JP2008090215A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of forming an image free from omission of image information and unnecessary blank by making images coincide with paper in full bleed printing. <P>SOLUTION: Two patterns are formed on an image carrier, and an interval between the two is detected. The results of the detection are given to a control system as feedback. Thereby, the moving speed of the image carrier is set to a prescribed value. In addition, the results of the detection of the speed of paper conveyance are given to a conveyance system as feedback. Thereby, the speed of paper conveyance is set to a proper value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of full bleed printing.

  In an image forming apparatus that forms an image on a sheet, it is necessary that the image be formed at a correct position on the sheet.

  A technique for controlling the image position and the image size corresponding to the paper size has been developed.

  For example, Patent Document 1 includes an image data size detection unit that detects the size of image data and a paper size detection unit, and controls the magnification of the image based on the detection result of both detection units to obtain the paper size. It has been proposed to form an image.

  Japanese Patent Application Laid-Open No. 2004-228561 proposes that a sheet fed from a manual sheet feeding unit is detected by a detection unit, and the length in the sheet conveyance direction is detected from the detection time and the sheet conveyance speed.

In Patent Document 3, in double-sided image formation, a dimensional change of a paper on which a back image is formed is detected, and image data for the back image is processed according to the dimensional change to adjust a scaling factor to form a back image. Has been proposed.
JP 9-312753 A JP 2005-53622 A JP 2004-347842 A

  In normal printing of a document or the like, an image in which a margin H is provided around the image G is formed on the paper P as shown in FIG.

  On the other hand, in full bleed printing, the image G is formed on the entire surface of the paper P without margins as shown in FIG. Note that the relationship between the image G and the paper P in full bleed printing is shown in FIGS.

  In full bleed printing, it is necessary that the image G and the paper P completely coincide with each other. If the image G protrudes from the paper P as shown in FIG. In addition, when the edge of the image G enters the inside of the paper P as shown in FIG. 1D, an unnecessary margin is formed and the print quality is deteriorated. Even if such missing information and unnecessary margins are in mm units, the print quality is degraded.

  In the conventional image forming apparatus, the image G and the paper P are not matched with the accuracy required in full bleed printing.

  The position of the image formed on the paper may be shifted due to an error of the apparatus, and may also be shifted due to an error in the size or shape of each sheet, resulting in the above-described problems in full bleed printing. End up.

  For example, in Patent Document 1, since the size of image data only corresponds to the standard paper size such as A4 and B4, it cannot correspond to the size variation between individual papers. 1 (c) and (d) cause a deviation between the image and the paper.

  In Patent Document 2, the paper size is detected, but control to match the image size is not performed.

  In Patent Document 3, in double-sided image formation, image formation corresponding to a change in paper length is performed at the time of backside image formation. However, there is no correction for variations in the size and shape of each paper used, and FIG. The problems in full bleed printing as in (c) and (d) cannot be solved.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of forming an image without a part of information or generating an unnecessary margin in full bleed printing.

The object is achieved by the following invention.
1.
Image carrier,
Drive means for driving the image carrier;
Image forming means for forming an image on the image carrier;
Transfer means for transferring an image on the image carrier to paper;
Pattern forming means for forming at least two patterns at a reference interval on the image carrier;
Pattern detection means for detecting the formed pattern;
Conveying means for conveying the sheet to a transfer position of the transfer means;
A sheet detecting means for detecting a sheet conveyed by the conveying means; and
Having control means,
The control means controls the drive means based on a time difference between detection signals of at least two patterns detected by the pattern detection means so that the moving speed of the image carrier becomes a specified value,
An image forming apparatus, wherein the conveyance speed of the conveyance unit is controlled so that a time difference between a sheet leading edge detection signal and a sheet trailing edge detection signal of the sheet detection unit becomes a specified value.
2.
2. The image forming apparatus as described in 1 above, wherein the image carrier is a photoconductor.
3.
2. The image forming apparatus according to 1 above, wherein the image carrier is an intermediate transfer member.
4).
4. The image forming apparatus according to claim 1, further comprising an image carrier speed adjustment mode for adjusting a moving speed of the image carrier.
5.
The image forming apparatus according to any one of claims 1 to 4, further comprising a conveyance speed adjustment mode for adjusting the conveyance speed.
6).
The image forming apparatus according to any one of 1 to 5, further comprising a storage unit that stores the conveyance speed.
7).
7. The image forming apparatus according to 6, wherein the conveyance speed stored in the storage unit is rewritable.
8).
8. The image forming apparatus according to any one of 1 to 7, further comprising a mode in which image formation is performed by adjusting the conveyance speed, and the mode can be set by an operator.

