JPH1020604A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately and completely reduce the deviation of AC color registration caused by the respective AC vibration components of different kinds of rotating bodies by relatively adjusting the rotational phases of the rotating bodies driven so that the amplitude peaks of the respective vibration components may not be overlapped on each other in the case the frequency of the vibration component by cyclic rotational fluctuation individually caused is different from each other. SOLUTION: The phase of the rotational fluctuation of respective photoreceptor drums 6K, 6Y, 6M and 6C is estimated from the results of the address computation of a minimum value in the rotational fluctuation of each drum, the address computation of a maximum value in the rotational fluctuation of each color, the address computation of leading edge zero cross and the address computation of trailing edge zero cross. Based on phase data obtained the last, how much the phase ϕ of the drums 6Y, 6M and 6C is deviated from the drum for black 6K is computed by a CPU. The rotational phase is adjusted in the drums 6Y, 6M and 6C so that their phases may be aligned with the phase of the drum 6K.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex image forming apparatus having a plurality of image forming means, such as a tandem type color copying machine or a color printer, or different colors formed by at least one image forming means. In an image forming apparatus that forms a color image by transferring a plurality of images onto a transfer belt, paper on a transfer belt, or an intermediate transfer member, a color shift component of a plurality of images having different colors formed by each image forming unit. The present invention relates to a registration control system that detects and corrects an image, and in particular, an image forming apparatus capable of reducing color misregistration caused by a rotating body such as a photosensitive drum or a transfer belt of each image forming unit. It is about.

[0002]

2. Description of the Related Art In recent years, color processing of documents processed in offices and the like is rapidly progressing, and image forming apparatuses such as copiers, printers, and facsimile machines that handle these documents are also rapidly being colored. At present, these color devices tend to have higher image quality and higher speed with higher quality and faster office processing in offices and the like. As a color device that can meet such a demand, for example, each image forming unit is provided for each color of black (K), yellow (Y), magenta (M), and cyan (C), and is formed by each image forming unit. Various so-called tandem-type color image forming apparatuses for forming a color image by multiply transferring images of different colors onto a conveyed transfer material or an intermediate transfer body have been proposed and commercialized.

A tandem type color image forming apparatus of this type is, for example, as follows. As shown in FIG. 30, the tandem type color image forming apparatus includes a black image forming unit 200K for forming a black (K) image and a yellow image forming unit 200Y for forming a yellow (Y) image. And a magenta image forming unit 200M for forming a magenta (M) color image
And four image forming units of a Sian color image forming unit 200C for forming an image of the Sian (C) color.
00Y, 200M, and 200C are horizontally arranged at a fixed interval from each other. Further, below the four image forming units 200K, 200Y, 200M, and 200C of the black, yellow, magenta, and cyan colors, the image forming units 200K, 200Y, and 200M with the transfer paper 201 electrostatically attracted. , A transfer belt 202 as an endless transfer material carrier that conveys the transfer paper 201 over the transfer position of the transfer sheet 200C.

The above four image forming units 200K, 2K
00Y, 200M, and 200C have the same configuration, and these four image forming units 200K, 20K
0Y, 200M, and 200C are configured to sequentially form toner images of four colors, respectively, as described above. The image forming units 200K, 200Y,
Each of 200M and 200C includes a photosensitive drum 203. After the surface of the photosensitive drum 203 is uniformly charged by a scorotron 204 for primary charging, a laser beam 205 for image formation is used in accordance with image information. Scanning exposure to form an electrostatic latent image. The electrostatic latent image formed on the surface of the photosensitive drum 203 is developed by a developing unit 206 of each image forming unit with a toner of each color of black, yellow, magenta, and cyan to become a visible toner image. These visible toner images are subjected to pre-transfer charging by a pre-transfer charger 207 and then transferred to a transfer charger 208.
The toner image is sequentially transferred to the transfer sheet 201 held on the transfer belt 202 by the charging of the transfer belt 202. The transfer paper 201 on which the toner images of the respective colors are transferred is separated from the transfer belt 202 and then subjected to a fixing process by a fixing device (not shown) to form a color image. In the drawing, 209 denotes a photosensitive member cleaner, 210 denotes a photosensitive member removing lamp, 211 denotes a sheet peeling corotron, 212 denotes a transfer belt removing corotron, 213 denotes a transfer belt cleaner, and 214 denotes a pre-cleaning corotron.

The tandem-type color image forming apparatus configured as described above is a system in which one image is formed using a plurality of image forming units. Therefore, a color image can be formed at a considerably high speed. It is possible. However, if the speed of image formation is increased, the alignment of images formed by the image forming units of each color, that is, color registration (hereinafter referred to as “register”) frequently deteriorates, and high image quality is maintained. Therefore, it has been extremely difficult to achieve both high image quality and high speed.
This is because the position and size of each image forming unit itself and the position and size of each component in the image forming unit are delicate due to a change in the internal temperature of the color image forming device and an external force applied to the color image forming device. Due to the change. Of these, changes in the internal temperature and external forces are inevitable.For example, daily operations such as recovery of paper jams, replacement of parts due to maintenance, and movement of the color image forming apparatus require external forces to be applied to the color image forming apparatus. Will be added.

Therefore, as disclosed in, for example, Japanese Patent Application Laid-Open No. 1-281468, a plurality of image forming units for forming a visible image corresponding to original image information and also forming a visible image of a position detection mark. And a position detecting mark detecting means for detecting a position detecting mark formed on each of the image forming units and transferred onto the moving member, and a detection signal output from the position detecting mark detecting means An image forming apparatus configured to control each of the image forming units so as to correct a transfer image shift based on the image forming apparatus has been proposed.

When this transfer image shift correction technique is applied to a so-called tandem type color image forming apparatus shown in FIG. 30, as shown in FIG. 31, four image forming units 200K, 200Y, 200M, 200C are formed. At a plurality of color misregistration detection patterns 220 along the traveling direction of the transfer belt 202 and the direction orthogonal to the traveling direction.
K, 220Y, 220M, 220C and 221K, 22
1Y, 221M and 221C are formed at predetermined intervals over the entire circumference of the transfer belt 102, and these color shift detection patterns 220K, 220Y, 220M and 220C and 221K, 221Y, 221M and 221C are transmitted from the light emitting element 223. Using the transmitted light, a large number of light receiving pixels are sampled by a linear light receiving element 222 such as a CCD sensor or the like, which is linearly arranged, and the color shift detection patterns 220K, 220Y, 220M, 220C, and 221 of each color are sampled.
K, 221Y, 221M, and 221C are calculated, and the positions and image forming timings of the image forming units 200K, 200Y, 200M, and 200C are corrected so that the intervals become equal to a predetermined reference value. It is to achieve. The transfer belt 202
Patterns 220K and 22 for color shift detection formed above
0Y, 220M, 220C and 221K, 221Y, 2
21M and 221C are removed by the transfer belt cleaner 213 after sampling.

However, in the case of the color image forming apparatus, the color misregistration detection pattern is formed on the seam portion 202a of the transfer belt 202 as shown in FIG. 30, and is removed by the transfer belt cleaner 213 after sampling. If it is insufficient and remains on the transfer belt, there is a problem in that the remaining toner adheres to the back surface of the transfer paper 201 held and conveyed on the transfer belt 202 at the time of forming the next color image, and the back surface is stained. Was. Also, the transfer belt 2
Since the seam portion 202a of No. 02 has a minute step, the color shift detection patterns 220 and 221 formed on the seam portion 202a may have density unevenness or chipping. There is a problem that if the pattern for use has a variation in density or chipping, etc., a detection error occurs when these color misregistration detection patterns are detected by the line-type light receiving element 222.

Therefore, the present applicant sets the sample start point and the sample width of the sampling control means and sets it repeatedly to measure the registration deviation when controlling the image sampling correction by the control means relating to the registration of the multiple image forming apparatus. Improve the detection accuracy of registration misregistration measurement pattern by generating a pattern, integrating sampling data or arithmetic processing data to obtain the pattern position, and setting the sample start point and sample width of the sampling control means. The proposed sampling correction method has already been proposed (Japanese Patent Laid-Open No. Hei 6-253151).
No.).

That is, the sampling correction method is as follows.
When the temperature inside the color image forming apparatus changes or the external force is applied to the apparatus, the position and size of each image forming unit itself and the position and size of the components in the image forming unit change slightly. This is to detect and correct a color registration deviation (hereinafter, referred to as “DC color registration deviation”) having a constant magnitude and direction.

