Patent Application
20090073219
A common way to form images on media, such as paper, is to use a fluid-ejection device, such as an inkjet-printing device. An inkjet-printing device has a number of inkjet nozzles that eject ink, such as differently colored ink, in such a way as to form a desired image on the media. Many inks are dye-based, whereas other inks are pigment-based. In some formulations, these inks may be or may become relatively viscous.
Such viscous inks can form viscous sludge inside the inkjet nozzles. This sludge can affect typical testing, such as single drop detect testing, to determine whether the inkjet nozzles properly eject the ink. For instance, the performance of a single drop detect test may result in an inkjet nozzle using a pigment-based ink being seemingly OK to properly eject ink, only to fail to eject ink thereafter.
When an inkjet nozzle has failed a test to determine whether it is properly ejecting ink, generally the nozzles undergo servicing so that they can indeed properly eject ink. Typically, the nozzles undergo servicing such that a least-severe servicing event is performed first. The least-severe servicing event causes less ink to be ejected than more-severe servicing events. However, this conventional approach of servicing can greatly lengthen the time it takes to service an inkjet nozzle for pigment-based inks.
So-called “spitting,” or ejecting, of ink from an inkjet nozzle has been found to be an efficient way to remove large volumes of ink from an inkjet mechanism, such as an inkjet printhead, including the nozzle, when needed. However, in the case of pigment-based inks, such spitting can result in viscous sludge forming on the inkjet mechanism. This conventional ink spitting is thus disadvantageous as well.
The inkjet-printing device 100 may eject pigment-based ink, dye-based ink, or another type of ink. The inkjet-printing device 100 includes at least two access doors: an access door 102, and an access door 104. The access door 104 is opened to permit a user to remove and insert ink cartridges into and from the inkjet printing device 100. The access door 102 is opened to permit a user to remove and insert inkjet printheads into and from the inkjet printing device 100.
In another embodiment, however, there may be just four ink cartridges 202. The ink cartridges 202 in this embodiment may include black, cyan, magenta, and yellow ink cartridges. Having four such ink cartridges enables the inkjet-printing device 100 to print full-color images on media, but generally not as photorealistic as when there are eight ink cartridges 202. In still another embodiment, there may be just a single black ink cartridge 202. In this embodiment, the inkjet-printing device 100 can print black-and-white and grayscale images on media, but not color images.
In another embodiment, however, there may be just two inkjet printheads 302, in the case where there are just four differently colored inks, cyan, magenta, yellow, and black. One of these inkjet printheads may be responsible for ejecting black ink, whereas the other printhead may be responsible for ejecting cyan, magenta, and yellow ink. In still another embodiment, there may be just a single inkjet printhead, in the case where there is just black ink, such that the single inkjet printhead ejects this black ink.
The embodiments of the invention that have been described in relation to
The inkjet printhead 402 includes a number of inkjet nozzles 404, which may more generally be referred to as fluid-ejection nozzles. The inkjet nozzles 404 are organized over a number of columns 406A, 406B, . . . , 406M, collectively referred to as the columns 406, and a number of rows 408A, 408B, . . . , 408N, collectively referred to as the rows 408. In one embodiment, for example, there may be four columns 406 and 528 rows 408, for a total of 2,112 of inkjet nozzles 404. It is noted that the inkjet nozzles 404 are organized in aligned columns 406 in the example of
The inkjet nozzles 404 are the orifices from which ink, or fluid, is ejected out of the inkjet printhead 402. The surface of the inkjet printhead 402 shown in
That is, as described in the background section, pigment-based ink can form sludge on the orifice plate and/or on or within the inkjet nozzles 404, impeding the ability of the inkjet nozzles 404 to properly eject ink onto the media to form desired images on the media, where such images may also include text in addition to graphics. Embodiments of the invention are thus concerned with detecting whether the inkjet nozzles 404 of the inkjet printhead 402 are able to properly eject ink. Embodiments of the invention are further concerned with detecting whether servicing the inkjet nozzles 404 of the inkjet printhead 402 when they are unable to properly eject ink.
Referring first to
Thus, the first drop detect test can be performed in one embodiment as follows. First, the inkjet printhead 402 is moved so that it is aimed against a drop detector (506), which is another term for a drop detect target. The inkjet nozzles 404 of the inkjet printhead 402 are then fired (508). Based on where and how much ink is deposited on the drop detect target, it can be determined which and how many of the inkjet nozzles 404 successfully (and actually) ejected ink (510).
As indicated by the arrows 604A and 604C, the inkjet nozzles 404A and 404C ejected ink 606A and 606C, respectively, against the drop detector 602. The drop detector 602 is able to detect this ink 606A and 606C, and correspond the ink 606A and 606C to the inkjet nozzles 404A and 404C, so that it can be concluded that the inkjet nozzles 404A and 404C properly ejected ink. By comparison, however, dried ink 608, or sludge, has formed over the inkjet nozzle 404B. As a result, the inkjet nozzle 404B did not successfully and properly eject ink, such that the drop detector 602 did not detect any ink being deposited thereon as a result of the inkjet nozzle 404B firing.
