JP4095567B2 - Curl correction device and image forming apparatus - Google Patents

Description

  The present invention relates to a curl correction apparatus and an image forming apparatus.

  In conventional electrophotographic image forming apparatuses such as copying machines, printers, and facsimiles, a toner image formed on a photosensitive drum (electrophotographic photosensitive member) that is an image carrier provided in an image forming unit is transferred to a sheet. After that, the sheet is conveyed to the fixing device. Here, the fixing device includes a heating roller for heating the toner image on the sheet and a pressure roller pressed against the heating roller, and the toner image is transferred by the heating roller and the pressure roller. By heating and pressurizing the sheet, the toner image is fixed on the sheet.

  Then, the sheet on which the toner image is fixed by the fixing device is sent to a sheet processing device that performs processing such as sorting, stapling, and punching. When images are formed on both sides of the sheet, the sheet on which the image is formed on one side is conveyed again to the image forming unit through a double-sided path (re-conveyance path), thereby forming an image on the back side. I am doing so.

  By the way, in the case of such an image forming apparatus, generally, when a large amount of toner image is placed on a sheet and fixed, curling that is concave on the toner image side that is warped on the image surface side on which the toner image is placed occurs. There is a case. Further, when fixing is performed on a thin sheet on which almost no toner is placed, curling that protrudes toward the toner image side that warps the non-image surface side on which the toner image is not placed may occur.

  Here, when the curled sheet is sent to a sheet processing apparatus, a double-sided path, or the like, there is a possibility that problems such as conveyance failure (jam) and sorting failure may occur. In addition, when a double-sided image is formed, if the sheet is conveyed again to the image forming unit, the sheet may be wound around the photosensitive drum depending on the size and orientation of the curl, causing poor separation from the photosensitive drum, or conversely, it may be wound well on the transfer drum. In some cases, transfer failure occurs without sticking.

  For this reason, in the conventional image forming apparatus, a curl correction device is provided, and the curl correction device removes the curl of the sheet or conversely corrects the curl to the sheet.

  FIG. 17 shows the configuration of such a conventional curl correction apparatus. In this curl correction apparatus, a hard roller 54 is pressed against a relatively soft roller 51 as shown in FIG. Alternatively, as shown in (b), a hard roller 54 is pressed against a relatively soft belt 53 so that the hard roller 54 is inserted into the soft roller 51 or the belt 53 to form a nip. Yes.

  Then, the sheet P is passed through the nip formed in this way, and at this time, the sheet P is conveyed while being bent toward the hard roller side, so that the curl is corrected (see, for example, Patent Document 1). ).

  For example, if the soft roller 51 is a sponge roller having an outer diameter of about φ20 and a rubber hardness of 25 ° (ASKARC), and the hard roller 54 is a metal roller of about φ6 to 8, an appropriate curl correction can be performed. . At this time, the pressing force for pressing the metal roller against the sponge roller requires about 50 to 60 N as a total pressure. Therefore, when pressing the metal roller against the sponge roller, the center part in the longitudinal direction of the metal roller supported at both ends is used. Will bend. Therefore, in order to prevent this, a support member 54 for preventing bending is provided at the center lower portion in the longitudinal direction of the metal roller.

  Further, in the fixing device, in order to prevent the toner and the sheet from adhering to the heating roller or the pressure roller, oil is applied to the sheet passing through the fixing device, or an oil component is given to the toner itself. However, when such a sheet passes through a curl correction device disposed downstream of the fixing device after fixing, dirt such as toner, oil, dust, and paper dust is transferred to the sponge roller and the metal roller, particularly metal. Dirt tends to accumulate on the contact surface with the central support member 54 that prevents the roller from bending.

  When the sheet passes through the curl correcting device in such a state, among the dirt transferred to the sponge roller and the metal roller, particularly the dirt accumulated on the contact surface with the central support member is transferred to the sheet. As a result, an image defect occurs. The same thing occurs not only on the image side of the sheet but also on the back side.

  Therefore, in order to prevent the occurrence of such image defects, for example, as shown in FIG. 18, a cleaning unit 55 is provided around the central support member 54 where accumulation of dirt is relatively large, and the sheet P is stained. As shown in FIG. 19, a cleaning member 56 is provided in the central support member 54 that supports the metal roller 52, and the sponge roller 51 and the metal roller 52 are attached to each other. A configuration has been proposed in which even if dirt is transferred, the cleaning member 56 absorbs the dirt.

