JPH08234545A - Electrifier - Google Patents

Abstract

PURPOSE: To prevent the generation of an afterimage caused by residual toner in a cleanerless process and the accumulation of depositions such as positively charged paper powder on an electrifying brush by alternately applying positive and negative potentials to a discharging brush. CONSTITUTION: The discharging brush 7 located between a brush electrifier 2 and a transfer roller 8 is provided and a means for applying a first voltage having the same polarity as that of the electrification of a photoreceptor 1 and a second voltage having a polarity opposite to that of the first voltage is provided on the discharging brush 7. The photoreceptor 1 is rotated counterclockwise and uniformly electrified to about -850V by the electrifying brush 2 and an electrostatic latent image corresponding to an output image is formed with laser light 3. Toner 5 negatively electrified after development by a developing unit 4 is transferred to a recording paper 6 carried in synchronization with the photoreceptor 1 by a positive electric field applied to the transfer roller 8. The toner remaining without being transferred by the transfer roller 8 is uniformly dispersed by the discharging brush 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a facsimile or a copying machine using an electrophotographic process, and more particularly to a cleanerless EP process.

[0002]

2. Description of the Related Art Conventionally, as a brush charging device of this type, as described in Japanese Patent Application No. 6-48204, which is the first prior art and is filed by the same applicant as the present application. ON / O voltage applied to brush charging device
A method of removing dirt adhering to the brush by performing FF has been proposed.

Japanese Patent Laid-Open No. 1-1 listed as the second prior art.
Japanese Patent No. 24877 proposes a charging device having two or more brush charging devices. That is, this second prior art is
The conductive brush is constructed by dividing it into two or more parts, and it is possible to replace only the frontmost split brush that is heavily contaminated during use and needs frequent replacement independently from the rear part. It was possible.

As a third prior art, Japanese Patent Laid-Open No. 60-151
The technique described in Japanese Patent No. 664 can be cited.

The third prior art disclosed in Japanese Patent Application Laid-Open No. 60-151664 makes contact with the surface of an object to be charged while rotating a charging roller provided with a large number of conductive contacts on the roller surface. In the brush charging device that applies a voltage to the charging roller to charge the body to be charged, two or more charging rollers having different rotation directions and peripheral speeds are arranged with their contact elements in contact with each other. This reduces the contact pressure between the member to be charged and the contact of each charging roller, and prevents the contact rollers from being sagging by interfering with each other the charging rollers having different rotation directions and peripheral speeds, thereby causing uneven charging. It was designed so that it would not exist.

As a fourth prior art, Japanese Patent Laid-Open No. 63-249
The technique described in Japanese Patent No. 867 can be mentioned.

The technique disclosed in Japanese Patent Laid-Open No. 63-249867 is an electrophotographic apparatus for transferring an image of an object to a transfer means by using a photosensitive body as a medium, and a main charging means for charging the photosensitive body. And an auxiliary charging unit composed of a conductive brush, and the surface portion of the photoconductor after the transfer of the toner becomes a high potential without being exposed and a portion having a low potential by the exposure by the auxiliary charging unit. It is characterized in that it is charged until the potential difference between it and the part where it is present is about 100 V, and charge is not removed.

Further, in Japanese Patent Laid-Open No. 64-50089, which is cited as a fifth prior art, a so-called memory for applying a polarity opposite to that of a toner in a so-called cleanerless process in which a cleaning device for collecting untransferred toner is omitted. Removal members have been proposed.

[0009]

However, in the brush charging device disclosed in the above-mentioned third and fourth prior arts, dirt such as shaving powder or paper powder of the photoconductor is accumulated on the fibers of the brush, There is a problem that the charging ability is lowered. As a result, when running, the charge potential of the image bearing member was lowered, and stains, fogging, etc. occurred, and the image quality deteriorated significantly.

In the structure disclosed in the second prior art, although the problems inherent in the third and fourth prior arts are slightly solved, the disassembled brush is frequently replaced. Was newly generated.

Further, although the stain can be removed by turning on / off the voltage applied to the brush charging device shown in the above-mentioned first prior art, the printing interval is lengthened and the brush is applied to the brush. It took time to remove the adhered dirt, resulting in a decrease in the processing speed of the printer.

Further, in the so-called cleanerless process disclosed in the fifth prior art, in which the cleaning device for recovering the untransferred toner is omitted, a so-called memory removing brush for applying a polarity opposite to that of the toner, and a photosensitive member. Although a charging brush that uniformly charges the battery is provided, when the continuous printing operation is performed, toner adheres to the memory removal brush and dirt such as paper dust that is charged opposite to the toner adheres to the charging brush. There was a problem that their abilities declined.

The present invention has been made in view of the above-mentioned conventional circumstances, and therefore, an object of the present invention is to provide a novel charging device capable of solving the above-mentioned drawbacks inherent in the prior art. Especially.

