JPH04367883A - Image density controller - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image density control device for an electrophotographic apparatus. The present invention can be used in various devices using electrophotographic processes, such as copying machines, facsimile machines, laser printers, etc.

0002

[Prior Art] Conventionally, under various conditions,
In order to obtain stable copy images, various development control methods have been proposed for copying machines. For example, there is a method in which the developing bias is changed according to the number of copies, and a method in which a measurement image pattern is developed on a photoreceptor for each new document and the density is read by an optical detection means. -33704 etc.).

0003

However, the above conventional method has the following problems. 1. In the proposed developing apparatuses, in both the two-component developing system and the one-component developing system, the causal system for fluctuations in developing ability is complex and cannot be modeled for control. 2. Toner charging ability and developer coating peeling off,
There are many parameters such as spent, which cannot be directly measured. 3. There will be a delay of several sheets in the toner replenishment response time.
It is vulnerable to continuous large amounts of toner consumption. 4. A huge amount of experimental data is required when designing and developing a developing device. 5. In the case of a method of creating a measurement image pattern for toner density measurement, the copying speed decreases and a burden is placed on the cleaning section.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image density control device that performs control to obtain a stable image despite changes in characteristics of a photoreceptor, toner density, etc. when replenishing toner in an electrophotographic process. shall be.

[0005]

[Means for solving the problem] The invention according to claim 1 includes:
an image density sensor that measures toner density on an image forming member such as a photoreceptor drum; a written image detection section that detects the image area of a written image; a toner replenishment device that replenishes toner to a developing device; a toner replenishment value determination unit that receives toner density information output from the sensor and written image information from the written image detection unit;
It is said that the configuration has the following.

[0006] The invention according to claim 2 provides a written image detection unit for detecting an image area of a written image, an image density sensor for measuring toner density on an image forming member, and a surface provided in an electrophotographic process mechanism. Various sensors such as electrometer, drum ammeter, drum rotation speed meter, copy count meter, exposure time meter, thermometer, hygrometer, toner concentration meter attached to the toner replenishment section in the developing device, and toner concentration information judgment a toner replenishment control section that controls toner replenishment to the toner replenishment section, toner concentration information output from the image density sensor, toner concentration information from the toner concentration information determination neural network, and the writing. The toner replenishment value determining section is configured to include a toner replenishment value determining section into which written image information from the image detecting section is input.

[0007]

[Operation] In the invention as set forth in claim 1, the toner replenishment value determination section estimates the toner concentration from a membership function that estimates the toner concentration based on the signal from the image density sensor and written image information from the written image detection section. Membership functions are registered in advance. Then, a predetermined fuzzy synthesis calculation is performed using a predetermined fuzzy rule, and the membership function obtained as a result is defuzzified to determine a toner replenishment operation value for the toner replenishment device. This makes it possible to perform optimal toner replenishment in consideration of the actual toner density on the photosensitive drum and the image area of the written image.

According to the second aspect of the invention, when the neural network for determining toner density information is trained, information from the various sensor units is input to the input layer of the neural network, and the toner density information input from the image density sensor is input to the input layer of the neural network for determining toner density information. Learning is performed as learning data given from the output layer of the neural network for determining toner density information. Also, during control,
In the same way as during learning, information from various sensor units is input to the input layer of the neural network for toner density information determination, and the toner density information obtained from the output layer, the image information from the written image detection unit, and the image density sensor are input. Based on the input toner concentration information, the toner replenishment value determination unit performs a predetermined fuzzy synthesis calculation using fuzzy rules registered in advance, and defuzzifies the membership function obtained as a result to determine the toner supply value. Determine the supply operation value. In other words, by using a neural network to obtain toner density information from sensor output information, the optimum toner replenishment amount for obtaining a stable image is determined in response to changes in the characteristics of the photoreceptor and various conditions.

