JPS58162971A - Magnetic brush developing device - Google Patents

Abstract

PURPOSE:To improve fluidity of a developer, by providing a mesh screen having one end pressed into contact with the circumference of a developing sleeve on the upstream side of the developer feed direction, and rotating amgnetic roll installed in the sleeve. CONSTITUTION:A developing sleeve 2 having a magnetic roll rotated in the inside is provided, and a screen mesh 5 made of nonmagnetic material is installed and one end of it is pressed into contact with the circumference of the sleeve 2 on the upstream side in he developer feed direction with respect to a developing region. The screen 5 is set along the direction following the developer feed direction. Means 6 for recovering the developer separated by hindering the feed of the developer with the screen 5 is installed.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a magnetic brush developing device having a developing sleeve having a magnetic roller rotatably driven therein.

PRIOR ART The magnetic developers used in the above-mentioned magnetic brush developing device (7) include a l-component magnetic developer consisting of only one type of magnetic toner, and a two-component magnetic developer consisting of a mixture of toner and a magnetic carrier. , or a magnetic developer made of a mixture of two or more types of toner including magnetic toner.These developers are sequentially circulated and conveyed in the developing device, and during the conveyance, an electrostatic latent image is formed. It is used to develop and visualize an electrostatic latent image carried on the surface of an electrostatic latent image carrier by rubbing the surface of the carrier.By the way, in the developing device, the amount of developer is It has been experienced that when circulation conveyance is repeated over a long period of time, various foreign substances are mixed into the developer, causing various problems.

As mentioned above, a typical example of the foreign matter mixed into the developer is a lump of toner that is gradually formed as a result of long-term circulation transportation. Such toner lumps are formed when the developer is subjected to physical force, heat, etc. during the circulation, and the toner particles in the developer are fused together. The tendency for such toner lumps to form is remarkable in so-called pressure fixing developers.

Furthermore, when the developing device is incorporated into a transfer type electrophotographic copying machine, foreign substances that may be mixed into the developer include paper dust and paper fibers from transfer paper. This tendency for paper powder, paper fibers, etc. to be mixed in is caused by the developing device in a copying machine that removes and collects the developer remaining on the surface of the photoreceptor and sends it back into the developing device after image transfer. This is noticeable when the system is incorporated.

The incorporation of such foreign matter into the developer not only deteriorates the fluidity of the developer itself, but also has an adverse effect on the development itself of the electrostatic latent image, resulting in white spots or black dots in the developed image. This will cause stains. Therefore, in order to eliminate such problems, it is necessary to remove foreign substances mixed into the developer from the developer.

On the other hand, since the developer itself is composed of fine powder, it is easily agglomerated under the influence of moisture, etc., and it has also been experienced that its fluidity is impaired. [2] The buoyancy of the developer with such impaired fluidity causes density unevenness in the developed image. Therefore, it is additionally necessary to apply a physical impact to the developer to loosen such agglomerated developer and improve its fluidity.

Purpose of the Invention The present invention has been made in response to the above-mentioned needs, and its purpose is to improve the fluidity of a developer, and to
An object of the present invention is to provide a magnetic brush developing device equipped with a novel mechanism for removing foreign matter from developer.

SUMMARY OF THE INVENTION The gist of the present invention is that a magnetic brush developing device according to the present invention includes a mesh screen having one end pressed against the circumferential surface of a developing sleeve on the front side in the developer conveying direction with respect to the developing area, and a mesh screen. The developing sleeve is provided with a means for recovering the developer that has been stopped at the 11th stop of conveyance, and a magnetic roller provided inside the developing sleeve is rotationally driven. As a result, the mesh screen selects and removes foreign matter from the developer, and the developer passes through the mesh screen.1. When the material is transported, it is loosened under the influence of an alternating magnetic field generated by the rotation of the magnetic roller, and its fluidity is improved.

Embodiment Referring to FIG. 1.2 (from 7 onwards, an embodiment of the magnetic-1J child developing device according to the present invention will be explained.The embodiment described below is incorporated into a powder image transfer type electrophotographic copying machine. Although shown as [7], the magnetic brush developing device according to the present invention may be incorporated into other electronic equipment.

