JPH0990699A - Color image forming equipment - Google Patents

Abstract

The present invention uses an output value of a photosensor up to the output saturation, obtains a stable output value in a wide range, accurately measures the toner density, and based on this measurement result. By predicting the image density and adjusting the process conditions, a stable, high-quality image is always output without being affected by environmental changes. A control unit (3) controls the visualization unit (2) on the basis of the output of a temperature / humidity sensor (8) constituting the visualization unit (2), and a photoconductor drum (4) constituting the visualization unit (2). Then, after writing and developing a matrix pattern of N × M dots, the toner density of the matrix pattern is measured by the photosensor 9 constituting the visualization unit 2, and based on the measurement result,
The image density when the image is actually printed is predicted, and various process conditions are adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus used in a device for printing a color image such as a copying machine, a printer device, a facsimile device and the like.

[0002]

2. Description of the Related Art Conventionally, as a color image forming apparatus used in a device for printing a color image such as a copying machine, a printer device, a facsimile device, etc., there is a conventional Japanese Patent Laid-Open No. 6-13076.
The "image forming apparatus" disclosed in Japanese Patent No. 8 is known. In order to set various process conditions, this image forming apparatus creates a pattern on a photoconductor drum by a pattern creating section, develops the pattern on the photoconductor drum by a developing device, and then uses the photosensor to perform the above-mentioned process. In addition to measuring the toner density of the pattern, the potential sensor measures the potential of the portion where the pattern is formed on the photosensitive drum, and based on each of these measured values, the unit area in the portion where the pattern is formed Calculate the toner adhesion amount of. Then, based on this calculation result, the image density after printing is predicted, and the image density obtained by this prediction operation (predicted image density) is compared with the preset image target image density (target image density). The process conditions are adjusted so that the target image density is printed out.

[0003]

However, since such an image forming apparatus uses a solid pattern or the like as a toner pattern, there is a problem that it is not possible to measure a fine density change. Therefore, the present inventors have proposed a new image forming apparatus capable of solving such a problem. This image forming apparatus uses a pattern of N × M dots (matrix pattern) as a toner patch pattern, measures the density of the dot pattern with a photosensor, and predicts the image density based on the measurement result. By adjusting the process conditions, stable and high-quality images are always output without being affected by environmental changes. However, in this image forming apparatus, since the structure of the matrix pattern is not specified at all, if it is desired to accurately predict the image density, the toner color, elapsed time, temperature, humidity, etc. should be taken into consideration. However, at the time of image formation, it is necessary to write a matrix pattern having an optimum configuration on the photosensitive drum to detect the image density and the like.

In view of the above circumstances, the present invention uses the output values of the photosensor up to the output saturation, obtains a stable output value in a wide range, and accurately measures the toner density. By predicting the image density based on this measurement result and adjusting various process conditions, it is possible to always output a stable and high-quality image without being affected by environmental changes. Is intended to provide. Further, in claim 2, even if the dot density in the matrix pattern becomes high, the toner density is accurately measured by reducing the influence of the protruding amount of the recording dot on the pixel, and the image density is measured based on the measurement result. Aiming to provide a color image forming apparatus capable of always outputting a stable and high-quality image by predicting the density and adjusting various process conditions without being affected by environmental changes. There is.

According to the third aspect, a plurality of matrix patterns having different densities are used to accurately predict the image density to be printed out, and various process conditions are adjusted based on the prediction result. Accordingly, it is an object of the present invention to provide a color image forming apparatus that can always output a stable and high-quality image without being affected by changes in the environment. Further, in claim 4, by using a plurality of matrix patterns having different densities, the image densities to be printed out are accurately predicted, and various conditions of the process are adjusted on the basis of the prediction results, so that the environment It is an object of the present invention to provide a color image forming apparatus which can always output a stable and high-quality image without being affected by the change of

According to the fifth aspect of the present invention, a matrix pattern suitable for density measurement is formed in accordance with the difference in toner color so that it is not affected by the color difference and is not affected by the environmental change. An object of the present invention is to provide a color image forming apparatus capable of constantly outputting stable and high-quality images by adjusting various process conditions. Further, according to claim 6, the toner concentration is accurately measured without being affected by the change in the detection characteristics of the photosensor due to the time change, and the process conditions are adjusted based on the measurement result, thereby changing the environment. It is an object of the present invention to provide a color image forming apparatus that can always output a stable and high-quality image without being affected by the above.