[0009]

[Examples] Examples of the present invention will be described below. FIG. 1 is a block diagram of an image density control device according to a first embodiment of the present invention. This image density control device includes a scanner section 2 that reads an original image, an image density sensor 10 that measures the toner density on an image forming member such as a photoreceptor drum, and information from the written image information from the scanner section 2 and the image density sensor 10. The toner replenishment control section 14 includes a toner replenishment value determining section 12 that determines a toner replenishment operation value from toner information, a toner replenishment control section 14 that replenishes toner according to the toner replenishment operation value, and a toner replenishment device 16.

The scanner unit 2 includes a CCD 4 as an optical sensor that reads image information, an A/D converter 6 that converts analog information of the CCD 4 into digital information, and an original image that estimates toner consumption of an original image from these digital information. It is composed of an image processing section 8.

FIG. 2 is a diagram showing a configuration in which the image density control device of this embodiment is applied to a copying machine. This copying machine irradiates a document 20 placed on a document table 18 with a lamp 22,
It is configured so that the reflected light is read by the CCD 4 described above. Similarly, light from the document 20 is configured to be irradiated onto the photosensitive drum 26 by a scanning optical system (not shown). A charger 28 for applying an electric charge to the photoreceptor drum 26, a developing section 32 having a developing roller 30, a transfer device 34, a separator 36, and an image density sensor 10 are arranged around the photoreceptor drum 26, respectively. . The developing section 32 is provided with a toner replenishing device 16, which supplies toner to the developing section 32. The image density sensor 10 is a sensor that optically reads the image on the photosensitive drum 26 developed by the developing section 32 and detects the image density. In addition,
In FIG. 2, paper from a paper feed cassette 40 is sent out by a delivery roller 42, transferred to a transfer device 34 and separated by a separator 3.
6, and is discharged by a discharge roller 44. In addition, in FIG. 2, the sensor section is shown surrounded by a double frame.

Toner replenishment value determining section 1 shown in FIGS. 1 and 2
2 stores fuzzy rules regarding toner density and fuzzy rules for written image information from the document image processing section 8 in advance, and stores toner density information from the image density sensor 10 and written image information from the scanner section 2 in advance. When input, the operation value is determined so as to stabilize the toner density at a predetermined density.

The manner of this determination will be explained with reference to FIGS. 3 and 4. For example, when the toner density is level 25% and the written image information is 53%, the toner replenishment operation value (
The membership function (shaded area) of the consequent part) is determined. In FIG. 3, (a) and (c) show the membership functions of the antecedent part, and (b) and (d) show the membership functions of the consequent part determined from them. In (a), the horizontal axis is the toner concentration, the vertical axis is the degree, and (c
), the horizontal axis represents written image information (corresponding to information on the proportion of the black area in the original image), and the vertical axis represents the degree. Using the fuzzy rules shown in FIG. 3(a), the membership function when the toner concentration is 25% is determined as shown in FIG. 3(b). Similarly, since the written image information accounts for 53% of the written image information, the membership function shown in (d) can be found using the fuzzy rule shown in (b).

After that, the membership function related to the toner density shown in FIG. 4(e) and the membership function related to the written image information shown in FIG. Obtain the membership function (hatched area). The toner replenishment operation value is determined by defuzzifying this membership function. There are several defuzzification methods, but for example, by calculating the center of gravity of the membership function (shaded area) (max-mini method), fuzzy inference can be obtained as -3% as shown in the figure.

In this way, in the first embodiment, the toner replenishment operation value is output from the toner replenishment value determining section 12 to the toner replenishment control section 14, and the toner replenishment operation value is outputted from the toner replenishment value determining section 12 to the toner replenishment control section 14, and the toner replenishment device 1 shown in FIG.
6 is driven. As a result, the optimum amount of toner replenishment is determined according to the toner density on the photoreceptor 26 and the amount of black portion of the read image at that time.

Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram of an image density control device according to a second embodiment of the present invention. The image density control device of the second embodiment is as follows:
An image density sensor 10 that measures the toner density on the image forming member, various sensor units 50 including a toner density meter that measures parameters related to toner consumption, and a toner density sensor that determines the toner density based on the output from the sensor unit 50. It is composed of a neural network 52 for information determination, a scanner unit 2, a toner replenishment control unit 14, a toner replenishment device 16 similar to those in the first embodiment, and a toner replenishment value determination unit 54 that is compatible with learning of the neural network. There is. The toner supply value determination unit 54 uses the neural network 5
Based on the toner density information obtained from the output layer 2, the image information from the written image detection section 8, and the toner information from the image density sensor 10, a predetermined fuzzy synthesis calculation is performed using fuzzy rules registered in advance. The function is to determine the toner replenishment operation value by defuzzifying the membership function obtained as a result.

FIG. 6 shows a configuration in which the image density control device shown in FIG. 5 is applied to a copying machine. In FIG. 6, the elements explained in FIG. 2 will be omitted from description. In this embodiment, a temperature sensor 60 that detects the temperature around the photoconductor drum 26, a humidity sensor 62 that detects the humidity, a drum rotation number counter 64 that measures the number of rotations of the photoconductor drum 26, and a A drum ammeter 66 for detecting the photoreceptor current flowing through the photoreceptor, and a copy counter 68 for measuring the number of copies placed on the feed roller 42 are provided, respectively. A toner density meter 38 is provided in the toner storage section of the developing section 32 . The charger 28 also has a charge control section 78 based on a signal from the charge operation value determination section 76.
The amount of charge is determined under the control of. Original image processing section 8
The image light from the document 20 is emitted from the exposure control section 72 through the exposure operation value determination section 70 . The exposure control section 72 controls the exposure time, intensity, etc., and includes an exposure time counter 7 that measures the exposure time.
4 is connected. A surface electrometer 80 for measuring the surface potential of the photoreceptor drum 26 is disposed around the photoreceptor drum 26 and above the developing section 32 . Also provided is an image density sensor 10 that optically reads the image developed on the photoreceptor drum 26 by the developing section 32 and detects the image density. All of these various sensors, except for the image density sensor 10, are configured to be input to a neural network 52 for determining toner density information (indicated by terminal A in the figure). The output of the image density sensor 10 is input to a toner replenishment value determining section 54 (indicated by terminal B in the figure). In addition, in FIG. 6, the sensor is shown surrounded by a double frame.

Next, regarding the sensor section, examples of parameters that affect toner density and calculation methods are listed below. <Sensors used, etc.> Toner density meter 38, <Parameter name> Toner density, <Parameters calculation method and meaning> In the case of a two-component development method, obtain the weight ratio of toner and developer in the toner box. <Sensors used, etc.> Surface electrometer 80, <Parameter name> Drum surface potential, <Parameter calculation method and meaning> A predetermined latent image pattern is created on the drum, and the surface potential of the image area and white background area is measured. . The goal of latent image control is to stabilize this surface potential at a target value.

<Sensors used, etc.> Drum ammeter 6
6. <Parameter name> Amount of charge passing through the drum, <Method for calculating parameters, meaning> Obtained by integrating the current supplied from the charger 28 to the photosensitive drum 26 over the usage time. The sensitivity of the photosensitive drum 26 gradually decreases due to repeated charging/discharging over a long period of time. It is expressed as a percentage of the usage limit value (maximum rated value) of the photosensitive drum 26.

<Sensors used, etc.> Drum rotation number counter 64, <Parameter name> Drum wear amount, <Parameters calculation method and meaning> The photosensitive drum 26 is scraped by the cleaning section, blade, etc., and its capacitance is reduced. do. Since this amount of wear is approximately proportional to the total number of rotations of the photoreceptor drum 26, this value is used as a substitute characteristic for the amount of wear of the photoreceptor drum 26. It is expressed as a percentage of the usage limit value (maximum rated value) of the photosensitive drum 26. <Sensors used, etc.> Exposure time counter 74, <Parameter name> Exposure fatigue amount, <Parameters calculation method and meaning> The sensitivity of the photoreceptor drum 26 changes due to repeated short-term exposure. Since this decrease in sensitivity due to exposure is proportional to the exposure time, this value is used as a substitute characteristic for the amount of exposure fatigue. It is expressed as a percentage of the usage limit value (maximum rated value) of the photosensitive drum 26.

