JP2001005357A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device capable of removing only paper powder well without the occurrence of electrification irregularity, even when difference between the surface potential of a photoreceptor and the applied voltage of a brush becomes large. SOLUTION: A brush-like member 86 is formed of the brush made of acrylic resin on which conductive processing is not performed, and a prescribed high voltage is applied to a conductive plate 84, to which the member 86 is attached by a constant voltage source 92 provided serially with a resistor 90. That is, a paper powder removing means is formed of the brush constituted of a fiber member, which is brought into contact with an image carrier and on which the conductive processing is not performed, and a bias voltage is applied to the paper powder removing means by a bias voltage applying means, so that a potential difference is generated between the paper powder removal means and the image carrier, and the paper powder electrified to a polarity which is opposite to the electrified polarity of developer can be captured well by the paper powder removing means.

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 provided with paper dust removing means for contacting a photosensitive member which carries and transports a toner image to a transfer material transfer position and removing paper dust on the photosensitive member. It belongs to the technical field.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus that forms an image by transferring a toner image on a photoconductor to paper, the transfer residual toner on the photoconductor is not scraped off by a blade or the like, but is developed by a developing device. A so-called cleaner-less development system in which the toner is collected and reused is employed. In such a scheme,
Since there is no need to provide a cleaner device, it has the advantage of being able to reduce the size and cost of the device, but on the other hand, the paper dust coming out of the paper is also collected by the developing device, and the paper dust is developed on the base or the like This has the disadvantage that printing defects occur.

[0003] In particular, when acidic paper is used as printing paper,
Talc, a filler contained in the acid paper, is mixed into the developing unit,
There is a problem that remarkable printing defects occur.

In view of the above, there has been proposed an image forming apparatus in which a paper dust removing means comprising a brush formed of fibers is provided between a transfer means and a developing device. According to this image forming apparatus, the fibers contained in the paper dust can be satisfactorily removed by the brush, and printing defects can be reduced.

However, when such a configuration is adopted, not only the paper dust but also the toner is captured by the brush, so that the brush is contaminated with the toner, and a problem that the paper dust removing capability is reduced.

In order to solve such a problem, a method has been proposed in which a brush is subjected to a conductive treatment, a voltage is applied, and only paper dust is captured by the force of an electric field. Paper powder generally exhibits negative chargeability, and is charged to a polarity opposite to that of the toner by a transfer bias between the transfer step and the charging step. Therefore, when a positively charged toner is used, the paper dust is strongly negatively charged, and by applying a voltage of the same polarity as the toner to the conductive-treated brush,
It is possible to satisfactorily capture only paper dust without capturing the toner with a brush as compared with a case where no voltage is applied.

[0007]

However, the surface potential of the photoreceptor after the transfer step is not constant, and fluctuates depending on environmental conditions or the type of paper as a transfer medium. It is very difficult to adjust the voltage applied to the brush, causing the following problems.

For example, if for some reason the surface potential of the photoreceptor falls below a normal value and the difference between the surface potential of the photoreceptor and the voltage applied to the brush becomes too large, the brush is transferred from the photoreceptor to the photoreceptor. A discharge phenomenon occurs to charge the photoreceptor non-uniformly, and if the non-uniformity is too large, there is a problem that uneven charging is difficult to correct even in the charging step. This problem is particularly noticeable when a static elimination lamp such as an EL is omitted in order to reduce the number of components.

The present invention has been made in view of the above problems, and even when the difference between the surface potential of the photoreceptor and the voltage applied to the brush is large, it is possible to satisfactorily remove only paper dust without causing charging unevenness. It is an object of the present invention to provide an image forming apparatus capable of performing such operations.

[0010]

According to a first aspect of the present invention, there is provided an image forming apparatus, wherein a visible image carried on an image carrier and visualized by a developer is transferred by a transfer unit. An image forming apparatus for forming an image by transferring to a medium, wherein the paper dust removing means is formed by a brush made of a fiber member that has not been subjected to a conductive treatment and is in contact with the image carrier. And a bias voltage applying means for applying a bias voltage to the means.

According to the image forming apparatus of the first aspect,
The image carrier, for example, the photoconductor is charged to a predetermined high voltage, and the developer charged by frictional charge is transferred to the image carrier due to a potential difference between the image carrier and the developer carrier. Thus, the electrostatic latent image is visualized. Further, the paper as the transfer medium is charged by the transfer means to have a polarity opposite to that of the developer. Here, since a bias voltage is applied to the paper dust removing unit formed by the brush made of the fiber member by the bias voltage applying unit, a potential difference occurs between the paper dust removing unit and the image carrier, and the Paper dust charged to the opposite polarity to the charge polarity of the agent is satisfactorily captured by the paper dust removing means. On the other hand, the brush made of the fiber member of the paper dust removing means,
Since the conductive treatment is not performed, even if a high bias voltage is applied from the bias voltage applying unit, the discharge from the paper dust removing unit to the image carrier hardly occurs, and uneven charging on the image carrier occurs. Nothing. Further, in the present invention, since a brush which has not been subjected to a conductive treatment is used, there is an advantage that the brush is less expensive than a brush which has been subjected to a conductive treatment.

According to a second aspect of the present invention, in order to solve the above-mentioned problem, in the image forming apparatus according to the first aspect, the bias voltage applying unit includes the paper dust removing unit of the image carrier. And a means for applying a voltage to the paper dust removing means such that a difference between a surface potential at a position facing the paper dust and a potential of the paper dust removing unit of the paper dust removing means is 1 kV or more. .

According to the image forming apparatus of the present invention,
The voltage applied to the paper dust removing means by the bias voltage applying means is such that the difference between the surface potential of the image carrier at the position facing the paper dust removing means and the potential of the paper dust removing part of the paper dust removing means is 1 kV or more. Therefore, an electric field sufficient to transfer the paper dust from the image carrier to the paper dust removing unit is generated between the paper dust removing unit and the image carrier. as a result,
The paper dust is reliably removed from the image carrier.

According to a third aspect of the present invention, there is provided an image forming apparatus according to any one of the first to third aspects, wherein the bias voltage applying unit includes the paper dust removing unit. A means for giving a predetermined upper limit to the value of the current flowing through the device.

According to the image forming apparatus of the third aspect,
Since the bias voltage applying means has a predetermined upper limit to the current value flowing through the paper dust removing means, it is possible to reduce discharge from the paper dust removing means to the image carrier, There is no charge unevenness.

According to a fourth aspect of the present invention, there is provided an image forming apparatus according to the first aspect, wherein the bias voltage applying unit is configured to:
A resistor is provided in series with the paper dust removing means.

According to the image forming apparatus of the fourth aspect,
Since the bias voltage applying means has a resistor in series with the paper dust removing means, the value of the current flowing through the paper dust removing means has a predetermined upper limit value. The discharge from the means to the image carrier can be reduced, and the charging unevenness on the image carrier does not occur.

According to a fifth aspect of the present invention, in order to solve the above-mentioned problem, a visible image carried on an image carrier and visualized by a developer is transferred to a transfer medium by a transfer unit. An image forming apparatus for forming an image, comprising: a paper dust removing unit formed of a brush made of a fiber member that has not been subjected to a conductive process and is in contact with the image carrier; and a paper dust removing unit of the image carrier. The difference between the surface potential at the position facing the paper dust and the potential of the paper dust removing unit of the paper dust removing means is 1
bias voltage applying means for applying a bias voltage of kV or more to the paper dust removing means.

According to the image forming apparatus of the fifth aspect,
The image carrier, for example, the photoconductor is charged to a predetermined high voltage, and the developer charged by frictional charge is transferred to the image carrier due to a potential difference between the image carrier and the developer carrier. Thus, the electrostatic latent image is visualized. Further, the paper as the transfer medium is charged by the transfer means to have a polarity opposite to that of the developer. Here, a bias voltage is applied to the paper dust removing means formed by the brush made of the fiber member by the bias voltage applying means so that the difference from the potential of the paper dust removing portion of the paper dust removing means becomes 1 kV or more. Therefore, a sufficient potential difference is generated between the paper dust removing means and the image carrier to transfer the paper dust from the image carrier to the paper dust removing means, and the potential difference is opposite to the charging polarity of the developer. Polarized paper dust is well captured by the paper dust removing means. On the other hand, since the brush made of the fiber member of the paper dust removing unit is not subjected to the conductive treatment, even when a high bias voltage is applied from the bias voltage applying unit, the discharge from the paper dust removing unit to the image carrier is almost completely prevented. It does not occur and does not cause uneven charging on the image carrier.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect of the present invention, the bias voltage applying unit is configured to control the current value flowing through the paper dust removing unit to a predetermined value. It is characterized in that the means has an upper limit value of

According to the image forming apparatus of the sixth aspect,
Since the bias voltage applying means has a predetermined upper limit to the current value flowing through the paper dust removing means, the discharge from the paper dust removing means to the image carrier can be reduced, and the charging on the image carrier can be reduced. There is no unevenness.

According to a seventh aspect of the present invention, there is provided the image forming apparatus according to the fifth aspect.
7. The image forming apparatus according to claim 6, wherein the bias voltage applying unit is provided with a resistor in series with the paper dust removing unit.

According to the image forming apparatus of the seventh aspect,
Since the bias voltage applying means has a resistor in series with the paper dust removing means, the value of the current flowing through the paper dust removing means has a predetermined upper limit value. The discharge from the means to the image carrier can be reduced, and the charging unevenness on the image carrier does not occur.

According to an eighth aspect of the present invention, in order to solve the above-mentioned problem, an image is formed by transferring a visible image carried on an image carrier and visualized by a developer to a transfer medium by a transfer unit. A paper dust removing means formed of a brush made of a fiber member having a resistance value of 10 ⁸ to 10 ¹⁰ Ω in contact with the image carrier; and a bias voltage applied to the paper dust removing means. And a bias voltage applying means for applying a bias voltage.

According to the image forming apparatus of the present invention,
The image carrier, for example, the photoconductor is charged to a predetermined high voltage, and the developer charged by frictional charge is transferred to the image carrier due to a potential difference between the image carrier and the developer carrier. Thus, the electrostatic latent image is visualized. Further, the paper as the transfer medium is charged by the transfer means to have a polarity opposite to that of the developer. Here, a bias voltage is applied to the paper dust removing means formed by the brush made of the fiber member so that the difference from the surface potential of the image carrier becomes 1 kV or more by the bias voltage applying means. A sufficient potential difference is generated between the removing means and the image carrier to transfer the paper dust from the image carrier to the paper dust removing means, and the paper dust charged to a polarity opposite to the polarity of the developer is charged. Is well captured by the paper dust removing means. On the other hand, since the brush made of the fiber member of the paper dust removing means has a resistance value set to 10 ⁸ to 10 ¹⁰ Ω, even if a high bias voltage is applied from the bias voltage applying means, the image is not transferred from the paper dust removing means. Discharge to the carrier can be reduced, and charging unevenness on the image carrier does not occur.

