JP5396700B2 - Image forming apparatus and fog elimination method - Google Patents

Description

  The present invention relates to an image forming apparatus and a fog elimination method.

  In an image forming apparatus using an electrophotographic technique, the ratio of defectively charged toner having a reduced charge amount in a developing device may increase due to various causes such as environment (mainly humidity) and aging. As a result, so-called “fogging” in which defectively charged toner adheres to the background portion (white background portion) of the image formed on the surface of the photoreceptor or intermediate transfer belt is likely to occur. This fog also occurs when the photosensitive member or the charger deteriorates the charging capability due to deterioration over time and the surface potential of the photosensitive member does not reach the specified potential. When the fog occurs, not only the image quality is deteriorated, but also the inside as well as the inside of the image forming apparatus may be contaminated. Further, there is a problem that toner is wasted. For this reason, conventionally, the fog is detected by various methods, and this is dealt with.

  The most common method for detecting fog is by visual observation. This is because the fog is generated by a very small amount of toner and is difficult to detect with an existing optical detector. If it is determined that it is fogging, it is removed manually.

  For this reason, a configuration for automatically detecting fogging is desired, and the following configuration has also been proposed.

  For example, a configuration is known in which fog is detected by controlling the development bias in the developing unit and the transfer bias in the transfer unit to make a stripe pattern appear on the recording medium (see, for example, Patent Document 1). ).

  In addition, the grid voltage and development bias voltage are set to predetermined values in advance, and the amount of toner adhering to the test pattern formed on the photosensitive drum is detected optically by a sensor by changing the grid voltage step by step by a predetermined amount. A configuration in which fog is detected by doing this is known (for example, see Patent Document 2).

JP 2005-62858 A JP-A-11-160930

  However, in the configuration described in Patent Document 1, it is necessary to combine the charging potential and the developing bias potential in a complicated manner in order to form a stripe pattern. Further, in order to detect fogging, it is necessary to transfer to a recording medium, and it is also necessary to separately provide a sensor for detecting the density. Moreover, this fog detection cannot be performed automatically.

  With the configuration described in Patent Document 2, fogging can be detected when the amount of toner attached is large, but detection is difficult when the amount is small.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus and a fog eliminating method capable of accurately detecting a fog with a simple and inexpensive configuration and eliminating the fog.

As a means for solving the above problems, the present invention provides:
The toner image formed on the intermediate transfer belt onto which the toner image developed on the photosensitive member is transferred by the primary transfer unit by the charging unit, the exposure unit, and the developing unit is transferred to a recording medium, and remains on the intermediate transfer belt . the toner, an image forming apparatus that is collected by detachably cleaning means to said intermediate transfer belt,
Toner adhesion amount detecting means for detecting the amount of toner adhesion on the intermediate transfer belt ;
A toner adhesion amount adjusting means for controlling a charging potential by the charging means, an exposure amount by the exposure means, and a developing bias voltage by the developing means to adjust the toner adhesion amount formed on the intermediate transfer belt ;
The cleaning means away from said intermediate transfer belt, the intermediate transfer belt is rotated a plurality of times, and adjusted by the toner adhesion amount adjusting means, the image forming conditions that the background portion is formed, deposited on the photosensitive member The toner image for fog detection is formed by overlappingly transferring the fog toner to the same portion of the intermediate transfer belt rotated a plurality of times by the primary transfer means, and the fog adhesion detection means by the toner adhesion amount detection means. Fog detection means for detecting fog based on the toner adhesion amount obtained by detecting the toner image of
If fog is detected by the fog detection means, fog elimination means for performing fog elimination processing;
It is equipped with.

  The fog detection means detects the toner adhesion amount obtained from the toner adhesion amount detection means and the toner image for fog detection in a state where the cleaning means is pressed against the intermediate transfer belt to collect toner. The obtained toner adhesion amount may be compared and it may be determined that fogging has occurred when the difference exceeds a set value.

  The fog eliminating unit may perform the fog eliminating process in a charging mode in which the toner of the developing unit is frictionally charged.

