EP0931653A1 - Piezoelectric actuator for ink jet printhead - Google Patents
Piezoelectric actuator for ink jet printhead Download PDFInfo
- Publication number
- EP0931653A1 EP0931653A1 EP99200090A EP99200090A EP0931653A1 EP 0931653 A1 EP0931653 A1 EP 0931653A1 EP 99200090 A EP99200090 A EP 99200090A EP 99200090 A EP99200090 A EP 99200090A EP 0931653 A1 EP0931653 A1 EP 0931653A1
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- EP
- European Patent Office
- Prior art keywords
- electrodes
- bottom face
- auxiliary
- piezoelectric actuator
- lead electrode
- 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.)
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Classifications
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- 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
- B41J2/14274—Structure of print heads with piezoelectric elements of stacked structure type, deformed by compression/extension and disposed on a diaphragm
Definitions
- the invention relates to a piezoelectric actuator for an ink jet printhead, comprising: a body of piezoelectric material having a bottom face through which the mechanical energy of the actuator is transferred to a receiving member, said body having an active part adjacent to the bottom face as well as an inactive part; a layered structure of alternating signal electrodes and common electrodes arranged in the active part in parallel with the bottom face and separated by layers of the piezoelectric material; a layered structure of altemating auxiliary electrodes and common electrodes arranged in the inactive part in parallel with the bottom face and separated by layers of the piezoelectric material; at least one signal lead electrode formed on a first side face of said body and interconnecting the signal electrodes; a ground lead electrode formed on a second side face opposite to said first side face and interconnecting the common electrodes; and an auxiliary lead electrode interconnecting the auxiliary electrodes.
- An actuator of this type is used for pressurizing liquid ink in an ink jet printhead, so that ink droplets can be jetted-out from nozzles of the printhead.
- the printhead has a linear array of nozzles, and each nozzle is connected to an ink channel that is filled with ink.
- the ink channels are arranged in parallel with each other and are covered by a sheet-like receiving member which is bonded to the bottom face of the actuator so that it may be deformed in accordance with the expansion and retraction strokes of the actuator in order to compress the ink in the ink channels.
- the active part of the piezoelectric body is divided into a plurality of parallel fingers respectively associated with the individual ink channels and separated by dicing cuts cut into the bottom face of the body.
- the inactive part of the body forms a bridge-like structure which interconnects the fingers on the side opposite to the bottom face.
- the signal lead electrodes are respectively associated with the individual fingers, so that an ink droplet from a selected one of the nozzles can be obtained by applying a voltage across the associated signal lead electrode and the ground lead electrode.
- the inactive bridge portion of the piezoelectric body serves as a backing member which bears the reaction forces of the active actuator fingers and also facilitates the manufacturing process in that it permits the production of a plurality of fingers as a one-piece construction, simply by forming dicing cuts in the piezoelectric body.
- the auxiliary electrodes in the inactive part are not needed when the printhead is operating. These auxiliary electrodes are only needed in the process of manufacturing the actuator.
- a piezoelectric device made for example of piezoelectric ceramic needs to be polarized during the manufacturing process in order to show the desired piezoelectric effect.
- This polarizing step is accompanied by an anisotropic shrinkage or expansion of the piezoelectric material,
- the plezoelectric body as a whole would behave like a bimorph element and would undesirably be distorted or even broken.
- the auxiliary electrodes are used for polarizing also the inactive part of the piezoelectric body.
- Fig. 4 illustrates an example of a printhead 10 in which a commercially available piezoelectric actuator 12 is employed.
- the printhead 10 comprises a support member 14 on which a channel plate 16 is disposed.
- a plurality of parallel ink channels 18 are formed in the top surface of the channel plate 16. Only one of these ink channels 18 is shown in Fig. 4.
- One end of the ink channel 18 is formed as a nozzle 20 from which ink droplets are to be expelled.
- the rear end of the ink channel is connected to an ink supply system (not shown) which is accommodated in the support member 14,
- a receiving member 22 is formed as a thin flexible sheet and is superposed on the channel plate 16 so that it covers all the ink channels 18 and nozzles 20.
- the actuator 12 comprises a body 24 made of piezoelectric ceramic and shaped as a parallelepiped having a bottom face 26 which is bonded to the receiving member 22.
