Patent Grant
8240802
1. Field of the Invention
The present invention relates to a method for adjusting a printing position of a dot in dot-matrix printing. Especially, it relates to a method for simplifying an adjustment process of the printing position at the time of exchange of a printing head etc. in a printing apparatus that uses a detachable printing head.
2. Description of the Related Art
In inkjet printing apparatuses, with the increased use of multiple colors in images, there have spread many ones each of which has a form such that a plurality of printing heads are mounted on a carriage and an image is printed while that carriage is being scanned. Regarding the printing head, there are many ones that are detachable to their carriages. In this case, adjustment of the printing position is regularly conducted each time the printing head is exchanged.
Hereafter, the adjustment of the printing position will be explained briefly. In the printing apparatus and the plurality of printing heads, a certain amount of variation is inevitably included therein because of its manufacture process, relationships of positions of the plurality of printing heads when being mounted on the carriage become various.
Contrary to this case, if there occurs an installation error, for example, among the printing head 91 or the carriage 96 that carries this, the ejection outlet array of the printing head 91 will have an inclination or will be shifted to the other three ejection outlet arrays.
If there is an error of a whichever kind in a whichever direction, in the state shown in
Therefore, in the printing apparatus whose printing head is exchangeable, it was common to detect deviation quantity of the printing position from a printed test pattern and then to adjust a timing of ejecting the ink depending on the acquired deviation quantity at the time of printing as is disclosed, for example, in Japanese Patent Laid-Open No. 2002-120360.
Digressing momentarily, the printing position deviation of the printing head has several kinds as follows: a printing position deviation among the plurality of printing heads (among ink colors); a deviation caused by the inclination of the each printing head; a printing position deviation between the outward scan and the return scan. Moreover, recently, cases where inks of many more colors consisting of fundamental four colors (CMYK) plus several additional colors are used in order to enhance color reproducibility are increasingly carried out into practice. Therefore, when detecting the printing position deviation, there arises a need for printing the test patterns different in these kinds or the ink colors and detecting the deviation quantities for the respective test patterns. However, if these test patterns are printed and the respective printing position deviations are detected not only at the time of delivery of the printing apparatus but also each time the printing head is exchanged, large quantities of inks, printing media, and time will be consumed for this detection.
The present invention is made in order to solve the above-mentioned problem. Therefore, what the present invention aims at is to provide a method for adjusting a printing position deviation that can stably adjust the printing position deviation while conducting as small a number of steps of detecting the printing position deviation as possible even in the case of the printing apparatus that carries a detachable printing head.
The first aspect of the present invention is a printing apparatus comprising: a mounting unit capable of mounting a printing head in which a plurality of ejection outlet ejecting an ink are arranged: the printing head storing a first parameter related to a printing position deviation inherent to the printing head; a printing unit configured to print dots on a printing medium by ejecting an ink from the printing head; a detecting unit configured to detect a printing position deviation with the printing head mounted on the printing apparatus; an unit configured to store a second parameter related to the printing position deviation with the printing head mounted on the printing apparatus; an unit configured to correct positions at which the printing head prints dots on the printing medium according to the second parameter; an unit configured to derive a third parameter related to the printing position deviation inherent to the printing apparatus from the first parameter and the second parameter; an unit configured to store the third parameter; and an updating unit configured to update the second parameter, when a new printing head is mounted on the printing apparatus, from the third parameter and the first parameter of the new printing head.
The second aspect of the present invention is a method for adjusting printing positions, comprising steps for: mounting a printing head for printing dots on a printing medium to a printing apparatus: the printing head storing a first parameter related to a printing position deviation inherent to the printing head; detecting a printing position deviation with the printing head mounted on the printing apparatus; storing a second parameter related to the printing position deviation with the printing head mounted on the printing apparatus; correcting positions at which the printing head prints dots on the printing medium according to the second parameter; deriving a third parameter related to the printing position deviation inherent to the printing apparatus from the first parameter and the second parameter; storing the third parameter; and updating the second parameter, when a new printing head is mounted on the printing apparatus, from the third parameter and the first parameter of the new printing head.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
In the figure, a component C is an ink jet cartridge (hereinafter referred to as a cartridge) that has an ink tank in its upper part and a printing head in its lower part, and is further provided with a connector for receiving signals for driving the printing head. In this embodiment, the four cartridges C are prepared corresponding to inks of four colors (cyan, magenta, yellow, and black), and each of them is mounted on a carriage 2 detachably.
