JP2000112207A - Development control method for potential divided development system and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an image to an initial image-level from a degraded state, caused by deterioration of developer with time and a fog increase due to scrape, by changing the set value of toner concentration from a first set value for ordinary printing to a second set value that is lower than the first set value, and returning it to the first set value after the discharge of toner onto a photoreceptor, thereby returning the toner concentration to the ordinary value. SOLUTION: In an idle running process in which a development process is carried out without transferring toner developed on a photoreceptor to a recording medium, a power source is set so that the development bias of a first developing machine has potential Vb1r that is nearer to the positive side than a photoreceptor surface potential Vw, and, at the same time, the set value of the toner concentration of developer is changed from an ordinary first set value to a second set value that is lower than the first set value. After the idle running process is carried out until the toner concentration in the developing device reaches the second set value, the development bias of the developing device is returned to an ordinary potential Vb1, at the same time, the set value of the toner concentration is returned to the ordinary first set value, and the idle running process is resumed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording apparatus for visualizing an image using toner, such as a printer, a facsimile, and a copying machine, and more particularly, to a developing apparatus for forming a toner image on the surface of a recording medium. The present invention relates to a developing method in a process and a recording apparatus using the same.

[0002]

2. Description of the Related Art A conventional developing method and a conventional developing device will be described below. 2. Description of the Related Art A recording apparatus using an electrophotographic method includes a developing step of developing toner as an image on a recording medium surface and a fixing step of fixing the developed toner image to a recording medium. In the developing step, first, toner particles, which are colored particles, are charged using a developer. The developer is a mixed powder of toner and carrier beads as magnetic particles. The developer is sealed in the developing device and is stirred there. The toner is charged by friction with carrier beads generated at that time. In the image forming process of the developing process, a method usually called bias development is used. The entire surface of the photoreceptor is once charged, and then is irradiated with light to partially discharge the photoreceptor. At that time, a potential contrast is formed on the photoreceptor surface by the charged region and the discharged region, and this is called an electrostatic latent image. In the bias development, a bias voltage is applied to a magnet roller called a developing roller that transports the developer to a position opposite to a developing position corresponding to the electrostatic latent image on the surface of the photoconductor of the developing device, thereby forming the image on the surface of the photoconductor. The toner particles charged by the action of the electric field generated between the latent image potential and the developing roller are separated from the developer on the developing roller surface and moved to the photoreceptor surface to form an image. The potential difference between the bias voltage of the developing roller and the latent image forming portion of the photoconductor is called a developing potential difference. If the development potential difference is large, the formed electric field (referred to as development electric field) becomes strong, so that the development performance is enhanced. Also, a method of reducing the distance between the developing roller and the photosensitive member and a method of reducing the electric resistance of the developer have an effect of similarly increasing the developing electric field, and can enhance the developing performance. Further, the developing performance is greatly affected by the charge amount of the developer. If the charge is too high,
Since the electric attraction force between the toner and the carrier beads is strong and the toner is hardly separated from the developer, the developing performance is reduced. If the charge amount is too low, the electric attraction between the toner and the carrier beads is weakened and the developing performance is enhanced. However, even when there is no developing electric field (when there is no electrostatic latent image), the toner is removed from the developer. It moves to the surface of the photoreceptor, and causes adhesion of toner other than the image portion, that is, an increase in fog. In order to perform electrophotographic image formation for a long period of time, a sensor always monitors the weight ratio of toner to carrier beads in the developing device (referred to as toner concentration), and uses the toner consumed in the developing process by the developing device. Replenishment is performed at any time from an attached toner supply device, and control is performed so that the toner concentration is always maintained at an appropriate value. There is a correlation between the charge amount of the developer and the toner concentration, and the charge amount changes with the change in the toner concentration. An appropriate value of the toner concentration is usually about 3 to 5% by weight. If the toner concentration is significantly out of the proper range, a shortage of toner supply to the surface of the photoreceptor and a change in developing performance due to a change in the amount of charge will adversely affect the developing process, resulting in image deterioration. In general, the level of the toner varies depending on the manufacturing method and the like, but there are variations in the properties relating to the developing performance such as the chargeability among the particles. Therefore, when printing is performed for a long time, toner having high developing performance is preferentially developed (referred to as selective development), and toner having low developing performance is accumulated in the developing device. For this reason, the ratio of toner having low developing performance in the developing device increases with time, causing a problem that the developing performance of the entire developing device is reduced.
