JP2008020818A - Image forming apparatus and image stabilization method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which a toner concentration of a 1-dot isolated image can be stabilized without exerting a burden to a user. <P>SOLUTION: The toner concentration of the 1-dot isolated image is predicted based on the results of the toner concentration detection of a reference toner image of one or more pixels that can be detected by a toner concentration detecting means, and the image forming process conditions in the image forming means are changed in such a manner that the 1-dot isolated image attains the prescribed toner concentration based on the predicted toner concentration of the 1-dot isolated image. As a result, the toner concentration of the 1-dot isolated image can be made into the prescribed concentration from the toner concentration of the reference toner image of the one or more pixels detected by the toner concentration detecting means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image stabilization method.

  Conventionally, in an image forming apparatus such as a copying machine, a facsimile machine, or a printer, a one-component developer composed only of toner or a two-component developer composed of toner and carrier is carried on a latent image carrier such as a photoreceptor. An image forming means for developing a latent image is known. When a plurality of factors such as a change in the toner charge amount depending on the environment used by the user, deterioration of the photosensitive member, filming on the surface of the developing roller, and the like change in a complicated manner, the toner density changes accordingly. As a result, for example, in a color image, the tone changes, or the gradation reproduction characteristic γ changes, so that the image in the high gradation part is crushed or, conversely, the low gradation image does not appear. Problems such as skipping occur.

  In order to solve the above problems, fluctuations due to endurance and environmental changes are detected, and if environmental changes exceed the specified values, the image forming process conditions such as charging bias, development bias, and exposure amount are optimized again. Controls are being made. Specifically, a solid test patch is printed, the toner density is read by an optical sensor serving as a toner density detecting means, and the image forming process conditions are changed so that the solid test patch has a target density. However, this alone stabilizes the solid density, but does not stabilize the gradation reproduction characteristic γ. For this reason, the gradation reproduction characteristic γ is stabilized by forming an intermediate gradation toner image, measuring its toner density, and stabilizing the formed intermediate gradation toner image density (for example, patents). Reference 1).

  However, this can stabilize the halftone density, but cannot stabilize the low gradation density. In particular, when image processing using the error diffusion method is performed, the stability of the lowest-tone one-dot isolated image (one-pixel toner image) density is important in creating an image. This is because by stabilizing the 1-dot isolated image density, it is possible to suppress missing dots and provide a smooth and image-free image.

JP 2002-211029 A

  However, even if a 1-dot isolated image (1-pixel toner image) is created and measured with an optical sensor, the sensor is greatly affected by the gloss noise of the substrate on which the 1-dot isolated image is created, and cannot be measured accurately. Moreover, the conventional sensor for measuring the solid density has insufficient sensitivity, and it has been difficult to directly measure the isolated one-dot image density with the sensor. As a result, there has been a problem that a one-dot isolated image cannot be detected by an optical sensor and the density of the one-dot isolated image cannot be stabilized based on the detection result.

  For this reason, conventionally, a gradation pattern including an isolated one-dot image is printed on a sheet of paper, and the user has set the printed sheet on the scanner, read it by the scanner, and includes an isolated one-dot image. The toner density of the gradation pattern is detected. Then, based on the toner density of the gradation pattern detected by the scanner, the density of one isolated dot is stabilized by correcting the image forming process conditions. On models without a scanner, the image forming process conditions are changed to print a plurality of gradation patterns, and the gradation reproduction characteristic γ that is optimal for the user is obtained from the paper on which the plurality of gradation patterns are printed. The tone pattern is determined, and the image forming process conditions are corrected by a user operation to stabilize the density of one isolated dot. For this reason, a great burden is placed on the user in order to stabilize the density of one isolated dot.

  The present invention has been made in view of the above background, and an object thereof is to provide an image forming apparatus capable of stabilizing the toner density of an isolated one-dot image without imposing a burden on the user. is there.

