JP2012025544A - Sheet conveying device and method of control thereof - Google Patents

Abstract

In a sheet conveying device, skew correction is performed by accurately detecting skew while maintaining an appropriate gap between sheets.
A sheet conveying device corrects skew of a sheet while conveying the sheet. The right and left rollers 1R and 1L are disposed at different positions in the width direction of the sheet intersecting the sheet conveyance direction, and are driven independently of each other to convey the sheet. The skew correction control unit 6 includes a first time that represents a time from when the trailing edge of the preceding sheet 9 is detected by both the right and left sensors until the right and left sensors detect the leading edge of the skew correction target sheet 10. The first and second detection times are obtained, and the first and second detection times are compared with a predetermined transport time, respectively, to obtain the first and second comparison results. The skew correction controller controls driving of the right and left rollers according to the first and second comparison results, respectively.
[Selection] Figure 2

Description

  The present invention relates to a sheet conveying apparatus for conveying a sheet such as recording paper, which is used in an image forming apparatus or the like, and a control method thereof.

  In general, an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic process is provided with a sheet conveying device for conveying a sheet such as a recording sheet to an image forming unit that performs image formation. In order to transfer the toner image formed by the image forming unit to the sheet satisfactorily, it is necessary to keep the posture of the sheet appropriately. Further, it is necessary to align the sheet and the toner image formed by the image forming unit. For this reason, some sheet conveying apparatuses have a skew correction function for correcting so-called skew of sheets.

  By the way, when correcting the skew of the sheet, there is one in which a loop is formed on the sheet by a pair of registration rollers to correct the skew of the sheet. However, in this correction method, the sheet needs to be temporarily stopped, and therefore, the time required for correcting the skew feeding becomes long.

  In order to prevent such an inconvenience, that is, to shorten the time required for correcting the skew, the sheet is conveyed by using two sheet detection sensors and a pair of skew correction rollers that rotate independently of each other. However, there is one that is made to turn while doing (see, for example, Patent Document 1).

  A method for correcting the skew of the sheet in this way is called an active resist method.

  In the above active registration system, the two sheet detection sensors are arranged on a coaxial line that is orthogonal to (intersects) the sheet conveyance direction in the sheet conveyance path. Then, when the leading edge of the sheet crosses the two sheet detection sensors, it is determined whether or not the sheet is skewed according to the time difference between the sheet detection signals output from the sheet detection sensor.

  That is, the skew amount indicating the degree of skew of the sheet is obtained in accordance with the sheet detection signal, and the rotational speed of each skew correction roller is independently controlled based on the skew amount. Specifically, the sheet conveyance speed by the left and right skew correction rollers arranged in the direction crossing the sheet conveyance path is changed according to the sheet skew amount to correct the sheet skew. Yes. At the time of skew correction, the sheet conveyance speed by one skew correction roller is made slower than the sheet conveyance speed by the other skew correction roller according to the sheet skew amount (skew deceleration control and Called) or faster (called skew speed increase control). Thereby, the skew of the sheet is corrected.

  In the active registration method as described above, skew correction can be performed without temporarily stopping the sheet conveyance, so that the sheet interval (the interval between the preceding sheet and the succeeding sheet) is narrower than other methods. can do. As a result, in the active registration method, sheet conveyance efficiency can be increased.

  For example, if an active resist system is used, the image forming speed can be substantially improved without increasing the image forming process speed in the image forming apparatus. Therefore, the active resist system can cope with the speeding up of the image forming operation in the image forming apparatus.

Japanese Patent Laid-Open No. 10-032682

  In recent years, there has been an increasing demand for improvement in productivity in image forming apparatuses such as copying machines and printers. In order to meet such a requirement, the sheet conveyance speed is increased. Furthermore, a countermeasure such as narrowing the interval between conveyed sheets is also considered.

  However, when the sheet conveyance speed is increased, the stability at the time of transferring the toner image to the sheet is inevitably impaired. Furthermore, the stability in the fixing process after transfer is also lost. And as mentioned above, when stability is impaired, the image quality in image formation will deteriorate.

  For this reason, there is a tendency to improve the productivity per unit time by narrowing the interval between conveyed sheets. Further, it is desired to realize a sheet conveying apparatus that does not cause a paper jam even when the interval between sheets is 10 mm or less.

  However, the skew amount in each sheet is about 15 mm at the maximum with A4 width (296 mm) due to the sheet feeding accuracy by the sheet feeding cassette. Therefore, when a sheet is transported between extremely narrow sheets, if the skew correction is performed without considering the distance between the preceding and succeeding sheets of the skew correction target sheet (the skew correction target sheet), the gap between the sheets is maintained. An inability to occur may occur.

  When the sheet is conveyed in such a state, the sheet detection sensor disposed in the sheet conveyance path cannot determine the leading and trailing edges of the sheet, and erroneously detects that the sheet conveyance is delayed. Will occur.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sheet conveying apparatus and a control method thereof capable of performing skew correction by accurately detecting skew while maintaining an appropriate sheet interval.

  In order to achieve the above object, a sheet conveying apparatus according to the present invention is arranged at different positions in the sheet width direction that intersect the sheet conveying direction in a sheet conveying apparatus that corrects the skew of the sheet while conveying the sheet. The first and second conveying members that are driven independently of each other and convey the sheet; the first and second sheet detecting means that are arranged at different positions in the width direction and detect the sheet; The leading edge of the skew correction target sheet after the trailing edge of the preceding sheet conveyed prior to the skew correction target sheet that is the correction target is detected by both the first and second sheet detecting means. The first and second detection times representing the time until the first and second sheet detection means detect the first and second detection times respectively, and the first and second detection times, the preceding sheet, and the skew are obtained. Line correction pair The first and second comparison results are obtained by comparing with a predetermined conveyance time when the sheet interval is the target interval, respectively, and the first and second comparison results are obtained according to the first and second comparison results, respectively. And control means for drivingly controlling the second transport member.

  The sheet conveying device according to the present invention is a sheet conveying device that corrects the skew of the sheet while conveying the sheet, and is disposed at different positions in the width direction of the sheet intersecting the sheet conveying direction, independently of each other. The first and second conveying members that are driven to convey the sheet, the first and second sheet detecting means that are disposed at different positions in the width direction and detect the sheet, and the first and second sheets In accordance with the detection timing of each of the sheet detection means, the interval between the trailing edge of the preceding sheet preceding the skew correction target sheet that is the skew correction target and the leading edge of the skew correction target sheet is a first. An interval detection unit that obtains an interval between the trailing edge of the skew correction target sheet and the leading edge of the succeeding sheet that follows the skew correction target sheet; and the first and second Drive control of the skew detection means for obtaining the skew amount of the skew correction target sheet according to the detection timing by each of the sheet detection means, and the first and second conveying members according to the skew amount. In addition, when the first interval is larger than the second interval, the speed of the first and second transport members is controlled to increase according to the difference between the first and second intervals. When the first control unit controls driving of the conveying member according to the skew amount, and the first interval is smaller than the second interval, the difference between the first and second intervals And second control means for controlling the speed of the first and second transport members to be reduced.

  According to the present invention, the conveying member is independently controlled in accordance with the time difference between the leading edge of the skew correction target sheet and the trailing edge of the preceding sheet and the predetermined conveying time. The skew correction can be performed on the skew correction target sheet while maintaining the interval with the line correction target sheet.

1 is a diagram illustrating an example of a configuration of an image forming apparatus in which an example of a sheet conveying device according to an embodiment of the present invention is used. FIG. 2 is a plan view showing in detail a first example of the configuration of the sheet conveying apparatus shown in FIG. 1. It is a block diagram which shows an example of a structure of the skew correction control part shown in FIG. FIGS. 3A and 3B are diagrams for explaining an example of the operation of the sheet conveying apparatus illustrated in FIG. 2, in which FIG. 3A illustrates a state in which a preceding sheet reaches a leading edge registration control roller, and FIG. It is a figure which shows the state detected by the sensor or sensor 5L. 3A and 3B are diagrams for explaining an example of the operation of the sheet conveying apparatus illustrated in FIG. 2, in which FIG. 3A illustrates a state in which a leading edge of a skew correction target sheet is detected by a left sensor, and FIG. It is a figure which shows the state by which the object sheet | seat is hold | maintained at both the right side roller and the left side roller. FIG. 6 is a diagram illustrating a state in which skew correction of a skew correction target sheet is performed while keeping a distance between a preceding sheet and a skew correction target sheet at a target distance in an example of the operation of the sheet conveying apparatus illustrated in FIG. 2. FIG. 3 is a diagram for explaining the operation of the sheet conveying apparatus shown in FIG. 2. FIGS. 3A and 3B are diagrams for explaining the speed transition of the skew feeding correction roller in the sheet conveying apparatus shown in FIG. 2, wherein FIG. 3A is a diagram illustrating the speed transition of the right roller, and FIG. is there. FIG. 6 is a plan view showing in detail a second example of the configuration of the sheet conveying apparatus shown in FIG. 1. It is a block diagram which shows an example of a structure of the skew feeding correction control part shown in FIG. FIGS. 10A and 10B are diagrams for explaining an example of the operation of the sheet conveying apparatus illustrated in FIG. 9, in which FIG. 9A illustrates a state in which the trailing end of the skew correction target sheet has passed the upstream sensor, and FIG. It is a figure which shows the state which the rear end passed the right side sensor. FIGS. 10A and 10B are diagrams for explaining an example of the operation of the sheet conveying apparatus illustrated in FIG. 9, in which FIG. 9A is a diagram illustrating a state in which a skew correction sheet is detected by a right sensor, and FIG. It is a figure which shows the state detected with the sensor. FIG. 10 is a diagram illustrating a state in which a skew correction target sheet is skew-corrected by a right roller and a left roller in an example of the operation of the sheet conveying apparatus illustrated in FIG. 9. FIG. 10 is a diagram (No. 1) for explaining the operation of the sheet conveying apparatus illustrated in FIG. 9; FIG. 10 is a second diagram for explaining the operation of the sheet conveying apparatus illustrated in FIG. 9; FIG. 10 is a third diagram for explaining the operation of the sheet conveying apparatus illustrated in FIG. 9; FIG. 10 is a view (No. 4) for explaining the operation of the sheet conveying apparatus shown in FIG. 9; 9A and 9B are diagrams for explaining the speed transition of the skew feeding correction roller in the sheet conveying apparatus shown in FIG. 9, in which FIG. 9A is a diagram illustrating the speed transition of the right roller, and FIG. is there.

