JPS61107366A - Developing device using magnetic brush - Google Patents

Abstract

PURPOSE:To feed toner from a hopper to a developing roll smoothly and to prevent picture quality from deterioration at the time of continuous copying by extending the lower end of wall surface ont he inflow side of circulated toner to the toner hopper lower than the lower end of the wall surface on the toner outflow side and arranging the outlet opening part of the toner hopper on a position where the weight of the stored toner is not directly affected to a developing roll. CONSTITUTION:Residual toner on the developing roll which is left after the completion of sliding with an electrostatic latent image is moved in the arrow (a) direction and circulated to the hopper opening part. When the developing roll is rotated moreover, the residual toner on the developing toner is deviated and moved by a circulated toner control plate formed on the leading end surface of the hopper 3 in the arrow (b) direction. The toner consumed by the develop ment is moved in the arrow (c) direction to be charged with new toner on the wall surface on the circulated toner inflow side on the developing roll. Therefore, the toner circulated from the developing roll and newly fed toner are agitated like a circle formed by the arrows (b) and (c) in an opening area formed by a timer 3 of the hopper 5 and a hopper 5-1.

Description

[Detailed description of the invention] The present invention relates to a magnetic brush developing device.

The latent electrostatic latent image formed on the surface of a photoconductor or dielectric material is developed by mixing fine colored particles called toner with iron powder called a carrier and adhering it to the toner electrostatic latent image by mutual frictional electrification. There are two-component development methods and one-component development methods, in which magnetic toner containing iron powder is given a charge by frictional charging, electrostatic induction, etc., and the toner is attached to the electrostatic latent image for development. be.

Two-component developers can form high-quality images with sufficient charge on the friction zone, but on the other hand, it is difficult to control the mixing ratio of toner and carrier, reduce the amount of load on the friction zone due to toner adhesion to the carrier surface, or reduce the load on the friction zone. There are problems such as increasing the size. -Unlike two-component developers, component developers do not suffer from problems such as deterioration in mixing ratio or chargeability, and have many advantages such as a simple structure of the device itself.

However, in the case of a -component developer, special cases are excluded in which charges are imparted to the retoner by frictional charging or the like.

Since the toner itself is developed by electrostatic induction, which has a true charge, the method of contacting the toner brush with the electrostatic latent image, the method of transporting the toner to the electrostatic latent image, or the method of transporting the toner from the hopper onto the developing roll may vary. In terms of the supply method, etc., the issue is how to increase the development effect and perform stable development. In particular, in the case of a -component development system, when a fixed amount of toner is supplied into the hopper and copies are made continuously, the image quality immediately after copying starts and the image quality when the amount of toner remaining in the hopper becomes extremely small are greatly affected. However, there is a major problem in that image quality, especially density, low density reproduction, and sharpness, decrease in proportion to the number of copies. In particular, in a copying system equipped with a developing machine with a 2-cycle cleaning function, the image quality deteriorates significantly.

The present invention has been made in view of the above-mentioned drawbacks, and provides a new developing device that can prevent the deterioration of image quality during continuous copying, which is peculiar to the developing method using -component developer, while maintaining the simplicity of the mechanism. The purpose is to provide.

The inventors of the present invention have made extensive studies regarding the maintenance of image quality during continuous copying, and have found that the cause of the deterioration lies in the method of supplying toner from the hopper to the developing roll.

This will be discussed in detail below with reference to the accompanying drawings, Figure 1.

Figure 1 is a schematic diagram of a conventional single-component developing machine.

The developing machine 10 is a non-magnetic cylinder! J-'21 and sleeve 1
A developing roll with a fixed magnet 2 installed inside, and
It is composed of a trimmer 3 that regulates the amount of toner supplied (toner thickness) and a hopper 5 that stores toner 4.

In the conventional developing machine shown in the figure, a fixed amount of 100 J'm of toner is put into the hopper 5, continuous copying is started, and the remaining amount of toner is 20 J'm. The image quality when it decreased to about Pm was compared with the initial image quality. As a result, as the number of copies increased, image density, low density reproducibility, and sharpness decreased, making it impossible to maintain the initial image quality. That is, image quality stability, in other words, development stability was lacking.

The inventors have conducted various studies on the cause of this problem.