However, in addition to the DC component, the color registration misregistration (hereinafter, referred to as the color registration misregistration) whose size and direction periodically fluctuates mainly due to a rotating body such as a photosensitive drum or a belt drive roll. In this regard, the sampling correction method according to the above-described sampling correction method uses A for such color registration misregistration.
At present, the C component is not a target of correction, and it is impossible to detect even the color registration deviation of the AC component.

In fact, in the above-described conventional color image forming apparatus, the rotation fluctuation of a rotating body such as a photosensitive drum or a belt drive roll is detected by using an encoder attached to a rotating shaft such as the photosensitive drum, and this encoder is used. The rotation fluctuation of the photosensitive drum or the like detected by the above is fed forward or fed back to the drive motor to reduce the rotation fluctuation of the photosensitive drum or the like.

However, even if the control for reducing the rotation fluctuation of the photosensitive drum or the like is performed based on the detection information from the encoder, the eccentricity of the photosensitive drum itself or the mounting of the photosensitive drum, Since there is an eccentricity due to a clearance error of a rotating shaft of a photosensitive drum, a belt drive roll, or the like, there is a problem that image quality is degraded due to an AC color registration shift generated due to such eccentricity. That is, in the conventional color image forming apparatus, the AC vibration component as described above is not controlled at all.

In order to solve such a problem, the present applicant has been constructed so that at least one rotation phase of a rotating body such as a photosensitive drum or a belt drive roll can be individually adjusted, and the above-described configuration is adopted. There has already been proposed an image forming apparatus capable of suppressing image quality deterioration due to an AC color registration shift caused by a factor (Japanese Patent Application No. Hei 7-30).
1381 application).

That is, in this application, the conventional color image forming apparatus uses one rotation of the photosensitive drum of each image forming unit in a fixed section of the transfer belt (an arbitrary transfer area for one rotation of the photosensitive drum of each color). As shown in FIG. 20 (a), the relationship between the AC vibration components in the photoconductors varies among the photosensitive drums, and it has been clarified that this causes image quality deterioration due to AC color registration deviation. . For example, between two colors of K (black) and Y (yellow), a color shift component as shown in FIG. 20B is generated due to a phase shift between the photosensitive drums of the two colors. It is presumed.

In this application, based on the above findings, a color misregistration detection pattern is formed on the transfer belt, a periodic rotation phase is detected from the detection information of the pattern, and the photosensitive drum is rotated by the rotation phase adjusting means. By adjusting the rotation phase, the influence of the rotation fluctuation is suppressed from appearing on the image. For example, the rotational phase is adjusted by adjusting the rotational phases of the photoconductor drums of the other three colors with reference to the black (K) photoconductor drum.
As shown in FIG. 21A, the phases of the AC vibration components between the photoconductor drums shown in FIG. 21A are uniformly aligned in an arbitrary transfer area for one rotation of the photoconductor. State. As a result, as shown in FIG.
-AC between photosensitive drums between two colors such as between Y colors
Since the color shift component approaches zero, color shift between the two colors hardly occurs.

[0017]

However, in the case of the image forming apparatus according to the above-mentioned application, although the AC color shift component between the photosensitive drums is improved as described above,
It is not always clear how to deal with AC displacement components between different rotating bodies, for example, AC displacement components that may occur between the four photosensitive drums and the drive roll of the transfer belt. Absent.

For this reason, for example, when the respective AC vibration components of the photosensitive drum and the belt drive roll of the transfer belt have different frequencies as shown in FIG. The component has a partially large amplitude (peak) as shown in FIG. Similarly, when the respective AC vibration components of the photosensitive drum and the belt drive roll have different frequencies as shown in FIG. 33A, the AC displacement component between the two components is shown in FIG. As shown in (1), it also has a partially large amplitude. In other words, between rotating bodies having a different frequency of each AC vibration component, such as between the photosensitive drum and the belt drive roll, the peaks of the amplitudes of the AC vibration components overlap with each other to further amplify. There is a case where an AC position shift component having the obtained amplitude peak occurs.

When there is such a large AC position shift component between different rotating members, A
Similar to the case where there is a C misregistration component, a misregistration phenomenon that is visually recognized as a color misregistration that can be sufficiently perceived by human eyes appears on an actual print as exemplified below, and image quality deteriorates. linked. That is, in a character image formed on a colored background (non-white paper) with a colored background, white spots occur around the outline of the character. Further, at the joint between the colored image portion and the colored image portion, the joint may appear as a streak of a different color or may be blank. Further, in the color ground area, a so-called banding phenomenon occurs, which is a density unevenness that appears periodically like a band.

Incidentally, Japanese Patent Publication No. 8-10372 discloses that
To prevent transfer misregistration (color misregistration) caused by rotational drive unevenness due to eccentricity of each photosensitive drum and gears in a plurality of image forming units, transfer of adjacent image forming units (actually, photosensitive drums) is performed. The distance (pitch) along the transfer belt between the positions is set to an integral multiple of the circumference of the photosensitive drum,
In addition, there has been proposed an image forming apparatus which detects marks provided at the same position on the phase of each photosensitive drum and changes the rotation speed thereof. However, even in this technique, countermeasures are taken for each photosensitive drum, but no particular countermeasures are taken for different types of rotating bodies such as each photosensitive drum and a transfer belt (belt drive roll). Therefore, it has not been possible to eliminate the AC displacement component that may occur between the photosensitive drums and the drive roll of the transfer belt as described above.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to provide various types of photosensitive drums, transfer belts, intermediate transfer belts and the like which are driven by rotation. Eccentricity caused by the rotator itself or its attachment, and periodic rotation fluctuation (AC vibration component) caused by eccentricity caused by a clearance error of the drive shaft of the rotator, and in particular, suppresses an AC color registration deviation. An object of the present invention is to provide an image forming apparatus capable of appropriately and sufficiently reducing an AC color registration deviation generated between different kinds of rotating bodies due to respective AC vibration components.

[0022]

As shown in FIG. 1, an image forming apparatus according to a first aspect of the present invention comprises at least one image forming unit having image-forming members 01K, 01Y, 01M, and 01C that are driven to rotate. Means 02K, 02Y, 02M, 02
C, images having different colors are formed, and the images having different colors formed by the image forming means 02K, 02Y, 02M, and 02C are transferred onto an endless carrier 03 which is driven to rotate, or a transfer material 04 or An image forming apparatus for forming an image by directly transferring an image onto an endless carrier, wherein an image is formed on a rotating body (25) for driving the image carriers 01K, 01Y, 01M, 01C and the endless carrier 03. When the frequencies of the vibration components due to the periodic rotation fluctuations occurring in the image carriers differ from each other, the image carriers 01K and 01K are controlled so that the amplitude peaks of the respective vibration components do not overlap each other.
The rotation phases of the rotating body (25) for driving the Y, 01M, 01C and the endless carrier 03 are relatively adjusted. The endless carrier is a transfer (paper conveyance) belt (drum), an intermediate transfer body belt (drum), or the like.

With this configuration, for example,
Assuming that there are rotating bodies that drive four image carriers and one endless carrier, the amplitude peaks of the periodic vibration components in each of the rotating bodies are avoided from overlapping, and as a result, the amplitude peaks of the respective amplitude peaks are avoided. An AC color shift component having a large amplitude peak generated by the overlap can be reduced. However, in this case, it is a prerequisite that the rotational phase between the same type of rotating bodies, that is, between the four image carriers, is uniformly set to suppress the AC color shift component. The phase adjustment between the same kind of rotating bodies is performed by, for example, the above-mentioned prior application (Japanese Patent Application No. 7-30138) of the present applicant.
1) can be performed using the technology described in the specification and the like according to No. 1).

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the rotation cycle of the image carrier and the rotation cycle of the rotator driving the endless carrier are different from each other. Are set to be odd or (1 / odd) times, or even or (1 / even) times.

By setting the rotation periods (diameters of the rotation members) of the different kinds of rotation members so as to have the above-described ratio relationship, the rotation period has a ratio relationship consisting of a numerical value other than a natural number. In principle, it is possible to minimize the case where the amplitude peaks of the periodic vibration components in each rotating body overlap with each other as much as possible. In other words, when the rotation cycle has a ratio relationship other than a natural number, an effect of avoiding the overlapping of the amplitude peaks of the periodic vibration components in each rotating body in the first round of alignment is expected to some extent. However, the phases of the amplitude peaks gradually begin to shift from the second round onward, and it is difficult to perform control to avoid overlapping of the amplitude peaks. In this regard, when the ratio is set as in the present invention, there is no such fear.

According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the first or second aspect, wherein one of the vibration component of the image carrier and the rotating body for driving the endless carrier is provided. So that the rotation phase of the rotating body that drives the image carrier and the endless carrier is relatively adjusted so that the plus amplitude peak of the image carrier has the same phase as the minus amplitude peak of the other vibration component. It is configured.