Further, since the accumulated toner having a low developing performance stays in the developing device for a long time and continuously receives a load, the toner is fused and fixed on the carrier bead surface (the carrier bead having the toner fused and fixed on the surface is referred to as spent carrier), and the carrier is removed. This causes problems such as lowering the charging performance of the beads with respect to the toner. As a modified example of the above-described electrophotographic bias developing method, for example, as has been seen for a long time in JP-A-48-37148 and the like, the potential of the charged region and the discharge region of the photoconductor is divided into two to set an intermediate potential region. A first developing device for performing reversal development in the discharge region to develop the first color toner, and a second developing device for performing regular development in the charged region to develop the second color toner. By doing
A development method in which two-color development is performed by one charging step and light irradiation step (exposure step) has also been proposed. In this development method,
The toner is not developed in an intermediate potential region on the photosensitive member having a voltage value between the bias voltage value of the first reversal developing device and the bias voltage value of the second regular developing device, and a white background portion is formed as an image. Accordingly, a two-color image including a white background portion, a first color image portion, and a second color image portion can be formed. In the present specification, this two-color developing method is called a potential division developing method. In principle, even if the first development is regular development and the second development is reversal development, the potential division development system is possible.
In normal one-color development, the development performance can be compensated for by performing control to increase the development potential difference against the decrease in the development performance caused by the deterioration of the developer in the developing device described above. However, in the potential division developing method, the potentials of the charged region and the discharged region of the photoconductor are divided into two to separate the first and second potentials.
Because the development potential difference that can be used for development per color is small and there is no control margin for the development potential difference, the development by the deterioration of the developer in the developing device is performed in the same manner as the one-color development described above. Performance degradation cannot be compensated for. As another problem different from the deterioration of the developer, not only the potential division developing method, but in the case of a method of developing two-color toner on the photoconductor, when the second color development is performed, There is a problem in that the developed first color toner image is rubbed, and the first color toner is mixed into the second developing device (called scraping), which adversely affects the image. In the case of the potential division developing method, the first color toner and the second color toner have different charging polarities. Therefore, the first color toner mixed in the second developing device is exposed to an electric field in a direction opposite to the electric field in which the second color toner is developed. Developed on the body. In the potential division developing method, the area having the largest potential on the photoconductor where the second color toner is not developed is based on the bias voltage value of the first reversal developing device and the second regular developing device. The first-color toner mixed in the second developing device is mainly developed on the white background portion, because it corresponds to an intermediate potential region in which the white background portion formed between the bias voltage values of the apparatus is formed, which causes an increase in fog. Further, the mixing speed of the first color toner into the second developing device is one
If the discharge speed is higher than the discharge speed of the color toner, the first color toner is accumulated with time in the second developing device. Second
The first color toner that has been stagnated in the developing machine for a long time has a different charging polarity, and thus affects the second color developer, causing problems such as an increase in fog of the second color toner.
In order to solve the above problem, it is most effective to lower the mixing speed of the first color toner into the second developing device by scraping. However, the mixing speed of the first color toner into the second developing device is as follows. The mixing and discharging speed should be designed so that the first color toner does not accumulate in the second developing device because it varies not only with the rubbing force of the second developing device on the photoreceptor but also with the printing amount of the first color image. Is difficult. The above-mentioned problems that increase in fog due to the first color toner mixed and accumulated in the second developing device being developed on a white background portion and that fog of the second color toner is caused by the first color toner that has been stagnated in the second developing device for a long time. In this specification, this is collectively referred to as “increased fog due to scraping”.

[0003]

As described above, in the image forming apparatus using the conventional potential division developing system, the image deteriorates due to the deterioration of the developer over time and the increase in fog due to scraping. There was a problem. The present invention has been made in order to solve the above-mentioned problems of the prior art, and its object is to reduce the deterioration of the developer over time and the deterioration of an image due to an increase in fog due to scraping to an initial good image level. An object of the present invention is to provide an improved development control method and an image forming apparatus using the same.

