JPH09297518A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently recover the reattached toner on an image carrier in a developing device by providing a reattached toner recovering roller which electrostatically recovers the toner reattached to a photo-receptor by a cleaning roller in the developing device. SOLUTION: The reattached toner recovering roller 18 is provided at a position on an upstream side from a developing roller 5 and on a downstream side from an electrifying roller 2 in the rotating direction of a photoreceptor 1, and arranged in a developer container 15. Plural magnets 18b arrayed in a circumferential direction are provided inside the roller 18. Two-component developer D in the container 15 is carried on the peripheral surface of the roller 18 by the action of magnetic force by the magnet 18b internally provided in the roller 18, and fed clockwise in figure. The magnet 18B is fixed so that it can not be rotated and the roller 18 is driven to be rotated clockwise by a driving device so as to feed the developer on the roller 18 clockwise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms an electrostatic latent image on a rotationally driven image carrier by means of latent image forming means,
The electrostatic latent image is visualized as a toner image by a developing device, the toner image formed on the surface of the image carrier is transferred to a recording medium by a transfer device, and the toner image is transferred on the image carrier. The present invention relates to an image forming apparatus that collects residual toner on a cleaning member and cleans the surface of the image carrier.

[0002]

2. Description of the Related Art In an image forming apparatus of the above type configured as a copying machine, a printer, a facsimile, or a complex machine thereof, an image carrier is repeatedly used, and therefore, the surface of the image carrier after the toner image is transferred. It is necessary to clean the surface of the image bearing member by removing and collecting the residual toner remaining on the image carrier by a cleaning member. Therefore, conventionally, various cleaning devices for cleaning the image carrier have been proposed and put into practical use, but the conventional cleaning device generally stores the toner collected from the image carrier in a waste toner tank or the like, It is configured to discard this.

By the way, in recent years, in an image forming apparatus of this type which employs an electrophotographic process, it is possible to further reduce the cost and further reduce the amount of toner to be discarded as part of measures against environmental problems. Is requested.

In view of such a point, if the transfer rate of the toner image from the image carrier to the recording medium is set to 100% to eliminate the residual toner after the toner image is transferred, a so-called cleanerless system is adopted. be able to. As a result, not only can the toner to be discarded be eliminated, but also the cleaning device can be omitted, and the image forming system can be simplified and the cost of the image forming device can be reduced. However, at present, it is difficult to make the transfer rate of the toner image 100%, and there is a problem from the viewpoint of reliability.

Therefore, as a second best measure, the transfer residual toner remaining on the surface of the image carrier after the transfer of the toner image is electrostatically adhered to the cleaning member to be temporarily recovered, and then this recovered toner is The toner that is electrostatically redeposited on the surface of the image bearing member that does not affect the formation of the electrostatic latent image, and the toner that is redeposited on the surface of the image bearing member is electrostatically collected by the developing device. A method of reuse in a developing device has been proposed (see, for example, Japanese Patent Publication No. 61-30274). This eliminates the need for a waste toner tank for storing the collected toner and a dedicated conveying means for transferring the collected toner to the developing device, thus reducing the cost of the image forming apparatus and recycling the toner. Since it can be used, waste toner can be eliminated.

By the way, in the conventional image forming apparatus of this type, the developer carrying and conveying member of the developing device is used to electrostatically collect the toner re-adhered to the image carrier to the developing device. . This developer carrying and carrying member carries and carries the developer contained in the developing container. By the developer thus conveyed, the electrostatic latent image formed on the image carrier is visualized as a toner image. At this time, in order to improve the image quality of the toner image formed on the image carrier,
During development, the developer carried by the developer carrying and carrying member is moved between the image carrying body and the developer carrying and carrying member so that the carried developer is moved in the same direction as the moving direction of the surface of the image carrying body. Transporting. Even when the redeposited toner on the image carrier is collected by the developing device, the developer on the developer carrying and carrying member is carried in the same direction as during development. However, with such a configuration, the mechanical scraping force, that is, the scavenging force, exerted on the redeposited toner on the image bearing member by the developer on the developer carrying / conveying member becomes small, and the recovery efficiency of the redeposited toner is reduced. And the toner image formed on the image carrier may be stained.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to electrostatically collect transfer residual toner on a cleaning member, electrostatically re-adhere the recovered toner to an image carrier, and then re-adhesion. An object of the present invention is to provide an image forming apparatus which solves the above-mentioned problems in the image forming apparatus of the type in which the toner is collected in the developing apparatus and which can efficiently collect the redeposited toner on the image carrier into the developing apparatus.