  Hereinafter, an example of a sheet conveying apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of the configuration of an image forming apparatus in which an example of a sheet conveying device according to an embodiment of the present invention is used. Although the image forming apparatus will be described as an example here, the sheet conveying apparatus can also be used for an apparatus that needs to supplement the skew of the sheet when conveying a sheet such as a sheet.

  Referring to FIG. 1, the illustrated image forming apparatus includes an image forming unit 300 and a sheet feeding unit 301. The image forming unit 300 includes a photosensitive drum (image carrier) 16. Around the photosensitive drum 16, a charger 20, a developing unit 22, and a cleaner 26 are arranged.

  In FIG. 1, only one image forming unit 300 is shown. However, in a color image forming apparatus for forming a color image, an image forming unit is arranged for each color.

  The photosensitive drum 16 is rotationally driven in the direction of arrow B in the figure by a motor (not shown). The surface of the photosensitive drum 16 is uniformly charged by the charger 20. Thereafter, the laser scanner 105 irradiates the photosensitive drum 16 with laser light corresponding to the image pulse, thereby forming an electrostatic latent image on the photosensitive drum 16. The electrostatic latent image is developed by the developing device 22 to be a toner image.

  A primary transfer unit 24 is disposed opposite to the photosensitive drum 16 with the endless transfer belt 14 interposed therebetween. The primary transfer unit 24 causes the toner image on the photosensitive drum 16 to be a primary transfer image on the transfer belt 14. Is transcribed. After the primary transfer, residual toner remaining on the photosensitive drum 16 is removed by the cleaner 26.

  The transfer belt 14 is installed and supported by three rollers 12 and is driven in the direction of arrow A in the figure by a motor (not shown). A secondary transfer roller 28 is disposed opposite to the lowermost roller 12 in the drawing, and a secondary transfer position defined by a nip portion between the transfer belt 14 and the secondary transfer roller 28 is described later. Then, sheets 9 and 10 such as recording paper are conveyed.

  Then, the primary transfer images 31 and 32 on the transfer belt 14 are sequentially transferred to the sheets 9 and 10 as secondary transfer images by the secondary transfer roller 28. Thereafter, the sheets 9 and 10 are sent to a fixing device (not shown), and the secondary transfer images (toner images) on the sheets 9 and 10 are fixed. After fixing, the sheets 9 and 10 are discharged to a discharge tray (not shown).

  The sheet feeding unit 301 has a paper feed cassette 50 that can be attached to and detached from the image forming apparatus main body. The paper feed cassette 50 stores sheets such as recording paper or OHP sheets. The sheets stored in the paper feed cassette 50 are sent one by one to the image forming unit 300 by the paper feed roller 51.

  As illustrated, a sheet conveying device 302 is disposed between the sheet feeding unit 301 and the image forming unit 300. The sheets 9 and 10 are fed from the sheet feeding unit 301 to the secondary transfer position by the sheet conveying device 302.

  As will be described later, the sheet conveying device 302 performs skew feeding correction and leading edge registration correction on the sheets 9 and 10. As a result, the sheet conveying device 302 increases the posture position accuracy of the sheets 9 and 10 and sends the sheets 9 and 10 to the secondary transfer position in accordance with the toner images 31 and 32 on the transfer belt 14.

  The laser scanner 105 has a built-in polygon mirror (polyhedral mirror), and the laser scanner 105 sends a laser light detection signal when the laser light reflected by the polygon mirror is detected by the laser light detection sensor.

  The image control unit 104 receives a laser light detection signal from the laser scanner 105. Then, the image control unit 104 sends an image pulse corresponding to the image data to the laser scanner 105 in synchronization with the laser light detection signal.

  The controller 103 temporarily stores image data sent from a PC (personal computer) or a document reading device (both not shown). Then, the controller 103 sends image data to the image control unit 104 based on the image request signal and the horizontal synchronization signal sent from the image control unit 104.

  The image control unit 104 generates a horizontal synchronization signal based on the laser light detection signal. Then, after counting a predetermined number of horizontal synchronization signals based on the image request signal, the controller 103 transmits image data to the image control unit 104 every predetermined number of lines in synchronization with the horizontal synchronization signal. As described above, this image data is converted by the image control unit 104 into image pulses having a pulse width corresponding to the data level.

  Here, the operation of the sheet conveying apparatus 302 shown in FIG. 1 will be described. First, in synchronization with a trigger signal issued from a CPU (not shown), the sheet 9 is sent out from the paper feed cassette 50 by the paper feed roller 51 as described above. Then, the sheet 9 passes through the conveying roller 52 and reaches the pre-registration roller 8. A sheet detection sensor (not shown) is disposed in the vicinity of each conveyance roller 52. When the passage of the sheet is detected by the sheet detection sensor, the CPU drives the conveyance roller 52 by a drive control unit (not shown).

  Now, when the sheet 9 passes the image reference detection sensor 100 and the image control unit 104 receives the image reference detection signal, the image control unit 104 outputs an image request signal to the controller 103. As described above, in response to the image request signal, the controller 103 sends the image data to the image control unit 104 in synchronization with the horizontal synchronization signal. Then, the image control unit 104 sends an image pulse corresponding to the image data to the laser scanner 105.

  As a result, as described above, the laser scanner 105 irradiates the photosensitive drum 16 with laser light corresponding to the image pulse, thereby forming an electrostatic latent image. Then, an image forming process is sequentially performed, and primary transfer images 31 and 32 are formed on the transfer belt 14 as described above.

  In FIG. 1, the sheet conveying apparatus 302 includes a skew feeding correction unit 6 </ b> A and a leading edge registration correction unit 101 </ b> A. First, the sheet 9 is conveyed by the pre-registration roller 8 to the skew correction unit 6A. Then, the skew of the sheet 9 is corrected when passing through the skew correction unit 6A.

  As illustrated, the skew correction unit 6A includes a skew correction control unit 6 and a pair of skew detection sensors 5. When the pair of skew detection sensors 5 detect the leading edge of the sheet 9, each pair of skew detection sensors 5 sends a sheet detection signal to the skew correction control unit 6.

  The skew correction control unit 6 obtains the skew amount of the sheet according to the difference in time when the pair of sheet detection signals are received. The skew correction controller 6 corrects the skew of the sheet by, for example, reducing the drive speed of one of the pair of skew correction rollers 1 according to the skew amount of the sheet.

  The leading edge registration correction unit 101A is disposed downstream of the skew feeding correction unit 6A in the transport direction. The sheet 9 is skew-corrected by the skew correction unit 6 </ b> A and then controlled by the leading edge registration correcting unit 101 </ b> A so that the leading edge position thereof matches the primary transfer image (toner image) 31. The tip registration correction unit 101A includes a tip registration control roller 7, a tip registration detection sensor 102, and a tip registration correction control unit 101.

  When the sheet 9 passes the image reference sensor 100, an image reference detection signal is given from the image reference sensor 100 to the leading edge registration correction control unit 101. The leading edge registration correction control unit 101 starts counting a built-in timer in response to the image reference detection signal. Then, the leading edge registration correction control unit 101 obtains the count value of the built-in timer when the sheet 9 passes through the leading edge registration detection sensor 102.

  The leading edge registration correction control unit 101 obtains a difference between the appropriate count value set so that the sheet 9 and the toner image 31 have an appropriate positional relationship and the above count value.

  Subsequently, the leading edge registration correction control unit 101 determines how much the sheet 9 has advanced or delayed with respect to the toner image 31 based on the above difference.

