JPH0836288A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the soiling on a recording material and to eliminate the adverse effect such as the density irregularity occurring on an image formed on the recorded material surface by providing a charge control device for uniformizing the electric charge distribution on the transfer belt surface. CONSTITUTION:The part of the transfer belt 1 after the recording paper 5 is separated, reaches the vicinity of the first charge removing device 9 by the rotation of transfer belt 1. By the corona charge of the charge removing device 9, the residual electric charge on the surface of the transfer belt 1 is removed. Then, the cleaning roller 11 of the cleaning device 10 is rotated in a state of held in contact with the transfer belt 1 with a circumferential speed difference from the transfer belt 1, thus the developer, the dust and so on sticking to the surface of the transfer belt 1 are removed. The transfer belt 1, after the foreign material is removed by the discharger charger 14, is corona charged by the second charge removing device 13 thus the electric charge distributed on the transfer belt 1 is removed and the electric charge distribution on the transfer belt l after removing the foreign material is made uniform.

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 or a printer, and more specifically, a cleaning device for removing the developer adhering to the surface of a transfer belt which conveys a recording material, and The present invention relates to an image forming apparatus provided with a charge control device that makes the charge distribution on the surface of the transfer belt uniform.

[0002]

2. Description of the Related Art As a conventional image forming apparatus, an electrostatic latent image is formed on the surface of a latent image carrier by a well-known electrophotographic process, and the electrostatic latent image is developed by a developing device to form a latent image carrier surface. It is known that a toner image is formed, the toner image is transferred to the surface of a recording material such as recording paper conveyed by a transfer belt by a transfer device, and then fixed by a fixing device to form an image. Here, in the transfer, the recording material is interposed between the transfer belt and the latent image carrier, and a transfer device is generated to generate an electric field in a direction in which the charged toner is electrostatically attracted to the recording material. Gives a charge to the transfer belt.

[0003]

However, according to this apparatus, the developer may adhere to the surface of the transfer belt that conveys the recording paper, and the developer may stain the recording material. In addition, according to this apparatus, the transfer belt surface may be unevenly charged due to the influence of humidity or the like in the apparatus. In this case, even if the transfer belt is uniformly charged by the transfer device so as to generate an electric field in the direction in which the charged toner is electrostatically attracted to the recording material, the transfer belt is transferred due to the uneven charging. The charge distribution on the belt surface becomes uneven. As a result, the electric field acting on the charged toner becomes non-uniform, uneven transfer occurs, and adverse effects such as uneven density occur on the image formed on the surface of the recording material. In a wet type image forming apparatus using a two-component developer including a toner and a carrier or a developer including a one-component developer including a toner as a developer,
Since a toner having a small particle size is used to obtain a high quality image, it is particularly important to keep the charge distribution of the transfer belt uniform. That is, for toner with a small particle size,
This is because the influence of the change in the electric field is easily exerted, so that the image is influenced even by the non-uniform charge distribution of the transfer belt, which has not been a problem in the past. The particle size of the toner used in a normal dry image forming apparatus is usually about 10 μm, whereas the toner having a particle size of 1 μm or less may be used in the wet image forming apparatus.

The present invention has been made in view of the above problems, and a first object thereof is an image capable of preventing the recording material from being contaminated due to the developer adhering to the surface of the transfer belt. To provide a forming apparatus. A second object is to provide an image forming apparatus capable of eliminating adverse effects such as uneven density generated in an image formed on the surface of a recording material due to uneven distribution of charges on the transfer belt surface. To provide.

In order to achieve the above-mentioned object, the invention of claim 1 is an image forming apparatus, wherein a latent image carrier on which a latent image is formed and a latent image carrier by a developer are carried. A developing device that develops the latent image on the body surface into a toner image, an endlessly movable transfer belt that conveys the recording material to the vicinity of the developing device, and the recording material between the latent image carrier. A transfer device for transferring an electric field between the latent image carrier and the recording member to transfer the toner image onto the surface of the recording material by applying an electric charge to the holding transfer belt, and the transfer device. A cleaning device for removing deposits adhering to the surface of the belt; and a downstream of a direction of rotation of the transfer belt with respect to the cleaning device for uniformizing the charge distribution on the surface of the transfer belt charged by the transfer device. And the transfer device It is characterized in that and a charge control device that is disposed at a position which is a rotating direction upstream of the transfer belt by.

