JP2812533B2 - Sheet conveying device using photoreceptor belt - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transport device for holding and transporting a sheet member such as a transfer sheet and a copy original of an electrostatic recording device by electrostatically adsorbing it to an endless belt-shaped transport member.

Prior art As a color copier using the electrostatographic process,
A color copying machine of a color separation image superimposing transfer system in which toner images of different colors sequentially formed on one photoreceptor are superimposed and transferred on the same transfer paper while being aligned and fixed to obtain a color copy. It has been known. In a color copying machine of this type, the transfer sheet is reciprocated and transported a plurality of times at a transfer section in contact with one photoconductor, or the transfer sheet is wrapped around a transfer drum and is rotated multiple times. In addition, the toner images of different colors are formed on a plurality of photoconductors at different timings, the transfer sections of the respective photoconductors are arranged in a straight line, and the transfer paper is conveyed so as to sequentially contact the transfer sections of the respective photoconductors. Also, a method of superimposing and transferring by superposition is known.

In the case where the transfer paper is reciprocated by passing through the transfer section of one photoconductor or the transfer paper is linearly transported by sequentially passing through the transfer sections of a plurality of photoconductors, the unfixed toner is transferred onto the transfer paper. Since the image is on the sheet, the sheet cannot be conveyed while being nipped by the conveying roller pair.

Not only color copiers but also black-and-white monochrome copiers, facsimile machines, electrostatic printers, etc., have a heater in the fixing device, so that the heat is transferred to the photoconductor to prevent deterioration. There is a considerable distance between the transfer position and the fixing device along which the transfer paper carrying the unfixed toner image must be transported.

As a transporting means of the transfer paper carrying the unfixed toner image as described above, a belt which moves and holds the transfer paper on the surface of a circulating endless belt so that the back surface of the toner image carrying surface does not come in close contact with and displaces. The method of transporting the transfer paper by entrainment is widely used.

As a method of holding and transporting a sheet such as a transfer sheet so as not to be in close contact with an endless belt, the following method has conventionally been adopted.

(A) Air suction system The endless belt is provided with a number of holes or is composed of a plurality of belts, and suctions air from a gap between adjacent belts into a suction box provided inside the belt, thereby seating the sheet on the belt surface. To hold and transport.

In this method, an air pump and an air passage are required for sucking air, and there is a disadvantage that the device becomes large.

(B) Grip method A gripper is provided on a belt, and the leading end of a fed sheet is gripped by the gripper to hold and convey the sheet.

In this method, the operation time of the grip is required, and it is difficult to continuously convey the sheet at a high speed.
There is a problem that a conveyance jam occurs due to a gripper grip error.

In the electrostatic recording apparatus, a sheet is conveyed by using an endless belt. In addition to the above-described transfer sheet conveying belt, an original is automatically fed onto a contact glass of a copying machine or an original reading apparatus. Automatic Document Feeder (Automatic Docu
ment Feeder: ADF) conveyor belt.

Currently used ADF transport belts include:
A rubber belt with a high coefficient of friction that is driven while the original is pressed against the surface of the contact glass is used,
When a document is conveyed while being pressed against a contact glass surface using a transfer belt made of a rubber-based material, there is a disadvantage that the surface is easily stained by contact with the document and the contact glass, and dirt is not easily removed from the belt surface. Furthermore, if the original is a highly translucent tracing paper or thin paper, the dirt pattern is also read and exposed to light, which degrades the quality of the captured image and the reproduced image. It has become.

Therefore, it has been proposed to mix an antifouling agent into the material of the belt, apply an antifouling oil, or contact a cleaning blade in order to make the belt less likely to become dirty. The fact is that the effect is low and the durability is lacking.

For the purpose of solving the above-mentioned drawbacks, there have been proposed some devices that use an electrostatic attraction force as a means for transporting a sheet such as a transfer sheet or a document on a transport belt without shifting the sheet.

For example, JP-A-53-116825 discloses that as an ADF transport belt, an electrode pattern is embedded in an insulator belt, a voltage is applied between the electrodes to create an electric field corresponding to the electrode pattern, and the electrostatic force is applied. 2. Description of the Related Art There has been proposed an apparatus that sucks and conveys a conveyed sheet. A device that embeds an electrode pattern on a sheet suction surface and suctions a sheet by applying a voltage is often used in a flatbed type pen plotter or the like because a stable suction force can be obtained. However, the endless belt in which the electrode pattern is embedded has a complicated structure of means for applying a high voltage to the rotating part, which not only increases the cost, but also causes the electrode pattern to be disconnected or fed due to bending at the roller winding part. There is a problem in durability such as abrasion of parts.