  If the sheet 9 is delayed from the toner image 31 before the sheet 9 reaches the secondary transfer position, the leading edge registration correction control unit 101 sets the peripheral speed of the leading edge registration control roller 7 within a predetermined correction time. To increase the speed. On the other hand, when the sheet 9 is ahead of the toner image 31, the leading edge registration correction control unit 101 decelerates the peripheral speed of the leading edge registration control roller 7 within a predetermined correction time.

  As a result, the leading edge registration correction control unit 101 performs proper registration (registration) between the toner image 31 and the sheet 9.

  After the toner image 31 is transferred to the sheet 9 in this way, the sheet 9 is discharged to the discharge tray via the fixing device 80 as described above. Following the sheet 9, the sheet 10 from the sheet feeding cassette 50 is also conveyed and skew-corrected in the same manner as the sheet 9, and the toner image 32 is transferred and discharged to the discharge tray via the fixing device 80.

  FIG. 2 is a plan view showing in detail a first example of the configuration of the sheet conveying apparatus 302 shown in FIG.

  Referring to FIG. 2, in the illustrated skew correction unit 6A, the pair of skew correction rollers 1 (first transport member and second transport member) are positioned on the right side in the transport direction when viewed from the upstream side in the transport direction. The skew correction roller is shown as a right roller 1R (first transport roller). A skew correction roller located on the left side in the transport direction is shown as a left roller 1L (second transport roller).

  The skew correction controller 6A may include a plurality of skew correction rollers 1. In this case, the plurality of skew correction rollers 1 are disposed along the sheet width direction orthogonal to (intersect) the sheet conveyance direction, and are driven independently of each other.

  The right roller 1R is driven by a stepping motor 2R, and similarly, the left roller 1L is driven by a stepping motor 2L. As illustrated, the right roller 1R and the left roller 1L are connected to stepping motors 2R and 2L by belts 3R and 3L, respectively.

  A driving current is supplied from the driver 4R to each of the stepping motors 2R and 2L. With respect to the pair of skew detection sensors 5 described in FIG. 1, a skew detection sensor located on the right side in the sheet conveyance direction is shown as a right sensor 5R (first sheet detection sensor).

  Further, a skew detection sensor located on the left side in the sheet conveyance direction is shown as a left sensor 5L (second sheet detection sensor). The distance between the right sensor 5R and the left sensor 5L is equal to the distance between the right roller 1R and the left roller 1L. The right sensor 5R and the left sensor 5L are disposed along the sheet width direction orthogonal to the sheet conveyance direction.

  When the skew correction control unit 6 receives a sheet detection signal from each of the skew detection sensors 5R and 5L, it sends a motor drive pulse signal to the drivers 4R and 4L. As a result, the left roller 1R and the right roller 1L are driven and controlled.

  In the tip registration correction unit 101A as well, the pair of tip registration control rollers 7 is driven independently by a driving source such as a stepping motor. Upon receiving a sheet detection signal from the leading edge registration detection sensor 102, the leading edge registration correction control unit 101 (FIG. 1) sends a motor driving pulse signal to the driver to drive and control the stepping motor.

  FIG. 3 is a block diagram showing an example of the configuration of the skew feeding correction control unit 6 shown in FIG.

  Referring to FIG. 3, the skew correction control unit 6 includes a sensor-off detection unit 20 and sensor-on detection units 21R and 21L. The sensor-off detection unit 20 receives sheet detection signals from the right sensor 5R and the left sensor 5L. In the following description, the sheet detection signal output from the right sensor 5R is referred to as a right sheet detection signal. The sheet detection signal output from the left sensor 5L is referred to as a left sheet detection signal.

  As illustrated, the right-side sheet detection signal and the left-side sheet detection signal are given to the sensor-on detection units 21R and 21L, respectively. The sensor-off detection unit 20 sends out a sensor-off signal when both the right sheet detection signal and the left sheet detection signal are turned off.

  On the other hand, the sensor-on detection units 21R and 21L send out a right sensor-on signal and a left sensor-on signal when the right sheet detection signal and the left sheet detection signal are turned on, respectively.

  The sensor off signal and the right sensor on signal are provided to the counter 22R (first counter means), and the sensor off signal and the left sensor on signal are provided to the counter 22L.

  When the counter 22R receives the sensor off signal, the counter 22R starts counting (counting) and outputs a right count signal (first count value). When the right sensor ON signal is received, the counter 22R stops timing. That is, the counter 22R counts the time from the signal output of the sensor-off detection unit 20 to the signal output of the sensor-on detection unit 21R (obtains the first detection time).

  Similarly, when the counter 22L (second counter means) receives the sensor-off signal, it starts timing and outputs a left count signal (second count value). When the left sensor ON signal is received, the counter 22L stops timing. That is, the counter 22L counts the time from the signal output of the sensor-off detection unit 20 to the signal output of the sensor-on detection unit 21L (obtains a second detection time).

  The right count signal and the left count signal are given to the time difference calculation units 23R and 23L, respectively. The time difference calculation unit 23R (first time difference calculation means) calculates a difference (first difference: absolute value) between a predetermined time (also referred to as a predetermined conveyance time) and a count value indicated by the right count signal, and Difference (time difference (first comparison result)).

  At this time, if the predetermined conveyance time> the count value, the time difference calculation unit 23R outputs a speed increase signal indicating speed increase as it is necessary to increase the speed. On the other hand, if the predetermined conveyance time is smaller than the count value, the time difference calculation unit 23R outputs a deceleration signal indicating deceleration as it is necessary to decelerate. That is, the time difference calculation unit 23R outputs an acceleration / deceleration signal (hereinafter referred to as a right acceleration / deceleration signal) in accordance with the relationship between the predetermined conveyance time and the count value.

  Similarly, the time difference calculation unit 23L (second time difference calculation means) calculates a difference (second difference) between a predetermined time (predetermined transport time) and a count value indicated by the left count signal, and calculates a left difference ( Second comparison result). Then, an acceleration / deceleration signal (hereinafter referred to as a left-side acceleration / deceleration signal) is output in the same manner as the time difference calculation unit 23R.

  The right side difference and the right side acceleration / deceleration signal are given from the time difference calculation unit 23R to the increase / decrease speed calculation unit 24R. Further, the left side difference and the left side acceleration / deceleration signal are given from the time difference calculation unit 23L to the increase / decrease speed calculation unit 24L.

  The increase / decrease speed calculation units 24R and 24L determine whether to increase or decrease the speed according to the right acceleration / deceleration signal and the left acceleration / deceleration signal, respectively. Then, the increase / decrease speed calculation unit 24R calculates the delay / advance distance by multiplying the right difference by the current conveyance speed (conveyance speed by the right roller 1R), and divides this delay / advance distance by a predetermined correction time. Thus, the acceleration amount or deceleration amount is used. The increase / decrease speed calculation unit 24R sends a right acceleration / deceleration amount signal indicating the acceleration amount or the deceleration amount to the pulse period conversion unit 25R.

  Similarly, the increase / decrease speed calculation unit 24L calculates the delay / advance distance by multiplying the left difference by the current conveyance speed (conveyance speed by the left roller 1L), and the delay / advance distance is calculated with a predetermined correction time. Divide to obtain the amount of acceleration or deceleration. The increase / decrease speed calculation unit 24L sends a left increase / decrease amount signal indicating the acceleration amount or the deceleration amount to the pulse period conversion unit 25L.

  The pulse cycle conversion unit 25R calculates the speed during acceleration / deceleration by adding the increase / decrease speed indicated by the right acceleration / deceleration amount signal to the steady speed. Then, the pulse period conversion unit 25R obtains a pulse period corresponding to the speed at the time of acceleration / deceleration, and gives the pulse period to the pulse generation unit 26R.

  Similarly, the pulse period conversion unit 25L adds the increase / decrease speed indicated by the left acceleration / deceleration amount signal to the steady speed, and calculates the speed during acceleration / deceleration. Then, the pulse cycle conversion unit 25L obtains a pulse cycle corresponding to the speed at the time of acceleration / deceleration, and gives the pulse cycle to the pulse generation unit 26L.

  As shown in the figure, the right sensor on signal and the left sensor on signal are provided to the delay unit 27 from the sensor on detectors 21R and 21L, respectively. When the delay unit 27 receives both the right sensor on signal and the left sensor on signal, it sends a trigger signal to the pulse generators 26R and 26L after a predetermined delay time.

  The pulse generator 26R generates a pulse signal (right pulse signal) having a pulse period during acceleration / deceleration in synchronization with the trigger signal, and supplies the pulse signal to the driver 4R. That is, the pulse generator 26R performs an output transition from a pulse having a period corresponding to the steady speed to a pulse signal having a pulse period at the time of acceleration / deceleration. When a predetermined skew correction time elapses, the pulse generator 26R makes an output transition to a pulse signal having a cycle corresponding to the steady speed again. Similarly, the pulse generation unit 26L generates a pulse signal (left pulse signal) having a pulse period at the time of acceleration / deceleration in synchronization with the trigger signal, and supplies the pulse signal to the driver 4L. Then, when a predetermined skew correction time elapses, the pulse generator 26L makes an output transition to a pulse signal having a cycle corresponding to the steady speed again.