According to a second aspect of the invention, there is provided the image forming apparatus according to the first aspect, characterized in that the charging control device is disposed in the vicinity of the transfer portion.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the developing device is a wet developing device that uses a developing solution as the developer, and the surface of the transfer belt is dried. A transfer belt drying device is provided.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the developing device is a wet developing device that uses a developing solution as the developer, and the charging control device is the The transfer belt is provided at a dry position.

According to a fifth aspect of the present invention, in an image forming apparatus, a latent image carrier on which a latent image is formed and a latent image on the surface of the latent image carrier is developed with a developer to form a toner image. By applying an electric charge to the developing device that holds the recording material between the developing device, the endlessly movable transfer belt that conveys the recording material to the vicinity of the developing device, and the latent image carrier. A transfer device for transferring an electric field between the latent image carrier and the recording member to transfer the toner image onto the surface of the recording material, and a cleaning device for removing deposits adhering to the surface of the transfer belt. And removing charges on the surface of the transfer belt charged by the transfer device, upstream of the cleaning device in the rotational direction of the transfer belt, and in the rotational direction of the transfer belt with respect to the transfer device. Before placed downstream It is to, characterized in that and a collector.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the front charge eliminating device is provided near a position where the recording material is separated from the transfer belt surface. To do.

According to a seventh aspect of the present invention, in an image forming apparatus, a latent image carrier on which a latent image is formed and a latent image on the surface of the latent image carrier is developed with a developer to form a toner image. By applying an electric charge to the developing device, the endlessly movable transfer belt that conveys the recording member to the vicinity of the developing device, and the transfer belt that holds the recording material between the latent image carrier. A transfer device for transferring an electric field between the latent image carrier and the recording member to transfer the toner image onto the surface of the recording material, and a cleaning device for removing deposits adhering to the surface of the transfer belt. And removing charges on the surface of the transfer belt charged by the transfer device, upstream of the cleaning device in the rotational direction of the transfer belt, and in the rotational direction of the transfer belt with respect to the transfer device. Placed downstream A static eliminator and a charge on the surface of the transfer belt that has not been removed by the previous static eliminator, which is downstream in the rotation direction of the transfer belt with respect to the cleaning device and of the transfer belt with respect to the transfer device. And a static eliminator disposed at a position upstream in the rotational direction, wherein the amount of static charge from the transfer belt surface by the front static eliminator is larger than the amount of static charge from the transfer belt surface by the post static eliminator. It is a feature.

[0011]

In the image forming apparatus according to the first aspect, when the developer adheres to the surface of the transfer belt, the developer is removed by the cleaning device. Further, in this image forming apparatus, after the developer, dust and the like adhering to the transfer belt surface are removed by a cleaning device, the charge distribution on the transfer belt is made uniform by the charge control device, and the charge on the transfer belt surface is transferred at the transfer portion. Try to keep the distribution uniform.

In the image forming apparatus of the second aspect, immediately after the charge control device makes the charge distribution on the transfer belt surface constant, the portion where the charge distribution on the transfer belt surface is uniform reaches the transfer portion. To do.

According to another aspect of the image forming apparatus of the present invention, the surface of the transfer belt which has been wet due to the developer adhering to the surface of the latent image carrier is dried by a drying device, and the transfer belt in the dry state is dried. The charge distribution is made uniform by the charge control means.

According to another aspect of the image forming apparatus of the present invention, the surface of the transfer belt, which has been moistened by the developer adhering to the surface of the latent image carrier, is dried by evaporating it with the lapse of time. The charge control device provided in the vicinity of the transfer belt in this state makes the charge distribution of the transfer belt uniform.

According to another aspect of the image forming apparatus of the present invention, the charge of the transfer belt is removed by the pre-electrification device, and electrostatic charges are applied between the transfer belt and foreign matter such as developer and dust adhering to the transfer belt surface. After the state in which the attractive force does not act, that is, the state in which it is easily removed from the transfer belt surface, the developer, dust and the like are removed from the transfer belt surface by a cleaning device.

In the image forming apparatus of the sixth aspect, the recording member conveyed while being electrostatically attracted to the surface of the transfer belt is provided near the position where the transfer belt and the recording member are separated. Separate with a static eliminator. In addition, in this device, the charge of the transfer belt is removed by the pre-charge eliminator so that the electrostatic attraction does not act between the transfer belt and foreign matter such as developer or dust adhering to the transfer belt surface. After that, the developer, dust and the like are removed from the transfer belt surface by a cleaning device.

