JP2021033020A - Image forming apparatus - Google Patents

Abstract

To make it possible to extend the time to replace developer even under a situation where the degree of progress of a first carrier deterioration state (carrier film shaven state) progresses.SOLUTION: An image forming apparatus develops a latent image on a latent image carrier 3K with developing means 7K by using a developer containing a toner and a carrier, and has toner forcible consumption control means 101 that performs toner forcible consumption control of forcibly consuming the toner in the developing means in a non-image forming period. The toner forcible consumption control means changes a toner forcible consumption that is the amount of toner to be forcibly consumed, according to a carrier deterioration state (carrier film shaven state and carrier spent state) specified on the basis of a cumulative driving amount of the developing means and a cumulative toner consumption.SELECTED DRAWING: Figure 2

Description

The present invention relates to an image forming apparatus.

Conventionally, an image forming apparatus for developing a latent image on a latent image carrier by a developing means using a developer containing toner and a carrier is known.

For example, in Patent Document 1, the driving of the replenishing means is controlled so that the detection result of the toner concentration of the developing agent in the developing means becomes a predetermined toner concentration target value, and the toner is replenished to the developing agent in the developing means. An image forming apparatus for controlling the above is disclosed. In this image forming apparatus, the developer is in either a first carrier deterioration state in which the carrier is scraped to cause carrier adhesion and a second carrier deterioration state in which the toner component adheres to the carrier and causes toner scattering. In order to prolong the replacement period (the life of the developer), the toner concentration target value is continuously corrected so that neither state is reached.

However, in the conventional image forming apparatus, the progress rate of the carrier deterioration state of the two may differ greatly depending on the type of the developer and the usage condition. In such a case, the method of correcting the toner concentration target value is used for development. It may not be possible to extend the drug change period sufficiently.

In order to solve the above-mentioned problems, the present invention is described in an image forming apparatus for developing a latent image on a latent image carrier by a developing means using a developer containing toner and a carrier during the non-image forming period. It has a toner forced consumption control means for forcibly consuming toner in the developing means, and the toner forced consumption control means is based on the cumulative drive amount and the cumulative toner consumption amount of the developing means. It is characterized in that the forced consumption of toner to be forcibly consumed is changed according to the specified carrier deterioration state.

According to the present invention, it is possible to extend the developer replacement period even under the condition that the progress of the first carrier deterioration state (carrier film scraping state) progresses depending on the type and usage condition of the developer. Become.

Explanatory drawing which shows the schematic structure of the printer of an embodiment. The enlarged block diagram which shows the process cartridge for K in the printer. The graph which shows the relationship between the number of prints and the carrier resistance by the difference of the toner consumption per cumulative driving amount of a developing apparatus. The graph which shows the relationship between the carrier adhesion quality and the development potential (development Pot) for each carrier resistance. The graph which shows the relationship between the carrier adhesion quality and the toner density for each carrier resistance. In (a), in a high image area deterioration developer used under a situation where the toner consumption per unit drive amount of the developing apparatus is large, the usable range of the toner concentration and the developing potential capable of satisfying the carrier adhesion quality is determined. It is a graph which shows. (B) indicates the usable range of the toner concentration and the development potential that can satisfy the carrier adhesion quality in the standard deterioration developer used under the condition that the toner consumption per unit drive amount of the developing device is standard. It is a graph which shows. (C) indicates the usable range of the toner concentration and the development potential that can satisfy the carrier adhesion quality in the low image area deterioration developer used under the condition that the toner consumption per unit drive amount of the developing apparatus is small. It is a graph which shows. The graph which shows the relationship between the number of prints and the toner charge capacity by the difference of the toner consumption per cumulative driving amount of a developing apparatus. A graph showing the relationship between toner scattering quality and toner concentration for each toner charging ability. The graph which shows the relationship between the toner scattering quality and the toner charge amount. A graph showing the relationship between the toner concentration and the toner charge amount for each usage environment (temperature, humidity). (A) is a toner concentration that can satisfy not only the carrier adhesion quality but also the toner scattering quality in the high image area deterioration developer used under the condition that the toner consumption per unit driving amount of the developing apparatus is large. It is a graph which shows the usable range of development potential. (B) is a toner concentration that can satisfy not only the carrier adhesion quality but also the toner scattering quality in the standard deterioration developer used under the condition that the toner consumption per unit driving amount of the developing device is standard. It is a graph which shows the usable range of development potential. (C) is a toner concentration that can satisfy not only the carrier adhesion quality but also the toner scattering quality in the low image area deterioration developer used under the condition that the toner consumption per unit driving amount of the developing device is small. It is a graph which shows the usable range of development potential. The graph which shows the relationship between the development potential and the amount of toner adhesion. (A) to (c) are graphs showing a straight line (broken line) showing the relationship between the toner concentration at which a desired toner adhesion amount can be obtained and the development potential on the graphs shown in FIGS. 11 (a) to 11 (c). .. (A) to (c) are graphs showing the relationship between the toner concentration control range and the number of printed sheets based on the graphs shown in FIGS. 13 (a) to 13 (c). The graph which shows the toner density | concentration control range at the time of executing the toner forced consumption control of embodiment when the toner consumption amount per cumulative driving amount of a developing apparatus is small. The graph which shows the toner density | concentration control range at the time of executing the toner forced consumption control of embodiment when the toner consumption amount per cumulative driving amount of a developing apparatus is large. The flowchart which shows the flow of the correction process of the image formation condition in an embodiment.

Hereinafter, an embodiment of the image forming apparatus according to the present invention will be described.
First, the basic configuration of the printer 100, which is the image forming apparatus of the present embodiment, will be described.
FIG. 1 is an explanatory diagram showing a schematic configuration of the printer 100 of the present embodiment.
As shown in FIG. 1, the printer 100 of the present embodiment is a toner of yellow, magenta, cyan, and black (hereinafter, each color is referred to as “Y”, “M”, “C”, and “K”). It includes four process cartridges 1Y, 1M, 1C, 1K for producing images. These use Y, M, C, and K toners of different colors as the image forming substance, but have the same configuration other than that, and are replaced at the end of the service life.

The optical writing unit 20 irradiates the photoconductors 3Y, 3M, 3C, and 3K of the process cartridges 1Y, 1M, 1C, and 1K with the laser beam L based on the image information. The configuration of the optical writing unit 20 is to irradiate each photoconductor 3Y, 3M, 3C, 3K through a plurality of lens mirrors while deflecting the laser light L emitted from the light source by the polygon mirror 21 rotationally driven by the motor. It is a thing. However, in addition to such a polygon scanning method, other configurations such as an LED array method can also be adopted.

