EP0197300B1 - Operating method to improve the printing quality of a printer - Google Patents

Operating method to improve the printing quality of a printer Download PDF

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Publication number
EP0197300B1
EP0197300B1 EP86102874A EP86102874A EP0197300B1 EP 0197300 B1 EP0197300 B1 EP 0197300B1 EP 86102874 A EP86102874 A EP 86102874A EP 86102874 A EP86102874 A EP 86102874A EP 0197300 B1 EP0197300 B1 EP 0197300B1
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EP
European Patent Office
Prior art keywords
oscillator
ink
pulse width
values
dac
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EP86102874A
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German (de)
French (fr)
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EP0197300A1 (en
Inventor
Jaques Dipl.-Informatiker Carrey (Fh)
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Gesellschaft fur Automationstechnik Mbh
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Gesellschaft fur Automationstechnik Mbh
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/07—Ink jet characterised by jet control
    • B41J2/115—Ink jet characterised by jet control synchronising the droplet separation and charging time

Definitions

  • the invention relates to a method for controlling and improving the font quality of a printer, in particular an ink color jet printer, wherein at least one color jet is generated by means of voltage and frequency applied to an oscillator through at least one nozzle of a nozzle plate and charged drops after a certain distance from the nozzle plate solve the ink jet, the drop tear-off distance from the nozzle plate is adjusted via a regulation of the oscillating voltage, and the flight time of a drop is measured from the drop tear-off point to a charge detector.
  • Ink color printers as a form of matrix printers are used today as peripheral devices for electronic computing systems for outputting data. Similar to the principle of a dot matrix printer, the print head of the inkjet printer has a series of vertically arranged nozzles, one below the other, through which jets of liquid ink are sprayed onto the material to be labeled under high pressure. Depending on which nozzles are open or closed, the image of the desired letters and numbers is created on the labeling material from dots of color.
  • nozzles and control devices for example for closing or for electrostatically or magnetically deflecting the undesired color rays
  • continuous color jet printers continuous jet system
  • an ink color jet is generated through a nozzle and then equally spaced ink drops of the same size, which have a charging electrode and a constant one generated by baffle plates pass electric field, the drops being deflected in one direction depending on their charge, while the deflection of the drop in the other direction is carried out by another suitable measure, for example moving the object to be labeled.
  • Disturbance parameters in any case lead to a reduction in the quality of the font.
  • they can be compensated for in a certain defined range by setting the optimum droplet detachment for the current operating state of the system. So far, this compensation has been done optically and manually.
  • the behavior of the droplet formation is observed with a magnifying glass over a stroboscope diode attached to the write head and readjusted by changing a vibration amplitude using a potentiometer. This method is quite unsafe because it depends on the subjective perception of the observer and requires a high degree of system knowledge and practice on the part of the user. This effort leads to a restriction in the range of applications and in the marketability of an ink color printer.
  • An ink color jet printer is known from US Pat. No. 4,496,954, in which the ink jet is passed through charging electrodes. After the drop has been torn off, the individual drops pass between baffle plates and from there either into a vacuum collector or another collector which is preceded by a sensor for determining the drops provided with charge. The oscillation voltage is set via the corresponding values, so that the drop break point is in the satellite-free range.
  • This device is only intended for the initial setup of the ink jet or for a re-setup before a new start, since the above-mentioned collector is engaged in the path of the drops to, for example, a paper to be labeled.
  • the nozzle head is aligned to the collector on the one hand and to a test station for the drop charge on the other.
  • a condition changes during normal operation of the printer such as the printer temperature, there is no further adjustment of the parameters relevant for drip flight.
  • EP-A 0 039 772 A further embodiment of the invention just mentioned can be found in EP-A 0 039 772.
  • two sensors are provided during normal operation of the printer, which detect the drip flight. These sensors measure the flight time of the drop from a drop break point to the respective sensor. These measurement results are compared with other values in an evaluation unit, and the oscillating voltage is thus changed.
  • this does not take into account the fact that, in particular, the change in the color viscosity results in a shift in the drop tear-off point, which can counteract an increase in the oscillating voltage to a certain extent, which is insufficient beyond a certain range and also leads to increased energy consumption.
  • the inventor has set itself the goal of developing an automatic process and integrating it into existing or new process units, which on the one hand regulates the optimal tear-off removal online to ensure the highest possible font quality and on the other hand an increase in the above-mentioned. Display and / or prevent disturbance parameters beyond a certain range.
  • the process is intended to take into account the respective characteristics of the oscillator and nozzle, which are configured in an ink-jet printer, in order not to require very tight manufacturing tolerances.
  • a printer leads to the solution of this task of the type mentioned above, in which the viscosity of the paint is regulated by observing the oscillation voltage and the tear-off distance.
  • a possible additional element of the present invention is the synchronization between drop separation and drop charging. It is first determined whether a charged drop is even displayed on the charge detector. If this is not the case, a phase jump is made at the charging pulse frequency. This continues until the detector indicates a charge.
  • the pulse width of the detected signal is then compared with the pulse width of a stored signal. If deviations are found here again, there is a further phase shift of the charging pulse frequency.
  • the flight time of the drop is only measured when there is a synchronization between drop charging and drop formation. This flight time is then to be compared with a stored flight time, for example from the measurement of the previous flight time. If the actual flight time deviates from the stored flight time, the oscillating voltage is changed until the current flight time is equal to or less than the stored value and the range of the optimal drop tear-off distance is reached.
  • the procedure is otherwise not tied to any specific form of implementation, i.e. it can be integrated into the system as a hardware solution and / or as a software solution. It is required to measure the controlled variable, i.e. the tear-off removal, only the existing components and measuring devices, which are integrated into the system to synchronize the drop charge with its tear-off. Good font quality is guaranteed over a relatively wide viscosity range of the color. Measurements have shown that systems with a defined operating viscosity of approx. 3.1 mPa x sec with a viscosity increase to over 7 mPa x sec still have a high font quality.
  • a device for controlling and improving the font quality of a printer, in particular an ink color jet printer, with an oscillator for generating at least one color jet through at least one nozzle of a nozzle plate, charging electrodes being assigned to the color jet and, after a certain distance from the nozzle plate, drops from the Loosen the ink jet and this drop tear-off distance from the nozzle plate can be adjusted by regulating the oscillating voltage and a drop tear-off control, which interacts with a phase control, is provided, the drop tear-off control is associated with a viscosity control for the paint.
  • the drop stop control contains a device for determining the flight time of a drop, which preferably consists of the charging electrode for applying a charging voltage to the drop, a charging detector for detecting the charge and a flight time counter.
  • a device for determining the flight time of a drop which preferably consists of the charging electrode for applying a charging voltage to the drop, a charging detector for detecting the charge and a flight time counter.
  • both the oscillator and the charging electrode are preceded by a frequency divider, both of which are jointly connected to a system clock feed.
  • the DAC counter is connected via a digital / analog converter to an amplifier which is connected between the oscillator and its pulse converter. In this way, the vibration voltage can be changed.
  • the DigitaVAnalog converter and the DAC counter replace the potentiometer previously used for automatic tracking of the manipulated variable (oscillating voltage).
  • other suitable actuators are also conceivable.
  • Switching elements for synchronizing the charging voltage or a charging pulse with the tear-off are switched on via a second start signal. These switching elements consist of a pulse counter, the above. Frequency divider for the charging electrode and a pulse width comparator. The charge pulse frequency emitted from the frequency divider can be phase-shifted via the latter, the pulse-width comparator being connected both to the charge detector and to the flight time counter and controlling the latter.
  • a pulse width memory is also assigned to the pulse width comparator and contains a value for comparing the current value of the pulse width comparator. This value should preferably be changeable in the pulse width memory, i.e. current values can be adjusted.
  • the flight time counter is followed by a time of flight comparator which compares the time of flight values with values from a time of flight memory and controls the DAC counter. These values in the flight time memory can also be changed by entering current values.
  • the flight time counter is provided with a measured value counter and possibly a rule Direction assigned for a certain number of measured values, wherein a flight time adder is interposed between the flight time counter and the flight time comparator to form an average.
