JP2001125447A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which can form an excellent image stably for a long period by effectively preventing toner having deteriorated in characteristics from entering a developing device as an image forming device which forms an image by a recycle system. SOLUTION: A refining mechanism comprises a stirring and mixing part 51 to which collected toner carried from a cleaning device is supplied, a magnet roller 52 which takes the collected toner out, and a normal electrostatically charged toner collection roller and a reverse electrostatically charged toner collection roller which are provided opposite the magnet roller; and the normal electrostatically charged toner collection roller is applied with a bias voltage having the opposite polarity from normal electrostatically charged toner to collect the normal electrostatically charged toner from on the magnet roller with an electrostatically attractive force and the reverse electrostatically charged toner collection roller is applied with a bias voltage having the same polarity with the normal electrostatically charged toner to collect reverse electrostatically charged toner from on the magnet roller with an electrostatically attractive force, so that the toner collected by the normal electrostatically charged toner collection roller is supplied into a developing device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
Related to an image forming apparatus such as a facsimile,
In particular, the present invention relates to an image forming apparatus employing a recycling system.

[0002]

2. Description of the Related Art In an image forming apparatus represented by a copying machine, the surface of a photosensitive drum is uniformly charged, and an electrostatic latent image corresponding to a document image is formed on the surface of the photosensitive drum by image exposure. The electrostatic latent image is developed to form a toner image on the surface of the photoconductor drum, and the toner image is transferred from the surface of the photoconductor drum onto a transfer material such as paper, and the transferred toner image is subjected to heat, pressure, or the like. By fixing, an image is formed.

In such an image forming apparatus, as a developer, a one-component magnetic developer composed of a magnetic toner,
A two-component magnetic developer composed of a toner and a magnetic carrier is widely used, and a developing device for performing development using such a magnetic developer usually includes a developing housing filled with a magnetic developer. The developer housing is accommodated in the developing housing so as to face the surface of the photosensitive drum. That is, the developer transfer sleeve has a structure in which a magnet having a plurality of magnetic poles is provided in a non-magnetic sleeve such as aluminum and the like. Area between the drum surface)
The development is performed.

Recently, from the viewpoint of resource saving and environmental friendliness, after a toner image is transferred onto a predetermined transfer material, the toner image is removed from the surface of the photoreceptor by a cleaning device such as a cleaning blade and collected. 2. Description of the Related Art An image forming apparatus employing a system for recycling and reusing toner in the above-described developing device has been widely used.

[0005]

In an image forming apparatus employing the above-mentioned recycling system, as the toner repeatedly circulates during the image forming process, the toner is aggregated under stress and the charging performance is reduced. Or
The original performance of the toner is gradually lost, and for example, the amount of the zero-charged toner or the oppositely-charged toner increases. Due to the toner having such reduced properties, toner scattering, reduction in image density,
Inconveniences such as fogging and toner dust in the image portion occur. Further, as the image forming process is repeated, paper dust generated from the transfer material (paper) is collected by the cleaning device, and the proportion of paper dust in the developer increases. Or the generation of the oppositely charged toner may be promoted.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus for forming an image in a recycling system, which effectively prevents the toner such as the above-mentioned reverse-charged or zero-charged toner or the like from deteriorating in characteristics and paper powder from being mixed in the developing device. Accordingly, it is an object of the present invention to provide an image forming apparatus capable of effectively solving problems such as toner scattering, reduction in image density, fog, and toner dust in an image portion, and stably forming a good image for a long period of time.

[0007]

According to the present invention, a toner image is formed by developing an electrostatic image formed on the surface of a photosensitive drum with a magnetic developer filled in a developing device. An image forming apparatus that transfers an image onto a predetermined transfer material, collects toner remaining on the surface of the photosensitive drum after transfer of the toner image with a cleaning device, and recycles the collected toner into the developing device. A purifying mechanism for the collected toner is provided in the middle of a path for conveying the toner collected by the device into the developing device, and the purifying mechanism includes a stirring and mixing unit into which the collected toner conveyed from the cleaning device is introduced. A magnet roller for taking out the collected toner introduced into the stirring and mixing section, a regular charged toner collection roller provided facing the magnet roller, and a reverse In the regular charged toner collecting roller, a bias voltage having a polarity opposite to that of the regular charged toner is applied, and the regular charged toner is collected from the magnet roller by electrostatic attraction. In the collecting roller, a bias voltage having the same polarity as that of the regular charged toner is applied, the oppositely charged toner is collected from the magnet roller by electrostatic attraction, and the toner collected by the regular charged toner collecting roller is transferred into the developing device. An image forming apparatus is provided.

