JPH10272773A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently remove air bubbles by performing suction treatment a reduced number of times by properly setting the cross section of an ink passage. SOLUTION: An almost circular nozzle 30 having the almost max. diameter capable of being set by the cross section of an ink passage is provided to the leading end of each ink passage and pressure is allowed to act on the ink in the ink passage by the bending of a side wall 20 to eject ink from the nozzle 30. The ink passage is formed so that a first depth H1 at a position separated from the nozzle 30 becomes a second depth H2 at a position approaching the nozzle 30 and a ratio of the second depth H2 to the first depth H1 is set to a range of 0.1-0.8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head for ejecting ink from nozzles by applying pressure to ink in an ink flow path.

[0002]

2. Description of the Related Art A communication device such as a facsimile device and an information processing device such as a personal computer usually have a recording device capable of recording data consisting of characters and figures as visual information so that the data can be recorded on paper. Have. Various recording methods such as an impact method, a heat-sensitive method, and an ink-jet method are adopted for this recording apparatus. In recent years, an ink-jet method which is excellent in quietness and can print on paper of various materials is adopted. Attention has been paid to an ink jet recording apparatus that has been used.

The above-described ink-jet recording apparatus has an ink-jet head having a large number of nozzles for ejecting ink droplets onto a sheet so as to print characters and figures on the sheet. The ink jet head usually has an ink flow path 105 communicated with the nozzle 100 as shown in FIG.
The side wall 101 is formed of a piezoelectric material that has been subjected to polarization processing, and is formed by forming an electrode 102 on the side wall surface. By applying a driving electric field to the side wall 101 via the electrode 102, the side wall 101 is bent to form an ink. Channel 105
By changing the volume of the ink, the discharge (ejection) and supply of the ink to the ink flow path 105 are performed by the increase and decrease of the ink pressure.

At this time, if the bubble 103 exists in the ink flow path 105, when the volume of the ink flow path 105 changes, the change in the volume is absorbed by the bubble 103 by compression and expansion. When the change in the volume of the ink flow path 105 is not sufficiently reflected in the increase and decrease in the ink pressure, the ink droplet ejection becomes insufficient, or when the bubble 103 grows, the ink flow path 105 and the nozzle 100 are blocked and the non-ejection occurs. Cause. Therefore, conventionally, at the start of printing or at the time of detection of non-ejection, a suction process is performed in which a suction unit is brought into close contact with the outside of the nozzle 100 to suction the bubbles 103 together with the ink in the ink flow path 105. I have.

[0005]

However, only by performing the suction process as in the above-mentioned conventional technique, if the bubbles 103 exist at the corners between the nozzle plate 104 and the ink flow path 105, the bubbles 103 Since the removal is likely to be insufficient, there is a problem that it is necessary to repeat these processes many times in order to reliably remove the bubbles 103.

Further, the bottom of the ink flow path 105 is
There is also proposed a configuration in which the ink flow is smoothened by rising while being raised to the vicinity of 00, so that the flow of the ink is made smooth and the bubble 103 is discharged together with the ejection of the nozzle (Japanese Patent Laid-Open No. 6-17 / 1994).
No. 1096), which merely reduces the cross-sectional area, and it is unclear what shape the bubble 103 can be sufficiently discharged.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ink jet head capable of sufficiently removing bubbles by a small number of suction processes by setting an ink flow path to an appropriate shape.

[0008]

According to a first aspect of the present invention, there is provided an ink flow path having a substantially circular shape having a substantially maximum diameter which can be set in a cross section of the ink flow path. An ink jet head that ejects ink from the nozzles by applying pressure to the ink in the ink flow path, wherein the ink flow path is located at a position away from the nozzle from a first depth. And at a position close to the second depth, the ratio of the second depth to the first depth is 0.1 to
It is characterized in that it is set in the range of 0.8.

By setting the first depth H1 relative to the second depth H2 of the ink flow path to the rising amount set in the above-mentioned ratio range, most of the bubbles existing in the ink flow path can be suctioned a small number of times. It can be removed from the nozzle by processing.