  • the time-of-flight comparator increments or decrements the DAC counter depending on the existing deviations in the time of flight and the oscillator voltage is changed via the DAC counter or the digital / analog converter and amplifier.
  • a flip-flop with which a DAC comparator is connected can be controlled via the first start signal.
  • This DAC comparator in turn compares the values of the DAC counter with values from a DAC reference memory.
  • the reference value in the DAC reference memory represents the vibrating voltage for an optimal drop tear-off depending on the vibrator used and a valid operating viscosity of the paint. It can also be changed if necessary.
  • the DAC comparator detects a difference between the reference value from the DAC reference memory and the value of the DAC counter, it controls a device for regulating the viscosity of the paint. Depending on the difference between the two values, either a valve of a tank for the paint or a valve of a solvent tank is opened and paint or solvent is let into a main tank.
  • the device works fully automatically and is completely independent of the subjective sensations of an observer.
  • the disturbance parameters e.g. The ambient temperature of the system and color pressure fluctuations in the hydraulic system are automatically compensated.
  • the operability of the system within a reaction time to replenish the viscosity is ensured by the optimal drop tear removal for the current ink viscosity is readjusted.
  • the reaction time of the replenishment is relatively short even with long hydraulic lines.
  • a nozzle 2 is arranged in a nozzle plate 1, through which ink color is pressed out of a nozzle prechamber 4. 3 with a supply line is indicated with ink.
  • An oscillator 5 is arranged in this nozzle prechamber 4.
  • the ink color forms an ink jet 6 with a diameter d s (see FIG. 2) and a flow velocity vs.
  • drops 7 form out of the ink jet 6, which then tear off from the ink jet 6 at a drop tear-off point 8 and continue to move at a drop distance ⁇ .
  • the drop-off removal from the drop-off point 8 to the nozzle plate 1 is designated Sa.
  • the drop break-off point lies between two charging electrodes 25, each drop being charged electrostatically differently (according to the shape of the character or matrix).
  • a downstream charge detector 27 checks whether the drops 7 are charged. Then the drop 7 flies through an electric field of two baffles 71 and 72, to which high voltage is applied. Depending on its charge, the drop 7 is deflected in one direction (here vertically). The drop is deflected in the other direction (here horizontally) by the movement of an object 73 to be labeled. If no writing process is triggered, the drop is not deflected by the deflection plates 71, 72, but flies into a collecting tube 74 or the like. and, not shown in detail, is conveyed back into a main tank 64 with a suction pump.
  • the drop detachment distance Sa is now to a considerable extent dependent on a voltage U applied to the oscillator 5, as is shown in FIG. 3.
  • the droplet detachment distance s a gradually decreases. As soon as the oscillating voltage has reached the level U w , the drop detachment distance Sa begins to rise again. The hatched, so-called satellite-free region 9 of droplet formation occurs between two levels U o and Um of the oscillating voltage. An optimal font quality of the system is only guaranteed in this area.
  • the oscillation voltage level U w lies between the two values U o and Um and is representative of the shortest drop tear-off distance.
  • FIG. 5 shows the satellite-free region as a function of the ink viscosity, limited by the oscillation voltage level U o and Um. This satellite-free area becomes smaller with increasing ink viscosity.
  • the course of the oscillation voltage level U w for an optimal droplet removal distance S a is indicated by a broken line.
  • An optical / manual readjustment of this level with increasing ink viscosity is very difficult, since the observer can only form his subjective opinion about the satellite state of the ink jet and not about the appropriate tear-off removal.
  • a circuit for carrying out the method according to the invention consists of three main blocks: a phase control 20, a drop break control 40 and a viscosity control 60 is excited which have the same frequency.
  • This initial value should be such that a sinusoidal voltage of 20 Vpp with a frequency of, for example, 64 kHz is present at the output of an amplifier 45 after a pulse set 44, generated by the frequency divider oscillator 43.
  • the output of the amplifier 45 supplies the oscillator 5 and is the manipulated variable of the entire drop separation control 40. Desired voltage changes for the oscillator 5 are input to the amplifier 45 via a digital / analog converter 54 via 55, which is connected to the DAC counter 41.
  • a pulse counter 21 is started via 11 a and, for 8 clock periods of the 64 kHz of the frequency divider 22, which, like the frequency divider oscillator 43, is connected to the system clock 15, charging voltages alternating between 8 V and 0 V via a charging pulse generator 23 and optionally an amplifier 24 applied to the charging electrode 25 and charged the ink droplets.
  • a flight time counter 46 is started, which is incremented synchronously with the system clock 15.
  • the flight time counter 46 can be stopped by the output 16 of a pulse width comparator 26, provided the drops 7 have been loaded with a charge.
  • the flight time counter 46 reaches a maximum counter reading and causes the charging pulse frequency to experience a phase jump 17 of approximately +12 ° with respect to the oscillator frequency.
  • This phase jump is achieved in that the divider factor of the frequency divider 22 is changed before the charge pulse generator 23 for one clock period.
  • the phase control is repeated until drops with charges are detected by the charge detector 27 and these values are applied as a rectangular pulse via a charge amplifier 28, optionally with pulse processing, at the input of the pulse width comparator 26.
  • the pulse width comparator 26 compares the current pulse width of the signal with the last maximum pulse width from a pulse width memory 29, which was originally input to the pulse width memory 29 via 30 by the pulse width comparator 26.
  • the flight time counter 46 is stopped via the output 16 and a measured value counter 47 is decremented via 16a. If the current pulse width is larger, the old value is overwritten with the new one in the memory 29 via 30 and the phase of the charging pulse generator 23 is shifted in the same direction as the last measurement process by 6 ° with respect to the oscillator frequency. If the current pulse width is smaller, the phase is shifted by +6 ° and both values are shifted by -6 ° .
  • the connections 18, 19 between pulse width comparator 26 and frequency divider 22 are intended for these phase jumps.
  • This phase control 20 ensures an optimal synchronization between the charging of the drops 7 with a specific charge and their tearing off. Furthermore, the electrical properties of the measuring device (charging electrode 25, charge detector 27 and amplifier 28) are automatically adapted by the adaptive method of pulse width evaluation.
  • the phase control 20 and drop break control 40 are interlinked via the pulse width comparator 26, among other things. As stated above, this stops the flight time counter 46 and decrements the measured value counter 47 only when the maximum pulse width has been detected by the phase control 20.
  • the counter reading at the output of the flight time counter 46 is directly proportional to the flight time of the drops 7, namely from their demolition 8 to a charge detector 27, that is to say inversely proportional to the drop detachment distance S a to the nozzle plate 1.
  • the current counter reading then becomes an average in a time-of-flight adder 48 added.
  • an output 33 of the measured value counter 47 activates a time-of-flight comparator 49, so that the current mean value of the drop flight time is compared with the last mean value from a time-of-flight memory 50. The last mean value is then overwritten with the current mean value in time-of-flight memory 50 through 34. If the current mean value of the drop flight time is greater than the last mean value, ie the drop tear-off distance Sa in relation to the nozzle plate 1 has become smaller, the DAC counter 41 is incremented via the connection 35 and the oscillating voltage is increased by approximately 2 V. This control process is repeated until the current mean value of the trop the flight time has become equal to or less than the last mean value and the range of optimal drop removal has been reached.
  • the DAC counter 41 is decremented via the connection 36.
  • a flip-flop 51 which was reset by the signal 10 "start control" via 10b, is set again, so that a DAC comparator 52 is activated via 37 and an output 38 of the DAC counter 41 with an output 39 of a DAC reference memory 53 for all other control processes are continuously compared.
  • the value at the output 38 of the DAC counter 41 is loaded when the flip-flop 51 is set in the DAC reference memory 53, as indicated by arrow 12. This value serves as a reference of the vibrating voltage for optimal droplet detachment depending on the vibrator 5 used and the valid operating viscosity of the ink.
  • the DAC counter 41 is decremented during the next control processes as long as the drop tear-off distance S a is to the right of the turning point U w or in the area 9 (see FIG. 3), ie the currently measured drop flight time is greater than that of the last measurement or at least the same.
  • the droplet detachment distance S a is larger and is therefore to the left of the area of the inflection point Uw (see FIG. 3).
  • the DAC counter 41 is incremented until the drop removal distance S a is again to the right of the area of the turning point Uw.
  • the output 61 from the DAC comparator 52 activates a valve 62 of an ink tank 63, so that a main tank 64 up to a maximum Level is refilled with ink. If, on the other hand, the value at the output 38 of the DAC counter 41 is greater than the reference value, the output 61 of the DAC comparator 52 activates a solvent valve 65 of a solvent tank 66 and the main tank 64 is refilled with solvent up to the maximum fill level. The ink viscosity in the main tank 64 thus decreases again.
  • a level monitor 67 is arranged in the main tank 64, the signals of which are sent to a level monitor 68.
  • Level monitoring 68, valves 62 and 65 and output 61 of 52 are connected to one another by corresponding suitable switching elements, such as AND gate 69 and amplifier 70.

