JPH06258964A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of stably attracting a recording material to a recording material carrier body, prolonging the life of the recording material carrier member and an attractive pressing member, etc., and always obtaining an excellent image. CONSTITUTION:The recording material is held by the recording material carrier sheet 5f with only the electrostatic attracting force of an attractive electrifying brush 5c and an attracting roller 5g. Though the attractive electrifying brush 5c is brought into press-contact with the recording material carrier sheet 5f, at least when the recording material passes through, the brush does not make the recording material carrier sheet 5f deviated out of a rotational circular orbit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an electrophotographic type or electrostatic recording type image forming apparatus, and more particularly, for example,
A recording material is electrostatically attracted and held on a flexible recording material carrier such as a dielectric sheet, and an electric field is applied to this recording material to form a visible image on the image carrier. It is preferably embodied in a color image forming apparatus such as a multicolor electrophotographic copying machine or a color printer which obtains a color image by superposing and transferring a (toner image) onto the recording material.

[0002]

2. Description of the Related Art Conventionally, many image forming apparatuses have been proposed to obtain a color image by using, for example, an electrophotographic method.
As one method, image carrier OPC, Se, a
-On an electrophotographic photosensitive drum having a photosensitive layer such as Si,
After forming a latent image according to the color separation signal of the original image and developing and visualizing with a colored toner, each time of development, after transferring to a recording material carried on a recording material carrier to form a multicolor toner image,
There is an image forming apparatus that fixes a toner image on a recording material to obtain a color copy. FIG. 7 shows an example of such a color image forming apparatus.

In this example, the color image forming apparatus has a digital color image reader section in the upper part and a digital color image printer section in the lower part.

In the 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 by the lens 33 on the full-color sensor 34, and color images are obtained. Obtain a decomposed 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 the printer section.

In the printer section, a photosensitive drum 1 which is an image bearing member is rotatably supported in a direction of an arrow, and a pre-exposure lamp 11, a corona charger 2, a laser exposure optical system 3 and a potential sensor are provided around the photosensitive drum 1. 12, four developing devices 4Y, 4M, 4C, 4K of different colors, on-drum light amount detecting means 13, transfer device 5, and cleaning device 6 are arranged.

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

During image formation in the printer section, the photosensitive drum 1
Is rotated in the direction of the arrow, the photosensitive drum 1 after the charge is removed by the pre-exposure lamp 11 is uniformly 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 develop the latent image on the photosensitive drum 1 to form a resin-based toner image on the photosensitive drum 1. The developing device is an eccentric cam 24.
By the operations of Y, 24M, 24C and 24K, the photosensitive drum 1 is selectively approached in accordance with each separated color and development is performed.

Further, the toner image on the photosensitive drum 1 is
The recording material is transferred from the recording material cassette 7 (7a, 7b, 7c) to the recording material supplied to the transfer position facing the photosensitive drum 1 via the transport system and the transfer device 5. The transfer device 5 usually includes a transfer drum 5a, a transfer charger 5b, an attraction charger 5c for electrostatically attracting a recording material, an attraction roller 5g facing the attraction roller 5g, an inner charger 5d, and an outer charger 5e. Further, the transfer drum 5a, which is rotatably driven, has a cylindrical recording material carrier 5f integrally stretched in an opening area of its peripheral surface. As the recording material carrier 5f, a dielectric sheet such as a polycarbonate film is used.

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

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 fixing device 9 is discharged, the transport path switching guide 19 is driven, and after being guided to the reversing path 21a through the transport vertical path 20, the reverse end of the reversing roller 21b causes the trailing end when fed to the beginning. Then, it is withdrawn in the direction opposite to the direction in which it was fed and is stored in the intermediate tray 22. After that, an image is formed on the other surface by the above-described image forming step.

The fur brush 14 and the recording material-carrying sheet 5 are used to prevent scattering of powder on the recording material-carrying sheet 5f of the transfer drum 5a and adhesion of oil on the recording material.
The backup brush 15 facing the brush 14 via f, the oil removing roller 16 and the recording material carrying sheet 5f
Backup brush 1 facing the roller 16 through
Cleaning is performed by the action of 7. Such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.

Further, in this embodiment, the eccentric cam 25 is operated at a desired timing and the cam follower 5i integrated with the transfer drum 5a is operated, so that the gap between the recording material carrying sheet 5f and the photosensitive drum 1 is made. The configuration can be set arbitrarily. For example, during standby or when the power is off, the transfer drum and the photosensitive drum are separated from each other.

