EP1336490B1 - Ink-jet head and ink-jet printer having ink-jet head - Google Patents
Ink-jet head and ink-jet printer having ink-jet head Download PDFInfo
- Publication number
- EP1336490B1 EP1336490B1 EP20030003699 EP03003699A EP1336490B1 EP 1336490 B1 EP1336490 B1 EP 1336490B1 EP 20030003699 EP20030003699 EP 20030003699 EP 03003699 A EP03003699 A EP 03003699A EP 1336490 B1 EP1336490 B1 EP 1336490B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- ink
- pressure chambers
- pressure chamber
- jet head
- pressure
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2/14201—Structure of print heads with piezoelectric elements
- B41J2/14209—Structure of print heads with piezoelectric elements of finger type, chamber walls consisting integrally of piezoelectric material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2/14201—Structure of print heads with piezoelectric elements
- B41J2/14209—Structure of print heads with piezoelectric elements of finger type, chamber walls consisting integrally of piezoelectric material
- B41J2002/14217—Multi layer finger type piezoelectric element
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2/14201—Structure of print heads with piezoelectric elements
- B41J2/14209—Structure of print heads with piezoelectric elements of finger type, chamber walls consisting integrally of piezoelectric material
- B41J2002/14225—Finger type piezoelectric element on only one side of the chamber
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2/14201—Structure of print heads with piezoelectric elements
- B41J2002/14306—Flow passage between manifold and chamber
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2002/14459—Matrix arrangement of the pressure chambers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2002/14491—Electrical connection
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2202/00—Embodiments of or processes related to ink-jet or thermal heads
- B41J2202/01—Embodiments of or processes related to ink-jet heads
- B41J2202/11—Embodiments of or processes related to ink-jet heads characterised by specific geometrical characteristics
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2202/00—Embodiments of or processes related to ink-jet or thermal heads
- B41J2202/01—Embodiments of or processes related to ink-jet heads
- B41J2202/20—Modules
Definitions
- the present invention relates to an ink-jet head for printing by ejecting ink onto a record medium, and to an ink-jet printer having the ink-jet head.
- an ink-jet head distributes ink, which is supplied from an ink tank, to pressure chambers.
- the ink-jet head selectively applies pulse pressure to each pressure chamber to eject ink through a nozzle connected with each pressure chamber.
- an actuator unit or the like may be used in which ceramic piezoelectric sheets are laminated. The printing operations are carried out while reciprocating such a head at a high speed in the widthwise direction of paper.
- ink-jet head As for arrangement of pressure chambers in such an ink-jet head, there are one-dimensional arrangement in which pressure chambers are arranged in, e.g., one or two rows along the length of the head, and two-dimensional arrangement in which pressure chambers are arranged in a matrix along a surface of the head. To achieve high-resolution and highspeed printing demanded in recent years, two-dimensional arrangement of pressure chambers is more effective.
- ink-jet head in which pressure chambers are arranged in a matrix along a surface of the head
- an ink-jet head is known in which a nozzle is disposed at the center of each pressure chamber in a view perpendicular to the head surface (see US Patent No. 5757400 ).
- the propagation time length of the pressure waves (i.e., AL: Acoustic Length) is extremely short, so long as a head is not large-sized.
- AL Acoustic Length
- the time period for the pressure waves to be reversed and returned becomes short, so that a time interval between timings for a negative pressure and for a positive pressure also becomes short. Because of this, a highly responsive and expensive drive circuit is necessary to be used in the ink-jet head.
- the "fill after fire” is performed in order to avoid the above necessity, a large energy has to be inputted to the ink-jet head, to that the problem of a pure energy efficiency can be raised.
- an ink-jet head according to the preamble of claims 1 and 3 can be taken.
- the pressure chamber may have a shape in plane view which is quadrilateral hexagonal or an ellipse.
- an ink-jet head can be taken, wherein pressure chambers are provided. Nozzles are connected with the pressure chambers on one end. An ink supply source is connected to the pressure chamber at the other end.
- the pressure chambers have a planar shape of a 2n-angled shape.
- a virtual parallelogram region confining a pressure chamber can be constructed such that the parallelogram region can be arranged that a first direction along a longer diagonal line of the parallelogram region and a second direction joining the one end and the other end coincide with each other. These parallelogram regions would overlap.
- an ink-jet head having a passage unit including a plurality of pressure chambers each having one end connected with a nozzle and the other end to be connected with an ink supply source.
- a piezoelectric sheet for changing the volume of each of the pressure chambers is disposed so as to extend over two or more of the pressure chambers.
- An object of the present invention is to provide an ink-jet head which can achieve a high resolution and a high printing speed and can improve energy efficiency, and to provide an ink-jet printer having the ink-jet head.
- an ink-jet head according to claim 1 or claim 3.
- an ink-jet printer according to claim 11 having an ink-jet head.
- a second direction joining one end connected with the nozzle and the other end connected with the ink supply source in each of pressure chambers is substantially parallel to a plane of the passage unit where the pressure chambers are arranged.
- a pressure wave to be generated in the pressure chamber propagates substantially along the plane of the passage unit where the pressure chambers are arranged.
- AL can be relatively long without increasing the head thickness (a length of the head in a direction perpendicular to the plane). This provides a margin in time for matching the timings of generation and reflection of the pressure wave, and thus, "fill before fire” can be performed, and improvement of energy efficiency is achieved compared with the case of the "fill after fire".
- FIG. 1 is a general view of an ink-jet printer including ink-jet heads according to a first embodiment of the present invention.
- the ink-jet printer 101 as illustrated in FIG. 1 is a color ink-jet printer having four ink-jet heads 1.
- a paper feed unit 111 and a paper discharge unit 112 are disposed in left and right portions of FIG. 1 , respectively.
- a paper transfer path is provided extending from the paper feed unit 111 to the paper discharge unit 112.
- a pair of feed rollers 105a and 105b is disposed immediately downstream of the paper feed unit 111 for pinching and putting forward a paper as an image record medium.
- the paper is transferred from the left to the right in FIG. 1 .
- two belt rollers 106 and 107 and an endless transfer belt 108 are disposed.
- the transfer belt 108 is wound on the belt rollers 106 and 107 to extend between them.
- the outer face, i.e., the transfer face, of the transfer belt 108 has been treated with silicone.
- a paper fed through the pair of feed rollers 105a and 105b can be held on the transfer face of the transfer belt 108 by the adhesion of the face.
- the paper is transferred downstream (rightward) by driving one belt roller 106 to rotate clockwise in FIG. 1 (the direction indicated by an arrow 104).
- Pressing members 109a and 109b are disposed at positions for feeding a paper onto the belt roller 106 and taking out the paper from the belt roller 106, respectively. Either of the pressing members 109a and 109b is for pressing the paper onto the transfer face of the transfer belt 108 so as to prevent the paper from separating from the transfer face of the transfer belt 108. Thus, the paper surely adheres to the transfer face.
- a peeling device 110 is provided immediately downstream of the transfer belt 108 along the paper transfer path.
- the peeling device 110 peels off the paper, which has adhered to the transfer face of the transfer belt 108, from the transfer face to transfer the paper toward the rightward paper discharge unit 112.
- Each of the four ink-jet heads 1 has, at its lower end, a head main body 1a.
- Each head main body 1a has a rectangular section.
- the head main bodies 1a are arranged close to each other with the longitudinal axis of each head main body 1a being perpendicular to the paper transfer direction (perpendicular to FIG. 1 ). That is, this printer 101 is a line type.
- the bottom of each of the four head main bodies 1a faces the paper transfer path.
- a number of nozzles are provided each having a small-diameter ink ejection port.
- the four head main bodies 1a eject ink of magenta, yellow, cyan, and black, respectively.
- the head main bodies 1a are disposed such that a narrow clearance is formed between the lower face of each head main body 1a and the transfer face of the transfer belt 108.
- the paper transfer path is formed within the clearance.
- the ink-jet printer 101 is provided with a maintenance unit 117 for automatically carrying out maintenance of the ink-jet heads 1.
- the maintenance unit 117 includes four caps 116 for covering the lower faces of the four head main bodies 1a, and a not-illustrated purge system.
- the maintenance unit 117 is at a position immediately below the paper feed unit 111 (withdrawal position) while the ink-jet printer 101 operates to print.
- a predetermined condition for example, when a state in which no printing operation is performed continues for a predetermined time period or when the printer 101 is powered off
- the maintenance unit 117 moves to a position immediately below the four head main bodies 1a (cap position), where the maintenance unit 117 covers the lower faces of the head main bodies 1a with the respective caps 116 to prevent ink in the nozzles of the head main bodies 1a from being dried.
- the belt rollers 106 and 107 and the transfer belt 108 are supported by a chassis 113.
- the chassis 113 is put on a cylindrical member 115 disposed under the chassis 113.
- the cylindrical member 115 is rotatable around a shaft 114 provided at a position deviating from the center of the cylindrical member 115.
- the shaft 114 By rotating the shaft 114, the level of the uppermost portion of the cylindrical member 115 can be changed to move up or down the chassis 113 accordingly.
- the cylindrical member 115 When the maintenance unit 117 is moved from the withdrawal position to the cap position, the cylindrical member 115 must have been rotated at a predetermined angle in advance so as to move down the transfer belt 108 and the belt rollers 106 and 107 by a pertinent distance from the position illustrated in FIG. 1 . A space for the movement of the maintenance unit 117 is thereby ensured.
- a nearly rectangular parallelepiped guide 121 (having its width substantially equal to that of the transfer belt 108) is disposed at an opposite position to the ink-jet heads 1.
- the guide 121 is in contact with the lower face of the upper part of the transfer belt 108 to support the upper part of the transfer belt 108 from the inside.
- FIG. 2 is a perspective view of the ink-jet head 1.
- FIG. 3 is a sectional view taken along line II-II in FIG. 2 .
- the ink-jet head 1 according to this embodiment includes a head main body 1a having a rectangular shape in a plan view and extending in one direction (main scanning direction), and a base portion 131 for supporting the head main body 1a.
- the base portion 131 supporting the head main body 1a further supports thereon driver ICs 132 for supplying driving signals to individual electrodes 35a and 35b (see FIG. 6 and FIG. 10 ), and substrates 133.
- the base portion 131 is made up of a base block 138 partially bonded to the upper face of the head main body 1a to support the head main body 1a, and a holder 139 bonded to the upper face of the base block 138 to support the base block 138.
- the base block 138 is a nearly rectangular parallelepiped member having substantially the same length of the head main body 1a.
- the base block 138 made of metal material such as stainless steel has a function as a light structure for reinforcing the holder 139.
- the holder 139 is made up of a holder main body 141 disposed near the head main body 1a, and a pair of holder support portions 142 each extending on the opposite side of the holder main body 141 to the head main body 1a.
- Each holder support portion 142 is as a flat member.
- These holder support portions 142 extend along the longitudinal direction of the holder main body 141 and are disposed in parallel with each other at a predetermined interval.
- Skirt portions 141a in a pair, protruding downward, are provided in both end portions of the holder main body 141a in a sub scanning direction (perpendicular to the main scanning direction). Either skirt portion 141a is formed through the length of the holder main body 141. As a result, in the lower portion of the holder main body 141, a nearly rectangular parallelepiped groove 141b is defined by the pair of skirt portions 141a.
- the base block 138 is received in the groove 141b.
- the upper surface of the base block 138 is bonded to the bottom of the groove 141b of the holder main body 141 with an adhesive.
- the thickness of the base block 138 is somewhat larger than the depth of the groove 141b of the holder main body 141. As a result, the lower end of the base block 138 protrudes downward beyond the skirt portions 141a.
- an ink reservoir 3 is formed as a nearly rectangular parallelepiped space (hollow region) extending along the longitudinal direction of the base block 138.
- openings 3b are formed each communicating with the ink reservoir 3.
- the ink reservoir 3 is connected through a not-illustrated supply tube with a not-illustrated main ink tank (ink supply source) within the printer main body.
- the ink reservoir 3 is suitably supplied with ink from the main ink tank.
- each opening 3b protrudes downward from the surrounding portion.
- the base block 138 is in contact with a passage unit 4 (see FIG. 3 ) of the head main body 1a at the only vicinity portion 145a of each opening 3b of the lower face 145.
- the region of the lower face 145 of the base block 138 other than the vicinity portion 145a of each opening 3b is distant from the head main body 1a.
- Actuator units 21 are disposed within the distance.
- a driver IC 132 is fixed with an elastic member 137 such as a sponge being interposed between them.
- a heat sink 134 is disposed in close contact with the outer side face of the driver IC 132.
- the heat sink 134 is made of a nearly rectangular parallelepiped member for efficiently radiating heat generated in the driver IC 132.
- a flexible printed circuit (FPC) 136 as a power supply member is connected with the driver IC 132.
- the FPC 136 connected with the driver IC 132 is bonded to and electrically connected with the corresponding substrate 133 and the head main body 1a by soldering.
- the substrate 133 is disposed outside the FPC 136 above the driver IC 132 and the heat sink 134.
- the upper face of the heat sink 134 is bonded to the substrate 133 with a seal member 149.
- the lower face of the heat sink 134 is bonded to the FPC 136 with a seal member 149.
- a seal member 150 is disposed to sandwich the FPC 136.
- the FPC 136 is fixed by the seal member 150 to the passage unit 4 and the holder main body 141. Therefore, even if the head main body 1a is elongated, the head main body 1a can be prevented from being bent, the interconnecting portion between each actuator unit and the FPC 136 can be prevented from receiving stress, and the FPC 136 can surely be held.
- protruding portions 30a are disposed at regular intervals along the corresponding side wall of the ink-jet head 1. These protruding portions 30a are provided at both ends in the sub scanning direction of a nozzle plate 30 in the lowermost layer of the head main body 1a (see FIG. 7 ).
