JP4978643B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multi-function machine combining two or more of these.

  There are various types of image forming apparatuses such as a copying machine, a printer, a facsimile machine, and a combination machine combining two or more of these. Among them, an electrostatic latent image is formed on an electrostatic latent image carrier. There is an image forming apparatus capable of forming a toner image by forming and developing the electrostatic latent image with a developing device.

  Developers used in this type of image forming apparatus are roughly classified into a one-component developer using a so-called one-component developer mainly composed of toner and a so-called two-component developer mainly composed of toner and carrier. There is a component developer.

  In general, the one-component developing device can charge the toner by allowing the toner to pass through a regulating portion formed by the toner carrier and a regulating plate pressed against the toner carrier, and can charge the toner. Therefore, it is advantageous in terms of simplification, size reduction, and cost reduction of the developing device.

Since the two-component developing device charges the toner by frictional charging by mixing with the carrier, the stress in charging the toner is small, and the toner is less likely to deteriorate compared to the one-component developing method, which is advantageous for toner deterioration. It is.
Furthermore, since the carrier, which is a charge imparting member to the toner, has a large surface area, it is easy to withstand contamination by toner and external additives.
These are advantageous for extending the life of the developing unit.

  In such a two-component developing type developing device, it is necessary to monitor the toner density of the developer in the developing device and replenish the consumed toner.

So,
(1) The toner concentration in the developing device is detected by a magnetic toner concentration sensor that detects the toner concentration in the developer by detecting the magnetic permeability of the developer, or by an optical toner concentration sensor, and insufficient toner. Toner replenishment control for replenishing toner (see JP-A-5-313495, JP-A-6-3959),
(2) A so-called don't count that calculates the amount of toner required for toner image formation from the number of image forming dots that can be grasped from image information supplied from a computer, etc. Toner replenishment control of the type (see Japanese Patent Laid-Open No. 6-11965) has been proposed.

  Japanese Patent Application Laid-Open No. 7-325438 focuses on the fact that the image density is substantially proportional to the toner density in the developer, and a developing bias voltage changing unit that changes the developing bias voltage in accordance with a user image density changing command, and an image An image forming apparatus including an image density target value changing unit that changes a target image density according to a density change command and gives a command to the toner density changing unit is proposed.

JP-A-5-313495 JP-A-6-3959 JP-A-6-11965 JP-A-7-325438

However, in the method of controlling the toner density in the developer using the toner density sensor, if the toner density sensor fails, it becomes difficult to control the toner density, and a good image cannot be formed.
Further, since the developer state and the toner density sensor characteristics change due to environmental changes and as image formation is repeated, the output value of the sensor is also affected and changes.

  In the method of controlling the toner concentration in the developer using the dot count method, the actual toner concentration is not measured, but the toner consumption is estimated. Therefore, a deviation from the actual consumption occurs due to changes in the surrounding environment. In addition, toner replenishment control and toner density control may become inaccurate. In particular, the error increases and the toner density is likely to deviate significantly from the reference density.

In the case of the image forming apparatus described in Japanese Patent Laid-Open No. 7-325438, since the density of the actually output image is determined by the overall development, transfer, and fixing process, other factors may be used even if the toner density is the target value. In many cases, the image density may not be as expected.
Even if the image density becomes the target value by setting the toner density to a reference value or higher, other problems such as fogging and toner scattering will occur at a high toner density.
Therefore, it is not preferable to correct the toner density based only on the image density, so that the toner density falls within a certain range (so that both high toner density and low toner density are not preferred, so that they fall within a certain range). It can be said that adjustment is desirable.

  As described above, in the above prior art, when the toner density once deviates from a predetermined reference value due to changes in the surrounding environment, it is difficult to return to the correct toner density, and the image forming operation is temporarily stopped. I have to.

  Even if the target image density can be changed indirectly by the user's command, the toner density may be changed indirectly, and control may be performed outside the reference value, causing troubles such as image defects and internal contamination. Is expensive.

  Accordingly, the present invention can form an electrostatic latent image on an electrostatic latent image carrier and develop the electrostatic latent image with a developing device to form a toner image. At least one of the developing devices includes a toner and a carrier. An image forming apparatus that is a two-component developer that develops an electrostatic latent image using a two-component developer mainly composed of a toner, wherein at least one of the two-component developers is a toner concentration of the developer inside the developer Can be readjusted to the correct toner density even when the toner has deviated greatly from the correct density, and the image forming apparatus as a whole can suppress the occurrence of troubles such as image defects and contamination within the apparatus. It is an issue to provide.

