JP2020059574A - Sheet conveying device - Google Patents

Abstract

To provide a sheet conveying device capable of preventing a sheet from being damaged when correcting skew thereof.SOLUTION: A sheet conveying device includes: a detecting member extended in parallel with a pair of rollers for correcting skew of a sheet by abutting a tip of the sheet against the pair of stopped rollers; and detection means for detecting at least one end of the detecting member by causing a loop of the sheet generated when a tip of the sheet abuts on the pair of rollers to push up the detecting member. The sheet is controlled in correction of the skew based on the time from when one end of the detecting member is detected by the detection means to when the other end thereof is detected by the detection means.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a sheet conveying device capable of correcting skew of a sheet.

  The image forming apparatus includes an image forming unit that forms an image on a sheet and a feeding unit that conveys the sheet toward the image forming unit. Further, in the image forming apparatus, various techniques are used as the sheet conveyance control for high-speed sheet conveyance. For example, in an apparatus that straightens the skew of a sheet by temporarily stopping the leading end of the conveyed sheet in the upstream portion of the image forming unit to form a loop of the sheet, the loop amount is determined according to the detected skew amount. Is known (Patent Document 1).

JP, 2004-161445, A

  When correcting the skew feeding of the sheet, if the skew feeding amount of the sheet is large, the loop amount formed by temporarily stopping the leading end of the sheet may exceed the loop amount allowed by the apparatus. In such a case, a jam or the like may be caused and the sheet may be damaged.

  An object of the present invention is to provide a sheet conveying device that prevents damage to a sheet when correcting skew of the sheet.

  In order to solve the above-mentioned problems, the sheet conveying apparatus according to the present invention includes a skew correction unit that corrects the skew of the sheet by abutting the leading end of the sheet being conveyed to an abutting portion, and Based on the difference between the loop amount of both ends of the sheet in the direction orthogonal to the sheet conveying direction detected by the detecting unit that detects the loop of the sheet caused by the leading end hitting the skew correcting unit, the And a control unit for controlling the skew correction by the skew correction unit.

  According to the present invention, damage to a sheet can be prevented when correcting skew of the sheet.

FIG. 3 is a diagram showing a configuration of an image forming apparatus. It is a figure which shows the structure of a sheet conveyance part. FIG. 6 is a perspective view of a sheet conveying unit. It is a flow chart which shows processing for starting skew correction. It is a figure for explaining the state of a sheet. It is a figure for explaining the state of a sheet. It is a figure for explaining the state of a sheet. It is a figure for explaining the state of a sheet. It is a figure for explaining the state of a sheet. It is a figure for explaining the state of a sheet. It is a figure for explaining the state of a sheet. It is a figure for explaining the state of a sheet. It is a figure for explaining the state of a sheet. It is a figure which shows the loop state which an apparatus can allow. It is a flow chart which shows processing for starting skew correction. It is a figure for explaining the state of a sheet. It is a figure for explaining the state of a sheet. FIG. 3 is a diagram showing a block configuration of a control system of the image forming apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the present invention according to the claims, and all combinations of features described in the present embodiments are not necessarily essential to the solving means of the present invention. . In addition, the same reference numerals are given to the same components, and the description thereof will be omitted.

[First Embodiment]
FIG. 1 is a diagram showing a schematic cross-sectional view of a color digital printer as an example of an image forming apparatus 100 to which a sheet conveying apparatus according to this embodiment is applied. First, the image forming unit will be described. The surfaces of the four photoconductor drums 101a, 101b, 101c and 101d are uniformly charged by the charging rollers 102a, 102b, 102c and 102d, respectively. Image signals of yellow (Y), magenta (M), cyan (C), and black (K) are input to the laser scanners 103a, 103b, 103c, and 103d, respectively. In accordance with the input image signal, the surface of the photoconductor drum is irradiated with laser light to neutralize the charge, and an electrostatic latent image is formed on the surface of the photoconductor drum.

