JPS5919965A - Developing device - Google Patents

Abstract

PURPOSE:To improve picture quality without causing a brush trace phenomenon, by attracting a developer carried to near an opening part facing the charge holding member of a developer container, and developing an electrostatic latent image on the charge holding member. CONSTITUTION:Developer toner in the container 11 of a developing device is stirred through the rotation of a stirrer 19 and a conductive sleeve 12 to be electrostatic charged, and the developer is attracted to the surface of developing rolls 22-20 when striking the developing rolls biased positively. The attracted and held toner is attracted to the electrostatic latent image on the charge holding member 2a by electrostatic attracting force to develop the latent image. This development eliminates the rubbing of the toner on the developing rolls against the surface of the charge holding member 2a and scatters the toner to the charge holding part 2a. Consequently, the picture quality is improved without the brush trace phenomenon and the breaking of lateral lines.

Description

[Detailed Description of the Invention] The present invention is based on the image I! ! In particular, the present invention relates to a developing device that can improve the quality of line drawings.

In electrostatic recording devices such as electrophotographic copying machines and facsimile machines, an electrostatic latent image of an image to be recorded is formed on a charge retention member such as a photoreceptor or dielectric, and this electrostatic latent image is transferred to a developer containing toner. It is developed into a visible image. The apparatus used for this development, or developing apparatus, is currently known as the glaze type developing apparatus. FIG. 1 shows a developing device # known as a magnetic brush developing device, in which a conductive sleeve 12 is rotatably installed in the direction of the arrow in the lower part of the inside of a developer ill that stores a developer. It is being Inside the sleeve 12, one main magnet 13a and several auxiliary magnets 13b are fixed to a magnet holder 14 at a slight distance from the sleeve 12. Conductive sleeve 1
A part of the charge holding member 2af made of a photoreceptor or a dielectric material is disposed in the opening 11a of the developer container 11 in the vicinity of the rotating drum 2 having the surface thereof, and this proximate position is the developing position. At the upper part of the developer container 11, there is provided a spike regulating plate 16 for regulating the thickness of the developer conveyed to the developing position by the sleeve 12, and the distance between its tip and the surface of the sleeve 12 is set to It varies depending on the component, but in one-component development that does not contain a carrier, Q,
It is set at 1 mm to 0.81 Km+.

When the conductive sleeve 12 rotates, the developer is attracted to the surface of the sleeve 12 and conveyed by the magnetic action of the internal auxiliary magnet group 13b, but the developer layer is not covered by the spike control plate 15.
The thickness is regulated to a certain level. Thus sleeve 12
When the developer conveyed by the main magnet 13a approaches the position of the main magnet 13a, it stands up like a brush. Is this brush-like developer spike an electric charge image? + Rub the surface of the part 2a.

When an electrostatic latent image is formed on the charge holding member 2a by the toner V in the developer (which is charged by being rubbed against each other during general transport), the toner is electrostatically charged due to electrostatic attraction. The electrostatic latent image is attracted to the latent image and becomes a visible image.

By the way, in the upper t11 magnetic brush developing device, since the conductive sleeve 12 rotates at a high speed of about 120,130 revolutions per minute (sleeve diameter 60 to 7 Q mta), there is a brush-shaped rise. When the spikes of the developer rub against the surface of the charge holding member 2a, fine lines tend to appear in the direction of rotation, which may appear as brush marks on the recorded image.

,′! ! 2, recorded image q) Among them, the rotary blade L2 of the conductive sleeve, and the intersecting la & l may appear as cuts due to the /.-edge phenomenon. This is thought to be because the toner once attached to the surface of the charge retention member is scraped off by the tip.

In order to prevent this phenomenon that causes image quality deterioration, methods have been proposed in which the developing device itself or the developing sleeve is moved from side to side, or the magnet arrangement inside the conductive sleeve is made diagonally. It is complicated and difficult to put into practical use.

In view of the above points, the present invention aims to eliminate the brush-eye phenomenon, improve image quality, and prevent toner scattering.
A developing opening of the developing device is provided with a transporting means for transporting the developer and a rotary developing means for adsorbing the transported developer and developing a latent image.

The present invention'CB will be explained below based on the drawings.

FIG. 2 shows a schematic configuration of an embodiment of the developing device according to the present invention, and the same reference numerals as in FIG. 1 indicate the same components.

In the figure, 17 is a developer replenishment device that appropriately replenishes developer into the developer container 11, and 18 is a scraper that scrapes off the developer on the conductive sleeve 12.

Reference numeral 19 denotes a stirrer for stirring the developer, and these are already well known. The feature of this embodiment is that the rotating drum 2
and the conductive sleeve 12 of the developing device, three developing rows 220, 21° 22, and covers 23 and 24 are arranged between the developing rollers 2o and 21 and between 21 and 22, respectively. The development rollers 20, 21 and 22 are provided with a bias potential as described later. Developing rollers 20 , 21 .

22 is made of conductive material 6 such as stainless steel, iron, or aluminum, and has a mirror finish or a finely roughened surface. Developing rollers 20 , 21 .

The direction of rotation of 22 may be entirely counterclockwise as shown, clockwise, or a combination of both.

