JPH1010889A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the attraction and transfer of transfer paper by means of a single bias power source and to obtain proper pressure necessary for toner- image transfer in a transfer nip. SOLUTION: A transfer belt unit 40 is freely swinguably supported around the shaft of a drive roller 44 so that a transfer roller 43, round which a transfer belt 45 is stretched, is brought into contact with an intermediate transfer body 34 via the transfer belt 45 and separated from it. Additionally, in the transfer nip between the transfer roller 43 and intermediate transfer body 34 with the transfer belt 45 between them, the toner image held on the intermediate transfer body 34 is transferred to the transfer paper 9 by a bias applied from a bias power source 46. Also, when the transfer roller 43 is brought into contact with the intermediate transfer body 43, the transfer paper 9 is attracted to the transfer belt 45 and carried.

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 printer, a facsimile, etc., which uses an electrophotographic system. The present invention relates to an image forming apparatus for transferring an image on an image carrier and further transferring the image on a recording material from a second image carrier.

[0002]

2. Description of the Related Art Conventional image forming apparatuses of this type include a first type.
A visible image (toner image) is formed on the image carrier, and the toner image is transferred onto a second image carrier (intermediate transfer member), and then transferred from the intermediate transfer member onto a transfer sheet as a recording material. For example, there is an apparatus configured as shown in FIG.

In FIG. 1, a charging drum 2 is arranged around a rotating drum type electrophotographic photosensitive member (hereinafter simply referred to as a "photosensitive drum") 1 as a first image carrier in order along the rotation direction. A yellow developing device 3, a magenta developing device 4, a cyan developing device 5, a black developing device 6, an intermediate transfer member 7 as a second image carrier, and a photosensitive drum cleaner 8
Are arranged. Further, a laser scanning unit 16 for irradiating a laser beam for forming an electrostatic latent image on the photosensitive drum 1 after being uniformly charged is provided.

A registration roller 10 for transporting the transfer paper 9 from a paper supply unit (not shown) and a timing for transferring the transfer paper 9 to a transfer nip portion in order from the upstream side to the downstream side in the transport direction of the transfer paper 9. A pre-transfer guide 11 for good conveyance, a transfer roller 12 made of rubber or sponge for forming a transfer nip portion with the intermediate transfer body 7, and a transfer paper 9
And a fixing unit 15 for fixing an unfixed toner image transferred to the transfer paper 9 is provided. Further, a fur brush 14 for cleaning the surface of the intermediate transfer member 7 after the transfer of the multiple toner image is provided on the downstream side of the transfer roller 12 in the rotation direction of the intermediate transfer member 7.

[0005] The operation of the image forming apparatus having the above configuration and shown in FIG. 4 will be described. The photosensitive drum 1 is uniformly negatively charged by the charging roller 2. Next, an electrostatic latent image is formed on the surface of the photosensitive drum 1 by the laser scanning unit 16 in accordance with a video signal output from a controller (not shown). Then, toner is adhered to the electrostatic latent image by the yellow developing device 3, and a toner image is formed on the photosensitive drum 1. The yellow toner image formed on the photosensitive drum 1 is primarily transferred from the photosensitive drum 1 to the intermediate transfer member 7 by a positive transfer bias applied to the intermediate transfer member 7. Thereafter, magenta, cyan, and black toner images are sequentially multiplex primary-transferred onto the intermediate transfer body 7. The transfer residual toner remaining on the photosensitive drum 1 at the time of the primary transfer of each color is collected by the photosensitive drum cleaner 8.
The transfer paper 9 is supplied from a paper supply unit (not shown). After that, the transfer roller 12 comes into contact with the intermediate transfer body 7,
When a positive transfer bias is applied to the transfer roller 12 and the transfer paper 9 is conveyed to the transfer nip by the pre-transfer guide 11 via the registration roller 10, the four color toner images on the intermediate transfer body 7 are transferred. 2 on paper 9
Next is transferred. The transfer paper 9 is neutralized by applying an AC bias to the corona charger 13 and is separated from the intermediate transfer body 7. Then, the toner image transferred to the transfer paper 9 separated from the intermediate transfer body 7 is fixed by the fixing device 15. The transfer residual toner remaining on the intermediate transfer member 7 is removed and collected by the fur brush 14. Thereby, the intermediate transfer member 7 is cleaned.

