JPH047236A - Sheet conveyer by sensitivity material belt - Google Patents

Abstract

PURPOSE:To more stably hold and convey a sheet by on-off controlling a light emitting element of a photoelectricity removal means in such a manner that an electrostatic pattern is generated coarse in a region corresponding to the point end part of a conveyed sheet and dense in a region corresponding to a part to the rear end of the conveyed sheet thereafter. CONSTITUTION:A light emitting element of a photoelectricity removal means 21 is on-off controlled to form an electrostatic pattern of low density in a region corresponding to the point end part of a conveyed sheet and an electrostatic pattern of high density in a region thereafter. In this way, the sheet, when it is separated from a belt 24 by utilizing its curvature, is easily separated by decreasing attraction force relating to the attracted sheet in a region on the belt 24 corresponding to the point end part of the sheet. The sheet is surely held to the conveying belt 24 and conveyed, even when attraction force is weak in the point end part, by increasing the attraction force of the attracted sheet in a region corresponding to a part after the sheet point end part.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a conveying device that electrostatically attracts and holds and conveys a sheet member such as a transfer sheet of an electrostatic recording device or a copy original to an endless belt-like conveying member.

As a color copying machine that uses the electrostatic photographic process, 1
A color copying machine employs a color separation image superimposition transfer method that transfers toner images of different colors sequentially formed on two photoreceptors onto the same transfer paper in a superimposed manner, and then fixes them to obtain a color copy. Are known. In this type of color copying machine, the transfer paper is repeatedly transported back and forth through a transfer section that contacts one photoreceptor multiple times, or the transfer paper is wound around a transfer drum and rotated multiple times. In addition, toner images of different colors are formed on multiple photoconductors at different timings, the transfer portions of each photoconductor are arranged in a straight line, and the transfer paper is conveyed so as to sequentially contact the transfer portion of each photoconductor. A method of superimposing and transferring images is also known.

When the transfer paper is conveyed back and forth through the transfer section of one photoconductor, or when the transfer paper is conveyed linearly through the transfer sections of multiple photoconductors in sequence, unfixed toner remains on the transfer paper. Since the image is on it, it cannot be conveyed by being held between a pair of conveyance rollers.

In addition, not only color copying machines, but also monochrome copying machines such as black and white, facsimile machines, electrostatic printers, etc., have a fixing device equipped with a heater. There is a considerable distance between the transfer position and the fixing device, and the transfer paper carrying the unfixed toner image must be conveyed between them.

As a conveyance means for the transfer paper carrying the unfixed toner image as described above, there is a belt that moves the transfer paper while holding the transfer paper on the surface of a rotating endless belt so that the back side of the toner image carrying surface does not shift. A method in which the transfer paper is carried along with the transfer paper is widely used.

A conventional method is used to convey a sheet such as a transfer paper while holding it tightly against an endless belt so that it does not shift.

(b) Air suction method The endless belt has many holes or is made up of multiple belts, and air is suctioned from the gap between adjacent belts into a suction box installed inside the belt. The material is held and transported by adsorption to the material.

This method requires an air pump and an air passage to suck air, which has the disadvantage of increasing the size of the device.

(b) Grip system A gripper is provided on the belt, and the leading edge of the fed sheet is gripped by the gripper to hold and convey the sheet.

In this method, the grip requires operating time, making it difficult to continuously convey the sheet at high speed, and there is also the problem that conveyance jams may occur due to gripping errors in the gripper.

Electrostatic recording devices that use endless belts to transport paper include, in addition to the above-mentioned belt for transporting transfer paper, devices that automatically feed originals onto the contact glass of copying machines and original reading devices. Automatic document feeder
c Document Feeder: A D F
) conveyor belt.

The currently commonly used ADF conveyor belts are:
A rubber belt with a high coefficient of friction is used, which is driven while the document is in pressure contact with the surface of the contact glass.
When a conveyor belt made of a rubber-based material is used to convey an original by pressing it against a contact glass surface, the surface tends to get dirty due to contact with the original and the contact glass, and there is a drawback that it is difficult to remove the dirt from the belt surface. Furthermore, if the original is made of highly translucent tracing paper or thin paper, the dirt pattern on the belt will be read and exposed, reducing the quality of copied and reproduced images and causing serious problems. It has become.

