JP2001051478A - Multiple color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a missalignment without lowering operability/produciblity for a user. SOLUTION: The correction mark is formed by color image forming unit 4C, 4Y, 4M and 4Bk forming and transferred on transfer belt 10. A rough adjustment correction is performed at the initial power on time at the device delivery time in reducing detection data by making the sampling time (width) longer by extending sampling interval correction marks, at the time of performing alignment correction of the respective image forming unit by detecting this by detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-color image forming method for forming a multi-color image on a transfer medium while detecting a correction image position, creating positional deviation correction data, and performing correction control using the positional deviation correction data. The present invention relates to a color image forming apparatus.

[0002]

2. Description of the Related Art A multicolor image forming apparatus having a plurality of latent image carriers and obtaining a multicolor image by superimposing images formed on the respective latent image carriers is well known. In such a multi-color image forming apparatus, each color image forming unit composed of a latent image carrier, a developing device, and the like is usually independent.
If the positional relationship between the respective color image forming units is shifted, an abnormal image in which the superimposed images are shifted is generated. At the time of shipment from the factory, images are output and image misalignment (positional misalignment of the image forming unit) is inspected. This may cause a positional shift when the user arrives at the destination. In addition, even in use in an office or the like, a position shift may occur due to movement or some other cause.

[0003] Conventionally, as a function of correcting the positional deviation, a correction mark is formed by a pattern generator in each image forming unit, and the position of the correction mark is read to obtain an image formed by each image forming unit. It has been proposed that the writing position, the skew of the main scanning line, and the like are changed to make corrections, and alignment (correction of image shift) is performed.

As a conventional image shift correcting technique, an image forming sequence and a positioning operation are executed at timings independent of each other (Japanese Patent No. 2633877), and each registration mark image read by reading means is sequentially stored. Having storage means (Japanese Patent No. 2609643)
Or a pattern generator that repeatedly generates a coarse resist misalignment pattern and a fine resist misalignment pattern, and selects a pattern according to a coarse adjustment mode and a fine adjustment mode (Japanese Patent Application Laid-Open No. 6-253151). Forming a plurality of registration marks having phases different from each other within the main misalignment period within a period n times the main misalignment period of the image (Japanese Patent Laid-Open No. 8-305110)
And a device for forming a misregistration correction pattern at intervals of an image forming process on a recording medium.
There is a method in which a rough correction is performed in a second interval, and the remaining positional deviation amount is corrected a plurality of times in a second and subsequent intervals.

[0005] The general alignment correction includes a coarse adjustment pattern correction for roughly correcting a positional deviation, and a fine adjustment pattern correction for performing further dot-by-dot correction after adjusting the position to some extent. This is generally due to mechanical accuracy and electric accuracy. First, mechanically, for example, moving the optical system with a stepping motor to correct skew,
Next, the writing start position is electrically changed or the writing magnification is changed.

In the case of electrical correction, since correction marks are sampled in dot units, if sampling is performed in a range including a mechanical shift amount, it takes time for data processing, which impairs copy speed and print speed. . It becomes necessary to mount more memory.

Therefore, usually, a small amount of displacement is mechanically reduced to some extent, and correction such as electrically changing the dot writing position is performed at the time of fine adjustment pattern correction, thereby performing accurate positioning. Like that.

[0008]

However, the correction of the positional deviation in the conventional image forming apparatus has a problem that the operability and productivity of the user are reduced because the correction processing takes a long time.

An object of the present invention is to provide a multi-color image forming apparatus which can solve the above-mentioned problem in the conventional image forming apparatus and can perform positional deviation correction without lowering user operability and productivity. Make it an issue.

