JPH06149077A - Belt transfer device for electrophotographic apparatus and electrophotographic apparatus - Google Patents

Abstract

(57) [Summary] [Construction] In the belt transfer device 7 using the endless dielectric belt 6, the photosensitive drum 3 is provided with a speed difference so as to be faster than the paper 2 within 0.5%, and the paper is conveyed. The paper guide is made conductive so that the volume resistance value of the system paper guide is 10 ¹¹ Ωcm or less, and the surface roughness of the dielectric belt is set to Rmax 5 μm or less to realize reliable and highly efficient transfer. . [Effect] By making the rotation speed of the photosensitive drum faster than the conveyance speed of the paper, shearing force acts on the contact portion between the photosensitive drum and the paper in the direction of separating the leading end of the paper from the photosensitive drum. By conducting the paper guide conductively so that the volume resistance value is 10 ¹¹ Ωcm or less, the amount of paper charged to the positive pole due to frictional contact between the paper and the plastic paper guide is reduced, and stable high-quality transfer is possible. It will be possible. By using a dielectric belt with a surface roughness Rmax of 5 μm or less,
The paper can be reliably electrostatically attracted to the belt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt transfer device effective for high-efficiency transfer in an electrophotographic device and an electrophotographic device equipped with this belt transfer device, and more particularly to a highly reliable belt transfer device.

[0002]

2. Description of the Related Art A belt transfer device using a dielectric belt conveys paper while the photosensitive drum and paper are in contact with each other and the paper and dielectric belt are in contact with each other. Conventionally, the speeds of the photosensitive drum, the dielectric belt, and the paper are the same. Furthermore, when the paper is conveyed, the relationship between the material (plastic, etc.) of the guide that contacts the paper and the transfer performance has not been fully considered, so the paper is frictionally charged by contact with the guide, and for example, the paper is attracted to the dielectric belt. It was difficult to do so, and there was a problem that it was wrapped around the photosensitive drum.

As described in Japanese Patent Application Laid-Open No. 62-161157, as a means for adhering a sheet to a belt by a transfer device using a belt so as to prevent the sheet from being wound around a photoreceptor, a charging dedicated to adsorption is used. Device, and Japanese Patent Laid-Open No. 2-956
As described in Japanese Patent No. 68, there has been a method of curling a sheet in the direction of peeling it from the photosensitive drum before the transfer section.

[0004]

In the transfer method using a dielectric belt, an endless dielectric belt is charged by a corona charger, paper is electrostatically adsorbed on the belt by this charged electric charge, and further the photosensitive drum is exposed. This is a method of transferring the toner by moving the toner onto the paper. Since the photosensitive drum and the paper, and the paper and the dielectric belt move while contacting each other, if the speeds of the photosensitive drum, the dielectric belt, and the paper are not matched, the behavior of the leading edge of the paper becomes unstable and the paper is exposed to light. Adsorption on the drum side, especially when performing double-sided printing, the moisture content of the paper is drastically reduced at the fixing unit, and the paper comes into contact with the guide to frictionally charge, leading to unstable behavior of the paper leading edge. , If the surface roughness of the dielectric belt is large,
Since the electrostatic attraction between the dielectric belt and the paper is reduced, the attraction of the paper to the dielectric belt becomes unstable, and the paper is attracted to the photosensitive drum, which causes a problem.

An object of the present invention is to provide a highly efficient and highly reliable belt transfer device capable of preventing paper from being wrapped around a photosensitive member in a transfer portion, and an electrophotographic apparatus provided with the belt transfer device. As still another object, in the belt transfer device, the speeds of the photosensitive drum, the dielectric belt, and the paper are matched, and in the transfer portion of the belt transfer device that is generated by frictional charging due to the contact between the paper and the transport guide in the paper transport system. To prevent the behavior of the leading edge of the paper from becoming unstable, and to prevent the attraction of the paper and the photosensitive drum due to the reduction of the electrostatic attraction force between the dielectric belt and the paper when the surface roughness of the dielectric belt is large. is there.

