JPS587669A - Magnetic brush developing device - Google Patents

Abstract

PURPOSE:To remove the bad influence to a development of an electrostatic latent image owing to a flocculated material generating in a developer, by providing a magnetic member for disturbing the developer opposite to a developing sleeve. CONSTITUTION:A developing sleeve 3 having a magnetic roller 4 which is provided rotatablty at the inside, is disposed opposite to a photosensitive drum 1. The sleeve 3 and the roller 4 are rotated in the same direction and receive a magnetic developer supplied from a bucket roller 6 and a developer layer 5 is formed on the sleeve 3 and is carried to a developing area. A developer disturbing plate 10 consisting of a magnetic material is provided opposite to the sleeve 3 on the way of carrying path of the developer. The developer layer 5 is disturbed magnetically by this disturbing plate 10 and a flocculated material contained in the developer is pulverized. By such a way, the bad influence to a development of an electrostatic latent image owing to the flocculated material is removed.

Description

TECHNICAL FIELD The present invention relates to a magnetic brush developing device for developing an electrostatic latent image carried on the surface of an electrostatic latent image carrier using a magnetic developer.

BACKGROUND ART At present, as the above-mentioned magnetic brush developing device, one having a developing sleeve having a magnetic roller disposed inside and a single supply stage for supplying magnetic developer to the circumferential surface of the developing sleeve is widely known. . In addition, the magnetic developer used in the magnetic brush developing device is one consisting only of magnetic toner.
2. Description of the Related Art Component magnetic developers or two-component magnetic developers consisting of a mixture of a magnetic carrier and an insulating toner are widely known.

On the other hand, in recent years, as a form of the two-component magnetic developer,
The present inventors have developed a magnetic carrier which is made by dispersing magnetic fine powder in an insulating resin and has an average particle diameter of 5 to 40 μm and has a resistance value of 1012Ω or less, and an average particle diameter smaller than the average particle diameter of the magnetic carrier. A new magnetic developer consisting of a mixture with an insulating toner of particle size has been proposed.

By the way, when this magnetic developer is used in the above-mentioned magnetic brush developing device, the electrostatic latent image can be developed extremely well, but on the other hand, due to the physical properties of the magnetic developer itself, The inventors have confirmed that such inconveniences can sometimes occur.

That is, the novel magnetic developer has a small particle size of the magnetic carrier in the developer, and also has a small specific gravity because the magnetic carrier has a structure in which fine magnetic powder is dispersed in an insulating resin ( Specifically, due to its specific gravity (about 2 to 2.5), it is slightly inferior in terms of fluidity compared to conventionally known two-component magnetic developers, and this causes electrostatic This sometimes has an adverse effect on the development of the latent image. Specifically, when this magnetic developer is loaded into the magnetic brush developing device and the electrostatic latent image is continuously developed, compressed and agglomerated toner may be included in the supplied developer, or, In the case where some of the magnetic developer is compressed and aggregated in the magnetic brush developing device, these aggregates are supplied to the circumferential surface of the developing sleeve, and historically, development occurs along the circumferential surface of the developing sleeve. As a result, these aggregates adversely affect the development of the electrostatic latent image. For example,
These aggregates do not have sufficient charge to develop the electrostatic latent image, and therefore adhere to the background of the electrostatic latent image.
Generates blemishes in the developed image. In addition, it may also adhere to the electrostatic latent image itself, and in this case, it causes density unevenness in the developed image, or when the developed image is transferred, it causes white spots in the transferred image.

In order to improve this inconvenience, while the magnetic developer is being conveyed along the curved surface of the developing sleeve, the magnetic developer itself is magnetically rolled to crush the aggregates. In order to achieve this, the present inventors have tried various methods such as rotationally driving the magnetic roller of the magnetic brush developing device. Not only is there a limit to
It is virtually impossible to sufficiently crush the agglomerates using only such a method.

OBJECTS OF THE INVENTION An object of the present invention is to provide a magnetic brush developing device that does not have the above-mentioned adverse effects on the development of electrostatic latent images even when the novel magnetic developer is used. . More specifically, if the supplied developer contains toner that has been compressed and agglomerated, or if some of the magnetic developer has been compressed and agglomerated in the magnetic brush developing device, these problems may occur. It is an object of the present invention to provide a magnetic brush developing device capable of eliminating the adverse influence of aggregates on the development of electrostatic latent images.

SUMMARY OF THE INVENTION The gist of the present invention is that a magnetic brush developing device according to the present invention includes a driving means for rotationally driving a magnetic roller in a fixed direction during development of an electrostatic latent image, and a developing device formed on the circumferential surface of a developing sleeve. A magnetic member for agitating developer is installed facing the circumferential surface of the developing sleeve with a gap equal to or greater than the thickness of the developer layer. When the magnetic developer is conveyed along the circumferential surface of the developing sleeve, it is not only magnetically rolled but also magnetically disturbed between the developing sleeve and the magnetic member.

