JPH07168454A - Transfer belt device and method for cleaning transfer belt - Google Patents

Abstract

PURPOSE:To remove reversely electrostatically charged toner and to prevent the back staining of a transfer material by providing a cleaning blade as the main cleaning mechanism of a cleaning device and a cleaning member by electric field as a sub- cleaning mechanism and impressing the electric field having a reverse polarity to impressed electric field on a charge applying means on the cleaning member by the electric field. CONSTITUTION:In addition to the cleaning blade 11 for wiping out residual toner adhering to the transfer belt 2, the cleaning member 12 by the electric field is provided and the electric field having the reverse polarity to the impressed electric field on the charge applying means 7 applying charge to the transfer belt 2 is impressed on the cleaning member 12. Namely, when transfer paper is fed and transfer bias having the reverse polarity to positively electrostatically charged toner is impressed by the means 7, residual reversely electrostatically charged toner adheres to the back side of the transfer paper and causes the back staining of the transfer paper. Then, the bias having the reverse polarity to transfer bias is impressed by the cleaning member 12 by the electric field, and the reversely electrostatically charged toner is recovered from the transfer belt 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer belt device in an image forming apparatus such as a copying machine, a printer and a facsimile, and more specifically, a transfer belt supported by a driving roller and a driven roller, and the transfer belt. And a charge removing unit for removing charge from the transfer belt, and a cleaning device for cleaning the surface of the transfer belt. The toner image on the image carrier is transferred onto the transfer material. And a transfer belt device that electrostatically attracts and conveys a transfer material.

Furthermore, the present invention relates to a method for cleaning a transfer belt by the transfer belt device.

[0003]

2. Description of the Related Art In a conventional transfer belt apparatus of the type described above, a transfer bias is applied to a transfer bias roller attached to the transfer belt during a copy mode. As a result, a charge having a polarity opposite to that of the toner on the photoconductor drum 1 is applied onto the transfer belt having a predetermined resistance, and the transfer is performed. The bias applied to the transfer belt for transferring the toner image on the image carrier onto the transfer material is usually the same polarity as the image carrier and the opposite polarity to the toner. Therefore, at the time of direct contact between the image carrier and the transfer belt before and after the transfer material, the application of the electric field is stopped as much as possible to prevent the toner from adhering to the transfer belt. However, in spite of that, there occurs a problem that an abnormal image called back stain occurs on the transfer material which is the first copy.

[0004]

When the cause of the above-mentioned abnormal image is investigated, the reversely charged toner in the toner is present on the transfer belt, and this reversely charged toner is transferred by the applied bias when the transfer material is conveyed. It was found that the ink adhered to the back side of the material and was transferred to the transfer material, which is the first sheet of the copy, causing back dirt.

An object of the present invention is to eliminate the above-mentioned reversely charged toner and eliminate the occurrence of back stain on the transfer material.

[0006]

According to the present invention, in the transfer belt device of the type described in the field of industrial application, a cleaning blade is provided as a main cleaning mechanism of a cleaning device and an electric field is provided as a sub cleaning mechanism. It is possible to solve the problem by providing a cleaning member according to (4) and applying an electric field having a polarity opposite to that of the applied electric field of the charge applying unit to the cleaning member due to the electric field.

Further, according to the present invention, in the transfer belt device having the above-mentioned structure, an electric field having a polarity opposite to that of the electric field applied by the charge applying means is applied to the cleaning member by the electric field, and the peripheral length of the transfer belt is increased. After the application for the above time, the operation is stopped, and then the copy mode is entered to apply the electric field by the charge applying means. When the copy mode ends, the application of the electric field by the charge applying means is stopped and the electric field is applied to the cleaning member again. This is solved by a method of performing the circumferential length of the transfer belt or more.

In order to solve the above-mentioned problems, the present invention stops the application of the electric field to the cleaning member due to the electric field during the copy mode in the above-mentioned method. Simultaneously with the electric field application to the cleaning member, an electric field having the same polarity as and higher than the applied electric field of the charge applying means is applied to the cleaning member,
After the end of the copy mode, the application of the electric field to the charge applying means and the application of the electric field to the cleaning member are stopped, and then the electric field applied to the cleaning member by the electric field is of the opposite polarity to the applied electric field to the charge applying means. Suggest to do more than the perimeter.

