JP2010100391A - Curl detection device and recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curl detection device accurately detecting the curvature of a curl based on a measuring result of a floating quantity of a sheet. <P>SOLUTION: This curl detection device has a sucking means 3 for sucking the sheet 4 in a carrying passage, and a detection means 1 for detecting the floating quantity of the sheet in the carrying passage, and detects the curl by detecting a shape change of the sheet when changing suction force of the sucking means in a detecting position of the sheet. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a curl detection device for detecting a curl state of a sheet conveyed in a recording device or the like, and a recording device having the detection device.

  In a recording apparatus such as a printer, a copying machine, or a facsimile, if the sheet has curl wrinkles, not only the quality of the recorded image is lowered, but also the end of the sheet is caught by a component inside the apparatus, and a paper jam occurs. Cause malfunctions. Such a problem is likely to occur particularly when a roll sheet wound in a roll shape is used. The degree and curvature of the sheet curl varies depending on the type of sheet, environment, recording amount, and the like.

  Accordingly, various methods have been proposed such as detecting the curl and correcting the curl by plastically deforming the sheet while conveying the sheet with a curvature opposite to the curl. For example, Patent Document 1 discloses a method for predicting a curl amount and a curl direction by using a curl discrimination table in consideration of total toner ratio, humidity information, and recording material conveyance direction information. Further, Patent Document 2 discloses a method for detecting the distance in the contact / separation direction between the ink head and the roll sheet and optimizing the distance in the contact / separation direction by raising and lowering the ink head in accordance with the detected value. Yes. According to such a method, even when the curled state varies depending on the winding curvature difference, ink can be landed at an optimum flight distance without requiring a platen.

Further, in Patent Document 3, using a sheet detection sensor provided in the middle of the sheet conveyance path, the distance from the recording head to the sheet at the position V0 of the leading end portion of the sheet and the position V1 past a certain distance from the leading end portion. A method of detecting is disclosed. According to this method, the direction and degree of curl can be determined based on the output difference between the detected values at the positions of V0 and V1.
JP 2001-213563 A JP 2004-188788 A Japanese Unexamined Patent Publication No. 08-198477

  However, the conventional method of detecting the curl state of the sheet or measuring the distance in the contact / separation direction between the recording head and the sheet has a problem that the degree of curl curvature cannot be detected with sufficient accuracy. For example, in the method of Patent Document 1 in which curl is detected using a prediction parameter corresponding to an environmental change, it is impossible to check whether an image is properly formed corresponding to curl, and necessary and sufficient curl correction is performed. Is difficult to realize. Further, in the method of Patent Document 2 in which the distance in the contact / separation direction with respect to the recording head at each position of the sheet is appropriately adjusted by raising and lowering the recording head according to the curl state, when the degree of curling exceeds a certain amount. There is a problem that it does not work effectively. In the method of Patent Document 2, it is necessary to newly provide a lifting drive motor, it is necessary to continue the height measurement by the sensor, and it takes time and effort to control the lifting operation when the curl amount changes. There was also.

  In the method of Patent Document 3 in which the curl is detected based on the difference in change in the sheet height in the sheet conveyance direction, the curl direction can be determined, but the detection accuracy of the curl curvature is greatly affected by the position of the sheet. There is a problem that it cannot be properly determined. Accordingly, in a recording apparatus or the like that records an image on a conveyed sheet, it is required to determine the curl direction of the sheet and to detect the decurling parameter that is an operation condition for curl correction control with a highly accurate measured value. It had been.

  The present invention has been made in view of such conventional techniques. An object of the present invention is to provide a curl detection device capable of accurately detecting a curvature of a curl based on a measurement result of a sheet floating amount, and a recording apparatus having such a curl detection device.

  The curl detection apparatus according to the present invention includes a suction unit that sucks a sheet in the conveyance path and a detection unit that detects a floating amount of the sheet in the conveyance path, and changes the suction force of the suction unit in the sheet detection position. The curl is detected by detecting a change in the shape of the sheet when the sheet is detected.

