Dynamic inkjet nozzle flushing mechanism

A method is disclosed. The method includes analyzing an image of a first flushing pattern applied on a medium during production of a print job to detect presence of one or more defective ink jet nozzles and adjusting to a second flushing pattern during the production of the print job upon detecting the presence of one or more defective print head nozzles.

FIELD OF THE INVENTION

The invention relates to the field of printing systems. Particularly, the invention relates to flushing the nozzles in an inkjet printer.

BACKGROUND

An ink jet printer is as an example of a printing apparatus that ejects droplets of ink onto a recording medium such as a sheet of paper for printing an image of the recording medium. Ink jet printers include one or more print engines having at least one ink jet print head provided with an ink cartridge that accommodates the ink. In operation of the print engine, ink is supplied from the ink cartridge to ejection nozzles in each print head so that a printing operation is performed by ejection of the ink droplets from selected ejection nozzles.

Periodically during printing an ink jet print head is required to be flushed to ensure that the individual jet nozzles stay wet in order to prevent defective jet conditions attributed to ink drying at unused nozzles. One commonly implemented flush method is referred to as “line flushing.” In line flushing all primary colors are printed on top of each other in straight line across the top or bottom of each printed page. Another flushing technique is referred to as “random flushing”, in which drops are frequently ejected from each nozzle during print production.

However, nozzles may continue to become clogged using these flushing techniques because the frequency, or volume, of ink to be ejected from the nozzles may need to be increased during print production in order to prevent nozzle drying. Currently, no process is available to adjust nozzle flushing frequency during print production without stopping the printer.

Consequently, what is a needed is a mechanism to dynamically adjust nozzle flushing frequency during print production.

SUMMARY

In one embodiment, a method is disclosed. The method includes analyzing an image of a first flushing pattern applied on a medium during production of a print job to detect presence of one or more defective ink jet nozzles and adjusting to a second flushing pattern during the production of the print job upon detecting the presence of one or more defective print head nozzles.

In a further embodiment a printing system is disclosed. The printing system includes one or more print engines each having a plurality of ink jet nozzles to print a flushing pattern on a medium, a reader to capture an image of the flushing pattern and a controller. The controller analyzes the image of the first flushing pattern applied on the medium during production of a print job to detect presence of one or more defective ink jet nozzles and adjusts to a second flushing pattern during the production of the print job upon detecting the presence of one or more defective ink jet nozzles.

DETAILED DESCRIPTION

FIG. 1illustrates one embodiment of a printing system100. Printing system100includes a host system2having printer software4to manage print jobs and to maintain print job information6on the status of print jobs managed by printer software4. In one embodiment, printer software4may be implemented using either InfoPrint Manager (IPM) or InfoPrint ProcessDirector (IPPD), although other types of printing software may be used instead.

The term print job as used herein refers a print job or any component thereof, including a page of print content, a page including multiple print items or elements, such as checks, pages, an element on a page, etc. The print job may further include one or more pages, where each page has one or more elements, e.g., checks. A page may include a unit of print output, where the page may be outputted on a single piece of a print medium or multiple pages may be outputted on a roll, ribbon or web of a print medium.

Pages may be outputted on a web of a print medium in different formats, such as 2-up duplex. Each of the pages on a web or roll of paper may include multiple elements. The web may include print jobs, where each print job is one or more pages, and where each page includes one or more elements. In this way, elements and pages may be grouped in print jobs.

Host system2may include a processor (not shown) and memory (not shown) in which printer software4and print job information6is stored for access by the processor. The host system2communicates print jobs to printer8, where each print job may have one or more pages or elements, and where each page may have one or more elements. The printer8includes first10and second12print engines to print output using first14and second16types of transfer media and a reader18capable of reading content printed using the first transfer medium14.

Transfer media14and16includes the material or energy that is used to cause the formation of content on print medium20. In one embodiment, transfer media14and16include wide-array inkjet print heads that employ multiple sets of nozzles that are implemented to spray droplets of ink in order to execute a print job. A print medium20, such as a piece of paper or other material or textile, is directed through a feed path22by mechanical components of the printer8, such as rollers, guides, etc. In the feed path22, the first print engine10prints first content of the one or more pages of one or more print jobs on the print medium20using the first transfer medium14. The first content that is printed may include an element, a page, a page of elements, etc.

A reader18provides print verification by reading the printed first print content to determine the quality of the output. The reader18may read each element on one or more pages to determine the quality of each outputted element. The reader18forwards the print medium20to the second print engine12to print second content using the second transfer medium16to produce printed output24including one or more print jobs of one or more pages having one or more elements printed using both transfer media14and16.

