JPS6128982A - Magnetic brush device - Google Patents

Abstract

PURPOSE:To execute a stable development of a high quality by constituting a titled device so that a number of revolution per unit time of a magnet roll of the time when a magnetic powder scraping means is abutting on the surface of a non-magnetic sleeve becomes lower than a number of revolution of the time when said means is being separated from the surface of the non-magnetic sleeve. CONSTITUTION:At the time of non-development, when a number of revolution of a magnet roll 11 is set to <=1/2 of a number of revolution of the time of development, a load applied to a doctor and developer control member 15 and a non- magnetic sleeve 10 is reduced, and also a deterioration of a developer 18 is prevented. It is because the developer 18 on the non-magnetic sleeve 10 moves smoothly and is separated easily from the non-magnetic sleeve 10, comparing with the case the magnet roll 11 is stopped completely. On the other hand, if the number of revolution of the magnet roll 11 remains a number of revolution which is not changed so much from the time of development, a developer bank is generated in the vicinity of the doctor and developer control member 15, and an excessive load is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic brush device used in image forming apparatuses and the like.

[Prior art]

Conventionally known developing devices include the following.

In the case shown in FIG. 2(a), the developing sleeve 2 is rotatable and the magnet roll 3 is fixed.

The developer is conveyed in the same direction as the rotational direction of the developing sleeve 2. Further, the developer can be removed from the surface of the developing sleeve 2 by the scraping plate 5 which can come into contact with and separate from the surface of the developing sleeve 2. Note that in the figure, 1 is a photoreceptor and 4 is a doctor.

The one shown in FIG. 2 (bl) is one in which the developing sleeve 2 and the magnet roll 3 are rotated in the same direction to convey the developer.

Then, simply by stopping the rotation of the magnet roll 3, the developer on the surface of the developing sleeve 2 is scraped off by the scraper 6. Further, a supply device 7 for conveying and supplying developer to the developing sleeve 2 is provided.

The developer on the developing sleeve 2 can also be removed during non-development by stopping the rotation of the supply device 7.

In addition, there is a device in which both the developing sleeve and the magnet roll are rotated, but in opposite directions.

[Problems with conventional technology]

However, in a device in which the developing sleeve is fixed to a rotational magnet roll, the developer is not easily conveyed on the developing sleeve, and the image quality is also degraded. Furthermore, when this type of device is used to develop an image that has already been visualized on the photoreceptor, such as in a color copying machine, the image on the photoreceptor is likely to be scraped off. . Therefore, it is not suitable as a developing device for color copying.

In addition, when the developing sleeve and magnet roll are rotated in the same direction, the image quality and the scraping during color development are improved, but the carrier is removed in areas with strong potential contrast, such as the boundary between the 1 image area and the non-image area. This will cause the image quality to deteriorate.

Furthermore, since the developing sleeve and the magnet roll rotate in the same direction, the developer layer is formed into a double layer, upper and lower layers, which move in opposite directions, which tends to cause toner scattering, and therefore does not pass through high-speed development.

Furthermore, a device in which the developing sleeve and the magnet roll rotate in opposite directions solves the problems of the above-mentioned developing device, and can be used for color copying, etc., but the developer on the developing sleeve during non-developing. Regulatory measures, good potatoes. Good. 4 ゎ Ah, Fig. 1 (Al, (((()))
If the developer regulating means shown in bl is applied, the load on the developing sleeve becomes large.

Developer deterioration occurs or developer is agitated.

There are inconveniences such as poor conveyance and an adverse effect on image quality when development is restarted.

[Purpose of the invention]

In view of the above-mentioned conventional drawbacks, the present invention can perform stable and high-quality development during development, and can also control the developer on the sleeve using a simple method.
A further object of the present invention is to provide a magnetic brush device that can be used in cleaning devices.