  With this configuration, it is possible to recover the toner charge amount and prevent the occurrence of fog by the simplest method of stirring the toner or sliding the brush or the like to frictionally charge the toner.

  In the charging mode, it is preferable that the longer the toner adhesion amount is set, the longer the friction charging time is based on the difference in the toner adhesion amount detected by the fog detecting means.

  With this configuration, it is possible to perform toner agitation processing in the minimum necessary time according to the difference in toner charge amount estimated from the toner adhesion amount, so the processing time is shortened and efficient fog elimination processing is executed. It becomes possible to do.

  The fog elimination unit may execute the fog elimination process in a toner consumption mode in which the cleaning unit is driven to consume toner of the developing unit.

  With this configuration, when the charge amount of the toner cannot be recovered only by stirring the developer, that is, when the toner itself is deteriorated, the toner of the developing unit is forcibly formed on the image carrier and collected by the cleaning unit. be able to. As a result, the toner deteriorated by the developing unit is collected by the cleaning unit, and the toner charge amount can be recovered by newly supplying the toner to the developing unit.

  The toner consumption mode is preferably set so that the greater the toner adhesion amount, the greater the toner consumption amount, based on the difference in toner adhesion amount detected by the fog detection means.

  With this configuration, it is possible to minimize the amount of toner to be replaced based on the amount of defective toner estimated from the toner adhesion amount.

The developing means includes
Supplied with a two-component developer comprising toner and carrier,
A toner concentration detection sensor for detecting the toner concentration;
After the fog elimination process is executed in the toner consumption mode, if the fog detection unit does not detect the fog, the developing unit is replenished based on the toner density detected by the toner density detection sensor at that time. It is preferable to further include toner supply control means for adjusting the toner amount.

  With this configuration, new toner is supplied to the developing unit depending on the toner consumption mode, and the carrier-to-toner mixing ratio (toner concentration) in the developer in the developing unit is corrected to an appropriate value that prevents fogging. Then, the subsequent image forming process can be performed.

  The fog eliminating unit may execute the fog eliminating process in an exchange mode instructing replacement of the developing unit.

  The fog elimination means consumes the toner of the developing means by driving the cleaning means when the fog detecting means detects the fog again after the toner agitation mode in which the developing means agitates the toner. It is preferable to execute the fog elimination process according to the toner consumption mode to be performed.

  With this configuration, since the toner is consumed only when the fog is not eliminated even when the toner is stirred, the toner is not wasted.

  The fog eliminating means executes fog elimination processing in an exchange mode for instructing replacement of the developing means when fog is detected again by the fog detecting means after the toner stirring mode and the toner consumption mode. It is preferable to do this.

  With this configuration, the developing means is replaced only when the toner is stirred and the fog is not eliminated even when the toner is consumed, so that the developing means can be used for a long time.

Further, the present invention provides a means for solving the above-described problems,
How to eliminate fogging
The cleaning unit is separated from the intermediate transfer belt , and the intermediate transfer belt is rotated a plurality of times. By the toner adhesion amount adjusting unit, the charging potential by the charging unit, the exposure amount by the exposure unit, and the developing unit that develops toner on the photosensitive member The fog toner adhered on the photosensitive member is rotated a plurality of times under the image forming conditions in which a background portion is formed by adjusting the toner adhesion amount formed on the intermediate transfer belt by controlling the developing bias voltage. Toner obtained by forming a toner image for fog detection by overlapping and transferring by the primary transfer means at the same location on the intermediate transfer belt , and detecting the toner image for fog detection by the toner adhesion amount detection means A fog detection step for detecting fog based on the amount of adhesion;
If fog is detected in the fog detection step, a fog elimination step for performing fog elimination processing;
Is performed by a method including

  The fog detection step detects fog by transferring the toner image developed on the photoconductor over the same portion of the intermediate transfer belt as the image carrier under the image forming conditions in which the background portion is formed. A fog image may be detected on the basis of the toner adhesion amount obtained by detecting the fog detection toner image formed on the intermediate transfer belt by the toner adhesion amount detection means. .
  The fog detection step detects the toner adhesion amount obtained from the toner adhesion amount detection means and the toner image for fog detection in a state where the cleaning means is pressed against the intermediate transfer belt to collect toner. It is preferable to compare the obtained toner adhesion amount and determine that fogging has occurred when the difference exceeds a set value.