[0008]

In order to achieve the above-mentioned object, the present invention provides an image carrier which is rotationally driven, a latent image forming means for forming an electrostatic latent image on the carrier, and a developing container. The contained developer is carried on the developer carrying and conveying member, and the developer carried on the developer carrying and carrying member is in the same moving direction as the surface of the image carrying body between the image carrying body and the developer carrying and carrying member. The developing device that conveys the carried developer in a direction moving in a direction and visualizes the electrostatic latent image as a toner image by the carried developer, and the toner image formed on the surface of the image carrier. A transfer device for transferring to the recording medium, and the transfer residual toner on the image carrier after the toner image transfer is electrostatically temporarily collected, and then the collected toner is transferred to an electrostatic latent image on the image carrier. A cleaning member that electrostatically redeposits on the surface portion that does not affect the formation. In an image forming apparatus that collects the toner reattached to the surface of the image carrier to a developing device, the developer is carried and transported, and the toner reattached to the image carrier is electrostatically transferred to the transported developer. In a state in which the re-adhesion toner recovery rotating body that is selectively recovered and returned together with the developer into the developer housed in the developing container is opposed to the surface of the image carrier,
Provided in the developing device, the developer carried on the rotating body is moved between the redeposited toner collecting rotating body and the image bearing body in a direction opposite to the moving direction of the surface of the image bearing body. The present invention proposes an image forming apparatus that conveys a sheet.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to the present invention. In the figure, a drum-shaped photoconductor 1 which is an example of the structure of an image carrier is rotationally driven in the clockwise direction in the figure by a drive device (not shown), and at this time, a static elimination lamp 13 which is an example of the static eliminator removes static electricity. The surface of the photoconductor 1 is uniformly charged to a predetermined polarity by the action of the charging roller 2 which is an example of a charging device. In this example, the charging roller 2 is connected to the voltage power source E ₁₀ , and uniformly charges the surface of the photoconductor 1 in the negative polarity while rotating in contact with the photoconductor 1. Due to the action of the charging roller 2, the surface of the photoconductor 1 is, for example, -85.
It is charged to 0V. As a charging device for uniformly charging the photoreceptor 1, a charging device disposed apart from the photoreceptor, such as a corona discharger, can be used.

Next, in the exposure section 3, an exposure scanning device (not shown) performs optical writing scanning with, for example, the light-modulated laser beam 11, so that a predetermined electrostatic latent image is formed on the surface of the photoconductor 1. Is formed. Photoconductor 1
The surface potential of the upper part A irradiated with the laser beam 11, that is, the surface potential of the electrostatic latent image is, for example, about −150 V, and the surface potential of the part B not irradiated with the laser beam 11, that is, the background potential of the background portion of the electrostatic latent image is almost It is maintained at -850V. As described above, in the present embodiment, the exposure scanning device and the charging device including the charging roller 2 form a latent image forming unit that forms an electrostatic latent image on the image carrier including the photoconductor 1. .

The developing device 4 includes a developing roller 5 which is an example of a developer carrying and conveying member which is arranged to face the photoconductor 1, a pair of stirring paddles 10A and 10B, and a re-adhesive toner recovery rotary member which is an example. Adhering toner collecting rollers 18 are provided in the developing container 15 of the developing device, and are rotatably supported in the developing container 15.
The developing roller 5 and the toner recovery rotator 18 face the photoconductor with a minute gap therebetween and extend parallel to the photoconductor 1.

The developing roller 5 is made of a non-magnetic conductive cylindrical body, and a plurality of magnets 5B arranged in the circumferential direction are provided inside the developing roller 5. A two-component developer D having toner and a magnetic pole carrier is accommodated in the developing container 15,
The toner and the carrier are frictionally charged with opposite polarities by the rotation of the stirring paddles 10A and 10B. Toner is
It is charged to a predetermined polarity, which is the same as the charging polarity of the photoconductor 1 in this example, that is, a negative polarity.

The developer having the toner and the carrier thus charged is magnetically carried on the peripheral surface of the developing roller 5 by the action of the magnetic force of the magnet 5B provided therein, and the developer in FIG. Transported in the clockwise direction. In the present example, the magnet 5B is non-rotatably fixed, whereas the developing roller 5 is rotationally driven in the counterclockwise direction opposite to the rotational direction of the photoconductor 1 by a drive device (not shown). Then, the developer on the developing roller 5 is conveyed in the same direction as the rotating direction of the developing roller 5. In the area where the photoconductor 1 and the developing roller 5 face each other, that is, in the developing section 6,
The developer on the developing roller 5 is conveyed in the same direction as the moving direction of the surface of the photoconductor 1. The developing roller 5 may be fixed and the magnet 5B may be rotated, or both may be relatively rotated to convey the developer on the developing roller 5 in the same direction as described above.

The developer carried and carried by the developing roller 5 is scraped by the developer regulating member 19. As shown in FIG. 2, the developer regulating member 19 is provided with projecting portions 19a and 19b which are opposed to the developing roller 5 and the re-adhered toner collecting roller 18 with a gap therebetween. The developer on the developing roller 5 is scraped by the portion 19a.