Landscapes

  • Particle Formation And Scattering Control In Inkjet Printers (AREA)
  • Dot-Matrix Printers And Others (AREA)
  • Fax Reproducing Arrangements (AREA)
  • Ink Jet (AREA)

Abstract

1. A method of controlling and improving the printing quality of a printer, in particular an ink jet printer, wherein at least one ink jet (6) is produced by means of the voltage and frequency applied to an oscillator (5) through at least one nozzle (2) of a perforated plate (1) and, after a certain distance from the perforated plate (1), charged droplets (7) are released from the ink jet (6), the droplet breakaway distance (Sa ) from the perforated plate (1) being optimally adjusted by regulation of the oscillator voltage, and the flight time of a droplet (7) from the droplet break-away point (8) to a charge detector (27) is measured, characterised in that the viscosity of the ink is regulated by observing the oscillator voltage and the droplet break-away distance (Sa ).

Description

Die Erfindung betrifft ein Verfahren zum Steuern und Verbessern der Schriftgüte eines Drukkers, insbesondere eines Tintenfarbstrahldrukkers, wobei zumindest ein Farbstrahl mittels an einen Schwinger angelegte Spannung und Frequenz durch zumindest eine Düse einer Düsenplatte erzeugt wird und sich aufgeladene Tropfen nach einer bestimmten Entfernung von der Düsenplatte aus dem Farbstrahl lösen, deren Tropfenabrißentfernung von der Düsenplatte über eine Regelung der Schwingerspannung eingestellt wird, und die Flugzeit eines Tropfens vom Tropfenabrißpunkt bis zu einem Ladungsdetektor gemessen wird.The invention relates to a method for controlling and improving the font quality of a printer, in particular an ink color jet printer, wherein at least one color jet is generated by means of voltage and frequency applied to an oscillator through at least one nozzle of a nozzle plate and charged drops after a certain distance from the nozzle plate solve the ink jet, the drop tear-off distance from the nozzle plate is adjusted via a regulation of the oscillating voltage, and the flight time of a drop is measured from the drop tear-off point to a charge detector.

