1. Field of the Invention
The present invention relates to a sheet conveying device and an image reading apparatus, and more particularly to a separating technique for separating multi-fed sheets when multi-feed occurs in a conveying mechanism that conveys sheets while separating the sheets one by one from a sheet bundle placed on a sheet tray.
2. Description of the Related Art
In an image reading apparatus provided with a conventional sheet conveying device, when two or more sheets are conveyed in a state overlapping each other, i.e. when multi-feed occurs, a sheet jam or defective image reading can take place. In either case, a user has to carry out work e.g. for removing sheets and setting sheets again, and hence the apparatus is inevitably stopped during execution of the work. To solve this problem, there has been proposed a sheet conveying device configured to be operable when multi-feed is detected, to convey multi-fed sheets in the reverse direction, i.e. toward a sheet tray by a predetermined distance and separate the sheets one from another using a separation mechanism again (see e.g. U.S. Patent Publication No. 5,384,631).
In the above-described conventional sheet conveying device, however, multi-feed occurs due to high adhesiveness between sheets, so that re-use of the same separation mechanism cannot reliably ensure separation of the sheets.
The present invention provides a sheet conveying device and an image reading apparatus, which make it possible to facilitate separation of multi-fed sheets to thereby improve sheet conveyance efficiency.
In a first aspect of the present invention, there is provided a sheet conveying device comprising a sheet feed unit configured to feed a sheet from a plurality of sheets placed on a sheet tray, on a one-by-one basis, by separating the sheets, a first conveying unit having a pair of conveying rollers configured to convey the sheet fed from the sheet feed unit in a state nipped therebetween, the conveying rollers having rotational axes extending in respective different directions, and a second conveying unit configured to further convey the sheet conveyed by the first conveying unit, wherein one roller of the conveying roller pair is disposed such that the roller conveys the fed sheet in a direction in which the sheet is to be conveyed by the second conveying unit, and the other roller of the conveying roller pair is disposed such that the roller conveys the sheet obliquely with respect to the sheet conveying direction of the second conveying unit.
In a second aspect of the present invention, there is provided an image reading apparatus comprising a sheet tray on which a plurality of sheets are placed, a sheet feed unit configured to feed a sheet from the sheets placed on the sheet tray, on a one-by-one basis, by separating the sheets, a first conveying unit having a pair of conveying rollers configured to convey the sheet fed from the sheet feed unit in a state nipped therebetween, the conveying rollers having rotational axes extending in respective different directions, a second conveying unit configured to further convey the sheet conveyed by the first conveying unit, and a reading unit configured to read an image from the sheet conveyed by the second conveying unit, wherein one roller of the conveying roller pair is disposed such that the roller conveys the fed sheet in a direction in which the sheet is to be conveyed by the second conveying unit, and the other roller of the conveying roller pair is disposed such that the roller conveys the sheet obliquely with respect to the sheet conveying direction of the second conveying unit.
According to the present invention, one of the pair of conveying rollers different in axial direction is disposed such that the roller performs sheet conveyance in a sheet conveying direction, and the other roller of the conveying roller pair is disposed such that the roller performs sheet conveyance obliquely with respect to the sheet conveying direction. This makes it easy to separate the multi-fed sheets, and makes it possible to improve sheet conveying efficiency.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
1, and
The present invention will now be described in detail below with reference to the accompanying drawings showing embodiments thereof.
In
In actuality, a case where the separation pad 21 and the separation roller 2 fail to separate only an uppermost sheet can occur depending on a sheet type or due to a difference in surface frictional force between sheets. In the present embodiment, sheets which are not separated one from another at the above-mentioned time and are fed in a state overlapping each other will be referred to as “multi-fed sheets”.
