JP2009102089A - Curl straightening device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curl straightening device capable of preventing the curl straightening amount from being inappropriate even when the curl of a recording material with oil deposited thereon is continuously straightened. <P>SOLUTION: Intrusion of hard rollers 303, 304 in soft rollers 305, 306 is set according to the combination of the toner carrying amount and the basic weight of recording materials. When the total number of the curl-straightened recording materials exceeds the predetermined value A, the control amount of the intrusion to be set to the same combination of the toner carrying amount with the basic weight of the recording materials is reduced by one stage. Thus, the swollen amount of the soft rollers 303, 304 caused by the absorption of oil deposited on the recording materials by a fixing device in the soft rollers 303, 304 is canceled to maintain the curl straightening capacity of a decurler 301A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a curl correction apparatus that is mounted on an image forming apparatus and corrects curling of a recording material to which an oil component is adhered, and more particularly, to control for reducing a change in the amount of curl correction caused by a change with time of a soft roller.

  2. Description of the Related Art A curl correction device that is disposed downstream of a fixing device in an electrophotographic image forming apparatus and corrects curling of a recording material on which a toner image is fixed has been put into practical use.

  Patent Document 1 discloses a curl correction apparatus that receives a recording material on which a toner image is fixed and corrects curling of the recording material. Here, a nip is formed by pressing a soft roller made of rubber material of sponge structure to a metal hard roller, and the amount of penetration of the hard roller into the soft roller can be variably set by the adjustment mechanism of the penetration amount Is possible. The intrusion amount of the hard roller is automatically set according to the image forming conditions such as the type of the recording material, the fixing temperature, the environmental humidity, and the amount of applied toner on the image. Is set larger.

Japanese Patent Laid-Open No. 05-221574

  When a curl correction device is disposed downstream of the fixing device, the amount of curl correction gradually increases as the number of image formations (number of corrections) increases, and curling in the opposite direction starts to be formed on the recording material. There was found.

  Then, when the curl correction device with an excessive curl correction amount was disassembled and the soft roller was observed, it was found that the rubber material of the sponge tissue was swollen with an oil component, and the diameter of the soft roller was increased. found.

  In the fixing device, a very small amount of oil is continuously applied to the surface of the fixing unit so that toner or the like does not adhere to the high-temperature fixing unit or is easily separated even if it adheres. In the case of a fixing device that wipes off dirt on the fixing unit by rubbing the web, oil impregnated in the web is applied to the surface of the fixing unit.

  The oil adhering to the surface of the fixing unit adheres to the recording material and is carried to the curl correction device, and is sucked into the sponge tissue along with the expansion and contraction of the sponge tissue of the nip, and a rubber material having affinity or reactivity with the oil is used. It was altered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a curl correction apparatus in which the amount of curl correction is not inappropriate even if the curl of a recording material to which an oil component is adhered is continuously corrected.

  The curl correction apparatus of the present invention forms a nip by pressing against the hard roller and the hard roller, and variably adjusts the soft roller softer than the hard roller, and the relative position of the soft roller and the hard roller. And an adjustment mechanism, and the curling of the recording material is corrected by passing the recording material to which oil has adhered through the nip. And a control unit configured to control the adjustment mechanism so as to adjust a relative position between the soft roller and the hard roller in accordance with an amount of oil absorbed by the soft roller.

  Another curl correction apparatus according to the present invention forms a nip by being pressed against the hard roller, and a soft roller softer than the hard roller, and the relative position of the soft roller and the hard roller is variable. And an adjusting mechanism for adjusting, and the curling of the recording material is corrected by passing the recording material to which oil is adhered through the nip. And detecting means for detecting the surface position of the soft roller, and an adjustment mechanism for adjusting the relative position between the soft roller and the hard roller based on the amount of change in the surface position detected by the detecting means. Control means for controlling.

  In the curl correction apparatus of the present invention, since the control unit controls the adjustment unit based on the amount of oil absorbed by the soft roller, the change in the curl correction amount due to the oil is reduced. Accordingly, it is possible to provide a curl correction device in which the amount of curl correction is not inappropriate even if the curl of the recording material to which the oil component is adhered is continuously corrected.

  Hereinafter, some embodiments of the present invention will be described in detail with reference to the drawings. The present invention is another implementation in which part or all of the configuration of each embodiment is replaced with an alternative configuration as long as the intrusion amount setting for the same image forming condition is different between a new state and a used state. It can also be implemented in the form.

  Therefore, the present invention is not limited to an image forming apparatus using an intermediate transfer member, and can also be implemented by an image forming device that directly transfers a photosensitive member to a recording material, an image forming device that transfers a toner image to a recording material carried on a recording material conveyance body, .

  In the embodiment, only main parts related to toner image formation / transfer will be described. However, the present invention includes a printer, various printing machines, a copier, a fax machine, and a multifunction machine in addition to necessary equipment, equipment, and a housing structure. Etc., and can be implemented for various applications.