Above the process cartridges 1Y, 1M, 1C, and 1K, an intermediate transfer unit 40 that moves endlessly while tensioning an intermediate transfer belt 41, which is an intermediate transfer body, is arranged. The intermediate transfer unit 40 includes four primary transfer bias rollers 45Y, 45M, 45C, 45K, a cleaning device 42, and the like, in addition to the intermediate transfer belt 41. Further, a secondary transfer backup roller 46, a cleaning backup roller 47, a tension roller 49 and the like are also provided. The intermediate transfer belt 41 is endlessly moved counterclockwise in the drawing by the rotational drive of at least one of the rollers while being stretched on these rollers.

The primary transfer bias rollers 45Y, 45M, 45C, and 45K form the primary transfer nip by sandwiching the intermediate transfer belt 41 that moves endlessly between the photoconductors 3Y, 3M, 3C, and 3K, respectively. These are of a method in which a primary transfer bias having a polarity opposite to that of the toner (for example, positive polarity) is applied to the back surface (inner peripheral surface) of the intermediate transfer belt 41. All rollers except the primary transfer bias rollers 45Y, 45M, 45C and 45K are electrically grounded.

The intermediate transfer belt 41 sequentially passes through the primary transfer nips for Y, M, C, and K as it moves endlessly, and Y, M, C, on the photoconductors 3Y, 3M, 3C, and 3K, The K toner images are superimposed and primary transferred. As a result, a toner image in which four colors are superimposed (hereinafter referred to as "four-color toner image") is formed on the intermediate transfer belt 41. The four-color toner image formed on the intermediate transfer belt 41 is conveyed to the secondary transfer nip facing the secondary transfer roller 50 as the intermediate transfer belt 41 moves endlessly.

On the other hand, the transfer paper P as a recording material is sent out by the paper feed roller 32a from the paper feed device 32 arranged below the printer 100. The transferred transfer paper P is conveyed through the paper feed path 33 by the transfer roller pair 34 and is conveyed to the resist roller pair 35. The resist roller pair 35 feeds the transfer paper P to the secondary transfer nip at the timing when the four-color toner image is fed to the secondary transfer nip. Then, the four-color toner image on the intermediate transfer belt 41 is secondarily transferred to the transfer paper P by the secondary transfer bias applied to the secondary transfer nip.

The transfer paper P on which the four-color toner image is transferred is then sent to the fixing device 60. The fixing device 60 is composed of a fixing belt 64 stretched on a fixing roller 63, a heating roller 66, and a tension roller 65, and a pressure roller 61, and is located at a contact point between the fixing belt 64 and the pressure roller 61. A anchoring nip is formed. When the transfer paper P passes through the fixing nip, the four-color toner image is fixed to the transfer paper P by heat and pressure. The fixed transfer paper P is discharged to the output tray 68 by the output roller 67.

FIG. 2 is an enlarged configuration diagram showing a process cartridge 1K for K in the present embodiment.
The process cartridge 1K has a charging device 23K, a developing device 7K, a drum cleaning device 15K, and the like around the photoconductor 3K. The photoconductor 3K is formed by sequentially laminating an organic photosensitive layer and a surface layer on the peripheral surface of a drum-shaped conductive support. Further, the organic photosensitive layer is composed of a charge generation layer, a charge transport layer and the like. The thickness of the charge transport layer may be appropriately selected in the range of 10 [μm] or more and 40 [μm] or less according to the desired photoconductor characteristics. Further, an undercoat layer may be formed between the conductive support and the organic photosensitive layer in the photoconductor 3K, if necessary.

The charging device 23K is composed of a charging roller and includes a cleaning brush roller 236K and the like. The charging roller of the charging device 23K is made of a core metal which is a conductive support, a roller portion coated on the peripheral surface of the central portion in the longitudinal direction of the core metal, and abutting rollers fixed to both ends of the core metal in the longitudinal direction. It is configured. A charging bias is applied to the core metal by a power source. Then, an electric discharge is generated between the conductive roller portion and the photoconductor through the charging gap, so that the surface of the photoconductor 3K is uniformly charged.

The cleaning brush roller 236K includes a metal core metal and a brush roller portion made of a plurality of conductive fibers electrostatically planted on the peripheral surface thereof. Then, while abutting against the roller portion of the charging roller by its own weight, the toner is scraped off from the roller portion of the charging roller by rotating with the rotation of the charging roller. In addition to the charging roller method, the charging device 23K may employ a method in which the charging brush roller is brought into contact with the image forming region of the photoconductor.

An electrostatic latent image is formed on the surface of the photoconductor 3K uniformly charged by the charging device 23K by light scanning with the laser beam L, and enters the developing region which is a position facing the developing device 7K. The developing apparatus 7K develops an electrostatic latent image using a two-component developer (hereinafter, simply referred to as “developer”) containing a magnetic carrier and a non-magnetic toner.

The developing device 7K delivers the new toner and the developer to be replenished by the toner replenishing device 4K as a replenishing means from the toner bottle 5K containing the replenishing toner to the stirring unit 8K and the stirring unit 8K while stirring. It is provided with a supply unit 9K that conveys the developed developer while stirring and supplies it to the tubular developing sleeve 12K. The control unit 101 of the printer 100 detects the toner concentration in the developer in the developing device 7K by the toner concentration sensor 6K provided in the developing device 7K, and the toner replenishing device 4K so that the detection result approaches the toner concentration target value. To adjust the amount of toner replenished.

The developing sleeve 12K faces the photoconductor 3K through an opening provided in the casing and has a magnet inside. The developing apparatus 7K performs the developing process by transferring the toner in the developing agent supported on the surface of the developing sleeve 12K to the photoconductor 3K. The developing device 7K has a doctor blade 14K or the like arranged so that the tip of the developing device 7K approaches the developing sleeve 12K. The magnet roller inside the developing sleeve 12K has a plurality of magnetic poles that are sequentially arranged along the sleeve rotation direction from a position facing the doctor blade 14K. Each of these magnetic poles exerts a magnetic force on the developer on the sleeve at a predetermined position in the rotational direction. As a result, the developer sent from the supply unit 9K is attracted to and supported on the surface of the developing sleeve 12K, and a magnetic brush along the lines of magnetic force is formed on the surface of the sleeve.

The developer supported on the developing sleeve 12K is regulated to an appropriate height (layer thickness) when passing through the position facing the doctor blade 14K as the developing sleeve 12K rotates, and then becomes the photoconductor 3K. It is transported to the opposite development area. Then, the toner is transferred onto the electrostatic latent image by the action of the developing electric field formed by the potential difference between the development bias applied to the developing sleeve 12K and the electrostatic latent image of the photoconductor 3K, and contributes to the development.

The K toner image formed on the surface of the photoconductor 3K by development by the developing apparatus 7K enters the primary transfer nip for K as the photoconductor 3K rotates. In this primary transfer nip, the K toner image on the photoconductor 3K is primarily transferred onto the intermediate transfer belt 41. Further, after passing through the primary transfer nip, the photoconductor 3K is cleaned of the transfer residual toner by the cleaning brush 19K and the cleaning blade 18K of the drum cleaning device 15K, and is statically eliminated by the static elimination light L'of the static elimination lamp.

