JP2009198997A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To output an image with no positional deviation without lowering continuous printing speed by carrying out alignment during continuous printing. <P>SOLUTION: An image forming apparatus comprises: an image forming part for superposing a plurality of monochromatic images to form a multicolor image, and forming a positional deviation-correcting pattern between the adjacent monochromatic image-forming sections; positional deviation detecting sensors 14, 15 and an alignment controller 203 for detecting the amount of positional deviation by optically reading the positional deviation-correcting pattern; and a system controller 201 for correcting the positional deviation of the image based on the amount of positional deviation detected by the positional deviation detecting sensors 14, 15. When the positional deviation-correcting pattern is a monochromatic linear pattern and the amount of positional deviation detected by the alignment controller 203 exceeds a preset threshold, the system controller 201 interrupts the continuous image formation by the image forming means and corrects the positional deviation of the image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a copying machine, a printer, a facsimile having a function of detecting and correcting a positional deviation of each color image of a color image created by superimposing a plurality of color images, and a digital having these functions combined. The present invention relates to an image forming apparatus such as a multifunction peripheral.

  In a color image forming apparatus that forms a multi-color image, unlike a black and white image, the images of each color are overlapped. Therefore, if the image position of each color is shifted, the color of the line drawing or character changes, or the color shift or image unevenness occurs. (Color unevenness) occurs. The occurrence of such deviation and unevenness leads to a decrease in image quality. Therefore, it is necessary to match the image positions of the respective colors as much as possible. For this reason, in an image forming apparatus that forms a color image using a plurality of photoconductors, there is a technique for correcting a positional shift between colors caused by various factors, such as a change in environmental temperature and a change in internal temperature. Patent Documents 1 and 2 disclose this.

  Among these, Patent Document 1 includes an LD unit that is controlled to be lit in accordance with image data, and a pixel clock generation unit that variably controls the phase of a lighting control clock (hereinafter referred to as pixel clock) of the LD unit. In a light beam writing apparatus that performs writing by scanning a light beam output from an LD unit on an image carrier that rotates or moves in a horizontal direction, the pixel clock generation unit sets the phase of the pixel clock to 1 in one cycle of the pixel clock. It is disclosed that the image magnification in the main scanning direction on the image carrier is corrected by changing it at one or a plurality of positions in the main scanning direction in units of / n (n is an integer of 2 or more).

Patent Document 2 includes a plurality of image forming units that form images of different colors, and records images of different colors formed by the plurality of image forming units directly or via an intermediate transfer member. In a color image forming apparatus that forms a color image by transferring onto a medium, the registration error detection pattern formed by each of the image forming units is transferred onto the same pattern detection member, and the pattern detection The registration error correction operation executing means for detecting the registration error detection pattern transferred on the member and executing the registration error correction operation, and the start condition of the registration error correction operation by the registration error correction operation executing means are arbitrarily set. Start condition setting means that can be set, and registration deviation correction operation execution conditions change from temperature at power-on and return from low-power mode Or, it is disclosed that determined by the number of printed sheets after the correction operation performed last.
JP 2004-295083 A JP 2003-149905 A

  In the invention described in Patent Document 1, the time when the light beam scans between the first light detection means and the second light detection means in the main scanning direction is counted at the start of printing, and writing is performed based on the count value. The main scanning magnification is corrected by changing the frequency, and the time between the first light detecting means and the second light detecting means is counted between sheets of continuous printing, and the phase of the writing frequency is changed. However, since only the main scanning magnification is corrected, there is a problem that an image having the sub-scanning image position cannot be obtained.

  Further, in the invention described in Patent Document 2, the registration misalignment correction operation execution condition is set, and the registration misalignment correction cannot be executed during continuous printing.

  Therefore, the problem to be solved by the present invention is to perform alignment during continuous printing, and to output an image without positional deviation without reducing the continuous printing speed.

  In order to solve the above problem, the first means is a pattern for forming a misregistration correction pattern between an image forming means for superposing a plurality of single color images to form a multicolor image and an adjacent single color image forming section. A misregistration detection unit that optically reads the formed misregistration correction pattern to detect a misregistration amount; and an image misregistration based on the misregistration amount detected by the misregistration detection unit. In the image forming apparatus, the misregistration correction pattern is a single-color linear pattern, and a misregistration amount detected by the misregistration detection unit is set to a preset threshold value. And a control unit that interrupts the continuous image formation by the image forming unit and corrects the positional deviation of the image by the correction unit. To.

  The second means includes a counting means for counting the number of continuous image formations in the first means, and the control means presets the positional deviation amount and the number of continuous image formations counted by the counting means. When the threshold value is exceeded, the continuous image formation by the image forming unit is interrupted, and the image misregistration is corrected by the correcting unit.

  The third means compares the temperature detection means for detecting the ambient temperature with the temperature detection means for detecting the ambient temperature and the ambient temperature at the time of detecting the misregistration detection pattern created between the papers. Comparing means, and when the comparison result between the positional deviation amount and the temperature compared by the comparing means exceeds a preset threshold value, the control means performs a continuous image by the image forming means. The formation is interrupted and the image misalignment is corrected by the correction means.

