JP3928719B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to an improvement of an image forming apparatus that transfers an image formed on an image forming carrier onto a recording material via an intermediate transfer member.
[0002]
[Prior art]
Conventional image forming apparatuses include, for example, a photosensitive drum (image forming carrier) on which an electrostatic latent image is formed and supported and the electrostatic latent image is visualized with toner, and the photosensitive drum. On the other hand, there is known a transfer roller or a paper transfer belt that is disposed so as to be able to contact and roll and transfers a visible image formed on a photosensitive drum to a recording material such as paper.
In this type of image forming apparatus, at the time of transfer to a recording material, the toner on the photosensitive drum is mechanically in close contact with the photosensitive drum by the pressing force of the transfer roll (or paper transfer belt), Increases physical adhesion.
For this reason, good transfer efficiency to the transfer roll (or paper transfer belt) cannot be obtained only by the electric force (Coulomb force).
Therefore, in order to increase the transfer efficiency, a peripheral speed difference of about 0.5% to 7.0% is provided between the photosensitive drum and the transfer roll (or paper transfer belt), and the toner and the photosensitive drum are mechanically connected. In general, a method of destroying the physical adhesion of the toner by applying a shear force between the two is used (see, for example, Patent Document 1 and Patent Document 2).
[0003]
On the other hand, as an example of a color image forming apparatus of the intermediate transfer type, for example, an intermediate transfer belt as an intermediate transfer member is disposed opposite to a photosensitive drum as an image forming carrier, and each color is formed on the intermediate transfer belt. It is already known that a component toner image is sequentially transferred to a recording material such as a sheet of paper from an intermediate transfer belt after primary transfer.
[0004]
[Patent Document 1]
JP-A-9-106194 (claims column, embodiment column, FIG. 1-3)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 10-161441 (claims column, embodiment column, FIG. 1)
[0005]
[Problems to be solved by the invention]
By the way, in this type of color image forming apparatus, in order to increase the transfer efficiency in the primary transfer portion, the above-described speed difference technique is applied. For example, the peripheral speed of the intermediate transfer belt is set to the peripheral speed of the photosensitive drum in the primary transfer portion. It is conceivable to set faster than the speed.
However, for example, if the peripheral speed of the intermediate transfer belt is made faster than the peripheral speed of the photosensitive drum in the primary transfer portion, the intermediate transfer belt pulls the photosensitive drum due to electrostatic adsorption force, so that the rotational speed of the photosensitive drum varies. This may cause banding and color misregistration.
This is because, for example, when the drive transmission of the photosensitive drum is performed by a gear transmission mechanism, the tooth surface of the driving gear applies a force to the tooth surface of the driven gear, thereby rotating the photosensitive drum. However, since the intermediate transfer belt pulls in the direction in which the photosensitive drum advances, the tooth surface of the driven gear floats from the tooth surface of the driving gear, resulting in fluctuations in the rotational speed of the photosensitive drum (transfer position). (Circumferential speed difference fluctuation) occurs.
[0006]
As described above, from the viewpoint of preventing banding and color misregistration, in the color image forming apparatus, it is desirable that the peripheral speeds of the photosensitive drum and the intermediate transfer belt are as fast as possible at the transfer position.
In other words, in a color image forming apparatus, the problem of improving transfer efficiency and the problem of preventing image quality defects such as banding and color overlay are contradictory, making it difficult to achieve both. Met.
The present invention has been made to solve the above technical problem, and is capable of stably obtaining good image quality (particularly color image quality) while effectively ensuring transfer efficiency. Is to provide.