According to another aspect of the image forming apparatus of the present invention, after the charge of the transfer belt is removed by the pre-electrification device so that the developer, dust and the like adhering to the surface of the transfer belt are easily removed from the surface of the transfer belt, In the cleaning device, the developer, dust, etc. are removed from the transfer belt surface, and the developer,
The charge is removed from the transfer belt surface with dust removed by the post-charge eliminator to make the charge distribution on the transfer belt surface uniform, so that the charge distribution on the transfer belt surface is kept uniform in the transfer section. To In addition, the front static eliminator
More charge is removed from the transfer belt surface than the post-static elimination device.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is a wet image forming apparatus will be described below. FIG. 1 is a front view showing a schematic configuration of a copying machine according to this embodiment. In this apparatus, in the vicinity of a transport unit 4 including a transfer belt 1, a driven roller 2, a drive roller 3 and the like, a recording paper 5 as a recording material that is electrostatically attracted to and transported by the transfer belt 1 is sequentially transferred. A yellow toner image forming unit Y that forms a toner image, a magenta toner image forming unit M, a cyan toner image forming unit C, and a black toner image forming unit B are provided.

The construction of each toner image forming unit Y, M, C, B will be described. However, since the toner image forming units Y, M, C, and B have the same configuration, the description will be given only for the yellow toner image forming unit Y, and for the other toner image forming units, the yellow toner image forming unit is shown in the drawing. For the parts corresponding to those in Y, M, C, and B are added after the numbers given to those in the unit, and the description is omitted. Yellow toner image forming unit Y
Around the photosensitive drum 30Y as the latent image carrier of
A charging device 31Y, an exposure device 32Y, a developing device 33Y, a transfer device 34Y, a charge removing device 35Y, and a cleaning device 36Y are arranged in order to form a yellow toner image on the surface of the photosensitive drum 30Y by an electrophotographic process. Here, the developing device 33Y is a wet developing device that uses, as a developer, a two-component developing solution including a toner and a carrier or a one-component developing solution including a toner. Also,
The transfer device 34Y includes the photosensitive drum 30Y and the transfer belt 1.
The recording paper 5 which is interposed between the photosensitive drum 3 and the recording paper 5 is
It is composed of a transfer charger which gives electric charges to the transfer belt 1 so as to generate an electric field in a direction in which the toner image formed on the 0Y surface is electrostatically attracted.

A first transport guide plate for supplying a recording paper 5 as a recording material to the transfer belt 1 from a paper feeding device (not shown) is provided upstream of the yellow toner image forming unit Y in the rotational direction of the transfer belt 1. 6 is provided. On the other hand, a separation charger 7 for separating the recording paper 5 from the transfer belt 1 is provided downstream of the black toner image forming unit B in the rotation direction of the transfer belt 1. The separation charger 7 removes electricity from the transfer belt 1 and the recording paper 5,
By weakening the electric attraction between the transfer belt 2 and the recording paper 5, the recording paper 5 is separated from the surface of the transfer belt 2 due to its rigidity. A second transport guide plate 8 for guiding the recording paper 5 separated from the surface of the transfer belt 1 to a fixing device (not shown) is provided near the separating portion.

A first static eliminator 9 as a pre-static eliminator for removing charges remaining on the surface of the transfer belt 1 is provided downstream of the separation charger 7 in the rotational direction of the transfer belt 1. A transfer belt cleaning device 10 for removing the developer, dust, and the like adhering to the surface of the transfer belt 1 is provided downstream of the first static eliminator 9 in the rotational direction of the transfer belt 1. This transfer belt cleaning device 10
A cleaning roller 11 which is provided in contact with the transfer belt 1 and removes a developer and the like from the surface of the transfer belt 1 by rotating at a peripheral speed difference from the transfer belt 1, and an arrow a in FIG.
As shown by (1), it is composed of a fan 12 for generating an air flow toward the surface of the cleaning roller 11 and evaporating the developer adhering to the surface of the cleaning roller 11 to dry the surface. In addition, the cleaning device 1
A second static eliminator 13 for removing charges on the surface of the transfer belt 1 and making the charge distribution on the surface of the transfer belt 1 uniform is provided downstream of the transfer belt 1 in the rotational direction of 0. The second static eliminator 13 is the "charge controller" described in the claims.
And is also a "post-static elimination device" described in the claims. The second static eliminator is a static eliminator charger 14
And a counter electrode 15 provided on the opposite side of the static elimination charger 14 to the transfer belt 1.