According to a ninth aspect of the present invention, in order to solve the above problem, in the image forming apparatus according to the first or fifth or eighth aspect, the bias voltage applying means is a paper voltage removing means using a constant voltage power supply. A means for applying a voltage to the

According to the image forming apparatus of the ninth aspect,
Since the bias voltage applying means applies a voltage to the paper dust removing means by a constant voltage power supply, the current value flowing through the paper dust removing means has a predetermined upper limit value, and the image is transferred from the paper dust removing means to the paper dust removing means. Discharge to the carrier can be reduced, and charging unevenness on the image carrier does not occur.

According to a tenth aspect of the present invention, in order to solve the above-mentioned problem, in the image forming apparatus according to the eighth aspect, the bias voltage applying unit is configured to determine a current value flowing through the paper dust removing unit to a predetermined value. It is characterized in that the means has an upper limit value of

According to the image forming apparatus of the present invention, since the bias voltage applying means has a predetermined upper limit to the value of the current flowing through the paper dust removing means, the bias voltage applying means can change the current from the paper dust removing means to the image carrier. Discharge to the image carrier can be reduced, and uneven charging on the image bearing member does not occur.

According to an eleventh aspect of the present invention, there is provided an image forming apparatus according to any one of the eighth to eleventh aspects, in order to solve the above problem.
In the above image forming apparatus, the bias voltage applying unit is provided with a resistor in series with the paper dust removing unit.

According to the image forming apparatus of the present invention, since the bias voltage applying means has a resistor in series with the paper dust removing means, a current flowing through the paper dust removing means is provided. Since the value has a predetermined upper limit, the discharge from the paper dust removing unit to the image carrier can be reduced, and the charging unevenness on the image carrier does not occur.

[0032]

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

(First Embodiment) FIG. 1 is a sectional view showing a schematic configuration of a laser beam printer 1 as an embodiment of the image forming apparatus of the present invention. In FIG. 1, the laser beam printer 1 includes a feeder unit for feeding paper (not shown) at the bottom of a main body case 2. The feeder unit includes a sheet pressing plate 10 urged upward by a spring (not shown), a sheet feeding roller 11, and a sheet feeding roller 11.
And a friction separating member 14 pressed against The paper stacked on the paper pressing plate 10 is pushed up so as to come into contact with the paper feed roller 11, and is fed at a predetermined timing.
Is rotated in the direction of the arrow in FIG. 1 so that only the uppermost sheet is separated and supplied between the sheet feeding roller 11 and the friction separating member 14.

A pair of registration rollers 12 and 1 are located on the downstream side in the sheet transport direction due to the rotation of the paper feed roller 11.
3 is rotatably supported, and conveys a sheet at a predetermined timing to a transfer position formed by a photosensitive drum 20 and a transfer roller 21, which will be described later.

The photosensitive drum 20 as a visible image carrier is
It is made of a positively chargeable material, for example, an organic photoreceptor mainly containing positively chargeable polycarbonate. More specifically, the photosensitive drum 20 has, for example, a cylindrical aluminum sleeve as a main body, and has a predetermined thickness (for example, about 20 μm) in which a photoconductive resin is dispersed in polycarbonate on an outer peripheral portion thereof.
m) is constituted by a hollow drum formed with a photoconductive layer, and is rotatably supported by the main body case 2 with the cylindrical sleeve grounded. Further, the photosensitive drum 20 is driven to rotate in a direction indicated by an arrow by driving means (not shown).

The charger 30 is, for example, a scorotron type charger for positive charging for generating corona discharge from a charging wire made of tungsten or the like.

The laser scanner unit 40 includes a laser generator (not shown) that generates a laser beam L for forming an electrostatic latent image on the photosensitive drum 20, and a polygon mirror (pentahedral mirror) 41 that is driven to rotate. , A pair of lenses 42 and 4
5 and reflection mirrors 43, 44 and 46.

The developing device 50 has a case 51 in which a toner storage chamber 52 as a developer chamber is formed.
An agitator 53 is provided inside 2 so as to be rotatable around a rotation shaft 54. The toner stored in the toner storage chamber 52 is a positively chargeable non-magnetic one-component developer,
A particle size of 6 μm obtained by adding a well-known coloring agent such as carbon black and a charge controlling agent such as nigrosine, triphenylmethane and quaternary ammonium salt to a styrene-acrylic resin formed into a spherical shape by suspension polymerization. It has toner base particles having a particle size of 10 to 10 μm and an average particle size of 8 μm. The toner 55 is configured by adding silica as an external additive to the surface of the toner base particles.

The photosensitive drum 20 in the toner storage chamber 52
On the side, a developing chamber 55 for performing development by communicating with the toner storage chamber 52 through an opening A is formed, and a supply roller 56 and a developing roller 57 are rotatably pivotally supported. The toner on the developing roller 57 is regulated to a predetermined layer thickness by a layer-thickness regulating blade 58 provided with a contact portion made of silicone rubber at the tip of a thin plate-like elastic metal plate, and is used for development.

The transfer roller 21 is pivotally supported rotatably.
It is made of a conductive foamed elastic body made of silicone rubber or urethane rubber. The transfer roller 21 is configured to reliably transfer the toner image on the photosensitive drum 20 to the paper by the applied voltage.

The fixing unit 70 includes the registration roller 12
The heating roller 71 and the pressing roller 72 are provided on the further downstream side in the sheet conveyance direction from the sheet feeding roller 13 to the pressure contact portion between the photosensitive drum 20 and the transfer roller 21. The toner image transferred to the sheet is pressed while being heated and is fixed on the sheet.

A pair of transport rollers 73 for transporting the paper are provided downstream of the fixing unit 70 in the transport direction, and a pair of discharge rollers 7 are located downstream of the transport roller 73.
4 and a paper discharge tray 75 are provided in this order.

Further, as shown in FIG. 2, a paper dust removing device 80 provided as a paper dust removing means provided adjacent to the photosensitive drum 20 has a holder 83 and a base end supported on an upper portion of the holder 83. Urethane sheet 8 covered with non-woven fabric 81 at the tip
2, a brush-like member 86 for scraping paper dust, and a conductive plate 84 that supports the brush-like member 86 and is mounted on a holder 83. Further, a constant voltage source 92 is connected to the plate 84 via a resistor 90, and a voltage is applied to the plate 84 and the brush-like member 86.

As the non-woven fabric 81, a non-woven fabric integrated by confounding constituent fibers was used. This is because it is preferable to use a constituent fiber having a high degree of freedom in capturing fine paper powder between the fibers. As a constituent material, for example, acrylic fiber or the like is used. The nonwoven fabric 81 was formed so as to have a length in the longitudinal direction substantially equal to the length in the longitudinal direction of the photosensitive drum 20, and was adhered to the front end portion of a urethane sheet 82 as a substrate made of a sheet-like member using a double-sided tape.

The urethane sheet 82 is a sheet-like member made of urethane rubber and has a hardness of 92 ° Hs (J
IS K-6301). Urethane sheet 8
2 is mounted at a position where the end of the urethane sheet 82 and the nonwoven fabric 81 reach a position where the photosensitive drum 20 is provided as shown by a dotted line in FIG.

The holder 83 has substantially the same length as the photosensitive drum 20 in the longitudinal direction of the photosensitive drum 20, and supports the photosensitive drum 20 at both ends in the longitudinal direction with screws 91. Screwed to the frame.
Further, a paper powder storage chamber is formed inside the photosensitive drum 2.
An opening is formed on the side opposite to 0. Further, a urethane film 87 is attached to a lower portion of the holder 83. The base end of the urethane film 87 is attached to the holder 83 using a double-sided tape, and the free end side is in contact with the photosensitive drum 20. By providing such a urethane film 87, it is possible to prevent paper powder from falling from the storage chamber of the holder 83.

As the brush member 86, a fiber member was used. In this embodiment, acrylic fiber (trade name Kanecaron) is used. This is because, as a result of the experiment, it was confirmed that paper powder could be captured extremely well when acrylic fiber was used. Further, in the present embodiment, the acrylic fiber is subjected to a degreasing treatment. This is because, as a result of the experiment, it was confirmed that the resistance value of the acrylic fiber was increased and the value was stabilized by performing the degreasing treatment. FIG. 3 shows the difference in the resistance value of the acrylic fiber depending on the presence or absence of the degreasing treatment. As shown in FIG. 3, when the degreasing treatment is not performed, a current of 1.4 μA is applied when the applied voltage is 0.5 kV, and a current is set when the applied voltage is 1.0 kV.
7.8 μA when the current is 9 μA and the applied voltage is 1.5 kV
Current flows through the acrylic fiber. On the other hand, when the degreasing treatment is performed, when the applied voltage is 1.0 kV, the current is 0.7 μA, which is a half of the above, when the applied voltage is 2.0 kV, the current is 2.2 μA, and the applied voltage is 3. At 0 kV, a current of 7.1 μA flows. As described above, it is found that by performing the degreasing treatment, the resistance of the acrylic fiber can be increased. In this embodiment, the resistance value of the brush-like member 86 is set to 10 ⁸ to ¹⁰ 10 by performing a degreasing treatment on the acrylic fiber.
Set to Ω.

The voltage value of the constant voltage power supply 92 is
Even when the surface potential of 0 fluctuates, a voltage value higher than the potential of the unexposed portion of the photosensitive drum 20 is set in order to minimize the discharge from the brush-like member 86 to the photosensitive drum 20. The voltage is applied by constant voltage control. In the present embodiment, the applied voltage is set to 2 kV.

(Example of Operation) In the laser beam printer 1 of the present embodiment as described above, the surface of the photosensitive drum 20 is uniformly charged by the charger 30 and the laser beam modulated by the laser scanner unit 40 in accordance with image information. When L is irradiated, an electrostatic latent image is formed on the surface of the photosensitive drum 20. This electrostatic latent image is visualized with toner by the developing device 50, and the visible image formed on the photosensitive drum 20 is transported by the photosensitive drum 20 to a transfer position.
At the transfer position, the paper is supplied via the paper feed roller 11 and the registration rollers 12 and 13, and the visible image is transferred to the paper by a transfer bias applied by the transfer roller 21.

Next, the sheet is conveyed to the fixing unit 70, and is nipped and conveyed by the heating roller 71 and the pressing roller 72 of the fixing unit 70, and the visible image on the sheet is pressed and heated to be fixed on the sheet. You. Then, the sheet is discharged to the discharge tray 75 above the laser beam printer 1 by the pair of transport rollers 73 and the discharge rollers 74, and the image forming operation is completed.

On the other hand, the toner remaining on the photosensitive drum 20 after the transfer is collected by the developing device 50 and is again used for development. As described above, the laser beam printer 1 of the present embodiment
Employs a so-called cleaner-less development method.
Therefore, since a waste toner storage container for scraping and storing the toner remaining on the photosensitive drum 20 is not required, the size of the apparatus can be reduced, and the toner can be effectively used.