In order to achieve the above object, a first aspect of the present invention is to form a toner image on the latent image carrier by developing the latent image carrier that carries the latent image and the latent image of the latent image carrier. And an image forming unit having a developing device, and the toner image formed on the latent image carrier is transferred to a recording material, or the toner image is transferred to the surface of the intermediate transfer member and then transferred onto the intermediate transfer member. In an image forming apparatus that forms an image on a recording material by transferring the toner image to a recording material, a toner density detecting means for detecting the toner density of the toner image, and one pixel that can be detected by the toner density detecting means The above reference toner image is formed, and based on the detection result when the toner density detecting unit detects the reference toner image of one pixel or more, the toner density of the toner image of one pixel is predicted, and the predicted one pixel Based on the toner density of the toner image Toner density of the toner image pixel is characterized in that a process condition changing means for executing a process of changing the image forming process conditions of said image forming means so as to have a predetermined toner density.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the storage unit stores the correlation between the toner density of the reference toner image and the toner density of the one-pixel toner image under the same image forming process conditions. And the process condition changing means includes a toner density when the toner density detecting means detects the reference toner image, a toner density of the reference toner image stored in the storage means, and a one-pixel toner. The toner image of one pixel is predicted from the correlation with the toner density of the image.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the image forming apparatus further includes an environment detecting unit that detects an environment in the apparatus, and the process condition changing unit executes the previous image forming process condition changing process. In some cases, when the detection result detected by the environment detection means has fluctuated more than a certain value, an image forming process condition changing process is executed.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the process condition changing unit executes an image forming process condition changing process based on a use state of the latent image carrier. It is characterized by this.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the process condition changing unit executes an image forming process condition changing process based on a use state of the developing device. It is a feature.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the storage means includes a toner density of a reference toner image and 1 under the same image forming process condition according to a use environment of the apparatus. A plurality of correlations with the toner density of the toner image of the pixel are stored, and the process condition changing means uses the reference toner image used when predicting the toner density of the toner image of one pixel according to the use environment of the apparatus. The correlation between the toner density of the toner and the toner density of the toner image of one pixel is changed.
According to a seventh aspect of the present invention, there is provided an image having a latent image carrier that carries a latent image, and a developing device that develops the latent image of the latent image carrier and forms a toner image on the latent image carrier. And a toner image formed on the latent image carrier is transferred to the recording material, or after the toner image is transferred to the surface of the intermediate transfer member, the toner image on the intermediate transfer member is used as the recording material. In an image forming apparatus for transferring or forming an image on a recording material, a toner density detecting means for detecting a toner density of the toner image, and a reference toner image having one or more pixels detectable by the toner density detecting means The image forming process of the image forming unit is configured so that the toner density of one pixel becomes a predetermined toner density based on the detection result when the toner density detecting unit detects the reference toner image of one or more pixels. Execute processing to change conditions Process condition changing means, and the process condition changing means includes the use status of the apparatus, the toner density of the reference toner image when the toner density of the toner image of one pixel becomes a predetermined toner density, and the use of the apparatus. From the correlation with the situation, the toner density of the reference toner image when the toner density of the toner image of one pixel becomes a predetermined toner density is specified, and the toner is set so that the reference toner image has the specified toner density The image forming process condition is changed based on a detection result when the density detecting unit detects the reference toner image.
According to an eighth aspect of the present invention, in the image forming apparatus of the seventh aspect, the usage status of the apparatus is a usage environment of the apparatus.
According to a ninth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the use state of the apparatus is a use state of the latent image carrier.
According to a tenth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the usage status of the device is a usage status of the previous developing device.
According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects, a plurality of the image forming means are provided, and toner images carried on a latent image carrier of each image forming means are sequentially transferred to the intermediate transfer. A tandem color image forming apparatus that is intermediately transferred to a body, wherein the toner density detecting means detects a toner density of a toner image transferred onto the intermediate transfer body.
According to a twelfth aspect of the present invention, there is provided an image having a latent image carrier that carries a latent image, and a developing device that develops the latent image of the latent image carrier and forms a toner image on the latent image carrier. In a method for stabilizing an image in an image forming apparatus including a forming unit and a toner density detecting unit that detects a toner density of the toner image, a step of forming a reference image of one or more pixels that can be detected by the image density detecting unit And a step of predicting the image density of one pixel based on the detection result when the image density detecting means detects the reference image of one pixel or more, and one pixel based on the predicted image density of one pixel. And a step of changing an image forming process condition of the image forming means so that the image density of the image becomes a predetermined image density.
According to a thirteenth aspect of the present invention, there is provided an image having a latent image carrier that carries a latent image, and a developing device that develops the latent image of the latent image carrier and forms a toner image on the latent image carrier. In an image stabilizing method in an image forming apparatus comprising a forming unit and a toner density detecting unit for detecting a toner density of the toner image, the usage status of the apparatus and a toner density of a toner image of one pixel is a predetermined toner Based on the correlation between the toner density of one or more reference toner images that can be detected by the image density detection means and the usage status of the apparatus, the toner density of the toner image of one pixel becomes a predetermined toner density. A step of specifying the toner density of the reference toner image, a step of forming a reference toner image of one or more pixels that can be detected by the image density detecting means, and the image density detecting means And a step of changing an image forming process condition of the image forming unit so that the reference toner image has a toner density of the specified reference toner image based on a detection result at the time of notification. It is.

  According to the first to thirteenth aspects, the toner density of the toner image of one pixel is predicted based on the toner density detection result of the reference toner image of one pixel or more that can be detected by the toner density detecting unit, and the predicted 1 Since the image forming process conditions of the image forming unit are changed so that the toner image of one pixel has a predetermined toner density based on the toner density of the toner image of the pixel, the following effects can be obtained. In other words, the toner density detecting means can change the image forming process conditions of the image forming means so that the toner image of one pixel has a predetermined toner density. The dot density can be stabilized. As a result, the density of the isolated 1 dot can be stabilized without imposing a burden on the user.

A first embodiment in which the present invention is applied to a printer 100 that is an image forming apparatus will be described below.
First, the overall configuration and operation of the printer 100 according to the first embodiment will be described.
The printer 100 forms a tandem image forming unit by arranging four image forming units of yellow, cyan, magenta, and black diagonally. In the tandem image forming unit, toner image forming units 20Y, 20C, 20M, and 20K as individual toner image forming units are arranged in order from the upper left in the drawing. Here, the suffixes Y, C, M, and K of the respective symbols indicate members for yellow, magenta, cyan, and black, respectively. In the tandem image forming unit, the individual toner image forming units 20Y, 20C, 20M, and 20K are arranged around the drum-like photosensitive drums 21Y, 21C, 21M, and 21K as latent image carriers, M, C, K, developing devices 10Y, C, M, K, a photoreceptor cleaning device, and the like are provided.