  The electrostatic latent image formed on the photosensitive drum is developed by the developing devices 104a, 104b, 104c, and 104d with yellow, magenta, cyan, and black toners, respectively. The toner developed on each photoconductor drum is sequentially transferred by the primary transfer rollers 105a, 105b, 105c, and 105d to the intermediate transfer belt 106, which is an endless belt-shaped image carrier, and then transferred onto the intermediate transfer belt 106. A full-color toner image is formed.

  The sheet S fed from one of the sheet feeding units of the feeding cassettes 111 and 112 is conveyed toward the skew feeding correction roller pair 120 by the conveying roller pairs 114, 135, and 116. Similarly, the sheet S fed from the manual feeding unit 113 can also be conveyed toward the skew feeding correction roller pair 120. The toner image on the intermediate transfer belt 106 is subjected to control such as registration adjustment so that the image does not deviate from the image on the sheet S conveyed by the skew correction roller pair 120. When the toner image is transferred onto the sheet S by the secondary transfer roller 109, the transferred toner image is heated and pressed by the fixing device 110 to be fixed onto the sheet S. After that, the sheet S is discharged to the outside of the apparatus main body from the discharge section 119a or 119b. Further, the image forming apparatus 100 is provided with an operation unit 1810 described later, and the user can input various information (size information, basis weight information, surface property information, etc.) regarding the sheet S from the operation unit 1810. is there.

  Each of the feeding cassettes 111 and 112 is provided with a size detection unit 130 for detecting the size of the contained sheet S and causing the control unit 1800 of the image forming apparatus 100, which will be described later, to recognize the size. The size detection unit 130 has a size lever that moves in conjunction with a side regulation plate that regulates the position of the sheet S in the width direction. The side regulating plate is movable in accordance with the side end portion of the sheet S, and the position of the sheet S in the width direction can be aligned with the image forming portion.

  The size detection unit 130 includes a plurality of sensors or switches (not shown) provided at positions corresponding to the size levers that are displaced to the mounting portions of the feeding cassettes 111 and 112 of the image forming apparatus. Therefore, when the feeding cassettes 111 and 112 are mounted on the image forming apparatus 100, the size detection lever selectively turns ON / OFF the detection element of the sensor or switch provided in the mounting portion of the apparatus body. As a result, signals of different patterns are sent from the sensor or the switch to the control unit 1800 of the image forming apparatus 100. Then, the control unit 1800 can recognize the size of the sheet S stored in the feeding cassette based on the signal. A similar mechanism may be provided in the manual feeding unit 113 as the size detecting unit 130.

  The side regulation plate has a function of preventing skew of the sheet S, but skew may occur during conveyance of the sheet S fed from the sheet feeding unit. Therefore, in the present embodiment, the leading end of the conveyed sheet S is nipped by the skew correction roller pair 120 that is stopped, and the conveyance is performed by the upstream conveying roller, so that a loop is formed on the sheet S. As a result, the skew of the sheet S is corrected. The carry amount at this time is determined based on the skew direction and the skew amount of the sheet S detected by the sheet transport unit 200. In the present embodiment, the image forming apparatus 100 is also referred to as a sheet conveying device having the sheet conveying unit 200.

  Next, the configuration of the sheet conveying unit 200 will be described with reference to FIGS. 2 and 3. 2 is a cross-sectional view of the sheet conveying unit 200 near the skew correction roller pair 120, and FIG. 3 is a perspective view of the sheet conveying unit 200. The skew correction roller pair 120 has a driving roller 121 positioned below and a driven roller 122 positioned above, and the transport roller pair 116 positioned upstream of the skew correction roller pair 120 is driven below. It has a roller 117 and a driven roller 118 located above. The drive rollers 121 and 117 are individually driven and controlled by a drive unit (not shown) such as a brushless motor, a stepping motor, and an electromagnetic clutch.

