Patent Description:
This disclosure relates to print head flow channels.

Printing high quality, high-resolution images with an inkjet printer generally requires a printer that accurately ejects a desired quantity of ink at a specified location on a printing medium. Typically, a multitude of densely packed ink ejecting devices, each including a nozzle and an associated ink flow path, are formed in a printhead structure. The ink flow path connects an ink storage unit, such as an ink reservoir or cartridge, to the nozzle. The ink flow path includes a pumping chamber. In the pumping chamber, ink can be pressurized to flow toward a descender region that terminates in the nozzle. The ink is expelled out of an opening at the end of the nozzle and lands on a printing medium. The medium can be moved relative to the fluid ejection device. The ejection of a fluid droplet from a particular nozzle can be timed with the movement of the medium to place a fluid droplet at a desired location on the medium. <CIT> describes that in its liquid ejection head substrate, the blocking of supply paths or the reduction of bubble releasability does not occur when the liquid ejection head substrate is mounted on a support member using an adhesive and the opening width of the supply paths can be reduced.

In one aspect, an apparatus includes the features of claims <NUM> to <NUM>.

Implementations include one or more of the features. The width of the fluid passage near the second surface of the substrate is smaller than the width near the bottom of the fluid passage. The width of the fluid passage near the bottom of the fluid passage is about <NUM>% to about <NUM>% greater than the width near the surface of the substrate. The cross section of the fluid passage is symmetric about a longitudinal axis extending from a top to the bottom of the fluid passage. The fluid passage has curved corners joining a bottom of the fluid passage to walls of the fluid passage. The curved corners have a radius of curvature.

In a further aspect, an apparatus includes the features of claims <NUM> to <NUM>.

Implementations include one or more of the features. The fluid passage has rounded corners joining the first portion and the second portion. The connecting passage has an angle of about <NUM> degrees to about <NUM> degrees. The first portion is at a first distance from the surface and the second portion is at a second distance from the surface. The fluid passage is fluidically connected to a reservoir remote from the substrate. The fluid passage fluidically connects fluid from the remote reservoir to the nozzle. A plurality of nozzles is included, and the fluid passage fluidically connects fluid from the remote reservoir to the plurality of nozzles.

In a further aspect, a system includes the features of claim <NUM>.

In a further aspect, a system includes The features of claim <NUM>.

Advantages of the approaches described here may include, but are not limited to, one or more of the advantages described below. The configuration of the flow pathways can improve the performance of the printhead by encouraging undesirable air bubbles to move freely along the flow pathways with the fluid flow and be purged from the printhead. The configuration of the flow pathways can reduce fluid resistance, thereby increasing the reliability of ink being introduced into the pumping chamber that can be actuated to eject fluid from the printhead as well as enabling air bubbles to move along the flow pathways without becoming trapped.

A fluid ejector, e.g., for an inkjet printer, can include flow pathways that enable an actuator to be actuated rapidly, e.g., at a rate between <NUM> and <NUM>, <NUM> and <NUM>, <NUM> and <NUM>, or higher. Fluid ejectors can enable the actuators associated with the fluid ejectors to be rapidly driven to eject fluid from the fluid ejectors. Fluid drop ejection can be implemented with a substrate, for example, a microelectromechanical system (MEMS) substrate, including a fluid flow body, a membrane, and a nozzle layer. The flow path body has a fluid flow path formed therein, which can include a fluid filled passage, a fluid pumping chamber, a descender, and a nozzle having an outlet. An actuator can be located on a surface of the membrane opposite the flow path body and proximate to the fluid pumping chamber. When the actuator is actuated, the actuator imparts a pressure pulse to the fluid pumping chamber to cause ejection of a droplet of fluid through the outlet of the nozzle. Frequently, the flow path body includes multiple fluid flow paths and nozzles, such as a densely packed array of identical nozzles with their respective associated flow paths. A fluid droplet ejection system can include the substrate and a source of fluid for the substrate. A fluid reservoir can be fluidically connected to the substrate for supplying fluid for ejection. The fluid can be, for example, a chemical compound, a biological substance, or ink.

