JP2013068705A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing failure in forming registration marks and suppressing a calculation error of toner image formation position according to a detection result of the registration mark.SOLUTION: The image forming device includes an adjustment sequence control unit and makes it execute a first adjustment step for calculating a toner image formation position according to a detection result of first registration mark comprising an aggregation of first toner patterns, and adjusting the toner image formation position according to the calculation result of the toner image formation position; and execute a second adjustment step for calculating a toner image formation position according to a detection result of a second registration mark comprising an aggregation of second toner patterns in which calculation errors of the toner image formation position are reduced than in the first toner patterns, and adjusting the toner image formation position according to the calculation result of the toner image formation position.

Description

  The present invention relates to an image forming apparatus that obtains a color toner image by superimposing a plurality of color toner images.

  Conventionally, an image forming apparatus that obtains a color toner image by superimposing a plurality of color toner images is known. In many of such image forming apparatuses, in order to superimpose toner images with high accuracy, adjustment of the toner image forming position in each toner image forming unit that forms toner images of respective colors is performed. Then, a method using a so-called registration mark, which is a set of toner patterns formed in the toner image forming portions of the respective colors, is used for detection of a current toner image forming position shift necessary for the adjustment. Many. In this method, the toner image formation position deviation is calculated based on the detection result obtained by detecting the position of a registration mark formed on a transfer medium such as an intermediate transfer belt.

  As a toner pattern that forms such a registration mark, a technique for forming a toner pattern for a color such as black (K), which has a small diffuse reflection with respect to irradiation light, inside the chromatic color toner pattern has been proposed. (For example, refer to Patent Document 1).

Japanese Patent No. 4497223

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of suppressing a registration mark formation failure and suppressing a calculation error of a toner image forming position based on a registration mark detection result.

The image forming apparatus according to claim 1 comprises:
A plurality of toner image forming units for forming different color toner images by sharing a plurality of color toners for each color; and
A transfer target that moves along the plurality of toner image forming portions and receives a plurality of toner images formed by the plurality of toner image forming portions;
A transfer device for further transferring a plurality of color toner images transferred onto the transfer medium onto a recording medium;
A fixing device for fixing a plurality of color toner images transferred onto the recording medium onto the recording medium;
A mark formation control unit that forms a registration mark consisting of a set of toner patterns for detecting a toner image formation position deviation in the plurality of toner image forming units on the transfer object by the plurality of toner image forming units;
A mark sensor for detecting a position of a toner pattern included in a registration mark formed on the transfer target;
A forming position deviation calculating unit that calculates a toner image forming position deviation in the plurality of toner image forming units based on a detection result by the mark sensor;
A forming position adjusting unit that adjusts toner image forming positions in the plurality of toner image forming units based on a calculation result by the forming position deviation calculating unit;
A first registration mark composed of a set of first toner patterns is formed, a toner image formation position deviation is calculated based on a detection result of the first registration mark, and a toner image formation position deviation is calculated based on the calculation result of the toner image formation position deviation. Performing a first adjustment process of adjusting the toner image forming position;
The toner pattern is a set of toner patterns, and a toner pattern for detecting a toner image forming position deviation in at least one toner image forming portion of the toner patterns includes the toner used in the toner image forming portion and the toner image forming portion. A second registration mark which is a second toner pattern in which a calculation error of a toner image formation position shift is reduced as compared with the first toner pattern by combining with a toner used in another toner image forming unit except An adjustment sequence for calculating a toner image formation position deviation based on the detection result of the second registration mark and performing a second adjustment process for adjusting the toner image formation position based on the calculation result of the toner image formation position deviation And a control unit.

The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1,
A storage unit for storing a correction value for correcting the calculation result of the toner image formation position shift in the formation position shift calculation unit used in the first adjustment process;
In the first adjustment process, the formation position deviation calculation unit calculates a toner image formation position deviation based on the detection result by the mark sensor, and further corrects the calculation result with the correction value to generate a final calculation result. In the second adjustment process, the toner image formation position deviation is calculated based on the detection result by the mark sensor, and the correction value is updated so as to reduce the deviation. .

  According to the image forming apparatus of the first aspect, it is possible to suppress the registration mark formation failure and to suppress the calculation error of the toner image formation position based on the detection result of the registration mark.

  According to the image forming apparatus of the second aspect, the second registration mark is formed in the second adjustment process as compared with the case where the calculation result of the toner image formation position deviation is not corrected in the first adjustment process. Can be further suppressed.

1 is an external perspective view of a copying machine that is an embodiment of an image forming apparatus of the present invention. FIG. 1 is an internal configuration diagram of a copier whose appearance is shown in FIG. 1. It is a figure which shows three types of registration marks formed when producing | generating an adjustment value. It is a figure which shows the pattern structure which the toner pattern which makes the multi-color registration mark shown to the part (A) of FIG. 3 has. It is a figure which shows the output signal of the light-receiving part of an optical sensor when the position of the toner pattern which comprises a registration mark is detected. 6 is a graph showing the spectral reflectance of a toner image formed with toner of each color of YMCK. It is a graph which shows the output signal from the light-receiving part obtained about the monochromatic registration mark shown to part (B) of FIG. It is a graph which shows the output signal from the light-receiving part obtained about the multi-color registration mark shown to part (A) of FIG. It is a flowchart showing the process which produces | generates the adjustment value used for a registration process.

  Hereinafter, specific embodiments of the image forming apparatus of the present invention will be described with reference to the drawings.

  FIG. 1 is an external perspective view of a copying machine as an embodiment of the image forming apparatus of the present invention.

  The copying machine 1 includes a document reading unit 1A and an image forming unit 1B.

  The document reading unit 1A is provided with a document feed table 11 on which documents are stacked. Documents placed on the document feed tray 11 are sent out one by one, and characters and images recorded on the document are read and discharged onto the document discharge tray 12.

  The document reading unit 1A has a hinge extending left and right on the back side, and the document feed table 11 and the document discharge table 12 are integrally lifted around the hinge as a rotation center. An original reading plate 13 (see FIG. 2) made of transparent glass is widened. In this method of reading by the document reading unit 1A, instead of placing a document on the document feeding table 11, only one document is placed on the document reading plate 13 downward, and characters from the document on the document reading plate 13 are written. There is also a method of reading images.

  On the front side of the document reading plate 13, various messages are displayed for the user, and various operation buttons are displayed so that the user can perform operations such as document reading and image formation instructions. A portion 14 is provided.

  The entire document reading unit 1A is supported by a support frame 15.

  In addition, the image forming unit 1B is provided with a paper discharge tray 21 on which the paper on which an image is formed is discharged. In addition, a front cover 22 is provided on the front surface of the image forming unit 1B. The front cover 22 can be opened to replace internal components such as a toner container and to remove paper jammed during conveyance. Below that, three drawer-type paper feed tables 23_1, 23_2, and 23_3 are accommodated in a state where sheets before image formation are stacked.

  Further, a lateral cover 24 that is opened when removing paper jammed during conveyance is provided on the left side surface of the image forming unit 1B.

  Furthermore, wheels 251 for moving the image forming unit 1B are attached to the bottom surface of the image forming unit 1B.

  FIG. 2 is an internal configuration diagram of the copying machine whose appearance is shown in FIG.

  A document reading optical system 30 is disposed under the document reading plate 13 made of transparent glass. The document reading optical system 30 includes a first block 31, a second block 32, and a photoelectric sensor 33. The first block 31 has a lamp 311 and a mirror 312, and the second block 32 has two mirrors 321 and 322. The photoelectric sensor 33 reads light representing an image and generates an image signal.

  The first block 31 and the second block 32 are attached to the document reading unit 1A so as to be movable in the direction of the arrow AA ′ along the document reading plate 13, and in the initial state, are positioned at the left side shown in FIG. is there.

  The documents S placed on the document feeding table 11 are fed one by one, and are transported by a transport roller 16 on a transport path 17 in contact with the document reading plate 13. When the document S is conveyed in contact with the document reading plate 13, the document 3 is irradiated by the lamp 311, and the reflected light from the document S is reflected by the mirrors 312, 321, 322 and read by the photoelectric sensor 33. The photoelectric sensor 33 generates an image signal representing characters and images recorded on the document S. The document S irradiated by the lamp 311 is further conveyed and sent out onto the document discharge table 12.

  When the original is placed on the original reading plate 13, the first block 31 and the second block 32 always have the same optical distance between the original reading position on the original reading plate 13 and the photoelectric sensor 33. Move in the direction of arrow A to keep During this time, the lamp 311 irradiates the original, and the photoelectric sensor 33 reads characters and images on the original and converts them into image signals.

  An image signal obtained by the photoelectric sensor 33 is input to the image processing unit 34. The image signal obtained by the photoelectric sensor 33 is an image signal representing each color of R (red), G (green), and B (blue). The image processing unit 34 converts the RGB image signal into image data composed of four colors Y (yellow), M (magenta), C (cyan), and K (black) and temporarily stores the image data. The YMCK image data is transmitted to the exposure control unit 41 in accordance with the exposure timing for forming a latent image, which will be described later.

