JPS62187368A - Developing device - Google Patents

Abstract

PURPOSE:To uniformize the layer thickness of a toner layer and to improve development performance by forming a blade so that the sectional shape perpendicular to the axial direction of a developing roller is convex at the press- contacting part pressed against the developing roller. CONSTITUTION:The press-contacting part between the developing roller 4 and blade 10 of a developing device is formed in a convex shape which is not wedgelike, and then the toner layer 13 conveyed toward the press-contacting part is scraped off by the blade 10 and run along the wall surface W of the convex part with the force of following toner layers as shown by an arrow A and slides on the layer 13 to fall into a hopper. Therefore, no toner is deposited and the layer thickness is held uniform; and the reliability and image quality of the device are improved with simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a developing device in an image forming apparatus such as a copying machine or a printer that uses electrophotography.

2. Description of the Related Art Development methods for electrophotography and electrostatic recording devices using dry toner can be roughly divided into two types: methods using a two-component developer and methods using a one-component developer.

The method using a two-component developer uses a mixed developer of carrier and toner, so the mixing ratio of the two is kept constant, as opposed to the method using a two-component developer, that is, the method using a developer containing only toner. This requires a toner concentration detection device, and has drawbacks such as deterioration of image quality due to deterioration of the carrier and periodic replacement of the carrier. Therefore, recently, a method using a pre-mt-component type developer has been attracting attention.

In this case, many methods have been proposed to charge the toner with a desired polarity, either positive or negative, by rubbing the toner with an appropriately selected substance. has been done. In particular, many proposals have been made to form a layer of charged toner having a predetermined thickness on the surface of the developing roller through friction between the toner carried on the surface of the developing roller and an elastic blade made of rubber or the like.

At this time, it is extremely important to form a single layer of toner with a uniform thickness on the developing roller in order to perform good development, but at present this problem cannot be completely solved. hard.

FIG. 3 shows a developing device disclosed in % Application No. 128738/1983. In FIG. 3, 1 is an insulating toner which is a developer, and 2 is a hopper having an outlet 3 at one end and storing the toner 1. 4 is a developing roller, for example, SUS, i
It is a metal roller with an uneven surface, and rotates counterclockwise in the figure. Further, the developing roller 4 is
It faces the photosensitive drum 8 with a certain gap therebetween. Reference numeral 5 denotes a fur brush, in which conductive fiber bristles 7 of, for example, rayon are implanted on the outer peripheral surface of a mandrel 6. Further, the seven hoop brush 5 is located within the toner 1 of the hopper 2 and is in sliding contact with the surface of the developing roller 24, for example, by rotating it clockwise. Furthermore, fur brush 6
The circumferential speed is faster than the circumferential speed of the developing roller 4, and also serves to scrape off a portion of the toner 9 adhering to the surface of the developing roller 24 after development. Reference numeral 10 denotes a rubber blade that is a regulating member that regulates the thickness of the toner on the developing roller 4.

11 is a scraping plate that comes into contact with the bristles 7 of the fur brush 5;
This is to equalize the amount of toner within the bristles 7.

The operation in FIG. 1 will be explained below.

The toner 1 in the hopper 2 is supplied into the bristles T as the fur brush 5 rotates. Next, the excess toner in the bristles 7 is scraped off by a scraping plate 11 and an appropriate amount is supplied, and the toner is positively charged by rubbing against the scraping plate. Furthermore, the appropriate amount of toner supplied by the rotation of the fur brush 6 is transferred to the developing roller 4.
transport it to a position facing the The toner supplied in an appropriate amount is further uniformly charged positively by the agitation effect caused by the rotation of the fur brush 5 and by the sliding friction with the surface of the developing roller 4. Next, by connecting the high voltage power supply 12 between the developing roller 4' and the fur brush 6 with the polarity shown, the positively charged toner is transferred onto the surface of the developing roller 4 by the action of the electric field.
The predetermined toner is coated to a thickness greater than one layer. At this time, the thickness of the toner layer on the surface of the developing roller 4 varies beyond a predetermined toner layer thickness. Next, the developing roller 4 rotates, and the charged toner 13 on the surface of the developing roller 4 is
When passing through the blade 1o, a portion of the toner is scraped off and the toner is regulated to a predetermined thickness. When the negatively charged latent image on the photosensitive drum 8 faces the positively charged toner 9 on the surface of the developing row 24, the toner 9 is transferred to the photosensitive drum 8.
It flies upwards and performs development.