With such a configuration, generally, the amplitude peaks of the periodic vibration components in each rotating body are prevented from overlapping, and the AC color shift having the amplitude peak amplified by overlapping the amplitude peaks of the vibration components. Components can be reduced. This is obtained when the rotational phases have an odd multiple relationship. In order to make the amplitude peak relationships as described above when the rotational phases have an odd multiple relationship, for example, the phase may be adjusted so that the rotational periods of different types of rotating bodies are shifted from each other by a half period.

According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the first or third aspect, wherein one of the vibration component of the image carrier and the rotating body driving the endless carrier is provided. The rotational phase of the rotator that drives the image carrier and the endless carrier is relatively adjusted so that the plus side amplitude peak of has the same phase as the zero cross point with the average value of the other vibration component. It is configured as follows.

With this configuration, generally, the amplitude peaks of the periodic vibration components in each rotating body are prevented from overlapping, and the AC color shift having the amplitude peak amplified by overlapping the amplitude peaks of the vibration components is generally avoided. Components can be reduced. This is obtained when the rotation phases have an even multiple relationship. In order to make the amplitude peak relationships as described above when the rotational phases have an even multiple relationship, for example, the phase may be adjusted so that the rotational periods of different types of rotating bodies are shifted from each other by １ ／ period.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an overall configuration diagram showing a digital color copying machine as an embodiment of the image forming apparatus according to the present invention.

In FIG. 2, an original 2 placed on a platen glass 1 is converted into RGB analog image signals by an image scanner having a color CCD sensor 3 via a scanning optical system including a light source and a scanning mirror. Read. The RGB analog image signals read by the color CCD sensor 3 are converted into KYMC image signals by the image processing unit 4 and temporarily stored in a memory provided inside the image processing unit 4.

As shown in FIGS. 2 and 3, the image processing unit 4 outputs image forming units 5 for each color of black (K), yellow (Y), magenta (M), and cyan (C).
K, 5Y, 5M, 5C ROS (Raster Out)
put Scanner) 8K, 8Y, 8M, and 8C sequentially output image data of each color, and the ROS 8K,
Laser beams LB emitted from 8Y, 8M, and 8C in accordance with image data are supplied to respective photosensitive drums 6K, 6K.
Scanning exposure is performed on the surfaces of Y, 6M, and 6C to form an electrostatic latent image. The electrostatic latent images formed on the photosensitive drums 6K, 6Y, 6M, and 6C are used as developing units 9K, 9Y, 9M, and 9C.
Thus, the toner images are developed as black (K), yellow (Y), magenta (M), and cyan (C) toner images, respectively.

Each of the photosensitive drums 6K, 6Y, 6M, 6
Transfer paper 1 for transferring toner images of each color formed on C
Reference numeral 4 denotes a plurality of paper feed cassettes 15 and 1 as shown in FIG.
The paper feed roller 18 and the paper transport roller pair 19, 20, 2,
1 is conveyed through a sheet conveyance path 22 composed of the first and second sheets. The supplied transfer paper 14 is sent out onto a transfer belt 24 as an endless carrier by a registration roll 23 which is rotated and driven at a predetermined timing, and is supplied to a charger 41 for holding the paper.
In addition, the toner image is held and conveyed on the transfer belt 24 by the charging roller 42. The transfer belt 24 includes a drive roll 25
, Stripping roll 26 and tension roll 2
7 and the idle roll 28 are wound around endlessly with a constant tension, and are driven in a predetermined direction in the direction of the arrow by a drive roll 25 that is rotationally driven by a dedicated drive motor having excellent constant speed (not shown). It is designed to be driven in circulation at a speed. As the transfer belt 24, for example, an endless belt is formed by forming a flexible synthetic resin film such as PET into a belt shape and connecting both ends of the synthetic resin film formed in a belt shape by means such as welding. What was formed in the shape is used.

The leading end of the transfer paper 14 conveyed by the transfer belt 24 and the leading end of the image on the first photosensitive drum 6K formed by the first image forming unit 5K are
The paper feed timing and the image writing timing are determined so that they coincide at the lowest transfer point of the photosensitive drum 6K. Transfer paper 1 that has reached the transfer point
Reference numeral 4 denotes the transfer of the visible image on the photosensitive drum 6K by the corotron 11K for transfer, and furthermore, the photosensitive drum 6Y
Reaches the transcription point just below This photosensitive drum 6Y
The transfer paper 14 that has reached the transfer point immediately below is transferred with the visible image on the photosensitive drum 6Y in the same manner as the transfer on the photosensitive drum 6K. Similarly, the transfer paper 14 after all the transfer is further conveyed by the transfer belt 24,
When reaching the vicinity of the stripping roll 26, the charge is removed by the stripping charge removing corotron 29 and the stripping roll 2 having a small radius of curvature is set.
6 and the peeling claw 30, the film is peeled from the transfer belt 24. Thereafter, the transfer paper 1 on which the four color toner images are transferred
4 is fixed by a heating roller 32a and a pressure roller 32b by a fixing device 31, and is discharged onto a discharge tray 34 shown in FIG. 2 by a discharge roller pair 33 to copy a color image.

When copying a full-color image on both sides of the transfer paper 14, as shown in FIG. 3, the transfer paper 14 on which a color image is formed on one side is not directly discharged by the discharge roll pair 33, The transfer direction of the transfer sheet 14 is switched downward by the switching plate 35, and the transfer sheet 14 is turned upside down via a sheet transfer path 40 including a pair of sheet transfer rolls 36, 37, 38, and 39. The transfer belt 24 passes through the paper transport path 22 again.
The sheet is conveyed upward, and a color image is formed on the back surface of the transfer sheet 14 by the same process as described above.

The photosensitive drums 6K, 6Y, 6
After the toner image transfer step is completed, the M and 6C are neutralized by the pre-cleaning neutralizers 12K, 12Y, 12M, and 12C, and are cleaned by the cleaners 13K, 13Y, 13M, and 1M.
3C removes residual toner and the like, and prepares for the next image forming process.

The transfer belt 24 is used to transfer the transfer paper 1
After the exfoliation of the transfer belt 4, the charge is removed by the transfer belt removing corotron pairs 43 and 44 in the orbit around the transfer belt, and the surface of the transfer belt 24 is
The toner and paper dust are removed by a cleaning device 47 including the blade 5 and the blade 46.

In the digital color copying machine constructed as described above, as a device for rotatingly driving the photosensitive drums 6K, 6Y, 6M, 6C, for example, the following device is used. The photosensitive drums 6K, 6Y, 6
A device for rotating and driving the M and 6C is provided for each photosensitive drum in the same manner, but the photosensitive drum 6K will be described here. As shown in FIG. 4, the driving device for the photosensitive drum includes a sub-frame 51 mounted on a first frame 50 located on the front side of the copying machine main body, and a second frame disposed in parallel with the first frame 50. 52, the photosensitive drum 6K is rotatably supported, and the rotating shaft 5 of the photosensitive drum 6K is
Drive shaft 56 connected to coupling 4 via coupling 55
Is rotatably supported between the second frame 52 and the third frame 57. The photosensitive drum 6K is driven by a driving motor 58 such as a stepping motor.
A motor shaft gear 60 provided on a rotating shaft 59 of the drive motor 58; a first intermediate gear 61 meshing with the motor shaft gear 60; and a second intermediate gear 61 fixed to the same shaft as the first intermediate gear 61. The intermediate gear 62 and the second intermediate gear 6
2 is driven to rotate by a photoreceptor drive gear 63 fixed to a drive shaft 56 of the photoreceptor drum 6K meshing therewith. The drive shaft 56 of the photosensitive drum 6K
Is provided with an encoder 64, which detects the rotation state of the photosensitive drum 6K, and outputs a detection signal via a control circuit 65 to the drive motor 58.
Of the photosensitive drum 6
The rotation speed of K is controlled to be constant. In addition,
In the figure, reference numeral 67 denotes a flywheel attached to the rotating shaft 59 of the photosensitive drum 6K.

The drive roller 25 for rotating the transfer belt 24 is also driven to rotate by a drive device similar to the drive device for the photosensitive drum 6.

In the digital color copying machine constructed as described above, for example, the photosensitive drums 6K, 6Y, 6M, 6C
, The cycle of the drive roll 25 of the transfer belt 24, the eccentric components of the respective photosensitive drums and drive rolls and the eccentric components of the mounting portions (flanges and the like), the gear 60 for driving them, 61, 62, 63
5, a relatively high-frequency rotation fluctuation, which fluctuates in a short cycle, such as a so-called walk or the like in which the transfer belt 24 moves in a direction orthogonal to the moving direction, occurs. Black, yellow, magenta,
It appears as rotation fluctuation of each color of Sian color. In addition, irregularities in the thickness of the transfer belt 24 and the like appear as rotation fluctuations of the transfer belt.

