JPH0815967A - Development device - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To prevent the reversely charged toner generated by the friction between the toners from being placed on the toner layer of the first toner conveying means,
And reduce. A first toner carrying means for carrying a one-component toner on a surface and carrying it, and a toner amount controlling means for restricting a toner layer thickness on the first toner carrying means and frictionally charging the toner. In Fig. 30, when a bias is applied between the first toner conveying means and the toner amount regulating means, the bias applied to the first toner conveying means is Vd, and the bias applied to the toner amount regulating means is Vb. , And the relationship is set so that | Vd | ≦ | Vb |.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a digital multi-function peripheral, a laser printer, a facsimile and the like.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a two-stage developing system in which a conveyor belt 6 is formed between a photosensitive member 1 and a developing sleeve 4. The developing sleeve 4 is a roller having a magnetic field generation layer,
Toner is held on the peripheral surface. The doctor blade 5 having elasticity is in contact with this roller. The toner layer thickness of the toner 3 held on the peripheral surface of the developing sleeve 4 is regulated by the doctor blade 5 and frictionally charged together with the toner layer thickness.

The surface of the conveyor belt 6 is a roller having a dielectric layer, and forms a region of a predetermined area and is in contact with the developing sleeve 4 and the photosensitive member 1. The frictionally charged toner 3 is transferred and adhered from the developing sleeve 4 to the conveyor belt 6 by an electric force, and then transferred and adhered to a latent image portion of a photoconductor on which an image is formed by a latent image means (not shown). , Form a visible image.

[0004]

However, when the toner is triboelectrically charged by the doctor blade, the oppositely charged toner is generated due to the friction between the toners. The oppositely charged toner is held in a mixed state in the toner layer of the developing sleeve. Of the held toner, when the properly charged toner is transferred from the developing sleeve onto the conveyor belt by an electric force, the oppositely charged toner may be transferred and transferred as it is. Therefore, at the time of development, the properly charged toner is transferred to the latent image portion of the image carrier to form a visible image, but the oppositely charged toner is transferred and stains at portions other than the latent image portion. This is transferred as a background stain on the recording paper.

It is an object of the present invention to provide a developing device in which the oppositely charged toner generated by the frictional electrification of the toners is prevented from being placed on the developing sleeve and reduced.

[0006]

In order to achieve the above object, a developing device according to a first aspect of the present invention comprises a first toner carrying means for carrying a one-component toner on its surface and carrying the toner. (1) Toner amount regulating means that regulates the amount of toner conveyed by the first toner conveying means and charges the toner, and sucks the charged toner in contact with the first toner conveying means by an electric force. The first toner carrying means includes a second toner carrying means for transferring the toner to the surface and an image carrier for developing the charged toner transferred from the second toner carrying means to a visible image. When the bias voltage applied is Vd and the bias voltage applied to the toner amount regulating means is Vb, the relationship is | Vd | ≦ | Vb |.

[0007]

According to the structure described in claim 1, when the toner layer thickness on the surface of the first toner conveying means is regulated by the toner amount regulating means or when the toner is stirred in the toner reservoir,
Due to friction between the toner particles, oppositely charged toner particles are generated. When the oppositely charged (positively charged) toner is transferred and transferred when the properly charged (negatively charged) toner is transferred from the first toner carrying means to the second toner carrying means by an electric force. There is. Therefore, it is pre-determined that the oppositely-charged toner is not preliminarily placed on the first toner conveying means or is eliminated beforehand. For this reason, a bias means is applied between the toner amount regulating means and the first toner conveying means. Then, the potential difference of the bias means to be applied is set to the same potential or a high potential on the toner amount regulating means side, whereby the oppositely charged toner is removed at the tip portion 30a of the toner amount regulating means, and the toner amount is The oppositely-charged toner existing on the first toner-conveying means in the vicinity of the regulating means is sucked, and the charge before the charging is positively injected to positively convey the oppositely-charged toner. In addition to preventing the toner from riding on the means, the generation of reversely charged toner is also reduced.