[0004]

The above object is achieved by changing the set value of the toner concentration of the developer from a normal first set value to a second set value lower than the first set value. After the toner is discharged onto the photoconductor, the problem is solved by setting the toner density set value to the normal first set value and returning the toner density to the normal value. Specifically, in a state where only the intermediate potential portion is formed on the photoconductor, the bias potential of the developing device in which the negatively charged toner is sealed is set to a positive side from the intermediate potential, and the set value of the toner concentration of the developer is set. From the normal first setting value to the first
Was changed to a second set value lower than the set value, and in a state where the transfer device was not operated, the negatively charged toner was developed into an intermediate potential portion and collected by the cleaner, and then the negatively charged toner was sealed. The problem is solved by setting the bias potential of the developing device to a minus side of the intermediate potential, returning the set value of the toner density to the normal first set value, and replenishing the toner until the toner density becomes the normal value. Is done. More preferably, the bias potential of the developing device in which the negatively charged toner is sealed is set to a positive side from the intermediate potential, and the set value of the toner concentration of the developer is changed from the first set value during normal printing to the second set value. When the negatively charged toner is changed to the second set value lower than the first set value and the negatively charged toner is developed to the intermediate potential portion, the toner density is detected as needed, and the bias of the developing device in which the negatively charged toner is sealed is determined. By controlling the potential based on the control curve of the potential difference between the toner density prepared in advance, the intermediate potential portion, and the developing device in which the negatively charged toner is sealed, the above control method can be performed in a short time without causing the adverse effect of carrier jump. It can be carried out. Also,
The same control as described above can be solved by setting the bias potential of the developing device in which the positively charged toner is sealed to a minus side from the intermediate potential. In a state where only the intermediate potential portion is formed on the photoconductor, the difference between the bias potential of the second developing device and the intermediate potential is larger than the difference between the bias potential of the second developing device and the intermediate potential during normal printing. The problem is solved by setting the bias potential of the second developing device so that the developing process is performed in a state where the transfer device does not function.

[0005]

(Embodiment 1) Hereinafter, the first embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of an image forming apparatus using a potential division developing system to which the present invention is applied, wherein 1 is a photosensitive drum, 2 is a first charger, 3 is an exposure device, 4 is a first developer, 5 is a second developing machine, 6
Is a second charging machine, 7 is a transfer machine, 8 is a cleaner, 9 and 1
0 is a toner density sensor, 11 and 12 are toner supply devices, 13 is a recording medium, 14 is a control device, 15 and 16
Is the power supply. FIG. 2A shows the potential distribution on the photoconductor surface during normal printing in the potential division development, and the first developing device and the second developing device.
Schematic diagram of the bias potential of the developing machine (referred to as photoconductor potential diagram)
FIG. 2B is a diagram schematically showing a state in which the toner is developed from the bias potential of the developing device to the potential on the photoconductor at that time (hereinafter, referred to as a development schematic diagram).
Is a charging potential portion potential, 21 is an intermediate potential portion potential, 22 is a discharging potential portion potential, 23 is a developing bias potential of the first developing device, 2
4 is a developing bias potential of the second developing machine, 25 is a positively charged toner, and 26 is a negatively charged toner. . FIG. 3A is a potential diagram of a photoconductor during a developing process performed to improve an adverse effect on an image due to deterioration of a developer in the first developing device.
(B) is a development schematic diagram at that time, and 27 is the first development image at that time.
This is the bias potential of the developing machine. FIG. 4A is a potential diagram of a photoconductor during a developing process performed to improve an adverse effect on an image due to deterioration of the developer in the second developing device, and FIG.
FIG. 28 shows the development potential at that time. FIG. 28 shows the bias potential of the second developing machine at that time. In the two-color image forming apparatus of the present invention shown in FIG. 1, a negatively charged OPC is used for the photosensitive drum 1,
A case where a positively charged toner is used as the first color toner and a negatively charged toner is used as the second color toner will be described. In FIG. 1, the photosensitive drum 1 is rotating clockwise. First, the surface of the photosensitive drum 1 is uniformly negatively charged by a first charger 2.
Above are three levels of surface potentials Vca (20) and Vw (2
1) An electrostatic latent image composed of Vda (22) is formed.
The value of this surface potential will be described with reference to the symbols in FIG. 2A. Specifically, Vca is -900 V, and Vw is -45.
0V and Vda are values around -50V. Next, power supply 1
The first developer 5 to which the developing bias Vb1 (−650 V) is applied by the first developing unit 5 develops the positively charged first toner on the Vca portion on the photosensitive drum 1. Subsequently, the negatively charged second toner image is developed on the Vda portion on the photosensitive drum 1 by the second developing device 6 to which the developing bias Vb2 (-250 V) is applied by the power supply 16. FIG. 2B shows that the positively charged toner is developed on the Vca portion on the photosensitive drum 1 from the bias potential of the first developing device, and that the negatively charged toner is Vda on the photosensitive drum 1 from the bias potential of the second developing device. 5 schematically shows the state of development in a part.

