JPH01290434A - Ink jet head - Google Patents

Abstract

PURPOSE:To stabilize ink droplets discharge characteristics and improve manufacturing yields by arranging a piezoelectric transducer of a specific structure consisting of first and second foil members and a piezoelectric element in the opening of a nozzle plate. CONSTITUTION:A piezoelectric transducer 37 is composed, in a laminated form, of a piezoelectric element, the Ni foil 34 which is junctioned across the one side of the element 35 and sandwiched between a frame 27 and a nozzle plate 21 jutting out of the left end of the element 35, the electrode foil provided across the other surface of the element 35, and the Ni foil 24 bound between the frame 27 and the frame 21. Therefore, the transducer 37 is of the double lever structure with both soft ends. If an electric signal is selectively applied to the element 35 by a jet head drive circuit 38, a bending moment is generated in the piezoelectric transducer 37 to allow the movable section of an oscillator located at the top of a nozzle opening 20 to oscillate in a direction in which the movable section almost crosses the plate 21. Thus, ink droplets remaining near the oscillator are sent flying.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording system such as a printer that flies ink droplets to form an ink image on a medium such as recording paper, 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. (Japanese Patent Publication No. 60-8953) In this structure, the vibrator constituting the piezoelectric transducer vibrates so as to be displaced in a direction approximately perpendicular to the nozzle plate, and the ink flow path between each nozzle communicates over a short distance. As a result, the ink droplet ejection efficiency and stability are high, and even if foreign matter such as gas or dust gets mixed into the ink, normal operation is possible without being affected by this. Further, the vibrator used is a cantilever-like vibrator arranged with a small gap between it and the nozzle plate, or a double-supported beam vibrator having a soft structure near both supporting ends.

[Problem to be solved by the invention]

The structure of the inkjet head using the cantilever piezoelectric transducer of the prior art described above has problems in that it is difficult to ensure accuracy, the ink droplet ejection characteristics are not stable, and retention in the manufacturing department is low. That is, since the gap between the nozzle plate and the movable part of the vibrator facing the nozzle plate affects the ink droplet ejection characteristics, it is necessary to manage the minute gap with high precision. However, in the case of a cantilever beam, since the length of the beam is longer than the support portion, the inclination toward the support direction at the support portion is expanded at the tip of the vibrator, which affects the gap between the vibrator and the nozzle plate. Therefore, there was a problem that the properties were not stable and retention in the manufacturing department was low.

In addition, in the double-supported beam vibrator based on the conventional technology, the vicinity of both support ends has a soft structure, so it is difficult to manage the gap between the vibrator and the nozzle plate during manufacturing, and electrical wiring work with the piezoelectric element is difficult. However, when adopting a structure using a plurality of vibrators, there was a problem in that a comb-teeth structure in which the support end on one side of the double-supported beam vibrator was shared was not possible.

An object of the present invention is to solve these problems and realize an inkjet head using a double-sided beam-shaped vibrator with stable ink droplet ejection characteristics and high retention in the manufacturing site.

[Means for Solving the Problems] An inkjet head of the present invention includes a nozzle plate having at least one or more nozzle openings, a layer of piezoelectric elements disposed opposite to the nozzle openings, and a layer of piezoelectric elements on one side of the piezoelectric elements. at least one bonded member protruding from one end of the piezoelectric element;
a first foil member having at least one layer and a second foil member having at least one layer bonded to the other surface of the piezoelectric element and protruding from the other end of the piezoelectric element;
A piezoelectric transducer has a laminated structure with a foil member, and has a double-supported beam structure with the protrusions of the first and second foil members as fixed ends; The present invention is characterized in that it includes ink that fills the periphery of the piezoelectric transducer, and a head drive circuit that selectively applies electrical signals to the first and second foil members.

Further, such an inkjet head may be provided with a hot melt ink that is in a solid state at room temperature, and a heat generating means for changing the hot melt ink from a solid state to a liquid state.

[Effect]

In the above configuration of the present invention, a selective electric signal is applied to the piezoelectric element constituting the piezoelectric transducer to generate a bending moment in the piezoelectric transducer, and the movable part of the vibrator above the nozzle opening is moved in a direction substantially perpendicular to the nozzle plate. make it vibrate. The vibration pushes out nearby ink and causes it to fly as ink droplets.

〔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, a 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 platen axis direction, selectively ejecting 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 surface of the recording paper.

