JP5142039B2 - Toner adhesion amount calculating device, image forming apparatus, and toner particle size estimating method - Google Patents

Description

  The present invention relates to a toner adhesion amount calculation device, an image forming apparatus, and a toner particle size estimation method.

  In this type of image forming apparatus, conventionally, an optical detection means is used to detect a toner pattern formed on an image carrier such as a photosensitive member or a transfer belt under predetermined image forming conditions so that an image density of an image to be formed is appropriate. The toner adhesion amount of each toner patch is calculated using the detection result and a predetermined adhesion amount calculation algorithm. The image forming conditions are controlled based on the calculated toner adhesion amount of each toner patch.

As an optical sensor for detecting a toner patch, a specular reflection type optical sensor that includes a light emitting element such as an LED and a light receiving element such as a phototransistor and detects regular reflection light of the light emitting element by the light receiving element is generally used. ing. When the detection surface is smooth, the specular reflection type optical sensor has a large amount of specular reflection light, so that the output value of the light receiving element is high. As the detection surface becomes rough, the specular reflection light decreases and the output value of the light receiving element decreases. That is, when the toner adhesion amount is small, a large amount of light is reflected from the surface of the smooth image carrier, so that the regular reflection light increases and the output value of the light receiving element is high. On the other hand, when the toner adhesion amount increases, the detection surface becomes uneven due to the toner particles, so that the regular reflection light decreases and the output value of the light receiving element decreases. As described above, since there is a correlation between the output value of the light receiving element and the toner adhesion amount, the toner density can be detected from the output value of the light receiving element.
However, the specular reflection type optical sensor has a problem in that it cannot accurately detect the density of a toner patch in a high density portion (a large amount of toner adhesion). This is because of the uneven state of the toner patch such that the detection surface on which the toner patch is formed is almost covered with toner particles, and the uneven state of the toner patch when the amount of adhesion is increased and the toner particles are stacked in layers. This is because there is not much difference.

  In the diffuse reflection light, when the toner adhesion amount is small, the amount of diffuse reflection light from the toner is small, and the output value of the light receiving element becomes low. On the other hand, when the toner adhesion amount is large, the amount of diffusely reflected light from the toner increases, and the output value of the light receiving element increases. As described above, also in the case of diffuse reflected light, since there is a correlation between the output value of the light receiving element and the toner adhesion amount, the toner density can be detected from the output value of the light receiving element. Furthermore, in the case of diffusely reflected light, even if the detection surface on which the toner patch is formed is covered with toner particles, the output value of the light receiving element increases according to the toner adhesion amount. It is possible to detect the amount of toner patch adhering when the amount of toner particles increases and the toner particles overlap.

  In such an optical sensor, there has been a problem that the output characteristics of the optical sensor fluctuate due to fluctuations in the amount of light emitted from the light emitting element and fluctuations in the output value of the light receiving element due to usage over time and environmental fluctuations. In the regular reflection type optical sensor, fluctuations in output characteristics of the optical sensor can be corrected by detecting the surface of the image carrier. In the correction of output characteristics in the specular reflection type optical sensor, the output value of the light receiving element obtained from the surface of the image carrier is stored in advance, and the output value when the surface of the image carrier is detected is stored in advance. By adjusting the amount of emitted light so that the output value is set, fluctuations in output characteristics can be corrected.

  However, in the case of an optical sensor that detects diffusely reflected light, the output value when the surface of the image carrier is detected is zero, so that it is impossible to correct the output characteristic fluctuation of a sensor such as a regular reflection type sensor. .

Patent Document 1 includes an optical sensor including a light receiving element that receives specularly reflected light and a light receiving element that receives diffusely reflected light, and uses the specularly reflected light output value to vary the output characteristics of diffusely reflected light. An image forming apparatus to be corrected is described.
In the image forming apparatus described in Patent Document 1, first, the surface of the image carrier is detected and the characteristic variation of the regular reflection light output is corrected. Specifically, the specular reflection light is calculated from the output value of the specular reflection light receiving element when the surface of the image carrier is detected (hereinafter referred to as specular reflection detection value) and the specular reflection detection value stored in advance. The fluctuation rate of the detected value is calculated. Next, a toner patch is formed on the image carrier, detected by an optical sensor, and a regular reflection light detection value when the toner patch is detected is normalized by a variation rate. The toner adhesion amount is calculated based on the normalized regular reflection light detection value and the regular reflection light adhesion amount conversion table. By normalizing the regular reflection light detection value with the variation rate, the normalized regular reflection light output value becomes a value in which the variation of the light emitting element and the variation of the regular reflection light receiving element are corrected. The toner adhesion amount calculated from the normalized specular reflection detection value is an accurate adhesion amount. Next, a target diffuse reflection light detection value is obtained based on the calculated accurate adhesion amount and the diffuse reflection light attachment amount conversion table. Next, a correction value for correcting the diffuse reflection light detection value is calculated from the output value of the diffuse reflection light receiving element when the toner patch is detected (hereinafter referred to as the diffuse reflection light detection value) and the target diffuse reflection light detection value. calculate.
The output value of the diffuse reflection light receiving element when the toner patch is detected is an output value including fluctuations in the amount of light emitted from the light emitting element and output fluctuations in the diffuse reflection light receiving element. On the other hand, the target diffuse reflection light output value is a value that does not include the fluctuations in the light emission amount and the output fluctuations of the diffuse reflection light receiving element. Therefore, the diffuse reflected light output value is corrected with a correction value for correcting the output value of the diffuse reflected light receiving element so that the output value of the diffuse reflected light receiving element when the toner patch is detected becomes the target diffuse reflected light output value. As a result, fluctuations in the amount of emitted light and output fluctuations in the diffuse reflection light receiving element can be removed from the output value of the diffuse reflection light receiving element.
Then, by correcting the diffuse reflected light detection value when the toner patch is detected with the correction value, and calculating the toner adhesion amount based on the corrected diffuse reflected light detection value and the diffuse reflected light adhesion amount conversion table, An accurate adhesion amount can be calculated from the diffuse reflected light detection value.

JP 2002-236402 A

However, even if the diffuse reflection detection value is corrected as described in Patent Document 1, there is a case where an accurate toner adhesion amount cannot be detected.
Therefore, as a result of intensive studies, the present inventor has found that when the toner particle size is different, the detection value of the optical sensor is different even though the adhesion amount is the same. As a result, it was found that when the particle size of the toner to be used is different, it is impossible to accurately calculate the adhesion amount.
In particular, in the case of the one-component development method, the toner particle size used for image formation differs between the initial use of the developer and the lapse of time, so that it was not possible to accurately calculate the adhesion amount from the initial use to the lapse of time. In the one-component development method, the layer thickness is regulated by the regulating blade when passing through the regulating blade arranged to face the developing roller, and the toner is conveyed to the development area. When passing through the regulating blade, an effect like a mechanical filter (sieving) works, and toner having a small particle size is more likely to pass through the regulating blade than toner having a large particle size on the developing roller. As a result, at the initial stage of use of the developer, the average particle diameter of toner used for image formation becomes small, and the average particle diameter of toner used for image formation becomes large as it is used. As a result, in the case of the one-component development method, it is impossible to accurately calculate the adhesion amount from the initial use to the lapse of time.

  SUMMARY An advantage of some aspects of the invention is that it provides a toner adhesion amount calculation device, an image forming apparatus, and a toner particle size estimation method capable of estimating the particle size of toner to be used. It is.

In order to achieve the above object, a first aspect of the present invention provides a toner patch forming means for forming a toner patch on an image carrier, and regular reflection light and diffuse reflection from the toner patch formed on the image carrier. In a toner adhesion amount calculation device, which has an optical detection means for detecting light, and calculates an adhesion amount of a toner patch based on a specular reflection light detection value and a diffuse reflection detection value of the optical detection means. A regular-reflected light normalizing means for normalizing a light detection value and a toner patch forming means for forming on the image carrier a particle size-dependent toner patch in which the detection value of the optical detection means depends on the toner particle size. The particle size-dependent toner patch is detected by the optical detection means, and is based on a normalized specular light detection value of the particle size-dependent toner patch and an adhesion amount conversion table corresponding to the toner particle size. The diffuse reflection light A temporary correction value is calculated using a correction value calculating means for calculating a correction value for correcting the output value, and an adhesion amount conversion table corresponding to a predetermined toner particle diameter predetermined by the correction value calculating means, The toner patch forming unit forms a saturated toner patch on the image carrier whose diffuse reflection light detection value of the optical detection unit does not depend on the toner particle size and the adhesion amount, and the saturated toner patch is detected by the optical detection unit The toner particle diameter used for forming the toner image based on the value obtained by correcting the diffuse reflected light detection value of the saturated toner patch with the provisional correction value and the diffuse reflected light detection value of the saturated toner patch obtained in advance through experiments. And a toner particle size estimating means for estimating the toner particle size.
According to a second aspect of the present invention, in the toner adhesion amount calculating device according to the first aspect, the storage unit stores an adhesion amount conversion table for each toner particle size, and the toner particle size estimated by the toner particle size estimation unit is calculated. A corresponding adhesion amount conversion table is specified, and the toner adhesion amount is calculated based on the specified adhesion amount conversion table and the detection result of the optical detection means.
According to a third aspect of the present invention, in the toner adhesion amount calculating device according to the second aspect, the correction value calculating unit corresponds to the toner particle size estimated by the toner particle size estimating unit after execution of the toner particle size estimating unit. An adhesion amount conversion table is specified, and the correction value is recalculated based on the specified adhesion amount conversion table.
According to a fourth aspect of the present invention, in the toner adhesion amount calculating apparatus according to any one of the first to third aspects, the regular reflection light normalizing means is based on a regular reflection light detection value when the surface of the image carrier is detected. The normalization value is calculated, and the specular light detection value detected based on the calculated normalization value is normalized.
According to a fifth aspect of the present invention, in the toner adhesion amount calculating device according to any one of the first to fourth aspects, the particle size-dependent toner patch is a toner patch having a toner layer of less than one layer. It is.
According to a sixth aspect of the present invention, there is provided an image forming means for forming a toner image of a plurality of colors on the image carrier, and a toner image on the image carrier is optically detected to determine the amount of adhesion of the toner image. In the image forming apparatus, comprising: a toner adhesion amount calculation unit to calculate; and a control unit that executes predetermined control using the toner adhesion amount of the toner image calculated by the toner adhesion amount calculation unit. The toner adhesion amount calculating device according to any one of claims 1 to 5 is used.
According to a seventh aspect of the present invention, there is provided image forming means for forming a toner image on an image carrier, optical detection means for detecting reflected light from the toner image on the image carrier, and on the image carrier. Forming an image quality adjustment pattern including a toner patch with a low adhesion amount at least, and detecting the image quality adjustment pattern of the optical detection means and an adhesion amount conversion table corresponding to the toner particle size; The image forming apparatus includes an image forming condition setting unit that calculates a toner adhesion amount of the toner patch in the image quality adjustment pattern based on the image quality adjustment pattern and sets an image forming condition based on the calculated toner adhesion amount. The image formation condition setting means is executed using the adhesion amount conversion table corresponding to the prescribed toner particle size, the provisional image formation conditions are set, and the optical detection means is expanded under the provisional image formation conditions. A toner particle size estimation unit is provided that forms a particle size-independent toner patch whose reflected light detection value does not depend on the toner particle size, and estimates the toner particle size based on the toner adhesion amount of the particle size-independent toner patch. It is characterized by this.
The invention according to claim 8 is the image forming apparatus according to claim 7, further comprising storage means for storing an adhesion amount conversion table for each toner particle diameter, and after executing the toner particle diameter estimation means, the toner particle diameter An adhesion amount conversion table corresponding to the toner particle size estimated by the estimation unit is specified, and the image forming condition setting unit is executed using the specified adhesion amount conversion table.
According to a ninth aspect of the present invention, in the image forming apparatus according to the seventh or eighth aspect, the particle size-independent toner patch is composed of one or more toner layers.
According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the sixth to ninth aspects, the optical detection unit detects infrared light, and the particle size-independent toner patch has a plurality of colors. The toner image is formed by superimposing the toner images.
The invention of claim 11 is a toner particle size estimation method for estimating the particle size of a toner, the step of creating a particle size dependent toner patch in which the detection value of the optical detection means depends on the particle size, Detecting the dependency toner patch with an optical detection means capable of detecting specular reflection light and diffuse reflection light, a specular reflection detection value when detecting the particle size dependency toner patch, and a predetermined regulation Calculating a ratio from the diffuse reflection detection value calculated based on the adhesion amount conversion table corresponding to the toner particle size and the diffuse reflection detection value when the particle size-dependent toner patch is detected; A step of creating a saturated toner patch whose diffuse reflected light detection value of the optical detection means does not depend on the toner particle size and the adhesion amount; a step of detecting the saturated toner patch by the optical detection means; and a detection of the saturated toner patch From the value obtained by multiplying the ratio diffuse reflection light detection value when, is characterized in that a step of estimating the particle size of the toner.
According to a twelfth aspect of the present invention, in the toner particle size estimation method for estimating the particle size of the toner, a step of creating an image quality adjustment pattern comprising a plurality of toner patches for setting image forming conditions, and an image quality adjustment pattern Is detected by an optical detection means capable of detecting regular reflection light and diffuse reflection light, an image quality adjustment pattern detection result, and an adhesion amount conversion table corresponding to a predetermined toner particle size determined in advance. The image quality adjustment pattern includes a step of calculating a toner adhesion amount of each toner patch, a step of setting an image formation condition based on the calculated toner adhesion amount, and a step of setting the optical detection unit based on the set image formation condition. Based on the step of creating a particle size independent toner patch whose diffuse reflected light detection value does not depend on the toner particle size, and the toner adhesion amount of the particle size independent toner patch It is characterized in that a step of estimating the particle size.

