JPH075730A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the surfaces of the recording carrier and the latent image carrier of a device from being stained by fixing oil specially when an image is formed on both surfaces of a recording material by executing developing by including a nonimage forming area when the final image is formed. CONSTITUTION:In the case that the image is formed by simultaneously carrying the plural sheets of recording materials when the image is formed on the back surface of the recording material at the image formation of both surfaces thereof, development is performed to a photoreceptor drum 1 including the non-image forming area when the final image is formed. By developing the area corresponding to the second side while the final image is formed, the oil retained on a recording material carrying sheet 5f by toner grains developed on the drum 1 can be blocked from being transferred and attached on the drum 1. Since the grain size of the toner (8 mum in average) is sufficiently larger than the thickness of an oil layer (about 2-3mum), the toner grain functions as a spacer grain and the oil is prevented from being transferred and attached to the drum 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, a copying machine, an LB.
The present invention relates to an electrophotographic type or electrostatic recording type image forming apparatus such as a P or a facsimile.

[0002]

2. Description of the Related Art Conventionally, for example, various full-color image forming apparatuses having a photosensitive drum as an electrostatic latent image carrier and a recording material carrier for supporting paper as a recording material have been proposed and implemented. ing.

FIG. 7 shows an example of such a general full-color image forming apparatus.

In this drawing, in this full-color image forming apparatus, a photosensitive drum 1 which is an image carrier is rotatably supported in the direction of an arrow, and a corona charger 2, an optical system 3, a developing device 4, and the like are provided around the photosensitive drum 1. Transfer device 5, cleaning device 14
Are arranged.

The optical system 3 is composed of a document scanning section and a color separation filter, and is a laser beam exposure apparatus as shown in the figure for irradiating the photosensitive drum 1 with a color-separated light image or a light image E corresponding thereto. is there.

The photosensitive drum 1 uniformly charged by the corona charger 2 is irradiated with a light image E for each separated color to form a latent image. The developing device 4 is a rotary developing device and has a central shaft 4b.
Around the four developing devices, that is, the black developing device 4Bk,
A cyan developing device 4c, a magenta developing device 4m, and a yellow developing device 4y are arranged, and a predetermined developing device is rotated to a developing position facing the photosensitive drum 1 to develop the latent image on the photosensitive drum 1, and the photosensitive drum 1 An image is formed on the upper surface of the resin-based toner.

Further, the toner image on the photosensitive drum 1 is supplied from the recording material cassette 7 via the conveying system and the transfer device 5 to a position facing the photosensitive drum 1 (according to the path shown by the dotted line in the drawing). It is transferred to the material. The transfer device 5 is
In this example, a transfer drum 5a, a transfer corona charger 5b, an attraction corona charger 5c for electrostatically attracting a recording material, an attraction roller 5g, an inner corona charger 5d, and an outer corona charger 5e are provided. A recording material carrying sheet 5f made of a dielectric material is integrally stretched in a cylindrical shape in an opening area of a peripheral surface of a transfer drum 5a which is rotatably supported.

As the transfer drum 5a rotates, the toner images on the photosensitive drum 1 are sequentially transferred onto the recording material carried on the recording material carrying sheet 5f by the transfer charger 5b.

A desired number of color images are transferred to the recording material sucked and conveyed by the recording material carrying sheet 5f to form a full-color image.

When the transfer of the desired number of toner images is completed in this way, the recording material is separated from the transfer drum 5a by the separating means 8 and discharged onto the tray 10 via the heat roller fixing device 9.

On the other hand, after the transfer, the photosensitive drum 1 and the recording material carrier sheet 5f are cleaned of the residual toner on their surfaces by the cleaning device 6 and the transfer cleaner 14, which are cleaning means, respectively, and then subjected to the image forming process again. Be offered.

When the peripheral length of the transfer drum 5a is more than twice the length of the recording material, two or more recording materials are carried on the transfer sheet 5f at the same time in order to increase the throughput during continuous image formation. A method of forming an image is adopted. For example, when two sheets of recording material can be carried simultaneously, when five consecutive images are formed, two sheets, two sheets, and one sheet are first carried to form two sheets, and finally the remaining one sheet is formed. This is a method of forming one image.

