JP2003091159A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus using a bias cleaning system cleaning means, which is capable of preventing staining on the rear side of a transfer paper without complicating a mechanism of attaching/detaching an image carrier to/from a transfer member. SOLUTION: Even after a toner image is formed on a photoreceptor by an image forming operation, the photoreceptor is rotated and also a developing bias AC and a developing bias DC are kept in an ON state so as to form a developing electrical field. By applying the developing bias in such a manner, the toner T remaining near a developing nip between a developing sleeve 22BK not rotating and the photoreceptor 11BK is moved toward the photoreceptor. And, the quantity of the toner lying near and at the developing nip is reduced when the rotary drive of the photoreceptor 11BK is turned off.

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 facsimile, a printer, etc.
An image carrier whose surface can be moved endlessly, a toner carrier which is provided so as to face the image carrier and supplies toner carried on the surface to the image carrier by the force of an electric field, and the toner carrier on the image carrier. A transfer unit that directly or indirectly transfers a toner image onto a transfer material carried on a transfer material transfer belt and a transfer belt cleaning unit of a bias cleaning system for removing toner adhering to the surface of the transfer material transfer belt. The present invention relates to an image forming apparatus having.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus,
As a cleaning means for removing the toner adhering to the transfer / transport belt for carrying and transporting the transfer paper, one using a cleaning means of a bias cleaning system is known (for example, Japanese Patent Laid-Open No. 2001-75331).

The bias cleaning type cleaning means removes the toner adhering to the portion to be cleaned by electrostatic force. This has the following merits as compared with the conventionally known blade cleaning type cleaning means.

First, in the blade cleaning system,
Since the toner is removed by the contact of the cleaning blade, the blade edge may be damaged due to the blade scraps and paper dust generated due to abrasion between the cleaning blade and the transfer / conveying belt, and the life of the cleaning unit itself is shortened. It tends to be short. On the other hand, in the bias cleaning method, since the cleaning is performed by the movement of the toner due to the electrostatic force, there is an advantage that the mechanical stress applied to the cleaning member is small and the life of the cleaning unit itself is long. Secondly, in the blade cleaning method, since a large mechanical stress is applied to the transfer / transport belt by the contact of the cleaning blade, the rotational speed of the transfer / transport belt is likely to be unstable. On the other hand, in the bias cleaning method, for example, a rotating bias cleaning roller is opposed to the bias cleaning method, and the force that impedes the transfer speed of the transfer transfer belt is relatively constant as compared with the case where the blade is brought into contact with the bias cleaning roller. Therefore, there is an advantage that the transport speed can be stabilized. Thirdly, in the blade cleaning method, a member such as a rubber blade is brought into direct contact with the portion to be cleaned, but the transfer / transport belt to be cleaned is made of a material having a high friction coefficient such as a rubber material. If so, there is a possibility that a problem such as a rubber blade being caught may occur. On the other hand, the bias cleaning method has an advantage that such a problem does not occur because mechanical removal by the blade is not performed. Further, since the transfer / transport belt is less likely to be worn, the life of the transfer / transport belt can be extended.

The bias cleaning type cleaning means has various advantages as described above, but also has the following disadvantages. In the bias cleaning method, the movement of the toner for cleaning depends on the electrostatic force, so that the toner that can be removed is limited to that charged to an arbitrary polarity. This means that some toner cannot be cleaned depending on the polarity of the toner and the charge strength of the toner, and in this case, the toner that cannot be removed remains.

In the image forming apparatus, the charging means, the exposing means, the developing means, the transferring means, and the cleaning means for the image carrier are generally provided around the image carrier from the upstream side to the downstream side in the moving direction of the surface of the image carrier. Are arranged.
Thereby, a toner image is formed on the image carrier, the formed toner image is transferred to the transfer material side by the transfer unit, and the transfer residual toner on the image carrier is removed by the image carrier cleaning unit,
It prepares for the next toner image formation. And
The developing means has a toner carrier for supplying toner to the latent image on the image carrier, and is provided so as to face the surface of the image carrier.

Here, the toner image formed on the conventional image carrier is transferred to a transfer paper at a nip with the transfer paper as a transfer material (hereinafter referred to as a transfer nip), and the rear end of the transfer paper has passed through the transfer nip. And the next transfer paper is not supplied (below,
At the end of the paper-passing job), drive control was performed to suspend each unit and put it in a standby state.

FIG. 5 is a timing chart showing an example of conventional timing control from the start of the image forming operation to the standby state after transfer. At the same time when the photosensitive member as the image bearing member is turned on, charging AC and DC as the charging means, driving of the developing sleeve as the toner bearing member, and developing bias A
Turn on C and DC respectively. When the toner image formation on the image carrier is completed, the charging DC, the developing sleeve drive, the developing bias AC and DC are turned off. On the other hand, the photoconductor is further driven to carry and convey the toner image to the transfer nip, and transfer it to the transfer paper. Also, the charge A
By leaving C activated, the development history on the photoconductor is eliminated. Then, when the transfer is completed and the sheet passing job is ended, the driving of both the photoconductor and the charging AC is turned off. Then, it is in a standby state until the next image formation is input.

At the driving timing as shown in FIG. 5, when the driving of the photosensitive member is stopped at the end of the paper passing job, the developing sleeve is stopped while being in contact with the photosensitive member with a certain amount of toner adhering to the surface. (See FIG. 6). Then, the toner T is left in the vicinity of the developing nip until the next driving is started.
Some of these toners T are mechanically transferred to the surface of the photoconductor while being left alone or when the next drive is started. Conventionally, there is an apparatus configured to control the reverse rotation of the photoconductor at the end of the paper passing job, but the reverse rotation control also causes the toner T to be transferred and attached to the photoconductor side at a position slightly displaced from the developing nip. .

[0010]

However, the toner T mechanically transferred and attached to the photoconductor side is conveyed to the transfer nip as the photoconductor is driven when the next image forming operation is started, and the transfer paper is transferred. Adheres to the surface of the transfer / conveying belt that does not carry. After that, the normal image forming process is started, and the transfer paper is carried and transferred onto the transfer transfer belt at the timing of transferring the toner image formed on the photoconductor, but since the transfer transfer belt is usually an endless belt, When the next transfer paper is carried on the portion where the toner transferred and adhered from the photoconductor is present, the toner may adhere to the back surface of the transfer paper and stain the back of the transfer paper.

