JPH0728286A - Electrophotographic recorder - Google Patents

Abstract

PURPOSE:To obtain constant and excellent image quality by attaining the exposing and development of plural times and changing an exposure at this time in accordance with the use environment and state of a device and a developer. CONSTITUTION:An image recognizing circuit 1 recognizing the kind of an image from input pixel data is provided and in the first exposing, all image parts are exposed with a constant exposure regardless of the kind of the image, to form an electrostatic latent image on a photosensitive drum 10 and develop the electrostatic latent image by a developing device 5. The developed photosensitive drum 10 is reexposed with the exposure larger than that in the first exposing, in the image part of a specific kind, based on the output of the image recognizing circuit 1, so that the capacitance of the developed image is changed and the image is formed by redevelopment. In other words, the result of the recognition is collated with a data base, to set the exposure for irradiating a photosensitive body and the first development is executed after the first exposing. Then, the second exposing is attained with a proper exposure again and then, the second development is attained to dotain constant image quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording apparatus for recording an image by an electrophotographic method, and more particularly to an exposure amount control device and an exposure amount control method in the electrophotographic recording apparatus.

[0002]

2. Description of the Related Art Images to be printed consist of line images such as characters and ruled lines, plane images (solid areas), and point images such as halftones. Among them, the electrostatic latent image of the line image has a large potential gradient with respect to the peripheral portion, and a large amount of toner adheres during development, so that the line image is printed thick and a predetermined resolution cannot be obtained. . Therefore, in order to obtain a predetermined resolution, when the light modulated by the image information is applied to the photoconductor drum by the exposure unit,
A method is known in which the exposure amount for a line image is reduced by recognizing that the printed image is a line image.
By reducing the exposure amount, the toner adhesion amount is reduced and the line thickening is suppressed. An example of such a case is Japanese Examined Patent Publication No. 62-26621.

[0003]

When the amount of exposure applied to the line image portion is reduced and printing is performed, the toner adhesion amount of the line image is reduced and a predetermined resolution can be obtained. But,
Printing with one exposure and one development has a distribution in the thickness of the toner layer that forms an image, so it cannot be said to be a good image.
An image that does not have excessive toner adhesion and that has a uniform toner layer thickness has a good appearance and can consume the minimum amount of toner. For that purpose, it is necessary to perform exposure and development a plurality of times with an appropriate amount of light.

As described above, in printing by one exposure and one development, there is a distribution in the thickness of the toner layer forming an image, and a good image cannot be obtained. Further, in the prior art, even if the exposure amount applied to the photoconductor is changed according to the type of image such as a surface image or a line image, the image is changed by changing the usage environment of the device or the charged state of the developer. There was a problem of change. Therefore, an object of the present invention is to obtain a line image having a predetermined resolution and a surface image having sufficient density at the same time, and to obtain an image having a toner layer with a uniform layer thickness, Exposure and development of the number of times,
It is an object of the present invention to provide an electrophotographic recording apparatus in which the exposure amount at that time is changed according to the use environment and state of the apparatus and the developer to obtain a constant and good image quality.

[0005]

In order to achieve the above object, the present invention provides an exposing means in an electrophotographic recording apparatus as follows. A recognition means for recognizing what kind of image the printed image is based on the input image data, a means for storing an appropriate exposure amount preset based on the developer characteristics and the developing bias, and an appropriate exposure. A means for exposing twice and a means for developing twice are provided.
Further, a means for measuring the sensitivity characteristic of the photoconductor is provided, and a means for calculating an appropriate exposure amount for irradiating the photoconductor based on the result of the sensitivity characteristic measurement is provided.

