JPH02125274A - Image adjusting method - Google Patents

Abstract

PURPOSE:To maintain a stable image with little environmental variation for all images over a long period of time by varying a replenishing quantity of developer based on a detecting signal of a first standard image, and compensating the developing electric field of an image part of an image carrier based on a detecting signal of a second standard image. CONSTITUTION:The first standard image and the second standard image area at least formed on the image carrier 1 by an electrophotographic process, the replenishing quantity of the developer is varied based on a detecting signal of the first standard image by an optical sensor 10, and at the same time, the developing electric field of the image part of the image carrier 1 is compensated based on the detecting signal of the second standard image. Furthermore, an image pattern which becomes a contact image after visualizing is used for the first standard image, and a dot or a line image is used for the second standard image. Thus, even when there is change in the surface potential of the image carrier by environmental variation or deterioration by aging, any of the contact, line, or not images can be obtained stably over a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image adjustment method in an image forming apparatus using electrophotography.

[Conventional technology]

In an image forming apparatus using an electrophotographic method, it is necessary to control the toner density of a developer in order to keep the image density constant at all times, and various control methods have been proposed and put into practical use. One such method is to form a reference image for toner density control on an image carrier, detect its optical density, and control the toner density.

[Problem to be solved by the invention]

This method is an excellent method in that it always keeps the image density constant, but it is also effective when environmental changes in the surface potential of the image area of the image carrier or changes over time due to deterioration of the image carrier occur. Therefore, the toner density may drop significantly or, conversely, may rise excessively.

If the toner concentration falls below the appropriate range, carrier deterioration will be accelerated; if it exceeds the appropriate range, the toner's charging ability will decrease, causing toner to adhere to the background, impairing image quality, and increasing the likelihood of toner scattering, resulting in contamination within the device. invite. Also, although it is possible to maintain the image density of so-called solid areas constant on an image, it is difficult to control images that are composed of lines or dots.

In other words, with the conventional method described above, it is possible to control changes in image density caused by toner density, but it is practically difficult to control changes in image density caused by potential fluctuations in the image area, and rather causes side effects. big. It is also possible to control the image area potential by directly detecting the surface potential of the image carrier with an electrometer, but this is disadvantageous in terms of cost and space, and it is not reliable considering the environment. is the actual situation.

The present invention has been made based on this background, and its purpose is to provide an image adjustment method that can maintain stable images for a long period of time with little environmental fluctuation for all images. is to provide.

[Means to solve the problem]

In order to achieve this object, the present invention forms a first reference image and a second reference image on an image carrier by an electrophotographic process, and detects a detection signal of the first reference image by an optical sensor. The present invention is characterized in that the amount of developer replenishment is varied based on the above, and the developing electric field in the image area of the image carrier is corrected based on the detection signal of the second reference image.

[Effect]

According to the present invention, when a reference image for toner density control is formed on an image carrier and a method is adopted in which the optical density is detected and the toner density is controlled, the image is Focusing on the fact that although the density hardly changes, it has a significant effect on images composed of lines and dots, a second reference image composed of lines or dots is formed, its optical density is detected, and the image area is By correcting and controlling the developing electric field, it is possible to prevent fluctuations in image density and image quality of lines and dots, and to prevent large fluctuations in toner density.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram of the image forming area of a laser beam printer using the present invention.

In this example, a reversal development system is used in which a negatively charged organic photoreceptor is used as an image carrier and a two-component developer containing negatively charged toner is used as a developer.

The photoconductor 1 rotates in the direction of the arrow and is uniformly charged by a charger 2, and then the photoconductor 1 is charged with a laser beam 3 corresponding to image information.
The image is scanned and exposed in a direction perpendicular to the direction of rotation. As a result, the electrostatic latent image formed on the photoreceptor 1 is visualized by the developing device 4. The visible toner image formed on the photoreceptor 1 is transferred onto a transfer material 6 by a transfer charger 5, and then the transfer material 6 is separated from the photoreceptor 1 by a separation static eliminator 7. Transfer material 6
The visible toner image transferred to the photoreceptor 1 is fixed by a fixing device (not shown), while the toner remaining on the photoreceptor 1 after the transfer is removed and cleaned by a cleaning device 8. Thereafter, the charge remaining on the photoreceptor 1 is eliminated by the discharge light from the lamp 9, and the above steps are repeated again.

On the other hand, the first reference image formed on the photoreceptor outside the image area is detected by a reflective 4-degree sensor 10 disposed close to and facing the photoreceptor l, and corresponds to the reflection density of the first reference image. A signal V31 is output.

