JP4724549B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus in which a plurality of image carriers are arranged along the moving direction of a transfer material.

Many image forming apparatuses form color images in accordance with market demands. As a color image forming apparatus for forming a color image, for example, an image carrier such as a single photosensitive drum and each color obtained by developing each color electrostatic latent image sequentially formed on the image carrier. A toner image is sequentially superimposed on a transfer material such as an intermediate transfer member or a recording material to obtain a color image. Hereinafter, this color image forming apparatus is referred to as a one-drum type image forming apparatus. Further, for example, a color image obtained by sequentially superimposing a plurality of image carriers corresponding to each color and each color toner image obtained by developing an electrostatic latent image formed on each image carrier on a transfer material. Is what you get. Hereinafter, this color image forming apparatus is referred to as a tandem type image forming apparatus.
Since the one-drum type image forming apparatus has one image carrier, the apparatus can be reduced in size and cost can be reduced. However, since a single image carrier is used, it is necessary to repeat a series of processes from formation of a latent image, development processing, and transfer to a transfer material for the number of colors (usually four times). This is disadvantageous in terms of speeding up image formation. On the other hand, the tandem type image forming apparatus has the disadvantage that the apparatus becomes large and the cost is high, but since the image carrier is provided for each color, the series of processes described above is only required once. This is advantageous in terms of speeding up image formation. In recent years, the tandem-type image forming apparatus has attracted attention because the image forming speed of a color image forming apparatus is as high as that of a monochrome image forming apparatus.

  In the above-described tandem type image forming apparatus, each toner image on a plurality of image carriers is sequentially superimposed on a transfer material to form a color image. Therefore, if the toner images overlap, Image position shift (color shift) occurs on the material. The main cause of this color misregistration is the periodic fluctuation of the surface movement speed (hereinafter referred to as “rotational speed”) of the image carrier having one rotation period of the image carrier caused by the eccentricity of the rotation axis of the image carrier. It is. That is, the toner image transferred from the image carrier to the surface of the transfer material due to this variation periodically expands and contracts according to the amplitude of the variation. Therefore, if the amplitudes and phases of the rotational speed fluctuations of the respective image carriers are not matched, the toner images on the surface of the transferred material that have been stretched or shrunk do not exactly overlap and color misregistration occurs.

  Patent Document 1 discloses an image forming apparatus that can suppress color misregistration caused by the rotation speed of an image carrier varying with one rotation period of the image carrier. This image forming apparatus forms a toner pattern (detection pattern) on a transfer material using a plurality of image carriers, and grasps the peak position of the rotational speed fluctuation of each image carrier by reading the toner patterns. . Also, one of the toner marks constituting the toner pattern is detected as a phase reference mark. Then, from the grasped peak position and the position of the phase reference mark, the phase of the rotational speed fluctuation between the image carriers so that the peak position of the rotational speed fluctuation of each image carrier matches on the transfer material. The relative rotational positions between these image carriers are adjusted.

  Patent Document 2 also discloses an image forming apparatus that can suppress color misregistration. This image forming apparatus includes an image carrier for each of yellow, magenta, cyan, and black, and adjusts the rotational positions of the other three color image carriers relative to the black image carrier. Specifically, in the case of adjusting the relative rotational position of the yellow image carrier, for example, the relative rotational position of the yellow image carrier with respect to the black image carrier is shifted by 45 [°], and each relative position is shifted. A toner pattern is formed on each of the yellow and black image carriers at a rotational position so as to have a predetermined positional relationship (for example, a positional relationship overlapping each other) on the transfer material. The amount of image position deviation on the transfer material is measured. Then, the relative rotation position when the image position shift amount is minimized is specified, and the yellow image carrier is set so that the relative rotation position of the yellow image carrier with respect to the black image carrier becomes the specified relative rotation position. Adjust the rotational position of the body. The rotational positions of the magenta and cyan image carriers are adjusted in the same manner.

JP 2000-221749 A JP 2005-55692 A

  However, there are cases where the color misregistration cannot be sufficiently suppressed by the method of adjusting the relative rotational position described in Patent Document 1. More specifically, the rotational speed fluctuation of the image carrier is also caused by the mounting eccentricity of the drive gear provided on the image carrier, the gear molding accuracy, the speed fluctuation caused by the joint portion that couples the drive gear and the image carrier. The rotational speed fluctuation component of the image carrier caused by these causes has a period different from the rotation period of the image carrier. That is, fluctuation components having various periods are superimposed on the rotation speed fluctuation of the image carrier. Since the fluctuation components having a period different from the one rotation period of the image carrier are thus superimposed, these become noise, and the peak position of the rotational speed fluctuation of the image carrier is the eccentricity of the image carrier. In some cases, it does not coincide with the peak position of the fluctuation component having one rotation period of the image carrier due to the above. As a result, even if the relative rotational position between the image carriers is adjusted so that the peak positions of the rotational speed fluctuations of the image carriers coincide with each other on the transfer material, it is caused by the eccentricity of the image carriers. The peak position of the fluctuation component having one rotation period of the image carrier cannot be made coincident, and a situation in which the color shift cannot be sufficiently suppressed may occur.

  Further, due to the influence of various fluctuation components having a period different from the rotation period of the image carrier, the peak positions of the fluctuation components having the rotation period of each image carrier are not necessarily matched with each other on the transfer material. It is not always possible to suppress the color shift most. That is, when the peak positions of the fluctuation components having one rotation period of each image carrier are shifted from each other on the transfer material, compared to the case where these peak positions are matched with each other on the transfer material, There may be little color misregistration. In this case, the method for adjusting the relative rotational position described in the above-mentioned Patent Document 1 cannot suppress optimal color misregistration.

  On the other hand, according to the method for adjusting the relative rotational position described in Patent Document 2, the image position displacement amount between the image carriers at each relative rotational position shifted by 45 ° can be grasped. The relative rotational position is adjusted so that the image position shift amount (color shift amount) is minimized between the carriers. That is, since a suitable relative rotational position is specified and adjusted based on the actually detected image position deviation amount, the color deviation can be suppressed more effectively than the adjustment method described in Patent Document 1.

  However, the adjustment method described in Patent Document 2 requires an operation of forming a toner pattern for each relative rotation position and detecting this in order to grasp the image position shift amount at each relative rotation position. For this reason, a large amount of toner is consumed, and the operation is repeated at each relative rotational position, which requires a long processing time.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce color consumption effectively with less toner consumption and shorter processing time than the image forming apparatus described in Patent Document 2. It is an object of the present invention to provide an image forming apparatus that can be suppressed.

