JPH1039640A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which can prevent back stain of recording material. SOLUTION: This image forming device is constituted by photosensitive drums (image carrier) on which a latent image is formed 1a-1d and a carry belt (recording material carrier) 8 for holding and carrying recording material 6 and a transfer charger (transfer means) 4a-4d for transferring a toner image obtained by developing the latent image on the photosensitive drums 1a-1d on the recording material 6 held on the carry belt 8 and a cleaning device (cleaning means) 14 with a web (cleaning member) 21 for contacting with the carry belt 8 and cleaning the same with it staticized and applied pressure and moving or turning to change an abut position to the carry belt 8. In this case, a conductive sponge roller (antistatic means) 70 contacted with the carry belt 8 is mounted between a position where the recording material 6 on the belt 8 is separated and an abut position of the web 21. Thereby, charged electric potential difference of the carry belt 8 is reduced and a surface of the carry belt for holding the recording material 6 is always cleaned and back stain of the recording material 6 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus for forming an image on a recording medium by an electrophotographic method.

[0002]

2. Description of the Related Art Conventionally, a plurality of image forming units are provided, and each image forming unit forms a toner image of a different color, and the toner images are sequentially superimposed on the same recording material and transferred to form a color image. Various color image forming apparatuses to be obtained have been proposed, and among them, a color electrophotographic copying machine using a multicolor electrophotographic method is particularly frequently used.

FIG. 4 shows an example of such a color electrophotographic copying machine.
In brief, the first, second, third, and fourth image forming units P are provided in the apparatus main body 10 of the color copying apparatus.
a, Pb, Pc, and Pd are arranged side by side, and each of the image forming units Pa, Pb, Pc, and Pd has a dedicated electrophotographic photosensitive drum 1a, 1b, 1c, or 1d as an image carrier.

The photosensitive drums 1a, 1b, 1c, 1d
Around the primary chargers 15a, 15b, 15c, 15
d, laser beam scanners 16a, 16b, 16c, 1
6d, developing units 3a, 3b, 3c, 3d and cleaner 5
a, 5b, 5c and 5d are arranged respectively.

Further, each of the image forming units Pa, Pb, Pc, Pd
A recording material conveying belt 8 as a recording material carrier is
Are provided inside the transfer chargers 4a, 4b, 4
Reference numerals c and 4d are arranged, and a cleaning device 14 is arranged outside on the lower track of the recording material conveying belt 8.

In the color electrophotographic copying machine having the above configuration, first, the photosensitive drum 1 of the first image forming portion Pa
A latent image of the black component color of the original image is formed on the image a by the laser beam scanner 16a. Then, the latent image is developed by a developer having a black toner in the developing device 3a and is visualized as a black toner image.

On the other hand, the recording material 6 accommodated in the recording material cassette 60 is supplied to the recording material transport belt 8 via the registration roller 13 and is transferred and carried by the transport belt 8 while being carried on the transport belt 8. Receives the transfer of the black toner image.

While the black toner image is being transferred onto the recording material 6 as described above, the second image forming portion Pb
A latent image of the magenta component color of the original image is formed on the photosensitive drum 1b by the laser beam scanner 16b, and this latent image is developed by the developing device 3b to be visualized as a magenta toner image. When the recording material 6 after the transfer at Pa is carried into the transfer charger 4b, a magenta toner image is transferred to a predetermined position on the recording material 6.

Thereafter, yellow and cyan toner images are formed in the third and fourth image forming portions Pc and Pd by the same operation as described above, and the transfer chargers 4c and 4d form predetermined toner images on the same recording material 6. The yellow toner image and the cyan toner image are sequentially transferred to the positions, and the recording material 6 is thus transferred.
A color image in which four color toner images are superimposed and transferred is obtained above.

When the above image forming process is completed, the four color toner images on the recording material 6 are fixed as permanent images on the recording material 6 by the fixing device 7, and the recording material 6 on which the color toner image has been fixed is fixed. Is discharged out of the apparatus body 10 as a copy.

Each of the photosensitive drums 1a, 1 after the transfer is completed.
Residual toners b, 1c and 1d are removed by cleaners 5a, 5b, 5c and 5d, and are prepared for the next image forming process. Also, during a series of image forming processes from the formation of the latent image to the transfer of the toner image, the toner (mainly from the developing devices 3a to 3d) Scattering toner and fogging toner)
Is removed and cleaned by the cleaning device 14 to prepare for the next image forming process.

The cleaning member used in the cleaning device 14 for the recording material conveying belt 8 includes:
A cleaning web 21 made of a non-woven fabric or the like is used. An advantage of using the web 21 is that the life of the member to be cleaned (the recording material transport belt 8 in the example shown in FIG. 4) can be reduced because cleaning by light pressure is possible. There is little damage, and the treatment of waste toner is simple.

