JPH1195528A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device excellent in quality by achieving enviromental protection and making the characteristics of a service life an image quality compatible. SOLUTION: It is decided whether image data after being transmitted to a data deciding circuit 6 is binary or multilevel data. When the image data is decided as the binary data, instructions to execute the application of a DC bias (DC electrification) are transmitted as a signal 10 to a high voltage control substrate, to electrify the surface of a photoreceptor by a DC electrifying system. When the decided data is the multilevel data, the instructions to apply an AC bias or an AC+DC bias are transmitted to electrify the surface to the photoreceptor by an AC or AC+DC electrifying system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital image forming apparatus using an electrophotographic system.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus of this type is provided with a photoreceptor, and forms a latent image on the photoreceptor based on obtained image data, and then develops the latent image. Transfer on a sheet.

In order to form a latent image on the photoreceptor, a charging device for charging the surface of the photoreceptor is provided. As a charging method using the charging device, a non-contact charging method such as corona charging or a blade charging method is used. And a contact charging method such as a roller charging method.

In recent years, a contact charging system such as a roller charging system is often used as a countermeasure against environmental pollution.

When this roller charging system is used, A
There are an AC charging system for applying a C + DC bias and a DC charging system for applying a DC bias. Conventionally, it has been configured to form a latent image using any one of these charging systems.

[0006]

However, in the case of the above-mentioned prior art, there are the following problems regardless of whether the AC charging system is used or the DC charging system is used. .

[0007] In the case of the AC charging system, although the image quality is excellent, the surface layer of the photoreceptor is greatly abraded compared to other charging systems, and the photoreceptor must be replaced frequently.
There is a problem that the durability life is short.

[0008] In the case of the DC charging system, although the service life is excellent, the charging ability changes due to the surface layer of the charging roller and the resistance of the roller, resulting in poor image quality from the beginning. Further, the image is further deteriorated due to the change in the resistance of the roller, and stripes and unevenness may occur particularly at an intermediate density (intermediate potential) portion called halftone.

For this reason, a roller cleaning mechanism and a control mechanism based on a change in resistance value are required. Further, when high image quality (a model that emphasizes halftone images) is required, there is a problem that this charging method cannot be employed. Was.

As described above, in the case of the roller charging system in the prior art, the long life and high image quality cannot be satisfied at the same time, and either the life or the image quality has to be sacrificed.

If another charging method such as corona charging is adopted, environmental measures must be sacrificed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to achieve environmental measures and achieve both excellent life and image quality to achieve excellent quality. An object of the present invention is to provide an image forming apparatus.

[0013]

According to the present invention, in order to achieve the above object, a charging method for charging the surface of a photoreceptor by bringing a charging member into contact with the charging member is a DC charging method, an AC charging method, or an AC + DC charging method. Switching means for switching to any one of the charging methods is provided.

Therefore, by providing the switching means, it is possible to switch to the DC charging system when giving priority to the life, and to switch to the AC charging system or the AC + DC charging system when giving priority to the image quality.

It is preferable that a determination means for determining the number of gradations of the image data to be sent is provided, and the switching means is switched according to the determination result of the determination means.

Further, it is possible to provide an identification means for identifying the type of input image data, and to switch the switching means according to the identification result of the identification means.

Further, it is possible to provide a selecting means for selecting an image mode of an image to be formed, and to switch the switching means in accordance with a result of the selection by the selecting means.

Further, the switching by the switching means can be arbitrarily set.

[0019]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, shape, relative arrangement, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

(First Embodiment) An image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1, 2 and 3. FIG.

FIG. 1 is a block diagram showing main functions of image processing of the image forming apparatus according to the first embodiment of the present invention, and FIG. 2 is a block diagram showing functions of main parts in the block diagram of FIG. FIG. 3 is an explanatory diagram of an image forming process of the image forming apparatus according to the first embodiment of the present invention.

As a digital image forming apparatus using an electrophotographic system, for example, there are a copying machine, a printer, a facsimile machine, and a device having all of these functions, but these are known technologies. The description is omitted, and only the image forming process will be briefly described with reference to FIG.

First, the photosensitive member 20 is uniformly charged by the charging means 30.

Then, a laser L based on the obtained image information, such as a read document image or an image sent from the outside, is irradiated onto the photoconductor 20 to form a latent image.

