JPS61240260A - Image recording device - Google Patents

Abstract

PURPOSE:To always make the potential in a developing point higher than the developing bias and to obtain an image of a high picture quality having no fog by detecting the potential of the surface of a photosensitive body on which plural potential detecting means is installed, and controlling an electrifying current so that the detected potential satisfies the reference potential of the installed part of each potential detecting means. CONSTITUTION:The potential which is detected by the first and the second potential sensors 9, 10 is inputted to a current controlling circuit 11 and the current controlling circuit 11 outputs this detected value to a correcting information storing circuit 12. The storing circuit 12 stores in advance the reference potentials V1, V2 required in a developing point 9a and a transfer point 10a and inputted potential detected values are compared with the reference potentials V1, V2, respectively. In case when at least one input value is under the reference potentials V1, V2, a signal is outputted to the current controlling circuit 11. Based on this signal, a high voltage power source 1 which is supplying an electrifying current to an electrifying device 2 is controlled and the electrifying current is corrected.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an image recording device such as an electrophotographic device.

BACKGROUND ART Conventionally, image signals are generated on a photosensitive recording medium by exposing a uniformly charged photosensitive recording medium such as a photosensitive selenium drum to light using a light emitting element such as a light emitting diode or a light amount control element such as a liquid crystal. An apparatus is known that records an image by forming an electrostatic latent image corresponding to the background image, developing the latent image by attaching a charged toner to the latent image, and transferring the obtained developed image onto recording paper.

An example of a conventional image recording apparatus of this type is shown in FIG. This image recording device includes a photosensitive recording medium (hereinafter referred to as a photoreceptor) 1 such as a photosensitive selenium drum, and the photoreceptor 1
A charger 21 and a light-emitting element 3 are arranged around the rotation direction in order.
．． Developing device 4. Transfer charger5. Charger for female 6. It is equipped with a cleaner 7 and a static elimination lamp 8.

This image recording device operates as follows.

The photoreceptor 1 is rotationally driven in the direction of the arrow 20 by a driving means not shown. The surface of the photoreceptor 1 is charged uniformly by a charger 2. Next, light emitting element 3
exposes the charged photoreceptor 1 to light in accordance with the applied image signal to form an electrostatic latent image on the photoreceptor 1. in this case,
Exposure is performed for a "black" image signal, and no exposure is performed for a "white" image signal. The electrostatic latent image formed on the photoconductor in this way is sent to the developing device 4, which attaches positively charged toner to the exposed area and develops it (toner image). becomes.

Next, this developed image is transferred to the transfer charger 5, and the transfer charger 5 performs negative charging, thereby transferring the toner onto the recording paper. This recording paper is then peeled off from the photoreceptor 1 by the peeling charger 6, sent to a fixing section (not shown), and subjected to a fixing process, thereby becoming a hard copy.

The residual toner on the photoreceptor 1 that has passed through the transfer charger 5 and the charger 6 is removed by a cleaner 7.

Thereafter, the photoreceptor 1 is neutralized by the neutralization lamp 8 and returns to the charger 2 again.

Such a developing method in which the photoreceptor and the toner have the same polarity and the toner is attached to the exposed portion of the photoreceptor surface is generally called a reversal development method.

In the positively charged reversal development system as described above, the developer is also positively charged, and its potential (this potential is called the development bias) is higher than the exposed portion of the photoreceptor, and the developing device is also positively charged. It is smaller than the potential of the part that is not covered. In other words, the exposed area has a lower potential than the developing bias, so
Toner does not adhere to the unexposed areas because the potential is higher than the developing bias. This allows a toner image to be formed on the photoreceptor.

Problems to be Solved by the Invention However, in such devices, the potential on the photoreceptor decreases and becomes lower than the development bias, causing unexposed areas (i.e., "white" and There was a problem in that the toner adhered even to the desired area (the area where the toner should be), so-called smearing, resulting in a significant deterioration in image quality.

The following three causes are known for the decrease in surface potential of the photoreceptor.

The first cause is an increase in dark decay. The potential of the photoreceptor is
Even when not exposed to light, it gradually decreases over time. This is generally called dark decay, but the speed of dark decay varies depending on the temperature of the photoreceptor and also due to so-called optical fatigue caused by repeated charging and neutralization.

The second cause is a decrease in charging efficiency. Even if the current value supplied from the charger to the photoreceptor is constant, the above-mentioned optical fatigue reduces the charging efficiency and lowers the surface potential.

