JPH04355146A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To discharge an air bubble by a discharge operation even when the air bubble generated in ink is stagnated in an ink passage by improving the shape of the ink passage. CONSTITUTION:The discharge properties of an air bubble are improved by air bubble discharge operation such as pump suction by setting the widths or depths of the supply paths 2a, 2b, 2c of the ink passage on a passage substrate 1 so that the viscosity resistances of the supply paths become R2a=R2b< R2c.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording head that performs recording by jetting ink and forming flying droplets.

0002

2. Description of the Related Art FIG. 9 shows a part of an ink flow path, in which there are three supply paths for one pressure chamber 4 (2a, 2b, 2c).
) A diagram showing a flow path substrate 1 of a conventional inkjet recording head having a flow path structure viewed from directly above. In addition, FIG. 10 shows D in FIG.
-D shows a cross-sectional view of the diaphragm laminated or bonded to the channel substrate 1. In FIGS. 9 and 10, the three supply channels 2a to 2c have the same width and depth, the viscous resistance of each supply channel is equal, and the ink flow rate flowing through each supply channel is the same. Moreover, 2a and 2c are connected to the wall 4a of the pressure chamber 4, and 2b is not connected to the wall 4a.

0003

[Problem to be solved by the invention] Supply path (2a to 2c)
Near the exit of the ink flow path, the ink flows from a place with a small cross-sectional area of the flow path to a place with a large cross-sectional area, so the ink flow rate becomes slow, and depending on the shape of the ink flow path, the flow tends to become turbulent. When air bubbles 8 flow into or are generated on the side wall of the pressure chamber 4 near the outlet of the supply path 2c and become stagnant as shown in FIG. 9, the nozzle 3 is capped with a cap 9 on the nozzle surface and pump suction is performed in the direction of the arrow 10. Even if the bubble ejection operation is performed, the flow of ink flowing around the bubbles 8 is not sufficient, so it tends to become turbulent and non-uniform, and as a result, the ink flow avoids the bubbles 8 and the bubbles are removed. Poor drainage.

[0004] In addition, an island-shaped portion 6 partitions the supply channels 2a to 2c.
Since the tip on the side of the pressure chamber 4 is formed of a circular arc, the ink flow rate suddenly slows down at the exits of the supply channels 2a to 2c, and there is also the problem that air bubble discharging performance is poor. This is a particularly important problem when the channel is formed of a polymeric material that has a contact angle with the ink of 50 degrees or more. If air bubbles remain in the pressure chamber 4, print quality will deteriorate or printing will become impossible, so good air bubble discharge performance is important in an inkjet recording head.

Accordingly, an object of the ink jet recording head of the present invention is to provide an ink flow path in which the ink flows uniformly near the outlet of the supply path and has excellent bubble discharge performance.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the inkjet recording head of the present invention has three or more supply channels for one pressure chamber, and the viscous resistance of the supply channel is connected to the side wall of the pressure chamber. The feature is that the ink flow rate is set lower than that of the remaining supply channels to make the ink flow rate larger than that of the remaining supply channels.

[0007]Furthermore, by making the change in the ink flow rate at the outlet of the supply passage more gradual, it is possible to improve the ability to discharge air bubbles stuck on the side wall of the pressure chamber near the outlet of the supply passage.

[0008]

[Example] Figure 1 shows that there are three or more supply channels of the present invention (2
a, 2b, 2c) are perspective views showing the configuration of an inkjet recording head having a channel structure.

As shown in FIG. 1, the inkjet recording head in this embodiment is constructed by laminating or bonding the channel substrate 1 and the vibration plate 7.

FIG. 2 is a plan view of the ink flow path substrate, and FIG. 3 is a cross-sectional view taken along line A--A in FIG.

The channel depths d of the supply channels (2a to 2c) are the same, but the channel widths are a=c>b. Therefore, the supply path (2a
-2c) When the viscous resistances are R2a, R2b, and R2c, R2a=R2c<R2b. Therefore, the ink flow rate is large in the supply channels 2a and 2c located on the side wall side of the pressure chamber 4, and the ink flow rate is large in the supply channels 2a and 2c located on the side wall side of the pressure chamber 4.
)Fewer.

As a result, even if air bubbles 8 flow to the pressure chamber side wall 4a near the outlet of the supply path 2c or 2a and become stagnant as shown in FIG. If this is done, the flow rate of ink in the supply path 2c will be large, so that the air bubbles 8 can be discharged without the ink flow avoiding the air bubbles 8. In this embodiment, the depth of the supply channel is constant and there are two or more widths, but the depth of the supply channel is
The width may be constant for more than one type, or the depth and width may be two or more types. Furthermore, the number of supply channels is not limited to three, and when there are five supply channels (supply channels 2a, 2b, ... 2e from the pressure chamber wall side 4a), R2a=R
2e<R (other supply paths) may be satisfied. Another embodiment of the present invention will be described with reference to FIG. 4 and FIG. 5, which is a sectional view taken along line BB in FIG. 4.

