JP2021164015A - Automatic document conveyance device, image reading device and image formation apparatus - Google Patents

Abstract

To provide an image reading device which improves the accuracy of electronic skew correction without increasing the size of the device and an image formation apparatus.SOLUTION: At a reading position 303 of an automatic document conveyance device which conveys a document D to the reading position of an image reading device by taking the document one by one from a document bundle, a reading guide 206 which is arranged so as to face the image reading device with a conveyance path of the document D held therebetween and reflects illumination light from the image reading device, and a conveyance roller pair as curl state change means which is arranged on the upstream side with respect to the reading position 303 in the conveyance direction of the document D and changes the curl state of the document D are installed. The conveyance roller pair brings a rigid roller 205 into pressure-contact with an elastic roller 204 to form a conveyance nip that is inwardly curved with respect to the reading surface of the document, and changes the curl state of the document D such that the tip of the document D is apart from the reading guide 206 at the reading position 303.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to an automatic document transporting device, an image reading device, and an image forming device, and more particularly to a technique for accurately performing electronic skew correction even when a document is curled.

In recent years, multi-function peripherals (MFPs) have become widespread mainly in offices and the like. The multifunction device is equipped with an image reading device for copying documents and transmitting by facsimile.

There are two reading methods for the image reading device: a platen set method and a sheet-through method. In the platen set method, the user reads the document placed in a predetermined position on the platen glass, whereas in the sheet-through method, an automatic document feeder (ADF) is used to read the document. The documents are read one by one from the bundle of documents placed on the tray. Therefore, even when the number of originals is large, the originals can be read without bothering the user, which is excellent for the convenience of the user.

However, when reading a document by the sheet-through method, the documents placed on the document tray may be uneven, wrinkled, uneven, or curled, or may be transported by an automatic document transport device. The manuscript may be skewed during the process. For these reasons, if skew occurs in which the orientation of the document is tilted with respect to the transport direction of the document, the image generated by scanning the document is also tilted, and the scanning quality is deteriorated. As a result, the copy image, the facsimile image, and the like are also inclined and the image quality is deteriorated.

To solve such a problem, for example, a resist roller is arranged on the transfer path of the original, and the tip of the original is abutted against the roller nip of the resist roller in a state where the resist roller is stopped to form a loop once. There is a technique to correct the skew by doing so. By adopting this technique, it is possible to correct the skew of the original and make the scanned image upright.

Japanese Unexamined Patent Publication No. 2-274165 Japanese Unexamined Patent Publication No. 2003-259090 Japanese Unexamined Patent Publication No. 2018-154474 Jikkenhei 4-029559 Gazette

In the skew correction technique according to the above-mentioned conventional technique, since the transfer of the original must be temporarily stopped, it is disadvantageous in improving the reading speed.

Therefore, a technique called electronic skew correction, in which the image data generated by reading a document is electronically skew-corrected, has been proposed (see, for example, Patent Documents 1 and 2). In the electronic skew correction, the position of the tip of the document is detected by detecting the shadow of the tip of the document projected on the background plate, and the amount of inclination of the document is specified from the detection result. In this way, it is not necessary to stop the transport of the original, so that the skew correction can be performed without suffering a disadvantage in improving the reading speed.

However, the shadow at the tip of the document projected on the background plate is not always constant. For example, when the document is curled and the tip of the document comes into contact with the background plate, the shadow of the tip of the document is less likely to be formed. Therefore, if the tip position of the document cannot be detected with high accuracy, the accuracy of skew correction will decrease.

To solve such a problem, for example, a curl correction mechanism for correcting curl generated by heat-fixing a toner image on a recording sheet has been proposed (see, for example, Patent Documents 3 and 4). If these conventional techniques are used, the curl of the original can be corrected at the time of image formation, but it is unavoidable that the original is curled due to the influence of the subsequent storage environment and the like. Therefore, it is not possible to sufficiently secure the accuracy of the electronic skew correction only by correcting the curl of the original document at the time of image formation.

The present disclosure has been made in view of the above-mentioned problems, and provides an image reading device and an image forming device capable of ensuring the accuracy of electronic skew correction regardless of the curl state of the original. The purpose.

In order to achieve the above object, the image reading device according to one embodiment of the present disclosure is an automatic document transporting device that feeds out documents one by one from a bundle of documents and transports them to a scanning position, and the scanning surface of the document at the scanning position. A reading guide arranged behind the image and a curl state in which the curl state of the document is changed so that the tip of the document is separated from the scanning guide at the scanning position by being arranged on the upstream side of the scanning position in the document transport direction. It is characterized by providing a means for changing.

In this case, the curl state changing means includes a roller pair for transporting the document in the document transport direction, and the roller pair is formed with a roller nip so that the document being passed through the paper is curved with the reading surface as the inside. May be good.