Further, in the present embodiment, the control unit 101 of the printer 100 functions as a toner forced consumption control means, and forcibly consumes the toner in the developing device 7 during a non-image forming period such as after the end of a print job. Toner forced consumption control is performed. Toner forced consumption control is also called toner refresh. Toner that has stayed in the developing apparatus 7 for a long period of time is subject to a lot of transfer of the developing agent in the developing apparatus 7 and rubbing due to stirring, which causes deterioration and causes image defects such as background stains.

Such long-stay toners are more present when the toner consumption per unit drive amount of the developing device 7 is smaller, such as when images with a low image area ratio are continuously formed, and image defects such as background stains are present. Is likely to occur. Therefore, when the toner consumption per unit drive amount of the developing device 7 is less than or equal to a predetermined specified value, the developer in the developing device 7 during the day image formation period such as after the end of the printing job. Toner forced consumption control is performed in which the toner is forcibly discharged (developed) onto the photoconductor 3 and collected by the drum cleaning device 15. By performing such forced toner consumption control, deteriorated toner staying in the developing device 7 for a long period of time can be removed from the developing device 7, and the amount is replaced by new toner from the toner replenishing device 4, so that the developing device is replaced. The amount of deteriorated toner in 7 can be reduced, and image defects such as background stains can be suppressed.

Whether or not the toner consumption per unit driving amount of the developing device 7 is equal to or less than a predetermined specified value is determined by, for example, an amount such that the average image area ratio of the image printed during the printing job causes background stains. It can be determined by whether or not the deteriorated toner is lower than the minimum image area ratio (specified value) that does not remain in the developing apparatus 7. When the average image area ratio in the print job is lower than the specified value, the toner forced consumption control is performed after the print job is completed to forcibly consume the toner in the developing apparatus 7.

The basic idea of toner forced consumption control in this embodiment is that, for example, if the minimum image area ratio (specified value) is 5%, when the average image area ratio in the print job is 0.5%, The toner forced consumption amount at the time of toner forced consumption control is set so as to forcibly consume the remaining 4.5% of toner. However, if the forced consumption of toner per unit time is too large, the toner discharged to the photoconductor 3 cannot be cleaned by the drum cleaning device 15. Further, since the time that can be applied to the toner forced consumption control is also limited, there is an upper limit to the toner forced consumption amount that can be set by one toner forced consumption control. Therefore, the amount of toner that could not be consumed by one forced toner consumption control will be additionally performed by the forced toner consumption control from the next time onward.

Since the toner forced consumption control may be performed at any time during the non-image forming operation period, for example, it is possible to perform the toner forced consumption control every time one image forming operation is completed. However, in this case, productivity may be reduced due to a decrease in image formation speed. Therefore, after the print job is completed, the number of prints in the print job is collected and the toner is insufficient for the minimum image area ratio. It is preferable to forcibly consume.

Next, the replacement time of the developer (life of the developer) will be described. In the following description, the color coding codes Y, C, M, and K will be omitted as appropriate.
In general, a first carrier deterioration state (hereinafter referred to as "carrier film scraping state") in which a carrier is scraped to cause carrier adhesion and a second carrier deterioration state (carrier spendt) in which a toner component adheres to a carrier and causes toner scattering. When the state becomes one of the states (state) and the state progresses to a state in which the state cannot be resolved even if the image forming conditions and the like are adjusted, the developer replacement time (developer life) comes.

In the carrier film scraping state, the carrier film is scraped due to wear due to use over time (stirring of the developer, etc.), the electrical resistance value of the carrier (hereinafter referred to as "carrier resistance") decreases, and carrier adhesion is likely to occur. The carrier is in a deteriorated state. When the carrier resistance is reduced, injection of the reverse polarity charge into the carrier by the developing electric field is likely to occur, and carrier adhesion is likely to occur in which the carrier adheres to the photoconductor 3. Usually, when the toner concentration of the developer is low or the development potential is high, injection of the reverse polarity charge into the carrier is likely to occur, and the carrier adhesion tends to be deteriorated. However, even if the carrier film scraping state progresses, the charging ability of the carrier does not change so much, so that the toner scattering does not deteriorate. When the carrier film scraping state progresses to the extent that it becomes difficult to suppress carrier adhesion even if the image formation conditions and the like are adjusted, it is time to replace the developer (the life of the developer).

The carrier spend state is a carrier deterioration state in which the toner component adheres to the carriers, so that the toner charging ability of the carriers is reduced and toner scattering is likely to occur. When the toner component adheres to the surface of the carrier, the chance that the carrier comes into contact with the toner to triboelectricly charge the toner is reduced, and the charging ability to charge the toner to a desired charging amount is reduced. When the toner charging ability is lowered, the amount of toner charged is insufficient, and toner is likely to scatter. Usually, in a high temperature and high humidity environment or when the toner concentration of the developer is high, the amount of charge of the toner tends to be insufficient, and the toner scattering tends to be deteriorated. However, as the carrier spending state progresses, the carrier resistance increases, so that the carrier adhesion is rather improved. When the carrier-spent state progresses to the extent that it becomes difficult to suppress toner scattering even if the image formation conditions and the like are adjusted, it is time to replace the developer (the life of the developer).

Table 1 below summarizes the above.

First, the state in which the carrier film is scraped will be described.
The degree of progress of the carrier film scraping state can be grasped from the cumulative driving amount and the cumulative toner consumption of the developing device 7 as the developing means.
The cumulative driving amount of the developing device 7 mainly indicates the amount (time) in which the developing agent is agitated inside the developing device 7, which has a correlation with the amount of carrier film scraping. Specific examples of the information that can be used as the index value include the mileage (rotational drive amount) of the developing sleeve 12 of the developing apparatus 7 from the start of use of the developing agent when the use of the new developing agent is started. For example, the distance traveled by the photoconductor, the number of prints (the number of images formed), and the like may be used as long as the information correlates with the cumulative drive amount of the device 7.
The cumulative toner consumption mainly indicates the amount of new toner replenished from the toner replenishing device 4 to the developing agent of the developing device 7. Specific examples of the information that can be used as this index value include the average image area ratio of images formed after the above-mentioned development agent use start time, but if the information correlates with the cumulative toner consumption, for example. The amount of toner replenished may be used.