In order to achieve the above object, a first aspect of the present invention provides a plurality of image carriers arranged along a moving direction of a transfer material, drive means for driving the plurality of image carriers, and the plurality of image carriers. An image forming apparatus comprising: an image forming unit that forms an image on the image carrier; and a transfer unit that transfers the images formed on the plurality of image carriers to the transfer material so as to overlap each other. In the above, the same image-detecting pattern consisting of a plurality of marks formed at equal time intervals along at least one rotation of the image carrier along the rotation direction of the image carrier, and control means for controlling the formation, the mark detecting means for detecting the mark after the mark on the plurality of image bearing member is transferred to the transfer material on the basis of a detection result of said mark detecting means , Each mer Storage means for storing the mark position information corresponding to each of the detection patterns, and on the transfer material of each reference mark constituting one reference detection pattern based on the mark position information stored in the storage means And calculating a reference difference value group consisting of a difference value between each reference position in the image and each position on the transfer material of each mark constituting another detection pattern corresponding to each reference mark. An amount corresponding to a predetermined rotation angle in the image carrier that is the rotation angle adjustment target on which the other detection pattern is formed from the reference position and each mark constituting the other detection pattern corresponding to each reference mark. Difference value calculation for calculating a difference value group after virtual rotation consisting of a difference value of each mark shifted from the position on the transfer material by changing the predetermined rotation angle by one rotation of the image carrier. Means and, from the said difference reference difference value group calculation means has calculated and one or more virtual rotation after the difference value group, after selecting one of the difference value group in accordance with a predetermined image position deviation correction condition, the one Relative to the rotational position of the reference image carrier on which the reference detection pattern is formed, the image carrier subject to rotation angle adjustment is relative to the predetermined rotational angle used when calculating the selected difference value group. A process execution means for performing processing necessary to correct an image position shift on the transfer material between the reference image carrier and the rotation angle adjustment target image carrier by rotating; Yes, and the predetermined image position deviation correction conditions are those wherein the sum of the absolute value of the difference value included in each difference value group is a condition that is the minimum.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the processing executed by the processing execution unit is a relative rotational position of the image carrier to be rotated with respect to the reference image carrier. Is a process of controlling the driving means so as to be the predetermined rotation angle used when calculating the selected difference value group.
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the minimum value of the predetermined rotation angle is equal to or greater than a minimum rotation angle that can be controlled using the driving unit. .
According to a fourth aspect of the present invention, in the image forming apparatus of the first aspect, the processing executed by the processing execution unit notifies the operator of the predetermined rotation angle used when calculating the selected difference value group. It is a process.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the difference value calculation unit calculates the difference value group after virtual rotation between two adjacent marks. The predetermined rotation angle is sequentially changed by an amount corresponding to the rotation angle of the image carrier whose rotation angle is to be adjusted corresponding to the interval.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the difference value calculating means determines the difference value group after the virtual rotation of two marks that are not adjacent to each other. The predetermined rotation angle is sequentially changed by an amount corresponding to the rotation angle of the image carrier whose rotation angle is to be adjusted corresponding to the interval .
Also, the invention of claim 9 is the image forming apparatus according to any one of claims 1 to 6, based on the mark position information stored in the storage means, constituting the other of the detection pattern And determining means for determining whether or not the maximum value of the deviation amount between the position of each mark and the ideal position of each mark is equal to or less than a predetermined value. When it is determined that the reference difference value group and the post-virtual rotation difference value group are not calculated, the reference difference value group and the post-virtual rotation difference value are determined when the determination unit determines that a predetermined value is exceeded. A group is calculated.

In the present invention, one of the plurality of image carriers is used as a reference image carrier, and the rotational position (relative to the reference image carrier) of another image carrier (image carrier subject to rotation angle adjustment). Color shift is suppressed by adjusting the rotation position. Specifically, based on the mark position information corresponding to the reference image carrier stored in the storage unit, each position on the transfer material of each reference mark constituting the reference detection pattern formed on the image carrier ( Grasp each reference position). Further, based on the mark position information corresponding to the rotation angle adjustment target image carrier stored in the storage means, each mark constituting the detection pattern formed on the image carrier (hereinafter referred to as “adjustment target mark”). )) On the transfer material (hereinafter referred to as “adjustment target position” as appropriate). Then, the difference value between the reference position of each reference mark and the adjustment target position of each adjustment target mark corresponding to each reference mark is calculated for the corresponding number, and these difference values are used as a reference difference value group. . More specifically, each reference mark and each adjustment target mark corresponding to each other are represented by a first reference mark, a first adjustment target mark, a second reference mark, a second adjustment target mark,. In the case of the nth adjustment target mark, the reference difference value group includes the difference value between the first reference position corresponding to the first reference mark and the first adjustment target position corresponding to the first adjustment target mark, as well as the second reference value. It consists of a difference value between the reference position and the second adjustment target position, ..., a difference value between the nth reference position and the nth adjustment target position. Note that the reference mark and the adjustment target mark corresponding to each other have an ideal positional relationship on the transfer material between them (the positional relationship when there is no deviation in the amplitude and phase of the rotational speed fluctuation between the image carriers). ) May be any marks that can be grasped in advance. Normally, the reference mark and the adjustment target mark that are to be transferred to the same position on the transfer material in the moving direction of the transfer material are associated with each other, but the present invention is not limited to this. In this example, it is possible to grasp the amount of image position deviation between the reference image carrier at the present time and the image carrier subject to rotation angle adjustment from the reference difference value group.
In addition to the calculation of the reference difference value group, each adjustment target position of each adjustment target mark that is shifted from each adjustment target mark corresponding to each reference mark by an amount corresponding to a predetermined rotation angle in the image carrier that is the rotation angle adjustment target And the corresponding reference position are calculated by the corresponding number, and these difference values are set as a difference value group after virtual rotation. This post-virtual rotation difference value group is calculated as one or more by changing the predetermined rotation angle by one rotation of the image carrier to be adjusted in rotation angle. More specifically, for example, when a deviation corresponding to a predetermined rotation angle is set to one mark, the post-virtual rotation difference value group includes the difference value between the first reference position and the second adjustment target position, the second reference position, It consists of a difference value between the third adjustment target position,..., A difference value between the nth reference position and the (n + 1) th adjustment target position. Note that when the detection pattern is just one rotation of the image carrier that is the object of rotation angle adjustment, the (n + 1) th adjustment object position is the first adjustment object position. Similarly, for example, when the deviation corresponding to the predetermined rotation angle is set to two marks, the post-virtual rotation difference value group includes the difference value between the first reference position and the third adjustment target position, the second reference position, and the second reference position. It consists of a difference value between the four adjustment target positions,..., A difference value between the nth reference position and the n + 2 adjustment target position. When the reference mark and the adjustment target mark that are to be transferred to the same position on the transfer material in the moving direction of the transfer material are associated with each other, the reference image carrier is obtained from the former virtual rotation difference value group. Image position difference between the reference image carrier and the rotation angle adjustment target image carrier when the image carrier subject to rotation angle adjustment is virtually rotated relative to the rotation angle corresponding to one mark. The amount can be grasped. Similarly, from the latter post-virtual rotation difference value group, when the image carrier subject to rotation angle adjustment is virtually rotated relative to the reference image carrier by a rotation angle corresponding to two marks. It is possible to grasp the image position deviation amount between the reference image carrier and the rotation angle adjustment target image carrier. In this way, the post-virtual rotation difference value group is calculated for one rotation of the image carrier to be adjusted for rotation angle, that is, for the number obtained by subtracting one from the number of marks for one rotation of the image carrier. Here, the case where the deviation corresponding to the predetermined rotation angle is one mark is illustrated, but the same applies to the case where the deviation corresponding to the predetermined rotation angle is equal to or more than two marks. Further, the amount of deviation of each predetermined rotation angle when calculating each post-virtual rotation difference value group is not necessarily constant.
Next, one difference value group is selected from the reference difference value group calculated in this way and one or more post-virtual rotation difference value groups according to a predetermined image position deviation correction condition. As described above, since the reference difference value group and the post-virtual rotation difference value group, it is possible to grasp each image position shift amount when the image carrier subject to rotation angle adjustment is virtually shifted by a predetermined rotation angle by one rotation. By appropriately setting a predetermined image position deviation correction condition that minimizes the image position deviation amount, the relative rotation position of the image carrier that is the rotation angle adjustment target that minimizes the image position deviation amount can be specified. Then, the process execution means, in order to correct the image position shift by the Turkey is rotated relative to the image bearing member based on the image bearing member rotational angle adjusted so that the specified relative rotational position Perform the necessary processing. Examples of this processing include processing as described in claims 2 to 4.

