JPH112946A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To strengthen sticking force with the edge part of an electrical pattern and to excellently stick recovered toner onto a photoreceptor drum by forming the electrical pattern on the photoreceptor drum, at the time of discharging the toner recovered by a cleaning roller onto the photoreceptor drum again. SOLUTION: The toner remaining after a transfer, stuck onto the photoreceptor drum by reversal development is temporarily recovered to the cleaning roller 110, in the contact part with the photoreceptor drum and then, discharged onto the photoreceptor drum again. In such a case, at the time of discharging the toner, a light destaticizer 19 is used as an exposure unit, for the nonimage forming region between image forming regions after a region where the toner remains after the transfer passes through, to expose the nonimage forming region charged on the photoreceptor drum and form the electrical pattern for a mesh like latent image. Then, in the nonimage forming region, a cleaning bias E1 for the cleaning roller is switched to a toner discharge bias V2 having the same polarity as that of the toner, to stick the recovered toner onto the photoreceptor drum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., which forms an image by arranging a charging means, an image exposing means, a developing means and the like around an image forming body. The present invention relates to an image forming apparatus of the type.

[0002]

2. Description of the Related Art Conventionally, as one type of an electrophotographic image forming apparatus, a charging means, an image exposing means and a developing means are arranged around an image forming body, and the charging of the image forming body by the charging means and image exposure are performed. Image forming apparatus for forming a latent image on an image forming body by means of an image exposing means, forming an image of the latent image by contact reversal development by a developing means, and then transferring the image to a transfer material by a transferring means Is used.

On the other hand, in order to make effective use of the toner, after the image is formed, the transfer residual toner remaining on the image forming body is cleaned by a cleaning means, and the cleaning toner is conveyed to a developing means using a screw pipe or the like. A toner recycling method for reuse in the process is generally used. However, since the toner recycling method of transporting the cleaning toner using the screw pipe has a complicated mechanism, a roller-shaped member is used as the cleaning means, and a bias is applied to transfer the residual toner of the image portion on the image carrier. Is temporarily recovered (moved) from the image forming body to the roller-shaped cleaning means, and a bias having a further opposite polarity is applied to the non-image portion to discharge (adhere) the toner on the cleaning means to the image forming body again and to the developing means. Carry,
Japanese Patent Application Laid-Open No. 8-166750 discloses a method in which toner on an image forming body is collected into a developing unit by a developing unit and reused.
It is proposed in JP-A-8-152832, JP-A-8-6454, JP-A-6-51672 and the like.

On the other hand, a transfer means for transferring a toner image on an image forming body by applying a bias to a roller-shaped member is used.

[0005]

However, in the cleaning means according to the above proposal, the residual toner on the image forming body has a strong adhesive force to the transfer residual toner at the edge of the latent image of the image on the image forming body. Recovery of the transfer residual toner is not performed well, and toner adhesion to the roller-shaped cleaning means is not uniform in some places, and thick and thin areas of the adhesion layer occur, resulting in a variation in the collection ability. There is a problem in that the recovery ability of the cleaning means in a place where the adhesion layer is thick is reduced.

The present invention solves the above-mentioned problems, and forms an image in which the transfer residual toner on the image forming body is collected by the cleaning means and the collected toner is discharged to the image forming body by the cleaning means. It is intended to provide a device.

[0007] Further, there is a problem that the toner adhered to the roller-shaped transfer means adheres to the transfer material, thereby causing image contamination.

[0008] The present invention further improves the above problems,
It is another object of the present invention to provide an image forming apparatus in which toner adhered to a roller-shaped transfer unit is satisfactorily discharged onto an image forming body and a transfer material is not stained.

Further, there arises a problem that the toner (adhered toner) discharged from the cleaning means to the image forming body has a strong adhesion to the image forming body, and the toner cannot be collected well from the image forming body by the developing means. .

Another object of the present invention is to provide an image forming apparatus in which the above-mentioned problems are solved and the toner adhered to the image forming body discharged from the cleaning means is collected by the developing means. I do.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus in which a transfer residual toner adhered to a rotating image forming body by reversal development is brought into contact with the image forming body and the image forming portion is brought into contact with the image forming body. In an image forming apparatus that collects the toner once on a roller-shaped cleaning unit that rotates in the same direction as the body and then discharges the toner onto the image forming body again, an electrical pattern is formed on the image forming body when the toner is discharged. (First invention).