Further, according to the present invention, even if the characteristics of the photosensitive drum change due to environmental temperature or the like, various process conditions can be adjusted without being affected by the characteristic changes of the photosensitive drum due to environmental changes. Accordingly, it is an object of the present invention to provide a color image forming apparatus that can always output a stable and high-quality image without being affected by changes in the environment. Further, in claim 8, the environmental temperature, the elapsed time,
Even if conditions such as the difference in toner color change, by selecting the optimum matrix pattern corresponding to this and adjusting the process conditions, it is always stable without being affected by environmental changes. An object of the present invention is to provide a color image forming apparatus capable of outputting a high quality image.

[0008]

In order to achieve the above-mentioned object, a color image forming apparatus according to the present invention, in claim 1, corresponds to a photosensitive drum rotatably and a plurality of color image forming signals. A latent image forming portion for forming an electrostatic latent image on the photosensitive drum, and a plurality of developing units for developing the electrostatic latent image on the photosensitive drum by a developer, for each color. In a color image forming apparatus that forms an electrostatic latent image on the photosensitive drum to obtain a color image, a pattern creating unit that creates an arbitrary N × M matrix dot pattern on the photosensitive drum. A photosensor for detecting the density of the dot pattern formed on the photosensitive drum, and a color image forming apparatus for changing various setting conditions based on the measurement values obtained by the photosensor. As a dot pattern generated by the over down creation unit is characterized by the use of the dot pattern to the output saturation of the photosensor.

According to a second aspect of the present invention, in the color image forming apparatus according to the first aspect, as the dot pattern created by the pattern creating section, the dot pattern arranged at the first position is used as a core to sequentially increase the weight. It is characterized by using dot patterns arranged in a line. According to a third aspect of the present invention, in the color image forming apparatus according to the first aspect, the dot pattern created by the pattern creating unit is a dot pattern formed in a matrix with a constant output power. There is.

According to a fourth aspect of the present invention, in the color image forming apparatus according to the first aspect, as the dot pattern created by the pattern creating section, the number of dots to be printed in the matrix is set to a fixed number, and the output power is set. It is characterized by using a dot pattern that changes.
According to a fifth aspect of the present invention, in the color image forming apparatus according to the first aspect, a dot pattern that is changed according to a toner color is used as the dot pattern created by the pattern creating unit.

According to a sixth aspect of the present invention, in the color image forming apparatus according to the first aspect, as the dot pattern created by the pattern creating section, a dot pattern changed over time is used. It has a feature. According to a seventh aspect, in the color image forming apparatus according to the first aspect, a temperature / humidity sensor is provided in the apparatus, and the pattern forming unit is configured to operate according to an environmental condition obtained by a measurement operation of the temperature / humidity sensor. It is characterized by changing the created dot pattern. According to an eighth aspect, in the color image forming apparatus according to the first aspect, the dot pattern created on the photosensitive drum by the pattern creating section is selected to detect the density.

According to the above structure, in the first aspect of the present invention, the photoconductor drum is configured to be rotatable, and the latent image is formed on the photoconductor drum in response to a plurality of color image forming signals. And a plurality of developing units for developing an electrostatic latent image on the photosensitive drum with a developer,
Of the color image forming apparatus for forming a color image by forming an electrostatic latent image on the photosensitive drum for each color,
A pattern creating section for creating an arbitrary N × M matrix dot pattern on the photoconductor drum, a photosensor for detecting the density of the dot pattern created on the photoconductor drum, and a measurement obtained by this photosensor. In the color image forming apparatus that changes various setting conditions based on the value, by using the dot pattern up to the output saturation of the photo sensor as the dot pattern created by the pattern creating unit, the output saturation of the photo sensor Output value up to, thereby obtaining a stable output value in a wide range, accurately measuring the toner density, predicting the image density based on this measurement result, and adjusting the process conditions As a result, a stable, high-quality image is always output without being affected by changes in the environment.

