JP2521237Y2 - Color image forming device - 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 is transferred onto 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 on a photosensitive drum, which is an image carrier, according to the number of separated colors of an original image,
There is a method in which a multicolor image is formed on the transfer drum by transferring the image on a transfer drum each time it is developed, and then transferring it on a recording paper to obtain a color copy. In the apparatus according to this method, in addition to the photosensitive drum, it is necessary to provide a transfer drum having a size capable of transferring one image on the peripheral surface thereof, and the apparatus is large and has a complicated structure. Unavoidable.

Further, for example, as disclosed in Japanese Patent Laid-Open No. 61-149972, latent images are formed and developed on the photoconductor drum in accordance with the number of color separations of the original image, and transferred to a transfer material at each development. This is a method of obtaining multicolor color copies. With this method, it is difficult to accurately superimpose multicolor images, and it is not possible to obtain a good-quality color copy.

Further, there is a method in which a latent image is formed on the photoconductor drum in accordance with the number of separated colors of the original image and development with color toner is repeated, and the color toner images are superposed on the photoconductor drum and then transferred to obtain a color image. The basic process for forming this multicolor image is described in Japanese Patent Application Laid-Open Nos. 60-75850, 60-76766,
No. 60-95456, No. 60-95458, No. 60-158475 and the like.

In a multi-color image forming apparatus which obtains a color image by such superposition, a plurality of developing devices accommodating color toners of different colors are arranged around the periphery of the photosensitive drum, and generally, Rotates the photosensitive drum multiple 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 the photoconductor is applied or mounted on a flexible belt together with the photoconductor drum whose photoconductor is applied or vapor-deposited on the peripheral surface of the drum as described above. Is also proposed. A belt-shaped image forming body (hereinafter also referred to as a photosensitive belt) has a shape determined by being stretched between rotating rollers including a driving roller.
This is effective when a color image forming apparatus having a compact shape is configured by effectively utilizing space. Also, since the photoconductor belt can run along a small curvature,
By using a small-diameter rotating roller and separating the transfer material by utilizing this curvature portion, it is possible to prevent the separation failure of the transfer material.

[Purpose of device]

In a color image forming apparatus using a photoconductor belt, an image forming unit such as a charging unit, an image exposing unit, and a developing unit composed of a plurality of developing units is provided on the peripheral portion of the photoconductor belt. The image forming means faces the rotating photoconductor belt with a constant gap.

As a means for facing the image forming means with respect to the photosensitive belt while keeping a constant interval, a method is used in which a backup roller is used and the backup roller is made to face it.
However, when backup rollers are used, a large number of rollers are required by disposing a number of backup rollers corresponding to the image forming means. Further, when the number of rollers is large, it becomes difficult to maintain the parallelism with the rotating roller. Further, as disclosed in Japanese Patent Application Laid-Open No. 57-34576, there is a proposal of a device which opposes a photoconductor belt on a guide member, but it is difficult to maintain the space by such a device.

It is an object of the present invention to provide a color image forming apparatus using a photoconductor belt in which an image forming unit accurately faces a photoconductor belt with a set gap and a good image can be obtained.

[Constitution of device]

The above object has a peripheral edge of a belt-shaped image forming body that has two rotating rollers and a guide member having a curvature between the rollers, is stretched between the rotating rollers, and moves while sliding on the guide members. In a color image forming apparatus in which image forming means including a plurality of developing means are opposed to each other and arranged, a linear or belt-like pressing member for pressing the belt-like image forming body so as to move along the curvature is provided. Is achieved by a color image forming apparatus.

〔Example〕

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

In FIG. 1, reference numeral 1 is a flexible photosensitive belt which is a belt-shaped image forming body, and the photosensitive belt 1 is installed between rotating rollers 2 and 3 and is driven by the rotating roller 2 to make a timepiece. Is conveyed in the direction.

