JP2007281777A - Original feeder and image forming apparatus provided with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an original feeder capable of preventing erroneous detection of overlapping feed even when originals with label paper and slip attached thereto are intermingled in an original bundle. <P>SOLUTION: The original feeder includes: at least one overlapping feed sensor that senses overlapping feed of originals and transmitting an overlapping feed sensing signal when overlapped originals are conveyed; a drive section for reciprocating the overlapping feed sensor in a direction orthogonal to the conveying direction of the originals; and a control section that controls the drive section and judges the occurrence of the overlapping feed of the originals on the basis of the overlapping feed sensing signal sensed by the overlapping feed sensor, wherein the control section judges the occurrence of the overlapping feed of the originals when detecting the overlapping feed sensing signal over a width of a prescribed value or more in the width direction orthogonal to the conveying direction of the originals. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document feeding device and an image forming apparatus including the document feeding device, and more particularly to a document feeding device having a double feeding detecting function for detecting document overlapping and an image forming apparatus including the document feeding device.

As a related art related to the present invention, in a paper feeding device having a function of detecting double feeding of an original by an optical sensor, when a document to be conveyed has a strip-like vertical stripe, light is applied to the vertical stripe portion of the original. In order to prevent the amount of transmitted light from being reduced and erroneously detecting double feeding, a paper feeding device is known in which an optical sensor can be disposed at an arbitrary position in a direction orthogonal to the document conveyance direction. (For example, refer to Patent Document 1).
JP 2003-146482 A

2. Description of the Related Art In recent years, image forming apparatuses such as copiers are mainly provided with an automatic document feeder (hereinafter referred to as “ADF”) for automatically conveying a document to an image reading unit. It has become.
The ADF feeds documents one by one from a bundle of documents placed on a document tray to a document conveyance path and conveys them to an image reading unit of the image forming apparatus.
Such an ADF has a function of detecting a double feed of a document in order to prevent the document from being transported to a document transport path in a double feed state in which the document is overlapped and causing a problem such as a document jam (jam). There is something.
As means for detecting double feeding of documents, there is a method using an optical sensor or an ultrasonic sensor provided in the document conveyance path.

In the method using an optical sensor, whether the original is normally conveyed one by one by detecting a change in the amount of light when the light emitted from the light emitter passes through the original and comparing it with a predetermined threshold, Or it is judged whether it is a double feed state.
On the other hand, in the method using an ultrasonic sensor, the ultrasonic wave transmitted from the transmitter is attenuated when it passes through the document, and the attenuation of the ultrasonic wave received by the receiver is set to a predetermined threshold value. By comparing, it is determined whether the originals are normally conveyed one by one or in a double feed state.

By the way, in a document bundle placed on the document tray of the ADF, there may be a mixture of a document in which a piece of sticky paper is pasted or a document in which a cut piece of paper is pasted.
In this case, in the method using the optical sensor, the amount of transmitted light is greatly reduced below the predetermined threshold at the portion where the sticky note or the piece of paper is pasted even though the original is normally conveyed one by one. It will be mistaken for sending.
In addition, even in the method using an ultrasonic sensor, the ultrasonic attenuation is larger than a predetermined threshold at a portion where a sticky note or a piece of paper is pasted, as in the method using an optical sensor, It will be misdetected.

The above-described conventional paper feeding device is configured such that the arrangement position of the optical sensor can be arbitrarily changed in a direction orthogonal to the document conveyance direction.
For this reason, if a sticky note or a piece of paper is pasted at a predetermined position of the document, the misdetection of double feeding is prevented by changing the position of the optical sensor in advance so as to avoid the position. It is considered possible.
However, if the sticking position of the sticky note or the piece of paper is not fixed in a plurality of originals constituting the original bundle, erroneous detection of double feeding cannot be prevented.

  The present invention has been made in consideration of the above-described circumstances, and provides a document feeding device that can prevent erroneous detection of double feeding even when a document with a sticky note or a piece of paper stuck to a bundle of documents is mixed. It is to provide.