  The image forming unit 1B is provided with an exposure unit 42. When forming a latent image, YMCK image data is sent from the exposure control unit 41 to the exposure unit 42. The exposure unit 42 emits exposure light 421Y, 421M, 421C, and 421K modulated by YMCK image data.

  Further, in FIG. 2, the main control unit 40 is shown at a position adjacent to the exposure control unit 41. The main control unit 40 is composed of a microcomputer and a program executed by the microcomputer. The main control unit 40 is connected to the exposure control unit 41, the display operation unit 14 (see FIG. 1), the image processing unit 34, and other various power supply circuits and drive circuits (not shown), and is responsible for overall control of the copying machine 1. ing. Further, the main control unit 40 is provided with a storage unit 40a for storing the above-mentioned program and various parameters used for executing the program.

  In the lower part of the image forming unit 1B, the above-described three paper feed tables 23_1, 23_2, and 23_3 are supported and accommodated by the left and right guide rails 24_1, 24_2, and 24_3. The sheets P are stored in a stacked state on each of the sheet feeding bases 23_1, 23_2, and 23_3. Each of the sheet feeding bases 23_1, 23_2, and 23_3 is configured to be guided and guided by the guide rails 24_1, 24_2, and 24_3 for replenishing the paper P.

  Of these three paper feed bases 23_1, 23_2, and 23_3, from the paper feed base designated by the operation of the display operation unit 14 (see FIG. 1) or the like (here, the paper feed base 23_1 as an example) The paper P is sent out by the pickup roll 25. The sheets P are separated one by one by the separating roll 26, and the one sheet P is conveyed upward by the conveying roll 27. Then, the paper P is conveyed further upward by adjusting the timing of the subsequent conveyance by the standby roll 28. The conveyance of the paper P after the standby roll 28 will be described later.

  In the central portion of the image forming unit 1B, four image forming units 50Y, 50M, 50C, and 50K that form toner images of YMCK toners are arranged in this order from the right side in the drawing. The four image forming units 50Y, 50M, 50C, and 50K correspond to an example of a plurality of toner image forming units referred to in the present invention.

  These four image forming units 50Y, 50M, 50C, and 50K have the same configuration except that the colors of the toners used are different. For this reason, here, the configuration of the Y-color image forming unit 50Y will be described.

  The image forming unit 50Y includes a photoconductor 51 that rotates in the direction indicated by an arrow B in FIG. 2, and a charger 52, a developing device 53, and a cleaner 55 are disposed around the photoconductor 51. A transfer unit 54 is placed at a position where an intermediate transfer belt 61 described later is sandwiched between the photosensitive member 51 and the intermediate transfer belt 61.

  The photoconductor 51 has a roll shape, holds charges by charging, releases the charges by exposure, and holds an electrostatic latent image on the surface thereof.

  The charger 52 charges the surface of the photoconductor 51 to a certain charging potential.

  The image forming unit 1B has the above-described exposure unit 42. The exposure device 42 receives an image signal from the exposure controller 41 and outputs exposure light 421Y, 421M, 421C, and 421K modulated in accordance with the input image signal. After being charged by the charger 52, the photosensitive member 51 is irradiated with the exposure light 421Y from the exposure device 42, and an electrostatic latent image is formed on the surface of the photosensitive member 51.

  The photoreceptor 51 is irradiated with the exposure light 421Y to form an electrostatic latent image on the surface, and then developed by the developing device 53, and a toner image (yellow (in this image forming unit 50Y, yellow (this image forming unit 50Y)) is developed on the surface of the photoreceptor 51. Y) toner image) is formed.

  The developing device 53 includes two augers 532 </ b> _ <b> 1 and 532 </ b> _ <b> 2 that stir the developer in a case 531 that contains a developer composed of toner and a carrier therein, and development that carries the developer to a position facing the photoconductor 51. A roll 533. In developing the electrostatic latent image formed on the photoreceptor 51, a bias voltage is applied to the developing roll 533. Due to the action of the bias voltage, the toner in the developer adheres on the photoreceptor 51 in accordance with the electrostatic latent image formed on the photoreceptor 51 to form a toner image.

  The toner image formed on the photoreceptor 51 by the development by the developing unit 53 is transferred onto the intermediate transfer belt 61 by the action of the transfer unit 54.

  The toner remaining on the photoconductor 51 after the transfer is removed from the photoconductor 51 by the cleaner 55.

  The intermediate transfer belt 61 is an endless belt that is wound around a plurality of rolls 62. The intermediate transfer belt 61 circulates in the direction of arrow C along the arrangement of the four image forming units 50Y, 50M, 50C, and 50K. The intermediate transfer belt 61 corresponds to an example of a transfer target according to the present invention.

  The toner images of the respective color toners formed by the image forming units 50Y, 50M, 50C, and 50K are transferred onto the intermediate transfer belt 61 so as to sequentially overlap in the order of YMCK, and the secondary transfer in which the transfer unit 63 is disposed. Transported to position. In synchronization with this, the paper P that has been transported to the standby roll 28 is transported to the secondary transfer position, and the toner image on the intermediate transfer belt 61 is transported by the action of the transfer unit 63. Transcribed above. The paper P that has received the transfer of the toner image is further conveyed, and the toner image on the paper is fixed on the paper P by the pressurization and heating by the fixing device 64. The paper P on which the image composed of the fixed toner image is formed on the paper is further conveyed and discharged onto the paper discharge table 21 by the discharge roller 65. The transfer device 63 corresponds to an example of the transfer device according to the present invention. The fixing device 64 corresponds to an example of a fixing device according to the present invention.

  After the toner image is transferred onto the paper P by the transfer device 63, the intermediate transfer belt 61 further circulates, and the toner remaining on the surface is removed from the intermediate transfer belt 61 by the cleaner 66.

  In addition, container mounting portions 29Y, 29M, 29C, and 29K are provided above the intermediate transfer belt 61 in the image forming portion 1B. In these container mounting portions 29Y, 29M, 29C, and 29K, toner containers 67Y, 67M, 67C, and 67K that store toner of each color of YMCK are mounted. The color toners stored in the toner containers 67Y, 67M, 67C, and 67K are replenished to the developing devices 53 in accordance with the amount of toner consumed in the corresponding developing devices 53.

  Here, in the image forming unit 1B, the transfer position of the toner image of each color toner on the intermediate transfer belt 61 due to, for example, vibration during operation, temperature change, or mounting position shift at the time of replacement of the image forming unit. Deviation may occur.

  Therefore, in the image forming unit 1B, the main control unit 40 performs the following registration process.

  The registration process adjusts the timing of exposure light irradiation to the photoconductor 51 of each image forming unit based on the image data input to the exposure control unit 41 to thereby form an electrostatic latent image formation position on the photoconductor 51. It is a process to adjust. The position of the toner image on the intermediate transfer belt 61 is a position corresponding to the position where the electrostatic latent image is formed on the photoreceptor 51. Hereinafter, the formation position of the electrostatic latent image on the photoreceptor 51 is referred to as a toner image formation position. By this registration processing, the toner image forming position is adjusted by the positional deviation between the color toner images. The function of the main control unit 40 for performing the registration processing corresponds to an example of the formation position adjusting unit according to the present invention.

  In the registration process, an adjustment value for adjusting the exposure light irradiation timing is used. This adjustment value is generated in response to various events, for example, when a predetermined number of images are formed, when the temperature / humidity environment changes, or when parts are replaced. In generating the adjustment value, a registration mark made of a toner pattern for each color of YMCK having a predetermined shape is used. When the adjustment value is generated, the registration mark is transferred to the intermediate transfer belt 61. Then, the toner pattern forming the registration mark is detected photoelectrically. Based on the detection result, the current toner image forming position deviation between the image forming units 50Y, 50M, 50C, and 50K of the respective colors is calculated. Further, an adjustment value for adjusting the toner image formation position by the calculated result is generated.

  In the image forming unit 1B, with respect to the moving direction of the intermediate transfer belt 61, the reflected light is received by irradiating light at a position downstream of the K-color image forming unit 50K and upstream of the transfer unit 63, An optical sensor 70 is provided that outputs a signal corresponding to the intensity of the reflected light. The optical sensor 70 includes an irradiation unit 71 that irradiates light having a wavelength of 940 nm, and a light receiving unit 72 that receives reflected light. The light receiving unit 72 is disposed at a position where the light irradiated from the irradiation unit 71 and specularly reflected on the intermediate transfer belt 61 is received. An output signal of the optical sensor 70 is sent to the main control unit 40. In the present embodiment, the position of the toner pattern forming the registration mark formed on the intermediate transfer belt 61 is photoelectrically detected by the optical sensor 70. This optical sensor 70 corresponds to an example of a mark sensor according to the present invention.

  The main control unit 40 measures the relative position between the toner patterns based on the signal output from the optical sensor 70 at the time of detecting the toner pattern, calculates the positional deviation amount of the toner image forming positions between the respective colors at the present time, And the adjustment value is generated. The function of the main control unit 40 that calculates the amount of misregistration of the toner image forming position corresponds to an example of a forming position deviation calculating unit according to the present invention.