Therefore, the U fruits are sufficiently crushed by being subjected to a large physical force due to the transfer and agitation of the magnetic developer.

Embodiment FIG. 1 is a diagram showing a main part of an embodiment of a magnetic brush developing device according to the present invention.

In FIG. 1, the electrophotographic photosensitive drum (1) has a circumferential speed of 1]
01111/'= in the direction of arrow (a), and as it rotates, an electrostatic latent image of negative polarity is formed on its surface by an image forming device (not shown). , and the carried electrostatic latent image is developed by a magnetic brush developing device (DE) according to the present invention. Incidentally,
The highest potential of the electrostatic latent image (potential of the dark part) is -55,
OV, the lowest potential (background potential) is -220V.

The magnetic brush developing device (DE) has an opening [1 (2) for development.
a) for developing an electrostatic latent image carried on the surface of the photoreceptor drum (1) using a trowel-based developer (5) contained in a developer tank (2) having a The magnetic developer (5) is made by dispersing magnetic fine powder in an insulating resin, and includes a small-diameter magnetic carrier with an average particle diameter of 20 μm and a resistance value on the 1014Ω side, and a small-diameter magnetic carrier with a resistance value on the 1014Ω side. Average grain size exhibiting positive wall friction charging characteristics.

It consists of a mixture with an insulating nonmagnetic toner having a diameter of 10 to 15 μm. Note that the mixing ratio of the toner to the entire developer is 3 to 15 wt%. In addition, the magnetic brush developing device (
DE) is for developing the electrostatic latent image with emphasis, so the above-mentioned magnetic developer (5
), but if it is intended for reversal development fψ, it is necessary to contain a developer that exhibits the opposite triboelectric properties compared to the magnetic developer (5) described above. be.

The developing sleeve (3) is provided above the developing tank (2) so as to face the surface of the photoreceptor drum (1) in close proximity. This developing sleeve (3) is made of a material that is both conductive and non-magnetic, specifically stainless steel, and has an outer diameter of 31 m = +, and when developing an electrostatic latent image, it is The developer tank (2) is rotated at a speed of 3 Q r, p, m.
) A packet roller (6) is provided so as to be partially submerged in the magnetic developer (5) contained in the magnetic developer (5). This packet roller (6) has a plurality of buckets I-(6a), (6b), (6C) made of stainless steel on its circumferential surface.
..., and is rotated in the direction of the arrow (e) to cause the magnetic developer (5) housed in the developer tank (2) to
) to the circumferential surface of the developing sleeve (3), and mixes and stirs the magnetic developer (5) housed in the developer tank (2) to remove the insulating toner in the magnetic developer (5). It has the function of triboelectrically charging to positive polarity (the polarity opposite to that of the electrostatic latent image).

A magnetic roller (4) is rotatably installed within the developing sleeve (3). This magnetic roller (4) is rotationally driven at a high speed of 130 Or, plm in the direction of arrow fc), that is, in the same direction as the rotational direction of the developing sleeve (3), by a drive source (not shown) when developing the electrostatic latent image. By doing so, the developing sleeve (
3) is conveyed along the circumferential surface of the developing sleeve (3) in the direction of arrow (d), that is, in the opposite direction to the rotational driving direction of the developing sleeve (3). do. Note that [9] between the developing sleeve (3) and the magnetic roller (4)
Since the rotating directions are the same and in addition, the conveying direction of the magnetic developer (5) is opposite to the rotational driving direction of the magnetic developer (5), the magnetic developer (5) rolls at high speed during the conveyance. As a result, the magnetic developer (5) is subjected to relatively large physical forces. The fact that the magnetic developer (5) is subjected to a relatively large physical force when the magnetic developer (5) is conveyed along the circumferential surface of the developing sleeve (3) in this way is due to the fact that the magnetic developer (5) ) is important in crushing the aggregates in the mixture.

A developing bias power source (not shown) is electrically connected to the developing sleeve (3). This developing bias power supply is connected to the developing sleeve (3) by the photoreceptor drano,
A developing bias voltage of the same polarity as the electrostatic latent image carried on the surface of il+ is applied to Fi to prevent development fog from occurring when developing the electrostatic latent image! It is something to watch. Incidentally, the developing bias voltage value is -300V.
degree, that is, 50 to 100 from the lowest potential of the electrostatic latent image.
v is set to a high value.