FIG. 6 is a schematic diagram showing the image forming section of the digital color copying machine together with the control section.

In FIG. 6, reference numeral 70 denotes a pattern detecting means for detecting a color shift on the transfer belt 24 formed by the image forming units 5K, 5Y, 5M and 5C. The pattern detecting means 70 includes a light source 73 and a light receiving element 74 which are arranged in pairs at both ends in the width direction of the image area of the transfer belt 24. The light source 73 is connected to the transfer belt 24.
It is composed of LEDs for producing background light necessary to detect the pattern image 71 for detecting color shift. The light receiving element 74 is disposed so as to face the light source 73 via the transfer belt 24, and is formed of a CCD as a line type light receiving element in which a large number of light receiving pixels are linearly arranged. . FIG. 7 shows the light receiving element 74.
And pattern image 71 for image position detection on transfer belt 24
Are three-dimensionally shown. In the drawing, reference numeral 82 denotes a sensor substrate on which the CCD of the light receiving element 74 and peripheral circuits for driving the CCD are mounted, and 84 denotes a gradient index lens array.

As described above, by disposing the color misregistration detecting pattern detecting means 70 at each of both ends in the width direction in the image area of the transfer belt 24, the shift in the main scanning direction of the copy and the sub It is possible to adjust in all directions of color shift such as a shift in the scanning direction, a magnification error in the main scanning direction, and an angle shift with respect to the main scanning direction.

In FIG. 6, 75K, 75Y, 7
5M and 75C are the image forming units 5K, 5Y, 5
An interface board for sending image signals to ROS 8K, 8Y, 8M, 8C in M, 5C, and a correction board 76 for controlling a color misregistration correction system. Reference numeral 77 denotes a memory and an image processing board which collectively handles image processing relations. Reference numeral 78 denotes a control board for managing all of these boards and the operation of the entire digital color copying machine.

The DC color shift detecting pattern 71 is, for example, as shown in FIG. 8, along the sub-scanning direction for detecting a shift in the main scanning direction which is a direction orthogonal to the traveling direction of the transfer belt 24. Color shift detection pattern 71b
(K), 71b (Y), 71b (M), 71b (C)
And color misregistration detection patterns 71a (K), 71a (Y), 71a (M), 7 along the main scanning direction for detecting misregistration in the sub-scanning direction which is the traveling direction of the transfer belt 24.
1a (C). Then, as shown in FIG. 6, a predetermined position 71 a is set on the transfer belt 24 so as to be read by the color misregistration detecting pattern detecting means 70 which is disposed one by one on the front side and the back side of the image forming unit. (K), 71a (Y), 71a (M), 7
1a (C), 71b (K), 71b (Y), 71b
(M) and 71b (C) are multiplex-transferred one set at a time over the entire circumference. Further, the color misregistration detection patterns 71a (K), 71a (Y), 71 in the main scanning direction and the sub-scanning direction.
a (M), 71a (C) and 71b (K), 71b
(Y), 71b (M), and 71b (C) are formed by forming a band pattern as a linear portion of each color of black (K), yellow (Y), magenta (M), and cyan (C) at predetermined intervals. They are arranged sequentially.

FIG. 9 is a block diagram showing an embodiment of the control unit of the sampling apparatus for the pattern for detecting color misregistration according to this embodiment. This control unit includes a correction substrate 76 shown in FIG.
It is provided within.

In the correction substrate 76, the driver 91 drives the CCD sensor in accordance with the clock generated by the CCD drive clock generation circuit 90, and sequentially reads the read image data of, for example, 8 bits and 256 gradations in pixel units to the receiver 92. take in. Then, the image data relating to the main scanning is stored in the main scanning high-speed image memory 94 through the bus control system 93, and the image data relating to the sub-scanning is averaged by the sub-scanning image calculation circuit 95, and then the bus control system The image data is stored in the sub-scanning high-speed image memory 96 through the line 93. The sample timing control circuit 97 captures image data into the sub-scanning image operation circuit 96, the main scanning high-speed image memory 94, and the sub-scanning high-speed image memory 99 according to the sample start timing, the sampling period, and the like set by the CPU 98. Is controlled. The main RAM 100 is used as a work area of the CPU 98, and the ROM 101 stores a control program of the CPU 98. Serial communication IC10
2. The serial communication driver 103 includes various control systems 104
The CPU 98 transmits control data such as setting parameters to the I / O interface 105.
Is for outputting an on / off signal to various correction systems 104, inputting an on / off signal from a sensor, and transmitting and receiving an on / off signal to and from the system controller 106. The serial communication driver 107 includes the CPU 98 and the system controller 1
06 is transmitted and received.

The CPU 98 controls the CCD drive clock generation circuit 90, the sample timing control circuit 97, and the bus control system 93 to take in the image data of the registration deviation measurement pattern 71 output on the transfer belt 24 and to set the image position address. The registration error amount is determined and the serial communication IC 1
02, the various correction systems 104 are controlled through the serial communication driver 103 or the I / O interface 105 and the serial communication 107.

The CPU 98 also controls the control circuit 65, Drive-K, Drive-Y, Drive-M, and D shown in FIGS.
The drive data is transmitted to drive control means such as drive-C, Belt Drive, etc., and each drive control means drives the rotation speed of the drive motor 58 for the photosensitive drum and the drive motor 80 for the belt drive roll based on the correction data. Etc. are controlled.

In this embodiment, a color misregistration detection pattern dedicated to AC component detection for detecting a periodic rotation fluctuation generated in the digital color copying machine is different from a DC color registration misregistration detection pattern. Are provided separately.

That is, in this embodiment, FIG.
As shown in FIG. 3, K, which is formed linearly in the main scanning direction on the transfer belt in order to detect rotation fluctuation in the sub-scanning direction,
Y, M, C four color patterns 110a (K), 110a
(Y), 110a (M), and 110a (C) are formed in parallel with each other at a constant fine pitch along the sub-scanning direction, and detect rotation fluctuations in the main scanning direction.
K, Y, M, C linearly formed in the sub-scanning direction
4b patterns 110b (K), 110b (Y), 1
10b (M) and 110b (C) are configured to form one set along one straight line in the sub-scanning direction. These AC color shift detection patterns 110a (K), 110
a (Y), 110a (M), 110a (C) and 110
b (K), 110b (Y), 110b (M), 110b
(C) is formed continuously along the moving direction of the transfer belt 24 (for example, all around the transfer belt 24) and is sampled. In addition, as shown in FIG.
In order to detect rotation fluctuations in the main scanning direction, patterns 110b (K), 110b (Y), 110b (M) of four colors of K, Y, M and C linearly formed in the sub-scanning direction.
110b (C) may be formed long in parallel with each other along the sub-scanning direction.

Also, of the color shift detection patterns dedicated to AC component detection, patterns 110a (K), 110a (Y), and 110a for detecting rotation fluctuation in the sub-scanning direction.
10A, the interval P in the moving direction of the transfer belt 24 corresponds to the frequency of the periodic rotation fluctuation generated in the digital color copying machine, as shown in FIG. Is set. At that time, the frequency of the periodic rotation fluctuation generated in the digital color copier is:
As described above, the photosensitive drums 6K, 6Y, 6M, 6C
, One cycle of the drive roll 25 of the transfer belt 24, vibration components and eccentric components of gears driving them, and walks of the transfer belt 24, and various other frequency components. Therefore, detecting all of these frequencies at once requires a very high sampling frequency. However, in practice, it is impossible to form a pattern corresponding to a very high sampling frequency due to the relationship between the pattern width and the calculation time.

Therefore, in this embodiment, a plurality of AC component detection dedicated patterns are provided, and a frequency to be detected is assigned to each AC component detection dedicated pattern. This makes it possible to obtain a high AC color registration deviation detection accuracy while suppressing the sampling frequency. However, the present invention is not limited to this. Only one AC component detection dedicated pattern is formed corresponding to a relatively high sampling frequency, and a plurality of ACs determined using this one AC component detection dedicated pattern are formed. Of course, it may be configured to detect the component.

