JP2011059178A - Toner consumption method for developing device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner consumption method and an image forming apparatus capable of preventing base-soiling and image-density lowering by consuming deteriorated toner in a developing unit at an appropriate timing, and then, capable of stably maintaining high quality images. <P>SOLUTION: The toner consumption method is configured as follows: a change in toner concentration in a developing device when a predetermined toner consumption pattern is developed is detected by a toner concentration sensor, and a toner consumption operation is performed by developing the toner consumption patterns a plurality of times so that phases of an output waveform of the sensor by the respective toner consumption operations are deviated from one another between the maximum value at the first round of the output waveform of the sensor and the maximum value at the second round of developer circulation, and then, the toner consumption operation is performed by forming and developing the toner consumption patterns so that the fluctuated waveform at the second round of the developer circulation of the composite waveform where the toner consumption waveforms generated by the respective toner consumption operations are overlapped with one another may be canceled. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a toner consumption method and an image forming apparatus in a two-component developing device.

  In recent image forming apparatuses such as copying machines and laser printers, high image quality is demanded and high stability is also desired. In other words, there is little change in image quality due to environmental fluctuations, and a stable image must be provided over time.

  Conventionally, a two-component developer composed of a non-magnetic toner and a magnetic carrier (hereinafter simply referred to as a developer) is held on a developer carrier (hereinafter referred to as a developing sleeve), and a magnetic brush is formed by a magnetic pole contained therein. 2. Description of the Related Art A two-component developing method is widely known in which development is performed by applying a developing bias at a position where a developing sleeve and a latent image carrier (hereinafter referred to as a photoconductor) face each other. The toner in the developer is consumed by being developed, and the toner is replenished to keep the toner density constant. In this way, the toner in the developing device is replaced.

  However, when outputting an image with a low image area ratio, the amount of toner used for development is small. That is, the amount of toner consumed is reduced. For this reason, when images with a low image area ratio are continuously output, the toner in the developing device is only slightly replaced, and as a result, the time that the toner exists in the developing device becomes long. Therefore, it is agitated for a long time and frictionally charged with the carrier. As described above, in a toner subjected to repeated stirring for a long period of time, a phenomenon in which an external additive such as silica or titanium oxide is embedded in the toner or detached from the surface occurs. Fluidity, charging characteristics, and physical adhesion between toner and carrier change. Such toner is called deteriorated toner. The deteriorated toner may cause problems such as background contamination due to a decrease in charging ability and charge holding ability, and a good image may not be obtained. Further, when images with a low image area ratio are continuously printed, as a result of an increase in the charge amount of the toner in the developing device, the developing ability is lowered and it is difficult to maintain the image density.

  As a countermeasure against the problems that occur during continuous printing of images with a low image area ratio as described above, there is known a method of forcibly consuming deteriorated toner in the developing device, supplying new toner, and replacing the toner in the developing device. Yes. This operation is called a toner refresh operation.

  For example, Japanese Patent Laid-Open No. 2008-216601 (Patent Document 1) describes a deteriorated toner in which a toner consumption pattern is created between transfer sheets (time or number of sheets from the end of previous image formation to the start of current image formation). Is disclosed.

  However, since this method creates a toner consumption pattern between transfer sheets, the area is small, and it is difficult to ensure a sufficient amount of toner consumption. Therefore, it is considered that the deteriorated toner cannot be consumed sufficiently. Further, although the consumption amount can be increased by increasing the frequency of creating the toner consumption pattern, the position of the deteriorated toner in the developing device is not considered at all, and the deteriorated toner cannot be consumed efficiently.

  Japanese Patent Laid-Open No. 2006-47651 (Patent Document 2) discloses a method of executing a toner refresh mode for recovering an image defect caused by deteriorated toner.

  In this countermeasure, first, an image sample is printed in order to determine whether an image defect due to deteriorated toner has occurred, and a toner refresh mode is executed in accordance with the result of the image sample. Here, when the toner consumption operation is performed, the deteriorated toner is consumed by creating a solid image patch having a size corresponding to one transfer sheet.

  Japanese Patent Application Laid-Open No. 2007-108623 (Patent Document 3) describes that a refresh operation is executed when the area ratio of an image being printed is lower than a threshold value. In this countermeasure method, a toner consumption pattern is created a plurality of times to consume a necessary amount of toner refresh.

  However, as described in Patent Document 2 and Patent Document 3, even if a toner consumption pattern that is larger than the toner consumption pattern between transfer sheets is created or a toner consumption pattern is created multiple times, it is efficient. Deteriorated toner may not be consumed. The deteriorated toner that can be consumed at a time in the toner consuming operation is a part of the developing device. Therefore, there are locations where the deteriorated toner has been consumed and locations where it has remained. In other words, even if a large toner consumption pattern is created or a toner consumption pattern is created multiple times, if the remaining deteriorated toner does not consume toner when it passes through the development area, the deteriorated toner will not enter the developer. It will remain.

  From the above, when performing toner consumption, it is necessary to execute the toner consumption operation at an accurate timing so that the deteriorated toner in the developing device can be efficiently discharged, but this has not been considered in the past, There is a problem that the deteriorated toner cannot be discharged efficiently.

  The present invention solves the above-mentioned problems in the conventional image forming apparatus, and prevents deterioration of the background stain and image density by consuming the deteriorated toner in the developing device at an appropriate timing, thereby stably producing a high-quality image. It is an object of the present invention to provide a toner refresh method and an image forming apparatus that can be maintained.

  According to the present invention, in the toner consumption method in the two-component developing device, the toner density sensor detects a change in toner density in the developing device when a predetermined toner consumption pattern is developed and the toner consumption operation is executed. Then, the phase of the output waveform of the toner density sensor by each toner consumption operation is between the maximum value of the first round in the output waveform of the detected toner density sensor and the maximum value of the second round due to developer circulation. The toner consumption pattern is developed a plurality of times so as to deviate, a toner consumption operation is executed, and the fluctuation waveform in the second round due to the developer circulation of the composite waveform in which the toner consumption waveforms generated by the respective toner consumption operations are superimposed is cancelled. This is solved by creating and developing a toner consumption pattern and performing a toner consumption operation.

  Further, it is preferable that the toner consumption operation is performed so that a peak portion of a toner consumption waveform by a toner consumption pattern for canceling the fluctuation waveform overlaps a valley portion of the fluctuation waveform of the second round due to the developer circulation of the composite waveform. .

  Further, the position of the minimum value of the fluctuation waveform of the second round due to the developer circulation of the composite waveform and the position of the maximum value of the toner consumption waveform by the toner consumption pattern for canceling the fluctuation waveform are substantially the same. It is preferable to perform a toner consumption operation.

