JPH02278277A - Electrophotograph duplicator - Google Patents

Abstract

PURPOSE: To transfer a developed image to a recording medium with high efficiency by providing flexible supporting members and supporting the rear surface of the recording medium for pressing it against the surface of a photoreceptor. CONSTITUTION: This electrophotographic copying device is provided with a transfer electrifier 13 for generating ion for forming a charge on the rear surface of the recording medium, to stick the recording medium to the photoreceptor surface 12 and transfer toner from the photoreceptor surface to the recording medium by electrostatic sticking when the recording medium is peeled from the photoreceptor surface 12, and flexible supporting members 40, 41 and 42, 43 arranged to mechanically support the rear surface of the recording medium in the ion outflow region of the transfer electrifier 13. Then the recording medium in stuck to the photoreceptor surface 12 with the charges from transfer corona electrifiers 33 and 34 on the line where the recording medium is released from mechanical pressure by the flexible supporting members 40, 41 or 42, 43. Thus, the existence of space and an air bubble between the recording medium and the photoreceptor surface can be eliminated and the occurrence of a void in the transfer of the toner can be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an image forming apparatus such as an electrophotographic printer or a copying machine, and particularly relates to an improvement in the transfer of developing toner to a recording medium.

B. Conventional technology Image creation devices such as electronic printers and copiers include:
Electrophotographic types are often used.

In this electrophotographic type of device, a printer generates an image to be printed on the surface of a photoreceptor and forms and fixes it on a recording medium. In an electrophotographic process using flat bond paper, a photoreceptor is mounted on a belt driven by a rotating drum or roller.

In the transfer process, the photoreceptor passes under a charger that applies a substantially constant charge to its entire surface, typically several hundred volts.

The photoreceptor then moves to an imaging station and, in the case of an electrophotographic reproduction machine, receives a beam of light that is modulated in accordance with the data to be printed. The light beam generating means generates a laser beam.

The light beam, which may be a light emitting diode array or other suitable light source, is directed onto a photoreceptor where the modulated light beam is used to form a charge pattern that is a latent image of information. The modulation signal is driven by image pattern data, typically stored digitized in computer-generated memory. Supplied by the character generator.

Similarly, in an electrophotographic copier, a beam of light is reflected from the document to be copied, and this beam is modulated in accordance with the data of the document.6 The reflected beam forms an electrostatic latent image of the document on a photoreceptor at the imaging station. generate. After forming an image on the photoreceptor, the next step in the electrophotographic process is to place a developing material called toner on the latent image in a developer. This material is
A color viewing powder that has a charge and is electrostatically deposited on the area to be developed. The photoreceptor with the developed image moves to a transfer station and the developed visible image is juxtaposed onto an image recording medium 1, usually paper. Since the back side of the recording medium is charged, when the recording medium is separated from the photoreceptor, the toner leaves the photoreceptor while remaining on the paper.

After transfer, residual toner is removed with a cleaner before the photoreceptor is used in the next cycle. The recording medium is sent to a fixing device, and toner is burned onto the recording medium.

During the transfer, the recording medium must be strongly pressed against the photoreceptor. If there is even a slight gap or air bubble between the recording medium and the surface of the photoreceptor, the transfer result will be poor and an empty transfer portion will exist on the recording medium. Furthermore, if cleaning is insufficient and untransferred toner is not sufficiently removed from the photoreceptor, a residual image will remain on the next recording paper.

In the prior art, as a means for attaching a recording medium to the surface of a photoreceptor, a transfer corona charger, that is, a means for applying an electric charge of a polarity opposite to that of the toner to the back surface of the recording medium is usually used. As a result, this charge attracts the recording medium to the photoreceptor surface, providing good transfer. However, sometimes gaps exist due to folds in the recording medium or twisting of the recording medium caused by fusing operations. These twists often occur in hot spots that accumulate in areas of high toner density versus cooler white background areas. These temperature differences cause the paper to twist, resulting in poor transfer results when the same paper is returned to the transfer station to print on the opposite side of the paper.

Other problems arise when using perforated forms or fanfold type papers that are lined or have perforations along the paper and are folded over before use. They produce creases along the perforations, which result in bulges near the creases away from the photoreceptor surface.