However, in the image forming apparatus using the transfer roller 12 shown in FIG. 4, a transfer bias power supply (not shown) is used in order to transfer the multiple primary toner images from the intermediate transfer member 7 to the transfer paper 9 secondarily. In addition to this, a separation bias power supply (not shown) for applying an AC bias to the corona charger 13 is required to separate the transfer paper 9 after the secondary transfer from the intermediate transfer body 7. Even when a bias is applied to the corona charger 13 from the separation bias power source, the transfer paper 9 may not be separated if the outer diameter of the intermediate transfer body 7 is large.

Further, there is a conventional image forming apparatus using an intermediate transfer member 7 and a transfer belt 20 as shown in FIG. 5, the same components as those in FIG. 4 are denoted by the same reference numerals. The primary transfer method is the same as that of the apparatus shown in FIG.
The configuration of the next transfer system is different. That is, the configuration of the secondary transfer system shown in FIG. 5 is a configuration in which the intermediate transfer belt unit 17 is brought into contact with the intermediate transfer body 7 to transport the transfer paper 9. That is, the intermediate transfer unit 17 includes the rollers 18 and 1 at both ends.
9 so that the transfer belt 20 is in contact with the intermediate transfer body 7 during the transfer.
And a corona charger 21 is provided at a secondary transfer nip portion via a transfer belt 20. Also, the one-side roller 18 and the suction blade 22
A bias power supply (not shown) for attracting the transfer paper 9 to the transfer belt 20 is provided between the two.

The toner images of each color are multiplexed on the intermediate transfer member 7.
After the next transfer, the transfer belt 20 contacts the intermediate transfer body 7. The transfer paper 9 conveyed by the registration rollers 10 is adsorbed and conveyed by the transfer belt 20 by a bias applied between the one-side roller 18 and the suction blade 22, and is transferred by the transfer nip between the intermediate transfer body 7 and the transfer belt 20. The secondary transfer is performed by the positive transfer bias applied to the corona charger 21 in the section. The transfer paper 9 is the transfer belt 2
The intermediate transfer belt unit 17 is conveyed while being adsorbed, and separated from the transfer belt 20 by the curvature of the other roller 19 of the intermediate transfer belt unit 17, and conveyed to the fixing device 15. Then, the transfer paper 9
Is fixed by the fixing device 15.

As described above, in the image forming apparatus using the transfer belt 20 shown in FIG. 5, a bias power supply (not shown) for attracting the transfer paper 9 to the transfer belt 20 and a multiplex primary toner image from the intermediate transfer body 7 are provided. And a transfer bias power supply (not shown) for performing secondary transfer to the transfer paper 9.

[0010]

However, in the conventional example, in the secondary transfer of the intermediate transfer member 7, at least two
One or more bias power supplies are required. In addition, in the case of the image forming apparatus using the transfer roller 12 shown in FIG. 4, a mechanical separation mechanism such as a corona charger 13 or a separation claw (not shown) for separating the transfer paper is essential. In addition, when the corona charger 13 is used, ozone is generated, and when the separation claw or the like is used, the transfer paper 9 is not only easily scratched, but also the image area is limited. There was a problem.

Also, in the case of the image forming apparatus using the transfer belt 20 shown in FIG. 5, two bias power sources, ie, a suction bias for the transfer paper 9 and a transfer bias for the transfer paper 9, are required. Is suspended between the one-side roller 18 and the other-side roller 19, and the angle of entry of the transfer paper 9 into the transfer nip cannot be changed. Has a problem that the toner is scattered on the transfer paper 9 due to the influence of the transfer electric field and the image quality of the toner image is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a single bias power supply performs adsorption and transfer of a recording material, and has a simple configuration and a large outer diameter of an image carrier. Even in such a case, an object of the present invention is to provide an image forming apparatus capable of stably separating a recording material and obtaining a high-quality toner image without toner scattering.

[0013]

To achieve the above object, according to the image forming apparatus of the present invention, the transfer belt unit includes a transfer belt and a roller on which the transfer belt is suspended. The toner image carried on the image carrier is transferred to a recording material at a transfer nip portion between the transfer belt and the image carrier, and the recording material is conveyed during the transfer of the toner image. Wherein one of the rollers on which the transfer belt is suspended is swingably supported about the axis of the other roller so as to contact and separate from the image carrier via the transfer belt, In addition, a bias power source is connected to the one roller.

According to a second aspect of the present invention, when the recording material enters the transfer nip portion between the image carrier and the transfer belt, the recording material is conveyed so as to enter from an angle parallel to the tension side of the transfer belt. A guide was provided.

According to a third aspect of the present invention, when one roller of the transfer belt unit contacts the image carrier via the transfer belt, the center of the image carrier and the center of the one roller are connected. The angle between the line and the tension side of the transfer belt is 91 to 95 degrees.

