JP2007003735A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve image position accuracy by accurately obtaining the position of a sheet while being transported so as to form an image according to the position of the sheet while being transported. <P>SOLUTION: The image forming apparatus is provided with: a sheet position detection means 15 which has a light emitting section 16 composed of at least one light emitting element 16-1 and a light receiving section 17 composed of a row of light receiving elements 17-2 where a plurality of light receiving elements 17-1 are arranged in a row at equal intervals, and detects the position of the sheet in a direction perpendicular to a transport direction; and a table 18 where the light emission amount of the light emitting section 16-1 is associated with the kind of the sheet. <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.

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

By the way, recent image forming apparatuses are beginning to enter the printing industry as their speed increases. In this industry, it is essential to increase the printing accuracy of printed matter, that is, the image position accuracy with respect to the paper, 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 OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of accurately grasping the position of a paper sheet being conveyed and performing image formation according to the position to improve the image position accuracy.

In order to achieve the above object, the invention according to claim 1 includes a light-receiving unit including at least one light-emitting element and a light-receiving unit including a plurality of light-receiving elements arranged in a line at equal intervals. An image forming apparatus including a sheet position detecting unit that detects a sheet position in a direction orthogonal to the direction and a table that associates the light emission amount of the light emitting unit with the sheet type is the main feature.
According to a second aspect of the present invention, the image forming apparatus according to the first aspect is characterized in that the light emitting unit and the light receiving unit are disposed at positions facing each other with the sheet to be conveyed interposed therebetween.
According to a third aspect of the present invention, the image forming apparatus according to the first aspect is characterized in that the light emitting unit and the light receiving unit are arranged in parallel on the same surface of the sheet to be conveyed.
The invention according to claim 4 is characterized in that the light emission amount of the light emitting section is adjustable.

  The present invention has a light-receiving section composed of at least one light-emitting element and a light-receiving section composed of a light-receiving element array in which a plurality of light-receiving elements are arranged in a line at equal intervals, and detects a sheet position in a direction orthogonal to the transport direction. Since it has a position detection unit and a table that matches the light emission amount of the light emitting unit and the paper type, it is possible to accurately grasp the paper position during conveyance, and image position accuracy is achieved by performing image formation accordingly. Can be increased.

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. Also, 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 sheet position detection means 15 includes a light emitting section 16 comprising at least one light emitting element 16-1 and a plurality of light receiving elements 17-1 arranged in a line at equal intervals. The light receiving unit 17 is composed of two. 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. .
FIG. 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 (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. In a state where no paper is detected (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 unit 17 gradually increases, and completely faces the paper (detects the paper) (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 light emission amount, and the adjustment value. As shown in the table (memory means) 18 of FIG. 6, the present invention holds a set value of the light emission amount for each of a plurality of paper types. Each setting 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. The setting value of the light emission amount corresponding to the paper type selected by the user is determined based on the table of FIG. 6 (this control is performed by a control means (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 performing image formation in accordance with the paper position.
In addition, the set value of the light emission amount and the threshold 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. It is a block diagram of a transmission type paper position detection means. It is a block diagram of a reflection type paper position detection means. FIG. 10 is an output characteristic diagram of a transmissive paper position detecting unit depending on the presence or absence of paper. FIG. 6 is an output characteristic diagram of a reflection type paper position detecting means depending on the presence or absence of paper. It is a figure which shows the table of the relationship between a paper type, light emission amount, and an adjustment value. It is a figure which shows the example of a display in the display panel of a display input device.

Explanation of symbols

15 Paper position detecting means 16 Light emitting part 16-1 Light emitting element 17 Light receiving part 17-1 Light receiving element 17-2 Light receiving element array 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 light emission amount of the light emitting unit is associated with the paper type.   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 the light emission amount of the light emitting unit is adjustable.

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