JPH05281859A - Image forming device with transfer belt - Google Patents

Abstract

PURPOSE:To properly use a transfer belt region, according to environment and a kind of paper, to secure excellent carrying properties and to prevent the occurrence of deviation in a position by providing plural different resistance value regions, in the circumferential direction of a transfer belt, thereon. CONSTITUTION:A transfer paper sent out of the inside of a cassette by the picking up of a paper feeding roller 10, passes a pair of resist rollers 11, and is sent onto the transfer belt 7 wound between a driving roller 12 and a driven roller 13. Then, yellow toner which is developed by a yellow developing unit 4 is transferred onto the transfer paper by biassing a backup roller 8 to a photosensitive body 1, the transfer belt 7 is switched back to transfer cyan on the transfer paper, and finally, the transfer paper passes a fixing device 9, to fix the toner. At this time, transfer belt 7 is constituted so that a half region in the circumferential direction of the transfer belt 7 has 10<7>OMEGA resistance value and the left half region has 10<11>OMEGA resistance value.

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 using a transfer belt, such as a laser printer, a copying machine and a facsimile.

[0002]

2. Description of the Related Art In recent image forming apparatuses, a type using a transfer belt as a transfer means is increasing. Compared with the corona transfer system, the system using such a transfer belt has advantages such as a smaller applied voltage, almost no ozone generation, and less transfer deviation at the trailing edge of the transfer paper.

Polycarbonate type and polyethylene terephthalate are known as the material of the transfer belt. For example, in the case of the polycarbonate type belt, the surface resistance and the volume resistance are 10 ⁷ to 10 ⁹ Ω, which is "medium resistance". Is used.

Generally, the belt is integrally molded endlessly or is formed into a sheet shape, and both end edges thereof are wound and joined, and the resistance value is uniform over the entire surface.

On the other hand, there are various types of paper used for the transfer material, such as thin paper, thick paper, OHP sheet, etc., and even if the same paper is used, its resistance value may vary greatly depending on the environment. Are known.

[0006]

Therefore, if the transfer conditions such as the resistance value of the transfer belt and the transfer bias are fixed, it is impossible to satisfy the paper transportability in all cases. That is, it is difficult for a belt with fixed transfer conditions to maintain good transferability when the environment or paper type changes.

For example, when the transfer bias applied to the transfer belt is constant, the relationship between the belt resistance value and the paper carrying property / positional deviation is as shown in FIG. When using, etc., shift to the higher resistance side. This is because, for example, at the time of high temperature and high humidity, the resistance value of the paper decreases, the electric charge applied to the belt easily escapes, and the adhesion between the transfer belt and the paper decreases.
If the adhesiveness remains low, conveyance failure may occur or color shift may occur during full-color copying using the switchback method.

In view of the above problems of the prior art, the present invention makes it easy to improve and improve the transportability and color misregistration in an image forming apparatus using a transfer belt for different environments and paper types. The object is to secure good transportability and transferability by using the configuration.

[0009]

The present invention has solved the above-mentioned problems in an image forming apparatus using a transfer belt, in which the transfer belt has a plurality of different resistance value regions in its circumferential direction. ..

A plurality of different resistance value regions are at least one.
A 0 ⁷ Ω part and a 10 ¹¹ Ω part are preferable.

The transfer belt may be formed by joining sheet members having different resistance values, or may be formed with different resistance value regions by a surface coating process.

It is necessary that each sheet member and each resistance value region to be joined are larger than the maximum transfer paper length.

It is preferable that the resistance value region is selected using a means for detecting temperature and humidity in the apparatus or a paper type detecting means.

When the paper type is plain paper, the low resistance value region is selected when the humidity is 70% or less, and the high resistance value region is selected when the humidity is 70% or more. When the paper type is thick paper or OHP paper, It is also preferable to select a high resistance value region.

It is preferable to control the transfer application bias according to each resistance value region of the transfer belt.

It is more convenient if the area of the transfer belt is selected according to the belt detection mark provided on the belt.

[0017]

The details of the present invention will be explained based on the embodiments shown in the drawings.

FIG. 1 schematically shows an embodiment of an image forming apparatus according to the present invention.

In the vicinity of the periphery of the drum-shaped photoconductor 1, the photoconductor 1
A charger 2 for uniformly charging the surface, a writing system 3 for exposing a pattern on the surface of the photoconductor 1 to form a latent image, developing devices 4, 5, 6 for developing the latent image, and toner on the photoconductor 1. A transfer belt 7 for transferring an image onto a transfer paper, a backup roller 8 and the like are provided, and a fixing device 9 for fixing the toner on the transfer paper is provided at the end of the paper conveyance path. Developers 4, 5,
Although the toners of yellow, magenta, and cyan are contained in 6 in any order, it is needless to say that the toner is not limited to this.

