JP2003295566A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control soiling of a main body due to toner scattering. <P>SOLUTION: Jumping developing is carried out for a Bk image by a fixed developing device. A color image is developed by a rotary developing device and oscillating component of AC bias in Bk developing is set to be lower when not forming an image than when forming an image. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for developing a latent image formed on an image carrier in a copying machine, an image forming / recording apparatus, a printer, a facsimile, etc., and more particularly to a color developing machine. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus for forming a color image by superposing toner images of a plurality of colors, an intermediate transfer member as shown in FIG. 1 has been conventionally used for the purpose of obtaining a color image without color shift. An image forming apparatus using is proposed.

This image processing apparatus is a copying machine or a laser beam printer using an electrophotographic process.
The configuration and operation of the image processing apparatus shown in FIG. 1 will be briefly described below.

A rotating drum type electrophotographic photosensitive member (hereinafter referred to as "photosensitive drum") 1 as an image bearing member is arranged inside the main body of the apparatus (hereinafter referred to as "inside the device"). An amorphous silicon photoconductor is used here, and a schematic diagram thereof is shown in FIG. 101 is a conductive support such as Al, 104 is the conductive support, and a charge injection blocking layer 102 for blocking injection of charges from 101 is made of at least an amorphous silicon-based material. Is a surface protective layer for protecting the photoconductive layer 102, and 105 is a long wavelength light absorption layer for preventing reflection from the conductive support 101.

The photosensitive drum 1 is rotationally driven in the direction of arrow R1 at a predetermined peripheral speed (process speed), and each image forming process described later is repeatedly performed on the surface thereof.

The photosensitive drum 1 is charged with a predetermined polarity and a predetermined surface potential by a charger 2 such as a corona discharger in the course of rotation in the direction of arrow R1, and then the exposure unit 3 is exposed.
(Image-forming exposure optical system based on color separation of color original image,
By receiving the image exposure L by the scanning exposure optical system by the laser scanner which outputs the laser beam modulated corresponding to the time series electric digital pixel signal of the image information, the color component image of the target color image (for example, M ( Magenta)
An electrostatic latent image corresponding to the component image) is formed.

An intermediate transfer belt is used as the intermediate transfer member. The intermediate transfer belt 5 is stretched around one conductive roller 6 and four turn rollers 7a, 7b, 7c, and 7d, which is a total of five rollers. The conductive roller 6 is
The intermediate transfer belt 5 is held in a state of being pressed against the photosensitive drum 1 with a predetermined pressing force. The intermediate transfer belt 5 is rotationally driven in the direction of arrow R5 at the same peripheral speed as the photosensitive drum 1, and the conductive roller 6 is biased by a bias power source to form and carry a toner image on the photosensitive drum 1 (hereinafter referred to as “toner image”). .) Of the toner charging polarity (negative in this embodiment) is applied.

The intermediate transfer belt 5 is, for example, a dielectric film of polyester, polyethylene or the like, or a composite layer type dielectric film in which the back surface (inner surface side) of a medium resistance rubber or the like is lined with a conductor. The magenta toner image of the first color, which is formed and carried on the surface of the photosensitive drum 1 described above, is generated by the electric field formed by the application of the transfer bias to the conductive roller 6.
In the process of passing through the transfer portion, the intermediate transfer is sequentially performed on the outer surface of the intermediate transfer belt 5.

The developing device is fixed by a black (Bk) developing device (hereinafter referred to as "Bk developing device") 401 fixedly arranged on the upstream side in the rotation direction of the photosensitive drum 1 (direction of arrow R1). The developing device 4a is composed of a developing device 4a and a rotary developing device 4b having other three color developing devices rotatably arranged on the downstream side. Rotating developing device 4b
Is a rotating body that rotates in the direction of arrow R4, and three developing devices mounted on the rotating body, that is, a developing device that contains magenta (M), cyan (C), and yellow (Y) toners, respectively. Devices 402, 403, 404 (hereinafter referred to as "M developing device 402, C developing device 403, Y developing device 40, respectively.
4 ”).

Further, the Bk developing device 401 is fixedly arranged between the exposure unit 3 on the upstream side and the rotary developing device 4b on the downstream side so as to separate them.