Further, since the bias means is also provided between the first toner carrying means and the second toner carrying means,
It is possible to prevent double transfer of the oppositely-charged toner on the toner conveying means onto the second toner conveying means, and prevent double transfer. Therefore, it is possible to highly accurately reduce the reversely charged toner before the development.

[0009]

EXAMPLE An example of the present invention will be described.

FIG. 1 shows the configuration of an image forming apparatus according to an embodiment of the present invention. 10 is the device body,
It is composed of an upper structure 10a and a lower structure 10b.
The upper structure 10a is rotatably supported by the lower structure 10b by a shaft 11 so as to be openable and closable. Reference numeral 12 is an image carrier, around which a charging means 13, a developing device 14, a transfer means 15,
A cleaning unit 16 and an optical writing unit 17 for forming a latent image on the image carrier 12 are arranged. Reference numeral 18 denotes a paper feed cassette containing a recording paper P therein. The recording paper P is fed out by a paper feed roller 19 and is conveyed to the lower side of the image carrier 12 in synchronization with the registration means 20. The image carrier 12 rotates in the direction of arrow A, is uniformly charged by the charging unit 13, and then is irradiated with the laser beam from the optical writing unit 17 to form an electrostatic latent image. This electrostatic latent image is visualized by the toner of the developing device. The visible image of the toner is transferred by the transfer means 15 onto the upper surface of the recording paper conveyed to the lower side of the image carrier 12 and further fixed by the fixing means 21.

A toner cartridge 24 has a replenishment toner portion 24a and a waste toner portion 24b for storing the collected toner.
It is integrated with. The toner filled in the replenishment toner portion 24a is a one-component magnetic toner or a one-component high-resistance toner, which is sent to a toner carrying roller 26 by an agitator 25, where the developing device 14 a proper amount.
Is replenished to the toner reservoir 14b. The agitation replenishing member 27 of the developing device 14 replenishes the first toner conveying unit 28 with an appropriate amount of toner.

FIG. 2 shows the main structure of the developing device.

Reference numeral 28 denotes a first toner conveying means, which is a roller having a magnetic field generating layer on its surface. Reference numeral 30 denotes a toner amount control means, which is made of a conductive material having elasticity and is in contact with the first toner carrying means 28. 29 is the second
In the toner conveying means, a roller having a dielectric layer formed of conductive rubber or the like is used to maintain an appropriate contact amount and the first
The toner carrying means 28 is in contact with the image carrier 12.

The toner replenished to the toner reservoir 14b is replenished to the first toner conveying means 28 in an appropriate amount by the stirring replenishing member 27, and the first toner conveying means 28 is replenished.
Is attracted and held by the magnetism of the magnetic field generating layer. At this time, when the toner is agitated by the agitation replenishing member 27, some toner is charged to an appropriate polarity, and conversely, some toner is oppositely charged due to friction between the toners.

The toner held on the first toner conveying means 28 is regulated by the toner amount regulating means 30 on the toner layer thickness and charged to an appropriate polarity. In this embodiment, the charging polarity is negative, but at this time as well, there is friction between the toner particles and a small amount of the oppositely charged toner 33b (plus) is generated. In this way, when the toner is agitated by the agitation replenishing member 27, the toner layer 33 is regulated by the toner amount regulating means 30 and the oppositely charged toner 33b generated at the time of frictional charging is used as the toner amount regulating means 30. Bias means 31 is applied between the first toner conveying means 28,
Further, a predetermined potential difference indicating whether the potential between the toner amount regulating means 30 and the first toner conveying means 28 is the same potential or the potential of the toner amount regulating means 30 is higher than that of the first toner conveying means 28. Is applied so that the reversely charged toner 33b from the toner reservoir 14b is adsorbed by the tip portion 30a of the toner amount regulating means 30 and is removed so as not to flow into the toner layer 33. The reversely charged toner 33b generated at the time of frictional charging of the regulation means 30 is also sucked so as not to ride on the toner layer 33, and the toner layer 33 is reversely charged to the toner 33b.
Is reduced. The toner layer 33 is a thin layer having a thickness of ten and several μm or less.