  In addition, about the general matter of the image forming apparatus shown by patent document 1, illustration is abbreviate | omitted and the overlapping description is abbreviate | omitted.

<First Embodiment>
FIG. 1 is a longitudinal section showing a schematic configuration of the image forming apparatus according to the first embodiment.

  As shown in FIG. 1, a color printer 100 is a one-drum type intermediate transfer type image forming apparatus including a rotary developing device.

  A photosensitive drum (hereinafter simply referred to as “photosensitive member”) 1 as an image carrier is driven by a motor (not shown) and rotates in the direction of arrow A. Around the photoreceptor 1, a primary charger 7, an exposure device 8, a rotary developer 13, a transfer device 10, and a cleaner device 12 are arranged.

  The rotating developer 13 includes developing devices 13Y, 13M, 13C, and 13K for four colors for full-color development. The developing devices 13Y, 13M, 13C, and 13K develop the latent images on the photoreceptor 1 with Y, M, C, and K toners, respectively.

  When developing the toner of each color, the rotating developer 13 is rotated in the direction of arrow R by driving the drive motor 42. Then, the position detection flag 73 laid on the rotary developer 13 is detected by the rotary developer HP sensor 60, thereby detecting the reference position of the rotary developer 13. By rotating the rotary developer 13 from the reference position by a predetermined rotation angle, the developing device for the color is aligned so as to contact the photoconductor 1.

  The containers 80, 81, 82, and 83 store toner to be replenished when the toner in the developing devices 13Y, 13M, 13C, and 13K decreases. The containers 80, 81, 82, and 83 supply toner to the developing devices 13Y, 13M, 13C, and 13K stopped at the position of the toner supply path 88 via the toner supply paths 84, 85, 86, 87, and 88.

  The drive motor 42 is a stepping motor that rotates the rotary developer 13. The solenoid 43 operates a lock mechanism for fixing the position of the rotary developer 13. The lock detection sensor 72 is a photo interrupter that detects the operation of the lock mechanism.

  The transfer device 10 charges the belt 2 to primarily transfer the toner image carried on the photoreceptor 1 to the belt 2. The cleaner device 12 removes and collects the toner that has escaped from the primary transfer and remained on the photoreceptor 1. The photoreceptor 1 from which the remaining toner has been removed and collected is uniformly discharged to near 0 volts by a charge removal device (not shown), and is ready for the next image forming cycle.

  The belt 2 is stretched around rollers including a driving roller 17, a tension roller 18, and a backup roller 19, and a predetermined tension is applied by the tension roller 18.

  A belt cleaner 22 is provided at a position facing the roller 17 with the belt 2 interposed therebetween, so that the residual toner on the belt 2 after the secondary transfer is scraped off by the cleaner blade.

  The recording material disposed in the recording material cassette 23 is pulled up to a position where it contacts the pickup roller 24 by the operation of the lifter motor 40. The recording material drawn from the recording material cassette 23 to the conveyance path by the pickup roller 24 is fed to the nip portion (contact portion) between the transfer roller 21 and the belt 2 by the roller pairs 25 and 26.

  The paper surface height sensor 50 detects the paper surface height in the recording material cassette 23. The conveyance sensors 51 to 58 are arranged on the conveyance path and detect the presence / absence of a recording material at each point or the conveyance timing of the recording material. The cassette attachment / detachment sensor 70 detects attachment / detachment of the recording material cassette 23. The door opening / closing switch 71 operates in response to the opening / closing of the door 41 enabling access to the inside of the main body, and cuts off / connects the power supply to the driving load.

  In the color printer 100, an image is formed as follows. First, a voltage is applied to the charging device 7 so that the surface of the photoreceptor 1 is uniformly negatively charged with a predetermined charged portion potential. Subsequently, exposure is performed by an exposure device 8 formed of a laser scanner so that a charged image portion on the photosensitive member 1 has a predetermined exposure portion potential, thereby forming a latent image.

  The image forming timing of the color printer 100 is controlled based on a signal ITOP with a predetermined position on the belt 2 as a reference. Between the tension roller 18 and the backup roller 19, a reflective position sensor 36 for detecting the reference position is disposed. The exposure device 8 starts exposure at the timing when the signal ITOP is detected. The exposure apparatus 8 forms a latent image corresponding to an image by turning on and off the exposure based on an image signal generated by an image control unit (not shown).

  A developing bias set in advance for each color is applied to the developing roller such as the developing device 13Y, and the latent image is developed with toner when passing through the position of the developing roller, and visualized as a toner image.

  The toner images of each color developed on the photosensitive member 1 are sequentially transferred onto the belt 2 as an intermediate transfer member by the transfer device 10, and the four color toner images are superimposed on the belt 2.

