JP2002214934A - Transfer device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer device by which an excellent transferred image free from image irregularity is obtained, and an image forming device using the transfer device. SOLUTION: A transfer nip N at a secondary transfer part is formed to be within a winding area L where an intermediate transfer belt 60 is wound round a laying roller 62 functioning as a supporting member. Thus, all the area of the belt 60 is supported and stably carried by the roller 62 in the transfer nip N, and partial deviation is not caused in the surface linear velocity of the belt 60 in the transfer nip. Therefore, transfer irregularity that the image carried on the surface of the belt 60 is rubbed and transferred to transfer paper P is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image carrying belt suspended on a support member and carrying an image on a surface thereof, and a transfer nip between the image carrying belt and an image carrying belt provided so as to be pressed against the image carrying belt. And an image forming apparatus such as a copier, a facsimile, or a printer having the transfer device. .

[0002]

2. Description of the Related Art Conventionally, as a transfer apparatus of this type, a predetermined transfer bias is applied by pressing a transfer bias roller as an opposing member to an image carrying belt carrying a toner image on a surface thereof, and transferring the image with the image carrying belt. In a transfer nip portion between the transfer roller and a bias roller, there is known a transfer nip portion in which a transfer sheet as an object to be transferred is passed at a constant speed to the surface of an image bearing belt in contact with the transfer sheet, and a toner image is transferred onto the transfer sheet. I have. This image carrying belt is an elastic belt made of a material containing an elastic body and is suspended by a supporting member at a predetermined tension.

[0003]

However, when an image was transferred onto a transfer sheet using the transfer device having the above-described structure, it was found that the transferred image might be disturbed as if rubbed.

The inventors of the present invention have conducted intensive studies on the cause of the disturbance of the transferred image and found the following.
FIG. 4A is an enlarged plan view of a transfer nip N of an example of a conventional transfer device. In this example, a transfer roller 80 is pressed against the surface of an image carrying belt 60 suspended by a suspending roller 62 as a support member, and a transfer nip N is formed at a pressure contact portion between the image carrying belt 60 and the transfer roller 80. Things. In this transfer device, the transfer nip N is formed so as to be slightly offset from a portion where the image carrying belt 60 is wound around the suspension roller 62.

In this case, the image carrying belt 60 in the transfer nip N is transferred to the region X where the back surface of the image carrying belt is pressed toward the transfer roller 80 by the suspending roller 62, and is not in contact with the suspending roller 62. It is divided into a region Y not pressed by the roller 80. Since the image carrying belt 60 itself contains an elastic body, the transfer roller 80
There is a difference in the degree of deformation of the image carrying belt 60 due to the compression between the region X pressed to the side and the region Y not pressed. Then, it is considered that the difference in the degree of the deformation causes a deviation in the linear velocity of the surface of the image carrying belt in the transfer nip N.

FIG. 4B is an enlarged plan view of a transfer nip N of another example of the conventional transfer device. This figure shows that the diameter of the suspension roller 62 is
Is extremely small with respect to the diameter of. In such a case, the image carrying belt 60 in the transfer nip N is divided into a winding region L wound around the suspension roller 62 and a linear region S which is not wound around the suspension roller 62 and is linear. It is considered that this difference also causes a deviation in the linear velocity of the surface of the image bearing belt in the transfer nip N.

When a deviation occurs in the linear velocity of the surface of the image carrying belt in the transfer nip N, the linear velocity is partially changed between the surface of the image carrying belt and the transfer paper conveyed while being in contact with the image carrying belt. A difference occurs, and the image is transferred while being rubbed on the transfer paper. This causes image disturbance such as rubbing on the transferred image.

[0008] The image disturbance as described above is not limited to a transfer device for transferring an image to a transfer paper, but may be any other than transfer paper.
For example, the same problem may occur in a transfer device that transfers an image to an intermediate transfer member for holding one end of an image before being transferred to transfer paper.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a transfer apparatus capable of obtaining a good transfer image without image disturbance, and an image using the transfer apparatus. It is to provide a forming device.

[0010]

According to a first aspect of the present invention, there is provided a transfer device, comprising: an image carrying belt having an elastic layer suspended on a support member and carrying an image on its surface; An opposing member that is provided so as to be in pressure contact with the image carrying belt and forms a transfer nip between the image carrying belt and the transfer nip. Wherein the transfer nip is formed in a region where the image carrying belt is wound around the support member.

