JP2008170578A - Device and method for adjusting toner density - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for adjusting toner density which enable toner density to be adjusted appropriately, by accurately detecting the density of a reference toner image formed on an image carrier means, regardless of the variations in sensor output due to the aging of the image carrier means or the variance in sensitivity of a sensor due to differences in devices. <P>SOLUTION: The device for adjusting toner density is equipped with an image density detection means of detecting the image density of a toner image that adheres to the image carrier means 51 to be transferred to a recording medium, and is so constituted that the position of the scanner pattern 100 of the image density detected by the image density detection means is the same position as that of an output pattern 101 detected by a toner density adjusting means 84. The device is equipped with a correction means to correct an output value from a toner density sensor 80 based on a difference between the image density detected by the image density detection means and the output value from the toner density sensor 80. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides a toner density that is provided in an image forming apparatus that transfers a toner image carried on an image carrying means to a recording medium, and that detects the density based on the amount of reflected light from a reference toner image carried on the image carrying means. The present invention relates to a toner density adjusting device and a toner density adjusting method including a sensor and toner density adjusting means for adjusting the density of the reference toner image to a predetermined density based on an output value of the toner density sensor.

  Conventionally, the toner image carrying unit is used as a toner adhesion amount measuring unit capable of accurately measuring the amount of toner carried on the toner image carrying unit regardless of the change in the surface state of the toner image carrying unit due to secular change or the like. A light projecting means for projecting a single polarized light at a predetermined inclination angle with respect to the normal direction of the means; and the toner image carrying means disposed on the opposite side of the light projecting means with respect to the normal direction. Polarized light separating means for separating the reflected light from the first polarized light same as the projected light and the second polarized light different from the projected light, and receiving the first and second polarized lights And a control means for determining the amount of toner adhesion on the toner image carrying means according to the difference between the first and second light receiving output signals. Yes.

The toner adhesion amount measuring unit has equal levels of the first and second light receiving output signals obtained when a predetermined amount of toner that does not generate reflected light from the surface adheres to the toner image holding means. The output levels of the first and second light receiving means are adjusted so that the first and second light receiving outputs obtained in a state where no toner adheres to the toner image holding means. Based on a value obtained by dividing a measured output value, which is a difference between the first and second received light output signals when the toner image is formed on the toner image holding unit, by the reference value, using the difference between the signals as a reference value. Thus, the corrected output value is obtained, and the toner adhesion amount of the toner image carrying means is obtained based on the corrected output value.
JP 2004-177608 A

  However, even if the technique described in Patent Document 1 described above is adopted, it cannot be sufficiently corrected when the roughness due to the surface wear of the toner carrying means increases, and the sensitivity decreases as shown in FIG. There was a problem. If the toner adhesion amount, that is, the toner density, is corrected based on the toner adhesion amount measured by the toner adhesion amount measuring unit, there is a problem that the image is overcorrected and the overall contrast is high and the gradation property is low. It was. In addition, there is room for further improvement in terms of further improving control accuracy because variations in sensitivity of each sensor constituted by the light projecting means and the light receiving means and variations due to machine differences are not sufficiently absorbed.

  Further, in Patent Document 1 described above, the toner density is corrected based on the output value of the toner density sensor. However, the output value detected by the toner density sensor and the image carrying means transferred to the recording medium are used. The toner density value detected by the image density detecting means for detecting the image density of the attached current toner image is not measured in the same process and at the same location, and thus uneven charging in development and uneven laser power. In other words, the correlation could not be correctly confirmed, and accurate adjustment could not be performed.

  An object of the present invention is to provide a density of a reference toner image formed on an image carrying unit regardless of fluctuations in sensor output due to aging or sensor sensitivity variations due to machine differences in view of the above-mentioned conventional drawbacks. The present invention provides a toner density adjusting device and a toner density adjusting method capable of accurately detecting the toner density and adjusting the density appropriately.

