JPS6347873Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a magnetic brush developing device, more specifically, a magnetic brush developing device equipped with a mechanism for separating foreign substances that may cause various harmful effects from the magnetic developer in the device. It is related to the device.

Prior Art The magnetic developer used in a magnetic brush developing device includes a one-component developer consisting only of magnetic toner, a two-component developer consisting of a mixture of an insulating toner and a magnetic carrier, and furthermore a magnetic developer consisting of a mixture of an insulating toner and a magnetic carrier. 2. Description of the Related Art Composite developers made of a mixture of several types of toners, etc., are known. These developers are
It is used to develop and visualize the electrostatic latent image carried on the surface of the electrostatic latent image carrier while being circulated through the magnetic brush developing device. As this process is repeated over a long period of time, foreign substances become cumulatively contained therein.

A typical example of the above-mentioned foreign matter is a lump of developer that gradually forms as the developer is repeatedly conveyed in a circulation (physical force or heat applied to the developer as it is conveyed in a circulation). They are formed by the toner particles in the developer sticking to each other (usually having a diameter close to 10 times the particle size of the toner in the developer), or they are formed by the toner particles gradually sticking into the developer. The paper fibers of the copy paper that are mixed into the
It is nearly 10 times longer. ) etc. are known. The contamination of paper fibers from copy paper is caused by the magnetic brush in a transfer-type electrophotographic copying machine that collects the developer remaining on the surface of the photoreceptor after image transfer and reuses the collected developer for development. This is particularly noticeable with respect to the developer in the developing device.

In transfer-type electrophotographic copying machines, etc., the presence of a large amount of foreign matter in the developer causes deterioration in the conveyance of the developer itself, occurrence of uneven development, and transfer images. This will cause harmful effects such as the appearance of white spots inside. Therefore, in order to prevent these harmful effects from occurring,
Preventing the accumulation of such foreign matter in the developer is a very important problem with magnetic brush development devices.

Purpose of the invention An object of the present invention is to provide a magnetic brush developing device having a function of successively separating the above-mentioned foreign substances from the developer. Another object of the present invention is to provide a magnetic brush developing device equipped with a foreign matter separation mechanism having a simple structure.

Summary of the invention The summary of the invention is that the magnetic brush developing device according to the invention includes a magnetic brush developing device provided with a magnetic brush at a position facing a guide surface of a developer scraping member within an area where the magnetic action of a magnetic roller can reach. The apparatus is equipped with a foreign matter separating member made of material, and is capable of separating such foreign matter from the developer guided along the guide surface by the action of an alternating magnetic field formed between a magnetic roller and the foreign matter separating member. be. Note that when a two-component developer consisting of a mixture of an insulating toner and a magnetic carrier is used as a developer, when the foreign matter is separated, toner having an electric charge unsuitable for development may also be separated. become.

Embodiment FIG. 1 is a diagram showing an embodiment of a magnetic brush developing device according to the present invention. In FIG. 1, the magnetic brush developing device is shown incorporated into a transfer type electrophotographic copying machine.

In FIG. 1, an electrophotographic photosensitive drum 1 is rotatably driven in the direction of arrow a while carrying on its surface an electrostatic latent image formed through an image forming process (not shown). And with that rotation,
The electrostatic latent image is developed by a magnetic brush developing device 2 and becomes visible. In this embodiment, the polarity of the electrostatic latent image is set to (-) polarity.

The magnetic brush developing device 2 includes a developing sleeve 3 installed at a position facing the surface of the photoreceptor drum 1;
It has a magnetic roller 4 rotatably provided inside the developing sleeve 3. The developing sleeve 3 is made of a non-magnetic material such as aluminum or stainless steel.
It has a diameter of 31mm. In this embodiment, the developing sleeve 3 is rotatably provided, and is moved in the direction of arrow b via a drive source (not shown).
It is designed to be rotated at a rotation speed of 30 rpm. On the other hand, the magnetic roller 4 is a roll-shaped roller having S and N poles sequentially magnetized around it, and is connected to the arrow b by the arrow b through a drive source (not shown) like the developing sleeve 3.
The developing sleeve 3 is rotated in the same direction as the rotating direction of the developing sleeve 3 at a rotation speed of 1300 rpm. For this reason, the magnetic developer 6 supplied onto the circumferential surface of the developing sleeve 3 by the bucket troller 5
is in the direction of arrow b as the developing sleeve 3 rotates.
On the other hand, as the magnetic roller 4 rotates, the developing sleeve 3
As a result, based on the above-mentioned setting of the rotational speed of both, the conveyance force is applied in the direction of arrow C along the circumferential surface of the developing sleeve 3. transported to.