  The particle size dependent toner patch, the particle size independent toner patch, and the saturated toner patch will be described.

First, the particle size-dependent toner patch will be described.
The particle size dependent toner patch is a toner patch in which the detection value of the optical detection means depends on the toner particle size. For example, a toner patch having less than one toner layer corresponds to this. The reason why the detection value of the optical detection means when detecting a toner patch having a toner layer of less than one layer depends on the toner particle size will be described below.
FIG. 1 is a diagram for explaining a particle size-dependent toner patch in which the detection value of the optical detection means depends on the toner particle size. FIG. 1A is a schematic configuration diagram of a toner patch formed using a toner having a large particle diameter. FIG. 1B is a schematic configuration diagram of a toner patch formed using toner having a small particle diameter. The toner adhesion amount [g / m ² ] of the toner patches in FIGS. 1A and 1B is the same, and the particle size of the toner having a large particle size is 2 of the particle size of the toner having a small particle size. It has doubled.
As shown in FIG. 1, since the toner particle size with a large particle size is twice the particle size of the toner with a small particle size, the height of the toner with a large particle size from the surface of the image carrier is small. It is twice as high as the toner. Since the adhesion amount is the weight per unit area, when the adhesion amount is the same, the smaller particle size in FIG. 1B is compared to the toner having a larger particle size in FIG. The height is low and spreads horizontally by the difference in height. For this reason, the toner covering the surface of the image carrier has a larger area for the toner having a small particle diameter than for the toner having a large particle diameter. Therefore, the exposure rate on the surface of the image carrier is smaller when the toner particle size is small even with the same adhesion amount. As a result, even if the amount of adhesion is the same, those having a small toner particle diameter increase in the case of diffuse reflection light and decrease in the case of regular reflection light compared to those having a large toner particle diameter. Therefore, even when the toner particle size is small and when the toner particle size is large, the detection value of the optical detection means is different and the adhesion amount calculated from the detection value is different although the same adhesion amount is actually the same. It ends up.
As described above, in a toner patch having less than one toner layer, the diffuse reflection light detection value and the regular reflection light detection value depend on the toner particle size. Therefore, a toner patch having less than one toner layer corresponds to a particle size-dependent toner patch in which the detection value of the optical detection means depends on the toner particle size.

Next, the particle size independent toner patch will be described.
The particle size-independent toner patch is a toner patch in which the diffuse reflected light detection value of the optical detection means does not depend on the toner particle size. For example, a toner patch having one or more toner layers corresponds to this. The reason why the diffuse reflected light detection value obtained by detecting a toner patch having one or more toner layers is not dependent on the toner particle size will be described below.
FIG. 2 is a view for explaining a particle size-independent toner patch whose detection value of the optical detection means does not depend on the toner particle size. FIG. 2A is a schematic configuration diagram of a toner patch formed so that toner having a large particle diameter is formed into two layers. FIG. 2B is a schematic configuration of a toner patch formed using a toner having a small particle diameter and having the same amount of adhesion as that of a toner patch formed so that a toner having a large particle diameter becomes two layers. FIG. Also in FIG. 2, the particle diameter of the toner having a large particle diameter is twice the particle diameter of the toner having a small particle diameter. In FIG. 2B, there are about four toner layers, and the layer thickness is substantially the same as in FIG.
When the toner patch is irradiated with light, both of them first diffusely reflect on the surface of the first layer of toner. This amount of reflection is about the same for both. If the toner layer thickness of the toner patch is more than one layer, the regular reflection light disappears and only the diffuse reflection light exists. Also, part of the light enters the toner layer and returns to the surface after being repeatedly diffused and reflected a plurality of times. When the thickness of the toner layer is 1 layer or more, the detection value of diffuse reflected light due to reflection inside the toner layer changes depending on the thickness of the toner layer. Therefore, the diffuse reflected light detection value depends on the thickness of the toner layer. As can be seen from FIGS. 2A and 2B, when the adhesion amount is the same, the layer thickness does not change when the toner particle size is large and when the toner particle size is small. Therefore, when the thickness of the toner layer is one layer or more, the influence of the toner particle size is eliminated. That is, when the thickness of the toner layer is one or more, the diffuse reflection detection value depends only on the thickness of the toner layer.
As described above, in a toner patch having one or more toner layers, the diffuse reflection detection value does not depend on the toner particle size. Therefore, a toner patch having one or more toner layers corresponds to a particle size-independent toner patch in which the diffuse reflected light detection value of the optical detection means does not depend on the toner particle size.
Since the thickness of the toner layer and the toner adhesion amount are correlated, the toner adhesion amount is not affected by the toner particle size from the diffuse reflected light detection value of one or more particle size-independent toner patches. Can be calculated.

Next, the saturated toner patch will be described. The saturated toner patch is a toner patch in which the diffuse reflection light detection value of the optical detection means does not depend on the toner particle diameter or the toner adhesion amount. For example, a toner patch exceeding a certain thickness corresponds to this. .
When the toner layer thickness exceeds a certain thickness, the diffuse reflection light detection value becomes the same value even if the toner adhesion amount is further increased and the toner layer is thickened. This is because the incident light hardly reaches the lowermost layer, and the light reflected by the lowermost layer hardly reaches the surface. That is, the amount of reflected light is constant regardless of the toner layer thickness (toner adhesion amount).
Therefore, as described above, in the toner patch in which the toner layer exceeds a certain thickness, the diffuse reflected light detection value does not depend on the toner particle size and the toner adhesion amount. Therefore, a toner patch whose thickness exceeds a certain thickness corresponds to a saturated toner patch whose diffuse reflected light detection value of the optical detection means does not depend on the toner particle size or toner adhesion amount.

  The phenomenon in the above-described particle size-independent toner patch and saturated toner patch is known as Kubelka-Munk's theory.

  According to the first aspect of the present invention, the normalized reflected light detection value and the adhesion amount conversion table corresponding to the predetermined toner particle diameter determined in advance are used to correct the diffuse reflected light output value. A temporary correction value is calculated, a saturated toner patch is formed on the surface of the image carrier, detected by an optical detection means, and a toner image is formed based on a value obtained by correcting the diffuse reflected light detection value of the saturated toner patch with the temporary correction value. The toner particle size used for the toner is estimated.

If the predetermined prescribed toner particle size corresponding to the adhesion amount conversion table used when calculating the temporary correction value is the same as the toner particle size used for the particle size-dependent toner patch, the temporary correction value The diffuse reflected light detection value corrected in (1) is a highly accurate diffuse reflected light detection value from which the characteristic variation of the optical detection means has been removed.
On the other hand, if the prescribed toner particle size corresponding to the adhesion amount conversion table used when calculating the temporary correction value is different from the toner particle size used for the particle size-dependent toner patch, the correction is made with the temporary correction value. The detected diffuse reflection light detection value does not become a highly accurate diffuse reflection detection value due to a toner particle size error.

As described above, the diffuse reflected light detection value obtained by detecting the saturated toner patch should be a predetermined value when there is no characteristic variation of the optical detection means. Therefore, if the predetermined prescribed toner particle size corresponding to the adhesion amount conversion table used when calculating the temporary correction value is the same as the toner particle size used for the particle size-dependent toner patch, The diffuse reflected light detection value of the saturated toner patch corrected with the correction value is a predetermined value.
On the other hand, if the prescribed toner particle size corresponding to the adhesion amount conversion table used when calculating the temporary correction value is different from the toner particle size used for the particle size-dependent toner patch, the correction is made with the temporary correction value. The diffuse reflected light detection value of the saturated toner patch that has been applied is not a predetermined value. Therefore, by checking how much the diffuse reflected light detection value of the saturated toner patch corrected with the temporary correction value is from a predetermined value, it is possible to estimate the toner particle size used for forming the toner image.