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

Therefore, the photoconductor on the outer peripheral surface of the photoconductor belt 1 is always kept in a constant relation position with respect to the surface of the guide member 4 even during conveyance, so that a stable image forming surface can be formed.

Reference numeral 6 is a scorotron charger as a charging means, 7 is a laser writing system unit as an image exposing 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 photosensitive belt 1 which is in contact with the guide member 4.

In addition to the optical system shown in the figure, the laser writing system unit 7 may be an optical system in which a light emitting portion and a converging optical transmission body are integrated.

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 maintains a predetermined gap with the photosensitive belt 1.
Equipped with 8A, 9A, 10A and 11A, it has a function of visualizing the latent image on the photosensitive belt 1 by a non-contact developing method. Unlike the contact development, this non-contact development has an advantage that it does not hinder the movement of the photosensitive belt.

12 is a transfer device, 12A is a static elimination bar, 13 is a cleaning device, and the blade 13A of the cleaning device 13 and the toner carrying roller 13B are kept at a position apart from the surface of the photosensitive belt 1 during image formation and after image transfer. Only at the time of cleaning, the surface of the photosensitive belt 1 is pressed against the surface as shown in the figure.

The color image forming process 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 the image data processing unit (second
Image data is created by performing arithmetic processing in FIG. 2B and is temporarily stored in the image memory (FIG. 2C). Then, the image memory is taken out at the time of recording and is inputted to the recording unit (FIG. 2D), 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 system unit 7, a laser beam generated by a semiconductor laser (not shown) in the laser writing system unit 7 is generated. Is rotated and scanned by the polygon mirror 7B rotated by the drive motor 7A, the optical path is bent by the mirrors 7D and 7E via the fθ lens 7C, and the photoconductor belt 1 charged in advance by the charger 6 as a charging means. A bright line is formed by being projected on the peripheral surface.

On the other hand, when scanning is started, the beam is detected by the index sensor, the modulation of the beam by the first color signal is started, and the modulated beam is transferred to the photosensitive belt 1.
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 the developing device 8 loaded with yellow (Y) toner (visual medium) in the developing means,
A toner image is formed on the drum surface. The obtained toner image passes through the cleaning device 13, which is a cleaning means separated from the peripheral surface of the photosensitive belt 1 while being held on the drum surface, and enters the next copy cycle.

That is, the photoconductor belt 1 is recharged by the charger 6, and then the second color signal output from the signal processing unit is input to the writing system unit 7, which is the case of the first color signal described above. 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, 11 is a developing device having black toner, which is formed by superposing a black toner image on the belt surface by the same process. A DC or further AC bias is applied to each sleeve of each of these developing devices 8, 9, 10 and 11,
Jumping development is performed by a two-component developer that is a developing means, and development is performed in a non-contact manner with the photoreceptor belt 1 whose base is grounded. Note that non-contact development using a one-component developer can also be used as the development.

Thus, the color toner image formed on the peripheral surface of the photosensitive belt 1 is transferred to the transfer material sent from the paper feed cassette 14 via the paper feed guide 15 in the transfer portion.

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

The transfer material, which has received the image transfer and the charge removal, is reliably separated from the photosensitive belt 1 which suddenly changes its direction along the rotating roller 2 and moves upward, and after the image is fused by the fixing roller 18, it is discharged. It is discharged onto the tray 20 via the paper roller 19.

On the other hand, the photoconductor belt 1 which has finished the transfer to the transfer material is further conveyed to remove the residual toner in the cleaning device 13 in which the blade 13A and the toner conveying roller 13B are brought into pressure contact with each other, and after the end, the cleaning is completed. The blade
13A is separated, and a little later, toner supply roller 13B
Removes the toner accumulated on the tip of the blade 13A and then separates the toner carrying roller 13B to start a new image forming process.