<FIG> depicts an example of a fluid delivery system <NUM> including a fluid ejector <NUM>, e.g., for a printhead <NUM> shown in <FIG>. The fluid delivery system <NUM> has a configuration of flow pathways that enables ejection of fluid from a pumping chamber <NUM> of the fluid ejector <NUM>. The fluid ejector <NUM> includes flow pathways to transport fluid from a reservoir to a nozzle <NUM> of the fluid ejector <NUM>. The fluid ejector <NUM> includes a descender <NUM> having a first end <NUM> and a second end <NUM>. The first end <NUM> defines a first fluid flow pathway <NUM> between the pumping chamber <NUM> and the nozzle <NUM>. The nozzle <NUM> is disposed at the second end <NUM> of the descender <NUM>. A second fluid flow pathway <NUM> is defined at the second end <NUM> of the descender <NUM>. The second fluid flow pathway <NUM>, for example, corresponds to a recirculation pathway to recirculate fluid in an ejection operation, e.g., a printing operation. The recirculated fluid is, for example, returned to the reservoir and reused for a subsequent ejection operation, e.g., a subsequent printing operation. The fluid ejector <NUM> includes an actuator <NUM> operable to pump fluid through the pumping chamber <NUM> toward the nozzle <NUM>.

The first fluid flow pathway <NUM>, for example, corresponds to a fluid flow pathway for fluid that is pumped out of the pumping chamber <NUM>. If the pumping chamber receives fluid from multiple fluid flow pathways, the first fluid flow pathway <NUM> receives the fluid from the multiple fluid flow pathways such that a single flow of fluid is directed through the descender <NUM>.

Referring to <FIG>, the printhead <NUM> ejects droplets of fluid, such as ink, biological liquids, polymers, liquids for forming electronic components, or other types of fluid, onto a surface. The printhead <NUM> includes one or more fluid ejectors <NUM>, each fluid ejector having a corresponding actuator <NUM>, as described with respect to <FIG>. The printhead <NUM> includes a substrate <NUM> coupled to a deformable membrane <NUM> of the fluid ejector <NUM> and to an interposer assembly <NUM>. The substrate <NUM> is, in some cases, a monolithic semiconductor body, such as a silicon substrate. The substrate has passages formed therethrough that define flow pathways for fluid through the substrate <NUM>. In some implementations, the substrate <NUM> and the membrane <NUM> together define the pumping chamber <NUM>. The substrate <NUM>, for example, defines the fluid conduits of the fluid ejector <NUM>, e.g., the pumping chamber <NUM>, the descender <NUM>, the nozzle <NUM>, as well as additional fluid passages <NUM> described below.

The printhead <NUM> includes a casing <NUM> having an interior volume divided into a fluid supply chamber <NUM> and a fluid return chamber <NUM>. In some cases, the interior volume is divided by a dividing structure <NUM>. The dividing structure <NUM> includes, for example, an upper divider <NUM> and a lower divider <NUM>. The bottom of the fluid supply chamber <NUM> and the fluid return chamber <NUM> is defined by the top surface of the interposer assembly <NUM>.

The fluid supply chamber <NUM> includes a reservoir to contain a supply of fluid to be ejected from the printhead <NUM>, e.g., to be ejected through the ejector <NUM>. The reservoir of the fluid supply chamber <NUM> supplies fluid to the pumping chamber <NUM>. The fluid return chamber <NUM> includes a reservoir to contain fluid recirculated through the printhead <NUM> through the second fluid flow pathway <NUM> described with respect to <FIG>. The fluid supply chamber <NUM> has a reservoir to contain the supply of fluid to be ejected from the printhead <NUM> in the short term, e.g., during a current printing operation or during a next time period. The fluid supply chamber is also in fluidic connection with another, upstream reservoir that contains fluid (e.g., ink) for later use. For example, the upstream reservoir may be an ink cartridge or ink supply.