  In the charging mode, it is more preferable to set the friction charging time longer as the toner adhesion amount is larger, based on the difference in the toner adhesion amount detected in the fog detection step.

  The fog elimination step preferably includes a toner consumption mode for consuming toner.

  More preferably, the toner consumption mode is set such that the greater the toner adhesion amount, the greater the toner consumption amount, based on the difference in toner adhesion amount detected in the fog detection step.

In the developing means, a two-component developer composed of toner and carrier is supplied,
After performing the fog elimination process in the toner consumption mode, if no fog is detected again in the fog detection step, the toner for adjusting the amount of toner to be replenished based on the toner density in the developing unit at that time Preferably it further includes a supply control step.

  The fog elimination step may include an exchange mode for instructing exchange of the developing means.

  In the fog elimination step, after the toner agitation mode in which toner is agitated by the developing means, when the fog is detected again by the fog detecting step, the cleaning means is driven to consume the toner of the developing means. It is preferable to execute the fog elimination process according to the toner consumption mode.

  In the fog elimination step, after the toner agitation mode and the toner consumption mode, the fog elimination process is executed in the exchange mode instructing the replacement of the developing means when the fog detection step is detected again by the fog detection step. It is preferable to do this.

  According to the present invention, after the toner image is forcibly formed on the image carrier, it is detected whether or not the image carrier is fogged. Therefore, the presence or absence of fog can be automatically detected. it can. If it is determined that fogging has occurred, the fog elimination process can be automatically executed, so that the conventional manual operation can be eliminated and the fog can be efficiently eliminated. In addition, with the elimination of fog, it is possible to realize a good use state over a long period of time while suppressing the cost without consuming paper as a recording medium and damaging the apparatus as in the past. .

  Embodiments according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a tandem color image forming apparatus to which an electrophotographic technique is applied according to this embodiment. The image forming apparatus generally includes an image forming unit 1, a transfer unit 2, an exposure unit 3, a cleaning unit 4, a paper feeding unit 5, and a fog detecting unit 6 (see FIG. 2).

  The image forming unit 1 includes a charging charger 9 as a charging unit, a developing roller 10 as a developing unit, a toner density detection sensor 11, and the like around a photosensitive drum 8 as an image carrier in a casing 7. Further, the image forming unit 1 is arranged at four locations along the intermediate transfer belt 13 of the transfer unit 2 and forms a color image on the surface of the intermediate transfer belt 13 by forming yellow, magenta, cyan, and black images, respectively. Form.

  The surface of the photosensitive drum 8 is charged uniformly by applying a charging potential by the charging charger 9 (the potential of the non-image portion at this time is V0 and the potential of the image portion is Vi). An electrostatic latent image is formed by exposure with the irradiated laser beam (the electric potential of the image background portion, which is the exposure portion at this time, is set to V1). The electrostatic latent image is visualized as a toner image when the toner in the casing 7 is negatively charged via the developing roller 10 and supplied. This toner image is transferred to the surface of the intermediate transfer belt 13 by a positive voltage (developing bias potential Vdc) applied to the back side of the intermediate transfer belt 13 by the primary transfer roller 14. The toner concentration detection sensor 11 detects the ratio (M / N: toner concentration) of the toner amount (N) to the carrier amount (M) in the developer contained in the casing 7.

  By the way, as shown in FIG. 3, the developing bias potential Vdc includes the potential Vi of the image portion (portion where the toner image is formed) and the image background portion (white portion where the toner image is not formed by exposure). Due to the relationship with the potential V1, the carrier does not adhere to the photosensitive drum 8, and the value is such that an appropriate toner adhesion amount can be obtained. That is, if the fog margin potential Vm (= | V1 | − | Vdc |) is increased, the fog amount decreases, but the carrier adhesion amount on the photosensitive drum 8 increases, and a desired toner adhesion amount cannot be obtained. . On the other hand, if the margin potential Vm is reduced, the fogging amount increases. For this reason, the fog margin potential Vm is determined to be the most appropriate value for satisfying the conflicting conditions of the two.

