JP3336615B2 - Inkjet head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus such as a printer that forms an ink image on a medium such as recording paper by flying ink droplets, and more particularly to an ink jet printer head.

[Conventional technology]

It has a nozzle forming substrate having a nozzle and a pressure generating member made of a piezoelectric transducer arranged one-to-one to face the nozzle, and displaces the piezoelectric transducer by an applied voltage to sandwich ink between the nozzle forming substrate and the nozzle. An on-demand type ink jet head which generates pressure and ejects ink droplets from a nozzle is disclosed in Japanese Patent Application Laid-Open No. Sho 60-8953.
In the ink jet head having this structure, the piezoelectric transducer is displaced almost at right angles to the nozzle forming substrate, and the ink flow path is short, so that the ink discharge efficiency and the discharge stability are high. There is an advantage that normal operation is possible without being affected even if mixed.

[Problems to be solved by the invention]

However, in order to realize stable ejection characteristics with such an ink jet head, it is necessary to strictly control the distance (hereinafter referred to as a gap) between the end of the pressure generating member and the nozzle forming substrate in units of microns. However, the members constituting the ink-jet are thermally contracted due to a change in the temperature of the environment, and the gap easily changes by about several microns, so that there is a problem that the discharge characteristics greatly change depending on the ambient temperature. Conventionally, when a plurality of pressure generating members are arranged, the gap differs between the pressure generating members due to manufacturing variations, which also causes a problem that the ejection characteristics vary.

Therefore, an object of the present invention is to change the temperature of the surrounding environment and cause the members constituting the inkjet head to thermally expand and contract.
An object of the present invention is to provide an ink jet head in which ejection characteristics do not change.

It is another object of the present invention to provide an ink jet head capable of performing uniform printing without variation in ink ejection characteristics even when a plurality of nozzles are arranged.

[Means for solving the problem]

In order to solve the above problem, an inkjet head according to the present invention includes a nozzle forming substrate having a nozzle for ejecting an ink droplet, and a piezoelectric element for generating a pressure for ejecting the ink droplet arranged opposite to the nozzle. An ink jet head provided with an ink chamber formed in a region where the nozzle-side end surface of the piezoelectric element is projected, and a groove extending in at least two directions from the ink chamber to the outside of the ink chamber; Is characterized in that it is in contact with the nozzle forming substrate in the ink droplet ejection standby state.

[Action]

In the ink jet head configured as described above, since the amount of ink supplied to the nozzle inlet and the pressure of the ink are determined by the size of the groove, the discharge characteristics such as the amount of dots and the speed are adjusted by the size of the groove. Can be.

Further, since the end surface of the pressure generating member and the nozzle forming substrate are in close contact with each other by magnetic force, the positional relationship between the pressure generating member and the nozzle forming substrate does not change even if each element constituting the ink jet head expands and contracts due to a temperature change. Therefore, the ejection characteristics of the inkjet head do not change due to a change in environmental temperature. Further, since the pressure generating member and the nozzle forming substrate are in close contact with each other, all the pressure generating members and the nozzle forming substrate are always at the same position. Therefore, variations in the ejection characteristics are reduced.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of a printer equipped with an inkjet head according to the present invention. The recording medium 1 is a feed roller
It is drawn around the platen 4 by a few insertion pressures, and is conveyed in the direction of arrow 5 as recording proceeds. An ink jet head 9 having a plurality of nozzles is mounted on a carriage 8 which is guided by guide shafts 6 and 7 and can move in a direction parallel to the axis of the platen 4. Ink droplets are ejected from the nozzles to form an ink image on the recording medium.

FIG. 2 shows a perspective view of the ink jet head according to the present invention. The pressure generating member 19 has a multilayer structure sandwiched between the electrodes 20 and 22 of the piezoelectric element 21. The width w of the pressure generating member 19 is 30
0 ± 20μm, thickness b is 300 ± 20μm, length l is 1 ± 0.05mm
It is. The pressure generating members 19 are arranged in a lattice, and the distance c between the pressure generating members 19 is 100 ± 20 μm. The pressure generating member 19 is joined on the substrate 71, and the electrodes 20, 2
2 is electrically connected to the electrodes 72 and 73 on the substrate 71. The piezoelectric element 21 expands and contracts in the direction of arrow 60 by d ₃₃ converse piezoelectric effect by applying a voltage between the electrodes 20 and 22. As a result, the pressure generating member end 70 is
Displaced toward 31. Nozzle 33 is provided on nozzle forming substrate 31
Are formed. The portion surrounded by the substrate 71, the nozzle forming substrate 31, and the casing 23 is filled with ink. Substrate 71 is a paramagnetic material such as ferrite, nozzle forming substrate
31 is made of a ferromagnetic material such as Ni. Therefore, the nozzle forming substrate 31 is sucked in the direction of the substrate 71 (the direction of the arrow 41) and comes into close contact with the pressure generating member end portion 70. Therefore, the positional relationship between the pressure generating member end 70 and the nozzle forming substrate 31 is the same for the plurality of pressure generating members 19, 18, and 17.

FIG. 3 shows a front view of the nozzle and the groove according to the present invention. FIG. 4 is a sectional view taken along the ZZ plane of FIG. The nozzle forming substrate 31 is made of Ni. The nozzle 30 penetrates the nozzle forming substrate 31, an ink chamber 36 is provided at the nozzle entrance on the side facing the pressure generating member 19, and a portion where the groove 37 is covered by the pressure generating member 19 (a portion surrounded by a broken line 80). ) To outside. Width α is 50 ± 10 [mu] m of groove 37, the depth t ₁ is 60 ± 10 [mu] m. The diameter d ₁ of the ink chamber 36 is 200 ± 20 [mu]
m, the diameter d _n of nozzles are moderated in accordance with the ink amount required by 50μm from 20.