  According to the invention of claim 6, the image forming condition setting means is executed using the adhesion amount conversion table corresponding to the prescribed toner particle size, the temporary image forming condition is set, and the temporary image forming condition is set. A particle size-independent toner patch is formed, and the toner particle size is estimated based on the toner adhesion amount of the particle size-independent toner patch of the optical detection means.

If the prescribed toner particle size corresponding to the adhesion amount conversion table used when setting the temporary image forming conditions is the same as the toner particle size used for forming the image quality adjustment toner pattern, good image quality Is set to such an image forming condition that can be obtained. Therefore, the particle size-independent toner patch formed under the provisional image forming conditions has a desired toner adhesion amount.
On the other hand, if the prescribed toner particle size corresponding to the attached amount conversion table used when setting the temporary image forming conditions is different from the toner particle size used for forming the image quality adjusting toner pattern, the calculation is performed. An error due to the toner particle size occurs in the toner adhesion amount. This is because the image quality adjustment toner pattern includes at least a low adhesion amount toner patch which is a particle patch having a particle size dependency. For this reason, the provisional image forming conditions set based on the adhesion amount having the toner particle size error include the toner particle size error, and the particle size-independent toner patch formed by the temporary image forming condition is The desired toner adhesion amount is not achieved due to the toner particle size error.
Therefore, the toner particle size can be estimated by examining how much the adhesion amount of the particle size-independent toner patch formed under the provisional image forming conditions differs from the desired adhesion amount.

  According to the present invention, since the particle diameter of the toner to be used can be estimated, the toner adhesion amount corresponding to the toner particle diameter can be calculated, and the adhesion amount can be calculated with high accuracy.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described.
First, the basic configuration of the printer will be described. FIG. 3 is a schematic configuration diagram showing the printer. In this figure, this printer is an image forming unit, and four toner images for forming yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K) toner images that are toner patch forming units. Process units 1Y, M, C, and K are provided. These use Y, M, C, and K toners of different colors as the image forming material, but the other configurations are the same and are replaced when the lifetime is reached. Taking a process unit 1K for forming a K toner image as an example, as shown in FIG. 4, a drum-shaped photosensitive member 2K as a latent image carrier, a drum cleaning device 3K, a charge eliminating device (not shown), and a charging device 4K. And a developing device 5K. The process unit 1K is detachable from the printer main body, so that consumable parts can be replaced at a time.

  The charging device 4K uniformly charges the surface of the photoreceptor 2K that is rotated clockwise in the drawing by a driving unit (not shown). The uniformly charged surface of the photosensitive member 2K is exposed and scanned by the laser beam L and carries an electrostatic latent image for K. The electrostatic latent image for K is developed into a K toner image by the developing device 5K using K toner. Then, intermediate transfer is performed on an intermediate transfer belt 36 described later. The drum cleaning device 3K removes the transfer residual toner adhering to the surface of the photoreceptor 2K after the intermediate transfer process. The static eliminator neutralizes residual charges on the photoreceptor 2K after cleaning. By this charge removal, the surface of the photoreceptor 2K is initialized and prepared for the next image formation. Similarly, in the process units (1Y, M, C) of other colors, (Y, M, C) toner images are formed on the photoreceptors (2Y, M, C) in the same manner on the intermediate transfer belt 36 described later. Intermediate transfer.

  The developing device 5K includes a vertically long hopper 6K that stores K toner (not shown) and a developing unit 7K. In the hopper 6K, an agitator 8K that is rotationally driven by a driving means (not shown), an agitation paddle 9K that is rotationally driven by a driving means (not shown) vertically below, and rotated by a driving means (not shown) below the vertical direction. A toner supply roller 10K to be driven is disposed. The K toner in the hopper 6K moves toward the toner supply roller 10K by its own weight while being stirred by the rotational drive of the agitator 8K and the stirring paddle 9K. The toner supply roller 10K has a metal cored bar and a roller portion made of foamed resin or the like coated on the surface of the metal core roller 10K, while adhering K toner in the hopper portion 6K to the surface of the roller portion. Rotate.

  In the developing unit 7K of the developing device 5K, a developing roller 11K that rotates while contacting the photoreceptor 2K and the toner supply roller 10K, and a thinning blade 12K that contacts the tip of the developing roller 11K are disposed. Yes. The K toner adhered to the toner supply roller 10K in the hopper 6K is supplied to the surface of the development roller 11K at the contact portion between the development roller 11K and the toner supply roller 10K. When the supplied K toner passes through the contact position between the roller and the thinning blade 12K as the developing roller 11K rotates, the layer thickness on the roller surface is regulated. Then, the K toner after the layer thickness regulation adheres to the electrostatic latent image for K on the surface of the photosensitive member 2K in the developing region which is a contact portion between the developing roller 11K and the photosensitive member 2K. By this adhesion, the electrostatic latent image for K is developed into a K toner image.

  Although the process unit for K has been described with reference to FIG. 4, the process units 1Y, M, and C for Y, M, and C are also subjected to Y, M, and C on the surfaces of the photoreceptors 2Y, M, and C by the same process. A C toner image is formed.

  3, the optical writing unit 90 is disposed above the process units 1Y, M, C, and K in the vertical direction. The optical writing unit 90, which is a latent image writing means, uses the laser light L emitted from the laser diode based on the image information to uniformly charge the photoreceptors 2Y, M, C in the process units 1Y, M, C, K. , K are optically scanned. By this optical scanning, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 2Y, M, C, and K. The optical writing unit 90 is a photosensitive member that passes through a plurality of optical lenses and mirrors while deflecting laser light (L) emitted from a light source in a main scanning direction by a polygon mirror that is rotationally driven by a polygon motor (not shown). Is irradiated. You may employ | adopt what performs optical writing by the LED light emitted from several LED of the LED array.

  Below the process units 1Y, 1M, 1C, and 1K, there is disposed a transfer unit 35 that moves the endless intermediate transfer belt 16 endlessly in the counterclockwise direction in the drawing. In addition to the intermediate transfer belt 36, the transfer unit 35 serving as transfer means includes a driving roller 37, a driven roller 38, four primary transfer rollers 39Y, 39M, 39C, and 40K, a secondary transfer roller 40, a belt cleaning device 41, a cleaning device. A backup roller 42 and the like are provided.

  The intermediate transfer belt 36 is stretched by a driving roller 37, a driven roller 38, a cleaning backup roller 42, and four primary transfer rollers 39Y, 39M, 39C, and 39K disposed inside the loop. Then, it is moved endlessly in the same direction by the rotational force of the drive roller 37 that is driven to rotate in the counterclockwise direction in the figure by a drive means (not shown).

  The four primary transfer rollers 39Y, 39M, 39C, and 39K sandwich the intermediate transfer belt 36 that is moved endlessly in this manner between the photoreceptors 2Y, 2M, 2C, and 2K. By this sandwiching, primary transfer nips for Y, M, C, and K where the front surface of the intermediate transfer belt 36 and the photoreceptors 2Y, 2M, 2C, and 2K abut are formed.

  A primary transfer bias is applied to each of the primary transfer rollers 39Y, 39M, 39C, and 39K by a transfer bias power source (not shown), whereby electrostatic latent images on the photoreceptors 2Y, 2M, 2C, and 2K, A transfer electric field is formed between the primary transfer rollers 39Y, 39M, 39C, and 39K. Instead of the primary transfer rollers 39Y, 39M, 39C, and 39K, a transfer charger, a transfer brush, or the like may be employed.

  When Y toner formed on the surface of the photoreceptor 2Y of the Y process unit 1Y enters the above-described primary transfer nip for Y as the photoreceptor 2Y rotates, the photosensitive member 2Y is exposed to light by the action of the transfer electric field and nip pressure. Primary transfer is performed on the intermediate transfer belt 36 from the body 2Y. The intermediate transfer belt 36 on which the Y toner image has been primarily transferred in this way passes through the primary transfer nip for M, C, K along with the endless movement thereof, and the photoreceptors 2M, C, K. The upper M, C, and K toner images are sequentially superimposed on the Y toner image and primarily transferred. A four-color toner image is formed on the intermediate transfer belt 36 by this superimposing primary transfer.

  The secondary transfer roller 40 of the transfer unit 35 is disposed outside the loop of the intermediate transfer belt 36, and the intermediate transfer belt 36 is sandwiched between the secondary transfer roller 40 and the driven roller 38 inside the loop. By this sandwiching, a secondary transfer nip where the front surface of the intermediate transfer belt 36 and the secondary transfer roller 40 abut is formed. A secondary transfer bias is applied to the secondary transfer roller 40 by a transfer bias power source (not shown). By this application, a secondary transfer electric field is formed between the secondary transfer roller 40 and the driven roller connected to the ground.

  Below the transfer unit 35 in the vertical direction, a paper feed cassette 50 that stores a plurality of recording papers P in a bundle of paper is slidably attached to the printer housing. In the paper feed cassette 50, a paper feed roller 50a is brought into contact with the uppermost recording paper P of the paper bundle, and the recording paper is rotated by rotating it in a counterclockwise direction in the drawing at a predetermined timing. P is sent out toward the paper feed path 51.

  A registration roller pair 52 is disposed near the end of the paper feed path 51. The registration roller pair 52 stops the rotation of both rollers as soon as the recording paper P delivered from the paper feed cassette 50 is sandwiched between the rollers. Then, rotation driving is restarted at a timing at which the sandwiched recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 36 in the above-described secondary transfer nip, and the recording paper P is directed to the secondary transfer nip. Send it out.

  The four-color toner image on the intermediate transfer belt 36 brought into close contact with the recording paper P at the secondary transfer nip is secondarily transferred onto the recording paper P under the influence of the secondary transfer electric field and nip pressure, and the recording paper Combined with the white color of P, a full color toner image is obtained. When the recording paper P having the full-color toner image formed on the surface in this way passes through the secondary transfer nip, the recording paper P is separated from the secondary transfer roller 40 and the intermediate transfer belt 36 by the curvature. Then, it is sent to a fixing device 54 described later via a post-transfer conveyance path 53.

  Transfer residual toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 36 after passing through the secondary transfer nip. This is cleaned from the belt surface by a belt cleaning device 41 in contact with the front surface of the intermediate transfer belt 36. A cleaning backup roller 42 disposed inside the loop of the intermediate transfer belt 36 backs up the cleaning of the belt by the belt cleaning device 41 from the inside of the loop.