As described above, the photoconductor belt 1 is brought into a tensioned state by the action of the tension roller 5 and is pressed against the guide member 4 with the tension of the belt itself. In the color image forming apparatus of the present invention, as shown in FIG. A pressing member 40 as shown is provided, and the photosensitive member belt 1 is forcibly pressed against the guide member 4 by applying tension to the pressing member 40.

A linear or narrow belt-shaped flexible material is used for the pressing member 40, and a PET film or the like having a large tensile strength and a smooth surface is used as the belt-shaped material.

The pressing members 40 are provided in a pair in the front and back so as to be located in the non-image areas on both side edges of the photosensitive belt 1, and tension springs 41 and 42 attached to both ends of the pressing members 40 are respectively attached to the spring hook pins 43 and 44 of the apparatus main body. It is in a state of being locked and always maintaining an appropriate tension.

Therefore, the photoconductor belt 1 is constantly urged by the tension of the photoconductor belt 1 and the tension of the pressing member 40 so that the photoconductor belt 1 is appropriately pressed against the guide member 40. Can be stabilized.

When the width of the photoconductor belt 1 is relatively narrow, the pressing member 40 can effectively function even if it is provided in either one of the non-image areas of both side edges of the photoconductor belt 1 to stabilize the photoconductor surface.

FIG. 3 shows the setting of the relative position of each image forming means with respect to the photoconductor belt 1 according to the present invention. The charging means is shown in FIG.
Further, regarding the developing means, the main part thereof is shown in FIG. 3 (B) with an arrow BB cross section, and regarding the image exposing means, an optical system having a convergent transmitting body instead of the laser optical system is shown with a similar cross section. It is shown in FIG.

In FIG. 3 (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 ₁ is an electrode wire stretched between the electrode blocks 6B. . W ₂ is a grid.

Each electrode block 6B is integrally formed with each projection 6C having a predetermined height as an abutting member, and the charger 6 presses each projection 6C against the guide member 4 on the outer side of the photosensitive belt 1. It is biased by an elastic member 6D such as a leaf spring.

Therefore, the electrode wire W ₁ and the grid W ₂ are always positioned at a constant distance from the peripheral surface of the photoconductor belt 1, and the photoconductor can be reliably charged to a predetermined potential.

Further, in FIG. 3B, 9A is a developing sleeve of the developing device 9, 9B is an abutting roller which is an abutting member, and the abutting roller 9B is rotatably supported by the rotating shaft 9C of the developing sleeve 9A. Has been done.

When the abutting roller 9B is pressed against the guide member 4, the abutting roller 9B is slightly smaller than the developing sleeve 9A so that a peripheral surface of the developing sleeve 9A and a peripheral surface of the photosensitive belt 1 can form a gap corresponding to a developing gap. 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 developing with the outer peripheral surface of the photosensitive 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 11, and the respective abutting rollers incorporated therein are pressed against the guide member 4 by a well-known biasing mechanism.

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

FIG. 4 shows a cross section of the developing device 9. Reference numeral 9A is a developing sleeve containing a fixed magnet roller, and a predetermined developing gap is provided between the developing roller 9 and the peripheral surface of the photoconductor belt 1 by an abutting roller 9B on the same axis. It is rotated and driven counterclockwise. 90A is a thin layer forming member having rigidity and magnetism, and is pressed against the developing sleeve 9A with a predetermined load in a state where no developer is present. 90B and 90C have a screw structure and are a pair of toner conveying screws that convey and circulate the developer in mutually opposite directions, and serve to thoroughly stir and mix the toner and the carrier and send them to the developing sleeve 9A as the developer. .

The toner carrying screw 90B and the toner carrying screw 90C are members that also function as stirring members that rotate in mutually opposite directions, and the toner and the carrier carried to the inner side by the thrust of the toner carrying screw 90B are the toner carrying screw 90C side. The developer is conveyed to the front side of the drawing by the thrust, and is made into a uniform developer that is triboelectrically charged by the mixing action of the toner and the carrier during that time, and is adhered in layers on the peripheral surface of the developing sleeve 9A.