  In the present invention, a pattern is formed on the image carrier, and the moving speed of the image carrier is adjusted using the formed pattern, and the conveyance speed is adjusted for each sheet. Accordingly, in full bleed printing, it is possible to form an image that matches the image and the paper and that lacks a part of the image or has no unnecessary margins.

  The present invention will be described below with reference to embodiments shown in the drawings, but the present invention is not limited to the embodiments.

  FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention.

  An image forming unit, that is, a charging device 2, an exposure device 3, and a developing device 4 are arranged around a photosensitive member 1 as an image carrier, and a transfer separation device 5 and a cleaning device 6 are further arranged. Reference numeral 11 denotes a fixing device, and reference numeral 12 denotes a re-feeding path through which a sheet is conveyed when the back side image is formed.

  The sheet P is conveyed from the registration roller 7 to a transfer position where the transfer separation device 5 faces the photoreceptor 1.

  The paper P is stored in the paper feed trays 10A, 10B, and 10C, and is fed to the registration roller 7 from any one of the paper feed cassettes.

  In image formation, an electrostatic latent image is formed on the photoreceptor 1 by charging by the charging device 2 and exposure by the exposure device 3, and the formed electrostatic latent image is developed by the developing device 4 and then on the photoreceptor 1. A toner image is formed.

  The formed toner image is transferred onto the paper P by the transfer separation device 5.

  The surface of the photoreceptor 1 after the transfer is cleaned by a cleaning device 6.

  The registration roller 7 conveys the paper P to the transfer position in synchronization with the exposure by the exposure device 3, whereby a toner image is formed at a predetermined position on the paper P.

  In the case of performing full bleed printing, an adjustment process for adjusting the sheet conveyance speed in accordance with the moving speed of the photosensitive member is executed prior to such an image forming process.

  FIG. 3 is a block diagram of the control system.

  The control means 20 rotates a drum motor 24 as a drive means for driving the image carrier at a predetermined speed, and controls the exposure device 3 as a pattern forming means to pattern the pattern on the photoconductor 1 at a predetermined timing. Form.

  The control means 20 activates a registration motor 22 that rotates the registration roller 7 in synchronization with the exposure of the exposure apparatus 3 and conveys the paper P. At the transfer position of the transfer / separation device 5, an image is formed at a specified position on the paper P where the image on the photoreceptor 1 is transferred onto the paper P.

  As will be described below, the control means 20 uses a signal from the IDC sensor 8 as a pattern detection means for detecting a pattern formed on the photoreceptor 1 and a signal from the paper sensor 9 as a paper detection means for detecting paper. Based on this, the registration motor 22 and the drum motor 24 are controlled using the timer 20a of the control means 20, and the position of the image on the paper P is adjusted.

  The IDC sensor 8 is a sensor that detects the density of an image on the photoconductor 1 and detects a pattern formed on the photoconductor. Further, pulse motors are used as the registration motor 22 and the drum motor 24, and the rotation speed is adjusted by frequency control.

  Hereinafter, the adjustment of the image position on the paper P will be described with reference to FIGS. 4 shows the speed adjusting process of the photosensitive member, FIG. 5 shows the paper conveying speed adjusting process, and FIG. 6 shows the image forming process.

  In STEP 1 of FIG. 4, the drum motor 24 is driven to rotate at a constant speed. The constant speed control in STEP 1 is a control to make the speed constant using an encoder provided in the motor.

  In STEP 2, the line 1 is formed in the shape of the photosensitive member 1 by exposure of the exposure device 3. The line-shaped pattern 1 and the pattern 2 on the line to be described later are for detecting the position of the circumferential surface of the photoreceptor, and are thin lines perpendicular to the moving direction of the circumferential surface of the photoreceptor.

  The timer 20a starts simultaneously with the exposure (STEP 3).

  The pattern 1 is detected by the IDC sensor 8 (STEP 4), the elapse of a predetermined time from the formation of the pattern 1 is monitored, and when the predetermined time elapses (STEP 6), the pattern 2 is formed by the exposure device 3 (STEP 7).

  The formed pattern 2 is detected by the IDC sensor 8 (STEP 8).

  If the time from the detection of pattern 1 in STEP 4 to the detection of pattern 2 in STEP 8 is not equal to the specified time (NO in STEP 9), the rotational speed of the drum motor 24 is adjusted in STEP 10.

  By repeating STEPs 2 to 10, the rotational speed of the drum motor 24 is adjusted so that the difference between the detection time of the pattern 1 and the detection time of the pattern 2 becomes a specified value.

  By the above adjustment, the peripheral surface of the photoreceptor 1 is adjusted so as to move at a constant speed.

  In STEP 21 of FIG. 5, the registration motor 22 is driven to rotate at a constant speed.