A slight amount of the oppositely charged toner 33b on the first toner conveying means 28 which is not completely absorbed by the toner amount regulating means 30 is mixed in the toner layer 33 and transferred to the second toner conveying means 29. However, at this time, the first toner conveying means 28 and the second toner conveying means 2
Since the bias means 32 is applied between the first toner transport means 28 and the bias means 32, only the properly charged toner 33a is transferred from the first toner transport means 28 to the second toner transport means 29 by the electric force. The reversely charged toner 33b is less likely to transfer. Therefore, only the properly charged toner 33a is transferred to the second toner carrying means 29, and the oppositely charged toner 33b remains on the first toner carrying means 28 and is collected in the toner reservoir 14b, or the toner amount regulation is carried out again. It is in the form of being regulated by the means 30 and being triboelectrically charged to a proper polarity.

Further, the toner amount regulating means 30 is the first
When a bias (negative potential) higher than that of the toner conveying means 28 is applied, the toner amount regulating means 30 is applied.
The toner existing in the vicinity of can be charged with a proper polarity to some extent. Therefore, also from this point, it is possible to prevent generation of the reversely charged toner 33b.

Further, the toner amount regulating means 30 may be a thin plate made of metal or the like and provided with elasticity, for example, a stainless thin plate material (SUS301-CSP or 420J).
2).

[0019]

As described above, according to the first aspect of the invention, the amount of reversely charged toner is reduced by applying the same potential or a high bias to the toner amount regulating means as the first toner conveying means. Further, since the toner can be adsorbed (peeled off) on the toner amount regulating means, the amount of the oppositely charged toner on the first toner conveying means can be reduced. Further, since the oppositely charged toner is prevented from being transferred when transferred from there to the second toner conveying means, double selection can be achieved and high precision can be reduced. Therefore, at the time of development, a visible image without background stains and uneven density can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating an outline of an image forming apparatus.

FIG. 2 is a configuration diagram of a main part of a developing device of the present invention.

FIG. 3 is a sectional view showing a conventional example of a developing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photosensitive member 2 ... Developing device 3 ... Toner 4 ... Developing sleeve 5 ... Doctor blade 6 ... Conveying belt 7 ... Roller 12 ... Image carrier 13 ... Charging means 14 ... Developing device 14a ... Toner supply port 14b ... Toner reservoir 15 ... Transfer unit 16 ... Cleaning unit 24 ... Toner cartridge 24a ... Replenishment toner unit 24b ... Waste toner unit 25 ... Agitator 26 ... Toner transport roller 27 ... Agitation replenishment member 28 ... First toner transport unit 29 ... Second toner transport unit 30 ... Toner Quantity control means 30a ... Tip part 31 ... First bias means 32 ... Second bias means 33 ... Toner layer 33a ... Properly charged toner 33b ... Reversely charged toner

Front Page Continuation (72) Inventor Iwao Matsumae 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Hiroshi Hosokawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Manjiro Uno 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Hiroshi Saito 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Eiji Takenaka 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Company (72) Inventor Toshihiro Sugiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Company (72) Inventor Tetsuo Yamanaka Ricoh Co., Ltd. 1-3-3 Nakamagome, Ota-ku, Tokyo (72) Inventor Eisaku Murakami 1-3-6 Nakamagome-Chome Magome, Ota-ku, Tokyo (72) Inventor Satoru Komatsubara Ota-ku, Tokyo Nakamagome 1-3-6, Ricoh Co., Ltd.

Claims (1)

[Claims] 1. A first toner carrying means for carrying a one-component toner on its surface and carrying the toner, a toner amount of the toner carried by the first toner carrying means is regulated, and the toner is charged. And a first biasing means for applying a bias voltage to the first toner conveying means and the toner amount regulating means,
Second toner conveying means for contacting the toner conveying means and attracting the charged toner by electric force to transfer it to the surface, and the charged toner from the first toner conveying means to the second toner conveying means. A second bias means for transferring the toner and an image carrier for developing the charged toner transferred from the second toner carrying means to a visible image are provided, and the bias voltage applied to the first toner carrying means is Vd. The developing device is characterized in that when the bias voltage applied to the toner amount regulating means is Vb, the relation is | Vd | ≦ | Vb |.