EP1036660B1 - Drop-on-Demand printhead with piezo bending transducers and driving method for the same - Google Patents

Drop-on-Demand printhead with piezo bending transducers and driving method for the same Download PDF

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Publication number
EP1036660B1
EP1036660B1 EP00105211A EP00105211A EP1036660B1 EP 1036660 B1 EP1036660 B1 EP 1036660B1 EP 00105211 A EP00105211 A EP 00105211A EP 00105211 A EP00105211 A EP 00105211A EP 1036660 B1 EP1036660 B1 EP 1036660B1
Authority
EP
European Patent Office
Prior art keywords
piezo
piezo bending
transducers
bending transducer
transducer
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
Application number
EP00105211A
Other languages
German (de)
French (fr)
Other versions
EP1036660A1 (en
Inventor
Joachim Professor Dr.-Ing. Heinzl
Ingo Dr. Ederer
Hermann Dipl.-Ing. Seitz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
XYZ Computerdrucker GmbH
Original Assignee
Tally Computerdrucker GmbH
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Publication date
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Publication of EP1036660A1 publication Critical patent/EP1036660A1/en
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Publication of EP1036660B1 publication Critical patent/EP1036660B1/en
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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
    • B41J2/015—Ink jet characterised by the jet generation process
    • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
    • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
    • B41J2/04525—Control methods or devices therefor, e.g. driver circuits, control circuits reducing occurrence of cross talk
    • 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
    • B41J2/015—Ink jet characterised by the jet generation process
    • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
    • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
    • B41J2/04581—Control methods or devices therefor, e.g. driver circuits, control circuits controlling heads based on piezoelectric elements
    • 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
    • B41J2/015—Ink jet characterised by the jet generation process
    • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
    • B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
    • B41J2/04501—Control methods or devices therefor, e.g. driver circuits, control circuits
    • B41J2/04596—Non-ejecting pulses
    • 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
    • B41J2/14282—Structure of print heads with piezoelectric elements of cantilever type
    • 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
    • B41J2002/14354—Sensor in each pressure chamber

