JP2565481B2 - Image forming device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to operation control of a pre-charge exposure device of an image forming apparatus capable of selectively forming both a multicolor image and a single color image.

(Background of the Invention) Conventionally, in this type of image forming apparatus such as a printer or a PPC copying machine, a highly sensitive selenium-tellurium-based or selenium-arsenic-based photoreceptor or an image forming body is used as an image forming body in order to reduce the size and increase the speed. An organic photoconductor or the like is used. However, since this type of photoconductor has light fatigue characteristics, the latent image formation, development, and transfer by the first image exposure are completed and cleaned, and uniform charging is performed for the second latent image formation. Also, the latent image of the first time remains as light fatigue (so-called optical memory). Due to this, especially when the demand method is used to shorten the image forming time in single-color image formation, the next transfer paper There was a problem of appearing as a ghost image.

As a means for solving this problem, the so-called masking of light fatigue due to the previous image exposure is performed by uniformly exposing the image forming body to uniform exposure before uniformly charging it. A means called pre-charge exposure is used.

FIG. 7 is a diagram for explaining changes in the surface potential of the image forming body. FIG. 6A shows the case where pre-charging exposure is not performed, and a is the potential due to image exposure, and the light fatigue due to this image exposure is 2
It is shown that the potential B remains after the uniform charge of the third rotation and remains as the potential C after the uniform charge of the third rotation. When the demand method is adopted in the single color mode, the position where the latent image is formed changes during continuous copying, so that potential B and potential C cause a ghost image.

FIG. 6B shows that the potentials B and C disappear when the pre-charge exposure is performed.

In the case of the multicolor mode, the toner remains attached until the toner image of the final color is formed on the image forming body in the case of the multicolor mode, so that the potential is smoothed as compared with the case where the toner is not attached. It indicates that

The hatched lines indicate that the potential has risen due to toner adhesion.

(Problems to be Solved by the Invention) However, the means of pre-charging exposure is well effective for monochromatic image formation and can prevent the generation of ghost images. in case of,
When the formation of the toner image of the first color is completed and the formation of the latent image of the second color is about to be started, the pre-charge exposure is performed from above the toner image of the first color. Then, since there is a difference in the amount of exposure between the portion on the surface of the image forming body where the toner is attached and the portion where the toner is not attached, there is a difference in the amount of static elimination and a potential difference. As a result, the charged toner is
The toner is scattered under the influence of the electric field generated by the potential difference.

Therefore, the means of pre-charging exposure cannot be used in the case of multi-color image formation in which toner images of respective colors are formed on the image forming body and then transferred to the transfer material at one time.

However, in the case of forming a multi-color image, unlike the case of forming a single-color image, the toner image is not transferred for each color and the toner remains attached. Due to the smoothing of the potential by the scorotron, the potential on the surface of the image forming body is relatively smoothed as shown in FIG. 7 (c). For this reason, the multicolor image forming apparatus is generally not provided with pre-charging exposure means.

However, a multicolor image forming apparatus usually has a monochromatic image forming function, and in the case of monochromatic image forming, a demand method is often adopted in order to reduce the time of continuous copying. .

Therefore, there is a problem that the above-mentioned ghost image is likely to occur. Of course, regardless of the demand method, there is a problem that a ghost image is generated even when a document or the like is changed and a different image is formed in a short time after the image formation is completed.

The object of the present invention is to solve these problems,
The multi-color image forming apparatus is also provided with pre-charging exposure means, and in the case of mono-color image formation (mono-color mode), the pre-charging exposure means is always operated before image exposure to form multi-color image formation (multi-color mode). In the case of, the pre-charging exposure unit is operated only before the formation of the latent image of the first color on which the toner image is not yet formed on the image forming body, so that the toner scattering in the multicolor mode does not occur, An object of the present invention is to provide an image forming apparatus capable of preventing the generation of a ghost image in the single color mode and the multicolor mode.

