JP4343149B2 - Image forming apparatus and color misregistration correction method - Google Patents

Description

  The present invention relates to a so-called tandem type multicolor image forming apparatus in which a plurality of image forming means are arranged in a line along a transport path of an image carrier such as an intermediate transfer belt or recording paper, and in particular, the image forming means. The present invention relates to a multicolor image forming apparatus having a color misregistration correction function for correcting color misregistration of a multicolor toner image formed on the image carrier.

In recent years, tandem color printers for forming toner images of different colors (for example, magenta (M), cyan (C), yellow (Y), black (K)) on recording paper conveyed by a conveyance belt, 2. Description of the Related Art An intermediate transfer belt type color printer that widely forms toner images of different colors (MCYK colors) on an intermediate transfer belt to form a multicolor toner image and then transfers the multicolor toner image onto a recording sheet is widely known. Yes. In each of these types of color printers, MCYK four-color image formation is performed almost simultaneously in a single image formation process, so that high-speed printing is possible as compared with a transfer drum type color printer. However, in the tandem method and the intermediate transfer belt method, image forming means (including a developing device and a photosensitive drum) corresponding to each color of MCYK are independently provided, so that the recording paper or the intermediate transfer belt can be used. The resulting multi-color toner image has a color caused by a shift in the mounting position of the image forming means, a difference in peripheral speed of the photosensitive drum, an error (shift) in writing timing of the electrostatic latent image on the photosensitive drum, and the like. There is a problem that deviation is likely to occur.
Therefore, a color misregistration correction function for correcting the color misregistration is conventionally provided in the tandem and intermediate transfer belt color printers (see Patent Documents 1 to 4).

Hereinafter, a conventional color misregistration correction process realized by the color misregistration correction function provided in the intermediate transfer belt type color printer will be briefly described with reference to FIG. For detailed processing contents, refer to the above patent documents. FIG. 7 is a schematic diagram showing an example of the color misregistration detection pattern 20 formed on the intermediate transfer belt 3 during the color misregistration correction process.
As shown in the figure, the color misregistration detection pattern 20 is a 45 ° inclined pattern for detecting the color misregistration amount in the main scanning direction orthogonal to the conveyance direction of the intermediate transfer belt 3 (the direction indicated by the arrow in the figure). 21 (21a to 21d), 22 (22a to 22d), and patterns 23 (23a to 23d) and 24 (24a to 24a) parallel to the main scanning direction for detecting the amount of color misregistration in the conveyance direction of the intermediate transfer belt 3. The patterns 21 and 23 are formed on the intermediate transfer belt 3 in the vicinity of one end in the main scanning direction and arranged in a line in the transport direction. The patterns 22 and 24 are formed on the intermediate transfer belt 3. It is formed in the same manner near the other end in the main scanning direction. Each of the patterns 21 to 24 includes patterns for four colors of magenta (M), cyan (C), yellow (Y), and black (K). Here, “a”, “b”, “c”, and “d” attached to the reference numerals indicating the patterns indicate magenta (M), cyan (C), yellow (Y), and black (K), respectively. Indicates that the pattern is a corresponding color pattern.
The above-described MCYK color patterns (for example, 21a to 21d) are transferred to the intermediate transfer belt in accordance with a predetermined timing (hereinafter referred to as “pattern writing timing”) by controlling the image forming means by a control unit provided in the color printer. 3 is formed. If there is no deviation in the mounting position of the image forming means or the peripheral speed difference between the photosensitive drums, or if color misregistration correction has already been properly performed, the MCYK color patterns are arranged at regular intervals d. It is formed.
In the vicinity of the downstream end of the intermediate transfer belt 3 in the transport direction, a CCD, a CIS, or a reflective photointerrupter that reads the patterns 21 to 24 formed near both ends of the intermediate transfer belt 3 in the main scanning direction. An optical sensor 5 (5a, 5b) (corresponding to an example of an image reading unit) is provided. In FIG. 7, reference numeral 5 a is an optical sensor for reading patterns 21 and 23, and reference numeral 5 b is an optical sensor for reading patterns 22 and 24. The optical sensor 5 is disposed vertically above the intermediate transfer belt 3 on which the pattern is formed, and at a position where each pattern can be read.
When the patterns of the respective colors are formed on the outer peripheral surface of the intermediate transfer belt 3, the patterns are transported in the transport direction (arrow direction in the figure) as the intermediate transfer belt 3 travels. Then, the color patterns sequentially conveyed by the optical sensor 5 are sequentially read, and the read pattern images are transferred to a correction control unit (not shown).
In the correction control unit, the amount of deviation of the mounting position of the image forming means by matching processing of each read pattern image, comparison processing between the reading timing when each pattern image is read and the above pattern writing timing, etc. And a difference in peripheral speed (peripheral speed deviation) of the photosensitive drum, and an error (deviation) in writing timing of the electrostatic latent image on the photosensitive drum, and the above-described deviation amount is obtained based on the obtained deviation amount. The attachment position of the image forming means, the peripheral speed of the photosensitive drum, the electrostatic latent image writing timing, and the like are finely adjusted. As a result, the formation position of the toner image formed by the image forming unit is corrected, and the color shift of the multicolor toner image formed on the intermediate transfer belt 3 is corrected.
JP 2001-209292 A JP 2002-14505 A JP 2003-186278 A JP 2004-252172 A

