JP2001265118A - Developing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate hysteresis of a thin toner layer remaining, after a developing process on a developing roller with the thin toner layer formed by a two- component magnetic brush, and to efficiently and surely return the removed toner into a developer storing part, using a simple constitution. SOLUTION: A cleaning roller 11 is arranged under the developing roller 6 between a part facing a photoreceptor drum 1 and a part facing a magnetic roller 7, then, the toner is recovered from the developing roller 6 by the cleaning roller 11, while coming into contact with the developing roller 6. A thin plate cleaning member 12 formed of rubber etc., is arranged as a cleaning means for removing the recovered toner from the cleaning roller 11, and the free end of the member 12 is brought into contact with the cleaning roller 11, to scrape the toner. The magnetic brush 9 of a magnet roller 7 is arranged, to come into contact with the toner scraped by the cleaning member 12, and the toner recovered by the magnetic brush 9 is carried to the developer storage part equipped with a stirring member 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for use in an electrophotographic image forming apparatus such as a printer, a facsimile, and a copying machine.

[0002]

2. Description of the Related Art In an electrophotographic method, a toner is applied to an electrostatic latent image on the surface of a photoreceptor to visualize the image by using a toner. It is roughly classified into a two-component developing method using a developer composed of a toner and a carrier.

[0003] In the one-component developing system, a visible image is generated by attaching a uniformly thinned toner around a developing roller to a latent image on the surface of a latent image carrier. The thin layer of toner around the developing roller is formed by applying toner to the developing roller by a supply roller or the like, and then regulating the thickness to a predetermined amount by a thinning blade. The one-component developing system is classified into a contact one-component developing system and a non-contact one-component developing system depending on whether or not the developing roller is brought into contact with the latent image carrier. In the contact one-component development system, since a development faithful to a latent image can be performed, a high-quality image can be obtained, which is also advantageous for higher resolution.
However, in the one-component developing method, since only the toner is continuously stirred in the developing device, the deterioration of the toner is apt to progress, and it is difficult to stabilize the image quality with time. Also, since the supply roller and the thinning blade are in sliding contact with the elastic developing roller, wear of the developing roller and toner sticking (filming) are caused.
Therefore, it is difficult to maintain the durability of the device itself for a long period of time.

In the two-component developing method, a latent image carrier is formed by forming a magnetic brush carrying a two-component developer composed of toner and carrier in a brush shape around a developing roller (magnet roller) having a magnet therein. The toner in the magnetic brush is adhered to the latent image on the surface to obtain a visible image. This two-component developing method is inferior to the contact one-component developing method in terms of image quality in terms of development that is faithful to a latent image, but has durability,
In terms of stability, it is superior to the one-component developing system.

In order to combine the advantages of the one-component developing system and the two-component developing system, a thin toner layer is formed on a developing roller by a two-component magnetic brush, and the latent image carrier is latently formed by the thin toner layer on the developing roller. A method of visualizing an image has been proposed. In a method in which a thin toner layer is formed on a developing roller by a two-component magnetic brush, stress on the developing roller and toner during the formation of the thin layer is smaller than that in the one-component method, and deterioration of the developing roller and toner is reduced. Since the stirring in the developing device is the same as in the two-component developing method, the same level of durability as in the two-component developing method can be obtained. Further, since the process of developing the latent image on the photoconductor with toner is a one-component system, high image quality of the one-component development system can be obtained.

However, such a developing system also has the following problems. That is, after the developing roller develops the latent image on the photoreceptor, there is a portion on the developing roller surface where the toner is consumed and the toner is lost and a portion where the toner is not consumed and the thin toner layer remains as it is, Next, it is difficult to eliminate the difference between the consumed portion and the unconsumed portion only by passing through the portion facing the two-component magnetic brush, and a density difference will occur at the time of the next image formation as it is. Therefore, there is a technique of providing a cleaning roller for removing toner from the developing roller and eliminating a difference between a toner consuming portion and a non-consumed portion in a direction from the photosensitive member facing portion to the magnetic brush facing portion in the developing roller rotation direction. However, in this technique, it is necessary to sequentially remove the toner from the cleaning roller, and there is a problem in processing the collected toner.