The developer whose conveyance amount is regulated by the developer regulating member 19 is conveyed toward the developing section 6 where the developing roller 5 and the photoconductor 1 face each other. At this time, the developing roller 5 is supplied with the voltage power supply E ₁ from the developing device 4 having the same polarity as the charging polarity of the toner of the developer D, for example, −600 V.
A bias voltage of a certain degree is applied. Therefore, the toner in the developer carried to the developing unit 6 is electrostatically attracted to the electrostatic latent image on the photoconductor 1 and adheres to that portion. That is,
Toner charged to the same negative polarity as the charge polarity of the photoconductor electrostatically adheres to the photoconductor surface portion A to which the laser light is applied, and the electrostatic latent image is visualized as a toner image. is there. Such a developing method is called a reversal developing method (negative / positive developing method).

As described above, in the developing device 4, the developer D contained in the developing container 15 is carried on the developer carrying / conveying member composed of the developing roller 5, and the developing device 4 and the image carrier composed of the photoconductor 1 are developed. Between the agent carrying and conveying member, that is, in the developing unit 6,
The developer carried on the developer carrying and carrying member is carried in the direction in which the developer carried in the same direction as the moving direction of the surface of the image carrier, and the carried developer is formed on the image carrier. The electrostatic latent image is visualized as a toner image. The image quality of the toner image formed on the photoconductor 1 by developing the electrostatic latent image while conveying the developer on the developing roller 5 in the above-described direction with respect to the moving direction of the surface of the photoconductor 1. Can be improved.

On the other hand, the re-adhered toner collecting roller 18 shown in FIG. 1 is located downstream of the charging roller 2 and upstream of the developing roller 5 with respect to the rotation direction of the photosensitive member 1. The roller 18 is provided in the developing container 15. Such reattachment toner collecting roller 18
Like the developing roller 5, is made of a non-magnetic conductive cylindrical body, and has a plurality of magnets 18B arranged in the circumferential direction inside thereof. The two-component developer D in the developing container 15 is also carried on the peripheral surface of the roller 18 by the action of the magnetic force of the magnet 18B provided therein, and is conveyed in the clockwise direction in FIG. In this example,
The magnet 18B is non-rotatably fixed, the re-adhered toner collecting roller 18 is rotationally driven in the clockwise direction by a driving device (not shown), and the developer on the roller 18 is conveyed in the clockwise direction. . In the area 6A where the photoconductor 1 and the re-adhesion toner recovery roller 18 face each other, that is, in the closest position between them, the developer on the re-adhesion toner recovery roller 18 moves in a direction opposite to the moving direction of the surface of the photo conductor 1. It is transported as if it were done.

It is also possible to fix the re-adhesion toner recovery roller 18 and rotate the magnet 18B, or to rotate both of them, so that the developer on the re-adhesion toner recovery roller 18 is conveyed in the same direction as described above. it can.

A part of the developer carried by the developing roller 5 and directed to the developer regulating member 19 is a part of the re-adhered toner collecting roller 1.
8 and is carried by this roller and conveyed in the direction of rotation of the roller 18. At this time, the developer is scraped by the developer regulating member 19. The developer on the redeposited toner collecting roller 18 is scraped by the protrusion 19b of the developer regulating member 19 shown in FIG.

At this time, at the time of development for visualizing the electrostatic latent image on the photosensitive member 1, the re-adhesion toner collecting roller 18 is also made to have the same charge polarity as the toner of the developer D by the voltage power source E ₆ . A voltage of, for example, -600 V having a polarity is applied, and the facing area 6A between the re-adhesion toner recovery roller 18 and the photoconductor 1
The toner in the developer carried to is electrostatically attracted to the surface portion A on the photoconductor 1, that is, the electrostatic latent image, and the latent image is visualized as a toner image.

As described above, in the image forming apparatus of this embodiment, the electrostatic latent image is visualized by the developer carried on the re-adhered toner collecting roller 18, and then carried on the developing roller 5. A visible image operation is executed by the developer, and a high quality toner image is formed on the photoconductor 1. Opposing area 6
The developer that has passed through A is further carried by the re-adhesion toner recovery roller and conveyed, scraped off from the re-adhesion toner recovery roller 18 by the scraper 20 opposite the re-adhesion toner recovery roller, and stored in the developing container 15. The developer D is returned to the existing developer.

A transfer roller 7, which is an example of a transfer device, is disposed below the photoconductor 1. The transfer roller 7 rotates in a direction in which the surfaces of the transfer roller 7 and the photoconductor 1 move in the same direction, that is, in the forward direction with respect to the photoconductor 1, and the transfer roller 7 and the photoconductor 1 facing the transfer roller 7 face each other. The recording medium composed of the transfer paper 16 is fed in the direction of arrow P toward the transfer portion 8 between the transfer roller 7 and the transfer roller 7.
Is pressed against the surface of the photoconductor 1 via the transfer paper 16 sent to the transfer unit 8, and at this time, the toner image formed on the photoconductor 1 is transferred onto the transfer paper 16 by the function of the transfer roller 7. To be done.