[0014]

In order to achieve the above object, a charging device according to the present invention is an image forming apparatus using an electrophotographic process for forming a toner image on an image carrier having photoconductivity. A first brush charging device in which conductive fibers are formed on a conductive member such as a metal plate, a transfer device for transferring a toner image on an image carrier to a recording medium, and the first brush charging device. And a second brush charger, which has a first voltage of the same polarity as the charge applied to the image carrier to the second brush charger, and a voltage opposite to the first voltage. It is characterized by having a means for applying a second voltage having a polarity.

As a brush charger, about 1 × 10 ³ -1
Approximately 1 × 10 ^{4 to} 5 × 10 ⁵ fibers / square inch of fibers such as acrylic and rayon having an electrical resistance value of × 10 ⁷ Ωcm
Using a charging brush formed in a brush shape with a density of about 30
It is characterized in that contact charging is performed by a constant voltage power source of 0 to 2 kV.

According to the present invention, the first brush charger has a first polarity which has the same polarity as the electric charge applied to the image carrier.
And the third voltage which is a lower absolute value than the first voltage.
It is characterized by having a means for applying the voltage and.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the accompanying drawings with reference to the accompanying drawings.

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

Referring to FIG. 1, the photosensitive member 1 rotates counterclockwise in the drawing, and the charging brush 2 uniformly rotates the photosensitive member 1 to about minus 85.
The electrostatic latent image corresponding to the output image is formed by the laser beam 3 by being charged to 0V. The negatively charged toner 5 developed by the developing unit 4 is transferred to the recording paper 6 conveyed in synchronization with the photoconductor 1 by the positive electric field applied to the transfer roller 8. The residual toner remaining without being transferred by the transfer roller 8 is uniformly dispersed by the charge eliminating brush 7.

FIG. 2 is a detailed view of the charging brush 2 of FIG. The charging brush 2 is made of conductive fibers such as acrylic, rayon, nylon, polyester, polypropylene, and polycarbonate, and has a length H of about 3.5 mm and a thickness of about 6 mm.
Denier, resistance about 1 × 10 ³ Ωcm to 1 × 10 ⁷ Ωc
It is composed of a fiber 11 having m and a metal plate 12 having conductivity such as SUS303, and the fiber 11 is about 1 × 10 ⁵ fibers /
It is held on the metal plate 12 with a density of inch ² , and the width W as a brush is about 5 mm. The base of the fiber 11 is a base cloth 1A.
The base cloth 1A is woven into a conductive double-sided tape 1B.
It is fixed to the metal plate 12. The structure of the static elimination brush 7 is also the same as that of the charging brush 2.

That is, in the present invention, as shown in FIG. 2, 1 × 10 ^{4 to} 5 × 1 fibers of acrylic, rayon or the like are used.
A fixed charging brush formed on the brush at a density of 0 ⁵ lines / square inch was used and charged by a constant voltage power source of 300 to 2 kV.

The fiber 11 is about 0.5 with respect to the photoreceptor 1.
Set the position of the charging brush 2 so that it sticks in ~ 1mm,
A voltage was applied to the photoconductor 1. A4 on the charging brush 2
Process speed of about 33m for 1 size of photoconductor
When a constant voltage of about -1200 V was applied at m / sec, a charging potential of about 700 V could be stably obtained.

FIG. 3 is a circuit diagram showing a driving circuit for driving the image forming apparatus of FIG. 1, FIG. 4 is a timing chart showing the operation thereof, and FIG. 5 is a definition and time of each symbol on the timing chart of FIG. It is a table.

In FIG. 3, the drive circuit is a power supply 2 which supplies a bias potential of about −150 V to the tube of the photoreceptor 1.
1, a power supply 23 that gives a negative potential to the charging brush 2, a switch 24 that connects a line 22 that supplies a common terminal to the charging brush 2, and a power supply 31 that gives a positive potential to the static elimination brush 7.
A switch 32 connected to the power supply 23 to give a negative potential, a power supply 25 giving a negative potential to the toner carrier 41 of the developing unit 4, a switch 27 connected to the toner carrier 41, and a current to the transfer roller 8.・ Current that supplies voltage ・
A voltage supply circuit 28, a paper edge sensor 18 for detecting the recording paper 6 as a recording medium, a main motor 30 for rotating the photoconductor 1, and a control circuit 40 for controlling the whole are included. By supplying a bias potential (minus) to the tube of the photoconductor 1, there is an advantage that the photoconductor 1 is not contaminated and the installation potential can be used as one power source.

At each time T0 to T13 in FIG.
It is defined by the output of 0.

In the charging brush 2, the switch 24 is "ON".
In the case of, it is connected to the power supply 23,
A DC voltage of 00V is applied as the charging voltage. When the switch 24 is "OFF", it is connected to the line 22,
It becomes the ground potential. The toner carrier 41 is connected to the power supply 25 when the switch 27 is "ON", and a DC voltage of about -430V is applied.

First, before driving the main motor 30,
The control circuit 40 turns ON the switch 24 for T0 time (1000 msec), and the charging brush 2 causes the brush contact portion of the photoconductor 1 to be negatively charged (about -800 V). T0 is the time when the bias voltage of the photosensitive film rises.