  A fourth means includes a counting means for counting the number of continuously formed images, a temperature detecting means for detecting an ambient temperature, and a monochrome image forming section adjacent to the ambient temperature at the start of continuous printing. Comparing means for comparing the ambient temperature at the time of detecting the position of the misregistration correction pattern formed on the control unit, and the control means includes the misregistration amount, the number of continuous image formations, and the ambient temperature. When all the comparison results exceed a preset threshold value, the continuous image formation by the image forming unit is interrupted, and the image misregistration is corrected by the correcting unit.

  A fifth means is the second or fourth means, wherein the counting means counts the number of printed sheets after alignment is performed, and the continuous image formation number is the number of sheets after the correction of the image misalignment by the correcting means. It is characterized by that.

  In the embodiments described later, the image forming unit is the image forming unit 1, the pattern forming unit is the image forming unit 1 and the system controller 201, the misregistration correction patterns are denoted by reference numerals 21 and 22, and the misregistration detecting unit is The first and second misregistration detection sensors 14 and 15 and the alignment controller 203, the correction means to the alignment controller 203 and the system controller 201, the control means to the system controller 201, and the counting means to the print number counter 17 The temperature detection means corresponds to the temperature sensor 19, and the comparison means corresponds to the system controller 201.

  According to the present invention, when the misregistration correction pattern is a single-color linear pattern and the misregistration amount exceeds a preset threshold, continuous image formation is interrupted and the misregistration of the image is corrected. Therefore, alignment can be performed during continuous printing, and an image without positional deviation can be output without reducing the continuous printing speed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating a configuration of a main part of a color image forming apparatus according to Example 1 of the present embodiment. This color image forming apparatus is a so-called direct transfer tandem color image forming apparatus. In the following description, Y, M, C, and K added after the reference numerals shown in the figure correspond to the colors yellow, magenta, cyan, and black, respectively. The subscript indicating is omitted.

  The image forming apparatus PR includes four image forming units 1 that form different colors, that is, a first station (Y) 1Y, a second station (M) 1M, a third station (C) 1C, and a fourth station ( K) 1K is provided, and each of these stations 1Y, 1M, 1C, 1K is arranged on a straight line along an image conveying belt 8 (hereinafter referred to as a conveying belt). Each image forming unit 1 is arranged around a photosensitive drum 2 that functions as an image forming medium, the photosensitive drum 2, and includes a charging device 3, an exposure device 4, a developing device 5, and a cleaning device 6. .

  The conveyor belt 8 is rotationally driven in the direction of arrow A by a roller 9 provided as one drive roller and the other as a driven roller. The surface of the photosensitive drum 2 is uniformly charged by the charging device 3 and then exposed by a pattern corresponding to an image to be output by the exposure device 4, and an electrostatic latent image is formed on the surface of the photosensitive drum 2. The The electrostatic latent image formed on each photoconductor drum 2 is developed by the developing device 5, and a toner image of each color is formed on each photoconductor drum 2.

  The recording paper 10 is fed out from the paper feed tray 11 and is conveyed by the conveyor belt 8 to the first station (Y) 1Y, the second station (M) 1M, the third station (C) 1C, and the fourth station (K). 1K is sequentially passed, and the respective color toner images formed on the respective photosensitive drums 2 at the respective transfer positions 7 are sequentially transferred and superimposed on the same position of the recording paper 10. In this way, one full-color image is obtained by superimposing four-color images. The recording paper 10 to which the four color toner images have been transferred is peeled off from the conveying belt 8, fixed by the fixing device 12, and discharged outside the apparatus.

  The toner remaining on the surface of the photosensitive drum 2 after the transfer of the color toner images formed on the photosensitive drums 2 is removed by the cleaning device 6 to prepare for the next image forming cycle.

  FIG. 2 is a perspective view showing the main part in FIG. 1, here the conveying belt 8 and the photosensitive drum 2. 2, the arrow B indicates the main scanning direction orthogonal to the moving direction of the conveying belt 8, and the arrow C indicates the sub-scanning direction parallel to the moving direction of the conveying belt 8. ing.

  FIG. 3 is a diagram showing a detection configuration of a misregistration detection pattern. FIG. 3 is obtained by adding a configuration in which a detection pattern is formed on the conveyor belt 8 and the detection pattern is optically detected by a detection device. A first and second light-reflective sensor composed of a light-emitting part and a light-receiving part is formed by forming the positional deviation detection patterns 21 and 22 on the conveying belt 8 at two locations in the main scanning direction by the respective photosensitive drums 2. The position deviation detection sensors 14 and 15 detect the analog signals, and convert the detected analog signals into digital signals by an A / D converter to obtain voltage values. An alignment controller 203 (to be described later) calculates the position of the position shift detection pattern from the acquired voltage value, and calculates a position shift correction amount. The image after the positional deviation correction amount calculation is formed by reflecting the newly calculated correction amount. The misregistration detection patterns 21 and 22 are formed by the image forming unit 1 writing a pattern composed of a single monochrome line in the sheet interval 8b in accordance with an instruction from the system controller 201. The length and width of the pattern are arbitrary, and are determined in consideration of the resolution of the displacement detection sensors 14 and 15 and the amount of consumed toner.