The interposer assembly <NUM> is attachable to the casing <NUM>, such as by bonding or another mechanism of attachment. The interposer assembly <NUM> includes, for example, an upper interposer <NUM> and a lower interposer <NUM>. The lower interposer <NUM> is positioned between the upper interposer <NUM> and the substrate <NUM>.

A flow pathway <NUM> is formed to connect, e.g., fluidically connect, the fluid supply chamber <NUM> to the fluid return chamber <NUM>. The upper interposer <NUM> includes an inlet <NUM> to the flow pathway <NUM> and an outlet <NUM> from the flow pathway <NUM>. The inlet <NUM> and the outlet <NUM>, for example, are formed as apertures in the upper interposer <NUM>. The flow pathway <NUM> is, for example, formed in the upper interposer <NUM>, the lower interposer <NUM>, and the substrate <NUM>. The flow pathway <NUM> enables flow of fluid from the supply chamber <NUM>, through the substrate <NUM>, into the inlet <NUM>, and to the fluid ejector <NUM> for ejection of fluid from the printhead <NUM>. The actuator <NUM> of the ejector <NUM>, when driven, ejects fluid from the pumping chamber <NUM> through the nozzle <NUM>. The flow pathway <NUM> also enables flow of fluid from the fluid ejector <NUM>, into the outlet <NUM>, and into the return chamber <NUM>.

As described with respect to <FIG>, the fluid ejector <NUM> includes the nozzle <NUM>. Fluid is selectively ejected from the nozzle <NUM> of the fluid ejector <NUM>. The fluid is, for example, ink that is ejected onto a surface to print an image on the surface. The nozzle <NUM> is formed in a nozzle layer of the substrate <NUM>, e.g., on a bottom surface or a top surface of the substrate <NUM>.

In one example, to be ejected from the printhead <NUM>, a portion of fluid flows through an inlet <NUM> of the fluid ejector <NUM>, through the pumping chamber <NUM>, through the first end <NUM> of the descender <NUM>, through the descender <NUM>, through the fluid ejector <NUM>, and out of the printhead <NUM> through the nozzle <NUM>. To be recirculated, a portion of fluid flows through the inlet <NUM>, through the pumping chamber <NUM>, through the first end <NUM> of the descender <NUM>, through the descender <NUM>, and through an outlet <NUM> of the fluid ejector <NUM>. The inlet <NUM> is, for example, an inlet to the pumping chamber <NUM>. The outlet <NUM> is, for example, an outlet from the descender <NUM>.

The inlet <NUM> is, for example, connected to a reservoir to enable fluid flow from the reservoir, e.g., the supply chamber <NUM>. An inlet feed channel <NUM> connects the supply chamber <NUM> to the inlet <NUM> of the fluid ejector <NUM>. The inlet <NUM> includes a first end connected to the supply chamber <NUM> through the inlet fluid channel <NUM> and a second end connected to the pumping chamber <NUM>.

While <FIG> and <FIG> show various passages, such as pumping chambers and descenders, these components may not all be in a common plane. In some embodiments, different passages and other features may lie in different planes. In some embodiments, portions of a single feature may lie in different planes, e.g., a fluid passage may be sloped so as to cross multiple planes within the printhead <NUM>. In addition, the relative dimensions of the components may vary, and the dimensions of some components have been exaggerated in for illustrative purposes.

The nozzle dimensions and the dimensions and shape of the fluid flow paths can affect printing quality, printing resolution, and energy efficiencies of the printing device.