  A lower guide 210 and an upper guide 220 are provided between the skew correction roller pair 120 and the conveying roller pair 116 to guide the conveyed sheet S. The lower guide 210 is a flat plate-shaped guide that conveys the sheet S substantially horizontally from the nip position of the pair of conveyance rollers 116 to the nip position of the pair of skew correction rollers 120. As shown in FIG. 2, the upper guide 220 forms a conveyance path on the skew correction roller pair 120 side so as to face the lower guide 210, and has a guide surface 221 having an open slope as it goes to the conveyance roller pair 116 side. Have. Further, a guide surface 222 for forming a wide space is formed toward the conveying roller pair 116 side.

  The skew correction roller pair 120 and the conveyance roller pair 116, and the lower guide 210 and the upper guide 220 form the sheet conveyance unit 200, and the maximum sheet width of the sheet S that can be conveyed (direction orthogonal to the conveyance direction). The roller pair and the guide shape are extended in a range exceeding. Further, a loop detection unit that detects a sheet loop (bend) is provided in the conveyance path between the skew correction roller pair 120 and the conveyance roller pair 116.

  In the present embodiment, the loop detection unit has a shape extending in the same cross section in a range exceeding the maximum sheet width of the sheet S that can be conveyed (the direction orthogonal to the conveyance direction, the direction parallel to the length of the conveyance roller pair 116). The loop detection member 300 (detection member) is arranged in the transport path. At both ends of the loop detection member 300, a sensor detection flag member 310 and a sensor detection flag member 320 having rotatable fulcrums 311, 321 are arranged. The configuration including the sensor detection flag member 310 on the right side in FIG. 3 corresponds to the configuration in FIG. A configuration similar to that of FIG. 2 is provided as the sensor detection flag member 320 on the left side in FIG. Oval holes 312 and 322 are formed in the sensor detection flag members 310 and 320, and both ends of the loop detection member 300 are inserted and supported. The loop detection member 300 is movable in the direction of arrow A along the concave portion 223 formed on the guide surface 221 having the inclined surface of the upper guide 220, and in conjunction with this, the sensor detection flag members 310 and 320 move the fulcrum 311, Swing around 321. Further, the loop sensor (A) 330 and the loop sensor (B) 340 are arranged in the vicinity of the sensor detection flag members 310 and 320 to detect that the loop detection member 300 has moved in the arrow A direction. The loop sensor (A) 330 and the loop sensor (B) 340 detect each movement of the sensor detection flag members 310 and 320, for example, by the structure of a photo coupler.

  Here, the block configuration of the control system of the image forming apparatus 100 will be described with reference to FIG. FIG. 18 is a diagram showing a block configuration of a control system of the image forming apparatus 100. As shown in FIG. 2, the control unit 1800 is configured as a controller board including a CPU 1801, a ROM 1802, a RAM 1803, an image controller 1804, and an A / D conversion unit 1806, and the CPU 1801 controls the entire image forming apparatus 100. To control. Further, the CPU 1801 has a timer function described later. The ROM 1802 is a general-purpose ROM, and stores various programs and data for performing image formation, for example. The RAM 1803 is a general-purpose RAM, and holds the program read from the ROM 1802, for example. When the RAM 1803 is used as a development area of image data or a working memory of the CPU 1801, for example, processing data and calculation results generated in the course of sheet processing are written and deleted at any time. The operation of the present embodiment is realized by, for example, the CPU 1801 reading a program stored in the ROM 1802 into the RAM 1803 and executing the program.

  The CPU 1801 acquires image data input from an external device such as a host computer via the external interface 1809 and the image controller 1804 and converts the image data into laser light irradiation information. The CPU 1801 drives various motors (fixing motor 1812, conveyance motor 1813, registration motor 1814, transfer motor 1815, paper discharge motor 1816) via the motor driver 1811 at the timing of inputting image data. The carry motor 1813 drives the drive rollers of the carry roller pairs 114, 135, and 116, and the registration motor 1814 drives the drive rollers of the skew correction roller pair 120. The fixing motor 1812 drives the fixing roller of the fixing device 110, and the transfer motor 1815 drives the roller of the intermediate transfer belt 106. Further, the paper discharge motor 1816 drives the drive rollers of the discharge units 119a and 119b. The external interface 1809 transmits / receives not only image data but also various commands such as jobs and status signals.

