JP2821771B2 - Color image forming equipment - Google Patents

Description

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

[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 according to the number of color separations of a document image on a photosensitive drum as an image carrier,
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 units that store color toners of different colors are arranged in the peripheral green of the photosensitive drum, Generally, the photosensitive drum is rotated several times,
The color image is obtained by developing the latent image on the photosensitive drum.

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]

In a color image forming apparatus using a photoreceptor belt, an image forming unit such as a charging unit, an image exposing unit, and a developing unit including a plurality of developing units is provided in a peripheral green portion of the photoreceptor belt. The image forming means is opposed to the rotating photosensitive belt with a certain gap.

As a means for opposing the image forming means to the photoreceptor belt while keeping a constant interval, a method of using a backup roller and opposing the image forming means by the backup roller has been adopted.
However, when a backup roller is used, many rollers are required by arranging backup rollers in a number corresponding to the image forming means. Also, when the number of rollers is large, it is also difficult to maintain the parallelism with the above-mentioned rotating roller. Further, as disclosed in Japanese Patent Application Laid-Open No. 57-34576, there has been proposed a device for facing a photosensitive belt on a guide member, but it is difficult to maintain the interval by such a device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a color image forming apparatus using a photoreceptor belt in which an image forming unit accurately opposes a photoreceptor belt with a set gap and obtains a good image.

[Configuration of the invention]

The above object has a guide member between two rotating rollers and the rollers, and a plurality of belt members are stretched between the rotating rollers and are provided on a peripheral green of a belt-shaped image forming body that moves while rubbing with the guide members. In a color image forming apparatus in which an image forming unit including a developing unit is opposed to and disposed, the guide member has a plurality of radius of curvature, and the image forming unit is provided to face the radius of curvature, The curvature of the radius of curvature portion is set to be smaller than the curvature of the belt-shaped image forming body on the side that slides and moves by the guide member, and has a relief portion of the guide member between the curvature radius portions. The color image forming apparatus is characterized in that a gap is provided between the back surface of the image forming body and the guide member.

〔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 serving as a belt-shaped image forming member. The photoreceptor belt 1 is provided between rotating rollers 2 and 3 and is driven clockwise by driving the rotating roller 2. Transported to

Reference numeral 4 denotes a guide member fixed to the apparatus main body so as to be inscribed in the photoreceptor belt 1. The photoreceptor belt 1 is tensioned by a mechanical action above the tension roller 5 so that the inner peripheral surface thereof is formed. Is rubbed against the guide member 4.

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.

Reference numeral 6 denotes a scorotron charger as charging means, 7 denotes a laser writing system unit as image exposure means, and 8 to 11 denote a plurality of developing means or developing devices each containing a developer of a specific color. The means is disposed facing the outer peripheral surface of the photoreceptor belt 1 with the guide member 4 on the back.

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, and a blade 13A and a toner conveying roller 13B of the cleaning device 13 are kept at a position separated from the surface of the photoreceptor belt 1 during image formation. It is pressed against the surface of the photoreceptor belt 1 only during cleaning, as shown in the figure.

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 developed by a developing unit 8 loaded with yellow (Y) toner (a visual medium) in the developing means.
A toner image is formed on the drum surface. The toner image thus obtained passes under the cleaning device 13 as cleaning means separated from the peripheral surface of the photoreceptor belt 1 while being held on the drum 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 developed by the developing device 9 loaded with magenta (M) toner as the 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, which forms a cyan (C) toner image on the drum 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 belt surface by the same processing. A DC or further bias is applied to each sleeve of each of these developing devices 8, 9, 10 and 11, and a jumping development is performed by a two-component developer as a visualizing means, and a photosensitive member whose base is grounded The belt 1 is developed in a non-contact manner. As the development, non-contact development using a one-component developer can also be used.

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. Supplied to.

The transfer material that has undergone image transfer and static elimination is reliably separated from the photoreceptor belt 1, which suddenly changes direction along the rotating roller 2, and is directed upward, where the image is fused by the fixing roller 18 and then discharged. The paper is discharged onto a tray 20 via a paper roller 19.

On the other hand, the photoreceptor belt 1 after the transfer to the transfer material is further conveyed and the remaining toner is removed by the cleaning device 13 in which the blade 13A and the toner conveying roller 13B are pressed against each other. The blade
13A, and slightly after that, the toner supply roller 13B
After the toner accumulates on the tip of the blade 13A, the toner supply roller 13B is separated to start a new image forming process.