By the way, depending on the selection of the material, it is possible to easily impart the property of absorbing the fixing oil to the web 21, so that the in-machine contamination by the oil at the time of double-sided recording or multiple recording can also be suppressed.

Therefore, as the material of the web, not only fibers such as acryl, rayon, and polyester but also various materials coated with a resin or using a conductive filler are widely used.

The cleaning device may be configured such that a core rod is provided on a sheet-like web made of the above-mentioned material, and the core rod is rotated to wind a predetermined amount of the web when an arbitrary amount of contamination is detected or predicted. In general, a new surface of the web is always in contact with a member to be cleaned (recording material transport belt), but as shown in FIG. The roller 22 is brought into contact with the cleaning member (recording material conveyance belt) 8 while the roller 22 is stationary, as shown in FIG. There has also been proposed a configuration in which the roller 22 is rotated by a predetermined angle when the portion becomes dirty.

As a method and timing for updating the contact surface of the web, generally, the web is rotated according to the operation amount of the member to be cleaned. The color electronic copying machine shown in FIG. 4 adopts a method of feeding the web 21 slowly while the conveyor belt 8 is rotating, or sending the web 21 when the conveyor belt 8 reaches a predetermined number of rotations. Have been. In some cases, the predetermined number of rotations for determining the timing for feeding the web may be predicted by another number (an arbitrary copy count in the color electrophotographic copying machine shown in FIG. 4).

[0017]

However, for example, in the conventional color electrophotographic copying machine shown in FIG.
The charge potential of the transport belt 8 after the separation of the recording material 6 is determined by the portion where the recording material 6 is carried and the space between the recording materials when carrying a plurality of recording materials 6 during recording (between adjacent recording materials 6). A difference occurs between the recording material 6 and the recording material 6 due to the potential difference, and the waste toner collected on the web 21 at the cleaning portion adheres again to the conveyor belt 8 due to the potential difference.
There was a problem that the back surface of the. This phenomenon occurs because the adhesive force between the toner accumulated on the web 21 and the transport belt 8 changes due to the potential difference, and the toner electrostatically adheres to the portion of the transport belt 8 that carried the recording material 6. It is thought to be caused by

Therefore, it is conceivable to eliminate the charge on the conveyor belt by means of a charge eliminator, and it has been proposed to use a corona charger as the charge eliminator. In addition, there is a problem in that charging unevenness occurs in the transport belt and the charge removing ability of the corona charger is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of preventing back contamination of a recording material.

[0020]

In order to achieve the above object, according to the first aspect of the present invention, there is provided an image carrier on which a latent image is formed, and a recording material carrier for carrying a recording material and transporting the same. ,
Transfer means for transferring a toner image obtained by developing the latent image on the image carrier to a recording material carried on the recording material carrier; and An image forming apparatus including a cleaning unit having a cleaning member capable of changing the position of contact with the recording material carrier by performing a cleaning action while being in contact with the recording material carrier. A charge eliminator for contacting the recording material carrier is provided between the position where the recording material is separated and the contact position of the cleaning member.

According to a second aspect of the present invention, in the first aspect of the present invention, the static elimination means is constituted by a grounded resistor.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the static elimination means comprises a pair of conductive rollers provided with the recording material carrier interposed therebetween. .

According to a fourth aspect of the present invention, in the third aspect of the invention, the material of the conductive roller is rubber or sponge.

According to a fifth aspect of the present invention, in the third or fourth aspect, the conductive roller includes a surface layer and an elastic layer inside the surface layer, and a contact angle of the surface layer. Is larger than the contact angle of the elastic layer.

According to a sixth aspect of the present invention, in the first or second aspect of the present invention, the static elimination means is constituted by a conductive blade.

According to a seventh aspect of the present invention, in the sixth aspect of the invention, the material of the conductive blade is rubber.

Therefore, according to the present invention, by providing the static elimination means, the charging potential of the recording material carrier after the recording material is separated can be divided into a portion carrying the recording material and a plurality of recording materials during recording. The difference between the recording material supporting portion and the portion between the recording materials is suppressed, and the surface of the recording material carrying member that carries the recording material is always kept in a cleaned state, thereby preventing the back stain of the recording material.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1> FIG. 1 is a longitudinal sectional view of a color electrophotographic copying machine according to Embodiment 1 of the present invention. Pa, Pb, Pc, and Pd are arranged, and a recording material conveying unit is provided below each of the image forming units Pa, Pb, Pc, and Pd. The recording material conveying means includes an idler roller 11, a driving roller 12, and both rollers 11, 1
2 is a transport belt 8 which is a recording material carrier wound around the transport belt 2, and the transport belt 8 is approximately 100 m in the direction of the arrow shown in the figure.
It is rotationally driven at a speed of m / sec.