A separation sensor 10 is disposed downstream of the separation pad 21 and the separation roller 2 in the sheet conveying direction. The separation sensor 10 is used for detection of an interval between sheets after separation, which is performed based on an output therefrom. Downstream of the separation sensor 10 is disposed a sheet width detection section 11 comprising a plurality of sheet detectors arranged in a direction intersecting with (e.g. orthogonal to) the sheet conveying direction (hereinafter simply referred to as “the conveying direction”). The sheet width detection section 11 detects the width of each fed sheet based on whether or not the fed sheet has been detected by the sheet detection sensors in predetermined timing before the sheet is brought into abutment with a registration roller 4. Note that the sheet width detection section 11 may be implemented by an array sensor, such as a CCD or a CIS.
A sheet having passed the sheet width detection section 11 is conveyed by a pull-off roller section 3 and is brought into abutment with the registration roller 4. At a time point when the sheet reaches the registration roller 4, the registration roller 4 is in a state not being driven but at rest, so that the leading edge of the sheet is prevented from being advanced. The sheet in this state is pushed toward the registration roller 4 by pushing operation of the pull-off roller section 3, whereby it is warped. Even when the conveying process up to this time has brought the sheet into a skewed state where the leading edge of the sheet is in an oblique relation to the conveying direction, the skew of the sheet is corrected by warping the sheet with its leading edge held in abutment with the registration roller 4. Then, the registration roller 4 is rotated to convey the sheet to a first conveying roller 5 and a roller 7, whereafter the sheet is conveyed by these rollers onto a platen glass 201. The reader section 200 reads a front-surface image from the sheet through the platen glass 201.
Then, the sheet is conveyed by a second conveying roller 6, and is passed through between a roller 16 and a back surface-reading glass 18. Then, the sheet is discharged onto a discharge tray 31 via a discharge flapper 20 and a discharge roller pair 8.
A back-surface image reading section 17 is a unit configured to optically read image information from a sheet and output an image signal subjected to photoelectric conversion to a subsequent stage. The back-surface image reading section 17 is disposed on the back side of the back surface-reading glass 18 opposed to the roller 16. The back-surface image reading section 17 reads a back-surface image on the sheet while the sheet is passing through a clearance between the roller 16 and the back surface-reading glass 18.
Each of sheet detection sensors 12, 13, and 14 detects whether or not there is a sheet at an associated sensor position. Further, conveyance guides, not shown, are disposed along the sheet conveying path so as to restrict a sheet from deviating from a predetermined range in a direction (hereinafter also referred to as “the main scanning direction) orthogonal to the conveying direction.
Similarly, the reader section 200 is a unit configured to optically read image information from a sheet and output an image signal subjected to photoelectric conversion to a subsequent stage. The reader section 200 comprises the platen glass 201, a platen glass 202, a scanner unit 209, a second mirror 205, a third mirror 206, a lens 207, and a CCD (charge coupled device) 208. Note that the scanner unit 209 comprises an illuminating lamp 203 and a first mirror 204.
In reading a front-surface image from a sheet, the scanner unit 209 is moved to a position below the platen glass 201 in advance. Then, the illuminating lamp 203 is turned on in this state, and reflected light from the front surface of the sheet passing on the moving reading glass is guided to the lens 207 via the first to third mirrors 204, 205, and 206, whereby it is caused to form an image on the CCD 208. After this process, the front-surface image from the sheet is photoelectrically converted to a digital image signal by the CCD 208.
In the reader section 200, a central processing unit (hereinafter acronymized as “the CPU”) 251 controls the ADF 100 and the reader section 200. Connected to the reader section 200 are a ROM 252 as a memory for storing programs and a RAM 253 as a memory for providing work areas. The ROM 252 stores control programs for the reader section 200 and the ADF 100, and the RAM 253 stores input data for use in control and working data.
Connected to the CPU 251 are a motor driver section 256 as a driver circuit for driving an optical motor that moves the scanner unit 209 and a front-surface image reading section 260. The front-surface image reading section 260 comprises the illuminating lamp 203 and the CCD 208 mentioned above, and a signal controller 259 for converting an output from the CCD 208 to a digital image signal. The CPU 251 controls the motor driver section 256 and the front-surface image reading section 260 to read an image from the front surface of an original.
