Patent Description:
Disclosed are fluid ejection dies and methods that utilize pumped fluid to reduce particle settling in the fluid and to cool the fluid ejection die. Particles, such as ink pigments, within the fluid being supplied to the fluid actuator may settle. Such settling may block the ejection orifice or otherwise impair performance of the fluid ejection die. The disclosed fluid ejection dies and methods recirculate the pumped fluid across the fluid actuator of a fluid ejector to reduce settling.

However, bulk fluid recirculation may result in a high pressure drop across the fluid actuator, reducing overall fluid flow. Such a reduction in the overall flow of fluid through the fluid ejection die may result in a heat buildup which may also impair performance of the fluid ejection die. The disclosed fluid ejection dies and methods provide additional fluid flow or fluid recirculation by allowing some of the pumped fluid to bypass the fluid actuator through a bypass passage. The additional fluid flow across the bypass passage provides enhanced cooling of the fluid ejection die. The circulating flow rate of fluid may also facilitate a more uniform and constant temperature across the different fluid ejectors for more reliable and consistent fluid ejection or printing performance.

The disclosed hybrid fluid circulation across both recirculation passages and bypass passages offers benefits in printers that utilize high print flux duty cycles to meet print flux demands while providing marginal flow across fluid ejectors to inhibit remnant air bubble accumulation and viscous plug formation. The bypass circulation passages enhance fluid flow to provide enhanced convective cooling for isothermal printing at lower total pressure drops. As result, a fluid ejection die may operate with high duty cycles while meeting print flux and nozzle health demands. For example, a print head designed to print fluid formulations with high weight percent solids at lower duty cycles may benefit by ratioing a larger portion of the recirculation flow across the fluid ejectors (between the fluid actuators and associated ejection orifices) to reduce viscous plug formation in the bore or ejection orifice. The size, number and distribution of multiple bypass passages in parallel may be modulated to enhance flow uniformity across the fluid ejectors and to tune the fluid flow characteristics to a particular print application.

Disclosed are example fluid ejection dies that may include a fluid actuator, a substrate supporting the fluid actuator, a chamber layer supported by the substrate and a bypass passage in the substrate. The substrate may include a closed inlet channel having an inlet opening for connection to an outlet of a fluid source and an outlet channel having an outlet opening of a first size for connection to an inlet of the fluid source. For purposes of this disclosure, the term "closed" when referring to an inlet channel or outlet channel shall mean that the channel does not lead to a destination, but has a dead end or closed end, wherein fluid flow is towards the closed end. To exit such a closed channel, fluid flows through openings connected to the sides, floor and/or ceiling of the channel. In the illustrated examples, fluid exits the closed inlet channel by flowing through recirculation passages and bypass passages. In different implementations, outlet channel may be closed or may instead lead to a return for fluid source <NUM>.

The chamber layer includes a recirculation passage to supply fluid for ejection by the fluid actuator through an ejection orifice and to circulate fluid across the fluid actuator from the closed inlet channel to the outlet channel. The bypass passage is of a second size less than the first size and connects the inlet channel to the inlet of the fluid source while bypassing any fluid actuator provided for ejecting fluid through an ejection orifice.

Disclosed are example fluid ejection methods. The example methods circulate fluid from a closed inlet channel that receives fluid from an outlet of a fluid supply to an outlet channel of a substrate of a fluid ejection die through a recirculation passage within a chamber layer of a fluid ejection die and across a fluid actuator that is supported by the substrate. The fluid actuator is to eject droplets of fluid from the recirculation passage through an ejection orifice. The method further includes circulating fluid from the closed inlet channel to the inlet of the fluid supply through a bypass passage within the substrate so as to bypass any fluid actuator provided for ejecting droplets through an ejection orifice.

Disclosed are example methods for forming example fluid ejection dies. The example methods may include providing a substrate supporting a fluid actuator, the substrate forming an inlet channel and outlet channel, the outlet channel having an outlet opening of a first size for connection to an inlet of a fluid source. The methods may include forming a second layer on the substrate, the second layer comprising a recirculation passage associated with the fluid actuator to supply fluid for ejection by the fluid actuator through an ejection orifice and to circulate fluid across the fluid actuator from the inlet channel to the outlet channel. The methods may include forming a bypass passage of a second size less than the first size in the substrate to connect the inlet channel to the outlet while bypassing any fluid actuator provided for ejecting fluid through an ejection orifice.

<FIG> schematically illustrates portions of an example fluid ejection die <NUM>. Fluid ejection die <NUM> provides for fluid circulation across both recirculation passages and bypass passages. Fluid circulation across the recirculation passages and across the fluid ejectors may inhibit remnant air bubble accumulation and viscous plug formation. Fluid circulation through the bypass passages may enhance fluid flow to provide enhanced convective cooling for isothermal printing at lower total pressure drops. Fluid ejection die <NUM> comprises substrate <NUM>, fluid actuator <NUM>, chamber layer <NUM> and bypass passage <NUM>.

Substrate <NUM> comprises a layer or multiple layers of material that form an inlet channel <NUM> and an outlet channel <NUM>. Inlet channel <NUM> may be directly or indirectly connected to an outlet <NUM> of a fluid source which supplies the fluid to be ejected, under pressure. The pressurized fluid is supplied to fluid actuator <NUM> from the fluid source <NUM> through inlet channel <NUM>. Outlet channel <NUM> may be directly or indirectly connected to an inlet <NUM> of the fluid source <NUM> to redirect fluid back to the fluid source <NUM>.