The first, second, third, and fourth image forming units Pa, Pb, P
c and Pd have photosensitive drums 1a, 1b, 1c and 1d, respectively, and primary chargers 15a, 15b, 15c and 15 are provided around the respective photosensitive drums 1a, 1b, 1c and 1d.
d, laser beam scanners 16a, 16b, 16c, 1
6d, developing units 3a, 3b, 3c, 3d and cleaner 5
a, 5b, 5c and 5d are arranged respectively.

Further, transfer chargers 4a, 4b, 4c and 4d are arranged inside the transport belt 8, and a cleaning device 1 is placed outside the lower track of the transport belt 8 on the track.
4 are arranged. The cleaning device 14 has a cleaning web 21 that comes into contact with the conveyor belt 8 in a state where the web 21 is statically pressed, and the web 21 moves to change (update) the contact position with the conveyor belt 8. You.

Incidentally, each of the laser beam scanners 1
Reference numerals 6a, 16b, 16c, and 16d each include a semiconductor laser, a polygon mirror, an fθ lens, and the like. These receive an electric digital image signal, and apply a laser beam modulated in accordance with the signal to the primary charger 15a. , 15b,
The photosensitive drums 1a, 1b, 1c, 1d are scanned in the generatrix direction between the developing units 15c, 15d and the developing units 3a, 3b, 3c, 3d to expose the photosensitive drums.

When an image forming operation start signal is input to the color electrophotographic copying machine, the first image forming section Pa
Starts rotating in the direction of the arrow, the photosensitive drum 1a is uniformly charged by the primary charger 15a, and the laser beam is modulated by the laser beam scanner 16a with an image signal corresponding to the black component image of the original image. Light is written, and a latent image is formed on the photosensitive drum 1a. Then, the latent image is developed by a developer having a black toner in the developing device 3a and is visualized as a black toner image.

On the other hand, the recording material 6 in the recording material cassette 60 is taken out of the recording material cassette 60 by the pickup roller 9, and the taken out recording material 6 is provided by a resist provided between the recording material cassette 60 and the transport belt 8. It is sent to the roller 13. The recording material 6 is the registration roller 1
After being stopped once in 3, it is fed by the registration roller 13 onto the conveyor belt 8 which has already started to rotate, in synchronization with the timing of the black toner image formed on the photosensitive drum 1 a. Recording material 6 sent on conveyor belt 8
The transfer charging unit 4 a of the image forming unit Pa receives transfer charge from the back surface side of the transport belt 8, and the black toner image on the photosensitive drum 1 a is transferred onto the recording material 6.

The series of image forming processes from the formation of the latent image to the transfer of the toner image is performed by the remaining image forming portions Pb and P
The same operation is performed for c and Pd. A magenta toner image, a yellow toner image, and a cyan toner image are sequentially superimposed and transferred on the recording material 6 on which the black toner image has been transferred, and a color image is formed on the recording material 6. Is done.

The recording material 6 on which the transfer of the four color toner images has been completed is applied to the driving roller 1 at the left end of the transport belt 8.
Substantially right above 2, it is separated from the transport belt 8 by the action of the separation charger 61 and sent to the fixing device 7.
In the fixing device 7, the toner images of four colors are fixed as permanent images on the recording material 6 by heat and pressure, and the recording material 6 on which the toner images are fixed is discharged out of the apparatus main body 10 as a color copy. Is done.

Each of the photosensitive drums 1a and 1 after the transfer is completed.
Residual toners b, 1c and 1d are removed by cleaners 5a, 5b, 5c and 5d, and are prepared for the next image forming process.

On the other hand, while the above-described series of image forming processes is being performed, the toner adhered to the surface of the conveyor belt 8 by the cleaning device 14 (mainly the developing devices 3a to 3d)
(Scattered toner and fogged toner) are removed and cleaned.

In this embodiment, the conductive sponge roller 70 having a resistance of about 10 ⁸ Ω is opposed to the drive roller 12 in a state in which the conductive sponge roller 70 is in contact with the conveyance belt 8 constituting the recording material conveyance means. The conductive sponge roller 70 and the driving roller 12 are grounded.

By providing the conductive sponge roller 70, the charging potential of the transport belt 8 after the recording material 6 is separated can be a portion where the recording material 6 is carried and a plurality of recording materials 6 during recording. The difference between the recording material 6 and the portion where the recording material 6 is formed is suppressed to a small value, the surface of the conveyor belt 8 supporting the recording material 6 is always kept in a cleaned state, and the back contamination of the recording material 6 is prevented.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a longitudinal sectional view of a color electrophotographic copying machine according to Embodiment 2 of the present invention. In this figure, the same elements as those shown in FIG. The description of is omitted.