FIG. 2 is a sectional view of an inkjet head showing an embodiment of the present invention. A spacer 23.33, a foil member 24.34, an electrically insulating seal member 25.32, and a common electrode plate 22 are stacked between the frame 27 and the nozzle plate 21, and the preliminary ink chamber 29 and The ink chamber 39 is fixedly formed. The piezoelectric transducer 37 includes a piezoelectric element 35 made of PZT, and a Ni foil 3 that is bonded over the entire area to one side of the piezoelectric element 35, protrudes from the left end of the piezoelectric element 35, and is sandwiched between the frame 27 and the nozzle plate 21.
4, an electrode foil 36 provided over the entire area on the other surface of the piezoelectric element 35, and a right end of the piezoelectric element 35 bonded to a part of the surface of the piezoelectric element 35 on which the electrode foil 36 is provided. It is constructed by laminating a Ni foil 24 that protrudes further and is fastened between the frame 27 and the nozzle plate 21. Therefore, the piezoelectric transducer 37 has a double-supported beam structure with both ends having a soft structure. Here, the Ni foil 34 and the Ni foil 24 have a -layer structure, but are not limited thereto, and may have a laminated structure of two or more layers. The ink chamber 39 is filled with recording ink 30, and the piezoelectric transducer 37 is present in the recording ink 30. The nozzle plate 21 is composed of a metal foil plate having a plurality of nozzle openings 20. It is known that the minute gap between the piezoelectric transducer 37 and the nozzle plate 21 has an important effect on the ink droplet ejection characteristics of the inkjet head, and it is necessary to manage the minute gap with high precision. Therefore, a spacer 23.33 having an appropriately set thickness is placed between the nozzle plate 21 and the Ni foil 24.34 protruding from both ends of the piezoelectric transducer 37. Also spacer 23
．． 33 does not need to be independent from the nozzle plate 21, and may have a structure integrated with the nozzle plate 21.

The frame 27 has a spare ink chamber 29 and a lid 28 for preventing dust, paper fluff, etc. from entering the ink. Head drive circuit 38 generates selective electrical signals that are applied to piezoelectric element 35. One of the selective electrical signals generated from the head drive circuit 38 passes through the Ni foil 24 and reaches the electrode foil 36. The common electrode is composed of a Ni foil 34, a spacer 33 having electrical conductivity, a nozzle plate 21 which also has electrical conductivity, and a common electrode plate 22. Here, the spacer 23 needs to have non-electrical conductivity.

Next, the operation will be explained. Ink is supplied from the preliminary ink chamber 29 to the vicinity of the nozzle to fill it. By applying a voltage between the common electrode and the electrode foil 36, the piezoelectric element 35 contracts due to the piezoelectric effect. On the other hand, since the layer of Ni foil 34 has a high modulus of elasticity, dimensional changes are restricted, and a bending moment is generated as the layer bends toward the Ni foil 34 side. As a result, the piezoelectric transducer 37 is deformed and displaced in the direction of the nozzle plate 21, causing recording ink 30 in the vicinity to be ejected from the nozzle opening 20.

Further, in FIG. 2, a heat generating member 4o as a heat generating means is attached to the frame 27. The recording ink 3o used at this time is a hot melt ink that is in a solid state at room temperature and undergoes a phase transformation and becomes a liquid state at a temperature of 60 degrees Celsius to 120 degrees Celsius. In particular, it is desirable that the frame 27 and the nozzle plate 21 be made of aluminum, zinc, or other metals that have good thermal conductivity. According to the configuration shown in FIG. 2, which is equipped with hot melt ink and heat generating means, a foil member such as Ni foil, which has better stress resistance than gold wire, is used for the two electrodes that make up the piezoelectric transducer 37. Furthermore, the electrodes will not be broken due to internal stress generated within the recording ink, ie, hot melt ink, during phase transformation. In addition, since it has a double-supported beam structure, it is possible to suppress bending deformation of the piezoelectric transducer 37 caused by the temperature difference between room temperature and high temperature and the difference in the coefficient of linear expansion of the components of the piezoelectric transducer 37. This has effects such as making it possible to control with high precision the minute gap between the piezoelectric transducer 37 and the nozzle plate 21, which is an important factor for ensuring the ink droplet ejection characteristics.

FIG. 3 also shows an embodiment of the present invention, and when a plurality of piezoelectric transducers 37 are arranged side by side in the embodiment shown in FIG.
FIG. 1 is a perspective view showing only part 1; Since the Ni foil 34 also serves as a common electrode, it has an integrated structure at the fixed portion.

Since the Ni foils 24 function as segment electrodes, they are separated from each other. As described above, since the Ni foil 34 has a comb-like structure, the positional accuracy can be easily managed between each piezoelectric transducer 37 and when mounting a plurality of piezoelectric transducers 37 and their corresponding nozzle openings 20. It has the effect of being able to.

Furthermore, in this embodiment, the Ni foil 24 has a wider width than the piezoelectric element 35. This is because the piezoelectric element 3
5 and the Ni foils 24 and 34 have the effect of preventing torsional vibration of the piezoelectric transducer 37 during operation even if the positions vary in the width direction.

