JP2008184259A - Sheet conveyer, image forming device, and image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet conveyer capable of correcting stably a skew, an image forming device and an image reader. <P>SOLUTION: This sheet conveyer is provided with conveying roller pairs 34 comprising a lower roller 301 and an upper roller 14 brought into pressure contact with the lower roller 301 contactably and separably and for conveying a sheet S to a skew correction part, in a sheet conveying directional upstream of the skew correction part, and each conveying roller pair 34 is constituted to bring the upper roller 14 into contactable and separable with/from the lower roller 301, when correcting the skew of the sheet by the skew correction part. Flanges 302 are provided to be projected in an upper side of a roller part 301a, in axial-directional both sides of the roller part 301a constituting the lower roller 301, and the sheet S is supported from an under side by the flanges 302 when the upper roller 14 is separated from the lower roller 301. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus, an image forming apparatus, and an image reading apparatus, and more particularly to a configuration for correcting skew feeding of a sheet.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, facsimiles, and image reading apparatuses are provided with a sheet conveying device that conveys a sheet such as a recording sheet or a document to the image forming unit or the image reading unit. Some sheet conveying apparatuses include a skew feeding correction unit in order to adjust the posture and position of the sheet before being conveyed to the image forming unit or the image reading unit.

  Here, as a correction method of such a skew correction unit, there is a correction method based on a side registration standard that corrects a positional deviation of a sheet with reference to a side edge of the sheet being conveyed (see Patent Documents 1 and 2). . In addition, an active device that corrects skew while transporting a sheet using two sensors provided on a coaxial line in the width direction perpendicular to the sheet transport direction and two skew correction rollers in the sheet transport path. There is a resist system (see Patent Document 3).

  FIG. 11 is a diagram for explaining a conventional correction method based on a side registration standard. In the case of the skew correction unit of this correction method, an abutting reference member 31 is provided on one side of the sheet transport path along the sheet transport direction, and a skew correction roller (not shown) is disposed on the sheet transport path. .

  Then, the skew correction roller causes the sheet being conveyed to be brought closer to the abutting reference member side, the side edge of the sheet is abutted against the abutting reference member 31, and the position deviation of the sheet side end in the width direction of the sheet Both the inclination of the sheet side edge with respect to the sheet conveying direction are corrected.

  Here, when the sheet side end is abutted against the abutting reference member 31, if the pressing force of the sheet against the abutting reference member 31 (the width-adjusting force by the skew feeding roller) is too strong, the sheet is jammed or corrected. The accuracy will be deteriorated.

  For this reason, conventionally, as shown in FIG. 11, the guide groove M is formed with the cross-sectional shape of the abutting reference member 31 being U-shaped, and the side of the sheet S is inserted into the guide groove M, whereby the sheet S is inserted. It suppresses from the vertical direction (sheet thickness direction) to suppress the occurrence of buckling and loops.

  Furthermore, gap variable means 601 to 603 for adjusting the gap of the guide groove M are provided. For example, by moving the gap variable means 601 in the direction of the arrow according to the thickness of the sheet S to be conveyed, The gap is adjusted to match the thickness of the sheet S.

  FIG. 12 is a diagram for explaining a skew correction method using a conventional active registration method. In the case of the skew correction unit of this correction method, drive control is independently performed by two sensors 702a and 702b and motors 703a and 703b with a predetermined interval on the same axis in the width direction before the photosensitive drum 701. A pair of skew correction rollers 704a and 704b is disposed.

  When skew correction is performed, control (not shown) is first performed based on detection signals from the sensors 702a and 702b when the leading edge of the sheet S conveyed in the sheet conveyance direction indicated by the arrow passes through the sensors 702a and 702b. The section detects the skew amount of the sheet S.

  Next, before the sheet S enters the photosensitive drum 701, the control unit controls the sheet conveyance amount by the skew correction roller pair 704a and 704b according to the skew amount detected by the sensors 702a and 702b. The skew of the sheet S is corrected by turning the sheet S. In addition, in order to improve the skew correction accuracy, there is a technique in which such skew correction is performed a plurality of times (see Patent Document 4).

JP-A-11-189355 JP 2002-356250 A JP 2001-58741 A JP 2001-31294 A

  By the way, in the conventional sheet conveying apparatus provided with such a skew correction unit, a driving roller that conveys a sheet upstream of the pair of skew correction rollers in the sheet conveying direction and a driven roller that presses and comes in contact with the roller. A pair of conveying rollers is provided. When the sheet is skewed, the driven roller is separated from the driving roller so as not to prevent the sheet feeding by the skew correction roller pair.