Here, if the transfer / conveyance belt is provided with the cleaning means for cleaning the belt surface as described above, even if toner adheres to the belt surface, it should be removed by cleaning. .

However, the toner, which is mechanically transferred and adhered to the surface of the photosensitive member whose driving is once stopped or stays in the developing nip, and is left as it is until the start of the next image forming operation, is discharged and left so-called nonpolar. The toner is a weakly or electrically charged toner. For this reason, when a bias cleaning type cleaning means is used as the cleaning means for the transfer / transport belt, some toner remains on the surface of the transfer / transport belt without being removed, and this toner passes through the cleaning nip and carries the next transfer paper. If it exists in the surface area of the belt to be conveyed, it adheres to the back surface of the carried transfer paper and causes stains on the back of the transfer paper.

The degree of leaving discharge of toner, which causes non-polar or weakly charged toner that cannot be removed by the bias cleaning means, increases as the length of time the photosensitive member is left standing is longer. That is, the longer the paper passing job interval, which is the waiting time between the previous paper passing job and the next paper passing job, the more non-polarized or weakly charged toner due to discharge.

It should be noted that the above-mentioned problem of stain on the backside of the transfer paper does not occur if a cleaning means such as a blade cleaning method is used for the transfer / transport belt, which cleaning performance is not influenced by the polarity or charge strength of the toner. However, considering the merits of the bias cleaning method, it is desired that the image forming apparatus uses the cleaning means of the bias cleaning method and that the backside of the transfer paper can be prevented from being soiled.

The above-mentioned stain on the backside of the transfer paper may occur in the so-called intermediate transfer type image forming apparatus in which the intermediate transfer body is interposed between the transfer of the toner image from the image carrier to the transfer paper. Because, 1 between the image carrier and the intermediate transfer member
The non-polar or weakly charged toner transferred from the image carrier to the surface of the intermediate transfer member at the secondary transfer nip is transferred to the intermediate transfer member while the transfer paper is not present in the secondary transfer nip between the intermediate transfer member and the transfer paper. This is because the transfer material may be transferred from the transfer material to the surface of the transfer / transport member, and the transfer paper may be carried in the transferred area to stain the back of the transfer paper.

In addition, Japanese Patent Application Laid-Open No. 2000-75670 proposes an invention of a color image forming apparatus capable of preventing back stain and image defect of a transfer material.
The present invention controls the timing at which the photoconductor drum and the transfer roller are brought into contact with each other only when the transfer paper is interposed therebetween. In this publication, although the cause of generation of toner that causes the backside of transfer paper is different from the present case, the backside of transfer paper, which is the subject of the present case, can be prevented. However, the present invention is applied to a one-drum color image forming apparatus, and when the invention is applied to an image forming apparatus using four photoconductors such as a four-tandem tandem, the photoconductor and the transfer member are brought into contact with each other. The separating mechanism becomes complicated and the cost increases.

The present invention has been made in view of the above background. An object of the present invention is to provide an image forming apparatus using a cleaning means of a bias cleaning system.
An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of stains on the back side of transfer paper without complicating the contact / separation mechanism between the image carrier and the transfer member.

[0018]

According to another aspect of the present invention, there is provided an image forming apparatus, comprising: an image carrier which carries a toner image on its surface and which is endlessly movable; and an image carrier which is provided so as to face the image carrier. And a toner carrier for forming a developing nip between the toner carrier and the image carrier, and an electric field in a direction for moving the toner on the toner carrier from the toner carrier to the image carrier side. Developing electric field forming means, a transfer means for directly or indirectly transferring a toner image on the image carrier onto a transfer material carried and carried by a transfer material carrying belt, and a transfer means attached to the surface of the transfer material carrying belt. In an image forming apparatus having a bias cleaning type conveyance belt cleaning unit for removing the accumulated toner, the amount of toner existing in the developing nip when the endless movement of the surface of the image carrier is stopped is reduced. It causes and is characterized in that a stop developing Nipputona amount reducing means. Here, to indirectly transfer a toner image on an image carrier onto a transfer material carried and carried by a transfer material carrying belt means that the endlessly moving surface is arranged so as to come into contact with the image carrying body and the transfer carrying belt. In the so-called intermediate transfer system, which has an intermediate transfer member, the toner image primarily transferred from the image carrier to the intermediate transfer member is secondarily transferred to the transfer material carried and conveyed from the intermediate transfer member to the transfer conveyance belt. Refer to the composition.

In the image forming apparatus of the first aspect, the toner amount in the developing nip is reduced by the stopped developing nip toner amount reducing means when the endless movement of the surface of the image carrier is stopped. Then, when the endless movement of the surface of the image carrier is started next, the amount of non-polar or weakly charged toner adhering to the surface of the image carrier by the mechanical force from the developing nip is reduced. This makes it possible to transfer and adhere from the image carrier to the transfer material transfer belt or transfer and adhere to the transfer material transfer belt via the intermediate transfer member without complicating the contact / separation mechanism between the image carrier and the transfer material transfer belt. The amount of non-polarized or weakly charged toner is reduced, and the amount of residual toner that cannot be removed by the cleaning means of the bias cleaning method is reduced.

An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the stop developing nip toner amount reducing means moves the surface of the toner carrier prior to stopping the endless movement of the surface of the image carrier. And the surface of the image bearing member is moved endlessly to form an electric field by the developing electric field forming means.

According to another aspect of the image forming apparatus of the present invention, the surface of the image carrier facing the surface of the toner carrier in the stopped state is moved endlessly, and a developing electric field is formed by the developing electric field forming means to form an image on the image carrier. The toner remaining on the surface area of the opposing toner carrier is transferred to the surface of the image carrier. When the endless movement of the surface of the image carrier is stopped, the formation of the developing electric field is also stopped. Thus, when the endless movement of the surface of the image carrier is stopped, the amount of toner existing in the developing nip where the image carrier and the toner carrier face each other is reduced. As described above, it is possible to prevent the toner existing in the developing nip from becoming non-polar or weakly charged toner and adhering to the transfer material carrying belt when the image carrying body and the toner carrying body are stopped.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the electric field forming operation by the developing electric field forming means is performed before the endless movement of the surface of the image carrier is stopped. It is characterized in that the endless movement of the surface of the carrier is continued during one or more rounds.

In the image forming apparatus of the third aspect, the entire area of the surface of the image bearing member which can face the toner bearing member is utilized at least once to reduce the amount of toner in the developing nip portion.