This thin developer layer adhered to the peripheral surface of the developing sleeve 9A forms a thin layer of the latent image on the peripheral surface of the photosensitive belt 1 which is conveyed in the clockwise direction in the developing area with the above-mentioned developing interval. Contact development causes reversal development to form a toner image.

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

The developer that has consumed the toner component has a high carrier ratio and is conveyed by the developing sleeve 9A to be scraped by the scraper 90D.
Are separated and collected, and the developer having a high toner ratio is mixed again.

On the other hand, 70 shown in FIG. 3 (C) is an image exposure means, which is composed of an optical system in which a convergent optical transmission body 70A and a light emitting portion 70B such as an LED are integrated, and the light emitting portion 70B projects from both ends of the casing. As this member, a protrusion 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 the protrusions 70C come into pressure contact with the guide member 4 on the outer side of the photoreceptor belt 1 as in the case of the charger 6.

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

Further, since the image forming means does not come into contact with the photosensitive belt 1, the vibration accompanying the movement of the photosensitive belt does not affect the image forming means. Since the photosensitive belt 1 does not come into contact with the image forming means, the photosensitive belt 1 is not worn. Since the photoconductor belt 1 does not come into contact with the image forming means, the photoconductor belt 1 has a small friction resistance and is easily transported.

Further, when the photosensitive belt 1 is conveyed, there is a risk that the conveying ability will be deteriorated due to frictional resistance caused by sliding friction with the guide member 4. Since the concave portions 4A are formed on the surfaces of the guide members 4 outside the facing areas to avoid contact with the photosensitive belt 1, frictional resistance is remarkably reduced and the photosensitive belt 1 can be moved with a sufficient conveying force. It has become.

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

Further, regarding the photosensitive belt 1, (A) of FIG.
As shown in (B) and (C), a pair of continuous guide rails 1A are integrally formed on the inner circumference thereof, and the guide rails 1A are engaged with the guide grooves 4B of the guide member 4, and the portions are further pressed by the pressing member. The pressing by 40 prevents the meandering of the photosensitive belt 1 which is likely to occur during the conveyance.

Further, since the pressing member is in contact with a wide area of the photosensitive belt 1, it can be used as a grounding means for the photosensitive belt. For this purpose, the surface of the pressing member on the photoconductor side is subjected to a conductive treatment or a conductive material is used as the pressing member, while the surface of the photoconductor with respect to the pressing member (this is located at the end of the photoconductor surface). This is done by exposing the ground portion to the ground.

[Effect of device]

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. It has become possible to provide a compact color image forming apparatus in which the above performance can be fully exhibited and a high quality color image can always be obtained.

[Brief description of drawings]

FIG. 1 is a 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 sectional view of main parts of the apparatus, and FIG. 4 is a sectional structural view of a developing device. . 1 ... Photosensitive belt, 2, 3 ... Rotating roller 4 ... Guide member, 4A ... Recessed portion 6 ... Charger, 6B ... Electrode block 6C ... Protrusion 7 ... Laser writing system unit 8, 9 , 10,11 …… Developer 8A, 9A, 10A, 11A …… Developing sleeve 9B …… Abutting roller, 40 …… Pressing member 41,42 …… Tension spring, 70 …… (for image exposure) Optical system 70C ...... Protrusion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References

Claims (2)

(57) [Scope of utility model registration request] 1. A belt-shaped image forming body which has two rotating rollers and a guide member having a curvature between the rollers, is stretched between the rotating rollers, and moves while sliding on the guide members. Opposing image forming means including a plurality of developing means on the periphery
The color image forming apparatus, wherein the color image forming apparatus has a linear or belt-like pressing member that presses the belt-shaped image forming body so as to move along the curvature. 2. The color image forming apparatus according to claim 1, wherein the pressing area by the pressing member includes at least one of a developing area, a charging area, and an exposing area by the image forming means.