IK-JET HEAD

Abstract

An ink-jet head includes a passage unit in which a common ink chamber and individual ink passages are formed, and an actuator unit fixed to the passage unit. A closed passage having a shape of the individual ink passage being partially closed is formed in the passage unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Other and further objects, features and advantages of the invention will appear more fully from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of an external appearance of an ink-jet head according to a first embodiment of the present invention;

FIG. 2 is a sectional view taken along line II-II shown in FIG. 1;

FIG. 3 is a plan view of a head main body as seen from above;

FIG. 4 shows on an enlarged scale a region enclosed with an alternate long and short dash line in FIG. 3;

FIG. 5A is a sectional view taken along line VA-VA shown in FIG. 4;

FIG. 5B is a sectional view taken along line VB-VB shown in FIG. 4;

FIG. 5C is a sectional view taken along line VC-VC shown in FIG. 4;

FIG. 6A is a sectional view showing on an enlarged scale a part around a boundary between an actuator unit and a passage unit;

FIG. 6B is a partial plan view showing on an enlarged scale a shape of an individual electrode formed on a surface of the actuator unit;

FIG. 7 is a plan view of the actuator unit;

FIG. 8 shows on an enlarged scale a region enclosed with an alternate long and short dash line in FIG. 4;

FIG. 9 is a partial plan view showing on an enlarged scale a head main body of an ink-jet head according to a second embodiment of the present invention;

FIG. 10 is a sectional view taken along line X-X shown in FIG. 9; and

FIG. 11 is a sectional view, in correspondence to FIG. 5B, of an ink-jet head according to a third embodiment of the present invention.

Claims

1. An ink-jet head including: a passage unit in which formed are a common ink chamber and a plurality of individual ink passages each extending from an outlet of the common ink chamber through a pressure chamber to an ink ejection port; andan actuator unit that is fixed to a plane defined by a surface of the passage unit and gives ejection energy to ink in the pressure chamber,wherein a closed passage having a shape of the individual ink passage being partially closed is formed in the passage unit.

2. The ink-jet head according to claim 1, wherein: the plurality of individual ink passages are arranged into one or a plurality of individual ink passage rows extending in one direction, in such a manner that, in each of the individual ink passage rows, positions of neighboring individual ink passages are shifted from each other at a predetermined interval in the one direction; andthe closed passage is formed at a position shifted in the one direction outward from the individual ink passage that is located outermost in each of the rows with respect to the one direction.

3. The ink-jet head according to claim 2, wherein the closed passage is formed at a position shifted in the one direction at the predetermined interval outward from the individual ink passage that is located outermost in each of the rows with respect to the one direction.

4. The ink-jet head according to claim 1, wherein the closed passage is, in its portion existing at the same level as the pressure chamber with respect to a direction perpendicular to the plane, not closed.

5. The ink-jet head according to claim 1, wherein the closed passage is closed between a counterpart to an outlet of the common ink chamber in the individual ink passage and a counterpart to an inlet of the pressure chamber in the individual ink passage.

6. The ink-jet head according to claim 5, wherein the closed passage is closed in a counterpart to an outlet of the common ink chamber in the individual ink passage.

7. The ink-jet head according to claim 1, wherein the closed passage is closed between a counterpart to an outlet of the pressure chamber in the individual ink passage and a counterpart to the ink ejection port in the individual ink passage.

8. The ink-jet head according to claim 7, wherein the closed passage is closed in a counterpart to the ink ejection port in the individual ink passage.

9. The ink-jet head according to claim 1, wherein: when a plurality of the ink ejection ports corresponding to a plurality of the pressure chambers are projected in a direction perpendicular to an imaginary line that is parallel to the plane, their projective points onto the imaginary line align at regular intervals;the plurality of individual ink passages are regularly formed in an active region that is enclosed by a contour of the actuator unit in a plan view and in addition has its both ends, with respect to a direction of the imaginary line, defined by positions of the two projective points located outermost on the imaginary line; andthe closed passage is formed in an outer region that is enclosed by the contour of the actuator unit in a plan view and in addition located outside the active region.

10. The ink-jet head according to claim 9, wherein a boundary between the active region and the outer region exists at a boundary between where a length of the actuator unit intercepted by an imaginary plane that is perpendicular to the imaginary line is constant regardless of a position of the imaginary plane and where the length varies as the imaginary plane is displaced.

11. The ink-jet head according to claim 9, wherein: a plurality of the closed passages, each of which is not closed in a counterpart to the ink ejection port in the individual ink passage, are formed in the outer region;in an ejection face having a plurality of the ink ejection ports formed thereon and extending in parallel to the plane, a plurality of the ink ejection ports and a plurality of openings provided at a plurality of closed passages constitute an ejection port group that corresponds to the actuator unit; anda boundary between the active region and the outer region exists at a boundary between where a length of a region defining the ejection port group intercepted by an imaginary plane that is perpendicular to the imaginary line is constant regardless of a position of the imaginary plane and where the length varies as the imaginary plane is displaced.

12. The ink-jet head according to claim 9, wherein: the actuator unit includes a common electrode common to the plurality of pressure chambers and kept at a constant potential, a plurality of individual electrodes disposed so as to be opposed to the plurality of pressure chambers, respectively, and supplied with a drive signal for driving the actuator unit, and a piezoelectric layer sandwiched between the common electrode and the plurality of individual electrodes;the plurality of individual electrodes constitute an individual electrode group on the piezoelectric layer; anda boundary between the active region and the outer region exists at a boundary between where a length of a region defining the individual electrode group intercepted by an imaginary plane that is perpendicular to the imaginary line is constant regardless of a position of the imaginary plane and where the length varies as the imaginary plane is displaced.

13. The ink-jet head according to claim 9, wherein a plurality of the actuator units having the same shape are arranged in one direction on the plane of the passage unit.

14. The ink-jet head according to claim 13, wherein three or more actuator units are fixed to the plane.

15. The ink-jet head according to claim 13, wherein in a plan view the actuator unit has a quadrangular shape with two acute angles.

16. The ink-jet head according to claim 9, wherein: a plurality of the closed passages are formed in the outer region; andeach of a plurality of the closed passages disposed adjacent to a boundary between the active region and the outer region is, in its portion existing at the same level as the pressure chamber with respect to a direction perpendicular to the plane, not closed.

17. The ink-jet head according to claim 1, wherein a plurality of the closed passages are arranged over an entire circumference of the active region.