An image forming apparatus according to a fourth aspect is the image forming apparatus according to the first aspect.
In the image forming apparatus 2 or 3, the endless movement operation is performed at two timings, immediately before the endless movement of the image carrier surface is stopped and immediately after the endless movement of the image carrier surface in the stopped state is started. It is characterized in that at least one of the endless moving operations has a moving direction opposite to a normal endless moving direction. Here, the normal endless movement direction on the surface of the image carrier is the movement direction of the surface of the image carrier during the image forming operation.

According to another aspect of the image forming apparatus of the present invention, the surface of the image carrier is moved in a direction opposite to the normal moving direction immediately before the endless movement of the image carrier is stopped or immediately after the endless movement is started. , Then stop. As a result, the toner, paper powder, etc. that are retained so as to be blocked in the nip portion between the abutting member such as a blade abutting on the image carrier surface and the image carrier surface are discharged from the nip part. It shifts or is wiped off. It prevents the contact member and the surface of the image bearing member from being mechanically stressed at the nip portion for a long time or performing an image forming operation while the stress is being applied.

An image forming apparatus according to a fifth aspect is the image forming apparatus according to the first aspect.
In the image forming apparatus of No. 2, 3, or 4, the image forming apparatus has a plurality of the image carriers, and the superposed toner images obtained by sequentially transferring the toner images on the plurality of image carriers are the transfer material. A tandem type that can be formed on the upper surface of the image carrier, and one of the image carriers is always interposed between the transfer material transport belt or between the image carrier and the transfer transport belt and is in contact with the surface of the image carrier. An image forming apparatus in a contact state of a transfer nip in contact with a transfer member, wherein the stopped developing nip toner amount reducing means is provided for at least the image carrier in the permanent state of the transfer nip, and is not in the contact state of the transfer nip. When the endless movement of the surface of the image bearing member is started with the surface area of the image bearing member facing the developing nip as the final developing nip region of the remaining image bearing member immediately before the start of the endless movement of the surface of the image bearing member. , The final Until the image nip region passes through the nip position between the image carrier and the transfer carrier belt to which the toner image is transferred, or the nip position between the image carrier and the intermediate transfer member, the transfer carrier belt or the intermediate member The transfer member is separated from the image carrier.

In the image forming apparatus according to the fifth aspect, the amount of toner existing in the developing nip is reduced at least in the image carrier which is in constant contact with the transfer nip and is always in contact with the transfer nip. This prevents non-polar or weakly charged toner from adhering to the surface of the image carrier from the transfer nip via the transfer medium transfer belt or the intermediate transfer belt even if the image carrier is moved endlessly. To do. In the remaining image carrier which is not in the contact state with the transfer nip, non-polar or weakly charged toner remains in the developing nip and mechanically transfers and adheres to the surface of the image carrier due to the start of endless movement of the surface of the image carrier. I'm afraid. However, by using the contact / separation mechanism for the transfer material transport belt or the intermediate transfer belt, which is originally provided, the transfer transport is performed to the final development nip position on the surface of the image carrier where the toner may be attached to the image carrier. It is separated from the image carrier so that the belt or the intermediate transfer member does not come into contact with it. By preventing the nonpolar or weakly charged toner from adhering to the intermediate transfer member, the nonpolar or weakly charged toner does not transfer from the intermediate transfer member to the transfer conveyance belt. As a result, in a tandem type image forming apparatus having a plurality of image bearing members, it is possible to prevent the occurrence of dirt on the back side of the transfer paper without providing a new contact / separation mechanism.

An image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to the fifth aspect, which is a tandem type image forming apparatus of a direct transfer system for directly transferring the toner image on the image carrier onto a transfer material. It is characterized by.

In the image forming apparatus of claim 6, of the tandem type image forming apparatus, since it is a direct transfer system, there is a possibility that non-polar or weakly charged toner may adhere to the transfer material conveying belt from the image carrier. It is higher than the transfer method and stains on the back of the transfer material are likely to occur. By applying the configuration of the fifth aspect to the image forming apparatus of the tandem type direct transfer system in which the backside of the transfer paper is easily generated, the effect of preventing the backside of the transfer paper is effectively exhibited.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to a wet electrophotographic copying machine which is an image forming apparatus will be described below.

An embodiment in which the present invention is applied to an electrophotographic color laser printer (hereinafter referred to as "laser printer") which is an image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of a laser printer according to the present embodiment. This laser printer has four sets of image forming means 1M, 1C, 1Y, 1BK for forming images of magenta (M), cyan (C), yellow (Y), and black (BK).
(Hereinafter, the subscripts M, C, Y, and BK of the respective symbols indicate the members for magenta, cyan, yellow, and black, respectively), but the moving direction of the transfer paper 100 as the transfer material (the arrow in the figure). They are arranged in order from the upstream side in the A direction). The image forming means 1M, 1C, 1Y, 1BK are respectively photosensitive drums 11M, 11C, 1 as image bearing members.
It includes a photoconductor unit having 1Y and 11BK and a developing unit. Further, the image forming means 1M, 1C, 1
The arrangement of Y and 1BK is set so that the rotation axes of the photoconductor drums 11M, 11C, 11Y and 11BK in the respective photoconductor units are parallel to each other and arranged at a predetermined pitch in the transfer paper moving direction. There is.

In addition to the image forming means 1M, 1C, 1Y, and 1BK, the laser printer of the present invention includes an optical writing unit 2,
Paper feed cassettes 3 and 4, a transfer unit 6 having a transfer belt 60 as a transfer material conveying belt that conveys the transfer material toward the transfer portion facing each of the photoconductor drums 11, and the transfer belt 60 as a transfer material. A registration roller 5 including a pair of rollers for supplying the transfer paper 100, a fixing unit 7 of a belt fixing system, a paper discharge tray 8 and the like are provided. The laser printer also includes a manual feed tray, a toner supply container, a waste toner bottle, a power supply unit, and the like, which are not shown.

The optical writing unit 2 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, etc., and each photoconductor drum 11M, 11C, 11Y, based on image data.
Irradiation is performed while scanning the laser beam on the surface of 11BK.