  According to the present invention, at least one double-feed detection sensor that detects double-feed of a document and generates a double-feed detection signal when the originals are transported in an overlapping manner, and the double-feed detection sensor are reciprocated in a direction perpendicular to the document transport direction. A drive unit that moves, and a control unit that controls the drive unit and determines whether or not a document is double-feeded based on a double-feed detection signal detected by a double-feed detection sensor. The control unit is orthogonal to the document conveyance direction. The present invention provides a document feeder characterized in that it is determined that a document double feed has occurred when a double feed detection signal is detected with a width greater than a predetermined value in the width direction.

  According to the present invention, the control unit controls the drive unit to reciprocate the double feed detection sensor in a direction orthogonal to the document conveyance direction, and has a width greater than a predetermined value in the width direction orthogonal to the document conveyance direction. Since it is determined that a double feed of a document has occurred when a double feed detection signal is detected, erroneous detection of double feed is prevented even if a document with a sticky note or a piece of paper is mixed in a bundle of documents.

  The document feeder according to the present invention includes at least one double feed detection sensor that detects a double feed of a document and generates a double feed detection signal when the documents are transported in an overlapping manner, and the double feed detection sensor is orthogonal to the document transport direction. And a control unit that controls the drive unit and determines whether or not to feed a document based on a double feed detection signal detected by a double feed detection sensor. It is characterized in that it is determined that a double feed of a document has occurred when a double feed detection signal is detected with a width of a predetermined value or more in the width direction orthogonal to the transport direction.

In the document feeding device according to the present invention, the double feed detection sensor means means for detecting double feeding of documents when the documents are conveyed while being overlapped.
Therefore, the double feed detection sensor may be an ultrasonic sensor or an optical sensor, or may be a mechanical displacement detection sensor that slides on the surface of the document being conveyed and is displaced according to the thickness of the document. .
The double feed detection signal means a signal obtained by converting a physical state of document double feed into an electrical signal by a double feed detection sensor.

The drive unit means a drive unit that reciprocates the double feed detection sensor in a direction orthogonal to the document conveyance direction, and includes, for example, a motor and a member that converts the rotational motion of the motor into a linear motion. The
Here, as a member that converts the rotational motion of the motor into a linear motion, for example, a pair of pulleys driven by the motor, a wire wound around the pulley, a worm gear driven by the motor, and a rack gear driven by the motor And pinion gears that mesh with each other.

In addition, the control unit means a microcomputer that controls the drive unit and determines the double feed of the document based on the double feed detection signal detected by the double feed detection sensor.
The microcomputer includes a CPU, a ROM that stores a control program, a RAM that stores various setting conditions, an I / O port connected to a double feed detection sensor and other sensors, and a driver that drives a drive unit based on the output of the CPU. It consists of a circuit.

In the document feeding device according to the present invention, the control unit selects a movement mode in which the double feed detection sensor is moved back and forth and a fixed mode in which the double feed detection sensor is not moved, and the document conveyance speed is set to the fixed mode when the movement mode is selected. The speed may be lower than the document transport speed at.
According to such a configuration, when a document on which a sticky note or a piece of paper is pasted is mixed in the original bundle, the reciprocating mode is selected to prevent erroneous detection of double feeding, and the sticky note or the piece of paper is pasted. When the attached original is not mixed in the original bundle, a usage method such as selecting the fixed mode becomes possible.
When the reciprocating mode is selected to prevent erroneous detection of double feed, the document transport speed is lower than the document transport speed in the fixed mode, so the scanning interval of the double feed detection sensor for the document is reduced. It becomes shorter and it becomes possible to detect double feeding with high accuracy.
In addition, if the document with sticky notes or paper pieces is not mixed in the document bundle and there is no need to worry about false detection of double feed, select the fixed mode and transport the document at high speed. It is possible to cope with high-speed printing processing of the image forming apparatus.

The document feeder according to the present invention may include a plurality of double feed detection sensors.
According to such a configuration, since a plurality of double feed detection sensors reciprocate with respect to the document, the scanning interval of the double feed detection sensor with respect to the document is shortened, and accuracy is high even when the document transport speed is high. Double feed can be detected.

In the above configuration including a plurality of double feed detection sensors, the control unit may control the drive unit so that the plurality of double feed detection sensors reciprocate alternately in a direction orthogonal to the document conveyance direction.
According to such a configuration, since the plurality of double feed detection sensors reciprocate alternately, the document can be scanned efficiently without omission, and the document can be accurately and efficiently overlapped even when the document transport speed is high. It is possible to detect feeding.

