JP2011197099A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the shift amount of the whole transfer belt without degrading productivity during continuous printing in a technology for forming a toner pattern image for correcting color shift on the transfer belt.SOLUTION: Each of a plurality of image forming means 103 has an optical unit and a photoreceptor for each toner color. The image forming means 103 forms the pattern image for correcting position shift at intervals of a process in which a toner image generated from print data is formed on the transfer belt 33. Assuming that a region between toner images generated from the two print data in the transfer belt 33 is "between the images", the image forming apparatus includes: a means 102 for obtaining position information between the images; and a means 101 for measuring the amount of position shift based on detection results obtained by reading the pattern for correcting position shift and on the position information between the images.

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for forming an image of a toner pattern for color misregistration correction on a transfer belt.

  In an electrophotographic image forming apparatus, a deviation may occur when toner images of respective colors are overlapped to form an image due to deformation of parts due to environmental changes and individual variations of parts. Therefore, a specific pattern is formed, and the amount of deviation is measured by detecting the pattern. Further, in a system that forms an image by superimposing each color on the transfer belt, the belt thickness and elongation are different at each location of the transfer belt, so a pattern for one round of the belt is formed and the deviation is measured. The deviation is suppressed by feeding back the measured deviation amount to the image forming timing.

  Since the correction control as described above takes time, it is considered that pattern image formation is performed between images during continuous printing to improve productivity during printing (for example, Patent Document 1).

  However, the above-described conventional correction control has the following problems because correction control is performed between images being printed. That is, in this correction control, a pattern is formed on the transfer belt at the timing between images, and the pattern is detected, but the distance and position between images depends on the type of image being printed and the printing conditions. Due to various differences, the position of the belt on which the pattern is formed cannot be specified, and the amount of deviation for one rotation of the transfer belt cannot be measured appropriately.

  In view of the above circumstances, an object of the present invention is to provide an image forming apparatus capable of appropriately measuring the shift amount of the entire transfer belt without reducing productivity during continuous printing.

  In order to achieve the above object, the present invention provides an image forming apparatus comprising: a plurality of image forming units each having an optical unit and a photoconductor for each toner color; and a transfer belt on which a toner image is formed by the image forming unit. The image forming unit is a unit that forms an image of a misregistration correction pattern on the transfer belt at an interval of processing for forming a toner image generated from print data on the transfer belt. Further, assuming that an area between the toner images generated from the two print data on the transfer belt is an inter-image area, an inter-image position information acquiring means for acquiring position information between the images, and the position A positional deviation amount measuring means for measuring the positional deviation amount based on the detection result obtained by reading the deviation correction pattern and the positional information between the images. Wherein, there is provided an image forming apparatus.

  According to the present invention, it is possible to provide an image forming apparatus capable of appropriately measuring the deviation amount of the entire transfer belt without reducing productivity during continuous printing.

1 is a diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. It is a schematic diagram which shows the structure of the transfer part of this embodiment. It is a functional block diagram of the principal part of this embodiment. FIG. 6 is a diagram illustrating an example of a deviation amount table storing positional deviation data associated with positional information on the transfer belt 33. It is a timing chart of the control signal at the time of continuous printing in this embodiment. It is a flowchart (the 1) which shows the flow of deviation | shift amount measurement control in this embodiment. It is a figure which shows an example of the deviation | shift amount table at the time of detecting abnormality at the time of continuous printing. It is a schematic diagram for demonstrating the color shift correction of this embodiment. 6 is a timing chart of a control signal when a printing speed is changed in the embodiment. It is a flowchart (the 2) which shows the flow of deviation | shift amount measurement control in this embodiment.

Embodiments of the present invention will be described below. In this embodiment, when detecting the amount of deviation for one belt revolution during continuous printing, in short, the belt position information corresponding to the images being continuously printed is acquired, and a pattern is formed between the images being continuously printed. The belt position where the deviation amount is measured is specified.
Hereinafter, the features described above will be described in detail with reference to the drawings.

