JP3486913B2 - Inkjet head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microactuator for precision equipment to which minute displacement and high speed vibration generated by electric signals are applied. In addition, the pressure generated by the microactuator causes ink droplets to fly,
The present invention relates to an image recording apparatus such as a printer that forms an ink image on a recording medium such as recording paper, and more specifically to an inkjet head.

[0002]

2. Description of the Related Art A piezoelectric material and a conductive (elastic) material are joined together,
Many industrial products apply fine displacement and high-speed vibration generated by electric signals, and are applied to quartz watches, ultrasonic motors, inkjet heads, and the like. Further, as a conventional example relating to the shape of the microactuator, as shown in FIG. 9, a ceramic member 9 is provided on an end surface of the laminated piezoelectric element 10, and the vibrating surface of the laminated piezoelectric element 10 is connected to the nozzle 1.
An on-demand type ink jet head characterized by being arranged so as to face an inlet opening is disclosed in JP-A-1-11563.
No. 8 publication.

[0003]

It is desirable that the laminated piezoelectric element that generates displacement for increasing the pressure in the pressure chamber has excellent displacement efficiency. However, when the end surface of the laminated piezoelectric element having the inactive portion that does not cause the displacement together with the active portion that causes the displacement is joined to the pressure transmitting member, the stress in the vicinity of the joint surface of the inactive portion becomes large. When the smooth surface of the laminated piezoelectric element and the smooth surface of the pressure transmitting member are joined, even if the adhesive is applied only to the active portion, it leaks to the inactive portions adjacent to both sides of the active portion. Due to such a phenomenon, occurrence of internal defects of the laminated piezoelectric element, peeling phenomenon of the bonding surface, and the like have been confirmed. Further, the pressure transmission member joined to the end face of the laminated piezoelectric element has no positioning because the joint surfaces of both the laminated piezoelectric element and the pressure transmission member are smooth surfaces.
As a result, there is a problem in that the positional accuracy with respect to the laminated piezoelectric element and the nozzle opening varies. From such a problem, it is apparent that the reliability and the print quality of the inkjet head are deteriorated and the displacement efficiency is also decreased. According to the present invention, which is intended to improve printing quality, reliability, and displacement efficiency, an inkjet head having excellent reliability and printing quality and low cost, and an inkjet recording apparatus equipped with the same are realized. be able to.

[0004]

An ink jet head of the present invention comprises a nozzle for ejecting ink, a pressure chamber communicating with the nozzle, and a pressure transmitting member for applying pressure to a diaphragm, which is one wall surface of the pressure chamber. In the ink jet head having a laminated piezoelectric element formed by alternately laminating a piezoelectric material and a conductive material for generating a pressure, and a driving unit for applying an electric signal to the laminated piezoelectric element, the pressure chamber of the pressure transmission member is provided. The opposing area is larger than the area of the laminated piezoelectric element, and the surface of the laminated piezoelectric element joined to the pressure transmitting member has a concave shape or a convex shape, and the laminated piezoelectric element of the pressure transmitting member. The surface to be joined to the element has a convex shape or a concave shape, and concave portions are formed on both sides of the active portion on the end surface of the laminated piezoelectric element to be joined to the pressure transmitting member. And butterflies.

Further, the height of the diaphragm is adjusted at the joint surface between the laminated piezoelectric element and the pressure transmitting member.

Further, the height of the diaphragm is adjusted by the thickness of the bonding material applied to the bonding surface between the laminated piezoelectric element and the pressure transmitting member.

Further, the bonding material is applied only to the active portion of the laminated piezoelectric element.

Further, the space formed by the concave shape or the convex shape is an escape groove for accommodating an excessive bonding material. Further, positioning is performed by fitting the inactive portion of the laminated piezoelectric element and the pressure transmitting member.

[0009]

By joining the end surface of the active portion of the laminated piezoelectric element to the fixing member, it is possible to provide an ink jet head having a microactuator which is superior in displacement efficiency and reliability as compared with the case where the inactive portion is also fixed.

