JP2002080158A - Curl correcting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a curl correcting system capable of surely and properly correcting the curl of a paper sheet even when curl correction based on a curl amount estimated by curl correcting devices is improperly performed due to the different conditions of sheets or the other different curling factor conditions and a change of curl correcting performance with the lapse of time. SOLUTION: The curl correcting system comprises the curl correcting devices 5A, 5B, curl amount measuring devices 7A, 7B for measuring the curl amount of the paper sheet after curl is corrected by the curl correcting devices, and a correction amount modifying means 8 for modifying a curl correction amount to be set based on the curling factor conditions by a correction amount setting means for the curl correcting devices, as required, in accordance with the curl amount after the curl correction measured by the curl amount measuring devices.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curl correction system for correcting curl (curved deformation) occurring on a sheet, and mainly has a process of fixing an image (toner image) on the sheet. The present invention relates to a curl correction system suitable for being applied to an image forming apparatus such as a printer, a printer, a facsimile, and a multifunction peripheral.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a printer using an electrophotographic technique, an electrostatic latent image formed on an image carrier such as a photoreceptor in accordance with image information is developed by a developer, and the developing is performed. Transferring the toner image obtained by the method directly onto paper or via an intermediate transfer member, and then fixing the toner image to the paper by passing the paper between a fixing heat roll and a pressure roll or a belt (pressing portion). , An image is formed, but a phenomenon in which the fixed paper is curved and deformed so as to warp upward (front side) or downward (back side), that is, a so-called curl occurs. In particular, such curling of the paper tends to occur more prominently due to an increase in the amount of toner on the paper and diversification of the type of paper (multiple types) due to colorization of the image. For this reason, in conventional image forming apparatuses, paper jams caused by such curling, reduction or disturbance of paper accommodation in a paper discharge unit, image quality deterioration due to poor transfer during double-sided image formation, and the like. For the purpose of avoiding the problem, there is a case where a curl correcting device for correcting the curl of the sheet generated after the fixing is used.

A curl correction device of this type employs, for example, a roll nip type curl correction mechanism composed of an elastic roll and a pressing roll that rotates while pressing the elastic roll to form a curved nip conveying section. And
Adopts a belt nip type curl correction mechanism consisting of a belt that is wound around the belt support roll and rotates, and a pressing roll that rotates while pressing the part between the support rolls of the belt to form a curved nip transport section. What is known is mainly. In such a curl correction device, any of the above-mentioned methods temporarily transports the fixed paper through a curved nip transport portion having a cylindrical curved shape between an elastic roll or a belt and a pressing roll. Then, the sheet is passed while being held while temporarily curving and deforming in the direction opposite to the direction in which the curl is generated, so that the sheet is corrected (corrected) so as to have no curl.

In such a curl correction device, the curl generated after fixing is determined by the conditions (size, basis weight, type, etc.) of the paper, the density of the image formed on the paper, and the temperature and humidity under the use environment. Since different results (states) occur due to differences in the curl generation factor conditions, the curl correction amount (curvature deformation degree) to be corrected by the curl correction device is adjusted according to predetermined parameters such as paper conditions and image density. (Japanese Unexamined Patent Publication No. Hei 6-144678,
-30712 publication). That is, in the above-described curl correction device, generally, the curl correction amount is adjusted by changing the pressing amount of a pressing roll for pressing an elastic roll or a belt, and the type of paper to be used, image density, The curl correction amount (the pressing amount of the pressing roll) is appropriately adjusted according to detection information such as humidity.

[0005]

However, in such a curl correction device capable of automatically adjusting the curl correction amount, the curl correction may not be performed properly. That is, the curl correction amount to be adjusted is based on the test data for the amount of curl generated on various types of paper with respect to the image density under each temperature and humidity condition, and is correlated in advance so as to match the predicted curl amount. Since the correction amount is the corrected amount, the curl correction based on the curl correction amount that is predicted and set when the paper type or the like changes due to the recent diversification of the paper type or the image density pattern diversifies and changes. In such a case, there is a problem that the curl cannot be sufficiently corrected, or a new curl is added due to excessive correction.

Conventionally, there has been proposed a curl correction device which detects the amount of curl at the leading end of a sheet discharged from a fixing device and adjusts the amount of curl for the sheet in advance based on the detected information. (JP-A-61-2654, JP-A-5-221574, JP-A-29697619, etc.). However, in such a curl correction device, the curl of the sheet after fixing is relatively large, and it is difficult to accurately measure the curl amount. Therefore, the curl correction amount based on the detection information is appropriately adjusted. In some cases, it is difficult to perform the curl correction properly. Further, even if the curl amount of the paper after the fixing can be accurately measured, the curl correction performance may change due to the component tolerance in the curl correction device or the wear of the components over time. May not work properly.

The present invention has been made in view of such circumstances, and a purpose thereof is to provide a paper curl correction system capable of more reliably and appropriately correcting (removing) paper curl. Is to provide.

[0008]

A curl correction system according to the present invention for achieving the above object holds a curled sheet while temporarily curving the sheet in a direction opposite to the direction in which the curl occurs. A curl correction mechanism that corrects the curl by passing the paper, an adjustment mechanism that adjusts the amount of curl correction by changing the degree of curl deformation of the curl correction mechanism with respect to the sheet, and a curl correction amount that is adjusted by the adjustment mechanism. And a curl correction device having a correction amount setting unit for setting a curl correction amount suitable for a curl amount predicted based on information of a curl generation factor condition including the curl correction factor. A curl amount measuring device for measuring the curl amount of the paper, and a curl correcting device based on the curl amount after the curl correction measured by the curl amount measuring device. It is characterized in being composed of the correction amount correction means for correcting, if necessary curl correction amount is set at a positive amount setting means.

Here, the number of the curl correction devices is not limited to one, and a plurality of curl correction devices may be used. As the curl correction mechanism in the curl correction device, for example, a roll nip type curl correction mechanism or a belt nip type curl correction mechanism as described in the description of the related art can be applied. Other configurations may be used.
Further, the curl occurrence factor conditions of the correction amount setting means in the curl correction device mainly include paper size, basis weight or type (coated paper, plain paper, etc.), image density, temperature and humidity, paper Conditions such as a transport mode until the sheet is sent to the curl correction device are exemplified.

The curl amount measuring device may be of any configuration as long as it can measure the curl amount of the paper after the curl correction by the curl correcting device. From the viewpoint of accurately grasping the result of the actual correction performed by the curl correction device, the vicinity is preferably downstream of the curl correction device in the sheet conveyance direction, but is not limited thereto. When a plurality of curl correction devices are used, the number of curl correction amount measurement devices corresponding to the number is used.

Further, the correction amount correcting means performs a test on the information of the curl amount after the curl correction in advance in accordance with the size of the curl amount, a condition of paper (eg, basis weight), a difference in image density, and other conditions. A suitable correction value of the curl correction amount obtained by the above is prepared as reference data, and the curl amount measured by the curl amount measurement device may be corrected according to the reference data if necessary. . In addition, it is preferable that the correction value in the case of the correction is stored in the storage means, and is used in the subsequent image forming operation under the same condition. The correction of the curl correction amount by the correction amount correction unit is performed, for example, on each sheet at the time of image formation, or the first sheet of paper in a series of image forming operations (jobs). Or a sheet in a predetermined order.

According to such a curl correcting device, the curl amount of the sheet after the curl correction by the curl correcting device is measured by the curl amount measuring device, and the correction amount correcting means based on the measured curl amount. The curl correction amount set by the correction amount setting means of the curl correction device is corrected as needed. As a result, when the curl correction based on the curl amount predicted by the curl correction device is not performed properly due to a difference in paper conditions or other curl generation factor conditions, or a change over time in curl correction performance. Even if there is, the actual state of curl correction on the paper after the curl correction is verified, the result is fed back and the curl correction amount is corrected as necessary, so that the curl correction after the correction is more appropriate Will be performed.

Such a curl correction system can be arbitrarily applied to an object requiring a paper curl correction. Further, for example, when the object is an image forming apparatus, the curl correction system is configured as a separate structure from the image forming apparatus, and is used by being detachably connected (coupled) to the image forming apparatus. Alternatively, it may be configured as a device that is incorporated as a part of the image forming apparatus and used in an integrated state.

[0014]

[Embodiment 1] FIG. 1 shows an image forming apparatus to which a curl correction system 3 according to Embodiment 1 of the present invention is applied. The curl correction system 3 is used in a state where it is integrally incorporated in a main body (housing) 10 of the image forming apparatus 1.

First, the image forming apparatus 1 forms a toner image according to image information (data), and transfers the toner image to a sheet P and then fixes the image.
And a paper feed system 4 for supplying a predetermined sheet P to the image forming system 2 and a curl correction system 3 for correcting a curl generated on the sheet P after fixing discharged from the image forming system 2. The installed printer and the like.

The image forming system 2 includes black (K),
Four image forming units 20K, 20Y, 20M, and 20C that form toner images of respective color components of yellow (Y), magenta (M), and cyan (C), and the respective image forming units 20K, 20Y, 20M, and 20C An intermediate transfer mechanism 30 for temporarily transferring the toner image formed by the above to the intermediate transfer body and then re-transferring the same to the sheet P, and a fixing device 37 for fixing the toner image transferred by the intermediate transfer mechanism 30 to the sheet P And the main part is constituted.

Each of the image forming units 20 forms a toner image by an electrophotographic process.
They are arranged at predetermined intervals in the horizontal direction. Also,
Each of the image forming units 20 is basically provided with a photosensitive drum 21 as an image carrier that is arranged to rotate in the direction of arrow A, and is arranged in the vicinity of the photosensitive drum 21 in a predetermined positional relationship. Charging device 22, latent image writing device 2
3, a developing device 24 and a transfer device 25. The charging device 22 is a roll type charging device, the latent image writing device 23 is a laser exposure device (ROS) that modulates the laser beam LB appropriately based on image data and exposes and scans the photosensitive drum 21, and the developing device 24. For example, a two-component developing system using a two-component developer composed of a toner composed of each color component and a carrier is used, and a roll-type charging device is used as the transfer device 25.

An intermediate transfer mechanism 30 includes an intermediate transfer belt 31 as an intermediate transfer member, and an arrow B in the direction of arrow B so as to support the intermediate transfer belt 31 and pass through the transfer position of the photosensitive drum 21 in each of the image forming units 20. The driving roller 32, the driven roller 33, and the backup roll 34 that rotate and run in a rotating manner, and a secondary transfer roll 35 that is disposed to face the backup roll 34 and constitutes a secondary transfer unit. The fixing device 37 has a schematic configuration including a heating roll 38 that is driven to rotate in a fixed direction, and a pressure contact belt 39 that is supported by a plurality of support rolls and rotated so as to press against the heating roll 38 to form a fixing nip portion. Have been. Reference numeral 36 in the figure denotes a double paper transport belt mechanism that transports the paper P after the secondary transfer on a transport belt to the fixing device 37.

The paper feed system 4 includes a plurality of paper feed trays 4 for storing paper P to be supplied to the image forming system 2.
0, 41, and 42, and a paper feed mechanism 43 for feeding the paper P one by one from each of the paper feed trays 40 to 42. In addition, the paper feed trays 40, 41, and 42 have
A paper type identification switch (reference numerals SW1 and SW in FIG. 6) for selecting and specifying the weight (basis weight) of the paper P stored in each tray.
2). Further, the paper feed system 4 may be configured so that the paper P can be supplied to the image forming system 2 from a manual feed tray (not shown) attached to the housing 10 as necessary.

