JPH10240094A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of transferring a toner image formed on the surface of a photoreceptor with a developing device to a transfer paper, then, efficiently removing/recovering residual toner after the transfer which is stuck to the surface of the photoreceptor with a cleaning device and carrying the recovered toner to the developing device as it is, so as to reuse the recovered toner. SOLUTION: The cleaning device 20 is provided with a cleaning belt 23 coming into press-contact with the surface of the photoreceptor 1, two rollers 21 and 22 on which the cleaning belt 23 is wound and a cleaning blade 24 for removing the tower transferred to the cleaning belt 23. This belt 23 comes into slidable contact with the surface of the photoreceptor 1 and the residual toner after the transfer is triboelectrified to the polarity of the charge of the toner at the time of attaining development.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image carrier which is driven to rotate, a latent image forming means for forming an electrostatic latent image on the image carrier, and an electrostatic latent image formed by a toner charged to a predetermined polarity. A developing device for visualizing the image as a toner image, a transfer device for transferring the toner image formed on the surface of the image carrier to a transfer material, and a transfer residual toner remaining on the surface of the image carrier after transfer of the toner image The present invention relates to an image forming apparatus including a cleaning device that collects toner and cleans the surface of an image carrier, and a toner conveying unit that conveys the toner collected by the cleaning device back to the developing device.

[0002]

2. Description of the Related Art An image forming apparatus of the above-mentioned type configured as a copier, a printer, a facsimile, or a multifunction machine having at least two of these functions returns toner collected from the surface of an image carrier to a developing device. Since the toner can be reused in the developing device, the toner can be effectively used.

By the way, the transfer residual toner adhering to the surface of the image carrier after the transfer of the toner image is charged to a polarity opposite to a predetermined polarity of the toner at the time of development due to the influence of the transfer operation by the transfer device. Many things are included. When such a transfer residual toner is removed from the surface of the image carrier by a cleaning device, and is conveyed to the developing device as it is, and the toner is reused for visualizing the electrostatic latent image, the toner is In addition, since there is also included one charged with a polarity opposite to the predetermined polarity, the image quality of the formed toner image is deteriorated.

For this reason, it is necessary to sufficiently charge the toner recovered from the surface of the image carrier by the cleaning device so that the charged polarity thereof becomes the predetermined polarity, and then return the toner to the developing device. Requires a charging means for charging the toner, which increases the cost of the entire image forming apparatus. Alternatively, the toner from the cleaning device may be returned to the developing device, and then the toner may be frictionally charged to a predetermined polarity inside the developing device. Is required, and the increase in the size of the structure of the developing device and the increase in the cost cannot be avoided.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus of the type described at the outset in which the above-mentioned conventional disadvantages are eliminated by a simple structure.

[0006]

In order to achieve the above object, the present invention provides an image forming apparatus of the type described at the beginning, wherein the cleaning device is wound around a plurality of rollers and is rotated while being driven. A cleaning belt that is in pressure contact with the surface of the image carrier and frictionally charges the untransferred toner with the image carrier surface so as to align the untransferred toner with a predetermined polarity during development; In order to electrostatically transfer the toner to the surface of the cleaning belt, the first roller of the plurality of rollers that presses the cleaning belt against the surface of the image carrier has a polarity opposite to the predetermined polarity. A voltage applying means for applying a voltage; and a cleaning belt which is in contact with a surface of a cleaning belt portion wound around a second roller different from the first roller. We propose an image forming apparatus characterized by comprising a scraping member for scraping toner transferred to the surface of (claim 1).

In this case, in the image forming apparatus according to the first aspect, it is advantageous that the scraping member comprises a cleaning blade having a tip pressed against the surface of the cleaning belt (claim 2).

The image forming apparatus according to claim 1 or 2, wherein a surface portion of said first roller is provided with said second roller.
It is advantageous that the roller is made of a material that is more easily elastically deformed than the surface portion of the roller (claim 3).

Further, in the image forming apparatus according to the third aspect, it is advantageous that the surface of the first roller is made of an elastic material and the surface of the second roller is made of a rigid body. ).

Further, in the image forming apparatus according to any one of claims 1 to 4, at least a portion of the scraping member which comes into contact with the cleaning belt contacts the toner on the surface of the cleaning belt to remove the toner. It is advantageous if it is made of a material that is triboelectrically charged to the polarity (claim 5).

