JP2759281B2 - 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 devices that store color toners of different colors are arranged on the periphery of the photosensitive drum. Rotates the photoconductor drum 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, image forming means such as a charging means, an image exposing means, and a developing means comprising a plurality of developing units are provided on a peripheral portion of the photoreceptor belt. The iso-image forming means faces the rotating photoreceptor belt with a certain gap.

As a means for opposing the image forming means to the photoreceptor belt while maintaining a constant interval, a method of opposing a backup roller by a 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. There is also a proposal by JP-A-60-102677.However, if the guide member and the photoreceptor belt are brought into contact over a wide range, the load on the photoreceptor belt increases, and slippage between the drive roller and the photoreceptor belt occurs. Will occur.

The present invention is directed to a color image forming apparatus using a photoreceptor belt such that a load on the photoreceptor belt is not excessively large and an image forming unit accurately opposes the photoreceptor belt at a predetermined interval to obtain a good image. The purpose is to provide.

[Configuration of the invention]

The above object has a guide member having a curvature between two rotating rollers and the rollers, and is provided between the rotating rollers and on a peripheral edge of a belt-shaped image forming body that moves while slidingly contacting the guide member. In a color image forming apparatus in which image forming means including a plurality of developing means are opposed to and arranged, the belt-shaped image forming body moves while slidingly contacting the guide member at a position facing the image forming means, and This is achieved by a color image forming apparatus characterized in that at a position not opposed to the guide member, the movable member faces the concave portion of the guide member and moves away from 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 in contact with the photoreceptor belt 1. The photoreceptor belt 1 is tensioned by the action of a tension roller 5 so that the inner peripheral surface thereof is guided by the guide member 4. To make sliding contact.

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 portion of the photoreceptor belt 1 which is in contact with the guide member 4.

As the laser writing system unit 7, in addition to the optical system shown in the figure, an optical system 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, and reference numeral 13 denotes a cleaning device. The blade 13A and the 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. As described above, the photosensitive belt 1 is pressed against the surface of the photosensitive belt 1.

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.

A developing unit 10 has a cyan (C) toner and 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 drum 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.

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 supply cassette 14 is carried out by the rotation of the paper supply roller 16 and is transferred to the transfer device by the timing roller 17 'in synchronization with the image formation on the photoreceptor belt 1. Supplied to 12.

The transfer material to which the image has been transferred is reliably separated from the photoreceptor belt 1 which suddenly changes its direction along the rotating roller 2 and heads upward. The image is fused by the fixing roller 18 'and then discharged. It is discharged onto the tray 20 via the rollers 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 transport roller 13B
And a new image forming process is started.

FIG. 3 shows the setting of the relative positions of the respective image forming means with respect to the photoreceptor belt 1. The charging means is shown in FIG. Fig. 3 (B) shows the main part with the BB section shown
FIG. 3 (C) shows an optical system having a convergent light transmitting body with a similar cross section with respect to the image exposure means.

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 device 9. 9A is a developing sleeve containing a magnet roller and a coaxial abutting roller.
9B, the photosensitive drum 1 is driven and rotated counterclockwise while maintaining a predetermined developing interval between the photosensitive belt 1 and the peripheral surface thereof. Reference numeral 19A is a rigid and magnetic thin layer forming member which is pressed against the developing sleeve 9A with a predetermined load in a state where no developer is interposed. 19
B and 19C 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 an upper developer by sufficiently stirring and mixing. .

The toner transport screw 19B and the toner transport screw 19C 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 rear side by the thrust of the toner transport screw 19B are on the toner transport screw 19C 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. Develop by contact to form a toner image.

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

The developer having consumed the toner component has a high carrier ratio and is conveyed by the developing sleeve 9A to be scraped by the scraper 19D.
And the developer with a high toner ratio is mixed again.

