JPS59116768A - Electrophotographic image controlling method - Google Patents

Abstract

PURPOSE:To prevent stains on a background by setting a developing bias value from a suspension period and a developer fatigue degree and gradually lowering said value in accordance with the number of copies produced from the start of a copying machine. CONSTITUTION:A developer-based copy quantity detection circuit 11 counts the number of copies from the time of feeding a fresh developer, and sends its signal to a bias control circuit 12. A copy quantity detection circuit 13 is cleared when a copying machine is suspended, and starts to count when it starts operation, and sends its signal to the circuit 12. A suspension time detection circuit 14 detects a length of time from the suspension of the machine or the stop of agitation of the developer to the restart, and sends its digitized value to the circuit 12. The circuit 12 receives these signals, sets a correct bias voltage value, and applies it to a developing roller 17. A toner is triboelectrified in polarity opposite to an electrostatic latent image by agitation with a blade wheel 19. The polarity of the bias voltage is opposite to that of the toner, lower than potential at the image part, and somewhat higher than potential at the background. Therefore, the toner adheres to the image part but not to the background part, thus preventing background stains.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an image adjustment method in an electrophotographic copying machine, and in particular, includes preventing background smear on a developed image by changing the value of a bias voltage applied to a developing electrode. This invention relates to an image adjustment method.

(Prior Art) As is well known, in electrophotography, a photoreceptor having a photoconductive layer on its surface is charged and exposed to light to form an electrostatic latent image corresponding to the original to be copied. A visible image is obtained by culturing an image using a developer (e.g., toner) that is charged to the opposite polarity. In other words, the charge in the part corresponding to the image area remains almost unchanged, and the charge in the part corresponding to the bright part of the original, that is, the background part, is discharged through the conductive curved base of the photoreceptor, so that the charge corresponding to the image of the original remains there. A pattern is formed. This is an electrostatic a-image. Although the potential of the background part of this electrostatic latent image decreases due to discharge, it does not become zero and remains slightly. When the agent is supplied, the toner adheres not only to the image area but also to the background area, staining the background area.

For this reason, conductive members called mark and image electrodes are placed close to and facing the surface of the photoreceptor, and a bias voltage slightly higher than the potential of the image background area is applied to the conductive members, so that the toner is transferred to these developing electrodes instead of the background area. It is generally practiced to prevent the development of the background area by attaching it to the surface.

However, once the developing bias voltage is set, it is not always possible to obtain a good image without background stains. This is because when the photoreceptor and the image ablation layer deteriorate due to repeated use, the background potential and the amount of charge on the toner change, so naturally the effectiveness of the bias voltage also changes. Therefore,
JP-A-50-46334 proposes a technique in which the bias voltage is increased in degrees Celsius in relation to the increase in the number of copies, focusing on the fact that the degree of deterioration of the leveling agent is proportional to the increase in the number of copies. ing. Further, Japanese Patent Laid-Open No. 110046/1983 proposes a technique for similarly adjusting the bias voltage, focusing on the fact that the degree of fatigue of the photoreceptor is similarly proportional to the increase in the number of copies. Furthermore, Japanese Patent Application Laid-Open No. 53-98841 states that the degree of fatigue of the photoreceptor is simply a ratio f/
11, but is also affected by the amount of light exposure, copy size, amount of charge, etc. Therefore, a technique has been proposed in which each of these changes and amounts is counted and integrated to determine the degree of fatigue of the photoreceptor.

Among such conventional techniques, the above P0')! The technique proposed in Japanese Patent Publication No. 52-110046 by FJ is superior in that it uses the copying stop time, ie, the time the photoreceptor is left in a dark place, as one of the parameters for controlling the bias voltage. This is because if the photoreceptor is left in a dark place, the fatigue of the photoreceptor will recover depending on the length of time the photoreceptor is left. Therefore, if this parameter is not taken into account, even though the photoreceptor has recovered from fatigue after being left in a dark place for a long time, the bias voltage applied when the photoreceptor is fatigued will be applied to the developing electrode. If the bias voltage is too high, the density of the developed image decreases, and the reproducibility of poor originals such as low-density originals or low-contrast originals deteriorates. For this reason, the upper Ni
In the technology described in the publication ('), the developing bias voltage is lowered in accordance with the time the photoreceptor is left in the dark. However, even with this method, when the copying machine starts operating, It is known from experience that copies with smeared backgrounds can be produced.

