JPH02139582A - Stabilizing method for electrophotographic picture - Google Patents

Abstract

PURPOSE:To stabilize density regardless of a combination of spot and consecutive copies by calculating fatigue during copying and during a dormant period as a function that increases with time and is saturated and a function that decreases and reaches zero and correcting picture density. CONSTITUTION:The perform initial copying while a copying machine operates, the value of the fatigue A is initialized, and the fatigue A is calculated by A=B[1-exp(-alphat)] as time (t) passes. According to the result, a controller C controls the quantity of light from a lamp 2 to correct the picture density. During the dormant period, the fatigue A is initialized and is calculated by A=B.exp(-betat) as time passes, and the picture density is corrected. B, alpha and betaare a constant and (t) shows time. Even if spot copying and consecutive copying are performed at random, a picture of density that is corrected to correspond with characteristics affecting the density of a picture on a photosensitive body can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates primarily to a method of correcting the density of an image formed by electrophotography and stabilizing the image.

(B) Prior art Regarding this type of image stabilization method, a method for stabilizing the image when making continuous copies is known (for example, see Japanese Patent Application Laid-Open No. 100863/1983).
.

(c) Problems to be Solved by the Invention However, in the conventional image stabilization method, it is difficult to separate the factors that change the characteristics of the photoreceptor during continuous copying from the factors that change the characteristics of the photoreceptor due to the pause time. Therefore, for example, when performing continuous copying after performing a single copy operation, and after performing a pause time, and when performing continuous copying after performing continuous copy operation, and then performing continuous copying after the above pause time, the original The image exposure intensity (or charging intensity) is similarly controlled, resulting in a problem that the density of the copied image differs.

This invention was made in consideration of these circumstances,
To provide an image stabilization method capable of always obtaining a stable image with a constant yield regardless of the combination of single-shot copying and continuous copying.

(d) Means for Solving the Problems This invention provides an image forming method in which image light is formed on a photoreceptor, the formed electrostatic latent image is developed, and transferred to transfer paper. A first function that increases and gradually saturates, and a second function that decreases from a predetermined value and gradually approaches O as time passes are set. During the next copying pause period, the second function is calculated using the final calculated value of the first function as the initial value, and during the next copying operation, the final calculated value of the second function is used as the initial value. An image stabilization method characterized in that the first function is calculated as follows, the first and second functions are sequentially calculated for copying operation/pause period, and the density of the copied image is corrected according to the calculation result. be. The above-mentioned correction of the copy image density is performed by controlling any one of the original exposure intensity, the charging intensity of the photoreceptor (the charging intensity by the main charger), and the bias voltage applied to the developing device. The function is, for example, A=B[1-e
xp(at), and the second function is expressed as A=B·exp (−βt) (where B, α, and β are constants, and t is time).

(E) Effect Generally, the characteristic of the photoreceptor that affects the image density (hereinafter referred to as fatigue) increases with copying time and gradually becomes saturated. Then, the fatigue gradually recovers from the saturation value and approaches 0 over time during the copy suspension period.

Therefore, by calculating the fatigue during the copying period using the first function and calculating the recovery from fatigue during the copying pause period using the second function, the degree of fatigue of the photoreceptor can be constantly calculated. By correcting the density of the copied image in accordance with the calculated degree of fatigue, a copy with uniform degree of roar can be obtained.

(f) Examples Hereinafter, the present invention will be described in detail based on examples shown in the drawings. This invention is not limited by this.

FIG. 1 is an explanatory diagram of the configuration of an electrophotographic copying machine to which the present invention is applied, in which 1 is a document placement table that is installed movably in the direction of the arrow, and 2 is a document placement table! An exposure lamp 3 exposes the original placed on the original when the original placing table L moves in the direction of the arrow;
an imaging lens that forms an electrostatic latent image by forming an image thereon; 5 a developing device that develops the electrostatic latent image; 6 a developing roller; 7 a registration roller that supplies transfer paper to the photosensitive drum 4; 9 is a transfer charger that transfers the toner image developed on the photoreceptor drum 4 onto a transfer paper, 9 is a separation charger that separates the transfer paper from the photoreceptor drum 4, and IO is a fixing device (not shown).
1 is a static elimination lamp that removes unnecessary charge from the photoreceptor drum 4; 12 is a cleaning unit that removes unnecessary toner from the photoreceptor drum 4; 13 is a photoreceptor. A main charger C that uniformly charges the surface of the drum 4 is a control device that controls the amount of light from the lamp 2.

