JP2010266644A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus capable of accurately and easily detecting an amount of positional deviation of a recording medium even if a magnification error is made in image formation. <P>SOLUTION: The electrophotographic image forming apparatus forms deviation detecting toner patterns T1 to T4 to extend over the recording medium and an intermediate transfer belt 21 at a position corresponding to a predetermined end y of the recording medium on the intermediate transfer belt. The toner patterns T1 to T4 include a plurality of groups A to D being assemblies of bar patterns having the same length (a), and are made to differ in arrangement at predetermined pitch b to the predetermined end (y) of the recording medium for each of the groups A to D. The toner patterns T1 to T4 are transferred onto the recording medium, and the deviation of the recording medium in a main-scanning direction Y is obtained by detecting the transferred toner pattern. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that finally transfers and fixes a toner image on a recording material by an electrophotographic method or the like.

  Image forming apparatuses such as copying machines and printers using an electrophotographic process are usually equipped with a plurality of paper feed trays or paper feed cassettes (hereinafter referred to as paper feed units) for feeding recording media one by one. These sheet feeding units are caused by variations in component dimensions, assembly variations, and the like, in the conveyance of the recording medium, in the conveyance direction (hereinafter also referred to as sub-scanning direction) or in the direction orthogonal to the conveyance direction (hereinafter, A positional deviation occurs in the main scanning direction). Conventionally, such positional deviation has been manually adjusted at the final stage of the manufacturing process or at the time of setup on the user side. However, manually adjusting the shift amount to 1 mm or less is very troublesome and takes a lot of time.

  Also, a test chart is read by a scanner, an image copied to a recording medium is measured with a ruler, a deviation amount and a correction value are calculated, and the correction value is input from a control panel to a control unit (CPU) to draw an image. It has also been carried out to adjust the image writing start position by the laser beam for this purpose. However, even in this method, troublesomeness such as measuring an image with a ruler, calculating a correction value, and inputting the key is not solved.

  Therefore, in Patent Document 1, a toner pattern for detecting misregistration is transferred to a sheet, and the amount of misregistration is automatically detected by reading the toner pattern on the sheet with a scanner, and the image writing start position is determined. A correction method is described. As a method for detecting the amount of misalignment, first, the distance from the paper edge to the toner pattern is calculated, and the amount of misalignment is obtained by the difference from a predetermined distance. Second, the toner pattern is formed so as to straddle the paper edge. It is described that when the positional deviation occurs due to the formation, the distance between the portion on the sheet during transfer and the portion remaining on the transfer belt changes, and the amount of deviation is obtained by this difference.

  In any of the detection methods described in Patent Document 1, it is necessary to detect the edge of the paper from the edge of the paper or from the edge of the toner pattern to the edge of the toner pattern. The image writing position is corrected based on the positional deviation amount. However, in such a method, when a magnification error occurs in the main scanning direction, the distance of the pattern that is actually formed is different from the predetermined distance. May be misjudged as misaligned. That is, there is a problem that the cause cannot be identified as a difference due to a magnification error in the main scanning direction or a difference due to a positional deviation.

JP-A-9-233254

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of accurately and easily detecting the amount of positional deviation of a recording medium even when a magnification error occurs in image formation.

In order to achieve the above object, an image forming apparatus according to an aspect of the present invention includes:
A toner image carrier;
Toner image forming means for forming a toner image on the toner image carrier;
Transfer means for transferring a toner image formed on the toner image carrier to a recording medium;
In an image forming apparatus comprising:
The toner image forming means forms a toner pattern for detecting a deviation amount so as to straddle the recording medium and the toner image carrier at a position corresponding to a predetermined end of the recording medium on the toner image carrier;
The deviation amount detection toner pattern is composed of a plurality of groups having a pattern of a predetermined length, and each group has a different arrangement at a predetermined pitch with respect to the predetermined end of the recording medium.
It is characterized by.

