JPH11254671A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an ink jet head for eliminating a complicated driving condition without increasing a size of the head. SOLUTION: In the ink jet head for supplying an ink from an ink tank to pressure chambers 21a, 21b via a channel to apply a pressure via a pressure applying means to the chamber at a predetermined time to inject ink particles from orifice discharge holes 11a, 11b, the one chamber 21a is provided for the one hole 11a, and a plurality of pressure applying means are provided for the one chamber 21a. And, the chamber 21a is divided into a plurality via communicating channels 32, and a plurality of the pressure applying means corresponding to the plurality of the chambers are constituted.

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, and more particularly to an ink-jet head for expressing gradation.

[0002]

2. Description of the Related Art In a conventional ink jet recording system, there are the following two methods for expressing gradation. A unit pixel is composed of a plurality of recording dots, and gradation is expressed by changing the number of recording dots in the pixel. The unit pixel is composed of one recording dot, and performs gradation expression by changing the dot diameter to be recorded.

[0003] Of the above methods, the method is relatively simple, but: The unit pixel is large.・ The number of dots to be printed increases compared to, and printing is slowed.・ The screen feels grainier than. This method requires a "head structure" or "control means" for ejecting recording dots of different diameters, and has a more complicated configuration than that, but has the following advantages.

[0004] The unit pixel is small.・ Recording is fast.・ The dot gradation is natural. The following method is used as a means for generating recording dots having different diameters to realize the above method.

(A) Several types of ejection means are provided in a head, and the size of a dot is changed for each of them. (B) Only a single type of ejection means is provided in the head, and in actual printing, the driving dot condition is changed by controlling the driving conditions applied to the ejection means in accordance with the gradation level. Value, drive pulse width, etc.).

[0006]

However, the method shown in (a) above requires a number of drive units corresponding to the number of gradations, increases the number of components, and increases the manufacturing costs such as component costs and assembly costs. . There is also a problem that the size of the head becomes large.

The method (b) has a simple structure of the head itself, but requires a plurality of levels of voltage generating means and different pulse width generating means. When the normal driving condition is changed, the ejection speed changes and the recording position also changes, so that a control algorithm for correcting the change is required. There is a problem.

The present invention has been made to solve the above problems, and has as its object to realize an ink jet head which does not require complicated driving conditions without increasing the size of the head.

[0009]

In order to achieve such an object, the present invention provides: Ink is supplied to the pressure chamber from the ink tank through the flow path, and when necessary, pressure is applied to the pressure chamber by the pressure applying means, and ink particles are ejected from the orifice ejection hole. An ink jet head comprising one pressure chamber and a plurality of pressure applying means for the one pressure chamber. 2. An ink jet head comprising: a plurality of pressure chambers divided into a plurality of pressure chambers through communication passages; and a plurality of pressure applying means corresponding to the plurality of pressure chambers.

[0010] 3. 3. The ink jet head according to claim 2, wherein the pressure chambers have different capacities. 4. 3. The ink jet head according to claim 2, wherein the pressure chambers are formed in parallel.

5. 3. The ink jet head according to claim 2, wherein the pressure chambers are formed in tandem. 6. 3. The ink jet head according to claim 1, wherein the pressure applying means is a piezoelectric actuator configured to be selectively driven by a plurality of vibration plates attached to predetermined portions of the plate-shaped piezoelectric material. 7. 3. The ink jet head according to claim 1, wherein the pressure applying means is a piezoelectric actuator configured to be selectively driven by a plurality of diaphragms and lead wires attached to predetermined portions of the plate-shaped piezoelectric material. 8. 3. The piezoelectric actuator according to claim 1, wherein the pressure applying means is a piezoelectric actuator configured to be selectively driven by a plurality of diaphragms and lead wires formed in a film shape at predetermined locations on the plate-shaped piezoelectric material. Ink jet head. It is what constituted.

[0012]

In the above configuration, the following operations are sequentially performed.
According to the first and second aspects, one pressure chamber is provided for one orifice discharge hole, and a plurality of pressure applying means are provided for this pressure chamber. A key change can be obtained. .

In the third aspect,. Since the pressure chambers are formed so as to have different capacities, fine gradation changes can be obtained. In the fourth and fifth aspects, by forming the pressure chambers in parallel or in tandem, the degree of freedom in designing the ink jet head can be increased.