  Note that the negatively charged toner has an amount such that the total charge amount is a value corresponding to the difference between the developing bias potential Vdc and the potential Vi at the image portion (ΔV = | Vdc | − | Vi |). It adheres to the drum 8. The toner in the casing 7 can be appropriately supplied from a toner cartridge (not shown). Further, the toner remaining on the surface of the photosensitive drum 8 even after the primary transfer is collected by a cleaning device (toner removal filter) (not shown) provided in the casing 7.

  The transfer unit 2 is configured such that an intermediate transfer belt 13 is bridged between a pair of rollers 12 and the intermediate transfer belt 13 is circulated in a direction of an arrow by a driving unit (not shown). A primary transfer unit and a secondary transfer unit Is provided. The primary transfer unit includes a primary transfer roller 14 that faces the photosensitive drum 8 of each image forming unit 1 with the intermediate transfer belt 13 held therebetween. The primary transfer roller 14 applies a positive voltage to the back surface of the intermediate transfer belt 13. The secondary transfer unit includes a secondary transfer roller 15 facing one of the rollers, and transfers the toner image transferred to the intermediate transfer belt 13 to a recording medium 17 (for example, paper).

  The exposure unit 3 irradiates the photosensitive drum 8 with laser light to form an electrostatic latent image corresponding to image data read by a scanner (not shown).

  The cleaning unit 4 can contact and separate from the intermediate transfer belt 13, and can collect toner remaining on the surface of the intermediate transfer belt 13 by approaching the cleaning unit 4.

  The paper feeding unit 5 sequentially transports the recording medium 17 accommodated in the cassette 16 to the secondary transfer section via a plurality of transport rollers 18, transfers the toner image, and the toner image transferred by the fixing unit 19. Is fixed, and then is carried out to the discharge tray 20.

  As shown in FIG. 2, the fog detection unit 6 includes a control unit 21, a toner adhesion amount detection sensor 22, a temperature / humidity detection sensor 23, a display unit 24, and the like. The control unit 21 determines whether or not fogging has occurred based on the amount of toner attached to the intermediate transfer belt 13 detected by the toner adhesion amount detection sensor 22, and determines that fogging has occurred. As will be described later, a fog elimination process for controlling the driving of each unit is executed. As the toner adhesion amount detection sensor 22, an optical sensor having a light emitting element and a light receiving element can be used. FIG. 4 is a graph showing the relationship between the toner adhesion amount on the intermediate transfer belt 13 and the output of the result detected by the toner adhesion amount detection sensor 22. According to the toner adhesion amount detection sensor 22, the amount of reflected light decreases and the output decreases as the toner adhesion amount increases. Incidentally, the toner adhesion amount detection sensor 22 may be provided at only one location, but it is preferable to provide a plurality of locations in the width direction of the intermediate transfer belt 13. By providing a plurality of locations, detection accuracy can be increased. That is, the fog determination process described later is executed for all the detection values of the toner adhesion amount detection sensors 22. Based on the detected value, if any one of the conditions for fogging is satisfied, it is determined that the intermediate transfer belt 13 is fogged. As a result, even if the fog is generated in the width direction of the intermediate transfer belt 13, it can be detected. A liquid crystal display panel or the like can be used for the display unit 24, and the state of occurrence of fogging, the current processing content, and the like can be displayed. The temperature / humidity detection sensor 23 is provided at an appropriate position in the image forming apparatus, and detects the temperature and humidity of the internal space.

  Next, fog elimination processing of the image forming apparatus having the above-described configuration will be described with reference to the flowcharts of FIGS. 5 to 7 and the time chart of FIG.

