JP2019018584A - Fluid ejection device - Google Patents

Abstract

To reduce ink blockage and/or clogging in a fluid ejection element.SOLUTION: A fluid ejection device includes a fluid slot, at least one fluid ejection chamber in communication with the fluid slot, a drop ejecting element within the at least one fluid ejection chamber, a fluid circulation channel in communication with the fluid slot and the at least one fluid ejection chamber, and a fluid circulating element in communication with the fluid circulation channel. The fluid circulating element is to provide on-demand circulation of fluid from the fluid slot through the fluid circulation channel and the at least one fluid ejection chamber.SELECTED DRAWING: Figure 6B

Description

BACKGROUND Fluid ejecting devices, such as printheads in inkjet printing systems, can use a thermal resistor or a film of piezoelectric material as an actuator in a fluid chamber to eject fluid drops (eg, ink) from nozzles. And the print medium are configured to print characters and other images on the print medium by ejecting ink droplets from the nozzles in an appropriate order as they move relative to each other.

  Decap is the time during which an inkjet nozzle can be left exposed to ambient conditions without a cap without causing degradation of the ejected ink droplets. Due to the effect of decap, the droplet trajectory, velocity, shape, and color can change, all of which can adversely affect print quality. Other factors associated with decap such as water and solvent evaporation can also cause pigment ink media separation (PIVS) and the formation of viscous closures. For example, during periods of storage or non-use, pigment particles may settle or “stay” in the ink medium, thereby inhibiting or blocking the flow of ink to the ejection chambers and nozzles. Sometimes.

It is a block diagram showing an example of an ink jet printing system including an example of a fluid ejecting apparatus. It is a schematic plan view which shows an example of a part of fluid ejecting apparatus. It is a schematic plan view which shows another example of a part of fluid ejecting apparatus. It is a schematic plan view which shows another example of a part of fluid ejecting apparatus. It is a flowchart which shows an example of the method of operating a fluid injection apparatus. FIG. 6 is a schematic diagram of an exemplary timing diagram for operation of a fluid ejection device. FIG. 6 is a schematic diagram of an exemplary timing diagram for operation of a fluid ejection device.

DETAILED DESCRIPTION In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. The drawings illustrate various specific examples in which the present disclosure can be implemented. It should be understood that other examples can be used and structural or logical changes can be made without departing from the scope of the present disclosure.

  The present disclosure generally helps to reduce ink clogging and / or clogging in an inkjet printing system by circulating (or recirculating) fluid through the fluid ejection chamber. The fluid circulates (or recirculates) through a flow path that includes a fluid circulation element or actuator for pumping or circulating the fluid.

  FIG. 1 shows an example of an ink jet printing system as an example of a fluid ejecting apparatus having a fluid circulation means as disclosed in the present specification. Inkjet printing system 100 provides power to at least the printhead assembly 102, ink supply assembly 104, mounting assembly 106, media transport assembly 108, electronic controller 110, and various electronic components of inkjet printing system 100. One power source 112. The printhead assembly 102 ejects ink through a plurality of orifices or nozzles 116 toward the print media 118 to print on the print media 118 (printhead 114). including.

  The print medium 118 may be any type of suitable sheet material or roll material such as paper, card paper, transparent film, Mylar®. The nozzles 116 are typically arranged in one or more rows or arrays, and as the printhead assembly 102 and print media 118 move relative to each other, the proper sequence of ink ejection from the nozzles 116 causes characters, symbols, etc. And / or other graphics or images are arranged to be printed on the print medium 118.

  The ink supply assembly 104 supplies fluid ink to the printhead assembly 102 and, in one example, includes a reservoir 120 for storing ink and is configured to allow ink to flow from the reservoir 120 to the printhead assembly 102. Ink supply assembly 104 and printhead assembly 102 may form a one-way ink supply system or a recirculating ink supply system. In the case of a unidirectional ink supply system, substantially all of the ink supplied to the printhead assembly 102 is consumed during printing. In the case of a recirculating ink supply system, only a portion of the ink supplied to the printhead assembly 102 is consumed during printing. Ink that was not consumed during printing is returned to the ink supply assembly 104.