Further, at the second scanning position where the back surface of the scanning surface of the document is read on the downstream side of the scanning position in the document transport direction, the second scanning guide arranged behind the back surface of the document and the document transport The second curl is provided with a second curl state changing means which is arranged on the downstream side of the reading position in the direction and on the upstream side of the second reading position and changes the curl state of the document. The state changing means may change the curled state of the document so that the tip of the document is separated from the second scanning guide at the second scanning position.

Further, the second curl state changing means includes a second roller pair for transporting the document in the document transport direction, and the second roller pair is such that the document being passed through the paper is curved with the reading surface as the inside. It is desirable that a roller nip is formed.

Further, the image reading device according to the first embodiment of the present disclosure is the automatic document conveying device according to the first aspect of the present disclosure, and the image reading device according to the present disclosure, in the reading position, from the upstream side to the downstream side in the document conveying direction with respect to the document conveying direction. From the light source that emits illumination in the oblique direction, the generation means that detects the amount of reflected light from the scanning position and generates the scanned image, the shadow of the document on the scanning guide in the scanned image, and the gradation difference between the document and the document. It is characterized by including a detecting means for detecting the tip of the document and a correcting means for correcting the skew of the scanned image according to the tilt angle of the tip of the document.

Further, the image reading device according to the first embodiment of the present disclosure is the automatic document conveying device according to the first aspect of the present disclosure, and the image reading device according to the present disclosure, in the scanning position, from the upstream side to the downstream side in the document conveying direction with respect to the document conveying direction. From the light source that emits illumination in the oblique direction, the generation means that detects the amount of reflected light from the scanning position and generates the scanned image, the shadow of the document on the scanning guide in the scanned image, and the gradation difference between the document and the document. A detection means for detecting the tip of the document, a correction means for correcting the skew of the scanned image according to the tilt angle of the tip of the document, and a second scanning position from the upstream side to the downstream side in the document transport direction. A second light source that emits illumination in a direction oblique to the document transport direction, a second generation means that detects the amount of reflected light from the second reading position and generates a second scanned image, and a second. A second detecting means for detecting the tip of the document from the shadow of the document on the second scanning guide in the second scanned image and the gradation difference from the document, and a second scanning according to the tilt angle of the tip of the document. It is characterized by comprising a second correction means for correcting the skew of the image.

Further, the image forming apparatus according to one form of the present disclosure is characterized by including an image reading device according to one aspect of the present disclosure and a forming means for forming an image using a read image generated by the image reading device. And.

By doing so, even if the document is back-curled, the shadow of the tip of the document appears clearly on the scanning guide by changing the curl state of the document, so that the position of the tip of the document can be detected accurately. Therefore, electronic skew correction can be performed. Further, by relaxing the curled state of the document D, the transportability of the document can be improved.

It is a figure which shows the main structure of the image forming apparatus 1 which concerns on embodiment of this disclosure. It is a figure which shows the main structure of the image reading unit 100. (A) is a diagram illustrating the shadow of the document D when the document D is not curled, and (b) is the output value of the line sensor 241 in pixel units when the shadow and the tip portion of the document D are detected. (C) is a diagram illustrating image data before electronic skew correction is applied, and (d) is a diagram illustrating image data after electronic skew correction is applied. (A) is a diagram for explaining back curl, (b) is a diagram for explaining face curl, and (c) is a diagram illustrating a conveyed state of the original D when the original D is face curled. be. (A) is a diagram illustrating the transport state of the document D when the document D is back curled, and (b) is a diagram illustrating the transport state of the document D with the back curl corrected. It is a figure which shows the main structure of the image reading part 100 which concerns on the modification of this disclosure. It is a figure which shows the main structure of the close contact type line sensor 504 which concerns on the modification of this disclosure. (A) is a diagram illustrating a configuration in which the tip of the document D is conveyed so as to abut on the outer peripheral surface of the rigid roller 205, and (b) a configuration in which the tip of the document D is conveyed so as to abut on the outer peripheral surface of the elastic roller 204. It is a figure exemplifying. (A) is a diagram illustrating a configuration in which the tip of the document D is conveyed so as to abut on the outer peripheral surface of the elastic roller 502, and (b) is a configuration in which the tip of the document D is conveyed so as to abut on the outer peripheral surface of the rigid roller 503. It is a figure exemplifying. (A) is a diagram showing a main configuration for raising the temperature of the rigid roller 205 constituting the transport roller pair 203, and (b) is a diagram showing the document D on the upstream side of the transport roller pair 203 in the transport direction of the document D. It is a figure which shows the structure which arranged the transport roller pair 1011 for raising the temperature.

Hereinafter, embodiments of the automatic document transporting device, the image reading device, and the image forming device according to the present disclosure will be described with reference to the drawings.
[1] Configuration of Image Forming Device First, the configuration of the image forming apparatus according to the present embodiment will be described.

As shown in FIG. 1, the image forming apparatus 1 is a so-called multi-function peripheral (MFP), and includes an image reading unit 100, an image forming unit 110, a paper feeding unit 120, and an operation panel 130. ..