The structure of the Bk developing device 401 in the fixed developing device 4a shown in FIG. 3 will be described. The developing container 40 has an opening extending in the longitudinal direction of the apparatus (a direction perpendicular to the paper surface of FIG. 1), and the developing sleeve 41 is installed in the opening. The developing sleeve 41 is made of, for example, aluminum or SUS.
It is made of materials such as. In the developing sleeve 41, as viewed in the drawing of the opening, the left substantially half peripheral surface projects into the container, and the right substantially half peripheral surface projects into the container 4.
0 is exposed outside and is rotatably provided laterally so as to face the photosensitive drum 1. A slight gap S-Dgap is provided between the developing sleeve 41 and the photosensitive drum 1, and the developing sleeve 41 is arranged in the rotational direction R1 of the photosensitive drum 1.
On the other hand, it is rotationally driven in the direction of arrow R4a.

A magnet 42 is provided in the developing sleeve 41 as a magnetic field generating means. In this embodiment, the magnet 42 is a permanent magnet. The magnet 42 is non-rotatably arranged in the developing sleeve 41 so as to generate a fixed magnetic field regardless of the rotation of the developing sleeve 41.

In the vicinity of the developing sleeve 41 in the developing container 40, there is provided a plate-shaped magnetic blade 43 as a developer regulating member whose fixed end is supported by the opening of the developing container and whose free end is close to the developing sleeve 41. The magnetic blade 43 is provided so that one pole of the magnetic pole of the magnet 42 is substantially opposed to the magnetic blade 43.

The magnetic toner 45 carried on the developing sleeve 41 by the agitating member 44 is then transferred to the developing sleeve 41.
Is rotated and the magnetic blade 43 is conveyed to the developing sleeve facing portion. The magnetic regulation formed in the gap between the magnetic blade 43 and the developing sleeve 41: S-Bgap
After the layer thickness is regulated by the sheet, a thin layer is formed on the developing sleeve 41, and then the regulating section: S-Bgap is exited to open a minute gap: S-Dgap with the photosensitive drum 1 and the sheet is conveyed to the opposing developing area. To be done. By applying an alternating voltage, in which a direct current and an alternating current are superposed, as a developing bias between the developing sleeve 41 and the photosensitive drum 1 in the developing region, the toner 45 on the developing sleeve 41 becomes an electrostatic latent image on the photosensitive drum 1. The electrostatic latent image is visualized and developed as a toner image by transferring and adhering to face each other.

Next, image formation by the Bk developing device 401 will be described.

First, the surface of the photosensitive drum 1 is replaced with the primary charger 2
Is uniformly charged to the drum surface potential Vd = + 400V. Then, a semiconductor laser with a wavelength of 680 μm is used to
Exposure L by PWM is performed at 0 dpi to form an electrostatic latent image on the photosensitive drum 1. The laser power at this time is set so that the electrostatic latent image becomes Vl = + 50V.

Subsequently, S-Bgap: 250 μm, S-D
Development is carried out by the Bk developing device 401 having a gap of 250 μm to visualize it as a toner image.

The developer used in this embodiment is a negative magnetic one-component toner, and the developing bias Vdc is +200 V DC voltage of 2700 Hz, 1500 Vpp, 50% Dut.
The AC voltage of y is superimposed to realize jumping development. This is the Bk development contrast V in regular development.
cont = 200V, fogging removal bias Vback =
This is because it is set to + 150V (Fig. 4).

By rotating in the direction of arrow R4, the rotary developing device 4b arranges the developing device (M developing device 402 in FIG. 1) for development at the developing position facing the surface of the photosensitive drum 1. Rotational direction R4 of the rotary developing device 4b
Is the same as the rotation direction R1 of the photosensitive drum 1 and is opposite to the rotation direction of the intermediate transfer belt 5 (direction of arrow R5).

The rotation direction of the rotary developing device 4b is indicated by the arrow R.
If the four colors are set and the four colors are developed in the order of M → C → Y → Bk as in the conventional example, the M developing device 402, the C developing device 403, and the Y developing device 403 of the rotary developing device 4b. The developing device 404 is arranged as shown in FIG.
Along the rotation direction (direction of arrow R4) of the M developing device 402,
The Y developing device 403 and the C developing device 404 are in this order.