[0006]

SUMMARY OF THE INVENTION The above-mentioned object is to provide a photoreceptor in which a toner is attached to an electrostatic latent image to visualize the toner, an endless dielectric belt which rotates by contacting the photoreceptor, and the dielectric belt. And a corona charger arranged on the inner peripheral side of the dielectric belt, and conveys the paper electrostatically attracted to the dielectric belt to a transfer unit that transfers the toner on the photoconductor to the paper. In a belt transfer device of an electrophotographic apparatus for transferring a toner onto a sheet, it is achieved by including a sheet speed delay unit that makes the sheet conveying speed slower than the rotation speed of the photoconductor.

Further, the delay amount for slowing the sheet conveying speed by the sheet speed delay means with respect to the photosensitive member rotation speed is within 0.5%.

The paper speed delay means sets the dielectric belt speed to be slower than the photosensitive member rotation speed, or sets the paper speed to be slower than the photosensitive member speed until the leading end of the paper passes the transfer portion. After passing through the transfer portion, the sheet speed control may be performed so that the sheet speed and the photoconductor speed are the same.

The speed of the paper may be controlled by controlling the speed of the dielectric belt.

Further, the surface roughness of the dielectric belt is Rmax.
It is sufficient to use one having a thickness of 5 μm or less.

Further, the above-mentioned object is to visualize a photosensitive member by attaching a toner to an electrostatic latent image, an endless dielectric belt which rotates in contact with the photosensitive member, and a means for rotating the dielectric belt. And a corona charger arranged on the inner peripheral side of the dielectric belt, and conveys the paper electrostatically attracted to the dielectric belt to a transfer unit that transfers the toner on the photoconductor to the paper,
In an electrophotographic apparatus that includes a belt transfer device that transfers toner to a sheet and a conveyance roller that conveys the sheet to the belt transfer device, a sheet speed delay that makes the sheet conveyance speed slower than the rotation speed of the photoconductor. It is achieved by providing means.

The paper speed delay means sets the paper speed to be slower than the photoconductor speed until the front end of the paper passes the transfer portion, and after the front end of the paper passes the transfer portion, the paper speed and the photoconductor speed are made equal. The control of the paper speed is performed by controlling the speed of the paper by controlling the speed of the conveyance roller, or after the paper is conveyed to the position immediately before the transfer unit, the rotation speed of the conveyance roller is set to Anything can be set as long as it is set lower than the rotation speed.

Further, the above-mentioned object is to provide a transfer device equipped with a photoconductor and an endless dielectric belt which rotates in contact with the photoconductor, and a toner on the photoconductor transferred onto a sheet by the transfer device. In an electrophotographic apparatus including a fixing device for fixing to a sheet, and a paper transport system for transporting a paper, using one of the transfer devices described above, the volume resistance value of the paper transport guide of the paper transport system is adjusted. This can be achieved by conducting a conductive treatment so as to be 10 ¹¹ Ωcm or less.

[0014]

By increasing the speed of the photosensitive drum within 0.5% of the paper speed, the shearing force acts on the contact portion between the photosensitive drum and the paper in the direction of separating the leading edge of the paper from the photosensitive drum.

Since the paper guide is subjected to the conductive treatment so that the volume resistance value is 10 ¹¹ Ωcm or less, the amount of the paper charged to the positive pole due to the frictional contact between the paper and the plastic paper guide is reduced, and a stable high value is obtained. Image quality transfer becomes possible.

By using a dielectric belt having a surface roughness Rmax of 5 μm or less, the paper can be surely electrostatically attracted to the belt.

[0017]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an electrophotographic apparatus to which the transfer device of the present invention is applied. The sheets of paper 2 accumulated in the hopper 1 are separated and fed one by one, and the separated sheets of paper 2 are conveyed to a transfer unit onto which the toner on the photosensitive drum 3 is transferred. An electrostatic latent image is formed on the photosensitive drum 3 by the optical system 4, and then the toner image is visualized by the developing device 5. The toner image formed on the photosensitive drum 3 is transferred to the sheet 2 by the belt transfer device 7 using the dielectric belt 6 by the belt charging of the corona charger 8 and conveyed to the fixing device 9. Fixed on top.

