JPH11160950A - Belt device, belt, transfer belt device, transfer belt, and image forming device - Google Patents

Abstract

(57) Abstract: At least two members (5b) including a driving roller (5b)
In the belt device having the belt 5d which is suspended and stretched between 5c and is rotated by the driving of the drive roller, the belt meandering caused by the play of the driving roller 5b in the thrust direction in the belt device is prevented, and the problem caused by the belt meandering is prevented. In the transfer belt device and the image forming apparatus equipped with the transfer belt device, the transfer belt can be prevented from meandering, and the problems caused by the transfer belt meandering can be eliminated, resulting in positional deviation, pitch unevenness, and transfer unevenness. In addition to obtaining high-quality images without any problems, the aim is to improve the reliability and durability of the device. SOLUTION: A driving gear 5g for rotating a driving roller 5b is a helical gear. The belt 5d has a multilayer structure including at least an elastic layer and a release layer, and the total thickness unevenness of the belt is 20% or less. The thickness unevenness of the elastic layer of the belt is 20% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt device having a belt suspended between at least two members including a driving roller and rotated by driving the driving roller, a belt of the belt device, and a driving device. At least 2 including rollers
The present invention relates to a transfer belt device having a transfer belt suspended between members and rotated by driving a drive roller, a transfer belt of the transfer belt device, and an image forming apparatus including the transfer belt device.

[0002]

2. Description of the Related Art Conventionally, in a transfer type image forming apparatus such as a copying machine or a laser printer, a transfer nip portion is formed by abutting an image carrier, and is formed and carried on the image carrier by an appropriate image forming process means. There is a transfer belt device as one of the contact transfer means for transferring the transferred toner image to a recording material (transfer material) at a transfer nip portion.

In this transfer belt device, basically, an endless transfer belt is suspended between a drive roller and a transfer roller (driven roller) disposed in parallel, and the drive roller is driven to rotate. The transfer belt is rotated by the frictional force between the front surface of the drive roller and the back surface of the transfer belt, and the rotating transfer belt conveys the recording material to the toner image transfer nip portion and transfers the recording material from the image carrier to the recording material. The transfer of the toner image, the separation of the recording material after the transfer of the toner image from the surface of the image carrier, and the conveyance of the separated recording material to a downstream process such as a fixing unit are performed.

The transfer belt needs to be electrically controlled to a medium resistance region of 10 ⁸ Ω to 10 ¹² Ω in order to obtain good transferability. It is necessary that the surface has an appropriate capacitance to obtain. Further, a material having releasability is selected so that even if dirt adheres, it is easy to clean.

Therefore, the transfer belt conventionally used has a multi-layer structure, mainly a two-layer structure, in order to separate the respective functions in order to satisfy the above functions.

Mechanically, since the transfer belt is driven to rotate under the application of tension, it must have excellent bending characteristics, tear strength characteristics and the like. Therefore, a rubber-elastomer type belt is mainly used rather than a resin belt type.

A transfer belt device in an image forming apparatus of a system in which a plurality of color toner images are sequentially superimposed and formed on an image carrier and the superimposed toner images are collectively transferred to a recording material is provided by a transfer belt device. The swing control is performed so that the toner image is brought into contact with the image carrier at the timing of transferring the toner image to the recording material, and is separated from the image carrier at other times.

[0008]

In the above-described transfer belt device, if the drive roller for rotating the transfer belt has a play in the thrust direction, the transfer belt rotated by the drive roller meanders. When the transfer belt meanders, the recording material adsorbed and conveyed to the transfer belt also meanders (obliquely moves), causing a problem that a transfer position from the image carrier to the recording material shifts and pitch unevenness occurs.

[0009] Further, when the meandering of the transfer belt is severe, the end of the transfer belt comes into contact with other parts and rotates, causing damage, and when severe, the transfer belt is torn. there were.

Furthermore, when the thickness unevenness of the transfer belt stretched and driven between the drive roller and the transfer roller is large, the elongation rate differs in the width direction of the transfer belt, which causes meandering and uneven resistance. In addition, the transferability of the toner image transferred from the image carrier to the recording material is not uniform, and the image quality is deteriorated.

The occurrence of belt meandering due to the play in the thrust direction of the drive roller as described above, and the problem caused by the belt meandering, are not limited to the transfer belt device, but are suspended between at least two members including the drive roller. This is also a common matter for a belt device having a belt that rotates when a driving roller is driven.

In view of the above, the present invention is to provide a transfer belt device and a transfer belt device which prevent the belt from meandering due to the play in the thrust direction of the driving roller in such a belt device and eliminate the problems caused by the belt meandering. In the image forming apparatus, the occurrence of the transfer belt meandering is prevented, the problem caused by the transfer belt meandering is eliminated, and a high-quality image free of positional deviation, pitch unevenness, transfer unevenness, etc. is obtained, and the reliability of the apparatus is improved. The purpose is to improve the properties and durability.

[0013]

SUMMARY OF THE INVENTION The present invention is a belt device, a belt, a transfer belt device, a transfer belt, and an image forming apparatus having the following structures.

(1) In a belt device having a belt suspended between at least two members including a drive roller and rotated by driving the drive roller, a drive gear for rotating the drive roller is a helical gear. A belt device, comprising:

(2) In a belt device having a belt suspended between at least two members including a driving roller and rotated by driving the driving roller, the belt includes at least an elastic layer and a release layer. A belt device having a multilayer structure, wherein a total thickness unevenness of the belt is 20% or less.