FIG. 2 is a graph showing temporal changes in the fatigue A of the photoreceptor drum 4, and (A) in the same figure shows a state in which 8 increases with time and saturates to the saturation value B when copying is performed continuously. It is expressed as A=B[1-exp(-at)]...(1), and the figure (b) shows that the fatigue A increases over time during the copying pause period.
This is a curve showing a state in which .

FIG. 3 is a graph showing changes in fatigue A of the photosensitive drum 4 during the copying operation period and during the copying pause period, and the fatigue A increases to AI during the first copying operation period tel, and then during the next copying operation period tel. It recovers to A2 during the copy suspension period tvl. Furthermore, the fatigue increases to A3 in the next copying operation period tc2, and recovers to A4 again in the next copying pause period tv2. In this way, the fatigue A changes in contrast to the copying operation period and the copying pause period, and the change in fatigue A is expressed by the formula (
1), and the power (can be calculated) using equation (2).

FIG. 4 is a flowchart showing a method for calculating fatigue A. In step lot, when the copying machine is in the copying operation period, the initial copying force (if performed (step 102)) An initial value is set (Step!03). Then, as time t elapses (Step 104), fatigue A is calculated using equation (1) (Step 105), and the calculated result is used to control the control device C (
The light intensity of the lamp 2 is controlled by the light intensity of the lamp 2 (FIG. 1), and the image density is corrected for fatigue (step 106).In other words, when the copied image becomes darker as the fatigue A increases, the exposure intensity of the lamp is increased to reduce the density of the copied image.Also, when the copying machine is in a copying suspension period (or, when the fatigue A/l calculated in step 105 at the end of copying is
It is set as an initial value (steps 107 and 108), and as time passes (step 109), fatigue A is
is calculated by equation (2) (step 1 0).

Note that if fatigue A is not positive (step 111),
The fatigue level thereafter is considered to be 0 (step 112).

Then, when the copying operation is started again, the routine returns to step 101, and when copying is started for the first time, step 11G is executed.
The final value calculated in is set as the initial value (step 103), fatigue A over time is calculated using equation (1) in the same way as described above, and image density correction is performed using the calculated A (step 103). 305, 106).

In this way, the fatigue A of the photoconductor shown in FIG. The density is faithfully corrected without any problems, and copies are always made with a constant density.

(G) Effects of the Invention According to the present invention, even if a combination of continuous copying and single-shot copying is performed, the image density is always properly corrected and an image with a constant density can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, FIG. 2 is a graph showing fatigue characteristics and fatigue recovery characteristics of the photoreceptor shown in FIG. 1, and FIG. 3 is a graph showing changes in fatigue of the photoreceptor over time. FIG. 4 is a flowchart illustrating the control method of the embodiment shown in FIG. 1, which is a graph shown in correspondence with the copying operation period and the copying suspension period. 117th document mounting table, 2... exposure lamp, control device, 4... photosensitive drum, developing device, 6... developing roller, registration roller, transfer charger. Tube diagram 1td! tv10c2 tv2, tc3-
the whistle diagram

Claims (1)

[Claims] 1. In an image forming method in which image light is formed on a photoreceptor, the formed electrostatic latent image is developed and transferred to transfer paper, the first function that increases and gradually becomes saturated with the passage of time and the time A second function that decreases from a predetermined value and gradually approaches 0 as time passes is set, and the first function is calculated as time passes from the start of the copy operation using the predetermined value as an initial value, and during the next copy pause period. is the second function with the final calculated value of the first function as the initial value.
During the next copying operation, the first function is calculated using the final calculated value of the second function as the initial value, and the first and second functions are sequentially calculated for the copying operation and pause period. An electrophotographic image stabilization method characterized by repeating the process and correcting the density of the copied image according to the calculation result.