Furthermore, in the image forming apparatus according to any one of claims 1 to 5, it is advantageous that the scraping member is made of a conductive material and is grounded (claim 6).

[0012]

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 partial sectional view showing an example of an image forming apparatus according to the present invention. When a print button of an operation unit (not shown) is pressed, a drum-shaped photosensitive member 1 as an example of the configuration of the image carrier is driven to rotate clockwise in the figure by a driving device (not shown). It is initialized by receiving a charge removing action by a charge removing lamp 27 which is an example of the device.

Next, a charging roller 2 which is an example of a charging device
, The surface of the photoconductor 1 is uniformly charged to either positive or negative polarity. In this example, the charging roller 2 is connected to the power supply 3 and charges the surface of the photoconductor 1 uniformly to a negative (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
For example, it is charged to -850V. 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, the photosensitive member 1 is subjected to, for example, an optical writing scan by a light-modulated laser beam L, ie, selective exposure, by an exposure scanning device (not shown) in an exposure section 4. As a result, a predetermined electrostatic latent image is formed on the surface of the photoconductor 1. The portion of the photoconductor 1 irradiated with the laser beam L, that is, the surface potential of the electrostatic latent image is
For example, the potential is -150 V, and the surface potential of the portion not irradiated with the laser beam L, that is, the surface potential of the background portion of the electrostatic latent image is substantially -85.
It is maintained at 0V.

As described above, in this embodiment, the charging device composed of the charging roller 2 and the exposure scanning device constitute a latent image forming means for forming an electrostatic latent image on the image carrier composed of the photoreceptor 1. This electrostatic latent image is visualized as a toner image by a developing device 5 described below.

The developing device 5 of the present embodiment includes a developing roller 6 which is an example of a developer-carrying / transporting member that is disposed to face the photosensitive member 1.
And a pair of stirring paddles 7A and 7B, which are provided in a developing casing 8 of the developing device, respectively, and are rotatably supported by the casing 8. The developing roller 6 is supplied to the developing roller 6 by a power source
A voltage of 50 V is applied. A voltage having the same polarity as the charging polarity of the photoconductor 1 is applied to the developing roller 6.

Further, in the developing device 5 exemplified here, a two-component developer D having a toner and a carrier is used.
The developer D is accommodated in the developing casing 8 and is stirred by rotation of the stirring paddles 7A and 7B, and the toner has a predetermined polarity due to friction with the carrier, in this example, the charge polarity of the photoconductor 1. It is charged to the same polarity, that is, negative polarity. As described above, in the image forming apparatus of the present embodiment, the predetermined charge polarity of the toner during development is negative. A developing device using a one-component developer having no carrier may be employed.

The developing roller 6 is driven to rotate in the counterclockwise direction in the figure, and the developer carried on the peripheral surface thereof is conveyed in the rotating direction of the developing roller 6 and It is scraped off by the developer regulating member 9 which is opposed to with a predetermined gap. The developer whose transport amount is regulated by the developer regulating member 9 is conveyed toward a development area DA, which is a minute gap area between the development roller 6 and the photoconductor 1, and in the development area DA, The toner is electrostatically attracted to the electrostatic latent image on the photoreceptor 1, and is transferred and adhered to that portion. That is, the toner charged to the same negative polarity as the charge polarity of the photoconductor is transferred to the surface of the photoconductor irradiated with the laser beam, and the electrostatic latent image is visualized as a toner image. in this way,
In the image forming apparatus of this embodiment, a reversal developing method (negative / positive developing method) is employed.

FIG. 2 schematically shows each particle of the toner T adhered to the surface of the photoreceptor 1 in an enlarged scale, and the sign of "-" attached to each toner particle is as follows. This indicates that the toner particles are negatively charged.

A transfer roller 14, which is an example of a transfer device, is provided below the photosensitive member 1. Transfer roller 14
Rotates in the forward direction with respect to the rotation direction of the photoconductor 1, and a transfer paper 13, which is an example of a transfer material, is moved toward a transfer area TA between the transfer roller 14 and the photoconductor 1 facing the transfer roller 14. It is sent in the direction of the arrow P. Then, the transfer roller 14 is pressed against the surface of the photoconductor 1 via the transfer paper 13 sent to the transfer area TA.
With the function described above, the toner image formed on the photoconductor 1 is transferred onto the transfer paper 13. That is, a voltage having a positive (positive) polarity opposite to the charging polarity of the toner on the photoreceptor 1 (applied current is, for example, +10 μA) is applied to the transfer roller 14 by the power supply 15, whereby the toner on the photoreceptor surface is Is formed toward the transfer paper 13. Thus, the negative toner T on the photoreceptor 1 (FIG. 2)
Is electrostatically attracted to the transfer paper 13 side and adheres to the surface of the transfer paper 13.