In such a color image forming apparatus,
In order to always obtain a stable image, the configuration of the transfer device 5 that multiple-transfers a multicolor image onto a recording material is particularly important.

FIG. 8 and FIG. 9 are cross-sectional structural views of the transfer drum 5a according to the conventional method. When the recording material P is guided by the guide and enters the transfer drum 5a, the suction roller 5g.
Comes into contact with the transfer drum 5a. At the same time, a current is supplied to the attraction charger 5c from a high voltage power source, and as a result, the recording material P is electrostatically attracted to the recording material carrying sheet 5f of the transfer drum 5a. At that time, the suction pressing member 5k functions to press the recording material carrying sheet 5f and the recording material P into close contact with each other. Then, as soon as the recording material P is adsorbed over the entire surface, the adsorption roller 5g returns to the original position.

On the other hand, the transfer charging device 5b sequentially and multiple-transfers toner images on the attracted recording material at each rotation.

[0019]

However, in the above-mentioned conventional example, the attraction pressing member 5 of the attraction charger 5c is used.
Since k is constantly in contact with and pressing the recording material carrying sheet 5f, the following problems are caused. (1) The recording material P that is electrostatically adsorbed is peeled off while sequentially rotating in multiple transfer. (2) Recording material carrying sheet 5 when the main body of the image forming apparatus is stopped
f is locally deformed. (3) The suction pressing member 5k is rapidly deteriorated.

A more detailed description will be given. Regarding (1) above, FIG. 9 shows a state in which the recording material P is electrostatically adsorbed on the recording material carrying sheet 5f and then comes back onto the adsorption pressing member 5k. As shown in the figure, at this time, since the suction roller 5g is retracted to the non-operating position, the recording material carrying sheet 5f is moved to the suction pressing member 5
When pressed by k, it deviates from the circular orbit and is partially deformed to the outside. Therefore, when the recording material P passes through the recording material P, the tip portion is separated from the recording material carrying sheet 5f particularly in the region deformed as shown in the figure, and as a result, the recording material carrying sheet 5f floats. . In this state,
When it is brought to the next transfer step, not only color misregistration and the like occur, but also the recording material P peels from the recording material carrying sheet 5f and is electrostatically adsorbed to the photosensitive drum 1 to cause a paper jam or the like. It may happen. Regarding (2) above: When the main body of the image forming apparatus is stopped,
Since the suction pressing member 5k presses a part of the recording material carrying sheet 5f, deforms and stops it, the recording material carrying sheet 5f is stopped.
Is distorted. As a result, at the start of the next image forming operation, a partial recording material suction defect or a transfer omission may occur. Regarding the above (3): Since the suction pressing member 5k formed of a brush or the like is constantly in contact with the recording material carrying sheet 5f, deformation or hair loss may occur during continuous use.

Therefore, it is an object of the present invention to stably adsorb a recording material to a recording material carrier, extend the life of the recording material carrying member and the suction pressing member, and always obtain a high quality image. An image forming apparatus is provided.

[0022]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is
In a image forming apparatus for forming an image by transferring a visible image formed on an image carrier to a recording material by a transfer device, the transfer device is a flexible recording material carrier that carries and conveys the recording material. And an adsorbing means for adsorbing the recording material onto the recording material carrier by static electricity, and at least one pressing member that abuts and presses against the recording material carrying body. An image, which is carried on the recording material carrier only by static electricity, and the pressing member presses the recording material carrier within a range that does not deviate the rotational orbital surface of the recording material carrier. It is a forming device.

The pressing member carries the recording material within a range in which the rotation track surface of the recording material carrier is not biased only when the recording material is carried on the recording material carrier and passes over the pressing member. Press the body. Further, the pressing member is at least an adsorption pressing member that presses the recording material carrier at the recording material adsorption position, or a transfer pressing member that presses the recording material carrier at the image transfer position. In response to the,
The pressing member is provided with means for controlling pressing on the recording material carrier. Further, the pressing member may be a charge applying means.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings. In the following examples, the invention is
It is assumed that the present invention is applied to the electrophotographic color image forming apparatus described with reference to FIG. 7, and therefore the description of the overall configuration and operation of the color image forming apparatus is omitted, and the characteristic portions of the present invention will be described below.

Embodiment 1 As shown in FIG. 1, in this embodiment, a contact charging means such as a brush charger is used as the transfer charger 5b and the attraction charger 5c.

