JP2019020457A - Image forming apparatus - Google Patents

Abstract

To obtain an image forming apparatus that prevents a reduction in image quality of a print caused by partial contact of a cleaning device that removes a toner image for calibration.SOLUTION: A cleaning device 11 is in contact with part of an intermediate transfer belt 4 in a main scanning direction and removes a toner image for calibration passing through a detection position for a density sensor 8 from the intermediate transfer belt 4. A density correction unit 42 performs correction of the density of a toner image for printing in the main scanning direction. In particular, the density correction unit 42 changes the strength of the density correction in a range where the cleaning device 11 is in contact with the intermediate transfer belt 4 according to the number of times of calibration.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus.

  An electrophotographic image forming apparatus forms a calibration toner image (so-called toner patch) on an intermediate transfer belt, measures the density of the toner patch with a density sensor, and adjusts the toner density, toner gradation, and the like. Is going.

  In some image forming apparatuses, such a toner patch is removed from the intermediate transfer belt by a cleaning roller before the secondary transfer roller. The cleaning roller is configured to partially contact the intermediate transfer belt at a toner patch passing position in the main scanning direction (see, for example, Patent Document 1).

  FIG. 5 is a diagram illustrating an example of a position where the toner patch is carried on the intermediate transfer belt. FIG. 6 is a diagram illustrating another example of a position where the toner patch is carried on the intermediate transfer belt. FIG. 7 is a diagram illustrating still another example of the position where the toner patch is carried on the intermediate transfer belt. For example, as shown in FIGS. 5 to 7, the toner patch is arranged avoiding the toner object (that is, the printing toner image) in the print image area. In the example shown in FIG. 7, a toner patch is arranged outside the print image area in the main scanning direction. In the example shown in FIG. 5 and FIG. 6, it extends over the rear end portion (the portion where there is no toner object) of the print image region of a page and the front end portion (portion where there is no toner object) of the print image region of the next page. Thus, a toner patch is formed.

  In particular, in the example shown in FIG. 6, since the toner object and the toner patch are arranged in parallel along the sub-scanning direction, a lot of toner patches can be formed. In this way, the cleaning roller comes into contact with only a part in the main scanning direction.

JP 2010-266536 A

  However, as described above, since the cleaning roller that removes the calibration toner image is in contact with only a part of the intermediate transfer belt in the main scanning direction, the state change of the surface of the intermediate transfer belt due to use is the main scanning. Not uniform in direction. For this reason, the secondary transfer rate and the like are not uniform in the main scanning direction, and the image quality of the printed matter is deteriorated.

  The present invention has been made in view of the above problems, and an object of the present invention is to obtain an image forming apparatus that suppresses deterioration in image quality of a printed matter caused by partial contact of a cleaning device that removes a calibration toner image. .

  An image forming apparatus according to the present invention includes an intermediate transfer belt that carries a calibration toner image, a density sensor that detects a density of the calibration toner image that passes a predetermined position, and the intermediate transfer belt in a main scanning direction. A cleaning device that removes the calibration toner image that has passed through the predetermined position from the intermediate transfer belt, and a density correction unit that performs density correction of the printing toner image in the main scanning direction. Prepare. The density correction unit changes the intensity of the density correction in a range where the cleaning device contacts the intermediate transfer belt in the main scanning direction according to the number of calibrations.

  According to the present invention, it is possible to obtain an image forming apparatus that suppresses deterioration in image quality of a printed matter due to partial contact of a cleaning device that removes a calibration toner image.

  These and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of the cleaning device 11 in FIG. FIG. 3 is a block diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a diagram illustrating an example of density correction executed by the density correction unit 42 in FIG. FIG. 5 is a diagram illustrating an example of a position where the toner patch is carried on the intermediate transfer belt. FIG. 6 is a diagram illustrating another example of a position where the toner patch is carried on the intermediate transfer belt. FIG. 7 is a diagram illustrating still another example of the position where the toner patch is carried on the intermediate transfer belt.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in FIG. 1 is an apparatus having an electrophotographic printing function, such as a printer, a facsimile machine, a copying machine, or a multifunction machine.