  Further, an optical writing unit 9 as a latent image forming unit is provided below the tandem image forming unit. The optical writing unit 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and is configured to irradiate the surface of each photosensitive drum 21 with laser light based on image data. Yes.

  Further, an endless belt-like intermediate transfer belt 1 is provided as an intermediate transfer member along a tandem image forming portion arranged obliquely. The intermediate transfer belt 1 is wound around support rollers 1a, 1b, and 1c, and a drive motor (not shown) serving as a drive source is connected to a rotation shaft of the drive roller 1a among the support rollers. When this drive motor is driven, the intermediate transfer belt 1 rotates in the counterclockwise direction in the figure and the followable support rollers 1b and 1c rotate. Inside the intermediate transfer belt 1, primary transfer devices 11Y, 11C, 11M, and 11K for transferring the toner images formed on the photosensitive drums 21Y, 21C, 21M, and 21K onto the intermediate transfer belt 1 are provided.

  In addition, a reflective optical sensor 15 as a toner density detecting means is installed at a position facing the surface of the intermediate transfer belt. The optical sensor 15 detects the optical reflectivity of the toner image on the intermediate transfer belt, obtains the toner adhesion amount from the detection result, and changes the image forming process conditions such as charging bias, developing bias, and exposure amount.

  Further, a secondary transfer roller 5 as a secondary transfer device is provided downstream of the primary transfer devices 11Y, 11C, 11M, and 11K in the driving direction of the intermediate transfer belt 1. A support roller 1b is disposed on the opposite side of the secondary transfer roller 5 and the intermediate transfer belt 1, and functions as a pressing member. Further, a paper feed cassette 8, a paper feed roller 7, a registration roller 6 and the like are provided. Further, a fixing device 4 for fixing an image on the transfer paper P is disposed downstream of the secondary transfer roller 5 with respect to the traveling direction of the transfer paper P as a recording medium to which the toner image is transferred by the secondary transfer roller 5. A paper roller 3 is provided.

  Next, the operation of the printer 100 will be described. The photosensitive drums 21Y, 21C, 21M, and 21K are rotated by individual image forming units, and the photosensitive drums 21Y, 21C, 21M, and 21K are first rotated by the charging devices 17Y, 21C, 21M, and 21K. , C, M, K surfaces are uniformly charged. Next, the image data is irradiated with writing light by a laser from the optical writing unit 9 to form an electrostatic latent image on the photosensitive drums 21Y, 21C, 21M, 21B. Thereafter, toner is attached by the developing devices 10Y, 10C, 10M, and 10K, and the electrostatic latent images are visualized to form yellow, cyan, magenta, and black on the photoreceptors 21Y, 21C, 21M, and 21K, respectively. The monochrome image is formed. Further, the drive roller 1a is driven to rotate by a drive motor (not shown), the other driven rollers 1b and 1c and the secondary transfer roller 5 are driven to rotate, the intermediate transfer belt 1 is rotated and conveyed, and the visible image is primary. The images are sequentially transferred onto the intermediate transfer belt 1 by the transfer devices 11Y, C, M, and K. As a result, a composite color image is formed on the intermediate transfer belt 1. The surface of the photoconductive drums 21Y, 21C, 21M, and 21K after image transfer is cleaned by removing residual toner with a photoconductor cleaning device to prepare for image formation again.

  Further, in accordance with the timing of image formation, the leading edge of the transfer paper P is fed from the paper feed cassette 8 by the paper feed roller 7 and conveyed to the registration roller 6 and temporarily stops. Then, the sheet is conveyed between the secondary transfer roller 5 and the intermediate transfer belt 1 while taking the timing with the image forming operation. Here, the intermediate transfer belt 1 and the secondary transfer counter roller 5 form a so-called secondary transfer nip across the transfer paper P, and the secondary transfer roller 5 transfers the toner image on the intermediate transfer belt 10 to the transfer paper P. Secondary transfer on top.

  The recording medium S after the image transfer is sent to the fixing device 4, where the fixing device 4 applies heat and pressure to fix the transferred image, and is discharged outside the apparatus. On the other hand, the intermediate transfer belt 1 after the image transfer is removed by the intermediate transfer body cleaning device 12 to remove residual toner remaining on the intermediate transfer belt 1 after the image transfer, so that the tandem image forming unit prepares for another image formation.

  The toner image forming portions 20Y, 20C, 20M, and 20K for the respective colors described above are integrally formed and are detachable process cartridges that can be attached to and detached from the main body. These integral process cartridges can be pulled out to the front side of the printer main body along a guide rail (not shown) fixed to the printer 100 main body. Further, the toner image forming unit can be loaded at a predetermined position by pushing the process cartridge into the back side of the printer 100 main body.