In order to solve the above problems, the present invention
An electrostatic latent image can be formed on the electrostatic latent image carrier, and the electrostatic latent image can be developed with a developing device to form a toner image. At least one developing device is mainly composed of toner and carrier 2 A two-component developer that develops an electrostatic latent image using a component developer, wherein at least one two-component developer;
A toner concentration adjustment unit for adjusting the toner concentration inside the developer,
A color information input operation unit for inputting color information representing a color based on the color difference between the toner of the internal developer and the carrier to the toner density adjustment unit ;
And a toner supply section for supplying toner to the developing device on the basis of the instructions of the toner density adjustment unit,
The toner concentration adjusting section, based on the toner density corresponding to the color in color and each stage of the plurality of stages associated in advance, the toner corresponding to the color information input from the color information input operation unit When the density information is color information indicating a toner density that is lower than a predetermined reference toner density, the toner replenishing unit is caused to replenish the toner so that the toner density of the developer approaches the reference toner density, and the input is performed. When the toner density corresponding to the color information to be displayed is color information indicating an excessive toner density than the reference toner density, the excess toner is developed from the developing device onto the electrostatic image carrier corresponding thereto. An image forming apparatus for discharging is provided.

According to the image forming apparatus of the present invention, for at least one two-component developer, the color tone based on the color difference between the toner and the carrier of the developer inside is grasped, and the color information is input to the color information input operation unit. To the toner density adjustment unit, and the toner density adjustment unit performs the color information input operation based on a plurality of color shades associated in advance and a toner density corresponding to the color tone at each step. When the toner density corresponding to the color information input from the section is color information indicating a toner density that is insufficient below a predetermined reference toner density, the toner density of the developer is supplied to the toner replenishing section. to perform the toner supply to be directed to, when the toner density corresponding to the color information being the input is color information indicating the excess of toner concentration than the reference toner density, then developing device The toner excess to the corresponding the latent electrostatic image bearing member is developed discharged. Thus, based on the color information based on the color difference between the developer toner and the carrier , the developer toner density can be set to a correct toner density based on the reference toner density.

Since this toner density control is based on the color information of the developer in the developing device, even if the toner concentration of the developer inside the developing device is greatly deviated from the correct concentration, it is restored to the correct toner concentration. As a whole, the image forming apparatus can suppress the occurrence of troubles such as image defects and contamination inside the apparatus. Even in the case where the toner density greatly deviates from the reference toner density by using the developing device for a long period of time, it can be readjusted to the correct toner concentration, so that the life of the developing device can be extended accordingly.
Furthermore, in a toner density sensorless image forming apparatus with a large error, when the toner density is shifted, it can be adjusted again to the correct toner density.

  Here, the grasping and input of “developer color information” is not limited to this, but as a representative example, a person grasps the color of the developer by visual observation, and the grasped color is obtained in advance. Visual comparison with a plurality of prepared color samples, and a case where the grasped color information is input to the toner density adjustment unit with the selection switch on the color information input operation unit indicated by the closest color sample. Can do. That is, a plurality of switches (in other words, keys or buttons) corresponding to the color are provided in the color information input operation unit.

In any case, the image forming apparatus according to the present invention may include a toner concentration sensor that detects a developer toner concentration of a developing device capable of adjusting a toner concentration by the toner concentration adjusting unit. In that case, the toner density can be normally adjusted based on the toner density detected by the toner density sensor and a preset reference toner density.
When the toner density is adjusted based on the color information input, the toner density sensor output after the toner density adjustment based on the color information by the toner density adjustment unit includes a reference output changing unit that changes the toner density sensor reference output. May be. As a result, the toner density detected by the toner density sensor has a small error from the actual toner density.

  Further, the developing device capable of adjusting the toner concentration by the toner concentration adjusting unit may have a stirring member for stirring the internal developer. In this case, the toner density adjusting unit prior to receiving the input, the stirring is performed so that more accurate color information can be grasped when the color information of the internal developer is input from the color information input operation unit. The developer may be stirred by a member.

