JP2003182911A - Ink jet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet printer having a curl straightening means capable of extensively setting the straightening quantity with excellent accuracy, and reliably straightening the curl of a recording paper sheet. <P>SOLUTION: In the ink jet printer having the curl straightening means for pressing the recording paper sheet in the direction opposite to the curl of the recording paper sheet, a part of the curl straightening means for pressing the recording paper sheet is formed of a curved surface symmetric to the curl of the recording paper sheet, and the curvature of the curved surface can be changed. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an ink jet printer having a curl correcting means for correcting the curl of recording paper supplied from a recording paper roll. 2. Description of the Related Art An ink-jet printer is a printer using a non-impact recording method, so that almost no noise is generated, and high-quality images with high definition, high gradation and excellent color reproducibility can be easily obtained. It has become very popular in recent years. [0003] Recording media to be printed by an ink jet printer include paper, plastic sheets,
Although there is a cloth or the like, a paper recording medium, that is, a so-called recording paper is generally used. There are two types of recording paper: cut paper and roll paper.Roll paper has advantages over cut paper in that the recording paper is less likely to jam in the transport path, is less likely to be fed multiple times, and can be used in smaller printers.
There is a strong demand for using roll paper as a recording medium for paper in inkjet printers. However, since the roll paper is formed by winding the recording paper in a roll shape, the pulled out recording paper is curled. When the curled recording paper is conveyed to the printing unit, the head and the recording paper are moved. The distance from the paper fluctuates with respect to the specified distance. As described above, when the distance between the head and the recording paper fluctuates, the print quality is affected for the following reasons. [0005] An ink jet printer performs printing by attaching ink droplets discharged from a discharge port of a head to a recording medium such as a recording sheet arranged opposite to the head. The ink droplets ejected toward the recording paper move in the scanning direction of the head until they reach the recording paper from the ejection ports. That is,
Since the ink droplet flies obliquely from the ejection port toward the recording paper, if the distance between the head and the recording paper changes, the ink droplet lands on a position deviating from a predetermined position on the recording paper. Further, in the case of bidirectional printing in which printing is performed while the head performs reciprocating scanning in the forward direction and the backward direction, the ejection timing is adjusted so that the landing positions match in any scanning in which the head movement direction is different. Has been adjusted,
When the distance between the paper and the head fluctuates, the landing position shifts during each of the reciprocating scans, so that the print quality is particularly deteriorated. Therefore, when roll paper is used as recording paper for an ink jet printer, curling of the recording paper poses a major problem. Therefore, as means for correcting the curl of the roll paper, those described in Japanese Patent Application Laid-Open No. Sho 56-48343,
Japanese Patent Application Laid-Open No. Sho 60-6552 has been proposed. [0008] Japanese Unexamined Patent Publication No. Sho 56-48343 discloses a method in which a metal roller having a small diameter is pressed against a soft rubber roller having a large diameter on a sheet used for a copying machine or a collating machine, and the sheet is placed between the two. This device corrects curl by sandwiching and bending the curl in the opposite direction. The amount of correction can be adjusted by the pressing force of the metal roller. Japanese Unexamined Patent Publication (Kokai) No. 60-6552 discloses a curl correcting device used in a copying machine. The curl correcting device wraps a recording paper around a curl removing roller, and curls the recording paper in an opposite direction. By applying the curl, the curl is removed, and the correction amount can be adjusted by the angle at which the recording paper is wound around the curl removing roller. [0010] In the above prior art, the curl can be corrected and the correction amount can be adjusted.
