JP2002068558A - Curl correcting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely and properly correct curl without causing a sheet jam and a damage load to sheet by the occurrence of a difference between a sheet carrying speed in a nip part of a nip mechanism and a sheet carrying speed by a sheet carrying means for carrying the sheet even when a sheet related condition such as a kind of the sheet and the image density is different including a condition of a pressing-down position of a pressing roller in the nip mechanism in a curl correcting device having the curved nip mechanism. SOLUTION: A control means is arranged for adjusting a rotating speed of an elastic rotary body composed of a belt or an elastic roller of the curved nip mechanism according to the sheet related condition and the condition of the pressing-down position of the pressing roller in the nip mechanism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curl correction device for correcting curl (curvature deformation) occurring on paper, and mainly relates to a copier, a printer, and a printer having a process for fixing an image on paper. The present invention relates to a sheet curl correction device suitable for application to an image forming apparatus such as a facsimile, a multifunction peripheral, or the like.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus using an electrophotographic technique, an electrostatic latent image formed on an image carrier such as a photoreceptor in accordance with image information is developed with a developer, and obtained by the development. After the transferred toner image is transferred directly to a sheet or via an intermediate transfer member, the sheet is fixed to the sheet by passing the sheet between a fixing heating roll and a pressure roll or a belt (pressing portion) to form an image. However, a phenomenon in which the fixed paper is curved and deformed so as to warp to the front side or the back side, that is, a so-called curl occurs. For this reason, some conventional image forming apparatuses avoid problems such as paper jams caused by such curling, bulkiness and disturbance in storage in a paper discharge unit, and deterioration in image quality during double-sided image formation. For the purpose, a curl correcting device for correcting the curl of the sheet generated at the time of fixing may be used.

As this type of curl correction device, for example, an elastic roll (a roll having a structure in which an elastic layer is formed on a roll shaft) driven by rotation and (an elastic layer of) the elastic roll
That adopts a roll nip mechanism composed of a pressing roll that is driven and rotated while forming a curved nip portion by pressing the belt, a belt that is driven around two or more belt supporting rolls and is driven to rotate, and a supporting roll for the belt 2. Description of the Related Art A belt nip mechanism including a pressing roll that is driven and rotated while forming a curved nip portion by pressing an intervening portion is mainly known. In any of such curl correction apparatuses, the paper after the fixing step is transported temporarily through a curved nip portion between an elastic roll or a belt and a pressing roll, and the paper is curled. In a direction opposite to the direction, the paper is temporarily deformed and held in a curved shape along the pressing roll surface, and is conveyed so as to be corrected (corrected) in a curl-free state.

Further, in such a curl correction apparatus, the curl generated after fixing is different depending on the type of paper, the density or density of an image formed on the paper, the use environment humidity, and the like (curl state). The curl correction amount to be corrected by the curl correction device is adjusted according to predetermined parameters such as the type of paper and the image density (Japanese Patent Laid-Open No. Hei 6-115791). That is, in the above-described curl correction device, generally, a pressing roll that presses against an elastic roll or a belt is displaceably provided, and the curling correction amount can be adjusted by changing the pressing position of the pressing roll and changing the pressing amount. Paper type, image density,
The curl correction amount is controlled so as to be appropriately changed according to detection information such as humidity.

[0005]

However, in such a curl correction device, the following problems arise because the pressing position of the pressing roll is changed to change the curl correction amount. is there.

First, FIG. 10 shows a main part of a curl correction device employing the above-described belt nip mechanism. In the figure, reference numeral 110 denotes a belt nip mechanism, 1
Reference numeral 20 denotes a belt constituting the belt nip mechanism 110;
Reference numeral 0 denotes a pressing roll that is displaceable in the direction of the arrow constituting the belt nip mechanism 110, 140 denotes a belt supporting roll that supports and rotates the belt 120, and 150 drives and rotates in the direction of the arrow by supporting the belt 120. The belt driving rolls 160 and 170 are a pair of paper transport rolls disposed before and after the belt nip mechanism 110.