An image forming apparatus according to the present invention is
An image density detecting unit for detecting the density of a toner image developed and formed by a developing device capable of adjusting the toner density by the toner density adjusting unit;
An image density abnormality detecting unit capable of detecting a density abnormality of the toner image from a developing bias applied to the developing unit at the time of developing an electrostatic latent image by the developing unit and image density information detected by the image density detecting unit; ,
A color information input instructing unit for instructing to input developer color information when the image density abnormality detecting unit detects an image density abnormality.

According to this image forming apparatus, an abnormality in the toner image density formed by the developing device capable of adjusting the toner density by the toner density adjusting unit is detected at the time of developing the electrostatic latent image by the developing device in the image density abnormality detecting unit. It can be detected from the developing bias applied to the developing device and the density information of the toner image detected by the image density detecting unit.
For detecting an abnormal image density from the developing bias and the detected image density, for example, if the image density detected by the image density detecting unit is too low or too high than the target, the target image density is reached. The development bias can be increased or decreased in the direction of the image, and upper and lower limits are set for the increase and decrease, and if the target image density cannot be obtained even if the development bias is changed to the upper limit or the lower limit, an image density abnormality is determined. You should be able to judge.

  In order to eliminate the image density abnormality, the image density abnormality detection unit can instruct the color information input instruction unit to input the developer color information when detecting the image density abnormality. The user can quickly input the color information of the developer to the toner density adjusting unit by seeing this instruction, and thereby the toner density can be quickly returned to the correct toner density.

Further, since the toner concentration in the developer may vary depending on the ambient temperature and / or humidity around the developing device, the ambient temperature and / or the developing device capable of adjusting the toner concentration by the toner concentration adjusting unit. the environment detection unit for detecting the humidity is provided, even if the indicated developer color information input to the temperature and (or) color information input instruction section when the humidity fluctuates predetermined value or more is detected by the environment detecting unit Good.

  As described above, according to the present invention, an electrostatic latent image can be formed on an electrostatic latent image carrier, and the electrostatic latent image can be developed with a developing device to form a toner image. The image forming apparatus is a two-component developer that develops an electrostatic latent image by using a two-component developer mainly composed of toner and a carrier, and at least one two-component developer is provided inside the developer. Even if the developer toner concentration deviates significantly from the correct concentration, it can be readjusted to the correct toner concentration, and the entire image forming apparatus can suppress the occurrence of troubles such as image defects and internal contamination. It is possible to provide an image forming apparatus capable of

1 is a diagram schematically illustrating a configuration of an example of an image forming apparatus according to the present invention. FIG. 2 is a diagram showing an outline of a cross section of a developing device used in the image forming apparatus of FIG. 1 together with a photoreceptor. FIG. 2 is a block diagram illustrating an outline of a control circuit of the image forming apparatus in FIG. 1. 4 is a flowchart illustrating an outline of a toner density control operation of a control unit in the control circuit of FIG. 3. 6 is a diagram illustrating an example of a relationship between a toner concentration in a developer and a color of a developer. FIG. It is a figure which shows the example of transition of the toner density detected with a magnetic toner density sensor.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 schematically shows the configuration of an example PR of an image forming apparatus according to the present invention. The image forming apparatus PR is a tandem type full color printer.

  The printer PR has a driving roller 81 and an endless intermediate transfer belt 8 wound around a roller 82 facing the driving roller 81. The transfer belt 8 is rotated counterclockwise (arrow direction in the figure) CCW in the figure by a driving roller 81 driven by a belt driving unit (not shown).

  A cleaning device 83 for cleaning the secondary transfer residual toner and the like on the transfer belt 8 faces the roller 82, and a secondary transfer roller 9 faces the drive roller 81.

The secondary transfer roller 9 is pressed against a portion of the intermediate transfer belt 8 supported by the driving roller 81 by a pressing means (not shown), forms a nip portion with the intermediate transfer belt 8, and rotates the intermediate transfer belt 8. It can be rotated following the movement of the recording medium S fed to the nip portion or driven by a driving unit (not shown).
A secondary transfer bias can be applied to the secondary transfer roller 9 from a power supply (not shown).

  A fixing device FX is disposed above the secondary transfer roller 9, a timing roller pair TR is disposed below, and a recording medium storage unit 10 that stores a recording medium S such as recording paper further below. Is arranged.