The operation of this device configured as described above will be described. In forming an image, a paper feeding device (not shown) feeds the recording paper 5 to the first conveyance guide plate 6,
The conveyance guide plate 6 conveys the recording paper 5 to the surface of the transfer belt 1. The transfer belt 1 attracts the recording paper 5 transported by the first transport guide plate 6 to the surface thereof by the electric charge applied by the transfer device 34Y. Here, the transfer belt 1 is rotated in the direction of arrow b by the rotational force transmitted from the drive roller 3 driven by a drive mechanism (not shown), and the transfer paper 5 is transferred to the toner image forming units Y, M, C, B.
Of the photoconductor drums 36Y, 36M, 36C,
It is conveyed at the same speed as the peripheral speed of 36B.

On the surface of the photosensitive drum 36Y which rotates at the same speed as the transfer belt 1, each device arranged around the photosensitive drum forms a yellow toner image. That is, the charging device 31Y uniformly charges the surface of the photosensitive drum 30Y, the exposure device 32Y forms an electrostatic latent image on the surface of the photosensitive drum 30Y, and the developing device 33Y supplies yellow toner to the electrostatic latent image. Finally, a yellow toner image is formed.
The transfer device 34Y transfers the yellow toner image onto the surface of the recording paper 5 conveyed by the transfer belt 1 to the nip portion NY formed by the transfer belt 1 and the photoconductor drum 30Y. That is, the transfer device 34Y applies an electric charge to the transfer belt 1 to generate an electric field in the vicinity of the nip portion N, and the photosensitive drum 3
6Y transfer the yellow toner image on the surface of the transfer sheet 5
Electrostatically move in the direction to transfer the yellow toner image onto the transfer paper 5. Further, the charge removing device 35 removes the residual charge on the surface of the photosensitive drum 36, and the cleaning device 36
Y removes the yellow toner remaining on the surface of the photosensitive drum 36Y.

The transfer belt 1 transfers the recording paper 5 having the yellow toner image adhered to the surface thereof by the above operation.
Nip portion NM formed by transfer belt 1 and magenta toner image forming unit M, nip portion NC formed by transfer belt 1 and cyan toner image forming unit C, and nip formed by transfer belt 1 and black toner image forming unit B It is sequentially conveyed to the part NB. Then, the magenta toner image forming unit M forms a magenta toner image on the recording paper 5 in the nip portion NM, the cyan toner image forming unit forms a cyan toner image in the nip portion NC, and the nip portion N.
In B, the black toner image forming unit B sequentially transfers the black toner images onto the transfer paper 5, and the toner images are superposed on the surface of the transfer paper 5. The operation of each toner image forming unit M, C, B to form a toner image and the operation of transferring the toner image to the recording paper 5 are the same as the operation of the yellow toner image forming unit Y.

By the above operation, the separating device 7 separates the recording paper 5 on which the four color toner images are superposed from the surface of the transfer belt 1. That is, the separation device 7
Part of the electric charge electrostatically adsorbing the recording paper 5 distributed on the transfer belt 1 is removed, and the electrostatic adsorption force between the transfer belt 1 and the recording paper 5 is weakened. The weakened electrostatic attraction force and the rigidity of the recording paper 5 combine to separate the recording paper from the surface of the transfer belt 1. Then, the recording paper 5 separated from the surface of the transfer belt 1 is conveyed by the second conveyance guide plate 8 to a fixing device (not shown), and the fixing device fixes the toner image on the recording paper. The recording paper 5 on which the fixing is completed is discharged to the outside of the apparatus by a mechanism (not shown).

The portion of the transfer belt 1 from which the recording paper 5 is separated reaches the vicinity of the first static eliminator 9 by the rotation of the transfer belt 1. As described above, the transfer belt 1 is charged with electric charges for transferring the toner images to the recording paper 5 by the transfer devices 34Y, 34M, 34C, and 34B, so that part of the electric charges is separated by the separation charger 7. Although removed, electric charges still remain in the vicinity of the first static eliminator 9. This residual charge electrostatically adsorbs foreign matter such as developer and dust.
If left as it is, it is difficult for the transfer belt cleaning device 10, which will be described in detail later, to remove the foreign matter. Therefore, the first static eliminator 9 removes the electric charges remaining on the surface of the transfer belt 1 by corona charging to remove foreign matters such as developer and dust that have adhered to the surface of the transfer belt 1 during the image formation process. The transfer belt cleaning device 10 facilitates removal.