  In the image forming apparatus, the positional information is given to the toner pattern for detecting the deviation amount in advance, and the toner pattern is formed so as to straddle the recording medium and the toner image carrier, so that it remains on the toner image carrier after the transfer. It is divided into a part and a part transferred onto the recording medium. Therefore, the amount of displacement of the recording medium is detected by detecting the toner pattern portion transferred onto the recording medium or the toner pattern portion remaining on the toner image carrier. That is, since the shift amount of the recording medium is detected from the detection information of the end of the toner pattern having the position information in advance, even if a magnification error occurs in the formation of the toner image, the shift amount is not affected by the error. Can be detected. Further, since the position information can be directly recognized from the toner pattern, it is not necessary to obtain the amount of deviation by complicated calculation. Then, by adjusting the image writing start position and the like based on the specified misregistration amount, it is possible to stably maintain the predetermined position on the recording medium regardless of the misregistration of the conveyance due to the individual error of the paper feeding unit. An image can be formed.

  According to the present invention, even when a magnification error occurs in image formation, the amount of positional deviation of the recording medium can be detected accurately and easily, and an image can be stably formed at a predetermined position on the recording medium. .

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention. FIG. 6 is an explanatory diagram illustrating an arrangement state of a deviation amount detection toner pattern on an intermediate transfer belt in the first embodiment. FIG. 6 is an explanatory diagram illustrating a reading range of a deviation amount detection toner pattern transferred onto a recording medium in the first embodiment. 4 is a graph showing a read output of a deviation amount detection toner pattern transferred onto a recording medium in the first embodiment. FIG. 10 is an explanatory diagram illustrating an arrangement state of deviation amount detection toner patterns on an intermediate transfer belt in a second embodiment. FIG. 10 is an explanatory diagram illustrating a reading range of a deviation amount detection toner pattern remaining on an intermediate transfer belt in a second embodiment. 6 is a graph showing a read output of a toner pattern for detecting a deviation amount remaining on an intermediate transfer belt in a second embodiment.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.

(Schematic configuration of image forming apparatus, see FIG. 1)
An image forming apparatus according to an embodiment of the present invention is a tandem type electrophotographic printer as shown in FIG. 1, and is a process unit for forming a toner image of each color of Y, M, C, and K roughly. 10 (10Y, 10M, 10C, 10K), an intermediate transfer unit 20, a paper feed unit 30 containing a recording medium, a fixing unit 35, and an image reading unit 40.

  Each process unit 10 is provided with a photosensitive drum 11, a charging charger 12, a developing device 13, an exposure device 14, etc., and is drawn on each photosensitive drum 11 by light emitted from the exposure device 14. The electrostatic latent image is developed by the developing device 13 to form a toner image of each color. The image data is transferred from the image reading unit 40 or from the computer to the control unit 50.

  The intermediate transfer unit 20 includes an intermediate transfer belt 21 that is driven to rotate endlessly in the direction of the arrow X, and an electric field applied from a transfer charger 22 that faces each of the photosensitive drums 11 is applied onto each photosensitive drum 11. The formed toner image is primarily transferred onto the intermediate transfer belt 21 and synthesized. Note that such an electrophotographic image forming process is well known, and a detailed description thereof will be omitted.

  A sheet feeding unit 30 having three trays for feeding recording media one by one is disposed at the lower part of the apparatus main body. The recording medium is connected to the intermediate transfer belt 21 from the sheet feeding roller 31 via the timing roller 32. The toner image (composite color image) is secondarily transferred to a nip portion with the secondary transfer roller 25. Thereafter, the recording medium is conveyed to the fixing unit 35 where the toner is heated and fixed, and is discharged to a tray portion 36 disposed on the upper surface of the apparatus main body.

(Refer to the first embodiment, FIGS. 2 to 4)
In the first embodiment, first, any one of the process units 10 is used to straddle the recording medium and the intermediate transfer belt 21 at a position corresponding to a predetermined end of the recording medium on the intermediate transfer belt 21. Then, toner patterns T1, T2, T3, and T4 (see FIG. 2) for detecting the shift amount are formed. The deviation detection toner patterns T1 to T4 are composed of a plurality of groups A to D, which are aggregates of bar-code patterns having the same length a and different intervals, and each group A to D has a recording medium. Are arranged at a predetermined pitch b in the main scanning direction Y with respect to the predetermined end portion.