In FIG. 1, a symbol R indicating a part of a chain line
Reference numeral 1 denotes a paper feed path for transporting the paper P sent from each paper feed tray to the secondary transfer unit of the image forming system 2. The paper feed path R1 includes a plurality of paper transport roll pairs 45 and a paper guide (not shown). It is composed of members (paper chute) and the like. In addition, reference numeral R2, which indicates a part of a one-dot chain line in FIG. 1, denotes a sheet P after fixing, which is discharged from the fixing device 37, via the curl correction system 3 (the curl correction device 5A thereof). Paper discharge path to transport
It is composed of a plurality of paper transport roll pairs 46 and a paper guide member (not shown). Reference symbol R3, which indicates a part of a dashed line, indicates a reversing path that is transported to reverse the front and back surfaces of the fixed sheet P discharged from the fixing device 37.
A switching pawl 47 for switching the transport path of the paper P, a plurality of paper transport roll pairs 48, and a paper guide member (not shown) are provided. Further, a symbol R indicating a part of a dashed line
Reference numeral 4 denotes a re-feeding path for feeding the sheet P whose front and back surfaces have been inverted by the reversing path R3 during double-sided image formation so that the sheet P is again fed into the sheet feeding path R1. It is composed of members and the like.

The curl correction system 3 according to the first embodiment is disposed in the middle of the paper discharge path R2, and is conveyed straight after fixing the paper discharge path R2 or in a state where it is reversed by the reverse path R3. First to correct curl of paper P
And a second curl which is disposed in the middle of the re-sending path R4 and corrects the curl of the sheet P which is conveyed after the image on the first side is formed during the double-sided image formation. Correction device 5B and first curl correction device 5A
A first curl amount measuring device 7A which is disposed on the paper discharge tray 44 on the downstream side of the sheet conveying direction and measures the curl amount of the use P after the curl correction by the curl correcting device 5A; The device P is disposed downstream of the device 5B in the sheet conveying direction and has a curl corrected by the curl correcting device 5B.
A second curl amount measuring device 7B for measuring the curl amount of
Based on the curl amount after the curl correction measured by the curl amount measurement devices 7A and 7B, the curl correction device 5
A correction amount correcting means 8 (see FIG. 6) for correcting the curl correction amounts set in A and 5B as necessary.

Among them, the first and second curl correction devices 5
Each of A and 5B has an upper curl correcting mechanism 50 for correcting curling upward, as shown in FIGS.
Lower curl correction mechanism 5 that corrects curl curled downward
1, a carry-in roll pair 57 for introducing the paper P into the correction device, and a switching pawl for switching the transport path so as to feed the introduced paper P to one of the first and second curl correction mechanisms 50 and 51. The main part is constituted by 58 and a carry-out roll pair 59 for discharging the paper P after the curl correction.

The upper curl correcting mechanism 50 and the lower curl correcting mechanism 51 are both of a belt nip type as shown in FIGS.
a and the belt 5 that rotates around the driven roll 52b
3 and a portion of the belt 53 between the rolls 52a and 52b, which is pressed by a predetermined amount and curved, and a nip transport portion N
And a pressing roll 54 that rotates while forming the image. As shown in FIG. 3, the pressing roll 54 is rotatably supported on a link member (not shown) serving as a displacement mechanism 60 that can be displaced in the direction of the double arrow. The link member is displaced in the direction of the arrow by rotation of an eccentric cam 62 as a cam mechanism via a cam follower 61 attached to a lower portion of the link member, whereby the movement amount of the pressing roll 54 is adjusted. Thus, the degree of the bending deformation of the belt 53 (corresponding to the curl correction amount) can be arbitrarily adjusted. Therefore, the displacement mechanism 60 functions as an adjustment mechanism for adjusting the curl correction amount.

In the curl correction devices 5A and 5B in which the curl correction mechanisms 50 and 51 are disposed in such a pair of upper and lower sides, the curl of the paper P that is transported and introduced into the respective correction devices 5A and 5B. Switching pawl 58 according to direction
Is switched, the sheet P having an upward (UP) curl in which the leading end and the rear end of the sheet are curved upward is sent to the upper curl correcting mechanism 50 side, and the downward (DOWN) curl in which the curl is curved downward. The sheet P on which the image is generated is sent to the lower curl correction mechanism 51 side. The curl correction devices 5A and 5B
In the above, the moving amount E of the pressing roll 54 is adjusted to a plurality of predetermined levels by the operation of the cam mechanism in the adjusting mechanism 60 (displacement mechanism) in accordance with the size of the curl generated on the sheet P conveyed and introduced. Accordingly, the curl correction amounts (levels) of the curl correction mechanisms 50 and 51 can be adjusted to a plurality of levels.

As shown in FIG. 4, the first curl amount measuring device 7A includes one or a plurality of first sheet detecting mechanisms 70 disposed on the device mounting side of the sheet discharge tray 44 and a substantially central portion thereof. And one or a plurality of second paper detection mechanisms 71 arranged in the first position. Each of the first sheet detecting mechanism 70 and the second sheet detecting mechanism 71 swings up and down around the support shaft 72a, and when the sheet P is not stored on the sheet discharging tray 44, When the paper P is stored on the paper output tray 44, the paper P is swung by a force such as a crane spring so as to be maintained in a state most protruded from the storage surface (a state shown by a solid line). A fan-shaped actuator 72 supported so as to swing downward (a state shown by a two-dot chain line) against the above-mentioned force in accordance with the weight, and a support shaft 72a of the actuator 72 A detection sensor 73 for detecting the presence / absence of minute detection holes 72b is provided on the opposite outer peripheral edge so as to be arranged in large numbers at equal intervals on a concentric circle.