The transfer paper sent out from the cassette by the pickup of the paper feed roller 10 is the registration roller pair 1.
1, and is sent out onto the transfer belt 7 that winds between the driving roller 12 and the driven roller 13. The yellow toner developed by the yellow developing unit 4 is transferred onto the transfer paper by pressing the backup roller 8 biased to the photosensitive member 1, the transfer belt 7 is switched back, and then the magenta is switched back again. Cyan is transferred onto the transfer paper. Finally, the transfer paper is passed through the fixing device 9 to fix the toner.

FIG. 2 shows the transfer belt 7 according to the present invention. In the transfer belt 7, a half region in the circumferential direction has a resistance value of 10 ⁷ Ω and the other half region has a resistance value of 10 ¹¹ Ω.

The resistance value of the belt is the surface resistance (Ω).
And volume resistivity (Ω-cm), and the resistance value may be volume resistivity. Further, the belts may be different only in surface resistance or may be different in only volume resistivity.

FIG. 3 shows the joined state. Surface resistance 1
The sheet portion (B) having a surface resistance of 0 ⁷ Ω and the sheet portion (C) having a surface resistance of 10 ¹¹ Ω are bonded together at the joint portion (D). Part B, C
The volume resistivity of both parts is 10 ⁹ Ω-cm. Also, instead of adhesion, they may be joined by ultrasonic welding or the like.

At room temperature and normal humidity, low temperature and low humidity, or when using thin paper or plain paper, use part B with low surface resistance,
At the time of high temperature and high humidity, or when using cardboard or postcards, the C portion having high surface resistance is controlled to be used.

Since the surface resistances of the B section and the C section are different from each other, when passing one sheet of paper, the respective resistance values are set so as not to extend over both the B section and the C section. Each of the sheet parts to be provided must be at least longer than the maximum transferable paper in the circumferential direction.

Instead of joining a plurality of sheet portions having different resistance values, a conventional belt having a uniform resistance value is coated with a thin film such as a fluorine coating to form 5 to 30.
A μm coat layer may be partially formed to change the surface resistance. In the case of a polycarbonate belt, the volume resistivity is changed by controlling the amount of carbon in the material at the manufacturing stage.

FIG. 4 shows an embodiment of a different configuration of the present invention.

In the vicinity of the periphery of the drum-shaped photoconductor 1, the photoconductor 1
A charging device 2 for uniformly charging the surface, a writing system 3 for exposing a pattern on the surface of the photoconductor 1 to form a latent image, a developing device 4 for developing the latent image, a toner image on the photoconductor 1 on a transfer paper. A transfer belt 7 for transferring, a backup roller 8, a temperature / humidity detecting means 14 and the like are provided.

The transfer paper sent out from the cassette by the paper feed roller 10 passes through the registration roller pair 11 and is sent out onto the transfer belt 7 which winds between the drive roller 12 and the driven roller 13. At that time, the temperature / humidity detecting means 14 detects the temperature / humidity in the apparatus, and based on the detected temperature / humidity, a proper resistance value region of the transfer belt 7 is selected. Developing device 4
The toner developed by is transferred onto the transfer paper by pressing the biased backup roller 8 against the photoconductor 1, and finally the transfer paper is passed through the fixing device 9 to fix the toner.

FIG. 5 shows an embodiment of still another configuration of the present invention.

When the transfer paper sent out from the cassette by the paper feed roller 10 passes through the registration roller pair 11, the paper type detection means 15 provided in the roller detects whether the paper is plain paper, thick paper or OHP paper. Then, a suitable resistance value region of the transfer belt 7 is selected.

The paper type detecting means 15 includes a displacement sensor and a pressure sensor. As shown in FIG. 6, the registration roller pair 11 includes two rollers, an upper registration roller 11 'and a lower registration roller 11 ". The lower registration roller 11 ″ is fixed, the upper registration roller 11 ′ is arranged so as to be movable up and down, and is pressed by the pressure springs at both ends, such as a digital micrometer or a strain detection member. The paper type detection unit 15 is provided in contact with the shaft portion of the upper registration roller 11 ′, and detects the displacement of the upper registration roller 11 ′ due to the paper type, in other words, the difference in paper thickness.

Table 1 shows the good resistance value of the belt under the environmental change due to the difference of the paper type.

