JPH05173414A - Electrophotographic copying device - Google Patents

Abstract

PURPOSE:To prevent toner from being splashed because the toner leaked from the sealing parts of both ends of a developing roller is attached on the non- electrostatic charge area of a photosensitive body. CONSTITUTION:The toner can be attached on the place of the photosensitive body 11 whose surface potential V1 is V1>-600, for example. Then, the significant width S of the photosensitive body, that means, the width size of the photosensitive body 11 within a range that it can be stably electrostatically charged by an electrostatic charger and the effective width E of electrostatic charge, that means, the width size of the electrostatic charge range on the photosensitive body 11 which is electrostatically charged by the electrostatic charger are formed to be longer than the length of the developing roller, that means, the whole length of the developing roller 14a and the sealing parts 14b thereof are faced to the area of the effective width E of the electrostatic charge (V1=-900). Thus, even when the toner is leaked from the sealing parts 14b at the time of developing, it is prevented from being electrostatically attached on the photosensitive body 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer, a copying machine, a facsimile, etc., which uses a laser, and which records on a sheet such as paper or an envelope by repeating charging, exposure, development, transfer, cleaning and charge removal. Regarding photographic equipment.

[0002]

2. Description of the Related Art Conventionally, for example, a laser printer is shown in FIG.
As shown in FIG. 3, while rotating the photoconductor 1 substantially in the center of the apparatus main body, the surface of the photoconductor 1 is sequentially charged by the surrounding charger 2, and the exposure device 3 irradiates laser light to form an electrostatic latent image on the surface. Then
The electrostatic latent image is visualized by attaching toner to the developing roller 4a of the developing device 4, and the visible image is transferred to the sheet 6 by the transfer device 5.
After the image transfer, the surface of the photoconductor 1 is cleaned by the cleaning blade 7a of the cleaning device 7 and discharged by the charge eliminator 8. Then, the image formed on the photoconductor 1 is recorded on the sheet 6 by repeating these electrophotographic processes of charging, exposure, development, transfer, cleaning and charge removal.

In this conventional laser printer,
For example, as described with reference to FIG. 3, the dimensions related to the electrophotographic process are set as follows.

(1) First, a reference dimension is obtained as the maximum sheet passing width (maximum width dimension of the sheet 6 used as a recording medium) P of the printer, and is set to P = 216 mm, for example. (2) Based on this maximum sheet passing width P, the maximum sheet passing width P
The effective exposure width (width dimension of the exposure range on the photoconductor 1 which is exposed by the exposure device 3 to form an electrostatic latent image) is further increased. For example, L = 216 + α ₁ mm. Further, the effective developing width (width dimension of the developing range on the developing roller 4a where toner adheres to the exposure range on the photoconductor 1) D is also made larger than the maximum sheet passing width P. For example, D = 216 + α ₂ = 218 mm.

(3) Next, the total length (developing roller length) R of the developing roller 4a is determined on the basis of the effective developing width D.
In that case, the developing roller 4a is provided with seal portions 4b at both ends thereof for preventing toner leakage. Therefore, the developing roller length R becomes larger than the effective developing width D by the seal portion 4b. For example, R = 218 + α ₃ = 230 mm. Further, the effective charging width E, that is, the width dimension of the charging range on the photoconductor 1 charged by the charger 2 is also made larger than the effective developing width D. For example, E = 218 + α ₄ = 222 mm. Further, the effective cleaning width C, that is, the photoconductor 1
The longitudinal width of the cleaning blade 7a of the cleaning device 7 for cleaning the surface of is also larger than the effective developing width D. For example, C = 218 + α ₅ = 223 mm.

(4) The effective width S of the photosensitive member, that is, the widthwise width of the photosensitive member 1 in which stable charging by the charger 2 is possible, is made larger than the effective charging width E. For example, S = 222 + α ₆ .

