Patent Application
20080180478
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-printing mechanisms, such as inkjet printheads. Each inkjet printhead 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, but other inks are pigment-based, which are usually more viscous than dye-based inks.
Inkjet printheads can lose water contained within the ink through the inkjet nozzles, as well as through the body of the printheads and the tubing that delivers the ink to the printheads. When too much water is lost from the ink, the viscosity of the ink can increase, and/or the ink suspension can become unstable. Either of these situations can result in poor image formation quality.
Ink can also gain air over time through the tubing that delivers the ink to an inkjet printhead. As this ink is brought into the inkjet printhead, the dissolved air outgases from the ink as the ink is temperature-cycled through usage of the printhead. This air becomes trapped within the housing or body of the inkjet printhead, decreasing the available volume for replenishment of the ink. As a result, poor image formation quality can occur in this situation as well.
The inkjet-printing device 100 may eject pigment-based ink, dye-based ink, or another type of ink. Differences between pigment-based inks and dye-based inks include that the former is generally more viscous than the latter among other differences. 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 523 rows 408, for a total of 2,112 inkjet nozzles 404.
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
When the inkjet printhead 402 remains unused for a period of time, and thus does not eject ink from the inkjet nozzles 404 thereof, two undesirable effects may transpire. First, water may be lost from the ink contained within the tubing 504, the inkjet nozzles 404, and/or the body of the inkjet printhead 402 itself, as indicated by arrows 506 in
Second, air may be gained within the ink within the tubing 504, the inkjet nozzles 404, and/or the body of the inkjet printhead 402 itself, as indicated by arrows 508 in
Embodiments of the invention are concerned with periodic performance of a non-user-initiated preventative maintenance mode of the inkjet printhead 402 to prevent these situations from occurring. In particular, by periodically performing such preventative maintenance that is not user-initiated, when the user subsequently initiates image formation on media by the inkjet nozzles 404 of the inkjet printheads 402, the ink contained within the printhead 402 will not be suffering from undue water loss or air gain. As a result, the image formed on the media will not as likely be degraded than where undue water loss and/or air gain occurs.
Initially, the rate of water loss from the ink within the inkjet-printing device 100 and the rate of air gain into this ink is determined (602), and one or more preventative maintenance mode parameters are determined based on this water loss rate and this air gain rate (604). The rate of water loss from the ink, as exemplified by
The non-user-initiated preventative maintenance mode parameters can include two parameters in particular: how often the preventative maintenance mode is to be determined, and how much ink is to be ejected when the preventative maintenance mode is performed. Other types of parameters may also be determined. The frequency at which the preventative maintenance mode is performed, together with how much ink is to be ejected when the preventative maintenance mode is performed, are typically empirically determined. Specifically, the water loss rate and the air gain rate, when left uncorrected, at some point will cause subsequently initiated image formation by the inkjet-printing device 100 to suffer from image quality degradation.
Therefore, how often the preventative maintenance mode is performed, and how much ink is ejected when this mode is performed, are determined so that image quality degradation does not result when the inkjet-printing device 100 is called upon to form images on media. For example, it may be empirically determined that if the inkjet-printing device 100 remains unused for four days, then image quality degradation results. Therefore, the preventative maintenance mode is determined to be performed at least every four days that the inkjet-printing device 100 remains unused. It may also be empirically determined that when the inkjet-printing device 100 remains unused for four days, 0.33 cubic centimeters (cc) of ink has to be ejected to replenish the ink within the inkjet printhead 402 such that image quality degradation does not result when the inkjet-printing device 100 is called upon to form images on media. Therefore, the preventative maintenance mode is performed such that at least 0.33 cc of ink is ejected from the inkjet nozzles 404 of the inkjet printhead 402.
It is noted that the water loss rate and the air gain rate determined in part 602 of the method 600, and the non-user-initiated preventative maintenance mode parameters determined in part 604 of the method 600, are usually particular to a given type of inkjet-printing device 100. That is, they are particular to a given type of inkjet printhead 402 employed within the inkjet-printing device 100, having a given type and number of inkjet-printing nozzles 404, and a given type of ink supplied by the inkjet cartridge 502. In addition, the water loss rate, the air gain rate, and the parameters are particular to a given type of tubing 504 that supplies the ink from the inkjet cartridge 502 to the inkjet printhead 402. This is why the water loss rate, the air gain rate, and the non-user-initiated preventative maintenance mode parameters are typically empirically determined.