In FIG. 1, an electrophotographic photosensitive drum (1) is driven to rotate in the direction of an arrow (at), and as the drum (1) rotates, an electrostatic layer 1 corresponding to an original image is formed on its surface by an image forming device (not shown). A magnetic brush developing device (MD) is installed facing the surface of the photoreceptor drum (1), and the electrostatic latent material carried on the surface of the photoreceptor drum (1) is The image is developed using 1) in a magnetic developer. This magnetic developer (1) 1) is a one-component magnetic developer consisting of only one type of magnetic toner, and the average particle size (coulometric average particle size) of the magnetic toner is 15 IIrrl.

The 11-grip developing device (MD) has a developing sleeve (2) provided at a position facing the surface of the photoreceptor drum (1).
The area where the peripheral surface of this developing sleeve (2) and the surface of the photoreceptor drum (11) closely face each other is defined as a developing area 17. This developing sleeve (2) is made of a non-magnetic conductive material,
It is made of non-magnetic stainless steel into a cylindrical shape, and its outer diameter is 31 mm.

In the developing device (fVID), the developing sleeve (2) is fixed, but may be driven to rotate as required.

On the other hand, inside the block method sleeve (2), during development, a drive source (not shown) is used to drive the sleeve (2) at 1000 r in the direction of arrow (b1).
A magnetic roller (3) is provided which is driven to rotate at a rotational speed of pm. This magnetic roller (3) has 8. The N poles are sequentially magnetized, and the magnetic force is set so that a magnetic field of 10,000 au s is formed on the circumferential surface of the developing sleeve (2). Therefore, the developer (DI) is attracted like a magnetic brush in the soil surrounding the developing sleeve (2), and is transported in the direction of arrow (C) along the periphery of the developing sleeve (2) during development. That will happen.

By the way, a developer tank (4) is provided between the pairs located above the developing sleeve (2), and the developer tank (4) is appropriately distributed to the circumferential surface of the developing sleeve (2).
) is supplied. In addition, the developing sleeve (
Below 2) is a mesh screen (5) that functions to select and remove foreign matter η from the developer (1) I) and to loosen the developer (IJI) and improve its fluidity.
is provided. The tip of this mesh screen (5) is pressed against the surface of the developing sleeve (2) in the developer conveying direction, that is, on the front side in the direction of arrow (C) with respect to the developing area. mesh screen (
5) The eye is installed along a direction that follows the developer transport direction. The other end is a foreign matter collection container (6
) is fixed for

Here, the mesh screen (5) is a non-magnetic metal υ
) and the size of the mesh is the developer (1) l
) is set to several times to several tens of times the particle size of the magnetic toner in the magnetic toner. Specifically, since the average particle size of the magnetic toner is 15 pm, the mesh size is set to 10
It is set to about 0 to 280 meshes, preferably about 170 to 200 meshes.

Therefore, the developer (DI) is transferred to this mesh screen (
When the developer (1) is transported through the developer (1) 5), the foreign matter η mixed in the developer (1) 1) is prevented from being transported. This is because toner lumps, paper dust, paper fibers, etc., which are cited as foreign particles, all have a particle size that is at least several tens of times larger than the particle size of the magnetic toner.

In such a configuration, the developer (Dl) supplied from the developer tank (4) onto the circumferential surface of the four-image sleeve (2) is transferred to the developing sleeve (2) by the magnetic force of the magnetic roller (3).
It is attracted like a magnetic brush on the circumferential surface of. Then, as the magnetic roller (3) is driven to rotate, the developer (1) is transported along the circumferential surface of the developing sleeve (2) in the direction of the arrow (C1). ), but some of the developer (Dl) is prevented from being transported by the mesh screen (5). The developer (1) 1) that is prevented from being conveyed in this way is mainly composed of toner lumps, paper dust, and paper fibers (D
s) is moved in the direction of the arrow (d1), and as a result, it falls into the foreign matter collection container (6) under its own weight and is collected as a foreign matter container.For this reason, it does not pass through the mesh screen (5). The developer (Dl) that reaches the developing area is substantially free of foreign particles, and the adverse effect of electrostatic latent phenomena on development caused by the inclusion of foreign particles is improved.

On the other hand, when the developer (DI) is conveyed through the mesh screen (5), an alternating magnetic field is also formed in the vicinity of the mesh screen (5) as the magnetic roller (3) is driven to rotate. Then, due to the action of this alternating magnetic field, the developer (
Dl) passes through the mesh screen (5) while being disturbed. As a result, mesh screen (5)
There is no risk that the developer (Dl) will get stuck in the mesh of the screen (5), and the developer (Dl) that has aggregated under the influence of moisture etc. will not be allowed to collide with the mesh screen (5) many times. , passing through the mesh], it will be crushed to the extent that it is obtained. Therefore, the developer (Dl) is passed through the mesh screen (5) and
As a result, the fluidity of the developer (DI) that reaches the development area is improved, and density unevenness in the developed image caused by deterioration in the fluidity of the developer (DI) is also improved.

