JP5441681B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet conveying device such as a skew correction device or a curling device that conveys a sheet by a conveying nip, and an image forming apparatus including the sheet conveying device.

  Conventionally, a conveyance roller, a conveyance belt, and the like are known as a mechanism for conveying a sheet. In particular, the conveyance roller has a simple configuration and has an advantage that conveyance control such as stop and acceleration / deceleration can be easily performed. A specific configuration of the transport roller is a combination of a drive roller that is rotationally driven by a drive motor and a driven roller that is disposed opposite to the drive roller and is pressed. One that conveys a sheet is mentioned. As an example of the sheet conveying apparatus provided with such a conveying roller, there is an image forming apparatus such as a printer or a printing machine. An example of the image forming apparatus is an electrophotographic full-color image forming apparatus. In the apparatus, a large number of conveying rollers for feeding, conveying, and discharging sheets are provided.

  Among such transport rollers, for example, those used in a skew correction device that corrects a skew of a sheet before transferring an image, a curling device that removes curl generated on a sheet, and the like are simply used. This is not to say that the sheet should be conveyed under certain conditions. In other words, it is easily influenced by characteristics such as sheet thickness, stiffness (rigidity), smoothness, and the like, and in order to obtain desired performance, it is necessary to set optimum conveying conditions according to these characteristics.

  A specific example will be described with reference to a skew feeding roller provided in the skew feeding correction device 65 shown in FIG. This skew correction device 65 is one of the representative methods of the skew correction device provided in the image forming apparatus, and FIG. 7 is a plan view thereof. The skew feeding correction device 65 is configured to feed the sheet by skew feeding rollers 75a to 75c disposed at a predetermined angle with respect to the sheet feeding direction F, and a feeding component perpendicular to the feeding direction generated by the skew feeding rollers 75a to 75c. An abutting reference member 76 for copying is provided. Such a skew correction device 65 can perform skew correction without stopping the sheet, which is advantageous in improving the productivity of the image forming apparatus. In addition, since skew correction is performed in accordance with the abutting reference, there is an advantage that a complicated principle is not required and the principle is simple.

  However, after the start of contact with the abutting reference member 76, the skew feeding rollers 75a to 75c are required to be transported with a certain degree of slip, and if there is too much slip, the skew correction is insufficient, and conversely If there is too little slip, buckling will occur with the butting. These slip states are closely related to the thickness, stiffness (rigidity), smoothness, and the like of the sheet, and vary greatly depending on media conditions such as thin paper and thick paper, plain paper and coated paper.

  In order to obtain stable skew correction performance even for such a change in conditions caused by the media, a configuration has been proposed in which the conveying force setting of the skew feeding roller is variable based on the selected media information ( (See Patent Documents 1 and 2). The technique described in Patent Document 1 is to change the operating length of the pressure spring, that is, the pressurizing force, using a cam for pressure adjustment, and the technique described in Patent Document 2 includes a roller material that forms a conveyance nip, That is, the friction coefficient is changed.

JP 2002-179293 A JP-A-10-157484

  However, in recent years, the fields of image forming apparatuses are diverse, such as consumers, offices, and printing, and the types of sheets used therewith are very diverse. In such a situation, there arises a problem that it is no longer possible to cope with all specification media only within the range of elastic deformation of the spring. That is, in the technique described in Patent Document 1 in which the pressing force is changed by adjusting the operating length of the pressurizing spring, the operating length of the pressurizing spring is extremely increased or the spring constant is set to an extremely large value. It can only respond in the direction to do. However, these measures cause an increase in space and buckling of the compression spring, or fluctuations in the nip pressure due to variations in operating length, and in some cases, it is difficult to set a stable nip pressure.

  Further, although the technique described in Patent Document 2 has been proposed in view of the above problems, a sufficient amount of nip crushing must be ensured in order to change the friction coefficient, and for that purpose, a large amount is required. It is necessary to change the pressure. For this reason, the same problem as the technique of the said patent document 1 is fundamentally faced.

  The present invention provides a sheet conveying apparatus that secures a wide and stable nip pressure range according to various media conditions without particularly increasing the operating length and spring constant, and not depending only on elastic deformation of the spring, and An object is to provide an image forming apparatus provided.

  The present invention has a conveying roller pair including a driving roller to which driving is transmitted and a driven roller pressed against the driving roller, and first and second arm portions provided with a rotation fulcrum interposed therebetween, A pressure arm portion that rotatably supports the driven roller at a tip portion of the first arm portion, and a first arm portion and a second action point that are different in distance from the rotation fulcrum on the second arm portion; The operating length changes of the first and second urging force applying members for applying the urging force to the first and second action points of the pressurizing arm and the first and second urging force applying members, respectively. The drive of the driven roller is selectively switched to decrease the other urging force of the first and second urging force applying members while increasing one urging force of the first and second urging force applying members. An adjustment drive unit that adjusts the pressure applied to the roller. It is a symptom.

  According to the present invention, the nip pressure of the conveying roller pair can be freely adjusted by the urging force of the first and second urging force applying members and the lever ratio of the pressure arm portion. It is possible to change the nip pressure in a wide range without increasing the value extremely. As a result, it is possible to stably and space-saving the conveyance nip state corresponding to various media conditions from thin paper to thick paper. For example, in the case of a sheet conveying device provided in an image forming apparatus, the media compatibility can be improved, so that an apparatus having a wide range of specifications can be provided.

FIG. 3 is a perspective view for explaining a pressure release mechanism of the oblique feeding roller according to the first embodiment of the present invention. The figure explaining the operation | movement at the time of thin paper correspondence in 1st Embodiment. The figure explaining the operation | movement at the time of the thick paper correspondence in 1st Embodiment. The figure explaining the adjustment range of a switch lever in detail. The graph which shows the change of the nip pressure in 1st Embodiment. 1 is a cross-sectional view illustrating an image forming apparatus according to the present invention. The top view explaining a skew feeding correction device. 1 is a block diagram showing a system configuration of a first embodiment according to the present invention. The flowchart explaining CPU control of 1st Embodiment. The perspective view which shows the curling apparatus of 2nd Embodiment which concerns on this invention. The block diagram which shows the system configuration | structure of 2nd Embodiment. The flowchart explaining CPU control of 2nd Embodiment. Sectional drawing which shows the curling apparatus provided with two driven pressure rollers.

<First Embodiment>
A first embodiment according to the present invention will be described. In the first embodiment, an application example to a skew feeding correction device that performs skew feeding correction of a sheet among the sheet conveying devices arranged inside the image forming apparatus will be described. FIG. 6 is a cross-sectional view of the image forming apparatus 60 in the present embodiment, and shows a color image forming apparatus using an electrophotographic system.

  Image forming apparatuses include a plurality of systems such as an electrophotographic system, an offset printing system, and an ink jet system. The image forming apparatus 60 shown in FIG. 6 is a color image forming apparatus using an electrophotographic system. . The image forming apparatus 60 employs a so-called intermediate transfer tandem system in which four color image forming units 613 are arranged side by side on an intermediate transfer belt 606, and this method is used for a thick sheet (thick paper) at the transfer unit. In recent years, it has become mainstream because of its excellent response capability, transportability, and print productivity. The image forming apparatus 60 includes a skew correction device 65 that corrects skew while conveying the sheet S. That is, the image forming apparatus 60 includes the image forming unit 613 that forms an image on a sheet, and the skew correction device 65 as a sheet conveying device that conveys the sheet to the image forming unit 613. Details of the skew feeding correction device 65 will be described later.

  The apparatus main body 60a of the image forming apparatus 60 includes an image forming unit 613, a sheet feeding unit 101 that conveys the sheet S, a transfer unit 103, and a sheet conveying device 100 that conveys the sheet. The transfer unit 103 transfers the toner image formed by the image forming unit 613 to the sheet S fed by the sheet feeding unit 101. The sheet conveying apparatus 100 includes a conveying unit 64, a skew feeding correction device 65 including a registration roller pair 7, a pre-fixing conveying unit 67, a branch conveying device 69, a reverse conveying device 601, a duplex conveying device 602, and the like.

  The image forming unit 613 forms an image on the sheet S conveyed by the sheet conveying apparatus 100. The image forming unit 613 includes a yellow (Y), a magenta (M), a cyan (C), and a black (with a photosensitive drum 608, an exposure device 611, a developing device 610, a primary transfer device 607, and a photosensitive cleaner 609, respectively. Bk) image forming unit. Note that there are four image forming units corresponding to yellow (Y), magenta (M), cyan (C), and black (Bk), but the number of colors is limited to four. In addition, the color arrangement order is not limited to that shown in FIG.

  The sheet feeding unit 101 includes a sheet storage unit 61 that stores sheets S stacked on the lifter 62, and a feeding unit 63 that feeds the sheets S stored in the sheet storage unit 61. Yes. Examples of the feeding unit 63 include a system that uses frictional separation by a sheet feeding roller and the like, and a system that uses separation and adsorption by air. In this embodiment, an example of a feeding system by air is used. Are listed.

  The transfer unit 103 includes an intermediate transfer belt 606 that is stretched by rollers such as a driving roller 604, a tension roller 605, and a secondary transfer inner roller 603 and is driven to rotate in the direction of an arrow n in the drawing. The intermediate transfer belt 606 transfers the toner image formed on the photosensitive drum 608 by a predetermined pressure and an electrostatic load bias given by the primary transfer device 607. The intermediate transfer belt 606 is undetermined on the sheet S by being given a predetermined pressure and an electrostatic load bias at the secondary transfer portion formed by the substantially opposite secondary transfer inner roller 603 and secondary transfer outer roller 66. Adhere the ringtone image.

[Sheet transport process]
In the image forming apparatus 60 having the above configuration, the sheets S are stored on the lifter 62 in the sheet storage unit 61 and are fed by the feeding unit 63 in accordance with the image forming timing. The The sheet S sent out by the feeding unit 63 passes through a transport path 64 a included in the transport unit 64 and is transported to the skew correction device 65. After the skew correction and timing correction are performed in the skew correction device 65, the sheet S is sent to the secondary transfer unit. The secondary transfer portion is a toner image transfer nip portion to the sheet S, which is formed by the opposing secondary transfer inner roller 603 and secondary transfer outer roller 66, and applies a predetermined pressure and electrostatic load bias. As a result, the toner image is adsorbed on the sheet S.

[Image creation process]
Next, a process for forming an image sent to the secondary transfer unit at the same timing as the conveyance process of the sheet S to the secondary transfer unit described above will be described.

  That is, the exposure unit 611 is driven on the basis of the signal of the image information sent to the photosensitive drum 608 whose surface is uniformly charged in advance by the charging unit and rotated in the direction of the arrow m in the figure, and the diffraction unit. An electrostatic latent image is formed via 612 and the like. The electrostatic latent image formed on the photosensitive drum 608 is developed as a toner image on the photosensitive drum 608 through toner development by the developing device 610. Thereafter, a predetermined pressure and an electrostatic load bias are applied by the primary transfer device 607, and the toner image is transferred onto the intermediate transfer belt 606. Thereafter, the transfer residual toner slightly remaining on the photoconductor drum 608 is collected by the photoconductor cleaner 609 to prepare for the next image formation again.

  The image forming processes for the respective colors that are processed in parallel by the image forming units 613 corresponding to Y, M, C, and Bk described above are superimposed on the upstream color toner image that is primarily transferred onto the intermediate transfer belt 606. Done. As a result, a full-color toner image is finally formed on the intermediate transfer belt 606 and conveyed to the secondary transfer unit.

[Process after secondary transfer]
As described above, the full-color toner image is secondarily transferred onto the sheet S in the secondary transfer portion by the sheet S conveying process and the image forming process described above. Thereafter, the sheet S is conveyed to the fixing device 68 by the pre-fixing conveyance unit 67. The fixing device 68 melts and fixes the toner image on the sheet S by applying a predetermined pressure by an opposing roller or belt or the like and generally a heating effect by a heat source such as a heater. The sheet S having a fixed image obtained in this way is discharged as it is onto the discharge tray 600 by the branch transfer device 69, or is transferred to the reverse transfer device 601 when double-sided image formation is required. Route selection is performed.

  When double-sided image formation is required, the sheet S sent to the reverse conveying device 601 is conveyed to a double-sided conveying device 602 that replaces the leading and trailing edges by performing a switchback operation. Thereafter, the sheets are merged from the refeed path 64b of the conveyance unit 64 in synchronization with the timing of the sheet S of the subsequent job conveyed from the feeding unit 63, and similarly sent to the secondary transfer unit. The image forming process on the back surface (second surface) is the same as that of the above-described front surface (first surface), and thus description thereof is omitted.

[Explanation of skew feeding registration method]
As described above, the image forming apparatus 60 includes the skew feeding correction device 65 for correcting the skew feeding of the sheet S. In the present embodiment, the skew feeding registration using the skew feeding roller and the abutting reference member is used. The method is used. The reason for this is that the skew correction can be performed without stopping the sheet S, and that the side edge whose position remains unchanged in the switchback operation executed during double-sided printing is corrected for skew. A point that can be taken on the reference side. These are advantageous in realizing high productivity and high accuracy.

  FIG. 7 is a plan view for explaining a conveyance unit including the skew feeding correction device 65. The sheet conveyance direction is the direction of arrow F in the figure, and is divided into a pre-registration conveyance unit, a skew feeding correction unit, and a slide unit from the upstream side. The pre-registration conveyance unit includes a conveyance guide 70, a pre-registration conveyance roller pair 71, a pre-registration conveyance sensor 72, and the like. If necessary, the sheet S may be temporarily stopped by the pre-registration conveyance unit with a leading edge passing signal of the sheet S by the pre-registration conveyance sensor 72 as a trigger. This configuration is a conveyance mode in which the conveyance by the oblique feeding roller in the next process is decomposed into two components of an arrow F direction and a direction orthogonal thereto, and slipping occurs after contact with the abutting reference member. This is based on the fact that there is a relatively large variation in conveyance due to such factors. As a result, the timing error accumulated during the long conveyance path after the feeding start by the feeding unit 63 can be reset once. The pre-registration conveyance roller pair 71 is configured such that the conveyance nip can be released as necessary by a separation mechanism using a motor, a cam, or the like.

  Further, the skew correction device 65 mainly includes a movable unit 74, a movable unit in which a skew feeding rollers 75a to 75c that are driving rollers to which driving is transmitted, a skew feeding sensor 73, and an abutting reference member 76 are integrated. A fixed guide 77 is included. The image forming apparatus 60 according to the present embodiment is a center-standard image forming apparatus in which the image forming and conveying standards are set at the center. In the movable unit, a sheet conveying direction F is driven by a drive motor (not shown) and a ball screw mechanism so that the abutting surface of the abutting reference member 76 is positioned at an optimum standby position Pw corresponding to the size of the sheet S to be conveyed. It can be freely moved in the width direction orthogonal to. In FIG. 7, the driven roller 6 (see FIG. 1), which is a driven roller that is disposed so as to face the oblique feeding rollers 75 a to 75 c and is pressed, is not shown. In the present embodiment, a pair of conveying rollers is constituted by the oblique feeding rollers 75a to 75c that are driving rollers and the driven roller 6 that is a driven roller.

  Here, the optimum standby position Pw is the distance D against the nominal end position Ps in the width direction (main scanning direction) orthogonal to the sheet conveying direction F of the image (or sheet) defined by the center reference. It means the added position. This is an offset measure for ensuring that the position of the sheet S conveyed in the center reference varies in the main scanning direction without being collided at the entrance of the abutting reference member 76. In this embodiment, the abutting distance D = 10 mm. For example, in the case of passing A3 size paper, the nominal standby position Pw with respect to the transport center CT is 148.5 mm. The position is 158.5 mm away from the center CT. Further, the oblique feeding rollers 75a to 75c are disposed so as to be inclined by a predetermined angle with respect to the transport direction F so as to generate an abutting conveyance component to the abutting reference member 76. When skew feeding by the skew feeding rollers 75a to 75c is started and the skew feeding sensor 73 detects the passage of the leading edge of the sheet S, the upstream pre-registration conveyance roller pair 71 inhibits the skew feeding operation using this detection signal as a trigger. Release the transfer nip so that it does not. Here, the number of the oblique feeding rollers 75a to 75c is three, but this is not restrictive.

  The slide portion mainly includes a conveyance guide 703, a registration roller pair 7, a registration driving gear 700, a registration driving motor 702, a motor gear 701, a pre-registration sensor 78, and a post-registration sensor 79. The registration roller pair 7 is rotationally driven in a direction in which the sheet can be conveyed in the direction of arrow F in FIG. 7 using the registration drive motor 702 as a drive source. Further, the registration roller pair 7 is supported so as to be slidable in the width direction (main scanning direction) orthogonal to the sheet conveyance direction (arrow F direction), and is slid by a slide drive motor (not shown). . As described above, this corrects that the sheet S that has been skew-corrected following the abutting reference member 76 is shifted from the nominal image position by the abutting distance D. Because.

  That is, the registration roller pair 7 sandwiches and conveys the sheet S in order to align the main scanning direction position of the sheet S offset by the abutting distance D with the image position on the intermediate transfer belt 606 (FIG. 6). It is to move the slide as it is. As a trigger for performing the slide movement, a signal passing through the leading edge of the sheet S from the pre-registration sensor 78 may be used as a trigger, and the tooth width of the motor gear 701 is set with respect to the registration drive gear 700 in consideration of the width of the slide movement. Widely taken. Note that when performing this sliding movement, the skew feeding rollers 75a to 75c need to release the conveyance nip, which will be described in detail later.

  Further, the leading edge passage signal of the sheet S by the post-registration sensor 79 is used as a trigger for adjusting the timing at which the sheet S reaches the downstream secondary transfer portion, and the alignment between the image and the leading edge of the sheet is performed with high accuracy. . When the sheet S is nipped and conveyed by the secondary transfer unit, the registration roller pair 7 releases the conveyance nip and slides back to the home position in the main scanning direction again.

[Detailed configuration of skew feeding roller]
In the oblique registration method, since the contact with the abutting reference member 76 is involved, the lower the stiffness (stiffness) is as in thin paper, the easier it is to buckle, and the higher the stiffness is as in thick paper. The conveyance force is insufficient and slip is likely to increase. In addition, the behavior during skew correction also varies greatly depending on the difference in smoothness of the sheet surface, such as plain paper, gloss coated paper, matte coated paper, and the like. Therefore, it is necessary for the skew feeding rollers 75a to 75c to adjust the conveying force to an optimal value as appropriate according to the type of the selected sheet. As already described, after the skew correction, in order not to disturb the sliding operation of the registration roller pair 7, a nip pressure releasing operation must be included in a series of operations.

  Here, the skew feeding correction device 65 in the present embodiment will be described in detail. FIG. 1 is a perspective view of one of the skew feeding rollers 75a to 75c of the skew feeding correction device 65, and includes a driving mechanism, a nip pressure adjusting mechanism, and a nip pressure releasing mechanism. As shown in FIG. 1, the oblique feeding roller 75 as a driving roller is driven obliquely through the timing belt 3 (FIG. 1A), the driving pulley 4 (FIG. 1B), the coupling 5, and the like. The rotational driving force of the motor 2 is transmitted. Further, the oblique feeding roller 75 is disposed so as to be inclined by a predetermined angle with respect to the driven roller (driven roller) 6 at the opposing position arranged along the sheet conveying direction.

  In the present embodiment, the material of the oblique feeding roller 75 is urethane rubber, and a general-purpose SUS bearing is used for the driven roller 6, and the inclination angle of the oblique feeding roller 75 is about 10 °. The driven roller 6 constitutes a skew feeding roller that is disposed at a predetermined angle with respect to the sheet conveying direction. The driven roller 6 is pressed against the oblique feeding roller 75 in order to generate a conveying force, and the pressing force is generated by the pressing arm 20 and the pressing springs 9a and 9b.

  The pressurizing arm 20 as an L-shaped pressurizing arm portion is rotatable (rotating) with respect to the driving support plate 19 via a rotating shaft (rotating fulcrum) 8 attached to the driving support plate 19. Is freely supported). The pressure arm 20 includes a first arm portion 20b and a second arm portion 20a provided with a rotation shaft (rotation fulcrum) 8 therebetween. These first and second arm portions 20 b and 20 a are formed to extend in two directions orthogonal to the rotation shaft 8. The follower roller 6 is rotatably supported at the tip of the first arm portion 20b, and the second arm portion 20a is provided with first and second action points having different distances from the rotation shaft 8. Yes. That is, the spring hooking portions 10a and 10b are formed at two points having different distances from the rotation shaft 8, respectively. The spring hooking portion 10a constitutes the first action point P1, and the spring hooking portion 10b is the second action. A point P2 is formed. The variable pressure release motor 1 is attached to the drive support plate 19 at a position facing the pressure arm (pressure arm portion) 20. A switch arm 11 facing the pressure arm 20 is fixed.

  As shown in FIGS. 2 to 4, the switch arm 11 constitutes a rotatable adjustment arm that faces the pressurizing arm 20 with a predetermined interval. The switch arm 11 has protrusions 21a and 21b that extend linearly in opposite directions from the motor shaft 13 of the variable pressure release motor 1 and have different distances from the motor shaft (rotating shaft) 13. The variable pressure release motor 1 constitutes an adjustment motor that applies a rotational force to a motor shaft 13 that is a rotation shaft of the switch arm 11.

  The protrusion 21a is formed so as to protrude a predetermined amount toward the spring hooking portion 10a of the pressure arm 20 that is opposed to the pressure arm 20 with a predetermined distance, and the protrusion 21b is formed on the pressure arm 20 that is opposed to the pressure arm 20 with a predetermined distance. A predetermined amount protrudes toward the spring hook 10b. Spring hooks 12a and 12b are provided in the vicinity of the protrusions 21a and 21b near the motor shafts 13, respectively. That is, the switch arm (adjustment arm) 11 includes a spring hooking portion 12a and a second locking portion, which are first locking portions that are arranged in a straight line across the motor shaft 13 and have different distances from the motor shaft 13. A certain spring hook 12b is formed.

  As shown in FIG. 1, a pressure spring 9a is hooked on one end and the other end on a spring hooking portion 12a and a spring hooking portion 10a, and a pressure spring 9b is hooked on the spring hooking portion 12b and the spring hooking portion 10b. One end and the other end are hooked to each other. The pressure spring 9a constitutes a first biasing force applying member that applies a biasing force (tensile force) to the first action point P1 of the pressure arm 20, and the pressure spring 9b is placed at the second action point P2. A second urging force applying member for applying an urging force (tensile force) is configured. The pressure spring 9a, which is a first urging force application member, is a first tension spring whose both ends are locked to the first action point P1 and the spring hooking portion (first locking portion) 12a. The pressurizing spring 9b, which is a second urging force application member, is a second tension spring whose both ends are locked to the second action point P2 and the spring hooking portion (second locking portion) 12b. As described above, the nip pressure of the skew feeding roller 75 in this embodiment is generated by the tension of the spring and the lever ratio of the arm.

  As shown in FIG. 4, the switch arm 11 has a flag portion 14 protruding from the pressure arm 20 on the opposite side (back side) to recognize the phase of the home position. As shown in FIG. 1, the flag portion 14 is read by a photo interrupter 15 attached to a mounting portion 19 a that is formed to project at a position opposite to the driving support plate 19. A support plate 22 is fixed to the right side of the drive support plate 19 in FIG. A pair of regulating shafts 17 are caulked and fixed to the support plate 22 with a predetermined distance left and right and up and left and right of the center portion. The slide arms 16a and 16b are guided to move by a pair of restriction shafts 17 respectively.

  The slide arm 16a has an elongated hole 16c that slidably fits a pair of restriction shafts 17 and 17, and the slide arm 16b is a length that fits another pair of restriction shafts 17 and 17 slidably. It has a hole 16d. The slide arms 16a and 16b are regulated so as to slide by a predetermined distance in the left-right direction in FIG. 1 by slidably fitting a pair of regulating shafts 17 and 17 into the elongated holes 16c and 16d, respectively. Supported. The slide arms 16a and 16b are respectively provided at the same height as the engagement position of the pressure springs 9a and 9b in the front view of FIG.

  The slide arms 16a and 16b are engaged with the right ends of the tension springs 18a and 18b in a state where the left ends in FIG. It is energized. In these slide arms 16a and 16b, at least in the state shown in FIGS. 2A and 3A, the left end portions are in contact with the projections 21a and 21b, respectively. In this state, the right ends of the slide arms 16a and 16b are spaced apart from the spring hooks 10a and 10b with gaps Ga and Gb (Ga <Gb), respectively. The lengths of the slide arms 16a and 16b are changed to obtain the difference between the gaps Ga and Gb in the state shown in FIGS. 2A and 3A, and the pressure is changed between the thin paper mode and the thick paper mode as will be described later. The variable release motor 1 is configured to have the same control amount (rotation angle).

  In the present embodiment, the switch drive (adjustment arm) 11 and the variable pressure release motor (adjustment motor) 1 constitute an adjustment drive unit. This adjustment drive part selectively switches the operating length change of the pressure springs 9a, 9b, decreases the other biasing force while increasing one biasing force of the pressure springs 9a, 9b, and The pressure applied to the skew feeding roller 75 is adjusted.

[Variation and release control of nip pressure]
First, the system configuration and control flow will be described. That is, a system configuration necessary for controlling the drive mechanism, nip pressure adjusting mechanism, and nip pressure releasing mechanism of FIG. 1 is shown in the block diagram of FIG. In this embodiment, it is the variable pressure release motor 1 that variably controls the nip pressure of the skew feeding roller 75 and performs an operation of releasing the nip pressure as necessary.

  As shown in FIG. 8, the CPU 92 that is provided in the image forming apparatus 60 and serves as a calculation unit and a control unit issues a specific control command to the variable pressure release motor 1, and the sheet specified by the operator from the operation unit 90 in advance. Receive information about types. Then, the control value is determined by referring to the optimum nip pressure setting from the table stored in the memory 91. In addition, as a kind of sheet | seat, a brand, basic weight, the presence or absence of a coating layer, a size, etc. are mentioned. Here, the control value specifically refers to the rotation direction and rotation angle of the variable pressure canceling motor 1 (in the case of a pulse motor, the number of pulses is also acceptable). As for the nip pressure release operation, the CPU 92 counts the timer using the leading edge passing signal and trailing edge passing signal of the pre-registration sensor 78 as triggers, and the pressure is variable in accordance with the arrival timing or removal timing of the sheet to the registration roller pair 7. A control value command is issued to the release motor 1.

