JP3328446B2 - Document double feed detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a facsimile apparatus, and an image reading apparatus used for a scanner and the like. The present invention relates to a sending detection device.

[0002]

2. Description of the Related Art In an image reading apparatus used for an image forming apparatus such as a copying machine, a printer, a facsimile apparatus and a scanner, an automatic document feeder for automatically feeding a document to a reading position such as a contact glass or a slit glass. A device is used. The automatic document feeder takes out documents one by one from a bundle of documents set in a stacked state on a platen and feeds them to the above-mentioned reading position. A separation mechanism is provided for separating the multi-feed state and conveying only one sheet to the reading position. However, no matter how the performance of the separation mechanism is improved, it is practically impossible to eliminate the double feed by 100%. In the image reading apparatus, when double feeding occurs, a page in a plurality of originals is lost, and a situation occurs in which the page is not read. In order to read the missing page, it is necessary to search for the missing page from among the read documents stacked on the document output tray, but to search for the missing page, the obtained copy paper It is necessary to perform while comparing. The larger the number of documents, the greater the amount of work and the longer the work time.

[0003] Japanese Patent Application Laid-Open No. Hei 5-43091 discloses that a transport path between a document feeding table and a document reading section is provided on a transport path.
A technique of arranging a paper thickness detecting means composed of a minute angle sensor or a transmission type photo sensor and a paper size detecting device, and judging the presence or absence of a double feed based on information on paper thickness and size obtained from two types of sensors. Is disclosed. However, the above-mentioned minute angle sensor has a limit in its accuracy when detecting a minute change in paper thickness in μm units, and if high accuracy is to be obtained, the cost may increase or failures may increase. There is. In addition, the transmission type photo sensor detects the presence or absence of double feeding based on the transmitted light amount of the detection light passing through the original.However, even if the paper thickness is the same, the density of the paper may vary depending on the manufacturer. Since there is variation, the method of determining the presence or absence of double feed based on only the amount of transmitted light is low in reliability. Further, since the amount of transmitted light varies depending on the presence or absence of an image on a document and the density, it is impossible to determine the presence / absence of double feeding only from the amount of transmitted light. Further, in this prior art, when the size of the document is different, the condition is satisfied on the assumption that the paper thickness is often different. There are many cases where the thickness is different or the paper thickness is the same even if the size is different, so that the reliability of this detection means has to be said to be extremely low.

In actual use of an image reading apparatus, a large number of originals of the same paper type and the same size, such as slips, are used as compared with a case where originals of different sizes and different paper types are used. Since the automatic feeding is often performed for reading, the above-described conventional example has an error in the precondition thereof, and its practicality is extremely doubtful. The double feed detection method disclosed in Japanese Patent Application Laid-Open No. SHO 60-144256 utilizes the fact that the paper feed roller is displaced in accordance with the thickness of the document passing through the nip portion of the paper feed roller pair. The double feed is detected by detecting the amount of displacement, but this detection method also has a problem in accuracy. That is, in this detection method, the movement of the end of the lever that moves up and down in conjunction with the vertical displacement of the rotation axis of the paper feed roller is detected as a change in resistance value using a variable resistor, or is detected using a photo interrupter. However, it is difficult to accurately detect a change in the sheet thickness in the unit of μm, and the mechanism around the sheet feeding roller is complicated, and the required assembling accuracy is high, which is a problem. Also, because multiple parts are used, tolerances between parts, backlash,
The amount of displacement of the paper thickness varies due to the eccentricity of the rollers, the behavior of the document, and the like, and erroneous detection often occurs.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has a high accuracy in the thickness of a document without increasing the number of parts, complicating the structure, increasing the cost, and increasing the mounting accuracy. An object of the present invention is to provide a document double feed detection device capable of detecting a difference and detecting occurrence of double feed. The present invention is also the most frequently used form of the image reading apparatus. When performing reading by automatic paper feeding using originals of the same paper type and size, the occurrence of double feeding of the originals is surely increased. Provided is a multi-document feed detection device which detects with reliability. Further, the present invention provides a document double feed detecting device capable of detecting double feed relatively accurately even if there is a difference in light transmittance due to fiber density as long as the paper thickness is substantially the same.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, engagement in claim 1
According to another aspect of the present invention , there is provided a document feeder comprising:
It is arranged between a paper mechanism and the reading unit, and is
Detects document length information about the length of documents transported from
Document length detecting means, the document length detecting means, and the reading section
And is detected by the document length detecting means.
Original paper thickness from 1/2 the original length
A document sheet thickness detecting means for detecting the thickness information, preset
Document reference length information on the reference length of the document
Document reference paper thickness information about the reference paper thickness of the document
Comparing the document reference length information with the document length information,
Compare the original reference paper thickness information with the original paper thickness information,
Based on each comparison result, the same paper type and size
And a control unit for determining the presence / absence of double feeding of the document .