  FIG. 4 is a schematic configuration diagram of an image formation control unit in the image forming apparatus, and shows a light beam scanning device and an optical unit in addition to the image formation control unit. The light beam scanning device is the exposure device 4 shown in FIG. 1, and in this embodiment, the light beam scanning device is a light beam scanning device that scans and writes the surface of the photosensitive drum 2 with laser light.

  The light beam scanning device 4 includes first and second synchronization detection sensors 44-1 and 44-2 that detect light beams at both ends in the main scanning direction, and the light beams that have passed through the fθ lens 43 are first and first. 2 are reflected by the mirrors 45-1 and 45-2, are collected by the first and second lenses 46-1 and 46-2, and enter the first and second synchronization detection sensors 44-1 and 44-2. It is configured.

  The image formation control unit includes a system controller 201, a pixel clock generation unit 202, an alignment controller 203, a synchronization detection lighting control unit 204, an LD control unit 205, and a polygon motor drive control unit 206. Although there is one system controller 201 for a plurality of colors, each of the other colors has the same one. The pixel clock generator 202 further includes a reference clock generator 2021, a VCO (Voltage Controlled Oscillator) clock generator 2022, and a phase-synchronized clock generator 2023. In addition, as described above, the first synchronization detection sensor 44-1 for detecting the light beam on the image writing side at the end portion in the main scanning direction of the light beam scanning device 4 emits light on the image writing end side at the end portion in the main scanning direction. A second synchronization detection sensor 44-2 for detecting the beam is provided, and the light beam transmitted through the fθ lens 123 as described above travels on the first and second synchronization detection sensors 44-1, 44-2. When passing, it enters the first and second synchronization detection sensors 44-1 and 44-2, and the alignment controller 203 receives the start-side synchronization detection signal XDETP from the first synchronization sensor 44-1. The end-side synchronization detection signal XEDETP is input from each of the synchronization sensors 44-2.

  The synchronization detection signal XDETP output from the first synchronization detection sensor 44-1 is input to the pixel clock generation unit 202, the synchronization detection lighting control unit 204, and the alignment controller 203, and the pixel clock generation unit 202 The pixel clock PCLK synchronized with the synchronization detection signal XDETP is generated and sent to the LD control unit 205 and the synchronization detection lighting control unit 204.

  The pixel clock generation unit 202 includes a reference clock generation unit 2021, a VCO (Voltage Controlled Oscillator) clock generation unit 2022, and a phase synchronization clock generation unit 2023.

  A VCO clock generation unit (PLL circuit: Phase Locked Loop) 2022 inputs a reference clock signal FREF from the reference clock generation unit 2021 and a signal obtained by dividing VCLK by N by a 1 / N divider 20221 to a phase comparator 20222. The phase comparator 20222 compares the falling edges of both signals and outputs an error component at a constant current. Then, unnecessary high-frequency components and noise are removed by an LPF (low-pass filter) and sent to the VCO. The VCO outputs an oscillation frequency that depends on the output of the LPF. Accordingly, the frequency of VCLK can be changed by variably controlling the frequency of FREF and the frequency division ratio N from the printer control unit 201. The phase synchronization clock generation unit 2023 generates a pixel clock PCLK synchronized with the synchronization detection signal XDETP from the VCLK generated by the VCO clock generation unit 2022.

  Further, the end-side synchronization detection signal XEDETP output from the second synchronization detection sensor 44-2 is input to the alignment controller 203. The alignment controller 203 measures the time from the falling edge of the start side synchronization detection signal XDETP to the falling edge of the end side synchronization detection signal XEDETP, compares it with the reference time difference, and changes the pixel clock frequency by the difference. Correct the image magnification.

  The synchronization detection lighting control unit 204 first turns on the LD forced lighting signal BD to forcibly light the LD in order to detect the synchronization detection signal XDETP. However, after detecting the synchronization detection signal XDETP, the synchronization detection signal XDETP is detected. Using the XDETP and the pixel clock PCLK, the LD is turned on at a timing at which the synchronization detection signal XDETP can be reliably detected without causing flare light, and the LD is turned off when the synchronization detection signal XDETP is detected. A signal BD is generated and sent to the LD control unit 205.

  The LD control unit 205 controls the lighting of the LD according to the image data synchronized with the synchronous detection forced lighting signal BD and the pixel clock PCLK. Then, a laser beam is emitted from the LD unit 42, reflected and deflected by the mirror surface of the polygon mirror 41, passes through the fθ lens 43, and scans on the photoreceptor 40.