In the present invention, a remarkable feature is that a toner purifying mechanism is provided in a transport path for recycling the toner collected from the surface of the photosensitive drum by a cleaning device including a cleaning blade into a developing device. is there. The toner refining mechanism includes a stirring / mixing unit into which the collected toner is introduced, a magnet roller for extracting the collected toner from the stirring / mixing unit, a regular charged toner collecting roller provided facing the magnet sleeve, and a reverse charging unit. And a toner collecting roller.

That is, in the stirring and mixing section, the collected toner is stirred and mixed, whereby the agglomerated toner is crushed, and the toner having a reduced charge amount such as a zero-charged toner is also sufficiently frictionally charged. Further, the collected toner sufficiently stirred and mixed in the stirring and mixing section is moved by a magnet roller.
Taken out. The magnet roller has a structure similar to that of a developer transfer sleeve provided in a developing device. A magnet having a plurality of magnetic poles is built in a non-magnetic sleeve such as aluminum.
By rotating the sleeve or rotating the magnet and fixing the sleeve, the collected toner is taken out on the magnet roller in the form of a magnetic brush. With the regular charged toner collection roller,
To this, a bias voltage having a polarity opposite to the charging polarity of the toner is applied, and regular charged toner is collected from the magnet roller by electrostatic attraction, and is conveyed into the developing device. In the oppositely charged toner collection roller, a bias voltage having the same polarity as the normal charge polarity of the toner is applied, and the oppositely charged toner is collected from the magnet roller by electrostatic attraction, and the collected oppositely charged toner is discarded. . In this way, in the image forming apparatus of the present invention provided with the toner refining mechanism, only the normally charged toner having a sufficient charge amount is collected from the collected toner, the oppositely charged toner is eliminated, and Since the toner such as a zero-charged toner having a reduced charging characteristic is charged again in the stirring and mixing section, there is no possibility that such toner is supplied into the developing device. Further, it is known that paper powder is generally negatively charged. Therefore, when a positively chargeable toner is used as the toner in the developer, paper dust is removed by the above-described reversely charged toner collection roller. On the other hand, when a negatively charged toner is used as the toner in the developer, the paper dust is collected by a regular charged toner collection roller and supplied to the developing device. Since the toner is charged to the same polarity as the normal toner, the influence on the image is extremely small, and there is almost no problem.

Preferably, the stirring and mixing section is filled with a magnetic developer in advance, so that the stirring and mixing of the recovered toner introduced little by little can be performed effectively and continuously. As the magnetic developer, either a one-component developer composed of a magnetic toner or a two-component developer composed of a non-magnetic toner and a magnetic carrier can be used. When used, it is particularly necessary to fill the two-component developer in the stirring and mixing section. In this case, the collected toner is non-magnetic and cannot be taken out by the magnet roller alone.

In the present invention, the stirring and mixing device provided in the stirring and mixing section is preferably a spiral, and a plurality of such spirals are arranged at an interval from each other along the coaxial direction with the magnet roller. In addition, it is preferable that the blades or the rotation directions of the adjacent spirals are set so as to convey the collected toner (developer) in the opposite directions. Thereby, the mixing and stirring of the collected toner can be performed reliably and effectively, and sufficient frictional charging can be achieved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to specific examples shown in the accompanying drawings. FIG. 1 shows an outline of the overall arrangement of an image forming apparatus of the present invention employing a recycling system, and FIG. 2 is a view showing a toner purification mechanism used in the image forming apparatus of FIG.

In FIG. 1, in this image forming apparatus, a main charging device 2, an exposure mechanism 3, a developing device 4, a transfer device are provided around a photosensitive drum 1 rotatably provided in the direction of the arrow in FIG. 5, the static elimination device 6, the cleaning device 7
The photosensitive drum 1 is arranged in this order along the rotation direction of the photosensitive drum 1, and paper or O 2 is placed between the photosensitive drum 1 and the transfer device 5.
A transfer material 10 such as an HP film is passed through, and a fixing device 11 is provided on a discharge path of the transfer material 10.