By the way, the developer (1) t), which has passed through the mesh screen (5) and is transported to the development area in this way, rubs the surface of the photoreceptor drum (1) in the development area [
7, the electrostatic latent image carried on the surface is developed.

At this time, as is not clear from the above content, the foreign matter has already been sorted out and removed from the developer (Dl) present in the development area, and the fluidity of the developer (Dl) has already been improved. Because of this, good development is carried out. Then, the developer (I) 1) passes through the development area, is transported in the direction of arrow (C), and is again processed in the same manner together with the developer (Dl) newly supplied from the developer tank (4). It will be used to develop electrostatic latent images.

The above is a description of one embodiment of the magnetic brush developing device according to the present invention, but this embodiment can be modified in various ways. For example, when a two-component magnetic developer is used as the developer, the developing device (Ml) shown in FIG. 2 can be modified. In addition, in Fig. 2, the photoreceptor drum (
1), the developing sleeve (2), and the magnetic roller (3) are the same as those shown in FIG. The magnetic roller (3) is similarly driven to rotate at a rotation speed of 130 rpm and is set as shown in FIG.

In Figure 9J2, magnetic developers (1) and 2) each have an average particle size (
A packet roller (7) which is a two-component magnetic developer consisting of a mixture of an insulating toner with a weight average particle diameter of 13.1111 and 19 prr+ and a pure resistive magnetic carrier and is driven to rotate in the direction of arrow (e). Developing sleeve (2)
). A mesh screen (15) having the same function as the mesh screen (5) shown in FIG. 1 is provided above the developing sleeve (2). In addition, the developing sleeve (2
) For the peripheral surface located below the scraper (8)
The tip of the developing sleeve (2) is pressed against the developer (Dl), which passes through the developing area and is transported in the direction of the arrow (C1) along the circumferential surface of the developing sleeve (2), and is scraped off from around the developing sleeve (2). It looks like this.

Here, the mesh size of the mesh screen (15) is such that the average particle diameter of the magnetic carrier in the developer (Dl) is 1.
(l ppr+, and the average particle size of the insulating toner is 131
Since xn is approximately equal to the average particle diameter of the magnetic toner in the developer (Dl), it is set to be the same as the mesh size of the mesh screen (5). 1. Above the mesh screen (15), there is a developer collection sleeve (12) and a magnetic roller (13L foreign matter collection container) as a structure for collecting the developer (Dl) whose conveyance has been blocked. (16), a scraper (18), and a mesh screen (25).

The developer collecting sleeve (12) is made of a non-magnetic conductive material, specifically, non-magnetic stainless steel, and is formed into a cylindrical shape, and has an outer diameter of 16J111. In the developing device (MD), this developer collection sleeve (12
) is fixed, but may be 17 so that it can be rotated as required. Note that only when the developer collection sleeve (12) is rotationally driven in the direction of the arrow (f), the developer (
In order to electrostatically attract Dl) to the developer collection sleeve (12), a constant bias voltage may be applied to the developer collection sleeve (12) at 17. The bias voltage in this case is suitably of a polarity opposite to that of the electrostatic latent image and approximately the same potential. Specifically, since the maximum potential of the electrostatic latent image formed on the surface of the photoreceptor drum (1) is 600 V (negative polarity), the bias voltage has a potential of about 600 V (positive polarity). Something is appropriate.

The magnetic roller (13) also has a developer collection sleeve (
12) so as to be rotatable.