<Sensors used, etc.> Copy counter 68, <Parameter name> Continuous use degree, <Parameter calculation method and meaning> Continuous use degree indicates how many copies were made within a predetermined period of time from the present to the past. This is the value shown. This means the ratio of short-term usage time to downtime. Continuous use of the photosensitive drum 26 causes a decrease in sensitivity and generation of residual potential. <Sensors used, etc.> Temperature sensor 60, <Parameter name> Temperature value, <Parameter calculation method and meaning> The sensitivity of the photoreceptor is greatly affected by the temperature value and its changes. This is due to changes in capacitance, leakage current during and after charging, etc., but it is difficult to understand the direct relationship.

<Sensors used, etc.> Humidity sensor 62
, <Parameter name> Humidity value, <Parameter calculation method and meaning> The sensitivity of the photoreceptor is greatly affected by the humidity value and its changes. This is due to changes in capacitance, leakage current during and after charging, etc., but it is difficult to understand the direct relationship. <Sensors used, etc.> Image density sensor 10, <Parameter name> Image density, <Parameter calculation method and meaning> A P sensor, etc. consisting of a laser diode and a photosensor is used, and the image on the photoreceptor is determined by the difference in reflectance. Measure the amount of toner adhering to the area.

Next, the operation of this embodiment will be explained. Toner replenishment control in a conventional electrophotographic process uses an image density sensor to measure toner density and replenish toner. In this case, generally when the toner concentration is low, toner is replenished, and when it is high, the toner supply is stopped. However, in this embodiment, the density of the output image is determined by making the neural network 52 learn the relationship between various information that affects the toner density and the actual toner density, thereby creating a toner density measurement pattern during control. Toner replenishment control can be performed without

[0024] The neural network 52 will be explained below by dividing it into its learning time and determination time. ■． Learning of the neural network 52: First, learning of the toner density determination neural network 52 will be described. During learning, each sensor information is acquired while creating a toner density determination pattern. FIG. 7 is a schematic diagram showing an example of the configuration of the toner concentration determination neural network 52. As shown in FIG. The toner concentration determination neural network 52 includes an input layer to which sensor output information is input, an intermediate layer, an output layer to which toner concentration information is output, and a network connecting them. Among these, parameters that influence toner density are input to the input layer of the toner density determination neural network 52, and the output value of the image density sensor 10 is provided as a teacher value to the output layer. In FIG. 7, the flow of the signal as the teacher value is shown by the broken arrow. As mentioned above, the parameters that affect the toner concentration include the toner concentration in the toner box, the surface electrometer that measures the charged potential on the photoreceptor,
Drum current, which measures the current flowing into the photoreceptor drum 26 from the charging section; the amount of drum wear and exposure fatigue that affects long-term deterioration of the drum; the degree of continuous use, which indicates the frequency of operation of the copying machine;
There are temperature, humidity, and other factors that affect the electrostatic capacity of the photoreceptor and the amount of triboelectric charging of the toner.

Through such learning, the network of coupling coefficients Wkj between the input layer and the intermediate layer and the network of coupling coefficients Sji between the intermediate layer and the output layer are optimized by taking into account various information that affects the toner density. control. Note that the output from the image density sensor 10 is used as learning data for the neural network 52 and at the same time is used by the toner replenishment value determining section 54 to determine the amount of toner replenishment. The toner replenishment value determination unit 54 inputs the toner concentration and needs to be adjusted in advance so as to output an optimal toner replenishment operation value. This adjustment work can be performed in parallel with the acquisition of neural network learning data.

