JP2002268293A - Toner concentration control method and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the number of pattern forming times for a pattern density sensor minimum and to obtain excellent image density. SOLUTION: In this toner concentration control method for the electrophotographic device, a toner concentration sensor 4 detecting toner concentration from the magnetic permeability of developer in a developing device 2 and a pattern density sensor 3 detecting the density of a reference pattern formed on a photoreceptor 1 are used, and then toner supply amount is decided from a difference between output from the sensor 4 and a reference value, the reference pattern is formed on the photoreceptor in specified timing so as to detect the density thereof by the sensor 3, and the electrified amount of toner is predicted according to a matrix consisting of the detected result by the sensor 3 and the output from the sensor 4 at normal operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner density control device for an electrophotographic apparatus using a two-component developer in an electrophotographic apparatus such as a copy machine, a facsimile machine, a printer, etc., and more particularly to a difference between a toner density of a developer and a reference value. And a toner density control device configured to correct the reference value according to the state of formation of the reference pattern on the photoconductor, and an electrophotographic apparatus to which the toner density control method is applied. is there.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic apparatus using a two-component developer, how to control the toner concentration of the developer has been an important issue. As a method of controlling the toner density, there is a technique of replenishing the toner to a constant toner density using a toner density sensor as disclosed in Japanese Patent Application Laid-Open No. 1-154179. In this case, as disclosed in Japanese Patent Application Laid-Open No. 63-58472, some circuit is added to suppress the variation of the output of the toner density sensor, and the output of the toner density sensor is adjusted to fall within a predetermined range. Was common.

However, such a technique for controlling the toner concentration to a constant level has the following disadvantages. That is, even if the toner density is the same, the density of the output image of the electrophotographic apparatus changes depending on the temperature and humidity of the surrounding environment and the usage conditions of the developer. This is a problem due to the fact that electrophotography performs development by frictionally charging toner, and is a very essential problem. As a toner density control method for solving this problem, there is a technique of forming a reference pattern on a photoreceptor and supplying toner so that the density of the pattern becomes constant. In such a control method for controlling the pattern density to be constant,
There are the following problems. In other words, if the toner density must be significantly increased in order to guarantee the pattern density depending on the temperature and humidity environment and the usage conditions, the toner cannot be charged sufficiently, and the toner blows out from the developing device to contaminate the inside of the machine and cause a failure. Conversely, when the toner concentration must be extremely reduced, the carrier may adhere to the photoreceptor and cause a failure. In such a case,
Even if the pattern density slightly deviates from the target, it is better to keep the toner density within a certain range. Therefore, a technique has been developed in which the toner density sensor is used in combination with a pattern density sensor for detecting the reflection density of the reference pattern of the photoconductor.

[0004] Such techniques include, for example, Japanese Patent Application Laid-Open
There is a technique described in Japanese Patent No. 34877. In this technique, normally, toner is replenished by a toner density sensor so as to keep the toner density constant, a reference pattern is formed at predetermined time intervals or every predetermined number of copies, and the pattern density is detected by the pattern density sensor. The control reference value is changed based on the output value of the toner density sensor according to the detection result. Then, a reference value corresponding to the upper and lower limit values of the toner density is determined in advance, and control is performed so that the reference value is not shifted outside the range of the upper and lower limit reference values even if the pattern density deviates from the target. By adopting this technology,
An electrophotographic apparatus capable of obtaining a stable image density without any trouble can be provided. However, the pattern for the pattern density sensor consumes unnecessary toner on the photoconductor. In addition, when the contact transfer unit is used from the viewpoint of ozone-lessness, the back surface of the recording paper is stained unless the photosensitive member and the transfer unit are brought into contact with and separated from each other every time a pattern is formed. The provision of the contact / separation mechanism increases costs. Further, it takes time to clean the transfer unit, and productivity is impaired.

Further, when the environmental conditions and the like are greatly changed and the appropriate target value of the toner density sensor is greatly changed, a pattern is formed many times to obtain an appropriate image density by using the density sensor. Unless corrected, an appropriate image density could not be obtained. During this time, for example, when the toner concentration is high, the blowing of the toner occurs, and the inside of the apparatus is stained or the image is stained. Further, when the toner concentration is too low, it is necessary to take a number of useless thin images, and the productivity is reduced.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to obtain a good image density while minimizing the number of times of forming a pattern for a pattern density sensor. .