(Object of the Invention) Accordingly, an object of the present invention is to provide an n-child photo self-portrait adjustment method that includes preventing the background smudges on the copy that occur mainly at the start of the copying operation after the copying machine has stopped.

The 1liII image adjustment method according to the present invention focuses on the fact that the longer the copying machine dwell time, the greater the initial copying background smudge, and the greater the developer fatigue, the more pronounced this background smudge, and it disappears after a certain amount of copying. It was developed as a special enemy for copying (determining the developing bias voltage using the rest time of the tack and fatigue level of the developer as parameters, and gradually lowering this voltage according to the number of copies made after the copying machine resumes operation). do.

The present invention will be described below with reference to the accompanying drawings.

(Structure of the Invention) The graph in Figure 1 shows the relationship between the inclination (・k! pause time and the degree of copying background staining at the time of starting the copying operation.) This figure is based on the measurement results obtained by the machine.As is clear from this figure,
The longer the stopping time of the copying machine is, the greater the degree of initial copy background smearing, and the greater the number of copies until the copying background smear becomes good. Furthermore, as shown in Figure 2, when the rest time is the same under normal use conditions, the greater the viewing agent fatigue, the worse the degree of background smearing. In this case, developer fatigue is measured by how many copies are lost in the same world-image-cutting device stored in the Ko-image device. Therefore, from these two graphs, it can be seen that the longer the copying machine pauses, the thicker the initial 1j4 copy background stain, and the greater the developer fatigue, the more pronounced the background stain is, and it disappears after a certain amount of copying. Please understand that it is put away.

The inventor of this application considered how such a phenomenon occurs and found that when the copying machine is stopped, the amount of charge on the toner in the developer decreases compared to when the copying machine is in continuous operation, as shown in Figure E-3. It was speculated that this is because When the leveling agent is a two-component system consisting of toner and carrier, the toner is charged to a polar group opposite to the W-charged polarity of the silent latent image by mixing with the carrier. When the imager is stopped and the imager is stopped, the developer is not stirred and the charge on the toner is thought to be gradually dissipated by the surrounding atmosphere. When the amount of charge of the toner decreases, the selective charging to the latent image area decreases, and more toner adheres to the background area of the latent image, resulting in background smearing. However, in addition to this, when the copying operation is started, the amount of toner band N increases as the developer in the developing device and device is stirred.
It will disappear in the next year of life. When the developer becomes fatigued, the amount of toner charge decreases rapidly during rest periods.
Furthermore, since recovery of the toner charge amount at the start of operation is delayed, the above-mentioned phenomenon appears to be noticeable.

Based on the above considerations, in order to prevent the initial background smearing of copies, it is necessary to detect the copying pause time and the degree of fatigue on the image side, increase the bias voltage value according to the increase in these, and It was concluded that the increased bias voltage value should be gradually lowered according to the number of copies made after the copying machine is stopped. Based on this conclusion, we conducted an experiment by adding the bias increment shown in Table 1.1 to the specified bias value, and as shown in Figure 4, we obtained good copies with almost no initial background smearing. was gotten.

Figures 1 and 5 schematically show, as a block diagram, an electric circuit for carrying out the image adjustment method of the present invention. The agent usage number detection circuit J1 counts the number of copies made one by one after a new developer is put into the developing device, and sends a signal to the bias system 1L111 circuit 12. After replacing the developer, be sure to turn on the reset switch and clear the count. Number of copies detected circuit J: (Similarly, the number of copies is counted one by one, but it is cleared when the copying machine stops, and when the copying machine starts operating, it counts each copy again and biases the signal. Send to control circuit 12. Downtime detection circuit j4
After the main switch of the copying machine is turned off and the copying process stops, or after the developing snowmaking motor stops and stirring on the willow/image side stops, until the copying machine is started again. The time is detected by a time meter or the like, converted into digital data, and then inputted to the bias control circuit 12. Note that this circuit 4 is operated by a power amplifier battery or the like even after the main switch of the copying machine is turned off. Bias open side J
When the circuit 12 receives these signals, it performs necessary processing to set an appropriate bias voltage value, and then connects the developing roller 1, which acts as a developing electrode in the developing device j6, through a bias T source 15.
7.

Developing equipment! ] 18 developer contained in 6, consisting of toner and carrier, is stirred by an impeller 9, so that the toner has a polarity opposite to that of the charged polar group of the electrostatic latent image on the photoreceptor 2.0. 1 A cow is charged with friction. +J1. The range of the bias voltage applied to the I'#' roller J7 is opposite to the charging polarity of the toner, and is lower than the image area potential of the static N latent image.
Slightly higher than the skin potential. Therefore, the toner adheres to the image area of the electrostatic latent image, but does not adhere to the background area.
Prevents scumming. If the bias voltage is too high, the image a degree will decrease and the reproducibility of poor originals will deteriorate, while if the bias voltage is too low, background smear will occur. In this invention, an appropriate bias value is set based on three factors: the stopping time of the copying machine, the fatigue level of the developer, and the number of copies, thereby achieving good reproduction of poor originals and effective prevention of scumming.

The operation in the bias control circuit 2 is carried out by a microco/peater as shown in 1' 6 [gl] which is used to control the copying speed. That is, the central processing unit fcPU sequentially reads microprograms written in the read-only memory ROM and controls necessary input/output operations while executing predetermined sequence processing. During this time, necessary data is exchanged between the central processing unit CPU and the external device, that is, each device of the copying machine, through the human IP/force control unit IOC and the interface circuit IF. Interface circuit IF
The signals that are input to the central processing unit CPU through the
4, JA, a detection signal from the agent usage number detection circuit 11 representing the degree of fatigue on the image side, a detection signal from the number-of-copies detection circuit 11, a timing signal, etc. The central processing unit CPU controls the bias control 'ljl' No. 18 and other signals according to these input signals.
・Strive. The detection signal from the @stem knowledge circuit 11, l:+, ]4 is once stored in the random access memory RAM, then input to the central processing unit CPU, and taken out as appropriate.

(Effects of the Invention) As described above, according to the image adjustment method of the present invention, the developing bias value is set using the copying machine down time and the fatigue level of the culture medium as parameters, and this value is set from the time when the copying machine is restarted. Since the number of copies was gradually decreased according to the number of copies, the first I
JJ background stains can be almost completely prevented, and poor originals can also be reprinted successfully.

Of course, the image adjustment method according to the present invention can be used in conjunction with other known image adjustment methods. It goes without saying that a one-component thread developer consisting only of toner can also be used on the image side.

[Brief explanation of the drawing]

``4. □ Figure 1 is a graph showing the relationship between the degree of scumming and the number of copies made until it disappears as the length of the copying machine stops, and Figures E and 2 are graphs showing the relationship between the degree of scumming and the number of copies made until it disappears. Figure 3 is a graph showing the relationship between the degree of background smearing and the downtime of Isha village, and Figure 3 is a graph showing the change in toner band @ amount during continuous operation and when the machine is stopped. , a graph similar to Figure 10J showing the effect of this invention, Figure 5 is:
A block diagram showing the outline of an electric circuit for carrying out this invention, Figure 6, is a block diagram of the bias control circuit shown in Figure i-5.
This is a professional tsuku diagram for explaining the layout of the work.

Claims (1)

[Claims] Electrophotography comprising means for developing an electrostatic latent image formed on a photoreceptor with a developer on a developing electrode, and means for adjusting the image by changing the pupil of a bias voltage applied to the developing electrode. In the copying machine, detecting the down time of the copying machine and increasing the bias voltage value as the time becomes longer; detecting the degree of fatigue of the developer and increasing the bias voltage value as the time increases; An electrophotographic image adjustment method comprising gradually lowering the increased bias voltage value according to the number of copies from when the copying machine resumes operation.