  The fixing device 54 forms a fixing nip with a fixing roller 54a containing a heat source such as a halogen lamp (not shown) and a pressure roller 54b that rotates while contacting the fixing roller 54a with a predetermined pressure. The recording paper P fed into the fixing device 54 is sandwiched between the fixing nips so that the unfixed toner image carrying surface is in close contact with the fixing roller 54a. Then, the toner in the toner image is softened by the influence of heating and pressurization, and the full color image is fixed.

  The recording paper P discharged from the fixing device 54 passes through the post-fixing conveyance path 55 and then reaches the branch point between the paper discharge path 56 and the pre-reversal conveyance path 61. On the side of the post-fixing conveyance path 55, a switching claw 62 that is rotationally driven about a rotation shaft 62a is disposed. By the rotation, the vicinity of the end of the post-fixing conveyance path 55 is closed. Or open. At the timing when the recording paper P is sent out from the fixing device 54, the switching claw 62 stops at the rotation position indicated by the solid line in the drawing, and the vicinity of the end of the post-fixing conveyance path 55 is opened. Therefore, the recording paper P enters the paper discharge path 56 from the conveyance path 55 after fixing, and is sandwiched between the rollers of the paper discharge roller pair 57.

  When the single-sided print mode is set by an input operation to an operation unit including a numeric keypad (not shown) or a control signal sent from a personal computer (not shown), the recording sandwiched between the paper discharge roller pair 57 is set. The paper P is discharged out of the machine as it is. Then, it is stacked on the stack portion that is the upper surface of the upper cover 70 of the housing.

  On the other hand, when the duplex printing mode is set, the trailing edge of the recording paper P conveyed through the paper discharge path 36 while the front end is sandwiched between the paper discharge roller pair 57 passes through the post-fixing conveyance path 55. The switching claw 62 is rotated to the position of the one-dot chain line in the drawing, and the vicinity of the end of the post-fixing conveyance path 55 is closed. At substantially the same time, the paper discharge roller pair 57 starts to rotate in the reverse direction. Then, the recording paper P is conveyed while the rear end side is directed to the top, and enters the pre-reversal conveyance path 61.

  FIG. 3 shows the printer from the left side. The near side in the direction perpendicular to the drawing is the left side of the printer, and the far side is the right side. Further, the right side of the printer is a front side and the left side is a back side. The right end portion of the housing of the printer is a reversing unit 60 that can be opened and closed with respect to the housing body by rotating about a rotation shaft 60a.

  When the paper discharge roller pair 57 rotates in the reverse direction, the recording paper P enters the pre-reversal conveyance path 61 of the reversing unit 60 and is conveyed from the upper side to the lower side in the vertical direction. Then, after passing between the rollers of the pair of reverse conveying rollers 63, it enters the reverse conveying path 64 that is curved in a semicircular shape. Furthermore, while the upper and lower surfaces are reversed as the sheet is conveyed along the curved shape, the traveling direction from the upper side in the vertical direction to the lower side is also reversed, and conveyed from the lower side in the vertical direction toward the upper side. Is done. Thereafter, the toner enters the secondary transfer nip again through the above-described paper feed path 51. Then, after the full-color image is secondarily transferred collectively to the other surface, the post-transfer conveyance path 53, the fixing device 54, the post-fixation conveyance path 55, the paper discharge path 56, and the paper discharge roller pair 57 are sequentially passed. And discharged outside the machine.

  The reversing unit 60 described above has an external cover 65 and a rocking body 66. Specifically, the outer cover 65 of the reversing unit 60 is supported so as to rotate about a rotation shaft 60a provided in the housing of the printer main body. By this rotation, the outer cover 65 opens and closes with respect to the housing together with the swinging body 66 held therein. As shown by the dotted line in the figure, when the outer cover 65 is opened together with the swinging body 66 therein, the paper feed path 51 formed between the reversing unit 60 and the printer main body, the secondary transfer nip, and after the transfer. The conveyance path 53, the fixing nip, the post-fixing conveyance path 55, and the paper discharge path 56 are divided into two parts and exposed to the outside. Thus, jammed paper in the paper feed path 51, the secondary transfer nip, the post-transfer conveyance path 53, the fixing nip, the post-fixation conveyance path 55, and the paper discharge path 56 can be easily removed.

  The swinging body 66 is supported by the external cover 65 so as to rotate around a swinging shaft (not shown) provided in the external cover 65 in a state where the external cover 65 is opened. When the swinging body 66 is opened with respect to the external cover 65 by this rotation, the pre-reversal conveyance path 61 and the reverse conveyance path 64 are vertically divided into two and exposed to the outside. As a result, the jammed paper in the pre-reversal conveyance path 61 and the reversal conveyance path 64 can be easily removed.

An optical sensor 69 serving as an optical detection means is provided on the intermediate transfer belt 36 on the downstream side in the intermediate transfer belt surface movement direction from the K primary transfer portion and on the upstream side in the intermediate transfer belt surface movement direction from the secondary transfer portion. It is disposed so as to face the front surface with a predetermined gap.
FIG. 5 is a schematic sectional view of the optical sensor 69. As shown in the figure, the optical sensor 69 mainly receives a light emitting element 311 as a light emitting means, a regular reflection light receiving element 312 as a first light receiving means for receiving specular reflection light, and diffuse reflection light. And a diffuse reflection light receiving element 313 as a second light receiving means. Light emitted from the light emitting element 311 is emitted toward the surface of the intermediate transfer belt 36. Then, the specularly reflected light regularly reflected by the surface of the intermediate transfer belt 36 and the toner patch transferred to the surface is received by the specular reflection light receiving element 312 and a voltage corresponding to the amount of received light is output. Further, the diffuse reflection light diffusely reflected by the surface of the intermediate transfer belt 36 and the toner patch transferred to the surface is received by the diffuse reflection light receiving element 313, and a voltage corresponding to the amount of received light is output.

  As the light emitting element 311 of the optical sensor 69, a GaAs light emitting diode having a peak emission wavelength of 940 [nm] is used. Further, as the regular reflection light receiving element 312 and the diffuse reflection light receiving element 313, those having a Si phototransistor having a peak spectral sensitivity wavelength of 850 [nm] are used. That is, this optical sensor detects infrared light of 830 [nm] or more with no significant difference in reflectance by color. By using such an optical sensor, it is possible to detect toner patches of all colors Y, M, C, and K with a single sensor.

  FIG. 6 is a block diagram showing the main part of the electric circuit of the copying machine. In FIG. 1, a control unit 100 as a control means includes a CPU (Central Processing Unit) 101 as a calculation means, a nonvolatile RAM (Random Access Memory) 102 as a data storage means, a ROM (Read Only Memory) 103 as a data storage means, and the like. Have. The control unit 100 is electrically connected to process units 1Y, 1M, 1C, and 1K, an optical writing unit 90, a transfer unit 50, an optical sensor 69, and the like. And the control part 100 controls these various apparatuses based on the control program memorize | stored in RAM102 or ROM103. Further, the control unit functions as a toner adhesion amount calculation unit that calculates the toner adhesion amount based on the output value of the optical sensor 69.

  The control unit 100 also controls image forming conditions for forming an image. Specifically, the control unit 100 performs control to individually apply a charging bias to each charging member in the process units 1Y, M, C, and K. As a result, the photoreceptors 2Y, 2M, 2C, and 2K of the respective colors are uniformly charged to the Y, M, C, and K drum charging potentials. The control unit 100 individually controls the powers of the four semiconductor lasers corresponding to the process units 1Y, M, C, and K of the optical writing unit 68. In addition, the control unit 100 performs control to apply the developing bias of the developing bias values for Y, M, C, and K to the developing rollers in the process units 1Y, M, C, and K. As a result, a developing potential for electrostatically moving the toner from the sleeve surface side to the photosensitive member side acts between the electrostatic latent images of the photosensitive members 2Y, 2M, 2C, and 2K and the developing sleeve. Develop.

The printer according to the present embodiment executes process control as image density control for optimizing the image density of each color when the power is turned on or whenever a predetermined number of prints are performed.
In the process control, first, the photosensitive members 2Y, 2M, 2C, and 2K shown in FIG. The charging potential at this time is gradually increased, unlike the uniform drum charging potential in the printing process. Then, eight patch electrostatic latent images for forming a gradation pattern image are formed on the photoreceptors 2Y, 2M, 2C, and 2K, respectively, by scanning with a laser beam, and these are used for Y, M, C, and K. Development is performed using a developing device. During this development, the control unit 100 gradually increases the value of the developing bias applied to the developing sleeve for Y, M, C, and K. By such development, Y, M, C, and K gradation pattern images are formed on the photoreceptors 2Y, 2M, 2C, and 2K. These are primarily transferred onto the intermediate transfer belt 36 so as to be arranged in the order of K, C, M, and Y from the downstream side in the belt moving direction to the upstream side. As a result, a test pattern image for toner adhesion amount detection in which four gradation pattern images K, C, M, and Y are sequentially arranged is formed.

  FIG. 7 is a schematic plan view showing a test pattern image for toner adhesion amount detection formed on the intermediate transfer belt 36. The arrows shown in the figure indicate the surface movement direction of the intermediate transfer belt (36) (not shown). The test pattern image Pt1 includes a K gradation pattern image Pk, a C gradation pattern image Pc, an M gradation pattern image Pm, and a Y gradation pattern image Py arranged in order from the downstream side to the upstream side in the belt movement direction. Yes. Further, each gradation pattern image includes eight toner patches (500K, C, M, Y) arranged at a predetermined pitch in the belt moving direction.

  For each of the colors Y, M, C, and K, the eight toner patches (500Y, M, C, and K) in the gradation pattern (Py, m, c, and k) have different drum charging potentials and developing biases. The toner adhesion amount (image density) per unit area gradually increases. Since the toner adhesion amount is correlated with the developing potential which is the difference between the drum charging potential and the developing bias, the relationship between the two becomes a substantially linear graph on the two-dimensional coordinates. Therefore, a development bias that obtains a desired image density (toner adhesion amount) by calculating a function (y = ax + b) showing a linear graph based on the result of detecting the toner adhesion amount in each toner patch by regression analysis. A value can be determined.

  The test pattern image Pt1 for detecting the toner adhesion amount is formed at the center in the belt width direction on the front surface of the intermediate transfer belt 36, as shown. Each toner patch (500K, C, M, Y) in each gradation pattern image (Pk, c, m, y) of the test pattern image Pt1 is opposed to the optical sensor 69 as the intermediate transfer belt 36 moves endlessly. Go through position. At this time, the optical sensor 69 receives an amount of light corresponding to the toner adhesion amount per unit area with respect to the toner patch. For this reason, the control unit 100 to which the output signal from the optical sensor 69 is input as a digital signal is an adhesion amount conversion constructed based on the relationship between the digital signal, the digital signal (reflected light detection value), and the toner adhesion amount. Using a table, conversion processing is performed on the toner adhesion amount (image density) per unit area. The details of the calculation of the adhesion amount will be described later.