  By the way, a sheet having a large basis weight or size changes abruptly in frictional resistance of the sheet depending on the humidity environment, and particularly in a high humidity environment, the rigidity (roughness) of the large size sheet is lost. For this reason, when the sheet is conveyed in a high humidity environment, the sheet is conveyed while covering the upper surface of the roller part of the conveying roller located below, and the friction with the surface of the roller part increases due to the humidity. As a result, the sheet conveyance resistance increases.

  FIG. 13 is a diagram illustrating a relationship between a roller portion formed of rubber, a sheet friction coefficient, and humidity. As shown in FIG. 13, when the humidity exceeds 50%, the frictional resistance (static coefficient of friction μ) of the sheet increases rapidly, so that the conveyance resistance at the trailing edge of the sheet increases as the humidity increases. Therefore, in a high humidity environment, the friction load with the conveyance roller at the rear end of the sheet becomes large, and the sheet conveyance at the time of skew feeding becomes unstable.

  Further, in the case of the sheet B which is a sheet exceeding the A3 size, the amount of the sheet applied to the roller portion becomes large. In this case, particularly in a high humidity environment exceeding 50%, the sheet is more than the conveying force of the skew correction roller. The conveyance resistance with the surface of the roller portion at the rear end becomes larger.

  For this reason, for example, when skew correction based on the side registration standard is performed in a high humidity environment, even if the driven roller is separated from the drive roller, the conveyance resistance at the trailing edge of the sheet increases, and therefore skew correction is performed. The skew feeding of the sheet by the roller pair is prevented. Further, as the sheet size increases, the number of conveying rollers in contact with the trailing edge of the sheet increases, so that the skew feeding becomes more unstable and the accuracy of skew correction decreases.

  Here, when the sheet conveyance resistance increases as described above, if the conveyance force of the skew feeding correction roller pair is increased to increase the width-adjusting force on the abutting reference member side, for example, rigidity is reduced like a thin sheet. In the case of a small sheet, buckling jam may occur in the guide groove. Such buckling jam can be generated to some extent by reducing the height of the upper and lower grooves of the guide groove, but if the conveying force of the skew correction roller pair is increased, the effect on buckling cannot be expected. .

  As described above, when the conveyance force of the skew correction roller pair is increased so that skew correction can be performed even in a high humidity environment, if a sheet with low rigidity is pressed against the reference member side, buckling occurs. There is a risk of jamming.

  On the other hand, even in the skew correction method using the active registration method, the conveyance resistance at the trailing edge of the sheet increases in a high humidity environment. Accuracy is reduced.

  Here, when the sheet conveyance resistance increases as described above, the conveyance force of the skew feeding correction roller pair is increased to increase the sheet turning force. The skew correction roller may buckle the sheet and cause wrinkles. In other words, if the conveyance force of the skew correction roller pair is increased so that skew correction can be performed even in a high humidity environment, the sheet may buckle and wrinkle if an attempt is made to rotate a sheet with low rigidity. There is.

  Accordingly, the present invention has been made in view of such a current situation, and an object thereof is to provide a sheet conveying device, an image forming apparatus, and an image reading apparatus capable of performing stable skew feeding correction. is there.

  According to the present invention, in a sheet conveying apparatus that conveys a sheet, a skew correction unit that corrects skew of a sheet, and a sheet that is conveyed upstream of the skew correction unit in the sheet conveyance direction, to the skew correction unit. And a pair of conveyance rollers configured to be separated according to the skew correction operation of the sheet by the skew correction unit, and when the conveyance roller pair is separated, And a support member for supporting the sheet being conveyed.

  According to the present invention, in a sheet conveying apparatus that conveys a sheet, a skew correction unit that corrects the skew of the sheet, and a sheet is conveyed to the skew correction unit upstream of the skew correction unit in the sheet conveyance direction. And a pair of conveyance rollers configured to be separated according to the skew correction operation of the sheet by the skew correction portion, and a contact portion capable of contacting the conveyed sheet A support member disposed so that the contact portion is positioned between the pair of transport rollers as viewed in the axial direction of the pair of transport rollers when the pair of transport rollers is separated. It is characterized by.

  According to the present invention, at the time of skew correction, when the conveyance roller pair is separated, the sheet is supported by the support member, so that the frictional load with the surface of the roller portion in the conveyed sheet is reduced, and the stable sheet Skew correction can be performed.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a color image forming apparatus which is an example of an image forming apparatus provided with a sheet conveying apparatus according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 100 denotes a color image forming apparatus, and 100A denotes a color image forming apparatus main body (hereinafter referred to as apparatus main body). The color image forming apparatuses are mainly classified into a tandem method in which a plurality of image forming units are arranged side by side and a rotary method in which a plurality of image forming units are arranged in a cylindrical shape. The transfer system is classified into a direct transfer system in which a toner image is directly transferred from a photosensitive drum to a sheet and an intermediate transfer system in which the toner image is once transferred to an intermediate transfer body and then transferred to a sheet material.

