, it is transported to the developing section where it comes into contact with the dielectric belt 18. On the other hand, on the surface of the dielectric belt 18 conveyed to this developing section, an electrostatic latent image formed at a proper place is carried, and an image having a predetermined polarity is formed here. The toner charged with the opposite polarity transfers and adheres only to that area, and the latent image becomes a visible image.In this case, the thickness, adhesion density, and potential of the toner thin layer used for development are all Since it is uniform, a good developing effect is exhibited, and high image quality without density changes, density unevenness, background stains, etc. can be obtained.

Thereafter, the toner 8- which is not used for development and remains on the circumferential surface of the developing roller 15 is conveyed to the downstream side as it rotates, is scraped off from the surface of the developing roller 15 by the second scraper 19, and is removed by the scraper roller 20. The toner is returned to the toner reservoir S, mixed with the fresh toner 8 as described above, and reused.

In the above embodiments, the present invention is applied to a normal developing method in which toner charged with the opposite polarity is applied to a charged image area, but a non-charged image area is applied. Even if the present invention is applied to reversal development of a low potential latent image developed with toner charged to the same polarity as the charge possessed by the image area,
Effects similar to those of the above embodiment are exhibited.

Effects As detailed above, according to the present invention, the charging potential, adhesion density, and layer thickness can be improved by mixing newly supplied toner and recycled toner that has already been supplied to the developing process. In both cases, a uniform thin toner layer suitable for development can be formed.

Therefore, it is possible to exhibit a good developing effect that provides high image quality without causing image quality defects such as density changes, density unevenness, and background stains. Also, in the reversal development method of low potential latent images,
Similarly, it is possible to exhibit the developing effect of obtaining the above-mentioned high image quality. It should be noted that the present invention should not be limited to the specific embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention. For example, the developing device of the present invention can also be applied to an electrophotographic copying machine using a photoreceptor.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional touchdown type developing device, and FIG. 2 is a schematic diagram showing an embodiment of the present invention. (Explanation of symbols) 11: Supply roller 13: First doctor blade 14: First scraper 15: Developing roller 17: Second doctor blade 19: Second scraper Patent applicant Ricoh Co., Ltd.

Claims (1)

[Claims] 1. A container for storing toner, a first toner feeding means rotatably disposed at the toner supply port of the container and having a magnetic field generating means inside, and a surface of the first toner feeding means. a first regulating member arranged at a predetermined distance apart and regulating the layer thickness of the toner supplied to the surface of the first toner feeding means; and rotation of the first regulating member on the surface of the first toner feeding means. a scraping means disposed to come into contact with a surface on the downstream side in the direction and scrape off the toner carried on the surface; and a scraping means that uses a retention area of the scraped toner as a passing area and an electrostatic latent image. a second toner feeding means rotatably disposed in contact with or in close proximity to the surface of the image carrier on which the image carrier is formed and having a magnetic field generating means therein; and a second regulating member disposed downstream of the retention area for regulating the layer thickness of the toner carried on the surface. A developing device characterized by: