JPH01267047A - Inkjet head - Google Patents

Abstract

PURPOSE:To stabilize the discharging property of ink drops and to enhance the manufacturing yield, by so arranging that a movable part of a center beam vibrator held by a predetermined space from a nozzle plate is vibrated in a direction orthogonal to said nozzle plate to press out ink in the vicinity of said nozzle plate and to let it fly as ink drops. CONSTITUTION:When a voltage is applied between a common electrode using a spacer 22 and a pattern electrode 26, a piezoelectric element 24 is contracted. On the other hand, since a layer 23 of Ni foil has a high modulus of elasticity, the change of size thereof is restricted. Therefore, such bending moment is consequently generated as to bend the element 24 to the side of the Ni foil 23. As a result, a piezoelectric converter 40 is deformed and shifted towards a nozzle plate and, the ink in the vicinity of the nozzle plate is discharged out of a nozzle opening 20. Therefore, it becomes possible to manage a small gap between the nozzle plate 21 and the piezoelectric converter 40 with high accuracy. The gap influences the characteristic of the inkjet head, and accordingly highly accurate size control of the gap brings about stabilization of the discharging property of ink drops of the inkjet head, while exerting great influence upon the manufacturing yield of the head. It is desirable that the gap is not larger than 100mum and not smaller than 5mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ink sheet type recording apparatus such as a printer that forms an ink image on a medium such as a recording paper by flying ink droplets, and more specifically, Regarding printer heads.

[Conventional technology]

A known structure of a conventional ink sheller head is a nozzle plate having a plurality of nozzles and a piezoelectric transducer behind the nozzle plate that is in direct contact with ink. (
(Japanese Patent Publication No. 60-8953) This structure-C is characterized in that the vibrator constituting the piezoelectric transducer vibrates by being displaced in a direction approximately perpendicular to the nozzle plate, and that the ink flow path between each nozzle is short. Because of this communication, the ink droplet ejection efficiency and stability are high, and even if foreign matter such as gas or dust gets mixed into the ink, it is not affected by this and normal operation is possible. Furthermore, the vibration P softens the cantilever shape or both supporting ends, which are arranged with a small gap between them and the nozzle plate.
A double-supported beam vibrator made of 14 structures is used.

[Invention or problem to be solved]

Ink sheath I using the above conventional cantilever vibrator
- The head structure had problems in that it was difficult to ensure l'N degree, the ink droplet ejection characteristics were unstable, and the manufacturing yield was low. That is, since the gap between the nozzle plate and the movable part of the vibrator facing the nozzle plate affects the ink 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 supporting portion, the inclination in the supporting direction at the supporting portion is expanded at the tip of the vibrator, which affects the gap between the vibrator and the nozzle plate. This overcomes the problem of unstable characteristics and low manufacturing yield.

In addition, since the double-supported beam vibrator based on the conventional technology has a soft structure near both support ends, 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 to realize an ink sheet using a double-sided beam-shaped vibrator with stable ink droplet ejection characteristics and a high manufacturing yield.

In addition, in the structure of the inkjet head using the cantilever vibrator of the above-mentioned prior art, when hot melt ink is used, the phase transformation from a solid phase to a liquid phase or vice versa occurs.
There was a problem in that a large internal stress was generated inside the Hemelt ink, and as a result, a large concentrated stress was also generated in the cantilever vibrator support.

Another objective of the present invention is to solve the following five problems: 'Never prevent and balance stress concentration on the vibrator support end': To realize a highly reliable ink sheet △, rad. be.

[Solving the problem/Second method]

The ink sheet I and the spatula I of the present invention are disposed facing a nozzle forming part (" and the nozzle gap L") having at least one or more nozzle openings, and have one layer of piezoelectric elements and at least one layer of piezoelectric elements. The piezoelectric element has a double-supported beam structure in which one end made of the laminated portion of the foil member is a fixed end, and the other end made of only the foil member is a fixed end. a piezoelectric transducer, the nozzle forming member and [)0
The piezoelectric transducer is characterized in that it is composed of ink filling the gap between the piezoelectric transducers and the periphery of the piezoelectric transducer, and an electric signal line connected to the piezoelectric transducer for transmitting a selective electric signal.

In addition, hot null 1 to ink, which is in a solid state at room temperature, is added to the ink sheller 1-head, and the hot null 1 to ink, which is in a solid state at room temperature, is added to the ink sheller 1-head.
A heat generating means for changing the ink from a solid state to a liquid state may be provided.