  Here, the intermediate transfer method does not require the sheet to be held on the transfer belt unlike the direct transfer method, and thus can be used for a wide variety of sheets such as ultra-thick paper and coated paper. Further, it is suitable for realizing high productivity due to the features of parallel processing in a plurality of image forming units and batch transfer of full-color images. The color image forming apparatus 100 according to the present embodiment is of an intermediate transfer tandem system in which four color image forming units are arranged side by side on an intermediate transfer belt.

  The image forming unit 513, the sheet feeding unit 100B that conveys the sheet S, and the toner image formed by the image forming unit 513 are transferred to the apparatus main body 100A onto the sheet S fed by the sheet feeding unit 100B. A transfer unit 100C is provided. Further, the apparatus main body 100A is provided with a sheet conveying apparatus 100D that conveys a sheet.

  Here, the image forming unit 513 includes a yellow (Y), a magenta (M), a cyan (C), and a black provided with a photosensitive drum 508, an exposure device 511, a developing device 510, a primary transfer device 507, and a cleaner 509, respectively. (Bk) image forming unit. Note that the colors formed by each image forming unit are not limited to these four colors, and the color arrangement order is not limited to this.

  The sheet feeding unit 100B includes a sheet storage unit 51 that stores the sheets S in a form of being stacked on the lift-up device 52, and a sheet feeding unit 53 that sends out the sheets S stored in the sheet storage unit 51. ing. Examples of the sheet feeding unit 53 include a method using frictional separation by a paper feed roller and the like, a method using air separation and adsorption, and the like. In the present embodiment, a paper feeding method using air is used. An example is given.

  The transfer unit 100C includes an intermediate transfer belt 506 that is stretched by rollers such as a driving roller 504, a tension roller 505, and a secondary transfer inner roller 503, and is conveyed and driven in the direction of arrow B in the drawing. .

  Here, the intermediate transfer belt 506 is to transfer the toner image formed on the photosensitive drum by a predetermined pressure and an electrostatic load bias given by the primary transfer device 507. In addition, the intermediate transfer belt 506 applies a predetermined pressure and an electrostatic load bias at the secondary transfer portion formed by the substantially opposite secondary transfer inner roller 503 and secondary transfer outer roller 56, so that the sheet S The non-fixed image is adsorbed to the head.

  The sheet conveyance device 100D includes a conveyance unit 54, a conveyance roller device 50, a skew correction device 55 constituting a skew correction unit, a registration roller 7, a pre-fixing conveyance unit 57, a branch conveyance device 59, a reverse conveyance device 501, and a double-side conveyance. It is comprised from the apparatus 502 grade | etc.,. Reference numeral 9 denotes a control unit that controls an image forming operation of the color image forming apparatus 100 and a sheet skew correction operation to be described later.

  In the color image forming apparatus 100 having such a configuration, when an image is formed, first, the photosensitive drum 508 is rotated in the direction of arrow A in the drawing, and the surface of the photosensitive drum is previously charged by a charging unit (not shown). Is uniformly charged.

  Thereafter, the exposure device 511 emits light to the rotating photosensitive drum 508 based on the transmitted image information signal, and this light is irradiated through the reflecting means 512 and the like as appropriate, thereby the photosensitive drum 508. A latent image is formed on top. Note that the transfer residual toner slightly remaining on the photosensitive drum 508 is collected by the cleaner 509 to prepare for the next image formation again.

  Next, toner development is performed on the electrostatic latent image formed on the photosensitive drum 508 in this way by the developing device 510, and a toner image is formed on the photosensitive drum. Thereafter, a predetermined pressure and an electrostatic load bias are applied by the primary transfer device 507, and the toner image is transferred onto the intermediate transfer belt 506.

  Note that image formation by the Y, M, C, and Bk image forming units of the image forming unit 513 is performed at the timing of superimposing on the upstream toner image primarily transferred onto the intermediate transfer belt. As a result, a full-color toner image is finally formed on the intermediate transfer belt 506.

  Further, the sheet S is sent out by the sheet feeding unit 53 in accordance with the image forming timing of the image forming unit 513. Thereafter, the sheet S passes through a conveyance path 54 a provided in the conveyance unit 54 and is conveyed to a skew feeding correction device 55 for correcting the positional deviation and skew feeding of the sheet being conveyed.

  Then, the sheet S in which the positional deviation and the skew feeding are corrected by the skew feeding correction device 55 is conveyed to the registration roller 7, the timing is corrected by the registration roller 7, and then the secondary transfer inner roller 503 and the secondary transfer. It is conveyed to the secondary transfer portion formed by the outer roller 56. Thereafter, a full-color toner image is secondarily transferred onto the sheet S in the secondary transfer portion.

