JP2007248856A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the position of a pattern image in each color and correct the displacement of the pattern image regardless of damage to and soil on a transfer belt. <P>SOLUTION: Each pattern image is formed on an intermediate transfer belt 13 by an image pattern formation means 3. A comparison means 14 compares the level of a detection signal from a first sensor 5, which detects the pattern image, with a predetermined value. Time required for an intermediate transfer belt 13 to make one rotation is repeatedly counted by a count means 15. The result of the comparison means 14 and the count value are recorded in a recording means 16. From the count value recorded in the recording means, the position of the pattern image is determined by a pattern determination means 17. Based upon the result, a pattern adjusting means adjusts the displacement of the pattern image. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus that writes image information on an image carrier with a light beam and transfers the image onto a recording medium.

  Electrophotographic image formation that uses a light beam such as laser light to write image information in the form of a latent image on a photoconductor as an image carrier, visualizes it with a developing device, and transfers it to a recording medium such as transfer paper The apparatus is widely used for copying machines, printers, facsimiles and the like. In such an image forming apparatus, there are an increasing number of image forming apparatuses capable of forming a color image in response to a demand from the market. As a color image forming apparatus, a plurality of juxtaposed photoconductors are each provided with a developing device, and a single color toner image of cyan, magenta, yellow, and black is formed on each photoconductor, and the single color toner images are formed. A so-called tandem type that sequentially transfers and records a composite color image on a recording medium is widely used. The tandem type image forming apparatus includes a direct transfer type in which images on a plurality of photosensitive members are sequentially transferred to a recording medium conveyed by a conveying belt by a transfer device, and an image on each photosensitive member is primarily transferred. There is an indirect transfer type in which an image is temporarily transferred to an intermediate transfer belt, which is an intermediate transfer body, by an apparatus, and then an image on the intermediate transfer belt is collectively transferred to a recording medium by a secondary transfer apparatus. Note that the belt is a transfer means for a recording medium to be transferred in the direct transfer system, and is an image transfer means in the indirect transfer system.

In the case of the tandem type, when the photosensitive member and the transfer belt are not integrated, but in separate modules, it is difficult to superimpose different color toners. Therefore, in Patent Document 1, for example, a pattern image of each color is formed on the intermediate transfer belt, the pattern image is detected by a sensor, and the amount of deviation from the original position is detected based on the detection result. A method of adjusting at the time of pattern formation has been proposed. This patent document 1 describes the indirect transfer method, but in the case of the direct transfer method, an image transfer portion is continuously provided at one end in a direction orthogonal to the conveyance direction of the conveyance belt, and a pattern image is formed in this portion. If it is formed, it can also be applied to a direct transfer system.
JP-A-2005-31168

  In the technique of Patent Document 1, it is effective to superimpose pattern images of different colors on the intermediate transfer belt, read the position with a sensor, and adjust the pattern formation position. However, there is a possibility that the sensor that reads the pattern image reacts to dirt that cannot be removed by a cleaning mechanism such as a cleaning blade on the intermediate transfer belt, or scratches generated while the transfer belt is rotating. When such a phenomenon occurs, a sensor for detecting a pattern image erroneously detects dirt and scratches as a pattern image. Then, an error may occur in the adjusting means for overlapping different colors, and it may occur that toners of different colors cannot be stacked.

  In order to prevent such pattern image position detection from being mistaken, in the conventional technique, if the number of detections is larger than that of the pattern image, it can be dealt with by erasing data as an error or re-execution, but this takes time. This is not effective because toner is also consumed.

  The present invention has been made in view of the actual situation of the prior art, and its purpose is to ignore the scratches and dirt on the transfer belt, detect the pattern image position without making a mistake, and correct the misalignment of the pattern image of each color. Thus, it is possible to adjust the deviation of the toner image more accurately.