[0007]
[Means for Solving the Problems]
That is, according to the present invention, as shown in FIG. 1, in an image forming apparatus for transferring an image formed on an image forming carrier 1 to a recording material 3 via an intermediate transfer member 2, the image forming carrier 1 and the intermediate One of the transfer bodies 2 is formed in a drum shape, and the other is formed in a belt shape that is stretched over a plurality of stretching rolls 4, and is formed in a belt shape along the outer shape of the drum-shaped member formed in the drum shape. The belt-shaped member is placed in contact over a predetermined area, and the circumferential length of the contact area m between the drum-shaped member and the belt-shaped member is upstream of the contact area m to form the contact area m. provided so as to be above the circumference of the disposed a tension roller 4a, of the contact region m, facing the portion excluding both ends a of the contact region m, B (the upstream end a, a downstream end B) and placing one or more transfer members 5 a transfer bias is applied It is characterized in that the peeling at the potential rise of the intermediary transfer member 2 is disposed a release time of potential rise suppression electrode 6 is suppressed to a downstream end B of the contact region m.
Reference numeral 7 denotes a secondary transfer member for transferring the transfer image on the intermediate transfer body 2 to the recording material 3.
[0008]
In such technical means, the present invention covers a wide range of intermediate transfer type image forming apparatuses. In particular, a color image forming apparatus is preferable in terms of a great technical effect, but even a black and white image forming apparatus can achieve higher image quality and higher transfer efficiency than a conventional image forming apparatus. is there.
The image forming carrier 1 and the intermediate transfer member 2 may be in the form of a drum and the other in the form of a belt. For the drum-shaped image forming member 1, a belt-like intermediate transfer member may be used. 2 (this combination is shown in FIG. 1), and a drum-shaped intermediate transfer body 2 may be used for the belt-shaped image forming carrier 1.
Further, the image forming carrier 1 and the intermediate transfer member 2 may be driven by separate drive systems, but the image forming carrier 1 and the intermediate transfer member 2 are arranged in contact with each other over a relatively large area. Therefore, it is possible to employ a method in which one of the image forming carrier 1 and the intermediate transfer member 2 is used as a drive source and the other is driven to rotate.
According to this aspect, one drive mechanism can be omitted, and accordingly, the apparatus can be reduced in size and cost.
[0009]
Moreover, the contact area m range should just be more than this reference value by making the circumference of the tension roll (upstream tension roll) 4a arrange | positioned upstream of the said contact area m into a reference value.
Here, the reason why the circumference of the upstream tension roll 4a is set as the reference value is as follows.
That is, as shown in FIG. 1, the belt-shaped intermediate transfer member (for example, intermediate transfer belt) 2 now varies in speed due to the swinging and eccentric components of the tension roll 4. Since the speed fluctuation is usually a sine waveform of one rotation period of the tension roll 4, as shown by a and b in FIG. Pushing and pulling occurs between the image (toner image) G and the surface of the drum-shaped image forming carrier (for example, the photosensitive drum) 1, and a mechanical shearing force F (see FIG. 4) can be obtained.
At this time, in order to obtain one cycle of the speed fluctuation component of the intermediate transfer belt 2 in which a portion with a high peripheral speed and a portion with a low peripheral speed alternately occur once each, the peripheral length of at least the upstream stretch roll 4a is equal to or greater. Need length.
Therefore, in the present invention, by making the circumferential length of the contact area m between the photosensitive drum 1 and the intermediate transfer belt 2 equal to or greater than the circumferential length of the upstream tension roll 4a of the intermediate transfer belt 2, For example, as shown in FIGS. 3A and 3B, the image is pushed and pulled between the transfer image (toner image) G and the surface of the photosensitive drum 1 by the change in the peripheral speed of the upstream tension roll 4a within the contact area m. Will happen.
[0010]
As a result, as shown in FIG. 4, a shearing force F is generated between the surface of the photosensitive drum 1 and the transfer image (toner image) G, and the transfer image G can be easily separated from the photosensitive drum 1. It becomes.
Further, although a shearing force F is generated, since the space between the photosensitive drum 1 and the intermediate transfer belt 2 is restricted by a relatively large area, the peripheral speed difference in the contact region m (slip of the intermediate transfer belt 2). Hardly occurs.