[0006] The two-color toner image formed by the first toner image and the second toner image formed on the photosensitive drum 1 by the above-described procedure is corona-irradiated by the second charger 6 to make the charging polarity negative. . Thereafter, the image is transferred to a recording medium 13 such as paper by the transfer device 7 and is fixed by a fixing device not shown in FIG. After the toner remaining on the photosensitive drum 1 after the transfer is removed by the cleaner 8, the next two-color image is formed. When the above-described developing process is continuously performed, the toner concentration in each developing device is always detected by the toner concentration sensors 9 and 10, and the toner is consumed in the developing process by the toner supply devices 11 and 12 attached to the developing device. The toner is replenished at any time, and the controller 14 controls the toner concentration so as to always maintain the toner concentration at an appropriate value. When the development process described above is performed for a long time, toner having high development performance is preferentially developed due to variation in properties related to development performance such as chargeability between toner particles. It is stored in the developing device. for that reason,
In the developing device, the ratio of the toner having low developing performance increases with time. Further, in the potential division developing method, since the developing potential difference cannot be made large, it is necessary to enhance the developing performance of the toner itself in order to secure the image density. When using a method of externally or internally adding an additive such as a conductive agent for lowering the resistance of the toner, a charge controlling agent for maintaining the charge amount to an appropriate value, and silica or the like in order to enhance the developing performance of the toner. In general, toners having improved developing performance by prescribing such additives as described above generally remain in the developing device for a long time, and when subjected to a load, the additives are peeled off or buried, so that the developing performance is improved. And the image deteriorates. First
A development control method in the case where a color image deteriorates will be described below. First, only the intermediate potential Vw is formed on the photoreceptor by exposure with the exposure device 3, the function of the transfer device 7 is turned off, and the developing process is performed without transferring the toner developed on the photoreceptor to the recording medium 13. Execute
Hereinafter, the above-described developing process is referred to as an idling process. At this time, as shown in FIG. 3, the power supply 15 is set so that the developing bias of the first developing device becomes the potential Vb1r on the positive side of the photosensitive member surface potential Vw, and at the same time, the set value of the toner concentration of the developer. Is changed from a normal first set value to a second set value lower than the first set value. When the idling process is performed in the above-described state, the developing bias of the first developing device is at a potential on the positive side with respect to the photoconductor surface potential Vw. And then collected by the cleaner 8. Cleaner 8
Is limited, the development potential difference, that is, | Vw−Vb1r |, is set so as not to exceed the toner collecting capability of the cleaner 8. Further, since the set value of the toner density is changed to the second set value lower than the first set value, the toner supply is performed even if the toner density of the developer is lower than the normal toner density. However, the toner concentration in the developing device gradually decreases. After performing the idling process until the toner concentration in the developing device reaches the second set value, the developing bias of the developing device is returned to the normal potential Vb1, and at the same time, the set value of the toner concentration is set to the normal first set value. Return and continue the idling process. In this state, since the developing bias of the first developing device is at a potential on the negative side of the photoconductor surface potential Vw, the positively charged toner in the first developing device is not developed on the Vw portion on the photoconductor. Further, since the toner concentration in the developing device is lower than the normal first set value, the toner supply device 1 is operated until the toner concentration becomes the normal value.
1 to supply toner. The idling process is terminated when the toner concentration in the developing device reaches a normal value. With only the intermediate potential portion formed on the photoconductor as described above, the bias potential of the developing device in which the negatively charged toner is sealed is set to a positive side from the intermediate potential, and the set value of the toner concentration of the developer is The normal first set value is changed to a second set value lower than the first set value, and in a state where the transfer device is not operated, the negatively charged toner is developed to the intermediate potential portion and collected by the cleaner. After that, the bias potential of the developing device in which the negatively charged toner is sealed is set to a minus side from the intermediate potential, the set value of the toner density is returned to the normal first set value, and the toner density is set to the normal value. In the present specification, a series of processes for replenishing the toner until is reached will be referred to as an idling development process. Similarly, when the image of the second color is deteriorated,
As shown in FIG. 4A, the value of the developing bias of the second developing device is set to a potential Vb2r on the negative side of the photoconductor surface potential Vw.