  In order to achieve the above object, the first means forms a toner image of a different color on each of the plurality of photoconductors, and a recording medium on the transfer belt that rotates or moves the toner image of each color. In the image forming apparatus that forms a color image by superimposing the pattern image, a pattern forming unit that forms the pattern image of each color on the transfer belt, a first detection unit that detects the pattern image, and the transfer belt are 1 A counting unit that repeatedly counts the rotation time; a recording unit that records a count value of the counting unit based on a detection output of the first detection unit; and a pattern image based on the count value recorded in the recording unit. A determination unit that determines a position; and a pattern adjustment unit that adjusts a shift of the pattern image based on a result of the determination unit. The features.

  The second means comprises comparison means for comparing the detection output of the detection means with a preset level in the first means, and the recording means replaces the detection output of the first detection means with the comparison. It records based on the comparison output of a means, It is characterized by the above-mentioned.

  The third means is characterized in that, in the first or second means, the counting means is reset when the preset time for one round of the transfer belt has elapsed, and the counting is performed again.

  The fourth means includes, in the first or second means, second detection means for detecting a mark provided on the transfer belt, and the counting means starts counting after detecting the mark, The count is stopped at the next detection.

  The fifth means is characterized in that, in the fourth means, the mark comprises a hole formed in the transfer belt, and the second detection means comprises an optical sensor for detecting light transmitted through the hole. To do.

  According to a sixth means, in the fourth means valley, the mark is made of a material having a reflectance different from that of the transfer belt, and the second detecting means is an optical sensor for detecting a change in reflectance. Features.

  The seventh means is characterized in that, in any one of the first to sixth means, the determination means determines the position of the pattern image by comparing with a recorded value of the transfer belt when the pattern image is not formed. And

  The eighth means is characterized in that, in any one of the first to seventh means, the determination means determines that the pattern image is the pattern image based on a count interval of the pattern images.

  According to a ninth means, in any one of the first to eighth means, if the output of the detection means when the recording means is not forming the pattern image is outside a set value, the count at the time of forming the pattern image is performed. The value is not recorded.

  According to a tenth means, in any one of the first to eighth means, if the output of the detection means when the pattern image is not formed is outside a set value, the pattern image forming means outputs the output outside the setting. A pattern is formed while avoiding the detection position. In the embodiment described later, the photosensitive member is the photosensitive drums 4a to 4d, the transfer belt is the intermediate transfer belt 13, the pattern forming unit is the image pattern forming unit 3, and the first sensor is the reference number 5. Means for reference number 14, counting means for reference number 15, recording means for reference number 16, determination means for pattern determination means 17, pattern adjustment means for reference number 18, and second sensor for reference number 19. Each corresponds.

  According to the present invention, scratches and dirt on the transfer belt are ignored, the pattern image position is detected without error, and the time that the transfer belt makes one round is actually counted, and there is a deviation from the ideal value of the elapsed time. For example, the deviation of the pattern image of each color can be corrected by a predetermined means, and the deviation of the toner image can be adjusted more accurately.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, indirect transfer type color image formation in which images on each photoconductor are sequentially transferred to an intermediate transfer member by a primary transfer device and then transferred onto a transfer sheet at once by a secondary transfer device. Taking the case of a device as an example.

  FIG. 1 is a diagram showing a schematic configuration of a color printer 1 to which the present invention is applied. The color printer 1 is configured such that paper is supplied from a paper feed cassette 2 provided at the bottom. The color printer 1 includes developing units 3a to 3d for forming images of each color of cyan (C), magenta (M), yellow (Y), and black (K). Photosensitive drums 4a to 4d for transferring an image to the intermediate transfer belt 13 are provided in the developing units 3a to 3d. Although not shown in each of the developing units 3a to 3d, each of the developing units 3a to 3d includes a known device for forming an image in an electrophotographic process, such as a charging device, a cleaning device, or a static eliminating device. . The intermediate transfer belt 13 that superimposes the images formed on the photosensitive drums 4 a to 4 d is stretched between a tension roller 6 that prevents the intermediate transfer belt 13 from sagging and a driving roller 7 that drives the intermediate transfer belt 13. Has been. On the intermediate transfer belt 13, the first sensor 5 composed of a light emitting element and a light receiving element for reading a pattern image formed by each of the photosensitive drums 4 a to 4 d on the intermediate transfer belt 13, and remained without being transferred to a sheet. A cleaning device 8 for removing toner on the transfer belt is disposed. Reference numeral 11 denotes a secondary transfer roller that applies pressure when the toner image on the intermediate transfer belt 13 is transferred to a sheet. Reference numeral 12 denotes a sheet feed roller for feeding the sheet in the sheet feed cassette 2 to the conveyance path 9. The paper discharged from the paper supply roller 12 is discharged from the drive roller 7 and the secondary transfer roller 11 to the outside of the apparatus through the fixing unit 10 that fixes the toner image on the paper to the paper with heat. It is sent out to the conveyance path 9. Note that the configuration for forming a color image with four colors C, M, Y, and K is well known, and a description thereof will be omitted.