[0007]

According to one aspect of the present invention, there is provided a toner density control method for an electrophotographic apparatus, comprising the steps of: determining a toner density from a magnetic permeability of a developer in a developing apparatus; And a pattern density sensor for detecting the density of the reference pattern formed on the photoreceptor. During normal operation, toner is supplied based on the difference between the output of the toner density sensor and the reference value. The amount of toner is determined, a reference pattern is formed on the photoconductor at a predetermined timing, the density is detected by the pattern density sensor, and the toner charge amount is predicted by a matrix composed of the detection result and the output of the toner density sensor. This is a density control method. The invention according to claim 2 is an electrophotographic apparatus, wherein a toner density sensor for detecting a toner density from a magnetic permeability of a developer in the developing apparatus, and a density of a reference pattern formed on a photoreceptor are detected. During normal operation, a toner replenishment amount is determined from a difference between the output of the toner density sensor and a reference value, and a reference pattern is formed on a photoreceptor at a predetermined timing to determine the density. An electrophotographic apparatus having toner density control means for detecting by a pattern density sensor and estimating the charge amount of toner by a matrix composed of the detection result and the output of the toner density sensor.

According to a third aspect of the present invention, there is provided a toner density control method for an electrophotographic apparatus, comprising: a toner density sensor for detecting a toner density from a magnetic permeability of a developer in a developing apparatus;
And a pattern density sensor for detecting the density of the reference pattern formed on the photoreceptor. During normal operation, the toner replenishment amount is determined from the difference between the output of the toner density sensor and the reference value, and at a predetermined timing. A reference pattern is formed on the photoreceptor by using the pattern density sensor, and the density is detected by the pattern density sensor. The toner charge amount is estimated by a matrix composed of the detection result and the output of the toner density sensor. Is calculated as a toner density control method. According to a fourth aspect of the present invention, there is provided an electrophotographic apparatus, wherein a toner density sensor for detecting a toner density from a magnetic permeability of a developer in the developing apparatus and a density of a reference pattern formed on a photoreceptor are detected. During normal operation, a toner replenishment amount is determined from a difference between the output of the toner density sensor and a reference value, and a reference pattern is formed on a photoreceptor at a predetermined timing to determine the density. An electrophotographic apparatus having a toner density control means for detecting the amount of toner by a matrix composed of the detection result and the output of the toner density sensor. .

According to a fifth aspect of the present invention, there is provided a toner density control method for an electrophotographic apparatus, comprising: a toner density sensor for detecting a toner density from a magnetic permeability of a developer in a developing apparatus;
And a pattern density sensor for detecting the density of the reference pattern formed on the photoreceptor. During normal operation, the toner replenishment amount is determined from the difference between the output of the toner density sensor and the reference value, and at a predetermined timing. A reference pattern is formed on the photoreceptor by using the pattern density sensor, and the density is detected by the pattern density sensor. The toner charge amount is estimated by a matrix including the detection result and the output of the toner density sensor. The toner density control method calculates the density and replenishes the toner to an appropriate amount while driving the developing roller 3 and the replenishing unit. The invention according to claim 6 is
An electrophotographic apparatus, comprising: a toner density sensor for detecting a toner density from a magnetic permeability of a developer in a developing apparatus; and a pattern density sensor for detecting a density of a reference pattern formed on a photoreceptor. During operation, a toner replenishing amount is determined from a difference between an output of the toner density sensor and a reference value, a reference pattern is formed on a photoconductor at a predetermined timing, and the density is detected by the pattern density sensor. A toner density control means for estimating a toner charge amount in a matrix composed of the result and an output of the toner density sensor and calculating an optimum toner density from the toner charge amount; An electrophotographic apparatus that supplies toner to an appropriate amount while driving the unit.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a schematic diagram showing a structure around a photosensitive member of an electrophotographic apparatus using a toner density control method of the present invention. In this electrophotographic apparatus, a photosensitive member 1 as a cylindrical image carrier is rotatably supported in the direction of an arrow, and a charging roller, an exposing unit, a developing device 2, a transfer device, a cleaning blade, etc. are provided around the photosensitive member 1. Are sequentially arranged, and each member except the transfer device is accommodated in the photoconductor 1 and the cleaning device. The developing device 2 is housed in a developing housing having an opening, and the developing roller 3 is rotatably supported at the position of the opening, and is disposed so as to be in close proximity to the surface of the photoconductor 1. A transport screw is disposed at a position facing the developing roller 3 in the developing housing, and is rotatably supported.

Next, the operation of the above-described electrophotographic apparatus will be described. The photoreceptor 1 is uniformly charged by a charging roller, and thereafter, is exposed to an image to form an electrostatic latent image on the photoreceptor 1. The developing device 2 contains a two-component developer T. The two-component developer is a mixture of a magnetic powder called a carrier and a non-magnetic toner. When the developer is stirred, the toner is charged by frictional charging. The developer containing the charged toner is pumped up onto the developing roller 3, conveyed with the rotation of the developing roller 3, and transferred to an electrostatic latent image on the photoconductor 1 at a position facing and close to the photoconductor 1, Form a toner image. A voltage having a polarity opposite to that of the toner is applied to the transfer device from a power supply. The electric field between the transfer device and the photoconductor 1 causes the toner image developed on the photoconductor 1 to be transferred between the photoconductor 1 and the transfer device. Is transferred onto the transfer paper sandwiched between the. The transfer paper is then conveyed by the transfer device, and when passing through the fixing device, the toner image is thermally fused onto the transfer paper. On the other hand, the toner remaining on the photoreceptor 1 without being transferred is blocked by a cleaning blade and stored in a cleaning device.

