JP2003186262A - Electrophotographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a permeability sensor is set in a developing unit in order to detect toner concentration in the developing unit and the detection of the mixing ratio of toner to magnetic carrier is required, which involves the high cost of the permeability sensor and hence hinders the decrease in the cost of the device. <P>SOLUTION: In the electrophotographic device using a two-component development system, estimation is performed from parameters such as, a pixel count value and temperature and humidity, by the use of a neural network. At the time, when the neural network learns, the neural network is made to learn the output of a permeability sensor as a teacher signal and, thus, the neural network can be made to function as a dummy permeability sensor. This way eliminates the need for a high cost permeability sensor and, therefore, realizes a reduction in the cost of the device. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus utilizing an electrophotographic process, and more particularly to an electrophotographic apparatus having a two-component developing type developing device using a developer in which a toner and a magnetic carrier are mixed.

[0002]

2. Description of the Related Art FIG. 5 shows the structure of an electrophotographic apparatus that forms an image using a generally known electrophotographic process.

In the electrophotographic apparatus shown in FIG. 5, an electrophotographic photosensitive drum 100 having an organic photosensitive layer is rotationally driven in a clockwise direction indicated by an arrow at a predetermined speed. Photoconductor drum 100
During the rotation process, the charging device 101 such as a charging roller receives a uniform charging process with a predetermined polarity and potential.

Then, the charged surface is subjected to scanning exposure processing of the target image information by the laser light output from the laser scanner 103. The laser scanner 103 modulates (turns on / off) corresponding to a time-series electric digital pixel signal of target image information from an image signal generator such as a computer (not shown).
The laser light that is turned off is output to scan and expose the surface of the photoconductor. This scanning exposure forms an electrostatic latent image on the surface of the photoconductor drum 100 corresponding to the target image information that has been subjected to scan exposure. A mirror 102 reflects the output laser light from the laser scanner 103 to the exposure position of the photosensitive drum 100.

After that, the developing device 104 develops the electrostatic latent image into a toner image corresponding to the toner color in the developing device. On the other hand, the recording paper is adjusted in timing by the registration roller 105, and is conveyed toward the transfer device 106 in order to fix the image developed on the photosensitive drum 100 on the surface thereof. The transfer device 106 transfers the toner image on the photoconductor drum 100 onto the conveyed recording paper. As it is, the toner image on the recording paper is in an unstable state, so that the fixing device 108 heat-fixes the toner image by sandwiching the recording paper with heating rollers. The cleaner 107 removes adhered residue such as toner that remains without being transferred. A desired image can be formed on the recording paper by the above series of flow.

In the above-mentioned electrophotographic process, various parameters such as the potential when the photoconductor drum 100 is charged by the charger 101, the exposure amount at the time of exposure, and the developing bias at the time of developing by the developing device 104 are set. Need to control. That is, the image density on the recording paper can be kept constant by correcting the parameters according to the surrounding environment or the state peculiar to the device. Here, the developing device 104
The inside is a two-component developing system, and the developing device 104 contains a magnetic carrier and a predetermined amount of toner. When the image is formed, the toner is electrostatically adsorbed on the surface of the photoconductor drum 100 by the magnetic carrier, so that the amount of toner in the developing device 104 is reduced. If it is left as it is, the toner density in the developing device 104 is gradually lowered, and the image density on the recording paper is also reduced. Therefore, the developing device 10
Place the toner bottle 109 containing toner in the vicinity of 4,
It is necessary to supply the reduced amount of toner from the developing device 104.

Generally, a magnetic permeability sensor is used to detect the toner density in the developing device 104. Developing device 10
Since the toner and the magnetic carrier are mixed at a constant ratio inside 4, the magnetic permeability in the developing device changes when the toner decreases due to image formation. The change is detected by a magnetic permeability sensor installed inside the developing device. FIG. 6 shows the relationship between the output of a general magnetic permeability sensor and the toner concentration. In this way, since the toner concentration in the developing device can be estimated from the output of the magnetic permeability sensor, the toner concentration in the developing device can be controlled using the output of the magnetic permeability sensor.

[0008]

As described above, in the conventional electrophotographic apparatus, in order to control the toner concentration inside the developing device, it was necessary to install a magnetic permeability sensor inside. However, this magnetic permeability sensor is by no means an inexpensive part, and in the case of a monochrome electrophotographic apparatus, only one is required, but in the case of a color machine, the number of developing devices is required. Therefore, it has been one of the factors that particularly increase the cost of color devices.