In the area where the circumferential surface of the developing sleeve (3) and the surface of the photoreceptor drum (1) are close, that is, the circumferential surface of the developing sleeve (3) located on the side opposite to the direction of arrow (d) with respect to the developing area. , developer agitation plates (10) are provided facing each other. In detail, the circumferential surface of the developing sleeve (3) and the bucket roller (
The developer agitation plate (10) is installed in a region close to the peripheral surface of the developer supply region 6), that is, in the middle of the developer transport path from the developer supply region to the development region. This disturbance plate (10) is made of a magnetic material, specifically a 16 mm thick iron plate, and is bent and formed into a roughly L-shape. The tip end (10a) is connected to the developing sleeve (3) while maintaining a gap equal to or greater than the thickness of the developer layer formed on the circumferential surface of the developing sleeve (3).
) is opposed to the circumferential surface of the In this example,
The thickness of the developer layer is 1.5 to 2.0. , the rotational drive speed of the developing sleeve (3), magnetic roller (4), etc. is set so that the gap is specifically 3-6I1.
．． , preferably maintained at 4 to 5. In addition,[)
;1 gap is between the circumferential surface of the developing sleeve (3) and the disturbance plate (1);
It is desirable that the value be set to the above-mentioned value so that a sufficiently strong magnetic field for developer agitation is formed between the tip end portion (10a) and the tip portion (10a). However, the above value is based on the magnetic force of the magnetic roller (4) on the circumferential surface of the developing sleeve (3) or 1200G.
It shows the optimal value when
The value of the gap should be appropriately set depending on the magnetic force value.

It is desirable that the magnetic field for agitating the developer is formed only between the curved surface of the developing sleeve (3) and the tip (10a) of the agitation plate (10). The other parts of the disturbance plate except for the part (10a) are sufficiently separated from the circumferential surface of the developing sleeve (3). That is,
The other portion is located at a position substantially beyond the influence of the magnetic force of the magnetic roller (4). Incidentally, instead of positioning the other parts as described above, the same effect can be obtained even if all the other parts are made of non-magnetic material. Furthermore, in this embodiment, the developing sleeve (3)
All members etc. close to the peripheral surface of the magnetic head are made of non-magnetic materials except for the disturbance plate (10).

Furthermore, the direction of the magnetic lines of force in the magnetic field for agitating the developer changes rapidly and in short cycles as the magnetic roller (4) is rotated. Therefore, in this embodiment, when the magnetic developer (5) supplied to the circumferential surface of the developing sleeve (3) is conveyed to the developing area along the circumferential surface of the developing sleeve (3), the developing sleeve (3) and a disturbance plate (lO
), and as a result, the magnetic developer (
5) is subjected to a relatively large physical force. Note that the physical force applied by this disturbance of the magnetic developer (5) is the same as the physical force applied by the magnetic developer (5) rolling as the magnetic roller (4) is rotated, as described above. It acts synergistically with the force, and therefore, for example, aggregates, specifically compressed and agglomerated toner, and particles in the magnetic developer supplied to the circumferential surface of the developing sleeve (3). )
Even if it contains a mechanically agglomerated developer,
These aggregates are sufficiently pulverized before the magnetic developer (5) is conveyed to the development area, and do not have any adverse effect on the development of the electrostatic latent image.

Further, for the developing sleeve (3), a scraper (7) made of a flexible non-magnetic material, specifically a 0-1 wtx thick polyester film, and a phosphor bronze plate is provided.
, and the cleaner (8) as shown in the figure, the developing sleeve (3
) are provided in pressure contact with the circumferential surface of the developing sleeve (3) in a reverse direction that follows the rotational direction of the developing sleeve (3) and in a forward direction that opposes it. The scraper (7) conveys the magnetic developer (5) used for developing the electrostatic latent image, that is, the magnetic developer (5), which passes through the development area and along the circumferential surface of the development sleeve (3) in the direction of arrow (d). The magnetic developer (5) is scraped off from the circumferential surface of the developing sleeve (3) and allowed to fall downward into the developing tank (2). The cleaner (8) also has a developing sleeve (
The magnetic developer (5) adhering to the circumferential surface of the developing sleeve (3) and being transported in the direction of the opposite arrow (d+ force) is scraped off from the circumferential surface of the developing sleeve (3), and is scraped off by the bucket roller (6). m,
f￥ Saturated developer (5) supplied to the circumferential surface of the sleeve (3)
), it serves to scrape off the excess from the circumferential surface of the developing sleeve (3) and to clean the circumferential surface of the developing sleeve (3). Note that the scraper (
7) and the cleaner (8) are integrally supported by a support member (9) made of a non-magnetic material, specifically aluminum.

Next, another embodiment of the magnetic brush developing device according to the present invention will be described with reference to FIG. In addition, in Figure 2, the first
Common parts with the magnetic brush developing device shown in the figure include the first
The same reference numerals as those in the figures are given, and detailed explanation thereof will be omitted in the following explanation.

