JP5397255B2 - Image forming apparatus - Google Patents

Description

  The present invention can form a color image composed of two or more colors of toner on recording paper, an overhead projector sheet or the like (hereinafter sometimes collectively referred to as “recording paper” or simply “paper”). The present invention relates to a color image forming apparatus having a drive unit driven for image formation, and particularly relates to color misregistration correction in a color image forming apparatus.

  In a color image forming apparatus, usually, a color image is formed by using two or more toners among a plurality of color toners such as yellow (Y), magenta (M), cyan (C), and black (K). it can. In such a color image forming apparatus, each color toner image for obtaining a desired color image is formed, these are finally transferred onto the recording paper, and the multiple toner images are applied to the recording paper under heat and pressure. A color image is formed by melting and fixing.

  However, in multi-toner image formation, color misregistration may occur between the color toner images constituting the multi-toner image. Such a color shift is originally caused by a timing shift when each color toner image is formed on the image carrier.

  For example, in an electrophotographic color image forming apparatus, the surface of an electrostatic latent image carrier such as a photoconductor is charged to a predetermined potential, image exposure is performed on the charged area, and each color constituting a color image to be formed is formed. An electrostatic latent image corresponding to the toner image is formed, the latent image is developed with a corresponding color toner to form a toner image, and each color toner image sequentially formed in this manner is generally transferred to a transfer belt. The primary transfer is sequentially performed on top of each other, and the primary transfer is performed at the timing when the respective color toner images are superimposed. The primary transfer multiple toner image is secondarily transferred onto the recording paper, and is fixed on the recording paper.

  In the process of forming a color image in this manner, for example, the timing of starting and ending the formation of an electrostatic latent image corresponding to each color toner image on the photoconductor by image exposure, each color toner image is transferred from the photoconductor to the transfer belt. Due to the transfer position deviation on the belt due to the extension of the belt at the time of primary transfer, color misregistration may occur in the multiple toner images on the transfer belt, and hence the color image on the recording paper.

For this reason, such color misregistration correction processing has been attempted in the past.
In the conventional color misregistration correction processing, before the color misregistration correction, a color misregistration amount is detected on a member of a drive unit for forming a color image (for example, the photoconductor in a drive unit including a photoconductor that is rotationally driven). A toner pattern called a resist (alignment) pattern is formed, and the resist pattern is usually transferred to an intermediate transfer belt, and the amount of color misregistration is detected from the resist pattern on the belt.

  The detection of the color misregistration amount is performed using an already known image density (toner density) sensor such as an optical type that reads the density of the toner patch for adjusting the image density, for example. The presence and position of the resist pattern is detected and grasped based on the detection information and the like.

  For example, as shown in FIG. 11, such a resist pattern is formed once by using a pattern combination composed of each color pattern of black (K), cyan (C), magenta (M), and yellow (Y) as one pattern unit. One block is formed by collecting a plurality of units for color misregistration correction (also referred to as “registration correction”).

  For example, in an electrophotographic color image forming apparatus, the resist pattern formed in this way is a primary transfer of an electrostatic latent image carrier such as a photoconductor or a toner image formed on the electrostatic latent image carrier. Due to the eccentricity of the roller around which the transfer belt is wound, for example, the formation position on the photoreceptor, which is a drive unit member for forming a resist pattern, may be shifted. If there is such a misregistration, the color misregistration amount detected from each pattern unit becomes a value that varies from the original color misregistration amount.

  When the member of the drive unit on which the resist pattern is formed is rotationally driven like the photosensitive member, for example, this variation periodically varies depending on the resist pattern forming position on the member.

  In the conventional registration correction, the drive unit member 1 for forming a resist pattern in order to cancel this periodic variation in color misregistration amount (hereinafter sometimes referred to as “offset”) and obtain an accurate color misregistration amount. The resist pattern of one block is formed per circumference, and the color misregistration amount in each pattern unit constituting the block is averaged to calculate the block color misregistration amount.

However, when the color misregistration amount is detected by forming a resist pattern constituting one long block as shown in FIG. 11, the print down time (time during which printing is not permitted) increases, and the toner consumption increases. As a result, the image productivity decreases accordingly.
As for the downtime of printing, for example, when registration correction is performed before printing, the start of printing is delayed, and when printing is interrupted, the entire printing time is prolonged.

  In this regard, in Japanese Patent Application Laid-Open No. 2004-251955, in order to shorten the resist pattern group, an offset amount (color misregistration variation) corresponding to a position on the drive unit member for forming the resist pattern is stored. A resist pattern of one block shorter than the circumference of the drive unit member is formed, and an offset amount at the position where the pattern is formed with respect to the color misregistration amount detected from the pattern (correction offset amount: the position used for correction) Describes a technique for correcting the periodic variation in color misregistration using the above-mentioned variation.

  On the other hand, when printing is interrupted before printing or during printing and registration correction is performed, a time during which printing cannot be performed occurs. Therefore, for the purpose of preventing the time during which printing cannot be performed, inter-sheet registration control has been proposed in which a resist pattern over a short range is formed between recording sheets in a printing operation to detect color misregistration.

  However, since the resist pattern is formed at the sheet interval in the inter-sheet resist, it is not known at which position on the drive unit member the resist pattern is formed. Therefore, the offset of the color misregistration amount due to the drive unevenness of the drive unit including the image carrier such as the photoconductor and the transfer belt cannot be suppressed.

  In this regard, Japanese Patent Application Laid-Open No. 2009-31739 discloses that a sheet is transported based on a fluctuation cycle of a unit member having a cyclic fluctuation such as a photosensitive member or a transfer belt so as not to be affected by a fluctuation with periodicity. It is described that the interval for forming and the position for forming the resist pattern are changed.

JP 2004-251955 A JP 2009-31739 A

By using the technique described in Japanese Patent Application Laid-Open No. 2004-251955, even when the resist pattern group is shorter than the circumference of the drive unit member that forms the resist pattern, the offset of the color misregistration amount due to the periodic variation of the drive unit is corrected. can do.
The offset amount to the color misregistration amount due to the eccentricity of the drive unit is periodic as shown in FIG. 9 of Japanese Patent Application Laid-Open No. 2004-251955. If the position on the unit on which the pattern is formed changes, it is taken in advance. From the stored data, the degree of variation is known and can be corrected.

  However, since the position corresponding to the offset amount data and the position where the resist pattern is actually formed do not completely match, the offset amount used for correction and the offset amount actually added to the color misregistration amount (actual offset amount) There is an error. If the resist pattern group is significantly shortened, the number of pattern units in one block decreases, and the difference between the correction offset (the offset amount used for correction) and the actual offset cannot be averaged. As a result, the amount of color misregistration affected by the variation is detected, and color misregistration detection with high accuracy cannot be performed.

  In addition, according to the technique described in Japanese Patent Application Laid-Open No. 2009-31739, the paper interval is widened and the image productivity is sacrificed, so that it is practically used in today's image forming apparatuses where energy saving and high productivity are required. Not right.

  Therefore, the present invention is an image forming apparatus that can form a color image composed of two or more colors of toner on a recording sheet and has a drive unit for forming a color image, and reduces image productivity. An object of the present invention is to provide an image forming apparatus capable of correcting color misregistration with high accuracy while suppressing the above-described problem.

In order to solve the above problems, the present invention provides the following image forming apparatus.
A color image composed of two or more colors of toner can be formed on a recording sheet , and has a drive unit for forming a color image , and the drive unit forms a color toner image as a drive unit member. An image forming apparatus including a rotationally driven image carrier and a rotationally driven transfer belt for transferring each color toner image formed on the image carrier ,
Color shift amount variation data creating means for creating data of periodic color shift amount variation due to drive unevenness of the drive unit;
First storage means for storing color misregistration amount variation data created by the color misregistration amount variation data creation means;
A resist pattern forming means for forming a resist pattern used for color misregistration correction on a portion on the image carrier corresponding to a recording paper interval during printing;
Color misregistration detection means for reading a resist pattern formed on the image carrier by the resist pattern forming means and transferred to the transfer belt , and obtaining a color misregistration amount from the resist pattern;
Color misregistration associating the color misregistration amount obtained by the color misregistration amount detection unit with the position on the image carrier or the transfer belt on which the resist pattern on which the color misregistration amount is obtained is formed Second storage means for storing quantity data;
Regarding the color misregistration amount data stored in the second storage means, the color misregistration amount depends on whether or not a predetermined number of data that can be recognized as color misregistration amount data correction data is stored. A color misregistration amount detection continuation necessity judging means for judging whether or not continuation of color misregistration amount detection by the detection means is unnecessary;
In the determination by the color misregistration amount detection continuation necessity determining unit, for all the color misregistration amount data stored in the second storage unit, the color from the time when the color misregistration amount data is acquired to the present is displayed. Color shift amount change determination means for determining whether or not the shift amount has changed;
Color misregistration amount data deleting means for deleting the color misregistration amount data determined by the color misregistration amount change determining means as being changed from the second storage means;
Based on the positional information of the color misregistration amount data stored in the second storage unit, provided that the color misregistration amount detection continuation necessity judging unit judges that the color misregistration amount detection is not continued. A correction unit that reads out a color shift amount variation value at a position from the first storage unit and corrects the color shift amount data stored in the second storage unit using the color shift amount variation value. The image forming apparatus.

Here, the “driving unit for forming a color image” is a unit that is driven for forming a color image, and here, as a driving unit member, a rotationally driven image carrier for forming each color toner image. And a transfer belt driven to rotate for transferring each color toner image formed on the body and the image carrier .

The “driving unevenness of the driving unit” is, for example, periodic driving unevenness due to eccentricity of a rotating member of the driving unit, for example, a rotating member such as a photosensitive member or an intermediate transfer belt.
The amount of color misregistration that occurs even when there is no drive unevenness varies if the drive unit has drive unevenness.

  The “resist pattern” is formed on a photoreceptor, for example, for use in detecting a deviation amount from the normal position of each color toner image when performing correction for alignment of each color toner image constituting a color image, A toner pattern transferred and formed on the intermediate transfer belt.

  Examples of the first storage unit include a first storage unit, and examples of the second storage unit include a second storage unit.

  Examples of the color misregistration amount detection unit include a unit that reads a resist pattern and a unit that can calculate a color misregistration amount based on the read information. As a means for reading a pattern, an image density that is already known per se, such as an optical method that reads the density of a toner patch for adjusting the image density, which is often used in an image forming apparatus. A toner density sensor can be exemplified. According to such an image density sensor, the amount of color misregistration can be grasped by detecting the presence and position of a resist pattern.

  According to the image forming apparatus of the present invention, the color misregistration amount variation data creating means creates the data of the periodic color misregistration amount variation due to the driving unevenness for the drive unit that is the resist pattern formation target. Stored in one storage means.

  The “color shift amount variation data” is formed, for example, by forming a resist pattern unit group as shown in FIG. 11 over a range that can substantially cover each part on the member forming the resist pattern of the drive unit. Obtain the color misregistration amount at each part on the member, obtain the difference between them and the average color misregistration amount obtained by averaging the color misregistration amounts at each part, and set the difference and its position as the color misregistration amount variation data. be able to.

  In this way, the color misregistration amount detection is performed without interrupting printing in order to prevent the image productivity from being lowered in a state where the color misregistration amount variation data is stored in the first storage unit. For this purpose, a resist pattern is formed by a resist pattern forming unit on a portion (for example, a portion on a photosensitive member or an intermediate transfer belt) on a drive unit member between recording sheets being printed.

  The color misregistration amount detecting means detects the color misregistration amount from the resist pattern formed in this way. The color misregistration amount obtained by the color misregistration amount detection means is stored in the second storage means in association with the position on the drive unit member where the resist pattern is formed.

The correction unit corrects the color misregistration amount stored in the second storage unit. At this time, the color misregistration amount data stored in the second storage unit is data that can be corrected. Therefore, it is desirable to have a predetermined number sufficient for correction.
As the number of such data, for example, a number that can be regarded as a number sufficient for correction based on one or more of previous experiments, past experiences, and the like can be adopted.

  However, in the image forming apparatus according to the present invention, in actual use, there are cases where continuous printing is not performed or a sleep mode is set after reading a resist pattern of several blocks. In these cases, it takes time from the start of color misregistration detection until the color misregistration amount of a sufficient number of resist patterns is obtained. If a long time elapses after the start of color misregistration detection and before the necessary color misregistration amount data is prepared, the resist pattern formation environment (especially temperature) may change and the color misregistration amount may change. . Then, the old color shift amount data acquired at an early stage may not match the current color shift level. If this old color misregistration amount data is used as it is to determine the color misregistration amount, the color misregistration amount cannot be detected correctly. Therefore, it is necessary to determine whether each color misregistration amount data is valid (can be regarded as data to be corrected). If it is determined that the color misregistration amount data is not valid, the color misregistration amount data is It should be discarded. By doing so, the color misregistration amount can be calculated using only data that matches the current color misregistration situation.

Therefore, in the image forming apparatus according to the present invention,
Whether or not a predetermined number of data that can be recognized as color misregistration amount data correction target data is stored by the color misregistration amount detection continuation necessity determining unit with respect to the color misregistration amount data stored in the second storage unit. Depending on whether or not, it is determined whether or not continuation of color misregistration detection by the color misregistration detection means is unnecessary.

Further, at this time (when the color misregistration amount detection continuation necessity judging means judges), the color misregistration amount change judging means performs the color misregistration amount with respect to all the color misregistration amount data stored in the second storage means. Determine whether the color misregistration amount has changed from the time the data was acquired to the present (in other words, whether the data is not recognized as data subject to color misregistration data correction). To do.
Then, the color misregistration amount data deletion unit deletes the color misregistration amount data determined to have changed by the color misregistration amount change determination unit from the second storage unit.