That is, the difference in peripheral speed between the photosensitive drum 1 and the intermediate transfer belt 2 is minimized (a non-slip level), and a mechanical shearing force is generated between the photosensitive drum 1 and the transfer image (toner image) G. F can be obtained, and accordingly, good transfer efficiency can be obtained while ensuring high banding and color misregistration prevention performance.
[0011]
In the present invention, as the upstream tension roll 4a, a tension roll positioned upstream of the contact area m is used to form the contact area m. Attari, or it is preferred wrap angle is largest tension roller.
For example, one of the causes that contributes to the occurrence of speed fluctuations in the belt-shaped intermediate transfer member (intermediate transfer belt) 2 is the effect of the swinging roll or eccentric component on the upstream side of the transfer position. In particular, the influence of the deflection and the eccentric component of the drive roll serving as the driving source, or the influence of the deflection and the eccentric component of the tension roll having the largest winding angle can be mentioned.
Accordingly, as the upstream tension roller 4a, but the stretching roller is used on the upstream side of the transfer position, in particular, the drive source to become the driving roll or wrap angle is more than the circumferential length of the largest stretch roll contact By doing so, a larger shearing force F can be applied in the contact area m , and high transfer efficiency can be obtained.
[0012]
Further, in the present invention, “facing the portion excluding both ends A and B (upstream end A and downstream end B) of the contact region m” between the drum-shaped member and the belt-shaped member means both ends A of the contact region m. , B are arranged to face each other (a gap 8 (see FIG. 5) is formed between the drum-like member and the belt-like member at a portion adjacent to both ends A, B, and image scattering is likely to occur). is there.
Here, the transfer member 5 is typically a transfer roll, but is not limited thereto, and a transfer brush, a transfer pad, or the like may be appropriately selected as long as it is a functional member capable of realizing a transfer operation.
Further, at this time, as shown in FIG. 5A, the transfer member 5 is in contact with the drum-like member (image forming carrier 1 in this example) and the belt-like member (intermediate transfer member 2), and the transfer operation. Is disposed in a stable region, and the transfer action area k of the transfer member 5 is separated from both ends A and B of the contact region m. Is difficult to be affected by the transcription working area k.
For this reason, in the gap 8 portion, abnormal flying scattering of the image material is unlikely to occur, and the image on the image forming carrier 1 can be faithfully transferred without being substantially destroyed.
[0013]
In particular, the transfer member 5 is preferably disposed so that the upstream end A position of the contact region m between the drum-like member and the belt-like member is out of the transfer action region k of the transfer member 5. If the position of the upstream end A deviates from the transfer action area k of the transfer member 5, the image scattering at the pre-nip portion between the drum-shaped member and the belt-shaped member (the gap 8 at the upstream end A of the contact area m) is effectively prevented. Can be prevented.
[0014]
In this regard, as shown in the comparative example of FIG. 5B, the transfer member 5 ′ is opposed to the nip portion n between the drum-like member (eg, the image forming carrier 1) and the belt-like member (eg, the intermediate transfer member 2). In the arrangement mode, the transfer working area k ′ of the transfer member 5 ′ is widened with respect to the narrow nip portion n, so that the transfer member inevitably enters the gap 8 ′ between the drum-like member and the belt-like member. Due to the influence of the 5 ′ transfer action area k ′, a strong transfer electric field acts on the gap 8 ′ or abnormal discharge occurs, so that the image material is likely to be scattered.
[0015]
In such a technical means, in the contact region m between the image forming carrier 1 and the intermediate transfer member 2, the image forming carrier 1 and the intermediate transfer member 2 are sufficiently in close contact due to the effect of the shearing force F. Therefore, the film is peeled off in a natural state at the downstream end B of the contact area m (the peeling portion between the image forming carrier 1 and the intermediate transfer member 2).