According to a second aspect of the present invention, there is provided the ink jet head according to the first aspect, wherein a nozzle plate having the nozzle is joined to an end surface of the actuator substrate having the ink flow path on the front end side of the ink flow path. It is characterized by:

[0011] This makes it possible to easily remove the air bubbles accumulated in the corner formed between the periphery of the nozzle of the nozzle plate and the tip of the ink flow path by the suction process.

According to a third aspect of the present invention, in the ink jet head according to the first or second aspect, the side wall of the ink flow path is deformed in a direction in which a cross-sectional area of the ink flow path is changed, thereby forming an ink. It is characterized in that it is configured to apply pressure.

[0013] With this, the side wall is largely deformed in the portion away from the nozzle in the ink flow path to apply pressure to the ink. Therefore, even if the cross-sectional area is formed small in the portion close to the nozzle, a sufficiently large pressure is applied. Can be used to eject ink.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, the inkjet head according to the present embodiment has an actuator substrate 2, a plate member 4, a nozzle plate 6, and a manifold member 7. Actuator board 2
Is made of a piezoelectric material made of a lead zirconate titanate (PZT) ceramic material, and has a plurality of ink grooves 14 formed by cutting with a diamond blade or the like on the upper surface. Note that a lead titanate (PT) ceramic material can be used as the piezoelectric material.

As shown in FIG. 3, the ink groove 14 has a substantially flat bottom surface.
4 is formed so as to have the first depth H1 from the rear end of the actuator substrate 2 to the intermediate portion,
It is raised so as to be shallow with a gentle curved surface from the middle part to the tip, and is formed to have the second depth H2 at the tip part 14b. Also, the ink grooves 14
Are set to have the same width so that the distance between the side walls of the ink flow path 10 described later is the same from the front end to the rear end. Note that the bottom surface of the ink groove 14 may be curved in a semicircular shape or a concave shape. The ink grooves 14 are arranged in parallel via a side wall 20 polarized in the thickness direction 27L of the actuator substrate 2, and an electric field is applied to the upper part of the side wall 20 in a direction perpendicular to the polarization direction 27L. An electrode 22 is formed by vapor deposition or plating over both ends of the side wall 20 so as to apply the voltage.

A flat plate member 4 made of a ceramic material or a resin material is joined to one surface of the actuator substrate 2 using an epoxy-based adhesive. As shown in FIG. 2, the plate member 4 is
The ink flow path 10 is in close contact with one surface of the side wall 20 in a liquid-tight manner through the surface of the ink groove 14, and covers the one surface of the ink groove 14 to form the ink flow path 10 having a rectangular flow path cross section. Then, one end (tip) of the actuator substrate 2 and the plate member 4 forming the ink flow path 10 in this manner is
The nozzle plate 6 is joined using the epoxy adhesive described above. The nozzle plate 6 is formed of a plastic such as polyalkylene or (for example, ethylene) terephthalate, polyimide, polyetherimide, polyetherketone, polyethersulfone, polycarbonate, or cellulose acetate.

The nozzle plate 6 has nozzles 30 corresponding to the ink flow paths 10. Nozzle 3
0 is formed in a substantially truncated cone shape, and as shown in FIG. 2, the diameter is enlarged from the outlet side to the ink flow path 10 side, and the flow path cross section of the ink flow path 10 at the end face on the ink flow path 10 side It is formed so as to have a substantially maximum diameter that can be set by the above. In other words, the diameter of the ink passage 10 is substantially inscribed in the cross section of the ink passage 10. In this case, the diameter of the nozzle may be slightly smaller than the cross section of the flow path in consideration of a positional shift in bonding the nozzle plate. The ink flow path 10 to which the nozzle 30 is communicated has a first position at a position away from the nozzle 30 so that the bubbles 92 can be sufficiently removed through the nozzle 30 by a small number of suction processes. The ratio of the second depth at a position close to the nozzle 30 with respect to the depth H1 is set in a range of 0.1 to 0.8. The ratio of the distance between the side walls to the height of the side walls is set in the range of 0.5 to 2.0 so that the bubbles 92 can be more sufficiently removed. It is desirable that it is set.

On the other hand, a manifold member 7 is joined to the other end (rear end) of the actuator substrate 2 and the plate member 4. An ink supply port 31 is formed in a part of the manifold member 7 so that ink is supplied from an ink tank (not shown). And
The manifold member 7 forms a common ink chamber 9 communicating with all the ink flow paths 10, and supplies ink to the ink flow path 10 when the volume of the ink flow path 10 increases. .