The image reading unit 100 includes an automatic document transporting unit 200 and a scanner unit 210. When reading a document by the sheet-through method, the automatic document transport unit 200 transports the documents one by one from the document bundle to the scanner unit 210. The scanner unit 210 reads the image data by reading the document being conveyed by the automatic document transfer unit 200, or by reading the document placed on the platen glass (not shown) when the original is read by the platen set method. Generate.

The image forming unit 110 forms an image by using the image data generated by the image reading unit 100, the image data received via a communication network (not shown), and the like. The paper feed unit 120 supplies a recording sheet used by the image forming unit 110 to form an image. The recording sheet on which the image is formed is discharged to the outside of the device.

The operation panel 130 includes, for example, a touch panel and hard keys, and presents information to the user of the image forming apparatus 1 using a liquid crystal display (LCD) constituting the touch panel, or displays the touch panel and hard keys. Accepts the user's instruction input. As a result, the image forming apparatus 1 accepts an image reading job and an image forming job. The image forming apparatus 1 may accept jobs via a communication network (not shown) such as a LAN (Local Area Network) or the Internet.
[2] Configuration of Image Reading Unit 100 The configuration of the image reading unit 100 will be further described.

As shown in FIG. 2, the image reading unit 100 includes a scanner unit 210 and an automatic document transporting unit 200. A platen glass 211 is arranged above the scanner unit 210, and the scanner unit 210 reads the document D placed on the platen glass 211 in the case of the platen set method and a slit in the case of the sheet-through method. An image is read from the document D transported by the automatic document transport unit 200 along the glass 215.

In the case of the platen set method, the scanner unit 210 rotationally drives the pulley 212 by a drive motor (not shown) and pulls the wire 213 around the pulley 212 in the direction of arrow A to drive the first slider 220 and the first slider 220. 2 Slider 230 slides in the direction of arrow A. In the case of the sheet-through method, the document D is stationary at the home position as shown in FIG. 2 so that the document D can be read directly under the background plate 206 provided in the automatic document transport unit 200.

The first slider 220 includes a light source 221 and a mirror 222. The light source 221 is used to illuminate the document D on the platen glass 211, and the reflected light L is guided to the second slider 230 by the mirror 222. The second slider 230 uses the mirror 231 and the mirror 232 to fold back the reflected light L and guide it to the lens 240.

The reflected light L is collected by the lens 240 and incident on the line sensor 241 to detect the amount of light for each pixel. The detection signal of the line sensor 241 is input to the control unit 250, and digital image data is generated. As the line sensor 241, a CCD (Charge Coupled Device) line sensor may be used, or another line sensor may be used. The first slider 220, the second slider 230, and the lens 240 form a light guide optical system that guides the reflected light L to the line sensor 241. Further, the first slider 220, the second slider 230, the lens 240, and the line sensor 241 constitute a reduction optical system and are used for reading the surface of the document D.

In the case of the sheet-through method, the automatic document transporting unit 200 feeds out the document D one by one from the bundle of documents placed on the document tray 201, and transports the documents D along the transport path 202 using a guide member such as a scooping guide 214. After that, the paper is discharged to the paper output tray 207. In the automatic document transport unit 200, a white background plate 206 is arranged at a position illuminated by the light source 221 of the first slider stationary at the home position.

On the upstream side of the background plate 206 in the transport path 202, a transport roller pair 203 that also serves as a curl state changing means is arranged. The transport roller pair 203 is obtained by pressing the rigid roller 205 against the elastic roller 204, and the rigid roller 205 is driven by the rotation of the elastic roller 204. The transport roller pair 203 is formed with a transport nip (also referred to as a roller nip) that is curved so that the rigid roller 205 bites into the elastic roller 204. By passing the document D through the transport nip, the curl state of the document D is changed.
[3] Electronic skew correction Next, the electronic skew correction will be described.

As shown in FIG. 3A, the document D is guided by the transport guide 301 and the step sheet 302 to the reading line-of-sight position (hereinafter, simply referred to as “reading position”) 303 along the main surface of the platen glass 211. NS. By separating the document D from the platen glass 211, the step sheet 302 prevents paper dust and toner from adhering to the platen glass and causing stains, and prevents deterioration of the quality of the scanned image.

Since the direction in which the light source 221 emits the illumination light and the direction in which the reflected light L received from the document is incident are different, when the tip of the document D reaches the transport position 304, the illumination light from the light source 221 is blocked. The scanning position 303 on the background plate 206 enters the shadow of the document D and becomes dark. As a result, the line sensor 241 detects the shadow of the document D.

After that, until the tip of the document D reaches the transport position 305, the scanning position 303 on the background plate 206 is in the shadow of the document D, so that the line sensor 241 continues to detect the shadow of the document D. When the tip of the document D reaches the transport position 305, the reading surface of the document D reflects the illumination light from the light source 221, so that the amount of the reflected light L incident on the line sensor 241 increases.

