JPH05261909A - Ink jet head - Google Patents

Abstract

PURPOSE:To provide an ink jet head constituted in a manner of discharging foams securely out of an ink passage. CONSTITUTION:An ink jet head is provided with a first base 10 with ink jetting nozzles 10a and 10b, at least one of them, and a second base 12 fixed to said first base, and ink pressure chambers 12a1 and 12b1 and ink passages 12a2 and 12b2 linked with said chambers are formed between the first base and the second base. Ink jetting nozzles are disposed in a manner of opening in an ink passage, and ink jetting nozzles 10a and 10b are positioned at the sites approximately 0.8mm or less from the ends of the ink passages 12a2 and 12b2 in the ink jet head provided with an electrical/mechanical conversion means 14 installed correspondingly to the zones of the ink pressure chambers of the second base for the purpose of generating pressure wave to the ink in the ink pressure chambers.

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 used in an ink jet printer, and more particularly, to a first substrate having at least one ink jet nozzle and a second substrate fixed to the first substrate. An ink pressure chamber and an ink passage communicating with the ink pressure chamber are formed between the first substrate and the second substrate, and the ink ejection nozzle is opened to the ink passage. And an inkjet head of the type configured as follows.

[0002]

2. Description of the Related Art Drop-on-demand
As one type of multi-nozzle inkjet head, a large number of ink jet nozzles are arranged on a first substrate at a predetermined pitch, and a second substrate is fixed to the first substrate. There is known an inkjet head having a configuration in which a plurality of corresponding ink pressure chambers and an ink flow path communicating with each of these ink pressure chambers are formed and each ink ejection nozzle is opened in each of the ink flow paths. There is. In this type of ink jet head, the second substrate is provided with electromechanical conversion means, such as piezoelectric elements, corresponding to the regions of the ink pressure chambers, and the operation of the piezoelectric elements causes pressure waves to be generated in the ink in each ink pressure chamber. Is generated, and as a result, an ink droplet is ejected from the corresponding ink ejection nozzle. Therefore,
By selectively operating the piezoelectric element based on the print data, characters, symbols and the like are recorded by ink dots on a recording medium such as recording paper. In order to obtain a predetermined print quality, a large number of ink ejection nozzles must be arranged with an arrangement pitch of the order of a few microns and with high precision, and along with this, the ink pressure chambers and ink flow paths with high precision. Although it is required to process, in the ink jet head of the type described above, the ink pressure chamber and the ink flow path are relatively easily etched on either the first substrate or the second substrate. And there is an advantage that it can be processed with high accuracy. The first and second substrates are made of a material suitable for etching such as stainless steel and glass.

[0003]

By the way, it has been pointed out that a problem with such an ink jet head is that bubbles tend to remain in the ink flow path. Needless to say, when bubbles are present in the ink flow path, the pressure wave generated in the ink pressure chamber is buffered by the bubbles, thus hindering the ejection of ink droplets from the ink ejection nozzles. become. Therefore, it is an object of the present invention to provide an inkjet head of the type described above, which is configured to reliably eliminate bubbles from the ink flow path.

[0004]

According to the present invention, there is provided a first substrate having at least one ink jet nozzle, and a second substrate fixed to the first substrate,
An ink pressure chamber and an ink channel communicating with the ink pressure chamber are formed between the first substrate and the second substrate, and the ink ejection nozzle is arranged so as to be opened in the ink channel. Further, in an ink jet head comprising electromechanical conversion means provided on the second substrate so as to correspond to the region of the ink pressure chamber so as to generate a pressure wave in the ink in the ink pressure chamber, the ink jet nozzle is provided with an ink jet nozzle. It is characterized in that it is positioned within about 0.8 mm from the tip of the channel.

[0005]

As apparent from the above construction, according to the present invention, the ink ejecting nozzle is about 0.8 mm from the tip of the ink flow path.
Bubbles can be reliably removed from the ink flow path because they are positioned at the following locations.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the ink jet head according to the present invention will be described below with reference to the accompanying drawings. Figure 1
Referring to FIG. 1, there is shown a first substrate 10 which is one component of the inkjet head according to the present invention, and the first substrate 10 is made of, for example, stainless steel, glass, ceramic or the like. As shown, in the present embodiment, two rows of ink ejection nozzles 10a and 10b are formed on the first substrate 10, and each row includes five ink ejection nozzles. The arrangement pitch of the ink jet nozzles 10a and 10b in each row is the same, but the ink jet nozzles 10a and 10b in both rows are arranged so as to be offset by a half pitch.