  The four-color toner images carried on the belt 2 are collectively transferred and transferred onto the recording material at the nip portion between the transfer roller 21 and the belt 2, thermally fixed by the fixing device 5, and discharged to the decurler 301 </ b> A.

  In the case of duplex printing, the flapper 32 is operated to convey the recording material in the direction of the conveyance roller 27. After the conveyance roller 28 conveys until it exceeds the flapper 33, the conveyance roller 28 is reversely rotated and the flapper 33 is operated to convey the recording material in the direction of the conveyance roller 29. The recording material is conveyed by conveying rollers 30 and 31 and joined to the conveying path from the recording material cassette 23, whereby an image is formed on the surface opposite to the first surface.

  The color printer 100 can use various recording materials from relatively thin paper called plain paper and recycled paper, which are widely used, to relatively thick special purpose paper called glossy paper and coated paper.

  Since plain paper and recycled paper are thin, even when the toner image is transferred and passed through the fixing device 5, the curl amount is relatively small. However, since the glossy paper and the coated paper are thick and the surface is coated, a very large curl is generated after passing through the fixing device 5.

  Accordingly, the recording material discharged from the color printer 100 passes through a decurler 301A which is an example of a curl correction device, corrects curl, and then is discharged to a discharge tray 302 or a finisher (not shown).

<Curl correction device>
2 is a longitudinal sectional view showing a schematic configuration of the decurler according to the first embodiment, FIG. 3 is an explanatory diagram of a schematic configuration of a decurler intrusion amount adjusting mechanism, and FIG. 4 is an explanatory diagram of a schematic configuration of a control device related to control of the decurler. It is.

  As shown in FIG. 2, the decurler 301A has two pairs of rollers formed of stainless hard rollers 303 and 304 and soft rollers 305 and 306 each having an elastic layer made of a urethane rubber material having a sponge structure. Be placed. On the upstream side (right side in the figure) of the recording material conveyance direction C, a hard roller 303 and a soft roller 305 form a roller pair, and on the downstream side (left side in the figure), a hard roller 304 and a soft roller 306. Is arranged by reversing the positional relationship of the roller pair.

  As shown in FIG. 2 with reference to FIG. 4, the hard roller 303 is driven to rotate by the drive motor 511, and the hard roller 304 is driven to rotate by the drive motor 512. The soft rollers 305 and 306 are driven and rotated by the hard rollers 303 and 304 that are in pressure contact with each other.

  In addition to this, in addition to this, the soft rollers 305 and 306 may be driven to drive the hard rollers 303 and 304, or both the hard rollers 303 and 304 and the soft rollers 305 and 306 may be driven. Good.

  However, if the soft rollers 305 and 306 are on the driving side, it is necessary to adjust the speed to cancel the change with time of the diameter, which will be described later. Therefore, the hard rollers 303 and 304 are preferably on the driving side. Moreover, since the drive transmission mechanism can be simplified, driving on one side is preferable. Therefore, in the first embodiment, the hard rollers 303 and 304 are driven and the soft rollers 305 and 306 are driven.

  The recording material is guided by the paper conveyance guides 307, 308, 309, 310, 311, and 312, and is nipped and conveyed by the nip between the hard rollers 303 and 304 and the soft rollers 305 and 306.

  The control device 501 detects whether or not the recording material has been completely discharged by a sensor 313 disposed on the most downstream side of the conveyance path. The control device 501 detects the output of the sensor 313, counts the number of recording materials that have passed through the decurler 301A, and stores it in the RAM 504.

  As shown in FIG. 3 with reference to FIG. 4, the soft rollers 305 and 306 are moved in directions A and B by the intrusion amount adjusting mechanisms 320 and 330, respectively, and pressed against the hard rollers 303 and 304.

  The upstream soft roller 305 is supported by a shaft 406 on a member 402 supported by the shaft 404 as a fulcrum. The member 402 is disposed in contact with a cam 408 supported with the shaft 410 as a fulcrum.

  The cam 408 moves the member 402 in the direction of arrow E by being rotated in the direction of arrow D about the shaft 410 by the motor 513. As a result, the member 402 is rotated in the direction of arrow F with the shaft 404 as a fulcrum, and the soft roller 305 on the upstream side moves in the direction of arrow A and is pressed against the hard roller 303.

  The downstream soft roller 306 is supported by a shaft 405 on a member 401 supported by a shaft 403 as a fulcrum. The member 401 is disposed in contact with a cam 407 supported with the shaft 409 as a fulcrum.

  The cam 407 moves the member 401 in the arrow H direction by being rotated in the arrow G direction about the shaft 409 by the motor 514. As a result, the member 401 is rotated in the direction of arrow I with the shaft 403 as a fulcrum, and the soft roller 306 on the downstream side moves in the direction of arrow B and is pressed against the hard roller 304.