According to a second aspect of the present invention, in the color image forming apparatus according to the first aspect, as the dot pattern created by the pattern creating section, the dot pattern arranged at the first position is used as a core to sequentially increase the weight. By using the dot pattern arranged in such a way, even if the dot density in the matrix pattern becomes high, the influence of the amount of protrusion of the recording dot to the pixel is reduced, and the toner density is accurately measured, By predicting the image density based on this measurement result and adjusting the various conditions of the process, a stable and high-quality image is always output without being affected by environmental changes.

According to a third aspect of the present invention, in the color image forming apparatus according to the first aspect, the dot pattern formed in the matrix with a constant output power is used as the dot pattern formed by the pattern forming section. By using multiple matrix patterns with different densities, it is possible to accurately predict the image density to be printed out and adjust the process conditions based on this prediction result to be affected by changes in the environment. Instead, it always outputs stable and high-quality images.

According to a fourth aspect of the present invention, in the color image forming apparatus according to the first aspect, as the dot pattern created by the pattern creating section, the number of dots to be printed in the matrix is set to a fixed number, and the output power is set. By using dot patterns with different densities, it is possible to accurately predict the image density to be printed out using multiple matrix patterns with different densities, and adjust the process conditions based on this prediction result. As a result, a stable, high-quality image is always output without being affected by changes in the environment.

According to a fifth aspect of the present invention, in the color image forming apparatus according to the first aspect, as the dot pattern created by the pattern creating section, a dot pattern changed according to a toner color is used. A matrix pattern suitable for density measurement is created according to each toner color difference, and by adjusting the process conditions without being affected by color differences and environmental changes, Always output stable, high-quality images.

According to a sixth aspect of the present invention, in the color image forming apparatus according to the first aspect, as the dot pattern created by the pattern creating section, a dot pattern changed over time is used. By accurately measuring the toner concentration without being affected by the fluctuations in the detection characteristics of the photo sensor due to changes in time, and adjusting the process conditions based on this measurement result, it will not be affected by environmental changes. , Always output stable and high-quality images.

According to a seventh aspect, in the color image forming apparatus according to the first aspect, a temperature / humidity sensor is provided in the apparatus, and the pattern is formed according to an environmental condition obtained by a measurement operation of the temperature / humidity sensor. By changing the dot pattern created by the creation unit, even if the characteristics of the photosensitive drum change due to environmental temperature, etc., it is not affected by the characteristic changes of the photosensitive drum due to environmental changes, etc. By adjusting, the stable high-quality image is always output without being affected by the change of environment.

According to an eighth aspect of the present invention, in the color image forming apparatus according to the first aspect, the dot temperature formed on the photosensitive drum by the pattern forming section is selected and the density is detected to detect the ambient temperature. Even if conditions such as time, elapsed time, and toner color change change, by selecting the optimum matrix pattern corresponding to this and adjusting the process conditions, it will not be affected by environmental changes. , Always output stable and high-quality images.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a schematic diagram showing an example of one embodiment of a color image forming apparatus according to the present invention. The color image forming apparatus 1 shown in this figure includes a visualization unit 2 and
The visualization unit 2 is provided with the control unit 3, and the visualization unit 2 is controlled by the control unit 3 on the basis of the output of the temperature / humidity sensor 8 constituting the visualization unit 2 and the like. A matrix pattern of N × M dots is written on the photosensitive drum 4, and after development, the toner density of the matrix pattern is measured by the photosensor 9 constituting the visualization unit 2, and based on this measurement result. By predicting the image density when an image is actually printed and adjusting various process conditions, a stable, high-quality image is always printed without being affected by changes in the environment.

The visualization unit 2 is arranged around the photoconductor drum 4 which receives an optical image to form an electrostatic latent image, and is arranged around the photoconductor drum 4, and receives a charging signal output from the control unit 3. Accordingly, a charging unit 5 for uniformly charging the photosensitive drum 4 and a charging unit 5 disposed around the photosensitive drum 4,
An optical image is formed according to a write signal output from the control unit 3 and is written on the photoconductor drum 4, and is arranged around the photoconductor drum 4 and output from the control unit 3. A developing device designated among the developing device for cyan, the developing device for magenta, the developing device for yellow, and the developing device for black is operated according to the developed signal to be formed on the photoconductor drum 4. The developing unit 7 which develops the electrostatic latent image thus formed into a toner image and the photosensitive drum 4 are arranged around the photosensitive drum 4, and the ambient temperature and the ambient humidity around the photosensitive drum 4 are measured. Of the temperature and humidity sensor 8 for supplying the control unit 3 to the control unit 3, and the toner density of the toner image formed on the photoconductor drum 4 arranged around the photoconductor drum 4, and the measurement result is controlled by the control unit. Uni Supplied to the door 3 photo sensor 9
And a transfer unit 10 arranged around the photosensitive drum 4 and biased at the time of transfer to transfer the toner image formed on the photosensitive drum 4 onto a transfer paper (not shown). There is.

Prior to the actual printing operation, the ambient temperature and the ambient humidity of the photosensitive drum 4 are measured, and the measurement results are supplied to the control unit 3 and based on various signals output from the control unit 3. , While rotating the photoconductor drum 4,
A charging process, an N × M matrix pattern writing process, a developing process, and a toner concentration measuring process are performed, and the toner concentration obtained by this measuring operation is supplied to the control unit 3 to actually print an image. Predict image density and adjust process conditions. After this, in fact,
When printing an image, the ambient temperature of the photosensitive drum 4,
The ambient humidity is measured, and the measurement result is given to the control unit 3
Is supplied to the photoconductor drum 4 while rotating the photoconductor drum 4 on the basis of various signals output from the control unit 3 to the photoconductor drum 4. By repeating the process, a color toner image is formed on the transfer paper and the color toner image is discharged.

Further, the control unit 3 takes in the measurement result output from the temperature / humidity sensor 8 while operating the visualization unit 2, and adjusts various process conditions, and a matrix pattern changing operation. And the like, a ROM 12 in which a program for defining the operation of the process control unit 11 and various constant data are stored, a number counter 13 for counting the number of printed sheets, and the process control unit 11 Based on a signal output from the optical writing unit 6, the optical writing unit 6 is controlled to output an N × M matrix pattern or an optical image on the photoconductor drum 4, and a photo sensor 9 outputs the photo pattern. 100% based on the measured results
The image density Dmax when it is assumed that the solid pattern is printed out, and the toner density calculation unit 15 that supplies the prediction result to the process control unit 11 and the like is provided.

Further, the control unit 3 controls the image density Dmax output from the toner density calculation unit 15 and the image density Dt output from the process control unit 11 which is the target of the apparatus (a solid of 100% writing density). A potential setting section 16 for comparing the image density Dt when the pattern is printed out and setting the developing bias necessary for obtaining the target image density Dt, and the potential setting section 1
Based on the developing bias set in 6 and a signal output from the process control unit 11 or the like, the charging unit 5 is controlled to uniformly charge the photoconductor drum 4, and the developing unit 7 is controlled. And a potential control section 17 for performing processing for developing the electrostatic latent image formed on the photosensitive drum 4.

Prior to the actual printing operation, based on the output of the temperature / humidity sensor 8 forming the visualization unit 2, the temperature characteristic and the humidity characteristic of the photosensitive drum 4 are taken into consideration, and the charging section 5 and the developing unit 5 are taken into consideration. While supplying a bias voltage to 7 and 7, a matrix pattern of N × M dots is written on the photosensitive drum 4 constituting the visualization unit 2 and developed, and then the visualization unit 2 is constructed. The photosensor 9 measures the toner density of the matrix pattern, and based on the measurement result, the image density when an image is actually printed is predicted, and various process conditions are adjusted.

After that, when actually printing the image,
Based on the output of the temperature / humidity sensor 8 forming the visualization unit 2 and various process conditions, a bias voltage is supplied to the charging unit 5 and the developing unit 7 while the photosensitive unit forming the visualization unit 2 is exposed. An optical image of an image to be printed is written on the body drum 4 and developed, then transferred onto a transfer paper and discharged.