[0009]

An electrophotographic apparatus according to the present invention counts the number of print pixels of an image to be output, and a two-component developing type developing device using a developer composed of toner and a magnetic carrier. Print pixel number detection means, parameter detection means for detecting the value of a parameter that affects the development amount of toner, and the developer after image output based on the detection values of the print pixel number detection means and the parameter detection means And a toner supply control means for controlling the toner supply amount so as to keep the toner density constant based on the toner density calculated by the toner density calculation means. It is a characteristic electrophotographic device. This eliminates the need for a magnetic permeability sensor or the like for measuring the toner concentration of the developer in the developing device, which is effective for cost reduction.

In addition to the above structure, a toner density estimating means for estimating the toner density of the developer by detecting the image density of the toner image formed on the photoconductor, the transfer body or the transfer material. Error signal calculation means for calculating a difference between the toner density estimated by the toner density estimation means and the toner density regarded as being kept constant by the toner density calculation means and the toner supply control means. The toner concentration calculating means outputs the toner based on the error signal calculated by the error signal detecting means in addition to the detection values of the print pixel number detecting means and the parameter detecting means It is preferable to calculate the concentration. Thus, by periodically feeding back the toner density estimated from the image density of the toner image, it is possible to correct the accumulated error of the toner density calculation value during long-term use.

Further, in the above arrangement, it is preferable that the toner concentration calculating means has a neural net. As a result, it is possible to accurately keep the toner density constant according to changes in the situation.

Further, in the above structure, the difference between the toner density, which is considered to be kept constant by the toner density calculation means and the toner supply control means, and the actually measured toner density is a constant value. It is preferable that the following learning is performed in advance. As a result, the toner density can be made constant with high accuracy.

Further, the neural network is learned so that the difference between the toner density estimated based on the detection values of the pixel number detecting means and the parameter detecting means and the actually measured toner density is a fixed value or less. It is also possible to replace with the table obtained by doing. This can further simplify the system.

When an input signal which is not in the table is input, linearly interpolating an output value obtained from input values around the input signal in the table,
It is preferable to calculate an output value corresponding to the corresponding input value. This improves accuracy and enables more stable control.

Further, it is preferable that the parameter affecting the developing amount of the toner is electrophotographic process conditions or temperature and humidity. As a result, it is possible to suppress the influence of errors due to changes in the environment and changes with time.

Further, it is preferable that the print pixel number detecting means counts the number of print pixels in the entire page. As a result, the amount of toner required to print one page is known in advance, so that toner can be supplied in advance and stable control can be performed even when printing an image that consumes a lot of toner.

Further, it is preferable that the print pixel number detecting means counts the print pixel number in each area obtained by dividing the entire page into a predetermined number for each area. As a result, when there is an image that partially consumes toner in one page, it is possible to supply the toner with finer timing, and more stable control is possible.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
It will be described in detail with reference to the drawings.

FIG. 1 is a schematic block diagram of an electrophotographic apparatus according to the present invention. In FIG. 1, the configuration other than the developing device 104 is the same as that described using FIG.
Inside the developing device 104, the magnetic permeability sensor 10 (hereinafter, Tc
There is a space where the sensor can be installed, and it will be installed if necessary.

FIG. 2 shows a block diagram of the toner density control system according to the present invention. The density controller 20, which is a toner density calculator, has a neural network structure inside,
The Tc sensor output predicted value B is output by internally calculating from various input signals. Here, as the parameters input to the density control unit, the output of the pixel count unit 23, which is the print pixel number detection unit, and the outputs of the development bias detection unit 24 and the temperature / humidity sensor detection unit 25, which are an example of the parameter detection unit, is there. The pixel counting unit 23
In the page to be printed, the number of pixels actually printed, that is, the number of pixels to which toner is attached is detected, and the total number of printed pixels is output. At this time, it is possible to divide the whole into several areas and output the number of print pixels for each area.

The developing bias detector 24 includes a developing device 104.
At, the value of the developing bias applied when developing the electrostatic latent image on the photosensitive drum 100 is detected. Normally, the value of the developing bias is not always constant, but is controlled by the device-specific state such as the surrounding environment such as temperature and humidity or the aging of the device. The temperature / humidity sensor detection unit 25 detects and outputs environmental conditions such as temperature and humidity at the position where the device is placed.