The paper 2 after fixing has a switchback section 10
The sheet 11 is inverted and conveyed to a stacker (not shown) in the gate 11 or to the D-side conveying path 12 for printing on the back side.

FIG. 2 is a perspective view showing the registration, transfer and fixing portions. The registration roller 13 and the photosensitive drum 3 are attached to independent side plates, and the drive system is also provided with a drive system A14 and a drive system B15, respectively. The belt transfer device 7 is rotatable by a drive pulley 16. The rotation of the dielectric belt 6 is performed by the drive pulley 16, and the drive pulley 16 is rotated by the roller of the fixing device 9 and one drive system C17.

The sheet 2 is curved between the transport roller 18 and the registration roller 13 to correct the skew of the sheet 2 and the photosensitive drum 3
The registration roller 13 is rotated in synchronism with the upper toner image, and the sheet 2 is conveyed. Paper 2 is dielectric belt 6
And is sent to the transfer section T. The speed of the dielectric belt 6 is controlled to be the same as that of the photosensitive drum 3 or slower within 0.5%. The speed of the dielectric belt 6 is Vb, the photosensitive drum 3
Vo is (1-0.005) Vo
It is represented by ≦ Vb ≦ Vo.

In this case, the paper 2 is conveyed at the speed of the dielectric belt 6.

Belt transfer device 7 using dielectric belt 6
The details are shown in FIG. The sheet 2 separated and fed from the hopper 1 is conveyed to the transfer portion while being guided by the front guide 19 with the surface being positively charged. The transfer portion T is provided with an auxiliary shaft A20 and an auxiliary shaft B21 inside the dielectric belt 6, and is arranged so that the dielectric belt 6 is in close contact with the photosensitive drum 3. The −charged toner image formed on the photosensitive drum 3 is transferred to the sheet 2 by the + charge of the transfer corotron 8.

The surface of the sheet 2 separated from the photosensitive drum 3 is negatively charged, and is electrostatically attracted to the positively charged dielectric belt 6 and conveyed. When the leading edge of the sheet 2 reaches the drive pulley 16, the sheet 2 is separated from the dielectric belt 6 due to the bending rigidity of the sheet 2.

The dielectric belt 6 is then charged by the charger 22. The toner remaining on the dielectric belt 6 is
It is adsorbed by the far brush 23 charged to the above, then collected by the bias roller 24, and accumulated in the discharge toner hopper 25.

FIG. 4 shows an enlarged view of only the transfer portion. The paper 2 contacts the photosensitive drum 3 by a mechanical pressing force and an electrostatic force, and this contact width is called a nip width.
Here, it is referred to as a transfer portion T. At the transfer portion T, the paper 2 is deformed following the photosensitive drum 3, so that an area A where a compressive force acts and an area B where a tensile force acts are formed.

Here, when the speed Vb of the dielectric belt 6 is rotated with respect to the speed Vo of the photosensitive drum 3 under the condition shown in the above relational expression of Vb and Vo, the distance between the photosensitive drum 3 and the paper 2 is increased. The shearing force acts to reduce the compressive force in the area A. As a result, the front end of the sheet 2 is deformed in the direction away from the photosensitive drum 3, so that the sheet 2 is easily attracted to the dielectric belt 6, and the obstacle that the sheet 2 is wound around the photosensitive drum 3 can be prevented.

FIG. 5 shows the type of wrapping of the paper 2 which is easily wound around the photosensitive drum 3, and the wrapping frequency (lap ratio) when the speed Vb of the dielectric belt 6 is changed. Speed ratio (photosensitive drum speed-dielectric belt speed) /
In terms of the photosensitive drum speed, it can be seen that wrapping can be prevented at a speed ratio of 0.3%.

