JP2802789B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming method in which a toner image is formed on a belt-shaped image forming body by an electrophotographic method and is transferred onto a transfer material to obtain an image. Related to the device.

[Background of the Invention]

Many methods and apparatuses have been proposed for obtaining a color image using electrophotography. For example, as disclosed in JP-A-61-100770, a latent image is formed and developed on a photosensitive drum as an image forming body according to the number of separation colors of a document image,
There is a method in which a multicolor image is formed on a transfer drum by transferring the image on a transfer drum each time development is performed and then transferred onto a recording paper to obtain a color copy. In the apparatus according to this method, it is necessary to provide a transfer drum having a size capable of transferring one image on the peripheral surface in addition to the photosensitive drum, and the apparatus has a large and complicated structure. Inevitable.

Further, as disclosed in, for example, JP-A-61-149972, a latent image is formed and developed on a photosensitive drum in accordance with the number of separated colors of an original image, and is transferred onto a transfer material each time development is performed. This is a method of obtaining a multi-color copy. In this method, it is difficult to accurately superimpose multi-color images, and a high-quality color copy cannot be obtained.

In addition, there is a method in which a latent image is formed on the photosensitive drum in accordance with the number of separated colors of the original image and development with color toner is repeated, and a color image is obtained by superimposing and transferring a color toner image on the photosensitive drum. The basic process of this multicolor image formation is described in Japanese Patent Application Laid-Open Nos. 60-75850 and 60-76766 by the present applicant,
Nos. 60-95456, 60-95458, 60-158475 and the like.

In a multi-color image forming apparatus that obtains a color image by such superposition, a plurality of developing devices that store color toners of different colors are arranged on the periphery of the photosensitive drum. Rotates the photoconductor drum several times,
The latent image on the photosensitive drum is developed by a non-contact developing method to obtain a color image.

As for the image forming body, a belt-shaped image forming body in which a photoconductor is applied or mounted on a flexible belt together with a photosensitive drum having a photoconductor applied or deposited on the drum peripheral surface as described above. Has also been proposed. The shape of a belt-shaped image forming body (hereinafter also referred to as a photoreceptor belt) is determined by being stretched between rotating rollers including a driving roller.
This is effective when a compact color image forming apparatus is configured by effectively utilizing the space. In addition, since the photoreceptor belt can travel along a small curvature, the transfer material can be separated by using a small-diameter rotating roller and utilizing the curvature portion, thereby preventing transfer material separation failure and the like. it can.

[Object of the invention]

Such a photoreceptor belt is a thin sheet-shaped photoreceptor having a conductive layer sandwiched between a substrate and an organic photosensitive layer, and is used in an endless form. A ring-shaped one is used.

For this reason, a step corresponding to the thickness of the photoreceptor is inevitably generated at the bonding portion, and the toner in the developer is unnecessarily adhered to the step even by non-contact development. When the carrier adheres, the photoconductor is damaged at the time of cleaning.

The present invention solves this problem, and as a result, provides an image forming apparatus capable of obtaining a high-quality image without attaching unnecessary toner and carrier even by using a photoreceptor belt having overlapping end portions. It is intended.

[Configuration of the invention]

The above object is achieved by disposing a developing device that stretches a belt-shaped image forming body having a belt end portion stuck up and down between a plurality of rotating rollers and performs non-contact development on a peripheral portion of the belt-shaped image forming body. The gap (D) between the developer layer of the developing device and the belt-shaped image forming member is set to be larger than the belt thickness (t) of the belt-shaped image forming member. This is achieved by an image forming apparatus characterized in that a superimposed voltage of a voltage and an AC voltage is applied.

〔Example〕

One embodiment of the color image forming apparatus of the present invention is shown in FIGS.

In FIG. 1, reference numeral 1 denotes a flexible photoreceptor belt as a belt-shaped image forming member, and the photoreceptor belt 1 is bridged between a rotation roller 2 composed of a rubber roller and a rotation roller 3 composed of a metal roller. The paper is conveyed clockwise by the rotation of the rotation roller 2.