Definitions

  • the invention relates to a method for driving a piezo print head and a piezo print head controlled by this method.
  • a conventional piezo bending transducer drop-on-demand printhead is e.g. from DE2527647A, DE3114259A and JP 01-271 248 A known.
  • a nozzle plate is a series of perpendicular to the plate plane Nozzles provided.
  • Piezo bending transducers are parallel to the nozzle plate in the form of an elongated tongue clamped on one side, so-called piezo-tongue transducers, arranged in a row next to each other in parallel so that their not clamped free ends each face one of the nozzles.
  • Piezo bending transducer has one parallel to the nozzle plate or perpendicular to the nozzles extending bending axis.
  • the piezo tongue is pushed through Applying a voltage bent so that the free end is away from the associated one Nozzle moved away.
  • the voltage is switched off and the free end snaps to the Nozzle and squeezes an amount of liquid through the nozzle, causing a drop to be expelled becomes.
  • the nozzles must be arranged very close to each other become.
  • the piezo bending transducers if possible, cover the entire assigned nozzle with its width. With a narrow nozzle arrangement, the mutually adjacent piezo bending transducers are therefore located as well as the nozzles assigned to them very close together.
  • the actuation of a As a result, the piezo bending transducer also has a fluid flow through the neighboring ones Nozzles associated with piezo bending transducers (crosstalk). Thereby a portion of the generated flow energy does not belong to the drop to be printed.
  • JP02024143 A shows a method and a piezo print head according to the preambles of the claims 1, 9, 15 and 16.
  • DE 691 19 088 T2 describes an operating method for a multichannel device for precipitation known from droplets.
  • a field of parallel channels provided with nozzles, which are uniformly spaced by channel-separating side walls, wherein the side walls have a wall compliance.
  • For ejecting a drop become the side walls separating the channel from the two adjacent channels deformed by the piezoelectric shear effect. This narrows the channel, and a drop is expelled.
  • the neighboring channels are widened which causes the liquid pressure to drop there. With a strong trigger pulse there is a risk that in the nozzles of the adjacent channels the meniscus is withdrawn so far that air can enter. This increases the strength of the drop output and the thus limited achievable flight speed of the drop. Adjacent nozzles can therefore not be controlled at the same time as droplet ejection.
  • EP 752312A shows a printhead with piezo elements from neighbors Ink chambers to be charged for compensation.
  • the invention is based on the problem of a method for driving a piezo print head of the type mentioned at the outset, which prevents crosstalk and to specify a piezo print head that can be controlled by this method, which can be produced with little manufacturing and assembly effort.
  • the object is achieved by a method with the features according to to claims 1 and 9 and by a piezo print head with the features claims 15 and 16, respectively.
  • Preferred embodiments are characterized in the subclaims.
  • the deflection of the adjacent piezo bending transducer by the compensation pulse causes a fluid movement locally at the nozzle assigned to the adjacent piezo bending transducer.
  • This fluid movement counteracts the fluid movement which occurs as a result of the triggering pulse and the movement of the triggered piezo bending transducer directly at the nozzle assigned to the adjacent piezo bending transducer.
  • the fluid movements compensate one another in whole or in part. A drop ejection does not occur at the nozzle (neighboring nozzle) assigned to the neighboring piezo bending transducer. Falsification of the printed image is prevented. The adverse effects of crosstalk are thus eliminated.
  • adjacent piezo bending transducers can be arranged so closely next to one another as the nozzle width allows. It can therefore be a printhead with a very high resolution can be achieved.
  • the narrow gap between the piezo bending transducer and the conventionally provided Partitions are eliminated.
  • a pull-out or reset movement of the piezo bending transducer can thus the flow of hydraulic fluid past the side the piezo bending transducer faster.
  • Another drop of droplet is thus shorter temporal distance to the previous one possible.
  • the print frequency can be increased become.
  • the piezo bending transducers can be acted upon by triggering pulses, which are a deflection of the piezo bending transducer to the assigned nozzle.
  • triggering pulses which are a deflection of the piezo bending transducer to the assigned nozzle.
  • the actual drop ejection movement of the piezo bending transducer then consists in the snap-back of the piezo structure due to the action of the trigger pulse and the associated Deflection built-up mechanical tension. Such a backward movement is generally faster than the deflection movement.
  • the neighboring piezo bending transducers with the closing control pulse are preferred assigned trigger pulse temporally preceding or simultaneously. To this ensures that the foreclosure is inserted when the droplets are expelled Movement of the piezo bending transducer with the trigger pulse already has occurred.
  • the adjacent piezo bending transducers can be acted upon by a closing control pulse whose amplitude is close to that of a trigger pulse. To be favoured it is subjected to a closing control pulse of an amplitude which is at most one Sixth of the amplitude of the trigger pulse is.
  • a closing control pulse of an amplitude which is at most one Sixth of the amplitude of the trigger pulse is.
  • This enables the use of Piezo bending transducers of two-pole type, i.e. Piezo-bimorph with passive position or monomorph. Since the trigger pulse usually moves the piezo bending transducer away from the nozzle deflects, the trigger pulse and the closing control pulse face each other. Bipolar Piezo bending transducers can actually only work in one direction, namely theirs Preferred direction are deflected. With a low amplitude it is also with two-pole Piezo bending transducers can be deflected against the preferred direction.
  • the compensation pulse is individual to the individual Piezo bending transducers adapted. In this way, even with existing manufacturing inaccuracies uniform droplet ejection at all nozzles or piezo bending transducers be ensured. If the trimming process is not just with individual Trigger pulses but with pulse combinations, i.e. triggering several at the same time Piezo bending transducer can be carried out in different constellations interactions of manufacturing or material inaccuracies of several piezo bending transducers Be taken into account.
  • the measurements can be made as part of the trimming process using one of the piezo bending transducers independent device.
  • the piezo bending transducers are preferred at the trimming process uses the piezo bending transducers as sensors by those resulting from the triggering of a piezo bending transducer, the ones caused thereby Fluid movement and the deflection of the neighboring piezo bending transducer induced in this are measured and to optimize the drop ejection or crosstalk behavior be evaluated. This means that no additional equipment is required and thus determine the crosstalk behavior at low cost. In that effects crosstalk behavior can be particularly noticeable in the printhead itself can be determined exactly.
  • the piezo bending transducers adjacent to the triggered piezo bending transducers are preferred during operation with compensation pulses or closing control pulses applied, determined for the amplitude, duration and / or time delay are caused by voltages caused by the triggering of a piezo bending transducer, the thereby causing fluid movement and the deflection of the neighboring piezo bending transducers can be induced, measured and processed in these. So one serves Adjacent piezo bending transducer after applying a trigger pulse initially as a sensor. The recorded data are evaluated and amplitude, duration and / or Time delay of the optimal compensation pulse are determined.
  • the serves Adjacent piezo bending transducers as an actuator and after the determined time delay the trigger pulse is the corresponding compensation pulse to the neighboring piezo bending transducer created. Interactions between the data recorded on several piezo bending transducers are taken into account. Likewise can be taken into account which piezo bending transducers act simultaneously become.
  • Such an adjustment of the pulses during operation can, in addition to the irregularities of droplet emissions caused by manufacturing and material inaccuracies are irregularities in droplet discharge caused by other factors can be compensated by adjusting the pulses.
  • Differences in the temperature conditions are taken into account.
  • irregularities the initial fluid-mechanical conditions at the start of the trigger pulse can be compensated, such as a residual flow due to the previous drop ejection.
  • vibrations can also be compensated.
  • the integrated in the company Aligning the pulses thus leads to a significant improvement in the printing result, in particular, to a large extent independence of the print result from external influences.
  • the ongoing adjustment when operating the piezo bending transducer drop-on-demand printhead can according to the invention instead of trimming or in addition to trimming before commissioning respectively.
  • the control device is suitably designed, e.g. as a computer with a corresponding control software.
  • the control device is preferably integrated Circuit trained.
  • the piezo bending transducers can e.g. than stretched out at both ends Piezo strips can be formed (piezo bridge transducers).
  • the piezo bending transducers are preferred designed as elongated tongues clamped on one side (piezo-tongue transducer).
  • the piezo-tongue transducers are further preferred Nozzles arranged in the area of the free ends of the piezo-tongue transducers.
  • the piezo bending transducers can be used as monomorphs, as bimorphs, each with a passive one Layer, as bimorphs with two active layers each, or as trimorphs. Further you can use the longitudinal effect of the piezoceramic or the transverse effect of the piezoceramic be exploited. You can use it as a single-layer converter or as a multi-layer converter be constructed.
  • the piezo bending transducers are preferred as bimorphs with two active layers or as Trimorphen formed and the control device is designed so that the neighboring Piezo bending transducers can be deflected in the opposite direction as that triggered piezo bending transducer by the other active position of the piezo transducer is applied with the compensation pulse.
  • This increases the risk of destruction of the piezo bending transducer switched off. This would exist if the deflection of the neighboring one Piezo bending transducer in the opposite direction by applying one opposite polarized voltage to the same position of a monomorph would. Contrary to the polarization direction, a piezoceramic can only with approx. 10% of the Maximum voltage can be applied.
  • the nozzles can be arranged so that the nozzle axis is parallel to the longitudinal direction of the piezo bending transducer and the nozzle in the extension of the piezo bending transducer is arranged (edge shooter).
  • the nozzles can also be arranged such that the nozzle axis is perpendicular to the Longitudinal direction of the piezo bending transducer and perpendicular to its bending axis and the nozzle is arranged in the region of the free end of the piezo bending transducer (sideshooter).
  • the piezo print head preferably has at least three-pole piezo bending transducers each two piezoceramic layers, and from the control device the trigger pulses to one piezoceramic layer and the closing control pulses to the other piezoceramic layer of the piezo bending transducer. In this way it is achieved that too the closing control pulse can have a larger amplitude without the risk a destruction of the piezo bending transducer, as is the case with a monomorph would be the case.
  • Patterns of pulses in which not only one is triggered can also be provided Piezo bending transducer immediately adjacent piezo bending transducer, but also the next but one or the next but one piezo bending transducer with compensation pulses, Closing control pulses or modified trigger pulses are applied.
  • FIGS. 1a to 1e The principle of the method according to the invention can be seen from FIGS. 1a to 1e.
  • Each of the figures shows schematically a section of a piezo bending transducer drop-on-demand Printhead.
  • a nozzle plate 1 In a nozzle plate 1 are three in a row perpendicular to the plane of the plate extending nozzles 11 are provided.
  • Parallel to the nozzle plate 1 are three piezo bending transducers 2 arranged in a row in parallel next to each other so that their not clamped free ends 21 each face one of the nozzles 11.
  • Piezo-bending transducer 2 is parallel to the nozzle plate 1 or perpendicular to the Nozzles 11 extending bending axis bendable.
  • the position of the three piezo bending transducers 2 is in a different one from each of FIGS. 1a to 1e Stage of the sequence of movements can be seen, which takes place when the middle of the three piezo bending transducers 2 is acted upon by a trigger pulse.
  • Figure 1b is the middle piezo bending transducer 2 due to the action of the trigger pulse in the deflection movement, so that its free end 21 from the associated nozzle 11 is moved away (see arrow).
  • Figure 1d are the two outer piezo bending transducers 2 with the compensation pulse acted upon and are consequently deflected so that their free ends 21 of the associated nozzles 11 are moved away (see arrows), while the middle Piezo bending transducer 2 continues to snap back due to the mechanical stresses, see above that its free end 21 is moved towards the associated nozzle 11 (see arrow).
  • the from the middle piezo bending transducer 2 to those assigned to the outer piezo bending transducers 2 Nozzles 11 displaced liquid is due to the deflection movements the outer piezo bending transducer 2 is sucked away from the associated nozzles 11 and does not emerge from the nozzles 11. There is therefore no falsification of the printed image.
  • the compensation pulses are also completed or in the decaying Phase and the outer piezo bending transducers 2 snap due to the mechanical stresses back so that their free ends 21 move toward the associated nozzles 11 be (see arrow).
  • the lower amplitude of the compensation pulses or one suitable decay edge leads to the backward movement of the outer piezo bending transducers 2 not to overcome the surface tension on the assigned Nozzles 11 and thus not to a drop.
  • a print head with actuators made of piezoceramic is used.
  • a piezo bending transducer 2 has a length of 5 mm, a height of 0.32 mm and a width of 0.4 mm. The free length is 3.2 mm.
  • the nozzle plate is made of silicon and has a thickness of 400 ⁇ m.
  • the nozzle diameter is 60 ⁇ m.
  • the nozzle channel length is 380 ⁇ m.
  • the Distance between the slats, i.e. the piezo bending transducer at rest, and the Nozzle plate is 20 ⁇ m. Diethyl succinate is used as the test medium for printing.
  • FIGS. 2a to 2d show the principle of the method according to the invention alternative embodiment can be seen.
  • Each of the figures shows a schematic section of a piezo bending transducer drop-on-demand printhead.
  • a nozzle plate 1 three nozzles 11 running perpendicular to the plate plane are provided in a row.
  • Parallel to the nozzle plate 1 are three piezo bending transducers 2 in a row parallel to each other arranged such that their unclamped free ends 21 each one of the Face nozzles 11.
  • Each of the piezo bending transducers 2 is parallel to or perpendicular to the nozzle plate 1 bending axis extending to the nozzles 11 bendable.
  • the position of the three piezo bending transducers 2 is in one from each of FIGS. 2a to 2d another stage of the sequence of movements that occurs when the middle of the three Piezo bending transducer 2 is acted upon by a trigger pulse.
  • Figure 2b is the middle piezo bending transducer 2 due to the action of the trigger pulse in the deflection movement, so that its free end 21 from the associated Nozzle 11 is moved away (see arrow).
  • the two outer piezo bending transducers 2 acted upon by the closing control pulse and are deflected as a result, so that their free ends 21 move toward the respectively assigned nozzles 11 be (see arrows).
  • the two outer piezo bending transducers 2 become so far the associated nozzles 11 moves that the nozzles 11 against the pressure fluid Filled liquid chamber completely or partially partitioned off by fluid mechanics become.
  • the middle piezo bending transducer 2 is due to the deflection in the The mechanical stresses built up in the structure completely jumped back into their starting position.
  • the two outer piezo bending transducers 2 are no longer used the closing control pulse and are consequently also due to the Deflect mechanical stresses built up in the structure entirely in their Starting positions jumped back.
  • FIG. 1 The structure of a piezo bending transducer according to the invention is shown schematically in FIG Drop-on-demand print head visible.
  • the nozzle plate 1 and the piezo bending transducers 2 corresponds to the structure of the representation according to FIGS. 1a to 1e, with more Nozzles 11 and piezo bending transducers 2 are shown.
  • Each of the piezo bending transducers 2 is connected to a control device 3 via a signal line 4.
  • the control device 3 is designed in such a way that with each Trigger pulse delayed compensation pulses to the triggered piezo bending transducer 2 neighboring piezo bending transducers 2 are delivered. This is with the Arrows along the signal lines 4 indicated.
  • the control device 3 is integrated Circuit trained.
  • Piezo bending transducers drop-on-demand printhead are provided. All shown Piezo bending transducers 2 are each in side view with the clamped end shown on the left. The axis around which the piezo bending transducer 2 is bent is perpendicular to the plane of the drawing.
  • a piezo bimorph with a passive position can be seen from FIG. 4a.
  • the piezo bending transducer 2 consists of two layers of piezoceramic, an active layer 22 and a passive one Layer 23.
  • a voltage U is only applied to the active layer 22, so that its length is changed. Since the length of the passive layer 23 remains constant, one occurs Bending the piezo bending transducer 2.
  • a piezo monomorph can be seen in FIG. 4b, in which the passive layer 23 is represented by a Layer 24 not made of piezoceramic is replaced.
  • FIG. 4c shows a piezo bimorph in which two active layers 22 are present are. These are oppositely polarized and are oppositely polarized Voltage U is applied, so that one layer shortens and the other lengthens.
  • FIG. 4d shows a piezo trimorph in which two active layers 22 are present are between which a layer 24 not made of piezoceramic is arranged. Such a structure enables greater deflections with the same voltage U.
  • FIG. 5a shows a structure in which the cross-effect of the piezoceramic is used becomes.
  • the polarization of the piezoceramic is perpendicular to the layers.
  • a positive voltage U applied along this polarization causes an expansion of the Material in the direction of polarization. Because of the mechanical cross contraction at the same time a contraction in the longitudinal direction of the piezo bending transducer 2, which because of the rigid other layer leads to the bend.
  • FIG. 5b shows a structure in which the longitudinal effect of the piezoceramic is used becomes.
  • the polarization of the piezoceramic runs in the longitudinal direction of the piezo bending transducer 2.
  • a positive voltage applied along this polarization causes an expansion of the material in the direction of polarization. Because of the rigid other layer it comes for bending the piezo bending transducer 2.
  • a multilayer structure of a piezoceramic layer can be seen from FIG. Instead of one uniformly polarized and with contacts at the two opposite ends Several layers are provided, each alternating with the opposite Polarization are provided. Between the layers are alternating the positive or negative contacts. In this way a large longitudinal effect of the piezoceramic is achieved with a small size.
  • FIGS. 4a to 4d with a longitudinal effect according to FIG 5a, possibly a multilayer structure according to FIG. 6, or with a transverse effect according to FIG. 5b can be used for used the piezo bending transducer of the piezo bending transducer drop-on-demand printhead become.
  • the bimorph-piezo bending transducer 2 is made of layers of piezoceramic over its entire thickness built up. Adjacent layers are each with opposite polarization Mistake.
  • Contact foils 26 are arranged between the layers. each second of the contact foils 26 is at one end of the piezo bending transducer 2 to one Earth contact bridge connected.
  • the ground contact bridge is on the ground contact 27 connected to the top of the piezo bending transducer 2 at a distance is arranged to the other end of the piezo bending transducer 2.
  • the ground contact 27 is connected to the control device 3 (not shown here) via a signal line 4.
  • the remaining contact foils 26 are assigned to the two active layers 22.
  • these contact foils 26 are attached to one another End of the piezo bending transducer 2 extending contact bridge connected to one first signal contact 28 is connected to the top of the piezo bending transducer 2 is arranged near the other end of the piezo bending transducer 2.
  • the first signal contact 27 is connected to the control device 3 (not shown here) via a signal line 4.
  • these contact foils 26 are attached to one at the other end of the piezo bending transducer 2 further contact bridge connected, which is connected to a second signal contact 29, the bottom of the piezo bending transducer 2 near the other end of the piezo bending transducer 2 is arranged.
  • the second signal contact 29 is via a signal line 4 to the control device 3 (not shown here) connected.
  • first signal contact 28 and second signal contact 29 can be seen.
  • the ground contact 27 and the first signal contact 28 both on the top of the piezo bending transducer 2 are arranged and isolated from each other.
  • FIG. 9 shows the time profile of the one directly on the piezoceramic applied voltage during the deflection phase, during the rebound phase of the piezo bending transducer and during the subsequent phase of Swinging out of the piezo bending transducer can be seen.
  • FIG. 10b shows a schematic structure and arrangement of one used in accordance with the invention Piezo bridge transducer can be seen.

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Description

Die Erfindung betrifft ein Verfahren zum Ansteuern eines Piezo-Druckkopfes und einen nach diesem Verfahren angesteuerten Piezo-Druckkopf.The invention relates to a method for driving a piezo print head and a piezo print head controlled by this method.

Ein herkömmlicher Piezo-Biegewandler Drop-on-Demand Druckkopf ist z.B. aus DE2527647A, DE3114259A und JP 01-271 248 A bekannt. In einer Düsenplatte ist eine Reihe von senkrecht zur Plattenebene verlaufenden Düsen vorgesehen. Parallel zu der Düsenplatte sind Piezo-Biegewandler in Gestalt einer einseitig eingespannten langgestreckten Zunge, sogenannte Piezo-Zungenwandler, in einer Reihe parallel nebeneinander derart angeordnet, dass ihre nicht eingespannten freien Enden jeweils einer der Düsen gegenüberstehen. Jeder der Piezo-Biegewandler weist eine parallel zu der Düsenplatte bzw. senkrecht zu den Düsen verlaufende Biegeachse auf. Zum Ausstoßen eines Tropfens wird die Piezozunge durch Anlegen einer Spannung gebogen, so dass sich das freie Ende von der zugeordneten Düse wegbewegt. Die Spannung wird abgeschaltet und das freie Ende schnellt zu der Düse hin und drückt eine Flüssigkeitsmenge durch die Düse, so dass ein Tropfen ausgestoßen wird.A conventional piezo bending transducer drop-on-demand printhead is e.g. from DE2527647A, DE3114259A and JP 01-271 248 A known. In a nozzle plate is a series of perpendicular to the plate plane Nozzles provided. Piezo bending transducers are parallel to the nozzle plate in the form of an elongated tongue clamped on one side, so-called piezo-tongue transducers, arranged in a row next to each other in parallel so that their not clamped free ends each face one of the nozzles. Everyone who Piezo bending transducer has one parallel to the nozzle plate or perpendicular to the nozzles extending bending axis. To eject a drop, the piezo tongue is pushed through Applying a voltage bent so that the free end is away from the associated one Nozzle moved away. The voltage is switched off and the free end snaps to the Nozzle and squeezes an amount of liquid through the nozzle, causing a drop to be expelled becomes.