JP-A-8-143206

  By the way, in such a conventional curl correction apparatus and an image forming apparatus equipped with the same, when a supporting member for preventing bending is provided at the center in the longitudinal direction of the metal roller, both ends of the metal roller are supported by the support frame. At the same time, the center in the longitudinal direction is supported by the support portion. That is, the metal roller is supported by the three support portions. Therefore, when a positional shift or twist occurs in the three support portions, the position shift or twist is caused by the metal roller or 3 It is absorbed by the twist of the two support parts.

  However, when the metal roller and the three support portions absorb displacement, twist, etc., the contact force between the metal roller and each of the three support portions increases, and the drive for driving the sponge roller and the metal roller. Torque will increase.

  Further, when the cleaning unit 55 as shown in FIG. 18 is provided, the entire apparatus is increased in size and at the same time the cost is increased. Further, as shown in FIG. 19, when the support member 54 is equipped with the cleaning member 56, the maintainability (maintenance property) is greatly deteriorated.

  On the other hand, since the amount of biting of the metal roller into the sponge roller has been constant, it has been difficult to correct the curl corresponding to the type of sheet and the size of the curl.

  Therefore, the present invention has been made in view of such a current situation, and while preventing an increase in driving load, it is possible to prevent an image defect with good maintainability and an image forming apparatus including the same. Is intended to provide. It is another object of the present invention to provide a curl correction apparatus capable of correcting curl corresponding to the type of sheet and the size of curl, and an image forming apparatus including the curl correction apparatus.

The present invention comprises a soft sheet conveying means and a hard sheet conveying means that presses against the soft sheet conveying means, and corrects curling of the conveyed sheet at the nip between the two sheet conveying means. In the curl correcting apparatus, a direction perpendicular to the sheet conveying direction in the hard sheet conveying means that is detachably mounted between the support portion provided in the apparatus main body and the hard sheet conveying means and is supported at both ends. A central support means for supporting the central portion of the sheet, and the central support means is rotatably supported around a central portion in a direction orthogonal to the sheet conveying direction, and is in contact with the hard sheet conveying means. A holding member that holds the portion, and the holding member is configured to move one of the three contact portions to one of two positions shifted in the sheet conveying direction. The contact portion provided at one position is arranged and held at a corresponding position between the other two contact portions provided at the other position, and the central support means is mounted. The hard sheet conveying means is pressed toward the soft sheet conveying means, and the holding force on the upstream side in the sheet conveying direction is applied to the hard sheet conveying means by the reaction force from the hard sheet conveying means due to the pressing. The contact portion of the member and the contact portion of the holding member on the downstream side in the sheet conveying direction are automatically rotated to positions where they abut each other.

  In the present invention, by making the central support means detachable, maintainability is improved and image defects can be prevented.

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

  FIG. 1 is a diagram showing a configuration of an image forming apparatus provided with a curl correction apparatus according to a first embodiment of the present invention.

  In the figure, reference numeral 1 denotes an image forming apparatus, and 2 denotes an image forming apparatus main body. A photosensitive drum 9 on which a toner image is formed, an intermediate transfer belt 30 and the like are formed above the image forming apparatus main body (hereinafter referred to as the apparatus main body). The left and right large-capacity paper feed decks 10A and 10B and the upper and lower two small-capacity paper feed cassettes 19A and 19B are vertically arranged below the image forming section 7. It is arranged. In addition, the apparatus main body 2 is provided with a manual sheet feeding portion 81E for manual sheet feeding.

  When forming an image, first, the sheets P stored in the right paper feeding deck 10A and the paper feeding cassettes 19A and 19B are fed and separated by the paper feeding sections 81A, 81C, and 81D, and are then transferred to the resist introduction path 16. Led. Further, the sheet P of the left sheet feeding deck 10B is fed / separated by the sheet feeding unit 81B, and is guided to the resist introduction path 16 through the sheet feeding deck path 50 and the duplex path 15.