The fixing device FX includes a fixing heating member heated by a heat source and a pressure member pressed against the fixing heating member. In this example, these members are all in the form of rollers.
The recording medium S accommodated in the recording medium accommodating unit 10 can be pulled out one by one by the medium supply roller 10r and supplied to the timing roller pair TR.

  Between the rollers 81 and 82 around which the intermediate transfer belt 8 is wound, the yellow image forming unit Y, the magenta image forming unit M, and the cyan image forming unit C are arranged along the transfer belt 8 from the roller 82 to the roller 81. And the black image forming portion K are arranged in this order.

  Each of the image forming units Y, M, C, and K includes a drum-type photoconductor 1 as an electrostatic latent image carrier, and a charger 2, an exposure device 3, a developer 4 and the like around the photoconductor. The cleaning devices 5 are arranged in this order.

  A primary transfer roller 6 is disposed opposite to the photoreceptor 1 of each image forming unit with a belt 8 therebetween. Each primary transfer roller 6 is pressed in the direction of the photosensitive member 1 by a pressing means (not shown) in this example, and can contact the belt 8 to be driven to rotate, and can bring the belt 8 into contact with the photosensitive member 1. In the color image forming mode, the primary transfer roller 6 can bring the belt 8 into contact with the photoreceptors 1 of the image forming units Y, M, C, and K. In the monochrome image forming mode, the image forming unit used for forming a monochrome image. The primary transfer roller corresponding to (image forming portion K in this example) can bring the belt 8 into contact with the photoreceptor 1 of the image forming portion.

  A primary transfer bias for primary transfer of the toner image formed on the photoreceptor 1 to the belt 8 can be applied to the primary transfer roller 6 from a power supply (not shown).

  The exposure device 3 can perform image exposure by dot (point) exposure on the photosensitive member 1 by blinking of a laser beam in accordance with image information provided from a personal computer (not shown), an image reading device, or the like.

  The photoreceptor 1 in each image forming unit is not limited to this, but is a negatively chargeable photoreceptor here, and can be driven to rotate clockwise in the figure by a photoreceptor drive motor (not shown).

  The charger 2 in each image forming unit is charged with a charging voltage from a power supply (not shown) at a predetermined timing, so that the surface of the photoreceptor 1 can be uniformly charged to a predetermined potential. The charger 2 is a non-contact type using corona discharge in this example, but may be a charging roller or the like.

  The developing device 4 in each image forming unit is a so-called two-component developing device. In this example, a so-called two-component developer mainly composed of a magnetic carrier and a nonmagnetic toner is used to form a static image formed on the photoreceptor 1. The electrostatic latent image can be reversely developed. The developing device 4 will be further described later with reference to FIG.

  As shown in FIG. 1, the image density detection sensor 72 faces the portion of the intermediate transfer belt 8 immediately after passing through the drive roller 81. Further, an in-machine environment sensor 73 for detecting the temperature and humidity in the printer PR (in-machine environment temperature and humidity) is disposed in the vicinity of the fixing device FX.

  The control part Cont in the control circuit of the printer PR schematically shown in the block diagram in FIG. 3 controls the operation of the printer PR. Each of the image forming units Y, M, C, and K, the recording medium transport mechanism, and the printer PR such as the fixing device 8 operate based on an instruction from the control unit Cont.

The image density information detected by the image density detection sensor 72 and the in-machine environment temperature and humidity detected by the in-machine environment sensor 73 are also input to the control unit Cont.
An operation panel PA is also connected to the control unit Cont (see FIG. 3), and an image forming mode, the number of images formed, and the like can be set on this panel. Those indicated by 101 and 102 on the operation panel PA will be described later.

According to this printer, an image can be formed using one or more of Y, M, C, and K image forming units.
Taking a case where a full color image is formed using all of the image forming portions Y, M, C, and K as an example, first, a yellow toner image is formed in the yellow image forming portion Y, and this is formed on the transfer belt 8 as a primary. Transcript.