By the way, when the color misregistration of the multicolor toner image formed on the intermediate transfer belt or the like is minute, the minute color misregistration can be corrected by one color misregistration correction process, but the color misregistration is large. However, there is a case where the color misregistration correction process cannot be sufficiently corrected in one time and the color misregistration correction process needs to be performed a plurality of times. It should be noted that a color printer after completion of assembly or a color printer that has been left without performing color misregistration correction processing for a long period of time has a high probability of causing a relatively large color misregistration.
Therefore, conventionally, in order to reliably correct the color misregistration, the color misregistration correction processing is executed a plurality of times (two times or more) regardless of the actual color misregistration in the image forming apparatus such as the color printer. So that it is controlled.
However, if a color misregistration detection pattern consisting of all colors as shown in FIG. 7 is formed a plurality of times on the intermediate transfer belt, there is a problem that a large amount of toner is consumed.
For example, when expressing a color image with four colors of MCYK, it is necessary to read a total of eight patterns (see FIG. 7) arranged in a line in the conveyance direction of the intermediate transfer belt, which takes a long time to read. However, the color misregistration correction process takes time.
Accordingly, the present invention has been made in view of the above circumstances, and the object of the present invention is to improve the color misregistration correction accuracy by reliably performing the color misregistration correction, while at the same time, the toner consumed during the color misregistration correction processing. An object of the present invention is to provide an image forming apparatus and a color misregistration correction method capable of reducing the amount and processing time.

In order to achieve the above object, the present invention comprises a plurality of image forming means which are arranged in a substantially line along the conveyance path of the image carrier and form a visible image of at least three colors on the image carrier. , A so-called color misregistration correction function possessed by an image forming apparatus provided with an image reading means for reading a visible image formed on the image carrier, wherein the color misregistration correction function is the image forming unit. By controlling the means, a visible image of two or more colors and less than all colors is formed on the image carrier, and the position of the visible image of the two or more colors and less than all colors read by the image reading means The shift amount of the image forming unit that forms the visible image of two or more colors and less than all the colors is measured based on the color shift, and the color shift caused by all the image forming units is corrected based on the measured shift amount. 1 color misregistration correction process is executed, and the first color misregistration correction process is executed. By controlling all the image forming means corrected by the above, the all color visible images are formed on the image carrier, and the positions of the all color visible images read by the image reading means are set. Based on this, the amount of deviation of all the image forming units is measured, and based on the measured amount of deviation, a second color misregistration correction process for correcting color misregistration by all the image forming units is executed. .
Here, the amount of deviation of the image forming means includes, for example, the amount of deviation of the mounting position of the image forming means itself, the amount of timing deviation when the image forming means forms a visible image on the image carrier, This corresponds to the amount of deviation of the peripheral speed of the photoconductive drum constituting the image forming means. Further, the color misregistration by the image forming means indicates color misregistration generated in the multicolor toner image formed on the image carrier due to the misregistration amount.
With such a configuration, first, a general color misregistration correction is performed by the first color misregistration correction process, and then a fine color misregistration correction is performed by the second color misregistration correction process. As a result, the color misregistration correction is surely performed and high color misregistration correction accuracy can be ensured. In addition, since the first color misregistration correction process has fewer patterns that are subtracted from the conventional color, Consumption can be reduced. Furthermore, the pattern reading processing time in the first color misregistration correction process is shortened, and as a result, the processing time spent for color misregistration correction is shortened.