  According to the present invention, it is possible to grasp each image position shift amount when the image carrier to be adjusted for rotation angle is shifted by a predetermined rotation angle by one rotation only by forming and detecting the detection pattern once. Therefore, an excellent effect is achieved in that the color misregistration can be effectively suppressed in a shorter processing time with less toner consumption than the image forming apparatus described in Patent Document 2.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic printer (hereinafter simply referred to as “printer”) will be described.
First, a basic configuration of the printer according to the present embodiment will be described.
FIG. 2 is a schematic configuration diagram illustrating the printer according to the present embodiment.
The printer 100 has four processes for generating toner images that are visible images of yellow, magenta, cyan, and black (hereinafter referred to as “Y”, “M”, “C”, and “K”, respectively). Cartridges 6Y, 6M, 6C, and 6K are provided. These use Y toner, M toner, C toner, and K toner of different colors as the image forming agent, but the other configurations are the same. Each of the process cartridges 6Y, 6M, 6C, and 6K is detachable from the main body of the printer 100 so that consumable parts can be replaced at a time. Hereinafter, the process cartridge 6Y for generating a Y toner image will be described as an example.

FIG. 3 is a schematic configuration diagram showing a process cartridge 6Y for generating a Y toner image.
The process cartridge 6Y includes a photosensitive drum 1Y as an image carrier, a drum cleaning device 2Y, a static eliminator (not shown), a charging device 4Y, a developing device 5Y that is an agent supply target, and the like. The charging device 4Y uniformly charges the surface of the photosensitive drum 1Y that is rotated clockwise in the drawing by a drum driving device that is a rotation driving device as a rotation driving means described later. The uniformly charged surface of the photosensitive drum 1Y is exposed and scanned by the laser beam L to carry a Y electrostatic latent image. The Y electrostatic latent image is developed into a Y toner image by the developing device 5Y using Y toner. Then, intermediate transfer is performed on the intermediate transfer belt 8. The drum cleaning device 2Y removes the toner remaining on the surface of the photosensitive drum 1Y after the intermediate transfer process. The static eliminator neutralizes residual charges on the photosensitive drum 1Y after cleaning. By this charge removal, the surface of the photosensitive drum 1Y is initialized and prepared for the next image formation. Similarly, in the other process cartridges 6M, 6C, and 6K, M toner images, C toner images, and K toner images are formed on the photosensitive drums 1M, 1C, and 1K, respectively. Transcribed.

  Further, as shown in FIG. 2, an exposure device 7 is disposed below each process cartridge 6Y, 6M, 6C, 6K in the drawing. The exposure device 7 serving as a latent image forming unit irradiates and exposes the photosensitive drums 1Y, 1M, 1C, and 1K in the process cartridges 6Y, 6M, 6C, and 6K with the laser light L emitted based on the image information. . By this exposure, Y electrostatic latent images, M electrostatic latent images, C electrostatic latent images, and K electrostatic latent images are formed on the photosensitive drums 1Y, 1M, 1C, and 1K, respectively. The exposure device 7 irradiates the photosensitive drum with a laser beam L emitted from a light source through a plurality of optical lenses and mirrors while scanning with a polygon mirror rotated by a motor. The exposure device 7 constitutes visible image forming means for forming a toner image as a visible image on the photosensitive drum together with the process cartridges 6Y, 6M, 6C, 6K and the like.

  In FIG. 2, on the lower side of the exposure apparatus 7 in the drawing, paper supply means including a paper storage cassette 26, a paper supply roller 27 incorporated in these, a registration roller pair 28, and the like are disposed. The paper storage cassette 26 stores a plurality of transfer papers P as recording materials, and a paper feed roller 27 is brought into contact with the uppermost transfer paper P. When the paper feeding roller 27 is rotated counterclockwise in the drawing by a driving means (not shown), the uppermost transfer paper P is fed toward the rollers of the registration roller pair 28. The registration roller pair 28 rotationally drives both rollers to sandwich the transfer paper P, but temporarily stops rotating immediately after sandwiching. Then, the transfer paper P is sent out toward a later-described secondary transfer nip at an appropriate timing.

In FIG. 2, an intermediate transfer unit 15 is disposed above the process cartridges 6Y, 6M, 6C, and 6K. The intermediate transfer unit 15 moves endlessly while the intermediate transfer belt 8 serving as an intermediate transfer member as a transfer material is stretched. It is installed. The intermediate transfer unit 15 includes a belt cleaning device 10 in addition to the intermediate transfer belt 8. Also provided are four primary transfer bias rollers 9Y, 9M, 9C, 9K, a secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14, and the like. The intermediate transfer belt 8 is endlessly moved in the counterclockwise direction in the figure by the rotational drive of at least one of the rollers while being stretched around these seven rollers. The primary transfer bias rollers 9Y, 9M, 9C, and 9K respectively sandwich the intermediate transfer belt 8 that is moved endlessly in this manner between the photosensitive drums 1Y, 1M, 1C, and 1K, respectively. Is forming. In these systems, a transfer bias having a polarity opposite to that of toner (for example, plus polarity) is applied to the back surface (inner circumferential surface of the loop) of the intermediate transfer belt 8. All the rollers except the primary transfer bias rollers 9Y, 9M, 9C, and 9K are electrically grounded. The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and the Y toner image on each of the photosensitive drums 1Y, 1M, 1C, and 1K. , The M toner image, the C toner image, and the K toner image are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as “four-color toner image”) is formed on the intermediate transfer belt 8.
Further, the intermediate transfer unit 15 is in contact with or separated from the photosensitive drums 1Y, 1M, and 1C (not shown) for contacting and separating the intermediate transfer belt 8 with respect to the photosensitive drums 1Y, 1M, and 1C in a state where the intermediate transfer belt 8 is in contact with the photosensitive drum 1K. A mechanism is also provided.

  The secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 between the secondary transfer roller 19 and forms a secondary transfer nip. The four-color toner image formed on the intermediate transfer belt 8 is transferred to the transfer paper P at the secondary transfer nip. Then, combined with the white color of the transfer paper P, a full color toner image is obtained. Untransferred toner that has not been transferred onto the transfer paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the belt cleaning device 10.

  In the secondary transfer nip, the transfer paper P is sandwiched between the intermediate transfer belt 8 and the secondary transfer roller 19 whose surfaces move in the forward direction, and is conveyed in the opposite direction to the registration roller pair 28 side. . When the transfer paper P sent out from the secondary transfer nip passes between the rollers of the fixing device 20, the full-color toner image on the surface is fixed under the influence of heat and pressure. Thereafter, the transfer paper P is discharged out of the apparatus through a pair of paper discharge rollers 29. A stack portion 50a is formed on the upper surface of the printer body. The transfer paper P discharged to the outside by the discharge roller pair 29 is sequentially stacked on the stack portion 50a.

  A bottle support portion 51 is disposed between the intermediate transfer unit 15 and the stack portion 50a located above the intermediate transfer unit 15. In the bottle support portion 51, toner bottles 52Y, 52M, 52C, and 52K are set as agent containers for storing the respective color toners. Each color toner in each of the toner bottles 52Y, 52M, 52C, 52K is appropriately supplied to the developing devices of the process cartridges 6Y, 6M, 6C, 6K by a toner supply device (not shown). The toner bottles 52Y, 52M, 52C, and 52K are detachable from the main body of the printer 100 independently of the process cartridges 6Y, 6M, 6C, and 6K.

Next, the configuration of the drum driving device that drives the photosensitive drum will be described.
FIG. 4 is a schematic diagram of the printer when the photosensitive drums 1Y, 1M, 1C, and 1K are viewed from the axial direction.
Drum driving gears 33Y, 33M, 33C, and 33K are provided at one end in the axial direction (end on the far side in the drawing) of each of the photosensitive drums 1Y, 1M, 1C, and 1K. The shaft of the drum driving gear is coupled to the shaft of the photosensitive drum by a joint portion, is fixed to the end of the photosensitive drum, and rotates with the photosensitive drum. The drum drive gears 33Y, 33M, 33C, and 33K are respectively meshed with drive transmission gears 32Y, 32M, 32C, and 32K that are rotationally driven by drive force from drive motors 31Y, 31M, 31C, and 31K as drive means. . As described above, since the printer includes the drive motors 31Y, 31M, 31C, and 31K for each of the photosensitive drums 1Y, 1M, 1C, and 1K, each of the photosensitive drums can be driven and controlled individually. Can do.

  The drive motors 31Y, 31M, 31C, and 31K have their rotational speed, rotation start timing, and stop timing controlled by the control unit 40 serving as a recognition unit and a drive control unit. The control unit 40 performs process control of the entire printer, and includes a CPU, a ROM, a RAM, and the like. Home position signals output from home position sensors 34Y, 34M, 34C, and 34K provided to detect the rotational positions of the photosensitive drums 1Y, 1M, 1C, and 1K are input to the controller 40. Based on the home position signal, the controller 40 controls the drive motors 31Y, 31M, 31C, and 31K, and controls the drive of the photosensitive drums 1Y, 1M, 1C, and 1K.

FIG. 5 is a perspective view showing the drum drive gear 33 in the present embodiment. In the following description, the yellow photosensitive drum 1Y is taken as an example, but the same applies to the other photosensitive drums 1M, 1C, and 1K. Also, the color code is omitted as appropriate.
In the illustrated drum driving gear 33, the photosensitive drum is positioned on the front side in the drawing. As shown in the drawing, on the circumference of the inner end face of the drum drive gear 33, a protruding portion (hereinafter referred to as a “home position mark”) 35 that partially protrudes in the photosensitive drum axial direction is fixedly disposed. The home position mark 35 moves on the orbit along with the rotation of the photosensitive drum 1Y by the driving force from the driving motor 31. In the present embodiment, the home position sensor 34 is configured by a general transmissive optical sensor, and a light emitting unit 34a and a light receiving unit 34b are arranged to face each other as illustrated. The home position sensor 34 is arranged so that the optical path (detection region) until the light emitted from the light emitting unit 34 a reaches the light receiving unit 34 b intersects the orbit of the home position mark 35. With such a configuration, when the home position mark 35 moves as the photosensitive drum 1Y rotates, and the home position mark 35 enters the detection area of the home position sensor 34 and blocks light, the home position sensor 34 is The home position mark 35 is detected.

The control unit 40 grasps the rotation position (rotation angle) of each photosensitive drum based on the home position signal from the home position sensor 34.
The ROM included in the control unit 40 stores in advance data for specifying the rotational position of the photosensitive drum 1Y when an H-level home position signal indicating the timing at which the home position mark 35 enters the detection area is received. ing. Therefore, when receiving the home position signal at the H level, the control unit 40 can recognize the rotational position of the photosensitive drum 1Y at the reception start timing (at the rising edge of the detection signal) based on the data in the ROM. . Since the average value of the rotational speed of the photosensitive drum 1Y is controlled to be constant, the control unit 40 can always grasp the rotational position of the photosensitive drum 1Y even after recognizing as described above. .

