JP2010217721A - Image forming apparatus, method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably perform color shift correction even when toner patterns on a transfer belt overlap by large color shift. <P>SOLUTION: In an image forming apparatus which forms an image by transferring image in a plurality of colors formed by each of a plurality of image forming units 1K, 1C, 1M, 1Y to transfer paper via an intermediate transfer belt 7, each of the plurality of image forming units 1K, 1C, 1M, 1Y includes: a reflection type sensor 16 which detects toner patterns in the plurality of colors for color shift correction formed on the intermediate transfer belt 7; a counter 23 which totals the number of toner patterns that the reflection sensor 16 detects within unit time; an overlap detection unit 25 which detects that the toner patterns overlap between colors with different toner patterns when the totaled value is smaller than a predetermined value; a color kind detection unit 26 which detects kinds of colors of the overlapped toner patterns; and a color shift correction unit 27 which performs the color shift correction for changing timing for forming the image of an image forming unit corresponding to the detected kinds of colors. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  2. Description of the Related Art Conventionally, in a color image forming apparatus, a predetermined toner pattern is formed with toner of each color on a transfer belt, and this toner pattern is detected using an optical sensor, whereby the amount of deviation between each color is determined in the main scanning direction. And color misregistration (position misalignment) of each color on the transfer belt (transfer paper) by calculating for each factor such as registration misalignment in the sub-scanning direction, magnification misalignment, skew, and bending, and performing feedback correction so that they match each other A method of color misregistration correction control that corrects the above is already known. By performing this correction process when the power is turned on, when the environment such as temperature changes, or when a certain number of sheets are printed, control is performed so that the color misregistration amount is always within a predetermined range. .

  In this color misregistration correction control method, if the transfer belt on which the toner pattern is formed has scratches or seams, the color misregistration correction cannot be performed correctly. For example, in Patent Document 1, if there is dirt or a flaw on the surface of an image carrier on which a toner pattern is formed, even if the output signal of the toner pattern detected by the detection means exceeds a predetermined threshold value, the positional deviation information For the purpose of improving the inapplicability, a configuration in which density error information of a toner pattern is not used when a toner pattern detection signal that is inappropriate as positional deviation information is extracted is disclosed.

  Further, the number of toner patterns formed on the transfer belt from the reference color to the reference color is counted, and if the count value exceeds a specified value, it is determined that there is a scratch or a seam, and color matching control is executed. A method of not using the detection signal is already known.

  On the other hand, a large distortion or the like may occur on the transfer belt, and an unexpectedly large color shift may occur. If color misregistration correction is attempted in this state, the adjacent toner patterns formed on the transfer belt may overlap each other due to the large amount of color misregistration. However, in the conventional color misregistration correction control, there is a problem that this overlap cannot be detected and appropriate color misregistration correction cannot be performed.

  The present invention has been made in view of the above, and an image forming apparatus, an image forming method, and an image forming apparatus capable of reliably performing color misregistration correction even when toner patterns on a transfer belt overlap due to large color misregistration. An object is to provide an image forming program.

  In order to solve the above-described problems and achieve the object, the present invention performs image formation by transferring a plurality of color images formed by each of a plurality of image forming units onto a transfer material via a transfer belt. An image forming apparatus, wherein each of the plurality of image forming units detects a toner pattern for correcting color misregistration of a plurality of colors formed on the transfer belt, and the toner pattern detecting unit is a unit. A totaling unit that counts the number of toner patterns detected in time, and when the first value that is a value totaled by the totaling unit is less than a predetermined value, the toner patterns overlap in different colors. Overlap detecting means for detecting, color type detecting means for detecting the color type of the overlapped toner pattern, and timing for forming an image of the image forming unit corresponding to the detected color type Further comprising a color misregistration correction means for performing color misregistration correction to change the grayed, and characterized.