  Next, the sheet S on which the toner image has been secondarily transferred in this way is conveyed to the fixing device 58 by the pre-fixing conveyance unit 57. In the fixing device 58, the toner is melted and fixed on the sheet S by applying a predetermined pressing force by a substantially opposed roller or belt and generally a heating effect by a heat source such as a heater.

  Next, the sheet S having the fixed image obtained in this manner is discharged as it is onto the discharge tray 500 by the branch conveyance device 59. When images are formed on both sides of the sheet S, the sheet is conveyed to the reverse conveying device 501 by switching a switching flapper (not shown).

  Here, when the sheet S is conveyed to the reverse conveying device 501 in this way, the sheet S is switched back and the leading and trailing ends thereof are exchanged and conveyed to the re-conveying path R provided in the double-sided conveying device 502. Thereafter, the sheet is merged from the re-feed path 54b of the conveyance unit 54 with the timing of the sheet of the subsequent job conveyed from the sheet feeding unit 100B, and similarly sent to the secondary transfer unit. Since the image forming process is the same as that of the first side, it is omitted.

  The transport unit 54, the branch transport device 59, the reverse transport device 501, and the double-side transport device 502 are provided with a large number of transport rollers. These conveying rollers convey the sheet by rotating the driving roller and the driven roller while the sheet is sandwiched between the driving roller and the driven roller. In addition, these conveying rollers set the pressure to nip the sheet between the two rollers by improperly driving the driven roller toward the driving roller by a biasing member such as a spring (not shown).

  In the present embodiment, the skew correction device 55 for correcting the positional deviation and skew of the sheet being conveyed is a side registration that corrects the positional deviation of the sheet with reference to the side edge of the sheet being conveyed. The correction method is based on a standard.

  For this reason, as shown in FIG. 2, the skew correction device 55 includes a fixed guide 33 that functions as a conveyance guide for the sheet S and a width direction (mainly indicated by an arrow corresponding to the size of the sheet S to be conveyed). A movable guide 30 movable in the scanning direction) is provided.

  Further, the movable guide 30 includes a plurality of skew feeding roller pairs 32 and 32a, which are a plurality of skew feeding rollers, and an abutting reference member 31 to which the sheet S which is skew fed by the skew feeding correction roller pairs 32 and 32a is abutted. Is suspended. The skew correction roller pair 32, 32a is attached to the movable guide 30 so as to be inclined by an angle α with respect to the sub-scanning direction so that an abutting conveyance component with respect to the abutting reference member 31 is obtained.

  As shown in FIG. 2, the conveyance roller device 50 that is disposed upstream of the skew feeding correction device 55 in the sheet conveyance direction and conveys a sheet to the skew feeding correction device 55 is provided with a plurality of conveyance roller pairs 34. . Here, as shown in FIG. 3, each of the plurality of conveying roller pairs 34 includes a driving roller 301 that is a lower roller, and an upper roller that conveys a sheet together with the driving roller 301 while being in pressure contact with the driving roller 301. And a driven roller 14.

  The driven roller 14 is in a position where it is in pressure contact with the driving roller 301 as shown in FIG. 3A when the sheet S conveyed from the conveying unit 54 is conveyed. Thus, after being conveyed from the conveyance unit 54, the sheet S is nipped by the plurality of conveyance roller pairs 34 and conveyed to the skew feeding correction device 55.

  On the other hand, when the sheet S reaches the most upstream skew correction roller pair 32 a in the sheet conveyance direction among the plurality of skew correction roller pairs 32 provided in the skew correction device 55, the driven roller 14 moves from the driving roller 301. Separate. Then, when the driven roller 14 is separated and the nip with the driving roller 301 is released, the sheet S is conveyed obliquely when the sheet S is obliquely fed by the skew feeding correction roller pair 32, 32a. It is possible to prevent the roller pair 34 from being obstructed.

  In FIG. 3, reference numeral 321 denotes a driving roller constituting the skew correction roller pair 32, 32a, and 322 denotes a driven roller that conveys the sheet together with the driving roller 321 while being in pressure contact with the driving roller 321. The drive roller 321 is attached to the movable guide 30 at an angle α with respect to the sub-scanning direction as described above.

  The registration roller 7 is also composed of a driving roller (not shown) and a driven roller that is in pressure contact with the driving roller and conveys the sheet together with the driving roller.

  Next, operations of the conveyance roller device 50 and the skew feeding correction device 55 configured as described above during sheet conveyance will be described.