  According to the present invention, a curl detection device capable of accurately detecting the curl curvature based on the measurement result of the sheet floating amount, and a recording apparatus having such a curl detection device are provided.

Embodiments of the present invention will be specifically described below with reference to the drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings.
[First Embodiment]
FIG. 1 is a configuration diagram of a recording apparatus having a curl detection apparatus to which the present invention is applied. FIG. 2 is a longitudinal sectional view of the curl detection unit. The sheet 4 unwound from the roll sheet wound around the spool 11 mounted on the recording apparatus is fed toward the image forming unit 10 by the first conveying unit 6. This sheet is fed through a conveyance guide to a nip between an LF (paper feed) roller 12 and a pinch roller 13 which are second conveyance means 9 arranged on the conveyance upstream side of the image forming unit 10. The image forming unit 10 is provided with a recording head 5 and a platen 2, and a gap for passing the sheet 4 is provided therebetween.

  The recording apparatus is an apparatus that records an image by a recording head based on image information. Here, an ink jet recording apparatus that performs recording by ejecting ink from the recording head to a sheet is exemplified. The fed sheet 4 hits the nip between the stopped LF roller 12 and the pinch roller 13 and is registered (front end aligned), and then conveyed to the recording start position on the platen 2 by the rotation of the LF roller 12. The Therefore, the entire image is recorded by alternately repeating the image formation for one line by the recording head 5 and the paper feed at a predetermined pitch. After the recording, the sheet 4 is conveyed to the outside and then cut by a cutter (not shown). The separated image recording portion is accommodated in a stacker or the like, and the remaining sheets are rewound to the recording start position.

  The first transport unit 6 has a function of a decurling unit for correcting curl wrinkles of the sheet 4 in addition to the transport function. The first transport means 6 includes a transport roller 16 that is a driving roller, a decurling roller 17 that is driven to rotate while being pressed against the transporting roller 16, and a support roller 7 that is disposed on the upstream side of transporting the decurling roller 17. Yes. The decurling roller 17 corrects curl by winding the convex side of the curl. The position of the support roller 7 can be adjusted in the direction of the double arrow with respect to the decurling roller 17, and the sheet winding angle with respect to the decurling roller 17 can be adjusted according to the state of the curl ridge.

  Adjacent to the recording head 5, for example, a detection means 1 for detecting the floating amount of the sheet from the upper surface (sheet passing surface) of the platen 2 that constitutes a part of the conveyance path is disposed at an integral or near position. . As the detection means 1, a sensor such as an optical distance sensor that detects the distance to the surface of the sheet 4 in the conveyance path is used. The platen 2 is provided with suction means 3 for sucking the sheet through the transport path. The suction means 3 is provided on the platen 2 disposed to face the recording head 5, and negative pressure generated by a negative pressure generation source such as a fan in a plurality of suction holes formed on the sheet passing surface of the platen 2. The platen 2 is configured to adsorb the back surface of the sheet 2 by applying a suction force.

  The suction means 3 can change the amount of floating of the sheet from the platen 2 by changing the suction force acting on the sheet 2. This change in the floating amount is detected by the detecting means 1. In the present embodiment, the suction unit 3 that sucks the sheet 4 in the conveyance path and the detection unit 1 that detects the floating amount of the sheet 4 in the conveyance path are provided, and the suction force of the suction unit 3 at the detection position of the sheet 4 is changed. The curl is detected by detecting a change in the shape of the sheet 4 at the time of being applied. According to such a detection method, the sheet 4 is conveyed by the conveying unit 9, and the curl direction and curvature of the sheet 4 can be detected by using the detecting unit 1 and the suction unit 3. The detected curl curvature is used as an operation parameter of the decurling means constituted by the first conveying means 6. Further, based on the curl state detected by the detection means 1 and the suction means 3, the decurling correction operation by the support roller 7 and the decurling roller 17 is controlled.