  The system bus 1805 connects the CPU 1801, ROM 1802, RAM 1803, and image controller 1804 to each other to exchange data. The A / D conversion unit 1806 inputs an analog signal from the sensor group 1808, performs A / D conversion, and supplies a digital signal to the CPU 1801. The sensor group 1808 includes, for example, a cover open / close detection sensor, a temperature sensor, a pre-registration sensor, a fixing sensor, and a sensor provided in the manual feeding unit 113 or the sheet feeding unit, which are not shown, for detecting the presence or absence of a sheet. The switch group 1807 includes, for example, a power switch (not shown) and a print switch for instructing to start printing.

  The operation unit 1810 includes a panel and hardware keys, receives various settings of the image forming apparatus 100 by the user, and displays various user interface screens of the image forming apparatus 100. For example, the operation unit 1810 can display a jam occurrence location on the panel. The operation unit 1810 also includes a configuration such as an LED, and can also notify the state of the device and the like.

  The image forming apparatus 100 according to this embodiment may be configured as a copying apparatus in combination with the configuration of FIG. 1 and a reading device (scanner) or the like. Further, it may be configured as a facsimile device having a transmission / reception function, or a multifunction peripheral device (MFP) in which these are integrated.

  The operation of the sheet conveying unit 200 in this embodiment will be described below with reference to FIG. The flowchart of FIG. 4 is realized, for example, by the CPU 1801 loading a program stored in the ROM 1802 into the RAM 1803 and executing the program.

  In S <b> 1, the CPU 1801 drives the carry motor 1813 to feed the sheet from the feeding cassette 111 or 112 toward the skew feeding roller pair 120. FIGS. 5, 6, and 7 are views for explaining the operation of S1 of FIG. 4, and FIG. 5A shows the conveyance path between the skew correction roller pair 120 and the conveyance roller pair 116. It is sectional drawing which shows the state of the sensor detection flag member 310, and FIG.5 (b) is a detailed perspective view.

  FIG. 6A is a cross-sectional view showing a state of the sensor detection flag member 320 in the conveyance path between the skew correction roller pair 120 and the conveyance roller pair 116, and FIG. 6B is a detailed perspective view. . 7 is a sectional view taken along line AA shown in FIGS. 5 and 6. The sheet S fed from one of the sheet feeding units of the feeding cassettes 111 and 112 is conveyed to the driving roller 117 and the driven roller 118 of the conveying roller pair 116 as shown in FIGS. The sheet is conveyed toward the skew correction roller pair 120 according to the arrow F.

  At this time, the sheet S is conveyed in a horizontal state until it reaches the nip position of the skew feeding correction roller pair 120, so that the sheet S does not come into contact with the loop detection member 300 and rotates in conjunction with it. The detection flag member 310 and the sensor detection flag member 320 also do not move. Therefore, both the loop sensor (A) 330 and the loop sensor (B) 340 are in the detection OFF state (not detected).

  Next, in S2, the CPU 1801 determines whether or not one of the loop sensor (A) 330 and the loop sensor (B) 340 is in the detection ON (detecting) state. Here, if it is determined that any one is in the detection ON state, the process proceeds to S3, and if it is determined that neither is in the detection ON state, the process of S1 is repeated.