Second, the length of the laminated layer consisting of the piezoelectric transducer and the foil member is set to be longer than the length of the laminated layer consisting only of the foil member, and the nozzle opening is The piezoelectric transducer may be located closer to the fixed end of the laminated portion consisting of the foil portion of the piezoelectric transducer having a double-sided beam shape.

Further, the gap between the nozzle forming member and the piezoelectric transducer of the ink sheller 1 to head may be set to 5 microns or more or less than 5 microns or less at the nozzle opening.

Further, electric wiring may be connected to the fixed end of the piezoelectric transducer having a laminated structure of a piezoelectric element and a foil member to the ink shell to the head.

Further, the ink sheller I/head may include an ink blocking member that surrounds ink to form an ink chamber, and electrical wiring at the fixed end of the piezoelectric transducer that projects outside the ink chamber.

[Effect]

In the above configuration of the present invention, the movable part of the double-sided beam-shaped vibrator, which is provided with a certain gap between the nozzle plate and the nozzle plate, vibrates in a direction perpendicular to the nozzle plate, pushing out ink in the vicinity and causing ink droplets to fly. .

〔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 [0] is wound around a platen 11 and pressed by feed rollers 12 and 13. An ink sheller 1-head 16 is mounted on a carriage 15 guided by a guide shaft 1.4.17 and movable in a direction parallel to the platen axis.
is listed and configured. 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 and selectively ejects ink droplets from the nozzles to form an ink image on the recording paper.

The recording paper 10 is conveyed in the sub-scanning direction perpendicular to the scanning direction by the rotation of the platen 11 and feed rollers ]-2 and 13, and printing is performed on the surface of the recording paper.

FIG. 2 is a sectional view of an ink shell to a head showing an embodiment of the present invention. Frame 28 and nozzle plays 1 to 21
A spacer 22.32 and a sealing member 27.31 are stacked in between, and the ink chamber 60 is fixedly formed using fixing screws 29, 30. Piezoelectric transducer 40 is constructed by joining a foil 23 and a piezoelectric element 24 made of PZT, one end of the laminated part made of the piezoelectric element 24 and Nl foil 23 is fixed, and
] - Return to the double-supported beam structure with the other end also fixed, consisting of only the foil 23. The ink chamber 60 is filled with recording ink 33, and the piezoelectric transducer 40 is present in the ink 33. A patterned electrode 26 is patterned on one side of the piezoelectric transducer 40 . A wiring 25 is connected to one side of the piezoelectric transducer 40 having the pattern electrode 26. Nozzle IH2
1kl: Consists of a metal foil plate having a plurality of nozzles 20. In addition, the spacers 22 and 32 are connected to the nozzle plate 2.
There is no need for the nozzle pulleys to be independent from the nozzle pulleys 1 to 2. The frame 28 has a cleaning chamber 61 and a lid 34 for preventing dust, paper fluff, etc. from entering the ink.

Next, the operation will be explained. Ink is supplied from the preliminary ink chamber 6 to the vicinity of the nozzle to fill it.

By applying a voltage between the common electrode using the spacer 22 and the pattern electrode 26, the piezoelectric element 24 contracts.

On the other hand, since the layer of N1 foil 23 has a high elastic modulus, dimensional changes are regulated and bending moment 1
~ will occur. As a result, the piezoelectric transducer 40 nozzle pre=
The nozzle is deformed in the direction of 1 and the ink in the vicinity is transferred to the book opening 20
Discharge from.

According to the above configuration, it becomes possible to manage the minute gap between the nozzle play 1/21 and the piezoelectric transducer 40 with high precision. If the gap is too wide, the ink will move without resistance due to the deformation of the piezoelectric transducer 40, and it cannot be expected that sufficient pressure will be generated to eject ink droplets to the ink near the nozzle opening 20. Conversely, if the void is too narrow,
The viscous resistance of the ink that tries to prevent the movement of the piezoelectric transducer 40 due to its deformation increases, and the time required for the pressure to rise increases, and the ink is supplied into the nozzle opening 20 after ejecting the ink droplet. There is a problem that the ink supply time becomes long. Therefore, the void is an important factor that affects the characteristics of the inkjet head, and highly accurate dimensional control of the void has a significant impact on stabilizing the ink gushing characteristics of the Ink Sheller I head and on the manufacturing yield. . Furthermore, it has been experimentally found that the spacing between the voids is preferably 100 micrometers or less and 5 micrometers or less.

