JPH1170652A - Structure of on-demand type multinozzle ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with a fixed part piezoelectric element by providing a support plate for a vibration plate to the surface on the side opposite to the wall surface of a pressure chamber of the vibration plate and forming an ink common supply passage on the support plate. SOLUTION: A pressure chamber 2 is formed by a pressure chamber plate 11 and the support plate 13 for reinforcing the vibration plate 3 is provided to the surface on the side opposite to the pressure chamber 2 of the vibration plate 3. Ink is allowed to flow from an upstream part to a downstream part in the order of a common ink supply passage 8, a restrictor 7, the pressure chamber 2 and an orifice 1. By forming this structure, a nozzle pitch can be reduced without using fixed piezoelectric elements. Further, since the common ink supply passage 8 is arranged on the support plate 13, the cross-sectional area of the passage can be selected regardless of the structure/vol. of an ink chamber and that of the common ink supply passage 8 can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand type ink jet head using a piezoelectric element, and more particularly to the structure of a multi-nozzle ink jet head in which a large number of nozzles are integrated at high density.

[0002]

2. Description of the Related Art There are two types of on-demand type ink jet heads for ejecting ink.
One is a thermal method in which bubbles are generated in the ink by an electric heater to eject the ink, and the other is a piezoelectric element method in which a part of the wall of the pressurizing chamber is deformed and the ink is ejected using a piezoelectric element. is there.

In the thermal method, fine processing is possible by the photolithography technique, and the nozzle pitch is set to 100 μm.
It has the following advantages, but has the disadvantage that the boiling point of the liquid to be injected is limited to about 100 ° C. and the frequency at the time of continuous injection is limited to about 10 kHz.

On the other hand, the driving frequency of the piezoelectric element method can be set to 20 kHz or more because the driving frequency depends on the shape of the piezoelectric element, and can be said to be a method suitable for increasing the printing speed. Also,
There is also an advantage that the type of ink is not selected unlike the thermal method. However, since the displacement of the piezoelectric element is small, it is necessary to increase the surface area of the diaphragm of the pressurizing chamber for ejecting ink, so that the nozzle pitch can be reduced only to about 140 μm. Therefore, high integration of the piezoelectric element type head is required.

A conventional example of a highly integrated head is disclosed in Japanese Unexamined Patent Publication No.
No. 142324. FIG. 5 is a cross-sectional view of the piezoelectric element viewed in the column direction, and FIG. 6 is a cross-sectional view of the piezoelectric element viewed in a direction perpendicular to the column.

In FIG. 5, a piezoelectric element 2 is placed on a substrate 20.
1 is fixed, cuts a rectangular parallelepiped rod-shaped piezoelectric element,
Divided. An ink common supply path 2 next to the pressurizing chamber 22
There are three. Further, as can be seen from FIG. 6, a fixed part piezoelectric element 24 is provided next to the piezoelectric element corresponding to the ink pressurizing chamber. This is presumably for fixing and supporting the diaphragm and the members forming the pressure chamber.

In the conventional structure, the common ink supply path 2
Since 3 is on the same side as the ink pressurizing chamber with respect to the vibration plate 25, the structures of the common ink supply path 23 and the pressurizing chamber 22 influence each other. Specifically, for ink ejection at a high driving frequency, the smaller the volume of the pressurizing chamber 22 is, the higher the Helmholtz frequency is, which is advantageous. However, when the volume of the pressurizing chamber 22 is reduced, in the case of the structure just taken up, the flow path cross-sectional area of the ink common supply path 23 is limited, which restricts the ink supply and increases the number of nozzles at high speed. Ink supply shortage when driven with
There is a risk of printing failure. Further, in the above-described structure, since the fixed portion piezoelectric element 24 is used as shown in FIG. 6, there is an obstacle in reducing the nozzle pitch.

[0008]

SUMMARY OF THE INVENTION The present invention proposes a highly integrated on-demand type multi-nozzle print head structure which eliminates the above-mentioned obstacles of ink supply and obstacles of shortening the nozzle pitch.

[0009]

According to the present invention, there is provided a pressure chamber for storing ink, a piezoelectric element for generating a pressure change in the pressure chamber by applying an electric signal, and A vibrating plate that forms at least a part of a wall surface of the chamber and is connected to the piezoelectric element with an elastic material, a restrictor serving as a flow path for supplying ink to the pressurizing chamber, and supplying ink to the restrictor In the structure of an on-demand type multi-nozzle ink jet head having a plurality of nozzles constituted by a common ink supply path and an orifice serving as an ejection port for ejecting ink droplets from a pressurizing chamber, the pressure of the vibration plate is increased. A support plate for supporting the vibration plate is provided on the surface opposite to the chamber wall surface, and the ink common supply path is formed on the support plate.

[0010] According to the above configuration, the fixed portion piezoelectric element becomes unnecessary. With this structure, it is possible to increase the cross-sectional area of the common ink flow path and reduce the nozzle pitch.

Preferably, the piezoelectric element is formed by fixing one end of a laminated piezoelectric element rod to a fixed substrate and then cutting a predetermined number corresponding to the nozzle. The plurality of nozzles may be arranged in at least two or more rows.

[0012]

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

FIG. 1 is a cross-sectional view showing the structure of a nozzle portion of a multi-nozzle ink jet head according to the present invention. This head can perform recording by ejecting ink in response to an input signal.

1 is an orifice, 2 is a pressurizing chamber, 3 is a vibration plate, 4 is a piezoelectric element, 5a and 5b are signal input terminals, 6 is a piezoelectric element fixed substrate, 7 is a common ink supply path 8 and a pressurizing chamber 2 , A restrictor 9 for controlling the flow of ink into the pressurizing chamber 2, an elastic material 9 (for example, a silicone adhesive) connecting the diaphragm 3 and the piezoelectric element 4, and a restrictor 10 for forming the restrictor 7. Reference numeral 11 denotes a pressure chamber plate forming the pressure chamber 2, 12 denotes an orifice plate forming the orifice 1, and 13 denotes a support plate for reinforcing the diaphragm 3.

The vibrating plate 3, restrictor plate 10, pressurizing chamber plate 11, and support plate 13 are made of, for example, stainless steel, and the orifice plate 12 is made of nickel. Further, the piezoelectric element fixing substrate 6 is made of an insulator such as ceramics or polyimide.

In order to increase the natural frequency of the piezoelectric element 4, it is necessary to reduce the length of the piezoelectric element substantially corresponding to the distance between the vibration plate 3 and the piezoelectric element fixing substrate 6, and the driving voltage is extremely high. What does not have to be good Therefore, in the present invention, a d33 type piezoelectric element was selected. However, as long as the piezoelectric element satisfies this condition, its displacement characteristics are not limited.

The ink flows from the upstream to the downstream in the order of the common ink supply path 8, the restrictor 7, the pressurizing chamber 2, and the orifice 1. The piezoelectric element 4 has signal input terminals 5a and 5b
It is attached so that it does not deform when there is no potential difference between the signal input terminals 5a and 5b when a potential difference is applied between the signal input terminals 5a and 5b.

FIG. 2 shows a nozzle array of an ink jet head showing an example of the present invention. As shown in the figure, 32 nozzles are arranged in one row. The figure shows a total of 12 nozzle rows.

FIG. 3 is a sectional view taken along the line AA 'of FIG. In the figure, reference numeral 6 denotes a piezoelectric element fixing substrate for fixing the piezoelectric element.

The order of manufacturing the ink jet head of the present invention will be described below with reference to FIG.

First, a plurality of piezoelectric element bars (not shown) are arranged and adhered and fixed to the piezoelectric element fixing substrate 6. afterwards,
The piezoelectric element rod is divided by a cutting means such as a dicing saw or a wire saw. At this time, each of the divided piezoelectric elements 4
Correspond to the pressurizing chamber 2 on a one-to-one basis. At the time of this division, the smaller the length of the piezoelectric element, the better the yield at the time of division and the longer the life of the cutting tool. In this sense, the piezoelectric element is preferably of the d33 type.

On the other hand, the orifice plate 12, the pressure chamber plate 11, the restrictor plate 10, the vibrating plate 3, and the support plate 13 are bonded together. This combination is called a laminated plate A. Further, the common ink supply path plate 14,
15. The three plates of the common ink supply path plate cover 16 are collectively adhered to prepare a laminated plate B. Next, a combination of the laminated plate A and the laminated plate B integrally bonded and fixed to the piezoelectric element fixing plate mounting plate 17 is referred to as a laminated plate C. By providing, for example, six rows of piezoelectric elements on the above-mentioned piezoelectric element fixing substrate 6, bonding two of them and bonding and fixing them to the laminated plate C, 12 rows of piezoelectric elements can be formed.

FIG. 4 shows a structure in which the heater 18 is attached to the common ink supply path plate cover 16, but this case is based on the assumption that a hot melt ink which is solid at room temperature is used as the ink. . When ink that is liquid at room temperature is used, there is no need to sandwich the heater 18.

With the above structure, the nozzle pitch can be reduced without using a fixed piezoelectric element. Further, since the common ink supply path is arranged on the support plate, the cross-sectional area of the common ink supply path can be selected independently of the structure and volume of the ink chamber, and the cross-sectional area of the common ink supply path can be selected. Can be increased. For this reason, it is possible to contribute to high-speed printing, and to eliminate a shortage of ink supply, which is a concern during high-speed printing.

[0025]

According to the present invention, the nozzle pitch can be reduced, the sectional area of the common ink supply path can be increased, the number of nozzles can be increased with the same volume, and high-speed printing can be performed. In addition, it is possible to avoid printing defects caused by insufficient ink supply, which is a concern during high-speed printing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a nozzle of an inkjet head according to an embodiment of the present invention.

FIG. 2 is a plan view showing the arrangement of an orifice as an example of the present invention.

FIG. 3 is a sectional view taken along line AA 'of FIG. 1;

FIG. 4 is a perspective view illustrating an assembled state of the jet pack.

FIG. 5 is a cross-sectional view of a nozzle of a conventional inkjet head.

FIG. 6 is a sectional view taken along the line BB ′ of FIG. 5;

[Explanation of symbols]

1 is an orifice, 2 is a pressure chamber, 3 is a vibration plate, 4 is a piezoelectric element, 5a and 5b are signal input terminals, 6 is a piezoelectric element fixed substrate, 7 is a restrictor, 8 is a common ink supply path, and 9 is silicon. Rubber, 10 is a restrictor plate, 11 is a pressure chamber plate, 12 is an orifice plate, 13 is a support plate, 14 and 15 are common ink supply path plates, 16 is a common ink supply path plate cover, and 17 is a piezoelectric element fixing plate. The mounting plate 18 is a heater.

Continuing on the front page (72) Inventor Kenichi Hisai 1060 Takeda, Hitachinaka-shi, Ibaraki Prefecture Inside Hitachi Koki Co., Ltd. (72) Inventor Nobuhiro Kurosawa 1060 Takeda, Hitachinaka-shi, Ibaraki Prefecture Inside Hitachi Koki Co., Ltd. (72) Inventor Akiyama Yoshitaka 1060 Takeda, Hitachinaka-city, Ibaraki Pref.Hitachi Koki Co., Ltd. (72) Inventor Nobuhiro Noto 1060 Takeda, Hitachinaka-shi, Ibaraki Pref.Hitachi Koki Co., Ltd. Koki Co., Ltd.

Claims (3)

[Claims] A pressure chamber for storing ink; a piezoelectric element for generating a pressure change in the pressure chamber by applying an electric signal; and a piezoelectric element forming at least a part of a wall surface of the pressure chamber for elasticity. A diaphragm connected by a material, a restrictor serving as a flow path for supplying ink to the pressurizing chamber, a common ink supply path for supplying ink to the restrictor, and ejecting ink droplets from the pressurizing chamber In the structure of an on-demand type multi-nozzle ink jet head having a plurality of nozzles constituted by orifices or the like serving as injection ports for performing a jetting operation, a supporting plate for supporting the diaphragm is provided on the surface of the diaphragm opposite to the wall surface of the pressure chamber. A structure of an on-demand type multi-nozzle ink jet head, wherein the common ink supply path is provided on the support plate. 2. The piezoelectric element according to claim 1, wherein the piezoelectric element is formed by fixing one end of a laminated piezoelectric element rod to a fixed substrate and cutting a predetermined number corresponding to a nozzle. Of on-demand type multi-nozzle inkjet head. 3. The on-demand type multi-nozzle ink jet head according to claim 1, wherein said plurality of nozzles are arranged in at least two rows.