  As shown in FIG. 4 with reference to FIG. 3, a CPU 502, a ROM 503, a RAM 504, and an I / O 505 are connected to the control device 501 by a bus 506. The above-described motor 511, motor 512, motor 513, and motor 514 are connected to motor drivers 507, 508, 509, and 510 connected to the I / O 505, respectively.

  The CPU 502 executes necessary calculations using the RAM 504 in accordance with the control program read from the ROM 503, and processes various inputs / outputs such as motors and sensors through the I / O 505.

  The motor 511 drives the hard roller 303 on the upstream side, and the motor 512 drives the hard roller 304 on the downstream side.

  The motor 513 drives the cam 408 to adjust the amount of penetration of the upstream roller pair, and the motor 514 drives the cam 407 to adjust the amount of penetration of the downstream roller pair. That is, by driving the cam 408, the relative position between the upstream soft roller 305 and the upstream hard roller 303 is adjusted in the upstream roller pair. The motor 514 drives the cam 407 to adjust the relative position of the upstream soft roller 306 and the downstream hard roller 304 in the downstream roller pair. As the motors 513 and 514, stepping motors suitable for position control were used, and the rotation amount was controlled by the number of pulses as an example of the adjustment amount.

  Sensors 515 and 516 are connected to the I / O 505 as a configuration for adjusting the intrusion amount of the roller pair to a predetermined value. Sensor 515 detects the reference position of cam 408, and sensor 516 detects the reference position of cam 407.

  The control device 501 rotates the cam 408 by an angle corresponding to the number of pulses supplied to the motor 513, using the reference position detected by the sensor 515 as a base point, and controls the position of the soft roller 305 to thereby detect the upstream hard roller. The amount of intrusion 303 is determined.

  The control device 501 rotates the cam 407 by an angle corresponding to the number of pulses supplied to the motor 514, using the reference position detected by the sensor 516 as a base point, and controls the position of the soft roller 306 so that the downstream hard roller The amount of intrusion 304 is determined.

  Prior to starting image formation, the control device 501 predictively sets the intrusion amount of the roller pair according to the image forming conditions, and waits for the fixed recording material. This is because a curl direction and amount of the curled recording material are detected and fed back to the intrusion amount, which may cause a fatal curl on the first recording material. In order to accurately estimate different curl amounts for each sheet and to set the penetration amount appropriately, it is necessary to average the curl amounts of several tens of sheets. However, if several tens of curled recording materials are stacked on the discharge tray 302, it is not possible to stack the curled recording material properly corrected thereon.

  The control device 501 detects the trailing edge of the recording material by the sensor 313 disposed on the most downstream side of the conveyance path, counts the total number of recording materials that have passed through the decurler 301 </ b> A, and stores it in the RAM 504.

The control device 501 estimates the durable state of the soft rollers 305 and 306 based on the total number of the curled correction recording materials after the soft rollers 305 and 306 are used in a new state. Then, by correcting the intrusion amount of the roller pair according to the total number of the curled correction recording materials, the change with time of the radius of the soft rollers 305 and 306 is offset. That is, the amount of oil absorbed by the soft rollers 305 and 306 is estimated based on the total number of recording materials. Based on the estimated amount of oil absorbed by the soft rollers 305 and 306, the relative positions of the soft rollers 305 and 306 and the hard rollers 303 and 304 are adjusted.
<Adjustment of penetration amount according to image formation conditions>
FIG. 5 is an explanatory diagram of the curl correction of the recording material in the decurler. In FIG. 5, (a) is the curl correction by the upstream nip, and (b) is the curl correction by the downstream nip.

  As shown in FIG. 5A, in the correction nip KU between the hard roller 303 and the soft roller 305 arranged on the upstream side, the hard roller 303 enters the soft roller 305 by ΔU, and a downwardly convex correction surface is formed. It is formed.

  The recording material P1 on which the toner image is transferred and fixed on the upper surface and is convexly curled upward is pressed by the soft roller 305 against the downwardly convex curved surface by the soft roller 305 in the process of passing through the correction nip KU. The convex curl is removed.

  As shown in FIG. 5B, in the correction nip KD between the hard roller 304 and the soft roller 306 arranged on the downstream side, the hard roller 304 enters the soft roller 306 by ΔD, and an upward convex correction surface is formed. It is formed.

  The recording material P1 on which the toner image is transferred and fixed on the upper surface and curled downwardly is pressed by the soft roller 306 against the upwardly convex curved surface by the soft roller 306 in the process of passing through the correction nip KD. The convex curl is removed.

  As shown in FIG. 4 with reference to FIG. 1, the control device 501 calculates the amount of applied toner transferred to the recording material from the yellow, magenta, cyan, and black image data supplied to the exposure device 8.

The control device 501 obtains the basis weight (weight per unit area: g / m ² ) with reference to the data table of the ROM 503 with the type of the recording material set by the operator.

