JP5221320B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that conveys a sheet-like medium such as a document and reads an image recorded on the sheet-like medium by an image reading unit.

  In general, an image reading apparatus that conveys a sheet-like medium (hereinafter referred to as an original) separates and conveys the original one by one from a paper feed port, and conveys the original to an image reading unit. The conveyance path interval, which is the gap between the conveyance paths, which is the space between the contact glass and the opposing member in the image reading unit, is fixed at a conveyance path interval that can convey the readable thickest document.

On the other hand, the image reading unit generally employs a configuration in which an original is illuminated by a light source, reflected light from the original is collected through a contact glass by, for example, a rod lens array, and the image is read by a line image sensor or the like. ing. In the configuration using the reading sensor of this type, the document conveyed on the contact glass is smoothly along the contact glass surface without changing the position in the thickness direction within the gap having the conveyance path interval. It is desirable to be conveyed. However, since the thickness of the thin document is thinner than the above-described conveyance path interval, the position in the thickness direction changes during conveyance within the gap, causing a focus shift or the like.

There is also an image reading apparatus that performs the following measures as a countermeasure against such a problem that the difference between the conveyance path interval and the document thickness occurs. A method of widening the conveyance path interval by manually switching the conveyance path of the reading unit in the thick paper mode. Alternatively, a change in the nip pressure in the upstream roller of the image reading unit is detected by a pressure sensor (see, for example, Patent Document 1), or a load fluctuation caused by a thick document due to a current change in a roller rotation driving motor on the upstream side of the image reading unit. And a device for automatically increasing the interval between the conveyance paths.

All of the above-described apparatuses have been intended to widen the conveyance path interval when special cardboard is conveyed. Therefore, the thickness of the original is not accurately measured, the conveyance path interval for handling from thin paper to plain paper is set in a normal state, and another conveyance path interval is set as the conveyance path interval for the thick paper, As retreating treatment when special cardboard transport is detected, transport is performed by switching to another transport path interval. Further, since the above apparatus uses a method of changing the stop position of the rotatable eccentric roller disposed at a position facing the image reading unit as a means for widening the conveyance path interval, the document contacts the eccentric roller. The impact and vibration received when touching the document caused the document to be violent.
Japanese Patent Laid-Open No. 07-112857

As described above, in the conventional image reading apparatus, the conveyance path interval of the image reading unit is substantially fixed to a value that can read a document from thin paper to thick paper, corresponding to the maximum thickness of the document that can be read as a specification. As a result, the resolution of the read image from the original conveyed while floating from the original glass surface is reduced due to the focus shift or the like. The present invention has been made in view of such problems, and an object thereof is to provide an image reading apparatus that can read high-quality images from documents of various thicknesses.

In order to solve the above-described problems, an image reading apparatus according to the present invention is transported by a document transport unit for transporting a document, an image reading unit that is disposed in the transport path and reads image information of the transported document. a thickness detecting means for detecting the thickness of the document, disposed opposite to a position out of the transport path to the image reading unit, the mobile unit the image reading unit Before moving in the thickness direction of the document to the conveying path If, have a control unit for controlling the moving portion, the image reading unit, the is biased to move side by a spring, wherein, based on a detection result by the thickness detecting means, By driving the moving unit, the image reading unit urged by the moving unit is moved accompanying the moving unit, together with a conveyance path interval between the image reading unit and a member facing the image reading unit, Change the image reading position of the image reading unit. The conveyance path changing intervals and the image reading position by said control unit, after passing the document that precedes the image reading position, characterized in that subsequent to the original is performed before reaching the said image reading position And

According to the present invention, even if the thickness of the sheet-like medium to be conveyed changes, the conveyance path interval is automatically changed, and the document is conveyed while being almost in close contact with the contact glass surface, so that a high-quality image can be read. An image reading apparatus can be realized. Also. An object of the present invention is to provide an image reading apparatus capable of automatically adjusting the optimum conveyance interval for each sheet even when the sheet materials having different thicknesses are mixed and read.

Hereinafter, an image reading apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 6 is a side sectional view illustrating the entire configuration of the image reading apparatus according to the embodiment of the invention. The illustrated configuration is schematic and is not limited to this configuration.