  The correction means determines that the color misregistration amount data stored in the second storage means is determined on the condition that the color misregistration amount detection continuation judging means determines that the color misregistration amount detection is not continued. The color shift amount variation value at the position based on the position information is read from the first storage unit, and the color shift amount data stored in the second storage unit is corrected using the color shift amount variation value.

Based on the color misregistration data corrected in this way, color misregistration in color image formation can be corrected to form a color image with suppressed color misregistration composed of two or more toners on a recording sheet.
Here, “correction of color misregistration in a color image” means that the misregistration between the color toner images constituting the color image is corrected according to the obtained color misregistration amount (here, the corrected color misregistration amount). In the case of an electrophotographic image forming apparatus, for example, the position of forming each color toner image on the photoconductor is adjusted based on the amount of color misregistration. This process corrects color misregistration.

  Thus, according to the image forming apparatus of the present invention, it is possible to perform color misregistration correction with high accuracy while suppressing a decrease in user convenience such as a decrease in image productivity and an increase in toner consumption.

  In addition to the color misregistration amount obtained by the color misregistration amount detecting means and the position on the drive unit member on which the resist pattern from which the color misregistration amount was obtained is stored in the second storage means, The number of prints at the time when the resist pattern is formed, the pattern formation time, and the pattern formation environmental conditions may be associated with each other and stored as color misregistration amount data.

In any case, in the image forming apparatus according to the present invention, the color shift amount detection continues necessity determination means, the second color shift amount data stored in the storage means the color shift amount data correction of the target Whether or not the data can be recognized is determined according to the position of the resist pattern on the drive unit member ( on the image carrier or the transfer belt) based on the color misregistration amount data. This is performed according to the reliability of the color misregistration amount data.

  In the above “determining according to the reliability”, for example, a plurality of areas are set in the drive unit member on which the resist pattern is formed, and the magnitude of the color shift amount variation in the area is determined according to the area. Larger ones (less reliable) have a smaller weight (count smaller than the original number of data), and smaller ones (higher reliability) have a higher weight (the same or close to the original number of data). Counting), and the number of data can be used as the number of data relating to the color misregistration amount.

Specific examples of the color misregistration amount change determining means include the following.
(1) determining that the amount of color misregistration has changed after a predetermined time has elapsed since the formation of the resist pattern;
(2) determining that the color misregistration amount has changed when a predetermined number of sheets or more are printed from the number of printed sheets when the resist pattern is formed;
(3) When the environmental temperature of the resist pattern is changed from a temperature at which the resist pattern is formed to a predetermined temperature, it is determined that the color misregistration amount has changed.
The “predetermined time from when the resist pattern is formed” in (1), the “predetermined number of prints” in (2), and the “predetermined temperature change” in (3) are ascertained through experiments and experience, for example. It is possible to adopt “time”, “number of prints”, and “temperature change” that can be regarded as the amount of color misregistration being changed.

Color misregistration data obtained from resist patterns respectively formed at diagonal positions of the rotating member (the image carrier) included in the drive unit , that is , at positions that divide the circumference of the image carrier surface by two can be grasped. In some cases, there may be provided means for calculating the color misregistration amount only from the color misregistration amount data at the bisecting position without performing the color misregistration amount data correction based on the color misregistration variation value.

As explained above, according to the present invention,
An image forming apparatus capable of forming a color image composed of two or more toners on a recording sheet and having a drive unit for forming a color image, while suppressing a decrease in image productivity, An image forming apparatus capable of correcting color misregistration with high accuracy can be provided.

1 is a diagram schematically illustrating a configuration of an example of an image forming apparatus according to the present invention. FIG. 2 is a block diagram schematically showing a control circuit of the image forming apparatus shown in FIG. 1. It is a figure which shows the example of the long resist pattern used for color shift amount offset data acquisition. FIG. 4 is a diagram illustrating an example of color misregistration amount data in the long resist pattern of FIG. 3. It is a figure which shows the resist pattern formed between the paper in printing. It is a figure which shows a mode that the resist pattern shown in FIG. 5 is formed between the paper in printing. FIG. 6 is a diagram illustrating a variation in color misregistration amount in each area by dividing the photoconductor into 16 areas. 2 is a flowchart showing an operation mainly related to registration correction of an engine control unit after the image forming apparatus shown in FIG. 1 is started. It is a flowchart which shows procedures, such as a validity judgment of the color misregistration amount data in an engine control part, the deletion of the data, and the necessity judgment of the same data preparation. It is a flowchart which shows the color shift amount correction | amendment procedure in an engine control part. It is a figure which shows 1 block which gathered several units by making the pattern combination which consists of each color pattern of YMCK into 1 pattern unit.

Hereinafter, an example of an image forming apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of the configuration of one example 10 of the image forming apparatus. The image forming apparatus 10 is a tandem type color image forming apparatus, and includes a printer part PR and an image reading apparatus 100, and is a complex machine that can be used as a copying machine, a printer, a facsimile machine, or the like.

  The printer portion PR has an endless intermediate transfer belt 7 wound around a driving roller 71 and a roller 72 facing the driving roller 71. The transfer belt 7 is rotated counterclockwise in the figure (arrow direction in the figure) CCW by a driving roller 71 driven by a belt driving unit 70.

  A cleaning device 73 for cleaning secondary transfer residual toner and the like on the transfer belt 7 faces the roller 72, and a secondary transfer roller 8 faces the drive roller 71 via the belt 7.

The secondary transfer roller 8 is pressed against a portion of the intermediate transfer belt 7 supported by the driving roller 71 by a pressing unit (not shown), forms a nip portion with the intermediate transfer belt 7, and rotates the intermediate transfer belt 7. It can be rotated following the movement of the recording paper S fed to the nip portion or driven by a drive unit (not shown).
A secondary transfer bias can be applied to the secondary transfer roller 8 from a power supply (not shown).

  A fixing device 9 is disposed above the intermediate transfer belt 7 and the secondary transfer roller 8, and a timing roller pair 11 is disposed below the intermediate transfer belt 7 and the secondary transfer roller 8. A recording sheet storage cassette 10S storing a recording sheet or the like S is disposed.

  Although not limited thereto, in this example, the fixing device 9 includes a fixing heating roller 91 heated by a heat source and a pressure roller 92 pressed against the fixing heating roller 91, and is passed through the nip portion of both rollers. The secondary transfer toner image can be melted and fixed on the recording paper under heat and pressure. Instead of the fixing heating roller 91, an endless belt may be wound around a heat roller and a roller facing the heat roller, and a recording sheet holding a toner image may be passed between the belt and the pressure roller.

  The recording paper S stored in the recording paper storage cassette 10 </ b> S can be pulled out one by one by the paper supply roller 101 and supplied to the timing roller pair 11.