The transfer paper 13 is fed from a paper feeding device (not shown), and when the registration roller pair 11 rotates, the leading end of the transfer paper 13 coincides with the leading end of the toner image on the surface of the photoconductor 1. Is fed to the photoconductor 1 while being guided by the guide 12. Further, a transfer device separated from the photoconductor 1, for example, a transfer device including a corona discharger can be used.

The transfer paper 13 onto which the toner image has been transferred is separated from the photoreceptor 1 by a separating device including a static elimination needle 16 to which a predetermined voltage is applied by a power supply 17, and a roller 18
Is transported in the direction of arrow Q by a transport belt 19 wound around another roller (not shown) and sent to a fixing device (not shown) where the toner image on the transfer paper 13 is fixed. Thus, the transfer paper 13 is discharged out of the image forming apparatus main body as copy paper.

On the other hand, the photosensitive member 1
The transfer residual toner remaining on the surface of the photoconductor 1 is conveyed to an area facing the cleaning device 20 by rotation of the photoconductor 1, that is, a cleaning area CA, where it is removed from the photoconductor surface by the cleaning device 20, and the photoconductor surface is removed. Be cleaned. Thereafter, the surface of the photoreceptor is subjected to a charge removing operation by a charge removing lamp 27. In this manner, a series of image forming processes is repeatedly executed.

[0025] Figure 2 is a toner transferred onto a transfer sheet 13, the respective toner particles of the residual toner remaining on the photosensitive member surface shown enlarged schematically, and reference numeral T _1, T in the respective toner ₂ is attached to each of them. The sign “+” or “−” attached to each toner particle indicates that the charge polarity is positive or negative, respectively. This also the toner T ₃ or T ₄ will be described later.

As will be described later in detail, a toner conveying means 28 is connected to the cleaning device 20 and the developing device 5, and the toner collected by the cleaning device 20 is returned to the developing device 5 by the toner conveying device 28. The toner is reused in the developing device 5.

As described above, the image forming apparatus according to the present embodiment includes an image carrier composed of the photoconductor 1 that is driven to rotate, a latent image forming means for forming an electrostatic latent image on the image carrier, and a predetermined image forming apparatus. A developing device 5 for visualizing the electrostatic latent image as a toner image with toner charged to a polarity, and a transfer roller 14 for transferring the toner image formed on the surface of the image carrier to a transfer material made of transfer paper 13 and more made transfer device, a discharging device consisting of neutralizing lamp 27, and to collect the residual toner T ₂ remaining on the surface of the image bearing member after the toner image transfer cleaning device 20 for cleaning the surface of the image bearing member, the cleaning And a toner conveying means 28 for conveying the toner collected by the device 20 back to the developing device 5. The charging device, the exposure unit 4, the developing device 5, the transfer device, the cleaning device 20, and the charge removing device are arranged in this order along the rotation direction of the image carrier.

Next, details of the cleaning device 20 will be described.

The cleaning device 20 includes a plurality of rollers,
In the illustrated example, the cleaning belt 23 is wound around two rollers 21 and 22 that are separated from each other, and is stretched.
The cleaning belt 23 is rotatably supported on each of the side walls before and after 9 and at least one of the rollers is rotationally driven, whereby the cleaning belt 23 is rotationally driven in a direction indicated by an arrow R in FIG. The cleaning belt 23 is made of an endless flexible belt made of a conductor or a medium resistor, and the surface of the cleaning belt 23 facing the photoconductor 1 is pressed against the surface of the photoconductor 1 by the roller 21 to cover almost the entire width of the photoconductor 1 in the axial direction. Over the entire surface, the surface of the cleaning belt 23 is in pressure contact.