Accordingly, at the time of peeling, the potential of the intermediate transfer member 2 becomes a high potential (usually 1 kV or more) due to a rise in the potential at the time of peeling, and the discharge after peeling causes the scattering of the image and the generation of reverse polarity toner.
At this time, if the peeling potential increase suppression electrode 6 is disposed at the downstream end B of the contact area m between the image forming carrier 1 and the intermediate transfer member 2, the peeling between the image forming carrier 1 and the intermediate transfer member 2 can be achieved. In addition, the charged charge of the intermediate transfer member 2 can be neutralized, and the potential of the intermediate transfer member 2 can be prevented from becoming high after peeling.
That is, as shown in FIG. 1, for example, when the drum-shaped image forming carrier (photosensitive drum) 1 has a negative potential and the charged color material (not shown) has a negative charge, the transfer arranged in the contact area m. When transferring a member (primary transfer electrode) 5 by applying a positive potential, the belt-like intermediate transfer member (intermediate transfer belt) 2 after transfer is charged to a positive potential. At the time of peeling, the CV (C: electric capacity, V: potential difference) in the gap between the photosensitive drum 1 and the intermediate transfer belt 2 changes so as to be constant before and after the peeling, and is originally charged to several hundred volts. Further, the potential of the intermediate transfer belt 2 rises to several kV (several tens of kV depending on conditions) at a site downstream of the peeling portion.
However, if the peeling potential increase suppression electrode 6 is disposed at the downstream end B of the contact area m, a rapid increase in the potential of the intermediate transfer belt 2 after peeling can be suppressed.
[0016]
Moreover, as an aspect of the potential increase suppression electrode 6 at the time of peeling, for example, a roll-shaped electrode or a flat plate electrode can be mentioned. Furthermore, these include a drum-shaped member (image forming carrier 1 in this example) and a belt-shaped member (in this example). It is preferable that the belt-shaped member is disposed across the contact area m side and the non-contact area side with the downstream end B of the contact area m with the intermediate transfer member 2) interposed therebetween.
Here, “arranged across” means that immediately after the downstream end B, if the intermediate transfer member 2 is peeled off from the image forming carrier 1, the potential of the intermediate transfer member 2 rapidly rises. This is intended to suppress the voltage increase at the time of peeling of the intermediate transfer body 2 by causing the potential increase inhibiting electrode 6 at the time of peeling to act in the region including the.
Further, the shape of the potential increase inhibiting electrode 6 at the time of peeling is not particularly limited and may be appropriately selected. However, an embodiment in which the nip pressure between the image forming carrier 1 and the intermediate transfer member 2 is not increased as much as possible is preferable.
Therefore, when the peeling potential rising suppression electrode 6 is a roll-like electrode, it is preferable that the electrode is constituted by a foamed roll having a low hardness, for example.
Moreover, when the potential increase suppression electrode 6 at the time of peeling is a flat plate electrode, it is preferable that the surface is formed with a conductor fiber. By embedding a soft material such as a conductor fiber on the surface of the potential increase inhibiting electrode 6 at the time of peeling, an increase in the nip pressure between the image forming carrier 1 and the intermediate transfer member 2 can be suppressed.
[0017]
Further, the potential increase inhibiting electrode 6 at the time of peeling may be set to ground or float in addition to a mode in which a low bias (for example, a bias (about 100 to 300 V) corresponding to the potential of the intermediate transfer body 2 before peeling) is applied. Good.
For example, when a high bias is applied to the potential rise suppression electrode 6 at the time of peeling, the potential of the intermediate transfer body 2 rapidly rises to the positive side after peeling.
On the other hand, when a bias corresponding to the potential of the intermediate transfer body 2 before peeling is applied to the potential increase suppression electrode 6 at the time of peeling, the potential of the intermediate transfer body 2 decreases to near 0 V after peeling, and the potential of the intermediate transfer body 2 becomes a high potential. Is deterred. Further, even when a float electrode is used, there is an effect of suppressing an increase in potential during peeling.