The greater the cumulative driving amount of the developing apparatus 7, the greater the degree of progress of the carrier film scraping state. On the other hand, as the cumulative toner consumption increases, the amount of new toner increases and the amount of toner component adhering to the carrier surface increases, so that the carrier resistance increases. Therefore, carrier adhesion due to the carrier film scraping state is less likely to occur, and the degree of progress of the carrier film scraping state is small. Considering these relationships, the toner consumption per unit driving amount of the developing apparatus 7 can be preferably used as an index value indicating the degree of progress of the carrier film scraping state. That is, as the toner consumption per unit drive amount of the developing apparatus 7 is smaller, the carrier film scraping state progresses, the carrier resistance is reduced, and carrier adhesion is more likely to occur.

FIG. 3 is a graph showing the relationship between the number of prints and the carrier resistance due to the difference in the amount of toner consumed per cumulative driving amount of the developing apparatus 7.
As shown by reference numeral A in FIG. 3, when the toner consumption per cumulative driving amount of the developing device 7 is large (when the image area ratio of the images formed so far is high), the carrier increases as the number of printed sheets increases. The resistance increases. Further, as shown by reference numeral B in FIG. 3, when the toner consumption per cumulative driving amount of the developing device 7 is standard (when the image area ratio of the images formed so far is standard), the number of printed sheets Carrier resistance tends to decrease slightly as the number of carriers increases. On the other hand, as shown by reference numeral C in FIG. 3, when the toner consumption per cumulative driving amount of the developing device 7 is small (when the image area ratio of the images formed so far is low), the number of printed sheets increases. As a result, the carrier resistance decreases. In this way, the carrier resistance can be predicted from the toner consumption per cumulative driving amount of the developing device 7.

FIG. 4 is a graph showing the relationship between the carrier adhesion quality and the development potential (development pot) for each carrier resistance.
FIG. 5 is a graph showing the relationship between the carrier adhesion quality and the toner concentration for each carrier resistance.
As shown in FIG. 4, in the case of a developer having a reduced carrier resistance, the reduction in the carrier resistance makes it easier for the reverse polarity charge to be injected into the carrier by the developing electric field, and as a result, the carrier adhesion tends to worsen. That is, as shown in FIG. 4, it is possible to suppress carrier adhesion by setting the developing potential low, but in the case of a developer with reduced carrier resistance, that is, per unit driving amount of the developing apparatus 7. In the case of a developing agent (hereinafter referred to as "low image area deterioration developing agent") used under the condition that the toner consumption of the above is low (reference numeral C'in FIG. 4), the allowable limit value of carrier adhesion should not be exceeded. The range of development potential that can be adjusted is narrow, and the life of the developer comes early. Similarly, as shown in FIG. 5, it is possible to suppress carrier adhesion by setting the toner concentration high, but in the case of a developer with reduced carrier resistance, that is, in the case of a low image area deterioration developer. In the case (reference numeral C'in FIG. 4), the toner concentration range that can be adjusted so as not to exceed the allowable limit value of carrier adhesion is narrow, and the life of the developer reaches early.

Further, as shown in FIG. 4, the higher the development potential, the more likely it is that the reverse polarity charge is injected into the carrier by the developing electric field, and as a result, the carrier adhesion tends to worsen.
Further, as shown in FIG. 5, the lower the toner concentration, the less likely it is that the toner component adheres, which causes an increase in carrier resistance, and the reverse polarity charge is likely to be injected into the carrier by the developing electric field, so that the carrier adhesion deteriorates. It's easy to do.

From the above, the toner concentration and development that can satisfy the carrier adhesion quality for each toner consumption per unit driving amount of the developing apparatus 7 (high image area deterioration developer, standard deterioration developer, low image area deterioration developer). The usable range of the potential is summarized in FIGS. 6 (a) to 6 (c).
As shown in FIGS. 6A to 6C, a developing agent having a low carrier resistance, that is, a developing agent used under a situation where the toner consumption per unit driving amount of the developing apparatus 7 is small (low image area deterioration). The more the developer), the narrower the range of the developing potential and the range of the toner concentration that can suppress carrier adhesion, so that the life of the developer reaches earlier.

Next, the carrier spend state will be described.
The degree of progress of the carrier spending state can also be grasped from the cumulative driving amount and the cumulative toner consumption of the developing device 7, as in the case of the carrier film scraping state described above. Since the cumulative driving amount of the developing device 7 indicates the amount (time) in which the developer is stirred inside the developing device 7 as described above, the toner component separated from the toner by stirring adheres to the carrier surface. Correlates with quantity. Further, since the cumulative toner consumption mainly indicates the amount of new toner replenished from the toner replenishing device 4 to the developing agent of the developing device 7, there is a correlation with the amount of the toner component that can adhere to the carrier surface. When the toner consumption per unit drive amount of the developing apparatus 7 described above is used as the index value indicating the progress of the carrier spend state, the larger the index value, the more chance that the new toner component adheres to the carrier surface. As the amount increases, the adhesion of the toner component to the carrier progresses, the toner charging ability decreases, and the toner scatters easily.

FIG. 7 is a graph showing the relationship between the number of printed sheets and the toner charging ability due to the difference in the amount of toner consumed per cumulative driving amount of the developing device 7.
As shown in FIG. 7, the larger the toner consumption per cumulative driving amount of the developing device 7 (the higher the image area ratio of the images formed so far), the more easily the toner charging ability is lowered. This is because as the amount of toner consumed per cumulative driving amount of the developing device 7 increases, the amount of new toner supplied from the toner replenishing device 4 to the developing agent of the developing device 7 increases, so that the toner component adhering to the carrier film This is because the amount of supply increases, the carrier-spent state tends to progress, and the toner charging capacity tends to decrease.

FIG. 8 is a graph showing the relationship between the toner scattering quality and the toner concentration for each toner charging ability.
FIG. 9 is a graph showing the relationship between the toner scattering quality and the toner charge amount.
FIG. 10 is a graph showing the relationship between the toner concentration and the toner charge amount for each usage environment (temperature, humidity).
As shown in FIGS. 8 and 9, as the carrier spending state progresses and the carrier charging ability decreases, the toner charging amount decreases, and as a result, the toner scattering quality deteriorates. That is, as shown in FIG. 8, it is possible to suppress toner scattering by setting the toner concentration low, but in the case of a developer having a reduced toner charging ability, that is, the unit drive amount of the developing apparatus 7. In the case of a developer (hereinafter referred to as "high image area deterioration developer") used under a situation where the amount of toner consumed per unit is large (reference numeral A'in FIG. 8), the allowable limit value of toner scattering is not exceeded. The toner concentration range that can be adjusted is narrow, and the life of the developer is shortened.

Further, as shown in FIG. 10, the toner charge amount varies depending on the usage environment (temperature, humidity), but as shown in FIG. 9, the smaller the toner charge amount, the worse the toner scattering. The higher the temperature and humidity, the lower the amount of toner charged, and the more easily toner scatters.