  Between the rollers 71 and 72 around which the intermediate transfer belt 7 is wound, the yellow color responsible imaging unit YH, the magenta color responsible imaging unit MH, and the cyan color responsible are arranged along the transfer belt 7 from the roller 72 toward the roller 71. The imaging unit CH and the black color responsible imaging unit KH are arranged in this order.

  The YH, MH, CH, and KH imaging units each include a drum-type photosensitive member 1 as an electrostatic latent image carrier, and a charger 2, a developing device 4, and a cleaning device 5 are provided around the photosensitive member 1. Arranged in order.

  A primary transfer roller 6 is disposed opposite to the photoreceptor 1 of each imaging unit with a belt 7 therebetween. Each primary transfer roller 6 is pressed in the direction of the photoconductor 1 by a pressing means (not shown) in this example, and can be driven to rotate by contacting the belt 7, and can bring the belt 7 into contact with the photoconductor 1.

  A primary transfer bias for primary transfer of the toner image formed on the photoreceptor 1 to the belt 7 can be applied to the primary transfer roller 6 from a power supply (not shown).

  The photosensitive member 1 of each imaging unit can be subjected to image exposure from the exposure unit 3 to form an electrostatic latent image corresponding to the color assigned to each imaging unit. The exposure unit 3 can perform image exposure on the photoreceptor 1 of each imaging unit in accordance with image information provided from a personal computer (not shown), the image reading apparatus 100, and the like.

  In FIG. 1, reference numeral 3y denotes a reflection mirror that reflects light for forming a yellow electrostatic latent image from the exposure unit 3 toward the photoreceptor 1 of the imaging unit YH. Similarly, the reflection mirror 3m reflects the light for forming the magenta electrostatic latent image toward the photoreceptor 1 of the unit MH, and the reflection mirror 3c reflects the light for forming the cyan latent image for the unit CH. The reflection mirror 3k reflects the light for forming the black electrostatic latent image toward the photoconductor 1 of the unit KH.

  The photoreceptor 1 in each imaging unit is not limited thereto, but in this example is a negatively chargeable photoreceptor, and can be rotated in the clockwise direction in the figure by a photoreceptor drive motor (not shown).

  The charger 2 in each imaging unit is a scorotron charger in this example, and a voltage for charging the photosensitive member is applied from a power supply (not shown) at a predetermined timing. The charger 2 may be one using a charging roller.

  The developing device 4 in each imaging unit uses a developer mainly composed of toner, and can reversely develop the electrostatic latent image on the photoreceptor 1 with a developing roller 41 to which a developing bias is applied from a power supply (not shown). . The developing device 4 may use a so-called two-component developer mainly composed of a carrier and toner as a developer.

  A density sensor SE that can detect the density of the toner pattern formed on the belt 7 is provided at a portion from the imaging unit KH to the driving roller 71 of the intermediate transfer belt 7. The density sensor SE is used for adjusting a density of an image to be formed in advance or detecting a resist pattern formed for color misregistration correction (registration correction) for aligning each color toner image on the belt 7. It is done.

  Furthermore, as will be described later, the density sensor SE can detect the presence of a resist pattern for correcting color misregistration formed on the belt 7 as will be described later. Based on the detection information, it can be used to detect the position of the pattern on the belt 7 and the color misregistration amount between the color toner images. Further, the fluctuation amount of the periodic color misregistration due to the eccentricity of the photosensitive member 1 and the eccentricity of the rollers 71 and 72 around which the belt 7 is wound is related to the position of the resist pattern on the photosensitive member and the position on the belt. It can also be used to ask.

  The image reading apparatus 100 reads an image for copying of a document image, facsimile transmission of the document image, reading of the document image and storage in a storage unit, and the like, which is a type already known per se. .

FIG. 2 is a block diagram illustrating an outline of a control circuit of the image forming apparatus 10.
The control circuit includes an engine control unit Cont1 and a control unit Cont2 referred to as an MFP control unit in this example.

  The engine control unit Cont1 controls the operation of the imaging unit and the like when forming a toner image. The control unit Cont1 is connected to the imaging units YH, MH, CH, and KH, the exposure unit 3, the drive unit 70 of the intermediate transfer belt 7, and the printer 100 such as the fixing device 9, which are connected to the control unit Cont1. It operates at a predetermined timing based on the instruction. The control unit Cont1 is also connected to a temperature sensor TS for detecting the temperature in the image forming apparatus [substantially the temperature of the exposure unit (PH temperature) in this example].

  The MFP control unit Cont2 is connected to the control unit Cont1, and a communication interface for connecting an external device such as an operation panel PA, the image reading apparatus 100, and a personal computer is connected to the control unit Cont2. On the operation panel PA, various image forming modes, setting of the number of image formations, setting of a recording paper size for image formation, and the like can be performed.

  The control unit Cont1 and the control unit Cont2 will be further described later.

According to the image forming apparatus 10, an image can be formed using one or more of the YH, MH, CH, and KH imaging units of the printer portion PR based on an instruction from the control unit Cont1 or the like.
Taking a case where a full color image is formed using all of the imaging units as an example, first, a yellow toner image is formed in the yellow color imaging unit YH, and this is primarily transferred to the transfer belt 7.

  That is, in the imaging unit YH, the photosensitive member 1 is rotated in the clockwise direction in the drawing, and the surface is uniformly charged to a predetermined potential by the charger 2, and image exposure for a yellow image is performed from the exposure unit 3 to the charged area. And an electrostatic latent image for yellow is formed on the photoreceptor 1. This electrostatic latent image is developed by a developing roller 41 to which a developing bias of the developing device 4 having yellow toner is applied, and becomes a visible yellow toner image. The yellow toner image is primarily transferred onto the transfer belt 7 by the primary transfer roller 6. At this time, a primary transfer bias is applied to the primary transfer roller 7 from a power supply (not shown).

  Similarly, a magenta toner image is formed in the imaging unit MH and transferred to the transfer belt 7, a cyan toner image is formed and transferred to the transfer belt 7 in the imaging unit CH, and a black toner image is formed in the imaging unit KH. Then, it is transferred to the transfer belt 7.

Yellow, magenta, cyan, and black toner images are formed at a timing when these toner images are transferred onto the intermediate transfer belt 7 in an overlapping manner.
Thus, the multiple toner image formed on the transfer belt 7 moves toward the secondary transfer roller 8 by the rotation of the transfer belt 7.

  On the other hand, the recording medium S is pulled out from the cassette 10S by the paper supply roller 101, supplied to the timing roller pair 11, and is on standby.

  In this way, the recording sheet S waiting at the timing roller pair 11 is supplied to the nip portion between the belt 7 and the secondary transfer roller 8 in accordance with the multiple toner image sent by the belt 7. The multiple toner image is secondarily transferred onto the recording paper S by a secondary transfer roller 8 to which a secondary transfer bias is applied from a power source (not shown).

  Thereafter, the recording paper S is passed through the fixing device 9 where the multiple toner images are fixed on the recording paper S under heat and pressure. Thereafter, the recording sheet S is discharged to the discharge tray 13 by the discharge roller pair 12.