Paper dust adheres to the photosensitive drum 20 after the transfer. Of the paper dust, large fibrous paper dust is caught by the brush-like member 86 and applied to the brush-like member 86. The electric field generated by the applied high voltage causes the brush-like member 86 to capture the electric field. Then, other fine paper powder is captured by the nonwoven fabric 81.

In this embodiment, the pressing force of the nonwoven fabric 81 against the photosensitive drum 20 is set to an extremely low value of 2.5 gf / cm. However, since the nonwoven fabric 81 is removed by entanglement of paper powder, Paper powder can be reliably removed even with such a low pressing force. Although the paper powder contains the fiber component and the filler, the nonwoven fabric 81 can reliably remove both the fiber component and the filler. Also,
Since the pressing force of the non-woven fabric 81 against the photosensitive drum 20 is kept low, the damage of the surface of the photosensitive drum 20 due to the fiber component of the paper powder and the filming due to the filler do not occur.

Here, the relationship between paper dust, damage to the surface of the photosensitive drum 20 and filming will be described in detail.
In addition to pulp fiber (cellulose extracted from hardwood and softwood), which is the main raw material for paper, fillers that make paper opaque and white, internal sizing agents to prevent ink bleeding, and sizing agents And an internal-size fixing agent that causes pulp fibers to be adsorbed. The above-mentioned acidic paper mainly uses talc or clay as a filler, a rosin sizing agent as an internal sizing agent, and a sulfate band (aluminum sulfate) as an internal sizing agent.

Among them, substances which particularly adversely affect the electrophotographic process are pulp fibers and filler talc. When pulp fibers are mixed in a developing device using a non-magnetic one-component developer, the pulp fibers may be caught between the layer thickness regulating blade and the developing roller, and may damage the layer thickness regulating blade and the developing roller. Further, when the pulp fiber passes through the layer thickness regulating blade together with the toner stuck to the pulp fiber and adheres to the paper, and is discharged as it is through the fixing process, it is conspicuous particularly when it adheres to a white background portion. It will be recognized by the naked eye as garbage. On the other hand, talc is a very strongly negatively charged substance, and in a process using a positively charged toner, if it is mixed in a developing device, the amount of charge of the toner is reduced to cause printing fog. Further, in a process using a negatively charged toner, similarly, it may cause print fogging, or even if not fog, the charge amount of the toner becomes excessively high, causing a decrease in image density. is there.

However, in the present embodiment, as described above, since a voltage having the same polarity as that of the toner is applied to the brush-like member 86, the pulp fibers of the paper powder can be surely removed from the brush-like member. 86 can be reliably captured and prevented from entering the developing device. Originally, paper powder has the property of being easily charged to negative polarity, but in addition to this, the paper is charged to the opposite polarity to the toner in the transfer process, so the paper powder after the transfer process is strongly charged to negative polarity. are doing. Therefore, the brush-like member 86 to which the voltage having the same polarity as the toner is applied is reliably captured by the action of the electric field.

The talc is captured by the non-woven fabric 81, but the non-woven fabric 81 is coated with the urethane sheet 8 having a low hardness.
2, the pressing force of the nonwoven fabric 81 against the photosensitive drum 20 is 2.5 gf / c.
m and an extremely low value. Therefore, the hard pulp fibers captured by the nonwoven fabric 81 do not damage the surface of the photosensitive drum 20, and filming due to the filler does not occur.

Accordingly, the incorporation of paper dust into the developing device 50 is reliably prevented, and no image defects occur.

Further, in this embodiment, since the voltage applied to the brush-like member 86 is a voltage having the same polarity as the charging polarity of the toner, the brush-like member 86 captures only paper dust and captures toner. Nothing. In addition, since the polymerized toner produced by the polymerization method is used as the toner, the toner base particles have a substantially spherical and gentle surface shape, and due to its high fluidity, the transfer efficiency is high and the residual toner itself is very small. Therefore, even if a small amount of toner remains on the photosensitive drum 20, the toner hardly adheres to the nonwoven fabric 81 and is reliably collected by the developing device 50.

As described above, according to the present embodiment, the paper dust consisting of the fiber component and the filler can be reliably removed by the paper dust removing device 80 without causing damage to the surface of the photosensitive drum 20 or filming. Since pulp fibers and talc are not mixed into the developing device 50 and transfer of the pulp fibers to the paper does not occur, image defects such as fog or paper stains can be reliably prevented. As an example, when an experiment was performed to form a continuous image of up to 15,000 sheets using acidic paper, no damage or filming of the photosensitive drum 20 occurred, and the image was good.

In particular, it was confirmed that a good image was formed without causing uneven charging of the photosensitive drum 20 even though a voltage as high as 2 kV was applied to the brush member 86. This is because the acrylic fiber constituting the brush-like member 86 has been increased in resistance without being subjected to a conductive treatment. Since the brush-like member 86 has high resistance,
Even if the above high voltage is applied to the brush-like member 86,
Electric discharge from the brush-like member 86 to the photosensitive drum 20 is minimized, and uneven charging of the photosensitive drum 20 can be suppressed.

Further, in this embodiment, a voltage higher than the surface potential of the unexposed portion of the photosensitive drum 20 is applied to the brush-like member 86 having a high resistance as described above by constant voltage control. Therefore, even if the transfer condition changes due to environmental conditions or paper type, and the surface potential of the photosensitive drum 20 changes, the potential of the brush-like member 86 always becomes higher than the surface potential of the photosensitive drum 20, and the polarity opposite to that of the toner. Paper powder that has been charged can always be satisfactorily captured.

(Experimental Example) Here, an experimental result of examining differences in paper dust removal performance and surface potential unevenness of the photosensitive drum with respect to the resistance value of the brush-like member 86, and the voltage value applied to the brush-like member 86 An experimental result of examining differences in paper dust removal performance and surface potential unevenness of the photosensitive drum will be described.

FIG. 4 is a graph showing the results of an experiment for examining differences in paper dust removal performance and unevenness in the surface potential of the photosensitive drum with respect to the resistance value of the brush-like member 86. In the experiment, a constant voltage of 2 kV was applied to the brush-like member. Also,
The paper dust removal performance was determined by visually checking the amount of paper dust on the photosensitive drum. The charging unevenness was evaluated based on the unevenness of the print image density.

As shown in FIG. 4, when the resistance value of the brush-like member 86 is 10 ⁷ Ω, some paper dust is confirmed on the photosensitive drum 20 after passing through the contact portion with the brush-like member 86.
After the charging step, it was confirmed that the charging unevenness of the photosensitive drum 20 was large. This is because the resistance of the brush-shaped member 86 is not sufficiently high, so that the application of a high voltage causes the discharge from the brush-shaped member 86 to the photosensitive drum 20, and the discharge between the brush-shaped member 86 and the photosensitive drum 20. This is considered to be due to the fact that a sufficient electric potential difference disappears, and uneven charging occurs due to non-uniform discharge on the photosensitive drum 20.

Next, the resistance value of the brush-like member 86 is 10 ⁸
In the case of Ω, almost no paper dust was found on the photosensitive drum 20 after passing through the contact portion with the brush-like member 86, and after the charging step, charging unevenness of the photosensitive drum 20 was slightly confirmed. This is because, since the resistance value of the brush-like member 86 is a high value, the discharge from the brush-like member 86 to the photosensitive drum 20 is reduced even by the application of a high voltage, so that the brush-like member 86 This is probably because a sufficient potential difference was maintained.

Next, the resistance value of the brush-like member 86 is 10 ⁹
In the case of Ω and 10 ¹⁰ Ω, no paper dust is found on the photosensitive drum 20 after passing through the contact portion with the brush-like member 86,
When the resistance value was 10 ¹⁰ Ω, paper powder was slightly recognized. After the charging step, the photosensitive drum 20
No uneven charging occurred. This is because the brush-like member 86 has a sufficiently high resistance value, so that even when a high voltage is applied, the brush-like member 86 hardly discharges to the photosensitive drum 20, and the brush-like member 86 and the photosensitive drum 20 are hardly discharged.
It is considered that a sufficient potential difference was maintained between the above.

Next, the resistance value of the brush-like member 86 is 10 ¹¹
In the case of Ω, a considerable amount of paper dust was found on the photosensitive drum 20 after passing through the contact portion with the brush-like member 86. However, no uneven charging of the photosensitive drum 20 occurred after the charging step. This is because the brush-shaped member 86 has a very high resistance value, so that even when a high voltage is applied, the brush-shaped member 86 does not discharge to the photosensitive drum 20. However, the brush-shaped member 86 has a too high resistance value. Is not raised to a sufficient value, and a sufficient potential difference between the brush-like member 86 and the photosensitive drum 20 could not be secured.

On the other hand, FIG. 5 is a diagram showing the results of an experiment for examining differences in paper dust removal performance and surface potential unevenness of the photosensitive drum with respect to a voltage value applied to the brush-like member 86. In the experiment, the resistance value of the brush-like member 86 was set to 10 ⁹ Ω.

As shown in FIG. 5, when the voltage applied to the brush member 86 was 1 kV, a considerable amount of paper dust was confirmed on the photosensitive drum 20. However, the photosensitive drum 2
No charging unevenness of 0 was observed. This is because the surface potential of the photosensitive drum 20 after the transfer process is usually about 400 to 600 V, and the voltage applied to the brush-like member 86 is 1 kV.
In this case, it is considered that the potential difference between the brush-like member 86 and the surface potential of the photosensitive drum 20 was about 400 to 600 V, and a sufficient potential difference for removing paper dust could not be secured. In addition, since the potential difference is small, discharge from the brush-like member 86 to the photosensitive drum 20 was not performed, and it is considered that uneven charging did not occur on the surface of the photosensitive drum 20 after the charging process.

Next, when the voltage applied to the brush-like member 86 is 1.5 kV, paper dust may not be found on the photosensitive drum 20, but paper dust may be less often seen. There was no. However, uneven charging of the photosensitive drum 20 was not confirmed. When the voltage applied to the brush member 86 is 1.5 kV, the potential difference between the brush member 86 and the surface potential of the photosensitive drum 20 is 0.9 kV to 1.1 k.
V or so. Considering in light of the results of the above experiments, within the range of this potential difference, there is a boundary value of the potential difference sufficient to perform paper dust removal, and when a potential difference exceeding this boundary value is secured, If no paper dust is found and this boundary value is not reached, it is likely that paper dust has been found. Also, with the potential difference in this range, the brush-like member 86
It is supposed that no discharge was caused to the photosensitive drum 20 from, and no charging unevenness occurred on the surface of the photosensitive drum 20 after the charging step.