Therefore, in order to make the belt less likely to get dirty, it has been proposed to mix antifouling agents into the belt material, apply antifouling oil, or bring a cleaning blade into contact with the belt. The reality is that it is less effective and also lacks durability.

In order to solve the above-mentioned drawbacks, several devices have been proposed that utilize electrostatic adsorption force as a means for holding and conveying sheets such as transfer paper or original documents on a conveyor belt so that they do not shift.

For example, in Japanese Patent Application Laid-open No. 53-116825, ADF
A device has been proposed in which an electrode pattern is embedded in an insulating belt using a conveyor belt, and a voltage is applied between the electrodes to create an electric field corresponding to the electrode pattern, thereby attracting and conveying the conveyed sheet using electrostatic force. There is. A device that embeds an electrode pattern on the sheet suction surface and applies a voltage to suction the sheet is often used in flat-bed pen plotters and the like because it provides a stable suction force. However, endless belts with embedded electrode patterns have a complicated structure for applying high voltage to the rotating parts, which not only increases costs, but also causes bending at the roller windings, which can lead to disconnection of the electrode patterns and power supply. There are problems with durability such as wear of parts.

In addition, Japanese Patent Application Laid-open No. 63-288844 discloses that the surface of the conveyor belt that contacts the conveyed member is the surface of the film-formed layer of an amorphous silicon photoreceptor, and that the friction coefficient of the surface, the difficulty in adhesion of dirt, and the cleaning of dirt are By taking advantage of the characteristics such as ease of transfer, it is possible to prevent the surface of the conveyor belt from becoming dirty, and to apply a voltage to the surface to charge the surface of the amorphous silicon layer, thereby electrostatically attracting the conveyed member. Let me transport it.

A conveyor belt device has been proposed in which static electricity is removed by lowering the potential over time using the dark current of a photoreceptor.

However, this method requires the formation of a belt by depositing amorphous silicon on a conductive substrate, and has the disadvantage that the belt itself is expensive because the film formation rate is slow.

In addition, a device that uniformly charges the surface of the photoreceptor and attracts a dielectric sheet such as paper has a lower attraction force than the device that embeds the electrode pattern described above and creates an unequal electric field. It is small and easily affected by changes in environmental conditions such as temperature and humidity, and has the disadvantage that it may not be possible to reliably suction the sheet depending on conditions such as high temperature and high humidity.

In view of the above-mentioned problems of various sheet holding and conveying systems using conventional electrostatic adsorption belts, the present applicant has previously proposed Japanese Patent Application No. 1-327,324 (filed on December 19, 1989).
We have proposed a sheet holding and conveying device that can reliably hold and convey sheets, etc. with a simpler configuration, and is low cost, compact, and highly durable.

In order to solve the above-mentioned problems, this sheet conveying device applies an alternating voltage to an endless belt-like holding and conveying member made of dielectric material such as polyester via a conductive blade or roller, thereby applying an alternating voltage to the surface of the holding and conveying member. The present invention is characterized in that an alternating charge density pattern is formed, and the sheet is supplied to the holding and conveying member in a range in contact with a support roller serving as a counter electrode of the voltage applying means.

Due to the alternating charge density pattern formed on the surface of the endless belt-shaped holding and conveying member, an unequal electric field is formed near the surface of the holding and conveying member. A sheet member such as transfer paper, which is a dielectric material, is supplied to the holding and conveying member in the range where it contacts the counter electrode of the voltage applying means, so it is attracted by a strong attraction force, and is attracted to the holding and conveying member by the above-mentioned unequal electric field. The paper is held in place so as not to be misaligned, and is transported by a holding and transporting member.

However, this method requires a high-voltage AC power supply to form alternating charge density patterns, and when a particularly high frequency is required, it is affected by stray capacitance, causes reactive current to flow, and increases the size of the power supply. There is a drawback that it does. Further, since the conductive blade or conductive roller is provided in a direction perpendicular to the belt running direction, the charge density pattern is limited to a striped pattern at equal intervals or preset irregular intervals perpendicular to the belt running direction. .