This magnetic roller (13) has 8. The N pole is sequentially magnetized, and the magnetic force is applied to the developer collection sleeve (
12) is set so that a magnetic field of 8000auss is formed on the circumferential surface of the magnet. On the other hand, the developing sleeve (
2), so that the magnetic action of the magnetic roller (3) in the magnetic roller (13) can extend to this magnetic roller (13), the distance between their axes is 30 mm, and the number of magnetic poles of the magnetic roller (3) is The number of magnetic poles of the magnetic roller (13) of the pair E7 lever is 4, whereas it has 8 poles. Therefore, this magnetic roller (13)
is driven to rotate in the opposite arrow direction (f1 direction) due to the magnetic action as the magnetic roller (3) is rotated.The number of rotations at this time is twice that of the magnetic roller (3), and is 2600.
rpm. This magnetic roller (13) carries the developer (which is prevented from being conveyed by the mesh screen (15)).
1) 2) is magnetically attracted to the developing sleeve (12), and as the developer rotates, the developer (1) 2)
is conveyed along the circumferential surface of the developing sleeve (12) in the direction of the arrow (f+ force). In the developing device (MD), this magnetic roller (13)
Although it is designed to be driven to rotate by the magnetic action of the magnet, it may also be rotationally driven via a separate drive source. Note that when the developer recovery sleeve (12) is rotationally driven in the direction of the arrow (f1), it may be fixed.Furthermore, a constant bias voltage is applied to the developer recovery sleeve (12). It may be omitted in some cases.

On the other hand, the mesh screen (25) collects the developer (D2) conveyed in the direction of the arrow along the surface of the developer collection sleeve (12), that is, the developer (D2) mainly consisting of foreign matter [F] (7). 2) in the developer collection sleeve (12) is scraped off from the circumferential surface of the developer collection sleeve (12) and guided into the foreign matter collection container (16). Then, the developer (IJ2) is transferred to the foreign matter collection container (1).
6) During the process of guiding the developer (D2) into the interior, the mesh once again separates the foreign matter (feces) in the developer (D2) from the insulating toner and magnetic carrier that can be used for development (2).
It is designed to guide only the town into the foreign matter collection container (16). The mesh size of this mesh screen (25) is slightly smaller than the mesh size of the mesh screen (5). Note that the mesh screen (15) is used to screen out foreign substances (F') from the developer (D2).
This mesh screen (25) may be replaced with a guide plate such as a skewer.

Further, the scraper (18) allows the developer (JJ2) that passes through the mesh of the mesh cleaner (25) and falls toward the door to be adsorbed again to the circumferential surface of the developer recovery sleeve (12). This prevents the paper from being transported in the direction of arrow (f).

In such a configuration, first, the mesh screen (15) removes foreign matter CF+ from the developer (D2).
A selection is made. The developer (D2) consisting mainly of foreign matter is adsorbed onto the circumferential surface of the developer collection sleeve (12) and is conveyed in the direction of the arrow (f1).Then, the mesh screen (25) The surrounding surface of the agent collection sleeve (12) is scraped off, and the foreign matter η is re-sorted and guided neatly into the foreign matter collection container (16). The agglomerated developer (D2
) will also be crushed and torn off. For this reason, the first
As in the case of the developing device (MD) shown in the figure, C etc.
Foreign matter (D
is removed and its fluidity is improved, so that good development can be performed even in the above configuration.

Effects of the Invention In the magnetic brush developing device according to the present invention, since foreign matter is sorted out and removed from the developer by the mesh screen, the development itself of the electrostatic latent image may be interrupted due to foreign matter entering the developer. There are no negative effects. In addition, when the developer is conveyed through the mesh screen, it is loosened by the alternating magnetic field created by the rotation of the magnetic roller, and its fluidity is improved. It does not seem to cause drastic unevenness. It is to be noted that this method is extremely effective since the removal of foreign matter and improvement of fluidity as described in hjj are performed on the developer just before it is transported to the development area.

In particular, the effects of the present invention as described above can be obtained when a developer for pressure fixing is used, or when copying is performed by removing and collecting the developer remaining on the surface of the photoreceptor after image transfer and sending it back into the developing device. This is particularly noticeable when installed in an aircraft.

[Brief explanation of drawings]

FIG. 1 is a drawing showing one embodiment of a magnetic brush developing device according to the present invention, and FIG. 2 is a drawing showing another embodiment. MD...Magnetic brush developing device Dl...One-component magnetic developer 1) 2...Two-component magnetic developer F...
- Foreign matter 2 - Developing sleeve 3... Magnetic roller 5.1
5...Mesh screen 6,16...Foreign matter collection container outlet 1 Customer Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. A developing sleeve having a rotationally driven magnetic roller therein, a mesh screen having one end pressed against the surface of the developing sleeve on the front side in the developer conveying direction with respect to the developing area, - A magnetic double-layer developing device characterized by comprising means for collecting developer whose conveyance is blocked from a nosh screen. 2. The magnetic brush developing device according to claim 1, wherein the mesh screen is installed along a direction that follows the developer conveyance direction. (a) The magnetic brush developing device according to claim 1, wherein the mesh screen is made of a non-magnetic material.