For this reason, it is possible to avoid image scattering and reverse polarity toner due to discharge, and transfer efficiency is improved.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 6 shows Embodiment 1 of an image forming apparatus to which the present invention is applied.
In FIG. 1, an image forming apparatus includes a photosensitive drum 10 and an intermediate portion that contacts the photosensitive drum 10 along a shape of the photosensitive drum 10 in a certain area in order to transfer a toner image from the photosensitive drum 10. A transfer belt 20.
In the present embodiment, the photosensitive drum 10 includes a photosensitive layer whose resistance value is reduced by light irradiation. Around the photosensitive drum 10, a charging device 11 for charging the photosensitive drum 10 and , An exposure device 12 for writing an electrostatic latent image of each color component (black, yellow, magenta, cyan in this example) on the charged photosensitive drum 10, and each color component latent image formed on the photosensitive drum 10. Are provided with four developing devices 13 to 16 that visualize each of the color component toners, the intermediate transfer belt 20, and a cleaning device 17 that cleans residual toner on the photosensitive drum 10.
[0019]
Here, as the charging device 11, for example, a charging roll is used, but a charging device such as a corotron may be used.
The exposure device 12 may be any device that can write an image on the photosensitive drum 10 with light. For example, a scanner that scans a laser beam with a polygon mirror, whether a print head using an LED or a print head using an EL. However, it may be selected as appropriate.
Further, the developing devices 13 to 16 may be appropriately selected, for example, as long as the toner adheres to a portion where the potential is lowered by exposure on the photosensitive drum 10, and the toner to be used is particularly limited in shape and particle size. There is no limitation as long as it is accurately placed on the electrostatic latent image on the photosensitive drum 10. In this example, four developing devices 13 to 16 are used, but a rotary developing device may be used.
Furthermore, the cleaning device 17 may be appropriately selected as long as it cleans the residual toner on the photosensitive drum 10 and employs a blade cleaning method. However, there may be a mode in which the cleaning device 17 is not used when toner having a high transfer rate is used.
[0020]
The intermediate transfer belt 20 may be appropriately selected from resin, rubber, etc. However, in order to effectively suppress image quality defects such as holocharacters, it is necessary to reduce the contact surface pressure with the photosensitive drum 10. In view of the viewpoint of walkless and tensionerless, it is preferable to use a belt material having an elastic rubber base.
In this case, the elastic rubber substrate of the intermediate transfer belt 20 needs to have a volume resistivity for maintaining the transfer performance, and a release layer is provided on the surface of the elastic rubber substrate in consideration of surface cleaning properties. It is preferable.
[0021]
Furthermore, in the present embodiment, the intermediate transfer belt 20 is stretched between a plurality of (for example, four) stretching rolls 21 to 24, and is positioned between the developing devices 13 to 16 and the cleaning device 17. A predetermined contact area m is closely arranged along the surface of the photosensitive drum 10 to be moved.
In the present embodiment, of the four stretching rolls 21 to 24, the stretching roll 21 positioned on the upstream side of the transfer position functions as, for example, a driving roll, and the winding angle of the intermediate transfer belt 20 is the largest. It is set large. Further, the stretching rolls 22 and 23 positioned downstream of the transfer position are driven rolls. Among these, the stretching roll 23 also serves as a backup roll (grounded in this example) for secondary transfer. Furthermore, the tension roll 24 is a driven roll, and also serves as a backup roll of a belt cleaning device (not shown), for example. In this example, the sizes of the four tension rolls 21 to 24 may be appropriately selected.
[0022]
In particular, in the present embodiment, the contact area m between the photosensitive drum 10 and the intermediate transfer belt 20 is ensured by an amount corresponding to an angular range of 90 degrees of the photosensitive drum 10, for example.