  In addition, when the number of development times of the toner consumption pattern that is the basis of the composite waveform is n, it is preferable that the number of development times of the toner consumption pattern for canceling the fluctuation waveform is (n−1) times or less.

Further, it is preferable that the toner consumption pattern for canceling the fluctuation waveform is different from the toner consumption pattern which is the basis of the composite waveform.
In addition, it is preferable that the toner consumption pattern for canceling the fluctuation waveform is different from the toner consumption pattern that is the basis of the combined waveform.

Further, it is preferable that the toner consumption pattern for canceling the fluctuation waveform is different from the toner consumption pattern that is the basis of the combined waveform.
Further, it is preferable that the toner consumption pattern for canceling the fluctuation waveform is different from the toner consumption pattern that is the basis of the combined waveform.

In addition, it is preferable to execute the toner replenishing operation so as to cancel the fluctuation of the toner density that occurs when the toner consuming operation is performed.
In addition, it is preferable to execute the toner replenishing operation on the consumption waveform portion of the second and subsequent rounds in addition to the consumption waveform portion of the first round due to developer circulation in the toner concentration sensor output waveform in the toner consumption operation.

The toner replenishing operation is preferably performed by changing the replenishment speed of the toner replenishing device.
The toner replenishing operation is preferably performed by changing the drive ON time and the drive OFF time of the toner replenishing device.

  In addition, according to the present invention, the above-described problem is solved by an image forming apparatus that includes a two-component developing device and performs a toner consumption operation by the toner consumption method according to claim 1.

  According to the toner consumption method of the present invention, the toner consumption operation is performed in the second circulation of the developer circulation to the portion that could not be consumed by the toner consumption operation in the first circulation of the developer circulation, and the deteriorated toner is surely removed. Can be consumed.

According to the configuration of the second aspect, it is possible to effectively consume the deteriorated toner by canceling the ripple of the fluctuation waveform.
According to the configuration of the third aspect, the ripple of the fluctuation waveform can be made flatter, so that the deteriorated toner can be consumed more reliably.

According to the configuration of the fourth aspect, an appropriate toner consumption operation can be performed by creating and developing the number of toner consumption patterns corresponding to the ripple valleys in the first circulation of the developer.
According to the fifth aspect of the present invention, it is possible to perform an appropriate toner consumption operation for the deteriorated toner that cannot be consumed by the toner consumption operation in the first round without consuming toner more than necessary.

According to the configuration of the sixth aspect, the toner consumption operation for the second round can be appropriately performed by changing the size of the pattern.
According to the configuration of the seventh aspect, the toner consumption operation for the second round can be appropriately performed by changing the density of the pattern.

With the configuration according to the eighth aspect, it is possible to appropriately perform the toner consumption operation in the second round by changing the pattern writing density.
According to the ninth aspect of the present invention, it is possible to efficiently replace the deteriorated toner and the new toner by replenishing toner at an appropriate timing to the portion where the deteriorated toner is consumed. Therefore, effective toner refresh can be performed, and it is possible to prevent background stains and image density from being lowered and to maintain a high-quality image stably.

  According to the configuration of claim 10, not only the toner consumption waveform of the first round but also the consumption waveform of the second and subsequent rounds generated by the circulation of the developer is used to prevent the charge amount from being lowered. It is possible to replenish the toner where the deteriorated toner has been consumed, and to effectively refresh the toner.

  According to the configuration of the eleventh aspect, the toner supply operation can be performed so as to cancel the toner consumption waveform by changing the supply speed of the toner supply device and changing the toner supply amount per unit time. A new toner can be surely replaced. Therefore, effective toner refresh can be performed.

  According to the configuration of the twelfth aspect, the toner supply operation can be performed so as to cancel the toner consumption waveform by changing the operation time and the non-operation time of the toner supply device, so that the deteriorated toner and the new toner are surely replaced. Is possible. Therefore, effective toner refresh can be performed.

  According to the image forming apparatus of the thirteenth aspect, it is possible to reliably consume the deteriorated toner in the developing device. Further, since the toner replenishing operation can be performed on the portion where the deteriorated toner is consumed, the deteriorated toner and the new toner can be efficiently replaced. Therefore, it is possible to effectively perform toner refresh, and it is possible to prevent background stains and a decrease in image density and stably maintain a high-quality image.

1 is a schematic diagram schematically illustrating an image forming unit of a full-color printer that is an example of an image forming apparatus to which the present invention is applied. FIG. 3 is a plan sectional view showing a state where the developing device is viewed from above. 6 is a graph showing output characteristics of a toner density sensor provided in the developing device. 6 is a graph showing an output value of a toner density sensor when a toner consumption pattern is developed and then the conveying screw of the developing device is continuously driven without toner supply / consumption. FIG. 6 shows simultaneously a toner consumption pattern created by changing the toner density in the developing device. FIG. 7 is a schematic diagram illustrating a toner consumption waveform when a toner consumption operation is performed in the embodiment. FIG. 6 is a schematic diagram illustrating a toner consumption waveform when a second toner consumption operation is performed with a phase shifted with respect to a toner consumption waveform in the first toner consumption operation. FIG. 10 is a schematic diagram illustrating an example in which a toner consumption operation is performed a plurality of times during the first round of developer circulation in the first toner consumption operation. FIG. 10 is a schematic diagram for explaining a state in which deteriorated toner is consumed by performing a toner consuming operation on a second round of the developer circulation in a toner consuming operation performed a plurality of times. It is a schematic diagram for demonstrating the characteristic of a toner consumption pattern. FIG. 10 is a schematic diagram illustrating a toner consumption waveform and a combined waveform when a toner consumption pattern is created a plurality of times at the shortest timing. FIG. 6 is a schematic diagram illustrating a toner consumption waveform when the size of a toner consumption pattern is changed in the sub-scanning direction. FIG. 6 is a schematic diagram illustrating toner consumption waveforms in toner consumption patterns having different densities. FIG. 6 is a schematic diagram illustrating a toner consumption waveform in toner consumption patterns having different writing densities. FIG. 6 is a schematic diagram illustrating toner consumption waveforms in toner consumption patterns having different sizes and densities. FIG. 6 is a schematic diagram illustrating an example of a toner consumption pattern consumed in the second round of developer circulation. 6 is a graph showing how the output value of a toner density sensor decreases due to toner replenishment. 2 shows a toner consumption waveform and a toner supply waveform when the present invention is not applied. 6 shows a toner consumption waveform and a toner supply waveform simultaneously when the present invention is applied. FIG. 6 is a schematic diagram illustrating a driving timing of a toner supply device with respect to a toner consumption waveform. FIG. 6 is a schematic diagram illustrating a driving timing of a toner replenishing device when toner consumption patterns created in the first and second rounds are different. FIG. 10 is a schematic diagram illustrating toner supply with respect to a toner consumption waveform when the rotation speed of the toner supply device is changed and when the ON time of toner supply drive is changed. 6 is a flowchart illustrating a toner refresh operation in the present embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram schematically showing an image forming unit of a full-color printer as an example of an image forming apparatus to which the present invention is applied. In the full-color printer shown in this figure, four image forming units 10 (Y, C, M, Bk) are arranged at substantially the center of the apparatus main body. These four image forming units 10 are arranged along the lower running side of the intermediate transfer belt 11 wound around a plurality of rollers.