In one implementation, substrate <NUM> may comprise a layer or multiple layers of silicon. In yet other implementations, substrate <NUM> may comprise other materials.

Fluid actuator <NUM> comprises a device that displaces fluid within an adjacent void or volume through an associated or corresponding ejection orifice <NUM> provided in chamber layer <NUM>. Fluid actuator <NUM> is supported by substrate <NUM>. In one implementation, electrically conductive traces, switches/transistors and other electronic componentry associated with the powering and control of fluid actuator <NUM> are also supported by substrate <NUM>.

In one implementation, fluid actuator <NUM> may comprise a thermal resistor which, upon receiving electrical current, heats to a temperature above the nucleation temperature of the fluid so as to vaporize a portion of the adjacent fluid to create a bubble which displaces the fluid through the associated orifice <NUM>. In other implementations, the fluid actuator <NUM> may comprise other forms of fluid actuators. In other implementations, the fluid actuator may comprise a fluid actuator in the form of a piezo-membrane based actuator, an electrostatic membrane actuator, mechanical/impact driven membrane actuator, a magnetostrictive drive actuator, an electrochemical actuator, and external laser actuators (that form a bubble through boiling with a laser beam), other such microdevices, or any combination thereof.

Layer <NUM> is coupled to substrate <NUM>. Layer <NUM> forms recirculation passage <NUM>. Recirculation passage <NUM> is associated with fluid actuator <NUM> to supply fluid for ejection by fluid actuator <NUM> through ejection orifice <NUM>. Recirculation passage <NUM> extends directly below or adjacent to fluid actuator <NUM>, between fluid actuator <NUM> and ejection orifice <NUM>. In addition to supplying fluid for ejection by fluid actuator <NUM>, recirculation passage <NUM> also circulates fluid across the fluid actuator <NUM> from inlet channel <NUM> to outlet channel <NUM>. Such recirculation reduces settling of particles suspended within the fluid, such as ink pigments. Although schematically illustrated as having a uniform width and height, it should be appreciated that recirculation passage <NUM> may vary along its width and/or height. In some implementations, recirculation passage <NUM> may have a different shape or size between fluid actuator <NUM> and ejection orifice <NUM> so as to form an ejection chamber.

In some implementations, layer <NUM> is formed from a photo-imageable epoxy. In some implementations, layer <NUM> is formed from SU8. In some implementations, layer <NUM> may be formed from other materials or combination of materials.

Bypass passage <NUM> comprises a passage or multiple separate or interconnected passages that extend partially, if not entirely, within substrate <NUM> and that directly or indirectly connect inlet channel <NUM> to the inlet <NUM> of fluid source <NUM>. Bypass passage <NUM> has a size less than a size of an outlet opening of channel <NUM> connecting channel <NUM> to the inlet <NUM> of fluid source <NUM> such that a portion of the fluid supplied to inlet channel <NUM> still circulates across recirculation passage <NUM>. In implementations where bypass passage <NUM> comprises multiple fluid passages, the collective cross-sectional area of the multiple fluid passages is such that the total flow through such passages is less than the total flow through the outlet opening of channel <NUM> to the inlet <NUM> of fluid source <NUM> such that a portion of the fluid supplied to inlet channel <NUM> still circulates across recirculation passage <NUM>. In some implementations, at least some, but less than <NUM>% of the total fluid supplied inlet channel <NUM> passes through the fluid passage or multiple fluid passages forming bypass passage <NUM>, whereas the remaining fluid supplied inlet channel <NUM> circulates across the collection of recirculation passages of die <NUM>.

In some implementations, bypass passage <NUM> comprises a fluid passage extending directly between inlet channel <NUM> and outlet channel <NUM> of substrate <NUM>, such as through a wall or rib that separates the two channels. Such a bypass passage <NUM> may comprise multiple passages, such as passages interspersed along the length of channel <NUM>, <NUM> or such as panels arranged at the ends of channels <NUM> and <NUM>.

In some implementations, bypass passage <NUM> may comprise a fluid passage that extends through a roof or ceiling of inlet channel <NUM> to the inlet <NUM> of fluid source <NUM>. For example, bypass passage <NUM> may comprise a fluid passage that extends through the ceiling of inlet channel <NUM> to another fluid passage that is returning fluid to fluid source <NUM>, through the inlet <NUM> of fluid source <NUM>. In some implementations, the bypass passage <NUM> extending through the ceiling may comprise a single slot or opening or may comprise an array of holes.

In some implementations, bypass passage <NUM> may comprise a fluid passage that extends through a floor of inlet channel <NUM>, across and within substrate <NUM> to the outlet channel <NUM>. Such a passage may extend through the floor, top or side of outlet channel <NUM>. In some implementations, bypass passage <NUM> may comprise combinations of each of a passage extending through a rib between channels <NUM>, <NUM>, a passage extending through a roof of channel <NUM> and a passage extending through the floor of inlet channel <NUM> to the outlet channel <NUM>. In some implementations, additional bypass passages may be provided in chamber layer <NUM> which facilitate the circulation of fluid from inlet channel <NUM> to outlet channel <NUM> within chamber layer <NUM> without the fluids circulating across any fluid actuator that is provided for ejecting fluid through a corresponding ejection orifice.

