Patent Application
20170021621
Field of the Invention
The present invention relates to a liquid discharge head.
Description of the Related Art
Liquid discharge heads that discharge liquid, such as ink, are known. In a liquid discharge head, a print element substrate having discharge port rows is mounted on a support member, and a liquid chamber inside the support member and supply ports, which are provided in the print element substrate so as to correspond to the respective discharge port rows, are connected to each other, forming liquid flow paths that are continuous from the liquid chamber to discharge ports. In recent years, due to the demand for high-speed recording, the number of discharge ports arranged in the liquid discharge head has been increased, and a flow path design that enables liquid to be supplied at a high flow rate is required.
Because liquid discharge heads handle fluid, such as ink, vibration of liquid causes menisci to vibrate at the discharge ports, which may deteriorate the discharge accuracy. The meniscus vibration tends to occur in liquid discharge heads that have a large number of discharge ports arranged in a high density and that have high liquid flow rates per unit time.
For example, when liquid discharge from the plurality of discharge ports is stopped at once, the inertial force that causes the liquid to move forward of the discharge ports increases, pushing out the liquid in the discharge ports and extruding out the menisci inside the discharge ports. Meanwhile, a typical liquid tank, which supplies liquid, is configured to be maintained at a negative pressure to prevent dripping of liquid from the supply port. Hence, the liquid supplied from the liquid tank is subjected to a force that tends to pull the liquid back to the upstream side (liquid tank side). Therefore, the liquid with the menisci extruding out at the discharge ports, as described above, subsequently tends to retract in to the opposite side.
As has been described, when the discharge is stopped, so-called meniscus vibration, in which menisci extrude out and retract in at the discharge ports, is induced. This vibration becomes large as the liquid flow rate per unit time increases.
When the subsequent discharge is performed in a state in which the menisci extrude out, fine ink droplets are splashed, whereas, when the subsequent discharge is performed in a state in which the menisci retract in, the discharge speed and the amount of discharge decrease. In either case, defective discharge, such as discharge irregularity, occur.
Furthermore, in a state in which the discharge is stopped, when liquid discharge from the plurality of discharge ports is started at once, the liquid starts to move from the stationary state. Therefore, after the first discharge of liquid, the inertial force that causes the liquid to move forward of the discharge ports may not be increased to a magnitude sufficient to fully fill the discharge ports with the liquid. Thus, when the subsequent discharge is started in a state in which the menisci in the discharge ports retract in, defective discharge, such as discharge irregularity, occur.
Japanese Patent Laid-Open No. 2006-240150 discloses a liquid discharge head in which meniscus vibration at discharge ports can be reduced. The liquid discharge head disclosed in Japanese Patent Laid-Open No. 2006-240150 has, in a liquid chamber, a buffer chamber that stores gas (for example, bubble). By using the gas in the buffer chamber, the meniscus vibration at discharge ports is absorbed and attenuated.
In recent years, demands for high image quality and reliability are more and more increasing. Under the circumstances, if liquid has been discharged or has not been discharged for a long time, gas dissolved in liquid, gas taken in after passing through a housing of a liquid discharge head, or the like may be combined with the gas in the buffer chamber, increasing the volume of the gas in the buffer chamber. As a result, the gas in the buffer chamber may expand until it reaches the discharge ports and the vicinity thereof. In this state, the expanded gas blocks the liquid flow paths, preventing the liquid from being supplied to the discharge ports and causing defective discharge.
The present invention provides a liquid discharge head in which the meniscus vibration at discharge ports is suppressed and in which defective discharge can be reduced.
A liquid discharge head includes a print element substrate provided with discharge ports, through which liquid is discharged; and a support member having a liquid chamber, which is provided with a communicating opening that communicates with the discharge ports, wherein the liquid chamber has a first surface provided with the communicating opening, and a second surface facing the first surface, the second surface is provided with a buffer chamber, which is a hollow space for storing gas, and the buffer chamber has, in the second surface, an opening having a projecting portion projecting toward the inner side of the opening.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Referring to the attached drawings, embodiments of the present invention will be described in detail below.
Embodiments of the present invention may be applied to a liquid discharge head 100, which has a configuration as shown in
In
A print element substrate 2, which discharges black ink and has a discharge port row having a length of about 1 inch, and a print element substrate 21, which discharges color ink and has six discharge port rows having a length of about 0.5 inches, are positioned and joined relative to the support member 10. The discharge port row in the print element substrate 2 is formed of a plurality of discharge ports arranged in the longitudinal direction of the print element substrate 2. The six discharge port rows in the print element substrate 21 are each formed of a plurality of discharge ports arranged in the longitudinal direction of the print element substrate 21.