  In the fog elimination process, it is first determined whether or not there is a fog detection input (step S1). The fog detection input is based on the operation of a button provided on the image forming apparatus, an external operation via a network protocol, a change (or change) in the environment setting of the image forming apparatus, the arrival of a specified number of prints, etc. A signal can be used.

  If it is determined that there is a fog detection input, the intermediate transfer belt 13 is cleaned (step S2), and a reference value Sbs for detecting the toner adhesion amount is acquired (step S3). In the cleaning process, while the intermediate transfer belt 13 is circulated and moved, the cleaning unit 4 is brought close to the intermediate transfer belt 13 to collect residual toner. In this case, the primary transfer roller 14 and the secondary transfer roller 15 are separated from the intermediate transfer belt 13. The reason why the cleaning process is executed before the acquisition of the reference value Sbs is to detect the amount of reflected light on the surface (base surface) of the intermediate transfer belt 13 before the toner is adhered by the toner adhesion amount detection sensor 22. It is. However, a preset value corresponding to the reflected light amount may be used as the reference value Sbs.

  If the reference value Sbs is acquired, the cleaning unit 4 is separated from the intermediate transfer belt 13, the primary transfer roller 14 to be fogged is pressed against the intermediate transfer belt 13, and toner transfer is started (step S4). In this case, the intermediate transfer belt 13 is kept circulating, and the development bias potential and the charging potential use the same values as those used for image formation. In the exposure unit 3, the gradation data is set to 0 gradation, and the intermediate transfer belt 13 is irradiated with laser light so that the background portion (white background portion) of the image is formed. The transfer of toner to the intermediate transfer belt 13 is performed until the intermediate transfer belt 13 is rotated N times, that is, transferred N times to the same position on the surface of the intermediate transfer belt 13. This makes it possible to detect “fogging” that is difficult to detect in a small amount at a time.

  Here, the rotation speed N of the intermediate transfer belt 13 is sufficiently detected by the toner adhesion amount detection sensor 22 to determine that the toner is adhered under conditions where fog is formed. Value. That is, the value detected by the toner adhesion amount detection sensor 22 varies from the reference value even if the surface of the intermediate transfer belt 13 is fouled or flawed. A value that can be distinguished from the detected value when fogging occurs is used. Here, the rotation speed N is 10 times. This is because even if fogging occurs once, the detection value of the toner adhesion amount detection sensor 22 is small, and it cannot be determined whether it is based on the variation factor or due to fogging. This is because the detected value is set to a value of 4 V or more that sufficiently exceeds 4.5 V at which it is determined that no fogging has occurred.

  When toner is transferred in this way, a detection signal from the toner adhesion amount detection sensor 22 is read (step S5), and the read value is set as a fog detection value Sn. Here, it is determined whether or not the difference (determination value ΔS) between the reference value Sbs set in step S3 and the fogging detection value Sn exceeds the specified value ε (Sbs−Sn> ε) (step S6: fogging). Detection means). Here, as the specified value ε, if the fog detection value Sn is smaller than the reference value Sbs and the difference between the two is smaller than this value, a value that does not cause a problem even if it is determined that “no fogging” is used. . Specifically, the prescribed value ε can be determined based on experimental results. For example, if the detected value in a state where fog is not generated is 4.5V, it may be 0.5V.

  If the determination value ΔS does not exceed the specified value ε (step S6: NO), it is determined that no fog has occurred, the fog elimination process is terminated, and printing is permitted. On the other hand, if the specified value is exceeded (step S6: YES), it is determined that fogging has occurred, and toner agitation processing is executed (step S7).

  In the toner agitation processing, it is determined to which range the determination value ΔS belongs based on Table 1 (step S21), and the agitation time is determined according to each determined range. Here, the toner agitation time is set to increase stepwise as the determination value increases. That is, if the determination value ΔS is ε <ΔS ≦ a, 60 seconds (s) (step S22), a <ΔS ≦ b is 120 seconds (s) (step S23), and b <ΔS ≦ c is 180 seconds (s (Step S24). In other words, the larger the determination value and the lower the charge amount of the toner, the longer the stirring time is set so that the charge amount can be recovered to a desired value. Then, toner stirring, that is, rotation of the developing roller 10 is started in the determined stirring time (step S25).