That is, the transfer roller 7 is powered by the power source E _3.
Is applied with a positive polarity voltage opposite to the charging polarity of the toner on the photoconductor 1, for example, a voltage of +950 V, and at this time, a negative polarity toner T forming a toner image on the photoconductor 1.
Are electrostatically attracted to the transfer paper 16 side and adhere to the transfer paper. It is also possible to use a transfer device separated from the photoconductor 1 such as a transfer device including a corona discharger.

The transfer paper 16 on which the toner image has been transferred is separated from the photoconductor 1 by a separating device (not shown) and is sent to a fixing device (not shown).
The toner image on 6 is fixed. In this way, the transfer paper 16 is ejected outside the image forming apparatus main body as copy paper.

As described above, the image forming apparatus of this embodiment has the image carrier composed of the photosensitive member 1 which is rotationally driven, the latent image forming means for forming an electrostatic latent image on the image carrier, and the latent image forming means. A developing device 4 that visualizes the electrostatic latent image as a toner image, and a transfer device that includes a transfer roller 7 that transfers the toner image formed on the surface of the image carrier to a recording medium including transfer paper 16 are provided. In addition, it is equipped with a cleaning member composed of a cleaning roller 12 and a static eliminator composed of the aforementioned static elimination lamp 13 described below. The charging device, the exposure unit 3 for the image carrier by the latent image forming means, the developing device 4, the transfer device, the cleaning member, and the charge eliminating device are arranged in this order along the rotation direction of the image carrier.

The toner image on the photoconductor 1 is transferred to the transfer paper 16 at the transfer portion 8. After the toner image is transferred, the photoconductor 1 is transferred.
The toner remaining on the photoconductor 1 without being transferred to the transfer paper 16 adheres to the surface of the. Transfer residual toner T ₁
When it reaches the cleaning unit 14, it is temporarily collected on the surface of the cleaning roller 12, which is an example of a cleaning member.

The cleaning roller 12 has a core member 12a made of a rigid body, and a conductive or medium-resistance elastic body 12b fixed to the surface of the core member 12a. In the illustrated example, the core member 12a. Is made of a round shaft-shaped conductive metal, and the elastic body 12b is made of a foamed body formed in a cylindrical shape concentric with the core member 12a. The cleaning roller 12 is housed in the cleaning case 17 shown in FIG. 1, and each end of the core member 12a is rotatably supported by the front and rear side walls 17a of the cleaning case 17. The cleaning roller 12 includes the developing roller 5, the charging roller 2, and the transfer roller 7 together with the photosensitive member 1.
Are positioned substantially parallel to.

Here, in FIG. 1, most of the toner T of the toner image directed from the developing section 6 to the transfer section 8 is toner having a charging polarity at the time of development, that is, a negative polarity toner in this example. On the other hand, when the toner image is transferred, a voltage having a polarity opposite to the toner charging polarity at the time of development, which is a positive polarity in this example, is applied to the transfer roller 7, so that the toner remains on the photoconductor 1 after the toner image is transferred. The adhered toner, that is, the transfer residual toner T ₁ is a toner in which positive and negative toners are mixed. The transfer residual toner is transferred to the cleaning unit 14 in a state in which both positive and negative polarity toners are mixed.

The cleaning roller 12, when collecting the residual toner T ₁ of the the photosensitive member 1 is rotated in the appropriate direction by a driving device not shown, in this example the clockwise direction (the arrow a direction in Fig. 1 ) That is, at the portion facing the photoconductor 1, the cleaning roller 12 and the surface of the photoconductor 1 are rotatably driven in directions opposite to each other (counter direction).
Rotate while rubbing against the surface of. Cleaning roller 1
2 has its surface portion pressed against the photosensitive member 1 so that the surface of the photosensitive member 1 can be elastically deformed, and a nip region N is formed at this pressed portion. The width of the nip area N in the circumferential direction of the photoconductor is, for example, about 1 mm, but the width of the nip area N is exaggerated in FIG.

In the nip region N, the transfer residual toner T ₁ of both positive and negative polarities is transferred to the cleaning roller 12 and the photosensitive member 1.
While being in contact with the surface of the toner, it is triboelectrically charged so that the toner has the same polarity (negative polarity in this example) as the toner at the time of development.
That is, the untransferred toner on the photoconductor 1 after the toner image transfer is developed by the cleaning member composed of the cleaning roller 12 and the image carrier composed of the photoconductor 1 so as to visualize the electrostatic latent image. The toner is triboelectrically charged so as to be aligned with the charging polarity (original polarity) of the toner at that time.

