JP2009128822A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the fiber direction of a paper, and to prevent failures from occurring due to the fiber direction. <P>SOLUTION: An image forming apparatus has a curved conveying path for conveying paper to a transfer unit for transferring image information to the paper. The image forming apparatus includes an imaging element 42 for reading the paper 28 that is conveyed to the outer periphery of a curved portion in the curved conveying path; and a light source 41 for irradiating an object to be read of the imaging element 42 with light, while arranging the optical axis 41a of the irradiating light is set at a predetermined angle to the curved portion in the curved conveying path to determine the fiber direction of the paper. The image forming apparatus determines the fiber direction of the paper, based on the imaging results of the imaging element 42 and changes the processing steps of forming the image according to the fiber direction of the paper thus determined. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a digital multifunction machine having a combination of these functions using an electrophotographic system or an inkjet system.

  An image forming apparatus such as a copying machine or a printer using an electrophotographic system or an inkjet system includes an image carrier that carries a latent image, a developing device that develops the latent image on the image carrier, and a developed image. The image forming apparatus includes a fixing device that heats and fixes a recording medium such as transfer paper. The paper used in such an image forming apparatus is required to be capable of printing on various types of paper as well as normal office document printing.

  On the other hand, the color image forming apparatus has a very severe aspect in the printing process. For example, in the case of paper, there are normal paper types, somewhat thick paper types, or OHP, etc. When printing on them, different process conditions are set in each case, that is, paper conveyance speed, fixing roller pressure, fixing temperature, etc. Only when the process conditions are set according to the paper type, a normal print result can be obtained. For this reason, for example, it is necessary to set the paper type of the recording medium to be used from the operation panel of the image forming apparatus and perform the image forming process under process conditions suitable for the paper type. If the setting is not performed correctly, not only a normal printing result cannot be obtained but also the apparatus main body may be damaged.

For this reason, for example, in Patent Document 1, the light reflectance, light transmittance, and the like of the paper are optically detected to identify the paper type, and the process conditions suitable for the paper type are automatically set. It has been proposed. Patent Document 2 proposes to measure the smoothness of the paper surface and perform image formation control according to the smoothness.
JP 2004-61755 A JP 2004-38879 A

  On the other hand, general paper used in such an image forming apparatus has a fiber direction in the vertical or horizontal direction. This is due to the paper manufacturing process, and the directionality is determined by arranging the long and thin fibers in the direction in which paper is drawn (paper making direction). Since the paper is continuously manufactured (made), it is completed as one roll, and is cut vertically or horizontally with respect to the paper making direction and processed into a sheet shape. Therefore, there is always a fiber direction in the vertical or horizontal direction with respect to the paper cut surface. FIG. 12 is a diagram for explaining the fiber direction of the paper. That is, if the paper making direction of the paper 1 is in the direction indicated by the white arrow, the fibers of the paper 1 are elongated in the vertical direction indicated by the solid line arrow. Therefore, when the paper 1 is placed vertically, it is said that the one along the fiber direction is the longitudinal eye 2, and the one that is orthogonal to the fiber direction is the transverse eye 3.

  By the way, the stiffness of the paper transport (sheet through) is determined by the fiber direction. A vertical eye is strong in the vertical direction and weak in the horizontal direction. The reverse is the opposite. The paper expands and contracts depending on the surrounding environment (temperature). When heated, the paper shrinks but the shrinkage rate shrinks in the horizontal direction if the fiber direction of the paper is vertical.

  Due to such paper characteristics, depending on the fiber direction of the paper, the image forming apparatus may cause problems such as jamming during paper conveyance, curling by the fixing roller, or distortion of the printed image due to shrinkage. To do.

  Therefore, the problem to be solved by the present invention is to determine the fiber direction of the paper and to avoid problems caused by the fiber direction.

  In order to achieve the object, the first means is an image forming apparatus having a curved portion in a conveyance path for conveying a sheet, wherein an optical axis is arranged in the direction of the center of curvature of the curved portion, and along the outer periphery of the curved portion. Reading means for optically reading the state of the surface of the paper conveyed and illumination light on the surface of the paper which is arranged at a predetermined angle with respect to the optical axis and which is conveyed along the outer periphery of the curved portion. And a discriminating means for discriminating the fiber direction of the paper based on the reading result of the reading means.

  The second means is the image pickup device according to the first means, wherein the reading means optically reads a predetermined area of the reading target portion that has received light from the light source, converts it into an electric signal, and outputs the electric signal. Features.