Further, the object of the present invention is to provide an image forming apparatus in which toner adhered to a roller-like transfer means which is in contact with the image forming body and rotates in the same direction as the image forming body at a contact portion with the image forming body. The second aspect of the present invention is achieved by an image forming apparatus wherein an electric pattern is formed on the image forming body, and the toner adhered to a roller-like transfer unit is discharged. .

It is another object of the present invention to provide an image forming apparatus in which a transfer residual toner adhered to a rotating image forming body by reversal development is brought into contact with the image forming body in the same direction as the image forming body at a contact portion with the image forming body. After the toner is once collected by a toner-collecting bias having a polarity different from that of the toner in the roller-type cleaning means that rotates, the toner on the cleaning means is discharged onto the image forming member again by the toner discharge bias having the same polarity as the toner between the images. In the forming apparatus, when the toner discharged onto the image forming body is recharged by a charging unit that charges the image forming body and then collected by a developing unit that develops the image forming body, a developing sleeve of the developing unit is used. Collecting the toner on the image forming body to the developing unit by lowering the value of the developing collection bias applied to the developing unit from the value of the developing bias at the time of developing the image forming body. It is achieved by an image forming apparatus, wherein (third invention).

[0014]

Embodiments of the present invention will be described below. The description of the present application does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope.

FIG. 1 shows the configuration and functions of an image forming process and each mechanism of an image forming apparatus according to an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a cross-sectional configuration diagram of a laser printer showing an embodiment of the image forming apparatus of the present invention, FIG. 2 is an enlarged view of a main part of FIG. 1, and FIG. FIG. 4 is a diagram showing a pattern, FIG. 4 is a diagram showing adhesion of discharged toner to an electric pattern, FIG. 5 is an operation timing chart of bias application to a transfer unit and a cleaning unit, and FIG. FIG. 4 is a diagram illustrating a method of collecting transfer residual toner to a developing unit.

According to FIG. 1 or FIG. 2, a photosensitive drum 10 as an image forming body has a peripheral speed (linear speed) of 150 m, for example.
At a speed of m / sec, it is driven and rotated in the direction indicated by the arrow in FIG. 1 and is uniformly distributed by corona discharge of the same polarity as toner (minus polarity in this embodiment) on the peripheral surface by a scorotron charger 11 as a corona charger. After being charged, image exposure based on an image signal is performed by an exposure optical system 12 as image exposure means.

The exposure optical system 12 rotationally scans a laser beam emitted from a laser light source (not shown) by a rotary polygon mirror 12b to form a latent image on the photosensitive drum 10 via an fθ lens 12c, a reflection mirror 12d, and the like. You.

A developing unit 13 is provided as developing means for developing with a one-component developer or a two-component developer composed of toner or toner and carrier, and develops a latent image formed on the photosensitive drum 10. Is performed by the developing sleeve 13a that carries the developer. The development is performed between the developing sleeve 13a and the photosensitive drum 10 between the developing sleeve 13a and the photosensitive drum 10 by the developing unit bias E3 applied between the developing sleeve 13a and the toner having the same polarity (minus polarity in the present embodiment) as −400 to −−. This is performed by contact reversal development to which a development bias V5 of 600 V is applied. As the toner used for the developer, a spherical toner having high recovery efficiency of the transfer residual toner described later is preferably used.

The recording paper P, which is a transfer material, is sent out by a feed roller 15a from a paper feed cassette 15 which is a transfer material storage means, is fed by a feed roller 15b, and is conveyed to a timing roller 15c.

The recording paper P is provided in contact with the photosensitive drum 10 in synchronization with the toner image formed on the photosensitive drum 10 by driving the timing roller 15c, and is provided at the contact portion. Photoreceptor drum 1 of transfer roller 14a as transfer means rotating in the same direction as
The toner is fed to a nip portion (transfer area) 14b formed between the toner and the toner, and has a reverse polarity (plus polarity in this embodiment) of 300 to 1500 V with respect to the toner indicated by the solid line in FIG. The negative polarity toner image on the peripheral surface of the photosensitive drum 10 is collectively transferred onto the recording paper P by the transfer roller 14a to which the transfer bias V3 is applied.

The transfer bias V3 is applied to the transfer roller 14a by the transfer roller bias E2 so that the toner image on the photosensitive drum 10 is completely transferred to the image forming area as shown in FIG. It is set larger than the formation area.