The operation of the ink jet head in the above configuration will be described. First, when the inkjet recording apparatus performs printing, as shown in FIG.
For example, when a specific ink channel 10B is selected according to the given print data, the selected ink channel 10B
Electrodes 22B and 22C are grounded and ink flow paths 10A and 10C located on both sides of the ink flow path 10B.
A drive voltage is applied to the electrodes 22A and 22D. Then, on the side walls 20A and 20B of the ink flow path 10B,
When the driving electric fields are generated toward the ink flow path 10B, the polarized side walls 20A and 20B are bent so as to approach each other due to the piezoelectric thickness-shear effect. Therefore, the ink flow path 10B is formed on both side walls 20A and 20B.
The ink flow path 1
When the ink in 0B is pressurized, an ink droplet is ejected from the nozzle 30.

Thereafter, when the driving voltage is stopped, the side wall 2
By returning 0A and 20B to the state before bending,
The ink pressure in the ink flow path 10B decreases. Thus, the ink in the common ink chamber 9 is supplied into the ink flow path 10B, and the ink corresponding to the ejection amount of the ink droplet is replenished, so that the ink is prepared for the next ejection of the ink droplet.
When the polarization direction is reversed or the electric field direction is reversed,
As shown in FIG. 6B, both side walls 20 are connected to the ink flow path 1.
It can be deformed in the direction in which 0 expands. Thereby, when the ink is supplied from the common ink chamber 9 to the ink flow path 10 and then the electric field applied to the side wall 20 is released,
The side wall may return to a linear shape, and a pressure may be applied to the ink in the ink flow path 10 so that the nozzle 30 ejects an ink droplet. Further, by combining a plurality of methods of changing the volume of the ink flow path 10, it is possible to stabilize the ejection of the ink droplets and to control the volume and the flying speed of the ink droplets.

When printing is performed by ejecting ink droplets in this manner, or when an ink cartridge (not shown) is replaced due to ink shortage, if bubbles 92 enter the ink flow path 10, the ink flow path 10 Even if the volume expands or contracts due to the bending of the side wall 20, the bubble 92 in the ink flow path 10 expands and compresses, so that an appropriate ink pressure cannot be obtained. Is blocked. In this case, a printing failure occurs, and when the inkjet recording apparatus has such a failure, a suction process is performed so as to remove the bubbles 92 from the ink flow path 10. .

That is, in the suction process, a cap is tightly attached to the front surface of the nozzle plate 6 so as to surround the nozzle 30 and the ink in the ink flow path 10 is suctioned from the nozzle 30 through the cap as is known, though not shown. Things. Although not shown in the drawings, the same effect can be obtained by providing a pressurizing means on the ink tank side and pushing out the ink in the ink flow path 10 from the nozzle 30 by the pressure. Include in the suction process. Then, in one or one cycle of the suction process, ink equal to or larger than the volume in the ink flow path 10 is sucked, and the bubbles 92 in the ink flow path 10 are discharged together with the ink.
In the present embodiment, as shown in FIG. 2, since the ratio of the second depth H2 to the first depth H1 is set in the range of 0.1 to 0.8, for example, 80% or more in one suction process Bubble 92 can be removed.

Next, the second depth H2 with respect to the first depth H1
It was confirmed that most of the bubbles 92 could be removed by a small number of suction processes when the ratio was set in the range of 0.1 to 0.8.

That is, as shown in FIG. 2 to FIG.
The ratio of the second depth H2 to the depth H1 is 0.05 to 1.
Various ink jet heads having a range of 0 were prepared. Note that the rising start position 14c of the ink groove 14 was set to the same position regardless of the increase or decrease of the ratio. Then, after a predetermined amount of the bubbles 92 are present in each of the ink jet heads, the above-described suction processing is performed on each of the ink jet heads.
The probability that can be removed was calculated. As a result, as shown in FIG. 5, the ratio of the second depth H2 to the first depth H1 is 0.1
It has been confirmed that when the value is set in the range of about 0.8, it is possible to remove approximately 80% or more of the bubbles 92 by one suction process. It is difficult to make the removal rate of the bubbles 92 100%, and since the frequency of the bubbles entering the ink flow path 10 is relatively low, there is no practical problem if the removal rate is 80%.