  The second conveyance unit 9, the detection unit 1, and the suction unit 3 constitute a curl detection unit 20 that detects the curl state of the sheet 4 in the platen 2 that is a part of the conveyance path. The control unit 8 controls the conveyance amount of the sheet 4 by the LF roller 12, the measurement of the floating amount by the detection unit 1, and the change (adjustment) of the suction force of the suction unit 3. Here, the sheet lift amount is the lift amount of the sheet from the platen 2 and is detected by measuring the height of the sheet, that is, the distance between the sheet 4 on the platen and the recording head 5 by the detection means 1. The Therefore, in this embodiment, the direction of curl is detected based on a change in the amount of floating of the sheet when the suction force of the suction unit 3 is changed at a plurality of positions of the sheet. Further, the curvature of the sheet curl (the degree of curl) is detected based on the difference in the change in the sheet floating amount when the suction force of the suction means 3 at a plurality of positions of the sheet 4 is changed. That is, the degree of curl (curl amount) at each position can be determined based on the difference in the float amount at each position, and the curvature of the curl is included by a change in shape such as a change rate of the float amount with respect to the distance in the sheet conveyance direction. The curl state can be determined.

  FIG. 3 is a flowchart of an operation for controlling the curl detection unit 20. FIG. 4 is a longitudinal sectional view showing a curl detection position of the sheet 4. FIG. 5 is a table showing specific examples of measured values of the sheet floating amount when the suction force of the suction means is gradually changed at each detection position of the sheet. In the sheet 4, the position B, the position C, the position D, and the position E are set in order of a predetermined distance as a detection position for detecting the floating amount, starting from the tip position A. By dynamically changing the suction force of the suction unit 3 according to the transport amount of the sheet 4, the floating amount of the sheet 4 is measured for each detection position, and the measured values are stored in the control unit 8. In the present embodiment, detection is performed at each of the positions A to E while moving the sheet 4 with respect to the detection unit 1, but this is because each position is detected while moving the detection unit 1 in the transport direction with respect to the sheet. The structure detected by A to E may be used.

  When the detection operation is started, first, the suction unit 3 is operated with a suction force of 100%, and the LF roller 12 is rotated until the leading end position A of the sheet 4 reaches the reading position of the detection unit. Measure the height. This floating amount is obtained by detecting the distance to the surface of the sheet 4 and subtracting the detected distance from the distance to the platen 2. Next, the rotation of the LF roller 12 moves the reading position on the sheet 4 from the position A to the positions B, C, D, and E, and the sheet height at each position is detected by the floating amount detection unit 1 with the suction force 100%. Then, the floating amount is measured (step S1). By the measurement so far, the amount of floating at the positions A to E on the sheet 4 when the suction force of the suction means 3 is 100% is stored in the control means 8. The row of 100% (attraction force 100%) in FIG. 5 is the actual floating amount at each position.

  Next, the position E is set to the reading position, and the suction force is gradually weakened from 100% to 90%, 80%, etc., and the floating amount at each suction force is measured. At this time, measurement is performed until the suction force becomes 0% as long as the floating amount is smaller than the distance between the recording head 5 and the platen 2, that is, unless the sheet contacts the recording head 5. Next, the position A is measured. That is, after the position E is measured, the LF roller 12 is rotated to move the sheet until the measurement position changes from the position E to the position A with a suction force of 100%. Then, as in the measurement at the position E, the suction force is gradually reduced from 100% to 90%, 80%, etc., as long as the floating amount is smaller than the distance between the recording head 5 and the platen 2 (the sheet contacts the recording head). Measure (unless otherwise). If all the above measurement results are zero, it is determined that the sheet 4 has not been lifted, and the measurement is terminated. Otherwise, the process proceeds to step S2 for determining whether or not the maximum suction force (%) is greater than zero. The maximum suction force is the suction force (%) when the suction force is weakened until the point when the sheet floating amount changes after the suction.