  In addition, the present invention is an image forming method executed by an image forming apparatus that performs image formation by transferring a plurality of color images formed by each of a plurality of image forming units to a transfer material via a transfer belt. A toner pattern detecting unit for detecting a plurality of color misregistration correction toner patterns formed on the transfer belt by each of the plurality of image forming units; A counting step for counting the number of toner patterns detected within a unit time in the pattern detection step; and a first value that is a value counted by the overlap detection means in the counting step is less than a predetermined value. An overlap detection step for detecting that the patterns are overlapped with each other, a color type detection unit for detecting the color type of the overlapped toner pattern, and a color shift Positive means, include a color shift correction step of performing color misregistration correction to change the timing to form an image of the image imaging unit corresponding to the type of the detected the color, and characterized.

  According to another aspect of the present invention, there is provided a computer, a toner pattern detecting unit that detects a plurality of color misregistration correction toner patterns formed on a transfer belt by each of a plurality of image forming units, and the toner pattern detecting unit is a unit. A totaling unit that counts the number of toner patterns detected in time, and when the first value that is a value totaled by the totaling unit is less than a predetermined value, the toner patterns overlap in different colors. Overlapping detecting means for detecting, color type detecting means for detecting the color type of the overlapped toner pattern, and color shift for changing the timing of forming an image of the image forming unit corresponding to the detected color type It functions as color misregistration correction means for performing correction.

  According to the present invention, even if the toner patterns on the transfer belt overlap, the overlap detection unit detects that the toner patterns overlap, and the color type detection unit detects how many colors and what color toner patterns overlap. Therefore, there is an effect that the color misregistration correction can be surely performed.

FIG. 1 is a diagram illustrating an example of an image forming unit of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing the main configuration of the image forming apparatus of the present invention. FIG. 3 is a diagram illustrating an example of the configuration of the reflective sensor. FIG. 4 is a diagram illustrating a positional relationship between a reflection pattern sensor and a toner pattern formed on the intermediate transfer belt. FIG. 5 is a diagram illustrating an output waveform of specularly reflected light when the toner pattern shown in FIG. 4 is detected by a reflective sensor. FIG. 6 is a diagram for explaining a method of counting the output waveform of FIG. 5 with a counter. FIG. 7 is a diagram illustrating a case where the toner patterns illustrated in FIG. 4 overlap. FIG. 8 is a diagram illustrating an output waveform of specularly reflected light when a toner pattern is detected by a reflective sensor in the case of FIG. FIG. 9 is a diagram for explaining a case where the output waveform of FIG. 8 is counted by a counter. FIG. 10 is a diagram illustrating the relationship between the toner pattern and the output waveform when Y is turned off. FIG. 11 is a diagram illustrating the relationship between the toner pattern and the output waveform when M is turned off. FIG. 12 is a flowchart illustrating the color misregistration correction control method.

  Exemplary embodiments of an image forming apparatus, an image forming method, and an image forming program according to the present invention are explained in detail below with reference to the accompanying drawings.

  FIG. 1 is a diagram illustrating an example of an image forming unit of an image forming apparatus according to an embodiment of the present invention. FIG. 5A shows an image forming unit in the case of a tandem color image forming apparatus employing an intermediate transfer member. One of the functions of the image forming unit is that the latent images formed on the four photosensitive drums 2K, 2C, 2M, and 2Y are converted into toner images of different colors by the four developing devices 4K, 4C, 4M, and 4Y, respectively. The image is developed, and the intermediate transfer belt 7 as an image carrier is primarily transferred in a state where these different color toner images are superimposed. The image forming unit includes four image forming units 1K, 1C, 1M, and 1Y, an intermediate transfer belt 7, and the like.

  The four image forming units 1K, 1C, 1M, and 1Y form black (K), cyan (C), magenta (M), and yellow (Y) images, respectively. The four image forming units 1K, 1C, 1M, and 1Y are respectively photoreceptor drums 2K, 2C, 2M, and 2Y, and charging devices 3K, arranged around these photoreceptor drums 2K, 2C, 2M, and 2Y. 3C, 3M, 3Y, developing devices 4K, 4C, 4M, 4Y, primary transfer rollers 5K, 5C, 5M, 5Y constituting a primary transfer device, and cleaning devices 6K, 6C, 6M, 6Y. Yes.

