BACKGROUND

[0001 Many infcjet printers print images on media by sweeping printheads back and forth across the width of the media while depositing printing fluid on each pass. Some inkjet printers advance the page after each sweep. These types of inkjet printers deposit ail the ink for tha t segment of the page in each sweep. Other inkjet printers may make multiple passes or sweeps with the prinfheads over the same place on the media while depositing some of the printing fluid for each segment in each pa ss.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 is an isometric par tial view of an example inkjet printer 100.

[0003] FIG. 2 is a top view of an example drive system.

[0004] FIG. 3 is a bottom view of an example carriage 106.

[0005] FIG. 4 is an example block diagram of a printer.

[0006] FIG. 5 is an example block diagram of the processor 402 coupled to memory 404.

[0007] FIG. 6 is an example flow chart for controlling the amount of ink deposited in each printin pass.

DETAILED DESCRIPTION

[0008] Papers come in many different sizes, for example letter, legal, ledger, A5,

A4 and A3 sized papers. Most of the common page sizes used in the home or office have a width that is 8.5 inches or less, for example letter, legal. A5 and A4 pages all have a width of 8.5 inches or less. Because the most common paper sizes used in the home or office have widths of 8.5 inches or less, most home or office printers can only print on media with a width of 8.5 inches or less. [0009] A user that has a need to print on wider pages ca purchase -a printer that has an oversized width, for example a B-sized printer. A typical B-sized printer has a width that is greater than 11.7 inches. This allows the printer to accommodate both ledger or B-sized pages (11x17 inches) and A3 pages (11.7x16.5 .inches). Most B-sized printers can also use media with smaller widths, for example letter, legal, A5 and A4 sizes. Some B-sized Inkjet printers have a higher rate of printhead crushing when printing B-sized media than when printing media with a smaller width.

[0010] Prmihead crushing occurs when the prmihead contacts the niedia as it is sweeping across the media during a printing pass or a retraction pass. A printing pass is defined as when the prmihead is sweeping across the media while depositing ink. Ink is broadly defined as any type of printing fluid where printing fluid can be any color of ink, a gloss coat, an under coat, specialty inks or the like. In some printers a printing pass can be done as the printhead sweeps across the media in either direction. In other printers a printing pass is only done when the priiithead is moving in one direction towards one side of the media. The priiithead is then moved back to the other side of the media without depositing any ink. A retraction pass is defined as when the printhead is sweeping across the media without depositing ink onto the media.

[0011] Printhead crushing can cause a number of problems. Priiithead crashing can cause streaks or smudges in the printed image. It can damage or shorten the life of the printhead. And it can cause the printhead to catch or crumple the media, potentially causing a media jam in the paper path of the printer.

[0012] Printhead crushing occurs more often when printing on wider paper for a number of reasons. One reason is that the paper fibers or grains are typically aligned differently in wide paper compared to narrower paper. For example, the grains in an A3 sized page are typically aligned perpendicular to the length of the page. The grains in a letter sized page are typically aligned parallel with the length of the page. When the paper gets wet the paper fibers or grains expand along the length of the fibers causin the paper to curl. For pages with the paper fibers or grains aligned parallel with the length of the page the curl is along the length of the pa ge. For pa ges with the paper fibers or grains aligned perpendicular to the length of the page the curl is along the width of the page. [0013] Curl along the length of a page is l ess of a problem than carl along the width of a page due to a number of factors. One factor is the typical ge.can.eiry of an infcjet printer. Many infc et printers have a pinch roller oil either side of the print zone, Tlie print zone is the area covered by the printheads as they sweep across the media while depositing ink. The pinch rollers keep tension in the page along the length of the page inside the print zone. Wheal the paper fibers expand along the length of the page the tension along the length of the page keeps the surface of the page flat. When the paper fibers are aligned perpendicular to the lengt of the page the fibers cause the widt of the page to increase when they expand. This causes curl along the width of the page.

Tension along the length of the page does not prevent the page from curling along the width of the page. Typically nothing in the printer puts tension along the width of the page.