  Next, the flow of a specific control command executed by the CPU 92 will be described using the flowchart shown in FIG. That is, at the time of job start (S100), the type of sheet used for the actual print job is selected by the operator. This selection operation is performed from the UI on the operation unit screen, and, for example, is a format that sequentially guides parameters related to the transportability of the oblique feeding roller 75 such as sheet basis weight, presence / absence of a coating layer, and size. ing. Alternatively, if there is a sheet frequently used by the operator, information on the brand can be registered and edited in advance, and the format may be such that it is called and selected.

  As described above, when the media selection information input from the operation unit 90 is recognized (S101), the optimum nip pressure setting information is referred to from a table stored in advance in the memory 91 (S102). Here, the table is categorized into a plurality of groups based on the previous selection parameter, and a control value of the variable pressure release motor 1 that generates an optimum nip pressure is assigned to each group.

  Based on the control value thus obtained, a signal of the rotation direction and rotation angle of the pressure variable release motor 1 is generated, and drive control for controlling the pressure variable release motor 1 to the corresponding setting mode is performed (S103). At this time, the nip pressure of the skew feeding roller 75 is in a standby state in accordance with the selected sheet, and the skew feeding drive motor 2 is driven to rotate (S104), thereby pushing the sheet against the butting reference member 76. Skew correction while applying. When the leading edge of the sheet whose skew has been corrected following the abutting reference member 76 is detected by the pre-registration sensor 78 shown in FIG. 7 (S105), the timer counter is activated so that the leading edge of the sheet is a pair of registration rollers. The timing to reach 7 is calculated. Further, the control value given to the variable pressure release motor 1 after a predetermined time is changed to the nip pressure release mode (S106).

  Specifically, control is performed to increase the rotation angle of the variable pressure release motor 1 to a value larger than the adjustment range used during sheet conveyance, which will be described in detail later with reference to FIGS. After the nip release of the skew feeding roller 75, the sheet is conveyed by the registration roller pair 7 and the trailing edge is detected by the pre-registration sensor 78 (S107). When there is a next page job (S108), the pressure is again applied. The control value of the variable release motor 1 is returned to the set value in the table (S103). As a result, the oblique feeding roller 75 enters a pressure state. The above is repeated over all pages of the print job, and the job is completed (S109).

  Next, details of the setting mode according to the sheet will be described. That is, the operation of step S103 described in the flowchart of FIG. 9 will be described in more detail. FIG. 2 shows an operation when a sheet having a small basis weight and a low rigidity (rigidity) is selected (hereinafter referred to as a thin paper mode), and FIG. 3 is a case when a sheet having a large basis weight and a high rigidity is selected (hereinafter referred to as a thin sheet mode). , Referred to as a cardboard mode), and corresponds to the cross-sectional view of the configuration diagram shown in FIG.

In the present embodiment, the pressure arm 20 includes a second arm portion 20b having a distance L from the rotation shaft 8 to the rotation center of the driven roller 6, and a distance from the rotation shaft 8 to the spring hook portions 10a and 10b. Are composed of the second arm portion 20a having x1, x2 (x1 <x2), respectively. The switch arm 11, as shown in FIG. 2 (a) and 3 (a), the axis S ₀ connecting the spring hooking portion 12a and a spring hook portion 12b is a sheet conveyance direction (the left-right direction in the drawing) The phase orthogonal to the vertical direction (the vertical direction (for example, the vertical direction) in the figure) is taken as the home position. The projecting portions 21a and 21b provided in the switch arm 11 are formed with the same convex amount, and the slide arms 16a and 16b are urged toward the projecting portions 21a and 21b. 2 and 3, the illustration of the pressure springs 9a and 9b and the tension springs 18a and 18b is omitted for convenience of explanation, but in actuality, they are hooked with the configuration described in FIG. ing.

Next, details of the switch arm 11 will be described with reference to FIG. The switch arm 11 has a spring hook 12a at a distance y1 from the motor shaft 13 of the variable pressure release motor 1, which is the rotation center, and a spring hook 12b at a distance y2 from the motor shaft 13, respectively. . An axis S ₀ connecting the spring hooks 12 a and 12 b passes through the center of the motor shaft 13. In the protrusions 21a and 21b provided in the vicinity of the spring hooks 12a and 12b, the distance from the motor shaft 13 is a ratio of y1: y2. When the rotation direction of the variable pressure release motor 1 is defined as positive in the CCW direction (counterclockwise direction) in FIG. 4, it corresponds to the adjustment range of the thick paper mode corresponding to the angle of + α and the angle of −α. The adjustment range of the thin paper mode can be selectively switched. Then, the axis S ₂ of the angle from the axis S ₀ + alpha becomes thick adjustment limit, the axial lines S ₁ of the angle -α from the axis S ₀ becomes thin adjustment limit. Further, when the rotation angle (absolute value) of the variable pressure release motor 1 is larger than ± α, the range is shifted from the thin paper mode and the thick paper mode, and both are switched to the nip pressure release mode.

  As described above, in this embodiment, the distance x2 from the rotation axis (rotation fulcrum) 8 of the second action point P2 is set larger than the distance x1 from the rotation axis 8 of the first action point P1. ing. A distance y2 from the motor shaft (rotating shaft) 13 of the spring hook (second locking portion) 12b is larger than a distance y1 from the motor shaft 13 of the spring hook (first locking portion) 12a. Is set.

FIG. 2B is a diagram showing the maximum adjustment in the thin paper mode in which the variable pressure release motor 1 is rotated by an angle −α, and the axis S ₀ is tilted to the axis S ₁ . At this time, when the state of the plain paper mode (the reference pressure state of the adjustment drive unit) shown in FIG. 2A is changed to the thin paper mode shown in FIG. The distance (interaxial distance, gap Ga) between the hook 12a increases. At the same time, the distance between the spring hooking portion 10b and the spring hooking portion 12b (the distance between the axes, the gap Gb) is changed in a contracting direction. The protrusion 21b presses one end (left end) of the slide arm 16b, so that the slide arm 16b is guided in the lateral direction (the horizontal direction in the figure) while the elongated hole 16d is guided by the pair of restriction shafts 17 and 17. ). The adjustment limit (−α) in the thin paper mode is defined as a range until the other end portion (right end portion) of the slide arm 16b comes into contact with the side surface of the spring hooking portion 10b, and the slide arm shown in FIG. The position 16b is the limit position. Thus, the rotation angle of the switch arm 11 that makes the distance between the spring hook 12a and the first action point P1 larger than the distance between the spring hook 12b and the second action point P2 is adjusted as described above. The low pressure adjustment range (thin paper mode) is lower than the reference pressure state of the drive unit (1, 11).

