JP2003076161A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a good image by carrying out transferring well by preventing adverse effects of warping when a diameter of a transfer roller is made small. SOLUTION: In the apparatus, the diameter of the transfer roller is made small as well as having it pressed by a back up roller from the back of the transfer roller. As a result, the warping of the transfer roller is prevented and the good image can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using electrophotography such as a laser beam printer and a copying machine.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using a laser using an electrophotographic method includes a laser beam printer, a copying machine, a facsimile and the like. Here, a laser beam printer will be described.

FIG. 9 is a sectional view of the main part of a laser beam printer.

Reference numeral 1 denotes a drum-shaped photosensitive member (organic photoconductive material, selenium, amorphous silicon, etc.) which is an image bearing member,
2 is a charging roller, L is a laser beam, 3 is a developing device, 4 is a paper feed roller, 5 is a registration roller pair, 6 is a transfer roller, and 7
Is a cleaner, 8 is a fixing input guide, 9 is a fixing device, P is a recording material, and T is toner.

As one of the conventional examples, in terms of dimensions, the outer diameter of the photoreceptor 1 having a drum structure is φ30, and the length is 346 mm.
The transfer roller 6 is a hollow cylinder, and the transfer roller 6 is made of foamed EPDM rubber that is electrically conductive to 10 ⁸ × 10 ⁹ Ω around a φ12 cored bar made of an iron material of SUM23L-D and has an outer diameter of φ20.
The rubber portion has a length of 297 mm and a hardness of 30 to 35 ° (Asker C hardness).

The transfer roller 6 is pressed toward both ends by a force of 5.88399 N on one side toward the photoconductor 1 from both sides by a compression spring.

Characters and image information converted into electric signals from a host computer (not shown) are input to an interface controller and subjected to signal processing, and the laser light L is appropriately emitted by this output. The photoconductor 1 rotates in the direction a, is uniformly charged by the charging roller 2, and then is irradiated with the laser light L described above. Laser light L
Since the charge on the photoconductor 1 is attenuated where is hit, the charge on the photoconductor 1 remains where the laser light L is not applied,
An electrostatic latent image is formed according to ON / OFF of the laser light L.

Next, the toner is reversely developed by the developing device 3 so that the toner is provided in accordance with the electrostatic latent image.
The visible image is obtained above.

Next, the recording materials P contained in the cassette 16 are taken out one by one by the paper feed roller 4, the recording materials P are taken out one by one by the registration roller pair 5, and the photosensitive member 1 is passed through the paper guide. The toner image on the photoconductor 1 is transferred onto the recording material P by the transfer roller 6 which is applied with a voltage having a polarity opposite to that of the toner. Recording material P
Is separated from the photoconductor 1 by its own weight of the recording material P and other static elimination,
The toner image on the recording material enters the fixing device 9 via the fixing input guide 8 and is fixed on the recording material P by heat and pressure. Then, it is discharged to a tray (not shown).

The photoconductor 1 is cleaned by the cleaner 7 after the transfer process is completed.
After the residual toner is removed by the cleaner blade 7A, the next image forming process is started.

[0011]

However, in the image forming apparatus of the above-mentioned conventional example, there is a case where the toner scatters immediately before transfer and disturbs the image as in the image of FIG. In particular, it may occur remarkably when the transfer voltage is increased when used in a low humidity environment.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus capable of performing good transfer and obtaining a good image as a result.

[0013]

An image forming apparatus provided by the present invention has the following configurations (1) to (3).

(1) A rotatable electrophotographic photosensitive member carrying an electrostatic latent image, charging means for charging the surface of the electrophotographic photosensitive member, and exposure for forming an electrostatic latent image on the surface of the electrophotographic photosensitive member. An image including at least means, a developing means for developing the electrostatic latent image with toner to form a toner image, and a rotatable transfer means for transferring the toner image formed on the electrophotographic photosensitive member onto a transfer material. In the forming apparatus, the transfer means includes a roller-shaped pressing member from a direction not on the electrophotographic photosensitive member side, and the transfer means is pressed toward the electrophotographic photosensitive member.

(2) The image forming apparatus as described in (1) above, wherein the roller-shaped pressing member presses only a substantially central portion of the transfer roller.

(3) The image forming apparatus according to (1) above, further comprising a roller-shaped pressing member that presses a transfer roller portion corresponding to a non-image area on the electrophotographic photosensitive member.