The alternate long and short dash line in FIG.
3 shows the transport route of the. The transfer paper 100 fed from the paper feed cassettes 3 and 4 is transported by the transport rollers while being guided by a transport guide (not shown), and is transported to a temporary stop position where the registration rollers 5 are provided. The transfer paper 100 is supplied to the transfer belt 60 by the registration rollers 5 at a predetermined timing, and is conveyed so as to pass through the transfer portions facing the photosensitive drums 11. As a result, the photoconductor drums 11M, 11C, 11Y and 11BK formed by the image forming units 1M, 1C, 1Y and 1BK.
The upper toner images are sequentially superposed and transferred onto the transfer paper to form a color image on the transfer material. The transfer paper 100 on which the color image is formed is discharged onto the paper discharge tray 8 after the toner image is fixed by the fixing unit 7.

FIG. 2 shows the image forming means 1M, 1C, 1Y,
FIG. 2 is an enlarged view showing a schematic configuration of a magenta image forming unit 1M of 1BK. The other image forming units 1C, 1Y, and 1BK have the same configuration, and the description thereof will be omitted. In FIG. 2, the image forming unit 1M includes the photoconductor unit 10M and the developing unit 20 as described above.
Equipped with M. The photoconductor unit 10M includes, in addition to the photoconductor drum 11M, a swingable cleaning blade 13M for cleaning the surface of the photoconductor drum, a non-contact type charging roller 15M for uniformly charging the surface of the photoconductor drum, and the like. There is. Further, a lubricant coating / erasing brush roller 12M having a function of applying a lubricant to the surface of the photosensitive drum and eliminating the charge on the surface of the photosensitive drum is also provided.
The brush portion of this lubricant application / erasing brush roller 12M is made of conductive fiber, and a core removing portion is connected to a neutralizing power source (not shown) for applying a neutralizing bias.

In the photoconductor unit 10M having the above structure, the surface of the photoconductor drum 11M is uniformly charged by the charging roller 15M to which a voltage is applied. When the surface of the photosensitive drum 11M is irradiated with the laser light modulated and deflected by the optical writing unit 2 while being scanned, an electrostatic latent image is formed on the surface of the photosensitive drum 11M. The electrostatic latent image on the photosensitive drum 11M is developed by a developing unit 20M described later to become a magenta toner image. At the transfer portion Pt through which the transfer paper 100 on the transfer belt 60 passes, the toner image on the photosensitive drum 11M is transferred to the transfer paper 100. Photosensitive drum 1 after the toner image is transferred
The surface of 1M is coated with a predetermined amount of lubricant by a lubricant coating / erasing brush roller 12M and is then discharged, and then a cleaning blade 1 as a photosensitive member cleaning means.
It is cleaned at 3M and prepared for the next electrostatic latent image formation.

The developing unit 20M uses a two-component developer containing a magnetic carrier and a negatively charged toner T as a developer for developing the electrostatic latent image. Further, the developing unit 20M includes a developing sleeve 22M as a developer carrying member arranged so as to be partially exposed from an opening of the developing case 21M on the photosensitive drum side, transport screws 23M and 24M, a developing doctor 25M, A toner concentration sensor (T sensor) 26M, a powder pump 27M and the like are provided. A developing bias voltage in which a negative DC voltage DC (DC component) is superimposed on an AC voltage AC (AC component) is applied to the developing sleeve 22M by a developing bias power source (not shown) as a developing electric field forming unit, and each developing sleeve is applied. Two
2M is biased to a predetermined voltage with respect to the metal base layer of the photosensitive drum.

In FIG. 2, the developer contained in the developing case 21M is triboelectrically charged by being stirred and conveyed by the conveying screws 23M and 24M. Then, a part of the developer is carried on the surface of the developing sleeve 22M, and the layer thickness is regulated by the developing doctor 25M.
It is conveyed to the developing position facing M. At the developing position, due to the charged toner T in the developer on the developing sleeve 22M,
The electrostatic latent image on the photoconductor drum 11M is developed. The toner concentration of the developer in the developing case 21M is detected by the toner concentration sensor 26M, and if necessary, the powder pump 27
The toner is replenished by M.

FIG. 3 is a schematic diagram of the transfer unit 6. As the material of the transfer belt 60 of the transfer unit 6, for example, PVDF (polyvinylidene fluoride) can be used. The transfer belt 60 is rotatably stretched around four grounded support rollers 61, 62, 63, 64. The exit roller 62 on the downstream side in the transfer paper moving direction is a drive roller that frictionally drives the transfer belt 60, and is connected to a drive source (not shown). The exit roller 62 causes the transfer belt 60 to rotate in the direction of the arrow, so that the pair of photosensitive drums 11M and 11M of the respective image forming units is rotated.
The transfer paper 100 is carried and conveyed toward each of the transfer units facing C, 11Y, and 11BK.

The supporting roller 6 for the transfer belt 60 is also used.
The transfer belt 6 is attached to the portion stretched by 3, 64.
A bias cleaning type bias cleaner 70 is provided as a conveyor belt cleaning means for removing the adhered toner adhering to the surface of No. 0. The bias cleaner 70 attracts the negatively charged toner to the cleaning roller 71 side between the cleaning roller 71 and the transfer belt 60, which is a conductive cleaning roller 71 disposed opposite to the surface of the transfer belt 60. And a cleaning electric field forming means for forming the cleaning electric field.

As the cleaning electric field forming means in this embodiment, a cleaning roller 71, a cleaning bias power source 75 for applying a voltage to the cleaning roller 71, and a biased counter roller 73 are used. Then, the cleaning roller 71 is applied with a constant voltage controlled positive voltage of 15 μA as a cleaning voltage from the power supply 75. As a result, a cleaning electric field for attracting the negatively charged toner to the cleaning roller 71 side is formed between the surface of the transfer belt 60 and the cleaning roller 71. Due to this cleaning electric field, the negatively charged toner adhering to the surface of the transfer belt 60 is transferred to the cleaning roller 71 by electrostatic force,
The surface of the transfer belt 60 is cleaned. The toner T transferred to the cleaning roller 71 is scraped off by the cleaning blade 72 and removed from the surface of the cleaning roller 71.