<FIG> is a flow diagram of an example method <NUM> that may be used to form a fluid ejection die, such as the example fluid ejection die <NUM> shown in Figures 1A, 1B and 1C. As indicated by block <NUM>, a substrate, such as substrate <NUM> is provided. The provided substrate supports a fluid actuator, such as fluid actuator <NUM>, and forms an inlet channel and an outlet channel. The outlet channel has an outlet opening of a first size for connection to an inlet of a fluid source, such as fluid source <NUM>. Substrate <NUM> may be molded to form channels <NUM> and <NUM> or may undergo material removal processes, such as sawing, etching and the like to form channels <NUM> and <NUM>. Channel <NUM> and <NUM> may be formed through masking and etching processes. The fluid actuator may be bonded to or encapsulated within substrate <NUM>. Electronic circuitry associated with the fluid actuator may be formed within or patterned on substrate <NUM>.

As indicated by block <NUM>, a second layer, such as layer <NUM>, is formed. The second layer is formed so as to have a recirculation passage, such as recirculation passage <NUM>, across the fluid actuator supported by the substrate. The recirculation passage is to supply fluid for ejection by the fluid actuator through an ejection orifice and to circulate fluid across the fluid actuator from the inlet channel to the outlet channel.

In some implementations, the second layer may be molded so as to form the recirculation passage and the bypass passage. In some implementations, the second layer may undergo material removal processes or patterning processes such as photolithography and etching to form the recirculation passage and the bypass passage. For example, in implementations where the second layer is formed from a photo-imageable epoxy, masking and etching processes may be applied to form the recirculation passage. In yet other implementations, a combination of different processes may be used to form the recirculation passage and the bypass passage.

As indicated by block <NUM>, a bypass passage, such as bypass passage <NUM>, is formed in substrate <NUM>. The bypass passage is of a second size less than the first size. The bypass passage connects the inlet channel to the outlet channel while bypassing any fluid actuator provided for ejecting fluid through an ejection orifice. In some implementations, the bypass passage <NUM> is formed prior to the joining of the second layer to the substrate. In some implementations, bypass passage <NUM> may be formed by molding or may be formed by the application of various material removal processes, such as etching, sawing and the like. In some implementations, bypass passage <NUM> may be formed by using various masking techniques or photolithography.

<FIG> is a flow diagram of an example fluid ejection method <NUM>. Method <NUM> reduces settling of particles within the fluid being ejected by recirculate fluid across a fluid actuator, between the fluid actuator and a corresponding ejection orifice. Method <NUM> additionally enhances the overall flow of fluid through a fluid ejection die by allowing a portion of the fluid to bypass the fluid actuator, enhancing the cooling of the fluid ejection die.

As indicated by block <NUM>, fluid is circulated from a closed inlet channel that receives fluid from an outlet of a fluid source, such as source <NUM>, to an outlet channel of the substrate of a fluid ejection die through a recirculation passage within a chamber layer of the fluid ejection die and across a fluid actuator that is supported by the substrate. The fluid actuator is to eject drops of fluid from the recirculation passage through an ejection orifice.

As indicated by block <NUM>, fluid is further circulated from the close inlet channel to the inlet of the fluid supply through a bypass passage within the substrate so as to bypass any fluid actuator provided for ejecting droplets through an ejection orifice.

<FIG>, <FIG> and <FIG> illustrate portions of an example fluid ejection die <NUM>. <FIG> is a perspective view illustrating a first cross-section of portions of an example fluid ejection die <NUM>. <FIG> illustrates the recirculation of fluid across fluid ejectors of die <NUM>. <FIG> is a perspective view illustrating a second cross-section of portions of the example fluid ejection die <NUM>. <FIG> illustrates the bypassing of fluid around or past the fluid ejectors. <FIG> is a bottom view of portions of the example fluid ejection die of <FIG>). In <FIG>, the main supply stream or flow of fluid from the fluid source is indicated by lines, recirculating fluid across fluid ejectors, across and between fluid actuator and its associated fluid ejection orifice is represented by dash-dot-dash broken lines and fluid flows that bypass a fluid ejector are represented by dash-dot-dot-dash broken lines. <FIG> and <FIG> are enlarged sectional views of portions of the fluid ejection die <NUM> of <FIG>. As with the above described die <NUM>, die <NUM> reduces particle settling by using recirculation channels and enhances cooling by using bypass passages. Fluid ejection die <NUM> comprises body <NUM>, layer <NUM>, layer <NUM>, fluid actuators <NUM>, layer <NUM>, layer <NUM> and bypass passages <NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> (collectively referred to as passages <NUM>).

Body <NUM> supports layers <NUM>, <NUM>, <NUM> and <NUM> while providing fan-out fluid passages <NUM>-<NUM> and <NUM>-<NUM> (collectively referred to as passages <NUM>). In the example illustrated, passage <NUM>-<NUM> receives fluid from a pressurized fluid source <NUM>. Passage <NUM>-<NUM> forms an outlet which ultimately receives fluid from the various bypass passages and directs the fluid back to the pressurized fluid source <NUM> for recirculation. In one implementation, body <NUM> comprises a single unitary polymeric body is formed from an epoxy mold compound. In other implementations, body <NUM> may be formed from other polymers. In one implementation, body <NUM> is molded to form fan-out fluid passages <NUM>. In other implementations, body <NUM> may be formed from other materials.

Layer <NUM> comprises a layer of material extending between body <NUM> and layer <NUM>. Layer <NUM> forms a port <NUM> for fluid passage <NUM>-<NUM> and a port <NUM> for fluid passage <NUM>-<NUM>. In one implementation, port <NUM> and port <NUM> comprise fluid holes. In another implementation, port <NUM> and port <NUM> comprise slots or channels.