  FIG. 2 is a block diagram showing an embodiment of a color matching apparatus according to the present invention. The color matching apparatus includes a first sensor 5 that reads a pattern on the transfer belt 13, a comparator 14 that includes a comparator that compares the intensity of a detection signal of the first sensor 5 with a set value, and an intermediate transfer belt 13. Count means 15 for counting one round, recording means 16 for recording the count value of the count means 15 and / or the intensity (signal level) of the detection signal, and determination means 17 for comparing and determining the count value with the pattern image The pattern adjusting means 18 is used for adjusting the pattern position from the count value in the recording means 16. Reference numeral 3 denotes an image pattern forming unit composed of the developing units 3a to 3d.

  In this embodiment, the counting means 15 resets and starts counting one rotation of the intermediate transfer belt 13 when a predetermined time for one round of the belt comes, but as shown in FIG. In addition, a second sensor 19 is provided separately, and the second sensor 19 detects one rotation of the intermediate transfer belt, that is, one turn, so as to check whether the intermediate transfer belt 13 makes one turn. Good. In this case, the second sensor 19 can be easily realized by using an optical sensor and making a hole in the intermediate transfer belt 13 or changing a reflectance of a part of the intermediate transfer belt 13.

  FIG. 4 is a flowchart of pattern image determination in the first embodiment, and FIG. 5 is an explanatory diagram of pattern image determination. Before starting color matching, the intermediate transfer belt 13 is examined for scratches, dirt, and the like that are erroneously detected as pattern images. That is, the intermediate transfer belt 13 is rotated (step S101), and then the signal from the intermediate transfer belt 13 is detected by the first sensor 5 (step S102). The signal level is compared with a set value (step S103). If the signal level is within the set value, the count value of the count means 15 at that time is recorded in the recording means 16 (step S104), and then it is determined from the count means 15 whether or not the intermediate transfer belt 13 has made one rotation (step S104). Step S105). If the signal level is outside the set value in step S103, the transfer belt 13 is rotated again without recording. This flow is performed for one round of the transfer belt, and a position erroneously recognized as a pattern image such as a scratch is recorded as a count value. The detection signal of the first sensor 5 at this time is as shown in the upper part of FIG.

  Next, a pattern image is formed on the intermediate transfer belt 13, and the position of the pattern is detected. First, a pattern image is formed on the intermediate transfer belt 13 (step S106), the intermediate transfer belt 13 is rotated (step S107), and signals are sequentially read from the first sensor 5 (step S108). The read signal is compared with the set value in the comparison means 14 (step S109). If it is within the set value, it is compared with the count value recorded in step S104 earlier (step S110), and if it is different, it is recorded in the recording means 16 (step S111). Next, it is determined whether the count value is read out of the pattern image × twice count value (step S112). If it has been read twice, the pattern position is adjusted based on the count value in step S112 (step S113). If the signal level is not within the set value in step S109, the count value is different in step S110, and if the image pattern cannot be read twice in step S112, the process returns to step S107. Thus, the count value of the pattern image X2 times can be read out. The detection signal of the first sensor 5 at this time is as shown in the lower part of FIG.