  Next, the sheet P guided to the resist introduction path 16 is conveyed to the image forming unit 7 via the registration roller 26. The sheet P manually fed by the manual paper feed unit 81E is conveyed to the image forming unit 7 via the registration roller 26. The sheet P thus transported to the image forming unit 7 forms a toner image on the sheet P and is fixed by the image forming unit 7, the toner image transfer roller 27, the transport unit 28 and the fixing unit 31. .

  In the case of single-sided copying, the sheet P is discharged out of the apparatus main body by the outer discharge roller 33 and stacked on the discharge tray 35. Also, in the case of reverse discharge, after curling in the reverse path 43, the curl attached to the sheet P is corrected by the belt decurler section β and stacked on the discharge tray 35.

  In the case of double-sided, the sheet P conveyed to the horizontal path 49 is reversed by the reversing path 43, and further passes through the double-sided path 15, and the curl attached to the sheet P is corrected by the sponge decurler portion α, and the resist Guided to the introduction path 16. Thereafter, the toner image is formed and fixed again by the image forming unit 7 and is discharged out of the apparatus main body 2.

  In the figure, reference numeral 8 denotes a conveyance frame having a duplex conveyance path 15 used for duplex copying. The conveyance frame 8 is similar to the sheet feeding decks 10A and 10B and the sheet feeding cassettes 19A and 19B. It can be pulled out from the front side. When a jam occurs in the transport frame 8, the transport frame 8 is first pulled out to the front, and thereafter, as shown in FIG. 2, the outer door 43A is rotatable around the shaft 43C in the direction of the arrow. Alternatively, the inner door 43B is opened.

  For example, when the jammed sheet P is in the lateral path 49 or the reverse path 43 shown in FIG. 1, the outer door 43A is opened, and when the jammed sheet P is in the fixing unit 31 shown in FIG. Opens the inner door 43B and processes the jammed sheet P.

  In the figure, reference numeral 55 denotes a double-sided guide constituting the bottom surface of the double-sided path 15, and this double-sided guide 55 can be opened in the direction of the arrow by a shaft (not shown) provided on the back side in the pull-out direction of the transport frame 8. It has become. When the jammed sheet P is in the double-sided path 15, the double-sided guide 55 is lowered to open the double-sided conveyance path 15, thereby processing the jammed sheet P. .

  By the way, in the present embodiment, the sponge decurler portion α and the belt decurler portion β described above are provided in the transport frame 8. Next, the sponge decurler part α as an example of the curl correcting apparatus which is a feature of the present invention will be described. The curl correcting device is a device that removes the curl from the sheet or conversely corrects the curl on the sheet.

FIG. 3 is a diagram showing the configuration of the sponge decurler α. In FIG. 3A, reference numeral 101 denotes a metal roller that is a hard sheet conveying means, and reference numeral 102 denotes a soft sheet conveying means that the metal roller 101 is pressed against. sponge roller, 103 is provided in the longitudinally central portion of the metal roller 101, a backup member is a central support means for supporting the central portion of the metal roller 101 to prevent the deflection of the metal roller 101, 120 is conveyed frame is 4 is a transport right frame that is a fixed member that sandwiches and fixes the backup member 103 together with the metal roller 101. The metal roller 101 and the sponge roller 102 are rotatably supported by the front and rear frames, respectively, and a nip is formed by pressure contact so that the metal roller 101 bites into the sponge roller 102.

  Reference numerals 109 and 110 denote an upstream upper guide and an upstream lower guide provided on the upstream side of the sponge decurler portion α of the double-sided guide 55, and 113 denotes a downstream lower guide provided on the downstream side of the sponge decurler portion α.

Here, a conveyance mylar 111 is attached to the upstream lower guide 110 so as to push the leading edge of the sheet up to the upstream upper guide 109 so that the leading edge of the sheet is not caught by the sponge roller 102. The transport mylar 111 is pushed up to the upstream upper guide side by a rib 112 provided on the upstream lower guide 110 . Further, the conveyance mylar 111 is set to a length that can secure a gap s so as not to contact the sponge roller 102 as shown in FIG. 3B when the double-sided guide 55 is opened downward. Yes.

