JP2003062994A - Ink-jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet head with the endurance with respect to repeated deformation improved in a vibration plate comprising an island part and a thin part to be bonded with a piezoelectric element. SOLUTION: The island shape is provided such that the island width is made wider toward the center part in the major axis direction with a larger displacement amount according to the displacement amount of the piezoelectric element tip end as the contact point of a piezoelectric element and an island part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of an on-demand type ink jet head used in office and industrial ink jet printers.

[0002]

2. Description of the Related Art In on-demand type ink jet, as a method for ejecting ink, a thermal method in which bubbles are generated in the ink by an electric heater to eject the ink, and a part of the wall surface of the pressure chamber is used by using a piezoelectric element. There is a piezoelectric element method that deforms and ejects ink.

The thermal method has an advantage that fine processing can be performed by a lithographic technique and the nozzle pitch can be 100 μm or less, but the boiling point of the ejected liquid is limited to about 100 ° C. However, it may be a hindrance in terms of industrial application due to the limitation of the types.

Unlike the thermal method, the piezoelectric element method has the advantage of not selecting the type of ink, and can be said to be suitable for industrial applications.

The present invention relates to a piezoelectric element system.

The piezoelectric element system can be classified into three types in terms of structure. First, a groove is provided in a block of a piezoelectric element, an electrode is provided on a wall of the groove, and the wall is moved in a share mode to eject ink. Secondly, a piezoelectric element plate is attached to a vibration plate and driven in a bending mode of the piezoelectric element. Thirdly, a long rod-shaped piezoelectric element is attached to a vibration plate at a right angle and driven in an expansion / contraction mode of the piezoelectric element. The present invention relates to the third method.

In general, an ink jet print head has a plurality of nozzles arranged in one head. When manufacturing this type, the following manufacturing method is used.

First, a plurality of laminated piezoelectric element rods are adhered to the piezoelectric element fixing plate, and the piezoelectric element rods are cut with, for example, a dicing saw so that one piezoelectric element piece corresponds to one nozzle.

As a measure for improving the dimensional accuracy,
The laminated piezoelectric element rod is adhered to the piezoelectric element fixing plate, and then, with reference to a specific position on the piezoelectric element fixing plate, from the specific position to the free end side of the laminated piezoelectric element rod in the d33 direction. On the piezoelectric element fixing plate, the distance to one side where the end surface and the side surface are in contact with each other and the distance between the two sides where the end surface and the side surface on the free end side in the d33 direction of the laminated piezoelectric element rod are in contact are constant values. Dicing is performed based on the specific position of.

In recent years, the nozzle pitch has tended to become smaller in order to improve the recording density of ink jet heads. Along with this, the pressure chambers also become denser and the width of the pressure chambers becomes smaller. Therefore, in order to efficiently deform the pressure chambers, it is more important to transmit the displacement of the piezoelectric element to the center of the pressure chambers. That is, depending on the positional relationship between the piezoelectric element and the vibrating plate, there are great adverse effects on the printing result, such as variations between nozzles and the occurrence of ink mist.

Therefore, in order to accurately transmit the displacement of the piezoelectric element to a predetermined position of the vibration plate to efficiently deform the entire pressure chamber, a convex portion, a so-called island portion, is formed at a predetermined position of the vibration plate of each pressure chamber. And a piezoelectric element is adhered to the island portion and a displacement of the piezoelectric element is transmitted to the diaphragm.

On the other hand, when the nozzle pitch is reduced, the compliance of the entire pressure chamber also decreases. Therefore, the compliance is adjusted to an appropriate value by further thinning the thin portion of the diaphragm or reducing the area of the island.

Also in the above structure, the piezoelectric element requires the same amount of displacement as the conventional one, and as a result, the force generated by the piezoelectric element is also equal.

If the thin portion is made thinner than the conventional one for adjusting the compliance of the pressure chamber, the thin portion may be damaged due to repeated fatigue.

Further, when the area of the island is made small, the adhesion area of the piezoelectric element and the island becomes small, and the adhesion part of the piezoelectric element and the island may be separated.

In particular, when a d33 type piezoelectric element is used, due to its structure, the amount of displacement of the central portion in the major axis direction of the island on the surface contacting the island is large, so that damage or piezoelectric damage occurs from the central portion of the thin portion. There is a problem that the central portion of the bonded portion between the element and the island is easily peeled off.

[0017]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to improve the durability of a diaphragm having an island portion and a piezoelectric element and an island portion. An object of the present invention is to provide a structure of an inkjet head that can improve the durability of the adhesive portion of the inkjet head.

[0018]

In order to achieve the above object, in the present invention, a pressure chamber for accumulating ink, a piezoelectric element for generating a pressure fluctuation in the pressure chamber by applying an electric signal, and a wall surface of the pressure chamber. A vibration plate that forms at least a part of the piezoelectric element and is connected to the piezoelectric element, an ink supply port that supplies ink to the pressure chamber, a common ink channel that supplies ink to the ink supply port, and an ink droplet. An ink jet head composed of an orifice for ejecting the ink from a pressure chamber and a piezoelectric element fixing plate for fixing the piezoelectric element, and the pressure chamber has an orifice at one longitudinal end and an ink supply port at the other end. And the diaphragm is formed as a flat recess having a major axis in one direction,
In the ink jet head for transmitting the displacement of the piezoelectric element to the pressure chamber via the island portion, the vibration plate has an island portion with a thin periphery, and the island portion has an end portion in the longitudinal direction and a center portion. It is characterized in that the width is different between the parts.

Further, the shape of the island portion is selected so that the width is narrow at the end portion side in the major axis direction and wide at the central portion.

Further, the island portion is divided into at least two or more.

Further, the island portion is divided into at least two or more in the major axis direction, the minor axis direction, or both axial directions.

Further, the area of each of the two or more divided island portions is different, and the area on the end side of the island portion in the long axis direction is small and the area is large at the central portion. Is selected.

In addition, the island portion divided into two or more has the same area per one, and the shape is such that the number of the islands is small on the end side in the long axis direction and is large in the central portion. Is selected.

The island portion is polygonal, elliptical, rhombic, cross-shaped or circular.

Further, the ratio of the width of the end portion of the island in the long axis direction to the width of the central portion thereof is proportional to the ratio of the displacement amounts of the respective abutting portions of the tip of the piezoelectric element abutting on the island portion. And

Further, the piezoelectric element has electrodes and piezoelectric materials alternately laminated in the ink ejection direction and has a piezoelectric constant d33. The piezoelectric element is in contact with the island portion and is fixed with an adhesive. It is characterized by

Further, on the end side in the major axis direction of the island portion, the width of the island portion is narrower than the width of the piezoelectric element, and in the central portion, the width of the island portion is wider than the width of the piezoelectric element. Characterize.

[0028]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings.

1 and 2 are a sectional view and a perspective view showing the structure of the nozzle portion of the ink jet head used in the present invention. This head can perform recording by ejecting ink according to an input signal.

In FIG. 1, 1 is an orifice, 2 is a pressure chamber, 3 is a vibrating plate, 3a is an island, 3b is a thin portion, 3
Reference numeral c is an outer peripheral portion, 4 is a d33 type piezoelectric element, 5 is a piezoelectric element fixing plate, 6 is a restrictor which connects the common ink supply passage 7 and the pressure chamber 2 and controls the inflow of ink into the pressure chamber 2, and 7 is Common ink supply path, 8 is a restrictor plate that forms the restrictor 6, 9 is a pressure chamber plate that forms the pressure chamber 2, 10 is an orifice plate that forms the orifice 1, 11 is a common ink supply path plate, and 12 is a filter , 13a, 13b are internal electrodes of the d33 type piezoelectric element.

The restrictor plate 9, the pressure chamber plate 10, and the common ink supply path plate 11 are made of, for example, stainless steel, and the orifice plate 11 is made of stainless or nickel that can be formed by electroforming. The piezoelectric element fixing plate 6 is made of an insulating material such as ceramics or polyimide.

Ink flows from upstream to downstream from an ink tank (not shown) in the order of the common ink flow path 8, the restrictor 6, the pressure chamber 2, and the orifice 1.

The piezoelectric element 4 is attached so as to expand when a potential difference occurs. For this reason, when the piezoelectric element 5 contracts, the diaphragm 3 contracts downward in the figure, whereby the pressure chamber 2 is filled with ink, and when a potential difference occurs again, the piezoelectric element 4 is restored and the diaphragm 3 Also deforms following this. Therefore, the ink droplet is ejected from the orifice 1.

Since the pressure chambers 2 are formed in a rectangular shape, it is possible to shorten the interval between adjacent nozzles and arrange them at a high density, and also to increase the axial length to secure the volume. In the piezoelectric element 4, the internal electrodes 13a and 13b intersect with each other around the center of the pressure chamber in the long axis direction.

FIG. 2 shows an example of a piezoelectric element fixed to the island, the thin portion, the outer peripheral portion and the island portion with an adhesive. The island portion 3a, which is an island-shaped convex portion that abuts the piezoelectric element 4, is formed. Has been formed.

The island portion 3a and the thin portion 3b are made of metal such as stainless steel or nickel, or silicon, glass,
It is made of photosensitive resin. There are two types of methods, a method of combining separate members and a method of molding one material.

As an example of a method of combining separate members, a material in which stainless steel and a photosensitive resin are laminated is used, and the photosensitive resin portion is exposed and developed to form a convex island portion, a thin portion, and an outer periphery. The part can be configured with high precision.

As a method for molding one material, a metal such as nickel can be molded by electroforming (electroforming) or silicon or glass can be molded by etching.

The piezoelectric element 4 is positioned on the island portion 3a and fixed with an adhesive.

By these manufacturing methods, it is possible to suppress the variation between nozzles or the generation of ink mist due to the problem of the bonding position accuracy between the piezoelectric element and the vibration plate.

Here, as shown in FIG. 4, a length of 1.5 m in the major axis direction in contact with the island portion of the d33 type piezoelectric element.
At m, the displacement amount is larger in the central portion. This is due to the structure of the piezoelectric element. Since the internal electrodes do not intersect at the end portions that contact the external electrodes (not shown), basically no displacement force is generated. Therefore, from the central portion where the displacement amount is large, the thin portion is easily damaged, or the adhesive portion between the piezoelectric element and the island is easily peeled off.
As shown in Fig. 3, the island is hexagonal, and the width of the island is made approximately proportional to the displacement of the piezoelectric element to widen the central part in the long axis direction. The applied stress is almost uniform, and the diaphragm is not damaged from the central portion where the displacement is large. For example, the displacement amount of the piezoelectric element is 0.2 μm at the end as shown in FIG.
It is 0.4 μm in the central portion. Therefore, the shape of the island is 0.05 mm at the end w1 of the piezoelectric element and 0.
It was set to 10 mm.

In the above-described example of the present invention, the island portion is formed as a hexagon, but as shown in FIG. 3A, it is oval, and as shown in FIG. A shape in which a part is inflated, a rhombus as shown in FIG. 3 (c), and an island part divided into two or more as shown in FIG. 3 (d) to gradually increase the size of the central island, As shown in FIG. 3 (d), it is obvious that the same effect is exerted even if the number of central islands is increased.

The width of the island in the minor axis direction may be longer or shorter than the width of the piezoelectric element. Especially, when the adhesive strength near the central portion of the bonded portion between the piezoelectric element and the island becomes a problem, In the long axis direction of the island, the width of the island is shorter than the width of the piezoelectric element at the end, and the width of the island is longer than the width of the piezoelectric element at the central portion where the displacement is large, so that the adhesive strength of the central portion is increased. It is possible to improve.

The island portion divided into two or more shown in FIGS. 3D and 3E needs to be formed inside the long side of the piezoelectric element. In the shapes shown in FIGS. 3D and 3E, the compliance of the thin portion can be easily controlled by the number and size of the islands, and in the high pitch nozzle, the design width of the compliance of the diaphragm is widened, Greater freedom of design.

[0045]

According to the present invention, a pressure chamber for storing ink, a piezoelectric element for generating pressure fluctuation in the pressure chamber by applying an electric signal, and at least a part of a wall surface of the pressure chamber are formed, A diaphragm connected to the element, and a restrictor serving as a flow path for supplying ink to the pressure chamber,
An on-demand type ink jet head having a common ink supply path for supplying ink to the restrictor, an orifice for ejecting ink droplets from a pressure chamber, and a plurality of nozzles configured by a piezoelectric element fixing plate or the like for fixing the piezoelectric element. The diaphragm is formed as a flat recess having a major axis in one direction, and the diaphragm has an island portion having a thin peripheral portion, and the displacement of the piezoelectric element is transferred through the island portion. In the inkjet head that transmits to the pressure chamber, the width of the central part of the island part in the long axis direction of the pressure chamber is made wider, so even if the displacement amount of the piezoelectric element is increased, the thin wall near the center where the piezoelectric element is displaced most There is no preferential damage from the part or peeling from the vicinity of the central part of the bonded part between the piezoelectric element and the island. In other words,
Even if the displacement amount of the piezoelectric element is the same as the conventional one, it is possible to cope with a larger number of driving times and to prolong the life.

[Brief description of drawings]

FIG. 1 is a nozzle cross-sectional view of an inkjet head used in the present invention.

FIG. 2 is a perspective view of a nozzle of the inkjet head used in the present invention.

FIG. 3 is an enlarged view showing a shape of an island portion used in the present invention.

FIG. 4 is a graph showing a displacement amount of the piezoelectric element used in the present invention and an example of a graph in which the width of the island in the minor axis direction is changed according to the displacement amount.

[Explanation of symbols]

1 is an orifice, 2 is a pressure chamber, 3 is a vibrating plate, 3a is an island part, 3b is a thin part, 3c is an outer peripheral part, 4 is a piezoelectric element, 5 is a piezoelectric element fixing plate, 6 is a restrictor, and 7 is a common ink. Supply path, 8 is a restrictor plate, 9 is a pressure chamber plate, 10 is an orifice plate, 11 is a common ink supply path plate, 12 is a filter, and 13a and 13b are piezoelectric element internal electrodes.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C057 AF68 AG47 AG53 AP25 BA03                       BA14

Claims (10)

[Claims] 1. A pressure chamber for storing ink, a piezoelectric element for generating pressure fluctuation in the pressure chamber by applying an electric signal, and at least a part of a wall surface of the pressure chamber, the piezoelectric element being connected to the piezoelectric element. A vibrating plate, an ink supply port for supplying ink to the pressure chamber, a common ink flow path for supplying ink to the ink supply port, an orifice for ejecting ink droplets from the pressure chamber, and the piezoelectric element. An inkjet head composed of a piezoelectric element fixing plate, etc.
The pressure chamber communicates with the orifice at one end in the major axis direction and the ink supply port at the other end, and the vibrating plate is
In an inkjet head, which is formed as a flat recess having a long axis in one direction, the vibrating plate has an island portion with a thin periphery, and the displacement of the piezoelectric element is transmitted to the pressure chamber via the island portion. The ink jet head is characterized in that the island portion has different widths at its longitudinal end and central portion. 2. The ink jet recording apparatus according to claim 1, wherein the island portion has a shape selected such that a width thereof is narrow at an end portion side in a long axis direction and a width thereof is wide at a central portion thereof. head. 3. The ink jet head according to claim 1, wherein the island portion is divided into at least two. 4. The island portion is divided into at least two or more in the major axis direction, the minor axis direction, or both axial directions thereof.
The inkjet head described in 1. 5. The island portion divided into two or more has a different area per one, and the area on the end side of the island portion in the long axis direction is small, and the area is large at the central portion. Is selected,
And the inkjet head described in 4. 6. The island portion divided into two or more has the same area per one, and is shaped so that the number of the islands is small on the end side in the long axis direction and is large in the central part. The inkjet head according to claim 4, wherein is selected. 7. The island portion has a polygonal shape, an elliptical shape, a rhombus shape, a cross shape, or a circular shape.
The inkjet head described in 1. 8. The ratio of the widths of the end portion and the central portion in the long axis direction of the island is proportional to the ratio of the displacement amounts of the abutting portions of the tip of the piezoelectric element abutting the island portion. The inkjet head according to claim 1. 9. The piezoelectric element has electrodes and piezoelectric materials alternately laminated in the ink ejection direction to have a piezoelectric constant d33,
The inkjet head according to claim 1, wherein the piezoelectric element is in contact with the island portion and is fixed with an adhesive. 10. A width of the island portion is narrower than a width of the piezoelectric element on an end portion side of the island portion in a long axis direction, and a width of the island portion is wider than a width of the piezoelectric element in a central portion. The ink jet head according to claim 1, which is characterized in that.