JP2011033926A - Image forming apparatus and control method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for preventing an output of a pattern image which does not faithfully reproduce the width of a line composing the pattern image when the pattern image expressing information such as a bar code is outputted. <P>SOLUTION: Positions are detected for specific portions Pa to Pb of respective pattern images 3a to 3d for detection of position shifting, which are transferred on an intermediate transfer belt 31. Correction processes of position shifting that correct the image forming positions in each of respective photoreceptor drums 11a to 11d is carried out based on the positions of the specific portions Pa to Pd for every pattern image for detection of position shifting 3a to 3d. Furthermore, size of the widths of the specific portions Pa to Pd based on the positions of the specific portions Pa to Pd for every pattern image 3a to 3d for detection of position shifting is calculated, and a confirming process for width reproduction which confirms the reproducing property for the printing width is carried out based on the calculated size of the widths of the specific portions Pa to Pd. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus having a plurality of image carriers on which images of different colors are respectively formed and transferring the images formed on the image carriers in a superimposed manner and a control method therefor.

  2. Description of the Related Art Conventionally, some image forming apparatuses that form an image on a sheet by electrophotography have a plurality of photosensitive drums and can form a color image. In such a color image forming apparatus, an electrostatic latent image of a corresponding color is formed on each of the photosensitive drums, and the electrostatic latent image formed on each of the photosensitive drums is converted into toner by the corresponding color toner. Visualized as an image. The toner images of the respective colors are transferred while being superimposed on the intermediate transfer belt. As a result, a color image is formed on the intermediate transfer belt. This color image is transferred onto the fed paper. The sheet on which the color image is transferred is discharged to the outside through the fixing device.

  When a pattern image representing information such as a barcode is formed using such an image forming apparatus, the reproducibility of lines constituting the pattern image, in particular, fine lines, is important. The reproducibility of fine lines of the pattern image, that is, the print width of the fine lines, is affected by the durability of the photosensitive drum, changes in the environment of the apparatus, changes in process conditions (conditions relating to latent images, development, transfer, and the like). Therefore, in order to maintain the reproducibility of the fine lines of the pattern image without being affected by these effects, a density correction pattern image is formed, and the process conditions and the like are changed based on the formed density correction pattern image. Such a correction method is used (see, for example, Patent Document 1).

JP-A-06-030271

  However, in the conventional image forming apparatus, it is impossible to confirm whether the actually output pattern image faithfully reproduces the width of the lines constituting the desired pattern, so that the pattern image that does not match the desired pattern. May be output.

  An object of the present invention is to provide an image that can prevent the output of a pattern image that does not faithfully reproduce the width of lines constituting the pattern image when outputting a pattern image representing information such as a barcode. It is to provide a forming apparatus and a control method thereof.

  In order to achieve the above object, the present invention forms images of corresponding colors on a plurality of image carriers, and superimposes the images formed on the plurality of image carriers, respectively. An image forming apparatus to be transferred onto the image forming apparatus, wherein each color misregistration detection pattern image having a specific portion having a predetermined width is formed on a corresponding image carrier, and the image is formed on the image carrier. The pattern image forming means for transferring the misregistration detection pattern images formed on the transfer body onto the transfer body at an interval and the pattern image forming means transferred from the predetermined reference position onto the transfer body. A plurality of image carriers based on detection means for detecting the position of a specific part of each positional deviation detection pattern image and the position of the specific part for each positional deviation detection pattern image detected by the detection means; Each shape on top A displacement amount between the images when the formed images are superimposed and transferred onto the transfer body is calculated, and an image forming position on each of the image carriers is corrected based on the calculated displacement amount. A correction processing means for performing a positional deviation correction process, and a width of a specific portion for each positional deviation detection pattern image based on the position of the specific portion for each positional deviation detection pattern image detected by the detection means Confirmation processing means for performing width reproducibility confirmation processing for confirming the reproducibility of the print width based on the calculated width of the specific portion for each of the positional deviation detection pattern images, and the width An image forming apparatus comprising: an output unit that outputs a result of the reproducibility check process.