[0006]

The image data from the host device such as a large-scale computer or OA device is sent to the memory in the order of printing by the electrophotographic recording device. The dot array of the image is determined based on the image data and is printed. The pattern recognition device recognizes what kind of image the printed image indicated by the data and the dot arrangement stored in the memory is, and sends the recognition result to the database. The database stores a surface image, a line image, and an appropriate exposure amount for irradiating an isolated point on the photoconductor, which are obtained in advance by experiments and analysis. The recognition result is collated with the database, the exposure amount to be applied to the photoconductor is determined, the first exposure is performed, and then the first development is performed. Then, the second exposure is performed again with an appropriate exposure amount, and then the second development is performed to obtain a constant image quality. In addition, the relationship between the exposure dose applied to the photoconductor and the post-exposure photoconductor surface potential is automatically measured at appropriate intervals, and the post-exposure photoconductor surface potential and line width are stored in memory in advance. The calculation means calculates an appropriate exposure amount using the data indicating the relationship with As a result, the photoconductor is exposed with an appropriate amount of exposure, so that a constant image quality can always be obtained.

[0007]

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

First, when an image is printed by an electrophotographic recording apparatus, if the surface potential of the photosensitive member after exposure changes or the charged state of the developer changes due to the difference in the operating environment of the apparatus, the image density of the surface image is changed. And the line width of the line image changes.

Therefore, the influence of the environment in which the device is used on the image quality will be described with reference to FIGS. FIG. 4 is a diagram showing the relationship between the exposure amount applied to the photoconductor and the photoconductor surface potential after the exposure. The exposure amount is represented by the product of laser output and laser irradiation time. Since the electrophotographic recording apparatus described here has a constant laser scanning speed, the laser output is proportional to the exposure amount applied to the photosensitive member. It can be seen from FIG. 4 that the surface potential becomes lower as the exposure amount applied to the photoconductor becomes larger. Further, even if the photoconductors of the same material have different sensitivities between the production lots, the surface potential of the photoconductors having a higher sensitivity is lowered when the photoconductors are irradiated with the same exposure amount. The figure shows the sensitivity characteristics of two photoconductors having different sensitivities.

FIG. 5 shows the photosensitive member surface potential after exposure and 480 dpi (dots) when the developing bias voltage is changed.
The relationship between the dot density (per inch) and the line width of one dot line is shown. Here, V1 to V3 are development bias voltages, and V1 <V2 <V3. The relationship between the surface potential and the line width does not change even when the sensitivity of the photoconductor is different. In the case of reversal development in which toner adheres to the exposed position, the lower the surface potential of the photoreceptor after exposure, the easier toner adheres during development, so the line width becomes thicker. Also, the line width increases as the bias voltage applied to the developing device increases. It can be seen from FIGS. 4 and 5 that the line width increases as the exposure amount increases and the bias voltage increases. Further, when the same exposure amount is applied to the photoconductor, the higher the sensitivity of the photoconductor, the lower the surface potential and the thicker the line width.

FIG. 6 is a diagram showing the relationship between the surface potential of the photosensitive member after exposure and the density of the surface image. V1 and V as in FIG.
2 is a developing bias voltage, and V1 <V2. As with the line image, the lower the surface potential of the photoconductor is, the easier the toner is attached to the photoconductor during development, so that a high-density image can be obtained.

Further, the charge amount of the toner may change depending on the usage period of the developer. Generally, the smaller the charge amount of the toner, the easier the toner is to adhere to the photoconductor, so the line width of the line image becomes thicker and the area image becomes darker. The present invention has revealed that a good image can be obtained by performing exposure and development a plurality of times based on the measurement results of the above characteristics, and provides a configuration and the like thereof.

Example 1 Since black toner has a small light transmittance, it suffices if the toner having a required layer thickness (hereinafter referred to as the minimum toner layer thickness) is filled in all the printing areas on the recording paper. An image with various densities can be obtained. However, at the edge portion of the line image or the plane image, the electric potential change on the surface of the photoconductor becomes large, so that the electric field at the time of development becomes large, and the toner is more likely to adhere than at the central portion of the plane image. Generally, when a printed image is obtained by one exposure and one development, the printed image has a toner layer thickness distribution. Figure 1
1 (a) is an example of a cross-sectional view of a toner layer of a surface image obtained by the above method. In order to obtain an image having a sufficient density over the entire area of the surface image, it is necessary to adhere toner having a minimum toner layer thickness or more to the entire area. In that case, the potential gradient of the electrostatic latent image is large at the edge of the surface image portion,
Since a large amount of toner adheres during development, the toner layer thickness is thicker than in the central portion of the surface image. On the other hand, in the line image portion, the potential gradient of the electrostatic latent image is large similarly to the edge portion of the surface image portion, and the toner layer thickness is equal to or larger than the minimum toner layer thickness. There is a problem that there is a difference in toner layer thickness between the line image and the surface image, or an image in which the distribution of the toner layer thickness is large among the surface images is inferior in image quality. Therefore, it is necessary to improve the image quality by forming a toner layer having a uniform layer thickness by reducing the exposure amount applied to the photoconductor at the edge portion of the line image or the plane image. Further, the amount of toner consumption can be saved by printing with the minimum required amount of toner.

Next, the outline of the printing method will be described with reference to FIG.

FIG. 1 is a sectional side view showing the structure of an electrophotographic recording apparatus according to one embodiment of the present invention.

Reference numeral 1 is an image recognition circuit, 2 is an exposure device control circuit, 3 is a first exposure device, 4 is a second exposure device, 5 is a first developing device, and 6 is a second developing device. The surface of the photoconductor drum 10 is uniformly charged by the charger 11, and the image recognition circuit 1 recognizes what kind of image the image information from the computer is. The exposure device control circuit 2 controls the first exposure device 3 and the second exposure device 4 so that the photosensitive drum 10 is exposed with an appropriate exposure amount.
The appropriate exposure amount will be described later. The first exposure device 3 exposes the photosensitive drum 10 with a constant exposure amount regardless of the type of image. The first developing device 5 develops the electrostatic latent image formed by the first exposure device 3. The exposure device control circuit 2 causes the second exposure device 4 to operate only the surface image portion other than the edge portion at an appropriate timing based on the recognition result of the image recognition circuit 1. Here, the exposure amount in the second exposure device 4 is set to the first
The exposure amount is set larger than the exposure amount of the exposure device 3. If the amount of exposure at this time is about the same as the amount of exposure in the conventional electrophotographic apparatus, the same effect as reducing the amount of exposure to the edge portions of the line image portion and the surface image portion can be obtained. Next, the second developing device 6 develops the electrostatic latent image formed by the second exposure device 4. After the toner image is formed by the development, the photosensitive drum 10 is further rotated, and the toner image is transferred onto the recording paper 15 by electrostatic force at a position facing the transfer device 14. The recording paper 15 is conveyed to the fixing device 17 by the conveying means 16, and the toner image is fused on the recording paper 15 by heat in the fixing device 17. In this way, an image is formed on the recording paper 15. After that, the recording paper 15 is sent out onto the tray (not shown) by the conveying means 16. On the other hand, after the toner image is transferred onto the recording paper 15, the photosensitive drum 10
The surface is erased by turning on the eraser lamp 18. The toner remaining on the surface of the photosensitive drum 10 is removed by the cleaner 19. After that, the photosensitive drum 10 further rotates, and the above process is repeated to perform continuous printing.

With the above arrangement, a good image can be printed from the image signal in which the surface image and the line image are mixed.