  4 to 7 are diagrams for explaining an example of the operation of the sheet conveying apparatus 302 shown in FIG.

  2 to 7, first, skew correction is performed on the preceding sheet 9 (see FIG. 4A). The skew correction control unit 6 determines whether or not the rear end of the preceding sheet 9 has passed through the right sensor 5R and the left sensor 5L (S1). If the sensor-off detection unit 20 does not output a sensor-off signal (NO in S1), the skew feeding correction control unit 6 waits until the rear end of the preceding sheet 9 passes through the right sensor 5R and the left sensor 5L.

  On the other hand, when sensor-off detection unit 20 outputs a sensor-off signal (YES in S1), counters 22R and 22L start counting (timekeeping) (S2). The preceding sheet 9 reaches the leading edge registration control roller 7 of the leading edge registration correction unit 101A (FIG. 1) (see FIG. 4A), and the skew correction control unit 6 determines that the leading edge of the skew correction target sheet 10 is the right sensor 5R. Alternatively, it is determined whether or not the left sensor 5L has been passed (S3).

  If the skew correction target sheet 10 is not detected by the right sensor 5R or the left sensor 5L (NO in S3), the skew correction control unit 6 determines that the leading edge of the skew correction target sheet 10 has moved to the right sensor 5R or the left sensor 5L. Wait until it passes.

  When the skew correction target sheet 10 is detected by the right sensor 5R or the left sensor 5L (YES in S3, see FIG. 4B), the right sensor 5R or the left sensor 5L outputs a right sensor on signal or a left sensor on signal. .

  FIG. 4B shows a state in which the front end of the sheet 10 is detected by the right sensor 5R. Therefore, here, the right sensor 5R outputs a right sensor ON signal.

  In response to the right sensor ON signal, the counter 22R stops counting (S4). Then, the counter 22R outputs a right count signal. As described above, the time difference calculation unit 23R obtains a difference (right difference) between the count value indicated by the right count signal and a predetermined conveyance time (for example, conveyance time when the sheet is between the target sheets (target interval)). Furthermore, the time difference calculation unit 23R determines whether or not the count value is greater than a predetermined transport time (S5).

  If the count value is smaller than the predetermined conveyance time (NO in S5), the right roller 1R is decelerated as described in FIG. 3 (S6). On the other hand, if the count value is longer than the predetermined conveyance time (YES in S5), the right roller 1R is accelerated as described in FIG. 3 (S7). Then, the skew correction control unit 6 once ends the process.

  Subsequently, when the leading edge of the skew correction target sheet 10 is detected by the left sensor 5L (see FIG. 5A), the sensor-on detection unit 21L similarly outputs a left sensor-on signal. As a result, the counter 22L stops counting and outputs a left count signal. Then, the time difference calculation unit 23L obtains a difference (left difference) between the count value indicated by the left count signal and a predetermined transport time. Furthermore, the time difference calculation unit 23L determines whether or not the count value is greater than a predetermined transport time. Thereafter, as described in FIG. 3, the left roller 1L is decelerated or accelerated.

  FIG. 8 is a diagram for explaining the speed transition of the skew feeding correction roller in the sheet conveying apparatus 302 shown in FIG. FIG. 8A is a diagram showing the speed transition of the right roller 1R, and FIG. 8B is a diagram showing the speed transition of the left roller 1L.

  Referring to FIG. 8, it is assumed that the count value is smaller than a predetermined conveyance time (also referred to as a target time) on the right roller 1R side. In this case, the time difference calculation unit 23R provides the increase / decrease speed calculation unit 24R with the time difference ΔtR obtained by subtracting the count value from the target time Tid as the right side difference (time difference information). Further, the time difference calculation unit 23R sends deceleration information = 0 to the increase / decrease speed calculation unit 24R as a right acceleration / deceleration signal (also referred to as acceleration / deceleration information).

  As shown in FIG. 8A, the increase / decrease speed calculation unit 24R multiplies the time difference ΔtR by the conveyance speed V0 of the sheet 10. That is, the increase / decrease speed calculation unit 24R calculates the distance difference between the target distance (V0 × Tid) between the skew correction target sheet 10 and the preceding sheet 9 and the actual distance as V0 × ΔtR (in FIG. 8A, a diagonal line). (See also FIG. 5B).

  Further, the increase / decrease speed calculation unit 24R calculates the deceleration width ΔVR by dividing the distance difference V0 × ΔtR by the skew correction time T. Then, the increase / decrease speed calculation unit 24R sends a speed V1R obtained by subtracting the deceleration width ΔVR from the conveyance speed V0 to the pulse cycle conversion unit 25R as a right side acceleration / deceleration amount signal.

  As a result, the pulse cycle conversion unit 25R sends pulse cycle information indicating the pulse cycle at which the peripheral speed of the right roller 1R becomes the speed V1R to the pulse generation unit 26R.

  Now, it is assumed that the count value is larger than the target time on the left roller 1L side. In this case, the time difference calculation unit 23R gives the time difference ΔtL obtained by subtracting the target time Tid from the count value to the increase / decrease speed calculation unit 24L as the left side difference (time difference information). Further, the time difference calculation unit 23R sends speed increase information = 1 to the increase / decrease speed calculation unit 24L as a left side acceleration / deceleration signal (also referred to as acceleration / deceleration information).

  As shown in FIG. 8B, the increase / decrease speed calculation unit 24L multiplies the time difference ΔtL by the conveyance speed V0 of the sheet 10. That is, the increase / decrease speed calculation unit 24L calculates the distance difference between the target distance (V0 × Tid) between the skew correction target sheet 10 and the preceding sheet 9 and the actual distance as V0 × ΔtL (in FIG. 8B, a diagonal line). (See also FIG. 5B).

  Further, the increase / decrease speed calculation unit 24L calculates the deceleration width ΔVL by dividing the distance difference V0 × ΔtL by the skew correction time T. Then, the increase / decrease speed calculation unit 24L sends a speed V1L obtained by subtracting the deceleration width ΔVL from the conveyance speed V0 to the pulse cycle conversion unit 25L as a left side acceleration / deceleration amount signal.

  As a result, the pulse cycle conversion unit 25L sends pulse cycle information indicating the pulse cycle at which the peripheral speed of the left roller 1L becomes the speed V1L to the pulse generation unit 26L.

  When the skew correction target sheet 10 is held by both the right roller 1R and the left roller 1L (see FIG. 5B), a pre-registration roller (hereinafter referred to as a conveyance roller) 8 is a nipping release mechanism ( (Not shown in the figure). Accordingly, the rear end of the skew correction target sheet 10 is released from the conveyance roller 8.

  As described above, when the trigger signal is given from the delay unit 27 to the pulse generation units 26R and 26L, the pulse signal is sent from the pulse generation units 26R and 26L to the drivers 4R and 4L.

  Thereby, the rotational speeds of the stepping motors 2R and 2L are controlled according to the drive currents from the drivers 4R and 4L, and the peripheral speeds of the right rollers 1R and 1L are the same as the speeds shown in FIGS. 8A and 8B described above. Become.

  As a result, in the above example, the right roller 1R is decelerated and the left roller 1L is accelerated. Then, the skew of the skew correction target sheet 10 is corrected.

  As a result, as shown in FIG. 8, the skew correction of the skew correction target sheet 10 is performed while the distance between the preceding sheet 9 and the skew correction target sheet 10 is maintained at the target distance (V0 × Tid). become.

  At this time, the leading edge registration control by the leading edge registration control roller 7 is performed on the preceding sheet 9 for which the skew feeding correction has already been performed. As described above, the leading edge registration correction control unit 101 starts counting by the built-in timer when receiving the image reference detection signal from the image reference sensor 100. When the preceding sheet 9 passes through the leading edge registration detection sensor 102, the leading edge registration correction control unit 101 confirms the count value of the built-in timer.

  When the count value is smaller than the predetermined target value (sheet arrives early), the leading edge registration correction control unit 101 performs deceleration control on the preceding sheet 9 by the same method as described in FIG.

  On the other hand, when the count value is larger than the target value (the sheet is delayed), the leading edge registration correction control unit 101 performs speed increase control on the preceding sheet 9 by the same method as that described with reference to FIG.

  Even when the leading edge registration correction control unit 101 performs the deceleration control on the preceding sheet 9, as described above, the sheet spacing is maintained for the skew correction target sheet 10 positioned upstream, so the sheet The rear end and the front end of each other do not overlap. As a result, the sheet can be stably conveyed.

  As described above, in the first example, the distance between the leading edge of the skew correction target sheet 10 and the trailing edge of the preceding sheet 9 is detected, and the pair of skew rollers 5 are controlled to increase / decrease independently of each other. I am doing so. Accordingly, the skew correction of the skew correction target sheet 10 can be performed while maintaining an appropriate gap between the skew correction target sheet 10 and the preceding sheet 9.

  FIG. 9 is a plan view showing in detail a second example of the configuration of the sheet conveying apparatus 302 shown in FIG.