  In the primary transfer of the toner image to the belt 7, transfer residual toner or the like remaining on the photoreceptor 1 is cleaned by the cleaning device 5, and secondary transfer residual toner or the like remaining on the belt 7 by the secondary transfer is cleaned by the cleaning device 73. It is cleaned with. Each of these cleaned and removed toners is sent to a waste container by a conveying means (not shown).

  As described above, an image is formed. In color image formation, color misregistration correction (registration correction) is performed in order to provide a high-quality image with suppressed color misregistration. . Hereinafter, this point will be described.

In the color misregistration correction in the image forming apparatus 10 described below, a periodic color misregistration amount fluctuation due to a deviation (eccentricity) of the rotation center of the photosensitive member 1, in other words, a periodic color misregistration amount offset is considered. The However, according to the present invention, for example, color in consideration of color shift variation such as periodic color shift amount variation due to the eccentricity of the intermediate transfer belt 7 due to the eccentricity of the rotation center of the rollers 71 and / or 72 in the intermediate transfer unit. It can also be applied to deviation correction.
Here, in the color misregistration correction in the image forming apparatus 10, a periodic color misregistration amount variation due to the deviation (eccentricity) of the rotation center of the photoconductor 1 is taken into account. For this reason, the control unit Cont1 includes the photoconductor 1. A color misregistration amount variation data creation unit C1 that creates data of periodic color misregistration amount variation of each color toner image formed thereon is included. The data creation procedure by the color shift amount variation data creation unit C1 will be described later.

  The control unit Cont1 includes a non-volatile memory ME, which includes an area of the first memory me1 and an area of the second memory me2. The color shift amount variation data created by the data creation unit C1 is stored in the memory me1 as a set in association with the position on the photoreceptor.

The control unit Cont1 also includes a color misregistration amount detection unit C2 that detects the color misregistration amount together with the above-described density sensor SE.
The color misregistration amount detection unit C2 obtains the color misregistration amount based on the resist pattern sampling data acquired by the density sensor SE, and the color misregistration amount is calculated for the time when the resist pattern is formed and until the resist pattern is formed. Are stored in the second memory me2 in association with the print integrated number of prints and the temperature (PH temperature) detected by the temperature sensor TS. The procedure for obtaining the color misregistration amount by the detection unit C2 will be described later.

The control unit Cont1 further includes the following.
(1) Regarding the color misregistration amount data stored in the second memory me2, the color misregistration amount depends on whether or not a predetermined number of data that can be recognized as color misregistration amount data correction data is stored. A color misregistration amount detection continuation necessity determination unit C3 for determining whether or not continuation of color misregistration detection by the detection unit C2 is unnecessary or necessary
(2) In the determination by the color misregistration amount detection continuation necessity determination unit C3, from the time when the color misregistration amount data is acquired to the present for all the color misregistration amount data stored in the two memories me2. The color misregistration amount change determination unit C4 for determining whether or not the color misregistration amount has changed (in other words, whether or not the data that is subject to color misregistration amount data correction is not recognized). 3) A color misregistration amount data deletion unit C5 that deletes the color misregistration amount data determined by the color misregistration amount change determination unit C4 from the second memory me2.
(4) The position information of the color misregistration amount data stored in the second memory me2 is used on condition that the color misregistration amount detection continuation necessity determination unit C3 determines that the color misregistration amount detection is not continued. The correction unit C6 reads out the color shift amount variation value at the base position from the first memory me1 and corrects the color shift amount data stored in the second memory me2 using the color shift amount variation value.

  These functional units C1 to C6 in the control unit Cont1 may have at least a part of their constituent parts shared with constituent parts such as other functional parts.

  In the image forming apparatus 10, a resist pattern used for resist correction can be formed on the photoreceptor 1 and transferred onto the intermediate transfer belt 7 as described below under the control of the control unit Cont 1 and the control unit Cont 2.

  The communication between the engine control unit Cont1 and the MFP control unit Cont2 is serial communication. The MFP control unit Cont2 performs printing, image stabilization (image density stabilization processing at timing before starting printing, etc.), registration correction through the image bus. Image data for the pattern is provided to the engine control unit Cont1.

  The resist pattern is a portion on the photosensitive member 1 corresponding to a space between the recording paper on which an image is to be formed in order to suppress a decrease in image productivity under the instruction of the control unit Cont1, and as a result, an intermediate transfer belt. 7 (hereinafter, these are sometimes referred to as “inter-sheet portions”).

  Thus, the resist pattern formed in the portion between the sheets on the belt 7 is detected by the density sensor SE, and the detection information is input to the control unit Cont1.

  More specifically, when the controller Cont1 detects a factor that requires the color misregistration amount data correction process, for example, the PH temperature detected by the temperature sensor TS changes by 2 ° C., it is stored in the second memory me2. It is determined whether or not a predetermined number of data that can be recognized as color misregistration amount data correction data is stored with respect to the color misregistration amount data, and if the number of data is insufficient (at this time, the determination unit If C3 determines that it is necessary to continue, the registration request T2 is transmitted to the MFP control unit Cont2. When the control unit Cont2 receives the registration request, it transmits a registration command T1 to the engine control unit Cont1 between the print sheets. When receiving the registration command T1, the engine control unit 1 causes the imaging unit to form an image in accordance with the image data of the registration pattern and transfers the image onto the transfer belt 7.

  However, regarding the color misregistration amount data stored in the second memory me2, if a predetermined number of data that can be recognized as color misregistration amount data correction data is stored (the determination unit C3 continues at this time). If it is determined that it is unnecessary, the control unit Cont1 transmits a registration stop request T2 to the control unit Cont2. When receiving the registration stop request, the control unit Cont2 stops registration command transmission between print sheets.

  In determining whether or not the color misregistration amount detection needs to be continued, the current determination is made from the time when the color misregistration amount data is acquired for all the color misregistration amount data stored in the second memory me2 (by the determination unit C4). Whether or not the color misregistration amount has changed in the meantime (in other words, whether or not the data subject to color misregistration amount data correction is not recognized), and the color misregistration amount has changed. The color misregistration amount data determined to be deleted is deleted from the second memory me2 (by the data deletion unit C5).

  “Color misregistration data whose color misregistration amount has changed”, in other words, “data that is no longer recognized as data subject to color misregistration data correction” does not match the current color misregistration amount. It is data.

  The position of the control unit Cont1 (particularly the correction unit C6) based on the position information of the color misregistration amount data stored in the second memory me2 on condition that it is determined not to continue the color misregistration amount detection. Is read from the first memory me1, and the color shift amount data stored in the second memory me2 is corrected using the color shift amount change value.

  The image forming apparatus 10 corrects the color misregistration by a method already known per se based on the color misregistration amount data thus corrected, and forms a color image composed of two or more colors of toner on the recording paper. it can.

  Next, creation of color misregistration amount offset data (color misregistration amount variation data) by the color misregistration amount variation data creation unit C1 will be described.