  The present invention also provides a method for controlling an image forming apparatus in order to achieve the above object.

  According to the present invention, when a pattern image representing information such as a barcode is output, it is possible to prevent the output of a pattern image that does not faithfully reproduce the width of the lines constituting the pattern image.

1 is a longitudinal sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is a longitudinal cross-sectional view which shows the principal part structure of the sensor unit 50 of FIG. It is a block diagram which shows the structure of the control unit 60 of FIG. FIG. 4 is a diagram showing a pulse signal S2 converted from a detection signal S1 from a sensor unit 50 in the pattern detection unit 66 of FIG. It is a figure which shows typically the relationship between the count value which shows the shape of each position shift detection pattern image 3a-3d, and the position of each specific part Pa-Pd, and the registers | resistors D-S of the storage part 67. FIG. It is a figure which shows typically the timing which stores the count value which shows the position of the specific part Pa of the pattern image 3a for position shift detection to corresponding register | resistor DG. It is a flowchart which shows the control procedure at the time of performing the position shift correction process and the width reproduction confirmation process by CPU61 of FIG. It is a figure which shows the shape of the pattern image for other position shift detection.

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

  FIG. 1 is a longitudinal sectional view showing a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view showing the configuration of the main part of the sensor unit 50 of FIG. FIG. 3 is a block diagram showing the configuration of the control unit 60 of FIG. FIG. 4 is a diagram showing a pulse signal S2 converted from the detection signal S1 from the sensor unit 50 in the pattern detection unit 66 of FIG. FIG. 5 is a diagram schematically showing the relationship between the shape of each of the misregistration detection pattern images 3 a to 3 d and the count values indicating the positions of the specific portions Pa to Pd and the registers D to S of the storage unit 67. FIG. 6 is a diagram schematically showing timings at which the count values indicating the positions of the specific portions Pa of the positional deviation detection pattern image 3a are stored in the corresponding registers D to G. Here, a so-called tandem type color image forming apparatus having a plurality of image forming units will be described.

  As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment includes an image reading unit 1a and an image output unit 1b. The image reading unit 1a optically reads an image on a document placed on a platen glass 1c or an image on a document conveyed by an automatic document feeder (not shown), and reads the read image as an image. The data is converted and sent to the image output unit 1b.

  The image output unit 1b includes an image forming unit 10, a feeding unit 20, an intermediate transfer unit 30, a fixing unit 40, two sensor units 50a and 50b, and a control unit 60.

  The image forming unit 10 includes four stations a to d, and each station a to d is an image (toner) of a different color (Y (yellow), M (magenta), C (cyan), K (black)). Image). Specifically, each station a to d includes four photosensitive drums (image carriers) 11 a to 11 d. Here, each of the stations a to d constitutes a pattern image forming unit that forms a positional deviation detection pattern image of each color described later.

  Around the photosensitive drums 11a to 11d, primary chargers 12a to 12d, exposure devices 13a to 13d, folding mirrors 16a to 16d, and developing devices 14a to 14d are arranged, respectively. Each of the exposure apparatuses 13a to 13d emits a laser beam. Each laser beam is irradiated on the surfaces of the corresponding photosensitive drums 11a to 11d through the folding mirrors 16a to 16 so as to expose and scan the surfaces of the corresponding photosensitive drums 11a to 11d. Thus, electrostatic latent images of corresponding colors (Y, M, C, K) are formed on the photosensitive drums 11a to 11d, respectively. The electrostatic latent images formed on the respective photosensitive drums 11a to 11d are developed and carried as toner images of corresponding colors by the corresponding developing devices 14a to 14d.