In the developing device disclosed in Japanese Patent Publication No. 6-67546, the electric field formed between the developer carrier and the toner carrier is changed so that the toner intermittently moves from the toner carrier to the developer carrier. The collected toner is returned to the developer carrying member by providing an electric field switching means or the like for switching the toner. However, the configuration of the developing device and the configuration of the electric field switching unit itself become complicated, and the cost increases.

Accordingly, the present invention eliminates the history of a thin toner layer on a developing roller after a developing process in a developing device for developing an electrostatic latent image with a developing roller having a thin toner layer formed by a two-component magnetic brush. It is another object of the present invention to efficiently and reliably return the toner removed from the developing roller after the developing process to the two-component developer accommodating section with a simple configuration.

[0009]

In order to achieve the above object, a fixing device according to a first aspect of the present invention visualizes an electrostatic latent image formed on the surface of a photoreceptor by carrying toner around it. Developing roller, a developer carrier that forms a two-component developer magnetic brush around and supplies toner to the developing roller, and the developing roller faces the photosensitive member in the rotation direction of the developing roller. A cleaning roller that rotates in contact with the developing roller between a region where the developing roller and the developer carrier face each other from a region, and a cleaning member that contacts the cleaning roller and removes toner on the surface of the cleaning roller. The developer carrier, the cleaning roller, and the toner such that the toner scraped by the cleaning member contacts the magnetic brush of the developer carrier. And characterized by being arranged serial cleaning member.

According to a second aspect of the present invention, in order to achieve the above object, in the area where the developing roller and the developer carrier face each other, the moving direction of the surface of the developing roller and the surface of the developer carrier are The rotation direction of the developer carrying member is set so that the moving direction is opposite to the moving direction.

According to a third aspect of the present invention, in order to achieve the above object, a casing member opposed to the space between the cleaning member and the developer carrier after the developer carrier has passed near the cleaning member is provided. Is partially set to 2 mm or less.

According to a fourth aspect of the present invention, in order to achieve the above object, a developer accommodating section for accommodating a developer to be supplied to the developer carrying member, and agitating and transporting the developer in the developer accommodating section. And a stirring / transporting member for transferring the developer to / from the developer carrying member, wherein the developer separated from the developer carrying member is capable of temporarily staying at a portion toward the stirring / conveying member. It is characterized in that the agent reservoir is formed in the casing.

According to a fifth aspect of the present invention, in order to achieve the above object, a developing roller for carrying a toner around the developing roller to visualize an electrostatic latent image formed on the surface of the photoreceptor, and a developing roller around the developing roller. A developer carrying member that forms a component developer magnetic brush and supplies toner to the developing roller, wherein the moving direction of the surface of the developer carrying member at a portion facing the developer carrying member and the developing roller; In a developing device having a direction opposite to the direction of movement of the surface of the developing roller, the magnetic brush on the developer carrier is temporarily held by the developer carrying member after passing through a portion opposed to and closest to the developing roller. The image forming apparatus is characterized in that a separating member for separating the developer from the body and bringing the developer into contact with the developing roller is provided.

According to a sixth aspect of the present invention, in order to achieve the above object, the magnetic brush is provided on the downstream side in the rotation direction of the developer carrying member at a position closest to the developing roller and the developer carrying member. It is characterized in that a linear member that comes into contact is provided.

According to a seventh aspect of the present invention, in order to achieve the above object, the magnetic brush is provided on the downstream side in the rotation direction of the developer carrying member at a position closest to the developing roller and the developer carrying member. It is characterized in that a plate-like member that comes into contact is provided.

According to another aspect of the present invention, in order to achieve the above object, the separating member is made of a magnetic material.