In the present embodiment, instead of the conductive sponge roller 70 used in the first embodiment, a surface coat roller 71 formed by coating the surface of the conductive sponge roller 70 with a resin having high toner releasability is used. It is characterized by having been.

The use of the surface coat roller 71 suppresses the adhesion of toner to the surface coat roller 71 by the resin having a high toner releasability coated on the surface of the roller 71. , It is possible to maintain the static elimination effect of the conveyor belt 8 for a long time. Thus, the surface coat roller 71
Preferably has a surface layer and an elastic layer inside the surface layer, and the contact angle of the surface layer is desirably set to be larger than the contact angle of the elastic layer.

Further, similarly to the first embodiment, by providing the surface coating roller 71, the charging potential of the transport belt 8 after the recording material 6 is separated is set to be equal to that of the portion carrying the recording material 6 during recording. The difference between the recording material 6 and the portion between the recording materials when the plurality of recording materials 6 are carried is kept small, and the surface of the conveyor belt 8 carrying the recording material 6 is always kept in a cleaned state. Back dirt is prevented.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a longitudinal sectional view of a color electrophotographic copying machine according to Embodiment 3 of the present invention. In this figure, the same elements as those shown in FIG. The description of is omitted.

The present embodiment is characterized in that a conductive rubber blade 73 is used instead of the conductive sponge roller 70 used in the first embodiment.

By using the conductive rubber blade 73, as in the first embodiment, the charging potential of the transport belt 8 after the recording material 6 is separated carries the recording material 6. The difference between the portion and the portion between the recording materials 6 when carrying a plurality of recording materials 6 during recording is kept small, and the surface of the transport belt 8 that carries the recording material 6 is always kept in a cleaned state. As a result, the back contamination of the recording material 6 is prevented.

[0048]

As is apparent from the above description, according to the present invention, an image carrier on which a latent image is formed, a recording material carrier for carrying a recording material and transporting the same, and the image carrier A transfer unit for transferring a toner image obtained by developing the latent image on the body onto a recording material carried on the recording material carrying member; An image forming apparatus including a cleaning unit having a cleaning member capable of changing a contact position with a recording material carrier by performing a cleaning action and moving or rotating the recording material on the recording material carrier. Is provided between the position where the recording material is separated and the contact position of the cleaning member, so that the charging potential of the recording material carrier after the recording material is separated is the charging potential of the recording material. Between the recording part and the recording material when a plurality of recording materials are being recorded. Part and the difference is kept small, the surface carrying the recording material of the recording material bearing member is effect that the backside contamination of the recording material is prevented always kept in a state of being cleaned.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a color electrophotographic copying machine according to Embodiment 1 of the present invention.

FIG. 2 is a longitudinal sectional view of a color electrophotographic copying machine according to Embodiment 2 of the present invention.

FIG. 3 is a longitudinal sectional view of a color electrophotographic copying machine according to Embodiment 3 of the present invention.

FIG. 4 is a longitudinal sectional view of a conventional color electrophotographic copying machine.

FIG. 5 is a sectional view showing a conventional cleaning unit.

FIG. 6 is a sectional view showing another conventional cleaning means.

[Explanation of symbols]

 1a to 1d Photosensitive drum (image carrier) 4a to 4d Transfer charger (transfer unit) 6 Recording material 8 Conveying belt (recording material carrier) 14 Cleaning device (cleaning unit) 21 Cleaning web (cleaning member) 70 Conductive sponge Roller (static elimination means) 71 Surface coat roller (static elimination means) 73 Conductive rubber blade (static elimination means)

Claims (7)

[Claims] 1. An image carrier on which a latent image is formed, a recording material carrier for carrying and transporting a recording material, and a toner image obtained by developing the latent image on the image carrier. A transfer unit for transferring the recording material to the recording material carried on the recording material carrier; An image forming apparatus including a cleaning unit having a cleaning member capable of changing a contact position with the cleaning member, wherein a position between a position where the recording material on the recording material carrier separates and a contact position of the cleaning member is An image forming apparatus, further comprising a static eliminator for contacting the recording material carrier. 2. The image forming apparatus according to claim 1, wherein said static eliminator is formed of a grounded resistor. 3. The image forming apparatus according to claim 1, wherein the charge removing unit includes a pair of conductive rollers provided so as to sandwich the recording material carrier. 4. The image forming apparatus according to claim 3, wherein said conductive roller is made of rubber or sponge. 5. The conductive roller includes a surface layer and an elastic layer inside the surface layer, wherein a contact angle of the surface layer is larger than a contact angle of the elastic layer. Item 5. The image forming apparatus according to item 3 or 4. 6. An image forming apparatus according to claim 1, wherein said static elimination means is constituted by a conductive blade. 7. An image forming apparatus according to claim 6, wherein said conductive blade is made of rubber.