A transfer bias applying member 67 is provided as a transfer electric field forming means for forming a transfer electric field in each transfer section.
M, 67C, 67Y, 67BK are provided. These transfer bias applying members 67M, 67C, 67Y, 6
The 7BK faces the photoconductor drums 11M, 11C, 11Y, and 11BK so as to contact the back surface of the transfer belt 60, and forms a transfer nip for transferring the toner image of each color. The transfer bias applying members 67M, 67C, 67Y, 67BK used in this embodiment are fixed brushes made of Myra, and each of the transfer bias power supplies 9M, 9C, 9B.
From Y and 9BK, a positive voltage having a polarity opposite to the charging polarity of the toner T is applied as a transfer bias. The transfer bias applied via the transfer bias applying member 67 imparts a transfer charge to the transfer belt 60, and a transfer electric field having a predetermined intensity is formed between the transfer belt 60 and the surface of the photosensitive drum at each transfer portion. To be done.

Further, the supporting roller 6 of the transfer unit 6
The electrostatic attraction roller 65 as an electrode member for attracting a transfer material so as to contact and face the transfer belt 60 at a portion facing 1 with the transfer belt 60.
Is provided. The electrostatic attraction roller 65 has a conductive metal foam layer formed on a core metal. Voltages are selectively applied to the electrostatic attraction roller 65 from a power source 65a for attracting the transfer paper and a power source 65b for the opposite polarity as voltage applying means. The power source 65a for attracting the transfer paper is a constant current control type power source, and
A charge having a positive polarity, which is opposite to the normal polarity of, is applied to the transfer paper 100.

In this embodiment, the current flowing through the support roller 61 is controlled to be, for example, plus 15 μA. The transfer paper 100 that has passed between the electrostatic attraction 65 and the entrance roller 61 in a state where power is being supplied from the transfer paper attraction power supply 65 a is electrostatically attracted onto the transfer belt 60. On the other hand, the power source 65b for the reverse polarity is the toner T
The negative polarity electric charge, which is the same as the normal polarity, is applied to the transfer paper 100. Also, the four photosensitive drums 11M, 11C,
BK photoconductor 1 on the most downstream side of 11Y and 11BK
Only 1BK is in a constant contact with the transfer nip, which is always in contact with the transfer belt, and the remaining photosensitive drums 11M, 11C, 1
1Y can be brought into and out of contact with the transfer belt.

Image formation of the laser printer according to this embodiment will be described below. First, a multicolor image forming mode for forming a color image on the transfer paper will be described. Four photosensitive drums 11M, 11C, 11Y, 11
Each of the BKs contacts the transfer belt 60. The electrostatic attraction roller 65 applies a charge having the same polarity as the polarity of the toner T to the transfer paper 100, and transfers the transfer paper 1 to the transfer belt 60.
00 is adsorbed. As a result, as described above, it becomes possible to eliminate the transfer failure of the toner image due to the charge-up of the transfer material.

The transfer paper 100 is conveyed while being attracted to the transfer belt 60, and is transferred to the upstream color drums 11M and 11M.
The magenta, cyan, and yellow color toner images formed on C and 11Y are sequentially transferred in an overlapping manner, and finally the black toner image formed on the BK drum 11BK is transferred in an overlapping manner. At this time, the transfer paper 100 is more strongly attracted to the transfer belt 60 as it goes downstream in the transfer paper conveyance direction by the transfer current applied to each transfer portion for transferring the toner image of each color. .

Here, for example, when the surface speed of the transfer belt 60 is 125 mm / sec, the surface speed of each photoconductor drum is 127 mm / sec. The speed difference between the surface of the transfer belt 60 and the surface of the photoconductor drum is particularly effective for improving the transferability of the toner image in the portion where two or more colors overlap onto the transfer paper 100. At this time,
The speed difference between the surface of the transfer belt 60 and the surface of the photosensitive drum 11 may make the transfer speed of the transfer paper 100 unstable, but the transfer current value of each color and the suction current value of the transfer paper 100 should be set appropriately. As a result, the transfer belt 60 and the transfer paper 10
The suction force of 0 can be increased, and the transfer speed of the transfer paper 100 does not become unstable.

Next, a monochromatic image forming mode for forming a monochromatic image on the transfer paper 100 will be described. Here, a case where a black image is formed as a monochromatic image will be described. In the single-color image forming mode, as shown in FIG. 3, the color drums 11Y, 11C, and 11M are separated from the transfer belt 60, and only the BK drum 11BK on which the toner image of the black toner T is formed is used as the transfer belt 60. Make sure they come into contact.

Here, the transfer paper 100 is directly B
Although it is conveyed to the transfer nip of the K drum 11BK, the attraction force between the transfer paper 100 and the transfer belt 60 is larger than that in the multicolor image forming mode because the transfer current is not applied to each color drum. It's getting weaker. Therefore, when the surface speed of the transfer belt 60 is 125 mm / sec, the BK drum drive motor is switched so that the surface speed of the drum 11BK is 125 mm / sec. As a result, the conveyance speed of the transfer paper 100 does not become unstable in the monochromatic image forming mode. That is, in this single-color image forming mode, unlike the multi-color image forming mode, toner images of two or more colors are not superposed and transferred, so that there is a speed difference between the surface of the transfer belt 60 and the surface of the photosensitive drum. The need to install it is low.

By the way, in the laser printer according to the present embodiment, the bias cleaner 70 is used as a cleaning means for the transfer belt 60. By using the cleaning means of the bias cleaning system, the transfer belt 6 as the transfer material carrier is formed.
It is possible to stabilize the rotation speed of 0 and extend the life of the transfer belt 60. When the bias cleaner 70 is used as a cleaning unit for the transfer belt 60, the mechanical force that hinders the transfer belt 60 from running can be controlled relatively constant as compared with a cleaning unit such as a blade that directly contacts the transfer belt 60. The transfer belt 60 can be conveyed at a constant speed. This is because the cleaning roller 71 of the bias cleaner 70 rotates. That is, in the method of directly contacting the blade with the transfer belt 60, the transfer belt is changed in accordance with the change in the frictional force between the blade and the transfer belt 60 (the change in the frictional force depends on the amount of toner input to the blade). 6
A force is generated that makes the running of 0 unstable. In contrast,
Cleaning roller 71 of the bias cleaner 70
In the case of using, the transfer speed of the transfer belt 60 can be made relatively constant, and a high-quality image without color misregistration or density unevenness in the sub-scanning direction can be obtained.