Regardless of the magnitude of the curl amount, since only one roller having a single diameter is used as the correction roller, it has been difficult to set the correction amount over a wide range with high accuracy. SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet printer having a curl correcting means capable of setting a correction amount over a wide range with high accuracy and reliably correcting the curl of a recording sheet. According to the present invention, there is provided an ink jet printer comprising a curl correcting means for pressing a recording sheet in a direction opposite to the curl of the recording sheet. The portion of the curl correction unit that presses the recording sheet is formed of a curved surface symmetrical to the curl of the recording sheet, and the curvature of the curved surface can be changed. According to the ink jet printer having the above configuration, the portion of the curl correcting unit that presses the curled recording paper is a curved surface whose curvature can be changed. If the curvature is changed, the curl of the recording paper can be corrected according to the curl amount of the recording paper. A first embodiment of an ink jet printer according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a view showing the overall configuration of an ink jet printer having a curl correcting means C according to the present invention. Reference numeral 1 denotes a recording paper roll in which the recording paper is wound in a roll shape, which is exchangeably mounted on the ink jet printer. Reference numeral 2 denotes a recording sheet pulled out from the recording sheet roll 1, and R1 to R5 denote a pair of conveying rollers for conveying the recording sheet 2. C denotes a curl correcting means for bringing the curl correcting member S into contact with the recording paper 2 and applying a reverse curl to correct the curl. Each pair of transport rollers R1 and R2 disposed with the curl correcting means C interposed therebetween regulates the tension of the recording sheet 2 in contact with the curl correcting member S of the curl correcting means C. Further, the recording sheet 2 is curled by the curl correcting member S.
Is determined by the winding angle of the recording sheet 2 around the curl correcting member S, in addition to the curvature of the curved surface of the curl correcting member S and the tension. Therefore, the transport rollers R1, R2 and the curl correcting member S
Is set so that the wrapping angle is optimal. The recording paper 2 on which the curl has been corrected by the curl correcting means C is then sent to the printing section H, where printing is performed by the head 3, and finally after being cut to a predetermined size by the cutter K. The sheet is discharged outside by a pair of transport rollers R5. The head 3 is provided with a plurality of ink ejection ports 4 for ejecting ink. The ink ejection ports 4 are provided at predetermined intervals between the recording paper 2 and the recording paper 2 so as to face the recording paper 2. ing. The head 3 is mounted on a carriage 5, and the carriage 5 reciprocates in the width direction of the recording paper 2 along a pair of guide rails 6 by driving means such as a motor, a pulley, and a belt (not shown). It is guided and supported so that it can move. When printing is performed by the ink jet printer, the carriage 5 is first driven in the forward direction on the stationary recording paper 2 to print one line. Next, the recording paper 2 is conveyed by one line, and the carriage 5 is driven in the backward direction to return the head 3 to the initial position. By repeating this operation, printing is performed on a desired area of the recording paper 2. In order to increase the printing speed, the recording paper 2 is conveyed by one line prior to driving the carriage 5 in the backward direction, and the carriage 5 is returned. It is also possible to perform bidirectional printing in which one line of printing is performed while scanning in the direction. Ink tank 7
And supplied to the head 3 by a pipe 8. FIGS. 2A and 2B are front views showing a first embodiment of the curl correcting means C used in the ink jet printer according to the present invention. Reference numerals 10 and 11 denote a pair of truncated conical rollers constituting the curl correcting member S, which are rotatably supported on a shaft 12 with their small diameter sides facing each other. Reference numeral 2 denotes a recording sheet wound around a roller. In these drawings, a cross section is shown, and the surface facing outward when the sheet is wound on the recording sheet roll 1 is in contact with the rollers 10 and 11. . When the recording paper 2 having the curl contacts the rollers 10 and 11 with tension, the curl in the opposite direction is added and the correction is performed. The rollers 10 and 11 can be moved along the axis 12 by driving means (not shown) so that the distance between them can be arbitrarily changed. The diameter of the recording paper roll 1 is large at the beginning of use and small at the end. Therefore, the curl amount of the recording paper 2 pulled out from the recording paper roll 1 is small at the beginning and large at the end. Therefore, if the amount of reverse curl applied to the recording paper 2 by the curl correcting means C is not reduced in the initial stage, curl in the opposite direction will be applied. In the final stage, the curl cannot be sufficiently corrected unless the amount of reverse curl is increased. Therefore, initially, the interval between the rollers 10 and 11 is narrowed as shown in FIG. As a result, the recording paper 2 comes into contact with portions where the curvatures of the rollers 10 and 11 are small (portions R and R where the radius of curvature is large). Also, at the end,
As shown in (b), the interval between the rollers 10 and 11 is widened, and the recording paper 2 is brought into contact with the portions of the rollers 10 and 11 having large curvatures (portions r and r having small curvature radii) to increase the reverse curl amount. To do. According to the curl correcting means according to this embodiment, the curvature of the curl correcting member S to be brought into contact with the recording paper 2 can be changed continuously and steplessly. The straightening operation can be performed by the straightening member having the optimum curvature. FIGS. 3A and 3B show a second embodiment of the curl correcting means C used in the ink jet printer according to the present invention. The parts 13 and 14 have three different diameter parts 13.