  The control device 501 refers to the data table of the ROM 503 based on the toner loading amount and the basis weight of the recording material, and obtains the expected curling direction and amount of the recording material after fixing.

  The control device 501, which is an example of setting means, operates the motors 513 and 514 in accordance with the curl direction and amount of the recording material expected after fixing, and enters the correction nip KU into the intrusion amount ΔU and the correction nip KD. An intrusion amount ΔD is set.

  When the expected curl of the recording material is convex upward, ΔU> ΔD is set, and ΔU is increased in four stages of L0, L1, L2, and L3 as the curl amount increases.

  When the expected curl of the recording material is convex downward, ΔU <ΔD is set, and ΔD is increased in four stages of L0, L1, L2, and L3 as the curl amount increases.

  Table 1 shows the intrusion amounts L0, L1, L2, and L3 at the settings 0, 1, 2, and 3 of the intrusion amount ΔU (ΔD), and the number of pulses supplied from the reference position to the motor 513 (514). Yes.

  As shown in Table 1, the intrusion amount ΔU (ΔD) is set in four stages from setting 0 to setting 3, and the intrusion amounts L0, L1, L2, and L3 are determined in advance. The rotation angles of the cams 408, 407 corresponding to the intrusion amounts L0, L1, L2, L3 are assigned as the number of drive pulses of the motors 513, 514.

  Needless to say, the motors 513 and 514 can be DC motors, and in this case, the driving time is assigned instead of the number of pulses.

  Table 2 is an intrusion amount conversion table set based on the basis weight of the recording material and the applied toner amount.

  The basis weight of the recording material is divided into four stages from the minimum a to the maximum d, and the applied toner amount is divided into four stages from the minimum A to the maximum D, and the setting 0 described in Table 1 for each combination. ~ Setting 3 is assigned.

  When receiving the image forming job, the control device 501 sets the intrusion amount ΔU (ΔD) based on the set recording material type and the received image data, and starts image formation. As shown in Table 2, settings 0, 1, 2, and 3 are selected according to the basis weight of the recording material and the applied toner amount, and as shown in Table 1, the number of pulses according to the settings 0, 1, 2, and 3 is selected. The control is executed.

  Here, in order to simplify the description, the adjustment according to the basis weight of the recording material and the applied toner amount has been described. In practice, however, the intrusion takes into account image forming conditions such as recording material transport speed, fixing device configuration, fixing temperature, recording material, environmental humidity, and toner material (type and amount of wax contained). The amount ΔU (ΔD) is set. This is because these image forming conditions also affect the curl direction and amount of the recording material after fixing.

<Intrusion amount correction according to the total number>
FIG. 6 is an explanatory diagram of the change with time of the soft roller, and FIG. 7 is a flowchart of the intrusion amount correction control according to the total number of sheets.

  As shown in FIG. 1, in the fixing device 5, oil is applied in order to prevent the internal fixing roller from being soiled. A cleaning member called a web for wiping off the fixing roller is disposed, and oil is applied to the cleaning member. Therefore, the oil on the surface of the fixing roller adheres to the surface of the recording material in the process of passing the recording material through the fixing device 5, and the soft rollers 305 and 306 of the sponge structure remove the oil in the process of passing through the downstream curl correction device 301A. Absorb.

  The toner filled in the developing devices 13Y, 13M, 13C, and 13K contains a resin such as wax, and these are also dissolved in oil and absorbed by the soft rollers 305 and 306.

  For this reason, as the total number of recording materials passing through the curl correcting device 301A increases, the soft rollers 305 and 306 swell with oil and wax and the radius increases. As the radius increases, the amount of curl correction increases, the amount of curl increases, and the appearance of the recording material stacking deteriorates.

  As shown in FIG. 6A, the penetration amount L is set in accordance with the image forming conditions in the new state of the soft roller 305 having the radius T.

  As shown in FIG. 6B, in the used state of the soft roller 305 in which the total number of images formed reaches 10,000, the soft roller 305 is swollen to a radius T ′. As a recording material containing the oil of the fixing device 5 on its surface passes, the oil is absorbed by the soft roller 305 having a sponge structure, and accumulates and continues to swell.

  At this time, if the intrusion amount L is set according to the image forming conditions, the substantial intrusion amount Lr increases by an increase in the radius T of the soft roller 305, and becomes Lr = L + (T−T ′).

  Therefore, in order to correct the substantial intrusion amount Lr to the necessary intrusion amount L, as shown in FIG. 6C, the corrected intrusion amount L ′ = L− (T−T ′). The intrusion amount L is corrected as follows.

  The change amount T-T ′ of the diameter of the soft roller 305 stores the conversion table shown in Table 3 in the ROM 503 as a numerical value corresponding to the total number of recording materials obtained experimentally.