  The intermediate transfer belt 7 is an endless belt. In this example, four photosensitive drums 2K, 2C, and 2D are formed on the upper side of the intermediate transfer belt 7 along the rotation direction A of the intermediate transfer belt 7. 2M and 2Y are arranged in parallel.

  The photosensitive drums 2K, 2C, 2M, and 2Y are rotationally driven in the rotation direction B. At this time, the charging devices 3K, 3C, 3M, and 3Y charge the surfaces of the photosensitive drums 2K, 2C, 2M, and 2Y to a predetermined polarity. Is done. Next, the charged surface is irradiated with laser light emitted from the exposure device 8, thereby forming electrostatic latent images on the photosensitive drums 2K, 2C, 2M, and 2Y, and the electrostatic latent images are developed into the developing device. 4K, 4C, 4M, and 4Y are visualized as toner images of respective colors.

  Primary transfer rollers 5K, 5C, 5M, and 5Y are arranged to face the respective photosensitive drums 2K, 2C, 2M, and 2Y, and the primary transfer rollers 5K, 5C, 5M, and 5Y and the photosensitive drums 2K, The intermediate transfer belt 7 is rotated between 2C, 2M and 2Y. The intermediate transfer belt 7 is supported by two axes of a driving roller 9 and a tension roller 10. Although it may be stretched by a plurality of rollers, in order to make it as small as possible, it is stretched by two axes to suppress the height of this unit.

  Next, toner images visualized on the photosensitive drums 2K, 2C, 2M, and 2Y are transferred onto the surface of the intermediate transfer belt 7 by the action of the primary transfer rollers 5K, 5C, 5M, and 5Y. . In this manner, the black, cyan, magenta, and yellow toner images are transferred on the intermediate transfer belt 7 in a state where they are accurately and sequentially superimposed, and a full-color composite color image is formed.

  On the other hand, a secondary transfer roller 11 is disposed opposite to the drive roller 9 (secondary transfer counter roller) with the intermediate transfer belt 7 interposed therebetween, and transfer paper P as a recording medium is fed from the paper feed unit 12. Then, it is fed between the driving roller 9 and the secondary transfer roller 11 at a predetermined timing by the rotation of the registration roller pair 13. Then, the composite color image carried on the intermediate transfer belt 7 is collectively transferred onto the transfer paper P by the action of the secondary transfer roller 11. The toner image on the transfer paper P is fixed by heat and pressure by the fixing device 14 and discharged onto a paper discharge tray (not shown).

  The transfer residual toner adhering to the surface of the intermediate transfer belt 7 after the toner image secondary transfer is removed by the cleaning device 15. Further, the reflection type sensor 16 is disposed at a certain fixed distance toward the intermediate transfer belt 7.

  In a tandem color image forming apparatus, each mounting error of an image forming unit, adjustment error / strain / environment and change with time of an exposure apparatus, rotation irregularity of a photosensitive drum, conveyance irregularity of an image carrier / transfer paper, etc. A color shift occurs in the formed image due to fluctuations caused by disturbance. Therefore, a toner pattern (color misregistration control pattern) to be a mark of each color is formed on the image carrier, and the position of each color of the toner pattern is detected by the optical reflective sensor 16, and each color is detected from the detection result. The amount of color misregistration is calculated and the adjustment of the exposure timing is fed back.

  Further, in a tandem color image forming apparatus, in order to obtain a high-quality full-color image, the image density of each color is required to be appropriately stable. For this reason, a toner pattern (density control pattern) serving as a density reference is formed on an image carrier (here, the intermediate transfer belt 7 but also including a conveyance belt), and the density of the toner patch is optically determined. Based on the detected density, feedback is performed for image forming conditions that affect the image density such as charging potential, exposure intensity, developing bias voltage, transfer voltage, and toner replenishment amount.