Referring to <FIG>, the substrate <NUM> includes many nozzles <NUM> such as the type described above with respect to <FIG> and <FIG>, arranged in an array <NUM>. The substrate <NUM> includes multiple flow pathways to transport fluid from reservoirs to eject the fluid, to recirculate the fluid from near the nozzles to be ejected during a subsequent ejection operation, and/or to remove ink from the array <NUM>. These flow pathways include fluid passages <NUM> (seen in <FIG>). The fluid passages <NUM> direct ink from a distant reservoir (e.g., an ink cartridge) to a closer reservoir (e.g., the supply chamber <NUM>). Multiple supply chambers <NUM> are defined within the substrate <NUM> to allow fluid to flow to each of the multiple nozzles <NUM> in the array <NUM>. Similarly, multiple fluid return chambers <NUM> can collect unused and non-recirculated ink for flow along additional fluid passages <NUM> and out from the substrate <NUM>.

As can be seen in <FIG>, the bottom surface of the substrate <NUM> includes several slots and holes that make up the various fluid channels and the nozzles <NUM>. Each of these bottom-surface features reduce the surface area <NUM> of the bottom surface. However, it is beneficial to increase the surface area <NUM> that is not given over to fluid passages <NUM>. For example, increasing the surface area <NUM> can prevent crack prorogation, and provides additional area for adhesive layering (e.g., addition of epoxy or other adhesive to attach the substrate <NUM> to other components such as the casing <NUM>). It is desirable to create as wide an area as possible between the outermost fluid passages <NUM> and the edges <NUM> of the printhead, while not increasing the overall size of the printhead. It is also desirable to increase the distance between fluid passages <NUM> and the edges <NUM> of the printhead, or to other features.

<FIG> is a close-up of a portion of <FIG>, showing a fluid passage <NUM> in greater detail. The fluid passage <NUM> has a curved, non-linear profile as viewed from below. The fluid passage <NUM> is generally a slot or trench with a long, curved passage machined (e.g., milled, etched, or otherwise fabricated) into the surface of the substrate <NUM>. The fluid passage <NUM> has an opening on the bottom surface of the substrate <NUM>.

One or more of the width and the cross sectional profile of the fluid passage <NUM> can vary along the length of the fluid passage. In the example of <FIG>, the width of the opening of the fluid passage <NUM> changes along the length of the fluid passage, with the width at the portion marked A being greater than the width at the portion marked B. The cross sectional profile of the fluid passage <NUM> also changes along the length of the fluid passage. <FIG> shows a cross sectional view of the fluid passage <NUM> at portion A and <FIG> shows a cross sectional view of the fluid passage <NUM> at portion B.

Referring to <FIG>, at portion A of the fluid passage <NUM>, the fluid passage <NUM> has a generally regular cross section 352A, e.g., a rectangular cross section. Sides 354A of the fluid passage <NUM> are generally straight and substantially parallel. The width of the fluid passage <NUM> at portion A is substantially constant from the opening 355A of the fluid passage <NUM> to the bottom 356A of the fluid passage <NUM>. The sides 354A of the fluid passage <NUM> meet the bottom 356A of the fluid passage <NUM> at curved corners 358A. The curved corners 358A are rounded with a radius of curvature 360A so that the sides 354A do not meet the bottom 356A at a right angle.

<FIG> shows a cross section 352B of the fluid passage <NUM> at portion B from <FIG>. Unlike the cross section 352A, the cross section 352B is not regular and sides 354B of the fluid passage <NUM> curve more than once before meeting the bottom 356B of the fluid passage <NUM>. The width of the fluid passage <NUM> at portion B varies across the height of the fluid passage such that the fluid passage is undercut, having a bottom portion <NUM> at the bottom 356B of the fluid passage <NUM> that is wider than a top portion <NUM> at the opening 355B of the fluid passage <NUM>. In some instances, the bottom portion <NUM> is <NUM>-<NUM>% wider than the top portion <NUM>. The sides 354B of the cross section 352B meet the bottom 356B of the fluid passage <NUM> at curved corners 358B that are rounded with a radius of curvature 360B.

