JPS5919969A - Developing device - Google Patents

Abstract

PURPOSE:To optimize the thickness of a toner layer through simple operation and to obtain an invariably stable picture regardless of an environmental change, by using an oval magnetic blade and rotating the blade around a shaft provided on its small-diameter side. CONSTITUTION:The magnetic blade 5 is made oval including two curves 5a and 5b having different radii and provided rotatably around the shaft 6 to distribute magnetic flux concentration to before and behind the blade 5 by the turn. When toner charge decreases according to an environmental change to cause a decrease in toner layer thickness and an decrease in picture density, the blade 5 is set on the downstream side to distribute the magnetic flux concentration downward. Therefore, toner entry to the blade 5 is made easy to recover the picture density. When the toner charge increases, on the other hand, the blade is set on the upstream side to suppress the toner entry. Consequently, even when temperature of humidity varies, the toner layer thickness is optimized through the simple operation to obtain the excellent picture.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a developing device, 4! A developer (hereinafter referred to as toner) is applied to a uniform thickness by a toner layer thickness regulating means on an endless developer holding means arranged at a minute distance from the electrostatic latent image holding member, and the electrostatic latent image is The present invention relates to a jumping developing device that causes toner to fly onto a surface of an electrostatic latent image holding means using an electric field of a latent image.

This type of jumping developing device performs development in a state where the surface of the electrostatic latent image holding means and the toner layer are not in contact with each other, and is therefore extremely effective in preventing background fog. However, due to changes in the usage environment, etc., the thickness of toner applied on the toner holding means changes, which may ultimately have an adverse effect on image characteristics.

That is, the toner coating thickness becomes thinner under high temperature and high humidity conditions due to the low resistance of the toner, and under low temperature and low humidity conditions due to the strong specular force.

As a means to solve this change in coating thickness.

It is conceivable to adjust the temperature of the developing unit containing all the toner to create a stable environment, or to correct the gap between the toner thickness regulating means, usually called a blade, and the toner holding means in response to environmental changes. However, the former makes the device complicated, and the latter complicates the correction operation due to ensuring accuracy, and it must be said that the possibility of practical use is still low.

The present invention has been proposed in view of the above, and its entire purpose is to provide a developing device that can easily ensure a stable toner coating layer through simple operations.

As a means for achieving the above object, the present invention includes an endless developer holding means arranged at a minute interval with respect to a latent image holding member, and a developer supplied onto the developer holding means so as to have a uniform thickness. [7. Of the two circular curves, the Hiko circular curve with the smaller radius is opposed to the developer holding means, and a magnetic material is rotatably supported around the center of the circular curve as the developer layer thickness regulating means. It is characterized by

DESCRIPTION OF THE PREFERRED EMBODIMENTS All drawings of an embodiment of the present invention will be described below.

Reference numeral 1 denotes a fixed shaft which holds a plurality of internal magnetic poles 2a to 2d at substantially regular intervals on its circumferential surface, and these internal magnetic poles are provided over the entire length of the fixed shaft. Reference numeral 3 denotes a non-magnetic sleeve (hereinafter simply referred to as the sleeve) fitted on the outside of the fixed shaft 1, and is mounted and supported between the side plates of the hopper 4 so as to be rotatable in the direction of the arrow, with a part exposed to the outside. . 5-layer thickness regulation means and [
There is a gap g between the two magnetic blades and the sleeve 3.
1 and is provided in the opening 4a of the hopper 4 so as to face the internal magnetic pole 2bK. 7 is the magnetic toner stored in the hopper 4, 8 is a latent image holding body which is rotatably mounted and supported on a machine body (not shown) in the direction of the arrow; They are placed opposite each other.

In the above configuration, the toner 7 in the hopper 4 is attracted by the internal magnetic pole 2CIIC, is attracted and held by the sleeve by the Coulomb force due to contact charging with the sleeve filter which is rotationally driven in the direction of the arrow, and is conveyed. Toner 7 transported in this way
is subjected to magnetic shearing force by the magnetic blade 5 and the internal magnetic pole 2b facing it, and after the toner is adjusted to the desired thickness, it is transferred to the developing position facing the latent image carrier 8. The toner 7 flies to the surface of the latent image carrier under the action of the electric field of the electrostatic latent image and is subjected to jumping development.

FIG. 2 is an explanatory diagram of the principle of regulating the thickness of the toner layer by the magnetic blade 5. The magnetic flux density is concentrated at the lower end of the magnetic blade, and the toner layer is thickened at the equilibrium point between the blades and the internal magnetic pole 2b. is divided.

The toner 7 adheres to the sleeve surface in a uniform thin layer due to the mirror force with the sleeve 3.

