JPH0691870A - Ink-jet print head and ink-jet printer - Google Patents

Abstract

PURPOSE:To realize precise and high-speed printing by neither thinning a base nor making driving voltage to be applied to a piezo-electric element high. CONSTITUTION:In an ink-jet print head to be obtained by fitting a piezo-electric head unit provided with a base 1 wherein an introduction port of ink supplying the ink to a common ink path surrounding a large number of pressurizing chambers arranged radially from an end part of the center of two rows arranged linearly and communicating with the pressurizing chambers is formed, a nozzle 5 formed in the end part of the center by penetrating through the base, an oscillation plate fitted to a pressurizing chamber forming surface of the nozzle 5 and a piezo-electric element fitted to the oscillation plate by corresponding to the pressurizing chambers each to a base rest, the end part of the center of the two rows arranged linearly is formed by inclining to a printing direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet print head used in, for example, printers, fax machines, plotters, bar code printers, digital copiers, etc., and in particular, ink is ejected from a thin nozzle in accordance with an image signal.
The present invention relates to an inkjet print head that is attached to a recording medium such as paper to obtain a recording.

[0002]

2. Description of the Related Art Conventional inkjet printing is roughly classified into a continuous type and an on-demand type.
The ink is water-based or oil-based.

In the continuous type, ink is continuously ejected from a nozzle, and ink unnecessary for recording is recovered and reused. The head has high responsiveness, but an ink recovery mechanism is required and the apparatus is complicated. It is expensive.

On the other hand, the on-demand type ejects ink only when necessary, and the response of the head is low, but the device is simple and inexpensive.

The on-demand type includes an electrostatic attraction type that draws ink from a nozzle by electrostatic force, and a pressure pulse type called an impulse jet that pressurizes ink in a pressure chamber and pushes ink from the nozzle.

The pressure pulse type includes a piezoelectric type and a bubble type. The piezoelectric type pressurizes ink by a piezoelectric (electrostrictive) element. The one-chamber type in which ink is supplied through a pressure chamber and the pressure type There is a two-chamber type having two chambers, a chamber and an ink supply chamber.

The one-chamber type includes a Kaiser type having a flat pressure chamber and a soltan type having a cylindrical pressure chamber. In addition, the two-chamber type includes a stem type that directly supplies ink to the vicinity of the nozzle.

FIG. 10 shows the basic principle of the above Kaiser type piezoelectric head unit. On the surface of the substrate 101, an ink supply passage 102, a pressure chamber 103 and a nozzle 104 are provided.
Are continuously formed. Then, the diaphragm 105 is arranged on the surface of the substrate 101, and the outer surface of the diaphragm 105 is
A piezoelectric element 106 is provided so as to face the pressure chamber 103, and a signal generation source 107 is connected so as to apply a voltage between the front and back surfaces of the piezoelectric element 106. An ink container 109 is connected to the ink supply path 102 via a pipe 108.

In the above structure, when a voltage is applied from the signal source 107 to the piezoelectric element 106, the piezoelectric element 106
Causes the vibrating plate 105 to bend, and the ink 1 in the pressure chamber 103
10 is ejected from the nozzle 104 as an ink droplet 110a onto the recording medium 111 for recording.

Then, when the voltage application to the piezoelectric element 106 is released after the ink is ejected, the vibrating plate 105 returns to its original state, and the ejected ink passes through the ink supply path 102 and the pipe 108 by the nozzle capillary force. It is supplied from the ink container 109.

FIG. 11 is a plan view showing a conventional ink jet print head using the above piezoelectric head unit, FIG. 12 is an enlarged plan view of a part of a nozzle forming portion, and FIG.
FIG. 13 is a cross-sectional view taken along the line BB of FIG.