The portion of the transfer belt 1 from which the residual charge has been removed by the first static eliminator 9 reaches the vicinity of the transfer belt cleaning device 10 by the rotation of the transfer belt 1. The cleaning roller 11 of the cleaning device 10 rotates with a peripheral speed difference from the transfer belt 1 in a state of being in contact with the transfer belt 1 to remove the developer, dust, and the like adhering to the surface of the transfer belt 1. As described above, the electric charge on the surface of the transfer belt 1 is removed to some extent by the first static eliminator, and the force of electrostatically adsorbing foreign matter to the transfer belt 1 is weakened. Foreign matter can be efficiently removed from the surface.

The portion of the transfer belt 1 from which foreign substances such as developer and dust have been removed by the cleaning device 10 reaches the vicinity of the second static eliminator 13 by the rotation of the transfer belt 1. As described above, the charge on the surface of the transfer belt 1 is removed by the first charge removing device 9, so that the charge distribution is once uniform. The charge distribution is only uniform in the presence of foreign matter such as dust. Therefore, when the foreign matter is removed by the cleaning device 10 thereafter, the foreign matter is removed together with the electric charge carried by the foreign matter, so that the transfer belt 1 after the foreign matter is removed.
The charge distribution on the surface becomes non-uniform. Therefore, the second static eliminator 13 is provided in order to make the charge distribution of the transfer belt 1 after the foreign matter is removed uniform. The second static eliminator 13 removes the electric charge distributed on the transfer belt 1 by corona charging the transfer belt 1 after the foreign matter is removed by the static eliminator charger 13, and the transfer belt 1 after the foreign matter is removed. To make the charge distribution uniform. As a result, the unevenly distributed charges on the surface of the transfer belt 1 cause the charged developer to be transferred to the photosensitive drums 36Y and 36Y.
It is possible to prevent an image defect such as density unevenness from occurring by adversely affecting the electric field that is electrostatically moved from M, 36C, and 36B toward the transfer paper 5. (Hereinafter, margin)

The state of the electric potential on the surface of the transfer belt 1 of this apparatus, which has been described above, will be described below.
The following description focuses on one point. FIG. 2 is an explanatory diagram showing the state of the potential on the surface of the transfer belt 1. In FIG. 2, the vertical axis represents the potential on the surface of the transfer belt 1, and the horizontal axis represents the transfer belt 1.
Indicates the position of. Here, in order to electrostatically adsorb the charged developer from the photoconductor drums 30Y, 30M, 30C, and 30B to the transfer paper 5, the transfer devices 34Y and 3Y are provided.
4M, 34C, and 34B give positive charges to the transfer belt 1. Based on this, the state of the electric potential of the transfer belt 1 will be specifically described below. As shown by the first potential level 50 in FIG. 2, the potential on the inner surface or the outer surface of the transfer belt 1 after the transfer paper 5 is separated and before the charge removal by the first charge removal device 9 is −800V. Even if the transfer belt cleaning device 10 tries to remove foreign matter such as developer and dust attached to the surface of the transfer belt 1 under the condition of this surface potential, the foreign matter cannot be easily removed because it is electrostatically adsorbed. Therefore, the first static eliminator 9 statically removes 700 V as the first static eliminator 51, and the surface potential of the transfer belt 1 is set to the second potential level 52 of minus 100 V, so that the foreign matter and the transfer belt 1 are electrostatically charged. The suction force is weakened, and in this state, the transfer belt cleaning device 10 removes the foreign matter. However, in the state where the charge is removed by the first charge eliminating device (second potential level 52), the potential on the surface of the transfer belt 1 is uniform with the foreign matter adhering to the surface of the transfer belt 1. When the foreign matter is removed, locally uneven potentials are generated. Therefore, the second static eliminator 13 again performs static erasing at 100 V, which is the second static eliminator 53, to set the potential of the surface of the transfer belt 1 to the third level.
The potential level 54 is set to 0 V to eliminate local unevenness of the potential. Since the nonuniformity of the electric potential on the surface of the transfer belt 1 caused by removing the foreign matter is local, the nonuniformity is not displayed at the second electric potential level 52 in FIG. Although not shown, the transfer belt 1 whose surface potential is 0 V (third potential level 54) is
Positive charges for transfer are applied by the transfer devices 34Y, 34M, 34C, and 34B, and after passing through the transfer device 34B, the voltage becomes −4000V, and the separation charger 7 weakens the electrostatic attraction force of the recording paper 5 to the transfer belt. The charge is removed to minus 800 V (first potential level 50). Focusing on one point on the surface of the transfer belt 1, the state described above is repeated with the image formation. As is clear from the above description, the static elimination amount of the first static eliminator 9 as the front static eliminator is 700 V (first static eliminator 51), and is the static elimination amount by the static eliminator of the second static eliminator as the post static eliminator. There is 10
It is larger than 0 V (second charge removal amount 53).