[0017]

The operation of the present invention will be described with reference to FIG. 4. The conventional transfer roller is 6, the transfer roller of this embodiment is 11, and the backup roller is 12.

The transfer roller 11 is made of foamed EPDM rubber which is electrically conductive to 10 ⁸ × 10 ⁹ Ω around a φ6 core metal made of a SUM23L-D iron material, and has an outer diameter of φ8. The rubber portion has a length of 297 mm and a hardness of 30 to 35 ° (Asker C hardness).

The backup roller 12 is a SUM 23.
Insulating ABS around φ6 cored bar made of L-D iron material
It is made of resin and has an outer diameter of φ10.

The voltage of the transfer bias power supply is applied to the transfer roller 6, and if the same voltage is applied, the toner T immediately before the recording material P enters the transfer nip N is generated by the electric field of the transfer roller 6 and the recording material P is discharged. The toner T is attracted in the P direction, and as a result, the toner T flies from the photoconductor 1 and the image is disturbed. However, in the transfer roller 11 of the present embodiment, the flying range of the toner T on the photoconductor 1 is narrow, and the disorder of the image is small. As a result, a good image is obtained.

However, when the diameter of the transfer roller is reduced, the core metal of the transfer roller is also reduced and the end portion of the core metal of the transfer roller is pressed by the compression spring in the direction of the photosensitive member 1. Therefore, as shown in FIG. Since the roller 11 has fallen down and a good image cannot be obtained, the backup roller 12 presses the transfer roller 11 toward the photoconductor 1, so that there is less deadness, and a uniform transfer process is performed. A good image can be obtained.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

[0023]

EXAMPLES (First Example) An image forming apparatus using a laser using an electrophotographic method will be described.

In FIG. 1, 1 is a photosensitive drum as an image carrier, 2 is a charging roller, 2A is a charging power source, 3 is a developing device,
3A is a developing bias power source, 4 is a paper feed roller, 11 is a paper cassette, 5 is a registration roller pair, 11 is a transfer roller, 11A is a power supply applied to the transfer roller, 12 is a backup roller, 10 is a discharging needle, and 10A is a discharging electricity. A power source applied to the needle, 8 is a fixing input guide, and 9 is a fixing device.

Characters and image information converted into electric signals from a host computer (not shown) are input to the interface controller 101 and converted into signals,
This output causes the laser diode 103 in the laser drive circuit 102 to emit light as appropriate. The laser light L is condensed by the collimator 104, and rotates the polygon mirror 1
After being projected on 05, the photosensitive drum 1 is scanned in a direction perpendicular to the rotation direction through an optical system (not shown) for correcting the surface tilt of the fθ lens 106 and the polygon mirror 105, and a reflecting mirror 107. While being projected. The photosensitive drum 1 is uniformly charged by the charging roller 2 and then irradiated with the above-mentioned laser light L. The electric charge on the photosensitive drum 1 is attenuated when the laser light is applied, and the electric charge is left on the photosensitive drum 1 where the laser light is not applied, so that an electrostatic latent image is formed according to ON / OFF of the laser. It

Next, a developer (not shown) is applied by the developing device 3 in accordance with the electrostatic latent image, and a visible image is obtained on the photosensitive drum 1. This visible image is obtained by bringing the recording materials P, which are taken out one by one from the paper cassette 16 by the paper feed roller 4, into contact with the photoconductor 1 via the paper guide at the same timing with the registration roller 5, and the toner. The transfer roller 11 and the backup roller 12 to which a voltage having a polarity opposite to that of T is applied are pressed upward in FIG. By this transfer process, the toner image on the photoconductor 1 is transferred onto the recording material P.

The recording material P is separated from the photosensitive member 1 by the weight of the recording material P, the waist, and the static elimination needle 10, and the image on the recording material P is fixed on the recording material P by the fixing device 9. Then, it is discharged to a tray (not shown).

After the transfer process is completed, the photoconductor 1 is cleaned by the cleaner 7
After the residual toner is removed by the edge of the cleaning blade 7A, the next image forming process is started.

Details of this embodiment will be described.