Now, in Fig. 3, as the developing device operates, the hopper 2
The following describes what happens after the toner inside is consumed and toner 1 decreases to the level indicated by the broken line. In this case, the toner layer 13 attached to the developing roller 4 from the fur brush 6 is
A portion 14 of which is partially scraped off by the blade 10 is already exposed on the surface of the toner 1, and the toner scraped off at this portion 14 gradually accumulates, as shown by diagonal lines in FIG. Fill the wedge portion 16 in the same way. The toner in the shaded area does not adhere uniformly over the entire length of the developing roller in the axial direction, and the amount of toner adhered varies. This is because when the toner is supplied from the fur brush 5 to the developing roller 4, there are already variations in the amount of toner supplied, and as a result, variations occur in the amount of toner scraped off by the blade 1o. At this time, if the toner in the shaded area exceeds a certain amount, the thickness of the thin toner layer 9 on the developing roller will vary mainly in the axial direction of the developing roller 4, corresponding to the variation in the adhesion amount. This development was confirmed. That is, in a portion of the wedge portion where a large amount of toner adheres, the toner on the developing roller corresponding to that portion also becomes thicker. In some cases, the variation in the thickness of a single layer of toner on the developing roller 4 can reach several tens of micrometers in the axial direction. Then, the amount of toner flying from above the developing roller 4 to the photosensitive drum 8 will also be reduced.
Due to the influence of this variation in layer thickness, the layer thickness is not uniform, and uniform and good-looking development cannot be achieved. The aim is to eliminate the deterioration in developing performance caused by variations in development performance.

Means for Solving the Problems The technical means of the present invention for solving the above-mentioned problems is to make the cross-sectional shape of the blade convex at least in the vicinity of the pressure contact portion including the pressure contact portion with the developing roller.

action The operation of this technical means will be explained.

In the conventional example, a plate-shaped blade is pressed into smooth contact with a cylindrical developing roller, and a triangular wedge formed by the blade and the developing roller is inevitably generated at the pressure-contact portion. The toner scraped off by the blade accumulates from the tip of this wedge, and the developing roller rotates in a direction that further feeds the scraped toner into the wedge. It remains within the wedge and becomes hard and deposited.

However, as mentioned above, by making the part of the blade in contact with the developing roller convex, this wedge is not substantially formed, and the scraped toner is guided into the hopper.
Since a space for toner circulation can also be secured, the above-mentioned inconvenient toner accumulation does not occur. That is, the present invention eliminates the occurrence of toner accumulation itself, which was the cause of the inconvenience, by the above-mentioned action,
This solves the above drawbacks.

Embodiment FIG. 1 shows a sectional view of a main part of a developing device according to an embodiment of the present invention. The same symbols as in FIG. 3 represent the same contents.

As shown in the figure, the blade 1o has a convex shape near the pressure contact portion including the pressure contact portion with the developing roller 4. Therefore, the portion where excess toner is scraped off on the developing roller does not become a sharp tip of a wedge as shown in the conventional example. Second
The figure shows an enlarged view of section B5 in FIG. In Figure 2,
The flow of toner in a toner scraping section is schematically shown. A portion of the toner layer 13 deposited on the developing roller 4 and conveyed toward the pressure contact portion with the blade 1o is scraped off by the blade 10. The scraped toner changes its flow in the direction of the arrow along the wall surface W of the blade convex part due to the force of the succeeding toner, and slides on the toner layer 13 and falls into the hopper.

As a result, the toner scraped off by the blade 10 does not accumulate. In other words, the disadvantage of the conventional method is that the toner is scraped off at the sharp tip of the wedge, that is, the part where the scraped toner cannot flow so that it can flow back into the hopper.
This problem was solved by providing a protrusion on the blade.

Regarding the height of the convex portion of this blade, since the amount of toner to be scraped off is not large, the height is sufficient to form a small space above the toner layer 13. If the amount of toner to be scraped off is small, a height of 0.5 M is sufficient for the height of the convex portion. Practically, 0.5~
It's about 4 screams.

Effects of the Invention The present invention described above can always keep the thickness of the toner on the developing roller uniform, and with a simple configuration brings about dramatic improvements in device reliability and image quality.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part of a developing device according to an embodiment of the present invention, FIG. 2 is an enlarged view of section B in FIG. 1, FIG. 3 is a cross-sectional view of a main part of a conventional developing device, and FIG. 3 is an enlarged view of the blade portion of FIG. 3. FIG. 1...Developer, 4...Developing roller, 1
0...Blade. Name of agent: Patent attorney Toshio Nakao and 1 other person31
Figure 2 Figure 3

Claims (1)

[Claims] A developing device comprising a rotating developing roller that carries a developer, and a blade that is pressed against the developing roller to form a layer of developer on the surface of the developing roller, the blade being in contact with the developing roller. A developing device in which a cross-sectional shape perpendicular to the axial direction of the developing device is convex at least in the vicinity of a pressure contact portion including a pressure contact portion with the developing roller.