The carriage 2 is made capable of performing a reciprocal movement in a main scanning direction (an X-direction) while being supported and guided by a scanning rail 11 with a driving force of a carriage motor 52 that is transferred through a driving belt 53. The each printing head ejects the ink toward a printing medium P following a printing signal during the movement in the X-direction (under scanning). Incidentally, at a position that is abreast with the printing head of the carriage 2, an optical sensor for reading a test pattern printed by the printing head is provided.
Each time the scanning by the printing head is performed once, the printing medium P is conveyed by an amount corresponding to a printing width of the printing head in a Y-direction crossing the X-direction. The printing medium P is sandwiched between a conveyance roller pair (5 and 6) placed on an upstream side of a printing area zoned by the printing head and a paper discharging roller pair (7 and 8) placed on a downstream side of the printing area, and is conveyed to the Y-direction with the rotation of theses roller pairs in a state where smoothness of the printing area is maintained. Furthermore, an unillustrated platen is disposed in the printing area and supports the printing medium P located in the printing area from the beneath.
At an end of a movement area of the carriage 2, a recovery system unit 300 for performing a maintenance processing of the printing head is disposed. The recovery system unit 300 performs capping on the printing head that has moved here, a suction recovery processing for removing impurities, bubbles, etc. in the printing head, etc., and does other things.
In the printing head 86, a plurality of ejection outlets serving as outlets of ink droplets are arranged in an ejection outlet plane 1 that is a bottom side of the view. Furthermore, in its interior, an ink path for guiding the ink supplied from the ink tank T to each ejection outlet and an electrothermal transducer for ejecting the ink in the ink path in response to the printing signal are placed.
Moreover, although not shown in the figure, the printing head of this embodiment is equipped with memory for storing information peculiar to the each printing head. In addition, at the time of manufacture of the printing head, an inclination of the arrangement direction of the ejection outlets of the each printing head, etc. are measured, and that information is stored in the memory. After the printing head is mounted on the carriage of the printing apparatus, that information is provided to the main board of the apparatus through the connector 85 and a flexible cable.
Upon reception of the image data from a host 200 connected to the outside of the printing apparatus 100, the CPU 201 temporarily stores this in a receive buffer 203. Since the image data stored in the receive buffer 203 is compressed, the CPU 201 decompresses this compressed data to first print memory 204. After that, the image data that is decompressed to the first print memory 204 is subjected to an HV conversion processing by an HV conversion circuit 205, and is stored in second print memory 206. The data memorized in this second print memory 206 becomes print data whereby the printing head actually carries out ejection and the CPU 201 transfers this to the connectors 85 of the respective colors on the printing head side each time the scanning is performed.
Hereafter, characteristic matters of this embodiment will be explained. Here, for simplicity, a case where correction values of printing position deviations caused by the inclination of one printing head and the inclination of the printing apparatus are acquired will be explained. This embodiment is characterized in that the printing position deviation inherent to the printing apparatus and the printing position deviation inherent to the printing head are managed individually.
Moreover,
On the other hand,
Further,
In this way, at the position where a dot is actually printed on the printing medium, the position deviations of both the carriage and the printing head have influenced, and, in the case of the printing apparatus whose printing head is exchangeable, a necessary correction quantity varies because a combination of the printing apparatus and the printing head changes.
At Step S2, inclination information α1 inherent to the printing head that is stored in the memory of the printing head is acquired, and at Step S3, this is primarily memorized in the RAM 207 of the printing apparatus as the first parameter. At succeeding Step S4, the actual measurement sequence of a printing position deviation quantity is performed.