Here, in FIG. 2, the toner T of the toner image on the photosensitive member from the developing area DA to the transfer area TA is shown.
Most of the toners are toners having a predetermined charge polarity (negative polarity in this example) of the toner during development. On the other hand, a voltage having a polarity (positive in this example) opposite to a predetermined charge polarity of the toner during development is applied to the transfer roller 14 at the time of transfer of the toner image. The toner transfer residual toner T ₂ remaining on the body 1 is
The toner is a mixture of a positive polarity toner and a negative polarity toner.
The untransferred toner T ₂ passes through the strong electric field in the transfer area TA, so that toners of both positive and negative polarities are mixed, and the toner T ₂ is transferred to the photoconductor 1.
Is transferred to the cleaning area CA where the cleaning belt 23 is in contact with the surface of the cleaning area CA.

Here, the rotating cleaning belt 23
There is a speed difference between the linear velocity on the surface of the photosensitive member 1 and the linear velocity on the surface of the photosensitive member 1. In the illustrated example, at the contact portion between the cleaning belt 23 and the photosensitive member 1, the two move in opposite directions. Rotates, and the surface of the cleaning belt 23 is
Rub on the surface of. At this time, the cleaning belt 23
Charge polarity of the residual toner T ₂ located between the photosensitive member 1 and the predetermined polarity of the toner at the time of development (negative polarity in this embodiment)
The transfer residual toner T ₂ is frictionally charged between the cleaning belt 23 and the photoconductor 1 so as to be aligned. Friction residual toner T ₂ is the surface of the cleaning belt 23, or friction with the photosensitive member surface, or is charged so as to be aligned in a predetermined polarity by friction with both surfaces. The material of the cleaning belt 23 is selected so as to obtain such an effect.

As described above, the cleaning belt 23
Is pressed against the surface of the image carrier composed of the photoreceptor 1 while being wound around the plurality of rollers 21 and 22 and driven to rotate,
In order to align the transfer residual toner T ₂ with a predetermined polarity at the time of development,
The residual toner T _2, form a for which frictional charging between the surface of the image bearing member.

Here, among the plurality of rollers that wind and support the cleaning belt 23, the cleaning belt 2
If the roller 21 that presses the roller 3 against the surface of the photoconductor is referred to as a first roller, and a roller 22 different from the first roller 21 is referred to as a second roller, at least a part of the first roller 21 Consists of a conductor. In this example, the core 21a of the first roller 21 made of a rigid body is made of a conductor, and a polarity opposite to the above-described predetermined polarity, that is, a positive voltage is applied to the core 21a by the power supply 26. . For example, a voltage of +200 V is applied to the first roller 21. As a result, the transfer residual toner T ₂ on the photoconductor 1, which has been aligned to the negative polarity by friction charging as described above, is electrostatically applied between the cleaning belt 23 and the photoconductor 1. An electric field in a pulling direction is formed, and the transfer residual toner T ₂ is transferred to the surface of the cleaning belt 23. The toner transferred to the surface of the cleaning belt 23 is carried on the surface of the cleaning belt 23 and is conveyed by the rotation of the cleaning belt 23. FIG. 2 schematically shows such toner particles in an enlarged scale.
And it is shown by reference numeral T _3.

On the other hand, the leading edge of a cleaning blade 24, which is an example of a scraping member, is pressed against the surface of the cleaning belt 23 wound around the second roller 22. The toner T ₃ held and conveyed is scraped off the surface of the cleaning belt by the cleaning blade 24 and falls to the lower portion of the cleaning case 29. A toner discharge screw 25, which is an example of a toner discharge device, is provided at a lower portion of the cleaning case. By the rotation of the screw 25, the toner dropped downward is discharged outside the cleaning case.

Since the scraping member composed of the cleaning blade 24 is in contact with the surface of the portion of the cleaning belt 23 supported by the second roller 22, the scraping member exerts a large force on the cleaning belt 23. The toner T ₃ on the cleaning belt 23 can be efficiently scraped off.

In this manner, the cleaning blade 2
No or little toner adheres to the surface of the cleaning belt 23 that has passed through No. 4.
The toner on the cleaning belt 23 does not retransfer to the surface of the photoconductor 1 again, and the toner does not accumulate on the surface of the cleaning belt 1 and the function of removing the transfer residual toner on the photoconductor 1 does not deteriorate. For this reason, it is possible to suppress the adhesion of the toner to the charging roller 2, effectively suppress the occurrence of background contamination of the toner image formed next on the surface of the photoconductor 1, and improve the image quality.