As the photosensitive drum 1, an inorganic photosensitive drum in which a photosensitive layer such as selenium or amorphous silicon is provided on a conductive base roller such as aluminum, or a charge generating agent or a charge transporting agent in a binder resin. An organic photosensitive drum provided with an organic photosensitive layer in which is dispersed is used. As the main charging device 2, there is a roller-type contact charging device, but generally, a corona charger is used, and the main charging device 2 causes the surface (photosensitive layer) of the photosensitive drum 1 to change the type of the photosensitive layer. , And is uniformly charged to a predetermined polarity. At this time, the main charging potential of the photoreceptor surface is usually 200 to 1000 V (absolute value). Next, the image exposure mechanism 3 irradiates the surface of the photoreceptor drum with dot light such as a laser beam corresponding to the original by reflected light of the original or an electric signal from a computer or the like. A latent image is formed, the electrostatic latent image is developed by the developing device 4, and a toner image 15 is formed on the surface of the photosensitive drum 1. The transfer device 5 generally includes a transfer charger 5a and a separating charger 5b, and the back surface of the transfer material 10 introduced between the transfer device 5 and the photosensitive drum 1 is transferred to the toner by the transfer charger 5a. The toner image 15 is transferred onto the transfer material 10 by an electrostatic attraction between the charge and the toner image 15 to form a transfer toner image 16. At the same time as the toner image 16 is formed, the transfer material 1 is charged with an alternating current by the separation charger 5b.
0 is quickly separated from the surface of the photosensitive drum 1. Note that a transfer roller can be used as the transfer device 5, and in this case, a transfer material separating device such as the separating charger 5a is not required.

The transfer material 10 having the transfer toner image 16 is
The transfer toner image 16 is conveyed to the fixing device 11 and is fixed on the surface of the transfer material 10 by heat, pressure or the like. On the other hand, after the toner image 15 is transferred onto the transfer material 10, the surface charge of the photosensitive drum 1 is removed by light irradiation by the charge removing device 6. Further, the toner remaining on the surface of the photosensitive drum 1 is scraped and collected by the cleaning device 7 having a cleaning blade or the like, and the next image forming process is performed. The toner collected in the cleaning device 7 is
Using a transport device such as a spiral, the toner is recycled to the developing device 4 according to the route indicated by 20, and is reused.

In the above-described image forming apparatus, the developing device 4 includes a developing housing 30 filled with a magnetic developer, and a developer conveying sleeve (developing sleeve) 31 faces the photosensitive drum 1. (The distance between the sleeve 31 and the drum 1 is generally 0.3 to 1.0.
mm). The developing sleeve 31 has a magnet having a plurality of magnetic poles fixed inside, and conveys the developer in the form of a magnetic brush by rotating the sleeve. That is, as shown in FIG. 1, the developing sleeve 31 rotates the photosensitive drum 1 in the opposite direction (moves in the same direction as the drum 1 in the region facing the drum 1, that is, moves downward from above). The magnetic brush 33 adjusted to have a fixed spike length by the spike blade 32 is applied to the photosensitive drum 1.
Is transported to the area (developing area) facing the.

As the developer, any of a two-component developer composed of a magnetic carrier and an insulating toner and a one-component developer composed of a magnetic toner can be used. A plurality of spirals or paddles 35 are provided in the developing housing 30 at a distance from the developing sleeve 31 so as to circulate and agitate the developer along the axis of the developing sleeve 31. It has become. By such circulating feeding and stirring, the toner uniformly mixed and frictionally charged to a predetermined polarity is conveyed in the form of a magnetic brush 33, and the toner causes the electrostatic latent image formed on the surface of the photosensitive drum 1 to be transferred. The toner image 1 is developed on the surface of the photosensitive drum 1
5 is formed. Toner, ie, toner image 15
The charge polarity of the photosensitive drum 1 is opposite to the charge polarity of the surface of the photosensitive drum 1 when image formation is performed by so-called regular development, and is opposite to the charge polarity of the surface of the photosensitive drum 1 when image formation is performed by reverse development. It has the same polarity as the charging polarity. In developing, generally, the photosensitive drum 1 and the developing sleeve 3
A bias voltage is applied between the two (normally about 100 to 300 V in absolute value in normal development and about 300 to 700 V in absolute value in reversal development).