At this time, the slide arm 16a slides in a state in which the long hole 16c is slidably fitted to the pair of restriction shafts 17 and 17 so that the leftward movement in the figure is restricted at a predetermined position. The portion 21a is separated from one end portion (left end portion) of the slide arm 16a. Further, FIG. 2C is a diagram showing a state in which the pressure state in the thin paper mode is switched to the nip pressure release mode, and the rotation angle of the pressure variable release motor 1 is −α _R , and the axis S ₁ Furthermore the axis S _R which is inclined in the same direction. At this time, since the protrusion 21b further presses one end of the slide arm 16b, the pressure arm 20 is rotated in a direction in which the driven roller 6 is separated from the oblique feeding roller 75, and the nip pressure is reduced. To release. That is, when the switch arm 11 rotates beyond the low-pressure adjustment range, the driven roller 6 is released from the conveying nip in which the driven roller 6 is separated from the skew feeding roller 75.

On the other hand, in the thick paper mode, the rotation direction of the switch arm 11 is reversed, but the basic principle is the same. 3 (a) is a state of the same plain paper mode the state shown in FIG. 2 (a) (reference pressure condition adjusting driver), the switch arm 11 is in the phase of the axis S _0. That is, the distance between the spring hooking portion (first locking portion) 12a and the first action point P1 is equal to the distance between the spring hooking portion (second locking portion) 12b and the second action point P2. The rotation angle of the switch arm 11 is set to the reference pressure state of the adjustment drive unit (1, 11).

FIG. 3B is a diagram illustrating the maximum adjustment in the thick paper mode in which the variable pressure release motor 1 is rotated by the angle + α, and the axis S ₀ is inclined to the axis S ₂ . When the state of FIG. 3 (a) is shifted to the state of FIG. 3 (b), the distance between the spring hooking portion 10a and the spring hooking portion 12a (interaxial distance, gap Ga) is reduced, and the spring hooking portion is reduced. The distance (the distance between the axes, the gap Gb) between 10b and the spring hooking portion 12b changes in a direction in which the distance increases. Then, the protrusion 21a presses one end of the slide arm 16a, and slides to the adjustment range until the other end of the slide arm 16a contacts the side surface of the spring hook 10a. Thus, the rotation angle of the switch arm 11 that makes the distance between the spring hook 12a and the first action point P1 smaller than the distance between the spring hook 12b and the second action point P2 is adjusted as described above. The high pressure adjustment range (thick paper mode) is higher than the reference pressure state of the drive unit (1, 11).

Furthermore, FIG. 3 (c) is a diagram showing a state in which switched from a pressurized state in the thick paper mode the nip pressure release mode, pressure variable rotation angle of the release motor 1 becomes alpha _R, further from the axis S ₂ the axis S _R which is inclined in the same direction. At this time, since the protrusion 21a further presses one end of the slide arm 16a, the pressure arm 20 is rotated in a direction in which the driven roller 6 is separated from the oblique feeding roller 75, and the nip pressure is reduced. To release. In other words, when the switch arm 11 is rotated beyond the high pressure adjustment range, the driven roller 6 is released from the conveying nip in which the driven roller 6 is separated from the skew feeding roller 75.

  In the present embodiment, the lengths of the slide arms 16a and 16b are changed so that the control amount (rotation angle) of the pressure variable release motor 1 is the same in the thin paper mode and the thick paper mode. As a result, in the plain paper mode shown in FIG. 3A (also in FIG. 2A), the ratio of the gap Ga to the gap Gb is the distance x1 from the rotation shaft 8 to the spring hooking portions 10a and 10b. And x2 are equal to each other.

The graph shows changes in the nip pressure F (pressure) in the plain paper mode (reference pressure state), thin paper mode (low pressure adjustment range), thick paper mode (high pressure adjustment range), and nip pressure release mode described above. As shown in FIG. In FIG. 5, the horizontal axis represents the displacement d ₁ of the pressure spring 9 a from the plain paper mode, and the vertical axis represents the nip pressure of the oblique feeding roller 75. In this embodiment, the pressure springs 9a and 9b use the same spring (spring constant: k), and the displacement from the natural length in the plain paper mode shown in FIG. 2 (a) or FIG. 3 (a). Is set to d ₀ , the spring tension T is expressed by the equations (1) and (2), respectively.

From leverage of formula (1) and (2), further pressure arm 20, the force to press the driven roller 6 at this time with respect to skew roller 75, i.e. the nip pressure (total pressure) F ₀ is the formula ( 3).

This value corresponds to the point 50 (when d ₁ = 0) shown in FIG. When the rotation angle of the switch arm 11 is α, the horizontal displacements (ie, displacements of the pressure springs 9a and 9b) d ₁ and d ₂ of the spring hooks 12a and 12b are respectively expressed by the equations (4) and (5). It becomes.

  Therefore, it is expressed by equation (6).

From the above, considering the case of the thin paper mode, the elongation of the pressure spring 9a is d _1, since the pressure spring 9b is a contraction of d _2, respectively spring tension T has the formula (7), and formula (8) Become.

  Therefore, the nip pressure (total pressure) changes as shown in Equation (9).

That is, since the transition to the nip pressure release mode is _made with the displacement d _1max at −α being the adjustment limit of the thin paper mode, which is represented by a straight line passing through the points 50 and 51 shown in FIG. To point 53 and thereafter F = 0.

Similarly, when considered thick paper mode, the pressure spring 9a is shrinkage of _{d 1,} since the pressure spring 9b is a stretch of _{d 2,} respectively spring tension T has the formula (10), the equation (11).

Thus, the nip pressure (total pressure) _{F 2} is changed as equation (12).

That is, it is represented by a straight line passing through the points 50 and 52 shown in FIG. 5, and similarly, the transition to the nip pressure release mode is made at the displacement d _1max at the time of α which is the adjustment limit of the cardboard mode. From 52 to point 53, after that, F = 0.

Thus, in the thin paper mode and the thick paper mode, it is possible to change the nip pressure (pressure force) linearly within a certain adjustment range. For this reason, for example, even in the thin paper mode, the nip pressure can be adjusted more finely as in the case of the basis weight of 52 g / m ² paper, 64 g / m ² paper, and 80 g / m ² paper. Of course, it is possible to make fine adjustments similarly in the thick paper mode.

  As described above, in the present embodiment, since the present invention is applied to the skew correction device 65, the thin paper mode and the thick paper mode can be realized by selectively switching the lever ratio of the pressure arm 20. . This does not correspond to the fact that the working lengths and spring constants of the pressure springs 9a and 9b are extremely increased as the types of sheets included in the specifications of the image forming apparatus 60 increase from thinner to thicker. You can do it. For this reason, the effect of eliminating the instability of the nip pressing force due to the downsizing of the apparatus and the manufacturing variation of the spring is remarkably obtained.