- the portion of the body 24 adjacent to the bottom face 26 is subdivided into a plurality of fingers 28 which are arranged in parallel with one another and with the ink channels 18.
- Each finger 28 is disposed directly above a respective one of the ink channels 18.
- the body 24 and also the fingers 28 thereof extend beyond the ink channels 18 on the side opposite to the nozzles 20.
- Only the part of the fingers 28 situated above the ink channels 18 is formed as an active part 30 of the piezoelectric actuator.
- This active part 30 comprises a layered structure with alternating signal electrodes 32 and common electrodes 34.
- the common electrodes 34 extend only over the active part 30, whereas the signal electrodes 32 extend over the entire length of the body 24 and, accordingly, are also present in an inactive part 36 which is offset from the ink channels 18.
- This inactive part 38 contains a layered structure with alternating common electrodes 34 and auxiliary electrodes 40.
- All the electrodes 32, 34 and 40 are formed by plane rectangular sheets of conductive material arranged in parallel with the bottom face 26 of the body 24 and separated from each other by layers of ceramic material.
- the signal electrodes 32 of each finger 28 are interconnected with each other by a signal lead electrode 42 formed on a rear side face of the body 24, i.e. the side face opposite to the nozzles 20.
- all the common electrodes 34 in the active part 30 and the inactive part 38 are interconnected by a common ground lead electrode 44 formed on the front side face of the body 24.
- the auxiliary electrodes 40 are interconnected by a common auxiliary lead electrode 46 formed again on the rear side face of the body 24 but separated from the signal lead electrodes 42 by a gap 48.
- the signal lead electrodes 42 and the ground lead electrode 44 are connected to respective contact electrodes 50 and 42 formed on the bottom face 26 of the body 24.
- the contact electrode 52 extends beyond the rear ends of the ink channels 18. All the contact electrodes 50 and 52 are electrically connected to a control circuit (not shown) via electrical leads formed on a connecting piece 54.
- the connecting piece 54 is formed by a flexible foil which is sandwiched between the bottom face 26 of the body 24 and the receiving member 22 below the inactive part 36.
- the connecting piece 54 is not provided between the active part 30 of the actuator and the receiving member 22 but is only provided in the rear of the ink channels 18.
- the body 24 has been extended rearwardly beyond the ink channels 18 in order to provide a sufficient contact area between the contact electrodes 50 and 52 and the connecting piece 54. Since the receiving member 22 cannot flex downwardly in this area because it is supported by the channel plate 16, the part 36 of the body 24 is inactive and does not contain common electrodes 34.
- the connecting piece 54 must be adjoined to the bottom face 26 because the front and rear side faces of the inactive top part of the body 24 are occupied by the ground lead electrode 44 and the auxiliary lead electrode 46 which are needed for connecting the common electrodes 34 and auxiliary electrodes 40 in the inactive part 38 during the polarizing step. It is an object of the present invention to provide a piezoelectric actuator which offers more freedom of design when the actuator is employed in an ink jet printhead.
- the auxiliary lead electrode is formed on a third side face of the block.
- first and second side faces of the block can be used in their entirety for connecting the signal electrodes and the common electrodes, which permits more freedom of choice in respect to the position where a connecting piece is adjoined to the piezoelectric block.
- the connecting piece may be adjoined to the block in a position remote from the bottom face, for example, on the top face opposite to the bottom face.
- this bonding step is a rather intricate procedure. Bonding is normally performed by means of an adhesive which needs to be cured at high temperatures. Thus, when a thin foil serving as the connecting piece is sandwiched between the actuator and the receiving member, this connecting piece may be deteriorated by the heat applied in the bonding step.
- the actuator may be shortened so that it is provided only above the ink channels and no longer needs to have an inactive part adjacent to the bottom face. As a result, the actuator becomes more compact and less expensive.
- the ink jet printhead 10 shown in Fig. 1 has the same general construction as the printhead that has already been described in conjunction with Fig. 4. Like parts are designated by like reference numerals, and as for details of the components that have already been described, reference is made to the introductory part of this specification.