(3) The thickness unevenness of the elastic layer of the belt is 20%.
The belt device according to (2), wherein:

(4) The belt device according to any one of (1) to (3), wherein the belt is a transfer belt that conveys a recording material on which a toner image is transferred.

(5) The belt device according to any one of (1) to (3), wherein the belt is an image carrier for forming a toner image.

(6) A belt that is suspended and stretched between at least two members including a driving roller, and is rotated by driving the driving roller. The belt has a multilayer structure including at least an elastic layer and a release layer. A belt characterized in that thickness unevenness is 20% or less.

(7) The belt according to (6), wherein the thickness unevenness of the elastic layer is 20% or less.

(8) The belt according to (6) or (7), which is a transfer belt for conveying a recording material on which a toner image is transferred.

(9) The belt according to (6) or (7), which is an image carrier for forming a toner image.

(10) A recording material is held between at least two members including a driving roller, which sandwiches and conveys the recording material between the recording material and the image carrier to transfer the toner image on the image carrier to the recording material. In a transfer belt device having a transfer belt that is rotated by driving a drive roller and forms a transfer nip portion with an image carrier, a drive gear that rotationally drives the drive roller is a helical gear. Transfer belt device.

(11) A recording material is held between at least two members including a driving roller, which sandwiches and conveys the recording material between the recording material and the image carrier to transfer the toner image on the image carrier to the recording material. In a transfer belt device having a transfer belt that is rotated by driving a drive roller and forms a transfer nip portion between the transfer belt and the image carrier, the transfer belt has a multilayer structure including at least an elastic layer and a release layer. A transfer belt device, wherein a total thickness unevenness of the transfer belt is 20% or less.

(12) The transfer belt device according to (11), wherein the thickness unevenness of the elastic layer of the transfer belt is 20% or less.

(13) The recording material is suspended between at least two members including a driving roller, is rotated by driving the driving roller, forms a transfer nip portion between the image bearing member, and conveys the recording material. A transfer belt having a multilayer structure including at least an elastic layer and a release layer, and having a total thickness unevenness of 20% or less.

(14) The transfer belt according to (13), wherein the thickness unevenness of the elastic layer is 20% or less.

(15) In an image forming apparatus having a contact transfer means for sandwiching and conveying a recording material between the image carrier and transferring the toner image on the image carrier to the recording material side,
The contact transfer unit may be any one of (10) to (12).
An image forming apparatus, comprising:

(16) In a color image forming apparatus in which toner images of a plurality of colors are sequentially formed on an image carrier and are collectively transferred to a recording material by using a contact transfer unit, the contact transfer unit is configured as described in (10) to (12). 20. An image forming apparatus, which is the transfer belt apparatus according to any one of the above.

(17) The image forming apparatus according to (15) or (16), wherein the image carrier is an intermediate transfer member.

<Operation> a) In a belt device having a belt suspended between at least two members including a driving roller and rotated by driving the driving roller, a driving device for driving the driving roller to rotate. When the gear is a helical gear, a drive component (thrust force) acts on the drive roller in one longitudinal direction, and the drive roller is constantly moved in one direction in the thrust direction during rotation.

Therefore, by regulating the movement of the drive roller by the regulating member by the regulating member, it is possible to eliminate the occurrence of the play of the drive roller in the thrust direction, and the occurrence of the belt meandering due to the play of the drive roller in the thrust direction. This can be prevented.

B) Further, by setting the total thickness unevenness of the belt to 20% or less of the total thickness, the belt is suspended between at least two members including the driving roller under the application of tension, and the driving roller is driven. Accordingly, the tension of the rotated belt in the width direction of the belt can be kept constant, and the meandering of the belt can be prevented.

C) By preventing the belt from meandering due to the play in the thrust direction of the drive roller as in the above a) and b), it is possible to eliminate the problem caused by the belt meandering.

In a transfer belt device and an image forming apparatus provided with the transfer belt device, meandering of the transfer belt is prevented, problems caused by meandering of the transfer belt are eliminated, and positional deviation, pitch unevenness, transfer unevenness and the like are eliminated. High-quality images without defects, and no critical damage such as damage to the end of the transfer belt.
There is also an effect that durability is improved, user and service maintenance is reduced, and running costs can be reduced.

By setting the total thickness unevenness of the transfer belt to 20% or less, the elongation rate in the width direction of the transfer belt can be made substantially constant. Therefore, the transfer belt is stretched between at least two members including the drive roller. In this state, the resistance value of the transfer belt can be made uniform, the transfer unevenness when transferring the toner image on the image carrier to the recording material is reduced, and a high-quality image can be obtained.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment (FIGS. 1 to 4) (1) Overall Schematic Configuration of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an image forming apparatus of the present embodiment.

The image forming apparatus of this embodiment is a full-color laser printer utilizing an electrophotographic process.

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier, which is rotated at a predetermined peripheral speed (process speed) clockwise as indicated by an arrow, and is repeatedly driven. used.

Reference numeral 2 denotes a charging means, which in this embodiment is a corona charger. The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined polarity and potential by the corona charger 2.

Reference numeral 3 denotes a laser scanner as exposure means. The laser scanner is a digital scanning exposure unit that outputs a laser beam modulated according to a time-series electric digital pixel signal of image information. The scanner 3 performs a laser beam scanning exposure L corresponding to the target image information on the surface of the rotating photosensitive drum 1 after the charging process.
An electrostatic latent image corresponding to the exposure is formed.