The guide member 4 has a conveying surface on which the photoreceptor belt 1 is slid in contact with one curved surface having a relatively large radius of curvature R,
Further, a plurality of curved surface portions having a radius of curvature r smaller than the radius of curvature R at a portion where the respective image forming means are opposed to each other on the curved surface.
Forming 4A.

The curved surface portion 4A is a developing sleeve 8A, 9A, 10A, 11 of each developing device.
A and six cylinders are provided corresponding to each part of the charger 6 and the exposure part of the laser optical system unit 7 facing each other,
The curved portions 4A are connected to each other with a plane slightly receding from the curved surface.

Therefore, the photoreceptor belt 1 comes into contact with the guide member 4 only at each of the tops of the curved surface portion 4A, and a reliable rubbing state with uniform pressing force is maintained. As a result, the photosensitive surfaces of the photoreceptor belts 1 facing each of the image forming means are always set correctly at a predetermined position, and even at the time of conveyance, the conveyance is smoothly carried out at a predetermined speed due to the effect of reducing the frictional resistance.

According to experiments, the radius of curvature r of the curved surface portion 4A is desirably at least 10 mm to 100 mm.
Is preferably 200 to 2000 mm. If the radius of curvature r is less than 10 mm, the contact surface lacks flatness, and the width (developing area or charged area) required for the image forming means cannot be secured. On the other hand, when the thickness is 100 mm or more, the flatness is sufficient, but the tension of the photoreceptor belt in the guide member direction is insufficient, and the photoreceptor belt is likely to float. On the other hand, if the radius of curvature R is less than 200 mm, the flatness of the photoreceptor belt is insufficient, and it is difficult to arrange the image forming means in parallel.
If the thickness is more than 2000 mm, the tension of the photoreceptor belt in the direction of the guide member is insufficient, and the photoreceptor belt is likely to float.

The guide member 4 is suitably manufactured by molding or extruding the respective curved surface portions 4A integrally. Alternatively, a flat plate having the respective curved surface portions 4A formed by sheet metal working is formed by adjusting the above-described radius of curvature R. It can also be used by mounting it curved.

FIG. 5 shows a cross-sectional shape of the guide member 4 having a curved surface portion. In FIG. 5 (a), each curved surface portion 4A is formed integrally with the guide member 4 by molding or extrusion. FIG. 5 (b) shows the case where the radii of curvature r and R are attached to the guide member 4 having the curved surface portion 4A by sheet metal working. FIG. 5 (c) shows a guide member having a radius of curvature R provided on a guide member having a radius of curvature R to form a curved surface portion 4A. Fig. 5 (d)
FIG. 5 (e) shows an example of a sectional view of a main part in which curved surfaces 4B, 4B 'are formed by using another member. The guide member 4 may be formed by sheet metal processing or resin processed. Good. The curved surface portions 4B, 4B 'may be made of a drawn metal material or a resin material.
It is fitted and fixed using an adhesive.

FIG. 3 shows the setting of the relative position of each image forming means to the photoreceptor belt 1 according to the present invention.
FIG. 3 (B) shows an essential part of the developing means as indicated by an arrow BB, and FIG. 3 (B) shows an image exposing means of an optical system having a convergent light transmitting body instead of a laser optical system. It is shown in FIG.

Backplate 6A in FIG. 3 (A) charger 6, 6B each electrode blocks attached to both ends of the back plate 6A, W ₁ is a wire electrode that is stretched between the electrode block 6B . W ₂ is the grid.

Each of the electrode blocks 6B is integrally formed with a projection 6C having a predetermined height as a contact member, and the charger 6 is configured such that each projection 6C is pressed against the guide member 4 outside the photoreceptor belt 1. It is urged by an elastic member 6D such as a leaf spring.

Thus the electrode wire W ₁ and grid W ₂ is always relative to the peripheral surface of the photosensitive belt 1 is located kept a certain distance, it is possible to reliably charge the photosensitive member to a predetermined potential.

In FIG. 3B, reference numeral 9A denotes a developing sleeve of the developing device 9, and 9B denotes an abutting roller serving as an abutting member. The abutting roller 9B is rotatably supported by a rotating shaft 9C of the developing sleeve 9A. Have been.

The abutting roller 9B is slightly larger than the developing sleeve 9A so that when pressed against the guide member 4, the circumferential surface of the developing sleeve 9A can form a gap corresponding to the developing gap between the outer circumferential surface of the photosensitive belt 1 and the developing sleeve 9A. It has a large outer diameter.

Therefore, the developing sleeve 9A forms a constant developing interval (0.3 to 1 mm) 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 and 10, and each of the built-in abutting rollers is pressed against the guide member 4 by a well-known urging mechanism.