  In addition, since the spring constant can be made smaller by using the pressure springs 9a and 9b as the two springs, a system that is not easily affected by variations in spring manufacturing (generally about ± 10%) is constructed. be able to. As a result, it is possible to realize the improvement in the media compatibility of the oblique registration method and the image forming apparatus 60 including the same in a space-saving and stable manner. Further, in both the thin paper mode and the thick paper mode, by having the nip pressure release mode on the extension of the adjustment range, the effect of shortening the switching time of steps S103 and S106 shown in FIG. It can also contribute to improvement of performance.

<Second Embodiment>
In the second embodiment of the present invention, an example of application to a curling device that imparts curl to a sheet among sheet conveying devices provided in an image forming apparatus 60 will be described. The image forming apparatus 60 of the present embodiment includes an image forming unit 613 (see FIG. 6) that forms an image on a sheet, and a curling device (not shown in FIG. 6) as a sheet conveying device that conveys the sheet to the image forming unit 613. As shown).

  FIG. 10 is a perspective view showing the main components of a curling device 48 that applies curl by applying a stiffness to a sheet. Specifically, it is provided as a pair of rollers such as a paper discharge unit 88 or a double-sided conveyance unit 89 of the image forming apparatus 60 shown in FIG. The sheet is curled or shrunk by the heat and pressure of the fixing device 68, or is poorly stacked on the paper discharge tray 600, or poorly delivered to the finisher attached to the image forming apparatus 60. This causes problems such as corner breakage and jamming during double-sided conveyance. The curling device 48 shown in FIG. 10 corrects the curl caused by the passage of the fixing device 68 by applying the curl in a direction to cancel these curls. Since the configuration and operation of the image forming apparatus 60 are the same as those described in the first embodiment, a description thereof is omitted here.

[Detailed configuration of curling device]
The curling device 48 shown in FIG. 10 forms a transport nip by the opposing sponge roller 81 and metal roller 82, and has both the curling and transport functions. In this embodiment, a sponge roller 81 as a driving roller and a metal roller 82 as a driven roller constitute a conveying roller pair as a curling roller that imparts a curl in a predetermined direction to the sheet.

  Here, in this embodiment, a combination of metal and sponge is used. However, basically, pressurizing two rollers with a large difference in hardness allows the high hardness roller to penetrate into a relatively low hardness roller, so that if the desired amount of penetration is obtained, Any combination of materials may be used. The sponge roller 81 as a driving roller rotates in the direction of arrow A in the figure when the driving force of the conveyance driving motor 80 is transmitted by a driving mechanism such as a pulley and a timing belt 3. The sponge roller 81 is rotatably supported at both ends of the roller shaft by bearings provided on the front and rear side plates. In FIG. 10, the front and rear side plates are not shown for convenience of explanation.

  On the other hand, the metal roller 82 that faces and presses the sponge roller 81 is rotatably supported at both ends of the roller shaft by the end portion of the first arm portion 20b of the pressure arm 20. The pressure arm 20 has the same configuration as that of the oblique feeding roller described in the first embodiment, and includes a rotating shaft 8 and two spring hooks 10a and 10b having different distances from the rotating shaft 8. And a second arm portion 20a provided. Both end portions of the pressure spring 9a are hooked on the spring hook portion 10a and the spring hook portion 12a of the switch arm 11. Further, both end portions of the pressure spring 9b are hooked on the spring hook portion 10b and the spring hook portion 12b of the switch arm 11.

  As described above, in this embodiment, the pressure variable mechanism 87 is basically the same as that described in the first embodiment, and two sets of these are arranged at both ends of the metal roller 82. . The phase of the switch arm 11 is managed by recognizing the home position by the flag unit 14 using the photo interrupter 15 (see FIG. 1). The rotation centers of the two switch arms 11 are integrally formed by a connecting shaft (rotating shaft of the adjusting arm) 86, and a pressure variable drive gear 85 is provided on the connecting shaft 86. The variable pressure drive gear 85 meshes with a motor gear 84 of a variable pressure motor 83 that is an adjustment motor, and can be controlled to an arbitrary rotation direction and rotation angle. The two pressure variable mechanisms 87 and the variable pressure motor 83 are supported by components constituting the unit casing such as front and rear side plates, motor support plates, or stay members, but are omitted in FIG. 10 for convenience of explanation. It is illustrated.

  By the pressure variable mechanism 87 described above, the metal roller 82 is pressed in a form having an intrusion amount with respect to the sponge roller 81 to form a conveyance nip. As a result, the metal roller 82 is driven to rotate in the direction of arrow B in the drawing, and curling can be performed while conveying the sheet in the direction of arrow C.

[Variable control of nip pressure]
Here, the system configuration and the flow of control will be described. That is, in this embodiment, the amount of penetration of the metal roller 82 is adjusted by controlling the rotation direction and rotation angle of the pressure variable motor 83. FIG. 11 is a block diagram showing a system configuration necessary for this, and FIG. 12 is a flowchart showing a flow of control executed by the CPU (calculation unit and control unit) 92 among them.

  In other words, the curl generated in the sheet depends on parameters depending on the sheet type, such as basis weight, presence / absence of a coating layer, fiber gap, etc., and parameters depending on the environment such as temperature and humidity that affect the moisture content. Change. Therefore, the environment sensor 110 is provided inside the image forming apparatus 60, and temperature and humidity detection information is recognized by the CPU 92 (S121 in FIG. 12). Further, the sheet information is acquired when the CPU 92 recognizes information (media selection information) selected by the operator from the operation unit 90 (S122 in FIG. 12). Based on these pieces of information, the CPU 92 refers to a table stored in advance in the memory 91 and obtains (refers to) a control value (pressure setting information) for realizing an optimum amount of metal roller penetration. (S123 in FIG. 12).

  Here, changing the intrusion amount means changing the nip pressing force, and specifically, the control value is the rotation direction and rotation angle of the pressure variable motor 83. Therefore, the table corresponds to a correspondence table of parameters depending on the type of sheet and parameters depending on the environment, and the rotation direction and rotation angle of the pressure variable motor 83. Based on the control value acquired in the above manner, the CPU 92 issues a command to the variable pressure motor 83 and controls the variable pressure motor 83 to the corresponding setting mode, so that the intrusion amount of the metal roller 82 is optimally controlled. Standby is performed (S124 in FIG. 12). Thereafter, when the conveyance drive motor 80 is driven to rotate, it is possible to perform optimum curling according to the situation while conveying the sheet (S125 in FIG. 12).