Further, in the above-described configuration including a plurality of double feed detection sensors, the control unit sets the drive unit so that the plurality of double feed detection sensors reciprocate and share in part in the document width direction to detect double feed. You may control.
According to such a configuration, the reciprocating movement of a part of the document in the width direction is performed so that a plurality of double feed detection sensors share the double feed detection, so the reciprocation interval of each double feed detection sensor is shortened. As a result, the scanning interval of the double feed detection sensor for the document can be shortened. In addition, since a plurality of double feed detection sensors share and detect double feed, it is possible to efficiently scan the document without omission.
Due to these effects, it is possible to detect double feeding with high accuracy and efficiency even when the document conveyance speed is high.

In the document feeder according to the present invention, the control unit may control the drive unit so that the double-feed detection sensor reciprocates a predetermined distance corresponding to the width of the document to be conveyed.
According to such a configuration, the double feed detection sensor is reciprocated by a distance corresponding to the width of the document, so that unnecessary scanning is eliminated, and as a result, the reciprocation interval of the double feed detection sensor is shortened. For this reason, the scanning interval of the double feed detection sensor for the document is shortened, and it is possible to detect the double feed accurately and efficiently even if the document conveyance speed is high.

In the document feeding device according to the present invention, the control unit may control the driving unit so that the double feed detection sensor reciprocates by a predetermined area in the document width direction.
According to such a configuration, when the pasting position of a tag or a piece of paper is known in advance in the width direction of the document, the scanning area is set in advance so that the double feed detection sensor scans the position. As a result, useless scanning can be eliminated, and as a result, the reciprocation interval of the double feed detection sensor is shortened. For this reason, the scanning interval of the double feed detection sensor for the document is shortened, and it is possible to detect the double feed accurately and efficiently even if the document conveyance speed is high.

From another point of view, the present invention also provides an image forming apparatus provided with the above document feeder according to the present invention.
Here, the image forming apparatus means an apparatus that forms an image on a recording sheet or sheet based on read image data or image data received from the outside, and examples thereof include a copying machine and a facsimile.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

Embodiment An automatic document feeder (document feeder) (hereinafter abbreviated as “ADF”) according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus equipped with an ADF according to an embodiment.

As shown in FIG. 1, an image forming apparatus 100 equipped with an ADF (automatic document feeder) 1 according to an embodiment of the present invention scans a document conveyed by the ADF 1. A monochrome image is formed on a predetermined recording sheet (sheet) according to the image data obtained in this way or image data transmitted from the outside.
The image forming apparatus 100 includes an ADF 1, an image reading unit 2, an optical writing unit 3, a developing device 4, a photoconductor 5, a charger 6, a cleaner unit 7, a transfer unit 8, a fixing unit 9, a paper transport path 10, and paper feeding. It is mainly composed of a tray 11 and a paper discharge tray 12.

The image reading unit 2 mainly includes a light source holder 13, a mirror group 14, and a CCD 15.
When scanning a document sent from the ADF 1, the image of the document is scanned while the light source holder 13 and the mirror group 14 are stationary.
When the document is conveyed from the ADF 1, the document is irradiated with light from the light source of the light source holder 13, and the light reflected from the document is converted into an optical path through the mirror group 14 and imaged on the CCD 15, and electronic image data. Is converted to
The specific structure and operation of the ADF 1 will be described in detail later.

The charger 6 is a charging means for uniformly charging the surface of the photoconductor 5 to a predetermined potential. In the image forming apparatus 100 according to the embodiment, the charger-type charger 6 is used. A roller-type or brush-type charger can also be used.
In this embodiment, a laser scanning unit (LSU) provided with laser irradiation units 16a and 16b and mirror groups 17a and 17b is used as the optical writing unit 3, but EL writing in which light emitting elements are arranged in an array. A head or an LED writing head can also be used.

The optical writing unit 3 employs a two-beam system including two laser irradiation units 16a and 16b in order to cope with high-speed printing processing, and the burden associated with increasing the irradiation timing is reduced.
Then, laser light is irradiated from the laser irradiation units 16a and 16b in accordance with the input image data, and the photosensitive member 5 uniformly charged by the charger 6 is exposed through the mirror groups 17a and 17b, thereby exposing the photosensitive member. An electrostatic latent image corresponding to the image data is formed on the surface 5.