On the other hand, the solid patch detecting section 21, which is a toner density estimating means, reads the image density of a predetermined patch, estimates the toner density in the developer from the value of the image density, and corresponds to this toner density. The predicted output value A of the Tc sensor is output. The error signal calculation unit 22, which is an error signal calculation unit, calculates and outputs the difference between the Tc sensor output prediction value A output by the solid patch detection unit 21 and the Tc sensor output prediction value B output by the density control unit 20. . The error signal output by the error signal calculation unit 22 is input to the density control unit 20 and serves as an input signal to the neural network in the density control unit 20. The Tc sensor output predicted value B output by the density control unit 20 is also input to the toner supply amount calculation unit 26, and T
c The toner supply amount based on the sensor output predicted value B is calculated. Here, based on the calculated toner supply amount, the actuator 27 is operated to supply the toner from the toner bottle 109 into the developing device 104.

The configuration of FIG. 2 is a configuration for performing control in an actual machine, but in practice, before that, the concentration control unit 20
It is necessary to train the neural network inside. FIG. 3 shows the configuration at the time of learning. At the time of learning, the Tc sensor 28 is used instead of the solid patch detection unit 21. In other words, only during learning, the actual developing device 1
The Tc sensor 10 is installed inside 04, and the neural network is learned using the output.

The structure of a general neural network is shown in FIG. Here, the input layer is 4 as the number of input parameters.
The number of output signals is 1, and the number of output signals is 1, and the number of output layers is 1
There were 5 steps. In the calculation of the neural network, basically, a predetermined weighting coefficient is set for all signals input from the previous stage, and the sum of the input signal value and the value obtained by multiplying the weighting coefficient is used as its output value. When learning is performed, a set of input / output signals in which the number of input / output signals of the corresponding neural network is the same is required.

When nothing is learned, each weighting coefficient is set to a predetermined initial value. When an input signal comes in, calculation is performed and some output value is output at the final stage. This output value is compared with the teacher signal that is the actual measurement value to reset the internal weighting coefficient.
This is repeated by sequentially using the set of input / output signals prepared first, and the weighting coefficient is updated each time. When the error between the output value of the neural network and the corresponding teacher signal becomes less than or equal to a predetermined value, learning is terminated. Once the learning is completed, when the set of input signals used in the learning is input, the corresponding output signal is output. Also, when a deviated signal is input, calculation is performed using the weighting coefficient determined by learning, and the result is output.

In FIG. 3, the weight coefficient is updated by comparing the output value calculated by the neural network with the value (teacher signal) actually output by the Tc sensor.
In this way, the neural network can be regarded as a pseudo Tc sensor by using the output value of the Tc sensor as the teacher signal. In other words, bringing the output value of the neural network close to the output value of the Tc sensor is nothing but trying to make the neural network operate in the same way as the Tc sensor, and replacing it with the Tc sensor at the end of learning. You can

After the learning is finished once, the weighting coefficient of the neural network is introduced into the density control unit having the configuration of FIG.
The actual control operation will be described below with reference to FIG.

The pixel count unit 23 expands the image data when printing, and outputs the detection result when the number of print pixels of the entire page is counted. The developing bias detector 24 also detects the developing bias value because the developing bias for the next printing is determined at that timing. The temperature / humidity sensor detection unit 25 constantly monitors the environment of the device, and therefore takes in the output of the temperature / humidity sensor at the same timing. The concentration control unit 20 outputs the Tc sensor output predicted value B which is the calculation result with almost no delay. On the other hand, the solid patch detection unit 21 forms a solid patch on the photosensitive drum 100 or recording paper, reads it with a density sensor, and obtains a sensor output. Generally, the image density of the formed solid patch,
Since the toner density in the developing device 104 is deeply correlated, the toner density can be almost uniquely obtained from the sensor output. The toner density obtained here is used as a Tc sensor output predicted value A.

The difference between the predicted Tc sensor output value A and the predicted Tc sensor output value B is fed back to the neural network as an error signal. The timing is not every page whether the image density of the toner adhered on the photoconductor drum 100 is detected or the image density of the toner image-formed on the recording paper is detected. To detect on the photosensitive drum 100, the photosensitive drum 10
You have to turn 0 longer than usual. In order to detect on the recording paper, a patch must be formed on the recording paper, and extra paper and toner are consumed by the user. Therefore, the predicted output value A that has been obtained once has the same value until the next solid patch is read.

The predicted Tc sensor output value B calculated by the neural network is converted into the toner supply amount, that is, the actuator operation time in the toner supply amount calculation unit 26, and the actuator 27 is operated for that time to supply the toner.

Up to this point, the density control unit 20 has been configured using a neural network, but it is not always necessary to use a neural network during control. For example, a table of input / output signals may be generated based on the learned arithmetic expression of the neural network, and the table may be referred to. At that time, when an input signal that is not in the table is input, the interpolation processing is performed using the data in the table.