The scanner unit 210 starts scanning earlier than the tip of the document D reaches the reading position 303 in synchronization with the transfer operation of the automatic document transfer unit 200. Further, the scanning is completed after a predetermined time has elapsed after the rear end of the document D has passed the scanning position 303. In this way, even if the document D is tilted with respect to the document transport direction, the shadow of the document D preceding the document D and the entire document D can be reliably read.

As shown in FIG. 3B, the amount of the reflected light L from the background plate 206 is greatly reduced at the time T1 when the state where the light is not in the shadow of the document D is changed to the state where the light is in the shadow of the document D. .. Therefore, the shadow of the document D can be detected by monitoring the decrease in the amount of the reflected light L. Further, since the amount of the reflected light L from the document D is larger than the amount of the reflected light L from the background plate 206 in the shadow of the document D, the increase in the amount of the reflected light L is monitored. As a result, the tip of the document D (the boundary position between the document D and the shadow) can be detected at time T2.

As described above, the tip of the document D is detected for each pixel in the main scanning direction. When the document D is tilted with respect to the transport direction (skew), the tip positions of the document D detected for each pixel are different from each other as illustrated in FIG. 3C. In the electronic skew correction, the predetermined pixel positions 314 and 315 in the main scanning direction are set as skew detection positions, the intervals in the main scanning direction of skew detection positions 314 and 315 are set as skew detection intervals W, and the originals at skew detection positions 314 and 315. The skew amount S is calculated using the following equation (1), where the interval of the tip position of D in the sub-scanning direction is the tip detection interval H.

S = (H / W) x 100 (%) ... (1)
Further, if the skew angle θ is defined using the following equation (2),
θ = tan ^-1 (S / 100)… (2)
For example, as illustrated in FIG. 3D, if the document D is rotated by an angle (−θ) in the direction of arrow B with the center 316 of the document D as the center of rotation, the skew of the document D is corrected. A straight image with no tilt can be obtained. Needless to say, the center of rotation in the electronic skew correction is not limited to the center 316 of the document D, and other positions may be set as the center of rotation.

Further, since the skew amount may differ for each document D, it is desirable to perform the electronic skew correction for each document D, and the skew amount of the actual image according to the state (unevenness, wrinkles, unevenness, curl, etc.) of each document D. If you correct with, you can get a stable and straight image every time.
[4] Change in curl state Originals usually have some curl due to the influence of paper streaks, storage environment, etc. As shown in FIG. 4A, a state in which the image surface 401 of the document D is curled so as to be on the outside is called back curl. Further, as shown in FIG. 4B, a state in which the image surface 402 of the document D is curled so as to be inside is called a face curl.

As shown in FIG. 5A, the back-curled document D is conveyed to the reading position 303 as it is, and when the tip of the document D comes into contact with the background plate 206 due to the curl, the document D precedes the tip of the document D. Shadows can no longer be detected. Further, even if the tip of the document D is not in contact with the background plate 206, if the distance between the tip of the document D and the background plate 206 becomes small, the shadow of the document D becomes too small and the skew of the document D is accurately skewed. It cannot be detected.

In response to such a problem, in the present embodiment, as shown in FIG. 5B, a transport roller pair that also serves as a curl state changing means is located upstream of the reading position 303 in the transport direction of the document D. 203 is arranged. As described above, in the transport roller pair 203, the rigid roller 205 is pressed against the elastic roller 204 by using an urging means (not shown) such as a spring, and the rigid roller 205 is driven to rotate by the rotation of the elastic roller 204. do.

The elastic roller 204 is preferably a sponge roller having an asker hardness of 10 (A) degrees or more and 50 (A) degrees or less, and the material of the elastic roller 204 is, for example, a urethane material or CR ( A chloroprene) material can be used, but other materials may be used. It is desirable that the elastic roller 204 has an outer diameter of 15 mm or more and 22 mm or less in a state where the rigid roller 205 is not pressure-welded.

As the material of the rigid roller 205, for example, a resin material such as POM (Polyoxymethylene) can be used, but other materials may be used. It is desirable that the outer diameter of the rigid roller 205 is 10 mm or more and 14 mm or less.

Since such an elastic roller 204 can be incorporated without significantly changing the configuration of the automatic document transport section 200, it is simple and inexpensive, and is not easily affected by changes in the streaks of the document D and the storage environment. Can be changed.

When the rigid roller 205 is urged and pressed against the elastic roller 204, a transport nip is formed in which the rigid roller 205 bites into the elastic roller 204. Further, the rigid roller 205 is arranged so as to abut the reading surface (image surface) of the document D at the reading position 303, and the elastic roller 204 is arranged so as to abut the back surface thereof.