例えば、ε：０．４ ａ：０．７５ ｂ：１．０ ｃ：１．２５

For example, ε: 0.4 a: 0.75 b: 1.0 c: 1.25

  When the toner agitation processing is completed, the detection signal (detection value Sn) from the toner adhesion amount detection sensor 22 is read again (step S8), and the difference (determination value ΔS) from the reference value Sbs exceeds the specified value ε. It is determined whether or not there is (step S9). If not, it is determined that the fog is not generated as described above, and the fog elimination process is terminated. If exceeded, toner consumption processing is executed (step S10).

  In the toner consumption process, similarly to the toner stirring process, the toner consumption amount is changed according to the range to which the determination value ΔS belongs. That is, based on Table 2, it is determined to which range the determination value ΔS belongs (step S31), and the toner consumption amount is determined according to each determined range. Here, the toner consumption is set to increase stepwise as the determination value ΔS increases. That is, when the determination value ΔS is ε <ΔS ≦ a, it is 10% (weight% with respect to the whole developer) (step S32), a <ΔS ≦ b is 20% (step S33), and 30% when b <ΔS ≦ c. (Step S34). In other words, as the determination value ΔS is larger and the toner withstand voltage decreases, the toner consumption increases, and the amount of newly supplied toner is increased so that the withstand voltage can be recovered to a desired value. Yes. At this time, the primary transfer roller 14 is pressed against the intermediate transfer belt 13 and the bias potential is applied until the toner consumption reaches the determined value. Further, the secondary transfer roller 15 is separated from the intermediate transfer belt 13 and the cleaning unit 4 is brought into pressure contact so that the toner can be collected.

例えば、ε：０．４ ａ：０．７５ ｂ：１．０ ｃ：１．２５

For example, ε: 0.4 a: 0.75 b: 1.0 c: 1.25

  When the toner consumption process ends, the detection signal (detection value Sn) from the toner adhesion amount detection sensor 22 is read again (step S11), and it is determined whether or not the determination value ΔS exceeds the specified value ε (step S11). S12). If not, it is determined that the fog is not generated as described above, and the fog elimination process is terminated. If exceeded, it is determined that the charge amount of the toner cannot be recovered by the process such as the toner stirring process or the toner consumption process, and the replacement of the image forming unit 1 is instructed (step S13). That is, the display unit 24 displays that the image forming unit 1 should be replaced (for example, “Please replace the image forming unit”).

  As a result of executing the toner agitation process and the toner consumption process in step S7 and step S10, if it is determined that “no fogging”, the toner density adjustment process in the casing 7 of the image forming unit 1 is executed. In the toner density adjustment process, a detection signal from the toner density detection sensor 11 in a state where “no fogging” is determined is read. The read value is set as a reference value. Then, if the toner concentration in the casing 7 is reduced by performing the image forming process, the toner is appropriately replenished from the toner cartridge into the casing 7 so that the standard value is maintained. As a result, the toner density can be maintained in a state determined as “no fogging” under new conditions, and a good image forming process can be performed.

  In the above-described embodiment, the image forming apparatus using the two-component developer has been described. However, the same processing can be executed even with an image forming apparatus using the one-component developer. It is. Further, as the developing method, various methods such as a dry electrophotographic method and a liquid developing method can be adopted. In addition to the intermediate transfer belt 13, an image carrier using a photosensitive drum 8 can be employed.

  In the above-described embodiment, the toner adhesion amount after the fog forming process is performed N times is detected by the toner adhesion amount detection sensor 22. You may make it detect. In this case, when the determination value calculated based on the detected toner adhesion amount exceeds the reference value, it may be determined that “fogging is present”, and the fog removal processing may be executed. However, if fog does not occur even after the fog forming process is performed N times, it is determined that the state is appropriate, and the image forming process is continued as usual.