In such a curl correction device, the paper P to be curled is corrected by the paper transport roll pair 16.
0, 170, the nip portion N of the belt nip mechanism 110
Is conveyed through the nip portion N, so that the paper P is temporarily deformed and held in a curved shape at the nip portion N. As a result, the curl is corrected. As described above, when the curl correction amount is adjusted by changing the pressing amount, the paper P conveyed through the nip portion N (although the rotation speed of the belt 120 does not vary) depending on the pressing position of the pressing roll. the actual transport speed S _p varies, thereby the sheet conveying speed S _a in the sheet conveying speed S _p and the preceding and succeeding sheet transport rolls 160 and 170 at the nip portion N, a speed difference between the S _B occurs Therefore, the paper P may be jammed in the belt nip mechanism 110 or may be forcibly pulled by the nip portion N or the paper transport roll pair 170. There has been a problem that receive the image.

That is, during normal operation, the belt nip mechanism 1
Sheet conveying speed in 10 of the nip portion N S _p and the paper conveying roller pair 160 and 170 by the sheet conveyance speed S _A, S _B
Is the same and, by the difference in pressing position of the pressing roll 130, for example, the pressing amount is large, the sheet conveying speed S _p at the nip portion N is the paper conveying roller pair 16
Each sheet conveying speed S _A by 0, 170, faster than S _B (abnormal 1), the less the pressing amount Conversely, according to the sheet conveying roller pair 160 and 170 than the paper conveying speed S _p in the nip N Each of the sheet transport speeds S _A and S _B tends to be slow (abnormality 2).

Further, such a belt nip mechanism 110
Variation of the sheet conveying speed S _p at the nip portion N of the curling subject to conditions of the paper P (thickness, paper type, size, etc.) and, similarly occurs by the density of the image formed on the sheet P In some cases, as a result, problems such as paper jam and paper damage due to the speed difference as described above may occur. Such a variation in the sheet conveying speed S _p, as illustrated in FIG. 11, during passage of the rush or during the nip N to the nip portion N of the belt nip mechanism 110 of the sheet P, the type of the sheet P It is presumed that the difference between the image density and the image density is caused by some influence on the behavior of the sheet and the sheet conveying force (action) of the nip portion N.

The present invention has been made to solve such a problem, and more specifically, a pressing position of a pressing roll in a nip mechanism such as a belt nip mechanism or a roll nip mechanism for adjusting a curl correction amount. Even if the conditions related to the paper, such as the type of paper and the image density, are different, the paper transport speed at the nip portion of the nip mechanism and the transport of the paper so as to pass through the nip portion It is an object of the present invention to provide a curl correction device in which a difference from a sheet conveyance speed of a sheet conveyance unit does not occur and a paper jam or a damage load on a sheet is not induced.

[0011]

According to the present invention, there is provided a curl correction device which is capable of achieving the above-mentioned object. A curling nip mechanism composed of a pressing roll forming a portion, and a paper conveying rotator disposed at front and rear positions of the curving nip mechanism to hold and convey the paper and to convey the paper to be subjected to the curl correction to the paper In a curl correction device for correcting the curl of a sheet by conveying the nip portion of the curved nip mechanism so as to pass through the nip portion of the curved nip mechanism, the rotation speed of the elastic rotator of the curved nip mechanism is controlled by the condition of the pressing position of the pressing roll And control means for adjusting according to conditions relating to paper.

Here, the conditions relating to the paper include the conditions (direct factors) of the paper itself which affect the speed at which the paper is actually transported (paper transport speed) in the nip portion of the curved nip mechanism, and the indirect effects on the paper. Conditions (indirect factors), such as paper thickness, paper type (particularly the type of coated paper and plain paper) or size, and image density formed on paper. It is not particularly limited to this. Also,
The control regarding the adjustment of the rotation speed of the elastic rotating body by the control device is basically performed when it is predicted that the sheet conveyance speed in the nip portion is increased by the condition of the pressing position of the pressing roll and the condition related to the sheet. When the rotation of the elastic rotator is increased, and conversely, when the paper transport speed is predicted to be reduced, the rotation of the elastic rotator is reduced, and when it is predicted that the paper transport speed does not fluctuate, The rotation of the elastic rotating body is performed at a constant speed (normal speed).