In the first curl amount measuring device 7A, when the paper P is discharged and stored in the discharge tray 44,
The number of the detection holes 72b when the actuator 72 swings downward by the sheet P is detected, and the amount of movement of the actuator 72 is calculated. It can measure the height condition of That is, when the sheet P is in a flat state without curl, the actuator 72 swings downward and moves by a certain amount until the actuator 72 is buried in the sheet discharge tray 44 (does not protrude). Detection hole 72
With reference to the detected number b, the state of separation of the sheet P from the storage surface of the sheet discharge tray 44, that is, the curl state (amount) of the sheet P can be measured from the difference. Also, the first
The paper detection mechanism 70 is used to measure the curl amount α of the paper P on which the upward curl has occurred (see FIG. 10A), while the second paper detection mechanism 71 is used to measure the curl amount of the paper P on which the downward curl has occurred. It is configured to be used to measure the quantity β (see FIG. 10b).

On the other hand, the second curl correction device 5B
As shown in FIG. 5 and FIG. 5, the sheet transport roll pairs 74a and 74b and the sheet transport guide
5, one or a plurality of first sheet detecting mechanisms 70 arranged on the upstream side of the sheet conveying path, and one or a plurality of second sheet detecting mechanisms 71 arranged on the downstream side thereof.
It is provided with. The first sheet detection mechanism 70 and the second
Each of the sheet detection mechanisms 71 swings up and down around a support shaft 72a almost in the same manner as each of the detection mechanisms 70 and 71 in the first curl amount measuring device 7A, and the sheet P passes through the sheet conveyance path. When the sheet P is conveyed and not passed, or when the sheet P without curl is conveyed and passed, a crane spring or the like is provided so as to be maintained in the sheet conveying path from the notch portions 75a and 75b of the sheet conveying guide member. When the curled sheet P is conveyed into the sheet conveying path and passes through the sheet P, the sheet P is swung upward or downward against the disturbing force by the curled portion of the sheet P. An actuator 72 having a fan-shaped projection 72c supported so as to be movable, and an outer peripheral edge opposite to the projection 72c of the actuator 72 on a concentric circle. It is composed of a detection sensor 73 for detecting the presence or absence of minute the detection hole 72b which is opened in a state as arranged number at intervals. In FIG. 5, reference numeral 76 denotes a swing guide bar for guiding the sheet P passing through the notches 75a and 75b of the sheet transport guide member, which is provided by an electric motor and a rotation transmission mechanism (gear mechanism or belt mechanism) (not shown). With this driving force, for example, it swings around the support shaft 72a. Reference numeral 77 is
A sheet detection sensor for detecting the passage of the rear end of the sheet P conveyed in the sheet conveyance path, and based on the detection information, the swing guide bar 65 causes the notch portions 75a, 75b of the sheet conveyance guide member to be moved. It swings to the position where it has been withdrawn from.

In the second curl amount measuring device 7B, when the sheet P is conveyed to the sheet discharge tray 44 through the re-sending path R4 and passes through the sheet conveying path, the actuator 72 is moved by the rear end of the sheet P. The number of detected holes 72b when swinging upward or downward is detected, whereby the amount of movement of the actuator 72 is calculated, and from the result, the curved height state of the paper P with respect to the paper transport path can be measured. It has become. In other words, when the paper P is in a flat state without curl, the actuator 72 remains stopped at a fixed position in the paper transport path without being rocked by the paper P. By detecting the number of detections of the detection holes 72b when the paper P is swung from above, the curved (warped) state of the paper P, that is, the curl state (amount) of the paper P can be measured. The first paper detection mechanism 70 is used to measure the curl amount α of the paper P on which upward curl has occurred (see FIG. 11B).
The second sheet detection mechanism 71 is configured to be used to measure the curl amount β of the sheet P on which curl has occurred downward (see FIG. 11C).

FIG. 6 is a block diagram showing a main configuration of a control system related to the curl correction system 3 in the image forming apparatus.

Reference numeral 12 in FIG. 6 denotes this image forming apparatus 1
It is a central controller (system controller) that comprehensively controls the entire operation, and is composed of an arithmetic processing unit (CPU), memories (ROM, RAM), and the like. The central controller 12 performs predetermined image processing of image information input from a document reading device (scanner) or an externally connected device (such as a personal computer), and sends the image information to the image forming system 2. The control unit 14 of the image forming and fixing system for controlling the operations of the image forming units 20 and the fixing device 37 of the image system 2, the sheet feeding mechanism 43 of the sheet feeding system 4, and the sheet conveying roll pairs of the conveying paths R1 to R4. And a control device 15 of a paper feed conveyance system for controlling each operation such as a switching pawl,
A control device 65 of a curl correction system for generally controlling each operation of the curl correction system 3 is connected.

The central controller 12 has a temperature / humidity sensor 27 for detecting the ambient temperature and relative humidity of the paper feed tray 40 and the like of the paper feed system 4 and a display including a liquid crystal panel for displaying desired information. A device 16 and an input device 17 provided with various input keys (switches and buttons) for inputting and selecting and setting predetermined information are connected. Among them, the display device 16 and the input device 17 are mainly used when instructing each operation of the image forming apparatus 1 or changing settings. The display device 16 and the input device 17 are not limited to those having separate and independent configurations as shown in the figure, but may be configured integrally.

The control unit 15 of the paper feed system selects the basis weight and the type (selection of coated paper or plain paper) of the paper P disposed in each of the above-mentioned paper trays. The switches SW1 and SW2 are connected so that information on the switches SW1 and SW2 to be designated is input.

Further, the control device 65 of the curl correction system includes a rotational drive (start and stop of rotation and rotation of the drive roll 52a of the upper curl correction mechanism 50 and the lower curl correction mechanism 51 in the above-described curl correction devices 5A and 5B. A rotation controller 520 for controlling speed adjustment and the like, and a switching controller 5 for controlling the switching operation of the switching pawl 58.
80 and the eccentric cam 6 in the adjusting mechanism 60 for adjusting the moving amount of the pressing roll 54 (corresponding to the curl correction amount).
2 is connected to a displacement system controller 540 for controlling the rotation drive. Further, the control device 65 of the curl correction system
Incorporates a recording device in which control information (programs and parameter tables) in the drivers 520, 580, and 540 is recorded. Incidentally, the control information in each of the drivers 520, 580, 540 may be stored in the memory of the central control device 12. Further, the control device 6 of the curl correction system
5 is connected to a control device 8 of a curl measuring system for controlling each operation of the curl amount measuring devices 7A and 7B.