In particular, according to the present invention, the attraction charging brush 5c is configured to be rotatable around the fulcrum 5l, and the solenoid 5m is connected to the end portion thereof. Solenoid 5m is O
When it becomes N, the attraction charging brush 5c contacts the recording material carrying sheet 5f in a pressed state. The position of the suction charging brush 5c at this time is determined by the stopper 5n. When the solenoid 5m is turned off, the electrostatic charging brush 5c is released by the action of the spring 5q and brought into a non-contact state with the recording material carrying sheet 5f, or the recording material carrying sheet 5f is not pressed. Touching.

FIG. 2 is a part of the operation sequence of the full-color image forming apparatus according to the first embodiment. here,
A sequence when full-color (four-color mode) copying is performed on a recording material of A4 size is shown based on the rotation speed of the transfer drum 5a.

Almost in synchronism with the recording material P being sent to the transfer drum 5a, the suction charging brush high voltage power source, the suction charging brush pressing solenoid 5m, and the suction opposing roller pressing solenoid are turned on. In this way, if the recording material P is electrostatically adsorbed on the transfer drum 5a, the adsorption charging brush pressing solenoid 5m and the adsorption counter solenoid are turned off.
Then, the suction charging brush 5c and the suction facing roller 5g are separated from the recording material carrying sheet 5f.

When the recording material P plunges into the transfer nip, that is, the transfer site, the transfer charging brush high-voltage power supply connected to the transfer charging brush 5b is turned on, and the photosensitive drum 1
The upper toner image is transferred onto the recording material P. This operation is 4
By repeating this process four times, toner images for four colors are formed on the recording material P.

While the recording material P is held on the recording material carrying sheet 5f by electrostatic attraction, the transfer charging brush 5b is used.
Is pressing the recording material carrying sheet 5f, but since the photosensitive drum 1 is located at the facing position, the recording material carrying sheet 5f
f does not deviate from the circular orbital plane. Further, as described above, the charging brush for attraction is separated from the recording material carrying sheet 5f in the non-operating state, or does not press the recording material carrying sheet 5f even though it is in contact with the recording material carrying sheet 5f. However, the circular orbit of the recording material carrying sheet 5f is guaranteed.

Embodiment 2 FIG. 3 shows a second embodiment of the present invention. In this embodiment, the transfer drum 5a has a suction charger 5c and a suction pressing member 5.
k, and the suction pressing member 5k is provided with means for controlling the pressing on the recording material carrying sheet 5f.
Further, a grounded suction facing roller 5g is arranged at a position facing each other with the recording material carrying sheet 5f interposed therebetween. A transfer charger 5b and a transfer pressing member 5j are provided at the transfer portion, and the transfer pressing member 5j is always in contact with the recording material carrying sheet 5f.

The attracting pressing member 5k operates almost in the same manner as the attracting charging brush 5c of the first embodiment.

That is, the suction pressing member 5k has a fulcrum 5l.
It is configured to be rotatable around the
m is connected. When the solenoid 5m is turned on, the suction pressing member 5k abuts the recording material carrying sheet 5f in a pressed state. Adsorption pressing member 5k at this time
The position of is determined by a stopper (not shown). When the solenoid 5m is turned off, the pressing member 5k for attraction is released by the action of a spring (not shown) and brought into a non-contact state with the recording material carrying sheet 5f, or the recording material carrying sheet 5f is pressed. It abuts without doing so.

FIG. 4 is a part of the operation sequence of the full-color image forming apparatus according to the second embodiment. here,
Similar to the case of the first embodiment, the sequence when full-color (four-color mode) copying is performed on an A4 size recording material,
The rotation number of the transfer drum 5a is shown as a reference.

Example 3 In Example 2 described above, the small size (A4
Etc.) and large size (A3 etc.) transfer drum 4
The rotation completes the multi-transfer of toner for four colors. However, due to the return time of the optical system for illuminating the original, the switching time of the developing device, etc., it is sometimes necessary to insert a dummy rotation between colors when a large-sized recording material is used. May occur. FIG. 6 shows the sequence at this time, and the transfer drum 5 used at this time.
The structure of a is shown in FIG. The outline of the operation will be described below.

In this embodiment, the transfer drum 5a is the same as that shown in FIG.
The configuration is the same as that of the transfer drum of Example 2 shown in
The third embodiment is different in that the transfer pressing member 5j can also be brought into and out of contact with the recording material carrying sheet 5f.