Soll mit einem Aufbau dieser Art ein Druck mit einer hohen Auflösung, d.h. großer Punktanzahl pro Länge, erzeugt werden, müssen die Düsen sehr eng nebeneinander angeordnet werden. Um einen sauberen Tropfenausstoß zu erreichen, müssen die Piezo-Biegewandler nach Möglichkeit mit ihrer Breite die ganze zugeordnete Düse abdecken. Bei enger Düsenanordnung liegen daher die einander benachbarten Piezo-Biegewandler ebenso wie die diesen zugeordneten Düsen sehr eng beieinander. Die Betätigung eines Piezo-Biegewandlers hat infolge dessen auch eine Fluidströmung durch die den benachbarten Piezo-Biegewandlern zugeordneten Düsen zur Folge (Übersprechen). Dadurch kommt ein Anteil der erzeugten Strömungsenergie nicht dem zu druckenden Tropfen zu. Ferner kann es zu einem Ausstoß eines Tropfens aus der Nachbardüse kommen, der in einer Verfälschung des angestrebten Druckbilds resultiert. JP02024143 A zeigt ein Verfahren und ein Piezo-Druckkopf gemäss Oberbegriffe der Ansprüche 1, 9, 15 und 16.If a structure of this type is to be used for printing with a high resolution, i.e. large number of points per length, the nozzles must be arranged very close to each other become. In order to achieve a clean drop ejection, the piezo bending transducers if possible, cover the entire assigned nozzle with its width. With a narrow nozzle arrangement, the mutually adjacent piezo bending transducers are therefore located as well as the nozzles assigned to them very close together. The actuation of a As a result, the piezo bending transducer also has a fluid flow through the neighboring ones Nozzles associated with piezo bending transducers (crosstalk). Thereby a portion of the generated flow energy does not belong to the drop to be printed. In addition, a drop may be ejected from the neighboring nozzle, which drops into falsification of the desired printed image results. JP02024143 A shows a method and a piezo print head according to the preambles of the claims 1, 9, 15 and 16.

Aus DE 691 19 088 T2 ist ein Betriebsverfahren für ein vielkanaliges Gerät zum Niederschlag von Tröpfchen bekannt. Dabei wird ein Feld mit Düsen versehener paralleler Kanäle, die gleichförmig durch kanaltrennende Seitenwände beabstandet sind, angeordnet, wobei die Seitenwände eine Wandnachgiebigkeit aufweisen. Zum Ausstoßen eines Tropfens werden die den Kanal von den beiden benachbarten Kanälen trennenden Seitenwände durch den piezoelektrischen Scher-Effekt verformt. Dadurch verengt sich der Kanal, und es wird ein Tropfen ausgestoßen. Die benachbarten Kanäle werden aufgeweitet, wodurch dort der Flüssigkeitsdruck sinkt. Bei einem starken Auslösepuls besteht die Gefahr, dass in den Düsen der benachbarten Kanäle der Meniskus so weit zurückgezogen wird, dass Luft eindringen kann. Dadurch wird die Stärke des Tropfenausstoßes und die damit erreichbare Fluggeschwindigkeit des Tropfens begrenzt. Benachbarte Düsen können deswegen nicht gleichzeitig zum Tropfenausstoß angesteuert werden. EP 752312A zeigt einen Druckkopf wobei Piezo elemente von benach barten Tintenkammern zur Kompensierung mit beaufschlagt werden.DE 691 19 088 T2 describes an operating method for a multichannel device for precipitation known from droplets. Here, a field of parallel channels provided with nozzles, which are uniformly spaced by channel-separating side walls, wherein the side walls have a wall compliance. For ejecting a drop become the side walls separating the channel from the two adjacent channels deformed by the piezoelectric shear effect. This narrows the channel, and a drop is expelled. The neighboring channels are widened which causes the liquid pressure to drop there. With a strong trigger pulse there is a risk that in the nozzles of the adjacent channels the meniscus is withdrawn so far that air can enter. This increases the strength of the drop output and the thus limited achievable flight speed of the drop. Adjacent nozzles can therefore not be controlled at the same time as droplet ejection. EP 752312A shows a printhead with piezo elements from neighbors Ink chambers to be charged for compensation.

Der Erfindung liegt das Problem zugrunde, ein Verfahren zum Ansteuern eines Piezo-Druckkopfes der eingangs genannten Art anzugeben, durch das ein Übersprechen verhindert ist, sowie einen durch dieses Verfahren ansteuerbaren Piezo-Druckkopf anzugeben, der mit geringem Fertigungs-und Montageaufwand herstellbar ist.The invention is based on the problem of a method for driving a piezo print head of the type mentioned at the outset, which prevents crosstalk and to specify a piezo print head that can be controlled by this method, which can be produced with little manufacturing and assembly effort.

Erfindungsgemäß wird die Aufgabe gelöst durch ein Verfahren mit den Merkmalen nach den Ansprüchen 1 bzw. 9 sowie durch einen Piezo-Druckkopf mit den Merkmalen nach den Ansprüchen 15 bzw. 16. According to the invention, the object is achieved by a method with the features according to to claims 1 and 9 and by a piezo print head with the features claims 15 and 16, respectively.

Bevorzugte Ausführungen sind in den Unteransprüchen gekennzeichnet.
Die Auslenkung des benachbarten Piezo-Biegewandlers durch den Kompensationspuls bewirkt lokal an der dem benachbarten Piezo-Biegewandler zugeordneten Düse eine Fluidbewegung. Diese Fluidbewegung wirkt der Fluidbewegung entgegen, die sich infolge des Auslösepulses und der Bewegung des ausgelösten Piezo-Biegewandlers unmittelbar an der dem benachbarten Piezo-Biegewandler zugeordneten Düse einstellt. Die Fluidbewegungen kompensieren einander gegenseitig ganz oder teilweise. Ein Tropfenausstoß an der dem benachbarten Piezo-Biegewandler zugeordneten Düse (Nachbardüse) kommt nicht zustande. Eine Verfälschung des Druckbildes wird verhindert. Die nachteiligen Wirkungen des Übersprechens werden somit ausgeschaltet.Preferred embodiments are characterized in the subclaims.
The deflection of the adjacent piezo bending transducer by the compensation pulse causes a fluid movement locally at the nozzle assigned to the adjacent piezo bending transducer. This fluid movement counteracts the fluid movement which occurs as a result of the triggering pulse and the movement of the triggered piezo bending transducer directly at the nozzle assigned to the adjacent piezo bending transducer. The fluid movements compensate one another in whole or in part. A drop ejection does not occur at the nozzle (neighboring nozzle) assigned to the neighboring piezo bending transducer. Falsification of the printed image is prevented. The adverse effects of crosstalk are thus eliminated.

Es sind keine Trennwände (siehe EP 713773A) zwischen einander benachbarten Piezo-Biegewandlern oder spezielle Düsenformen erforderlich. Die Düsenplatte und die Wandung der Flüssigkeitskammer können einfach gestaltet sein. Fertigungs- und Montagekosten werden somit gering gehalten.There are no partition walls (see EP 713773A) between adjacent piezo bending transducers or special nozzle shapes required. The nozzle plate and the wall of the liquid chamber can be simply designed. Manufacturing and assembly costs are thus kept low.

Ferner können einander benachbarte Piezo-Biegewandler so eng nebeneinander angeordnet werden, wie es die Düsenbreite gestattet. Es kann daher ein Druckkopf mit einer sehr hohen Auflösung erreicht werden.Furthermore, adjacent piezo bending transducers can be arranged so closely next to one another as the nozzle width allows. It can therefore be a printhead with a very high resolution can be achieved.

Die engen Spalte zwischen dem Piezo-Biegewandler und den herkömmlich vorgesehenen Trennwänden entfallen. Während einer Aushol- oder Rückstellbewegung des Piezo-Biegewandlers kann somit das Nachströmen von Druckflüssigkeit seitlich vorbei an dem Piezo-Biegewandler schneller erfolgen. Ein weiterer Tropfenausstoß wird somit in kürzerem zeitlichen Abstand zu dem vorangehenden möglich. Die Druckfrequenz kann erhöht werden. The narrow gap between the piezo bending transducer and the conventionally provided Partitions are eliminated. During a pull-out or reset movement of the piezo bending transducer can thus the flow of hydraulic fluid past the side the piezo bending transducer faster. Another drop of droplet is thus shorter temporal distance to the previous one possible. The print frequency can be increased become.

Die Piezo-Biegewandler können mit Auslösepulsen beaufschlagt werden, die eine Auslenkung des Piezo-Biegewandlers zu der zugeordneten Düse hin bewirken. Bevorzugt werden die Piezo-Biegewandler jedoch mit Auslöseimpulsen beaufschlagt, die eine Auslenkung des Piezo-Biegewandlers von der zugeordneten Düse weg bewirken. Die eigentliche Tropfenausstoßbewegung des Piezo-Biegewandlers besteht dann in dem Zurückschnellen der Piezostruktur aufgrund der während des Einwirkens des Auslösepulses und der damit verbundenen Auslenkung aufgebauten mechanischen Spannung. Eine solche Rückschnellbewegung ist im allgemeinen schneller als die Auslenkungsbewegung.The piezo bending transducers can be acted upon by triggering pulses, which are a deflection of the piezo bending transducer to the assigned nozzle. The are preferred Piezo-bending transducers, however, acted on by trigger pulses that deflect the Effect the piezo bending transducer away from the assigned nozzle. The actual drop ejection movement of the piezo bending transducer then consists in the snap-back of the piezo structure due to the action of the trigger pulse and the associated Deflection built-up mechanical tension. Such a backward movement is generally faster than the deflection movement.

Die Auslenkung der benachbarten Piezo-Biegewandler und deren Festhalten bei den diesen zugeordneten Düsen sorgt dafür, dass die Düsen gegen die mit Druckflüssigkeit gefüllte Flüssigkeitskammer ganz oder teilweise strömungsmechanisch abgeschottet werden. Infolge dessen kann aus diesen Düsen kein Tropfen austreten. Eine Verfälschung des Druckbilds wird verhindert.The deflection of the neighboring piezo bending transducers and their retention by them assigned nozzles ensures that the nozzles against the one filled with hydraulic fluid Liquid chamber can be completely or partially partitioned off by fluid mechanics. As a result no drop can escape from these nozzles. A falsification of the printed image will be prevented.

Bevorzugt werden die benachbarten Piezo-Biegewandler mit dem Schließ-Steuerimpuls dem zugeordneten Auslösepuls zeitlich vorangehend oder gleichzeitig beaufschlagt. Auf diese Weise wird sichergestellt, dass die Abschottung beim Einsetzen der den Tropfen ausstoßenden Bewegung des mit dem Auslösepuls beaufschlagten Piezo-Biegewandlers bereits eingetreten ist.The neighboring piezo bending transducers with the closing control pulse are preferred assigned trigger pulse temporally preceding or simultaneously. To this This ensures that the foreclosure is inserted when the droplets are expelled Movement of the piezo bending transducer with the trigger pulse already has occurred.