  The image forming apparatus of this embodiment has a tandem color developing device. The color developing device includes photosensitive drums 1a to 1d, exposure devices 2a to 2d, and developing devices 3a to 3d for the respective colors. The photoconductor drums 1a to 1d are four-color photoconductors of cyan, magenta, yellow, and black. The exposure apparatuses 2a to 2d are apparatuses that form electrostatic latent images by irradiating the photosensitive drums 1a to 1d with laser light. The exposure apparatuses 2a to 2d have a laser diode that is a light source of laser light, and optical elements (lenses, mirrors, polygon mirrors, etc.) that guide the laser light to the photosensitive drums 1a to 1d, on the photosensitive drums 1a to 1d. Are irradiated with light to form electrostatic latent images on the photosensitive drums 1a to 1d.

  The developing devices 3a to 3d are equipped with toner containers filled with toners of four colors, cyan, magenta, yellow and black. A developing bias is applied to each of the developing devices 3a to 3d, and the developing devices 3a to 3d are supplied from the toner containers based on the respective potential differences between the developing devices 3a to 3d and the photosensitive drums 1a to 1d. A toner image is formed by attaching toner to the electrostatic latent images on the photosensitive drums 1a to 1d. For example, when a two-component developer is used, the toner is stirred together with the carrier in the developing devices 3a to 3d.

  The photosensitive drum 1a, the exposure device 2a, and the developing device 3a develop magenta, and the photosensitive drum 1b, the exposure device 2b, and the developing device 3b develop cyan, the photosensitive drum 1c, and the exposure device 2c. The developing device 3c performs yellow development, and the photosensitive drum 1d, the exposure device 2d, and the developing device 3d perform black development.

  The intermediate transfer belt 4 is an image carrier that carries a toner image transferred from the photosensitive drums 1a to 1d, and is an endless (that is, annular) intermediate transfer member. The intermediate transfer belt 4 is stretched around the driving roller 5 and circulates in the direction from the contact position with the photosensitive drum 1d to the contact position with the photosensitive drum 1a by the driving force from the driving roller 5.

  The intermediate transfer belt 4 carries a printing toner image based on user-desired image data during printing, and carries a calibration toner image within a predetermined range in the main scanning direction during calibration.

  The secondary transfer roller 6 brings the conveyed paper into contact with the intermediate transfer belt 4 and secondarily transfers the toner image on the intermediate transfer belt 4 to the paper. The sheet on which the toner image has been transferred is conveyed to the fixing device 9 and the toner image is fixed on the sheet.

  The cleaning device 7 has a cleaning roller, and the cleaning roller is brought into contact with the intermediate transfer belt 4 to remove the toner remaining on the intermediate transfer belt 4 after the secondary transfer of the toner image onto the paper. The cleaning device 7 may use a cleaning blade instead of the cleaning roller.

  The density sensor 8 is a reflection type optical sensor that detects toner on the intermediate transfer belt 4 and irradiates the intermediate transfer belt 4 with light in order to detect the density of the calibration toner image at the time of calibration or the like. The reflected light is detected. At the time of calibration, the density sensor 8 irradiates light to a predetermined region through which a calibration toner image (toner patch group) formed on the intermediate transfer belt 4 passes, and detects reflected light of the light. An electric signal corresponding to the detected light amount is output.

  The density sensor 8 is arranged at a calibration toner image passage position in the main scanning direction, and detects the density of the calibration toner image passing through the position.

  The cleaning device 11 is disposed between the density sensor 8 and the secondary transfer roller 6, and a part of the intermediate transfer belt 4 (that is, a printing toner image) in the main scanning direction during calibration by a moving mechanism (not shown). The calibration toner image that has passed through the detection position of the density sensor 8 is removed from the intermediate transfer belt 4. This eliminates the need for secondary transfer of the calibration toner image. That is, the calibration toner image is formed within the transferable range by the secondary transfer roller 6 in the main scanning direction, but is removed by the cleaning device 11.

  The cleaning device 11 includes a contact member 11a such as a roller, a blade, or a brush, and the contact member 11a contacts the intermediate transfer belt 4 by a moving mechanism (not shown). In the main scanning direction, the length of the contact member 11a is equal to or larger than the width of the calibration toner image and smaller than the width of the print image area (maximum width of the print toner image). Note that a predetermined number of toner patch arrays along the sub-scanning direction are formed as calibration toner images. The number of contact members 11a is the same as the number of calibration toner images arranged in the main scanning direction (that is, the number of toner patch rows).