To achieve the above object, the present invention
The present invention relates to a platen and a paper feeder for taking out a document from the platen.
And read the image of the original conveyed by the paper feeding mechanism.
In the document conveying apparatus having a reading portion, said feeding
A mechanism is disposed between the mechanism and the reading unit, and the
Source for detecting document length information related to the length of the conveyed document
A draft length detecting means, and the document length detecting means and the reading unit
And is detected by the document length detecting means.
Documents related to document thickness from multiple locations in the center of the document length
A document sheet thickness detecting means for detecting paper thickness information, preset
Original reference length information about the original reference length
Document reference paper thickness information on the reference paper thickness of
Comparing the document reference length information with the document length information,
Average of the document reference paper thickness information and a plurality of the document paper thickness information
Compared with the averaged original paper thickness information,
Based on the comparison result, the weight of originals of the same
And a control unit for determining the presence or absence of sending . In order to achieve the above object, the invention according to claim 3 is:
In addition to the configuration of the invention according to claim 1, the original paper thickness detecting means
When measuring the paper thickness of a document using a step,
It is characterized in that it is slower than the normal transport speed .

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the accompanying drawings. In the present invention, the usage of the actual image reading apparatus, which size of the document to be read, if the paper type is the same has been made based on the fact that a majority, a document length detecting means , Based on data obtained from the reflection type paper thickness detection means, respectively.
It is characterized by a configuration in which the presence or absence of double feed is determined. Also, the configuration is characterized in that the occurrence of double feed can be detected relatively accurately even if there is a slight difference in paper thickness or size.

FIG. 1 is an explanatory view of a main part of an image reading apparatus to which an original double feed detecting device according to the present invention is applied. The original table 1 on which a plurality of originals D are set in a stacked state, Paper feed mechanism 2 for taking out an image, a reading unit 3 for reading an image of a document conveyed by the paper feed mechanism 2, and a conveyance roller 4
, The paper discharge roller 5, and the paper discharge roller 5.
An original length detecting unit 10 , an original sheet thickness detecting unit 11, and a control unit (not shown) are provided. The paper feeding mechanism 2 includes a pickup roller 15 for taking out a document in contact with the document on the document table, and a separation roller pair 16 for separating the taken-out document.

The document length detecting means 10 is a reflection type photosensor, and detects the passage of the document edge from the fluctuation of the amount of light when the detection light emitted from the light emitting element toward the conveyance path is received by the light receiving element. The control unit determines the length of the document based on the detection timing of the leading edge of the document and the trailing edge. The control unit controls the length of the document detected by the document length detection unit 10 and a preset reference length of the document , that is,
The document length is compared with the document reference length information, and if the detected length is longer than the reference length, it is determined that double feeding has occurred.

An original paper thickness detecting means 11 includes a light emitting element (LED) 21 inside a hollow box 20 having a light shielding property.
And a position detecting element (a light receiving element, for example, a position detecting element manufactured by OMRON Corporation) 22. The light emitting element 21 emits detection light from an emission hole 20 a formed through the surface of the box facing the document guide plate 23. The detection light reflected on the guide plate 23 or on the upper surface of the document D passing therethrough passes through the entrance hole 2 provided at a proper position.
0b enters the box. The detection light incident from the entrance hole 20b is received by the position detection element 22, and the difference in the light reception position is determined by the reflection position of the light emitted from the light emitting element 21 (on the guide plate 23, on the document D1, or on the document D2). ) Is detected as a difference.

The control unit controls the same paper type and the same paper type based on the original length information on the original length from the original length detecting means 10 and the original thickness information on the original thickness from the original thickness detecting means 11. Assuming that the originals have the same size, the presence or absence of double feed is determined. That is, the document length detection hand
If the length of the original is longer than the reference length according to the detection signal from the stage 10, it is determined that double feeding has occurred. If the detected length is the same as the reference length, the paper thickness detecting means 11 measures the paper thickness at the center of the document in the transport direction, and this paper thickness is set to a preset reference paper thickness, that is, the document reference paper thickness. If it is larger than the information, it is determined to be a double feed and detected. The reference document length and paper thickness may be measured when the fixed-size document is conveyed along the reading path and stored in the memory.

The paper thickness detecting method by the original paper thickness detecting means 11 will be described. When no original is present on the guide plate 23, the light emitted from the light emitting element 21 is reflected on the guide plate 23 and travels along the path S1. Is received from the entrance hole 20b to the detection surface of the position detection element 22. Information on the light receiving position is sent to the control unit. When light emitted from the light emitting element is reflected on the upper surface of one document D1, the reflected light is received by the detection surface of the position detection element 22 via the path of S2, and this data is sent to the control unit. Is done. The emitted light reflected on the upper surface of the second document D2 is received by the position detecting element 22 via the path of S3.