[0014] Another geometric fac tor that ca uses the curl along the width of the page to be more of a problem is the print zone dimensions. The distance in the print zone along the width of the page is greater for B-sized media than for letter sized media. B-sized pages are typically 3 inches wider than letter sized pages. Because B-sized pages are wider, it takes longer for the printhead to sweep across the entire print zone. This increases the amount of time the wet media remains in the print zone and increases the time between printing passes. The increase in time can cause more curl.

[0015] Printhea d crashing can be reduced by moving the page out of the print zone after the ink has been deposited onto the media. For example, the printhead can make a printing pass across the media by depositin a swath of ink onto the media. The freshly printed swath can then be advanced out of the print zone before the printhead makes another printing pass or a retr action pass across the media. This works well for printers that print using a single printing pass.

[0016] Many printers use multiple printing passes over the same area of the media to deposit all the ink for the image onto the media. Some printers use two printing passes to deposit all the ink to a given area of the page. Other printers may use 3, 4 or more printing passes to deposit ail the ink to a given area of the pa ge. In some cases the printers use a retraction pass between each printing pass such that the printing passes are all moving in the same direction. [0017] Typically each printing pass deposits the same amount of ink. For example, a two pass printer would deposit 50% of the ink on the first printing pass and 50% of the ink on the second printing pass. A four pass printer would deposit 25% of the ink dining each printing pass. Depositing the same percentage of the total amoun of ink for a given segment of the image is known as an even distribution of ink. In one example of the invention, a printer will use an uneven distribution of ink deposited hi each pass when printing on wide media. Depositing different percentages of the ink in different passes for a given segment of the image is known as an uneven distribution of ink. In one example of the invention the uneven distribution will have more ink deposited in the last pass than in other passes. For example, when a two pass printer is printing on wide media the amount of ink deposited on the first printing pass will be less that the amount of ink deposited in the second printing pass. A four pass printer will have more ink deposited in the 4* printing pass than in each of the other three printing passes.

[0018] Figure 1 is an isometric, partial view of an example inkjet printer 100.

Inkjet printer 100 comprises a pair of linefeed pinch rollers 102 and 104, a carnage 106, a starwheel pinch roller 108, a pair of take-up pinch rollers 110 and 112 and some support ribs 114. The drawing is for illustration purposes only and is not to scale. The pair of linefeed pinch roiiers (102 and 104), the starwheel pinch roller 108 and the pair of take-up pinch rollers (110 and 112) make up a media feeding system in this example. A media feeding system is any set of parts that direct media into and through a print zone. The linefeed pmch rollers 102 and 104 feed paper into a print zone shown as area 118. The support ribs 114 support the paper in the print zone. As the paper is fed past the print zone 118. the starwheel pinch roller directs the leading edge of the paper towards the take-up pinch rollers 110 and 112.

[0019] Once the leading edge of the paper reaches the take-up pinch rollers (110 and 1 12 ) the actions of the linefeed pinch rollers (102 and 104 ) can be coordinated with the actions of the take-up pinch rollers (1 10 and 112) to put tension along the length of the page in the print zone 118. A page 116 is shown loaded in the paper path between the linefeed pmch rollers and the take-up roiiers. The paper feeding direction is along the length of the page and is shown by arrow P. In one example the distance Dl between the linefeed pinch rollers (102 and 104) and the take-up rollers {1 10 and 1 12) is

approximately between 3 to 3.5 inches.

[0026] Carriage i 06 is mounted in a drive system (see figure 2) that moves carriage 106 back and forth across the width of the page along axis X. One or more printheads mounted in carriage 1 6 deposit ink onto the page as the carriage sweeps across the page (see figure 3). Print zone 1 18 is the area covered by the printheads as they sweep across the media while depositing ink. In one example the printheads are 1.15 inches long (see distance D3 in figure 3). Therefore the print zone 1 18 is 1.15 inches wide along the axis of the paper movement (direction P). The length of the print zone (distance D2) for a B-sized printer is slightly larger than 11.7 inches in length.