Further, newly supplied toner is supplied into the developing device 2 from the toner supply port. Another object of the present invention is to determine the amount of toner to be supplied. Therefore, it is necessary to accurately grasp the state of the toner such as the toner concentration and the amount of charge in the developing device 2. For this purpose, one is provided with a toner concentration sensor (hereinafter referred to as "T sensor") 4 for detecting the toner concentration from the magnetic permeability of the developer in the developing device. FIG. 2 is a graph showing the relationship between the toner density and the toner density sensor. The detection of the T sensor 4 has an advantage that the dependence on the environment or the like is small.
Further, a pattern detection sensor (hereinafter, referred to as “P sensor”) 3 for detecting the density of the reference pattern formed on the photoconductor is provided. FIG. 3 is a graph showing the relationship between the P sensor output and the image density.

However, the image density is determined by
The toner density and the toner charge amount. Conventionally, it has been difficult to measure the toner charge amount using a sensor or the like.
It is quantified by sampling the mixture of carrier and toner and measuring the opposing charge generated by blowing off the toner through the mesh.An apparatus is provided for quantifying the amount of toner charge, and an actual device is provided. It was difficult to measure automatically in an electrophotographic apparatus. But,
To grasp the toner charge amount is an essential element for adjusting the image, and if it can be easily measured, it is an important element for easily improving the image quality. However, the amount of toner charge greatly changes depending on environmental conditions and copy frequency, which is a factor of deteriorating image quality. Generally, as the toner dries due to environmental fluctuations, the toner charge amount tends to increase. Conversely, when the humidity is high, the charge amount of the toner decreases. Accordingly, the image density changes.

FIG. 4 is a graph showing the relationship between the toner density and the image density when the toner charge amounts are different. When the toner charge amount is constant, a logarithmic law curve is obtained as shown in FIG. If the toner charge amount is constant and low, draw a curve on the side where the toner concentration (mass ratio between developer and toner) is low,
When the toner charge amount is constant and high, the curve falls and the curve is drawn on the side where the toner density is high. Further, if the image is continuously output, the charge amount of the toner increases. In this case, as in the case of the environmental change, the curve falls and the curve is drawn on the side where the toner density is high. From this, if the toner density can be detected and the image density can be detected, the toner charge amount can be predicted. For example, when several tens of sheets are used per day, the amount of toner charge is low, and a curve is drawn on the side where the toner concentration is low. When the toner charge amount is constant, it has been found that the toner density and the image density are uniquely determined. If the toner density (output of the T sensor) and the image density (output of the P sensor) are known, the toner charge is determined. The amount can be predicted. FIG. 5 is a table for estimating the toner charge amount from the T sensor output and the P sensor output. The toner charge amount can be predicted by referring to the value mapped in this table.

(Second Embodiment) The toner charge amount (toner charge amount) and the toner concentration (toner concentration) required to make the image density 1.35, for example, are as shown in FIG.
We found that there was a correlation. FIG. 6 is a graph showing that the image density is determined by the toner charge amount and the toner density. Using the relationship of FIG. 6 with respect to the toner charge amount predicted from the (P sensor, T sensor) matrix shown in FIG. 5, it is possible to set an appropriate toner density target value for setting the image density to 1.35, for example. . In this example, the density is 1.35, but the density may be changed as needed.

(Third Embodiment) For example, when the device is used in a high-humidity state, and the air-conditioner or the like is activated, the amount of toner charge rises at a stretch if the humidity rapidly decreases. When this change is detected and control is performed, control for rapidly increasing the toner concentration is performed. Conventionally, the toner density was gradually increased, so that the proper toner density was not easily obtained, and the image quality was deteriorated. However, in the present invention, the toner is replenished to the proper toner density at a stretch. As a side effect, a large amount of uncharged and unstable toner is present in the development due to insufficient stirring of the toner, which causes a problem of background contamination and toner blowing. In the present invention, since the toner supplied by driving the developing roller 3 and the replenishing unit is charged and the density of the entire toner and carrier is kept constant, unstable toner is not generated, and the target toner density is maintained. Can be raised.