Reference numeral 4 denotes a rotary moving type color developing device.
Yellow toner developing device 4Y, magenta toner developing device 4
M, cyan toner developing device 4C, black toner developing device 4
It is equipped with four color developing units of BK. The necessary developing device is rotationally controlled based on the switching signal, and the necessary developing device is rotated and moved to a predetermined opposing position D (developing position) where the developing operation can be performed on the photosensitive drum 1.

The electrostatic latent image on the surface of the rotating photosensitive drum 1 is subjected to reversal development processing as a toner image in any of the four developing units 4Y, 4M, 4C and 4BK of the developing device 4. The toner used in this embodiment is a non-magnetic toner having an average particle diameter of 8
μm, the average toner tribo in a normal environment (25 ° C., 50% RH) is about −25 μC / g.

Reference numeral 5 denotes a transfer belt device (transfer unit) as a transfer means disposed below the photosensitive drum 1. The transfer belt device 5 will be described in detail in the following section (2), and is controlled to move toward and away from the photosensitive drum 1. The transfer nip portion T is formed between the photosensitive drum 1 and the photosensitive drum 1 by being in contact with the photosensitive drum 1. Then, a recording material (transfer material) P is fed to the transfer nip portion T at a predetermined control timing from a paper feeding portion (not shown) via a registration roller 6 and a pre-transfer guide 7, so that the transfer nip portion T is transferred. The recording material P is sandwiched and conveyed between the rotary photosensitive drum 1 and the rotary transfer belt 5d, and a predetermined transfer bias is applied to the transfer belt device from the transfer bias source 12, so that the toner image on the photosensitive drum 1 surface side is transferred to the recording material. It is sequentially transferred to the surface.

The recording material P which has passed the transfer of the toner image through the transfer nip portion T is separated from the surface of the rotating photosensitive drum 1 by the rotating transfer belt 5d of the transfer belt device 5, and
The toner image is conveyed and introduced into the fixing device 8 and subjected to a heat fixing process.

Reference numeral 9 denotes a cleaner for removing the transfer residual toner remaining on the photosensitive drum surface and cleaning the photosensitive drum surface.
The movement of the photosensitive drum 1 is controlled by moving means (not shown).

The formation of a full-color image in the printer of this embodiment is executed by the following device operation. Normally, the transfer belt device 5 and the cleaner 9 are held at positions separated from the surface of the photosensitive drum 1 in a non-contact manner.

[0048] Charging 2 of the rotating photosensitive drum 1 → exposure L of a yellow component image as a first color component image of a target full-color image / latent image formation → development by a yellow toner developing unit 4Y. Charging 2 of the rotating photosensitive drum 1 → exposure L of a magenta component image as a second color component image / latent image formation → development by a magenta toner developing unit 4M. Charging 2 of the rotating photosensitive drum 1 → exposure L of a cyan component image as a third color component image / latent image formation → development by cyan toner developing device 4C. The charging 2 of the rotary photosensitive drum 1 → the exposure L as the fourth color component image / latent image formation → the development by the black toner developing unit 4BK The yellow toner image / magenta image on the same surface of the rotary photosensitive drum 16 The four toner images of the toner image, the cyan toner image, and the black toner image are aligned with each other and are superimposed to form a full-color toner image corresponding to the target full-color image.

Then, at the predetermined control timing when the superimposition formation of the last black toner image is started and the leading end of the full-color toner image synthesized and formed on the surface of the rotary photosensitive drum 1 reaches the transfer portion, the transfer belt device 5 Is contact-controlled with the rotating photosensitive drum 1 and pressed against the photosensitive drum 1 with a predetermined pressing force, thereby forming a transfer nip portion T with the photosensitive drum 1, rotating the transfer belt 5d, and applying a transfer bias. Is made. In this embodiment, the transfer bias is +10 μA under constant current control.

The rotary transfer belt 5 of the transfer belt device 5
When the transfer nip T is formed by pressing against d, the leading end of the full-color toner image synthesized and formed on the surface of the rotary photosensitive drum 1 reaches the transfer nip T, the leading end of the recording material P is also just transferred to the transfer nip. The recording material P is transferred to the transfer nip T
Is sent to

Thus, the transfer nip T is moved to the recording material P
Is conveyed, and a full-color toner image formed on the surface of the photosensitive drum 1 is sequentially and collectively transferred to the surface of the recording material P.

The recording material P having received the transfer of the full-color toner image through the transfer nip portion T is separated from the surface of the rotating photosensitive drum 1 by the rotating belt 5d of the transfer belt device 5, and is transported and introduced into the fixing device 8. Then, the toner image is subjected to a fixing process.

At a predetermined control timing after the rear end of the recording material P has passed through the transfer nip T, the transfer belt device 5 is switched to a position separated from the surface of the rotating photosensitive drum 1 in a non-contact manner. Is done.

The cleaner 9 is controlled to move in contact with the surface of the rotating photosensitive drum 1 after transfer at a predetermined control timing, and the transfer residual toner remaining on the surface of the photosensitive drum 1 is removed by the cleaner 9. The surface is cleaned. Thereafter, the cleaner 9 is switched and held at a position separated from the surface of the photosensitive drum 1 in a non-contact manner at a predetermined control timing.

A monochrome image can be output using only the black toner developing device 4BK.

(2) Transfer Belt Device 5 FIG. 2 is an external perspective view of the transfer belt device 5, FIG. 3 is an exploded perspective view thereof, and FIG. 4 is a schematic diagram of a layer structure of the transfer belt.