Die benachbarten Piezo-Biegewandler können mit einem Schließ-Steuerimpuls beaufschlagt werden, dessen Amplitude der eines Auslösepulses nahekommt. Bevorzugt werden sie mit einem Schließ-Steuerimpuls einer Amplitude beaufschlagt, die höchstens ein Sechstel der Amplitude des Auslösepulses beträgt. Dies ermöglicht die Verwendung von Piezo-Biegewandlern zweipoliger Bauart, d.h. Piezo-Bimorph mit passiver Lage bzw. Monomorph. Da der Auslösepuls den Piezo-Biegewandler üblicherweise von der Düse weg auslenkt, sind Auslösepuls und Schließ-Steuerimpuls einander entgegengerichtet. Zweipolige Piezo-Biegewandler können aber eigentlich nur in einer Richtung, nämlich ihrer Vorzugsrichtung ausgelenkt werden. Bei geringer Amplitude ist aber auch bei zweipoligen Piezo-Biegewandlern eine Auslenkung gegen die Vorzugsrichtung möglich.The adjacent piezo bending transducers can be acted upon by a closing control pulse whose amplitude is close to that of a trigger pulse. To be favoured it is subjected to a closing control pulse of an amplitude which is at most one Sixth of the amplitude of the trigger pulse is. This enables the use of Piezo bending transducers of two-pole type, i.e. Piezo-bimorph with passive position or monomorph. Since the trigger pulse usually moves the piezo bending transducer away from the nozzle deflects, the trigger pulse and the closing control pulse face each other. Bipolar Piezo bending transducers can actually only work in one direction, namely theirs Preferred direction are deflected. With a low amplitude it is also with two-pole Piezo bending transducers can be deflected against the preferred direction.

Sowohl bei den Ausführungsformen des erfindungsgemäßen Verfahrens mit Kompensationspulsen als auch bei der alternativen Ausführungsform mit Schließ-Steuerimpulsen wird bevorzugt, vor oder bei Inbetriebnahme des Piezo-Biegewandler Drop-on-Demand Druckkopfes ein Trimmverfahren durchzuführen. D.h. für jeden der Piezo-Biegewandler wird vor Inbetriebnahme Amplitude, Dauer und/oder Zeitverzögerung der Kompensationspulse bzw. Schließ-Steuerimpulse mit einem Trimmverfahren ermittelt, bei dem für vorgesehene Konstellationen von Auslösepulsen die jeweils angelegten Kompensationspulse bzw. Schließ-Steuerimpulse hinsichtlich Amplitude, Dauer und/oder Zeitverzögerung variiert und unter Messen des Tropfenausstoß- bzw. Übersprechverhaltens optimiert werden. Auf diese Weise kann Herstellungsungenauigkeiten bzw. Inhomogenitäten der Piezokeramik Rechnung getragen werden. Der Kompensationspuls wird individuell an den einzelnen Piezo-Biegewandlern angepasst. Auf diese Weise kann auch bei vorhandenen Herstellungsungenauigkeiten ein gleichmäßiger Tropfenausstoß an allen Düsen bzw. Piezo-Biegewandlern sichergestellt werden. Wenn das Trimmverfahren nicht nur mit einzelnen Auslösepulsen sondern mit Pulskombinationen, d.h. gleichzeitigem Auslösen mehrerer Piezo-Biegewandler in unterschiedlichen Konstellationen durchgeführt wird, kann dabei auch Wechselwirkungen von Herstellungs- bzw. Materialungenauigkeiten mehrerer Piezo-Biegewandler Rechnung getragen werden.Both in the embodiments of the method according to the invention with compensation pulses as well as in the alternative embodiment with closing control pulses preferred, before or when commissioning the piezo bending transducer drop-on-demand printhead perform a trimming process. That for each of the piezo bending transducers Commissioning amplitude, duration and / or time delay of the compensation pulses or closing control impulses determined with a trimming method, in which for intended Constellations of triggering pulses the compensation pulses respectively applied Closing control pulses vary in terms of amplitude, duration and / or time delay and be optimized by measuring the drop ejection or crosstalk behavior. On In this way, manufacturing inaccuracies or inhomogeneities of the piezoceramic can Be taken into account. The compensation pulse is individual to the individual Piezo bending transducers adapted. In this way, even with existing manufacturing inaccuracies uniform droplet ejection at all nozzles or piezo bending transducers be ensured. If the trimming process is not just with individual Trigger pulses but with pulse combinations, i.e. triggering several at the same time Piezo bending transducer can be carried out in different constellations interactions of manufacturing or material inaccuracies of several piezo bending transducers Be taken into account.

Bevorzugt werden bei dem Trimmverfahren ausschließlich Dauer und/oder Zeitverzögerung von Kompensationspulsen bzw. Schließ-Steuerimpulsen variiert. Dies ermöglicht, dass das Trimmverfahren bei geringem Aufwand durchgeführt wird. Ferner können die Piezo-Biegewandler ausschließlich bei den Spannungsamplituden betrieben werden, für die sie ausgelegt sind.Only duration and / or time delay are preferred in the trimming method of compensation pulses or closing control pulses varied. This makes possible, that the trimming process is carried out with little effort. Furthermore, the Piezo bending transducers can only be operated at the voltage amplitudes for which they are designed for.

Die Messungen können im Rahmen des Trimmverfahrens mit einer von den Piezo-Biegewandlern unabhängigen Vorrichtung durchgeführt werden. Bevorzugt werden bei dem Trimmverfahren die Piezo-Biegewandler als Sensoren verwendet, indem Spannungen, die infolge des Auslösens eines Piezo-Biegewandlers, der dadurch hervorgerufenen Fluidbewegung und des Auslenkens der benachbarten Piezo-Biegewandler in diesen induziert werden, gemessen und zur Optimierung des Tropfenausstoß- bzw. Übersprechverhaltens ausgewertet werden. Dadurch lässt sich ohne zusätzlichen apparativen Aufwand und somit kostengünstig das Übersprechverhalten ermitteln. Dadurch, dass Effekte im Druckkopf selbst aufgenommen werden, kann das Übersprechverhalten besonders exakt ermittelt werden.The measurements can be made as part of the trimming process using one of the piezo bending transducers independent device. Are preferred at the trimming process uses the piezo bending transducers as sensors by those resulting from the triggering of a piezo bending transducer, the ones caused thereby Fluid movement and the deflection of the neighboring piezo bending transducer induced in this are measured and to optimize the drop ejection or crosstalk behavior be evaluated. This means that no additional equipment is required and thus determine the crosstalk behavior at low cost. In that effects crosstalk behavior can be particularly noticeable in the printhead itself can be determined exactly.

Bevorzugt werden die den ausgelösten Piezo-Biegewandlern benachbarten Piezo-Biegewandler im laufenden Betrieb mit Kompensationspulsen bzw. Schließ-Steuerimpulsen beaufschlagt, für die Amplitude, Dauer und/oder Zeitverzögerung ermittelt werden, indem Spannungen, die infolge des Auslösens eines Piezo-Biegewandlers, der dadurch hervorgerufenen Fluidbewegung und des Auslenkens der benachbarten Piezo-Biegewandler in diesen induziert werden, gemessen und verarbeitet werden. So dient ein benachbarter Piezo-Biegewandler nach Anlegen eines Auslösepulses zunächst als Sensor. Die aufgenommenen Daten werden ausgewertet und Amplitude, Dauer und/oder Zeitverzögerung des optimalen Kompensationspulses werden ermittelt. Dann dient der benachbarte Piezo-Biegewandler als Aktor und um die ermittelte Zeitverzögerung nach dem Auslösepuls wird der entsprechende Kompensationspuls an den benachbarten Piezo-Biegewandler angelegt. Bei der Auswertung können Wechselwirkungen zwischen den an mehreren Piezo-Biegewandlern aufgenommenen Daten berücksichtigt werden. Ebenfalls kann berücksichtigt werden, welche Piezo-Biegewandler gleichzeitig beaufschlagt werden.The piezo bending transducers adjacent to the triggered piezo bending transducers are preferred during operation with compensation pulses or closing control pulses applied, determined for the amplitude, duration and / or time delay are caused by voltages caused by the triggering of a piezo bending transducer, the thereby causing fluid movement and the deflection of the neighboring piezo bending transducers can be induced, measured and processed in these. So one serves Adjacent piezo bending transducer after applying a trigger pulse initially as a sensor. The recorded data are evaluated and amplitude, duration and / or Time delay of the optimal compensation pulse are determined. Then the serves Adjacent piezo bending transducers as an actuator and after the determined time delay the trigger pulse is the corresponding compensation pulse to the neighboring piezo bending transducer created. Interactions between the data recorded on several piezo bending transducers are taken into account. Likewise can be taken into account which piezo bending transducers act simultaneously become.

Durch einen solchen Abgleich der Pulse beim Betrieb können neben den Unregelmäßigkeiten des Tropfenausstoßes, die durch Herstellungs- und Materialungenauigkeiten hervorgerufen sind, auch noch anders bedingte Unregelmäßigkeiten des Tropfenausstoßes durch eine Anpassung der Pulse ausgeglichen werden. So kann z.B. Unterschieden in den Temperaturbedingungen Rechnung getragen werden. Es können z.B. Unregelmäßigkeiten der strömungsmechanischen Anfangsbedingungen bei Beginn des Auslösepulses ausgeglichen werden, so etwa eine Restströmung infolge des vorherigen Tropfenausstoßes. Z.B. können auch Erschütterungen kompensiert werden. Der in den Betrieb integrierte Abgleich der Pulse führt somit zu einer erheblichen Verbesserung des Druckergebnisses, insbesondere zu einer weitgehenden Unabhängigkeit des Druckergebnisses von äußeren Einflüssen.Such an adjustment of the pulses during operation can, in addition to the irregularities of droplet emissions caused by manufacturing and material inaccuracies are irregularities in droplet discharge caused by other factors can be compensated by adjusting the pulses. For example, Differences in the temperature conditions are taken into account. For example, irregularities the initial fluid-mechanical conditions at the start of the trigger pulse can be compensated, such as a residual flow due to the previous drop ejection. For example, vibrations can also be compensated. The integrated in the company Aligning the pulses thus leads to a significant improvement in the printing result, in particular, to a large extent independence of the print result from external influences.

Der laufende Abgleich beim Betrieb des Piezo-Biegewandler Drop-on-Demand Druckkopfes kann erfindungsgemäß anstelle des Trimmens oder neben dem Trimmen vor Inbetriebnahme erfolgen.The ongoing adjustment when operating the piezo bending transducer drop-on-demand printhead can according to the invention instead of trimming or in addition to trimming before commissioning respectively.

Die Steuervorrichtung ist auf geeignete Weise ausgebildet, z.B. als Computer mit einer entsprechenden Steuersoftware. Bevorzugt ist die Steuervorrichtung als integrierter Schaltkreis ausgebildet. The control device is suitably designed, e.g. as a computer with a corresponding control software. The control device is preferably integrated Circuit trained.