FIG. 1 shows a configuration example of an image forming apparatus according to the present embodiment.
As shown in the figure, the image forming apparatus according to the present embodiment includes the photosensitive members 1-a, 1-b, 1-c, 1-d (hereinafter collectively “photosensitive”) for each color (four in this example). A transfer belt 33 in contact with the photosensitive member, and LD devices 3-a, 3-b, 3-c, 3-d for irradiating the photosensitive member 1 of each color with laser diode light, A sensor 4 for reading the density of the toner image on the transfer belt 33, transfer rollers 5-a and 5-b for transferring the toner image to the paper, and a fixing unit for fixing the toner image on the paper by applying heat to the toner image. Rollers 6-a and 6-b, a paper tray 7 for setting paper, a paper feed roller 8 for feeding the paper set in the paper tray 7 to the transfer unit, and confirming whether the paper has been fed. Registration sensor 9 and a transport roller 10 for transporting the paper to the transfer unit a, 10-b, paper discharge rollers 11-a, 11-b for discharging the paper to the outside of the apparatus, paper discharge sensor 12 for checking whether the paper is discharged from the apparatus, and heat to the fixing roller The heater 13, a cleaning unit 14 for cleaning toner on the transfer unit, and a toner box 15 for storing toner removed from the transfer unit. Further, although the toner cartridge is not shown, it is assumed that it is installed adjacent to each of the photosensitive 1-a, 1-b, 1-c and 1-d.

  A mechanism such as a sensor related to the transfer belt 33 in FIG. 1 and the transfer belt 33 are hereinafter referred to as a “transfer portion”.

FIG. 2 shows a configuration example of the transfer unit. FIG. 3 is a functional block diagram centering on the arc transfer portion.
As shown in FIG. 2, the transfer unit includes a transfer belt 33, a secondary transfer unit 34, and a driving roller 35. The transfer belt 33 is an endless belt to which a toner image is transferred from a developing device that develops the toner image. The secondary transfer unit 34 is a mechanism for transferring the image transferred on the transfer belt 33 to a sheet. The drive roller 35 is a mechanism that drives the transfer belt 33. Further, it is assumed that the reading sensor 36 that reads the misregistration correction pattern transferred onto the transfer belt 33 is fixed to the housing in a non-contact state with the transfer belt 33.

  FIG. 2 shows a state in which the toner images 37a and 37b at the time of continuous printing are transferred onto the transfer belt 33 and the positional deviation correction pattern 42 is transferred between the images 39. A section 40 represents a section in which the misregistration correction pattern 42 is written.

  The image forming unit 103 in FIG. 3 calculates the timing between the images, and writes the misalignment correction pattern 42 in a specific section between the images 39. The misregistration correction pattern 42 written between the images 39 is detected by the reading sensor 36 and stored as misregistration data. When storing the positional deviation data, the positional information on the transfer belt 33 is stored in association with each other. This position information is acquired by the inter-image position information acquisition unit 102 according to the procedure described below.

  The position of the misregistration correction pattern 42 written between the images 39 on the transfer belt 33 is specified by using the distance 38 of the belt that has traveled from the adjustment start image writing timing to the misalignment correction pattern 42 formation timing. . That is, the belt position corresponding to the image is acquired (calculated) from the image writing timing during continuous printing, the image length in the image feed direction, and the printing speed, and the belt position where the pattern between the images is formed is specified. According to this method for specifying the belt position, a mechanism for specifying the position of the pattern is unnecessary, and therefore, it can be realized without increasing the cost.

  On the other hand, as a more accurate position specifying method, there is a method of specifying using the marks 43 and 44 and the reading sensor 45 arranged in an area not used for image formation on the transfer belt 33.

  The marks 43 and 44 are arranged in advance, for example, at equal intervals. The mark 43 has a pattern different from that of the other marks 44, and the position of each mark on the transfer belt 33 is specified. For example, if the position deviation correction pattern 42 is read by the reading sensor 36 when the fifth mark 44 is read after reading the mark 43, the position of the position deviation correction pattern 42 is the fifth mark. It can be identified as corresponding to position 44. Since the marks 43 and 44 are arranged in advance, the absolute position of the misregistration correction pattern 42 on the transfer belt can be specified.

  In the present embodiment, since the absolute position on the transfer belt of the misregistration correction pattern 42 can be specified using the position specifying mark as described above, it is easy to specify the position when the adjustment is interrupted. Furthermore, since the mark is fixed on the transfer belt 33, the accuracy of the specified position is high.

  In the following description, the belt misalignment correction pattern 42 written between the images 39 on the transfer belt 33 using the distance 38 of the belt that has traveled from the image start timing of adjustment start to the position misalignment correction pattern 42 formation timing. A description will be given on the assumption that the position of the position is specified.

