Patent Publication Number: US-10766272-B2

Title: Fluid ejection device

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     The present application is a continuation application claiming priority under 35 USC § 120 from U.S. patent application Ser. No. 15/521,286, filed Apr. 22, 2017, which is a US National Application claiming domestic benefit from PCT/US2014/63369, filed Oct. 31, 2014, each of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating one example of an inkjet printing system including an example of a fluid ejection device. 
         FIG. 2  is a schematic plan view illustrating one example of a portion of a fluid ejection device. 
         FIG. 3  is a schematic plan view illustrating another example of a portion of a fluid ejection device. 
         FIG. 4  is a schematic plan view illustrating another example of a portion of a fluid ejection device. 
         FIG. 5  is a flow diagram illustrating one example of a method of operating a fluid ejection device. 
         FIGS. 6A and 6B  are schematic illustrations of example timing diagrams of operating a fluid ejection device. 
         FIG. 7  is a schematic illustration of an example timing diagram of operating a fluid ejection device. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
       FIG. 1  illustrates one example of an inkjet printing system as an example of a fluid ejection device with fluid circulation, as disclosed herein. Inkjet printing system  100  includes a printhead assembly  102 , an ink supply assembly  104 , a mounting assembly  106 , a media transport assembly  108 , an electronic controller  110 , and at least one power supply  112  that provides power to the various electrical components of inkjet printing system  100 . Printhead assembly  102  includes at least one fluid ejection assembly  114  (printhead  114 ) that ejects drops of ink through a plurality of orifices or nozzles  116  toward a print medium  118  so as to print on print media  118 . 
     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 . 
       FIG. 2  is a schematic plan view illustrating one example of a portion of a fluid ejection device  200 . Fluid ejection device  200  includes a fluid ejection chamber  202  and a corresponding drop ejecting element  204  formed or provided within fluid ejection chamber  202 . Fluid ejection chamber  202  and drop ejecting element  204  are formed on a substrate  206  which has a fluid (or ink) feed slot  208  formed therein such that fluid feed slot  208  provides a supply of fluid (or ink) to fluid ejection chamber  202  and drop ejecting element  204 . Substrate  206  may be formed, for example, of silicon, glass, or a stable polymer. 
     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 . 
     As illustrated in the example of  FIG. 2 , fluid ejection device  200  includes a fluid circulation channel  220  and a fluid circulating element  222  formed in, provided within, or communicated with fluid circulation channel  220 . Fluid circulation channel  220  is open to and communicates at one end  224  with fluid feed slot  208  and communicates at another end  226  with fluid ejection chamber  202  such that fluid from fluid feed slot  208  circulates (or recirculates) through fluid circulation channel  220  and fluid ejection chamber  202  based on flow induced by fluid circulating element  222 . In one example, fluid circulation channel  220  includes a channel loop portion  228  such that fluid in fluid circulation channel  220  circulates (or recirculates) through channel loop portion  228  between fluid feed slot  208  and fluid ejection chamber  202 . 
     As illustrated in the example of  FIG. 2 , fluid circulation channel  220  communicates with one (i.e., a single) fluid ejection chamber  202 . As such, fluid ejection device  200  has a 1:1 nozzle-to-pump ratio, where fluid circulating element  222  is referred to as a “pump” which induces fluid flow through fluid circulation channel  220  and fluid ejection chamber  202 . With a 1:1 ratio, circulation is individually provided for each fluid ejection chamber  202 . 
     In the example illustrated in  FIG. 2 , drop ejecting element  204  and fluid circulating element  222  are both thermal resistors. Each of the thermal resistors may include, for example, a single resistor, a split resistor, a comb resistor, or multiple resistors. A variety of other devices, however, can also be used to implement drop ejecting element  204  and fluid circulating element  222  including, for example, a piezoelectric actuator, an electrostatic (MEMS) membrane, a mechanical/impact driven membrane, a voice coil, a magneto-strictive drive, and so on. 
       FIG. 3  is a schematic plan view illustrating another example of a portion of a fluid ejection device  300 . Fluid ejection device  300  includes a plurality of fluid ejection chambers  302  and a plurality of fluid circulation channels  320 . Similar to that described above, fluid ejection chambers  302  each include a drop ejecting element  304  with a corresponding nozzle opening or orifice  312 , and fluid circulation channels  320  each include a fluid circulating element  322 . 