The untransferred toner T ₁ on the photoconductor 1 after the toner image is transferred onto the recording medium made of the transfer paper 16 is collected by a cleaning member composed of a cleaning roller 12 which rotates while being pressed against the photoconductor 1. However, when the toner is collected, the core member 12a of the cleaning roller 12 has a polarity opposite to the charging polarity of the toner frictionally charged between the roller 12 and the photoconductor 1, a positive voltage in this example, for example, +200.
The voltage of V is applied by the voltage power supply E ₄ . Therefore, the residual toner after the transfer of the toner image that has passed through the transfer portion 8, that is, the transfer residual toner T ₁ frictionally charged between the photoconductor 1 and the cleaning roller 12 is the residual toner of the cleaning roller 12 to which the positive voltage is applied. It is electrostatically attracted to the surface, adheres to the surface of the roller 12, and is temporarily collected by this roller.

The surface potential of the photosensitive member 1 which has passed through the transfer roller 7 is, for example, about -50 V due to the influence of the transfer roller 7 to which a positive voltage is applied, but +200.
A cleaning roller 12 to which a voltage of V is applied,
The potential difference between the surface of the photoreceptor residual toner T ₁ is attached, the residual toner T ₁ of the negative charge polarity is of being electrostatically attracted to the surface of the cleaning roller 12. As a result, the surface of the photoconductor 1 is cleaned.

As described above, the cleaning roller 12 and the photosensitive member 1 are not transferred to each other by the transfer residual toner T on the photosensitive member.
_1, so that an electric field can be sucked electrostatically to the surface of the cleaning roller 12 is formed, (in this example the positive polarity) opposite polarity to the charging polarity of the toner in development is the voltage is applied.

As described above, the cleaning roller 12
In the figure, the toner collected on the surface of the toner is indicated by reference numeral T ₂ . 3 to 9, the residual toner T ₁ of the the photosensitive member 1 is collected by the cleaning roller 12, then an example of an operation to re-adhered to the recovery toner T ₂ the surface of the photosensitive member 1 as described below FIG. 3 is an explanatory diagram, and FIG. 3 is a diagram illustrating a toner image on the photoconductor 1 that is transferred onto a transfer paper 16 that is conveyed in the direction of arrow P, and the transfer residual toner T _{1 on} the surface of the cleaning roller 12. It is a schematic diagram showing a situation when being collected.

The surface portion of the photoconductor 1 that has been cleaned by the cleaning roller 12 is subjected to static elimination action by the static elimination lamp 13, and the surface potential thereof is lowered to the reference value. The charge eliminating lamp 13 continues to be turned on during the image forming operation. The surface of the photoconductor that has been subjected to the static elimination is continuously charged by the charging roller 2, and the above-mentioned image forming operation is continued.

In this way, one sheet of toner image is formed on the photosensitive member 1 while the photosensitive member 1 is rotated several times,
This is continuously transferred onto the transfer paper 16, and the circumferential area on the photoreceptor 1 where such a toner image is formed is the image forming area. In FIG. 3, this image forming area is designated by a reference numeral X, and the tip end thereof in the rotation direction of the photosensitive member is designated by a reference numeral Y. Similarly, in FIG. 4, a symbol Z is attached to the rear end of the image forming area X in the rotation direction of the photoconductor.

When the tip Y of the image forming area X reaches the cleaning roller 12, the cleaning roller 1
The operation for collecting the transfer residual toner T ₁ to the second transfer toner T ₁ is started, and in the illustrated example, the operation for collecting the transfer residual toner T ₁ is continued until the trailing edge Z of the image forming area X reaches the cleaning roller 12. The portion of the image forming area X that has passed the cleaning roller 12 has already been cleaned by the cleaning roller.

As shown in FIG. 4, when the rear end Z of the image forming area X in the direction of rotation of the photoconductor passes through the charging roller 2, the charging roller 2 is separated from the surface of the photoconductor 1 at this time. (See Figure 5). At the same time, the switch S ₁₀ shown in FIG. 1 is switched to turn off the voltage application to the charging roller 2.

At the time of development for visualizing the electrostatic latent image, a voltage having the same polarity as the charge polarity of the toner at the time of development is applied to the re-adhesion toner collecting roller 18, but the rear end Z of the image forming area is applied. but, as shown in FIG. 5, when passing through the redeposited toner recovery roller 18, is switched switch S ₃ shown in FIG. 1, redeposited toner recovery roller 18 and the voltage source E ₇
A positive voltage opposite to the charging polarity of the toner is applied to the re-adhesion toner collecting roller 18 so that the toner does not adhere to the photoconductor 1. For example, a voltage of + 500V is applied to the reattachment toner collecting roller 18.

Similarly, the rear end Z of the image forming area is the developing device 4.
Switch S shown in FIG. 1 when passing through the developing roller 5 of
₁ , the developing roller 5 is connected to the voltage power source E ₂ , and the developing roller 5 also has a positive voltage opposite to the charging polarity of the toner so that the toner does not adhere to the photoconductor 1, for example, A voltage of + 500V is applied.