(Photosensitive drum speed-dielectric belt speed) /
When the speed ratio of the photosensitive drum speed is set, the change of the image length necessarily appears. In order to avoid this, as shown in FIGS. 6 and 7, control is performed along the above-described relational expression between Vb and Vo until the point O at which the front end of the paper passes through the transfer portion T, and thereafter, the photosensitive drum speed is reached. By making the dielectric belt speed constant, it is possible to prevent a change in the image length and reduce the lap ratio.

The paper 2 is sent by the registration roller 13,
After passing through the sheet detection sensor-S, the dielectric belt speed is reduced within 0.005 · Vo, and after the leading edge of the sheet passes through the point O passing through the transfer section T, the dielectric belt speed is returned to Vo. The controller 17 controls the motor 17.

The range of the deceleration start point of the dielectric belt speed is
This is possible at any point indicated by the alternate long and short dash line shown in FIG.
For example, until the leading edge of the sheet passes through the registration roller 13 and the point O where the leading edge of the sheet passes through the transfer section T, the dielectric belt speed is set to 0.
You may decelerate within 005xVo. Also, the dielectric belt speed is set to Vo until just before the O point where the leading edge of the paper passes through the transfer section T, and the dielectric belt speed is reduced within 0.005 × Vo until the leading edge of the paper passes through the O point of the transfer section T. Control may be performed in which the dielectric belt speed is returned to Vo after the front end passes through the point O passing through the transfer portion T.

Instead of controlling the speed of the dielectric belt 6 to reduce the wrap rate, the speed of the registration roller 13 is accelerated / decelerated to stabilize the behavior of the leading edge of the paper 2 and prevent wrapping. Even if the same effect can be expected. The structure of this system is shown in FIG.

Further, FIG. 9 shows changes in the registration roller speed when the sheet passes each position in the structure of FIG.

The paper 2 is sent by the registration roller 13,
After passing the sheet detection sensor-S, the registration roller speed is reduced within 0.005 × Vo, and the leading edge of the sheet is transferred to the transfer portion T.
After passing the O point, the registration roller speed is set to Vo.
Control to return to.

The range of the deceleration start point of the registration roller speed can be any point shown by the alternate long and short dash line in the figure. For example, the registration roller speed may be reduced within 0.005 × Vo until it passes through the registration roller 13 and the point O where the leading edge of the paper passes through the transfer portion T.

The registration roller speed is set to Vo until just before the O point where the front end of the paper leaves the transfer section T, and the registration roller speed is set to 0.0 until the front end of the paper passes the O point of the transfer section T.
Control may be performed in which the registration roller speed is returned to Vo after decelerating within 05 × Vo and passing the point O where the leading edge of the paper passes through the transfer portion T.

In order to realize good transfer with less toner scattering and transfer with a small wrap ratio at the transfer section T, it is necessary to reduce the charge amount of the paper 2 conveyed to the transfer section T. The electric resistance of the paper 2 greatly changes depending on the environmental conditions, the paper type, and before and after fixing, so that the transfer performance also changes. The charge amount of the sheet 2 is greatly affected by the electric resistance values of the sheet conveying guides 25, 26 and 27 having a high degree of frictional contact between the sheet 2 and the sheet conveying guide shown in FIG. Therefore, in order to reduce the frictional contact charge amount between the sheet 2 and the sheet conveying guides 25, 26 and 27, the sheet conveying guides 25, 26 and 27 are used.
It is preferable to reduce the electric resistance of. However, the cost of the metallic paper transport guide is high, and the paper transport guide that often requires a complicated shape has a problem in mass production.

Therefore, in order to put the plastic material into practical use, it is necessary to manufacture the paper transport guide with an upper limit electric resistance value that can reduce the frictional contact charge amount between the plastic material and the paper 2. Generally, the cost of plastic materials depends on the electrical resistance value. This is because the fluidity of raw materials and the yield are reduced.

FIG. 11 shows the results of measuring the charging potential of the paper transport guides in the width direction of the paper when the electrical resistance values of the paper transport guides 25, 26 and 27 shown in FIG. 10 were manufactured at 10 ¹¹ Ωcm or less. Show.