And the same idling development process as that of the first developing machine is performed. The idling development process as described above may be performed when the operator visually confirms that the image has deteriorated, or automatically when the image recognition device attached to the printing apparatus determines that the image has deteriorated. You may. Alternatively, the span of the image deterioration due to the deterioration of the developer may be grasped in advance, and the idling development process may be automatically performed periodically. As described above, by performing the idling development process (development control) when the deterioration of the image is visually recognized by the operator or when the image recognition device recognizes the deterioration of the image, the deteriorated toner accumulated in the developing device is discharged and replaced with new toner. In addition, the deterioration of the developing ability can be improved to the initial level, and a good image can be obtained again. (Embodiment 2) In general, when the toner concentration decreases, a phenomenon (referred to as carrier skipping) in which carrier beads are developed from the developing device onto the photoreceptor surface tends to occur. Further, the carrier jump has a property that it increases as the difference between the bias of the developing device and the photoconductor surface potential (developing potential difference) increases. FIG. 5 is a diagram showing a range in which carrier jump occurs and a range in which carrier jump does not occur when the development potential difference and the toner density are used as parameters. FIG. 5 shows only a general tendency, and the boundary at which carrier jump occurs varies depending on the magnetic force of the developing roll, the electric resistance of the carrier beads, the magnetic properties, and the like. Reference numeral 30 denotes a developing bias potential control curve. In the developing control method described in the first embodiment, the power supply 15 is set so that the developing bias of the first developing device is set to a potential Vb1r on the positive side of the photosensitive member surface potential Vw, and at the same time, the set value of the toner density of the developer Is changed from the normal first set value to the second set value lower than the first set value, and the idling process is performed, the toner density decreases to a value lower than the normal toner density set value. . At this time, if the developing potential difference | Vw-Vb1r | is set small so as not to cause carrier jump, it takes a long time to discharge the deteriorated toner. On the other hand, in order to increase the discharge speed of the deteriorated toner, the development potential difference | Vw−V
If b1r | is set to a large value, carrier jump occurs when the toner concentration decreases, and the carrier developed on the photoreceptor is collected by the cleaner 8, which causes deterioration of the performance of the cleaner 8. Therefore, the correlation characteristics between the carrier jump and the toner concentration and the development potential difference as shown in FIG. 5 specific to the developing device are grasped in advance, and based on the detected toner concentration information, as shown in the developing bias control curve 30,
Development potential difference | V as long as carrier jump does not occur
By controlling the value of Vb1r so as to increase w-Vb1r |, it is possible to reduce the discharge time of deteriorated toner without causing carrier jump. (Embodiment 3) In the potential division developing method, two-color toner is developed on the photoconductor, so that when developing the second color, the toner image of the first color already developed on the photoconductor is rubbed. The first color toner is mixed into the second developing device (referred to as scraping). In the case of the potential division developing method, the first color toner and the second color toner have different charging polarities. Therefore, the first color toner mixed in the second developing device is exposed to an electric field in a direction opposite to the electric field in which the second color toner is developed. Developed on the body. In the potential division developing method, based on the second developing machine,
The area having the largest potential area on the photoreceptor where the second color toner is not developed is a white background portion formed between the bias voltage value of the first reversal developing device and the bias voltage value of the second regular developing device. Therefore, the first color toner mixed in the second developing device is mainly developed on a white background portion, which causes an increase in fog. Also, 1
When the mixing speed of the color toner is higher than the discharging speed of the first color toner to the white background, the first color toner is accumulated with time in the second developing device. The first color toner that has been stagnated in the second developing device for a long time affects the second color developer because the charging polarity is different. As a result, the first color toner accumulated in the second developing device causes an increase in fog due to scraping. When the fog exceeds an allowable level due to an increase in fog due to scraping, the developing bias of the second developing machine is controlled to Vb2s (29) shown in FIG. 6 to perform the idling process. Vb2s is | Vb2s-Vw
|> | Vb2−Vw |. Since the first color toner mixed in the second developing device is positively charged, the first color toner is developed on the Vw portion on the photoconductor, and thereafter collected by the cleaner 8. As the potential of Vb2s increases as | Vb2s−Vw | increases, the discharging ability of the first color toner increases, and thus the value of Vb2s may be set to the plus side potential. In this case, the polarity inversion function is provided. Since a power supply must be used, the cost of the power supply is increased. Also,
If | Vb2s−Vw | is too large, a phenomenon occurs in which the polarity of the toner is inverted due to the injection of charge into the negatively charged toner of the second color and the toner is developed in the Vw portion.
s-Vw | has an upper limit of about 600V. In the two-color image forming apparatus of the example shown in the first embodiment, it is desirable that the value of Vb2s is set to around 0V. Note that the above idling process may be performed when the operator visually confirms image deterioration, or may be automatically performed when image deterioration is determined by the image recognition device attached to the printing device. Good. Further, the above-described idling process may be automatically performed periodically by grasping in advance a span exceeding an allowable limit of increase in fog due to scraping. As mentioned above,
By performing the idling process (development control) when the increase in fog due to scraping is recognized visually by an operator or by an image recognition device, the second process can be performed efficiently and in a short time.
The first color toner accumulated in the developing device can be discharged, the increase in fog due to scraping can be reduced, and the fog can be returned to an allowable level.