Here, for example, consider a case where a two-color pattern is formed on the image carrier in the first color misregistration correction process in a four-color printer. In this case, in the first color misregistration correction process, the misregistration amount of the image forming means corresponding to the two colors is measured, and the mounting position of the image forming means, the image forming timing, etc. are measured based on the measured misregistration amount. Is corrected, the amount of deviation of the other image forming means is calculated (predicted or calculated) from the corrected mounting position, timing, etc., and another image is calculated based on the calculated amount of deviation. The attachment position of the forming unit, the image formation timing, and the like are corrected.
However, for example, when the two-color image forming units are adjacent to each other, the misalignment indexing accuracy (prediction accuracy and calculation accuracy) of other image forming units may be low, which is not preferable. For example, when the positional deviation of the image forming means itself is corrected, it is obvious that the accuracy of determining the deviation amount of the other image forming means is lowered.
For this reason, the image forming means for forming the visible image of two or more colors and less than all the colors includes image formability means arranged in the front row and the rear row among the image forming devices arranged in a row. It is desirable that Therefore, for example, when a two-color pattern is formed by the first color misregistration correction process, the two-color pattern is formed by the image forming means having the most distant positional relationship. As a result, the accuracy of determining the shift amount of the other image forming means is increased.

Incidentally, the correction function provided in the image forming apparatus includes a density correction function in addition to the color misregistration correction function. Normally, when the correction process is performed in the image forming apparatus, the color misregistration correction process and the density correction process are often performed at the same time. In this case, when the density correction processing is performed prior to the color misregistration correction processing, if color misregistration occurs, a reference density visible image (so-called density patch) of each color formed on the intermediate transfer belt or the like. Image) may overlap each other. In this case, since the density of the overlapping portion of the color is detected and density correction is performed based on the density, there may occur a case where accurate density correction cannot be performed.
Therefore, in the present invention, first, the first color misregistration correction process is performed. Then, by controlling all the image forming means corrected by the first color misregistration correction processing, a density correction pattern consisting of the reference density visible images of all the colors is formed on the image carrier, The density of each of the reference density visible images of all colors is detected from the density correction pattern read by the image reading means, and the density correction of all the image forming means is performed based on the detected density. It is controlled to do. As a result, the density correction patterns for the respective colors do not overlap each other and accurate density correction can be performed.
Further, if the color misregistration correction by the second color misregistration correction process and the density correction by the density correction process are executed substantially in parallel, the time spent for the correction process can be shortened. In this case, it is necessary to provide an image reading unit for reading the density correction pattern separately from the image reading unit.

Further, the present invention may be regarded as a color misregistration correction method for correcting color misregistration by the image forming unit. That is, a plurality of image forming units that are arranged in a line along the conveyance path of the image carrier and that form a visible image of at least three colors on the image carrier, and formed on the image carrier. and an image reading means for reading a visible image, the visible image formed on said image bearing member by controlling the upper Kizo forming means to read the said image reading means, the read the visible image A color misregistration correction method for an image forming apparatus comprising: a correction control unit that corrects color misregistration by all the image forming units based on the position of the image forming unit, wherein the correction control unit controls the image forming unit By forming the visible image of two or more colors and less than all colors on the image carrier, and based on the position of the visible image of the two or more colors and less than all colors read by the image reading means An image formed with the visible image of two or more colors and less than all the colors The shift amount of growth means to measure a first color shift correction process of correcting the color shift due to all of the image forming means on the basis of the measured displacement amount, the correction control section, the first color By controlling all the image forming means corrected by the shift correction processing step, the visible image of all colors is formed on the image carrier, and the visible colors of all colors read by the image reading means are formed. A second color misregistration correction processing step for measuring a deviation amount of all the image forming units based on the position of the image, and correcting a color misregistration due to all the image forming units based on the measured deviation amount; Even if the color misregistration correction method is provided, the same effects as those of the image forming apparatus of the present invention described above can be obtained.