  That is, in the yellow image forming portion Y, the photosensitive member 1 is rotated in the clockwise direction in the drawing, and the surface is uniformly charged to a predetermined potential by the charger 2, and the yellow region for the yellow image is transferred from the exposure device 3 to the charged area. Image exposure is performed, and a yellow electrostatic latent image is formed on the photoreceptor 1. This electrostatic latent image is developed by the developing device 4 having yellow toner to become a visible yellow toner image. The yellow toner image is primarily transferred onto the transfer belt 8 by the primary transfer roller 6. At this time, a primary transfer bias is applied to the primary transfer roller 6 from a power supply (not shown).

  Similarly, a magenta toner image is formed in the magenta image forming unit M and transferred to the transfer belt 8. A cyan toner image is formed in the cyan image forming unit C and transferred to the transfer belt 8. In the black image forming unit K. A black toner image is formed and transferred to the transfer belt 8.

Yellow, magenta, cyan, and black toner images are formed at the timing when these toner images are transferred onto the intermediate transfer belt 8.
Thus, the multiple toner image formed on the transfer belt 8 moves toward the secondary transfer roller 9 by the rotation of the transfer belt 8.

  On the other hand, the recording medium S is pulled out from the recording medium container 10 by the medium supply roller 10r, supplied to the timing roller pair TR, and is on standby.

  Thus, the recording medium S waiting at the timing roller pair TR is supplied to the nip portion between the transfer belt 8 and the secondary transfer roller 9 in accordance with the multiple toner image sent by the intermediate transfer belt 8. . This multiple toner image is secondarily transferred onto the recording medium S by a secondary transfer roller 9 to which a secondary transfer bias is applied from a power supply (not shown).

  Thereafter, the recording medium S is passed through the fixing device FX, where the multiple toner images are fixed on the recording medium S under heat and pressure. The recording medium S is continuously discharged to the discharge tray DT by the discharge roller pair DR.

  In the primary transfer of the toner image to the belt 8, transfer residual toner or the like remaining on the photoreceptor 1 is cleaned by the cleaning device 5, and secondary transfer residual toner or the like remaining on the belt 8 by the secondary transfer is cleaned by the cleaning device 83. It is cleaned with. Each of these cleaned and removed toners is sent to a waste container by a conveying means (not shown).

  The image density detection sensor 72 detects the image density from the image density adjustment patch image formed on the intermediate transfer belt 8 at a predetermined timing other than the time of normal image formation, and sends the information to the control unit Cont. input. Based on the image density information, the control unit Cont adjusts the charging voltage applied to the charger 1 of the image forming unit that formed the patch image, the developing bias applied to the developing sleeve 41, and the like, so that the image density is determined in advance. The image density is adjusted so as to be within the range (target image density).

  In this example, if the image density detected by the sensor 72 is too low or too high than the target, the control unit Cont increases or decreases the development bias toward the target image density at least, and sets the development bias in advance. If the target image density is not obtained even if the upper limit or the lower limit is changed, the image density abnormality detection unit determines that the image density is abnormal.

Although the image is formed as described above, the developing device 4 will be further described. The developing device 4 is as shown in FIG. FIG. 2 shows an outline of a sectional structure of the developing device 4.
The developing device 4 includes a developer carrier 41 in the form of a sleeve and a magnet body 42 in the form of a roller, which is fixedly disposed inside the developer carrier.

Developing device 4 includes further a first stirring and conveying member 43 and the second stirring and conveying member 44 for supplying the door toner and carrier in the developer uniformly stirring to the developing sleeve 41. Here, the first member 43 is a screw conveying member in which a screw blade (spiral blade) 432 is provided around the rotating shaft 431, and the second member 44 is also a screw carrier in which the screw blade (spiral blade) 442 is provided around the rotating shaft 441. It is a member.

The developing sleeve 41 and the agitating / conveying members 43 and 44 are all housed in the developing device housing 40 and are rotatably supported by the housing. A part of the developing sleeve 41 protrudes to the outside of the housing 40 so as to face the photoreceptor 1 when the developing device 4 is installed in the printer PR. The agitating and conveying members 43 and 44 are accommodated in the developing device housing 40.

The housing 40 of the developing device 4 in each of the yellow, cyan, and magenta image forming portions is at least partly so that the color of the developer in the housing can be visually recognized without removing the developing device 4 from the image forming apparatus PR. Is formed transparent.
One or more of these developing units may be removed from the image forming apparatus PR so that the color of the internal developer can be visually recognized.