  FIG. 2 is a diagram illustrating an example of the cleaning device 11 in FIG. The cleaning device 11 shown in FIG. 2 includes a cleaning roller 21, and the cleaning roller 21 includes two cylindrical contact members 11a. The calibration toner image 101 that has passed the detection position of the density sensor 8 is removed by the contact member 11a. The toner removed by the contact member 11a is recovered from the contact member 11a and discarded by a recovery mechanism (not shown).

  FIG. 3 is a block diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention.

  The image forming apparatus according to this embodiment includes a printing apparatus 31 having a mechanical configuration as shown in FIGS. 1 and 2, a controller 32, a moving mechanism driving unit 33 such as a motor for driving the above-described moving mechanism, and the like. Is provided.

  The controller 32 controls a developing source and a transfer source (not shown) for driving the roller and the like, a bias circuit for applying a primary transfer bias, developing devices 3a to 3d, and exposure devices 2a to 2d. And fixing, feeding, printing, and paper discharge are executed. The primary transfer bias is applied between the photosensitive drums 1 a to 1 d and the intermediate transfer belt 4. The controller 32 includes, for example, a computer that operates according to a control program, an ASIC (Application Specific Integrated Circuit), and the like, and operates as various processing units. In this embodiment, the controller 32 operates as a calibration processing unit 41 and a density correction unit 42.

  The calibration processing unit 41 performs calibration processing (adjustment of toner maximum density and toner halftone density gradation) periodically or at a predetermined timing.

  The density correction unit 42 performs density correction so that the density characteristics of the printing toner image are constant in the main scanning direction.

  For example, due to the optical characteristics of the exposure devices 2a to 2d, even if exposure is performed with a constant light amount in the main scanning direction, a constant toner density is not obtained. Therefore, the density correction unit 42 performs density correction according to the position in the main scanning direction.

  The density correction unit 42 performs density correction by correcting the value of the image data or correcting the level of the driving signal of the light source of the exposure devices 2a to 2d (that is, correcting the exposure light amount).

  The density correction unit 42 is arranged in the main scanning direction in accordance with the number of calibrations from the start point of use of the intermediate transfer belt 4 (that is, when the image forming apparatus is shipped or when the intermediate transfer belt 4 is replaced). The intensity of density correction in the range (hereinafter referred to as additional correction range) in which the contact member 11a) contacts is changed.

  FIG. 4 is a diagram illustrating an example of density correction executed by the density correction unit 42 in FIG.

  In this embodiment, the density correction unit 42 has an intensity corresponding to each of the correction blocks obtained by dividing the print image area in the main scanning direction into a predetermined number (for example, 16, 32, 64) according to the optical characteristics described above. The amount of exposure light is corrected, and thereby density correction is performed.

  In this embodiment, the length of the contact member 11a or the length of the correction block is set so that the end of the additional correction range matches the boundary between the correction blocks. By doing in this way, the cleaning apparatus 11 adds the correction amount according to the number of calibrations about the correction block corresponding to an additional correction range among the correction amounts for every correction block according to the above-mentioned optical characteristic. The partial contact can be easily corrected (that is, only one light amount correction is required).

  As the number of calibrations increases, the amount of exposure light in the additional correction range is increased, and the intensity of density correction in the additional correction range is increased. As a result, image quality degradation at locations corresponding to the additional correction range on the printed matter is suppressed.

  Next, the operation of the image forming apparatus will be described.

(A) Operation during calibration

  When the calibration execution timing arrives, the calibration processing unit 41 controls the printing device 31 to use (a) the exposure devices 2a, 2b, 2c, 2d and the developing devices 3a, 3b, 3c, 3d. The calibration toner image is developed, and (b) the calibration toner image is primarily transferred to the intermediate transfer belt 4 as shown in FIG. 5, FIG. 6, or FIG. 7, and (c) the density sensor 8 A calibration toner image is detected, the density of the calibration toner image is specified based on the output signal of the density sensor 8, and the toner density characteristic and the toner gradation characteristic are adjusted based on the specified density.