  The control unit 100 sequentially calculates the image density (toner adhesion amount) of each toner patch based on the output signal corresponding to each toner patch sequentially sent from the optical sensor 69 and stores it in the RAM 102. Then, for each of the colors Y, M, C, and K, regression analysis is performed using each development bias value and image density data of eight toner patches, and a function (regression equation) showing a linear graph on two-dimensional coordinates. ) Further, an appropriate development bias value is calculated by substituting the target value of image density into this function, and stored in the RAM 102 as corrected development bias values for Y, M, C, and K.

  The RAM 102 stores an image forming condition data table in which several tens of development bias values and appropriate drum charging potentials individually corresponding to the values are associated in advance. The control unit 100 selects the developing bias value closest to the corrected developing bias value from the image forming condition table for each of the process units 1Y, M, C, and K, and specifies the drum charging potential associated therewith. To do. The specified drum charging potential is stored in the RAM as Y, M, C, and K correction drum charging potentials. When all the corrected development bias values and corrected drum charging potentials are stored in the RAM 102, the Y, M, C, and K development bias value data are corrected to the same values as the corresponding corrected development bias values. Store again. Also, the drum charging potentials for Y, M, C, and K are corrected to values equivalent to the corresponding correction drum charging potentials and stored again. By such correction, the image forming conditions for forming an image are corrected to conditions that can form a toner image having a desired image density.

  The test pattern image Pt1 for detecting the toner adhesion amount after passing through the position facing the optical sensor 69 as the belt moves endlessly is printed on the front surface of the belt by the belt cleaning device 41 shown in FIG. Removed from.

Next, toner adhesion amount calculation, which is a characteristic point of the present embodiment, will be described.
In this embodiment, as described in Patent Document 1, the amount of Y, M, and C toner adhesion is calculated using specularly reflected light that is regularly reflected by a toner patch and diffusely reflected light that is diffusely reflected. The toner adhesion amount is calculated. By calculating the toner adhesion amount using the regular reflection light and the diffuse reflection light, the detection range of the high adhesion amount can be expanded as compared with the case where the toner adhesion amount is calculated using only the regular reflection light. Further, by using the toner adhesion amount calculation method described in Patent Document 1, an accurate toner adhesion amount can be obtained even when the output of the light emitting element or the light receiving element changes due to temperature change, deterioration with time, or the like.
On the other hand, in the case of K-color toner, the irradiated light is absorbed by the toner surface, and thus there is a characteristic that the sensitivity of diffuse reflected light cannot be obtained. Therefore, the toner adhesion amount is detected using only the regular reflection light in the K color toner.

Next, calculation of Y, M, and C toner adhesion amounts will be described in detail.
In the case of the K color toner, the irradiated light is absorbed by the toner surface as described above, and therefore, the diffuse reflected light component is hardly included and can be ignored. Therefore, the amount of adhesion can be detected using the regular reflection light output Vreg of the optical sensor 69 as the regular reflection light component as it is.
However, in the case of Y, M, and C colors, since the light irradiated on the toner surface is diffusely reflected, the regular reflection light output Vreg of the optical sensor 69 includes many diffuse reflection components in addition to the regular reflection component. . Therefore, in the case of Y, M, and C color toners, even if the regular reflection light output Vreg is used as it is, it cannot be used as a regular reflection light component. On the other hand, since the diffuse reflection output Vdif of the optical sensor 69 measured simultaneously is only the diffuse reflection light component, by using the diffuse reflection output Vdif, the diffuse reflection component is removed from the regular reflection light output Vreg of the optical sensor 69. The specular reflection component can be extracted. As a result, the Y, M, and C colors can be calculated from the specularly reflected light component in the same manner as the K color.

However, the calculation of the adhesion amount using the specularly reflected light component has a problem in that the adhesion amount cannot be detected when the adhesion amount increases. That is, as described above with reference to FIG. 2, when the toner patch completely covers the intermediate transfer belt 36, only the diffuse reflection light component and the regular reflection light component become zero. On the other hand, as described with reference to FIG. 2, the diffuse reflected light component is diffused because the diffuse reflected light component depends on the layer thickness even if the toner patch completely covers the intermediate transfer belt 36. The toner adhesion amount can be obtained from the reflected light component.
When the toner particle size is 0.01 [mm], it is possible to detect with a regular reflection light component up to a toner adhesion amount of 4.5 [g / m ² ]. Further, when the toner particle size is 0.006 [mm], it is possible to detect with a regular reflection light component up to a toner adhesion amount of 2.5 [g / m ² ]. However, since the toner adhesion amount set as the solid image adhesion amount in this printer is 5.0 [g / m ² ] or more, the regular image light component cannot detect the solid image adhesion amount.
For this reason, for the Y, M, and C colors, the adhesion amount is calculated using the diffuse reflected light component, so that the toner adhesion amount can be calculated up to a high adhesion amount.

  The diffuse reflected light output Vdif of the optical sensor 69 greatly depends on the light emission amount of the light emitting element 311. For this reason, when the amount of light emitted from the light emitting element 311 fluctuates due to a temperature change or a change with time, the diffuse reflected light output Vdif fluctuates greatly, and an accurate toner adhesion amount is calculated using the diffuse reflected light component. I can't.

For this reason, in this printer, the fluctuation component of the amount of emitted light is removed from the diffuse reflected light output Vdif as follows. This will be specifically described below.
FIG. 8 is a basic control flow for calculating the adhesion amount of the color toner patch.
First, the surface of the intermediate transfer belt is detected, and the ratio (variation rate α) between the regular reflection light output Vreg and a predetermined value stored in advance is calculated (S1).
Next, in the gradation pattern, a regular positive light component is extracted by extracting only the specular reflection light component from the specular reflection light output Vreg and the diffuse reflection light output Vdif when a low-adhesion toner patch that exposes the surface of the intermediate transfer belt is detected. The reflected light output Vreg1 is calculated, and the regular reflected light output is normalized by multiplying the calculated regular reflected light output Vreg1 by the variation rate α. (S2). The normalized regular reflection light output Vreg2 is a value from which the light emission amount of the optical sensor and the variation of the regular reflection light receiving element are removed. Next, a correction value K for correcting the diffuse reflected light output Vdif is calculated (S3).
The correction value K is calculated as follows. First, the toner adhesion amount is calculated from the obtained normalized specular reflection light output Vreg2 and the regular reflection light adhesion amount conversion table in which the specular reflection light output and the toner adhesion amount are associated with each other. Next, the target diffuse reflection light output is calculated from the calculated toner adhesion amount and the diffuse reflection light adhesion amount conversion table in which the diffuse reflection light output and the toner adhesion amount are associated with each other. Then, the correction value K is calculated from the ratio between the diffuse reflected light output Vdif and the target diffuse reflected light output.

  When the correction value K is calculated, the diffuse reflection light output Vdif when the toner patch of the gradation pattern is detected is multiplied by the calculated correction value K, and the diffuse reflection light output Vdif1 after correction and the diffuse reflection light toner amount conversion are converted. The adhesion amount is calculated based on the table (S4).

In this way, by calculating the correction value K and correcting the diffuse reflected light output Vdif when detecting each toner patch of the gradation pattern with the correction value K, the amount of emitted light is added to the corrected diffuse reflected light output Vdif1. Can be removed. Thereby, an accurate toner adhesion amount can be calculated.
Note that the method of correcting the diffuse reflected light output Vdif is not limited to this, and may be, for example, the method described in Japanese Patent Application Laid-Open No. 2005-76885.

The printer of this embodiment is a one-component developing system, and when the toner in the hopper unit 6 runs out, the process unit 1 is replaced. When the process unit is new, the toner used for image formation is reduced in particle size by the so-called particle size selection effect. In the printer of this embodiment, when the process unit is initially used, an average toner of 0.006 [mm] is used for image formation, and as the toner is used, the particle diameter of the toner used for image formation increases. Then, when the toner in the hopper 6 has been reduced and is about to be replaced, toner having a large particle diameter of 0.01 [mm] on average is used for image formation.
Thus, the particle size of the toner used for image formation varies depending on the use time of the process unit. Therefore, as described above with reference to FIG. 1, when the toner patch has a low adhesion amount, the regular reflection light output Vreg and the diffuse regular reflection light output Vdif differ depending on the particle diameter even if the adhesion amount is the same.

FIG. 9 is a graph showing the relationship between the toner adhesion amount and the regular reflection light output of the optical sensor. FIG. 10 is a graph showing the relationship between the toner adhesion amount and the diffuse reflected light output of the optical sensor. The solid line in the figure is when the toner particle diameter is 0.006 [mm], and the dotted line in the figure is when the toner particle diameter is 0.01 [mm]. The toner adhesion amount is precisely measured with a balance after the optical sensor 69 detects a toner patch on the intermediate transfer belt and then sucks the toner from the intermediate transfer belt 69 with air.
As shown in FIG. 9, it can be seen that the specularly reflected light output varies depending on the particle size even with the same amount of adhesion. Further, as shown in FIG. 10, it can be seen that when the toner adhesion amount is 6 [g / m ² ] or less, the specular reflection light output varies depending on the particle diameter even with the same adhesion amount.

In the calculation of the Y, M, and C color toner adhesion amounts described above, since the particle size is not taken into account, for example, the relationship between the default specular reflection component and the toner adhesion amount, and the default diffuse reflection component When it is considered that the relationship with the toner adhesion amount is designed with a toner particle size of 0.01 [mm], the following results are obtained. That is, for example, when the calculated regular reflection light output Vreg2 is 0.3, the calculated toner adhesion amount is 3.5 [g / m ² ] (see FIG. 9). However, the actual toner particle size is not 0.01 [mm], and when the toner particle size used in the initial stage of use of the process unit is 0.006 [mm], the true toner adhesion amount is 2.0 [m / g ² ], and an error in the toner particle diameter causes an adhesion amount calculation error of 1.5 [g / m ² ]. As a result, at the initial use of the process unit, image density control with high accuracy cannot be performed, and good image quality cannot be obtained even if image density control is performed.
Therefore, in the present embodiment, the toner particle diameter is estimated by the method as shown in Examples 1 and 2 below, and the Y, M, and C toner adhesion amounts are calculated based on the estimated toner particle diameter. Is going. Thereby, it is possible to calculate the toner adhesion amount with high accuracy without any toner particle size error.