- the nozzle plate 30 is bent by about 90 degrees along the boundary line between each protruding portion 30a and the other portion.
- the protruding portions 30a are provided at positions corresponding to the vicinities of both ends of various papers to be used for printing.
- Each bent portion of the nozzle plate 30 has a shape not right-angled but rounded. This makes it hard to bring about clogging of a paper, i.e., jamming, which may occur because the leading edge of the paper, which has been transferred to approach the head 1, is stopped by the side face of the head 1.
- FIG. 4 is a schematic plan view of the head main body 1a.
- an ink reservoir 3 formed in the base block 138 is imaginarily illustrated with a broken line.
- the head main body 1a has a rectangular shape in the plan view extending in one direction (main scanning direction).
- the head main body 1a includes a passage unit 4 in which a large number of pressure chambers 10 and a large number of ink ejection ports 8 at the front ends of nozzles are formed (as for both, see FIGS. 5 , 6 , and 7 ), as described later.
- Trapezoidal actuator units 21 arranged in two lines in a staggered shape are bonded onto the upper face of the passage unit 4.
- Each actuator unit 21 is disposed such that its parallel opposed sides (upper and lower sides) extend along the longitudinal direction of the passage unit 4.
- the oblique sides of each neighboring actuator units 21 overlap each other in the lateral direction of the passage unit 4.
- the lower face of the passage unit 4 corresponding to the bonded region of each actuator unit 4 is made into an ink ejection region.
- a large number of ink ejection ports 8 are arranged in a matrix, as described later.
- an ink reservoir 3 is formed along the longitudinal direction of the base block 138.
- the ink reservoir 3 communicates with an ink tank (not illustrated) through an opening 3a provided at one end of the ink reservoir 3, so that the ink reservoir 3 is always filled up with ink.
- pairs of openings 3b are provided in regions where no actuator unit 21 is present, so as to be arranged in a staggered shape along the longitudinal direction of the ink reservoir 3.
- FIG. 5 is an enlarged view of the region enclosed with an alternate long and short dash line in FIG. 4 .
- the ink reservoir 3 communicates through each opening 3b with a manifold channel 5 disposed under the opening 3b.
- Each opening 3b is provided with a filter (not illustrated) for catching dust and dirt contained in ink.
- the front end portion of each manifold channel 5 branches into two sub-manifold channels 5a.
- two sub-manifold channels 5a extend from each of the two openings 3b on both sides of the actuator unit 21 in the longitudinal direction of the ink-jet head 1. That is, below the single actuator unit 21, four sub-manifold channels 5a in total extend along the longitudinal direction of the ink-jet head 1.
- Each sub-manifold channel 5a is filled up with ink supplied from the ink reservoir 3.
- FIG. 6 is an enlarged view of the region enclosed with an alternate long and short dash line in FIG. 5 .
- Either of FIGS. 5 and 6 is a vertical view of a plane in which many pressure chambers 10 are arranged in a matrix in the passage unit 4. Pressure chambers 10, apertures 12, nozzles 8, sub-manifold channels, etc., as components of the passage unit 4, are disposed at different levels from one another perpendicularly to FIGS. 5 and 6 (see FIG. 7 ).
- a number of rhombic regions 10x are so arranged adjacent to each other in a matrix in two directions, a first arrangement direction and a second arrangement direction as indicated by arrows in FIG. 6 , that they do not overlap each other but share their individual sides.
- the first arrangement direction and the second arrangement direction are parallel to the plane of a trapezoidal ink ejection region, as shown in FIG. 5 .
- the first arrangement direction is coincident with the longitudinal direction of the passage unit 4, whereas the second arrangement direction is coincident with the direction along one oblique side of the rhombic region 10x.
- the pressure chamber 10 has a substantially elliptic planar shape slightly smaller than the rhombic regions 10x and is individually housed in the region 10x.
- Each of the pressure chambers 10 is connected at its one end with the nozzle and at its other with the sub-manifold channel 5a, as will be described in detail.
- the one end connected with the nozzle and the other end connected with the sub-manifold channel 5a in each pressure chamber 10 are disposed separately at the two ends of the longer diagonal of each rhombic region 10x.
- the direction taken along the longer diagonal line of the rhombic region 10x i.e., the diagonal direction: a first direction
- the direction joining the one end and the other end of each pressure chamber 1 i.e., the two-end direction: a second direction
- the pressure wave propagating in the direction joining the one end and the other end of the pressure chamber 10 i.e., the two-end direction: the second direction
- the two-end direction the second direction
- the planar shape of the pressure chamber 10 is symmetrically with respect to an origin, such as a circle or a polygon.
- AL Acoustic Length
- the planar shape of the pressure chamber 10 is slender along the propagation direction of the pressure waves, i.e., the direction joining the one end and the other end (i.e., the two-end direction: the second direction).
- the planar shape of the pressure chamber 10 shown in FIG. 6 is elliptical, in which the length in the two-end direction (the second direction) is longer than the length in the direction perpendicular thereto.
- the first arrangement direction and the second arrangement direction of the matrix arrangement of the pressure chambers 10 do not intersect at a right angle but make an acute angle 'theta'.
- the spacing between each of the ink ejection ports 8 in the scanning direction of the ink-jet head 1 is narrowed.
- FIG. 6 illustrates pairs of individual electrodes 35a and 35b each overlapping the corresponding pressure chamber 10 in a plan view and having a shape in a plan view similar to that of the pressure chamber 10 and somewhat smaller than the pressure chamber 10.
- FIG. 7 is a partial sectional view of the head main body 1a of FIG. 4 .
- each ink ejection port 8 is formed at the tip end of a tapered nozzle.
- an aperture 12 extends substantially in parallel with the surface of the passage unit 4, like the pressure chamber 10. This aperture 12 is for restricting the ink flow to give the passage a suitable resistance, thereby achieving the stabilization of ink ejection.
- Each ink ejection port 8 communicates with a sub-manifold channel 5a through a pressure chamber 10 (length: 900 ⁇ m, width: 350 ⁇ m) and an aperture 12.
- ink passages 32 each extending from an ink tank to an ink ejection port 8 through an ink reservoir 3, a manifold channel 5, a sub-manifold channel 5a, an aperture 12, and a pressure chamber 10.
- each of the pressure chamber 10, the aperture 12, and the sub-manifold channel 5a is formed within layered sheet members. In a view perpendicular to the surface of the passage unit 4, they are disposed so as to overlap one another.
- FIGS. 5 and 6 to make it easy to understand the drawings, the pressure chambers 10, the apertures 12, etc., are illustrated with solid lines though they should be illustrated with broken lines because they are below the actuator unit 21.
- pressure chambers 10 are arranged within an ink ejection region in two directions, i.e., a direction along the length of the ink-jet head 1 (a first arrangement direction) and a direction somewhat inclining from the width of the ink-jet head 1 (a second arrangement direction).
- the first and second arrangement directions form an angle 'theta' somewhat smaller than the right angle.
- the ink ejection ports 8 are arranged at 50 dpi (dots per inch) in the first arrangement direction.
- the pressure chambers 10 are arranged in the second arrangement direction such that the ink ejection region corresponding to one actuator unit 21 may include twelve pressure chambers 10.
- ink-jet head 1 by ejecting ink droplets in order through a large number of ink ejection ports 8 arranged in the arrangement directions A and B with relative movement of a paper along the width of the ink-jet head 1, printing at 600 dpi in the main scanning direction can be performed.
- pressure chambers 10 are arranged in lines in the first arrangement direction at predetermined intervals at 500 dpi. Twelve lines of pressure chambers 10 are arranged in the second first arrangement directions the whole, the pressure chambers 10 are two-dimensionally arranged in the ink ejection region corresponding to one actuator unit 21.
- the pressure chambers 10 are classified into two kinds, i.e., pressure chambers 10a in each of which a nozzle is connected with the upper acute portion in FIG. 8 , and pressure chambers 10b in each of which a nozzle is connected with the lower acute portion.
- Pressure chambers 10a and 10b are arranged in the first arrangement direction to form pressure chamber rows 11a and 11b, respectively.
- FIG. 8 in the ink ejection region corresponding to one actuator unit 21, from the lower side of FIG. 8 , there are disposed two pressure chamber rows 11a and two pressure chamber rows 11b neighboring the upper side of the pressure chamber rows 11a.
- the four pressure chamber rows of the two pressure chamber rows 11a and the two pressure chamber rows 11b constitute a set of pressure chamber rows.
- Such a set of pressure chamber rows is repeatedly disposed three times from the lower side in the ink ejection region corresponding to one actuator unit 21.
- two first pressure chamber rows 11a and two pressure chamber rows 11b in which nozzles connected with pressure chambers 10 are disposed at different positions, are arranged alternately to neighbor each other. Consequently, as the whole, the pressure chambers 10 are arranged regularly.
- nozzles are arranged in a concentrated manner in a central region of each set of pressure chamber rows constituted by the above four pressure chamber rows.
- each four pressure chamber rows constitute a set of pressure chamber rows and such a set of pressure chamber rows is repeatedly disposed three times from the lower side as described above, there is formed a region where no nozzle exists, in the vicinity of the boundary between each neighboring sets of pressure chamber rows, i.e., on both sides of each set of pressure chamber rows constituted by four pressure chamber rows.
- Wide sub-manifold channels 5a extend there for supplying ink to the corresponding pressure chambers 10.
- four wide sub-manifold channels 5a in total are arranged in the first arrangement direction, i.e., one on the lower side of FIG. 8 , one between the lowermost set of pressure chamber rows and the second lowermost set of pressure chamber rows, and two on both sides of the uppermost set of pressure chamber rows.
- nozzles communicating with ink ejection ports 8 for ejecting ink are arranged in the first arrangement direction at regular intervals at 50 dpi to correspond to the respective pressure chambers 10 regularly arranged in the first arrangement direction.
- twelve pressure chambers 10 are regularly arranged also in the second arrangement direction forming an angle 'theta' with the first arrangement direction
- twelve nozzles corresponding to the twelve pressure chambers 10 include ones each communicating with the upper acute portion of the corresponding pressure chamber 10 and ones each communicating with the lower acute portion of the corresponding pressure chamber 10, as a result, they are not regularly arranged in the second arrangement direction at regular intervals.
- the nozzles are regularly arranged also in the second arrangement direction at regular intervals.
- nozzles are arranged so as to shift in the first arrangement direction by a distance corresponding to 600 dpi as resolution upon printing per pressure chamber row from the lower side to the upper side of FIG. 8 .
- the shift of nozzle position in the first arrangement direction per pressure chamber row from the lower side to the upper side of FIG. 8 is not always the same.
- a band region R will be discussed that has a width (about 508.0 ⁇ m) corresponding to 50 dpi in the first arrangement direction and extends perpendicularly to the first arrangement direction.
- any of twelve pressure chamber rows includes only one nozzle. That is, when such a band region R is defined at an optional position in the ink ejection region corresponding to one actuator unit 21, twelve nozzles are always distributed in the band region R.
- the positions of points respectively obtained by projecting the twelve nozzles onto a straight line extending in the first arrangement direction are distant from each other by a distance corresponding to 600 dpi as resolution upon printing.
- the twelve nozzles included in one band region R are denoted by (1) to (12) in order from one whose projected image onto a straight line extending in the first arrangement direction is the leftmost, the twelve nozzles are arranged in the order of (1), (7), (2), (8), (5), (11), (6), (12), (9), (3), (10), and (4) from the lower side.
- a character, a figure, or the like having a resolution of 600 dpi can be formed. That is, by selectively driving active layers corresponding to the twelve pressure chamber rows in order in accordance with the transfer of a print medium, a specific character or figure can be printed on the print medium.
- a case will be described wherein a straight line extending in the first arrangement direction is printed at a resolution of 600 dpi.
- nozzles communicate with the same-side acute portions of pressure chambers 10.
- ink ejection starts from a nozzle in the lowermost pressure chamber row in FIG. 8 .
- Ink ejection is then shifted upward with selecting a nozzle belonging to the upper neighboring pressure chamber row in order.
- Ink dots are thereby formed in order in the first arrangement direction with neighboring each other at 600 dpi.
- all the ink dots form a straight line extending in the first arrangement direction at a resolution of 600 dpi.
- ink ejection starts from a nozzle in the lowermost pressure chamber row 11a in FIG. 8 , and ink ejection is then shifted upward with selecting a nozzle communicating with the upper neighboring pressure chamber row in order in accordance with transfer of a print medium.
- ink dots formed in order in the first arrangement direction in accordance with the transfer of the print medium are not arranged at regular intervals at 600 dpi.
- ink is first ejected through a nozzle (1) communicating with the lowermost pressure chamber row 11a in FIG. 8 to form a dot row on the print medium at intervals corresponding to 50 dpi (about 508.0 ⁇ m).
- a nozzle (7) communicating with the second lowermost pressure chamber row 11a ink is ejected through the nozzle (7).
- ink is ejected through the nozzle (5).
- ink dots are formed with selecting nozzles communicating with pressure chambers 10 in order from the lower side to the upper side in FIG. 8 .
- N the number of a nozzle in FIG. 8
- FIG. 9 is a partial exploded view of the head main body 1a of FIG. 4 .
- a principal portion on the bottom side of the ink-jet head 1 has a layered structure laminated with ten sheet materials in total, i.e., from the top, an actuator unit 21, a cavity plate 22, a base plate 23, an aperture plate 24, a supply plate 25, manifold plates 26, 27, and 28, a cover plate 29, and a nozzle plate 30.
- nine plates other than the actuator unit 21 constitute the passage unit 4.
- the actuator unit 21 is laminated with five piezoelectric sheets and provided with electrodes so that three of them may include layers to be active when an electric field is applied (hereinafter, simply referred to as "layer including active layers") and the remaining two layers may be inactive.
