JPH0470874A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To eliminate deviation of a toner image and developer and to prevent disturbance of the toner image by making circumferencial speed of a developing roll and circumferencial speed of a photosensitive body in a second image recording part onward to be approximately the same. CONSTITUTION:First, the photosensitive body 1 is electrified by a first electrifying device 3a, exposed by light modulated by a signal corresponding to black of the image at an exposure device 3b, and reversal developing is carried out by a black tone TK within the developer at the developing device 3c. Next, the black developed part is electrified again by the electrifying device 4a, exposed by the light modulated by a signal corresponding to red of the image at an exposure device 4b, and developed by red toner. At this time, the two component developer D is brought into contact with the already formed black toner, and since the rotating speed of a developing roll 4d is controlled to the same circumferencial speed as the speed of movement of the photosensitive body 1, there is no deviation of the black toner image and the developer D in the direction of the movement of the photosensitive body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multicolor image forming apparatus that forms a multicolor image with one rotation of a photoreceptor.

[Conventional technology]

There are various types of multicolor image forming devices using electrophotographic technology, one of which is to form a toner image for each color on a photoreceptor, and then sequentially superimpose each color toner image on recording paper. Some images are transferred to form multicolor images. In this case, a charger, an exposure section, a plurality of developing machines corresponding to each color, a transfer section, and a cleaning device are arranged around the drum-shaped photoconductor, and each rotation of the photoconductor performs charging, exposure, and development. .

Repeat the process of transferring and cleaning. As a result, each color toner image is sequentially transferred onto the recording paper in an overlapping manner each time the photoreceptor rotates, forming a multicolor image.

[Problem to be solved by the invention]

However, in the above-mentioned conventional multicolor image forming apparatus, since the photoreceptor must be rotated by the number of required colors, there is a problem that it takes a long time to obtain the final multicolor image. Further, since developing machines for each color must be arranged around the drum-shaped photoreceptor, when the number of developing machines increases, the diameter of the photoreceptor must be increased, resulting in an increase in the size of the apparatus.

Also known is a multicolor image forming apparatus using a one-time transfer method in which toner images of each color are stacked on a drum-shaped photoreceptor and a multicolor image is formed on recording paper in one transfer. in this case,
The transfer drum and accompanying charger can be omitted, and the apparatus can be simplified. However, until the final color is formed, transfer to recording paper cannot be performed, which is disadvantageous for high-speed operation. Furthermore, the cleaning member that comes into contact with the photoreceptor must be mechanically retracted, making the apparatus complicated.

In addition, when developing in the second and subsequent developing machines, the unfixed toner images formed on the photoreceptor by the preceding developing machines are also developed, so the toner images formed after this are also processed. It is necessary to adopt a developing method that does not cause disturbance to the image. Such developing methods include the soft-touch developing method and the DC electric field flying type, as disclosed in "Basics and Applications of Electrophotographic Technology", Electrophotographic Technology Edition, Corona Publishing, June 15, 1988, p.564. Although non-contact development methods are being considered, they have not yet reached a sufficient technical level. For example, there are problems with the stability of thin layer formation. - As an example, the use of an elastic blade has been proposed as a technique for forming a thin layer, but it is still not at a sufficient level from the viewpoint of durability.

Further, the method of applying an alternating current bias is not preferable because it affects the adhesion force of toner and causes image disturbance.

The present invention was devised to solve the above-mentioned problems, and an object of the present invention is to stably develop each color.

[Means to solve the problem]

The multicolor image forming apparatus of the present invention includes, along the surface of the photoreceptor,
A plurality of image recording sections each having a charger, an exposure device, and a developing device and forming images of mutually different colors on the photoreceptor are sequentially arranged, and the circumferential speed of the developing roller in at least the second and subsequent image recording sections is arranged in sequence. and the circumferential speed of the photoreceptor is approximately 1.

As the developing device, one using a two-component developer consisting of toner and carrier can be used. In this case, at least the developer in the two-component developer immediately before the development area in the second and subsequent image recording sections can be used. It is desirable to provide an excitation electrode that attracts said toner toward the surface.

Furthermore, it is preferable that the excitation electrode be attached to an elastic member in order to enhance the electrode effect and ensure sealing performance.

