JP2020104946A - Sheet conveying device and image forming device including the same - Google Patents

Abstract

To provide a sheet conveying device capable of accurately detecting a skew amount of sheets having various sizes and a positional deviation amount thereof in a width direction with a simple constitution, and an image forming device including the same.SOLUTION: The sheet conveying device includes a sheet conveying part, an edge detection sensor, and a control unit. The edge detection sensor has a detection region which is smaller than a width direction size of the sheet and which is divided into an A region, a B region and a C region in the width direction, and the C region overlaps one side end edge of the shee. The control unit determines skew to an A region direction when only the C region detects a tip edge, determines skew to an A region direction by 1 line when the C and B regions detect the tip edges, determines skew to a C region direction when only the A region detects the tip edge, determines skew to the C region direction by 1 line when the A and B regions detect the tip edges, and determines no skew when the A, B and C regions detect the edges in a conveying direction.SELECTED DRAWING: Figure 8

Description

The present invention is a sheet conveying apparatus that is installed in an image forming apparatus such as a facsimile machine, a copying machine, and a printer, and includes a conveyance deviation amount detection mechanism that detects a skew amount of a sheet-shaped recording medium and a deviation amount of a conveyance position in the width direction. The present invention relates to an apparatus and an image forming apparatus.

An image forming apparatus such as a facsimile, a copying machine, a printer, etc. is configured to record an image on a recording medium such as paper, cloth, OHP sheet and the like. These image forming apparatuses can be classified into an electrophotographic system, an inkjet system, and the like depending on the recording system.

When printing on a recording medium using the image forming apparatus, when the recording medium is skewed with respect to the conveying direction, or is misaligned in a direction orthogonal to the conveying direction (recording medium width direction). If so, the print position of each recording medium is displaced. In particular, when an inkjet recording apparatus is used, the ink easily penetrates into the recording medium and the show-through easily occurs, so that the printing position accuracy in double-sided printing is required to be extremely high (for example, a few mm or less).

Conventionally, a CIS (contact image sensor) that detects the position of the widthwise end of the paper (recording medium) is arranged, and the position of the widthwise end of the paper S is detected based on the intensity difference of the light received by the CIS. The method is known.

For example, in Japanese Patent Application Laid-Open No. 2004-242242, a deviation amount detecting unit that detects the lateral deviation amount and the skew amount of the sheet S by CIS, and if the detected positional deviation amount of the sheet is larger than a predetermined threshold value, the sheet is regarded as an error sheet. An error sheet detection unit that detects the occurrence, a sheet detection unit in the double-sided path that detects whether a sheet exists in the double-sided path when an error sheet occurs, and an error occurs when the sheet exists in the double-sided path. The sheet is a sheet conveyed from the sheet storage section or a sheet conveyed through a double-sided path, and the sheet is determined based on the determination result. An image forming apparatus including a sheet discharging unit configured to discharge a discharged sheet is disclosed.

Further, in Patent Document 2, the output value of the CIS arranged on the transport path of the transported object (paper) is binarized, and the position at which the binarized value is switched is stored for each size of the transported object. An edge detection device is disclosed that determines the edge position of a transported object when it is within the edge detection range. It is also described that the transported object is shifted in the width direction based on the amount of deviation between the detected edge position and the reference position.

JP, 2003-327345, A JP, 2016-145814, A

However, the methods of Patent Documents 1 and 2 have a problem in that they cannot be applied to sheets of a size larger than the effective reading range of CIS. In addition, even the largest existing CIS is compatible with A3 size, so if a large CIS that supports paper larger than A3 size is installed, it will be a custom-made product and the image forming apparatus will have a high cost. there were.

In view of the above problems, the present invention provides a sheet conveying device capable of accurately detecting the skew feeding amount and the positional deviation amount in the width direction of sheets of various sizes with a simple configuration, and an image forming apparatus including the same. The purpose is to

In order to achieve the above-mentioned object, a first configuration of the present invention is a sheet conveying device including a sheet conveying section, an edge detection sensor, and a control section. The sheet transport unit transports a sheet. The edge detection sensor is arranged in the sheet conveying unit, and has a detection region in which a plurality of photoelectric conversion elements are arranged corresponding to a pixel which is a minimum unit of an image along a width direction orthogonal to a sheet conveying direction, The pixel position where the output signal of the photoelectric conversion element is switched by scanning the passing sheet along the width direction is detected as the leading edge in the carrying direction and the side edge positions on both sides in the width direction. The control unit detects the skew of the sheet and the positional deviation in the width direction based on the detection result of the edge detection sensor. The detection area of the edge detection sensor is smaller than the size of the sheet conveyed by the sheet conveying unit in the width direction, and is divided into an A area, a B area, and a C area in which the detection result can be individually output along the width direction. The area is arranged at a position overlapping one side edge of the sheet passing through the edge detection sensor. The control unit determines that the skew in the direction of the area A of the sheet is detected when only the area C detects the edge in the transport direction, and moves toward the area A of the sheet when only the areas C and B detect the edge in the transport direction. It is determined that the skew is for one line, and when only the area A detects the edge in the carrying direction, it is determined as the skew toward the area C of the sheet, and when only the areas A and B detect the edge in the carrying direction, the sheet C is detected. It is determined that the sheet is skewed for one line in the area direction, and when all of the A area, the B area, and the C area detect edges in the transport direction, it is determined that the sheet is not skewed.