  FIG. 4B shows an image forming unit in the case of a tandem color image forming apparatus that employs a conveyance body. When the intermediate transfer member is employed, the image is transferred onto the transfer paper P via the secondary transfer roller 11. When the transport member is employed, the transfer is directly performed on the transfer paper P. There is no other significant difference, and the other basic structure is the same as that shown in FIG.

  FIG. 2 is a diagram showing the main configuration of the image forming apparatus of the present invention. In the figure, a CPU 17 controls the entire image forming apparatus according to a ROM 18 in which various control programs are stored.

  The CPU 17 includes a toner pattern formation instructing unit 24, an overlap detection unit 25, a color type detection unit 26, a color misregistration correction unit 27, and a toner density correction unit 28 when classified according to their functions. The toner pattern formation instruction unit 24 instructs the formation of a toner pattern (color misregistration control pattern and density control pattern) on the intermediate transfer belt 7. The overlap detection unit 25 detects that the toner patterns overlap in different colors. The color type detection unit 26 detects what color and what color the overlapping toner patterns are. The color misregistration correction unit 27 performs color misregistration correction that changes the timing of forming the image of the image forming unit corresponding to each color. The toner density correction unit 28 performs density correction for correcting the density of an image formed by each image forming unit.

  The RAM 19 includes various necessary parameters and a work area area for overall control of the image forming apparatus. The I / F unit 20 is connected to an external device (not shown) via a wired LAN, a wireless LAN, a USB, or the like, or is connected to another component (not shown) of the image forming apparatus. The writing unit 21 separates the image data received from the I / F unit 20 into image digital signals of K, C, M, and Y colors, and these signals are according to the toner density and color misregistration parameters stored in the RAM 19. To the exposure device 8.

  In the color misregistration correction control and the toner density control, first, while the intermediate transfer belt 7 is moved at a constant speed, the toner pattern (color misregistration control pattern and density control pattern) is transferred to the intermediate transfer belt 7 at the timing stored in the RAM 19. Form on top. Next, the color misregistration information and the toner density information detected by the reflective sensor 16 are input to the I / O unit 22 and calculated by the CPU 17 based on the information, and the correction parameters (color misregistration amount and toner density amount) are set. It is stored in the RAM 19 and is inherited to the next image forming operation.

  The counter 23 is a counter for counting the number of toner patterns (color shift control patterns and density control patterns) formed on the intermediate transfer belt 7.

  FIG. 3 is a diagram illustrating an example of the configuration of the reflective sensor 16. The reflective sensor 16 is disposed toward the intermediate transfer belt 7 and detects the density of each toner pattern 29 formed on the surface of the intermediate transfer belt 7 and the position of each color. The reflective sensor 16 comprises a light emitting element 30 such as an infrared light emitting diode, phototransistor / photodiode light receiving elements 31 and 32, and a holder 33 that accommodates these elements. The toner concentration and position of each color are determined by an output voltage signal. Measure.

  The light receiving element 31 detects regular reflection light from the toner pattern 29, and the light receiving element 32 detects diffuse reflection light from the toner pattern 29. By detecting both, it is possible to detect each color of black, cyan, magenta, and yellow in a range from a low density to a high density. On the other hand, if only the position of each color is detected, it can be detected only by the light receiving element 31 that detects regular reflection light. Then, when the colors of the toner pattern 29 overlap each other due to deformation of the intermediate transfer belt 7 or the like, the detected value of the specularly reflected light fluctuates extremely. This will be described later.

  FIG. 4 is a diagram showing a positional relationship between the example of the toner pattern 29 formed on the intermediate transfer belt 7 and the reflective sensor 16. In this example, three reflective sensors 16 are provided. The toner pattern (color misregistration control pattern) 29 is formed at the center and near both ends of the intermediate transfer belt 7, and the reflective sensors 16a, 16b, and 16c corresponding to the positions respectively detect the specularly reflected light. The position of each color of the color misregistration control pattern is detected.