The contact area between the toner in the hopper and the developing roll, that is, the opening width of the hopper (W);
It is clear that this is due to the distance between the
did. In other words, in FIG. 1, when the developing roll is rotated so that the toner movement direction is in the direction of arrow a, the toner that did not participate in the electrostatic latent development (not shown) is transferred to the trimmer 3. , some of them in the direction indicated by the arrow mb (
(in the upper direction of the hopper) and a portion passes through the trimmer 3 and is supplied to the electrostatic latent image. On the other hand, the toner that adheres to the electrostatic latent image and is consumed is supplied from the hopper onto the developing roll as shown by arrow C on the right side of the hopper in the figure. What should be noted here is that when the opening width of the hopper is large, the toner in the hopper is agitated as shown by the arrow bc in the figure along with the movement of the toner on the developing roll.

When the toner in the hopper is stirred, the toner has a certain particle size distribution, so it tends to adhere to the electrostatic a-image, that is, when it is developed, toner particles that are easily developed are sequentially At the same time, it is thought that the toner present in the hopper opening on the developing roll is also selectively consumed in order from particles with higher developability.

In order to verify this, in the developing machine, hopper 1
After adding 001m of toner, the particle size distribution of the toner on the developing roll was measured at fixed intervals using a Coulter counter, the charge distribution of the toner particles adhering to the latent image at that time was measured using a charge spectrograph, and the image quality was measured using a charge spectrograph. Each was measured. As a result, as for the particle size distribution, the ratio of fine particles decreases as time passes after the start of development, and the particles gradually become coarser, and when the remaining amount of toner in the hopper is 2011 m, the average It was confirmed that the particle size increased by about 5μ.The charge distribution also became narrower over time, and the positive electrode side (Se was used for the photoreceptor) and Q/d ( It was confirmed that the toner charge amount per unit particle size also decreased.

Similarly, image quality changes over time, including density and low density reproducibility.

It was also confirmed that the sharpness decreased.

The above verification has shown that in a configuration where the opening width of the hopper is large and the weight of the toner in the hopper is directly applied to the developing roll, as shown in Figure 1, selective development of toner is promoted, and image quality stability and development stability are improved. It turned out that there was a very big flaw.

Therefore, in the device of the present invention, the opening width of the hopper is narrowed, and the arrangement is such that the weight of the toner in the hopper is not directly applied to the developing roll. In the hopper opening area, the toner returned from the developing roll collides with the bottom surface of the trimmer. In addition, in the trimming area, a trimmer is installed to prevent toner backing, and the new toner and toner returned from the developing roll are mixed and stirred at a substantially constant ratio, and their movement does not propagate into the hopper. The above-mentioned drawbacks are solved by making the shape different.

1. More specifically, the present invention comprises a developing roll in which a magnet roll is arranged inside a non-maternal 7-leap, and a toner hopper containing magnetic toner and having a trimmer at the tip of the toner outlet side wall surface.

In a magnetic brush developing device that mixes the refluxed toner remaining on the developing roll after passing through the developing area with new toner supplied from the toner hopper and transporting the mixed toner to the developing area again, the surface of the trimmer facing the developing roll is a trimmer. The distance between the trimmer and the developing roll is approximately parallel to the connection of the developing roll at the shortest position, and the distance between the trimmer and the developing roll gradually increases in accordance with the rotating direction of the developing roll. The lower end of the wall surface on the inflow side of the refluxed toner to the hopper is extended downward from the lower end of the wall surface on the toner outflow side, and the outlet opening of the toner hopper is arranged so that the weight of the stored toner does not directly act on the developing roll.

This will be explained below using an example.

FIG. 2 is a schematic diagram of one embodiment of a one-component developing machine according to the present invention. In the figure, members having the same functions as those shown in FIG. 1 are designated by the same reference numerals. As can be easily understood from the figure, the difference from the WI1 figure is particularly in the shape O position of the hopper and trimmer including the opening. The illustrated trimmer 3 has a solid tip, and its surface acts as a control plate for the refluxed toner, and the surface of the trimmer facing the developing roll is a developing roller at a position where the distance between the trimmer and the developing roll is the shortest. It is approximately parallel to the tangent line of the roll.