[0021] Printer 100 may have multiple printing modes. In some printing modes the carriage makes only one printing pass across each sectio of the page while depositing all the ink for that section in one swath, i this printing mode the paper is advanced after each printing pass. In a multi-pass printing mode the printer may make multiple printing passes across each segment of the pa ge, depositing some portion of the ink for tha t segment with each printing pass. Once the last printing pass in the multi-printing mode has been completed, the media can be advanced such that the area just printed is moved out of the print zone before the printhead makes another pass across the print zone. In other print modes the ink of on swath may overlap with the ink of previous swaths. In print modes with overlapping swaths only part of the swath is moved out of the print zone after the last printing pass.

[0022] In one example, printer 100 uses an uneven ink distributio across the multiple printing passes in the multi-pass printing mode when printing on wide media. Using an uneven ink distribution, printer 100 concentrates more of the ink into the last printing pass. By concentrating more of the ink into the last printing pass the amount of curl caused during earlier printing passes will be reduced. Therefore the amount of head crashing in the earlier printing passes will also be reduced. Because the paper can be moved out of the print zone after the last printin pass, the increase in the amount of ink used in the la st printing pass will not increase the amount of printhead crashing.

Therefore the total amount of head crashing will be reduced. [0023] Figure 2 is a top view of an example drive system. Drive system 200 comprises guide rod 220, two drive gears 222 and drive belt 224. Carnage 10 is mounted on guide rod 220 and can translate on guide rod 220 along axis X. D ive gears 222 are mounted on each si de of the printer. Drive belt 224 is attached ^' to carriage 106 and looped around the two drive gears 220. One of the two drive gears 222 is attached to a motor (not shown) that turns the drive gear. As the drive gear rotates, the eairiage 106 is moved along the guide rod 220 in the X axis. In other examples, drive system 200 may use a worm drive instead of a drive belt.

[0024] Figure 3 is a bottom view of an example carriage 106. Mounted to the bottom side of carriage 106 are four prmtheads (330, 332. 334 and 336). In this example each printhead is used to deposit a single color of ink onto media as the carriage moves along the X axis. Piintheads 330, 332, 334 and 336 are used to deposit cyan, magenta, yellow and black ink, respectively. In some examples there may be additional prmtheads used to deposit other ink colors onto the media. The additional ink colors may include, light cyan ink, light magenta ink, light yellow ink. light grey ink and the like. In other examples a single printhead may be used to deposit all of the differently colored inks onto the media. The prmtheads may be removably mounted to the carriage and user replaceable or may be permanently attached to the carriage. The four piintheads (330, 332, 334 and 336) have length D3. Distance D3 is typically between .5 inches and 2 inches, for example 1.15 inches.

[0025] Carriage 106 also has a sensor 338 mounted to the bottom surface. Sensor

338 can view media as the carriage travels back and forth across the print zone 118. Using sensor 338, the printer can determine the width of the media loaded in the print zone 118. In other examples the printer may determine the media width using other sensors located in otiier places within the printer paper path, for example in a media tray. In yet another example, the printer may determine the width of the media being used by examining the data contained in the print job sent to the printer.

[0026] Figure 4 is an example block diagram of a printer. Printer comprises a processor 402, memory 404, input/output (I/O) module 406, print engine 408 and controller 410 all coupled together on bus 412. In some examples printer may also have a user interface module, an input device, and the like, but these items are not shown for clarity. Processor 402 ma comprise a central processing unit (CPU), a micro-processor, an application specific integrated circuit (ASIC), or a combination of these devices. Memory 404 may comprise volatile memory, non-volatile memory, and a storage device. Memory 404 is a non-transitory computer readable medium. Examples of non-volatile memory include, but are not limited to, electrically erasable programmable read only memory (EEPROM) and read only memory (ROM). Examples of volatile memory include, but are not limited to, static random access memory (SRAM), and dynamic random access memory (DRAM). Examples of storage devices include, but are not limited to, hard disk drives, compact disc drives _. , digital versatile disc drives, optical drives, and flash memory devices.