In claims 6, 7, and 8, Since the pressure applying means is selectively driven by a plurality of diaphragms formed in a film shape at predetermined positions of the plate-shaped piezoelectric material, assembly is simple and accurate.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. 1 (a) and 1 (b) show an ink jet head showing an example of an embodiment of the present invention. FIG. 1 (a) is an assembled view, and FIG. 1 (b) is an exploded perspective view of FIG. 1 (a). FIG.
As shown in FIG. 1B, the ink jet head shown in FIG. 1A has an orifice plate 1 having first and second orifice discharge holes 11a and 11b, first and second recesses 21a and 21b, and a common ink chamber 22. Base plate 2 having ink supply port 23 and ink supply port 23
And a flow path plate 3 in which first and second through holes 33 and 34 formed corresponding to the shapes of the first and second recesses 21a and 21b, the communication flow path 32, and the ink flow path 31 are formed. Main diaphragm 7
3. The sub vibrating plate 74 and a plate-like piezoelectric material made of a piezoelectric material such as PZT on which the electrode terminals 72 and the lead wires 83 are formed are laminated by bonding with an adhesive or the like.

The first through hole 33b and the second through hole 34b
Are separated by partitioning pieces 35, and an electrode is formed on the back surface of the piezoelectric material 7, and the back surface electrode is set to the ground potential by wiring of another path (not shown). The shape of the first and second concave portions 21a and 21b is described later with reference to FIG.
As shown in FIG. 7, the inclined portion is formed so as to be inclined toward the bottom and open above the orifice hole.

Of the above members, the orifice plate 1 and the flow path plate 3 are formed by metal etching, metal pressing, or the like by appropriately using, for example, a stainless steel plate having a thickness of about several tens to 200 μm. The diaphragms 73 and 74 are formed in a film shape by silver printing, plating, or the like. Orifice discharge hole 11
Is about 30 to 100 μm, but is formed at the same time as the orifice plate 1 is formed by etching.

In the above configuration, in a state where the respective members are stacked, the first concave portion 21a of the base plate 2, the first through hole 33a of the flow path plate 3, and The main vibrating plate 73a formed on the piezoelectric material 7 is disposed so as to be positioned, and the second concave portion 21b of the base plate 2 and the first
The through hole 33b and the main diaphragm 73b formed in the piezoelectric material 7
Are arranged to be located.

Here, the first and second concave portions 21a and 21b and the first through holes 33a and 33b form a main pressure chamber, and the second through holes 34a and 34b form a sub pressure chamber. That is, the main pressure chambers are formed by the first and second concave portions 21a, 21a formed in the base plate 2.
1b and the first through holes 33a, 33 formed in the flow path plate 3.
3b plus the volume formed by the area and thickness,
The sub-pressure chambers are formed in the second through holes 34a, 34a formed in the flow path plate 3.
The volume is formed by the area and the thickness of 4b.

After the ink is filled from the ink tank (not shown) through the common ink chamber 23, the ink flow path 31, and the first and second recesses to the orifice discharge hole 11, a voltage pulse is applied to the piezoelectric material 7. To eject ink. Hereinafter, the ejection operation will be described with reference to FIGS. In these figures, the figure (a) is an assembled sectional view,
FIG. 2B shows a state in which the piezoelectric material 7 is partially distorted by pulse application.

In FIG. 2A, the surface electrode 5 of the piezoelectric material 7
2, a drive voltage pulse is applied from a drive circuit (not shown) via the electrode terminal 81 at each timing of instructing ink ejection (applied voltage is, for example, 50 V, about 100 μsec). As a result, an electric field is generated in the piezoelectric material 7 in the vertical direction in the figure, and a strain (stress) in a contraction direction is generated in a plane direction orthogonal to the electric field.

The piezoelectric material 7 constitutes a unimorph actuator together with the vibrating plates 73 and 74 attached or formed in a film shape, and this stress causes a drum-shaped displacement as shown in FIG. The generated drum-shaped displacement increases the pressure in the pressure chamber 21 and causes ink to be ejected from the orifice ejection hole 11 of the orifice plate 1.

After the desired amount of ink has been ejected, the voltage application to the piezoelectric material 5 is completed, the displacement of the actuator returns to its original state, the pressure in the pressure chamber 21 once returns to a negative pressure, and then returns to the atmospheric pressure. At this time, ink is supplied from a not-shown ink tank to the pressure chamber 21 via the ink supply port 23, the common ink chamber 22, and the ink flow path 31.

According to the structure shown in FIG. 1, the degree of ink ejection can be changed in two ways when only the main diaphragm 73 or the sub diaphragm 74 is driven, and when both diaphragms are driven simultaneously. , Printing with different gradations becomes possible. By setting the number of pressure chambers and the number of diaphragms corresponding to the pressure chambers to two or more, two or more gradations can be realized.

When configuring such a unimorph type actuator, it is desirable from the viewpoint of driving efficiency that the elastic coefficient and the thickness of the piezoelectric material and the flow path plate be selected in the following relationship. E1 · (t1) ² = E2 · (t2) ² where E1 and E2 are the elastic modulus of the piezoelectric material and the diaphragm t1 and t2 are the thickness of the piezoelectric material and the diaphragm

FIGS. 3A and 3B show another embodiment. FIG. 3A is an assembled perspective view, and FIG. 3B is an exploded perspective view. The reference numerals shown in FIG. 3 have the same functions as those shown in FIG. In this embodiment, for example, the main vibrating plates 73 (a) and 73 (b) and the sub vibrating plate 74 (a) having the same shape as shown in FIG. , (B), the lead wire 83 and the electrode terminal 72 are formed simultaneously. On the back surface of the piezoelectric material 7 (see FIG. 3C), the same function as that formed on the base plate 2 and the flow path plate 3 shown in FIG. 1B is formed by using a technique such as silver printing or plating. I do.

That is, the main pressure chamber 33 in FIG.
The sub-pressure chamber 34 corresponds to the first through holes 33a and 33b of the flow path plate 3 described in FIG.
And the first through holes 34a and 34b of the common ink chamber 22.
1 corresponds to the common ink chamber 22 formed in the base plate 2 shown in FIG. 1B, and the ink flow path 31 corresponds to the ink flow path 31 of the flow path plate 3. However, in the case of this embodiment, the volume of the main pressure chamber is smaller than that of FIG.

Such a structure on both sides of the piezoelectric material 7 can be formed by first forming a silver electrode in a desired shape, and then depositing nickel of a required thickness on the silver electrode by electroplating. . With such a configuration, the flow path plate 3 and the base plate 2 used in FIG.
The number of parts and the number of assembling steps can be reduced. In this embodiment, the shape of the ink supply port 23 is different from that shown in FIG. 1, but does not affect the function of the ink jet head.

FIGS. 4A and 4B show another embodiment. FIG. 4A is an assembled perspective view, and FIG. 4B is an exploded perspective view. The reference numerals shown in FIG. 4 have the same functions as those shown in FIG. In this embodiment, four orifice holes 11 are formed in the orifice plate 1, and four concave portions 21 serving as main pressure chambers are arranged in parallel in the base plate 2 corresponding to the orifice holes 11. Then, four first through-holes 33 corresponding to the concave portions 21 and four second through-holes 34 are formed in the first through-hole in the flow path plate 3 in tandem.
The main vibration plate 73 and the sub vibration plate 74 corresponding to the first and second through holes are formed on the surface by silver printing or plating.

In this embodiment, the first and second through holes 3
The channels 3 and 34 communicate with each other through a flow path 32. According to such a configuration, three gradations can be realized from the four orifice holes 11 as in the case shown in FIG.

FIGS. 5A and 5B show another embodiment. FIG. 5A is an assembled perspective view, and FIG. 5B is an exploded perspective view. The reference numerals shown in FIG. 5 have the same functions as those shown in FIG. In the present embodiment, for example, the main vibration plates 73 (a) and 73 (b) and the sub vibration plate 74 (a) having the same shape as shown in FIG. , (B), the lead wire 83 and the electrode terminal 72 are formed simultaneously. Also, a common ink chamber 22, an ink flow path 31, a communication flow path 32, and a communication flow path corresponding to FIG. 4 are simultaneously formed on the back surface (see FIG. C) of the piezoelectric material 7 using a technique such as silver printing or plating. I do.

The structure of both sides of the piezoelectric material 7 is shown in FIG.
First, a silver electrode is formed in a desired shape as in
Next, it can be formed by depositing nickel of a required thickness on the silver electrode by electroplating. With this configuration, the flow path plate 3 and the base plate 2 used in FIG.
Can be eliminated, and the number of parts and the number of assembling steps can be reduced. In this embodiment, although the shape of the ink supply port 23 is different from that shown in FIG. 4, it does not affect the function of the ink jet head.

FIGS. 6A and 6B show another embodiment. FIG. 6A is an assembled perspective view, and FIG. 6B is an exploded perspective view. Note that the reference numerals shown in FIG. 6 have the same functions as those shown in FIG. This embodiment is different from the first embodiment only in that the communication channel 32 connecting the first and second through holes formed in the channel plate 3 shown in FIG. 4 is not formed, and only one through hole 33a is provided. Also in such a configuration, two gradations can be realized from the four orifice holes 11 as in the case of FIG.

FIGS. 7A and 7B show another embodiment. FIG. 7A is an assembled perspective view, and FIG. 7B is an exploded perspective view. Note that the reference numerals shown in FIG. 7 have the same functions as those shown in FIG. In the present embodiment, for example, the main vibration plates 73 (a) and 73 (b) and the sub vibration plate 74 (a) having the same shape as shown in FIG. , (B), the lead wire 83 and the electrode terminal 72 are formed simultaneously. The common ink chamber 2 shown in FIG. 6 is also applied to the back surface of the piezoelectric material 7 (see FIG.
2. Ink channel 31, pressure chamber 33 corresponding to through hole 33
Are simultaneously formed.

The structure of both sides of the piezoelectric material 7 is also shown in FIG.
First, a silver electrode is formed in a desired shape as in
Next, it can be formed by depositing nickel of a required thickness on the silver electrode by electroplating. With this configuration, the flow path plate 3 and the base plate 2 used in FIG.
Can be eliminated, and the number of parts and the number of assembling steps can be reduced.

It is to be noted that the above description of the present invention has been presented by way of explanation and illustration only of particular preferred embodiments. Thus, it will be apparent to one skilled in the art that the present invention may be modified or modified in many ways without departing from its essentials. The scope of the present invention defined by the description in the claims section is intended to cover alterations and modifications within the scope.

[0037]

As described above, according to the present invention, 1) a plurality of pressure chambers for one orifice discharge hole;
By providing a plurality of pressure applying means corresponding to the plurality of pressure chambers and controlling the number of driving the pressure applying means, a change in gradation can be obtained.

2) By forming the pressure chambers in parallel or in tandem, the degree of freedom in designing the ink jet head can be increased. 3) It is easy to assemble because it is formed by applying techniques such as sticking or silver printing or plating to predetermined portions of the plate-shaped piezoelectric material.
And it can be manufactured with high accuracy. 4) Since the ink jet head is selectively driven by the plurality of diaphragms, the size of the ink jet head can be reduced, and the gradation can be expressed without increasing the size. 5) There is no increase in the number of components due to gradation.

6) In addition, by driving a plurality of vibrating sections associated with the same discharge port at different timings,
Higher order resonance vibration in the recording head can be suppressed,
The efficiency of ink supply from the common ink chamber to the pressure chamber can be increased, and the pressure in the pressure chamber can be adjusted for each time to adjust the shape of the discharged droplet.

[0040]

[Brief description of the drawings]

FIG. 1 is a perspective view (a) and an exploded perspective view (b) of an ink jet head showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating an ink ejection state of the inkjet head of the present invention.

FIG. 3 is a perspective view (a) and an exploded perspective view (b) of an ink jet head showing another embodiment of the present invention.

FIG. 4 is a perspective view (a) and an exploded perspective view (b) of an ink jet head showing another embodiment of the present invention.

FIG. 5 is a perspective view (a) and an exploded perspective view (b) of an ink jet head showing another embodiment of the present invention.

FIG. 6 is a perspective view (a) and an exploded perspective view (b) of an inkjet head showing another embodiment of the present invention.

FIG. 7 is a perspective view (a) and an exploded perspective view (b) of an ink jet head showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Orifice plate 2 Base plate 3 Flow path plate 7 Piezoelectric material 8 Voltage application member 11 Orifice hole 21 Depression (pressure chamber) 22 Common ink chamber 23 Ink supply port 31 Flow path 35 Partition piece 72 Electrode terminal 73, 74 Vibration plate 83 Lead line

Claims (8)

[Claims] 1. An ink jet head in which ink is supplied from an ink tank to a pressure chamber via a flow path, and pressure is applied to the pressure chamber by a pressure applying means when necessary to eject ink particles from an orifice discharge hole. An ink jet head, wherein one pressure chamber is provided for one orifice discharge hole, and a plurality of pressure applying means are provided for the one pressure chamber. 2. The ink jet head according to claim 1, wherein the pressure chamber is divided into a plurality of sections through a communication channel, and a plurality of pressure applying means corresponding to the plurality of pressure chambers are provided. 3. The ink jet head according to claim 2, wherein the pressure chambers have different capacities. 4. The ink jet head according to claim 2, wherein the pressure chambers are formed in parallel. 5. The ink jet head according to claim 2, wherein the pressure chambers are formed in tandem. 6. The piezoelectric actuator according to claim 1, wherein the pressure applying means is a piezoelectric actuator configured to be selectively driven by a plurality of diaphragms attached to predetermined portions of the plate-shaped piezoelectric material. The inkjet head according to the above. 7. The piezoelectric actuator according to claim 1, wherein the pressure applying means is a piezoelectric actuator configured to be selectively driven by a plurality of diaphragms and lead wires attached to predetermined portions of the plate-shaped piezoelectric material. The inkjet head according to any one of the above. 8. The piezoelectric actuator according to claim 1, wherein the pressure applying means is a piezoelectric actuator configured to be selectively driven by a plurality of diaphragms and lead wires formed in a film shape at predetermined locations of the plate-shaped piezoelectric material. 6. The ink jet head according to any one of 1 to 5.