  As shown in Table 3, up to the total number A, which is an example of the specified value, pulses for the setting N (N = 0, 1, 2, 3) for the upstream intrusion amount ΔU and the downstream intrusion amount ΔD. The initial value Zn (Zn = Z0, Z1, Z2, Z3) is used for the number.

  From the total number A to the total number B, which is an example of the specified value, the correction value Za1n (Za10,...) Is set to the number of pulses for the setting N (N = 0, 1, 2, 3) for the upstream intrusion amount ΔU. Za11, Za12, Za13) are used. For the downstream intrusion amount ΔD, a correction value Zb1n (Zb10, Zb11, Zb12, Zb13) smaller than the correction value Za1n is used as the number of pulses for the setting N (N = 0, 1, 2, 3).

  The reason why the setting is different between the upstream side and the downstream side is that the oil is first absorbed in the upstream nip first, so the upstream soft roller 305 swells more than the downstream soft roller 306. This is because the value to be corrected increases.

  When the number B of sheets to be passed exceeds the correction value Za2n (Za20, Za21, Za22, Za23) is used for the number of pulses for the setting N (N = 0, 1, 2, 3) for the upstream intrusion amount ΔD. . For the downstream intrusion amount ΔD, a correction value Zb2n (Zb20, Zb21, Zb22, Zb23) smaller than the correction value Za2n is used as the number of pulses for the setting N (N = 0, 1, 2, 3). The reason why the setting is different between the upstream side and the downstream side is as described above.

  The correction values Za1n, Zb1n, Za2n, and Zb2n are set in consideration of factors that affect the swelling speed of the soft rollers 305 and 306 in the decurler 301A and the image forming apparatus 100. Specifically, the amount and type of oil applied in the fixing device 5, the amount of toner applied, the component and amount of resin contained in the toner, the configuration of the decurler 301A, the temperature environment, the soft rollers 305 and 306 Material.

  As shown in FIG. 7 with reference to FIGS. 1 to 4, the control device 501 determines deterioration with time of the soft rollers 305 and 306 from the total number of recording materials that have passed through the decurler 301 </ b> A.

  The control device 501 determines whether or not the total number of recording materials that have passed through the decurler 301A exceeds a predetermined number A (S101).

  When the predetermined number A is not exceeded (no in S101), the control device 501 sets the number of pulses to Zn (S102).

  When the total number exceeds the predetermined number A (Yes in S101), the control device 501 determines whether the total number exceeds the predetermined number B (S103).

  When the total number does not exceed the predetermined number B (no in S103), the control device 501 sets the number of pulses to Za1n and Zb1n (S104).

  When the total number exceeds the predetermined value B (Yes in S103), the control device 501 sets the number of pulses to Za2n and Zb2n (S105).

  In the decurler 301A of the first embodiment, the problems due to the aging of the soft rollers 305 and 306 are eliminated by correcting the number of control pulses. Therefore, it is possible to continue using the soft rollers 305 and 306 that are swollen and have a large diameter. it can. Up to now, the swollen soft rollers 305 and 306 that had to be replaced can be extended for two replacements, and the curling of the recording material can be continued to be properly corrected, so that maintenance for replacing the rollers can be reduced.

  Prior to the image forming condition, the number of pulses is set in a predictive manner according to the image forming condition, so that a fatal curl or a jam caused by the curl does not occur in the first recording material. There is no need to wait for image formation of several tens of sheets in order to accurately estimate the curl amount. Without damaging this feature, by correcting the pulse amount so that the substantial intrusion amount maintains a predetermined value according to the total number of recording materials, long and appropriate curl correction and recording material conveyance can be performed. Become.

  Accordingly, it is possible to realize a curl correction apparatus that does not require replacement of the soft rollers 305 and 306 in maintenance periodically performed by a service person and that requires less maintenance.

<Modification of First Embodiment>
FIG. 8 is an explanatory diagram of the intrusion amount adjustment with respect to the total number of sheets in the first modification.

  In the first embodiment, the control for adjusting the number of pulses in two stages according to the total number of sheets has been described, but in Modification 1, the control is performed in real time according to the total number of sheets.

  As shown in FIG. 8A, after starting to use the soft rollers 305 and 306 in a new state, the amount of increase in radius from the new state increases as the total number of curled recording materials increases. As a result, as described above, the substantial intrusions ΔU and ΔD of the hard rollers 303 and 304 with respect to the soft rollers 305 and 306 increase.

  Therefore, as shown in FIG. 8B, the control device 501 calculates the reduction number of the number of pulses by multiplying the total number of corrections by the correction constant, and calculates the intrusion amount by the number of pulses subtracted from the number of pulses shown in Table 1. ΔU and ΔD are set. As a result, a constant curl correction effect can be maintained by finely adjusting the number of pulses in real time in response to changes in the diameter of the soft rollers 305 and 306.