In the above laser printer, when the electrophotographic process is repeated as described above, when the surface potential V ₁ of the photoconductor ₁ is charged by the charger 2 as shown in FIG. -90 in the range of width E
The voltage is set to 0V, and then, when the exposure is performed by the exposure device 3, it is set to −140V in the range of the exposed portion. Further, the developing potential V ₂ of the developing roller 4a is set to −400V. When developing with the developing device 4, the toner adheres to the photoconductor 1 from the developing roller 4a when V ₁ -V ₂ > -200V. That is, the photoreceptor 1 has a surface potential V ₁ of V ₁
Toner adheres to the part of> -600V. Therefore, within the range of the exposed portion, the surface potential V ₁ there is
Is −140 V, toner is attached and development is possible.
However, since the surface potential V ₁ there is −900 V, the toner does not adhere to the area within the effective charging width E of the unexposed portion.

[0008]

However, in the prior art, since the photoconductor potential V ₁ is 0 V in the non-charged area outside the effective charging width E, the toner is electrostatically charged due to the relationship of V ₁ > −600 V. It is in a state where it easily adheres. In this state, if the seal portion 4b of the developing roller 4a was not sufficiently sealed, the toner leaked to the seal portion 4b, and the leaked toner was electrostatically adhered to the non-charged regions on both ends of the photoconductor 1. Then, the toner drops by its own weight, or the photosensitive member 1
Due to the centrifugal force caused by the rotation of the roller, the particles are scattered and scattered, which causes various inconveniences such as soiling the device and the sheet 6 in the apparatus main body.

Therefore, an object of the present invention is to prevent the toner leaked from the seal portions at both ends of the developing roller from adhering to the non-charged area of the photosensitive member to cause toner scattering.

[0010]

Therefore, according to the first aspect of the present invention, for example, as shown in the following illustrated embodiments, the sheet formed by transferring the image formed on the photoreceptor 11 by charging, exposing and developing is transferred. In the electrophotographic apparatus for recording on No. 18, the photosensitive member effective width S is formed longer than the roller length R of the developing roller 14a, and the effective charging width E is formed.

According to a second aspect of the present invention, as shown in the following illustrated embodiment, for example, in the electrophotographic apparatus of the first aspect, the cleaning effective width C is formed to be longer than the developing roller length R. It is characterized by

[0012]

According to the first aspect of the invention, even if toner leaks from the seal portion 14b of the developing roller 14a during development, such leaked toner may not be transferred to the non-conductive member of the photoconductor 11. Prevents electrostatic attachment to charged areas.

According to the second aspect of the present invention, even if the leaked toner is electrostatically adhered to the photoconductor 11, the leaked toner is removed by the cleaning device 16 during cleaning.
Scrape off with.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an overall schematic configuration of an internal mechanism of a laser printer which is an embodiment of the present invention. Reference numeral 10 in the figure denotes the apparatus main body. A drum-shaped photosensitive member 11 that rotates clockwise in the drawing is provided in the center of the apparatus main body 10. Around the photoconductor 11, a charging device 12, an exposure device 13, a developing device 14, a transfer device 15, a cleaning device 16, and a static eliminator 17 are sequentially arranged in the rotation direction.

On the other hand, on the right side of the apparatus main body 10 in the drawing, paper feed cassettes 19 containing sheets 18 are detachably attached in two upper and lower stages. The registration roller pair 20 is arranged on the right side of the transfer device 15. On the other hand, on the side opposite to the registration roller 20 with the transfer device 15 interposed therebetween, the transport device 21.
The fixing devices 22 are arranged in order.

Therefore, in the illustrated laser printer, the sheet feeding rollers 23, 23 are appropriately selected and driven to drive the sheet 18
Are sent out from the paper feed cassette 19 one after another, and
Stop at La 20.