According to the first configuration of the present invention, even when the detection area of the edge detection sensor is smaller than the widthwise length of the sheet, the skew direction, the skew amount, and the widthwise positional deviation amount of the sheet can be accurately detected. Therefore, since it is not necessary to mount a large edge detection sensor corresponding to the maximum size sheet, it is possible to reduce the size and cost. Then, by performing skew correction and width direction misalignment correction based on the detected skew direction, skew amount, and width direction misalignment amount, the printed image does not tilt with respect to the sheet and also in the width direction. Printing is possible without the center position shifting. Further, since it is possible to detect a state in which the sheet is skewed by one line, it is possible to clearly distinguish it from a state in which the sheet is not skewed, and it is possible to correct a slight skew for one line.

A side sectional view showing a schematic structure of a printer 100 including a sheet conveying device 21 according to an embodiment of the present invention. An external perspective view of the sensor unit 30 installed in the printer 100 of the present embodiment. Side sectional view of the sensor unit 30 Plan view of the correction unit 31 seen from above Side view of the correction unit 31 as seen from the upstream side in the paper transport direction Block diagram showing an example of a control path of the printer 100 of the present embodiment In the printer 100 of the present embodiment, a plan view of the state immediately before the sheet S passes through the CIS 40 as seen from above. 6 is a flowchart showing lateral misalignment and skew correction control in the printer 100 of the present embodiment, which is a flowchart showing control for detecting the skew direction of the paper S and the degree of skew. 6 is a flowchart showing lateral misalignment and skew correction control in the printer 100 of the present embodiment, which is a flowchart showing right side skew correction control. 6 is a flowchart showing lateral misalignment and skew correction control in the printer 100 of the present embodiment, which is a flowchart showing right side one-line skew correction control. 6 is a flowchart showing lateral misalignment and skew correction control in the printer 100 of the present embodiment, which is a flowchart showing left side skew correction control. The figure which shows the relationship between the pixel position P'of one scan before and the pixel position P of this scan when detection of the front edge of the paper S is continuing by the C area|region of CIS40. FIG. 8 is a diagram showing a relationship between a pixel position P′ before the first scanning and a pixel position P at the current scanning when the corner of the sheet S enters the area C. 5 is a flowchart showing lateral misalignment and skew correction control in the printer 100 of the present embodiment, which is a flowchart showing skew correction control for one line on the left side. 6 is a flowchart showing lateral misalignment and skew correction control in the printer 100 of the present embodiment, which is a flowchart showing skew-free correction control. FIG. 9 is a plan view of a modified example of the printer 100 of the present embodiment using the CIS 40 capable of individually outputting the detection results from the 12 blocks B1 to B12, which is a top view of a state immediately before the sheet S passes through the CIS 40.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing a schematic structure of an inkjet recording type printer 100 including a sheet conveying device 21 according to an embodiment of the present invention.

As shown in FIG. 1, in the printer 100, a paper feed cassette 2a, which is a paper storage unit, is arranged in a lower portion inside the printer body 1, and a manual paper feed tray 2b is provided outside the right side surface of the printer body 1. ing. A sheet feeding device 3a is arranged above the sheet feeding cassette 2a on the downstream side (the right side of the sheet feeding cassette 2a in FIG. 1) in the sheet conveying direction. Further, a sheet feeding device 3b is arranged on the downstream side of the manual sheet feeding tray 2b in the sheet conveying direction (on the left side of the manual sheet feeding tray 2b in FIG. 1). The sheets S are separated and fed one by one by the sheet feeding devices 3a and 3b.

A first paper transport path 4a is provided inside the printer 100. The first paper feed path 4a is located on the upper right side of the paper feed cassette 2a and on the left side of the manual paper feed tray 2b. The paper S delivered from the paper feed cassette 2a is conveyed vertically upward along the side surface of the printer body 1 through the first paper conveyance path 4a, and the paper S delivered from the manual paper feed tray 2b is the first paper feed tray 2b. The sheet is conveyed to the left substantially horizontally through the sheet conveying path 4a.

A sensor unit 30 for detecting the position (edge position) of the end portion of the paper S in the width direction (direction perpendicular to the paper transport direction) is provided at the downstream end of the first paper transport path 4a with respect to the paper transport direction. It is arranged.

A correction unit 31 is provided immediately downstream of the sensor unit 30. The correction unit 31 feeds the sheet S toward the first belt conveying unit 5 while correcting the skew of the sheet S and the positional deviation in the width direction. Detailed structures of the sensor unit 30 and the correction unit 31 will be described later. The sensor unit 30 and the correction unit 31 together with the CPU 70, which will be described later, constitute the sheet conveying device 21 of the present invention.

The first belt transport unit 5 and the recording unit 9 are arranged immediately downstream of the correction unit 31. The first belt transport unit 5 includes an endless first transport belt 8 wound around the first drive roller 6 and the first driven roller 7. The first conveyor belt 8 is provided with a large number of air suction holes (not shown) for sucking air. The paper S delivered from the pair of registration rollers 13 passes below the recording unit 9 while being adsorbed and held by the first conveyor belt 8 by the paper suction unit 20 provided inside the first conveyor belt 8.