  When an event for generating an adjustment value used for the registration process arrives, there is a case where it is necessary to wait for execution of adjustment value generation such as a print operation being executed at that time. For this reason, in this embodiment, when an event for generating an adjustment value arrives, an adjustment value generation request flag is first set. Thereafter, the flag is referred to at the timing when the processing such as the printing operation is completed. When the flag is set, the main control unit 40 causes registration marks to be formed on the image forming units 50Y, 50M, 50C, and 50K for each color of YMCK and transferred onto the intermediate transfer belt 61. The main control unit 40 corresponds to an example of a mark formation control unit referred to in the present invention.

  Subsequent to the formation of the registration mark, reception of reflected light by the optical sensor 70 and generation of an adjustment value by the main control unit 40 are executed.

  The generated adjustment value is stored in the storage unit 40a included in the main control unit 40. The adjustment value is used for registration processing at the time of image formation until a new adjustment value is next generated.

  Here, in the present embodiment, three types of registration marks described below are formed in the process represented by the flowchart described later, which generates an adjustment value used in the registration process.

  FIG. 3 is a diagram showing three types of registration marks formed when generating adjustment values.

  Part (A) of FIG. 3 shows a multicolor registration mark 100 in which each toner pattern is formed by a combination of two colors of toner. Also, part (B) of FIG. 3 shows a single color registration mark 200 in which each toner pattern is formed of a single color toner. Also, part (C) of FIG. 3 shows a large size single color registration mark 300 in which each toner pattern is formed of a single color toner and the size is larger than the size of the toner pattern of the single color registration mark 200. Has been.

  A multi-color registration mark 100 shown in part (A) of FIG. 3 has toner patterns 101Y, 101M, 101C, and 101K for each color of YMCK.

  The Y color toner pattern 101Y detects a positional deviation of the toner image forming position of the Y color image forming unit 50Y shown in FIG. 2 from the toner image forming position of the K color image forming unit 50K as described later. The toner pattern. The M color toner pattern 101M is a toner pattern for detecting a positional deviation of the toner image forming position of the M color image forming unit 50M from the toner image forming position of the K color image forming unit 50K. The C-color toner pattern 101C is a toner pattern for detecting a positional deviation of the toner image forming position of the C-color image forming unit 50C from the toner image forming position of the K-color image forming unit 50K. The K-color toner pattern 101K is a toner pattern for indicating the toner image formation position of the K-color image forming unit 50K serving as a reference position.

  The toner patterns 101Y, 101M, 101C, and 101K for each color of YMCK have the same shape. That is, these toner patterns have a shape in which an arm inclined downward to the right in the figure and an arm inclined upward to the right are connected in a convex arrowhead shape on the left side in the figure.

  The toner patterns 101Y, 101M, 101C, and 101K for each color of YMCK of the multicolor registration mark 100 have the following pattern structure.

  FIG. 4 is a diagram showing a pattern structure possessed by the toner pattern forming the multicolor registration mark shown in Part (A) of FIG.

  FIG. 4 shows one arm 101_1 of the two arms of the toner pattern 101 forming the multicolor registration mark 100 having an arrowhead shape.

  Note that the YMCK color toner patterns forming the multicolor registration mark 100 have the same pattern structure, and FIG. 4 shows a toner pattern 101 in which the distinction of colors is discarded.

  As shown in FIG. 4, the arm 101_1 is inclined by 27 ° with respect to the left-right direction in the drawing orthogonal to the moving direction of the intermediate transfer belt 61 indicated by the arrow C shown in FIG. It has a width of dots (1 dot = 42 μm).

  The toner pattern 101 including the arm 101_1 has an inner pattern 102 whose width in the moving direction of the intermediate transfer belt 61 is 12 dots. Further, the toner pattern 101 has an outer pattern 103. The outer pattern 103 is sandwiched from both sides in the moving direction of the intermediate transfer belt 61 (see FIG. 2) indicated by an arrow C without a gap between the outer pattern 103 and the inner pattern 102 by design.

  Returning to part (A) of FIG. 3, the description of the multicolor registration mark 100 will be continued.

  The toner patterns 101Y, 101M, and 101C for the YMC three colors of the multicolor registration mark 100 shown in Part (A) of FIG. 3 are YMC from the downstream side to the upstream side in the moving direction of the intermediate transfer belt 61 indicated by the arrow C. They are lined up in order. In addition, toner patterns 101K for K color are arranged alternately with toner patterns 101Y, 101M, and 101C for YMC colors. As a result, the YMC toner patterns 101Y, 101M, and 101C are sandwiched between the K color toner patterns 101K from both sides of the moving direction indicated by the arrow C.

  In FIG. 3, for simplicity of illustration, one YMC toner pattern 101Y, 101M, and 101C is shown. The registration mark 100 according to this embodiment includes a plurality of toner patterns 101Y, 101M, and 101C for each color of YMC. Each Y color toner pattern 101Y is sandwiched between K color toner patterns 101K. Also, each M color toner pattern 101M is sandwiched between K color toner patterns 101K. Further, each C color toner pattern 101C is sandwiched between K color toner patterns 101K.

  The K-color toner pattern 101K has an inner pattern 102C formed of C-color toner and an outer pattern 103K formed of K-color toner.

  That is, the K-color toner pattern 101K is used in a K-color toner used in the K-color image forming unit 50K and a C-color image forming unit 50C different from the K-color image forming unit 50K. And a C-color toner.

  The C-color inner pattern 102C is designed so that the C-color toner is distributed without leaving a gap in the moving direction indicated by the arrow C. The K-color outer pattern 103K is designed to sandwich the C-color inner pattern 102C from both sides of the moving direction indicated by the arrow C without leaving a gap between the K-color inner pattern 102C.

  The Y-color toner pattern 101Y has an inner pattern 102K formed of K-color toner and an outer pattern 103Y formed of Y-color toner.

  The Y-color toner pattern 101Y is used in a Y-color toner used in the Y-color image forming unit 50Y and a K-color image forming unit 50K different from the Y-color image forming unit 50Y. It is formed by combining with K color toner.

  The K-color inner pattern 102K is designed such that the K-color toner is distributed without leaving a gap in the moving direction indicated by the arrow C. The Y-color outer pattern 103Y is designed so as to sandwich the K-color inner pattern 102K from both sides of the moving direction indicated by the arrow C without leaving a gap between the Y-color outer pattern 103Y.

  The M-color toner pattern 101M has an inner pattern 102K formed of K-color toner and an outer pattern 103M formed of M-color toner.

  The M-color toner pattern 101M is used in the M-color toner used in the M-color image forming unit 50M and in the K-color image forming unit 50K different from the M-color image forming unit 50M. It is formed by combining with K color toner.

  The M-color outer pattern 103M is designed to sandwich the K-color inner pattern 102K from both sides of the moving direction indicated by the arrow C without leaving a gap between the M-color outer pattern 103M.

  The C-color toner pattern 101C includes an inner pattern 102K formed with K-color toner and an outer pattern 103C formed with C-color toner.

  The C-color toner pattern 101C is used in a C-color toner used in the C-color image forming unit 50C and a K-color image forming unit 50K different from the C-color image forming unit 50M. It is formed by combining with K color toner.

  The C-color outer pattern 103C is designed such that the K-color inner pattern 102K is sandwiched from both sides in the movement direction indicated by the arrow C without leaving a gap between the C-color outer pattern 103K.

  In the present embodiment, all of the YMCK toner patterns 101Y, 101M, 101C, and 101K of the multi-color registration mark 100 have an inner pattern. However, the multicolor registration mark is not limited to this, and only the toner pattern for K color has an inner pattern, and the toner patterns for other colors of YMC are formed only with toner of each color. It may be.

  Further, in the present embodiment, an example in which the K-color toner pattern 101K of the multicolor registration mark 100 has the C-color inner pattern 102C is illustrated. However, the K-color toner pattern may have a Y-color inner pattern, and the K-color toner pattern may have a M-color inner pattern.

  The single color registration mark 200 shown in part (B) of FIG. 3 also has toner patterns 201Y, 201M, 201C, and 201K for each color of YMCK.

  The outer shapes of the toner patterns 201Y, 201M, 201C, and 201K are the same as the outer shapes of the toner patterns 101Y, 101M, 101C, and 101K for the respective colors of the multicolor registration mark.

  The arrangement of the toner patterns 201Y, 201M, 201C, and 201K for each color of the single color registration mark 200 is the same as the arrangement of the toner patterns 101Y, 101M, 101C, and 101K for each color of the multicolor registration mark. .

  However, the toner patterns 201Y, 201M, 201C, and 201K for each color of YMCK of the single color registration mark 200 are formed only with toners of each color of YMCK.

  The large size single color registration mark 300 shown in part (C) of FIG. 3 also has toner patterns 301Y, 301M, 301C, and 301K for each color of YMCK.

  The arrangement of the toner patterns 301Y, 301M, 301C, and 301K for each color of the large size single color registration mark 300 is also the same as the arrangement of the toner patterns 101Y, 101M, 101C, and 101K for each color of the multicolor registration mark. is there. In addition, the toner patterns 301Y, 301M, 301C, and 301K for each color of the large-size single-color registration mark 300 are each formed only with YMCK each color toner.