Subsequently, as shown in FIG. 6, when the trailing edge Z of the image forming area passes through the transfer portion 8, at this time, the transfer roller 7
The voltage application to is stopped. At this time, in this example, the transfer roller 7 is separated from the photoconductor 1 (see FIG. 7).

As described above, the cleaning roller 12 electrostatically temporarily collects the transfer residual toner T ₁ on the photosensitive member 1 after the transfer of the toner image to clean the surface of the photosensitive member 1. The formed toner T ₂ is reattached to the surface portion of the photosensitive member 1 that does not affect the formation of the electrostatic latent image. In the illustrated example, the trailing edge Z of the image forming area after the toner image is transferred to the transfer paper 16 is the cleaning roller 1 as shown in FIG.
2, the switch S ₂ shown in FIG. 1 is switched, the cleaning roller 12 is connected to the voltage power source E _5, and the core member 12 a of the cleaning roller 12 is
The toner has the same negative polarity as the charge polarity of the toner at the time of development, for example,
A voltage of 000V is applied. In this way, the cleaning roller 12 and the photosensitive member 1 are positioned farther than the rear end Z of the image forming area.
Between the toner T ₂ on the cleaning roller 12 and the non-image forming area W (FIG. 7) on the surface of the photoreceptor on the rear side in the rotation direction of the toner.
Thus, an electric field in the direction of being emitted toward the photoconductor 1 is formed.

Due to the electric field, as shown in FIG.
The toner T ₂ temporarily collected on the cleaning roller 12 is reattached to the non-image forming area W on the photoconductor 1 and returned. At this time, the cleaning roller 12 of this example is
The photoconductor 1 is rotationally driven in the forward direction (counterclockwise in FIG. 8). Toner T redeposited on the photoconductor 1
_As shown in FIG. 9, the photosensitive drum ₃ passes below the charge removing roller 13 and the charging roller 2 separated from the photosensitive drum 1 by the subsequent rotation of the photosensitive drum 1, and is transferred to the re-adhered toner collecting roller 18 as shown in FIG. Reach At this time, since the positive polarity voltage opposite to the charging polarity of the toner at the time of development is applied to the redeposited toner collecting roller 18 as described above, the negative polarity redeposited on the photoconductor 1 is applied. The toner T ₃ is electrostatically transferred to the redeposited toner collecting roller 18 side. As shown in the figure, the developer D is carried on the peripheral surface of the re-adhesion toner collecting roller 18 and is conveyed in the rotating direction of the roller 18, and the developer D is contained in the developer D. The redeposited toner T ₃ on No. 1 is electrostatically collected.

As shown in FIG. 1, the re-adhered toner collecting roller 18 is provided inside the developing container 15 and has a leading edge portion.
By the action of the scraper 20 arranged so as to face
Developer D on the redeposited toner recovery roller 18 shown in FIG. 10, the toner T ₃ recovered to the roller 18
It is scraped off from the peripheral surface of and is returned into the developing container 15 (FIG. 1). As described above, the re-adhesion toner recovery rotator including the re-adhesion toner recovery roller 18 provided in the developing device 4 carries a developer in a state of facing the surface of the image carrier composed of the photoconductor 1. The toner T ₃ that has been conveyed and redeposited on the image carrier is electrostatically collected by the conveyed developer and returned to the developer D housed in the developing container 15 together with the developer. is there. In this way, the toner T ₃ redeposited on the surface of the image carrier is collected by the developing device 4 and reused in the developing device 4. With this configuration, waste toner can be eliminated, and the toner collected by the cleaning roller 12 can be used as the developing device 4.
It is not necessary to provide a toner conveying pipe for returning to the above.

When the re-adhesion toner recovery roller 18 cannot completely collect the re-adhesion toner T ₃ that has passed through the re-adhesion toner recovery roller 18, the re-adhesion toner has a positive polarity opposite to the charging polarity of the toner. When the developing roller 5 to which a positive voltage, for example, +500 V is applied, is reached, the developer on the developing roller 5 is electrostatically recovered.

When the image forming operation is continued,
When the next image forming area X1 shown in FIG. 9 and FIG. 10 is continuously subjected to the static elimination action by the static elimination lamp 13, and the leading end Y1 of the photoconductor rotating direction moves to the position of the charging roller 2, the charging roller 2 is exposed to light. By contacting the surface of the body 1 and charging the next image forming area X1 with a negative polarity, an electrostatic latent image is formed on the next image forming area X1 in exactly the same manner as described above. As shown, it is visualized as a toner image in the developing device 4. At this time, a negative voltage is applied to the redeposited toner collecting roller 18 and the developing roller 5. When the leading edge Y1 of the image forming area reaches the transfer section 8, the transfer roller 7 is pressed against the photoconductor 1, and the leading edge of the next transfer paper 16 reaches the transfer section 8, and the next image forming area X1 is reached. The toner image formed on the transfer paper 16 is transferred to the transfer paper 16. The transfer residual toner at this time is electrostatically temporarily collected by the cleaning roller 12 as described above, and the above-described operation is repeated. In this way, the image forming operation is repeated a predetermined number of times.