Referring to FIG. 2, a second substrate 12 is shown, which is also a component of the inkjet head of the present invention. The second substrate 12 is made of stainless steel, glass, or the like, and has two rows of recesses 12a and 12b formed on one side surface thereof by etching or the like. Each row includes five recesses, and the array pitch is It is the same as the arrangement pitch of the ink ejection nozzles 10a and 10b. Therefore, the first substrate 10 of FIG.
When the ink jet nozzles 10a and 10b of the two rows are superposed on the substrate 12 of the above, the two rows of the concave portions 12a are formed.
And 12b, the ink ejection nozzles 10a and 10b are opened to the corresponding recesses 12a and 12b. Each recess 12a, 12b has a central region 1
2a ₁ and 12b ₁ and tip regions 12a ₂ and 12b ₂ that gradually narrow and extend from the first substrate 10
When the second substrate 12 and the second substrate 12 are stacked and fixed to each other, the central regions 12a ₁ and 12b ₁ form ink pressure chambers, and the tip regions 12a ₂ and 12b ₂ form ink flow paths. First substrate 10 and second substrate 12
The adhesion between the two substrates may be heat fusion, or both substrates may be bonded by an adhesive. The recesses 12a and 12b are communicated with the common ink supply path 12d through the restrictor portion 12c, and the ink supply path 12 is provided.
d is connected to an ink supply source, that is, an ink supply tank (not shown) through the through hole 12e. Note that, like the recesses 12a and 12b, the restrictor portion 12c and the ink supply path 12d are also formed by etching or the like.

FIG. 3 shows a first substrate 10 and a second substrate 1.
Fig. 2 III-II when the two are stacked and fixed to each other
A cross-sectional view taken along the line I is shown, and as is apparent from the same drawing, the second substrate 12 corresponds to the central regions of the recesses 12a and 12b, that is, the regions of the ink pressure chambers 12a ₁ and 12b _1. An electromechanical conversion means, for example, a piezoelectric element 14 is fixed, and an electrode plate 16 is applied to this piezoelectric element 14.
When the second substrate 12 is formed of a conductive material such as stainless steel, the second substrate 12 itself is grounded as a counter electrode of the electrode plate 16, and the second substrate 1 is also used.
When 2 is formed from an insulating material such as glass,
A conductive layer made of, for example, a conductive paste is interposed between the second substrate 12 and the piezoelectric element 14, and this conductive layer serves as a counter electrode of the electrode plate 16. When a predetermined drive voltage is applied to the electrode plate 16, the piezoelectric element 14 is instantly distorted, which locally vibrates the second substrate 12. At this time, a pressure wave is generated in the ink in the ink pressure chambers 12a ₁ and 12b ₁ , and the ink droplets are ejected from the ink ejection nozzle 10a. Therefore, by selectively operating the piezoelectric element 14 based on the print data, characters,
Symbols and the like are recorded by ink dots on a recording medium such as recording paper. As described above, the two rows of ink ejection nozzles 10a and 10b are arranged so as to be offset from each other by a half pitch, and when the inkjet head is moved with respect to the recording medium, on the same straight line perpendicular to the movement direction. Ink ejection nozzles 10a, 10b in each row
Since the ink droplets are ejected from the ink ejection nozzles, the dot pitch for recording with ink dots is set to the ink ejection nozzles 10a, 1
It is half of the arrangement pitch of 0b.

When performing printing operation, all ink
Pressure chamber 12a₁And 12b₁And the ink flow path 12
a₂And 12b₂Fill the inside with ink.
And the inkjet head is
When installed in a jet printer, the ink supply
The ink side or press the ink jet nozzle
Connect to a mechanism (not shown) to force the ink to flow
Road 12a₂And 12b₂I have to pull in
Yes. However, when the ink drawing is completed,
Ink channel 12a₂And 12b₂There are often air bubbles inside
It was confirmed that the residue would remain. As mentioned earlier,
Channel 12a₂And 12b₂When air bubbles remain inside
The ink pressure chamber 12a₁And 12b₁Generated by
The generated pressure wave is buffered by the bubbles and thus
Of small ink droplets from the ink jet nozzles 10a and 10b
Is hindered. According to the study by the present inventors, such bubbles
The remaining problem is that the ink ejection nozzles 10a, 10b and the ink
Channel 12a₂And 12b ₂Is closely related to
It turned out to be giving. That is, as shown in FIG.
To the center position of the ink ejection nozzles 10a and 10b.
Channel 12a₂, 12b₂Various distances to the tip of
Set and pull in the ink 10 for each set value.
After repeating 0 times, the results shown in Table 1 below were obtained.
Was given.

[0010]

[Table 1]

As is clear from Table 1, ink ejection
The nozzles 10a and 10b are the ink flow paths 12a.₂, 12b₂
If it is positioned within 0.8mm from the tip of the
Bubbles in the ink flow path 12 even once during 100 times of ink drawing
a₂, 12b₂It did not remain inside. Also,
The ink jet nozzles 10a and 10b to the ink flow path 12a.₂,
12b₂When positioned at 0.85 mm from the tip of
Is the ink flow path 12 only 30 times during 100 times of ink drawing.
a₂, 12b₂No air bubbles remained inside
However, after 70 times, air bubbles remained. Furthermore,
The ink jet nozzles 10a and 10b are connected to the ink flow path 12
a₂, 12b₂Positioned 0.90 mm or more from the tip of
When deciding, the ink flow path is always maintained during 100 ink draws.
12a₂, 12b ₂Remaining air bubbles were observed inside. Na
For such an experiment, the ink pressure chamber 12a₁1
2b₁The width w (Fig. 4) of the range of 0.5 to 1.5 mm
In addition, the depth (thickness) of the ink channel is 0.05 to 0.1 mm.
The results were shown in Table 1 above.
Was similar to. In short, the ink flow path 12a₂, 12
b₂Whether or not air bubbles remain inside the tip and the ink jet
To depend only on the distance between the nozzles 10a and 10b
Was found. Therefore, the ink jet nozzle
Position it within about 0.8 mm from the tip of the ink flow path.
This ensures that air bubbles are removed from the ink flow path,
Thus, stable printing can be maintained.

Referring to FIG. 5, a variation of the above-described embodiment is illustrated, in which the second substrate 12 is formed from two separate members, a flow plate 12f and a diaphragm 12g. Except for this, it is similar to the above-described embodiment. According to the variant embodiment of FIG. 5, it is possible to form the second substrate from different materials. For example, the flow channel plate 12f can be formed of stainless steel, and the vibrating plate 12g can be formed of glass, ceramic, or the like. In this case, the flow channel plate 12f is provided with an ink pressure chamber, an ink flow channel, or the like by electric discharge machining or the like. Can be formed.

Referring to FIG. 6, there is shown another modified example of the above-described embodiment, in which an ink pressure chamber, an ink flow path, etc. are formed in the first substrate 10 by etching or the like.
In this case, the second substrate 12 will function as a diaphragm.

[0014]

As is apparent from the above description, according to the ink jet head of the present invention, the bubbles are surely removed from the ink flow path when the ink is drawn in, so that the stable printing operation is guaranteed and thus the high printing performance is ensured. It is possible to obtain a quality print record.

[Brief description of drawings]

FIG. 1 is a plan view showing a first substrate which is a component of an inkjet head according to the present invention.

FIG. 2 is a plan view showing a second substrate which is one component of the inkjet head according to the present invention.

3 is a cross-sectional view taken along line III-III of FIG. 2 when the first substrate of FIG. 1 and the second substrate of FIG. 2 are stacked and fixed to each other.

FIG. 4 is a schematic diagram showing a relative positional relationship between an ink ejection nozzle and an ink flow path.

5 is a sectional view similar to the sectional view of FIG. 3, showing a modification of the embodiment of the present invention.

6 is a sectional view similar to the sectional view of FIG. 3, showing another modification of the embodiment of the present invention.

[Explanation of symbols]

10 ... first substrate 10a ... ink ejection nozzles 10b ... ink ejection nozzles 12 ... second substrate 12a ... concave portion 12a ₁ ... ink pressure chambers 12a ₂ ... ink channel 12b ... recess 12b ₁ ... ink pressure chamber 12b ₂ ... Ink Flow path 12c ... Restrictor part 12d ... Ink supply path 12e ... Through hole 12f ... Flow path plate 12g ... Vibration plate 14 ... Piezoelectric element 16 ... Electrode plate

Claims (3)

[Claims] 1. At least one ink jet nozzle (1)
0a, 10b) and a first substrate (10)
Second substrate (12) fixed to the substrate, and ink pressure chambers (12a ₁ , 12b ₁ ) between the first substrate and the second substrate, and the ink An ink flow path (12a ₂ , 12b ₂ ) communicating with the pressure chamber is formed, the ink ejecting nozzle is arranged so as to be opened to the ink flow path, and a pressure wave is generated in the ink in the ink pressure chamber. In the ink jet head including the electromechanical conversion means (14) provided on the second substrate corresponding to the area of the ink pressure chamber so that the ink jet nozzles (10a, 10b) can flow the ink. An inkjet head characterized in that it is positioned at a position of about 0.8 mm or less from the tip of the passages (12a ₂ , 12b ₂ ). 2. The ink jet head according to claim 1, wherein the ink pressure chambers (12a ₁ , 12b ₁ ) and the ink flow paths (12a ₂ , 12b ₂ ) are etched in the second substrate (12). An ink jet head formed by processing. 3. The ink jet head according to claim 1, wherein the ink pressure chambers (12a ₁ , 12b ₁ ) and the ink flow paths (12a ₂ , 12b ₂ ) are etched in the first substrate (10). An ink jet head formed by processing.