JPS5919970A - Developing device - Google Patents

Abstract

PURPOSE:To secure optimum toner layer thickness through simple operation and to obtain an excellent picture regardless of an environmental change, by varying the specified angle of a magnetic blade to internal magnetic poles in a developing sleeve. CONSTITUTION:The magnetic blade 5 is arranged facing an internal magnetic pole 2b with a gap g1 to a nonmagnetic sleeve 3 and tilts forward and backward around a fitting shaft 5a to vary its specified angle, distributing magnetic flux concentration to before and behind the blade 5. When the charge of toner 7 decreases owing to an environmental change to decrease the toner layer thickness and picture density, the blade 5 is set on the downstream side to distribute the magnetic flux concentration to the downstream side, and the toner is allowed to enter to the blade 5 easily, recovering the density by increasing the thickness of the toner layer. When the toner charge decreases, on the other hand, the opposite operations are performed. Consequently, even if 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 applies a developer (hereinafter referred to as toner) to a toner layer on an endless developer holding means arranged at a minute distance from an electrostatic latent image holder in a developing device W9%. The present invention relates to a jumping developing device in which toner is applied to a uniform thickness by a thickness regulating means and is caused to fly onto the surface of an electrostatic latent image holding means by the electric field of an electrostatic 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, the thickness of toner applied on the toner holding means changes due to changes in the usage environment, etc., which may adversely affect the final image characteristics.

That is, the toner coating thickness was reduced under high temperature and high humidity conditions due to the lower resistance of the toner. At low temperatures and low humidity, the coating becomes thinner and crumbles due to the strong mirroring force.

As a means to solve this change in coating thickness.

It is conceivable to adjust the temperature of the developing unit containing 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, so it must be said that the possibility of practical use is still low.8 The present invention has been proposed in view of the above. With simple operations, you can easily ensure a stable toner coating layer.

It is an object of the present invention to provide a developing device that can always stably produce good images regardless of environmental changes.

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. In the developing device, the developer layer thickness regulating means is provided with a regulating angle (a tangent of the developer retaining means) with respect to an opposing magnetic pole provided in the developer retaining means. It is characterized by making the angle (angle formed with) variable.

An embodiment of the present invention will be described below with reference to the drawings.

Reference numeral 1 denotes a fixed shaft that holds a plurality of internal magnetic poles 23 to 2d at approximately equal intervals on its circumferential surface, and these internal magnetic poles are provided over approximately the entire length of the fixed shaft. Reference numeral 6 denotes a non-magnetic sleeve (hereinafter simply referred to as a sleeve) fitted on the outside of the fixed shaft 1, and is rotatably supported between the side plates of the hopper 4 with a portion exposed to the outside. Reference numeral 5 denotes a magnetic blade serving as a toner thickness regulating means, and the opening 4a of the hopper 4 is arranged so as to leave a gap 21 between it and the sleeve 3 and to face the internal magnetic pole 2b.
It is set in. Reference numeral 7 denotes magnetic toner stored in the hopper 4, 8 a latent image carrier mounted and supported rotatably in the direction of the arrow on a machine body (not shown);
are arranged facing each other with a gap 22 in between.

In the above configuration, ′, I? The toner 7 in the hopper 4 is attracted by the internal magnetic pole 2CIC, is attracted to and held by the sleeve 3 due to the Coulomb force due to contact charging with the sleeve 3 which is rotationally driven in the direction of the arrow, and is generally transported. The toner 7 conveyed in this way is transferred to the magnetic blade 5 and the inner part 11#1 facing the magnetic blade 5.
The desired toner r@ is subjected to magnetic shearing force by
After being adjusted to a thickness of i8, the toner 7 is transferred to a development position opposite to the latent image carrier 8, and 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 a jumping phenomenon. Ru.

-The above-mentioned toner 1-1 regulation is as shown in Figure 2.

In the vicinity of the magnetic blade, the toner i- is divided at the magnetic flux density at the magnetic equilibrium point of the magnetic blade 4 and the equilibrium point between the sleeve and the blades due to the mirror force, and the toner 7 is divided by the mirror force between the sleeve 3 and the sleeve surface. It adheres in a uniform thin layer.

Therefore, the thickness of the toner layer is determined by the charging 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 3 decreases, the thickness of the toner layer becomes thinner and the density of one image decreases significantly.

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 4 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 be extremely high, characters and fine lines will be crushed, the resolution and degree of fogging will deteriorate, and it will become impossible to obtain a uniform layer of toner, which will cause the image to deteriorate. There may be uneven density. In this case, the thickness of the toner can be further suppressed 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. 3(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 this state, the toner near the magnetic blade becomes easier to enter the thickness regulating section, and the amount of toner entering the regulating section is increased compared to the standard state shown in FIG. Furthermore, when the magnetic flux is concentrated on the upstream side of the magnetic blade 5 as shown in FIG. The progress of toner is suppressed, and the amount of toner entering the regulating 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 can always be thicker to an appropriate thickness and the image can be stabilized.

Focusing on the above points, the present invention is configured such that the magnetic blade 5 is tilted back and forth about the middle point between the magnetic blade 5 and the sleeve groove, that is, the mounting M5a of the blade 5, and It has become possible to easily distribute the magnetic flux concentration at the regulating portion to the upstream side and the downstream side of the magnetic blade.

That is, the magnetic blade 5 has a constant thickness, and the magnetic flux is concentrated at both edges of its lower end (end facing the sleeve). Therefore, by tilting the magnetic blade and bending the direction of the magnetic flux so as to concentrate the magnetic flux on one of the two edge parts, the magnetic flux can be concentrated on the upstream side or the downstream side of the magnetic blade. In this case, it is preferable that the magnetic blade 5 has a size at least 15 mm or more at its lower end. A shape in which the thickness and width increase toward the top is desirable.

Since the present invention has the above configuration, the magnetic blade is tilted in response to large seasonal environmental changes.

By selecting the magnetic flux concentration upstream or downstream of the magnetic blade, the thickness of the toner on the sleeve can always be maintained properly.

Good images can always be maintained regardless of environmental changes.

In particular, the developing device of the present invention is
It is good to apply the jumping phenomenon method using the insulating component toner described in the publication, but depending on the type of toner, the range of regulation angle (angle between the tangent of the sleeve and the magnetic blade) and the shape of the magnetic blade.

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

Furthermore, automation can be easily performed by combining the magnetic blade of the above configuration with an environmental sensor, a sensor for developing concentration, etc., and controlling the tilting.

The gap 21 is normally about 2.50μ, but when the magnetic blade 5 is tilted, it changes by about 20μ to 230μ. However, even if the gap 21 changes by 10 to 3 nμ, the toner 1-
The thickness does not change much (because the thickness of the toner layer depends on the balance of the magnetic force <7-7-rl> and the mirror force due to the tribo), and does not affect development.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the developing device of the present invention. FIG. 2 is an explanatory diagram of the principle of regulating the toner thickness with respect to the sleeve, and FIGS. 3(a) and 3(b) are diagrams showing changes in magnetic flux concentration with respect to the rotation direction of the magnetic blade. 6 a sleeve as a toner retaining means; 5 a magnetic blade as a toner thickness regulating means; 7 a toner; 8 a latent image retainer. Figure 3 (6) Figure 4 Figure 2 Figure 2?

Claims (1)

[Claims] An endless developer holding means arranged at a minute interval with respect to the latent image holding member, and a developer 1-thickness regulating means for regulating the developer supplied onto the developer holding means to a uniform thickness. 1. A developing device comprising: a regulating angle of said developer layer thickness regulating means with respect to opposing magnetic poles provided in said developer holding means;