  The feeding unit 20 includes two feeding cassettes 21 a and 21 b that store paper P and a manual feed tray 27. Each sheet P in each of the feeding cassettes 21a and 21b and the manual feed tray 27 is sent out toward the registration roller pair 25 through the feeding guide 24 by the pickup rollers 22a, 22b and 26 and a plurality of feeding roller pairs 23. It is. The registration roller pair 25 temporarily stops the paper P for skew correction of the paper P, and then sends it to the secondary transfer position Te in accordance with the image forming timing of the image forming unit 10.

  The intermediate transfer unit 30 includes an endless intermediate transfer belt 31 that is stretched around a driving roller 32, a tension roller 33, and a driven roller 34. The intermediate transfer belt 31 constitutes a transfer body to which images formed on the respective photosensitive drums 11a to 11d are transferred. The toner images formed at the stations a to d are sequentially superimposed on the intermediate transfer belt 31 by primary transfer chargers 35 a to 35 d provided at corresponding primary transfer positions Ta to Td, respectively. Transferred (primary transfer).

  The toner image transferred to the intermediate transfer belt 31 is transferred onto the sheet P sent to the secondary transfer position Te by the secondary transfer roller 36 (secondary transfer). The sheet P on which the toner image is transferred is sent to the fixing unit 40.

  The fixing unit 40 includes a fixing roller 41a and a heating roller 41b, and a nip portion for narrowly conveying the paper P is formed between the fixing roller 41a and the heating roller 41b. When the sheet P passes through the nip portion, it is heated and pressurized, and the toner image on the sheet P is fixed to the sheet P. The paper P that has passed through the fixing unit 40 is discharged onto a paper discharge tray 48.

  The sensor unit 50 constitutes detection means for detecting a specific portion of each color misregistration detection pattern image (toner image) primary-transferred onto the intermediate transfer belt 31 in cooperation with a pattern detection unit 66 described later. It is a unit to do.

  As shown in FIG. 2, the sensor unit 50 includes a light emitting diode (hereinafter referred to as LED) 51 and a photodiode (hereinafter referred to as PD) 52. The LED 51 is disposed so as to irradiate light from a position above the center line of the transfer surface (surface on which the toner image is transferred) of the intermediate transfer belt 31 toward a position on the center line of the transfer surface. . The light emitted from the LED 51 is reflected by the transfer surface of the intermediate transfer belt 31, and the reflected light is received by the PD 52. When the PD 52 receives the reflected light, the PD 52 outputs a detection signal S1 indicating the amount of the reflected light to the pattern detection unit 66 described later.

  The control unit 60 is a unit for controlling the entire color image forming apparatus 1 including the operations of the image reading unit 1a and the image output unit 1b. As shown in FIG. 3, the control unit 60 includes a CPU 61, a ROM 63, a RAM 62, a motor driver 64, a sensor unit driver 65, a pattern detection unit 66, and a storage unit 67.

  The CPU 61 controls the operations of the image reading unit 1a and the image output unit 1b according to a program stored in the ROM 63, and executes various processes including a positional deviation correction process and a width reproduction confirmation process, which will be described later. When this control or various processes are executed, the RAM 62 is used as a work area for the CPU 61.

  The motor driver 64 is a driver for driving a plurality of motors such as a motor for driving the feeding roller 23 and a motor for driving the folding mirrors 16a to 16d based on an instruction from the CPU 61. Here, the folding mirrors 16a to 16d can be driven in the direction of changing the optical path length or the optical path of the laser light from the folding mirrors 16a to 16d to the photosensitive drums 11a to 11d by the corresponding motors. It is configured.

  The sensor unit driver 65 is a driver for turning on or off the LED 51 of the sensor unit 50 based on an instruction from the CPU 61.

  Based on the detection signal S1 output from the sensor unit 50, the pattern detection unit 66 generates data (count value of the counter) indicating the position of a specific portion of the misregistration detection pattern image of each color.

  Specifically, when the sensor unit 50 detects a specific portion of the image for detecting the displacement pattern, for example, as shown in FIG. 4, the sensor unit 50 detects a detection signal S1 having a signal portion indicating a light amount equal to or less than a threshold Th. Is output. This detection signal S1 is converted by the pattern detection unit 66 into a pulse signal S2 having a width W corresponding to a signal portion indicating a light amount equal to or smaller than the threshold Th of the detection signal S1.