  The polygon motor control unit 206 controls rotation of the polygon motor that rotationally drives the polygon mirror 41 at a specified number of rotations based on a control signal from the printer control unit 201.

  The first and second misregistration detection sensors 14 and 15 for detecting the image misregistration correction pattern are light reflection type optical sensors, and image pattern information detected by the sensors 14 and 15 is sent to the system controller 201. Sent. The system controller 201 calculates a positional deviation amount based on the image pattern information 21 and 22, generates correction data, and stores it in a correction data storage unit (not shown). The correction data storage unit stores correction data for correcting image position deviation and magnification deviation, that is, data for determining the timing of the XLGATE and XFGATE signals, and data for determining the frequency of the pixel clock PCLK. In accordance with an instruction from 201, correction data is set in each control unit.

  FIG. 5 is a diagram illustrating a misregistration detection pattern formed in the non-image forming unit. An image area 8a on which the recording paper 10 is electrostatically adsorbed and an image is transferred is set on the conveyance belt 8, and each color is placed at a position in the sub-scanning direction X [mm] from the rear end in the conveyance direction of the image area 8a. The misregistration detection patterns 21 and 22 are created and detected by the misregistration detection sensors 14 and 15. The position where the misregistration detection patterns 21 and 22 are formed is a so-called paper interval 8b. The misregistration detection patterns 21 and 22 are monochromatic, and are composed of diagonal lines or one line parallel to the main scanning direction. The example shown in FIG. 3 is an example of a general pattern.

  FIG. 6 is a block diagram showing a circuit configuration of the positional deviation correction circuit. In the figure, the misregistration correction circuit is mainly composed of the alignment controller 203 and the system controller 201 also shown in FIG. The alignment controller 203 receives an output from the converter 16 that performs A / D conversion on outputs from the position deviation detection sensors 14 and 15 and a write start signal for each page. The alignment controller 203 and the system controller 201 are connected to a printed sheet counter 17, a time measuring unit (timer) 18, and a temperature sensor 19 so as to be able to send and receive signals to each other. As a result, the count value of the printed sheet counter 17, the measured value at the time measuring unit 18, and the temperature detected by the temperature sensor 19 are input to the alignment controller 208 and the system controller 201.

  The system controller 201 creates misregistration detection patterns 21 and 22 for each page in the sheet space 8b in the print image area. The alignment controller 203 detects the time from the output time of the write start signal to the detection of the misalignment pattern of each station 1Y, 1M, 1C, 1K. This time is measured by the time measuring unit 18.

First station detection time t1 [sec]
Second station detection time t2 [sec]
3rd station detection time t3 [sec]
Station 4 detection time t4 [sec]
Then, the time difference between each station can be calculated from the detected time. The time difference between the first station 1Y and the second, third and fourth stations 1M, 1C, 1K is
tx2_1 = t2-t1
tx3_1 = t3-t1
tx4_1 = t4−t1
The time difference between the second station 1M and the third and fourth stations 1C, 1K is
tx3_2 = t3-t2
tx4_2 = t4−t2
The time difference between the third station 1C and the fourth station 1K is
tx4_3 = t4−t3
It becomes.

Assuming that the theoretical values of the write timing differences between stations are t2_1 [sec], t3_1 [sec], t4_1 [sec], t3_2 [sec], t4_2 [sec], t4_3 [sec], the theoretical value and the actual measurement value Ty1 = tx2_1−t2_1
ty2 = tx3_1-t3_1
ty3 = tx4_1-t4_1
ty4 = tx3_2−t3_2
ty5 = tx4_2−t4_2
ty6 = tx4_3-t4_3
Is a time difference indicating the amount of positional deviation between the stations.

  The alignment controller 203 compares the amounts of misalignment, and requests the system controller 201 to execute alignment when a predetermined threshold value tt [sec] or more is reached. When the system controller 201 receives the alignment execution request, the printing is temporarily suspended, the alignment is executed, and the printing is resumed after the alignment is completed.

  FIG. 7 is a diagram showing a state of misalignment for explaining misalignment detection in the sub-scanning direction. FIG. 9A shows the case where the misregistration detection pattern is shaded (21, 22), and FIG. 9B shows the case where the displacement detection pattern is a horizontal line (21 ', 22'). In the figure, the half-dotted pattern is a pattern when no positional deviation occurs, and the white pattern is a pattern when a positional deviation occurs. 7A shows the main scanning deviation, sub-scanning deviation, main and sub-scanning deviation states from above, and FIG. 7B shows the main scanning deviation, sub-scanning deviation, main and sub-scanning deviation states. , Respectively.

  From FIG. 7, in the case of the hatched pattern, even when a main scanning deviation occurs, a deviation of x1 [msec] occurs at the detection timing of the positional deviation detection sensor as compared to when there is no positional deviation. Therefore, the amount of deviation can be calculated from the detection time (x1 [msec]) and the linear velocity of the conveyor belt 8.