Layer <NUM> comprises a layer or multiple layers of material forming inlet channel <NUM> and outlet channel <NUM>. Inlet channel <NUM> extends within layer <NUM> from port <NUM> of layer <NUM>. Outlet channel <NUM> extends within layer <NUM> from port <NUM>. Inlet channel <NUM> and outlet channel <NUM> are separated by an intervening rib <NUM> of layer <NUM>. Rib <NUM> supports fluid actuators <NUM>. Layer <NUM> may additionally support electrically conductive traces, switches or other electronic componentry associated with the fluid actuators <NUM>.

Although illustrated as two separate layers, in some implementations, layers <NUM> and <NUM> may comprise a single unitary or monolithic layer. In some implementations, both of layers <NUM> and <NUM> are formed from silicon. In other implementations, layers <NUM> and <NUM> may be formed from different materials. In some implementations, layer <NUM> may be formed from silicon while layer <NUM> is formed from other materials such as polymers, ceramics, glass and the like. In some implementations, layer <NUM> may be formed from materials other than silicon.

Layer <NUM> comprises a layer or multiple layers of a material or materials joined to an underside of layer <NUM> and forming recirculation passages <NUM> (shown in <FIG>) and bypass passages <NUM> (shown in <FIG>). Recirculation passages <NUM> comprise fluid passages that extend between and provide for fluid flow from channel <NUM> to channel <NUM> between an associated fluid actuator <NUM> and an ejection orifice <NUM> associated with the particular fluid actuator <NUM>. In the example illustrated, each of recirculation passages <NUM> has a ceiling provided by layer <NUM>, internal sides provided by layer <NUM> and a floor provided by layer <NUM>.

As shown by arrow <NUM> in <FIG>, a mainstream or flow of fluid from fluid source <NUM> is delivered to each of the fluid ejectors of die <NUM> across fluid passage <NUM>-<NUM>. As shown by arrow <NUM>, a diverted portion of the main flow passes through port <NUM> into the underlying inlet channel <NUM>. As shown by the dash-dot-dash broken line arrow <NUM>, a portion of the diverted flow passes through inlet <NUM> into the underlying recirculation passage <NUM> and flows across the fluid ejector formed by fluid actuator <NUM> and its corresponding ejection orifice <NUM>. As indicated by arrow <NUM>, a recirculating portion of the fluid, fluid that was not ejected through orifice <NUM>, exits recirculation passage <NUM> through outlet <NUM> and enters outlet channel <NUM>. Thereafter, the recirculated portion of the fluid flow circulates along outlet channel <NUM> and up through port <NUM> of passage <NUM>-<NUM>. As indicated by arrow <NUM>, passage <NUM>-<NUM> directs the recirculating portion of the fluid to the inlet <NUM> of fluid source <NUM>. In one implementation, each of inlets <NUM> and outlets <NUM> comprise fluid holes formed in layer <NUM>. In other implementations, inlet <NUM> and outlets <NUM> may be partially formed within layer <NUM>. In some implementations, inlets <NUM> and outlets <NUM> may each comprise multiple fluid holes or an array of fluid holes. In some implementations, inlets <NUM> and outlets <NUM> may comprise slots or channels.

Recirculation passages <NUM> supply their respective fluid actuators <NUM> with fluid for ejection through the corresponding ejection orifice <NUM>. Recirculation passages <NUM> additionally circulate fluid across their respective fluid actuators <NUM> from channel <NUM> to channel <NUM> to reduce settling.

Layer <NUM> comprises a layer of material or multiple layers of material joined to layer <NUM> and forming ejection orifices <NUM>. In some implementations, layer <NUM> is formed from the same material as layer <NUM>. For example, in some implementations, layers <NUM> and layer <NUM> both formed from a photo-imageable epoxy. In some implementations, layer <NUM> is formed from a different material as layer <NUM>. In some implementations, layers <NUM>, <NUM> and <NUM> are formed as a single fluid ejection die which is joined to body <NUM> by layer <NUM>. In some implementations, layers <NUM>, <NUM>, <NUM> and <NUM> are formed as a single fluid ejection die which is otherwise joined to body <NUM>.

As shown in <FIG>, the example die <NUM> comprises three different example types of bypass passages. Each of the example bypass passages <NUM> extends from layer <NUM> and is in direct or indirect communication with fluid passage <NUM>-<NUM> which is directly or indirectly connected to the inlet of fluid source <NUM>. Bypass passages <NUM> facilitate the circulation of fluid from inlet channel <NUM> to the inlet of the fluid source <NUM> without flowing through any fluid ejector. With each of the different types of bypass passages, the bypass passages are sized such that a portion of the fluid continues to flow across recirculation passage <NUM>.

Bypass passage <NUM>-<NUM> comprises a fluid passage extending directly between inlet channel <NUM> and outlet channel <NUM> of layer <NUM>, through the rib <NUM> that separates the two channels. As shown by <FIG>, in some implementations, bypass passage <NUM>-<NUM> may comprise a hole or tunnel within and through rib <NUM>, wherein the interior sides of passage <NUM>-<NUM> are formed by those portions of layer <NUM> forming rib <NUM>. As shown by <FIG>, in some implementations, bypass passage <NUM>-<NUM> may comprise a gap within our interruption of rib <NUM>, wherein the top or ceiling of bypass passage <NUM>-<NUM> is formed by layer <NUM>.