According to a ninth aspect of the present invention, in order to achieve the above object, a voltage for generating an electric field for attracting toner from above the developing roller is applied to the separating member.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of the periphery of a photosensitive drum of an image forming apparatus using an embodiment of a developing device according to the present invention, and FIG. 2 is an enlarged view of a main part of the apparatus of FIG. The surface of the photosensitive drum 1 is uniformly charged by the charging device 2 and then exposed by an optical system (not shown) to form an electrostatic latent image. The developing device 3 transports the toner inside the device to a developing nip area A facing the photosensitive drum 1 by a developing roller 6, and attaches the toner to the electrostatic latent image formed on the photosensitive drum 1 to visualize the toner. Become The toner image is transferred to the transfer paper 20 in a transfer area B where the photoconductor drum 1 and the transfer device 21 face each other, to be an image on the transfer paper 20. Cleaning device 23
The cleaning blade 24 removes toner remaining on the photosensitive drum 1 without being completely transferred onto the transfer paper 20. Thereafter, the surface of the photosensitive drum 1 that has passed through the cleaning device 23 is uniformly charged by the charging device 2, and the next image forming process is repeated.

The developing device 3 has a developing roller 6, a magnet roller 7, a developer regulating member 8, and a stirring member 10 inside a developing casing 4. Magnet roller 7,
The two-component developer 5 is accommodated in a region where the developer regulating member 8 and the stirring member 10 are provided.
0, the carrier and the toner are mixed, and the magnetic roller 7
Conveyed to. The magnet roller 7 has a fixed magnet inside, and has a structure around which a cylindrical sleeve rotates. The sleeve is formed of a non-magnetic metal such as aluminum. The two-component developer is attracted to the sleeve by the magnetic force of the fixed magnet, and is transported as the sleeve rotates.

The layer thickness of the two-component developer 5 around the magnet roller 7 is regulated by a developer regulating member 8, and after passing through the developer regulating member 8, a magnetic brush 9 having a predetermined thickness is conveyed. Is done. Although the magnet roller 7 itself and the developing roller 6 are not in contact with each other and a predetermined gap is set, the magnetic brush 9 is in contact with the developing roller 6. Magnet roller 7
A bias voltage is applied to the developing roller 6 so as to generate a predetermined potential difference, and the toner in the magnetic brush 9 moves onto the developing roller 6 due to an electric field generated between the rollers 6 and 7. , A thin toner layer is formed. The developing roller 6 rotates while being in contact with and in contact with the photosensitive drum 1, and makes toner adhere to the latent image on the photosensitive drum 1 to visualize the latent image.

The magnet roller 7 rotates in the direction of rotation.
After passing through the area facing the developing roller 6, the stirring member 1
The magnetic brush 9 is separated from the surface of the magnet roller 7 by a magnetic force arrangement of the internal fixed magnet immediately before facing the magnetic roller 9. The developer separated from the surface of the magnet roller 7 and dropped on the stirring member 10 is stirred so as to have a uniform toner concentration. After the magnetic brush 9 is separated, the stirring member 10 supplies the developer with a uniform toner concentration to the surface of the magnet roller 7 until then.

The stirring member facing the magnet roller 7 is rotating in the same direction (counterclockwise) as the magnet roller 7 as shown in the figure, so that the developer separated from the magnet roller 7 is moved away from the magnet roller 7. Stirring member 10
To supply the developer to the magnet roller 7 above the stirring member 10. In this way, the developer having a uniform and desired toner concentration is always supplied to the magnet roller 7 to form the magnetic brush 9.

After the developing roller 6 causes toner to adhere to the latent image on the surface of the photosensitive drum 1 and develops the toner, and passes through the area facing the photosensitive drum 1, the toner is consumed as described above. There are portions that have disappeared and portions where thin layers have not been consumed. After that, even if toner is supplied by the magnetic brush 9 at a portion facing the magnet roller 7, it is difficult to eliminate the difference between the consumed portion and the unconsumed portion. When forming images, abnormal images such as density unevenness and afterimages are generated.

Therefore, in the present embodiment, a cleaning roller 11 is provided below the developing roller 6 between the portion facing the photosensitive drum 1 and the portion facing the magnet roller 7. The cleaning roller 11 includes the developing roller 6
, While rotating in the direction in which the movement directions of the respective surfaces are the same. The moving speed of the surface of the cleaning roller 11 is set to be equal to or higher than the moving speed of the surface of the developing roller 6. Further, a predetermined bias voltage is applied to the cleaning roller 11 so that a potential difference at which toner moves from the developing roller 6 to the cleaning roller 11 is generated.