The image forming operation in the image processing apparatus of this embodiment shown in FIG. 1 will be described below by dividing it into processes (1) to (5). Incidentally, FIG. 1 shows the M developing device 402 among the three developing devices in the rotary developing device 4b.
Indicates that it is standing by at the current position. (1) First, a latent image of an M image of the first color is formed on the photosensitive drum 1, and development is performed in the state shown in FIG. Developing device 4
M on the photosensitive drum 1 revealed by M toner by 02.
The toner image is sequentially and intermediately transferred onto the outer peripheral surface of the intermediate transfer belt 5 while rotating in the direction of arrow R1 (counterclockwise). Then, the surface of the photosensitive drum 1 that has finished transferring the M toner image of the first color to the intermediate transfer belt 5 is cleaned by the cleaning device 8. (2) Subsequently, a latent image of the C image which is the second color is formed, but in order to perform the C development, the rotary developing device 4b moves the arrow R4.
Rotate in the same direction (counterclockwise as the photosensitive drum 1). Then, similarly, (3) C development → C toner development on the intermediate transfer belt 5 → intermediate transfer of the C image on the intermediate transfer belt 5 → cleaning of the surface of the photosensitive drum 1 by the cleaning device 8. (4) Then, as in (2) to (3), Y phenomenon → intermediate transfer of Y image to the intermediate transfer belt 5 → cleaning of the surface of the photosensitive drum 1 by the cleaning device 8. (5) Next, the image exposure L corresponding to the fourth Bk component image L →
Development with Bk toner of the Bk developing device 401 → intermediate transfer of Bk toner image onto the intermediate transfer belt 5 → cleaning of the surface of the photosensitive drum 1 by the cleaning device 8.

The above four toner images (toner images of magenta, cyan, yellow, and black) are superposed on the outer surface of the intermediate transfer belt 5 by sequentially performing the above processes (1) to (5). By being transferred, a composite color toner image (mirror image) corresponding to the target color image is formed.

Next, from the paper feed cassette 9 to the paper feed roller 1
The transfer material (paper sheet) P is separated and conveyed by 0 by 0, passes through the registration roller pair 11, the transfer guide 12, and is transferred to the transfer portion formed by the transfer device 13 (corona charger) and the turn roller 13a. It is fed at a predetermined timing.

The conductive roller 6 is applied with 0 V or the same bias (negative in this example) as the toner charging polarity opposite to the transfer process from the bias power source.
Further, on the transfer material P fed at a predetermined timing, when the toner image is transferred, a bias power source is used to polarize the toner (negative in this example) and reverse polarity (plus).
Is applied to the transfer device 13.

By repeating the above-mentioned series of image forming processes, the transfer composite color images are sequentially intermediate-transferred onto the intermediate transfer belt 50, and the intermediate-transferred color toner images are successively sent to the transfer section. The final transfer is performed on the subsequent transfer material P that comes.

When the transfer process ends, a transfer bias (minus) of 0 V or the same polarity as the toner charging polarity (minus in this example) is applied to the intermediate transfer belt 5. The transfer material P, on which the toner image on the intermediate transfer belt 5 has been transferred through the transfer portion, passes through the conveyance guide 14 and the fixing device 1
5, the fixing roller 15 is heated and regulated to a predetermined value.
The toner image is fixed by being heated and pressed by a and the pressure roller 15b, and is output as a final color image formed product.

On the other hand, the intermediate transfer belt 5 after the toner image transfer
Are cleaned by the belt cleaning device 16.
The belt cleaning device 16 is a cleaning device for the intermediate transfer belt 5, and is normally kept inactive with respect to the intermediate transfer belt 5. However, when the transfer of the toner image onto the transfer material P is completed, The outer surface of the intermediate transfer belt 5 is cleaned by operating the cleaning device 16 on the outer surface of the transfer belt 5.

Depending on the outer peripheral length of the transfer belt 5, it is possible to carry two or more transfer materials P at one time and form two images at once by one rotation of the transfer material P.

[0029]

However, in the jumping developing method found in the Bk developing device 401, the toner reciprocates between the photosensitive drum and the scattering, which is a serious problem. Further, in the case where a color developing device is arranged downstream as in the present configuration, scattered toner is mixed into them and the image quality is impaired not only in a monochrome image but also in a full color image.

Further, since the toner is wasted, the running cost is lowered, which hinders the provision of inexpensive products.

