JP2000321879A - Image forming device - Google Patents

Abstract

(57) [Problem] To provide an image forming apparatus using a belt as an intermediate transfer member, the image of which is improved in color misregistration by controlling the bias of the belt to stabilize the image quality. It is intended to provide a forming apparatus. An image forming apparatus according to the present invention forms a latent image corresponding to each color component on an image carrier, and develops the latent image with a developer corresponding to each color component. Then, in the image forming apparatus in which the developed image is superimposedly transferred onto the rotating intermediate transfer member and then collectively transferred onto a transfer material to obtain a multicolor image, the intermediate transfer member is an endless intermediate transfer belt. 3a, characterized in that it has a rib 3b at one end in the width direction for regulating the deviation of the belt, and generates a deviation force on the opposite side of the rib 3b.

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 color copying machine or a color printer, and more particularly to an intermediate transfer member for carrying a plurality of developed images.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, there has been proposed a structure in which a developed image of a plurality of colors is transferred for each color to the same transfer material to obtain a color image, particularly like a color image forming apparatus. ing. For example, a latent image is formed for each color on a photosensitive drum which is an image carrier, the latent image is formed into a developed image by a plurality of developing devices, and the developed image is sequentially transferred to a transfer material held by a transfer device. There is a method for obtaining a color image.

[0003] However, as described above, in an apparatus for directly transferring a transfer material a plurality of times, there are many restrictions on the thickness and size of the transfer material, and the transfer route of the transfer material is complicated. Therefore, there is an image forming apparatus in which, instead of the transfer material, the image is temporarily transferred onto an intermediate transfer body such as a belt or a film in a superimposed manner, and then collectively transferred onto the transfer material to obtain a color image. In this method, the transfer path of the transfer material is the same as that for a single developed image, so there are many types of transfer materials that can be used. It is easy to plan.

[0004]

However, in an apparatus using a belt as an intermediate transfer member, when the intermediate transfer belt is stretched, a biasing force is generated in one of the axial directions and the meandering or one-sided force is generated. I will move in the direction. Therefore, conventionally, as shown in FIG. 5, a configuration is adopted in which a rib 81 (projection) is formed on the inner surface of the intermediate transfer belt 80 for restricting deviation, and the deviation of the belt is restricted together with a groove flange 82 for receiving the rib 81. Have been.

In the intermediate transfer belt in which the ribs are formed only on one side of the intermediate transfer belt 80, it is not known whether the direction of the belt shifts toward the rib side or the non-rib side. Therefore, as shown in FIG. The belt may move in the width direction by an amount equal to the gap δ from the belt 82, which causes the sequentially superimposed colors to shift in the width direction.

If the force on the rib side is too large, the belt on the non-rib side will move on the rib side. However, since the rib 81 is regulated by the groove flange 82, wrinkles are generated on the intermediate transfer belt 80, and an image is formed. There was also a problem of being disturbed.

In view of the above, the present invention provides an image forming apparatus using a belt as an intermediate transfer member, in which color shift is improved by controlling the biasing force of the belt to stabilize image quality. It is intended to be.

[0008]

In order to solve the above-mentioned problems, an image forming apparatus according to the present invention forms a latent image corresponding to each color component on an image carrier, and this latent image corresponds to each color component. In the image forming apparatus, the developed image is obtained by superposingly transferring the developed image onto a rotating intermediate transfer member and then collectively transferring the image onto a transfer material to obtain a multicolor image. A belt-shaped belt having a rib-shaped protrusion at one end in the width direction for restricting the movement of the belt, and generating a biasing force on a side opposite to the rib-shaped protrusion.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] An embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of an image forming apparatus according to the present embodiment, FIG. 2 is a side view of an intermediate transfer body, and FIG. 3 is a top view of the intermediate transfer body. In the present embodiment, an image forming apparatus will be described using a laser beam printer as an example.

The image forming apparatus shown in FIG. 1 develops an electrostatic latent image formed on the image carrier 4 by a developing unit 5 equipped with four rotatable movable developing units 6, and converts the developed image. After the primary transfer is superimposed on the intermediate transfer member 3, it is secondarily transferred onto the transfer material 2 supplied from the feeding unit 1 at a time, and then a color image is formed by applying heat and pressure by the fixing unit 7. The sheet is discharged to a discharge section 9 at the top of the apparatus by a discharge roller pair 8. The components will be described below in order.