On the other hand, the surface of the photoconductor 11 is sequentially charged by the charger 12 while rotating clockwise in the figure, and the next exposure unit 1
In step 3, the laser light is irradiated to expose the latent image to form an electrostatic latent image on the surface. When the toner passes through the position of the developing device 14, toner is attached by the developing roller 14a to form the electrostatic latent image. Sequential development and visualization. Then, the registration roller 20 is driven in synchronization with the image to drive the sheet 18 to the photoconductor 11
Send it to. Then, the visible image on the photoconductor 11 is transferred onto the surface of the sheet 18 by the transfer device 15. After the transfer, the surface of the photoconductor 11 is cleaned by the cleaning device 16 and the charge is removed by the charge remover 17, while the sheet 18 is removed.
The transport device 21 sends it to the fixing device 22, and the fixing device 22 fixes the transferred image. Then, the sheet is discharged to the discharged stack section 26 through the sheet discharge path 25.

By the way, in FIG. 1, from the bottom in the figure,
The maximum paper passing width P and developing roller length R of this laser printer
The development effective width D, the exposure effective width L, the charging effective width E, the photosensitive member effective width S, and the cleaning effective width C are shown side by side, and their sizes are shown for comparison. In this laser printer, similarly to the above-described conventional case, first, the maximum sheet passing width P is set as a reference dimension, and the effective exposure width L of the photoconductor 11 and the effective developing width D of the developing roller 14 are larger than the maximum sheet passing width P. Form. Next, based on the effective development width D, the developing roller length R, the effective charging width E, and the effective cleaning width C are formed larger than the effective development width D. However, in this laser printer, as shown in FIG. 1, in particular, the effective width S of the photosensitive member is formed longer than the developing roller length R. Also, the effective charging width E is formed longer than the developing roller length R. Further, the effective cleaning width C is also formed to be longer than the developing roller length R.

Further, in the illustrated laser printer, when the electrophotographic process such as charging and exposure is repeated as described above, the photosensitive member potential V ₁ within the effective charging width E when charged is the same as in the conventional case. -900V, and then, when exposed to light, the photoconductor potential V ₁ in the range of the exposed portion is-
140V. Further, the developing potential V of the developing roller 14a
_{2 is set} to -400V. Then, at the time of development, the toner adheres to the surface of the photoconductor 11 when the photoconductor potential V ₁ is V ₁ > −600V.

In this laser printer, however, the photosensitive member effective width S and the charging effective width E are formed longer than the developing roller length R, and the seal portion 14b is formed in the area of the effective charging width E (V ₁
= -900).

Then, in the above laser printer,
Even if the seal of the seal portion 14b of the developing roller 14a is insufficient at the time of development and the toner leaks from the seal portion 14b, the leaked toner is prevented from electrostatically adhering to the photoconductor 11.

Further, in this embodiment, even if the leaked toner adheres to the photoconductor 11, the leaked toner is scraped off by the cleaning blade 16a shown in FIG. 1 at the time of cleaning.

[0023]

Therefore, according to the first aspect of the invention, the toner leaked from the seal portions at both ends of the developing roller during development is prevented from electrostatically adhering to the photosensitive member. It is possible to prevent various inconveniences such as sheet stains from occurring.

According to the second aspect of the present invention, even if the leaked toner may adhere from the seal portion to the non-charged area of the photoconductor, the adhered toner is scratched by the cleaning device during cleaning. Since it is dropped, it is possible to more reliably prevent the occurrence of such an inconvenience.

[Brief description of drawings]

FIG. 1 is a comparative explanatory diagram of dimensions related to an electrophotographic process in a laser printer which is an embodiment of the present invention.

FIG. 2 is an overall schematic configuration diagram showing an internal mechanism of the laser printer.

FIG. 3 is a comparative explanatory diagram of dimensions related to an electrophotographic process in a conventional laser printer.

FIG. 4 is a schematic explanatory view of the conventional laser printer.

[Explanation of symbols]

 11 photoconductor 18 sheet R developing roller length S photoconductor effective width E charging effective width C cleaning effective width

Claims (2)

[Claims] 1. An electrophotographic apparatus for recording an image on a sheet by transferring an image formed on a photosensitive member by charging, exposing and developing, and forming an effective width of the photosensitive member longer than a developing roller length, and charging effective. An electrophotographic device having a width. 2. The electrophotographic apparatus according to claim 1, wherein a cleaning effective width is formed longer than the developing roller length.