Stepped rollers having a, 13b, 13c, 14a, 14b, and 14c are rotatably supported on a shaft 15 with their small diameter sides facing each other. Reference numeral 2 denotes a recording sheet wound around the rollers 13 and 14, and a cross section is shown in these figures, and a surface facing outward when the recording sheet is wound on the recording sheet roll 1 contacts the rollers 13 and 14. In contact. As in the case of the first embodiment, when the recording paper 2 having curl abuts on these rollers 13 and 14 with tension, curl in the opposite direction is added and correction is performed. The rollers 13 and 14 are moved along a shaft 15 by driving means (not shown), similarly to the frusto-conical rollers 10 and 11 of the first embodiment.
The distance between the four can be arbitrarily changed. If the diameter of the recording paper roll 1 is large in the initial stage of use, the curvature of the portion where the recording paper 2 is in contact with the curl correcting member S is reduced, as in the case of the first embodiment. To prevent the curl amount from becoming excessive,
As shown in FIG. 3A, the recording paper 2 is wrapped around the large diameter portions 13a and 14a. On the other hand, when the diameter of the recording paper roll 1 is reduced at the end of use, the curvature of the curl correction member S with which the recording paper 2 is in contact is the same as in the first embodiment. In order to increase the amount of reverse curl by increasing the distance between the rollers 13 and 1 as shown in FIG.
4, the recording paper 2 is wrapped around the small diameter portions 13c and 14c. According to the curl correcting means according to the present embodiment, it is possible to select the optimum curvature portion corresponding to the curl amount of the target recording sheet 2, so that the curl can be corrected reliably. . In the first embodiment and the second embodiment,
Although a pair of right and left rollers 10, 11, 13, and 14 is used, in each embodiment, only one of the pair of rollers may be used. In the first and second embodiments, the movement of the rollers 10, 11, 13, and 14 on the shafts 12 and 15 may be performed by a manual operation in addition to the driving means. Further, in the first and second embodiments, each of the rollers 10, 11, 13, and 14 is in contact only with the vicinity of both ends of the recording paper 2. Therefore, depending on the stiffness of the recording paper 2, the reverse curl may not be sufficiently applied to the center of the recording paper 2, so that the endless belt having a width equal to or larger than that of the recording paper is applied to the rollers 10,
When the recording paper is wrapped around 11, 13, and 14, and the recording paper is wrapped around the belt, a reverse curl can be given to the entire width of the recording paper, and the curl correction can be performed more effectively. In the first embodiment and the second embodiment,
When the recording paper 2 is in contact with the small-diameter portions of the rollers 10, 11, 13, and 14, the wrapping angle of the recording paper 2 with respect to the rollers 10, 11, 13, and 14 is greater than when the recording paper 2 is in contact with the large-diameter portions. And the amount of reverse curl applied to the recording paper 2 decreases. For this reason, when sufficient curl correction cannot be obtained, at least one of the rollers and the transport rollers R1 and R2 can be arbitrarily changed, and the recording paper 2 is moved to the rollers 10, 11, 13 and 14 are in contact with the small diameter portion of the roller 14,
It is preferable to change their positional relationship so that the wrapping angles with respect to 3 and 14 become large. Specifically, the rollers 10, 11, 13, 1
4 can be moved in a direction perpendicular to a straight line connecting the points where the transport rollers R1 and R2 sandwich the recording paper 2;