  Then, the pattern detection unit 66 stores a count value that constitutes position data indicating the position of a specific portion for each positional deviation detection pattern image transferred onto the intermediate transfer belt 31 based on the pulse signal S2. 67. As will be described later, the storage unit 67 includes a plurality of registers D to S, and each register D to S stores a corresponding count value.

  Here, each color misregistration detection pattern image (toner image) has a shape having two specific portions detected by the sensor unit 50, for example, an image 3 a having a “<” shape as shown in FIG. 5. ~ 3d. Here, in each of the color misregistration detection pattern images 3 a to 3 d, the two portions Pa to Pd correspond to specific portions detected by the sensor unit 50. The color misregistration detection pattern images 3 a to 3 d corresponding to the colors K, C, M, and Y are stored in the ROM 63 in advance.

  In the formation and primary transfer of the misregistration detection pattern images 3a to 3d having such a shape, the misregistration detection pattern images 3a to 3d of the respective colors are transferred to the intermediate transfer belt 31 at predetermined intervals. As done. Each of the misregistration detection pattern images 3 a to 3 d transferred to the intermediate transfer belt 31 is sequentially detected by the sensor unit 50.

  For example, it is assumed that the sensor unit 50 detects the positional deviation detection pattern image 3a, and the detection signal S1 output from the sensor unit 50 is converted into a pulse signal S2 as shown in FIG. The pattern detection unit 66 generates a latch timing signal S3 synchronized with the rise and fall of the pulse signal S2, operates the counter in accordance with the latch timing signal S3, and resets it. Then, the count value of the counter is stored in the corresponding registers D to S of the storage unit 67 in synchronization with the latch timing signal S3. In the case of FIG. 6, the count value “0” is stored in the register D. Subsequently, the register E stores the count value “100”, the register F stores the count value “150”, and the register G stores the count value “110”. Thereafter, the count value is similarly stored in the corresponding register.

  Based on the count values stored in the registers D to S of the storage unit 67, the CPU 61 determines the positions (start and end positions) Xm of the specific portions Pa to Pd for each of the misregistration detection pattern images 3a to 3d. m = 1 to 16) is calculated. The positions Xm of the specific portions Pa to Pd of the positional deviation detection pattern images 3a to 3d are positions from the starting end position (reference position) of one specific portion Pa of the positional deviation detection pattern image 3a. Further, based on the count values stored in the registers D to S of the storage unit 67, the widths W (Pa) to W of the specific portions Pa to Pd for the misregistration detection pattern images 3a to 3d, respectively. (Pd) is calculated.

  For example, as shown in FIG. 6, positions X1 to X4 of each specific portion Pa are calculated for two specific portions Pa of the positional deviation detection pattern image 3a. The position X1 is a position corresponding to the count value (= 0) of the register D, and the position X2 is a position corresponding to the count value (= 100) of the register E. The position X3 is a position corresponding to the count value of the register F + the count value of the register E (= 250), and the position X4 is a position corresponding to the count value of G + the count value of the register F + the count value of the register E (= 360). . Also, the width W (Pa) of the two specific portions Pa is calculated. In this case, one width W (Pa) is a size corresponding to the difference (= 100) between the count value of the register E and the count value of the register D. The other width W (Pa) is a size corresponding to the difference (= 110) between the count value of the register G and the count value of the register F.