Such a bulge makes it difficult to flatly attach the recording medium near the perforation to the surface of the photoreceptor, so printing near the crease must be stopped.

The present invention attempts to improve the efficiency of transfer by mechanically flattening the recording medium inside the transfer corona and pressing it against the surface of the photoreceptor.

The charge generated on the back side of the recording medium by this method is
No gaps or bubbles on the transfer surface of the recording medium.

If it is a cut paper, it is attached to the front or rear edge, if it is a fanfold type, it is attached near the perforation, or to the main body of the recording medium.

U.S. Pat. No. 4,101,212 relates to a paper suppression means in which a roller or plate presses the paper against the surface of a photoreceptor. The pressing means is, for example, Mylar (MYLA).
R=Trademark of DuPont Co.) and is placed outside the transfer corona to press the paper against the photosensitive surface before it enters the transfer section.

This technique is not very effective.

The device of US Pat. No. 3,620,617 involves a mylar flap covering a portion of the transfer charger.

The flap is attached to the shielding plate of the transfer charger,
The flap is adapted to receive a negative charge to provide an electrostatic charge between the flap and the photoreceptor, which does not have time to contact the print paper. The purpose of the flap is to provide a uniform electrostatic magnetic field and eliminate streaks.

U.S. Pat. No. 4,673,280 relates to a static metal paper id placed in a shield voltage section. The guide does not touch the back side of the recording paper, but the guide's clip extends into the corona radiation area. The purpose of this clip is to limit the application of the transfer device extending around the photosensitive drum to a predetermined angle, and the purpose of applying a voltage to the guide is to This is to prevent charges from escaping in the lateral direction of the paper.

US Pat. No. 4,110,027 relates to a printer in which continuously perforated paper is used. 1 of 2 rollers
One is placed in front of the corona charger, and the other one is placed after the charger, and holds the transfer paper on the photosensitive drum. These rollers do not press any part of the back of the copy paper in the corona radiation region.

C1 Problems to be Solved by the Invention The first object of the present invention is to transfer a developed image to a recording medium with high efficiency.

Another object of the present invention is to prevent or reduce the formation of voids near the leading edge or trailing edge of a cut recording medium, or near the crease of a perforated recording medium. be.

Another object of the present invention is to prevent the formation of air bubbles in the body portion of the recording medium. Still another object is to press the recording medium against the photoreceptor surface in the peak discharge region by the transfer corona charger, so that as soon as the recording medium leaves the support member, the recording medium receives a charge from the transfer corona charger, thereby causing the recording medium to It is an object of the present invention to provide a recording medium supporting device that allows the recording medium to be attached to the surface of a photoreceptor without creating gaps or bubbles.

Another object of the present invention is to provide a support device having multiple lengths so that recording media of different sizes can be firmly pressed against the photoreceptor surface at the transfer station.

Still another object of the present invention is to provide a means for supporting a recording medium that can be retracted to a home position where the recording medium does not come into contact with the surface of the photoreceptor when the recording medium is not in the transfer section.

Yet another object is to provide a support means made of metal, such as spring steel, covered in sequence with plastic, wear-resistant material and insulation.

Means for Solving the D0 Problem The present invention relates to the positioning of a flexible support member in the vicinity of a transfer volume with a transfer corona charger in an electrophotographic reproduction apparatus. The end of the support member extends into the corona emitter, preferably near the peak current emission region for maximum effectiveness.

The flexible support member supports the back side of the recording medium in order to press the recording medium against the surface of the photoreceptor.

The extension of the flexible support member into the E0 active transfer zone ensures that the recording medium receives a charge from the transfer corona when it leaves the line of relief from the mechanical pressure applied by the support means. supported on a supporting surface.

The recording medium is attached to the photoreceptor surface by electrostatic force before the void is formed. This method eliminates voids and air bubbles, thereby improving transfer and reducing the amount of residual toner remaining on the photoreceptor surface after transfer.

F. Embodiment FIG. 1 shows an example of an electrophotographic copying machine or printer embodying the present invention.