  FIG. 3 shows a long resist pattern used for obtaining color misregistration amount offset data. In FIG. 3, Y is a yellow resist pattern formed using the imaging unit YH, M is a magenta resist pattern formed using the imaging unit MH, and C is a cyan resist formed using the imaging unit CH. K is a black resist pattern formed using the imaging unit KH.

  In this example, when mounting of a new imaging unit including a photoconductor is detected by a detection unit (not shown), a long resist pattern shown in FIG. 3 is formed on the photoconductor 1 and eventually on the intermediate transfer belt 7. This is read by the density sensor SE, and color misregistration amount offset data is obtained from the read data.

  In this example, the diameter of the photoreceptor 1 of each imaging unit is 60 mm, and the circumference is 188.5 mm. Since the offset of the color misregistration amount requires data for one rotation of the photoreceptor, the pattern length of the long resist pattern is also set to 188.5 mm. The KCMY four-color pattern is one unit, and 16 units are one pattern.

FIG. 4 shows an example of the color misregistration amount data of the cyan resist pattern with respect to the black resist pattern K in the long resist pattern. The position where the first unit of the long resist pattern is detected is set to 0, and the data of the color shift amount variation value at the position where each unit is formed is acquired. The data acquired in this way is shown in the following table. The following table is a table of color misregistration amounts between K and C.
Color shift amount of long resist pattern
i 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
d (i) 116 133 145 149 146 135 119 100 80 64 53 50 55 66 84 100

Then, d (i) is the color misregistration amount actually detected in the i th unit, and di is the true value of the color misregistration amount in the i th unit. Here, the true value di of the color misregistration amount is an average of the color misregistration amounts in all units as shown in the following equation.
di = [d (0) + d (1) + d (2) + ... d (n-1) + d (n)] / n (n: number of units)

  Therefore, the color misregistration variation amount O (i) in each unit is the difference between the detected color misregistration amount d (i) and the color misregistration amount true value di. That is, O (i) = d (i) −di.

In the case as shown in FIG. 4, the color shift amount true value di is 99.7 μm, and the color shift fluctuation amount O (i) in each unit is as shown in the following table.
Color shift variation of each unit
i 0 1 2 3 4 5 6 7 8 9 10
O (i) 16.3 33.3 45.3 49.3 46.3 35.3 19.3 0. 3 -20 -36 -47

i 11 12 13 14 15
O (i) -50 -45 -34 -16 -0.3

  Similarly, the color shift amount fluctuation value is obtained for magenta and yellow.

Next, color misregistration detection by the color misregistration amount detection unit C2 will be described with reference to FIGS. FIG. 5 shows a resist pattern formed between sheets being printed, and FIG. 6 shows a state where such a resist pattern is formed between sheets being printed.
As shown in FIG. 6, a short resist pattern is formed between the sheets being printed to detect the amount of color misregistration.

  When the conditions necessary for resist control (in this example, the PH temperature indicating the exposure unit temperature detected by the temperature sensor TS substantially changes by ± 2 ° C. or more) are satisfied, a resist pattern is formed as shown in FIG. . Each resist pattern is read by the density sensor SE, and the amount of color misregistration is calculated. In this example, the calculated color misregistration amount, the position on the photoconductor on which the resist pattern is formed, and the temperature detected by the temperature sensor TS at that time are stored in the second memory me2 as one color misregistration amount data.

  The color misregistration amount in the color misregistration amount data obtained from the nth formed resist pattern is G (n), the pattern formation position on the photoconductor is pc (n), and the temperature detected by the temperature sensor TS is T (n ). A plurality of resist patterns are formed, and each resist pattern has color shift amount data.

  When the number of pieces of color misregistration data necessary for detecting the color misregistration is obtained, the formation of the resist pattern between the print sheets is finished (see the last sheet interval in FIG. 6), and the color from which the color misregistration fluctuation is removed The amount of deviation is calculated.

  The “color misregistration amount Gx (n) from which the color misregistration amount variation has been removed” is the color misregistration amount variation value O (pc (n)) stored in the first memory me1 from the calculated color misregistration amount G (n). This is a subtraction correction. That is, the correction color misregistration amount Gx (n) = G (n) −O (pc (n)).

  For example, it is assumed that the position pc (1) on the photoconductor on which the first resist pattern is formed is area 0. Referring to the table of “color shift fluctuation amount”, the color shift fluctuation value O (area 0) in area 0 is 16.3 μm. When the calculated color misregistration amount G (1) is 150 μm, the color misregistration amount Gx (1) from which the color misregistration amount variation is removed is approximately 133 μm.

  The correction color misregistration amount acquisition from which such color misregistration amount variation is removed is performed for all the color misregistration amount data. Then, an average color misregistration amount is calculated by taking an average of all the “color misregistration amounts Gx (n) from which the color misregistration amount variation is removed”. Using this average color misregistration amount as the final correction color misregistration amount, color misregistration correction (registration correction) processing may be performed.

Next, the determination by the color misregistration amount detection continuation necessity determination unit C2 will be described with reference to FIG. FIG. 7 shows the color shift amount fluctuation value of each area by dividing the photosensitive member 1 into 16 areas.
In this example, the number of detected color misregistration amount data is counted, and when the number reaches a predetermined value, it is determined that “detection is completed”. However, since the variation of the color misregistration amount variation value varies depending on the position on the photoconductor where the resist pattern is formed, the number of color misregistration amount data is counted by weighting according to the position where the pattern is formed.

  As shown in FIG. 7, the photosensitive member 1 is divided into 16 areas, and the color shift amount variation value in each area is used for correcting the color shift amount. It is divided into three groups according to the width of variation in color shift variation values in the area. A group with a large variation requires a large number of data in order to smooth the error of the actual color misregistration amount variation and the color misregistration amount variation used in the correction. Therefore, the weight is reduced. Conversely, in an area where the variation width is small, smoothing can be performed even if the number of data points is small, so that the weight becomes large.

  In this example, the weight groups are divided as follows. A group having a large variation width in the area is group A, a group having a normal variation width is group B, and a group having a small variation width in the area is group C. Each group is weighted, and a resist pattern is formed in a portion corresponding to the space between the sheets on the belt 7 until the sum of the weighted points reaches a predetermined value, and the amount of color misregistration is detected. These are shown in the following table.

Group according to variation width in area
Group area Weight W
Group A 0,5,6,7,8,13,14,15 0.5
Group B 1, 4, 9, 12 0.8
Group C 2, 3, 10, 11 1.0

Next, determination of a color shift amount change by the color shift amount change determination unit C4 will be described.
In this determination, it is determined by determining whether or not the color misregistration amount data matches the current degree of color misregistration.

  When continuous printing is not performed or when the sleep mode is set after reading several blocks of resist patterns, it takes time until the necessary data is prepared after the start of color misregistration detection. During this time, the degree of color shift may change, and the color shift amount data stored in the second memory me2 may not match the current color shift state. In that case, the color misregistration amount data is discarded.