[0010]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view showing the structure of a main portion of an ink jet head using the actuator of the present invention.
Reference numeral 2 shown in FIG. 1 is a nozzle formation substrate on which a plurality of nozzles 1 are formed. The opening area of the nozzle 1 and the thickness of the nozzle forming substrate 2 have a great influence on the ink ejection characteristics. In order to ensure excellent printing quality, these variations must be suppressed among a plurality of nozzles, so extremely high processing accuracy is required. Therefore, the nozzle forming substrate 2 is formed by a precision pressing method, an electroforming method of nickel, an etching process of a silicon wafer, or the like. The flow path substrate 3 bonded to the nozzle forming substrate 2 is a member formed with the pressure chamber 4, the segment ink supply path 5, the common ink chamber 6, and the communication port of the ink supply pipe 7. When the flow path substrate 3 is bonded to the nozzle forming substrate 2, the nozzle 1 is positioned and joined so that the nozzle 1 is located at the center of the pressure chamber 4. The base substrate 8 is a member for fixing a plurality of laminated piezoelectric elements 10, and segment electrodes 15 and a common electrode 16 for transmitting an electric signal independent of the driver 30 are formed to each laminated piezoelectric element 10. When a selective electric signal is applied to the laminated piezoelectric element 10 from the driver 30, the laminated piezoelectric element 10 is distorted. Since the laminated piezoelectric element 10 is bonded on the base substrate 8 such as alumina having a high Young's modulus, the bonding surface with the pressure chamber 4 is preferentially displaced to increase the pressure in the pressure chamber 4. The ink jet head described in this embodiment is used in an image recording apparatus that forms an ink image on a recording medium by ejecting ink from the nozzle 1 based on such a principle.

2 and 3 are partial sectional views of an ink jet head for explaining the first embodiment of the present invention. The base substrate 8 is a fixing member that fixes the laminated piezoelectric element 10, and the pressure transmission member 19 is the pressure chamber 4 of the laminated piezoelectric element 10.
The displacement area is equal to or larger than the area opposed to. The vibrating plate 18, the flow path substrate 3, and the nozzle forming substrate 2 form a pressure chamber 4. Then, in the pressure chamber 4, the volume of the pressure chamber 4 changes rapidly due to the change of the vibration plate 18. The segment electrode 15 and the common electrode 16 formed on the base substrate 8 are bonded to the side surface electrodes of the laminated piezoelectric element 10 by the conductive bonding member 24, and are displaced in the direction toward the nozzle 1 when an electric signal is applied. Occur. Due to this displacement, the vibrating plate 18 is bent via the pressure transmitting member 19, and the ink filled in the pressure chamber 4 is pressurized and ejected from the nozzle 1. In such an ink jet head, according to the present invention, the pressure transmitting member 19 of the laminated piezoelectric element 10 is used.
The surface to be joined with is convex so that only the active portion 11, which is the region where the electrodes intersect, is formed. The surface to which the pressure transmission member 19 is joined has a concave shape. In this way, the inactive portion 12 and the pressure transmitting member 19 are not joined by forming the laminated piezoelectric element 10 and the pressure transmitting member 19 so that the surface of the laminated piezoelectric element 10 to be joined is the active portion 11 only. As a result, the stress due to the inactive portion 12 which is a region where the electrodes do not intersect can be relieved, and the displacement efficiency and the reliability of the actuator can be improved. Further, since the surface of the laminated piezoelectric element 10 to be joined to the pressure transmitting member 19 is convex and the surface of the pressure transmitting member 19 to be joined to the laminated piezoelectric element 10 is concave, the convex and concave shapes are formed. Since the fitting can be assembled by the shape, there is no variation in the positional accuracy of the pressure transmission member 19 with respect to the laminated piezoelectric element 10. Also, the pressure transmission member 1
By making the area of the laminated piezoelectric element 10 facing the nozzle 9 larger than that of the laminated piezoelectric element 10, it is possible to obtain a displacement area that is equal to or larger than the area of the laminated piezoelectric element 10 opposed to the pressure chamber 4, thus improving ink ejection efficiency. You can also let it.

Further, the base substrate 8 and the laminated piezoelectric element 10
By providing the convex portion 23 on the base substrate also on the joint surface with the, the stress due to the inactive portion 12 of the laminated piezoelectric element 10 can be relieved, and the displacement efficiency and the reliability of the actuator can be improved. it can. Furthermore, since the surfaces to be joined have three sides by using the uneven shape, the adhesive force between the laminated piezoelectric element 10 and the pressure transmission member 19 can be made stronger.

Further, as shown in FIG. 3, the laminated piezoelectric element 1
It is apparent that the same effect is obtained even when the joint surface of the pressure transmitting member 19 of 0 is concave and the joint surface of the pressure transmitting member 19 on the laminated piezoelectric element 10 side is convex. However, when the side surface of the inactive portion 12 is joined to the pressure transmitting member 19, the stress in the vicinity of the joint surface of the inactive portion 12 becomes large. Therefore, when the laminated piezoelectric element 10 is processed or molded into a concave shape, it is preferable to form the shape inside the active portion 11 that generates displacement.

By the way, it is apparent that the pressure transmitting member 19, which is a feature of the present invention, has the same operation even if it is made of the same member as the diaphragm 18.

FIG. 4 is a partial cross-sectional view of an ink jet head for explaining another embodiment of the present invention, in which the laminated piezoelectric element 10 and the pressure transmission member 19 are joined via another member. Multilayer piezoelectric element 10 and pressure transmitting member 19
The separate member spacer 17 is joined to. Even in this case, the concave portion formed in the laminated piezoelectric element 10 so as to be bonded only to the active portion 11 is provided in the region of the active portion 11 so that the spacer 17 can be positioned. There is. The pressure transmitting member 19 also has a spacer 1
7 is provided with a concave portion for joining with the laminated piezoelectric element 1
The position accuracy with respect to 0 can be obtained.

5 and 6 show the laminated piezoelectric element 10 when the vibrating plate 18 is bonded to the base substrate 8 and the pressure transmitting member 19.
FIG. 7 is a partial cross-sectional view of an inkjet head for explaining an embodiment in which height adjustment is performed at a joint between a pressure transmission member 19 and a pressure transmission member 19. The vibration plate 18 receives strain generated by the electric field of the laminated piezoelectric element 10 and changes the volume in the pressure chamber 4. Therefore, the vibration plate 18 must be securely bonded to the pressure transmission member 19 and the base substrate 8. In order to make the ink ejection efficiency from the nozzle 1 constant, the volume of the pressure chamber 4 needs to be precisely controlled, and in order to make the volume constant, the vibration plate 18 needs to be flat. However, the diaphragm 18
The base substrate 8 and the pressure transmitting member 19 that join the two are separate members, and there is no guarantee that they will be the same height when assembled. To make both heights the same, either the base substrate 8 or the pressure transmitting member 19 is required. The height of one of them is measured, and either one needs some processing such as polishing. The present invention facilitates this height adjustment, and as shown in FIG. 5, the laminated piezoelectric element 10 having a convex shape on the surface to be joined to the pressure transmission member 19 is fixed to the base substrate 8 to fix the piezoelectric element assembly. To form. Further, the vibration transmission plate 19 and the pressure transmitting member 19 having a concave shape on the surface to be joined to the laminated piezoelectric element 10 are joined in advance to form a convex shape and pressure transmission formed on the laminated piezoelectric element 1 of the piezoelectric element assembly. The members 19 are joined by a concave fit. An adhesive 28 is applied in advance to the gap formed at the joint portion between the laminated piezoelectric element 10 and the pressure transmitting member 19. By filling the gap with the adhesive 28, the laminated piezoelectric element 10 and the pressure transmitting member are formed. 19 can be joined. Thereby, even if the heights of the base substrate 8 and the pressure transmission member 19 are different, the laminated piezoelectric element 10
Since the height difference is absorbed by the adhesive 28 filled in the joint surface between the pressure transmitting member 19 and the pressure transmitting member 19, the volume of the pressure chamber can be made constant even if the height varies, and the ink ejection efficiency is kept constant. be able to.

As shown in FIG. 6, the height when the joint surface of the laminated piezoelectric element 10 with the pressure transmitting member 19 is concave and the joint surface of the pressure transmitting member 19 with the laminated piezoelectric element 10 is convex. It is clear that the same effect is exerted at the time of joining in adjustment.

7 and 8 are partial cross-sectional views of the ink jet head for explaining that the adhesive escape groove 29 is provided in the laminated piezoelectric element 10 when the pressure transmission member 19 is joined to the laminated vibrator 10.

It is desirable that the laminated piezoelectric element 10 that generates displacement for increasing the pressure in the pressure chamber 4 has excellent displacement efficiency. However, when the end face of the laminated piezoelectric element 10 having the inactive portion 12 which does not generate displacement together with the active portion 11 which produces displacement is joined to the pressure transmitting member 19, the inactive portion 1 is formed.
The stress near the joint surface of No. 2 becomes large. Multilayer piezoelectric element 1
When the smooth surface of 0 and the smooth surface of the pressure transmitting member 19 are joined, there is a risk that even if the adhesive 28 is applied only to the active portion 11, the adhesive 28 protrudes to the inactive portions 12 adjacent to both sides of the active portion 11. high. It has been confirmed that such a phenomenon is likely to cause the destruction of the laminated piezoelectric element 10 and the phenomenon of peeling of the bonding surface. In the embodiment, the adhesive 28 is prevented from flowing out to the inactive portion 12. As shown in FIG. 7, the adhesive 28 applied only to the active portion 11 of the laminated piezoelectric element 10 is bonded to the pressure transmission member 19 and the laminated piezoelectric element 10, so that the inactive portions 12 on both sides of the active portion 11 are bonded. By providing the adhesive escape grooves 29 on both sides of the active portion 11 in order to prevent the adhesive portion from protruding into the area of
The protruding adhesive 28 only flows into the adhesive escape groove 28 without flowing off to the adjacent inactive portion 12.
As a result, it is possible to prevent the bonding of the adhesive 28 to the inactive portion 12, and the displacement of the laminated piezoelectric element 10 is not hindered. Further, it becomes possible only by forming the grooves of the adhesive escape 29 on both sides of the active portion 11 without processing the laminated piezoelectric element 10 into a convex shape, and by fitting the outer shape of the laminated piezoelectric element 10 with the pressure transmitting member 19. By performing the above, it becomes easy to ensure the positional accuracy. The laminated piezoelectric element 10
When the adhesive 28 is applied not only to the active portion 11 of the laminated piezoelectric element 10 but also to the entire joint surface of the laminated piezoelectric element 10 with the pressure transmitting member 19, as shown in FIG. By making only the part that joins with the convex shape,
It is possible to prevent the inert portion 12 and the pressure transmission member 19 from being joined. As described above, the adhesive 28 that may be generated during manufacturing
In the bonding with the inactive portion 12 due to the protrusion, it is possible to prevent the displacement efficiency of the laminated piezoelectric element 10 from being lowered by providing the adhesive escape 29 in the laminated piezoelectric element 10, and to improve the ink ejection characteristics of the inkjet head. It has been confirmed as a further effect of the present invention that variation can be effectively suppressed.

[0021]

By configuring as described above, an inkjet head having a microactuator having high efficiency and high reliability can be provided, and thus an inkjet head having excellent ink ejection efficiency can be provided. Further, since the stress applied to the microactuator can be suppressed, it is possible to provide an inkjet head having excellent reliability. Further, with such an improvement effect, it is possible to provide a low cost and high performance image recording apparatus.

[Brief description of drawings]

FIG. 1 is a structural explanatory perspective view of a main part of an inkjet head using an actuator of the present invention.

FIG. 2 is a partial cross-sectional view of a main part of an inkjet head illustrating a first embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of a main part of the inkjet head for explaining the first embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of an inkjet head for explaining another embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of an inkjet head illustrating an example in which height adjustment is performed at a joint portion between the laminated piezoelectric element 10 and the pressure transmission member 19.

FIG. 6 is a partial cross-sectional view of an inkjet head for explaining another embodiment in which the height is adjusted at the joint between the laminated piezoelectric element 10 and the pressure transmission member 19.

FIG. 7 is a partial cross-sectional view of an inkjet head for explaining an embodiment in which a relief of an adhesive is provided on the laminated piezoelectric element 10.

FIG. 8 is a partial cross-sectional view of an ink jet head for explaining another embodiment in which an adhesive escape is provided on the laminated piezoelectric element 10.

FIG. 9 is a structural explanatory view of a main part of an inkjet head showing a conventional example related to the present invention.

[Explanation of symbols]

1 ... Nozzle 2 Nozzle substrate 3 ... Flow path substrate 4 Pressure chamber 5 Segment ink supply port 6 ... Common ink chamber 7 Ink supply pipe 8: Base substrate 9 ... Ceramic member 10 Multilayer piezoelectric element 11 ... Active part 12: Inactive section 15 ... Segment electrodes 16: Common electrode 17 Spacer 18 ... Diaphragm 19 ... Pressure transmission member 23. Projection of base substrate 24 .. Conductive joining member 28 ... Adhesive 29 ... Adhesive escape groove 30 driver

Continuation of front page (56) Reference JP-A-1-115638 (JP, A) JP-A-4-57374 (JP, A) JP-A-3-145775 (JP, A) JP-A-4-145675 (JP , A) Japanese Unexamined Patent Publication No. 6-24017 (JP, A) Japanese Unexamined Patent Publication No. 4-347643 (JP, A) Japanese Unexamined Patent Publication No. 4-105374 (JP, A) Actual Kaihei No. 1-153660 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 41/083 B41J 2/045 B41J 2/055

Claims (6)

(57) [Claims] 1. A nozzle that ejects ink, a pressure chamber that communicates with the nozzle, and a piezoelectric material and a conductive material that alternately generate a pressure on a diaphragm that is one wall surface of the pressure chamber via a pressure transmission member. In an ink jet head having a laminated piezoelectric element formed by stacking the laminated piezoelectric element and a driving unit that applies an electric signal to the laminated piezoelectric element, an area of the laminated piezoelectric element facing the pressure chamber of the pressure transmission member is the area of the laminated piezoelectric element. And a concave shape or a convex shape on a surface of the laminated piezoelectric element that is joined to the pressure transmitting member, and a convex shape on a surface of the pressure transmitting member that is joined to the laminated piezoelectric element. Alternatively, an ink jet head having a concave shape, in which concave portions are formed on both sides of an active portion on an end surface of the laminated piezoelectric element joined to the pressure transmitting member. 2. The ink jet head according to claim 1, wherein the height of the diaphragm is adjusted at a joint surface between the laminated piezoelectric element and the pressure transmission member. 3. The inkjet head according to claim 1, wherein the height of the vibration plate is adjusted by the thickness of the bonding material applied to the bonding surface between the laminated piezoelectric element and the pressure transmitting member. 4. The ink jet head according to claim 1, wherein the bonding material is applied only to the active portion of the laminated piezoelectric element. 5. The ink jet head according to claim 1, wherein the space formed by the concave shape or the convex shape is an escape groove for accommodating an excessive bonding material. 6. The ink jet head according to claim 1, wherein positioning is performed by fitting an inactive portion of the laminated piezoelectric element and the pressure transmitting member.