When the AC component is detected, it becomes more difficult to obtain the number of repetitive samples at a lower frequency due to the time required for the detection. Therefore, there is a problem how to improve the accuracy of low frequency sampling. Now, it is assumed that the plurality of AC vibration frequencies of the digital color copying machine system are A, B, and C (A>B> C). When detecting the low frequency C, the sampling frequency is deliberately set to the high frequency A or B itself or its divisor, and when there is no problem in the sampling of C, as shown in FIG. It is set to sample together. For example, A = 30 Hz, B = 20 Hz, C
When = 3 Hz, the sample frequency is set to 10 Hz. On the other hand, if there is a problem, the sampling frequency is set to a frequency which is more susceptible to accuracy or a divisor thereof. For example, A = 30 Hz, B = 5 Hz, C = 3 Hz
In the case of, set the sampling frequency to 10 or 15 or 30
Set to Hz. In this case, the vibration component B and the vibration component C
If the amplitude of either is not small, it is difficult to separate B and C. For example, the amplitude of the vibration component B
When the amplitude is smaller than the amplitude, the vibration component B can be ignored, and only the vibration component C can be detected.

By setting the sampling frequency in this manner, as shown in FIG. 12, the vibration components of the frequencies A and B can be made dead zones, so that the detection and analysis of only the vibration component C can be easily performed. And the sample accuracy can be improved.

Based on the above theoretical considerations, in this embodiment, the frequency for sampling the color misregistration detection pattern dedicated to AC component detection is determined by changing the frequency of a plurality of periodic rotational fluctuations generated in the digital color copying machine. Of these, the setting is made in accordance with the high-frequency rotation fluctuation.

Now, the rotational frequency of the photosensitive drum 6 is set to 0.
Assuming that the rotation frequency of the drive roller 25 of the transfer belt 24 is 5 Hz, the sampling frequency of the color misregistration detection pattern 110 dedicated to AC component detection is 5 Hz, which is equal to the rotation frequency of the drive roller 25 of the transfer belt 24 having a high frequency. Is set to As a result, the process speed of the digital color copying machine was increased to 160 mm / sec.
Assuming that c, patterns 110a (K), 110a (Y), 110a for detecting rotation fluctuation in the sub-scanning direction among the color shift detection patterns 110 dedicated to AC component detection.
10 (M) and 110a (C), as shown in FIG. 10, the interval P of the same color pattern in the transfer belt moving direction 24 is, for example, 160 (mm / sec) ｓｅ5 (Hz) =
The distance p is set to 32 (mm), and the interval p between adjacent patterns having different colors is set to 8 mm. However, it is not limited to this, and the sampling frequency is set to 5 Hz.
When the frequency is half of 2.5 Hz, the interval P between patterns of the same color may be set to about 64 mm.

The color misregistration detection pattern 110 dedicated to the AC component detection is detected by the pattern detection means 70 as shown in FIG. 5K,
5Y, 5M, 5C photoconductor drums 6K, 6Y, 6M, 6
The phase relationship and the amplitude of the vibration component representing the AC rotation fluctuation depending on C, the belt drive roll 25 of the transfer belt 24, and the like are detected by the color misregistration correction substrate 76 also serving as the phase and amplitude detecting means. Further, the rotation phases of the photosensitive drums 6K, 6Y, 6M, 6C, the belt drive roll 25, and the like are appropriately adjusted based on information such as the phase and the amplitude detected by the phase and amplitude detection means. .

In the above configuration, in the color image forming apparatus according to this embodiment, the effects of eccentricity due to the photosensitive drum or the transfer belt itself or its attachment, eccentricity due to the clearance error of the rotating shaft, etc. will be described as follows. And the AC displacement caused by each AC vibration component between different kinds of rotating bodies such as between the photosensitive drum and the transfer belt (belt drive roll) can be reduced. I have.

That is, in the digital color copying machine, the position and size of each image forming unit itself, and further, each of the image forming units 5K, 5Y, and 5M is generated by a change in the internal temperature of the machine and an external force applied to the digital color copying machine. , 5C
The position and size of parts inside may change slightly.
Of these, changes in the internal temperature and external forces are unavoidable. For example, daily work such as recovery from paper jams, replacement of parts by maintenance (maintenance inspection work), and movement of digital color copier External force is applied to the copying machine. When a change in the internal temperature or an external force acts on the digital color copying machine, the alignment of the images formed by the image forming units 5K, 5Y, 5M, and 5C for the respective colors is deteriorated, and a DC-like color registration shift occurs. This causes difficulty in maintaining high image quality.

In the above digital color copying machine, for example, the cycle of one rotation of the photosensitive drum 6, the cycle of one rotation of the drive roll 25 of the transfer belt 24, the walk of the transfer belt 24, or the like is long. There is also an AC-like color registration deviation which fluctuates at a relatively low frequency and an AC-like color registration deviation having a relatively high frequency such as a vibration component and an eccentric component of a gear for driving the photoconductor and the drive roll.

In order to meet the demand for higher image quality in the digital color copying machine, it is necessary to suppress the color registration deviation to a high precision, for example, about 70 μm or less. To this end, by improving the manufacturing accuracy of the image forming unit and the transfer belt itself and the accuracy of the driving device, etc., the absolute amount of the color registration deviation of the DC component and the AC component is reduced, and the photosensitive drum, the transfer belt, and the like are reduced. The rotation fluctuation of the drive system of the
In some cases, it is necessary to perform active control so as to cancel the effect of the color registration deviation of the components.

Therefore, in the above digital color copying machine,
When the power of the apparatus is turned on, after a paper jam recovery operation, or at other predetermined timing, before the start of the normal image forming mode (print mode) or during the normal image forming mode (print mode), as necessary. The sampling operation of the DC color shift detection pattern and the correction mode based thereon are performed, and the sampling operation of the AC color shift detection pattern and the predetermined operation based thereon are performed. At this time, the sampling operation of the AC color shift detection pattern and the predetermined operation based thereon may be executed every time the DC color shift detection pattern sampling operation and the correction mode based thereon are performed. , Only once in the color misregistration correction cycle immediately after turning on the device,
The sampling operation of the AC color misregistration detection pattern and a predetermined operation based thereon are set.

First, in this embodiment, immediately after the power of the apparatus is turned on, it is determined whether or not to execute a color misregistration correction cycle as shown in FIG. 13 (step S10). In step S11, a color misregistration detection coarse adjustment pattern sample for performing coarse adjustment of DC color misregistration is performed. The pitch of the color misregistration detection coarse adjustment pattern is set to be larger than the pitch of the detection pattern 72 shown in FIG. In this color misregistration detection pattern sample, sample data of the pattern is taken in, and the sampling data is calculated to determine the image position. When the image positions for all the sampling data are obtained, the correction values of the various DC registers are calculated (step S12), and the correction values of the various DC registers are set (step S13).
When the correction value setting of the cash register is completed, the correction value is transmitted to the system board by communication (step S14).

Subsequently, in order to detect the presence or absence of an AC color registration deviation caused by the photosensitive drum, the transfer belt 24 is used.
After performing a pattern sample of the color shift detection pattern 110 dedicated to AC component detection formed thereon (step S1)
5), perform an AC register calculation for each color drum (step S1)
6).

The AC component detection / correction cycle is performed after the DC color registration correction cycle immediately after the power of the apparatus is turned on. This means that the AC component detection and correction cycle is D
If performed before the C color registration correction cycle, DC
Since there is a variation in the color registration, if the sample period of the AC color misregistration detection pattern is shortened, there is a possibility that patterns of other colors before and after overlap, and if the sample area is not increased when sampling, This is because a pattern may not enter the sample area and an efficient sample cannot be formed, so that the pattern interval cannot be reduced. On the other hand, if the correction is performed after the DC color registration correction cycle, the dispersion of the DC color registration becomes small, so that the pattern interval can be reduced. It is more preferable that the AC component detection / correction cycle is performed between the coarse adjustment and the fine adjustment in the DC color registration correction cycle. This is because the influence of the AC component is reduced and the detection accuracy of the DC component is higher when the detection of the DC component is performed with a small amount of the AC component than when the detection is performed with a large amount of the AC component remaining. This is because accurate DC color registration correction can be performed.

Here, the sampling operation of the AC color misregistration detection pattern and the control operation based thereon will be described in detail.

First, in the sampling operation of the AC color misregistration detection pattern and the control mode based thereon, as shown in FIG. 6, a command is issued to each section by the control board 78, and each of the interface boards 75K, 75Y, 7
The image forming units 5M and 75C correspond to the image data of the AC color shift detection pattern 110 for the photosensitive drum by the built-in color shift detection pattern output means.
K, 5Y, 5M, and 5C are sequentially output. At this time,
Each interface board 75K, 75Y, 75M, 75
The timing when C starts outputting image data is exactly the same as the timing in the normal image forming mode (print mode). Thereby, each image forming unit 5K, 5K
Y, 5M, and 5C form a predetermined color misregistration detection pattern 110 based on the image data, and sequentially perform multiple transfer to the transfer belt 24 at the same timing as in a normal image forming mode (print mode), and A color misregistration detection pattern 110 for the body drum is formed on the transfer belt 24.