  In FIG. 9, the same components as those in the sheet conveying apparatus 302 shown in FIG. A sheet conveying apparatus 302 shown in FIG. 9 newly includes a sheet detection sensor 33 and a pair of conveying rollers 34.

  The sheet detection sensor 33 is disposed on the upstream side in the sheet conveyance direction from the conveyance roller 8. The pair of transport rollers 34 is disposed upstream of the sheet detection sensor 33 in the sheet transport direction. The illustrated skew correction control unit is different from the skew correction control unit 6 shown in FIG.

  In the example illustrated in FIG. 9, it is assumed that the skew correction target sheet 10 is conveyed following the preceding sheet 9, and the subsequent sheet 35 is conveyed subsequent to the skew correction target sheet 10.

  The sheet detection sensor 33 is for detecting the interval between the rear end of the correction target sheet 10 and the front end of the subsequent sheet 35, and the sheet detection sensor 33 is connected to the skew correction control unit 40. .

  FIG. 10 is a block diagram showing an example of the configuration of the skew feeding correction control unit 40 shown in FIG.

  Referring to FIG. 10, the illustrated skew correction control unit 40 includes sensor-on detection units 50, 51, 55, 58, and 62 and also includes sensor-off detection units 54, 57, and 61.

  When the right sensor 5R is ON (sheet detection), the sensor ON detection units 50 and 55 output a right sensor ON signal. The sensor-on detection units 51 and 58 output a left-side sensor-on signal when the left-side sensor 5L is on (sheet detection).

  On the other hand, when the right sensor 5R is turned off, the sensor off detector 54 outputs a right sensor off signal, and when the left sensor 5L is turned off, the sensor off detector 57 outputs a left sensor off signal.

  Further, when the upstream sensor 33 (third sheet detection sensor) is turned off, the sensor off detection unit 61 outputs an upstream sensor off signal, and when the upstream sensor 33 is turned on, the sensor on detection unit 62 outputs an upstream sensor on signal.

  When the right sensor on signal and the left sensor on signal are respectively given from the sensor on detection units 50 and 51, the skew detection unit 52 calculates the difference between the times when the right sensor on signal and the left sensor on signal are received as the input time difference.

  Further, the skew detection unit 52 determines which of the right sensor ON signal and the left sensor ON signal is input first, and sets the skew flag R and the skew flag L (sets to 1).

  For example, when the right sensor ON signal is input before the left sensor ON signal, the skew detection unit 52 sets the skew flag R = “1”. On the other hand, when the left sensor ON signal is input before the right sensor ON signal, the skew detection unit 52 sets the skew flag L = “1”. When the right sensor on signal and the left sensor on signal are input simultaneously, the skew detection unit 52 keeps both the skew flag R and the skew flag L at ‘0’.

  The right sensor off signal is supplied to the counter 56. When the counter 56 receives the right sensor off signal, the counter 56 starts counting (clocking). When the counter 56 receives the right sensor ON signal, the counter 56 stops counting and outputs a right count signal.

  Similarly, the left sensor off signal is given to the counter 59, and when the counter 59 receives the left sensor off signal, the counter 59 starts counting (clocking). When the counter 59 receives the left sensor ON signal, the counter 59 stops counting and outputs a left count signal.

  The right count signal and the left count signal are provided to the intermediate value calculation unit 64, and the intermediate value calculation unit 64 calculates the intermediate value of the count values indicated by the right count signal and the left count signal, as will be described later.

  Further, the upstream sensor off signal and the upstream sensor on signal are given to the counter 63. When the counter 63 receives the upstream sensor off signal, it starts counting, and when it receives the upstream sensor on signal, it stops counting and outputs an upstream count signal.

  The intermediate value calculation unit 64 gives the intermediate value to the time difference calculation unit 65 as the preceding sheet interval, and the counter 63 gives the upstream count signal to the time difference calculation unit 65 as the subsequent sheet interval.

  The time difference calculation unit 65 obtains a difference (time difference) between the intermediate value and the count value indicated by the upstream count signal. The time difference calculation unit 65 sets the delay flag and the advance flag as a signal indicating the relationship between the skew target sheet 10 and the succeeding sheet 32.

  For example, if the intermediate value is larger than the count value of the upstream count signal, the time difference calculation unit 65 sets the delay flag = ‘1’. On the other hand, when the intermediate value is smaller than the count value of the upstream count signal, the time difference calculation unit 65 sets the advance flag = “1”. If the intermediate value and the count value of the upstream count signal are the same, the time difference calculation unit 65 keeps both the delay flag and the advance flag at ‘0’.

  The delay flag and the advance flag are given to the increase / decrease speed calculation units 66R and 66L. The skew flags R and L described above are also given to the increase / decrease speed calculators 66R and 66L.

  Further, the input time difference, which is the output of the skew detection unit 52, is halved (1/2) and supplied to the increase / decrease speed calculation units 66R and 66L. The difference which is the output of the time difference calculation unit 65 is also halved (1/2) and is given to the increase / decrease speed calculation units 66R and 66L.

  The increase / decrease speed calculation units 66R and 66L calculate the acceleration amount or the deceleration amount for correcting the difference and the input time difference. For example, when the skew flag L = '1', the increase / decrease speed calculation unit 66R uses 1/2 of the input time difference as the speed increase amount, and when the skew flag R = '1', 1 / of the input time difference 2 is the deceleration amount.

  The increase / decrease speed calculation unit 66L uses 1/2 of the input time difference as the speed increase amount when the skew flag R = '1', and calculates 1/2 of the input time difference when the skew flag L = '1'. Deceleration amount.

  Further, the increase / decrease speed calculation units 66R and 66L both increase the acceleration amount by 1/2 of the difference when the delay flag = '1', and reduce 1/2 of the difference when the advance flag = '1'. Amount.

  As described above, the increase / decrease speed calculation units 66R and 66L add / subtract the input time difference and the difference based on the skew flag R, the skew flag L, the delay flag, and the advance flag. Then, the increase / decrease speed calculation units 66R and 66L calculate the delay / advance distance by multiplying the addition / subtraction result by the conveyance speed.

  Further, the increase / decrease speed calculation units 66R and 66L divide the delay / advance distance by the skew correction time, and output an increase / decrease amount. The increase / decrease speed calculation units 66R and 66L give the acceleration / deceleration amounts to the pulse cycle conversion units 25R and 25L, respectively, as a right acceleration / deceleration amount signal and a left acceleration / deceleration amount signal. Thus, skew correction control is performed as described with reference to FIG.

  11 to 13 are diagrams for explaining an example of the operation of the sheet conveying apparatus 302 shown in FIG. 14 to 17 are diagrams for explaining an example of the operation of the sheet conveying apparatus 302 shown in FIG.

  With reference to FIGS. 9 to 17, in the following description, it is assumed that the correction target sheet 10 is skewed in the state shown in FIG. 9. First, skew correction is performed on the preceding sheet 9 (FIG. 11A). The skew correction control unit 40 determines whether or not the rear end of the preceding sheet 9 has passed through the right sensor 5R (S10). If sensor-off detection unit 54 does not output a sensor-off signal (NO in S10), skew correction control unit 40 waits until the rear end of preceding sheet 9 passes right sensor 5R.

  On the other hand, when the rear end of the preceding sheet 9 passes the right sensor 5R in the state shown in FIG. 11B, that is, when the sensor-off detection unit 54 outputs a sensor-off signal (YES in S10), the counter 56 is Counting (timing) is started (S11). The skew correction controller 6 determines whether or not the leading edge of the skew correction target sheet 10 has passed through the right sensor 5R (S12).

  If the skew correction target sheet 10 is not detected by the right sensor 5R (NO in S12), the skew correction control unit 40 waits until the leading edge of the skew correction target sheet 10 passes the right sensor 5R.

  When the skew correction sheet 10 is detected by the right sensor 5R (YES in S12, see FIG. 12A), the sensor-on detection unit 55 outputs a right sensor-on signal. In response to the right sensor ON signal, the counter 56 stops counting (S13). The counter 56 outputs a right count signal.

  Further, the skew correction control unit 40 determines whether or not the rear end of the preceding sheet 9 has passed the left sensor 5L (S14). If sensor off detection unit 57 does not output the left sensor off signal (NO in S14), skew correction control unit 40 waits until the rear end of preceding sheet 9 passes through left sensor 5L.

  On the other hand, when the rear end of the preceding sheet 9 passes the left sensor 5R in the state shown in FIG. 11B, that is, when the sensor off detection unit 57 outputs the left sensor off signal (YES in S14), the counter 59 Starts counting (timekeeping) (S15). The preceding sheet 9 reaches the leading edge registration control roller 7 of the leading edge registration correction unit 101A (FIG. 1) (see FIG. 9). The skew correction controller 6 determines whether or not the leading end of the skew correction target sheet 10 has passed the left sensor 5L (S16).

  If the skew correction target sheet 10 is not detected by the left sensor 5L (NO in S16), the skew correction control unit 40 waits until the leading edge of the skew correction target sheet 10 passes the left sensor 5L.