That is, the contact area m between the photosensitive drum 10 and the intermediate transfer belt 20 is much larger than the circumference of the tension roll 21 located upstream of the transfer position (πD: D is the diameter of the tension roll 21). It is secured.
A primary transfer roll 31 as a primary transfer member is disposed in contact with a part of the contact area m where the intermediate transfer belt 20 is in close contact with the photosensitive drum 10 from the back side of the intermediate transfer belt 20, and a predetermined primary transfer bias 32. Is applied.
[0023]
Further, the downstream end B of the contact area m between the photosensitive drum 10 and the intermediate transfer belt 20 extends from the back surface side of the intermediate transfer belt 20 to the contact area m side and the non-contact area side with the downstream end B interposed therebetween. A roll-like electrode 33 is disposed as an electrode for suppressing potential rise during peeling, and a predetermined low bias 34 (about 100 V in this example) corresponding to the potential of the intermediate transfer belt 20 in the contact region m is applied.
Here, the roll-shaped electrode 33 is constituted by, for example, a foam roll having low hardness from the viewpoint of preventing an increase in the nip pressure between the photosensitive drum 10 and the intermediate transfer belt 20.
In this example, the low bias 34 is applied to the roll-shaped electrode 33. However, the present invention is not limited to this, and the roll-shaped electrode 33 may be appropriately selected such as being grounded or floated.
[0024]
Further, a secondary transfer roll 40 as a secondary transfer member is disposed opposite to the stretch roll 23 of the intermediate transfer belt 20 with the stretch roll 23 as a backup roll. For example, the secondary transfer roll A predetermined secondary transfer bias 41 is applied to 40, and a stretching roll 23 that also serves as a backup roll is grounded.
[0025]
According to the present embodiment, each color component toner image is sequentially formed on the photosensitive drum 10 and sequentially transferred to the intermediate transfer belt 20 via the contact area m (primary transfer position), and then to the secondary transfer position. Are collectively transferred to the recording material 60.
In such an image forming process, a transfer electric field by the primary transfer roll 31 acts in the contact area m between the photosensitive drum 10 and the intermediate transfer belt 20, but the transfer action area of the primary transfer roll 31 is in the contact area m. The contact area m hardly affects the air gap 50 between the both ends A and B of the contact area m.
For this reason, the toner image on the photosensitive drum 10 is accurately transferred onto the intermediate transfer belt 20 in the contact area m, and an image transfer process without image distortion is performed with high transfer efficiency.
At this time, the strong transfer electric field does not act or abnormal discharge occurs in the gap 50 at both ends A and B of the contact area m. To be avoided.
[0026]
In such an image forming process, the speed of the intermediate transfer belt 20 fluctuates due to the deflection or eccentric error of the stretching roll 21. In the contact area m, the toner image on the photosensitive drum 10 is, for example, as shown in FIG. Due to the behavior shown, it is separated from the intermediate transfer belt 20 by receiving the mechanical shearing force F, and the peripheral speed difference between the photosensitive drum 10 and the intermediate transfer belt 20 hardly occurs in the contact area m.
For this reason, it is possible to easily obtain a beautiful color image without banding or color misregistration.
[0027]
Further, at this time, the intermediate transfer belt 20 is peeled from the photosensitive drum 10 immediately after the downstream end B of the contact area m, and the potential of the intermediate transfer belt 20 rapidly rises due to the occurrence of the potential increase at the time of peeling. By applying the roll electrode 33 to which the low bias 34 corresponding to the potential of the intermediate transfer belt 20 before peeling is applied in B, the potential of the intermediate transfer belt 20 after peeling can be kept low.
Therefore, the occurrence of discharge can be prevented, the toner charge on the intermediate transfer belt 20 can be stabilized, and the occurrence of image scattering and reverse polarity toner can be suppressed.
As a result, the transfer rate of about 98% was improved to 99% or more. Similarly, when the roll electrode 33 is set to a float, a high transfer efficiency of 99% or more can be obtained.