When a shift occurs only in the sub-scanning direction, and a shift occurs in both the main scanning direction and the sub-scanning direction, timing shifts of x2 [msec] and x3 [msec] occur, respectively. Including the case where only the direction is displaced,
Position shift amount = time shift time (time difference) × position shift amount can be calculated from the linear velocity of the conveyor belt.

  That is, the actual deviation amount is obtained by multiplying the time difference indicating the positional deviation amount between the stations by the linear velocity of the conveyor belt 8.

  In the case of a horizontal line, as shown in FIG. 7B, if a positional shift occurs in the sub-scanning direction, for example, if it is only sub-scanning, for example, y2 [msec], and if it is in both main and sub-scanning directions, y3 [ msec], the actual deviation amount can be calculated by multiplying the deviation amount of the detection time by the linear velocity of the conveying belt 8 as in the case of the oblique line. However, as can be seen from the upper diagram of FIG. 7B, in the case of a shift only in the main scanning direction, there is no change in the detection time in the sub-scanning direction, so this embodiment for detecting the shift time in the sub-scanning direction. The position detection amount cannot be detected by the form detection method.

  FIG. 8 is a diagram for explaining detection of misalignment in the main scanning direction. FIG. 4A shows the relationship between the write clock and the written line immediately after alignment, FIG. 4B shows the case where the count value is large, and FIG. 4C shows the case where the count value is small. In each case, when a line for 3 clocks is drawn, the line position is shifted in the write start direction when the count value is large ((b) in the figure), and in the direction opposite to the write start direction when the count value is small. . As a result, the magnification changes and color misregistration occurs.

  In the main scanning magnification correction during printing, the count value (for example, N0) between the two points when the alignment is performed and the count value (for example, N0) between the two points that are executed during printing (for example, The difference from N1) is referred to as a positional deviation amount.

Further, this embodiment is configured to execute the alignment control based on the number of printed sheets.
The alignment execution timing is when the positional deviation amount becomes larger than a preset amount. For this reason, the alignment controller 203 stores the count value Ps of the printed sheet counter 17 in a non-illustrated nonvolatile memory at the start of printing. The system controller 201 counts up the printed sheet counter 17 every time printing is completed. The alignment controller 203 acquires the count value Ps of the print counter 17 when the positional deviation amount is equal to or greater than a preset threshold value tt [sec], and the count value Pp of the print number counter 17 at the start of printing and the position. A difference from the count Ps when the deviation amount exceeds the threshold value tt is taken, and when the difference is equal to or larger than a preset threshold value Pt, the system controller 201 is requested to execute alignment.

  Upon receiving the alignment execution request from the alignment controller 203, the system controller 201 temporarily stops printing, executes alignment, and resumes printing after the alignment is completed. Note that the count value Ps of the print counter 17 when the misregistration amount is equal to or greater than a preset threshold value tt [sec] is also stored in the nonvolatile memory.

  FIG. 10 is a flowchart showing a processing procedure of the system controller 201 when a registration execution request is received. As can be seen from the flowchart of FIG. 10, when the system controller 201 receives the alignment execution request from the alignment controller 203 (step S <b> 301), the system controller 201 stores that the alignment execution request has been received. At the end of printing, the system controller 201 confirms whether or not an alignment execution request has been received (step S302). If an alignment execution request has been received, alignment is executed (step S303) and stored. The received alignment execution request reception information is deleted (step S304).

  On the other hand, the user can set whether or not to perform alignment during continuous printing. FIG. 11 is a flowchart showing a control procedure when the user sets whether or not alignment is possible.

  This process is started when the user sets whether or not the alignment is executed during continuous printing using an operation unit (not shown). Therefore, when the system controller 201 receives the alignment execution request, the system controller 201 acquires the set alignment execution condition (step S401). If the alignment execution condition is executed during continuous printing (step S401) (Step S402-Yes), printing is temporarily interrupted (Step S403), alignment is executed (Step S404), and printing is resumed after completion of alignment (Step S405). On the other hand, when the alignment execution condition is after the end of continuous printing (step S402-No), the fact that the alignment execution request has been received is stored in the nonvolatile memory (step S406). At the end of printing, as shown in the flowchart of FIG. 10, when the system controller 201 has received an alignment execution request (steps S301 and S302), the system controller 201 executes alignment (step S303) and stores it. The received alignment execution request reception information is deleted (step S304).

  Note that the processes of FIGS. 10 and 11 are similarly executed in other embodiments including the second and third embodiments.