  In one example, the printhead assembly 102 and the ink supply assembly 104 are housed together in an inkjet cartridge, or pen. In another example, the ink supply assembly 104 is disposed independently of the printhead assembly 102 and supplies ink to the printhead assembly 102 through an interface connection such as a supply tube. In either example, the reservoir 120 of the ink supply assembly 104 may be removed, replaced, and / or refilled. When the printhead assembly 102 and the ink supply assembly 104 are housed together in an ink jet cartridge, the reservoir 120 includes not only a local reservoir located within the cartridge, but also a larger reservoir located independently of the cartridge. included. This independent larger reservoir serves to replenish the local reservoir. Thus, independent larger reservoirs and / or local reservoirs 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. Accordingly, a print zone 122 is defined proximate the nozzle 116 in the region between the printhead assembly 102 and the print medium 118. In one example, the printhead assembly 102 is a scanning printhead assembly. Accordingly, the mounting assembly 106 includes a carriage for moving the printhead assembly 102 relative to the media transport assembly 108 and scanning the print media 118. In another example, the printhead assembly 102 is a non-scanning printhead assembly. Accordingly, the mounting assembly 106 secures the printhead assembly 102 in place relative to the media transport assembly 108. The media transport assembly 108 then positions the print media 118 relative to the printhead assembly 102.

  The electronic controller 110 typically communicates with the processor, firmware, software, one or more storage components including volatile and non-volatile storage components, and the printhead assembly 102, mounting assembly 106, and media transport assembly 108; Includes other printer electronics to control them. The electronic control unit 110 receives data 124 from a host system such as a computer and temporarily stores the data 124 in a memory. Data 124 is typically sent to inkjet printing system 100 along an information transmission path by electrical, infrared, optical, or other means. Data 124 represents, for example, a document and / or file to be printed. The data 124 forms a print job for the inkjet printing system 100 and includes one or more print job commands and / or command parameters.

  In one example, the electronic controller 110 controls the printhead assembly 102 and ejects ink drops from the nozzles 116. Thus, the electronic control device 110 defines a pattern of ejected ink droplets from which characters, symbols, and / or other graphics or images are formed on the print medium 118. The pattern of ejected ink drops is determined by a print job command and / or command parameters.

  Printhead assembly 102 includes one or more printheads 114. In one example, the printhead assembly 102 is a wide array printhead assembly or a multihead printhead assembly. In one embodiment of the wide array assembly, the printhead assembly 102 includes a carrier having a plurality of printheads 114 to provide electrical communication between the printhead 114 and the electronic control circuit 110 and the printhead 114. Provide fluid communication with the ink supply assembly 104.

  In one example, the inkjet printing system 100 is a drop-on-demand thermal inkjet printing system and the printhead 114 is a thermal inkjet (TIJ) printhead. The thermal ink jet print head includes a thermal resistance ejecting element for generating bubbles in the ink chamber that vaporizes ink and pushes ink and other fluid droplets from the nozzle 116. In another example, inkjet printing system 100 is a drop-on-demand piezoelectric inkjet printing system, and printhead 114 includes a piezoelectric material actuator as an ejection element that generates pressure pulses that push ink drops out of nozzles 116. A piezoelectric inkjet (PIJ) printhead.

  In one example, the electronic controller 110 includes a flow circulation module 126 stored in the memory of the controller 110. The flow circulation module 126 runs on the electronic controller 110 (ie, the processor of the controller 110) and is integrated into the printhead assembly 102 as a pump element to control fluid circulation within the printhead assembly 102. Controlling the operation of one or more fluid actuators.

