JPH03132679A - Color image forming device - Google Patents

Abstract

PURPOSE:To accurately oppose respective image forming means to a photosensitive belt with a set interval and to obtain an effective image by pressing and abutting a supporting body to/upon gap holding members attached to respective image forming means. CONSTITUTION:A guide member 4 is constituted by forming a carrying face to be slided on the photosensitive belt 1 as a curved face having a comparatively large radius R of curvature and holding plural movable members 4A having a radius (r) of curvature smaller than the radius R on parts opposed to respective image forming means 8 to 11 on the curved face so as to be projected. Respective members 4A are engaged with the groove parts of the member 4 through an elastic member 4B such as moltbren and press the belt 1 to the outside by the proper elastic force of the member 4B to make the belt 1 tensive state. Thereby the photosensitive face of the belt opposed to respective image forming means 8 to 11 is correctly set up on an always prescribed position and a color image with high quality can be always obtained.

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-like image forming member by an electrophotographic method and transferred onto a transfer material to obtain an image. The present invention relates to a forming device.

[Background of the invention]

There are many ways to obtain color images using electrophotography.
A device has been proposed. For example, JP-A-61-10077
As disclosed in Publication No. 0, a latent image is formed and developed in accordance with the number of separated colors of the original image on a photoreceptor drum serving as an image carrier, and each time the development is performed, the latent image is transferred onto a transfer drum. There is a method of forming a multicolor image on a paper and then transferring it onto recording paper to obtain a color copy. A device using this method requires a transfer drum large enough to transfer one sheet of image onto its circumferential surface in addition to the photoreceptor drum, and the device does not have a large and complicated structure. Inevitable.

For example, as disclosed in Japanese Patent Laid-Open No. 61-149972, a latent image is formed and developed on a photoreceptor drum according to the number of separated colors of the original image, and is transferred onto a transfer material each time it is developed. This is a method of obtaining multicolor copies. With this method, it is difficult to overlap multicolor images with high precision, and it is impossible to obtain high-quality color copies.

Another method is to repeatedly form a latent image on a photoreceptor drum according to the number of separated colors of an original image and develop it with color toner, and then overlap the color toner images on the photoreceptor drum and then transfer the images to obtain a color image. The basic process of forming a multicolor image is disclosed in Japanese Patent Application Laid-open No. 60-75850 and No. 60-7 by the present applicant.
No. 6766, No. 60-95456, No. 60-9545
No. 8, No. 60-158475, etc.

In a multicolor image forming apparatus that obtains a color image through such superimposition, a plurality of developing units containing different color toners are arranged around the periphery of the photoreceptor drum. The photoreceptor drum is rotated multiple times to develop the latent image on the photoreceptor drum to obtain a color image.

As for the image forming body, a photoconductor is coated or vapor-deposited on the circumferential surface of the drum as explained above, and a photoconductor is coated or deposited on a flexible belt along with the photoconductor drum. Image forming bodies have also been proposed. The shape of the belt-shaped image forming body (hereinafter also referred to as a photoconductor belt) is determined by stretching it between rotating rollers including a drive roller, so it is possible to effectively utilize space and create a compact color image forming apparatus. It is effective when configured. In addition, since the photoreceptor belt can run along a small curvature, it is possible to prevent poor separation of the transfer material by using a rotating roller with a small diameter and using this curvature to separate the transfer material. can.

[Purpose of the invention]

In a color image forming device using a photoreceptor belt,
Image forming means such as a charging means, an image exposure means, and a developing means consisting of a plurality of developing device groups are provided on the peripheral edge of the photoreceptor belt, and a certain gap is provided between the rotating photoreceptor belt and the second image forming means. They will face each other with

As a means for opposing the image forming means to the photoreceptor belt while maintaining a constant interval, a method has been adopted in which a backup roller is used and the image forming means is opposed to the photoreceptor belt. However, when backup rollers are used, many rollers are required because the number of backup rollers corresponds to the number of image forming means. Furthermore, when the number of rollers is large, it becomes difficult to maintain parallelism with the rotating rollers. Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 57-34576, a device has been proposed in which the photoreceptor belt is opposed to the photoreceptor belt on a guide member, but it is difficult to maintain the distance using such a device.

In the case of a drum-shaped photoreceptor, regarding the developing device that is the image forming means, a rotating roller is provided coaxially with the developing roller as a gap holding member, and the developing device is pressed against the drum-shaped photoreceptor. There is. However, when rotating rollers are used as gap-maintaining members for the photoreceptor belt and the rollers are brought into contact with the photoreceptor belt, the load during rotation of the photoreceptor belt increases, causing slips, etc. I don't like it.