Tintenfarbstrahldrucker als eine Form von Matrixdruckem finden heute als Peripheriegeräte für elektronische Rechenanlagen zur Ausgabe von Daten Anwendung. Ähnlich dem Prinzip eines Nadeldruckers besitzt der Schreibkopf des Tintenstrahldruckers eine Reihe von senkrecht unter- und nebeneinander angeordneten Düsen, durch die Strahlen flüssiger Tintenfarbe unter hohem Druck auf das zu beschriftende Material gespritzt werden. Je nach dem, welche Düsen geöffnet oder geschlossen sind, entsteht auf dem Beschriftungsmaterial aus Farbpünktchen das Bild der gewünschten Buchstaben und Ziffern. Beim Schreiben wandern Düsen und Steuervorrichtungen (beispielsweise zum Schließen oder zum elektrostatischen oder magnetischen Ablenken der nicht gewünschten Farbstrahlen) zeilenweise am Beschriftungsmaterial vorbei und spritzen ein Zeichen nach dem anderen.Ink color printers as a form of matrix printers are used today as peripheral devices for electronic computing systems for outputting data. Similar to the principle of a dot matrix printer, the print head of the inkjet printer has a series of vertically arranged nozzles, one below the other, through which jets of liquid ink are sprayed onto the material to be labeled under high pressure. Depending on which nozzles are open or closed, the image of the desired letters and numbers is created on the labeling material from dots of color. When writing, nozzles and control devices (for example for closing or for electrostatically or magnetically deflecting the undesired color rays) pass line by line past the labeling material and inject one character after the other.

Im weiteren sind sogenannte Dauer-Farbstrahldrucker (kontinuierliches Jet-System) bekannt, beispielsweise aus der DE-PS 2 446 740. Bei ihm wird ein Tintenfarbstrahl durch eine Düse und danach gleichbeabstandete Tintentropfen gleicher Größe erzeugt, die eine Ladeelektrode und ein durch Ablenkplatten erzeugtes konstantes elektrisches Feld passieren, wobei die Tropfen je nach ihrer Ladung eine Ablenkung in eine Richtung erfahren, während die Ablenkung des Tropfens in die andere Richtung durch eine andere geeignete Maßnahme, beispielsweise das Bewegen des zu beschriftenden Gegenstandes erfolgt.In addition, so-called continuous color jet printers (continuous jet system) are known, for example from DE-PS 2 446 740. In it, an ink color jet is generated through a nozzle and then equally spaced ink drops of the same size, which have a charging electrode and a constant one generated by baffle plates pass electric field, the drops being deflected in one direction depending on their charge, while the deflection of the drop in the other direction is carried out by another suitable measure, for example moving the object to be labeled.

Im wesentlichen beeinflussen zwei Störparameter die Schriftgüte eines derartigen Dauer-Tintenfarbstrahldruckers, nämlich

  • - die Umgebungstemperatur des Systems, welche die Viskosität der Tinte verändert (besonders bei alkohollöslichen Tinten, wie MEK (Methyläthylketon) und Äthanol und
  • - Tintendruckschwankungen im Hydrauliksystem.
Essentially, two disturbance parameters influence the font quality of such a continuous ink color printer, namely
  • - The ambient temperature of the system, which changes the viscosity of the ink (especially with alcohol-soluble inks such as MEK (methyl ethyl ketone) and ethanol and
  • - Ink pressure fluctuations in the hydraulic system.

Die o.g. Störparameter führen in jedem Fall zu einer Minderung der Schriftgüte. Sie können jedoch in einem bestimmten definierten Bereich kompensiert werden, indem für den jeweils aktuellen Betriebszustand des Systems die optimale Tropfenabrißentfemung eingestellt wird. Diese Kompensation erfolgt bislang optisch-manuell. Dabei wird das Verhalten der Tropfenbildung mit einer Lupe über einer am Schreibkopf angebrachten Stroboskopdiode beobachtet und durch Änderung einer Schwingeramplitude mittels eines Potentiometers nachgesteuert. Dieses Verfahren ist recht unsicher, da es von dem subjektiven Empfinden des Beobachters abhängt, und verlangt seitens des Anwenders ein hohes Maß an Systemkenntnis und Übung. Dieser Aufwand führt zu einer Einschränkung im Einsatzspektrum und in der Marktfähigkeit eines Tintenfarbstrahldruckers.The above Disturbance parameters in any case lead to a reduction in the quality of the font. However, they can be compensated for in a certain defined range by setting the optimum droplet detachment for the current operating state of the system. So far, this compensation has been done optically and manually. The behavior of the droplet formation is observed with a magnifying glass over a stroboscope diode attached to the write head and readjusted by changing a vibration amplitude using a potentiometer. This method is quite unsafe because it depends on the subjective perception of the observer and requires a high degree of system knowledge and practice on the part of the user. This effort leads to a restriction in the range of applications and in the marketability of an ink color printer.

Aus der US-A 4 496 954 ist ein Tintenfarbstrahldrucker bekannt, bei welchem der Tintenstrahl durch Ladeelektroden hindurchgeführt wird. Nach erfolgtem Tropfenabriß gelangen die einzelnen Tropfen zwischen Ablenkplatten und von dort entweder in einen Vakuumsammler oder einen anderen Sammler, dem ein Sensor zur Ermittlung der mit Ladung versehenen Tropfen vorgeschaltet ist. Über die entsprechenden Werte wird die Schwingerspannung eingestellt, so daß der Tropfenabrißpunkt im satellitenfreien Bereich liegt.An ink color jet printer is known from US Pat. No. 4,496,954, in which the ink jet is passed through charging electrodes. After the drop has been torn off, the individual drops pass between baffle plates and from there either into a vacuum collector or another collector which is preceded by a sensor for determining the drops provided with charge. The oscillation voltage is set via the corresponding values, so that the drop break point is in the satellite-free range.