The AC shown in step 16 in FIG.
In the subroutine for calculating the color misregistration detection pattern 110 dedicated to component detection, as shown in FIG. 14, the variable N is first set to 0, and then 1 is added to N (step S30,
31) Then, as shown in FIG. 15, the data of the Nth block (the first block) is cut out from the beginning as shown in FIG. 15, with one round of each color drum of the sample pattern as one block (step S32). Next, as shown in FIG. 16, the address calculation of the minimum value (Min) in the rotation fluctuation of the photosensitive drums 6K, 6Y, 6M, 6C of each color, the address calculation of the maximum value (Max) in the rotation fluctuation of each color, and each color The rising zero cross address and the falling zero cross address of each color are calculated (step S33). Then, the rotational phase of each photoconductor drum is estimated from the results of the four addresses for each color (step S34), and the average of the phase estimation results of the four addresses for each color is calculated (step S3).
5). Thereafter, it is determined whether or not the variable N becomes the predetermined value N, and whether the extraction of the data of the N blocks and the estimation of the phase and the like are completed (step S36), and the extraction of the data of the N blocks and the estimation of the phase are completed. The above operation is repeated (steps S36 to S35). Then, finally, the average of the phase estimation results of the N addresses of each color is calculated (step S37), and the algorithm of the AC registration calculation subroutine for the photosensitive drum ends.

At this time, the photosensitive drums 6K, 6Y, 6
As the phases of the AC components of M and 6C, for example, a value of N (for example, 3 to 7) is set so as to detect the pattern 110 substantially corresponding to one rotation of the transfer belt 24 for each color. By doing so, it is possible to consider at least rotation fluctuations caused by one rotation of the transfer belt 24.

When the calculation of the AC registration phase of each color drum is completed, it is determined in step S17 shown in FIG. 13 whether there is a phase shift of the AC color registration of the photosensitive drums 6K, 6Y, 6M, and 6C of each color. As shown in FIG. 17, when there is an AC deviation between the photosensitive drums of the respective colors with respect to the same transfer point on the transfer belt 24, the CP
U98 is the phase shift amount φ of the AC vibration component of the other photosensitive drums 6Y, 6M, 6C with respect to the black photosensitive drum 6K.
(Step S18), the correction value is transmitted by communication to the drive control board 66 (FIG. 4) of each of the Y, M, and C photoconductor drums 6Y, 6M, and 6C (step S19).

The above calculation of the phase shift amount is performed by first calculating the main R
Pattern 1 for detecting color misregistration of each color stored in AM100
On the basis of the sampling data at intervals of ten, one round of each color drum of the sample pattern is defined as one block in FIG.
As shown in FIG. 5, the first block of data is cut out from the beginning. Then, the address calculation of the minimum value (Min) in the rotation fluctuation of each of the cut out photosensitive drums, the calculation of the address of the maximum value (Max) in the rotation fluctuation of each color, the calculation of the rising zero cross address of each color, and the calculation of the falling zero cross address of each color. I do. Here, the minimum value (Min) address calculation, the maximum value (Max) address calculation, the color rise zero cross address calculation,
And the zero crossing address calculation for each color fall
In accordance with the sampling frequency, discrete interval data of the color misregistration detection pattern 110 of each color as shown in FIG. 15 is sampled, and as shown in FIG. 18, an average value is calculated based on the following equation. Average value = Σ (f (X) / n) Here, Σ is taken from X = X _−n to X = X _n .

Each photosensitive drum 6 calculated in this way is
K, 6Y, 6M, the minimum value (Mi) in the rotation fluctuation of 6C
n), the rotation fluctuation of each photosensitive drum 6K, 6Y, 6M, 6C from the result of the address calculation of the maximum value (Max) in the rotation fluctuation of each color, the calculation of the rising zero cross address, and the calculation of the falling zero cross address. Guess the phase of At this time, the accuracy of the phase detection can be improved by averaging the address values obtained from the four elements shown in FIG. 16, and by averaging the obtained phases for N blocks, Can be further improved in the detection accuracy. Since the values of the rising zero-cross address calculation and the falling zero-cross address calculation can be obtained by interpolating or extrapolating the zero-cross point, the detection accuracy is better than the maximum value or the minimum value.

Finally, based on the obtained phase data, the CPU 98 calculates how much the phase φ of the other photosensitive drums 6Y, 6M, 6C is shifted from the black photosensitive drum 6K.

Then, the Y, M, and C photosensitive drums 6Y, 6 to which the calculation result regarding the above-described phase shift is transmitted.
In M and 6C, the rotation phase is adjusted so that the phase matches the phase of the black photosensitive drum 6K. The adjustment of the rotation phase at this time is performed, for example, by idling the photosensitive drum 6 by a necessary amount.
The phase adjustment by idle rotation is preferably performed while the color copying machine is on standby. At the time of the phase adjustment, at least the transfer baffles 48K, 48Y, 48M, 48 for bringing the respective photosensitive drums 6 for adjusting the phase into contact with the transfer belt 24.
By lowering C (in FIG. 3), the transfer belt 2
It is possible to prevent the photoconductor drums 6 from being worn or damaged by slipping in a state where the photoconductor drums 4 and the respective photoconductor drums 6 are in contact with each other.

At this time, each of the photosensitive drums 6Y, 6Y
The phase adjustment of M and 6C may be performed by using the encoders 64 attached to the drive shafts of the photosensitive drums 6, respectively. That is, each drive control means (Drive) of the photosensitive drum 6 is set to the rotational phase of the encoder 64 by M
(M: natural number)
As shown in FIG. 9, the absolute phase specified by communication from the CPU 98, that is, the sensor 64 of the encoder 64
A pulse Z is output once per rotation of the encoder 64 at a reference phase determined by the mounting position of a.
The phase 64b (the reference point for one rotation) is adjusted, or the rotation of the photosensitive drum 6 is adjusted by the increase or decrease of the designated phase, so that the phase is adjusted. Now, as shown in FIG. 17, the rotational phase φ of the yellow photosensitive drum 6Y is
Is delayed (or advanced) by 周期 cycle with respect to the black photosensitive drum 6K, the CPU 98 transmits the calculation result to the drive control board 65 of the photosensitive drum 6Y,
The rotation phase of the photosensitive drum 6Y is controlled so as to advance by １ ／ cycle. This control can be performed by, for example, stopping the photoconductor drum 6Y by rotating the photoconductor drum 6Y more by 180 degrees and stopping the photoconductor drum 6Y by 180 degrees to advance the phase by 180 degrees.

Further, the phase adjustment at this time may be performed by changing the photosensitive drum 6 by a necessary time for a necessary time. At this time, it is desirable to control the amount of slip between the transfer belt 24 and the photosensitive drum 6 by making the speed of the photosensitive drum slightly slower or faster.

The control for performing these phase adjustments includes the waiting time of the paper feeder immediately after the registration control cycle, the pressing of the start key, the density detection cycle, and the like.
The correction time can be reduced by executing the timing at a timing when the image is not formed.

By performing the above-described phase adjustment, FIG.
Each of the photosensitive drums 6K, 6Y, 6M, and 6C having the AC vibration component relationship as shown in FIG. 17 is in a state in which all the rotational phases match as shown in FIG.

Subsequently, in step S20 of FIG. 13, the A of each photosensitive drum and the transfer belt drive roll
In order to check the presence or absence of the C registration phase shift, a detection pattern for a belt drive roll is formed and sampling is performed. As the detection pattern at this time, a pattern set to a sample frequency sufficiently higher than the frequency of the drive roll of the transfer belt is used. After the execution of the pattern sample, an operation relating to the AC registration phase between the photosensitive drum and the transfer belt drive roll is performed (step S2).
1).

In the subroutine for calculating the AC registration of the photosensitive drum and the belt drive roll, as shown in FIG. 22, a variable N is first set to 0, and 1 is added to N (steps S40 and S41). As shown in FIG. 23A, an Nth block (the first block is the first block) from the beginning with a sample frequency sufficiently higher than the frequency of the drive roll of the transfer belt with one round of each color drum of the sample pattern as one block. Cut out the data (step S4
2). Next, the AC vibration component (FIG. 23B) of the photosensitive drum after the above-described phase adjustment is subtracted from the cut-out data relating to the AC vibration component, whereby the data shown in FIG.
As shown in (c), only the AC vibration component of the drive roll is extracted (step S43). Next, the phase of the drive roll is estimated from the extracted result of the AC vibration component of the drive roll in the same manner as the method of calculating the phase of the photosensitive drum (see FIG. 14) (step S44). Thereafter, it is determined whether or not the variable N has reached the predetermined value N, and the extraction of the data of the N blocks and the estimation of the phase have been completed (step S45). The operation is repeated (steps S41 to S44). Finally, an average of the results of the phase estimation for N times is obtained (step S46), and the algorithm of the subroutine of the AC register calculation of the drum versus the drive roll ends.