The present invention provides a photoreceptor belt that does not increase the load on the photoreceptor belt that rotates unnecessarily, allows the image forming means to face the photoreceptor belt with a precisely set gap, and provides a good image. The object of the present invention is to provide a color image forming apparatus using the present invention.

[Structure of the invention]

The above object is a color image forming apparatus having a belt-like image forming member which is stretched between a plurality of rollers and rotates in sliding contact with a support, and a plurality of image forming means facing the belt-like image forming member. This is achieved by a color image forming apparatus characterized in that the support body is pressed by an elastic member and abuts against a gap holding member provided in each image forming means. Here, examples of the image forming means include a charger, an exposure device, and a developing device.

〔Example〕

An embodiment of a color image forming apparatus according to the present invention is shown in FIGS. 1 to 6.

In FIG. 1, reference numeral I designates a flexible photoreceptor belt as a belt-like image forming member, and the photoreceptor belt 1 is installed between rotating rollers 2 and 3, and is rotated clockwise by the rotational roller 2. transported to.

Reference numeral 4 denotes a support member or guide member fixed to the main body of the apparatus so as to be inscribed in the photoreceptor belt l, and the photoreceptor belt l is kept under tension by the upward mechanical action of the tension roller 5. The inner circumferential surface is rubbed by the guide member 4.

Therefore, the photoreceptors on the outer circumferential surface of the photoreceptor belt 1 are always maintained at a constant position relative to the surface of the guide member 4 even during conveyance, making it possible to form a stable image forming surface.

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

In addition to the optical system shown in the drawings, the laser writing system unit 7 may also include an optical system that integrates a light emitting section and a convergent light transmission body.

Each of the developing units 8.9.10.11 accommodates, for example, yellow magenta, cyan, and black developers, respectively, and each developing sleeve 8A, 9A, 10A maintains a predetermined gap with the photoreceptor belt l. , 11A, and has a function of visualizing the latent image on the photoreceptor belt l by a non-contact development method. This non-contact development is different from contact development,
It has the advantage of not interfering with the movement of the photoreceptor belt.

12 is a transfer device; 12 is a static elimination bar; 13 is a cleaning device; the blade 13A and toner conveying roller 13B of the cleaning device 13 are kept at a position apart from the surface of the photoreceptor belt l during image formation; Only during cleaning, it is pressed against the surface of the photoreceptor belt 1 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. In other words, the color image data input section (Figure 2 (a)) where the image sensor scans the original image.
) is processed by the image data processing section (FIG. 2 (b)) to create image data, which is then stored in the image memory (FIG. 2 (c)). Then, the image memory is taken out at the time of recording and sent to the recording section (FIG. 2 (d)).
For example, the image data is input to 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 system unit 7, the laser writing system unit 7 outputs a laser beam generated by a semiconductor laser (not shown). is rotated and scanned by a polygon mirror 7B rotated by a drive motor 7A, and passes through an fθ lens 7C to mirrors 7D and 7E.
The optical path is bent by this, and the light is projected onto the circumferential surface of the photoreceptor belt 1, which has been charged in advance by a charger 6, which is a charging means, 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 scans the circumferential surface of the photoreceptor belt l. Therefore, by main scanning by the laser beam and sub-scanning by conveying the photoconductor belt I, the photoconductor belt I is
A latent image corresponding to the first color is formed on the circumferential surface of -1. This latent image is created using yellow (Y) toner (
The toner image is developed by the developing device 8 loaded with a developing medium (developing medium), and a toner image is formed on the drum surface. The obtained toner image, while being held on the drum surface, passes under a cleaning device 13, which is a cleaning means 1, which is separated from the circumferential surface of the photoreceptor belt 1, 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 section is input to the writing system unit 7, and the second color signal is inputted to the writing system unit 7, and the second color signal is inputted to the writing system unit 7. In the same manner, writing is performed on the drum surface to form a latent image. The latent image is developed by a developing device 9 loaded with toner of magenta (CM) as the second color.

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

IO is a developing device having cyan (C) toner, and forms a cyan (C) toner image on the drum surface based on a control signal generated by a signal processing section.

Furthermore, 11 is a developing device having black toner, and forms a black toner image superimposed on the belt surface by the same process. These developing units 8, 9, 10 and 11
A direct current or even alternating current bias is applied to each sleeve, and jumping development is performed using a two-component developer as a developing means.
Development is now possible without contact. Incidentally, as the development, non-contact development using a -component developer can also be used.