  Further, the outer shapes of the toner patterns 301Y, 301M, 301C, and 301K for each color of the large size single color registration mark 300 are similar to the outer shapes of the toner patterns for the respective colors of the multi-color registration mark 100 and the single color registration mark 200 described above. doing.

  However, in the large size single color registration mark 300, the length of each color toner pattern 301Y, 301M, 301C, 301K is equal to the length of each color toner pattern 201Y, 201M, 201C, 201K. Longer than the length of.

  Further, the interval between the toner patterns 301Y, 301M, 301C, and 301K for each color is larger than the interval between the toner patterns for each color of the multicolor registration mark 100 and the single color registration mark 200.

  In part (C) of FIG. 3, the Y color toner pattern upstream of the M color toner pattern 301 </ b> M in the moving direction of the intermediate transfer belt 61 indicated by the arrow C due to the size shown in the figure. Illustration of the 301Y and K color toner patterns 301K is omitted.

  Here, in the present embodiment, the K color toner pattern is alternately arranged with the YMC toner patterns of the multi-color registration mark 100, the single color registration mark 200, and the large size single color registration mark 300. Is illustrated. However, the registration mark may have a form in which a plurality of sets of toner patterns for each color of YMCK are simply arranged in the order of YMCK.

  In the present embodiment, when generating the adjustment values necessary for the registration process, three types of registration marks shown in FIG. 3 are formed on the intermediate transfer belt 61 in the process represented by the flowchart described below.

  When the intermediate transfer belt 61 moves in the moving direction indicated by the arrow C, the light spot SP irradiated by the irradiation unit 71 included in the optical sensor 70 shown in FIG. 2 crosses each toner pattern on the intermediate transfer belt 61. Then, the surface of the intermediate transfer belt 61 and the reflected light reflected by each toner pattern are received by the light receiving unit 72.

  Here, in this embodiment, the reflectance of the specular reflection on the surface of the intermediate transfer belt 61 is higher than the reflectance of the specular reflection on the toner image formed on the surface. For this reason, when the spot SP crosses each toner pattern, the intensity of the reflected light received by the light receiving unit 72 decreases. In this embodiment, the position of the toner pattern constituting the registration mark is detected by detecting the decrease in the intensity of the reflected light. Based on the detection result of the toner pattern position, an adjustment value necessary for the registration process is generated.

  The adjustment value generation method includes a multi-color registration mark 100 shown in part (A) of FIG. 3, a single-color registration mark 200 shown in part (B), and a large-size single-color registration mark 300 shown in part (C). The same generation method is used. Hereinafter, a method for generating the adjustment value will be described by taking the monochromatic registration mark 200 shown in Part (B) as an example.

  FIG. 5 is a diagram illustrating an output signal of the light receiving unit of the optical sensor when the position of the toner pattern constituting the registration mark is detected.

  A monochromatic registration mark 200 is shown in part (A) of FIG.

  The light receiving unit 72 shown in FIG. 2 changes the intensity level of the received reflected light with respect to the moving distance of the spot SP on the intermediate transfer body 61 after starting the reception of the reflected light according to an instruction from the main control unit 40. A signal representing is output. In part (B) of FIG. 5, the level change of the signal output by the light receiving unit 72 receiving the reflected light with respect to the moving distance of the spot SP is associated with the shape of the toner pattern, and is schematically represented by the first line L1. Has been shown. In this part (B), the signal level is lower toward the right side in the figure. In the present embodiment, the moving distance of the spot SP is handled in units of dots (1 dot = 42 μm).

  As described above, each toner pattern has an arrowhead shape, and has two arms that are spaced apart toward the right side in the figure. As indicated by the first line L1, the signal level of the output signal of the light receiving unit 72 decreases when the spot SP passes over each arm of each toner pattern.

  Such an output signal is input to the main control unit 40 shown in FIG. 2 and binarized by comparison with the threshold value TH as follows. In the present embodiment, an intermediate level between the reference level BL corresponding to the intensity of the reflected light on the surface of the intermediate transfer belt 61 and the bottom of the decrease at the largest peak is adopted as the threshold TH. .

  By this binarization, the output signal of the light receiving unit 72 is converted into a pulse signal indicated by the second line L2 in Part (C) of FIG. Even in this part (C), the signal level is lower toward the right side in the figure. Each pulse appearing in this pulse signal corresponds to each of the two arms of each toner pattern.

  Here, the origins for forming the toner images of the respective colors are present on the respective photoreceptors 51 of the image forming units 50Y, 50M, 50C, and 50K of the respective colors.

  The point where the origin of each photoreceptor 51 of YMC image forming units 50Y, 50M, and 50C is mapped onto intermediate transfer belt 61 is ideally the origin of photoreceptor 51 of K image forming unit 50K. Overlaps with the point mapped on the intermediate transfer belt 61.

  Hereinafter, the point where the origin of each photoconductor 51 is mapped onto the intermediate transfer belt 61 is referred to as the origin of the toner image formation position for each color image forming unit 50Y, 50M, 50C, 50K. If there is, for example, an attachment error of the photoconductor 51 between the image forming units 50Y, 50M, 50C, and 50K for the respective colors, the origins that should originally overlap are shifted. Such a deviation of the origin causes a positional deviation of the toner image forming position between the image forming units 50Y, 50M, 50C, and 50K of the respective colors. Hereinafter, the positional deviation of the origin of the toner image forming position is simply referred to as a positional deviation of the toner image forming position.

  In the present embodiment, in the main controller 40, based on the pulse signal, the toner of the K image forming unit 50K at the toner image forming positions of the YMC image forming units 50Y, 50M, and 50C shown in FIG. A positional deviation amount with respect to the origin of the image forming position is calculated.

  On the other hand, for the K-color image forming unit 50K, the origin of the toner image forming position of the K-color image forming unit 50K is the reference for the positional deviation. In other words, the positional deviation amount is always regarded as “0” for the K-color image forming unit 50K.

  Then, the main control unit 40 generates an adjustment value used in the registration process based on the amount of misregistration calculated for the YMC image forming units 50Y, 50M, and 50C. On the other hand, as for the K-color image forming unit 50K, the positional deviation amount is always regarded as “0” as described above, and therefore the adjustment value is always “0”.

  In the present embodiment, as described above, an example in which the adjustment value is generated based on the origin of the toner image forming position of the K-color image forming unit 50K is illustrated. However, the adjustment value may be generated based on the origin of the toner image forming position of the image forming unit other than the K color. Alternatively, a design reference position may be provided for each of the YMCK image forming units 50Y, 50M, 50C, and 50K. In this case, the amount of positional deviation from the reference position of the origin of the respective toner image forming positions of the image forming units 50Y, 50M, 50C, and 50K for each color of YMCK is calculated. Then, an adjustment value is generated based on the positional deviation amount. In addition, the adjustment value is not generated based on the positional deviation amount from the reference position, but the positional deviation amount of the toner image forming position between the adjacent image forming units is calculated, and the positional deviation is calculated. The form which produces | generates an adjustment value based on quantity may be sufficient.

  Since the generation of the adjustment value in the present embodiment is the same for each color of YMC, the generation of the adjustment value will be described here by taking the adjustment value for Y color as an example.

  In generating the Y-color adjustment value, the following five pulse intervals shown in FIG. 5 are used.

  The first pulse interval T1 is a pulse interval of two pulses corresponding to the K color toner pattern 201K on the downstream side in the moving direction of the intermediate transfer belt 61 indicated by the arrow C with respect to the Y color toner pattern 201Y.

  The second pulse interval T2 is a pulse corresponding to the arm on the downstream side in the moving direction and a pulse corresponding to the downstream K-color toner pattern 201K among the pulses corresponding to the Y-color toner pattern 201Y. Of these, the pulse interval with the pulse corresponding to the arm on the upstream side.

  The third pulse interval T3 is a pulse interval of two pulses corresponding to the Y color toner pattern 201Y.

  The fourth pulse interval T4 includes a pulse corresponding to the arm on the upstream side in the moving direction and a pulse corresponding to the upstream K-color toner pattern 201K among pulses corresponding to the Y-color toner pattern 201Y. Of these, the pulse interval with the pulse corresponding to the arm on the downstream side.

  The fifth pulse interval T5 is a pulse interval of two pulses corresponding to the downstream K color toner pattern 201K.

  The positional deviation of the Y-color toner image forming position includes a positional deviation in the main scanning direction along the rotation axis of the photosensitive member 51 (see FIG. 2) and a positional deviation in the sub-scanning direction along the rotational direction of the photosensitive member 51. There is.

  When the Y-color toner image forming position deviates from the reference position in the main scanning direction, the Y-color toner pattern 201Y is orthogonal to the moving direction of the intermediate transfer belt 61 (the direction of arrow C in FIG. 5). In the direction, the toner pattern 201K for K color is shifted. Such positional deviation between the toner patterns is a difference between the third pulse interval T3 and the first pulse interval T1, or a difference between the third pulse interval T3 and the fifth pulse interval T5. Appear.

  Therefore, in the present embodiment, the positional deviation amount L in the main scanning direction of the toner image forming position is calculated using the following equation (1).