[0013]

However, in the conventional image forming method in which a plurality of recording materials are simultaneously carried on the recording material carrying sheet to form an image, especially when the images are formed on both sides of the recording material. However, there is a problem that oil stains due to the fixing oil occur on the recording material carrying sheet, the surface of the photosensitive drum and the like.

To explain this problem in detail, when an image is formed on the front surface of the recording material and then the toner is transferred to the back surface of the transfer drum, the recording material contains the fixing oil that has once passed through the heat roller fixing device. Since the molten oil adheres to the smooth surface of the toner, the fixing oil first transfers onto the recording material carrying sheet 5f of the transfer drum 5a. Further, the fixing oil transferred onto the recording material carrying sheet 5f is transferred onto the surface of the photosensitive drum 1 when the photosensitive drum 1 and the recording material carrying sheet 5f contact at the transfer portion. Therefore, when the double-sided image formation is continuously performed, the fixing oil accumulates on the surface of the photosensitive drum 1.

When normal image formation is performed in this state, the toner adheres to a region that should originally be a white background and appears as fog due to the adhesive force of the fixing oil. On the other hand, the toner is not sufficiently transferred from the photosensitive drum 1 to the recording material due to the adhesive force of the fixing oil, so that a light image is formed even in the area that should originally be a solid portion.

In order to deal with such a problem, an image forming apparatus provided with a cleaning device for removing the fixing oil adhering to the recording material carrying sheet of the transfer drum has been conventionally proposed.

However, this cleaning device is
The cleaning timing is performed after the transfer of the final color. Therefore, in the above-described plural-sheet simultaneous carrying image forming method, for example, in the case where an odd number of images are continuously formed by carrying two sheets at the same time, when the image is formed. It is impossible to prevent the fixing oil accumulated on the side not carrying the last one recording material from transferring to the photosensitive drum. Of course, it is possible to remove the oil accumulated on the recording material carrying sheet of the transfer drum by the oil removal cleaner, but doing this work during image formation gives a shock to the transfer drum and causes color misregistration. Not preferable.

Therefore, it is an object of the present invention to prevent oil stains from being caused by the fixing oil on the surfaces of the recording material carrier and the latent image carrier of the apparatus, especially when images are formed on both sides of the recording material. An image forming apparatus is provided.

[0019]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is
A latent image carrier on which a latent image is formed, a developing device that develops the latent image formed on the latent image carrier into a visible image, and a plurality of recording materials are carried at the same time. In an image forming apparatus having a recording material carrier for transferring an image onto the recording material at a portion closest to the latent image carrier, a plurality of recording sheets is formed at least during double-sided image formation of the recording material. The image forming apparatus is characterized in that when a material is simultaneously carried to form an image, the latent image carrier is developed including a non-image forming area at the time of final image formation.

It is preferable that the development includes a blank development that does not form a latent image on the latent image carrier.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. In the embodiments described below, the present invention is described as being embodied in an electrophotographic color image forming apparatus.

Embodiment 1 In this embodiment, the color image forming apparatus shown in FIG. 1 has a digital color image reader section in the upper part and a digital color image printer section in the lower part.

In the digital color image reader unit, the original 30 is placed on the original table glass 31 and exposed and scanned by the exposure lamp 32, so that the reflected light image from the original 30 is condensed on the full color sensor 34 by the lens 33. ,
Obtain a color separation image signal. The color-separated image signal is processed by a video processing unit (not shown) via an amplifier circuit (not shown) and sent to a digital color image printer section.

In the digital color image printer section,
The photosensitive drum 1, which is an image bearing member, is a photosensitive member made of an organic photoconductor, which will be described later, and is rotatably supported in the direction of the arrow. Around the photosensitive drum 1, a pre-exposure lamp 11, a corona charger 2, Laser exposure optical system 3, potential sensor 12, four developing devices 4y, 4c, 4m, 4Bk having different colors, on-drum light amount detecting means 13, transfer device 5, cleaning device 6
Are placed.

In the laser exposure optical system 3, the image signal from the reader section is converted into an optical signal for image scan exposure by a laser output section (not shown), and the converted laser light is reflected by the polygon mirror 3a. , Is projected onto the surface of the photosensitive drum 1 via the lens 3b and the mirror 3c.

When forming an image on the print section, the photosensitive drum 1
Is rotated in the direction of the arrow, and the photosensitive drum 1 after the charge is removed by the pre-exposure lamp 11 is uniformly negatively charged by the charger 2, and the light image E is emitted for each separated color to form a latent image. .