  In the embodiment, the toner agitation process is executed first when the fog is detected. However, the toner consumption process may be executed, or only the toner consumption process may be executed. Also good. Further, in the toner agitation processing, agitation is performed by rotating the developing roller 10 in the casing 7 of the image forming unit 1. If the toner can be frictionally charged, a blade is slidably contacted with the toner, etc. Other methods can also be used.

1 is a schematic explanatory diagram of an image forming apparatus according to an exemplary embodiment. FIG. 2 is a block diagram of the image forming apparatus in FIG. 1. FIG. 6 is a diagram illustrating a relationship between a surface state of an intermediate transfer belt and a surface potential of a photosensitive drum. 6 is a graph showing a relationship between a toner adhesion amount on the surface of an intermediate transfer belt and an output from a toner adhesion amount detection sensor. It is a flowchart which shows a fog elimination process. 6 is a flowchart showing toner agitation processing in FIG. 5. 6 is a flowchart illustrating toner consumption processing of FIG. 5. 6 is a chart showing the relationship between the number of rotations when the intermediate transfer belt is circulated and the output from the toner adhesion amount detection sensor, and the operating state of each member around the intermediate transfer belt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming unit 2 ... Transfer unit 3 ... Exposure unit 4 ... Cleaning unit 5 ... Paper feed unit 6 ... Fog detection unit 7 ... Casing 8 ... Photoconductor drum 9 ... Charger charger 10 ... Developing roller 11 ... Toner density detection sensor 12 ... Roller 13 ... Intermediate transfer belt 14 ... Primary transfer roller 15 ... Secondary transfer roller 16 ... Cassette 17 ... Recording medium 18 ... Conveying roller 19 ... Fixing unit 20 ... Discharge tray 21 ... Control unit 22 ... Toner adhesion amount detection sensor 23 ... Temperature / humidity detection sensor 24 ... Display section

Claims (20)