In addition to the configuration of the embodiment described above, as shown in FIG. 3, a fan 16 as a transfer belt drying device may be provided upstream of the second charge removing device 13 in the rotational direction of the transfer belt 1. . If the fan 16 is provided, by generating an air flow in the direction of arrow c, the developing solution adhering to the surface of the transfer belt 1 can be evaporated and the transfer belt can be dried. Therefore, the function of the second static eliminator is not impaired when the transfer belt 2 is wet with the developer.

Further, as shown in FIG. 3, the second static eliminator 13 in the above-described embodiment is provided with a photosensitive drum 36Y.
From the nip portion NY as a transfer portion where the transfer is performed from the transfer belt 1 to the transfer paper 5, in the rotation direction of the transfer belt 1, and
It may be provided in the immediate vicinity of the nip portion NY. If this configuration is adopted, the portion of the transfer belt 1 where the electric field distribution is made uniform by the second static eliminator 13 immediately reaches the nip portion NY, so that the charge distribution is uniform before reaching the nip portion. The electric charge distribution in the portion where is not affected by humidity or the like does not become non-uniform again. Further, by providing the second static eliminator 13 at this position, even if the transfer belt 1 becomes wet with the developing solution in the vicinity of each toner image forming unit, the portion of the transfer belt 1 wet with the developer becomes the second portion. Before reaching the vicinity of the static eliminator 13, since it has already dried, the second
The function of the static eliminator is not impaired by the fact that the transfer belt surface is wet.

The first static eliminator 9 described above may be provided at the position where the recording paper 5 is separated from the surface of the transfer belt 1, that is, at the position where the separation charger 7 was provided. According to this configuration, since the first static eliminator 9 can be used also as a separation charger, it is not necessary to separately provide a separation charger.

[0033]

According to the first aspect of the invention, the developer adhering to the surface of the transfer belt is removed by the cleaning device, so that the recording material can be prevented from being contaminated with the developer. Further, according to the present invention, before the transfer device transfers the toner image from the latent image carrier to the recording material,
Since the charge control device makes the charge distribution on the transfer belt surface uniform, the charge is unevenly distributed on the transfer belt surface, resulting in an uneven electric field that conveys toner from the transfer belt toward the recording material. It is possible to prevent image defects such as density unevenness from occurring. Further, according to the present invention, after the cleaning device removes the foreign material such as the developer and dust on the transfer belt surface, the charge control device makes the charge distribution on the transfer belt surface uniform, so that the charge on the surface of the transfer belt becomes Unlike the case where the foreign matter adhering to the surface of the transfer belt is removed and transferred as it is after the distribution is made uniform,
Once the charge distribution of the transfer belt is made uniform, the charge distribution does not become non-uniform again when the foreign matter and the charges on it are removed. Therefore, the charge distribution on the transfer belt after removing the foreign matter becomes nonuniform, and accordingly, the electric field that conveys toner from the transfer belt toward the recording material becomes nonuniform, resulting in image defects such as density unevenness in the image. Can be prevented.

According to the invention of claim 2, in addition to the effect similar to that of claim 1, the charge on the surface of the transfer belt is immediately after the charge distribution on the surface of the transfer belt is made uniform by the charge control device. Since the portion of which the distribution is constant reaches the transfer device, the charge distribution on the surface of the transfer belt is affected by, for example, the humidity in the image forming apparatus before the transfer belt reaches the transfer device. It is possible to prevent the occurrence of non-uniformity again. Therefore, it is possible to more effectively prevent the electric field for transfer from becoming non-uniform due to the non-uniform charge on the surface of the transfer belt, and the image from being disturbed.