  By the way, the backup member 103 is detachably mounted (inserted) in the space between the transport right frame 120 and the metal roller 101. When inserted into this space, as shown in FIG. 3A, the metal roller 101 is bent by being pressed by the backup member 103, and the metal roller 101 further bites into the sponge roller 102, and the metal roller 101. The position is fixed by being pressed against a fixed surface 120a as a support member of the transport right frame 120 by a repulsive force f from the sponge roller 102 applied to the carrier.

  FIG. 4 is a perspective view of such a backup member 103. In FIG. 4, 104 is a backup holder, 104a is a backup member attaching / detaching knob, 104b is a downstream upper guide, 104c is a sticking surface, and 104d is a conveyance right frame. A fixing rib 104e and 120e are guide ribs for mounting the backup member 103 as will be described later.

  Here, at least three backup rollers 105, 106, and 107 that constitute a holding member that holds the metal roller 101 in contact with the central portion of the metal roller 101 are rotatably attached to the backup holder 104. In the present embodiment, the three backup rollers 105, 106, and 107 are provided at two positions shifted in the mounting direction of the backup member 103, and constitute three contact portions that contact the central portion of the metal roller 101. It is supposed to be.

  A cleaning pad 108 for cleaning the metal roller surface is attached to the attachment surface 104c. Then, by attaching the cleaning pad 108, which is a cleaning means for cleaning the surface of the metal roller, to the backup member 103 (the attaching surface 104c) in this way, by bringing the cleaning pad 108 into contact with the surface layer of the metal roller 101, It is possible to prevent dirt adhering to the metal roller 101 from being transferred to the sheet, and to prevent image defects.

  Further, in the present embodiment, after the conveyance frame 8 is pulled out from the front side of the apparatus main body 2, the backup member 103 is held in the horizontal direction as shown in FIG. The cleaning pad 108 can be easily replaced by pulling it out. Further, by removing the backup member 103 in this manner, the backup rollers 105, 106, and 107 can be easily cleaned. Furthermore, as described above, the metal roller 101 and the sponge roller 102 are exposed by opening the double-sided guide 55, so that cleaning is easy.

  Next, a mounting method and a fixing method of such a backup member 103 will be described.

  When mounting the backup member 103, first, as shown in FIG. 5A, the backup member 103 is pushed in between the fixed surface 120a of the transport right frame 120 and the metal roller 101 from the direction indicated by the arrow. To wear.

  When the backup member 103 is pushed in this way, first, the backup roller 106 located at the front end side in the pushing direction (mounting direction) of the backup member 103 comes into contact with the central portion in the longitudinal direction of the metal roller 101. As shown in b), the central portion in the longitudinal direction of the metal roller 101 is deformed in the downward direction indicated by the arrow a.

Thereafter, when the backup member 103 is further pushed in, the contact with the backup roller 106 is released, and the central portion in the longitudinal direction of the metal roller 101 returns to the upward direction indicated by the arrow b by its elastic force (restoring force), and the tip side The backup rollers 106 and the two backup rollers 105 and 107 located at other positions on the upstream side of the backup rollers 106 are moved to positions where they contact each other.

  Then, the metal roller 101 abuts on the three backup rollers 105, 106, and 107 arranged so as to be displaced in the push-in direction, thereby fixing the position of the metal roller 101 and the backup member 103. Is held and fixed by the metal roller 101 rotatably held by the three backup rollers 105, 106, and 107 and the transport right frame 120 (fixed surface 120a thereof).

  FIG. 6 shows a state in which the backup member 103 is fixed to the fixed surface 120a of the transport right frame 120 as described above. 6A is a view of the fixed backup member 103 as viewed from above, and FIG. 6B is a view of the fixed backup member 103 as viewed from the upstream side in the sheet conveying direction. FIG.

  As shown in FIG. 6A, relief holes 120b, 120c, 120d corresponding to the backup rollers 105, 106, 107 are formed in the fixed surface 120a. Further, as shown in (b), a guide surface 120e that is flush with the downstream lower guide is formed on the bottom surface of the transport right frame 120.

  Furthermore, when the backup holder 104 is pushed in, the interval between the two fixing ribs 104d that faces both sides of the fixing surface 120a is 2x wider than the width of the fixing surface 120a. For this reason, when the backup holder 104 is pushed in, a gap is formed between the backup member 103 (the two fixing ribs 104d) and the transport right frame 120 (the fixing surface 120a thereof). Further, the backup holder 104 is made of a material having good sliding properties (for example, POM).