  FIG. 2 is a schematic plan view illustrating an example of a part of the fluid ejecting apparatus 200. The fluid ejecting apparatus 200 includes a fluid ejecting chamber 202 and a corresponding droplet ejecting element 204 formed in or provided in the fluid ejecting chamber 202. The fluid ejection chamber 202 and the droplet ejection element 204 are formed on a substrate 206, where a fluid (or ink) supply slot 208 is formed in the substrate 206, and the fluid (or ink) supply slot 208 is a fluid (or ink). ) Is supplied to the fluid ejecting chamber 202 and the droplet ejecting element 204. The substrate 206 may be formed from, for example, silicon, glass, or a stable polymer.

  In one example, the fluid ejection chamber 202 is formed in or is defined by a barrier layer (not shown) provided on the substrate 206 such that the fluid ejection chamber 202 provides a “well” in the barrier layer. Configured. The barrier layer may be formed of, for example, a photoimageable epoxy resin such as SU8.

  In one example, a nozzle or orifice layer (not shown) is formed or extends over the barrier layer, and a nozzle opening or orifice 212 formed in the orifice layer has a respective fluid ejection chamber 202. It is comprised so that it may communicate with. The nozzle opening or orifice 212 may be circular, non-circular, or other shape.

  The droplet ejecting element 204 may be any device capable of ejecting a fluid droplet through a corresponding nozzle opening or orifice 212. Examples of the droplet ejecting element 204 include a thermal resistor and a piezoelectric actuator. A thermal resistor as an example of a droplet ejecting element is typically formed on the surface of a substrate (substrate 206) and includes a thin film stack that includes an oxide layer, a metal layer, and a passivation layer, and when driven, Heat from the resistor causes the fluid in the fluid ejection chamber 202 to vaporize, thereby generating bubbles that eject fluid drops through the nozzle opening or orifice 212. A piezoelectric actuator as an example of a droplet ejecting element generally includes a piezoelectric material provided on a movable film connected to the fluid ejecting chamber 202, and when driven, the piezoelectric film causes the movable film relative to the fluid ejecting chamber 202 to be driven. , Thereby generating a pressure pulse that ejects a fluid droplet through the nozzle opening or orifice 212.

  As shown in the example of FIG. 2, the fluid ejection device 200 includes a fluid circulation passage 220, a fluid formed in the fluid circulation passage 220, provided in the fluid circulation passage 220, or in fluid communication with the fluid circulation passage 220. A circulation element 222. The fluid circulation passage 220 is open to the fluid supply slot 208 at one end 224, communicates with the fluid supply slot 208, and communicates with the fluid ejection chamber 202 at the other end 226, thereby providing a fluid supply. The fluid from the slot 208 is configured to circulate (or recirculate) through the fluid circulation passage 220 and the fluid ejection chamber 202 based on the flow caused by the fluid circulation element 222. In one example, the fluid circulation passage 220 includes a passage loop portion 228, whereby fluid in the fluid circulation passage 220 circulates (or recirculates) between the fluid supply slot 208 and the fluid ejection chamber 202 through the passage loop portion 228. It is configured to circulate).

  As shown in the example of FIG. 2, the fluid circulation passage 220 communicates with one (ie, a single) fluid ejection chamber 202. Thus, the fluid ejection device 200 has a 1: 1 nozzle to pump ratio, where the fluid circulation element 222 is referred to as a “pump” that causes fluid flow through the fluid circulation passage 220 and the fluid ejection chamber 202. . Having a 1: 1 ratio provides a separate circulation for each fluid ejection chamber 202.

  In the example shown in FIG. 2, both the droplet ejecting element 204 and the fluid circulation element 222 are thermal resistors. Each of these thermal resistors may include, for example, a single resistor, a split resistor, a comb resistor, or multiple resistors. However, various other devices may be used to implement the droplet ejecting element 204 and fluid circulation element 222, for example, piezoelectric actuators, electrostatic (MEMS) membranes, mechanically / impact driven A film, a voice coil, a magnetostrictive drive element, or the like may be used.