According to the invention of claim 3, in addition to the same effect as the invention of claim 1, the surface of the transfer belt in which the developing solution is adhered is dried by a drying device, and thereafter,
Since the transfer belt in this dry state is kept constant by the charge control device, it is possible to prevent the charge control device from not fully functioning due to the transfer belt being in a wet state. Therefore, even if the transfer belt is once wetted by the developing solution at the transfer portion, the charge control device can sufficiently function and the charge distribution on the transfer belt surface can be made uniform, so that the transfer in the transfer device can be performed. Therefore, it is possible to suppress the occurrence of the disturbance of the electric field for preventing the occurrence of image defects on the surface of the recording material.

According to the invention of claim 4, in addition to achieving the same effect as that of the invention of claim 1, the developing solution evaporates with the passage of time on the transfer belt surface with the developing solution attached thereto. As a result, the charge control device is dried, and the dried portion is made constant by the charge control device. Therefore, it is possible to prevent the charge control device from not fully functioning due to the wet state of the transfer belt. Therefore, even when the transfer belt is in a wet state after passing through the transfer portion, it is dried before it reaches the charging control device, so that it is possible to prevent the occurrence of a defective image on the surface of the recording material as in the third aspect. it can.

According to the fifth aspect of the present invention, since the developer and the like attached to the surface of the transfer belt are removed by the cleaning device, it is possible to prevent the recording material from being soiled with the developer. Further, according to the present invention, the electric charge on the surface of the transfer belt is removed by the pre-charge eliminator, so that the electric attraction force between the transfer belt and the foreign matter such as the developer and dust adhering to the surface of the transfer belt is reduced. After that, the cleaning device removes the developer, dust, and the like, so that the developer, dust, and other foreign matter can be efficiently removed from the transfer belt surface.

According to the sixth aspect of the present invention, the recording material conveyed while being attracted to the surface of the transfer belt is separated by the static eliminator provided near the position where the transfer belt and the recording material are separated. Therefore, it is not necessary to provide a separate charger in the image forming apparatus in addition to the static eliminator, the number of parts is reduced, and the manufacturing cost is reduced.

According to the seventh aspect of the present invention, since the developer and the like attached to the surface of the transfer belt are removed by the cleaning device, the recording material can be prevented from being contaminated with the developer. Further, according to the present invention, before the transfer device transfers the toner image from the latent image carrier to the recording material,
The charge eliminator makes the charge distribution on the transfer belt surface uniform, so that the charge is unevenly distributed on the transfer belt surface.
It is possible to prevent the occurrence of image defects such as color unevenness caused by non-uniformity of the electric field that conveys toner from the transfer belt toward the recording material. According to the invention,
After removing foreign materials such as developer and dust on the transfer belt surface with the cleaning device, the charge distribution on the transfer belt surface is made uniform by the post-electrification device. It is possible to prevent the charge distribution of the transfer belt in a state where the foreign matter is removed and the foreign matter is removed from becoming nonuniform. Therefore, the charge distribution on the transfer belt after removing the foreign matter becomes non-uniform, and accordingly, the electric field that conveys toner from the transfer belt toward the recording material becomes non-uniform, resulting in image defects such as color unevenness in the image. Can be prevented. Further, according to the present invention, the electric charge on the surface of the transfer belt is removed by the pre-charge eliminator, so that the electric attraction force between the transfer belt and the foreign matter such as the developer and dust adhering to the surface of the transfer belt is reduced. After that, since the foreign matter is removed by a cleaning device, the foreign matter such as developer and dust can be efficiently removed from the transfer belt surface. Further, according to the present invention, since the amount of electric charges removed from the transfer belt surface by the pre-electrification device is larger than the amount of electric charges removed by the post-electrification device from the transfer belt surface, the cleaning device removes the developer from the transfer belt surface. Before the removal of dust and the like, the pre-charge eliminator can remove sufficient charges from the transfer belt surface.
Therefore, after the electric attraction force between the transfer belt and the foreign matter such as the developer and dust adhering to the surface of the transfer belt is sufficiently reduced, the foreign matter is removed by the cleaning device, so that the foreign matter is efficiently transferred. It can be removed from the belt surface.

