JPS62169186A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a simple developing device which can prevent deterioration of a developing agent caused by the difference of copies in size and improve density variation of copies, by making magnetic fields different from each other between an area where developing agent consumption is high and another area where the consumption is low. CONSTITUTION:This developing device is designed so as to prevent deterioration of a developing agent by making the magnetic circulation of the developing agent in an area where developing agent consumption is low weak in degree and the peak position of the magnetic pole (Pole S2) of a fixed magnet 3 controlling the circulation of a magnetic developing agent 4 in a hopper in the axial direction of a sleeve is changed. This magnetic pole S2 is formed so that the magnet roll 3 can have different magnetic-pole constitutions which are shifted in the peripheral direction between the central part and both end sections. Since the inter-magnetic-pole angle between both end sections of the magnetic pole S2 and another magnetic pole N1 is larger than that at the central part of the magnetic pole S2, the circulating speed of the developing agent in a hopper at both end sections of the nonmagnetic sleeve 2 becomes slower than that at the central part.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention is an electrostatic copying machine, an electrostatic recording machine, etc., in which an electrostatic latent image formed on the surface of an electrostatic latent image support is transferred to a magnetic toner. The present invention relates to an improvement of a developing device that performs development by flying together (developer).

[Background of the invention]

Conventionally, in electrophotographic copying machines, depending on the size of the transfer paper, specifically, in an A3 size machine, a B4
When copying an A4 original using a B4 size machine,
A so-called blackening mechanism is provided to suppress static defects in rounding to suppress developer consumption in size difference areas. Therefore, the developer disappearance scene in the longitudinal direction of the developing device is different, and in extreme cases,
When copying a large number of reader-sized originals, the developer in the developing tray tends to deteriorate due to repeated friction in the size difference area where there is no current consumption, and when copying dog-sized originals. , partially reduced by 4 degrees of copying.

This phenomenon is particularly noticeable in pressure fixing toners made of relatively soft resins, which tend to cause blurring.

In order to solve these problems, methods have been disclosed, such as providing a spiral screw for transporting and stirring the developer in the longitudinal direction of the developing device, but the developing device becomes complicated and large. In addition, it has always been the case that the increase in stirring torque tends to accelerate the deterioration of the developer.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a simple developing device that eliminates the drawbacks of the prior art described above, prevents developer deterioration due to differences in copy size, and improves copy density fluctuations.

[Summary of the invention]

In the present invention, as shown in FIG. 3, the circulating motion of the (Iil) developer in the development chamber depends on the magnetic pole opening angle θ (magnetic pole Nl, 82 in the figure) and the magnetic flux density of the magnetic pole S2. The larger the magnetic pole opening angle θ is, the larger the magnetic pole S2 is.
Since the magnetic flux density tends to be slower as the density of the magnetic flux decreases, by creating a difference in the magnetic field between areas with high and low developer consumption, the circulation speed of developer in areas with low developer consumption is made slower. It is.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 shows a sectional view of an embodiment of a developing device according to the present invention. In the figure, reference numeral 1 denotes a photosensitive drum, which is a static support that rotates in the direction of arrow a while holding an electrostatic charge on its surface by a charging/exposure device (not shown). Reference numeral 2 denotes a non-magnetic sleeve of the developing device, which is a toner conveying surface member made of aluminum, stainless steel, etc., which extends in the axial direction of the photosensitive drum 1 and rotates in the direction of the arrow.
4 is a fixed magnet roll included in the non-magnetic sleeve 2; 4 is a magnetic developer; 5 is disposed facing the non-magnetic sleeve 2 with a gap therebetween, forming a uniform thin layer of the magnetic developer 4 on the surface of the sleeve 2; It shows the doctor blade. Further, an alternating (AC) electric field is formed in the gap between the photosensitive drum 1 and the nonmagnetic sleeve 2 by a power source (not shown).

Due to the rotation of the non-magnetic sleeve 2 and the magnetic field of the internal fixed magnet roll 3, the magnetic developer 4 comes into contact with the surface of the non-magnetic sleeve 2 and is charged to a desired polarity by frictional charging. Then, the non-magnetic sleeve 2 and the doctor blade 5
As the magnetic developer 4 passes through the gap, a thin layer of magnetic developer is formed on the surface of the non-magnetic sleeve 2, and as the non-magnetic sleeve rotates, it is brought to face the photosensitive drum 1 having an electrostatic charge. Due to the electric field between the drum 1 and the non-magnetic sleeve 2, a developing agent flies and adheres to the latent image depending on the potential of the latent image, and development is performed.