  When the skew correction sheet 10 is detected by the left sensor 5L (YES in S16, see FIG. 12B), the sensor-on detection unit 58 outputs a left sensor-on signal. In response to the left sensor ON signal, the counter 59 stops counting (S17). Then, the counter 59 outputs a left count signal.

  The intermediate value calculation unit 64 outputs the intermediate value between the count value indicated by the right count signal and the count value indicated by the left count signal as the interval ITVLa (first interval) between the preceding sheet 9 and the skew correction target sheet 10. (S18).

  As shown in FIG. 12B, the distance between the preceding sheet 9 and the skew correction target sheet 10 is V0 × ITVLa.

  Further, the skew correction control unit 40 determines whether or not the rear end of the skew correction target sheet 10 has passed through the upstream sensor 33 (S19). If the sensor-off detection unit 61 does not output the upstream sensor off signal (NO in S19), the skew correction control unit 40 waits until the rear end of the skew correction target sheet 10 passes the upstream sensor 33.

  On the other hand, in the state shown in FIG. 11A, when the rear end of the skew correction target sheet 10 passes the upstream sensor 33, the sensor-off detection unit 61 outputs an upstream sensor-off signal. When sensor off detector 61 outputs the upstream sensor off signal (YES in S19), counter 63 starts counting (timekeeping) (S20). The skew correction control unit 6 determines whether the leading edge of the succeeding sheet 35 has passed through the upstream sensor 33 (S21).

  If the succeeding sheet 35 is not detected by the upstream sensor 33 (NO in S21), the skew correction control unit 40 waits until the leading edge of the succeeding sheet 35 passes the upstream sensor 33.

  In the state shown in FIG. 11B, when the leading edge of the trailing sheet 35 passes the upstream sensor 33, the sensor-on detection unit 62 outputs an upstream sensor-on signal. That is, when the leading edge of the trailing sheet 35 is detected by the upstream sensor 30 (YES in S21), the sensor-on detection unit 62 outputs an upstream sensor-on signal.

  In response to the upstream sensor ON signal, the counter 63 stops counting. Then, the counter 59 outputs the right count signal as an interval ITVLb (second interval) between the succeeding sheet 35 and the skew correction target sheet 10 (S22).

  As shown in FIG. 11B, the distance between the skew correction target sheet 10 and the succeeding sheet 35 is V0 × ITVLb.

  Incidentally, the skew correction control unit 40 determines whether or not the leading edge of the skew correction target sheet 10 has simultaneously passed through the right sensor 5R and the left sensor 5L (S23). That is, the skew detection unit 52 monitors whether the right sensor on signal output from the sensor on detection unit 50 and the left sensor on signal output from the sensor on detection unit 51 are input simultaneously.

  If the right sensor ON signal and the left sensor ON signal are not input simultaneously (NO in S23), the skew detection unit 52 determines whether the leading edge of the skew correction target sheet 10 has passed the right sensor 5R (S24). . That is, the skew detection unit 52 determines whether or not the right sensor on signal is input.

  If the right sensor ON signal is not input (NO in S24), the skew detection unit 52 determines whether the leading edge of the skew correction target sheet 10 has passed the left sensor 5L (S25). That is, the skew detection unit 52 determines whether or not the left sensor ON signal is input.

  If the left sensor ON signal is not input (NO in S25), the skew detection unit 52 determines whether or not the leading edge of the skew correction target sheet 10 has simultaneously passed through the right sensor 5R and the left sensor 5L (S23).

  When the right sensor ON signal is input (YES in S24), the skew detection unit 52 sets the skew flag R = '1' and starts counting (S26). Then, the skew detection unit 52 determines whether or not the leading end of the skew correction target sheet 10 has passed the left sensor 5L (S27).

  If the left sensor ON signal is not received (NO in S27), the skew detection unit 52 waits until the left sensor ON signal is received. On the other hand, when the left sensor ON signal is received (YES in S27), the skew detection unit 52 stops counting (S28).

  When the left sensor ON signal is input (YES in S25), the skew detection unit 52 sets the skew flag L = '1' and starts counting (S29). Then, the skew detection unit 52 determines whether or not the leading end of the skew correction target sheet 10 has passed the right sensor 5R (S30).

  If the right sensor on signal is not received (NO in S30), the skew detection unit 52 waits until the right sensor on signal is received. On the other hand, when the right sensor ON signal is received (YES in S30), skew detection unit 52 stops counting (S28).

  Here, the time difference calculation unit 65 determines whether or not the interval ITVLa and the interval ITVLb are equal (S31). If interval ITVLa and interval ITVLb are not equal (NO in S31), time difference calculation unit 65 determines whether or not interval ITVLa> interval ITVLb (S32).

  If interval ITVLa <interval ITVLb (NO in S32), time difference calculation unit 65 outputs half (Δt2) of (interval ITVLb−interval ITVLa) as advance flag = “1” (S33).

  If interval ITVLa> interval ITVLb (YES in S32), time difference calculation unit 65 outputs half (Δt1) of (interval ITVLa−interval ITVLb) as delay flag = “1” (S34).

  Subsequently, each of the increase / decrease speed calculation units 66R and 66L determines whether or not the skew flag R = '1' (S35). When the skew flag R = '1' (YES in S35), the increase / decrease speed calculation unit 66R obtains a deceleration amount for reducing the peripheral speed of the right roller 1R by V0 × (Δt1 + Δt2) / T ( S36).

  When the skew flag R = '1', the increase / decrease speed calculation unit 66L determines whether Δt1> Δt2 is satisfied (S37). If Δt1> Δt2 (YES in S37), the increase / decrease speed calculation unit 66L obtains a speed increase amount for increasing the peripheral speed of the left roller 1L by V0 × (Δt1−Δt2) / T ( S38), the process is terminated.

  If Δt1> Δt2 is not satisfied (NO in S37), the increase / decrease speed calculation unit 66L obtains a deceleration amount for reducing the peripheral speed of the left roller 1L by V0 × (Δt2−Δt1) / T (S39), End the process.

  If the skew flag R is not “1” (NO in S35), each of the increase / decrease speed calculation units 66R and 66L determines whether the skew flag L is “1” (S40). When the skew flag L = '1' (YES in S40), the increase / decrease speed calculation unit 66L obtains a deceleration amount for reducing the peripheral speed of the left roller 1L by V0 × (Δt1 + Δt2) / T ( S41).

  When the skew flag L = '1', the increase / decrease speed calculation unit 66R determines whether Δt1> Δt2 is satisfied (S42). If Δt1> Δt2 (YES in S42), the increase / decrease speed calculation unit 66R obtains a speed increase amount for increasing the peripheral speed of the right roller 1R by V0 × (Δt1−Δt2) / T ( S43), the process is terminated.

  If Δt1> Δt2 is not satisfied (NO in S42), the increase / decrease speed calculation unit 66R obtains a deceleration amount for decelerating the peripheral speed of the right roller 1R by V0 × (Δt2−Δt1) / T (S44), End the process.

  If the skew flag L is not “1” (NO in S40), the increase / decrease speed calculation units 66R and 66L obtain the deceleration amounts by which the peripheral speeds of the right roller 1R and the left roller 1L are reduced by V0 × Δt2 / T, respectively. (S45), and the process ends.

  Each of the increase / decrease speed calculation units 66R and 66L determines whether or not the skew flag R = '1' (S46). If the skew flag R = '1' (YES in S46), the increase / decrease speed calculation unit 66L increases the speed increase amount for increasing the peripheral speed of the left roller 1L by V0 × (Δt1 + Δt2) / T. Obtain (S47).

  When the skew flag R = '1', the increase / decrease speed calculation unit 66R determines whether Δt1> Δt2 is satisfied (S48). If Δt1> Δt2 (YES in S48), the increase / decrease speed calculation unit 66R obtains a deceleration amount for reducing the peripheral speed of the right roller 1R by V0 × (Δt1-Δt2) / T (S49). The process is terminated.

  If Δt1> Δt2 is not satisfied (NO in S48), the increase / decrease speed calculation unit 66R obtains a speed increase amount for increasing the peripheral speed of the right roller 1R by V0 × (Δt2−Δt1) / T (S50). ), The process is terminated.

  If the skew flag R is not "1" (NO in S46), each of the increase / decrease speed calculation units 66R and 66L determines whether or not the skew flag L is "1" (S51). When the skew flag L = '1' (YES in S51), the increase / decrease speed calculation unit 66R increases the speed increase amount for increasing the peripheral speed of the right roller 1R by V0 × (Δt1 + Δt2) / T. Obtained (S52).

  When the skew flag L = '1', the increase / decrease speed calculation unit 66L determines whether Δt1> Δt2 is satisfied (S53). If Δt1> Δt2 (YES in S53), the increase / decrease speed calculation unit 66L obtains a speed increase amount for increasing the peripheral speed of the left roller 1L by V0 × (Δt1−Δt2) / T ( S54), the process is terminated.

  If Δt1> Δt2 is not satisfied (NO in S42), the increase / decrease speed calculation unit 66L obtains a deceleration amount for decelerating the peripheral speed of the left roller 1L by V0 × (Δt2−Δt1) / T (S55), End the process.