  FIG. 3 is a schematic plan view showing another example of part of the fluid ejection device 300. The fluid ejection device 300 includes a plurality of fluid ejection chambers 302 and a plurality of fluid circulation passages 320. Similar to that described above, each fluid ejection chamber 302 includes a droplet ejection element 304 having a corresponding nozzle opening or orifice 312, and each fluid circulation passage 302 includes a fluid circulation element 322.

  In the example shown in FIG. 3, each of the fluid circulation passages 320 is open to the fluid supply slot 308 at one end 324, communicates with the fluid supply slot 308, and others such as ends 326a, 326b, for example. At the end, it communicates with a plurality of fluid ejection chambers 302 (ie, two or more fluid ejection chambers). In one example, the fluid circulation passage 320 includes a plurality of passage loop portions, such as passage loop portions 328a, 328b, each passage loop portion communicating with a different fluid ejection chamber 302, thereby providing a fluid supply slot. Based on the flow induced by the corresponding fluid circulation element 322, fluid from 308 circulates (or recirculates) through the fluid circulation passage 320 (including the passage loop portions 328 a, 328 b) and the associated fluid ejection chamber 302. It is configured to circulate).

  As shown in the example of FIG. 3, each of the fluid circulation passages 320 communicates with the two fluid ejection chambers 302. Thus, the fluid ejection device 300 has a 2: 1 nozzle to pump ratio, where the fluid circulation element 322 causes fluid flow through the corresponding fluid circulation passage 320 and associated fluid ejection chamber 302. Called “pump”. Other nozzle to pump ratios (eg, 3: 1, 4: 1, etc.) are possible.

  FIG. 4 is a schematic plan view illustrating another example of a part of the fluid ejecting apparatus 400. The fluid ejection device 400 includes a plurality of fluid ejection chambers 402 and a plurality of fluid circulation passages 420. Similar to that described above, each fluid ejection chamber 402 includes a droplet ejection element 404 having a corresponding nozzle opening or orifice, and each droplet circulation path 420 includes a fluid circulation element 422.

  In the example shown in FIG. 4, each of the fluid circulation passages 420 is open to the fluid supply slot 408 at one end 424 and communicates with the fluid supply slot 408, and for example, ends 426 a, 426 b, 426 c,. .. communicated with the plurality of fluid ejection chambers 402 at the other end. In one example, the fluid circulation passage 420 includes a plurality of passage loop portions 428 a, 428 b, 428 c,..., Each passage loop portion communicating with the fluid ejection chamber 402 and thereby from the fluid supply slot 408. , Based on the flow induced by the corresponding fluid circulation element 422, through the fluid circulation passage 420 (including the passage loop portions 428 a, 428 b, 428 c,...) And the associated fluid ejection chamber 402. It is configured to circulate (or recirculate).

  FIG. 5 is a flow diagram illustrating an example method 500 for operating a fluid ejection device, such as the fluid ejection devices 200, 300, and 400 described above and illustrated in the examples of FIGS. is there.

  At 502, the method 500 includes fluid circulation passages such as fluid circulation passages 220, 320, and 420, fluid slots such as fluid supply slots 208, 308, and 408, and at least such as fluid ejection chambers 202, 302, and 402. Communicating with one fluid ejection chamber. Fluid circulation passages such as fluid circulation passages 220, 320 and 420 have fluid circulation elements such as fluid circulation elements 222, 322 and 422 in communication with the fluid circulation passages, and fluid ejection chambers 202, 302 and A fluid ejection chamber such as 402 has droplet ejection elements such as droplet ejection elements 204, 304 and 404.