When a corona transfer device directly facing the image forming member is used as the transfer means, the toner polarity is inverted by corona discharge with respect to the toner when there is no transfer material or the toner outside the transfer material even if there is a transfer material. (The positive polarity in the present embodiment), and the transfer residue on the image forming body by the cleaning unit to which the toner collecting bias V1 having the opposite polarity (positive polarity in the present embodiment) to the toner described later is applied. It makes it difficult to collect toner. In the above-described transfer roller or transfer belt, the transfer roller or the transfer belt is preferable because the toner outside the transfer material is transferred to the transfer unit side with the negative polarity without reversing the polarity, and the load on the cleaning unit is reduced. Used.

The recording paper P after the transfer is separated from the photosensitive drum 10 by a curvature, and is conveyed by a conveyor belt 16 to a heating fixing roller 17 having a heater inside at least one of the rollers.
a and a pressure roller 17b, the toner is conveyed to the fixing device 17 and heat and pressure are applied between the heating fixing roller 17a and the pressure roller 17b to fix the toner adhered on the recording paper P. The sheet is discharged to the outside of the apparatus by a discharge roller 18.

The toner remaining in the untransferred toner area on the peripheral surface of the photoreceptor drum 10 after the transfer of the image forming area where the toner image is formed is, for example, an optical charge removing device 19 as a charge removing means using an LED. Accordingly, the latent image at the edge portion of the image having particularly strong toner adhesion is smoothed by uniform light elimination, and the potential level of the photosensitive drum 10 is reduced to substantially zero over the entire surface. FIG. 2 shows the cleaning bias E1 for the cleaning roller.
A toner collection bias V1 of 300 to 1500 V having a polarity opposite to that of the toner indicated by the solid line (positive polarity in the present embodiment) is applied, and comes into contact with the photosensitive drum 10 in the same direction as the photosensitive drum 10 at the contact portion. The toner is collected on the outer peripheral surface of the cleaning roller 110 by the cleaning roller 110 as a rotating cleaning unit. As described above, in order to completely recover the transfer residual toner in the transfer residual toner region, the toner recovery bias application region is formed slightly longer on both sides than the image forming region as shown in FIG.

The potential level of the photosensitive drum 10 is reduced to substantially zero by the light neutralization of the light neutralizer 19, so that the electrostatic attraction of the transfer residual toner to the photosensitive drum 10 is weakened, and the transfer residual toner is easily moved. In addition, the transfer to the cleaning roller 110 to which the toner collection bias V1 of the opposite polarity (positive polarity) to the transfer residual toner is applied is facilitated, and the collection efficiency is improved.

Further, a speed difference is provided between the rotation speed of the cleaning roller 110 and the rotation speed of the photosensitive drum 10 so that the cleaning roller 110 is deviated from the photosensitive drum 10 and is forcibly driven to rotate. The adhesive force is mechanically weakened to facilitate the movement of the toner. The speed difference of the cleaning roller 110 with respect to the photosensitive drum 10 is preferably 1 to 10%, and if it is less than 1%, the effect of weakening the adhesive force is not sufficient, and if it exceeds 10%, the speed difference is too large and toner is scattered. Also, toner filming on the image forming body easily occurs, which is not preferable. When the rotation speed of the cleaning roller 110 is higher than the rotation speed of the photosensitive drum 10 by 1 to 10%, the cleaning roller 110 bites into the photosensitive drum 10 to remove toner, and the toner on the photosensitive drum 10 is removed. Preferred without spillage.

The collected toner adhered to the cleaning roller 110 is made uniform by a toner leveling plate 111 having elasticity as a toner leveling member attached to a cleaning casing 112 of the cleaning device 100. As the toner leveling member, a friction-charging member that does not change the toner polarity is selected. Toner leveling plate 1
By making the toner layer uniform by 11, the toner is efficiently collected by the cleaning roller 110. When the toner locally adheres to the cleaning roller 110, a bias is not sufficiently applied due to the charge of the toner, and the frictional force with the image forming body also decreases. For this reason, it is desirable to make the toner layer uniform. Further, it also facilitates the discharge of toner from the cleaning roller 110 described below to the photosensitive drum 10. As the toner leveling plate 111, a resin film, Mylar, or the like is used.