The transfer belt device 5 is basically a flat box-shaped device frame (transfer frame) 5 having an open upper surface.
a, a driving roller 5b and a transfer roller 5c are respectively provided in the back and front sides thereof in parallel with bearings 5e, 5e, 5f, 5f.
The rollers 5b are rotatably held through
A transfer belt 5d is stretched between 5c and a drive gear 5g is fixedly provided on one shaft end of the drive roller 5b.

The transfer belt device 5 positions and holds the bearings 5e and 5e of the drive roller 5b in a receiving portion (not shown) of the printer main body below the photosensitive drum 1 in the printer main body. Transfer roller 5c at the center
The side is freely swingable.

The device frame 5 of the transfer belt device 5
A pressure spring 5h, which is an elastic body pressing member, and a pressure piece 5i are arranged on the lower surface of the transfer roller 5c on the side of a.

A pressure cam (eccentric cam) 10 corresponding to the pressure piece 5i is provided on the printer body side. 1
Reference numeral 1 denotes a cam shaft to which the pressure cam 10 is fixed, and the rotation of the cam shaft 11 is controlled by an electromagnetic clutch (not shown), whereby the rotation of the pressure cam 10 is controlled.

When the rotation of the pressure cam 10 is controlled so that the top (maximum diameter portion) is directed upward, the transfer belt device 5 causes the pressure piece 5i and the pressure spring 5 to move around the drive roller bearings 5e.
h. As a result, the transfer roller 5c is brought into pressure contact with the lower surface of the photosensitive drum 1 at a predetermined transfer pressure via the transfer belt 5d, and finally, in this embodiment, at a total pressure of about 4 kg, so that the photosensitive drum 1 and the transfer belt device 5 A transfer nip portion T is formed at the bottom. FIG. 1 shows this state.

When the rotation of the pressure cam 10 is controlled and the top escapes from the pressure piece 5i, the transfer belt device 5 is lowered by its own weight around the drive roller bearings 5e. Is held at a position separated from the surface of the non-contact.

In the case of this embodiment, as described above, the transfer belt device 5 is normally kept in a non-contact state away from the photosensitive drum 1 surface.
When the toner image is transferred from the recording medium P to the recording material P, the state is brought into contact with the surface of the photosensitive drum 1 and is held.

The drive gear 5g of the drive roller 5b of the transfer belt device 5 is a helical gear, and meshes with a gear of a drive system (not shown) on the printer main body side to receive a rotational drive force to rotate the drive roller 101. Drive roller 5
By using a helical gear as the drive gear 5g for rotating b, a drive component (thrust force) acts on the drive roller 5b in one longitudinal direction, and the drive roller 5b is always moved in one direction in the thrust direction during rotation. . In the present embodiment, the drive gear 5g is a helical gear that directs the drive roller 5b toward the non-drive gear.

By the rotation of the driving roller 5b, the transfer belt 5d stretched between the driving roller 5b and the transfer roller 5c is moved in the forward direction with respect to the rotation of the photosensitive drum 1 by the frictional force with the driving roller 5b. Counterclockwise and the photosensitive drum 1
Is driven to rotate at the same peripheral speed as the rotational peripheral speed. The transfer roller 5d is driven to rotate.

In this embodiment, as described above, the driving roller 5b
The drive gear 5g is a helical gear having an angle such that a thrust force for moving the drive roller 5b to the non-drive side acts, so that the drive roller 5b moves in the direction of arrow A in FIG. The end on the side abuts against the abutting portion 5j of the device frame 5a, the position in the thrust direction is determined, and the device is driven to rotate. Since the transfer belt 5d is driven by the drive roller 5b whose positioning in the thrust direction is thus firm, it is rotated at a predetermined speed without meandering.

The transfer roller 5c is made of a core metal such as SUS (resistance 1).
0 ⁴ Omega hereinafter) and a conductive surface layer of urethane rubber (resistance 10
⁴ to 10 ⁷ Ω). This transfer roller 5c
A predetermined transfer bias is applied from the transfer bias power supply 13 at a predetermined control timing for a predetermined period.

The photosensitive drum 1 facing the transfer belt 5d as a transfer means has a charged area Vd and an area V1 where toner is developed, and usually has a potential difference of 300 to 500V. These potential differences, when transferring the toner image,
In other words, unless transfer is performed with a voltage sufficient to absorb the difference in load impedance, the toner on the paper will scatter after transfer.

This is because when the transfer voltage is low, a large amount of transfer charge is supplied to the Vd portion and a small amount of transfer charge is supplied to the V1 portion due to the difference in load impedance described above. And the toner on the paper after the transfer is V1 to V
It is caused by scattering to the d part. Therefore, it is necessary to use a transfer belt having a somewhat high resistance which generates a transfer voltage high enough to absorb the difference in load impedance.

The transfer belt 5d used in this embodiment is the same as that shown in FIG.
As shown in FIG. 2, the base layer 5d1 is a thermosetting urethane elastomer, the surface layer 5d2 is a two-layer structure made of vinylidene fluoride rubber, and the total thickness t = 0.3 mm.
The total resistance is about 10 ¹⁰ Ω. The transfer belt 5d suspended and stretched between the drive roller 5b and the transfer roller 5c.
(Elongation of the belt when the belt is pulled and broken in the belt rotation direction) is about 10%.

The transfer belt 5d has a thickness 29 of the base layer 5d1.
0 μm, and the thickness of the surface layer 5d2 is 10 μm. The thickness variation of the transfer belt 5d is within 20% of the total thickness (that is, the total thickness is 300 ± 15 μm and the base layer thickness is 290 ± 15 μm). Preferably, it is within 10%.