  When the paper sensor 9 detects the leading edge of the paper, the timer 20a for detecting the paper length starts (STEPs 22 and 23).

  When the paper sensor 9 detects the trailing edge of the paper, the timer 20a stops (STEP 25). The length of the sheet is detected by the time of the timer 20a that counts the time from STEP23 to STEP25.

  In STEP 26, the control means 20 calculates the length of the sheet from the time measured by the timer 20a, calculates a difference from the specified length of the sheet, and further calculates an adjustment value for the registration motor 22 from this difference.

  The adjustment value is a speed adjustment value of the registration motor 22 that makes the time from detection of the leading edge of the paper sensor 9 to detection of the trailing edge a specified time.

  In STEP 27, the adjustment value calculated by the calculation is stored in the memory 23 as a storage means.

  STEP 31 in FIG. 6 is a step for determining whether the print mode is the normal print mode or the full bleed mode, and this determination is made based on the setting by the operator in the operation unit 25 in FIG. In STEP 31, in the normal image print mode, in STEP 32, a normal specified speed is loaded as the driving speed of the registration motor 22, and in STEP 33, the registration motor 22 is rotationally driven at the normal specified speed.

  The timer 20a starts based on the leading edge detection signal from the sheet sensor 9 in STEP 34 (STEPs 34 and 35), the timer 20a stops when the trailing edge of the sheet sensor 9 is detected (STEP 37), and the sheet is measured from the time measured by the timer 20a. In step 38, an appropriate conveyance speed is calculated.

  The calculated appropriate conveyance speed is stored in the memory 23 (STEP 39).

  Normal printing is executed by setting the conveyance speed of the registration motor 22 in STEP 33 to a specified value, and the conveyance speed stored in STEP 39 is used in full bleed printing as will be described below.

  In STEP 31, in the case of full bleed printing, an appropriate transport speed is loaded in STEP 40.

  As the appropriate transport speed, a specified value in normal printing is used as an initial value.

  As in STEP 39 and STEPs 48 to 50, which will be described later, when a proper transport speed is required in a print job, the proper transport speed stored in the memory 23 is loaded in STEP 40.

  In STEP 41, the registration motor 22 is rotationally driven at the appropriate transport speed to transport the paper, and STEP 42 to STEP 46 are executed in the same manner as STEP 34 to 38 in normal printing to calculate the proper transport speed for the transported paper. .

  In STEP 47, the initial transport speed, that is, the proper transport speed loaded in STEP 40 is compared with the transport speed calculated in STEP 46, and the passing time detected in STEP 44, which is the basis of the calculation, is loaded in STEP 40. When the passage time corresponding to the conveyance speed is the same, the time is not changed (STEP 50). When the time is long, the speed is increased (STEP 49). When the time is short, the speed is decreased (STEP 48). This change value is based on the appropriate conveyance speed calculated in STEP46.

  The conveyance speed adjusted in this way is stored in the memory 13 (STEP 51) and used in the next image formation.

  The conveyance speed adjusted in this way and stored in the memory 23 is used for the paper to be subsequently conveyed, but is individually stored and used for each of the paper feed trays 10A to 10C.

  The sheets stored in the sheet feeding trays 10A, 10B, and 10C have different sizes for each bundle of sheets, but there is no difference in size between the sheets constituting the bundle. By performing the adjustment described above, in the full bleed print, a print in which the paper and the image are completely coincided as shown in FIG. 2B is obtained.

  In the double-sided image formation, the paper conveyance speed in the front surface image formation is adjusted by adjusting the surface image formation in step 40 or less in FIG. 5, and the conveyance speed is further adjusted in the back surface image formation by adjustment in step 40 or less. The

  Backside image formation will be described with reference to FIG.

  In the rear surface image formation, the sheet P is heated in the fixing device 11 and contracts, and the length thereof becomes shorter than that in the front surface image formation. Therefore, in the rear surface image formation, it is necessary to form an image by conveying the sheet at a further adjusted conveyance speed with respect to the conveyance speed adjusted at the time of forming the front surface image.

  For this purpose, after adjusting the conveyance speed from STEP 40 to STEP 50 for the surface image formation as described above, the surface image is formed and fed to the transfer position through the fixing device 11 and the refeed path 12. The transport speed of the paper P to be detected is detected, and an appropriate transport speed is determined and stored in the memory 23.

  Next, the adjustment of the conveyance speed described above will be described using a specific example.

  Patterns 1 and 2 having an interval of 105 mm are formed on the photosensitive member 1 every time it rotates at a linear speed of 210 mm / s.

  The time difference between the detection signals of the IDC sensor 8 is 0.5 seconds. In the photosensitive member speed adjustment process of FIG. 3, the detection time difference of the 1DC sensor 8 is adjusted to be 0.5 seconds.