  At 504, the method 500 includes the operation of fluid circulation elements such as fluid circulation elements 222, 322, and 422, fluid circulation passages such as fluid circulation passages 220, 320, and 420, and fluid ejection chambers 202, 302, and 402. Providing on-demand circulation of fluid from fluid slots, such as fluid supply slots 208, 308 and 408, through such at least one fluid ejection chamber.

  6A and 6B are exemplary timing diagrams 600A of the operation of a fluid ejection device, such as the fluid ejection devices 200, 300, and 400 described above and illustrated in the examples of FIGS. , And 600B, respectively. More specifically, timing diagrams 600A and 600B are based on the operation of fluid circulation elements such as fluid circulation elements 222, 322, and 422, respectively, fluid circulation passages such as fluid circulation passages 220, 320, and 420; And on-demand circulation of fluid from fluid slots such as fluid supply slots 208, 308 and 408 through fluid ejection chambers such as fluid ejection chambers 202, 302 and 402.

  In the example shown in FIGS. 6A and 6B, timing diagrams 600A and 600B include a horizontal axis representing the time of operation (or non-operation) of a fluid ejection device, such as fluid ejection devices 200, 300, and 400. . In timing diagrams 600A and 600B, high and thin vertical lines 610A and 610B represent the operation of droplet ejecting elements such as droplet ejecting elements 204, 304 and 404, respectively, and low and thick vertical lines 620A, And 620B represent the operation of fluid circulation elements such as fluid circulation elements 222, 322, and 422, respectively. Droplet ejector operations (lines 610A, 610B) may include not only printing operations, but also nozzle warming and / or service providing operations.

  In the example shown in FIGS. 6A and 6B, the time between different periods of operation of the droplet ejecting element, ie the unrelated periods (lines 610A, 610B), is the decap time 630A and 630B of the fluid ejector. Represents each. Thus, the decap times 630A and 630B include, for example, the time between nozzle warming / service provision and printing (and vice versa), the first printing operation, sequence or sequence (eg, the first print job). And a second printing operation, sequence or sequence (eg, a second print job).

  As shown in timing diagram 600A, the operation of the fluid circulation element, ie, fluid circulation through the fluid circulation passage, is provided on demand during decap time 630A. More specifically, fluid circulation element operation (line 620A) is provided at the end of the decap time prior to droplet ejection element operation (line 610A). However, the on-demand circulation is invalid during the inoperative period of the droplet ejecting element, and such invalid time is in the decap time 630A. Accordingly, fluid circulation is provided after a period of inactivity of the droplet ejecting element and prior to subsequent operation of the droplet ejecting element.

  In one example, the on-demand circulation of timing diagram 600A is provided with a delay (Δt) prior to operation of the droplet ejecting element. In one example, this delay is less than the frequency of operation of the droplet ejecting element. Thus, the operation of the fluid circulation element (line 620A) provides on-demand fluid circulation through the fluid circulation path at the end of the decap time 630A prior to the operation of the droplet ejecting element (line 610A).

  As shown in timing diagram 600B, the operation of the fluid circulation element, ie, fluid circulation through the fluid circulation passage, is provided on demand during decap time 630B. More specifically, fluid circulation element operation (line 620B) is provided at the end of the decap time prior to droplet ejection element operation (line 610B). However, the on-demand circulation is invalid during the inoperative period of the droplet ejecting element, and such invalid period is in the decap time 630B. Accordingly, fluid circulation is provided after a period of inactivity of the droplet ejecting element and prior to subsequent operation of the droplet ejecting element.

  In one example, the on-demand circulation of timing diagram 600B is provided without a delay before operation of the droplet ejecting element. Thus, the operation of the fluid circulation element (line 620B) provides on-demand fluid circulation through the fluid circulation path at the end of the decap time 630B immediately before the operation of the droplet ejecting element (line 610B).