Next, image position deviation correction processing for minimizing the position deviation amount (image position deviation amount) of each color toner image transferred onto the intermediate transfer belt 8 will be described.
FIG. 6 is a flowchart showing a flow of drive control of each photosensitive drum performed by the control unit 40.
When a print instruction is input to the printer from a personal computer or the like (S1), the control unit 40 first controls the drive motors 31Y, 31M, 31C, and 31K, and the photosensitive drums 1Y, 1M, and 1C. , 1K rotational driving is started (S2). Accordingly, the control unit 40 also makes other preparations necessary for the image forming operation, such as starting driving of the intermediate transfer belt 8. When the time until the rotational speeds of the photosensitive drums 1Y, 1M, 1C, and 1K reach a steady state has elapsed (S3), the home position signals from the home position sensors 34Y, 34M, 34C, and 34K are received. Based on the home position signal, the rotational positions of the photosensitive drums 1Y, 1M, 1C, and 1K are recognized (S4).

  Next, the control unit 40 controls each of the drive motors 31Y, 31M, and 31C so that the amount of deviation between the color toner images transferred from the photosensitive drums onto the intermediate transfer belt 8 is minimized. The relative rotational position between the photosensitive drums is adjusted (S5). More specifically, the control unit 40 is provided with a RAM (not shown) as a storage means. As will be described later, the RAM 40 has a misalignment amount between the color toner images overlapping each other on the intermediate transfer belt 8. Relative rotational position data indicating rotational positions (relative rotational positions) of the other photosensitive drums 1Y, 1C, and 1M with respect to the black photosensitive drum 1K serving as a reference is stored so that (image position deviation amount) is minimized. The Then, the control unit 40 controls the drive motors 31Y, 31M, and 31C so that the relative relationship between the rotational positions of the photosensitive drums is a relative relationship specified by the relative rotational position data stored in the RAM. . In the present embodiment, the rotational positions of the other photosensitive drums 1Y, 1M, and 1C are adjusted with reference to the black photosensitive drum 1K. Specifically, for example, the rotational speeds of the photosensitive drums 1Y, 1M, and 1C other than black are adjusted by increasing or decreasing. In this case, when the rotational speeds of the photosensitive drums 1Y, 1M, and 1C other than black are changed and then returned to the same rotational speed as that of the black photosensitive drum 1K, the rotational position between the photosensitive drums. Are adjusted so that the relative relationship of the two becomes the relative relationship specified by the relative rotational position data.

  During this adjustment, the intermediate transfer belt 8 is separated from the photosensitive drums 1Y, 1M, and 1C by the contact / separation mechanism described above. Such separation is also effective in reducing the contact time between the photosensitive drums 1Y, 1M, and 1C and the intermediate transfer belt 8 and extending the life of these photosensitive drums. Therefore, for example, monochrome image formation in which image formation is performed using only the black photosensitive drum 1K may be performed in a state where the photosensitive drums 1Y, 1M, and 1C other than black are separated from the intermediate transfer belt 8. Good.

Next, a process (drum rotation position adjustment process) that adjusts the relative rotational position of the other photosensitive drums 1Y, 1M, and 1C with respect to the reference black photosensitive drum 1K, which is a characteristic part of the present invention, will be described.
Even printers manufactured through the same manufacturing process have individual differences. Therefore, the eccentricity of the photosensitive drum, the mounting eccentricity of the drum driving gear provided on the photosensitive drum, the gear molding accuracy, the speed fluctuation due to the joint portion that couples the driving gear and the image carrier, etc. are subtly different for each printer to be manufactured. Different. Accordingly, the relative rotational position between the photosensitive drums is such that the amount of positional deviation between the color toner images transferred from the photosensitive drums 1Y, 1M, 1C, and 1K onto the intermediate transfer belt 8 is minimized. Each printer must be specified individually.

FIG. 1 is a flowchart showing the flow of drum rotation position adjustment processing in the present embodiment. This flowchart illustrates the adjustment of the relative rotational position of the yellow photosensitive drum 1Y with respect to the black photosensitive drum 1K, but the same applies to the magenta and cyan photosensitive drums.
In the present embodiment, the control unit 40 first forms a test toner image (detection pattern) for detecting the amount of color misregistration on the surface of each of the photoreceptor drums 1Y, 1M, 1C, and 1K, and intermediately forms them. Transfer onto the transfer belt 8. Each test toner image on the intermediate transfer belt 8 thus transferred is read by the pattern sensor 36 as the mark detection means shown in FIG. 4 (S11). This test toner image was obtained by, for example, irradiating laser light L from the exposure device 7 at equal time intervals and developing an electrostatic latent image formed for one rotation of the photosensitive drum along the rotation direction of the photosensitive drum. It consists of a plurality of marks obtained by transferring the toner image onto the intermediate transfer belt 8. The same test toner image is formed on each photoconductor drum, and a black test toner image (reference detection pattern: hereinafter referred to as “reference test toner image”) and a test toner image of each other color. The two marks corresponding to each other are formed at the same position in the surface movement direction of the intermediate transfer belt 8 if the amplitude and phase of the rotational speed fluctuation are exactly matched between the photosensitive drums. Become. However, in practice, the amplitude and phase of the rotational speed fluctuations are not exactly the same between the photosensitive drums, so that two marks corresponding to each other according to the difference in the amplitude and phase of the rotational speed fluctuations. Are formed at positions shifted from each other in the surface moving direction of the intermediate transfer belt 8. Therefore, by grasping the positional deviation amount of each pair of marks corresponding to each other between the reference test toner image and the test toner image of each color, the positional deviation amount profile for one rotation of the photosensitive drum between them is grasped. be able to.

FIG. 7 is an explanatory diagram showing a reference test toner image and a yellow test toner image transferred onto the intermediate transfer belt 8.
In this embodiment, a reference test toner image composed of a black toner image is formed in the right end area of the intermediate transfer belt 8 in the drawing, and a yellow test toner image is formed in the left end area of the intermediate transfer belt 8 in the drawing. . Pattern sensors 36 are arranged opposite to each other on both end regions on the intermediate transfer belt 8, and each pattern sensor 36 detects each mark constituting the test toner image. Detection signals from the pattern sensors 36 are sent to the control unit 40. The control unit 40 stores mark position information indicating the absolute positions of the marks K1, K2,..., Kn constituting the reference test toner image based on the detection signal from the pattern sensor 36 that reads the reference test toner image. Is stored in the RAM (S12). This mark position information is used to grasp the amount of positional deviation between black and yellow. Further, the control unit 40, based on the detection signal from the pattern sensor 36 that reads the yellow test toner image, marks positions indicating the absolute positions of the marks Y1, Y2,..., Yn constituting the yellow test toner image. Information is stored in RAM.