  As shown in FIG. 2, when the sheet S is conveyed to the conveyance roller device 50 with the skew angle β, the sheet S is sent to the skew correction device 55 by the conveyance roller pair 34. Then, as shown in FIG. 4A, the sheet S is sandwiched between the skew correction roller pairs 32 and 32 a and is conveyed obliquely toward the abutting reference member 31. When the sheet S starts to be conveyed by the most upstream skew correction roller pair 32a, the nip of the conveyance roller pair 34 is released (see FIG. 3B).

  Next, as shown in FIG. 4B, the sheet S is moved to the downstream registration roller 7 while the end surface of the sheet S is pressed against the abutting reference member 31 by the skew correction roller pair 32 and 32a. It is conveyed. Then, the sheet S is conveyed while being pressed (contacted) against the abutting reference member 31, thereby correcting the skew of the sheet S and the positional deviation in the width direction.

  In the present embodiment, in consideration of variations in the main scanning direction of the position of the conveyed sheet S, when the sheet S is conveyed to the skew feeding correction device 55, the conveyed sheet S is conveyed. So that the abutting reference member 31 is offset so as not to crash.

  Therefore, next, when the sheet S reaches the registration roller 7 and then the conveyance of the sheet S is started by the registration roller 7, the registration roller 7 holds the sheet S as shown in FIG. It moves in the main scanning direction indicated by the arrow while being conveyed. Thereby, the center positions of the sheet S and the image on the intermediate transfer belt can be matched.

  Before the registration roller 7 moves in the main scanning direction as described above, the skew feeding correction roller pair 32 is in a separated state, whereby the movement of the registration roller 7 is performed by the skew feeding correction roller pair 32. It is possible to prevent the movement of the sheet S from being hindered. Further, after delivering the sheet S to the secondary transfer portion, the registration roller 7 releases the nip and moves in the direction opposite to the arrow shown in FIG. 4C to enter a standby state for the next sheet S1. Return.

  By the way, as shown in FIG. 5, the driving roller 301 constituting the conveying roller pair 34 of the conveying roller device 50 includes a roller portion 301a formed of a friction member such as rubber and a roller shaft to which the roller portion 301a is fixed. 301b. Further, flanges 302 are attached to the roller shaft 301b on the side of the roller portion 301a, in this embodiment, on both sides of the roller portion 301a.

  Here, the flange 302, which is a support member provided on both sides of the roller portion 301a in the axial direction, is formed of a highly slidable member, and the outer diameter D of the flange 302 is the outer diameter of the roller portion 301a. The diameter is larger than the diameter d. The outer periphery of the flange 302 forms an abutting portion on which a conveyed sheet can abut. The driven roller 14 is in pressure contact with the driving roller 301 to form a nip N when the sheet is conveyed.

  In FIG. 5, R1 is a sheet conveying path, 401 is an upper guide that forms the upper surface of the sheet conveying path R1, and 402 is a lower guide that forms the lower surface of the sheet conveying path R1. A gap G is formed between the upper guide 401 and the flange 302 so that the sheet conveyed from the conveying unit 54 can pass through.

  Here, since the flange 302 has a diameter capable of forming a gap G through which the sheet can pass between the flange 302 and the upper guide 401, even when the flange 302 is provided, the conveyance roller pair 34 is provided. Thus, the sheet S can be held and conveyed.

  6A and 6B are views showing the state of the transport roller device 50 when the sheet reaches the skew feeding correction device 55. As described above, when the sheet reaches the skew feeding correction device 55, FIG. Thus, the driven roller 14 is separated from the driving roller 301.

  In a state in which the driven roller 14 is separated from the driving roller 301, the contact portion that contacts the outer peripheral sheet of the flange 302 has a pair of rollers 14 separated from each other as viewed from the roller axial direction, as shown in FIG. , 301.

  FIG. 7 is a view showing a mechanism for separating the driven roller 14 from the drive roller 301 in this way. In FIG. 7, 101 is an arm member that rotatably holds the driven roller 14. The arm member 101 is swingably supported by the stay member 18 via the swing shaft 12 and is biased in a direction in which the driven roller 14 is pressed against the drive roller 301 by a biasing member (not shown).

  Reference numeral 103 denotes an eccentric roller, and an end of the arm member 101 opposite to the driven roller is in pressure contact with the eccentric roller 103 by a biasing member (not shown). The eccentric roller 103 is rotated by a stepping motor 104 that is transmitted through gears 105 and 106.

  When the driven roller 14 is separated from the driving roller 301, the eccentric roller 103 is rotated by the stepping motor 104 to press the end of the arm member 101 opposite to the driven roller side. As a result, the arm member 101 swings from the position shown in FIG. 7A in a direction in which the driven roller 14 is separated from the driving roller 301. As a result, the driven roller 14 is shown in FIG. 14 is separated from the driving roller 301.