Therefore, without separately using an AC power source as a means for forming an alternating charge density pattern on the conveyor belt, the applicant has developed a sheet conveyor belt that is attached to the outer surface of a base material whose outermost layer is at least a conductive layer or a semiconductor layer. A charging means configured by providing a photoreceptor layer and charging the photoreceptor layer around the sheet conveyance belt in the order of its running direction, a flashable static eliminator that removes the charge from the charged photoreceptor meter layer by light irradiation, and A sheet conveyance device has been proposed in which a conveyance sheet supply position is provided, the photoreceptor layer is uniformly charged by the above-mentioned charging means, and an alternating charge density pattern is formed by blinking the optical charge eliminating means at a predetermined timing.

This proposal makes it possible to realize a conveyor belt device that eliminates the need for a large AC or alternating current power source, is low in cost, has a long life, and provides stable conveyance performance. As the above-mentioned charging means, a corona discharger type charger similar to the charging means for a photoreceptor as a latent image carrier can be used, and contact charging using a conductive roller can also be used. The latter case is advantageous in that no ozone is generated due to corona discharge as in the former case.

Problems to be Solved by Akira In view of the above-mentioned actual situation of conventional sheet conveying devices using endless belts, the present invention aims to more stably hold and convey sheets by taking advantage of the features of devices that use photoreceptor belts as endless belts. An object of the present invention is to provide a sheet conveying device that can perform the following functions.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a sheet conveying device using a photoreceptor belt having the above-mentioned configuration, which was separately proposed by the applicant, in which the optical static elimination means is arranged in the circumferential direction of the endless photoreceptor belt. The electrostatic pattern is arranged in a straight line across the entire width of the belt in a direction perpendicular to the belt, and is composed of a large number of light emitting elements that can be individually blinked. The present invention is characterized in that the light-emitting elements of the optical charge eliminating means are controlled to blink so as to become denser in a region corresponding to the rear end of the sheet to be conveyed thereafter.

Operation - With the above configuration, a low-density electrostatic pattern is formed in the region corresponding to the leading end of the conveyed sheet, and a high-density electrostatic pattern is formed in the subsequent region.

FIG. 4 shows the difference in the lines of electric force formed by the potential difference of the pattern depending on the density of the charged pattern formed on the endless photoreceptor belt.

The upper part of the figure shows the potential profile of negative charging, and the corresponding lines of electric force formed on the surface of the photoreceptor belt are shown below.

Electric lines of force are formed in the direction indicated by the arrow in FIG. 1 from a location of high potential to a location of low potential. The strength of the electric field becomes stronger at the edges of the potential pattern where the density of electric lines of force is high.

In areas with low electrostatic pattern density, the distance between the charges remaining on the photoreceptor belt increases, so the electric field generated by the potential difference between the areas with remaining charges and the areas with no charges is formed over a greater distance. be done. At the same time, since this is the edge portion of the charge pattern with a high potential gradient, when the density of the pattern is low, the density of the portion with a high potential gradient is low, so the suction force on the attracted sheet becomes small. In other words, although a suction force is exerted on the sheet at a position away from the photoreceptor belt, the suction force on the sucked sheet is small. On the other hand, in areas with high electrostatic pattern density,
The suction force for a distant position is small, but the suction force for the sucked sheet is large.

In other words, when the conveyed sheet is guided toward the photoreceptor belt and approaches the photoreceptor belt, the electrostatic attraction force acts even when the leading edge of the sheet is still away from the photoreceptor belt, and the sheet Helps the tip stick to the belt. However, since the suction force against the sucked sheet is small in the area on the belt corresponding to the leading end of the sheet, the sheet is easily separated from the belt when the curvature of the belt is used to separate the sheet. Since the adsorption force of the attracted sheet is strong in the region corresponding to the leading edge of the sheet and beyond, the sheet is reliably held and conveyed by the conveyor belt even if the suction force at the leading edge is weak.

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a diagram showing an example of a two-color laser printer equipped with a sheet conveying device using a photoreceptor belt according to the present invention.