  Then, the back-up member 103 attaches the metal roller 101 to the sponge roller 102 by forming a gap with the fixed surface 120a when formed with a material having good slidability and being pushed in. When the metal roller 101 is pressed against the fixed surface 120a by the pressing force f generated when the nip is formed, the backup holder 104 slides on the fixed surface 120a as follows.

  That is, as shown in FIG. 7, three axial directions formed by three contact portions of the respective backup rollers 105, 106, 107 and the metal roller 101 coincide with the axial direction of the metal roller 101. The backup holder 104 slides and rotates on the fixed surface 120a in the direction of the arrow about the intersection O between the axis of the contact portion and the axis of the metal roller 101. The position of the backup holder 104 is fixed by sliding and rotating in this way.

  That is, when the backup member 103 is pressed against the fixed surface 120a by the reaction force from the metal roller 101, the backup member 103 is fixed so that the backup rollers 105, 106, and 107 are pressed against the metal roller 101 with equal pressure. The roller 120 is slidably rotated on the surface 120a and automatically aligned so that the axial centers of the metal roller 101 and the backup rollers 105, 106, 107 are directed in the same direction, and the backup rollers 105, 106, 107 and the metal roller 101 are aligned. And the axial direction of the metal roller 101 coincide with each other.

  As a result, the contact force between the metal roller and the three contact portions of the backup rollers 105, 106, 107 and the metal roller 101 is reduced, and at least the driving torque for driving the metal roller 101 can be reduced.

  FIG. 8 is a diagram showing a drive system of the sponge decurler α, and the drive from the drive motor 130 is transmitted to the sponge roller 102 via the pulleys 131 and 132 and the belt 133, whereby the sponge roller 102 is The metal roller 101 is driven to rotate as the sponge roller 102 rotates. Further, the drive from the drive motor 130 is transmitted to the transport roller pair 121 and 122 upstream of the sponge roller 102 by gears 135 and 136.

  Here, the setting in the present embodiment is set such that, for example, the sponge roller 102 has an outer diameter of 18.8, a rubber hardness of 15 ° (Asker A), the metal roller 101 has an outer diameter of φ8, and the metal roller 101 enters the sponge roller 102 by 1 amount. 5. The sheet clamping force by the conveying roller pair 121, 122 is 10N. In this case, the maximum driving torque of the motor 130 during sheet conveyance is about 0, 24 N · m when the backup roller is directly fixed to the conveyance right stay 120, and is about 0.2 N when the backup member 103 of the present embodiment is used.・ It was m, and about 20% of the driving load was reduced.

  In this way, by making the backup member 103 detachable, the metal roller 101 and the sponge roller 102 are exposed when the backup member 103 is removed, so that the maintainability of each roller is improved, and sheet conveyance defects, image defects, etc. are eliminated. Can be prevented. Further, when mounting the backup member 103, the backup member 103 is pressed by the metal roller 101 toward the conveyance right frame 120 (fixed surface 120 a), and the backup roller of the backup member 103 is pressed by the pressing force of the metal roller 101. By automatically moving 105, 106, and 107 (holding members) to positions that hold the metal roller 101 evenly, it is possible to prevent an increase in driving load due to misalignment or twisting. Note that the curl can be optimally corrected by mounting or not mounting the backup member 103 in accordance with the material or rigidity of the sheet.

  In addition, although this embodiment was described using the sponge decurler part α as an example of the curl correction apparatus so far, the belt decurler part β as another example of the curl correction apparatus has the same effect, Any decurler configuration (curl correction configuration) can be accommodated.

  In the above description, the holding member for the backup member 103 is provided with three backup rollers 105, 106, and 107 (see FIG. 4). However, as shown in FIG. An arcuate contact recess 104f may be provided as a holding portion at a portion facing the metal roller 101 of the backup holder 104 made of a good material.

  Here, in the case where such an arc-shaped contact recess 104f is provided, when the backup member 103 is pressed against the fixed surface 120a by the metal roller 101, the backup member 103 slides in a direction so that the metal roller 101 enters the contact recess 104f. Thus, the backup member 103 can be automatically aligned.