  In order to achieve the above-mentioned object, the first characteristic configuration of the toner density adjusting device according to the present invention is that the toner image carried on the image carrying means is recorded on the recording medium as described in claim 1 of the claims. A toner density sensor that is provided in an image forming apparatus that transfers to a toner image and detects density based on the amount of reflected light from a reference toner image carried on the image carrying means; and the reference toner based on an output value of the toner density sensor A toner density adjusting device comprising toner density adjusting means for adjusting an image density to a predetermined density, wherein the current toner image attached to the image carrying means transferred to the recording medium Image density detecting means for detecting image density is provided, and the position of the scanner pattern of the image density detected by the image density detecting means is detected by the toner density adjusting means. And a correction unit configured to correct the output value of the toner density sensor based on the image density detected by the image density detection unit and the output value of the toner density sensor. It is in.

  According to the above configuration, when the density detecting unit detects the image density of the current toner image attached to the image carrying unit transferred to the recording medium, the scanner pattern as a detection position is the toner density output sensor. Is measured at the same position as the output position for detecting the density, and the correction means corrects the output value from the difference between the density detected by the density detection means and the output value output by the toner density sensor. The output value of the toner density sensor can be accurately corrected.

  The second characteristic configuration is that, as described in the second aspect, the circumferential length of the developing roller disposed in the vicinity of the image carrying means becomes an asynchronous pattern in the sub-scanning direction.

  According to the above configuration, when the vertical direction of the paper surface is the sub-scanning direction and the horizontal direction of the paper surface is the main scanning direction, the circumferential length of the developing roller is made asynchronous so that the toner density sensor in the sub-scanning direction. Even if the detected image density is irregular and the image forming unit has development unevenness that occurs periodically, the influence can be reduced.

  In order to achieve the above-mentioned object, a first characteristic configuration of the toner density adjusting method according to the present invention is that the toner image carried by the image carrying means is recorded on the recording medium as described in claim 3 of the claims. A toner density step for detecting density based on the amount of reflected light from a reference toner image carried on the image carrying means, and the reference toner based on an output value of the toner density step. A toner density adjustment method comprising a toner density adjustment step for adjusting an image density to a predetermined density, wherein the image density of the reference toner image transferred and fixed to the recording medium is detected. An image density detecting step for detecting a scanner pattern of the image density detected by the image density detecting step by the toner density adjusting step. It is configured to be the same pattern as the output pattern for measuring the output value lies in that the image density on the basis of the image density detected by the detecting step comprises a step of correcting an output value of the toner density sensor.

  As described above, according to the present invention, the density of the reference toner image formed on the image carrier means can be accurately determined regardless of the sensor output fluctuation due to secular change or the sensor sensitivity variation due to machine differences. Therefore, it is possible to provide a toner concentration adjusting device and a toner concentration adjusting method that can detect and appropriately adjust the concentration.

  Hereinafter, an embodiment in which a toner density adjusting device and a toner density adjusting method according to the present invention are applied to a tandem type digital multi-function peripheral will be described.

  As shown in FIG. 3, the digital multi-function peripheral includes a color CCD 10, an image reading unit 1 that reads a document image by photoelectric conversion, and gradations for image data of RGB components read by the image reading unit 1. Image processing unit 2 that performs image processing such as conversion, color adjustment, magnification conversion, and the like, and converts it into output image data using each component of YMCK, and each color component of YMCK based on the output image data converted by image processing unit 2 An image forming unit 3 for forming a toner image, a paper feeding unit 4 for supplying a sheet as a recording medium to the image forming unit 3, a transfer unit 5 for transferring the toner image to the fed paper, and a toner image The image forming apparatus includes a fixing unit 6 that fixes the recording medium on which the toner is transferred, and a control unit 7 that includes a microcomputer that controls them.

  As shown in FIG. 1, the image forming unit 3 is arranged in M (magenta), C (cyan), Y (yellow), and K (black) colors arranged along a transfer belt 51 as an image carrier. Each of the photosensitive units 30 includes a charging charger 32, an exposure head 33, a developing roller 34, a cleaner 35, a static elimination lamp 36, and the like along the circumferential direction of the photosensitive body 31. Has been.