This printer has two sets of laser writing optical systems that share a rotating polygon mirror 3 as a deflector for optical scanning. 3. 1st
A laser beam 2 comprising an f-theta lens 4 and mirrors 5.5' and 5'', carrying image information to be developed in a first color, for example black, is passed through the first writing optical system to a charger. The photoreceptor drum 7, which is uniformly charged by the photoreceptor 6, is irradiated and scanned at a first writing position directly above the photosensitive drum 7, thereby forming a first latent image.

This first latent image is developed into a first color (black in this example) by a first developing device 8 provided subsequent to the first writing position.

On the other hand, the second writing optical system includes a second laser oscillation device 9, a rotating polygon mirror 3. 2nd f-theta lens 11, mirror 12.12'
A laser beam 10 carrying image information to be developed in a second color (for example, a chromatic color such as red or blue) is transmitted to a position following the first developing device 8 via the second writing optical system. The second writing position provided at the second writing position is irradiated and scanned to form a second latent image. The second latent image is developed into a second color by a second developing device 13 provided downstream of the second writing position.

Since the charge of the latent image developed with the first color is not completely recovered by development and the latent image remains, the threshold value of the development potential is Measures have been taken to appropriately set the image forming voltage and apply an appropriate developing bias.

The two-color toner images formed in the same image forming area of the photoreceptor 7 in this way are transferred onto the transfer paper fed by the paper feeding device 14 under the action of the transfer charger 15.
A sheet conveying device 16 using a photoreceptor belt according to the present invention conveys the sheet to a fixing device 17, fixes the sheet, and discharges the sheet.

After the transfer, the toner remaining on the photoreceptor drum 7 is cleaned by a cleaning device 18, and the charge is removed to prepare for the next image formation.

As shown in FIG. 2, the photoreceptor belt conveying device 16 includes a photoreceptor endless belt 24 that is supported by a driving roller 22 and a driven roller 23 and rotates in the direction of the arrow, a charger 20 that charges the photoreceptor belt, and a charger 20 that charges the photoreceptor belt. The photoreceptor belt 24 is composed of a photoremoval device 21 that irradiates the charged photoreceptor belt 24 with light while blinking to eliminate the static electricity and form an electrostatic pattern.
They are provided in this order in the circumferential direction of the transfer paper and on the upstream side of the transfer paper introduction position.

The optical static eliminator 21 is arranged in a straight line across the entire width of the photoreceptor belt 24 in a direction perpendicular to the circumferential direction of the photoreceptor belt 24, and is formed as an array consisting of a large number of light emitting elements that can be blinked individually. . Although not shown in the figure, the high-voltage power supply connected to the charger 20, the blinking of the optical static eliminator 21, the on/off of the high-voltage power supply, the on/off of the belt drive, the sea fence of the printer, the image forming conditions, etc. It is equipped with a control device for controlling the same.

The transfer paper is fed from the paper feeding device 14, the toner image is transferred by the transfer separation device 115, and the transfer paper is separated from the photosensitive drum 7. The transfer paper is guided to the sheet conveyance device 16.

In time for the leading edge of the transfer paper to reach the sheet conveying device, the driving of the conveying device is started, and the electrostatic charger 20 and the optical static eliminator 21 are driven. a).

A charge pattern like that shown in (b) appears on the photoreceptor belt 2.
The transferred paper formed on the photoreceptor belt 24
When the transfer paper reaches the position of the drive roller 22, the transfer paper is separated from the photoconductor belt 24 due to the curvature of the photoconductor belt 24 and the stiffness of the transfer paper, and is conveyed to the fixing device.

In addition to the above basic configuration, a cleaning device for the photoreceptor belt 24 after separation of the transfer paper or a static eliminator for initializing by removing static electricity before the next charging by the charger 20 may be provided. can. Furthermore, at the end of printing or in an area where there is no need to adsorb the transfer paper, it is also possible to turn off the power to the charger or to continuously turn on the optical charge eliminating means 21 to eliminate the charge from the entire area of the photoreceptor belt 24.

FIG. 3 is a diagram showing a sheet conveying device using a photoreceptor belt, which uses a conductive roller 20' instead of a corona discharger type charger as a charging means. The same reference numerals are given. The use of a conductive roller as the charging means has the advantage of eliminating ozone generation.