  According to the present invention configured as described above, first, the color misregistration correction is generally performed by the first color misregistration correction processing, and then the fine color misregistration correction is performed by the second color misregistration correction processing. . As a result, the color misregistration correction is surely performed and high color misregistration correction accuracy can be ensured. In addition, since the first color misregistration correction process has fewer patterns that are subtracted from the conventional color, Consumption can be reduced. Furthermore, the pattern reading processing time in the first color misregistration correction process is shortened, and as a result, the processing time spent for color misregistration correction is shortened.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a schematic sectional view showing a schematic configuration of an image forming unit 100 of an intermediate transfer type color printer according to an embodiment of the present invention. FIG. 2 is a schematic sectional view showing a schematic configuration of an image forming unit 10a. FIG. 3 is a block diagram showing a schematic configuration of the correction control unit 30 for executing the color misregistration correction process, FIG. 4 is a flowchart for explaining an example of the procedure of the color misregistration correction process executed by the correction control unit 30, and FIG. FIG. 6 is a schematic diagram illustrating an example of a color misregistration detection pattern used in the color misregistration correction process, and FIG. 7 is a flowchart illustrating another example of the procedure of color misregistration correction executed by the correction control unit 30. FIG. 8 is a schematic diagram illustrating an example of a color misregistration detection pattern formed on the intermediate transfer belt 3 during a conventional color misregistration correction process, and FIG. 8 illustrates an example of a color misregistration detection pattern including a density correction pattern 25. It is a schematic view.

  First, the schematic configuration of the image forming unit 100 of the color printer according to an embodiment of the present invention will be described with reference to the schematic diagrams of FIGS. 1 and 2. The color printer described in this embodiment employs an intermediate transfer system, but is a color printer of the tandem system (a system in which toner images are sequentially formed (transferred) directly onto a recording sheet to be conveyed). Even if it exists, it is possible to apply this invention. The color printer is an example of an image forming apparatus, and other examples include a facsimile machine, a copier, or a multifunction machine having these functions.

As shown in FIG. 1, the image forming unit 100 is roughly divided into image forming units 10 (10a to 10d) corresponding to respective colors of magenta (M), cyan (C), yellow (Y), and black (K). ), An intermediate transfer belt 3 (an example of an image carrier), a driving roller 9a and driven rollers 9b and 9c that rotatably support the intermediate transfer belt 3, and an optical sensor such as a CCD, a CIS, or a reflection type photo interrupter. 5 (5a, 5b) (an example of an image reading unit) and a secondary transfer roller 4 for transferring a multicolor toner image formed on the outer peripheral surface of the intermediate transfer belt 3 to the recording paper S. Has been. The image forming unit 10 corresponds to an example of an image forming unit that forms a predetermined toner image (corresponding to a visible image) such as a color misregistration detection pattern described later on the surface of the intermediate transfer belt 3.
In the image forming unit 100, the image forming units 10 (10a to 10d) corresponding to the MYCK colors correspond to the conveyance direction of the intermediate transfer belt 3 along the outer peripheral surface of the intermediate transfer belt 3 (arrow P in FIG. 1). ) In the order of the above MYCK.
In this embodiment, an example in which the image forming unit 100 includes the image forming units 10 (10a to 10d) corresponding to the four colors of MCYK will be described. It is sufficient if a multicolor toner image is formed on the intermediate transfer belt 3 by three or more color image forming units.

The optical sensors 5 (5a, 5b) are arranged in the vicinity of both ends in the main scanning direction (direction orthogonal to the transport direction) near the downstream end of the intermediate transfer belt 3 in the transport direction.
The optical sensor 5 only needs to be configured to include at least a light emitting diode such as an LED and a light receiving diode that outputs an electrical signal (current or voltage) corresponding to the amount of received light. And image sensors such as CIS are not limited.