[Key points of the invention]

In order to achieve the above object, the present invention provides a magnetic brush device that adsorbs and conveys a magnetic brush made of magnetic powder onto a rotatable non-magnetic sleeve that has a built-in magnet roll that can rotate twice. A detachable magnetic powder scraping means is provided, and at least while the magnetic powder scraping means is in contact with the surface of the non-magnetic sleeve,
7) The number of rotations per unit time of the magnet roll is lower than the number of rotations per unit time of the magnet roll when the magnetic powder scraping means is separated from the surface of the non-magnetic sleeve. shall be.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings. 1 and 3 are cross-sectional views showing one embodiment of the present invention. In this embodiment, the magnetic brush device according to the present invention is used as a magnetic brush developing device, and FIG. 1 shows the non-developing state, and FIG. 3 shows the developing state.

The magnetic brush developing device 8 is constructed by having each member arranged at a predetermined position within a flopper 9.

The magnet roll 11 is provided so as to be rotatable in a clockwise direction, and a non-magnetic sleeve 10 is provided on a concentric circle around the circumferential surface of the magnet roll 11, and the non-magnetic sleeve 10 rotates in the opposite direction (counterclockwise direction) to the magnet roll 11. Rotated independently.

A scraper 12 made of a thin plate of phosphor bronze, Mylar film, etc. is disposed below the non-magnetic sleeve IO so that one end is in contact with the circumferential surface of the sleeve IO, and a small conveyance device 13 is disposed below the scraper 12. .

Further, a large stirring and conveying device 14 is provided in parallel with the non-magnetic sleeve 10, and a toner replenishing device 16 is arranged above the flopper 9 above the Wl stirring and conveying device 14.

Further, above the non-magnetic sleeve 10, a doctor/developer regulating member 15 is provided which can come into contact with and separate from the surface of the non-magnetic sleeve 10.

Next, the operation in the above configuration will be explained.

During development as shown in FIG.
The upper layer rotates counterclockwise on the non-magnetic sleeve 10 due to the rotating magnetic field of the magnet roll 11 which rotates clockwise (101000 rpm), and the non-magnetic sleeve 1
0 counterclockwise rotation (30 rpm) causes the lower layer to overlap with the lower layer which also moves counterclockwise due to the frictional force with the surface of the non-magnetic sleeve 10.

The developer layer is formed as an upper and lower double layer moving in the same direction. The developer layer formed in this manner has a contact force of soft I· with respect to the surface of the photoreceptor 1, which is the surface to be developed.
Therefore, there is less amount of scraping during overlapping development.

During development, the doctor/developer regulating member 15 is separated from the surface of the non-magnetic sleeve 10 with a predetermined gap. Therefore, the developer layer formed on the non-magnetic sleeve 10 is regulated to a constant thickness by the doctor/developer regulating member 15.
Subsequently, it comes into contact with the surface of the photoreceptor 1, and develops the electrostatic latent image formed on the photoreceptor 1. Furthermore, the developer 18 after passing through the developing section is scraped off from the surface of the non-magnetic sleeve 10 by a scraper 12, and is stirred by a stirring device 13.

It is sent to the stirring and conveying device 14. Developer sent 18
The non-magnetic sleeve 1 is sufficiently stirred by the stirring and conveying device 14 with the toner supplied by the toner replenishing device 16.
0 is transported upward, and the above development operations are repeated.

On the other hand, when not developing as shown in Figure 1,
By the operation of the I-lenoid I7, one end of the doctor/developer regulating member 15 is pressed against the circumferential surface of the non-magnetic sleeve 10 with an appropriate pressure. Therefore, the developer 18 is regulated so as not to be conveyed to the circumferential surface of the non-magnetic sleeve 10 facing the photoreceptor 1. The regulated developer 18 flows toward the agitation and conveyance device 14 and is agitated without accumulation, improving agitation efficiency.

Also, at this time, the number of rotations (N,') of the magnet roll 11
is the number of rotations during development (N, + in this example, N m = 1
100Orp) or lower (for example, if the rpm is 10100rp, the doctor/developer regulating member 15 and the non-magnetic sleeve 1
The load applied to the developer 18 is reduced, and deterioration of the developer 18 is also prevented. This is because the developer 18 on the non-magnetic sleeve 10 moves better and is easier to separate from the non-magnetic sleeve 10 than when the magnet roll 11 is completely stopped, and the rotational speed of the magnet roll 11 increases. If the rotational speed remains the same as that during development, developer will accumulate near the doctor/developer regulating member 15, resulting in an extra load.

