JPH11352841A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image having excellent quality by always stably rotating an intermediate transfer drum. SOLUTION: A rotary shaft 7e penetrating the flanges 7a and 7b of the intermediate transfer drum 7 is provided with a friction holder 7k, a stopper 7i, a spring 7j, a friction ring 7g and a friction plate 7h constituting a braking means. A constant load is imparted to the friction plate 7h and the friction ring 7g by the pressing force of the spring 7j, so that rotational force is imparted in a direction reverse to the rotating direction (c) of the intermediate transfer drum 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art An image carrier in a conventional image forming apparatus will be described with reference to FIG.

The image carrier 100 comprises a cylinder 100f having an elastic layer on its surface, and flanges 100a and 100b fitted at both ends thereof.
Bearings 100c and 100d are fixed to 100b, and the rotating shaft 1 is fixed by the bearings 100c and 100d.
00e is provided. At this time, the image carrier 100 is free with respect to the rotation axis 100e.

A gear portion 100a1 is formed integrally with one flange 100a, as shown in FIGS.
As shown in FIG.
1 is driven by an image carrier driving gear 101 in the direction of the arrow.

[0005]

However, since the image carrier 100 is free with respect to the rotating shaft 100e, that is, as shown in FIG.
Since the gear portion 100a1 rotates in both directions, rotation unevenness easily occurs due to load fluctuation, and image blur, color shift, and the like occur. These were caused by a load variation of the image carrier due to the contact of the transfer device with the image carrier and a load variation of the image carrier at the time of contact of the rotationally movable developing device with the image carrier.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of always providing a stable rotation to an image carrier and forming a high quality image.

[0007]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A rotatable image carrier, and image forming means for forming an image on the image carrier, wherein the image on the image carrier is transferred to a transfer material by the image forming device; When an image is formed on the image carrier or when an image is transferred from the image carrier to a transfer material, a braking force applying unit that applies a braking force to the rotation of the image carrier is provided. An image forming apparatus.

Preferably, the image carrier is an intermediate transfer member on which a plurality of color toner images are superimposed. According to another aspect, the image carrier is preferably a photosensitive drum on which toner images of a plurality of colors are superimposed.

Preferably, the braking force applying means includes at least a biasing member and a friction member. According to another aspect, it is preferable that the braking force applying means is of a hydraulic damper type.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an image forming apparatus of the present embodiment.

In FIG. 1, the image forming apparatus includes a photosensitive drum 1, a charging roller 2, an exposing device 3, a developing device 4, a transfer device 5, a fixing device 6, and the like, which are first image carriers.

The photosensitive drum 1 has a photoconductive layer on a drum base made of aluminum, and has a predetermined peripheral speed (process speed) V.
Is driven to rotate in the direction of arrow a.

The charging roller 2 is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force, rotates following the rotation of the photosensitive drum 1, and applies a charging bias to apply a charging bias.
To a predetermined polarity and potential.

The developing device 4 includes a yellow (Y) developing device 4
Y, magenta (M) developing device 4M, cyan (C) developing device 4
C, a black (Bk) developing unit 4Bk is mounted on the rotating body 4a, and the rotating body 4a is driven by a rotation driving device (not shown).
, The yellow developing device 4Y, the magenta developing device 4M, the cyan developing device 4C, and the black developing device 4Bk face the photosensitive drum 1 during the developing process.
Placed in

The transfer device 5 is an intermediate transfer drum (intermediate transfer member) 7 as a second image carrier having a roller-like multilayer structure for performing primary transfer, and a transfer as a secondary transfer member for performing secondary transfer. And a belt 8.

The intermediate transfer drum 7 contacts the surface of the photosensitive drum 1 and the surface of the transfer belt 8 and is driven by an intermediate transfer drum drive gear 22 in the direction of arrow c.

A primary transfer bias power supply 9 is connected to the intermediate transfer drum 7, and a predetermined
Next transfer bias is applied.

The transfer belt 8 is an endless belt stretched and wound around a transfer roller 10 and a drive roller 11, contacts the intermediate transfer drum 7 from below, and the upper surface of the belt is transferred by the transfer roller 10 and the drive roller 11. It rotates in the direction of arrow d. The transfer roller 10 has a secondary transfer bias power source 1.
2 is connected, and applies a predetermined secondary transfer bias to the transfer roller 10.

The transfer roller 10 and the driving roller 11 are supported by bearings on a transfer frame 13.
A pressure spring 14 and a pressure piece 15 are arranged at one end of the block 3. The pressure piece 15 is supported by a pressure cam 16, and the transfer belt 8 is subjected to intermediate transfer at a predetermined timing by rotation of the pressure cam 16 by rotation of an electromagnetic clutch (not shown) and a driving unit (not shown). The drum 7 can be freely contacted and separated. The transfer roller 10 is brought into contact with the intermediate transfer drum 7 at a predetermined secondary transfer pressure by the spring force of the pressure spring 14.

On the outer peripheral surface of the intermediate transfer drum 7, a roller-shaped multi-layer intermediate transfer drum cleaning roller 17 is disposed so as to be able to contact / separate freely. The intermediate transfer drum cleaning roller 17 has a cleaning bias power supply 1
8, a predetermined bias is applied.

The fixing device 6 has a fixing roller 6a and a pressure roller 6b pressed against the fixing roller 6a. Both rollers have a built-in heater, and transfer material P such as paper is transferred to both rollers. During the passage, the toner image on the transfer material P is fixed as a permanent image by heat and pressure.

Next, an image forming operation in the image forming apparatus will be described.

At the time of image formation, the photosensitive drum 1 is driven to rotate in a direction indicated by an arrow a at a predetermined peripheral speed V by a driving means (not shown), and a charging roller 2 to which a predetermined charging bias is applied.
As a result, charging is performed to a predetermined polarity and potential.

Then, an image exposure L by a laser beam is given to the charged photosensitive drum 1 by the exposure device 3 by the exposure device 3, and a first color component image (for example,
An electrostatic latent image corresponding to the yellow component image is formed. Next, the electrostatic latent image is developed by the yellow developing device 4Y with the first color yellow toner.

The yellow toner image of the first color formed and carried on the photosensitive drum 1 passes through a primary nip T1 between the photosensitive drum 1 and the intermediate transfer drum 7 in the course of passing through the primary nip T1.
Pressure at primary transfer nip T1 and primary transfer bias power supply 9
The primary transfer (intermediate transfer) is performed on the outer peripheral surface of the intermediate transfer drum 7 by the electric field formed by the primary transfer bias applied to the intermediate transfer drum 7 from the first.

Hereinafter, similarly, the magenta developing device 4M,
The magenta toner image of the second color, the third cyan toner image, and the fourth black toner image formed and carried on the photosensitive drum 1 by the cyan developing unit 4C and the black developing unit 4Bk are sequentially superimposed on the intermediate transfer drum 7. The image is transferred to form a composite color toner image corresponding to the target color image. This step is called primary transfer.

On the other hand, a transfer material P such as paper is fed from a paper feed cassette (not shown), and a pair of registration rollers 19,
The paper is fed through a pre-transfer guide 20 to a secondary transfer nip T2 between the intermediate transfer drum 7 and the intermediate transfer belt 8. At this time, the secondary transfer bias power supply 12
The next transfer bias is applied, and the composite color toner image superimposedly transferred (primary transfer) onto the intermediate transfer drum 7 is transferred onto the transfer material P.

After the transfer material P is conveyed to the fixing device 6 and the transferred image is fixed, the transfer material P is discharged onto a discharge tray (not shown) on the upper surface of the device by a discharge roller (not shown).

The secondary transfer residual toner remaining on the intermediate transfer drum 7 without being subjected to the secondary transfer is brought into contact with the intermediate transfer drum cleaning roller 17 and a bias is applied to the toner so that the toner has its original polarity. Is converted to the opposite polarity and electrostatically attracted to the photosensitive drum 1, and the intermediate transfer drum 7 is cleaned. The secondary transfer residual toner adsorbed on the photosensitive drum 1 is thereafter collected by the cleaning blade 21a of the cleaning device 21.

Next, the braking means provided inside the intermediate transfer drum 7, which is a characteristic part of the present invention, that is, the braking force applying means will be described.

As shown in FIG. 2, the intermediate transfer drum 7
Roller-shaped cylinder 7 comprising an aluminum support 7f1 and an elastic layer 7f2 of rubber or the like provided thereon.
f, and flanges 7a and 7b are fitted to both ends of the cylinder 7f, respectively. A rotation stopper X is provided between the cylinder 7f and the flanges 7a and 7b, as shown in FIG.

Bearings 7c and 7d are fixed to the central portions of the flanges 7a and 7b, respectively, and the bearings 7c and 7d support an intermediate transfer drum rotating shaft 7e.

A friction holder 7k is fixed to the intermediate transfer drum rotating shaft 7e on one flange 7a side by screws 7m. The friction holder 7k includes a cylindrical portion 7k1 fitted to the intermediate transfer drum rotating shaft 7e, and a flange 7k2 provided at an end of the cylindrical portion 7k1 on the flange 7a side.

Then, on the friction holder 7k, a stopper 7i, a spring 7j as a biasing member, a friction ring 7g, and the like are arranged in order from the center to the end of the rotary shaft 7e of the intermediate transfer drum 7e, that is, toward the flange 7a. And friction plate 7h
Are arranged. In this embodiment, a resin (POM) is used for the friction ring 7g and a SUS plate is used for the friction plate 7h.

The friction plate 7h and the friction holder 7
A rotation stopper (not shown) is provided between the stopper 7i and the friction holder 7k during the interval k. Further, as shown in FIG. 3, detents Y and Z are provided between the friction ring 7g and the flange 7a.

The stopper 7i is fixed to a predetermined position where the spring 7j is sufficiently bent, that is, a position where a sufficient urging force is obtained, and includes a friction plate 7h and a friction ring 7g.
Always receives a constant load from the spring 7j. At this time, the friction plate 7h is connected to the flange 7k2 of the friction holder 7k.
Is pressed against.

On the other hand, as shown in FIG. 4, the intermediate transfer drum (specifically, the cylinder 7f and the flanges 7a and 7b) is driven by an intermediate transfer drum driving gear via an intermediate transfer drum gear portion 7a1 provided on the flange 7a. 22 is driven in the direction of arrow c. At this time, the flange 7a and the friction ring 7g are connected by the rotation stoppers X and Y, and the frictional force due to the load of the spring 7j acts between the friction ring 7g and the friction plate 7h. ,
During the rotation of the intermediate transfer member, a constant braking force is always applied in the opposite direction, that is, in the direction indicated by the arrow f, from the direction indicated by the arrow c, as shown in FIG. Therefore, the engagement between the intermediate transfer drum gear portion 7a1 and the intermediate transfer drum drive gear 22 is always performed on one side W of the gear teeth as shown in FIG. 5, and the intermediate transfer drum 7 can always rotate stably.

Therefore, by providing the above-described intermediate transfer body brake means on the intermediate transfer drum 7, the transfer belt 8 is moved during the primary transfer, the formation of the latent image on the photosensitive drum 1, and the secondary transfer. 7, the load on the intermediate transfer drum 7 due to the rotation of the developing device 4 being in contact with the photosensitive drum 1, and the cleaning roller 17 for the intermediate transfer drum. Irrespective of any variation in the load on the intermediate transfer drum 7 caused by contact with the drum 7, the intermediate transfer drum 7 can always achieve stable rotation with little rotation unevenness, no image blurring, and clear images with little color shift. Can be obtained.

Further, since the image forming apparatus of this embodiment is provided with the intermediate transfer drum 7, the toner is not loaded on the nip T 1 between the photosensitive drum 1 and the intermediate transfer drum 7. In the case, slip is likely to occur because of the difference in the frictional force between the photosensitive drum 1 and the intermediate transfer drum 7. Further, the same slip as described above due to the amount of toner on the nip T1 and the same slip as described above due to changes in toner characteristics due to environmental changes such as low temperature, low humidity, and high temperature and high humidity are likely to occur.

However, by providing the intermediate transfer drum 7 with the brake means of the present invention, the slip is reduced, the intermediate transfer drum can be rotated stably, and a high quality image can be obtained.

Further, the present invention is characterized in that a braking means is provided inside the intermediate transfer drum 7 in order to apply a stable brake torque to the intermediate transfer drum 7, thereby providing a space in the design of the image forming apparatus. Can also be an advantageous configuration.

Therefore, according to the present embodiment, a high-quality output image can be obtained without being affected by load fluctuation, vibration, or the like applied to the image carrier during the image forming process.

By providing the brake means inside the image carrier, the size of the apparatus can be reduced.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG.

In FIG. 6, a color image carrier 23 as a photosensitive drum is rotated at a predetermined process speed by a color image carrier drive gear 29, and is charged by a charger 24 to a predetermined polarity and potential. . The charged color image carrier 23 is subjected to the first color Y (yellow) image exposure by the exposure device 25, and an electrostatic latent image corresponding to the Y (yellow) color component image of the target color image. Is formed.