On the other hand, after the reading of the yellow test toner image by the pattern sensor 36 is completed, the magenta test toner image is formed in the left end region in the drawing together with the reference test toner image in the same manner as the yellow test toner image. Therefore, in the present embodiment, the magenta test toner image is also read using the pattern sensor 36 used for the yellow test toner image. Then, the control unit 40 stores the mark position information of the reference test toner image in the RAM again based on the detection signal from the pattern sensor 36 that reads the reference test toner image. This mark position information is used for grasping the amount of positional deviation between black and magenta. Further, the control unit 40, based on the detection signal from the pattern sensor 36 that reads the magenta test toner image, marks positions indicating the absolute positions of the marks M1, M2,..., Mn constituting the magenta test toner image. Information is stored in the RAM (S12).
The same applies to the cyan test toner image.

In this embodiment, the case where the pattern sensor 36 used for reading the yellow, magenta, and cyan test toner images is shared has been described. However, each color test toner image is read by an individual pattern sensor. Also good. In that case, as shown in FIG. 8, test toner images of all colors can be formed on the intermediate transfer belt 8 at a time, and the reading processing time of each color test toner image can be shortened.
In this embodiment, the mark position information of the reference test toner image is individually used for each of yellow, magenta, and cyan, but common mark position information may be used. In this case, the amount of black toner consumed can be kept low, and the test toner image reading processing time can be shortened.

  After the mark position information of all the test toner images is stored in the RAM in this way, the control unit 40 then positions the reference marks K1, K2,. Position) and the absolute values | Y1-K1 |, | Y2-K2 |,... Of the difference values between the yellow marks Y1, Y2,. .., | Yn−Kn | are calculated, and these values are set as a reference difference value group (S13). Then, the sum of the values included in the reference difference value group is calculated, and this is stored in the RAM as a reference index value for the image position deviation amount (S14).

  Next, the control unit 40 determines the reference positions of the reference marks K1, K2,... Kn, and the adjustment target positions of the yellow marks Y2, Y3,. , | Yn + 1−Kn | are calculated as absolute value | Y2−K1 |, | Y3−K2 |,..., | Yn + 1−Kn | Then, the sum of each value included in the first virtual post-rotation difference value group is calculated, and this is stored in the RAM as the first index value of the image position shift amount. In the present embodiment, each mark constituting each test toner image is created for one rotation of each photosensitive drum 1Y, 1M, 1C, 1K. Therefore, the adjustment target position of “Yn + 1” is the adjustment target. The calculation target position of “Y1” can be used by performing a calculation of subtracting the photosensitive drum circumference length which is a fixed value from the target position. However, such a calculation is not required if the marks constituting each test toner image are created for two revolutions of each photosensitive drum 1Y, 1M, 1C, 1K.

Subsequently, the control unit 40 determines the reference positions of the reference marks K1, K2,... Kn, and the adjustment target positions of the yellow marks Y3, Y4,. Absolute values | Y3-K1 |, | Y4-K2 |,..., | Yn + 2-Kn | are calculated, and these values are used as a second post-virtual rotation difference value group. Then, the sum of each value included in the second virtual post-rotation difference value group is calculated and stored in the RAM as the second index value of the image position shift amount.
In this way, the absolute value of the difference value from each reference position is obtained while shifting the adjustment target positions of the yellow marks Y1, Y2,. A difference value group after virtual rotation is calculated (S15), and the first to (n-1) th index values are stored in the RAM (S16).

  Next, an index value having the smallest value is selected from the reference index values and (n−1) index values stored in the RAM (S17), and a difference value group corresponding to the index value is calculated. The relative rotational position at the time is determined (S18). That is, in the present embodiment, the image position deviation correction that the total sum of the values included in the difference value group is the minimum among the calculated reference index value and the (n−1) post-virtual difference value group. According to the condition, one difference value group is selected, and the relative rotation position when the difference value group is calculated is specified.

  Here, the rotation angle of the photosensitive drum corresponding to the deviation by one mark is 360 [°] / n. Accordingly, the relative rotation position when the difference value group after the x-th virtual rotation corresponding to the selected index value is calculated is 360 [°] × x / n. The index value of the differential value group after the x-th virtual rotation is the image position when the yellow photosensitive drum 1Y is virtually rotated relative to the black photosensitive drum 1K by a rotation angle corresponding to x marks. It corresponds to the index value of the deviation amount. Therefore, the relative rotation position specified in S18 is the relative rotation of the yellow photosensitive drum 1Y with respect to the black photosensitive drum 1K when the index value is minimized, that is, when the image position deviation amount is minimized. Position. Thereafter, the control unit 40 stores the data of the relative rotational position in the RAM as yellow relative rotational position data (S19).

The drum rotation position adjustment process as described above is sufficient if it is performed at the factory shipment stage of the printer. However, the amount of misalignment between the color toner images transferred onto the intermediate transfer belt 8 may change due to use over time. In this case, the proper relative rotational position data of the printer is different from that at the factory shipment stage, and there is a possibility that color shift occurs over time. Therefore, in the present embodiment, the drum rotation position adjustment process described above is performed every time the cumulative number of prints (cumulative image formation number) printed by the printer reaches a predetermined number.
Also, if the photoconductor drum is removed after maintenance work, etc. and then replaced or a new photoconductor drum is installed, and the photoconductor drum is replaced, the color misregistration is minimized. There is a possibility that the relative relationship between the rotational positions of the photosensitive drums will be broken. In this case, it is necessary to perform the above-described drum rotational position adjustment process as in the factory shipment stage and store appropriate relative rotational position data in the RAM again. Therefore, in the present embodiment, the drum rotation position adjustment process described above is performed before the image formation is started after the replacement of the photosensitive drum.