The paper detection sensor 77 is connected to the control device 8 of the curl measurement system, and detects the passage of the rear end of the paper P conveyed in the paper conveyance path of the second curl amount measurement device 7B. The detected information is input.
The control unit 700 (71) controls the detection sensors 73 that measure the curl amount in the first paper detection mechanism 70 and the second paper detection mechanism 71 of each of the curl amount measurement devices 7A and 7B.
0) and is connected to the detection sensor 7 of each detection mechanism.
3, the detection information on the curl amount after the curl correction is input. Further, it is connected to a drive control unit 760 that controls a drive unit of the swing guide bar 76 in the second sheet detection mechanism 71. Then, the control device 8 of the curl measuring system includes the curl amount measuring devices 7A and 7A.
When it is determined that it is necessary to correct the curl correction amount set by the curl correction system control device 65 based on the information on the curl correction amount after the curl correction is measured and input in B, the curl correction amount is determined. The correction value is transmitted to the control device 65 of the curl correction system.

The curl correction devices 5A and 5B
In the control device 65, the curl correction amount by each of the curl correction mechanisms 50 and 51 is determined based on the type (basis weight) of the sheet P, image density, humidity, and transport mode (strade discharge mode, reverse discharge mode, double-sided image, It can be set in accordance with parameter information such as the formation transport mode). In this embodiment, in view of the fact that the amount of curl generated on the paper P tends to be different depending on the type of curl, such as the type, image density, temperature and humidity, and the form of paper conveyance, the curl amount used in the image forming apparatus 1 For each type (basis weight) of the paper P for which is predicted, an appropriate curl correction amount (level) according to each condition of the image density, temperature, humidity, and conveyance mode is experimentally checked, and the result is determined based on the curl correction amount. It is created in advance as decision information (parameter table) and stored in the storage means. In performing such automatic control of the curl correction amount, the type of the paper P as a parameter is determined by the paper type identification switches SW1 and SW1 disposed on the paper feed trays 40 to 42 described above.
The information obtained from the SW2 is used, the information obtained from the image processing device 13 is used for the image density, and the information obtained from the temperature and humidity sensor 27 is used for the temperature and humidity. ing.

In the curl correction system 3, when it is necessary to correct the curl correction amount set by the curl correction system control device 65 by the curl measurement system control device 8, the curl correction amount is changed. It is supposed to be fixed.

FIG. 7 shows the curl amount after curl correction measured by the curl amount measuring devices 7A and 7B and the correction value of the curl correction amount according to the curl amount (each curl correction mechanism 5).
(Corresponding to a level corresponding to the amount of movement of the pressing roll 54 at 0 and 51). FIG. 7A shows the relationship between the upward curl amount and the correction value when the upward curl remains after the curl correction, and FIG. 7B shows the relationship between the downward curl amount and the correction value when the downward curl remains. Is shown. FIG.
Are classified into differences between the basis weight (gsm) of the paper P and the image density ratio (%). The image density is (image count value of each full color / A
Maximum image count value for 3 plate paper) × ｛(29
7 × 420) / paper size｝ × 100. The image count value is the sum of the gradation values for each pixel. As is apparent from the data shown in FIG. 7, even when the curl amount after the curl correction is measured, it may not be necessary to correct the curl correction amount.

Then, in the control device 8 of the curl measuring system,
The correction value of the curl correction amount corresponding to the curl amount after the curl correction measured by each of the curl amount measurement devices 7A and 7B is determined based on the data shown in FIG. The determined correction value of the curl correction amount is stored in the storage unit of the control device 65 of the curl correction system, and is reflected in the curl correction value at the time of curl correction in the image forming operation executed under the same conditions, which is performed thereafter. It is supposed to be.

Next, the basic operation of the image forming apparatus will be described.

First, in this image forming apparatus 1, when a condition setting or an instruction for executing image formation is input,
Image information is input from a document reading device or an externally connected device connected to the image forming apparatus 1, and an image forming operation (printing) is performed according to the image information and conditions. Here, a case where a full-color image is formed is exemplified.

That is, after color image information input from the outside is subjected to predetermined image processing by the image processing device 13,
When the image signal is sent to the image forming system 2 as an image signal separated into colors, in each image forming unit 20 of the image forming system 2, the latent image writing device is charged on the photosensitive drum 21 uniformly charged by the charging device 22. 23, a laser beam LB based on the image signal is scanned and exposed to form an electrostatic latent image. Subsequently, the latent image is developed with a developer of a predetermined color component supplied from a developing device 24 to form an electrostatic latent image. Of the toner image. Thereby, four color toner images of yellow, magenta, cyan, and black are individually formed on each photosensitive drum 21. Next, the toner images of the four colors are electrostatically primary-transferred so as to be superposed on the surface of the intermediate transfer belt 31 passing between the photosensitive drum 21 and the transfer device 25, and then the rotation of the belt 31 is performed. Due to the movement, the sheet is conveyed to a secondary transfer section facing the secondary transfer roll 35.

On the other hand, in the paper feeding system 4, the image forming system 2 is synchronized with the image forming process described above,
The sheet P of the type specified at the time of the image formation is sent out from the sheet feed tray (any one of 40 to 42) stored by the sending mechanism 43, and is conveyed to the secondary transfer unit via the sheet feed path R1. Is done.