The recording unit 9 includes line heads 10C, 10M, 10Y and 10K. The line heads 10</b>C to 10</b>K record an image on the sheet S that is sucked and held by the transport surface of the first transport belt 8 and transported. Ink of four colors (cyan, magenta, yellow, and black) stored in an ink tank (not shown) is supplied to each of the line heads 10C to 10K for each color of the line heads 10C to 10K.

Ink of four colors of yellow, magenta, cyan, and black is superposed on the paper S by sequentially ejecting the inks from the respective line heads 10C to 10K toward the paper S adsorbed on the first conveyor belt 8. Recorded full-color image. The printer 100 can also record a monochrome image.

A second belt transport unit 11 is arranged on the downstream side (left side in FIG. 1) of the first belt transport unit 5 with respect to the sheet transport direction. The paper S on which the image is recorded in the recording unit 9 is sent to the second belt transport unit 11, and the ink ejected on the surface of the paper S is dried while passing through the second belt transport unit 11. Since the configuration of the second belt transport unit 11 is the same as that of the first belt transport unit 5, the description thereof will be omitted.

A decurler unit 14 is provided on the downstream side of the second belt transport unit 11 with respect to the sheet transport direction and near the left side surface of the printer body 1. The sheet S whose ink has been dried by the second belt transport unit 11 is sent to the decurler unit 14 and the curl generated on the sheet S is corrected.

A second paper transport path 4b is provided on the downstream side (upper side in FIG. 1) of the decurler unit 14 with respect to the paper transport direction. When the double-sided recording is not performed, the paper S that has passed through the decurler unit 14 is discharged from the second paper transport path 4b to the paper discharge tray 15 provided outside the left side surface of the printer 100 via the discharge roller pair. When recording is performed on both sides of the sheet S, the sheet S that has finished recording on one side and has passed through the second belt conveyance unit 12 and the decurler unit 14 passes through the second sheet conveyance path 4b to the reverse conveyance path 16. Be transported. The sheet S sent to the reverse transport path 16 has its transport direction switched to reverse the front and back sides, passes through the upper portion of the printer 100, and is transported to the registration roller pair 13. After that, the recording medium is conveyed again to the first belt conveying unit 5 with the surface on which the image is not recorded facing upward.

A maintenance unit 19 is arranged below the second belt transport unit 12. The maintenance unit 19 moves below the recording unit 9 when performing maintenance of the recording heads of the respective line heads 10C to 10K, wipes the ink ejected (purged) from the ink ejection nozzles of the recording head, and is wiped off. Collected ink.

Next, the detailed structure of the sensor unit 30 will be described. 2 is an external perspective view of the sensor unit 30 mounted on the printer 100, and FIG. 3 is a side sectional view of the sensor unit 30. 2 and 3, the paper width direction is indicated by the arrow AA' direction, and the paper conveyance direction is indicated by the arrow B direction.

The sensor unit 30 includes a unit housing 32, a pair of transport rollers (sheet transport unit) 33, a CIS 40 and a light source unit 41. The unit housing 32 rotatably supports the pair of transport rollers 33 and houses the CIS 40 and the light source unit 41. An entrance guide 35 that guides the paper S to the nip portion of the transport roller pair 33 is provided at the upstream end of the unit housing 31 with respect to the paper transport direction (arrow B direction).

The CIS 40 and the light source unit 41 are housed below and above the unit housing 32, respectively, and the CIS 40 is based on the light intensity difference between the portion where the light from the light source portion 41 is incident and the portion where the paper S is shielded. Thus, the edge positions of the paper S in the transport direction and the width direction are detected. The light source unit 41 has an LED 41a arranged at one end in the paper width direction, and a light guide plate 41b that diffuses the light emitted from the LED 41a in the entire paper width direction and guides the light to the CIS 40. Two contact glasses 42a and 42b are arranged to face each other between the CIS 40 and the light source unit 41. The upper surface of the contact glass 42a and the lower surface of the contact glass 42b form a part of the sheet conveyance path.

4 is a plan view of the correction unit 31 as viewed from above, and FIG. 5 is a side view of the correction unit 31 as viewed from the upstream side (downward direction in FIG. 4) in the sheet transport direction. The correction unit 31 includes a correction roller pair 50, a roller holder 51, a carriage 53, a roller drive motor 55, a skew correction motor 57, and a lateral deviation correction motor 59.

A plurality of correction roller pairs 50 (four pairs here) are arranged in the paper width direction. Each correction roller pair 50 is composed of a driving roller 50a and a driven roller 50b. The roller holder 51 rotatably supports the rotation shaft 52 of the drive roller 50a. A swing fulcrum 51a is provided on one end side (left end in FIGS. 4 and 5) of the roller holder 51 in the paper width direction, and the other end side (FIG. 4) with respect to the carriage 53 centered on the swing fulcrum 51a. , The right end side in FIG. 5) is swingable in the paper transport direction. The carriage 53 is supported so as to be movable in the paper width direction with respect to the front and rear frames 101a and 101b of the printer 100.