Next, the latent image is developed (usually a toner image) by the developing means 40.

Then, this development is transferred by the transfer means 50 onto the sheet conveyed in the direction indicated by the dotted arrow in the drawing.

The sheet on which the image has been transferred is conveyed further downstream and fixed as a permanent image by fixing means (not shown).

The above is the general image forming process.

Here, in this embodiment, a roller charging system, which is a contact charging system, is adopted as a measure against environmental pollution, and a charging roller as a charging member is brought into contact with the surface of the photoconductor 20 to be charged. .

Next, the image processing will be described with reference to the block diagram shown in FIG.

First, the analog processor circuit 1 converts analog data of a document image read by a photoelectric conversion element such as a CCD into digital data.

Then, by the shading circuit 2,
The image data digitalized by the analog processor circuit 1 is corrected for a CCD, a lens, an illumination lamp, and the like.

Next, the whole processing circuit 3 scales, moves, mirrors, italics, repeats, folds, etc. the image data corrected by the shading circuit 2 or the image data sent from the external input data 9. Is performed.

Thereafter, the pattern processing circuit 4 performs processing such as negative / positive inversion, trimming and masking on the image data processed by the overall processing circuit 3.

Here, the image data up to the pattern processing circuit 4 is luminance data having a linear characteristic with respect to the amount of reflected light from the original, whereas the density felt when the original is visually observed is the amount of reflected light. Is not linear, it is necessary to correct it and convert it to luminance data and density data.

The density processing circuit 5 converts the image data up to the pattern processing circuit 4 from the luminance data into density data, and additionally changes the density (copy density key on the operation unit), and the AE measurement results. Density correction is performed in a copy mode (photo mode and text mode).

The data determination circuit 6 which is a determination means which is a feature of the present embodiment, the image data up to the density processing circuit 5 has a gradation number of 2 for the image data.
It is determined whether the data is value data or multi-value data.

Next, the D / A conversion circuit 7 converts the digital data so far into analog data in order to convert the digital data into a laser output value.

Then, the converted analog data is sent to the laser driver board 8 and the laser driver board 8
The laser is irradiated onto the photoconductor 20 according to the image information.

Reference numeral 9 denotes a facsimile machine (hereinafter referred to as FA).
X) and an external input data circuit for processing image data sent by input means other than copying such as a laser beam printer (hereinafter referred to as LBP). This is a signal sent to the high-voltage control board which constitutes the switching means for determining the charging method depending on whether the image data is binary data or multi-valued data.

Next, the determination of the charging method will be described.

As described above, the image sent to the data determination circuit 6 via the analog processor circuit 1, the shading circuit 2, the external input data circuit 9, the overall processing circuit 3, the pattern processing circuit 4, and the density processing circuit 5 It is determined whether the data is binary data or multi-valued data as shown in FIG.

If the image data determined here is binary data, the signal 10 to the high voltage control board is
A command to apply C bias (DC charging) is sent and D
The surface of the photoconductor 20 is charged by the C charging method.

If the determined data is multi-valued data, a command to apply an AC bias or an AC + DC bias is sent, and the AC charging method or A
The photoconductor 20 is charged by the C + DC charging method.

As described above, the number of gradations of image data (in this embodiment, binary data or multi-valued data) is determined, and DC charging, AC or AC + D is performed according to the determination result.
It is configured to switch to C charging (in the present embodiment, DC charging is used for binary data, and AC or AC + DC charging is used for multi-valued data).

Therefore, in the case of the number of gradations at which sufficient image quality can be obtained by DC charging (or image quality is not so required) (in the case of binary data in the present embodiment), DC Longer life can be prioritized as the charging method.

However, even in the case of multi-valued data, when the number of gradations is low (4 gradations, 8 gradations, etc.), a DC charging system may be used.

In the case of the number of gradations for which image quality is required (in the case of multi-valued data (especially in the case of high gradation) in the present embodiment), priority is given to image quality as an AC charging method. (Particularly, it is possible to prevent poor image quality in the halftone density portion).

As described above, even in a digital image forming apparatus using a contact charging system such as roller charging as an environmental measure, charging is switched in accordance with image data, so that charging can be performed in an appropriate system corresponding to each. It is possible to achieve both longevity and image quality.