FIG. 5, FIG. 6, and FIG. 7 are operation diagrams of the ink jet head of the present invention. Here, the substrate 71 is made of a paramagnetic material such as ferrite, and the nozzle forming substrate 31 is made of a ferromagnetic material such as Ni. Therefore, as shown in FIG. 5, when no electric field is applied to the pressure generating member 19, the nozzle forming substrate 31 is sucked in the direction of the substrate 71 (the direction of the arrow 41) and comes into close contact with the pressure generating member end 70. .

The charge switch 26 is closed as shown in FIG.
The piezoelectric element 21 upon application of an electric field opposite to the polarization direction of the piezoelectric element 21 between 0,22 shrinks in the direction of arrow 38 by d ₃₃ piezoelectric reverse effect. At this time, the nozzle forming substrate 31 does not move due to inertia due to mass. Therefore, between the pressure generating member 19 and the nozzle forming substrate 31, it occurs gap h _0. As a result, the ink 25 passes through the groove 37 in the direction of the arrow 40 in the ink chamber 36.
Supplied to Width α in this case the groove 37, but the flow rate of the ink in the dimension of the depth t ₁ is determined by the managing these dimensions microns by etching techniques to manage the flow rate exactly, the inkjet head discharging The amount of ink ejection to be performed can be determined. Also for displacing from a state in which the pressure generating member 19 in close contact with the nozzle forming substrate 31, the displacement amount h ₀ is always constant, it is not affected by the expansion and contraction of the members due to temperature. Therefore, there is an advantage that the amount of ink flowing through the groove 37 is stabilized.

As shown in FIG. 7, the discharge switch 27 is closed and the electrodes 20, 2 are closed.
When the electric charge stored in 2 is discharged, the pressure generating member 19 is displaced in the direction of arrow 39 to eject the ink droplet 28. The pressure to be discharged at this time is determined by the pressure generating member end 70 and the nozzle forming substrate.
Width of the gap and the groove 37 between the 31 alpha, depends on the size of the depth t _1. In the state at the start of the ejection, the change in the gap is always constant irrespective of the expansion and contraction of the pressure generating member 19 and the like due to the temperature due to the close contact between the pressure generating member end 70 and the nozzle forming substrate 31.

〔The invention's effect〕

In the ink jet head of the present invention, as described above, the one end face of the piezoelectric element faces the nozzle opening and the ink chamber, and the groove communicating with the ink chamber is formed, so that the ejection efficiency and the responsiveness can be improved. At the same time, the groove allows the discharge amount and the discharge speed to have desired characteristics. Further, since the nozzle forming substrate and the end surface of the pressure generating member are in close contact with each other due to the magnetic force, even if the environmental temperature changes, the positional relationship between the nozzle forming substrate and the pressure generating member does not change, and the amount of the ejected ink droplets and There is an advantage that ejection characteristics such as speed are stabilized. As an application field of the inkjet head of the present invention, a full-color printer for office use, a serial printer, a page printer, and the like can be considered. However, the use environment is various, and the ejection characteristics are stable with respect to the temperature of the environment. Very important.

Further, since the pressure generating member and the nozzle forming substrate even when arranging a plurality of pressure generating member is in close contact in the initial state, there is little variation in the amount of displacement h ₀ of each of the pressure generating member,
There is an advantage that the ejection characteristics become uniform. Especially when applying an inkjet head to a full color printer, it is necessary to have multiple nozzles and pressure generating members in multiple colors,
Variations in the discharge characteristics appear as a light and shaded stripe pattern in the print, which is problematic. In such a case, the present invention is effective.

In addition, since a groove communicating with the nozzle inlet is provided on the pressure generating member side of the nozzle forming substrate, the width and depth of the groove are controlled to the micron unit by etching technology, and the discharge amount and discharge speed of the inkjet head are called. It is possible to finely change the ejection characteristics to obtain desired characteristics.

As described above, the inkjet head according to the present invention has stable ejection characteristics with respect to environmental temperature changes, and has uniform characteristics even when a plurality of ink jet heads are arranged, so that various ink ejection characteristics can be obtained. An inkjet printer having printing characteristics can be supplied to various fields.

[Brief description of the drawings]

FIG. 1 is a perspective view of an ink jet printer showing an embodiment according to the present invention. FIG. 2 is a perspective view of an ink jet head showing an embodiment according to the present invention. FIG. 3 is a front view of a nozzle forming substrate showing an embodiment according to the present invention. FIG. 4 is a sectional view of a nozzle forming substrate showing an embodiment according to the present invention. 5, 6, and 7 are operation diagrams of the ink jet head showing the embodiment according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Recording medium, 2, 3 ... Feed roller 4 ... Platen, 6, 7 ... Guide shaft 8 ... Carriage 9 ... Inkjet head 17-19 ... Pressure generating member 21 ... Piezoelectric element, 20, 22 ... Electrode 23 ... Casing, 24 ... Power supply 25 ... Ink, 26 ... Charge switch 27 ... Discharge switch, 28 ... Ink drop 30 ... Nozzle, 31 ... Nozzle forming board 36 ... Ink chamber , 37… Groove 71… Substrate, 72… Substrate electrode 73… Substrate electrode

Claims (1)

(57) [Claims] 1. An ink jet head comprising: a nozzle forming substrate having a nozzle for discharging an ink droplet; and a piezoelectric element arranged to face the nozzle and generating a pressure for discharging an ink droplet. An ink chamber formed in a region where the nozzle-side end surface of the piezoelectric element is projected, and a groove extending in at least two directions from the ink chamber to the outside of the region are formed on the formation substrate, and the piezoelectric element is formed of an ink. An ink jet head which is in contact with the nozzle forming substrate in a droplet discharge standby state.