FIG. 10 shows the construction of an embodiment of a control device for controlling the exposure means used in the present invention. 121 is a host device, 122 is image data, 123 is a memory, 124 is a pattern recognition device, 125 is a database, 126 is a current converter, and 127 is a light emitting device. The image data 122 sent from the host device 121 such as a large-sized computer or OA device to the electrophotographic recording device is pixel data obtained by sampling the image by an appropriate method and quantized. In order to achieve the object of the present invention, it is necessary to determine the amount of light emitted from the light emitting device 127 in the electrophotographic recording device. For that purpose, first, it is necessary to recognize what kind of image the image data 122 is. The pattern recognition device 124 uses the image data 1 stored in the memory 123.
22, the recognition target pixel and the peripheral pixel data are used to recognize what part of the image the recognition target pixel is. The more pixel data you reference, the more accurate
And various recognition is possible.

FIG. 7 shows an example of a method for recognizing a plane image.
Reference is made to a total of 25 pieces of pixel data including the recognition target dot shown in a black frame and its surrounding reference dots. If all of the 25 pixel data are "1", that is, "printing dots", the recognition target pixel is a surface image. Recognized as part of If it is not recognized as a part of the plane image, it is recognized as a part of the line image. In the above recognition method, since the two dots at the edge of the surface image portion do not satisfy the recognition standard for the surface image, they are recognized as a line image instead of being recognized as a surface image, and the second exposure is not performed. Since the edge portion of the surface image portion is a portion to which toner easily adheres, it is a portion to reduce the amount of exposure to be irradiated to reduce the toner adhesion amount. Therefore, it does not matter even if the two dots at the edge of the surface image portion are recognized as the line image portion and the second exposure is not performed.

By the way, the printed image includes an isolated point image in addition to the surface image and the line image. Since the isolated point image is not a surface image, the second exposure is not performed. However, in the part of the isolated dot image on the photoconductor, 1
The isolated point-like low potential portion formed on the surface of the photoconductor after the second exposure is buried in the surrounding high potential portion, and is not printed as an isolated point image during development. Therefore, it is necessary to expose the isolated point image a second time to facilitate printing of the point image. Also in the line image, the thin diagonal lines weaken the connection between the dots, so that it may be difficult to print as in the case of the isolated point image. Also in this case, it is necessary to perform the second exposure similarly to the isolated point image.

FIG. 8 shows an example of recognizing a dot image, and FIG. 9 shows an example of recognizing a diagonal line. Similar to the case of FIG. 7, nine pixel data including the recognition target dot indicated by a black frame and its surrounding reference dots are referred to. If the array of FIG. 8 is satisfied, the recognition target dot is recognized as an isolated point image. If the array shown in FIG. 9 is satisfied, the dots to be recognized are recognized as shaded areas, and the second exposure is performed.

The amount of exposure for a surface image and the amount of exposure for an isolated point image or diagonal line are different depending on the developing conditions, so the amount of exposure is determined by the state of printing. The exposure amount is determined in advance by an experiment and stored in the database 125 shown in FIG.

Next, an outline of a method for changing the exposure amount according to the type of image to be printed will be described with reference to FIG. Figure 3
FIG. 9 is a diagram showing a method of recognizing the type of image to be printed and adjusting the exposure amount. Reference numeral 50 is image data, 51 is an image recognition circuit, 52 is a light emitting device, 53 is a mirror, and 54 is a mirror motor. The image data 50 from the computer or the like is recognized by the image recognition circuit 51 as to what kind of image the image indicated by the information is. An electric signal is output according to the recognition result to drive the light emitting device 52. The light is irradiated onto the photoconductor 10 via the mirror 53 rotated by the motor 54. By thus changing the exposure method depending on the type of image, it is possible to print a surface image with sufficient density and a line image with a predetermined resolution.

A method of printing an image using the above-mentioned exposure means will be described below.