Although not shown in FIG.
An experiment was performed by changing the applied voltage to 4 kV and 1.3 kV. In the case of 1.4 kV, there were cases where paper dust was found and cases where paper dust was not found, but always at 1.3 kV. Paper dust was found. In the case of 1.4 kV,
The potential difference between the brush-like member 86 and the surface potential of the photosensitive drum 20 is about 0.8 kV to 1.0 kV. Also, 1.3
In the case of kV, the potential difference between the brush-like member 86 and the surface potential of the photosensitive drum 20 is about 0.7 kV to 0.9 kV. From this experimental result, it is considered that the boundary value of the potential difference sufficient to remove paper dust is 1.0 kV.

Next, when the voltage applied to the brush-like member 86 was 2.0 kV or 3.0 kV, no paper dust was observed on the photosensitive drum 20. Further, charging unevenness of the photosensitive drum 20 was not confirmed. When the voltage applied to the brush-like member 86 is 2.0 kV and 3.0 kV, the potential difference between the brush-like member 86 and the surface potential of the photosensitive drum 20 is 1.4 kV to 1.6 kV, or 2.
It is about 4 kV to 2.6 kV, which exceeds the boundary value. Therefore, it is considered that a sufficient potential difference was secured between the brush-like member 86 and the photosensitive drum 20 for removing paper dust, and no paper dust was observed. Also, 2.0
With an applied voltage of up to 3.0 kV, discharge from the brush-like member 86 to the photosensitive drum 20 was not performed, and it is considered that uneven charging did not occur on the surface of the photosensitive drum 20 after the charging process.

Next, when the voltage applied to the brush-like member 86 was 4.0 kV, no paper dust was found on the photosensitive drum 20. However, charging unevenness of the photosensitive drum 20 was slightly confirmed. When the voltage applied to the brush member 86 is 4.0 kV, the potential difference between the brush member 86 and the surface potential of the photosensitive drum 20 is 3.4 kV or less.
It is about 3.6 kV, which exceeds the boundary value. Therefore, it is considered that a sufficient potential difference was secured between the brush-like member 86 and the photosensitive drum 20 for removing paper dust, and no paper dust was observed. Also, at a high applied voltage of 4.0 kV, the photosensitive drum 20
Is discharged, and it is considered that uneven charging occurs on the surface of the photosensitive drum 20 after the charging step.

From the results of the above experiments, the resistance value of the brush-like member 86 is preferably 10 ⁸ Ω to ^{10 10} Ω. In particular, if the resistance value of the brush-like member 86 is set to 10 ⁹ Ω, the cost can be reduced. It can be easily used because it can achieve high paper dust removal effect and high charge unevenness prevention effect.

The voltage applied to the brush member 86 should be such that the potential difference between the photosensitive drum 20 and the photosensitive drum 20 is 1 kV or more, so that a high paper dust removing effect and a high charge unevenness preventing effect can be obtained. It turned out to be preferable in that it can be obtained. That is, if the voltage applied to the brush-like member 86 is set to a voltage equal to or higher than the surface potential of the unexposed portion of the photosensitive drum 20, a potential difference necessary for removing paper dust is always obtained regardless of the surface potential of the photosensitive drum 20. I found that I could do it.

Even if such a high voltage is applied, since the resistance value is set to a high value as described above, the current supplied to the brush-like member 86 can be limited to an appropriate value. Discharge from the brush-like member 86 to the photosensitive drum 20 can be prevented, and occurrence of uneven charging can be prevented.

On the other hand, in a conventional apparatus in which the members constituting the paper dust removing means are subjected to a conductive treatment such as dispersing conductive particles, when the voltage applied to the paper dust removing means is increased, the paper dust is reduced. The resistance value of the member constituting the powder removing means decreases exponentially with respect to the voltage, and when an excessively high voltage is applied, a breakdown occurs and the resistance value suddenly decreases.

Therefore, the device of the present embodiment can exhibit extremely excellent effects as compared with the conventional device.
In addition, since there is no occurrence of charging unevenness, it is possible to omit a static elimination lamp such as an EL, and it is possible to reduce costs and simplify the configuration by reducing the number of components.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, as shown in FIG. 6, a brush roller 88 is provided as a paper dust removing device, and a predetermined high voltage is applied to the core of the brush roller 88 by a constant voltage source 92. Also in this embodiment, the brush uses a high-resistance acrylic fiber that has not been subjected to a conductive treatment.

With such a configuration, the brush roller 88
While preventing a discharge from the brush roller 88 to the photosensitive drum 20 while keeping a potential difference sufficient for removing paper dust between the photosensitive drum 20 and the photosensitive drum 20, uneven charging of the photosensitive drum 20 can be prevented. Therefore, the number of parts can be reduced by omitting a static elimination lamp such as an EL.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the present embodiment, as shown in FIG. 7, a corona discharge wire 31, a shield 32, a grid electrode 3
3, a scorotron charger 30 integrally provided with a shield 32 and a grid electrode 33, an opening B is formed in a holding portion 34 of the shield 32, and a charge trapping electrode is formed so as to cover the opening B. 90 are provided. Then, one end of the charge trapping electrode 90 is extended to the brush member 86 side, and one end of the charge trapping electrode 90 and the plate 84 of the brush member 86 are electrically connected by a screw 85.

With this configuration, a dedicated power supply for the brush-like member 86 can be omitted, and the number of parts can be further reduced.

In the above-described embodiment, the photosensitive member is used as an example of the image bearing member. However, the present invention is not limited to this. For example, an intermediate transfer member in a color image forming apparatus may be used as an image bearing member. The present invention can be applied to a body.

Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. Can easily be inferred.

[0088]

According to the image forming apparatus of the present invention, the paper dust removing means is formed by a brush made of a fiber member which has not been subjected to a conductive treatment and comes into contact with the image carrier, and a bias voltage applying means. As a result, since a bias voltage is applied to the paper dust removing means, a potential difference is generated between the paper dust removing means and the image carrier, and the paper dust charged to the opposite polarity to the charging polarity of the developer is removed by the paper dust removing means. Can be captured well.
In addition, even if a high bias voltage is applied to the brush made of the fiber member of the paper dust removing unit that is not conductive, the discharge from the paper dust removing unit to the image carrier can be reduced. The occurrence of the above charging unevenness can be reliably prevented. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the second aspect,
The difference between the surface potential of the image carrier and the surface potential at the position facing the paper dust removing unit is 1 due to the bias voltage applying unit.
Since a voltage of kV or more is applied, an electric field sufficient to transfer paper dust from the image carrier to the paper dust removing unit side can be generated between the paper dust removing unit and the image carrier. Thus, paper dust can be reliably removed from the image carrier.

According to the image forming apparatus of the third aspect,
Since the bias voltage applying means gives a predetermined upper limit to the current value flowing through the paper dust removing means, the occurrence of discharge from the paper dust removing means to the image carrier is reliably restricted, and The occurrence of uneven charging can be prevented. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the fourth aspect,
Since the bias voltage applying means has a resistor in series with the paper dust removing means, a current value flowing through the paper dust removing means can have a predetermined upper limit value. It is possible to reduce the discharge from the means to the electrostatic latent image carrier and reliably prevent the occurrence of charging unevenness on the image carrier.
Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the fifth aspect,
The paper dust removing means is formed by a brush made of a fiber member which has not been subjected to the conductive treatment and is brought into contact with the image carrier, and a bias voltage applying means is provided at a position of the image carrier facing the paper dust removing means. Since a bias voltage such that the difference from the surface potential is 1 kV or more is applied to the paper dust removing means, paper dust can be satisfactorily removed, and the discharge from the paper dust removing means to the image carrier is reduced. It is possible to reliably prevent the occurrence of uneven charging on the carrier. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the present invention, the bias voltage applying means gives a predetermined upper limit to the value of the current flowing through the paper dust removing means. And the occurrence of uneven charging on the image carrier can be reliably prevented. Therefore, EL
And so on, and the elimination of such lamps can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of parts.

According to the image forming apparatus of the seventh aspect,
Since the bias voltage applying means has a resistor in series with the paper dust removing means, a current value flowing through the paper dust removing means can have a predetermined upper limit value. It is possible to reduce the discharge from the means to the electrostatic latent image carrier and reliably prevent the occurrence of charging unevenness on the image carrier.
Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

The image forming apparatus according to claim 8, wherein the paper dust removing means is provided with a resistance value of 10 ⁸ to 10 for contacting the image carrier.
It is formed by a brush made of a ¹⁰ Ω fiber member, and a bias voltage is applied to the paper dust removing means by a bias voltage applying means. And the occurrence of uneven charging on the image carrier can be reliably prevented.
Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the ninth aspect,
Since a voltage is applied to the paper dust removing means by the constant voltage power supply by the bias voltage applying means, a current value flowing through the paper dust removing means can have a predetermined upper limit value. Limiting the discharge to the latent image carrier,
It is possible to reliably prevent the occurrence of charging unevenness on the image carrier. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the present invention, the bias voltage applying means gives a predetermined upper limit to the value of the current flowing through the paper dust removing means. The discharge to the image carrier can be reduced, and the occurrence of charging unevenness on the image carrier can be reliably prevented. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the eleventh aspect, since the bias voltage applying means includes a resistor in series with the paper dust removing means, a current flowing through the paper dust removing means is provided. The value can have a predetermined upper limit, the discharge from the paper dust removing means to the electrostatic latent image carrying is reduced,
It is possible to reliably prevent the occurrence of charging unevenness on the image carrier. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view around a paper dust removing device in the image forming apparatus of FIG. 1;

FIG. 3 is a diagram showing a relationship between an applied voltage and a current in a brush-like member of the paper dust removing device of FIG. 2;

4 is a diagram showing a relationship between a resistance value of a brush-like member, a paper dust removing performance, and charging unevenness in the paper dust removing device of FIG. 2;

FIG. 5 is a diagram showing a relationship between an applied voltage to a brush-like member, paper dust removing performance, and charging unevenness in the paper dust removing device of FIG. 2;

FIG. 6 is a diagram illustrating a process cartridge including a paper dust removing device according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a periphery of a paper dust removing device according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 laser beam printer 20 photosensitive drum 80 paper dust removing device 81 nonwoven fabric 82 urethane sheet 84 conductive plate 86 brush-like member 88 brush roller 90 resistor 92 constant voltage source

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 14, 1999 (1999.7.1)
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Image forming apparatus

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with paper dust removing means for contacting a photosensitive member which carries and transports a toner image to a transfer material transfer position and removing paper dust on the photosensitive member. It belongs to the technical field.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus that forms an image by transferring a toner image on a photoconductor to paper, the transfer residual toner on the photoconductor is not scraped off by a blade or the like, but is developed by a developing device. A so-called cleaner-less development system in which the toner is collected and reused is employed. In such a scheme,
Since there is no need to provide a cleaner device, it has the advantage of being able to reduce the size and cost of the device. This has the disadvantage that printing defects occur.

[0003] In particular, when acidic paper is used as printing paper,
Talc, a filler contained in the acid paper, is mixed into the developing unit,
There is a problem that remarkable printing defects occur.

In view of the above, there has been proposed an image forming apparatus in which a paper dust removing means comprising a brush formed of fibers is provided between a transfer means and a developing device. According to this image forming apparatus, the fibers contained in the paper dust can be satisfactorily removed by the brush, and printing defects can be reduced.

However, when such a configuration is adopted, not only the paper dust but also the toner is captured by the brush, so that the brush is contaminated with the toner, and a problem that the paper dust removing capability is reduced.

In order to solve such a problem, a method has been proposed in which a brush is subjected to a conductive treatment, a voltage is applied, and only paper dust is captured by the force of an electric field. Paper powder generally exhibits negative chargeability, and is charged to a polarity opposite to that of the toner by a transfer bias between the transfer step and the charging step. Therefore, when a positively charged toner is used, the paper dust is strongly negatively charged, and by applying a voltage of the same polarity as the toner to the conductive-treated brush,
It is possible to satisfactorily capture only paper dust without capturing the toner with a brush as compared with a case where no voltage is applied.

[0007]

However, the surface potential of the photoreceptor after the transfer step is not constant, and fluctuates depending on environmental conditions or the type of paper as a transfer medium. It is very difficult to adjust the voltage applied to the brush, causing the following problems.

For example, if for some reason the surface potential of the photoreceptor falls below a normal value and the difference between the surface potential of the photoreceptor and the voltage applied to the brush becomes too large, the brush is transferred from the photoreceptor to the photoreceptor. A discharge phenomenon occurs to charge the photoreceptor non-uniformly, and if the non-uniformity is too large, there is a problem that uneven charging is difficult to correct even in the charging step. This problem is particularly noticeable when a static elimination lamp such as an EL is omitted in order to reduce the number of components.

The present invention has been made in view of the above problems, and even when the difference between the surface potential of the photoreceptor and the voltage applied to the brush is large, it is possible to satisfactorily remove only paper dust without causing charging unevenness. It is an object of the present invention to provide an image forming apparatus capable of performing such operations.

[0010]

According to a first aspect of the present invention, there is provided an image forming apparatus, wherein a visible image carried on an image carrier and visualized by a developer is transferred by a transfer unit. An image forming apparatus for forming an image by transferring to a medium, wherein the paper dust removing means is formed by a brush made of a fiber member that has not been subjected to a conductive treatment and is in contact with the image carrier. And a bias voltage applying means for applying a bias voltage to the means.

According to the image forming apparatus of the first aspect,
The image carrier, for example, the photoconductor is charged to a predetermined high voltage, and the developer charged by frictional charge is transferred to the image carrier due to a potential difference between the image carrier and the developer carrier. Thus, the electrostatic latent image is visualized. Further, the paper as the transfer medium is charged by the transfer means to have a polarity opposite to that of the developer. Here, since a bias voltage is applied to the paper dust removing unit formed by the brush made of the fiber member by the bias voltage applying unit, a potential difference occurs between the paper dust removing unit and the image carrier, and the Paper dust charged to the opposite polarity to the charge polarity of the agent is satisfactorily captured by the paper dust removing means. On the other hand, the brush made of the fiber member of the paper dust removing means,
Since the conductive treatment is not performed, even when a high bias voltage is applied from the bias voltage applying unit, the discharge from the paper dust removing unit to the image carrier hardly occurs, and uneven charging on the image carrier occurs. There is no. Further, in the present invention, since a brush which has not been subjected to a conductive treatment is used, there is an advantage that the brush is less expensive than a brush which has been subjected to a conductive treatment.

According to a second aspect of the present invention, in order to solve the above-mentioned problem, in the image forming apparatus according to the first aspect, the bias voltage applying unit includes the paper dust removing unit of the image carrier. And a means for applying a voltage to the paper dust removing means such that a difference between a surface potential at a position facing the paper dust and a potential of the paper dust removing unit of the paper dust removing means is 1 kV or more. .

According to the image forming apparatus of the present invention,
The voltage applied to the paper dust removing means by the bias voltage applying means is such that the difference between the surface potential of the image carrier at the position facing the paper dust removing means and the potential of the paper dust removing part of the paper dust removing means is 1 kV or more. Therefore, an electric field sufficient to transfer the paper dust from the image carrier to the paper dust removing unit is generated between the paper dust removing unit and the image carrier. as a result,
The paper dust is reliably removed from the image carrier.

According to a third aspect of the present invention, there is provided an image forming apparatus according to any one of the first to third aspects, wherein the bias voltage applying unit includes the paper dust removing unit. A means for giving a predetermined upper limit to the value of the current flowing through the device.

According to the image forming apparatus of the third aspect,
Since the bias voltage applying means has a predetermined upper limit to the current value flowing through the paper dust removing means, it is possible to reduce discharge from the paper dust removing means to the image carrier, There is no charge unevenness.

According to a fourth aspect of the present invention, there is provided an image forming apparatus according to the first aspect, wherein the bias voltage applying unit is configured to:
A resistor is provided in series with the paper dust removing means.

According to the image forming apparatus of the fourth aspect,
Since the bias voltage applying means has a resistor in series with the paper dust removing means, the value of the current flowing through the paper dust removing means has a predetermined upper limit value. The discharge from the means to the image carrier can be reduced, and the charging unevenness on the image carrier does not occur.

According to a fifth aspect of the present invention, in order to solve the above-mentioned problem, a visible image carried on an image carrier and visualized by a developer is transferred to a transfer medium by a transfer unit. An image forming apparatus for forming an image, comprising: a paper dust removing unit formed of a brush made of a fiber member that has not been subjected to a conductive process and is in contact with the image carrier; and a paper dust removing unit of the image carrier. The difference between the surface potential at the position facing the paper dust and the potential of the paper dust removing unit of the paper dust removing means is 1
bias voltage applying means for applying a bias voltage of kV or more to the paper dust removing means.

According to the image forming apparatus of the fifth aspect,
The image carrier, for example, the photoconductor is charged to a predetermined high voltage, and the developer charged by frictional charge is transferred to the image carrier due to a potential difference between the image carrier and the developer carrier. Thus, the electrostatic latent image is visualized. Further, the paper as the transfer medium is charged by the transfer means to have a polarity opposite to that of the developer. Here, a bias voltage is applied to the paper dust removing means formed by the brush made of the fiber member by the bias voltage applying means so that the difference from the potential of the paper dust removing portion of the paper dust removing means becomes 1 kV or more. Therefore, a sufficient potential difference is generated between the paper dust removing means and the image carrier to transfer the paper dust from the image carrier to the paper dust removing means, and the potential difference is opposite to the charging polarity of the developer. Polarized paper dust is well captured by the paper dust removing means. On the other hand, since the brush made of the fiber member of the paper dust removing unit is not subjected to the conductive treatment, even if a high bias voltage is applied from the bias voltage applying unit, the discharge from the paper dust removing unit to the image carrier is almost completely prevented. It does not occur and does not cause uneven charging on the image carrier.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect of the present invention, the bias voltage applying unit is configured to control the current value flowing through the paper dust removing unit to a predetermined value. It is characterized in that the means has an upper limit value of

According to the image forming apparatus of the sixth aspect,
Since the bias voltage applying means has a predetermined upper limit to the current value flowing through the paper dust removing means, the discharge from the paper dust removing means to the image carrier can be reduced, and the charging on the image carrier can be reduced. There is no unevenness.

According to a seventh aspect of the present invention, there is provided the image forming apparatus according to the fifth aspect.
7. The image forming apparatus according to claim 6, wherein the bias voltage applying unit is provided with a resistor in series with the paper dust removing unit.

According to the image forming apparatus of the seventh aspect,
Since the bias voltage applying means has a resistor in series with the paper dust removing means, the value of the current flowing through the paper dust removing means has a predetermined upper limit value. The discharge from the means to the image carrier can be reduced, and the charging unevenness on the image carrier does not occur.

According to an eighth aspect of the present invention, in order to solve the above-mentioned problem, an image is formed by transferring a visible image carried on an image carrier and visualized by a developer to a transfer medium by a transfer unit. A paper dust removing means formed of a brush made of a fiber member having a resistance value of 10 ⁸ to 10 ¹⁰ Ω in contact with the image carrier; and a bias voltage applied to the paper dust removing means. And a bias voltage applying means for applying a bias voltage.

According to the image forming apparatus of the present invention,
The image carrier, for example, the photoconductor is charged to a predetermined high voltage, and the developer charged by frictional charge is transferred to the image carrier due to a potential difference between the image carrier and the developer carrier. Thus, the electrostatic latent image is visualized. Further, the paper as the transfer medium is charged by the transfer means to have a polarity opposite to that of the developer. Here, a bias voltage is applied to the paper dust removing means formed by the brush made of the fiber member so that the difference from the surface potential of the image carrier becomes 1 kV or more by the bias voltage applying means. A sufficient potential difference is generated between the removing means and the image carrier to transfer the paper dust from the image carrier to the paper dust removing means, and the paper dust charged to a polarity opposite to the polarity of the developer is charged. Is well captured by the paper dust removing means. On the other hand, since the brush made of the fiber member of the paper dust removing means has a resistance value set to 10 ⁸ to 10 ¹⁰ Ω, even if a high bias voltage is applied from the bias voltage applying means, the image is not transferred from the paper dust removing means. Discharge to the carrier can be reduced, and charging unevenness on the image carrier does not occur.

According to a ninth aspect of the present invention, in order to solve the above problem, in the image forming apparatus according to the first or fifth or eighth aspect, the bias voltage applying means is a paper voltage removing means using a constant voltage power supply. A means for applying a voltage to the

According to the image forming apparatus of the ninth aspect,
Since the bias voltage applying means applies a voltage to the paper dust removing means by a constant voltage power supply, the current value flowing through the paper dust removing means has a predetermined upper limit value, and the image is transferred from the paper dust removing means to the paper dust removing means. Discharge to the carrier can be reduced, and charging unevenness on the image carrier does not occur.

According to a tenth aspect of the present invention, in order to solve the above-mentioned problem, in the image forming apparatus according to the eighth aspect, the bias voltage applying unit is configured to determine a current value flowing through the paper dust removing unit to a predetermined value. It is characterized in that the means has an upper limit value of

According to the image forming apparatus of the present invention, since the bias voltage applying means has a predetermined upper limit to the value of the current flowing through the paper dust removing means, the bias voltage applying means can change the current from the paper dust removing means to the image carrier. Discharge to the image carrier can be reduced, and uneven charging on the image bearing member does not occur.

According to an eleventh aspect of the present invention, there is provided an image forming apparatus according to any one of the eighth to eleventh aspects, in order to solve the above problem.
In the above image forming apparatus, the bias voltage applying unit is provided with a resistor in series with the paper dust removing unit.

According to the image forming apparatus of the present invention, since the bias voltage applying means has a resistor in series with the paper dust removing means, a current flowing through the paper dust removing means is provided. Since the value has a predetermined upper limit, the discharge from the paper dust removing unit to the image carrier can be reduced, and the charging unevenness on the image carrier does not occur.

[0032]

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

(First Embodiment) FIG. 1 is a sectional view showing a schematic configuration of a laser beam printer 1 as an embodiment of the image forming apparatus of the present invention. In FIG. 1, the laser beam printer 1 includes a feeder unit for feeding paper (not shown) at the bottom of a main body case 2. The feeder unit includes a sheet pressing plate 10 urged upward by a spring (not shown), a sheet feeding roller 11, and a sheet feeding roller 11.
And a friction separating member 14 pressed against The paper stacked on the paper pressing plate 10 is pushed up so as to come into contact with the paper feed roller 11, and is fed at a predetermined timing.
Is rotated in the direction of the arrow in FIG. 1 so that only the uppermost sheet is separated and supplied between the sheet feeding roller 11 and the friction separating member 14.

A pair of registration rollers 12 and 1 are located on the downstream side in the sheet transport direction due to the rotation of the paper feed roller 11.
3 is rotatably supported, and conveys a sheet at a predetermined timing to a transfer position formed by a photosensitive drum 20 and a transfer roller 21, which will be described later.

The photosensitive drum 20 as a visible image carrier is
It is made of a positively chargeable material, for example, an organic photoreceptor mainly containing positively chargeable polycarbonate. More specifically, the photosensitive drum 20 has, for example, a cylindrical aluminum sleeve as a main body, and has a predetermined thickness (for example, about 20 μm) in which a photoconductive resin is dispersed in polycarbonate on an outer peripheral portion thereof.
m) is constituted by a hollow drum formed with a photoconductive layer, and is rotatably supported by the main body case 2 with the cylindrical sleeve grounded. Further, the photosensitive drum 20 is driven to rotate in a direction indicated by an arrow by driving means (not shown).

The charger 30 is, for example, a scorotron type charger for positive charging for generating corona discharge from a charging wire made of tungsten or the like.

The laser scanner unit 40 includes a laser generator (not shown) that generates a laser beam L for forming an electrostatic latent image on the photosensitive drum 20, and a polygon mirror (pentahedral mirror) 41 that is driven to rotate. , A pair of lenses 42 and 4
5 and reflection mirrors 43, 44 and 46.

The developing device 50 has a case 51 in which a toner storage chamber 52 as a developer chamber is formed.
An agitator 53 is provided inside 2 so as to be rotatable around a rotation shaft 54. The toner stored in the toner storage chamber 52 is a positively chargeable non-magnetic one-component developer,
A particle size of 6 μm obtained by adding a well-known coloring agent such as carbon black and a charge controlling agent such as nigrosine, triphenylmethane and quaternary ammonium salt to a styrene-acrylic resin formed into a spherical shape by suspension polymerization. It has toner base particles having a particle size of 10 to 10 μm and an average particle size of 8 μm. The toner 55 is configured by adding silica as an external additive to the surface of the toner base particles.

The photosensitive drum 20 in the toner storage chamber 52
On the side, a developing chamber 55 for performing development by communicating with the toner storage chamber 52 through an opening A is formed, and a supply roller 56 and a developing roller 57 are rotatably pivotally supported. The toner on the developing roller 57 is regulated to a predetermined layer thickness by a layer-thickness regulating blade 58 provided with a contact portion made of silicone rubber at the tip of a thin plate-like elastic metal plate, and is used for development.

The transfer roller 21 is pivotally supported rotatably.
It is made of a conductive foamed elastic body made of silicone rubber or urethane rubber. The transfer roller 21 is configured to reliably transfer the toner image on the photosensitive drum 20 to the paper by the applied voltage.

The fixing unit 70 includes the registration roller 12
The heating roller 71 and the pressing roller 72 are provided on the further downstream side in the sheet conveyance direction from the sheet feeding roller 13 to the pressure contact portion between the photosensitive drum 20 and the transfer roller 21. The toner image transferred to the sheet is pressed while being heated and is fixed on the sheet.

A pair of transport rollers 73 for transporting the paper are provided downstream of the fixing unit 70 in the transport direction, and a pair of discharge rollers 7 are located downstream of the transport roller 73.
4 and a paper discharge tray 75 are provided in this order.

Further, as shown in FIG. 2, a paper dust removing device 80 provided as a paper dust removing means provided adjacent to the photosensitive drum 20 has a holder 83 and a base end supported on an upper portion of the holder 83. Urethane sheet 8 covered with non-woven fabric 81 at the tip
2, a brush-like member 86 for scraping paper dust, and a conductive plate 84 that supports the brush-like member 86 and is mounted on a holder 83. Further, a constant voltage source 92 is connected to the plate 84 via a resistor 90, and a voltage is applied to the plate 84 and the brush-like member 86.

As the non-woven fabric 81, a non-woven fabric integrated by confounding constituent fibers was used. This is because it is preferable to use a constituent fiber having a high degree of freedom in capturing fine paper powder between the fibers. As a constituent material, for example, acrylic fiber or the like is used. The nonwoven fabric 81 was formed so as to have a length in the longitudinal direction substantially equal to the length in the longitudinal direction of the photosensitive drum 20, and was adhered to the front end portion of a urethane sheet 82 as a substrate made of a sheet-like member using a double-sided tape.

The urethane sheet 82 is a sheet-like member made of urethane rubber and has a hardness of 92 ° Hs (J
IS K-6301). Urethane sheet 8
2 is mounted at a position where the end of the urethane sheet 82 and the nonwoven fabric 81 reach a position where the photosensitive drum 20 is provided as shown by a dotted line in FIG.

The holder 83 has substantially the same length as the photosensitive drum 20 in the longitudinal direction of the photosensitive drum 20, and supports the photosensitive drum 20 at both ends in the longitudinal direction with screws 91. Screwed to the frame.
Further, a paper powder storage chamber is formed inside the photosensitive drum 2.
An opening is formed on the side opposite to 0. Further, a urethane film 87 is attached to a lower portion of the holder 83. The base end of the urethane film 87 is attached to the holder 83 using a double-sided tape, and the free end side is in contact with the photosensitive drum 20. By providing such a urethane film 87, it is possible to prevent paper powder from falling from the storage chamber of the holder 83.

As the brush member 86, a fiber member was used. In this embodiment, acrylic fiber (trade name Kanecaron) is used. This is because, as a result of the experiment, it was confirmed that paper powder could be captured extremely well when acrylic fiber was used. Further, in the present embodiment, the acrylic fiber is subjected to a degreasing treatment. This is because, as a result of the experiment, it was confirmed that the resistance value of the acrylic fiber was increased and the value was stabilized by performing the degreasing treatment. FIG. 3 shows the difference in the resistance value of the acrylic fiber depending on the presence or absence of the degreasing treatment. As shown in FIG. 3, when the degreasing treatment is not performed, a current of 1.4 μA is applied when the applied voltage is 0.5 kV, and a current is set when the applied voltage is 1.0 kV.
7.8 μA when the current is 9 μA and the applied voltage is 1.5 kV
Current flows through the acrylic fiber. On the other hand, when the degreasing treatment is performed, when the applied voltage is 1.0 kV, the current is 0.7 μA, which is a half of the above, when the applied voltage is 2.0 kV, the current is 2.2 μA, and the applied voltage is 3. At 0 kV, a current of 7.1 μA flows. As described above, it is found that by performing the degreasing treatment, the resistance of the acrylic fiber can be increased. In this embodiment, the resistance value of the brush-like member 86 is set to 10 ⁸ to ¹⁰ 10 by performing a degreasing treatment on the acrylic fiber.
Set to Ω.

The voltage value of the constant voltage power supply 92 is
Even when the surface potential of 0 fluctuates, a voltage value higher than the potential of the unexposed portion of the photosensitive drum 20 is set in order to minimize the discharge from the brush-like member 86 to the photosensitive drum 20. The voltage is applied by constant voltage control. In the present embodiment, the applied voltage is set to 2 kV.

(Example of Operation) In the laser beam printer 1 of the present embodiment as described above, the surface of the photosensitive drum 20 is uniformly charged by the charger 30 and the laser beam modulated by the laser scanner unit 40 in accordance with image information. When L is irradiated, an electrostatic latent image is formed on the surface of the photosensitive drum 20. This electrostatic latent image is visualized with toner by the developing device 50, and the visible image formed on the photosensitive drum 20 is transported by the photosensitive drum 20 to a transfer position.
At the transfer position, the paper is supplied via the paper feed roller 11 and the registration rollers 12 and 13, and the visible image is transferred to the paper by a transfer bias applied by the transfer roller 21.

Next, the sheet is conveyed to the fixing unit 70, and is nipped and conveyed by the heating roller 71 and the pressing roller 72 of the fixing unit 70, and the visible image on the sheet is pressed and heated to be fixed on the sheet. You. Then, the sheet is discharged to the discharge tray 75 above the laser beam printer 1 by the pair of transport rollers 73 and the discharge rollers 74, and the image forming operation is completed.

On the other hand, the toner remaining on the photosensitive drum 20 after the transfer is collected by the developing device 50 and is again used for development. As described above, the laser beam printer 1 of the present embodiment
Employs a so-called cleaner-less development method.
Therefore, since a waste toner storage container for scraping and storing the toner remaining on the photosensitive drum 20 is not required, the size of the apparatus can be reduced, and the toner can be effectively used.

Paper dust adheres to the photosensitive drum 20 after the transfer. Of the paper dust, large fibrous paper dust is caught by the brush-like member 86 and applied to the brush-like member 86. The electric field generated by the applied high voltage causes the brush-like member 86 to capture the electric field. Then, other fine paper powder is captured by the nonwoven fabric 81.

In this embodiment, the pressing force of the nonwoven fabric 81 against the photosensitive drum 20 is set to an extremely low value of 2.5 gf / cm. However, since the nonwoven fabric 81 is removed by entanglement of paper powder, Paper powder can be reliably removed even with such a low pressing force. Although the paper powder contains the fiber component and the filler, the nonwoven fabric 81 can reliably remove both the fiber component and the filler. Also,
Since the pressing force of the non-woven fabric 81 against the photosensitive drum 20 is kept low, the damage of the surface of the photosensitive drum 20 due to the fiber component of the paper powder and the filming due to the filler do not occur.

Here, the relationship between paper dust, damage to the surface of the photosensitive drum 20 and filming will be described in detail.
In addition to pulp fiber (cellulose extracted from hardwood and softwood), which is the main raw material for paper, fillers that make paper opaque and white, internal sizing agents to prevent ink bleeding, and sizing agents And an internal-size fixing agent that causes pulp fibers to be adsorbed. The above-mentioned acidic paper mainly uses talc or clay as a filler, a rosin sizing agent as an internal sizing agent, and a sulfate band (aluminum sulfate) as an internal sizing agent.