According to the invention described in claim 4, the angle is preferably 92 degrees.

According to a fifth aspect of the present invention, the image bearing member comprises:
It is a rotating drum type electrophotographic photosensitive member.

According to a sixth aspect of the present invention, the image bearing member comprises:
It is a rotary drum type intermediate transfer member.

According to the present invention, the intermediate transfer member has a volume resistivity of 10 ⁸ to 10 ¹⁰ Ωcm.

[Operation] Based on the above configuration, the transfer belt unit is arranged about the axis of the other roller so that one roller on which the transfer belt is suspended comes into contact with or separates from the image carrier via the transfer belt. Is swingably supported. Further, at a transfer nip portion between one roller on which the transfer belt is interposed and the image carrier, a toner image carried on the image carrier is transferred to a recording material by a bias from a bias power supply,
When one of the rollers comes in contact with the image carrier, the recording material is conveyed by adsorbing the recording material on the transfer belt.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. <First Embodiment> FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to a first embodiment of the present invention. In the figure, around a rotating drum type electrophotographic photosensitive member (hereinafter, simply referred to as “photosensitive drum”) 30 as a first image carrier, a charging roller 31 and a black roller are sequentially arranged along the rotation direction of arrow R30. A developing device 32, a rotatable developing device holding rotary 33, an intermediate transfer member 34 as a second image carrier, and a photosensitive drum cleaner 35 are provided. The photosensitive drum 30 that has been uniformly charged is provided with a laser scanning unit 48 that irradiates a laser beam to form an electrostatic latent image. Further, the intermediate transfer member 34
Is a rotary drum type.

The photosensitive drum 30 is formed by applying a photosensitive layer to the surface of a grounded conductive substrate, and forms a toner image by an image forming process such as an electrophotographic process. Then, any one of the yellow developing device 36, the magenta developing device 37, and the cyan developing device 38 mounted on the developing device holding rotary 33 selectively contacts the photosensitive drum 30 to develop a toner image of any color. Is performed.

The transfer paper 9 transported from a paper supply unit (not shown) is formed on the intermediate transfer body 34 in order from the upstream side to the downstream side in the transport direction of the transfer paper 9 as the third image carrier. together with the transfer belt unit 40 to form a secondary transfer nip N ₂ is disposed between the registration rollers 39 and the intermediate transfer member 34, for conveying a predetermined timing in accordance with the tip of the multiple toner images, Fixing device 4 for fixing the unfixed toner image transferred to transfer paper 9
1 is provided. Further, on the downstream side of the transfer belt unit 40 in the rotation direction of the intermediate transfer member 34, a cleaning roller 42 for removing the toner remaining on the surface of the intermediate transfer member 34 after the transfer of the multiple toner image is provided. .

The intermediate transfer member 34 is formed by applying a conductive rubber layer to the outer periphery of a metal substrate and further applying a urethane layer. An image can be formed. The volume resistivity of the intermediate transfer member 34 is 10 ⁹ Ωcm when 1000 V is applied.

The transfer belt unit 40 includes a transfer roller 43 having a diameter of 20 mm, a drive roller 44 having a diameter of 20 mm, and a conductive roller wound around a metal shaft or formed of a cylindrical metal. A transfer belt 45 made of urethane or rubber that can be stretched and suspended is provided between the drive rollers 44, and the transfer roller 43 is moved around the shaft of the drive roller 44 via the transfer belt 45. It is supported so as to be swingable in the direction of the arrow S40 in the drawing so as to be able to contact and separate therefrom.

When the transfer roller 43 comes into contact with the intermediate transfer member 34, the center of the intermediate transfer member 34 and the transfer roller 43
Is set to 92 degrees between a line connecting the center of the transfer belt 45 and the tension side of the transfer belt 45. The transfer roller 43 is 1-4 this when abutting the secondary transfer nip portion N ₂
It is supported by a spring (not shown) so that a pressure of kg is applied. A high voltage is applied to the transfer roller 43 from a transfer bias power supply 46, and a high voltage is also applied to the intermediate transfer body 34 from a bias power supply 47. The transfer speed of the transfer paper 9 is 20 mm / sec.

Next, the operation will be described. The photosensitive drum 30 is uniformly charged to a negative potential by the charging roller 31. Then, an electrostatic latent image is formed on the photosensitive drum 30 by the laser scanning unit 48 according to a video signal output from a controller (not shown).