Development is carried out by using two developing devices, and the second developing device 6 develops so that the toner layer thickness distribution after the second development is equal to the layer thickness distribution after the first development. The method of setting the conditions is described. In order to make the toner layer thickness distribution uniform, the toner should be attached at the position where the toner should not be attached at the time of the first development during the second development. Is to scrape off the toner at the position where excessively adhered at the time of the second development. When the first exposure is performed on all the images with a small exposure amount, there is a position where the toner does not adhere to the surface image portion other than the edge portion during the first development. The surface image portion other than the edge portion is exposed with an exposure amount larger than the first exposure amount. After the second exposure, the second development is performed, and the toner is attached to the position where the toner was not attached during the first development. . In the method of recognizing the surface image portion shown in FIG. 7, the two dots at the edge of the surface image portion are not recognized as a surface image, and the edge to which a large amount of toner tends to adhere is not exposed for the second time. At the time of the second development, new toner hardly adheres to the edge of the surface image. Here, the second developing device 6
Is set to be lower than the bias voltage of the first developing device 5, the toner is attached only to the position where the toner should originally be attached, and the toner is attached from the position where the excessive toner is attached to the second developing device 6. Can be collected. That is, since the edge portions of the line image portion and the surface image portion pass through the second developing device 6 without being exposed by the second exposure device 4, the toner does not adhere, and conversely, the toner excessively adheres. Only in this case, the toner is scraped off and collected by the second developing device 6. The developing gap of each developing device for forming such a uniform toner layer is set as follows.
When the distance between the photoconductor drum 10 and the developing roll of the developing device is wide, the electric field formed between the two during the development gathers at the re-approaching portion, so that a line image with a predetermined resolution can be easily obtained.
On the other hand, when the distance is small, the electric field formed during development becomes close to parallel in the development area, so that the surface image can be developed uniformly. The first developing device 5 is set so that a line image is printed with high quality, and the distance between the second developing device 6 and the photoconductor drum 10 is set to the distance between the first developing device 5 and the photoconductor drum 10. By setting the width to be narrower than that of the above, it is possible to print with high quality and uniform toner layer thickness.

FIG. 11 (b) shows a cross section of the toner layer in the surface image portion in the case of developing by the above method. The left side of the figure is a toner layer formed by the first developing device 5,
The right side shows the toner layer formed after passing through the second developing device 6. In this case, the thickness of the toner layer at the edge of the first developing device 5 is appropriate and the toner at the center is insufficient. By the second developing device 6, the toner is attached to the central portion without changing the thickness of the toner layer on the edge portion.

The toner layer thickness during development is determined by the surface potential of the photosensitive drum 10 after exposure, the developing bias voltage, the toner charge amount, and the like. Since the surface potential of the photosensitive drum 10 after exposure is determined by the exposure amount of the photosensitive drum 10, the developing bias is fixed, and if the toner charge amount does not change, the exposure amount is determined to determine the exposed portion. The toner layer thickness after development can be determined.

An appropriate exposure amount in the exposure device will be described. The appropriate exposure amount in the first exposure device 3 is the exposure amount at which the toner layer thickness at the edge of the surface image portion becomes the minimum toner layer thickness when the development in the first developing device 5 is completed, The line image is also exposed with this exposure amount. As a result, the edge heights of the surface image portion and the toner heights of the line image portion match, and the toner layer thicknesses of the two even after the development by the second developing device 6. The exposure amount in the first exposure device 3 is set by an experiment based on the magnitude of the bias voltage of the first developing device 5 and the sensitivity characteristic of the photoconductor. The appropriate exposure amount in the second exposure device 4 is determined by the time when the development in the second development device 6 is completed.
The amount of exposure is such that the total toner layer thickness of the surface image portion becomes the minimum toner layer thickness. FIG. 11B is a diagram showing the state of the toner layer thickness when printing is performed by the above-described exposure method.

By the way, depending on the charged state of the developer,
When developing with the second developing device 6, the toner on the edge of the surface image portion may be scraped off. In that case, the exposure amount in the first exposure device 3 is increased by the thickness of the toner layer scraped off. At the time when the development by the first developing device 5 is completed, the thickness of the toner layer at the edge portion is large, the toner at the edge portion is scraped off at the time of the second development, and the toner is replenished to the toner-deficient portion in the central portion. To be done. FIG. 11C shows the toner layer thickness in this case.