As shown by arrow <NUM> in <FIG>, a supply stream or flow of fluid from fluid source <NUM> is delivered to each of the fluid ejectors of die <NUM> to and across fluid passage <NUM>-<NUM>. As shown by arrow <NUM>, a diverted portion of the supply flow (diverted portion <NUM>) passes through port <NUM> into the underlying inlet channel <NUM>. As shown by the dash-dot-dot-dash broken line <NUM>, bypass passage <NUM>-<NUM> directs a bypass portion of the diverted flow <NUM> through the rib <NUM> to the outlet channel <NUM>. Thereafter, the bypass portion of the fluid flow flows along outlet channel <NUM> and up through port <NUM> of passage <NUM>-<NUM>, as indicated by arrow <NUM>. As indicated by arrow <NUM>, passage <NUM>-<NUM> directs the bypass portion to the inlet <NUM> of fluid source <NUM>. As shown by <FIG>, in some implementations, an inlet channels <NUM> and an outlet channel <NUM> may be connected by multiple bypass passages <NUM>-<NUM> uniformly or non-uniformly distributed along the length of such channels.

Bypass passage <NUM>-<NUM>-<NUM> comprises a fluid passage that extends between inlet channel <NUM> and fluid passage <NUM>-<NUM>. Bypass passage <NUM>-<NUM>-<NUM> extends through a roof or ceiling of inlet channel <NUM> to the port <NUM> of fluid passage <NUM>-<NUM>. In some implementations, the bypass passage <NUM>-<NUM>-<NUM> extending through the ceiling may comprise a single slot or opening or may comprise an array of holes. As shown by the dash-dot-dot-dash broken line <NUM> in <FIG>, a portion of the diverted flow <NUM> that has circulated across the length of inlet channel <NUM> and that has not circulated across any fluid ejector may pass upwards through fluid bypass <NUM>-<NUM>-<NUM> into the overlying outlet channel <NUM>-<NUM>. As indicated by arrow <NUM>, passage <NUM>-<NUM> directs the bypass portion to the inlet <NUM> of fluid source <NUM>. In some implementations, each of the multitude of inlet channels <NUM> along the length of die <NUM> may include a bypass passage <NUM>-<NUM>-<NUM>, similar to the one shown. In other implementations, a portion of the inlet channels may omit bypass passages <NUM>-<NUM>-<NUM>.

Bypass passage <NUM>-<NUM>-<NUM> comprises a fluid passage that extends between outlet channel <NUM> and fluid passage <NUM>-<NUM>. Bypass passage <NUM>-<NUM>-<NUM> extends through a roof or ceiling of outlet channel <NUM> to fluid passage <NUM>-<NUM>. In some implementations, the bypass passage <NUM>-<NUM>-<NUM> extending through the ceiling may comprise a single slot opening or may comprise an array of holes. As shown by the dash-dot-dot-dash broken line arrow <NUM> in <FIG>, a portion of the supply stream of fluid (indicated by arrow <NUM>) may enter bypass passage <NUM>-<NUM>-<NUM> (such as through a floor of passage <NUM>-<NUM>), wherein the diverted flow of fluid then flows along outlet channel <NUM>, through port <NUM> and along passage <NUM>-<NUM> back to the fluid source <NUM>. In some implementations, each of the multitude of outlet channels <NUM> along the length of die <NUM> may include a bypass passage <NUM>-<NUM>-<NUM>, similar to the one shown. In other implementations, a portion of the outlet channels may omit bypass passages <NUM>-<NUM>-<NUM>.

Bypass passage <NUM>-<NUM> comprises a fluid passage that extends through a floor of inlet channel <NUM>, across and within layer <NUM> to the outlet channel <NUM>. As shown by arrow <NUM> in <FIG>, a mainstream or flow of fluid from fluid source <NUM> is delivered to each of the fluid ejectors of die <NUM> to and across fluid passage <NUM>-<NUM>. As shown by <FIG>, a diverted portion (diverted flow <NUM>) of the supply flow passes <NUM> through port <NUM> into the underlying inlet channel <NUM>. As shown by the dash-dot-dot-dash broken line <NUM>, bypass passage <NUM>-<NUM> directs a bypass portion of the diverted flow <NUM> through the rib <NUM> to the outlet channel <NUM>. Thereafter, the bypass portion of the fluid flow circulates along outlet channel <NUM> and up through port <NUM> of passage <NUM>-<NUM>, as indicated by arrow <NUM>. As indicated by arrow <NUM>, passage <NUM>-<NUM> directs the bypass portion to the inlet <NUM> of fluid source <NUM>.

Although die <NUM> is illustrated as including each of the three different types of bypass passages <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>, in other implementations, fluid ejection die <NUM> may comprise different combinations of less than each of the three different types of bypass passages <NUM>. For example, in some implementations, die <NUM> may just include bypass passages <NUM>-<NUM>, just include bypass passages <NUM>-<NUM> or may just include bypass passages <NUM>-<NUM>. In some implementations, die <NUM> may include two of the three different types of fluid bypass passages <NUM>.

As shown by <FIG>, in the example illustrated, die <NUM> additionally comprises bypass passage <NUM>. Bypass passage <NUM> comprises a fluid passage that extends within chamber layer <NUM> between holes or slots connected to inlet channel <NUM> and outlet channel <NUM>. Bypass passage <NUM> provides for fluid flow from channel <NUM> to channel <NUM> without passing a fluid actuator that is to eject fluid through a corresponding ejection orifice. In the example illustrated, bypass passage <NUM> has a ceiling provided by layer <NUM>, internal sides provided by layer <NUM> and a floor provided by layer <NUM>. In other implementations, bypass passage <NUM> may be wholly contained within layer <NUM>.

