JPS58132246A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain picture images of constant density by providing a means for detecting the using extent of a photoreceptor, and calibrating the control level of exposure to the level corresponding to the characteristics of the photoreceptor when the preset using extent is attained. CONSTITUTION:The rise and fall characteristics of a photosensitive drum 1 are compensated by controlling the exposure upon the photoreceptor, and a counter which counts the number of revolutions of the photoreceptor is used as a means for detecting the using extent of the photoreceptor, so that the control level of exposure is calibrated and controlled in accordance with the change in the photosensitive characteristics corresponding to the count number. More specifically, as the control circuit is shown in the figure, a counter 10 is so arranged as to count the number of revolutions of the photoreceptor 1, that is, the times of formation of latent images. The counter 10 is reset at every exchange of the photoreceptor 1. The quantity of light is controlled by changing the lighting voltage for a halogen lamp 11 which is a light source for irradiation of light images according to the output of the counter 10.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention applies a process including charging and exposure to a photoreceptor using a photoconductive substance to form a latent image, and develops the latent image. Material: 2 Transfer and fix, or once the formed latent flaw is transferred to the dielectric surface, the transferred latent image is developed, and then developed gI! The present invention relates to a transfer type image forming apparatus in which a photoreceptor is used repeatedly, and a copy is created by fixing the liquid on a dielectric surface or transferring and fixing it on a transfer material surface.

When a copying cycle is continuously repeated in such an image forming apparatus, even if the charger output and exposure amount in each copying cycle are constant, as the copying cycle progresses, the characteristics of the photoreceptor itself change. The latent image potential increases over time (rising characteristic), and the latent image potential decreases over time (falling characteristic). The rise and fall characteristics of the image have a negative effect on image quality. For example, in the case of a rising characteristic, the image density gradually increases as the copying cycle progresses, and a so-called capri occurs in the white background area. In addition, in the case of a falling edge, the density gradually decreases and the image is interrupted in places.

These rise and fall characteristics are the time required for the latent image potential on the photoreceptor to reach a constant potential (saturation potential) when a constant charger voltage is applied to the photoreceptor and a constant amount of light is applied to the photoreceptor (saturation time). , and the difference between the saturation potential and the initial potential on the photoreceptor (
This potential variation value is considered to be a potential variation value of IJIn"1"lA* using a photoreceptor.

It is highly dependent on time (downtime).

Therefore, it has been conventionally considered to control the amount of exposure, the amount of charge, etc. in order to compensate for this rising or falling characteristic.

For example, it attempts to stabilize the image quality throughout the entire copying cycle by changing at least one of the amount of light exposure and the amount of charge on the photoconductor by an appropriate amount as the copying cycle progresses, depending on the rest time of the photoconductor. be.

However, in the long term, control deviations gradually occur. That is, as a photoreceptor is repeatedly used (used) thousands or tens of thousands of times, the photosensitive characteristics of the photoreceptor, particularly of the photoconductive layer, change due to changes in the amount of carriers, fatigue of the photoconductive layer, and the like. As the photosensitive characteristics change as the photosensitive member is used, the potential fluctuation value based on the rising and falling C% characteristics of the photosensitive member also changes. Figures 1 and 2 show a new point in time (a) when the accumulated number of uses is small, and a point in time after 10,000 uses (b).
3 is a graph showing changes in potential fluctuation value for a photoreceptor made of a photoconductor, and changes in latent image potential with respect to exposure amount. Therefore, if the above exposure amount and/or charge amount control is continuously performed for each copying cycle, which is set based on the potential fluctuation value based on the rise and fall characteristics shown when the photoreceptor is new, the accumulated usage of the photoreceptor It may be fine if the number of times is small, but as the photoreceptor is used, it becomes impossible to compensate for the rise and fall characteristics of the photoreceptor, resulting in control deviations and changes in image density for each copying cycle.

The present invention incorporates into the control conditions the rise and fall characteristics of the photoreceptor that change as the photoreceptor is used (usage), and appropriately controls the amount of exposure and/or charge for each copying cycle to always achieve the desired level. This is a book designed to produce copies with a constant density.

That is, in a transfer type image forming apparatus that repeatedly uses a photoreceptor, the process conditions such as exposure amount and charge amount are controlled to change as the copying cycle progresses in order to compensate for the rise or fall characteristics of the photoreceptor. A means for detecting the degree of use of the photoconductor is provided, and when a preset degree of use is reached, the process condition change control level such as exposure amount and charge amount is set to the photoconductor start-up 9 or The gist of the present invention is an image forming apparatus characterized in that it is configured to be calibrated to a level corresponding to the falling edge characteristic.