Therefore, when the original D is passed through the transfer nip, the curl state is changed so that the back curl of the original D is corrected or reduced, so that the original D is conveyed as it is without changing the curl state. The distance from the background plate 206 when the document D passes through the reading position 303 is increased as compared with the case where the document D is separated. When the tip of the document D is separated from the background plate 206, the shadow of the document D on the background plate 206 becomes large by the scanner unit 210, so that the tip of the document D can be accurately identified and electronic skew correction can be performed.

If the document D is not curled or is face curled, the curl state is changed so that the document D is face curled. When the original D is face-curled, the tip of the original D is further moved away from the background plate 206 at the reading position 303, and the shadow of the original D can be read more clearly than when the curled state is not changed. ..

For example, as shown by the alternate long and short dash line in FIG. 4C, if the document D is not curled, the tip of the document D advances along the step sheet 302, and when the transport position 411 is reached, the shadow of the document D appears. Start to be detected. Further, when the tip of the document D advances to the transport position 412 corresponding to the reading position 303, the tip of the document D is detected.

On the other hand, when the document D is face-curled as shown by a thick solid line, the shadow of the document D starts to be detected when the tip of the document D is displaced in the direction of the arrow C and reaches the transport position 421. Further, when the tip of the document D reaches the transport position 422 corresponding to the reading position 303, the tip of the document D is detected.

The transport position 421 at which the shadow of the document D starts to be detected when the document D is face-curled is compared with the transport position 411 where the shadow of the document D starts to be detected when the document D is not curled. It is on the upstream side in the transport direction of. Therefore, when the document D is face-curled, the shadow of the document D starts to be detected earlier than when the document D is not face-curled, so that the shadow of the document D becomes large and clear.

By changing the curl state of the document D using the transport roller pair 203 in this way, the shadow of the document D can be detected with high accuracy, so that the electronic skew correction of the document D can be performed with high accuracy.
[5] Modified Examples Although the present disclosure has been described above based on the embodiments, it goes without saying that the present disclosure is not limited to the above-described embodiments, and the following modified examples can be implemented. ..
(5-1) In the above embodiment, the case where the image reading unit 100 reads only one side of the document D has been described as an example, but it goes without saying that the present disclosure is not limited to this, and instead of this, the following You may do so.

For example, there is an image reading unit 100 that reads both sides of the document D in one transfer for the purpose of improving the reading efficiency (reading speed) of the double-sided document D. The present disclosure may be applied to such an image reading unit 100 for double-sided reading. As shown in FIG. 6, the image reading unit 100 according to this modification has substantially the same configuration as the image reading unit 100 according to the above embodiment, while one image surface of the document D at the reading position 303 (hereinafter, , "Surface"), and then at the reading position 506 downstream of the reading position 303 in the document transport direction, the contact image sensor (CIS) 504 is used to use the other side of the document D. The image surface (hereinafter referred to as “back surface”) is read, and the document D is ejected to the output tray 207.

In this modification, white shading rollers 206 and 505 are used instead of the background plate 206, but the functions and characteristics of the electron skew correction are the same as those of the background plate 206. In the present specification, the background plate and the shading roller are collectively referred to as a "reading guide".

As shown in FIG. 7, the close contact type line sensor 504 obliques the emitted light of the light source 701 from the downstream side to the upstream side in the transport direction of the document D by using the light guide member 702 with respect to the transport direction. Guide in the direction of intersection. As a result, the emitted light of the light source 701 is guided to the document D and the shading roller 505. The light source 701 and the light guide member 702 are supported by the support member 703, and the support member 703 is fixed to the frame 707.

The reflected light L, which is the light emitted from the light source 701 reflected by the document D or the shading roller 505, is guided to the line sensor 706 by the lens 705, and an image signal is generated. That is, the lens 705 constitutes a close contact optical system. The lens 705 is also fixed to the frame 707. The line sensor 706 is mounted on the sensor substrate 708, and the sensor substrate 708 is fixed to the frame 707. The line sensor 706 may be a CMOS (Complementary Metal Oxide Semiconductor) line sensor, or may be another line sensor such as a CCD line sensor.

A close contact type line sensor may be arranged instead of the slider 220 to read the surface of the document D.

A transfer roller pair 501 is arranged on the transfer path 202 of the document D from the reading position 303 to the reading position 506. Similar to the transfer roller pair 203, the transfer roller pair 501 has a configuration in which the rigid roller 503 is urged and pressed against the elastic roller 502, and the transfer nip is formed so that the rigid roller 503 bites into the elastic roller 502. Is formed.

The rigid roller 503 is arranged so as to abut the back surface of the document D, and the elastic roller 502 is arranged so as to abut the front surface thereof. The elastic roller 502 is rotationally driven by a drive source (not shown), and the rigid roller 503 is driven by the elastic roller 502 to rotate. As a result, the document D that has passed through the transport nip is transported to the reading position 506.