[0027] I/O module 406 is used to couple printer to oilier devices, for example the internet or a computer. Printer lias code, typically called firmware, stored in the memory 404. The firmware is stored as computer readable instructions in the non-transitory computer readable medium (i.e. the memory 404). Processor 402 generally retrieves and executes the instructions stored in the non-transitory computer-readable medium to operate the printer and to execute functions. In one example, processor executes code that controls the amount of ink deposited in each printing pass.

[0028] Figure 5 is an example block diagram of the processor 402 coupled to memory 404. Memory 404 contains software 520. Software 520 contains an ink control module 524. The processor 402 executes the code in ink control module 524 to control the amount of ink deposited in each printing pass.

[0029] A printer may use different print modes for different areas of a page, depending on what is being printed in that area. For example, when printing text or simple graphics the printer may use a single pass printing mode. When printing images, for example a photograph, the printer may use a multi-pass printing mode. Figure 6 is an example ilow chart for an ink control module. The ink control module is used for controlling the amount of ink deposited in each printing pass when using a multi-pass print mode. Flow start at 660 where the media width for the print job is compared to a threshold. The tlireshold is typically set at the width of typical office paper (i.e. 8.5 inches wide). [0030] When the media width, is not greater than the threshold, flow moves to 662.

At 662 the page is printed where each pass in the multi-pass print mode deposits the same percentage of the total amount of ink for a given segment of the image . Depositing the same percentage of the total amount of ink for a gi ven segment of the image is known, as an even distribution of ink. For example, in a two pass print mode each printing pass would deposit 50% of the ink for that segment of the page.

[0031] When the media width is greater than the threshold flow moves to 664. At

664 the page is printed where the last pass in the multi-pass print mode deposits more ink than earlier passes of the multi-pass print mode. Depositing different percentages of the ink i different passes for a given segment of the image is known as an uneven distribution of ink. For example, in a two pass prmt mode the first printing pass would deposit less ink than the second printing pass for a given segment of the page.

[0032] When using an uneven distribution of ink hi a multi-pass printing mode, the distribution of ink between the printing passes can vary over a wide range of values. For example, a two pass printing mode may have only 5% of the ink deposiied in the first pass and 95% of the ink deposited in the second pass. In another example the first printing pass may deposit 45% of the ink and the second pass may deposit 55% of the ink.

[0033] When using a multi-pass printing mode that has more than two printing passes, the distribution of ink between the earlier printing passes may use an even or uneven distribution. An example of a eve distribution for earlier passes is depositing 10% of the ink in each of the first three printing passes of a four pass printin mode and depositing 70% of the ink in the last pass. An example of an uneven distribution for earlier passes is depositing 20% of the ink in tiie first printing pass of a three pass printing mode, depositing 30% of the ink in the second printing pass and depositing 50% of the ink in the last pass.

[0034] In one example, the distribution of ink between printing passes will be the same for each color of ink. For example, when using a four pass printing m de, in each of the first, second and third printing pass, 20% of the cyan ink, 20% of the magenta ink, and 20% of the yellow ink would be deposited. In the last pass 40% of the cyan, magenta and yeliow ink would be deposited. In aiioiber example the distribution of ink between printing passes will be different for some colors. For example, in a two pass printing mode 95% of the yellow ink and 5% of the cyan and magenta ink will be deposi ted in the first printing pass and 5% of the yellow and 95% of the cyan and magenta ink will be deposited i the second printing pass. In some examples ail the black ink will be deposited in the last printing pass. In other examples some of the black in will be deposited in the earlier printing passes and more will be deposited in the last printing pass.

[0035] The printer described above may be integrated into a multifunction peripheral (MFP). A multifunction peripheral (MFP) is a device that typically contains a printer and an imaging system, typically a scanner. The MFP can be used as a printer, a scanner, a copier, a facsimile machine (FAX) or the like. MFPs are also called all-in-one devices (AiO), multifunction devices, multifunction printers or the like.