  A third means is characterized in that, in the first or second means, the reading means is arranged on the upstream side in the paper transport direction with respect to the correction means for correcting the skew of the paper.

  According to a fourth aspect of the present invention, in any one of the first to third means, a control unit that further controls image formation based on the fiber direction of the paper determined by the determination unit. To do.

  According to a fifth means, in the fourth means, the discrimination means discriminates whether the fiber direction of the paper is a vertical eye or a horizontal eye, and the control unit performs paper conveyance control based on the discrimination result. Features.

  The sixth means is characterized in that, in the fifth means, the control section performs skew correction of the paper and adjustment of the paper transport amount when the determination result is a vertical eye.

  A seventh means is the fifth means, wherein the control unit controls the fixing temperature based on the determination result.

  The eighth means is characterized in that, in the fifth means, the control section performs control to eliminate a temperature difference between the heating roller and the pressure roller of the fixing device when the determination result is a horizontal line.

  According to a ninth means, in the fourth means, the discrimination means discriminates whether the fiber direction of the paper is vertical or horizontal, and the control unit performs image writing control based on the discrimination result. Features.

  A tenth means is the ninth means, wherein, when the discrimination result is a vertical eye, the control section performs image writing with enlargement / reduction in the main scanning direction by an amount reduced by thermal contraction. To do.

  The eleventh means is characterized in that, in the ninth means, the control section performs image writing by enlarging / magnifying in the sub-scanning direction by an amount reduced by thermal contraction when the determination result is a horizontal eye. .

  In the embodiment described later, the paper is indicated by reference numeral 28, the curved portion is indicated by the curved conveyance path 32a, the reading means and the imaging means are indicated by the imaging element 42, the light source is indicated by reference numeral 41, and the determination means is indicated by the paper determination portion 60. The control unit corresponds to reference numeral 56, the correction means corresponds to the registration roller 35, the fixing device corresponds to reference numeral 33, the heating roller corresponds to the fixing heating roller 33a, and the pressure roller corresponds to the fixing pressure roller 33b. .

  According to the present invention, it is possible to discriminate the fiber direction of the paper and to avoid the occurrence of problems due to the state of the fiber direction based on the result.

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

  FIG. 1 is a configuration diagram showing an outline of an example of an image forming apparatus to which the present invention is applied. The image forming apparatus 10 takes an example in which a color image can be formed with toners of four colors of yellow (Y), magenta (M), cyan (C), and black (K). That is, the image data for each color from the polygon mirror 11 is divided into a photoconductor 12y that is an image carrier that forms a yellow toner image, a photoconductor 12m that is also an image carrier that forms a magenta toner image, and a cyan toner. The photosensitive member 12c, which is also an image carrier for forming an image, and the photosensitive member 12k, which is also an image carrier for forming a black toner image, are irradiated. The structures of the photoconductors 12y to 12k of the respective colors are the same except that the color of the toner used is different. Therefore, the photoconductor 12y that forms a yellow toner image will be described as an example.

  Around the photosensitive member 12y, a charging roller 13y, a developing roller 14y, and a cleaning roller 15y are arranged, and the surface of the photosensitive member 12y between the charging roller 13y and the developing roller 14y receives exposure light from the polygon mirror 11. It is the composition of. The toner in the toner cartridge 16y positioned above is supplied to the developing roller 14y via the supply roller 17y. Reference numeral 18y denotes a paddle for stirring the toner.

  Further, a transfer belt 19 for transferring the toner image on each of the photoconductors 12y to 12k is disposed so as to contact the photoconductors 12y to 12k. The transfer belt 19 is stretched between a tension roller 21 and a driving roller 22. On the back surface of the transfer belt 19, primary transfer rollers 23y, 23m, 23c, and 23k for transferring the toner images on the photoconductors 12y to 12k to the transfer belt 19 are provided. A toner sensor 24 that detects toner on the transfer belt 19 is disposed near the tension roller 21, and a belt cleaner 25 that cleans the transfer belt 19 is disposed near the drive roller 22.

  A waste toner box 26 for storing waste toner is provided below the transfer belt 19. Below the waste toner box 26, a paper cassette unit 27 for storing paper is located. The paper 28 in the paper cassette unit 27 is pulled out one by one by a paper feeding / conveying roller 31, and is transferred by a secondary transfer roller 32 to a transfer belt. 19 toner images are transferred, and the toner images are fixed on the paper 28 by passing through a fixing device 33 constituted by a fixing heating roller 33a and a fixing pressure roller 33b. The Reference numeral 35 denotes a registration roller that controls the conveyance of the paper 28 such as the conveyance timing of the paper 28 delivered by the paper feed conveyance roller 31 and correction of the oblique conveyance, 36 denotes a registration sensor that detects the paper 28 delivered to the registration roller 35, and 37 denotes This is a paper discharge sensor for detecting paper to be discharged. In this image forming apparatus, a double-sided printing conveyance path is provided so as to form an image on the back side of the paper, and the double-sided sensor 38 detects the paper for double-sided printing.