In the transfer device according to the first aspect, the entire area of the transfer nip of the image carrying belt is a wrapped area wrapped around the support member. As a result, the image bearing belt, which is pressed by the opposing member in the transfer nip and is easily deformed in the pressing direction by the elasticity of the elastic layer, is supported by the support member from the belt back surface over the entire transfer nip, and partial deformation occurs. prevent. By preventing partial deformation of the image bearing belt at the transfer nip, deviation of the linear velocity of the image bearing belt surface at the transfer nip caused by partial deformation is eliminated.

According to a second aspect of the present invention, in the transfer apparatus of the first aspect, the linear velocity immediately before the image carrier belt surface enters the transfer nip and the linear velocity immediately after the image carrier belt exits the transfer nip are: The transfer nip may be within a range of ± 5% of a passing linear velocity of the object to be transferred.

[0013] Here, based on the intensive research of the present inventors,
It was found that the linear velocity immediately before the image carrying belt entered the transfer nip and the linear velocity immediately after exiting from the transfer nip tended to change from the normal belt linear velocity. FIG. 5 is a partially enlarged view near the transfer nip N. As shown in this figure,
The image bearing belt 60 including the elastic layer includes a suspension roller 62 as a support member for suspending the belt and a transfer roller 80.
C1 immediately before entering the transfer nip N and c immediately after leaving
In 2, the thickness changes rapidly, and the belt surface shrinks or expands. As a result, the surface linear velocity of the belt c1 immediately before entering the transfer nip N and c2 immediately after exiting the transfer nip N largely change as compared with other areas, and the linear velocity of the belt surface becomes uneven even in the transfer nip, and the transfer is performed. It was found that the transferred image at the nip N was disturbed.

In the transfer apparatus according to the present invention, the linear velocity immediately before the image carrying belt enters the transfer nip and the linear velocity immediately after the image carrying belt escapes from the transfer nip are determined by the linear velocity ± 5 of the surface moving speed of the transfer object at the transfer nip. % So that the linear velocity of a portion of the image carrying belt in a region close to the transfer nip before and after the transfer nip does not largely deviate from the linear movement speed of the transfer target of the transfer nip. As a result, the speed unevenness of the linear velocity of the belt surface in the transfer nip is reduced, and the image transferred to the transfer target is not disturbed.

According to a third aspect of the present invention, in the transfer device of the second aspect, the thickness of the elastic layer of the image carrying belt immediately before entering the transfer nip and the thickness immediately after exiting from the transfer nip are equal to the thickness of the support. The thickness of the elastic layer of the image bearing belt suspended by a member and not in contact with other members is within ± 33% of the thickness of the elastic layer.

According to a third aspect of the present invention, the thickness of the elastic layer of the image bearing belt, which changes immediately before entering the transfer nip and immediately after exiting from the transfer nip, of the image bearing belt is suspended by the support member. The thickness of the elastic layer in a non-contact state (hereinafter, referred to as a normal state) is within a range of ± 33%. As a result, the belt linear velocity immediately before entering the transfer nip and immediately after exiting from the transfer nip falls within the range of ± 5% of the linear velocity of the surface of the transfer object at the transfer nip. FIG. 3 is a graph showing the relationship between the thickness of the belt stretched on the support member and the surface linear velocity. This data shows that the thickness of the elastic layer is 0.45 mm,
A belt having an overall thickness of 0.6 mm was used, and a suspension roller having a diameter of 16 mm was used as a support member for suspending the belt. “A” in this graph shows a state in which it is stretched around the suspension roller 62 and is not in contact with other members. Then, as shown in FIG. 5, the transfer roller 80 is pressed against the image carrying belt 60 to form a transfer nip N, and when the contact pressure of the transfer roller 80 is variously changed, c1 and c1 just before the image carrying belt 60 enters the nip. Immediately after escape, the thickness of the elastic layer of the belt c2 and the linear velocity of the belt surface at that position were measured, and the results were graphed. Note that the relationship shown in this graph is
It has been found that a normal belt having an elastic layer that can be used for an image bearing belt always obtains the same result regardless of the material and size. According to this graph, in order to keep the surface linear velocity of the belt immediately before entering the transfer nip and immediately after exiting the belt within the range of normal linear velocity ± 5%, the thickness of the elastic layer of the belt at each position is set to the normal state. It has been found that the thickness should be within the range of the thickness of the elastic layer of the belt ± 33%. In the present invention, the thickness of the image carrying belt is set within the above range, so that the linear velocity of the belt surface in the area close to before and after the transfer nip is set within the range of claim 2.