[0028]
Embodiment 2
FIG. 7 shows Embodiment 2 of the image forming apparatus to which the present invention is applied.
In the present embodiment, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment, in the form along the surface of the photosensitive drum 10 positioned between the developing devices 13 to 16 and the cleaning device 17. The transfer belt 20 is disposed in close contact with a predetermined contact area m. Unlike the first embodiment, two primary transfer rolls 35 and 36 are provided at portions other than the upstream end A and the downstream end B of the contact area m. Predetermined transfer biases 37 and 38 are applied to the primary transfer rolls 35 and 36, respectively.
Furthermore, it is possible to use two primary transfer rolls 35 and 36 to perform transfer in multiple stages, or to install primary transfer rolls 35 and 36 of different types (material, pressing force, resistance, diameter, etc.). It is also possible to use properly depending on the conditions.
Furthermore, when only one primary transfer roll 35 is normally used and a problem occurs in one of the primary transfer rolls 35, it is possible to switch to another primary transfer roll 36 for use.
[0029]
In the present embodiment, the downstream end B of the contact region m between the photosensitive drum 10 and the intermediate transfer belt 20 is not in contact with the contact region m side across the downstream end B from the back side of the intermediate transfer belt 20. A flat plate electrode 55 is provided as a member for suppressing the potential increase at the time of peeling across the region side, and a predetermined low (about 100 to 300 V in this example) corresponding to the potential of the intermediate transfer belt 20 in the contact region m. A bias 56 is applied.
Components similar to those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted here.
[0030]
Also according to the present embodiment, as in the first embodiment, an image transfer process without image distortion is performed with high transfer efficiency, and it is possible to easily obtain a clean color image without banding or color overlay.
At this time, the flat plate electrode 55 suppresses an increase in potential when the intermediate transfer belt 20 is peeled off from the photosensitive drum 10, and the toner charge on the intermediate transfer belt 20 can be stabilized. Image scattering is suppressed.
Furthermore, according to the present embodiment, since the two primary transfer rolls 35 and 36 are disposed in the region excluding the upstream end A and the downstream end B of the contact area m between the photosensitive drum 10 and the intermediate transfer belt 20, Many opportunities for transfer and time required for transfer can be secured.
[0031]
Embodiment 3
FIG. 8 shows Embodiment 2 of an image forming apparatus to which the present invention is applied.
In the present embodiment, in the second embodiment model of FIG. 7, conductor fibers 55a are planted on the surface of the plate electrode 55 as a peeling potential increase suppressing member.
Other configurations are substantially the same as the configuration requirements described in the second embodiment.
According to the present embodiment, since the surface of the plate electrode 55 is provided with a soft material such as the conductor fiber 55a, even if the plate electrode 55 is brought into contact with the back side of the intermediate transfer belt 20, the photosensitive drum 10 and An increase in nip pressure with the intermediate transfer belt 20 can be avoided.
[0032]
Embodiment 4
In the present embodiment, the photosensitive drum 10 is used as a drive source and the intermediate transfer belt 20 is driven to rotate through a contact area m in any of the embodiment models shown in FIGS. .
Other configurations are substantially the same as the configuration requirements described in the first or second embodiment.
In the present embodiment, a unique drive mechanism for the intermediate transfer belt 20 is omitted, but since the binding force between the photosensitive drum 10 and the intermediate transfer belt 20 is large, the intermediate transfer belt 20 is interlocked with the photosensitive drum 10. The intermediate transfer belt 20 can be stably rotated.
For this reason, it is possible to eliminate the peripheral speed difference at a level at which the original intermediate transfer belt 20 slips as compared with the aspect having the respective unique drive sources, and the primary transfer operation is stable with no image displacement. Become.