In the state shown in FIG. 9, neither the electrostatic latent image nor the toner image has been formed in the next image forming area X1. To be precise, the area X1 shown in FIG. It can be said that the area is to be the next image forming area. Further, in FIGS. 1 and 3 to 11, the toner T, T ₁ , T ₂ , T on the photoconductor 1 or the cleaning roller 12 is used.
_{As for 3} , these are schematically enlarged.

As described above, the toner T ₂ collected by the cleaning roller 12 is the non-image forming area W on the photoconductor 1.
The redeposited toner T ₃ does not affect not only the electrostatic latent image at the time of the image forming operation described above but also the electrostatic latent image formed next.

Collection of transfer residual toner to the cleaning roller 12 and reattachment of the collected toner to the photoconductor 1 can be performed at various timings. In either case, latent image formation on the photoconductor 1 is not possible. It is necessary to re-attach the collected toner to the unaffected surface portion.

By the way, in the conventional image forming apparatus, the developing roller 5 is exclusively used for collecting the toner re-adhered to the photoreceptor 1 (FIG. 1) to the developing device 4. That is, conventionally, the re-adhesion toner recovery roller 18 is not provided, and the re-adhesion toner is recovered by the developer carried and carried on the peripheral surface of the developing roller 5.

For the purpose of improving the image quality, the developing roller 5 is rotationally driven at the portion facing the photoconductor, that is, the developing portion 6, in such a direction that both surfaces move in the same direction at the time of development. The developing roller 5 rotates in the same direction even when the redeposited toner is collected. However, when the re-adhered toner on the photoconductor 1 is electrostatically collected by only the developing roller 5, the developer on the developing roller 5 mechanically scrapes the re-adhered toner on the photoconductor 1 (scavenging action). As a result, the re-adhered toner collection efficiency decreases.

On the other hand, in the image forming apparatus of this embodiment, a re-adhesion toner recovery rotator including the re-adhesion toner recovery roller 18 is provided in addition to the developing roller 5, and the re-adhesion toner recovery rotator and the photosensitive member 1 are provided. Between the image carriers, the developer carried on the rotating body conveys the developer in a direction in which the developer moves in a direction opposite to the moving direction of the surface of the image carrier, and the image carrier is carried in the developer. Since the reattachment toner T ₃ on the body surface is electrostatically collected, a large scavenging force of the developer is applied to the reattachment toner, and the reattachment toner recovery rotation is efficiently performed. The toner can be electrostatically collected in the developer on the body, and the background stain of the toner image can be effectively prevented. In addition, since the developing roller 5 rotates in a direction in which the surfaces of the developing roller 5 and the surface of the photoconductor 1 move in the same direction at the time of development, the deterioration of the image quality of the toner image formed on the photoconductor 1 is prevented. it can. Even if the rotation direction of the developing roller 5 is not changed, the transfer residual toner can be efficiently collected in the developing device.

Further, at the time of development, a voltage for development similar to that of the developing roller 5 is applied to the re-adhesion toner recovery roller 18 by the voltage power source E ₆ , so that the re-adhesion toner recovery roller 18 is supported. By the conveyed developer, the electrostatic latent image formed on the photoconductor 1 can be visualized as a toner image in cooperation with the developing roller 5, and a so-called two-stage developing method can be adopted. . However, at the time of development, the redeposited toner collecting roller 18 is largely separated from the surface of the photosensitive member,
Alternatively, the supply of the developer to the redeposited toner collecting roller 18 may be stopped so that the developing operation by the developer carried on the redeposited toner collecting roller 18 is prohibited.

In addition, the re-adhered toner collecting roller 18 shown in FIG.
Even if the re-adhesion toner recovery roller 18 is provided at a position downstream of the transfer roller 7 and upstream of the transfer roller 7, re-adhesion on the photoconductor 1 is performed as in the case where the re-adhesion toner recovery roller 18 is provided at the position shown in FIG. Toner can be collected.

In the embodiment described above, the transfer residual toner is removed from the cleaning roller 1 for each image forming area X.
2, and the toner is re-attached to the photoconductor 1 each time. However, the transfer residual toner in the plurality of image forming areas is collected by the cleaning roller 12 for each image formation, The collected toners may be collectively reattached to the photoconductor 1. That is, the cleaning roller 12 is
For example, by rotating in the direction a in FIG. 1 to collect the transfer residual toner for each image formation, and after collecting a plurality of times, the cleaning roller 12 is moved to the arrow a in FIG. 1, for example.
It is also possible to rotate the toner in the direction opposite to the direction indicated by and re-attach the toner collected for each image formation to the photoconductor 1 all together.