[0010]

According to the present invention, a plurality of latent image carriers are provided, and a latent image formed on the latent image carrier is developed and a visible image is sequentially superimposed on a recording medium. In a multicolor image forming apparatus for obtaining a multicolor image by transferring, a correction mark detecting means for detecting a mark for alignment correction formed by each of the latent image carriers, and a correction mark detecting means for detecting a mark based on a detection result of the correction mark detecting means. Image position correcting means for correcting the position of an image formed on each latent image carrier, performing coarse adjustment with less detection data of the correction mark after power-on in an initial state at the time of device delivery, In the subsequent image position correction, it is proposed to perform fine adjustment which includes a large amount of detection data of the correction mark.

In order to solve the above-mentioned problems, the present invention comprises a plurality of latent image carriers, and sequentially superimposes a visible image obtained by developing a latent image formed on the latent image carrier onto a recording medium. A multi-color image forming apparatus that obtains a multi-color image by performing a correction mark detection unit that detects a mark for alignment correction formed by each of the latent image carriers, and a correction mark detection unit that detects a mark based on a detection result of the correction mark detection unit. Image position correcting means for correcting the position of an image formed on each latent image carrier, performing coarse adjustment with a small amount of detection data of the correction mark after turning on the apparatus power, and in the subsequent image position correction It is proposed to perform fine adjustment with a large amount of detection data of the correction mark.

Further, in order to solve the above-mentioned problem, the present invention proposes that when the deviation amount of the correction mark during the coarse adjustment exceeds a predetermined range, it is determined that the correction mark is abnormal.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a schematic configuration of a laser printer as an example of an image forming apparatus according to the present invention. The laser printer 1 shown in FIG. 1 has a configuration in which a paper feed unit 2 is disposed at a lower portion of an apparatus main body, and an image forming unit 3 is disposed thereon. In the image forming unit 3, cyan (C), yellow (Y), magenta (M), black (Bk)
Image forming units 4C, 4Y, 4M, 4Bk
Is provided. A transport belt 10 is provided on the right side of each color image forming unit 4. A recording medium (transfer paper or the like) fed from the paper feed unit 2 is conveyed by a conveyor belt 10, the images formed by the respective color image forming units 4 are transferred onto the transfer paper in a superimposed manner, and fixed on the paper by a fixing device 11. Then, the paper is discharged onto the paper discharge tray 12.

As shown in FIG. 2, each of the color image forming units has a charging means (charging roller) 6, a developing device 7, a cleaning device 8,
A static eliminator (not shown) and the like are arranged, and an exposure device (optical system) 9 is provided on a side (left side in the figure) of these devices, so that an image can be formed independently for each unit. ing.

Although the detailed description of the image forming operation of each color image forming unit by the electrophotographic method is omitted, the exposure device 9 uses an LD (laser diode) based on image data sent from a host machine such as a personal computer. Drive to irradiate the polygon mirror with laser light, guide the reflected light onto the photosensitive drum 5 via a cylinder lens or the like,
An electrostatic latent image is formed on the photosensitive drum 5. Exposure device 9
Are cyan, yellow, and black, excluding the image forming unit for black.
The magenta image forming unit has a mechanism (optical system tilt adjusting unit) 14 for adjusting the tilt in the main scanning direction. This is to quantitatively change the inclination of the exposure unit (the folding mirror, the entire optical system, etc.) by the stepping motor 15 or the like, thereby changing the inclination (skew) in the main scanning direction.

The transport belt 10 disposed on the right side of the photosensitive drum 5 is driven to rotate in the direction of the arrow (clockwise in the figure). The cyan, yellow, magenta, and black images formed on the photosensitive drum 5 of each color unit are sequentially transferred onto the transfer paper conveyed on the conveyer belt, and finally transferred to the fixing device 11.
To get a copy of the full color image.

In the present embodiment, an image (toner image) can be formed on the conveyor belt 10, and the image is detected by the image detecting means 13. The position where the image detecting means 13 is provided is located downstream of the last image forming unit (the conveying belt 1).
0), that is, a unit that forms an image of the color to be transferred last when the images formed by the respective color image forming units are sequentially overlaid and transferred (the black unit 4Bk in the present embodiment). On the downstream side of The image detected by the image detecting means 13 is a mark for correcting a positional deviation of the image forming unit, which is hereinafter referred to as a registration mark, and the image detecting means 13 is referred to as a correction mark detecting means.

In the present embodiment, the transport belt 10 is made of a transparent material, and is formed on the belt by image detecting means 13 including a light emitting section and a light receiving section disposed on the front and back of the belt with the belt 10 interposed therebetween. The registration mark is grasped by detecting the applied toner image. In the present embodiment, the determination of the transfer position deviation of each image forming unit (the determination of the image deviation) is a method in which the position of the registration mark on the transport belt is detected and the determination is made based on the timing deviation.

Specifically, a registration mark is formed on the conveyor belt 10 at a predetermined timing for each color image forming unit. That is, a toner image (registration mark) formed on the photosensitive drum 5 for each color image forming unit
Is transferred onto the conveyor belt 10 at a predetermined timing. The registration marks are formed in pairs on both sides of the conveyor belt for each color. In order to detect the pair of registration marks, the correction mark detection means 13 is disposed one at each side end of the conveyor belt 10. Although only one correction mark detection unit 13 is shown in the figure, two correction mark detection units 13 are provided in a direction orthogonal to the moving direction of the transport belt 10 (that is, the main scanning direction). As described above, the correction mark detecting means 13 includes the light emitting section and the light receiving section, and two correction mark detecting means 13 including the light emitting section and the light receiving section are provided in the main scanning direction.

The above-mentioned registration marks are detected by the correction mark detecting means 13 in accordance with the movement of the conveyor belt 10. L on back side
A light-emitting portion composed of a light-emitting element such as an ED is disposed, and a photodiode (P
D) A light-receiving unit consisting of a light-receiving element such as D) is placed, and the registration mark is detected by reading the fluctuation of the output signal from the PD due to the interruption of the irradiation light by the registration mark when the irradiation light of the LED is taken in by the PD. It is carried out.

FIG. 3 (C) shows the timing chart at a certain interval.
FIG. 3 shows registration marks formed by one image forming unit. As shown in this figure, the registration mark in the present embodiment is formed in a straight line.

If there is no displacement between the four image forming units, the four registration marks for each color formed at the same predetermined timing are equally spaced and have the same width as shown in FIG. It becomes a straight line, and the starting point and the ending point of each straight line are also aligned at the same position in the main scanning direction (the left-right direction in FIG. 3). Conversely, if each image forming unit is misaligned,
The intervals between the straight lines are not the same, and the positions of the ends of the straight lines in the main scanning direction are also different. In correcting the positional deviation of the image forming unit, the distance between each registration mark is measured to correct the amount of deviation in the sub-scanning direction, the position of the registration mark formed in pairs in the main scanning direction is detected, and the skew in the main scanning direction is detected. Has been corrected.

The analog data from the PD which drives the conveyor belt 10 to light the LED of the correction mark detecting means 13 and reads the registration mark has a waveform as shown in FIG. The horizontal axis represents time, and the vertical axis represents optical power received by the PD. One peak represents one registration mark, and the center position of the registration mark is determined by the maximum value of the PD output. One resist mark is several lines (several dots), and therefore, the sampling interval is in units of ns.
1 for one color for accurate median calculation
About ten thousand samples are required, and the amount of sampling data is considerable. Furthermore, if the sampling width is set so as to include a mechanical shift, an enormous amount of data is determined and stored.

By the way, the analog data from the photodiode (PD) of the correction mark detecting means 13 is A / D converted and taken into the CPU as a digital value to determine the maximum value (the center position of the registration mark). The judgment time (processing time) greatly changes depending on the amount of data. Therefore, first, instead of increasing (widening) the sampling width, in the alignment correction using the coarse adjustment mark,
By increasing the time between samplings (sampling intervals), the number of samplings is reduced, and rough displacement correction is performed so that a large amount of data need not be processed.