According to this curl correcting device, the rotation speed of the elastic rotating body of the curving nip mechanism is adjusted by the control means in accordance with the condition of the pressing position of the pressing roll and the condition relating to the paper. Can be controlled so that there is no speed difference between the paper transport speed at the nip portion and the paper transport speed by the paper transport rotator before and after the curved nip mechanism.

Further, such a curl correction device is configured as a separate structure from an application object (for example, an image forming apparatus) that requires paper sheet curl correction, and is connected to the application object in a detachable manner ( ), Or as a device that is used by being incorporated as a part of the object to be applied and integrated.

[0015]

[First Embodiment] FIG. 1 shows a curl correction device according to a first embodiment of the present invention and an image forming apparatus to which the correction device is applied. In the figure, reference numeral 1 denotes a curl correction device, and 2 denotes an image forming device.

First, an image forming apparatus 2 to which the curl correction apparatus 1 is applied is a copying machine having an image forming system for forming a toner image according to image information, transferring the toner image to a sheet, and then fixing the image. , An image forming apparatus such as a printer and a multifunction peripheral.

The image forming apparatus 1 according to the present embodiment
An image forming unit 21 that forms a toner image on a photoconductor through an electrification process, an image exposure process, and a development process using an electrophotographic technique, and image information (dotted line) Input unit 22 composed of a document reading device (scanner) or an externally connected device (PC, etc.)
And a paper supply unit 24 for feeding paper P for transferring the toner image formed on the photoconductor to the image forming unit 21 one by one from the storage tray 23, and the toner image transferred by the image forming unit 21. The fixing unit 25 mainly fixes the toner image to the sheet P through a nip portion between the heating roll or the belt and the pressing member. In the drawing, a chain line with an arrow indicates a conveyance path of the sheet P, a reference numeral 26 indicates a discharge roll pair for discharging the sheet P after fixing from the apparatus main body 20 and sending it to the curl correction device 1, and 27 indicates a discharge roll thereof. Vs. 2
6, a paper discharge sensor for detecting the passage of the paper P discharged out of the apparatus main body 20;
2 shows a paper discrimination sensor or switch for detecting the type (thickness, paper type, and size) of the paper P attached to.

In the image forming apparatus 2, the sheet P to which the toner image formed by the image forming section 21 is transferred is fixed in the fixing section 25 by the fixing action of heating and pressing. At that time, the paper P is curled. For this reason, in order to correct the curl generated on the sheet P, the sheet P after fixing is fed to the curl correction device 1.

Subsequently, the curl correcting device 1 has a curving device comprising a rotating belt 3 and a pressing roll 4 which is displaceably pressed against the belt 3 to form a curved nip portion N in the main body 10 of the device. The apparatus includes a nip mechanism 5 and a pair of paper transport rolls 6 and 7 that are disposed before and after the curved nip mechanism 5 and that hold and transport the paper P.
Reference numeral 11 in the drawing denotes a paper discharge tray that finally discharges and stores the paper P.

As shown in FIGS. 1 and 2, the belt 3 in the curved nip mechanism 5 is wound around a driven belt support roll 31 and a driven belt drive roll 32, and the driving force of the belt drive roll 32 is used. To rotate in the direction of the arrow.

The pressing roll 4 in the curved nip mechanism 5 is rotatably supported above a link member 42 in a curl amount adjusting displacement mechanism 41 as shown in FIGS. The link member 42 is displaced in the direction of the arrow by rotation of an eccentric cam 44 as a cam mechanism via a cam follower 43 attached to a lower part of the link member 42. Thus, the pressing position of the pressing roll 4 against the belt 3 is adjusted, so that the degree of curvature of the belt 3 (corresponding to the curl correction amount) can be adjusted arbitrarily. Further, the pressing roll 4 is used to control the paper type (coated paper and plain paper), basis weight and size of the paper P,
By rotating the eccentric cam 44 of the displacement mechanism 41 by a predetermined angle in accordance with the image density to be formed in the image forming apparatus and the temperature and humidity in the use environment, the pressing position is changed to a plurality of levels (for example, as shown in FIG. 3B). Levels 1 to 3) are selected. In FIG. 3B, reference numerals α1 to α3 indicate the degree of curl (curl correction amount) of the belt 3 at each level with respect to the no-load state, and these have a magnitude relationship of α1 <α2 <α3.