Like the elastic roller 204, the elastic roller 502 is preferably a sponge roller having an asker hardness of 10 (A) degrees or more and 50 (A) degrees or less, and the elastic roller 502 is used as a material. For example, a urethane material or a CR (chloroprene) material can be used, but other materials may be used. It is desirable that the elastic roller 502 has an outer diameter of 15 mm or more and 22 mm or less in a state where the rigid roller 503 is not pressure-welded.

As the material of the rigid roller 503, for example, POM (Polyoxymethylene) can be used, but other materials may be used. It is desirable that the outer diameter of the rigid roller 503 is 10 mm or more and 14 mm or less.

As described in the above embodiment, the transport roller pair 203 changes the curl state of the surface of the document D so as to reduce the back curl of the document D or to curl the face. Therefore, there is a possibility that the curl state of the back surface of the document D is changed so that the document D is back curled. When the curl state is changed in this way, if the shading roller 505 comes into contact with the shading roller 505 at the reading position 506 or the distance from the shading roller 505 becomes too small, it is sufficient to perform electronic skew correction on the shading roller 505. There is a risk that the shadow of the large document D will not be formed.

In response to such a problem, if the curl state is changed so as to reduce the back curl or face curl on the back surface of the document D by using the transfer roller pair 501, the back surface of the document D can be read. However, since the shadow of the document D can be enlarged, the electronic skew correction can be performed with high accuracy by reliably detecting the shadow of the document D.

As for the assembly of the transfer roller pair 501, the configuration of the automatic document transfer unit 200 does not need to be changed significantly as in the case of the assembly of the transfer roller pair 203. It can be realized simply and inexpensively that the curl of the document D is less likely to be affected by changes in the streaks and the storage environment.
(5-2) Although not particularly mentioned in the above embodiment, since the transfer roller pair 203 is formed by pressing the rigid roller 205 against the elastic roller 204 to form the transfer nip, when the original D is passed through the paper. Has a large transfer resistance. If the transport resistance is large, it becomes difficult for the tip of the document D to bite into the transport nip, which may cause a problem such as a paper jam. In order to avoid such a problem, it is considered effective to take measures to guide the document D so that the document D smoothly enters the transport roller pair 203.

It is difficult to make sure that the tip of the document D is directly inserted into the transfer nip of the transfer roller vs. 203 each time the document D is conveyed. Therefore, the tip of the document D once abuts on either the elastic roller 204 or the rigid roller 205 constituting the transport roller pair 203, and then is guided to the transport nip of the transport roller pair 203.

When the tip of the document D hits the outer peripheral surface of the elastic roller 204, the outer peripheral surface of the elastic roller 204 has a high coefficient of friction and the tip of the document D is likely to hit. Cannot smoothly enter the transport nip. Therefore, the ears of the document D are likely to be broken, wrinkled, or tilted.

On the other hand, when the tip of the document D hits the outer peripheral surface of the rigid roller 205, the rigid roller 205 uses a resin material such as POM and the friction on the outer peripheral surface is small, so that the tip of the document D is rigid. It smoothly enters the transport nip of the transport roller vs. 203 while sliding along the outer peripheral surface of the roller 205.

As shown in FIG. 8A, the automatic document transport section 200 includes transport guides 801 and 802, and the transport guides 801 and 802 guide the document D to the transport roller pair 203 along the transport path 202. .. Here, since the transport path 202 is greatly curved, the document D is transported along the transport guide 801 outside the transport path 202 by its own stiffness (elastic restoring force).

When the elastic roller 204 is arranged on the extension of the transport guide 801 in the transport direction of the document D as shown in FIG. 8B, the tip of the document D transported along the transport path 202 abuts on the elastic roller 204. Therefore, as described above, the document D cannot smoothly enter the transport nip.

On the other hand, when the rigid roller 205 is arranged on the extension of the transport guide 801 in the transport direction of the document D as shown in FIG. 8A, the tip of the document D transported along the transport path 202 becomes the rigid roller 205. bump into. Therefore, as described above, the document D can be smoothly entered into the transport nip.

Regarding the transfer roller pair 501, after the document D is conveyed so as to protrude toward the platen glass 211 side, it is conveyed along the transfer path 202 so as to be scooped up by the transfer guide 801 and is conveyed along the transfer path 202. Enter the nip. Therefore, when the elastic roller 502 is arranged on the extension of the transport guide 901 in the transport direction of the document D as shown in FIG. 9A, the tip of the document D transported along the transport path 202 is the tip of the elastic roller 502. The document D cannot smoothly enter the transport nip.

On the other hand, when the rigid roller 503 is arranged on the extension of the transport guide 901 in the transport direction of the document D as shown in FIG. 9B, the tip of the document D transported along the transport path 202 is brought to the rigid roller 503. bump into. Therefore, as described above, the document D can be smoothly entered into the transport nip.
(5-3) In the above embodiment, there is an example in which the curl state of the document D is changed by using the transfer roller pair 203 arranged immediately upstream of the reading position 303 in the transfer path 202 of the document D. It goes without saying that the present disclosure is not limited to this, and instead of this, the following may be used.