Recording media for copiers and printers such as cut paper and binding paper 1. The sheets are loaded in the entrance side cassette 10, and are sent out from there toward the exit side cassette 11 along a substantially straight sheet feeding path. A transfer device 13 transfers the image on the photoreceptor surface 12 to recording paper. In the apparatus shown in FIG.
is installed on top of. Photoreceptor 12 is corona charger 1
5, corona charger 15 creates a relatively constant electrostatic charge on photoreceptor surface 12. An electrostatic latent image is formed by irradiating the photoreceptor surface 12 with a beam of light 16 . In the configuration of FIG. 1, the imager and the transfer device 13 are located at the same position. The photoreceptor (photoconductive storage body) 12 continues to rotate, and the developer 1 deposits toner on the latent image to develop it.
Move to 7. The developed image is turned off2
It passes under the corona charger 15 and the pre-transfer lamp 18
The image is then moved to a transfer device 13, where the developed image is transferred onto recording paper.

The recording paper is fed from the entrance cassette 10, and its relative position is controlled by the paper feeding means so that the leading edge of the recording paper coincides with the leading edge of the image. When the recording paper is separated from the photoreceptor 12, toner is transferred onto the recording paper. After the transfer, the photoreceptor rotates toward a developer 17, which serves as a cleaning device, where residual toner left after the transfer is removed.

Photoreceptor 12 then advances to corona charger 15 to begin a new image reproduction cycle.

The apparatus shown in FIG. 1 described above is an apparatus in which the photoreceptor needs to rotate twice in order to complete two cycles, that is, to complete one print. In the first cycle of rotation of the drum,
As previously mentioned, photoreceptor surface 12 is charged, imaged thereon, and developed. In the second cycle, the developed image is transferred to recording paper and residual toner is removed from the photoreceptor surface.

In the apparatus of FIG. 1, there are other elements around the drum including a detector 19 which detects when the recording paper remains unseparated from the drum after transfer. Additionally, a pre-clean removal lamp 20, an edge removal lamp 21, and a sensor 22 for measuring the density of toner on the photoreceptor surface are located adjacent to the drum.

The electrostatic probe 23 is used to detect the level of charge applied to the surface of the photoreceptor by the corona charger 15,
Intermediate removal lamp 24 is used to remove charge in areas not affected by the imaging beam prior to development.

After the transfer, the recording paper moves on the underside of the vacuum conveyor 26,
If a cut sheet is used, the sheet is returned to the transfer device 13 via a dual path 28 to a fuser 27 which fixes the toner to the recording sheet, resulting in a double-sided copy that prints on both sides of the sheet.

FIG. 2 shows the paper entrance guide 30 of the transfer device 13. 0 sheets and other recording media pass under the 1 paper entrance guide 30 toward the transfer device 13 as shown by arrow B. Ru. The corona charger is located in a transfer area of the transfer device 13, which is divided by a side plate 31 on the input side and a side plate 32 on the exit side. Corona wire 3
3 and 34 extend along the surface of the photoreceptor 12, and by applying a voltage to both wires, a corona discharge is generated toward the charged photoreceptor surface moving in the transfer section, and an ion flow is generated from the wire. By positioning the recording paper between the corona wire and the photoreceptor, ions hit the back of the recording paper,
A recording paper is electrostatically attached to the surface of the photoreceptor 12.

For example, polyetherimide
A flexible member 40 made of a plastic insulating material such as ide) is connected to a flexible metal member 4 made of a material such as spring steel.
It is attached to 1. The combination of the metal member 41 and the insulating member 40 constitutes a flexible support member in the present invention. The metal member 41 provides a constant spring constant and does not require setting, thereby reducing stress on the plastic member 40.

The metal member 41 comes into contact with the recording paper, serves as a main support means for the back surface of the paper, and acts to eliminate idle transfer. A plastic insulating member also contacts the paper. Metal member 41
is coupled to shaft 44.

There is a similar combination of a metal member 43 and a plastic member 42, with the metal member 43 being coupled to a shaft 44.

The presence of the two sets of flexible support means is to accommodate two different sizes of recording paper.
The 0 member 41 used to support the back side of the 355.degree. 6 m (14 inch) sheet of paper together with the member 4o is used to support the back side of the 355.degree. 6 m (14 inch) sheet of paper.

FIG. 3 shows a shaft 4 to which flexible steel members 41 and 43 are fixed.
4 is a perspective view of FIG. Plastic parts 40 and 42 are fixed to steel parts 41 and 43.