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

That is, the top layer of the transfer material stored in the paper feed cassette 14 is carried out by the rotation of the paper feed roller 16, and transferred to the transfer device 12 via the timing roller 17 in synchronization with the image formation on the photoreceptor belt l. supplied to.

The transfer material that has undergone image transfer and static electricity removal is transferred to the rotating roller 2.
The image is reliably separated from the photoreceptor belt l, which suddenly changes direction along the direction, and moves upward, and after the image is fused by the fixing roller 18, it is ejected onto the tray 20 via the ejection roller 19.

On the other hand, the photoreceptor belt 1 that has completed the transfer to the transfer material continues to be conveyed to the blade 13A and the toner conveying roller 13B.
The remaining toner was removed in the cleaning device 13 which was brought into pressure contact with the blade 13A, and at the end of the process, the blade 13A was separated again by a ball, and a little later, the toner supply roller 13B smoothed out the toner accumulated on the tip of the blade 13A. Afterwards, the toner supply roller 13B is separated and a new image forming process begins.

The guide member 4 has a conveying surface on which the photoreceptor belt 1 slides, which is a curved surface with a relatively large radius of curvature R, and a portion of the curved surface that faces each of the image forming means has a curvature smaller than the radius of curvature R. A plurality of movable members 4A having a radius r are held in a projectable state.

Each of the movable members 4A is engaged with the groove of the guide member 4 through an elastic member 4B such as maltbren, and the photoreceptor bell l-1 is pressed outward by the appropriate elasticity of the elastic member 4B. This makes her nervous.

The movable member 4A is a developing sleeve 8A, 9 of each developing device.
A, IOA, IIA, and 6 parts for each part where the charger 6 and the exposure part of the laser optical system unit 7 face each other.
There are places set up.

Therefore, the photoreceptor bell l-1 comes into contact with the guide member 4 only at each top of the movable member 4A, and a reliable sliding condition is maintained due to uniform pressure contact. As a result, the photosensitive surfaces of the photosensitive belts l facing each image forming means are always correctly set at predetermined positions, and during conveyance, due to the effect of reducing frictional resistance, the images are conveyed smoothly at a predetermined speed.

On the other hand, in each developing unit, the relative position between the developing sleeve and the photosensitive surface of the photosensitive belt l is regulated by the pressure contact of the movable member 4A against a gap holding member described later, and as a result, a developing area with an appropriate gap is formed. is formed, and the above-mentioned non-contact development is performed.

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

Figure 3 shows the details of the developing device 9, and Figure 4 shows its arrow AA.
It shows a cross section.

In the figure, 9A is the developing sleeve containing the magnet roller, 9B is its rotating shaft, and developing sleeve 9A is the rotating shaft 9.
It is driven and rotated by the power system of the main body of the apparatus via the gear 9C at the end of the B axis in the same conveying direction as the photoreceptor belt 1, that is, in the counterclockwise direction in FIG. 3.

90A is a thin layer forming member having rigidity and magnetism and is pressed against the developing sleeve 9A with a predetermined load without the presence of developer. Reference numerals 90B and 90G are a pair of toner conveying screws having a screw structure and conveying and circulating the developer in mutually opposite directions, which function to send to the developing sleeve 9A as a positive developer in which toner and carrier are sufficiently stirred and mixed. .

The toner conveyance screw 90B and the toner conveyance screw 90G are members that also serve as stirring members that rotate in opposite directions, and the toner and carrier conveyed to the back side by the thrust of the toner conveyance screw 90B are transferred to the toner conveyance screw 90C. The toner is moved to the side and is conveyed to the front side of the drawing by the thrust, and the toner and carrier are mixed therebetween to form a homogeneous developer that is triboelectrically charged and adheres in a layer on the eight circumferential surface of the developing sleeve 9.

This developer layer, which forms a thin layer by adhering to the circumferential surface of the developing sleeve 9A, spreads the latent image on the circumferential surface of the photoreceptor belt 1, which is conveyed clockwise in the developing area, by the above-mentioned development interval. A toner image is formed by reversal development upon contact.

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

The developer that has consumed the toner components has a higher carrier ratio and is transported by the developing sleeve 9A to form a scrape/<9
It is peeled off and collected by 0D, and a developer with a high toner ratio is mixed again.