  FIG. 8, FIG. 9, and FIG. 10 are diagrams for explaining the operation of S2 to S3 of FIG. As shown in FIGS. 5 and 6, the sheet S is conveyed toward the skew feeding correction roller pair 120 according to the arrow F, but the driving roller 121 of the skew feeding correction roller pair 120 stops driving and the feeding roller pair is conveyed. Since the sheet is continuously conveyed from 116, when the leading edge of the sheet S of the skew feeding correction roller pair 120 hits the nip position and stops, a loop L is formed as shown in FIG. 8A.

  The sheet S is conveyed by the conveying roller pair 116 toward the skew feeding correction roller pair 120 in accordance with the arrow F, and the sheet feeding portion of either one of the feeding cassettes 111 and 112 and the left and right sides of the conveying roller pair 116 are provided. Due to a pressure balance difference, bending when setting a sheet, and the like, the leading edge of the sheet S may hit the nip position of the skew feeding correction roller pair 120 in a skewed state, and a one-sided loop may occur.

  When the leading edge of the sheet S on the side of the loop sensor (A) 330 abuts the nip position first and is continuously conveyed by the pair of conveying rollers 116, a loop L is formed. Then, the loop detection member 300 is pushed upward by the formed loop and moves in the direction of arrow A along the concave portion 223 formed in the guide surface 221 having the inclined surface of the upper guide 220. Then, as shown in FIGS. 8A and 8B, the sensor detection flag member 310 is interlocked and moves around the fulcrum 311, and the loop sensor (A) 330 is in the detection ON state.

  On the other hand, as shown in FIG. 9, the leading edge of the sheet S on the side of the loop sensor (B) 340 has not reached the nip position of the skew feeding correction roller pair 120 because of a delay due to skew feeding. Therefore, the loop is not formed yet. Therefore, since the loop sensor (B) 340 side of the sheet S is not in contact with the loop detection member 300, the sensor detection flag member 320 does not move and the loop sensor (B) 340 does not move as shown in FIGS. (B) 340 is in a detection OFF state. When a loop occurs at one end and a loop does not occur at the other end as shown in FIGS. 8 and 9, the loop sensor (A) 330 is in the detection ON state. As a result of the determination, the process proceeds to S3.

  In S3, the CPU 1801 activates a timer. When the leading edge of the sheet S hits the nip position and one-side loop occurs when the sheet S is skewed, a time difference detected by the loop L between the loop sensor (A) 330 and the loop sensor (B) 340 occurs. The larger the time difference, the larger the skew amount of the sheet S to be fed. In the present embodiment, as a configuration for controlling the allowable loop amount, a timer that measures the start time in S3 at the time when either the loop sensor (A) 330 or the loop sensor (B) 340 detects it. Measures the time from when the other starts to detect the other.

  In S4, the CPU 1801 determines whether or not the value measured by the timer (elapsed time) is the jam time T or less. When it is determined that the jam time is equal to or less than the jam time, the process proceeds to S5, and when it is determined that the jam time is longer than the jam time T, the process proceeds to S8.

  Hereinafter, the operation of S4 will be described with reference to FIG. As described in S3 above, in the present embodiment, the timer for measuring the start time is activated when either the loop sensor (A) 330 or the loop sensor (B) 340 detects it, and the other side is activated. The timer is terminated when the loop sensor (B) 340 detects it. Then, the detected time difference between the photosensors is defined as a skew time Δt. It can be said that the larger the time difference, the larger the skew amount of the sheet S to be fed. In FIG. 14, a loop that can be tolerated by the apparatus (capable of preventing jamming / paper folding) is shown as'L '(solid line). When the time to reach the loop amount is defined as the jam time T, in S4, when the jam time T is exceeded before the other side loop sensor (B) 340 detects, the CPU 1801 in S8. Causes the conveyance motor 1813 to temporarily stop the conveyance of the conveyance roller pair 116. Then, the CPU 1801 controls the carry motor 1813 to carry the sheet S in the direction opposite to the carrying direction. After S8, the re-feeding operation is performed by repeating the process of S1. With such a configuration, it is possible to prevent the loop from exceeding the allowable amount and causing a jam.