The bucket troller 5 is constructed by installing a plurality of buckets 5a between two rotating disks,
By being rotationally driven in the direction of arrow d, a developer 6 contained in a developer tank 13 (to be described later) is drawn up by a bucket 5a and supplied onto the circumferential surface of the developing sleeve 3. Further, in this embodiment, the developer 6 is made by stirring and mixing 90 wt% of small-diameter magnetic carrier and 10 wt% of insulating toner, and the insulating toner is charged by friction with the carrier (+ ) polarity, that is, charged to a polarity opposite to that of the electrostatic latent image. Specifically, the carrier is made by dispersing magnetic fine powder in a resin, and has an average particle size of 20 to 25 μm and a resistance value of 10 ¹⁴ Ω·cm. In addition, insulating toner is non-magnetic and has an average particle size of 10~
It is 15 μm.

On the other hand, above the developing sleeve 3, an upper casing 7 made of resin is provided. The arcuate inner circumferential surface of this casing 7 is connected to the developing sleeve 3.
The developing sleeve 3 is kept at a constant distance from the circumferential surface of the developing sleeve 3, and is lightly rubbed by the developer 6 conveyed along the circumferential surface of the developing sleeve 3. and,
A seal 8 made of polyurethane film is attached to the end surface of the casing 7 on the photosensitive drum 1 side. One end of the seal 8 is brought into light pressure contact with the surface of the photosensitive drum 1, and its surface on the developing sleeve 3 side is located approximately on an extension of the circumferential surface of the casing 7.

Further, below the developing sleeve 3, a scraper 9 and a cleaner are installed so that their respective tips come into contact with the rotating direction of the developing sleeve 3, that is, in the opposite direction following the arrow b direction, and in the opposite forward direction. 10 are provided. The scraper 9 passes through the developing area, specifically, the area where the photosensitive drum 1 and the developing sleeve 3 are close to each other, and the developer is conveyed in the direction of arrow c along the circumferential surface of the developing sleeve 3. 6 from the circumferential surface of the developing sleeve 3 and guide it away from the circumferential surface of the developing sleeve 3 along the guide surface 9a in that direction. Made of thick phosphor bronze sheet. The cleaner 10 removes the excess amount of the developer 6 supplied onto the circumferential surface of the developing sleeve 3 by the bucket troller 5. The developer 6 that is moving in the direction of arrow b as the sleeve 3 rotates is scraped off from the circumferential surface of the developing sleeve 3, and is removed by 100 μm.
Made of thick phosphor bronze sheet. Note that the rear ends of the scraper 9 and the cleaner 10 are attached to a support 1 made of a non-magnetic material, specifically, aluminum.
1, and its tip is pressed against the circumferential surface of the developing sleeve 3 by its own bending.

Furthermore, a developer scattering prevention plate 12 is provided in the vicinity of the tip of the scraper 9 and at a position opposite to the edge of the tip so as to maintain a certain distance from the scraper 9. This developer scattering prevention plate 1
2 physically and electrically suppresses the scattering of the developer 6 that may occur when the developer 6 is scraped off the peripheral surface of the developing sleeve 3, and is made of a conductive material and is electrically conductive. is grounded.

Furthermore, the guide surface 9 of the scraper 9 is within the area where the magnetic action of the magnetic roller 4 can reach.
A foreign matter separating plate 14 is fixed to the developing tank 13 with one edge facing the magnetic roller 4 at a position facing a. This foreign matter separation plate 14 is
It is made of magnetic material, specifically iron, and has a thickness of 1 mm. Note that the distance l ₁ between the leading edge of the foreign matter separating plate 14 and the guide surface 9a is set to about 4 mm, and the foreign matter separating plate 14 is designed to prevent direct contact. On the other hand, foreign matter separation plate 1
The distance l ₂ between the tip edge of 4 and the developing sleeve 3 is 12
As a result, the foreign matter separating plate 14 is positioned sufficiently away from the circumferential surface of the developing sleeve 3. Due to this positioning, in this embodiment, despite the presence of the foreign matter separation plate 14, the rotational torque of the magnetic roller 4 does not substantially increase, and even when the magnetic roller 4 rotates at high speed. Regardless, a large vibration force is not applied to the foreign matter separation plate 14.