By the way, as in the above-mentioned structure, the transfer belt 6
When the cleaning of 0 is performed using the bias cleaner 70, the back surface of the transfer paper may be easily soiled. That is, when the driving of the photoconductor 11 is stopped, the toner T is attached to the surface of the developing sleeve 22 to a certain extent and stops while keeping contact with the photoconductor. Then, as shown in FIG. 6, the toner T, which is left in the vicinity of the developing nip while remaining in the toner nip, may be left to discharge and become non-polar or weakly charged toner T. Then, when the driving of the photoconductor is started next time, the toner T is mechanically transferred and adhered to the surface of the photoconductor, carried and carried on the photoconductor, and adhered to the transfer belt side at the transfer nip, the toner T is non-polar or Since the toner T is weakly charged, it may not be satisfactorily removed by a bias cleaning type cleaning device.
Then, when the transfer paper 100 is supplied onto the transfer belt 60, the toner T may adhere to the back surface of the transfer paper and stain the back surface of the transfer paper.

Therefore, in the printer of this embodiment, of the four photoconductors 11BK, 11Y, 11C, and 11M, the BK photoconductor 11BK that is always in contact with the transfer belt when the photoconductor 11BK is in a stopped state. In addition, as a stop developing nip toner amount reducing means for reducing the amount of toner T staying in the vicinity of the developing nip between the developing sleeve 22BK and the developing sleeve 22BK, a developing bias is applied so that the toner can be transferred and adhered to the photoreceptor side to be removed. . Therefore, the timing of applying the developing bias is set to a different timing from the conventional timing control. Here, regarding the other image forming means 1M, 1C, 1Y, the conventional timing control shown in FIG. 5 is performed as it is.

[Embodiment 1] FIG. 4 is a timing chart showing an example of timing control from the start of the image forming operation to the standby state after transfer according to Embodiment 1 as a characteristic portion of the present embodiment. First, of the four image forming means, the black image forming means 1BK will be described. In FIG. 4, at the same time when the endless movement of the photoconductor as the image carrier is turned ON, the charging AC and DC as the charging means, the developing sleeve drive as the toner carrier, and the developing biases AC and D are shown.
Turn on C respectively. This is the same as the conventional one. When the toner image formation on the photoconductor is completed, charging D
Up to the point where C and the developing sleeve drive are turned off, it is the same as the conventional one. And the developing biases AC and DC are ON
In this state, a developing electric field is formed for a period of m in the figure. This is the stop development nip toner amount reduction means. Here, since the surface potential of the photoconductor is 0 V, excessive DC bias application causes adverse effects such as carrier adhesion. Therefore, the applied DC bias is 0 to 400 V, preferably +50 to 100 V.
V is suitable. In this embodiment, the DC bias is + 50V. By applying such a DC bias, the toner T in the developer carried on the surface of the developing sleeve 22BK whose rotation is stopped at the developing nip and in contact with the photoconductor 11BK moves to the photoconductor side by electrostatic force. To do. Further, by applying the AC bias, not only the toner T in the developer carried on the surface of the developing sleeve 22BK whose rotation is stopped at the developing nip and in contact with the photoconductor 11BK, but also at a position slightly apart from the photoconductor 11BK. The toner T in a certain developer also moves to the photoconductor side. After rotating the photoconductor 11BK once in this state, the developing bias AD
And turn off DC. Further, development biases AD and D
Even after C is turned off, the photoconductor drive and charging AC are continuously turned on to eliminate the development history on the photoconductor surface and drive both of them.
F to enter the standby state.

By performing the timing control as described above, it is possible to reduce the amount of toner existing in the developing nip and in the vicinity thereof when the rotational drive of the photoconductor 11BK is turned off. Further, in the present embodiment, the toner amount in the developing nip is reduced by applying the developing biases AD and DC. This is effective even if only the developing bias AD and only the developing bias DC are applied. When both the AD bias and the DC bias are applied as in the present embodiment, it is possible to most effectively reduce the toner amount in the developing nip portion in contact with the photoconductor 11BK.

By controlling the driving timing as described above, it is possible to reduce the amount of the toner T existing in the developing nip when the driving of the photoconductor 11BK is stopped. Then, the non-polar or weakly charged toner T mechanically attached to the surface of the photoreceptor 11BK in the stopped state.
Alternatively, the amount of non-polar or weakly charged toner T attached to the surface of the photoconductor 11BK by the mechanical force from the developing nip when the image forming operation is started next time can be reduced. Therefore, the amount of the nonpolar or weakly charged toner T transferred from the contact position between the photoconductor 11BK and the transfer belt 60 to the transfer belt 60 side can be reduced. Therefore,
Even in a printer provided with the bias cleaner 70 of the bias cleaning system, it is possible to prevent the back surface of the transfer paper conveyed by the transfer belt 60 from being soiled.

Next, the remaining image forming means 1C, 1Y, 1
The BK will be described. The remaining image forming means 1M, 1C, 1Y on the upstream side of the black image forming means 1BK are originally in the standby state and the photoconductor 11 with respect to the transfer belt 60.
It has a transfer contact / separation motor for separating the M, 11C, and 11Y. This is to enable the formation of a monochrome black image. In this embodiment, this contact / separation mechanism is used.

Before the start of the driving of the photoconductor, the transfer contact is performed until the region of the surface of the photoconductor 11M, 11C, 11Y at the developing nip position (hereinafter referred to as the final developing nip region) passes through the portion facing the transfer belt 60. The transfer belt 60 is separated from the photoconductor by the separation motor. by this,
Even if the toner T staying in the developing nip portion mechanically transfers and adheres to the surface of the photosensitive member due to the start of driving the photosensitive members 11M, 11C, and 11Y, the final developing nip region where the toner T may adhere The cleaning blade 13M, 13
C and 13Y are used to remove from the surface of the photoconductor.
Therefore, these photoreceptors 11M, 11C, 11Y
Even if the amount of staying toner in the developing nip portion is not reduced by applying a developing bias in the stopped state, the non-polar or weakly charged toner T adheres to the transfer belt, and Does not generate dirt. Also, since the contact / separation mechanism between the photoconductor and the transfer belt uses the transfer contact / separation motor originally provided in the apparatus,
There is no cost to install a new mechanism.

According to the first embodiment described above, regarding the photoconductor 11BK which is always in contact with the transfer belt, the photoconductor 11BK
The amount of the non-polar or weakly charged toner T transferred from BK to the transfer belt 60 side can be reduced. Further, the remaining three photoconductors 11M, 11C, 11Y are prevented from adhering the non-polar or weakly charged toner T to the transfer belt 60 by using the transfer contact / separation motor originally provided in the apparatus. can do. As a result, by reducing the toner layer to some extent at the cleaning nip with the bias cleaner 70, it was possible to obtain a toner adhesion amount at a level that cannot be recognized as stains on the back of the transfer paper.
Therefore, even if the bias cleaner 70 of the bias cleaning system is used as the cleaning system of the transfer belt 60, the backside of the transfer paper can be prevented from being soiled.