- the cavity plate 22 is made of metal, in which a large number of substantially rhombic openings are formed corresponding to the respective pressure chambers 10.
- the base plate 23 is made of metal, in which a communication hole between each pressure chamber 10 of the cavity plate 22 and the corresponding aperture 12, and a communication hole between the pressure chamber 10 and the corresponding ink ejection port 8 are formed.
- the aperture plate 24 is made of metal, in which, in addition to apertures 12, communication holes are formed for connecting each pressure chamber 10 of the cavity plate 22 with the corresponding ink ejection port 8.
- the supply plate 25 is made of metal, in which communication holes between each aperture 12 and the corresponding sub-manifold channel 5a and communication holes for connecting each pressure chamber 10 of the cavity plate 22 with the corresponding ink ejection port 8 are formed.
- Each of the manifold plates 26, 27, and 28 is made of metal, which defines an upper portion of each sub-manifold channel 5a and in which communication holes are formed for connecting each pressure chamber 10 of the cavity plate 22 with the corresponding ink ejection port 8.
- the cover plate 29 is made of metal, in which communication holes are formed for connecting each pressure chamber 10 of the cavity plate 22 with the corresponding ink ejection port 8.
- the nozzle plate 30 is made of metal, in which tapered ink ejection ports 8 each functioning as a nozzle are formed for the respective pressure chambers 10 of the cavity plate 22.
- the ink passage 32 first extends upward from the sub-manifold channel 5a, then extends horizontally in the aperture 12, then further extends upward, then again extends horizontally in the pressure chamber 10, then extends obliquely downward in a certain length to get apart from the aperture 12, and then extends vertically downward toward the ink ejection port 8.
- FIG. 10 is a lateral enlarged sectional view of the region enclosed with an alternate long and short dash line in FIG. 7 .
- the actuator unit 21 includes five piezoelectric sheets 41, 42, 43, 44, and 45 having the same thickness of about 15 ⁇ m. These piezoelectric sheets 41 to 45 are made into a continuous layered flat plate (continuous flat layers) that is so disposed as to extend over many pressure chambers 10 formed within one ink ejection region in the ink-jet head 1.
- each of the piezoelectric sheets 41 to 45 is made of a lead zirconate titanate (PZT)-base ceramic material having ferroelectricity.
- an about 2 ⁇ m-thick common electrode 34a is interposed between the uppermost piezoelectric sheet 41 of the actuator unit 21 and the piezoelectric sheet 42 neighboring downward the piezoelectric sheet 41.
- the common electrode 34a is made of a single conductive sheet extending substantially in the whole region of the actuator unit 21. Also, between the piezoelectric sheet 43 neighboring downward the piezoelectric sheet 42 and the piezoelectric sheet 44 neighboring downward the piezoelectric sheet 43, an about 2 ⁇ m-thick common electrode 34b is interposed having the same shape as the common electrode 34a.
- many pairs of common electrodes 34a and 34b each having a shape larger than that of a pressure chamber 10 so that the projection image of each common electrode projected along the thickness of the common electrode may include the pressure chamber may be provided for each pressure chamber 10.
- many pairs of common electrodes 34a and 34b each having a shape somewhat smaller than that of a pressure chamber 10 so that the projection image of each common electrode projected along the thickness of the common electrode may be included in the pressure chamber may be provided for each pressure chamber 10.
- the common electrode 34a or 34b may not always be a single conductive sheet formed on the whole of the face of a piezoelectric sheet. In the above modifications, however, all the common electrodes must be electrically connected with one another so that the portion corresponding to any pressure chamber 10 may be at the same potential.
- an about 1 ⁇ m-thick individual electrode 35a is formed on the upper face of the piezoelectric sheet 41 at a position corresponding to the pressure chamber 10.
- the individual electrode 35a has a nearly elliptical shape (length: 850 ⁇ m, width: 250 ⁇ m) in a plan view similar to that of the pressure chamber 10, so that a projection image of the individual electrode 35a projected along the thickness of the individual electrode 35a is included in the corresponding pressure chamber 10 (see FIG. 6 ).
- an about 2 ⁇ m-thick individual electrode 35b having the same shape as the individual electrode 35a in a plan view is interposed at a position corresponding to the individual electrode 35a.
- Electrode is provided between the piezoelectric sheet 44 and the piezoelectric sheet 45 neighboring downward the piezoelectric sheet 44, and on the lower face of the piezoelectric sheet 45.
- Each of the electrodes 34a, 34b, 35a, and 35b is made of, e.g., an Ag-Pd-base metallic material.
- the common electrodes 34a and 34b are grounded in a not-illustrated region. Thus, the common electrodes 34a and 34b are kept at the ground potential at a region corresponding to any pressure chamber 10.
- the individual electrodes 35a and 35b in each pair corresponding to a pressure chamber 10 are connected to a driver IC 132 through an FPC 136 including leads independent of another pair of individual electrodes so that the potential of each pair of individual electrodes can be controlled independently of that of another pair(see FIGS. 2 and 3 ).
- the individual electrodes 35a and 35b in each pair vertically arranged may be connected to the driver IC 132 through the same lead.
- the piezoelectric sheets 41 to 43 are polarized in their thickness. Therefore, the individual electrodes 35a and 35b are set at a potential different from that of the common electrodes 34a and 34b to apply an electric field in the polarization, the portions of the piezoelectric sheets 41 to 43 to which the electric field has been applied works as active layers and the portions are ready to expand or contract in thickness, i.e., in layers, and to contract or expand perpendicularly to the thickness, i.e., in a plane, by the transversal piezoelectric effect.
- the actuator unit 21 has a so-called unimorph structure in which the upper (i.e., distant from the pressure chamber 10) three piezoelectric sheets 41 to 43 are layers including active layers and the lower (i.e., near the pressure chamber 10) two piezoelectric sheets 44 and 45 are inactive layers.
- the lowermost face of the piezoelectric sheets 41 to 45 is fixed to the upper face of partitions partitioning pressure chambers 10 formed in the cavity plate 22, as a result, the piezoelectric sheets 41 to 45 deform into a convex shape toward the pressure chamber side by contracting in a plane by the transversal piezoelectric effect (unimorph deformation). Therefore, the volume of the pressure chamber 10 is decreased to raise the pressure of ink. The ink is thereby ejected through the ink ejection port 8. After this, when the individual electrodes 35a and 35b are returned to the original potential, the piezoelectric sheets 41 to 45 return to the original flat shape and the pressure chamber 10 also returns to its original volume. Thus, the pressure chamber 10 sucks ink therein through the manifold channel 5.
- all the individual electrodes 35a and 35b are set in advance at a different potential from that of the common electrodes 34a and 34b so that the piezoelectric sheets 41 to 45 deform into a convex shape toward the pressure chamber 10 side.
- the corresponding pair of individual electrodes 35a and 35b is once set at the same potential as that of the common electrodes 34a and 34b.
- the pair of individual electrodes 35a and 35b is again set at the different potential from that of the common electrodes 34a and 34b.
- the piezoelectric sheets 41 to 45 return to their original shapes.
- the corresponding pressure chamber 10 is thereby increased in volume from its initial state (the state that the potentials of both electrodes differ from each other), to suck ink from the manifold channel 5 into the pressure chamber 10.
- the piezoelectric sheets 41 to 45 deform into a convex shape toward the pressure chamber 10.
- the volume of the pressure chamber 10 is thereby decreased and the pressure of ink in the pressure chamber 10 increases to eject ink.
- the piezoelectric sheets 41 to 45 deform into a concave shape toward the pressure chamber 10 by the transversal piezoelectric effect. Therefore, the volume of the pressure chamber 10 is increased to suck ink from the manifold channel 5. After this, when the individual electrodes 35a and 35b return to their original potential, the piezoelectric sheets 41 to 45 also return to their original flat, shape. The pressure chamber 10 thereby returns to its original volume to eject ink through the ink ejection port 8.
- the two-end direction (or the second direction) joining the one end connected with the nozzle and the other end connected with the sub-manifold channel 5a of the pressure chamber 10 is substantially parallel with the plane of the passage unit 4 where the pressure chambers 10 are arranged. Therefore, the pressure wave to be generated in the pressure chamber 10 propagates substantially along the plane of the passage unit 4. In case the pressure wave propagates in the direction perpendicular to the plane of the passage unit 4, the AL is shortened so long as the thickness of the head 1 (i.e., the length of the head 1 in the direction perpendicular to the plane) is not increased.
- the AL can be relatively long without increasing the thickness of the head 1. This provides a margin in time for matching the timings of generation and reflection of the pressure wave, and thus, the so-called "fill before fire” higher in energy efficiency than the "fill after fire” can be performed.
- the "fill before fire” is a method, in which a voltage is applied in advance to all the individual electrodes 35a and 35b to reduce the volumes of all pressure chambers 10, in which the voltage on the individual electrodes 35a and 35b is released only from the pressure chamber 10 for the ink ejecting action to enlarge its volume thereby to generate negative pressure waves, and in which the voltage is applied again to the individual electrodes 35a and 35b to reduce the volume of the pressure chambers 10 thereby to superpose the positive pressure waves at a timing for the negative pressure waves generated beforehand to reach after inverted and reflected, so that the ejection pressure is efficiently applied to the ink by using the pressure waves propagating in the pressure chambers 10.
- the pressure chamber 10 has the elliptical planar shape having no corner bulging in the direction to leave the line joining the one end and the other. Therefore, the spacing between the adjoining pressure chambers 10 can be enlarged to suppress the crosstalk which might otherwise raise a problem in case the pressure chambers 10 are arranged adjacent to each other.
- the planar shape of the pressure chamber 10 is formed into the elliptical shape having no corner as a whole so that the spacing between the adjoining pressure chambers 10 can be enlarged to suppress the crosstalk which might otherwise cause a problem in case the pressure chambers 10 are arranged close to each other.
- the flow of ink is smoothed, and the discharge of air bubbles in the ink by the purge is made easy so that the bubbles are hard to accumulate in the ink. Therefore, it is possible to eliminate the problem that the normal discharge of ink is obstructed by the bubbles.
- the direction along the longer diagonal line of the rhombic region 10x confining the pressure chamber 10 i.e., the diagonal direction: the first direction
- the direction joining the one end and the other of the pressure chamber 10 i.e., the two-end direction: the second direction
- the AL is the larger, moreover, it is the easier to control the "fill before fire".
- the effect to enlarge the AL can also be obtained because the planar shape of the pressure chamber 10 on the surface of the passage unit 4 is slender along the direction joining the one end and the other (i.e., the two-end direction: the second direction) or the propagation direction of the pressure waves.
- the planar shape of the pressure chamber 10 is symmetrical with respect to the axis in the propagation direction of the pressure wave or the direction joining the one end and the other (i.e., the two-end direction: the second direction). Therefore, the pressure waves to be generated in the pressure chamber 10 are symmetrically reflected to provide an effect that the discharge of ink is stabilized.
- the passage unit 4 is formed with nine sheet members 22 to 30 laminated each other and each having corresponding openings, the manufacture of the passage unit 4 is easy.
- the increase in shift of each actuator unit 21 from the accurate position on the passage unit 4 is restricted, and both can accurately be positioned to each other. Therefore, as to even an individual electrodes 35a and 35b being relatively apart from a mark, the individual electrodes 35a and 35b can not considerably be shifted from the predetermined position to the corresponding pressure chamber 10.
- the actuator unit 21 since the piezoelectric sheets 41 to 43 are sandwiched by the common electrodes 34a and 34b and the individual electrodes 35a and 35b, the volume of each pressure chamber 10 can easily be changed by the piezoelectric effect. Besides, since the piezoelectric sheets 41 to 45 are made into a continuous layered flat plate (continuous flat layers), the actuator unit 21 can easily be manufactured.
- the ink-jet head 1 has the actuator units 21 each having a unimorph structure in which the piezoelectric sheets 44 and 45 near each pressure chamber 10 are inactive and the piezoelectric sheets 41 to 43 distant from each pressure chamber 10 include active layers. Therefore, the change in volume of each pressure chamber 10 can be increased by the transversal piezoelectric effect. As a result, in comparison with an ink-jet head in which a layer including active portions is provided on the pressure chamber 10 side and a non-active layer is provided on the opposite side, lowering the voltage to be applied to the individual electrodes 35a and 35b and/or high integration of the pressure chambers 10 can be achieved.
- each pressure chamber 10 can be made small in size. Besides, even in case of a high integration of the pressure chambers 10, a sufficient amount of ink can be ejected. Thus, a decrease in size of the head 1 and a highly dense arrangement of printing dots can be realized.
- each actuator unit 21 has a substantially trapezoidal shape.
- the actuator units 21 are arranged in two lines in a staggered shape so that the parallel opposed sides of each actuator unit 21 extend along the length of the passage unit 4, and the oblique sides of each neighboring actuator units 21 overlap each other in the width of the passage unit 4. Since the oblique sides of each neighboring actuator units 21 thus overlap each other, in the length of the ink-jet head 1, the pressure chambers 10 existing along the width of the passage unit 4 can compensate each other. As a result, with realizing high-resolution printing, a small-size ink-jet head 1 having a very narrow width can be realized.
- planar shape of the pressure chamber on the passage unit 4 may not be slender along the direction joining the one end connected with the nozzle and the other end connected with the sub-manifold channel 5a(i.e., the two-end direction: the second direction). In this case, however, it is impossible to expect the high integration of the pressure chambers.
- the matrix arrangement direction of the pressure chambers on the surface of the passage unit 4 may not be limited to the first arrangement direction and the second arrangement direction, as shown in FIG. 6 , but may take various directions, as long as it is along the surface of the passage unit 4.
- the region for confining the pressure chamber 10 may be a parallelogram but may not be limited to the rhombic shape.