  When the maximum suction force is greater than 0%, the process proceeds to the next step S3, and when the maximum suction force is 0% or less, the measurement ends. In step S3, the maximum suction force is determined in order from the largest suction force, and the suction force immediately after the change in the floating amount (sheet height) at the position A or the position E is set as the maximum suction force. Next, in step S4, the suction force is changed in order from the larger one. If it is determined that the sheet 4 will come into contact with the recording head 5 if no suction force is generated, the suction force (%) immediately before that is set as the minimum suction force, and the minimum suction force when the sheet floating amount is zero. Is 0%. Based on such measurement results, the maximum suction force (%) and the minimum suction force (%) of the suction means 3 for the sheet 4 are determined. From the measurement result of FIG. 5, the maximum suction force is 70% and the minimum suction force is 0%.

  Then, the suction means 3 is set to the maximum suction force, and while the sheet 4 is moved by the LF roller 12, the sheet floating amount (sheet height) at each of the positions A to B is measured and controlled. Stored by means 8 (step S5). Next, the suction means 3 is set to the minimum suction force, and the sheet lift at the positions E to A is measured while the sheet 4 is moved in the reverse direction by the LF roller 12. (Step S6). FIG. 6 is a specific example of the floating amount at each position when sucking at the maximum suction force (70%) and the detection result (measured value) of the floating amount at each position when sucking at the minimum suction force (0%). It is a table | surface which shows the difference. The detection result of the shape change at the maximum suction force at each of the positions A to E in FIG. 4 and the shape change of the minimum suction force is expressed as a sheet floating amount at each position in FIG.

  From the table of FIG. 6, it can be seen that the floating amount at the position A is larger than the floating amount at the position E. Based on the change in the floating amount at positions A to E, it is possible to determine that the sheet is curled in the direction of increasing, that is, the direction of curling. Further, the curl direction and the curl amount (curl curvature or degree) can be determined (determined) by obtaining the difference between the float amount at the minimum suction force and the float amount at the maximum suction force (step). S7). Each numerical value in the difference column in FIG. 6 indicates the difference in the floating amount between the minimum suction force and the maximum suction force at each position. As described above, the curl direction and curvature (curl amount) of the sheet 4 in the conveyance path can be detected.

  As described above, the curl detection apparatus includes the suction unit 3 that sucks the sheet 4 through the conveyance path, and the detection unit 2 that detects the floating amount of the sheet 4 through the conveyance path. The curl is detected by detecting a change in the shape of the sheet 4 when the suction force of the suction means 3 at the sheet detection positions A to E is changed. Accordingly, the curl curvature can be detected with high accuracy based on the measurement result of the sheet floating amount. Such a curl detection may be performed before or after the recording head 5 records an image on the sheet. The detected curvature of the curl can be used as a decurling parameter of the decurling means 6 or used for determining the decurling effect by the decurling means 6. Furthermore, curl correction is performed after the curl amount is detected, and if the curl amount detection result is more than the set value from the target value, correction is performed and the decurling operation (curl correction operation) is performed again. Is also possible.

[Second Embodiment]
In the first embodiment described above, the case where the curl curvature is obtained by measuring the difference in the floating amount when the suction force at the detection positions set in the plurality of positions A to E in the sheet conveyance direction is changed is described. explained. On the other hand, in the present embodiment, when the detection position is set at the front end position of the sheet and the suction force at the front end of the sheet is changed, the curl is determined by the difference between the maximum suction force and the suction force when the front end moves. Detect the curvature of. Other configurations of the present embodiment are the same as those of the first embodiment.

  Next, the curl detection operation in this embodiment will be described. First, the suction force of the suction means 3 is set to 100% by the control means 8. Next, the sheet 4 is conveyed by the LF roller 12. By measuring the distance from the recording head 5 to the platen 2 and the distance from the recording head 5 to the sheet 4 by the detection unit 1, it is determined that the leading end (position A) of the sheet 4 has reached the measurement position by the detection unit 1. To do. After the leading edge of the sheet 4 reaches the measurement position, the suction force is gradually weakened from 100%. Meanwhile, it is continuously confirmed that the tip position and the measurement position match. When the sheet has curls, if the suction force is weakened, the shape of the sheet whose curl amount has been reduced by the suction force changes. That is, the sheet that has been flattened by the suction force is curled from the position A to the position B by the curl that originally existed.