A sheet conveying guide processed with a material having an electric resistance value of 10 ¹⁴ Ωcm or more was charged to a minimum of -2 kV.
On the other hand, the paper 2 side was charged to +2 kV.

In the paper transport guide processed with a material having an electric resistance value of 10 ¹¹ Ωcm or less, the minimum electrification was -200V. A material having an electric resistance value of about 10 ¹¹ Ωcm can be realized by a molding process equivalent to that of a material which has not been subjected to a conductive treatment.

FIG. 12 shows the relationship between the electrical resistance value of the paper guide and the lap ratio. As shown in the figure, the electric resistance is 1
In the case of 0 ¹⁵ Ωcm, the lap rate was about 14%, but 10 ¹¹ Ω
In the case of cm, the wrap rate was 0%, winding around the photoconductor was completely eliminated, and good transfer performance could be obtained.

The surface roughness of the two types of transfer belts is shown in FIGS. 13 and 14. FIG. 13 shows the surface roughness of the transfer belt having a surface roughness Rmax of 6 μm, and FIG. 14 shows the surface roughness of the transfer belt having a surface roughness of Rmax 4 μm or less. FIG. 15 shows the evaluation result of the transfer device using the transfer belt having these surface roughnesses. From the figure, it is understood that the lap frequency is high in the transfer belt having the Rmax surface roughness of 6 μm or more. Therefore, the surface roughness of the transfer belt needs to be Rmax 5 μm or less.

[0044]

In the transfer device using the transfer method using the dielectric belt, the rotation speed of the photosensitive drum is set within 0.5% of the transfer speed of the paper so that the paper is not wound around the photosensitive member. It can be prevented and transfer to paper can be performed with high reliability.

Further, the volume resistance value of the paper guide is 10 ¹¹ Ω.
By conducting the conductive treatment so that it becomes cm or less, the amount of the paper charged to the positive pole due to the frictional contact between the paper and the plastic paper guide is reduced, and stable high-quality transfer is possible. Furthermore, by using a dielectric belt having a surface roughness Rmax of 5 μm or less, it is possible to securely electrostatically attract the paper to the belt.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an electrophotographic apparatus including a belt transfer device of the present invention.

FIG. 2 is a schematic perspective view of a registration section, a transfer section and a fixing section of FIG.

FIG. 3 is a diagram illustrating a configuration of a transfer unit in FIG.

FIG. 4 is an enlarged view of a transfer nip portion.

FIG. 5 is a diagram illustrating a relationship between a speed ratio between a photosensitive drum and a dielectric belt and a lap ratio.

FIG. 6 is an explanatory diagram of speed control of a dielectric belt.

FIG. 7 is a relationship diagram between each position shown in FIG. 6 and belt speed.

FIG. 8 is an explanatory diagram of speed control of a registration roller.

FIG. 9 is a relationship diagram between each position shown in FIG. 8 and belt speed.

FIG. 10 is a layout view of a paper guide guide.

FIG. 11 is a relationship diagram between the electrical resistance value of the paper guide guide and the amount of paper charge.

FIG. 12 is a relationship diagram between an electric resistance value of a sheet guide guide and a wrap rate.

FIG. 13 is a result of measuring surface roughness of a transfer belt having Rmax of 6 μm.

FIG. 14 is a result of measuring surface roughness of a transfer belt having Rmax of 4 μm.

FIG. 15 is a diagram showing the relationship between the surface roughness of the transfer belt and the lapping rate.

[Explanation of symbols]

1 ... Hopper, 2 ... Paper, 3 ... Photosensitive drum, 4 ... Optical system,
5 ... Developing device, 6 ... Dielectric belt, 7 ... Belt transfer device,
8 ... Corona charger, 9 ... Fixing device, 10--Switchback section, 11 ... Gate, 12 ... D surface conveying path, 13 ... Registration roller, 14 ... Driving system A, 15 ... Driving system B, 16 …
Drive pulley, 17 ... Drive system C, 18 ... Conveyor roller, 19
... Front guide, 20 ... Auxiliary shaft A, 21 ... Auxiliary shaft B, 22 ...- Charger, 23 ... Far brush, 24 ... Bias roller, 25 ... Paper transport guide A, 26 ... Paper transport guide B, 27 ... Paper transport guides C, 30, 32 ... Control device.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masato Miwa 2-6-2 Otemachi, Chiyoda-ku, Tokyo Inside Nirititsu Koki Co., Ltd. (72) Kazuo Uno 2--6, Otemachi, Chiyoda-ku, Tokyo No. 2 Nitto Koki Co., Ltd.