Next, an electric wiring substrate 22 is positioned and joined relative to the support member 10, and the wires of the electric wiring substrate 22 are joined to the print element substrates 2 and 21, thus forming a liquid discharge unit 20.
Next, the liquid flow path unit 3 and the liquid discharge unit 20 are joined together with screws 23, with a joint member 9 disposed therebetween. The electric wiring substrate 22 is fixed to the housing 3a and joined to a wiring substrate (not shown) of a liquid discharge device body, thus forming the liquid discharge head 100 shown in
A first embodiment of the present invention will be described below. In the first embodiment, components having the same configurations as those of the liquid discharge head 100 shown in
This embodiment will be described with reference to
As shown in
Each buffer chamber 4 is provided with two plate-like projections 8a at the end on the surface 7b side. The projections 8a project toward the inner side of an opening 5 of the buffer chamber 4 in the surface 7b. Thus, the opening 5 is formed so as to have projecting portions 8 projecting toward the inner side of the opening 5. Furthermore, the opening 5 is partially narrowed in the width direction, which is perpendicular to the longitudinal direction, of the liquid chamber 7. In this embodiment, the opening 5 is formed so as to have the two projecting portions 8 projecting toward the center of the opening 5.
Ink flowing out of the ink tank attached to the liquid flow path unit 3 flows through the flow path plate 3b and the joint member 9 into the liquid chamber 7, from the inflow port 14. When the ink is charged into the liquid chamber 7, the buffer chambers 4 are not filled with the ink, and air remains therein. The surfaces 7b of the liquid chamber 7 are inclined relative to the surface 7a so that bubbles (gas) are not accumulated in the liquid chamber 7. The surfaces 7b may be either smoothly tapered or stepped to an extent that does not inhibit the flow of ink and bubbles (gas).
The ink charged into the liquid chamber 7 is charged, through the through-opening 13, into a large number of pressure chambers (not shown), which have the discharge port row 2a and print elements (not shown). The print elements are, for example, heating resistance elements or piezoelectric elements. By selectively driving predetermined print elements in the pressure chambers, ink is discharged from the discharge ports 2b.
In this embodiment, 1280 discharge ports 2b, each of which discharges 12 pl of droplet, are arranged at a density of 1200 dpi in the print element substrate 2, and the maximum discharge frequency at the discharge ports 2b is 24 kHz. Therefore, the liquid discharge head according to this embodiment may be installed in a printing apparatus that discharges ink at a flow rate of 22 ml/min by discharging ink from all the discharge ports.
Next, a method for removing air, which is gas protruding out of the buffer chambers 4 (hereinbelow referred to as “buffer spillover bubbles”), will be described.
However, if the liquid discharge unit 20 has been used or has not been used for a long time, bubbles (gas) released into the ink from the components of the liquid flow path unit 3 or the liquid discharge unit 20 or bubbles (gas) dissolved in ink are combined with the air in the buffer chambers 4, forming buffer spillover bubbles.
As shown in
To prevent such a situation, the buffer spillover bubbles are removed before the buffer spillover bubbles block the discharge ports 2b. When the buffer spillover bubbles are removed, the air in the buffer chambers 4 needs to be left to keep the meniscus vibration suppressed.
Therefore, it is desirable that the air in the buffer chambers 4 and the buffer spillover bubbles be separated at the openings 5, and the buffer spillover bubbles be discharged.
Because the projecting portions 8 in the opening are provided to reduce the spillover-bubble sectional area, one projecting portion 8 is enough to obtain the advantage of the present invention. Therefore, at least one projecting portion 8 projecting toward the inner side of the opening 5 may be provided at the opening 5. Furthermore, the projecting portion 8 may project toward somewhere other than the center C of the opening 5.
Furthermore, as shown in
Next, the operation for separating the buffer spillover bubbles from the opening 5 will be described.
In this embodiment, the gap A between the projecting portions 8 is smaller than the wall-to-wall distance, D, of the buffer chamber 4, and hence, as shown in
For example, flows generated by a suction recovery operation, which is performed to suppress clogging of the discharge ports 2b with ink by sucking the ink in the discharge ports 2b when the discharge is stopped, are used to separate and discharge the buffer spillover bubbles.
When the buffer spillover bubbles are separated by using ink flows generated by the suction recovery operation, the directions of the ink flows in the vicinity of the openings 5 are, mainly, the directions oriented from the inflow port 14 to the surface 7a, along the surfaces 7b (hereinbelow referred to as “main directions”). Therefore, the ink flows in the vicinity of the openings 5 are less likely to become irregular or attenuated when the spaces, in the main directions, at the openings 5 are smaller.