Japanese Patent Application Laid-Open No. 63-288844 discloses that the surface of a conveyor belt in contact with a member to be conveyed is a film forming layer surface of an amorphous silicon photoreceptor, and the surface has a coefficient of friction, difficulty in adhering dirt, and cleaning of dirt. Utilizing characteristics such as ease of cleaning, it prevents contamination on the surface of the conveyor belt and provides a means for applying a voltage to the surface to charge the amorphous silicon layer surface, and electrostatically attracts the member to be transferred. There has been proposed a conveyor belt device which conveys the photosensitive member and reduces the potential with time by the dark current of the photoreceptor to remove the charge.

However, this method has a drawback that it is necessary to form a belt by depositing amorphous silicon on a conductive substrate, and the belt itself is expensive because the film formation speed is low.

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

In view of the above-mentioned problems of various sheet holding / conveying systems using a conventional electrostatic attraction belt, the present applicant has previously proposed a simple configuration using Japanese Patent Application No. 1-327,324 (filed on December 19, 1989). Proposed a low cost, compact, and highly durable sheet holding / conveying device that can securely hold and convey sheets and the like.

In order to solve the above-mentioned problems, the sheet conveying device applies an alternating voltage to the dielectric endless belt-shaped holding / conveying member such as polyester via a conductive blade or a roller, thereby applying a voltage to the surface of the holding / conveying member. An alternating charge density pattern is formed, and a position at which the sheet is supplied to the holding and conveying member is set in a range in contact with a support roller serving as a counter electrode of the voltage applying unit.

Due to the alternating charge density pattern formed on the surface of the endless belt-shaped holding and conveying member, an uneven electric field is formed near the surface of the holding and conveying member. The sheet material such as transfer paper, which is a dielectric, is supplied to the holding / transporting member in a range in contact with the counter electrode of the voltage applying means, and is attracted by a strong suction force, and is attracted to the holding / transporting member by the uneven electric field. The sheet is held so as not to be displaced, and is conveyed while being carried by the holding / conveying member.

However, this method requires a high-voltage AC power supply to form an alternating charge density pattern.Especially, when a high-frequency power supply is required, it is affected by stray capacitance, reactive current flows, and the power supply becomes larger. There is a disadvantage of doing so. or,
Since the conductive blade or the conductive roller is provided in a direction perpendicular to the belt running direction, the charge density pattern is limited to a stripe pattern having an equal interval or a preset unequal interval orthogonal to the belt running direction.

Therefore, the present applicant separately requires, without using an AC power supply as a means for forming an alternating charge density pattern on the transport belt, the sheet transport belt at least on the outer surface of the base material whose outermost layer is a conductive layer or a semiconductor layer. A charging unit configured to provide a photoreceptor layer, charging the photoreceptor layer around the sheet conveying belt in the running direction, a flashable discharging unit for discharging the charged photoreceptor storage layer by light irradiation, The present invention has proposed a sheet conveying apparatus in which a conveying sheet supply position is provided, the photosensitive layer is uniformly charged by the charging unit, and an alternating charge density pattern is formed by blinking a light removing unit at a predetermined timing. This proposal eliminates the need for large AC or alternating power supplies, and is low cost, long life,
In addition, it has become possible to realize a transport belt device capable of obtaining stable transport performance. As the above charging means,
A corona discharger type charger similar to the charging means of the photoreceptor as the latent image carrier can be used, and contact charging by a conductive roller can also be employed. The latter case is advantageous in that ozone is not generated by corona discharge as in the former case.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances of a conventional sheet conveying apparatus using an endless belt, and takes advantage of the characteristics of an apparatus using a photosensitive belt as an endless belt to more stably hold and convey a sheet. It is an object of the present invention to provide a sheet conveying device that can perform the above-described operations.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a sheet conveying apparatus using a photosensitive belt having the above-mentioned configuration separately proposed by the present applicant. Are arranged on a straight line at right angles to the belt over substantially the entire width of the belt,
The electrostatic pattern is composed of a large number of light-emitting elements that can be individually turned on and off, and the electrostatic pattern is coarse in a region corresponding to the leading end of the conveyed sheet, and dense in a region corresponding to a rear end of the conveyed sheet thereafter. As described above, the light emitting device of the above-mentioned light discharging means is controlled to blink.

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

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

The upper part of the figure shows a negatively-charged potential profile, and below it shows the lines of electric force correspondingly formed on the surface of the photoreceptor belt. The lines of electric force are formed in a direction indicated by an arrow in the drawing from a place having a high potential to a place having a low potential. The intensity of the electric field becomes strong at the edge of the potential pattern where the density of the electric flux lines is high.