A different explanation will be given below based on an illustrated example.

Example 1 Figure 3 shows the so-called NP a* bus (4I Kosho 42-23910
1 shows a very schematic configuration of an example of a drum-type electrophotographic copying machine according to the following (No. 43-24748), in which sulfurized cadmium ζram is bonded as a photoconductive layer on a drum-shaped conductive substrate made of, for example, an aluminum alloy. A drum-shaped photoreceptor (hereinafter referred to as drum) that is constructed by dispersing it in an adhesive and coating it with a transparent insulating layer on its surface, and is driven to rotate in the direction of the arrow.
, 2 to 8 are NP process execution devices sequentially arranged around the drum 10. That is, 2 is a primary charger, 3 is a secondary discharger that performs KAC discharge simultaneously with light image irradiation L (slit exposure) or discharge with a polarity opposite to that of -order charging (the optical mechanism for light exposure is omitted from the figure); 4 is a full exposure device.

5 is a developing device, 6 is a transfer device (charger in this example), 7 is a cleaner, and 8 is a fixing device.

A high-contrast electrostatic latent image corresponding to the pattern of the irradiated light image is formed directly on the rotating drum by the primary charger 2 to the full-surface exposure device 4, and then the latent image is developed by the developing device 5. The developed image is transferred to the surface of the transfer material P fed between the transfer device 6 and the drum 1 in synchronization with the rotation of the drum from a paper feeding section (not shown) in the transfer device 6 section. The transfer material P on which the image has been transferred is separated from the surface of the drum 1, introduced into the fixing device 8, where the image is fixed, and then discharged outside the machine as a copy. On the other hand, the surface of the drum 1 from which the transfer material P has been separated is cleaned by a cleaner 7 to remove residual images, etc., and is used repeatedly.

In this embodiment, the rise and fall characteristics of the drum 1, that is, the photoreceptor, are compensated for by controlling the amount of exposure to the photoreceptor.
In addition, a counter that counts the number of rotations of the photoreceptor is used as a means of detecting the degree of use of the photoreceptor, and the output (number of counts) of this counter is used to respond to changes in photosensitive characteristics that occur as the photoreceptor is used. to calibrate the exposure control level (
4), and FIG. 5 shows an example of its control circuit. That is, 10 is a counter, and the counter counts the number of rotations of the photoreceptor or the number of times a latent image is formed. Also, it can be reset to 0 each time the photoreceptor is replaced.

The light amount is controlled by a halogen lamp (original illumination lamp) 110, which is a light source for irradiating a light image, according to the output of the counter IO.
This is done by changing the lighting voltage.

For example, in a device that forms one latent image each time the photoconductor 1 rotates, if you want to reduce the light intensity after using the photoconductor 10,000 times, use a 6-digit counter io to count the number of rotations of the photoconductor 1. A well-known readout counter is used which outputs a decimal output in which each digit can be preset.

The output terminals of each digit of this counter 10 consist of 11 output terminals, one common terminal, and 10 terminals represented by numbers 0 to 9. In this operation, when the counter 1o is 00, only the output terminal displayed as 0 is electrically connected to the common terminal. Using this six-digit counter, the output terminal A@B of this counter is connected to a light amount correction circuit in order to change the amount of change in light amount of optical information with respect to the rest time in accordance with the number of times the photoreceptor is used. The halogen lamp 11 for irradiating a light image is turned on by a lamp power regulator 12, and the lamp power regulator 12 is controlled by a light amount correction circuit 13.

The light amount correction circuit 13 is configured to automatically vary the light amount depending on the rest time of the photoreceptor, and when used continuously, the light amount gradually changes depending on the number of sheets used continuously. Further, the value of the light amount is controlled by the counter 10 according to 1.

In this example, the B terminal of the counter is 10. This is the output terminal of the OO0th position. Also, the terminal A is the output terminal of rOJ. Therefore, while the counter 10 indicates 0 to 9999, the inside of the counter is electrically conductive, so the terminals 8 and 8 are short-circuited, and the input voltage Va of the light amount correction value of the light amount correction circuit 13 is
is maintained at the initial setting value (1), and the control level sight correction shown in the graph (A') of FIG. 4 is performed. But the counter is 1
Indicates 0.000. In other words, the same photoreceptor is 10. OO0
If the counter is used repeatedly, the inside of the counter becomes open and current does not flow through the power Q counter, so the light amount correction circuit 13
When the number of times iaooo is reached, the subsequent light amount correction circuit 13
The light intensity correction level is calibrated to the level shown in graph (4') in Figure 4), that is, it is calibrated to an appropriate level corresponding to the degree of change in photoconductor characteristics due to use of the photoconductor.
□ Even after repeated use for more than 20 times, a good electromagnetic image is continuously formed on the photoreceptor, and no change in image density depending on the rest time occurs. This also increases the apparent life of the photoreceptor.

