JP2007003736A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of accurately grasping the position of a form during conveyance and then performing image formation matching it to increase image position precision. <P>SOLUTION: The image forming apparatus is equipped with a form position detecting means 15 which has a light emission section 16 comprising at least one light emitting element 16-1 and a photodetection section 17 comprising a light receiving element array 17-2 wherein a plurality of light receiving elements 17-1 are arranged in a line at equal intervals and detects a form position in a direction orthogonal to a conveyance direction, and a table 18 in which thresholds of light reception section output for deciding form ends are made to correspond to form kinds. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine.

The image forming apparatus is required to automatically and accurately form a document image at the correct position on the sheet even when the position of the document and the position of the sheet are deviated. 1 is proposed.
JP-A-8-171266

By the way, recent image forming apparatuses have started to enter the printing industry as their speed increases. In this industry, printing accuracy of printed matter, that is, image position accuracy with respect to a sheet is indispensable, and the accuracy is required to be higher than ever.
For example, when cutting images formed with bookbinding printing or saddle stitch printing together, if the image position is shifted with respect to the paper, margins may remain depending on the image or the image may be missing. Since the quality of the finished product is affected, there is a risk that the product may malfunction. Therefore, even if there is a technique for adjusting the image position as described above, further image position accuracy is required.
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of accurately grasping the position of a sheet being conveyed and performing image formation in accordance with the position of the sheet during conveyance to increase the image position accuracy.

In order to achieve the above object, the invention according to claim 1 has a light-emitting unit composed of at least one light-emitting element and a light-receiving unit composed of a light-receiving element array in which a plurality of light-receiving elements are arranged in a line at equal intervals. The image forming apparatus includes a sheet position detection unit that detects a sheet position in a direction orthogonal to the transport direction, and a table that associates a threshold value of a light receiving unit output for determining a sheet edge with a sheet type.
The invention according to claim 2 is characterized in that the light emitting portion and the light receiving portion are arranged at positions facing each other across the sheet to be conveyed.
The invention according to claim 3 is characterized in that the light emitting portion and the light receiving portion are arranged in parallel on the same surface of the sheet to be conveyed.
According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein an output threshold value of the light receiving unit is adjustable.

  According to the present invention, there is provided a light receiving portion comprising a light emitting portion comprising at least one light emitting element and a light receiving element row in which a plurality of light receiving elements are arranged in a line at equal intervals, and detects a paper position in a direction perpendicular to the transport direction. Paper position detection means and a table that associates the threshold value of the light receiving unit output for determining the edge of the paper with the paper type, so that the paper position being conveyed can be accurately grasped, and an image corresponding thereto Image position accuracy can be improved by forming

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. An image forming unit 1 is disposed at the center of the image forming apparatus, and a paper feeding unit 2 is disposed immediately below the image forming unit 1. A plurality of paper feed units 2 are provided, each having a paper feed tray 21. Above the image forming unit 1, a reading unit 3 for reading a document is disposed. A paper discharge storage unit 4 is formed on the left side of the image forming unit 1, and a sheet on which an image is formed is discharged and stored.
An image forming unit 6 is disposed in the image forming unit 1. Around the drum-shaped photoconductor 61, a charging unit 62 that performs charging processing on the surface, an exposure unit 7 that irradiates image information with laser light on the surface, A developing unit 63 that visualizes the electrostatic latent image formed by exposing the surface and a cleaning unit 64 that removes and collects toner remaining on the photoreceptor 61 are disposed.
In addition, a transfer unit 8 that transfers a toner image formed on the photoconductor 61 to a sheet and a fixing unit 9 that fixes the toner image on the sheet are arranged. The sheet that has passed through the fixing unit 9 is discharged to the discharge storage unit 4 by the discharge roller 10. At the time of duplex printing, the sheet is branched by the branching unit 11, the sheet is reversed by the reversing duplex unit 12 and conveyed to the registration roller 23, the sheet skew is corrected by the registration roller 23, and the back side image forming operation is performed.
In the paper supply unit 2, unused paper is stored in the paper supply tray 21, and the bottom plate 24 supported so as to be rotatable is raised to a position where the uppermost paper comes into contact with the pickup roller 25. As the paper feed roller 26 rotates, the uppermost paper is sent out from the paper feed tray 21 and conveyed to the registration roller 23.