The non-user-initiated preventative maintenance mode parameters may be programmed into the inkjet-printing device 100, such that the non-user-initiated preventative maintenance mode is periodically performed (605). As has been noted, the preventative maintenance mode is not user-initiated, but rather is initiated by the inkjet-printing device 100 itself. Furthermore, the preventative maintenance mode is typically performed when the inkjet-printing device 100 is idle, and is not currently ejecting ink onto media in response to a user-initiated print job to form a desired image on the media. In these respects, the preventative maintenance mode of embodiments of the invention differs from conventional preventative maintenance modes that may have to be initiated by the user. Because users often forgot to initiate such preventative maintenance, embodiments of the invention are advantageous.
The non-user-initiated preventative maintenance mode is periodically performed in two specific situations: while the inkjet-printing device 100 is on (606)—i.e., while the inkjet-printing device 100 has been on for a length of time—and, when the inkjet-printing device 100 is turned on after having been turned off for a length of time (608). In the former case, the inkjet-printing device 100 keeps track of how long it has remained on and unused. When it has been determined that the inkjet-printing device 100 has remained on and unused for more than a predetermined length of time (608), then one or more servicing operations are performed as the non-user-initiated preventative maintenance mode (610).
For example, the predetermined length of time may be four days. This period of time can correspond to the typical five-day work week of a user, where the user may turn on the inkjet-printing device 100 when he or she arrives at work on Monday morning, and where the user may then turn off the device 100 when he or she leaves work on Friday evening. Therefore, having the predetermined length of time set at four days ensures that the inkjet-printing device 100 performs a non-user-initiated preventative maintenance mode one time during the work week if the user does not use the device 100 during the work week.
Performance of the servicing operations of the preventative maintenance mode is designed to result in the ink within the inkjet printhead 402 being sufficiently fresh so as not to affect image formation quality when the inkjet-printing device 100 is called upon to form images on media. Thus, performance of the preventative maintenance mode ejects at least some of the ink from the inkjet printhead 402. This results in the refilling of fresh ink from the ink cartridge 502 into the inkjet printhead 402. The service operations are performed with sufficient regularity so that water loss and air gain within the inkjet-printing device 100 do not reach the level at which they compromise the ink within the inkjet printhead 402 and undesirably affect image formation quality.
The servicing operations performed may include a series of spit-wipe operations. Each spit-wipe operation in turn includes one or more spit operations and one or more wipe operations. A spit operation ejects a predetermined amount of ink from the inkjet nozzles 404 of the inkjet printhead 402. A wipe operation wipes the inkjet nozzles 404 of the inkjet printhead 402. In one embodiment, substantially 11,000 drops of ink (either per nozzle or per color) may be ejected from the inkjet nozzles during each spit operation, where each wipe operation is preceded by a spit operation. There may be a total of three such spit-wipe operations performed in one embodiment of the invention.
Periodically performing the non-user-initiated preventative maintenance mode while the inkjet-printing device 100 is on in part 606 of the method 600 of
Therefore, increasing the usage of the inkjet-printing device 100 by periodically performing the non-user-initiated preventative maintenance mode forces the average age of the ink within the inkjet printhead 402 to decrease. As a result, for instance, the ink usage of the fifth percentile of the users of the inkjet-printing device 100 (where no preventative maintenance is performed) may increase to the level of ink usage of the eighteenth percentile of the users of the device 100. Although periodic performance of the preventative maintenance mode thus does increase ink usage, the net effect is beneficial, in that image formation quality does not degrade due to water loss and air gain. It can therefore be said that periodically performing the non-user-initiated preventative maintenance mode increases usage of the inkjet-printing device 100 such that the average age of the ink within the inkjet printhead 402 decreases to that of a X-percentile user (e.g., such as the eighteenth percentile) and does not reach that of a Y-percentile user (e.g., such as the fifth percentile).