The roller drive motor 55 is connected to the rotating shaft 52 via a plurality of gears, and rotates and stops the rotating shaft 52. The skew correction motor 57 is connected via a plurality of gears to a rack 51b provided at the swing end of the roller holder 51, and varies the inclination of the roller holder 51 with respect to the sheet transport direction. The lateral misalignment correction motor 59 is connected to rack teeth (not shown) formed on the edge of the carriage 53, and reciprocates the carriage 53 in the paper width direction. As the roller drive motor 55, the skew correction motor 57, and the lateral deviation correction motor 59, stepping motors that can accurately control the rotation direction and the rotation amount (rotation angle) by pulse control are used.

FIG. 6 is a block diagram showing a control path of the printer 100 of this embodiment. The CPU 70 controls the printer 100 as a whole. When the printing operation on the paper S by the printer 100 is started in response to the print data received from the external computer or the like, the CPU 70 makes various settings for the CIS control circuit 71 to read signals from the CIS 40. ..

The CIS control circuit 71 sends to the CIS 40 a reference clock signal for reading a signal from the CIS 40 and an accumulation time determination signal for determining the charge accumulation time in the CIS 40 according to the contents set by the CPU 70. Further, the CIS control circuit 71 sends out a PWM signal to the LED drive circuit 73 in order to set the value of the current flowing through the LED 41a. The LED drive circuit 73 generates a DC voltage according to the PWM signal from the CIS control circuit 71, and uses this DC voltage as a reference voltage for the current flowing through the LED 41a. The CIS control circuit 71 also generates a comparison reference voltage (threshold voltage) for binarizing the analog signal (output signal) from the CIS 40 by the binarizing circuit 75.

At the timing when the sheet S is conveyed toward the recording unit 9 (see FIG. 1), the CPU 70 instructs the CIS control circuit 71 to detect the edge position. The CIS control circuit 71, which receives the edge position detection instruction from the CPU 70, sends a control signal for lighting the LED 41a to the LED drive circuit 73 in synchronization with the accumulation time determination signal. The LED drive circuit 73 lights the LED 41a for a certain period according to the control signal from the CIS control circuit 71.

The CIS 40 has a detection area 40a (see FIG. 7) in which a plurality of photoelectric conversion elements are arranged corresponding to a pixel which is the minimum unit of an image along the width direction orthogonal to the paper transport direction, and the LED 41a is lit. In addition, a voltage corresponding to the amount of light accumulated in each pixel (photoelectric conversion element) of the pixel group (pixel group) in the detection region 40a is output as a pixel-by-pixel output signal according to the next accumulation time determination signal and the reference clock signal. Output. The output signal (analog signal) output from the CIS 40 is binarized by comparison with a comparison reference voltage (threshold voltage) in a binarization circuit (comparator) 75, and is converted into a digital signal by GPIO (General-purpose input/output). output) port to the CIS control circuit 71. Alternatively, an analog signal may be received as it is at an AD (Analog/Digital) port, and a threshold value may be internally provided.

The CIS control circuit 71 sequentially checks the value of 0/1 of the digital signal binarized in the binarization circuit 75 pixel by pixel for each of the output signals output from the CIS 40. Then, the CIS control circuit 71 detects the pixel position (the position of the photoelectric conversion element) of the detection region 40a where the value of the digital signal switches from 0 to 1 or from 1 to 0.

When the pixel position where the value of the digital signal is switched is detected by the CIS control circuit 71, the switched pixel position is determined as the edge position of the paper S in the transport direction and the width direction. The CPU 70, based on the edge position in the width direction determined by the CIS control circuit 71, the edge position when the sheet S is transported at an ideal transport position (reference transport position) that passes through the center position of the sheet passing area. A shift amount (width direction shift amount) from the (reference edge position) is calculated.

Further, the CPU 70 calculates the skew amount (skew angle) of the sheet S based on the timing when the leading edge of the sheet S passes through the predetermined area of the CIS 40, the number of scans of the CIS 40, and the sheet transport speed. The calculated widthwise shift amount and skew amount are transmitted to the correction unit control unit 77. The correction unit control unit 77 transmits a control signal to the correction unit 31 in accordance with the transmitted widthwise displacement amount and skew amount, and corrects the lateral displacement and skew of the paper S.

The scanning speed and resolution by the CIS 40 are sufficient from the correction amount (correction angle) per pulse of the skew correction motor 57 and the lateral deviation correction motor 59 of the correction unit 31 arranged on the downstream side of the CIS 40 in the transport direction of the paper S. It is necessary to select a scanning speed and a resolution that can achieve a high resolution. For example, when the correction amount per pulse of the lateral deviation correction motor 59 is 1 mm, the CIS 40 that can detect skew and lateral deviation with a resolution of 1 mm or more (several hundreds of μm) is used.

Next, the lateral deviation and skew correction of the paper S in the printer 100 of this embodiment will be described. FIG. 7 is a plan view of a state immediately before the sheet S passes through the CIS 40 in the printer 100 of this embodiment, as viewed from above. In the present embodiment, the CIS 40 having a detection area of A4 vertical size (210 mm) is used, and as shown in FIG. 7, when a sheet S of a size larger than the detection area (for example, A4 horizontal size) passes through, one side The edge on the right side in FIG. 7 cannot be detected.