The developing device 4 disposed in the vicinity of the photoconductor 5 visualizes the electrostatic latent image formed on the surface of the photoconductor 5 with black toner.
A cleaner unit 7 disposed around the photoconductor 5 removes and collects toner remaining on the surface of the photoconductor 5 after development and image transfer.

The image forming apparatus 100 includes a control unit (not shown) that performs integrated control of the entirety.
The control unit receives signals from the CPU, a ROM that stores a control program executed by the CPU, a RAM that provides a work area to the CPU, a non-volatile memory that holds control data, and each unit detection unit of the image forming apparatus 100. The circuit includes an input circuit, an actuator that operates each unit drive mechanism of the image forming apparatus 100, a driver circuit that drives the motor, and an output circuit that drives the laser irradiation units 16a and 16b.

As described above, the electrostatic image visualized on the surface of the photoconductor 5 is applied by applying an electric field having a polarity opposite to that of the electrostatic image from the transfer unit 8 to the conveyed paper. Transferred onto recording paper.
For example, when the electrostatic image has a charge of (−) polarity, the polarity applied to the transfer unit 8 is (+) polarity.
The transfer belt 19 of the transfer unit 8 is stretched by a driving roller 20, a driven roller 21, and other rollers, and has a predetermined resistance value (for example, a range of 1 × 10 ⁹ to 1 × 10 ¹³ Ω · cm). ing.
An elastic conductive roller 22 that has conductivity and can apply a transfer electric field is disposed at a contact portion between the photosensitive member 5 and the transfer belt 19.

The electrostatic image (unfixed toner) transferred onto the recording paper by the transfer unit 8 is conveyed to the fixing unit 9 so that the unfixed toner is melted and fixed on the recording paper.
The fixing unit 9 includes a heating roller 23 and a pressure roller 24, and a heat source that makes the surface of the heating roller 23 a predetermined temperature (fixing temperature: approximately 160 to 200 ° C.) is built in the inner peripheral portion of the heating roller 23. Has been.
On the other hand, a pressure member (not shown) is arranged at both ends of the pressure roller 24 so as to come into pressure contact with the heating roller 23 with a predetermined pressure.
As a result, the unfixed toner on the conveyed recording paper is heated and melted by the heating roller 23 at the pressure contact portion (called a fixing nip portion) between the heating roller 23 and the pressure roller 24, and is thrown at the pressure contact portion. It is fixed on the recording paper by a repulsive action.

The plurality of paper feed trays 11 are trays for storing recording sheets used for image formation, and are provided below the apparatus in the image forming apparatus 100 of the embodiment.
Since the image forming apparatus 100 of the embodiment is intended for high-speed printing processing, each of the paper feed trays 11 has a capacity capable of storing 500 to 1500 standard-size recording sheets.
Further, a large-capacity paper feed cassette (LCC) 25 capable of storing a large amount of a plurality of types of recording papers and a manual feed tray 26 mainly used for printing of an irregular size are provided on the side surface of the image forming apparatus 100.

  The paper discharge tray 12 is disposed on the side opposite to the manual feed tray 26. However, instead of the paper discharge tray 12, a paper discharge paper post-processing device (stapling, punching, etc.) or multi-stage paper discharge is provided. The tray can be arranged as an option.

Configuration and Operation of ADF The ADF 1 mounted on the above-described image forming apparatus 100 will be described with reference to FIGS. FIG. 2 is a schematic diagram showing a schematic configuration of an ADF (original feeding device) according to the embodiment, FIGS. 3 and 4 are enlarged explanatory views of main parts of the ADF shown in FIG. 2, and FIG. 5 is each part of the ADF of the control unit. FIG. 6 to FIG. 8 are explanatory diagrams showing the trajectory scanned by the transmitter that reciprocates the conveyed document, and the fluctuation of the electrical energy converted by the receiver, and FIG. It is a flowchart figure which shows the control flow of a control part.