From the above, not only the carrier adhesion quality but also the toner scattering quality is satisfied for each toner consumption per unit driving amount of the developing apparatus 7 (high image area deterioration developer, standard deterioration developer, low image area deterioration developer). The usable range of the toner concentration and the developing potential that can be used is summarized in FIGS. 11 (a) to 11 (c).

FIG. 12 is a graph showing the relationship between the development potential and the amount of toner adhered.
FIG. 12 shows three graphs γ1, γ2, and γ3 with different developments γ. The development γ is a parameter (image formation condition) corresponding to the slope of the toner adhesion amount with respect to the development potential. Generally, the higher the toner charge amount, the lower the development γ, and the lower the toner charge amount, the higher the development γ.

13 (a) to 13 (c) show straight lines (broken lines) showing the relationship between the toner concentration at which a desired toner adhesion amount can be obtained and the development potential on the graphs shown in FIGS. 11 (a) to 11 (c). It is a graph.
As shown in FIGS. 13 (a) to 13 (c), a desired toner can be used within a usable range of toner concentration and development potential capable of suppressing both carrier adhesion and toner scattering by adjusting the target value of development γ. The amount of adhesion can be obtained. Then, the control range of the toner density (target range of the toner density) also changes according to the adjustment of the target value of the development γ.

14 (a) to 14 (c) are graphs showing the relationship between the toner concentration control range and the number of printed sheets based on the graphs shown in FIGS. 13 (a) to 13 (c).
The control range of the toner concentration corresponding to each toner consumption per unit driving amount of the developing apparatus 7 (high image area deterioration developer, standard deterioration developer, low image area deterioration developer) is shown in FIGS. 14 (a) to 14 (a). It becomes as shown in c). As shown in FIGS. 14 (a) to 14 (c), as the number of printed sheets increases (as the unit drive amount of the developing apparatus 7 increases), the carrier deterioration state (carrier film scraping state, carrier spend state) progresses. As a result, carrier adhesion and toner scattering are likely to occur, and as a result, the adjustment range of the target value of development γ is narrowed, and the control range of toner concentration is also narrowed.

In the present embodiment, the developer has reached the end of its life when the toner concentration control range narrowed in this way (difference between the upper limit value and the lower limit value of the toner concentration control range) becomes equal to or less than a predetermined life threshold value. And encourage the replacement of the developer. This is because when the toner concentration control range becomes narrower as the difference between the upper limit value and the lower limit value of the toner concentration control range becomes equal to or less than the life threshold value, the actual toner concentration easily deviates from the toner concentration control range, resulting in toner scattering and carrier adhesion. This is because the situation can occur.

In the present embodiment, the toner concentration control range is appropriately changed as shown in FIGS. 14 (a) to 14 (c) according to the carrier deterioration state, and the toner concentration target value (for example, the toner concentration control range) is appropriately changed accordingly. By adjusting (set to the median value of), the period during which image formation can be performed with the desired amount of toner adhesion while suppressing carrier adhesion and toner scattering compared to the case where the toner concentration control range is set regardless of the carrier deterioration state ( The life of the developer) is extended.

However, when the degree of progress of carrier film scraping is progressing, it is difficult to sufficiently delay the degree of progress simply by appropriately changing the toner concentration control range and adjusting the toner concentration target value as described above. .. Specifically, as shown in FIG. 14 (c), when the degree of progress of carrier film scraping is progressing, the toner concentration of the developer is increased by adjusting the toner concentration target value to be high. By increasing the amount of new toner to be replenished, increasing the toner component adhering to the carrier film, increasing the carrier resistance, and suppressing the carrier adhesion, the occurrence of carrier adhesion can be suppressed. However, even if the toner concentration of the developer is increased, there is a limit in relation to securing a desired amount of toner adhering and toner scattering. Moreover, in a situation where an image having a low image area ratio is formed, the amount of new toner that can be replenished is limited even if the toner concentration target value is increased. Therefore, the toner component adhering to the carrier film is increased to increase the carrier resistance. There is a limit to how much it can be increased to suppress carrier adhesion.

Therefore, in the present embodiment, the above-mentioned forced toner consumption control is used, and when the degree of progress of carrier film scraping is progressing, the forced toner consumption is increased to suppress carrier adhesion and develop. The life of the agent is further extended.

As shown in FIG. 14C, FIG. 15 shows the present implementation when the toner consumption per cumulative driving amount of the developing device 7 is small (when the image area ratio of the images formed so far is low). It is a graph which shows the toner density control range at the time of executing the toner forced consumption control of a form.
In the toner forced consumption control of the present embodiment, when the toner consumption amount per cumulative driving amount of the developing device 7 is small, the toner forced consumption amount is increased so that more new toner can be replenished to the developer. .. As a result, the toner component adhering to the carrier film can be increased to compensate for the decrease in carrier resistance due to the scraping of the carrier film, and carrier adhesion can be suppressed. As a result, as shown in FIG. 15, the lower limit of the toner concentration control range can be set to a lower value.

At this time, the toner charging ability of the carrier is lowered by increasing the forced toner consumption so that more new toner can be replenished to the developer and increasing the toner component adhering to the carrier film. Therefore, as shown in FIG. 15, the upper limit of the toner concentration control range is slightly lowered. However, the range in which the lower limit of the toner concentration control range can be lowered by suppressing carrier adhesion by increasing the forced toner consumption is the upper limit of the toner concentration control range due to the deterioration of toner scattering due to the increase in the forced toner consumption. Will be larger than the width of the decrease. Therefore, the difference between the upper limit value and the lower limit value of the toner concentration control range becomes wider, and as shown in FIG. 15, the time when the difference between the upper limit value and the lower limit value of the toner concentration control range reaches the life threshold value (life of the developer). Can be delayed.

Further, even when the progress of the carrier spend is progressing, it is difficult to sufficiently delay the progress by simply changing the toner concentration control range appropriately and adjusting the toner concentration target value as described above. .. Specifically, as shown in FIG. 14A, when the progress of the carrier spend is progressing, the toner concentration of the developer is replenished by adjusting the toner concentration target value to be low and lowering the toner concentration of the developer. It is possible to reduce the amount of new toner to be produced, reduce the toner component adhering to the carrier film, and suppress the decrease in the toner charging ability due to the carrier, thereby suppressing the decrease in the toner charging amount and suppressing the occurrence of toner scattering.

However, there is a limit to reducing the toner concentration of the developer from the viewpoint of securing a desired toner adhesion amount and the relationship with carrier adhesion. Moreover, in a situation where an image having a high image area ratio is formed, even if the toner concentration target value is lowered, the amount of new toner replenished cannot be sufficiently limited, so that the toner component adhering to the carrier film is reduced. There is also a limit to suppressing the decrease in toner charging ability and suppressing the occurrence of toner scattering.