Therefore, in the present embodiment, the widthwise deviation amount and skew amount of the paper S are detected by using the CIS 40 capable of outputting the detection result divided into three blocks in the paper width direction as shown in FIG. 7, and based on the detection result. The correction unit 31 corrects the lateral deviation and skew of the sheet S. Hereinafter, the three blocks of the detection area 40a of the CIS 40 will be referred to as area A, area B, and area C in this order from the right side of FIG.

8 to 13 are flowcharts showing the lateral deviation and skew correction control in the printer 100 of this embodiment. A procedure for correcting the lateral deviation and skew of the sheet S will be described in detail along the steps of FIGS. 8 to 13 with reference to FIGS. 1 to 7 as necessary.

First, the skew direction and the degree of skew of the paper S are detected according to the flowchart of FIG. When the paper S is conveyed from the paper feed cassette 2a (or the manual paper feed tray 2b), the CIS 40 detects the leading edge of the paper S (step S1). Next, the CIS control circuit 71 determines whether the leading edge of the sheet S (the left corner of the leading edge of the sheet S) is detected in the C area of the CIS 40 (step S2). When it is detected in the C area of the CIS 40 (Yes in step S2), it is determined whether or not the leading edge of the paper S is also detected in the B area of the CIS 40 at the same time as the C area (step S3).

When the leading edge of the paper S is not detected in the B area of the CIS 40 (No in step S3), the CPU 70 determines that the paper S is skewed to the right (step S4). Then, the process proceeds to the right skew correction control shown in FIG.

In the right-side skew correction control of FIG. 9, first, the CPU 70 starts detecting the amount of deviation in the width direction of the sheet S (step S411), and the value of the digital signal is switched in the width direction of the area C (the leading edge of the sheet S is changed). The pixel position (paper edge position E1) at which the left corner is detected is stored (step S412). Next, a difference ΔE between the stored paper edge position E1 and the reference edge position E0 (see FIG. 7) set at a predetermined position in the C area is calculated (step S413).

Then, the calculated ΔE is converted into the number of motor pulses of the lateral misalignment correction motor 59 required to correct the misalignment of the paper S in the width direction (step S414). The converted motor pulse number is transmitted from the correction unit control unit 77 to the lateral misalignment correction motor 59, and the lateral misalignment correction motor 59 is driven by the number of transmitted motor pulses to perform the lateral misalignment correction of the paper S ( Step S415).

On the other hand, the CPU 70 starts detecting the right skew amount at the same time as detecting the widthwise shift amount (step S421), and starts counting the number of scans of the CIS 40 (step S422). Next, the CIS control circuit 71 determines whether or not the leading edge of the paper S is detected at an arbitrary point in the area A (or area B) of the CIS 40 (step S423). When it is detected in the area A (or area B) of the CIS 40 (Yes in step S423), the count of the number of scans of the CIS 40 is stopped (step S424).

Then, the paper transport speed v, the scanning time t per line (one scan) of the CIS 40, the scanning count value n of the CIS 40, and the pixel position of the area C where the leading edge of the paper S has passed and the area A (or area B). From the distance d from the pixel position of
θ=tan ⁻¹ {(v×t×n)/d} (1)
Then, the skew amount θ is calculated (step S425).

For example, if the sheet conveyance speed v is 400 mm/sec and the scanning time t per line of the CIS 40 is 400 μsec, the movement distance of the sheet S in the reading scanning of one line of the CIS 40 is v×t=400 mm/sec×400 μsec=160 μm. Becomes The number of scans n of the CIS 40 from the passage of the leading edge of the paper S through the area C to the passage of the area A (or the area B) is 5, and the pixel position of the area C where the leading edge of the paper S has passed and the area A If the distance d from the pixel position of (or B region) is 300 mm, θ=tan−1(160×5/300)=0.1528°. It is preferable to use the pixel position of the area A because the calculation accuracy of the skew amount θ is higher when the distance d from the pixel position of the area C is longer to some extent.

Then, the calculated skew amount θ is converted into the number of motor pulses of the skew correction motor 57 necessary for correcting the right skew of the sheet S (step S426). The converted motor pulse number is transmitted from the correction unit controller 77 to the skew correction motor 57, and the skew correction motor 57 is driven by the transmitted motor pulse number to execute the skew correction of the sheet S (step S427).

Returning to FIG. 8, when the leading edge of the paper S is detected in the C area and the B area of the CIS 40 at the same time (Yes in step S3), the CIS control circuit 71 causes the leading edge of the paper S to be in the A area of the CIS 40. It is determined whether or not they are simultaneously detected (step S5). When the leading edge of the paper S is not detected in the area A of the CIS 40 (No in step S5), the paper S is in the state of being detected only in the areas C and B at the same time, and one line of the CIS 40 is on the right side. It is determined that there is a skew (step S6). Then, the control shifts to the right one-line skew correction control shown in FIG.

In the skew correction control for one line on the right side of FIG. 10, first, the CPU 70 starts detection of the widthwise deviation amount of the paper S (step S611). The procedure for detecting the widthwise shift amount (steps S612 to S615) is the same as the procedure for detecting the widthwise shift amount in the right skew control shown in FIG. 9 (steps S6412 to S415).