  Here, when the driven roller 14 is separated from the driving roller 301, the sheet S that has been pushed down by the driven roller 14 and is in pressure contact with the driving roller 301 until that time, as shown in FIG. It is supported by 302 and conveyed while sliding. When the driven roller 14 moves upward in this manner, the sheet can be prevented from covering the upper surface of the roller portion 301 a of the driving roller 301 by being conveyed while sliding on the flange 302.

  Since the sheet S is conveyed while sliding on the flange in this way, even when the rigidity of the sheet S is lost in a high humidity environment, the sheet S is supported by the flange 302, so the roller portion 301a. It is not transported while covering the top surface.

  When the driven roller 14 is separated from the driving roller 301 in this way, the sheet S is supported by the flange 302 so that the frictional resistance received from the roller portion 301a is eliminated or reduced, thereby stabilizing the sheet S. Can be skewed.

  As described above, in the present embodiment, when the driven roller 14 is separated by the flanges 302 provided on both sides in the axial direction of the roller portion 301a of the driving roller 301 so as to protrude above the roller portion 301a. Supports the sheet S from below.

  Thereby, at the time of skew feeding correction of the sheet S in a high humidity environment, contact with the roller portion 301a having a high frictional resistance can be avoided, and the conveyance resistance at the trailing edge of the sheet can be reduced. As a result, it is possible to reduce the width-shifting force on the abutting reference member 31, and the sheet transportability at the time of abutting alignment is stabilized.

  In addition, by reducing the conveyance resistance, it is possible to minimize the width-shifting force, thereby suppressing the occurrence of jamming due to buckling of a sheet having low rigidity, such as a thin sheet, particularly during sheet skew feeding. be able to. Thereby, the skew of the sheet can be corrected stably in a high humidity environment regardless of the rigidity of the sheet.

  In this embodiment, the flange 302 is provided on both sides of the roller portion 301a. However, the position of the flange 302 is not limited to this. For example, if the sheet S can be supported from below, the flange 302 is provided with two roller portions. It may be provided between 301a.

  Next, a second embodiment of the present invention will be described.

  In the present embodiment, an active registration method is used as a correction method used in the skew feeding correction device 55.

  FIG. 8 shows the configuration of the skew feeding correction device 55 and the transport roller device according to the present embodiment using such an active registration method. In FIG. 8, the same reference numerals as those in FIG. 2 described above indicate the same or corresponding parts.

  In FIG. 8, 72 a and 72 b are two sensors that are provided in the sheet conveyance path R <b> 1 in the width direction and on the same axis and constitute a skew detection unit that detects the skew of the sheet S. 74a and 74b are correction roller pairs which are provided in the width direction of the sheet conveyance path R1 and coaxially, and are independently driven and controlled by the motors 73a and 73b.

  In such a skew correction device 55, first, when the leading edge of the sheet S conveyed by the conveyance roller device 50 passes through the two sensors 72a and 72b, the two sensors 72a and 72b send detection signals to the control unit. 9 (see FIG. 1). Then, the control unit 9 detects the skew amount of the sheet S based on the timing when the detection signals from the two sensors 72a and 72b are input.

  Next, before the sheet S enters the registration roller 7, the control unit 9 controls the conveyance amount of the sheet S by the correction roller pair 74a and 74b in accordance with the skew amount detected by the sensors 72a and 72b. Accordingly, the sheet S is turned to correct the skew of the sheet S. When the sheet S reaches the correction roller pair 74a, 74b, the driven roller 14 is separated from the driving roller 301 as shown in FIG. Accordingly, the conveyance roller pair 34 can prevent the skew feeding of the sheet S in the skew feeding correction device 55 from being hindered.

  Next, when the sheet reaches the registration roller 7 and the conveyance of the sheet S is started by the registration roller 7 thereafter, the registration roller 7 moves in the main scanning direction while nipping and conveying the sheet S. Thereby, the center positions of the sheet S and the image on the intermediate transfer belt can be matched. Before the registration roller 7 moves in the main scanning direction as described above, the correction roller pair 74a and 74b are in a separated state, whereby the registration roller 7 is moved by the correction roller pair 74a and 74. It is possible to prevent the movement of the sheet S from being hindered.

  Here, also in this embodiment, when the skew feeding of the sheet S is corrected by the correction roller pair 74 a and 74, the driven roller 14 is separated from the driving roller 301. When the driven roller 14 is separated from the driving roller 301 in this way, the sheet S that has been pushed down by the driven roller 14 and pressed against the driving roller 301 until then is supported by the flange 302 by its rigidity (koshi). It is conveyed while sliding (see FIG. 6).