  Each image forming unit 10 includes a photosensitive drum 1 as an image carrier. Around the photosensitive drum 1, a charging unit 2, a developing device 3, a cleaning unit 4, and the like are arranged. Further, a transfer as a primary transfer unit is provided inside the intermediate transfer belt 11 at a position facing each photosensitive drum 1. A roller 5 is provided. Note that the four image forming units 10 have the same structure, and the developer colors handled by the developing devices of the respective image forming units are different from four colors of yellow, magenta, cyan, and black. In order to avoid the complexity of the figure, only the devices that constitute the image forming unit 10Y are denoted by reference numerals, and the symbols of the devices that configure other image forming units are omitted. Above the intermediate transfer belt 11, toner bottles 6 (Y, C, M, Bk) containing toner to be supplied to the developing device 3 of each color image forming unit 10 are arranged.

  An optical writing device 15 is provided below the four image forming units 10. Although not shown, the optical writing device 15 has a polygon mirror, a mirror group, and the like, and irradiates the surface of the photosensitive drum 1 of each color image forming unit with light-modulated laser light. The optical writing device may be provided for each image forming unit 10 individually.

  A paper feed cassette (not shown) is disposed below the optical writing device 15. A recording medium such as transfer paper (hereinafter referred to as paper) fed from the paper feed cassette is conveyed to the registration roller pair 16 by a conveyance roller (not shown). Above the pair of registration rollers 16, a transfer roller 17 as a secondary transfer unit is provided to face a transfer counter roller 13 that is one of the rollers on which the intermediate transfer belt 11 is stretched. A fixing device 18 is provided above the secondary transfer unit. An optical sensor 14 that detects the image density on the intermediate transfer belt 11 is disposed at a position facing the support roller 12.

An image forming operation in the full color printer of this example configured as described above will be briefly described.
The photosensitive drum 1 of the image forming unit 10 is rotated in the clockwise direction in the drawing by a driving unit (not shown), and the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity by the charging unit 2. The charged surface of the photosensitive member is irradiated with laser light from the optical writing device 15, whereby an electrostatic latent image is formed on the surface of the photosensitive drum 1. At this time, the image information exposed on each photosensitive drum 1 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. Each color toner is applied from the developing device 3 to the electrostatic latent image formed in this way, and visualized as a toner image.

  Further, the intermediate transfer belt 11 is driven to run counterclockwise in the drawing as indicated by an arrow, and each color toner image is sequentially transferred from the photosensitive drum 1 to the intermediate transfer belt 11 by the action of the primary transfer roller 5 in each image forming unit 10. Overprinted. In this way, the intermediate transfer belt 11 carries a full-color toner image on the surface thereof.

  Note that any one of the image forming units 10 can be used to form a single-color image or a two-color or three-color image. In the case of monochrome printing, image formation is performed using the rightmost Bk unit in the figure among the four image forming units.

  The residual toner adhering to the surface of the photoconductive drum after the toner image is transferred is removed from the surface of the photoconductive drum by the cleaning device 4, and then the surface is subjected to the action of a static eliminator (not shown) to obtain the surface potential. Is initialized to prepare for the next image formation.

  On the other hand, paper is fed from a paper feed cassette at the lower part of the apparatus, and is sent toward the secondary transfer position by the registration roller pair 16 in synchronization with the toner image carried on the intermediate transfer belt 11. In this example, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the surface of the intermediate transfer belt is applied to the transfer roller 17, whereby the toner image on the surface of the intermediate transfer belt is collectively transferred onto the sheet. When the sheet on which the toner image has been transferred passes through the fixing device 18, the toner image is fused and fixed to the sheet by heat and pressure. The fixed transfer material is discharged to a paper discharge tray (not shown) formed on the upper surface of the apparatus main body.

FIG. 2 is a plan sectional view showing the developing device 3 as viewed from above. In FIG. 2, the left side of the drawing is the back side of the full color printer of FIG. 1, and the right side of the drawing is the front side of the device.
As shown in FIGS. 1 and 2, the developing device 3 includes a developing roller 31 that is a developer carrying member, and the developing roller 31 is disposed so as to face the photosensitive drum 1. Further, the developing device 3 is provided with a double conveying screw including a first screw 32 and a second screw 33. The developer is circulated and conveyed in the developing device by the two conveying screws 32 and 33 as shown by thick arrows in FIG.

  In the portion where the first conveying screw 32 is installed, the developer is pumped up to the surface of the developing roller 31, and the developer that has passed through the developing region is returned. As shown in FIG. 1, a toner density sensor 34 is provided in the lower part of the developer chamber on the second screw 33 side. As the toner concentration sensor 34, for example, a sensor that measures the toner permeability in the developing device is used. Further, a toner replenishing unit 35 that communicates with the developer chamber on the second screw 33 side is provided, and toner is replenished from the toner bottle 6.

  FIG. 3 is a graph showing the output characteristics of the toner density sensor 34. The vertical axis represents the output value of the toner density sensor, and the horizontal axis represents the toner density. As can be seen from this graph, the toner concentration sensor 34 has a characteristic that the output value decreases as the toner concentration in the developing device increases. The relationship between the toner density and the output value of the toner density sensor can be approximated by a straight line.

  Here, in the toner density control, the output value: Vt of the toner density sensor is compared with the control reference value: Vtref of the toner density, and the toner replenishment amount is calculated from an arithmetic expression according to the difference, and a toner replenishing device (not shown) is installed. By driving, toner is supplied into the developing device through the toner supply unit 35.

Hereinafter, the toner refresh operation in the present embodiment will be described.
FIG. 4 is a graph showing the output value of the toner density sensor 34 when all solid images are developed on the side of A4, and then the conveying screw of the developing device 3 is continuously driven without supplying and consuming toner. As can be seen from this graph, the output value of the toner density sensor changes as a result of toner consumption (the change in the output value of the toner density sensor caused by the creation of this toner consumption pattern is hereinafter referred to as a toner consumption waveform).