The control circuit 40 turns the main motor 30 to "O".
At the same time, the switch for controlling the removal of the photoconductor scraping powder from the fiber 11 of the brush charger 2 is controlled to N ″.
It is switched to "OFF" in (91 msec) time.
During the period of T10, the electric fields on the surface of the photosensitive member and the fibers of the charging brush 2 are opposite to each other, so that stains having a positive charge attached to the fibers 11 are removed.

The toner carrying member 41 is connected to the power source 25 by the switch 27 at the time T1 after the memory motor 30 is driven, and a phenomenon voltage of about -480 V is applied. When the recording paper 6 passes the paper edge sensor 18, the latent image formation by the laser starts.

The control circuit 40 conveys the recording paper 6 at the timing when the image developed by the toner reaches the transfer roller 8, and generates a voltage for transferring the image to the transfer roller 8 by using a current voltage. A signal is sent to the generation circuit 28.

The control circuit 40 turns on the switch 32 in accordance with the untransferred toner remaining on the photoconductor 1 reaching the static elimination brush 7, and connects the static elimination brush 7 to the power source 31. About + 500V is applied to the static elimination brush 7,
The residual toner is attracted to the static elimination brush 7 and made uniform. In order to prevent the residual toner on the photoconductor 1 from affecting the next image formation, the switch 32 is turned “ON”.
The time T11 to be performed may be a time corresponding to the difference between the length of the image of one page and the interval between pages.

In the present invention, the process speed is about 33.07 mm / sec in a printer having a printing speed of 6 sheets of A4 size paper per minute per minute. The image formation time for one page is about 8.83 seconds, and the page interval is about 1.
Since it is 17 seconds, the time T11 is about 7.66 seconds. At times other than the time T11, the switch 32 is turned off,
The voltage of the power supply 23 of about -1200V is applied to the charge removal brush 7. The untransferred toner adhered to the charge removal brush 7 during the “OFF” is attracted to the photoconductor 1. Since the static elimination brush 7 was cleaned page by page, the accumulation of untransferred toner was reduced, and even after the 6000 page life test, halftone dot ghost images did not occur.

[0033]

As described above, according to the present invention, by alternately applying a negative potential and a positive potential to the charge eliminating brush, in the cleanerless process, generation of memory (afterimage) due to residual toner is prevented, and The effect of preventing non-adherent substances such as positively charged paper powder from being deposited on the charging brush is obtained.

Therefore, according to the present invention, it is possible to realize a compact printing apparatus which does not require an untransferred toner collecting container.
It is possible to obtain a stable image without stains even during running printing.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing details of the charging brush shown in FIG.

3 is a detailed diagram of a drive circuit for explaining the operation of the charging brush shown in FIG. 2 and driving the image forming apparatus of FIG.

FIG. 4 is a timing chart showing the operation of FIG.

5 is a table showing the definition and time of each symbol on the timing chart of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photosensitive member 2 ... Charging brush 3 ... Laser light 4 ... Development unit 5 ... Toner 6 ... Recording paper 7 ... Eliminating brush 8 ... Transfer roller 9 ... Fixing device 21, 23, 25 ... Power supply 28 ... Current / voltage generation circuit 30 ... memory motor 40 ... control circuit 41 ... toner carrier 42 ... developing roller

Claims (7)

[Claims] 1. A first brush charger in which an electrically conductive fiber is formed on an electrically conductive member such as a metal plate in an image forming apparatus using an electrophotographic process for forming a toner image on an image carrier having photoconductivity. And a second brush charger located between the transfer device for transferring the toner image on the image carrier to the recording medium and the first brush charger, and the second brush charger. Charging, characterized in that it has means for applying to the container a first voltage having the same polarity as the charge applied to the image carrier and a second voltage having the opposite polarity to the first voltage. apparatus. 2. The brush charger according to claim 1,
About 1 × 10 ^{4 to} 5 × 10 ⁵ fibers of acrylic, rayon, etc. having an electric resistance value of about 1 × 10 ³ to 1 × 10 ⁷ Ωcm are used.
The charging device according to claim 1, further comprising contact charging with a constant voltage power source of about 300 to 2 kV, using a charging brush formed in a brush shape with a density of books / square inch. 3. The first brush charger and / or the second brush charger.
The fibers of the brush charger for the image carrier are about 0.
The charging device according to claim 1, further comprising setting a mounting position of the first brush charging device and / or the second brush charging device so as to be bited in by 5 to 1.0 mm. 4. A first voltage having the same polarity as the electric charge applied to the image carrier with respect to the first brush charger, and a third voltage having a lower absolute value than the first voltage. The charging device according to claim 1, further comprising means for applying a voltage. 5. The charging device according to claim 1, further comprising means for applying a fourth voltage to the tube of the image carrier. 6. The charging device according to claim 1, further comprising means for switching and applying a fifth voltage and a third voltage to the toner carrier which is in contact with the image carrier. 7. The first applied to the first brush charger
5. The charging device according to claim 1, further comprising a common power source for generating the first voltage to be applied to the second brush charger and the power source for switching the same to be used.