  The first agitating / conveying member 43 faces the developing sleeve 41 and is disposed in parallel with the developing sleeve. The second agitating / conveying member 44 is parallel to the first member 43 with the partition wall 45 therebetween and below the member 43. Has been placed. The partition wall 45 has developer distribution openings (not shown) on the back side and the near side, respectively.

  The developer in the developing device housing 40 is conveyed while being agitated from the back side to the near side by the rotation of the agitating and conveying member 44, and is transferred from the near side opening to the agitating and conveying member 43 side. It is conveyed while being agitated, and moves from the rear opening to the member 44 side again. In this way, the developer is stirred and circulated, and is supplied to the developing sleeve 41 while being conveyed by the member 43.

  The developing sleeve 41 holds a developer brush (a magnetic brush made of a developer) on the peripheral surface by the action of an internal magnet body 42, and the developer amount is regulated by the developer regulating member 400 in the middle of the developing sleeve 41. It can be transported to a development zone facing the body 1 and used for development of an electrostatic latent image.

  Each developing device 4 is provided with a magnetic toner concentration sensor 71 for detecting the toner concentration of the developer in the developing device housing 40 (ratio of toner to carrier). The toner density information detected by the sensor 71 is input to the control unit Cont.

As shown in FIG. 1, the yellow toner can be supplied to the developing device 4 of the yellow image forming unit Y from the yellow toner supply unit YC by the toner supply conveyor Ty.
The developing device 4 of the magenta image forming unit M can be supplied with magenta toner from the magenta toner supply unit MC by the toner supply conveyor Tm.
The cyan toner can be supplied to the developing unit 4 of the cyan image forming unit C from the cyan toner supply unit CC by the toner supply conveyor Tc.
The black toner can be supplied to the developing device 4 of the black image forming unit K from the black toner supply unit KC by the toner supply conveyor Tk.
These toner replenishing conveyors can replenish toner to the corresponding developing devices based on instructions from the control unit Cont (see FIG. 3).

The control unit Cont normally compares the toner density input from the toner density sensor 71 attached to the developing device 4 of the yellow image forming section with a predetermined reference yellow toner density, and the toner is insufficient. If so, the yellow toner supply unit YC is instructed to supply yellow toner, and the toner concentration in the developer is adjusted toward the reference yellow toner concentration. If the toner is excessive, the photosensitive member 1 is developed and discharged by an electric field or left as it is.
The control unit Cont performs the same toner density adjustment on the other developing devices 4 based on the toner density information from the toner density sensor 71.

  A portion denoted by reference numeral 101 in the operation panel PA is a color information input operation unit for inputting information on the color of the developer in the developer that can be visually recognized for each developer 4. A portion denoted by reference numeral 102 is a tint information input instruction unit that displays a tint information input instruction or the like from the control unit Cont.

  In the printer PR, the toner density of the developer in the developing device 4 can be adjusted using the magnetic toner density sensor 71 attached to each developing device as described above. For each of the developing units 4 of parts Y, M, and C, the toner density can be adjusted based on the color of the internal developer.

The reason why the toner density can be adjusted based on the color of the developer only for the developing devices 4 of the image forming units Y, M, and C is as follows.
In general, since the carrier is black and has little color difference from the black toner, it is difficult to visually distinguish the toner concentration of the black developer even if the toner concentration changes. FIG. 5 shows the relationship between the toner density of the yellow developer and the color difference. As can be seen from FIG. 5, the color tone of the developer including yellow, magenta, and cyan toners is sensitive to the toner concentration unlike the black developer, so that the toner concentration can be distinguished visually.

  The toner density adjustment operation by the developer color information input by the controller Cont will be described with reference to FIG. The toner density adjustment is performed by the toner density adjustment unit in the control unit Cont as follows.

  As described above, the toner density of the developer in each developer is usually monitored by the toner density sensor 71. If the toner density is high, the toner is developed and discharged to the corresponding photoreceptor 1 by an electric field. The toner is consumed or left as it is, and if the toner density is low, the toner is supplied from the corresponding toner supply unit and adjusted to the reference toner density range.