Referring back to
It has been found, for instance, that where a single drop detect test is performed and indicates that the inkjet nozzles of an inkjet printhead are properly ejecting ink, the inkjet printhead may nevertheless may have residual clogs or sludge that did not prevent the single drop detect test from succeeding, but that will soon affect ink ejection by the nozzles. Therefore, this is why two drop detect tests are performed in the embodiment of
It is noted that performing more than one drop detect test does not have to be performed for all colors of ink. Rather, just one drop detect test may be performed for some of the differently colored inks, and more than one drop detect may be performed for other of the differently colored inks. In one embodiment, for instance, more than one drop detect test is performed just for matte black ink. Empirical testing can be performed, as can be appreciated by those of ordinary skill within the art, to determine whether one or more than one drop detect test should be performed for a given color of ink.
In one embodiment, the criterion against which the results of the second (i.e., last) drop detect test are compared is a number of the inkjet nozzles 404 of the inkjet printhead 402 that did not successfully eject ink, as detected by the drop detect target. For instance, this criterion may be twenty nozzles. If more than twenty nozzles did not eject ink during the drop detect test, then the drop detect test is considered as having failed the criterion. If twenty or less nozzles did not eject ink during the drop detect test, then the drop detect test is considered as having passed the criterion, by comparison.
Assuming that the results of the second drop detect test in the embodiment of
The severity of a servicing event is thus dependent on which operations are performed as part of the servicing event. For example, as will be described in more detail, a servicing event can include one or more spit operations, one or more wipe operations, and/or one or more prime operations designed to unclog any clogged of the inkjet nozzles 404 of the inkjet printhead 402. A spit operation is specifically an operation in which a predetermined amount of ink is ejected from an inkjet nozzle. The inkjet nozzle may be fired a number of times at high frequency to eject this predetermined amount of ink. A wipe operation is an operation in which a wiper is moved in relation to the inkjet nozzle, to clean any ink on or around the nozzle. A prime operation is specifically an operation in which ink is removed from an inkjet nozzle by using suction. Examples of spit and wipe operations are described in more detail later in the detailed description. The amount of ink removed from an inkjet nozzle by all the various operations of a given servicing event in total thus is indicative of the severity of this servicing event.
In one embodiment, one of three servicing events, corresponding to counter values of zero, one, and two, is performed in part 516 of the method 500. As has been noted, the first servicing event is most severe, and may include performing heavy prime, light prime, spit, and wipe operations. The second servicing event is less severe, and may include performing heavy prime, spit, and wipe operations. The third servicing event is least severe, and may include performing light prime, spit, and wipe operations.
It is noted that performing the most-severe servicing event first is unlike the prior art, and indeed is somewhat counterintuitive. Conventionally, the least-severe servicing event is performed first, and any other servicing events are performed in order in increasing degrees of severity, such that the most-severe servicing event is performed last. The motivation behind doing so is to decrease servicing time, insofar as the greater the severity of a servicing event, the longer it takes to perform the servicing event.
However, what has been found is that with pigment-based inks in particular, the least-severe servicing event either does not usually clear the clogged inkjet nozzles for at least certain colors of ink such as matte black ink, and/or clears the clogged inkjet nozzles but not enough to prevent image formation degradation from occurring soon thereafter. Therefore, performing the most-severe servicing event first is accomplished so that image formation degradation does not occur soon after servicing is performed, and to ensure that the clogged inkjet nozzles are more likely to be cleared the first time a servicing event is performed. This will become more apparent as the remainder of
Once the servicing event has been performed, the counter is incremented (518). The counter is then compared against a predetermined threshold (520). In one embodiment, this threshold is three. Thus, if the value of the counter is less than three, then the method 500 repeats at part 504. Otherwise, once the value of the counter has reached three, then the method 500 proceeds to part 522 in
Where the threshold against which the counter is compared is three, this means that at most three different servicing events are performed in the various iterations of part 516. In the first iteration of part 516, the most-severe servicing event is performed. Performing the most-severe servicing event takes longer than performing less-severe servicing events. However, the likelihood that performing the most-severe servicing event will clear the clogged nozzles 404 of the inkjet printhead 402 is greater than if less-severe servicing events were instead performed. Thus, the likelihood that the second drop detect test (in the embodiment of
That is, what has been found in relation to pigment-based inks in particular is that performing servicing events in order from least-severe to most-severe during successive iterations still results in the most-severe servicing event more often than not having to be performed to clear the clogged inkjet nozzles 404. Therefore, while intuition would suggest that the least-severe servicing event be performed first, since it takes less time to complete such that servicing time may be minimized if performance of this servicing event yields cleared nozzles, it has been found in actuality that least-severe servicing event does not often clear the clogged inkjet nozzles 404 when performed first. Instead, performing the most-severe servicing event first, even though taking more time, is more likely to clear the clogged nozzles 404, so that less-severe servicing events do not have to be performed.