[0034]

[Table 1]

In the case of plain paper, when the humidity is 70% or less, the resistance value of the transfer belt 7 of 10 ⁷ Ω part region is selectively used and 70%.
In the above, the region of the resistance value of 10 ¹¹ Ω is selectively used. This is because in the case of plain paper, when the humidity is 70% or more, the resistance of the paper decreases, and when the 10 ⁷ Ω area is used, transfer omission occurs or paper conveyance failure occurs. Also thick paper and OH
In the case of P paper, the resistance value is always 10 ¹¹ regardless of changes in the environment.
Use the Ω area. 10 ⁷ Ω for thick paper and OHP paper
If the partial area is used, transfer failure will occur.

As described above, good transferability and transportability can be obtained by selectively using the belt region depending on the paper type and environment.

FIG. 7 shows an embodiment of a different structure of the present invention.

The transfer bias 17 is controlled in accordance with the resistance value region selected by the temperature / humidity sensor 14 and the paper type sensor 15. As shown in an enlarged scale in FIG.
Belt detection marks 18 and 19 are provided at the tip and side edges of the resistance value regions of the 0 ⁷ Ω portion region and the 10 ¹¹ Ω portion region, respectively.
The detection means 16 provided correspondingly detects the resistance value region of the belt and controls the transfer bias 17. The detection mark may be provided only in one of the resistance value areas,
All resistance value regions can be discriminated by detection and time management.

[0039]

In the image forming apparatus according to the first aspect of the present invention, the transfer belt has a plurality of different resistance value areas in the circumferential direction thereof. It is possible to use properly, secure good transportability, and prevent positional deviation.

In the image forming apparatus of the third aspect, since the transfer belt is constructed by joining the sheet members having different resistance values, the transfer belt can be easily formed.

In the image forming apparatus of the fourth aspect, since the respective sheet members to be joined are larger than the maximum transfer paper length, the transfer paper should be placed over the same resistance value region during the transfer work. Can be prevented.

In the image forming apparatus of claim 5, the means for detecting temperature and humidity in the apparatus is used, and in the image forming apparatus of claim 6, the paper type detecting means is used to select the resistance value region. Therefore, depending on the situation, the optimum transferability,
Transportability can be obtained.

In the image forming apparatus of the ninth aspect, since the transfer application bias is controlled according to each resistance value area of the transfer belt, the best transferability can be obtained.

In the image forming apparatus of the tenth aspect, since the area of the transfer belt is selected according to the belt detection mark provided on the belt, the area can be surely selected with a simple structure.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to the present invention.

FIG. 2 is a diagram showing that the transfer belt according to the present invention has a plurality of regions.

FIG. 3 is a diagram showing a configuration state of a transfer belt according to the present invention.

FIG. 4 is a schematic view showing another embodiment of the present invention.

FIG. 5 is a schematic view showing still another embodiment.

FIG. 6 is a schematic diagram showing a configuration example of a paper type detection unit.

FIG. 7 is a schematic view showing an embodiment of a different configuration of the present invention.

FIG. 8 is a diagram showing a state in which a detection mark is attached to the transfer belt according to the present invention.

FIG. 9: Belt resistance and transportability depending on environment and paper type,
It is a figure which shows the relationship with the degree of transferability.

[Explanation of symbols]

 7 Transfer Belt 8 Backup Roller 9 Fixing Device 12 Drive Roller 13 Driven Roller 14 Temperature / Humidity Detection Means 15 Paper Type Detection Means 17 Transfer Bias

Claims (10)

[Claims] 1. An image forming apparatus using a transfer belt, wherein the transfer belt has a plurality of different resistance value regions in its circumferential direction. 2. The image forming apparatus according to claim 1, wherein the plurality of different resistance value regions are at least 10 ⁷ Ω portions and 10 ¹¹ Ω portions. 3. The image forming apparatus according to claim 1, wherein the transfer belt is formed by joining sheet members having different resistance values. 4. The image forming apparatus according to claim 3, wherein each sheet member to be joined is larger than the maximum transfer paper length. 5. The image forming apparatus according to claim 1, wherein the resistance value region is selected by using a means for detecting temperature and humidity inside the apparatus. 6. The paper type detection means is used to select the resistance value region.
The image forming apparatus according to item 1. 7. When the paper type is plain paper, the low resistance region is selected when the humidity is 70% or less, and the high resistance region is selected when the humidity is 70% or more. 1
Alternatively, the image forming apparatus according to claim 2. 8. The image forming apparatus according to claim 1, wherein when the paper type is thick paper or OHP paper, the high resistance value region is selected. 9. The image forming apparatus according to claim 1, wherein the transfer application bias is controlled according to each resistance value region of the transfer belt. 10. The image forming apparatus according to claim 5, wherein the area of the transfer belt is selected according to a belt detection mark provided on the belt.