  When the photosensitive member 31 whose surface is uniformly charged by the charging charger 32 is scanned and exposed by the exposure head 33 driven based on image data, an electrostatic latent image corresponding to the image data is formed on the surface. Is done. After the toner image attached to the electrostatic latent image by the developing roller 34 is first transferred onto the transfer belt 51, the residual toner on the surface of the photoreceptor 31 is removed by the cleaner 35, and the charge removal The image forming process of being erased by the lamp 36 is repeated.

  The developing roller 34 is filled with toners of M (magenta), C (cyan), Y (yellow), and K (black). For example, a photosensitive unit in which the developing roller 34 of M (magenta) is set. In the configuration 30, an M component toner image that is scanned and exposed based on the M component image data is formed.

  The transfer unit 5 includes an endless transfer belt 51 supported by three rollers 50, a plurality of transfer rollers 52 and 53 disposed in contact with the transfer belt 51, a cleaner 54, and the like. . Each of the M (magenta), C (cyan), Y (yellow), and K (black) toner images formed by the photoconductor unit 30 is applied to the transfer roller 52 by the action of a transfer voltage. The image is primarily transferred onto the paper 51 and secondarily transferred onto the paper fed from the paper feed unit 4 by the action of a transfer voltage applied to the transfer roller 53. After the secondary transfer, the toner remaining on the transfer belt 51 is removed by the cleaner 54.

  The density of each color is detected based on the amount of reflected light from the reference toner image of each color carried on the transfer belt 51 so that the density of the toner image formed by the image forming unit 3 is maintained at a predetermined density. A toner density sensor 80 and toner density adjusting means 84 for adjusting the density of the reference toner image to a predetermined density based on the output value of the toner density sensor 80 are provided.

  The toner density sensor 80 is arranged on the downstream side of the photoconductor unit 30 arranged along the rotation direction of the transfer belt 51. More specifically, as shown in FIG. 4, the toner density sensor 80 includes a light projecting unit 81 that projects a single polarized light at a predetermined inclination angle with respect to the normal direction of the transfer belt 51, and A first polarized light that is disposed on the opposite side of the light projecting unit 81 with respect to the normal direction and that reflects light from the transfer belt 51 is the same as the projected light and a second polarized light that is different from the projected light. A polarization separation unit 82 that separates light into light and a first and second light receiving unit 83 that receive the first and second polarized light are configured.

  The toner density sensor 80 has equal levels of the first and second light receiving output signals obtained when a predetermined amount of toner is attached to such an extent that no reflected light from the surface of the transfer belt 51 is generated. The output levels of the first and second light-receiving portions 83 are adjusted so that the toner density adjusting means 84 is configured so that the first and second toner images when the reference toner image is formed on the transfer belt 51 are adjusted. The measured output value, which is the difference between the two received light output signals, is divided by the reference value, which is the difference between the first and second received light output signals obtained without toner adhering to the transfer belt 51. The value is calculated as a toner density value.

  That is, the toner density value is 1 when the surface of the transfer belt 51 where the reference toner image is not formed is detected, and the toner density value becomes lower as the density of the reference toner image becomes higher.

  For example, the control unit 7 turns on the reference toner image formed in the image forming unit 3 at a predetermined time before the warm-up is completed when the power switch of the apparatus is turned on and a normal image forming process is possible. Control is performed so that the toner image is transferred to the transfer belt 51, and the toner density adjusting means 84 is caused to execute a toner density adjusting operation.

  As shown in FIG. 5, the reference toner image is formed on the basis of a plurality of test patch data representing a preset gradation pattern of 8 to 10 gradations output from the image processing unit 2. A plurality of test patches 20 formed by the section 3 are composed of a plurality of toner images having different gradations transferred to the transfer belt 51, and the toner density adjusting unit 84 is read by the toner density sensor 80. The toner density value is obtained from the reflection density of each test patch 20, and the density of the toner image formed by the image forming unit 3, that is, the toner adhesion amount is determined so that the toner density value is maintained at a predetermined density value. adjust. The toner density sensor 80 is configured to detect the position of the scanner pattern 100 which is the same location as the image density detecting means for detecting the image density of the fixed reference toner image.