Therefore, in the present embodiment, the toner forced consumption control described above is used, and when the progress of the carrier spend is progressing, the toner forced consumption amount is reduced (including making it zero). Toner scattering is suppressed to further extend the life of the developer.

As shown in FIG. 14A, FIG. 16 shows the present implementation when the toner consumption per cumulative driving amount of the developing device 7 is large (when the image area ratio of the images formed so far is high). It is a graph which shows the toner density control range at the time of executing the toner forced consumption control of a form.
In the toner forced consumption control of the present embodiment, when the toner consumption amount per cumulative driving amount of the developing device 7 is large, the toner forced consumption amount is reduced (or set to zero), and new toner is replenished to the developer. Make sure that the amount of toner is suppressed. As a result, the amount of toner components adhering to the carrier film can be suppressed, the progress of the decrease in toner charging ability can be delayed, and toner scattering can be suppressed. As a result, as shown in FIG. 16, the upper limit of the toner concentration control range can be set to a higher value.

At this time, as a result of reducing the amount of forced toner consumption and suppressing the amount of new toner supplied to the developer to a small amount, the toner component adhering to the carrier film is reduced, so that the carrier resistance is increased. As shown in, the lower limit of the toner concentration control range is slightly increased. However, the range in which the upper limit of the toner concentration control range can be raised by suppressing toner scattering by reducing the forced toner consumption is the lower limit of the toner concentration control range due to the deterioration of carrier adhesion due to the decrease in the forced toner consumption. It will be larger than the width that increases. Therefore, the difference between the upper limit value and the lower limit value of the toner concentration control range becomes wider, and as shown in FIG. 16, the time when the difference between the upper limit value and the lower limit value of the toner concentration control range reaches the life threshold value (the life of the developer). Can be delayed.

FIG. 17 is a flowchart showing a flow of correction processing of image formation conditions in the present embodiment.
When the mileage (cumulative drive amount of the developing device 7) from the previous correction process has passed a predetermined mileage (Yes in S1), the control unit 101 of the printer 100 first obtains the current environmental information (Yes). Information on temperature and humidity) is acquired (S2). In addition, the toner consumption (cumulative toner consumption) from the previous correction process to the present is calculated from the information of the average image area ratio of the images formed from the previous correction process to the present, and the calculated toner consumption is calculated as the previous time. Toner consumption per mileage is calculated by dividing by the mileage from the correction process to the present (S3). Further, the control unit 101 detects and acquires the current toner concentration of the developer in the developing device 7 by the toner concentration sensor 6 provided in the developing device 7 (S4).

Next, the control unit 101 is shown in FIGS. 11A to 11C based on the toner consumption per mileage calculated in the processing step S3 and the current toner concentration acquired in the processing step S4. In addition, the usable range (upper limit value and lower limit value) of the development potential and the toner concentration control range (upper limit value and lower limit value) are determined (S5).

After that, the control unit 101 determines whether or not the difference between the upper limit value and the lower limit value (the width of the upper and lower limits of the toner concentration) of the toner concentration control range determined in the processing step S5 is larger than the first threshold value (S6). .. When it is determined that it is larger than the first threshold value (Yes in S6), the toner concentration target value and the development potential are determined and the development γ is corrected (S7) as usual.

On the other hand, when the control unit 101 determines in the processing step S6 that the value is equal to or lower than the first threshold value (No in S6), the control unit 101 then determines the difference between the upper limit value and the lower limit value of the toner concentration control range determined in the processing step S5 (No in S6). It is determined whether or not (the width of the upper and lower limits of the toner concentration) is larger than the life threshold value (S8). When it is determined that the life threshold is equal to or less than the life threshold (No in S8), it is determined that the developer has reached the end of its life, and a process of displaying an error message is executed (S9).

When it is determined in the processing step S8 that it is larger than the life threshold value (Yes in S6), the control unit 101 next determines the toner consumption per mileage calculated in the processing step S3 in order to determine the carrier deterioration state. It is determined whether or not it is equal to or less than the second threshold value (S10). In this determination, when the toner consumption per mileage is equal to or less than the second threshold value (Yes in S10), it is determined that the carrier film scraping state is in progress. On the other hand, when the toner consumption per mileage is larger than the second threshold value (No in S10), the control unit 101 controls the toner per mileage in order to confirm whether or not the carrier spending state is progressing. It is determined whether or not the consumption amount is further equal to or less than the third threshold value (S11), and if it is larger than the third threshold value (No in S11), it is determined that the carrier spend state is progressing.

When the control unit 101 determines that the toner consumption per mileage is larger than the second threshold value and further larger than the third threshold value (No in S10, No in S11), the carrier spending state progresses. Therefore, the toner forced consumption amount during the toner forced consumption control is reduced to zero. That is, the toner forced consumption control (toner refresh) is turned off (S12) so that the toner forced consumption control is not performed even when the execution timing of the toner forced consumption control arrives.

As a result, as described above, the forced consumption of toner is reduced, and the amount of new toner supplied to the developer can be suppressed to a small amount, so that the toner component adhering to the carrier film is reduced and the progress of the carrier spend is delayed. Can be done. As a result, as shown in FIG. 16, the difference between the upper limit value and the lower limit value of the toner concentration control range widens, and the time when the difference between the upper limit value and the lower limit value of the toner concentration control range reaches the life threshold value (the life of the developer). The time to reach) can be delayed.

On the other hand, when the control unit 101 determines that the toner consumption per mileage is larger than the second threshold value and is equal to or lower than the third threshold value (No in S10, Yes in S11), the carrier deterioration state is standard. The toner forced consumption amount of the toner forced consumption control is not changed (S13).

On the other hand, when the control unit 101 determines that the toner consumption per mileage is equal to or less than the second threshold value (Yes in S10), the carrier film scraping state is progressing, so that the toner is forced during the toner forced consumption control. The consumption amount is increased by a predetermined amount (desired amount) (S14). As a result, as described above, the forced consumption of toner increases and the amount of new toner supplied to the developer can be increased, so that the toner component adhering to the carrier film increases, the carrier resistance increases, and the carrier film is scraped. It is possible to suppress the occurrence of carrier adhesion due to the above. As a result, as shown in FIG. 15, the difference between the upper limit value and the lower limit value of the toner concentration control range widens, and the time when the difference between the upper limit value and the lower limit value of the toner concentration control range reaches the life threshold value (the life of the developer). The time to reach) can be delayed.

Here, the toner forced consumption amount of the toner forced consumption control is preferable because the larger the toner forced consumption amount per unit time, the shorter the toner forced consumption control time. However, if the forced consumption of toner per unit time is too large, the toner discharged to the photoconductor 3 cannot be cleaned by the drum cleaning device 15. Therefore, there is an upper limit to the forced toner consumption per unit time in relation to the cleaning performance. On the other hand, since the time that can be applied to the toner forced consumption control is also limited, there is an upper limit to the toner forced consumption amount that can be set by one toner forced consumption control.