As described above, according to this embodiment,
1) Since an execution condition for misregistration correction is determined based on the misregistration calculation amount based on the misregistration detection pattern, it is possible to perform alignment during continuous printing before a significant deviation and output an image without misregistration. can do.
2) Since the misregistration calculation amount is determined by combining the misregistration calculation amount based on the misregistration detection pattern with the continuous printing number, it is possible to reduce the number of times the alignment is performed, thereby improving productivity. Can do.
3) Since the misregistration calculation amount is determined by combining the misregistration calculation amount based on the misregistration detection pattern with the number of continuous prints after the alignment has been performed, it is possible to reduce the number of times the alignment is performed. Can be improved.
4) Since alignment is not executed during continuous printing, printing output can be performed without reducing productivity during continuous printing.
5) Since it is possible to set whether or not the alignment is executed during continuous printing by the user's selection, the user can select whether to place importance on image quality or productivity, thereby improving operability. it can.
6) A single line misregistration detection pattern is created in a single color that does not require a gap between sheets, and alignment is executed during continuous printing based on the misregistration amount calculated by reading the pattern. Thus, it is possible to determine an appropriate alignment execution condition without lowering. Further, by performing alignment based on the alignment execution condition, it is possible to output an image without positional deviation.
There are effects such as.

In this embodiment, the alignment control is executed based on the temperature change.
The alignment controller 203 stores the detected temperature Ts [° C.] of the temperature sensor 19 in a non-illustrated non-volatile memory at the start of printing. The alignment controller 203 acquires the detected temperature Tp [° C.] of the temperature sensor 19 when the positional deviation amount is equal to or greater than a preset threshold value tt [sec], and the temperature Ts [° C.] at the start of printing and the position A difference between the temperature Tp [° C.] when the deviation amount is equal to or greater than a preset threshold value tt [sec] and the detected temperature Tp [° C.] is obtained, and the difference is set to a preset threshold value Tt [ If it is equal to or higher than [° C.], the system controller 201 is requested to execute alignment.

  Upon receiving the alignment execution request from the alignment controller 203, the system controller 201 temporarily stops printing, executes alignment, and resumes printing after the alignment is completed. Note that the detected temperature Tp [° C.] of the temperature sensor 19 when the positional deviation amount is equal to or greater than a preset threshold value tt [sec] is also stored in the nonvolatile memory. Further, the system controller 201 executes the processing shown in FIG. 10, executes alignment at the end of printing, and erases the stored alignment execution request reception information.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

As described above, according to this embodiment,
1) Since the temperature deviation is determined by combining the temperature condition with the main scanning magnification correction amount and the positional deviation calculation amount based on the positional deviation detection pattern, it is possible to reduce the number of alignment executions, thereby improving productivity. Can be improved.
2) Since the positional deviation calculation amount is determined by combining the positional deviation calculation amount based on the positional deviation detection pattern with the temperature condition after the alignment is performed, it is possible to reduce the number of times that the alignment is performed. Improvements can be made.
There are effects such as.

  This embodiment is an example in which the alignment control is executed based on the number of printed sheets and the temperature change, and corresponds to a combination of the first and second embodiments.

  FIG. 9 is a flowchart showing a processing procedure in the present embodiment. In this embodiment, as shown in the flowchart of FIG. 9A, the alignment controller 203 stores the count value Ps of the printed sheet counter 17 and the temperature Ts [° C.] of the temperature sensor 19 at the start of printing. (Step S101).

  When calculating the amount of displacement, processing is performed as shown in the flowchart of FIG. That is, when the positional deviation amount is equal to or larger than the preset threshold value tt [sec] (step S201—Yes), the alignment controller 203 acquires the count value Pp of the printed sheet counter, and the difference between Pp and Ps is When it is equal to or higher than the preset threshold value Pt (step S202—Yes), the temperature Tp [° C.] of the temperature sensor is acquired, and the difference between Tp [° C.] and Ts [° C.] is set to the preset threshold value Tt [° C. ] If it is above (step S203-Yes), a positioning execution request is transmitted to the system controller 201 (step S204). Upon receiving the alignment execution request from the alignment controller 203, the system controller 201 temporarily stops printing, executes alignment, and resumes printing after the alignment is completed.

  Further, the system controller 201 executes the processing shown in FIG. 10, executes alignment at the end of printing, and erases the stored alignment execution request reception information.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

  As described above, according to the present embodiment, since the misregistration calculation amount based on the misregistration detection pattern is combined with the continuous printing number and the temperature condition to determine the misregistration correction execution condition, the number of alignment executions is reduced. This makes it possible to improve productivity.

  In this embodiment, main scanning magnification correction is executed during printing.

  In this embodiment, first, the alignment controller 203 clears the main scanning magnification correction amount Xs to 0 when executing magnification correction at the start of printing. Next, the system controller 201 requests the alignment controller 203 to execute main scanning magnification correction during printing during continuous printing. Upon receiving a printing main scanning magnification correction execution request from the system controller 201, the alignment controller 203 executes main scanning magnification correction and adds the main scanning magnification correction amount to Xs.

  The alignment controller 203 performs alignment with the system controller 201 when the amount of positional deviation is equal to or greater than a preset threshold value tt [sec] and the added main scanning magnification correction amount Xs is equal to or greater than a preset threshold value Xt. Request execution. Upon receiving the alignment execution request, the system controller 201 temporarily stops printing and executes alignment, and resumes printing after completion of alignment.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

  As described above, according to the present embodiment, the execution condition of the misregistration correction is determined based on the main scanning magnification correction amount and the misregistration calculation amount based on the misregistration detection pattern. It is possible to perform alignment, and an image without positional deviation can be output.