Furthermore, when the regulation of the developer 18 on the surface of the non-magnetic sleeve 10 facing the photoreceptor 1 is completed, the non-magnetic sleeve I
It is also possible to stop the rotation of O. FIG. 4 is a timing chart of operations in this embodiment. It takes some time for a sufficient magnetic brush to be formed, so slightly before starting development, rotate the magnet roll 11 at the developing state rotation speed (
Nn, ), the solenoid 17 is turned off, and the doctor/developer regulating member 15 is separated from the surface of the non-magnetic sleeve 10.

As described above, during development, stable development is performed without scraping during overlapping development, and during non-development, the developer layer can be blocked off without developer pooling, preventing developer from spilling from the device. Scattering can also be prevented to a minimum. Therefore, if multiple developing devices are used, such as in a multi-color developing device,
This is effective when one developing device must be in a developing state and the other developing devices must be in a non-developing state. Further, when developing directly on a recording paper as in an electrostatic recording apparatus, it is possible to prevent stains caused by developer flowing around to the back surface of the recording paper from the leading edge or trailing edge of the recording paper.

In this embodiment, a case has been described in which the magnetic brush device according to the present invention is used as a magnetic brush developing device, but it can also be used as a magnetic brush cleaning device with a similar configuration. For example, multiple copies can be obtained with one exposure. In a so-called multi-sheet copying device, after the charging and exposure steps are completed, the development and transfer steps are repeated multiple times, followed by cleaning, so the cleaning device is kept completely inactive and static during the repetition of the development and transfer steps. It must be ensured that the electrostatic latent image is not adversely affected. Therefore, the magnetic brush device according to the present invention can also be used as a magnetic brush cleaning device in such a multi-sheet copying machine.

〔Effect of the invention〕

As explained in detail above, the magnetic brush device of the present invention can perform stable and high-quality development during development, can regulate the amount of developer on the sleeve in a simple manner and without any inconvenience, and can also be used for cleaning. It can also be applied as a device.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 3 are sectional views showing one embodiment of the present invention, and FIGS. 2(a) and 2(b) are sectional views of a conventional developing device. FIG. 4 is a timing chart of operations in one embodiment of the present invention. ■...Photoreceptor, 8...Magnetic brush developing device, 10...Nonmagnetic sleeve. DESCRIPTION OF SYMBOLS 11... Magnet roll, 14... Stirring and conveyance device, 15... Doctor and developer regulating means, 18... Developer.

Claims (4)

[Claims] (1) In a magnetic brush device that attracts and conveys a magnetic brush made of magnetic powder onto a rotatable non-magnetic sleeve containing a rotatable magnetic roll, a magnetic powder scraping means that can move toward and away from the surface of the non-magnetic sleeve. and at least while the magnetic powder scraping means is in contact with the non-magnetic sleeve surface, the number of revolutions per unit time of the magnetic roll is controlled so that the magnetic powder scraping means is separated from the non-magnetic sleeve surface. A magnetic brush device characterized in that the number of rotations per unit time of the magnet roll is lower than that when the magnetic roll is being rotated. (2) The magnetic brush device according to claim 1, wherein the rotation directions of the magnet roll and the non-magnetic sleeve are opposite to each other. (3) At least while the magnetic powder scraping means is in contact with the surface of the non-magnetic sleeve, the number of rotations per unit time of the magnetic roll is controlled so that the magnetic powder scraping means is separated from the surface of the non-magnetic sleeve. 1/2 of the number of rotations per unit time of the magnetic roll when
Claim 1 characterized in that it is reduced to:
The magnetic brush device according to item 1 or 2. (4) When the magnetic powder scraping means is separated from the surface of the non-magnetic sleeve, the number of rotations per unit time of the magnet roll is at least 10 times the number of rotations per unit time of the non-magnetic sleeve. A magnetic brush device according to any one of claims 1 to 3, characterized in that: