JPH10186790A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a magnetic field from being formed between a magnetic pole constraining a magnetic particle constituting a magnetic brush and a dispersing member in an image forming device having the magnetic brush for charging a photoreceptor and the dispersing member for dispersing the residual toner after transfer, and provide satisfactory charging property. SOLUTION: A dispersing member 5 for dispersing the residual toner after transfer is formed by supporting a brush 5b formed of nonmagnetic fiber by a stainless support member 5a of nonmagnetic body, and the dispersing member 5 is set on the rotating directional upstream side of a photoreceptor 1 to a magnetic brush 2 for charging the photoreceptor 1, whereby a magnetic field is prevented from being formed between the magnetic brush 2 and the dispersing member 5. Therefore, the magnetic conductive particle 2c of the magnetic brush 2 is prevented from being attracted by the dispersing member 5, whereby satisfactory charging property can be provided.

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 using an electrophotographic process, such as a copying machine, a laser beam printer, and a facsimile.

[0002]

2. Description of the Related Art As shown in FIG. 2, for example, an image forming apparatus such as a copying machine, a laser beam printer, and a facsimile using an electrophotographic process has a drum type electrophotographic photosensitive member as an image carrier as a main component. (Hereinafter simply referred to as a “photoconductor”) 101 and a charging roller 1 around the body 101
02, exposure device 103, developing device 104, transfer roller 1
05, a cleaning member 106 is provided.

In the image forming apparatus having the above-described structure, at the time of forming an image, the photosensitive member 101 is driven to rotate by a motor (not shown) as a driving means, and the surface of the photosensitive member 101 is driven by a charging roller 102 driven by the photosensitive member 101. Is charged.
Then, an image exposure L by a laser beam is given to the charged photoconductor 101 by the exposure device 103 to form an electrostatic latent image corresponding to the input image information. Is developed as a toner image. Then, the toner image on the photoreceptor 101 is transferred to a transfer material P such as paper by a transfer roller 105, and the transfer material P on which the toner image has been transferred is conveyed to a fixing device (not shown). The image is fixed on the surface as a permanently fixed image and discharged. Further, residual toner and the like adhering to the surface of the photoconductor 101 are removed by the cleaning member 1.
06.

The charging by the charging roller 102, which is a contact-type charging means, is performed by
01, the charging is started by applying a voltage higher than a certain threshold voltage.
For example, a charging roller 102 is applied to a photoconductor 101 having a photoconductive layer made of an organic photoconductor having a thickness of 25 μm on the surface.
When the charging process is performed by applying pressure to the charging roller 102, the surface potential of the photoconductor 101 starts to increase by applying a voltage of, for example, 640 V or more to the charging roller 102, and thereafter, the applied voltage is Photoreceptor 1 linearly at a predetermined inclination
01 surface potential increases (hereinafter, this threshold voltage is defined as charging start voltage Vth).

As described above, in order to obtain the photoconductor surface potential Vd required for electrophotography, the charging roller 102 needs to have a voltage Vd (photoconductor surface potential) + Vth (charging start voltage) which is higher than the required voltage. DC (direct current) voltage is required.
As described above, a system in which only the DC voltage is applied to the charging roller 102 serving as a contact-type charging unit to charge the photosensitive member 101 is referred to as a DC charging system.

In this DC charging system,
The resistance of the charging roller 102 fluctuates due to environmental fluctuations and the like,
Further, it is difficult to make the potential of the photoconductor 101 a desired value because the thickness of the photoconductive layer changes due to the shaving of the surface of the photoconductor 101 and the charging start voltage Vth fluctuates. For this reason, in order to further uniform the charging, the DC voltage corresponding to the desired photoconductor surface potential Vd is reduced to 2%.
× AC having a peak-to-peak voltage equal to or higher than the charging start voltage Vth
An AC charging method has been proposed in which an oscillating voltage on which an (AC) component is superimposed is applied to a charging roller 102 serving as a contact-type charging means to charge the photosensitive member 101 (for example, an AC charging method).
JP-A-63-149669, etc.).

This AC charging system aims at a leveling effect of the potential caused by AC, and the potential of the photosensitive member 101 converges on the photosensitive member surface potential Vd which is the center of the peak of the AC voltage, thereby reducing the environmental potential. It is not affected by external disturbances. However, even in this AC charging system, the essential charging mechanism uses a discharging phenomenon from the charging member (charging roller) to the photoconductor, and therefore, as described above, the voltage required for charging is the same as that of the photosensitive member. Values above body surface potential are required,
A small amount of ozone is generated.

For this reason, as a new charging method, a charging method by directly injecting electric charge into a photosensitive member has been recently proposed (for example, Japanese Patent Application Laid-Open No. 6-3921). In this charging method, a voltage is applied to a contact charging member such as a charging roller, a charging brush, or a charging magnetic brush, and a charge is injected into a charge holding member such as a trap level or conductive particles on the surface of the photoreceptor, and the contact injection charging is performed. How to do.

In this charging system, since the discharge phenomenon is not dominant, the voltage required for charging is only the desired photoconductor surface potential and no ozone is generated. Further, as the contact charging member, a magnetic brush charger using magnetic conductive particles is preferable because it can closely contact the photoconductor.

Further, in recent years, for the purpose of downsizing the apparatus, there is an image forming apparatus without the above-mentioned cleaning member or a structure without a cleaner container for storing toner (developer) remaining after transfer. In this case, by attaching a brush-like scattering member for scattering the residual toner after the transfer on the photosensitive member in front of the charging member, the residual toner after the transfer is prevented from affecting the image.

[0011]

By the way, in the image forming apparatus of the charging type by direct injection of electric charges using the above-mentioned magnetic brush charger, the above-mentioned scattering member is provided near a charging member such as a magnetic brush charger. In this case, when a magnetic material is used in the dispersing member, a magnetic field is formed between the magnetic pole that restricts the magnetic particles constituting the charging brush as the charging member and the magnetic material in the distributing member.

For this reason, the magnetic particles constituting the charging brush, which is a charging member, are constrained by the above-described magnetic field, and the contact area between the charging member and the photoreceptor is reduced. The problem of lowering occurs.

Therefore, the present invention provides a magnetic brush charger,
In an image forming apparatus having a dispersing member for dispersing the residual toner after transfer, a magnetic field is formed between a magnetic pole constraining magnetic particles constituting a charging brush charger and a magnetic material in the dispersing member, It is an object of the present invention to provide an image forming apparatus capable of preventing magnetic particles of a charging brush charger from being attracted to a scattering member and obtaining good charging properties.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has magnetic particles on a surface which comes into contact with or contacts an image carrier and charges the image carrier by applying a voltage. A magnetic brush charger, and after transferring a toner image obtained by developing the electrostatic latent image formed on the surface of the image carrier, removes residual toner adhering to the surface of the image carrier after transfer of the toner image. An image forming apparatus provided with a dispersing member for dispersing the light from the non-magnetic member.

Further, the dispersing member includes a brush made of a number of elongated non-magnetic fibers having a tip end in contact with the surface of the image carrier, and a non-magnetic support member for fixing and supporting the other end of the brush. It is characterized by being composed.

[0016] Further, the invention is characterized in that the dispersing member is disposed on the upstream side in the rotation direction of the image carrier with respect to the magnetic brush charger.

(Function) According to the structure of the present invention, the dispersing member for dispersing the residual toner after transfer from the surface of the image carrier is formed of a non-magnetic material, so that a magnetic field is provided between the magnetic brush charger and the dispersing member. Is prevented from being formed. Therefore, since the magnetic particles of the magnetic brush charger are not attracted to the scattering member, a decrease in the charging contact surface between the magnetic particles contributing to charging and the image carrier can be prevented, and poor charging can be prevented. .

[0018]

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

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention. This image forming apparatus includes:
The image forming apparatus includes a rotating drum type photosensitive member 1 serving as an image carrier, a magnetic brush 2 serving as a contact charging member, a developing device 3, a transfer roller 4, a scattering member 5, a fixing device 6, and an exposure device (not shown). , The magnetic brush 2, the developing device 3, and the scattering member 5 are included in the cartridge 7.

The photoreceptor 1 has a diameter of, for example, 30 mm and has a photoconductive layer (not shown) made of an organic photoconductor on the surface, and is rotated in the direction of arrow A at a predetermined process speed. The magnetic brush 2 is a contact charging unit that comes into contact with the surface of the photoconductor 1, and a direct current (DC) bias voltage is applied by a power supply 8.

The magnetic brush 2 includes a non-magnetic rotatable charging sleeve 2a, a magnet roll 2b fixed in the charging sleeve 2a, and magnetic conductive particles 2c on the charging sleeve 2a. The surface is rotationally driven at a speed of almost 100% of the speed of the photoconductor 1 in a direction opposite to the rotation direction of the photoconductor 1 (direction of arrow A). In the present embodiment, the average particle diameter of the magnetic conductive particles 2c is 30 μm, the volume resistance is 1 × 10 ⁷ Ωcm, the maximum magnetization is 60 Am ² / kg,
Ferrite particles having a density of 2.2 / cm are used.

When the distance between the charging sleeve 2a and the surface of the photosensitive member 1 is 500 μm and the amount of magnetic conductive particles (ferrite particles) on the charging sleeve 2a is 10 g, the magnetic conductive particles are Photoconductor 1 between
A contact surface having a width of about 2 mm is formed in the rotation direction. Further, since the magnetic brush 2 is rotating at a peripheral speed with respect to the photoreceptor 1, a particle pool having a width of about 3 mm is formed on the upstream side in the rotation direction of the charging sleeve 2a. Is about 5 mm.

The electric resistance of the magnetic brush 2 was measured by using an aluminum drum in place of the photoreceptor 1 and applying a voltage to the magnetic brush 2 to measure the amount of current flowing at that time. When DC100V was applied to the brush 2, the value was 5 × 10 ⁶ Ω.

The developing device 3 is a reversal developing device in which a magnet 3c is contained in a non-magnetic developing sleeve 3b having a diameter of, for example, 16 mm, and a developing bias voltage is applied from a power source 9 to the developing sleeve 3b. Reference numeral 3a denotes a toner which is a non-magnetic one-component insulating developer having a negative chargeability and an average particle diameter of 7 μm.

The transfer roller 4 is a medium-resistance contact transfer unit that comes into contact with the surface of the photosensitive member 1, and a transfer bias voltage is applied by a power supply 9. In this embodiment, the transfer roller 4
Is 5 × 10 ⁸ Ω.

The dispersing member 5 is arranged on the upstream side in the rotation direction of the photosensitive member 1 with respect to the magnetic brush 2, and the residual toner adhering to the surface of the photosensitive member 1 after transfer is transferred to a stainless steel supporting member 5a as a non-magnetic member. It is constructed by winding a brush 5b made of non-magnetic material such as rayon and medium resistance fiber (fur) made of carbon fiber into a base fabric and folded into a pile shape. In the present embodiment, the brush 5b
The length is 6 mm, the density is about 100,000 pieces per 1 cm 2, the distance between the support member 5 a and the photoreceptor 1 is set to about 5 mm, and the tip of the brush 5 b is in contact with the surface of the photoreceptor 1. ing.

The fixing device 6 is a heating and fixing means for heating and fixing the transfer material P having the toner image transferred onto the surface thereof, and has a fixing roller 6a and a pressure roller 6b.

Next, the operation of the image forming apparatus 1 will be described.

At the time of image formation, the photosensitive member 1 is rotationally driven by a driving means (not shown) at a predetermined process speed (for example, 94 mm / sec) in the direction of arrow A. At this time, a DC bias voltage of, for example, -730 V is applied from the power supply 16 to the magnetic brush 2 to charge the surface of the photoconductor 1 to a negative polarity.

Then, an image exposure L by a laser beam is given to the charged surface of the photoreceptor 1 from an exposure device (not shown), and the charge of the image portion is removed in accordance with the input image information. A latent image is formed. The electrostatic latent image on the surface of the photoconductor 1 is developed as a toner image by applying a negatively charged toner 3a having the same polarity as that of the electrostatic latent image to the developing sleeve 3b by a reversal developing method in a developing device 3. . At this time, the developing bias voltage applied to the developing sleeve 3b from the power supply 9 is a DC voltage of -500V and a frequency of 1800H.
z, a rectangular AC voltage having a peak-to-peak voltage of 1600 V is superimposed, and one-component jumping development is performed between the developing sleeve 3 b and the photoconductor 1.

When the toner image on the surface of the photosensitive member 1 reaches the transfer nip portion T between the transfer roller 4 and the photosensitive member 1, a transfer material P such as paper is conveyed to the transfer nip portion at this timing. Then, a positive charge is applied to the back side of the transfer material P by the transfer roller 12 to which a transfer bias voltage (for example, a DC voltage of 2000 V) is applied from the power supply 10, and the toner image on the surface of the photoconductor 1 is transferred to the front side. Is done. The transfer material P to which the toner image has been transferred is conveyed to the fixing device 6, where the transferred toner image is fixed on the transfer material P as a permanent fixed image and discharged.