In this state, the transfer belt 5d is
b and the transfer roller 5c, the transfer belt 5d
And the overall resistance (10
^{About 10} Ω).

As an experiment, thickness irregularities ± 30 μm and ± 4 μm
As a result of producing a transfer belt of 0 μm and ± 50 μm, ± 3
0 μm was an acceptable limit in terms of both meandering / resistance stability.

As described above, in this embodiment, the transfer belt 5d can be driven to rotate stably without meandering, and the total resistance in the stretched state can be made uniform. It is possible to obtain a high-quality full-color image without positional deviation and transfer unevenness.

Second Embodiment (FIG. 5) This embodiment is a full-color laser printer utilizing an electrophotographic process, using an intermediate transfer member and a transfer belt device.

The same components as those of the full-color laser printer of the first embodiment described above are denoted by the same reference numerals, and the description thereof will not be repeated.

Reference numeral 13 denotes an intermediate transfer drum (intermediate transfer roller) serving as an intermediate transfer member, which is pressed against the photosensitive drum 1 with a predetermined pressing force, and rotates clockwise in the forward direction with respect to the rotation of the photosensitive drum 1. The photosensitive drum 1 is rotationally driven at the same peripheral speed as the rotational peripheral speed.

The press-contact portion between the intermediate transfer drum 13 and the photosensitive drum 1 is a primary transfer nip portion T1. A transfer bias having a polarity opposite to that of the toner is applied to the intermediate transfer drum 13 from a bias applying source 14 to rotate the photosensitive drum 1. The toner image formed on the first surface is sequentially primary-transferred onto the surface of the rotary intermediate transfer drum 13 at the primary transfer nip T1. The intermediate transfer drum 13 serves as a second image carrier when the photosensitive drum 1 is used as a first image carrier.

The transfer belt device 5 includes an intermediate transfer drum 13
, The vertical swing means 5h, 5i, 10
11 controls the movement toward and away from the lower surface of the intermediate transfer drum 13, and forms a secondary transfer nip T2 by contact.

Reference numeral 15 denotes an intermediate transfer drum cleaning roller, and reference numeral 16 denotes a bias application source for the roller 15. The cleaning roller 15 is controlled to move toward and away from the intermediate transfer drum 13 by moving means (not shown).

The primary charging means 2 of the photosensitive drum 1 uses a contact charging roller in this embodiment. Further, the cleaner 9 for the photosensitive drum 1 is always in a state of acting on the photosensitive drum 1.

The formation of a full-color image in the printer of this embodiment is executed by the following device operation. The transfer belt device 5 and the cleaning roller 15 are normally kept at a position separated from the surface of the intermediate transfer drum 13 in a non-contact manner.

[0083] Charging of the rotating photosensitive drum 1 → Exposure L of a yellow component image as a first color component image of a target full-color image, formation of a latent image → Development by a yellow toner developing device 4Y → Transfer of a yellow toner image to the intermediate transfer drum 13 Primary transfer → cleaning of photosensitive drum surface. Charging of the rotating photosensitive drum 1 → Exposure L of a magenta component image as a second color component image / latent image formation → Development by magenta toner developing device 4M → Primary transfer of magenta toner image to intermediate transfer drum 13 surface (first (Superimposition transfer to the yellow toner image that has been primarily transferred) → Cleaning of the photosensitive drum surface. Charging of the rotating photosensitive drum 1 → exposure L of a cyan component image as a third color component image / latent image formation → development by cyan toner developing device 4C → intermediate transfer drum 1 for cyan toner image
Primary transfer to three surfaces (superimposed transfer to a yellow toner image and a magenta toner image that has been primarily transferred earlier) → Cleaning of photosensitive drum surface. Charging of the rotating photosensitive drum 1 → exposure L of a black component image as a fourth color component image / latent image formation → development by the black toner developing device 4BK → primary transfer of the black toner image to the surface of the intermediate transfer drum 13 (first (Superimposed transfer to the primary-transferred yellow toner image, magenta toner image, and cyan toner image) → Cleaning of photosensitive drum surface The surface of the rotating intermediate transfer drum 13 has a yellow toner image / magenta By superimposing the toner image, the cyan toner image, and the black toner image, a full-color toner image corresponding to the target full-color image is formed.

Here, during the above-mentioned device operations, the transfer belt device 5 and the intermediate transfer drum cleaning roller 15 are held at a position separated from the surface of the rotary intermediate transfer drum 13 in a non-contact manner. The primary transfer toner image on the transfer drum 13 is not destroyed.

Then, the primary transfer of the last black toner image to the surface of the rotary intermediate transfer drum 13 is started, and the leading end of the full-color toner image synthesized and formed on the surface of the rotary intermediate transfer drum 13 reaches the secondary transfer portion. At a predetermined control timing, the transfer belt device 5
The secondary transfer nip portion T2 is formed between the intermediate transfer drum 13 and the intermediate transfer drum 13 by being pressed against the intermediate transfer drum 13 by contact movement control with respect to
A transfer bias is applied.