In the magnetic brush developing device (DF, ) shown in FIG. 2, the rotational speed of the developing sleeve (3) and the magnetic roller (
4) The rotation speed is 1500r, p, m, 33,5r,
p and m, and the magnetic force of the magnetic roller (4) at the surface of the developing sleeve (3) is set to 100OG.

In addition, in this embodiment, as in the previous embodiment, I+, ! of the developer layer formed on the circumferential surface of the developing sleeve (3). The disturbance is set to be 1.5 to 20 ηm, and the disturbance plate (20
) also maintains a gap of 3 to 6 mm, preferably 4 to 5 mm, with respect to the circumferential surface of the developing sleeve (3).

In this embodiment, the magnetic developer (5) supplied to the circumferential surface of the developing sleeve (3) is conveyed along the circumferential surface of the developing sleeve (3) to the developing region, during which: A casing (11) having an arcuate surface that can be rubbed by the magnetic developer (5) is installed, and therefore the agitation plate (20) is fixed to a part of this casing (11). It is installed in In addition, the disturbance plate (20)
The casing (11) is made of phenolic resin, which is a non-magnetic material. For this reason,
In this embodiment as well, the magnetic developer χj agent (5) supplied to the circumferential surface of the developing sleeve (3) is magnetically transferred and disturbed on the way to the developing area, as in the previous embodiment. It is supposed to happen.

On the other hand, a sole plate (12) made of polyurethane or polyethylene is fixed to the photosensitive drum (1) side of the casing (11). Prevents developer from scattering & (
13) or furthermore, the opening (2a) for development in the developer tank (2). A developer leak prevention plate (14) kept at the same potential as the developing sleeve (3) is installed at gH.

The anti-scattering plate (13) and the anti-leak plate (14) are made of an aluminum material that is both electrically conductive and non-magnetic.

Effects of the Invention In the magnetic brush developing device according to the present invention, as described above, since the magnetic developer is magnetically transferred and disturbed, aggregates are not formed in the magnetic developer powder supplied to the circumferential surface of the developing sleeve. If it does, the agglomerate will be subjected to a large physical force and will be sufficiently pulverized. Therefore, even if the supplied developer contains toner that has been compressed and agglomerated, or if some of the magnetic developer has been compressed and agglomerated in the magnetic brush developing device, these agglomerates may , the adverse effect on the development of electrostatic latent images is eliminated.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing a main part of one embodiment of a magnetic brush developing device according to the present invention, and FIG. 2 is a drawing showing a main part of another embodiment. DE Magnetic brush developing device 3...Developing sleeve 4...
・Magnetic roller 5...Magnetic developer 6・Packet roller 10.20...Developer agitation Sakae Applicant Minolta Camera Co., Ltd. Ajikumo 4 Aji

Claims (1)

[Scope of Claims] 1. A developing sleeve having a magnetic roller rotatably installed therein, a driving means for rotationally driving the magnetic roller in a fixed direction during development of an electrostatic latent image, and a magnetic developer for moving the magnetic developer into the developing sleeve. A magnetic member for agitating the developer is provided opposite to the circumferential surface of the developing sleeve with a gap equal to or greater than the thickness of the developer layer formed on the circumferential surface of the developing sleeve. A magnetic brush developing device characterized in that magnetic developer supplied to the circumferential surface of the developing sleeve is magnetically disturbed between the developing sleeve and a magnetic member. 2. A patent claim characterized in that the magnetic member is installed in the middle of a conveyance path along which the magnetic developer supplied to the circumferential surface of the developing sleeve is conveyed to the developing area along the circumferential surface of the developing sleeve. The magnetic brush developing device according to item 1. 3. The magnetic brush developing device according to claim 1 or 2, wherein the developing sleeve is rotationally driven during development of the electrostatic latent image. 4. The magnetic brush developing device according to claim 3, wherein the rotational driving direction of the developing sleeve is the same as the rotational driving direction of the magnetic roller. 5. The magnetic brush developing device according to claim 4, wherein the direction of rotation of the developing sleeve and the magnetic roller is opposite to the direction in which the magnetic developer is conveyed along the circumferential surface of the developing sleeve. 6. Any one of claims 1 to 5, wherein the supply means supplies a magnetic developer made of a mixture of a magnetic carrier and an insulating toner to the peripheral surface of the developing sleeve. The magnetic brush development device described. 7. The supplying means is formed by dispersing magnetic fine powder in an insulating resin, and includes a magnetic carrier having an average particle diameter of 5 to 40 μm and having a resistance of 10 12 Ω· or more, and an average particle smaller than the average particle diameter of the magnetic carrier. A magnetic brush developing device according to any one of claims 1 to 5, characterized in that a magnetic developer made of a mixture with an insulating toner having a diameter of 100 mm is supplied to the circumferential surface of the developing sleeve.