  FIG. 2 is a diagram illustrating a schematic configuration of the developing device 10. The developing device 10 is disposed in contact with and opposite to the photosensitive drum 21, and a developing roller 107 that develops toner on the photosensitive drum, a supply roller 108 provided in contact with the developing roller 107, and a toner layer regulating member 110. And a toner storage chamber 101 for storing a one-component developer (toner) 300.

  The one-component developer (toner) 300 in the toner storage chamber 101 is moved to the toner supply chamber 103 by the toner conveying member 102. The toner 300 that has moved to the toner supply chamber 103 adheres to the surface of the supply roller 106 and is applied and supplied to the surface of the developing roller 107. The toner supplied to the developing roller 107 is made a certain amount of thin layer by the toner layer regulating member 110. The toner thinned by the toner layer regulating member 110 on the surface of the developing roller 107 is transported to a developing position facing the photosensitive drum 21 by the rotation of the developing roller 107, and the developing bias applied to the developing roller 107. In accordance with the latent image electric field formed by the electrostatic latent image on the photosensitive drum 21, it moves to the surface of the photosensitive drum 21 and is developed.

  The developing device 10 of the present embodiment uses a one-component developer, forms a toner layer on the developing roller 107, and conveys the toner layer on the developing roller 107 so as to be in contact with the photosensitive drum 1. Although the contact one-component development for developing the electrostatic latent image on the photosensitive drum 1 is performed, the present invention is not limited to this. The same applies to a non-contact one-component developer and a non-contact two-component developer.

Next, a process control mode for stabilizing an image, which is a feature point of the first embodiment, will be described.
FIG. 3 is a functional block diagram of a control unit that controls the image forming apparatus. The control unit 200 actually performs overall control of the entire copying machine, but in the drawing, only functions necessary for executing the process control mode are displayed.
As shown in the figure, the control unit 200 is a control unit that controls the entire copying machine, and includes a CPU and the like. Based on the toner density formed on the intermediate transfer belt detected by the optical sensor 15, the controller 200 develops the developing bias of the developing device, the exposure amount (laser power / exposure time) of the optical writing unit, and the charging of the charging device. It has a function as a process condition changing means for changing a bias or the like.
The storage unit 201 includes a look-up table that associates the toner density of a one-dot isolated image (one-pixel toner image) with the adjustment amount of the exposure amount (laser power), and a humidity sensor when process control is executed. The environmental state (temperature, humidity, etc.) detected by the environment detection unit 202 is stored.
Further, the control unit 200 counts the number of rotations of the photosensitive drum 21, the number of rotations of the developing roller 107, the number of formed images, and the like, and detects the usage state of the photosensitive drum 21 and the developing device 10. Then, when the number of rotations of the photosensitive drum 21, the number of rotations of the developing roller 107, the number of image formations, etc. has been a predetermined value or more after the previous execution of the process control mode, the process control mode is executed. ing. Further, the control unit 200 executes the process control mode based on the detection result of the environment detection unit 201 such as a temperature / humidity sensor. Specifically, when the process control is executed, the control unit 200 detects the environment with the environment detection unit 202 and stores the detection result in the storage unit 201. Then, the control unit 200 detects the environment by the environment detection unit at a predetermined timing, and executes the process control mode when the detection result has changed more than the specified value amount from the detection result stored in the storage unit 201. To do.

FIG. 4 is a control flow when the process control mode is executed.
As described above, the control unit 200 executes the process control mode when the usage state of the photosensitive drum 21 and the developing device and the environmental change become a predetermined value or more (S1).
When the process control mode is executed, the control unit 200 first adjusts the output value of the optical sensor 15 serving as the toner density detecting means (S2).

  Specifically, the optical sensor 15 receives an LED (not shown) that is a light emitting element that emits light toward the front surface of the intermediate transfer belt 1 and diffusely reflected light from the belt front surface, according to the amount of light received. And a diffuse reflection type light receiving element (not shown) that outputs a voltage. As shown in FIG. 5, the light receiving element increases the toner adhesion amount when the toner adhesion amount per unit area of the front surface of the intermediate transfer belt 1 is taken on the horizontal axis and the output voltage value is taken on the vertical axis. A linear characteristic that decreases the output voltage value according to In the calibration of the optical sensor 15, the output voltage value Vref of the light receiving element when the light reflected from the intermediate transfer belt 1 is detected with the intermediate transfer belt 1 regarded as a reference plate and the light emission by the LED is turned on is a reference. The light emission amount of the LED is adjusted so that the (base) voltage Vba is obtained. The reference voltage Vba is stored in advance in the storage unit 202, and the amount of light emitted from the LED is adjusted by adjusting the current If flowing through the LED.

  Once the output value of the optical sensor 15 has been adjusted, the control unit 200 next executes process control for stabilizing the solid image (S3). The process control for stabilizing the solid image is to fix the exposure amount (laser power) and charging bias, change the development bias voltage output in multiple stages, and create a plurality of toner pattern images with different toner adhesion amounts. Image. Then, the developing bias voltage is adjusted so that the toner adhesion amount detected by the optical sensor 15 becomes a target value.