Next, the developing device holding rotary 33 is rotated, and the yellow developing device 36 is held at the position closest to the photosensitive drum 30, and the photosensitive drum 30 and the yellow developing device 3 are rotated.
6, the yellow toner charged negatively by the yellow developing device 36 visualizes the electrostatic latent image on the photosensitive drum 30 to form a yellow toner image. Thereafter, the toner image on the photosensitive drum 30 is primary-transferred to the intermediate transfer body 34 by applying a bias voltage of +100 V from the bias power supply 47 to the primary transfer nip portion N ₁ .

The untransferred toner that has not been transferred to the intermediate transfer member 34 during the primary transfer is scraped off into the cleaner container 35b by the blade 35a of the photosensitive drum cleaner 35. Thus, the surface of the photosensitive drum 30 is cleaned.

Thereafter, the toner images of the respective colors are developed on the photosensitive drum 30 by the magenta developing device 37 and the cyan developing device 38 in the same manner.
Next is transferred. Further, a black toner image is also developed on the photosensitive drum 30 by the black developing device 32 and is primarily transferred onto the intermediate transfer body 34.

As described above, the transfer paper 9 is transferred to the transfer belt unit 40 by the registration roller 39 at a predetermined timing in accordance with the leading edge of the multiplex toner image on the intermediate transfer body 34 by the rotation at which the last toner image is primarily transferred. Conveyed.

At this time, the transfer belt unit 40 swings around the axis of the drive roller 44 and transfers the transfer roller 43 to the intermediate transfer body 34 via the transfer belt 45 so that the angle θ becomes 92 degrees. Abut. Then, a voltage of 1000 to 4000 V and a current of 4 to 2
A bias of 5 μA is applied to the transfer roller 43, whereby the multiple toner image is secondarily transferred onto the transfer paper 9.

The transfer paper 9 is attracted to the transfer belt 45 at the secondary transfer at the same time as the secondary transfer nip N _2, the transfer belt 4
It is transported according to the turning of No. 5. Then, when the transfer paper 9 is attracted to the transfer belt 45 and reaches the portion of the drive roller 44, the transfer paper 9 is separated by the curvature of the drive roller 44, and is conveyed to a fixing device 41 for fixing an unfixed toner image.

The so-called secondary transfer residual toner remaining on the intermediate transfer member 34 transferred to the transfer paper 9 in the secondary transfer is:
The so-called secondary transfer residual toner, which has been negatively charged at the time of the primary transfer, has been negatively charged at the time of the primary transfer, and has been inverted to be positive by the secondary transfer. By bringing the cleaning roller 42 into contact with the intermediate transfer body 34 against the secondary transfer residual toner and applying a positive bias from a high-voltage power supply (not shown), the secondary transfer residual toner is strongly positively charged. The charged secondary transfer residual toner is added by a bias power supply 47 to +1.
By applying the intermediate transfer member 34 continues to bias 00V, is transferred to the photosensitive drum 30 side at the primary transfer nip N ₁ between the photosensitive drum 30 and the intermediate transfer member 34,
It is collected by the photosensitive drum cleaner 35.

In the present embodiment, the transfer belt unit 40 is swung about the axis of the drive roller 44 and the angle θ is set to 92 degrees.
Is set in the range of 91 to 95 degrees, and when the angle θ is set to 90 degrees or less or 96 degrees or more. It has been confirmed by experiments that the probability that the toner does not adhere to the transfer belt 45 but to the intermediate transfer body 34 and is jammed is much lower in the former case.

In particular, when the angle is set to 92 degrees, the transfer paper 45 is transferred from the transfer belt 45 to the transfer paper 9 including the transfer behavior of the transfer paper 9.
Was the best. FIG. 2 shows an experimental result of the state of occurrence of separation failure due to the angle. The intermediate transfer member 34 used at this time is provided with NBR rubber and a surface layer made of urethane and PTFE. The transfer belt 45 is made of urethane 20
Volume resistivity of 10 ⁸ Ωcm provided with a PTFE surface layer at 0 μm
(When 1000 V is applied). Transfer roller 4
Numeral 3 supports both ends with springs and is in contact with the intermediate transfer member 34 at 2.5 kg on one side. Thereby, the secondary transfer nip N
_Second , an appropriate pressure required for transferring the toner image can be obtained.

The volume resistivity of the intermediate transfer member 34 is 10 ⁹ Ωcm
Therefore, transfer and separation can be performed by the method of the present embodiment.

The present inventors examined the volume resistivity of the intermediate transfer member 34 and found that the volume resistivity was 10 ¹⁰ Ωcm or less.
And similar results were obtained.