  The suction force at the time when the sheet becomes round and the leading end cannot be detected by the detection means 1 is measured and stored. From the stored value of the suction force, it is possible to determine whether the tip is curled enough to detect a change in the tip position by decreasing the suction force from 100% to what percentage. The degree of curl curvature can be detected by using the difference in suction force between them as a curl amount parameter. The direction of curl can be detected by measuring the change in the amount of floating when the suction force is changed according to the first embodiment. Further, by combining the curl detection in the first embodiment with the present embodiment, the degree of curl curvature can be determined with higher accuracy.

  Also in the curl detection apparatus according to the second embodiment, the curl can be detected by detecting the shape change of the sheet 4 when the suction force of the suction means 3 at the sheet detection positions A to E is changed. . Therefore, according to the second embodiment, the curl curvature can be accurately detected based on the measurement result of the sheet floating amount.

  Also in the second embodiment, the curl detection time may be before or after the image is recorded on the sheet by the recording head 5. The detected curvature of the curl can be used as a decurling parameter of the decurling means 6 or used for determining the decurling effect by the decurling means 6. Furthermore, curl correction is performed after the curl amount is detected, and if the curl amount detection result is more than the set value from the target value, correction is performed and the decurling operation (curl correction operation) is performed again. Is also possible.

  In the above embodiment, the case where the curl of the sheet unrolled from the roll sheet is detected has been described. However, the present invention detects the curl of other forms such as a cut sheet cut to a certain size. The same applies to the above. Various materials such as paper, plastic sheets, photographic printing paper, and cloth can be used for the sheet. Further, the curl detecting apparatus according to the present invention is a serial recording apparatus that alternately repeats image formation for one line and paper feed at a predetermined pitch, or a line type that forms an image batch by line only by paper feed. It can be similarly implemented in any of the recording apparatuses.

1 is a configuration diagram of a recording apparatus having a curl detection apparatus to which the present invention is applied. It is a longitudinal cross-sectional view of a curl detection part. It is a flowchart of the operation | movement which controls a curl detection part. It is a longitudinal cross-sectional view which shows the curl detection position of a sheet | seat. It is a table | surface which shows the specific example of the measured value of the floating amount of a sheet | seat when the attraction | suction force of an adsorption | suction means is changed gradually in each detection position of a sheet | seat. It is a table | surface which shows the specific example of the floating amount of each position when attracting | sucking with the maximum suction force, and the detection result (measured value) of the floating amount of each position when attracting | sucking with the minimum suction force, and the difference.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Detection means 2 Platen 3 Adsorption means 4 Sheet 5 Recording head 6 1st conveyance means (decal means)
8 Control unit 9 Second transport unit 10 Image forming unit 12 LF roller 17 Decal roller 20 Curl detection unit

Claims (9)

  Equipped with a suction unit that sucks the sheet in the conveyance path and a detection unit that detects the floating amount of the sheet in the conveyance path, and detects a change in the shape of the sheet when the suction force of the suction unit at the sheet detection position is changed A curl detecting device that detects curl by   The curl detection apparatus according to claim 1, wherein the curl direction is detected by a change in a floating amount of the sheet when the suction force at a plurality of positions of the sheet is changed.   The curl detection device according to claim 1, wherein the curl curvature is detected based on a difference in change in the floating amount of the sheet when the suction force is changed at a plurality of detection positions of the sheet.   The curl detection apparatus according to claim 1, wherein a curvature of the curl is detected based on a difference in the suction force when the front end of the sheet moves when the suction force at the front end of the sheet is changed.   A recording apparatus for recording an image on a sheet by a recording head, comprising the curl detection apparatus according to claim 1.   The recording apparatus according to claim 5, wherein the recording is performed by discharging ink from the recording head.   The recording apparatus according to claim 5, wherein the detection unit is disposed adjacent to the recording head.   The recording apparatus according to claim 5, wherein the suction unit is provided on a platen disposed to face the recording head.   The recording apparatus according to claim 8, wherein the detection unit detects a floating amount of the sheet by measuring a distance between the sheet on the platen and the recording head.

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