Next, the toner density measuring operation, process condition setting operation, etc., which are performed prior to the actual printing operation, will be described in detail. First, the pattern creating unit 14 determines an N × M matrix pattern, for example, the matrix pattern 20 in which only one dot is a writing dot (printing dot) as shown in FIG. 2A or only adjacent three bits are writing dots. The number of dots to be printed is changed from each other, such as the matrix pattern 20, and several types of matrix patterns 20 having different densities are formed, and the optical writing unit 6 causes the photosensitive drum 4 as shown in FIG. After writing each matrix pattern 20 in each measurement pattern area formed in the length X mm and the width Y mm, the developing unit 7 develops it, and the photosensor 9 measures the toner density of each matrix pattern 20. It

At this time, in the case of each matrix pattern (measurement pattern) 20 formed by the dot pattern, the number of dots in the matrix pattern 20 changes due to the change of the writing density, so that the photosensor is changed according to the writing density. Light from the light emitting portion of 9 hits the color toner,
Since the amount of reflection changes and the amount of reflected light received by the light receiving portion of the photo sensor 9 changes, the voltage value of the measurement signal output from the photo sensor 9 decreases as the writing density increases. After that, the toner density calculator 15 registers the color toner amount of the measurement pattern developed on the photosensitive drum 4 and the measurement patterns output from the photosensor 9 registered in the ROM 12 or the like as shown in FIG. A graph showing the relationship with the voltage value (measured value) of the measurement signal in the area is used. Under the current setting conditions, the write density is 100%.
When the solid pattern of is printed out, the image density Dmax under the assumption is predicted.

Next, the image density Dmax obtained by the prediction operation of the toner density calculation unit 15 by the potential setting unit 16
And the image density Dt when a solid pattern with a target writing density of 100% is printed out by the present apparatus are compared, and based on the comparison result, the target image density Dt is compared.
The value of the developing bias to be supplied to the developing unit 7 is set so as to obtain, and the charging applied voltage to be supplied to the charging unit 5 is set so as to correspond to this developing bias. Then, the value of the developing bias supplied to the developing unit 7 and the charging application voltage supplied to the charging unit 5 based on the developing bias and the charging application voltage set by the potential setting unit 16 by the potential control unit 17. The value of is changed.

Next, the dot pattern used in the above-described toner density measuring operation will be described in detail. <Relationship Between Toner Color and Dot Pattern> First, since cyan toner, magenta toner, yellow toner, and the like on the photoconductor drum 4 have the characteristic of reflecting the light emitted from the light emitting portion of the photosensor 9, When the toner density of a solid pattern formed by cyan toner, magenta toner, yellow toner, etc. on the surface of the photoconductor drum 4 is measured by the photosensor 9, as shown in FIG. Although the voltage value of the measurement signal output from the photosensor 9 gradually decreases as the amount increases, when the amount of color toner on the photosensitive drum 4 exceeds a certain value (threshold value), A phenomenon occurs in which the voltage value of the measurement signal output from the sensor 9 starts to increase. This phenomenon occurs even in a pattern other than such a solid pattern, for example, a dot pattern such as the matrix pattern 20 used in the present apparatus, when the dot density of this dot pattern becomes high, and the range exceeding the threshold value is reached. Since the sensitivity of the photosensor 9 is remarkably reduced by the above, it is necessary to set the dot density of the dot pattern within a range not exceeding the threshold value even when using such a dot pattern.

<Setting of Threshold for Photo Sensor Output> When such a dot pattern is used, when the dots are concentrated in the matrix pattern 20, the toner amount / photo sensor output shown in FIG. 6 is obtained. When the dots are dispersed, the toner amount / photo sensor output characteristic shown in FIG. 7 is obtained. As can be seen by comparing the toner amount / photo sensor output characteristics shown in FIG. 6 with the toner amount / photo sensor output characteristics shown in FIG. 7, the dot concentration type dot pattern shown in FIG.
Since the protrusion to the pixel can be ignored, the area until the photosensor output is saturated becomes longer, and the photosensor 9 can be made to detect the toner density over a wider density area. For the above reasons, the present invention uses the dot concentration type dot pattern as the measurement pattern.