However, when the toner density sensor 71 is broken, the surrounding environment changes, or the toner density sensor output abnormality occurs due to aging, the toner density deviates from the reference value. If the toner density deviates from the reference value, the image density is also affected. Therefore, the image density is temporarily made normal by adjusting the developing bias and the charger voltage based on the image density information detected by the image density detection sensor 72. Can be returned.

  However, when the toner density is greatly deviated and the normal image density is not obtained even when the voltage is adjusted, the image density abnormality detection unit in the control unit Cont detects the image density information detected by the image density detection sensor 72 and the image density information. When the image density abnormality is detected from the development bias at the time, and the image density abnormality is detected, the control unit Cont notifies the color information input instruction unit 102 on the operation panel PA of the image forming unit in which the image density abnormality has occurred. A display prompting input of color information of the developer in the developing device 4 is displayed (step S1).

  The timing when the control unit Cont prompts the user to input the color information of the developer in the developing device 4 on the color information input instruction unit 102 is not only when the image density abnormality occurs as described above, When the temperature or humidity of the ink plate changes more than a predetermined value, the case where the number of printed sheets exceeds a predetermined number is also included.

  The user of the image forming apparatus PR responds with a switch displayed on the instruction unit 102 as to whether or not to follow a display prompting toner density adjustment (color information input) (Yes). If “No”, the image forming operation is continued while recognizing the abnormality, but if “Yes”, the agitating members 43 and 44 in the developing device 4 are rotated for a predetermined period of time in the developing device. The color of the developer is made uniform (step S2). Subsequently, the color information input permission is displayed on the instruction unit 102 (step S3).

  Here, the user visually grasps the color of the developer in the developing device 4 to be adjusted for toner density, and from among a plurality of color selection switches displayed on the color information input operation unit 101 of the operation panel PA, The switch showing the color closest to the visually recognized color is selected, and the color information is input by operating the switch (step S4). At this time, the user compares the visually recognized developer color with a plurality of types of color samples prepared in advance, selects the switch indicated by the color sample closest to the visually recognized color, and inputs the color information. do it.

  The color sample may be a developer contained in a container made of the same transparent material as the transparent portion of the developing device, or may be a color sample printed on paper or the like.

The toner density adjustment unit of the control unit Cont converts the input color to toner density (step S5), calculates the adjusted toner amount from the obtained toner density (step S6), and when the toner density is low, The toner replenishing unit is instructed to replenish toner (step S71). When the toner density is high, unnecessary toner is developed and conveyed to the photosensitive member 1, and the cooling device from the photosensitive member 1 or the intermediate transfer belt 8 is used. It collects (step S72).
The conversion of the input color to the toner density in step 5 is not limited to this, but in this example, as shown in FIG. 5, there is a correlation between the color of the developer and the toner density in the developer. For this reason, this relationship is grasped in advance for each color toner by an experiment or the like, and a table showing a plurality of levels of color tone and toner density corresponding to each level color tone is created for each color toner. The toner density corresponding to the input color is obtained from the table.

  Next, the reference output changing unit in the control unit Cont uses the toner density sensor 71 to detect the reference toner density (toner density sensor reference output value) used when the toner density sensor 71 adjusts the toner density. The sensor output is changed and set again (step S8). Thereafter, the instruction unit 102 displays the end of toner density adjustment (step S9).

  In this way, even when the toner density deviates from the reference value due to a failure of the toner density sensor, an output abnormality or the like, it can be readjusted toward the reference toner density by inputting the color information. In addition, the setting of the toner density sensor 71 can be changed with the toner density after readjustment being used as a reference output at the reference toner density.

FIG. 6 shows the transition of the detected toner density by the sensor when continuous image formation is performed using the toner density sensor in which output abnormality has occurred in the image forming unit C.
An example is shown in which the toner density can be readjusted based on the color of the developer when a sensor output abnormality occurs in the toner density detection by the magnetic toner density sensor 71 and the toner density greatly deviates from the reference toner density. Yes.
Similarly, in the image forming units M and Y, the toner density can be readjusted based on the color of the developer.

The image forming apparatus described above is a tandem type color image forming apparatus. However, the color image forming apparatus to which the present invention can be applied is not limited to this. For example, a plurality of developing devices are moved to a developing position. The present invention is also applicable to a so-called cycle type color image forming apparatus. Furthermore, the present invention can also be applied to a monochrome image forming apparatus.
Further, the present invention can be applied not only to a printer but also to a copying machine and a facsimile machine, and can also be applied to a multifunction machine in which two or more of a printer, a copying machine, a facsimile machine, and the like are combined.