- the piezoelectric actuator 12 according to the invention has been employed and that the connecting piece 54 is adjoined to the top face of the body 24 of the actuator. Accordingly, the contact electrodes 50 and 52 are formed on the top face of the body 24 and are electrically connected to the signal electrodes 32 and common electrodes 34, respectively, by signal lead electrodes 42 and a ground lead electrode 44 which extend over the total height of the rear and front side faces of the block 24.
- auxiliary electrodes 40 must of course be electrically isolated from the signal and ground lead electrodes 42, 44 and can therefore be led out neither to the rear side face nor to the front side face of the block 24. Instead, these auxiliary electrodes 40 are led out to one or both lateral side faces of the block 24 and are electrically interconnected by auxiliary lead electrodes 46 formed on these lateral side faces, as is shown in Fig. 2.
- Auxiliary contact electrodes 56 are formed on both lateral ends of the top face of the body 24 and are electrically connected to the respective auxiliary lead electrodes 46. Thus, when the printhead is operating and the auxiliary electrodes 40 are not used, they may be short-circuited with the common electrodes 34 by means of leads which are formed on the connecting piece 54 and interconnect the contact electrodes 52 and 56. It will be observed that, in Fig. 2, the fingers 28 of the actuator are not yet separated from one another. In order to complete the actuator, it is necessary to separate these fingers by forming dicing cuts in the bottom face of the block 24.
- the signal lead electrodes 42 and the contact electrodes 50 for each finger are formed in a stripe configuration so that they are electrically isolated from those for the neighbouring fingers also in the top part of the body 24.
- the length of the body 24 in longitudinal direction of the ink channels 18 is smaller than in Fig. 4 and that the actuator is provided only above the ink channels 18.
- the connecting piece 54 is adjoined to the top face of the actuator and need not be sandwiched between the bottom face of the actuator and the receiving member 22.
- the inactive part 36 of the body 24 adjacent to the bottom face 26 can be omitted in Fig. 1, and the actuator according to this embodiment of the invention is only divided into a lower active part 30 adjacent to the bottom face 26 and an inactive part 38 superposed thereon.
- Fig. 3 shows a modified embodiment of the actuator 12 which has contact electrodes 50, 52 formed on both the top face and the bottom face, so that a connecting piece may be applied either to the top face or the bottom face, as desired.
- this actuator has an inactive part 36 extending vertically over the entire height of the block 24.
- the auxiliary electrodes 40 in the upper portion of the block 24 are provided continuously in both inactive parts 38 and 36.
- the inactive part 36 includes additional dummy electrodes 58 which are flush with the common electrodes 34. Within the fingers 28 the dummy electrodes 58 are alternating with the signal electrodes 32, whereas, in the upper portion of the inactive part 36, these dummy electrodes are altemating with the auxiliary electrodes 40.
- the auxiliary electrodes 40 and the dummy electrodes 58 are connected to auxiliary lead electrodes provided on the lateral side faces of the block 24.
- the auxiliary electrodes 40 and the dummy electrodes 58 are short-circuited with the signal electrodes 32 whereas the common electrodes 34 are grounded.
- a voltage drop will occur only across the alternating electrodes in the active part 30 and the inactive part 38, so that the piezoelectric material will be polarized in these parts.
- all the auxiliary electrodes 40 and dummy electrodes 58 are at a high potential during the polarizing step, so that no voltage drop occurs and the piezoelectric material is not polarized, just as in the conventional design.
- the provision of the dummy electrodes 58 facilitates the manufacturing process in that they permit to obtain a block 24 of even thickness simply by laminating electrode layers and layers of piezoelectric material one upon the other.
Landscapes
- Particle Formation And Scattering Control In Inkjet Printers (AREA)
Abstract
- a body (24) of piezoelectric material having a bottom face (26) through which the mechanical energy of the actuator is transferred to a receiving member (22), said body having an active part (30) adjacent to the bottom face as well as an inactive part (36, 38);
- a layered structure of alternating signal electrodes (32) and common electrodes (34) arranged in the active part (30) in parallel with the bottom face (26) and separated by layers of the piezoelectric material;
- a layered structure of alternating auxiliary electrodes (40) and common electrodes (34) arranged in the inactive part (38) in parallel with the bottom face and separated by layers of the piezoelectric material;
- at least one signal lead electrode (42) formed on a first side face of said body (24) and interconnecting the signal electrodes (32);
- a ground lead electrode (44) formed on a second side face opposite to the first side face and interconnecting the common electrodes (34);
- and an auxiliary lead electrode (46) interconnecting the auxiliary electrodes (40), characterized in that the auxiliary lead electrode (46) is formed on a third side face of the block (24).