     In the example illustrated in  FIG. 3 , fluid circulation channels  320  each are open to and communicate at one end  324  with fluid feed slot  308  and communicate at another end, for example, ends  326   a ,  326   b , with multiple fluid ejection chambers  302  (i.e., more than one fluid ejection chamber). In one example, fluid circulation channels  320  include a plurality of channel loop portions, for example, channel loop portions  328   a ,  328   b , each communicated with a different fluid ejection chamber  302  such that fluid from fluid feed slot  308  circulates (or recirculates) through fluid circulation channels  320  (including channel loop portions  328   a ,  328   b ) and the associated fluid ejection chambers  302  based on flow induced by a corresponding fluid circulating element  322 . 
     As illustrated in the example of  FIG. 3 , fluid circulation channels  320  each communicate with two fluid ejection chambers  302 . As such, fluid ejection device  300  has a 2:1 nozzle-to-pump ratio, where fluid circulating element  322  is referred to as a “pump” which induces fluid flow through a corresponding fluid circulation channel  320  and associated fluid ejection chambers  302 . Other nozzle-to-pump ratios (e.g., 3:1, 4:1, etc.) are also possible. 
       FIG. 4  is a schematic plan view illustrating another example of a portion of a fluid ejection device  400 . Fluid ejection device  400  includes a plurality of fluid ejection chambers  402  and a plurality of fluid circulation channels  420 . Similar to that described above, fluid ejection chambers  402  each include a drop ejecting element  404  with a corresponding nozzle opening or orifice  412 , and fluid circulation channels  420  each include a fluid circulating element  422 . 
     In the example illustrated in  FIG. 4 , fluid circulation channels  420  each are open to and communicate at one end  424  with fluid feed slot  408  and communicate at another end, for example, ends  426   a ,  426   b ,  426   c  . . . , with multiple fluid ejection chambers  402 . In one example, fluid circulation channels  420  include a plurality of channel loop portions  428   a ,  428   b ,  428   c  . . . each communicated with a fluid ejection chamber  402  such that fluid from fluid feed slot  408  circulates (or recirculates) through fluid circulation channels  420  (including channel loop portions  428   a ,  428   b ,  428   c  . . . ) and the associated fluid ejection chambers  402  based on flow induced by a corresponding fluid circulating element  422 . Such flow is represented in  FIG. 4  by arrows  430 . 
       FIG. 5  is a flow diagram illustrating one example of a method  500  of operating a fluid ejection device, such as fluid ejection devices  200 ,  300 , and  400  as described above and illustrated in the examples of  FIGS. 2, 3, and 4 . 
     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 of a plurality of fluid ejection chambers, 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 plurality of fluid ejection chambers, such as fluid ejection chambers  202 ,  302 , and  402 , each have one of a plurality of drop ejecting elements, such as drop ejecting elements  204 ,  304 , and  404 , therein. 
     At  504 , method  500  includes providing continuous 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 the 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 . 
       FIGS. 6A and 6B  are schematic illustrations of example timing diagrams  600 A and  600 B, respectively, of operating a fluid ejection device, such as fluid ejection devices  200 ,  300 , and  400  as described above and illustrated in the examples of  FIGS. 2, 3, and 4 . More specifically, timing diagrams  600 A and  600 B each provide for continuous circulation of fluid from fluid slots, such as fluid feed slots  208 ,  308 , and  408 , through fluid circulation channels, such as fluid circulation channels  220 ,  320 , and  420 , and respective fluid ejection chambers, such as fluid ejection chambers  202 ,  302 , and  402 , based on operation of respective fluid circulating elements, such as fluid circulating elements  222 ,  322 , and  422 . 
     In the examples illustrated in  FIGS. 6A and 6B , timing diagrams  600 A and  600 B include a horizontal axis representing a time of operation (or non-operation) of a fluid ejection device, such as fluid ejection devices  200 ,  300 , and  400 . In timing diagrams  600 A and  600 B, taller, thinner vertical lines  610 A and  610 B, respectively, represent operation of the drop ejecting elements, such as drop ejecting elements  204 ,  304 , and  404 , and shorter, wider vertical lines  620 A and  620 B, respectively, represent operation of the fluid circulating elements, such as fluid circulating elements  222 ,  322 , and  422 . Operation of the drop ejecting elements (lines  610 A,  610 B) may include operation for nozzle warming and/or servicing as well as operation for printing. 