  After stabilization of the solid image, the control unit 200 next executes process control for low gradation and adjusts an exposure amount (laser power) as an image forming process condition (S4).

The low gradation process control mode of the present embodiment performs a process for stabilizing the density of the one-dot isolated image. By stabilizing the toner density of the 1-dot isolated image, it is possible to suppress dot dropout and provide a smooth and image-free image. However, the 1-dot isolated image cannot be detected by the optical sensor 15.
FIG. 6 is a diagram illustrating a change in the output voltage value Vref of the light receiving element of the optical sensor 15 when the reflected light from the intermediate transfer belt 1 is detected. As shown in the figure, in the output voltage Vref, stationary noise is generated due to dust and dirt adhering to the intermediate transfer belt 1. For this reason, the detection result (| Vref−Vba |) of the 1-dot isolated image (pattern 1) shown in FIG. 7A enters the steady noise range (Vba noise width), and the 1-dot isolated image The toner density cannot be detected.

Therefore, the low gradation process control mode of the present embodiment is a reference toner image of one pixel or more in which the detection result (| Vref−Vba |) of the optical sensor is a detection result equal to or greater than the Vba noise width. A reference toner image of 2by2 image (pattern 2) shown in (b) is formed, and the optical sensor 15 detects the toner density (toner adhesion amount per unit area: g / m ² ) of the reference toner image. Based on the detection result, the image forming process conditions are adjusted so as to stabilize the toner density of the one-dot isolated image. The reference toner image used for predicting a one-dot isolated image is not limited to a 2-by2 image, but is preferably a low-tone toner image.
Below, it demonstrates concretely based on Example 1,2.

[Example 1]
Hereinafter, the low gradation process control mode according to the first embodiment will be described.
In the low gradation process control mode of Example 1, the correlation between a 2-by2 reference toner image (pattern 2) and a 1-dot isolated toner image (pattern 1) as shown in FIG. Based on the correlation shown in FIG. 8 and the toner density of the 2by2 image (pattern 2) detected by the optical sensor 15, the toner density of the 1-dot isolated image (pattern 1) is predicted, and the 1-dot isolated image It stabilizes the toner density.

FIG. 9 is a control flow of the low gradation process control mode according to the first embodiment.
As shown in the figure, the control unit 200 creates a reference toner image of 2by2 image (pattern 2) shown in FIG. 7B, which is a reference toner image of one pixel or more (S11). Next, the optical sensor 15 detects the toner density (toner adhesion amount per unit area: g / m ² ) of the reference toner image transferred to the intermediate transfer belt 1 (S12). Next, the control unit 200 predicts the toner density of the one-dot isolated image (pattern 1) based on the correlation shown in FIG. 8 and the toner density of the 2by2 image (pattern 2) detected by the optical sensor 15. (S13). The control unit 200 determines the exposure amount (laser power) of the toner density of the pattern 1 (one dot isolated) predicted in this way and the toner density of the pattern 1 previously obtained by experiments stored in the storage unit 201. From the lookup table associated with the adjustment amount, the adjustment amount of the exposure amount is found (S14). The control unit 200 adjusts the exposure amount (laser power) as the image forming process condition by the found adjustment amount (S15). Although the exposure amount is mentioned as the image forming process condition, the initial charging potential on the surface of the photosensitive member may be changed by controlling the charging device so that the toner density of the one-dot isolated image becomes a predetermined toner density. Good.

  Thereby, the 1-dot isolated image density can be adjusted to a predetermined value, and the 1-dot isolated image density can be stabilized. As a result, missing dots can be suppressed, and a smooth and image-free image can be provided.

[Modification]
Next, a modification of the first embodiment will be described.
As shown in FIG. 10, the relationship between the toner density of pattern 1 (one dot isolated) and the toner density of pattern 2 (2by2) varies depending on the use environment conditions of the image forming apparatus. Condition 1 in FIG. 10 is a graph showing the toner density correlation between pattern 1 and pattern 2 in a high-temperature and high-humidity environment. It is a graph which shows correlation. Condition 3 is a graph showing the toner density correlation between pattern 1 and pattern 2 in a low-temperature and low-humidity environment.

FIG. 11 is a control flow of a low gradation process control mode according to a modification of the first embodiment.
In the low gradation process control mode of the modification of the first embodiment, the storage unit 201 stores the correlation between the pattern 1 and the pattern 2 in the condition 1 (high temperature and high humidity environment) and the pattern in the condition 2 (medium temperature and medium humidity environment). The toner density correlation between 1 and pattern 2 and the toner density correlation between pattern 1 and pattern 2 under condition 3 (low temperature and low humidity) are stored. As shown in the figure, when the toner density of the reference toner image is detected by the optical sensor 15 (S22), the control unit 200 detects the environment by the environment detection unit 202 (S23), and the use environment of the apparatus is a condition. It is determined which of the conditions 1 to 3 corresponds (S24). Next, the control unit 200 reads the toner density correlation between the pattern 1 and the pattern 2 corresponding to the determined condition from the storage unit 201 (S25), and changes the toner density correlation between the read pattern 1 and the pattern 2 to the toner density correlation. Based on this, the toner density of pattern 1 is predicted (S26).
Then, the same processing as described above is executed to adjust the exposure amount (laser power) as the image forming process condition (S27 to S28).
As a result, the density of the pattern 1 according to the environmental conditions can be predicted, and more accurate one-dot isolation can be predicted.