Next, for the non-image forming area between the image forming areas after passing through the transfer residual toner area, the charged non-image forming area on the photosensitive drum 10 is used by using the light neutralizer 19 as an exposure device. To form an electric pattern EP of a mesh-like latent image shown in FIG. Reticulated electrical pattern E
In the non-image forming area where the latent image of P is formed, the cleaning bias E1 for the cleaning roller is applied with a voltage of -300 to -1500V having the same polarity (minus polarity in the present embodiment) as the toner indicated by the dotted line in FIG. The toner is discharged (adhered) to the photosensitive drum 10 by switching to the toner discharge bias V2. As shown in FIG. 4, the toner on the cleaning roller 110 is more strongly attracted to the edge portion of the latent image of the reticulated electric pattern EP by the stronger electric field than the portion where the charge is removed by the exposure. 1
From 10, good discharge (adhesion) to the photosensitive drum 10 is performed. This mesh preferably has a period L of 1 to 10 mm and a width L1 of the non-exposed portion of about 0.1 to 3.0 mm, which is less than half the period L. At this time, as shown in FIG. 5, the toner discharge bias application area is between the toner recovery bias application areas and is set slightly shorter than the image formation area (non-image formation area). Is set shorter than the toner discharge bias application area,
All the collected toner on the cleaning roller 110 is discharged (adhered) onto the photosensitive drum 10.

As in the case of discharging the toner by the cleaning roller 110, the charged non-image forming area on the photosensitive drum 10 is exposed by a pre-transfer exposure device 14c using, for example, an LED, and the mesh described with reference to FIG. The transfer roller bias E2 is set to the same polarity as the toner indicated by the dotted line in FIG. 2 in the non-image forming area where the electric pattern EP of the latent image is formed and the latent image of the electric pattern EP is formed. −300 to − of (in the present embodiment, negative polarity)
Switching to the transfer toner discharge bias V4 to which 1500 V is applied discharges (adheres) the toner on the transfer roller 14a onto the photosensitive drum 10. As shown in FIG. 4, the toner on the transfer roller 14a is more strongly attracted to the edge by the strong electric field at the edge of the latent image of the reticulated electric pattern EP, so that the toner is transferred from the transfer roller 14a to the photosensitive drum 10. Good discharge (adhesion) is performed.

Further, the negative polarity toner on the transfer roller 14a to which the transfer toner discharge bias V4 is applied is repelled by the negative polarity transfer toner discharge bias V4 and moves onto the photosensitive drum 10, thereby causing the transfer roller 14a to move. Will be cleaned. At this time, as shown in FIG. 5, the transfer toner discharge bias application area is between the toner recovery bias application areas and is set slightly shorter than the image formation area (non-image formation area). (Length for one round) is set shorter than the toner discharge bias application area so that all the toner adhering to the transfer roller 14a is discharged (adhered) to the photosensitive drum 10.

Reference numeral 113 denotes a cleaning casing which has a leading end on the photosensitive drum 10 close to the photosensitive drum 10 for preventing toner spillage from the cleaning device 100.
12 is a film member provided. Film member 1
As 13, urethane rubber, a brush or the like is used.

As shown in FIG. 6A, a toner layer is formed on the photosensitive drum 10 whose potential level is substantially zero. The attached toner is attached to the photosensitive drum 10 with a negative polarity by the toner discharge bias V2, and the potential level of the toner layer is approximately -50V.

Subsequently, the surface potential of the photosensitive drum 10 is applied to the photosensitive drum 10 to which the discharged toner is attached by a DC voltage of the same polarity as the toner (minus polarity in this embodiment) by a scorotron charger 11 as charging means. But-
When the recharging is performed at 750 V, as shown in FIG. 6B, the potential level of the surface of the photosensitive drum 10 is charged to, for example, about -650 V, and the potential level of the toner layer adhered becomes Due to the recharging, the voltage slightly increases to about -100V.