FIG. 3 shows a functional block diagram of the main part of the present embodiment.
As shown in the figure, the main part of the present embodiment is configured to include reading sensors 36 and 45, an inter-image position information acquisition unit 102, a positional deviation amount measurement unit 101, and an image forming unit 103 with a transfer belt 33 as a center. . As described with reference to FIG. 2, the inter-image position information acquisition unit 102 uses “the distance 38 of the belt traveled from the image writing timing to the pattern formation timing” or the position specifying marks 43 and 44. Position information between images. The misregistration amount measurement unit 101 calculates the misregistration amount based on at least the detection result obtained by reading the misregistration correction pattern 42 and the inter-image position information acquired by the inter-image positional information acquisition unit 102. Measure and output to image forming means 103. The image forming unit 103 executes actual correction processing (described later with reference to FIG. 5 and the like) based on the positional deviation amount.

FIG. 4 shows an example of a deviation amount table in which positional deviation data associated with positional information on the transfer belt 33 is stored.
The deviation amount table shown in FIG. 4 is a table that stores the deviation amount measurement state of each position of the belt and the measured deviation amount. The above table is updated when measurement of the deviation amount between images during continuous printing is started. This table is created for each color. The “relative position (mm)” described in the deviation amount table is a distance from the image writing timing during continuous printing at the time when deviation amount measurement is started (that is, distance 38 in FIG. 2). is there. “Measurement state” is information indicating whether or not the deviation amount of the corresponding section has been measured. The “deviation amount” indicates how much a certain color is displaced in the image feed direction.

  For example, if the distance 38 shown in FIG. 2 is 750 mm and the interval between images is 300 mm, the position corresponding to the interval between images is 750 mm to 1050 mm from the image writing timing. When a table corresponding to this position is searched, No. Since it can be seen that it is 9, 10, 11, the deviation measurement pattern is drawn at positions of 800 mm, 900 mm, and 1000 mm from the image writing timing, and the deviation amount is measured. The measured result is the corresponding No. Save it at the location corresponding to.

When the belt is rotated one or more times from the image writing timing, it cannot be searched in the above table. Therefore, the cumulative transport distance D from the image writing timing is stored, the cumulative travel distance D and the belt one-round length S, image Using the belt rotation speed N at the writing start time, the relative position RD is obtained as follows.
RD = D-S * N

Next, timing control during continuous printing by the image forming unit 103 will be described.
FIG. 5 shows a timing chart of control signals during printing. In FIG. 5, an image generation signal 50 is for generating print data while active. The pattern generation signal 51 generates shift amount detection pattern data while active. The mark read signal 52 is a data signal obtained by irradiating the mark with light and quantizing the amount of reflection.

  When the start-up operation of each device is completed after the print instruction, the image generation signal 50 is activated and exposure is started. When the exposure for the image length is completed, the image generation signal 50 is made negative and the image generation is ended. The timing for making the pattern generation signal 51 active is the timing described in the embodiment of the deviation amount table. In the case of the above condition, if the belt conveyance speed is 100 mm / s, the time 53 from the image formation timing shown in the figure to the timing when the pattern generation signal 51 is activated is 800/100 = 8 seconds. Therefore, the pattern generation signal is activated 8 seconds after the image formation timing. If the distance from the exposed photoconductor position to the pattern reading sensor is 500 mm, the time from the pattern formation to the pattern reaching the reading sensor is 500 mm / 100 = 50 seconds. Accordingly, the pattern reading timing 54 is 50 seconds after the pattern formation, and reading is started at that timing.

  Next, the flow of deviation amount measurement control during continuous printing will be described. Refer to the flowchart of FIG.