In this embodiment, the case where the threshold value for switching the charging system is binary or not (multi-valued) has been described. However, the threshold value is not limited to this, and the threshold value is not limited to four values. The threshold value for determination may be determined based on image data that does not require gradation, such as eight values or less, and data that does not require gradation, such as eight or less.

In the above description, the case of so-called primary charging has been described. However, the present invention is not limited to this.
It can be applied wherever charging is required,
For example, it is also preferable to apply the present invention to a transfer charging portion.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention. In the first embodiment, the configuration in which the number of gradations of the image data is compared with the threshold value and the charging method is switched in accordance with the result of the determination has been described. The configuration in which the type of data is identified and the charging method is switched according to the identification result is shown. Other configurations and operations are the same as those of the first embodiment, so that the same components are denoted by the same reference numerals and description thereof will be omitted.

FIG. 4 is a diagram showing a relationship between image data and a charging system (applied bias) of the image forming apparatus according to the second embodiment of the present invention.

In this embodiment, the charging system (applied bias) is identified by identifying the input image data by an identification means (not shown) without using the data determination circuit 6 in FIG. 1 described in the above embodiment. ).

That is, since the number of gradations is usually determined depending on the type of input image data, this is used.

Hereinafter, the present embodiment will be described with reference to FIG.

If the input image is a copy (copy) as shown in FIG. 4 and the copy is output using multivalued data, the reproducibility of the halftone density portion is required. In such a case, the charging method is determined to be the AC charging method or the AC + DC charging method at the same time as performing the copy job.

Next, when the input image is a facsimile,
Normally, in FAX, it is binary, and the pixel unit is PEL. However, when this is output by copy or LBP, the data is d
Data converted into units of pi (dpi conversion or resolution conversion) is used.

At this time, the converted data becomes multi-value data. When the main body does not handle multi-valued data but uses all binary data, there is a case where FAX data is also simulated as binary data. In this case, it is assumed that multi-valued data can be handled.

Therefore, even when FAX data is input, it is necessary to reproduce the halftone density.
A C charging system or an AC + DC charging system is used.

Next, when the input image is a printer, the printer data is (currently) usually binary data, so that when the printer data is input, it is not necessary to reproduce the halftone density. Therefore, the charging method is a DC charging method.

As described above, depending on the type of data of an input image, if the number of gradations of the data (in this embodiment, whether it is binary or multi-valued) is known in advance,
The charging method can be determined according to the type of image data, and by using this method, a mechanism for data determination is not required. Therefore, the configuration is simplified and the effect of cost reduction is obtained.

In the above description, copying is multi-valued, F
AX is multi-valued and the printer is binary, but in the opposite case, the charging method is reversed, so that the DC charging method is used for binary data and the AC is used for multi-valued data. What is necessary is just to perform a charging system.

The image data may be a file or the like in addition to the above. In such a case, the charging method may be determined in advance according to the type of data.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention. In the first embodiment, the configuration in which the number of gradations of the image data is compared with the threshold value and the charging method is switched in accordance with the result of the determination has been described. A configuration is shown in which the charging method is switched according to the result. Other configurations and operations are the same as those of the first embodiment, so that the same components are denoted by the same reference numerals and description thereof will be omitted.

FIG. 5 is a diagram showing the relationship between the image mode (copy mode) and the charging system (applied bias) of the image forming apparatus according to the third embodiment of the present invention.

In the present embodiment, the charging system (applied bias) is determined by the selection result of the image mode (copy mode) selection unit (not shown) without using the data determination circuit 6 in FIG. 1 described in the above embodiment. ).

That is, when copying (copying), there are cases where the original is a character original containing only characters, a photograph original, or a character / photo original where characters and photographs are mixed. Therefore, the requirements for image quality are different, and the charging method is to be switched according to these requirements.

Hereinafter, the present embodiment will be described with reference to FIG.

As shown in FIG. 5, in the copy mode, even when multi-valued data is used for normal copy data, for example, in the case of a document including only characters, halftone density is not used, and Is close to binary data of whether or not hit. In some cases, multi-valued data may be slightly generated at the edge of the line, but ideally, the edges of the character should be sharp and binary.