Furthermore, the present invention proposes, in the last proposal, to neutralize the transfer belt by a neutralization member arranged at a position close to the front and rear of the cleaning member by the electric field.

[0010]

In the apparatus of the present invention, the cleaning device for cleaning the surface of the transfer belt is provided with a cleaning member for wiping the residual toner adhering to the transfer belt, and a cleaning member by an electric field. Further, an electric field having a polarity opposite to that of the electric field applied by the charge applying means for applying an electric charge to the transfer belt is applied. Thereby, the oppositely charged toner existing on the transfer belt is removed.

According to the method of the present invention, in the above-mentioned transfer belt device, an electric field having a polarity opposite to that of the electric field applied by the charge applying means is applied to the cleaning member by the electric field, and the application is stopped after the application over the circumference of the transfer belt. , Then the copy mode is applied and the electric field is applied by the charge applying means,
When the copy mode ends, the application of the electric field to the charge applying unit is stopped, and the application of the electric field to the cleaning member is performed again for the circumference of the transfer belt or more. This allows
The reversely charged toner existing on the transfer belt is removed, and the influence of the electric field cleaning method in the copy mode on the transfer belt is eliminated.

In the above-mentioned method, the application of the electric field to the cleaning member due to the electric field during the copy mode is stopped, but the electric field is applied to the charge applying means at the same time as the electric field is applied to the charge applying means at the start of the copy mode. An electric field having the same polarity and larger than that is applied to the cleaning member, and the application of the electric field to the charge applying unit and the application of the electric field to the cleaning member are stopped after the copy mode ends. In this way, by applying a strong electric field to the cleaning member during the copy mode, it is possible to increase the margin for cleaning the transfer belt.

Further, by disposing a charge eliminating member at a position close to the front and rear of the cleaning member to eliminate the charge on the transfer belt, the above-mentioned adverse effect due to the application of a strong electric field is prevented.

[0014]

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

In FIG. 1, a photosensitive drum 1 which is an image bearing member is rotatably provided, and an outer peripheral surface of the photosensitive drum 1, which is not shown in the figure, removes electricity from the surface of the photosensitive drum 1. Device for uniformly charging the surface of the photosensitive drum, an exposure device for scanning the charged portion of the photosensitive drum 1 with an optical signal to form an electrostatic latent image, a developing device for developing the electrostatic latent image, and a photosensitive member after transfer. A process unit such as a cleaning device that cleans the surface of the body drum 1 is arranged. Below the photoconductor drum 1, a transfer belt 2 having a predetermined resistance is wound around a driving roller 3 and a driven roller 4.

The transfer sheet that has been fed to the registration roller pair 5 and is on standby is delivered from the registration roller pair 5 in time with the front end of the toner image formed on the photosensitive drum 1 rotating in the direction of the arrow. When the leading edge of the transfer paper comes close to the nip portion between the photosensitive drum 1 and the transfer belt 2, the transfer belt 2 is pushed up by the push-up lever 6 and abuts on the photosensitive drum 1. Then, when the transfer sheet enters the nip portion, a transfer bias is applied to the transfer bias roller 7, and a charge having a polarity opposite to that of the toner on the photosensitive drum 1 is applied to the transfer belt 2 to transfer the transfer. Done. The charges applied to the transfer belt 2 and the transfer paper are removed by the contact plate 8 arranged on the downstream side in the traveling direction thereof.

The cleaning device 10 for cleaning the surface of the transfer belt is provided with a cleaning blade 11 made of polyurethane as a main cleaning mechanism to wipe off the residual toner adhering to the transfer belt 2 and
Further, a cleaning member 12 by an electric field is provided as a sub cleaning mechanism. This cleaning member 12
For this, a bias roller method, a fur brush method, or the like can be used. 13 is a toner recovery coil.