[0007]

According to the present invention described above, deterioration of the developer over time and deterioration of an image due to an increase in fog due to scraping can be improved to an initial good image level.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a two-color image forming apparatus of the present invention.

FIG. 2 is a schematic diagram of a potential distribution on a photoreceptor surface and a development in potential division development.

FIG. 3 is a schematic diagram of a potential distribution on the surface of a photoconductor and development when a development control is performed on a first developing device.

FIG. 4 is a schematic diagram of a potential distribution on the surface of a photoconductor and development when a development control is performed on a second developing device.

FIG. 5 is a control curve of a carrier jump characteristic and a developing bias when developing control is performed.

FIG. 6 is a schematic diagram of a potential distribution on the surface of a photoconductor and a development when a development control for improving an increase in fog due to scraping is performed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... 1st charging machine, 3 ... Exposure device, 4 ...
1st developing machine, 5 ... 2nd developing machine, 6 ... 2nd charging machine, 7 ... Transfer machine, 8 ... Cleaner, 9, 10 ... Toner density sensor, 1
1, 12: toner supply device, 13: recording medium, 14: control device, 15, 16: power supply, 20: charged potential portion potential, 2
Reference numeral 1 denotes an intermediate potential portion potential, 22 denotes a discharge potential portion potential, 23 denotes a developing bias potential of the first developing device, 24 denotes a developing bias potential of the second developing device, 25 denotes a positively charged toner, and 26 denotes a negatively charged toner. Bias potential of the first developing device during development control for improving the deterioration of the image due to the deterioration of the developer, 28 bias of the second development device during the development control for improving the deterioration of the image due to the deterioration of the developer Potential, 29: bias potential of the second developer during the idling process for improving the increase of fog due to scraping, 30: developing bias potential control curve.

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Claims (7)