Description
- The invention relates to a piezoelectric actuator for an ink jet printhead, comprising: a body of piezoelectric material having a bottom face through which the mechanical energy of the actuator is transferred to a receiving member, said body having an active part adjacent to the bottom face as well as an inactive part; a layered structure of alternating signal electrodes and common electrodes arranged in the active part in parallel with the bottom face and separated by layers of the piezoelectric material; a layered structure of altemating auxiliary electrodes and common electrodes arranged in the inactive part in parallel with the bottom face and separated by layers of the piezoelectric material; at least one signal lead electrode formed on a first side face of said body and interconnecting the signal electrodes; a ground lead electrode formed on a second side face opposite to said first side face and interconnecting the common electrodes; and an auxiliary lead electrode interconnecting the auxiliary electrodes.
- An actuator of this type is used for pressurizing liquid ink in an ink jet printhead, so that ink droplets can be jetted-out from nozzles of the printhead. Typically, the printhead has a linear array of nozzles, and each nozzle is connected to an ink channel that is filled with ink. The ink channels are arranged in parallel with each other and are covered by a sheet-like receiving member which is bonded to the bottom face of the actuator so that it may be deformed in accordance with the expansion and retraction strokes of the actuator in order to compress the ink in the ink channels. The active part of the piezoelectric body is divided into a plurality of parallel fingers respectively associated with the individual ink channels and separated by dicing cuts cut into the bottom face of the body. The inactive part of the body forms a bridge-like structure which interconnects the fingers on the side opposite to the bottom face.
- The signal lead electrodes are respectively associated with the individual fingers, so that an ink droplet from a selected one of the nozzles can be obtained by applying a voltage across the associated signal lead electrode and the ground lead electrode.
- The inactive bridge portion of the piezoelectric body serves as a backing member which bears the reaction forces of the active actuator fingers and also facilitates the manufacturing process in that it permits the production of a plurality of fingers as a one-piece construction, simply by forming dicing cuts in the piezoelectric body. The auxiliary electrodes in the inactive part are not needed when the printhead is operating. These auxiliary electrodes are only needed in the process of manufacturing the actuator.
- As is well known in the art, a piezoelectric device made for example of piezoelectric ceramic needs to be polarized during the manufacturing process in order to show the desired piezoelectric effect. This polarizing step is accompanied by an anisotropic shrinkage or expansion of the piezoelectric material, Thus, when only the active part were polarized, the plezoelectric body as a whole would behave like a bimorph element and would undesirably be distorted or even broken. This is why the auxiliary electrodes are used for polarizing also the inactive part of the piezoelectric body.
- Fig. 4 illustrates an example of a
printhead 10 in which a commercially availablepiezoelectric actuator 12 is employed. - The
printhead 10 comprises asupport member 14 on which achannel plate 16 is disposed. A plurality ofparallel ink channels 18 are formed in the top surface of thechannel plate 16. Only one of theseink channels 18 is shown in Fig. 4. One end of theink channel 18 is formed as anozzle 20 from which ink droplets are to be expelled. The rear end of the ink channel is connected to an ink supply system (not shown) which is accommodated in thesupport member 14, A receivingmember 22 is formed as a thin flexible sheet and is superposed on thechannel plate 16 so that it covers all theink channels 18 andnozzles 20.