In this state, the discharged toner which has been recharged and adhered to the photosensitive drum 10 reaches the developing device 13, and the developing device bias E3 applied to the developing device 13 described with reference to FIG.
Is switched from a developing bias V5 of -400 to -600 V to a developing recovery bias V6 shown by a dotted line in FIG.
As shown in (c) of FIG.
The developing bias V5 of 00V is lower than the developing bias V5 and is rubbed with the developer of the developing sleeve 13a of the developing device 13 to which a developing recovery bias V6 of the same polarity as the toner (minus polarity in this embodiment), for example, -200V is applied. Then, the photosensitive drum 10 is cleaned (collected) from the photosensitive drum 10 to the developing device 13. At this time, even if all the toner is not collected, the toner is not used for the next image forming area, so that there is no problem in the image. Further, the value of the development recovery bias V6 is set to a value of -200 to -300V lower than the value of the development bias V5 used for reversal development at the time of image formation by 200 to 400V (both have negative polarities). By doing so, it becomes possible to satisfactorily attract the toner to the developing sleeve 13a. Further, the value of the development recovery bias V6 is lower by 300 to 500 V (both have negative polarities) than the potential level of the surface of the photosensitive drum 10 due to recharging of about -650 V, -200 to -300 V.
To the developing sleeve 13a.
It becomes possible to be attracted favorably.

The photosensitive drum 10 from which the residual toner has been removed by the cleaning device 100, the scorotron charger 11 and the developing device 13 is uniformly charged again by the scorotron charger 11, and enters the next image forming cycle.

Cleaning roller 1 in the above description
In the toner collection and toner discharge by the photoreceptor 10, the photoconductor potential has irregularities unless there is a light neutralization by the light neutralizer 19 as the neutralization means or the electric pattern EP. Adhesion is not reduced. Therefore, the photoreceptor is smoothed to make the potential of the photoreceptor smooth to enable uniform and high recovery, or the electric pattern EP is used to improve the adhesion to enable high discharge power. This facilitates toner collection by the developing means. Further, since the toner is attracted to the photosensitive drum 10 by electrostatic electric force and does not stain the charging unit at the time of recharging, it is possible to use a charging roller as the charging unit. Also,
The toner discharged by the cleaning means is transferred to the photosensitive drum 10
As a developing method, a two-component magnetic brush development, a one-component magnetic brush development, or a one-component non-magnetic development is used so that the toner can be collected in the developing device 13 more easily. Further, the toner used for the developer is preferably a spherical polymerized toner (spherical toner) capable of high image quality. Since the toner is spherical, the mechanical adhesion to the photosensitive drum 10 is small, and the electrostatic adhesion of the particles is also small. Adhesion is small, and it has higher recovery efficiency and higher discharge efficiency as compared with pulverized toner (irregular toner). Conventionally, when cleaning with a general rubber blade, it is possible to use a spherical toner that is more likely to be rubbed off than a blade.

The structure of the cleaning means will be described with reference to FIGS. 7, 8 and 1. FIG. 7 is a side sectional view showing a first example of the structure of the cleaning means, FIG. 8 is a sectional view showing second and third examples of the structure of the cleaning means, and FIG. FIG. 8B is a cross-sectional view showing a second example of the structure of the cleaning means, and FIG. 8B is a cross-sectional view showing a third example of the structure of the cleaning means.

In the above-described embodiment, it is important for the cleaning roller 110 as a cleaning means that the mechanical characteristics of an appropriate contact pressure with the image forming body and the electrical characteristics of giving a sufficient amount of charge to the transfer residual toner are important. Become.

As mechanical characteristics, the cleaning roller 1
In the relationship between the contact pressure with the image forming body of No. 10 and the collection efficiency,
In general, as the contact pressure increases, the collection efficiency increases and the collection variation also decreases. However, when the contact pressure becomes excessive, partial cleaning failure occurs in the image forming area or at the end. This phenomenon is due to the fact that the toner layer is pressed against the surface of the photoreceptor drum 10 and the untransferred toner aggregates, thereby increasing the mechanical adhesion. In particular, this is likely to occur when the pressure of the cleaning roller 110 is too high, when the toner layer is thick, or when the toner fluidity is poor. For this reason, the cleaning roller 110 serving as a cleaning unit is used.
Therefore, a roller having soft elasticity that does not cause agglomeration of the transfer residual toner is required, and a roller having a configuration in which the electrical and mechanical characteristics shown in FIG. 110a
Is a metal shaft, 110b is a conductive sponge, 1
The cleaning roller 110 is constituted by a sponge rubber 10c, a conductive layer 110d, and a resistance layer 110e covering the outer peripheral surface of the conductive layer 110d.