  FIG. 2 is a partial side view showing the configuration of the paper imaging unit, FIG. 3 is a diagram of the paper imaging unit viewed from below, and FIG. 4 is an explanatory diagram showing the positional relationship between the light source of the paper imaging unit and the imaging device.

  The sheet imaging unit for determining the fiber direction of the sheet 28 includes a light source 41 such as a lamp that irradiates light to the sheet 28 that passes through the curved conveyance path 31a (see FIG. 4) that is the outer peripheral surface of the sheet feeding conveyance roller 31. , And an image pickup element 42 such as a CCD for picking up the reflected light. The image sensor 42 is arranged in the central direction of the curved conveyance path 31a, and the light source 41 is arranged in an oblique direction on the same conveyance line as the image sensor 42.

  As a result, a shadow is generated in a portion where the distance from the light source 41 of the paper image pickup unit is long, but the lightness and darkness further differ depending on the fiber direction of the paper 28. For example, as shown in FIG. 5, when the fiber direction of the paper 28 is a horizontal direction (horizontal eye) orthogonal to the transport direction, the light from the light source 41 is easily shaded and the upper part becomes dark. Although not shown, when the fiber direction of the paper 28 is the longitudinal direction (longitudinal) extending in the transport direction, the bright state is obtained. That is, as shown in FIG. 6, when the paper fiber direction is vertical, the whole is bright as shown in (a), and when the paper fiber direction is horizontal, the upper part is dark as shown in (b). By capturing this image with the image sensor 42, the fiber direction of the paper can be known. The position of the light source 41 may be disposed below or above the image sensor 42.

  FIG. 7 is a block diagram illustrating a schematic control mechanism of the image forming apparatus. A fixing motor 51 for rotating the fixing roller of the fixing device 33, a fixing heater 52 for heating the fixing roller, a fixing thermistor 53 for detecting the temperature of the fixing device 33, a writing unit 54 such as the photoreceptors 12y to 12k, a paper feed The sheet feeding and conveying motor 55 that drives the conveying roller 31, the registration sensor 36, and the image sensor 42 are controlled by the control unit 56. The control unit 56 controls the driving of the fixing motor 51, the paper feeding / conveying motor 55 driven by the registration sensor 36, and the like, and the fixing control unit 58 controls the fixing thermistor 53 based on temperature information from the fixing thermistor 53. And a writing control unit 59 that controls the writing unit 54, and discriminates the vertical and horizontal eyes of the paper based on information from the image sensor 42, and a drive control unit 57, a fixing control unit 58, and a writing control unit 59. And a sheet discriminating unit 60 for sending information to the printer.

An image signal is output from the image pickup element 42, and the paper fiber direction is discriminated by the paper discriminating unit 60. The control unit 56 includes a CPU, a ROM, and a RAM (not shown). The CPU reads a program code stored in the ROM, and executes control according to the program code using the RAM as a work area. The control units 57, 58, 59 and the determination unit 60 of the control unit 56 are basically configured by software functions.

  Control based on the discrimination result of the paper fiber direction by the paper discrimination unit 60 will be described with reference to FIGS.

  FIG. 8 is a flowchart showing an operation procedure for explaining basic operation control of the present invention. In FIG. 8, when the paper feeding and conveyance is started and the registration sensor 36 is turned on, the imaging device 42 starts imaging the paper 28 (step S101-Yes, step S102). Then, the fiber direction of the paper 28 is determined based on the imaging result (step S103), and image formation control that matches the fiber direction of the paper is performed based on the determination result (step S104).

  FIG. 9 is a flowchart showing an operation procedure when the conveyance amount of the paper is controlled by the direction of the paper fiber. In FIG. 9, when the paper feed conveyance is started and the registration sensor 36 is turned on (step S <b> 201), the paper 28 is imaged by the image sensor 42 (step S <b> 202), and the conveyance amount provided in the control unit 56 is controlled at the same time. The timer for counting starts counting (step S203). On the other hand, it is checked whether the direction of the paper fiber is vertical or horizontal from the image captured in step S202 (step S204). If the direction of the paper fiber is vertical, it counts up to a count value that is + α with the normal timer value. Then, the paper feed motor 55 is stopped (step S205). If the direction of the paper fiber is horizontal, the paper feed motor 55 is stopped when the normal timer value is counted up to the count value (step S206). In this way, the count value of the timer in step S203 is used to set the processing timing in steps S205 and S206. After stopping the paper feed / conveyance motor 55 in steps S205 and S206, the paper feed / conveyance motor 55 is restarted (step S207), and the paper is fed from the registration roller 35 to the image forming unit.