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

  FIG. 10 is a diagram illustrating a configuration of a sponge decurler unit (curl correction device) according to the present embodiment. In the figure, the same reference numerals as those in FIG. 3 denote the same or corresponding parts.

  In FIG. 10, reference numeral 152 denotes a fixing plate for fixing the backup member 103, and this fixing plate 152 is attached to the transport right frame 120 via the rotation bush 151 so as to be rotatable in the direction of the arrow. In this embodiment, since the width of the two positioning ribs 104d of the backup holder 104 and the width of the fixing plate 152 are substantially the same, the backup member 103 is inserted from the direction of the arrow shown in FIG. When (mounted), the backup holder 104 (backup member 103) is completely fixed to the fixed plate 152.

  Then, by fixing the backup member 103 to the rotatable fixing plate 152 in this way, the backup member 103 can rotate in the direction of the arrow shown in FIG.

  That is, in the first embodiment described above, the backup member itself can be rotated in the direction of the arrow, but in this embodiment, the backup member 103 can be rotated via the fixed plate 152. Therefore, also in this embodiment, the same effect as that of the first embodiment described above can be obtained.

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

  11 and 12 are diagrams showing the configuration of the sponge decurler unit (curl correction device) according to the present embodiment. In the figure, the same reference numerals as those in FIG. 8 indicate the same or corresponding parts.

  In the figure, 161 is a cam for adjusting the amount of penetration of the metal roller 101 into the sponge roller 102, 162 is a cam drive shaft of the cam 161, and this cam drive shaft 162 is provided on the conveyance right frame 120. Further, it is rotatably held by a bearing 160b that is suspended from the fixed portion 160a. The cam 161 (cam drive shaft 162) is driven by a cam drive motor (not shown) capable of detecting and controlling the rotation phase. Further, both ends of the metal roller 101 and the sponge roller 102 are rotatably held by a conveyance stay (not shown).

  Reference numeral 163 denotes a backup support plate rotatably supported on the rotation shaft 164, and the backup member 103 is attached to the rotation end portion of the backup support plate 163.

  In the present embodiment, the rotation end portion of the backup support plate 163 is located below the fixed portion 160a provided on the transport right frame 120, and the rotation end portion is, for example, as described above. A fixed surface having the same configuration as the fixed surface 120a of the transport right frame 120 of the first embodiment is provided.

  The backup member 103 is detachably inserted (attached) into the space between the fixed surface and the metal roller 101. When the backup member 103 is inserted into this space, the backup member 103 is pressed against the rotating end of the backup member 103 by the repulsive force f from the sponge roller 102 applied to the metal roller 101 as described above. The position is fixed by being applied.

  By the way, this figure shows a state where the cam 161 is retracted most. At this time, the amount of the metal roller 101 entering the sponge roller 102 in the longitudinal center is Z0 as shown in FIG. There are few.

  On the other hand, FIGS. 13A and 12B show a state in which the cam 161 is rotated by 90 °. In this case, the amount of the metal roller 101 entering the sponge roller 102 at the center in the longitudinal direction is Z1. At this time, the metal roller 101 and the sponge roller 102 are substantially parallel to each other.

  In the present embodiment, the metal roller 101 and the sponge roller 102 are fixed by the conveyance stay so that the amount of entry is Z1 at both ends of the roller. For this reason, when the amount of entry is Z0 as shown in FIG. 12A, the metal roller 101 is pushed and bent by the sponge roller 102 as shown in FIG. Yes.

  FIGS. 13B and 12C show a state in which the cam 161 rotates 180 ° and the metal roller 101 bites most. In this case, the metal roller 101 has a central portion in the longitudinal direction. The amount of the ink entering the sponge roller 102 is Z2, and at this time, the metal roller 101 is pushed and bent by the backup 104 and the central portion is bent downward.

  FIG. 14 is a diagram illustrating the relationship between the amount of the metal roller 101 entering the sponge roller 102 and the curl correction capability. Here, in the figure, the solid line shows the curl correction ability when only the longitudinal center portion of the metal roller 101 is moved by the cam 161 to enter the sponge roller 102 and the amount of entry is changed from Z0 to Z2. Yes.