Therefore, the present invention solves the above-mentioned problems, and provides a developing method and an electrophotographic image forming apparatus capable of suppressing toner scattering, improving toner consumption efficiency, and providing a good image. It is provided.

[0032]

An image carrier on which an electrostatic latent image is formed, exposure means for exposing the image carrier to form a latent image, and for developing the latent image with a developer. In addition, a fixed developer carrier positioned with respect to the image carrier, a rotary developer carrier rotatably supporting at least two developing means, and an electric field applied to the developer carrier member are varied. In an image forming apparatus having a bias power supply device capable of performing the image formation, the amplitude component Vpb of the AC voltage bias applied to the fixed developer holding member during non-image formation during image formation by the fixed developer support is V during image formation.
It is preferable that Vpb> Vpa with respect to pa.

It is preferable that the fixed developer carrying member is arranged between the rotating developer carrying member and the exposing means.

The fixed developer carrier is in non-contact with the image carrier and has a magnet inside, and the layer thickness of the developer layer on the developer carrier is the same as that of the developer carrier in the developing section. It is preferable that the bias power source output a developing bias in which the AC voltage is superimposed on the DC voltage, which is smaller than the distance from the image carrier.

The member for regulating the layer pressure of the developer layer on the fixed developer carrier is preferably a magnetic body.

It is preferable that the fixed developer carrying member develops using a one-component developer containing a magnetic material.

It is preferable that the bias voltage is applied to the fixed developer carrying member during non-image formation after the developing process is completed.

It is preferable that the bias voltage application to the fixed developer bearing member during non-image formation is a post-rotation step.

It is preferable that the bias voltage applied to the fixed developer carrying member during non-image formation is between transfer materials when images are continuously formed on a plurality of transfer materials.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) In the present embodiment 1, the structure of the main body and Bk developing device 401 is the same as the conventional example (FIG. 1).

Next, the conventional image forming sequence for Bk single color will be described (FIG. 5).

With the start of image formation, the developing bias DC component first reaches a predetermined potential, then the sleeve drive and developing AC bias rise, and the image leading edge position is set at the time of one revolution of the sleeve drive.

This state is maintained during continuous image formation, and after the necessary image formation is completed, the developing AC bias is first turned off.
Then, the sleeve drive and the development DC bias are applied in this order.
F is going.

In this case, the developing AC bias is continuously applied from the start to the end of image formation. However, this is originally intended to cause the toner to fly onto the photosensitive drum, and is not required in the space between the sheets where the image is not formed.

Therefore, in this embodiment, as shown in FIG. 6, it is proposed to intermittently turn off the developing AC bias between the sheets. As a result, unnecessary reciprocal movement of the toner is reduced, thereby suppressing the scattering and deterioration of the toner.

Experimental results showing the effect will be described below.

1. First, the developer existing in the M, C, Y developing units 402, 403, 404 in the rotary developing device is removed, and B
Only k development is performed.

2. Subsequently, a Bk developing device is used to continuously form a monochrome image (10% density for the entire A4 image area).

This is performed for 20000 sheets, and M,
Scattering is quantified by collecting scattered Bk toner (magnetic material) adhered to the magnetic sleeves of the C, Y developing devices 402, 403, and 404 due to the magnetic binding force, and this is quantified by the durability test 50 times (500,000 sheets). It was done (Fig. 7). At the same time, a solid image sample by Bk development was sampled and the density transition was observed (FIG. 8).

From the above, by intermittently turning the developing AC bias between the sheets OFF and ON, it is possible to suppress scattering, stabilize image quality, and improve durability.

(Second Embodiment) In the previous embodiment, the object of the present invention is achieved as described above. However, 5
In the endurance test of 0,000 sheets, an image defect at the leading end of the image has occurred, and the cause will be described below.

FIG. 9 shows the waveform transition of the developing AC bias in the previous embodiment. Based on the sequence, the AC bias is OFF between the sheets, but when it is turned ON again, it is unstable at the leading edge of the image, and the amplitude component 1500 Vpp originally required for development has not reached. This is because the configured high voltage substrate for bias application is delayed in the response of the sequence. In order to solve this, it is necessary to improve the responsiveness of the high-voltage board, which requires a considerable cost increase from the present situation.