A secondary transfer nip T2 is formed by pressing the transfer belt device 5 against the rotary intermediate transfer drum 13, and the secondary transfer nip T2 is attached to the secondary transfer nip T2.
When the leading end of the full-color toner image synthesized and formed on the three surfaces reaches the leading end of the recording material P, the recording material P is also transferred to the registration roller 7 and the pre-transfer guide at the control timing to reach the secondary transfer nip T2. 7, the secondary transfer nip T
2

As a result, the recording material is nipped and conveyed through the secondary transfer nip portion T2, and the composite full-color toner image is secondarily transferred to the surface of the intermediate transfer drum 13 sequentially and collectively on the surface of the recording material. .

The recording material P which has passed through the secondary transfer nip portion T2 and receives the transfer of the full-color toner image is separated from the surface of the rotary intermediate transfer drum 13 by the rotary transfer belt 5d of the transfer belt device 5, and the fixing device 8 And is subjected to a fixing process of the toner image.

At a predetermined control timing after the rear end of the recording material P has passed through the secondary transfer nip T2, the transfer belt device 5 is located at a position separated from the surface of the rotary intermediate transfer drum 13 in a non-contact manner. Is switched and held.

The cleaning roller 15 is brought into contact with the surface of the rotary intermediate transfer drum 13 after the secondary transfer at a predetermined control timing and is pressed against the roller 15 with a predetermined pressing force. By applying a predetermined bias, the polarity of the residual toner on the surface of the intermediate transfer drum 13 after the secondary transfer of the toner image to the recording material is reversed to the polarity opposite to the normal charging polarity. As a result, the secondary transfer residual toner on the surface of the intermediate transfer drum 13 whose polarity has been inverted is carried to the primary transfer nip portion T1 and electrostatically attracted to the surface of the rotating photosensitive drum 1 to be transferred. The surface of the transfer drum 13 is cleaned. Further, the toner transferred from the surface of the intermediate transfer drum 13 to the surface of the rotary photosensitive drum 1 is rotated by the photosensitive drum cleaner 9.
Removed from the surface.

The intermediate transfer drum 13 used in this embodiment is
For example, a drum shape (roller shape) having at least an elastic layer made of rubber, elastomer, and resin on a cylindrical conductive support (core metal), and a shape having one or more coating layers on the elastic layer. Things.

As the cylindrical conductive support, a metal or alloy such as aluminum, iron, copper and stainless steel, a conductive resin in which carbon, metal particles and the like are dispersed, and the like can be used. Such a cylinder, a cylinder having a shaft penetrating the center of the cylinder, a cylinder having a reinforced interior, and the like can be given. The conductive support used in the present embodiment is obtained by reinforcing the inside of a 3 mm-thick aluminum cylinder.

The thickness of the elastic layer is desirably 0.5 to 7 mm in terms of the shape of the transfer nip, color shift due to rotation, material cost, and the like.
In order to transmit it further to the upper layer or the photosensitive drum surface,
It is preferable to form a thin layer, specifically, 20 to 200 μm
m is desirable.

In this embodiment, the thickness of the elastic layer is 5 t, the thickness of the surface layer is 30 μm, and the total outer diameter is 180 mm.

The elastic layer has a volume resistivity of 10 ⁵ to 10 by emphasizing only the resistance value and dispersing ketjen black as a conductive material in acrylonitrile butadiene rubber (NBR) as a conductive material.
^The one controlled to ⁸ Ωcm was used. In this embodiment, it is set to 10 ⁷ Ωcm.

For the surface layer, urethane resin is used as a binder and P
A dispersion of 200 parts of TFE powder was used. In the molding method, spray coating and polishing are performed on the elastic layer.

The intermediate transfer drum 1 thus produced
The resistance value of No. 3 was 2 × 10 ⁷ Ω.

Here, in the method of measuring the resistance of the intermediate transfer member, the rubber portion of the intermediate transfer member was cut out into a sheet of 100 × 100 mm, and R8340A and R1340 manufactured by Advantest were used.
2704, applied voltage 100V, discharg
e5sec, charge3sec and measure
e Measured under the condition of 30 sec. The measuring device can measure the volume resistivity, the surface resistance, and the actual resistance, and the resistance value in the text indicates the actual resistance. The measurement was performed at normal temperature and normal humidity.

When the intermediate transfer drum 13 as described above is used, the diameter of the intermediate transfer drum 13 is often larger than that of a normal photosensitive drum.

Since the intermediate transfer drum 13 is a transfer medium, a medium resistance region of 10 ⁷ to 10 ⁸ Ω is essential for obtaining high transfer efficiency. In such a case, the electrostatic capacity and the resistance value change more greatly than in a conventional photosensitive drum or the like due to an environmental change, so that the separation property of the paper becomes very severe.

Therefore, in order to ensure high separation from a low-humidity environment to a high-humidity environment, a transfer belt having a good balance between capacitance and resistance must be used.

Further, in order to transfer (secondary transfer) the image once transferred (primary transfer) again, high transfer efficiency is also required, and the resistance value at which the transfer efficiency is optimal and the above-mentioned resistance value deviate. It may come.

However, the transfer belt 5d of this embodiment has a larger electrostatic capacity than the intermediate transfer drum 13 from a low humidity environment to a high humidity environment, and has a smaller resistance fluctuation than that of the intermediate transfer drum, so that it is stable. A good separability can be secured.

The relationship between the helical angle of the helical gear as the driving gear 5g of the transfer belt device 5 and the thickness unevenness of the transfer belt 5d is the same as that of the transfer belt device in the first embodiment described above, and has the same operation and effect.

As described above, according to this embodiment, even in a color image forming apparatus using the intermediate transfer member 13, the first
As in the embodiment, a high-quality full-color image without transfer position deviation and transfer unevenness can be obtained.