The registration roller 23 is controlled so as to start rotation at a timing so that the conveyance of the sheet is temporarily stopped and the positional relationship between the toner image on the surface of the photosensitive member 61 and the leading end of the sheet becomes a predetermined position.
In the reading unit 3, in order to read and scan a document placed on the contact glass 31, the reading traveling bodies 32 and 33 including a document illumination light source and a mirror reciprocate. Image information scanned by the reading traveling bodies 32 and 33 is read as an image signal into a CCD 35 installed behind the lens 34.
The read image signal is digitized and image processed by an image processing unit (not shown). In the image forming unit 1, an electrostatic latent image is formed on the surface of the photoreceptor 61 by light emission of a laser diode LD (not shown) in the exposure unit 7 based on the image signal processed by the image processing unit. The optical signal from the LD reaches the photosensitive member 61 via a known polygon mirror or lens. An automatic document feeder 100 that automatically feeds a document is attached above the reading unit 3.
The image forming apparatus according to the present embodiment exchanges image information of a document with a remote location by a control unit (not shown) in addition to a function as a so-called digital copying machine that reads a document, digitizes it, and copies it on a sheet as described above. It is a multifunctional image forming apparatus having a function of a fax machine and a so-called printer function for printing image information handled by a computer on paper. The setting as the copying machine is performed by an operation unit that can be arbitrarily set by the user. Further, all images formed by any function (paper on which images are formed) are discharged to the paper discharge storage unit 4.
The paper is branched by the branching claw 11, reversed through the reverse double-sided part 12, discharged through the reverse paper discharge roller 13, and stacked on the paper discharge storage part 4 with the image side down. Even if the processing order of documents handled by copying, facsimile, and printer is printing from the first page, the first page is the top when taken out from the paper discharge storage unit 4, and the pages are aligned again. Free from work.

The image forming apparatus of the present invention aligns an image with respect to a sheet. The sheet position detecting means 15 disposed on the upstream side of the image forming unit 1 detects the end of the sheet, and the image forming unit 1 detects the edge of the sheet. The image is formed on the paper. Hereinafter, the contents will be described with reference to the drawings.
As shown in FIGS. 2 and 3, the paper position detection means 15 includes a light receiving element array 17 in which a light emitting unit 16 including at least one light emitting element 16-1 and a plurality of light receiving elements 17-1 are arranged in a line at equal intervals. -2 comprising the light receiving unit 17. FIG. 2 shows the transmissive paper position detecting means 15. FIG. 3 shows the reflection type paper position detecting means 15 ((1) shows a state facing the paper, and (2) shows a plane).
When the paper edge detecting unit 15 detects the paper edge, when the light emitting unit 16 emits light, the edge is determined by the change in the output value depending on the presence or absence of the paper in the light receiving unit 17, and a threshold value is provided. Judgment is made (whether or not it is the edge of the paper). In addition to ordinary plain paper, the paper can be image-formed by the image forming unit 1 such as thick paper, thin paper, second original drawing, or high-reflectivity paper, plain paper, and low-reflectivity paper. .
4 is an output characteristic diagram of the transmission type paper position detecting means (shown in FIG. 2) depending on the presence / absence of paper, and FIG. 5 is an output characteristic diagram of the reflection type paper position detecting means (shown in FIG. 3) depending on the presence / absence of paper. These drawings show microscopically the output in the vicinity of the sheet edge.
First, the output characteristics of FIG. 4 will be described. In a state where no paper is detected (on the left side of the paper edge), the output of the light receiving unit 17 is at a high level. When some of the light receiving elements 17-1 begin to face the paper in the vicinity of the paper edge, the output of the light receiving portion 17 gradually decreases and completely faces the paper (detects the paper) (paper) On the right side of the end, the output of the light receiving unit 17 is at a low level.
Here, in the case of plain paper, the edge of the paper matches the threshold value, so the paper edge is accurately detected. In the case of thick paper, the output of the light receiving unit 17 reaches the threshold value just before the accurate paper edge position. The opposite is true for thin paper.