Die Piezo-Biegewandler können z.B. als an beiden Enden eingespannte langgestreckte Piezostreifen ausgebildet sein (Piezo-Brückenwandler). Bevorzugt sind die Piezo-Biegewandler als einseitig eingespannte langgestreckte Zungen ausgebildet (Piezo-Zungenwandler). Weiter bevorzugt sind die den Piezo-Zungenwandlern zugeordneten Düsen im Bereich der freien Enden der Piezo-Zungenwandler angeordnet.The piezo bending transducers can e.g. than stretched out at both ends Piezo strips can be formed (piezo bridge transducers). The piezo bending transducers are preferred designed as elongated tongues clamped on one side (piezo-tongue transducer). The piezo-tongue transducers are further preferred Nozzles arranged in the area of the free ends of the piezo-tongue transducers.

Die Piezo-Biegewandler können als Monomorphen,als Bimorphen mit je einer passiven Lage, als Bimorphen mit je zwei aktiven Lagen oder als Trimorphen ausgebildet sein. Ferner können sie den Längseffekt der Piezokeramik oder den Quereffekt der Piezokeramik ausnutzend ausgebildet sein. Sie können als Einzelschichtwandler oder als Mehrschichtwandler aufgebaut sein.The piezo bending transducers can be used as monomorphs, as bimorphs, each with a passive one Layer, as bimorphs with two active layers each, or as trimorphs. Further you can use the longitudinal effect of the piezoceramic or the transverse effect of the piezoceramic be exploited. You can use it as a single-layer converter or as a multi-layer converter be constructed.

Bevorzugt sind die Piezo-Biegewandler als Bimorphen mit zwei aktiven Lagen oder als Trimorphen ausgebildet und ist die Steuervorrichtung so ausgebildet, dass die benachbarten Piezo-Biegewandler in die entgegensetzte Richtung ausgelenkt werden wie der ausgelöste Piezo-Biegewandler, indem die jeweils andere aktive Lage des Piezowandlers mit dem Kompensationspuls beaufschlagt wird. Dadurch wird die Gefahr der Zerstörung des Piezo-Biegewandlers ausgeschaltet. Diese bestünde, wenn die Auslenkung des benachbarten Piezo-Biegewandlers in die entgegengesetzte Richtung durch Anlegen einer entgegengesetzt polarisierten Spannung an dieselbe Lage eines Monomorphen erfolgen würde. Entgegen der Polarisationsrichtung kann eine Piezokeramik nur mit ca. 10 % der Maximalspannung beaufschlagt werden.The piezo bending transducers are preferred as bimorphs with two active layers or as Trimorphen formed and the control device is designed so that the neighboring Piezo bending transducers can be deflected in the opposite direction as that triggered piezo bending transducer by the other active position of the piezo transducer is applied with the compensation pulse. This increases the risk of destruction of the piezo bending transducer switched off. This would exist if the deflection of the neighboring one Piezo bending transducer in the opposite direction by applying one opposite polarized voltage to the same position of a monomorph would. Contrary to the polarization direction, a piezoceramic can only with approx. 10% of the Maximum voltage can be applied.

Die Düsen können so angeordnet sein, dass die Düsenachse parallel zu der Längsrichtung des Piezo-Biegewandlers verläuft und die Düse in der Verlängerung des Piezo-Biegewandlers angeordnet ist (Edgeshooter). The nozzles can be arranged so that the nozzle axis is parallel to the longitudinal direction of the piezo bending transducer and the nozzle in the extension of the piezo bending transducer is arranged (edge shooter).

Die Düsen können auch so angeordnet sein, dass die Düsenachse senkrecht zu der Längsrichtung des Piezo-Biegewandlers und senkrecht zu dessen Biegeachse verläuft und die Düse im Bereich des freien Endes des Piezo-Biegewandlers angeordnet ist (Sideshooter).The nozzles can also be arranged such that the nozzle axis is perpendicular to the Longitudinal direction of the piezo bending transducer and perpendicular to its bending axis and the nozzle is arranged in the region of the free end of the piezo bending transducer (sideshooter).

Der Piezo-Druckkopf weist bevorzugt mindestens dreipolige Piezo-Biegewandler mit je zwei Piezokeramikschichten auf, und von der Steuervorrichtung werden die Auslösepulse an die eine Piezokeramikschicht und die Schließ-Steuerimpulse an die andere Piezokeramikschicht des Piezo-Biegewandlers angelegt. Auf diese Weise wird erreicht, dass auch der Schließ-Steuerimpuls eine größere Amplitude aufweisen kann, ohne dass die Gefahr einer Zerstörung des Piezo-Biegewandlers besteht, wie dies bei einem Monomorphen der Fall wäre.The piezo print head preferably has at least three-pole piezo bending transducers each two piezoceramic layers, and from the control device the trigger pulses to one piezoceramic layer and the closing control pulses to the other piezoceramic layer of the piezo bending transducer. In this way it is achieved that too the closing control pulse can have a larger amplitude without the risk a destruction of the piezo bending transducer, as is the case with a monomorph Would be the case.

Es können auch Muster von Pulsen vorgesehen sein, bei denen nicht nur die einem ausgelösten Piezo-Biegewandler unmittelbar benachbarten Piezo-Biegewandler, sondern auch die übernächsten oder überübernächsten Piezo-Biegewandler mit Kompensationspulsen, Schließ-Steuerimpulsen oder modifizierten Auslösepulsen beaufschlagt werden.Patterns of pulses in which not only one is triggered can also be provided Piezo bending transducer immediately adjacent piezo bending transducer, but also the next but one or the next but one piezo bending transducer with compensation pulses, Closing control pulses or modified trigger pulses are applied.

Ausführungsformen der Erfindung werden in Verbindung mit der Zeichnung beschrieben. In der Zeichnung zeigen:

  • Figuren 1a bis 1e schematisch die Arbeitsweise eines mit dem erfindungsgemäßen Verfahren angesteuerten Piezo-Biegewandler-Drop-on-Demand Druckkopfes;
  • Figuren 2a bis 2d schematisch die Arbeitsweise eines mit der alternativen Ausführungsform des erfindungsgemäßen Verfahrens angesteuerten Piezo-Biegewandler Drop-on-Demand Druckkopfes bzw. eines nach diesem Verfahren arbeitenden erfindungsgemäßen Piezo-Biegewandler Drop-on-Demand Druckkopfes;
  • Figur 3 schematisch den Aufbau eines erfindungsgemäßen Piezo-Biegewandler Drop-on-Demand Druckkopfes;
  • Figuren 4a bis 4d schematisch den Aufbau von Piezo-Biegewandlern mit unterschiedlichen Schichtanordnungen gemäß unterschiedlichen Ausführungsformen des erfindungsgemäßen Piezo-Biegewandler Drop-on-Demand Druckkopfes;
  • Figuren 5a und 5b schematisch den Aufbau von Piezo-Biegewandlern mit unterschiedlichen Kontaktierungsanordnungen gemäß unterschiedlichen Ausführungsformen des erfindungsgemäßen Piezo-Biegewandler Drop-on-Demand Druckkopfes;
  • Figur 6 schematisch den Aufbau eines Piezo-Biegewandlers mit einer Mehrschichtanordnung gemäß einer Ausführungsform des erfindungsgemäßen Piezo-Biegewandler Drop-on-Demand Druckkopfes;
  • Figur 7 in perspektivischer Darstellung drei als Bimorph aufgebaute Piezo-Biegewandler mit dreipoliger Kontaktierung;
  • Figur 8 schematisch im Querschnitt einen als Bimorph aufgebauten Piezo-Biegewandler mit dreipoliger Kontaktierung;
  • Figur 9 schematisch die Arbeitsweise eines Piezo-Biegewandlers beim Ausstoßen eines Tropfens zusammen mit dem zugehörigen Verlauf der an dem Piezo-Biegewandler anliegenden Spannung; und
  • Figuren 10a und 10b schematisch Aufbau und Anordnung eines Piezo-Zungenwandlers bzw. eines Piezo-Brückenwandlers.
    • Embodiments of the invention will be described in connection with the drawing. The drawing shows:
  • FIGS. 1 a to 1 e schematically show the mode of operation of a piezo bending transducer drop-on-demand print head controlled by the method according to the invention;
  • FIGS. 2a to 2d schematically illustrate the mode of operation of a piezo-bending transducer drop-on-demand print head controlled by the alternative embodiment of the method according to the invention, or of a piezo-bending transducer drop-on-demand print head working according to this method;
  • Figure 3 shows schematically the structure of a piezo bending transducer drop-on-demand printhead according to the invention;
  • Figures 4a to 4d schematically the structure of piezo bending transducers with different layer arrangements according to different embodiments of the piezo bending transducer according to the invention drop-on-demand print head;
  • 5a and 5b schematically show the structure of piezo bending transducers with different contacting arrangements according to different embodiments of the piezo bending transducer according to the invention drop-on-demand printhead;
  • FIG. 6 schematically shows the structure of a piezo bending transducer with a multilayer arrangement according to an embodiment of the piezo bending transducer according to the invention drop-on-demand print head;
  • FIG. 7 shows a perspective view of three piezo bending transducers constructed as bimorphs with three-pole contacting;
  • FIG. 8 shows schematically in cross section a bimorph piezo bending transducer with three-pole contact;
  • FIG. 9 shows schematically the mode of operation of a piezo bending transducer when ejecting a drop together with the associated profile of the voltage applied to the piezo bending transducer; and
  • Figures 10a and 10b schematically structure and arrangement of a piezo-tongue transducer or a piezo-bridge transducer.

    • Aus den Figuren 1a bis 1e ist das Prinzip des erfindungsgemäßen Verfahrens ersichtlich. Jede der Figuren zeigt schematisch einen Ausschnitt eines Piezo-Biegewandler Drop-on-Demand Druckkopfes. In einer Düsenplatte 1 sind in Reihe drei senkrecht zur Plattenebene verlaufende Düsen 11 vorgesehen. Parallel zu der Düsenplatte 1 sind drei Piezo-Biegewandler 2 in einer Reihe parallel nebeneinander derart angeordnet, dass ihre nicht eingespannten freien Enden 21 jeweils einer der Düsen 11 gegenüberstehen. Jeder der Piezo-Biegewandler 2 ist um eine parallel zu der Düsenplatte 1 bzw. senkrecht zu den Düsen 11 verlaufende Biegeachse biegbar.The principle of the method according to the invention can be seen from FIGS. 1a to 1e. Each of the figures shows schematically a section of a piezo bending transducer drop-on-demand Printhead. In a nozzle plate 1 are three in a row perpendicular to the plane of the plate extending nozzles 11 are provided. Parallel to the nozzle plate 1 are three piezo bending transducers 2 arranged in a row in parallel next to each other so that their not clamped free ends 21 each face one of the nozzles 11. Everyone who Piezo-bending transducer 2 is parallel to the nozzle plate 1 or perpendicular to the Nozzles 11 extending bending axis bendable.

    Aus jeder der Figuren 1a bis 1e ist die Stellung der drei Piezo-Biegewandler 2 in einem anderen Stadium der Bewegungsfolge ersichtlich, die abläuft, wenn der mittlere der drei Piezo-Biegewandler 2 mit einem Auslösepuls beaufschlagt wird.The position of the three piezo bending transducers 2 is in a different one from each of FIGS. 1a to 1e Stage of the sequence of movements can be seen, which takes place when the middle of the three piezo bending transducers 2 is acted upon by a trigger pulse.

    In Figur 1a sind alle drei Piezo-Biegewandler 2 in Ruhestellung.In Figure 1a, all three piezo bending transducers 2 are in the rest position.