  In this way, when the paper fiber direction is vertical, the amount of paper bending (paper conveyance amount) created by the registration roller 35 installed downstream of the conveyance path is increased from the normal amount. Thereby, the correction of the oblique conveyance of the sheet can be reliably performed. This is because if the paper fibers are in the longitudinal direction, the stiffness of the paper with respect to the transport direction is strong, and it is difficult for bending to perform oblique correction, which also means that transport jams are likely to occur. Yes. In this case, the image sensor 42 needs to be provided on the upstream side of the position where the registration roller 35 is disposed.

  FIG. 10 is a flowchart showing an operation procedure when the paper fixing control is performed according to the direction of the paper fiber. In FIG. 10, when the paper feeding and conveyance is started and the registration sensor 36 is turned on (step S301-Yes), it is checked whether or not the sheet is the first sheet (step S302). If the sheet is the second sheet or later (step S302-No), the image of the sheet 28 is captured by the image sensor 42 (step S303), and then the direction of the sheet fiber is the vertical or horizontal direction from the result captured in step S303. Is checked (step S304). If the direction of the paper fiber is horizontal, the paper conveyance is stopped at the position of the registration roller 35 and waits in the stopped state (step S305). In the meantime, while the temperature of the fixing thermistor 54 is monitored (step S305), the fixing heating roller 33a and the fixing pressure roller 33b in the fixing device 33 are idled for a certain period of time so as to equalize the roller temperature. When the temperature of the fixing thermistor 54 reaches the set temperature, the registration roller 35 is driven to resume the conveyance of the sheet (step S307), and the sheet is fixed (step S308). If it is confirmed in step S302 that the sheet is the first sheet and if the fiber direction of the sheet 28 is confirmed to be vertical in step S304, the fixing process is performed as it is in step S308.

  The reason for this processing is to suppress paper curl. In other words, when the paper fiber direction is the horizontal direction (horizontal eye), the fixing device 33 is likely to wind the paper, and the discharged paper is likely to curl. As a result, paper misalignment is likely to occur in the discharge tray. This is often caused by temperature nonuniformity of the fixing heating roller 33a and the fixing pressure roller 33b, and is likely to occur in the second and subsequent sheets. Therefore, the roller temperature is made uniform when the direction of the paper fiber is determined to be horizontal for the second and subsequent sheets by the processing procedure of FIG. As described above, when the paper fiber direction is horizontal, temperature control for eliminating the temperature difference between the fixing heating roller 33a and the fixing pressure roller 33b, in other words, control for eliminating the temperature difference is performed, thereby preventing the fixing curl of the paper. can do. Note that the control for eliminating the temperature difference in this embodiment means that the fixing heating roller 33a and the fixing pressure roller 33b are idled for a certain period of time as described above to equalize the temperature of both rollers, and the temperature between both rollers. This means control that prevents the difference from occurring.

  FIG. 11 is a flowchart showing an operation procedure corresponding to the shrinkage of the sheet generated by the heat of fixing. In FIG. 11, when the paper feeding and conveyance is started and the registration sensor 36 is turned on (step S401-Yes), the paper 28 is imaged by the image sensor 42 (step S402), and the direction of the paper fiber is checked from the imaging result. (Step S403). If the fiber direction of the paper 28 is vertical according to the imaging result, the main scanning direction is scaled by the amount contracted by the thermal contraction in the writing unit 54 (step S404), the expanded image is written, and the process proceeds to the next process (step S404). Step S405). On the other hand, when the fiber direction of the paper 28 is horizontal, the sub scanning direction is scaled by the amount contracted by the thermal contraction in the writing unit 54 (step S406), and an image expanded in the sub scanning direction is written.

  This is because the paper has the property of expanding and contracting in the direction intersecting the fiber direction, but shrinkage due to the heat of fixing causes an image equality defect. Therefore, if the fiber direction is vertical, the writing unit 54 scales the main scanning direction by the thermal contraction, and if it is horizontal, the sub scanning direction is enlarged by the thermal contraction. By scaling and writing the scaled images, the occurrence of image defects due to heat shrinkage is prevented.