Here, since the foreign matter separating plate 14 is made of a magnetic material and is provided in an area where the magnetic action of the magnetic roller 4 can reach, the foreign matter separating plate 14 itself is magnetized by the magnetic action of the magnetic roller 4. A magnetic field is formed between the magnetic roller 4 and the foreign matter separating plate 14. This magnetic field is applied by the scraper 9 to the developing sleeve 3.
Since it is provided so as to cross between the guide surface 9a of the scraper 9 and the foreign matter separation plate 14, it is formed so as to intersect with the guide path for the developer 6 along the guide surface 9a of the scraper 9. When the magnetic roller 4 is in the position shown in FIG. 2, a portion of the developer 6 being guided along the guide surface 9a of the scraper 9 is moved to As shown in FIG. 2, the particles are magnetically attracted to the tip edge of the foreign matter separating plate 14 in a brush-like manner. The developer 6 thus magnetically attracted in a brush-like manner is subjected to the action of an alternating magnetic field as the magnetic roller 4 rotates in the direction of arrow b, and is greatly disturbed as shown by arrow A in FIG. Specifically, it returns to the guide surface 9a and is further guided to the lower left in FIG. 2 along the guide surface 9a. The developer 6 that is magnetically attracted to the tip edge of the foreign matter separation plate 14 in a brush-like manner is constantly replaced by new developer 6 that is guided along the guide surface 9a. Due to such disturbance and replacement, if foreign matter 16 is included in the developer 6, the foreign matter 16 will be scattered to the right in FIG. The particles are collected into a foreign material collection container 15 provided near the foreign material separation plate 14.
The foreign matter collection container 15 is made of a non-magnetic material, specifically aluminum.
A constant bias voltage is applied to the foreign matter collection container 15 in order to electrically prevent the powdery developer 6 from leaking from between the end of the drum 3 and the surface of the photoreceptor drum 1. There is.

In this embodiment, for convenience, the foreign matter separation plate 14 itself constitutes a part of the foreign matter collection container 15, but while the foreign matter collection container 15 is formed separately from the foreign matter separation plate 14, It may be made detachable from the developer tank 13. This makes it convenient to dispose of the foreign matter 16 collected in the foreign matter collection container 15. Further, although the foreign matter separating plate 14 is entirely made of a magnetic material, only the vicinity of the tip edge may be made of magnetic material, and the other portion may be made of non-magnetic material.
Furthermore, as confirmed by the present inventor, the depth (l3) of the foreign matter collection container 15, in other words,
The distance (l3) from the tip edge of the foreign matter separation plate 14 to the bottom surface of the foreign matter collection container 15 was suitably about 3 mm. This is because, in this embodiment, when an experiment was conducted by changing the distance (l3), the collection efficiency of the foreign matter 16 into the foreign matter collection container 15 decreased when the distance was 2 mm or less, and when it was 5 mm or more, the collection efficiency of the foreign matter 16 into the foreign matter collection container 15 decreased. This is because a phenomenon in which the developer 6 was mixed in was confirmed. However, the optimum value of the distance (I3) varies greatly depending on the type of developer 6 used, etc., and the above value is only the optimum value in this embodiment.

Next, the movement of the developer 6 in this embodiment described above will be schematically explained.

First, when the magnetic brush developing device 2 is in operation, the developer 6 supplied onto the circumferential surface of the developing sleeve 3 by the bucket troller 5 is applied to the circumferential surface of the developing sleeve 3 based on the rotation of the magnetic roller 4. is conveyed in the direction of arrow c. When the photoreceptor drum 1 is transported through the development area, the surface of the photoreceptor drum 1 is rubbed, and if an electrostatic latent image is carried on the surface of the photoreceptor drum 1, the electrostatic latent image is developed. Visualize.
The developer 6 that has passed through the development area is further conveyed in the direction of arrow c, and is then scraped off from the circumferential surface of the development sleeve 3 by the scraper 9.
It is guided in a direction away from the circumferential surface of the developing sleeve 3 along the guide surface 9a.