As shown in FIG. 2, the ADF 1 mounted on the above-described image forming apparatus 100 (see FIG. 1) receives a document from the document tray 27 on which the document bundle is placed, and the document bundle placed on the document tray 27. A pick-up roller 28 that feeds one by one to the document transport path S1, a pair of paper feed rollers 29 and a separation roller 30 that transport the document sent to the document transport path S1 by the pickup roller 28 to the downstream side of the document transport path S1. A plurality of pairs of conveyance rollers 31 and driven rollers 32 provided along the document conveyance path S1, a registration roller 33 that once chucks the conveyed document and conveys the document to the reading unit 34 at a predetermined timing, and reads an image The paper is mainly composed of a paper discharge roller 35 that discharges the finished document to the paper discharge tray 36.
Further, the ADF 1 according to the embodiment is provided with a sub-tray 37 in order to deal with originals such as thick paper, and the originals placed on the sub-tray 37 join the original conveyance path S1 through a substantially linear original conveyance path S2. It is configured as follows.

As shown in FIG. 2, in the document transport path S1 between the paper feed roller 29 and the separation roller 30 of the ADF 1 and the transport roller 31 and the driven roller 32, when the document is transported in an overlapped manner, the document is double fed. A double feed detection sensor 38 is provided for detecting a double feed detection signal.
The double feed detection sensor 38 includes a transmitter 39 that emits ultrasonic waves and a receiver 40 that receives ultrasonic waves that are transmitted from the transmitter 39 and attenuated when passing through the original. That is, the double feed detection sensor is composed of a pair of the transmitter 39 and the receiver 40.

As shown in FIGS. 3 and 4, the transmitter 39 and the receiver 40 are a pair of pulleys that are driven by a pulse motor 41 that is arranged at both ends of the document transport path S <b> 1 and is controlled to be able to rotate forward and backward. The wire 43 wound around the wire 42 is fixed via a holder 44.
In order to move the holder 44 stably, a shaft 45 is disposed between the pair of pulleys 42 so as to penetrate the center of the holder 44.

When the pair of pulleys 42 is rotated by the pulse motor 41, the wire 43 rotates between the pair of pulleys 42, and the holder on which the transmitter 39 and the receiver 40 are mounted as the wire 43 rotates. 44 respectively move on the document transport path S1 in a direction orthogonal to the transport direction of the document D.
When the rotation direction of the pulse motor 41 is reversed, the wire 43 also rotates in a reverse direction between the pair of pulleys 42, and the holder 44 on which the transmitter 39 and the receiver 40 are mounted has the above direction. Move in opposite directions.
As a result, the transmitter 39 and the receiver 40 reciprocate along the document conveyance path S1 in a direction orthogonal to the document D conveyance direction.

The pulse motor 41 is driven and controlled by the above-described control unit mounted on the image forming apparatus 100. As shown in FIG. 5, the control unit 46 detects the document width by moving the pulse motor 41, the wave transmitter 39 and the wave receiver 40, and the sheet restriction plate 47 (see FIG. 2) by the user. The width detection sensor 48 is connected to a pickup roller driving unit 49 that drives the pickup roller 28, and these are integratedly controlled.
When a print request is made to the image forming apparatus 100 shown in FIG. 1, the control unit 46 shown in FIG. 5 drives the pickup roller 28 by the pickup roller driving unit 49 to send out the document to the document conveying path S1 and pulse it. The motor 41 is driven.
At this time, the control unit 46 moves the pulse motor 41 so that the transmitter 39 and the receiver 40 reciprocate in a direction orthogonal to the document conveyance direction by the distance of the document width detected by the document width detection sensor 48. Drive.

When the transmitter 39 and the receiver 40 shown in FIGS. 3 and 4 reciprocate in the direction orthogonal to the conveyance direction of the document D, the document D is transmitted with a locus as shown by a one-dot chain line in FIG. The scanner 39 will be scanned.
At this time, the ultrasonic wave transmitted from the transmitter 39 is attenuated when passing through the document D and received by the receiver 40, and the level of the electric energy converted by the receiver 40 (multifeed detection signal). Is a value as shown in the lower part of FIG. 6, and this value is sent to the control unit 46 as an electrical signal.

  On the other hand, as shown in FIG. 7, when the sticky note 50 is pasted on the document D, the ultrasonic wave transmitted from the transmitter 39 is greatly attenuated at the portion where the sticky note 50 is pasted and received. The level of the electrical energy converted by the waver 40 becomes a value in which the electrical energy is locally reduced as shown in the lower part of FIG. 7, and this value is sent to the control unit 46 as an electrical signal.