As described above, as shown in FIG. 1, the ink jet head according to the present embodiment is provided at the tip of the ink flow path 10 (ink flow path) with almost the maximum settable cross section of the ink flow path 10. A nozzle 30 having a substantially circular diameter is provided, and ink is ejected from the nozzle 30 by applying pressure to the ink in the ink flow path 10. The ink flow path 10 is located at a position away from the nozzle 30. At a position close to the nozzle 30 from the first depth H1, the second
The second depth H2 is formed to have a depth H2, and the ratio of the second depth H2 to the first depth H1 is set in a range of 0.1 to 0.8. Thus, the first depth H1
Is configured to set the ratio of the second depth H2 to the range of 0.1 to 0.8, most of the bubbles 92 existing in the ink flow path 10 are removed from the nozzles 30 by a small number of suction processes. be able to.

In the present embodiment, the pressure is applied to the ink by bending the polarized side wall 20 by applying an electric field. However, the present invention is not limited to this. Heat the ink to generate bubbles,
The pressure may be applied by the expansion pressure of the bubble, or a diaphragm may be provided along the ink flow path 10,
The diaphragm may be vibrated by a piezoelectric element or other means to apply pressure.

In the present embodiment, the end face of the actuator substrate 2 having the ink flow path 10 on the front end side is
The nozzle plate 6 having the nozzles 30 is joined. Thus, the bubbles 92 remaining in the corner formed between the periphery of the nozzle 30 of the nozzle plate 6 and the tip of the ink flow path 10 can be easily removed by the suction process.

In this embodiment, the ink flow path 1
Although the distance between the side walls of 0 is set to be the same distance from the front end to the rear end of the ink flow path 10, the side wall 20 of the ink flow path 10 is deformed in a direction that changes the cross-sectional area of the ink flow path 10. Alternatively, the pressure may be applied to the ink. In this case, even if the cross-sectional area of the cross section of the flow path is reduced in a portion close to the nozzle 30, a large pressure can be applied to the ink by the deformation of the side wall 20, and efficient ejection can be performed. Can be.

Further, in the present embodiment, the explanation has been made using an ink jet head in which the side wall 20 forming the ink flow path 10 is polarized only in the -direction 27L.
It is not limited to this. That is, as shown in FIG. 7, for example, as shown in FIG. 7, the inkjet head joins the actuator substrate 2 polarized in the direction 27L to the piezoelectric member 25 polarized in the opposite direction 27U via the adhesive layer 26, The piezoelectric member 25 and the actuator substrate 2 may be cut to form the ink grooves 14, and the electrodes 22L and 22U may be formed on the side wall 20 having a two-layer structure.

As shown in FIG. 8, the ink jet head has side walls 20U and 20L of the ink grooves 14U and 14L.
By joining the actuator substrates 2U and 2L having the electrodes 22U and 22L formed on the upper and lower sides in a pair, the side walls 20U polarized in opposite directions 27U and 27L are formed.
-It may be configured to have 20L. Further, a space may be provided between each ink flow path 10 so that the ink does not enter the ink flow path and does not eject ink droplets.

[0031]

According to the first aspect of the present invention, a substantially circular nozzle having a substantially maximum diameter which can be set in the flow path cross section of the ink flow path is provided at the tip of the ink flow path, and the ink in the ink flow path is provided. An ink jet head that ejects ink from the nozzles by applying pressure to the nozzles, wherein the ink flow path is from a first depth at a position away from the nozzles to a second depth at a position close to the nozzles. And a ratio of the second depth to the first depth is set in a range of 0.1 to 0.8.

As described above, by setting the first depth H1 with respect to the second depth H2 of the ink flow path to the rising amount set in the above-described ratio range, most of the bubbles existing in the ink flow path can be reduced by a small number of times. It is possible to provide an ink jet head which is practically excellent, for example, it can be removed from the nozzles by the suction process, whereby the printing operation can be started early, and the amount of ink discarded by the suction process can be reduced. To play.