Diese Vorrichtung ist nur für die erstmalige Einrichtung des Farbstrahles oder für eine Wiedereinrichtung vor einem neuerlichen Beginn gedacht, da der oben genannte Sammler in den Weg der Tropfen zu beispielsweise einem zu beschriftenden Papier eingeschaltet ist. In diesem Vorabtest wird der Düsenkopf einmal zu dem Sammler hin ausgerichtet und zum anderen zu einer Teststation für die Tropfenladung. Ändert sich jedoch beim normalen Betrieb des Druckers eine Bedingung, wie beispielsweise die Druckertemperatur, so findet keine weitere Anpassung der für den Tropfenflug maßgeblichen Parameter statt.This device is only intended for the initial setup of the ink jet or for a re-setup before a new start, since the above-mentioned collector is engaged in the path of the drops to, for example, a paper to be labeled. In this preliminary test, the nozzle head is aligned to the collector on the one hand and to a test station for the drop charge on the other. However, if a condition changes during normal operation of the printer, such as the printer temperature, there is no further adjustment of the parameters relevant for drip flight.

Eine weitere Ausgestaltung der eben genannten Erfindung findet sich in der EP-A 0 039 772. Dort sind zwei Sensoren im normalen Betrieb des Druckers vorgesehen, welche den Tropfenflug detektieren. Diese Sensoren messen die Flugzeit des Tropfens von einem Tropfenabrißpunkt zu dem jeweiligen Sensor. In einer Auswerteeinheit werden diese Meßergebnisse mit anderen Werten verglichen und so die Schwingerspannung verändert. Dabei bleibt jedoch unberücksichtigt, daß insbesondere sich durch die Veränderung der Farbviskosität eine Verschiebung des Tropfenabrißpunktes ergibt, der zwar eine Erhöhung der Schwingerspannung in gewissem Umfang entgegenwirken kann, was über einen gewissen Bereich hinaus ungenügend ist und zudem zu einer erhöhten Energieaufnahme führt.A further embodiment of the invention just mentioned can be found in EP-A 0 039 772. There, two sensors are provided during normal operation of the printer, which detect the drip flight. These sensors measure the flight time of the drop from a drop break point to the respective sensor. These measurement results are compared with other values in an evaluation unit, and the oscillating voltage is thus changed. However, this does not take into account the fact that, in particular, the change in the color viscosity results in a shift in the drop tear-off point, which can counteract an increase in the oscillating voltage to a certain extent, which is insufficient beyond a certain range and also leads to increased energy consumption.

Der Erfinder hat sich zum Ziel gesetzt, ein automatisches Verfahren zu entwickeln und in bestehende bzw. neue Prozeßeinheiten zu integrieren, das einerseits die optimale Tropfenabrißentfemung On-line regelt, um eine höchstmögliche Schriftgüte zu gewährleisten und andererseits eine Zunahme der o.g. Störparameter über einen bestimmten Bereich hinaus anzuzeigen und/oder zu verhindern. Dabei soll das Verfahren die jeweiligen Charakteristiken von Schwinger und Düse berücksichtigen, die in einem Tintenfarbstrahldrucker konfigurieren, um keine sehr engen Fertigungstoleranzen erforderlich zu machen.The inventor has set itself the goal of developing an automatic process and integrating it into existing or new process units, which on the one hand regulates the optimal tear-off removal online to ensure the highest possible font quality and on the other hand an increase in the above-mentioned. Display and / or prevent disturbance parameters beyond a certain range. The process is intended to take into account the respective characteristics of the oscillator and nozzle, which are configured in an ink-jet printer, in order not to require very tight manufacturing tolerances.

Zur Lösung dieser Aufgabe führt ein Drucker der o.g. Art, bei welchem über eine Beobachtung der Schwingerspannung und der Tropfenabrißentfernung die Viskosität der Farbe geregelt wird.A printer leads to the solution of this task of the type mentioned above, in which the viscosity of the paint is regulated by observing the oscillation voltage and the tear-off distance.

Dadurch erfolgt nach der Regelung der optimalen Tropfenabrißentfemung ein ständiger Vergleich der Schwingerspannungswerte zum Beispiel mit Referenzwerten aus einem Speicher. Diese Referenzwerte sind Werte einer Schwingerspannung für eine optimale Tropfenabrißentfernung in Abhängigkeit des eingesetzten Schwingers und einer gültigen Betriebsviskosität der Farbe. Werden Abweichungen der Schwingerspannungswerte von diesem Referenzwert festgestellt, so wird erfindungsgemäß die Viskosität der Farbe verändert. Es ist bekannt, daß eine zunehmende Farbviskosität eine stetige Erhöhung der Schwingerspannung erfordert, so daß bei einer gewissen Farbviskosität der Regelbereich der optimalen Tropfenabrißentfernung verlassen wird. Dies wird durch die Beeinflussung der Farbviskosität selbst vermieden.As a result, after the regulation of the optimal droplet removal, there is a constant comparison of the vibration voltage values, for example with reference values from a memory. These reference values are values of an oscillation voltage for an optimal droplet removal depending on the oscillator used and a valid operating viscosity of the paint. If deviations of the vibration voltage values from this reference value are determined, the viscosity of the color is changed according to the invention. It is known that an increasing color viscosity requires a constant increase in the oscillation voltage, so that the control range of the optimum drop tear-off distance is left at a certain color viscosity. This is avoided by influencing the color viscosity itself.

Ein mögliches zusätzliches Element der vorliegenden Erfindung ist die Synchronisation zwischen Tropfenabriß und Tropfenaufladung. Dabei wird zuerst festgestellt, ob ein geladener Tropfen am Ladungsdetektor überhaupt angezeigt wird. Ist dies nicht der Fall, wird bei der Ladeimpulsfrequenz ein Phasensprung vorgenommen. Dies geschieht solange, bis der Detektor eine Ladung anzeigt.A possible additional element of the present invention is the synchronization between drop separation and drop charging. It is first determined whether a charged drop is even displayed on the charge detector. If this is not the case, a phase jump is made at the charging pulse frequency. This continues until the detector indicates a charge.

Danach wird die Pulsbreite des detektierten Signals mit der Pulsbreite eines abgespeicherten Signals verglichen. Werden hier wiederum Abweichungen festgestellt, so erfolgt eine weitere Phasenverschiebung der Ladeimpulsfrequenz.The pulse width of the detected signal is then compared with the pulse width of a stored signal. If deviations are found here again, there is a further phase shift of the charging pulse frequency.