On the other hand, since the right-side skew amount is for one scanning line, the skew amount θ can be calculated using the formula (1) from the paper transport speed and the scanning speed per line of the CIS 40. The calculated skew amount θ is converted into the number of motor pulses of the skew correction motor 57 necessary for correcting the right skew of the paper S (step S621). For example, when there is no difference between the scanning speed of the CIS 40 and the transportation speed of the paper S, the motor pulse number is about 1 to 2 pulses. When the transport speed of the paper S is higher than the scanning speed of the CIS 40, the number of motor pulses may be greater than 2 pulses.

The converted motor pulse number is transmitted from the correction unit control unit 77 to the skew correction motor 57, and the skew correction motor 57 is driven by the transmitted motor pulse number to execute the skew correction of the sheet S (step S622).

Returning to FIG. 8, when the leading edge of the paper S is not detected in the C area of the CIS 40 (No in step S2), the leading edge of the paper S is detected in the area A (step S7). Next, the CIS control circuit 71 determines whether the leading edge of the paper S is detected in the B area of the CIS 40 (step S8).

When the leading edge of the paper S is not detected in the B area of the CIS 40 (No in step S8), it is determined that the paper S is skewed to the left (step S9). Then, the process proceeds to the left skew correction control shown in FIG.

In the left-side skew correction control of FIG. 11, first, the CPU 70 starts detecting the amount of deviation in the width direction of the paper S (step S911), and the CIS control circuit 71 determines whether the leading edge of the paper S is detected in the C area. Is determined (step S912). When the leading edge of the paper S is detected in the C area (Yes in step S912), the pixel position where the leading edge is detected is stored for each scan of the CIS 40 (step S913). It is assumed that the pixel position increases from the area A side (right side in FIG. 7) of CIS 40 toward the area C side (left side in FIG. 7).

Next, the CIS control circuit 71 determines whether or not the absolute value ΔP (=|P−P′|) of the difference between the pixel position P′ before the first scanning and the pixel position P at the current scanning is equal to or less than a predetermined value. It is determined (step S914). As shown in FIG. 12, while the detection of the leading edge of the paper S continues, the pixel position P becomes larger than the pixel position P′ at a constant rate, so that ΔP also continues to be larger than a predetermined value. .. That is, ΔP continues to take a constant value larger than the predetermined value. On the other hand, when the side edge (sheet edge position E1) of the sheet S is detected, the increase in pixel position stops. That is, since the pixel position P at the current scanning does not increase from the pixel position P'at one scanning before, ΔP becomes equal to or less than a predetermined value. Therefore, it can be estimated that the detection has switched from the detection of the leading edge of the sheet S to the detection of the side edge when ΔP becomes equal to or less than the predetermined value.

When it is determined that ΔP is equal to or less than the predetermined value (Yes in step S914), the CIS control circuit 71 determines whether or not the pixel position P′ of one scan before is larger than the pixel position P of the current scan. The determination is made (step S915). If it is determined that P′ is larger than P (Yes in step S915), the pixel position P′ is stored as the paper edge position E1.

In step S914, it is detected that ΔP is less than or equal to the predetermined value. However, even if ΔP is less than or equal to the predetermined value, if the pixel position P′ is smaller than the pixel position P (on the right side), the pixel position P is the paper S. Is considered to be a corner portion (paper edge position E1). As shown in FIG. 13, when the corner of the paper S enters the area C, the pixel position P′ is always larger than the pixel position P (on the left side). Therefore, if it is confirmed in step S915 that the pixel position P'is larger than the pixel position P (the positions of P and P'in the width direction are switched), the detection of the leading edge of the sheet S to the detection of the side edge is performed. It can be judged that the switching has been made surely. The side edge position E1 of the sheet S is the locus of the left corner of the sheet S (two-dot chain line in FIG. 13).

Next, the difference ΔE between the stored sheet edge position E1 and the reference edge position E0 (see FIG. 7) set at the predetermined position in the C area is calculated (step S916).

Then, the calculated ΔE is converted into the number of motor pulses of the lateral misalignment correction motor 59 required to correct the misalignment of the paper S in the width direction (step S917). The converted motor pulse number is transmitted from the correction unit control unit 77 to the lateral misalignment correction motor 59, and the lateral misalignment correction motor 59 is driven by the number of transmitted motor pulses to perform lateral width misalignment correction of the paper S ( Step S918).

On the other hand, the CPU 70 starts detecting the left-side skew amount at the same time as detecting the width-direction deviation amount (step S921). The procedure for detecting and correcting the skew amount (steps S922 to S927) is the same as the procedure for detecting and correcting the skew amount (steps S422 to S427) in the right-side skew control shown in FIG. 9 except that it is symmetrical.

Returning to FIG. 8, when the leading edge of the sheet S is detected in the B area of the CIS 40 (Yes in step S8), the sheet S is in the A and B areas, and the sheet S is in the CIS 40. It is determined that the line is skewed to the left by one line (step S10). Then, the process shifts to skew correction control for the left one line shown in FIG.