[Effect]

In the present invention, when development is performed in the second and subsequent image recording sections, the developer of the developing roller is applied to the previously formed toner image on the photoreceptor at the same speed as the circumferential speed of the photoreceptor. Contact. Therefore, no misalignment occurs between the toner image and the developer, and disturbance of the toner image is prevented.

Further, when the developer passes through the excitation electrode position and reaches the development area, the toner in the developer is collected toward the surface by the excitation electrode, apparently increasing the toner concentration on the top.

Furthermore, since the excitation electrode is pressed against the developer by the elastic member, it comes into close contact with the developer, improving the electrode effect. Further, since the elastic member functions as a member for the developer, sealing performance is ensured.

〔Example〕

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, features of the present invention will be specifically described based on examples with reference to the drawings.

FIG. 1 is a diagram showing the basic configuration of an embodiment of a multicolor image forming apparatus according to the present invention.

A belt-shaped photoreceptor 1 is arranged horizontally around a drive roller 2a and an idler roller 2b2C. Photoreceptor 1 is rotationally driven in the direction of arrow P by drive roller 2a.

Around this photoreceptor 1, there are first to fourth image recording sections 3 to 6.
, a transfer section 7, a cleaning device 8, and the like are arranged.

The first to fourth image recording units 3 to 6 are the first to fourth image recording units 3 to 6, respectively.
Fourth charger 33-5a, first to fourth exposure devices 3b-6b
, first to fourth developing machines 3C to 60, etc.

Developing rollers 3d to 6d provided in each of the first to fourth developing machines 3C to 6C form respective color images on the photoreceptor 1 using black, red, edge, and blue color toners.

Each of the developing machines 3C to 6C employs a magnetic brush development method using an insulating two-component developer consisting of toner and a magnetic carrier.
The developing machines 4C to 6C operate differently. That is, in the first developing device 3C, in order to supply a sufficient amount of toner, as in the conventional case, the developing roller is moved at a circumferential speed that is 2 to 3 times the moving speed of the photoreceptor 1. The rotation of 3d is controlled, but in the second to fourth developing machines 4C to 6C,
The developing rollers 4d to 4d are arranged so that the peripheral speed is the same as the moving speed of the photoreceptor 1, that is, the peripheral speed ratio is 1.
The rotation of 6d is controlled. In addition, the second to fourth developing machines 4C to
6C is provided with an excitation electrode to improve development efficiency, as described below. In this example, the magnetic brush development method using a two-component developer is employed because it has excellent color reproducibility.

Since the second to fourth developing machines 4C to 6C have the same configuration, the second to fourth developing machines 4C to 6C will be commonly explained with reference to FIG. 2, taking the second developing machine 4C as an example.

The developing roller 4d of the second developing device 4C is composed of a fixed magnet roller 11 and a non-magnetic sleeve 12 that rotates around the magnet roller 11. The light body 1 is placed close to the light body 1 at a distance of about l+r++++.

The sleeve 12 is supplied with, for example, 3
A bias voltage of 00v is applied. Further, a trimmer 14 is provided close to the surface of the sleeve 12.

Further, an excitation electrode 15 is provided in a region where the developing roller 4d and the photoreceptor 1 are close to each other, that is, on the upstream side of the developing region Q. This excitation electrode 15 is attached to the tip of an insulating film-like body 16 made of an elastic member such as urethane, whose base end is fixed to the trimmer 14, and the elasticity of the film-like body 160 causes the developing roller to 4d
slightly biased in the direction. Further, a bias voltage of, for example, about 0 to +500V is applied to the excitation electrode 15 from a bias power supply 17.

Next, the operation of the multicolor image forming apparatus described above will be explained.

The photoreceptor 1, which is rotationally driven in the direction of arrow P by the drive roller 2a, is first uniformly charged by the first charger 3a in the first image recording section 3, as shown in FIG. 3(a). As a result, the surface potential of the photoreceptor 1 is, for example, Vp
(However, v is a negative value).