[Example 1]
First, Example 1 will be described.
In the first embodiment, a temporary correction value is calculated using a toner adhesion amount conversion table corresponding to a prescribed toner particle size. Next, a saturated toner patch is formed, and the toner particle size is estimated based on a value Vdif1 ′ obtained by correcting the diffuse reflected light output Vdif of the saturated toner patch with a temporary correction value.
Specifically, as shown in FIG. 11, three saturated toner patches PS1 to PS3 are formed after the test pattern image Pt1 for detecting the toner adhesion amount. In the first embodiment, three saturated toner patches (PS1 to PS3) are formed, but the toner particle size can be estimated even with one. As shown in FIG. 10, the saturated toner patch adhesion amount is the saturation region adhesion amount (adhesion amount 12 [g / m ² ]) in which the diffuse reflected light output Vdif does not change even if the toner adhesion amount or the particle diameter changes. Above). Specifically, the target adhesion amount of PS1 is set to 12 [g / m ² ], the target adhesion amount of PS2 is set to 15 [g / m ² ], and the target adhesion amount of PS3 is set to 18 [g / m ² ]. Yes. Since these target adhesion amounts are too large for a single color and cannot be realized, they are realized by superimposing toners of three colors C, M, and Y on the intermediate transfer belt. For example, in the saturated toner patch PS1, the target adhesion amount of each color is 4.0 [g / m ² ], and in the saturated toner patch PS2, the target adhesion amount of each color is 5.0 [g / m ² ], In the saturated toner patch PS3, the target adhesion amount of each color is set to 6.0 [g / m ² ]. Image forming conditions (development bias Vb or laser power LP) are adjusted so that the toner adhesion amount of each color becomes the target adhesion amount, and a toner patch is formed on each photoconductor. These toner patches are superposed on the intermediate transfer belt 36 to obtain saturated toner patches PS1 to PS3 having a desired target adhesion amount.

  As shown in FIG. 11, the three saturated toner patches formed after the test pattern image Pt1 for detecting the toner adhesion amount on the intermediate transfer belt are detected by the optical sensor 69 after the gradation pattern is detected. As described above, since the optical sensor 69 detects infrared light with no significant difference in reflectance by color, a saturated toner patch created by superimposing three colors can be detected well. Further, since these saturated toner patches are created in the previous stage of image density control, the toner adhesion amount may be different from the target adhesion amount. However, as described above, since the saturated toner patch has an adhesion amount in the saturated region, there is no problem even if the adhesion amount slightly varies with respect to the target adhesion amount.

  Temporary correction values Ky, Km, and Kc for each color are calculated from a low adhesion amount toner patch that is a particle size-dependent toner patch of Y, M, and C tone patterns. The temporary correction values Ky, Km, and Kc for each color are calculated from the toner adhesion amount conversion table corresponding to the prescribed toner particle size. That is, based on the regular reflection light output value Vreg2 of the low adhesion amount toner patch in the normalized gradation pattern and the regular reflection light toner adhesion amount conversion table corresponding to the specified toner particle size, The adhesion amount of the low adhesion amount toner patch is calculated. Next, a temporary target diffuse reflection light output value is calculated based on the calculated adhesion amount and the diffuse reflection light toner adhesion amount conversion table corresponding to the prescribed toner particle size. A temporary correction value is calculated by calculating a ratio between the diffuse reflected light output value Vdif when the low adhesion amount toner patch is detected and the temporary target diffuse reflected light output value.

For example, the specified toner particle size is 0.01 [mm], the toner particle size used for creating the gradation pattern is 0.006 [mm], and the actual adhesion amount of the low adhesion toner patch is 1.8 [mm]. If it is g / m ² ], as shown in FIG. 9, the normalized regular reflection output value Vreg2 is 0.4. As a result, the toner adhesion amount calculated from the normalized regular reflection output value Vreg2 (0.4) and the regular reflection light toner adhesion amount conversion table corresponding to the prescribed toner particle size 0.01 [mm] is 3 [g / m ² ]. Therefore, as can be seen from FIG. 10, the target diffuse reflection light output value is 0.6. On the other hand, from the solid line in FIG. 10 (the relationship between the diffuse reflection light output value and the toner adhesion amount when the toner particle size is 0.06 [mm]) and the actual toner adhesion amount 1.8 [g / m ² ]. As can be seen, the diffuse reflected light output value Vdif when detecting a low adhesion amount toner patch is 0.5. As a result, the calculated temporary correction value is (0.6 / 0.5). Here, the explanation is made on the assumption that there is no fluctuation in the amount of emitted light, etc., and the actual diffuse reflected light output value Vdif is obtained by adding 0.5 to the amount of emitted light quantity fluctuation component, and is calculated temporarily. The correction value also has a light emission quantity fluctuation component added.

  As a result, the relationship between the diffusely reflected light output Vdif1 ′ after provisional correction and the actual toner adhesion amount is as shown by the dotted line in FIG. That is, if the prescribed toner particle size is 0.006 [mm], the relationship between the diffuse reflection light output Vdif1 after correction and the toner adhesion amount is the relationship shown by the solid line shown in FIG. It should be. However, when the prescribed toner particle size is different from 0.01 [mm] and the toner particle size used for forming the gradation pattern, the temporarily reflected light output Vdif1 ′ after the temporary correction and the toner adhesion amount The relationship is as shown by the dotted line in FIG.

  Next, the diffuse reflected light output Vdif1 ′ of the saturated toner patch after the temporary correction of Y color is calculated by multiplying the diffuse reflected light output Vdif of the saturated toner patch by the temporary correction value Ky. Similarly, the diffuse reflected light output Vdifc1 ′ of the saturated toner patch after the C color temporary correction and the diffuse reflected light output Vdifm1 ′ of the saturated toner patch after the M color temporary correction are calculated.

As shown in FIG. 12, in the particle size-independent region and the saturation region where the toner particle size does not affect the output value, the diffuse reflected light output and the toner when the toner particle size is 0.01 [mm] which is the specified toner particle size. It can be seen that the relationship between the adhesion amount and the relationship between the corrected reflected light output Vdif1 ′ after correction and the toner adhesion amount are greatly different depending on the temporary correction value. This is because the diffuse reflected light output does not change depending on the toner particle size in the particle size-independent region and the saturation region. That is, as shown in FIG. 10, if the toner adhesion amount is the same, the diffuse reflection output is obtained when the toner particle size is 0.006 [mm] and when the particle size is 0.01 [mm]. It becomes the same value. Accordingly, the relationship between the corrected diffuse reflected light output Vdif1 and the toner adhesion amount in the particle size-independent region and the saturated region should overlap the 0.01 mm line originally, but is included in the temporary correction value. The relationship between the diffusely reflected light output Vdif1 ′ after provisional correction and the toner adhesion amount does not overlap due to the toner particle size error component. Then, focusing on the saturation region as shown in FIG. 10, the diffuse reflected light output value is approximately 1.62 [V] regardless of the toner adhesion amount.
Therefore, the toner particle size can be estimated by examining how much the diffusely reflected light output Vdif1 ′ after the temporary correction is different from 1.62 [V]. If a table in which an output difference and a toner particle size are associated with each other by experimenting in advance is stored, the toner particle size can be easily estimated. Specifically, the toner particle size is estimated from the calculated output difference and a table.

  Such an output difference is obtained by diffusing reflected light output Vdif1 ′ of the saturated toner patch after provisional correction of Y color, diffusing reflected light output Vdifm1 ′ of the saturated toner patch after provisional correction of M color, and after provisional correction of C color. This is performed for the diffuse reflected light output Vdifc1 ′ of the saturated toner patch, and the Y color output difference, the M color output difference, and the C color output difference are respectively calculated. In this embodiment, since three saturated toner patches are created, an output difference is calculated for each saturated patch and averaged. Then, the Y toner particle size is estimated from the averaged Y color output difference and a table in which the output difference and the toner particle size are associated with each other. Similarly, the M toner particle size is estimated from the averaged M color output difference and a table in which the output difference and the toner particle size are associated with each other. The C toner particle size is estimated from the averaged C color output difference and a table in which the output difference is associated with the toner particle size.

  In the above description, the toner particle size is estimated by calculating the output difference. However, the toner particle size may be estimated from the ratio by calculating the ratio. Specifically, the ratio between 1.62 [V], which is a predetermined value obtained in advance through experiments, and the diffusely reflected light output Vdif1 ′ after provisional correction is calculated. Then, the toner particle diameter is estimated from a table in which the calculated ratio, the ratio obtained in advance by experiment, and the toner particle diameter are associated with each other.

  Further, the toner particle size may be calculated based on the diffusely reflected light output Vdif1 ′ after the temporary correction. That is, if the diffusely reflected light output Vdif1 ′ after provisional correction is 1.62 [V], it can be estimated that the toner particle diameter is 0.01 [mm], and the diffusely reflected light output Vdif1 ′ after provisional correction is obtained. If it is 1.94 [V], it can be estimated that the toner particle size is 0.006 [mm]. Further, if the diffusely reflected light output Vdif1 ′ after the temporary correction is between 1.94 and 1.62 [V], the toner particle diameter is between 0.006 and 0.01 [mm]. Is estimated.

  After the toner particle size is estimated in this way, correction values Ky, Km, and Kc for Y color, M color, and C color are recalculated. In the present embodiment, an adhesion amount conversion table corresponding to the toner particle size is stored in a memory such as a ROM that is a storage unit, and the corresponding adhesion amount conversion table is specified based on the estimated toner particle size. . Then, the correction values Ky, Km, and Kc are recalculated using the specified adhesion amount conversion table. For example, when the estimated toner particle size is 0.006 [mm], the diffuse reflected light output Vdif1 corrected with the normal correction value calculated using the adhesion amount conversion table corresponding to the estimated toner particle size and The relationship between the toner adhesion amount and the toner adhesion amount is the same as the relationship between the diffuse reflection light output Vdif1 having a particle diameter of 0.006 [mm] and the toner adhesion amount shown by the solid line in FIG.

  The diffuse reflected light output of each toner patch of the Y, M, and C gradation patterns is corrected with a normal correction value that has been recalculated. Based on the corrected diffuse reflected light output value Vdif1 and the estimated toner particle size. The adhesion amount of each toner patch is calculated based on the specified toner adhesion amount conversion table.

  Thereby, the adhesion amount of each toner patch in the Y, M, and C gradation patterns can be accurately calculated, and good image density adjustment can be performed over time from the initial use of the process unit.

  In the above description, the saturated toner patch is formed using Y, M, and C color toners. However, the saturated toner patch may be formed using one color. In this case, the secondary transfer roller 40 and the cleaning blade of the belt cleaning device 41 are separated from the intermediate transfer belt 36. After the first toner patch is formed, a second toner patch is formed at a predetermined timing, and is superposed on the first toner patch that has made one turn on the intermediate transfer belt. A similar operation is performed to superimpose the third layer toner patch on the two layer toner patch on the intermediate transfer belt. Thereby, a saturated toner patch made of a single color toner can be created. The saturated toner patch composed of this one color toner is detected by the optical sensor 69, and the toner particle size is estimated by the same method as described above. After the saturated toner patch is detected by the optical sensor 69, the cleaning blade is brought into contact with the intermediate transfer belt 36 to remove the saturated toner patch on the intermediate transfer belt, and then the secondary transfer roller 40 is brought into contact with the intermediate transfer belt 36. Let Thus, by making a saturated toner patch with one color, it is possible to estimate the toner particle size with higher accuracy.