(Supplying Unit) The feeding unit 1 supplies the transfer material 2 to the intermediate transfer body 3, and a feeding cassette 1 a containing a plurality of transfer materials 2 is placed on the inner bottom of the apparatus main body A. I'm loading. At the time of image formation, the feed roller 1b is driven and rotated in accordance with the image forming operation, separates and feeds the transfer material 2 in the feed cassette 1a one by one, is guided by the guide plate 1c, and passes through the registration roller pair 1d. It is transported to the transfer body 3.

(Image Carrier) Image Carrier 4 According to the Present Embodiment
Is formed by applying an organic photoconductor layer to an outer peripheral surface of an aluminum cylinder having a diameter of about 47 mm, and a rotating shaft is rotatably supported on the image carrier unit cover 4a. A primary charging unit 4b and a cleaner 4c are arranged on the periphery of the image carrier 4,
Further, by transmitting a driving force of a driving motor (not shown) to one end of the rotating shaft, the image carrier 4 is rotated in the direction of arrow B in FIG. 1 in accordance with an image forming operation. This unit is detachable from the apparatus main body, and can be easily replaced according to the life of the image carrier.

Exposure to the image carrier 4 is sent from a scanner unit 10. That is, when an image signal is given to a laser diode (not shown), the laser diode irradiates the corresponding image light to the polygon mirror 10a. The polygon mirror 10a is rotated at a high speed by a scanner motor, and the image light reflected by the polygon mirror 10a selectively exposes the image carrier 4 via the imaging lens 10b and the reflection mirror 10c.

The primary charging means 4b employs a so-called contact charging method as disclosed in Japanese Patent Application Laid-Open No. 63-149669, in which a conductive roller is brought into contact with the image carrier 4 and The surface of the image carrier 4 is uniformly charged by applying a voltage.

The cleaner 4c removes the toner remaining on the image carrier 4 after the developer (hereinafter referred to as toner) visualized on the image carrier 4 by the developing unit 5 is transferred to the transfer material 2. Is what you do. In this embodiment, the cleaner 4c is a blade disposed on the image carrier 4 in a counter direction, and the waste toner cleaned by the blade is sent into a waste toner container, and is removed when the waste toner container is full. Exchange.

(Developing means) In order to visualize the latent image, the developing unit 5 has four developing units (yellow 6Y, yellow 6Y,
Magenta 6M, cyan 6C, black 6Bk) are arranged. At the time of image formation, the developing unit 5 is rotated about the shaft 5a, and each of the developing devices 6Y to 6Y corresponding to a color to be developed.
6Bk stops at a position facing the image carrier 4. Further, the developing sleeve 6b is arranged at a minute interval (300 μm
Position) so as to face each other.

The toner in the container corresponding to the color to be developed is fed to the coating roller 6a by a feeding mechanism, the thin film of the toner is coated on the outer circumference of the rotating coating roller 6a and the rotating developing sleeve 6b by the blade 6d, and the toner is charged. (Triboelectric charging). This developing sleeve 6b
By applying a developing bias to the image carrier 4 on which the latent image is formed, toner development is performed on the image carrier 4 according to the latent image. This is repeated for each color, so that a visible image is formed on the image carrier 4 by the toner sequentially.

Further, the developing sleeve 6b of each developing device 6 holds the main assembly A of the apparatus when each developing device 6 is rotated to the developing position.
Are connected to a high-voltage power supply (not shown) for developing each color, and a voltage is selectively applied for each development of each color. The rotatable developing device is configured to be individually detachable from the apparatus main assembly A.

(Fixing Unit) The fixing means 7 fixes the image formed on the transfer material 2 and, as shown in FIG. And a fixing roller 7b for applying pressure. That is, the transfer material 2 on which the toner on the intermediate transfer belt 80 has been collectively transferred is conveyed by the driving roller 7a when passing through the fixing unit 7, and is also applied with heat and pressure by the fixing roller 7b. As a result, the image forming toner is fixed on the transfer material 2.

(Intermediate Transfer Body) The intermediate transfer body 3 is a body in which the developed images of the respective colors are sequentially transferred in a superimposed manner, and then transferred collectively to the transfer material 2. In the present embodiment, the intermediate transfer member 3
Is constructed by stretching an endless intermediate transfer belt 3a having a circumference of about 440 mm by three rollers of a drive roller 12, a secondary transfer opposing roller 13, and a driven roller 14.