- the planar shape of the pressure chamber 10 itself contained in that region may be suitably changed in various shapes, as long as it is confined in that region and it is an elliptical shape or a 2n-angled shape (n: a natural number, n ⁇ 3) having no corner bulging in the direction to leave the line joining the one end and the other.
- n a natural number, n ⁇ 3
- a first modification is exemplified by a pressure chamber 60 having a substantially hexagonal planar shape, in which the corners corresponding to the obtuse portions of a rhombic region 60x are cut off substantially in parallel to the direction joining the one end and the other of the pressure chamber 10 (i.e., the two-end direction: the second direction).
- a second modification is exemplified by a pressure chamber 70 having a substantially elliptical planar shape more slender than that of the aforementioned embodiment along the direction joining the one end and the other of the pressure chamber 10 (i.e., the two-end direction: the second direction).
- Each of individual electrodes 65a and 65b and individual electrodes 75a and 75b has respectively a substantially hexagonal shape and a elliptical shape, which is substantially similar to and slightly smaller than the pressure chambers 60 and 70.
- FIGS. 11A and 11B and FIGS. 12A and 12B show neither a nozzle connected with the one end of the pressure chamber 60 nor a sub-manifold channel connected with the other end of the pressure chamber 60. However, a nozzle and a sub-manifold channel are formed respectively at the two ends on the longer diagonal line of rhombic region 60x and 70x.
- Each of the arrows in FIGS 11A and 11B shows the propagation direction of the pressure wave.
- FIG. 11B and FIG. 12B show the states, in which the pressure chambers 60 and 70 according to the first and second modifications illustrated in FIG. 11A and 12B are arranged in a 3 x 3 matrix, respectively.
- the spacing, as taken in the direction parallel to the shorter diagonal line of the rhombic region 60x, between the adjoining pressure chambers 60 and 60 is designated by d1.
- the aforementioned spacing in the pressure chambers 70 having the substantially elliptical plane according to the second modification and arranged in the matrix shown in FIG. 12B is designated by d2.
- the spacing between the adjoining pressure chambers is larger than that of the case in which the individual pressure chambers have shapes similar to and slightly smaller than those of the rhombic regions 60x and 70x. With this enlarged spacing, such a crosstalk hardly occurs as might otherwise raise a problem in case the pressure chambers are arranged close to each other.
- the spacing between the pressure chambers 60 arranged in the matrix can be efficiently enlarged by cutting off the corners substantially in parallel to the direction joining the one end and the other end of the pressure chambers 60 (i.e., the two-end direction: the second direction).
- the spacing between the pressure chambers 60 can be enlarged to suppress the crosstalk without drastically reducing the area of the pressure chambers 60.
- the pressure chambers 60 have a relatively simple planar shape such as the substantially hexagonal shape, so that they can be formed relatively easily.
- planar shape of the pressure chambers may also be a decagonal or deformed elliptical shape, for example.
- passage unit 4 may not be formed with laminated sheet members.
- each of the piezoelectric sheets and electrodes is not limited to those described above, and it may be changed to another known material.
- Each of the inactive layers may be made of an insulating sheet other than a piezoelectric sheet.
- the number of layers including active layers, the number of inactive layers, etc., may be changed properly.
- piezoelectric sheets as layers including active layers included in an actuator unit 21 are put in three or five layers in the above-described embodiment, piezoelectric sheets may be put in seven or more layers. In this case, the numbers of individual and common electrodes may properly be changed in accordance with the number of layered piezoelectric sheets.
- each actuator unit 21 includes two layers of piezoelectric sheets as inactive layers in the above-described embodiment, each actuator unit 21 may include only one inactive layer. Alternatively, each actuator unit 21 may include three or more inactive layers as far as they do not hinder the expansion or contraction deformation of the actuator unit 21.
- each actuator unit 21 of the above-described embodiment includes inactive layers on the pressure chamber side of layers including active layers, a layer or layers including active layers may be disposed on the pressure chamber 10 side of the inactive layers. Alternatively, no inactive layer may be provided. However, by providing the inactive layers 44 and 45 on the pressure chamber 10 side of the layers including active layers, it is expected to further improve the deformation efficiency of the actuator unit 21.
- common electrodes are kept at the ground potential in the above-described embodiment, this feature is not limitative.
- the common electrodes may be kept at any potential as far as the potential is in common to all pressure chambers 10.
- trapezoidal actuator units 21 are arranged in two lines in a staggered shape. But, each actuator unit may not always be trapezoidal. Besides, actuator units may be arranged in a single line along the length of the passage unit. Alternatively, actuator units may be arranged in three or more lines in a staggered shape. Further, not one actuator unit 21 is disposed to extend over pressure chambers 10 but one actuator unit 21 may be provided for each pressure chamber 10.
- each of the common electrodes 34a and 34b may not always be made of a single conductive sheet provided in the substantially whole region of each actuator unit 21. In such a case, however, the parts of each common electrode must be electrically connected with one another so that all the parts corresponding to the respective pressure chambers 10 are at the same potential.
Landscapes
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
Description
- The present invention relates to an ink-jet head for printing by ejecting ink onto a record medium, and to an ink-jet printer having the ink-jet head.
- In an ink-jet printer, an ink-jet head distributes ink, which is supplied from an ink tank, to pressure chambers. The ink-jet head selectively applies pulse pressure to each pressure chamber to eject ink through a nozzle connected with each pressure chamber. As a means for selectively applying pulse pressure to the pressure chambers, an actuator unit or the like may be used in which ceramic piezoelectric sheets are laminated. The printing operations are carried out while reciprocating such a head at a high speed in the widthwise direction of paper.
- As for arrangement of pressure chambers in such an ink-jet head, there are one-dimensional arrangement in which pressure chambers are arranged in, e.g., one or two rows along the length of the head, and two-dimensional arrangement in which pressure chambers are arranged in a matrix along a surface of the head. To achieve high-resolution and highspeed printing demanded in recent years, two-dimensional arrangement of pressure chambers is more effective. As an example of ink-jet head in which pressure chambers are arranged in a matrix along a surface of the head, an ink-jet head is known in which a nozzle is disposed at the center of each pressure chamber in a view perpendicular to the head surface (see
US Patent No. 5757400 ). In this case, when pulse pressure is applied to a pressure chamber, a pressure wave propagates in the pressure chamber perpendicularly to the head surface. Ink is then ejected through the corresponding nozzle disposed at the center of the pressure chamber in a view perpendicular to the head surface. - Here, in case of ejecting ink by using a pressure wave, there are known so-called "fill after fire" method, in which a positive pressure is applied to a pressure chamber, and so-called "fill before fire" method, in which at first a negative pressure is applied to a pressure chamber and then at a predetermined timing after a negative pressure wave has been reversed and reflected a positive pressure is applied. In these two methods of "fill after fire" and the "fill before fire", it is said that the "fill before fire" generally presents a higher energy efficiency. Moreover, in case a pressure wave propagates in a pressure chamber perpendicularly to the head surface as in the aforementioned conventional example, the propagation time length of the pressure waves (i.e., AL: Acoustic Length) is extremely short, so long as a head is not large-sized. Furthermore, if the "fill before fire" is performed in case of short AL, the time period for the pressure waves to be reversed and returned becomes short, so that a time interval between timings for a negative pressure and for a positive pressure also becomes short. Because of this, a highly responsive and expensive drive circuit is necessary to be used in the ink-jet head. In addition, if the "fill after fire" is performed in order to avoid the above necessity, a large energy has to be inputted to the ink-jet head, to that the problem of a pure energy efficiency can be raised.
- From
EP 1 138 493 Aclaims - From
JP 08-267743 A - The pressure chambers have a planar shape of a 2n-angled shape. A virtual parallelogram region confining a pressure chamber can be constructed such that the parallelogram region can be arranged that a first direction along a longer diagonal line of the parallelogram region and a second direction joining the one end and the other end coincide with each other. These parallelogram regions would overlap.
- From
US 2001/020968 A1 an ink-jet head can be taken having a passage unit including a plurality of pressure chambers each having one end connected with a nozzle and the other end to be connected with an ink supply source. A piezoelectric sheet for changing the volume of each of the pressure chambers is disposed so as to extend over two or more of the pressure chambers. - An object of the present invention is to provide an ink-jet head which can achieve a high resolution and a high printing speed and can improve energy efficiency, and to provide an ink-jet printer having the ink-jet head.
- According to an aspect of the present invention provided is an ink-jet head according to
claim 1 orclaim 3. - Since no corner bulges out perpendicularly to the line joining the ends the flow can be improved.
- According to another aspect of the present invention provided is an ink-jet printer according to
claim 11 having an ink-jet head. - In this construction, in an ink-jet head and an ink-jet printer capable of achieving the high resolution and the high printing speed, a second direction joining one end connected with the nozzle and the other end connected with the ink supply source in each of pressure chambers is substantially parallel to a plane of the passage unit where the pressure chambers are arranged. As a result, a pressure wave to be generated in the pressure chamber propagates substantially along the plane of the passage unit where the pressure chambers are arranged. In case the pressure wave thus propagates along the plane of the passage unit having the pressure chambers arranged, AL can be relatively long without increasing the head thickness (a length of the head in a direction perpendicular to the plane). This provides a margin in time for matching the timings of generation and reflection of the pressure wave, and thus, "fill before fire" can be performed, and improvement of energy efficiency is achieved compared with the case of the "fill after fire".
- 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 general view of an ink-jet printer including ink-jet heads according an embodiment of the present invention; -
FIG. 2 is a perspective view of an ink-jet head according to the embodiment of the present invention; -
FIG. 3 is a sectional view taken along line II-II inFIG. 2 ; -
FIG. 4 is a plan view of an head main body included in the ink-jet head ofFIG. 2 ; -
FIG. 5 is an enlarged view of the region enclosed with an alternate long and short dash line inFIG. 4 ; -
FIG. 6 is an enlarged view of the region enclosed with an alternate long and short dash line inFIG. 5 ; -
FIG. 7 is a partial sectional view of the head main body ofFIG. 4 taken along line III-III inFIG. 6 ; -
FIG. 8 is an enlarged view of the region enclosed with an alternate long and two short dashes line inFIG. 5 ; -
FIG. 9 is a partial exploded perspective view of the head main body ofFIG. 4 ; -
FIG. 10 is a lateral enlarged sectional view of the region enclosed with an alternate long and short dash line inFIG. 7 ; -
FIG. 11A is a diagram showing a first modification in a planar shape of a pressure chamber; -
FIG. 11B is a diagram showing the state, in which the pressure chambers illustrated inFIG. 11A are arranged in a 3 x 3 matrix; -
FIG. 12A is a diagram showing a second modification in the planar shape of a pressure chamber; and -
FIG. 12B is a diagram showing the state, in which the pressure chambers illustrated inFIG. 12A are arranged in a 3 x 3 matrix. -
FIG. 1 is a general view of an ink-jet printer including ink-jet heads according to a first embodiment of the present invention. The ink-jet printer 101 as illustrated inFIG. 1 is a color ink-jet printer having four ink-jet heads 1. In thisprinter 101, apaper feed unit 111 and apaper discharge unit 112 are disposed in left and right portions ofFIG. 1 , respectively. - In the
printer 101, a paper transfer path is provided extending from thepaper feed unit 111 to thepaper discharge unit 112. A pair offeed rollers paper feed unit 111 for pinching and putting forward a paper as an image record medium. By the pair offeed rollers FIG. 1 . In the middle of the paper transfer path, twobelt rollers endless transfer belt 108 are disposed. Thetransfer belt 108 is wound on thebelt rollers transfer belt 108 has been treated with silicone. Thus, a paper fed through the pair offeed rollers transfer belt 108 by the adhesion of the face. In this state, the paper is transferred downstream (rightward) by driving onebelt roller 106 to rotate clockwise inFIG. 1 (the direction indicated by an arrow 104). - Pressing
members belt roller 106 and taking out the paper from thebelt roller 106, respectively. Either of thepressing members transfer belt 108 so as to prevent the paper from separating from the transfer face of thetransfer belt 108. Thus, the paper surely adheres to the transfer face. - A
peeling device 110 is provided immediately downstream of thetransfer belt 108 along the paper transfer path. Thepeeling device 110 peels off the paper, which has adhered to the transfer face of thetransfer belt 108, from the transfer face to transfer the paper toward the rightwardpaper discharge unit 112. - Each of the four ink-
jet heads 1 has, at its lower end, a headmain body 1a. Each headmain body 1a has a rectangular section. The headmain bodies 1a are arranged close to each other with the longitudinal axis of each headmain body 1a being perpendicular to the paper transfer direction (perpendicular toFIG. 1 ). That is, thisprinter 101 is a line type. The bottom of each of the four headmain bodies 1a faces the paper transfer path. In the bottom of each headmain body 1a, a number of nozzles are provided each having a small-diameter ink ejection port. The four headmain bodies 1a eject ink of magenta, yellow, cyan, and black, respectively. - The head
main bodies 1a are disposed such that a narrow clearance is formed between the lower face of each headmain body 1a and the transfer face of thetransfer belt 108. The paper transfer path is formed within the clearance. In this construction, while a paper, which is being transferred by thetransfer belt 108, passes immediately below the four headmain bodies 1a in order, the respective color inks are ejected through the corresponding nozzles toward the upper face, i.e., the print face, of the paper to form a desired color image on the paper. - The ink-
jet printer 101 is provided with amaintenance unit 117 for automatically carrying out maintenance of the ink-jet heads 1. Themaintenance unit 117 includes fourcaps 116 for covering the lower faces of the four headmain bodies 1a, and a not-illustrated purge system. - The
maintenance unit 117 is at a position immediately below the paper feed unit 111 (withdrawal position) while the ink-jet printer 101 operates to print. When a predetermined condition is satisfied after finishing the printing operation (for example, when a state in which no printing operation is performed continues for a predetermined time period or when theprinter 101 is powered off), themaintenance unit 117 moves to a position immediately below the four headmain bodies 1a (cap position), where themaintenance unit 117 covers the lower faces of the headmain bodies 1a with therespective caps 116 to prevent ink in the nozzles of the headmain bodies 1a from being dried. - The