  More specifically, the toner density adjusting unit 84 adjusts the developing bias of the developing roller 34 so that the toner density with respect to the test patch 20 becomes a predetermined density, and when the developing bias cannot be adjusted, for example, the image processing unit In step 2, the tone conversion table data for density adjustment is rewritten.

  The gradation conversion table is a look-up table for numerically converting the input image data so that the output image data can ensure a desired gradation, and has gradation characteristics as shown in FIG. is there. The toner density adjusting unit 84 corrects the table data so that the gradient of the gradation characteristic is increased when the detected density by the toner density sensor 80 is low, that is, the toner density is increased, and when the detected density is high. The table data is corrected so that the gradient of the gradation characteristic is small, that is, the toner density is low.

  Thus, by adjusting the toner density value for the test patch 20 to a predetermined density by the toner density adjusting means 84, an image with a constant quality can be formed in a normal image forming process. However, if the surface state changes due to the occurrence of abrasion or scratches on the surface of the transfer belt 51 due to repeated execution of the image forming process, the density detected by the toner density sensor 80 fluctuates, and an accurate toner density value is obtained. Cannot be obtained. The final output image density is improperly adjusted due to machine differences including variations in the toner density sensor 80, variations in the components of the image forming unit 3 and the transfer unit 5 and assembly errors. There is also a fear.

  Therefore, the toner density adjusting unit 84 detects the image density of the fixed reference toner image, and the output of the toner density sensor 80 based on the image density detected by the image density detecting unit. Correction means for correcting the toner density value obtained from the above. The image density detecting means is configured to detect the density in the output pattern 101 at the same position as the scanner pattern 100 detected by the toner density sensor 80.

  The control unit 7 determines a predetermined time when it is determined that the toner density cannot be accurately detected based on the amount of light reflected from the surface of the transfer belt 51 by the toner density sensor 80, that is, the toner density cannot be detected accurately. The amount of reflected light from the surface of the transfer belt 51 detected by the toner density sensor 80 when the toner density adjusting unit 84 is operated, here, the output value of either the first or second light receiving unit 83 described above is used. Control is performed so as to shift to a setup mode in which the test patch 20 formed on the transfer belt 51 is transferred to and fixed on a sheet and output when the reflected light amount detected in the initial stage is attenuated by a certain level.

  Note that a specific determination method for shifting to the setup mode is not limited to the above-described method, and for example, the first method obtained in a state where toner is not attached to the surface of the transfer belt 51. The difference between the first and second received light output signals may be shifted when a certain percentage of the initial value is attenuated relative to the initial value, and a sensor for detecting the roughness of the surface of the transfer belt 51 is provided separately. A transition may be made when it is determined that the roughness detected by the sensor exceeds a certain range with respect to the initial value.

  When a sheet on which a test patch 20 is printed as shown in FIG. 7 in the setup mode is set on the original reading unit 1 by an operator and a start switch of an operation unit (not shown) is pressed, the original reading unit 1 The test patch 20 is read, and the image processing unit 2 calculates the density of the region of the output pattern 101 that is a region corresponding to the test patch 20. That is, the document reading unit 1 and the image processing unit 2 constitute the image density detection unit.

  The correcting means includes appropriate image density data to be detected by the image density detecting means for the test patch 20 having an appropriate density printed on a sheet, and the toner density sensor 80 corresponding to the appropriate image density data. The toner density value obtained by the toner density sensor 80 for the same test patch 20 is previously provided with a relation table as shown by the solid line in FIG. It is determined whether or not the value and the image density value detected by the image density detecting means satisfy the correlation shown in the relation table. If the relation is shifted as shown by the broken line in FIG. Correction data for calibrating the toner density value based on the toner density sensor 80 so as to be maintained is generated.

  For example, as shown in FIG. 8, when the toner density value is detected as Dt, the detected image density value must be Dd in a predetermined relationship. However, the toner density value may be detected as Dt when the detected image density value is Dd1, or the toner density value may be detected as Dt when the detected image density value is Dd2. That is, when the toner density value is Dt, the toner density is low when the detected image density value is Dd1, and when the detected image density value is Dd2, the toner density is high.