The toner image on the intermediate transfer belt 31 of the image forming system 2 is secondarily electrostatically transferred to a sheet P fed to the secondary transfer portion. The sheet P after the secondary transfer of the toner image is transferred to a sheet conveying belt mechanism 3.
6, the toner image is heated and pressurized and fixed by passing through a belt nip portion between the heating roll 38 and the pressure belt 39 in the fixing device 37. Next, the sheet P after fixing is sent to the conveyance path R2 during one-side printing, and is sent to the reversing path R3 when the sheet is inverted and discharged with the image forming surface facing down (face down state) and when both sides are printed. Can be However, no matter which transport pattern is used, the first curl correction device 5A that is ultimately in the middle of the paper discharge path R2 is used.
And is discharged to the discharge tray 44. Further, the sheet P after the image formation on the first side in the two-sided image forming operation is
The second curl correction device 5 is retransmitted through the retransmission path R4.
The sheet passes through B and is sent to the sheet feeding path R1. The curl of the sheet P sent to the first curl correcting device 5A or the second curl correcting device 5B in this manner is corrected by each curl correcting device.

Next, the operation of the curl correction system 3 applied to the image forming apparatus 1 will be described with reference to FIGS.

First, as described above, when a condition setting for an image forming operation (printing) and a command to start the printing operation are made in the input device 16 or the like (step 10:
S10) The curl correction system control device 65 sends the information on the curl generation factor conditions such as the size and basis weight of the paper P, image density, temperature and humidity, and the paper transport mode (mode) to the central control device 12.
(S11). At this time, it is determined whether the data of the correction value of the curl correction amount obtained in the previous image forming operation is in the storage unit of the control device 65 (S12). The value is read out to the control device 65 (S13).

Subsequently, the control device 65 of the curl correction system controls the correction mechanism 5 of each of the curl correction devices 5A and 5B based on the information on the curl generation factor condition and the read correction value.
The curl correction amount (including the correction direction) at 0 (51) is determined (S14). Based on the determined curl correction amount, the pressing roll 54 of the correction mechanism 50 (51) of each of the curl correction devices 5A and 5B is displaced to a predetermined position (level) corresponding to the curl correction amount by the adjustment mechanism 60. Is adjusted (S15). After the adjustment of the curl correction amount, the sheet P is sent to one of the curl correction devices 5A and 5B and is subjected to the curl correction mechanism 50 (51).
, The type and image density of the paper P,
The curl correction based on the curl correction amount set according to the humidity or the like is executed (S16).

For example, the first curl correction device 5A or the second
In the curl correction device 5B, when the sheet P to be fed is predicted to have an upward curl, the switching pawl 58 is switched to a direction in which the sheet P is fed to the upper curl correction mechanism 50 side. The cam mechanism of the adjustment mechanism 60 in the curl correction mechanism 50 is
The pressing roll 54 is driven to rotate by a predetermined angle corresponding to the position so that the predicted curl amount is displaced to a position of a level to be corrected. As a result, the paper P that has entered each curl correction device is sent to the upper curl correction mechanism 50 by the path switching action of the switching pawl 58 on the downstream side of the introduction roll pair 57, and is bent by the pressing roll 54 and the pressing roll 54. The belt 53 is caused to pass through a belt nip portion that has become a curved conveyance path between the deformed belts 53. As a result, the paper P is temporarily curved and deformed in the downward direction at the predetermined curl correction level, and as a result, upward curl generated on the paper P is corrected.

The sheet P having been subjected to the curl correction in this manner is subjected to the curl correction devices 5A, 5A by the discharge roll pair 58.
It is discharged from B. At this time, the sheet curled by the first curl correction device 5A is discharged and stored in the discharge tray 44 via the discharge path P2. Further, the sheet P curled by the second curl correcting device 5B is re-sent to the sheet feeding path R1 via the re-sending path R4, and is used for image formation on the second side.

The paper P, which has been subjected to the curl correction by the first curl correction device 5A or the second curl correction device 5B, is placed on the first curl amount measuring device 7A or the first (2) The curl amount after the curl correction is measured by the curl amount measuring unit 7B.

First, as shown in FIG. 8, it is determined whether or not the sheet P subjected to the curl correction by the first curl correcting device 5A is the first print (S17).
If it is the first print sheet P, the discharge tray 44
The curl amount after curl correction is measured by the first curl amount measuring device 7A when the paper is ejected and stored in the printer (S18). Incidentally, when the curl-corrected sheet P is the second or subsequent sheet, the curl amount of the second and subsequent sheets cannot be measured due to the configuration of the first curl amount measuring device 7A. No measurement is made.

At this time, the curl amount is measured by the first curl amount measuring device 7A as follows. That is,
As shown in FIG. 10A, when the sheet P to be measured is a sheet P (U) having an upward curl, the sheet P
Of the second sheet detecting mechanism 71 that touches the center of the sheet P swings downward by the weight of the sheet, while the upwardly warped end of the sheet P (rear part in the discharge direction) touches. The actuator 72 of the first sheet detection mechanism 70 swings downward by the weight given by touching the sheet, and as a result, the movement amount due to the swing of each actuator 72 is detected by the detection sensor 73. Is detected. As a result, the difference between the movement amounts of the actuators 72 in the two sheet detection mechanisms 70 and 71 is measured as the curl amount α of the sheet P (U) having an upward curl. On the other hand, as shown in FIG. 10B, when the sheet P to be measured is the sheet P (D) having a downward curl, the downwardly warped end of the sheet P (the rear part in the discharge direction) touches. While the actuator 72 of the first paper detection mechanism 70 swings downward due to the weight of the paper, the actuator 72 of the second paper detection mechanism 71 touches the center of the paper P. As a result, the amount of movement of each actuator 72 due to the swing is detected by the detection sensor 73. Thereby, the difference between the movement amounts of the actuators 72 in the two sheet detection mechanisms 70 and 71 is measured as the curl amount β of the sheet P (D) having the downward curl.

It is determined whether the curl amount measured by the first curl amount measuring device 7A needs to be corrected based on the data shown in FIG. 7 (S19). If it is necessary, the correction value is determined, and the information of the correction value is transmitted to the control device 65 and stored in the storage means (S20). After this,
This is repeated until the printing by the image forming apparatus 1 is the last one. Then, in the curl correction performed by the first curl correction device 5A at the time of printing executed thereafter, the correction value determined in step S20 is reflected when the curl correction amount is determined in step S14. As a result, the paper P that has been subjected to the curl correction by the first curl correction device 5A using the corrected curl correction amount is subjected to a proper curl correction compared to before the correction by the correction of the curl correction amount. The correction is made more reliably.