  In the first embodiment, the control for reducing the control amounts of the intrusion amounts ΔU and ΔD as the total number of recording materials increases has been described. However, in the case of the soft rollers 305 and 306 in which the tissue contracts due to absorption of oil and the radius decreases with time, control for increasing the control amounts of the intrusion amounts ΔU and ΔD as the total number of recording materials increases. It becomes.

  In the first embodiment, the control for changing the control amounts of the intrusion amounts ΔU and ΔD according to the total number of recording materials has been described. This is because the total number of recording materials is easy to detect and reflects the oil absorption amount of the soft rollers 305 and 306 relatively accurately. However, the parameter reflecting the amount of oil absorbed by the soft rollers 305 and 306 is not limited to the total number.

  In the second modification, the total area of the recording material that has passed through the decurler 301A is calculated, and the control amounts of the intrusion amounts ΔU and ΔD are corrected. This is because the total area is not as easy to detect as the total number of sheets, but more accurately reflects the amount of oil absorbed (impregnation amount) by the soft rollers 305 and 306.

  In the second modification, the control device 501 calculates the total area of the recording material that has passed through the decurler 301 </ b> A from the number of recording materials for each job and the size of the output recording material, and stores it in the RAM 504. The control device 501 estimates the oil absorption amount of the decurler 301 </ b> A according to the total area stored in the RAM 504, and changes the intrusion amount of the roller pair. When the total amount of the area of the recording material that has passed through the nip exceeds a predetermined area, the number of pulses set corresponding to the same image forming conditions is reduced, and the substantial penetration amount of the roller pair is kept constant.

  In the third modification, the control device 501 counts the video count of the image data formed on the output recording material and stores it in the RAM 504. The control device 501 changes the intrusion amount of the roller pair according to the video count value stored in the RAM 504. From the video count value, the oil absorption amount of the decurler is estimated based on the integrated amount of the density integrated value of the image formed on the recording material. When the integrated amount of the density integrated value of the image formed on the recording material exceeds a predetermined amount, the number of pulses set corresponding to the same image forming condition is reduced, and the substantial intrusion amount of the roller pair is made constant. Keep on.

Second Embodiment
FIG. 9 is a longitudinal sectional view showing a schematic configuration of a decurler according to the second embodiment, and FIG. 10 is an explanatory diagram of a schematic configuration of a control device related to control of the decurler.

  A decurler 301B of the second embodiment is installed in the color printer 100 shown in FIG. 1 by replacing the decurler 301A of the first embodiment.

  The decurler 301B of the second embodiment is configured in the same manner as the decurler 301A of the first embodiment, except that the temporal changes of the soft rollers 305 and 306 are determined by distance measuring sensors 314 and 315 that detect the diameters of the rollers. Controlled. Accordingly, in FIGS. 9 to 11, the components common to the first embodiment are denoted by the same reference numerals as those in FIGS. 1 to 6, and redundant description is omitted.

  As shown in FIG. 9, a distance measuring sensor 314 for monitoring the state of the diameter of the soft roller 305 is in the vicinity of the soft roller 305, and a distance measuring sensor 315 for monitoring the state of the diameter of the soft roller 306 is a soft roller. Each of them is arranged in the vicinity of 306. The distance measuring sensors 314 and 315 continuously detect the distance from the surface of the soft rollers 305 and 306 and monitor changes in the roller diameter. The distance measuring sensors 314 and 315 are fixedly disposed on a member to which the soft rollers 305 and 306 are attached so that the distance measuring sensors 314 and 315 move in accordance with the intrusion of the soft rollers 305 and 306.

  As shown in FIG. 10, distance measuring sensors 314 and 315 are disposed in order to detect temporal changes in the roller diameters of the soft rollers 305 and 306, respectively. The outputs of the distance measuring sensors 314 and 315 are connected to the A / D 517, and the A / D 517 is connected to the CPU 502.

  The control device 501 detects a change in the output of the distance measuring sensors 314 and 315 and calculates the amount of swelling of the radius of the soft rollers 305 and 306, and only corresponds to the amount of increase in radius as in the first embodiment. Reduce the number of pulses to control the amount of penetration.

<Intrusion amount correction according to the total number>
FIG. 11 is an explanatory diagram of changes with time of the soft roller, and FIG. 12 is a flowchart of intrusion amount correction control according to the output of the distance measuring sensor.

  As shown in FIG. 11A, in the new state of the soft roller 305 having a radius T, the distance X is detected by the distance measuring sensor 314, and the intrusion amount L is set according to the image forming conditions. A distance measuring sensor 314 is arranged in the vicinity of the soft roller 305 at a predetermined distance X, and the distance measuring sensor 314 is a member that supports the rotating shaft of the soft roller 305 so as to move together with the soft roller 305. Mounted on top.

