JPH10333523A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set the position of a cleaning means with respect to a transfer means, without soiling transfer materials with toner by applying a toner discharge bias having the same polarity as that of the toner, to a transfer roller and a cleaning roller, in a non-image forming area and specifying the interval between the transfer materials fed to the transfer means. SOLUTION: The interval L1 between recording papers P fed to a transferring area 14b, in accordance with an image forming region is longer than the double of the length L2 of the arc from the contact position of the transfer roller 14a with a photoreceptor drum 10 to the contact position of the cleaning roller 110 with the drum 10. Then, the electrostatic charge of the toner remaining in a region where the toner remains after transfer, on the periphery of the drum 10 after the image forming region is transferred is removed with light by a light destaticizer 16, to make a potential level on the drum 10 nearly zero. After that, a toner recovering bias V1 having a polarity opposite to that of the toner is applied by a bias E1 and toner on the outer periphery of the cleaning roller 110 is recovered by rotating it in the same direction as that of the drum 10, in the contact part with the drum 10.

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 effectively use the toner, after the image formation, 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]

When the cleaning means according to the above proposal is used, a bias for collection and discharge is required. However, using the roller-like cleaning means and the roller-like transfer means according to the above-mentioned proposal. It has been found that the bias at the time of collecting the toner by the cleaning unit and the bias at the time of transferring the toner to the transfer material by the transfer unit have the same polarity and the same value when performing the image formation, and can be used together.

However, when the bias is also used, the timing of toner collection and discharge by the cleaning means differs from the transfer timing by the transfer means, and toner smears on the transfer material, and the two rollers of the cleaning means and the transfer means Positioning turned out to be a problem. In addition, there is also a problem that a power supply becomes complicated because a bias is applied to both.

The present invention solves the above-mentioned problems, and an image forming method in which the position of the cleaning unit and the transfer unit is set without causing toner contamination on the transfer material even when the bias of the transfer unit and the cleaning unit is used. It is intended to provide a device.

[0008]

The object of the present invention is to provide a charging means, an image exposing means and a developing means on an outer peripheral surface of an image forming body,
The image forming body is charged, subjected to image exposure and reversal contact development to form a toner image on the image forming body, and the toner image is transferred onto a transfer material by a transfer unit, and then brought into contact with the image forming body. In an image forming apparatus, the transfer residual toner on the image forming body is cleaned by a roller-shaped cleaning unit that rotates in the same direction as the image forming body in a contact portion.
The transfer unit is a first roller member that comes into contact with the image forming body and rotates in the same direction as the image forming body at a contact portion; and the cleaning unit comes into contact with the image forming body and the image is formed at the contact portion. A second roller member that rotates in the same direction as the formed body, and applies a toner movement bias having a polarity opposite to that of the toner to the first and second roller members including the image forming area, and in a non-image forming area, Applies a toner discharge bias of the same polarity as the toner to the first and second roller members, and sets a gap between the transfer material fed to the transfer unit in the rotation direction of the image forming member. The image forming apparatus is characterized in that the length of the image forming body from the contact position of the transfer unit to the cleaning unit to the contact position of the cleaning unit is twice as long.

[0009]

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 an image forming process of an embodiment of the image forming apparatus of the present invention, and the structure and functions of each mechanism.
This will be described with reference to FIG. 1 is a sectional view 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 method of collecting bias residual toner to a developing unit, and FIG. 5 is a side sectional view showing a first example of the structure of a cleaning unit. FIG.
FIGS. 6A and 6B are cross-sectional views showing second and third examples of the structure of the cleaning means, FIG. 6A is a cross-sectional view showing a second example of the structure of the cleaning means, and FIG. FIG. 13 is a cross-sectional view illustrating a third example of the structure of the cleaning unit.

Referring to FIGS. 1 to 4, 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 device 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 by reversal development of a contact in which a DC developing bias having the same polarity as the toner (in this embodiment, a negative polarity) is applied between the developing sleeve 13a and the photosensitive drum 10. As the toner used for the developer, a spherical toner having high recovery efficiency of the transfer residual toner described later is preferably used.

Transfer 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, fed by a feed roller 15b, and 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. A first roller member (transfer roller) as a transfer unit that rotates in the same direction as the drum 10
The sheet is fed to a nip (transfer area) 14b formed between the photosensitive drum 10 and the photosensitive drum 14a, and has a common bias E1 at a common switching timing with a common polarity and a bias of a cleaning unit to be described later. 3 of the opposite polarity (positive polarity in this embodiment) to the toner indicated by the solid line
A transfer roller 14a to which a toner movement bias (also referred to as a toner collecting bias in the case of a cleaning unit) V1 of 00 to 1500 V is applied collectively collects the negative polarity toner images on the peripheral surface of the photosensitive drum 10 on the recording paper P. Transcribed above.