  Next, details of the setting mode (S124) according to the sheet will be described. The detailed operation of the control flow S124 shown in FIG. 12 is basically the same as the control flow S103 (see FIG. 9) described in the first embodiment, and the operation and nip shown in FIGS. It has a pressure adjustment range. The difference from the first embodiment is that the nip pressure release mode is not always necessary in the case of the curling device. In this case, the components of the slide arms 16a and 16b and the restriction shaft 17 are reduced, and the pressure variable motor 83 is controlled with the adjustment range shown in FIGS. 2B and 3B as the upper limit in both rotation directions. That's fine. Of course, if the slide arms 16a and 16b and the restriction shaft 17 are used as in the first embodiment, the nip pressure release mode shown in FIG. 2C and FIG. If necessary in the sequence, it can be easily handled.

  In this embodiment, the switch arm (adjustment arm) 11 and the variable pressure motor (adjustment motor) 83 constitute an adjustment drive unit. The adjustment drive unit selectively switches the operating length change of the pressure springs 9a and 9b, decreases the other biasing force while increasing one biasing force of the pressure springs 9a and 9b, and The pressure applied to the sponge roller 81 is adjusted.

  In the present embodiment, the metal roller 82 is driven and pressed as shown in FIG. 10, but it is of course possible to use a structure in which the sponge roller is driven and pressed. FIG. 10 shows a system in which one roller is driven and pressed. However, as shown in FIG. 13, a system in which two rollers (131a and 131b) are driven and pressed against the driving roller 130 is also used. I do not care. This configuration has both the correction effect brought about by the intrusion amount determined by the pressure spring 132 and the bending effect caused by sandwiching the two driven rollers 131a and 131b. This configuration is a system that provides a large curling effect to the sheet guided by the conveyance guide 133. The pressure variable mechanism 87 shown in FIG. 10 is used for the pressure configuration of the individual driven rollers 131a and 131b. Basically, it is the same.

  As described above, when the present invention is applied to the curling device 48, the thin paper mode and the thick paper mode can be realized by selectively switching the lever ratio of the pressure arm 20. This does not need to be dealt with by extremely increasing the operating length and spring constant of the pressure spring as the type of sheet included in the specifications of the image forming apparatus increases from thinner to thicker. For this reason, the effect of eliminating the instability of the nip pressing force due to the downsizing of the apparatus and the manufacturing variation of the spring is remarkably obtained. Moreover, since the spring constant can be basically reduced by using two springs, a system that is not easily affected by variations in spring manufacturing (generally about ± 10%) can be constructed. Further, the curl is caused not only by the media but also by the environment such as temperature and humidity, so that the effect of widening the allowable range can be obtained for the operating environment of the image forming apparatus 60. As a result, it is possible to improve the media handling ability and the environment handling ability of the curling device 48 and the image forming apparatus 60 including the curling device 48.

DESCRIPTION OF SYMBOLS 1 ... Adjustment motor (variable pressure release motor), 6,75 ... Conveying roller pair (a driven roller (driven roller), a driving roller (an oblique feeding roller)), 8 ... A rotation fulcrum (rotation shaft), 9a ... 1st Energizing force applying member, first tension spring (pressing spring), 9b ... second energizing force applying member, second tension spring (pressing spring), 11 ... adjusting arm (switch arm), 12a ... first locking portion (Spring hook), 12b ... Second locking part (Spring hook), 13 ... Rotating shaft (motor shaft) of adjusting arm, 20 ... Pressurizing arm (pressurizing arm), 20b ... First arm , 20a ... second arm portion, 48 ... sheet conveying device (curling device), 60 ... image forming device, 65 ... sheet conveying device (skew correction device), 81,82 ... conveying roller pair, curling roller (drive) Roller (sponge roller), driven roller (metal roller)), 8 ... adjusting motor (pressure variable motor), 86 ... rotational shaft of the adjusting arm (connecting shaft), 613 ... image forming section, P1 ... first working point, P2 ... second action point

Claims (7)

A pair of conveying rollers including a driving roller to which driving is transmitted and a driven roller pressed against the driving roller;
The first and second arm portions are provided with a rotation fulcrum interposed therebetween, the driven roller is rotatably supported at a tip portion of the first arm portion, and the rotation is performed on the second arm portion. A pressurizing arm portion provided with first and second action points having different distances from the fulcrum;
First and second urging force applying members for applying an urging force to the first and second action points of the pressurizing arm, respectively;
The operating length change of the first and second urging force applying members is selectively switched, and the first and second urging force applying members of the first and second urging force applying members are increased while increasing one of the urging forces of the first and second urging force applying members. An adjustment drive unit that reduces the other urging force and adjusts the pressure applied to the drive roller of the driven roller,
A sheet conveying apparatus. The adjustment drive unit includes a rotatable adjustment arm that is opposed to the pressure arm unit at a predetermined interval, and an adjustment motor that applies a rotational force to the rotation shaft of the adjustment arm,
The adjustment arm has first and second locking portions arranged on a straight line across the rotation shaft and having different distances from the rotation shaft,
The first urging force applying member is a first tension spring whose both ends are locked to the first action point and the first locking portion, and the second urging force applying member is the second action. A second tension spring having both ends locked to a point and the second locking portion;
The sheet conveying apparatus according to claim 1. The distance from the rotation fulcrum of the second action point is set larger than the distance from the rotation fulcrum of the first action point, and the distance from the rotation axis of the second locking part is the The first locking portion is set to be larger than the distance from the pivot shaft;
The rotation angle of the adjustment arm that makes the distance between the first locking portion and the first action point equal to the distance between the second locking portion and the second action point is adjusted as described above. Set the reference pressure state of the drive unit,
The rotation angle of the adjustment arm that makes the distance between the first locking portion and the first action point larger than the distance between the second locking portion and the second action point is the adjustment. The low pressure adjustment range is lower than the reference pressure state of the drive unit,
The rotation angle of the adjustment arm that makes the distance between the first locking portion and the first action point smaller than the distance between the second locking portion and the second action point is the adjustment. The high pressure adjustment range is higher than the reference pressure state of the drive unit,
The sheet conveying apparatus according to claim 2. When the adjustment arm rotates beyond the low pressure adjustment range, the driven roller is released from the conveyance nip separated from the driving roller, and when the adjustment arm rotates beyond the high pressure adjustment range, the conveyance nip is released. Become,
The sheet conveying apparatus according to claim 3. The driven roller is a skew feeding roller arranged to be inclined at a predetermined angle with respect to the sheet conveying direction.
The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus. The conveying roller pair is a curling roller that imparts a curl in a predetermined direction to the sheet.
The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus. An image forming unit for forming an image on a sheet;
A sheet conveying apparatus according to any one of claims 1 to 6, which conveys a sheet to the image forming unit.
An image forming apparatus.

Images