FIG. 4 is also an embodiment of the present invention, and for explaining another embodiment of the piezoelectric transducer 37 shown in FIG. It is a diagram. In this embodiment, the foil member 24 is used as a piezoelectric element 35.
It is characterized by its placement over the entire area. At this time, in order for the piezoelectric transducer 37 to exhibit a piezoelectric bimetal effect, the foil member 24 and the foil member 34 need to have different bending stiffnesses, and preferably the difference in bending stiffness is larger. If the foil member 24 and the foil member 34 are the same member, one of the foil members, that is, the foil member 24, must be thinner, as shown in FIG. At this time, since the spacer 23 side of the power transport converter 37 is deformed and displaced more greatly during driving, the nozzle frontage 20 is disposed to the right of the piezoelectric converter 37 in the drawing.

FIG. 5 also shows another embodiment of the present invention, and only the piezoelectric transducer 37, spacers 23, 33, and nozzle plate 21 are shown to explain another embodiment of the piezoelectric transducer 37 shown in FIG. FIG. Piezoelectric transducer 37 in this embodiment
is constructed by cutting a rod-shaped vibrator made of a laminated layer of Ni foil 34, piezoelectric element 35, and electrode foil 36 from the Ni foil 34 side and from the electrode foil 36 side, respectively. The cut-out portion constitutes a soft structure near the fixed end of the double-supported vibrating beam. As the cutting method, cutting with a dicing saw or the like and etching are carried out. In this embodiment, a rectangular cut is made, but the cut is not particularly limited to a rectangle. When a circular cut is made, the piezoelectric transducer 37
It is possible to prevent stress concentration on the notched portion due to the vibration movement of the inkjet head, thereby realizing an inkjet head with excellent durability and reliability. Furthermore, since the depth of the cut and the width of the cut can be set appropriately at both locations, it is possible to design and manufacture the rigidity of the soft structure portions near both fixed ends freely and with high precision. Furthermore, if the rigidity of the soft structural parts near both fixed ends of the 2@ locations is designed to be the same, the vibration motion of the piezoelectric transducer 37 is stabilized, and an inkjet head with stable ink droplet ejection characteristics can be obtained. According to this embodiment, as in other embodiments of the present invention, it is possible to separate two signal lines for applying voltage to the piezoelectric element 35 at both fixed ends of the piezoelectric transducer 37. .

That is, the electrode foil 36 and foil member 34 in FIG. 5 correspond to the foil member 24 having the function of a segment electrode and the foil member 34 having the function of a common electrode shown in FIG. 3, respectively, and the segment electrode wire 22b and the common electrode The wire 22a can be connected, making it possible to obtain a highly durable inkjet head that is miniaturized and can be retained in the manufacturing department. Further, according to the configuration of this embodiment, the thickness of the spacers 23 and 33 can be made the same, and the thickness of the piezoelectric transducer 37 and the nozzle plate 21 can be made the same.
It becomes possible to manage minute gaps between the two with high precision.

[Effects of the Invention] As described above, according to the above configuration of the present invention, the gap between the nozzle plate and the movable part of the piezoelectric transducer, which needs to be managed with high precision in order to stabilize the ink droplet ejection characteristics, can be appropriately managed. This has the effect that it is possible to realize an inkjet head with stable characteristics that can be driven at low voltage and has a high retention rate in the manufacturing department.

Further, according to the above configuration of the present invention, it is possible to realize a highly reliable inkjet head in which the electrical wiring does not break even when the piezoelectric transducer vibrates or external shock occurs.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a printer equipped with an inkjet head showing one embodiment of the present invention. FIG. 2 is a sectional view of an inkjet head showing an embodiment of the present invention. FIG. 3 is an embodiment according to the present invention, and is a perspective view showing a case where a plurality of piezoelectric transducers are arranged. FIG. 4 is a sectional view of an inkjet head showing an embodiment of the present invention. FIG. 5 is a sectional view of an inkjet head showing an embodiment of the present invention. 10 Recording paper 13 Roller 16 Inkjet head 20 Nozzle opening 21 Nozzle plate 24.34 Foil member 35 Piezoelectric element 37 Piezoelectric transducer and above Applicant Seiko Epson Co., Ltd. agent Patent attorney Kizobe Suzuki and 1 other person 16 Infujie, Tohead No. 1 Figure 20 Nozuru Sekiguchi 20 Noseru Frontage 21 Noself' Tote Figure 3

Claims (2)

[Claims] (1) A nozzle plate having at least one or more nozzle openings, a one-layer piezoelectric element disposed opposite to the nozzle opening, and at least one piezoelectric element bonded to one side of the piezoelectric element and protruding from one end of the piezoelectric element. It has a laminated structure of a first foil member of at least one layer and a second foil member of at least one layer that is bonded to the other surface of the piezoelectric element and protrudes from the other end of the piezoelectric element, and a piezoelectric transducer having a double-supported beam structure with the protrusion of the foil member as a fixed end; ink filling a gap between the piezoelectric transducer and the nozzle plate and a periphery of the piezoelectric transducer; 1. An inkjet head comprising: a head drive circuit for applying a selective electric signal to a foil member. (2) The inkjet head according to claim 1, wherein the ink is a hot melt ink that is in a solid state at room temperature, and is equipped with a heat generating means for changing the hot melt ink from a solid state to a liquid state. .