If 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 in the absence of the transfer material or the toner outside the transfer material even if the transfer material is present. (The positive polarity in the present embodiment), and the transfer residue on the image forming body by the cleaning unit to which the toner movement 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.

At the end of the application of the toner movement bias V1 at the transfer roller 14a, an image forming area (transfer residual toner area) is a cleaning roller 1 as a cleaning means.
10, it is necessary to cut the photosensitive drum 10 from the contact position of the transfer roller 14 a to the photosensitive drum 10 in the rotation direction of the photosensitive drum 10 to the contact position of the cleaning roller 110. It is necessary to break after passing the passage time t1 of the photosensitive drum 10 having the arc length L2. Further, a cleaning roller 110 described later is used.
It is necessary to apply the toner collection bias V1 to the cleaning roller 110 earlier than the passage time t1 of the photosensitive drum 10 after the transfer residual toner is collected before entering the image forming area. Therefore, the interval L1 between the recording sheets P fed to the transfer area 14b corresponding to the image forming area needs to be larger than twice the length L2 of the arc of the photosensitive drum 10.

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 to be formed is removed by a light neutralizer 19 as a neutralizing means.
After the electric charge is removed, the potential level of the photoconductor drum 10 is reduced to substantially zero, and then the cleaning device 100 or the photoconductor drum 10 is brought into contact with the photoconductor drum 10 and the bias E1 reverses the polarity of the toner indicated by the solid line in FIG. The toner collecting bias (toner moving bias) V1 of 300 to 1500 V (positive polarity in the embodiment) is applied to the photosensitive drum 10.
The toner is collected on the outer peripheral surface of the cleaning roller 110 by a second roller member (cleaning roller) 110 as a cleaning unit that rotates in the same direction as the photosensitive drum 10 at the contact portion. As described above, the transfer residual toner in the transfer residual toner area is completely collected.
The both sides of the toner collection bias application area are formed slightly longer than t1 than the image formation area.

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 residual toner on the photosensitive drum 10 is weakened, and the 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.

Also, 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, in the non-image forming area between the image forming areas after passing the transfer residual toner area, a bias time E1 is set before and after the passing time t1 of the photosensitive drum 10, and a bias E1 is set in FIG.
Is switched to the toner discharging bias V2 to which −300 to −1500 V of the same polarity (minus polarity in the present embodiment) as the toner indicated by the dotted line is applied, and the collected toner on the cleaning roller 110 is discharged onto the photosensitive drum 10 ( Adhere). At this time, the toner discharge bias application area is between the toner recovery bias application areas, and is set to be shorter than the image formation area (non-image formation area) by providing twice the passage time t1 of the photosensitive drum 10 as described above. However, the length of the cleaning roller 110 for 2 to 10 rotations is set shorter than the length of the toner discharge bias application area (recording paper P
Of the cleaning roller 110 or the transfer roller 1
4a is set to be larger than the sum of the length of 2 to 10 rotations of 4a and the length of the moving amount twice as long as the passage time t1 of the photosensitive drum 10), and the collected toner on the cleaning roller 110 is entirely on the photosensitive drum 10. To be discharged (adhered) to
At this time, the photosensitive drum 10 is subjected to light elimination by the light eliminator 19. The potential level of the photosensitive drum 10 is reduced to substantially zero by the light elimination, thereby facilitating the adhesion of the discharged toner to the photosensitive drum 10.

When the toner is discharged by the cleaning roller 110, the transfer roller 14a also switches the bias E1 so that the toner discharge bias V2 having the same polarity as the toner indicated by the dotted line in FIG. The negative polarity toner on the roller 14a is repelled by the negative polarity toner discharge bias V2 and moves onto the photosensitive drum 10, whereby the transfer roller 14a
Is cleaned.

Reference numeral 113 denotes a cleaning casing that has a leading end on the photosensitive drum 10 close to the photosensitive drum 10 in order to prevent 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 described above, even if the bias of the transfer unit and the cleaning unit is used, the toner is not stained on the transfer material, and the appropriate positions of the two roller members of the cleaning unit and the transfer unit are set. In addition, the power supply can be simplified by using a common power supply.