[Claims] 1. A photoconductor having at least a photoconductor, a charging unit, an exposure device, a developing device, and a toner replenishing device. The photoconductor is charged by the charging unit, and the exposure amount is changed by the exposure device. A three-stage electrostatic image consisting of a charged potential portion, a discharge potential portion, and a potential portion intermediate between them is formed thereon, and potential portions other than the intermediate potential portion are developed with positively charged toner and negatively charged toner. In an image forming apparatus that forms two types of toner images on a photoconductor, a second setting lower than the first setting value when the setting value of the toner concentration of the developer at the time of printing is the first setting value A developing control method that returns the toner density setting value to the first setting value and returns the toner density to the value at the time of printing, after changing the toner density onto the photosensitive member. 2. The method according to claim 1, further comprising at least a photoreceptor, a charging unit, an exposure device, a developing device, a transfer device, a toner replenishing device, and a cleaner, wherein the charging unit charges the photoreceptor and the exposure device changes an exposure amount. Thereby, the charged potential portion on the photoreceptor,
Forming a three-stage electrostatic image consisting of a discharge potential portion and an intermediate potential portion, and developing the image at a potential between the intermediate potential portion and the discharge potential portion or between the intermediate potential portion and the charging potential portion; An image forming apparatus that develops a potential portion other than an intermediate potential portion with a positively charged toner and a negatively charged toner by a machine to form two types of toner images on a photoreceptor, and transfers the toner image to paper by the transfer device. With only the intermediate potential portion formed on the photoreceptor, the bias potential of the developing device in which the negatively charged toner is sealed is set to the plus side from the intermediate potential, and the set value of the toner concentration of the developer at the time of printing is set to the positive value. When the set value was 1, the value was changed to the second set value lower than the first set value, and the negatively charged toner was developed to the intermediate potential portion and collected by the cleaner in a state where the transfer device was not operated. After that, the developing machine filled with negatively charged toner Developing control wherein the as potential is set to a minus side of the intermediate potential, the set value of the toner density is returned to the first set value, and toner is supplied until the toner density reaches the value at the time of printing. Method. 3. A photoconductor having at least a photoconductor, a charging device, an exposure device, a developing device, a transfer device, a toner replenishing device, and a cleaner. To form a charge potential portion, a discharge potential portion, and an intermediate potential portion on the photoreceptor.
Form an electrostatic image of the stage, between the intermediate potential portion and the discharge potential portion,
Alternatively, the developing unit set at a potential between the intermediate potential portion and the charged potential portion develops a potential portion other than the intermediate potential portion with a positively charged toner and a negatively charged toner, and forms two types of toner on the photosensitive member. In an image forming apparatus for forming an image and transferring the image to a sheet by the transfer device, the bias potential of the developing device in which the positively charged toner is sealed is set to a minus side from the intermediate potential, and the toner concentration of the developer during printing is adjusted. When the set value is the first set value, the cleaner changes the second set value to a second set value lower than the first set value, and develops the positively charged toner to the intermediate potential portion in a state where the transfer device is not operated. After that, the bias potential of the developing device in which the positively charged toner is sealed is set to the plus side from the intermediate potential, and the set value of the toner density is returned to the first set value, and the toner density is set at the time of printing. Replenish toner until the value A developing control method. 4. When the bias potential of the developing device in which the negatively charged toner is sealed is set to the plus side from the intermediate potential, and the set value of the toner concentration of the developer at the time of printing is set to a first set value, Change to a second set value lower than the set value of 1,
When developing the negatively charged toner to the intermediate potential portion, the toner concentration is detected as needed, and the bias potential of the developing device in which the negatively charged toner is sealed is adjusted to the previously prepared toner concentration, the intermediate potential portion, and the negatively charged toner. 3. The control according to claim 2, wherein the control is performed based on a control curve of a potential difference of the developing machine in which the developer is sealed.
The development control method described in the above. 5. When the bias potential of the developing device in which the positively charged toner is sealed is set to a minus side from the intermediate potential, and the set value of the toner concentration of the developer at the time of printing is set to a first set value, Change to a second set value lower than the set value of 1,
When developing the positively charged toner to the intermediate potential portion, the toner density is detected as needed, and the bias potential of the developing device in which the positively charged toner is sealed is adjusted to the toner density and the intermediate potential portion prepared in advance and the positively charged toner. 4. The development control method according to claim 3, wherein the control is performed based on a control curve of a potential difference of the developing machine in which the developer is sealed. 6. At least a photoconductor, a charging unit, an exposure device, a first developing machine, a second developing machine, a transfer device, and a cleaner, the photoconductor is charged by the charging device, and the exposure amount is set by the exposure device. Is changed into three stages, so that a charge potential portion, a discharge potential portion, and a potential portion intermediate therebetween are formed on the photosensitive member.
Form an electrostatic image of the stage, between the intermediate potential portion and the discharge potential portion,
Alternatively, the developing unit set at a potential between the intermediate potential portion and the charged potential portion develops a potential portion other than the intermediate potential portion with a positively charged toner and a negatively charged toner, and forms two types of toner on the photosensitive member. In an image forming apparatus for forming an image and transferring the image to a sheet by the transfer device, the difference between the bias potential of the second developing device and the intermediate potential in a state where only the intermediate potential portion is formed on the photoreceptor during normal printing. Second
A developing control method comprising: setting a bias potential of a second developing device so as to be larger than a difference between a bias potential of a developing device and an intermediate potential; and performing a developing process in a state where a transfer device is not operated. 7. An image forming apparatus using the development control method according to claim 1.