Bypass passage <NUM> receives fluid from channel <NUM> through an inlet <NUM> and discharges fluid to channel <NUM> through an outlet <NUM>. In one implementation, each of inlets <NUM> and outlets <NUM> comprise fluid holes formed in layer <NUM>. In other implementations, inlet <NUM> and outlets <NUM> may be partially formed within layer <NUM>. In some implementations, inlets <NUM> and outlets <NUM> may each comprise multiple fluid holes or an array of fluid holes. In some implementations, inlets <NUM> and outlets <NUM> may comprise slots or channels.

As indicated by arrow <NUM> in <FIG>, bypass passage <NUM> allows a portion of the fluid being supplied by channel <NUM> to bypass recirculation passages <NUM> and its corresponding fluid actuator <NUM>. As a result, flow between channels <NUM> and <NUM> is increased. The increased flow of fluid may assist in absorbing and carrying away excess heat to provide convective cooling for fluid ejection die <NUM>. In some implementations, bypass passage <NUM> and the associated inlet <NUM> and outlet <NUM> may be omitted.

<FIG>, <FIG>, <FIG> and <FIG> illustrate an example fluid ejection die <NUM>. Such figures illustrate an example arrangement of bypass passages that are similar to bypass passages <NUM>-<NUM> and <NUM>-<NUM> described above. For ease of illustration, portions of the die are transparently shown with the layer containing the bypass passages being stippled. <FIG> and <FIG> are bottom views of the die while <FIG> is a sectional view from above the bypass passages. <FIG> is a sectional view along a length of the die <NUM>.

As shown by <FIG>, die <NUM> comprises layers <NUM>, <NUM>, <NUM> and <NUM> which substantially correspond to layers <NUM>, <NUM>, <NUM> and <NUM>, respectively, of die <NUM>. Layer <NUM> extends between body <NUM> (shown in <FIG>) and layer <NUM>. In the example illustrated, layer <NUM> comprises three ports <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> (collectively referred to as ports <NUM>) and two ports <NUM>-<NUM> and <NUM>-<NUM> (collectively referred to as ports <NUM>). Ports <NUM> deliver fluid from a pressurized fluid source <NUM> through a supply passage such as passage <NUM>-<NUM> shown in <FIG>. Ports <NUM> deliver fluid to the pressurized fluid source <NUM> through a passage such as passage <NUM>-<NUM> shown in <FIG>.

Layer <NUM> forms a series of alternating inlet and outlet channels, wherein the inlet channels are individually connected to ports <NUM> and wherein the outlet channels are individually connected to ports <NUM>. <FIG> illustrates three example inlet channels <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> and two example outlet channels <NUM>-<NUM> and <NUM>-<NUM>. Inlet channels <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> receive pressurized fluid through ports <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>, respectively, of layer <NUM> while outlet channels <NUM>-<NUM> and <NUM>-<NUM> discharge fluid through ports <NUM>-<NUM> and <NUM>-<NUM>, respectively, of layer <NUM>. Similar to channels <NUM> and <NUM> of die <NUM>, channels <NUM> and <NUM> are separated by intervening walls or ribs <NUM> (shown in <FIG>) which support fluid actuators <NUM> (shown in <FIG>) generally opposite to an ejection orifice <NUM>, formed in layer <NUM>. In the example illustrated, each of channels <NUM> and <NUM> is Chevron -shaped, facilitating a staggering offset relationship between different ejection orifices <NUM> of different fluid ejectors arranged between the channels <NUM>, <NUM>.

In one implementation, layer <NUM> may comprise a layer or multiple layers of silicon. In yet other implementations, layer <NUM> may comprise other materials.

Layer <NUM> extends over layer <NUM> between layer <NUM> and layer <NUM>. Layer <NUM> forms a two-dimensional array of recirculation passages. As shown by <FIG> and <FIG>, recirculation passages <NUM> connect adjacent inlet channels <NUM> and outlet channels <NUM>. Each of circulation passages <NUM> receives fluid from an overlying inlet channel <NUM> through a fluid feed hole <NUM> and discharges fluid to an overlying outlet channel <NUM> through a fluid discharge hole <NUM>. In the example illustrated, recirculation passages <NUM> are arranged in sets <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM> and sets <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>. Sets <NUM>-<NUM> and <NUM>-<NUM> are arranged opposite ends of channels <NUM>-<NUM> and <NUM>-<NUM>, interconnecting channels <NUM>-<NUM> and <NUM>-<NUM>. Sets <NUM>-<NUM> and <NUM>-<NUM> are arranged opposite ends of channels <NUM>-<NUM> and <NUM>-<NUM>, interconnecting channels <NUM>-<NUM> and <NUM>-<NUM>. Sets <NUM>-<NUM> and <NUM>-<NUM> are arranged opposite ends of channels <NUM>-<NUM> and <NUM>-<NUM>, interconnecting channels <NUM>-<NUM> and <NUM>-<NUM>. Sets <NUM>-<NUM> and <NUM>-<NUM> are arranged opposite ends of channels <NUM>-<NUM> and <NUM>-<NUM>, interconnecting channels <NUM>-<NUM> and <NUM>-<NUM>.