  In the toner consumption waveform, the portion where the toner concentration sensor output value is high (the toner concentration is low) is the portion where the toner is consumed by creating the toner consumption pattern. Conversely, a portion where the toner density sensor output value is low (toner concentration is high) is a portion where toner consumption is not performed. In this way, it is possible to know from the toner consumption waveform where the toner is consumed in the developing device.

  Further, it can be seen from the toner consumption waveform that the toner density fluctuation has periodicity. This is because the developer in the developing device is always circulated in the developing device as it is conveyed while being agitated, so the portion where the toner has been consumed makes a round in the developing device and is again detected by the toner concentration sensor. It was because it was circulated until. This is shown in the second waveform shown in FIG. That is, the portion where the toner is consumed due to the creation of the toner consumption pattern and the sensor output value is high (the peak of the first-round waveform) shows a high output value in the second-round waveform after the circulation cycle has elapsed.

  FIG. 5 simultaneously shows a case in which the toner consumption pattern of A4 horizontal all-solid is created by changing the toner density in the developing device. Here, the toner density was changed in three stages. As can be seen from this graph, the toner consumption waveform is substantially the same even if the toner density in the developing device changes.

  From these facts, it is possible to grasp the location where the toner is consumed in the developing device and the circulation cycle in which the developer goes around the developing device. In FIG. 4, a section indicated by a double arrow is a circulation cycle. Therefore, it is possible to know in advance the timing at which the portion where the toner has been consumed reaches the developing area again.

  As described above, a portion where the toner concentration sensor output value is low (toner concentration is high) in the toner consumption waveform is a portion where toner consumption is not performed. That is, the deteriorated toner is not consumed and remains in the developing device. Therefore, if the toner consumption pattern is developed at the timing when the portion (part) where the deteriorated toner remains is circulated to the development area, the remaining deteriorated toner can be efficiently consumed. .

  FIG. 6 shows a toner consumption waveform when a toner consumption pattern is created and developed and a toner consumption operation is performed. When such a toner consumption waveform is obtained, a second toner consumption operation is performed as shown in FIG. 7 when the phase is shifted from the first toner consumption waveform. At this time, a portion having a high toner density (a portion where the deteriorated toner remains) may remain. In other words, the deteriorated toner in the developing device may not be consumed even by the toner consumption operation twice.

Therefore, the deteriorated toner is reliably consumed by performing the toner consumption operation a plurality of times between the peak value of the first round and the peak value of the second round of the first toner consumption waveform.
Here, among the toner consumption waveforms performed a plurality of times, the peak portion of the first round of the toner consumption waveform is not overlapped with the peak portion of the second round of the toner consumption waveform created first (first). It is desirable to create it. This is to prevent the toner consuming operation from being performed again at the portion consumed in the first toner consuming operation.

The number of toner consumption operations will be described with reference to FIG.
As described above, FIG. 6 shows a toner consumption waveform when a toner consumption pattern is created and developed and a toner consumption operation is performed. First, a time T from the position at which the output of the toner consumption waveform in the first round starts to rise until the output of the toner density sensor in the second round starts to rise is measured. This time T coincides with a circulation cycle in which the developer makes a round in the developing device.

  Next, t_s which is the width of the consumption waveform in the first round is obtained. Then, T / t_s is calculated, and a value obtained by rounding down the decimal part of the quotient is set as the number of times of toner consumption operation. In this way, by obtaining the number of times of performing the toner consumption operation, a plurality of toner consumption waveforms can be created so as to fall within the time T. FIG. 8 shows an example in which the toner consumption operation is performed three times during the time T.

  Further, the timing of performing the toner consuming operation is as long as the time T is divided by the number of times the toner consuming operation is performed and the toner consuming operation is executed after the start of the previous toner consuming operation. Thus, it is possible to perform the toner consumption operation evenly distributed. Here, the delay time is assumed to be td. As shown in FIG. 8, since the toner consumption waveform (consumption waveform of the first round) is accommodated during time T, the peak portion of the first round of the final (third) toner consumption waveform to be created is the first time. It does not overlap with the peak portion of the second round of the (first) toner consumption waveform.

The toner consumption waveform is referred to as “first round” while the developing device circulates once around the developing device, and the waveform that forms after the second round of circulation is referred to as “second round”.
In FIG. 9A, a combined waveform obtained by creating and developing a toner consumption pattern three times in the first round and superposing the toner consumption waveforms is indicated by a dotted line. The first waveform is indicated by a solid line, the second waveform is indicated by a one-dot chain line, and the third waveform is indicated by a thick solid line.

  As can be seen from the composite waveform (result of superposition), the toner consumption operation by the first toner consumption operation can be performed multiple times evenly around the inside of the developing device. It becomes possible to consume reliably.

  However, in the combined waveform as a result of superposition, there is a portion where the toner consumption waveform is low (toner density is high), such as a circled portion. This valley portion indicates that some deteriorated toner remains. Therefore, if the toner consumption operation is performed again so as to cancel the ripple of the composite waveform, the deteriorated toner can be reliably consumed.

  Therefore, the toner consumption operation is performed at the timing when the valley portion (the portion having a high toner density) in the combined waveform circulates again in the development area (for the second round of the developer circulation). Thereby, the deteriorated toner can be consumed reliably. Although FIGS. 9B and 9C will be described later, FIG. 9B shows a toner consumption waveform by a toner consumption operation performed in the second round. (C) shows the result of superposing the toner consumption waveforms. From the waveform shown in (c), it can be seen that the ripple after the second week is small, that is, how the deteriorated toner is consumed reliably.

  Here, the reason for performing the toner consumption operation in the second round (the toner in the second round when the valley portion in the combined waveform obtained by superimposing the toner consumption waveforms generated by the creation of the toner consumption pattern circulates and reaches the development area again) The reason why the consumption operation is performed and the deteriorated toner is consumed will be described.

  In this embodiment, the toner consumption pattern is created as shown in FIG. The sub-scanning length of the toner consumption pattern is set within the inter-station pitch of each color. In this way, toner consumption patterns can be created simultaneously without overlapping. For this reason, it is not necessary to perform a delay or the like for creating a consumption pattern for other colors, and an extra time is not required.

  In addition, if the toner consumption patterns are created in an overlapping manner, the amount of toner that is input to the cleaning member at a time increases, which increases the burden on the cleaning member. Therefore, it is desirable that the toner consumption patterns of the respective colors are created so as not to overlap from the point of poor cleaning.

FIG. 11 shows a waveform of a result of superposing the toner consumption waveform and each toner consumption waveform when the toner consumption pattern is created at the shortest timing.
Here, the description will be made by paying attention to the Y toner consumption pattern. Once the Y toner consumption pattern is created once, the position where the next Y toner consumption pattern is created is the place where the consumption pattern of another color (for three stations) is away from the creation position of the first consumption pattern. Become. In other words, a Y toner consumption pattern cannot be created at the location of the consumption pattern of another color.