The image forming units 10a to 10d respectively form an M color toner image, a C color toner image, a Y color toner image, and a K color toner image. The configuration of the image forming unit 10a corresponding to M color will be specifically described below. Since the image forming units 10a to 10d have the same configuration, only the image forming unit 10a will be described here, and description of the other color image forming units 10b to 10d will be omitted.
The image forming unit 10a irradiates the surface of the photosensitive drum 15a with the photosensitive drum 15a carrying the electrostatic latent image, the charging device 11a for uniformly charging the surface of the photosensitive drum 15a, and the surface of the photosensitive drum 15a. An exposure device 12a including a laser scanner unit that forms an electrostatic latent image, a developing device 13a that forms a toner image on the surface of the photosensitive drum 15a by attaching toner to the electrostatic latent image, and a developed toner. An intermediate transfer roller 2a for transferring the image onto the intermediate transfer belt 3, a charge eliminating device for removing residual charges remaining on the surface of the photosensitive drum 15a after the toner image transfer, a cleaning device 14a for removing residual toner, and the like are provided. Has been configured. The color shift of the multi-color toner image formed on the intermediate transfer roller 3 is not only the shift of the mounting position of each color image forming unit itself, but also the shift of the mounting position of each photosensitive drum, the peripheral speed of the photosensitive drum. This also occurs due to a difference (peripheral speed deviation), a deviation in writing timing of the electrostatic latent image by the exposure apparatus, and the like.
The intermediate transfer roller 2a corresponding to each photosensitive drum 15a is disposed at a position facing the photosensitive drum 15a with the intermediate transfer belt 3 interposed therebetween. To this intermediate transfer roller 2a, a transfer bias having a polarity opposite to that of the toner is applied in order to transfer the toner image carried on the surface of the photosensitive drum 15a onto the intermediate transfer belt 3. As a result, an M toner image formed on the photosensitive drum 15 a is formed on the outer peripheral surface of the intermediate transfer belt 3.

When an image formation instruction is input to the image forming unit 100 configured as described above, first, on the outer peripheral surface of the intermediate transfer belt 3 driven in the transport direction by the image forming unit 10a. An M toner image is formed in the image forming area. When an M color toner image is formed on the intermediate transfer belt 3, the image forming area is moved downstream in the transport direction by the intermediate transfer belt 3, and sequentially the C color is formed by the image forming units 10b, 10c, and 10d. , Y and K color toner images are formed. In this way, a multicolor toner image is formed in the image forming area.
The formed multi-color toner image is further conveyed to the position of the secondary transfer roller 4 and transferred to the recording paper S fed by a paper feeding device (not shown) by the secondary transfer roller 4, and thereafter not shown. It is fixed on the recording paper S by a fixing device.

In the color printer having the image forming unit 100 having the above-described configuration, the image forming units 10 (10a to 10d) are arranged in substantially one row, so that the color misregistration is caused in the multicolor toner image formed on the intermediate transfer belt 3. However, if the color misregistration correction function provided in the color printer is used, the color misregistration can be corrected.
Hereinafter, the configuration of the correction control unit 30 that realizes the color misregistration correction process by the color misregistration correction function and the procedure of the color misregistration correction process executed by the correction control unit 30 will be described with reference to FIGS.

First, the schematic configuration of the correction control unit 30 will be described with reference to FIG.
The correction control unit 30 has been transferred from a rewritable data memory 33 such as a CPU 31, a RAM 32, an EEPROM, a network communication unit 35 that enables communication with a host computer (host PC) 40 via a LAN 41, and the host PC 40. It comprises an HDD 34 for storing print data, a bus I / F 36, and the like.
The bus I / F 36 transmits data and control signals to the image forming units 10 (10a to 10d) of the image forming unit 100 via an internal bus or the like, or is read from the optical sensor 5. An input / output port for inputting predetermined image data.

In the data memory 33, the image forming units 10a to 10d are formed with the above-described color misregistration detection pattern 20 (see FIG. 7) used for the color misregistration correction processing described later executed by the correction control unit 30. And various information (data) used for the color misregistration correction processing such as timing information for forming the color misregistration detection pattern 20 'shown in FIG. 6 in the image forming units 10a to 10d is stored. ing. In the following, for convenience of explanation, the color misregistration detection pattern 20 ′ shown in FIG. 6 is referred to as a first color misregistration detection pattern 20 ′, and the color misregistration detection pattern 20 shown in FIG. This is called a detection pattern 20.
Here, the first color misregistration detection pattern 20 ′ shown in FIG. 6 is different from the above-described second color misregistration detection pattern 20 (FIG. 7), as shown in FIG. Of the image forming units 10a to 10d, the image forming units 10a to 10d are formed only by the image forming units 10a and 10d disposed at the frontmost row and the rearmost row in the transport direction. That is, the cyan (C color) pattern and the yellow (Y color) pattern are omitted from the second color misregistration detection pattern 20, and only the magenta (M color) pattern and the black (K color) pattern are represented. Is.
The first and second color misregistration detection patterns 20 ′ and 20 are formed on the intermediate transfer belt 3 according to the timing information when a color misregistration correction process described later is executed. Normally, when no color misregistration occurs, each pattern is formed at equal intervals d as shown in FIGS. On the other hand, when a color shift occurs, an error occurs in the pattern interval or an image shift occurs in the main scanning direction.