Erst wenn danach eine Synchronisation zwischen Tropfenaufladung und Tropfenbildung erfolgt ist, wird die Flugzeit des Tropfens gemessen. Diese Flugzeit ist dann mit einer gespeicherten Flugzeit beispielsweise aus der Messung der vorangegangenen Flugzeit zu vergleichen. Beim Abweichen der tatsächlichen Flugzeit von der gespeicherten Flugzeit wird die Schwingerspannung verändert, bis die aktuelle Flugzeit gleich oder kleiner ist als der gespeicherte Wert und dadurch der Bereich der optimalen Tropfenabrißentfernung erreicht ist.The flight time of the drop is only measured when there is a synchronization between drop charging and drop formation. This flight time is then to be compared with a stored flight time, for example from the measurement of the previous flight time. If the actual flight time deviates from the stored flight time, the oscillating voltage is changed until the current flight time is equal to or less than the stored value and the range of the optimal drop tear-off distance is reached.

In der Praxis hat es sich als günstig erwiesen, nicht jede einzelne Flugzeit mit dem Wert aus dem Speicher zu vergleichen, sondern eine Vielzahl von Flugzeiten aufzuaddieren und daraus einen Mittelwert zu bilden, welcher mit einem Mittelwert aus dem Speicher verglichen wird.In practice, it has proven to be advantageous not to compare each individual flight time with the value from the memory, but to add up a large number of flight times and to form an average from this, which is compared with an average from the memory.

Das Verfahren ist im übrigen an keine bestimmte Realisierungsform gebunden, d.h. es kann als Hardwarelösung und/oder als Softwarelösung in das System integriert werden. Es benötigt zur Meßung der Regelgröße, d.h. der Tropfenabrißentfemung, ausschließlich die vorhandenen Komponenten und Meßeinrichtungen, welche zur Synchronisation der Tropfenaufladung auf ihren Abriß in das System integriert sind. Es wird eine gute Schriftqualität über einen relativ breiten Viskositätsbereich der Farbe gewährleistet. Messungen haben gezeigt, daß Systeme mit einer definierten Betriebsviskosität von ca. 3,1 mPa x sec bei einer Viskositätszunahme auf über 7 mPa x sec noch eine hohe Schriftgüte besitzen.The procedure is otherwise not tied to any specific form of implementation, i.e. it can be integrated into the system as a hardware solution and / or as a software solution. It is required to measure the controlled variable, i.e. the tear-off removal, only the existing components and measuring devices, which are integrated into the system to synchronize the drop charge with its tear-off. Good font quality is guaranteed over a relatively wide viscosity range of the color. Measurements have shown that systems with a defined operating viscosity of approx. 3.1 mPa x sec with a viscosity increase to over 7 mPa x sec still have a high font quality.

Bei einer erfindungsgemäßen Vorrichtung zum Steuern und Verbessern der Schriftgüte eines Druckers, insbesondere eines Tintenfarbstrahldruckers, mit einem Schwinger zum Erzeugen zumindest eines Farbstrahls durch zumindest eine Düse einer Düsenplatte, wobei dem Farbstrahl Ladeelektroden zugeordnet sind und nach einer bestimmten Entfernung von der Düsenplatte sich Tropfen aus dem Farbstrahl lösen und diese Tropfenabrißentfernung von der Düsenplatte über eine Regelung der Schwingerspannung einstellbar sowie eine Tropfenabrißregelung, die mit einer Phasenregelung zusammenwirkt, vorgesehen ist, ist mit der Tropfenabrißregelung eine Viskositätsregelung für die Farbe verbunden. Die Tropfenabrißregelung enthält eine Einrichtung zum Bestimmen der Flugzeit eines Tropfens, die bevorzugt aus der Ladeelektrode zum Anlegen einer Ladespannung an den Tropfen, einem Ladedetektor zum Detektieren der Ladung und einem Flugzeitzähler besteht. Sowohl dem Schwinger wie auch der Ladelektrode ist außer einem Impulsgenerator bzw. Impulsumsetzer ein Frequenzteiler vorgeschaltet, welche beide gemeinsam mit einer Systemtakteinspeisung verbunden sind.In a device according to the invention for controlling and improving the font quality of a printer, in particular an ink color jet printer, with an oscillator for generating at least one color jet through at least one nozzle of a nozzle plate, charging electrodes being assigned to the color jet and, after a certain distance from the nozzle plate, drops from the Loosen the ink jet and this drop tear-off distance from the nozzle plate can be adjusted by regulating the oscillating voltage and a drop tear-off control, which interacts with a phase control, is provided, the drop tear-off control is associated with a viscosity control for the paint. The drop stop control contains a device for determining the flight time of a drop, which preferably consists of the charging electrode for applying a charging voltage to the drop, a charging detector for detecting the charge and a flight time counter. In addition to a pulse generator or pulse converter, both the oscillator and the charging electrode are preceded by a frequency divider, both of which are jointly connected to a system clock feed.

Ober ein Startsignal wird ein DAC-Zähler (DAC = Digital-Analog-Converter) angeregt, welcher wiederum mit einem DAC-Anfangswert-Speicher verbunden ist. Der DAC-Zähler steht über einen Digital/Analog-Wandler mit einem Verstärker in Verbindung, welcher zwischen den Schwinger und seinen Impulsumsetzer eingeschaltet ist. Auf diese Weise kann die Schwingerspannung verändert werden. Hier ersetzt der DigitaVAnalog-Wandler und der DAC-Zähler das zur automatischen Nachführung der Stellgröße (Schwingerspannung) bislang verwendete Potentiometer. Es sind jedoch auch andere geeignete Stellglieder denkbar.A DAC counter (DAC = digital-to-analog converter) is excited via a start signal, which in turn is connected to a DAC initial value memory. The DAC counter is connected via a digital / analog converter to an amplifier which is connected between the oscillator and its pulse converter. In this way, the vibration voltage can be changed. Here, the DigitaVAnalog converter and the DAC counter replace the potentiometer previously used for automatic tracking of the manipulated variable (oscillating voltage). However, other suitable actuators are also conceivable.