  Specifically, the toner pattern (color misregistration control pattern) 29 is formed by arranging yellow, black, cyan, and magenta toner patterns side by side with straight lines and diagonal lines. Then, using black as a reference color, the color misregistration amount of each color is detected from the positional relationship between black and each color of yellow, cyan, and magenta. Specifically, the amount of color misregistration in the transport direction is detected between straight toner patterns, and the amount of color misregistration in the main scanning direction is detected between straight toner patterns and diagonal toner patterns. The positional relationship can be understood by counting the passage timing of these toner patterns with the counter 23. The CPU 17 (color misregistration correction unit 27) performs color misregistration correction control for controlling the writing timing in the writing unit 21 based on the color misregistration amount from the count value.

  On the other hand, the density control pattern (not shown) has toner patterns (for example, 10 types of toner patterns in the case of 10 gradations) each representing a single color gradation of yellow, black, cyan, and magenta. The gradation is determined in advance as 10% density, 20%,... When the density control pattern is detected by the reflective sensor 16, the CPU 17 (toner density correction unit 28) converts the detected value into an image density based on the relationship with the image density, and based on the result, process conditions are converted. Density correction control is performed to control

  Each toner pattern 29 (only the color misregistration control pattern shown) formed on the intermediate transfer belt 7 is conveyed in the conveyance direction (sub-scanning direction) of the intermediate transfer belt 7, and each of the toner patterns 29 has three reflection types. When passing directly below the sensors 16a, 16b, and 16c, the toner patterns 29 of each gradation and color shift are sequentially detected in parallel by these reflective sensors.

  FIG. 5 is a diagram illustrating an output waveform of regular reflection light when the toner pattern (color misregistration control pattern) 29 illustrated in FIG. 4 is detected by the reflective sensor 16. Among the color misregistration control patterns 29, black has a slightly lower reflectance than the other colors (yellow, cyan, magenta), so the output voltage value is lower than the other colors, but the other colors are almost the same. This is the output voltage value. Then, when color misregistration is detected, the center value is obtained by dividing the sum of the falling intersection and the rising intersection by 2, using the predetermined threshold as a reference, and setting it as the detected value. On the other hand, although not shown, the output voltage value of the output waveform when the density control pattern is detected by the reflective sensor 16 decreases sequentially according to the gradation. When the toner density is detected, the amplitude value of this waveform is detected and used as a detection value.

  FIG. 6 is a diagram for explaining a method of counting the output waveform of FIG. When the output waveform value crosses the threshold value once, the counter 23 counts once. The count number by the counter 23 is stored in the RAM 19. Further, a prescribed count value per unit time is developed in the RAM 19 by the CPU 17, and a comparison is made as to whether or not the count value of the counter 23 per unit time is equal to the prescribed count value by the CPU 17 (overlap detector 25). Arithmetic processing is performed every unit time.

(When toner pattern colors overlap)
Next, color misregistration correction control when the colors of the toner patterns 29 formed on the intermediate transfer belt 7 overlap each other will be described. FIG. 7 is a diagram illustrating a case where the toner patterns 29 illustrated in FIG. 4 overlap. In this example, a large color shift occurs due to some cause such as deformation of the intermediate transfer belt 7, and the C and M toner patterns overlap. When toner patterns overlap in this way, it is not possible to perform control for detecting the amount of color misregistration of magenta from the positional relationship between black and magenta using black as a reference color. That is, control is performed to detect the amount of color misregistration in the conveyance direction between black and magenta straight toner patterns, and the amount of color misregistration in the main scanning direction between black and magenta straight toner patterns and diagonal toner patterns. As a result, color misregistration correction cannot be performed for magenta.

  FIG. 8 is a diagram showing an output waveform of regular reflection light when the toner pattern 29 is detected by the reflective sensor 16 in the case shown in FIG. The output waveform when the portion where the toner pattern 29 is actually overlapped is detected to have a wider shape. Since the output waveform spreads in this way, the center value obtained by adding the falling intersection and the rising intersection and dividing by 2 deviates from the center value of the actual cyan toner pattern, so the detected value fluctuates extremely. Therefore, not only magenta but also cyan cannot perform normal color misregistration correction.