  If the skew flag L is not “1” in S51 (NO in S51), the increase / decrease speed calculation units 66R and 66L increase the peripheral speeds of the right roller 1R and the left roller 1L by V0 × Δt2 / T, respectively. The amount of speed increase is obtained (S56). And the increase / decrease speed calculation parts 66R and 66L complete | finish a process.

  If interval ITVLa and interval ITVLb are equal (YES in S31), each of increase / decrease speed calculation units 66R and 66L determines whether or not skew flag R = '1' (S57). If the skew flag R = '1' (YES in S57), the increase / decrease speed calculation unit 66R obtains a deceleration amount for reducing the peripheral speed of the right roller 1R by V0 × Δt1 / T (S58). . Further, the increase / decrease speed calculation unit 66L obtains a speed increase amount for increasing the peripheral speed of the left roller 1L by V0 × Δt1 / T (S58). And the increase / decrease speed calculation parts 66R and 66L complete | finish a process.

  If the skew flag R is not “1” (NO in S57), each of the increase / decrease speed calculation units 66R and 66L determines whether the skew flag L is “1” (S59). If the skew flag L = '1' (YES in S59), the increase / decrease speed calculation unit 66L obtains a deceleration amount for reducing the peripheral speed of the left roller 1L by V0 × Δt1 / T (S60). . Further, the increase / decrease speed calculation unit 66R obtains a speed increase amount for increasing the peripheral speed of the right roller 1R by V0 × Δt1 / T (S60). And the increase / decrease speed calculation parts 66R and 66L complete | finish a process. If the skew flag L is not “1” (NO in S59), the increase / decrease speed calculation units 66R and 66L end the process.

  By the way, as described above, after the skew detection unit 52 stops counting, the increase / decrease speed calculation units 66R and 66L determine whether or not the skew flag L = '1' (S61). If the skew flag L = '1' (YES in S61), the increase / decrease speed calculation unit 66L sets half of the skew amount (Δt1) as the deceleration amount of the left roller 1L (S62). Further, the acceleration calculation unit 66R sets half the skew amount (Δt1) as the acceleration amount of the right roller 1R (S62).

  Subsequently, each of the increase / decrease speed calculation units 66R and 66L determines whether or not the advance flag = '1' (S63). If the advance flag = '1' (YES in S63), the increase / decrease speed calculation unit 66L obtains a deceleration amount for reducing the peripheral speed of the left roller 1L by V0 × (Δt1 + Δt2) / T (S41). .

  On the other hand, if the advance flag is not “1” (NO in S63), each of the increase / decrease speed calculation units 66R and 66L determines whether or not the delay flag is “1” (S64). When the delay flag is “1” (YES in S64), the increase / decrease speed calculation unit 66R obtains a speed increase amount for increasing the peripheral speed of the right roller 1R by V0 × (Δt1 + Δt2) / T ( S52). If the delay flag is not “1” (NO in S64), the increase / decrease speed calculation units 66L and 66R respectively reduce the amount of deceleration for reducing the peripheral speed of the left roller 1L by V0 × Δt1 / T and the right roller 1R. A speed increase amount for increasing the peripheral speed by V0 × Δt1 / T is obtained (S60).

  If the skew flag L is not “1” (NO in S61), the increase / decrease speed calculation unit 66R sets half the skew amount (Δt1) as the deceleration amount of the right roller 1R (S65). Further, the acceleration calculation unit 66L sets half the skew amount (Δt1) as the acceleration amount of the left roller 1L (S65). As shown in FIG. 12B, the skew amount of the skew correction target sheet 10 is V0 × 2Δt1.

  Subsequently, each of the increase / decrease speed calculation units 66R and 66L determines whether or not the advance flag = '1' (S66). If the advance flag is “1” (YES in S66), the increase / decrease speed calculation unit 66R is for the increase / decrease speed calculation unit 66R to reduce the peripheral speed of the right roller 1R by V0 × (Δt1 + Δt2) / T. A deceleration amount is obtained (S36).

  On the other hand, if the advance flag is not “1” (NO in S66), each of the increase / decrease speed calculation units 66R and 66L determines whether or not the delay flag is “1” (S67). If delay flag = '1' (YES in S67), increase / decrease speed calculation unit 66L obtains a speed increase amount for increasing the peripheral speed of left roller 1L by V0 × (Δt1 + Δt2) / T ( S47). If the delay flag is not “1” (NO in S67), the increase / decrease speed calculation units 66R and 66L reduce the circumferential speed of the right roller 1R by V0 × Δt1 / T and the left roller 1L, respectively. A speed increase amount for increasing the peripheral speed by V0 × Δt1 / T is obtained (S58).

  When the right sensor ON signal and the left sensor ON signal are input simultaneously (YES in S23), skew detection unit 52 outputs skew flags R and L as described above. At this time, each of the increase / decrease speed calculation units 66R and 66L determines whether or not the advance flag = '1' (S68). If the advance flag is “1” (YES in S68), the increase / decrease speed calculation units 66R and 66L obtain the deceleration amount by which the peripheral speeds of the right roller 1R and the left roller 1L are reduced by V0 × Δt2 / T, respectively. (S45).

  On the other hand, if the advance flag is not “1” (NO in S68), each of the increase / decrease speed calculation units 66R and 66L determines whether or not the delay flag is “1” (S69). If delay flag = '1' (YES in S69), increase / decrease speed calculation units 66R and 66L increase the peripheral speeds of right roller 1R and left roller 1L, respectively, by V0 × Δt2 / T. The speed is obtained (S56). If the delay flag is not "1" (NO in S69), each of the increase / decrease speed calculation units 66R and 66L ends the process.

  Here, it is assumed that the interval between the skew correction target sheet 10 and the preceding sheet 9 is larger than the interval between the skew correction target sheet 10 and the succeeding sheet 32. In this case, the intermediate value that is the output of the intermediate value calculation unit 64 is larger than the count value that is the output of the counter 63. As a result, the time difference calculator 65 outputs a delay flag = '1'.

  Then, the time difference calculation unit 65 sends Δt2 that is ½ of the difference between the intermediate value and the count value to the increase / decrease speed calculation units 66R and 66L as the acceleration amount. The increase / decrease speed calculation unit 66R uses Δt1 as the deceleration amount as described above.

  Here, if Δt1> Δt2, as shown in FIG. 18A, the increase / decrease speed calculation unit 66R multiplies (Δt1−Δt2) by the conveyance speed V0 of the skew correction target sheet 10. Then, the increase / decrease speed calculation unit 66R calculates the correction distance = V0 × (Δt1−Δt2) (indicated by hatching in FIG. 18A).

  Further, the increase / decrease speed calculation unit 66R calculates the deceleration width ΔVR by dividing the correction distance by the skew correction time T. Then, the increase / decrease speed calculation unit 66R sends a speed V1R obtained by subtracting the deceleration width ΔVR from the transport speed V0 to the pulse period conversion unit 25R.

  On the other hand, the increase / decrease speed calculation unit 66L sets Δt1 as the speed increase amount. As illustrated in FIG. 18B, the increase / decrease speed calculation unit 66L multiplies (Δt1 + Δt2) and the conveyance speed V0 of the skew correction target sheet 10. Then, the increase / decrease speed calculation unit 66L calculates the correction distance = V0 × (Δt1 + Δt2) (indicated by hatching in FIG. 18B).

  Further, the increase / decrease speed calculation unit 66L calculates the deceleration width ΔVL by dividing the correction distance by the skew correction time T. Then, the increase / decrease speed calculation unit 66L sends the speed V1L obtained by subtracting ΔVL from the transport speed V0 to the pulse period conversion unit 25L.

  The subsequent operation is the same as in the first example described above. As a result, as shown in FIG. 13, the skew correction target sheet 10 is skew-corrected by the right roller (skew correction roller) 1R and the left roller (skew correction roller) 1L.

  Then, the skew correction target sheet 10 is conveyed while keeping the distance between the preceding and succeeding sheets 9 and 32 equal to V0 × (ITVLa−Δt2) = V0 × (ITVLb + Δt2).

  As described above, in the second example, the pair of skew rollers 5 that are driven independently of each other by detecting the intervals of the preceding sheet 9, the skew correction target sheet 10, and the succeeding sheet 35 from each other. Is controlled to increase / decrease speed. Therefore, not only the interval between the preceding sheet 9 and the skew correction sheet 10 but also the interval between the skew correction target sheet 10 and the succeeding sheet 35 is properly maintained, and the skew correction of the skew correction target sheet 10 is performed. It can be carried out.

  As is clear from the above description, in FIG. 3, the right sensor 5R, the left sensor 5L, the sensor-off detection unit 20, and the sensor-on detection units 21R and 21L function as sheet detection means.

  Counters 22R and 22L, time difference calculation units 23R and 23L, increase / decrease speed calculation units 24R and 24L, pulse period conversion units 25R and 25L, and pulse generation units 26R and 26L function as control means. In this case, the increase / decrease speed calculation unit 24R, the pulse period conversion unit 25R, and the pulse generation unit 26R function as a first speed control unit. And the increase / decrease speed calculation part 24L, the pulse period conversion part 25L, and the pulse generation part 26L function as a 2nd speed control means.