Über ein zweites Startsignal werden Schaltelemente zum Synchronisieren der Ladespannung bzw. eines Ladeimpulses mit dem Tropfenabriß zugeschaltet. Diese Schaltelemente bestehen aus einem Impulszähler, dem o.g. Frequenzteiler für die Ladeelektrode und einem Pulsbreitecomparator. Ober letzteren kann die aus dem Frequenzteiler abgegebene Ladeimpulsfrequenz phasenverschoben werden, wobei der Pulsbreitecomparator sowohl mit dem Ladungsdetektor wie auch mit dem Flugzeitzähler in Verbindung steht und letzteren steuert. Dem Pulsbreitecomparator ist im übrigen ein Pulsbreitespeicher zugeordnet, welcher einen Wert zum Vergleichen des aktuellen Wertes des Pulsbreitecomparators enthält. Bevorzugt soll dieser Wert im Pulsbreitespeicher veränderbar, d.h. aktuellen Werten angleichbar sein.Switching elements for synchronizing the charging voltage or a charging pulse with the tear-off are switched on via a second start signal. These switching elements consist of a pulse counter, the above. Frequency divider for the charging electrode and a pulse width comparator. The charge pulse frequency emitted from the frequency divider can be phase-shifted via the latter, the pulse-width comparator being connected both to the charge detector and to the flight time counter and controlling the latter. A pulse width memory is also assigned to the pulse width comparator and contains a value for comparing the current value of the pulse width comparator. This value should preferably be changeable in the pulse width memory, i.e. current values can be adjusted.

Dem Flugzeitzähler folgt ein Flugzeitcomparator nach, welcher die Flugzeitwerte mit Werten aus einem Flugzeitspeicher vergleicht und den DAC-Zähler ansteuert. Auch diese Werte im Flugzeitspeicher können durch Eingabe von aktuellen Werten verändert werden.The flight time counter is followed by a time of flight comparator which compares the time of flight values with values from a time of flight memory and controls the DAC counter. These values in the flight time memory can also be changed by entering current values.

Bevorzugt soll jedoch nicht jede einzelne Flugzeit mit einem Wert aus dem Flugzeitspeicher verglichen werden. Zur Erfassung einer Mehrzahl von Werten bzw. deren Mittelwert ist dem Flugzeitzähler ein Meßwertzähler und gegebenenfalls eine Regeleinrichtung für eine bestimmte Anzahl von Meßwerten zugeordnet, wobei zwischen Flugzeitzähler und Flugzeitcomparator ein Flugzeitaddierer zum Bilden eines Mittelwertes zwischengeschaltet ist.However, preferably not every individual flight time should be compared with a value from the flight time memory. To record a plurality of values or their mean value, the flight time counter is provided with a measured value counter and possibly a rule Direction assigned for a certain number of measured values, wherein a flight time adder is interposed between the flight time counter and the flight time comparator to form an average.

Der Flugzeitcomparator inkrementiert oder dekrementiert den DAC-Zähler je nach den vorhandenen Abweichungen der Flugzeit und über den DAC-Zähler bzw. den Digital/Analog-Wandler und Verstärker wird die Schwingerspannung verändert.The time-of-flight comparator increments or decrements the DAC counter depending on the existing deviations in the time of flight and the oscillator voltage is changed via the DAC counter or the digital / analog converter and amplifier.

Weiterhin ist über das erste Startsignal ein Flipflop ansteuerbar, mit dem ein DAC-Comparator verbunden ist. In diesem DAC-Comparator werden wiederum die Werte des DAC-Zählers mit Werten aus einem DAC-Referenzspeicher verglichen. Der Referenzwert im DAC-Referenzspeicher stellt die Schwingerspannung für eine optimale Tropfenabrißentfernung in Abhängigkeit des eingesetzten Schwingers und einer gültigen Betriebsviskosität der Farbe dar. Auch er kann gegebenfalls verändert werden. Stellt der DAC-Comparator eine Differenz zwischen dem Referenzwert aus dem DAC-Referenzspeicher und dem Wert des DAC-Zählers fest, so steuert er eine Einrichtung zur Regelung der Viskosität der Farbe an. Je nach Differenz der beiden Werte wird entweder ein Ventil eines Tanks für die Farbe oder ein Ventil eines Lösungsmitteltanks geöffnet und Farbe bzw. Lösungsmittel in einen Haupttank eingelassen.Furthermore, a flip-flop with which a DAC comparator is connected can be controlled via the first start signal. This DAC comparator in turn compares the values of the DAC counter with values from a DAC reference memory. The reference value in the DAC reference memory represents the vibrating voltage for an optimal drop tear-off depending on the vibrator used and a valid operating viscosity of the paint. It can also be changed if necessary. If the DAC comparator detects a difference between the reference value from the DAC reference memory and the value of the DAC counter, it controls a device for regulating the viscosity of the paint. Depending on the difference between the two values, either a valve of a tank for the paint or a valve of a solvent tank is opened and paint or solvent is let into a main tank.

Insgesamt arbeitet die Vorrichtung vollautomatisch und ist völlig unabhängig von subjektiven Empfindungen eines Beobachters. Die Störparameter, wie z.B. Umgebungstemperatur des Systems und Farbdruckschwankungen im Hydrauliksystem, werden automatisch ausgeglichen. Die Betriebsfähigkeit des Systems innerhalb einer Reaktionszeit zur Nachdosierung der Viskosität wird gewährleistet, indem die optimale Tropfenabrißentfernung für die aktuelle Tintenviskosität nachgeregelt wird. Im übrigen ist die Reaktionszeit der Nachdosierung auch bei langen Hydraulikleitungen relativ gering.Overall, the device works fully automatically and is completely independent of the subjective sensations of an observer. The disturbance parameters, e.g. The ambient temperature of the system and color pressure fluctuations in the hydraulic system are automatically compensated. The operability of the system within a reaction time to replenish the viscosity is ensured by the optimal drop tear removal for the current ink viscosity is readjusted. In addition, the reaction time of the replenishment is relatively short even with long hydraulic lines.