When the calculation of the AC registration phase between the drum and the drive roll is completed, in step S22 shown in FIG. 13, the A values of the photosensitive drums 6K, 6Y, 6M, and 6C of the respective colors are changed.
It is determined whether or not there is a phase shift of the C color register. If there is a phase shift of the AC color register, the four photosensitive drums (FIG. 21) whose phases are aligned and the AC vibration component of the belt drive roll are determined. Phase and amplitude (especially peak value)
(Step S23).

In this embodiment, the relationship between the rotation period (actually, the diameter) of the photosensitive drum and the belt drive roll is odd or (1 / odd) times such as 3: 1 or 1: 3. The ratio is set so as to be a ratio relationship or a ratio relationship of an even number or (1 / even number) such as 2: 1 or 1: 2. As a result, A caused by the photosensitive drum
The relationship between the frequency of the C vibration component and the frequency of the AC vibration component caused by the belt drive roll is also approximately one of the above ratio relationships. FIG.
Is an eccentric rotator A having a ratio relationship of odd number times or the like.
It shows the AC vibration components of the rotating body B (for example, a belt drive roll) and the rotating body B (for example, a photosensitive drum), and has three times, five times, and seven times the rotating period when the rotating body B is used as a reference. Each of the rotators A is illustrated. FIG. 25 shows AC vibration components of a rotating body A (for example, a photosensitive drum) and a rotating body B (for example, a belt drive roll) due to eccentricity in a ratio relationship such as an even number multiple. In reference to the reference, the rotator A having four times and six times the rotation period is illustrated.

In step S23, there are two cases, namely, a case where the frequency of each AC vibration component of the photosensitive drum and the belt drive roll has an odd multiple ratio and a case where the frequencies have even ratios. Roughly, an optimum phase relationship and amplitude relationship between the two are calculated.

That is, the frequency of each AC vibration component of the photosensitive drum and the belt drive roll is an odd multiple or (1/1).
In the case of a ratio relationship of (odd number) times, as shown in FIG. 24, the plus amplitude peak (+ P) of one of the AC vibration components becomes the minus amplitude peak (−P) of the other AC vibration component. ), The rotation phases of the corresponding photoconductor drum 6 and the belt drive roll 25 are relatively adjusted. In FIG. 24, A of the rotating body A and the rotating body B
The case where the frequencies of the C vibration component are in a relationship of 1: 3 and 1: 7 indicates a state in which the phase relationship between the plus side amplitude peak and the minus side amplitude peak is as described above. In addition, when the average value obtained from the maximum value and the minimum value of the amplitude of the AC vibration component is assumed to be zero, the plus side amplitude is an amplitude region that appears above the average value. In other words, the negative amplitude refers to an amplitude region that appears below the average value.

On the other hand, when the frequencies of the respective AC vibration components of the photosensitive drum and the belt drive roll are in an even number ratio or a (1 / even number) ratio, as shown in FIG. The rotation phase of the corresponding photoconductor drum 6 and belt drive roll 25 so that the plus amplitude peak (+ P) of the AC vibration component has the same phase as the point (Q) at which the average value of the other vibration components crosses zero. Is adjusted relatively. In FIG. 25, AC of the rotating body A and the rotating body B
Both of the frequencies of the vibration components having a relationship of 1: 4 and 1: 6 indicate a state in which the phase relationship between the plus-side amplitude peak and the zero-cross point is as described above.

When the calculation of the phase and amplitude relationship of the AC vibration components of the photosensitive drum and the belt drive roll is completed, the K, Y, M, and C photosensitive drums 6K, 6Y, 6
The correction value is transmitted by communication to the drive control board (Drive) of the M and 6C and the BELT / Drive of the drive roller 25 of the transfer belt (step S24). Based on the content of the correction value, the rotation phase of the photosensitive drum or the belt drive roll to be controlled is appropriately adjusted. The phase adjustment at this time can be performed in the same manner as the adjustment method described above. The phase adjustment target (photosensitive drum or belt drive roll) may be configured so as to preferentially select and set, for example, one with a smaller phase adjustment amount or one with which adjustment can be performed more easily.

For example, as shown in FIG.
If there is a photoconductor drum and a belt drive roll having a frequency of vibration components of 3: 1, and the photoconductor drum and the belt drive roll have the same rotational phase relationship, as shown in FIG. An AC position shift component having a large amplitude peak (PP), which is amplified by overlapping the two amplitude peaks, occurs. Therefore, in this embodiment, as shown in FIG.
The plus amplitude peak (+ P) of the C vibration component is the minus amplitude peak (−) of the AC vibration component of the belt drive roll.
For example, phase adjustment is performed such that the belt drive roll 25 side is shifted by a half cycle so as to be in phase with P).

By performing such a phase adjustment, an AC displacement component between the photosensitive member and the belt drive roll can be obtained as shown in FIG. In other words, this phase adjustment eliminates the occurrence of a large amplitude peak (PP) that causes the amplitude peaks of the AC vibration components to overlap each other and amplifies, and the maximum value of the amplitude is reduced as a whole of the displacement component compared to before the correction. Is done. As a result, it is possible to suppress (reduce) AC color registration deviation caused by eccentricity due to the photosensitive drum or the transfer belt drive roll itself or its attachment, eccentricity due to a clearance error of the rotating shaft, and the like.

As shown in FIG. 33 (a), when there is a photosensitive drum and a belt drive roll in which the frequency of the AC vibration component is in a relation of 2: 1, the photosensitive drum and the belt drive roll are left as they are. If there is a rotational phase relationship, as in the above case, an AC position shift component having a large amplitude peak (PP) that is amplified by overlapping the amplitude peaks of the two as shown in FIG. . Therefore, in this embodiment, as shown in FIG. 27A, the plus amplitude peak (+ P) of the AC vibration component of the photosensitive drum is the minus amplitude peak (-P) of the AC vibration component of the belt drive roll. Phase adjustment is performed so that, for example, the belt drive roll 25 side is shifted by a half cycle so as to have the same phase.

By performing such a phase adjustment, an AC displacement component between the photosensitive member and the belt drive roll is obtained as shown in FIG. In other words, this phase adjustment eliminates the occurrence of a large amplitude peak (PP) that causes the amplitude peaks of the AC vibration components to overlap each other and amplifies, and the maximum value of the amplitude is reduced as a whole of the displacement component compared to before the correction. Is done. As a result, it is also possible to suppress (reduce) AC color registration deviation caused by eccentricity due to the photosensitive drum or the transfer belt drive roll itself or its attachment, eccentricity due to a clearance error of the rotating shaft, and the like.

After the control relating to the rotation phase of the photosensitive drum and the belt drive roll is performed, or if there is no phase shift of the AC register in steps S27 and S22, a DC color shift correction cycle is executed ( Steps S25 to S28). That is, a color shift detection coarse adjustment pattern sample for performing fine adjustment of the DC color shift is performed (step S25). The color misregistration detection fine adjustment pattern
The pattern is set as shown in FIG. In this color misregistration detection pattern sample, sample data of the pattern is taken in, and the sampling data is calculated to determine the image position. When the image positions for all the sampling data are obtained, the correction values of various DC registers are calculated (step S26), and the correction values of various DC registers are set (step S27). When the setting is completed, this is transmitted to the system board by communication (step S28).

By executing such a series of correction cycles, different types of rotation, such as between the photosensitive drum and the transfer belt drive roll, including the AC color shift caused by the AC vibration component between the photosensitive drums. AC in the body
The AC displacement caused by the vibration component is appropriately reduced.

In this embodiment, the control (correction) for reducing the AC displacement between the photosensitive drum and the belt drive roll is executed in the AC color registration correction cycle performed after the DC color registration correction cycle. Although the case of performing the operation is exemplified, the present invention may be executed independently, for example, after recovery from a paper jam or when attaching / detaching or replacing components during maintenance.