  As can be seen from the dotted line obtained by superimposing the toner consumption waveforms, there is a portion where the toner consumption waveform is low. This portion indicates that the deteriorated toner remains. If the toner consumption operation is performed so as to cancel the ripple of the toner consumption waveform, the deteriorated toner can be consumed.

  However, a Y toner consumption pattern cannot be created between the first and second toner consumption patterns in the first round. This is because other colors and patterns do not overlap as in the previous operation.

  Therefore, as described above with reference to FIG. 9, the toner is such that the low portion (valley portion) of the combined waveform (superposed toner consumption waveform) cancels the low toner consumption waveform portion in the second turn through the developing device. Create consumption patterns.

  By doing as described above, it becomes possible to perform the toner consuming operation in the second lap of the developer circulation to the portion that could not be consumed by the toner consuming operation in the first lap in the developer circulation. It becomes possible to reliably consume the deteriorated toner.

Next, a toner consumption pattern created at the second round in the developer circulation will be described.
As described above, there are a plurality of portions where the toner consumption waveform decreases when the toner consumption operation is performed a plurality of times while the developer circulates once. Since the position where the toner consumption waveform decreases is a portion between the consumption waveform and the consumption waveform overlapped, the portion where the toner consumption waveform decreases is [number of consumption patterns to be created-1]. Therefore, in order to cancel the toner ripple, [the number of times of toner consumption pattern created in the first round minus 1] times may be created in the second round.

  The toner consumption pattern consumed in the second round of developer circulation may be different from the pattern created in the first round. This is because it suffices to execute toner consumption as much as to cancel the ripple of the toner consumption waveform superimposed on the first round. If the same pattern as that created in the first round is created, the toner may be consumed excessively and the toner density ripple may become excessive. Therefore, it is necessary to create an amount of toner consumption pattern suitable for canceling the ripple of the toner consumption waveform.

  FIG. 12 shows a toner consumption waveform when the size of the toner consumption pattern is changed in the sub-scanning direction. As the toner consumption pattern, a long “A” pattern and a short “B” pattern are created in the sub-scanning direction. At this time, the length in the main scanning direction is the same for both “A” and “B”. In the figure, the toner consumption waveform of the “A” pattern is indicated by a solid line, and the toner consumption waveform of the “B” pattern is indicated by a one-dot chain line.

  It can be seen from FIG. 12 that “A” and “B” have different peak position amplitudes. This is because the toner consumption amount is smaller in the “B” pattern, and the decrease in the toner density of the developer is small. Further, the position where the waveform of the second round generated by the circulation of the developer starts to rise is the same for both “A” and “B”. This is because the circulation cycle in which the developer makes one round is the same. Also, “B” has a narrower consumption waveform width than “A”, and the timing at which the peak position arrives is earlier.

  FIG. 13 shows a toner consumption waveform when the density of the toner consumption pattern is changed. The “B” pattern has a lower density than the “A” pattern. In this case, since the toner consumption amount is smaller in the “B” pattern, the amplitude of the consumption waveform becomes smaller. Since the areas of the patterns to be created are the same, the width of the consumption waveform is the same for “A” and “B”. In order to change the density of the toner consumption pattern to be created, the development potential may be changed. For example, (development bias when creating “B” pattern) <(development bias when creating “A” pattern) Change the concentration.

  FIG. 14 shows a toner consumption waveform when the writing density of the toner consumption pattern is changed. The “A” pattern creates a solid consumption pattern, and the “B” pattern creates a halftone consumption pattern. As in the case of FIG. 14, the “B” pattern consumes less toner than the “A” pattern, so the amplitude of the consumption waveform is small.

  FIG. 15 shows a toner consumption waveform when the size and density of the consumption pattern are changed. In this figure, a pattern obtained by changing both the size and density from the “A” pattern is shown as a “C” pattern. The “C” pattern and the “B” pattern have the same pattern size and low density. Thus, by changing the pattern size and density in combination, the width and amplitude of the consumption waveform can be changed simultaneously.

  As described above, the toner consumption waveform can be changed by changing the size, density, and writing density of the toner consumption pattern to be created. Therefore, if a toner consumption pattern suitable for canceling the ripple of the superimposed toner consumption waveform in the first round is created in the second round, an appropriate toner consumption operation can be performed without excessive toner consumption. It becomes.

  For example, when the ripple width of the toner consumption waveform formed by superimposing the toner consumption waveforms of the first round created a plurality of times is small, the length of the toner consumption pattern created in the second round may be shortened. . Further, when the amplitude of the ripple of the superimposed toner consumption waveform is small, it is possible to create a toner consumption waveform with a small amplitude by setting the density of the consumption pattern low or the writing density low.

  As described above, it is only necessary to create a toner consumption pattern suitable for canceling the ripple of the toner consumption waveform generated as a result of overlapping the toner consumption waveforms generated by creating the toner consumption pattern a plurality of times.

  FIG. 16 shows an example of a toner consumption pattern consumed in the second round of developer circulation. The toner consumption pattern shown in this figure has a shorter length in the sub-scanning direction than the pattern shown in FIG.

  In this embodiment, the toner consumption pattern created in the first round of developer circulation is the same every time. For this reason, the magnitude of the ripple generated when toner consumption waveforms are superimposed is the same every time. That is, the toner consumption pattern created to cancel the ripple in the second round is the same every time.

  Therefore, a toner consumption pattern suitable for canceling the ripple is set in advance, and the portion where the toner density sensor output of the superimposed toner consumption waveform in the first round is low (the portion where the toner concentration is high) is circulated again to the development region. If the preset toner consumption pattern is created and developed and the toner consumption operation is performed (with respect to the second round of the developer circulation) at a given timing, an appropriate toner consumption operation can be performed. Thus, it is possible to reliably consume the deteriorated toner.

Next, the writing timing of the toner consumption pattern for the second round will be described with reference to FIG. Here, a case where the toner consumption pattern is generated three times will be described.
FIG. 9A shows a result (composite waveform) obtained by creating a toner consumption pattern three times and superposing the respective toner consumption waveforms with a dotted line. The first-time toner consumption waveform is indicated by a solid line, the second time by a one-dot chain line, and the third time by a thick solid line. FIG. 9B shows a toner consumption waveform generated by creating a toner consumption pattern for the second round. The number of toner consumption operations performed in the second round is 3-1 = 2, and the toner consumption operation is performed twice.

  First, a time t1 from the start of the toner consumption operation to the maximum value is measured. As described above, the time for starting the second toner consumption pattern creation is td. The timing of starting the creation of the third toner consumption pattern is a time further delayed by td from the start of the creation of the second toner consumption pattern.