On the other hand, the basic operation of the toner forced consumption control of the present embodiment is when the average image area ratio of the images printed during the print job is lower than the minimum image area ratio (specified value) after the end of the print job. , The toner is forcibly consumed by the difference. Therefore, as the number of images formed in one print job increases, the amount of toner forced consumption under the toner forced consumption control after the end of the print job increases.

Therefore, when increasing the toner forced consumption amount during the toner forced consumption control (S14), when the number of images formed by the print job is large, simply increasing the toner forced consumption amount by a predetermined amount (desired amount) is performed once. There is a risk of exceeding the maximum value of the toner forced consumption that can be set by the toner forced consumption control of.

Therefore, in the present embodiment, when increasing the toner forced consumption amount during the toner forced consumption control (S14), the average number of image formations (average Page / Job) in the past print job is calculated, and the average Page / Job is the first. It is determined whether or not it is equal to or greater than the four thresholds (S15). If it is determined by this judgment that the average Page / Job is equal to or higher than the fourth threshold value (Yes in S15), and if the toner forced consumption is increased by a predetermined amount (desired amount), the future The toner forced consumption amount in the toner forced consumption control after the printing job may exceed the above-mentioned maximum value. Therefore, in this case, the toner forced consumption is increased to the maximum value (S16). On the other hand, when it is determined in the determination of the processing step S15 that the average Page / Job is smaller than the fourth threshold value (No in S15), the amount (desired amount) corresponding to the average Page / Job is increased (S17). ..

What has been described above is an example, and has a unique effect in each of the following aspects.
[First aspect]
In the first aspect, an image forming apparatus (for example, a printer 100) that develops a latent image on a latent image carrier (for example, a photoconductor 3) by a developing means (for example, a developing apparatus 7) using a developer containing toner and a carrier. The toner forced consumption control means (for example, the control unit 101) for forcibly consuming the toner in the developing means during the non-image forming period (after the completion of the printing job) is provided. The consumption control means is forcibly forced according to a carrier deterioration state (for example, a carrier film scraping state or a carrier spend state) specified based on the cumulative drive amount (for example, mileage) and the cumulative toner consumption of the developing means. It is characterized in that the forced consumption of toner to be consumed is changed.
In general, either the first carrier deterioration state in which the carrier is scraped to cause carrier adhesion or the second carrier deterioration state in which the toner component adheres to the carrier and causes toner scattering adjusts the image formation conditions and the like. If the situation cannot be resolved, it is time to replace the developer (the life of the developer).
The first carrier deterioration state (carrier film scraping state) is a state in which the carrier film is scraped over time, the electrical resistance value (carrier resistance) of the carrier is reduced, and carrier adhesion is likely to occur. When the carrier resistance decreases to the extent that it becomes difficult to suppress carrier adhesion even after adjusting the above, it is time to replace the developer (life of the developer). However, even if the deterioration state of the first carrier progresses, the charging ability of the carrier does not change so much, so that the toner scattering does not deteriorate.
The second carrier deterioration state (carrier-spent state) is a state in which the toner component adheres to the carrier, so that the toner charging ability of the carrier is reduced and toner scattering is likely to occur. Therefore, the image forming conditions and the like are adjusted. However, when the adhesion of the toner component to the carrier progresses to the extent that it becomes difficult to suppress the toner scattering, it is time to replace the developer (the life of the developer). However, as the second carrier deterioration state progresses, the carrier resistance increases, so that the first carrier deterioration state that causes carrier adhesion is rather improved.
Here, the degree of progress of the first carrier deterioration state (carrier film scraping state) can be grasped from the cumulative drive amount and the cumulative toner consumption amount of the developing means. For example, when the toner consumption per unit driving amount of the developing means is used as an index value, the smaller the index value, the smaller the carrier resistance. Further, the degree of progress of the second carrier deterioration state (carrier spend state) can also be grasped from the cumulative drive amount and the cumulative toner consumption amount of the developing means. For example, as described above, when the toner consumption per unit driving amount of the developing means is used as an index value, the larger the index value, the larger the toner replenishment amount, and the chance that the new toner component adheres to the carrier surface. As the amount increases, the adhesion of the toner component to the carrier progresses, and the toner charging ability decreases. In this way, it is possible to grasp the progress of the carrier deterioration state (carrier film scraping state and carrier spending state) from the cumulative driving amount and the cumulative toner consumption amount of the developing means.
However, when the progress of the first carrier deterioration state (carrier film scraping state) is progressing, it is difficult to sufficiently delay the progress by the conventional method of correcting the toner concentration target value. More specifically, conventionally, by correcting the toner concentration target value to be higher and increasing the toner concentration of the developer, the amount of new toner to be replenished is increased, the carrier resistance is increased, and the first carrier is used. Delay the progress of the deterioration state. However, in addition to the fact that there is a limit to increasing the toner concentration of the developer, the amount of new toner that can be replenished is also limited in the situation where an image having a low image area ratio is formed. Therefore, even if the toner concentration target value is increased, it is difficult to sufficiently increase the amount of new toner to be replenished to attach the toner component to the carrier, and it is difficult to sufficiently delay the progress of the first carrier deterioration state.
In this embodiment, a toner forced consumption control means is provided so that the toner in the developing means can be forcibly consumed, and the carrier deterioration state specified based on the cumulative drive amount and the cumulative toner consumption amount of the developing means is met. Therefore, the forced toner consumption can be changed. According to this, when the progress of the first carrier deterioration state (carrier film scraping state) is progressing, more new toner can be replenished (replaced) with the developer by increasing the forcible toner consumption. Therefore, it is possible to sufficiently delay the progress of the first carrier deterioration state. Therefore, even under the condition that the progress of the first carrier deterioration state (carrier film scraping state) progresses depending on the type and usage condition of the developing agent, the progress of the first carrier deterioration state is sufficiently delayed. It is possible to extend the developer replacement period.

[Second aspect]
The second aspect is characterized in that, in the first aspect, the carrier deterioration state is specified based on the toner consumption per unit driving amount of the developing means.
As described in the above-described embodiment, the carrier deterioration state (carrier film scraping state and carrier spending state) can be specified from the toner consumption per unit driving amount of the developing means.

[Third aspect]
In the third aspect, in the second aspect, when the toner consumption amount per unit driving amount of the developing means is equal to or less than a predetermined toner consumption increase threshold value (for example, a second threshold value), the toner forced consumption control means (for example, processing). Yes) in step S10 is characterized in that the forced toner consumption is increased.
When the toner consumption per unit driving amount of the developing means is equal to or less than a predetermined toner consumption increase threshold value, it can be determined that the type of carrier deterioration state is the carrier film scraping state. Therefore, in this case, by increasing the forcible consumption of toner, the toner component adhering to the carrier increases, the carrier resistance increases, and the carrier adhering is suppressed, so that the progress of the carrier film scraping state can be delayed. ..