On the other hand, reference numeral 17 shown in FIG. 3 (C) denotes an image exposure means, which comprises an optical system in which a convergent light transmitting body 17A and a light emitting portion 17B such as an LED are integrated, and the light emitting portion 17B abuts on both ends of the casing. As a member, a projection 17C having a predetermined height is integrally formed.

The optical system 17 is urged by an elastic member such as a leaf spring in the same manner as in the charger 6 so that each of the protrusions 17C is pressed against the guide member 4 outside the photoreceptor belt 1.

Therefore, the optical system 17 is also always located at a constant distance from 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.

Further, when the photoreceptor belt 1 is conveyed, there is a possibility that the conveyability of the photoreceptor belt 1 may be reduced due to frictional resistance due to rubbing with the guide member 4, but in the present invention, the charging device 6, the optical system 17, and the developing devices Since the concave portion 4A is formed on the surface of the guide member 4 outside the mutually facing range of the developing sleeve, thereby avoiding the contact of the photosensitive belt 1, the frictional resistance is remarkably reduced, and the photosensitive belt 1 has a sufficient conveying force. Can be moved.

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

The area of the recess 4A is preferably provided between the developing units as shown in FIG. In the non-contact development used in the present invention, unlike the contact development, the force acting on the photoreceptor belt 1 is small, so that a wide concave area can be provided. The width at the position corresponding to the developing device where the concave portion 4A is not provided may be only the area required for development, and this width is 5 mm to 30 m.
m is good. If the width is too narrow, the developing width is not secured, and if it is too wide, the frictional resistance of the photoreceptor belt 1 is large, and the carrying capacity is reduced. In addition, it is effective to provide the region of the concave portion between the charging position and the exposure position, and between the exposure position and the developing device.

Further, regarding the photoreceptor belt 1, FIG.
As shown in (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.

FIG. 5 shows the setting of the relative position of the concave portion 4A with respect to the photoreceptor belt 1 to which the image forming means does not correspond, and the sectional direction is the same as that of FIG. FIG. 5 (A) shows a case where a portion of the guide member inside the guide rail 1A of the photoreceptor belt 1 forms a concave portion, and FIG. 5 (B) shows the inside of the guide rail 1A of the photoreceptor belt 1; The case where the guide member portion forms the concave portion 4A on the outside is shown. This improves the carrying capacity of the photosensitive belt and prevents the photosensitive belt 1 from meandering, which is likely to occur during the carrying.

〔The invention's effect〕

According to the present invention, even in a color image forming apparatus having a flexible belt-shaped image forming body, it is possible to convey the photosensitive belt at a stable speed by reducing the frictional resistance, thereby eliminating color shift and distortion. A compact color image forming apparatus capable of obtaining a high quality 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. . FIG. 5 is a sectional view of a concave portion of the guide member. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor belt, 2, 3 ... Rotating roller 4 ... Guide member, 4A ... Depression 6 ... Charger, 6B ... Electrode block 6C ... Projection 7 ... Laser writing system unit 8, 9 , 10,11… Developing unit 8A, 9A, 10A, 11A… Developing sleeve 9B… Abutting roller, 17… (Image exposure) optics 17A… Convergent light transmitting body 17B… Light emitting unit 17C …… Protrusion

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-151561 (JP, A) JP-A-60-171906 (JP, A) JP-A 1-146266 (JP, U) JP-A 62-151 109164 (JP, U)

Claims (2)

(57) [Claims] 1. A peripheral edge of a belt-shaped image forming member which has a guide member having a curvature between two rotating rollers and said roller, and is stretched between said rotating rollers and moves while slidingly contacting said guide member. Image forming means including a plurality of developing means
In the color image forming apparatus arranged, the belt-shaped image forming body moves while slidingly contacting the guide member at a position facing the image forming unit, and faces a concave portion of the guide member at a position not facing the image forming unit. A color image forming apparatus that moves away from the guide member. 2. A color image forming apparatus according to claim 1, wherein a contact member is provided between said image forming means and said guide member for abutting the two members.