  According to timing diagrams 600A and 600B, the clustering or grouping of fluid circulation element operations (line 620A) includes multiple pulses (ie, multiple pulses) of circulation provided by the fluid circulation element operation. In one example, the recirculation frequency and / or the number of pulses are not fixed. Rather, the recirculation frequency is synchronized to the printing frequency and is configured to optimize relevant parameters of on-demand circulation (eg, recirculation frequency and / or number of pulses) for a particular printing system. The Thus, multiple frequencies and / or multiple pulse counts are possible for on-demand cycling.

  Further, according to timing diagrams 600A and 600B, on-demand circulation occurs immediately before the operation of the droplet ejecting element (line 610B) to print image data. In this regard, a controller, such as a flow circulation module (FIG. 1), monitors the image data and initiates on-demand circulation based on idle time (eg, violating the decap time limit) and image data. Thus, on-demand circulation is provided only as needed. Further, in one example, on-demand circulation is provided for the particular droplet ejecting element (s) that are to be used to print the image data. Thus, the specific fluid circulation element (s) associated with the droplet ejecting element (s) to be used for printing are activated. Again, on-demand circulation is only provided as needed.

  A fluid ejection element that includes circulation as described herein reduces ink blockage and / or clogging. Therefore, the decap time, and consequently the nozzle normality, is improved. In addition, pigment ink media separation (PIVS) and the formation of viscous closures are reduced or suppressed. Further, ink efficiency is improved by reducing ink consumption during service provision (eg, by minimizing ink ejection to maintain nozzles normal). Furthermore, the fluid ejection device including the circulation means is useful for managing the bubbles by removing the bubbles from the ejection chamber during the circulation.

  While various specific examples have been illustrated and described herein, various modifications may be made to those illustrated and described without departing from the scope of the present disclosure, as will be appreciated by those skilled in the art. Alternate and / or equivalent embodiments can be used instead. This application is intended to cover any modifications and variations of the specific examples described herein.

Exemplary embodiments of the present invention are listed below.
1. A fluid ejection device, comprising: a fluid slot; at least one fluid ejection chamber in communication with the fluid slot; a droplet ejection element in the at least one fluid ejection chamber; the fluid slot and the at least one fluid A fluid circulation passage in communication with the ejection chamber; and a fluid circulation element in communication with the fluid circulation passage, the fluid circulation element passing through the fluid circulation passage and the at least one fluid ejection chamber. A fluid ejection device that provides on-demand circulation of fluid from a fluid slot.
2. 2. The fluid ejecting apparatus according to 1, wherein the operation of the fluid circulation element is provided before the operation of the droplet ejecting element.
3. 3. The fluid ejecting apparatus according to 2, wherein the operation of the fluid circulation element is provided in a form having a delay before the operation of the droplet ejecting element.
4). 4. The fluid ejecting apparatus according to 3, wherein the delay is less than a frequency of operation of the droplet ejecting element.
5. 3. The fluid ejecting apparatus according to 2, wherein the operation of the fluid circulation element is provided without a delay before the operation of the droplet ejecting element.
6). 3. The fluid ejecting apparatus according to 2, wherein the operation of the fluid circulation element is provided at the end of a decap time before the operation of the droplet ejecting element.
7). 2. The fluid ejecting apparatus according to 1, wherein the on-demand circulation includes a plurality of circulation pulses based on an operation of the droplet ejecting element.
8). 2. The fluid ejecting apparatus according to 1, wherein the on-demand circulation is provided after a non-operation period of the droplet ejecting element and before a subsequent operation of the droplet ejecting element.
9. A method of operating a fluid ejection device, wherein a fluid circulation passage is in communication with a fluid slot and at least one fluid ejection chamber, the fluid circulation passage having a fluid circulation element in communication with the fluid circulation passage, The at least one fluid ejection chamber has a droplet ejection element, and the operation of the fluid circulation element causes the fluid to be turned on from the fluid slot through the fluid circulation passage and the at least one fluid ejection chamber. Providing a demand cycle.
10. The method of claim 9, wherein providing the on-demand circulation includes providing the on-demand circulation prior to operation of the droplet ejecting element.
11. The method of claim 10, wherein providing the on-demand circulation includes providing a delay between the on-demand circulation and operation of the droplet ejecting element.
12 12. The method according to 11, wherein the delay is less than the frequency of operation of the droplet ejecting element.
13. 11. The method of 10, wherein providing the on-demand circulation includes providing the on-demand circulation without a delay between the on-demand circulation and operation of the droplet ejecting element.
14 11. The method of 10, wherein providing the on-demand circulation includes providing the on-demand circulation at the end of a decap time before operation of the droplet ejecting element.
15. Providing the on-demand circulation includes providing the on-demand circulation after a period of inactivity of the droplet ejecting element and prior to subsequent operation of the droplet ejecting element; 9 The method described in 1.