As the first reference image, an image pattern that becomes a hexagonal image after development can be effectively used. Desirably, the toner adhesion amount on the photoreceptor 1 is about 0.3 to 0.7 mg/cm". It is what happens.

FIG. 2 is a flowchart showing the flow of the control procedure based on the first detection signal VS+.

First, is the reflection from the surface of the photoconductor l where there is no toner image? a degree VSC
Detect step 1 1). Determine whether Vsc is appropriate or not. Step 1-2). If it is not appropriate (No in step 1-2), there is a possibility that the concentration sensor 10 or photoreceptor 1 is abnormal. Since it is high, display an abnormality (Step 1-
3). If VSG is appropriate, detect the detection signal V5+ of the first reference image (step 1-4), and establish the relationship shown in the diagram with the preset comparison signal VMI (Vs+/Vsc>V
ia/Vsc) (step 1-5)
). If the determination is affirmative, the toner content in the developer is appropriate, and the mode shifts to the next mode. If the determination is negative, it is determined that the toner content is too low, and after determining the remaining amount of toner (Step 1-6), the toner replenishing roller 11 is rotated for a certain period of time, and an appropriate amount of toner is replenished (Step 1-6). 1-7). Alternatively, if the remaining amount of toner is insufficient, a toner end display is performed (step 1-8).

Through the above control, a constant image density is always maintained based on the settings of ■□.

However, with this alone, the vector image density can be maintained constant when the image portion potential, that is, the developing electric field fluctuates as shown in FIG. 5, but the fluctuations are large for dot and line images. Further, since the toner content is also out of the appropriate range, the present invention uses a second reference image of dots or lines to carry out the control shown in the flowchart of FIG. 1.

As the second reference image, image patterns such as those shown in FIGS.
and d2 is desirably about 30 to 300 μm, and is preferably formed finer than the resolution of the density sensor 10. Further, it is desirable that the area ratio of the toner image in the image pattern is 50% or less. This is because when it exceeds 50%, the characteristics become similar to those of a solid area.

The second reference image is also formed in the same manner as the first reference image, is detected by the reflection density sensor 10, and a detection signal VSt corresponding to the average reflection density of the second reference image is output.

FIG. 1 is a flowchart showing the flow of the control procedure based on the second detection signal V32.

First, detect V5G (step 2-1), make appropriate judgment (
After step 2-2), if appropriate, step 2-3
If the condition is not appropriate, the process proceeds to step 2-4, where an abnormal state is displayed. In step 23, the detection signal VSZ of the second reference image is detected, and a preset comparison signal Vl1 is detected.
2. The relationship shown with VH3 (VR3/Vsc>VS
Z/V5G>V12/VSG) It is determined whether or not (Step 2-5). If the judgment is affirmative, the image portion potential is within the appropriate range, and the mode shifts to the next mode δ. If the determination is negative, it is determined that the image area potential is too low or too high, and the output of the laser beam is varied. That is, in step 26, the amount of light is increased, and in step 2-7, the amount of light is decreased.

The power of the laser beam may be varied continuously or in steps.

With the above control, the toner content is always maintained within the appropriate range based on the settings of ■7□ and V*3, and at the same time, a dot or line image is maintained.

Further, in the above example, the output of the laser beam was varied based on the signal of VS2, but the same effect can be obtained even when the developing bias potential is varied. Further, in the above example, the case of a reversal development system using laser beam scanning was explained, but the invention can be similarly applied to the case of regular development regardless of the type of optical system.

Further, it is not necessary to detect the first and second detection signals vs+ and VSt every time, and in particular, the image portion potential does not change suddenly, but gradually changes depending on the usage environment and usage conditions. Therefore, control when the power is turned on or every certain number of sheets is sufficient.

〔Effect of the invention〕

As explained above, according to the present invention, even if there are fluctuations in the surface potential of the image carrier due to environmental changes or deterioration over time, stable images can be maintained for a long period of time regardless of whether the image is a solid image, a line image, or a dot image. Obtainable.

[Brief explanation of drawings]

1 and 2 are flowcharts showing control of solid images, lines, and dot images according to the present invention, and FIG. 3 is a block diagram of the image forming area of an electrophotographic image forming apparatus to which the present invention is applied.
FIG. 4 is a diagram of each image pattern used as the second reference image, and FIG. 5 is a diagram showing the relationship between image portion potential, ID (image density), and toner content. Figure 2 Figure 4 Figure 3 Figure 5

Claims (1)

[Claims] At least a first reference image and a second reference image are formed on the image carrier by an electrophotographic process, and the amount of developer supplied is varied based on a detection signal of the first reference image by an optical sensor. An image adjustment method comprising: correcting a developing electric field in an image area of an image carrier based on a detection signal of a reference image.