belt rollers transfer belt 108 are supported by achassis 113. Thechassis 113 is put on acylindrical member 115 disposed under thechassis 113. Thecylindrical member 115 is rotatable around a shaft 114 provided at a position deviating from the center of thecylindrical member 115. Thus, by rotating the shaft 114, the level of the uppermost portion of thecylindrical member 115 can be changed to move up or down thechassis 113 accordingly. When themaintenance unit 117 is moved from the withdrawal position to the cap position, thecylindrical member 115 must have been rotated at a predetermined angle in advance so as to move down thetransfer belt 108 and thebelt rollers FIG. 1 . A space for the movement of themaintenance unit 117 is thereby ensured. - In the region surrounded by the
transfer belt 108, a nearly rectangular parallelepiped guide 121 (having its width substantially equal to that of the transfer belt 108) is disposed at an opposite position to the ink-jet heads 1. Theguide 121 is in contact with the lower face of the upper part of thetransfer belt 108 to support the upper part of thetransfer belt 108 from the inside. - Next, the construction of each ink-
jet head 1 according to this embodiment will be described in more detail.FIG. 2 is a perspective view of the ink-jet head 1.FIG. 3 is a sectional view taken along line II-II inFIG. 2 . Referring toFIGS. 2 and3 , the ink-jet head 1 according to this embodiment includes a headmain body 1a having a rectangular shape in a plan view and extending in one direction (main scanning direction), and abase portion 131 for supporting the headmain body 1a. Thebase portion 131 supporting the headmain body 1a further supports thereondriver ICs 132 for supplying driving signals toindividual electrodes FIG. 6 andFIG. 10 ), andsubstrates 133. - Referring to
FIG. 2 , thebase portion 131 is made up of abase block 138 partially bonded to the upper face of the headmain body 1a to support the headmain body 1a, and aholder 139 bonded to the upper face of thebase block 138 to support thebase block 138. Thebase block 138 is a nearly rectangular parallelepiped member having substantially the same length of the headmain body 1a. Thebase block 138 made of metal material such as stainless steel has a function as a light structure for reinforcing theholder 139. Theholder 139 is made up of a holdermain body 141 disposed near the headmain body 1a, and a pair ofholder support portions 142 each extending on the opposite side of the holdermain body 141 to the headmain body 1a. Eachholder support portion 142 is as a flat member. Theseholder support portions 142 extend along the longitudinal direction of the holdermain body 141 and are disposed in parallel with each other at a predetermined interval. -
Skirt portions 141a in a pair, protruding downward, are provided in both end portions of the holdermain body 141a in a sub scanning direction (perpendicular to the main scanning direction). Eitherskirt portion 141a is formed through the length of the holdermain body 141. As a result, in the lower portion of the holdermain body 141, a nearlyrectangular parallelepiped groove 141b is defined by the pair ofskirt portions 141a. Thebase block 138 is received in thegroove 141b. The upper surface of thebase block 138 is bonded to the bottom of thegroove 141b of the holdermain body 141 with an adhesive. The thickness of thebase block 138 is somewhat larger than the depth of thegroove 141b of the holdermain body 141. As a result, the lower end of thebase block 138 protrudes downward beyond theskirt portions 141a. - Within the
base block 138, as a passage for ink to be supplied to the headmain body 1a, anink reservoir 3 is formed as a nearly rectangular parallelepiped space (hollow region) extending along the longitudinal direction of thebase block 138. In thelower face 145 of thebase block 138,openings 3b (seeFIG. 4 ) are formed each communicating with theink reservoir 3. Theink reservoir 3 is connected through a not-illustrated supply tube with a not-illustrated main ink tank (ink supply source) within the printer main body. Thus, theink reservoir 3 is suitably supplied with ink from the main ink tank. - In the
lower face 145 of thebase block 138, the vicinity of eachopening 3b protrudes downward from the surrounding portion. Thebase block 138 is in contact with a passage unit 4 (seeFIG. 3 ) of the headmain body 1a at the only vicinity portion 145a of eachopening 3b of thelower face 145. Thus, the region of thelower face 145 of thebase block 138 other than the vicinity portion 145a of eachopening 3b is distant from the headmain body 1a.Actuator units 21 are disposed within the distance. - To the outer side face of each
holder support portion 142 of theholder 139, adriver IC 132 is fixed with anelastic member 137 such as a sponge being interposed between them. Aheat sink 134 is disposed in close contact with the outer side face of thedriver IC 132. Theheat sink 134 is made of a nearly rectangular parallelepiped member for efficiently radiating heat generated in thedriver IC 132. A flexible printed circuit (FPC) 136 as a power supply member is connected with thedriver IC 132. TheFPC 136 connected with thedriver IC 132 is bonded to and electrically connected with the correspondingsubstrate 133 and the headmain body 1a by soldering. Thesubstrate 133 is disposed outside theFPC 136 above thedriver IC 132 and theheat sink 134. The upper face of theheat sink 134 is bonded to thesubstrate 133 with aseal member 149. Also, the lower face of theheat sink 134 is bonded to theFPC 136 with aseal member 149. - Between the lower face of each
skirt portion 141a of the holdermain body 141 and the upper face of thepassage unit 4, aseal member 150 is disposed to sandwich theFPC 136. TheFPC 136 is fixed by theseal member 150 to thepassage unit 4 and the holdermain body 141. Therefore, even if the headmain body 1a is elongated, the headmain body 1a can be prevented from being bent, the interconnecting portion between each actuator unit and theFPC 136 can be prevented from receiving stress, and theFPC 136 can surely be held. - Referring to
FIG. 2 , in the vicinity of each lower corner of the ink-jet head 1 along the main scanning direction, six protrudingportions 30a are disposed at regular intervals along the corresponding side wall of the ink-jet head 1.
These protrudingportions 30a are provided at both ends in the sub scanning direction of anozzle plate 30 in the lowermost layer of the headmain body 1a (seeFIG. 7 ). Thenozzle plate 30 is bent by about 90 degrees along the boundary line between each protrudingportion 30a and the other portion. The protrudingportions 30a are provided at positions corresponding to the vicinities of both ends of various papers to be used for printing. Each bent portion of thenozzle plate 30 has a shape not right-angled but rounded. This makes it hard to bring about clogging of a paper, i.e., jamming, which may occur because the leading edge of the paper, which has been transferred to approach thehead 1, is stopped by the side face of thehead 1. -
FIG. 4 is a schematic plan view of the headmain body 1a. InFIG. 4 , anink reservoir 3 formed in thebase block 138 is imaginarily illustrated with a broken line. Referring toFIG. 4 , the headmain body 1a has a rectangular shape in the plan view extending in one direction (main scanning direction).
The headmain body 1a includes apassage unit 4 in which a large number ofpressure chambers 10 and a large number ofink ejection ports 8 at the front ends of nozzles are formed (as for both, seeFIGS. 5 ,6 , and7 ), as described later.Trapezoidal actuator units 21 arranged in two lines in a staggered shape are bonded onto the upper face of thepassage unit 4. Eachactuator unit 21 is disposed such that its parallel opposed sides (upper and lower sides) extend along the longitudinal direction of thepassage unit 4. The oblique sides of each neighboringactuator units 21 overlap each other in the lateral direction of thepassage unit 4. - The lower face of the
passage unit 4 corresponding to the bonded region of eachactuator unit 4 is made into an ink ejection region. In the surface of each ink ejection region, a large number ofink ejection ports 8 are arranged in a matrix, as described later. In thebase block 138 disposed above thepassage unit 4, anink reservoir 3 is formed along the longitudinal direction of thebase block 138. Theink reservoir 3 communicates with an ink tank (not illustrated) through an opening 3a provided at one end of theink reservoir 3, so that theink reservoir 3 is always filled up with ink. In theink reservoir 3, pairs ofopenings 3b are provided in regions where noactuator unit 21 is present, so as to be arranged in a staggered shape along the longitudinal direction of theink reservoir 3. -
FIG. 5 is an enlarged view of the region enclosed with an alternate long and short dash line inFIG. 4 . Referring toFIGS. 4 and5 , theink reservoir 3 communicates through eachopening 3b with amanifold channel 5 disposed under theopening 3b. Eachopening 3b is provided with a filter (not illustrated) for catching dust and dirt contained in ink. The front end portion of eachmanifold channel 5 branches into twosub-manifold channels 5a. Below a single one of theactuator unit 21, twosub-manifold channels 5a extend from each of the twoopenings 3b on both sides of theactuator unit 21 in the longitudinal direction of the ink-jet head 1. That is, below thesingle actuator unit 21, foursub-manifold channels 5a in total extend along the longitudinal direction of the ink-jet head 1. Eachsub-manifold channel 5a is filled up with ink supplied from theink reservoir 3. -
FIG. 6 is an enlarged view of the region enclosed with an alternate long and short dash line inFIG. 5 . Either ofFIGS. 5 and6 is a vertical view of a plane in whichmany pressure chambers 10 are arranged in a matrix in thepassage unit 4.Pressure chambers 10,apertures 12,nozzles 8, sub-manifold channels, etc., as components of thepassage unit 4, are disposed at different levels from one another perpendicularly toFIGS. 5 and6 (seeFIG. 7 ). - As shown in
FIG. 6 , a number ofrhombic regions 10x (as shown by alternate long and short dash lines) are so arranged adjacent to each other in a matrix in two directions, a first arrangement direction and a second arrangement direction as indicated by arrows inFIG. 6 , that they do not overlap each other but share their individual sides. The first arrangement direction and the second arrangement direction are parallel to the plane of a trapezoidal ink ejection region, as shown inFIG. 5 . The first arrangement direction is coincident with the longitudinal direction of thepassage unit 4, whereas the second arrangement direction is coincident with the direction along one oblique side of therhombic region 10x. Thepressure chamber 10 has a substantially elliptic planar shape slightly smaller than therhombic regions 10x and is individually housed in theregion 10x. - Each of the
pressure chambers 10 is connected at its one end with the nozzle and at its other with thesub-manifold channel 5a, as will be described in detail. The one end connected with the nozzle and the other end connected with thesub-manifold channel 5a in eachpressure chamber 10 are disposed separately at the two ends of the longer diagonal of eachrhombic region 10x. In other words, the direction taken along the longer diagonal line of therhombic region 10x (i.e., the diagonal direction: a first direction) and the direction joining the one end and the other end of each pressure chamber 1 (i.e., the two-end direction: a second direction) are coincident with each other, as shown inFIG. 6 . Of the pressure waves which are generated in thepressure chamber 10 when a pressure is applied to thepressure chamber 10 by theactuator unit 21, therefore, the pressure wave propagating in the direction joining the one end and the other end of the pressure chamber 10 (i.e., the two-end direction: the second direction) is used as to contribute to the ejection of ink. - In case the propagating direction of the pressure wave used for ejection (as will be shortly called the "pressure wave") is perpendicular to the plane, it is usual that the planar shape of the
pressure chamber 10 is symmetrically with respect to an origin, such as a circle or a polygon. In case the propagation direction of the pressure wave is along the plane of thepassage unit 4 as in this embodiment, however, for elongating the propagation time length of the pressure waves (i.e., AL: Acoustic Length), it is preferable that the planar shape of thepressure chamber 10 is slender along the propagation direction of the pressure waves, i.e., the direction joining the one end and the other end (i.e., the two-end direction: the second direction). For this reason, the planar shape of thepressure chamber 10 shown inFIG. 6 is elliptical, in which the length in the two-end direction (the second direction) is longer than the length in the direction perpendicular thereto. - As shown in
FIG. 6 , the first arrangement direction and the second arrangement direction of the matrix arrangement of thepressure chambers 10 do not intersect at a right angle but make an acute angle 'theta'. As a result, the spacing between each of theink ejection ports 8 in the scanning direction of the ink-jet head 1 is narrowed. Thus, the image formation of a high resolution by the printing method described hereinafter. -
FIG. 6 illustrates pairs ofindividual electrodes corresponding pressure chamber 10 in a plan view and having a shape in a plan view similar to that of thepressure chamber 10 and somewhat smaller than thepressure chamber 10. -
FIG. 7 is a partial sectional view of the headmain body 1a ofFIG. 4 . As apparent fromFIG. 7 , eachink ejection port 8 is formed at the tip end of a tapered nozzle. Between apressure chamber 10 and asub-manifold channel 5a, anaperture 12 extends substantially in parallel with the surface of thepassage unit 4, like thepressure chamber 10. Thisaperture 12 is for restricting the ink flow to give the passage a suitable resistance, thereby achieving the stabilization of ink ejection. Eachink ejection port 8 communicates with asub-manifold channel 5a through a pressure chamber 10 (length: 900 µm, width: 350 µm) and anaperture 12. Thus, within the ink-jet head 1 formed areink passages 32 each extending from an ink tank to anink ejection port 8 through anink reservoir 3, amanifold channel 5, asub-manifold channel 5a, anaperture 12, and apressure chamber 10. - When viewing perpendicularly to
FIG. 6 , theaperture 12 communicating with apressure chamber 10 is disposed so as to overlap anotherpressure chamber 10 neighboring thatpressure chamber 10. A cause making this arrangement possible is that theaperture 12 is disposed on thesub-manifold channel 5a side of thepressure chamber 10 with respect to a direction perpendicular toFIG. 6 and it is provided at the different level from thepressure chamber 10. Referring toFIG. 7 , each of thepressure chamber 10, theaperture 12, and thesub-manifold channel 5a is formed within layered sheet members. In a view perpendicular to the surface of thepassage unit 4, they are disposed so as to overlap one another. - In
FIGS. 5 and6 , to make it easy to understand the drawings, thepressure chambers 10, theapertures 12, etc., are illustrated with solid lines though they should be illustrated with broken lines because they are below theactuator unit 21. - In the plane of
FIGS. 5 and6 ,pressure chambers 10 are arranged within an ink ejection region in two directions, i.e., a direction along the length of the ink-jet head 1 (a first arrangement direction) and a direction somewhat inclining from the width of the ink-jet head 1 (a second arrangement direction). The first and second arrangement directions form an angle 'theta' somewhat smaller than the right angle. Theink ejection ports 8 are arranged at 50 dpi (dots per inch) in the first arrangement direction. On the other hand, thepressure chambers 10 are arranged in the second arrangement direction such that the ink ejection region corresponding to oneactuator unit 21 may include twelvepressure chambers 10. The shift to the first arrangement direction due to the arrangement in which twelvepressure chambers 10 are arranged in the second arrangement direction, corresponds to onepressure chamber 10. Therefore, within the whole width of the ink-jet head 1, in a region of the interval between twoink ejection ports 8 neighboring each other in the first arrangement direction, there are twelveink ejection ports 8. At both ends of each ink ejection region in the first arrangement direction (corresponding to an oblique side of the actuator unit 21), the above condition is satisfied by making a compensation relation to the ink ejection region corresponding to theopposite actuator unit 21 in the width of the ink-jet head 1. Therefore, in the ink-jet head 1 according to this embodiment, by ejecting ink droplets in order through a large number ofink ejection ports 8 arranged in the arrangement directions A and B with relative movement of a paper along the width of the ink-jet head 1, printing at 600 dpi in the main scanning direction can be performed. - Next, the construction of the