Claims (15)

A fluid ejection device comprising:
A fluid slot;
At least one fluid ejection chamber in communication with the fluid slot;
A droplet ejection element in the at least one fluid ejection chamber;
A fluid circulation passage in communication with the fluid slot and the at least one fluid ejection chamber;
A fluid circulation element in communication with the fluid circulation passage;
Operation of the fluid circulation element is provided only during a decap time of the droplet ejection element, and through the fluid circulation passage and the at least one fluid ejection chamber during the decap time of the droplet ejection element. A fluid ejection device that provides on-demand circulation of fluid from a fluid slot.   The fluid ejecting apparatus according to claim 1, wherein an operation of the fluid circulation element is provided before an operation of the droplet ejecting element.   The fluid ejecting apparatus according to claim 2, wherein the operation of the fluid circulation element is provided in a form having a delay before the operation of the droplet ejecting element.   The fluid ejecting apparatus according to claim 2, wherein the operation of the fluid circulation element is provided without a delay before the operation of the droplet ejecting element.   The fluid ejection device according to claim 1, wherein an operation of the fluid circulation element is provided at the end of the decap time.   The fluid ejecting apparatus according to claim 1, wherein the on-demand circulation includes a plurality of circulation pulses based on an operation of the droplet ejecting element.   A controller configured to monitor image data to be printed by the fluid ejection device and to initiate the on-demand circulation based on an idle time of the droplet ejection element and the image data; The fluid ejecting apparatus according to claim 1.   The fluid ejecting apparatus according to claim 7, wherein the on-demand circulation is started based on the idle time that violates a time limit of the decap time and the image data. A method of operating a fluid ejection device comprising:
A fluid circulation passage is in communication with a fluid slot and at least one fluid ejection chamber, the fluid circulation passage having a fluid circulation element in communication with the fluid circulation passage, and the at least one fluid ejection chamber is a droplet. Has an injection element,
Providing operation of the fluid circulation element only during a decap time of the droplet ejection element, and through the fluid circulation passage and the at least one fluid ejection chamber during the decap time of the droplet ejection element. Providing on-demand circulation of fluid from the fluid slot.   The method of claim 9, wherein providing the on-demand circulation comprises providing the on-demand circulation prior to operation of the droplet ejecting element.   The method of claim 10, wherein providing the on-demand circulation comprises providing the on-demand circulation with a delay between the on-demand circulation and operation of the droplet ejecting element. .   The method of claim 10, wherein providing the on-demand circulation includes providing the on-demand circulation without a delay between the on-demand circulation and operation of the droplet ejecting element. .   13. A method according to any one of claims 9 to 12, wherein providing the on-demand cycle comprises providing the on-demand cycle at the end of the decap time.   Providing the on-demand circulation includes monitoring image data to be printed by the fluid ejecting device and initiating the on-demand circulation based on an idle time of the droplet ejecting element and the image data. The method according to claim 9, comprising: 15. The method of claim 14, wherein providing the on-demand circulation includes initiating the on-demand circulation based on the idle time that violates a time limit on the decap time and the image data.

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