  In this way, when the driven roller 14 moves upward, the sheet is conveyed while sliding on the flange 302 as a support member, thereby preventing the sheet from covering the upper surface of the roller portion 301a of the driving roller 301. Can do.

  As a result, the conveyance resistance at the trailing edge of the sheet can be reduced, and the swivel conveyance performance of the sheet can be stabilized, and the swivel force can be suppressed to the minimum necessary, especially for a thin sheet such as a thin sheet. Jam caused by buckling can be suppressed. Thereby, the skew of the sheet can be corrected stably in a high humidity environment regardless of the rigidity of the sheet.

  Next, a third embodiment of the present invention will be described.

  FIG. 9 is a diagram illustrating a configuration of the transport roller device according to the present embodiment. In FIG. 9, the same reference numerals as those in FIGS. 5 and 6 described above indicate the same or corresponding parts.

  In FIG. 9, reference numeral 403 denotes a rib provided as a support member provided on the lower guide 402 and extending in the sheet conveying direction. The height H of the rib 403 from the center line of the roller shaft 301b of the driving roller 301 has a relationship of d / 2 <H with respect to the radius (d / 2) of the roller portion 301a. That is, the rib 403 serving as the support member protrudes above the roller portion 301a, that is, toward the sheet conveyance path, and the tip (upper end) of the rib 403 serves as a contact portion that can contact the sheet. Yes.

  Further, in the state where the driven roller 14 is separated from the driving roller 301, the abutting portion that abuts the sheet at the tip (upper end) of the rib 403 is in the axial direction of the roller as shown in FIGS. 10 (a) and 10 (b). It is comprised so that it may be located between the roller pairs 14 and 301 spaced apart from each other.

  Here, when the sheet S conveyed by the conveyance roller pair 34 reaches the most upstream skew correction roller pair 32a (see FIG. 2) of the skew correction device 55, the driven roller 14 moves upward from the position shown in FIG. It moves away from the drive roller 301 as shown in FIGS. 10 (a) and 10 (b). Along with this, the sheet S that has been pushed down by the driven roller 14 is then fed obliquely by the skew correction roller pair 32, 32a (see FIG. 2) of the skew correction device 55 due to its rigidity. Along with the operation, the sheet is conveyed while sliding on the contact portion of the rib 403.

  When the driven roller 14 moves upward as described above, the sheet is supported by the rib 403 and is conveyed while sliding, thereby preventing the sheet S from covering the upper surface of the roller portion of the driving roller 301. Can do.

  As a result, the sheet S can be stably fed obliquely without receiving frictional resistance from the corners or peripheral surface of the roller portion 301a of the driving roller 301. The rib 403 may be formed integrally with the lower guide 402, or the rib 403 may be formed as a separate sliding member and attached to the lower guide 402 by adhesion or double-sided tape.

  Further, the rib 403 may be separated from the lower guide 402 and configured to be movable to a position retracted to the lower side of the lower guide 402 and a position protruding from the lower guide 402 shown in FIGS. 9 and 10. . When the driven roller 14 is in pressure contact with the drive roller 301, the rib 403 is positioned below the lower guide 402, and the rib 403 protrudes from the lower guide 402 in conjunction with the operation of separating the driven roller 14. To support the sheet.

  In the description so far, the case where the skew feeding correction device 55 is arranged upstream of the secondary transfer unit in the sheet conveying direction has been described, but the position of the skew feeding correction device 55 is not limited to this. For example, it may be arranged in a paper discharge system after fixing, or in the case of a direct transfer type image forming apparatus, it may be arranged on the upstream side in the sheet conveying direction of the photosensitive drum.

  In the above description, the case where the sheet conveying apparatus according to the present invention is used in a color image forming apparatus which is an example of an image forming apparatus has been described. However, the present invention is not limited to this. For example, the image reading unit can be applied to an image reading apparatus so that the image reading unit is not inclined and accurate alignment can be performed in the image reading unit.

1 is a diagram illustrating a schematic configuration of a color image forming apparatus that is an example of an image forming apparatus including a sheet conveying device according to a first embodiment of the present invention. FIG. 3 is a plan view illustrating a configuration of a skew feeding correction device and a conveyance roller device provided in the sheet conveyance device. FIG. 3 is a side view illustrating the configuration of a skew feeding correction device and a conveyance roller device provided in the sheet conveyance device. The figure explaining operation | movement of the said skew feeding correction apparatus and a conveyance roller apparatus. The figure explaining the conveyance roller pair and flange provided in the said conveyance roller apparatus. FIG. 4 is a diagram illustrating a state of a conveyance roller device when a sheet reaches the skew feeding correction device. The figure which shows the mechanism for separating the driven roller which comprises the said conveyance roller pair from a drive roller. FIG. 6 is a diagram illustrating a configuration of a skew feeding correction device and a conveyance roller device provided in a sheet conveyance device according to a second embodiment of the present invention. FIG. 10 is a diagram illustrating a configuration of a conveyance roller device provided in a sheet conveyance device according to a third embodiment of the present invention. The figure which shows a state when a sheet | seat reaches | attains the skew feeding correction apparatus of the said conveyance roller apparatus. The figure explaining the correction method by the conventional side registration standard. The figure explaining the skew feeding correction method by the conventional active registration system. The figure which shows the relationship between the conventional roller part, the friction coefficient of a sheet | seat, and humidity.