The outer diameter of the photoconductor 1 is φ30, and the length is 346.
mm hollow cylinder, transfer roller 11 is SUM23L ・ D
The outer diameter is φ8, which is made of foamed EPDM rubber that is electrically conductive to 10 ⁸ × 10 ⁹ Ω around the iron material φ6 core metal. The rubber part has a length of 297 mm and a hardness of 30 to 35 ° (Asker C
Hardness).

As shown in FIG. 2, the backup roller 12 is fixed to the transfer roller 11 by an axial distance, and a compression spring is applied to the member to push the photosensitive member 1 from both sides to the both ends with a force of 5.88399 N on one side.
Is pressed in the direction.

The backup roller 12 is SUM23L-
Insulating resin is adhered around the iron material φ8 core metal of D, and has an outer diameter φ12. The length of the resin portion is 297 mm.

With this structure, when the photoconductor 1 rotates, the transfer roller 11 follows the photoconductor 1.

As shown in FIG. 3, the transfer roller 11 does not recede and the center thereof is not separated from the surface of the photosensitive member 1.

(Second Embodiment) The difference from the first embodiment is that, as shown in FIG. 6, the backup roller 14 is made of an insulating resin, for example, an ABS material, in the center of the core metal and has an axial length of 100 mm. Is.

That is, the backup roller 14 is pressed in the drum direction after the transfer roller 11.

Since the amount of insulating resin can be reduced, the cost can be reduced.

(Third Embodiment) The difference from the second embodiment is that the transfer roller 11 is driven by the drive of the photosensitive member 1 as shown in FIG.

By driving, the transfer roller 11 does not slip and disturb the image.

(Fourth Embodiment) The difference from the first embodiment is that, as shown in FIG. 8, the backup roller 15 is made of an insulating resin such as a POM material, and the insulating resin is at both ends outside the image area of the photoconductor 1. Located in.

As a result, the backup roller 15 does not scrape off the transfer roller 2 which is related to the image.

[0042]

As described above, according to the present invention,
If the diameter of the transfer roller is reduced, the transfer roller is pressed down. Therefore, in order to prevent this, a backup roller is pressed after the transfer roller to perform good transfer, and as a result, a good image is obtained.

[Brief description of drawings]

FIG. 1 is a transverse cross-sectional view of the outline of a laser beam printer according to a first embodiment.

FIG. 2 is a schematic perspective view of a transfer unit according to the first embodiment.

FIG. 3 is a schematic perspective view of a transfer unit.

[Fig. 4] Outline of transfer unit for explanation

FIG. 5 Example image for illustration

FIG. 6 is a schematic perspective view of a transfer unit according to the second embodiment.

FIG. 7 is a schematic perspective view of a transfer unit according to the third embodiment.

FIG. 8 is a schematic perspective view of a transfer portion according to the fourth embodiment.

FIG. 9 is a cross-sectional view of the outline of a conventional laser beam printer.

[Explanation of symbols]

1 photoconductor 2 charger 2A charging power supply 3 developer 3A development bias power supply 4 paper feed rollers 5 Registration roller pair 6 Transfer roller 7 cleaner 7A cleaner blade 8 Fixing entrance guide 9 Fixing device 10 Static elimination needle 11 Transfer roller 12 Backup roller 14 Backup roller 15 Backup roller 16 paper cassettes 101 Interface controller 102 laser drive circuit 103 laser diode 104 collimator 105 polygon mirror 106 fθ lens 107 reflective mirror L laser light N transfer nip P recording material T toner

Claims (3)

[Claims] 1. A rotatable electrophotographic photosensitive member carrying an electrostatic latent image, charging means for charging the surface of the electrophotographic photosensitive member, and exposure means for forming an electrostatic latent image on the surface of the electrophotographic photosensitive member. And an image forming means including at least developing means for developing the electrostatic latent image with toner to form a toner image, and rotatable transfer means for transferring the toner image formed on the electrophotographic photosensitive member onto a transfer material. In the image forming apparatus, the transfer means includes a roller-shaped pressing member from a direction not on the electrophotographic photosensitive member side, and the transfer means is pressed toward the electrophotographic photosensitive member. 2. The image forming apparatus according to claim 1, wherein the roller-shaped pressing member presses only a substantially central portion of the transfer roller. 3. The image forming apparatus according to claim 1, further comprising a roller-shaped pressing member that presses a transfer roller portion corresponding to a non-image area on the electrophotographic photosensitive member.