Prize: When using the above counter, change the number of digits to get 100. Of course, it is possible to change the light amount correction amount for the 10,000th time in LOGo.

Example 2 Changes in the latent image potential due to changes in characteristics due to repeated use of the photoreceptor can be achieved by changing the amount of discharge to the photoreceptor in addition to the above method.

As the photoreceptor and the latent image forming process, those described in the above Example 1 are applied. In this example, it is noted that the change in latent image potential with respect to the rest time of the photoreceptor is due to a decrease in electrical resistance due to the photoreceptor being left in a dark place.
This reduction in the latent image on the photoreceptor is intended to be corrected by the amount of discharge applied to the photoreceptor.

To change the amount of corona discharge to the photoreceptor,
As shown in FIG. 6 or FIG. 7, the power supply voltage of the primary charger 2 was changed. As a result, the latent image potential change was corrected regardless of the repeated use of the photoreceptor, and the photoreceptor was used in the same manner as in Example 1. It is possible to extend the limit.

FIG. 8 shows an example of a control circuit that changes corona discharge amount correction for rest time according to the number of times the photoreceptor is used.
10 is the same counter as in Example 1 above, A (0 times).
B (1 false 000 times) terminal. Reference numeral 14 denotes an oscillation circuit which is driven by a primary potential correction circuit 15. Then, the output from the oscillation circuit 14 is made into a high voltage by the high voltage transformer 16, and the voltage is applied to the primary four-way charger 2 and generated from the four-way charger 2 according to the output of the oscillation circuit. . The primary potential correction circuit 15 is configured to automatically vary the output of the oscillation circuit 14 depending on the rest time of the photoreceptor 1, and the correction value changes depending on the input voltage V.

In the above configuration, until the counter 10 indicates 1QOO0, the terminals A and B are in a conductive state as in the first embodiment, and the input vb to the primary potential correction circuit 15 is V.

However, when counter 1o becomes 1 ao 00, terminal A
Manual vII because the counter side between s8 is insulated
iivs'. As a result, the primary charging potential correction circuit 1
A charging correction value of 5 is given. That is, the degree of use of the photoreceptor is io and oo in terms of rotational speed.

At the point in time, the subsequent charge correction level by the primary potential correction circuit 15 is calibrated to an appropriate level corresponding to the degree of change in photoreceptor characteristics due to use of the photoreceptor. Therefore, as in the case of Example 1, lo and oo.

Good image formation continues even after repeated use.

In Examples 1 and 2 above, the usage level of the photoconductor is measured by the counter 10.
Detection was done based on the cumulative number of rotations of the photoreceptor, but 1
It can also be determined by the amount of current applied to the corona discharge electrode for subsequent charging and other image forming means, the number of sheet materials (transfer members) conveyed, and the like. Moreover, the exposure amount control of Example 1 and Example 2
It is also possible to perform control in combination with charge amount control. As the photoreceptor, it is applicable to a conventionally used conductive substrate and one having a photoconductive layer thereon or a surface insulating layer. As a photoconductive layer, Se-based, CdS-based, ZnO-based,
Examples include photoconductive materials such as OPC-based materials.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between photoreceptor rest time and electrostatic contrast, Figure 2 is a graph showing the relationship between pre-exposure amount and electrostatic contrast, and Figure 3 is a graph showing an example of a transfer type image forming apparatus. A very schematic configuration diagram, Figure 4 is a graph showing the details of light amount correction, Figure 5 is a control circuit diagram of Example 10, and Figure 6 is a graph showing the relationship between the voltage applied to the primary charger and electrostatic contrast. , FIG. 7 is a graph showing the details of the correction of the primary potential,
FIG. 8 is a control circuit diagram of the second embodiment. 1 is a photoconductor, 10 is a counter.

Claims (1)

[Claims] (1) A transfer type image forming apparatus that repeatedly uses a photoreceptor, in which process conditions such as exposure amount and charge amount are changed as the copying cycle progresses in order to compensate for the rise and fall characteristics of the photoreceptor. In the control device, means is provided to detect the degree of use of the photoreceptor, and when a preset degree of use is reached, the control level for changing process conditions such as exposure amount and charge amount is set to the level of the photoreceptor at the time of use. An image forming apparatus characterized in that the image forming apparatus is configured to calibrate to a level corresponding to an upward or downward characteristic.