[0026]■. When executing control: When executing control, it is desired to avoid creating a toner density measurement pattern as much as possible, so a pattern is created every several copies or more. Therefore, the toner density cannot be measured for several sheets without pattern formation. Therefore, in this embodiment, the neural network 52 is used to estimate the toner concentration at an arbitrary timing and perform toner replenishment control. For example, optimal toner replenishment can be performed for each sheet by acquiring sensor information such as charging potential and drum current for each sheet and estimating toner density information in conjunction with written image information obtained from the CCD 4. In this case, the toner replenishment value determining unit 54 uses toner density information obtained from the output layer of the neural network 52, image information from the written image detection unit 8, and toner density information from the image density sensor 10, as in the first embodiment. Based on the density information, a predetermined fuzzy synthesis calculation is performed using fuzzy rules registered in advance, and the membership function obtained as a result is defuzzified to determine a toner replenishment operation value. This fuzzy inference performs processing based on almost the same principle as the first embodiment.

The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the sensor for detecting various information that affects the toner concentration is not limited to the above-mentioned embodiments, and various types of sensors can be used.

[0028]

According to the invention as set forth in claim 1, toner replenishment can be performed while actually considering the written image information.
When replenishing toner in an electrophotographic process, it is possible to control the toner supply so that a stable image can be obtained.

According to the second aspect of the invention, compared to the conventional control method that does not specify the cause of drum deterioration, optimal control can be performed for each deterioration factor, so the control range is wide and runaway etc. This makes it possible to prevent sudden fluctuations in toner consumption. Therefore, when replenishing toner in an electrophotographic process, it is possible to obtain an image that is stable against changes in characteristics such as the photoreceptor and toner density. Furthermore, since there is no need to identify a control model for a complex system such as a developing system, the amount of experiments performed during process design and development can be reduced, which has the effect of reducing the development period and cost of the copying machine.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an image density control device according to a first embodiment.

FIG. 2 is a configuration diagram in which the first embodiment is applied to a copying machine.

FIG. 3 is a diagram showing an example of fuzzy rules used for toner supply control.

FIG. 4 is a diagram showing an example of fuzzy rules used for toner supply control.

FIG. 5 is a block diagram of an image density control device according to a second embodiment.

FIG. 6 is a configuration diagram in which the second embodiment is applied to a copying machine.

FIG. 7 is a diagram illustrating a configuration example of a neural network for determining toner concentration.

[Explanation of symbols]

8 Original image processing unit 10 Image density sensor 12 Toner replenishment value determining unit 16 Toner replenishing device 38 Toner density meter 50 Various sensor units 52 Neural network for determining toner density information 54 Toner replenishment value determining unit

Claims (2)

[Claims] 1. An image density sensor that measures toner density on an image forming member, a written image detection section that detects an image area of a written image, a toner replenishment device that replenishes toner to a developing device, and a toner replenishment device that replenishes toner to a developing device. It has a toner replenishment value determining section that receives toner density information output from the sensor and written image information from the written image detecting section as input, and the toner replenishment value determining section uses fuzzy rules registered in advance. An image density control device characterized in that a toner replenishment operation value for the toner replenishing device is determined by performing a predetermined fuzzy synthesis calculation and defuzzifying a membership function obtained as a result. 2. A written image detection section that detects an image area of a written image, an image density sensor that measures toner density on an image forming member, and a surface electrometer and a drum ammeter provided in an electrophotographic process mechanism. , various sensor sections such as a drum rotation speed meter, a copy count meter, an exposure time meter, a thermometer, a hygrometer, a toner concentration meter attached to the toner supply section in the developing device, and a neural network for determining toner concentration information;
a toner replenishment control section that controls toner replenishment to the toner replenishment section; toner concentration information output from the image density sensor; toner concentration information from a neural network for toner concentration information determination; and toner concentration information from the written image detection section. and a toner replenishment value determining section into which write image information is input, and when learning the toner density information determination neural network, information from the various sensor sections is input into the input layer, and information from the image density sensor is input. Learning is performed using the input toner concentration information as learning data given from the output layer of the neural network for determining toner concentration information, and during control, the input layer of the neural network for determining toner concentration information is input from various sensors during control. The information is input, and based on the toner density information obtained from the output layer and the image information from the written image detection section, a predetermined fuzzy synthesis calculation is performed using fuzzy rules registered in advance, and the resulting member is An image density control device characterized in that a toner replenishment operation value is determined by defuzzifying a ship function.