Embodiment 2 In Embodiment 1, there is a problem that the cost becomes high because two exposure devices and two development devices are used. In FIG. 1, the second exposure device 4 and the second developing device 6 are removed, and the problem is solved by printing by exposing and developing twice each while the photosensitive drum 10 rotates twice.

FIG. 2 is a sectional view of the electrophotographic recording apparatus of this embodiment. First, in the first exposure device 3, the photosensitive drum 20 is exposed with a constant exposure amount regardless of the type of image.
The first developing device 5 develops the electrostatic latent image formed by the first exposure device 3. After that, the transfer device 14 is retracted from the photoconductor drum 10, the photoconductor drum 10 is advanced without transferring the toner image on the recording paper 15, the eraser lamp 18 is turned off, and the cleaner 19 is also retracted. When the photosensitive drum 10 enters the second rotation, the exposure apparatus control circuit 2
On the basis of the recognition result of the image recognition circuit 1, the first exposure device 3 is operated at an appropriate timing so that only the surface image portion is exposed. Here, the exposure amount in the first exposure device 3 is set to be larger than the exposure amount in the first exposure, and the first developing device 5 develops the electrostatic latent image formed by the first exposure device 3.
At the time of the second development, the bias voltage setting device 7 controls the bias voltage to be smaller than that at the first development, and the development gap is controlled to be smaller than that at the first development. You can After that, the transfer device 14 is brought close to the photoconductor drum 10 to transfer the toner image onto the recording paper 15, and the conveying device 16 conveys the recording paper 15 to the fixing device 17, and the fixing device 17 forms the toner image on the recording paper. Weld on 15. After the transfer of the toner image, the eraser lamp 18 is turned on to eliminate the charge on the surface of the photosensitive drum 10, and the cleaner 19 is brought close to the photosensitive drum 10 to remove the toner remaining on the surface. How to set the light intensity,
This is the same as in the first embodiment.

Example 3 In this example, an example of a method of setting the light amount when the sensitivity changes depending on the usage state of the photoconductor will be described.

Since the sensitivity decreases as the photoconductor is used for a long time, the surface potential of the photoconductor used for a long time becomes higher than that of a new photoconductor when the same exposure amount is applied. Therefore, in order to obtain a line image with the same width, the exposure amount for a new photoconductor and the exposure amount for a photoconductor that has been used for a long time must be set differently. Since the degree of reduction in the sensitivity of the photoconductor depends on the printing amount, a counter for recording the printing amount is provided in the electrophotographic recording device, and the first and second photoconductors are irradiated according to the printing amount. It is necessary to correct the exposure amount to be used. In advance, measure the deterioration characteristics of the photoconductor according to the printing amount, find the appropriate exposure amount for each 50,000 page printing,
By storing the data in the database 125 shown in FIG. 10, it is possible to obtain the effect of always obtaining a constant image quality.

Embodiment 4 In this embodiment, an example of a method for setting the light quantity when the toner charge quantity changes depending on the usage state of the developer will be described.

The charge amount of the toner changes as the developer is used for a long time. The toner adhesion amount depends on the photoreceptor surface potential after exposure and the toner charge amount.Therefore, even if the photoreceptor surface potential after exposure is kept constant by setting the exposure amount constant, the toner adhesion amount depends on the usage of the developer. Changes,
The toner layer thickness of the image changes. Therefore, it is necessary to provide a counter for recording the printing amount in the electrophotographic recording apparatus and correct the exposure amount applied to the first and second photoconductors according to the printing amount. By previously measuring the charge amount change characteristic of the developer according to the printing amount, obtaining an appropriate exposure amount for each printing of 5,000 pages, and storing it in the database 125 of FIG. The effect of being obtained is obtained.

Embodiment 5 This embodiment describes an example of a light quantity setting method corresponding to the lot variation of the photoconductor sensitivity.