FIG. 13 is a flowchart illustrating toner particle size estimation according to the first exemplary embodiment.
As shown in the drawing, first, a low-adhesion amount toner patch having a toner layer, which is a particle size-dependent toner patch, of less than one layer is formed on the intermediate transfer belt (S11) and detected by an optical sensor (S12). Next, a target diffuse reflection light detection value is calculated based on a regular reflection light detection value when a low adhesion amount toner patch is detected and an adhesion amount conversion table corresponding to a predetermined prescribed toner particle size ( S13). That is, the toner adhesion amount is calculated based on the specular reflection light detection value when the low adhesion amount toner patch is detected and the specular reflection light adhesion amount conversion table corresponding to a predetermined toner particle diameter determined in advance. The target diffuse reflection light detection value is calculated based on the applied toner adhesion amount and the diffuse reflection light adhesion amount conversion table corresponding to a predetermined toner particle diameter determined in advance. Next, a ratio (temporary correction value K) is calculated from the target diffuse reflection light detection value and the diffuse reflection detection value when the low adhesion amount toner patch is detected (S14).
Next, a saturated toner patch is created (S15) and detected by an optical sensor (S16). The diffuse reflected light detection value Vdif when the saturated toner patch is detected is multiplied by the ratio (provisional correction value K) (S17), and the particle size of the toner is estimated from the multiplied value (S18). Specifically, the toner particle size is estimated by comparing the diffuse reflection light detection value Vdif3 multiplied by the ratio (provisional correction value K) with the diffuse reflection light output value Vdif of the saturated toner patch stored in advance.

  In this printer, a toner patch for adjusting image quality is used as a low-adhesion-amount toner patch having a toner layer that is a particle size-dependent toner patch and having less than one toner layer. In the flow of FIG. 13, the saturated toner patch is created after calculating the temporary correction value K. However, it may be formed simultaneously with the low adhesion amount toner patch. Further, when there is a change in the light emission amount of the optical sensor, the regular reflection detection value is normalized by the method described in Patent Document 1 or Japanese Patent Application Laid-Open No. 2005-76885, and the normalized positive The target diffuse reflected light may be calculated based on the reflected light detection value Vreg2.

[Example 2]
Next, Example 2 will be described.
In the second embodiment, the adhesion amount of each toner patch of the gradation pattern is calculated using an adhesion amount conversion table corresponding to a prescribed toner particle size, and provisional image forming conditions (development bias, etc.) are set. . Then, a particle size-independent toner patch is formed under temporary image forming conditions, and the toner particle size is estimated based on the detected value of the particle size-independent toner patch.

First, a test pattern image Pt1 for toner adhesion amount detection as shown in FIG. 7 is formed on the intermediate transfer belt 36, and image density control is executed. At this time, a toner adhesion amount conversion table corresponding to a prescribed toner particle diameter is used for calculating the toner adhesion amount of each toner patch in the Y, M, and C color gradation patterns.
The prescribed toner particle size corresponding to the adhesion amount conversion table used for calculating the adhesion amount of each toner patch is 0.01 [mm], and the toner particle size used for creating the gradation pattern is 0.1. In the case of 006 [mm], the calculated toner adhesion amount is larger than the actual adhesion amount. As a result, the relationship between the actual toner adhesion amount and the development bias differs from the relationship between the calculated toner adhesion amount and the development bias. Accordingly, the influence of the toner particle size error appears in the provisional image forming conditions that are corrected so that a toner image having a desired image density can be formed from the relationship between the calculated toner adhesion amount and the developing bias.

When temporary image forming conditions are set in this way, three particle size-independent toner patches PT1, PT2, and PT3 are created on the intermediate transfer belt 36 based on the temporary image forming conditions. As shown in FIG. 10, the target adhesion amount of these particle size-independent toner patches varies depending on the toner adhesion amount, but the diffuse reflection light output Vdif does not change even if the particle size changes. The amount of adhesion of the non-dependent region is 6 to 12 [g / m ² ]. In this embodiment, the target adhesion amount of the particle size-independent toner patch is set to 9.0 [g / m ² ]. PT1 is formed by superimposing the M-color toner patch of the target coating weight 4.5 [g / ^{m 2],} a toner patch of Y color target coating weight ^{4.5 [g / m 2],} R It is a (red) color toner patch. PT2 is formed by overlaying the Y-color toner patch of the target coating weight 4.5 [g / ^{m 2],} a toner patch of C color target coating weight ^{4.5 [g / m 2],} G It is a (green) color toner patch. PT3 is formed by overlapping the C-color toner patch of the target coating weight 4.5 [g / ^{m 2],} a toner patch of the M color of the target coating weight ^{4.5 [g / m 2],} B (Blue) color toner patch.

If the prescribed toner particle size corresponding to the adhesion amount conversion table used when calculating the adhesion amount is the same as the toner particle size used for creating the gradation pattern, the provisional image forming condition is Since the toner image is correctly corrected so that a toner image having an image density can be formed, the toner adhesion amount of the particle size-independent toner patch formed under the provisional image forming conditions is the target adhesion amount. However, if the specified toner particle size corresponding to the adhesion amount conversion table used when calculating the adhesion amount is different from the toner particle size used to create the gradation pattern, the provisional image forming conditions The toner adhesion amount of the particle size-independent toner patch to be imaged is greatly deviated from the target adhesion amount.
As an example, the provisional image forming conditions are set such that the prescribed toner particle size is 0.01 [mm] and the toner particle size used to create the gradation pattern is 0.006 [mm]. Even if each color toner patch is imaged so that the target adhesion amount is 4.5 [g / m ² ], the actual adhesion amount is 3.0 [g / m ² ] that is (2/3) times that amount. It becomes. Therefore, the actual adhesion amount of the particle size-independent toner patch is 6.0 [g / m ² ].

As shown in FIG. 10, the diffuse reflected light output Vdif of the optical sensor when the adhesion amount (6 to 12 [g / m ² ]) of the particle size independent region is detected is affected by the toner particle size. Therefore, even when the toner particle size used in the particle size-independent toner patch is 0.01 [mm] or 0.006 [mm], the adhesion amount of the particle size-independent toner patch is small. If it is 9.0 [g / m ² ], it will be about 1.5 [V]. Further, when the adhesion amount of the particle size-independent toner patch is 6.0 [g / m ² ], even when the toner particle size is 0.01 [mm] or 0.006 [mm] The diffuse reflected light output value of the optical sensor is about 1.3 [V]. Therefore, even if the adhesion amount is calculated with the toner adhesion amount conversion table corresponding to the toner particle size 0.01 [mm], the adhesion amount is calculated with the toner adhesion amount conversion table corresponding to the toner particle size 0.006 [mm]. Even if is calculated, the same calculation result is obtained.

Therefore, the toner particle size can be estimated based on the toner adhesion amount calculated from the diffuse reflection light output Vdif of the particle size independent toner patch. That is, when the calculated toner adhesion amount is 9.0 [g / m ² ], it can be estimated that the toner particle size of the particle size-independent toner patch is 0.01 [mm]. If the calculated toner adhesion amount is 6.0 [g / m ² ], it can be estimated that the toner particle size of the particle size-independent toner patch is 0.006 [mm]. When the calculated toner adhesion amount is between 6.0 [g / m ² ] and 9.0 [g / m ² ], the toner particle size is 0.006 [mm] to 0.01 [mm]. It is estimated that the toner particle size is between.

Since the toner particle sizes of Y, M, and C colors are different, the adhesion amount error due to the toner particle size varies depending on the color. Therefore, the toner particle size of each color is obtained as follows. When the Y-color toner adhesion amount is Ty, the M-color toner adhesion amount Tm, and the C-color toner adhesion amount is Tc, the adhesion amount of each color can be obtained as follows.
Ty = (Tr + Tg−Tb) / 2
Tm = (Tb + Tr−Tg) / 2
Tc = (Tg + Tb-Tr) / 2
Tr is the toner adhesion amount of the particle size-dependent toner patch PT1, Tg is the toner adhesion amount of the particle size-dependent toner patch PT2, and Tb is the toner adhesion amount of the particle size-dependent toner patch PT3. is there.

From the toner adhesion amounts Ty, Tm, and Tc of each color, the toner particle size of each color can be obtained. That is, if the toner adhesion amount is 4.5 [g / m ² ] of the target adhesion amount, the toner particle size of this color can be estimated to be 0.01 [mm]. If the toner adhesion amount is 3.0 [g / m ² ], it can be estimated that the toner particle size of this color is 0.006 [mm]. Further, if the toner adhesion amount is between 3.0 and 4.5 [g / m ² ], it can be estimated that the toner particle size is between 0.006 and 0.01 [mm].

  If the toner particle size can be estimated in this way, the image forming conditions for Y, M, and C colors are reset using the adhesion amount conversion table corresponding to the estimated toner particle size. The diffuse reflection light output value when each toner patch of the Y, M, C color gradation pattern formed to estimate the toner particle size is detected is stored in the memory and specified based on the estimated toner particle size. The adhesion amount of each toner patch is recalculated using the toner adhesion amount conversion table corresponding to the estimated toner particle diameter. Since the calculated adhesion amount is calculated from the adhesion amount conversion table corresponding to the estimated toner particle size, the adhesion amount calculation result is highly accurate. Then, based on the calculated adhesion amount of each toner pattern, the image forming conditions are reset for each of the Y, M, and C colors. Thereby, a high quality image can be obtained.

FIG. 14 is a flowchart illustrating toner particle size estimation according to the second exemplary embodiment.
A gradation pattern composed of a plurality of toner patches for setting image forming conditions is created (S21) and detected by an optical sensor (S22). The toner adhesion amount of each toner patch of the gradation pattern is calculated based on the detection result of the gradation pattern and the adhesion amount conversion table corresponding to a predetermined specified toner particle size (S23). An image forming condition is set based on the calculated toner adhesion amount (S24), and a particle size-independent toner patch is created based on the set image forming condition (S25). Then, based on the toner adhesion amount of the particle size-independent toner patch, the toner particle size is estimated (S26).