As described above, the printer according to the above embodiment includes the photosensitive drums 1Y, 1M, 1C, and 1K as the image bearing members arranged along the moving direction of the intermediate transfer belt 8 that is a transfer material, and these photosensitive members. Drive motors 31Y, 31M, 31C, 31K as drive means for driving the drums, charging devices, exposure devices, developing devices, etc. as image forming means for forming images on these photosensitive drums, and these photosensitive members Primary transfer bias rollers 9Y, 9M, 9C, and 9K are provided as transfer means for transferring the toner images (images) formed on the body drum to the intermediate transfer belt 8 so as to overlap each other. Further, the image forming means generates the same detection pattern (test toner image) composed of a plurality of marks formed at equal time intervals along at least one rotation of the photosensitive drum along the rotation direction of the photosensitive drum. A control unit 40 as control means for controlling the formation of the body drums 1Y, 1M, 1C, and 1K, and mark detection for detecting the marks after the marks on these photosensitive drums are transferred onto the intermediate transfer belt 8 A pattern sensor 36 as means and a RAM as storage means for storing mark position information corresponding to each mark for each test toner image based on the detection result of the pattern sensor 36. The control unit 40, based on the mark position information stored in the RAM, each reference position on the intermediate transfer belt 8 of each reference mark K1, K2,... .., Cn between the adjustment target marks Y1, Y2,..., Yn, M1, M2,..., Mn, C1, C2,. A reference difference value group consisting of a difference value from each position (adjustment target position) on the transfer belt 8 is calculated, and each adjustment that constitutes a test toner image of another color corresponding to each reference position and each reference mark. A difference value (| Y1−) between the adjustment target position on the intermediate transfer belt 8 of each adjustment target mark shifted from the target mark by an amount corresponding to a predetermined rotation angle in the photosensitive drums 1Y, 1M, and 1C of the other colors. 1 |, | Y2-K2 |, ..., | Yn-Kn |, | M1-K1 |, | M2-K2 |, ..., | Mn-Kn |, | C1-K1 |, | C2- .., | Cn−Kn |,) also functions as difference value calculation means for calculating a difference value group after virtual rotation by changing a predetermined rotation angle by one rotation of the photosensitive drum. In addition, the control unit 40 corrects the image position deviation that the sum of the difference values included in the difference value group is the minimum from the calculated reference difference value group and the first to n post-virtual rotation difference value groups. After selecting one difference value group according to the conditions, the photosensitive drums 1Y of the other colors corresponding to the predetermined rotation angle used when calculating the selected difference value group with respect to the rotation position of the reference photosensitive drum 1K. , 1M, and 1C are relatively rotated to correct image positional deviation on the intermediate transfer belt 8 between the reference photosensitive drum 1K and the photosensitive drums 1Y, 1M, and 1C of other colors. It also functions as processing execution means for executing necessary processing.
As described above, the printer only forms and detects a test toner image once for each color, and the photosensitive drums 1Y, 1M, and 1C of other colors are shifted by a predetermined rotation angle by one rotation. Therefore, it is possible to grasp all the image position deviation amounts with respect to the reference photosensitive drum 1K, and to specify the relative rotational positions of the respective photosensitive drums 1Y, 1M, and 1C with the smallest image position deviation amount, so that the image position deviation is corrected. By executing the processing necessary to achieve this, it is possible to correct the image position shift amount to be the smallest in a short processing time with a small amount of toner consumption, and the color shift can be effectively suppressed.

In the present embodiment, the control unit 40 calculates the selected difference value group based on the relative rotational positions of the photosensitive drums 1Y, 1M, and 1C whose rotation angles are to be adjusted with respect to the reference photosensitive drum 1K. Processing for controlling the drive motors 31Y, 31M, 31C, and 31K is performed so as to achieve the predetermined rotation angle used in the above. This eliminates the need for the operator to manually adjust the relative rotational positions of the photosensitive drums 1Y, 1M, and 1C, thereby reducing the operator's workload.
However, the smaller the minimum value of the predetermined rotation angle, the more accurate the image position deviation correction becomes possible. However, the relative rotation positions of the photoconductive drums 1Y, 1M, and 1C with respect to the reference photoconductive drum 1K are controlled by a drive motor. It cannot be controlled at an angle smaller than the minimum controllable rotation angle. Therefore, even if the minimum value of the predetermined rotation angle is made smaller than the minimum rotation angle that can be controlled using the drive motors 31Y, 31M, 31C, and 31K, the accuracy of the image position misalignment correction cannot be increased, which is useless. Become. Therefore, the minimum value of the predetermined rotation angle is not less than the minimum rotation angle that can be controlled using the drive motors 31Y, 31M, 31C, and 31K.
In the present embodiment, the drive motors 31Y, 31M, 31C, and 31K are controlled to adjust the relative rotational positions of the photosensitive drums 1Y, 1M, and 1C whose rotation angles are to be adjusted with respect to the reference photosensitive drum 1K. Although the case has been described, it is also possible to adjust manually by the worker. In this case, the control unit 40 performs processing for notifying the operator of the predetermined rotation angle used when calculating the selected difference value group. Thereby, the worker can grasp the rotation angle to be adjusted for each of the photosensitive drums 1Y, 1M, and 1C to be adjusted in rotation angle.
In this embodiment, the control unit 40 calculates the post-virtual rotation difference value group by sequentially changing the predetermined rotation angle by the photosensitive drum rotation angle corresponding to the interval between two adjacent marks. As a result, when exactly n marks are formed at equal time intervals per one rotation of the photosensitive drum, the photosensitive drums 1Y, 1M, and 1C subject to rotation angle adjustment are virtually each 360 [°] / n. It is possible to calculate a difference value group after each virtual rotation when the relative rotation is performed. At this time, if the number of marks formed on the entire circumference of the photosensitive drum is increased, the difference value group after each virtual rotation can be calculated by a correspondingly small rotation angle, so that the accuracy of image position deviation correction can be improved. it can.
Of course, the control unit 40 may calculate the difference value group after virtual rotation by sequentially changing the predetermined rotation angle by the photosensitive drum rotation angle corresponding to the interval between two marks not adjacent to each other.
In the present embodiment, the predetermined image position deviation correction condition is a condition that the sum of the absolute values of the difference values included in each difference value group is minimum. By setting it as such conditions, a color shift can be suppressed effectively.
Instead of this condition, a condition that the standard deviation of the difference values included in each difference value group is the minimum may be used. Even under this condition, color shift can be effectively suppressed.
In the present embodiment, the case where the drum rotation position adjustment process is always performed for the photosensitive drums 1Y, 1M, and 1C whose rotation angles are to be adjusted has been described. If it is small, the accuracy of the image position deviation correction does not increase much even if these photosensitive drums 1Y, 1M, 1C are adjusted to any relative rotational position. Therefore, based on the mark position information stored in the RAM, the difference between each adjustment target position and the corresponding ideal position (position when no rotational speed fluctuation occurs in the photosensitive drums 1Y, 1M, and 1C). The control unit 40 functions as a determination unit that determines whether or not the maximum value of the quantity is equal to or less than the predetermined value. When the control unit 40 determines that the maximum value is equal to or less than the predetermined value, the reference difference value group and the post-virtual rotation difference value The group calculation is not performed, that is, the drum rotation position adjustment process is not performed, and the drum rotation position adjustment process may be performed only when it is determined that the predetermined value is exceeded. In this case, as a result of omitting the drum rotation position adjustment process for the photosensitive drum determined to be equal to or less than the predetermined value, the entire processing time can be shortened.