When the photosensitive member is used for a long time, the surface potential of the photosensitive member after exposure is not lowered to a predetermined potential by only lowering the sensitivity and increasing the exposure amount, or the surface of the photosensitive member is damaged. You will need to change your body. However, the sensitivities of the photoconductors are not always the same before and after the photoconductors in the electrophotographic recording apparatus are replaced. The variation in the sensitivity of the photoconductor due to the difference in lot is not so small that it can be ignored, and the printed images differ with the same exposure amount. Even if another photoconductor having a different sensitivity is used, if the conditions other than the sensitivity are the same, the relationship between the surface potential of the photoconductor shown in FIG. 5 and the line width of the line image and the surface potential shown in FIG. Since the relationship between image density and image density does not change,
If the relationship between the exposure intensity applied to the photoconductor as shown in FIG. 4 and the surface potential of the photoconductor at that time is measured in advance, an appropriate exposure amount for illuminating the photoconductor after replacement can be obtained. By rewriting the contents of the database 125 or replacing the ROM of the database 125 when the photoconductor of the electrophotographic recording apparatus is replaced, the effect of always obtaining a constant image quality can be obtained.

Embodiment 6 In Embodiments 4 and 5, the exposure amount is set according to the characteristics of the photoconductor that is grasped in advance, and the exposure amount is stored in the database for printing. This embodiment describes a method of measuring the characteristics of the photoconductor and the temperature of the photoconductor surface and determining the exposure amount based on the result.

The sensitivity of the photoconductor changes depending on the temperature of the photoconductor surface. Further, as described in the third embodiment, the sensitivity of the photoconductor also changes depending on the usage state of the photoconductor. When the exposure amount is set based on the sensitivity characteristic of the photoconductor that is grasped in advance, the expected image is not always obtained.
Therefore, as indicated by the dotted line in FIG.
A surface potential measuring device 40 is installed between the developing device 5 and a mechanism for measuring the sensitivity characteristic of the photoconductor as shown in FIG. 4 is provided, and the temperature of the photoconductor surface is measured to expose the photoconductor. It is necessary to obtain an appropriate exposure amount that
Before operating the electrophotographic recording device, etc., obtain the sensitivity characteristics of the photoconductor by automatically measuring the relationship between the exposure amount and the photoconductor surface potential after exposure, and the photoconductor surface temperature using a thermocouple or the like. , Calculate an appropriate exposure amount and store it in the database.
As a result, a constant image quality can be obtained even if the use environment of the electrophotographic apparatus changes.

[0040]

According to the present invention, since a device for storing the relationship between the exposure amount applied to the photosensitive member and the surface potential and the combination of the developing bias and the standard exposure amount is stored, a constant image quality can be obtained. There is an effect. Further, even when the photoconductor or the developer of the electrophotographic recording apparatus is replaced, an appropriate exposure amount is stored in the database in advance, so that there is an effect that a certain image quality can be obtained. Further, since a mechanism for measuring the sensitivity characteristic of the photoconductor is provided and means for calculating and storing an appropriate exposure amount is provided, there is an effect that a constant image quality can be obtained even if the use environment of the electrophotographic apparatus changes. .

[Brief description of drawings]

FIG. 1 is a sectional side view showing the configuration of an electrophotographic recording apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional side view showing the configuration of an electrophotographic recording apparatus according to another embodiment of the present invention.

FIG. 3 is a diagram showing a method of recognizing an image type and adjusting an exposure amount.

FIG. 4 is a diagram showing the relationship between the exposure intensity and the surface potential of the photoconductor after exposure.

FIG. 5 is a diagram showing a relationship between a surface potential of a photoconductor after exposure and a line width.

FIG. 6 is a diagram showing the relationship between the surface potential of a photoreceptor after exposure and the density of a surface image.

FIG. 7 is a diagram showing an example of recognizing a plane image.