As shown in FIG. 2, the paper transport roll pairs 6 and 7 are disposed at front and rear positions with respect to the paper transport path of the curved nip mechanism 5, respectively. The driven roll 6 which presses against this driving roll
2, 72. In addition, before and after the sheet transport roll pairs 6 and 7 and at a portion reaching the curved nip mechanism 5,
A plurality of guide members 12 for guiding the paper P in the transport direction are provided. The guide member 12 and the pair of paper transport rolls 6 and 7 form a paper transport path. Reference numeral 15 in FIG. 2 denotes an entrance side paper passage detection sensor that detects the passage of the paper P sent from the image forming apparatus 2 to the curl correction device 1, and 16 detects the passage of the paper P discharged from the curving nip mechanism 5. This is a discharge side paper passage detection sensor.

In the curl correction device 1, as shown in FIG. 2, a belt drive roll 32 for driving and rotating the belt 3 of the curved nip mechanism 5, and drive rolls 61 and 71 in the pair of paper transport rolls 6 and 7 are provided. Are driven by one electric motor 51. The rotational driving force of the electric motor 51 is supplied to each of the rolls 32, 61, 7 by a known rotation transmission mechanism (dashed line in the figure).
1 are transmitted at basically the same rotational speed. Further, in the present embodiment, the rotational driving force of the electric motor 51 is transmitted to only the rotation transmitting mechanism between the electric motor 51 and the belt driving roll 32 by appropriately adjusting the speed such as deceleration or speed increase as necessary. Automatic transmission mechanism 5 for shifting
2 are provided. As such an automatic transmission mechanism 52, for example, a mechanism using an electromagnetic clutch is used. That is, the automatic transmission mechanism 52 using such an electromagnetic clutch is provided with a plurality of rotation transmitting gears disposed between the electric motor 51 and the drive roll 32 to be shifted, on the same shaft for deceleration, constant speed, and speed increase. Gears each having the same number of teeth for each gear, and a driven gear for receiving each gear is attached to another same shaft so as to face each other, and whether the rotational driving force received by each driven gear is transmitted to the corresponding shaft or not. The electromagnetic clutch is arranged to correspond to each of the driven gears for switching, and the respective electromagnetic clutches are appropriately operated, so that the rotational power from the electric motor 51 can be reduced, fixed, and increased. The rotation is transmitted to the drive roll 32 on the output side at any rotational speed.

Further, in the curl correction device 1,
As shown in FIG. 2, the control device 8 including a microcomputer and the like, as described above,
The cam drive unit 40 of the displacement mechanism 41 of the pressing roll 4 is rotated by a predetermined amount according to the basis weight and size, the image density formed on the paper P, and the temperature and humidity in the use environment, and the curl correction by the curved nip unit 5 is performed. The amount can be automatically adjusted, and the automatic rotation in the rotary drive system can be adjusted according to the pressing position of the pressing roll 4, the thickness, type and size of the paper P, and the image density formed on the paper P. By operating the transmission mechanism 52, the rotation speed of the belt 3 in the curved nip mechanism 5 can be automatically adjusted.
Further, the control device 8 receives from the control unit of the image forming apparatus 2 information such as the timing of the image forming operation and the like, various information of the sheet (information by the sheet discrimination sensor or the switch 28), and ejection information (information by the sheet ejection sensor 26). Control information (CS) including detection information) and the like, and detection information from the entrance-side paper passage detection sensor 15 and the discharge-side paper passage detection sensor 16 of the curl correction device 1 are input. ing.