As shown in FIG. 4A, a toner layer is formed on the photosensitive drum 10 having the potential level 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 adhered by a scorotron charger 11 as a charging means by using a DC voltage having the same polarity as that of the toner (minus polarity in this embodiment). But-
When the recharging is performed at 750 V, as shown in FIG. 4B, the potential level on 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 unit 13 and, as shown in FIG. 4C, has the same polarity as the toner lower than the photosensitive member potential (this embodiment). In the negative polarity) -100 ~
The photosensitive drum 10 is cleaned (recovered) from the photosensitive drum 10 by being rubbed by the developer on the developing sleeve 13a of the developing device 13 to which the -650 V cleaning developing bias is applied. 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 toner is attracted to the developing sleeve 13a by setting the developing bias for cleaning to be equal to or lower than the developing bias used for reversal development during image formation.

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 recovery and toner discharge by the photoreceptor 10, the photoconductor potential has irregularities unless the photoremoval is performed by the photoremover 19 as the rejection means. . For this reason, photoremoval is performed to smooth the potential of the photoconductor, thereby enabling uniform and high recovery or discharge. 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 means at the time of recharging, a charging roller can be used as the charging means.

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 toner discharged by the cleaning means can be easily collected from the photosensitive drum 10 to the developing device 13. . 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.

In the above 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.

The mechanical properties of 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 aggregation of the transfer residual toner is necessary, 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.

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 11
In some cases, an abnormal discharge occurs at a contact portion with zero, and destruction of the photosensitive drum 10 may occur due to concentration of current. If the roller resistance is small, the recovery 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 1
0 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. 6A, 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. 6B, 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, it is preferable that the total pressure of the cleaning roller as the cleaning means to the image forming body is maintained at 0.5 to 2 kg. Further, in order to prevent the toner from adhering to the cleaning roller at the time of a paper jam, before printing, the non-image forming area has a polarity (in the present embodiment, about −300) of the same polarity as the toner (minus polarity).
A toner discharge bias of a DC voltage of -1500 V is applied to the cleaning roller to electrostatically discharge the toner adhered to the image forming member from the cleaning roller. At this time, the transfer roller can be cleaned at the same time. In addition, the above-described bias control allows a stable recovery characteristic to be obtained for various transfer materials and various environments. Environmental fluctuations, contamination of the image forming body, soft contact with the image forming body, and electrical and
It is important to always maintain stability in consideration of mechanical damage, hysteresis loss, cleaning of the cleaning roller, and the like, and it is preferable to provide a retracting mechanism for the cleaning roller in terms of contamination of the image forming body or hysteresis loss.

[0041]

According to the first and second aspects, even when the bias of the transfer means and the bias of the cleaning means are used, the transfer material is not stained with toner and the cleaning means and the transfer means can be used.
The appropriate position setting of the three roller members is performed. Further, the power source can be simplified.

[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 an operation timing chart of bias application to a transfer unit and a cleaning unit.

FIG. 4 is a diagram illustrating a method of collecting transfer residual toner to a developing unit.

FIG. 5 is a side sectional view showing a first example of the structure of the cleaning unit.

FIG. 6 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 19 light eliminator 100 cleaning device 110, 120, 130 cleaning roller E1 bias V1 toner transfer bias (toner recovery bias) V2 toner discharge bias

Claims (2)

[Claims] A charging unit, an image exposing unit, and a developing unit disposed on an outer peripheral surface of the image forming body, and charge, image exposure, and reverse contact development are performed on the image forming body to form a toner image on the image forming body. After the toner image is transferred onto a transfer material by a transfer unit, the image forming member is brought into contact with the image forming member, and is rotated by the roller-shaped cleaning unit in the contact portion in the same direction as the image forming member. In the above image forming apparatus for cleaning the transfer residual toner, the transfer unit is a first roller member that comes into contact with the image forming body and rotates at a contact portion in the same direction as the image forming body. A second roller member abutting on the image forming body and rotating in the same direction as the image forming body at a contact portion, wherein the first and second roller members including an image forming area have opposite polarities to toner. Toner transfer tray In the non-image forming area, a toner discharge bias having the same polarity as the toner is applied to the first and second roller members, and the interval between the transfer materials fed to the transfer unit is adjusted to the image. The image forming apparatus according to claim 1, wherein a length of the image forming body from a contact position of the transfer unit to the image forming body to a contact position of the cleaning unit in the rotation direction of the forming body is larger than twice as long. 2. The image forming apparatus according to claim 1, wherein the toner discharge bias is applied for at least one rotation of the second roller member.