According to a second aspect of the present invention, there is provided the ink jet head according to the first aspect, wherein a nozzle plate having the nozzle is joined to an end surface of the actuator substrate having the ink flow path on the front end side of the ink flow path. Configuration. Thus, there is an effect that bubbles accumulated in the corner formed between the periphery of the nozzle of the nozzle plate and the tip of the ink flow path can be easily removed by the suction process.

According to a third aspect of the present invention, there is provided the ink jet head according to the first or second aspect, wherein the side wall of the ink flow path is deformed in a direction in which a cross-sectional area of the ink flow path is changed, thereby forming an ink. It is configured to exert pressure.

With this, the side wall is largely deformed at the portion away from the nozzle in the ink flow path and acts on the ink. Therefore, even if the cross-sectional area is formed small at the portion close to the nozzle, the ink is applied with a sufficiently large pressure. Is produced.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an inkjet head.

FIG. 2 is a longitudinal sectional view of the inkjet head.

FIG. 3 is a cross-sectional view of the inkjet head.

FIG. 4 is a cross-sectional view of the inkjet head.

FIG. 5 is a graph showing the relationship between the depth ratio (H2 / H1) and the probability of air bubble removal.

FIG. 6 is an explanatory diagram showing a state of an ink flow path.

FIG. 7 is an exploded perspective view of the inkjet head.

FIG. 8 is an exploded perspective view of the inkjet head.

FIG. 9 is a longitudinal sectional view of a conventional inkjet head.

[Explanation of symbols]

 2 Actuator substrate 4 Plate member 6 Nozzle plate 7 Manifold member 9 Common ink chamber 10 Ink flow path 11 Dummy ink chamber 14 Ink groove 15 Dummy ink groove 20 Side wall 22 Electrode 30 Nozzle 31 Ink supply port

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[Procedure amendment]

[Submission date] May 2, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

As shown in FIG. 2 , most of the ink grooves 14 have a flat bottom surface.
4 is formed so as to have the first depth H1 from the rear end of the actuator substrate 2 to the intermediate portion,
It is raised so as to be shallow with a gentle curved surface from the middle part to the tip, and is formed to have the second depth H2 at the tip part 14b. Also, the ink grooves 14
Are set to have the same width so that the distance between the side walls of the ink flow path 10 described later is the same from the front end to the rear end. Note that the bottom surface of the ink groove 14 may be curved in a semicircular shape or a concave shape. The ink grooves 14 are arranged in parallel via a side wall 20 polarized in the thickness direction 27L of the actuator substrate 2, and an electric field is applied to the upper part of the side wall 20 in a direction perpendicular to the polarization direction 27L. An electrode 22 is formed by vapor deposition or plating over both ends of the side wall 20 so as to apply the voltage.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

That is, in the suction process, a cap is tightly attached to the front surface of the nozzle plate 6 so as to surround the nozzle 30 and the ink in the ink flow path 10 is suctioned from the nozzle 30 through the cap as is known, though not shown. Things. Alternatively, although not shown, the same effect can be obtained by providing a pressurizing means on the ink tank side and pushing out the ink in the ink flow path 10 from the nozzles 30 by the pressure. Include in. Then, in one or one cycle of the suction process, ink equal to or larger than the volume in the ink flow path 10 is sucked, and the bubbles 92 in the ink flow path 10 are discharged together with the ink.
In the present embodiment, as shown in FIG. 2, since the ratio of the second depth H2 to the first depth H1 is set in the range of 0.1 to 0.8, for example, 80% or more in one suction process Bubble 92 can be removed.

Claims (3)

[Claims] 1. An ink jet apparatus comprising: a substantially circular nozzle having a substantially maximum diameter which can be set in a flow path cross section of the ink flow path; and applying a pressure to ink in the ink flow path. An ink jet head that ejects ink from the nozzle, wherein the ink flow path is a first ink jet head at a position away from the nozzle.
The second depth is formed at a position close to the nozzle from the depth, and a ratio of the second depth to the first depth is set in a range of 0.1 to 0.8. Inkjet head. 2. The ink jet head according to claim 1, wherein a nozzle plate having said nozzle is joined to an end surface of said actuator substrate having said ink flow path on a front end side of said ink flow path. 3. The side wall of the ink flow path is deformed in a direction that changes the cross-sectional area of the ink flow path,
3. The ink jet head according to claim 1, wherein the ink jet head is configured to apply pressure to the ink.