[Example 2]
Next, the process control mode of the second embodiment will be described.
As described above, the correlation between the toner density of pattern 1 (one-dot isolated image) and the toner density of pattern 2 (2-by2 image) varies depending on the usage status of the apparatus such as the environmental conditions of the apparatus. In the method shown in the modification of the first embodiment, it is necessary to store the correlation between the pattern 1 and the pattern 2 for each use state of the apparatus, and it is necessary to increase the storage capacity of the storage unit.

  Therefore, in the process control mode of the second embodiment, based on the correlation between the toner density of the 2-by2 image (pattern 2) when the toner density of 1-dot isolated (pattern 1) is a predetermined toner density and the usage state of the apparatus. Thus, the toner density of pattern 1 is set to a predetermined density. Since the toner density of pattern 1 is adjusted to a predetermined value, if the correlation between the toner density of pattern 2 when the toner density of pattern 1 is the predetermined toner density and the usage status of the apparatus is known, a one-dot isolated image Can be adjusted to a predetermined toner density.

FIG. 12 is a control flow when the process control mode is executed according to the second embodiment.
First, the control unit 200 detects the absolute humidity of the device, which is the usage status of the device, by the environment detection unit 202 (S31). Next, the control unit 200 detects the detected absolute humidity, the absolute humidity of the apparatus shown in FIG. 13 stored in the storage unit 201, and the toner density of the pattern 2 when the toner density of the pattern 1 is a predetermined toner density (pattern Based on the correlation of (2 set density), the set density of pattern 2 is specified (S32). Next, the control unit 200 adjusts the exposure amount so that the pattern 2 has the specified set density (S33), and forms an image (reference toner image) of the pattern 2 (S34). Then, the toner density of the formed pattern 2 (reference toner image) is detected (S35), and it is checked whether or not the detection result is a set toner density (S36). If the detection result is a set toner density (YES in S36), it can be predicted that the pattern 1 (one-dot isolated image) has a predetermined density, and the process ends.
On the other hand, when the set toner density is not reached (NO in S36), it is predicted that the pattern 1 (one-dot isolated image) does not have a predetermined density, and therefore the density of the pattern 2 becomes the set density. Thus, the exposure amount is adjusted (S37).

  As described above, by adjusting the density of the pattern 2 based on the correlation between the toner density of the pattern 2 and the absolute humidity when the pattern 1 has the predetermined density, the toner density of the pattern 1 is set to the predetermined density. Can do. Thereby, it is possible to predict a one-dot isolated image with higher accuracy. Further, since it is only necessary to store the correlation between the toner density of pattern 2 and the absolute humidity when pattern 1 shown in FIG. 13 has a predetermined density, each time the apparatus is used, as in the modification of the first embodiment. The capacity of the storage unit can be reduced as compared with the case where the toner density correlation between the pattern 1 and the pattern 2 is stored.

  In the above, the set density of the pattern 2 is adjusted based on the use environment (absolute humidity) of the apparatus as the use status of the apparatus. The correlation between 1 and pattern 2 changes. Therefore, based on FIG. 14 showing the correlation between the toner density of pattern 2 (2-by2 image) and the film thickness of the photoreceptor when the toner density of pattern 1 (one dot isolated) is a predetermined toner density, The pattern 1 may be adjusted to a predetermined density by adjusting the set density.

  Further, the toner in the developing device is stirred and deteriorated every time image formation is performed, and the correlation between the pattern 1 and the pattern 2 changes. Therefore, the setting of pattern 2 is based on FIG. 15 showing the correlation between the toner density of pattern 2 (2-by2 image) and the number of images formed when the toner density of pattern 1 (one-dot isolated image) is a predetermined toner density. The pattern 1 may be adjusted to a predetermined density by adjusting the density.

  As described above, according to the image forming apparatus of the present embodiment, one dot as the toner image of one pixel is detected from the toner density of the reference toner image detected by the optical sensor 15 and detected by the optical sensor as the toner density detection unit. The toner density of the isolated image can be set to a predetermined density. Therefore, the user is not burdened to stabilize the one-dot isolated image.

  Further, the correlation between the toner density of the reference toner image and the toner density of the 1-dot isolated image under the same image forming process condition is stored in the storage unit 201, and the toner density when the optical sensor detects the reference toner image is stored. A one-dot isolated image is predicted from the correlation between the toner density of the reference toner image and the toner density of the one-dot isolated image. As a result, a one-pixel toner image can be predicted from the toner density when the optical sensor detects the reference toner image.

  In addition, since the image formation process condition change is executed when the detection result detected by the environment detection means when the previous image formation process condition change process has been changed is more than a certain level, the image of the isolated 1 dot is changed due to the environmental change. Can be prevented from deviating from a predetermined toner concentration. Thereby, the image density of one isolated dot can be stabilized.