Next, in the first M optical device 3b, the surface of the photoreceptor 1 is exposed to light modulated by a signal corresponding to the black of the image, and the potential of the exposed portion is changed to, for example, ■, (however, ■, (see figure (b)). Next, this exposed portion advances to the first developing device 3C, where it is reversely developed by the black toner T1 in the developer (see Fig.
See C). The development in the first developing device 3c is normal magnetic brush development, and is
The rotation of the developing roller 3d is controlled so that the peripheral surface speed is ~3 times as high. Even after this development, the surface potential of the imaged area remains reduced.

Next, the black developed portion advances to the second image recording section 4 and the second
The photoreceptor 1 is charged again by the charger 4a, and the surface potential of the photoreceptor 1 rises to near vP (see (c) in the same figure). Next, in the second N optical device 4b, the surface of the photoreceptor 1 is exposed to light Lm modulated by a signal corresponding to the red color of the image, and the potential of the exposed portion is reduced to vIl (see (e) in the same figure).
reference). Next, this exposed portion advances to the second developing device 4C, where it is reversely developed by the red toner Ta in the developer (see (f) in the same figure).

Even after this red development, the surface potential of the red image area remains reduced.

The developing process in the second developing machine 4C will be described in detail with reference to FIG. 2.

In the second developing device 4C, a two-component developer consisting of toner and magnetic carrier is magnetically attracted to the surface of the sleeve 12 by a fixed magnet roller 11. Since the sleeve 12 is rotating in the direction of arrow R, the two-component developer moves in the direction of arrow R as the sleeve 120 rotates, and is adjusted to a predetermined thickness by the trimmer 14. The two-component developer after the thickness adjustment passes between the surface of the sleeve 12 and the excitation electrode 15. The excitation electrode 15 is connected to the sleeve 12
Although the excitation electrode 15 is biased with a weak force in the direction, due to the presence of the two-component developer layer, the excitation electrode 15 is lifted from the sleeve 12 by the thickness of the two-component developer layer.

In the two-component developer before passing the excitation electrode 15 position,
As shown in FIG. 4(a), carrier C and red toner T8
are mixed approximately evenly. When this two-component developer passes through the excitation electrode 15 position, the excitation electrode 15 has a voltage (0
~+500 V) is being applied, so the negatively charged red toner T is attracted by electrostatic force in the direction of the excitation electrode 15, and is drawn toward the surface of the two-component developer as shown in Figure 4, et al. get together. That is, the upper toner density apparently increases. When the sleeve 12 further rotates, the two-component developer reaches the development area Q and comes into contact with the surface of the photoreceptor 1. The photoreceptor 1 has a surface potential of, for example, about 800 V in the background area and about 100 V in the image area, and the developing bias is set at a potential between them (300 V).
＞, red toner T1 with negative charge
1 is attracted to the photoreceptor 1 by electrostatic force, and the electrostatic latent image on the photoreceptor 1 is developed by the red toner Tm.

At this time, the two-component developer comes into contact with the black toner T9 previously formed by the first developing device 3C, but the two-component developer is kept at the same circumferential speed as the moving speed of the photoreceptor 1.
That is, since the rotational speed of the developing roller 4d is controlled so that the peripheral speed ratio is 1, the black toner T on the photoreceptor 1
There is no misalignment between the image formed by the image and the two-component developer on the developing roller 4d in the moving direction of the photoreceptor 1. Therefore, the black toner T is not scraped off by the two-component developer, and the image formed by the black toner T is not disturbed.

During development in the second developing machine 4C, the number of revolutions of the developing roller 4d is 172 to 1/3 that of a normal developing machine, so the supply amount of the two-component developer itself decreases; As mentioned above, since the red toner T is collected on the surface side of the two-component developer, development is performed with sufficient toner concentration.

Further, the excitation electrode 15 is connected to a film-like body 1 which is an elastic member.
6, the excitation electrode 15 and the developer come into close contact with each other, improving the electrode effect. Furthermore, since the film-like body 16 functions as a sealing material for the toner, sealing performance is ensured and the generation of toner cloud is prevented.

After the development in the second developing device 4C, the photoreceptor l advances further, and the third. Although the toner image passes through the fourth image recording sections 5 and 6, since these image recording sections 5 and 6 are inactive, the toner images of each color are not affected.