The cleaning roller 11 includes a developing roller 6
Cleaning roller 1
It is necessary to remove the toner from 1. Therefore, in the present embodiment, a cleaning member 12 in the form of a thin plate made of rubber or PET is used as a cleaning means of the cleaning roller 11. The cleaning member 12 has one end fixed to the developing casing 4 and the free end abutted against the cleaning roller 11 in the counter direction to scrape off the toner on the cleaning roller 11.

From the developing roller 6 to the cleaning roller 11
To the cleaning member 12 from the cleaning roller 11.
The amount of toner scraped off by this is equal to or greater than the amount of toner consumed in image formation, and this toner needs to be returned to the developer or toner replenishing device in order to use it again for image formation. Therefore, in the present embodiment, the magnet roller 7, the cleaning roller 11, and the cleaning member 1 are so arranged that the magnetic brush 9 of the magnet roller 7 comes into contact with the toner scraped by the cleaning member 12.
2 are arranged, and the toner is conveyed by a magnetic brush 9 to a developer accommodating section provided with a stirring member 10. Since the rotation direction of the magnet roller 7 is the same as the rotation direction of the developing roller 6 as shown in the figure, after the scraped toner is collected by the magnetic brush 9, the magnetic brush 9 is separated from the developer accommodating portion. .

If the space where the toner scraped off by the cleaning member 12 accumulates is large, the toner that is not in contact with the magnetic brush 9 continues to accumulate without being replaced, resulting in wasteful toner and full of toner. In this embodiment, the space where the scraped toner is stored is narrowed so that the scraped toner is immediately conveyed by the magnetic brush 9. Specifically, the interval between the cleaning member 12 and the magnet roller 7 is partially 2 mm or less, or
The gap between the developing roller 4 and the magnet roller 7 that the magnet roller 7 faces after passing near
m or less. By doing so, the magnetic brush 9 comes into contact with the scraped toner at least in the narrowest part of the interval. However, when the cleaning roller 11 comes into contact with the magnetic brush 9 of the magnet roller 7, the toner of the magnetic brush 9 is removed by the potential difference between the two.
Since the toner is developed on one side, the interval between the cleaning roller 11 and the magnet roller 7 needs to be at least a distance that does not make contact with the magnetic brush 9.

FIG. 3 is an enlarged view of a main part showing another embodiment of the developing device according to the present invention. The magnetic brush 9 transporting the scraped toner as described above and entering the developer accommodating portion is
It falls away from the magnet roller 7. The developer containing the collected toner is stirred under the stirring member 10 and supplied to the magnet roller 7 again above the stirring member 10 while being mixed with the developer originally in the developer container. However, the amount of charge of the toner collected from the cleaning roller 11 may be different from a target value. Therefore, it is desirable that the toner is sufficiently stirred with the developer before being supplied to the magnet roller 7 again. Therefore, in the present embodiment, the shape of the developing casing 4 is assumed to have a developer retaining portion C for temporarily retaining the developer dropped from the magnet roller 7 before being taken into the stirring member 10, and the developer Earn enough to be able to mix well. Other configurations and operations are the same as those of the previous embodiment.

FIG. 4 is a schematic diagram around a photosensitive drum of an image forming apparatus using another embodiment of the developing device according to the present invention,
FIG. 5 is an enlarged view of a main part of the apparatus of FIG. In this embodiment,
Instead of the cleaning roller 11 of the previous embodiment, as shown in the drawing, a magnetic field that contacts the magnetic brush 9 on the magnet roller 7 is located downstream of the developing roller 6 and the magnet roller 7 in the rotation direction of the magnet roller 7. A brush peeling member 26 is provided.