  The time between the maximum value of the first toner consumption waveform and the maximum value of the second toner consumption waveform is td. Similarly, the time between the second time and the third time is td. The developer circulation cycle is T.

Next, in the toner consumption pattern created in the second round, the time tm from the start of writing of the toner consumption pattern to the maximum value is measured.
Here, the position (valley position) where the combined waveform obtained by superimposing the three toner consumption waveforms in FIG. 9A is lowered (the position of the valley) is an approximately halfway point between the maximum value and the maximum value of each toner consumption waveform. . Therefore, if the maximum value of the toner consumption waveform comes to the middle point between the maximum value and the maximum value at the second turn in the developer circulation, the toner ripple can be canceled more flatly.

  Toner consumption waveform The first minimum value of the first round of superimposed toner consumption waveform created in two lap (composite waveform 1 round valley portion of the portion of the valley in the second round that can be circulated) to the maximum value of overlap as a trigger to start writing of the first toner consumption patterns, it may start writing [t1 + td / 2 + T-tm] = 2 lap toner consumption patterns after ta seconds elapse . t1 + td / 2 is the position of the minimum value of the superimposed toner consumption waveform. The time for which the minimum value circulates once is T. Therefore t1 + td / 2 + T s after the may be a write start of the toner consumption pattern of the second lap from the previous tm seconds to as the maximum value of the toner consumption waveform of toner consumption patterns to create overlap substantially in the second round.

  The second minimum value of the superimposed toner consumption waveform in the first round is after the elapse of td from the first. This is because it is between the maximum values of the second and third toner consumption waveforms. For this reason, the toner consumption waveform for canceling this may be created after ta + td seconds.

  As a result of superposing the toner consumption waveforms by performing the toner consumption operation at the above timing, that is, the respective toner consumption waveforms of the three toner consumption operations in (a) and the two toner consumption operations in the second round of (b). The result of overlaying is shown in FIG. As can be seen from the combined waveform shown in FIG. 9C, the ripple of the toner consumption waveform that occurred in FIG. 9A is eliminated.

  As described above, the toner consumption operation is executed in the second round of the developer, so that the toner consumption operation can be performed in the portion where the deteriorated toner remains, so that the deteriorated toner can be consumed more effectively. .

  The above is the description of the toner consumption operation in the present embodiment. In the actual toner refresh operation, it is necessary not only to consume the deteriorated toner but also to replenish the toner in order to replace it with a new toner. Next, the toner supply operation in the present embodiment will be described.

  FIG. 17 shows the result of driving the toner replenishing motor (performing the toner replenishing operation), and then stirring with the conveying screw without performing toner replenishment and consumption, and measuring the toner concentration in the developing device with the toner concentration sensor. is there. As can be seen from the graph of FIG. 17, it can be seen that when the toner is replenished, the output value of the toner density sensor decreases (the change in the output value of the toner density sensor caused by the toner replenishment is hereinafter referred to as a toner replenishment waveform). This toner replenishment waveform is almost the same every time when the same amount of toner is replenished.

  FIG. 18 shows a toner consumption waveform and a toner supply waveform simultaneously when the present invention is not applied. Here, the toner density sensor output in the developing device is the sum of the toner consumption waveform and the toner supply waveform. Therefore, the toner density sensor output value is as shown by a thick line.

  In the case shown in FIG. 18, the toner supply operation is performed three times at the rising edge of the toner consumption waveform. In this case, a large ripple is generated in the toner density sensor output value as indicated by a bold line. This means that the toner density in the developing device varies. In other words, there are locations in the developing device where the toner concentration is increased due to toner replenishment and locations where the toner concentration is low without toner replenishment.

  The purpose of the toner refresh operation is to consume the deteriorated toner and supply and replace it with new toner. For this reason, if the toner replenishment operation is not properly performed, there is a portion where the deteriorated toner is consumed and the replacement with new toner is not performed.

  On the other hand, FIG. 19 shows the case where the present invention is applied, and shows the output value of the toner density sensor when the toner supply timing is changed and toner is supplied three times. At this time, the total toner replenishment amount is the same as in FIG. In FIG. 19, it can be seen that the thick line waveform (corresponding to the toner density sensor output value) obtained by adding the toner consumption waveform and the toner supply waveform is flatter.

  By changing the toner supply timing in this way, it is possible to eliminate the occurrence of toner density ripple. This means that the toner has been replenished evenly where the toner is consumed. That is, the toner replenishment operation is accurately performed at the place where the deteriorated toner is consumed.

  Here, it can be seen from FIG. 19 that if the toner supply operation is performed so as to cancel the waveform of the first round of the toner consumption waveform, the toner density is constant from the second round onward. For this reason, the toner consumption waveform for the second round does not occur (no peaks occur), so it is not necessary to replenish the toner for the toner consumption waveform for the second round.

Similarly, when the toner consumption operation is performed at the second round of the developer circulation, the toner supply operation may be performed so as to cancel the waveform of the first round of the toner consumption waveform.
From the above, if the toner replenishment operation is performed at a timing that cancels the toner consumption waveform in the first round, new toner can be replenished to the portion where the deteriorated toner is consumed, and the toner can be accurately replaced. It becomes possible. A specific toner supply operation will be described later.

  In this embodiment, the toner consumption pattern created by the toner refresh operation creates a pattern of the same size every time. Therefore, as described above, the toner consumption waveform is substantially the same every time. In other words, the time until the portion where the toner density is consumed and circulates in the developing device reaches the toner replenishing port is almost the same timing each time.

  From the above, it is possible to set in advance the toner replenishment timing that cancels the toner consumption waveform. That is, the toner replenishment operation can be performed at the timing when the toner consumption waveform is canceled with the start of writing of the toner consumption pattern as a trigger.

  As shown in the toner replenishing operation (a) in FIG. 20, if the toner replenishing operation is executed so as to cancel each of the toner consumption waveforms generated by the toner consuming operation performed a plurality of times, the portion where the deteriorated toner is consumed is accurately obtained. Since toner can be replenished, toner refresh can be performed effectively.

  When the toner consumption pattern created in the first round differs from the toner consumption pattern created in the second round, as shown in FIG. 21, the toner supply timing is set so as to cancel the consumption waveform for each toner consumption pattern. It may be set in advance and toner supply may be executed.

  The method of canceling the toner consumption waveform may be performed not only on the toner consumption waveform of the first round, but also on the consumption waveforms of the second and subsequent rounds generated by the circulation of the developer.

  For example, in a high-temperature and high-humidity environment, since the developer contains a large amount of moisture, charges are easily released, and the charge amount of the toner is reduced. In such a situation, when the toner is replenished so as to cancel the toner consumption waveform in the first round as described above, a large amount of toner is replenished in the developer while the developer makes one round in the developer. Will be. When a large amount of toner is replenished, the chance of contact between the toner and the carrier decreases, and the amount of charge becomes difficult to increase. Therefore, in order to increase the charge amount, it is necessary to replenish toner as much as possible.