On the other hand, the magnetic developer 4 in the hopper circulates in the direction of arrow C while rubbing against the surface of the non-magnetic sleeve 2 due to the magnetic field generated by the magnetic poles Nl and S2 of the fixed magnet roll 3.

By the way, as described in the above-mentioned conventional example, when continuous copying is performed on a small-sized original, the magnetic developer 4 in the size difference area is not transferred to the photosensitive drum l and consumed in the developing device, so that the above-mentioned While repeating the circular motion, it rubs against the sleeve 2 many times. Generally, when a magnetic developer is subjected to excessive friction, it tends to undergo deterioration phenomena such as a decrease in the fluidity of the developer, agglomeration, and a decrease in the amount of charge, which causes a so-called development density decrease phenomenon.

This is observed even when the developing device is rotated independently outside the machine, and is particularly noticeable in high-speed copying machines in which pressure fixing toner and sleeves made of soft resin are rotated at high speeds.

As described above, the present invention aims to prevent deterioration of the developer by weakening the degree of magnetic circulation of the developer in areas where developer consumption is low. As shown in FIGS. 1 and 2, the peak position in the sleeve axial direction of the magnetic pole (pole S2 in the figure) of the fixed magnet 3 that governs the circulation of the magnetic developer 4 in the Holanow is changed. In this embodiment, since the copying machine uses a central reference document, the circulation speed of the developer in both end regions of the non-magnetic sleeve 20 is slowed down, and the S2 magnetic pole drawn by the broken line is connected to the non-magnetic sleeve 2. The peak positions at both end regions are shown.

This S2 magnetic pole is formed in a magnetic configuration in which the center portion and both end portions are offset in the circumferential direction, as shown in FIG. There is.

Therefore, since the magnetic pole opening angle between both end portions of the magnetic pole S2 and the magnetic pole N1 is larger than that at the center portion of the magnetic pole S2, the circulation speed of the developer in the hole at both end portions of the non-magnetic sleeve 2 is greater than that at the center portion. It will be more gradual.

Next, another embodiment will be described based on FIG. 4.

The embodiment shown in Figures 1 and 2 shows a magnetic pole configuration in which the circulation and stirring speed of the magnetic developer is changed by changing the magnetic pole opening angle θ in the axial direction of the sleeve. Since the circulation and agitation speed of human blood becomes slower as the magnetic flux density of the magnetic pole S2 decreases, in this embodiment, the human blood magnetic flux density in both end regions of the magnetic pole S2 is made smaller than in the central region.

(2) When one side of the original is used as a reference, the surface magnetic flux density on the opposite end side to the reference side may be made smaller, as shown by broken n.

〔Effect of the invention〕

As explained above, according to the present invention, since the toner circulation agitation speed is different in the area where the toner consumption is high and the area where the toner consumption is low in the toner storage unit, it is possible to prevent the deterioration of the toner in the area where the toner consumption is low. This makes it possible to provide high-quality images.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the developing device according to the present invention, Fig. 2 is an exploded view of the magnet roll, and Fig. g3 shows the circulation movement of the magnetic developer in the developing device hollow and the magnetic pole configuration. The figure shown in FIG. 4 shows another example and is a chart showing the magnetic flux density in the axial direction of the magnet roll. 1... Photosensitive drum 2... Non-magnetic sleeve 3
...Fixed magnet roll 4...Magnetic developer 5...Doctor blade Figure 1 Figure 21/! A

Claims (1)

[Claims] a toner conveying surface member that faces the surface of the electrostatic latent image support member at a distance and extends in the width direction thereof, and is disposed so as to be able to come into contact with the magnetic toner in the toner storage section; a toner regulating blade extending in the width direction; and a fixing member having a first magnet for at least the toner regulating blade and a second magnet for the toner storage portion along the width direction on the back side of the toner conveying surface member. magnetic field generating means, the toner regulating blade holds the magnetic toner on the toner conveying surface member by movement of the toner conveying surface member and magnetic field action by the first magnet and the second magnet of the magnetic field generating means. conveyed through the
The toner is caused to fly and adhere to the surface of the electrostatic latent image support by an electric field between the toner conveying surface member and the electrostatic latent image support, thereby developing the electrostatic latent image on the surface of the electrostatic latent image support. A developing device characterized in that the second magnet of the magnetic field generating means has a magnetic field different at least at one end thereof in the longitudinal axis direction.