On the other hand, on the surface of the photoreceptor 1 after the transfer of the toner image, residual toner and other deposits remaining after transfer are adhered to the surface, and these are transferred by the brush 5b of the scattering member 5 in contact with the surface of the photoreceptor 1. By being scattered from the surface of the photoreceptor 1, residual toner and other adhering substances are removed from the image exposure L
Is not shaded.

The support member 5 constituting the distribution member 5
Since a and the brush 5b are non-magnetic materials, no magnetic field is formed between the magnetic brush 2 and the scattering member 5, and a good chargeability can be obtained stably.

Next, in order to confirm the effect of the non-magnetic dispersing member 5 of the image forming apparatus described above, a supporting member 5a of the dispersing member 5 is formed of a metal having magnetism for a comparative example. And the state of charge on the surface of the photoreceptor 1 was compared.

In a comparative image forming apparatus in which the supporting member 5a of the scattering member 5 is made of a metal having magnetism, the magnetic brush 2 is used.
A magnetic field is formed between the magnetic pole of the magnet roll 2b and the support member 5b of the dispersing member 5, and the magnet roll 2b
A magnetic field is formed between the magnetic pole of the magnetic roll 2b and the support member 5b, and a magnetic force acts to restrain the magnetic conductive particles 2c between the magnetic pole of the magnet roll 2b and the support member 5b. Due to this magnetic force, the magnetic conductive particles 2c on the charging sleeve 2a were dispersed and stayed between the member 5 and the charging sleeve 2a, and the magnetic conductive particles 2c contributing to the charging contact surface were reduced. This allows
The charged contact surface becomes uneven, and the magnetic conductive particles 2c
When the chance of contact between the photoconductor 1 and the photoconductor 1 decreases, the charging ability for injection decreases, and poor charging occurs.

On the other hand, the support member 5 of the distribution member 5
In the image forming apparatus made of stainless steel that is not a magnetic material as in the present embodiment, a magnetic force that restrains the magnetic conductive particles 2c between the magnetic pole of the magnet roll 2b and the support member 5b of the scattering member 5 is generated. Since it does not work, the magnetic conductive particles 2c can move smoothly, so that the charged contact surface does not decrease and a good image free from poor charging can be obtained. . In addition, since the movement of the magnetic conductive particles 2c is smooth,
The charging contact surface can be made uniform, and the charging uniformity can be improved.

In the above-described embodiment, the charging method is an example of the injection charging method. However, the same effect can be obtained in the magnetic brush charging using the discharge.

In the present embodiment, stainless steel is used for the support member 5a of the distribution member 5, but other than this,
For example, a material having no magnetism or having a low magnetic susceptibility, such as a resin such as aluminum, glass fiber, carbon graphite, and polyphenylene sulfide, may be used.

Further, in this embodiment, the distribution member 5
Although a voltage is not applied to the power supply, a configuration in which a DC or AC voltage is applied is also possible.

[0040]

As described above, according to the present invention,
By forming the dispersing member for dispersing the residual toner after transfer from the surface of the image carrier with a non-magnetic material, no magnetic field is formed between the magnetic brush charger and the dispersing member. By preventing the magnetic particles from being attracted to the scattering member, the charging contact surface between the magnetic particles contributing to charging and the image carrier is not reduced, and good charging properties can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an image forming apparatus according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor (image carrier) 2 Magnetic brush (magnetic brush charger) 2a Charging sleeve 2b Magnet roll 2c Magnetic conductive particles (magnetic particles) 3 Developing device 4 Transfer roller 5 Dispersing member 5a Supporting member 5b Brush 6 Fixing device

Claims (5)

[Claims] A magnetic brush charger having magnetic particles on a surface of the image carrier that is in contact with or in contact with the image carrier and charges the image carrier by applying a voltage; and an electrostatic latent image formed on the surface of the image carrier. After the transfer of the toner image obtained by developing
An image forming apparatus comprising: a dispersing member for dispersing residual toner adhering to the surface of the image carrier from the surface of the image carrier; wherein the dispersing member is formed by a non-magnetic member. . 2. A dispersing member comprising: a brush made of a number of elongated non-magnetic fibers having a tip end contacting the image carrier surface; and a non-magnetic support member for fixing and supporting the other end of the brush. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 2, wherein said brush is formed of rayon and carbon fiber. 4. The image forming apparatus according to claim 2, wherein said support member is made of stainless steel. 5. The image forming apparatus according to claim 1, wherein the scattering member is provided upstream of the magnetic brush charger in a rotation direction of the image carrier.