As indicated by arrows <NUM>-<NUM>, sets <NUM>-<NUM> and <NUM>-<NUM> direct the flow of fluid from channel <NUM>-<NUM>, across associated fluid actuators <NUM> and ejection orifices <NUM>, to channel <NUM>-<NUM>. As indicated by arrows <NUM>-<NUM>, sets <NUM>-<NUM> and <NUM>-<NUM> direct the flow of fluid from channel <NUM>-<NUM>, across associated fluid actuators <NUM> and ejection orifices <NUM>, to channel <NUM>-<NUM>. As indicated by arrows <NUM>-<NUM>, sets <NUM>-<NUM> and <NUM>-<NUM> flow from channel <NUM>-<NUM>, across associated fluid actuators <NUM> and ejection orifices <NUM>, to channel <NUM>-<NUM>. As indicated by arrows <NUM>-<NUM>, sets <NUM>-<NUM> and <NUM>-<NUM> direct the flow of fluid from channel <NUM>-<NUM>, across associated fluid actuators <NUM> and ejection orifices <NUM>, to channel <NUM>-<NUM>.

In the example illustrated, layer <NUM> additionally forms a pair of spaced pillars <NUM> on opposite sides of each fluid actuator <NUM> and ejection orifice <NUM>. Pillars <NUM> are spaced to allow fluid flow therebetween and past such pillars. Pillars <NUM> serve to filter the fluid flowing across the fluid actuator <NUM> and its associated ejection orifice <NUM>. In some implementations, other arrangements of pillars <NUM> or other filtering mechanisms may be employed. In other implementations, pillars <NUM> may be omitted.

Bypass passages <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM> (collectively referred to as bypass passages <NUM>-<NUM>) are each similar to bypass passages <NUM>-<NUM>-<NUM> described above. Bypass passages <NUM>-<NUM> comprise fluid passages that extend through a roof or ceiling of a respective inlet channel to the port <NUM> of fluid passage <NUM>-<NUM> which extends across the passages <NUM>, <NUM>. In the example illustrated, bypass passage <NUM>-<NUM>-<NUM> extends through the ceiling of inlet channel <NUM>-<NUM> into communication with the overlying passage <NUM>-<NUM> (shown in <FIG>). Bypass passage <NUM>-<NUM>-<NUM> extends through the ceiling of inlet channel <NUM>-<NUM> into communication with the overlying passage <NUM>-<NUM>. Bypass passage <NUM>-<NUM>-<NUM> extends through the ceiling of inlet channel <NUM>-<NUM> into communication with the overlying passage <NUM>-<NUM>. In the example illustrated, each of bypass passages <NUM>-<NUM> comprises an array of holes, such as a pair of holes. In other implementations, each of bypass passages <NUM>-<NUM> may comprise a single opening or a slot. Bypass passages <NUM>-<NUM> direct a portion of the fluid supplied to each of the inlet channels <NUM> to flow directly to an outlet channel <NUM>, without flowing across a fluid ejector, without flowing between a fluid actuator <NUM> and its associated ejection orifice <NUM>. As a result, overall fluid flow across the die <NUM> is increased for enhanced convective cooling of die <NUM>.

Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> (collectively referred to as bypass passages <NUM>-<NUM>) extend through the ceilings of outlet channels <NUM>-<NUM> and <NUM>-<NUM>, respectively, into communication with the overlying passage <NUM>-<NUM> which extends across each of channels <NUM>, <NUM>. Bypass passages <NUM>-<NUM> provide additional fluid flow into outlet channels <NUM> and across outlet channels <NUM> to provide additional convective cooling. In the example illustrated, each of bypass passages <NUM>-<NUM> comprises an array of holes, such as a pair of holes. In other implementations, each of bypass passages <NUM>-<NUM> may comprise a single opening or a slot. In some implementations, bypass passages <NUM>-<NUM> or bypass passages <NUM>-<NUM> may be omitted.

<FIG> and <FIG> illustrate portions of an example fluid ejection die <NUM>. For ease of illustration, portions of the die <NUM> are transparently shown with the layer containing the bypass passages being stippled. <FIG> is a sectional view from above the bypass passages. <FIG> is an enlarged view of a portion of die <NUM>. Die <NUM> illustrates one example arrangement of bypass passages which are similar to bypass passage <NUM>-<NUM> described above. Die <NUM> is similar to die <NUM> except that die <NUM> comprises bypass passages <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> (collectively referred to as bypass passages <NUM>). The remaining components of die <NUM> which correspond to components of die <NUM> are numbered similarly.

Each of bypass passages <NUM> extends through a rib <NUM> and provides fluid communication between a respective fluid inlet channel <NUM> and one of fluid outlet channels <NUM>. Bypass passages <NUM> are sized to circulate fluid from inlet channels <NUM> to outlet channels <NUM> at a rate such that fluid is directed across recirculation passages <NUM> at a sufficient rate to meet the rate at which fluid is being ejected and to also provide sufficient recirculation to inhibit remnant air bubble accumulation and viscous plug formation.

In the example illustrated, bypass passages <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> are located on a first end of channels <NUM>, <NUM>, proximate to ports <NUM>-<NUM>, <NUM>-<NUM>. Bypass passages <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> are located on a second opposite end of channels <NUM>, <NUM>, proximate to ports <NUM>-<NUM>, <NUM>-<NUM> and <NUM>-<NUM>. Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> to outlet channel <NUM>-<NUM>. Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> outlet channel <NUM>-<NUM>. Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> to outlet channel <NUM>-<NUM>. Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> to outlet channel <NUM>-<NUM>. The particular size, number and distribution of bypass passages <NUM> may vary from one fluid ejection die to another fluid ejection die depending upon the size and number of fluid ejectors, the rate at which fluid is to be ejected in the rate at which fluid is supplied to inlet channels <NUM>.