In FIG. 2, the photosensitive drum 1 is applied with a negative bias, and the toner on the surface thereof is positively charged, but the toner is charged with the opposite polarity. Things exist. The reversely charged toner is transferred to and held by the transfer belt 2 by pressure transfer. The transfer belt 2 has a substrate formed of rubber and the surface of which is coated with resin and has poor smoothness. Further, since the inversely charged toner has a small particle size, the inversely charged toner can be cleaned from the transfer belt. difficult. Therefore, the reversely charged toner may remain on the transfer belt 2. When the transfer paper 15 is conveyed and the transfer bias roller 7 applies a transfer bias (an electric field having the same polarity as the photoconductor drum 1) having a polarity opposite to that of the positively charged toner to the remaining reversely charged toner. Then, it is pressed against the back side of the transfer paper 15 and adheres to the back side of the transfer paper 15. Reference numeral 16 is a developing roller, and 17 is a peeling claw.

As shown in FIG. 3, in the present invention, a cleaning member 12 by an electric field is provided, and a bias having a polarity opposite to that of the transfer belt application bias is applied to collect the reversely charged toner from the transfer belt 2. The back stain of the transfer paper 15 is prevented.

The advantageous timing of applying the bias to the cleaning member 12 will be described with reference to the flow chart shown in FIG.

(A) At time t _{2 when the} copy mode is started, the transfer paper 15 is conveyed to the transfer belt 2 and comes into contact therewith,
This continues until time t ₃ when the copy mode ends.

(B) The transfer belt 2 is already driven and rotated at time t ₁ before the start of the copy mode.

(C) At time t ₂ , a negative electric field transfer bias is applied to the transfer bias roller 7 and ends at time t ₃ .

(D) A positive electric field bias is applied to the cleaning member 12 from time t ₁ before the start of the copy mode to time t ₂ . The bias application from the time t ₁ to the time t ₂ is applied over the entire circumference of the transfer belt 2, and the bias application is stopped during the copy mode. As a result, the influence of the electric current generated in the cleaning member 12 in the copy mode on the transfer belt 2 is eliminated, and the occurrence of abnormal images such as honeycombs and prints and the smearing of the transfer paper 15 are prevented.

The contact between the transfer belt 2 and the transfer paper 15 and the application of the transfer bias to the transfer bias roller 7 are finished at the end time t ₃ of the copy mode, and after this, the bias is applied to the cleaning member 12. Is performed over the entire circumference of the transfer belt 2 again.

In the embodiment shown in FIG. 5, the steps (a), (b) and (c) of FIG. 4 are the same, but the step (d) of applying a bias to the cleaning member 12 is as follows. Deformed and performed.

(D ') After the bias is applied to the cleaning member 12 from the time t ₁ to the time t ₂ , the cleaning member 12 is in the copy mode from the time t ₂ to the time t _3.
Then, an electric field having the same polarity as the transfer bias applied to the transfer bias roller 7 and larger than this transfer bias is applied.

As described above, this is because the transfer belt 2 has a substrate made of rubber and the surface of which is coated with a resin, and the smoothness is not good, and cracks may occur in the coating layer. Since the cleaning blade alone cannot perform sufficient cleaning, the cleaning performance margin is increased and the reversely charged toner is prevented from adhering to eliminate back stain.

In the embodiment shown in FIG. 6, the charge removing members 18 and 19 are arranged in front of and behind the cleaning member 12 by the electric field of the transfer belt cleaning device 10. This eliminates the influence on the transfer belt of the current generated in the cleaning member 12 during the copy mode in the embodiment of applying the electric field to the cleaning member 12 described in FIG.
Generation of abnormal images such as honeycombs and prints, and transfer paper 15
This is to prevent the backside from being soiled.

[0030]

EFFECTS OF THE INVENTION By removing the oppositely charged toner on the transfer belt, the backside of the first sheet of transfer paper is prevented (Claim 1).

By measuring the timing of applying the electric field to the cleaning member by the electric field, the influence on the transfer belt current in the copy mode is eliminated, and the occurrence of an abnormal image and the backside smearing of the transfer paper are prevented (claim 2).