(Means for Solving the Problem) The present invention has the following means configuration in order to achieve the above object. That is, the image forming apparatus of the present invention has a series of steps of uniform charging, image exposure and development on the image forming body, and repeating these steps to superimpose a plurality of color toner images to form a multicolor image on the surface of the image forming body. When a multi-color image is formed by forming a toner image and transferring it to a transfer material (multi-color mode), one color is developed on the surface of the image forming body for one image exposure after uniform charging. Image formation capable of selecting a case where a single color image is formed by forming a toner image of one color or by forming two toner images of two colors by development of two colors and transferring the toner images onto a transfer material (single color mode) In the apparatus; pre-charging exposure means for uniformly exposing the image forming body before uniformly charging; and in the monochromatic mode, at least the image forming area on the image formation is continuously pre-charging exposure before charging / image exposing. And when in multicolor mode Control for performing pre-charging exposure on at least the image forming area on the image forming body prior to charging / exposure of the color and not performing pre-charging exposure on at least the image forming area in the second and subsequent steps. And an image forming apparatus.

(Operation) Although the image forming apparatus of the present invention has the pre-charging exposure means as is apparent from the above-mentioned means configuration, it is not always operated, but the single color mode is controlled by the control means. Occasionally, at least the latent image (image) forming area on the image forming body is continuously subjected to pre-charge exposure every time prior to charging / image exposure, but in the multicolor mode, charging / charging for the first color is performed.
Prior to the image exposure, at least the latent image (image) forming area on the image forming body is subjected to the pre-charge exposure, and in the steps of the second and subsequent colors, at least the latent image (image) forming area is not subjected to the pre-charge exposure. .

Therefore, it is possible to remove a ghost image that is likely to occur when continuously forming different images, and particularly when the demand method is adopted in the single color mode, but there is no problem of toner scattering in the multicolor mode. In addition, in the single color mode,
In addition to the case of developing with one type of toner, the same latent image is
There is a case where a toner image of two kinds of colors is superposed and overlapped to obtain a monochromatic image by color mixture, but in this case as well, as in the case of only one kind of toner, the pre-charging exposure is performed before the charging / image exposure every time. Done.

(Examples) Examples of the image forming apparatus of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing main components of an embodiment of an image forming apparatus of the present invention.

The image forming body 1 is uniformly charged by the charger 3 while rotating in the direction of the arrow, and then subjected to image exposure by the image exposing device 4 to form a latent image. In the multicolor mode, this latent image formation is performed for each color-separated color component, for example, for each color image signal of blue, green, red, and black, and the latent image is formed by the color image signal of the first color. Then, the toner image is formed on the image forming body by the developing device that contains the toner of the color corresponding to the first color, and after one rotation, the toner image is uniformly charged by the charging device 3 again. The latent image is formed on the toner image by the color image signal of the second color, and the process of repeatedly forming the toner images by the developing device containing the toner of the corresponding color is repeated on the image forming body 1. A multicolor toner image is formed, and this is transferred once to a transfer material to form a multicolor image. In the single color mode, the latent image is formed once and developed with toner of a desired color and then transferred to a transfer material to be fixed, and the same latent image is developed twice with toner of different colors and a toner image of two colors is formed. There is a case in which an image of one intermediate color is formed by overlapping and forming and transferring and melting and mixing at the time of fixing.

As the pre-charging exposure means 2 in the present invention, a fluorescent discharge lamp such as a cold cathode tube or a neon tube, a tungsten lamp, or an LED is used, and the charger 3 is used with the rotational direction of the image forming body 1 as a reference.
Is provided on the upstream side of.

In this embodiment, a cold cathode tube that emits green light was used. The pre-charging exposure means 2 is controlled by the control means 5 so that the exposure is always performed before the image exposure in the single-color mode, and the exposure is performed only before the latent image formation of the first color is started in the multi-color mode. To be done.

FIG. 2 is a diagram showing a specific configuration example of the pre-charging exposure means 2 and the control means 5, taking a fluorescent discharge lamp as an example of the pre-charging exposure means.

The control means 5 comprises a CPU 10, an inverter 11 and a relay 12, and when a mode selection signal is input to the CPU 10, C
The PU 10 outputs a control signal that is predetermined for each mode. The inverter 11 converts this control signal into a drive signal for driving the relay 12 and applies the drive signal to the relay 12.

The relay 12 turns on / off the current supplied from the fluorescent discharge lamp power supply 13 to the fluorescent discharge lamp 15 which is an exposure light source. The pre-charging exposure means 2 comprises a fluorescent discharge lamp power source 13, a fluorescent discharge lamp ballast 14 and a fluorescent discharge lamp 15. Then, turn on relay 12
When it is turned off, power is supplied to the fluorescent discharge lamp 15 from the fluorescent discharge lamp power supply 13 via the fluorescent discharge lamp ballast 14 or is cut off.