  FIG. 6 is a flowchart of pattern image determination in the second embodiment, and FIG. 7 is an explanatory diagram of pattern image determination. In the second embodiment, there is no operation of recording the count value for one rotation of the intermediate transfer belt 13 as in steps S101 to S105 of the first embodiment. Instead, the count value obtained by detecting the pattern image is used as the pattern image interval. Comparing. That is, the intermediate transfer belt 13 is rotated (step S201), a pattern image is formed on the intermediate transfer belt 13 (step S202), and signals are sequentially read by the first sensor 5 (step S203). It is determined whether or not the detection signal is within the set value (step S204), and if it is within the set value, it is recorded in the recording means 16 (step S205). Next, it is determined by the counting means 15 whether or not the intermediate transfer belt 13 has been rotated by the amount corresponding to the pattern image (step S206). If it has been rotated, it is determined whether or not the count value interval is within the set value range. (Step S207). If the level of the detection signal is outside the set value in step S204, if the intermediate transfer belt 13 is not rotated by the pattern image in step S206, the process returns to step S201.

  If the interval between the count values is outside the set range, the count value is deleted (step S208), and it is determined whether or not all the count values have been read again (step S209). When the count value interval is within the set range in step S207, the process directly proceeds to step S209. If all count values have not been read in step S209, the next count value is read (step S210). The reading of the count value may be returned to step S207. If all the count values have been read in step S209, the process proceeds to step S211. As a result, as shown in FIG. 7, only the count values that fall within the preset minimum and maximum range of the count value interval of the pattern image remain, so that the position adjustment is performed based on the count value (step S211).

  FIG. 8 is a flowchart of pattern image determination in the third embodiment, and FIG. 9 is an explanatory diagram of pattern image determination. In the third embodiment, as in the first embodiment, the count value for one rotation of the intermediate transfer belt 13 is recorded. That is, the intermediate transfer belt 13 is rotated (step S301), a signal from the intermediate transfer belt 13 is detected by the first sensor 5 (step S302), and the signal level is compared with a set value by the comparison unit 14 (step S302). Step S303). If the signal level is within the set value, the count value of the counting means 15 at that time is recorded in the recording means 16 (step S304), and it is determined from the counting means 15 whether or not the intermediate transfer belt 13 has made one rotation (step S304). (S305) If the rotation is once, a pattern image is formed on the intermediate transfer belt 13 (step S306), the intermediate transfer belt 13 is rotated, and the position of the pattern is detected (step S307). If the signal level is outside the set value in step S303, the process proceeds to step S305. If the intermediate transfer belt 13 has not made one rotation in step S305, the process returns to step S301. The detection signal of the first sensor 5 at this time is as shown in the upper part of FIG.

  After detecting the position of the pattern in step S307, it is determined whether the detected signal is the same as the count value recorded in step 304 (step S308). If not, the signal is sequentially sent from the first sensor 5. Reading (step S309), the read signal is compared with the set value in the comparison means 14 (step S310). If it is within the set value, it is recorded in the recording means 16 (step S311). Next, it is determined whether the count value is read out of the pattern image × 2 times (step S312). If it has been read twice, the pattern position is adjusted based on the count value in step S112 (step S313). If the signal level is not within the set value in step S309, if the count value is different in step S310, and if the image pattern cannot be read twice in step S312, the process returns to step S307. Thus, the count value of the pattern image X2 times can be read out. The detection signal of the first sensor 5 at this time is as shown in the lower part of FIG. 9, and the position of the pattern image can be accurately detected.

  FIG. 10 is a flowchart of pattern image determination in the fourth embodiment, and FIG. 11 is an explanatory diagram of pattern image determination. In the fourth embodiment, the first sensor 5 forms a pattern image based on the count value in which the scratches and dirt positions of the intermediate transfer belt 13 are recorded. That is, the intermediate transfer belt 13 is rotated (step S401), a pattern image is formed (step S402), a signal from the intermediate transfer belt 13 is detected by the first sensor 5 (step S403), and the detection signal is detected. If the detected signal is within the set value, the comparator 14 compares the signal level with the set value (step S404). Step S405). Next, it is determined by the counting means 15 whether or not the intermediate transfer belt 13 has made one rotation (step S406). If the intermediate transfer belt 13 has made one rotation, the count value detected in step S405 is avoided as shown in the lower part of FIG. Then, a pattern image is formed on the intermediate transfer belt 13 (step S407). Then, the intermediate transfer belt 13 is rotated (step S408), the position of the pattern is detected by the first sensor 5 (step S409), and it is determined whether or not the level of the detection signal is a set value (step S410). . If the level of the detection signal is within the set value, it is recorded in the recording means 16 (step S411), and the position is adjusted based on the count value (step S412).