Still referring to
If the time that the inkjet-printing device 100 has been turned off is unknown (614), then the method 600 may perform one or more drop detect tests (616) in one embodiment of the invention, to determine whether the inkjet nozzles 404 of the inkjet printhead 402 are properly ejecting ink. A drop detect test determines which and how many of the inkjet nozzles 404 of the inkjet printhead 402 are properly ejecting ink, as opposed to, for instance, being clogged. Drop detect tests include electrostatic drop detect tests and optical drop detect tests, among other types of drop detect tests. An electrostatic drop detect test detects the charge of an ink drop that is induced upon the ink drop by an electrostatic field. The amount of charge that is detected by a capacitive sensor is related to the amount of ink that is deposited on the target. By comparison, an optical drop detect test optically determines whether and how much ink has been deposited on a target. For instance, an ink drop may pass through a light beam, breaking up the light beam such that it is known that the drop has been ejected. A spot sensor may further be used to scan a target to determine whether a drop is present, and if so, the size of the drop.
Thus, the 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, which is another term for a drop detect target. The inkjet nozzles 404 of the inkjet printhead 402 are then fired. 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.
As indicated by the arrows 904A and 904C, the inkjet nozzles 904A and 904C ejected ink 906A and 906C, respectively, against the drop detector 902. The drop detector 902 is able to detect this ink 906A and 906C, and correspond the ink 906A and 906C 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 908, 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 902 did not detect any ink being deposited thereon as a result of the inkjet nozzle 404B firing.
In one embodiment, where results of the drop detect tests indicate failure of the inkjet printhead 402 according to a given criterion, then it is determined how many iterations of the preventative maintenance mode would have been performed if the inkjet-printing device 100 had been on and had remained unused for a predetermined length of time (618). The criterion may be that more than twenty of the inkjet nozzles 404 failed to eject ink during the last-performed drop detect test. In another embodiment, the drop detect tests of part 616 are not performed, and instead part 618 is automatically performed without first performing such drop detect tests.
The predetermined length of time on which basis it is determined how many iterations of the preventative maintenance mode would have been performed if the inkjet-printing device 100 had been on and had remained unused may be four weeks in one embodiment of the invention. Because there are twenty-eight days in four weeks, where the inkjet-printing device 100 performs a non-user-initiated preventative maintenance mode every four days of non-use, this means that seven such iterations of the preventative maintenance mode would have been performed if the device 100 had been on and had remained unused for four weeks. This predetermined length of time may be empirically determined, as can be appreciated by those of ordinary skill within the art, or arbitrarily specified.
For example, the designers and/or the engineers of the inkjet-printing device 100 may find that after four weeks of the inkjet-printing device 100 remaining on and not being used, seven iterations of the preventative maintenance mode is sufficient to replenish the water-depleted ink within the inkjet printhead 402. That is, even if the inkjet-printing device 100 remained on and idle for more than four weeks, no more than seven iterations of the preventative maintenance mode may be needed to replenish the ink within the inkjet printhead 402. Therefore, the predetermined length of time is set as four weeks, which is the length of time in which seven such iterations of the preventative maintenance mode would normally be performed.
If, on the other hand, the time that the inkjet-printing device 100 has been turned off is known (614), then the method 600 just determines the number of iterations of the preventative maintenance mode that would have been performed if the device 100 had been on and idle during this time (620). For example, if the inkjet-printing device 100 had been turned off for eight days, and where the non-user-initiated preventative maintenance mode is normally performed every four days, then two iterations of the preventative maintenance mode would have been performed during this length of time in which the device 100 was turned off. The number of iterations determined in part 620 may be capped at a predetermined maximum number. For instance, as noted above, there may be no need to perform more than seven iterations of the preventative maintenance mode to properly replenish the ink within the inkjet printhead 402. Therefore, if the number of iterations that the inkjet-printing device 100 would normally have performed if it had been on and idle is greater than seven, this number may nevertheless be capped at seven. In one embodiment, part 620 may be preceded by performance of a drop detect test, similar to how part 618 is preceded by the drop detect test of part 616, such that part 620 is proceeded to just if this drop detect test fails.
After performing part 618 or part 620, the method 600 proceeds to perform the number of iterations of the non-user-initiated preventative maintenance mode that has been determined (622). Such performance of the preventative maintenance mode may be the same as the one or more servicing operations performed in part 610 as has been described. As such, one or more series of spit-wipe operations may be performed so that the inkjet-printing device 100 subsequently properly forms images on media without image quality degradation due to air gain or water loss.
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 600 of