When the toner images of each color advance to the transfer section 7, recording paper 9 is fed in synchronization with this, and the toner images of each color are transferred to the photoreceptor 1.
The image is transferred from the 0 surface to the recording paper 9.

After the transfer, the recording paper 9 is peeled off from the photoreceptor I and conveyed to a fixing device (not shown), where the toner image is fixed on the recording paper 9.

As described above, since one sheet of multicolor image recording paper is output by one rotation of the photoreceptor, a multicolor image can be obtained in a short time.

In the above embodiment, only two colors, red and black, have been described, but an image may be formed using any combination of four colors, black, red, green, and blue, or using a single color.

Further, the colors are not limited to the above four colors, but can be black, yellow, magenta, or system, and in this case, full color reproduction is possible.

Further, the number of image recording units is not limited to four, and the present invention can be applied to any number of image recording units that is two or more.

Further, in this embodiment, the format of the first developing device F83c and the format of the second to fourth developing devices 40 to 6C are different, but the structure of the first developing device 3C is changed to the structure shown in FIG. Second
It is also possible to match the structure of the fourth developing machines 40 to 6C.

Although it is desirable that the circumferential speed ratio between the photoreceptor and the developing roller be exactly 1, a circumferential speed ratio of 0.8 to 1.2 is actually acceptable. Note that the means for setting the circumferential speed ratio to 1 is not particularly limited, but for example, if the photoreceptor and each developing roller are driven by independent motors, the number of revolutions of each motor may be set to 1. The motor drive circuit may be set so that the circumferential speed ratio is 1. Furthermore, if each developing roller is driven by a common motor, it is only necessary to control this common motor. Further, if the photoreceptor and each developing roller are driven by a common motor, the gear ratio, boolean ratio, etc. of the power transmission system may be set.

〔Effect of the invention〕

As described above, according to the present invention, in the image recording section, the circumferential speed of the developing roller is made to match the moving speed of the photoreceptor, so that the toner image developed first is developed in the subsequent image recording section. There will be no sliding contact with the agent. This results in
The previously developed toner image is not disturbed and a high quality multicolor image can be obtained.

Furthermore, since the toner in the developer is collected on the surface prior to development, the development efficiency is improved, and even when the amount of developer itself supplied is small, it is possible to perform development with a sufficient toner concentration.

Further, since the excitation electrode is pressed against the developer by the elastic member and comes into close contact with the developer, the electrode effect is improved.

Further, since the elastic member functions as a sealing material for the developer, sealing performance is ensured and the generation of toner cloud is prevented.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram showing an embodiment of the multicolor image forming apparatus of the present invention, FIG. 2 is an enlarged view of main parts of a developing machine, and FIG. 3 is an explanatory diagram showing the process of forming a multicolor image. Figure 4(a), (
b) is an explanatory diagram showing the state of the two-component developer before and after the excitation electrode. 1: Belt-shaped photoreceptor 2b, 2C: Idler roller 3a-6a: Charger 30-6C: Developing device 7: Transfer section 9: Recording paper 12 sleeve 14: Trimmer 16: Film-like body 2a: Drive roller 3-6: Image recording sections 3b to 6b = Exposure devices 3d to 6d: Developing roller 8: Cleaning device 11: Magnet roller 13: Bias power source 15: Excitation electrode 17: Bias power source C: Carrier T*+TIl:)ner D two-component developer Q :Development area Figure 2

Claims (1)

[Scope of Claims] 1. A plurality of image recording units each having a charger, an exposure device, and a developing device and forming images of different colors on the photoconductor are sequentially arranged along the surface of the photoconductor. With,
A multicolor image forming apparatus, characterized in that the ratio of the circumferential speed of the developing roller and the circumferential speed of the photoreceptor in at least the second and subsequent image recording sections is approximately 1. 2. The developing machine uses a two-component developer consisting of toner and carrier, and the toner in the two-component developer is transferred in the surface direction immediately before the development area in at least the second and subsequent image recording sections. 2. The multicolor image forming apparatus according to claim 1, further comprising an excitation electrode that attracts the image. 3. The multicolor image forming apparatus according to claim 2, wherein the excitation electrode is attached to an elastic member.