  Therefore, for example, only half of the toner supply amount necessary to cancel the toner consumption waveform in the first round is supplied, and the remaining half is supplied in the second round. If such replenishment is performed, the chance that the toner and the carrier come into contact with each other increases, and the effect of increasing the charge amount can be obtained.

  The toner replenishment operation (b) in FIG. 20 is performed by dividing the required toner replenishment amount into a toner consumption waveform for the first round and a toner consumption waveform for the second round. In this way, as the toner replenishment timing for the second and subsequent rounds, the replenishment may be performed by delaying the timing that should originally be performed in the first round by the amount of circulation of the developer one round. By doing so, it is possible to perform the replenishment operation accurately with respect to the consumption position of the deteriorated toner as in the case of replenishment only in the first round.

  As described above, while preventing a decrease in the charge amount by performing the toner replenishment, it is possible to supply toner to a portion where the deteriorated toner is consumed, the effectively possible to perform toner refresh.

Next, a toner replenishing method using a system that can change the toner replenishment amount and the toner replenishment amount per unit time will be described.
In such a toner supply system, if the rotation speed of the toner supply device is increased, the supply amount per unit time increases, and if the rotation speed of the toner supply device is decreased, the supply amount per unit time may be reduced. it can. As described above, the toner consumption waveform is known in advance. Therefore, as shown in the replenishing device rotation drive (c) in FIG. 22, if toner is replenished by changing the toner replenishing amount (rotation speed of the toner replenishing device) per unit time so as to cancel the toner consumption waveform, the deteriorated toner Therefore, it is possible to accurately replenish toner to the portion where the toner is consumed. This makes it possible to perform effective toner refresh. Next, a system in which the replenishment amount per unit time of the toner replenishing device is constant and the ON time and OFF time of the toner replenishment drive can be made variable is used. A toner replenishing method will be described.

  In such a toner replenishment system, the toner replenishment amount can be changed by changing a single replenishment operation time (time from when the replenishment motor is driven to when it is stopped). Specifically, the toner supply amount increases as the ON time increases, and the toner supply amount decreases as the ON time decreases.

  Therefore, as shown in the toner supply operation in FIG. 22 (d), carried out the toner supply by changing the ON time of the toner supply drive so as to cancel the toner consumption waveform, precisely relative locations deteriorated toner is consumed Toner can be replenished.

  As described above, since the toner consumption operation by the first toner consumption operation makes one round of the inside of the developing device, the toner consumption operation can be performed evenly multiple times, so that the deteriorated toner can be reliably consumed. . In addition, it is possible to efficiently replace the deteriorated toner and the new toner by replenishing toner at an appropriate timing to the portion where the deteriorated toner is consumed. Therefore, effective toner refresh can be performed, and it is possible to prevent background stains and image density from being lowered and to maintain a high-quality image stably.

Next, the toner refresh operation in this embodiment will be described with reference to the flowchart of FIG.
First, the travel distance of the developing motor is acquired (S1). This obtains the driving time of the developing motor, and calculates and obtains the motor driving distance (traveling distance) from the rotational speed of the motor.

Next, the accumulated image area [cm ^ 2] is acquired (S2). Here, the accumulated image area is obtained by the following equation 1. That is, the image area written for each transfer sheet is acquired, and the written image area is accumulated every time one sheet is printed.
Cumulative image area = cumulative image area up to the previous time + current image area (Formula 1)
Note that the unit of the image area in Equation 1 is all [cm ^ 2].

  For example, when the printing of a high image area is continuously performed, the value of the cumulative image area becomes large. On the other hand, when the printing of a low image area is continuously performed, the cumulative image area becomes a small value. As a specific example, when 10 sheets of an image area of 50 [cm ^ 2] are continuously printed, the accumulated image area is 500 [cm ^ 2].

Then, the required refresh image area is calculated (S3). The required refresh image area is a value representing how much toner needs to be consumed with respect to the travel distance of the developing motor so that the toner in the developing device does not deteriorate. Defined.
Necessary refresh image area [cm ^ 2] = Development motor travel distance [m] x Necessary refresh threshold [cm ^ 2 / m]-Cumulative image area [cm ^ 2] ... (Formula 2)

  The required refresh threshold value in Equation 2 means how much toner needs to be consumed with respect to the travel distance of the developing motor. For this value, the amount of toner consumption necessary for preventing the toner from deteriorating is calculated in advance by experiments or the like. The necessary toner consumption can be calculated by multiplying the necessary refresh threshold by the developing motor travel distance. However, when printing is performed, toner is consumed according to the printed image area. Therefore, by obtaining the difference in the actually consumed toner from the necessary toner consumption amount, it is possible to determine how much toner consumption amount is necessary so that the toner does not deteriorate. This value is the required refresh image area.

  Here, depending on the value of the accumulated image area, the value of the required refresh area may be negative. In this case, since the toner is consumed more than necessary because the toner does not deteriorate, it can be determined that the toner consumption operation is not necessary.

The calculation of the required refresh image area will be described below using specific numerical examples.
If the acquired developing motor travel distance is 90 [m] and the accumulated image area is 600 [cm ^ 2], and the required refresh threshold is 25 [cm ^ 2 / m], the required refresh image area is It is calculated as follows.
Necessary refresh image area = 90 × 25−600 = 1650 [cm ^ 2]
Therefore, it is necessary to consume toner having an image area of 1650 [cm 2].

As another example, if the acquired travel distance is 90 [m], the required refresh threshold is 25 [cm ^ 2 / m], and the cumulative image area is 3000 [cm ^ 2],
Necessary refresh image area = 90 × 25−3000 = −750 [cm ^ 2]
Is required.

When the value of the necessary refresh image area is negative, it can be determined that the toner refresh operation is not necessary because the toner is sufficiently consumed in the printing operation.
In this way, the current required refresh image area is calculated. Then, the refresh area calculated this time is added to the required refresh area up to the previous time to obtain the cumulative refresh area (S4).
Cumulative refresh image area [cm ^ 2] = Cumulative refresh image area [cm ^ 2] + Necessary refresh image area [cm ^ 2] (Formula 3)

  Then, the execution of the refresh operation is determined (S5). The cumulative required refresh image area value obtained in S4 is compared with a predetermined refresh execution determination threshold value, and if the cumulative required refresh image area value is greater than or equal to the predetermined refresh execution determination threshold value, the process proceeds to a refresh operation. .