For example, when a plurality of transport roller pairs are arranged on the upstream side of the reading position 303 in the transport path 202 of the document D, a transport roller pair other than the transport roller pair 203 is used immediately upstream of the document D. The curl state may be changed. In this way, even if the arrangement of the transport roller pair for changing the curl state is restricted by the size and shape of the automatic document transport unit 200, the transport roller pair for changing the curl state can be arranged. By selecting the arrangement, it is possible to respond flexibly.

Further, when the curl state of the document D cannot be sufficiently changed only by the transfer roller pair 203, the curl state of the document D may be changed by using a plurality of transfer roller pairs. Even in this case, when three or more transport roller pairs are arranged on the upstream side of the reading position 203 in the transport path 202 of the document D, the transport roller pair used for changing the curl state is appropriately selected. It is suitable if

Further, the transport roller pair 203 may be provided with the elastic roller 204 and the rigid roller 205 over the entire width of the paper in the axial direction, or may be provided with the elastic roller 204 and the rigid roller 205 intermittently in the axial direction. .. When the elastic roller 204 and the rigid roller 205 are provided over the entire width of the paper in the axial direction, the curl state of the document D can be changed more reliably.

Further, if the elastic roller 204 and the rigid roller 205 are provided over the entire width of the paper in the axial direction, the elastic roller 204 and the rigid roller 205 are intermittently provided in the axial direction when the curl state of the document D is changed too much. If it is provided, the degree to which the curl state of the document D is changed can be relaxed.

Further, the smaller the outer diameter of the rigid rollers 205 and 503, the larger the curl state of the document D can be changed. Conversely, the larger the outer diameter of the rigid rollers 205 and 503, the larger the curl state of the document D is changed. It can be suppressed.
(5-4) In the above embodiment, the case where the curl state of the original document D at room temperature is changed has been described as an example, but it goes without saying that the present disclosure is not limited to this, and the original document D is raised instead. The curl state may be changed by warming.

For example, instead of POM as the material of the rigid rollers 205 and 503, a conductive material such as metal is used, and as illustrated in FIG. 10A, the power supply 1001 is electrically connected to the rotating shafts of the rigid rollers 205 and 503. The rigid rollers 205 and 503 may be energized by turning on the switch 1002 for connecting to the rigid rollers 205 and 503 to raise the temperature of the rigid rollers 205 and 503.

By doing so, the curl state can be changed while raising the temperature of the document D by passing the document D through the transfer nip of the transfer roller pairs 203 and 501. Therefore, the document at room temperature can be changed to the transfer nip. Compared with the case where D is passed through, the curl state of the original D can be surely changed. When the scanning of the document D is completed, the switch 1002 is turned off.

The switch 1002 may be turned on every time the document D is read, or may be turned on only when specified by the user. Further, the environmental temperature may be detected prior to reading the document D, and the switch 1002 may be turned on only when the environmental temperature does not reach a predetermined threshold temperature. The point is that the switch 1002 may be turned on when the document D is largely curled or when it is difficult to change the curled state of the document D, which is particularly effective in such a case.

The image forming unit 110 may control the switch 1002, or the scanner unit 210 may control the switch 1002. Further, the automatic document transfer unit 200 itself may perform the operation.

Further, as illustrated in FIG. 10B, a transport roller pair 1011 having a transport roller 1012 which uses a conductive material and raises the temperature by energization is provided on the upstream side of the transport roller pair 203 in the transport direction of the document D. The curl state of the document D may be changed by using the transfer roller pair 1011 to raise the temperature of the document D and then using the transfer roller pair 203.

Either of the transport rollers 1012 and 1013 constituting the transport roller pair 1011 may be heated, and the configuration for raising the temperature of the transport rollers 1012 and 1013 is, for example, as shown in FIG. 10 (a). Is. However, it goes without saying that the temperature may be raised by using another method.

By raising the temperature of the document D, the curl state can be changed with a smaller force as compared with the case where the document D is at room temperature. Therefore, even when the pressure contact force of the rigid rollers 205 and 503 with respect to the elastic rollers 204 and 502 is reduced and the torque of the elastic rollers 204 and 502 is suppressed, the curl state can be sufficiently changed. The power consumption for rotationally driving the 204 and 502 can be suppressed, and the deterioration of the elastic rollers 204 and 502 and the rigid rollers 205 and 503 with time can be suppressed to improve the durability.

Further, paying attention to the fact that the elastic rollers 204 and 502 expand and contract depending on their own temperature, the rigid roller 205 is made according to the environmental conditions such as the environmental temperature and the environmental humidity, the paper type of the manuscript D, and the user's instruction. By changing the temperature of 503, the contact pressure of the transport nip and the nip width can be changed by changing the degree of expansion of the elastic rollers 204 and 502.