FIG. 4 shows the adjustment of the rotation speed of the belt 3 performed by the control device 8. That is, as shown in FIG. 4, the adjustment of the rotation speed of the belt 3 starts with the curl correction amount (the degree of the level) corresponding to the pressing position of the pressing roll 4, the thickness of the sheet P (the degree of the thickness), Depending on the paper type (difference between coated paper, plain paper, and the like) and size (degree of size) and image density (degree of density), the automatic transmission mechanism 52 selects any one of “deceleration”, “constant speed”, and “increased speed”. This is done by switching between the crabs.
More specifically, the automatic transmission mechanism 52 can be switched between deceleration, constant speed, and speedup by a preset combination of the factors that cause "deceleration" or "speedup" shown in FIG. In the case of a constant speed, the rotation speed is maintained at the same rotation speed as that of the pair of sheet transport rolls 6 and 7. Adjustment of the rotation speed of the belt 3 by the control device 8 is performed by the entry-side paper passage detection sensor 1.
5 is set to be executed based on the detection signal.

Next, the operation of the curl correction device will be described with reference to FIG.

First, a desired image forming operation is designated and set in the image forming apparatus 2. At this time, the curl correction device 1
In the control device 8, the control information (C · S) relating to the curl correction such as the various conditions (thickness, paper type, size, basis weight, etc.) of the paper P used at the time of image formation and image density, temperature and humidity, ) Is obtained (step S1). Thereby, the control device 8 determines the curl correction amount in the curving nip mechanism 5 based on the obtained control information based on the parameter table stored in advance (S11), as shown in FIG. The adjustment of the rotation speed of the belt 3 is determined in light of the adjusted content (S
12).

Then, when the image forming operation is started under the set conditions instructed in the image forming apparatus 2, the image is formed and the sheet P which has passed through the fixing step is discharged from the image forming apparatus 1 side to perform curl correction. It is sent to the device 1 one after another.

At this time, the control device 8 of the curl correction device 1 determines whether it is necessary to adjust the curl correction amount for the fed sheet P (S1).
3). If it is necessary to adjust the curl correction amount, the paper P (the rear end) passes through the paper discharge sensor 27 on the image forming apparatus 2 and is detected (S1).
4) After the paper passage is detected by the sensor 27, the curl correction amount is adjusted (S14). That is, the operation of the cam drive unit 40 is controlled by the control device 8, and the cam 44 rotates by a required angle to displace the pressing roll 4 to a pressing position corresponding to a predetermined level (see FIG. 3).

After the adjustment of the curl correction amount is completed, or if it is determined in step S13 that the adjustment of the curl correction amount is unnecessary, it is necessary to adjust the rotation speed of the belt 3 in the curl correction for the fed sheet P. It is determined whether or not there is (S16). If the rotation speed of the belt 3 needs to be adjusted, the control unit 15 waits until the leading edge of the sheet P passes through the entry-side sheet passing sensor 15 and is detected (S17). Is detected, the adjustment of the belt rotation speed is executed (S1).
8). That is, the automatic transmission mechanism 56 is controlled by the control device 8.
Is operated to switch the rotational driving force from the electric motor 55 to one of the deceleration, constant speed, and speed increasing states and transmit the state to the belt driving roll 32, whereby the belt 3 is transmitted at the speed of the transmitted rotational driving force. It rotates (see FIGS. 2 and 4).

When the adjustment of the rotation speed of the belt is completed or it is determined in step S16 that the adjustment is unnecessary, the corresponding sheet P is bent by the curling nip mechanism by the conveying force of the sheet conveying roll pair 6. 5 and is discharged from the curved nip mechanism 5 by the nipping and conveying force of the belt 3 and the pressing roll 4 and the conveying force of the sheet conveying roll pair 7 at the nip N. The sheet is conveyed and conveyed so as to pass through the nip portion N of the curved nip mechanism 5 to execute curl correction (S19). The sheet P having been subjected to the curl correction is discharged to the discharge tray 11 and stored.

Finally, it is determined whether the sheet P discharged after the curl correction is the last sheet (S20). If not, the process returns to step S13 to repeat the same operation. However, if it is the last sheet, the operation of the curl correction device 1 ends.