As described above, the cleaning device 2 of this embodiment
0 is the transfer residual toner T on the surface of the image carrier formed of the photoconductor 1
Of the plurality of rollers 21 and 22 around which the cleaning belt 23 is wound, the cleaning belt 23 is pressed against the surface of the image carrier composed of the photoreceptor 1 in order to electrostatically transfer ₂ to the surface of the cleaning belt 23. The first roller 21 includes a voltage application unit including a power supply 26 that applies a voltage having a polarity opposite to a predetermined polarity, which is the charging polarity of the toner during development. Moreover, the cleaning device 20 comes into contact with the surface of the cleaning belt portion wound around the second roller 22 different from the first roller 21 to scrape off the toner transferred to the surface of the cleaning belt 23. It has a scraping member.

With such a configuration, the operation of removing the transfer residual toner on the photosensitive member 1 can be performed by the surface portion of the cleaning belt on which the toner is not always adhered, and the cleaning failure of the surface of the photosensitive member 1 and the It is possible to prevent the toner from re-adhering to the surface of the photoreceptor, and it is ensured that the surface of the photoreceptor can be cleaned well.

As the scraping member, a fur brush or a cleaning roller which contacts the surface of the cleaning belt 23 can be used. In the illustrated example, the scraping member has its tip pressed against the surface of the cleaning belt 23. Cleaning blade 24,
The toner T ₃ adhering to the cleaning belt surface can be effectively removed, it is possible to effect the above-described in more reliable.

The toner dropped to the bottom of the cleaning case 29 is conveyed out of the cleaning case 29 by the toner discharge screw 25, and then returned to the developing device 5 by the above-mentioned toner conveying means 28, where the toner image is formed. At this time, the transfer residual toner T ₂ is subjected to a frictional charging action from the cleaning belt 23 and the photoreceptor 1 as described above, and its charging polarity is a predetermined polarity of the toner at the time of development, that is, Since the toner is arranged to have a negative polarity, the toner returned to the developing device 5 by the toner conveying means 28 also has a predetermined negative polarity. Therefore, a high quality toner image can be formed even if the toner is returned to the developing device 5 as it is and the toner is used immediately for forming a toner image. The toner returned to the developing device 5 is agitated by, for example, a special agitating means, and its charging polarity is adjusted to a negative polarity, and then sent to the developing device 5, or the toner returned to the developing device is frictionally charged for a long time. It is not necessary to use the toner for forming a toner image after the charging polarity is adjusted to a predetermined polarity. Therefore, the configuration of the entire image forming apparatus can be simplified, and a high-quality toner image can always be formed.

Further, the toner conveying means 28 shown in FIG.
A hollow duct member 30 is connected to each of the openings formed in the cleaning case 29 of the cleaning device 20 and the developing casing 8 of the developing device 5 at each end opening. A toner conveying member including a screw 31 is provided. The toner fed from the cleaning case 29 to the duct member 30
Due to the rotation of 1, the developer is conveyed in the duct member 30 and returned into the developing casing 8 of the developing device 5. Here, this toner is mixed with the developer D of the developing device 5 and used for visualizing the electrostatic latent image formed on the photoconductor 1 as described above.

By the way, the transfer residual toner T ₂ on the photosensitive member 1
When the toner is frictionally charged as described above, the charging efficiency is increased, and the charged toner is transferred to the cleaning belt 2.
In order to transfer the cleaning belt 23 to the surface of the photoconductor 1 efficiently, the width in the circumferential direction of the photoconductor 1 where the cleaning belt 23 contacts the surface of the photoconductor 1
That is, it is desirable to increase the nip width N (FIG. 2). To do so, it is necessary to lower the hardness of the surface portion of the first roller 21 that presses the cleaning belt 23 against the surface of the photoreceptor 1, and to form the first roller 21 from a soft material that is easily elastically deformed.

On the other hand, in order for the cleaning blade 24 to efficiently scrape off the toner T ₃ transferred onto the cleaning belt 23 without shortening the life of the cleaning belt 23, the second roller 2 is required.
It is desirable to increase the hardness of the surface portion of No. 2.