According to a fourth aspect of the present invention, there is provided an image forming apparatus, a latent image carrier, a developing device for visualizing a latent image formed on the latent image carrier, and a developing device for developing the image visualized by the developing device. An image forming apparatus having a transfer device for transferring an image on a transfer target, wherein the image support for holding an image immediately before being transferred onto the transfer target is a belt-shaped image holding belt, and The transfer device according to any one of claims 1, 2 and 3 is used.

According to a fourth aspect of the present invention, the transfer device of the first, second, or third aspect is used as a transfer device of the image forming apparatus, and the formed image is satisfactorily transferred without causing disturbance of the image. To be transcribed.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a wet color electrophotographic copying machine (hereinafter, referred to as a color copying machine) which is a wet image forming apparatus will be described below. Figure 1
1 is a schematic configuration diagram of a main part of a color copying machine according to the present embodiment. The color copying machine is provided with image forming units 1Y, 1M, 1C, and 1Bk for each color for forming a color image in a color image forming process.
Each image forming unit is provided with a photoreceptor 10Y, 10M, 10C, 10Bk as a latent image carrier as described later, a wet developing device 40Y, 40M, 40C, 40Bk, and the like. In this embodiment, the image forming units 1Bk are for black, 1C is for cyan, 1M is for magenta, 1Y is for yellow, and the photoconductors 10Y,
It is configured to form visible images having different print colors on 0M, 10C, and 10Bk. Each of the photoconductors 10Y, 10M, 10C, and 10Bk has a part of its peripheral surface formed by each of the image forming units 1Y, 1M, 1C, and 1B.
k are exposed from the opening of the housing and are arranged so as to be rotatable in the direction of arrow A, respectively.

Around the photosensitive members, a charging device, an exposure device, a photosensitive member cleaning device, and the like, which are not shown, are provided.

Each of the image forming units 1Y, 1M, 1
Above C and 1Bk, an intermediate transfer belt 60 as an image carrying belt is provided. This intermediate transfer belt 6
0 is a plurality of suspension rollers 62, 63 as support members,
It is stretched so as to have a predetermined tension by 64, 65, 66, 67, 68 and each photoconductor, and can be moved in the direction of arrow B in the figure.

The suspension roller 6 of the intermediate transfer belt 60
A belt cleaning device 70 that cleans the surface of the intermediate transfer belt 60 is provided so as to face the portion where the intermediate transfer belt 8 is wound. On the other hand, the suspension roller 6 of the intermediate transfer belt 60
The toner image on the intermediate transfer belt 60 is transferred to a transfer sheet P as a transfer receiving body in the vicinity of the wrapped portion 2 (secondary transfer).
A transfer device for performing the transfer is provided. This transfer device has a transfer roller 80 as an opposing member that comes into pressure contact with the intermediate transfer belt 60, and forms a transfer nip N with the intermediate transfer belt. The transfer roller 80 is a conductive roller to which a secondary transfer bias for transferring the toner image onto the transfer paper P is applied.

Each of the wet developing devices 40Y, 40M, 40C,
40Bk have substantially the same configuration, respectively, and have a carrier liquid in which each color toner is dispersed at a high concentration.
A developing solution tank 42 containing a high-viscosity developer 18 of 000 mPa · s, a developing roller 41 as a developer carrying member provided at a developing position in contact with the surface of the photoconductor, and a lower part in the developing solution tank 42. And a coating roller 43 for applying the pumped developer 18 to the developing roller 41.

Next, the image forming operation of the color copying machine will be described. Here, each of the image forming units 1Y, 1M,
1C and 1Bk, image formation is performed based on the same principle. Therefore, here, only the yellow image forming process on the photoconductor 10Y located on the left end side in FIG. 1 will be described. 10C, 10Bk
The description of the image forming process will be omitted.

In FIG. 1, after the photosensitive member 10Y is uniformly charged by the charge from the charging device 20 while rotating in the direction of arrow A, a laser beam modulated based on yellow image information from an exposure device (not shown) To form an electrostatic latent image on the surface. The yellow latent image formed on the photoconductor 10Y is developed by the yellow developer 18 of the yellow wet developing device 40Y, and a yellow toner image is formed on the photoconductor 10Y.