In the image forming apparatus according to the present invention, a toner refining mechanism 50 is provided in the middle of the above-mentioned circulation path 20 of the collected toner. The structure of the toner purification mechanism 50 is
FIG. 2 shows an example in which a mixture of a positively charged non-magnetic toner and a magnetic carrier is used as a developer.

In FIG. 2, the toner refining mechanism 50
Roughly includes a mixing / stirring chamber 51, a magnet roller 52, a normally-charged (positively-charged) toner collection chamber 53,
And an oppositely charged (negatively charged toner) recovery chamber 54.

In the mixing and stirring chamber 51, a cleaning device 7 is provided.
Is introduced through the path 20 by a transport spiral or the like. The mixing and stirring device 51 is filled with a magnetic developer 60 composed of a positively charged toner and a magnetic carrier.
a, 61b and 61c are arranged substantially in parallel at intervals in the coaxial direction, so that the collected toner introduced into the mixing and stirring chamber 51 is mixed and stirred with the magnetic developer 60.

In FIG. 2, the spirals 61a and 61 are described with reference to the enlarged portion of the planar structure of the mixing and stirring chamber 51.
A guide plate 62 is arranged between 1b and 61c, and the adjacent spirals agitate and feed the magnetic developer 60 in directions opposite to each other. That is, the spiral 61a is provided so as to stir and feed the magnetic developer 60 in both end directions.
1b is provided so as to stir and feed the magnetic developer 60 in the center direction thereof, and the spiral 61c is provided so as to stir and feed the magnetic developer 60 in both end directions.
Therefore, the collected toner introduced into the mixing and stirring chamber 51 is
Spirals are sent from the spiral 61a to the spiral 61c via the spiral 61b through both ends or the center of each spiral. In this way, the collected toner is mixed and stirred with the magnetic developer 60, and the crushing of the aggregated toner and the triboelectric charging of the zero-charged toner are sufficiently performed.

A magnet roller 52 is disposed above the spiral 61c, and the collected toner that has been agitated and fed to the spiral 61c is a magnetic brush 63.
In the form of a magnet roller 52 together with the magnetic developer 60.
Taken out on top.

On both sides of the magnet roller 52, a normally charged (positively charged) toner collecting chamber 53 and a reversely charged (negatively charged) toner collecting chamber 54 are arranged. A conductive toner collecting roller 65 is provided in the normally charged toner collecting chamber 53 so as to face the magnet roller 52, and a collecting blade 66 is in contact with the roller 65. On the other hand, a conductive toner collecting roller 68 is provided in the reverse charge collecting chamber 54 so as to face the magnet roller 52, and a collecting blade 69 is in contact with the roller 68. That is, as is clear from FIG. 2, a negative bias voltage is applied to the collection roller 65 of the normally charged toner collection chamber 53, and the normally charged toner (positively charged toner) is discharged from the magnet roller 52 by electrostatic attraction. It is collected and collected by the blade 66. The collected positively charged toner is supplied into the developing device 4 via a toner supply hopper or a toner cartridge (not shown) through a path 20 by a conveying spiral or the like, or directly. A positive bias voltage is applied to the collection roller 68 in the oppositely charged collection chamber 54, and the oppositely charged toner (negatively charged toner) is collected from the magnet roller 52 by electrostatic attraction and collected by the blade 69. And discarded. Since paper dust is generally negatively charged, paper powder is also included in the oppositely charged toner.