Therefore, the Tora-1 thickness is determined by the charge state of the toner and the state of concentration of magnetic flux density on the magnetic blade. When the charge of the toner decreases due to changes in the environment and the adsorption force of the toner layer due to the mirror image force to the sleeve 6 decreases, the toner layer becomes thinner and the image density decreases sharply. At this time, in order to recover the density of the 9th image, that is, the thickness of the toner, it is sufficient to reduce the concentration of magnetic flux on the magnetic blade 5 in accordance with the decrease in the charged state of the toner. On the other hand, if the thickness of the toner increases due to the increase in toner charge, the image density will rise to an extreme level, characters and fine lines will become flat, the resolution and degree of fog will deteriorate, and it will be difficult to obtain a uniform layer of toner. This results in uneven density throughout the image. In this case, it may be sufficient to further suppress the toner thickness 'k' by increasing the concentration of magnetic flux on the magnetic blade 5.

As a result of repeated development and research by the present inventor, as shown in FIG. 6(a), when the magnetic flux is concentrated on the downstream side of the magnetic blade 5, the magnetic flux is sparse on the upstream side of the magnetic blade 5. In state and h, the toner near the magnetic blade becomes easier to enter into the thickness regulating section, and the amount of toner entering the regulating section is increased compared to the standard state shown in FIG. -Also, when the magnetic flux is concentrated on the upstream side of the magnetic blade 5 as shown in FIG. Toner entry is suppressed, and the amount of toner entering the restriction portion is reduced compared to the standard state shown in FIG. That is, it has been found that by shifting the magnetic flux concentration to the upstream side or the downstream side of the magnetic blade 5 depending on environmental changes, the toner thickness can always be properly increased and the image can be stabilized.

Focusing on the above points, the present invention has developed two
A magnetic material having a substantially oval cross section included in the two circular curves 5a and 5b' is called a magnetic blade 5. Among the two circular curves, the circular curve 5b with the smaller radius is placed between the sleeve and the gap g.
Open 2 and face each other.

The hopper 4 is rotatably mounted and supported between the side plates of the hopper 4 by a shaft 6 passing through the center of the circular curve.

By configuring the magnetic blade 5 as described above, the gap gl- is always constant regardless of the rotation angle θ of the magnetic blade 5, and the tilting angle of the magnetic blade when the rotation angle is small is Even if it is small, it is now possible to easily distribute the magnetic flux concentration to the upstream and downstream sides of the magnetic blade 5.

That is, the substantial center of magnetic capacity of the magnetic blade 5 is located at the handle of the magnetic blade, and when the magnetic blade 5 is rotated upstream from the normal line of the sleeve B passing through its center of rotation, the direction of magnetic flux becomes magnetic. This is because the magnetic flux is biased toward the upstream side by bending the entire blade 5 toward the first flow side.

Fig. 4 shows an enlarged front view of the magnetic board 1/-5.
Gap g1 with radius B of circular curve 5b on the rotation center side. A type of toner (depending on the strength of the Al pole, etc., 60 on the sleeve surface)
When the gap g1 is 3C1Oμ or less in a magnetic field '1tLVc having a magnetic flux density of 0 Gauss or more, the magnetic pole width t (second
(Figure) Good results were obtained with the following, preferably 2AA or less.

On the other hand, the radius A of the upper circular curve 5a that forms substantially the entire magnetic center must be at least 1.5 times the radius B of the circular curve 5b, and the distance between the centers of both circular curves 5a and 5b is as described above. A value of 10 times or less of the sum of both radii was considered good.

Since the present invention has the above-mentioned configuration, by rotating the magnetic blade according to environmental changes and selecting the magnetic flux concentration to be on the upstream side or the downstream side of the magnetic blade, the thickness of the toner layer on the sleeve can always be maintained at an appropriate level. As a result, a good image can always be maintained regardless of environmental changes.

The developing device of the present invention is particularly suitable for use in the jumping developing method using an insulating component toner described in Japanese Patent Laid-Open Nos. 55-18656-9.

The regulation angle (the angle between the tangent of the sleeve and the magnetic blade) range and the shape of the magnetic blade depend on the toner paper.

The best results can be obtained by appropriately adjusting the restriction (width of the magnetic blade facing the sleeve).

Moreover, automation can be easily achieved by controlling the tilting of the magnetic blade having the above structure by combining it with an environmental sensor, a sensor for developing concentration, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the developing device of the present invention. Figure 2 is an explanatory diagram of the principle of regulating the thickness of toner to the sleeve, Figures 3 (al and b) are diagrams showing changes in magnetic flux concentration with respect to the rotating direction of the magnetic blade, and Figure 4 is applied to the developing device of the present invention. 3 is a sleeve as a toner holding means, 5 is a magnetic blade as a toner thickness regulating means, 7 is a toner, and 8 is a latent image holding member. Patent applicant: Canon Co., Ltd.

Claims (1)

[Claims] It includes an endless developer holding means arranged at a minute interval with respect to the latent image holding member, and a developer layer thickness regulating means for regulating the developer supplied onto the developer holding means to a uniform thickness. The developing device has a substantially oval cross-sectional shape including two circular curves with different centers and radii, and the circular curve with the smaller radius of the two circular curves is opposed to the developer holding means. 1. A developing device characterized in that the developer layer thickness regulating means is a magnetic material rotatably supported about the center of a circular curve.