When the second roller 22 is made of a soft material, the cleaning blade 24 pressed against the surface of the second roller 22 via the cleaning belt 23 compresses the second roller 22 greatly. Since the cleaning belt 23 is deformed, the cleaning belt 23 is locally bent and deformed with a large curvature, and an excessive stress is generated therein, and the cleaning blade may be damaged at an early stage.
If the second roller 22 is soft, the cleaning blade 24 scrapes off the toner T ₃ attached to the surface of the cleaning belt.
4 needs to be pressed against the surface of the cleaning belt 23 with a large force, and the cleaning belt 23 is more likely to be damaged. Thus, the cleaning belt 23
In order to efficiently scrape off the toner T ₃ without shortening the life of the second roller 22, it is advantageous to increase the hardness of the surface portion of the second roller 22 pressed against the cleaning blade 24 via the cleaning belt 23.

In view of the above, in the illustrated cleaning device 20, the surface of the first roller 21 is made of a soft material that is more elastically deformable than the surface of the second roller 22.

For example, the outer layer 21b integrally laminated on the outer peripheral surface of the core material 21a made of the rigid body of the first roller 21 is
A core member 22a made of an elastic material such as rubber, soft synthetic resin or its foam, and made of a rigid body of the second roller 22;
The outer layer 22b integrally formed on the outer side of the base member is formed of a rigid body such as a metal or a hard synthetic resin. The surface of the first roller 21 is made of an elastic material, and the surface of the second roller 22 is made of a rigid body.

According to the above-described structure, the transfer residual toner T ₂ on the photoreceptor 1 can be efficiently frictionally charged and the toner can be efficiently transferred to the surface of the cleaning belt 23 in order to make the charge polarity uniform. Further, the toner can be efficiently scraped off from the cleaning belt 23 by the cleaning blade 24 while preventing the cleaning belt 23 from being damaged.

In order to increase the nip width N of the cleaning belt 23 pressed against the photosensitive member 1, it is effective to increase the outer diameter of the first roller 21. that time,
Since the outer diameter of the second roller 22 does not need to be particularly large, even if the outer diameter of the first roller 21 is increased, the problem that the overall structure of the cleaning device 20 becomes excessively large can be prevented. . By setting the outer diameter of the first roller 21 to be larger than the outer diameter of the second roller 22, the nip width N of the cleaning belt 23 pressed against the photoconductor 1 is increased, and the size of the cleaning device 20 is increased. You can stop it.

There is also a known cleaning device in which the transfer residual toner on the photosensitive member is removed by a cleaning roller pressed against the surface of the photosensitive member, and the toner adhered to the cleaning roller surface is scraped by a cleaning blade pressed against the surface. According to this configuration, in order to increase the nip width of the cleaning roller against the photosensitive member,
If the surface portion of the cleaning roller is made of a soft material, the cleaning blade may bite into the surface of the cleaning roller and damage the cleaning roller early. Conversely, if the surface of the cleaning roller is made of a hard material in order to prevent the cleaning roller from being damaged, then the pressure nip width of the cleaning roller against the photoreceptor is reduced, and the friction of the transfer residual toner is reduced. The charging efficiency and its cleaning performance are reduced. As described above, when the cleaning roller is used, it is not possible to simultaneously satisfy the requirement of improving the frictional charging efficiency and the cleaning property of the transfer residual toner and the requirement of improving the scraping property of the toner on the cleaning roller.

In contrast, the illustrated cleaning device 2
Reference numeral 0 denotes a configuration in which the cleaning belt 23 is wound around the first and second rollers 21 and 22.
Thus, the hardness and outer diameter can be set to desired sizes, and the above two requirements can be satisfied simultaneously without any trouble.

As described above, according to the cleaning device 20 shown in FIG. 1, the transfer residual toner T ₂ on the photosensitive member 1 is efficiently adjusted to a predetermined polarity, and the toner T ₃ on the cleaning belt 23 is efficiently removed. It can be well scraped off from the cleaning belt 23, but when such an amount of residual toner T ₂ which is attached to the photosensitive member surface is large, it is impossible to align the charging polarity of the toner T ₂ 100% Further, the toner T ₃ attached to the surface of the cleaning belt 23 is
% It may not be possible to scrape.

