Fluid ejection devices, such as printheads in inkjet printing systems, may use thermal resistors or piezoelectric material membranes as actuators within fluidic chambers to eject fluid drops (e.g., ink) from nozzles, such that properly sequenced ejection of ink drops from the nozzles causes characters or other images to be printed on a print medium as the printhead and the print medium move relative to each other.
Decap is the amount of time inkjet nozzles can remain uncapped and exposed to ambient conditions without causing degradation in ejected ink drops. Effects of decap can alter drop trajectories, velocities, shapes and colors, all of which can negatively impact print quality. Other factors related to decap, such as evaporation of water or solvent, can cause pigment-ink vehicle separation (PIVS) and viscous plug formation. For example, during periods of storage or non-use, pigment particles can settle or “crash” out of the ink vehicle which can impede or block ink flow to the ejection chambers and nozzles.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure.
The present disclosure helps to reduce ink blockage and/or clogging in inkjet printing systems generally by circulating (or recirculating) fluid through fluid ejection chambers. Fluid circulates (or recirculates) through fluidic channels that include fluid circulating elements or actuators to pump or circulate the fluid.
Print media 118 can be any type of suitable sheet or roll material, such as paper, card stock, transparencies, Mylar, and the like. Nozzles 116 are typically arranged in one or more columns or arrays such that properly sequenced ejection of ink from nozzles 116 causes characters, symbols, and/or other graphics or images to be printed on print media 118 as printhead assembly 102 and print media 118 are moved relative to each other.
Ink supply assembly 104 supplies fluid ink to printhead assembly 102 and, in one example, includes a reservoir 120 for storing ink such that ink flows from reservoir 120 to printhead assembly 102. Ink supply assembly 104 and printhead assembly 102 can form a one-way ink delivery system or a recirculating ink delivery system. In a one-way ink delivery system, substantially all of the ink supplied to printhead assembly 102 is consumed during printing. In a recirculating ink delivery system, only a portion of the ink supplied to printhead assembly 102 is consumed during printing. Ink not consumed during printing is returned to ink supply assembly 104.
In one example, printhead assembly 102 and ink supply assembly 104 are housed together in an inkjet cartridge or pen. In another example, ink supply assembly 104 is separate from printhead assembly 102 and supplies ink to printhead assembly 102 through an interface connection, such as a supply tube. In either example, reservoir 120 of ink supply assembly 104 may be removed, replaced, and/or refilled. Where printhead assembly 102 and ink supply assembly 104 are housed together in an inkjet cartridge, reservoir 120 includes a local reservoir located within the cartridge as well as a larger reservoir located separately from the cartridge. The separate, larger reservoir serves to refill the local reservoir. Accordingly, the separate, larger reservoir and/or the local reservoir may be removed, replaced, and/or refilled.
Mounting assembly 106 positions printhead assembly 102 relative to media transport assembly 108, and media transport assembly 108 positions print media 118 relative to printhead assembly 102. Thus, a print zone 122 is defined adjacent to nozzles 116 in an area between printhead assembly 102 and print media 118. In one example, printhead assembly 102 is a scanning type printhead assembly. As such, mounting assembly 106 includes a carriage for moving printhead assembly 102 relative to media transport assembly 108 to scan print media 118. In another example, printhead assembly 102 is a non-scanning type printhead assembly. As such, mounting assembly 106 fixes printhead assembly 102 at a prescribed position relative to media transport assembly 108. Thus, media transport assembly 108 positions print media 118 relative to printhead assembly 102.
Electronic controller 110 typically includes a processor, firmware, software, one or more memory components including volatile and no-volatile memory components, and other printer electronics for communicating with and controlling printhead assembly 102, mounting assembly 106, and media transport assembly 108. Electronic controller 110 receives data 124 from a host system, such as a computer, and temporarily stores data 124 in a memory. Typically, data 124 is sent to inkjet printing system 100 along an electronic, infrared, optical, or other information transfer path. Data 124 represents, for example, a document and/or file to be printed. As such, data 124 forms a print job for inkjet printing system 100 and includes one or more print job commands and/or command parameters.
In one example, electronic controller 110 controls printhead assembly 102 for ejection of ink drops from nozzles 116. Thus, electronic controller 110 defines a pattern of ejected ink drops which form characters, symbols, and/or other graphics or images on print media 118. The pattern of ejected ink drops is determined by the print job commands and/or command parameters.
Printhead assembly 102 includes one or more printheads 114. In one example, printhead assembly 102 is a wide-array or multi-head printhead assembly. In one implementation of a wide-array assembly, printhead assembly 102 includes a carrier that carries a plurality of printheads 114, provides electrical communication between printheads 114 and electronic controller 110, and provides fluidic communication between printheads 114 and ink supply assembly 104.
In one example, inkjet printing system 100 is a drop-on-demand thermal inkjet printing system wherein printhead 114 is a thermal inkjet (TIJ) printhead. The thermal inkjet printhead implements a thermal resistor ejection element in an ink chamber to vaporize ink and create bubbles that force ink or other fluid drops out of nozzles 116. In another example, inkjet printing system 100 is a drop-on-demand piezoelectric inkjet printing system wherein printhead 114 is a piezoelectric inkjet (PIJ) printhead that implements a piezoelectric material actuator as an ejection element to generate pressure pulses that force ink drops out of nozzles 116.
In one example, electronic controller 110 includes a flow circulation module 126 stored in a memory of controller 110. Flow circulation module 126 executes on electronic controller 110 (i.e., a processor of controller 110) to control the operation of one or more fluid actuators integrated as pump elements within printhead assembly 102 to control circulation of fluid within printhead assembly 102.