The present invention can also be applied to an image forming apparatus configured to collect toner from the image bearing member or to reattach the collected toner to the image bearing member while the cleaning member is stopped. is there.

Further, according to the present invention, an image forming apparatus using not only a roller-shaped cleaning member but also an endless belt-shaped cleaning member, or a drum-shaped endless belt-shaped image carrier. It can also be applied to image forming apparatuses, and uses an intermediate transfer member as a recording medium.
It can also be applied to an image forming apparatus of a type in which a toner image is transferred from an image carrier to this intermediate transfer member and then transferred to a transfer material. Further, according to the present invention, after the image bearing member is charged by the charging device, an electrostatic latent image is formed by a portion which is not irradiated with light at the time of image exposure on the surface thereof, and the electrostatic latent image is charged to a polarity opposite to the polarity of the latent image potential. It can also be applied to a so-called positive / positive developing type image forming apparatus in which toner is attached to the electrostatic latent image for development.

[0059]

According to the image forming apparatus of the present invention, the transfer residual toner on the image carrier is electrostatically recovered by the cleaning member, and the recovered toner is electrostatically recovered by the image carrier. In an image forming apparatus that adheres and electrostatically collects the re-adhered toner to the developing device, the re-adhered toner on the image bearing member can be efficiently removed without deteriorating the image quality of the toner image formed on the image bearing member. Can be collected in the developing device. As a result, it is possible to effectively suppress the occurrence of background stain on the toner image formed on the image carrier.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional explanatory view of an image forming apparatus according to an exemplary embodiment of the present invention, in which the toner on a photoconductor and a cleaning roller is schematically illustrated and enlarged.

FIG. 2 is a diagram showing a relative positional relationship among a photoconductor, a developing roller, and a re-adhered toner collecting roller.

FIG. 3 is an explanatory diagram illustrating a relative positional relationship between a charging roller, a developing roller, a transfer roller, a cleaning roller, and a photoconductor, and illustrating a state in which residual toner remaining on the photoconductor is collected by the cleaning roller. Is.

FIG. 4 is an explanatory diagram similar to FIG. 3, showing a state in which a rear end of the image forming area reaches a portion facing a charging roller.

FIG. 5 is an explanatory diagram similar to FIG. 3, showing a state in which a rear end of the image forming area reaches a portion facing the redeposited toner collecting roller.

FIG. 6 is an explanatory view similar to FIG. 3, showing a state when the rear end of the image forming area reaches a portion facing the transfer roller.

FIG. 7 is an explanatory diagram similar to FIG. 3, showing a state when the rear end of the image forming area reaches a portion facing the cleaning roller.

FIG. 8 is an explanatory diagram similar to FIG. 3, showing a state in which the collected toner on the cleaning roller is reattached to the photoconductor.

FIG. 9 is an explanatory view similar to FIG. 3, showing how redeposited toner on the photoconductor is conveyed toward the developing device.

FIG. 10 is an explanatory view similar to FIG. 3, showing a state in which the reattachment toner on the photoconductor is collected by a reattachment toner collection roller.

FIG. 11 is an explanatory diagram similar to FIG. 3, showing a state when the leading edge of the next image forming area reaches a portion facing the transfer roller.

[Explanation of symbols]

4 developing device 15 developing container D developer T ₁ toner T ₂ toner T ₃ toner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masako Yoshii 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (1)

[Claims] 1. A rotationally driven image carrier, a latent image forming means for forming an electrostatic latent image on the carrier, a developer contained in a developing container, and a developer carrying member carrying the developer. Between the image bearing member and the developer carrying member, in the direction in which the developer carried by the developer carrying member moves in the same direction as the moving direction of the image carrier surface, the carrying developer is carried, A developing device that visualizes the electrostatic latent image as a toner image by the conveyed developer, a transfer device that transfers the toner image formed on the surface of the image carrier to a recording medium, and an image after the toner image is transferred. The transfer residual toner on the carrier is electrostatically temporarily collected, and then the collected toner is electrostatically redeposited on the surface portion of the image carrier that does not affect the formation of the electrostatic latent image. A cleaning member is provided, and the toner reattached to the surface of the image carrier is collected in the developing device. In the image forming apparatus, a developer is carried and conveyed, and the toner redeposited on the image carrier is electrostatically collected in the conveyed developer, and is accommodated in a developing container together with the developer. The re-adhesion toner recovery rotator for returning to the developer being provided is provided in the developing device in a state of facing the surface of the image carrier, and the rotator is provided between the re-adhesion toner recovery rotator and the image carrier. An image forming apparatus characterized in that the developer carried on the sheet conveys the developer in a direction in which the developer moves in a direction opposite to the moving direction of the surface of the image carrier.