  The present invention is an image forming apparatus using a two-component developing device, and at least one two-component developing device is correct even when the toner concentration of the developer inside the developing device is greatly deviated from the correct concentration. The present invention can be used to provide an image forming apparatus that can be readjusted to the toner density and can suppress the occurrence of troubles such as image defects and contamination within the apparatus as a whole.

Example of PR image forming device (printer)
Y Yellow image forming unit M Magenta image forming unit C Cyan image forming unit K Black image forming unit 1 Photoconductor 2 Charging device 3 Exposure device 4 Developing device 41 Developing sleeve 42 Magnet body 43 First stirring and conveying member 44 Second stirring and conveying member 45 Partition 40 Developer housing 5 Cleaning device 6 Primary transfer roller 71 Toner density sensor 72 Image density detection sensor 73 In-machine environment sensor 8 Intermediate transfer belt 81 Driving roller 82 Opposing roller 83 Cleaning device 9 Secondary transfer roller FX Fixing device TR Timing Roller pair 10 Recording medium storage unit S Recording medium Cont control unit PA Operation panel 101 Color information input operation unit 102 Color information input instruction unit YC Yellow toner supply unit MC Magenta toner supply unit CC Cyan toner supply unit KC Black toner supply unit Ty, Tm, Tc, Tk Toner supply Conveyor

Claims (6)

An electrostatic latent image can be formed on the electrostatic latent image carrier, and the electrostatic latent image can be developed with a developing device to form a toner image. At least one developing device is mainly composed of toner and carrier 2 A two-component developer that develops an electrostatic latent image using a component developer, wherein at least one two-component developer;
A toner concentration adjustment unit for adjusting the toner concentration inside the developer,
A color information input operation unit for inputting color information representing a color based on the color difference between the toner of the internal developer and the carrier to the toner density adjustment unit ;
And a toner supply section for supplying toner to the developing device on the basis of the instructions of the toner density adjustment unit,
The toner concentration adjusting section, based on the toner density corresponding to the color in color and each stage of the plurality of stages associated in advance, the toner corresponding to the color information input from the color information input operation unit When the density information is color information indicating a toner density that is lower than a predetermined reference toner density, the toner replenishing unit is caused to replenish the toner so that the toner density of the developer approaches the reference toner density, and the input is performed. When the toner density corresponding to the color information to be displayed is color information indicating an excessive toner density than the reference toner density, the excess toner is developed from the developing device onto the electrostatic image carrier corresponding thereto. An image forming apparatus for discharging. A toner density sensor for detecting a developer toner density of a developing device capable of adjusting a toner density by the toner density adjusting unit;
The toner density adjustment unit toner density adjusted to the toner concentration sensor output further comprises claims 1 image forming apparatus according to the reference output changing section for changing the toner concentration sensor reference output based on the color information input by. The developing device capable of adjusting the toner density by the toner density adjusting unit has an agitating member for agitating the internal developer, and the toner density adjusting unit receives the internal developer from the color information input operation unit. 3. The image forming apparatus according to claim 1, wherein, when inputting color information, the developer is stirred by the stirring member prior to receiving the input. 4. An image density detecting unit for detecting the density of a toner image developed and formed by a developing device capable of adjusting the toner density by the toner density adjusting unit;
An image density abnormality detecting unit capable of detecting a density abnormality of the toner image from a developing bias applied to the developing unit and an image density information detected by the image density detecting unit when developing the electrostatic latent image by the developing unit; ,
4. The image forming apparatus according to claim 1, further comprising: a color information input instructing unit that instructs to input developer color information when the image density abnormality detecting unit detects an image density abnormality. An environment detection unit for detecting the ambient temperature and / or humidity of the developing device capable of adjusting the toner concentration by the toner concentration adjustment unit;
From claim 1, further comprising a color information inputting instruction unit temperature and (or) the humidity is detected by the environment detection unit instructs the developer color information input to vary a predetermined value or more in any of 4 The image forming apparatus described. The at least one two-component developing device is formed at least partially transparent so that a color based on a color difference between the toner of the internal developer and the carrier can be visually observed. Image forming apparatus.

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