L = ((T1 + T5) / 2−T3) / 2 (1)
Here, at the time of forming the registration mark 200 used for calculating the positional deviation amount L in the main scanning direction, a registration process using the adjustment value stored in the storage unit 40a of the main control unit 40 at that time is performed. Has been done. The positional deviation amount represented by the value L generated by the above equation (1) is the positional deviation amount in the main scanning direction that has occurred without being able to be adjusted by this registration process.

  Therefore, when the main control unit 40 shown in FIG. 2 calculates the positional deviation amount L in the main scanning direction, the main image forming position at the present time is shifted so as to shift the toner image forming position in the direction opposite to the positional deviation of the amount represented by the value L. The adjustment value in the scanning direction is corrected to generate a new adjustment value in the main scanning direction.

  Further, when the Y toner image forming position is shifted in the sub-scanning direction, the Y toner pattern 201Y is moved in the direction of movement of the intermediate transfer belt 61 (the direction of the arrow C in FIG. 5) and one of the K colors. The toner pattern 201K is approached. In this case, the interval between the Y color toner pattern 201Y and the upper K color toner pattern 201K in the drawing, and the interval between the Y color toner pattern 201Y and the lower K color toner pattern 201K in the drawing are as follows. Different from each other.

  In this embodiment, (T1 / 2 + T2) is employed as a value representing the interval between the Y color toner pattern 201Y and the upper K color toner pattern 201K in the drawing. Further, (T5 / 2 + T4) is adopted as a value representing the interval between the Y color toner pattern 201Y and the lower K color toner pattern 201K in the figure. A positional deviation amount P in the sub-scanning direction of the toner image formation position is calculated using the following equation (2).

P = (T1 / 2 + T2)-(T5 / 2 + T4) (2)
When the main control unit 40 shown in FIG. 2 calculates the positional deviation amount P in the sub-scanning direction, the current sub-image forming position is shifted so as to shift the toner image forming position in the direction opposite to the positional deviation of the amount represented by the value P. The adjustment value in the scanning direction is corrected to generate a new adjustment value in the sub-scanning direction.

  New adjustment values for the MC colors are also generated by the same generation method as that for the Y color.

  The adjustment value in the storage unit 40a of the main control unit 40 is updated with the newly generated adjustment value. The new adjustment value is used for registration processing until a new adjustment value is generated next.

  In the present embodiment, the adjustment value for each YMC color is calculated using a pulse interval related to two K color toner patterns sandwiching the YMC toner patterns. However, the adjustment value of each YMC color may be calculated using, for example, a pulse interval related to one K color toner pattern adjacent to the YMC toner pattern.

  Here, in general, a toner image formed with toner of each color of YMCK has the following spectral reflectance.

  FIG. 6 is a graph showing the spectral reflectance of a toner image formed with toner of each color of YMCK.

  In the graph G1 shown in FIG. 6, the horizontal axis represents the wavelength of light, and the vertical axis represents the spectral reflectance. The graph G1 describes a curve representing a change in spectral reflectance with respect to the wavelength of light for a toner image formed with toner of each color of YMCK.

  In the present embodiment, the wavelength of light emitted by the irradiation unit 71 included in the optical sensor 70 illustrated in FIG. 2 is 940 nm as described above. As can be seen from the graph G1 shown in FIG. 6, for the light having a wavelength of 940 nm, each of the YMC three color toner images has a spectral reflectance higher than that of the K color toner image.

  The K-color toner pattern 101K of the multi-color registration mark 100 of FIG. 3 has a spectral reflectance relatively relative to the C-color inner pattern 102C having a relatively high spectral reflectance from both sides of the moving direction indicated by the arrow C. The structure is sandwiched between the lower K-color outer patterns 103K.

  The Y-color toner pattern 101Y of the multi-color registration mark 100 has a relatively high spectral reflectance from both sides of the moving direction indicated by the arrow C in the K-color inner pattern 102K having a relatively low spectral reflectance. The structure is sandwiched between Y-color outer patterns 103Y.

  The M-color toner pattern 101M of the multi-color registration mark 100 has a relatively high spectral reflectance from both sides of the moving direction indicated by the arrow C in the K-color inner pattern 102K having a relatively low spectral reflectance. The structure is sandwiched between M-color outer patterns 103M.

  Further, the C-color toner pattern 101C of the multicolor registration mark 100 has a relatively high spectral reflectance from both sides of the moving direction indicated by the arrow C in the K-color inner pattern 102K having a relatively low spectral reflectance. The structure is sandwiched between C-color outer patterns 103C.

  The multi-color registration mark 100 and the other two types of single-color registration marks 200 and 300 have different waveforms of output signals from the light receiving unit 72 of the optical sensor 70 shown in FIG.

  First, output signal waveforms obtained for the two types of single-color registration marks 200 and 300 will be described. Here, the single color registration mark 200 whose outer shape of the toner pattern coincides with the double color registration mark 100 out of the two types of single color registration marks 200 and 300 will be described as an example.

  FIG. 7 is a graph showing an output signal from the light receiving unit obtained for the monochromatic registration mark shown in Part (B) of FIG.

  In the graph G2 of FIG. 7, the level (voltage) of the output signal from the light receiving unit 72 is taken on the vertical axis, and the time is taken on the horizontal axis. Note that the time on the horizontal axis indicates the movement distance of the spot SP on the intermediate transfer body 61 after the light receiving unit 72 starts receiving reflected light in response to an instruction from the main control unit 40. It is converted into the elapsed time since then.

  The graph G2 includes a third line L3 indicating the output signal obtained for the C color toner pattern and a fourth line L4 indicating the output signal obtained for the K color toner pattern. Have been described.

  In this graph G2, the time line is shifted so that the position where the signal level is lowered in the third line L3 is approximately the same as the position where the signal level is lowered in the fourth line L4. Has been.

  As can be seen from this graph G2, the waveform of the output signal obtained for the K-color toner pattern and the waveform of the output signal obtained for the C-color toner pattern are inconsistent with each other. Specifically, the amount of decrease in the level of the output signal obtained for the toner pattern for K color is larger than the amount of decrease in the level of the output signal obtained for the toner pattern for C color.

  In general, reflected light reflected from a toner image is reflected in a state of being diffused and spread around the surface of the toner image, in addition to reflected light (specularly reflected light) reflected from the surface of the toner image. Reflected light (diffuse reflected light) is included.

  With respect to the toner pattern for K color, since the spectral reflectance is small, the diffuse reflection light is very small, and the decrease in the specular reflection light when the spot SP of the light irradiated by the irradiation unit 71 crosses the toner pattern is almost as it is. It appears as a drop in the level of the output signal from 72.

  On the other hand, the spectral reflectance of the C color toner pattern is higher than that of the K color toner pattern. For this reason, even if the specular reflection light decreases when the light spot SP crosses the toner pattern, diffuse reflection light having a certain value is received by the light receiving unit 72, so that the output signal from the light receiving unit 72 The amount of level decrease is smaller than that of the K color toner pattern.

  Also, for the Y-color and M-color toner patterns, similarly to the C-color toner pattern, the amount of decrease in the level of the output signal from the light-receiving unit 72 due to the influence of diffuse reflection is K-color toner pattern. Smaller than.

  Here, as described above, the adjustment value used in the registration process is generated using the above-described equations (1) and (2). These expressions are expressions using pulse intervals T1,..., T5 in a pulse signal obtained by binarizing the output signal from the light receiving unit 72 shown in Part (C) of FIG.

  The misregistration amounts L and P in the main scanning direction and the sub-scanning direction calculated by these equations are the same for each color if the waveform of the K color output signal and the waveform of the output signal of each YMC color match each other. When there is no deviation between the toner image forming positions, both become “0”. In this case, the adjustment value stored in the storage unit 40a of the main control unit 40 at that time is subsequently used in the subsequent registration processing.

  Here, as shown in the graph G2 of FIG. 7, in the monochromatic registration mark 200, the waveform of the output signal of K color and the waveform of the output signal of each color of YMC are not consistent with each other. As a result, inconsistency tends to occur between the first, third, and fifth pulse intervals T1, T3, and T5 that should match each other when there is no deviation between the toner image forming positions of the respective colors. Similarly, a mismatch is likely to occur between the second and fourth pulse intervals T2 and T4.

  Such a discrepancy between the pulse intervals T1,..., T5 is also caused when there is no deviation between the toner image formation positions of the respective colors in the positional deviation amounts L and P in the main scanning direction and the sub-scanning direction. Some value (offset value) is taken. Such an offset value is a factor that promotes a calculation error of the positional deviation amounts L and P in the main scanning direction and the sub-scanning direction.

  Further, the situation that the offset value is generated due to the mismatch between the pulse intervals T1,..., T5 also occurs in the large size single color registration mark 300 shown in FIG.

  Next, the waveform of the output signal from the light receiving unit 72 of the optical sensor 70 shown in FIG. 2 obtained for the multicolor registration mark 100 shown in Part (A) of FIG. 3 will be described.

  FIG. 8 is a graph showing an output signal from the light receiving unit obtained for the multicolor registration mark shown in part (A) of FIG.