  The time for an A3-sized image to pass through one point is 2.0 seconds.

  In backside image formation, when the paper length is reduced by 0.5%, the difference between the paper leading edge passing time and the trailing edge passing time detected by the paper sensor 9 is 1.99 seconds, which is 2.1 mm long. Images are lost.

  The paper absorbs moisture after image formation and expands by 5% and returns to the original state, but a part of the image is lost.

  By the adjustment explained above, the detection signal of the paper sensor 9 that detects the reduction of 0.5% is fed back to the driving of the registration motor 23 for the conveyance speed adjustment at the time of the back side image formation. Missing image information can be avoided.

  Correction for positional deviation and size deviation in a direction perpendicular to the sheet conveyance direction is performed by polygon rotational speed control or image processing in laser exposure, as described below.

  As described above, the paper and the image can be matched by adjusting the conveyance speed, but the magnification of the image is changed by the adjustment. Even in full bleed printing, there is a case where it is desirable to maintain the magnification and allow printing that allows deviation between the paper and the image. To meet such needs, the mode and image matching the paper and the image are required. It is preferable to be able to select a mode that places importance on maintaining the magnification.

  The example described above is an example in which a photoconductor is used as the image carrier, but the present invention can also be used in an image forming apparatus using an intermediate transfer member as the image carrier. In such an image forming apparatus, after the pattern is formed on the photosensitive member, the pattern is transferred to the intermediate transfer member, and the pattern on the intermediate transfer member is detected by the pattern detection means to adjust the moving speed of the intermediate transfer member. Control is performed.

  FIG. 7 is a block diagram of a control system that detects and corrects a positional deviation, a size difference, and an image tilt in the direction X perpendicular to the transport direction Y of the paper P.

  The pattern sensors 26A and 26B detect the side edges of the paper P and output detection signals.

  The control means 20 detects the width (length in the X direction) of the paper P based on the detection signals of the pattern sensors 26A and 26B, and compares it with a specified length, for example, a short side 210mm of A4 size. Calculate the difference.

  The control unit 20 controls the image processing unit 27 based on the calculated value to adjust the size in the main scanning direction in the laser scanning. As the adjusting means, a well-known device such as image clock frequency adjustment or pixel thinning / interpolation is used.

  By detecting the paper edge of the pattern sensor 26A or 26B twice at a predetermined time interval, the inclination θ of the paper P is detected.

  The control unit 20 detects the inclination θ, controls the image processing unit 25 based on the detection result, and performs control to adjust the angle of the image to the inclination of the paper P, thereby matching the paper and the image.

  The adjustment to adjust the image width to the paper width can also be performed by controlling the polygon motor of the exposure apparatus 3 that performs laser exposure and adjusting the rotation speed of the polygon motor.

It is a figure explaining normal printing and full bleed printing. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is a block diagram of a control system. 6 is a flowchart showing separation of a speed adjusting process of a photoreceptor. 6 is a flowchart illustrating a paper conveyance speed adjustment step. It is a flowchart which shows an image formation process. It is a block diagram of a control system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging apparatus 3 Exposure apparatus 4 Developing apparatus 7 Registration roller 8 IDC sensor 9 Paper sensor 20 Control means 20a Timer 22 Registration motor 23 Memory 24 Drum motor

Claims (8)

Image carrier,
Drive means for driving the image carrier;
Image forming means for forming an image on the image carrier;
Transfer means for transferring an image on the image carrier to paper;
Pattern forming means for forming at least two patterns at a reference interval on the image carrier;
Pattern detection means for detecting the formed pattern;
Conveying means for conveying the sheet to a transfer position of the transfer means;
A sheet detecting means for detecting a sheet conveyed by the conveying means; and
Having control means,
The control means controls the drive means based on a time difference between detection signals of at least two patterns detected by the pattern detection means so that the moving speed of the image carrier becomes a specified value,
An image forming apparatus, wherein the conveyance speed of the conveyance unit is controlled so that a time difference between a sheet leading edge detection signal and a sheet trailing edge detection signal of the sheet detection unit becomes a specified value. The image forming apparatus according to claim 1, wherein the image carrier is a photoconductor. The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer member. The image forming apparatus according to claim 1, further comprising an image carrier speed adjustment mode for adjusting a moving speed of the image carrier. The image forming apparatus according to claim 1, further comprising a conveyance speed adjustment mode for adjusting the conveyance speed. The image forming apparatus according to claim 1, further comprising a storage unit that stores the conveyance speed. The image forming apparatus according to claim 6, wherein the conveyance speed stored in the storage unit is rewritable. The image forming apparatus according to claim 1, further comprising a mode in which image formation is performed by adjusting the conveyance speed, and the mode can be set by an operator.

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