<FIG> illustrate portions of an example fluid ejection die <NUM> having bypass passages located on the ends of the inlet and outlet channels. For ease of illustration, portions of the die <NUM> are transparently shown with the layer containing the bypass passages being stippled. <FIG> is a bottom view of the die <NUM>. <FIG> is a sectional view along a length of the fluid ejection die <NUM> shown in <FIG>. Die <NUM> is similar to die <NUM> except that die <NUM> comprises bypass passages <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> (collectively referred to as bypass passages <NUM>). The remaining components of die <NUM> which correspond to components of die <NUM> are numbered similarly.

Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> to outlet channel <NUM>-<NUM>. Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> to outlet channel <NUM>-<NUM>. Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> to outlet channel <NUM>-<NUM>. Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> to outlet channel <NUM>-<NUM>. The particular size, number and distribution of bypass passages <NUM> may vary from one fluid ejection die to another fluid ejection die depending upon the size and number of fluid ejectors, the rate at which fluid is to be ejected in the rate at which fluid is supplied to inlet channels <NUM>.

<FIG> illustrate portions of an example fluid ejection die <NUM>. For ease of illustration, portions of the die are transparently shown with the layer containing the bypass passages being stippled. <FIG> is a bottom view of fluid ejection die <NUM>. <FIG> is a sectional view along a length of a portion of die <NUM>. Die <NUM> illustrates one example arrangement of bypass passages which are similar to bypass passage <NUM>-<NUM> described above. Die <NUM> is similar to die <NUM> except that die <NUM> comprises bypass passages <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM>, <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> (collectively referred to as bypass passages <NUM>). The remaining components of die <NUM> which correspond to components of die <NUM> are numbered similarly.

Each of bypass passages <NUM> comprises a fluid passage that extends through a floor of a respective one of inlet channels <NUM>, across and within layer <NUM> to an adjacent one of outlet channels <NUM>. Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> outlet channel <NUM>-<NUM>. Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> to outlet channel <NUM>-<NUM>. Bypass passages <NUM>-<NUM>-<NUM> and <NUM>-<NUM>-<NUM> direct the flow of fluid from inlet channel <NUM>-<NUM> to outlet channel <NUM>-<NUM>.

In the example illustrated, each of inlet channels <NUM> has a single bypass passage <NUM> at its two opposite ends. The bypass passages <NUM> are centrally located amongst the respective set of recirculation passages <NUM> to provide a more symmetric bypass flow of fluid. In other implementations, each of inlet channel <NUM> may have more than one bypass passage <NUM> at each end. In some implementations, bypass passages <NUM> may be provided on a single end of inlet channels <NUM>. In some implementations, bypass passage may be provided at the ends of channels <NUM>. The particular size, number a single bypass passage <NUM> and distribution of bypass passages <NUM> may vary from one fluid ejection die to another fluid ejection die depending upon the size and number of fluid ejectors, the rate at which fluid is to be ejected in the rate at which fluid is supplied to inlet channels <NUM>.

Each of dies <NUM>, <NUM>, <NUM> and <NUM> illustrate different types of fluid bypass passages. Although each of dies <NUM>, <NUM>, <NUM> and <NUM> is illustrated having a single type of fluid bypass passage, in some implementations, each of such dies <NUM>, <NUM>, <NUM> and <NUM> may additionally include any of the other types of fluid bypass passages. For example, die <NUM> may additionally include bypass passages <NUM>, <NUM> and/or <NUM>. Die <NUM> may additionally include bypass passages <NUM>, <NUM> and/or <NUM>. Die <NUM> may additionally include bypass passages <NUM>, <NUM> and/or <NUM>. Die <NUM> may additionally include bypass passages <NUM>, <NUM> and/or <NUM>. Each of dies <NUM>, <NUM>, <NUM> and <NUM> may still additionally include fluid bypass passages <NUM> (shown and described above with respect to <FIG>) in layer <NUM>.

Claim 1:
A fluid ejection die (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprising:
a fluid actuator (<NUM>, <NUM>, <NUM>);
a substrate (<NUM>) supporting the fluid actuator, the substrate (<NUM>) comprising:
a closed inlet channel (<NUM>, <NUM>, <NUM>-n, <NUM>, <NUM>-n) having an inlet opening for connection to an outlet (<NUM>, <NUM>, <NUM>) of a fluid source (<NUM>, <NUM>);
an outlet channel (<NUM>, <NUM>, <NUM>, <NUM>-n) having an outlet opening of a first size for connection to an inlet (<NUM>, <NUM>, <NUM>, <NUM>) of the fluid source;
a chamber layer supported by the substrate, the chamber layer comprising a recirculation passage (<NUM>, <NUM>, <NUM>) associated with the fluid actuator to supply fluid for ejection by the fluid actuator through an ejection orifice (<NUM>, <NUM>, <NUM>) and to circulate fluid across the fluid actuator from the closed inlet channel to the outlet channel; and
a bypass passage (<NUM>, <NUM>, <NUM>-n, <NUM>, <NUM>, <NUM>-n, <NUM>, <NUM>-n, <NUM>, <NUM>-n, <NUM>, <NUM>-n) in the substrate (<NUM>) to connect the inlet channel to the inlet of the fluid source while bypassing any fluid actuator provided for ejecting fluid through an ejection orifice (<NUM>, <NUM>, <NUM>),
characterized in that the bypass passage is of a second size less than the first size.