    In Figur 1b ist der mittlere Piezo-Biegewandler 2 infolge des Einwirkens des Auslösepulses in der Auslenkungsbewegung, so dass dessen freies Ende 21 von der zugeordneten Düse 11 wegbewegt wird (vgl. Pfeil).In Figure 1b is the middle piezo bending transducer 2 due to the action of the trigger pulse in the deflection movement, so that its free end 21 from the associated nozzle 11 is moved away (see arrow).

    In Figur 1c ist der Auslösepuls abgeschlossen, die auslenkende Spannung wirkt nicht mehr, und der mittlere Piezo-Biegewandler 2 schnellt infolge der beim Auslenken in der Struktur aufgebauten mechanischen Spannungen zurück, so dass das freie Ende 21 zu der zugeordneten Düse 11 hin bewegt wird (vgl. Pfeil). In Figure 1c, the trigger pulse is completed, the deflecting voltage does not work more, and the middle piezo bending transducer 2 is accelerating due to the deflection in the Structure built up mechanical stresses back so that the free end 21 too the associated nozzle 11 is moved (see arrow).

    In Figur 1d sind die beiden äußeren Piezo-Biegewandler 2 mit dem Kompensationspuls beaufschlagt und werden infolgedessen ausgelenkt, so dass deren freie Enden 21 von den jeweils zugeordneten Düsen 11 wegbewegt werden (vgl. Pfeile), während der mittlere Piezo-Biegewandler 2 weiter infolge der mechanischen Spannungen zurückschnellt, so dass dessen freies Ende 21 zu der zugeordneten Düse 11 hin bewegt wird (vgl. Pfeil). Die von dem mittleren Piezo-Biegewandler 2 zu den den äußeren Piezo-Biegewandlern 2 zugeordneten Düsen 11 hin verdrängte Flüssigkeit wird infolge der Auslenkungsbewegungen der äußeren Piezo-Biegewandler 2 von den zugeordneten Düsen 11 weggesaugt und tritt nicht aus den Düsen 11 aus. Es kommt daher nicht zu einer Verfälschung des Druckbildes.In Figure 1d are the two outer piezo bending transducers 2 with the compensation pulse acted upon and are consequently deflected so that their free ends 21 of the associated nozzles 11 are moved away (see arrows), while the middle Piezo bending transducer 2 continues to snap back due to the mechanical stresses, see above that its free end 21 is moved towards the associated nozzle 11 (see arrow). The from the middle piezo bending transducer 2 to those assigned to the outer piezo bending transducers 2 Nozzles 11 displaced liquid is due to the deflection movements the outer piezo bending transducer 2 is sucked away from the associated nozzles 11 and does not emerge from the nozzles 11. There is therefore no falsification of the printed image.

    In Figur le sind auch die Kompensationspulse abgeschlossen bzw. in der abklingenden Phase und die äußeren Piezo-Biegewandler 2 schnellen infolge der mechanischen Spannungen zurück, so dass deren freie Enden 21 zu den zugeordneten Düsen 11 hin bewegt werden (vgl. Pfeil). Infolge der geringeren Amplitude der Kompensationspulse bzw. einer geeigneten Abklingflanke führt die Rückschnellbewegung der äußeren Piezo-Biegewandler 2 nicht zu einer Überwindung der Oberflächenspannung an den zugeordneten Düsen 11 und damit nicht zu einem Tropfenaustritt.In Figure le, the compensation pulses are also completed or in the decaying Phase and the outer piezo bending transducers 2 snap due to the mechanical stresses back so that their free ends 21 move toward the associated nozzles 11 be (see arrow). As a result of the lower amplitude of the compensation pulses or one suitable decay edge leads to the backward movement of the outer piezo bending transducers 2 not to overcome the surface tension on the assigned Nozzles 11 and thus not to a drop.

    Es werden konkrete Ausführungsbeispiele beschrieben.Specific exemplary embodiments are described.

    Es wird ein Druckkopf mit Aktoren aus Piezokeramik verwendet. Ein Piezo-Biegewandler 2 hat eine Länge von 5 mm, eine Höhe von 0,32 mm und eine Breite von 0,4 mm. Die freie Länge beträgt 3,2 mm. Die Düsenplatte ist aus Silizium und weist eine Dicke von 400 µm auf. Der Düsendurchmesser beträgt 60 µm. Die Düsenkanallänge beträgt 380 µm. Der Abstand zwischen der Lamelle, d.h. dem Piezo-Biegewandler in Ruhestellung, und der Düsenplatte beträgt 20 µm. Als Testmedium zum Verdrucken wird Diethylsuccinat verwendet.A print head with actuators made of piezoceramic is used. A piezo bending transducer 2 has a length of 5 mm, a height of 0.32 mm and a width of 0.4 mm. The free length is 3.2 mm. The nozzle plate is made of silicon and has a thickness of 400 µm. The nozzle diameter is 60 µm. The nozzle channel length is 380 µm. The Distance between the slats, i.e. the piezo bending transducer at rest, and the Nozzle plate is 20 µm. Diethyl succinate is used as the test medium for printing.

    Gemäß einer Ausführungsform arbeitet die Ansteuerung mit den folgenden Pulsen:

  • Auslösepuls:
  • Impulsbreite 50 µs, Rechteckimpuls, Amplitude 55 V,
  • Kompensationspuls:
  • lmpulsbreite 17 µs, Rechteckimpuls, Amplitude 55 V,
  • Zeitverzögerung zum Auslöseimpuls: 67 µs
    • According to one embodiment, the control works with the following pulses:
  • Trigger pulse:
  • Pulse width 50 µs, rectangular pulse, amplitude 55 V,
  • Compensation Pulse:
  • pulse width 17 µs, rectangular pulse, amplitude 55 V,
  • Time delay to trigger pulse: 67 µs

    • Gemäß einer anderen Ausführungsform arbeitet die Ansteuerung mit den folgenden Pulsen:

  • Auslösepuls:
  • lmpulsbreite 50 µs, Rechteckimpuls, Amplitude 55 V
  • Kompensationspuls:
  • Impulsbreite 7 µs, Rechteckimpuls, Amplitude 55 V,
  • Zeitverzögerung zum Auslöseimpuls: 64 µs
    • According to another embodiment, the control works with the following pulses:
  • Trigger pulse:
  • Pulse width 50 µs, rectangular pulse, amplitude 55 V
  • Compensation Pulse:
  • Pulse width 7 µs, rectangular pulse, amplitude 55 V,
  • Time delay to trigger pulse: 64 µs

    • Aus den Figuren 2a bis 2d ist das Prinzip des erfindungsgemäßen Verfahrens gemäß der alternativen Ausführungsform ersichtlich. Jede der Figuren zeigt schematisch einen Ausschnitt eines Piezo-Biegewandler Drop-on-Demand Druckkopfes. In einer Düsenplatte 1 sind in Reihe drei senkrecht zur Plattenebene verlaufende Düsen 11 vorgesehen. Parallel zu der Düsenplatte 1 sind drei Piezo-Biegewandler 2 in einer Reihe parallel nebeneinander derart angeordnet, dass ihre nicht eingespannten freien Enden 21 jeweils einer der Düsen 11 gegenüberstehen.FIGS. 2a to 2d show the principle of the method according to the invention alternative embodiment can be seen. Each of the figures shows a schematic section of a piezo bending transducer drop-on-demand printhead. In a nozzle plate 1 three nozzles 11 running perpendicular to the plate plane are provided in a row. Parallel to the nozzle plate 1 are three piezo bending transducers 2 in a row parallel to each other arranged such that their unclamped free ends 21 each one of the Face nozzles 11.

    Jeder der Piezo-Biegewandler 2 ist um eine parallel zu der Düsenplatte 1 bzw. senkrecht zu den Düsen 11 verlaufende Biegeachse biegbar.Each of the piezo bending transducers 2 is parallel to or perpendicular to the nozzle plate 1 bending axis extending to the nozzles 11 bendable.

    Aus jeder der Figuren 2a bis 2d ist die Stellung der drei Piezo-Biegewandler 2 in einem anderen Stadium der Bewegungsfolge ersichtlich, die abläuft, wenn der mittlere der drei Piezo-Biegewandler 2 mit einem Auslösepuls beaufschlagt wird.The position of the three piezo bending transducers 2 is in one from each of FIGS. 2a to 2d another stage of the sequence of movements that occurs when the middle of the three Piezo bending transducer 2 is acted upon by a trigger pulse.

    In Figur 2a sind alle drei Piezo-Biegewandler 2 in Ruhestellung.In Figure 2a, all three piezo bending transducers 2 are in the rest position.

    In Figur 2b ist der mittlere Piezo-Biegewandler 2 infolge des Einwirkens des Auslösepulses in der Auslenkungsbewegung, so dass dessen freies Ende 21 von der zugeordneten Düse 11 wegbewegt wird (vgl. Pfeil). Gleichzeitig sind die beiden äußeren Piezo-Biegewandler 2 mit dem Schließ-Steuerimpuls beaufschlagt und werden infolgedessen ausgelenkt, so dass deren freie Enden 21 zu den jeweils zugeordneten Düsen 11 hin bewegt werden (vgl. Pfeile). Dabei werden die beiden äußeren Piezo-Biegewandler 2 so weit zu den diesen zugeordneten Düsen 11 hin bewegt, dass die Düsen 11 gegen die mit Druckflüssigkeit gefüllte Flüssigkeitskammer ganz oder teilweise strömungsmechanisch abgeschottet werden. In Figure 2b is the middle piezo bending transducer 2 due to the action of the trigger pulse in the deflection movement, so that its free end 21 from the associated Nozzle 11 is moved away (see arrow). At the same time, the two outer piezo bending transducers 2 acted upon by the closing control pulse and are deflected as a result, so that their free ends 21 move toward the respectively assigned nozzles 11 be (see arrows). The two outer piezo bending transducers 2 become so far the associated nozzles 11 moves that the nozzles 11 against the pressure fluid Filled liquid chamber completely or partially partitioned off by fluid mechanics become.

    In Figur 2c ist der Auslösepuls abgeschlossen, die auslenkende Spannung wirkt nicht mehr, und der mittlere Piezo-Biegewandler 2 schnellt infolge der beim Auslenken in der Struktur aufgebauten mechanischen Spannungen zurück, so dass das freie Ende 21 zu der zugeordneten Düse 11 hin bewegt wird (vgl. Pfeil). Dadurch wird an der dem mittleren Piezo-Biegewandler 2 zugeordneten Düse 11 der Tropfenausstoß bewirkt. Die beiden äußeren Piezo-Biegewandler 2 sind weiterhin mit dem Schließ-Steuerimpuls beaufschlagt. Deren freie Enden 21 werden infolgedessen weiter in einer Stellung nahe den jeweils zugeordneten Düsen 11 gehalten. Dabei werden die den beiden äußeren Piezo-Biegewandlern 2 zugeordneten Düsen 11 weiterhin gegen die mit Druckflüssigkeit gefüllte Flüssigkeitskammer ganz oder teilweise strömungsmechanisch abgeschottet. Infolgedessen kann die Rückschnellbewegung des mittleren Piezo-Biegewandlers 2 zwar zu einer Strömungsbewegung im Bereich der den äußeren Piezo-Biegewandlern 2 zugeordneten Düsen 11 führen, infolge der strömungsmechanischen Abschottung kommt es aber an diesen Düsen 11 nicht zu einem Tropfenaustritt.In Figure 2c, the trigger pulse is complete, the deflecting voltage does not work more, and the middle piezo bending transducer 2 is accelerating due to the deflection in the Structure built up mechanical stresses back so that the free end 21 too the associated nozzle 11 is moved (see arrow). This is the middle Piezo-bending transducer 2 associated nozzle 11 causes the drop ejection. The two outer ones Piezo bending transducers 2 are still subjected to the closing control pulse. As a result, their free ends 21 become further in a position close to the respectively assigned Nozzles 11 held. The two outer piezo bending transducers 2 assigned nozzles 11 against the fluid chamber filled with hydraulic fluid completely or partially partitioned off by fluid mechanics. Consequently the return movement of the middle piezo bending transducer 2 can indeed become one Flow movement in the area associated with the outer piezo bending transducers 2 Guide nozzles 11, but due to the fluidic partition it matters these nozzles 11 do not cause drops to escape.