The third cause is a decrease in surface potential caused by negative potential charging by the transfer charger. The transfer charger starts operating just before the recording paper begins to pass through, and ends its operation immediately after. As a result, when the recording paper is passing between the transfer charger and the photoconductor, the effect of negative charging can be ignored, but before and after the recording paper passes, the effect of negative charging is Since there is no recording paper in between, its influence cannot be ignored. At this time, the photoreceptor is given a negative charge; however, if the potential of the photoreceptor is low, the photoreceptor is negatively charged. In general, a photoreceptor for positive charging does not have photoconductivity for negative charging, so once it is negatively charged, this negative charge is removed by the static elimination lamp 8.
When the charge is not removed by the transfer charger 1 and should be uniformly charged by the next charger 1, the potential of the portion negatively charged by the transfer charger becomes lower than that of the portion not negatively charged. That is, on the surface of the photoreceptor, only the portion that passes near the transfer charger immediately before or after the recording paper passes has a low potential.

The above three factors are the main causes of a decrease in the potential of the photoreceptor. 1st. Since the decrease in potential due to the second cause is a continuous change, a means for detecting the potential such as a potential sensor is provided on the photoconductor, and the current supplied from the charger to the photoconductor is adjusted so that the surface potential is constant. can be dealt with by controlling the situation, and is already being done. However, since the potential drop due to the third cause is a partial potential drop of the photoreceptor, it cannot be handled by the method using the potential sensor described above.

For this reason, a positive charger is installed just before the transfer charger, and a sufficient positive potential is applied to the photoconductor in advance so that the photoconductor does not become negative potential due to the transfer charger. There are generally known methods for preventing the potential from decreasing. In other words, the first and second causes are dealt with by the potential sensor, and the third cause is dealt with by the above-mentioned positive charger.

However, since K using such a method requires a new charger, a charging power source, etc., a new problem arises in that the manufacturing cost increases.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and aims to provide an image recording apparatus that can control the potential of a photoreceptor and obtain high image quality using simple and inexpensive means.

Means for Solving the Problems In order to achieve this object, the present invention provides a photosensitive recording medium (hereinafter referred to as a potential detecting means necessary for performing photosensitive recording) that is uniformly charged by a charger. The reference potential at the installation location is memorized in advance, the detected potential value is input, this detected value is compared with the reference potential, and if at least one detected value is less than the reference potential, the current value of the charger is corrected. and a correction information storage circuit that outputs a signal.

Operation: The plurality of potential detection means simultaneously detect the potentials of the photoreceptor at the installed positions, and input these detected values to the correction information storage circuit. This detected value is compared with a reference potential stored in advance, and if the detected value is lower than the reference potential, a signal is outputted to increase the current of a charger that supplies charge to the photoreceptor.

Embodiment FIG. 1 is a block diagram showing an image recording apparatus according to an embodiment of the present invention, and FIG. 2 is a control block diagram of the apparatus shown in FIG.

In FIGS. 1 and 2, numerals 1 to 8 and 2o correspond to the numbers assigned to the same members in FIG. 5. Further, in this embodiment, a case is shown in which two potential sensors, a first potential sensor 9 and a second potential sensor 10, are used as potential detecting means.

The first and second potential sensors 9 and 1o are installed near the developing device 4 and near the transfer charger 5, respectively.

In addition, as shown in FIG. 2, the installation locations are development point 9& and transfer point 10&, respectively. second potential sensor 9,
The potential detected at 1o is input to the current control circuit 11. The current control circuit 11 outputs this detected value to the correction information storage circuit 12. The storage circuit 12 stores a development point 91L for recording at a predetermined density.

The reference potentials V,, V2 required at the transfer point 10 & are stored in advance, and the input potential detection values are compared with the reference potentials V,, V2, respectively, and at least one of the input values is less than the reference potentials V,, V2. If so, a signal is output to the current control circuit 11. Based on this signal, the high-voltage power supply 13 that supplies charging current to the charger 2 is controlled to correct the charging current.

The principle of charging current correction will be explained below.