  The CPU 61 shifts the toner image forming positions on the photosensitive drums 11a to 11d based on the calculated positions Xm (m = 1 to 16) of the specific portions Pa to Pd of the calculated misregistration detection pattern images 3a to 3d. A misalignment correction process is performed to correct. Specifically, based on the position Xm, the amount of deviation between the toner images when the toner images formed on the photosensitive drums 11a to 11d are superimposed and transferred onto the intermediate transfer belt 31 is the photosensitive drum 11a. The toner image forming position is calculated as a reference. Then, based on the calculated deviation amount, settings for performing electrical correction and / or mechanical correction on the toner image forming positions on the photosensitive drums 11a to 11d and control amounts for performing electrical correction and / or mechanical correction. Is set. The electrical correction is to shift the pixel position by shifting the readout timing of the pixels of each color constituting the image to be formed on each of the photosensitive drums 11a to 11d. In the mechanical correction, each folding mirror 16a to 16d is driven by a corresponding motor, and the optical path length or the optical path of the laser light from each folding mirror 16a to 16d to each photosensitive drum 11a to 11d is changed.

  Further, the CPU 61 determines the print width of each color image based on the widths W (Pa) to W (Pd) of the specific portions Pa to Pd of the calculated positional deviation detection pattern images 3a to 3d. A width reproduction confirmation process for confirming reproducibility is performed. Specifically, the calculated widths W (Pa) to W (Pd) of the specific portions Pa to Pd are compared with the reference width stored in the ROM 63, and the result of the comparison is compared. Based on this, it is confirmed whether or not the reproducibility of the print width for each color image is obtained. Here, it is individually compared whether or not the calculated widths W (Pa) to W (Pd) of the specific portions Pa to Pd match the reference width stored in the ROM 63, respectively. Then, it is confirmed for each color whether or not the reproducibility of the print width is obtained.

  The positional deviation correction process and the width reproduction confirmation process are performed at an arbitrary timing, for example, at the time of power-on, before starting the formation of an image including a pattern representing information such as a barcode.

  Control performed by the CPU 61 when performing the positional deviation correction process and the width reproduction confirmation process will be described with reference to FIG. FIG. 7 is a flowchart showing a control procedure when the positional deviation correction process and the width reproduction confirmation process by the CPU 61 of FIG. 3 are performed. The procedure shown in the flowchart of FIG. 7 is executed by the CPU 61 in accordance with a program stored in the ROM 63.

  When performing the positional deviation correction process and the width reproduction confirmation process, as shown in FIG. 7, the CPU 61 first controls the drive roller 32 to drive the intermediate transfer belt 31 to rotate (step S1). . Then, the CPU 61 performs control so as to perform the formation of the positional deviation detection pattern images 3a to 3d on the photosensitive drums 11a to 11d and the transfer of the positional deviation detection pattern images 3a to 3d onto the intermediate transfer belt 31. (Step S2).

  Next, the CPU 61 controls the LED 51 of the sensor unit 50 to be lit through the sensor unit driver 65 in order to start detection of the positions of the specific portions Pa to Pd for the positional deviation detection pattern images 3a to 3d. (Step S3). Then, the CPU 61 waits for the detection of the positions of the specific portions Pa to Pd for each of the misregistration detection pattern images 3a to 3d by the pattern detection unit 66 to end (step S4). In the sensor unit 50, when the LED 51 is turned on, the detection signal S1 is output from the PD 52 to the pattern detection unit 66, and the detection signal S1 is converted into a pulse signal S2. Then, the count values indicating the positions of the specific portions Pa to Pd for each of the misregistration detection pattern images 3a to 3d are stored in the corresponding registers D to S of the storage unit 67 in accordance with the pulse signal S2.

  When the detection of the positions of the specific portions Pa to Pd for each of the positional deviation detection pattern images 3a to 3d is completed, the CPU 61 controls the LED 51 of the sensor unit 50 to be turned off via the sensor unit driver 65 (Step S1). S5). Then, the CPU 61 controls to stop the driving roller 32 and stop the rotation of the intermediate transfer belt 31 (step S6).

  Next, the CPU 61 performs the above-described misregistration correction process (step S7), and subsequently performs the above-described width reproduction confirmation process (step S8). Then, the CPU 61 outputs and displays the result of the width reproduction confirmation process on, for example, a display unit (not shown) (step S9), and ends this process.