    In Figur 2d, ist der mittlere Piezo-Biegewandler 2 infolge der beim Auslenken in der Struktur aufgebauten mechanischen Spannungen vollständig in seine Ausgangslage zurückgeschnellt. Die beiden äußeren Piezo-Biegewandler 2 werden nicht mehr weiter mit dem Schließ-Steuerimpuls beaufschlagt und sind infolgedessen ebenfalls infolge der beim Auslenken in der Struktur aufgebauten mechanischen Spannungen vollständig in ihre Ausgangslagen zurückgeschnellt.In Figure 2d, the middle piezo bending transducer 2 is due to the deflection in the The mechanical stresses built up in the structure completely jumped back into their starting position. The two outer piezo bending transducers 2 are no longer used the closing control pulse and are consequently also due to the Deflect mechanical stresses built up in the structure entirely in their Starting positions jumped back.

    Aus Figur 3 ist schematisch der Aufbau eines erfindungsgemäßen Piezo-Biegewandler Drop-on-Demand Druckkopfes ersichtlich. Die Düsenplatte 1 und die Piezo-Biegewandler 2 betreffend entspricht der Aufbau der Darstellung gemäß Figuren 1a bis 1e, wobei mehr Düsen 11 und Piezo-Biegewandler 2 dargestellt sind. Jeder der Piezo-Biegewandler 2 ist über eine Signalleitung 4 an eine Steuervorrichtung 3 angeschlossen. Die Steuervorrichtung 3 ist so gestaltet, dass entsprechend dem erfindungsgemäßen Verfahren mit jedem Auslösepuls zeitlich verzögert Kompensationspulse an die dem ausgelösten Piezo-Biegewandler 2 benachbarten Piezo-Biegewandler 2 abgegeben werden. Dies ist mit den Pfeilen entlang den Signalleitungen 4 angedeutet. Die Steuervorrichtung 3 ist als integrierte Schaltung ausgebildet.The structure of a piezo bending transducer according to the invention is shown schematically in FIG Drop-on-demand print head visible. The nozzle plate 1 and the piezo bending transducers 2 corresponds to the structure of the representation according to FIGS. 1a to 1e, with more Nozzles 11 and piezo bending transducers 2 are shown. Each of the piezo bending transducers 2 is connected to a control device 3 via a signal line 4. The control device 3 is designed in such a way that with each Trigger pulse delayed compensation pulses to the triggered piezo bending transducer 2 neighboring piezo bending transducers 2 are delivered. This is with the Arrows along the signal lines 4 indicated. The control device 3 is integrated Circuit trained.

    Aus den Figuren 4a bis 4d, 5a und 5b sowie 6 sind unterschiedliche Typen von Piezo-Biegewandlern ersichtlich, die bei unterschiedlichen Ausführungsformen des erfindungsgemäßen Piezo-Biegewandler Drop-on-Demand Druckkopfes vorgesehen sind. Alle dargestellten Piezo-Biegewandler 2 sind jeweils in Seitenansicht mit dem eingespannten Ende auf der linken Seite dargestellt. Die Achse, um die der Piezo-Biegewandler 2 gebogen wird, verläuft jeweils senkrecht zur Zeichnungsebene.4a to 4d, 5a and 5b and 6 are different types of piezo bending transducers can be seen in different embodiments of the invention Piezo bending transducers drop-on-demand printhead are provided. All shown Piezo bending transducers 2 are each in side view with the clamped end shown on the left. The axis around which the piezo bending transducer 2 is bent is perpendicular to the plane of the drawing.

    Aus Figur 4a ist ein Piezo-Bimorph mit passiver Lage ersichtlich. Der Piezo-Biegewandler 2 besteht aus zwei Schichten von Piezokeramik, einer aktiven Lage 22 und einer passiven Lage 23. Nur an die aktive Lage 22 wird eine Spannung U angelegt, so dass deren Länge verändert wird. Da die Länge der passiven Lage 23 konstant bleibt, kommt es zu einer Biegung des Piezo-Biegewandlers 2.A piezo bimorph with a passive position can be seen from FIG. 4a. The piezo bending transducer 2 consists of two layers of piezoceramic, an active layer 22 and a passive one Layer 23. A voltage U is only applied to the active layer 22, so that its length is changed. Since the length of the passive layer 23 remains constant, one occurs Bending the piezo bending transducer 2.

    Aus Figur 4b ist ein Piezo-Monomorph ersichtlich, bei dem die passive Lage 23 durch eine nicht aus Piezokeramik bestehende Lage 24 ersetzt ist.A piezo monomorph can be seen in FIG. 4b, in which the passive layer 23 is represented by a Layer 24 not made of piezoceramic is replaced.

    Aus Figur 4c ist ein Piezo-Bimorph ersichtlich, bei dem zwei aktive Lagen 22 vorhanden sind. Diese sind entgegengesetzt polarisiert und werden mit entgegengesetzt polarisierter Spannung U beaufschlagt, so dass sich die eine Lage verkürzt und die andere verlängert. FIG. 4c shows a piezo bimorph in which two active layers 22 are present are. These are oppositely polarized and are oppositely polarized Voltage U is applied, so that one layer shortens and the other lengthens.

    Aus Figur 4d ist ein Piezo-Trimorph ersichtlich, bei dem zwei aktive Lagen 22 vorhanden sind, zwischen denen eine nicht aus Piezokeramik bestehende Lage 24 angeordnet ist. Ein solcher Aufbau ermöglicht größere Auslenkungen bei gleicher Spannung U.FIG. 4d shows a piezo trimorph in which two active layers 22 are present are between which a layer 24 not made of piezoceramic is arranged. Such a structure enables greater deflections with the same voltage U.

    Aus Figur 5a ist ein Aufbau ersichtlich, bei dem der Quereffekt der Piezokeramik genutzt wird. Die Polarisation der Piezokeramik verläuft in Richtung senkrecht zu den Lagen. Eine entlang dieser Polarisation angelegte positive Spannung U bewirkt eine Dehnung des Materials in Polarisationsrichtung. Wegen der mechanischen Querkontraktion erfolgt gleichzeitig eine Kontraktion in Längsrichtung des Piezo-Biegewandlers 2, der wegen der starren anderen Schicht zur Biegung führt.5a shows a structure in which the cross-effect of the piezoceramic is used becomes. The polarization of the piezoceramic is perpendicular to the layers. A positive voltage U applied along this polarization causes an expansion of the Material in the direction of polarization. Because of the mechanical cross contraction at the same time a contraction in the longitudinal direction of the piezo bending transducer 2, which because of the rigid other layer leads to the bend.

    Aus Figur 5b ist ein Aufbau ersichtlich, bei dem der Längseffekt der Piezokeramik genutzt wird. Die Polarisation der Piezokeramik verläuft in Längsrichtung des Piezo-Biegewandlers 2. Eine entlang dieser Polarisation angelegte positive Spannung bewirkt eine Dehnung des Materials in Polarisationsrichtung. Wegen der starren anderen Schicht kommt es zur Biegung des Piezo-Biegewandlers 2.5b shows a structure in which the longitudinal effect of the piezoceramic is used becomes. The polarization of the piezoceramic runs in the longitudinal direction of the piezo bending transducer 2. A positive voltage applied along this polarization causes an expansion of the material in the direction of polarization. Because of the rigid other layer it comes for bending the piezo bending transducer 2.

    Aus Figur 6 ist ein Mehrschichtaufbau einer Piezokeramiklage ersichtlich. Anstelle einer einheitlich polarisierten und an den zwei entgegengesetzten Enden mit Kontakten versehenen Schicht sind mehrere Schichten vorgesehen, die jeweils abwechselnd mit entgegengesetzter Polarisation versehen sind. Zwischen den Schichten sind abwechselnd an den Plus- bzw. an den Minuspol angeschlossene Kontakte vorgesehen. Auf diese Weise wird bei geringer Baugröße ein großer Längseffekt der Piezokeramik erzielt.A multilayer structure of a piezoceramic layer can be seen from FIG. Instead of one uniformly polarized and with contacts at the two opposite ends Several layers are provided, each alternating with the opposite Polarization are provided. Between the layers are alternating the positive or negative contacts. In this way a large longitudinal effect of the piezoceramic is achieved with a small size.

    Jede der aus den Figuren 4a bis 4d ersichtlichen Bauformen mit Längseffekt gemäß Figur 5a, ggf. Mehrschichtaufbau gemäß Figur 6, oder mit Quereffekt gemäß Figur 5b kann für die Piezo-Biegewandler des Piezo-Biegewandler Drop-on-Demand Druckkopfes verwendet werden.Each of the designs shown in FIGS. 4a to 4d with a longitudinal effect according to FIG 5a, possibly a multilayer structure according to FIG. 6, or with a transverse effect according to FIG. 5b can be used for used the piezo bending transducer of the piezo bending transducer drop-on-demand printhead become.

    Aus den Figuren 7 und 8 ist ersichtlich, wie die dreipolige Kontaktierung eines als Bimorph aufgebauten Piezo-Biegewandlers 2 ausgebildet ist. Aus Figur 8 ist im Querschnitt ein Bimorph-Piezo-Biegewandler 2 mit dreipoliger Kontaktierung ersichtlich, der als Mehrschicht-Piezo-Biegewandler ausgebildet ist. Der Piezo-Biegewandler 2 weist eine obere und eine untere aktive Lage 22 auf.From Figures 7 and 8 it can be seen how the three-pole contacting one as a bimorph constructed piezo bending transducer 2 is formed. From Figure 8 is a cross section Bimorph piezo bending transducer 2 with three-pole contacting can be seen, which as a multi-layer piezo bending transducer is trained. The piezo bending transducer 2 has an upper one and a lower active layer 22.