  Next, in S5, the CPU 1801 determines that the other loop sensor (the other end), that is, either the loop sensor (A) 330 or the loop sensor (B) 340 is in the detection ON state (is being detected). Determine if there is. If it is determined that the other loop sensor is in the detection ON state, the process proceeds to S6, and if it is determined that none of the loop sensors is in the detection ON state, the process of S5 is repeated.

  The process of S6 will be described below. 11 to 13 are diagrams for explaining the operation of S5 to S6 of FIG.

  In the state of proceeding from S2 to S3, the loop pushes the loop detection member 300 upward with the leading edge of the sheet S on the side of the loop sensor (A) 330 hitting the nip position first as shown in FIG. 8A. The loop sensor (A) 330 is in the ON state in which the movement is detected. At that time, as shown in FIG. 9A, since the loop sensor (B) 340 side of the sheet S has not reached the nip position, no loop is formed. Since the sheet S is not in contact with the loop detection member 300, the loop sensor (B) 340 is in the detection OFF state, and the skew feeding correction roller pair 120 is in the drive stopped state. The sheet S is continuously conveyed by the conveying roller pair 116 in a state where the skew correction roller pair 120 is not driven, and as shown in FIG. 11A, the loop sensor (A) 330 side of the sheet S is provided. Loop increases from L (broken line) to'L (solid line). On the other hand, on the loop sensor (B) 340 side of the sheet S, as shown in FIG. 12A, the leading end of the sheet S hits the nip position to form a loop L, and the loop sensor (B) 340 is in the detection ON state. . The CPU 1801 ends the timer at the time when the loop sensor (B) 340 on the other side detects, and saves the detected time difference between the photosensors as a skew time Δt in a storage area such as the RAM 1803.

  After the processing of S6, the process proceeds to S7. The process of S7 will be described below. In S7, the CPU 1801 compares the detected time difference between the photosensors at the time when the loop sensor (B) 340 on the other side detects, that is, the skew time Δt with the jam time T. When it is determined that the skew time Δt is longer than the jam time T, in S8, the CPU 1801 temporarily stops the conveyance of the conveyance roller pair 116, conveys the sheet S in the direction opposite to the conveyance direction, and performs the refeed operation. Control to be able to do. On the other hand, when it is determined that the skew feeding time Δt is equal to or less than the jam time T, it is determined that the skew feeding is a loop amount capable of correcting the skew feeding (allowable loop amount), and in S9, the CPU 1801 is in the stopped state. The driving operation of the skew correction roller pair 120 is started. After S9, the process of FIG. 4 ends. After the processing of FIG. 4, the toner image is transferred to the skew-corrected sheet S by the secondary transfer roller 109.

  As described above, according to the present embodiment, the time difference detected by the sensors in the vicinity of both ends regardless of the size range such as various standards (ISO / ASME / etc.) As the sheet size that can be fed. Based on, it is possible to detect whether the loop is acceptable or not. Further, as for the detection configuration, two detection units (sensors) may be provided at both ends outside the maximum sheet width of the sheet that can be conveyed (direction orthogonal to the conveying direction). Therefore, it is not necessary to provide a plurality of sheet sensor flags corresponding to the respective sheet sizes at the widthwise ends of the sheet sizes that can be fed.

  In the present embodiment, when the skew time Δt is equal to or less than the threshold value, it means that the degree of skew is small. Therefore, if the loop amount smaller than the predetermined loop amount is reached, skew correction may be performed. good. With such a configuration, the feeding start speed can be increased. Further, according to the present embodiment, even when the loop amount exceeds the loop amount allowed by the sheet conveying apparatus, it is possible to damage the sheet by rotating the conveying roller in the opposite direction and re-feeding. It is possible to prevent the waste of sheets.