Here, the developing operation by the wet developing device 40Y will be described. The application roller 43 draws up the developer 18 by rotation, and applies the developer 18 to the surface of the development roller 41.
Is applied. In this process, the developing solution 18 becomes a thin film, and the developing solution 18 having a certain thickness is formed on the developing roller 41.
Is formed. The thin layer of the developer 18 on the developing roller 41 is transported by the rotation of the developing roller 41 to a developing area where the developing roller 41 at the developing position and the photoconductor 10Y are in contact. Then, in the developing region, a developing bias as a developing voltage is applied from the electrode 45a,
The photosensitive member 10Y is peeled off from the developing roller 41 in a thin layer state.
The process proceeds to the portion where the latent image is formed. On the other hand, the developer 18 not used for development is removed by the peeling blade 44 and falls into the developer tank 42 by gravity.

Then, the yellow toner image formed on the photoconductor 10Y is primarily transferred to the intermediate transfer belt 60 rotating in the direction of arrow B in synchronization with the photoconductor 10Y. on the other hand,
After the transfer, the untransferred developer 18 is removed from the photoreceptor 10Y by a cleaning member (not shown) to prepare for the next image formation.

The above-described steps are sequentially repeated for the single-color images of yellow, magenta, cyan, and black by the image forming unit corresponding to each color and the intermediate transfer belt 60, so that the intermediate transfer belt 60 is superimposed. A full color image is formed.

The full-color image formed on the intermediate transfer belt 60 is secondarily transferred to the transfer paper P by the above-described transfer device. That is, the transfer roller 80 is pressed against the intermediate transfer belt 60 by a transfer contact / separation mechanism (not shown).
Thereafter, a predetermined secondary transfer bias is applied to the transfer roller 80 to form a secondary transfer electric field in the transfer nip N. Thus, the full-color image on the intermediate transfer belt 60 is collectively transferred onto the transfer paper P. The transfer paper P conveyed to the transfer nip N is fed at the timing when the leading end of the toner image on the intermediate transfer belt 60 reaches the transfer nip N. After the transfer, the transfer sheet P is separated from the intermediate transfer belt 60, subjected to a fixing process by a fixing device (not shown), and discharged outside the apparatus.

By the way, looking at the images transferred collectively on the transfer paper P, it was found that the transferred images may be disturbed as if rubbed. This is because the deviation of the linear velocity on the surface of the intermediate transfer belt 60 occurs in the transfer nip N for performing the secondary transfer, and the linear velocity difference between the transfer paper P and the image on the intermediate transfer belt 60 is partially increased. It turned out to be. The following will describe a transfer device capable of preventing the rubbing of the transferred image by the intensive research of the present inventors.

FIG. 2 is a partially enlarged view of the secondary transfer portion showing the features of the present invention. This intermediate transfer intermediate transfer belt 60
Means that the thickness of the elastic layer is 0.45 mm and the total thickness is 0.6
mm. In this figure, the transfer nip N in the secondary transfer portion is formed so as to be contained in a winding area L around which the intermediate transfer belt 60 is wound around the suspension roller 62.

Further, the thickness of the elastic layer of the belt c1 immediately before the intermediate transfer belt 60 enters the transfer nip and the thickness c2 immediately after the intermediate transfer belt 60 escapes from the transfer nip is determined in such a manner that the intermediate transfer belt 60 in the normal state where the transfer roller 80 or the like is not pressed. The pressing force of the transfer roller 80 on the intermediate transfer belt 60 is adjusted so that the thickness of the elastic layer of 0.45 mm is within the range of increase and decrease within ± 33%.

The amount of deformation of the intermediate transfer roller 80 with respect to the pressing force of the transfer roller differs depending on the thickness of the elastic layer, the material of the belt, and the like. It has been found that the same relationship can be obtained even if used. The relationship is shown in the graph of FIG. According to this graph, when the thickness of the elastic layer of the belt is within the range of ± 33% of the thickness of the elastic layer of the belt in the normal state, the surface linear velocity of the belt immediately before entering the transfer nip and immediately after exiting the transfer nip is calculated as the normal linear velocity. It can be seen that it can be kept within the range of ± 5%.