  As shown in FIG. 11B, in the used state of the soft roller 305 in which the total number of image formation reaches 10,000, the soft roller 305 swells to the radius T ′, and as a result, the distance sensor 314 causes the distance X 'Is detected.

  As a result, the intrusion amount L increases by an increase X-X ′ of the radius of the soft roller 305 and becomes L + (X−X ′). Therefore, in order to maintain the necessary intrusion amount L, as shown in FIG. 11C, the intrusion amount is corrected so that the corrected intrusion amount L ′ = L− (XX ′). .

  As for the correction amount, control using the tables in Table 1, Table 2, and Table 3 may be adopted. However, as described in Modification 1, correction is performed in real time according to the output of the distance measuring sensor 314. Is preferred. Specifically, the amount of change TT ′ in the radius of the soft roller 305 is judged from the reading value of the distance measuring sensor 314, and the correction amount Z ( XX ′) is reduced from the control amount Z for generating the intrusion amount L.

  As shown in FIG. 12 with reference to FIG. 10, the control device 501 directly changes the temporal change of the soft rollers 305 and 306 from the output change of the distance measuring sensors 314 and 315 that detect the surface positions of the soft rollers 305 and 306. Detect.

  The control device 501 reads the output of the distance measuring sensors 314 and 315 and reads the initial distance X (S111).

  The control device 501 reads the distance X ′ for each image formation (S112), and calculates the amount of change (X−X ′) in the radius of the soft rollers 305 and 306.

  The control device 501 reduces the drive amount Z (X-X ′) of the motors 513 and 514 corresponding to the radius change amount (X−X ′) from the predetermined drive amount Z (S113).

1 is a longitudinal section showing a schematic configuration of an image forming apparatus according to a first embodiment. It is a longitudinal cross-sectional view which shows schematic structure of the decurler of 1st Embodiment. It is explanatory drawing of schematic structure of the intrusion amount adjustment mechanism of a decurler. It is explanatory drawing of schematic structure of the control apparatus in connection with control of a decurler. It is explanatory drawing of the curl correction of the recording material in a decurler. It is explanatory drawing of a time-dependent change of a soft roller. It is a flowchart of the correction | amendment control of the intrusion amount according to the total number of sheets. It is explanatory drawing of intrusion amount adjustment with respect to the total number of sheets in the modification 1. FIG. It is a longitudinal cross-sectional view which shows schematic structure of the decurler of 2nd Embodiment. It is explanatory drawing of schematic structure of the control apparatus in connection with control of a decurler. It is explanatory drawing of a time-dependent change of a soft roller. It is a flowchart of the correction | amendment control of the intrusion amount according to the output of a ranging sensor.

Explanation of symbols

301A, 301B Curl correction device (Decurler)
302 Paper discharge tray 303, 304 Hard roller 305, 306 Soft roller 313 Sensor 314, 315 Detection means (ranging sensor)
407, 408 Adjustment mechanism (cam)
501 Control means (control device)
502 CPU
503 ROM
504 RAM
505 I / O
506 Buses 507, 508, 509, 510 Motor drivers 511, 512, 513, 514 Motor

Claims (4)

A hard roller,
A nip formed by pressure contact with the hard roller; a soft roller softer than the hard roller;
An adjustment mechanism that variably adjusts the relative position of the soft roller and the hard roller,
In the curl correction apparatus for correcting the curl of the recording material by passing the recording material to which oil has been attached to the nip,
A curl straightening device comprising control means for controlling the adjustment mechanism so as to adjust the relative position between the soft roller and the hard roller in accordance with the amount of oil absorbed by the soft roller. The control means, after starting to use the soft roller in a new state,
(1) Number of recording materials that have passed through the nip,
(2) The area of the recording material that has passed through the nip,
(3) a density integrated value of an image formed on the recording material that has passed through the nip;
The curl correction apparatus according to claim 1, wherein the amount of oil absorbed by the soft roller is estimated based on a total amount of any of the above. A hard roller,
A nip formed by pressure contact with the hard roller; a soft roller softer than the hard roller;
An adjustment mechanism that variably adjusts the relative position of the soft roller and the hard roller,
A curl correction device that corrects curling of a recording material by passing the recording material to which oil has adhered through the nip,
Detecting means for detecting the surface position of the soft roller;
Curl correction comprising: control means for controlling an adjustment mechanism so as to adjust a relative position between the soft roller and the hard roller based on a change amount of the surface position detected by the detection means. apparatus. Two pairs of the hard roller and the soft roller that form the nip are arranged in the recording material conveyance path by reversing the positional relationship between the hard roller and the soft roller,
The control means is characterized in that an adjustment amount of an intrusion amount in the roller pair positioned upstream in the recording material conveyance direction is larger than an adjustment amount of the intrusion amount in the roller pair positioned downstream. The curl correction apparatus according to any one of claims 1 to 3.

Images