In the copy mode, an electric field having the same polarity as and higher than the electric field applied by the charge applying means is applied to the cleaning member to clean the toner on the uneven portion of the transfer belt and improve the cleaning margin ( Claim 3).

In the above-mentioned case where a strong electric field is applied to the cleaning member during the copy mode, since the transfer belt charge eliminating member is arranged at a position close to the front and rear of the cleaning member, the transfer belt is generated by the current generated in the cleaning member during the copy mode. It is possible to prevent the occurrence of an abnormal image such as a honeycomb or a print and to prevent the transfer paper from being smeared on the back side (claim 4).

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part of a copying machine to which the present invention is applied.

FIG. 2 is an explanatory diagram of a state of charged electric charges in a transfer portion of the copying machine.

FIG. 3 is a functional explanatory diagram of a cleaning member using an electric field according to the present invention.

FIG. 4 is a flowchart of applying an electric field to a cleaning member in the copying machine.

FIG. 5 is a flowchart of another embodiment of applying an electric field to a cleaning member.

FIG. 6 is a diagram showing a modified example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum (image bearing member) 2 Transfer belt 3 Drive roller 4 Followed roller 7 Transfer bias roller 10 Cleaning device 11 Cleaning blade 12 Cleaning member by electric field 15 Transfer paper 18, 19 Static elimination member

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Satoshi Takano 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (4)

[Claims] 1. A transfer belt supported by a driving roller and a driven roller, a charge applying unit for applying an electric charge to the transfer belt, a charge removing member for removing charge from the transfer belt, and a surface of the transfer belt. And a cleaning device for transferring the toner image on the image carrier onto the transfer material and electrostatically adsorbing and transferring the transfer material, a cleaning blade as a main cleaning mechanism of the cleaning device. And a cleaning member by an electric field is provided as a sub-cleaning mechanism, and an electric field having a polarity opposite to that of the electric field applied by the charge applying unit is applied to the cleaning member by the electric field. 2. A transfer belt supported by a driving roller and a driven roller, a charge applying unit for applying an electric charge to the transfer belt, a charge removing member for removing charge from the transfer belt, and a surface of the transfer belt. And a cleaning device for cleaning the toner image on the image carrier onto the transfer material. The cleaning device includes a cleaning blade as a main cleaning mechanism and a cleaning member by an electric field as a sub cleaning mechanism. In a transfer belt device for electrostatically adsorbing and transporting the electric field, an electric field having a polarity opposite to that of the electric field applied to the charge applying means is applied to the cleaning member by the electric field, and the application is stopped after the application over the circumferential length of the transfer belt. In the copy mode, an electric field is applied to the charge applying means, and when the copy mode ends, the charge applying hand is applied. A method for cleaning a transfer belt, characterized in that the application of an electric field to the step is stopped and the application of an electric field to the cleaning member is performed again for the circumference of the transfer belt or more. 3. A transfer belt supported by a driving roller and a driven roller, a charge applying unit for applying an electric charge to the transfer belt, a charge removing member for removing the charge from the transfer belt, and a surface of the transfer belt. And a cleaning device for cleaning the toner image on the image carrier onto the transfer material. The cleaning device includes a cleaning blade as a main cleaning mechanism and a cleaning member by an electric field as a sub cleaning mechanism. In a transfer belt device that electrostatically attracts and conveys the electric field, an electric field having a polarity opposite to that of the electric field applied to the charge applying unit is applied to the cleaning member by the electric field over the circumference of the transfer belt, and then the copy mode is set. An electric field is applied to the charge applying means, and at the same time, it has the same polarity as the applied electric field of the charge applying means and is larger than this. A threshold electric field is applied to the cleaning member, the application of the electric field to the charge applying means and the application of the electric field to the cleaning member are stopped after the end of the copy mode, and then the electric field applied to the cleaning member is reversed from the electric field applied to the charge applying means. A method for cleaning a transfer belt, which comprises applying a polarity electrolysis to a circumference of the transfer belt or more. 4. The method of cleaning a transfer belt according to claim 3, wherein the transfer belt is destaticized by a destaticizing member arranged at a position close to the front and rear of the cleaning member by the electric field.