Next, a predetermined developing device is operated to reverse-develop the latent image on the photosensitive drum 1 to form a toner image on the photosensitive drum 1 with a negative toner made of resin as a base. The developing device selectively approaches the photosensitive drum 1 in accordance with each separated color by the operation of the eccentric cams 24y, 24c, 24m, and 24Bk to perform development.

Further, the toner image on the photosensitive drum 1 is transferred from the recording material cassettes 7a, 7b, 7c to the recording material supplied to the transfer position facing the photosensitive drum 1 via the conveying system and the transfer device 5. In this embodiment, the transfer device 5 includes a transfer drum 5a having a peripheral length that is at least twice the maximum recording material length, a transfer charger 5b, and a suction roller facing the suction charger 5c for electrostatically sucking the recording material. 5g, an inner charger 5d, and an outer charger 5e. Further, the transfer drum 5a, which is rotatably driven, has a recording material carrying sheet 5f carrying a recording material, which is integrally stretched on a cylinder in an opening area of its peripheral surface. A polycarbonate film or the like is used as the recording material carrying sheet 5f.

As the transfer device 5, that is, the transfer drum 5a is rotated, the toner image on the photosensitive drum is transferred onto the recording material carried on the recording material carrying sheet 5f by the transfer charger 5b. In this way, the recording material carrying sheet 5f
A desired number of color images are transferred to the recording material sucked and conveyed to form a full-color image.

In the case of forming a full-color image, when the transfer of the four color toner images is completed in this way, the recording material is separated from the transfer drum 5a by the action of the separation claw 8a, the separation push-up roller 8b and the separation charger 5h, Heat roller fixing device 9
The sheet is discharged to the tray 10 via the.

On the other hand, after the transfer, the photosensitive drum 1 is subjected to the image forming process again after the residual toner on the surface is cleaned by the cleaning device 6.

When images are formed on both sides of the recording material,
Immediately after the recording material is discharged from the fixing device 9, the conveyance path switching guide 19 is driven, the conveyance vertical path 20 is passed, and then the reversing path 21a.
Then, the reversing roller 21b is reversely rotated, and the trailing end of the recording material when fed to the reversing path 21a is made to be the leading end and is retracted in the direction opposite to the feeding direction, and is temporarily stored in the intermediate tray 22. Next, an image is formed again on the other surface of the recording material by the above-mentioned image forming step.

Further, the recording material carrying sheet 5f is operated by operating the eccentric cam 25 at a desired timing and operating the cam follower 5i integrated with the transfer drum 5a.
The gap between the photosensitive drum 1 and the photosensitive drum 1 can be arbitrarily set. For example, the distance between the transfer drum and the photosensitive drum can be increased during standby or when the power is off.

In this image forming apparatus, the transfer cleaner 14 for removing the residual toner on the recording material carrying sheet 5f is used.
Is provided for cleaning the recording material carrying sheet 5f.

Since the transfer cleaner 14 also serves as an oil remover, it is a web type cleaner as shown in FIG. In the figure, the transfer cleaner 14 includes an unwinding roller 14b around which an unused web 14a is wound, a pressing member 14c for bringing the web 14a unwound in the direction of the arrow into contact with the recording material carrying sheet 5f at a predetermined pressure, and It is composed of a winding roller 14d that winds up the used web 14a, whereby the toner and oil are removed while the web 14a rubs the recording material carrying sheet 5f.

The material of the web in this embodiment is as follows.

Material of fiber: synthetic non-woven fiber of nylon and polyester Fiber thickness: average thickness 4 μm, 10 μ in thickness distribution
Percentage of m or less 90% Density of non-woven fabric: 0.17 g / cm ³ Average spacing between fibers: 2.5 μm Thickness of non-woven fabric: 500 μm By using such non-woven fabric, the oil on the recording material carrying sheet 5f is almost completely removed. Could be removed.

In addition to the above materials, there are polypropylene, rayon, acrylic, nylon, polyester, vinylon, and synthetic fibers thereof as the material of the fibers constituting the non-woven fabric. There was no.

The fiber density of this nonwoven fabric is 0.05.
The range is preferably 0.80 g / cm ³ and particularly 0.1
The oil removal ability was excellent in the range of 0.5 g / cm ³ .