For example, when sampling is performed at a sampling interval of 50 ns and sampling is performed at a sampling interval of 200 ns with respect to a sampling width of a certain unit time, the number of samples of the former is four times that of the latter, and the data of the former is four times larger. The amount is four times that of the latter. Therefore, even if the sampling width is increased, if the sampling interval is increased, the number of samples can be reduced, the data amount can be reduced, and the processing time can be reduced. In the present invention, after the power is turned on in the initial state delivered to the user, the alignment correction using the coarse adjustment mark is performed, and the rough deviation correction is performed.

Next, a description will be given of the alignment correction (coarse adjustment) using the coarse adjustment mark. FIG. 4A shows an example of a registration mark formed at the timing of superposition in each image forming unit before the positional deviation is corrected after the power is turned on in an initial state immediately after delivery. Since they are formed at the same timing (timing at which the registration marks formed in the respective image forming units overlap), if there is no shift between the image forming units, the four lines should intersect with each other and become one line. However, even if the image forming units are made in the same manner, exactly the same product cannot be made, and the mounting position is slightly shifted when the machine is moved, so that the formed image is different. Here, C,
The registration marks of the respective colors M and Y are considerably skewed (inclined), and the positions (end positions of the straight lines) in the main scanning direction (the horizontal direction in FIG. 3) are also different. The position of the registration mark in the main scanning direction is determined by the laser beam scanning start position of the writing section or the writing start timing.

When a registration mark as shown in FIG. 4A is detected, it is necessary to correct the skew (inclination) in all of C, M, and Y. Therefore, the optical system inclination adjusting mechanism 14 (FIG. 2) is used. Correct the tilt. In the present embodiment, the adjustment is performed by moving the stepping motor 15 of the adjusting mechanism 14 in accordance with the detected deviation amount of the registration mark. When the skew is corrected, the writing position and length are corrected by the writing magnification at the writing timing, thereby correcting the positional deviation in the main scanning direction.

Highest value (median value) when detecting a registration mark
Is performed at approximately the timing of the mark position. However, as shown in FIG. 4A, if the amount of deviation is large, the sampling time (sampling width) increases, and the processing time of the CPU is burdened. However, in the coarse adjustment, a large sampling interval (for example, 200
ns), the number of samples can be reduced and the time required for data processing can be reduced.

By performing such a coarse adjustment after turning on the power supply in an initial state immediately after delivery, first, a rough alignment correction is performed, thereby facilitating the subsequent fine adjustment (fine adjustment), and the user is in use. Therefore, it is possible to obtain a high-quality full-color image with no color shift without reducing the time required for fine adjustment of the image as much as possible and reducing the operability and productivity.

FIG. 4B shows a registration mark formed at the timing of superposition after performing the coarse adjustment. If the shift amount of the registration mark of each color is within the range that can be grasped by the CPU (as shown in FIG. 4B), the sampling time can be shortened and the processing time can be shortened. Therefore, in consideration of this sampling time (sampling width), rough coarse mark alignment correction is performed when the machine is installed, and fine copy mark position is not spent during normal copying (printing) without skew correction. By performing only the alignment correction, it is possible to obtain a copy that is faithful to a document without positional deviation.

Next, a description will be given of the fine-adjustment mark alignment correction (fine-adjustment correction) performed during normal copying (printing). The registration marks in the fine adjustment are formed at regular intervals, for example, as shown in FIG. The detection output of the registration mark is as shown in FIG. 5, and sampling is performed for each color. In the fine adjustment, the sampling interval is reduced (for example, 50n).
s) Perform precise sampling. Comparing at the same sampling time (sampling width), fine adjustment at a sampling interval of 50 ns is coarse adjustment (sampling interval of 20 ns).
0 ns), and the amount of data is four times as large as that of the first embodiment. The present invention does not specify the timing at which the fine adjustment is performed.