As shown in FIG. 4, each supply path 2a, 2b, 2
The angle θ of the tip of the pressure chamber 4 side of the island-like part 6 that partitions the c is 12
By setting the angle to 0° or less, the flow velocity of the ink flowing from the supply paths 2a, 2b, 2c to the pressure chamber 4 is made gentler, thereby making the flow uniform. Therefore, it becomes possible to discharge the air bubbles 8 that remain on the side walls of the pressure chamber 4 near the outlets of the supply channels 2a and 2c by a discharge operation such as pump suction.

[0014] As yet another embodiment of the present invention,
This will be explained with reference to FIG. 6 and FIG. 7, which is a sectional view taken along line CC in FIG.

As shown in FIG. 6, supply channels 2a, 2b, 2c
In the ink flow path where the depth of the flow path is different from the depth of the pressure chamber 4, the depth of the flow path of the supply paths 2a, 2b, and 2c is equal to or greater than the tip on the pressure chamber 4 side of the island-shaped portion 6 that partitions each supply path. By increasing the length, the change in ink flow velocity from the supply paths 2a, 2b, 2c to the pressure chamber 4 can be made more gradual, and the ink flow can be made uniform.

[0016] Therefore, it becomes possible to discharge the air bubbles remaining on the side wall of the pressure chamber 4 near the outlet of the supply channels 2a, 2c by a discharge operation such as pump suction. However, supply paths 2a, 2b,
If the channel depth section 2c is made too long, the air bubbles 8 may remain in that section, so it is preferable to make the length up to the pressure chamber side tip of the island-shaped section 6 that partitions each supply channel.

Furthermore, if the ink flow path is tapered at the boundary between the two depths of the flow path as shown in FIG. 8, the change in ink flow velocity from the supply path to the pressure chamber will be more gradual.
Ink flow becomes more even. Therefore, the supply path 2a,
The efficiency of evacuation of air bubbles accumulated on the side wall of the pressure chamber 4 near the outlet 2c by evacuation operations such as pump suction is further improved.

[0018]

Effects of the Invention: By individually setting the width or depth of the supply channel, extending the shallow part of the supply channel, and improving the shape of the island-like part that partitions each supply channel, the present invention improves the area near the outlet of the supply channel. It is possible to improve the evacuation of air bubbles that accumulate on the side wall of the pressure chamber.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an inkjet recording head consisting of a flow path substrate and a diaphragm.

FIG. 2 is an embodiment of an ink flow path of the present invention in which the width of the supply path is individually set.

FIG. 3 is a cross-sectional view taken along line AA in FIG. 2;

FIG. 4 is a diagram showing an embodiment of the present invention in which the shape of an island-shaped portion that partitions a supply path is changed.

FIG. 5 is a sectional view taken along line BB in FIG. 4;

FIG. 6 is a diagram showing an embodiment of the present invention in which a shallow portion of the supply channel is extended.

FIG. 7 is a sectional view taken along line CC in FIG. 6;

8 is a cross-sectional view of the ink flow path of FIG. 7 with a tapered boundary between different flow path depths; FIG.

FIG. 9 is a diagram showing the shape of a conventional ink flow path.

FIG. 10 is a sectional view taken along line DD in FIG. 9;

[Brief explanation of symbols]

1 Flow path board 2a Supply path 2b Supply path 2c Supply path 3 Nozzle 4 Pressure chamber 5 Ink chamber 6 Island-shaped part 7. Vibration plate 8. Bubbles 9 Cap

Claims (3)

[Claims] Claim 1: In an inkjet recording head having three or more supply channels for one pressure chamber, the viscous resistance of the supply channel connected to the pressure chamber side wall is equal to the viscous resistance of the supply channel not connected to the pressure chamber side wall. An inkjet recording head that is characterized by its low performance. 2. The inkjet recording head according to claim 1, wherein the tip of the island-shaped portion that partitions each supply path on the pressure chamber side has an angle of 120° or less. 3. A channel depth of the supply channel is different from a channel depth of the pressure chamber, and the channel depth of the supply channel is determined by a pressure chamber-side tip of the island portion partitioning each supply channel. The inkjet recording head according to claim 1, characterized in that the length is greater than or equal to the length.