In FIGS. 11 to 13, a substrate 121 made of photosensitive glass is provided with a plurality of pressure chambers arranged in a radial pattern from the central ends of two rows arranged in a straight line orthogonal to the printing direction. 122a-122n, this pressure chamber 122a-12
A common ink path 123 that surrounds 2n and communicates with the pressure chamber, and an ink introduction port 124 that supplies ink to the common ink path 123 are formed by etching. A nozzle 125 is formed at the straight center end of each of the pressure chambers 122a to 122n so as to penetrate in the plate thickness direction. In this case, the nozzle 125 is formed by the etching process so as to be tapered toward the ink ejection port with an inclination of about 2 °. Further, by forming the pressure chambers 122a to 122n radially, the number of nozzles per single area can be increased.

FIG. 14 shows a vibration plate 126 on the substrate 121,
It is a cross-sectional view showing an inkjet print head to which a piezoelectric head unit to which piezoelectric elements 127a to 127n are attached is applied.

The vibrating plate 126 is made of glass, for example, and is attached to the pressure chambers 122a to 122n of the substrate 121, the common ink 123, and the surface on which the ink introducing port 124 is formed by screws, adhesion or the like.

The piezoelectric elements 127a to 127n are the pressure chamber 12
It is attached to the position of the diaphragm 126 corresponding to each of 2a to 122n. And each piezoelectric element 127a-
A flexible cable 128 for applying a signal voltage from a signal generation source (not shown) is connected to 127n.

Piezoelectric elements 127a to 127n are mounted on a base 129 made of a metal or a resin having a high rigidity for mounting the substrate 121.
The concave portion 130 is formed in the portion corresponding to the above, and the peripheral portion and the central portion of the diaphragm 126 are bonded and fixed to the base 129 by the adhesive 131 in the other portions.

Next, the operation will be described. Due to the distortion of the piezoelectric element to which the signal voltage is applied, the vibrating plate 126 in the portion corresponding to the voltage element is deformed, and the volume of the pressure chamber is changed by this deformation to eject ink from the nozzle 125. In this case, the diaphragm 126 corresponding to the nozzle 125
Since the position of is supported by the projection 129a of the base 129 as a support portion, the vibrating plate portion of the piezoelectric element adjacent to the deformed piezoelectric element is not unnecessarily bent.

When the vibrating plate 126 returns to the original state after the ink is ejected, the ejected ink is replenished to the pressure chamber through the ink introduction port 124 and the common ink passage 123.

[0019]

Since the conventional ink jet print head is constructed as described above,
The central ends of the two linearly arranged rows must be formed within a limited area. Therefore, for example, 360 dp
In the case of the print density of i, even if the nozzles are arranged in two rows, the nozzle interval is 141 μ, and if the wall thickness separating the nozzle and the ink flow path is 50 μ, the width of the ink flow path is 91 μ. Can be only this width at maximum.

On the other hand, focusing on the substrate forming the ink flow path, the thickness is 0.5 mm or 1.0 depending on how to handle it.
mm is standard, and when the depth of the ink flow path is 0.1 mm, the nozzle depths are 0.4 mm and 0.9 mm,
The ink receives a large resistance during ejection.

Therefore, in order to reduce the ink ejection resistance in the nozzle portion, it is conceivable to reduce the plate thickness of the substrate forming the ink flow path, but the piezoelectric element is susceptible to vibration. It is also possible to increase the drive voltage applied to the piezoelectric element, but in this case, it takes time to attenuate the vibration of the piezoelectric element, and in either case, high-speed printing is difficult.

The present invention has been made to solve the above problems, and reduces the flow path resistance of ink to make the substrate thin and increase the drive voltage applied to the piezoelectric element. It is an object of the present invention to obtain an inkjet print head and an inkjet printer that can realize high-speed printing with high accuracy without any problem.

[0023]

SUMMARY OF THE INVENTION An ink jet print head according to the present invention has a plurality of pressure chambers radially arranged from a central end portion of two linearly arranged lines and surrounding the pressure chambers. A substrate having a common ink passage communicating with the chamber, an ink inlet for supplying ink to the common ink passage, and a straight center end of each pressure chamber formed through the substrate. An ink jet in which a piezoelectric head unit including a nozzle, a vibration plate attached to the pressure chamber forming surface of the substrate, and a piezoelectric element attached to the vibration plate corresponding to each pressure chamber is attached to a base. In the print head, the central ends of the two linear rows are inclined with respect to the printing direction.