  Here, the curl correction ability in each state is minimum in the state (1), maximum in the state (3), and intermediate between (1) and (3) in the state (2).

  A dotted line indicates the curl correction ability when the entire metal roller 101 is moved to enter the sponge roller 102 and the amount of entry is changed from Z0 to Z2. As is apparent from this figure, in the states (1) and (3), the difference between the case where only the central portion of the metal roller is moved and the case where the entire metal roller 101 is moved increases. It can also be seen that the curl correction ability increases in accordance with the amount of entry.

  Therefore, even if the entire metal roller is not moved, if only the central portion of the metal roller is moved by the cam 161 according to the curl state of the sheet and the amount of entry is changed, the curl of the sheet is properly corrected. It becomes possible. Therefore, if only the central part of the metal roller is moved and the amount of entry is changed as in the present embodiment, the curl correction corresponding to the sheet type and the curl size can be performed with a small force. it can.

  By the way, when the penetration amount of the metal roller 101 with respect to the sponge roller 102 is fixed and the rubber hardness of the sponge roller 102 is relatively high, the curl correction ability increases as the sheet thickness increases, and the sheet thickness decreases. The curl correction ability tends to be smaller.

  Thus, for example, the state (1) where the metal roller 101 enters the sponge roller 102 is small for thick paper, the state where the amount of penetration is medium (2) is for plain paper, and the state where the amount of penetration is large (3) is for thin paper. With this setting, curl correction can be performed to the same extent on any sheet.

  In the present embodiment, the configuration in which the cam 161 is used to change the amount of the metal roller 101 entering the sponge roller 102 in the longitudinal center portion has been described. For example, FIGS. ), The distance between the backup rollers 105, 106, 107 and the sponge roller 102 when they are fixed to a height position where the amount of entry of the metal roller 101 is Z0 to Z2, in other words, is different. A plurality of backup members 103A, 103B, 103C provided at such height positions are prepared, and these are selectively mounted according to the type and curl amount of the sheet, whereby the sponge at the longitudinal center of the metal roller 101 is provided. The amount of entry into the roller 102 can be changed.

  Also, as shown in FIGS. 16A to 16C, a plurality of spacer members 150 and 151 having a predetermined thickness such that the amount of entry of the metal roller 101 is Z0 to Z2 are prepared. By selectively mounting according to the type and curl amount, the amount of entry of the metal roller 101 into the sponge roller 102 at the longitudinal center can be changed.

  When the sponge roller 102 is on the driving side, the sheet conveyance speed tends to increase as the amount of the metal roller 101 entering the sponge roller 102 increases. As shown in FIG. 8 described above, when the drive system of the sponge decurler α is the same drive as the pair of conveying rollers 121 and 122 upstream (or downstream) of the sponge roller 102, the backup member 103 Depending on the position, the conveying speed of the sheet changes, and as a result, the sheet may be pulled or pushed in between the sponge roller 102 and the conveying roller pair 121 and 122.

  In such a case, the metal roller using the backup members 103A, 103B, 103C and the spacer members 150, 151 as shown in FIGS. 15 (a) to 15 (c) or FIG. 16 (a) to (c). By adjusting the amount of entry of 101, it is possible to prevent the sheet from being pulled or pushed in due to the difference in the conveyance speed between the sponge roller 102 and the conveyance roller pair 121, 122.