  Therefore, when the detected image density value is Dd1, correction data is generated so that the toner density value is corrected downward to Dt1 that should be detected, and when the detected image density value is Dd2, the toner density value is changed. By generating correction data that upwardly corrects the toner density value at Dt2 that should be detected, the toner density with respect to the toner density value is corrected to a predetermined density.

  Here, the image densities of the respective colors M (magenta), C (cyan), Y (yellow), and K (black) detected by the image density detection unit with respect to the test patch 20 are R (red) and G (green). ) And B (blue) color component data, the G (green) component that is a complementary color as the pattern density of M (magenta), and the R (red) component that is a complementary color as the pattern density of C (cyan), B (blue), which is a complementary color, is referred to as a Y (yellow) pattern density, and a G (green) component is referred to as a K (black) pattern density, and image density data is calculated based on these values.

  The correction means generates the correction data based on the image density of the test patch 20 detected by the image density detection means and the relation table.

  Thereafter, the toner density adjusting unit 84 adjusts the toner density based on a calibration toner density value obtained by calibrating the toner density value obtained by the toner density sensor 80 based on the correction data.

  Thereafter, the amount of reflected light from the surface of the transfer belt 51 detected in the setup mode is set as an initial value, and the amount of reflected light from the surface of the transfer belt 51 detected when the toner density adjusting unit 84 is operated is attenuated by a certain level. Repeat the transition to setup mode.

  Note that the time to shift to the setup mode is a predetermined time set in advance, for example, a maintenance time such as when the cumulative number of copies has reached a predetermined number or when the cumulative operation time has reached a predetermined time, or by a service person. It may be during any maintenance.

  That is, in an image forming apparatus for transferring a toner image carried on an image carrying unit to a recording medium, a toner density detecting step for detecting a density based on a reflected light amount from a reference toner image carried on the image carrying unit; A toner density adjustment method comprising a toner density adjustment step for adjusting a density of the reference toner image to a predetermined density based on an output value of a sensor detected in the toner density detection step, An image density detecting step for detecting an image density of the reference toner image transferred and fixed to the recording medium, and an output value of the toner density sensor is corrected based on the image density detected by the image density detecting step. A toner density adjustment method including a correction step is realized.

  Another embodiment will be described below. In the above-described embodiment, the operator sets the sheet on which the test patch 20 is printed in the setup mode on the document reading unit 1. However, as shown in FIG. It is also possible to provide a path for transporting the paper on which the image is printed to the document reading unit 1, and automatically transport the sheet by the control unit 7 to read the image density of the test patch 20.

  In the embodiment described above, the toner density adjusting means 84 for adjusting the toner density projects the single polarized light at a predetermined inclination angle with respect to the normal direction of the transfer belt 51, and A first polarized light that is disposed on the opposite side of the light projecting unit 81 with respect to the normal direction and that reflects light from the transfer belt 51 is the same as the projected light and a second polarized light that is different from the projected light. The toner concentration sensor 80 including a polarization separation unit 82 that separates light into light and first and second light receiving units 83 that receive the first and second polarized light, and the toner concentration sensor 80. The first and second light receiving output signals obtained when a predetermined amount of toner that does not generate reflected light from the surface of the transfer belt 51 is attached are equal in level. 1 and the output level of the second light receiving unit 83 is adjusted. Then, the toner density adjusting unit 84 outputs a measured output value, which is a difference between the first and second light receiving output signals when the reference toner image is formed on the transfer belt 51, on the transfer belt 51. A value obtained by dividing by a reference value which is a difference between the first and second light receiving output signals obtained when no toner is attached to the toner is calculated as a toner density value, and is corrected by a correction means provided in the toner density adjusting means. The toner density value is corrected, but the toner density adjusting method performed by the toner density adjusting means is not limited to this.