In areas where the density of the electrostatic pattern is low, the distance between the charges remaining on the photoreceptor belt increases, so the electric field generated by the potential difference between the remaining charge and the remaining charge forms a greater distance. Is done. At the same time, since it is the edge portion of the charge pattern having a high potential gradient, when the density of the pattern is low, the density of the portion having a high potential gradient is low, and the suction force on the sucked sheet is small. That is, a suction force is exerted on a sheet at a position distant from the photosensitive belt, but the suction force on the sucked sheet is small. On the other hand, in a region where the density of the electrostatic pattern is high, the suction force at a distant position is small, but the suction force at the sucked sheet is large.

In other words, when the conveyed sheet is guided and approached to the photoreceptor belt, the electrostatic attraction force acts from the time when the leading end of the sheet is still at a position far from the photoreceptor belt, and the sheet is conveyed. Helps the tips stick to the belt. However, in the region on the belt corresponding to the leading end of the sheet, the suction force on the sucked sheet is small, so that the sheet is easily separated from the belt by using the curvature of the belt. In the area corresponding to the leading end of the sheet and thereafter, the attraction force of the attracted sheet is strong, so that even if the attraction force of the leading end is weak, the sheet is reliably held and transported by the transport belt.

Examples Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

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

This printer has two sets of laser writing optical systems sharing a rotary polygon mirror 3 as a deflector for optical scanning.
The writing optical system includes a first laser oscillator 1, a rotary polygon mirror 3,
The first f-θ lens 4 and the mirrors 5, 5 ', 5 "
The laser beam 2 carrying the image information to be developed in a color, for example, black, passes through the first writing optical system to the first directly above the photosensitive drum 7 uniformly charged by the charging charger 6.
The writing position is irradiated and scanned to form a first latent image. The first latent image is stored in a first latent image provided next to the first writing position.
The developing device 8 develops the first color (black in this example).

On the other hand, the second writing optical system includes a second laser oscillation device 9, a rotary polygon mirror 3, a second f-θ lens 11, and mirrors 12 and 12 ', and has a second color (for example, a chromatic color such as red or blue). The laser beam 10 carrying image information to be developed in the first and second developing optical systems is irradiated and scanned via the second writing optical system at a second writing position provided at a position following the first developing device 8. 2 are formed. 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 latent image developed with the first color is not completely recovered by the development and the latent image remains, the threshold value of the development potential is set so that the latent image is developed by the second developing device 13 so that color mixing does not occur. Are set appropriately, and appropriate developing bias is applied.

The two-color toner images formed in the same image forming area of the photoreceptor 7 are transferred onto the transfer paper fed from the paper feeder 14 under the action of the transfer charger 15, and the present invention is applied thereto. The sheet is conveyed to a fixing device 17 by a sheet conveying device 16 using a photosensitive belt, and is fixed and discharged.

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

As shown in FIG. 2, the conveying device 16 using the photoreceptor belt includes a photoreceptor endless belt 24 supported by a driving roller 22 and a driven roller 23 and circulating in the direction of the arrow, and a charger 20 for charging the photoreceptor belt. The charged photoreceptor belt 24 comprises a light eliminator 21 for irradiating light while blinking and erasing light to form an electrostatic pattern, and the charging charger 20 and the light eliminator 21 are moved with respect to the circumferential direction of the photoreceptor belt 24. They are provided in this order and upstream of the transfer paper introduction position.

The light removing device 21 is linearly arranged in a direction perpendicular to the circumferential direction of the photoreceptor belt 24 and substantially over the entire width of the belt, and is formed as an array of a large number of light-emitting elements that can be turned on and off individually. . Although not shown in the figure, the high-voltage power supply connected to the charging charger 20, the light erasing device 21 blinks, the high-voltage power supply is turned on / off, and the belt drive is turned on / off.
A control device is provided for controlling the turning off together with the sequence of the printer, image forming conditions, and the like.

The transfer paper fed from the paper feeding device 14, the toner image transferred by the transfer / separation device 15, and separated from the photosensitive drum 7 is guided to the sheet conveying device 16. The driving of the transporting device is started so that the leading end of the transfer paper reaches the sheet transporting device, and the charging charger 20 and the light neutralizing device 21 are driven. When a charge pattern as shown in a) and (b) is formed on the photoreceptor belt 24 and the introduced transfer paper is adsorbed on the photoreceptor belt 24 and conveyed, and reaches the position of the drive roller 22, The transfer paper is separated from the photoreceptor belt 24 by the curvature of the photoreceptor belt 24 and the stiffness of the transfer paper, separated and conveyed to the fixing device.

In addition to the above basic configuration, a cleaning device for the photoreceptor belt 24 after the transfer paper is separated, or a static eliminator for initializing by performing static elimination prior to the next charging by the charging charger 20 may be provided. it can. Further, at the end of printing or in an area where it is not necessary to adsorb the transfer paper, the power supply of the charger may be turned off, or the light removing means 21 may be continuously turned on to remove the charge of the photosensitive belt 24 over the entire area.