  In the above description, the sensor detection flag members 310 and 320 that move in conjunction with the loop detection member 300 have been described as transmissive sensors that shield the optical sensor, but reflective sensors, mechanical switches, etc. A sensor may be used. Further, although the configuration in which the sensor detection flag members 310 and 320 that move in association with the loop detection member 300 are detected by the optical sensor has been described, the configuration may be such that the sensor detection flag members 310 and 320 are not interposed. For example, the movement of the loop detection member 300 may be directly detected by the sensors arranged at both ends outside the maximum sheet width of the loop detection member 300 (direction orthogonal to the transport direction).

[Second Embodiment]
Regarding the second embodiment, the points different from the first embodiment will be described. In the first embodiment, the conveyance roller pair 116 conveys the sheet S toward the skew feeding correction roller pair 120. In this embodiment, the user manually feeds the sheet S toward the skew correction roller pair 120.

  The operation of the sheet conveying unit 200 in this embodiment will be described with reference to FIG. Each process illustrated in FIG. 15 is realized by, for example, the CPU 1801 of the control unit loading a program stored in the ROM 1802 into the RAM 1803 and executing the program. 16 and 17 are diagrams for explaining the operation of S11 of FIG. FIG. 16A is a cross-sectional view showing a state of the sensor detection flag member 310 in the conveyance path between the skew feeding correction roller pair 120 and the manual sheet feeding port 400. FIG. 16B is a cross-sectional view showing the state of the sensor detection flag member 320 in the conveyance path between the skew feeding correction roller pair 120 and the manual sheet feeding port 400. FIG. 16C is a cross-sectional view taken along line AA shown in FIGS. 16A and 16B.

  In S11, the CPU 1801 determines that the sheet S has been placed on the paper feed tray 500 by the user as shown in FIGS. 16A and 16B, and has been manually fed toward the skew correction roller pair 120 according to the arrow F. To detect.

  As shown in FIG. 16C, the sheet S at this time is kept in a horizontal state and conveyed until it reaches the nip position of the skew correction roller pair 120, so that the sheet S comes into contact with the loop detection member 300. Without this, the sensor detection flag members 310 and 320 that can rotate in conjunction do not move. Therefore, both the loop sensor (A) 330 and the loop sensor (B) 340 are in the detection OFF state.

  In S12, the CPU 1801 determines whether or not one of the loop sensor (A) 330 and the loop sensor (B) 340 is in the detection ON (detecting) state. Here, if it is determined that any of them is in the detection ON state, the process proceeds to S13, and if it is determined that neither is in the detection ON state, the process of S11 is repeated.

  The operation of S12 to S13 of FIG. 15 will be described with reference to FIG. When the sheet S is manually fed toward the skew feeding correction roller pair 120 according to the arrow F, the driving roller 121 of the skew feeding correction roller pair 120 is in a driving stopped state. When the leading end hits the nip position and the sheet S is further inserted, a loop L is formed as shown in FIG.

  Here, the sheet S is conveyed by the user toward the skew correction roller pair 120 according to the arrow F. However, when the user inserts the end of the sheet S in the width direction with one hand, the sheet S is skewed. In this state, the leading edge of the sheet S may hit the nip position, and as a result, a single loop may occur.

  In FIG. 17A, the loop S (broken line) is formed because the sheet S is further conveyed in a state where the leading edge of the sheet S on the side of the loop sensor (A) 330 of the sheet S hits the nip position first. The loop detection member 300 is pushed upward by the formed loop and moves in the direction of arrow A along the recess 223 formed in the guide surface 221 having the inclined surface of the upper guide 220. Then, in conjunction with each other, the sensor detection flag member 310 swings around the fulcrum 311, and the loop sensor (A) 330 detects the movement and is in the ON state. On the other hand, the broken line in FIG. 17B shows the leading edge of the sheet S on the loop sensor (B) 340 side. The leading edge of the sheet S on the side of the loop sensor (B) 340 has not reached the nip position due to the conveyance delay due to skew feeding, and no loop is formed. In that state, since the sheet S is not in contact with the loop detection member 300, the sensor detection flag member 320 does not move and the loop sensor (B) 340 is in the detection OFF state. As described above, in the states of FIGS. 17A and 17B, the process proceeds from S12 to S13.