  In FIG. 2, the position indicated by the dotted line y is the end of the recording medium in the normal conveyance state. The range in which the toner patterns T1 to T4 are formed is sufficient in a range in which a shift in the main scanning direction Y of the recording medium is assumed. The number of groups may be 4 or more.

  Next, a recording medium is fed from a specific one of the paper feeding units 30, and the deviation amount detection toner patterns T 1 to T 4 formed on the intermediate transfer belt 21 are transferred. At this time, the end portion of the recording medium passes in the vicinity of the dotted line y (passes on the dotted line y if there is no misalignment), and the toner patterns T1 to T4 remain on the intermediate transfer belt 21 and on the recording medium. It is divided into parts to be transcribed.

  FIG. 3 shows toner patterns t1 to t4 transferred onto the recording medium. The toner patterns t <b> 1 to t <b> 4 are fixed and discharged onto the tray unit 36, and then optically read by an image reading unit (scanner) 40. The reading area here is a range corresponding to the length a of the toner patterns T1 to T4 as indicated by a dotted line in FIG. FIG. 4 shows a read output in the image reading unit 40. The output values are summed in the main scanning direction Y with respect to the dots in the sub-scanning direction Z (conveyance direction) from this reading output, and the case where the output value is completely within the reading area is defined as 100%. It is determined that any of the groups A to D that have exceeded the output value corresponds to the shift amount.

  In FIG. 4, group C corresponds to the amount of deviation, and in this case, the amount of deviation in the main scanning direction Y is detected as 0 on the recording medium. As described above, the positional deviation amount of the recording medium can be directly obtained from the detection information of the toner patterns t1 to t4 transferred onto the recording medium. For example, when an image reading unit 40 with a resolution of 600 dpi mounted on a general facsimile multifunction peripheral is used, a = 1.0 mm and b = 0.1 mm are set, and the threshold is 95% or more and less than 100%. When the range is set, it is possible to detect a positional deviation with an accuracy of 0.1 mm or less.

  The image writing start position by the exposure device 14 is adjusted with respect to the positional deviation amount in the main scanning direction Y of the recording medium detected as described above. As a result, the amount of displacement of the recording medium can be accurately measured and the toner pattern can be measured even if a magnification error has occurred in image formation, regardless of the displacement of the conveyance due to the error of each tray of the sheet feeding unit 30. And complicated calculations are not required, and an image can be stably formed at a predetermined position on the recording medium.

(Refer 2nd Example and FIGS. 5-7)
In the case of an image forming apparatus equipped with an image reading unit (scanner) 40, it is possible to read the image with the scanner and correct the positional deviation of the recording medium as in the first embodiment. However, such a method cannot be corrected by a printer or the like not equipped with a scanner. In such a printer, as shown in FIG. 1, an area sensor SE1 capable of reading a toner image formed on the intermediate transfer belt 21 is provided, and a deviation amount remaining on the intermediate transfer belt 21 is detected by the sensor SE1. It is necessary to detect the amount of deviation by reading the toner pattern. Such a detection method will be described below as a second embodiment.

  In the second embodiment, first, as in the first embodiment, recording is performed on the intermediate transfer belt 21 at a position corresponding to a predetermined end of the recording medium using any one of the process units 10. Deviation amount detection toner patterns T1 to T4 (see FIG. 5) are formed so as to straddle the medium and the intermediate transfer belt 21. In this case, toner patterns T1 to T4 are formed in the reverse relationship in the main scanning direction Y with respect to the arrangement shown in FIG. 2 with reference to the dotted line y (the end of the recording medium in a normal conveyance state). The length a and pitch b of the toner patterns T1 to T4 are the same as in the first embodiment.