In the above embodiment, the description has been given of the configuration in which the color toner images respectively formed on the plurality of photosensitive drums are once transferred onto the intermediate transfer belt 8 and then secondarily transferred onto the transfer paper to obtain a color image. The same applies to a configuration in which each color toner image respectively formed on a plurality of photosensitive drums is directly transferred onto a transfer sheet. In this case, the test toner image of each color may be transferred onto a recording material conveying member that carries the transfer paper on the surface and conveys it.
In the above embodiment, the case where the test toner images respectively formed on the plurality of photosensitive drums are once transferred onto the intermediate transfer belt 8 and then detected by the pattern sensor 36 has been described. A test toner image may be detected.
As the test toner image to be used, an image in which one rotation of the photosensitive drum is emphasized by coherent integration may be used. In this embodiment, since the difference value is repeatedly calculated for one rotation of the photosensitive drum while shifting the adjustment target mark, the result of the coherent integration is calculated so that at least the rotation fluctuation of the photosensitive drum is two cycles. To do.

6 is a flowchart illustrating a flow of drum rotation position adjustment processing in the printer according to the embodiment. FIG. 2 is a schematic configuration diagram illustrating the printer. FIG. 2 is a schematic configuration diagram illustrating a process cartridge for generating a Y toner image provided in the printer. FIG. 3 is a schematic diagram of the printer when the photosensitive drums provided in the printer are viewed from the axial direction. The perspective view which shows the drum drive gear of the photoconductor drum. 6 is a flowchart showing a flow of drive control of each photosensitive drum. FIG. 3 is an explanatory diagram showing a reference test toner image and a yellow test toner image transferred on an intermediate transfer belt provided in the printer. FIG. 10 is an explanatory diagram illustrating a modified example of a test toner image formation position.

Explanation of symbols

1Y, 1M, 1C, 1K Photosensitive drum 6Y, 6M, 6C, 6K Process cartridge 8 Intermediate transfer belt 9Y, 9M, 9C, 9K Primary transfer bias roller 31Y, 31M, 31C, 31K Drive motor 33Y, 33M, 33C, 33K drum drive gear 34Y, 34M, 34C, 34K Home position sensor 35 Home position mark 36 Pattern sensor 40 Control unit

Claims (7)

A plurality of image carriers disposed along the moving direction of the transfer material;
Drive means for driving the plurality of image carriers;
Image forming means for forming images on the plurality of image carriers,
In an image forming apparatus comprising transfer means for transferring the images formed on the plurality of image carriers to the transfer material so as to overlap each other,
Form the same detection pattern consisting of a plurality of marks formed at equal time intervals over at least one rotation of the image carrier along the rotation direction of the image carrier on each of the plurality of image carriers. Control means for performing control, and
A mark detecting means marked on said plurality of image bearing member detects the mark after being transferred to the transfer material on,
Storage means for storing mark position information corresponding to each mark for each detection pattern based on the detection result of the mark detection means;
Based on the mark position information stored in the storage means, each reference position on the transfer material of each reference mark constituting one reference detection pattern, and other detection patterns corresponding to each reference mark A reference difference value group consisting of a difference value between each mark constituting each mark and each position on the transfer material is calculated, and each other reference pattern and each other detection pattern corresponding to each reference mark are calculated. It consists of a difference value between the position of each mark and the position on the transfer material that is shifted by an amount corresponding to a predetermined rotation angle in the image carrier on which the other detection pattern is formed. Difference value calculation means for calculating a difference value group after virtual rotation by changing the predetermined rotation angle by one rotation of the image carrier;
After one difference value group is selected in accordance with a predetermined image position deviation correction condition from the reference difference value group calculated by the difference calculation means and one or more post-virtual difference value groups, the one reference detection Relative rotation of the image carrier whose rotation angle is to be adjusted with respect to the rotation position of the reference image carrier on which the pattern is formed, by the predetermined rotation angle used when calculating the selected difference value group. Accordingly, it possesses a process execution means for executing processing required to correct the image position shift on該被transfer material between the image bearing member and the rotary angle image bearing member to be adjusted in the reference,
The image forming apparatus according to claim 1, wherein the predetermined image position deviation correction condition is a condition that a sum of absolute values of difference values included in each difference value group is minimum . The image forming apparatus according to claim 1.
The processing executed by the processing execution means includes a predetermined rotation angle used when the relative rotation position of the image carrier to be adjusted with respect to the reference image carrier calculates the selected difference value group. As described above, an image forming apparatus is a process for controlling the driving unit. The image forming apparatus according to claim 2.
The minimum value of the predetermined rotation angle is equal to or greater than the minimum rotation angle that can be controlled using the driving unit. The image forming apparatus according to claim 1.
The process executed by the process execution unit is a process of notifying an operator of a predetermined rotation angle used when calculating the selected difference value group. The image forming apparatus according to any one of claims 1 to 4, wherein:
The difference value calculating means sequentially changes the predetermined rotation angle by the rotation angle of the image carrier that is the rotation angle adjustment target corresponding to the interval between two adjacent marks. An image forming apparatus characterized by calculating. The image forming apparatus according to any one of claims 1 to 4, wherein:
The difference value calculation means sequentially changes the predetermined rotation angle by the rotation angle of the image carrier to be adjusted for rotation angle corresponding to the interval between two marks not adjacent to each other after the virtual rotation difference value group. An image forming apparatus characterized by calculating. The image forming apparatus according to any one of claims 1 to 6 ,
Based on the mark position information stored in the storage means, it is determined whether or not the maximum deviation amount between the position of each mark constituting the other detection pattern and the ideal position of each mark is equal to or less than a predetermined value. Having a judgment means to judge,
The difference value calculating means does not calculate the reference difference value group and the virtual post-rotation difference value group when the determining means determines that it is equal to or less than a predetermined value, and determines that the determining means exceeds a predetermined value. An image forming apparatus characterized in that the reference difference value group and the virtual post-rotation difference value group are sometimes calculated.

Images