The magnetic brush peeling member 26 is, for example, provided with a member such as a wire or a wire extending in the axial direction of the magnet roller 7. Most of the magnetic brush 9 on the surface of the magnetic brush 7 passes outside the magnetic brush peeling member 26 (the developing roller 6 side) with respect to the magnet roller 7. The developing roller 6 is provided at a position close to the developing roller 6 so that the developer separated from the magnet roller 7 contacts the developing roller 6.

Thus, before the magnet roller 7 supplies toner to the developing roller 6 to form a thin toner layer, the magnetic brush 9 is temporarily separated from the surface of the magnet roller 7 and the magnetic brush 9 is raised. Then, the developer is brought into contact with the developing roller 6, and the thin toner layer is mechanically scraped off from the developing roller 6. That is, the history of the developing roller 6 is eliminated by mechanically scraping off the thin toner layer remaining on the surface of the developing roller 6 after the developing process. After the developer on the developing roller 6 from which the toner has been removed passes through the magnetic brush peeling member 26, it is attracted to the magnet roller 7 again and collected in the developer accommodating portion.

FIG. 6 is an enlarged view of a main part showing still another embodiment of the developing device according to the present invention. As shown in the drawing, in the present embodiment, a magnetic brush peeling member 27 formed of a thin plate member is used in place of the magnetic brush peeling member 26 made of a wire or the like in the embodiment shown in FIGS. The use of the thin plate-shaped magnetic brush peeling member 27 can increase the distance (length) of the portion along the outer peripheral direction of the developing roller 6, and the time for which the developer contacts the developing roller 6 becomes longer, so that the toner thinner can be obtained. The ability to remove layers is improved.

The above-described magnetic brush peeling members 26 and 27
Is made of a magnetic material so as to hold the developer, the amount of the developer contacting the developing roller 6 increases, and the ability to scrape the toner from the developing roller 6 further improves.

Further, by applying a voltage to the magnetic brush peeling members 26 and 27 so as to generate an electric field for moving the toner from the developing roller 6 to the magnetic brush peeling members 26 and 27, the thin toner layer can be mechanically formed. In addition to scraping the toner, the toner can be electrically removed, and the toner on the surface of the developing roller 6 can be reliably removed.

[0035]

According to the first and second aspects of the present invention, as described above, the magnetic brush is brought into contact with the toner scraped from the cleaning roller, and the developer accommodating portion is moved by the magnetic brush. Has the effect that the toner collected from the developing roller after the development can be efficiently returned to the developer accommodating portion without complicating the developing device and the component parts and increasing the cost. .

According to the third aspect of the present invention, as described above, the toner scraped off from the cleaning roller surely comes into contact with the magnetic brush. There is an effect that it can be performed reliably.

As described above, in the developing device according to the fourth aspect, the toner scraped from the cleaning roller is transported to the developer accommodating section and then sufficiently stirred before being used for development. In addition to the effect, there is an effect that the deterioration of the image due to the collected toner can be prevented.

According to a fifth aspect of the present invention, as described above, the magnetic brush is temporarily moved to the upstream side of the portion where the magnet roller supplies toner to the developing roller in the rotation direction of the developing roller. By separating from the surface, raising the magnetic brush, bringing the developer into contact with the developing roller, and mechanically scraping the thin toner layer remaining on the developing roller surface after the developing process, eliminating the history of the developing roller, There is an effect that a good image without an afterimage can be obtained.

As described above, the developing device according to the sixth aspect has a simple structure in which a wire is provided in the axial direction of the magnet roller downstream of the area where the developing roller and the magnet roller face each other in the rotation direction of the magnet roller. Thereby, the effect of the device according to claim 5 can be obtained.

In the developing device according to the seventh aspect, as described above, by forming the magnetic brush peeling member with a plate-like member, in addition to the same effects as the device according to the fifth aspect,
Gain the distance that the peeled developer contacts the developing roller,
There is an effect that the scraping effect of the toner thin layer by the developer is improved.

In the developing device according to the eighth aspect, as described above, by forming the magnetic brush peeling member from a magnetic material, the same effects as those of the devices according to the fifth to seventh aspects can be obtained. Since the amount of the contacting developer can be increased, there is an effect that the ability of the developer to scrape off the thin toner layer is improved.