  For example, as described in Japanese Patent No. 2729976, the present invention includes a light projecting unit 81 that projects a single polarized light at a predetermined inclination angle with respect to the normal direction of the transfer belt 51, and A first polarized light that is disposed on the opposite side of the light projecting unit 81 with respect to the normal direction and that reflects light from the transfer belt 51 is the same as the projected light and a second polarized light that is different from the projected light. In the toner concentration sensor 80, which includes a polarization separation unit 82 that separates light into light and a first and second light receiving unit 83 that receive the first and second polarized light, the first and second The difference between the two received light output signals may be obtained and the difference value may be corrected.

  Further, the toner density sensor provided in the toner density adjusting means may use visible light, and may obtain a toner density value using an individual color sensor having a spectral sensitivity characteristic of YMCK. The toner density may be corrected based on the toner density value obtained by the color sensor.

  In the above-described embodiment, the image carrying unit is configured by the transfer belt 51. However, the image carrying unit is not limited to such a configuration, and may be configured by a transfer drum. In this case, the image forming unit includes a single photoconductor unit in which developing rollers of M (magenta), C (cyan), Y (yellow), and K (black) are arranged around a single photoconductor. Consists of.

  In the above-described embodiment, the case where the toner density adjusting device according to the present invention is applied to a digital multi-function peripheral provided with the image reading unit 1 has been described. In this case, each density of the test patch 20 printed on the paper is measured by an image density measuring device including a scanner, a reflection densitometer, and the like, and the measurement data is input to the correction unit. Also good. What is necessary is just to comprise suitably what inputs as electronic data via a handy terminal or a network, what inputs via an operation panel, etc. as an input form.

  The above-described embodiments are merely examples of the present invention, and the scope of the present invention is not limited by the description, and the specific configuration of each part is appropriately changed within the scope of the effects of the present invention. It goes without saying that it can be done.

Explanatory diagram of the image forming unit Detection characteristics of toner density on the transfer belt Longitudinal explanatory diagram showing the schematic configuration of a digital multifunction device Illustration of toner density sensor Illustration of the test patch transferred onto the transfer belt Characteristic chart of gradation conversion lookup table Illustration of the paper on which the test patch is printed Graph showing correlation between detected image density value and toner density value Longitudinal explanatory diagram showing a schematic configuration of a digital multi-function peripheral according to another embodiment

Explanation of symbols

1: Image reading unit 3: Image forming unit 20: Test patch 30: Photoreceptor unit 31: Photoreceptor 32: Charging charger 33: Exposure head 34: Developing roller 35: Cleaner 36: Static elimination lamp 5: Transfer unit 51: Transfer belt 52, 53: transfer roller 80: toner density sensor 84: toner density adjusting means 81: light projecting section 82: polarization separating section 83: light receiving section

Claims (3)

A toner density sensor provided in an image forming apparatus for transferring a toner image carried on an image carrying unit to a recording medium, and detecting a density based on a reflected light amount from a reference toner image carried on the image carrying unit; A toner density adjusting device comprising toner density adjusting means for adjusting the density of the reference toner image to a predetermined density based on an output value of a toner density sensor;
Image density detecting means for detecting the image density of the current toner image attached to the image carrying means transferred to the recording medium, and the position of the scanner pattern of the image density detected by the image density detecting means is It is configured to be in the same position as the output pattern detected by the toner density adjusting means, and corrects the output value of the toner density sensor based on the image density detected by the image density detecting means and the output value of the toner density sensor. A toner density adjusting device comprising correction means for performing   The toner density adjusting device according to claim 1, wherein the circumferential length of the developing roller disposed in the vicinity of the image carrying unit is an asynchronous pattern in the sub-scanning direction. A toner density step provided in an image forming apparatus for transferring a toner image carried on an image carrying means to a recording medium, and detecting a density based on a reflected light amount from a reference toner image carried on the image carrying means; A toner density adjustment method comprising a toner density adjustment step for adjusting the density of the reference toner image to a predetermined density based on an output value of a toner density step,
An image density detecting step for detecting an image density of the current toner image attached to the image carrying step transferred to the recording medium, and the position of the scanner pattern of the image density detected by the image density detecting step is It is configured to be at the same position as the output pattern detected by the toner density adjustment step, and the output value of the toner density sensor is corrected based on the image density detected by the image density detection step and the output value of the toner density sensor A toner density adjustment method including a correction step.