In one example, fluid ejection chamber 202 is formed in or defined by a barrier layer (not shown) provided on substrate 206, such that fluid ejection chamber 202 provides a “well” in the barrier layer. The barrier layer may be formed, for example, of a photoimageable epoxy resin, such as SU8.
In one example, a nozzle or orifice layer (not shown) is formed or extended over the barrier layer such that a nozzle opening or orifice 212 formed in the orifice layer communicates with a respective fluid ejection chamber 202. Nozzle opening or orifice 212 may be of a circular, non-circular, or other shape.
Drop ejecting element 204 can be any device capable of ejecting fluid drops through corresponding nozzle opening or orifice 212. Examples of drop ejecting element 204 include a thermal resistor or a piezoelectric actuator. A thermal resistor, as an example of a drop ejecting element, is typically formed on a surface of a substrate (substrate 206), and includes a thin-film stack including an oxide layer, a metal layer, and a passivation layer such that, when activated, heat from the thermal resistor vaporizes fluid in fluid ejection chamber 202, thereby causing a bubble that ejects a drop of fluid through nozzle opening or orifice 212. A piezoelectric actuator, as an example of a drop ejecting element, generally includes a piezoelectric material provided on a moveable membrane communicated with fluid ejection chamber 202 such that, when activated, the piezoelectric material causes deflection of the membrane relative to fluid ejection chamber 202, thereby generating a pressure pulse that ejects a drop of fluid through nozzle opening or orifice 212.
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At 502, method 500 includes communicating a fluid circulation channel, such as fluid circulation channels 220, 320, and 420, with a fluid slot, such as fluid feed slots 208, 308, and 408, and at least one fluid ejection chamber, such as fluid ejection chambers 202, 302, and 402. The fluid circulation channel, such as fluid circulation channels 220, 320, and 420, has a fluid circulating element, such as fluid circulating elements 222, 322, and 422, communicated therewith, and the fluid ejection chamber, such as fluid ejection chambers 202, 302, and 402, has a drop ejecting element, such as drop ejecting elements 204, 304, and 404, therein
At 504, method 500 includes providing on-demand circulation of fluid from the fluid slot, such as fluid feed slots 208, 308, and 408, through the fluid circulation channel, such as fluid circulation channels 220, 320, and 420, and at least one fluid ejection chamber, such as fluid ejection chambers 202, 302, and 402, by operation of the fluid circulating element, such as fluid circulating elements 222, 322, and 422.
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As illustrated in timing diagram 600A, operation of the fluid circulating elements and, therefore, fluid circulation through the fluid circulation channels is provided on-demand during decap time 630A. More specifically, operation of the fluid circulating elements (lines 620A) is provided at an end of the decap time before operation of the drop ejecting elements (lines 610A). As such, the on-demand circulation is inactive during a period of non-operation of the drop ejecting elements, such inactive period being during decap time 630A. Thus, fluid circulation is provided after a period of non-operation of the drop ejecting elements and before subsequent operation of the drop ejecting elements.
In one example, the on-demand circulation of timing diagram 600A is provided with a delay (Δt) before operation of the drop ejecting elements. In one example, the delay is less than a frequency of operation of the drop ejecting elements. As such, the operation of the fluid circulating elements (lines 620A) provide on-demand fluid circulation through the fluid circulation channels at an end of decap time 630A before operation of the drop ejecting elements (lines 610A).
As illustrated in timing diagram 600B, operation of the fluid circulating elements and, therefore, fluid circulation through the fluid circulation channels is provided on-demand during decap time 630B. More specifically, operation of the fluid circulating elements (lines 620B) is provided at an end of the decap time before the operation of the drop ejecting elements (lines 610B). As such, the on-demand circulation is inactive during a period of non-operation of the drop ejecting elements, such inactive period being during decap time 630B. Thus, fluid circulation is provided after a period of non-operation of the drop ejecting elements and before subsequent operation of the drop ejecting elements.
In one example, the on-demand circulation of timing diagram 600B is provided without a delay before operation of the drop ejecting elements. As such, the operation of the fluid circulating elements (lines 620B) provide on-demand fluid circulation through the fluid circulation channels at an end of decap time 630B immediately before operation of the drop ejecting elements (lines 610B).
With timing diagrams 600A and 600B, the clustering or grouping of operation of the fluid circulating elements (lines 620A) includes a number of pulses (i.e., multiple pulses) of circulation provided by operation of the fluid circulating elements. In one example, the recirculation frequency and/or number of pulses is not fixed. Rather, the recirculation frequency is asynchronous to the printing frequency such that associated parameters of the on-demand circulation (e.g., recirculation frequency and/or number of pulses) may be optimized for a specific printing system. Thus, a plurality of frequencies and/or a plurality of pulse counts are possible for the on-demand circulation.
In addition, with timing diagrams 600A and 600B, the on-demand circulation occurs right before operation of the drop ejecting elements (lines 610B) for printing image data. In this regard, the controller, for example, flow circulation module 126 (
With a fluid ejection device including circulation as described herein, ink blockage and/or clogging is reduced. As such, decap time and, therefore, nozzle health are improved. In addition, pigment-ink vehicle separation and viscous plug formation are reduced or eliminated. Furthermore, ink efficiency is improved by lowering ink consumption during servicing (e.g., minimizing spitting of ink to keep nozzles healthy). In addition, a fluid ejection device including circulation as described herein, helps to manage air bubbles by purging air bubbles from the ejection chamber during circulation.
Although specific examples have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein.
This is a continuation of U.S. application Ser. No. 15/521,284, having a national entry date of Apr. 22, 2017, which is a national stage application under 35 U.S.C. § 371 of PCT/US2014/063365, filed Oct. 31, 2014, which are both hereby incorporated by reference in their entirety.
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Child | 16834546 | US |