In the curl correction device 1 according to the present embodiment, as is apparent from the adjustment contents shown in FIG. 4, when the curl correction amount is at a high level (for example, level 3 illustrated in FIG. 3B), Since the paper transport speed by the nip portion N in the curved nip mechanism 5 tends to increase, the belt 3 is driven and rotated by being reduced by the automatic transmission mechanism 56, whereby the paper transport speed by the nip portion N is reduced. The difference between the paper transport speed and the paper transport speed between the transport roll pairs 6 and 7 is prevented. Conversely, when the curl correction amount is at a low level (for example, level 1 illustrated in FIG. 3B), the paper conveyance speed of the nip portion N tends to be slow, and the belt 3 is decelerated by the automatic transmission mechanism 56. The sheet is driven to rotate, so that the sheet conveyance speed of the nip portion N does not differ from the sheet conveyance speed of the sheet conveyance roll pairs 6 and 7.

When the thickness of the paper P is large, when it is a coated paper, or when it is a large size (for example, A3 size paper), the paper transport speed by the nip portion N tends to be high. The belt 3 is driven to rotate at a reduced speed, so that the above-mentioned speed difference does not occur. Conversely, when the thickness of the paper P is thin, plain paper, or small size (for example, postcard size), the paper transport speed of the nip portion N tends to be slower, so that the belt 3 The motor is rotated at a reduced speed, so that the speed difference as described above does not occur. Further, even when the image density is high, since the paper transport speed by the nip portion N tends to increase, the belt 3 is driven to rotate at a reduced speed, so that the above-described speed difference does not occur. become. Conversely, when the image density is low, the paper transport speed due to the nip portion N tends to be slow.
Is decelerated and driven to rotate, whereby the speed difference as described above does not occur.

Accordingly, in the curl correction device 1, the curl correction amount (that is, the pressing roll 4
Nip portion N in the sheet curving nip mechanism 5 even when the paper pressing conditions), paper conditions and image density are different.
The speed difference between the paper transport speed due to the paper transport speed and the paper transport speed due to the paper transport roll pairs 6 and 7 does not occur.
The paper P is conveyed so as to pass through the nip portion N of the curved nip portion 5 without causing damage due to unnecessary pulling to the nip portion, and the curl correction due to the passage of the nip portion N is ensured. Will be done.

[Other Embodiments] In the first embodiment, in order to adjust the rotation speed of the belt 3, a configuration as shown in FIG. 6 can be adopted.

That is, in the curl correction device 1 shown in FIG. 6, the belt drive roll 32 of the curved nip mechanism 5 and the drive rolls 61, 71 of the sheet transport roll pairs 6, 7 are respectively driven by dedicated electric motors 55-57. While being driven, the control device 8 is configured to adjust the rotation speed of the belt 3 by changing the rotation speed of the electric motor 55 for rotatingly driving the belt drive roll 32, and otherwise to adjust the rotation speed of the first embodiment. The configuration was the same as in the case.
Then, the rotation speed of the electric motor 57 of the belt drive roll 32 is set to one of the deceleration, constant speed, and speedup by changing the frequency of the applied voltage, for example, according to the adjustment contents shown in FIG. The rotation speed of the belt 3 is adjusted.

Further, in the first embodiment, the case where a belt nip type is applied as the curved nip mechanism 5 has been exemplified. However, as shown in FIG. 7, a roll nip type curved nip mechanism 50 can be applied. .

The curved nip mechanism 50 of the roll nip type shown in FIG. 7 is similar to the curved nip of the first embodiment except that an elastic roll 30 having an elastic layer 30b formed around a roll shaft 30a is used instead of the belt 3. It has the same configuration as the mechanism 5. That is, the curved nip mechanism 50 includes the elastic roll 30 that is driven to rotate, and the pressing roll 4 that is displaceably pressed against the elastic roll 30 to form the curved nip portion N. The pressing position of the pressing roll 4 is adjusted by the displacement mechanism 41 as in the first embodiment (FIG. 7A), and the pressing amount (curl correction amount) can be changed to a plurality of levels. (FIG. 7b). The rotation speed of the elastic roll 30 may be appropriately adjusted by the control device 8 according to the conditions of the sheet P and the image density, as in the first embodiment (see FIG. 4). ).