As shown in FIG. 2, each of the rollers 12 to 14 has a bearing 12 facing a side plate 16 connected by stays (not shown).
The drive roller 12 is rotatably supported by a, 13a, and 14a, and rotates in the direction of arrow A shown in FIG. 1 in accordance with the image forming operation when the drive roller 12 rotates. And the bearing 12a of each roller
Are accurately positioned on both side plates 16, and the distance between the three axes is arranged so as to be substantially an integral multiple of the outer peripheral length of the image carrier 4 so that the primary transfer images to be repeatedly transferred overlap without being shifted. I have.

As shown in FIG. 3, a rib 3b for restricting deviation is formed on the inner surface of one end of the intermediate transfer belt 3a. On the other hand, groove flanges 12b and 14b are provided at the end of the roller, and are fitted to the ribs 3b to regulate the movement of the intermediate transfer belt 3a in the axial direction.

In general, a belt stretched over a plurality of shafts should not shift in the axial direction unless a force is applied in the axial direction. However, the belt is stretched in the width direction due to the accuracy of the distance between the shafts and the change in the thickness of the belt. If the tension is imbalanced between the left and right, a biasing force is generated in a direction where the tension is large. Therefore, when the deviation is restricted by the rib 3b, the rib 3b is deviated in an unspecified direction on either the left or right of the groove flange 12b.

Therefore, in the present embodiment, the center distances A1 and A2 between the rib side and the non-rib side shown in FIG.
2> A1. As a result, the tension on the non-rib side always increases, and the intermediate transfer belt 3a
In order to approach the side opposite to b, the direction of the approach of the rib 3b can always be specified to one side of the groove flanges 12b, 13b. As described above, when the rib 3b receives a constant tension,
A stable belt rotation can be obtained without fluctuation in the axial direction, and an image with high color overlay accuracy can be formed.

A detachable cleaning unit 11 is provided at a predetermined position on the outer periphery of the intermediate transfer belt 3a, and removes residual toner remaining after the batch transfer to the fed transfer material 2. The cleaning unit 11 includes a charging roller 11a.
Is brought into contact with the intermediate transfer belt 3a, and the toner is electrostatically collected by the image carrier 4 by applying a reverse voltage to the toner at the time of transfer, and is collected by the cleaner 4c of the image carrier 4. .

The method of cleaning the intermediate transfer belt 3a is not limited to the electrostatic cleaning described above, but may be a mechanical method such as a blade or a fur brush, or a combination of these methods.

(Image Forming Operation) Next, a description will be given of an operation when an image is formed by the above-described apparatus. The image carrier 4 is rotated in the direction of arrow B in FIG. 1 in synchronization with the rotation of the intermediate transfer belt 3a, and the surface of the image carrier is uniformly charged by the primary charging means 4b with respect to the image carrier 4.
A black image is formed on the image carrier 4 by irradiating a black image with light by the scanner unit 10. At the same time as the formation of the latent image, the black developing device 6Bk is driven, and a voltage having the same polarity and substantially the same potential as the charging polarity of the image carrier 4 is applied so that the black toner adheres to the latent image on the image carrier 4. And develop
A voltage having a polarity opposite to that of the toner is applied to the primary transfer roller 15 to transfer the toner on the image carrier 4 onto the intermediate transfer belt 3a.

When the transfer of the black toner is completed, the next developing unit 6 rotates and is positioned at a position facing the image carrier 4, and the magenta, cyan, and yellow latent images are formed in the same manner as in the case of black. The formation and toner transfer are sequentially performed to form a color image on the intermediate transfer belt 3a, and the color image is collectively transferred to the transfer material 2 fed from the feeding unit 1 by the secondary transfer means 19.

After the image formation, the transfer material 2 is fixed to the fixing means 7.
After the toner is fixed by the fixing unit 7, the toner is discharged to the discharge unit 9 by the discharge roller pair 8, and the image formation is completed.

[Second Embodiment] Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings.
FIG. 4 is a plan view illustrating the intermediate transfer belt according to the present embodiment. In the first embodiment, the intermediate transfer belt 3
Although a difference is provided in the inter-axis distance as a configuration for stably generating a biasing force toward a, the present embodiment is characterized by the configuration of the belt itself.

As shown in FIG. 4, the intermediate transfer belt 17 according to the present embodiment has a rib 17a on the inner surface side, and a core 18 is arranged vertically and horizontally inside the belt. Here, when the intermediate transfer belt 17 is stretched between the shafts, a force is applied to the core 18 inside the belt, and tension is generated. In which a core is disposed. The tension between the axes is mainly generated in the vertical cores 18a arranged in the belt rotation direction, and the horizontal core 18b suppresses the belt elongation in the axial direction.