Reference numeral 4 denotes a guide member which is inscribed in the photoreceptor belt 1. The photoreceptor belt 1 is tensioned by the action of a tension roller 5 which is urged outward, so that the inner peripheral surface thereof is formed by the guide member. 4 rub.

Accordingly, the photosensitive member on the outer peripheral surface of the photosensitive belt 1 is always kept at a fixed relation to the surface of the guide member 4 even during the conveyance, so that a stable image forming surface can be formed.

6 is a scorotron charger as charging means, 7 is a laser writing system unit as image exposure means, and 8 to 11 are developing devices as a plurality of developing means each containing a developer of a specific color. Is disposed at a position opposing the guide member 4 of the photoreceptor belt 1. Then, in order to maintain the gap without hindering the movement of the photoreceptor belt 1, the guide member 4 is brought into contact with the guide member 4 outside the photoreceptor belt 1 with a gap holding means.

As the laser writing system unit 7, in addition to the optical system shown in the figure, an optical system or the like in which a light emitting unit and a converging light transmitter are integrated is used.

Each of the developing units 8, 9, 10, and 11 contains, for example, each of yellow, magenta, cyan, and black developers, and each developing sleeve that maintains a predetermined gap from the photosensitive belt 1.
8A, 9A, 10A, and 11A, and has a function of visualizing a latent image on the photosensitive belt 1 by a non-contact developing method. Unlike the contact development, the non-contact development has an advantage of not hindering the movement of the photosensitive belt.

Reference numeral 12 denotes a transfer unit, 12A denotes a static elimination bar, 13 denotes a cleaning device as cleaning means, and a blade 13A and a toner collecting roller 13B of the cleaning device 13 are kept at a position separated from the surface of the photosensitive belt 1 during image formation. It is pressed against the surface of the photoreceptor belt 1 as shown in FIG.

The process of forming a color image by the color image forming apparatus is performed as follows.

First, the formation of a multicolor image according to this embodiment is performed according to the image forming system shown in FIG. That is, the data obtained by the color image data input unit (FIG. 2A) in which the image sensor scans the original image is converted into an image data processing unit (2
The image data is created by performing arithmetic processing in FIG. 2B, and is temporarily stored in the image memory (FIG. 2C). Next, the image memory is taken out at the time of recording and inputted to a recording section (FIG. 2 (d)), for example, the color image forming apparatus shown in the embodiment of FIG.

That is, when a color signal output from an image reading device separate from the printer is input to the laser writing unit 7, the laser writing unit 7 generates a laser beam generated by a semiconductor laser (not shown). Is scanned by a polygon mirror 7B rotated by a drive motor 7A, the optical path of which is bent by mirrors 7D and 7E via an fθ lens 7C, and charged by a charger 6 as a charging means in advance. It is projected on the peripheral surface to form a bright line.

On the other hand, when scanning is started, the beam is detected by the index sensor, modulation of the beam by the first color signal is started, and the modulated beam is transmitted to the photosensitive belt 1.
Is scanned on the peripheral surface of. Therefore, a latent image corresponding to the first color is formed on the peripheral surface of the photosensitive belt 1 by the main scanning by the laser beam and the sub-scanning by the conveyance of the photosensitive belt 1. This latent image is reversibly developed in a non-contact state by a developing unit 8 loaded with yellow (Y) toner (visual image medium) of the developing means, and a toner image is formed on the belt surface. The obtained toner image passes under the cleaning device 13 as a cleaning means separated from the peripheral surface of the photoreceptor belt 1 while being held on the belt surface, and enters the next copy cycle.

That is, the photoreceptor belt 1 is charged again by the charger 6, and then the second color signal output from the signal processing unit is input to the writing system unit 7. Similarly, writing is performed on the drum surface to form a latent image. The latent image is reversely developed in a non-contact state by a developing device 9 loaded with magenta (M) toner as a second color.

The magenta (M) toner image is formed in the presence of the previously formed yellow (Y) toner image.

Reference numeral 10 denotes a developing device having cyan (C) toner, and forms a cyan (C) toner image on the belt surface based on a control signal generated by a signal processing unit. Further, reference numeral 11 denotes a developing device having a black toner, which forms a black toner image on the drum surface by the same processing. A DC or further AC bias is applied to each sleeve of each of these developing devices 8, 9, 10 and 11, and jumping development with a one-component or two-component developer as a developing means is performed.
Reversal development is performed on the photosensitive belt 1 whose base is grounded in a non-contact manner.