     In the examples illustrated in  FIGS. 6A and 6B , a period of time between different or disassociated periods of operation of the drop ejecting elements (lines  610 A,  610 B) represents a decap time  630 A and  630 B, respectively, of the fluid ejection device. Decap time  630 A and  630 B, therefore, may include, for example, a period of time between nozzle warming/servicing and printing (and vice versa), and a period of time between a first printing operation, sequence or series (e.g., first print job) and a second printing operation, sequence or series (e.g., second print job). 
     As illustrated in timing diagram  600 A, operation of the fluid circulating elements does not take into consideration (or is independent of) operation of the drop ejecting elements. More specifically, as illustrated by the nesting or overlap in the timing of operation of the fluid circulating elements (lines  620 A) and the timing of operation of the drop ejecting elements (lines  610 A), the operation of the fluid circulating elements (lines  620 A) and, therefore, the circulation of fluid with timing diagram  600 A, is not synchronized with (i.e., is asynchronous with) the operation of the drop ejecting elements (lines  610 A). Namely, the operation of the fluid circulating elements occurs during periods of operation of the drop ejecting elements. Nonetheless, timing diagram  600 A provides for continuous circulation of fluid during decap time  630 A. 
     As illustrated in timing diagram  600 B, operation of the fluid circulating elements does take into consideration (or is dependent on) operation of the drop ejecting elements. More specifically, the operation of the fluid circulating elements (lines  620 B) and, therefore, the circulation of fluid with timing diagram  600 B, is synchronized with (i.e., is synchronous with) the operation of the drop ejecting elements (lines  610 B). Namely, the operation of the fluid circulating elements is limited to periods of non-operation of the drop ejecting elements. As such, timing diagram  600 B provides for continuous circulation of fluid during decap time  630 B. 
     As illustrated in the examples of  FIGS. 6A and 6B , with timing diagrams  600 A and  600 B, a frequency of operation of the fluid circulating elements and, therefore, a frequency of the continuous circulation, is constant (substantially constant) during decap times  630 A and  630 B. 
       FIG. 7  is a schematic illustration of an example timing diagram  700  of operating a fluid ejection device, such as fluid ejection devices  200 ,  300 , and  400  as described above and illustrated in the examples of  FIGS. 2, 3, and 4 . Similar to timing diagrams  600 A and  600 B as described above and illustrated in the examples of  FIGS. 6A and 6B , timing diagram  700  provides for continuous circulation of fluid from a fluid slot, such as fluid feed slots  208 ,  308 , and  408 , through fluid circulation channels, such as fluid circulation channels  220 ,  320 , and  420 , and respective fluid ejection chambers, such as fluid ejection chambers  202 ,  302 , and  402 , based on operation of respective fluid circulating elements, such as fluid circulating elements  222 ,  322 , and  422 . 
     Similar to timing diagrams  600 A and  600 B, taller, thinner vertical lines  710  represent operation of drop ejecting elements, such as drop ejecting elements  204 ,  304 , and  404 , and shorter, wider vertical lines  720  represent operation of fluid circulating elements, such as fluid circulating elements  222 ,  322 , and  422 . In addition, similar to timing diagrams  600 A and  600 B, a period of time between different or disassociated periods of operation of the drop ejecting elements (e.g., nozzle warming/servicing and printing) represents a decap time  730  of the fluid ejection device. 
     In the example illustrated in  FIG. 7 , with timing diagram  700 , a frequency of operation of the fluid circulating elements and, therefore, a frequency of the continuous circulation is variable. More specifically, a frequency of the continuous circulation is variable based on operation of the drop ejecting elements. The frequency of the continuous circulation may be variable with the example asynchronous timing diagram  600 A of  FIG. 6A , and/or may be variable with the example synchronous timing diagram  600 B of  FIG. 6B . As such, in either example, the frequency of the continuous circulation is variable during decap time  730 . 
     In one example, the variable frequency of the continuous circulation is a function of an amount of time between disassociated periods of operation of the drop ejecting elements. More specifically, the variable frequency of the continuous circulation is a function of a length of decap time  730 . For example, as illustrated in  FIG. 7 , as the decap time increases, the frequency of the continuous circulation increases. 
     In another example, the variable frequency of the continuous circulation is a function of an amount of operation of the drop ejecting elements. More specifically, the variable frequency of the continuous circulation is a function of a number of drops ejected by the drop ejecting elements. For example, as illustrated in  FIG. 7 , as the number of drops ejected by the drop ejecting elements decreases (represented, for example, by fewer vertical lines  710 ), the frequency of the continuous circulation increases. Conversely, as the number of drops ejected by the drop ejecting elements increases, the frequency of the continuous circulation decreases. 
     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.