On the other hand, unlike the case of the first curl amount measuring device 7A (FIG. 8), the sheet P curled by the second curl correcting device 5B is, as shown in FIG. The second curl amount measuring device 7B, one by one.
, The curl amount after the curl correction is sequentially measured (S2).
8). However, if necessary, the curl amount of a part of the paper P may be measured by the second curl amount measuring device 7B.

The curl amount measurement by the second curl amount measuring device 7B at this time is performed as follows. That is,
First, in the second curl amount measuring device 7B, the paper guide bar 76 is closed so as to be located within the cutout portion 75a of the paper transport path (the state shown by the solid line in FIG. 5). The paper P conveyed by the pair of paper conveying rolls 74a into the inside smoothly advances without being caught by the notch 75a. Thereafter, when the trailing edge of the sheet P is detected by passing through the sheet detection sensor 77, as shown in FIG.
Swings so as to be located at a position retracted from the notch portion 75a of the sheet transport path, and becomes an open state. Then
As shown in FIG. 11B, when the sheet P to be measured is a sheet P (U) having an upward curl, the sheet P
The actuator 72 of the first sheet detecting mechanism 70, which comes into contact with the upwardly warped rear end, swings upward due to the warped rear end of the sheet, and as a result, the actuator 72 swings. The amount of movement by the detection sensor 73
Is detected by. At this time, the actuator 72 of the second sheet detection mechanism 71 is not swung by the sheet P. Thereby, the movement amount of the actuator 72 in the first sheet detection mechanism 70 is measured as the curl amount α of the sheet P (U) having the upward curl. On the other hand, as shown in FIG. 11C, the paper P to be measured is a paper P having a downward curl.
In the case of (D), the downwardly warped rear end of the sheet P comes into contact with the actuator 72 of the second sheet detection mechanism 71, and the actuator 72 swings downward due to the warped rear end of the sheet. As a result, the movement amount due to the swing of the actuator 72 is detected by the detection sensor 73. At this time, the actuator 72 of the first sheet detection mechanism 71 is not swung by the sheet P. Thus, the amount of movement of the actuator 72 in the second sheet detection mechanism 71 is measured as the curl amount β of the sheet P (D) having a downward curl.

The curl amount measured by the second curl amount measuring device 7B needs correction of the curl correction amount based on the data shown in FIG. 7, similarly to the case of the first curl amount measuring device 7A. Is determined (S2).
9) If necessary, the correction value is determined, and the information on the correction value is transmitted to the control device 65 and stored in the storage means (S30). Thereafter, the printing by the image forming apparatus 1 is repeated until the last print. Then, in the curl correction performed by the second curl correction device 5B at the time of printing executed thereafter, the correction value determined in step S30 is reflected when the curl correction amount is determined in step S14. As a result, the paper P that has been subjected to the curl correction by the second curl correction device 5B using the corrected curl correction amount is subjected to a proper curl correction compared to before the correction by the correction of the curl correction amount. Correction is assured.

[Other Embodiments] FIG. 12 shows another configuration example of the first curl amount measuring device 7A in the curl correction system 3. This first curl amount measuring device 7A
A plurality of reflection type detection sensors 78 are vertically arranged on the vertical wall surface of the paper discharge tray 44 on the device mounting side, and the rear end side of the paper P stored in the paper discharge tray 44 in the discharge direction is a tray. Soft pad 79a to be pressed against the housing side
Is provided with a paper pressing roll 79 attached to the outer peripheral surface.

In the first curl amount measuring device 7A, when the paper P after the curl correction by the first curl correction device 5A is stored in the discharge tray 44, the paper P is curled (FIG. 12). In FIG. 12, the light emitted from the reflection type sensor 78 is blocked and reflected and detected by the curl as shown in FIG. The curl amount is measured by the number of the sensors 78. Also,
When the measurement of the curl amount is completed, as shown in FIG. 13, the paper pressing roll is rotated half a turn, so that the soft pad 79 a presses the end of the paper P downward and presses the paper P onto the receiving surface of the paper discharge tray 44. It is configured to be kept in a distorted state (b in the figure). Thus, the measurement of the curl amount for the next sheet P is not hindered. Also,
In the first curl amount measuring device 7A, it is possible to measure the curl amount of all the sheets P stored in the paper discharge tray 44, but after the measurement, the paper P is stacked and stored on the paper discharge tray 44. Then, a process of subtracting the height corresponding to the number of sheets of paper P from the measured value of the curl amount to eliminate the influence of the paper stacking height. When the first curl amount measuring device 7A is applied, the curl amount is measured on the first sheet of paper P in the same manner as in the case of the second curl amount measuring device 7B (see FIG. 9). It can be performed for all things without limitation.

FIG. 14 shows another example of the configuration of the second curl amount measuring device 7B in the curl correction system 3. The second curl amount measuring device 7B is different from the structure of the first and second sheet detection mechanisms 70 and 71 by the actuator 72 and the detection sensor 73, and the height of the object is determined by the difference in the reflection angle of the irradiated laser light. The first and second paper detection mechanisms 70 with a height sensor 80 capable of measuring (distance),
71.

Then, in the second curl amount measuring device 7B, as shown in FIG. 15, the sheet P after the curl correction by the second curl correcting device 5B is sent to the sheet conveying path, and the trailing end thereof is moved. When the sheet is detected by the sheet detection sensor 77, the sheet P is opened after the sheet guide bar 76 is opened.
When the paper P has an upward curl, when the rear end of the paper P having the upward curl passes through the first paper detection mechanism 70, the rear end (position) of the upwardly warped paper is at a height. Since it is detected by the sensor 80, the upward curl amount is measured thereby (FIG. 15A).
On the other hand, if the paper P has curl downward,
As shown in FIG. 2B, when the rear end of the sheet P having a downward curl passes through the second sheet detecting mechanism 71, the downwardly warped sheet rear end (position) is detected by the height sensor 80. Therefore, the downward curl amount is thereby measured.