The undercut shape of the fluid passage <NUM> as shown in <FIG> advantageously provides a fluid passage with a large cross sectional area and narrow surface opening 355B. With this undercut configuration, the size of the opening 355B of the fluid passage <NUM> on the bottom surface of the substrate <NUM> can be smaller than the opening 355A would be in a non-undercut configuration of the same cross sectional area, enabling the surface area <NUM> of the bottom surface of the substrate <NUM> to be larger. For instance, with an undercut fluid passage <NUM>, a wide space can exist between the opening 355B of the fluid passage <NUM> and the substrate edge <NUM> or some other feature such as feature <NUM> in <FIG>.

The fluid passage <NUM> at portion B, with the undercut cross section 352B, has a cross sectional area (e.g., the area of both the top portion <NUM> and the bottom portion <NUM>) that is greater than the cross sectional area of a fluid passage with a rectangular cross sectional area having the width of the top portion <NUM>. The fluid resistance of a fluid flowing in a channel (such as ink in the fluid passage <NUM>) is directly proportional to the channel's width. Fluid flowing in a narrow channel (e.g., a rectangular cross section channel having the width of the top portion <NUM>) experiences a higher fluid resistance than that of the same fluid flowing in a wider (but shallower) channel of the same cross sectional area. The undercut profile of the cross section 352B reduces how much fluid flows through a narrowed area of the fluid passage <NUM>, e.g., through the top portion <NUM>, reducing the overall fluid resistance as compared to a fluid passage with rectangular cross section of the width of the top portion <NUM>.

The sum of the area of the top portion <NUM> and the area of the bottom portion <NUM> of the cross section 352B can be equal to the area of the cross section 352A, or greater than or less than the area of the cross section 352A. The width of the bottom portion <NUM> at portion B can be wider than the width of the cross section 352A. The radius of curvature 360A and radius of curvature 360B can be the same, or can differ. For example, the radius of curvature 360B can be smaller than the radius of curvature 360A. The radius of curvature 360A and radius of curvature 360B affect the fluid resistance as it is a function of the shape, the cross sectional area, and the aspect ratio of a fluid channel. Generally, the lowest resistance per unit area is achieved with a circular duct, whereas a square duct of the same area has more resistance because the inscribed circle is smaller and the flow in the corners is small. The radius of curvature 360A and radius of curvature 360B help improve the uniformity of flow in the channel.

Referring to <FIG>, there are several manufacturing steps to create an undercut cross sectional profile such as that shown in <FIG>. First, a cutter is used to drill or mill the fluid passage to the desired top width <NUM> (e.g., the width of top portion <NUM>) by removing material from the surface of the substrate <NUM> down to the desired depth <NUM> of the cross section 352B. This machining creates a straight vertical slot of width <NUM>, as shown by the dotted lines. Next, a wider cutter, such as a T-slot cutter or a relieved cutter, is inserted into the slot of width <NUM> and height <NUM> along the centerline of the slot. Once inserted, the wider cutter is used to create the wider bottom of width <NUM> by shifting the wider cutter to the left and following the edge of the slot for the desired length, and then shifting the wider cutter to the right and following the edge for the desired length on the corresponding side facing the left edge. The curved corners 358B and radius of curvature 360B can be formed using a rounding tool. Alternatively, the curved corners <NUM> and radius of curvature <NUM> can result from the shape of the wider cutter. Typically, the resulting cross section 352B is symmetric about its central axis. The result of these steps is an undercut slot with a bottom wider than the throat, resulting in reduced flow resistance while reducing the area removed from the surface of the printhead.

The size and shape of the cross section of the fluid passages <NUM> can vary along the length of each fluid passage. For example, slots having undercut cross sectional profiles with different dimensions can be present on the same printhead and within the same fluid passage. Modifying the profiles of the fluid passages can compensate for flow imbalance within the nozzle array <NUM>, e.g., by increasing or decreasing the fluid resistance to differing parts of the array <NUM>.

As mentioned above, different components interacting with and within the substrate <NUM> may not all lie in a common plane. Referring to <FIG>, a fluid passage <NUM> may itself not lie in a common plane along its entire length. For instance, a fluid passage <NUM> may have a portion that is positioned deeper within the substrate <NUM> (referred to as a deep portion of the fluid passage) than another portion of the fluid passage <NUM> (referred to as a shallow portion of the fluid passage). In the example shown, the fluid passage <NUM> has a general downwards slant from left to right, as well as a more precipitous change in height at a connecting passage <NUM>.