In the skew correction control for one line on the left side of FIG. 14, first, the CPU 70 starts detecting the amount of deviation in the width direction of the paper S (step S1011). The width direction deviation amount detection and correction procedure (steps S1012 to S1015) is the same as the width direction deviation amount detection procedure (steps S912 to S918) in the left skew correction control shown in FIG.

On the other hand, since the left-side skew amount is one scanning line, the skew amount θ is the same as the skew amount calculation in the right-side one-line skew control shown in FIG. It can be calculated from the equation (1). The calculated skew amount θ is converted into the number of motor pulses (1 to 2 pulses) of the skew correction motor 57 necessary for correcting the left skew of the paper S (step S1021). The converted motor pulse number is transmitted from the correction unit control unit 77 to the skew correction motor 57, and the skew correction motor 57 is driven by the transmitted motor pulse number to execute the skew correction of the sheet S (step S1022).

Returning to FIG. 8, when the leading edge of the paper S is detected in the C area, the B area, and the A area of the CIS 40 (Yes in step S5), it is determined that the paper S is not skewed (no skew). (Step S11). Then, the process proceeds to the skew-free correction control shown in FIG.

In the skew-free correction control of FIG. 15, first, the CPU 70 starts detection of the widthwise deviation amount of the sheet S (step S1111). In FIG. 15, a predetermined waiting time is provided until the pixel position (paper edge position E1) in the C area is stored after the leading edge of the paper S is detected (step S1112). As a result, even when the corner of the sheet S is folded, the pixel position is stored at the time when the detection of the leading edge of the sheet S passes through the folded portion and the switching to the detection of the side edge is surely performed. be able to. Note that step S1112 can be omitted if the edge of the sheet S is not taken into consideration. The width-direction deviation amount detection and correction procedure (steps S1113 to S1116) is the same as the width-direction deviation amount detection procedure (steps S411 to S415) in the right skew correction control shown in FIG.

Further, since the skew of the sheet S has not occurred, the number of motor pulses of the skew correction motor 57 is set to 0 (step S1121). Then, skew correction is executed (step S1122). Since the number of motor pulses is 0, the skew correction motor 57 is not actually driven.

According to the control described above, even when the detection area of the CIS 40 is smaller than the width direction length of the sheet S (A4 horizontal size) (A4 vertical size), the skew direction of the sheet S, the skew amount, and the width direction positional deviation amount are accurately determined. Can be detected well. Then, based on the detected skew direction, skew amount, and width direction position shift amount, the skew correction and the width direction shift correction are performed using the correction unit 31, so that the print image does not tilt with respect to the paper S, Further, it is possible to print without shifting the center position in the width direction.

Further, since it is not necessary to stop the sheet S by the registration roller pair, it is possible to reduce the collision noise of the sheet S on the registration roller pair. Further, in continuous printing, there is no restriction on the interval (sheet interval) between the sheets S in consideration of the sheet stop time between the pair of registration rollers, so that productivity (image forming efficiency) can be improved.

Others The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, an example using the transmissive CIS 40 including the detection unit 43 that receives the laser light from the light source unit 41 is shown. However, for example, a light emitting unit that emits light to the paper S is provided and the The edge position of the sheet S is determined by the difference in intensity between the reflected light from the sheet S and the reflected light from the non-passage area of the sheet S by using the reflection type CIS 40 that detects the reflected light from the sheet S in the section 43. Can also In this case, a color different from the color (white) of the paper S is located at a position facing the detection area 40a of the CIS 40 so that the intensity difference between the reflected light from the paper S and the reflected light from the non-passage area of the paper S becomes large. It is preferable to arrange the background member of.

Further, in the above-described embodiment, the example in which the CIS 40 capable of individually outputting the detection results from the three blocks (A to C regions) in the width direction is used as the sensor for detecting the edge position of the paper S has been described. As shown in FIG. 16, in the case of a CIS 40 capable of individually outputting detection results from 12 blocks B1 to B12, 4 blocks B1 to B4 are in the A area, 4 blocks B5 to B8 are in the B area, and B9 is B9. The same control as that of the above-described embodiment can be performed by setting the four blocks from to B12 as the C area. Alternatively, a sensor other than CIS such as CCD may be used.

Further, in the above-described embodiment, the left edge of the paper S is arranged so as to pass through the C area of the CIS 40 in the transport direction. However, for example, the CIS 40 is horizontally reversed so that the right edge of the paper S is in the C area of the CIS 40. It can also be arranged to pass through. In this case, the left and right of the sheet S may be reversed and the control shown in FIGS. 8 to 15 may be executed.

In the above embodiment, the inkjet recording type printer 100 that discharges ink from the ink discharging nozzles of the line heads 10C to 10K onto the paper S to record an image has been described as an example. In addition to the printer 100 of the type, an electrostatic latent image is formed by irradiating a laser on an image bearing member such as a photosensitive drum, and toner is attached to the electrostatic latent image to form a toner image. It can also be applied to an electrophotographic image forming apparatus in which an image is transferred onto a sheet (recording medium) and the transferred unfixed toner is heated and pressed to form a permanent image.

INDUSTRIAL APPLICABILITY The present invention is applicable to a sheet conveying device that conveys a sheet-shaped recording medium. By utilizing the present invention, it is possible to provide a sheet conveying device capable of accurately detecting the skew amount of a sheet and the positional deviation amount in the width direction regardless of the size of the sheet with a simple configuration, and an image forming apparatus including the same. it can.