The developing device 9 has an abutting portion 91A having a predetermined height with respect to the developing sleeve 9A as a gap retaining member formed on the upper side of the front side of the developing container 91, and the abutting portion 91A has a predetermined height with respect to the developing sleeve 9A. In this state, each of the abutting portions 91A is placed in a position to receive pressure contact from the movable member 4A. The gap between the image forming sleeve 9A and the photosensitive surface of the photosensitive belt 1 is correctly set to a predetermined value.

Further, regarding the charger 6 and the image exposure means, the movable members 4 facing each other are similar to the developing sleeves of the respective developing devices.
By pressing A, the gap between the photoreceptor belt I and the photosensitive surface is set to a predetermined value.

In FIG. 5(A), 6A is a back plate of the charger 6, 6B is each electrode block attached to both ends of the back plate 6A, and W+ is an electrode wire stretched between the electrode blocks 6B. W2 is a grid.

Each of the electrode blocks 6B is integrally formed with a projection 6C having a predetermined height relative to the wire Wl as a gap maintaining member, and the charger 6 has each projection 6C connected to the guide member on the outside of the photoreceptor belt l. By being pressed by the movable member 4A of No. 4, the photoreceptor belt l is set at an accurate position relative to the photosensitive surface.

Furthermore, FIG. 5(B) shows an optical system 70 having a convergent light transmitter as an image exposure means in place of a laser optical system, and an optical system that integrates a convergent light transmitter 70A and a light emitting section 70B such as an LED. The light emitting part 70B is integrally formed with a projection 70C having a predetermined height as a gap maintaining member at both ends of the casing, and the movable member 4A of the guide member 4 is pressed against the projection 70C at the mounting position. As a result, a gap is formed on the photosensitive surface of the photoreceptor bell I-1 through which an accurate image can be formed by image exposure.

In FIG. 4, the developing container and the guide member 4 including the photoreceptor belt are constructed as separate bodies, and each can be attached and detached independently, but the process section including the photoreceptor and the developing device is integrated. It can also be configured to be detachable.

Although this embodiment has described an apparatus that forms a color image by four rotations of the photoreceptor belt, the present invention is also applicable to an image forming apparatus which forms a full color image by one rotation of the photoreceptor belt 501 as shown in FIG. It can also be applied to.

Such an image forming apparatus includes a plurality of chargers 110, 210, 310 for forming a latent image corresponding to each color in parallel with a plurality of developing devices 130, 230, 330, 430 containing toner of each color. 410 and a plurality of image exposure devices 1
Since the developing units 130, 230, 330, 420 are arranged at 20°, the guide member 504 has the developing units 130, 230, 330, 43
Four movable members 504A corresponding to 0 and the charger 110
, 210, 310, 410 and image exposure devices 120, 220
, 320.420, a total of eight movable members are provided, including four movable members 504B corresponding to each combination of
The position of the photosensitive surface of the photosensitive belt corresponding to each image forming means is set by pressing the respective gap holding members in the same manner as in the previous embodiment.

〔Effect of the invention〕

The present invention enables a flexible belt-like image forming body used in an image forming apparatus to be conveyed at a stable speed while being accurately set at a predetermined position, thereby allowing each image forming body to be conveyed at a stable speed. A compact color image forming apparatus has been provided which can fully utilize the performance of its means and consistently produce high quality color images.

[Brief explanation of the drawing]

1 and 6 are cross-sectional views of the color image forming apparatus of the present invention, FIG. 2 is a block diagram showing the image forming system, and FIG.
4 are sectional views of the developing device, and FIGS. 5(A) and 5(B) are sectional views of the charger and the image exposure optical system. l... Photoreceptor belt 4... Guide member 4A.
...Movable member 4B...Elastic member 6...Charger 7...Laser writing system unit 8.9.10.11...Developer 8A, 9A, IOA, IIA...Developing sleeve 90A... Thin layer forming member 90B, 90C... Toner conveying screw 90D...
・Scraper 91...Developer container 91A...Abutting portion (a) (b) (c) (d) Figure 3 Figure 5 (A) Figure 5 (B)

Claims (2)

[Claims] (1) In a color image forming apparatus having a belt-like image forming member stretched between a plurality of rollers and rotating in sliding contact with a support, and a plurality of image forming means facing the belt-like image forming member. . A color image forming apparatus, wherein the support body is pressed by an elastic member and abuts against a gap holding member provided in each image forming means. (2) The color image forming apparatus according to claim 1, wherein the image forming means is any one of a charger, an exposure device, and a developing device.