FIG. 3 schematically shows the state at this time. In this case, the toner T ₃ transferred to the surface of the cleaning belt 23 includes the toner charged to the positive polarity opposite to the predetermined polarity. Also partially mixed. Also, a small amount of T _{4 that} has not been scraped off by the cleaning blade 24 and has passed through the cleaning blade 24 adheres to the surface of the cleaning belt 23. The toner T ₄ comes into contact with the surface of the photoreceptor 1 again by the rotation of the cleaning belt 23.
_Assuming that the toner ₄ is charged to a positive polarity opposite to a predetermined polarity (negative in this example) at the time of development, the toner T is charged by the action of the above-described electric field formed between the photoreceptor 1 and the cleaning belt 23. No. ₄ is transferred to the surface of the photoreceptor 1 again, thereby causing a problem that a cleaning failure occurs and the toner adheres to the charging roller 2.

Therefore, in this embodiment, at least a portion of the scraping member made of the cleaning blade 24 which comes into contact with the surface of the cleaning belt 23 comes into contact with the toner T ₃ on the surface of the cleaning belt 23 to develop the toner T ₃ . It is made of a material that is frictionally charged to a predetermined polarity that is the charging polarity of the toner at the time, that is, negative polarity. For example, the cleaning blade 24 is made of silicone rubber or urethane rubber, and the cleaning blade 24 is pressed against the surface of the cleaning belt 23 to mechanically scrape off the toner T ₃ attached to the surface.
Than it is frictionally charged the toner T ₃ to a predetermined negative polarity.

In this way, the cleaning belt 2
Also in the toner T ₃ on 3 have charged toner to the positive polarity is present, the toner is charged to a predetermined negative polarity due to friction with the cleaning blade 24. Therefore, even if the toner T ₄ which passes through the cleaning blade 24 is present without scraped by the cleaning blade 24, the charging polarity of the toner, has a predetermined polarity, ie negative polarity. For this reason, even if the toner T ₄ that has passed through the cleaning blade 24 comes into contact with the photoconductor 1 again, the toner T ₄ does not transfer to the photoconductor 1 due to the electric field described above, but passes through the cleaning area CA and is cleaned again. It is conveyed to the site of the blade 24.

In this way, the transfer residual toner is transferred to the cleaning belt 23 without being frictionally charged to a predetermined polarity between the cleaning belt 23 and the photosensitive member 1, and the toner passes through the cleaning blade 24. Even if it is done, it can be prevented from transferring to the photoconductor 1 again, and it is possible to prevent the cleaning property of the photoconductor 1 from being deteriorated.

The scraping member composed of the cleaning blade 24 can be made of either an insulating material or a conductive material. However, if the scraping member is made of an insulating material, the cleaning blade 24 is attached to the cleaning belt 23 and the toner. Since it is in contact with T ₃ , electric charge accumulates on the cleaning blade 24 due to the friction,
Due to the charge-up, the toner may electrostatically adhere to the cleaning blade 24, and eventually, the adhered toner may adhere to the cleaning blade 24.
With such toner is adhered to the cleaning blade 24, the cleaning blade 24 scrapes function of toner by drops, or the ability to frictionally charge the toner T ₃ on the cleaning belt 23 is reduced. this is,
The same applies when the scraping member is made of something other than the cleaning blade.

Therefore, in the cleaning device 20 of this embodiment, the scraping member composed of the cleaning blade 24 is made of a conductive material, and the scraping member is grounded as shown in FIG. For this reason, it is possible to prevent charges from accumulating on the cleaning blade 24 and accumulating the charge.
The toner can be effectively prevented from sticking to the toner. Accordingly, the cleaning blade 24 can efficiently remove the toner T ₃ on the cleaning belt 23 and efficiently frictionally charge the toner T ₃ to a predetermined polarity. 1 can be efficiently prevented from re-adhering to the toner.

The present invention can be applied to an image forming apparatus using an endless belt as well as a drum as an image carrier. Also, an intermediate transfer member is used as a transfer material, and the image carrier is used as an intermediate member. The present invention is also applicable to an image forming apparatus of a type in which a toner image is transferred to a transfer body and then transferred to a final transfer material such as transfer paper. Further, according to the present invention, after the image carrier is charged by the charging device, an electrostatic latent image is formed by a portion not irradiated with light at the time of image exposure on the surface, and the latent image is charged to a polarity opposite to the polarity of the latent image charge. The present invention is also applicable to an image forming apparatus of a so-called positive / positive developing system in which toner is adhered to the electrostatic latent image to perform development.