The toner image formed on the intermediate transfer belt onto which the toner image developed on the photosensitive member is transferred by the primary transfer unit by the charging unit, the exposure unit, and the developing unit is transferred to a recording medium, and remains on the intermediate transfer belt . the toner, an image forming apparatus that is collected by detachably cleaning means to said intermediate transfer belt,
Toner adhesion amount detecting means for detecting the amount of toner adhesion on the intermediate transfer belt ;
A toner adhesion amount adjusting means for controlling a charging potential by the charging means, an exposure amount by the exposure means, and a developing bias voltage by the developing means to adjust the toner adhesion amount formed on the intermediate transfer belt ;
The cleaning means away from said intermediate transfer belt, the intermediate transfer belt is rotated a plurality of times, and adjusted by the toner adhesion amount adjusting means, the image forming conditions that the background portion is formed, deposited on the photosensitive member The toner image for fog detection is formed by overlappingly transferring the fog toner to the same portion of the intermediate transfer belt rotated a plurality of times by the primary transfer means, and the fog adhesion detection means by the toner adhesion amount detection means. Fog detection means for detecting fog based on the toner adhesion amount obtained by detecting the toner image of
If fog is detected by the fog detection means, fog elimination means for performing fog elimination processing;
An image forming apparatus comprising: The fog detection means detects the toner adhesion amount obtained from the toner adhesion amount detection means and the toner image for fog detection in a state where the cleaning means is pressed against the intermediate transfer belt to collect toner. 2. The image forming apparatus according to claim 1 , wherein the obtained toner adhesion amount is compared, and it is determined that fogging has occurred when the difference exceeds a set value. The head eliminating means is an image forming apparatus according to claim 1 or 2, characterized in that executing the head resolving process by the charging mode for triboelectric charging of the toner of the developing unit. The charging mode, on the basis of the toner adhesion amount of the difference detected by the head detecting means, the more the toner adhesion amount, according to claim 3, characterized in that setting time longer for triboelectric charging Image forming apparatus. 3. The image forming apparatus according to claim 1, wherein the fog eliminating unit executes the fog eliminating process in a toner consumption mode in which the toner of the developing unit is consumed by driving the cleaning unit. . The toner consumption mode, based on the amount of toner adhesion difference detected by the head detecting means, the more the toner adhesion amount, claim, characterized in that set so that the toner consumption increases 5 The image forming apparatus described in 1. The developing means includes
Supplied with a two-component developer comprising toner and carrier,
A toner concentration detection sensor for detecting the toner concentration;
After the fog elimination process is executed in the toner consumption mode, if the fog detection unit does not detect the fog, the developing unit is replenished based on the toner density detected by the toner density detection sensor at that time. the image forming apparatus according to claim 5 or 6, further comprising a toner supply control means for adjusting the amount of toner. The head eliminating means is an image forming apparatus according to claim 1 or 2, characterized in that executing the head resolving process by exchange mode instructing replacement of the developing unit. The fog elimination means consumes the toner of the developing means by driving the cleaning means when the fog detecting means detects the fog again after the toner agitation mode in which the developing means agitates the toner. the image forming apparatus according to claim 1 or 2, characterized in that to perform the fog resolving process by a toner consumption mode to. The fog eliminating means executes fog elimination processing in an exchange mode for instructing replacement of the developing means when fog is detected again by the fog detecting means after the toner stirring mode and the toner consumption mode. The image forming apparatus according to claim 9 . The cleaning unit is separated from the intermediate transfer belt , and the intermediate transfer belt is rotated a plurality of times. By the toner adhesion amount adjusting unit, the charging potential by the charging unit, the exposure amount by the exposure unit, and the developing unit that develops toner on the photosensitive member The fog toner adhered on the photosensitive member is rotated a plurality of times under the image forming conditions in which a background portion is formed by adjusting the toner adhesion amount formed on the intermediate transfer belt by controlling the developing bias voltage. Toner obtained by forming a toner image for fog detection by overlapping and transferring by the primary transfer means at the same location on the intermediate transfer belt , and detecting the toner image for fog detection by the toner adhesion amount detection means A fog detection step for detecting fog based on the amount of adhesion;
If fog is detected in the fog detection step, a fog elimination step for performing fog elimination processing;
A method for eliminating fogging, comprising: The fog detection step detects the toner adhesion amount obtained from the toner adhesion amount detection means and the toner image for fog detection in a state where the cleaning means is pressed against the intermediate transfer belt to collect toner. The fog elimination method according to claim 11 , wherein the obtained toner adhesion amount is compared, and it is determined that fogging has occurred when the difference exceeds a set value. 13. The fog elimination method according to claim 11 or 12 , wherein the fog elimination step includes a charging mode in which toner in the developing unit is frictionally charged. 14. The charging mode according to claim 13 , wherein the charging time is set longer as the toner adhesion amount is larger, based on a difference in toner adhesion amount detected in the fog detection step. Cover removal method. 13. The fog elimination method according to claim 11 or 12 , wherein the fog elimination step includes a toner consumption mode in which toner in the developing means is consumed by driving the cleaning means. The toner consumption mode, on the basis of the toner adhesion amount of the difference detected by the head detecting step, the more toner adhesion amount, claim and sets so that the toner consumption increases 15 The method for eliminating fogging described in 1. In the developing means, a two-component developer composed of toner and carrier is supplied,
After performing the fog elimination process in the toner consumption mode, if no fog is detected again in the fog detection step, the toner for adjusting the amount of toner to be replenished based on the toner density in the developing unit at that time The fog elimination method according to claim 15 or 16 , further comprising a supply control step. The fog elimination method according to claim 11 or 12 , wherein the fog elimination step includes an exchange mode for instructing exchange of the developing means. In the fog elimination step, after the toner agitation mode in which toner is agitated by the developing means, when the fog is detected again by the fog detecting step, the cleaning means is driven to consume the toner of the developing means. The fog elimination method according to claim 11 or 12 , wherein the fog elimination process is executed in a toner consumption mode. In the fog elimination step, after the toner agitation mode and the toner consumption mode, the fog elimination process is executed in the exchange mode instructing the replacement of the developing means when the fog detection step is detected again by the fog detection step. The fog eliminating method according to claim 19 , wherein:

Images