Explanation of symbols

7 registration roller 14 driven roller 30 movable guide 31 abutting reference member 32, 32a skew correction roller pair 33 fixed guide 34 transport roller pair 50 transport roller device 55 skew correction devices 72a, 72b sensors 74a, 74b correction roller pair DESCRIPTION OF SYMBOLS 100 Color image forming apparatus 100A Color image forming apparatus main body 100D Sheet conveying apparatus 301 Driving roller 301a Roller part 301b Roller shaft 302 Flange 401 Upper guide 402 Lower guide 403 Rib 513 Image forming part R1 Sheet conveying path G Gap (gap)
S sheet

Claims (12)

In a sheet conveying apparatus that conveys a sheet,
A skew correction unit for correcting the skew of the sheet;
Provided upstream of the skew feeding correction unit in the sheet feeding direction for feeding the sheet to the skew feeding correction unit, and configured to be separated according to the skew feeding correction operation of the sheet by the skew feeding correction unit. A pair of transport rollers,
A support member for supporting the sheet being conveyed between the separated conveying roller pairs when the conveying roller pair is separated;
A sheet conveying apparatus comprising:   2. The sheet conveying apparatus according to claim 1, wherein the support member is provided on a roller shaft of one roller of the conveying roller pair, and is configured by a flange having a diameter larger than the diameter of the one roller.   The sheet conveying apparatus according to claim 1, wherein the support member includes a rib disposed on a side of the conveying roller pair. In a sheet conveying apparatus that conveys a sheet,
A skew correction unit for correcting the skew of the sheet;
Provided upstream of the skew feeding correction unit in the sheet feeding direction for feeding the sheet to the skew feeding correction unit, and configured to be separated according to the skew feeding correction operation of the sheet by the skew feeding correction unit. A pair of transport rollers,
A contact portion capable of contacting a sheet to be conveyed; and when the conveyance roller pair is separated, the contact portion is disposed between the separated conveyance roller pairs when viewed from the axial direction of the conveyance roller pair. A support member arranged to be located;
A sheet conveying apparatus comprising:   The pair of conveying rollers includes an upper roller and a lower roller, and the upper roller is separated from the lower roller in accordance with a skew correction operation by the skew correction unit, and is in contact with the lower roller. The sheet conveying apparatus according to claim 4, wherein the support member is provided on an axial side of the roller portion with the portion protruding upward. The sheet conveyance path in which the pair of conveyance rollers is arranged is composed of an upper guide and a lower guide,
The support member is provided on the roller shaft of the lower roller and has a larger diameter than the roller portion of the lower roller, and a gap through which the sheet can pass between the upper guide and the upper guide constituting the upper surface of the sheet conveyance path The sheet conveying apparatus according to claim 5, wherein the sheet conveying apparatus is positioned between the conveying roller pair when the abutting portions on the outer periphery of the flange are separated from each other. The sheet conveyance path in which the pair of conveyance rollers is arranged is composed of an upper guide and a lower guide,
The support member is a rib provided in the lower guide constituting the lower surface of the sheet conveyance path, and is positioned between the conveyance roller pair when the abutting portion at the tip of the rib is separated. The sheet conveying apparatus according to claim 5.   The sheet conveying apparatus according to claim 1, wherein the support member is formed of a member having high slidability.   The skew feeding correction portion includes a skew feeding roller that feeds the sheet obliquely, and an abutting reference member that abuts a side edge of the sheet obliquely fed by the skew feeding roller and corrects the skew feeding of the sheet. The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus.   The skew correction unit includes a skew detection unit that detects the skew of the sheet, and a correction that corrects the skew of the sheet by turning the sheet according to the skew amount of the sheet detected by the skew detection unit. The sheet conveying apparatus according to claim 1, further comprising a pair of rollers. The sheet conveying device according to any one of claims 1 to 10,
An image forming unit that forms an image on a sheet conveyed by the sheet conveying device;
An image forming apparatus comprising: The sheet conveying device according to any one of claims 1 to 10,
An image reading unit that reads an image formed on a sheet conveyed by the sheet conveying device;
An image reading apparatus comprising:

Images