[0033]
【The invention's effect】
As described above, according to the present invention, in an embodiment in which one of the image forming carrier and the intermediate transfer member is in the form of a drum and the other is in the form of a belt, the image forming carrier and the intermediate transfer member are the circumferential length of the contact arrangement and and the contact area and sets over the circumference of the tension roller located upstream of the contact area, the transfer bias facing the region excluding the both ends of both the contact areas One or a plurality of transfer members to be applied are arranged, and a potential rise suppression electrode at the time of peeling is arranged at the downstream end of the contact area, so that the difference in peripheral speed between the two is minimized (non-slip level) and image formation is carried It is possible to obtain a mechanical shearing force between the image transfer body and the transfer image, and suppresses an increase in potential when the intermediate transfer member is peeled off from the image bearing member, and the image is scattered by discharge. To prevent transfer efficiency While effectively secured, with no banding or color misregistration good quality (especially color quality) can be obtained stably.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of an image forming apparatus according to the present invention.
FIG. 2 is an explanatory diagram showing an operation of the image forming apparatus according to the present invention.
3 is an explanatory diagram showing the behavior of an image between an intermediate transfer member (intermediate transfer belt) and an image forming carrier (photosensitive drum) in the states a and b of FIG.
FIG. 4 is an explanatory diagram showing an image transfer behavior between an intermediate transfer member (intermediate transfer belt) and an image forming carrier (photosensitive drum) according to the present invention.
FIGS. 5A and 5B are explanatory views showing the operation of the primary transfer device according to the present invention, and FIG. 5B is an explanatory view showing the operation of the primary transfer device according to the comparative example.
6 is an explanatory diagram showing an image forming apparatus according to Embodiment 1. FIG.
FIG. 7 is an explanatory diagram showing an image forming apparatus according to a second embodiment.
FIG. 8 is an explanatory diagram showing an image forming apparatus according to a third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Image formation support body, 2 ... Intermediate transfer body, 3 ... Recording material, 4 ... Stretching roll, 4a ... Upstream tension roll, 5 ... Transfer member, 6 ... Electrolytic potential rise suppression electrode at peeling, 7 ... Secondary Transfer member, m ... contact area, A, B ... both ends (A ... upstream end, B ... downstream end)

Claims (5)

In an image forming apparatus for transferring an image formed on an image forming carrier to a recording material via an intermediate transfer member,
Either one of the image forming carrier and the intermediate transfer member is formed in a drum shape, and the other is formed in a belt shape that is stretched over a plurality of stretching rolls.
A belt-shaped member formed in a belt shape along the outer shape of the drum-shaped member formed in a drum shape is placed in contact over a predetermined region,
The circumferential length of the contact area between the drum-shaped member and the belt-shaped member is provided so as to be equal to or greater than the circumferential length of the tension roll disposed upstream of the contact area to form the contact area ;
Among the contact area, the peeling at the potential rise of the intermediate transfer member to a downstream end of one or arranging a plurality of transfer members and said contact area a transfer bias is applied facing the region excluding the both ends of the contact area An image forming apparatus comprising an electrode for suppressing an increase in potential during peeling, which is suppressed. The image forming apparatus according to claim 1.
The peeling-off potential rise suppression electrode is a roll-like electrode and is disposed across the contact area side and the non-contact area side of the belt-like member across the downstream end of the contact area between the drum-like member and the belt-like member. An image forming apparatus. The image forming apparatus according to claim 1.
The peeling-off potential rise suppression electrode is a flat plate electrode and is disposed across the contact area side and the non-contact area side of the belt-shaped member across the downstream end of the contact area between the drum-shaped member and the belt-shaped member. An image forming apparatus. The image forming apparatus according to claim 3.
An image forming apparatus, wherein a surface of the flat electrode is formed of a conductor fiber. The image forming apparatus according to claim 1,
An image forming apparatus, wherein one of an image forming carrier and an intermediate transfer member is used as a drive source, and the other is driven to rotate.

Images