Returning again to the embodiment shown in FIG. 2, in this configuration, since a laminated portion of the highly rigid N1 foil 23 and the piezoelectric element 24 is provided at one support end during manufacturing, the mounting condition can be controlled with high precision. In addition, the part corresponding to the free end of the cantilevered vibrator is thinner than the cantilevered vibrator.
Since it is fixed via the foil 23, it also has the feature that the natural vibration period can be shortened without reducing the amount of deformation due to the bimetal effect with respect to a unit applied voltage. This feature makes it possible to realize an inkjet head with a high response frequency. In addition, the Ni foil 23 constituting the piezoelectric transducer 40
It is desirable that the length ratio of the laminated portion consisting of the Ni foil 23 and the piezoelectric element 24 to the laminated portion consisting only of the N1 foil 23 is longer. This is because the longer N1 foil portion means an increase in the natural vibration period and difficulty in mounting the vibrator at a position of 1'N degrees. The position of the nozzle opening 20 is desirably placed in a vicinity that provides maximum deflection when the piezoelectric transducer 40 is deformed due to the bimetallic effect. Therefore, in this embodiment, the nozzle opening 20 is
N] - located closer to the fixed end of the laminated portion consisting only of foil 23.

In the embodiment of the inkjet head of the present invention shown in FIG. 2, one of the features is that the electrical wiring 25 to the piezoelectric transducer 40 is provided on the fixed end of the laminated portion consisting of the Nj foil 23 and the piezoelectric element 24. It is a characteristic. In the conventional example, since the vicinity of the support end has a soft structure, there is a possibility that the size of the minute gap between the nozzle plate 21 and the piezoelectric transducer 40 changes during the process of connecting the electric wiring 25. However, in the second embodiment, since the wiring is on the fixed end, the second problem does not occur.

FIG. 3 is also an embodiment of the inkjet head according to the present invention, and is a perspective view for explaining in detail the piezoelectric transducer 40 shown in FIG. 2. This perspective view shows nozzle plate 2.
1 and the piezoelectric transducer 40 are shown. Piezoelectric transducer 40
Each of the vibrators is cut into a comb-like shape, and each vibrator is installed so as to face a plurality of nozzle openings arranged on the nozzle plays 1 and 21. According to the above configuration, it is possible to realize an inkjet head using a double-sided beam-shaped vibrator, in which the electrical wiring work to the pattern electrode 26 is easy, the reliability is high, and the yield is high.

Both FIGS. 4 and 5 are sectional views showing other embodiments of the inkjet head according to the present invention. This embodiment also explains the piezoelectric transducer 40 in more detail.
This is an example in which the heights of both fixed ends from the nozzle plate 21 are different. Therefore, even if the piezoelectric transducer 40 bends during installation due to differences in linear expansion coefficients of the components of the piezoelectric transducer 40, the height of the fixed end of the piezoelectric transducer 40
By designing according to the curvature of the nozzle plate, not only can installation be performed easily, but also the positional accuracy of the piezoelectric transducer 40 and the nozzle plates 1 and 21, which affect the ink droplet ejection characteristics, can be easily ensured.

FIG. 6 is also a sectional view showing another embodiment of the inkjet head according to the present invention. This embodiment uses a hot melt ink 33 which is in a solid state at room temperature and undergoes a phase transformation from 80 degrees Celsius to 120 degrees Celsius to become a liquid state. In this case, the nozzle plate 21, the frame 28, and the seal member 3 are made of a material with good thermal conductivity. Heat generating members 35 and 36 are attached to the frame 28.

When the hot melt ink 33 undergoes a phase transformation from a liquid phase to a solid phase, it undergoes volumetric contraction, resulting in the generation of large internal stress. In the bamboo cantilever vibrator, large concentrated stress occurs at the fixed end, which may lead to damage. On the other hand, a double-supported beam-shaped vibrator is less likely to lead to destruction.