  FIG. 9 is a diagram for explaining a case where the output waveform of FIG. Compared with FIG. 6, since the toner patterns 29 overlap, the overlapping output waveforms of C and M cross the threshold once, and the counter 23 counts one with the overlapping C and M toner patterns 29. It becomes operation. For this reason, the count value per unit time is smaller than the above-mentioned specified count value.

  As described above, when the actual count value decreases with respect to the specified count value per unit time, the CPU 17 (overlap detection unit 25) determines that the toner patterns 29 overlap. If the CPU 17 (overlap detection unit 25) determines that the toner patterns 29 overlap, the CPU 17 stores the decreased count value in the RAM 19.

  Next, the CPU 17 (color type detection unit 26) performs the following control. First, the laser beam emitted from the exposure device 8 is turned off for only one color, and in this state, an instruction is given to form a toner pattern 29 as a color misregistration control pattern on the intermediate transfer belt 7 again. Next, the toner pattern 29 is detected by the reflection type sensor 16, and the output waveform by the regular reflection light is counted by the counter 23. Finally, the measured count value per unit time is compared with the count value stored in the RAM 19. If the measured count value is less than the count value stored in the RAM 19, it is determined that the extinguished color is not an overlapping color. If both count values are the same, the extinguished color is the overlapping color. It is judged that.

  The CPU 17 (color type detection unit 26) performs these controls for all colors. That is, K is extinguished and a toner pattern is formed to determine whether K is a color overlapping, then C is extinguished and a toner pattern is formed to determine whether C is an overlapping color. Then, M is extinguished and a toner pattern is formed to determine whether M is a color that overlaps. Finally, Y is extinguished and a toner pattern is formed to determine whether Y is an overlapping color. Note that the order of determining whether the colors overlap is not necessarily the order of K, C, M, and Y, and is arbitrary.

  FIG. 10 is a diagram illustrating the relationship between the toner pattern 29 and the output waveform when Y is turned off. In this case, since the count value is smaller than that in FIG. 9, it is determined that the extinguished color (Y) is not an overlapping color. On the other hand, FIG. 11 is a diagram showing the relationship between the toner pattern 29 and the output waveform when M is turned off. In this case, since the count value is the same as in FIG. 9, it is determined that the extinguished color (M) is an overlapping color. In the case of this example, the CPU 17 (color type detection unit 26) can detect that the overlapping toner patterns are C and M after controlling all of K, C, M, and Y.

  Finally, the CPU 17 (color misregistration correction unit 27) performs color misregistration correction with one of the overlapping colors (C in this example) turned off, and the other color (M in this example). Color misregistration correction is performed with the indicator turned off. As described above, even when the colors of the toner patterns 29 formed on the intermediate transfer belt 7 overlap each other, the color misregistration correction control can be surely performed.

(Color misregistration correction control method)
Next, a color misregistration correction control method by the image forming unit will be described. FIG. 12 is a flowchart illustrating the color misregistration correction control method.

  First, the toner pattern formation instructing unit 24 instructs the formation of a toner pattern (color shift control pattern) 29 on the intermediate transfer belt 7 (step S1), and the toner pattern 29 is formed on the intermediate transfer belt 7. . Next, the CPU 17 (overlap detector 25) detects (counts) the number of toner patterns 29 per unit time (step S2).

  Next, the CPU 17 (overlap detection unit 25) determines whether or not the detected number of toner patterns 29 per unit time is the same as the specified number (step S3). When the CPU 17 (overlap detection unit 25) determines that the number of detected toner patterns 29 per unit time is the same as the specified number, that is, the color of the toner pattern 29 formed on the intermediate transfer belt 7. When it is determined that they are not overlapped (step S3: Yes), the CPU 17 (color misregistration correction unit 27) performs color misregistration correction (step S4) and ends the process.

  On the other hand, when the CPU 17 (overlap detection unit 25) determines that the detected number of toner patterns 29 per unit time is not the same as the specified number, that is, the toner patterns 29 formed on the intermediate transfer belt 7. When it is determined that the two colors overlap each other (step S3: No), the detected number of toner patterns 29 per unit time is stored in the RAM 19 (step S5).