That is, the transfer pressing member 5j has a fulcrum 5s.
It is configured to be rotatable around the
t is connected. When the solenoid 5t is turned on, the transfer pressing member 5j abuts the recording material carrying sheet 5f in a pressed state. Adsorption pressing member 5j at this time
The position of is determined by a stopper (not shown). When the solenoid 5t is turned off, the pressing member 5j for attraction is released by the action of a spring (not shown) and brought into a non-contact state with the recording material carrying sheet 5f, or the recording material carrying sheet 5f is pressed. It abuts without doing so.

With the above structure, the recording material P first fed
As described above, the recording material P is sandwiched between the adsorption pressing member 5k and the adsorption counter roller 5g, and a high voltage for adsorption charging is applied at approximately the same timing, and the recording material P is electrostatically adsorbed to the recording material carrying sheet 5f. . Then, the transfer charger 5b transfers the toner image on the photosensitive drum 1 to the recording material.

Thereafter, since the optical system for illuminating the original returns to the home position, the transfer drum 5a makes a dummy rotation. At this time, the transfer drum swing solenoid and the swing cam (not shown) are operated, and the transfer drum 5a moves to the photosensitive drum 1
From the drive transmission gear (not shown) while keeping the meshing state. That is, the transfer drum 5a is rotated by being driven by the photosensitive drum 1, but the surface of the transfer drum and the photosensitive drum 1 are not in contact with each other. At this time, the solenoid 5t of the transfer pressing member 5j is turned off to stop pressing the recording material carrying sheet 5f. Therefore, the rotating circular orbit of the recording material carrying sheet 5f is maintained even at the transfer portion.

After the dummy rotation, the transfer pressing member solenoid 5t is turned on again, the transfer drum swing solenoid is turned off, and the recording material carrying sheet 5f is
It is pressed against the photosensitive drum 1 again, and the transfer of the second color is started.

[0041]

As described above, in the image forming apparatus according to the present invention, when the recording material is held on the recording material holding sheet only by the electrostatic attraction force, the recording material holding sheet is pressed, Since the suction pressing member that bends the recording material carrying sheet out of the rotational circular orbit is configured to stop the pressing of the recording material carrying sheet at least when the recording material passes,
It is possible to stably adsorb the recording material to the recording material supporting member, extend the life of the recording material supporting member and the suction pressing member, and always obtain a high quality image.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a transfer drum of an image forming apparatus according to the present invention.

FIG. 2 is an operation sequence for explaining the operation of the transfer drum of FIG.

FIG. 3 is a schematic configuration diagram showing another embodiment of the transfer drum of the image forming apparatus according to the present invention.

4 is an operation sequence for explaining the operation of the transfer drum of FIG.

FIG. 5 is a schematic configuration diagram showing another embodiment of the transfer drum of the image forming apparatus according to the present invention.

FIG. 6 is an operation sequence for explaining the operation of the transfer drum of FIG.

FIG. 7 is a cross-sectional configuration diagram of an electrophotographic color image forming apparatus to which the present invention can be applied.

FIG. 8 is a schematic configuration diagram showing a conventional transfer drum.

FIG. 9 is an enlarged view showing a suction charging unit of a conventional transfer drum.

[Explanation of symbols]

 1 image carrier (photosensitive drum) 5 transfer device 5a transfer drum 5b transfer charger 5c adsorption charger 5f recording material carrier (recording material carrying sheet)

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Ken Jojo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. An image forming apparatus for forming an image by transferring a visible image formed on an image carrier to a recording material by a transfer device, wherein the transfer device is flexible to carry and convey the recording material. The recording material carrier, the adsorption means for electrostatically adsorbing the recording material on the recording material carrier, and at least one pressing member that abuts and presses the recording material carrier, The recording material carrier is carried by the attracting means only by static electricity, and the pressing member presses the recording material carrier within a range in which the rotational orbit surface of the recording material carrier is not biased. An image forming apparatus characterized by. 2. The range in which the pressing member does not deviate from the rotation track surface of the recording material carrier only when the recording material is carried on the recording material carrier and passes over the pressing member. The image forming apparatus according to claim 1, wherein the recording material carrier is pressed inside. 3. The pressing member is at least a suction pressing member that presses the recording material carrier at the recording material suction position, or a transfer pressing member that presses the recording material carrier at the image transfer position. The image forming apparatus according to claim 1 or 2. 4. The image forming apparatus according to claim 3, wherein the pressing member has means for controlling pressing on the recording material carrier. 5. The image forming apparatus according to claim 1, wherein the pressing member is a charge applying unit.