In this embodiment, as shown in
In the suction recovery operation, it is desirable that the ink present in the end regions of the liquid chamber 7 (more specifically, in the liquid chamber 7, portions 71 farther from the inflow port 14 than the openings 5) be discharged or partially heated before suction. By doing so, the viscosity of ink in these portions decreases, improving the flowability of ink. If the flowability of ink at these portions is improved, the ink easily flows along the openings 5, making the separation and recovery of the buffer spillover bubbles even more easy. Furthermore, it is desirable that the projecting portions 8 have angled ends, as such a configuration allows the bubbles to be more easily separated.
Using
The shape of the opening 5 shown in
The openings 5 shown in
In the projecting portions 8 according to this embodiment, the relationship between the lengths, Y, of the projecting portions 8 in the direction in which they project and the lengths, X, of the projecting portions 8 in the width direction is Y>X. The projecting portions 8 may project either in the main directions or the directions opposite thereto.
In general, larger buffer chambers 4 suppress more meniscus vibration. This also applies to the area of the gas-liquid interface at the opening 5 in a state without the buffer spillover bubbles, and, the larger the area of the opening 5 is, the more meniscus vibration is suppressed. Meanwhile, when the gap A between the projecting portions 8 in the opening 5 or a gap B between the projecting portion 8 and a wall 4a of the buffer chamber 4 is smaller, the ink flow rate needed to separate and discharge the buffer spillover bubbles is smaller.
In this embodiment, because the relationship between the length Y of the projecting portion 8 in the direction in which it projects and the length X of the projecting portion 8 in the width direction is Y>X, it is possible to increase the area of the opening 5 by reducing the area of the projecting portion 8, while narrowing the gaps A and B shown in
Note that, at an initial stage of the movement of the buffer spillover bubbles by an ink flow, narrower ends of the projecting portions 8 (i.e., smaller contact areas between the buffer spillover bubbles and the end regions of the projecting portions 8) make the buffer spillover bubbles move more easily. Hence, it is desirable to make the ends of the projecting portions 8 narrow.
Referring to
Although this embodiment is the same as the first embodiment in that the opening 5 of the buffer chamber 4 has the projecting portions 8, the sectional shape of the buffer chamber 4 parallel to the surface 7b is unchanged to a top surface 4b of the buffer chamber 4. Because larger buffer chambers 4 suppress more meniscus vibration, the vibration suppressing effect achieved in this embodiment is smaller than the first embodiment. However, from the standpoint of the ease of stamping in the manufacturing process, this embodiment is advantageous.
A fourth embodiment of the present invention will be described using
Although the shape of the buffer chamber 4 according to this embodiment is similar to the buffer chamber 4 according to the third embodiment, the sectional area of the buffer chamber 4 parallel to the surfaces 7b gradually decreases toward the top surface 4b of the buffer chamber 4. This configuration may be more advantageous than the third embodiment, from the standpoint of the ease of stamping in the manufacturing process. Furthermore, because the gap A between the projecting portions 8 in the opening 5 is maintained, the same advantage as the first embodiment may be obtained, from the standpoint of separation of the buffer spillover bubbles.
Referring to
In this embodiment, the sectional area of the buffer chamber 4 parallel to the surface 7b gradually decreases from the top surface 4b toward the opening 5. Because the area of the opening 5 is small in this configuration, it is advantageous from the standpoint of separation of the buffer spillover bubbles. Furthermore, because the air in the buffer chamber 4 is less likely to escape from the buffer chamber 4, the air retention property of the buffer chamber 4 is good.
Although the meniscus-vibration suppressing effect obtained in this embodiment is smaller than that in the third embodiment shown in
Referring to
In this embodiment, the buffer chambers 4 are formed at positions closer to the ends 72 of the liquid chamber 7.
When the liquid chamber 7 is formed such that the distance between the surface 7a and the surfaces 7b decreases toward the ends 72, the period at which the vibrations of ink in the liquid chamber 7 are reflected at the wall of the liquid chamber 7 decreases at positions closer to the ends 72. Therefore, the meniscus vibration, and consequently, the discharge irregularity, is more likely to occur in the discharge ports closer to the ends 72.
As in this embodiment, by forming the buffer chambers 4 at positions closer to the ends 72 of the liquid chamber 7, the meniscus-vibration suppressing effect achieved by the buffer chambers 4 can be more reliably obtained.
In the above-described embodiments, the illustrated configurations are merely examples, and the present invention is not limited to such configurations.
The present invention can reduce the meniscus vibration at the discharge ports and thus can reduce the defective discharge.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2015-146459, filed Jul. 24, 2015, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-146459 | Jul 2015 | JP | national |
