JPH03132676A - Color image forming device - Google Patents

Abstract

PURPOSE:To obtain a satisfactory image by confronting an image forming means with a photosensitive belt with high accuracy and keeping a set gap by abutting each gap holding member provided coaxially with the developing roller of each developing device with the side terminal part of a supporting body by pressing with an elastic member. CONSTITUTION:The supporting body fixed at a device main body so as to be inscribed with the photosensitive belt 1, i.e. a guide member 4 is provided. The photosensitive belt 1 is set at a stretched state by the dynamic function of a tension roller 5 an in upper direction, and the inner peripheral plane of the belt is slided with the guide member 4. Thereby, a photosensitive material on the outer peripheral plane of the photosensitive belt 1 can be always kept at a constant position against the surface of the guide member 4 even while it is carried, and a stable image forming plane can be comprised.

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, Japanese Patent Publication No. 61100770
As disclosed in the publication, a latent image is formed and developed on a photosensitive drum, which is an image carrier, according to the number of separated colors of the original image, and is transferred onto a transfer drum each time it is developed. There is a method of forming a multicolor image 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.

Regarding image forming bodies, as explained above, there are photosensitive drums in which a photoconductor is coated or deposited on the drum surface, as well as belt-shaped image forming bodies in which a photoconductor is coated or mounted on a flexible belt. 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. Also, since the photoreceptor belt can run along a small curvature,
By using a rotating roller with a small diameter and separating the transfer material using this curvature, it is also possible to prevent poor separation of the transfer material.

[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

A method of using a backup roller to oppose the image forming means to the photoreceptor belt while maintaining a constant distance therebetween has been adopted.

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 photoconductor, the developing device facing the photoconductor is provided with a roller that rotates coaxially with the developing roller as a gap maintaining member to press the developing device against the drum-shaped photoconductor. . 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.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color image forming apparatus using a photoreceptor belt in which an image forming means faces the photoreceptor belt with a precisely set gap, and a good image can be obtained.

[Structure of the invention]

The above object is to provide 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 developing devices facing the belt-like image forming member. , achieved by a color image forming apparatus, characterized in that each gap holding member provided coaxially with the developing roller of each developing device is pressed against the side end of the support by an elastic member and abuts. Ru.

〔Example〕

An embodiment of the color image forming apparatus of the present invention is shown in FIGS. 1 to 4.

In FIG. 1, 1 is a flexible photoreceptor belt which is a belt-like image forming member, and the photoreceptor belt t-1 is installed between rotating rollers 2 and 3, and is driven by the rotating roller 2. Transported clockwise.

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 devices 8.9.10.11 accommodates, for example, yellow magenta, cyan, and black developers, respectively, and the developing sleeve 8A of each developing roller maintains a predetermined gap with the photoreceptor bell l-1. Equipped with 9A, IOA, lIA,
It has a function of visualizing the latent image on the photoreceptor bell l-1 by a non-contact development method. Unlike contact development, this non-contact development has the advantage of not interfering with the movement of the photoreceptor belt.

12 is a transfer device, 12A is a static elimination bar, 13 is a cleaning device, and 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 1 during image formation, and are cleaned after image transfer. Only when the photoreceptor belt 1 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 l, which has been charged in advance by a charger 6 serving as 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, a latent image corresponding to the first color is formed on the circumferential surface of the photoreceptor belt 1 by the main scanning by the laser beam and the sub-scanning by the conveyance of the photoreceptor belt 1. This latent image is developed by a developing device 8 loaded with yellow (Y) toner (developing medium) of the developing means, 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, which is separated from the circumferential surface of the photoreceptor belt 1, and enters the next copy cycle.

That is, the photoreceptor belt l is charged again by the charger 6, and then the second color signal outputted 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 developer 9 loaded with magenta (M) toner as a 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 devices 8, 9° IO 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, which is a developing means, and development is performed without contact on the photoreceptor belt l whose base is grounded. It has become. 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 bell l-1 is transferred to a transfer material fed from the paper feed cassette 14 via the paper feed guide 15 in 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 1. 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 the blade 13A was removed again after the cleaning was completed. 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 conveyance surface on which the photoreceptor belt l slides, and has a curved surface with a relatively large radius of curvature R, and further has a plurality of text portions 4A formed on the portions of the curved surface where the image forming means face each other. are doing.

The text portion 4A is the developing sleeve 8A, 9A of each developing device.

10A, IIA, and the exposed portions of the charger 6 and the laser optical system unit 7 are provided in six locations, and each text section 4A is connected by a plane that is slightly set back from the text section. .