  In the graph G3 of FIG. 8, the level (voltage) of the output signal from the light receiving unit 72 is taken on the vertical axis, and the time is taken on the horizontal axis. The time on the horizontal axis in the graph G3 is also the distance traveled by the spot SP on the intermediate transfer body 61 after the light receiving unit 72 starts receiving the reflected light, and the elapsed time from the start of the light reception. It is converted to. The graph G3 includes a fifth line L5 indicating the output signal obtained for the C-color toner pattern and an eighth line L8 indicating the output signal obtained for the K-color toner pattern. Have been described.

  In the graph G3 as well as the graph G2 in FIG. 7 described above, the position where the signal level is lowered in the fifth line L5 is the position where the signal level is lowered in the eighth line L8. The time axis is shifted so that they are almost the same.

  As can be seen from this graph G3, in the multi-color registration mark 100, the difference between the waveform of the output signal for the K color toner pattern and the waveform of the output signal for the C color toner pattern is as follows. Smaller than the mark 200.

  For the K color toner pattern, the decrease in the level of the output signal from the light receiving unit 72 when the light spot SP irradiated by the irradiation unit 71 crosses the toner pattern is caused by the diffusely reflected light from the C color inner pattern. It can be suppressed.

  For this reason, in the multi-color registration mark 100, the waveform of the output signal obtained for the K color toner pattern is closer to the waveform of the output signal obtained for the YMC toner patterns than in the single color registration mark 200. .

  In the multi-color registration mark 100, the diffuse reflection light is suppressed by the K-color inner pattern for the C-color toner pattern. As a result, a decrease in the level of the output signal from the light receiving unit 72 when the light spot SP irradiated by the irradiation unit 71 crosses the toner pattern is promoted.

  Therefore, in the multi-color registration mark 100, the waveform of the output signal obtained for the C color toner pattern is closer to the waveform of the output signal obtained for the K color toner pattern than in the single color registration mark 200. .

  Also, with respect to the Y color and M color toner patterns, similarly to the C color toner pattern, the diffuse reflection light is suppressed by the K color inner pattern, and the level of the output signal from the light receiving unit 72 is reduced. Promoted. For this reason, in the multi-color registration mark 100, the waveform of the output signal obtained for the toner pattern for each of the YM colors is closer to the waveform of the output signal obtained for the K-color toner pattern than in the single-color registration mark 200. .

  As described above, in the multicolor registration mark 100, the difference between the waveform of the output signal obtained for the toner pattern for K color and the waveform of the output signal obtained for the toner pattern for each color of YMC is different from the single color registration mark 200. Smaller than that.

  For this reason, in the multi-color registration mark 100, the mismatch between the pulse intervals T1,..., T5 is smaller than that in the single-color registration mark 200. Smaller than the mark 200. That is, in the multi-color registration mark 100, calculation errors of the positional deviation amounts L and P in the main scanning direction and the sub-scanning direction are reduced.

  Further, in the multi-color registration mark 100, in the vicinity of the signal level compared with the threshold value TH in the binarization described with reference to FIG. 5, the waveform of the K color output signal and the output of each YMC color are output. The waveform of the signal coincides with the extent that the difference is almost ignored. For this reason, in the multi-color registration mark 100, the offset value is regarded as almost “0” in the first place. Therefore, in the multi-color registration mark 100, the calculation error of the positional deviation amounts L and P in the main scanning direction and the sub-scanning direction is regarded as substantially “0”.

  Here, in the multi-color registration mark 100, the misregistration amount calculation error is regarded as almost “0” when the multi-color registration mark 100 is a normal mark in which the inner pattern is positioned inside the outer pattern. Limited to certain cases.

  If the formation of the multicolor registration mark 100 fails and the inner pattern protrudes from the outer pattern, the waveform of the output signal as described above is greatly different between the K color and each of the YMC colors, and the positional deviation amount The calculation error may increase on the contrary.

  In other words, based on the multicolor registration mark 100, the amount of misregistration calculated with high accuracy with a calculation error of almost “0” prevents the formation failure of the multicolor registration mark 100 and the inner pattern is the outer pattern. This is the amount of displacement within the range that fits inside.

  On the other hand, the two types of single-color registration marks 200 and 300 have a larger calculation error than the normal multi-color registration mark 100. However, in these single color registration marks 200 and 300, even if the positional deviation amount is somewhat large, if individual toner patterns are identified, the positional deviation amount is calculated without causing an increase in calculation error.

  Here, the individual toner patterns are identified such that adjacent toner patterns are not overlapped so as to be indistinguishable from each other, and the light spots SP irradiated by the irradiation unit 71 are two toner patterns. Means crossing arms. That is, in the above-described two types of single color registration marks 200 and 300, if an individual toner pattern is identified, it is regarded that the formation is successful, and the amount of positional deviation is calculated.

  As described above, the two types of single-color registration marks 200 and 300 have a wider range of misalignment in which formation failure is avoided than that of the multi-color registration mark 100.

  In addition, as described above, the single-color registration mark 200 and the large-size single-color registration mark 300 have a larger interval between the toner patterns and the length of the arm of the toner pattern. Long. For this reason, the range of the positional deviation amount in which the formation failure is avoided is larger in the large size single color registration mark 300 than in the single color registration mark 200.

  In the present embodiment, the above-described three types of registration marks having different misalignment amount calculation errors and misalignment range ranges where formation failures are avoided are formed in the process represented by the flowchart described below. Is done.

  Each of the monochromatic registration mark 200 and the large size monochromatic registration mark 300 corresponds to an example of the first registration mark according to the present invention. The multicolor registration mark 100 corresponds to an example of a second registration mark according to the present invention.

  FIG. 9 is a flowchart showing a process for generating an adjustment value used in the registration process.

  The processing represented by this flowchart is started in the main control unit 40 when the adjustment value generation request flag is set at the timing when the processing such as the printing operation is completed after the arrival of various events such as the formation of a predetermined number of images. .

  When the processing is started, first, the main control unit 40 forms the monochrome registration marks 200 shown in Part (B) of FIG. 3 on the intermediate transfer belt 61 in the four image forming units 50Y, 50M, 50C, and 50K. (Step S101). The monochromatic registration mark 200 is formed through a registration process using the adjustment values stored in the storage unit 40a at the time of formation.

  Further, in step S101, the main control unit 40 irradiates the irradiation unit 71 of the optical sensor 70 shown in FIG. 2 with light and causes the light receiving unit 72 to receive the reflected light and outputs an output signal. The output signal from the light receiving unit 72 is input to the main control unit 40, and the main control unit 40 binarizes the output signal as described with reference to FIG. 5 to obtain a pulse signal.

  Next, based on the pulse signal, the main control unit 40 determines whether or not the monochromatic registration mark 200 formed in step S101 is a normal mark as follows (step S102). That is, the main control unit 40 determines whether or not the number of pulses included in the pulse signal is a value that is twice the number of toner patterns constituting the single color registration mark 200.

  As can be seen from FIG. 5, in the normal monochromatic registration mark 200, one pulse is obtained corresponding to each of the two arms of each toner pattern. That is, in the normal single color registration mark 200, the number of pulses that is twice the number of toner patterns constituting the single color registration mark 200 is obtained. Note that one pulse can be obtained for each arm of each toner pattern as in the normal multicolor registration mark 100 and the normal large size single color registration mark 300.

  On the other hand, when adjacent toner patterns overlap each other so as to be indistinguishable from each other, or when any one of the toner patterns is shifted to a position off the passing line of the light spot SP irradiated by the irradiation unit 71, The number of pulses is different from the above double number.

  In this embodiment, the number of toner patterns of the multicolor registration mark 100, the single color registration mark 200, and the large size single color registration mark 300 is the same. The number of patterns in the toner pattern is stored in the storage unit 40a of the main control unit 40.

  In step S102 in FIG. 9, the main control unit 40 determines whether or not the number of pulses in the pulse signal obtained by binarization matches the number of patterns stored twice in the storage unit 40a. judge. Thereby, the main control unit 40 determines whether or not the monochromatic registration mark 200 formed in step S101 is a normal mark.

  When it is determined that the monochromatic registration mark 200 is a normal mark (success determination in step S102), the main control unit 40 calculates the amount of positional deviation in the main scanning direction and the sub-scanning direction for each color of YMC as follows ( Step S103).

  In step S103, the main control unit 40 first calculates the positional shift amounts L and P in the main scanning direction and the sub-scanning direction for each color of YMC using the above equations (1) and (2).

  Here, in the present embodiment, the offset value assumed when the positional shift amounts L and P in the main scanning direction and the sub scanning direction are calculated based on the single color registration mark 200 is stored in the storage unit 40a. ing.

  As described above, the offset value indicates that the waveform of the output signal output from the light receiving unit 72 of the optical sensor 70 is inconsistent between the K single color toner pattern and the other YMC single color toner patterns. This is a value derived from the optical sensor 70 caused by the cause.

  In this embodiment, the offset value is measured at the factory using a test optical sensor of the same type as the optical sensor 70 mounted on the copying machine 1 of FIGS. 1 and 2. The measurement of the offset value is performed using an ideal single color registration mark 200 in which the toner pattern is formed in a straight line at equal intervals and the positional deviation amount should be “0”. In the measurement of the offset value, the ideal single color registration mark 200 is detected by the test optical sensor. Based on the detection result, the amount of positional deviation in the main scanning direction and the sub-scanning direction is calculated for each color of YMC. In the factory, such detection and calculation are performed multiple times. Then, an average value of a plurality of misregistration amounts in each of the YMC colors in the main scanning direction and the sub-scanning direction is generated as an offset value of each YMC color in the main scanning direction and the sub-scanning direction at the time of manufacture. The copying machine 1 shown in FIGS. 1 and 2 is shipped with these offset values obtained by the above-described measurement at the factory stored in the storage unit 40a.