  Further, as shown in FIG. 8, when double feeding of the document D occurs, the ultrasonic wave transmitted from the transmitter 39 is greatly attenuated at the portion where the double feeding occurs and is converted by the wave receiver 40. The level of the electric energy thus obtained is a value in which the electric energy is partially reduced with a certain width as shown in the lower part of FIG. 8, and this value is sent to the control unit 46 as an electric signal.

Here, a description will be given of a criterion for the control unit 46 to determine that double feeding has occurred in the document.
Basically, when the control unit 46 detects that the ultrasonic wave is attenuated more than a predetermined value as shown in FIGS. 7 and 8, that is, the electric energy is lower than a predetermined value (one level), It is determined that double feeding has occurred in the document.
However, in order not to determine that the local electric energy decrease due to the sticky note 50 as shown in FIG. It is discriminated whether the electric energy is reduced due to feeding or simply because the sticky note 50 is stuck.

Assuming that the full width of the original is L and the moving speed of the receiver 40 is V, the time T required for the receiver 40 to move in the forward path is obtained by the following equation 1, and the threshold T ₀ is obtained by the following equation 2. It is done.
The control unit 46 compares the time T ₁ when the electric energy becomes less than a predetermined value with the threshold value T _0, and when T ₁ is longer than T ₀ , the control unit 46 exceeds the predetermined value in the full width direction orthogonal to the document conveyance direction. It is determined that a double feed detection signal has been detected with the width of, and it is determined that double feed has occurred in the document.
On the other hand, when T ₁ is shorter than T _0, it is regarded as a local electrical energy drop simply due to the sticky note 50 being pasted, and it is not determined that double feeding has occurred in the document. .

In Expression 2 below, α is a slight amount so that it can be determined as double feeding even when the originals D are not overlapped so that they completely coincide with each other in the width direction as shown in FIG. This is the time deliberately deducted as a margin.
As the value of α is set larger, even if the originals are greatly shifted in the width direction and overlapped, it can be determined that they are double-fed, but a wide sticky note 50 (see FIG. 7) or the like is pasted. If it is, it will be judged as double feed.
For this reason, the value of α should be appropriately set from the viewpoint of how much the deviation width in the width direction between the documents is assumed in the double feed detection, and it is not possible to set the value of α too large. This is not preferable from the viewpoint of preventing erroneous detection of double feeding, which is the object of the present invention.

Hereinafter, a series of control flows performed by the control unit 46 will be described with reference to a flowchart shown in FIG.
As shown in FIG. 9, when the user makes a print request to the image forming apparatus 100 (see FIG. 1), the control unit 46 drives the pickup roller 28 to start document conveyance (step 1).
When the conveyance of the original is started in step 1, the process proceeds to step 2 where the pulse motor 41 is driven to reciprocate the transmitter 39 and the receiver 40 in the direction perpendicular to the original conveyance direction (step 2).
When the reciprocating movement of the transmitter 39 and the receiver 40 is started in step 2, the process proceeds to step 3 to determine whether or not the level of the electric energy converted by the receiver 40 has decreased below a predetermined value. .

If it is not determined in step 3 that the level of electrical energy has decreased below a predetermined value, the process proceeds to step 6 to determine whether or not all the originals have been conveyed.
If it is determined in step 6 that the conveyance of all the originals has been completed, the series of flows is terminated, and if it is determined that the conveyance of all the originals has not been completed, the process returns to step 3.

If it is determined in step 3 that the level of electrical energy has fallen below a predetermined value, the process proceeds to step 4 to start a timer and wait until the level of electrical energy drops below a predetermined value until it recovers to a predetermined value or more. to count the T _1.
In step 4, when the time T ₁ from when the level of the electric energy is reduced below the predetermined value until it is restored to the predetermined value or more is counted, the process proceeds to step 5 and the time T ₁ counted in step 4 is equal to or greater than the threshold value T _0. It is determined whether or not.