FIGS. 5(a) and 5(b) show examples of electrostatic patterns formed on a photoreceptor belt according to the present invention. In either case,
The electrostatic pattern is coarse in the region corresponding to the leading edge of the sheet to be conveyed, and the electrostatic pattern is densely formed in the region corresponding to the rear end of the sheet to be conveyed. In addition,
In the case of FIG. 5(a), all the light-emitting elements of the optical static eliminator are repeatedly turned on and off at the same time, so that the electric potential is displayed on the photoreceptor belt 24 in the conveying direction. A striped electrostatic pattern extending perpendicularly to the sheet is formed, and the width and interval of the stripes are widened in the area corresponding to the leading edge of the sheet and narrowed in the subsequent areas.

In the case of Fig. 5(b), the two light emitting elements of the optical static eliminator are blinked alternately as one unit in the area corresponding to the sheet leading edge, and the light emitting elements that blink every certain width are reversed. A coarse checkered electrostatic pattern is formed, and in the subsequent parts, each light emitting element blinks alternately, and by switching the blinking at twice the switching speed of the sheet leading edge, fine patterns are created. It forms a checkered electrostatic pattern.

In this way, by forming the electrostatic pattern coarsely in the area corresponding to the leading edge of the conveyed sheet and densely forming it in the subsequent areas, the electrostatic pattern is formed to be more dense in the area corresponding to the leading edge of the conveyed sheet. Even if the leading edge is still far from the photoconductor belt, the suction force acts and attracts the sheet, and even if the leading edge has a weak suction force, the remaining portion's strong suction force will cause the sheet to stick to the photoconductor belt. The sheet is reliably carried and conveyed by the belt, and the sheet can be easily peeled off from the photoreceptor belt by utilizing the curvature.

Note that the length of the region where a low-density electrostatic pattern is formed at the tip portion is preferably about the radius of curvature when separated by one separation. Alternatively, when the sheet is guided and approaches the belt, the positional relationship is determined so that the leading edge of the sheet approaches first, or the positional relationship is determined such that the part behind the leading edge approaches first. You can stay longer if you are there.

Alternatively, the length may be changed depending on the thickness of the sheet to be conveyed, the strength of the waist, etc.

Effects As described above, according to the present invention, the sheet can be guided toward the conveyor belt at the leading edge of the sheet and quickly attracted, and the attracted sheet can be reliably attracted by the strong suction force in the area after the leading edge. At the curvature separation position, the weak adsorption force at the tip ensures separation.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing the overall schematic configuration of an example of an image forming apparatus equipped with a sheet conveying device according to the present invention, and FIG. 3 is a sectional view showing the configuration of a modified embodiment thereof, and FIG. 4 is a schematic diagram showing differences in the lines of electric force formed depending on the density of the electrostatic pattern formed on the sheet conveying belt. , FIGS. 5(a) and 5(b) are plan views showing examples of electrostatic patterns formed on a sheet conveying belt according to the present invention. 16...Sheet conveyance device 2 using photoreceptor belt
0.20'...Charging means 21...Photostatic neutralization means 22...Drive roller 23...Followed roller 24...Photoreceptor belt (a) (b)

Claims (1)

[Scope of Claims] An endless photoreceptor belt comprising a photoreceptor layer formed on a base material whose outermost layer is a conductive layer or a semiconductor layer; a charging means for charging the photoreceptor layer; a flashable optical charge removal means for removing the charge from the charged photoreceptor layer by light irradiation; and a means for introducing the sheet to be conveyed into the endless belt; The photoreceptor layer, which has been uniformly charged by the photoreceptor, is irradiated with blinking light by the optical static eliminating means to form an electrostatic pattern on the photoreceptor layer depending on the level of potential, and the introduced sheet to be conveyed is attracted to the surface of the endless belt. In a sheet conveying device that supports and conveys a sheet, the optical charge eliminating means is arranged in a straight line across the entire width of the endless photoreceptor belt in a direction perpendicular to the circumferential direction of the endless photoreceptor belt, and has a large number of light emitting lights that can be blinked individually. The light emission of the optical static elimination means is configured by an element, and the electrostatic pattern is coarse in a region corresponding to the leading edge of the conveyed sheet, and dense in a region corresponding to the rear end of the conveyed sheet. A sheet conveyance device characterized by blinking elements.