[0059]

According to the image forming apparatus of the present invention, while the transfer residual toner adhered to the surface of the image carrier is frictionally charged by the cleaning belt stretched over the plurality of rollers, the cleaning belt is The toner is transferred electrostatically, and the transferred toner is scraped off from the surface of the cleaning belt by the scraping member. Therefore, it is possible to always clean the surface of the image carrier by the surface of the cleaning blade to which no toner is attached. Further, it is possible to effectively suppress the occurrence of toner reattachment from the cleaning blade to the image carrier due to poor cleaning of the image carrier.

Further, when the toner is transferred from the image carrier to the cleaning belt, the charge polarity of the toner is
Since the charge polarity of the toner at the time of development is adjusted, even if the toner collected by the cleaning device is returned to the developing device as it is by the toner conveying means, it can be used immediately for forming a toner image. Thus, the configuration of the entire image forming apparatus can be simplified, and the cost can be reduced.

According to the image forming apparatus of the second aspect,
Since the scraping member is formed of the cleaning blade, the toner on the surface of the cleaning belt can be efficiently removed, and the above-described effect can be further ensured.

According to the image forming apparatus of the third and fourth aspects, the transfer residual toner on the surface of the image carrier can be more efficiently removed, and the toner on the surface of the cleaning belt can be scraped more efficiently. .

According to the image forming apparatus of the fifth aspect,
Even if the transfer residual toner between the cleaning belt and the image bearing member cannot be adjusted to a predetermined polarity, and a portion of the toner transferred to the cleaning belt may pass through the scraping member, the toner may not be transferred. It is possible to prevent the toner from re-adhering to the surface of the image carrier, and to prevent the cleaning property of the image carrier from lowering.

According to the image forming apparatus of the sixth aspect,
Since it is possible to prevent charge from being accumulated in the scraping member and thereby prevent toner from sticking to the scraping member, it is possible to effectively prevent the toner scraping function of the scraping member from being reduced.

[Brief description of the drawings]

FIG. 1 is a partial sectional explanatory view of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram schematically showing the state of toner adhered to a photoconductor, transfer paper, and a cleaning blade, and indicating the polarity of the charged toner by + and-symbols.

FIG. 3 is an explanatory view similar to FIG. 2, schematically showing a state in which a part of the toner transferred to the cleaning belt remains positive, and a part of the toner passes through a cleaning blade. It is.

[Explanation of symbols]

5 developing device 20 the cleaning device 21 roller 22 roller 23 cleaning belt 24 cleaning blade 28 conveying means T ₂ toner T ₃ Toner

Claims (6)

[Claims] 1. An image carrier which is driven to rotate, a latent image forming means for forming an electrostatic latent image on the image carrier, and the electrostatic latent image can be converted into a toner image by toner charged to a predetermined polarity. A developing device for visualizing the image, a transfer device for transferring the toner image formed on the surface of the image carrier to a transfer material, and a transfer device for collecting a transfer residual toner remaining on the surface of the image carrier after transfer of the toner image to carry the image. An image forming apparatus comprising: a cleaning device that cleans a body surface; and a toner conveying unit that conveys the toner collected by the cleaning device back to the developing device, wherein the cleaning device is wound around a plurality of rollers. A cleaning device that is pressed against the surface of the image carrier while being rotated, and frictionally charges the remaining transfer toner with the surface of the image carrier so that the remaining transfer toner has a predetermined polarity during development. A belt and a first roller that presses the cleaning belt against the image carrier surface of the plurality of rollers to electrostatically transfer residual toner on the surface of the image carrier to the surface of the cleaning belt; Voltage applying means for applying a voltage having a polarity opposite to the predetermined polarity,
And a scraping member that abuts on a surface of a cleaning belt portion wound around a second roller different from the first roller and scrapes toner transferred to the surface of the cleaning belt. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the scraping member comprises a cleaning blade having a tip pressed against a surface of the cleaning belt. 3. The image forming apparatus according to claim 1, wherein a surface portion of the first roller is made of a material that is more easily elastically deformed than a surface portion of the second roller. 4. The image forming apparatus according to claim 3, wherein a surface portion of the first roller is made of an elastic material, and a surface portion of the second roller is made of a rigid body. 5. The cleaning device according to claim 1, wherein at least a portion of the scraping member that comes into contact with the cleaning belt is made of a material that contacts the toner on the surface of the cleaning belt and frictionally charges the toner to the predetermined polarity. 5. The image forming apparatus according to any one of 4. 6. The image forming apparatus according to claim 1, wherein said scraping member is made of a conductive material and is grounded.