  In this embodiment, a process unit that is a toner patch forming unit that forms a toner patch on an intermediate transfer belt that is an image carrier, and an optical sensor that is an optical detection unit that detects regular reflection light and diffuse reflection light from the toner patch And a controller serving as an adhesion amount calculating means for calculating the adhesion amount of the toner patch for calculating the adhesion amount of the toner patch based on the detected specular reflection light value and the diffuse reflection light detection value of the optical sensor. doing. According to this toner adhesion amount calculation device, a temporary correction value for correcting the diffuse reflected light output value is calculated using an adhesion amount conversion table corresponding to a prescribed toner particle diameter, and the saturated toner patch is placed on the intermediate transfer belt. The saturated toner patch is detected by an optical sensor, and the diffuse reflected light detection value of the saturated toner patch is corrected with a temporary correction value, and the diffuse reflected light detection value of the saturated toner patch obtained in advance by experiment is used. Based on this, the toner particle size is estimated. Thus, since the toner particle size of the toner used for forming the toner image can be estimated, the toner adhesion amount corresponding to the estimated toner particle size can be calculated. Thereby, it is possible to calculate the adhesion amount with high accuracy.

  Further, by specifying an adhesion amount conversion table corresponding to the estimated toner particle size and calculating the toner adhesion amount based on the specified adhesion amount conversion table and the detection result of the optical sensor, a highly accurate adhesion amount can be obtained. Calculations can be made.

  In addition, after estimating the toner particle size, the correction value is recalculated based on the adhesion amount conversion table corresponding to the estimated toner particle size, so that the diffuse reflected light output value corrected by the correction value is obtained. It can be a value with no error.

  Also, a normalization value is calculated based on the specular reflection light detection value when the surface of the intermediate transfer belt is detected, and the specular reflection detection value detected based on the calculated normalization value is normalized to thereby correct the normal reflection light detection value. The reflected light detection value can be set to a value obtained by removing the fluctuation of the light emitting element and the regular reflection light receiving element.

  In addition, according to the image forming apparatus of the present embodiment, it is possible to calculate the adhesion amount with high accuracy by including the above-described toner adhesion amount calculation device.

  In addition, according to the image forming apparatus of the present embodiment, temporary image forming conditions are set by executing image density control as image forming condition setting means using an adhesion amount conversion table corresponding to a prescribed toner particle size. Then, a particle size-independent toner patch is formed under temporary image forming conditions, and the toner particle size is estimated based on the toner adhesion amount calculated from the detection value of the particle size-independent toner patch of the optical sensor. Thereby, the toner particle diameter can be estimated.

  After estimating the toner particle size, an adhesion amount conversion table corresponding to the estimated toner particle size is specified, and image density control is executed using the specified adhesion amount conversion table, thereby performing highly accurate image density control. be able to. Thereby, a favorable image can be obtained.

  Further, since the particle size-independent toner patch is composed of one or more toner layers, the output value of the optical sensor does not vary depending on the particle size, and the toner particle size can be estimated.

  Further, by using an optical sensor that detects infrared light, it is possible to eliminate a significant difference in the reflectance by color. In addition, the particle diameter-independent toner patches are formed by superimposing a plurality of color toner images, whereby the toner diameters of the plurality of colors can be estimated.

The figure explaining the particle size dependence toner patch whose detection value of an optical detection means depends on a toner particle size. FIG. 6 is a view for explaining a particle size-independent toner patch in which a detection value of an optical detection unit does not depend on a toner particle size. 1 is a schematic configuration diagram of an electrophotographic printer as an image forming apparatus to which the present invention is applied. The expansion block diagram which shows the process unit for K. The schematic sectional drawing of an optical sensor. The block diagram which shows the principal part of an electric circuit. FIG. 5 is a schematic plan view showing a test pattern image for detecting the amount of toner adhesion formed on an intermediate transfer belt. FIG. 5 is a basic control flow diagram for calculating an adhesion amount of a color toner patch. The graph which showed the relationship between toner adhesion amount and the regular reflection light output of an optical sensor. The graph which showed the relationship between the toner adhesion amount and the diffused light output of an optical sensor. FIG. 5 is a schematic plan view showing three saturated toner patches formed after a test pattern image for detecting the toner adhesion amount. The graph which shows the relationship between the diffuse reflected light output Vdif after temporary correction | amendment, and the toner adhesion amount. 6 is a flowchart of toner particle size estimation according to the first exemplary embodiment. 10 is a flowchart of toner particle size estimation according to the second exemplary embodiment.

Explanation of symbols

1Y, M, C, K: Process unit 2Y, M, C, K: Photoconductor 5K: Developing device 36: Intermediate transfer belt 69: Optical sensor

Claims (12)

Toner patch forming means for forming a toner patch on the image carrier;
Optical detection means for detecting regular reflection light and diffuse reflection light from a toner patch formed on the image carrier,
In a toner adhesion amount calculation device for calculating an adhesion amount of a toner patch based on a regular reflection light detection value and a diffuse reflection light detection value of the optical detection unit,
Regular reflection light normalizing means for normalizing the regular reflection detection value;
In the toner patch forming unit, a particle size dependent toner patch whose detection value of the optical detection unit depends on a toner particle size is formed on an image carrier, and the particle size dependent toner patch is formed by the optical detection unit. A correction value for detecting and correcting the diffuse reflection detection value based on the normalized specular reflection detection value of the particle size-dependent toner patch and the adhesion amount conversion table corresponding to the toner particle size Correction value calculating means for calculating
A temporary correction value is calculated using an adhesion amount conversion table corresponding to a predetermined toner particle diameter determined in advance by the correction value calculating means, and the diffuse reflected light detection value of the optical detection means is calculated by the toner patch forming means. A saturated toner patch that does not depend on the toner particle size and adhesion amount is formed on the image carrier, the saturated toner patch is detected by the optical detection means, and the diffuse reflected light detection value of the saturated toner patch is corrected by the temporary correction value. And a toner particle size estimating means for estimating a toner particle size used for forming a toner image based on the diffuse reflection light detection value of the saturated toner patch obtained in advance through experiments. Adhesion amount calculation device. In the toner adhesion amount calculation apparatus according to claim 1,
Storage means for storing an adhesion amount conversion table for each toner particle diameter;
An adhesion amount conversion table corresponding to the toner particle size estimated by the toner particle size estimation unit is specified, and a toner adhesion amount is calculated based on the specified adhesion amount conversion table and the detection result of the optical detection unit. A toner adhesion amount calculating device. In the toner adhesion amount calculation device according to claim 2,
The correction value calculating unit specifies an adhesion amount conversion table corresponding to the toner particle size estimated by the toner particle size estimating unit after executing the toner particle size estimating unit, and based on the specified adhesion amount conversion table, A toner adhesion amount calculation device that recalculates a correction value. In the toner adhesion amount calculation device according to any one of claims 1 to 3,
The regular reflection light normalizing means calculates a normalization value based on the regular reflection detection value when the surface of the image carrier is detected, and calculates the regular reflection detection value detected based on the calculated normalization value. A toner adhesion amount calculating apparatus characterized by normalizing. In the toner adhesion amount calculating device according to any one of claims 1 to 4,
The toner particle amount calculation device according to claim 1, wherein the particle size dependent toner patch is a toner patch having a toner layer of less than one layer. Image forming means for forming toner images of a plurality of colors on the image carrier;
A toner adhesion amount calculating means for optically detecting a toner image on the image carrier and calculating an adhesion amount of the toner image;
An image forming apparatus comprising: a control unit that executes predetermined control using the toner adhesion amount of the toner image calculated by the toner adhesion amount calculation unit;
An image forming apparatus using the toner adhesion amount calculation device according to claim 1 as the toner adhesion amount calculation means. Image forming means for forming a toner image on the image carrier;
Optical detection means for detecting reflected light from the toner image on the image carrier;
An image quality adjustment pattern including a toner patch of at least a low adhesion amount is formed on the image carrier, and corresponds to a detection value and a toner particle size when the optical detection means detects the image quality adjustment pattern. An image forming apparatus comprising: an image forming condition setting unit configured to calculate a toner adhering amount of a toner patch in the image quality adjustment pattern based on the adhering amount conversion table and set an image forming condition based on the calculated toner adhering amount. In
The image forming condition setting unit is executed using an adhesion amount conversion table corresponding to a predetermined prescribed toner particle diameter, the temporary image forming condition is set, and the optical detection unit is diffused under the temporary image forming condition. A toner particle size estimation unit is provided that forms a particle size-independent toner patch whose reflected light detection value does not depend on the toner particle size, and estimates the toner particle size based on the toner adhesion amount of the particle size-independent toner patch. An image forming apparatus. The image forming apparatus according to claim 7.
Storage means for storing an adhesion amount conversion table for each toner particle diameter;
After executing the toner particle size estimating means,
An adhesion amount conversion table corresponding to the toner particle size estimated by the toner particle size estimation unit is specified, and the image forming condition setting unit is executed using the specified adhesion amount conversion table. Image forming apparatus. The image forming apparatus according to claim 7 or 8,
The toner adhesion amount calculation device, wherein the particle size independent toner patch is composed of one or more toner layers. The image forming apparatus according to any one of claims 6 to 9,
As the optical detection means, one that detects infrared light,
An image forming apparatus, wherein the particle size independent toner patch is formed by superimposing a plurality of color toner images. In the toner particle size estimation method for estimating the particle size of the toner,
Creating a particle size dependent toner patch in which the detection value of the optical detection means depends on the particle size;
Detecting the particle size-dependent toner patch with an optical detection means capable of detecting regular reflection light and diffuse reflection light;
A diffuse reflection detection value calculated based on a specular reflection detection value when a particle size dependent toner patch is detected, and an adhesion amount conversion table corresponding to a predetermined toner particle size determined in advance, and a particle size Calculating a ratio from the diffuse reflected light detection value when the dependency toner patch is detected;
Creating a saturated toner patch in which the diffuse reflected light detection value of the optical detection means does not depend on the toner particle size and adhesion amount;
Detecting a saturated toner patch with the optical detection means;
And a step of estimating the particle size of the toner from a value obtained by multiplying the detected value of the diffuse reflected light when the saturated toner patch is detected by the ratio. In the toner particle size estimation method for estimating the particle size of the toner,
Creating an image quality adjustment pattern composed of a plurality of toner patches for setting image forming conditions;
Detecting an image quality adjustment pattern with an optical detection means capable of detecting regular reflection light and diffuse reflection light; and
Calculating a toner adhesion amount of each toner patch of the image quality adjustment pattern based on a detection result of the image quality adjustment pattern and an adhesion amount conversion table corresponding to a predetermined prescribed toner particle diameter;
Setting image forming conditions based on the calculated toner adhesion amount;
A step of creating a particle size-independent toner patch based on the set image forming conditions, wherein the diffuse reflected light detection value of the optical detection means does not depend on the toner particle size;
And a step of estimating the particle size of the toner based on the toner adhesion amount of the particle size-independent toner patch.

Images