Further, in the ink jet print according to the present invention, the ink jet print head is built in a carriage and is reciprocated in the row direction of the recording paper.

[0025]

In the ink jet print head according to the present invention, the central ends of the two linearly arranged rows are inclined with respect to the printing direction to form a straight line. It is possible to widen the end interval and to widen the ink flow path from the pressure chamber to the ink ejection port at the tip of the nozzle. As a result, the flow path resistance of the ink to the nozzle can be reduced, the drive voltage applied to the piezoelectric element may be low, and the vibration damping of the piezoelectric element is accelerated. Further, the substrate forming the ink flow path does not need to be thin, and the influence on the vibration of the piezoelectric element is small,
Responsiveness is improved and accurate high-speed printing can be realized.

[0026]

Embodiment 1 Embodiments of the present invention will be described below with reference to the drawings. Figure 1
Is a plan view of the piezoelectric head unit, and FIG. 2 is an enlarged plan view of a part of the nozzle forming portion.

In FIGS. 1 and 2, a substrate 1 made of a photosensitive glass is provided with a plurality of pressure chambers arranged in a radial pattern from the central end portions of two rows which are linearly inclined and inclined in the printing direction. 2a to 2n, a common ink passage 3 that surrounds the pressure chambers 2a to 2n and communicates with the pressure chamber, and an ink inlet 4 that supplies ink to the common ink passage 3 are formed by etching. A nozzle 5 is formed at the straight center end of each of the pressure chambers 2a to 2n so as to penetrate in the plate thickness direction.

As shown in FIG. 3, is the nozzle 5 tapered toward the ink discharge port with an inclination of 4 ° or more (this system 1)? Alternatively, as shown in FIG. 4, the pressure chamber 2a (~
This is formed so that the outlet size of the nozzle that discharges ink droplets is 1/3 or more of the inlet size of the nozzle 5 that communicates with 2n9 (this method 2).

As described above, the nozzle 5 is connected to the pressure chambers 2a ...
Processing is performed with a taper from the inlet to the outlet communicating with 2n. Alternatively, as a means for processing so that the inlet size is 2.5 or more with respect to the outlet size of the nozzle 5, for example, a photosensitive glass substrate having a pattern mask on its surface is mounted and fixed on the processing base, and the processing base is rotated. By exposing each nozzle forming portion with an exposure optical system (not shown) while rotating and tilting about the axis, the exposure amount around each nozzle forming portion changes. Therefore, when the etching process is performed, the etching amount of the photosensitive glass substrate changes depending on the exposure amount, and it is possible to form a nozzle having a tapered inclination. This processing means is already known.

The nozzles 5 formed at the central ends of the two rows
When the zigzag pattern is formed, the nozzle intervals can be made wider in combination with the fact that the central ends of the two rows are inclined with respect to the printing direction.

A piezoelectric head unit is constructed by attaching a vibrating plate, a piezoelectric element, etc. to the substrate 1 processed as described above, and is assembled on a base as shown in FIG. 14 to construct an ink jet print head. Since it is the same as the conventional one, duplicate description will be omitted.

Next, the operation will be described. Due to the strain of the piezoelectric element to which the signal voltage is applied, the vibrating plate 6 in the portion corresponding to the piezoelectric element is deformed, and the volume of the pressure chamber is changed by this deformation to eject ink from the nozzle 5. After the ink is ejected, when the vibration plate returns to the original state, the ejected ink is replenished in the pressure chamber. This action is also the same as the conventional example shown in FIG. To do.

However, according to the present invention, as described above, the two central rows of the central end nozzles 5 are arranged in a straight line so as to be inclined in the printing direction.
Therefore, for example, in the case of a density of 360 dpi, as shown in FIG. 5, the pitch is 315 μ (141 × √5), and even if the wall thickness separating the flow channels is 50 μ, the flow channel width is 265 μ, and when not slanted. Is about 3 times that of 91 μ.

The ink flow to the nozzle 5 can be made by tapering the nozzle 5 toward the ink ejection port at an inclination of 4 ° or more, or by making the outlet dimension 1/3 or more of the inlet dimension. The path resistance becomes small, and the piezoelectric measures 7a to 7
High-speed printing is possible even if the drive voltage applied to n is low.

The ink flow path resistance (R (N.S /
m ⁵ ) is R = 2 × p × L × U ² / S ^3, where p is viscosity (N · S / m ⁵ ), L is flow path length (m) U is flow path cross-section peripheral length (M) S can be calculated from the flow path cross section (m ² ).

Therefore, regarding the conventional example, method 1 and method 2 of the present invention, the ink flow path resistance R is calculated by the above equations.
When (N · S / m ⁵ ) is calculated, as shown in Table 1, in comparison with the conventional example, in the method 1, the ink flow path resistance R is about 1/2,
In method 2, the ink flow path resistance R is reduced to about 1/3.

Table 1 Conventional example Present method 1 Present method 2 Pressure chamber → nozzle 3.2 × 10 ¹¹ 1.69 × 10 ¹¹ 1.73 × 10 ¹¹ nozzle 3.7 × 10 ¹² 2.39 × 10 ¹² 1. 19 × 10 ¹² whole 4.0 × 10 ¹² 2.56 × 10 ¹² 1.36 × 10 ¹² Example 2 FIG. 6 is a plan view of a substrate showing Example 2 of the present invention.
In the second embodiment, the pressure chambers 2a to 2 are arranged so that the ink ejection characteristics from the nozzles 5 are equalized and the ink flow path resistances from the pressure chambers 2a to 2n to the nozzles 5 are substantially equalized.
The plan shape of n is devised.

Therefore, the center end portions of the pressure chambers 2a to 2n are linearly arranged in two rows inclining with respect to the printing direction, and the nozzle spacing is widened to reduce the ink flow path resistance. Together, the ink can be ejected more smoothly.

Embodiment 3 FIGS. 7, 8 and 9 show the overall structure of an ink jet printer according to the present invention, in which the above mentioned ink jet print head is incorporated.

In each of the drawings, the ink jet printer includes a flat platen 20 in order to make it small and thin as a facsimile, plotter or bar code printer, and a recording sheet not shown in the drawing is a flat platen 20 as shown by an arrow A in FIG. Sent to. In order to properly feed the recording paper, feed rollers 21 and 22 are provided in front of and behind the flat platen 20, respectively, and the recording paper is sandwiched between the idle rollers 23 and 24 facing each other to perform a predetermined amount of feeding action. be able to.

A pair of carriage guides 25 and 26 are provided above the flat platen 20, and a carriage 27 is supported by the carriage guides 25 and 26 so as to be capable of reciprocating in the row direction of the recording paper. Although not shown in detail in the carriage 27, a drive system is connected so that the carriage 27 can be moved to an arbitrary position in the row direction with respect to the recording paper by a driving force such as a stepping motor. Therefore, the carriage 27 can reciprocate in the direction indicated by the arrow BC in the figure.

The carriage 27 incorporates the above-mentioned ink jet print head shown in FIGS. 1 to 6, and the above-mentioned one row of nozzles 5 are arranged so as to face the recording paper guided onto the platen 20. ing.

An ink cartridge 28 is provided below the flat platen 20 in order to supply ink to an ink jet print head built in the carriage 27. From the ink cartridge 28, an ink introduction port of the ink jet print head. The required ink supply towards 4 is provided, for example, through a flexible tube.

Further, the apparatus is provided with a cleaning unit 29 so that the nozzles of the inkjet print head do not solidify when not in use, and the carriage 27 directs the inkjet print head toward the cleaning unit 29 during non-printing. Evacuated.

In order to apply a desired driving force to the recording paper feeding and cleaning unit 29 described above, the feed motor 3 is provided in the ink jet printer as shown in FIG.
0, and a carriage drive motor 31 for driving the above-mentioned carriage 27, each of which is provided with a feed roller 21, through a transmission mechanism (not shown).
22 and the carriage 27 are being driven.

[0046]

As described above, according to the present invention, since the central ends of the two rows are formed in a straight line by inclining with respect to the printing direction, in the case of forming a straight line in a direction orthogonal to the printing direction. It is possible to widen the end interval and to widen the ink flow path from the pressure chamber to the ink ejection port at the tip of the nozzle. As a result, the ink ejection resistance from the nozzle is reduced, the drive voltage applied to the piezoelectric element may be low, and the vibration damping of the piezoelectric element is accelerated. Further, it is not necessary to reduce the plate thickness of the substrate that forms the ink flow path, and the effect on the vibration of the piezoelectric element is small, and high-speed printing with high accuracy can be achieved.

[Brief description of drawings]

FIG. 1 is a plan view of a piezoelectric head unit from which a diaphragm according to a first embodiment is removed.

FIG. 2 is an enlarged plan view of a part of the nozzle forming portion of FIG.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a cross-sectional view of a nozzle portion.

FIG. 5 is an explanatory view of the principle of the present invention.

FIG. 6 is a plan view of a piezoelectric head unit from which a diaphragm according to the second embodiment is removed.

FIG. 7 is a plan view of a main part of an inkjet printer having a print head according to the present invention built therein.

FIG. 8 is a front view of a main part of the inkjet printer shown in FIG.

FIG. 9 is a side view of essential parts of the inkjet printer according to the present invention shown in FIGS.

FIG. 10 is a diagram showing the basic principle of a piezoelectric head unit.

FIG. 11 is a plan view of a piezoelectric head unit with a diaphragm removed.

FIG. 12 is an enlarged plan view of a part of the nozzle forming portion of FIG. 11.

13 is a cross-sectional view taken along the line BB of FIG.

14 is a cross-sectional view of a conventional inkjet printhead in which the piezoelectric head unit of FIG. 12 is assembled on a base.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2a-2n Pressure chamber 3 Common ink path 4 Ink inlet 5 Nozzle 126 Vibrating plate 127a-127n Piezoelectric element

Front page continued (72) Inventor Akihiro Shimohiro, 21, Saiin Mizozaki-cho, Ukyo-ku, Kyoto City, Kyoto Prefecture Rome Co., Ltd. (72) Inventor Shinsaku Takada, 21st Saizo Mizozaki-cho, Ukyo-ku, Kyoto City, Kyoto Prefecture

Claims (4)

[Claims] 1. A large number of pressure chambers radially arranged from a central end portion of two linear rows, a common ink passage surrounding each pressure chamber and communicating with the pressure chambers, and a common ink passage. A substrate having an ink inlet for supplying ink to the nozzle, a nozzle formed at the linear center end of each pressure chamber through the substrate, and attached to the pressure chamber forming surface of the substrate. And a piezoelectric element attached to the vibrating plate corresponding to each of the pressure chambers, the ink jet print head having a piezoelectric head unit mounted on a base. An inkjet print head, wherein a central end portion of a row is formed to be inclined with respect to a printing direction. 2. The ink jet print head according to claim 1, wherein the nozzle is formed with a taper inclination of 4 ° or more toward the terminal ejection port. 3. The ink jet print head according to claim 1, wherein an inlet size of the nozzle to which ink is supplied is 2.5 or more with respect to an outlet size of the nozzle communicating with the pressure chamber. 4. A carriage that is capable of reciprocating in a row direction with respect to a platen holding a recording sheet, the carriage being provided with an ink jet print head, and the ink jet print head is linearly arranged in two rows. A substrate formed with a large number of pressure chambers arranged in a radial manner from the central end of the A nozzle formed by penetrating the substrate at the linear center end of each pressure chamber, a vibration plate attached to the pressure chamber forming surface of the substrate, and corresponding to each pressure chamber. A piezoelectric head unit including: a piezoelectric element attached to the vibration plate; and a piezoelectric head unit including the piezoelectric element are assembled to a base, and the central ends of the two linearly arranged rows are inclined with respect to the printing direction. Special Inkjet printer to.