  Further, by changing the image forming process condition based on the usage state of the photosensitive member as the latent image carrier, it is possible to prevent the one-dot isolated image from deviating from a predetermined toner density due to the deterioration of the photosensitive member. be able to. Thereby, the 1-dot isolated image density can be stabilized.

  Further, by changing the image forming process condition based on the usage state of the developing device, it is possible to suppress the one-dot isolated image from deviating from a predetermined toner density due to toner deterioration in the developing device. it can. Thereby, the 1-dot isolated image density can be stabilized.

  Further, since the correlation between the toner density of the reference toner image and the 1-dot isolated image is changed according to the use environment of the apparatus, the toner density of the 1-dot isolated image can be correctly predicted from the toner density of the reference toner image. . Thus, even if the use environment of the apparatus fluctuates, the image forming process conditions can be adjusted from the predicted toner density of the one-dot isolated image so that the toner density of the one-dot isolated image becomes a predetermined density.

  Further, as shown in the second embodiment, 1 dot is determined based on the correlation between the usage status of the apparatus and the toner density of the reference toner image when the toner density of the 1-dot isolated image is a predetermined toner density and the usage status of the apparatus. The toner density of the reference toner image when the isolated image density becomes a predetermined toner density is specified. Then, the image forming process condition is changed so that the reference toner image has the specified toner density based on the detection result when the toner density detection unit detects the reference toner image. As described above, also in the second embodiment, the toner density of the one-dot isolated image can be set to a predetermined density from the toner density of the reference toner image of one pixel or more detected by the optical sensor 15 as the toner density detecting unit. Therefore, the user is not burdened to stabilize the one-dot isolated image.

  Further, since the correlation between the 1-dot isolated image and the reference toner image varies depending on the use environment of the apparatus, the set density of the reference toner image is adjusted by adjusting the set density of the reference toner image based on the use environment of the apparatus as the use state of the apparatus. The dot isolated image can be stabilized.

  Further, since the correlation between the one-dot isolated image and the reference toner image also changes depending on the usage state of the photoconductor, the set density of the reference toner image is adjusted based on the usage status of the photoconductor as the usage status of the apparatus. Thus, a 1-dot isolated image can be stabilized.

  Further, since the correlation between the 1-dot isolated image and the reference toner image also changes depending on the usage state of the developing device, the set density of the reference toner image is adjusted based on the usage state of the developing device as the usage state of the device. Thus, a 1-dot isolated image can be stabilized.

  Further, the optical sensor 15 serving as the toner density detecting means detects the toner density of the toner image transferred onto the intermediate transfer belt serving as the intermediate transfer member. Therefore, the single optical sensor 15 forms the toner image serving as each image forming means. The toner density of the reference toner image formed by the portions 20Y, 20C, 20M, and 20K can be detected. Therefore, the apparatus can be manufactured at a lower cost as compared with the toner image forming units 20Y, 20C, 20M, and 20K that detect the toner density of the reference toner on the photoreceptor.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. FIG. 2 is a schematic configuration diagram of a developing device. FIG. 3 is a functional block diagram of a control unit that controls the image forming apparatus. The control flow figure at the time of process control mode execution. The figure which shows the relationship between the output voltage value from an optical sensor, and the toner density of the reference | standard toner image which the optical sensor detected. FIG. 6 is a diagram illustrating a change in an output voltage value of an optical sensor when an intermediate transfer belt is detected. (A) is a figure which shows 1 dot isolated image (pattern 1). FIG. 5B is a diagram illustrating a 2by2 image (pattern 2). The figure which shows the correlation of the density | concentration of 1 dot isolated image (pattern 1 density | concentration) and the density of 2by2 image (pattern 2 density | concentration). FIG. 3 is a control flow diagram of a low gradation process control mode according to the first embodiment. The figure which shows the relationship between the toner density of 1 dot isolated image (pattern 1) and the toner density of 2by2 image (pattern 2) in each environment. FIG. 10 is a control flow diagram of a low gradation process control mode in a modification of the first embodiment. FIG. 10 is a control flowchart of a low gradation process control mode according to the second embodiment. The figure which shows the correlation of the toner density and absolute humidity of 2by2 image (pattern 2) when the toner density of 1 dot isolated image (pattern 1) is a predetermined toner density. FIG. 6 is a diagram showing a correlation between the toner density of a 2-by2 image (pattern 2) and the photosensitive member film thickness when the toner density of a one-dot isolated image (pattern 1) is a predetermined toner density. FIG. 6 is a diagram showing a correlation between a 2-by2 image (pattern 2) and the number of images formed when the toner density of a one-dot isolated image (pattern 1) is a predetermined toner density.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Intermediate transfer belt 3 Paper discharge roller 4 Fixing device 5 Secondary transfer roller 6 Registration roller 7 Paper feed roller 8 Paper feed cassette 9 Optical writing unit 10 Developing device 11 Primary transfer device 12 Intermediate transfer body cleaning device 21 Photosensitive drum 22 Photosensitive belt 100 Printer

Claims (13)