[Fourth aspect]
A fourth aspect is the second or third aspect, when the toner forced consumption control means has a toner consumption amount per unit drive amount of the developing means larger than a predetermined toner consumption increase threshold value (for example, a second threshold value). , The toner forced consumption amount is not changed.
When the toner consumption per unit drive amount of the developing means is larger than the predetermined toner consumption increase threshold, the carrier film scraping state has not progressed so much, and the toner forced consumption amount according to the carrier film scraping state. By not changing (increasing) of, unnecessary control can be avoided.

[Fifth aspect]
In the fifth aspect, in the fourth aspect, when the toner consumption amount per unit drive amount of the developing means is larger than a predetermined toner consumption reduction threshold value (for example, a third threshold value), the toner forced consumption control means (processing step). No) of S11 is characterized in that the forced toner consumption amount is reduced or the forced toner consumption control is not performed.
When the toner consumption per unit driving amount of the developing means is larger than the predetermined toner consumption reduction threshold value, it can be determined that the type of carrier deterioration state is the carrier spend state. Therefore, in this case, by reducing or reducing the forced toner consumption to zero, the toner component adhering to the carrier can be reduced, and the progress of the carrier spending state can be delayed.

[Sixth aspect]
A sixth aspect is the toner concentration detecting means (for example, the toner density sensor 6) for detecting the toner concentration of the developer in the developing means and the developing agent in the developing means in any one of the first to fifth aspects. A replenishment means for replenishing toner (for example, a toner replenishment device 4) and a toner concentration control means for controlling the drive of the replenishment means so that the detection result by the toner concentration detection means is within a predetermined toner concentration control range. The upper limit value and the lower limit value of the toner concentration control range are determined based on the cumulative drive amount and the cumulative toner consumption amount of the developing means, and the toner forced consumption control means is the toner concentration control range. When the difference between the upper limit value and the lower limit value of is equal to or less than a predetermined upper / lower limit difference threshold value (for example, the first threshold value) (for example, No in the processing step S6), the toner forced consumption amount is changed. is there.
When the difference between the upper limit value and the lower limit value of the toner concentration control range is larger than the predetermined upper and lower limit difference threshold values, the carrier deterioration state has not progressed so much, and in this case, the carrier deterioration state is adjusted. By not changing the forced toner consumption, unnecessary control can be avoided.

[7th aspect]
In the seventh aspect, in any one of the first to sixth aspects, the toner forced consumption control means performs the toner forced consumption control after the end of the continuous image forming operation (for example, after the end of the print job), and the toner forced consumption control means. When the toner forced consumption amount is increased, the toner forced consumption amount is determined according to the number of image formations (average Page / Job) per continuous image formation operation.
According to this, it is possible to realize a necessary and sufficient forcible toner consumption without excessively increasing the forcible toner consumption.

[8th aspect]
In the eighth aspect, in any one of the first to seventh aspects, the toner forced consumption control means performs the toner forced consumption control after the end of the continuous image forming operation (for example, after the end of the print job), and the toner forced consumption control means. When the forcible toner consumption is increased, when the number of image formations (average Page / Job) per continuous image formation operation is equal to or higher than a predetermined image formation number threshold (for example, the fourth threshold) (for example, Yes in processing step S15). Is characterized in that the forced toner consumption is set to the maximum value within the permissible range.
According to this, it is possible to prevent the forced toner consumption from exceeding the maximum value within the permissible range.

1: Process cartridge 3: Photoreceptor 4: Toner replenishment device 5: Toner bottle 6: Toner concentration sensor 7: Development device 12: Development sleeve 14: Doctor blade 15: Drum cleaning device 20: Optical writing unit 23: Charging device 40: Intermediate transfer unit 41: Intermediate transfer belt 45: Primary transfer bias roller 50: Secondary transfer roller 60: Fixing device 100: Printer 101: Control unit

Japanese Unexamined Patent Publication No. 2016-0574223

Claims (8)

In an image forming apparatus that develops a latent image on a latent image carrier by a developing means using a developer containing toner and a carrier.
It has a toner forced consumption control means for forcibly consuming toner in the developing means during a non-image forming period.
The toner forced consumption control means is characterized in that the toner forced consumption amount to be forcibly consumed is changed according to a carrier deterioration state specified based on the cumulative driving amount and the cumulative toner consumption amount of the developing means. Image forming device. In the image forming apparatus according to claim 1,
An image forming apparatus, characterized in that the carrier deterioration state is specified based on the toner consumption per unit driving amount of the developing means. In the image forming apparatus according to claim 2,
The toner forced consumption control means is an image forming apparatus that increases the toner forced consumption amount when the toner consumption amount per unit driving amount of the developing means is equal to or less than a predetermined toner consumption increase threshold value. In the image forming apparatus according to claim 2 or 3.
The toner forced consumption control means is an image forming apparatus that does not change the toner forced consumption amount when the toner consumption amount per unit driving amount of the developing means is larger than a predetermined toner consumption increase threshold value. In the image forming apparatus according to any one of claims 2 to 4.
When the toner consumption amount per unit drive amount of the developing means is larger than a predetermined toner consumption reduction threshold value, the toner forced consumption control means reduces the toner forced consumption amount or performs the toner forced consumption control. An image forming apparatus characterized by the absence. In the image forming apparatus according to any one of claims 1 to 5,
Toner concentration detecting means for detecting the toner concentration of the developing agent in the developing means, and
A replenishing means for replenishing the developer in the developing means and a replenishing means.
It has a toner concentration control means that controls the drive of the replenishment means so that the detection result by the toner concentration detection means is within a predetermined toner concentration control range.
The upper limit value and the lower limit value of the toner concentration control range are determined based on the cumulative driving amount and the cumulative toner consumption amount of the developing means.
The toner forced consumption control means is an image forming apparatus characterized in that the toner forced consumption amount is changed when the difference between the upper limit value and the lower limit value of the toner concentration control range is equal to or less than a predetermined upper and lower limit difference threshold value. .. In the image forming apparatus according to any one of claims 1 to 6.
When the toner forced consumption control means performs the toner forced consumption control after the end of the continuous image forming operation and increases the toner forced consumption amount, the toner forced consumption amount is used to form an image per the continuous image forming operation. An image forming apparatus characterized in that it is determined according to the number of times. In the image forming apparatus according to any one of claims 1 to 7.
When the toner forced consumption control means performs the toner forced consumption control after the continuous image forming operation is completed and the toner forced consumption amount is increased, the number of image formations per continuous image forming operation is a predetermined image formation. An image forming apparatus characterized in that when the number of times is equal to or greater than a threshold value, the forced toner consumption is set to the maximum value within an allowable range.

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