Among them, substances which particularly adversely affect the electrophotographic process are pulp fibers and filler talc. When pulp fibers are mixed in a developing device using a non-magnetic one-component developer, the pulp fibers may be caught between the layer thickness regulating blade and the developing roller, and may damage the layer thickness regulating blade and the developing roller. Further, when the pulp fiber passes through the layer thickness regulating blade together with the toner stuck to the pulp fiber and adheres to the paper, and is discharged as it is through the fixing process, it is conspicuous particularly when it adheres to a white background portion. It will be recognized by the naked eye as garbage. On the other hand, talc is a very strongly negatively charged substance, and in a process using a positively charged toner, if it is mixed in a developing device, the amount of charge of the toner is reduced to cause printing fog. Further, in a process using a negatively charged toner, similarly, it may cause print fogging, or even if not fog, the charge amount of the toner becomes excessively high, causing a decrease in image density. is there.

However, in the present embodiment, as described above, since a voltage having the same polarity as that of the toner is applied to the brush-like member 86, the pulp fibers of the paper powder can be surely removed from the brush-like member. 86 can be reliably captured and prevented from entering the developing device. Originally, paper powder has the property of being easily charged to negative polarity, but in addition to this, the paper is charged to the opposite polarity to the toner in the transfer process, so the paper powder after the transfer process is strongly charged to negative polarity. are doing. Therefore, the brush-like member 86 to which the voltage having the same polarity as the toner is applied is reliably captured by the action of the electric field.

The talc is captured by the non-woven fabric 81, but the non-woven fabric 81 is coated with the urethane sheet 8 having a low hardness.
2, the pressing force of the nonwoven fabric 81 against the photosensitive drum 20 is 2.5 gf / c.
m and an extremely low value. Therefore, the hard pulp fibers captured by the nonwoven fabric 81 do not damage the surface of the photosensitive drum 20, and filming due to the filler does not occur.

Accordingly, the incorporation of paper dust into the developing device 50 is reliably prevented, and no image defects occur.

Further, in this embodiment, since the voltage applied to the brush-like member 86 is a voltage having the same polarity as the charging polarity of the toner, the brush-like member 86 captures only paper dust and captures toner. Nothing. In addition, since the polymerized toner produced by the polymerization method is used as the toner, the toner base particles have a substantially spherical and gentle surface shape, and due to its high fluidity, the transfer efficiency is high and the residual toner itself is very small. Therefore, even if a small amount of toner remains on the photosensitive drum 20, the toner hardly adheres to the nonwoven fabric 81 and is reliably collected by the developing device 50.

As described above, according to the present embodiment, the paper dust consisting of the fiber component and the filler can be reliably removed by the paper dust removing device 80 without causing damage to the surface of the photosensitive drum 20 or filming. Since pulp fibers and talc are not mixed into the developing device 50 and transfer of the pulp fibers to the paper does not occur, image defects such as fog or paper stains can be reliably prevented. As an example, when an experiment was performed to form a continuous image of up to 15,000 sheets using acidic paper, no damage or filming of the photosensitive drum 20 occurred, and the image was good.

In particular, it was confirmed that a good image was formed without causing uneven charging of the photosensitive drum 20 even though a voltage as high as 2 kV was applied to the brush member 86. This is because the acrylic fiber constituting the brush-like member 86 has been increased in resistance without being subjected to a conductive treatment. Since the brush-like member 86 has high resistance,
Even if the above high voltage is applied to the brush-like member 86,
Electric discharge from the brush-like member 86 to the photosensitive drum 20 is minimized, and uneven charging of the photosensitive drum 20 can be suppressed.

Further, in this embodiment, a voltage higher than the surface potential of the unexposed portion of the photosensitive drum 20 is applied to the brush-like member 86 having a high resistance as described above by constant voltage control. Therefore, even if the transfer condition changes due to environmental conditions or paper type, and the surface potential of the photosensitive drum 20 changes, the potential of the brush-like member 86 always becomes higher than the surface potential of the photosensitive drum 20, and the polarity opposite to that of the toner. Paper powder that has been charged can always be satisfactorily captured.

(Experimental Example) Here, an experimental result of examining differences in paper dust removal performance and surface potential unevenness of the photosensitive drum with respect to the resistance value of the brush-like member 86, and the voltage value applied to the brush-like member 86 An experimental result of examining differences in paper dust removal performance and surface potential unevenness of the photosensitive drum will be described.

FIG. 4 is a graph showing the results of an experiment for examining differences in paper dust removal performance and unevenness in the surface potential of the photosensitive drum with respect to the resistance value of the brush-like member 86. In the experiment, a constant voltage of 2 kV was applied to the brush-like member. Also,
The paper dust removal performance was determined by visually checking the amount of paper dust on the photosensitive drum. The charging unevenness was evaluated based on the unevenness of the print image density.

As shown in FIG. 4, when the resistance value of the brush-like member 86 is 10 ⁷ Ω, some paper dust is confirmed on the photosensitive drum 20 after passing through the contact portion with the brush-like member 86.
After the charging step, it was confirmed that the charging unevenness of the photosensitive drum 20 was large. This is because the resistance of the brush-shaped member 86 is not sufficiently high, so that the application of a high voltage causes the discharge from the brush-shaped member 86 to the photosensitive drum 20, and the discharge between the brush-shaped member 86 and the photosensitive drum 20. This is considered to be due to the fact that a sufficient electric potential difference disappears, and uneven charging occurs due to non-uniform discharge on the photosensitive drum 20.

Next, the resistance value of the brush-like member 86 is 10 ⁸
In the case of Ω, almost no paper dust was found on the photosensitive drum 20 after passing through the contact portion with the brush-like member 86, and after the charging step, charging unevenness of the photosensitive drum 20 was slightly confirmed. This is because, since the resistance value of the brush-like member 86 is a high value, the discharge from the brush-like member 86 to the photosensitive drum 20 is reduced even by the application of a high voltage, so that the brush-like member 86 This is probably because a sufficient potential difference was maintained.

Next, the resistance value of the brush-like member 86 is 10 ⁹
In the case of Ω and 10 ¹⁰ Ω, no paper dust is found on the photosensitive drum 20 after passing through the contact portion with the brush-like member 86,
When the resistance value was 10 ¹⁰ Ω, paper powder was slightly recognized. After the charging step, the photosensitive drum 20
No uneven charging occurred. This is because the brush-like member 86 has a sufficiently high resistance value, so that even when a high voltage is applied, the brush-like member 86 hardly discharges to the photosensitive drum 20, and the brush-like member 86 and the photosensitive drum 20 are hardly discharged.
It is considered that a sufficient potential difference was maintained between the above.

Next, the resistance value of the brush-like member 86 is 10 ¹¹
In the case of Ω, a considerable amount of paper dust was found on the photosensitive drum 20 after passing through the contact portion with the brush-like member 86. However, no uneven charging of the photosensitive drum 20 occurred after the charging step. This is because the brush-shaped member 86 has a very high resistance value, so that even when a high voltage is applied, the brush-shaped member 86 does not discharge to the photosensitive drum 20. However, the brush-shaped member 86 has a too high resistance value. Is not raised to a sufficient value, and a sufficient potential difference between the brush-like member 86 and the photosensitive drum 20 could not be secured.

On the other hand, FIG. 5 is a diagram showing the results of an experiment for examining differences in paper dust removal performance and surface potential unevenness of the photosensitive drum with respect to a voltage value applied to the brush-like member 86. In the experiment, the resistance value of the brush-like member 86 was set to 10 ⁹ Ω.

As shown in FIG. 5, when the voltage applied to the brush member 86 was 1 kV, a considerable amount of paper dust was confirmed on the photosensitive drum 20. However, the photosensitive drum 2
No charging unevenness of 0 was observed. This is because the surface potential of the photosensitive drum 20 after the transfer process is usually about 400 to 600 V, and the voltage applied to the brush-like member 86 is 1 kV.
In this case, it is considered that the potential difference between the brush-like member 86 and the surface potential of the photosensitive drum 20 was about 400 to 600 V, and a sufficient potential difference for removing paper dust could not be secured. In addition, since the potential difference is small, discharge from the brush-like member 86 to the photosensitive drum 20 was not performed, and it is considered that uneven charging did not occur on the surface of the photosensitive drum 20 after the charging process.

Next, when the voltage applied to the brush-like member 86 is 1.5 kV, paper dust may not be found on the photosensitive drum 20, but paper dust may be less often seen. There was no. However, uneven charging of the photosensitive drum 20 was not confirmed. When the voltage applied to the brush member 86 is 1.5 kV, the potential difference between the brush member 86 and the surface potential of the photosensitive drum 20 is 0.9 kV to 1.1 k.
V or so. Considering in light of the results of the above experiments, within the range of this potential difference, there is a boundary value of the potential difference sufficient to perform paper dust removal, and when a potential difference exceeding this boundary value is secured, If no paper dust is found and this boundary value is not reached, it is likely that paper dust has been found. Also, with the potential difference in this range, the brush-like member 86
It is supposed that no discharge was caused to the photosensitive drum 20 from, and no charging unevenness occurred on the surface of the photosensitive drum 20 after the charging step.

Although not shown in FIG.
An experiment was performed by changing the applied voltage to 4 kV and 1.3 kV. In the case of 1.4 kV, there were cases where paper dust was found and cases where paper dust was not found, but always at 1.3 kV. Paper dust was found. In the case of 1.4 kV,
The potential difference between the brush-like member 86 and the surface potential of the photosensitive drum 20 is about 0.8 kV to 1.0 kV. Also, 1.3
In the case of kV, the potential difference between the brush-like member 86 and the surface potential of the photosensitive drum 20 is about 0.7 kV to 0.9 kV. From this experimental result, it is considered that the boundary value of the potential difference sufficient to remove paper dust is 1.0 kV.

Next, when the voltage applied to the brush-like member 86 was 2.0 kV or 3.0 kV, no paper dust was observed on the photosensitive drum 20. Further, charging unevenness of the photosensitive drum 20 was not confirmed. When the voltage applied to the brush-like member 86 is 2.0 kV and 3.0 kV, the potential difference between the brush-like member 86 and the surface potential of the photosensitive drum 20 is 1.4 kV to 1.6 kV, or 2.
It is about 4 kV to 2.6 kV, which exceeds the boundary value. Therefore, it is considered that a sufficient potential difference was secured between the brush-like member 86 and the photosensitive drum 20 for removing paper dust, and no paper dust was observed. Also, 2.0
With an applied voltage of up to 3.0 kV, discharge from the brush-like member 86 to the photosensitive drum 20 was not performed, and it is considered that uneven charging did not occur on the surface of the photosensitive drum 20 after the charging process.

Next, when the voltage applied to the brush-like member 86 was 4.0 kV, no paper dust was found on the photosensitive drum 20. However, charging unevenness of the photosensitive drum 20 was slightly confirmed. When the voltage applied to the brush member 86 is 4.0 kV, the potential difference between the brush member 86 and the surface potential of the photosensitive drum 20 is 3.4 kV or less.
It is about 3.6 kV, which exceeds the boundary value. Therefore, it is considered that a sufficient potential difference was secured between the brush-like member 86 and the photosensitive drum 20 for removing paper dust, and no paper dust was observed. Also, at a high applied voltage of 4.0 kV, the photosensitive drum 20
Is discharged, and it is considered that uneven charging occurs on the surface of the photosensitive drum 20 after the charging step.