Claims (10)

[Claims] 1. A photoconductor in which a toner is attached to an electrostatic latent image to make it visible, an endless dielectric belt which rotates by contacting with the photoconductor, a means for rotating the dielectric belt, and this dielectric. It is equipped with a corona charger arranged on the inner circumference side of the body belt, and conveys the paper electrostatically attracted to the dielectric belt to the transfer unit that transfers the toner on the photoconductor to the paper and transfers the toner to the paper. A belt transfer device for an electrophotographic apparatus, comprising: a paper speed delaying unit that makes a paper conveyance speed slower than a rotation speed of a photoconductor. 2. The belt transfer of an electrophotographic apparatus according to claim 1, wherein the delay amount for slowing the sheet conveying speed by the sheet speed delaying unit with respect to the photosensitive member rotation speed is within 0.5%. apparatus. 3. The belt transfer device for an electrophotographic apparatus according to claim 1, wherein the paper speed delay means sets the dielectric belt speed to be slower than the photosensitive member rotation speed. 4. The sheet speed delay means according to claim 1, wherein the sheet speed delay means sets the sheet speed to be lower than the photoconductor speed until the leading edge of the sheet passes through the transfer section, and after the leading edge of the sheet passes through the transfer section. A belt transfer device for an electrophotographic apparatus, which controls a paper speed such that the speed and the speed of the photoconductor are the same. 5. A belt transfer device for an electrophotographic apparatus according to claim 4, wherein the control of the paper speed is performed by speed control of the dielectric belt. 6. A belt transfer device for an electrophotographic apparatus according to claim 1, wherein a dielectric belt having a surface roughness Rmax of 5 μm or less is used. 7. A photoreceptor, which is visualized by attaching a toner to an electrostatic latent image, an endless dielectric belt which rotates by contacting with the photoreceptor, a means for rotating the dielectric belt, and this dielectric. It is equipped with a corona charger arranged on the inner circumference side of the body belt, and conveys the paper electrostatically attracted to the dielectric belt to the transfer unit that transfers the toner on the photoconductor to the paper and transfers the toner to the paper. An electrophotographic apparatus including a belt transfer device and a transport roller for transporting a sheet to the belt transfer device, characterized by comprising a sheet speed delay means for making the transport speed of the paper slower than the rotation speed of the photoconductor. Electrophotographic device. 8. The sheet speed delay means according to claim 7, wherein after the sheet is conveyed to immediately before the transfer section, the rotation speed of the conveyance roller is set lower than the rotation speed of the photoconductor. Electrophotographic device. 9. The sheet speed delay means according to claim 7, wherein the sheet speed is set to be lower than the photoconductor speed until the leading edge of the sheet passes the transfer section, and after the leading edge of the sheet passes the transfer section. An electrophotographic apparatus for controlling a paper speed such that the speed and the speed of a photoconductor are the same, wherein the control of the paper speed is performed by a speed control of a transport roller speed. 10. A transfer device comprising a photoconductor and an endless dielectric belt which rotates in contact with the photoconductor, and a fixing device for fixing the toner on the photoconductor transferred onto the paper by the transfer device onto the paper. In an electrophotographic apparatus comprising an apparatus and a sheet conveying system for conveying a sheet, the transfer apparatus according to any one of claims 1 to 6 is used, and the volume resistance value of a sheet conveying guide of the sheet conveying system is 10 An electrophotographic device characterized by being subjected to a conductive treatment so as to be ¹¹ Ωcm or less.