FIG. 8 is a diagram showing an example of recognizing an isolated point image.

FIG. 9 is a diagram showing an example of recognizing diagonal lines.

FIG. 10 is a diagram illustrating a control device that controls an exposure amount.

FIG. 11 is a cross-sectional view of a toner layer of a surface image.

[Explanation of symbols]

1 ... Image recognition circuit, 2 ... Exposure device control circuit, 3 ... First exposure device, 4 ... Second exposure device, 5 ... First developing device, 6 ... Second developing device, 10 ... Photosensitive drum, 11 ... Charging Bowl, 12
... exposure means, 13 ... developing device, 14 ... transfer device, 15 ... recording paper, 16 ... conveying means, 17 ... fixing device, 18 ... eraser lamp, 19 ... cleaner.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Kikuchi 2-6-2 Otemachi, Chiyoda-ku, Tokyo Nititsu Koki Co., Ltd.

Claims (12)

[Claims] 1. An electrophotographic recording apparatus comprising at least a photoconductor, an exposing means for exposing the photoconductor on the basis of input pixel data to form an electrostatic latent image, and a developing means for developing the electrostatic latent image. An image recognition means for recognizing the type of image from the input pixel data is provided, and at the first exposure, all image portions are exposed with a constant exposure amount regardless of the type of image, and an electrostatic latent image is formed on the photoconductor. And the electrostatic latent image is developed by the developing means, and the developed photoconductor is exposed to a larger amount of light than the first exposure for a specific type of image portion based on the output of the image recognition means. An electrophotographic recording apparatus, wherein the electrostatic capacity of the developed image is changed by re-exposure and the image is formed by re-developing. 2. The electrophotographic recording apparatus according to claim 1, wherein the specific type of image is a surface image. 3. The electrophotographic recording apparatus according to claim 2, wherein the image of the specific type includes isolated points. 4. The electrophotographic recording apparatus according to claim 2, wherein the specific type of image includes oblique lines. 5. The photosensitive member according to claim 1, wherein one photosensitive member is provided, two first and second exposing units and two first and second developing units are arranged, and the first exposing unit is The electrostatic latent image formed by the first exposure device is exposed by a constant exposure amount, and the electrostatic latent image formed by the first exposure device is developed by the first developing device, and the second exposure device is of a specific type based on the output of the image recognition device. Forming an electrostatic latent image of the image, and developing the electrostatic latent image of the specific type by a second developing unit. 6. The electrophotographic recording apparatus according to claim 1, wherein the exposure amount applied to the photoconductor is changed according to the degree of use of the photoconductor. 7. The electrophotographic recording apparatus according to claim 1, wherein an exposure amount applied to the photoconductor is set according to a change in sensitivity of the photoconductor. 8. The device according to claim 1, further comprising means for measuring a sensitivity characteristic of the photoconductor and means for calculating an exposure amount applied to the photoconductor on the basis of the measured sensitivity characteristic. Electrophotographic recording device. 9. The electrophotographic recording apparatus according to claim 5, wherein the distance between the second developing means and the photoconductor is set narrower than the distance between the first developing means and the photoconductor. . 10. The electrophotographic recording apparatus according to claim 5, wherein the developing bias voltage of the second developing means is set smaller than the bias voltage of the first developing means. 11. The photosensitive member according to claim 1, further comprising: one exposing unit that exposes the photosensitive member to form an electrostatic latent image; and one developing unit that develops the electrostatic latent image. An electrophotographic recording apparatus which forms an image by performing a first exposure and development on the eye and a second exposure and development on the second rotation. 12. The method according to claim 11, wherein the developing condition of the developing means is set to the developing condition of the second developing when the first developing is finished, and the developing condition of the second developing is finished when the second developing is finished. An electrophotographic recording apparatus, wherein the developing condition of the developing means is controlled so as to be reset to a developing bias voltage and a developing gap at the first developing.