A sheet interval correction section 254 corrects parameters of the signal controller 259 according to a sheet interval (i.e. an interval between the trailing edge of a preceding sheet and the leading edge of the following sheet) between fed sheets. Although in the present embodiment, the sheet interval is handled as a time parameter, it may be handled as a distance parameter. An image processing section 255 processes an image signal read by the front-surface image reading section 260 or the back-surface image reading section 17, generates a timing signal, and transmits the signals to the image controller 300. An image buffer 261 is controlled by the image processing section 255. The image buffer 261 is provided for temporarily storing the image signal read by the front-surface image reading section 260 or the back-surface image reading section 17.
The ADF 100 is connected to the input/output ports of the CPU 251. Connected to the output port are a motor group 103 for driving the conveying rollers, a solenoid group 101, and a clutch group 102. On the other hand, connected to the input port are a sensor group 104 for generating sheet conveying timing signals and the sheet width detection section 11 for detecting the size of each sheet during sheet conveyance.
The CPU 251 executes a control program stored in the ROM 252, to thereby control sheet conveying operation in the ADF 100. The back-surface image reading section 17 comprises an illuminating lamp 307 for back-surface image reading, a CIS (contact image sensor) 308, and a signal controller 107. The back-surface image reading section 17 is connected to the CPU 251. The back-surface image reading section 17 reads a back-surface image from a sheet according to a control signal from the CPU 251 and transfers the read image to the image processing section 255.
Image signals stored in the image buffer 261 are read out into the image processing section 255 in synchronism with a timing signal, and is sequentially transferred to the image controller 300 via a controller interface section 350.
The image controller 300 has a CPU 301, a ROM 302, and a RAM 303 for image control, independently of the reader section 200. The image signals delivered from the image processing section 255 to the image controller 300 are subjected to input/output control by an image input/output unit 304, and are sequentially stored and accumulated as image data in an image memory 305.
An image processing section 310 performs various kinds of image processing on image signals input from the image input/output unit 304 or image data accumulated in the image memory 305. A console section 309 is capable of notifying a user of the status of the apparatus by screen display. Further, the console section 309 receives operation instructions given by the user to the apparatus. In response to the instructions received via the console section 309, the CPU 301 reads out image data from the image memory 305 and executes processing e.g. for transferring an image and information to an external apparatus or a personal computer through a telephone line or a network connected to an external interface 312.
Although in the present embodiment, the front-surface image reading section of the reader section 200 is provided with the CCD and the back-surface image reading section of the ADF 100 is provided with the CIS, this is not limitative, but any other sensor which is capable of image reading may be used in place of the CCD or the CIS.
Next, the pull-off roller section 3 will be described in detail.
The pull-off roller section 3 comprises a conveying roller pair formed by upper and lower rollers 3a and 3b. The upper roller 3a and the lower roller 3b rotate with a sheet P nipped therebetween, to thereby convey the sheet P in the conveying direction. The upper roller 3a and the lower roller 3b are driven by respective different motors (included in the motor group 103 in
The upper roller 3a and the lower roller 3b have respective rotational axes extending in different directions, respectively. Specifically, the lower roller 3b is a conveying roller having a rotational axis extending in the same direction as the rotational axes of the sheet feed roller 1 and the separation roller 2 and that of the registration roller (i.e. in the direction orthogonal to the sheet conveying direction) and configured to convey a sheet P straight in the downstream direction. On the other hand, the upper roller 3a is an obliquely conveying roller having a rotational axis horizontally inclined with respect to the direction orthogonal to the sheet conveying direction. In the present embodiment, the inclination angle of the upper roller 3a with respect to the lower roller 3b is set to 20 degrees. Note that the inclination angle can be changed according e.g. to the material, size, or frictional force of a roller, and therefore it is not limited to 20 degrees. Further, the directional relationship between the rotational axis of the upper roller 3a and that of the lower roller 3b may be reversed.
The upper roller 3a and the lower roller 3b are configured to apply respective different conveying forces to a sheet. The reason for this will be described hereinafter.