FIGS. 3 (a), 3 (b) and 3 (c) are diagrams showing such a double feed detection pattern. In the case where both originals partially overlap as shown in FIGS. 3 (a) and 3 (b). Can be used for both length detection and paper thickness detection. In both cases,
+1 or 1/2 of a + l '
Measured by Further, when the two originals are completely overlapped as shown in (c), the length cannot be detected, but the double feed can be determined by detecting the paper thickness. By detecting the paper thickness at at least one location of the document thus detected, for example, at a position corresponding to の of the detected total length, the duty of the document paper thickness detecting means 11 can be reduced.

The paper thickness at a half length position of the original detected by the original length detecting means 10 is measured at a plurality of positions (a plurality of points over a required width in a direction along the transport direction). Multiple manuscript papers that are the data obtained as a result of each measurement
The thickness information it is possible to accurately measure the paper thickness by obtaining an average of the average document paper thickness information, there is no erroneous detection of double feed detection. Further, even when the length of the original conveyed by one sheet in the non-multi-feed state is slightly longer than the reference original, if the paper thickness is almost close to the reference value, the original It is also possible to program based on the data to detect that no double feed has occurred (given an error width to the reference value). Further, even if there are some differences in the sheet thickness detected by the original sheet thickness detecting means 11, and it is in the allowable error range, and the document length detecting hands
If the length detected by the stage 10 is equal to the reference value, it may be configured to determine that non-multi feeding is performed.

In the above-described embodiment, an example has been described in which the half position of the detected original document is detected, but the half position is used as the detection position for two sheets. This is because it is easy to identify the position where the originals overlap, and as described above, the duty of the original paper thickness detecting means 11 can be reduced. However, over the entire length of the original in the transport direction or the predetermined length in the transport direction. When the paper thickness measurement is performed, it is preferable to reduce the document conveyance speed in order to increase the detection accuracy. That is, the number of detections per unit length (detection density) can be increased by reducing the document conveyance speed,
As a result, it is less likely to be affected by the above behavior, and erroneous detection during double feed detection is reduced.

[0017]

As described above, according to the present invention, a double feed can be generated by detecting a difference in the thickness of a document with high accuracy without incurring a complicated structure, an increase in cost, and an increase in assembly accuracy. Can be detected. Also, when performing reading by automatic sheet feeding using originals of the same paper type and size, which is the most frequent form of use of the image reading device,
Provided is a document double feed detection device which reliably detects occurrence of double feed of a document with high reliability. Further, since the transmission type detection means is not used, double feed can be detected relatively accurately even if there is a difference in light transmittance due to the fiber density, as long as the paper thickness is substantially the same. In addition, since the number of components is small, erroneous detection can be prevented without being affected by tolerance of components, play, or the like.

[Brief description of the drawings]

FIG. 1 is a schematic configuration explanatory view of one embodiment of the present invention.

FIG. 2 is a configuration explanatory view of an example of a document sheet thickness detecting means of the present invention.

FIGS. 3 (a), (b) and (c) are views showing a double feed mode.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 document table, 2 paper feed mechanism, 3 reading section, 4 transport roller, 5 discharge roller, 10 document length detecting means, 11
Document thickness detection means, 15 pickup rollers, 16 separation roller pairs, 20 boxes, 21 light emitting elements (LED), 2
2 Position detecting element.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B65H 7/12 G03G 15/00 107

Claims (3)

(57) [Claims] And 1. A platen, a paper feeding mechanism for taking out the document from the document table, the document conveying apparatus having a reading unit, the read image of the original conveyed by the sheet feed mechanism, the paper feed mechanism And the reading unit,
Checks document length information on the length of documents transported from the mechanism.
Document length detecting means to be known, disposed between the document length detecting means and the reading unit,
1/2 of the original length detected by the original length detecting means
Source that detects document thickness information about the document thickness from the position
Document thickness detection means and document reference length information on the preset document reference length
And the original reference paper relating to the preset reference paper thickness of the original
Thickness information, the document reference length information and the document length information
And compares the original reference paper thickness information with the original paper thickness information.
And the same paper type based on the result of each comparison.
And a control unit for determining the presence / absence of double feeding of originals of the same size.
And a document double feed detecting device. 2. A document table, and a sheet supply for taking out a document from the document table.
A paper mechanism and an image of the original conveyed by the paper feeding mechanism are read.
And a reading unit, which is disposed between the paper feeding mechanism and the reading unit, and
Checks document length information on the length of documents transported from the mechanism.
Document length detecting means to be known, disposed between the document length detecting means and the reading unit,
The center of the document length detected by the document length detection means
Detect document thickness information about document thickness from multiple locations
Document thickness detection means and document reference length information on a preset document reference length
And the original reference paper relating to the preset reference paper thickness of the original
Thickness information, the document reference length information and the document length information
And compares the document reference paper thickness information with the plurality of document papers.
Compare the average document thickness information with the averaged document thickness information to the thickness information,
Based on each comparison result, the same paper type and the same size
And a control unit for determining the presence or absence of double feed of
And a double feed detecting device. 3. The method according to claim 1, wherein the document sheet thickness detecting means detects a document sheet thickness.
When measuring, set the document transport speed to
2. The document double feed detecting device according to claim 1, wherein the detection is delayed .