1 is a diagram illustrating a configuration of an image forming apparatus including a curl correction device according to a first embodiment of the invention. FIG. 3 is a diagram illustrating a configuration of a conveyance frame provided in the image forming apparatus. The figure which shows the structure of the sponge decurler which is an example of the said curl correction apparatus. The perspective view of the backup member provided in the said sponge decurler. The figure explaining the attachment / detachment method and fixing method of the said backup member. The figure which shows the state by which the said backup member is being fixed to the fixed surface of the conveyance right frame. The figure explaining the automatic alignment operation | movement of the said backup member. The figure which showed the drive system of sponge decurler part (alpha). The perspective view which shows the other structure of the said backup member. The figure which shows the structure of the sponge decurler part (curl correction apparatus) which concerns on the 2nd Embodiment of this invention. The figure which shows the structure of the sponge decurler part (curl correction apparatus) which concerns on the 3rd Embodiment of this invention. The figure explaining the relationship between the state of the cam provided in the said sponge decurler part, and the approach amount to the sponge roller of the longitudinal direction center part of a metal roller. The perspective view explaining the relationship between the state of the said cam and the approach amount to the sponge roller of the longitudinal direction center part of a metal roller. The figure which shows the relationship between the approach amount to the sponge roller of the said metal roller, and curl correction capability. The figure explaining the structure of the multiple types of backup member provided in the said sponge decurler part. The figure explaining the multiple types of spacer member pinched | interposed between the backup member of the said sponge decurler part, and a conveyance right frame. The figure which shows schematic structure of the conventional curl correction apparatus. The figure which shows schematic structure of the curl correction apparatus provided with the conventional cleaning unit. The figure which shows schematic structure of the curl correction apparatus which provided the conventional cleaning member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 7 Image forming part 8 Conveying frame 101 Metal roller 102 Sponge roller 103 Backup member 103A, 103B, 103C
Backup member 104 Backup holder 104f Contact recess 105, 106, 107
Backup roller 120 Transport right frame 120a Fixed surface 108 of transport right frame Cleaning pads 150 and 151
Spacer member 152 Fixing plate 161 Cam α Sponge decurler portion β Belt decurler portion P Sheet

Claims (8)

A curl correction apparatus comprising: a soft sheet conveying unit; and a hard sheet conveying unit that presses against the soft sheet conveying unit so as to correct a curl of the conveyed sheet at a nip between the two sheet conveying units. In
It is detachably mounted between a support portion provided in the apparatus main body and the rigid sheet conveying means, and supports a central portion in a direction perpendicular to the sheet conveying direction in the rigid sheet conveying means supported at both ends. With central support means ,
The central support means is
A holding member that is supported rotatably around a central portion in a direction orthogonal to the sheet conveying direction and holds at least three contact portions in contact with the hard sheet conveying means, the holding member includes the three contact points One of the contact portions is provided at one of the two positions shifted in the sheet conveyance direction, and the other two contact portions provided at the other position with the contact portion provided at the one position. Placed in the corresponding position between and hold ,
Further, the central support means, when attached, presses the hard sheet conveying means toward the soft sheet conveying means, and the hard sheet conveying means by a reaction force from the hard sheet conveying means due to the pressing. The curl correction apparatus is characterized in that the means automatically rotates to a position where the contact portion of the holding member on the upstream side in the sheet conveyance direction and the contact portion of the holding member on the downstream side in the sheet conveyance direction are in contact with each other . When it is said central supporting means GaSo wearing, the central support means presses the sheet conveying means of the rigid sheet conveying means side of the soft, the reaction force from the sheet conveying means of said rigid by pressing pressure The curl correction apparatus according to claim 1, wherein the central support means is sandwiched between the hard sheet conveying means and the support portion. 3. The curl correction apparatus according to claim 1, wherein the central support unit includes a cleaning unit for cleaning a surface layer of the hard sheet conveying unit. Wherein the central support means movable in a direction of the sheet conveying means of the hard, of claims 1 to 3, characterized in that a changeable amount of engagement for said soft sheet conveying means in the sheet conveying means of the hard The curl correction apparatus according to any one of the above. 5. The curl correcting apparatus according to claim 4, wherein the central support means is moved in the direction of the hard sheet conveying means by a cam. The hard sheet is selectively mounted by selectively mounting one of a plurality of central support means having a holding member configured to have a different distance from the soft sheet conveying means when mounted. 5. The curl correcting apparatus according to claim 4 , wherein a biting amount of the conveying unit with respect to the soft sheet conveying unit can be changed. A spacer member having a different thickness is selectively inserted between the central support means and a support member provided in the apparatus main body, and the amount of biting of the hard sheet conveyance means with respect to the soft sheet conveyance means can be changed. The curl correction apparatus according to claim 4, wherein An image forming unit for forming an image on a sheet, any one of the claims 1 to 7 to correct a curl of the sheet which is conveyed the sheet image is formed by the image forming unit or the image forming section An image forming apparatus comprising the curl correction apparatus described in 1.

Images