Here, if the ejection outlet array of the printing head does not have the inclination to the conveyance direction (the Y-direction) of the printing medium, positions of the dots printed by two scans become like
The explanation returns to the flowchart of
Supposing that the pattern selected here is 402 of
Incidentally, here, although the sequence was explained supposing that a pattern with least density fluctuation was selected out of a plurality of patterns and the inclination information γ1 of the ejection outlet array was deduced, the selection criterion of the pattern and a method for determining the inclination amount are not limited to this. For example, in the case where in the optical density that the optical sensor detects, when an optical density fall by the white streak is larger than an optical density rise by the black streak, a pattern whose average density over the whole pattern is the highest may be selected. Alternatively, it is also possible to approximate a relationship of the inclination amount and the optical density using a linear expression or higher-order polynomial expression from the shift quantity (the number of shifted pixels) and the average density of the individual pattern and to compute a more accurate inclination amount from the obtained approximate curve.
The explanation returns to the flowchart of
After that, the process proceeds to Step S6, where an inclination amount β related to the printing apparatus is computed from the inclination amount γ1 memorized at Step S5 and an inclination amount α1 of the printing head memorized at Step S3. The inclination amount γ1 acquired at Step S4 is a value acquired by actually printing the test pattern with the printing head mounted on the printing apparatus. That is, this inclination amount γ1 is an inclination amount in which the inclination amount β1 inherent to the printing apparatus and the inclination amount α1 inherent to the printing head are composed. Therefore, at Step S6, the inclination amount β inherent to the printing apparatus is acquired by subtracting the inclination amount α1 inherent to the printing head that is acquired in advance from the inclination amount γ1 obtained by the actual measurement (β=γ1−α1), and the inclination amount β is stored in the memory (RAM 207) of the printing apparatus as a third parameter. The inclination amount β (the third parameter) inherent to this printing apparatus does not vary even if exchange of the printing head is done after that.
On the other hand, when it is determined that this printing position adjustment sequence is not the first after the time of the delivery of the apparatus at Step S1, the process proceeds to Step S7.
At Step S7, it is determined whether the printing head is exchanged after the printing position adjustment sequence was performed last time. If it is determined that the printing head is not exchanged, it will be determined that it is not necessary to perform the printing position adjustment sequence this time, and this processing will be ended. On the other hand, if it is determined that the printing head is exchanged, the process will proceed to Step S8, where an inclination amount α2 of this printing head will be acquired from the memory of the new printing head currently mounted. After that, at Step S9, the inclination amount α2 is stored in the memory of the printing apparatus as the first parameter.
At succeeding Step S10, an inclination amount γ2 of the ejection outlet array to the conveyance direction resulting from a current combination of the printing apparatus and the printing head is computed from the inclination amount β inherent to the printing apparatus stored in the memory (RAM 207) of the printing apparatus and the inclination amount α2 inherent to the printing head memorized at Step S9. That is, γ2 is computed by defining γ2=α2+β, and this is memorized in the memory as a new second parameter of the printing apparatus. After doing the above, this processing is ended.
When actually performing the printing, what is necessary is for the CPU just to perform control so that each ejection outlet may eject the ink with a shifted timing based on an occasional γ, i.e. the inclination of the ejection outlet array relative, to the conveyance direction. Specifically, if the inclination γ of the ejection outlet array to the conveyance direction is, for example, Θ (γ=Θ) shown in
Moreover, although the above embodiment was explained with a description that the inclination amount of the ejection outlet array to the Y-direction, the inclination amount inherent to the printing apparatus, and the inclination amount inherent to the printing head are acquired, respectively, and these are stored in the memory of the printing apparatus, the parameter to memorize may be not the inclination amount but an actual correction value. In this case, the correction value is equivalent to a value for adjusting the ejection timing from each ejection outlet and, for example, the correction value can be set to +1 in the case where the ink is ejected at a timing later than the reference value by one pixel. Similarly, the correction value can be set to −1 in the case where the ink is ejected at a timing earlier than the reference value by one pixel. Moreover, if the printing apparatus is of a configuration of being capable of controlling the ejection timing using a 1/2 pixel as a minimum unit as described above, it is also possible to set to unity a minimum unit by which the ejection timing can be controlled and to set to +2 (−2) a correction value in the case where the ink is ejected at a timing later (earlier) than the reference value by one pixel. Even if such correction values are replaced with α, β, and γ, a relationship γ=α+β can be maintained. In all cases, if it can be done to independently manage the first parameter α related to the inclination amount inherent to the printing apparatus and the third parameter β related to the inclination amount inherent to the printing head and to derive the second parameter γ related to the actual inclination amount of the ejection outlet array to the Y-direction, this embodiment will function effectively.