  Next, a recording medium is fed from a specific one of the paper feeding units 30, and the deviation amount detection toner patterns T 1 to T 4 formed on the intermediate transfer belt 21 are transferred. At this time, the toner patterns T1 to T4 are divided into a portion remaining on the intermediate transfer belt and a portion transferred onto the recording medium.

  FIG. 6 shows toner patterns t1 to t4 remaining on the intermediate transfer belt 21. FIG. The toner patterns t1 to t4 are optically read by the area sensor SE1. The reading area here is a range shown by hatching in FIG. 6, and FIG. 7 shows the reading output of the sensor SE1. From this reading output, the output values for the dots in the sub-scanning direction Z (conveyance direction) are summed in the main scanning direction Y, respectively, and the pattern is completely left in the reading area. It is determined that any of the groups A to D having an output value exceeding S corresponds to the shift amount. This point is the same as in the first embodiment. However, in the second embodiment, it is assumed that a plurality of groups are recognized as exceeding a threshold value. In such a case, the correction amount is determined by selecting the group with the smallest positional deviation value. For example, in the example shown in FIG. 7, the groups C and D are recognized, but the group C with a small deviation amount is selected as the detection pattern, and the correction amount is determined. This method can also be applied to the first embodiment. The operational effects of the second embodiment are the same as those of the first embodiment.

(Adjustment in the sub-scanning direction)
The amount of positional deviation of the recording medium in the sub-scanning direction Z (conveyance direction) can also be detected and corrected using the toner patterns T1 to T4. In this case, the toner patterns T1 to T4 are arranged in a direction orthogonal to the sub-scanning direction Z and are formed at positions corresponding to the leading edge or the trailing edge of the recording medium. The image forming position in the sub-scanning direction Z can be corrected by controlling the timing roller 32 in addition to controlling the image writing timing.

(Other examples)
Note that the image forming apparatus according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist thereof.

  In particular, the image forming apparatus to which the present invention is applied may be a printer, a facsimile, a complex machine of these, or a monochrome image forming apparatus in addition to a tandem type electrophotographic copying machine. In addition to the intermediate transfer belt, the image carrier that forms the deviation amount detection toner pattern may be a photosensitive drum, a photosensitive belt, or an intermediate transfer drum. Further, the deviation amount detection toner pattern does not necessarily have to be gathered by the same length of the bar pattern in a plurality of groups, and each group may be composed of at least one pattern.

  As described above, the present invention is useful for an image forming apparatus, and is particularly excellent in that a displacement amount of a recording medium can be accurately and easily detected even when a magnification error occurs in image formation. .

DESCRIPTION OF SYMBOLS 10 ... Process unit 11 ... Photosensitive drum 12 ... Charger charger 13 ... Developing device 14 ... Exposure apparatus 21 ... Intermediate transfer belt 25 ... Secondary transfer roller 40 ... Image reading unit (scanner)
T1 to T4: Toner pattern for detecting deviation SE1 ... Area sensor

Claims (5)

A toner image carrier;
Toner image forming means for forming a toner image on the toner image carrier;
Transfer means for transferring a toner image formed on the toner image carrier to a recording medium;
In an image forming apparatus comprising:
The toner image forming means forms a toner pattern for detecting a deviation amount so as to straddle the recording medium and the toner image carrier at a position corresponding to a predetermined end of the recording medium on the toner image carrier;
The deviation amount detection toner pattern is composed of a plurality of groups having a pattern of a predetermined length, and each group has a different arrangement at a predetermined pitch with respect to the predetermined end of the recording medium.
An image forming apparatus.   The image forming apparatus according to claim 1, wherein the plurality of groups are aggregates of bar patterns having the same length.   3. The image forming apparatus according to claim 1, further comprising a detection unit configured to detect the deviation amount detection toner pattern transferred onto the recording medium.   The image forming apparatus according to claim 3, wherein the detection unit is a document image reading apparatus.   3. The image forming apparatus according to claim 1, further comprising a detection unit configured to detect the toner pattern for detecting the deviation amount remaining on the toner image carrier after transfer to the recording medium.

Images