  Next, referring to the color misregistration detection patterns 20 ′ and 20 of FIGS. 6 and 7, the color misregistration executed by the correction control unit 30 (CPU 31) according to a predetermined program using the flowchart of FIG. 4. An example of the procedure of the correction process will be described. In the figure, S10, S20,... Indicate process procedure (step) numbers, and the process starts from step S10. In the processing after step S10, for example, an execution instruction signal for the color misregistration correction process is input from the outside, or a flag set for periodically executing the color misregistration correction process is set. It starts on the condition.

First, in step S 10, the image forming units 10 a and 10 d are controlled by the correction control unit 30, so that the first color misregistration detection pattern 20 ′ (see FIG. 6) is transferred to the intermediate transfer belt 3. It is formed on the outer peripheral surface.
When the first color misregistration detection pattern 20 ′ is formed on the intermediate transfer belt 3, the first color misregistration detection pattern 20 ′ is transported by the intermediate transfer belt 3 (in the direction of arrow P in FIG. 1). ) It is conveyed downstream and is read by the optical sensor 5 (5a, 5b). Specifically, the pattern 21 ′ and the pattern 23 ′ included in the first color misregistration detection pattern 20 ′ are sequentially read by the optical sensor 5a. The optical sensor 5b sequentially reads the pattern 22 'and the pattern 24' included in the first color misregistration detection pattern 20 '.
Subsequently, in step S20, it is determined whether the reading process by the optical sensor 5 is completed. This determination is made, for example, based on whether or not the four patterns 21a, 21d, 23a, and 24d are read by the optical sensor 5a. The reading process by the optical sensor 5 is continuously performed until it is determined in step S20 that the reading is completed.

If it is determined in step S20 that the reading is completed, the first color misregistration correction process is executed after temporarily stopping the driving of the optical sensor 5 and the intermediate transfer belt 3 (step S30). Such processing includes, for example, obtaining deviations in the reading timings of the patterns 21a, 21d, 23a, and 23d read by the optical sensor 5a, and determining the position of each pattern from the deviation and the conveyance speed of the intermediate transfer belt 3. Calculate the deviation. If the calculated misregistration is less than a predetermined allowable range, the color misregistration correction process is interrupted. On the other hand, if it is not less than the allowable range, the shift amounts of the image forming units 10a and 10d forming the first color misregistration detection pattern 20 ′ are converted based on the calculated misregistration. Based on the converted shift amount, first, color misregistration by the image forming units 10a and 10d is corrected. Specifically, the timing information stored in the data memory 33 is updated to adjust the exposure timing by the exposure devices 12a and 12d, the drum rotation speed of the photosensitive drums 15a and 15d, and the like. As a result, a shift in image formation timing by the image forming units 10a and 10d is corrected. When the image forming units 10a and 10d are movably arranged by a motor or the like, the positional deviation of the image forming units 10a and 10d is corrected by controlling the motor.
Thereafter, from the corrected image forming timings and mounting positions of the image forming units 10a and 10d, the exposure timing, drum rotation speed, mounting position, and the like in the other image forming units 10b and 10c are estimated, and based on the estimated values. Thus, the image forming timing and the mounting position of the image forming units 10b and 10c are generally corrected.
Here, the correction control unit 30 that executes the first color misregistration correction processing (step S30) corresponds to first color misregistration correction processing means.