With the above construction, compared to the cleaning method in which a blade or the like is directly applied to the transfer belt 60, the mechanical force that inhibits the running of the transfer belt 60 can be controlled relatively constant, and the transfer belt 60 can be conveyed at a constant speed. Can be done more reliably in. This is because the bias cleaning roller rotates while contacting the transfer belt 60. On the other hand, in the method of directly contacting the transfer belt 60 with the blade, a force that makes the transfer belt 60 run unstable is generated as the frictional force between the blade and the transfer belt 60 changes. Therefore, when the bias cleaning roller is used, the transfer speed of the transfer belt 60 can be kept relatively constant, and a high-quality image without color misregistration or density unevenness in the sub-scanning direction can be obtained. Further, when the bias cleaning roller 71 is used, there is no problem such as damage to the blade edge due to paper dust or the like, so that there is an advantage that the life is relatively long compared to the blade method. Further, in the case of the blade method, when the transfer belt 60 is made of a rubber material, if the rubber blade is brought into contact with the transfer belt 60, the friction coefficient becomes high and there is a possibility that problems such as entrainment may occur. There is an advantage as a cleaning method that it can be used regardless of the material of the transfer belt 60.

In order to prevent the backside of the transfer paper from being soiled, the rotation of the photosensitive member is started to transfer the toner adhering to the final developing nip to the transfer belt, and the toner adhered to the transfer belt to which the toner adheres. It is conceivable to feed the transfer paper at a timing so that the transfer paper is not carried in the portion. However, in this method, the first printing time, which is the time from the driving of the motor to the start of feeding the paper to the transfer nip, becomes long, and the productivity of the printed matter decreases. On the other hand, in the present embodiment, if the final developing nip of the photoconductor passes through the transfer nip, the photoconductor can be brought into contact with the transfer belt and immediately fed. Therefore, the first printing time can be shortened and the productivity of printed matter can be prevented from lowering.

As a modification of the first embodiment, the transfer bias is applied to the transfer nip when the developing bias is applied in order to reduce the toner amount in the developing nip of the black photoconductor 11BK. May be. This makes it possible to selectively transfer normally charged toner in the transfer nip to the transfer belt side. Therefore, of the toner staying in the developing nip, among the toner T adhering to the photoconductor 11BK by the developing bias, only the normally charged toner is transferred to the transfer belt at the transfer nip facing the transfer belt 60. It is possible to transfer and transfer the non-polar or weakly charged toner to the downstream side while adhering to the surface of the photoconductor, and remove it by the cleaning blade 13BK.

In the first embodiment, the developing nip toner amount at the time of stop is reduced only for the black photoconductor 11BK which is always in contact with the transfer belt, but the remaining photoconductors 11M, 11C, 11Y are also reduced. Similar control may be performed. By doing so, it is possible to more reliably prevent the backside of the transfer paper from being soiled.

[Second Embodiment] Next, a second embodiment will be described. In the second embodiment, 2 immediately before the driving of the photoconductor is stopped and immediately after the driving of the photoconductor in the stopped state is started.
At one timing, the photoconductors 11BK, 11Y, 11C,
11M is slightly rotated in the direction opposite to the rotation direction during normal image formation.

By the reverse rotation performed immediately before the driving of the photoconductor is stopped, the mechanical stress applied to the cleaning blades 13BK, 13Y, 13C and 13M abutting on the photoconductor surface is released, and the photoconductors 11BK and 11Y are released. , 11
Toner T that is retained so as to be dammed between C, 11M and the contact members such as the cleaning blades 13BK, 13Y, 13C, 13M and the developing sleeves 22BK, 22Y, 22C, 22M that are in contact with the surfaces thereof. And remove paper dust, etc. from the nip part. After that, the photoconductors 11BK, 11Y, 11C, 11M
Stop driving. In addition, by the reverse rotation performed immediately after the start of driving the photoconductors, the photoconductors 11BK, 11Y, 11C, 1
The mechanical stress applied to the member in contact with 1M is released, and the toner T, paper dust, etc. accumulated in the nip portion are displaced or wiped off from the nip portion. Then, the image forming operation is started.

As in the third embodiment, the photoconductors 11BK, 1
By performing the reverse rotation of the photoconductor immediately before the driving of 1Y, 11C, and 11M is stopped and immediately after the driving is started, the life of the image carrier and the contact member can be extended, and the functions of the respective contact members can be improved. It can be exhibited well. Also,
It is possible to prevent problems that may occur due to toner T, paper dust, and the like staying between the photoconductors 11BK, 11Y, 11C, and 11M and the contact member.

In the above embodiment, the toner T formed on the photoconductors 11M, C, Y and BK is transferred onto the transfer paper 1 by the toner T.
This is an example of a tandem type image forming apparatus of a direct transfer type in which the image is directly transferred to 00. Instead of this, the present invention is also applicable to an intermediate transfer type printer in which a toner image on a photoconductor is primarily transferred onto an intermediate transfer member, and the image primarily transferred onto the intermediate transfer member is secondarily transferred onto a transfer paper. Can be applied.

[0067]

According to the image forming apparatus of the present invention, the toner that cannot be removed by the cleaning means of the bias cleaning method and remains on the surface of the transfer / conveying belt is reduced, so that the image using the cleaning means of the bias cleaning method is used. In the forming apparatus, it is possible to reduce the non-polar or weakly charged toner on the image carrier that causes the backside of the transfer paper, and to clean the backside of the transfer paper without complicating the contact / separation mechanism between the photoconductor and the transfer member. There is an excellent effect that the occurrence of can be reliably prevented.

According to the image forming apparatus of the second aspect, by utilizing the developing electric field forming means provided for developing as the stopped developing nip toner amount reducing means, the image carrier and the transfer member are complicated. There is an excellent effect that the backside of the transfer paper can be prevented from being soiled without providing a contacting / separating mechanism.

According to the image forming apparatus of the third aspect, there is an excellent effect that stains on the back of the transfer paper can be prevented more effectively.