The color toner image thus formed on the peripheral surface of the photoreceptor belt 1 is transferred to a transfer material sent from the paper feed cassette 14 via the paper feed guide 15 at the transfer section.

That is, one of the uppermost layers of the transfer material accommodated in the paper feed cassette 14 is carried out by the rotation of the paper feed roller 16, and the transfer material is transferred to the transfer device 12 via the timing roller 17 in synchronization with the image formation on the photosensitive belt 1. Is supplied to the static elimination bar 12A.

The transfer material that has undergone image transfer and static elimination is surely separated from the photoreceptor belt 1 that suddenly changes its direction along the rotating roller 2 without being affected by image quality such as toner scattering due to the static elimination effect. After the image is fused by the fixing roller 18, the image is discharged onto the tray 20 via the discharge roller 19.

On the other hand, the photoreceptor belt 1 after the transfer to the transfer material is further conveyed to the cleaning device 13 in which the blade 13A facing the rotating roller 3 and the toner collecting roller 13B made of a rotating sponge member are pressed against each other. The remaining toner is removed, and after the end, the blade 13A is separated again, and a little later, the toner collecting roller 1 is removed.
3B is separated and a new image forming process is started.

The photoreceptor belt 1 has a base 1A made of PET (polyethylene terephthalate) having a thickness of 30 to 100 μm and a conductive layer
After coating the OPC layer 1C having a thickness of 10 to 30 μm comprising a charge generation layer and a charge transfer layer as a photoreceptor layer with 1B interposed therebetween, the entire thickness of the photoreceptor sheet having a thickness of about 0.1 mm is cut into a specific shape and then cut. The ends are bonded together to form a ring.
The OPC layer 1C is stretched outward with respect to the rotating rollers 2 and 3, and is circulated and transported in the direction of arrow A in an endless form.

In the moving direction of the photoreceptor belt 1, that is, in the direction indicated by the arrow A, the front end E1 of the belt is overlapped with the rear end E2 of the belt within a range of about 0.3 to 3 mm from the inside of the ring and connected by ultrasonic bonding.

On the other hand, each of the developing devices has the following structure.

FIG. 3 (A) shows a cross section of the developing device 9 and 9A is
A predetermined developing interval is maintained between the developing roller and the peripheral surface of the photoreceptor belt 1 by contacting the abutting rollers 9B provided on both sides on the same axis with the guide member 4 with a developing sleeve containing a fixed magnet roller. It is driven and rotated counterclockwise. Reference numeral 9C denotes a rigid and magnetic thin layer forming member which is pressed against the developing sleeve 9A with a predetermined load in a state where the developer is not interposed. 9D and 9E have a screw structure, and are a pair of toner conveying screws for conveying and circulating the developer in opposite directions to each other, and function to send the toner and the carrier to the developing sleeve 9A as the upper developer sufficiently stirred and mixed. .

The toner transport screw 9D and the toner transport screw 9E are members that also serve as a stirring member that rotates in opposite directions, and the toner and the carrier transported to the back side by the thrust of the toner transport screw 9D are on the toner transport screw 9E side. The toner is conveyed to the front side of the drawing by the thrust, and becomes a homogeneous developer triboelectrically charged by the mixing action of the toner and the carrier therebetween, and adheres in a layer on the peripheral surface of the developing screw 9A.

This layer of the developer adhered on the peripheral surface of the developing sleeve 9A becomes a thin layer in the course of passing through the thin layer forming member 9C, and the photosensitive layer 1 is conveyed clockwise in the developing area. The latent image on the surface is reversibly developed in a non-contact manner with a development interval therebetween to form a toner image.

During this non-contact development, a developing bias including an AC component in addition to a DC component is supplied from a power source (not shown) to the developing sleeve 9A.
As a result, only the toner in the developer is selectively transferred to and adhered to the surface of the latent image on the developing sleeve 9A.

The developer having consumed the toner component has a higher carrier ratio, is conveyed by the developing sleeve 9A, is separated and collected by the scraper 9F, and is mixed with the developer having the higher toner ratio again.