passage unit 4 will be described in more detail with reference toFIG. 8 . Referring toFIG. 8 ,pressure chambers 10 are arranged in lines in the first arrangement direction at predetermined intervals at 500 dpi. Twelve lines ofpressure chambers 10 are arranged in the second first arrangement directions the whole, thepressure chambers 10 are two-dimensionally arranged in the ink ejection region corresponding to oneactuator unit 21. - The
pressure chambers 10 are classified into two kinds, i.e.,pressure chambers 10a in each of which a nozzle is connected with the upper acute portion inFIG. 8 , andpressure chambers 10b in each of which a nozzle is connected with the lower acute portion.Pressure chambers pressure chamber rows FIG. 8 , in the ink ejection region corresponding to oneactuator unit 21, from the lower side ofFIG. 8 , there are disposed twopressure chamber rows 11a and twopressure chamber rows 11b neighboring the upper side of thepressure chamber rows 11a. The four pressure chamber rows of the twopressure chamber rows 11a and the twopressure chamber rows 11b constitute a set of pressure chamber rows. Such a set of pressure chamber rows is repeatedly disposed three times from the lower side in the ink ejection region corresponding to oneactuator unit 21. A straight line extending through the upper acute portion of each pressure chamber in eachpressure chamber rows - As described above, when viewing perpendicularly to
FIG. 8 , two firstpressure chamber rows 11a and twopressure chamber rows 11b, in which nozzles connected withpressure chambers 10 are disposed at different positions, are arranged alternately to neighbor each other. Consequently, as the whole, thepressure chambers 10 are arranged regularly. On the other hand, nozzles are arranged in a concentrated manner in a central region of each set of pressure chamber rows constituted by the above four pressure chamber rows. Therefore, in case that each four pressure chamber rows constitute a set of pressure chamber rows and such a set of pressure chamber rows is repeatedly disposed three times from the lower side as described above, there is formed a region where no nozzle exists, in the vicinity of the boundary between each neighboring sets of pressure chamber rows, i.e., on both sides of each set of pressure chamber rows constituted by four pressure chamber rows. Widesub-manifold channels 5a extend there for supplying ink to thecorresponding pressure chambers 10. In this embodiment, in the ink ejection region corresponding to oneactuator unit 21, four widesub-manifold channels 5a in total are arranged in the first arrangement direction, i.e., one on the lower side ofFIG. 8 , one between the lowermost set of pressure chamber rows and the second lowermost set of pressure chamber rows, and two on both sides of the uppermost set of pressure chamber rows. - Referring to
FIG. 8 , nozzles communicating withink ejection ports 8 for ejecting ink are arranged in the first arrangement direction at regular intervals at 50 dpi to correspond to therespective pressure chambers 10 regularly arranged in the first arrangement direction. On the other hand, while twelvepressure chambers 10 are regularly arranged also in the second arrangement direction forming an angle 'theta' with the first arrangement direction, twelve nozzles corresponding to the twelvepressure chambers 10 include ones each communicating with the upper acute portion of thecorresponding pressure chamber 10 and ones each communicating with the lower acute portion of thecorresponding pressure chamber 10, as a result, they are not regularly arranged in the second arrangement direction at regular intervals. - If all nozzles communicate with the same-side acute portions of the
respective pressure chambers 10, the nozzles are regularly arranged also in the second arrangement direction at regular intervals. In this case, nozzles are arranged so as to shift in the first arrangement direction by a distance corresponding to 600 dpi as resolution upon printing per pressure chamber row from the lower side to the upper side ofFIG. 8 . Contrastingly in this embodiment, since four pressure chamber rows of twopressure chamber rows 11a and twopressure chamber rows 11b constitute a set of pressure chamber rows and such a set of pressure chamber rows is repeatedly disposed three times from the lower side, the shift of nozzle position in the first arrangement direction per pressure chamber row from the lower side to the upper side ofFIG. 8 is not always the same. - In the ink-
jet head 1 according to this embodiment, a band region R will be discussed that has a width (about 508.0 µm) corresponding to 50 dpi in the first arrangement direction and extends perpendicularly to the first arrangement direction. In this band region R, any of twelve pressure chamber rows includes only one nozzle. That is, when such a band region R is defined at an optional position in the ink ejection region corresponding to oneactuator unit 21, twelve nozzles are always distributed in the band region R. The positions of points respectively obtained by projecting the twelve nozzles onto a straight line extending in the first arrangement direction are distant from each other by a distance corresponding to 600 dpi as resolution upon printing. - When the twelve nozzles included in one band region R are denoted by (1) to (12) in order from one whose projected image onto a straight line extending in the first arrangement direction is the leftmost, the twelve nozzles are arranged in the order of (1), (7), (2), (8), (5), (11), (6), (12), (9), (3), (10), and (4) from the lower side.
- In the thus-constructed ink-
jet head 1 according to this embodiment, by properly driving active layers in theactuator unit 21, a character, a figure, or the like, having a resolution of 600 dpi can be formed. That is, by selectively driving active layers corresponding to the twelve pressure chamber rows in order in accordance with the transfer of a print medium, a specific character or figure can be printed on the print medium. - By way of example, a case will be described wherein a straight line extending in the first arrangement direction is printed at a resolution of 600 dpi. First, a case will be briefly described wherein nozzles communicate with the same-side acute portions of
pressure chambers 10. In this case, in accordance with transfer of a print medium, ink ejection starts from a nozzle in the lowermost pressure chamber row inFIG. 8 . Ink ejection is then shifted upward with selecting a nozzle belonging to the upper neighboring pressure chamber row in order. Ink dots are thereby formed in order in the first arrangement direction with neighboring each other at 600 dpi. Finally, all the ink dots form a straight line extending in the first arrangement direction at a resolution of 600 dpi. - On the other hand, in this embodiment, ink ejection starts from a nozzle in the lowermost
pressure chamber row 11a inFIG. 8 , and ink ejection is then shifted upward with selecting a nozzle communicating with the upper neighboring pressure chamber row in order in accordance with transfer of a print medium. In this embodiment, however, since the positional shift of nozzles in the first arrangement direction per pressure chamber row from the lower side to the upper side is not always the same, ink dots formed in order in the first arrangement direction in accordance with the transfer of the print medium are not arranged at regular intervals at 600 dpi. - More specifically, as shown in
FIG. 8 , in accordance with the transfer of the print medium, ink is first ejected through a nozzle (1) communicating with the lowermostpressure chamber row 11a inFIG. 8 to form a dot row on the print medium at intervals corresponding to 50 dpi (about 508.0 µm). After this, as the print medium is transferred and the straight line formation position has reached the position of a nozzle (7) communicating with the second lowermostpressure chamber row 11a, ink is ejected through the nozzle (7). The second ink dot is thereby formed at a position shifted from the first formed dot position in the first arrangement direction by a distance of six times the interval corresponding to 600 dpi (about 42.3 µm) (about 42.3 µm × 6 = about 254.0 µm). - Next, as the print medium is further transferred and the straight line formation position has reached the position of a nozzle (2) communicating with the third lowermost
pressure chamber row 11b, ink is ejected through the nozzle (2). The third ink dot is thereby formed at a position shifted from the first formed dot position in the first arrangement direction by a distance of the interval corresponding to 600 dpi (about 42.3 µm). As the print medium is further transferred and the straight line formation position has reached the position of a nozzle (8) communicating with the fourth lowermostpressure chamber row 11b, ink is ejected through the nozzle (8). The fourth ink dot is thereby formed at a position shifted from the first formed dot position in the first arrangement direction by a distance of seven times the interval corresponding to 600 dpi (about 42.3 µm) (about 42. 3 µm × 7 = about 296.3 µm). As the print medium is further transferred and the straight line formation position has reached the position of a nozzle (5) communicating with the fifth lowermostpressure chamber row 11a, ink is ejected through the nozzle (5). The fifth ink dot is thereby formed at a position shifted from the first formed dot position in the first arrangement direction by a distance of four times the interval corresponding to 600 dpi (about 42.3 µm) (about 42. 3 µm × 4 = about 169.3 µm). - After this, in the same manner, ink dots are formed with selecting nozzles communicating with
pressure chambers 10 in order from the lower side to the upper side inFIG. 8 . In this case, when the number of a nozzle inFIG. 8 is N, an ink dot is formed at a position shifted from the first formed dot position in the first arrangement direction by a distance corresponding to (magnification n = N - 1) × (interval corresponding to 600 dpi). When the twelve nozzles have been finally selected, the gap between the ink dots to be formed by the nozzles (1) in the lowermostpressure chamber rows 11a inFIG. 8 at an interval corresponding to 50 dpi (about 508.0 µm) is filled up with eleven dots formed at intervals corresponding to 600 dpi (about 42.3 µm). Therefore, as the whole, a straight line extending in the first arrangement direction can be drawn at a resolution of 600 dpi. -
FIG. 9 is a partial exploded view of the headmain body 1a ofFIG. 4 . Referring toFIGS. 7 and9 , a principal portion on the bottom side of the ink-jet head 1 has a layered structure laminated with ten sheet materials in total, i.e., from the top, anactuator unit 21, acavity plate 22, abase plate 23, anaperture plate 24, asupply plate 25,manifold plates cover plate 29, and anozzle plate 30. Of them, nine plates other than theactuator unit 21 constitute thepassage unit 4. - As will be described later in detail, the
actuator unit 21 is laminated with five piezoelectric sheets and provided with electrodes so that three of them may include layers to be active when an electric field is applied (hereinafter, simply referred to as "layer including active layers") and the remaining two layers may be inactive. Thecavity plate 22 is made of metal, in which a large number of substantially rhombic openings are formed corresponding to therespective pressure chambers 10. Thebase plate 23 is made of metal, in which a communication hole between eachpressure chamber 10 of thecavity plate 22 and the correspondingaperture 12, and a communication hole between thepressure chamber 10 and the correspondingink ejection port 8 are formed. Theaperture plate 24 is made of metal, in which, in addition toapertures 12, communication holes are formed for connecting eachpressure chamber 10 of thecavity plate 22 with the correspondingink ejection port 8. Thesupply plate 25 is made of metal, in which communication holes between eachaperture 12 and the correspondingsub-manifold channel 5a and communication holes for connecting eachpressure chamber 10 of thecavity plate 22 with the correspondingink ejection port 8 are formed. Each of themanifold plates sub-manifold channel 5a and in which communication holes are formed for connecting eachpressure chamber 10 of thecavity plate 22 with the correspondingink ejection port 8. Thecover plate 29 is made of metal, in which communication holes are formed for connecting eachpressure chamber 10 of thecavity plate 22 with the correspondingink ejection port 8. Thenozzle plate 30 is made of metal, in which taperedink ejection ports 8 each functioning as a nozzle are formed for therespective pressure chambers 10 of thecavity plate 22. - These ten
plates 21 to 30 are put in layers with being positioned to each other to form such anink passage 32 as illustrated inFIG. 7 . Theink passage 32 first extends upward from thesub-manifold channel 5a, then extends horizontally in theaperture 12, then further extends upward, then again extends horizontally in thepressure chamber 10, then extends obliquely downward in a certain length to get apart from theaperture 12, and then extends vertically downward toward theink ejection port 8. - Next, the construction of the
actuator unit 21 will be described.FIG. 10 is a lateral enlarged sectional view of the region enclosed with an alternate long and short dash line inFIG. 7 . Referring toFIG. 10 , theactuator unit 21 includes fivepiezoelectric sheets piezoelectric sheets 41 to 45 are made into a continuous layered flat plate (continuous flat layers) that is so disposed as to extend overmany pressure chambers 10 formed within one ink ejection region in the ink-jet head 1. Since thepiezoelectric sheets 41 to 45 are disposed so as to extend overmany pressure chambers 10 as the continuous flat layers, theindividual electrodes pressure chambers 10 formed at positions corresponding to theindividual electrodes piezoelectric sheets 41 to 45 is made of a lead zirconate titanate (PZT)-base ceramic material having ferroelectricity. - Between the uppermost
piezoelectric sheet 41 of theactuator unit 21 and thepiezoelectric sheet 42 neighboring downward thepiezoelectric sheet 41, an about 2 µm-thickcommon electrode 34a is interposed. Thecommon electrode 34a is made of a single conductive sheet extending substantially in the whole region of theactuator unit 21. Also, between thepiezoelectric sheet 43 neighboring downward thepiezoelectric sheet 42 and thepiezoelectric sheet 44 neighboring downward thepiezoelectric sheet 43, an about 2 µ m-thick common electrode 34b is interposed having the same shape as thecommon electrode 34a. - In a modification, many pairs of
common electrodes 34a and 34b each having a shape larger than that of apressure chamber 10 so that the projection image of each common electrode projected along the thickness of the common electrode may include the pressure chamber, may be provided for eachpressure chamber 10. In another modification, many pairs ofcommon electrodes 34a and 34b each having a shape somewhat smaller than that of apressure chamber 10 so that the projection image of each common electrode projected along the thickness of the common electrode may be included in the pressure chamber, may be provided for eachpressure chamber 10. Thus, thecommon electrode 34a or 34b may not always be a single conductive sheet formed on the whole of the face of a piezoelectric sheet. In the above modifications, however, all the common electrodes must be electrically connected with one another so that the portion corresponding to anypressure chamber 10 may be at the same potential. - Referring to
FIG. 10 , an about 1 µm-thickindividual electrode 35a is formed on the upper face of thepiezoelectric sheet 41 at a position corresponding to thepressure chamber 10. Theindividual electrode 35a has a nearly elliptical shape (length: 850 µm, width: 250 µm) in a plan view similar to that of thepressure chamber 10, so that a projection image of theindividual electrode 35a projected along the thickness of theindividual electrode 35a is included in the corresponding pressure chamber 10 (seeFIG. 6 ). Between thepiezoelectric sheets individual electrode 35b having the same shape as theindividual electrode 35a in a plan view is interposed at a position corresponding to theindividual electrode 35a. No electrode is provided between thepiezoelectric sheet 44 and thepiezoelectric sheet 45 neighboring downward thepiezoelectric sheet 44, and on the lower face of thepiezoelectric sheet 45. Each of theelectrodes - The