<Relationship between Toner Density and Dot Pattern>
Further, in order to predict the image density Dmax, several dot patterns are generated, the toner density of each of these dot patterns is measured by the photosensor 9, and various settings are made based on the toner density of each of these dot patterns. When adjusting the conditions, dots are written with a constant output as shown in FIGS. 8A to 8C, and the toner density is changed by the number of dots written in the matrix pattern 20.
At this time, the output when writing a dot is usually 10
It is preferable to use an output level of 0%, but if the writing level of each dot in the matrix pattern 20 is the same level, what kind of output level will be used within a range in which the toner density can be measured by the photosensor 9? May be. Also, the toner density of each matrix pattern 20 is measured by the photosensor 9, and the image density Dmax is predicted based on the inclination of the line segment connecting the toner density of each matrix pattern 20 obtained by this measurement operation. The inclination of the line segment changes due to environmental changes due to temperature and humidity, toner color, and time changes.

When the image density Dmax is predicted, the larger the gradient of the toner density (density gradient value), the more stable the value of the image density Dmax obtained by the prediction operation is. It is necessary to set the matrix pattern 20 so that
For example, the light reflection characteristics of the black toner and the cyan toner are different between when the electrostatic latent image of each matrix pattern 20 formed on the photosensitive drum 4 is developed with black toner and when it is developed with cyan toner. Therefore, as shown in FIG. 9, even if the amount of toner on the photosensitive drum 4 is the same, the voltage value of the measurement signal output from the photosensor 9 differs depending on the color of the toner. In other words, even if the same dot pattern is used, the gradient of the toner density changes depending on the toner color, so it is necessary to change the dot pattern according to the toner color.

<Relationship between ambient temperature and dot pattern> Further, even when the same dot pattern is used and the same toner color is used, when the ambient temperature of the photosensitive drum 4 changes, the resistance value of the photosensitive drum 4 changes. Changes and the voltage value of the measurement signal output from the photosensor 9 changes as shown in FIG. Therefore, it is necessary to change the dot pattern according to the measurement result of the temperature / humidity sensor 8 so that the inclination of the toner density can be made large. <Relationship Between Elapsed Time and Dot Pattern> In addition, since the amount of toner adhered on the photosensitive drum 4 changes with the aging of the apparatus, the number of prints counted up to that time is counted by the number counter 13. It is necessary to change the dot pattern accordingly. <Selection of Dot Pattern> Then, the optimum dot pattern corresponding to the above-described conditions, the relationship between the toner density gradient value and the image density Dmax is stored in the ROM 12, and the process control unit 11 performs the actual printing operation prior to the actual printing operation. Based on conditions such as the value of the measurement signal output from the temperature / humidity sensor 8, information indicating the color of toner used during development, and the aged value indicated by the value of the number of sheets counter 13, the ROM 12
With reference to the data stored in, the most suitable dot pattern is selected for each of these conditions.

As described above, in this embodiment, the control unit 3 controls the visualization unit 2 based on the output of the temperature / humidity sensor 8 constituting the visualization unit 2, and the visualization unit 2 Photoconductor drum 4
After writing a matrix pattern of N × M dots on the top and developing it, the toner density of the matrix pattern is measured by the photosensor 9 constituting the visualization unit 2, and an actual image is obtained based on this measurement result. Since the image density at the time of printing is predicted and various conditions of the process are adjusted, it is possible to obtain a stable output value in a wide range by using the output value up to the output saturation of the photo sensor 9. This allows the toner density to be accurately measured, the image density to be predicted based on this measurement result, and the process conditions to be adjusted to ensure stable, high-quality images without being affected by environmental changes. Can be output.

Further, in the above embodiment, the toner density of the plurality of matrix patterns 20 formed on the photosensitive drum 4 is measured by the photo sensor 9, and the gradient of the toner density is obtained based on the measurement result. Although the image density Dmax is predicted, the image density Dmax may be predicted by a method other than this. For example, one matrix pattern 2 on the photosensitive drum 4
The relationship between the potential when 0 is written (post-exposure potential) and the image density Dmax in the portion where this potential is obtained is measured in advance, and the relationship is graphed as shown in FIG. And the output value of the photo sensor 9 are obtained. Then, prior to the actual printing operation, when the post-exposure potential fluctuates on the photoconductor drum 4 at the time of image density adjustment performed, after writing a dot pattern capable of measuring the density difference with the photo sensor 9. The potential of the dot pattern portion is measured (after exposure), and the image density Dmax is predicted based on the measurement result.

Next, the image density Dma obtained by the prediction operation
x is compared with the target image density Dt of this apparatus, and the value of the developing bias supplied to the developing unit 7 is set based on the comparison result so that the target image density Dt is obtained. The charging applied voltage supplied to the charging unit 5 is set so as to correspond to this developing bias.
Then, based on the developing bias and the charging applied voltage set by the potential setting unit 16, the value of the developing bias supplied to the developing unit 7 by the potential control unit 17 and the charging applied voltage supplied to the charging unit 5 are set. Change the value. Also, when the image density Dmax is predicted using this method, the dot pattern necessary for detecting the density changes due to the toner color, environmental changes, temporal changes, etc., as in the case described above. The data of each dot pattern and various conditions, the relationship between the output value of the photo sensor 9 and the image density Dmax are stored in the ROM 12 in advance, and the toner color, environmental change,
The most suitable dot pattern at that time is selected according to the change over time and the like is written on the photosensitive drum 4.

Further, in the above-mentioned embodiment, the density of the matrix pattern 20 is changed by making the writing level of each dot forming the matrix pattern 20 constant and changing the number of dots. As shown in 12, the number of dots may be the same, the writing level of each dot may be changed, and the density of the matrix pattern 20 may be changed. Further, in the above-described embodiment, the most suitable dot pattern is selected at that time and is written on the photosensitive drum 4 as the matrix pattern 20, but the temperature and humidity, the toner color, the elapsed time, etc. Then, after writing a plurality of corresponding dot patterns as the matrix pattern 20 on the photosensitive drum 4 and developing them, the optimum matrix pattern 20 is selected from the matrix patterns 20 according to the conditions at that time. Alternatively, the gradient of the toner density may be obtained.

[0039]

As described above, according to the present invention, in claim 1, the output value up to the output saturation of the photosensor is used to obtain a stable output value in a wide range, and the toner density is accurately measured. By predicting the image density based on this measurement result and adjusting the process conditions, it is possible to always output a stable and high-quality image without being affected by environmental changes. . Further, in claim 2, even if the dot density in the matrix pattern becomes high, the toner density is accurately measured by reducing the influence of the protruding amount of the recording dot on the pixel, and the image density is measured based on the measurement result. By predicting the density and adjusting the process conditions, it is possible to always output a stable, high-quality image without being affected by changes in the environment.

In the third aspect, a plurality of matrix patterns having different densities are used to accurately predict the image density to be printed out, and various process conditions are adjusted based on the prediction result. As a result, it is possible to always output a stable and high-quality image without being affected by changes in the environment. Further, in claim 4, by using a plurality of matrix patterns having different densities, the image densities to be printed out are accurately predicted, and various conditions of the process are adjusted on the basis of the prediction results, so that the environment It is possible to always output a stable and high-quality image without being affected by the change of.

According to the present invention, a matrix pattern suitable for density measurement is formed in accordance with the difference in toner color so that the color difference and the environment change are not affected. By adjusting the process conditions, it is possible to always output stable and high-quality images. Further, according to claim 6, the toner concentration is accurately measured without being affected by the change in the detection characteristics of the photosensor due to the time change, and the process conditions are adjusted based on the measurement result, thereby changing the environment. It is possible to always output a stable and high-quality image without being affected by.

Further, according to the present invention, even if the characteristics of the photosensitive drum change due to environmental temperature or the like, the process conditions can be adjusted without being affected by the characteristic changes of the photosensitive drum due to environmental changes. As a result, it is possible to always output a stable and high-quality image without being affected by changes in the environment. Further, in claim 8, even if various conditions such as the environmental temperature, the elapsed time, and the difference in toner color are changed, the optimum matrix pattern corresponding to them is selected and the various process conditions are adjusted. It is possible to always output stable and high-quality images without being affected by changes in the environment.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a form of a color image forming apparatus according to the present invention.

2A and 2B are schematic views showing an example of an N × M matrix pattern created by a pattern creating section shown in FIG.