According to the image forming apparatus of the fourth aspect, at the nip portion between the image carrier and the contact member such as a blade which is in contact with the surface of the image carrier, the contact member and the surface of the image carrier are mechanically contacted. Since it is possible to prevent a state in which various stresses are applied for a long time, it is possible to prolong the life of the image carrier and the contact member. Further, there is also an excellent effect that the function of the abutting member with respect to the image carrier can be satisfactorily exhibited when performing the image forming operation.

According to the image forming apparatus of the fifth aspect, in the tandem type image forming apparatus having a plurality of image carriers,
Since it is possible to prevent the stain on the back side of the transfer paper without providing a new contact / separation mechanism, it is possible to prevent the stain on the back side of the transfer paper without complicating the contact / separation mechanism between the image carrier and the transfer member. It has the excellent effect that Even for the remaining image carriers not in the contact state of the transfer nip, the effect of preventing the smearing of the transfer paper can be further improved by reducing the amount of toner existing in the developing nip by the stopped development nip toner amount reducing means.

According to the image forming apparatus of claim 6, in the tandem type direct transfer type image forming apparatus in which the backside of the transfer paper is apt to occur, the effect of preventing the backside of the transfer paper can be effectively exhibited. There is an effect.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a laser printer according to an embodiment.

FIG. 2 is an enlarged view showing a schematic configuration of a magenta image forming unit in the printer according to the present embodiment.

FIG. 3 is a schematic configuration diagram of a transfer unit in the printer according to the present embodiment.

FIG. 4 is a timing chart showing an example of timing control from the start of the image forming operation according to the first embodiment to the standby state after transfer.

FIG. 5 is a timing chart showing an example of conventional timing control from the start of an image forming operation to the standby state after transfer.

FIG. 6 is an explanatory diagram showing a toner retention state in the developing nip when the driving of the photoconductor is stopped.

[Explanation of symbols]

1 Image forming means 5 Registration roller pair 6 Transfer unit (transfer transfer device) 9 Transfer bias power supply 10 Photoconductor unit 11 Photosensitive drum 12 Lubricant application and static elimination brush roller 13 Cleaning blade 15 Charging roller 20 Development unit 60 transfer belt 61, 62, 63, 64 Support roller 65 Electrostatic attraction roller (electrode member for attracting transfer material) 65a Constant current control type power supply 65b Constant voltage control type power supply 67 Transfer bias applying member 70 Bias Cleaner 71 Cleaning roller 72 cleaning blade 75 Cleaning bias power supply 100 transfer paper T toner

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/06 101 G03G 15/16 15/16 15/08 507H 21/14 21/00 372 F term (reference) ) 2H027 DA38 ED02 ED08 ED09 ED24 EE01 EE04 EE05 EE07 EE08 EF02 EF06 EF13 2H030 AB02 AD03 AD17 BB33 BB34 BB42 BB44 BB56 BB63 2H073 AA09 BA04 BA09 BA13 CA03 CA22 2H077 AD06 AD36 BA03 CA19 DB08 DB21 EA03 GA13 2H200 FA08 GA12 GA23 GA29 GA45 GA47 GA57 GB12 GB22 GB25 HA02 HA28 HA29 HB12 HB22 HB48 JA02 JA28 JA29 JB06 JB10 JB25 JB42 JB45 JC03 JC12 LA24 LB03 LB08 LB15 LB38 MA04 MA20 NA02 NA06 NA16 PA02 PA10 PA12 PA26 PA30

Claims (6)

[Claims] 1. An image carrier which carries a toner image on its surface and which is endlessly movable, and an image carrier which is provided so as to face the image carrier and carries toner on its surface. A toner carrier forming a developing nip therein, and a developing electric field forming means for forming an electric field in the developing nip in a direction for moving the toner on the toner carrier from the toner carrier toward the image carrier.
Transfer means for directly or indirectly transferring a toner image on the image carrier onto a transfer material carried and carried by a transfer material carrying belt, and bias cleaning for removing toner adhering to the surface of the transfer material carrying belt. In the image forming apparatus having the system type conveyance belt cleaning means, the stopped development nip toner amount reduction means for reducing the toner amount existing in the development nip when the endless movement of the image carrier surface is stopped is provided. An image forming apparatus characterized by the above. 2. The image forming apparatus according to claim 1, wherein the stopped developing nip toner amount reducing means stops the movement of the toner carrier surface prior to stopping the endless movement of the image carrier surface, and An image forming apparatus, characterized in that an electric field is formed by the developing electric field forming means in a state where the surface of the carrier is moved endlessly. 3. The image forming apparatus according to claim 2, wherein the electric field forming operation by the developing electric field forming means, which is performed before the endless movement of the surface of the image bearing member is stopped, is performed once for the endless movement of the surface of the image bearing member. An image forming apparatus characterized by being continued while performing the above. 4. The image forming apparatus according to claim 1, 2 or 3, immediately before the endless movement of the surface of the image carrier is stopped and immediately after the endless movement of the surface of the image carrier in the stopped state is started. The image forming apparatus, wherein the moving direction of at least one endless moving operation of the two endless moving operations is set to a direction opposite to the normal endless moving direction. 5. The image forming apparatus according to claim 1, 2, 3, or 4, wherein the image forming apparatus has a plurality of the image carriers, and toner images on the plurality of image carriers are sequentially transferred. Is a tandem type capable of forming a superimposed toner image on the transfer material, and one of the image carriers is always interposed between the transfer material transport belt or the image carrier and the transfer transport belt. An image forming apparatus in a state where a transfer nip is in constant contact with an intermediate transfer member that is in contact with the surface of the image carrier, wherein the stop development nip toner amount reducing means is provided for at least the image carrier in the permanent transfer nip state. The transfer nip is provided with respect to the remaining image carrier that is not in a normal contact state.
Immediately before the start of the endless movement of the surface of the image carrier, the area of the surface of the image carrier facing the developing nip is defined as the final developing nip area, and when the endless movement of the surface of the image carrier is started, the final developing nip area is Until the toner image on the image carrier is transferred to the transfer conveyor belt or the nip position between the image carrier and the intermediate transfer member, the transfer conveyor belt or the intermediate transfer member is imaged. An image forming apparatus characterized by being separated from a carrier. 6. The image forming apparatus according to claim 5, wherein the toner image on the image carrier is directly transferred onto a transfer material.
An image forming layer apparatus, which is a direct transfer tandem type image forming apparatus.