In this example, the total number of printed sheets when the resist pattern is formed, the temperature detected by the temperature sensor TS (substantially the temperature of the exposure unit, the resist pattern forming environment temperature), and the time when the resist pattern is formed are defined as the color misregistration amount. Stored in the second memory me2 as color misregistration amount data as a set, from the time of resist pattern formation
(1) When 2000 or more sheets are printed,
(2) If the temperature detected by sensor TS changes by 2 ° C or more,
(3) When more than 20 minutes have passed, it is determined that the color misregistration data corresponding to at least one of the predetermined values no longer matches the current color misregistration level, and the color misregistration amount changes. Judge that you have done.
In the example described with reference to the flowcharts of FIGS. 8 to 10, the position and temperature are stored as a color misregistration amount and a set.

  The color misregistration amount data determined in this way is deleted from the second memory me2 by the color misregistration amount data deleting unit C5.

FIG. 8 is a flowchart showing the operation of the engine control unit Cont1 after the image forming apparatus 10 is activated.
When the image forming apparatus 10 is activated, the control unit Cont1 starts an initial operation of the process in step S000. In the following description, each step in the flowchart may omit only the “step” character and indicate only the “S” character and the subsequent step number.

  In S000, the initial position of the device in the apparatus 10 is returned. When the initial operation of the process is completed, it is determined whether or not a new part that can be replaced in S001 (shown as “new unit” in FIG. 8) is installed in the apparatus 10, and the new unit is installed. When detected, in S002, as described with reference to FIGS. 3 and 4, color shift amount variation value data is created and stored in the first memory me1. The new unit in this example is a new imaging unit including a photoconductor.

  In S003, it is necessary to monitor whether the temperature detected by the sensor TS has changed by 2 ° C or more from the previous color misregistration correction considering the color misregistration variation. If the temperature change is not detected in S003, it is necessary to correct the color misregistration. Therefore, monitoring is continued until the detected temperature of the sensor TS changes by 2 ° C. or more (in the case of “None” in S003).

If the temperature change is detected in S003, there is a high possibility of color misregistration, so registration control is performed in the following steps.
In S004, it is determined whether the color misregistration data acquired so far is data that matches the current color misregistration degree. Details of S004 will be described later with reference to FIG.

  In this example, since a resist pattern is formed at the sheet interval during printing, it waits for a registration command to be transmitted from the MFP controller Cont2 between the sheets being printed in S005. When the registration command is received, a registration pattern shown in FIG. 5 is formed on the transfer belt 7 between the sheets in S006. Next, in S007, the resist pattern formed in S006 is read by the density sensor SE, the color misregistration amount G (n) is calculated from the input data of the pattern, and stored in the second memory me2.

In S008, the amount of color misregistration G (n) and the position of the resist pattern on the basis of the calculation (in other words, the position on the belt 7 corresponding to the position) pc (n) are used as the amount of color misregistration. G (n) is stored in the second memory me2, and in S009, the temperature detected by the temperature sensor TS at that time (substantially exposure unit temperature: PH temperature) T (n) is also the color misregistration amount G (n ) And stored in the second memory me2.
Thus, color misregistration amount data in which the color misregistration amount G (n), the position pc (n), and the detected temperature T (n) are set as described above is stored in the second memory me2.

It is determined whether or not sufficient amount of color misregistration data has been acquired after S010. A counter Cnt that counts the obtained color misregistration amount data points is counted up. In S010, the position where the pattern is formed is determined. In this example, as shown in the “Group by area variation width” table above, the weight W is 0.5 (S011) for group A, the weight W is 0.8 (S012) for group B, and the weight for group C. W is assumed to be 1.0 (S013).

  In S014, the counter Cnt is incremented by adding the weight W determined in S010 to S013. In S015, it is determined whether a sufficient number of color shift amount data has been acquired. If the counter Cnt is 2 or more, it is determined that sufficient data for smoothing the error of the actual color misregistration amount variation and the color misregistration amount variation used in the correction is obtained, and “pattern formation of the inter-paper resist pattern is completed”. To do. However, if the counter Cnt has not reached 2, it is determined that the data amount is insufficient, a pattern is formed between the print sheets, and the acquisition of the color misregistration amount data is continued.

If the pattern formation is ended in S015, the average color misregistration amount is calculated using the detected color misregistration amount in S016. Details of S016 will be described later with reference to FIG.
When the average color misregistration amount is detected, the detection temperature (substantially exposure unit temperature: PH temperature) T (n) at the time of the previous registration (color misregistration correction) T (n) is updated to “current temperature” in S017. .

  With reference to FIG. 9, a description will be given of whether or not the color misregistration amount data stored in the second memory me2 is valid, and deletion of data when it is not valid (step S004 in FIG. 8). This determination is a determination by the color shift amount change determination unit C4, and the data deletion is a data deletion by the color misregistration amount data deletion unit C5.

  Specifically, in this example, when the temperature detected by the sensor TS changes by ± 2 ° C. or more from the PH temperature when the pattern is formed, the color misregistration data is deleted. In this example, the determination is made based on the PH temperature. However, if the time, the total number of printed sheets, and the like have changed by a predetermined value or more, a method of deleting the color misregistration amount data may be used.

Get the current PH temperature Tonow in S100. The following control flow is executed for all stored color misregistration amount data.
The PH temperature T (i) at the time when the pattern (i-th) for which the color misregistration data has been acquired in S101 is formed is acquired from the second memory me2.
In S102, the two PH temperatures are compared. If the absolute value of the difference between the two PH temperatures is less than 2 ° C., the color misregistration amount data remains, and the process proceeds to determination of the next color misregistration amount data (S109). If the temperature difference is 2 ° C. or more, it is determined that the color misregistration amount data does not coincide with the current degree of color misregistration, and is erased (S108).

Since it is necessary to subtract the point of the erased color misregistration data, it is determined to which group the position where the color misregistration data pattern erased in S103 is formed belongs.
In the case of group A shown in the above-mentioned “Group by area variation width” table, the weight W is 0.5 (S104),
For group B, the weight W is 0.8 (S105).
For group C, the weight W is 1.0 (S106).

In S107, the weight W determined in S104 to 106 is subtracted from the counter Cnt.
If the color misregistration data is erased in S108, the process proceeds to determination of the next color misregistration data (S109).

  Next, correction of the detected color misregistration amount by the color misregistration amount correction unit C6 will be described with reference to FIG. As shown in FIG. 10, the position pc (n) on the photoconductor on which the resist pattern is formed is acquired from the second memory me2 in S200. Based on the position acquired in S200, the color shift amount variation value O (pc (n)) at that location is acquired from the first memory me1 (S201). In S202, the color misregistration amount obtained by subtracting the color misregistration amount variation value O (pc (n)) at the same position from the detected color misregistration amount G (n) (see also step S008 in FIG. 8) to remove the color misregistration amount variation. obtain.