[Brief description of drawings]

FIG. 1 is a front view showing a schematic configuration of an electrophotographic copying machine according to an embodiment.

FIG. 2 is an explanatory diagram showing a potential on a surface of a transfer belt of the electrophotographic copying machine shown in FIG.

FIG. 3 is a front view showing a schematic configuration of an electrophotographic copying machine according to a modified example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 transfer belt 2 driven roller 3 drive roller 4 transport unit 5 recording paper 6 first transport guide plate 7 separation charger 8 second transport guide plate 9 first static eliminator 10 transfer belt cleaning device 11 cleaning roller 12 fan 13 second static eliminator 14 static eliminator charger 15 counter electrode 16 fan 30 photoconductor drum 31 charging device 32 exposure device 33 developing device 34 transfer device 35 static eliminator 36 cleaning device 50 first potential level 51 first static charge level 52 second potential level 53 second static charge level 54 Third potential level Y Yellow toner image forming unit M Magenta toner image forming unit C Cyan toner image forming unit B Black toner image forming unit NY Nip portion NM Nip portion NC Nip portion NB Nip portion

Claims (7)

[Claims] 1. A latent image carrier on which a latent image is formed, a developing device for developing a latent image on the surface of the latent image carrier with a developer to form a toner image, and a recording material near the developing device. Between the latent image carrier and the recording target member, by applying an electric charge to the transfer belt that holds the recording target member between the transferable endless transfer transfer belt and the latent image supporting member. An electric field to transfer the toner image onto the surface of the recording material, a cleaning device for removing deposits adhering to the transfer belt surface, and a transfer belt surface charged by the transfer device. A charge control device that makes the charge distribution uniform, is provided at a position downstream of the cleaning device in the rotational direction of the transfer belt and upstream of the transfer device in the rotational direction of the transfer belt, Is equipped with That the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the charge control device is disposed in the vicinity of a transfer portion. 3. The image forming apparatus according to claim 1, wherein the developing device is a wet developing device that uses a developing solution as the developer, and further comprises a transfer belt drying device that dries a transfer belt surface. apparatus. 4. The wet developing device in which the developing device uses a developing solution as the developer, and the charge control device is provided at a dry position of the transfer belt. 1. The image forming apparatus of 1. 5. A latent image carrier on which a latent image is formed, a developing device for developing a latent image on the surface of the latent image carrier with a developer to form a toner image, and a recording material near the developing device. Between the latent image carrier and the recording target member, by applying an electric charge to the transfer belt that holds the recording target member between the transferable endless transfer transfer belt and the latent image supporting member. A transfer device that transfers an electric field to the surface of the recording material by generating an electric field on the recording material; a cleaning device that removes deposits adhering to the surface of the transfer belt; and a transfer belt surface charged by the transfer device. And a pre-charge eliminator disposed upstream of the cleaning device in the rotation direction of the transfer belt and downstream of the transfer device in the rotation direction of the transfer belt. Image forming apparatus characterized in that 6. The image forming apparatus according to claim 5, wherein the precharger is provided at a position where the recording material is separated from the surface of the transfer belt. 7. A latent image carrier on which a latent image is formed, a developing device for developing a latent image on the surface of the latent image carrier with a developer to form a toner image, and a recording member near the developing device. Between the latent image carrier and the recording target member, by applying an electric charge to the transfer belt that holds the recording target member between the transferable endless transfer transfer belt and the latent image supporting member. A transfer device that transfers an electric field to the surface of the recording material by generating an electric field on the recording material; a cleaning device that removes deposits adhering to the surface of the transfer belt; and a transfer belt surface charged by the transfer device. And a pre-charge eliminator for removing the electric charges of the pre-charge eliminator, which is disposed upstream of the cleaning device in the rotational direction of the transfer belt and downstream of the transfer device in the rotational direction of the transfer belt. Not removed by device After the charge is removed from the surface of the transfer belt, the charge is removed at a position downstream of the cleaning device in the rotational direction of the transfer belt and upstream of the transfer device in the rotational direction of the transfer belt. Static eliminator,
An image forming apparatus, comprising: a static electricity removal amount from the transfer belt surface by the front static eliminator, and a static electricity removal amount from the transfer belt surface by the rear static eliminator.