Theactuator 12 comprises abody 24 made of piezoelectric ceramic and shaped as a parallelepiped having abottom face 26 which is bonded to the receivingmember 22. The portion of thebody 24 adjacent to thebottom face 26 is subdivided into a plurality offingers 28 which are arranged in parallel with one another and with theink channels 18. Eachfinger 28 is disposed directly above a respective one of theink channels 18. However, it can be seen in Fig. 4 that thebody 24 and also thefingers 28 thereof extend beyond theink channels 18 on the side opposite to thenozzles 20. Only the part of thefingers 28 situated above theink channels 18 is formed as anactive part 30 of the piezoelectric actuator. Thisactive part 30 comprises a layered structure withalternating signal electrodes 32 andcommon electrodes 34. Thecommon electrodes 34 extend only over theactive part 30, whereas thesignal electrodes 32 extend over the entire length of thebody 24 and, accordingly, are also present in aninactive part 36 which is offset from theink channels 18. - The portion of the
body 24 bridging theindividual fingers 28 and situated above theactive part 30 forms anotherinactive part 38. Thisinactive part 38 contains a layered structure with alternatingcommon electrodes 34 andauxiliary electrodes 40. - All the
electrodes bottom face 26 of thebody 24 and separated from each other by layers of ceramic material. - The
signal electrodes 32 of eachfinger 28 are interconnected with each other by asignal lead electrode 42 formed on a rear side face of thebody 24, i.e. the side face opposite to thenozzles 20. Similarly, all thecommon electrodes 34 in theactive part 30 and theinactive part 38 are interconnected by a commonground lead electrode 44 formed on the front side face of thebody 24. Theauxiliary electrodes 40 are interconnected by a commonauxiliary lead electrode 46 formed again on the rear side face of thebody 24 but separated from thesignal lead electrodes 42 by agap 48. - The
signal lead electrodes 42 and theground lead electrode 44 are connected torespective contact electrodes bottom face 26 of thebody 24. Thecontact electrode 52 extends beyond the rear ends of theink channels 18. All thecontact electrodes piece 54. The connectingpiece 54 is formed by a flexible foil which is sandwiched between thebottom face 26 of thebody 24 and the receivingmember 22 below theinactive part 36. - When an energizing signal is supplied to one of the
signal lead electrodes 42 via the associatedcontact electrode 50 and the connectingpiece 54, theactive part 30 of thecorresponding finger 28 performs an expansion stroke, so that thereceiving member 22 is flexed downward and compresses the ink contained in theink channel 18, thereby expelling an ink droplet from thenozzle 20. - In order to avoid losses in the mechanical energy transferred to the receiving
member 22, it is preferable that the connectingpiece 54 is not provided between theactive part 30 of the actuator and the receivingmember 22 but is only provided in the rear of theink channels 18. Thebody 24 has been extended rearwardly beyond theink channels 18 in order to provide a sufficient contact area between thecontact electrodes piece 54. Since the receivingmember 22 cannot flex downwardly in this area because it is supported by thechannel plate 16, thepart 36 of thebody 24 is inactive and does not containcommon electrodes 34. - It will be noted that in the
conventional actuator 12 shown in Fig. 4 the connectingpiece 54 must be adjoined to thebottom face 26 because the front and rear side faces of the inactive top part of thebody 24 are occupied by theground lead electrode 44 and theauxiliary lead electrode 46 which are needed for connecting thecommon electrodes 34 andauxiliary electrodes 40 in theinactive part 38 during the polarizing step.
It is an object of the present invention to provide a piezoelectric actuator which offers more freedom of design when the actuator is employed in an ink jet printhead. - This object is achieved with the features indicated in claim 1.
- According to the invention, the auxiliary lead electrode is formed on a third side face of the block.
- This has the advantage that the first and second side faces of the block can be used in their entirety for connecting the signal electrodes and the common electrodes, which permits more freedom of choice in respect to the position where a connecting piece is adjoined to the piezoelectric block. In particular, the connecting piece may be adjoined to the block in a position remote from the bottom face, for example, on the top face opposite to the bottom face.
- In a piezoelectric printhead the actuator must be firmly bonded to the receiving member because the actuator must be capable of not only performing compression strokes but also expansion strokes in order for sucking ink into the ink channel. In view of the extremely small width dimensions of the ink channels and the associated piezoelectric fingers, this bonding step is a rather intricate procedure. Bonding is normally performed by means of an adhesive which needs to be cured at high temperatures. Thus, when a thin foil serving as the connecting piece is sandwiched between the actuator and the receiving member, this connecting piece may be deteriorated by the heat applied in the bonding step. This problem can easily be avoided by the design according to the present invention, because it permits to adjoin the connecting piece at the top face of the piezoelectric body after the actuator has been bonded to the receiving member and the adhesive has been cured. This offers the remarkable additional advantage that electronic components which would be destroyed by high temperatures can be integrated on the connecting piece.