Furthermore, as a result of using the above material as a cloth by appropriately weaving it as a non-woven fabric, uneven wiping of the oil occurs in the weaving direction, that is, the knitting direction, and it is necessary to use it as an oil cleaning member. The range of setting conditions was narrowed, which was not preferable.

Further, in order to improve the oil absorbability, the transfer cleaner may be composed of two layers, an oil removing layer and an oil absorbing layer.

Further, as the transfer cleaner shape, not only the web but also the roller shape can obtain the same effect. In addition, there is an advantage that the device can be simplified as compared with the web system by using the roller shape.

Next, the image forming sequence in the image forming apparatus of this embodiment will be described with reference to the sequence chart of FIG.

As shown in the figure, the first and second two sheets are carried on the transfer drum to form an image,
Finally, one sheet is carried and image formation is performed. Here, when the first sheet side when two sheets are carried is called the A side and the second sheet side is called the B side, it is carried during the image formation of the final image, that is, in the present embodiment, the A side. Even during the four-color image formation on the fifth recording material, the photosensitive drum is developed in the band (non-image forming area) corresponding to the B side of the transfer drum on which the recording material is not carried. Is shown.

By developing the area corresponding to the B side during image formation of the final image, the oil accumulated on the recording material carrying sheet is transferred to the photosensitive drum by the toner particles developed on the photosensitive drum. You can block. This is the thickness of the oil layer (about 2-3 in this embodiment).
μm) to the toner particle size (average particle size of about 8 in this embodiment)
(μm) is sufficiently large, the toner particles function as spacer particles, and transfer of oil to the photosensitive drum is prevented. Further, since the development of the B side is performed to achieve such a blocking effect, so-called blank development in which a latent image is not formed on the photosensitive drum may be used in order to reduce the toner consumption amount. Even in such a blank development, a so-called fog in which toner adheres to the photosensitive drum occurs in the developing portion, so that the spacer effect is sufficient.

The separation operation is also performed during the same rotation in which the final color (black Bk in this embodiment) on the A side during the image formation of the final image is developed, and the transfer cleaner also operates. Then, since the B side passes through the transfer portion while the A side of the transfer drum is being cleaned, in this embodiment, the black Bk is blank-developed to prevent the transfer of oil to the photosensitive drum. ing.

Next, in order to clarify the present embodiment,
An image forming sequence in the conventional image forming apparatus will be described with reference to the sequence chart of FIG. 4 by taking as an example the case of forming two consecutive images of five sheets as in the present embodiment.

Similar to the present embodiment, two sheets are first and secondly carried to form an image, and one sheet is finally carried to form an image. In this case, the final image is formed. B during image formation, that is, during image formation of four colors on the A side
The side (non-image forming area) is not developed. Therefore, the final color on the A side (black Bk in this case)
During the same rotation, the separation operation is performed and the transfer cleaner also operates. In this case, since the B side passes through the transfer portion while the A side is being image-formed and cleaned, the oil is transferred onto the photosensitive drum and adversely affects the subsequent image.

Next, with reference to the sequence chart of FIG. 5, the image forming sequence in the image forming apparatus of this embodiment will be described by taking the case of continuous image formation of two sheets and six sheets as an example.

In this case, as shown in the drawing, the transfer drum carries two images from the beginning to the end so that image formation is carried out, that is, there is no non-image forming area. As in the past, no blank development was performed.

However, in this case, the apparent length of the recording material becomes long by carrying two recording materials, and when the leading edge of the first recording material passes through the transfer sheet cleaning section, the second recording material is still formed. Since the transfer of the final color is being performed, when the transfer cleaner is operated, the shock causes a color shift. Therefore, when two sheets are carried to the end, idle rotation is carried out while carrying the recording material, and thereafter, the recording material carrying sheet is cleaned during the same rotation as the separation.

The image forming sequence for 6-sheet continuous image formation carrying two sheets similar to the above in the conventional image forming apparatus is the same as the above, and therefore its explanation is omitted.

As described above, by using the image forming sequence including the blank development, in the image forming apparatus for carrying out the simultaneous two-sheet carrying image formation as described above, the oil which has been conventionally produced when the double-sided image formation is carried out. It is possible to eliminate the adverse effect on the image due to transfer.