  That is, as a result of the toner refresh execution determination in S5, if execution is necessary, the process proceeds to S6, and the toner refresh operation is executed. Here, the same toner consumption pattern is created every time. In this embodiment, the toner consumption pattern is created as shown in FIG. The sub-scanning length of the toner consumption pattern is set within the inter-station pitch of each color. In this way, toner consumption patterns can be created simultaneously without overlapping. For this reason, it is not necessary to perform a delay or the like for creating a consumption pattern for other colors, and an extra time is not required.

  In addition, if the toner consumption patterns are created in an overlapping manner, the amount of toner that is input to the cleaning member at a time increases, which increases the burden on the cleaning member. Therefore, it is desirable that the toner consumption patterns of the respective colors are created so as not to overlap from the point of poor cleaning.

  The toner consumption pattern created in the second round of the developer circulation cycle is a pattern as shown in FIG. In this way, a toner consumption pattern different from that in FIG. 10 is created. In the pattern of FIG. 16, the toner consumption pattern is obtained by changing the length in the sub-scanning direction to reduce the toner consumption amount and obtaining the toner consumption waveform for flattening the ripple generated as a result of superposing the toner consumption waveforms. Yes.

  The toner consumption pattern is created a number of times that the deteriorated toner in the developing device can be consumed sufficiently. The number of creations is changed depending on the developing device and the size of the toner consumption pattern to be created.

  Subsequently, the toner replenishing operation is executed as described above (S6), and the toner replenishing operation is performed on the portion where the deteriorated toner is consumed. Toner replenishment is performed in parallel with the toner consumption operation in order to cancel the toner consumption waveform.

When both the toner consumption operation and the toner replenishment operation are completed, the execution of the toner refresh operation is terminated, and in S7, the cumulative refresh image area is updated. As shown in the following Expression 4, the image area corresponding to the amount of toner consumed is subtracted from the accumulated refresh image area.
Cumulative refresh image area [cm ^ 2] = Cumulative refresh image area [cm ^ 2] −Toner consumption image area [cm ^ 2] (Formula 4)

  When the process is finished at S7, or at S8, if the toner refresh operation is determined to be unnecessary executed in S5, and specifications when calculating the required refresh image area in S3, the developing motor driving distance, the cumulative image area The value is cleared to 0 and the process ends.

  The above is the toner refresh operation in this embodiment. By calculating the refresh image area required according to the accumulated value of the image area that is printed with this traveling distance of the developing motor, the state of the developer is possible to determine whether it is necessary toner refreshing it can.

  Further, in the toner refresh operation, the remaining deteriorated toner can be reliably consumed by grasping the location where the deteriorated toner is consumed in the developing device. As a result, it is possible to prevent a decrease in image density and stably maintain a high-quality image.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. For example, the number of toner replenishment operations performed during one cycle is not limited to three, and an appropriate number can be set. In addition, the number of times when the toner replenishment operation is performed in the second round of developer circulation is appropriately set according to the number of times the toner is replenished in the first round.

  The configuration of each part of the developing device and the configuration of the image forming unit of the image forming apparatus are also arbitrary, and the arrangement order of the color process cartridges in the tandem type is arbitrary. In addition to the tandem type, a configuration in which a plurality of developing devices are arranged around a single photosensitive member, or a configuration using a revolver type developing device is also possible. The present invention can also be applied to a full color machine using three color toners, a multicolor machine using two color toners, or a monochrome apparatus. Of course, the image forming apparatus is not limited to a printer, and may be a copier, a facsimile machine, or a multifunction machine having a plurality of functions.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 3 Developing device 6 Toner bottle 10 Image forming unit 11 Intermediate transfer belt 15 Optical writing device 18 Fixing device 31 Developing roller 32 First screw 33 Second screw 34 Toner density sensor 35 Toner supply part

JP 2008-216601 A JP 2006-47651 A JP 2007-108623 A

Claims (13)

In a toner consumption method in a two-component developing device,
A change in toner density in the developing device when a predetermined toner consumption pattern is developed and a toner consumption operation is executed is detected by a toner density sensor, and the detected maximum value of the first round in the output waveform of the toner density sensor is detected. The toner consumption pattern is developed a plurality of times to execute the toner consumption operation so that the phase of the output waveform of the toner density sensor by each toner consumption operation is shifted between the maximum value of the second round due to the developer circulation. ,
A toner consumption operation is performed by creating and developing a toner consumption pattern so as to cancel out a fluctuation waveform in the second round due to developer circulation of a composite waveform obtained by superimposing toner consumption waveforms generated by the respective toner consumption operations. Consumption method.   The toner consumption operation is performed such that a peak portion of a toner consumption waveform according to a toner consumption pattern for canceling the fluctuation waveform overlaps a valley portion of a fluctuation waveform of the second round due to developer circulation of the composite waveform. The toner consumption method according to claim 1.   The toner consumption is such that the position of the minimum value of the fluctuation waveform on the second round due to the developer circulation of the composite waveform and the position of the maximum value of the toner consumption waveform by the toner consumption pattern for canceling the fluctuation waveform are substantially the same. The toner consumption method according to claim 1, wherein an operation is performed. When n is the number of times of developing and developing the toner consumption pattern that is the basis of the composite waveform,
The toner consumption method according to any one of claims 1 to 3, wherein the number of times of developing and developing a toner consumption pattern for canceling the fluctuation waveform is (n-1) times or less.   The toner consumption method according to claim 1, wherein a toner consumption pattern for canceling the fluctuation waveform is different from a toner consumption pattern that is a source of the combined waveform.   6. The toner consumption method according to claim 5, wherein the toner consumption pattern for canceling the fluctuation waveform is different from the toner consumption pattern that is the basis of the combined waveform.   The toner consumption method according to claim 5 or 6, wherein the toner consumption pattern for canceling the fluctuation waveform is different from the toner consumption pattern which is a source of the combined waveform.   The toner consumption method according to claim 5, wherein a toner consumption pattern for canceling the fluctuation waveform is different from a toner consumption pattern for canceling the fluctuation waveform.   The toner consumption method according to claim 1, wherein the toner replenishment operation is executed so as to cancel out a change in toner density that occurs when the toner consumption operation is performed.   The toner replenishing operation is performed not only on the consumption waveform portion of the first round due to developer circulation in the toner concentration sensor output waveform in the toner consumption operation but also on the consumption waveform portion of the second and subsequent rounds. Item 10. The toner consumption method according to Item 9.   11. The toner consumption method according to claim 9, wherein the toner supply operation is performed by changing a supply speed of a toner supply device.   11. The toner consumption method according to claim 9, wherein the toner supply operation is performed by changing a drive ON time and a drive OFF time of the toner supply device. An image forming apparatus comprising a two-component developing device and performing a toner consumption operation by the toner consumption method according to claim 1.

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