- In addition, when the connecting piece no longer needs to be sandwiched between the actuator and the receiving member, there is no need to extend the piezoelectric body of the actuator beyond the ink channels, Thus, the actuator may be shortened so that it is provided only above the ink channels and no longer needs to have an inactive part adjacent to the bottom face. As a result, the actuator becomes more compact and less expensive.
- More specific optional features of the invention are indicated in the dependent claims. An ink jet printhead employing the actuator according to the invention is claimed in claim 8.
- Preferred embodiments of the invention will now be described in conjunction with the accompanying drawings in which:
- Fig. 1
- is a perspective view of an ink jet printhead employing a piezoelectric actuator according to the invention, with parts broken away for illustration purposes;
- Fig. 2
- is a perspective view of a piezoelectric block which is to be processed further to form the actuator according to Fig. 1;
- Fig. 3
- shows a piezoelectric actuator according to another embodiment of the invention; and
- Fig. 4
- shows a printhead with a conventional actuator.
- The
ink jet printhead 10 shown in Fig. 1 has the same general construction as the printhead that has already been described in conjunction with Fig. 4. Like parts are designated by like reference numerals, and as for details of the components that have already been described, reference is made to the introductory part of this specification. - The main difference between the printheads shown in Figs. 4 and 1 is that, in Fig. 1, the
piezoelectric actuator 12 according to the invention has been employed and that the connectingpiece 54 is adjoined to the top face of thebody 24 of the actuator. Accordingly, thecontact electrodes body 24 and are electrically connected to thesignal electrodes 32 andcommon electrodes 34, respectively, bysignal lead electrodes 42 and aground lead electrode 44 which extend over the total height of the rear and front side faces of theblock 24. - The
auxiliary electrodes 40 must of course be electrically isolated from the signal andground lead electrodes block 24. Instead, theseauxiliary electrodes 40 are led out to one or both lateral side faces of theblock 24 and are electrically interconnected byauxiliary lead electrodes 46 formed on these lateral side faces, as is shown in Fig. 2. -
Auxiliary contact electrodes 56 are formed on both lateral ends of the top face of thebody 24 and are electrically connected to the respective auxiliarylead electrodes 46. Thus, when the printhead is operating and theauxiliary electrodes 40 are not used, they may be short-circuited with thecommon electrodes 34 by means of leads which are formed on the connectingpiece 54 and interconnect thecontact electrodes
It will be observed that, in Fig. 2, thefingers 28 of the actuator are not yet separated from one another. In order to complete the actuator, it is necessary to separate these fingers by forming dicing cuts in the bottom face of theblock 24. Thesignal lead electrodes 42 and thecontact electrodes 50 for each finger are formed in a stripe configuration so that they are electrically isolated from those for the neighbouring fingers also in the top part of thebody 24. - It will further be observed in Fig. 1 that the length of the
body 24 in longitudinal direction of theink channels 18 is smaller than in Fig. 4 and that the actuator is provided only above theink channels 18. This is possible because the connectingpiece 54 is adjoined to the top face of the actuator and need not be sandwiched between the bottom face of the actuator and the receivingmember 22. Thus, theinactive part 36 of thebody 24 adjacent to thebottom face 26 can be omitted in Fig. 1, and the actuator according to this embodiment of the invention is only divided into a loweractive part 30 adjacent to thebottom face 26 and aninactive part 38 superposed thereon. - Fig. 3 shows a modified embodiment of the
actuator 12 which hascontact electrodes inactive part 36 extending vertically over the entire height of theblock 24. - The
auxiliary electrodes 40 in the upper portion of theblock 24 are provided continuously in bothinactive parts inactive part 36 includesadditional dummy electrodes 58 which are flush with thecommon electrodes 34. Within thefingers 28 thedummy electrodes 58 are alternating with thesignal electrodes 32, whereas, in the upper portion of theinactive part 36, these dummy electrodes are altemating with theauxiliary electrodes 40. - Similarly as in Fig. 2, the
auxiliary electrodes 40 and thedummy electrodes 58 are connected to auxiliary lead electrodes provided on the lateral side faces of theblock 24. When theblock 24 according to Fig. 3 is polarized during the manufacturing process, theauxiliary electrodes 40 and thedummy electrodes 58 are short-circuited with thesignal electrodes 32 whereas thecommon electrodes 34 are grounded. Thus, a voltage drop will occur only across the alternating electrodes in theactive part 30 and theinactive part 38, so that the piezoelectric material will be polarized in these parts. In theinactive part 36 which extends vertically over the total height of theblock 24, all theauxiliary electrodes 40 anddummy electrodes 58 are at a high potential during the polarizing step, so that no voltage drop occurs and the piezoelectric material is not polarized, just as in the conventional design. - The provision of the
dummy electrodes 58 facilitates the manufacturing process in that they permit to obtain ablock 24 of even thickness simply by laminating electrode layers and layers of piezoelectric material one upon the other. - It should be noted that the thickness of the electrodes is exaggerated in the drawings for illustration purposes and, on the other hand, the number of electrode layers may be considerably larger than shown in the drawings.