  Next, the CPU 17 (color type detection unit 26) instructs the laser light emitted from the exposure device 8 to be turned off by one color and to form the toner pattern 29 on the intermediate transfer belt 7 again in this state ( In step S6), the toner pattern 29 is formed on the intermediate transfer belt 7 again. Next, the CPU 17 (color type detection unit 26) again detects (counts) the number of toner patterns 29 per unit time (step S7).

  Next, the CPU 17 (color type detection unit 26) determines whether or not the number of toner patterns 29 detected again per unit time is the same as the number of toner patterns 29 stored in the RAM 19 (step S8). . When the CPU 17 (color type detection unit 26) determines that the number of toner patterns 29 detected again per unit time is the same as the number of toner patterns 29 stored in the RAM 19 (step S8: Yes), It is determined that the extinguished color is an overlapping color (step S9), and the process proceeds to step S11.

  On the other hand, when the CPU 17 (color type detection unit 26) determines that the number of toner patterns 29 detected again per unit time is not the same as the number of toner patterns 29 stored in the RAM 19 (step S8: No). ), It is determined that the extinguished color is not an overlapping color (step S10), and the process proceeds to step S11.

  In step S11, the CPU 17 (color type detection unit 26) determines whether or not the processing of S6 to S10 has been performed for all colors. If the CPU 17 (color type detection unit 26) determines that the processing of S6 to S10 has not been performed for all colors (step S11: No), it returns to step S6 and repeats the following steps.

  On the other hand, if the CPU 17 (color type detection unit 26) determines that the processing of S6 to S10 is being performed for all colors (step S11: Yes), the CPU 17 (color misregistration correction unit 27) overlaps. Instructed to form the toner pattern 29 on the intermediate transfer belt 7 again with one of the colors turned off (step S12), and the toner pattern 29 is formed on the intermediate transfer belt 7 again.

  Next, the CPU 17 (color misregistration correction unit 27) performs color misregistration correction for colors other than those that are turned off (step S13). Next, the CPU 17 (color misregistration correction unit 27) determines whether or not color misregistration correction has been performed for all the overlapping colors (step S14). If the CPU 17 (color misregistration correction unit 27) determines that the color misregistration correction has not been performed for all the overlapping colors (step S14: No), the process returns to step S12 and the following steps are repeated.

  On the other hand, if the CPU 17 (color misregistration correction unit 27) determines that the color misregistration correction has been performed for all the overlapping colors (step S14: Yes), it is determined that the color misregistration correction has been performed for all the colors. Then, the process ends. Through the above steps, the color misregistration correction control is completed.

  As described above, according to the image forming apparatus of the present embodiment, even if the toner patterns on the intermediate transfer belt overlap, the overlap detection unit detects that the toner patterns overlap, and the color type detection unit Since it is possible to detect how many color toner patterns are overlapped, the color misregistration correction unit can surely perform color misregistration correction.

  The image forming program executed by the image forming apparatus according to the present embodiment is provided by being incorporated in advance in a ROM or the like.

  In addition, an image forming program executed by the image forming apparatus according to the present embodiment can be installed in a file in an installable or executable format, such as a CD-ROM, a flexible disk (FD), a CD-R, and a DVD (Digital Versatile Disk). ) Or the like may be recorded and provided on a computer-readable recording medium.

  Furthermore, the image forming program executed by the image forming apparatus according to the present embodiment may be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. The image forming program executed by the image forming apparatus according to the present embodiment may be provided or distributed via a network such as the Internet.

  The image forming program executed by the image forming apparatus of the present embodiment includes the above-described units (toner pattern formation instructing unit 24, overlap detecting unit 25, color type detecting unit 26, color misregistration correcting unit 27, and toner density correction). Unit 28), and the actual hardware is a CPU (processor) that reads out and executes an image forming program from the ROM, and loads each unit onto the main storage device to form a toner pattern. An instruction unit 24, an overlap detection unit 25, a color type detection unit 26, a color misregistration correction unit 27, and a toner density correction unit 28 are generated on the main storage device.