Here, the configuration of a control section for controlling the above-described alignment correction in the laser printer of the present embodiment will be briefly described with reference to FIG. In the block diagram shown in FIG. 5, a CPU 20 is a main CPU of the laser printer. All alignment corrections in the present embodiment are processed by the CPU 20. The light emitting section 21, the light receiving section 22, and the A / D conversion section 23 of the correction mark detecting means 13 are also controlled by the main CPU 20. Further, an operation unit 24 of the printer, a pattern generator 25 for generating correction mark data, a writing control unit (image processing unit) 26 in the image forming unit, a developing unit 27, and other unit control units 28 are also connected to the main CPU 20. Controlled.

In detecting the correction mark (registration mark), the LED of the light emitting section 21 emits light at the timing of the sequence, and the light is received by the PD (photodiode) of the light receiving section 22. The output waveform generated by the light reception by the PD driving plate is sent to the A / D converter 23, converted into a digital value, and input to the main CPU 20. To generate a registration mark, a command is sent from the CPU 20 to the pattern generator 25, and the data is sent to the writing control unit 26 to form a toner image, which is transferred onto the transport belt 10. The timing of forming registration marks is determined by the CPU.
In the pattern generator 25, a rough coarse mark and a fine fine mark are selected.

By the way, it is conceivable that the amount of deviation of each image forming unit exceeds the range that can be corrected by the alignment correction. In the present embodiment, rough sampling is performed by setting a large sampling time (sampling width) in the coarse adjustment, and when the registration mark cannot be detected even by the sampling (when the deviation exceeds a predetermined range). Is configured to determine that an abnormality has occurred and display a warning display on the operation unit of the printer. This allows
The user or the service person can be notified that a mechanical abnormality has occurred, and the abnormality can be promoted.

As described above, since there is a possibility that a factor causing a dot shift mechanically occurs at the time of first arrival at the user, the coarse adjustment is always performed when the power is turned on in the initial delivery state of the apparatus. Like that.
After that, if only fine adjustment is performed, rough correction is performed in the initial state, so that fine positioning can be easily performed, and the time required for correction during use can be minimized, and the correction time can be reduced. Can be shortened.

In an image forming apparatus such as a copier, a facsimile, and a printer, the power supply is often turned on in the initial state of delivery of the apparatus by a service person.
Even if the misregistration correction using the coarse adjustment mark is performed, the influence on the operability and productivity of the user is small, and the usability of the user is not spoiled. Even when the user turns on the power supply in the initial state of delivery, the correction process does not take much time in the actual work after the initial state, so that the influence on the operability and productivity of the user is small.

Next, the second aspect of the present invention will be described. The basic configuration of the laser printer according to the embodiment of the present invention is the same as that of the above-described embodiment, except that the timing for performing the positional shift correction (coarse adjustment) using the coarse adjustment mark is different. Therefore, duplicate description will be omitted, and only different portions will be described.

The power is turned off, not only when the apparatus is loaded.
If a certain period of time has passed since then, there is often a possibility that a factor causing a dot shift mechanically has occurred. Therefore, in the present embodiment, the position shift correction (coarse adjustment correction) using the coarse adjustment mark is always performed when the power is turned on. That is, the coarse adjustment is performed not only when the user first arrives but also when the power is turned on. This facilitates subsequent misalignment correction (fine adjustment) using the fine adjustment mark,
The time required for correction when the apparatus is used can be minimized and the correction time can be reduced.

When the registration mark cannot be detected (when the deviation exceeds a predetermined range) when the coarse adjustment is performed, it is determined that an abnormality has occurred, and a warning display is displayed on the operation unit of the printer. The configuration is the same as in the above embodiment.