When the color misregistration by all the image forming units 10 (10a to 10d) is corrected in step S30, the optical sensor 5 and the intermediate transfer belt 3 that have been temporarily stopped are subsequently driven, and then By controlling all the image forming units 10 (10a to 10d) by the correction control unit 30, the second color misregistration detection pattern 20 (see FIG. 7) is formed on the outer peripheral surface of the intermediate transfer belt 3. Is done.
The second color misregistration detection pattern 20 formed on the intermediate transfer belt 3 is then transported downstream in the transport direction (the direction of arrow P in FIG. 1), and the optical sensor 5 (5a, 5b). The reading process is started. Then, in the same manner as in step S20, it is determined whether or not the reading process of the second color misregistration detection pattern 20 by the optical sensor 5 has been completed (step S50).
If it is determined that the reading is completed, the second color misregistration correction process is executed after the driving of the optical sensor 5 and the intermediate transfer belt 3 is temporarily stopped (step S60). Note that the second color misregistration correction process performed here is based on the misregistration of each of the read patterns 21 to 24 including all the colors included in the second color misregistration detection pattern 20. This is a color misregistration correction process similar to the conventional one for correcting color misregistration by all the image forming units 10 (10a to 10d).
Here, the correction control unit 30 that executes the second color misregistration correction processing (step S60) corresponds to second color misregistration correction processing means.
In this way, in step S30, first, the first color misregistration correction is performed by reading the first color misregistration detection pattern 20 'composed of two colors of M and K, and then the first color misregistration correction is performed. After the color misregistration correction is performed, in step S60, the second color misregistration detection pattern 20 including all the colors of MCYK is read and the second color misregistration correction is performed. Compared to reading the second color misregistration detection pattern 20 composed of all colors twice and repeating the same correction processing as the second color misregistration correction twice, the process of reading the color misregistration detection pattern is more effective. Time spent can be shortened, and wasteful toner consumption can be suppressed.

In the above-described embodiment, the processing example in which only the color misregistration correction processing is executed by the correction control unit 30 has been described. Here, so-called density correction processing, which is one of the correction functions provided in the color printer, is described. An example of processing executed by the correction control unit 30 at the same time as the color misregistration correction processing will be described with reference to the flowchart of FIG. 5 and FIG. FIG. 5 is a flowchart for explaining another example of the procedure of the color misregistration correction process executed by the correction control unit 30. FIG. 8 is an example of the color misregistration detection pattern 20 including the density correction pattern 25. It is a schematic diagram shown.
Usually, when correction processing is performed in an image forming apparatus such as a color printer, the color misregistration correction and the density correction are performed at the same time in consideration of the efficiency of the correction processing.
In general, as shown in FIG. 8, the above density correction processing is for density correction in which one or more patch patterns composed of density patch images 25a to 25d (corresponding to a reference density visible image) of each color of MCYK are continuously arranged. The pattern 25 is formed on the outer peripheral surface of the intermediate transfer belt 3, and the density correction pattern 25 is read by the optical sensor 5c similar to the optical sensors 5a and 5b. When the density correction process is executed prior to the process or in parallel with the conventional color misregistration correction process, the density patch images 25a to 25d of the respective colors of the density correction pattern 25 are superposed due to the color misregistration, and an accurate density is obtained. The correction pattern 25 is not formed, and as a result, there is a problem that the density correction is not properly performed.
Therefore, in this embodiment, as shown in the flowchart of FIG. 5, after the first color misregistration correction process is performed in step S30, the density correction pattern 25 is formed in step S41, and the density correction pattern is formed. 25 is read by the optical sensor 5c (Yes in step S51), density correction processing is executed (step S61).
Thus, the density correction process is executed after the color misregistration by all the image forming units 10 (10a to 10d) is corrected by the first color misregistration correction process (step S30), so that the density correction is appropriately performed. Can be executed.
As shown in the flowchart of FIG. 4, the optical sensor 5c is provided between the optical sensors 5a and 5b so that the second color misregistration correction process and the density correction process are performed in parallel. Thus, the processing time spent for the correction process can be greatly reduced. Of course, after the second color misregistration detection pattern 20 is formed, the density correction pattern 25 may be formed and read by the optical sensor 5a or 5b to execute each correction process. Absent. In this case, the optical sensor 5c can be eliminated, and the configuration of the color printer can be simplified.