A latent image carrier that carries a latent image; and an image forming unit that develops the latent image of the latent image carrier and forms a toner image on the latent image carrier; The toner image formed on the carrier is transferred to the recording material, or the toner image on the intermediate transfer member is transferred to the recording material after the toner image is transferred to the surface of the intermediate transfer member. In an image forming apparatus for forming an image,
A toner density detecting unit configured to detect a toner density of the toner image; and a reference toner image having one or more pixels detectable by the toner density detecting unit; and the toner density detecting unit configured to generate the reference toner image having the one pixel or more. Based on the detection result at the time of detection, the toner density of the toner image of one pixel is predicted, and based on the predicted toner density of the toner image of one pixel, the toner density of the toner image of one pixel becomes a predetermined toner density. An image forming apparatus comprising: process condition changing means for executing processing for changing an image forming process condition of the image forming means. The image forming apparatus according to claim 1.
Storage means for storing the correlation between the toner density of the reference toner image and the toner density of the one-pixel toner image under the same image forming process condition; and the process condition changing means includes the toner density detecting means A one-pixel toner image is predicted from the correlation between the toner density when the reference toner image is detected and the toner density of the reference toner image stored in the storage unit and the toner density of the one-pixel toner image. An image forming apparatus. The image forming apparatus according to claim 1 or 2,
An environment detecting unit for detecting an environment in the apparatus, wherein the process condition changing unit is changed more than a certain amount from a detection result detected by the environment detecting unit when the previous image forming process condition changing process was executed; And an image forming process condition changing process. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the process condition changing means executes an image forming process condition changing process based on a use state of the latent image carrier. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the process condition changing unit executes an image forming process condition changing process based on a usage state of the developing device. The image forming apparatus according to claim 1,
The storage means stores a plurality of correlations between the toner density of the reference toner image and the toner density of the toner image of one pixel under the same image forming process condition according to the use environment of the apparatus. The means changes the correlation between the toner density of the reference toner image and the toner density of the one-pixel toner image used when predicting the toner density of the one-pixel toner image according to the use environment of the apparatus. An image forming apparatus. A latent image carrier that carries a latent image; and an image forming unit that develops the latent image of the latent image carrier and forms a toner image on the latent image carrier; The toner image formed on the carrier is transferred to the recording material, or the toner image on the intermediate transfer member is transferred to the recording material after the toner image is transferred to the surface of the intermediate transfer member. In an image forming apparatus for forming an image,
A toner density detecting unit configured to detect a toner density of the toner image; and a reference toner image having one or more pixels detectable by the toner density detecting unit; and the toner density detecting unit configured to generate the reference toner image having the one pixel or more. And a process condition changing unit that executes a process of changing an image forming process condition of the image forming unit so that the toner density of one pixel becomes a predetermined toner density based on a detection result at the time of detection. The condition changing means determines whether the toner for one pixel is based on the correlation between the usage condition of the apparatus and the toner density of the reference toner image when the toner density of the toner image of one pixel becomes a predetermined toner density and the usage condition of the apparatus. The toner density of the reference toner image when the toner density of the image becomes a predetermined toner density is specified, and the detection when the toner density detecting means detects the reference toner image. Result image forming apparatus characterized by changing the image forming process conditions such that the toner density reference toner image is specified based on. The image forming apparatus according to claim 7.
An image forming apparatus characterized in that the usage status of the apparatus is a usage environment of the apparatus. The image forming apparatus according to claim 7.
An image forming apparatus according to claim 1, wherein the use state of the apparatus is a use state of the latent image carrier. The image forming apparatus according to claim 7.
An image forming apparatus characterized in that the usage status of the apparatus is the usage status of the developing device in the previous period. The image forming apparatus according to claim 1,
A tandem color image forming apparatus comprising a plurality of the image forming means, wherein the toner images carried on the latent image carrier of each image forming means are sequentially intermediate-transferred to the intermediate transfer body, wherein the toner density detecting means comprises: An image forming apparatus for detecting a toner density of a toner image transferred onto the intermediate transfer member. An image forming means having a latent image carrier for carrying a latent image; a developing device for developing the latent image of the latent image carrier to form a toner image on the latent image carrier; and toner for the toner image In an image stabilization method in an image forming apparatus provided with a toner density detecting means for detecting density,
An image density of one pixel is formed based on a step of forming a reference image of one pixel or more that can be detected by the image density detection unit, and a detection result when the image density detection unit detects the reference image of one pixel or more. And a step of changing the image forming process condition of the image forming unit so that the image density of one pixel becomes a predetermined image density based on the predicted image density of one pixel. Image stabilization method. An image forming means having a latent image carrier for carrying a latent image; a developing device for developing the latent image of the latent image carrier to form a toner image on the latent image carrier; and toner for the toner image In an image stabilization method in an image forming apparatus provided with a toner density detecting means for detecting density,
The usage status of the apparatus, the toner density of one or more reference toner images that can be detected by the image density detection means when the toner density of the toner image of one pixel reaches a predetermined toner density, and the usage status of the apparatus From the correlation, the step of specifying the toner density of the reference toner image when the toner density of the toner image of one pixel becomes a predetermined toner density, and the reference toner image of one pixel or more that can be detected by the image density detecting means And forming the image so that the reference toner image has a toner density of the specified reference toner image based on a detection result when the image density detection unit detects the reference image of one pixel or more. Changing the image forming process conditions of the means.

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