According to this embodiment explained above, only at the time of delivery of the printing apparatus, printing of such a pattern as explained in
Incidentally, as was explained already, in the actual printing position deviations, there exist various printing position deviations, such as the printing position deviation between the outward scan and the return scan, and the printing position deviation among ink colors (among the printing heads) in the X-direction or the Y-direction, in addition to the printing position deviation accompanying the above-mentioned inclination of the nozzle array. Regarding these printing position deviations, the deviation quantities can be acquired separately by printing the test pattern appropriate to each of them and by detecting these test patterns using the optical sensor. Then, the printing step of these test patterns and the detection step thereof using the optical sensor can be performed simultaneously with the step of detecting the inclination amount in Step S12 and Step S13 in the flowchart explained in
In the ink jet printing head equipped with a heater, there may be a case where energy being put into the ink is not maintained at a proper quantity even when the same voltage pulse is applied to the heater because a color material component is accumulated on a heater surface or a protective film on the heater surface deteriorates as the number of times of ejection increases. In this case, a fluctuation of input energy affects speed and quantity of the ejected ink droplets, and thereby there may be a case where the deviation occurs in printing position on the printing medium even when the printing is performed at the same timing.
This embodiment is characterized by adopting the same configuration as that of the first embodiment, and also by adding adjustment to the correction quantity of the printing position deviation by predicting a variation of the printing position deviation accompanying the number of times of ejection by some degree. Therefore, the printing apparatus of this embodiment shall be equipped with means for counting the number of times of ejection of the printing head mounted thereon and means for memorizing the number of times of ejection. Then, since it is difficult to manage the number of times of ejection for each ejection outlet in fact, an average of the number of times of ejection of each ejection outlet is found from the number of times of ejection of the whole printing head, and this value is used as a standard of the adjustment.
In this embodiment, at Step S7, if it is determined that the printing head currently mounted is not exchanged from a time when the printing position adjustment sequence was performed last time, the process proceeds to Step S11 and determines whether the number of times of ejection of the each printing head is equal to or more than a threshold N. If it is determined that the number of times of ejection is equal to or more than the threshold N, the process will proceed to Step S12, where a new inclination amount γ3=γ2+δ will be computed by adding an adjustment value δ to the inclination amount γ2 currently grasped. On the other hand, if it is determined that the number of times of ejection of the printing head is neither equal to nor more than the threshold N at Step S11, it will be determined that there is no necessity of performing the printing position adjustment sequence this time, and this processing will be ended.
According to this embodiment explained above, similarly with the first embodiment, the inclination amount of the nozzle array to the conveyance direction is actually measured by performing the printing of the test pattern and the reading of the pattern with the optical sensor only at the time of delivery of the printing apparatus. Then, when the printing head is exchanged, information of the inclination amount inherent to the printing head that is memorized in the printing head is read, and if the number of times of ejection of the printing head is large, a correction is given to the deviation quantity of the printing position depending on the number of times of ejection. This configuration makes it possible to stably output the uniform image by performing an appropriate correction to the printing position deviation while controlling small a time and the consumables required to grasp the printing position deviation quantity.
Incidentally, in this embodiment, it is also possible to prepare values of the adjustment value δ for multiple stages depending on the number of times of ejection.
Incidentally, in the embodiment explained above, although the explanation was given based on the premise that each one of the printing heads is of a configuration that has a single nozzle array, the present invention is not limited to such a configuration. For example, the nozzle array of each color may be of a form constructed with two nozzle arrays whose ejection outlets are placed on the right and left sides alternately. Moreover, the printing head may have a configuration such that only the ejection outlet array 90 of black is larger than the ink ejection outlet arrays 91, 92, and 93 of other colors in the number of the ink ejection outlets.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2009-148826, filed Jun. 23, 2009, which is hereby incorporated by reference herein in its entirety.
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