  Next, in S13, the CPU 1801 determines whether or not the other loop sensor, that is, one of the loop sensor (A) 330 and the loop sensor (B) 340 is in the detection ON (detecting) state. To judge. If it is determined that the other loop sensor is in the detection ON state, the process proceeds to S14, and if it is determined that none of the loop sensors is in the detection ON state, the process of S13 is repeated.

  When the user further inserts the sheet S from the state of S12 with the skew feed correction roller pair 120 stopped driving, as shown in FIG. 17A, the loop sensor (A) 330 side of the sheet S is inserted. Loop increases from L (broken line) to'L (solid line). On the other hand, on the loop sensor (B) 340 side of the sheet S, as shown in FIG. 17B, the leading end of the sheet S hits the nip position to form a loop L, and the loop sensor (B) 340 is in the detection ON state. Become.

  Then, when the sensor detection flag members 310 and 320 move and both the loop sensor (A) 330 and the loop sensor (B) 340 are in the detection ON state, in S14, the CPU 1801 causes the skew correction roller in the stopped state. The driving of the pair 120 is started. After S14, the processing of FIG. 15 ends. After the processing of FIG. 15, the toner image is transferred to the skew-corrected sheet S by the secondary transfer roller 109.

  As described above, if the sensor detection flag member and the sensor detection flag member move and both of the two sensor detection flag members 310 and 320 at both ends are not in the detection ON state, the skew correction roller pair 120 is driven. Do not start. As a result, since the skew feeding correction roller pair 120 is driven after the loops at both ends of the sheet are formed, skew feeding can be surely performed.

  100 Image forming device: 116 Conveying roller pair: 120 Skew correction roller pair: 200 Sheet conveying device: 300 Loop detection member: 310, 320 Sensor detection flag member: 330, 340 Loop sensor: 1801 CPU: 1802 ROM: 1803 RAM

Claims (9)

By abutting the leading end of the conveyed sheet to an abutting portion, a skew feeding correcting means for correcting the skew feeding of the sheet,
A detection unit that detects a loop of the sheet that occurs when the leading edge of the sheet hits the skew correction unit,
Based on the difference in the loop amount of both ends of the sheet in the direction orthogonal to the sheet conveying direction detected by the detecting means, control means for controlling the skew correction by the skew correction means,
A sheet conveying device comprising: The skew feeding correcting means corrects the skew feeding of the sheet by abutting the tip of the sheet against the roller pair as the abutting portion,
The detection means detects each displacement of both ends of a detection member extending in parallel with the roller pair,
The control unit controls the skew correction by the skew correction unit based on the time from the detection unit detecting one end of the both ends to the detection of the other end.
The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus.   The sheet conveying device according to claim 2, wherein the control unit stops the skew correction by the skew correction unit when the time is longer than a predetermined time.   Even if the detection unit does not detect the other end, the control unit may stop the skew correction by the skew correction unit when the predetermined time is reached after detecting the one end. The sheet conveying device according to claim 3.   5. The sheet conveying apparatus according to claim 3, wherein the control unit conveys the sheet in a reverse direction when the skew correction is stopped by the skew correction unit.   The control unit causes the skew correction unit to correct the skew when the time is equal to or less than the predetermined time. Sheet transport device.   7. The sheet conveying apparatus according to claim 6, wherein the control unit starts driving the roller pair when the skew correction is performed by the skew correction unit.   The said detection means detects the said detection member pushed up by the loop of the said sheet | seat by the sensor located above the said detection member, The any one of Claim 2 thru | or 7 characterized by the above-mentioned. Sheet transport device.   The sheet conveyance device according to claim 8, wherein the sensor is provided at each position corresponding to both ends of the detection member.

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