1 is a schematic cross-sectional view showing a schematic configuration of an image forming unit 100 of an intermediate transfer type color printer according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a schematic configuration of an image forming unit 10a. FIG. 3 is a block diagram showing a schematic configuration of a correction control unit 30 that executes color misregistration correction processing. 6 is a flowchart for explaining an example of a procedure of color misregistration correction processing executed by the correction control unit 30. 9 is a flowchart for explaining another example of the procedure of color misregistration correction processing executed by the correction control unit 30. FIG. 4 is a schematic diagram illustrating an example of a color misregistration detection pattern used in a color misregistration correction process executed by a correction control unit 30. FIG. 10 is a schematic diagram illustrating an example of a color misregistration detection pattern formed on an intermediate transfer belt during a conventional color misregistration correction process. FIG. 4 is a schematic diagram illustrating an example of a color misregistration detection pattern including a density correction pattern.

Explanation of symbols

2. Intermediate transfer roller 3 Intermediate transfer belt (an example of an image carrier)
4 ... Secondary transfer roller 5 ... Optical sensor (an example of image reading means)
9a ... Driving rollers 9b, 9c ... Driven roller 10 ... Image forming unit (an example of image forming means)
DESCRIPTION OF SYMBOLS 11 ... Charging device 12 ... Exposure device 13 ... Developing device 14 ... Cleaning device 15 ... Photoconductor drum 30 ... Correction control unit 100 ... Image forming unit

Claims (5)

A plurality of image forming means arranged in substantially a line along the conveyance path of the image carrier, and forming a visible image of at least three colors on the image carrier;
Image reading means for reading a visible image formed on the image carrier;
By controlling the image forming means, the visible image formed on the image carrier is read by the image reading means, and based on the position of the read visible image, all the image forming means Color misregistration correction means for correcting color misregistration;
An image forming apparatus comprising:
The color misregistration correction means is
By controlling the image forming means, the visible image of two or more colors and less than all colors is formed on the image carrier, and the two or more colors read by the image reading means and less than all colors are acceptable. Based on the position of the visual image, the amount of deviation of the image forming means that formed the visible image of two or more colors and less than all the colors is measured, and based on the measured amount of deviation, the color deviation caused by all the image forming means First color misregistration correction processing means for correcting
The visible image of all the colors is formed on the image carrier by controlling all the image forming means corrected by the first color misregistration correction processing means, and read by the image reading means. Second color misregistration correction that measures the shift amounts of all the image forming units based on the positions of all color visible images and corrects the color shifts of all the image forming units based on the measured shift amounts. Processing means;
An image forming apparatus comprising: Image forming means for forming the visible image than the two or more colors and the all colors, comprising an image type forming means disposed in the front row and the last of the image forming means arranged in a row The image forming apparatus according to claim 1.   By controlling all the image forming means corrected by the first color misregistration correction processing means, a density correction pattern consisting of the reference density visible images of all the colors is formed on the image carrier, and The density of each of the reference density visible images of all the colors is detected from the density correction pattern read by the image reading means, and the density correction of all the image forming means is performed based on the detected density. The image forming apparatus according to claim 1, further comprising a density correction processing unit.   The image forming apparatus according to claim 1, wherein the color misregistration correction by the second color misregistration correction processing unit and the density correction by the density correction processing unit are executed substantially in parallel. A plurality of image forming means that are arranged in substantially a line along the conveyance path of the image carrier and that form a visible image of at least three colors on the image carrier, and a plurality of image forming means formed on the image carrier. an image reading means for reading the visual image, the visible image formed on said image bearing member by controlling the upper Kizo forming means to read the said image reading means, the read position of the visible image A color misregistration correction method for an image forming apparatus comprising: a correction control unit that corrects color misregistration by all the image forming units based on
The correction control unit controls the image forming unit to form the visible image of two or more colors and less than all colors on the image carrier, and the two or more colors read by the image reading unit and Based on the positions of the visible images of less than all colors, the amount of displacement of the image forming means that formed the visible images of two or more colors and less than all colors is measured, and all the above-mentioned are based on the measured amounts of displacement. A first color misregistration correction processing step for correcting color misregistration by the image forming means;
The correction control unit controls all the image forming means corrected in the first color misregistration correction processing step to form the visible images of all colors on the image carrier, and the image reading unit. The shift amounts of all the image forming means are measured based on the positions of the visible images of all the colors read by the means, and the color shifts by all the image forming means are corrected based on the measured shift amounts. A second color misregistration correction processing step;
A color misregistration correction method comprising:

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