The shaft 44 has a one-step difference 45, and as shown in FIG. 2, the members 42 and 43 are placed at a position slightly apart from the photoreceptor 12.

Note that FIG. 2 is a sectional view taken along line 2-2 in FIG. 3.

In FIG. 3, plastic insulation members 40 and 42 completely cover metal members 41 and 43 to shield them from corona discharge and prevent arcing.

FIG. 4 shows flexible members 40 and 42 mounted on shafts disposed along photoreceptor 12, in operation.
and 42 are metal members 41 and 43 as soon as they come into contact with the back side of the recording paper.
Although not visible in FIG. 4, it also comes into contact with the recording paper in the operating state. Shaft 44 is connected to a stepper motor 46 which moves flexible member 40 from a home position to an operative position in which members 40-43 contact the back side of a 14 inch recording sheet.

In the home position, the 1 members 40-43 do not contact the photoreceptor surface 12, so the photoreceptor surface passes under the flexible support member without contact.The insulating piece 47 of the 0 member 40 supports the recording paper. It's in a good position. The insulating piece 47 is connected to the recording paper beyond that line.

A "release line" that is not affected by the mechanical pressure exerted on the recording paper by the member 4o is defined.

279. In the operation of the paper having a width of 4 mm, the 5 paper moves on the photoconductor surface 12 toward the transfer section 13, and immediately after the leading edge of the recording paper passes the leading edge 47 of the flexible insulating member 40, the photoconductor The stepper motor 46 connects the elastic members 40 and 41 so as to contact the elastic members 40 and 41.
Move to the back of the recording paper.

If 355.6 mm wide paper is used, the stepper motor 46 will move further 1 and the flexible insulating member 4
2 comes into contact with the recording paper together with the member 43.

Until the leading edge of the recording paper comes in, the flexible support member 40
43 are not under pressure, members 40-43 are not in direct contact with the photoreceptor surface, and therefore.

Does not damage the surface of the photoreceptor.

Similarly, the support member is not contaminated with toner.

In addition to eliminating idle transfer in the main body of the recording paper, the supporting means improves the transfer at the leading and trailing edges of the recording paper, and prevents the recording paper from leaving the surface of the photoreceptor and touching the side wall 3 of the corona charger 13. It has the effect of reducing the possibility of collision.

The support member operates to firmly adhere the recording paper to the surface of the photoreceptor, even over wide variations in temperature and humidity.

In addition to embodiments, by drilling holes in series in the support member, some capacitive coupling of the recording paper to the photoreceptor can be initiated before the recording paper moves beyond the leading edge of the support member.

Additionally, the dimensions of the support member may be slightly narrower than the dimensions of the paper to provide marking tolerances for the paper. As a result, before the recording paper leaves the leading edge of the support member.

The leading edge of the paper can be electrostatically bonded. Therefore, the edge of the paper may bond too quickly to the photoreceptor surface, which may cause the recording paper to bend. In order to prevent such a situation, it is preferable to provide a portion of the support member at the edge of the paper to block the transfer flow, and this portion must be provided at a position where it does not come into direct contact with the surface of the photoreceptor.

The tips 47 of the insulating members 40 and 42 are preferably provided in the region of the peak value of the corona current, that is, in the vicinity directly below the corona wire 33 in FIG. As a result, ions generated by the corona wire 33 strike the back surface of the recording paper immediately after leaving the support members 40 and 42, and as a result, the recording paper is electrostatically attached to the surface of the photoreceptor without forming any voids. let However, if the support member extends into the transfer area, the benefits of attaching the recording paper to the photoreceptor are significantly greater. The maximum profit is 1. This is obtained when the tip 47 is located directly below the corona wire.

As described above, the metal members 41 and 43 are the main members that mechanically contact the paper in order to eliminate voids that are not transferred. The insulating members 40 and 42 also contact the paper, but typically do not apply significant mechanical force, since this arrangement can create triboelectric effects if the plastic insulating members are forced into contact with the paper. Such effects electrically charge the paper and cause premature toner transfer from the thermal surface to the paper, creating problems in the background areas.

The metal members 41 and 43 solve this problem, and also have improved wear resistance and can extend the time for parts replacement. Nevertheless, in some types of machines, triboelectric effects are not a problem, and in such cases the benefits of the present invention can be achieved even with plastic parts alone.