<Third Embodiment> (FIG. 6) In this embodiment, the intermediate transfer is performed in a full-color laser printer using an electrophotographic process and using an intermediate transfer member and a transfer belt device according to the second embodiment. The intermediate transfer drum 13 is replaced with an intermediate transfer belt 13A, and the transfer belt device 5 is replaced with a transfer roller 17.

The intermediate transfer belt 13A is suspended between three parallel rollers of a primary transfer auxiliary roller 13a, a secondary transfer auxiliary roller 13b, and a tension roller 13c. The primary transfer auxiliary roller 13a is used as a driving roller, and when the roller 13a is driven, the frictional force between the roller surface and the inner surface of the intermediate transfer belt 13A causes the intermediate transfer belt 13
A is driven to rotate clockwise in the forward direction of the rotation of the photosensitive drum 1 at the same peripheral speed as that of the photosensitive drum 1. The secondary transfer assist roller 13b and the tension roller 13c are driven to rotate by the rotation of the intermediate transfer belt 13A.

The primary transfer assist roller 13a is pressed against the photosensitive drum 1 with a predetermined pressing force with the intermediate transfer belt 13A interposed therebetween to form a primary transfer nip portion T1.

The transfer roller 17 is held by an oscillating frame 17a, and the oscillating frame 17a is oscillated by up and down oscillating means including a pressing spring 17h, a pressing piece 17i, a pressing cam 10, a cam shaft 11, and the like. Thus, at the position of the secondary transfer assist roller 13b, the transfer roller 17
The secondary transfer nip T2 is formed by contact and separation movement control with respect to the surface A, and by contact.

At the position of the tension roller 13c, the cleaning roller 15 is controlled to move toward and away from the surface of the intermediate transfer belt 13A.

Reference numeral 18 denotes a fixing device 8 from the secondary transfer nip T2.
The guide member guides the recording material.

The formation of a full-color toner image on the intermediate transfer belt 13A is performed in the same manner as on the intermediate transfer drum 13 in the printer of the second embodiment, and the transfer roller 17 transfers the full-color toner image onto the recording material P at a time. It is.

A driving gear (not shown) of the primary transfer auxiliary roller 13a as a driving roller of the intermediate transfer belt 13A is a helical gear, and receives a rotational driving force by meshing with a gear of a driving system (not shown) of the printer main body. Roller 13a
Is driven to rotate.

By using a helical gear as the drive gear for rotating the drive roller 13a, a drive component (thrust force) acts on the drive roller 13 in one longitudinal direction, so that the drive roller 13 always rotates in one direction in the thrust direction during rotation. Receive a shift. In the present embodiment, the drive gear is a helical gear that directs the drive roller 13a toward the non-drive gear.

Therefore, the drive roller 13a moves toward the counter-drive gear side during its rotation, and the end on the shift side abuts against the abutting portion (not shown), so that the position in the thrust direction is determined. Receive rotational drive.

The intermediate transfer belt 13A is driven by the drive roller 13 whose positioning in the thrust direction is firm.
Since it is driven by a, it is driven to rotate at a predetermined speed without meandering.

The intermediate transfer belt 13A has a low volume efficiency of 10 ⁵ by dispersing Ketjen black as a conductive material with emphasis on the resistance value in acrylonitrile butadiene rubber (NBR) or a thermosetting urethane elastomer as a base layer. ~
The surface layer was controlled at 10 ⁸ Ωcm, and the surface layer was formed by dispersing 200 parts of PTFE powder using a urethane resin as a binder. In the molding method, the surface of the surface layer is spray-coated and polished. The thickness of the surface layer is 1 mm,
The thickness of the surface layer was 10 μm. The resistance value of the intermediate transfer belt 13A thus formed was 2 × 10 ⁷ Ω.

The method of measuring the resistance of the intermediate transfer belt 13A is the same as the method of measuring the resistance of the intermediate transfer drum 13 of the second embodiment.

The intermediate transfer belt 13 may be reinforced with a metal fiber such as SUS or a fiber such as carbon as a core material for a base layer in order to prevent elongation.

The process of forming a color image, transferring it collectively onto the transfer material P, and fixing it by heating with the fixing device 17 is the same as that of the second embodiment even when the intermediate transfer belt 30 is used as described above. .

Drive roller 13a of intermediate transfer belt 13A
The relationship between the helical angle of the helical gear as the driving gear and the thickness unevenness of the intermediate transfer belt 13 is set to 20% or less in the same manner as in the first and second embodiments, thereby preventing the intermediate transfer belt 13A from meandering. It is possible to form a full-color toner image without transfer unevenness on the intermediate transfer belt 13A.

According to this embodiment, the intermediate transfer belt 13A
As in the first and second embodiments, it is possible to obtain a high-quality full-color image free from transfer position deviation and transfer unevenness in a color image forming apparatus using the same.

As described above, according to the first to third embodiments, while the transfer belt in the transfer unit used in the transfer unit of the image forming apparatus using the electrophotographic method is driven to rotate, the transfer from the photosensitive drum is performed. When transferring a toner image or transferring a toner image to a recording material, it is possible to prevent the transfer belt from meandering without any special meandering prevention control or mechanism, and to achieve clear color output images without positional deviation and pitch unevenness. Can be obtained.

Furthermore, since the unevenness of the overall resistance of the transfer belt when the transfer belt is stretched can be made uniform, a high-quality color output image without transfer unevenness can be obtained.

Further, since the end portion of the transfer belt can be prevented from being damaged or cracked, the life of the transfer belt can be extended, and the user and service maintenance can be reduced.
Running costs can also be reduced.

Furthermore, the basic performance of separating and transporting the recording material from the image carrier can be improved, and problems such as jams are reduced, so that the quality and stability of the image forming apparatus are also improved. I was able to.

<Others> a) Although the belt device of the embodiment is a transfer belt device or an intermediate belt device, the present invention is suspended between at least two members including a driving roller, and the driving roller is driven. As a result, the present invention can be applied to a belt device having a rotating belt and a belt of the belt device, and is of course effective.

B) The exposure means in the color image forming apparatus of each embodiment may be a color separation / imaging exposure optical system for a color original.

C) The image forming apparatus is not limited to a color image forming apparatus.

D) The image forming apparatus is not limited to electrophotography,
Other appropriate image forming principles and processes may be used.

[0131]

As described above, according to the present invention,
Suspended between at least two members including a driving roller,
In a belt device having a belt that rotates when the drive roller is driven, it is possible to prevent the belt from meandering due to the play in the thrust direction of the drive roller and to eliminate the problem caused by the belt meander.

In a transfer belt device and an image forming apparatus equipped with the transfer belt device, meandering of the transfer belt is prevented, problems caused by meandering of the transfer belt are eliminated, and positional deviation, pitch unevenness, transfer unevenness and the like are eliminated. It is possible to obtain high-quality images without defects and improve the reliability and durability of the device.

[Brief description of the drawings]

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

FIG. 2 is an external perspective view of a transfer belt device.

FIG. 3 is an exploded perspective view of a transfer belt device.

FIG. 4 is a schematic diagram of a layer structure of a transfer belt.

FIG. 5 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 6 is a schematic configuration diagram of an image forming apparatus according to a third embodiment.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum (image carrier) 2 corona charger or contact charging roller 3 laser scanner 4 switchable color developing device 5 transfer belt device 5b drive roller 5c transfer roller 5d transfer belt 5g drive gear (helical gear) 6 registration roller 7 before transfer Guide 8 Fixing device 9 Cleaner 13.13A Intermediate transfer drum or intermediate transfer belt

Claims (17)

[Claims] 1. A belt device having a belt that is suspended and stretched between at least two members including a driving roller and that rotates when the driving roller is driven, wherein the driving gear that rotationally drives the driving roller is a helical gear. A belt device characterized by the above-mentioned. 2. A belt device having a belt suspended between at least two members including a driving roller and rotated by driving the driving roller, wherein the belt has at least a multi-layer comprising an elastic layer and a release layer. A belt device, wherein the belt has a total thickness unevenness of 20% or less. 3. The belt device according to claim 2, wherein the thickness unevenness of the elastic layer of the belt is 20% or less. 4. The belt according to claim 1, wherein the belt is a transfer belt that conveys a recording material onto which a toner image is transferred.
4. The belt device according to any one of claims 1 to 3. 5. The belt according to claim 1, wherein the belt is an image carrier for forming a toner image.
The belt device according to any one of the above. 6. A belt that is suspended and stretched between at least two members including a driving roller and that rotates when the driving roller is driven, has a multilayer structure including at least an elastic layer and a release layer, and has a total thickness. A belt characterized in that unevenness is 20% or less. 7. The belt according to claim 6, wherein the thickness unevenness of the elastic layer is 20% or less. 8. A transfer belt for conveying a recording material on which a toner image is transferred.
The belt described in. 9. The belt according to claim 6, wherein the belt is an image carrier that forms a toner image. 10. A driving device, which is suspended between at least two members including a driving roller, which sandwiches and conveys a recording material between the recording material and an image carrier to transfer a toner image on the image carrier to the recording material. In a transfer belt device having a transfer belt that forms a transfer nip between the image carrier and a roller that is rotated by driving the roller, a driving gear that rotationally drives the driving roller is a helical gear. Transfer belt device. 11. A driving device, which is suspended between at least two members including a driving roller for sandwiching and conveying a recording material between the recording material and an image carrier to transfer a toner image on the image carrier to the recording material. In a transfer belt device having a transfer belt that forms a transfer nip between the image carrier and the roller that is rotated by being driven by the roller, the transfer belt has a multilayer structure including at least an elastic layer and a release layer, The transfer belt apparatus according to claim 1, wherein the transfer belt has a total thickness unevenness of 20% or less. 12. The thickness unevenness of the elastic layer of the transfer belt is 20.
%. The transfer belt device according to claim 11, wherein 13. A transfer nip portion is formed between an image bearing member and a driving roller. The driving roller is rotated by driving the driving roller. A transfer belt, wherein the transfer belt has a multilayer structure including at least an elastic layer and a release layer, and has a total thickness unevenness of 20% or less. 14. The transfer belt according to claim 13, wherein the thickness unevenness of the elastic layer is 20% or less. 15. An image forming apparatus having a contact transfer unit that sandwiches and conveys a recording material between the recording medium and an image carrier to transfer a toner image on the image image carrier to the recording material side. Item 13. An image forming apparatus, which is the transfer belt device according to any one of Items 10 to 12. 16. A color image forming apparatus for sequentially forming toner images of a plurality of colors on an image carrier and collectively transferring toner images to a recording material using a contact transfer unit, wherein the contact transfer unit is any one of claims 10 to 12. An image forming apparatus, which is the transfer belt device according to any one of the above. 17. The image forming apparatus according to claim 15, wherein the image carrier is an intermediate transfer member.