The curl state of the transport rollers 203 and 501 can be changed significantly as the contact pressure is higher and the nip width is larger. Therefore, if the curl state is appropriately changed according to various conditions, the electrons can be accurately changed. Skew correction can be performed.
(5-5) As the material used for the transport roller on the drive side, mainly EPDM (Ethylene Propylene Diene Monomer) material, urethane material, CR material, SBR (Styrene Butadiene Rubber) material, and silicon material are used, and the driven side A resin such as POM is used for the transport roller. Further, the transport roller on the drive side often has an asker hardness in the range of 50 (A) degrees to 80 (A) degrees. Even if such a general transport roller is used, a transport nip that can sufficiently change the curl state of the document D can be formed by adjusting the urging force that presses the rigid roller 205 against the elastic roller 204.

However, if the pressure contact force between the rigid roller 205 and the elastic roller 204 is made too large, the transportability of the document D may decrease. Therefore, it is desirable to determine the material and pressure contact force of the rigid roller 205 and the elastic roller 204 in consideration of not only the ability to change the curl state of the document D but also the transportability of the document D. In this case, it is preferable to consider the paper quality and condition of the document that is expected to be used, the curl habit characteristic due to the path R (curvature) of the document transport device, and the like.
(5-6) In the above embodiment, the case where the present disclosure is applied to the image forming apparatus 1 which is a multifunction device has been described as an example, but it goes without saying that the present disclosure is not limited to this. The same effect can be obtained by applying the present disclosure to a single-function device such as an image reading device equipped with an automatic document transporting device, a copying device equipped with the image reading device, and a facsimile device having a facsimile communication function. ..

The automatic document transporting device, the image reading device, and the image forming device according to the present disclosure are useful as devices capable of accurately executing the electronic skew legislation even if the document D to be read is curled.

1 ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… Image forming unit 120 ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… …… Scanner unit 203, 501 ………………………… Conveying roller pair 204, 502 ………………………… Elastic roller 205, 503 ………………………… Rigid roller 206, 505 ……………………… Reading guide 303, 506 ……………………… Reading position 801, 802, 901, 902… Transport guide

Claims (7)

An automatic document transfer device that feeds documents one by one from a stack of documents and conveys them to the reading position.
In the scanning position, the scanning guide placed behind the scanning surface of the document,
It is characterized by being arranged on the upstream side of the scanning position in the document transport direction, and provided with a curl state changing means for changing the curl state of the document so that the tip of the document is separated from the scanning guide at the scanning position. Automatic document transfer device. The curl state changing means includes a pair of rollers for transporting the original in the document transport direction.
The automatic document transporting apparatus according to claim 1, wherein the roller pair is formed with a roller nip so that the document being passed through the paper is curved with the reading surface as the inside. A second scanning guide arranged behind the back surface of the document at a second scanning position for scanning the back surface of the scanning surface of the document on the downstream side of the scanning position in the document transport direction.
A second curl state changing means for changing the curl state of the document, which is arranged on the downstream side of the reading position in the document transport direction and on the upstream side of the second reading position, is provided.
The second curl state changing means according to claim 1 or 2, wherein the curl state of the original is changed so that the tip of the original is separated from the second reading guide at the second reading position. Automatic document transfer device. The second curl state changing means includes a second roller pair for transporting the document in the document transport direction.
The automatic document transfer device according to claim 3, wherein the second roller pair is formed so that its roller nip protrudes toward the back surface of the document. The automatic document transfer device according to claim 1 or 2,
A light source that emits illumination in a direction obliquely intersecting the document transport direction from the upstream side to the downstream side in the document transport direction at the scanning position.
A generation means that detects the amount of reflected light from the reading position and generates a scanned image,
A detection means that detects the tip of the document from the shadow of the document on the scanning guide in the scanned image and the gradation difference from the document.
An image reading device including a correction means for correcting skew of a scanned image according to an inclination angle of the tip of a document. The automatic document transfer device according to claim 3 or 4,
At the scanning position, a light source that emits illumination in a direction obliquely intersecting with the document transport direction from the upstream side to the downstream side in the document transport direction.
A generation means that detects the amount of reflected light from the reading position and generates a scanned image,
A detection means that detects the tip of the document from the shadow of the document on the scanning guide in the scanned image and the gradation difference from the document.
A correction means that corrects the skew of the scanned image according to the tilt angle of the tip of the document,
At the second reading position, a second light source that emits illumination in a direction obliquely intersecting with the document transport direction from the upstream side to the downstream side in the document transport direction,
A second generation means that detects the amount of reflected light from the second reading position and generates a second read image,
A second detecting means for detecting the tip of the document from the shadow of the document on the second scanning guide in the second scanned image and the gradation difference from the document.
An image reading device comprising: a second correction means for correcting skew of a second scanned image according to an inclination angle of the tip of a document. The image reading device according to claim 5 or 6,
An image forming apparatus comprising: a forming means for forming an image using a scanned image generated by an image reading apparatus.

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