Next, the output characteristics of FIG. 5 will be described. When no paper is detected (on the left side of the paper edge), the output of the light receiving unit 17 is at a low level. When some of the light receiving elements start to face the paper near the edge of the paper, the output of the light receiving portion 17 gradually increases, and is completely in contact with the paper (paper detected) (right side of the paper edge). In, the output of the light receiving unit 17 is at a high level.
Here, in the case of plain paper, the edge of the paper matches the threshold value, so the paper edge is accurately detected. In the case of high reflectivity paper, the output of the light receiving unit 17 reaches the threshold value immediately before the accurate sheet edge position. The opposite is true for low reflectivity paper.
As described above, it is difficult to determine the edge of the sheet with the same light emission amount and the same threshold value for all the sheet types. In other words, unless one or both of the threshold value and the light emission amount of the light emitting unit 16 is changed depending on the paper type, accurate paper edge detection cannot be performed.
FIG. 6 is a diagram showing a table of the relationship between the paper type, the threshold value, and the adjustment value. As shown in the table (memory means) 18 of FIG. 6, the present invention holds the threshold value setting value of the light receiving unit output for determining the sheet edge for each of a plurality of sheet types. Each set value such as plain paper, thick paper, thin paper, and the second original drawing (or high reflectivity paper, plain paper, low reflectivity paper) is held as a default in the image forming apparatus.
FIG. 7 is a diagram showing a display example on the display panel of the display input device. On the display panel 19, the type of paper to be used (in this example, thin paper, plain paper, thick paper) is selected. Based on the table shown in FIG. 6, the threshold value of the light receiving unit output corresponding to the paper type selected by the user is determined (this control is performed by a control unit (CPU) not shown) of the image forming apparatus.
As a result, regardless of the type of paper, the paper edge can always be detected accurately. Therefore, it is possible to improve image position accuracy by forming an image in accordance with the paper position.
In addition, the threshold setting value can be adjusted. This setting value defaults to a value corresponding to a typical paper type in plain paper, thick paper, thin paper, 2nd original drawing, etc., so it can be set to correspond to all paper types used by the user. The value can be adjusted. As a result, the image position accuracy can be improved for all types of paper.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. The block diagram of a transmissive | pervious sheet | seat position detection means. The block diagram of a reflection type paper position detection means. FIG. 6 is an output characteristic diagram of a transmissive paper position detecting unit depending on the presence or absence of paper. The output characteristic figure of the reflection type paper position detection means by the presence or absence of paper. The figure which shows the table of the relationship between a paper type, a threshold value, and an adjustment value. The figure which shows the example of a display in the display panel of a display input device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 15 Paper position detection means, 16 Light emission part, 16-1 Light emitting element, 17 Light receiving part, 17-1 Light receiving element, 17-2 Light receiving element row | line | column, 18 table

Claims (4)

  A paper position detecting means for detecting a paper position in a direction perpendicular to the transport direction, having a light emitting part comprising at least one light emitting element and a light receiving part comprising a light receiving element array in which a plurality of light receiving elements are arranged in a line at equal intervals And a table in which the threshold value of the light receiving unit output for determining the edge of the sheet and the sheet type are associated with each other.   The image forming apparatus according to claim 1, wherein the light emitting unit and the light receiving unit are disposed at positions facing each other with a sheet to be conveyed interposed therebetween.   The image forming apparatus according to claim 1, wherein the light emitting unit and the light receiving unit are arranged in parallel on the same surface of the sheet to be conveyed. The image forming apparatus according to claim 1, wherein an output threshold value of the light receiving unit is adjustable.

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