  The above steps S200 to S202 are repeated for the color misregistration amount data stored in the second memory me2 (S2021). When the removal of the color misregistration amount variation is completed for all the color misregistration amount data, an average value of the color misregistration amounts from which the variation values are removed is calculated in step S203, and the calculated color misregistration amount (corrected color misregistration amount) is calculated. )

  According to the image forming apparatus 10, the resist pattern is formed in a portion corresponding to the recording paper of the drive unit such as the photoconductor and the intermediate transfer belt, so that the reduction in image productivity is suppressed and the drive is performed. It is possible to correct the color shift with high accuracy by correcting the influence of the eccentricity of the unit.

In the image forming apparatus 10, the diagonal position on the photosensitive member 1 ( the position that divides the circumferential distance of the photosensitive member surface into two, in other words, the opposite position at the center angle interval of 180 degrees on the photosensitive member surface, for example, in FIG. Color misregistration data obtained from the resist patterns respectively formed at the upper positions “0” and “8”) can be grasped. Therefore, the controller Cont1 does not perform color misregistration data correction based on the color misregistration variation value. Means for calculating the color misregistration amount only from the color misregistration amount data at the diagonal position may be provided. Then, such a color misregistration amount calculation and the above-described color misregistration amount calculation may be appropriately selected, for example, on the operation panel PA or the like.

The image forming apparatus 10 described with reference to FIG. 1 is a tandem type full-color image forming apparatus, but the present invention can also be applied to a so-called cycle type color image forming apparatus.
The cycle type color image forming apparatus, for example, forms an electrostatic latent image on an electrostatic latent image carrier such as a photoconductor with an exposure unit, and moves the electrostatic latent image to an electrostatic latent image developing area. A toner image is formed by developing with a developing device that holds the assigned color toner corresponding to the electrostatic latent image among a plurality of possible developing devices, and the toner image is primarily transferred to an intermediate transfer belt, A monochrome toner image or a multiple toner image composed of two or more toner images can be formed on the intermediate transfer belt, and the toner image on the intermediate transfer belt can be secondarily transferred to a recording sheet and fixed.

  Such an image forming apparatus can also be regarded as having a plurality of imaging units sharing a photoconductor.

  According to the present invention, when performing color misregistration correction processing in a color image forming apparatus, it is possible to suppress a decrease in image productivity and to correct the color misregistration correction with high accuracy by correcting the influence of the eccentricity of the drive unit. Available to:

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 100 Image reader PR Printer part YH Yellow imaging unit MH Magenta imaging unit CH Cyan imaging unit KH Black imaging unit 1 Photoconductor 2 Charger 3 Exposure unit 4 Developing unit 41 Developing roller 5 Cleaning device 6 Primary transfer roller 7 Intermediate transfer belt 71 Drive roller 72 Opposing roller 73 Cleaning device 8 Secondary transfer roller 9 Fixing device 10S Recording paper supply cassette 101 Recording paper supply roller 11 Timing roller pair 12 Recording paper discharge roller pair 13 Recording medium discharge tray S Recording medium SE Image density sensor TS Temperature sensor Cont1 Engine control unit Cont2 MFP control unit C1 Color shift amount variation data creation unit C2 Color shift amount detection unit C3 Color shift amount detection continuation necessity determination unit C4 Color Deviation amount change determination unit C5 Color deviation amount data deletion unit C6 Correction unit

Claims (6)

A color image composed of two or more colors of toner can be formed on a recording sheet , and has a drive unit for forming a color image , and the drive unit forms a color toner image as a drive unit member. An image forming apparatus including a rotationally driven image carrier and a rotationally driven transfer belt for transferring each color toner image formed on the image carrier ,
Color shift amount variation data creating means for creating data of periodic color shift amount variation due to drive unevenness of the drive unit;
First storage means for storing color misregistration amount variation data created by the color misregistration amount variation data creation means;
A resist pattern forming means for forming a resist pattern used for color misregistration correction on a portion on the image carrier corresponding to a recording paper interval during printing;
Color misregistration detection means for reading a resist pattern formed on the image carrier by the resist pattern forming means and transferred to the transfer belt , and obtaining a color misregistration amount from the resist pattern;
Color misregistration associating the color misregistration amount obtained by the color misregistration amount detection unit with the position on the image carrier or the transfer belt on which the resist pattern on which the color misregistration amount is obtained is formed Second storage means for storing quantity data;
Regarding the color misregistration amount data stored in the second storage means, the color misregistration amount depends on whether or not a predetermined number of data that can be recognized as color misregistration amount data correction data is stored. A color misregistration amount detection continuation necessity judging means for judging whether or not continuation of color misregistration amount detection by the detection means is unnecessary;
In the determination by the color misregistration amount detection continuation necessity determining unit, for all the color misregistration amount data stored in the second storage unit, the color from the time when the color misregistration amount data is acquired to the present is displayed. Color shift amount change determination means for determining whether or not the shift amount has changed;
Color misregistration amount data deleting means for deleting the color misregistration amount data determined by the color misregistration amount change determining means as being changed from the second storage means;
Based on the positional information of the color misregistration amount data stored in the second storage unit, provided that the color misregistration amount detection continuation necessity judging unit judges that the color misregistration amount detection is not continued. A correction unit that reads out a color shift amount variation value at a position from the first storage unit and corrects the color shift amount data stored in the second storage unit using the color shift amount variation value. and,
The color misregistration amount detection continuation necessity determination unit determines whether the color misregistration amount data stored in the second storage unit can be recognized as the color misregistration amount data correction target data. An image forming apparatus, which performs the processing according to the reliability of the color shift amount data corresponding to the position of the resist pattern on which the shift amount data is based on the image carrier or the transfer belt . The second storage means is provided on the image carrier or the transfer belt on which the resist pattern on which the color misregistration amount obtained by the color misregistration amount detection means and the color misregistration amount are obtained is formed. 2. The image forming apparatus according to claim 1 , wherein in addition to the position, color misregistration amount data in which the number of prints at the time when the resist pattern is formed, the pattern forming time, and the pattern forming environmental conditions are also associated is stored . The image forming apparatus according to claim 1, wherein the color misregistration amount change determination unit determines that the color misregistration amount has changed after a predetermined time or more has elapsed since the resist pattern was formed . 3. The image forming apparatus according to claim 1, wherein the color misregistration amount change determination unit determines that the color misregistration amount has changed when a predetermined number of sheets or more are printed from the number of prints when the resist pattern is formed . 3. The image formation according to claim 1, wherein the color misregistration amount change determination unit determines that the color misregistration amount has changed when a resist pattern formation environment temperature changes in advance from a temperature at which the resist pattern is formed. apparatus. When the color misregistration data obtained from the resist patterns formed respectively at positions that divide the circumference of the image carrier surface included in the drive unit into two can be grasped, the color misregistration data correction by the color misregistration variation value 6. The image forming apparatus according to claim 1, further comprising: a unit that can calculate a color misregistration amount using only the color misregistration amount data at the two-divided positions without performing the step .

Images