If it is determined in step 5 that the time T ₁ is equal to or greater than the threshold value T ₀ , the process advances to step 7 to stop the conveyance of the document and confirm that the document has been double-fed on the display unit of the image forming apparatus 100. This is displayed (step 8), and the series of flows is completed.
On the other hand, if it is determined in step 5 that the time T ₁ is not equal to or greater than the threshold value T ₀ , the process proceeds to step 6 to determine whether or not all the originals have been conveyed.
If it is determined in step 6 that the conveyance of all the originals has not been completed, the process returns to step 3 to repeat the above-described processing, and if it is determined that the conveyance of all the originals has been completed, the series of flow ends. To do.

As described above, in the ADF 1 according to the embodiment of the present invention, the control unit 46 moves the double feed detection sensor 38 including the pair of the transmitter 39 and the receiver 40 in a direction orthogonal to the conveyance direction of the document D. By comparing the time T ₁ from when the electric energy drops below a predetermined value to when it recovers to a predetermined value or more, the time T ₁ is compared with a predetermined threshold value T _0. It can be determined whether the energy is decreased or the electrical energy is decreased due to the double feeding in which the document D is conveyed in a superimposed manner.
Thereby, it is possible to reliably prevent erroneous detection of double feeding, which is a problem of the present invention.

It should be noted that the arrangement, number, and movement method of the double feed detection sensors are not limited to those of the above-described embodiments, and various configurations and movement methods can be employed.
FIG. 10 is an enlarged explanatory view of a main part showing a first modified example in which the arrangement of the double feed detection sensors is changed, and FIG. 11 is an explanatory diagram showing a trajectory in which the original is scanned by the transmitter in the first modified example shown in FIG. is there.

As shown in FIG. 10, in the first modification, two pairs of double feed detection sensors 38 are provided, and the two pairs of double feed detection sensors 38 reciprocate alternately in a direction orthogonal to the conveyance direction of the document D. It is configured.
Each double feed detection sensor 38 is configured by a pair of transmitters and receivers (not shown) as in the above-described embodiment, and is driven by a pulse motor 41.
The trajectory of the document D scanned by the transmitter of each double feed detection sensor 38 is as shown by a one-dot chain line in FIG. 11, and the entire area of the document D is not leaked by the two pairs of double feed detection sensors 38. Scanned efficiently.
Thereby, it is possible to reliably prevent erroneous detection of double feed while conveying the document D at high speed.

Also, a configuration as shown in FIG. 12 can be adopted. FIG. 12 is an enlarged view of a main part showing the second modification, and FIG. 13 is an explanatory diagram showing a trajectory in which the original is scanned by the transmitter in the second modification.
As shown in FIG. 12, in the second modification, two pairs of double feed detection sensors 38 are provided, and the two pairs of double feed detection sensors 38 share the entire width of the document D and detect double feed. The document D is configured to reciprocate a half distance in the width direction of the document D.
Each double feed detection sensor 38 is configured by a pair of transmitters and receivers (not shown) as in the above-described embodiment, and is driven by a pulse motor 41.
The trajectory of the document D scanned by the transmitter of each double feed detection sensor 38 has a short reciprocation interval and a scan interval as shown by a one-dot chain line in FIG. The entire area of D is scanned efficiently without omission.
Thereby, it is possible to reliably prevent erroneous detection of double feed while conveying the document D at high speed.

Further, as a third modification, a scanning method as shown in FIG. 14 can be adopted. FIG. 14 is an explanatory diagram showing a trajectory in which the document conveyed in the third modification is scanned by the wave transmitter.
As shown in FIG. 14, in the third modification, only the region preset by the user is scanned in the width direction of the document D using the apparatus configuration shown in FIGS.
That is, in the case where the attachment position of the sticky note is known in advance in the width direction of the document D, it is not always necessary to scan the entire width of the document D, so that the position is scanned by the user. By arbitrarily setting a scanning area and scanning only the set area, useless scanning can be eliminated.
As a result, the scanning interval is shortened, and it is possible to efficiently prevent erroneous detection of double feeding while conveying the document D at high speed.