  First, the deviation amount table is created based on the previous image formation timing between images whose deviation amounts are to be measured. At this time, the position where the deviation amount is detected is created so as to compensate for one belt revolution. In the example of the table, the table is created by setting the interval for measuring the deviation amount to 100 mm and the distance of one round of the belt to 2000 mm. (Step S101)

  The belt position between the target images is acquired (calculated) from the previous image formation timing between the target images and the image length. For example, if the distance 38 shown in FIG. 2 is 750 mm and the interval between images is 300 mm, the position corresponding to the interval between images is 750 mm to 1050 mm from the image writing timing. (Step S102)

  A measurement section corresponding to the interval between the images obtained in step S102 is searched from the table. Details are described in the description of the deviation amount table, and thus will be omitted. (Step S103)

  An image to be printed is formed with the image signal turned on, and the image signal is turned off at the timing when the image length ends. It is determined from the table obtained in step S102 whether or not the pattern generation timing is between images. When the formation timing is reached, the pattern generation signal is turned ON, the pattern is formed, and the pattern generation signal is turned OFF when the pattern length ends. To do. Although not described in the flow, the formed measurement pattern is detected by the pattern reading sensor and stored in the table as a deviation amount. (Steps S104 to S108)

  If the measurement in the measurement section corresponding to the interval between the images obtained in step S103 has been completed, the measurement of the shift amount between the images ends. If the measurement in the measurement section corresponding to the interval between the images has not been completed, the process returns to step S106, and pattern formation and displacement amount detection are performed. (Step S109)

  When the printing operation is finished, the measurement between images is finished, but it is also assumed that the measurement for one round of the belt is not completed, for example, when the number of printed sheets is small. When the printing is finished, the deviation amount table is searched, and if the measurement is completed at all the belt positions, the deviation amount measurement ends. If there is an unmeasured section, a detection pattern is formed and corrected for the unmeasured section. (Steps S110-113)

  If the amount of shift between images is not updated, the gap between the images is biased to a specific position on the belt, so the image formation timing during the next printing is delayed and the gap between the images corresponds to the unmeasured position. Change to (Steps S114-115)

Next, deviation correction control when abnormality is detected during continuous printing will be described.
FIG. 7 shows an example of a deviation amount table when an abnormality is detected during continuous printing.
When detecting the amount of misalignment between images during continuous printing, if for some reason an error such as paper conveyance failure occurs in the device, the printing operation and the amount of misalignment will be Resume measurement. Since the relative distance in the deviation amount table is based on the image writing timing, the printing operation is restarted in accordance with the image writing timing when restarting. In order to obtain the image writing timing before stopping, the belt travel distance S from the image writing timing before stopping is stored. Stopping because the relationship between the relative distance of the table of deviation and the image formation timing becomes correct by resuming continuous printing at the timing when the belt travel distance S becomes an integral multiple of the belt circumference. You can resume the measurement you were doing before.

The color misregistration correction in the present embodiment is realized by the image forming unit 103 controlling the image forming timing.
FIG. 8 is a schematic diagram for explaining color misregistration correction according to the present embodiment.
When a color misregistration amount is detected by forming a pattern between images during continuous printing, if the position where the color misregistration amount is acquired matches the image formation timing, the image formation timing is corrected. Whether or not the position where the color misregistration amount is acquired coincides with the timing of image formation is determined using the timing exposed from the LD device 46 and the distance 47 on the photosensitive member from the exposed point to the transfer belt. To do. If the exposure start position reaches the transfer belt from the distance 47 and the rotational speed of the photosensitive member, the time required to reach the transfer belt is calculated. If the shift amount table is searched for the position 48 on the transfer belt at that time, the shift amount is known. The image formation timing of each color is corrected.
The printing speed is changed by controlling the image forming timing as described above.

  FIG. 9 is a timing chart of control signals when the printing speed is changed. 9 are a print start signal 55, a print speed state 58, an image generation signal 50, a pattern generation signal 51, and a mark reading signal 52 in order from the top.

  The print start signal 55 is a signal that changes the state of the image forming apparatus to the print state when activated. A printing speed state 58 represents a printing speed state. The image generation signal 50 is a signal for generating print data while active. The pattern generation signal 51 is a signal for generating shift amount detection pattern data while active. The mark read signal 52 is a data signal obtained by irradiating the mark with light and quantizing the amount of reflection.

  When the printing speed changes during continuous printing, the shape of the pattern formed between images is changed according to the speed. The printing speed information is determined when the printing start signal 55 becomes active. In the timing chart of FIG. 9, when the print start signal 55 is active 56, the printing speed is operating at the normal speed 59, and the speed is decreased from the normal speed starting from the print request of the active 57 (speed 60). This is an example. As shown in the generation signal 62 compared with the generation signal 61 between the images in a state where the printing speed is lowered, the pattern generation interval is widened and the pattern shape is read as the read pattern 63 even if the printing speed is changed. The pattern 64 is controlled to be the same.