In this way, the developer 6 guided along the guide surface 9a is magnetically attracted to the leading edge of the foreign matter separation plate 14 during the guide, and is further disturbed greatly as shown by arrow A in FIG. . Therefore, foreign matter 16 such as paper fibers of the copy paper or developer lumps, which do not themselves have magnetism, are scattered to the right in FIG. It will be gathered inside. Also,
In the case of the type of developer 6 used in this embodiment, toner having a polarity unsuitable for development, specifically, a (-) polarity that is the same as the polarity of the electrostatic latent image, or a (+) Toner and the like having a polar charge but with an insufficient amount of charge are collected in the foreign matter collection container 15 in the same way as the foreign matter 16 because they have lost their adhesion to the magnetic carrier. Then, the developer 6 consisting only of toner and carrier having a sufficient charge of polarity suitable for development can return onto the guide surface 9a.

Next, the developer 6 that has been subjected to the disturbance and after the foreign matter 16 has been separated is returned onto the guide surface 9a,
Further, it is guided along the guide surface 9a, and falls from the guide surface 9a under its own weight in an area where the magnetic action of the magnetic roller 4 cannot substantially reach, and reaches the inside of the developer tank 13. And Sarado Bucket Trawler 5
Therefore, it is expected to be supplied onto the circumferential surface of the developing sleeve 3.

The above is a general description of the movement of the developer 6 in this embodiment. The present inventor incorporated the magnetic brush developing device 2 of this embodiment into a transfer-type electrophotographic copying machine, and conducted a copying experiment of 60,000 sheets of A4 size using this copying machine. Even though the developer remaining on the surface of the printer was collected and reused for development, there were no problems such as deterioration in the conveyance of the developer itself, uneven development, or white spots in the transferred image. Nakatsuta. Furthermore, there were virtually no foreign substances contained in the developer. In addition, during the above experiment, about 2 g of foreign matter was separated and recovered per 10,000 copies.

Effect of the invention In the magnetic brush developing device according to the invention, the developer is guided along the guide surface of the developer scraping member by the action of an alternating magnetic field formed between the magnetic roller and the foreign matter separating member. Since the foreign matter is successively separated from the developer, the foreign matter does not become cumulatively contained in the developer. In addition, as for the mechanism for separating foreign matter, the magnetic action of the magnetic roller and the alternating magnetic field generated by the rotational drive of the magnetic roller are skillfully utilized, and essentially only a foreign matter separating member is attached. It is structurally simple.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of a magnetic brush developing device according to the present invention, and FIG. 2 is a diagram showing an enlarged main part thereof. 2...Magnetic brush developing device, 3...Developing sleeve, 4...Magnetic roller, 5...Bucket troller,
6...Magnetic developer, 9...Scraper, 9a...
Guide surface, 10... Cleaner, 14... Foreign matter separation plate, 15... Foreign matter collection container, 16... Foreign matter.

Claims (1)

[Claims for Utility Model Registration] 1. A developing sleeve made of a non-magnetic material, a magnetic roller rotatably provided inside the developing sleeve, and a developer supply means for supplying magnetic developer onto the circumferential surface of the developing sleeve. and a magnetic roller driving means for rotationally driving the magnetic roller to convey the supplied developer along the circumferential surface of the developing sleeve.
a developer scraping member made of a non-magnetic material that scrapes the transported developer from the circumferential surface of the developing sleeve and guides it in a direction away from the circumferential surface of the developing sleeve along a guide surface; and a developer scraping member made of a non-magnetic material; a foreign matter separating member made of a magnetic material and provided at a position facing the guide surface of the developer scraping member within the action area;
A magnetic brush developing device characterized in that foreign matter is separated from the developer guided along the guide surface by the action of an alternating magnetic field formed between the magnetic roller and the foreign matter separating member. 2 Utility model registration claim 1, characterized in that the developer scraping member is provided in a state that crosses between the developing sleeve and the foreign matter separating member.
The magnetic brush developing device described in Section 1. 3. The magnetic brush developing device according to claim 1 or 2, wherein the developing sleeve is rotatably provided and driven to rotate. 4. The magnetic brush developing device according to claim 3, wherein the direction of rotation of the developing sleeve and the direction of rotation of the magnetic roller are the same. 5. The magnetic brush developing device according to claim 4, further comprising a cleaning member for removing developer excessively supplied onto the circumferential surface of the developing sleeve from the circumferential surface of the developing sleeve. 6. The magnetic brush developing device according to any one of claims 1 to 5, wherein the foreign matter separating member is provided at a position sufficiently distant from the circumferential surface of the developing sleeve. . 7. The magnetic brush developing device according to any one of claims 1 to 6, which is characterized by comprising a foreign matter collection container provided in the vicinity of the foreign matter separating member.