Next, the electrostatic latent image is developed on a predetermined developing area D by yellow toner of a Y (yellow) developing device 26Y in a rotary moving type developing unit 26.
Then, the above process is sequentially performed on each of the M (magenta), C (cyan), and Bk (black) toners contained in the magenta developing device 26M, the cyan developing device 26C, and the black developing device 26Bk. A desired composite color image is formed on the top.

Then, the transfer material P is fed from a feeding unit (not shown), and the transfer device 27 which can freely contact and separate comes into contact at the transfer unit T, and the color composite image is collectively transferred to the transfer material P. .
Thereafter, the transfer material P is fixed by the fixing device 28, and is discharged to a paper discharge tray (not shown) by a conveyance roller (not shown). After the transfer, the residual toner remaining on the color image carrier 23 is cleaned by contacting a cleaning device (blade) 30 provided to be able to contact and separate from the color image carrier 23.

In this color image forming apparatus, the first
By providing the brake applying means of the present invention inside the color image carrier 23 as in the embodiment, the color image carrier is brought into contact with the transfer device 27 at the time of transfer and at the time of latent image formation. 23, load fluctuation of the color image carrier 23 due to the rotation of the developing device 26 being in contact with the color image carrier 23, and color variation due to the contact of the cleaning device 30 with the color image carrier 23. Irrespective of the load variation of the image carrier 23, the color image carrier 23 can always achieve stable rotation with little rotation unevenness, without image blur,
A clear image with little color shift can be obtained.

In the above-described embodiment, the case where the brake means of the present invention includes an urging member and a friction member has been described as an example. However, a hydraulic damper system as shown in FIG. 7 can be applied. .

The hydraulic damper 7n schematically shown in FIG.
Inner part 7n2 connected to intermediate transfer drum rotating shaft 7e
And an outer portion 7n1 coupled to the flange 7a of the intermediate transfer drum 7. A liquid having a certain viscosity is interposed between the inner portion 7n2 and the outer portion 7n1. As a result, a certain load is applied to the intermediate transfer drum 7 when rotating.

In this case, in order to reduce the change in the viscosity of the oil due to the change in the temperature environment, that is, the change in the brake torque applied to the image carrier, it is advantageous to provide the inside of the image carrier in a more stable temperature environment.

[0053]

As is apparent from the above description, according to the present invention, there is provided means for applying a braking force to the rotation of the image carrier, and the braking force applying means is provided inside the image carrier. Thus, a stable rotation is always given to the image carrier, and a high-quality image can be formed.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing an internal structure of the intermediate transfer drum of FIG.

FIG. 3 is a perspective view showing a brake unit.

FIG. 4 is an explanatory diagram illustrating an intermediate transfer drum driving gear unit.

FIG. 5 is an explanatory diagram showing meshing between an intermediate transfer drum driving gear and an intermediate transfer drum gear portion.

FIG. 6 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment of the present invention.

FIG. 7 is an explanatory view showing an intermediate transfer drum provided with a hydraulic damper which is a modified example of the brake means according to the present invention.

FIG. 8 is a schematic configuration diagram showing an internal structure of a conventional image carrier.

FIG. 9 is an explanatory view showing a drive gear section of the image carrier of FIG. 7;

FIG. 10 is an explanatory diagram showing meshing between an image carrier driving gear and an image carrier gear.

FIG. 11 is an explanatory diagram showing a state in which the image carrier gear moves to both sides.

[Explanation of symbols]

 7 Intermediate transfer drum (image carrier) 7g Friction ring (friction member) 7h Friction brake (friction member) 7i Stopper 7j Spring (biasing member) 7k Friction holder 23 Photosensitive drum (image carrier)

Claims (5)

[Claims] 1. An image forming apparatus comprising: a rotatable image carrier; and image forming means for forming an image on the image carrier, wherein the image on the image carrier is transferred to a transfer material. When forming an image on the image carrier by the image forming means,
Alternatively, the image forming apparatus includes a braking force applying unit that applies a braking force to the rotation of the image carrier when transferring an image from the image carrier to a transfer material. 2. The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer member on which a plurality of color toner images are superimposed. 3. The image forming apparatus according to claim 1, wherein the image carrier is a photosensitive drum on which a plurality of color toner images are superimposed. 4. The apparatus according to claim 1, wherein said braking force applying means includes at least an urging member and a friction member.
2 or 3 image forming apparatuses. 5. An image forming apparatus according to claim 1, wherein said braking force applying means is of a hydraulic damper type.