This embodiment is another example in which main scanning magnification correction is executed during printing.
In this embodiment, first, the alignment controller 203 clears the main scanning magnification correction amount Xc to 0 and stores it in a non-illustrated non-volatile memory when performing alignment. Next, the alignment controller 203 adds the correction amount to the main scanning magnification correction amount Xc and saves it in the nonvolatile memory when executing the main scanning magnification correction during printing. If the positional deviation amount is equal to or greater than a preset threshold value tt [sec] and the added main scanning magnification correction amount Xc is equal to or greater than a preset threshold value Xt, the alignment controller 203 determines that the system controller 201 Request alignment execution.
When the system controller 201 receives a registration execution request from the registration controller 203, the system controller 201 suspends printing and executes registration, and resumes printing after the registration is completed.
Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

In the fourth and fifth embodiments, when the misregistration detection pattern is a linear pattern 21 ′, 22 ′ in a direction orthogonal to the sub-scanning direction as shown in FIG. 12, in other words, a direction parallel to the main scanning direction. This is a preferable processing example. Note that the misregistration detection patterns shown in FIG. 12 correspond to the misregistration detection patterns 21 ′ and 22 ′ shown in FIG. 7B.
In place of the fourth and fifth embodiments, it is possible to request the execution of alignment based on the result of predicting the shift amount. That is, the alignment controller 203 determines that if the sub-scanning deviation amount that can be calculated based on the time difference and the positional deviation amount predicted from the correction amount of the main scanning magnification correction are equal to or greater than the threshold value tt [sec] and the threshold value Xt, respectively. It is also possible to request the registration execution.

As described above, according to this embodiment,
1) Since the misregistration correction execution condition is determined based on the main scanning magnification correction amount and the misregistration calculation amount based on the misregistration detection pattern after the alignment is performed, the alignment is executed during continuous printing before a large deviation. This makes it possible to output an image with no positional deviation.

2) Since the position shift pattern is calculated only in the sub-scanning direction, the inter-page distance (paper interval) can be shortened by changing the pattern shape. This makes it possible to form an image more efficiently.
There are effects such as.

  This embodiment is a modification of the fifth embodiment. That is, in the fifth embodiment, the alignment controller 203 adds the correction amount to the main scanning magnification correction amount Xc and stores it in the nonvolatile memory when executing the main scanning magnification correction during printing. If the main scanning magnification correction amount Xc is equal to or greater than a preset threshold value Xtp, the system controller 201 is requested to create a single color misregistration detection pattern.

  When the system controller 201 receives a monochrome misregistration detection pattern creation request, the system controller 201 creates a monochromatic misregistration detection pattern between pages until printing ends or alignment is executed.

  If the misalignment amount is equal to or greater than a preset threshold value tt [sec] and the added main scanning magnification correction amount Xc is equal to or greater than the preset threshold value Xt, the alignment controller 203 determines that the system controller 201 Request alignment execution. When the system controller 201 receives a registration execution request from the registration controller 203, the system controller 201 suspends printing and executes registration, and resumes printing after the registration is completed.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

  According to the present embodiment, since the misregistration pattern detection condition is set after it is predicted that an image misalignment has occurred from the main scanning magnification correction amount, the number of pattern outputs can be reduced, and toner consumption due to pattern output can be reduced. Can be reduced.

  This embodiment is an example in which misalignment correction is performed based on the time from the start of printing. That is, in the seventh embodiment, the alignment controller 203 acquires the start time Times [sec] from the time measurement unit at the start of printing and stores it. When the positional deviation amount is equal to or greater than a preset threshold value tt [sec], the alignment controller 203 acquires a time Timp [sec] when the positional deviation amount is equal to or greater than the threshold value from the time measurement unit 18, and the time Timp [ When the difference between sec] and the start time Times [sec] is equal to or greater than a preset threshold value Timt [sec], an alignment execution request is output to the system controller 201.

  When the system controller 201 receives a registration execution request from the registration controller 203, the system controller 201 suspends printing and executes registration, and resumes printing after the registration is completed.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

  As described above, according to the present embodiment, since the misregistration calculation amount based on the misregistration detection pattern is combined with the continuous printing number, the temperature condition, and the operation time, the misregistration correction execution condition is determined. This makes it possible to reduce the number of times, thereby improving productivity.

  This embodiment is an example in which misalignment correction is performed based on the time when alignment is executed. In other words, the alignment controller 203 acquires the time Timeout [sec] at the time of execution from the time measurement unit 18 at the time of alignment, and stores it in a nonvolatile memory (not shown). The alignment controller 203 acquires a time Timp [sec] when the positional deviation amount is equal to or greater than a preset threshold value tt [sec], and obtains the time Timp [sec] and the position. When the difference from the time Timeout [sec] at the time of alignment is equal to or greater than a preset threshold value Time [sec], an alignment execution request is output to the system controller 201.