The structure and function of each developing device will be described using the developing device 9 as an example.

FIG. 4 shows a cross section of the developing unit 9. Reference numeral 9A denotes a developing sleeve containing a fixed magnet roller, and a predetermined developing interval between the peripheral surface of the photoreceptor belt 1 and a coaxial abutting roller 9B. And is driven and rotated counterclockwise. Reference numeral 90A 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. 90B and 90C 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 by sufficiently stirring and mixing. .

The toner transport screw 90B and the toner transport screw 90C are members that also serve as a stirring member that rotates in directions opposite to each other, and the toner and the carrier transported to the back side by the thrust of the toner transport screw 90B are on the toner transport screw 90C side. The toner is transported to the near side of the drawing by the thrust, and is made into 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 sleeve 9A.

This developer layer adhered on the peripheral surface of the developing sleeve 9A to form a thin layer is used to transfer the latent image on the peripheral surface of the photoreceptor belt 1 conveyed clockwise in the development area at a distance of the above-described development interval. The toner image is formed by reversal development upon contact.

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 and is conveyed by the developing sleeve 9A to be scraped by the scraper 90D.
And the developer with a high toner ratio is mixed again.

On the other hand, reference numeral 70 shown in FIG. 3 (C) denotes an image exposure means, which is composed of an optical system in which a convergent light transmitting body 70A and a light emitting section 70B such as an LED are integrated, and the light emitting section 70B projects from both ends of the casing. As the member, a projection 70C having a predetermined height is integrally formed.

The optical system 70 is urged by an elastic member such as a leaf spring so that each of the projections 70C is pressed against the guide member 4 outside the photoreceptor belt 1 as in the case of the charger 6.

Therefore, the optical system 70 is also always kept at a constant interval with respect to the peripheral surface of the photoreceptor belt 1, so that an image can be accurately formed on the photoreceptor.

Further, since the image forming means does not come into contact with the photoreceptor belt 1, the vibration accompanying the movement of the photoreceptor belt does not affect the image forming means. Since the photoreceptor belt 1 does not come into contact with the image forming means, the photoreceptor belt 1 does not wear. Since the photoreceptor belt 1 does not come into contact with the image forming unit, the frictional resistance is small and the conveyance is easy.

Therefore, image shift and distortion due to the slip of the photosensitive belt 1 are prevented beforehand.

Further, regarding the photoreceptor belt 1, FIG.
(B) and (C), a pair of continuous guide rails 1A are integrally formed on the inner periphery thereof, and the guide rails 1A are engaged with the guide grooves 4B of the guide member 4, so that the guide rails 1A are likely to be generated during conveyance. The meandering of the photoreceptor belt 1 is prevented.

〔The invention's effect〕

The present invention enables a flexible belt-shaped image forming body used in an image forming apparatus to be accurately set at a predetermined position and to be conveyed at a stable speed. Thus, a compact color image forming apparatus capable of fully exhibiting the performance of the means and always obtaining a high quality color image has been provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a color image forming apparatus of the present invention, FIG. 2 is a block diagram showing an image forming system, FIG. 3 is a cross-sectional view of main parts of the apparatus, and FIG. . 5 (a) to 5 (e) show cross-sectional configuration diagrams of each curvature portion provided on the guide member. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor belt, 2, 3 ... Rotating roller 4 ... Guide member, 4A ... Curved surface part 6 ... Charger, 6B ... Electrode block 6C ... Projection 7 ... Laser writing system unit 8, 9,10,11… Developer 8A, 9A, 10A, 11A… Developing sleeve 9B… Abutting roller, 70… (for image exposure) optics 70A… Convergent light transmitter, 70B… Emission Part 70C …… Protrusion, R, r …… Radius of curvature

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-61-151561 (JP, A) JP-A-60-171906 (JP, A) JP-A-60-4971 (JP, A) JP-A 64-64 7092 (JP, A) JP-A 1-146266 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 21/00 340-360

Claims (1)

(57) [Claims] 1. A belt-like image forming body which has a guide member between two rotating rollers and said rollers, is stretched between said rotating rollers, and moves while sliding on said guide member. In a color image forming apparatus in which an image forming unit including a plurality of developing units is opposed to / arranged, the guide member has a plurality of radius of curvature, and the image forming unit is provided to face the radius of curvature, The curvature of the radius of curvature portion is set to be smaller than the curvature of the belt-shaped image forming body on the side that slides and moves by the guide member, and has a relief portion of the guide member while connecting the radius of curvature portions. A color image forming apparatus, wherein a gap is provided between the back surface of the belt-shaped image forming body and the guide member.