  The above offset value corresponds to an example of a correction value referred to in the present invention. And the memory | storage part 40a which has memorize | stored the offset value is equivalent to an example of the memory | storage part said to this invention.

  In step S103 of FIG. 9, the main control unit 40 calculates the following equation based on the calculation results of the positional deviation amounts L and P in the main scanning direction and the sub-scanning direction and the offset value in the storage unit 40a at the time of the calculation. Use this to calculate the amount of misalignment for generating adjustment values.

  The positional shift amounts L ′ and P ′ for generating adjustment values in the main scanning direction and the sub-scanning direction are expressed by the following equations using the offset values Ol and Op in the main scanning direction and the sub-scanning direction. Note that the calculation of the positional deviation amount for generating the adjustment value is performed for each YMC color by using the calculation result of the positional deviation amount of each YMC color and the offset value of each YMC color. The formula used for the calculation is the same between the YMCs. For this reason, in the following expression, the distinction between each color of YMC is omitted.

L ′ = L + Ol (3)
P ′ = P + Op (4)
When the positional deviation amount for generating the adjustment value is calculated in this way, the main control unit 40 at the current time in the storage unit 40a so as to shift the toner image formation position in the direction opposite to the positional deviation of the amount represented by the calculation result. The adjustment value is corrected to generate a new adjustment value (S104). The main control unit 40 updates the current adjustment value in the storage unit 40a to the new adjustment value.

  When the generation of the adjustment value for the registration process is thus completed, the main control unit 40 forms the multicolor registration mark 100 shown in part (A) of FIG. 3 (step S105). The formation of the multicolor registration mark 100 in step S105 is also performed through a registration process using the adjustment value stored in the storage unit 40a at the time of formation. However, the adjustment value stored in the storage unit 40a at the time of step S105 is the adjustment value generated in step S104.

  Further, in step S105, the main control unit 40 irradiates the irradiation unit 71 with light and causes the light receiving unit 72 to receive reflected light to output an output signal, and binarizes the output signal to obtain a pulse signal. Based on the pulse signal, the main control unit 40 calculates the misregistration amounts L and P in the main scanning direction and the sub-scanning direction for each YMC color using the above equations (1) and (2). To do.

  Subsequently, the main control unit 40 calculates the positional shift amounts L and P calculated using the equations (1) and (2) in step S105 with high accuracy with a calculation error of almost “0”. Is determined as follows (step S106).

  In step S106, the main control unit 40 first determines that the multicolor registration mark 100 formed in step S105 is normal based on the determination similar to the determination in step S102 based on the pulse signal obtained in step S105. It is determined whether or not it is a mark.

  In step S106, the main control unit 40 further determines whether or not the positional deviation amounts L and P obtained in step S105 are positional deviation amounts within a range in which the inner pattern falls within the outer pattern. In the present embodiment, the range of misalignment within which the inner pattern fits inside the outer pattern is obtained from the pattern structure of the multicolor registration mark 100 described with reference to FIG. 4 when the copying machine 1 is designed. ing. Then, the obtained range of the positional deviation amount is stored in the storage unit 40 a of the main control unit 40. The main control unit 40 determines whether or not the positional deviation amounts L and P obtained in step S105 are within the range stored in the storage unit 40a.

  In step S106, the main control unit 40 determines that the multi-color registration mark 100 is a normal mark and determines that the positional deviation amounts L and P are within the above range. It is determined that the values L and P are calculated with high accuracy.

  When it is determined that the positional deviation amounts L and P calculated in step S105 are calculated with high accuracy (success determination in step S106), the main control unit 40 makes a new adjustment based on the calculation result. A value is generated (step S107). In step S107, since the calculation errors of the positional deviation amounts L and P are considered to be substantially “0”, the main control unit 40 generates an adjustment value without using an offset value, unlike step S104.

  That is, in this step S107, the main control unit 40 corrects the current adjustment value in the storage unit 40a so as to shift the toner image formation position in the direction opposite to the positional shift of the amounts represented by the positional shift amounts L and P. Thus, a new adjustment value is generated. Then, the main control unit 40 updates the current adjustment value in the storage unit 40a to the new adjustment value. The latest adjustment value updated in this way is used for registration processing during image formation after the update.

  Here, as described above, although the calculation error regarding the positional deviation amount is relatively small based on the double-color registration mark 100, the range of the positional deviation amount that avoids the formation failure of the double-color registration mark 100 is as follows. Relatively narrow. On the other hand, based on the monochromatic registration mark 200, the calculation error regarding the misregistration amount is relatively large, but the range of misregistration amount where the formation failure of the monochromatic registration mark 200 is avoided is relatively wide.

  In this embodiment, prior to the calculation of the misregistration amount based on the multicolor registration mark 100, first, the misregistration amount based on the single color registration mark 200 and the adjustment value generation based on the calculation result are performed. Is called. The multi-color registration mark 100 is formed through a registration process using the adjustment value thus generated. Then, based on the multi-color registration mark 100 formed as described above, the amount of positional deviation is calculated with high accuracy. That is, in the present embodiment, the failure of forming the multicolor registration mark 100 is suppressed, and the calculation error of the toner image formation position is suppressed.

  Here, if it is determined in step S106 that the calculated positional deviation amounts L and P are not calculated with high accuracy (failure determination in step S106), the following is meant. . That is, it means that the normal multicolor registration mark 100 was not formed even after the registration process using the adjustment value based on the single color registration mark 200. In this case, there is a possibility that a component failure or the like has occurred in the image forming units 50Y, 50M, 50C, and 50K or the optical sensor 70 and adjustment of the positional deviation is impossible. Therefore, in this embodiment, in this case, the main control unit 40 displays a message notifying the user of the occurrence of an error on the display operation unit 14 shown in FIG. 1 (step S108).

  On the other hand, when the adjustment value of the registration process is generated in step S107, the main control unit 40 performs the following process for correcting the offset value in the storage unit 40a (step S109).

  In step S109, the main control unit 40 corrects the offset value in the storage unit 40a using the positional deviation amounts L and P calculated in step S105, and the offset value in the storage unit 40a is corrected. Update to the offset value.

  For the positional deviation amounts L and P calculated within the above range calculated based on the normal multicolor registration mark 100, the calculation error is regarded as almost “0” as described above. In other words, the positional shift amounts L and P are the positional shift amounts remaining without being adjusted even by the registration process based on the adjustment value generated using the offset value in the storage unit 40a.

  That is, the misregistration amounts L and P are calculated based on the offset value in the storage unit 40a used for generating the adjustment value in step S104 and the misregistration amount based on the monochrome registration mark 200 at the present time. This corresponds to the difference from the current offset value expected in some cases. This difference is due to individual differences between the test optical sensor used when generating the offset value in the factory and the optical sensor 70 mounted on the copying machine 1 shown in FIGS. This is caused by a change in the internal environment of the copying machine 1 after the update.

  Therefore, the current offset values Ol ′ and Op ′ in the main scanning direction and the sub-scanning direction are expressed by the following equations using the positional deviation amounts L and P calculated in step S105 and the offset values Ol and Op in the storage unit 40a. It is represented by The calculation of the current offset value is performed for each YMC color using the positional shift amount of each YMC color and the offset value of each YMC color in the storage unit 40a. The formula used for the calculation is the same between the YMCs. For this reason, in the following expression, the distinction between each color of YMC is omitted.

Ol ′ = Ol + L (5)
Op ′ = Op + P (6)
When the current offset values Ol ′ and Op ′ are generated in this way, the main control unit 40 updates the offset values Ol and Op in the storage unit 40a to the current offset values Ol ′ and Op ′. The current offset values Ol ′ and Op ′ updated in this manner are used to calculate the positional deviation amount for generating the adjustment value using the above-described equations (3) and (4) in step S103 after the update. Used when. Thereby, the calculation accuracy of the positional deviation amount for generating the adjustment value based on the single color registration mark 200 after the update is increased. As a result, the formation failure of the multi-color registration mark 100 performed through the registration process using the adjustment value based on the single-color registration mark 200 is further suppressed.

  If it is determined in step S102 described above that the monochromatic registration mark 200 is not a normal mark (failure determination in step S102), the process proceeds to step S109.

  In step S109, the main control unit 40 forms a large size single color registration mark 300 shown in part (C) of FIG. 3 (step S109).

  As described above, the range of the misregistration amount in which the formation failure is avoided is larger in the large size single color registration mark 300 than in the single color registration mark 200.

  That is, in the present embodiment, when the formation of the single color registration mark 200 fails, the formation of the large size single color registration mark 300 that is relatively likely to avoid the formation failure is executed.

  The large size single color registration mark 300 is also formed through a registration process using adjustment values stored in the storage unit 40a at the time of formation. In step S110, the main control unit 40 irradiates the irradiating unit 71 with light and causes the light receiving unit 72 to receive reflected light to output an output signal, and further binarizes the output signal to obtain a pulse signal.