Further, in the first embodiment, the adjustment of the rotation speed of the belt 3 by the control device 8 is performed by the introduction side paper passing sensor 1.
5 is configured to be executed after detecting the passage of the leading end of the sheet P to be curled (see step S17 in FIG. 6).
6 may be configured to execute the process for the next correction target sheet P after detecting the passage of the rear end of the sheet P. In the first embodiment, a paper transport belt may be used instead of the paper transport rolls 6 and 7.

In the first embodiment, the case where only one set of the curl correction unit including the curved nip mechanism 5 (50) and the pair of paper transport rolls 6 (7) is used has been described.
In the curl correction device 1 of the present invention, the curl correction unit
You may comprise so that it may use more than a pair. In such a case, the curl correction units of each set may be arranged so as to be shifted in front of and behind the paper transport path so as to be in series with the paper transport path. You may comprise so that it may be arrange | positioned so that it may be in a parallel state.

FIG. 8 shows a main part of a curl correction apparatus 100 in which two sets of curl correction units each including a curving nip mechanism 5 and a pair of sheet transport rolls 6 and 7 are arranged in parallel.

In FIG. 8, reference numeral 101A denotes a first curl correction unit for correcting the curl of a paper P curled mainly upward, and 101B denotes a curl of the paper P curled mainly downward. This is a second curl correction unit for correcting. The first curl correction unit 101A and the second
Each of the curl correction units 101B includes a curved nip mechanism 5, sheet transport roll pairs 6, 7 and sheet passing sensors 15, 16 in substantially the same manner as in the first embodiment. Reference numeral 44A in the figure denotes a curved nip mechanism 5 of the first curl correction unit 101A.
A, the eccentric cam of the displacement mechanism of the pressing roll 4A in FIG.
B is an eccentric cam of the displacement mechanism of the pressing roll 4B in the curved nip mechanism 5B of the second curl correction unit 101B. Further, the curl correction device 100 is provided with a path switching pawl 102 for switching and feeding the sheet P to be curled to either the first curl correction unit 101A or the second curl correction unit 101B. Path switching pawl 1
Numeral 02 swings around the fulcrum 102a. The position for feeding the sheet P to the first curl correction unit 101A (the state shown by the solid line in the figure) and the position of the sheet P
A position (2 in the figure) for feeding the sheet into the curl correction unit 101B.
(Indicated by a dashed line).

FIG. 9 is a block diagram showing a configuration of a control system of the curl correction device 100. Reference numeral 80 in the figure is
It is a central control device composed of a microcomputer or the like, and is an entrance-side paper passing sensor 1 of the first curl correction unit 101A.
5A and the discharge-side paper passage sensor 16A, and the entrance-side paper passage sensor 1 of the second curl correction unit 101B.
5B and the discharge side sheet passing sensor 16B are connected. Further, similarly to the control device 8 in the first embodiment, necessary control signals C and S are input from the image forming device 2 side. Further, the central control device 80 is connected to a drive unit 81 that drives the swinging operation of the course switching pawl 102, a first curl correction unit control unit 82, and a second curl correction unit control unit 83. . Both the first and second curl correction section controllers 82 and 83 are provided with the first cam 44A and the second cam 44A.
The operation related to the drive units 40A and 40B of the cam 44B and the drive units 51 (55 to 55) of the belt 3 and the sheet transport rolls 6 and 7 are performed.
57) is controlled. Similarly to the control device 8 according to the first embodiment, the central control device 80 determines the curl correction amount according to the information of each condition such as the condition of the sheet P and the image density, and the curl correction amount is added to the information of each condition. Belts 3A, 3B
(See FIGS. 4 and 5).