When the secondary transfer section is constructed as described above, the entire area of the intermediate transfer belt 60 at the transfer nip is within the area L wound around the suspension roller 62, so that the intermediate transfer belt 60 within the transfer nip N is suspended. Because it is stably transported by being supported by the rollers 62, and there is no partial deformation,
No partial deviation occurs in the surface linear velocity of the intermediate transfer belt 60. Further, by keeping the deformation amount of the elastic layer of the belt 60 immediately before entering and leaving the transfer nip N within the above range, the surface linear velocity of the belt immediately before entering and leaving the transfer nip can be reduced to a normal linear velocity ± It can be kept within the range of 5%.

With the above arrangement, the variation in the linear velocity of the surface of the intermediate transfer belt at the transfer nip of the secondary transfer portion can be reduced to such an extent that the secondary transfer image does not rub. This makes it possible to obtain a good image without rubbing the transferred image on the transfer paper P.

Further, in the above-described embodiment, the configuration in which the image on the intermediate transfer belt 60 can be prevented from being rubbed in the secondary transfer section for secondary transfer to the transfer paper P has been described. The present invention can be applied to a transfer apparatus having a configuration in which an image carried on a surface of an image-bearing member is transferred onto a transfer target body by a transfer nip. Therefore, for example, the present invention can be applied to a transfer device for primary transfer for transferring an image developed on the photoreceptor belt to the transfer paper P or another transfer target by using the image carrying belt as a photoreceptor belt.

[0037]

According to the transfer device of the first aspect, it is possible to eliminate the deviation of the linear velocity of the surface of the image carrying belt at the transfer nip, so that it is possible to obtain a good transferred image without image disturbance. Has an excellent effect.

According to the transfer device of the second aspect, image distortion on the transferred image due to a change in the linear velocity immediately before the image carrying belt enters the transfer nip and the linear velocity immediately after the image carrying belt exits the transfer nip. There is an excellent effect that can be prevented.

According to the transfer device of the third aspect, it is possible to change the thickness of the elastic layer of the image carrying belt by utilizing the fact that the surface linear velocity of the belt changes according to the thickness of the elastic layer of the image carrying belt. By defining the range, there is an excellent effect that the surface linear velocity of the image carrying belt can be kept within a desired range.

According to the image forming apparatus of the fourth aspect, there is an excellent effect that it is possible to obtain a good transfer image without disturbing the image transferred to the transfer object.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part of an image forming apparatus according to an embodiment.

FIG. 2 is a partially enlarged view of a secondary transfer portion showing a feature of the present invention.

FIG. 3 is a graph showing a relationship between a thickness of a belt stretched over a roller and a surface linear velocity.

FIG. 4A is a plan view illustrating an example of a transfer nip N of a conventional transfer device. FIG. 4B is a plan view showing another example of the transfer nip N of the conventional transfer device.

FIG. 5 is a partially enlarged view in the vicinity of a transfer nip N showing a conventional problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming unit 10 Photoreceptor 18 Developing solution 40Y, 40M, 40C, 40Bk Wet developing device 41 Developing roller 43 Application roller 60 Intermediate transfer belt (image carrying belt) 62 Suspension roller 70 Belt cleaning device 80 Transfer roller P Transfer paper N 2 Next transfer nip L Belt winding area S Straight belt area

Claims (4)

[Claims] An image bearing belt suspended on a support member and having an elastic layer carrying an image on a surface thereof, and an opposing member provided to be in pressure contact with the image bearing belt and forming a transfer nip between the image bearing belt and the image bearing belt A transfer device that transfers an image on the image carrying belt to the transfer object by passing the transfer object through the transfer nip, wherein the transfer nip is a support member of the image carrying belt. A transfer device formed in a region where the transfer device is wound around the transfer device. 2. The transfer device according to claim 1, wherein the linear velocity immediately before the surface of the image carrying belt enters the transfer nip and the linear velocity immediately after exiting from the transfer nip are the same. The transfer linear velocity is within a range of ± 5%. 3. The transfer device according to claim 2, wherein the thickness of the elastic layer of the image carrying belt immediately before entering the transfer nip and the thickness immediately after exiting from the transfer nip are suspended by the support member. ± 33% of the thickness of the elastic layer of the image bearing belt in a non-contact state with the member
A transfer device that is within the range of. 4. A latent image carrier, a developing device for visualizing a latent image formed on the latent image carrier, and an image visualized by the developing device is transferred onto a transfer object. An image forming apparatus having a transfer device, wherein the image carrier that carries the image immediately before being transferred onto the transfer target is a belt-shaped image carrier belt, and the transfer device is used as the transfer device. Or an image forming apparatus using the transfer device of 3.