As described above, by providing the toner refining mechanism 50, the toner is collected by the cleaning device 7,
The toner recycled into the developing device 4 hardly contains a toner having a reduced characteristic such as a zero-charged toner, and the oppositely-charged toner and paper dust are also effectively removed. In FIG. 2, the case where the positively charged toner is used as the developer is shown as an example. However, when the negatively charged toner is used as the developer, the collection roller 65 of the normally charged toner collection chamber 53 includes Apply a positive bias voltage,
A negative bias voltage may be applied to the collection roller 68 of the reverse charging collection chamber 54. In this case, the paper dust is collected in the normally-charged toner collection chamber 53 and supplied to the developing device 4, but is charged to the same polarity as the normally-charged toner (negatively-charged toner). Show behavior. That is,
The paper dust forms an image together with the normally charged toner, and is embedded in the transfer toner image on the transfer paper by fixing. Therefore, the presence of paper dust is hardly observed from the outside, and when negatively charged toner is used as a developer,
Even if paper dust is recycled into the developing device 4, there is almost no problem.

In the above-described present invention, the conductive toner collecting rollers 65 and 68 are formed of a conductive material such as a good conductor such as a metal or a conductive powder such as a metal powder or carbon black mixed in a resin or rubber. It is composed of rubber and the like. The bias voltage applied to these rollers is about 100 to 1 kV in absolute value.

[0026]

According to the present invention, by providing a toner refining mechanism having a predetermined structure in the circulation path of the recycled toner, a toner such as a zero-charged toner or the like, a reverse-charged toner, or a toner having a deteriorated charging characteristic, or a paper powder. Is effectively prevented from being mixed into the developing device, and scattering of toner, reduction in image density, fog, toner dust in an image portion, and the like are effectively prevented, and a good image can be stably formed over a long period of time.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of an overall arrangement of an image forming apparatus of the present invention employing a recycling system.

FIG. 2 is a diagram showing a structure of a toner purification mechanism which is a main part of the present invention used in the image forming apparatus of FIG.

[Explanation of symbols]

1: Photoreceptor drum 4: Developing device 10: Transfer material 15, 16: Toner image 20: Recycled toner circulation path 50: Toner purification mechanism 51: Mixing / stirring chamber 52: Magnet roller 53: Regularly charged toner collecting chamber 54: Reverse Charged toner collection chamber

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 21/00 310 (72) Inventor Masahiro Tsutsumi 1-2-28 Tamazo, Chuo-ku, Osaka Mita MFG Inside (72) Inventor Eiji Tanmura 1-2-28 Tamazo, Chuo-ku, Osaka-shi Mita Corporation (72) Inventor Shinji Kikuta 1-2-28 Tamazo, Chuo-ku, Osaka Mita Corporation (72) Inventor Joh Nanjo 1-2-28 Tamazo, Chuo-ku, Osaka-shi F-term (reference) 2M034 AA03 BF00 CB01 CB02 2H077 AA37 AC02 AC12 AC16 AD32 AE06 CA01 EA01

Claims (4)

[Claims] An electrostatic image formed on the surface of a photosensitive drum is developed with a magnetic developer filled in a developing device to form a toner image, and the toner image is transferred onto a predetermined transfer material. In the image forming apparatus, the toner remaining on the surface of the photosensitive drum after the transfer of the toner image is collected by a cleaning device, and the collected toner is recycled into the developing device. A purification mechanism for the recovered toner is provided in the middle of a path for transporting the collected toner. The purification mechanism includes a stirring and mixing unit into which the recovered toner conveyed from the cleaning device is introduced, and a collected and mixed toner introduced into the stirring and mixing unit. It consists of a magnet roller to be taken out, a regular charged toner collecting roller and a reversely charged toner collecting roller provided facing the magnet roller. In the regular charged toner collecting roller, a bias voltage having a polarity opposite to that of the regular charged toner is applied, and the regular charged toner is collected from the magnet roller by electrostatic attraction. A bias voltage of the same polarity is applied, the oppositely charged toner is collected from the magnet roller by electrostatic attraction, and the toner collected by the regular charged toner collection roller is supplied into the developing device. Image forming device. 2. The image forming apparatus according to claim 1, wherein the stirring and mixing section in the refining mechanism is previously filled with a magnetic developer. 3. The image forming apparatus according to claim 2, wherein a two-component developer composed of a mixture of a non-magnetic toner and a magnetic carrier is used as the magnetic developer. 4. A plurality of spirals extending along an axial direction of a magnet roller are provided at intervals in the stirring and mixing section, and adjacent spirals are provided with a developer or a collected toner in opposite directions. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to send an image.