According to the ninth aspect of the present invention, as described above, by applying an electric force in addition to the scraping effect due to the contact of the developer, the same effect as the above-described apparatuses of the fifth to eighth aspects is obtained. In addition, there is an effect that the toner on the developing roller can be reliably removed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram around a photosensitive drum of an image forming apparatus using an embodiment of a developing device according to the present invention.

FIG. 2 is an enlarged view of a main part of the apparatus of FIG.

FIG. 3 is a main part enlarged view showing another embodiment of the developing device according to the present invention.

FIG. 4 is a schematic diagram around a photosensitive drum of an image forming apparatus using another embodiment of the developing device according to the present invention.

FIG. 5 is an enlarged view of a main part of the apparatus of FIG.

FIG. 6 is an enlarged view of a main part showing still another embodiment of the developing device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 charging device 3 developing device 4 developing casing 5 two-component developer 6 developing roller 7 magnet roller 8 developer regulating member 9 magnetic brush 10 stirring member 11 cleaning roller 12 cleaning member 20 transfer paper 21 transfer device 22 transfer belt 23 Cleaning Device 24 Cleaning Blade 25 Photoreceptor Collection Toner Conveying Member 26, 27 Magnetic Brush Peeling Member A Development Nip Area B Transfer Area C Developer Retaining Part

Claims (9)

[Claims] A developing roller for carrying a toner around the developing roller to visualize an electrostatic latent image formed on the surface of the photoreceptor;
A developer carrier that forms a component developer magnetic brush and supplies toner to the developing roller; and a developing roller and the developer from a region where the developing roller faces the photoconductor in the rotation direction of the developing roller. A developing roller comprising: a cleaning roller that rotates in contact with the developing roller between regions where the carrier is opposed; and a cleaning member that contacts the cleaning roller and removes toner on the surface of the cleaning roller. A developing device comprising the developer carrier, the cleaning roller, and the cleaning member arranged such that the toner scraped off by the method contacts the magnetic brush of the developer carrier. 2. The developer carrier so that the direction of movement of the surface of the developing roller and the direction of movement of the surface of the developer carrier are opposite to each other in a region where the developing roller and the developer carrier face each other. 2. The developing device according to claim 1, wherein the rotation direction is set. 3. The distance between the cleaning member and the developer carrier or the distance between the developer carrier and a casing member facing after the developer carrier has passed near the cleaning member is partially 2 mm.
3. The developing device according to claim 1, wherein: 4. A developer accommodating portion for accommodating a developer to be supplied to the developer carrier, and a stirring device for agitating and transporting the developer in the developer accommodating portion to transfer the developer to and from the developer carrier. It has a transport member, and a developer reservoir portion in which the developer separated from the developer carrier can move toward the agitating transport member to temporarily store the developer is formed in the casing. The developing device according to claim 1. 5. A developing roller for carrying a toner around to develop an electrostatic latent image formed on the surface of the photoreceptor and visualizing the developing roller.
A developer carrying member that forms a component developer magnetic brush and supplies toner to the developing roller, wherein the moving direction of the surface of the developer carrying member at a portion facing the developer carrying member and the developing roller; In a developing device having a direction opposite to the direction of movement of the surface of the developing roller, the magnetic brush on the developer carrier is temporarily held by the developer carrying member after passing through a portion opposed to and closest to the developing roller. A developing device comprising a separating member for separating the developer from the body and bringing the developer into contact with the developing roller. 6. A linear member that comes into contact with the magnetic brush is provided on a downstream side in the rotation direction of the developer carrying member at a position closest to the developing roller and the developer carrying member facing each other. Item 6. The developing device according to Item 5. 7. A plate-like member which comes into contact with said magnetic brush is provided on a downstream side in a rotation direction of said developer carrier from a closest part of said developer roller and said developer carrier opposed to each other. Item 6. The developing device according to Item 5. 8. The developing device according to claim 5, wherein said separating member is made of a magnetic material. 9. The developing device according to claim 5, wherein a voltage for generating an electric field for attracting toner from above the developing roller is applied to the separating member.