  In this way, when the paper fiber direction is vertical, the paper shrinks in the main scanning direction due to heat of fixing, so the image written in advance in the main scanning direction is written at the time of image formation, and when the paper fiber direction is horizontal, Since the sheet shrinks in the sub-scanning direction due to the heat of fixing, an image that has been previously expanded in the sub-scanning direction is written at the time of image formation. Thereby, it is possible to reliably prevent the occurrence of an abnormal image due to the contraction.

1 is a diagram illustrating a schematic configuration of an example of an image forming apparatus according to an embodiment of the present invention. It is a partial side view showing a configuration of a sheet imaging unit. It is the figure which looked at the paper image pick-up part from the lower part. It is explanatory drawing which shows the positional relationship of the light source of a paper imaging part, and an image pick-up element. It is explanatory drawing which shows the imaging state of the paper by a paper imaging part. It is explanatory drawing which shows the imaging state which changes with fiber directions of a paper. 2 is a block diagram illustrating an outline of a control configuration of the image forming apparatus. FIG. It is a flowchart which shows the basic operation | movement procedure of this invention. 6 is a flowchart illustrating an operation procedure for controlling a conveyance amount of a sheet according to a direction of a sheet fiber. 6 is a flowchart illustrating an operation procedure of sheet fixing control according to the direction of the sheet fiber. 6 is a flowchart illustrating an operation procedure corresponding to a contraction of a sheet generated by heat of fixing. It is explanatory drawing which shows the fiber direction of a paper.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12y-12k Photoconductor 19 Transfer belt 27 Paper cassette part 28 Paper 31 Paper feed conveyance roller 32a Curved conveyance path
33 Fixing Device 35 Registration Roller 36 Registration Sensor
DESCRIPTION OF SYMBOLS 41 Light source 42 Image pick-up element 51 Fixing motor 52 Fixing heater 53 Fixing thermistor 54 Writing unit 55 Feeding conveyance motor 56 Control part 57 Drive control part 58 Fixing control part 59 Writing control part 60 Paper discrimination | determination part

Claims (11)

In an image forming apparatus having a curved portion in a conveyance path for conveying paper,
A reading means for optically reading the state of the surface of the sheet, the optical axis being arranged in the direction of the center of curvature of the bending portion, and being conveyed along the outer periphery of the bending portion;
A light source that is arranged at a predetermined angle with respect to the optical axis and that irradiates illumination light onto the surface of the sheet conveyed along the outer periphery of the curved portion;
Discriminating means for discriminating the fiber direction of the paper based on the reading result of the reading means;
An image forming apparatus comprising: The image forming apparatus according to claim 1.
An image forming apparatus, wherein the reading unit is an image pickup device that optically reads a predetermined area of a reading target portion that receives light from the light source, converts the light into an electric signal, and outputs the electric signal. The image forming apparatus according to claim 1 or 2,
The image forming apparatus according to claim 1, wherein the reading unit is disposed upstream of a correction unit that performs oblique correction of the sheet in a sheet conveyance direction. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus, further comprising: a control unit that controls image formation based on the fiber direction of the paper determined by the determination unit. The image forming apparatus according to claim 4.
The image forming apparatus according to claim 1, wherein the determination unit determines whether the fiber direction of the paper is a vertical or horizontal eye, and the control unit performs paper conveyance control based on the determination result. The image forming apparatus according to claim 5.
The image forming apparatus according to claim 1, wherein when the determination result is a vertical eye, the control unit performs an oblique sheet correction and an adjustment of a sheet conveyance amount. The image forming apparatus according to claim 5.
The image forming apparatus, wherein the control unit controls a fixing temperature based on the determination result. The image forming apparatus according to claim 5.
The image forming apparatus according to claim 1, wherein the controller performs control to eliminate a temperature difference between the heating roller and the pressure roller of the fixing device when the determination result is a horizontal line. The image forming apparatus according to claim 4.
The image forming apparatus according to claim 1, wherein the determining unit determines whether the fiber direction of the sheet is vertical or horizontal, and the control unit performs image writing control based on the determination result. The image forming apparatus according to claim 9.
The image forming apparatus according to claim 1, wherein when the determination result is vertical, the control unit performs image writing control by enlarging or scaling in the main scanning direction by an amount reduced by thermal contraction. The image forming apparatus according to claim 9.
The image forming apparatus according to claim 1, wherein when the determination result is horizontal, the control unit performs image writing control by enlarging or scaling in the sub-scanning direction by an amount reduced by thermal contraction.

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