The flow of processing from the measurement of the deviation amount to the correction using the deviation amount described so far is performed during continuous printing. Therefore, time-consuming color misregistration correction can be performed during continuous printing, and productivity can be improved. However, the image forming apparatus according to the present embodiment does not measure the deviation amount only during continuous printing, but can also measure the deviation amount from the standby time for image forming processing or the like. This configuration realizes further improvement in productivity.
The flow of processing for shifting from the deviation amount measurement during standby to the deviation amount measurement between images will be described below. Refer to the flowchart of FIG.

  When measuring a deviation amount during standby, first, a belt position serving as a reference for measuring the deviation amount is stored. The deviation amount table is created for each distance from the reference position (displacement amount measurement reference position). When the creation of the deviation amount table is completed, the position of the belt is confirmed, and if the pattern generation timing is reached, pattern formation is performed. (Steps S201 to S205)

  After pattern formation is completed, the table is searched, and if there is no print request and there is an unmeasured section, the flow from step S203 is repeated. However, if a print request is received, the measurement of the deviation amount during standby ends. Before entering the adjustment flow between images being printed, the first image forming position is set as the shift amount measurement reference position. By doing so, the relative distance of the deviation amount table in the middle of measurement can be applied as it is during printing. When this processing is completed, the flow proceeds to a measurement flow between images (FIG. 6).

33 Transfer belt 34 Secondary transfer unit 35 Drive roller 36, 45 Reading sensor 37a, 37b Toner image 39 Between images 40 Section 42 Misalignment correction pattern 43, 44 Mark 101 Misalignment measuring means 102 Interimage position information obtaining means 103 Image forming means

JP 2006-171352 A

Claims (10)

An image forming apparatus comprising: a plurality of image forming units each having an optical unit and a photoreceptor for each toner color; and a transfer belt on which a toner image is formed by the image forming unit,
The image forming unit is a unit that forms an image of a misregistration correction pattern on the transfer belt at an interval of a process for forming a toner image generated from print data on the transfer belt.
further,
When the area between the toner images generated from the two print data on the transfer belt is an inter-image, an inter-image position information acquisition unit that acquires position information between the images;
A positional deviation amount measuring means for measuring a positional deviation amount based on a detection result obtained by reading the positional deviation correction pattern and positional information between the images;
An image forming apparatus comprising:   The misregistration amount measuring unit calculates a belt position corresponding to an image from an image writing timing during continuous printing, an image length in an image feeding direction, and a printing speed, and specifies a belt position where a pattern between images is formed. The image forming apparatus according to claim 1.   The positional deviation amount measuring means forms a pattern during continuous printing, associates the belt position where the deviation amount is detected with the measured deviation amount, stores it as a deviation amount table, and forms the pattern when forming the pattern. The image forming apparatus according to claim 2, wherein a search is made from a table to determine whether the amount of deviation is measured.   The positional deviation amount measuring means searches for whether or not the deviation amount of the belt position where the pattern is formed has been measured when forming a pattern during continuous printing, and determines whether or not the pattern is formed. The image forming apparatus according to claim 3.   4. The image forming apparatus according to claim 3, wherein the positional deviation amount measuring unit delays a next image formation timing when the deviation amount of the deviation amount table is not updated.   The misregistration amount measuring means stores the belt position at the time when the abnormality occurs when an abnormality occurs during continuous printing and the printing operation is stopped while detecting the misalignment amount during continuous printing. The image forming apparatus according to claim 1, wherein a shift amount measurement start position is specified when the amount detection is resumed.   The misregistration amount measuring unit corrects the image formation timing of each color when an image forming position on the transfer belt corresponds to a position where the misregistration amount is measured when an image is formed during continuous printing. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the positional deviation amount measuring unit switches a pattern to be formed when the printing speed is changed during continuous printing.   The positional deviation amount measuring means searches the table when continuous printing ends, and if there is a position where the deviation amount is not detected, a pattern is formed at a position where the deviation amount is not detected after printing is completed. 4. The image forming apparatus according to claim 3, wherein a deviation amount is measured.   The positional deviation amount measuring means interrupts measurement of the deviation amount and starts a printing operation when there is a print instruction when measuring the deviation amount for one rotation of the belt continuously during standby. The image forming apparatus according to claim 1, wherein the shift amount is measured by using the image forming apparatus.

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