5 First Belt Conveying Section 9 Recording Section (Image Forming Section)
21 sheet transport device 30 sensor unit 31 correction unit 33 transport roller pair (sheet transport unit)
40 CIS (edge detection sensor)
41 light source section 50 correction roller pair 51 roller holder 55 roller drive motor 57 skew correction motor 59 lateral deviation correction motor 70 CPU (control section)
71 CIS control circuit (control unit)
100 Printer (image forming device)
P paper (sheet)
O opening surface

Claims (8)

A sheet conveying unit that conveys a sheet,
The plurality of photoelectric conversion elements are arranged in the sheet conveying unit and have a detection region arranged corresponding to a pixel which is a minimum unit of an image along a width direction orthogonal to a sheet conveying direction, and the photoelectric conversion elements pass therethrough. An edge detection sensor that detects a pixel position at which the output signal of the photoelectric conversion element is switched by scanning the sheet along the width direction as a leading edge in the conveyance direction and side edge positions on both sides in the width direction,
A control unit for detecting the skew of the sheet and the positional deviation in the width direction based on the detection result of the edge detection sensor;
In a sheet conveying device equipped with
The detection region is smaller than the size in the width direction of the sheet conveyed by the sheet conveying unit, and is divided into an A region, a B region, and a C region in which the detection result can be individually output along the width direction, The C region is arranged at a position overlapping with one of the side edge edges of the sheet passing through the edge detection sensor,
The control unit determines that the sheet is skewed toward the A area when only the C area detects the leading edge, and the sheet of the sheet when only the C area and the B area detect the leading edge. It is determined that the skew is one line in the direction of the area A, and when only the area A detects the leading edge, it is determined that the sheet is skew in the direction of the area C, and only the areas A and B are When the leading edge is detected, it is determined that the sheet is skewed by one line in the direction of the C area, and when the leading edge is detected in all of the A area, the B area, and the C area, the sheet is skewed. A sheet conveying device characterized by determining that there is not. When the controller detects a skew in the direction of the area A or a skew for one line in the direction of the area A,
Storing a pixel position where the side edge is detected by the C region as a width direction edge position E1 of the sheet;
Calculating a difference ΔE between the width direction edge position E1 and a reference edge position E0 as a width direction deviation amount of the sheet;
The sheet conveying apparatus according to claim 1, wherein the sheet width direction misalignment amount detection control including the following is executed. When the control unit detects the skew in the C region direction or the skew for one line in the C region direction,
Storing the pixel position where the leading edge is detected for each scan of the edge detection sensor after detecting the leading edge in the area C;
Calculating an absolute value ΔP of a difference between the pixel position P′ at which the leading edge is detected one scan before and the pixel position P at which the leading edge is detected in the current scanning;
Determining whether or not the pixel position P′ is closer to the C area than the pixel position P when the ΔP is less than or equal to a predetermined value;
Determining the pixel position P′ as a width direction edge position E1 of the sheet when the position of the pixel position P′ and the position of the pixel position P in the width direction are exchanged;
Calculating a difference ΔE between the width direction edge position E1 and a reference edge position E0 as a width direction deviation amount of the sheet;
The sheet conveying apparatus according to claim 1, wherein the sheet width direction misalignment amount detection control including the following is executed. When the control unit detects that the sheet is not skewed,
The pixel position in which the side edge is detected by the C area after a lapse of a predetermined time after the C area detects the leading edge is stored as a width direction edge position E1 of the sheet. The sheet conveying device described. The control unit detects the skew amount θ of the sheet by the following equation (1) when detecting the skew in the C region direction or the skew in the A region direction. The sheet conveying device according to claim 3.
θ=tan ⁻¹ {(v×t×n)/d} (1)
However,
v: the transport speed of the sheet,
t: scanning time per line of the edge detection sensor,
n; the C region or the B region after the C region detects the leading edge until the A region or the B region detects the leading edge, or after the A region detects the leading edge. The number of scans of the edge detection sensor until it detects the leading edge,
d; the distance between the pixel position of the C region where the leading edge passes and the pixel position of the A region or the B region, or the pixel position of the A region where the leading edge passes and the C region or the B region The distance to the pixel position of,
Is. A correction unit that is arranged on the downstream side of the edge detection sensor with respect to the sheet conveyance direction and corrects skew and widthwise deviation of the sheet,
6. The control unit executes the width direction deviation correction and the skew correction of the sheet by the correction unit based on the width direction deviation amount and the skew amount of the sheet. The sheet conveying device according to any one of claims. The correction unit is
A pair of correction rollers for correcting the skew and the widthwise deviation of the sheet while conveying the sheet,
A skew correction motor that tilts a roller holder that supports the correction roller pair in the transport direction,
A lateral deviation correction motor that moves the roller holder in the width direction,
Have
The sheet conveyance device according to claim 6, wherein the skew correction motor and the lateral deviation correction motor are stepping motors capable of controlling a rotation direction and a rotation amount by pulse control. A sheet conveying device according to any one of claims 1 to 7,
An image forming unit that forms an image on the sheet conveyed by the sheet conveying device,
An image forming apparatus provided with.

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