That is, if the main function of the developing rollers 20, 21, and 22 is to focus on developing performance, the same direction as the rotating direction of the rotary drum 20, that is, counterclockwise, is preferable, and if the main function is to prevent toner scattering, then the first flow side is preferable. The developing roller 2o may be oriented counterclockwise, and the downstream developing roller 22h may be oriented clockwise.

What is the distance between the rotating drum 2 and each of these developing rollers 20, 21, 22? .

Ranks 01 to 11j are preferred.

FIG. 3 shows how the bias potential is applied to the developing roller. In the example shown in FIG. In this example, a lower positive potential is applied, and the potential applied to the developing roller can be varied by a variable resistor H. Moreover, the covers 23 and 24 are also connected to the charge retaining member 2a. In the example in Figure 3 (b), the developing roller 2
In this example, the same positive potential as that of the conductive sleeve 12 is applied to terminals 0', 21, and 22, and the covers 23 and 24 are grounded. Further, as shown in FIG. 3(C), a positive potential is applied to the conductive sleeve 12, and the developing rollers 20, 21, 22 are applied with an electric potential.
In this example, the covers 23 and 24 are grounded.

Next, the developing action in the developing device due to misfire ψj will be explained.

The developer toner in the reservoir 11 of the developing device is agitated and charged by the rotation of the agitator 19 and the 24t sleeve 12.
For example, as shown in FIG. 3(a), when it hits the positively biased developing rollers 22.degree. 21.20, it is attracted to the surfaces of these developing rollers. Developing roller 20.21.2
The toner adsorbed and held on the surface of the charge holding member 23 is attracted to the electrostatic latent image on the charge holding member 23 by electrostatic attraction force, and development is performed. In this way, development is performed by the developing rollers 20, 21, and 22, but due to this type of development, the toner on the developing roller does not rub against the surface of the charge holding member 2a, but the toner flies to the charge holding member 11a. Therefore, no brush marks or breaks in horizontal lines occur.

Furthermore, since the upstream side of the developing roller is not open, toner does not scatter on the upstream side, and since the developing roller is interposed in the tangential direction of the charge holding member, toner does not scatter downstream. Toner scattering can be more reliably prevented by rotating the developing roller 20 in a counterclockwise direction and rotating the imaging roller 22 in a time-open direction. Another important effect is that, as mentioned above, there is no opening for the developing device.

It is possible to increase the amount of toner in the developer, and therefore, as the toner concentration increases, more charged toner will be attracted to the developing roller. As the toner content increases, the triboelectric charging becomes considerably poorer overall, and the deteriorated toner hardly generates any charging, so it is less likely to be attracted to the surface of the developing roller, and the image quality improves.

As illustrated in FIG. 3(c), when no potential is applied to the developing roller, the charge held by the toner in the developing container
For example, a positive charge) causes a charge of the opposite polarity (for example, a negative charge) to develop on the surface of the developing roller, and this charge causes the toner to adhere to the developing roller. Due to the polarity of the electrostatic latent image formed on the holding member 2a and the charge cover, the electrostatic latent image is attracted and visualized.In this way, even when no potential is applied to the developing roller, development is performed by the developing roller. In this case as well, since development is performed by toner flying from the developing roller to the charge holding member, a high-quality image is obtained without the brush-eye phenomenon.

In the above embodiment, a so-called two-component developer consisting of toner and carrier was used as the developer, but the present invention can also be applied to a single-component developer containing carrier. Furthermore, the number of developing rollers and covers is not limited;
Further, the electric potential applied to these may be not only the exemplified direct current but also alternating current.

As explained above, in the present invention, the developer conveyed toward the opening is adsorbed near the opening σ) of the developer container facing the holding member 4i'f. Since a rotary developing means is provided to develop the electrostatic latent image on the charge retaining member from the developer rc, the electrostatic latent image is developed by flying the developer rather than by rubbing, so there is no cross-eye phenomenon. Image quality, especially the reproducibility of fine lines, can be improved.

Furthermore, since the opening space is reduced compared to conventional magnetic brush developing devices, scattering of developer can be prevented. Furthermore, for the same reason, it is possible to increase the amount of toner in the developer, making it difficult for development to occur with deteriorated toner, and in this respect as well, image quality can be improved.

[Brief explanation of drawings]

The first part shows the schematic configuration of a conventional magnetic brush imaging device.
Figure 2 is a cross-sectional view of the fI11 plane showing the schematic configuration of the developing station according to the present invention; Figure 3 (a), (b), and (c) are cross-sectional views of the current @ apparatus according to the present invention. FIG. 7 is a diagram showing different modes of applying potential to the developing roller used. 2... Rotating drum, 2a... Charge retention member, 11.
...Developer container, 12...Isoelectric sleeve, 17...
Replenishment device, 18... scraper, 19... stirrer,
20, 21, 22... Developing row 2, 23, 24...
cover.

Claims (1)

[Claims] a developer container having an opening formed to face the charge retention member; a conveyance means for conveying the developer toward the opening; and a developer provided near the opening in the container and conveyed by the conveyance means. 1. A developing device comprising a rotary developing means for adsorbing the developer and developing the electrostatic latent image on the charge retaining member with the developer.