In order to obtain high image quality, the potential of the photoreceptor surface is higher than the development bias at the development position, and the potential at the transfer position is
It is necessary to keep the potential high enough to prevent the photoreceptor from becoming negatively charged. In this embodiment, potential sensors 9 and 1o are provided at the development point 91L and the transfer point 10B, respectively, in the vicinity of the development position and the transfer position, so that the potential at the image point is equal to the respective reference potentials V, V2. Correct the charging current to meet the requirements. In other words, at one of the two points, the reference potential v
If it falls below 1°v2, the potential at that point becomes the reference potential V,...
The charging current is increased to exceed V2. If these potentials are above the reference potential, there is no problem in terms of image quality. Below, when the potential at the transfer point 10a is below the reference potential v2 (Example 1), the potential at the development point 9& is below the reference potential v1. - The case (Example 2) will be specifically explained.

Example 1 FIG. 3 is a diagram illustrating correction of the charging current when the potential at the transfer point 102L is lower than the reference potential v2. In the figure, the horizontal axis indicates the time since the photoconductor 1 is charged by the charger 2, T1 corresponds to the time it takes for the charged part of the surface of the photoconductor 1 to pass the development point, and T2 corresponds to the transfer point. The vertical axis indicates the potential on the surface of the photoreceptor 1, V indicates the reference potential at the development point 9a, and v2 indicates the reference potential at the transfer point 102L.

When the potential of the photoreceptor 1 exhibits a dark decay characteristic as indicated by the figure, the correction information storage circuit 12 determines that the potential of the transfer point IC1& is smaller than the reference potential v2, and a signal for correcting the charging current is generated. is output to the current control circuit 11. Then, a charging current exhibiting a potential change as shown by B in the figure is supplied from the charger 2 to the photoreceptor 1, so that the potentials at both points are filled.

Example 2 FIG. 4 is a diagram illustrating correction of the charging current when the potential at the developing position 9a is lower than the reference potential 'vl. ”
l l T21 vI l v2 is the same as in FIG.

Similar to Example 1 shown in FIG. 3, when the potential of the photoreceptor 1 exhibits a dark decay characteristic as shown by the figure, the potential of the developing point 9& is smaller than the reference potential V, which means that the correction information is stored. circuit 1
2, and a signal for correcting the charging current is output to the current control circuit 11. Then, a charging current showing a potential change as shown by B in the figure is supplied from the charger 2 to the photoreceptor 1, so that the potentials at both points are filled.

Above, we have described the method of directly detecting the potential at the development point and the transfer point using the potential sensors 9 and 10. However, it is also possible to provide a plurality of potential sensors at positions on the photoreceptor 1 and detect the potential at each point. Figure 3.

A dark attenuation curve as shown in FIG. 4 may be calculated, and the potentials at the development point 91L and the transfer point 10& may be calculated based on the calculated dark attenuation curve.

Effects of the Invention According to the present invention, the potential on the surface of a photoreceptor on which a plurality of potential detection means are installed is detected, and the charging current is adjusted so that the detected potentials both satisfy the reference potential at the location where each potential detection means is installed. Since the potential at the development point is always higher than the development bias, it is possible to obtain a high-quality image without fogging.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an image recording apparatus according to an embodiment of the present invention, FIG. 2 is a control block diagram of the apparatus shown in FIG. 1, and FIG. 3 shows that the potential at the transfer point is higher than the reference potential. FIG. 4 is a diagram for explaining the correction of the charging current when the potential at the development point is below the reference potential. FIG. 1 is a schematic configuration diagram showing an example of a conventional image recording device. 1...Photoreceptor, 2...Charger, 3...
...Exposure device, 4...Developer, 5...
・Charger for transfer, 6...Charger for female, 7.
...Cleaner, 8...Static elimination lamp, 9.
10... Static elimination lamp, 11... Current control circuit, 12... Correction information storage circuit. Name of agent: Patent attorney Toshio Nakao and one other person δ−
---Correctioned electric 1st bar, T1-1-so gun, 6 shots, temple darkness 4th figure T+ Tz time 7--ゑlight body Z--1 Tei Dendon 4--1 development version

Claims (1)

[Claims] A charger, a photosensitive recording medium that retains the electric charge supplied via the charger, a developer that develops and visualizes an electrostatic latent image formed on the photosensitive recording medium, and the developer. Installation of a transfer charger for transferring an image onto recording paper, a plurality of potential detection means for detecting the potential of the photosensitive recording medium, and the potential detection means necessary for recording at a predetermined density. The reference potential at the location is memorized in advance, the detected values of the potential detecting means are input, and these detected values are compared with the corresponding reference potential, and if at least one detected value is less than the reference potential, the charged An image recording device comprising a correction information storage circuit that outputs a signal for correcting a current value of a device.