While only specific embodiments of the invention have been described above, it will occur to a person skilled in the art that various modifications can be made within the scope of the appended claim.
Claims (10)
- Piezoelectric actuator (12) for an ink jet printhead (10), comprising:a body (24) of piezoelectric material having a bottom face (26) through which the mechanical energy of the actuator is transferred to a receiving member (22), said body having an active part (30) adjacent to the bottom face as well as an inactive part (36, 38);a layered structure of alternating signal electrodes (32) and common electrodes (34) arranged in the active part (30) in parallel with the bottom face (26) and separated by layers of the piezoelectric material;a layered structure of alternating auxiliary electrodes (40) and common electrodes (34) arranged in the inactive part (38) in parallel with the bottom face and separated by layers of the piezoelectric material;at least one signal lead electrode (42) formed on a first side face of said body (24) and interconnecting the signal electrodes (32);a ground lead electrode (44) formed on a second side face opposite to the first side face and interconnecting the common electrodes (34);and an auxiliary lead electrode (46) interconnecting the auxiliary electrodes (40), characterized in that the auxiliary lead electrode (46) is formed on a third side face of the block (24).
- Piezoelectric actuator according to claim 1, wherein the active part (30) is divided into a plurality of fingers (28) arranged in parallel to one another and integrally connected with each other by a bridge-like inactive part (38) of the block (24).
- Piezoelectric actuator according to claim 1 or 2, wherein contact electrodes (50) respectively connected to each of the signal lead electrodes (42) and a contact electrode (52) electrically connected to the ground lead electrode (44) are formed on a top face of the block (24) opposite to said bottom face (26).
- Piezoelectric actuator according to claim 3, wherein at least one additional contact electrode (56) is formed on an edge portion of the top face of the body (24) and is electrically connected to the auxiliary lead electrode (46).
- Piezoelectric actuator according to any of the preceding claims, wherein contact electrodes (50, 52, 56) are formed on both the top face and the bottom face (26) of the body (24).
- Piezoelectric actuator according to any of the preceding claims, wherein the body (24) comprises a second inactive part (36) adjacent to a portion of the bottom face (26).
- Piezoelectric actuator according to claim 6, wherein the auxiliary electrodes (40) extend over both inactive parts (36, 38) of the body (24), and dummy electrodes are provided in the second active part (36), each dummy electrode (58) being arranged in the same plane as a corresponding one of the common electrodes (34) and being electrically connected to the auxiliary lead electrode (46).
- Ink jet printhead comprising at least one ink channel (18) terminating in a nozzle (20) and covered by a flexible receiving member (22), and a piezoelectric actuator (12) bonded to said receiving member (22), characterized in that the piezoelectric actuator (12) has the construction specified in any of the preceding claims.
- Ink jet printhead according to claim 8, characterized in that a connecting piece (54) electrically connecting the signal electrodes (32) and common electrodes (34) of the actuator (26) is disposed on a top face of the body (24) opposite to the bottom face (26) thereof.