FIG. 3 is a schematic view showing an example of each matrix pattern written on the photosensitive drum 4 shown in FIG.

4 shows the relationship between the color toner amount of the measurement pattern registered in the ROM shown in FIG. 1 and the voltage value (measurement value) of the measurement signal of each measurement pattern area output from the photosensor 9. FIG. It is a graph.

5 is a graph showing the relationship between the amount of color toner on the photosensitive drum shown in FIG. 1 and the voltage value of the measurement signal output from the photo sensor.

6 is a graph showing an example of toner amount / photo sensor output characteristics when a dot-concentrated matrix pattern is written on the photosensitive drum shown in FIG.

7 is a graph showing an example of toner amount / photo sensor output characteristics when a dot dispersion type matrix pattern is written on the photosensitive drum shown in FIG.

8A, 8B, and 8C are schematic diagrams showing examples of constant output level type matrix patterns written on the photosensitive drum shown in FIG.

9 is a graph showing an example of toner amount / photo sensor output characteristics when the matrix pattern formed on the photosensitive drum shown in FIG. 1 is developed with cyan toner and black toner.

10 is an ambient temperature of the photosensitive drum portion shown in FIG.
6 is a graph showing an example of a relationship with a gradient of toner density.

FIG. 11 is a graph showing an example of image density / post-exposure potential characteristics used in another example of the color image forming apparatus according to the present invention.

12 (a), (b) and (c) are schematic views showing an example of an output level changing type matrix pattern used in another example of the color image forming apparatus according to the present invention.

[Explanation of symbols]

1 color image forming apparatus, 2 visualization unit 2, 3
Control unit, 4 photoconductor drums, 5 charging section, 6 light writing section (latent image forming section), 7 developing unit, 8 temperature and humidity sensor, 9 photo sensor, 10 transfer section, 11 process control section, 12 ROM, 13 sheets Counter, 1
4 pattern creating section, 15 toner density calculating section, 16
Potential setting unit, 17 potential control unit, 20 matrix pattern

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsugu Sugiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Kenshi Shinohara 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Company Ricoh

Claims (8)

[Claims] 1. A photoconductive drum configured to be rotatable,
A latent image forming unit that forms an electrostatic latent image on the photosensitive drum in response to a plurality of color image forming signals, and a plurality of developing devices that visualize the electrostatic latent image on the photosensitive drum with a developer. And a unit for forming an electrostatic latent image on the photoconductor drum for each color to obtain a color image. In the color image forming apparatus, an arbitrary N × M matrix dot pattern is formed on the photoconductor drum. A pattern creating unit created above, a photo sensor that detects the density of the dot pattern created on the photosensitive drum, and a color image that changes various setting conditions based on the measurement values obtained by this photo sensor. In the forming apparatus, a dot pattern up to the output saturation of the photosensor is used as the dot pattern created by the pattern creating unit. Place. 2. The color image forming apparatus according to claim 1, wherein the dot pattern created by the pattern creating unit is arranged such that the dot pattern arranged first is a core, and the dot patterns are sequentially thickened. A color image forming apparatus using a different dot pattern. 3. The color image forming apparatus according to claim 1, wherein the dot pattern created by the pattern creating unit is a dot pattern printed in a matrix with a constant output power. Image forming apparatus. 4. The color image forming apparatus according to claim 1, wherein the dot pattern created by the pattern creating unit has a fixed number of dots to be printed in a matrix, and the output power is changed. A color image forming apparatus characterized by using a pattern. 5. The color image forming apparatus according to claim 1, wherein a dot pattern changed according to a toner color is used as the dot pattern created by the pattern creating unit. apparatus. 6. The color image forming apparatus according to claim 1, wherein a dot pattern that is changed over time is used as the dot pattern created by the pattern creating unit. Forming equipment. 7. The color image forming apparatus according to claim 1, wherein a temperature / humidity sensor is provided in the apparatus, and the color image forming apparatus is created by the pattern creating unit according to an environmental condition obtained by a measurement operation of the temperature / humidity sensor. A color image forming apparatus characterized by changing a dot pattern. 8. The color image forming apparatus according to claim 1, wherein the pattern forming section selects a dot pattern formed on the photosensitive drum to detect the density.