As shown in FIG. 6, the image reading apparatus 1 includes a pickup roller 4 that picks up a document 3 set on a paper feed tray 2, and a feed roller 5 that supplies the document 3 picked up by the pickup roller 4 into the apparatus. And a separation roller 6 for separating the picked-up documents 3 one by one. In addition, the image reading apparatus 1 includes a registration roller pair 7 disposed for conveying the document 3. Furthermore, an image reading unit 22 that reads the back side of the document and a transparent contact glass 14 that enables image information of the document 3 to be read by a line image sensor (not shown) in the image reading unit 22 are provided.

The image reading unit 21 that reads the surface of the document includes a line image sensor that reads image information of the document 3 through the contact glass 13. In the middle of the conveyance path of the image reading apparatus 1, there are conveyance roller pairs 8, 9, 10, and 11 that convey the document while holding the document. A pair of paper discharge rollers 12 is provided.

A description will be given along the route along which the document is conveyed. The image reading apparatus 1 takes the document 3 into the apparatus by a pickup roller 4 and a feeding roller 5 and separates the original 3 one by one by a separation roller 6. The document 3 is sandwiched between the registration roller pair 7 and the transport roller pairs 8 and 9, the back image reading unit 22 reads the image on the back surface of the document 3, and the front image reading unit 21 reads the image on the front surface of the document 3. . Then, the paper is discharged out of the apparatus by the paper discharge roller pair 12.

4 and 5 are explanatory diagrams of a thickness measuring unit that measures the thickness of a document that is a sheet medium. FIG. 4 shows a case where the sheet medium 54 has not reached the sheet thickness measurement unit. The roller 5 is in contact with the conveyance plate 51 which is one wall surface of the conveyance path. This is the state when the sheet thickness “0” is detected. When a change with time due to roller wear is expected, an error due to wear of the roller 5 is eliminated by resetting “0” before the thickness measurement.

  In FIG. 5, when the document passes, the roller 5 is displaced by the thickness of the sheet medium 54. The roller 5 is supported by a metal roller holder 52. When the document starts to pass, the roller holder 52 rises and approaches the proximity sensor 53 installed on the upper portion thereof. The eddy current is generated in the roller holder 52 by the alternating magnetic field generated by the proximity sensor 53, whereby the signal output from the proximity sensor 53 is changed and the displacement amount can be known. As described above, the sheet thickness measuring unit as described above is installed on the upstream side of the reading unit. In this embodiment, the displacement is output by the proximity sensor, but the measurement method is not limited, such as using an optical sensor or a piezoelectric sensor. As described above, the image reading apparatus of the present invention includes a mechanism for measuring the thickness of the sheet medium.

FIG. 1 is an explanatory diagram for explaining a state of an image reading unit when a thin original is read in the image reading apparatus of the present embodiment. FIG. 2 is a state of an image reading unit when a thick original is read in the image reading apparatus of the present embodiment. It is explanatory drawing explaining these. The cam 61 is rotated by a stepping motor in response to an instruction for the conveyance path interval in the reading unit from a control unit (not shown) in the apparatus according to the measurement result of the thickness of the original in the thickness measuring unit 60. The cam 61 is provided on the front side and the back side in FIG. 1 outside the conveyance path, and is in direct or indirect contact with the reading unit 22. The reading unit 22 is moved upward as indicated by an arrow by a spring 62. 1 is moved in the vertical direction in FIG. In this way, the conveyance path intervals 63 and 64 of the reading unit corresponding to the thickness of the conveyance medium are secured.

At that time, the front conveyance guide plate 65 and the rear conveyance guide plate 66 movably connected to the reading unit 22 by a link mechanism form a conveyance path in conjunction with the movement of the reading unit 22 in the vertical direction in FIG. To do. In the image reading apparatus having the mechanism of this embodiment, when the originals are sequentially conveyed from a bundle of originals having different thicknesses mixed together, the conveyance path interval of the reading unit can be controlled for each sheet by a cam. It is.