When the recording paper 2 is in contact with the small diameter portions of the rollers 10, 11, 13, and 14, it is easy to separate the rollers 10, 11, 13, and 14 from the straight line so as to increase the winding angle. The above configuration can be implemented. As another means for changing the curvature of the curl correcting member, the curl correcting means C is provided with a plurality of rollers having different diameters, and a desired roller is selected from the rollers to move the curl correcting member C along the conveyance path of the recording paper 2. The recording paper 2 may be arranged in contact with the recording paper 2. Specifically, a roller is attached to the tip of the radial arm, and the desired roller can be positioned at a predetermined position by rotating the arm. Further, the ink jet printer according to the present invention is further provided with means for detecting the diameter of the recording paper roll 1, and the recording paper 2 is applied in conjunction with the information on the diameter of the recording paper roll 1 obtained thereby. If the curvature of the curl correction member S in contact is changed, the curvature of the curl correction member S can be automatically changed according to the degree of curl of the recording paper 2. Other information that is used as a basis for changing the curvature of the curl correcting member S includes, for example, the total printing time of the ink jet printer since the start of using the new recording paper roll 1 and the length of the used paper. Can be used. Further, if the information is processed in consideration of the paper quality of the recording paper 2 and the humidity of the use atmosphere of the ink jet printer, which are factors affecting the curl amount, the curl can be corrected more accurately. Although a rotating roller is used as the curl correcting member S in the above embodiment, a member having a curved surface that does not rotate may be used. In this case, in order to change the curvature of the curved surface, the member forming the curved surface should be deformable,
In order to lower the coefficient of friction of the portion of the member that comes into contact with the recording paper 2, it is preferable that the member be coated with a fluorine resin. Also, if the curl correcting member S is kept in contact with the recording paper for a long time even during non-printing, the paper will be excessively reversely curled. Is desirable. The effects obtained by correcting the curl and flattening the printing paper include the prevention of deterioration of the printing quality, the prevention of stain on the recording paper, and the prevention of damage to the head due to the recording paper being hit. Prevention and recording failure due to paper dust adhering to the discharge port. Further, since the posture of the sheet at the time of conveyance is stabilized, the accuracy of cutting the sheet is improved, and the paper jam is prevented. As an effect of the present invention, the portion of the curl correcting means which presses the recording paper is formed of a curved surface symmetrical to the curl of the recording paper, and the curvature of the curved surface can be changed. Therefore, the correction amount can be accurately set in a wide range, and the correction can be reliably performed from a case where the curling amount of the recording sheet is large to a case where the curling amount is small. Therefore, it is possible to prevent the recording quality from deteriorating due to the curl of the recording paper.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of an inkjet printer according to a first embodiment of the present invention. FIGS. 2A and 2B are explanatory diagrams illustrating a state of the curl correcting unit according to the embodiment, in which FIG. 2A illustrates a state in which a recording sheet is wrapped around a large-diameter portion of a truncated cone-shaped roller, and FIG. 5 shows a state in which recording paper is wrapped around a small diameter portion of a shaped roller. FIG. 3 is an explanatory diagram of a state of a curl correcting unit of the inkjet printer according to the second embodiment of the present invention,
(A) shows a state where the recording paper is wrapped around the large diameter portion of the stepped roller, and (b) shows a state where the recording paper is wrapped around the small diameter portion of the stepped roller. DESCRIPTION OF SYMBOLS 1 ... Recording paper roll, 2 ... Recording paper, 10, 11 ... Truncated conical roller, 13,14 ... Stepped roller, C ... Curl correction means, S ... Curl correction member

Claims (1)

Claims: 1. An ink jet printer comprising a curl correcting unit for pressing a recording sheet in a direction opposite to the curl of the recording sheet, wherein the curl correcting unit presses the recording sheet. An ink jet printer, comprising a curved surface symmetrical to the curl of the recording paper, wherein the curvature of the curved surface is changeable.