- Ink jet printhead according to claim 8 or 9, wherein the length of the actuator (12) in longitudinal direction of the ink channels (18) is equal to or smaller than the length of the ink channels.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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EP19990200090 EP0931653B1 (en) | 1998-01-23 | 1999-01-12 | Piezoelectric actuator for ink jet printhead |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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EP98200189 | 1998-01-23 | ||
EP98200189 | 1998-01-23 | ||
EP19990200090 EP0931653B1 (en) | 1998-01-23 | 1999-01-12 | Piezoelectric actuator for ink jet printhead |
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EP0931653A1 true EP0931653A1 (en) | 1999-07-28 |
EP0931653B1 EP0931653B1 (en) | 2004-04-14 |
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EP19990200090 Expired - Lifetime EP0931653B1 (en) | 1998-01-23 | 1999-01-12 | Piezoelectric actuator for ink jet printhead |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1336494A1 (en) * | 2002-02-19 | 2003-08-20 | Brother Kogyo Kabushiki Kaisha | Ink-jet head and its manufacture method, ink-jet printer and method for manufacturing actuator unit |
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JPH05198860A (en) * | 1992-01-21 | 1993-08-06 | Seiko Epson Corp | Laminated piezoelectric displacement element and ink jet type print head |
GB2283206A (en) * | 1993-10-07 | 1995-05-03 | Seiko Epson Corp | Piezo-electric driver for an ink jet recording head |
JPH07223315A (en) * | 1994-02-15 | 1995-08-22 | Fujitsu Ltd | Piezoelectric actuator and head for ink-jet printer |
EP0723866A1 (en) * | 1993-10-14 | 1996-07-31 | Citizen Watch Co. Ltd. | Ink jet head, method for producing the same and method for driving the same |
EP0757939A1 (en) * | 1994-03-29 | 1997-02-12 | Citizen Watch Co. Ltd. | Ink jet head and method of manufacturing the same |
JPH09156100A (en) * | 1995-12-11 | 1997-06-17 | Seiko Epson Corp | Piezoelectric oscillator unit for ink jet recording head and its manufacture |
-
1999
- 1999-01-12 EP EP19990200090 patent/EP0931653B1/en not_active Expired - Lifetime
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EP0518380A2 (en) * | 1991-06-13 | 1992-12-16 | Seiko Epson Corporation | On-demand type ink jet print head |
JPH05198860A (en) * | 1992-01-21 | 1993-08-06 | Seiko Epson Corp | Laminated piezoelectric displacement element and ink jet type print head |
GB2283206A (en) * | 1993-10-07 | 1995-05-03 | Seiko Epson Corp | Piezo-electric driver for an ink jet recording head |
EP0723866A1 (en) * | 1993-10-14 | 1996-07-31 | Citizen Watch Co. Ltd. | Ink jet head, method for producing the same and method for driving the same |
JPH07223315A (en) * | 1994-02-15 | 1995-08-22 | Fujitsu Ltd | Piezoelectric actuator and head for ink-jet printer |
EP0757939A1 (en) * | 1994-03-29 | 1997-02-12 | Citizen Watch Co. Ltd. | Ink jet head and method of manufacturing the same |
JPH09156100A (en) * | 1995-12-11 | 1997-06-17 | Seiko Epson Corp | Piezoelectric oscillator unit for ink jet recording head and its manufacture |
Non-Patent Citations (3)
Title |
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PATENT ABSTRACTS OF JAPAN vol. 017, no. 629 (E - 1462) 19 November 1993 (1993-11-19) * |
PATENT ABSTRACTS OF JAPAN vol. 095, no. 011 26 December 1995 (1995-12-26) * |
PATENT ABSTRACTS OF JAPAN vol. 097, no. 010 31 October 1997 (1997-10-31) * |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1336494A1 (en) * | 2002-02-19 | 2003-08-20 | Brother Kogyo Kabushiki Kaisha | Ink-jet head and its manufacture method, ink-jet printer and method for manufacturing actuator unit |
US6973703B2 (en) | 2002-02-19 | 2005-12-13 | Brother Kogyo Kabushiki Kaisha | Method for manufacturing an ink-jet head |
EP1733887A2 (en) * | 2002-02-19 | 2006-12-20 | Brother Kogyo Kabushiki Kaisha | Ink-jet head and its manufacture method, ink-jet printer and method for manufacturing actuator unit |
EP1733887A3 (en) * | 2002-02-19 | 2007-04-04 | Brother Kogyo Kabushiki Kaisha | Ink-jet head and its manufacture method, ink-jet printer and method for manufacturing actuator unit |
US7263752B2 (en) | 2002-02-19 | 2007-09-04 | Brother Kogyo Kabushiki Kaisha | Method for manufacturing an ink-jet head |
Also Published As
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