Any abrupt changes in the depth of the fluid passage <NUM> act as a bubble trap for undesirable air bubbles in the ink flow, such as air bubbles created from air entering imperfectly formed nozzles. Air bubbles in the ink flow can change the acoustic characteristics of the fluid ejectors <NUM>, or even completely impede the ink flow, negatively affecting the quality and consistency of the printing action carried out by the printhead <NUM>.

A sharp transition from a deep portion to a shallow portion of a fluid passage creates a vertical step that acts as a trap for any air bubble in the ink flow. As shown in <FIG>, the fluid passage <NUM> can be angled such that the depth of the fluid passage <NUM> changes from one depth <NUM> to another depth <NUM> at the fluid connecting passage <NUM>. The angle at the fluid connecting passage <NUM> is not sharp, e.g., the angle is less than <NUM> degrees. For instance, the angle can be between <NUM> to <NUM> degrees. The fluid connecting passage <NUM> can be a simple height transition from one depth to another (as in <FIG> and <FIG>) or can also include a branching of fluid passages <NUM> where multiple fluid channels are fluidically connected, e.g., a junction. In some instances, the fluid connecting passage <NUM> can be straight up and down (e.g., moves ink from one gravitational level to another gravitational level). In other instances, the fluid connecting passage <NUM> can also move the ink laterally along the substrate <NUM>.

As seen in <FIG>, the rounded corners 358A or 358B of the fluid passage <NUM> assist in moving air bubbles along the center of the fluid passage <NUM> without the air bubble becoming trapped. If the corners 358A, 358B of the fluid passage <NUM> were sharp (e.g., at right angles), the fluid flow would tend to force any air bubble into the corners. For fluid flow in a channel, the fluid flow in corners is slower than at other portions of the channel, such as at the center. The air bubble forced into a sharp corner would then become more easily trapped due to the slower fluid flow at the corner.

The rounded corners 358A or 358B with their radii of curvature 360A, 360B do not provide low-flow sharp corners. Instead, the rounded corners 358A, 358B encourage an air bubble to go to the center of the channel, keeping the air bubble in the position where most fluid flows around it and thus is exposed to a relatively strong force to move the air bubble along the fluid passage <NUM> in the direction of the fluid flow.

In some implementations, the fluid passage <NUM> having a non-uniform cross section can encourage air bubbles to flow with the fluid. The cross sectional area of the fluid passage <NUM> can vary along the length of the fluid passage, as discussed above. Positioning a connecting passage <NUM> at a location where the cross sectional area of the fluid passage is narrow (and hence fluid flow is fast) encourages air bubbles to move with the fluid to a greater extent than positioning the connecting passage <NUM> at a place where the cross sectional area is wide and the fluid flow slow (or at a place with a uniform, unchanging cross section).

Claim 1:
An apparatus comprising:
a nozzle (<NUM>) formed on a first surface of a substrate (<NUM>);
a fluid passage (<NUM>) defined in the substrate (<NUM>) and fluidically connected to the nozzle (<NUM>), wherein during use of the apparatus, fluid in the fluid passage (<NUM>) is supplied to the nozzle (<NUM>),
the fluid passage (<NUM>) being nonlinear along at least a portion of a length of the fluid passage (<NUM>) and having a cross section (352B) that varies along the length of the fluid passage (<NUM>), wherein the fluid passage (<NUM>) has a width near a second surface of the substrate (<NUM>) that is different from a width near a bottom (356B) of the fluid passage (<NUM>); and
a recirculation flow passage defined in the substrate (<NUM>) and fluidically connected to the nozzle (<NUM>), wherein during use of the apparatus, fluid that is not ejected from the nozzle (<NUM>) is recirculated through the recirculation flow passage.