Embodiment 2 Next, with reference to FIG. 6, a second embodiment of the image forming apparatus according to the present invention will be described.
An example will be described. The first embodiment will be described first.
The description of the same parts as those in the above embodiment will be omitted, and only different parts will be performed.

The feature of this embodiment is that the transfer cleaner 14 in the first embodiment is improved. That is, the transfer cleaner of the first embodiment uses only one web-type or roller-type cleaner, and such a cleaner strongly rubs the recording material-carrying sheet 5f of the transfer drum 5a, and thus the recording material. It is not preferable considering the life of the supporting sheet. Further, such rubbing cleaning is necessary for removing oil, but if it is only for removing toner, it is relatively soft for cleaning a recording material carrying sheet such as a fur brush cleaner. It is enough.

Therefore, in this embodiment, as shown in the figure, two types of cleaners, that is, a fur brush cleaner 14 'as a toner removing cleaner and an oil removing cleaner 16 are provided. The oil removal cleaner 16
The web-type or roller-type cleaner in the first embodiment is used for this.

Further, since the oil removing cleaner 16 rubs the surface of the recording material carrying sheet, it is preferable to operate only during double-sided image formation. To prevent clogging of the oil removing cleaner with toner, the oil removing cleaner 16 is also used for removing toner. It is preferably used together with the cleaner 14 '. Therefore, the oil removing cleaner 16 is preferably arranged next to the toner removing cleaner 14 'with respect to the rotating direction of the rotary drum 5a.

The description of the image forming sequence is omitted because it is the same as that of the first embodiment. However, in the present embodiment as well, the use of the above image forming sequence not only causes color misregistration but also adversely affects the image due to oil transfer. Can also be resolved.

Third Embodiment Next, a third embodiment will be described. The present embodiment relates to an image forming apparatus for simultaneously carrying and forming a plurality of sheets of three or more sheets. For example, the size of the recording material is small like B5 size, and the peripheral length of the transfer drum is 3 times the length of the recording material. In the case where the recording amount can be doubled or more, three recording materials are simultaneously carried on the transfer drum to form an image.

In this case, for example, when forming an image of 8 sheets in succession, 3 sheets are carried first, then 3 sheets, and finally 2 sheets.
Since the sheet is carried, the empty development is performed on the empty portion of the third sheet when the final image is formed, that is, the non-image forming area.

By using such an image forming sequence, it is possible to eliminate the adverse effect on the image due to the oil transfer even when the simultaneous carrying image formation of three or more sheets is carried out.

[0062]

As is apparent from the above description, in the image forming apparatus according to the present invention, a plurality of recording materials are simultaneously carried to form an image at least during backside image formation during double-sided image formation of the recording material. During the final image formation, development is performed including the non-image forming area to prevent the fixing oil accumulated on the recording material carrier from transferring to the latent image carrier via the non-image forming area. Therefore, the latent image bearing member and the recording material bearing member are free from oil stains, so that a good image without fog or thin image can be obtained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of an image forming apparatus according to the present invention.

FIG. 2 is an enlarged view of a transfer cleaner in the image forming apparatus of FIG.

FIG. 3 is a sequence chart showing the features of the present invention when forming an odd number of images.

FIG. 4 is a sequence chart similar to FIG. 3 when forming an odd number of images in the conventional technique.

FIG. 5 is a sequence chart when forming an even number of images.

FIG. 6 is an overall configuration diagram of a second embodiment of the image forming apparatus.

FIG. 7 is a schematic configuration diagram showing a conventional image forming apparatus.

[Explanation of symbols]

 1 Latent image carrier (photosensitive drum) 4y, 4c, 4m, 4Bk Developer carrier (developing device) 5 Recording material carrier (transfer device) 9 Heat roller fixing device 14 Transfer cleaner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Tamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (2)

[Claims] 1. A latent image carrier on which a latent image is formed, a developing device for developing the latent image formed on the latent image carrier into a visible image, and a plurality of recording materials are carried at the same time. Then, in an image forming apparatus having a recording material carrier that transfers the visible image onto the recording material at a portion closest to the latent image carrier, at least during backside image formation during double-sided image formation of the recording material. In the case of carrying out image formation by carrying a plurality of recording materials at the same time, the latent image carrier is developed including the non-image forming area at the time of final image formation. . 2. The image forming apparatus according to claim 1, wherein the development includes a blank development that does not form a latent image on the latent image carrier.