In order to solve the above, the developing AC bias amplitude component is set to Vpa: 1500 Vpp during image formation,
It is suggested to set Vpb: 300Vpp between sheets.

The waveform of the AC bias waveform changes from Vpa to Vp.
b, Vpb → Vpa are both stable. This is because when the amplitude component is variable in the AC bias, its responsiveness is higher than when OFF-ON (FIG. 10).

As a result, in the durability test, Vpb: 300
Both the scattering and the density at Vpp were at the same level as in the OFF-ON state, and no image defect occurred at the image front end portion (FIGS. 11 and 12).

(Embodiment 3) In this embodiment, it is proposed to change the frequency component in addition to the variable amplitude component in order to further suppress the scattering.

As compared with the previous embodiment, regarding the developing AC bias during the paper interval, at the time of image formation: 2.7 kHz, 1500 V
pp, non-image part: set to 3.3 kHZ, 300 Vpp, and the amount of scattering was quantified (FIG. 13).

From this, it was confirmed that the same effect as the development AC bias OFF was obtained.

[0059]

As described above, according to the present invention, in an image processing apparatus for forming a multicolor image using a fixed developing device and a rotary developing device, toner scattering is suppressed and toner consumption efficiency is improved. Therefore, it is possible to provide a good image.

[Brief description of drawings]

FIG. 1 is a schematic view of the outside of a main body of an image forming apparatus used in the present invention.

FIG. 2 is a schematic sectional view of an amorphous silicon photoconductor used in the present invention.

FIG. 3 is a schematic view of a developing device in the fixed developing device used in the present invention.

FIG. 4 shows a developing bias configuration during image formation in a fixed developing device.

FIG. 5 is a development sequence diagram in a conventional setting.

FIG. 6 is a development sequence diagram in the first embodiment.

FIG. 7 is a measurement result of the amount of Bk toner scattering in the first embodiment.

FIG. 8 is a Bk solid density durability test result in the first embodiment.

FIG. 9 is a waveform transition of the developing AC bias in the first embodiment.

FIG. 10 is a waveform transition of a developing AC bias in the second embodiment.

11 is a measurement result of Bk toner scattering amount in Embodiment 2. FIG.

FIG. 12 is a Bk solid density durability test result in the second embodiment.

13 is a measurement result of Bk toner scattering amount in Embodiment 3. FIG.

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Claims (9)

[Claims] 1. An image bearing member on which an electrostatic latent image is formed, and an exposing unit for exposing the image bearing member to form a latent image,
A first fixed developer carrier positioned with respect to the image carrier for developing the latent image with a developer;
An image forming apparatus having a second rotary developer carrying member rotatably supporting at least two developing means and a bias power supply device capable of varying an electric field applied to the developer carrying member. When an image is formed by, the amplitude component Vpb of the AC voltage bias applied to the fixed developer carrying member during non-image formation is Vp with respect to Vpa during image formation.
An image forming apparatus characterized in that b <Vpa. 2. The image forming apparatus according to claim 1, wherein the fixed developer carrying member is arranged between the rotating developer carrying member and the exposing means. 3. The fixed developer bearing member is not in contact with the image bearing member and has a magnet inside, and the layer thickness of the developer layer on the developer bearing member is equal to 3. The image forming apparatus according to claim 1, wherein the bias power source is smaller than the distance between the body and the image carrier, and the bias power source outputs a developing bias in which an AC voltage is superimposed on a DC voltage. 4. The image forming apparatus according to claim 1, wherein the member for regulating the layer pressure of the developer layer on the fixed developer carrier is a magnetic body. 5. The image forming apparatus according to claim 1, wherein the fixed developer carrying member develops using a one-component developer containing a magnetic material. 6. The developing process by the developer carrying member is a normal development for latent image formation.
5. The image forming apparatus according to item 5. 7. The image forming apparatus according to claim 1, wherein the bias voltage applied to the fixed developer bearing member during non-image formation is after the development process is completed. 8. The image forming apparatus according to claim 1, wherein the bias voltage application to the fixed developer bearing member during non-image formation is a post-rotation step. 9. The method according to claim 1, wherein the bias voltage applied to the fixed developer carrying member during non-image formation is continuously applied to a plurality of transfer materials between transfer materials during image formation. The image forming apparatus described.