Further, since the cleaning loss is caused by a strong mechanical adhesive force, as described above, a speed difference is provided between the cleaning roller 110 and the photosensitive drum 10 to shift the toner in the moving direction of the photosensitive drum 10. As a result, the mechanical adhesion between the photosensitive drum 10 and the transfer residual toner is weakened, and cleaning omission is reduced. For example, when the speed of the photoconductor drum 10 is 150 mm / sec, if a speed difference of about several percent is provided, cleaning omission can be greatly reduced, and when the speed of the photoconductor drum 10 is 80 to 350 mm / sec,
As mentioned above, a speed difference of 1-10% is preferred. Also,
It is preferable that the speed difference between the cleaning roller 110 and the photosensitive drum 10 is faster.

The cleaning roller 11 has electrical characteristics.
It is important to select a roller resistance of zero. If the roller resistance is too low, the photosensitive drum 10 and the cleaning roller 110
Abnormal discharge may occur in the contact portion with the photoconductor drum 10, and the concentration of current may cause the destruction of the photosensitive drum 10. If the roller resistance is low, the collection efficiency is significantly reduced in a high-temperature, high-humidity environment. This is because a low resistance roller tends to inject a reverse charge from the roller into the toner, and reduces the toner charge amount to weaken the electrostatic force. Conversely, in a high-resistance roller, the electric field applied to the toner is reduced, and the collection efficiency is reduced. The optimum volume resistance value range of the cleaning roller 110 is 10 ⁸ to 10 ¹²
Ω · cm.

The resistance value of the cleaning roller 110 or the recording paper P as a transfer material changes by about two digits depending on the atmosphere, and the collection characteristic changes accordingly. For this reason, stable recovery cannot be performed by constant voltage control with respect to environmental fluctuations. On the other hand, in the constant current control, stable recovery is performed with high resistance to environmental fluctuations. Alternatively, it is also possible to adopt a method of performing a constant voltage control as a calculation process by selecting an applied voltage stored in a ROM table, for example, from an appropriate current value of the cleaning roller 110 that enables good recovery.

As another configuration of the cleaning means, as shown in FIG. 8A, a metal shaft 120a has a thickness of 5 mm, a surface roughness Rz of 8 μm or less, and a hardness of 3
A conductive urethane rubber 120b having a volume resistance of 10 ⁴ to 10 ¹⁰ Ω · cm is provided, and the urethane rubber 120b is provided.
About 20 μm thick and surface roughness Rz = 5 μm
It is also possible to use a cleaning roller 120 provided with the following semiconductive fluororesin coating layer 120c.

As shown in FIG. 8B, an E-cell having a cell diameter of 100 to 200 μm is formed around the outer periphery of the metal shaft 130a.
PDM (ethylene propylene di)
(ene rubber) A conductive powder is dispersed in the foam, and a hardness of 25 to 40 degrees (Asker C: measured by an Asuka C rubber hardness meter), a volume resistance value of 10 ⁸ to 10 ¹² Ω · cm, and a rubber layer 130 b having an outer diameter of 17 mm. It is also possible to use a one-layer cleaning roller 130.

In the above embodiment, the photosensitive drum 1 of the cleaning roller 110 as a cleaning means
The total pressure to 0 is preferably maintained at 0.5-2 kg. Further, in order to prevent the toner from adhering to the cleaning roller 110 at the time of a jam, a DC voltage of about -300 to -1500 V having the same polarity as the toner (minus polarity in the present embodiment) in the non-image forming area before printing. Is applied to the cleaning roller 110, and the toner adhered to the photosensitive drum 10 is electrostatically discharged from the cleaning roller 110. Further, after the printing is completed, a toner discharge bias V2 of a DC voltage of about −300 to −1500 V having the same polarity as the toner (minus polarity in the present embodiment) in the non-side image forming area is applied to the cleaning roller 110, and Cleaning roller 110
The toner adhered to the photosensitive drum 10 is further discharged to clean the toner adhered to the cleaning roller 110 during image formation. Similarly, a transfer toner discharge bias V4 of a DC voltage of about -300 to -1500 V having the same polarity (minus polarity in this embodiment) as the toner in the non-image forming area before and after printing is simultaneously applied to the transfer roller 14a. By applying the voltage, the transfer roller 14a can also be cleaned.