  Subsequently, based on the pulse signal, the main control unit 40 determines whether or not the large size single color registration mark 300 formed in step S110 is a normal mark by the same determination as in step S102. Determination is made (step S111).

  When it is determined that the large size single color registration mark 300 is not a normal mark (failure determination in step S111), this means the following. That is, it means that the large-size single-color registration mark 300 having the highest possibility of avoiding the formation failure among the above three types of registration marks was not formed normally. In this case, there is a possibility that a component failure or the like has occurred in the image forming units 50Y, 50M, 50C, and 50K or the optical sensor 70 and adjustment of the positional deviation is impossible. Therefore, in this embodiment, also in this case, the main control unit 40 displays a message notifying the occurrence of an error on the display operation unit 14 shown in FIG. 1 (step S112).

  On the other hand, when it is determined that the large-size single-color registration mark 300 is a normal mark (success determination in step S111), the main control unit 40 generates an adjustment value for registration processing from the pulse signal obtained in step S110. (Step S113).

  In step S113, the main control unit 40 calculates the misregistration amounts L and P in the main scanning direction and the sub-scanning direction using the above equations (1) and (2) for each color of YMC.

  Here, in the present embodiment, for the large size single color registration mark 300, the positional deviation amounts L and P obtained from the equations (1) and (2) are used for adjusting value generation without considering the offset value. Is used as it is.

  This is because the adjustment value based on the large-size single-color registration mark 300 need only be a rough adjustment value so that a normal single-color registration mark 200 is formed through the registration process using the adjustment value. .

  In step S113, the main control unit 40 obtains an adjustment value of each color that corrects the calculated amount of misregistration of each YMC color, and updates the adjustment value stored in the storage unit 40a to the obtained adjustment value.

  When the generation of the adjustment value for the registration process is completed in this way, the main control unit 40 forms the monochromatic registration mark 200 shown in part (B) of FIG. 3 (step S114). The formation of the monochromatic registration mark 200 in step S114 is performed through a registration process using the adjustment value stored in the storage unit 40a at the time of formation. However, the adjustment value stored in the storage unit 40a at the time of step S114 is the adjustment value generated in step S113.

  Further, in this step S114, the main control unit 40 irradiates the irradiation unit 71 with light and causes the light receiving unit 72 to receive reflected light, outputs an output signal, and further binarizes the output signal to generate a pulse signal. obtain.

  Subsequently, the main control unit 40 determines whether or not the single color registration mark 200 formed in step S114 is a normal mark by the same determination as the determination in step S102 for the pulse signal (step S102). S115).

  When it is determined that the monochromatic registration mark 200 is not a normal mark (failure determination in step S115), the following is meant. That is, it means that the normal monochromatic registration mark 200 was not formed even after the registration process using the adjustment value based on the large size monochromatic registration mark 300. In this case, there is a possibility that a component failure or the like has occurred in the image forming units 50Y, 50M, 50C, and 50K or the optical sensor 70 and adjustment of the positional deviation is impossible. Therefore, in this embodiment, also in this case, the process proceeds to step S112, and the main control unit 40 displays a message notifying the occurrence of an error on the display operation unit 14 shown in FIG.

  On the other hand, when it is determined that the monochromatic registration mark 200 is a normal mark (success determination in step S115), the processing from step S103 to step S109 is executed.

  Then, with the update of the offset value at step S109 and the display of the message notifying the occurrence of the error at step S108 or step S112, the process for generating the adjustment value for the registration process shown in the flowchart of FIG. 9 is completed.

  The process from step S101 to step S104 and the process from step S110 to step S115 to step S104 in the flowchart of FIG. 9 correspond to an example of a first adjustment process according to the present invention. Further, the process from step S105 to step S107 in the flowchart of FIG. 9 corresponds to an example of a second adjustment process according to the present invention. The function of the main control unit 40 that performs the processing shown in the flowchart of FIG. 9 corresponds to an example of the adjustment sequence control unit according to the present invention.

  In this embodiment, when the formation of the single-color registration mark 200 fails, the large-size single-color registration mark 300 is formed, and an error is notified when the formation of the large-size single-color registration mark 300 fails. Illustrated. However, when the formation of the monochromatic registration mark 200 fails, an error may be notified immediately.

  In the present embodiment, an adjustment value based on the multi-color registration mark 100 is generated, and the offset value in the storage unit 40a is corrected using the positional shift amount calculated based on the multi-color registration mark 100. The form is illustrated. However, such an offset value correction may not be performed, and the offset value measured before shipment in the factory and stored in the storage unit 40a may be continuously used.

  Moreover, in this embodiment, the form which correct | amends the offset value in the memory | storage part 40a whenever the adjustment value based on the multi-color registration mark 100 is produced | generated is illustrated. However, such an offset value correction may be performed only once, and thereafter, the offset value after the one correction may be continuously used. Alternatively, the offset value may be corrected every time the adjustment value based on the multicolor registration mark 100 is generated a prescribed number of times, for example, five times.

  In the present embodiment, YMCK four-color toner is exemplified as the multi-color toner. However, the toner of a plurality of colors may be a toner of five or more colors obtained by adding a toner of another color to these four colors.

  In this embodiment, a color copying machine 1 is illustrated as an example of an image forming apparatus. However, the image forming apparatus may be a color printer, a color facsimile, or the like.

DESCRIPTION OF SYMBOLS 1 Copier 1A Document reading part 1B Image formation part 11 Document feeding stand 12 Document discharge stand 13 Document reading plate 14 Display operation part 15 Support frame 16 Conveyance roller 17 Conveyance path 21 Discharge stand 22 Front cover 23_1, 23_2, 23_3 Paper feed table 24 Horizontal cover 24_1, 24_2, 24_3 Guide rail 25 Pickup roll 26 Separation roll 27 Transport roll 28 Standby roll 29Y, 29M, 29C, 29K Container mounting section 30 Document reading optical system 31 First block 32 Second block 33 Photoelectric Sensor 34 Image processing unit 40 Main control unit 41 Exposure control unit 42 Exposure unit 50Y, 50M, 50C, 50K Image forming unit 51 Photoconductor 52 Charger 53 Development unit 54 Transfer unit 55 Cleaner 61 Intermediate transfer belt 62 Roll 63 Transfer unit 64 Fixing device 65 Discharge La 66 Cleaner 67Y, 67M, 67C, 67K Toner container 70 Optical sensor 71 Irradiation unit 72 Light reception unit 100 Multicolor registration mark 101, 101Y, 101M, 101C, 101K, 201Y, 201M, 201C, 201K, 301Y, 301M, 301C , 301K toner pattern 102, 102Y, 102M, 102C, 102K inner pattern 103, 103Y, 103M, 103C, 103K outer pattern 200 single color registration mark 300 large size single color registration mark

Claims (2)

A plurality of toner image forming units for forming different color toner images by sharing a plurality of color toners for each color; and
A transfer body that moves along the plurality of toner image forming portions and receives a plurality of toner images formed by the plurality of toner image forming portions;
A transfer device for further transferring a plurality of color toner images transferred onto the transfer medium onto a recording medium;
A fixing device that fixes a plurality of color toner images transferred onto the recording medium onto the recording medium;
A mark formation control unit configured to form a registration mark including a set of toner patterns for detecting a toner image formation position shift in the plurality of toner image forming units on the transfer target by the plurality of toner image forming units;
A mark sensor for detecting a position of a toner pattern included in a registration mark formed on the transfer target;
A forming position deviation calculating unit that calculates a toner image forming position deviation in the plurality of toner image forming units based on a detection result by the mark sensor;
A forming position adjusting unit that adjusts toner image forming positions in the plurality of toner image forming units based on a calculation result by the forming position deviation calculating unit;
A first registration mark composed of a set of first toner patterns is formed, a toner image formation position deviation is calculated based on a detection result of the first registration mark, and the calculation result of the toner image formation position deviation is calculated. Performing a first adjustment process for adjusting the toner image forming position based on
The toner pattern is a set of toner patterns, and a toner pattern for detecting a toner image forming position deviation in at least one toner image forming unit of the toner patterns includes a toner used in the toner image forming unit and the toner image forming unit. The second registration which is a second toner pattern in which the calculation error of the toner image formation position deviation is reduced as compared with the first toner pattern by combining with the toner used in another toner image forming unit other than the first toner pattern. A second adjustment process is performed in which a mark is formed, a toner image formation position deviation is calculated based on the detection result of the second registration mark, and a toner image formation position is adjusted based on the calculation result of the toner image formation position deviation. And an adjustment sequence control unit. A storage unit for storing a correction value for correcting a calculation result of the toner image formation position shift in the formation position shift calculation unit used in the first adjustment process;
In the first adjustment process, the formation position deviation calculation unit calculates a toner image formation position deviation based on a detection result by the mark sensor, and further corrects the calculation result with the correction value to obtain a final calculation result. In the second adjustment process, a toner image formation position deviation is calculated based on a detection result by the mark sensor, and the correction value is updated so as to reduce the deviation. The image forming apparatus according to claim 1.

Images