The printer8may include a printer controller26to control printing operations and interface with the printer software4to execute the commands from the printer software4and provide feedback thereto. The print engines10and12may include the hardware and/or software to control the printing of content using the first14and second16types of transfer media, respectively.

The printed output24is forwarded to a post processing component28which performs various post processing operations on the printed output24. In one embodiment, post processing includes a separator30that separates the paper web into separated print job output. Additional post processing may also be performed on the separated output pieces, including include stapling, collating, printing, labeling, etc.

The post processing component28subsequently outputs the separated output in a final form, which may include envelopes having the separated output pieces. The post processing component28may include a post processing controller38to control post processing operations and interface with the printer controller26and printer software4to execute the commands from the printer software4and provide feedback thereto.

An interface40provides intercommunication among the host2, the printer8, and the post processing component20. The interface40may include a network, such as a Local Area Network (LAN), a Wide Area Network (WAN), a wireless network, etc. Alternatively, the interface40may include a bus interface, parallel interface, serial interface, or other direct line connection. In the embodiment of described herein, the host2, printer8, and post processing component20are shown as included in separate boxes. In an alternative embodiment, the printer8and post processing component20may be included in a single machine connected via one connection to the host2. In other embodiments, all three devices2,8, and20may be included in one machine.

As discussed above, flushing is performed at ink jet print heads to ensure that the individual nozzles remain sufficiently wet to maintain print quality.FIGS. 2A-2Dillustrate embodiments of flushing schemes for a print head having twenty four nozzles.FIG. 2Aillustrates one embodiment of a line4flushing scheme in which each nozzle fires two drops in a straight line at the top or bottom of each medium20page of a print job.FIG. 2Billustrates another embodiment of a random2flushing scheme, where all nozzles flush two drops of ink at every 3.2 inches on a page.FIGS. 2C and 2Dillustrate embodiments of random1and random ½ flushing schemes, respectfully. For such schemes, the nozzles are flushed less frequently than random2flushing (e.g., for every 6.4 inches and 12.8 inches).

As mentioned above, nozzles may continue to become clogged using the above flushing schemes because of a need to increase the frequency, or volume, of ink ejected from the nozzles during print production. According to one embodiment, printer controller26dynamically adjusts flushing data based on the state of print head nozzles. In such an embodiment, the state of the nozzles may be determined by examining printed output and/or nozzle response using reader18.

In one embodiment, printer controller26analyzes the image of printed flushing patterns captured by reader18in order to detect the presence of a defective nozzle. According to one embodiment, printer controller26analyzes the image by measuring color values of the captured flushing pattern. For example, printer controller26may measure color values to identify tints and their transition locations/indices from the image. Once the printed image data is captured and the color values of the image data are measured, print irregularities associated with the flushing pattern are determined.

In one embodiment, the print irregularities are determined by estimating original optical density values for the color values in the flushing pattern and comparing those values to the measured color values to determine differences in order to detect a density and color change of the flush line pattern. A more detailed discussion of using a reader to capture printer output to determine nozzle state can be found in patent application Ser. No. 13/042,857 entitled, Jet Out Detection, herein incorporated by reference.

FIG. 3is a flow diagram for one embodiment of performing dynamic nozzle flushing. At processing block310, the sheet data is rasterized. At processing block320, a pre-selected flushing pattern is combined with the sheet data. In one embodiment, the flushing pattern may include a one, two and three dots per inch patterns, as well as line2and line4patterns. At decision block340, a determination is made as to whether a defective nozzle has been detected as a result of a previously captured flushing pattern image analysis.

If no defective nozzles have been detected, the combined flushing pattern and sheet data are forwarded for printing, processing block350. However, if a defective nozzle has been detected, the flushing pattern is increased to a next level flushing pattern (e.g., one dot/inch to two dots/inch), and combined with the rasterized sheet for the defective nozzle, processing block340. In one embodiment, the next level flushing pattern is user defined. For example, the next level flushing pattern may be generated using a flushing pattern preference table.

In one embodiment, the next level flushing pattern is used for a user selected number of sheets after the increase. However in other embodiments, the next level flushing pattern may used for a predetermined number of feet of the print medium. At processing block350, the combined next level flushing pattern and sheet data are forwarded for printing.

The above-described mechanism performs dynamic flushing pattern adjustments during print production to prevent the drying of print head nozzles.