Therefore, in a character mode which does not require halftone density, a DC charging system is used.

Conversely, in the photographic mode, reproducibility of halftone density is often required, and high image quality is required.

Therefore, in the case of the photograph mode, the AC system or A
A C + DC charging method is used.

In the character / photo mode in which characters and photos are mixed, it is desirable to use the same charging method as in the photo mode with priority given to the image quality of the photo.

As described above, even in the case of using as a copy, finer control can be performed by switching the charging method depending on the image mode.

In addition to the above-described modes, the printing method is set so that the charging method is changed depending on which of the printed copy (printed material is usually binary (halftone dot)) is given priority by DC charging or character / photo. Has the same effect.

(Fourth Embodiment) FIG. 6 shows a fourth embodiment of the present invention. In the first embodiment, the configuration in which the number of gradations of the image data is compared with the threshold value and the charging method is switched in accordance with the determination result has been described. Indicates that the charging method can be switched to an arbitrary charging method. Other configurations and operations are the same as those of the first embodiment, so that the same components are denoted by the same reference numerals and description thereof will be omitted.

FIG. 6 is a diagram showing the relationship between the setting mode and the charging method (applied bias) of the image forming apparatus according to the fourth embodiment of the present invention.

In the present embodiment, an arbitrary charging system can be arbitrarily set as desired by the operator without using the data determination circuit 6 in FIG. 1 described in the above embodiment. .

Hereinafter, the present embodiment will be described with reference to FIG.

As shown in FIG. 6, a setting mode is provided.
For example, if you want to output with high image quality, select the AC charging system or AC + DC charging system as the high image quality mode, and if you want to extend the life of the photoconductor and obtain cheaper output than the image quality, select the DC charging and charging system. Keep it.

When it is desired to use the image quality and the lifetime with the same emphasis, the fuzzy mode may be used in combination with the first to third embodiments.

This method can be arbitrarily set by a user or a service person, and can select either image quality or life.

[0084]

According to the present invention, since the surface of the photoreceptor is charged by contacting the charging member, environmental measures can be taken, and the charging method can be a DC charging method, an AC charging method, or an AC + DC charging method. By providing a switching means for switching to any one of them, the switching is switched to the DC charging system when priority is given to the life, and the switching is switched to the AC charging method or the AC + DC charging method when the image quality is prioritized. Quality and image quality can be compatible, and the quality is improved.

Here, the switching means can be switched according to the determination result of the determination means for determining the number of gradations of the image data to be sent.

The switching means can be switched according to the identification result of the identification means for identifying the type of input image data. In this case, the configuration can be simplified.

Further, the switching means can be switched according to the selection result of the selection means for selecting the image mode of the image to be formed.

Further, the switching by the switching means can be arbitrarily set as desired by the operator.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating main functions of image processing of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing functions of main parts in the block diagram of FIG. 1;

FIG. 3 is an explanatory diagram of an image forming process of the image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a relationship between image data and a charging method (applied bias) of an image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a relationship between an image mode (copy mode) and a charging method (applied bias) of an image forming apparatus according to a third embodiment of the present invention.

FIG. 6 is a diagram illustrating a relationship between a setting mode and a charging method (applied bias) of an image forming apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Analog processor circuit 2 Shading circuit 3 Overall processing circuit 4 Pattern processing circuit 5 Density processing circuit 6 Data judgment circuit 7 D / A conversion circuit 9 External input data circuit 10 Signal to high voltage control board 20 Photoconductor 30 Charging means

Claims (5)

[Claims] And a switching means for switching a charging method for charging the surface of the photosensitive member by contacting the charging member to one of a DC charging method, an AC charging method, and an AC + DC charging method. Image forming apparatus. 2. The image forming apparatus according to claim 1, further comprising a determining unit that determines the number of gradations of the image data to be sent, and switching the switching unit according to a result of the determination by the determining unit. 3. The image forming apparatus according to claim 1, further comprising an identification unit for identifying a type of input image data, wherein the switching unit is switched according to an identification result of the identification unit. 4. The image forming apparatus according to claim 1, further comprising a selection unit for selecting an image mode of an image to be formed, and switching the switching unit according to a selection result of the selection unit. 5. The image forming apparatus according to claim 1, wherein the switching by said switching means can be set arbitrarily.