1 is a schematic diagram showing an overall configuration of an image forming apparatus equipped with an ADF (automatic document feeder) according to an embodiment of the present invention. It is the schematic which shows the schematic structure of ADF by an Example. FIG. 3 is an enlarged explanatory view of a main part of the ADF shown in FIG. 2. FIG. 3 is an enlarged explanatory view of a main part of the ADF shown in FIG. 2. It is a block diagram which shows the relationship between a control part and each part of ADF. It is explanatory drawing which shows the locus | trajectory scanned by the transmitter with which the conveyed original document is reciprocated, and the fluctuation | variation of the electrical energy converted by the receiver. It is explanatory drawing which shows the locus | trajectory scanned by the transmitter with which the conveyed original document is reciprocated, and the fluctuation | variation of the electrical energy converted by the receiver. It is explanatory drawing which shows the locus | trajectory scanned by the transmitter with which the conveyed original document is reciprocated, and the fluctuation | variation of the electrical energy converted by the receiver. It is a flowchart figure which shows the control flow of a control part. FIG. 10 is an enlarged explanatory view of a main part showing a first modification. It is explanatory drawing which shows the locus | trajectory by which the original document conveyed in the modification 1 shown by FIG. FIG. 10 is an enlarged explanatory diagram of a main part showing a second modification. FIG. 13 is an explanatory diagram illustrating a trajectory in which a document conveyed in the second modification illustrated in FIG. 12 is scanned by a wave transmitter. FIG. 10 is an explanatory diagram illustrating a trajectory in which a document conveyed in Modification 3 is scanned by a wave transmitter.

Explanation of symbols

1 ... ADF (automatic document feeder)
DESCRIPTION OF SYMBOLS 2 ... Image reading part 3 ... Optical writing unit 4 ... Developing device 5 ... Photoconductor 6 ... Charger 7 ... Cleaner unit 8 ... Transfer unit 9 ... Fixing Unit 10 ... paper transport path 11 ... feed tray 12, 36 ... discharge tray 13 ... light source holder 14, 17a, 17b ... mirror group 15 ... CCD
16a, 16b ... laser irradiation part 19 ... transfer belt 20 ... drive roller 21 ... driven roller 22 ... elastic conductive roller 23 ... heating roller 24 ... pressure roller 25. ··· Large-capacity paper feed cassette 26 ··· Manual feed tray 27 ··· Document tray 28 ··· Pickup roller 29 ··· Feed roller 30 ··· Separation roller 31 ··· Feed roller 32 · · · Follower roller 33 ... Registration roller 34 ... Reading unit 35 ... Discharge roller 37 ... Sub-tray 38 ... Double feed detection sensor 39 ... Transmitter 40 ... Receiver 41 ... Pulse motor 42 ... pulley 43 ... wire 44 ... holder 45 ... shaft 46 ... control unit 47 ... paper regulating plate 48 ... document width detection sensor 49 ... pickup Over La driving unit 50 ... sticky note 100 ... image forming apparatus D ... original S1, S2 ... document feed path

Claims (7)

  At least one double-feed detection sensor that detects double-feed of a document and generates a double-feed detection signal when the documents are transported in an overlapping manner, and a drive unit that reciprocates the double-feed detection sensor in a direction orthogonal to the document transport direction And a control unit that controls the driving unit and determines double feeding of the document based on the double feed detection signal detected by the double feed detection sensor, the control unit in the width direction orthogonal to the document conveyance direction. An original feeding apparatus, wherein when a double feed detection signal is detected with a width greater than or equal to a predetermined value, it is determined that a double feed of a document has occurred.   The control unit selects a movement mode in which the double feed detection sensor is moved back and forth and a fixed mode in which the double feed detection sensor is not moved. When the movement mode is selected, the document conveyance speed is lower than the document conveyance speed in the fixed mode. The document feeder according to claim 1, wherein:   The document feeder according to claim 1, further comprising a plurality of double feed detection sensors.   4. The document feeding apparatus according to claim 3, wherein the control unit controls the driving unit so that the plurality of double feed detection sensors alternately reciprocate in a direction orthogonal to the document conveyance direction.   4. The document according to claim 3, wherein the control unit controls the driving unit so that a plurality of multi-feed detection sensors reciprocate and share a part of the document in the width direction to detect multi-feed. 5. Feeder.   2. The document feeding apparatus according to claim 1, wherein the control unit controls the driving unit so that the double feed detection sensor reciprocates a predetermined distance corresponding to the document to be conveyed.   An image forming apparatus comprising the document feeder according to claim 1.

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