When tension is applied to the vertical core body 18a, a component force in a direction having an angle with respect to the rotation direction is generated in the horizontal core body 18b, and due to the action, a biasing force in the width direction is generated in the intermediate transfer belt 17. I do. Therefore, the intermediate transfer belt 17 is configured to have an angle α in the rotation direction from the rib side to the non-rib side in the direction of the horizontal core body 18b, so that a biasing force on the opposite side to the rib 17a is generated, and The direction of the shift of 17a can always be specified to one side of a not-shown groove flange.
Therefore, stable belt rotation can be obtained without fluctuation in the axial direction, and an image with high color overlay accuracy can be formed.

Here, the angle α of the horizontal body 18b is 0 ° <α ≦ 30.
° is desirable. If α <0 °, the direction of the deviation is reversed, so that the deviation is toward the rib side, and wrinkles are generated on the belt. If the angle α is too large, the biasing force becomes too large, which affects the strength of the ribs and the like.

In the present embodiment, it is preferable that the inter-axis distance be left and right with a certain degree of accuracy. However, as shown in the first embodiment, the relation of the inter-axis distance that is shifted to the side opposite to the rib 17a is also possible. Good.

[0035]

As described above, in the image forming apparatus according to the present invention, the belt-developing force is generated in the direction opposite to the rib for regulating the deviation.
There is no fluctuation in the width direction of the intermediate transfer member, and at the same time, wrinkling of the intermediate transfer member can be prevented. Therefore, stable belt rotation can be obtained, and an image with good color overlay accuracy can be formed.

[Brief description of the drawings]

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

FIG. 2 is a side view of the intermediate transfer member.

FIG. 3 is a top view of the intermediate transfer member.

FIG. 4 is a plan view illustrating an intermediate transfer belt according to a second embodiment.

FIG. 5 is a diagram illustrating a mechanism for restricting deviation of an intermediate transfer member according to a conventional example.

[Explanation of symbols]

 A: Main body 1 ... Feeding section 1a ... Feeding cassette 1b ... Feeding roller 1c ... Guide plate 1d ... Registration roller pair 2 ... Transfer material 3 ... Intermediate transfer member 3a ... Intermediate transfer belt 3b ... Rib 4 ... Image carrier 4a: Image carrier unit cover 4b: Primary charging means 4c: Cleaner 5: Developing unit 5a: Shaft 6: Developing device 6a: Coating roller 6b: Developing sleeve 6d: Blade 7: Fixing means 7a: Driving roller 7b: Fixing roller 8 ... Discharge roller pair 9 ... Discharge part 10 ... Scanner part 10a ... Polygon mirror 10b ... Imaging lens 10c ... Reflection mirror 11 ... Cleaning unit 11a ... Charging roller 12 ... Drive roller 12a ... Bearing 12b ... Flange flange 13 ... Secondary transfer facing Roller 13a: Bearing 13b: Groove flange 14: Driven roller 14a: Bearing 15: Primary transfer roller 16: Both side plates 17: During transfer belt 17a ... ribs 18 ... core 18a ... Tateshintai 18b ... Yokoshintai

Claims (4)

[Claims] 1. A latent image corresponding to each color component is formed on an image carrier, and the latent image is developed with a developer corresponding to each color component.
In an image forming apparatus for obtaining a multicolor image by transferring the developed image onto a rotating intermediate transfer member in a superimposed manner and then collectively transferring the developed image onto a transfer material, the intermediate transfer member is an endless belt, An image forming apparatus comprising: a rib-shaped protrusion at one end in a direction to restrict the belt from moving; and a biasing force generated on a side opposite to the rib-shaped protrusion (hereinafter referred to as a non-rib side). 2. A configuration for generating a biasing force of the intermediate transfer member, wherein the total distance between the axes of at least two rollers that stretch the belt is A1 on the rib side and A2 on the non-rib side.
2. The image forming apparatus according to claim 1, wherein 2> A1. 3. A structure for generating a biasing force of the intermediate transfer body, wherein the belt of the intermediate transfer body has a core structure formed by weaving a vertical core and a horizontal core, and the vertical core has a belt rotation direction. 2. The image forming apparatus according to claim 1, wherein the horizontal body is configured to have an angle in a rotational direction from the rib side to the non-rib side. 3. 4. An image forming apparatus according to claim 3, wherein the angle α of the horizontal body is 0 ° <α ≦ 30 °.