The plastic member preferably has a high glass transition temperature. In other words, polyetherimide is more desirable as an insulating material than polyester, which has greater abrasion resistance.The combination of polyester's transparency and relatively low glass transition temperature makes it possible to soften or melt old, worn-out products. It tends to accumulate at the edges and increase in length irregularly. In some instances this problem is not present and polyester is sufficient.

It is desirable that the rectangular sides of the insulating member and the metal member come into contact with the surface of the photoreceptor, but in the worst case within the tolerance,
The plastic part and the metal part come into contact initially, causing wear of the plastic part.

Such tolerances may also result in only the metal parts being in contact, thereby increasing the tip spacing slightly. It is surprising that the metal member, especially at high temperatures, does not come into contact with the paper and cause the paper to release the transferred charge. Such release is time dependent and does not adversely affect image transfer at sufficiently fast processing speeds.

In the embodiment, an example in which the photoreceptor is provided on the drum surface has been described, but the photoreceptor may be provided on a belt.

Furthermore, there are various methods for imparting flexibility to the support member. For example, the member may be made of flexible plastic. Non-flexible members may be made flexible using springs, screw remoters, or other resilient devices.

G. Effect: It is possible to eliminate the presence of gaps and air bubbles between the recording medium and the surface of the photoreceptor, thereby minimizing the occurrence of voids in toner transfer.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall configuration of an electrophotographic apparatus in which the present invention is implemented. FIG. 2 is a cross-sectional view showing details of the transfer section of the device of FIG. 1, including a flexible support member of the present invention. 3 is an enlarged perspective view of the support member of FIG. 2, and FIG. 4 is a perspective view of the support member and photoreceptor of FIG. 1. Explanation of symbols 12...Photoreceptor 13...Transfer device 15...Corona charger 17...Developer 4o...Insulating member 41 ...Flexible metal parts applicant International Business Machines Corporation agent Patent attorney Takashi Tonmiya - (1 other person)

Claims (7)

[Claims] (1) A photoconductor that moves continuously through various processing sections, a charger that applies a uniform electrostatic charge to the surface of the photoconductor, and a charger that applies a uniform electrostatic charge to the surface of the photoconductor to form an electrostatic latent image. a developing device that holds chargeable toner and places the charged toner on the surface of the photoreceptor to develop the latent image; A medium is attached to the photoreceptor surface, and a charge is applied to the back surface of the recording medium to cause the toner to be transferred from the photoreceptor surface to the recording medium by electrostatic adhesion when the recording medium is peeled from the photoreceptor surface. a flexible support member arranged to mechanically support the back surface of the recording medium in the ion outflow area of the transfer charger. , characterized in that the charge from the transfer corona charger causes the recording medium to adhere to the surface of the photoreceptor on a line where the recording medium is released from mechanical force by the flexible support member. An electrophotographic copying device. (2) The electrophotographic copying apparatus according to claim 1, wherein the flexible support member includes a spring metal member covered with a plastic insulating material. (3) An electrophotographic copying apparatus including a flexible support member used with a photoreceptor surface that moves continuously through various processing sections, the processing section applying an electric charge to the back surface of the recording medium. a transfer device having a corona charger that generates ions, the flexible support member being disposed within the region of the ion flow generated by the corona charger and mechanically against the back surface of the recording medium; and a plastic insulating member in contact with the electrophotographic copying apparatus. (4) The flexible support member is within the ion outflow region,
4. The electrophotographic copying apparatus according to claim 3, wherein the ion flow extends to a vicinity where the ion flow reaches a maximum value. (5) The electrophotographic copying apparatus according to claim 4, wherein the flexible support member is divided into a plurality of parts so as to be adaptable to a plurality of sizes of the recording medium. (6) Connected to the flexible support member, from a first position where the flexible support member does not contact the photoreceptor surface to a second position where the flexible support member contacts the recording medium on the photoreceptor surface from the back side. 4. The electrophotographic copying apparatus according to claim 3, further comprising driving means for moving the electrophotographic copying apparatus. (7) The flexible support member has a spring metal member covered with a plastic insulator, and the spring metal member contacts the back surface of the recording medium and applies a main force to the back surface of the recording medium. An electrophotographic copying apparatus according to claim 3, characterized in that: