JPH01186329A - Ink jet head - Google Patents

Abstract

PURPOSE:To realize an ink jet head having stable characteristics and using a cantilevered beam like vibrator by constituting the ink jet head so that an electromechanical converter has the cantilevered beam like vibrator formed by laminating an electromechanical converter element layer and a prescription layer and the electromechanical converter element layer has a layer for prescribing the deformation of the electromechanical converter element layer to the opposite surface of the prescription layer at a support part. CONSTITUTION:In a piezoelectric converter 31, a common electrode layer 53 composed of a thin Au-layer is provided to the single surface of a piezoelectric element 30 composed of PZT and, further, a spacer layer 51 composed of a thin Ni-layer is laminated to a vibrator support part to form a base layer 58 composed of two layers and a prescription layer 54 composed of the thin Ni-layer is provided to the other surface of the element 30. The piezoelectric converter 31 is separated along notches 56 to constitute may vibrators 52. The nozzles 28 respectively corresponding to the vibrators through fine gaps (a) provided in the vicinity of the leading end parts of the vibrators are arranged in opposed relationship. By this method, since no bending moment is generated at the vibrator support part of the piezoelectric converter, the fixing state of the support part is not changed and a vibration characteristic can be kept.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an inkjet printing apparatus such as a printer that forms an ink image on a medium such as a recording paper by flying ink droplets, and more particularly relates to an inkjet printer head. .

[Conventional technology]

A known structure of a conventional inkjet head includes a nozzle plate having a plurality of nozzle openings and a piezoelectric transducer behind the nozzle plate that is in direct contact with ink. (Equity 1989-89.53, etc.) In this structure, the vibrator constituting the piezoelectric transducer vibrates as if displaced in a direction approximately perpendicular to the nozzle plate, and the ink flow path between each nozzle communicates over a short distance. Even if foreign matter such as gas or dust gets mixed into the ink, normal operation is possible without being affected by the ink droplet ejection efficiency and stability. Furthermore, a cantilever-like or double-end-beam-like vibrator is used as the vibrator, which is arranged with a small gap between the nozzle plate and the nozzle plate.

[Problem to be solved by the invention]

The conventional structure of an inkjet head using a beam-shaped vibrator has a problem in that it is difficult to firmly fix the vibrator supporting portion and the characteristics are unstable. In other words, it is desirable for the support part of the vibrator to be firmly fixed and supported by the support member in order to maintain stable vibration characteristics, but since it has a bimorph structure, the support part bends when voltage is applied to the vibrator. . As a result, problems such as the support portion lifting up, the support member being pushed up, etc., caused play during long-term use, and the support for the adjacent vibrator became incomplete.

An object of the present invention is to solve these problems and realize an ink sheet head using a cantilever vibrator with stable characteristics.

[Means to solve the problem]

The inkjet head of the present invention includes a nozzle forming member having a plurality of nozzle openings and an electromechanical transducer, and in the inkjet head in which ink is filled between the nozzle forming member and the piezoelectric transducer, the electromechanical transducer The device has a beam-shaped vibrator formed by laminating an electromechanical transducer layer and a regulation layer, and the electromechanical transducer layer has a supporting portion that causes deformation of the electromechanical transducer layer on the opposite side of the regulation layer. It is characterized by having a regulating layer.

[Effect]

In the above configuration of the present invention, since no bending moment is generated in the vibrator supporting portion of the piezoelectric transducer, the fixed state of the supporting portion does not change and stable vibration characteristics can be maintained.

〔Example〕

Next, the present invention will be explained based on examples.

FIG. 1 is a perspective view of a printer showing an embodiment of the present invention. In the figure, recording paper 10 is wound around a platen 11 and is pressed by feed rollers 12 and 13. The inkjet head 16 is mounted on a carriage 15 that is guided by guide shafts 14 and 17 and movable in a direction parallel to the platen axis. The inkjet head 16 has a plurality of nozzles that can independently control the ejection of ink droplets, and is scanned in the planar axis direction to selectively eject ink droplets from the nozzles to form an ink image on the recording paper 10.

The recording paper 10 is conveyed in the sub-scanning direction perpendicular to the scanning direction by rotation of the platen 11 and feed rollers 12 and 13, and printing is performed on the recording paper surface.

FIG. 2 shows a cross section of the ink jet head.

The piezoelectric transducer 31 and the nozzle plate 27 are laminated on the frame 26 with the elastic sheet 25 in between, and fixed using fixing screws 32 and 33. The nozzle plate 27 is composed of a thin metal plate having a plurality of nozzles 28. The piezoelectric transducer 31 is shown in a perspective view in FIG. Au on one side of the piezoelectric element 30 made of PZT.
A base layer 58 is formed by laminating a common electrode layer 53 made of a thin layer, a vibrator supporting portion, and a spacer layer 51 made of a thin Ni layer. A Ni thin plate is placed on the pond surface.
It has a regulation layer 54 consisting of. The piezoelectric transducer 31 is separated by a notch 56 to form a plurality of vibrators 52. Again in FIG. 2, the corresponding nozzles 28 are arranged so as to face each other in the vicinity of the tip of the vibrator with a small gap a interposed therebetween. The regulation layer also serves as a pattern electrode for selectively applying voltage, and is individually connected to wiring 29. The thickness of the base layer has the same value as the nozzle gap and is formed to be 10 to 100 μm depending on the ink characteristics.

Next, the operation will be explained. Ink (not shown) is supplied from the ink reservoir 24 to the vicinity of the nozzle to fill it.

By applying a voltage between the common electrode 53 and the regulating layer 54, the piezoelectric element 30 contracts due to the piezoelectric effect. On the other hand, regulation layer 5
4 has high tensile stiffness. Tensile rigidity can be evaluated by (tensile modulus of elasticity) x (cross-sectional area) or (tensile modulus of elasticity) x (layer thickness). Since dimensional changes are restricted on the regulating layer side, a bending moment is generated as if bending toward the common electrode 53 side. The free end of the vibrator 52 is thereby deformed and displaced in the direction of the nozzle plate, causing nearby ink to be ejected from the nozzle. For the above operation, the piezoelectric element is 0°05~0.2mm, and the regulation layer is 1
The thickness is 0 to 100 μm, and the tensile rigidity of the latter is sufficiently large compared to the former for regulatory functions, and is set to an appropriate value that does not prevent bending and deformation. According to experiments conducted by the inventors, in the case of the material combination of this example, in order to ensure tip displacement, the tensile rigidity of the regulation layer is set to 1/10 or more and 10 times or less of the tensile rigidity of the piezoelectric element layer. There was a need.

On the other hand, in the support part, regulation layers 54 are provided on both sides of the piezoelectric element.
and a base layer 58, respectively, but the common electrode layer is to
It has a thickness of about 1.2 oz (onm), and its thin surface also has a small elastic modulus. The spacer layer and the base layer have approximately the same thickness, and the tensile rigidity of the base layer is the sum of the tensile rigidities of the common electrode layer and the spacer layer.Since the tensile rigidity of the base layer is approximately determined by the rectangular rigidity of the spacer layer, it is equal to the tensile rigidity of the regulation layer. Almost equal. Therefore, both sides of the piezoelectric element have approximately the same tensile stiffness. Even when an electric field acts on the piezoelectric element and causes it to contract, no bending moment is generated in the supporting portion, no force is applied, and no backlash or the like occurs. Note that the appropriate layer thicknesses of the base layer and the regulation layer depend on the values of the tensile rigidity and bending rigidity of the three layers. It is desirable that at least the tensile rigidity of the base layer is comparable to the tensile rigidity of the regulation layer. It is more preferable that the base layer and the regulation layer are made of the same material and the same thickness. Although it is difficult to quantitatively evaluate the appropriate range, in the configuration of this example, the base layer,
The desired characteristics were obtained by setting the tensile stiffness of the piezoelectric element layer and the regulating layer to 1:1:1, and it is considered that the tensile rigidity ratio between the base layer and the regulating layer should be 1/10 to 10.

FIG. 4 shows a perspective view of another embodiment of the piezoelectric transducer. This embodiment differs from the previous embodiment in that it has a double-supported beam structure. In this embodiment, the tip portion of the comb-like piezoelectric transducer is also fixed to the nozzle plate. The operation and other operations are the same as before, and the explanation will be omitted.

Furthermore, although the embodiment has been described with respect to a vibrator using a piezoelectric element, it is also possible to construct an electromechanical transducer using electromechanical transducers of various types such as thermal expansion and phase transformation.

〔Effect of the invention〕

As described above, according to the above structure of the present invention, the supporting part vibrates, and since the piezoelectric element (electromechanical transducer) has layers having approximately the same tensile rigidity on both sides, bending deformation occurs in the supporting part due to the bending moment. This has the effect that an inkjet head using a cantilever vibrator with stable characteristics can be realized without any force being applied to the supporting portion.

Another advantage is that the spacer layer can be used to secure a gap between the nozzle plate and the vibrator.

Furthermore, it also has the effect of preventing warping of the fixing part caused by temperature changes. That is, if the regulating layer and the piezoelectric element (electromechanical transducer) layer have different thermal expansions, warping occurs due to changes in ambient temperature. However, by providing layers having the same thermal Bti EB characteristics on both sides of the piezoelectric element (electromechanical transducer) layer, it is possible to prevent the occurrence of warpage.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a printer equipped with an ink jet head showing one embodiment of the present invention. FIG. 2 is a sectional view of an ink sheet head showing an embodiment of the present invention. FIG. 3 is a perspective view of a piezoelectric transducer of an inkjet head showing one embodiment of the present invention. FIG. 4 is a perspective view of a piezoelectric transducer of an inkjet head showing another embodiment of the present invention. 16 Ink sheller I head 27 Nozzle plate 28 Nozzle 30 Piezoelectric element 31 Piezoelectric transducer 51 Spacer layer 52 Vibrator 53 Common electrode layer 54 Regulation layer 58 Base layer or above

Claims (1)

[Scope of Claims] An inkjet head comprising a nozzle forming member having a plurality of nozzle openings and an electromechanical transducer, wherein ink is filled between the nozzle forming member and the piezoelectric transducer, the electromechanical transducer The device has a beam-shaped vibrator formed by laminating an electromechanical transducer layer and a regulation layer, and the electromechanical transducer layer has a supporting portion that causes deformation of the electromechanical transducer layer on the opposite side of the regulation layer. An inkjet head characterized by having a regulating layer.