FIG. 16 shows another configuration example of the second curl amount measuring device 7 B in the curl correction system 3. In the second curl amount measuring device 7B, a paper transport path formed by a pair of paper transport rolls 74a and 74b and a paper guide member 75 is formed so as to extend in the vertical direction, and a cutout portion 75a of the paper guide member is formed. , Actuator 72
And first and second paper detection mechanisms 70 and 71 each including a detection sensor 73. Reference numeral 81 in the figure denotes an electric motor serving as a drive source for the swing operation of the paper guide bar 76, and reference numeral 82 denotes a rotation transmission gear mechanism for transmitting the driving force of the electric motor 71 to each paper guide bar 76.

According to the second curl amount measuring device 7B, the paper P is held vertically when the curl amount is measured by the first and second paper detecting mechanisms 70 and 71, and the rear end of the paper P is Since the effect of unnecessary movement of the actuator 72 due to its own weight can be eliminated, more accurate measurement of the curl amount can be performed.

FIG. 17 shows another example of the configuration of the second curl amount measuring device 7B in the curl correction system 3. The first and second curl amount measuring devices 7B shown in FIG.
16 except that the first and second sheet detecting mechanisms 70 and 71 are configured by the height sensor 80 described above, instead of the configuration of the sheet detecting mechanisms 70 and 71 of FIG. It has the same configuration as the above. Also in this case, there is an advantage that the curl amount can be measured more accurately, as in the case of the curl amount measuring device 7B shown in FIG.

FIG. 18 shows another configuration example of the second curl amount measuring device 7 B in the curl correction system 3. In the second curl amount measuring device 7B, a sheet conveying path which forms a part of the re-sending path R4 is constituted by a belt conveying device including a belt supporting roll 84 and a belt 85, and the sheet when it is placed on the belt 85 The height sensor 80 for measuring the curl amount of P is provided.

[0064]

As described above, according to the curl correction system of the present invention, the curl correction based on the amount of curl predicted by the curl correction device can be performed with a difference in paper conditions and other curl generation factor conditions, and further with a curl correction. Even if correction may not be performed properly due to changes in correction performance over time,
Since the curl correction amount is corrected as needed, the curl of the sheet can be more reliably and appropriately corrected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a main part of an image forming apparatus to which a curl correction system according to a first embodiment is applied.

FIG. 2 is a schematic diagram showing a configuration of each curl correction device in the curl correction system.

FIG. 3 is a schematic diagram illustrating a configuration of a curl correction mechanism of the curl correction device.

FIG. 4 is a schematic diagram showing a first curl amount measuring device.

FIG. 5 is a schematic diagram showing a second curl amount measuring device.

FIG. 6 is a block diagram illustrating a main configuration of a curl correction system and a control system of the image forming apparatus.

FIG. 7 is a graph showing a correlation (data) between a curl amount after curl correction and a correction value of the curl correction amount.

8 is a flowchart showing a curl correction amount correcting operation of the curl correction system when the first curl amount measurement device shown in FIG. 4 is used.

FIG. 9 is a flowchart showing an operation of correcting the curl correction amount of the curl correction system when the second curl amount measurement device (or the first curl amount measurement device shown in FIG. 12) is used.

FIG. 10 is a schematic diagram showing a measurement state of the first curl amount measurement device shown in FIG.

11 is a schematic diagram showing a measurement state of the second curl amount measurement device shown in FIG.

FIG. 12 is a schematic diagram showing another configuration example of the first curl amount measuring device.

FIG. 13 is a schematic diagram showing a measurement state of the first curl amount measurement device shown in FIG.

FIG. 14 is a schematic diagram showing another configuration example of the second curl amount measuring device.

15 is a schematic diagram showing a measurement state of the second curl amount measurement device shown in FIG.

FIG. 16 is a schematic diagram showing another configuration example of the second curl amount measuring device.

FIG. 17 is a schematic diagram showing another configuration example of the second curl amount measuring device.

FIG. 18 is a schematic diagram showing another configuration example of the second curl amount measuring device.

[Explanation of symbols]

3: Curl correction system, 5A, 5B: Curl correction device, 7A, 7B: Curl amount measurement device, 8: Curling measurement system control device (correction amount correction means), 50, 51: Curl correction mechanism, 60: Displacement mechanism (Adjustment means), 65th control device for curl correction system (correction amount setting device), P: paper, α,
β: curl amount after curl correction.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hideo Kinugi 2274 Hongo, Ebina-shi, Kanagawa Prefecture, within Fuji Xerox Co., Ltd. (72) Inventor Kei Iwasaka 2274 Hongo, Ebina-shi, Kanagawa Prefecture, within Fuji Xerox Co., Ltd. F term (reference) 3F053 HB01 HB09 HB24 LA02 LA05 LA07 LB03

Claims (1)

[Claims] A curl correction mechanism for correcting a curl by holding and passing a curled sheet while temporarily curving the sheet in a direction opposite to the direction in which the curl occurs, and a sheet of the curl correction mechanism. And an adjustment mechanism for adjusting the amount of curl correction by changing the degree of curl deformation, and adjusting the amount of curl correction by the adjustment mechanism to the amount of curl predicted based on information on the curl occurrence factor condition including the paper condition. A curl correction device having a correction amount setting means for setting a curl correction amount; a curl amount measurement device for measuring a curl amount of the paper after the curl is corrected by the curl correction device; and a curl amount measurement device. Based on the measured curl amount after the curl correction, a correction amount correction for correcting the curl correction amount set by the correction amount setting means of the curl correction device as necessary. Curl correction system, characterized in that it consists of a unit.