That is, after the paper jam has been recovered, or when parts have been attached or detached or replaced during maintenance, for example, if the transfer belt unit is pulled out and inspection is performed, FIG.
The state in which the respective phases of the photosensitive drum and the belt drive roll are set in an appropriate relationship as shown in FIG. 7A is changed to the phase relationship (phase) of the belt drive roll with respect to the photosensitive drum as shown in FIG. The reference point R) collapses.
Therefore, when the phase relationship between the photosensitive drum and the belt drive roll is broken due to the influence of such special work, an AC color shift between the photosensitive drum and the belt drive roll is performed as a dedicated color shift correction cycle. It is effective to perform control (correction) for reduction alone. On this occasion,
The phase adjustment may be performed based on the information on the optimal phase relationship between the photosensitive drum and the belt drive roll stored in the normal state. For example, it is possible to make a correction to judge from the Z phase of the encoder attached to the rotation shaft of the belt drive roll and to restore the phase by the amount of the shift. If the phase adjustment is performed in this way, it can be corrected instantaneously.

In this embodiment, the phase of each photosensitive drum or transfer belt is detected from an AC vibration component corresponding to N rotations of each photosensitive drum or transfer belt. In such a case, the time required to detect the phase is increased by the amount of rotating the photosensitive belt or the transfer belt N times. Therefore, for this phase detection, each phase may be detected from pattern data of one rotation of each photosensitive drum or transfer belt. At this time, if the phase of each photosensitive drum or the like is detected from the pattern data for one round of each photosensitive drum or the like, the detection error of the phase may increase. For this reason, one photoconductor drum etc.
As shown in FIG. 29, the average value of the rotation fluctuation data is taken from the pattern data for the circumference, and the maximum address value of each color, the minimum address value of each color, the rising zero cross address value of each color, From each of the zero-cross address values at the falling edge of each color, the phase of each photoconductor drum and transfer belt is obtained, and the phase values obtained from the four address values of each color are averaged. The rotational movement of the drum or the like is determined. Thereby, the phase can be determined with higher accuracy.

[0098]

As described above, according to the first aspect of the present invention,
In the image forming apparatus described above, in particular, the image carrier and the endless carrier caused by eccentricity caused by the image carrier or the endless carrier itself or its attachment, eccentricity caused by a clearance error of the drive shaft of the rotating body, and the like. When the amplitude peaks of the AC vibration components overlap each other, the occurrence of a large amplitude peak that is amplified can be reduced. As a result, it is possible to appropriately and sufficiently reduce the AC displacement caused by the respective AC vibration components of the image carrier and the endless carrier.

Therefore, when a color image is formed by the image forming apparatus of the present invention having the above-described effects, a color image excellent in image quality without color misregistration or positional misalignment can be obtained. In particular, the effect is remarkably obtained in the case of the following images. For example, in a character image formed on a colored background with a colored background, white spots do not occur around the outline of the character. Also,
At the seam between the colored image portion and the colored image portion, the seam does not look like a streak of a different color or becomes white. Further, a so-called banding phenomenon does not occur in the color ground area.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an image forming apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of a digital color copying apparatus according to the present invention.

FIG. 3 is a configuration diagram showing a main part of the digital color copying apparatus of FIG. 2;

FIG. 4 is a configuration diagram illustrating a driving device of a photosensitive drum.

FIG. 5 is a graph showing rotation fluctuations of the photosensitive drum of each color.

FIG. 6 is a perspective view illustrating a main part of a control unit related to a photosensitive drum.

FIG. 7 is a perspective view of a main part showing an installation state of a pattern detection unit.

FIG. 8 is a plan view showing a pattern for DC registration deviation measurement.

FIG. 9 is a block diagram illustrating a control circuit.

FIG. 10 is a plan view showing a representative example of a pattern for AC registration deviation measurement.

FIG. 11 is a table showing a representative example of the relationship between the frequency of rotation fluctuation and the sampling frequency.

FIG. 12 is a graph showing a sampling example of rotation fluctuation.

FIG. 13 is a flowchart illustrating a color misregistration correction operation.

FIG. 14 is a flowchart illustrating a color misregistration correction operation.

FIG. 15 is a graph showing the rotation fluctuation of the photosensitive drum of each color.

FIG. 16 is an explanatory diagram illustrating a method of detecting a rotation phase of a photosensitive drum, a belt drive roll, and the like.

FIG. 17 shows the AC of the photosensitive drum of each color before correction.
It is explanatory drawing which shows a mode of a vibration component.

FIG. 18 is a graph showing how to determine the maximum value and the minimum value of the color misregistration detection pattern.

FIG. 19 is an explanatory diagram showing a reference position of an encoder.

20A is an explanatory diagram showing an AC vibration component of the photosensitive drum of each color before correction, and FIG. 20B is an explanatory diagram showing an AC color shift component between the KY colors at that time. is there.

21A is an explanatory diagram showing another state of the AC vibration component of the photosensitive drum of each color after correction, and FIG. 21B is an explanatory diagram showing the state of the AC color shift component between the KY colors at that time. FIG.

FIG. 22 is a flowchart illustrating a color misregistration correction operation.

FIG. 23 is an explanatory diagram showing a sampling procedure of an AC vibration component.

FIG. 24 is a conceptual diagram showing a typical example of an AC vibration component between rotating bodies having a frequency of an odd multiple of the frequency of the AC vibration component.

FIG. 25 is a conceptual diagram showing a representative example of an AC vibration component between rotating bodies having a frequency of an AC vibration component that is an even multiple.

26A and 26B show a correction state between the photosensitive drum and the belt drive roll in which the frequency of the AC vibration component is an odd multiple ratio (3: 1). FIG. 26A shows the corrected AC vibration component. FIG. 7B is an explanatory diagram showing a state, and FIG. 8B is an explanatory diagram showing a state of an AC color shift component between the two after correction.

27A and 27B show a correction state between the photosensitive drum and the belt drive roll in which the frequency of the AC vibration component is in a ratio relationship (2: 1) that is an even number multiple, and FIG. FIG. 7B is an explanatory diagram showing a state, and FIG. 8B is an explanatory diagram showing a state of an AC color shift component between the two after correction.

28A is an explanatory diagram showing an optimal rotation phase state between the photosensitive drum and the belt drive roll in a normal state, and FIG. 28B is a broken rotational phase between the photosensitive drum and the belt drive roll in an abnormal state; It is explanatory drawing which shows a state.

FIG. 29 is a graph showing how to determine the maximum value and the minimum value of the color misregistration detection pattern.

FIG. 30 is a configuration diagram showing a digital color copying machine to which a conventional color misregistration detection pattern sampling device is applied.

FIG. 31 is a plan view showing a conventional color misregistration detection pattern.

FIG. 32 (a) shows the AC of the photosensitive drum and the belt drive roll whose frequency of the AC vibration component is an odd multiple.
Explanatory drawing showing an example of a vibration component, FIG.
FIG. 9 is an explanatory diagram illustrating a state of a C color shift component.

FIG. 33 (a) shows the AC of the photosensitive drum and the belt drive roll in which the frequency of the AC vibration component is a multiple of an even number.
Explanatory drawing showing an example of a vibration component, FIG.
FIG. 9 is an explanatory diagram illustrating a state of a C color shift component.

[Explanation of symbols]

01: image carrier, 02: image forming means, 03: endless carrier, 04: transfer material, 06: color shift detection / correction means (phase amplitude detection means).

Claims (5)

[Claims] 1. An image forming apparatus according to claim 1, wherein at least one image forming unit having a rotatable image carrier forms images of different colors, and the images of different colors formed by the image forming unit are rotatably driven. An image forming apparatus for forming an image by directly transferring onto a transfer material carried on a body or the endless carrier, wherein the image carrier and the rotator driving the endless carrier are individually provided. When the frequencies of the vibration components due to the generated periodic rotation fluctuations are different from each other, the rotational phases of the rotating members that drive the image carrier and the endless carrier are relatively adjusted so that the amplitude peaks of the respective vibration components do not overlap each other. An image forming apparatus comprising: an image forming apparatus; 2. The method according to claim 1, wherein the ratio of the rotation period of the image carrier to the rotation period of the rotating member for driving the endless carrier is an odd multiple or (1/1).
2. The image forming apparatus according to claim 1, wherein the relationship is set to be (odd) times. 3. The ratio of the rotation period of the image carrier to the rotation period of the rotator driving the endless carrier is an even multiple or (1/1).
2. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to have a relationship of (even number) times. 4. A method in which the plus amplitude peak of one of the vibration components of the image carrier and the rotating body driving the endless carrier is in phase with the minus amplitude peak of the other vibration component. The image forming apparatus according to claim 1, wherein a rotation phase of a rotating body that drives the image carrier and the endless carrier is relatively adjusted. 5. The plus amplitude peak of one of the vibration components of the image carrier and the rotating body that drives the endless carrier is in phase with the zero-cross point of the average value of the other vibration component. 2. The method according to claim 1, further comprising: adjusting a rotation phase of a rotator that drives the image carrier and the endless carrier.
Or the image forming apparatus according to 3.