Further, the upper roller 3a and the lower roller 3b are constructed such that switching can be performed between contact and separation states. This is because if the two rollers different in axial direction are rotated in direct contact with each other in a state where no sheet exists therebetween, abrasion or deformation can occur to cause damage to the rollers. Switching between contact and separation between the upper roller 3a and the lower roller 3b is performed by driving a specific solenoid of the solenoid group 101 according to a control signal from the CPU 251. In short, the specific solenoid functions as a switching unit for switching between contact and separation between the upper roller 3a and the lower roller 3b. Note that any other construction and method may be employed for switching between contact and separation between the upper roller 3a and the lower roller 3b.
Next, a description will be given, with reference to
Now, a description will be given of conveying forces of the respective upper and lower rollers 3a and 3b for conveying a sheet. It is assumed that the conveying forces are determined using, as parameters, driving forces of the motors for driving the respective upper and lower motors 3a and 3b, the frictional forces of the respective two rollers, angle difference between the rotational axes of the respective rollers, and so forth.
First, a case where the sheet P has been conveyed as a single sheet will be described.
Next, a description will be given of a case where the sheet P has been conveyed in a state overlapping another sheet.
When the upper roller 3a and the lower roller 3b are switched to the contact state, the upper sheet P of the multi-fed sheets receives a force acting in an oblique direction from the upper roller 3a. On the other hand, a lower sheet Pa receives a force acting straight in the conveying direction from the lower roller 3b. As a consequence, a twist occurs between the upper sheet and the lower sheet of the multi-fed sheets, which causes separation between the sheet P and the sheet Pa fed together with the sheet P, as shown in
First, in response to a reading operation start instruction from the image controller 300, the CPU 251 performs control such that a sheet pickup operation for picking up a sheet on the ADF is started (step S800). Specifically, the sheet feed roller 1 is turned on whereby it is driven and lowered into contact with the upper surface of a sheet bundle S to convey sheets P to the separation roller 2. The separation roller 2 attempts to separate an uppermost sheet P and then conveys the separated sheet P into the apparatus.
Then, when a predetermined time period elapses after the start of the pickup operation, the CPU 251 causes the sheet width detection section 11 to start sheet width detection (step S801).
Thereafter, the CPU 251 waits until the sheet P reaches the pull-off roller section 3 (step S802). Immediately before the sheet P reaches the pull-off roller section 3, the CPU 251 switches the pull-off roller section 3 held in the separation state in advance to the contact state, and causes rotation of the upper roller 3a and the lower roller 3b (step S803). Then, the CPU 251 drivingly controls the upper roller 3a and the lower roller 3b to pull off (separate) the sheet P as shown in
Next, the CPU 251 terminates the pickup operation in timing substantially synchronous with execution of the step S803 to thereby facilitate the sheet pull-off operation by the pull-off roller section 3 (step S804). Specifically, the CPU 251 stops driving of the sheet feed roller 1 to allow the same to move upward away from the sheet bundle S, and stops driving of the separation roller 2 at the same time to thereby facilitate the sheet pull-off operation by the pull-off roller section 3.
Then, the CPU 251 determines, based on a change in sheet width detected by the sheet width detection section 11, whether or not the sheet P currently conveyed is in a state overlapping another sheet (step S805).
Now, a description will be given of determination of multi-feed of sheets with reference to
In the present embodiment, multi-feed determination is performed based on a sheet width detected by the sheet width detection section 11.
In the illustrated example, a detected sheet width L0 of the sheet P detected by the sheet width detection section 11 is the same as the actual sheet width of the sheet P.
Now, a detected sheet width of the sheet P detected by the sheet width detection section 11 in the
Now, a detected sheet width of the sheet P detected by the sheet width detection section 11 in the
Referring to
Therefore, when it is determined, by referring to time-varying change in the sheet width detected after a sheet P reaches the pull-off roller section 3, that the degree of the change has exceeded e.g. a predetermined threshold value T, it is possible to judge that the conveyed sheet P is in a state overlapping another sheet.
Although in the present embodiment, multi-feed determination is performed based on a change in sheet width detected by a sheet width detection sensor, this is not limitative, but a dedicated sensor for detecting multi-feed may be additionally provided.