common electrodes 34a and 34b are grounded in a not-illustrated region. Thus, thecommon electrodes 34a and 34b are kept at the ground potential at a region corresponding to anypressure chamber 10. Theindividual electrodes pressure chamber 10 are connected to adriver IC 132 through anFPC 136 including leads independent of another pair of individual electrodes so that the potential of each pair of individual electrodes can be controlled independently of that of another pair(seeFIGS. 2 and3 ). In this case, theindividual electrodes driver IC 132 through the same lead. - In the ink-
jet head 1 according to this embodiment, thepiezoelectric sheets 41 to 43 are polarized in their thickness. Therefore, theindividual electrodes common electrodes 34a and 34b to apply an electric field in the polarization, the portions of thepiezoelectric sheets 41 to 43 to which the electric field has been applied works as active layers and the portions are ready to expand or contract in thickness, i.e., in layers, and to contract or expand perpendicularly to the thickness, i.e., in a plane, by the transversal piezoelectric effect. On the other hand, since the remaining twopiezoelectric sheets individual electrodes common electrodes 34a and 34b, they can not deform in their selves. That is, theactuator unit 21 has a so-called unimorph structure in which the upper (i.e., distant from the pressure chamber 10) threepiezoelectric sheets 41 to 43 are layers including active layers and the lower (i.e., near the pressure chamber 10) twopiezoelectric sheets - Therefore, when the
driver IC 132 is controlled so that an electric field is produced in the same direction as the polarization and theindividual electrodes common electrodes 34a and 34b, active layers in thepiezoelectric sheets 41 to 43 sandwiched by theindividual electrodes common electrodes 34a and 34b contract in a plane, while thepiezoelectric sheets FIG. 10 , the lowermost face of thepiezoelectric sheets 41 to 45 is fixed to the upper face of partitions partitioningpressure chambers 10 formed in thecavity plate 22, as a result, thepiezoelectric sheets 41 to 45 deform into a convex shape toward the pressure chamber side by contracting in a plane by the transversal piezoelectric effect (unimorph deformation). Therefore, the volume of thepressure chamber 10 is decreased to raise the pressure of ink. The ink is thereby ejected through theink ejection port 8. After this, when theindividual electrodes piezoelectric sheets 41 to 45 return to the original flat shape and thepressure chamber 10 also returns to its original volume. Thus, thepressure chamber 10 sucks ink therein through themanifold channel 5. - In another driving method, all the
individual electrodes common electrodes 34a and 34b so that thepiezoelectric sheets 41 to 45 deform into a convex shape toward thepressure chamber 10 side. When an ejecting request is issued, the corresponding pair ofindividual electrodes common electrodes 34a and 34b. After this, at a predetermined timing, the pair ofindividual electrodes common electrodes 34a and 34b. In this case, at the timing when the pair ofindividual electrodes common electrodes 34a and 34b, thepiezoelectric sheets 41 to 45 return to their original shapes. Thecorresponding pressure chamber 10 is thereby increased in volume from its initial state (the state that the potentials of both electrodes differ from each other), to suck ink from themanifold channel 5 into thepressure chamber 10. After this, at the timing when the pair ofindividual electrodes common electrodes 34a and 34b, thepiezoelectric sheets 41 to 45 deform into a convex shape toward thepressure chamber 10. The volume of thepressure chamber 10 is thereby decreased and the pressure of ink in thepressure chamber 10 increases to eject ink. - In case that the polarization occurs in the reverse direction to the electric field applied to the
piezoelectric sheets 41 to 43, the active layers in thepiezoelectric sheets 41 to 43 sandwiched by theindividual electrodes common electrodes 34a and 34b are ready to elongate perpendicularly to the polarization. As a result, thepiezoelectric sheets 41 to 45 deform into a concave shape toward thepressure chamber 10 by the transversal piezoelectric effect. Therefore, the volume of thepressure chamber 10 is increased to suck ink from themanifold channel 5. After this, when theindividual electrodes piezoelectric sheets 41 to 45 also return to their original flat, shape. Thepressure chamber 10 thereby returns to its original volume to eject ink through theink ejection port 8. - As described above, in the ink-
jet head 1 of this embodiment, as shown inFIG. 6 , the two-end direction (or the second direction) joining the one end connected with the nozzle and the other end connected with thesub-manifold channel 5a of thepressure chamber 10 is substantially parallel with the plane of thepassage unit 4 where thepressure chambers 10 are arranged. Therefore, the pressure wave to be generated in thepressure chamber 10 propagates substantially along the plane of thepassage unit 4. In case the pressure wave propagates in the direction perpendicular to the plane of thepassage unit 4, the AL is shortened so long as the thickness of the head 1 (i.e., the length of thehead 1 in the direction perpendicular to the plane) is not increased. In case the pressure wave propagates along the surface of thepassage unit 4 as in this embodiment, however, the AL can be relatively long without increasing the thickness of thehead 1. This provides a margin in time for matching the timings of generation and reflection of the pressure wave, and thus, the so-called "fill before fire" higher in energy efficiency than the "fill after fire" can be performed.
The "fill before fire" is a method, in which a voltage is applied in advance to all theindividual electrodes pressure chambers 10, in which the voltage on theindividual electrodes pressure chamber 10 for the ink ejecting action to enlarge its volume thereby to generate negative pressure waves, and in which the voltage is applied again to theindividual electrodes pressure chambers 10 thereby to superpose the positive pressure waves at a timing for the negative pressure waves generated beforehand to reach after inverted and reflected, so that the ejection pressure is efficiently applied to the ink by using the pressure waves propagating in thepressure chambers 10. In short, according to the aforementioned construction, it is possible to improve the energy efficiency in the ink-jet head 1. - Moreover, the
pressure chamber 10 has the elliptical planar shape having no corner bulging in the direction to leave the line joining the one end and the other. Therefore, the spacing between the adjoiningpressure chambers 10 can be enlarged to suppress the crosstalk which might otherwise raise a problem in case thepressure chambers 10 are arranged adjacent to each other. - Moreover, the planar shape of the
pressure chamber 10 is formed into the elliptical shape having no corner as a whole so that the spacing between the adjoiningpressure chambers 10 can be enlarged to suppress the crosstalk which might otherwise cause a problem in case thepressure chambers 10 are arranged close to each other. Moreover, the flow of ink is smoothed, and the discharge of air bubbles in the ink by the purge is made easy so that the bubbles are hard to accumulate in the ink. Therefore, it is possible to eliminate the problem that the normal discharge of ink is obstructed by the bubbles. - Moreover, the direction along the longer diagonal line of the
rhombic region 10x confining the pressure chamber 10 (i.e., the diagonal direction: the first direction) and the direction joining the one end and the other of the pressure chamber 10 (i.e., the two-end direction: the second direction) are coincident to achieve the high integration of thepressure chambers 10 and the smooth flow of ink and to enlarge the AL effectively. As the AL is the larger, moreover, it is the easier to control the "fill before fire". - Moreover, the effect to enlarge the AL can also be obtained because the planar shape of the
pressure chamber 10 on the surface of thepassage unit 4 is slender along the direction joining the one end and the other (i.e., the two-end direction: the second direction) or the propagation direction of the pressure waves. - Moreover, the planar shape of the
pressure chamber 10 is symmetrical with respect to the axis in the propagation direction of the pressure wave or the direction joining the one end and the other (i.e., the two-end direction: the second direction). Therefore, the pressure waves to be generated in thepressure chamber 10 are symmetrically reflected to provide an effect that the discharge of ink is stabilized. - Further, since the
passage unit 4 is formed with ninesheet members 22 to 30 laminated each other and each having corresponding openings, the manufacture of thepassage unit 4 is easy. - Further, in the head
main body 1a of the ink-jet head 1,separate actuator units 21 corresponding to the respective ink ejection regions are bonded onto thepassage unit 4 to be arranged along the length of thepassage unit 4. Therefore, each of theactuator units 21 apt to be uneven in dimensional accuracy because they are formed by sintering or the like, can be positioned to thepassage unit 4 independently from anotheractuator unit 21. Thus, even in case of a long head, the increase in shift of eachactuator unit 21 from the accurate position on thepassage unit 4 is restricted, and both can accurately be positioned to each other. Therefore, as to even anindividual electrodes individual electrodes corresponding pressure chamber 10. As a result, good ink ejection performance can be obtained and the manufacture yield of the ink-jet heads 1 is remarkably improved. On the other hand, differently from the above, if a long-shapedactuator unit 4 is made like thepassage unit 4, the more theindividual electrodes individual electrodes corresponding pressure chamber 10 in a plan view when theactuator unit 21 is laid over thepassage unit 4. As a result, the ink ejection performance of apressure chamber 10 relatively apart from the mark is deteriorated and thus the uniformity of the ink ejection performance in the ink-jet head 1 is not obtained. - Further, in the
actuator unit 21, since thepiezoelectric sheets 41 to 43 are sandwiched by thecommon electrodes 34a and 34b and theindividual electrodes pressure chamber 10 can easily be changed by the piezoelectric effect. Besides, since thepiezoelectric sheets 41 to 45 are made into a continuous layered flat plate (continuous flat layers), theactuator unit 21 can easily be manufactured. - Further, the ink-
jet head 1 has theactuator units 21 each having a unimorph structure in which thepiezoelectric sheets pressure chamber 10 are inactive and thepiezoelectric sheets 41 to 43 distant from eachpressure chamber 10 include active layers. Therefore, the change in volume of eachpressure chamber 10 can be increased by the transversal piezoelectric effect. As a result, in comparison with an ink-jet head in which a layer including active portions is provided on thepressure chamber 10 side and a non-active layer is provided on the opposite side, lowering the voltage to be applied to theindividual electrodes pressure chambers 10 can be achieved. By lowering the voltage to be applied, the driver for driving theindividual electrodes pressure chamber 10 can be made small in size. Besides, even in case of a high integration of thepressure chambers 10, a sufficient amount of ink can be ejected. Thus, a decrease in size of thehead 1 and a highly dense arrangement of printing dots can be realized. - Further, in the head
main body 1a of the ink-jet head 1, eachactuator unit 21 has a substantially trapezoidal shape. Theactuator units 21 are arranged in two lines in a staggered shape so that the parallel opposed sides of eachactuator unit 21 extend along the length of thepassage unit 4, and the oblique sides of each neighboringactuator units 21 overlap each other in the width of thepassage unit 4. Since the oblique sides of each neighboringactuator units 21 thus overlap each other, in the length of the ink-jet head 1, thepressure chambers 10 existing along the width of thepassage unit 4 can compensate each other. As a result, with realizing high-resolution printing, a small-size ink-jet head 1 having a very narrow width can be realized. - Here, the planar shape of the pressure chamber on the
passage unit 4 may not be slender along the direction joining the one end connected with the nozzle and the other end connected with thesub-manifold channel 5a(i.e., the two-end direction: the second direction). In this case, however, it is impossible to expect the high integration of the pressure chambers. - Moreover, the matrix arrangement direction of the pressure chambers on the surface of the
passage unit 4 may not be limited to the first arrangement direction and the second arrangement direction, as shown inFIG. 6 , but may take various directions, as long as it is along the surface of thepassage unit 4. - Moreover, the region for confining the
pressure chamber 10 may be a parallelogram but may not be limited to the rhombic shape. The planar shape of thepressure chamber 10 itself contained in that region may be suitably changed in various shapes, as long as it is confined in that region and it is an elliptical shape or a 2n-angled shape (n: a natural number, n ≥ 3) having no corner bulging in the direction to leave the line joining the one end and the other. For example, a modification of the planar shape of the pressure chamber is shown inFIG. 11A andFIG. 12A . InFIG. 11A , a first modification is exemplified by apressure chamber 60 having a substantially hexagonal planar shape, in which the corners corresponding to the obtuse portions of arhombic region 60x are cut off substantially in parallel to the direction joining the one end and the other of the pressure chamber 10 (i.e., the two-end direction: the second direction). InFIG. 12A , a second modification is exemplified by apressure chamber 70 having a substantially elliptical planar shape more slender than that of the aforementioned embodiment along the direction joining the one end and the other of the pressure chamber 10 (i.e., the two-end direction: the second direction). Each ofindividual electrodes individual electrodes pressure chambers FIGS. 11A and 11B andFIGS. 12A and 12B show neither a nozzle connected with the one end of thepressure chamber 60 nor a sub-manifold channel connected with the other end of thepressure chamber 60. However, a nozzle and a sub-manifold channel are formed respectively at the two ends on the longer diagonal line ofrhombic region FIGS 11A and 11B shows the propagation direction of the pressure wave. -
FIG. 11B andFIG. 12B show the states, in which thepressure chambers FIG. 11A and12B are arranged in a 3 x 3 matrix, respectively. when thepressure chambers 60 having a substantially hexagonal plane according to the first modification are arranged in the matrix, as shown inFIG. 11B , the spacing, as taken in the direction parallel to the shorter diagonal line of therhombic region 60x, between the adjoiningpressure chambers pressure chambers 70 having the substantially elliptical plane according to the second modification and arranged in the matrix shown inFIG. 12B is designated by d2. It will be understood that the spacing between the adjoining pressure chambers is larger than that of the case in which the individual pressure chambers have shapes similar to and slightly smaller than those of therhombic regions - Particularly for the
pressure chambers 60 according to the first modification, as shown inFIGS. 11A and 11B , the spacing between thepressure chambers 60 arranged in the matrix can be efficiently enlarged by cutting off the corners substantially in parallel to the direction joining the one end and the other end of the pressure chambers 60 (i.e., the two-end direction: the second direction). In other words, the spacing between thepressure chambers 60 can be enlarged to suppress the crosstalk without drastically reducing the area of thepressure chambers 60. Moreover, thepressure chambers 60 have a relatively simple planar shape such as the substantially hexagonal shape, so that they can be formed relatively easily. - Moreover, the planar shape of the pressure chambers may also be a decagonal or deformed elliptical shape, for example.