  As described above, the positional deviation correction process can eliminate the deviation between the toner images when the toner images formed on the respective photosensitive drums 11 a to 11 d are superimposed and transferred onto the intermediate transfer belt 31. In addition, it is possible to know whether or not the reproducibility of the print width is obtained for each color by the width reproducibility confirmation process. As a result, when outputting an image including a pattern representing information such as a barcode, it is possible to prevent the output of a pattern image that does not faithfully reproduce the print width of lines constituting the pattern image, in particular, fine lines. Can do.

  In the present embodiment, an image having a “<” shape as shown in FIG. 5 is used as the misregistration detection pattern image of each color. Instead, for example, as shown in FIG. An image 80 having a “cross” shape can also be used.

  When the misregistration detection pattern image 80 having such a “cross” shape is used, the widths of the two specific portions 81 and 82 of the misregistration detection pattern image 80 can be detected. That is, in addition to the width W (81) in the sub-scanning direction, the width W (82) in the main scanning direction can be detected, and a pattern image representing information such as a barcode is formed. It is possible to confirm whether or not the print width of the line to be reproduced can be reproduced more faithfully.

  In the present embodiment, a configuration of a batch transfer system using an intermediate transfer belt 31 as a transfer member is shown. Instead of this, it goes without saying that the principle of the present invention can also be applied to a multiple transfer system using a transfer material conveying belt serving as a transfer material conveying means for conveying the paper P.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1b Image output apparatus 11a-11d Photosensitive drum 31 Intermediate transfer belt 50 Sensor unit 51 LED
52 PD
61 CPU
63 ROM
66 Pattern detector 67 Storage unit

Claims (2)

An image forming apparatus that forms images of corresponding colors on a plurality of image carriers, and superimposes the images formed on the plurality of image carriers, and transfers the images onto a transfer member,
A misregistration detection pattern image of each color having a specific portion with a predetermined width is formed on a corresponding image carrier, and a misregistration detection pattern image formed on each of the image carriers. A pattern image forming means for transferring the image onto the transfer body at intervals,
Detecting means for respectively detecting the position of a specific portion of each of the misregistration detection pattern images transferred onto the transfer body from a predetermined reference position;
Based on the position of the specific portion for each of the misregistration detection pattern images detected by the detection means, the images formed on the plurality of image carriers are superimposed and transferred onto the transfer body. Correction processing means for calculating a shift amount between the images at the time, and performing a shift correction process for correcting an image forming position in each of the image carriers based on the calculated shift amount;
Based on the position of the specific portion for each of the misregistration detection pattern images detected by the detecting means, the width of the specific portion for each of the misregistration detection pattern images is calculated, and the calculated misalignment Confirmation processing means for performing width reproducibility confirmation processing for confirming the reproducibility of the print width based on the width of the specific portion for each detection pattern image;
An image forming apparatus comprising: an output unit that outputs a result of the width reproducibility check process. A method of controlling an image forming apparatus, wherein images of corresponding colors are formed on a plurality of image carriers, and the images formed on the plurality of image carriers are superimposed and transferred onto a transfer member. There,
A misregistration detection pattern image of each color having a specific portion with a predetermined width is formed on a corresponding image carrier, and a misregistration detection pattern image formed on each of the image carriers. A step of transferring onto the transfer body at intervals;
Detecting each position of a specific portion of each misalignment detection pattern image transferred onto the transfer body from a predetermined reference position;
Based on the position of the specific portion for each of the detected positional deviation detection pattern images, each of the images formed on the plurality of image carriers is superimposed and transferred onto the transfer body. Calculating a displacement amount between the images, and performing a displacement correction process for correcting an image forming position in each of the image carriers based on the calculated displacement amount;
Based on the detected position of the specific portion for each of the misregistration detection pattern images, the width of the specific portion for each of the misregistration detection pattern images is calculated, and the calculated misregistration detection pattern A step of performing a width reproducibility confirmation process for confirming the reproducibility of the print width based on the width of the specific portion for each image;
And a step of outputting a result of the width reproducibility confirmation processing.