  In the above embodiment, the image forming apparatus according to the present invention is described by taking an example in which the image forming apparatus is applied to a multifunction machine having at least two functions among a copy function, a printer function, a scanner function, and a facsimile function. The present invention can be applied to any image forming apparatus such as a printer, a scanner apparatus, and a facsimile apparatus.

1K, 1C, 1M, 1Y Image forming unit 2K, 2C, 2M, 2Y Photosensitive drum 3K, 3C, 3M, 3Y Charging device 4K, 4C, 4M, 4Y Developing device 5K, 5C, 5M, 5Y Primary transfer roller 6K, 6C, 6M, 6Y Cleaning device 7 Intermediate transfer belt 8 Exposure device 9 Drive roller 10 Tension roller 11 Secondary transfer roller 12 Paper feed unit 13 Registration roller pair 14 Fixing device 15 Cleaning device 16 Reflective sensor 17 CPU
18 ROM
19 RAM
20 I / F section 21 Writing section 22 I / O section 23 Counter 24 Toner pattern formation instruction section 25 Overlap detection section 26 Color type detection section 27 Color misregistration correction section 28 Toner density correction section 29 Toner pattern 30 Light emitting element 31, 32 Light receiving element 33 Holder P Transfer paper

JP-A-2005-352291

Claims (6)

An image forming apparatus that performs image formation by transferring a plurality of color images formed by each of a plurality of image forming units to a transfer material via a transfer belt,
Toner pattern detection means for detecting a plurality of color misregistration correction toner patterns formed on the transfer belt by each of the plurality of image forming units;
A counting unit that counts the number of toner patterns detected by the toner pattern detection unit within a unit time;
An overlap detection means for detecting that the toner patterns overlap with each other when the first value, which is the value counted by the counting means, is less than a predetermined value;
Color type detection means for detecting the color type of the overlapping toner patterns;
Color misregistration correction means for performing color misregistration correction to change the timing of forming an image of the image forming unit corresponding to the detected color type;
An image forming apparatus. The color type detecting means is
Selecting one image forming unit from the plurality of image forming units, and instructing the image forming unit other than the selected image forming unit to form the toner pattern;
When the value obtained by summing up the number of the toner patterns formed in this state is the same as the first value, determining that the color formed by the selected image forming unit is one of overlapping colors;
The image forming apparatus according to claim 1. The color misregistration correction means includes
Instructing the image imaging unit other than the image imaging unit corresponding to any one of the overlapping colors to form the toner pattern,
Performing the color misregistration correction based on the color misregistration amount calculated from the toner pattern formed in this state;
The image forming apparatus according to claim 1, wherein: Further comprising storage means for storing the first value and the predetermined value;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An image forming method executed by an image forming apparatus that performs image formation by transferring a plurality of color images formed by each of a plurality of image forming units to a transfer material via a transfer belt,
A toner pattern detecting step for detecting a plurality of color misregistration correction toner patterns formed on the transfer belt by each of the plurality of image forming units;
A counting step in which the counting means counts the number of the toner patterns detected within a unit time in the toner pattern detection step;
An overlap detection step for detecting that the toner patterns overlap with each other when the first value, which is a value counted in the counting step, is less than a predetermined value,
A color type detection step in which a color type detection means detects the color type of the overlapping toner patterns;
A color misregistration correction unit that performs color misregistration correction for changing a timing of forming an image of the image forming unit corresponding to the detected color.
An image forming method. Computer
Toner pattern detection means for detecting a plurality of color misregistration correction toner patterns formed on the transfer belt by each of the plurality of image forming units;
A counting unit that counts the number of toner patterns detected by the toner pattern detection unit within a unit time;
An overlap detection means for detecting that the toner patterns overlap with each other when the first value, which is the value counted by the counting means, is less than a predetermined value;
Color type detection means for detecting the color type of the overlapping toner patterns;
An image forming program for functioning as color misregistration correction means for performing color misregistration correction for changing a timing of forming an image of the image forming unit corresponding to the detected color type.

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