FIG. 3 is a view showing a sheet conveying device using a photosensitive belt using a conductive roller 20 'instead of a corona discharger type charger as a charging means. Members having the same functions as those in FIG. The same reference numerals are given. The use of a conductive roller as the charging means has the advantage of eliminating the generation of ozone.

FIGS. 5A and 5B show an example of an electrostatic pattern formed on a photoreceptor belt according to the present invention. In any case, the electrostatic pattern is coarse in a region corresponding to the leading end of the conveyed sheet, and densely formed in a region corresponding to the subsequent portion of the conveyed sheet to the rear end. In the drawing, the level of the potential is indicated by black and white.

In the case of FIG. 5 (a), by repeatedly turning on and off all the light emitting elements of the optical charge removing device at the same time, a striped electrostatic pattern extending in a direction perpendicular to the conveying direction on the photosensitive belt 24 is formed. The width and interval of the stripes are widened in a region corresponding to the leading end of the sheet, and narrowed in a portion thereafter.

In the case of FIG. 5 (b), in the region corresponding to the leading end of the sheet, the two light emitting elements of the photo-static eliminator are alternately blinked as one unit, and the light emitting elements which blink at every certain width are reversed. A coarse-grained checkered electrostatic pattern is formed, and subsequent portions alternately flash on and off with one light-emitting element as a unit. A checkered electrostatic pattern is formed.

As described above, since the electrostatic pattern is coarse in the area corresponding to the leading end of the conveyed sheet and densely formed in the area after that, as described in the operation section, the electrostatic pattern is formed on the sheet fed to the photosensitive belt. Even if the leading edge is still at a position away from the photoreceptor belt, the suction force acts to adsorb the sheet, and after the suction, even if the adsorbing force at the leading end is weak, the remaining part of the sheet is strongly adsorbed due to the strong attraction force. The sheet is reliably carried and conveyed on the belt, and the sheet is easily peeled from the photosensitive belt using the curvature.

Note that the length of the region where the electrostatic pattern with the coarse density at the tip portion is formed is preferably about the radius of curvature at the time of separation. Alternatively, when the sheet is guided and approaches the belt, when the positional relationship is determined so as to approach from the leading edge of the sheet, the positional relationship is determined such that the portion behind the leading edge approaches first earlier. You can make it longer when you are there. Alternatively, the length may be changed according to the thickness of the sheet to be conveyed, the strength of the waist, and the like.

Effects As described above, according to the present invention, the sheet can be guided toward the transport belt at the front end of the sheet and quickly adsorbed, and the adsorbed sheet can be reliably secured by a strong suction force in the portion subsequent to the front end. At the curvature separation position, separation is ensured by the weak suction force at the tip.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an overall schematic structure of an example of an image forming apparatus provided with a sheet conveying device according to the present invention, and FIG. 2 shows a structure of an embodiment of the sheet conveying device of the present invention provided in the device. FIG. 3 is a cross-sectional view showing the configuration of a modified embodiment of the present invention, and FIG. 4 is a schematic diagram showing differences in lines of electric force formed due to the density of an electrostatic pattern formed on a sheet conveying belt. 5 (a) and 5 (b) are plan views showing examples of an electrostatic pattern formed on a sheet conveying belt according to the present invention. 16 ... Sheet conveying device by photoreceptor belt 20, 20 '... Charging means 21 ... Light eliminating means 22 ... Drive roller 23 ... Driving roller 24 ... Photoreceptor belt

Claims (1)

(57) [Claims] 1. An endless photoreceptor belt having a photoreceptor layer formed on a substrate having at least an outermost layer being a conductive layer or a semiconductor layer, and arranged around the endless photoreceptor belt in the circumferential direction. Charging means for charging the photoreceptor layer, blinking light discharging means for discharging the charged photoreceptor layer by light irradiation, means for introducing a conveyed sheet into the endless belt, the charging means The photoreceptor layer uniformly charged by the above is blinked and irradiated by the above-mentioned light removing means to form an electrostatic pattern on the photoreceptor layer according to the level of the potential, and the introduced conveyed sheet is adsorbed and carried on the surface of the endless belt. A plurality of light emitting elements which are arranged in a straight line substantially in the direction perpendicular to the circumferential direction of the endless photoreceptor belt over substantially the entire width of the belt, and which can blink individually. Composed of The light emitting element of the light removing unit is controlled to blink so that the electrostatic pattern is coarse in a region corresponding to the leading end portion of the conveyed sheet and dense in a region corresponding to a rear end portion of the conveyed sheet thereafter. A sheet conveying device characterized by the above-mentioned.