- Further, the
passage unit 4 may not be formed with laminated sheet members. - Further, the material of each of the piezoelectric sheets and electrodes is not limited to those described above, and it may be changed to another known material. Each of the inactive layers may be made of an insulating sheet other than a piezoelectric sheet. The number of layers including active layers, the number of inactive layers, etc., may be changed properly. For example, although piezoelectric sheets as layers including active layers included in an
actuator unit 21 are put in three or five layers in the above-described embodiment, piezoelectric sheets may be put in seven or more layers. In this case, the numbers of individual and common electrodes may properly be changed in accordance with the number of layered piezoelectric sheets. Although eachactuator unit 21 includes two layers of piezoelectric sheets as inactive layers in the above-described embodiment, eachactuator unit 21 may include only one inactive layer. Alternatively, eachactuator unit 21 may include three or more inactive layers as far as they do not hinder the expansion or contraction deformation of theactuator unit 21. Although eachactuator unit 21 of the above-described embodiment includes inactive layers on the pressure chamber side of layers including active layers, a layer or layers including active layers may be disposed on thepressure chamber 10 side of the inactive layers. Alternatively, no inactive layer may be provided. However, by providing theinactive layers pressure chamber 10 side of the layers including active layers, it is expected to further improve the deformation efficiency of theactuator unit 21. - Further, although the common electrodes are kept at the ground potential in the above-described embodiment, this feature is not limitative. The common electrodes may be kept at any potential as far as the potential is in common to all
pressure chambers 10. - Further, in the above-described embodiment, as illustrated in
FIG. 4 ,trapezoidal actuator units 21 are arranged in two lines in a staggered shape. But, each actuator unit may not always be trapezoidal. Besides, actuator units may be arranged in a single line along the length of the passage unit. Alternatively, actuator units may be arranged in three or more lines in a staggered shape. Further, not oneactuator unit 21 is disposed to extend overpressure chambers 10 but oneactuator unit 21 may be provided for eachpressure chamber 10. - Further, a large number of
common electrodes 34a and 34b may be formed for eachpressure chamber 10 so that a projection image of the common electrodes in the thickness of the common electrodes includes a pressure chamber region or the projection image is included within the pressure chamber region. Thus, each of thecommon electrodes 34a and 34b may not always be made of a single conductive sheet provided in the substantially whole region of eachactuator unit 21. In such a case, however, the parts of each common electrode must be electrically connected with one another so that all the parts corresponding to therespective pressure chambers 10 are at the same potential.
Claims (11)
- An ink-jet head (1) having a passage unit (4) including a plurality of pressure chambers (10) each having one end connected with a nozzle (8) and the other end to be connected with an ink supply source,
wherein each of said pressure chambers (10) is confined in each of a corresponding one of a plurality of parallelogram regions (10x) and
wherein a first direction along a longer diagonal line of said parallelogram region (10x) and a second direction along a line joining said one end and said other end in each of said pressure chambers (10) are substantially coincident with each other,
characterized in that
each of said pressure chambers (10) has a planar shape of a 2n-angled shape (n: a natural number, n ≥ 3) with no corner pointing in a direction substantially perpendicularly away from a line joining said one end and said other end in each of said pressure chambers (10), in a plane of said passage unit (4) where said pressure chambers (10) are arranged, and
said plurality of parallelogram regions (10x) are non-overlapping and arranged adjacent to each other so that the regions share their individual sides. - The ink-jet head (1) according to Claim 1,
wherein said planar shape of said pressure chamber (60) is hexagonal. - An ink-jet head (1) having a passage unit (4) including a plurality of pressure chambers (10) each having one end connected with a nozzle (8) and the other end to be connected with an ink supply source,
wherein each of said pressure chambers (10) is confined in each of a corresponding one of a plurality of parallelogram regions (10x) and
wherein a first direction along the longer diagonal line of said parallelogram region (10x) and a second direction along a line joining said one end and said other end in each of said pressure chambers (10) are substantially coincident with each other,
characterized in that
each of said pressure chambers (10) has an elliptical planar shape with the major axis along a line joining said one end and said other end in each of said pressure chambers (10), in a plane of said passage unit where said pressure chambers (10) are arranged, and
said plurality of parallelogram regions (10x) are non-overlapping and arranged adjacent to each other so that the regions share their individual sides. - The ink-jet head (1) according to one of Claims 1 to 3,
wherein the planar shape of said pressure chamber (10) is slender along said second direction. - The ink-jet head according to one of Claims 1 to 4,
wherein the planar shape of said pressure chamber (10) is axially symmetrical with respect to said second direction. - The ink-jet head (1) according to one of Claims 1 to 5,
wherein said pressure chambers (10) are arranged in a matrix along the plane of said passage unit (4). - The ink-jet head according to one of Claims 1 to 6,
wherein a piezoelectric sheet (41-45) for changing the volume of each of said pressure chambers (10) is disposed so as to extend over two or more of said pressure chambers (10). - The ink-jet head (1) according to one of Claims 1 to 6, further comprising: an actuator unit (21) arranged so as to extend over said pressure chambers (10) for changing the volume of said pressure chambers.
- The ink-jet head (1) according to one of claims 1 to 8,
wherein the second direction along a line joining said one end and said other end in each of said pressure chambers (10) is substantially in parallel with a plane of said passage unit (4) where said pressure chambers (10) are arranged. - The ink-jet head (1) according to Claim 9,
wherein said parallelogram regions (10x) are arranged adjacent to each other in a matrix in a third direction corresponding to a longitudinal direction of said passage unit (4) and in a fourth direction different from said third direction, in a plane of said passage unit (4) where said pressure chambers (10) are arranged. - An in-jet printer including an ink-jet head (1), as claimed in one of claims 1 to 10.
Applications Claiming Priority (8)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2002040524 | 2002-02-18 | ||
JP2002040524 | 2002-02-18 | ||
JP2002044626 | 2002-02-21 | ||
JP2002044650 | 2002-02-21 | ||
JP2002045146 | 2002-02-21 | ||
JP2002045146 | 2002-02-21 | ||
JP2002044650 | 2002-02-21 | ||
JP2002044626 | 2002-02-21 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP1336490A2 EP1336490A2 (en) | 2003-08-20 |
EP1336490A3 EP1336490A3 (en) | 2003-11-05 |
EP1336490B1 true EP1336490B1 (en) | 2008-10-01 |
Family
ID=27625455
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP20030003699 Expired - Lifetime EP1336490B1 (en) | 2002-02-18 | 2003-02-18 | Ink-jet head and ink-jet printer having ink-jet head |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP1336490B1 (en) |
CN (2) | CN2732483Y (en) |
DE (1) | DE60323773D1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100667845B1 (en) * | 2005-12-21 | 2007-01-11 | 삼성전자주식회사 | Array printing head and ink-jet image forming apparatus having the same |
WO2011052691A1 (en) * | 2009-10-28 | 2011-05-05 | 京セラ株式会社 | Liquid discharge head, liquid discharge apparatus employing the same, and recording device |
JP5509316B2 (en) * | 2010-03-26 | 2014-06-04 | 京セラ株式会社 | Driving device, recording apparatus, and recording method for driving liquid ejection head |
EP2727732B1 (en) * | 2011-06-28 | 2020-08-19 | Kyocera Corporation | Liquid discharge head and recording device using same |
WO2013014977A1 (en) | 2011-07-28 | 2013-01-31 | 京セラ株式会社 | Piezoelectric acuator, liquid discharge head, and recording device |
JP6123998B2 (en) * | 2013-03-27 | 2017-05-10 | セイコーエプソン株式会社 | Liquid ejecting head and liquid ejecting apparatus |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4317124A (en) * | 1979-02-14 | 1982-02-23 | Canon Kabushiki Kaisha | Ink jet recording apparatus |
EP0577383B1 (en) * | 1992-06-29 | 2003-10-08 | Hewlett-Packard Company, A Delaware Corporation | Thin film resistor printhead for thermal ink jet printers |
JPH0825628A (en) * | 1994-07-19 | 1996-01-30 | Fujitsu Ltd | Ink jet head |
JPH08267743A (en) * | 1995-03-30 | 1996-10-15 | Seikosha Co Ltd | Ink jet head |
US6604817B2 (en) * | 2000-03-07 | 2003-08-12 | Brother Kogyo Kabushiki Kaisha | Print head for piezoelectric ink jet printer, piezoelectric actuator therefor, and process for producing piezoelectric actuator |
US6488355B2 (en) * | 2000-03-21 | 2002-12-03 | Fuji Xerox Co., Ltd. | Ink jet head |
-
2003
- 2003-02-18 DE DE60323773T patent/DE60323773D1/en not_active Expired - Lifetime
- 2003-02-18 EP EP20030003699 patent/EP1336490B1/en not_active Expired - Lifetime
- 2003-02-18 CN CNU032014996U patent/CN2732483Y/en not_active Expired - Fee Related
- 2003-02-18 CN CN 03106110 patent/CN1280095C/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
EP1336490A3 (en) | 2003-11-05 |
CN1442297A (en) | 2003-09-17 |
EP1336490A2 (en) | 2003-08-20 |
CN2732483Y (en) | 2005-10-12 |
CN1280095C (en) | 2006-10-18 |
DE60323773D1 (en) | 2008-11-13 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US11305536B2 (en) | Ink-jet head having passage unit and actuator units attached to the passage unit, and ink-jet printer having the ink-jet head | |
EP1336495B1 (en) | Ink-jet head and ink-jet printer | |
US6945636B2 (en) | Ink-jet head, method for manufacturing ink-jet head and ink-jet printer having ink-jet head | |
US6984027B2 (en) | Ink-jet head and ink-jet printer having ink-jet head | |
US7014294B2 (en) | Ink-jet head and ink-jet printer having ink-jet head | |
EP1338420B1 (en) | Ink-jet head and ink-jet printer | |
EP1338419B1 (en) | Ink-jet head and ink-jet printer | |
EP1336488B1 (en) | Ink-jet head and ink-jet printer having ink-jet head | |
EP1336490B1 (en) | Ink-jet head and ink-jet printer having ink-jet head | |
JP4539064B2 (en) | Inkjet head | |
JP4206776B2 (en) | Ink jet head and ink jet printer having ink jet head | |
JP3960236B2 (en) | Ink jet head and ink jet printer having ink jet head |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PT SE SI SK TR |
|
AX | Request for extension of the european patent |
Extension state: AL LT LV MK RO |
|
PUAL | Search report despatched |
Free format text: ORIGINAL CODE: 0009013 |
|
AK | Designated contracting states |
Kind code of ref document: A3 Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PT SE SI SK TR |
|
AX | Request for extension of the european patent |
Extension state: AL LT LV MK RO |
|
17P | Request for examination filed |
Effective date: 20040206 |
|
AKX | Designation fees paid |
Designated state(s): DE FR GB |
|
17Q | First examination report despatched |
Effective date: 20060228 |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
GRAS | Grant fee paid |
Free format text: ORIGINAL CODE: EPIDOSNIGR3 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: HIROTA, ATSUSHI;C/O BROTHER KOGYO KK Inventor name: SAKAIDA, ATSUO;C/O BROTHER KOGYO KK |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: FG4D |
|
REF | Corresponds to: |
Ref document number: 60323773 Country of ref document: DE Date of ref document: 20081113 Kind code of ref document: P |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed |
Effective date: 20090702 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: PLFP Year of fee payment: 14 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: PLFP Year of fee payment: 15 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: PLFP Year of fee payment: 16 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20220125 Year of fee payment: 20 Ref country code: DE Payment date: 20220112 Year of fee payment: 20 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20220119 Year of fee payment: 20 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R071 Ref document number: 60323773 Country of ref document: DE |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: PE20 Expiry date: 20230217 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION Effective date: 20230217 |