Further, the distance between the facing surface of the trimmer and the developing roll is arranged so as to gradually increase in accordance with the rotating direction of the developing roll. The trimmer described above may be either a member integrally formed with the left side wall of the hopper or, as shown, a separate member fixed to the left side wall of the trimmer. In addition, the opening width of the hopper is set to be much narrower than that shown in Figure 1, and the perpendicular line at the tip of the hopper opening (in the figure) (tip of the hopper 3) is provided at a position that does not interfere with the outer periphery of the developing roll.

The movement of toner in this configuration will be explained below using Figure 2.

The residual toner on the developing roll that has finished rubbing against the electrostatic latent image moves in the direction of arrow a and is returned to the hopper opening. When the developing roll further rotates, the residual toner on the developing roll is biased and moved in the direction indicated by the arrow by the reflux toner control plate formed at the front end surface of the hopper 3. On the other hand, the toner consumed during development is replenished onto the developing roll at the wall surface on the side where the refluxed toner flows in, so that the toner moves in the direction shown by arrow C.

Therefore, in the opening region defined by the trimmer 3 of the hopper 5 and the hopper 5-1, the toner flowing back from the developing roll and the newly supplied toner are stirred in a circular shape formed by arrows A and C. Therefore, the toner that remains in the opening area after being stirred always has a constant ratio of refluxed toner and new toner. In addition, the shape of the hopper 5 itself is an inverted triangle and is open.

The opening is much narrower than before, and it is arranged so that the perpendicular line of the end surface that defines the opening does not cross the outer peripheral surface of the developing roll, so the backing due to the weight of the toner inside the hopper 4 is prevented by the trimmer. Since this is avoided at the end face and opening area of No. 3, stirring of the above-mentioned refluxed toner and new toner is promoted, and this stirring development is prevented from affecting the toner above the hopper.

When the e-maid quality of the apparatus of the embodiment shown in FIG. 2 was investigated in the same manner as explained using FIG. It was also extremely good.

The features of the apparatus of the present invention explained above are listed below.

The shape of the hopper is an inverted triangle, the opening is narrower than before, and the perpendicular line at the tip of the opening of the hopper is located at a position that does not interfere with the outer peripheral surface of the developing roll.

The surface of the trimmer facing the developing roll is approximately parallel to the tangent to the developing roll at the position where the distance between the trimmer and the developing roll is the shortest, and the distance between the trimmer and the developing roll is in the rotation direction of the developing roll. They are arranged so that they gradually increase in size. The end face that is set to define the opening of the trimmer has a planar shape.

Although the present invention has been described above using a developing device that uses a one-component developer, the same good results can be obtained when a developing device that also functions as a cleaner is used in a two-cycle, one-copy, one-type copying machine. The results were obtained.

Furthermore, unlike conventional devices, the present invention does not need to be installed on the axis of a hopper-like developing roll, so there is greater freedom in positioning the developing device relative to the photoreceptor.

[Brief explanation of the drawings] Figure 1 is a schematic diagram of the conventional single-component
The figure is a schematic diagram of a one-component developing machine according to the present invention. (In the figure, symbol 1: Non-magnetic cylindrical sleeve, 2: Magnet, 3 Nitrimer, 4: Toner, 5: Hopper, arrows a, b
, c:) Na movement direction times. Continued from page 1 Akira Kume Yoshihiko Fujimura 2 Hongo, Ebina City
274 address office

Claims (1)

[Claims] It is equipped with a developing roll in which a magnetic roll is arranged inside a non-magnetic sleeve, and a toner hopper containing magnetic toner and having a trimmer at the tip of the wall surface on the outflow side of the toner, so that the toner remains on the developing roll after passing through the developing area. In a magnetic brush developing device that mixes refluxed toner and new toner supplied from a toner hopper and transports the toner to the developing area again, the surface of the trimmer facing the developing roll has a distance between the trimmer and the developing roll. The trimmer is arranged so that it is approximately parallel to the tangent line of the developing roll at the shortest position, and the distance between the trimmer and the developing roll gradually increases in accordance with the rotating direction of the developing roll. A magnetic brush developing device characterized in that the lower end of the side wall surface extends downward from the lower end of the toner outflow side wall surface, and the outlet opening of the toner hopper is arranged at a position where the weight of the stored toner does not directly act on the developing roll.