The present invention relates generally to a method of ejecting fluid from an ejection device.
In contrast to many other types of printers, inkjet printers provide fast, high resolution, black-and-white and color printing on a wide variety of media and at a relatively low cost. As a result, inkjet printers have become one of the most popular types of printers for both consumer and business applications. Nevertheless, printer technology continuously advances to keep pace with ever-increasing customer demands for printers that print faster, at a higher resolution, and at a lower cost.
The printhead of the printer controls the application of ink to the printing medium (e.g., paper). Generally, printheads include a plurality of ink ejection mechanisms formed on a substrate. Each ink ejection mechanism includes a firing chamber with at least one ejection orifice. Each ink ejection mechanism also includes one or more firing resistors (or heating elements), located in the firing chamber. The substrate is connected to an ink cartridge or other ink supply. Channel structures formed on the substrate direct the ink from the ink supply to the firing chambers. Control circuitry, located on the substrate and/or remote from the substrate, supplies current to the firing resistors in selected firing chambers. The ink within the selected chambers is superheated by the firing resistors, causing the ink in close proximity to the resistors to be vaporized. This forms a drive bubble that pushes ink through the chamber orifice toward the printing medium in the form of an ink droplet.
One problem that may occur in printheads is damage to the firing resistors caused by residual ink collapsing back into the chamber, and thus onto the resistor, after the collapse of the bubble. Several structural approaches have been developed to alleviate this problem. For example, one approach involves forming the firing resistors of thicker layers that are less vulnerable to mechanical stress and impact. Another approach involves forming a protective layer or layers over the resistors to absorb the impact. However, both approaches increase the thermal mass that is heated to eject the ink, and thus may decrease the thermal efficiency of the ink ejection mechanism. Furthermore, additional protective layers increase the complexity and cost of manufacturing the printheads.
In one embodiment, a method of ejecting fluid from an ejection device is described. This method includes adding fluid to a firing chamber, and passing a first amount of charge through a heating element of the firing chamber. The first amount of charge causes the heating element to emit a first quantity of thermal energy, thereby forming a vapor bubble in fluid adjacent the heating element to eject fluid from the firing chamber. A second amount of charge is passed through the heating element to cause the heating element to emit a second amount of thermal energy that is insufficient to eject fluid from the firing chamber.