[0017]

As described above, according to the first or second aspect of the present invention, the toner charge amount can be predicted during the operation of the electrophotographic apparatus without using a large-scale apparatus, so that the image quality is improved. Can be adjusted well. Moreover, costs can be reduced. Further, in the invention according to claim 3 or 4, since the image quality is adjusted by performing the correction temporarily while detecting the image density, the change may not be able to be followed. In addition, the pattern image must be made many times, wasteful consumption of toner is caused, and the transfer roller is soiled. These problems have been solved because the proper toner density is calculated and controlled by one detection. Further, in the invention according to claim 5 or claim 6,
Further, even if a sharp toner replenishment operation is performed, side effects such as background contamination and toner blowing can be suppressed, and a good image can always be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration around a photosensitive member of an electrophotographic apparatus using a toner density control method of the present invention.

FIG. 2 is a graph showing a relationship between a toner density and a toner density sensor.

FIG. 3 is a graph illustrating a relationship between a P sensor output and an image density.

FIG. 4 is a graph showing a relationship between toner density and image density when toner charge amounts are different.

FIG. 5 is a table for estimating a toner charge amount from a T sensor output and a P sensor output.

FIG. 6 is a graph showing that an image density is determined by a toner charge amount and a toner density.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing device 3 Developing roller 4 T sensor 5 P sensor

Claims (6)

[Claims] 1. A toner density control method for an electrophotographic apparatus, comprising: a toner density sensor for detecting a toner density from a magnetic permeability of a developer in a developing device; and a density of a reference pattern formed on a photoreceptor. Pattern density sensor to detect
During normal operation, the toner replenishment amount is determined from the difference between the output of the toner density sensor and the reference value, a reference pattern is formed on the photoconductor at a predetermined timing, and the density is detected by the pattern density sensor. And a method for predicting the amount of charge of the toner using a matrix including the detection result and the output of the toner density sensor. 2. An electrophotographic apparatus, comprising: a toner density sensor for detecting a toner density from a magnetic permeability of a developer in a developing device; and a pattern density sensor for detecting a density of a reference pattern formed on a photoconductor. During normal operation, a toner replenishment amount is determined from a difference between the output of the toner density sensor and a reference value, a reference pattern is formed on a photoconductor at a predetermined timing, and the density is determined by the pattern density sensor. An electrophotographic apparatus comprising: a toner density control unit that detects, and predicts a charge amount of a toner using a matrix including a detection result and an output of a toner density sensor. 3. A toner density control method for an electrophotographic apparatus, comprising: a toner density sensor for detecting a toner density from a magnetic permeability of a developer in a developing apparatus; and a density of a reference pattern formed on a photoreceptor. During normal operation, a toner replenishment amount is determined from the difference between the output of the toner density sensor and a reference value, and a reference pattern is formed on the photoconductor at a predetermined timing to determine the density. A toner density control method, wherein the toner density is detected by the pattern density sensor, the charge amount of the toner is predicted by a matrix composed of the detection result and the output of the toner density sensor, and the optimum toner density is calculated from the toner charge amount. 4. An electrophotographic apparatus, comprising: a toner density sensor for detecting a toner density from a magnetic permeability of a developer in a developing device; and a pattern density sensor for detecting a density of a reference pattern formed on a photoreceptor. During normal operation, a toner replenishment amount is determined from a difference between the output of the toner density sensor and a reference value, a reference pattern is formed on a photoconductor at a predetermined timing, and the density is determined by the pattern density sensor. An electrophotographic apparatus having a toner density control unit for detecting, detecting a toner charge amount using a matrix including a result of the detection and an output of a toner density sensor, and calculating an optimum toner density from the toner charge amount. 5. A toner density control method for an electrophotographic apparatus, comprising: a toner density sensor for detecting a toner density based on a magnetic permeability of a developer in a developing apparatus; and a density of a reference pattern formed on a photoreceptor. Pattern density sensor to detect
During normal operation, the toner replenishment amount is determined from the difference between the output of the toner density sensor and the reference value, a reference pattern is formed on the photoconductor at a predetermined timing, and the density is detected by the pattern density sensor. Then, the amount of toner charge is predicted using a matrix composed of the detection result and the output of the toner concentration sensor, and the optimum toner concentration is calculated from the amount of toner charge. A toner concentration control method characterized by replenishing the toner. 6. An electrophotographic apparatus, comprising: a toner density sensor for detecting a toner density from a magnetic permeability of a developer in a developing device; and a pattern density sensor for detecting a density of a reference pattern formed on a photoreceptor. During normal operation, a toner replenishment amount is determined from a difference between the output of the toner density sensor and a reference value, a reference pattern is formed on a photoconductor at a predetermined timing, and the density is determined by the pattern density sensor. Detecting a toner charge amount in a matrix including the detection result and the output of the toner density sensor, and calculating an optimal toner density from the toner charge amount. The toner density control means includes: An electrophotographic apparatus characterized in that toner is replenished to an appropriate amount while a developing roller 3 and a replenishing unit are driven.