Referring again to
Now, a description will be given, with reference to
Note that in
In a state shown in
Referring again to
If it is determined in the step S806 that multi-feed has not occurred, the CPU 251 continues sheet conveyance to cause the sheet to reach the registration roller 4. Then, after confirming arrival of the sheet at the registration roller 4 (step S812), the CPU 251 stops driving of the pull-off roller section 3 in a predetermined timing to thereby return the upper roller 3a and the lower roller 3b to the separation state (step S813). Finally, the CPU 251 stops operation of the sheet width detection section 11 (step S814) to thereby terminate sheet width detection and multi-feed detection based on time-varying change of a width detection signal. This completes a sequence of sheet-pulling off operations.
Although in the sheet conveying device of the present embodiment, the conveying force of the lower roller 3b configured to convey a sheet in the same conveying direction as the registration roller 4 does is set to be smaller than that of the upper roller 3a, the upper roller 3a may have a smaller conveying force than the lower roller 3b.
As described above, according to the above-described embodiment, one roller of the pair of conveying rollers different in axial direction is disposed such that it conveys a sheet in the conveying direction, and the other roller is disposed such that it conveys a sheet obliquely with respect to the conveying direction so as to separate multi-fed sheets. This makes it possible to facilitate separation of multi-fed sheets to thereby improve sheet conveyance efficiency. Further, it is not required to stop the apparatus, and hence it is possible to further improve sheet conveyance efficiency.
In the above-described embodiment, since the registration roller 4 is disposed downstream of the pull-off roller section 3 in the conveying direction, it is determined in the steps S808 and S812 whether or not a sheet has reached the registration roller 4. However, a roller that can be disposed downstream of the pull-off roller section is not limited to the registration roller, but another kind of roller may be disposed downstream of the pull-off roller section.
Next, a second embodiment of the present invention will be described with reference to drawings.
As shown in
At the rear (upper side as viewed in
Each of separation rollers 1002 has its pull-in angle set such that the axis of the separation roller 1002 is directed in a direction orthogonal to the gradient of a portion of the sheet guide member 1040 with which a sheet bundle side is brought into contact. The cross-sectional view of the ADF 1100 is substantially the same as
A conveying roller pair of a pull-in roller section 1003 is disposed such that an upper roller as one of the rollers conveys a sheet in the sheet conveying direction and a lower roller as the other of the rollers conveys a sheet in the same direction as a direction in which a sheet bundle S on the sheet tray is pulled in. In short, the lower roller is disposed so as to convey a sheet obliquely with respect to the sheet conveying direction.
The conveying forces of the two conveying rollers of the pull-in roller section 1003 are set such that the conveying force of the upper roller for conveying a sheet in the conveying direction is larger than that of the lower roller.
Note that the image reading apparatus of the present embodiment is identical in configuration to that of the first embodiment, and therefore a control block diagram thereof and description thereof are omitted.
Next, the behavior of a sheet P in the pull-in roller section 1003 will be described with reference to
Control of the pull-in roller section 1003 in the present embodiment is performed following the same control procedure as in the first embodiment, and therefore description thereof is omitted.
As described above, also in the sheet conveying device having the sheet tray extending in a manner expanding toward the front side so as to facilitate user operation for placing sheets on the sheet tray, the pull-in roller section 1003 is formed by the pair of rollers different in conveying direction. This makes it possible to switch the sheet conveying direction to the direction of conveyance by a downstream conveying roller (e.g. the registration roller 4) and positively perform separation of multi-fed sheets.
Although in the above-described first and second embodiments, the image reading apparatus provided with the sheet conveying device is described, this is not limitative, but the present invention is also applicable to an image forming apparatus including an image forming section (printer section) in addition to an image reading section having the above-described construction.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims priority from Japanese Patent Application No. 2011-069970 filed Mar. 28, 2011, and Japanese Patent Application No. 2012-064026 filed Mar. 21, 2012, which are hereby incorporated by reference herein in their entirety.
Number | Date | Country | Kind |
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2011-069970 | Mar 2011 | JP | national |
2012-064026 | Mar 2012 | JP | national |