Referring next to
In one embodiment, the sustainability purge operation is performed by performing parts 524 and 530. A first series of spit-wipe operations is performed (526). Such a series of spit-wipe operations includes performing one or more spit operations (526), substantially interleaved with performing one or more wipe operations (528). A spit operation ejects a predetermined amount of ink from the inkjet nozzles 404 by firing the inkjet nozzles 404 a number of times at high frequency. A wipe operation cleans the nozzles 404 by moving the nozzles 404 against a stationary wiper, or by moving a wiper against the nozzles 404 as they remain stationary. A second series of spit-wipe operations is performed (530) after the first series of spit-wipe operations is performed.
It is noted that in at least one embodiment, the sustainability purge operation of part 522 of
Referring back to
The performance of both spit and wipe operations in a sustainability purge of the inkjet nozzles 404 of the inkjet printhead 402 differs from the prior art, and is somewhat counterintuitive. Conventional sustainability purges, for instance, typically just involve a number of spit operations, since the motivation is to clear the inkjet nozzles as much as possible. However, what has been found is that such conventional sustainability purges can result in undesired sludge buildup on the inkjet nozzles 404 where pigment-based inks are used, resulting in later image formation or printing problems. Therefore, although performing one or more wipe operations is not intuitively performed during a purge operation, embodiments of the invention nevertheless perform such wipe operations to clean the sludge buildup on the inkjet nozzles 404 resulting from the spit operations.
After the sustainability purge operation has been performed, an alignment operation of the inkjet nozzles 404 of the inkjet printhead 402 may be performed (532). This operation is performed to align the ink droplets ejected by the nozzles 404 relative to one another, and as such adjusts the relative positioning of the ink droplets. Such an alignment operation may be performed as is conventional, as can be appreciated by those of ordinary skill within the art.
Likewise, a color calibration operation of the inkjet nozzles 404 of the inkjet printhead 402 may be performed (534). This operation is performed to ensure that the colors that are formed by ejecting differently colored of the inks match predetermined profiles or other criteria. This operation adjusts how much of each ink is ejected to ensure a given color results. Such a color calibration operation may be performed as is conventional, as can be appreciated by those of ordinary skill within the art. Finally, the most-severe servicing event is again performed (536), to potentially clear any of the nozzles 404 that may have been clogged, or that may soon clog when normal image formation or printing commences, as a result of the operations of parts 532 and 534.
Referring finally to
The first servicing event may include performing heavy prime, spit, and wipe operations. The second servicing event is less severe than the first servicing event, and may include performing light prime, spit, and wipe operations. The third servicing event is more severe than the first servicing event, and may include performing scrub, spit, and wipe operations. A scrub operation is similar to a wipe operation. However, where a wipe operation moves the wiper in relation to the printhead back and forth in smooth motions, a scrub operation moves the wiper in relation to the printhead back and forth in jerky motions. As such, a scrub operation may be considered a mechanically agitated wipe operation. The fourth servicing event is identical to the first servicing event. Thus, in part 546, unlike in part 516, the first servicing event performed is not the most-severe servicing event.
The counter is then incremented (548), and where the current value of the current is less then a predetermined threshold, such as four, the method 500 repeats at part 540 (550). Therefore, at most four servicing events are performed in various iterations of part 548, depending on whether the second drop detect test fails the criterion in part 544, which may, as before, be whether more than twenty of the inkjet nozzles 404 of the inkjet printhead 402 failed to eject ink. Where the second drop detect test satisfies the criterion in part 544, or once the counter has reached the predetermined threshold in part 550, the method 500 is finished (552). As such, the inkjet-printing device 100 is ready to form images on media by ejecting ink.
In conclusion,
The inkjet printhead 402 is depicted as part of the inkjet-printing device 100 in
The logic 1002 may be implemented in software, hardware, or a combination of software and hardware, and may be considered the means that performs various functionality. The logic 1002 can perform, or cause the inkjet printhead 402 to perform, the method 500 of
As another example, the logic 1002 can cause the inkjet printhead 402 to be serviced by performing one or more servicing events, where the most-severe servicing event is performed first, as has been described. As a final example, the logic 1002 can cause ink to be purged from the inkjet nozzles 404 by performing a number of series of spit-wipe operations, where both spit operations and wipe operations are performed. Thus, the logic 1002 can determine whether servicing has to be performed, and cause such servicing to be performed if needed.