    Der Bimorph-Piezo-Biegewandler 2 ist über seine gesamte Dicke aus Schichten von Piezokeramik aufgebaut. Benachbarte Schichten sind jeweils mit entgegengesetzter Polarisation versehen. Zwischen den Schichten sind jeweils Kontaktfolien 26 angeordnet. Jede zweite der Kontaktfolien 26 ist an dem einen Ende des Piezo-Biegewandlers 2 an eine Massekontaktbrücke angeschlossen. Die Massekontaktbrücke ist an den Massekontakt 27 angeschlossen, der an der Oberseite des Piezo-Biegewandlers 2 mit einem Abstand zu dem anderen Ende des Piezo-Biegewandlers 2 angeordnet ist. Der Massekontakt 27 ist über eine Signalleitung 4 an die Steuervorrichtung 3 (hier nicht gezeigt) angeschlossen. Die übrigen Kontaktfolien 26 sind den beiden aktiven Lagen 22 zugeordnet. Im Bereich der oberen aktiven Lage 22 sind diese Kontaktfolien 26 an eine an dem anderen Ende des Piezo-Biegewandlers 2 verlaufende Kontaktbrücke angeschlossen, die an einen ersten Signalkontakt 28 angeschlossen ist, der an der Oberseite des Piezo-Biegewandlers 2 nahe dem anderen Ende des Piezo-Biegewandlers 2 angeordnet ist. Der erste Signalkontakt 27 ist über eine Signalleitung 4 an die Steuervorrichtung 3 (hier nicht gezeigt) angeschlossen. Im Bereich der unteren aktiven Lage 22 sind diese Kontaktfolien 26 an eine an dem anderen Ende des Piezo-Biegewandlers 2 verlaufende weitere Kontaktbrücke angeschlossen, die an einen zweiten Signalkontakt 29 angeschlossen ist, der an der Unterseite des Piezo-Biegewandlers 2 nahe dem anderen Ende des Piezo-Biegewandlers 2 angeordnet ist. Der zweite Signalkontakt 29 ist über eine Signalleitung 4 an die Steuervorrichtung 3 (hier nicht gezeigt) angeschlossen.The bimorph-piezo bending transducer 2 is made of layers of piezoceramic over its entire thickness built up. Adjacent layers are each with opposite polarization Mistake. Contact foils 26 are arranged between the layers. each second of the contact foils 26 is at one end of the piezo bending transducer 2 to one Earth contact bridge connected. The ground contact bridge is on the ground contact 27 connected to the top of the piezo bending transducer 2 at a distance is arranged to the other end of the piezo bending transducer 2. The ground contact 27 is connected to the control device 3 (not shown here) via a signal line 4. The remaining contact foils 26 are assigned to the two active layers 22. In the area In the upper active layer 22, these contact foils 26 are attached to one another End of the piezo bending transducer 2 extending contact bridge connected to one first signal contact 28 is connected to the top of the piezo bending transducer 2 is arranged near the other end of the piezo bending transducer 2. The first signal contact 27 is connected to the control device 3 (not shown here) via a signal line 4. In the area of the lower active layer 22, these contact foils 26 are attached to one at the other end of the piezo bending transducer 2 further contact bridge connected, which is connected to a second signal contact 29, the bottom of the piezo bending transducer 2 near the other end of the piezo bending transducer 2 is arranged. The second signal contact 29 is via a signal line 4 to the control device 3 (not shown here) connected.

    Aus Figur 7 ist in perspektivischer Darstellung die räumliche Anordnung von Massekontakt 27, erstem Signalkontakt 28 und zweitem Signalkontakt 29 ersichtlich. Insbesondere ist ersichtlich, dass der Massekontakt 27 und der erste Signalkontakt 28 beide an der Oberseite des Piezo-Biegewandlers 2 angeordnet sind und gegeneinander isoliert sind.The perspective arrangement of ground contact is shown in FIG. 7 in perspective 27, first signal contact 28 and second signal contact 29 can be seen. In particular is can be seen that the ground contact 27 and the first signal contact 28 both on the top of the piezo bending transducer 2 are arranged and isolated from each other.

    Aus Figur 9 ist für einen Auslösepuls der zeitliche Verlauf der unmittelbar an der Piezokeramik anliegenden Spannung während der Auslenkphase, während der Phase des Zurückschnellens des Piezo-Biegewandlers und während der anschließenden Phase des Ausschwingens des Piezo-Biegewandlers ersichtlich.For a trigger pulse, FIG. 9 shows the time profile of the one directly on the piezoceramic applied voltage during the deflection phase, during the rebound phase of the piezo bending transducer and during the subsequent phase of Swinging out of the piezo bending transducer can be seen.

    Aus Figur 10a ist schematisch Aufbau und Anordnung eines erfindungsgemäß verwendeten Piezo-Zungenwandlers ersichtlich.From Figure 10a is a schematic structure and arrangement of one used according to the invention Piezo-tongue transducer can be seen.

    Aus Figur 10b ist schematisch Aufbau und Anordnung eines erfindungsgemäß verwendeten Piezo-Brückenwandlers ersichtlich.FIG. 10b shows a schematic structure and arrangement of one used in accordance with the invention Piezo bridge transducer can be seen.

    Claims (19)

    1. A method for controlling a piezo-pressure head for ejecting liquid droplets in a drop-on-demand operation, said piezo-pressure head including a jet plate with a row of jets located on a single liquid chamber and one bar-like piezo bending transducer each assigned to each jet whereby a sequence of trigger pulses is applied to each piezo bending transducer, said sequence corresponding to a desired print image and effecting a droplet ejection motion for each pulse respectively,
      characterised in that,
      after switching off the trigger pulse for the piezo bending transducer effecting the droplet ejection, a pulse weaker than the trigger pulse is applied to neighbouring piezo bending transducers with a delay such that they carry out an opposite motion of smaller deflection compared to the piezo bending transducer effecting the droplet ejection.
    2. The method according to claim 1,
      characterised in that,
      the weaker impulse is carried out with a lesser amplitude when compared to the trigger pulse.
    3. The method according to one of the claims 1 or 2,
      characterised in that,
      the weaker impulse is carried out with a lesser duration when compared to the trigger pulse.
    4. The method according to one of the claims 1 to 3,
      characterised in that
      the amount of the smaller deflection is dependent on the number of piezo bending transducers which are located between the neighbouring triggering piezo bending transducers effecting the droplet ejection.
    5. The method according to one of the claims 1 to 3,
      characterised in that,
      the trigger pulses are applied to two groups of piezo bending transducers, with a time delay between groups, whereby adjacent piezo bending transducers are assigned to different groups respectively.
    6. The method according to one of the claims 1 to 4,
      characterised in that,
      differing trigger pulses are applied to piezo bending transducers in a single group and the trigger pulses of the triggered piezo bending transducers are dependent on whether both, one or none of the neighbouring piezo bending transducer(s) has or have been triggered.
    7. The method according to claim 6,
      characterised in that,
      for a simultaneous triggering of a number of adjacent piezo bending transducers, a trigger pulse of a smaller amplitude is applied than for the case where a smaller number of adjacent piezo bending transducers is triggered simultaneously.
    8. The method according to one of the claims 1 to 4,
      characterised in that
      impulses are applied to simultaneously triggered, adjacent piezo bending transducers, said impulses having a gently falling edge.
    9. A method for controlling a piezo-pressure head for ejecting liquid droplets in a drop-on-demand operation, said piezo-pressure head including a jet plate with a row of jets located on a single liquid chamber and one bar-like piezo bending transducer each assigned to each jet whereby a sequence of trigger pulses is applied to each piezo bending transducer, said sequence corresponding to a desired print image and effecting a droplet ejection motion for each pulse respectively,
      characterised in that,
      corresponding to each trigger pulse, a closing control impulse is applied to each neighbouring piezo bending transducer that received said trigger pulse such that the neighbouring piezo bending transducer is deflected towards the jet assigned to it in order to close the jet off against ejection of liquid and to keep the jet closed for a period of time.
    10. The method according to claim 9,
      characterised in that
      the closing control impulse has an amplitude which is no more than one sixth of the amplitude of the trigger pulse.
    11. The method according to one of the claims 9 to 10,
      characterised in that,
      prior to commissioning of the piezo print head, amplitude, duration and/or delay of the closing control impulses are determined with a trimming procedure for each of the piezo bending transducers whereby, for available constellations of trigger pulses, the closing control impulses being activated at the time are varied in terms of amplitude, duration and/or delay and optimised based on measurements of the droplet ejection or the crosstalk behaviour.
    12. The method according to claim 11,
      characterised in that,
      during the trimming procedure, varying takes place exclusively for duration and/or delay of the closing control impulses.
    13. The method according to one of the claims 11 or 12,
      characterised in that,
      during the trimming procedure, the piezo bending transducers are used as sensors whereby voltages, which are induced into said sensors as a result of triggering a piezo bending transducer, the fluid motion triggered thereby and the deflection of the neighbouring piezo bending transducers, are measured and evaluated for the optimisation of the droplet ejection or the crosstalk behaviour.
    14. The method according to one of the claims 9 or 13,
      characterised in that
      closing control impulses are applied to the neighbouring piezo bending transducers while in operation, for which amplitude, duration and/or time delay are ascertained by measuring and processing the voltages which have been induced into them as a result of triggering a piezo bending transducer, the fluid motion resulting from that and the deflection of the neighbouring piezo bending transducers.
    15. A piezo pressure head for ejecting liquid droplets in a drop-on-demand operation comprising
      a jet plate (1) with a row of jets (11) located on a single liquid chamber and one bar-like piezo bending transducer (2) each assigned to one jet (11) each,
      a control unit (3) for applying a relevant sequence of trigger pulses to the piezo bending transducer (2), said sequence corresponding to a desired print image and effecting a droplet ejection motion for each pulse respectively,
      characterised in that,
      after switching off the trigger pulse for the piezo bending transducer (2) effecting the droplet ejection, the control unit (3) applies a pulse weaker than the trigger pulse is applied to neighbouring piezo bending transducers (2) with a delay such that they carry out an opposite motion of smaller deflection compared to the piezo bending transducer (2) effecting the droplet ejection
    16. The piezo pressure head for ejecting liquid droplets in a drop-on-demand operation comprising
      a jet plate (1) with a row of jets (11) located on a single liquid chamber and one bar-like piezo bending transducer (2) each assigned to one jet (11) each,
      a control unit (3) for applying a relevant sequence of trigger pulses to the piezo bending transducer (2), said sequence corresponding to a desired print image and effecting a droplet ejection motion for each pulse respectively,
      characterised in that,
      corresponding to each trigger pulse, a closing control impulse is applied by the control unit (3) to each neighbouring piezo bending transducer (2) that received said trigger pulse, by which the neighbouring piezo bending transducer (2) is deflected towards the jet (11) assigned to it in order to close the jet (11) off against ejection of liquid and to keep the jet (11) closed for a period of time.
    17. The piezo pressure head according to claim 16,
      characterised in that
      the piezo bending transducer (2) has at least three poles with two active layers (22) of piezo ceramics, and that the control unit (3) sends the trigger pulses to one active layer (22) and the closing control impulses to the other active layer (22).
    18. The piezo pressure head according to one of the claims 16 or 17,
      characterised in that
      the piezo bending transducers (2) are designed as piezoelectric reed transducers.
    19. The piezo pressure head according to one of the claims 16 or 17,
      characterised in that
      the piezo bending transducers (2) are designed as piezoelectric bridge transducers.
    EP00105211A 1999-03-15 2000-03-13 Drop-on-Demand printhead with piezo bending transducers and driving method for the same Expired - Lifetime EP1036660B1 (en)

    Applications Claiming Priority (2)

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    DE19911399A DE19911399C2 (en) 1999-03-15 1999-03-15 Method for controlling a piezo print head and piezo print head controlled according to this method
    DE19911399 1999-03-15

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    EP1036660A1 EP1036660A1 (en) 2000-09-20
    EP1036660B1 true EP1036660B1 (en) 2002-08-28

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    US (1) US6460979B1 (en)
    EP (1) EP1036660B1 (en)
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    CN1182962C (en) 2005-01-05
    EP1036660A1 (en) 2000-09-20
    JP2000296619A (en) 2000-10-24
    DE19911399A1 (en) 2000-09-28
    DE19911399C2 (en) 2001-03-01
    US6460979B1 (en) 2002-10-08
    CN1266783A (en) 2000-09-20

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