  When the system controller 201 receives the alignment execution request, the printing is temporarily interrupted to execute the alignment, and the printing is resumed after the alignment is completed.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

  As described above, according to the present embodiment, the misregistration correction execution condition is determined by combining the misregistration calculation amount based on the misregistration detection pattern with the number of continuously printed sheets after the alignment is performed, the temperature condition, and the operation time. It is possible to reduce the number of executions of alignment, thereby improving productivity.

  In this embodiment, as shown in FIGS. 2 and 3, the misregistration detection patterns 21 and 22 are created on the recording paper transport belt 8, and the misalignment detection formed on the recording paper transport belt 8 is detected. However, the tandem type image forming apparatus shown in FIG. 1 includes a direct transfer type and an indirect transfer type, and indirect transfer. In this case, the misregistration detection pattern is written on the intermediate transfer belt, and the misregistration detection pattern on the intermediate transfer belt is detected to perform the same misregistration correction control. Executed.

  The present invention is not limited to this embodiment, and includes all technical matters included in the technical idea of the invention described in the claims.

1 is a schematic configuration diagram illustrating a configuration of a main part of a color image forming apparatus according to Example 1 of the present embodiment. FIG. 2 is a perspective view illustrating a relationship between a conveyance belt, which is a main part in FIG. 1, and a photosensitive drum. It is a figure which shows the detection structure of the pattern for position shift detection. FIG. 2 is a schematic configuration diagram of an image formation control unit in the image forming apparatus. It is a figure which shows the pattern for position shift detection formed in the non-image formation part. It is a block diagram which shows the circuit structure of a position shift correction circuit. It is a figure which shows the state of the position shift for demonstrating the position shift detection of a subscanning direction. It is a figure for demonstrating the position shift detection of the main scanning direction. 10 is a flowchart illustrating a processing procedure in the third embodiment. It is a flowchart which shows the process sequence of a system controller when a position alignment execution request is received. It is a flowchart which shows the control procedure when a user sets the positioning possibility. It is a figure which shows the example which formed the pattern for position shift detection as a linear pattern of the direction parallel to the main scanning direction.

Explanation of symbols

1 Image forming unit 4 Exposure device (light beam scanning device)
8 Conveying belt 8a Image area 8b Paper interval 14, 15 Sensor for detecting misalignment 16 A / D converter 17 Printed sheet counter 18 Time measuring unit (timer)
19 Temperature sensor 21, 22 Misalignment detection pattern 201 System controller 202 Pixel clock generator 203 Positioning controller

Claims (5)

Image forming means for forming a multicolor image by superimposing a plurality of single color images;
Pattern forming means for forming a misregistration correction pattern between adjacent monochrome image forming sections;
A displacement detection means for optically reading the formed displacement correction pattern and detecting a displacement amount;
Correction means for correcting the positional deviation of the image based on the positional deviation amount detected by the positional deviation detection means;
In an image forming apparatus comprising:
The misregistration correction pattern is a monochromatic linear pattern,
Control means for interrupting continuous image formation by the image forming means and correcting the positional deviation of the image by the correction means when the amount of positional deviation detected by the position deviation detection means exceeds a preset threshold value An image forming apparatus comprising: The image forming apparatus according to claim 1.
Provided with a counting means for counting the number of continuous image formation,
The control unit interrupts the continuous image formation by the image forming unit when the positional deviation amount and the number of continuous image formations counted by the counting unit exceed a preset threshold, and the correction unit An image forming apparatus characterized in that the positional deviation of the image is corrected. The image forming apparatus according to claim 1.
Temperature detecting means for detecting the ambient temperature;
Comparison means for comparing the ambient temperature at the start of continuous printing and the ambient temperature at the time of detecting a misregistration detection pattern created between papers;
With
The control unit interrupts continuous image formation by the image forming unit when the comparison result between the positional deviation amount and the temperature compared by the comparing unit exceeds a preset threshold, and the correcting unit An image forming apparatus characterized in that the positional deviation of the image is corrected. The image forming apparatus according to claim 1.
A counting means for counting the number of continuous image formations;
Temperature detecting means for detecting the ambient temperature;
A comparison means for comparing the ambient temperature at the start of continuous printing and the ambient temperature at the time of position detection of a misregistration correction pattern formed between adjacent monochrome image forming sections;
With
The control means interrupts the continuous image formation by the image forming means when all of the comparison results of the positional deviation amount, the number of continuous image formation sheets, and the ambient temperature exceed a preset threshold value. An image forming apparatus, wherein the image misregistration is corrected by the correcting means. The image forming apparatus according to claim 2 or 4,
The counting means counts the number of printed sheets after alignment is performed,
2. The image forming apparatus according to claim 1, wherein the number of continuous image formations is the number of images after correction of image misregistration by the correction unit.

Images