Further, the above-described bias control is used to obtain a stable recovery characteristic for various transfer materials and various environments. Environmental fluctuations, contamination of the image forming body, soft contact with the image forming body, electrical and mechanical damage of the image forming body, hysteresis loss, cleaning of the cleaning roller to ensure good recovery and discharge operation of the cleaning roller It is important to always obtain stability in consideration of the above, and it is preferable to provide a retracting mechanism for the cleaning roller in view of contamination of the image forming body or hysteresis loss.

[0047]

According to the first aspect of the present invention, the adhesion of the electric pattern formed on the image forming body is enhanced by the edge portion, and the collected toner on the roller-shaped cleaning means is satisfactorily deposited on the image forming body. Discharged (adhered).

According to the second aspect, the edge portion of the electrostatic latent image on the image forming body is smoothed by light neutralization to reduce the adhesive force, and the transfer residual toner on the image forming body is a roller-shaped cleaning means. Good recovery on top.

According to the third aspect, the adhesive force is strengthened by the edge portion of the electric pattern formed on the image forming body,
Adhered toner on the roller-shaped transfer means is satisfactorily discharged (adhered) onto the image forming body, and contamination of the transfer material is prevented.

According to the present invention, the toner discharged onto the image forming body by the cleaning means is favorably collected in the developing means.

According to the seventh aspect, the image contamination by the toner on the cleaning means is prevented.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of a laser printer showing an embodiment of an image forming apparatus of the present invention.

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

FIG. 3 is a diagram showing an electric pattern on an image forming body.

FIG. 4 is a diagram showing adhesion of discharged toner to an electric pattern.

FIG. 5 is an operation timing chart of bias application to a transfer unit and a cleaning unit.

FIG. 6 is a diagram illustrating a method of collecting transfer residual toner to a developing unit.

FIG. 7 is a side sectional view showing a first example of the structure of the cleaning unit.

FIG. 8 is a cross-sectional view showing second and third examples of the structure of the cleaning unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 14 c pre-transfer exposure device 19 light erasing device (exposure device) 100 cleaning device 110, 120, 130 cleaning roller E1 cleaning roller cleaning bias E2 transfer roller bias E3 development Unit bias EP Electrical pattern V1 Toner recovery bias V2 Toner discharge bias V3 Transfer bias V4 Transfer toner discharge bias V5 Development bias V6 Development recovery bias

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 21/08 G03G 21/00 326 342

Claims (7)

[Claims] A roller that contacts the image forming body with the transfer residual toner adhered to the rotating image forming body by reversal development and rotates in the same direction as the image forming body at a contact portion with the image forming body. An image forming apparatus which once collects in a cleaning means and discharges the image on the image forming body again, wherein an electric pattern is formed on the image forming body when toner is discharged. 2. The image forming apparatus according to claim 1, wherein at the time of collecting the toner, a latent image of the image on the image forming body is subjected to light elimination. 3. A toner attached to a roller-shaped transfer means which is in contact with the image forming body and rotates in the same direction as the image forming body at a contact portion with the image forming body, is discharged onto the image forming body. An image forming apparatus that forms an electric pattern on the image forming body and discharges toner adhered to a roller-shaped transfer unit. 4. A roller which contacts transfer residual toner adhered on a rotating image forming body by reversal development and rotates in the same direction as the image forming body at a contact portion with the image forming body. An image forming apparatus that once collects the toner with a toner collecting bias having a different polarity from the toner to the cleaning member, and discharges the toner on the cleaning unit onto the image forming member again with a toner discharging bias having the same polarity as the toner between images. When the toner discharged on the image forming body is recharged by a charging unit for charging the image forming body and then collected by a developing unit for developing the image forming body, a development applied to a developing sleeve of the developing unit An image characterized in that a value of a collection bias is made lower than a value of a development bias at the time of development of the image forming body, and toner on the image forming body is collected to the developing unit. Forming apparatus. 5. A developing and collecting bias applied to the developing sleeve at the time of collecting is set to 30 based on the value of the recharging potential.
The image forming apparatus according to claim 4, wherein the voltage is set lower by 0 to 500 V. 6. The image forming apparatus according to claim 4, wherein the value of the developing bias at the time of collecting applied to the developing sleeve is set to be 200 to 400 V lower than the value of the developing bias at the time of developing the image forming body. 6. The image forming apparatus according to 5. 7. The image forming apparatus according to claim 4, wherein the toner is discharged by the cleaning unit before the image formation is started or after the image formation is completed.