  If the signal level is outside the set value in step S404, or if the intermediate transfer belt 13 has not made one rotation in step S406, the process returns to step S401.

  In the above-described embodiment, the indirect transfer type tandem type image forming apparatus has been described as an example. However, as described above, in the case of the direct transfer type tandem type image forming apparatus, If an image transfer portion is continuously provided at one end portion and a pattern image is formed at this portion, it can be applied to a direct transfer method.

1 is a diagram illustrating a schematic configuration of a color printer to which the present invention is applied. It is a block diagram which shows one Embodiment of the color matching apparatus which concerns on this invention. It is a block diagram which shows another embodiment of a color matching apparatus. 3 is a flowchart of pattern image determination in the first embodiment. It is explanatory drawing of the pattern image determination in Example 1. FIG. 10 is a flowchart of pattern image determination in the second embodiment. It is explanatory drawing of the pattern image determination in Example 2. FIG. 10 is a flowchart of pattern image determination in the third embodiment. It is explanatory drawing of the pattern image determination in Example 3. FIG. 14 is a flowchart of pattern image determination in the fourth embodiment. It is explanatory drawing of the pattern image determination in Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color printer 3 Image pattern formation means 3a-3d Development unit
4a to 4d Photosensitive drum 5 First sensor 10 Fixing unit 13 Intermediate transfer belt 14 Comparison means 15 Count means 16 Recording means 17 Pattern determination means 18 Pattern adjustment means 19 Second sensor

Claims (10)

An image forming apparatus that forms toner images of different colors on a plurality of photoconductors and superimposes the toner images of the respective colors on a transfer belt that rotates or moves or on a recording medium on the transfer belt to form a color image. In
Pattern forming means for forming a pattern image of each color on the transfer belt;
First detection means for detecting the pattern image;
Counting means for repeatedly counting the time for which the transfer belt makes one rotation;
Recording means for recording the count value of the counting means based on the detection output of the first detection means;
Determination means for determining a position of a pattern image from the count value recorded in the recording means;
Pattern adjustment means for adjusting the shift of the pattern image based on the result of the determination means;
An image forming apparatus comprising: Comparing means for comparing the detection output of the detection means with a preset level;
2. The image forming apparatus according to claim 1, wherein the recording unit performs recording based on a comparison output of the comparison unit instead of a detection output of the first detection unit.   3. The image forming apparatus according to claim 1, wherein the counting unit is reset when a preset time for one round of the transfer belt has elapsed, and performs counting again.   2. A second detection unit that detects a mark provided on the transfer belt, wherein the counting unit starts counting after detecting the mark, and stops counting at the next detection. 3. The image forming apparatus according to 1 or 2.   The image forming apparatus according to claim 4, wherein the mark includes a hole formed in the transfer belt, and the second detection unit includes an optical sensor that detects light transmitted through the hole.   5. The image forming apparatus according to claim 4, wherein the mark is made of a material having a reflectance different from that of the transfer belt, and the second detection unit is an optical sensor that detects a change in reflectance.   7. The image formation according to claim 1, wherein the determination unit determines the position of the pattern image in comparison with a recording value of the transfer belt when the pattern image is not formed. apparatus.   The image forming apparatus according to claim 1, wherein the determination unit determines that the pattern image is the pattern image based on a count interval of the pattern image.   9. The recording apparatus according to claim 1, wherein the recording means does not record the count value when the pattern image is formed when the output of the detection means when the pattern image is not formed is outside a set value. 2. The image forming apparatus according to item 1.   The pattern image forming unit forms a pattern by avoiding an output detection position outside the setting when the output of the detecting unit when the pattern image is not formed is out of a set value. 9. The image forming apparatus according to any one of items 8 to 8.

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