Therefore, the photoreceptor belt 1 comes into contact with the guide member 4 only at each top of the text portion 4A, and a reliable sliding condition is maintained due to uniform pressing force. 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 device, the position of each developing sleeve is regulated by pressure contact of a later-described gap retaining agent against each text portion 4A, and as a result, a gap between each developing sleeve and the photosensitive surface of the photosensitive belt l is set. Then, 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 in the same conveying direction as the photoreceptor belt 1, that is, in the counterclockwise direction in FIG. 3, by the power system of the main body of the apparatus via the gear 9C at the end of the B axis.

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 90C are a pair of toner conveying screws that have a screw structure and transport and circulate the developer in opposite directions, and function to sufficiently stir and mix toner and carrier and send the resulting developer to the developing sleeve 9A. .

The toner conveying screw 90B and the toner conveying screw 900 are members that also serve as stirring members that rotate in mutually different directions, and the toner and carrier conveyed to the back side by the thrust of the toner conveying screw 90B are transferred to the toner conveying 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 circumferential surface of the developing sleeve 9A.

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 l, 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 alternating current component in addition to a direct current component is applied from a power source (not shown) to the nine developing sleeves, and only the toner in the developer is selectively transferred to the latent image onto the image sleeve 9A. It migrates and adheres to surfaces.

The developer whose toner components have been consumed has a higher carrier ratio and is transported by the developing sleeve 9A to the scraper 90.
It is peeled off and collected by step D, and then mixed with a developer having a high toner ratio again.

The toner conveying screws 90B and 90G are directly mounted and supported by the outer frame 91 that integrally accommodates each developing device, while the developing sleeve 9A, thin layer forming member 90A, and scraper 90D are mounted inside the outer frame 91(7). The installation is supported by a middle frame 92 that can slide up and down.

The middle frame 92 is a rectangular cylindrical container with an open top and bottom, and also serves as a gap retaining member with an abutting portion 92A having a predetermined height relative to the developing sleeve 9A formed at the upper part of the front and rear sides. It is constantly urged upward by the reaction force of the elastic member 93, that is, the compression spring 93, which is press-fitted between it and 91.

Therefore, the abutting portion 92A is the text portion 4A of the guide member 4.
is pressed against the outer side end of the photoreceptor belt 1, and the peripheral surface of the image forming sleeve 9A is correctly set at a predetermined position with respect to the photoreceptor surface without causing any hindrance to the conveyance of the photoreceptor belt 1-1. .

FIG. 5 shows an example in which the position of the developing sleeve is regulated by a tension spring instead of a compression spring, in which a pair of protrusions 104A and 192B facing each other are provided on the guide member 4 and the middle frame 192, respectively. By tensioning the tension spring 193 between the protrusions, the middle frame 192 is constantly urged upward, thereby pushing the abutting portion 192A of the middle frame 192 against the guide member 1.
It is made to come into pressure contact with the text part of No. 04. In this case, it is desirable that each of the projections 104A and 192B be provided on an extension of a vertical line passing through the axis of the developing sleeve 109A.

In FIG. 5, the outer frame 191 and the guide member 104 including the photoreceptor belt are configured as separate bodies, each of which 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.

In such an image forming apparatus, each of the plurality of developing devices 130, 230, 330, 430 containing toner of each color includes each charger 110, 210, 310, 410 and each image exposure device 12.
0, 220, 320°, and 420 are arranged in groups, but as in the previous embodiment, each developing device is configured with a fixed, integral outer frame and an inner frame that moves up and down to the sides of the developing device. Therefore, in this embodiment as well, a similar gap holding member can be formed in the middle frame, and the accurate relative position of the developing sleeve with respect to the photosensitive surface can be set.

〔Effect of the invention〕

The present invention provides a flexible belt-like image forming body used in an image forming apparatus that is accurately set at a predetermined position and stabilized;
This made it possible to convey images at high speeds, and as a result, the performance of each image forming means was sufficiently improved to provide a compact color image forming apparatus that could always 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.
FIG. 4, and FIG. 5 are sectional views showing the structure of the developing device. ■... Photoreceptor belt 4... Guide member 4
A...Text section 6...Charger゛7...
・Laser writing system unit 8.9.10.11...
Developing units 8A, 9A, IOA, IIA...Developing sleeve 90A
...Thin layer forming members 90B, 90C... Toner conveying screw 90D.
...Scraper 91...Outer frame 92...Inner frame 92A...Abutting portion 93...Compression spring

Claims (2)

[Claims] (1) A color image forming apparatus having a belt-like image forming member that is stretched between a plurality of rollers and rotates in sliding contact with a support, and a plurality of developing devices that face the belt-like image forming member,
A color image forming apparatus characterized in that each gap holding member provided coaxially with a developing roller of each developing device is pressed against and abutted against a side end portion of the support body by an elastic member. (2) The color image forming apparatus according to claim 1, wherein the plurality of developing devices are integrated.