For a volume resistivity of less than 10 ⁸ Ωcm, 2
Practically, 10 ⁸ to 10 ¹⁰ Ωcm
The intermediate transfer member having the following volume resistivity is desirable. <Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG.

In the first embodiment, the transfer paper 9 is attracted to the transfer belt 45 at the secondary transfer nip N ₂ simultaneously with the secondary transfer, and is conveyed according to the rotation of the transfer belt 45. In the present embodiment, the transport guide 4 is provided before the secondary transfer nip portion N ₂ between the transfer belt 45 and the intermediate transfer body 34.
9 disposed, which is constituted so as to transport by contacting a transfer sheet 9 to the intermediate transfer member 34 by the conveying guide 49 before the transfer electric field is applied to the transfer paper 9 at the secondary transfer nip N _2. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

In the above-described embodiment, the recording material is described as a transfer paper. However, the present invention is not limited to this.
The recording material may be, for example, recording paper, printing paper, a card, an envelope, a postcard, and the like, and the material is not limited to paper.

In the above embodiment, the image forming apparatus has been described in which the toner image formed on the photosensitive drum 30 is transferred to the transfer paper 9 by the transfer belt unit 40 via the intermediate transfer body 34. An image forming apparatus having a configuration in which a toner image formed on a photosensitive drum is transferred onto transfer paper by a transfer belt unit can be similarly applied, and the same effects as those of the above-described embodiment can be obtained.

[0043]

As described above, according to the first aspect of the present invention, one of the rollers on which the transfer belt is suspended is brought into contact with or separated from the image carrier to form a transfer nip portion.
Since a bias power supply is connected to the one roller, the functions of applying a transfer bias and adsorbing a recording material can be shared, so that the configuration of the transfer belt unit can be simplified, and An appropriate pressure required for transferring the toner image to the nip can be obtained.

According to the second aspect of the present invention, the transfer guide is provided before the transfer nip portion between the transfer belt and the image carrier, so that the recording material is brought into contact with the image carrier and the transfer electric field is increased. Therefore, a high-quality image without toner scattering can be obtained.

Further, by setting the contact angle of the transfer belt to the image carrier in the range of 91 to 95 degrees, stable separation of the recording material can be performed even in an image carrier having a large diameter.

[Brief description of the drawings]

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

FIG. 2 shows an experimental result of an occurrence state of separation failure caused by an angle between a line connecting a center of an intermediate transfer member and a center of a transfer roller and a tight side of a transfer belt according to the first embodiment of the present invention. FIG.

FIG. 3 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram illustrating an example of a conventional image forming apparatus.

FIG. 5 is a schematic configuration diagram illustrating another example of a conventional image forming apparatus.

[Explanation of symbols]

 Reference Signs List 9 recording material (transfer paper) 30 image carrier (photosensitive drum) 34 image carrier (intermediate transfer member) 40 transfer belt unit 43 one roller (transfer roller) 44 the other roller (drive roller) 45 transfer belt 46 bias power supply

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Hiroshima 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (7)

[Claims] The transfer belt unit includes a transfer belt and a roller on which the transfer belt is suspended, and transfers a toner image carried on the image carrier between the transfer belt and the image carrier. An image forming apparatus configured to transfer the recording material at the time of transferring the toner image while transferring the recording material at a transfer nip portion, wherein one of the rollers on which the transfer belt is suspended An image forming apparatus, wherein the image forming apparatus is supported so as to be swingable about the axis of the other roller so as to be in contact with and separated from the carrier, and a bias power supply is connected to the one roller. 2. A conveyance guide is provided so that when the recording material enters a transfer nip portion between the image carrier and the transfer belt, the recording material enters from an angle parallel to a tight side of the transfer belt. The image forming apparatus according to claim 1, wherein: 3. A line connecting the center of the image carrier and the center of the one roller when one roller of the transfer belt unit contacts the image carrier via a transfer belt.
The image forming apparatus according to claim 1, wherein an angle between the transfer belt and the tension side is 91 to 95 degrees. 4. The image forming apparatus according to claim 3, wherein the angle is preferably 92 degrees. 5. The image bearing member according to claim 1, wherein the image bearing member is a rotary drum type electrophotographic photosensitive member.
The image forming apparatus as described in the above. 6. The image bearing member according to claim 1, wherein the image bearing member is a rotary drum type intermediate transfer member.
The image forming apparatus as described in the above. 7. The intermediate transfer member has a volume resistivity of 10 ^8.
The image forming apparatus according to claim 6, wherein the pressure is 10 to 10 ¹⁰ Ωcm.