From the results of the above experiments, the resistance value of the brush-like member 86 is preferably 10 ⁸ Ω to ^{10 10} Ω. In particular, if the resistance value of the brush-like member 86 is set to 10 ⁹ Ω, the cost can be reduced. It can be easily used because it can achieve high paper dust removal effect and high charge unevenness prevention effect.

The voltage applied to the brush member 86 should be such that the potential difference between the photosensitive drum 20 and the photosensitive drum 20 is 1 kV or more, so that a high paper dust removing effect and a high charge unevenness preventing effect can be obtained. It turned out to be preferable in that it can be obtained. That is, if the voltage applied to the brush-like member 86 is set to a voltage equal to or higher than the surface potential of the unexposed portion of the photosensitive drum 20, a potential difference necessary for removing paper dust is always obtained regardless of the surface potential of the photosensitive drum 20. I found that I could do it.

Even if such a high voltage is applied, since the resistance value is set to a high value as described above, the current supplied to the brush-like member 86 can be limited to an appropriate value. Discharge from the brush-like member 86 to the photosensitive drum 20 can be prevented, and occurrence of uneven charging can be prevented.

On the other hand, in a conventional apparatus in which the members constituting the paper dust removing means are subjected to a conductive treatment such as dispersing conductive particles, when the voltage applied to the paper dust removing means is increased, the paper dust is reduced. The resistance value of the member constituting the powder removing means decreases exponentially with respect to the voltage, and when an excessively high voltage is applied, a breakdown occurs and the resistance value suddenly decreases.

Therefore, the device of the present embodiment can exhibit extremely excellent effects as compared with the conventional device.
In addition, since there is no occurrence of charging unevenness, it is possible to omit a static elimination lamp such as an EL, and it is possible to reduce costs and simplify the configuration by reducing the number of components.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, as shown in FIG. 6, a brush roller 88 is provided as a paper dust removing device, and a predetermined high voltage is applied to the core of the brush roller 88 by a constant voltage source 92. Also in this embodiment, the brush uses a high-resistance acrylic fiber that has not been subjected to a conductive treatment.

With such a configuration, the brush roller 88
While preventing a discharge from the brush roller 88 to the photosensitive drum 20 while keeping a potential difference sufficient for removing paper dust between the photosensitive drum 20 and the photosensitive drum 20, uneven charging of the photosensitive drum 20 can be prevented. Therefore, the number of parts can be reduced by omitting a static elimination lamp such as an EL.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the present embodiment, as shown in FIG. 7, a corona discharge wire 31, a shield 32, a grid electrode 3
3, a scorotron charger 30 integrally provided with a shield 32 and a grid electrode 33, an opening B is formed in a holding portion 34 of the shield 32, and a charge trapping electrode is formed so as to cover the opening B. 90 are provided. Then, one end of the charge trapping electrode 90 is extended to the brush member 86 side, and one end of the charge trapping electrode 90 and the plate 84 of the brush member 86 are electrically connected by a screw 85.

With this configuration, a dedicated power supply for the brush-like member 86 can be omitted, and the number of parts can be further reduced.

In the above-described embodiment, the photosensitive member is used as an example of the image bearing member. However, the present invention is not limited to this. For example, an intermediate transfer member in a color image forming apparatus may be used as an image bearing member. The present invention can be applied to a body.

Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. Can easily be inferred.

[0088]

According to the image forming apparatus of the present invention, the paper dust removing means is formed by a brush made of a fiber member which has not been subjected to a conductive treatment and comes into contact with the image carrier, and a bias voltage applying means. As a result, since a bias voltage is applied to the paper dust removing means, a potential difference is generated between the paper dust removing means and the image carrier, and the paper dust charged to the opposite polarity to the charging polarity of the developer is removed by the paper dust removing means. Can be captured well.
In addition, even if a high bias voltage is applied to the brush made of the fiber member of the paper dust removing unit that is not conductive, the discharge from the paper dust removing unit to the image carrier can be reduced. The occurrence of the above charging unevenness can be reliably prevented. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the second aspect,
The difference between the surface potential of the image carrier and the surface potential at the position facing the paper dust removing unit is 1 due to the bias voltage applying unit.
Since a voltage of kV or more is applied, an electric field sufficient to transfer paper dust from the image carrier to the paper dust removing unit side can be generated between the paper dust removing unit and the image carrier. Thus, paper dust can be reliably removed from the image carrier.

According to the image forming apparatus of the third aspect,
Since the bias voltage applying means gives a predetermined upper limit to the current value flowing through the paper dust removing means, the occurrence of discharge from the paper dust removing means to the image carrier is reliably restricted, and The occurrence of uneven charging can be prevented. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the fourth aspect,
Since the bias voltage applying means has a resistor in series with the paper dust removing means, a current value flowing through the paper dust removing means can have a predetermined upper limit value. The discharge from the means to the image carrier can be reduced, and the occurrence of uneven charging on the image carrier can be reliably prevented. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the fifth aspect,
The paper dust removing means is formed by a brush made of a fiber member which has not been subjected to the conductive treatment and is brought into contact with the image carrier, and a bias voltage applying means is provided at a position of the image carrier facing the paper dust removing means. Since a bias voltage such that the difference from the surface potential is 1 kV or more is applied to the paper dust removing means, paper dust can be satisfactorily removed, and the discharge from the paper dust removing means to the image carrier is reduced. It is possible to reliably prevent the occurrence of uneven charging on the carrier. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the present invention, the bias voltage applying means gives a predetermined upper limit to the value of the current flowing through the paper dust removing means. And the occurrence of uneven charging on the image carrier can be reliably prevented. Therefore, EL
And so on, and the elimination of such lamps can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of parts.

According to the image forming apparatus of the seventh aspect,
Since the bias voltage applying means has a resistor in series with the paper dust removing means, a current value flowing through the paper dust removing means can have a predetermined upper limit value. The discharge from the means to the image carrier can be reduced, and the occurrence of uneven charging on the image carrier can be reliably prevented. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

The image forming apparatus according to claim 8, wherein the paper dust removing means is provided with a resistance value of 10 ⁸ to 10 for contacting the image carrier.
It is formed by a brush made of a ¹⁰ Ω fiber member, and a bias voltage is applied to the paper dust removing means by a bias voltage applying means. And the occurrence of uneven charging on the image carrier can be reliably prevented.
Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the ninth aspect,
By the bias voltage applying means, since application of a voltage to the paper dust removing means by the constant voltage power source, can have a predetermined upper limit value to a current value flowing through the paper dust removing means, image from the paper dust removing means Discharge to the carrier can be limited, and occurrence of uneven charging on the image carrier can be reliably prevented. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

[0097] According to the image forming apparatus according to claim 10, wherein the bias voltage applying means, so to have a predetermined upper limit value to a current value flowing through the paper dust removing unit, the image bearing member from the paper dust removing means Discharge to the image carrier and the occurrence of uneven charging on the image carrier can be reliably prevented. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

According to the image forming apparatus of the eleventh aspect, since the bias voltage applying means includes a resistor in series with the paper dust removing means, a current flowing through the paper dust removing means is provided. The value can have a predetermined upper limit , and the discharge from the paper dust removing unit to the image carrier can be reduced, and the occurrence of charging unevenness on the image carrier can be reliably prevented. Therefore, a static elimination lamp such as an EL can be omitted, and simplification of the configuration and cost reduction can be realized by reducing the number of components.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view around a paper dust removing device in the image forming apparatus of FIG. 1;

FIG. 3 is a diagram showing a relationship between an applied voltage and a current in a brush-like member of the paper dust removing device of FIG. 2;

4 is a diagram showing a relationship between a resistance value of a brush-like member, a paper dust removing performance, and charging unevenness in the paper dust removing device of FIG. 2;

FIG. 5 is a diagram showing a relationship between an applied voltage to a brush-like member, paper dust removing performance, and charging unevenness in the paper dust removing device of FIG. 2;

FIG. 6 is a diagram illustrating a process cartridge including a paper dust removing device according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a periphery of a paper dust removing device according to a third embodiment of the present invention.

[Description of Reference Numerals] 1 laser beam printer 20 photosensitive drum 80 paper dust removing device 81 nonwoven fabric 82 urethane sheet 84 conductive plate 86 brush-like member 88 brush roller 90 resistor 92 constant voltage source

Claims (11)

[Claims] 1. An image forming apparatus for forming an image by transferring a visible image carried on an image carrier and visualized by a developer onto a transfer medium by a transfer unit, wherein the image forming apparatus contacts the image carrier. Image forming apparatus comprising: a paper dust removing unit formed by a brush made of a fiber member that has not been subjected to a conductive treatment; apparatus. 2. The paper dust removing device according to claim 2, wherein the bias voltage applying device applies a voltage to the paper dust removing device such that a difference from a surface potential of the image carrier at a position facing the paper dust removing device is 1 kV or more. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a unit. 3. An image forming apparatus according to claim 1, wherein said bias voltage applying means is means for giving a predetermined upper limit value to a current value flowing through said paper dust removing means. 4. The image forming apparatus according to claim 1, wherein the bias voltage applying unit includes a resistor provided in series with the paper dust removing unit. 5. An image forming apparatus for forming an image by transferring a visible image carried on an image carrier and visualized by a developer to a transfer medium by a transfer unit, wherein the image forming apparatus is configured to contact the image carrier. And a difference between a surface potential of the image carrier at a position facing the paper dust removing unit, which is formed by a brush made of a fiber member that has not been subjected to a conductive treatment, is 1 kV or more. An image forming apparatus comprising: a bias voltage applying unit that applies a bias voltage to the paper dust removing unit. 6. An image forming apparatus according to claim 5, wherein said bias voltage applying means is means for giving a predetermined upper limit value to a current value flowing through said paper dust removing means. 7. The image forming apparatus according to claim 5, wherein said bias voltage applying means includes a resistor provided in series with said paper dust removing means. 8. An image forming apparatus for forming an image by transferring a visible image carried on an image carrier and visualized by a developer to a transfer medium by a transfer unit, wherein the image forming apparatus is configured to contact the image carrier. Paper dust removing means formed of a brush made of a fiber member having a resistance value of 10 ⁸ to 10 ¹⁰ Ω, and bias voltage applying means for applying a bias voltage to the paper dust removing means. Image forming apparatus. 9. An image forming apparatus according to claim 1, wherein said bias voltage applying means is means for applying a voltage to said paper dust removing means by a constant voltage power supply. 10. The image forming apparatus according to claim 8, wherein said bias voltage applying means is means for giving a predetermined upper limit to a current value flowing through said paper dust removing means. 11. The image forming apparatus according to claim 8, wherein the bias voltage applying unit includes a resistor provided in series with the paper dust removing unit.