FIG. 3 is a flowchart illustrating the overall flow. After feeding the document (step S101), the thickness of the document is measured by the above method (step S102). The measured data is sent to a control board built in the reading apparatus main body, and calculation is performed to obtain an optimum conveyance path interval (step S103). Assuming that the measurement result is T mm, for example, by performing a calculation that sets the conveyance path interval of the reading unit to 1.2 Tmm, a conveyance path interval slightly larger than the thickness of the document to be conveyed is provided.

In addition, in an apparatus capable of conveying a document having various thicknesses with a large range of corresponding document thicknesses, when the thickness of the document is 0.2 mm or less, the conveyance path interval of the reading unit is set to 1.2 Tmm, for example. When the thickness of the document exceeds 0.2 mm, the conveyance path interval of the reading unit can be set to T + 0.1 mm, for example. In this case, the conveyance path interval is 1.1 mm for a document having a thickness of 1 mm, which can be kept smaller than the conveyance path interval of 1.2 mm calculated from the calculation formula (1.2T). As described above, according to the present invention, it is possible to provide a technique for providing a conveyance path interval that is equal to or greater than the thickness of the document to be conveyed, and calculating and controlling the conveyance path interval suitable for the apparatus.

Next, in order to set the gap of the image reading unit to the optimum conveyance path interval in accordance with the calculation result, the stepping motor for rotating the cam 61 is sent in which direction, how many steps should be sent, or the rotation angle is calculated. (Step S104), a command is issued (Step S105). The stepping motor is rotated to a position shown in FIGS. 1 and 2, for example, by a driver circuit (not shown) to change the conveyance path interval of the reading unit. The timing at which the conveyance path interval is changed while sequentially conveying the originals from the original bundle is preferably set until the preceding original passes through the reading unit and reaches the subsequent original.

The figure for demonstrating the mechanism which changes the conveyance path space | interval of an image reading part narrowly. The figure for demonstrating the mechanism which changes the conveyance path space | interval of an image reading part widely. The flowchart regarding the control which changes the conveyance path interval of this invention Illustration for explaining the thickness measurement of a document Illustration for explaining the thickness measurement of a document Sectional drawing which shows schematic structure of image reading apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reading apparatus 2 Paper feed tray 3 Document 4 Pickup roller 5 Feed roller 6 Separation roller 7 Registration roller 8 Conveyance roller 9 Conveyance roller 10 Conveyance roller 11 Discharge roller 12 Discharge roller 13 Surface contact glass 14 Back surface contact glass 21 Surface image Reading unit 22 Back surface image reading unit 50 Roller 51 Conveying plate 52 Roller holder 53 Proximity sensor 54 Sheet medium 60 Medium thickness measuring unit 61 Cam 62 Spring 63 Conveyance path interval of narrowed image reading unit 64 Widened conveying path of image reading unit Interval 65 Front conveyance guide 66 Rear conveyance guide 78 Thick sheet medium 79 Thin sheet medium

Claims (2)

An original conveying means for conveying an original;
An image reading unit that reads image information of a document that is arranged and conveyed in the middle of the conveyance path;
A thickness detecting means for detecting the thickness of the conveyed document;
And said image is disposed opposite to a position out of the transport path with respect to the reading unit, the mobile unit the image reading unit Before moving in the thickness direction of the document to the transport path,
Have a control unit for controlling said moving part,
The image reading unit is biased by a spring to the moving unit side,
The control unit moves the image reading unit biased by the moving unit by driving the moving unit based on a detection result by the thickness detecting unit, and moves the image reading unit and the image The image reading position of the image reading unit is changed together with the conveyance path interval between the member and the member facing the reading unit,
The change of the conveyance path interval and the image reading position by the control unit is performed after the document preceding the image reading position passes and before the subsequent document reaches the image reading position. An image reading apparatus.   A conveyance guide member for forming a conveyance path is provided at least near the upstream side in the conveyance direction and near the downstream side in the conveyance direction of the image reading unit, and the image reading unit is displaced in the thickness direction of the document with respect to the conveyance path The image reading apparatus according to claim 1, wherein the conveyance guide member forms a conveyance path while moving in conjunction with the image reading unit.

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