In this way, the relationship between the pre-charging exposure whose blinking is controlled and the steps of uniform charging, image exposure, development, transfer and cleaning is shown in chronological order as shown in FIGS. 3 to 5. become that way.

Both cases show the case of continuous copying twice. FIG. 3 shows the case of the multicolor mode, and FIG. 4 shows one of the single color modes.
FIG. 5 shows a case of developing with only toners of different colors, and FIG. 5 shows a case of developing a single latent image in a single color mode twice with toners of different colors to obtain a single color by mixing two colors. In the monochrome mode of FIG. 5, an example is shown in which the pre-charging exposure means is turned on only in the image forming area (area with a slight margin in the image forming area), but similar to FIG. 4, continuous copying is performed. In this case, the pre-charging pre-exposure means can be always turned on.

FIG. 6 is a diagram showing the surface potential of the image forming body when the same latent image is developed twice with toners of different colors.

FIG. 6 (a) shows a state in which the potential of the portion exposed by image exposure is lowered and a latent image is formed.

FIG. 6B shows a state in which the potential is increased by being developed with the first color toner. The shaded area shows the amount of potential increase due to toner adhesion.

FIG. 6C shows that the toner of the second color is attached and the potential is further increased by the amount of the reverse diagonal line.

The pre-charge exposure in FIG. 3 is turned on only when it corresponds to the image exposure of the first color, and in FIG. 4, the pre-charge exposure is turned on while image formation continues, and
The figure also shows that pre-charge exposure is always performed prior to each image exposure. Note that it is common to pre-rotate (pre-rotate) the image forming body before the image formation actually starts after the copy button is pressed.
Prior to the charging / image exposure for the first image formation, the pre-charging exposure for uniformly exposing at least the image forming area is performed during the preliminary rotation, or the charging for the first image formation during the preliminary rotation. -Of course, the present invention also includes the case where the process is continuously performed before the image exposure.

(Effects of the Invention) As described above, the image forming apparatus of the present invention causes the pre-charge exposure unit to always perform the pre-charge exposure prior to the image exposure in the single color mode, and the first color in the multi-color mode. Since a control means for controlling pre-charge exposure only before latent image formation is provided, ghost images are prevented from occurring in both the single-color mode and the multi-color mode without causing toner scattering in the multi-color mode. There is an advantage that you can.

[Brief description of drawings]

FIG. 1 is a diagram showing main components of an embodiment of the present invention, FIG. 2 is a diagram showing a concrete configuration of pre-charging exposure means and control means of the embodiment of FIG. 1, and FIG. 3 is FIG. 4 is an explanatory view of each step operation of multi-color mode two-time continuous copying in FIG. 4, FIG. 4 is an explanatory view of each step operation of single-color mode two-time continuous copying with only one kind of toner, and FIG. 5 is two kinds of toner FIG. 6 is an explanatory view of the operation of each step of continuous copying twice in a single color mode by mixing the above, FIG. 6 is an explanatory view of the surface potential of the image forming body in the two color developing single color mode, and FIG. 7 is an explanatory view of the surface potential of the image forming body. 1 ... Image forming member, 2 ... Pre-charging exposure means, 3 ... Charging device, 4 ... Image exposure device, 5 ... Control means, 6,7,8,9 ...
Developing device, 10 ... CPU, 11 ... Inverter, 12 ... Relay, 13 ... Fluorescent discharge lamp power supply, 14 ... Fluorescent discharge lamp ballast,
15 ... Fluorescent discharge lamp.

Claims (1)

(57) [Claims] 1. A multi-color toner image is formed on the surface of an image forming body by repeating a series of steps of uniform charging, image exposure and development of the image forming body, and repeating these steps. When a multicolor image is formed by transferring this to a transfer material (multicolor mode), one color toner image is obtained by developing one color on the surface of the image forming body for one image exposure after uniform charging. In the image forming apparatus capable of selecting a case (a single color mode) in which a toner image of two colors is formed by superimposing or forming two color toner images and transferring the toner images to a transfer material; Pre-charging exposure means for uniformly exposing the body before uniform charging; in the monochromatic mode, at least the image forming area on the image-forming body is continuously subjected to pre-charging exposure prior to charging / image exposure. Charging / image of the first color in color mode Control means for performing pre-charging exposure to at least the image forming area on the image forming body prior to light and controlling not to pre-charging exposure to at least the image forming area in the second and subsequent steps. An image forming apparatus characterized by the above.