The curl correction device 100 operates roughly as follows. First, when the sheet P to be corrected is fed into the curl correcting apparatus 100, the path switching pawl 102 is rotated by the operation of the path switching pawl driving section 81, and the sheet P is fed to the curl correcting section to which the sheet P is to be fed. Is displaced to the position where it is released. This is because, for the direction of the curl generated on the paper P, control information set in advance based on information on the paper conditions, image density, temperature and humidity, etc. is created and stored in the memory of the control device 80. The configuration is such that the path switching pawl 102 is displaced to a predetermined position based on the control information. By the route guidance of the route switching claw 102, the sheet P is sent to a desired curl correction unit side. Subsequently, in each of the curl correction units 101A and 101B to which the sheet P has been sent, each of the cam driving units 40A and 40B and the driving units 55 to 59 such as a belt are all provided with the curved nip mechanism of the curl correction unit in the first embodiment. As in the case of No. 5, the adjustment of the curl correction amount suitable for the paper P and the adjustment of the rotation speed of the belt 3 are performed based on the information of the conditions (including the conditions of the curl correction amount) of the paper P and the image density. After each adjustment, the paper P is transported by the paper transport roll pairs 6 and 7 so as to pass through the nip portion N of the curved nip portion 5. In this way, the curl correction by each of the curl correction units 101A and 101B can be performed well and reliably without the occurrence of paper jams and the load of damage to the paper regardless of the amount of curl correction, paper conditions, differences in image density, etc. Performs properly.

[0046]

As described above, according to the curl correction device of the present invention, the rotation speed of the elastic rotating body in the curved nip mechanism is adjusted by the control means, so that the pressing position of the pressing roll in the nip mechanism is adjusted. Even if conditions related to the paper, such as the type of paper and image density, differ, the paper transport speed at the nip of the nip mechanism and the paper that transports the paper so that it passes through the nip Good curl correction can be performed without causing a paper jam or a damage load on the paper due to a difference from the paper transport speed by the transport means.

[Brief description of the drawings]

FIG. 1 is a schematic diagram schematically illustrating a main part of a curl correction device according to a first embodiment and an image forming apparatus to which the correction device is applied;

FIG. 2 is an explanatory diagram illustrating a configuration of a curl correction unit in the curl correction device.

FIG. 3 is an explanatory diagram showing a configuration of a belt nip type curved nip mechanism and a set level of a curl correction amount by the mechanism.

FIG. 4 is a table showing adjustment contents of a rotation speed of a belt.

FIG. 5 is a flowchart illustrating an operation procedure of the curl correction device.

FIG. 6 is an explanatory diagram showing another configuration of the curl correction unit in the curl correction device.

FIG. 7 is an explanatory diagram showing another configuration of the curved nip mechanism (the configuration of the roll nip type curved nip mechanism and the set level of the curl correction amount by the mechanism).

FIG. 8 is a schematic diagram illustrating a configuration example of a curl correction device in which two sets of curl correction units are arranged in parallel.

FIG. 9 is a block diagram illustrating a main configuration of a control system in the curl correction device of FIG. 8;

FIG. 10 is an explanatory diagram showing a correlation between a paper transport speed at a nip portion in a conventional nip mechanism and a paper transport speed of a paper transport mechanism.

FIG. 11 is an explanatory diagram showing, in an enlarged manner, a state in which a sheet is conveyed in a nip portion in the nip mechanism.

[Explanation of symbols]

1,100: curl correction device, 3: belt (elastic rotating body), 4: pressing roll, 5: belt nip type nip mechanism (curved nip mechanism), 30: elastic roll (elastic rotating body), 50: roll nip type , A nip mechanism (curved nip mechanism), 6, 7... A sheet transport roll pair (a sheet transport rotating body), 8, 80... A control device (control means), and P.

Continued on the front page (72) Inventor Hideo Kinugi 2274 Hongo, Ebina-shi, Kanagawa Prefecture, within Fuji Xerox Co., Ltd. Reference) 3F053 HA03 HB01 HB09 HB24 LA02 LA05 LA07 LB03

Claims (1)

[Claims] 1. A curved nip mechanism comprising: an elastic rotating body made of an elastic roll or belt driven to rotate; and a pressing roll forming a curved nip portion by being displaceably pressed against the elastic rotating body; and the curved nip mechanism. A paper transport rotating body disposed at front and rear positions for holding and transporting the paper, and transporting the paper to be curled by the paper transport rotating body so as to pass through the nip portion of the curved nip mechanism. In a curl correction device that corrects curl of a sheet, a control unit that adjusts a rotation speed of an elastic rotating body of the curved nip mechanism according to a condition of a pressing position of the pressing roll and a condition related to a sheet is provided. Characteristic curl correction device.