FIG. 3B shows a cross section taken along the line AA of the developing device 9 in FIG. 3A. In FIG. 3 (B), 9A is a developing sleeve of the developing device 9, 9B is a striking roller as a striking member, and the striking roller 9B is on both sides of the developing sleeve 9A and is freely rotatable about the rotation axis S. The bearing is supported.

When the abutting roller 9B is pressed against the guide portion 4, the circumferential surface of the developing sleeve 9A can form a gap corresponding to a developing interval of 0.2 to 1.0 mm between the circumferential surface of the developing sleeve 9A and the circumferential surface of the photosensitive belt 1. It has an outer diameter slightly larger than that of the developing sleeve 9A.

In the developing sleeve 9A, as shown in FIG. 4, the developer layer on the peripheral surface formed by the thin layer forming member 9C is larger than the thickness t of the photosensitive belt 1 with respect to the image forming surface of the photosensitive belt 1. The abutting rollers 9B are opposed to each other with a gap D therebetween.
The position is set by abutting on the guide member 4.

As a result, the developing sleeve 9A can transport the developer layer on the peripheral surface without contacting the step formed by the superposition of the photosensitive belts 1. That is, since the thickness of the photoreceptor belt is usually around 100 μm, the developing gap is set to have a gap of 100 μm or more. It is desirable that the value of the gap D be at least twice the thickness t, if possible.
Adhesion of toner and carrier to the step caused by the superposition of E1 and E2 is more reliably prevented.

Further, in order to perform development with a large development interval, it is preferable that the developing bias has an AC component in addition to a DC component to improve the developing performance. When the stepped portion passes through the developing area, when the developing sleeve is stopped, the developing bias applied to the developing sleeve 9A is switched to only the DC component or is floated. This makes it possible to more effectively prevent toner and carrier from adhering.

The edge of the belt rear end portion E2 is chamfered at an angle, and the conductive layer exposed at the chamfered portion is sealed with a high-resistance sealing material.

Thus, the developing sleeve 9A forms a fixed developing interval suitable for non-contact development between the developing sleeve 9A and the outer peripheral surface of the photoreceptor belt 1, and the developing device 9 can always perform an appropriate developing process. The same applies to the other developing devices 8, 10, and 11. Each of the built-in abutting rollers is pressed against the guide member 4 by a well-known urging mechanism, and development is performed in a stable state.

〔The invention's effect〕

According to the present invention, the developing device can be set while maintaining an appropriate developing interval between the belt and the photosensitive surface of the belt-shaped image forming body without attaching toner or carrier to the step formed by bonding the edges to the belt-shaped image forming body. As a result, an image forming apparatus capable of obtaining a high-quality image even when a belt-shaped image forming body using simple manufacturing means is used is provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus of the present invention, FIG. 2 is a block diagram showing an image forming system, and FIGS. 3 and 4 are cross-sectional views of a developing device of the above-described apparatus and main parts thereof. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor belt, 4 ... Guide member 6 ... Charging device 7 ... Laser writing system unit 8, 9, 10, 11 ... Developing device 8A, 9A, 10A, 11A ... Developing sleeve 9B ... Protrusion Roller, 9C: Thin layer forming member 9D, 9E: Toner transport screw 9F: Scraper, 12: Transfer unit 13: Cleaning device, E1: Belt end E2: Belt rear end

Continuation of the front page (56) References JP-A-63-279278 (JP, A) JP-A-58-125047 (JP, A) JP-A-63-10175 (JP, A) JP-A-63-231458 (JP, A) , A) Fully open 1987-60964 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 21/00 340-360 G03G 13/09 G03G 15/09-15/09 101

Claims (1)

(57) [Claims] 1. A developing device for stretching a belt-shaped image forming body having a belt end portion stuck up and down between a plurality of rotating rollers and performing non-contact development on a peripheral portion of the belt-shaped image forming body. The gap (D) between the developer layer of the developing device and the belt-shaped image forming member is set to be larger than the belt thickness (t) of the belt-shaped image forming member. An image forming apparatus for applying a superimposed voltage of a DC voltage and an AC voltage.