  At that time, the calibration processing unit 41 controls the moving mechanism driving unit 33 to bring the cleaning device 11 into contact with the intermediate transfer belt 4 and cause the cleaning device 11 to remove the calibration toner image. At this time, the contact member 11 a of the cleaning device 11 contacts a part of the intermediate transfer belt 4 in the main scanning direction.

  After the calibration is completed, the calibration processing unit 41 controls the moving mechanism driving unit 33 to separate the cleaning device 11 from the intermediate transfer belt 4. That is, at the time of image printing, the cleaning device 11 is separated from the intermediate transfer belt 4, and the printing toner image is not removed by the cleaning device 11.

  In addition, a counter value of the number of times of calibration is stored in a non-volatile storage device (not shown), and the calibration processing unit 41 updates the counter value by incrementing by 1 each time calibration is executed. . The counter value is zero at the time of shipment, and is reset to zero when the intermediate transfer belt 4 is replaced.

(B) Operation during image printing

  When receiving the print request, the controller 32 acquires the image data of the print request and executes necessary image processing on the image data. At this time, the density correction unit 42 performs density correction in the additional correction range in the main scanning direction corresponding to the contact member 11a of the cleaning device 11 based on the counter value of the number of calibrations as described above. Then, the image to which the density correction is applied is printed by the printing device 31.

  As described above, according to the above-described embodiment, the cleaning device 11 contacts the part of the intermediate transfer belt 4 in the main scanning direction and passes the calibration toner image that has passed through the detection position of the density sensor 8 in the middle. Remove from the transfer belt 4. The density correction unit 42 corrects the density of the printing toner image in the main scanning direction. In particular, the density correction unit 42 changes the intensity of density correction in a range where the cleaning device 11 contacts the intermediate transfer belt 4 according to the number of calibrations.

  As a result, image quality degradation of the printed matter due to partial contact with the intermediate transfer belt 4 by the cleaning device 11 that removes the calibration toner image is suppressed.

  For example, even if the secondary transfer rate at the contact location is lower than that at the non-contact location due to the partial contact of the cleaning device 11 at the time of calibration, the density correction corrects the printed matter (that is, after the secondary transfer). Deterioration in image quality of the toner image is suppressed.

  Various changes and modifications to the above-described embodiment will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. That is, such changes and modifications are intended to be included within the scope of the claims.

  For example, in the above embodiment, the density correction unit 42 may gradually change the density correction intensity at the end of the above-described additional correction range. In that case, even if an image density change occurs due to a change in density correction intensity at the end, the image density change becomes inconspicuous.

  In the above embodiment, the density correction unit 42 may vary the position of the end of the additional correction range in the main scanning direction along the sub-scanning direction. In that case, even if an image density change occurs due to a change in density correction intensity at that end, the occurrence position of the image density change in the main scanning direction varies along the sub-scanning direction. Changes are less noticeable.

  The present invention is applicable to, for example, an electrophotographic image forming apparatus.

4 Intermediate transfer belt 8 Density sensor 11 Cleaning device 42 Density correction unit

Claims (4)

An intermediate transfer belt carrying a calibration toner image;
A density sensor that detects the density of the calibration toner image passing through a predetermined position;
A cleaning device that contacts a part of the intermediate transfer belt in the main scanning direction and removes the calibration toner image that has passed the predetermined position from the intermediate transfer belt;
A density correction unit that performs density correction of the printing toner image in the main scanning direction,
The density correction unit changes the intensity of the density correction in a range where the cleaning device contacts the intermediate transfer belt according to the number of calibrations;
An image forming apparatus. The density correction unit performs the density correction at an intensity corresponding to each of the correction blocks obtained by dividing the print image area in the main scanning direction into a predetermined number;
An end of a range in which the cleaning device contacts the intermediate transfer belt in the main scanning direction coincides with a boundary between the correction blocks;
The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the density correction unit gradually changes the intensity of the density correction at an end of a range in which the cleaning device is in contact with the intermediate transfer belt in the main scanning direction.   4. The density correction unit according to claim 1, wherein the position of the end of the range in which the cleaning device contacts the intermediate transfer belt in the main scanning direction varies along the sub-scanning direction. The image forming apparatus according to claim 1.

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