In the above description, since the number of print pixels on the entire page is counted, the density control unit 2 is set for each page.
It is assumed that the calculation at 0 is performed. However, it is also possible to divide one page by a predetermined number and count the number of print pixels for each area to perform calculation in the density control unit 20 for each area and supply toner.

Although the developing bias is used here as the electrophotographic process condition, the charging potential of the photosensitive drum or the exposure energy at the time of exposure may be used instead. Of course, these may be used at the same time.

Further, although the pixel counting section 23, the developing bias detecting section 24, and the temperature / humidity sensor detecting section 25 are used in the present embodiment, the present invention is not limited to the case where all of them are used, and at least one of them is used. The effect of the present invention can be obtained by using one of these.

[0035]

As described above, according to the electrophotographic apparatus of the present invention, the output value of the Tc sensor is learned as a teacher signal during learning of the neural network, so that the neural network functions as if it were a Tc sensor. You can This Tc sensor is expensive in terms of parts, and as many as the number of developing units are required, so that four Tc sensors are required in a color device. In the electrophotographic apparatus of the present invention, since the neural network functions as a pseudo Tc sensor, the sensor becomes unnecessary,
Significant cost reduction is expected.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus according to the present invention.

FIG. 2 is a block diagram of a toner density control method according to the present invention.

FIG. 3 is a block diagram at the time of learning a neural network of a toner density control method according to the present invention.

FIG. 4 is a structural diagram of a general neural network.

FIG. 5 is a schematic configuration diagram of a conventional electrophotographic apparatus.

FIG. 6 is a graph showing the relationship between the output of a general magnetic permeability sensor and the toner concentration of the surroundings.

[Explanation of symbols]

10 Tc sensor 20 Concentration control unit 21 Solid patch detector 22 Error signal calculator 23 pixel count section 24 Development bias detector 25 Temperature / humidity sensor detector 26 Toner Supply Amount Calculation Unit 27 Actuator 28 Tc sensor 100 photoconductor drum 104 developing device 109 toner bottle

Continued front page    F term (reference) 2H027 DA10 DA11 DA14 DB01 DD07                       DE04 DE07 EA06 EC02 EC06                       EC09 EC10 ED06 ED10 EE07                 2H077 AD35 DA03 DA10 DA18 DA42                       DA47 DA49 DA52 DA78 DA80                       DB01 DB22 EA03

Claims (9)

[Claims] 1. A two-component development type developing device using a developer composed of toner and a magnetic carrier, a print pixel number detecting means for counting the print pixel number of an image to be output, and a developing amount of toner. Parameter detecting means for detecting the value of an influencing parameter, and toner density calculating means for calculating the toner density in the developer after image output based on the detection values of the print pixel number detecting means and the parameter detecting means. An electrophotographic apparatus, comprising: a toner supply control unit that controls a toner supply amount so as to keep the toner concentration constant based on the toner concentration calculated by the toner concentration calculation unit. 2. A toner density estimating means for estimating the toner density of the developer by detecting the image density of a toner image formed on a photoconductor, a transfer body or a transfer material, and the toner density estimating means. And an error signal calculation means for calculating a difference between the toner density estimated by the toner density calculation means and the toner density which is considered to be kept constant by the toner density calculation means and the toner supply control means. However, in addition to the detection values of the print pixel number detection means and the parameter detection means, the toner concentration in the developer after image output is calculated based on the error signal calculated by the error signal detection means. The electrophotographic apparatus according to claim 1, which is characterized in that. 3. The electrophotographic apparatus according to claim 1, wherein the toner density calculation means has a neural net. 4. The difference between the measured toner density and the toner density, which is considered to be kept constant by the toner density calculation means and the toner supply control means, of the neural network is less than a certain value. The electrophotographic apparatus according to claim 3, wherein the electrophotographic apparatus is previously learned. 5. The difference between the toner density that the neural network is considered to be kept constant by the toner density calculation means and the toner supply control means, and the actually measured toner density is less than a certain value. The electrophotographic apparatus according to claim 3, wherein the table is replaced with a table obtained by learning. 6. When an input signal that is not in the table is input, linearly interpolating an output value obtained from an input value around the input signal in the table, an output corresponding to the corresponding input value. The electrophotographic apparatus according to claim 5, wherein a value is calculated. 7. The electrophotographic apparatus according to claim 1, wherein the parameter affecting the development amount of the toner is an electrophotographic process condition or a temperature / humidity condition. 8. The electrophotographic apparatus according to claim 1, wherein the print pixel number detection means counts the print pixel number in the entire page. 9. The printing pixel number detecting means counts the number of printing pixels in each area obtained by dividing the entire page into a predetermined number for each area, according to any one of claims 1 to 7. Electrophotographic device.