  In FIG. 10, the right sensor 5R, the left sensor 5L, the upstream sensor 33, the sensor-off detection units 54, 57, and 61, and the sensor-on detection units 50, 51, 55, 58, and 62 function as sheet detection means.

  In addition, the counters 56, 59, and 63, the intermediate value calculation unit 64, and the time difference calculation unit 65 function as interval detection means. At this time, the interval detection unit obtains the interval between the trailing end of the preceding sheet and the leading end of the skew correction target sheet as the first interval according to the detection timing by each of the sheet detection units, and the skew correction target sheet. The distance between the trailing edge and the leading edge of the succeeding sheet is obtained as the second distance.

  Then, the skew detection unit 52 functions as a skew detection unit, and obtains the skew amount of the skew correction target sheet according to the detection timing of each of the sheet detection units.

  Further, the increase / decrease speed calculation units 66R and 66L, the pulse period conversion units 25R and 25L, and the pulse generation units 26R and 26L collectively function as a first control unit and a second control unit.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by a computer provided in the sheet conveying apparatus. At this time, the control method includes at least a comparison step and a control step. The control method may include at least a first interval detection step, a second interval detection step, a skew amount detection step, a drive control step, an acceleration control step, and a deceleration control step.

  Further, software (program) that realizes the functions of the above-described embodiments may be supplied to a system or an apparatus via a network or various computer-readable recording media. Then, a computer (or CPU, MPU, etc.) of the system or apparatus may read and execute the program.

1R, 1L Skew correction roller 6 Skew correction control unit 20 Sensor off detection unit 21R, 21L Sensor on detection unit 22R, 22L Counter 23R, 23L Time difference calculation unit 24R, 24L Increase / decrease speed calculation unit 25R, 25L Pulse period conversion unit 26R, 26L Pulse generator

Claims (9)

In the sheet conveying apparatus that corrects the skew of the sheet while conveying the sheet,
First and second conveying members that are arranged at different positions in the width direction of the sheet that intersect the conveying direction of the sheet and are driven independently of each other to convey the sheet;
First and second sheet detecting means arranged at different positions in the width direction for detecting a sheet;
The skew correction target sheet after the trailing edge of the preceding sheet conveyed prior to the skew correction target sheet, which is the skew correction target, is detected by both the first and second sheet detecting means. The first and second detection times representing the time until the first and second sheet detecting means respectively detect the leading edge of the sheet, and the first and second detection times and the preceding sheet and The first and second comparison results are obtained by comparing with a predetermined conveyance time when the interval of the skew correction target sheet is a target interval, respectively, and according to the first and second comparison results, respectively. And a control unit that drives and controls the first and second transport members. When the first detection time is longer than the predetermined transport time, the control means determines the first time according to a first time difference defined by a difference between the first detection time and the predetermined transport time. The speed of the first transport member is controlled to increase, and when the first detection time is shorter than the predetermined transport time, the speed of the first transport member is controlled to be reduced according to the first time difference,
When the second detection time is longer than the predetermined transport time, the second transport member is moved in accordance with a second time difference defined by the difference between the second detection time and the predetermined transport time. The speed is controlled to increase, and if the second detection time is shorter than the predetermined transport time, the speed of the first transport member is controlled to be reduced according to the second time difference. Item 2. The sheet conveying apparatus according to Item 1. The control means detects the leading edge of the skew correction target sheet with the first sheet detecting means after the trailing edge of the preceding sheet is detected with both the first and second sheet detecting means. First counter means for obtaining a first count value until
A second count from when the trailing edge of the preceding sheet is detected by the first and second sheet detecting means to when the leading edge of the skew correction target sheet is detected by the second sheet detecting means. Second counter means for obtaining a value;
First time difference calculating means for setting the first difference indicating the difference between the first count value and the predetermined transport time as the first time difference;
A second time difference calculating means that uses a second difference indicating the difference between the second count value and the predetermined transport time as the second time difference;
When the first count value is greater than the predetermined transport time, the speed of the first transport member is increased according to the first difference, and the first count value is the predetermined transport time. Less than the first speed control means for decelerating the speed of the first conveying member according to the first difference;
When the second count value is greater than the predetermined transport time, the speed of the second transport member is increased according to the second difference, and the second count value is the predetermined transport time. 3. The sheet conveying apparatus according to claim 2, further comprising: a second speed control unit that decelerates the speed of the second conveying member according to the second difference. In the sheet conveying apparatus that corrects the skew of the sheet while conveying the sheet,
First and second conveying members that are arranged at different positions in the width direction of the sheet that intersect the conveying direction of the sheet and are driven independently of each other to convey the sheet;
First and second sheet detecting means arranged at different positions in the width direction for detecting a sheet;
Depending on the detection timing of each of the first and second sheet detecting means, the trailing edge of the preceding sheet preceding the skew correction target sheet that is the skew correction target and the skew correction target sheet An interval detecting unit that obtains the interval between the leading edge as a first interval and obtains the interval between the trailing edge of the skew correction target sheet and the leading edge of the succeeding sheet following the skew correction target sheet as a second interval; ,
Skew detection means for obtaining a skew amount of the skew correction target sheet in accordance with detection timings of the first and second sheet detection means;
When the first and second transport members are driven and controlled according to the skew amount, and the first interval is larger than the second interval, the difference between the first and second intervals A first control means for controlling the speed of the first and second transport members in response to a speed increase,
When the conveyance member is driven and controlled according to the skew amount, and the first interval is smaller than the second interval, the first and second intervals are set according to a difference between the first and second intervals. And a second control unit that performs deceleration control of the speed of the second conveying member.   Each of the first and second control means detects the skew correction target sheet by the first sheet detection means before the skew correction target sheet is detected by the second sheet detection means. When the leading edge is detected, ½ of the skew amount is set as a speed increasing amount for increasing the speed of the second transport member, and ½ of the skew amount is set as the first transport member. The sheet conveying apparatus according to claim 4, wherein the speed is a deceleration amount for decelerating.   Each of the first control unit and the second control unit detects the skew correction target sheet by the second sheet detection unit before the first sheet detection unit detects the skew correction target sheet. When the leading edge is detected, 1/2 of the skew feed amount is set as a speed increase amount for increasing the speed of the first transport member, and 1/2 of the skew feed amount is set as the second transport member. The sheet conveying apparatus according to claim 5, wherein the speed is a deceleration amount that decelerates the speed. When the first interval is larger than the second interval, the first control means sets the first and the second as a speed increase amount by ½ of the difference between the first and the second intervals. 2 to control the speed of the conveying member,
When the first interval is smaller than the second interval, the second control means sets the first and second as a deceleration amount by ½ of the difference between the first and second intervals. The sheet conveying apparatus according to claim 5, wherein the speed of the conveying member is controlled. The first and second conveying members that are arranged at different positions in the width direction of the sheet that intersect the conveying direction of the sheet and are driven independently of each other to convey the sheet, and arranged at different positions in the width direction, In a control method of a sheet conveying apparatus that includes first and second sheet detecting means for detecting the skew and corrects skew of a conveyed sheet,
The skew correction target sheet after the trailing edge of the preceding sheet conveyed prior to the skew correction target sheet, which is the skew correction target, is detected by both the first and second sheet detecting means. The first and second detection times representing the time until the first and second sheet detecting means respectively detect the leading edge of the sheet, and the first and second detection times and the preceding sheet and A comparison step of obtaining first and second comparison results by respectively comparing a predetermined conveyance time when the interval of the skew correction target sheet is a target interval;
And a control step of controlling driving of the first and second transport members in accordance with the first and second comparison results, respectively. The first and second conveying members that are arranged at different positions in the width direction of the sheet that intersect the conveying direction of the sheet and are driven independently of each other to convey the sheet, and arranged at different positions in the width direction, In a control method of a sheet conveying apparatus that includes first and second sheet detecting means for detecting the skew and corrects skew of a conveyed sheet,
Depending on the detection timing of each of the first and second sheet detecting means, the trailing edge of the preceding sheet preceding the skew correction target sheet that is the skew correction target and the skew correction target sheet A first interval detection step for obtaining the interval from the tip as the first interval;
The interval between the trailing edge of the skew correction target sheet and the leading edge of the succeeding sheet following the skew correction target sheet is set according to the detection timing of each of the first and second sheet detection means. A second interval detection step obtained as an interval;
A skew detection step of obtaining a skew amount of the skew correction target sheet in accordance with a detection timing by each of the first and second sheet detecting means;
A drive control step of driving and controlling the first and second transport members according to the skew amount;
When the first interval is larger than the second interval, the speed increase control for increasing the speed of the first and second transport members according to the difference between the first and second intervals. Steps,
When the conveyance member is driven and controlled according to the skew amount, and the first interval is smaller than the second interval, the first and second intervals are set according to a difference between the first and second intervals. A control method for the sheet conveying apparatus, comprising: a deceleration control step for performing deceleration control of the speed of the second conveying member.

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