Although the present invention has been described with reference to each embodiment, the present invention is not limited to the above embodiment. For example, the configuration of the image forming unit, the form of the registration mark, the sampling time (sampling width), the sampling interval, and the like can be appropriately set. Further, the configuration of the detecting means for detecting the registration mark, the configuration of the optical system tilt adjusting mechanism in the image forming unit, and the like can also be changed.

[0041]

As described above, according to the multicolor image forming apparatus of the present invention, after the power is turned on in the initial state at the time of delivery of the apparatus, coarse adjustment with a small amount of detection data of the correction mark is performed. In the image position correction, fine adjustment is performed with a large amount of detection data of the correction mark, so that a rough correction is performed in an initial state, thereby facilitating subsequent fine positioning, and minimizing a time required for correction during use. And the correction time can be shortened.

According to the second aspect of the present invention, after turning on the power of the apparatus, coarse adjustment with a small amount of detection data of the correction mark is performed, and fine adjustment with a large amount of detection data of the correction mark is performed in the subsequent image position correction. By performing a rough correction at the time of turning on the power, fine positioning can be easily performed thereafter, the time required for correction during use can be minimized, and the correction time can be shortened.

According to the third aspect of the present invention, if the amount of deviation of the correction mark during the coarse adjustment exceeds a predetermined range, it is determined that an abnormality has occurred. This can be notified and the abnormality can be resolved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a laser printer as an example of an image forming apparatus according to the present invention.

FIG. 2 is a cross-sectional configuration diagram illustrating an image forming unit of the laser printer.

FIG. 3 is a schematic diagram illustrating a mark for alignment correction.

FIG. 4 is a graph showing detection data of correction marks formed at regular intervals.

FIG. 5 is a block diagram illustrating a configuration of a control unit that controls alignment correction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Paper feed part 3 Image forming part 4 Image forming unit 5 Latent image carrier (photosensitive body) 9 Optical system (exposure part) 10 Conveyor belt 13 Correction mark detecting means 14 Optical system inclination adjustment mechanism 15 Stepping motor 20 Main CPU 26 Write control unit (image processing unit)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Shinohara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Yasufumi Nakazato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Mitsui Sugiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Nobuo Iwata 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Motoki Hanada 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H027 DA38 DA50 EB04 EC03 EC06 EC20 ED24 EE02 EE07 EF01 EF06 EF09 HA02 HB06 2H030 AA01 AB02 AD12 AD17 BB02 BB44 BB56 5B057 AA04 CC01 CD02 DB02 5C076 AA17 BA02 CA06

Claims (3)

[Claims] 1. A multicolor image forming apparatus comprising a plurality of latent image carriers, and sequentially superimposing and transferring a visible image obtained by developing a latent image formed on the latent image carrier onto a recording medium to obtain a multicolor image. A correction mark detecting means for detecting a mark for alignment correction formed by each latent image carrier; and a position of an image formed on each latent image carrier based on a detection result of the correction mark detecting means. Image position correcting means for correcting the correction mark, performing coarse adjustment with a small amount of detection data of the correction mark after power-on in an initial state when the apparatus is delivered, and detecting the correction mark in the subsequent image position correction. A multicolor image forming apparatus, which performs fine adjustment with a large amount of data. 2. A multicolor image forming apparatus comprising a plurality of latent image carriers, and sequentially superimposing and transferring a visible image obtained by developing a latent image formed on the latent image carrier onto a recording medium to obtain a multicolor image. A correction mark detecting means for detecting a mark for alignment correction formed by each latent image carrier; and a position of an image formed on each latent image carrier based on a detection result of the correction mark detecting means. Image position correcting means for correcting the correction mark, performing coarse adjustment with less detection data of the correction mark after turning on the apparatus power, and performing fine adjustment with more detection data of the correction mark in subsequent image position correction. A multi-color image forming apparatus. 3. The multicolor image forming apparatus according to claim 1, wherein when the shift amount of the correction mark during the coarse adjustment exceeds a predetermined range, it is determined that the mark is abnormal.