Furthermore, as shown in the embodiment of FIG. 6, it is also possible to install the electrical wiring 25 at the fixed end of the piezoelectric transducer 40 that projects outside the ink chamber 60. In this case, the electrical wiring 25 is cut off from the ink 33 in the ink chamber 60 by an ink cutoff member composed of the frame 28 and the nozzle plate 21. According to the above configuration, there is no occurrence of peeling or disconnection in the electrical wiring taken out from the inkjet head, especially due to the influence of the phase transformation of the hot melt ink 33, and the composition is compatible with all inks, not just the hot melt I ink 33. There is no melt I from the electric wiring structure ladle to the ink, and nozzle clogging due to melt precipitation in the ink does not occur. , FIG. 7 is also a block diagram of an ink sheet I printer showing another embodiment of the present invention. The recording paper 10 is attached along the platen], and is composed of a frame 28, a nozzle plate 21, and a piezoelectric transducer 40, and a guide shaft 14.17.
The inkjet head is guided by an inkjet head and is arranged to face the recording paper 10, an ink supply tube 50 that supplies ink to the inkjet head, and an ink tank 51. The nozzle opening 20 is located at the support end tm of only the N1 foil 23 of the piezoelectric transducer 40, and as a result, the structure above the nozzle opening of the inkjet head can be made smaller.

The ink droplet penetrates the piezoelectric element 240 that constitutes the piezoelectric transducer 40.
The signal line 27.52 and the signal line 2 connected on both sides
The liquid is ejected by the operation of the drive circuit 53 which applies a voltage to the piezoelectric element 24 via 7.52. The recording paper 10 is pressed by a roller 13 and a roller lever 54 above the inkjet head. Therefore, the above embodiment has the feature that the dimension a from the contact point of the roller 13 on the recording paper coat O to the position facing the nozzle opening can be shortened.

As a result, the upper blank area where printing is not possible when using cut paper can be reduced.

[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 vibrator, which needs to be managed with high precision in order to stabilize the ink droplet ejection characteristics, can be appropriately managed and reduced. This has the effect that it is possible to realize an inkjet head using a double-sided beam-shaped vibrator that has stable characteristics that can be driven by voltage and has a high manufacturing yield.

Further, according to the configuration F of the present invention, it is possible to realize an inkjet head with a high response frequency using a double-sided beam-shaped vibrator with a shortened natural vibration period without reducing the amount of deformation due to the bimetal effect with respect to a unit applied voltage. .

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a printer equipped with an inkjet head according to an embodiment of the present invention. FIG. 2 is a sectional view of an inkjet head according to an embodiment of the present invention. FIG. 3, FIG. 4, and FIG. 5 are cross-sectional views of an inkjet head showing one embodiment of the present invention. FIG. 6 is also a sectional view of an inkjet head showing an embodiment according to the present invention. FIG. 7 is a perspective view of a printer equipped with an inkjet head showing one embodiment of the present invention. ] 0 Recording paper 13 Roller 16 Inkjet head 20 Nozzle plate 23 Ni foil 24 Piezoelectric element 25 ηI air line 26 Pattern electrode 40 Piezoelectric transducer and above Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kisanbe Suzuki and 1 other person ('8)

Claims (6)

[Claims] (1) Consisting of a nozzle forming member having at least one or more nozzle openings, and a laminated layer of one layer of piezoelectric element and at least one or more layer of foil member arranged opposite to the nozzle opening, the piezoelectric element and A piezoelectric transducer having a double-supported beam structure in which one end made of the laminated portion of the foil member is a fixed end and the other end made only of the foil member is a fixed end, and a gap between the nozzle forming member and the piezoelectric transducer. An inkjet head comprising: an ink filling the periphery of the piezoelectric transducer; and an electrical signal line that propagates a selective electrical signal and is connected to the piezoelectric transducer. (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. . (3) The laminated length of the piezoelectric element and foil member of the double-sided beam-shaped piezoelectric transducer is longer than the laminated length of the foil member only, and the nozzle opening is formed only of the foil member of the double-sided beam-shaped piezoelectric transducer. 2. The inkjet head according to claim 1, wherein the inkjet head is located closer to the fixed end of the laminated portion. (4) The inkjet head according to claim 1, wherein the gap between the nozzle forming member and the piezoelectric transducer is 5 micrometers or more and 100 micrometers or less at the nozzle opening. (5) The inkjet head according to claim 1, wherein electrical wiring is connected to a fixed end of the piezoelectric transducer which is made of a laminated structure of a piezoelectric element and a foil member. (6) The inkjet head according to claim 1 or 2, further comprising an ink blocking member that surrounds the ink to form an ink chamber, and an electric wiring at a fixed end of the piezoelectric transducer that projects outside the ink chamber.