Weitere Vorteile, Merkmale und Einzelheiten der Erfindung ergeben sich aus der nachfolgenden Beschreibung eines bevorzugten Ausführungsbeispiels, sowie anhand der Zeichung; diese zeigt in

  • Figur 1 eine vergrößerte schematisierte Darstellung der Arbeitsweise eines Farbstrahldrucker;
  • Figur 2 ein vergrößerter Ausschnitt aus Fig. 1;
  • Figur 3 eine graphische Darstellung der Abhängigkeit der Tropfenabdßentfemung von der an einen Schwinger angelegten Spannung;
  • Figur 4 eine graphische Darstellung der Abhängigkeit eines Schwingerspannungspegels von der Farbviskosität;
  • Figur 5 eine graphische Darstellung der Abhängigkeit eines satellitenfreien Bereichs von der Farbviskosität;
  • Figur 6 ein Blockschaltbild einer Schaltung zur Durchführung des erfindungsgemäßen Verfahrens zur Regelung der Tropfenabrißentfernung.
Further advantages, features and details of the invention result from the following description of a preferred exemplary embodiment and from the drawing; this shows in
  • Figure 1 is an enlarged schematic representation of the operation of a color jet printer;
  • FIG. 2 shows an enlarged detail from FIG. 1;
  • Figure 3 is a graphical representation of the dependence of droplet removal distance on the voltage applied to an oscillator;
  • FIG. 4 shows a graphical representation of the dependence of an oscillation voltage level on the color viscosity;
  • FIG. 5 shows a graphical representation of the dependence of a satellite-free region on the color viscosity;
  • FIG. 6 shows a block diagram of a circuit for carrying out the method according to the invention for controlling the droplet removal.

Nach Figur 1 ist in einer Düsenplatte 1 eine Düse 2 angeordnet, durch welche Tintenfarbe aus einer Düsenvorkammer 4 gepreßt wird. Mit 3 ist eine Versorgungsleitung mit Tinte angedeutet. In dieser Düsenvorkammer 4 ist ein Schwinger 5 angeordnet. Die Tintenfarbe bildet nach der Düse 2 einen Tintenstrahl 6 mit einem Durchmesser ds (siehe Fig. 2) und einer Strömungsgeschwindigkeit vs. Nach einer gewissen Entfernung von der Düsenplatte 1 formen sich aus dem Tintenstrahl 6 Tropfen 7 heraus, welche dann an einem Tropfenabrißpunkt 8 von dem Tintenstrahl 6 abreißen und sich mit einem Tropfenabstand λ weiter bewegen. Die Tropfenabrißentfemung vom Tropfenabrißpunkt 8 zur Düsenplatte 1 ist mit Sa bezeichnet.According to FIG. 1, a nozzle 2 is arranged in a nozzle plate 1, through which ink color is pressed out of a nozzle prechamber 4. 3 with a supply line is indicated with ink. An oscillator 5 is arranged in this nozzle prechamber 4. After the nozzle 2, the ink color forms an ink jet 6 with a diameter d s (see FIG. 2) and a flow velocity vs. After a certain distance from the nozzle plate 1, drops 7 form out of the ink jet 6, which then tear off from the ink jet 6 at a drop tear-off point 8 and continue to move at a drop distance λ. The drop-off removal from the drop-off point 8 to the nozzle plate 1 is designated Sa.

Der Tropfenabrißpunkt liegt zwischen zwei Ladeelektroden 25, wobei jeder Tropfen unterschiedlich (entsprechend der Form des Zeichens oder Matrize) elektrostatisch aufgeladen wird. Ein nachgeschalteter Ladungsdetektor 27 prüft, ob die Tropfen 7 geladen sind. Anschließend duchfliegt der Tropfen 7 ein elektrisches Feld zweier Ablenkplatten 71 und 72, an welche Hochspannung angelegt ist. Entsprechend seiner Ladung wird der Tropfen 7 in eine Richtung (hier vertikal) abgelenkt. Die Ablenkung des Tropfens in die andere Richtung (hier horizontal) erfolgt durch die Bewegung eines zu beschriftenden Gegenstandes 73. Ist kein Schreibprozeß ausgelöst, wird der Tropfen nicht von den Ablenkplatten 71, 72 abgelenkt, sondern fliegt in ein Fangrohr 74 od.dgl. und wird, nicht näher gezeigt, mit einer Absaugpumpe wieder in einen Haupttank 64 zurückbefördert.The drop break-off point lies between two charging electrodes 25, each drop being charged electrostatically differently (according to the shape of the character or matrix). A downstream charge detector 27 checks whether the drops 7 are charged. Then the drop 7 flies through an electric field of two baffles 71 and 72, to which high voltage is applied. Depending on its charge, the drop 7 is deflected in one direction (here vertically). The drop is deflected in the other direction (here horizontally) by the movement of an object 73 to be labeled. If no writing process is triggered, the drop is not deflected by the deflection plates 71, 72, but flies into a collecting tube 74 or the like. and, not shown in detail, is conveyed back into a main tank 64 with a suction pump.

Die Tropfenabrißentfemung Sa ist nun in erheblichem Maße von einer an den Schwinger 5 angelegten Spannung U abhängig, wie dies in Figur 3 gezeigt ist.The drop detachment distance Sa is now to a considerable extent dependent on a voltage U applied to the oscillator 5, as is shown in FIG. 3.

Wird die Schwingerspannung U, beginnend mit Ub kontinuierlich erhöht, so nimmt die Tropfenabrißentfemung sa allmählich ab. Sobald die Schwingerspannung den Pegel Uw erreicht hat, beginnt die Tropfenabrißentfemung Sa wieder anzusteigen. Zwischen zwei Pegeln Uo und Um der Schwingerspannung stellt sich der schraffierte sog. satellitenfreie Bereich 9 der Tropfenbildung ein. Eine optimale Schriftgüte des Systems ist ausschließlich in diesem Bereich gewährleistet.If the oscillating voltage U is continuously increased, starting with U b , the droplet detachment distance s a gradually decreases. As soon as the oscillating voltage has reached the level U w , the drop detachment distance Sa begins to rise again. The hatched, so-called satellite-free region 9 of droplet formation occurs between two levels U o and Um of the oscillating voltage. An optimal font quality of the system is only guaranteed in this area.

Der Schwingerspannungspegel Uw liegt zwischen den beiden Werten Uo und Um und ist für die kürzeste Tropfenabrißentfernung stellvertretend.The oscillation voltage level U w lies between the two values U o and Um and is representative of the shortest drop tear-off distance.

Eine Zunahme der Tintenviskosität bei unveränderter Systemkonfiguration (Schwinger/Düse) und bei konstantem Tintendruck würde eine Kurvenschar mit unterschiedlichen Werten für die Schwingerspannungspegel Uw, Uo und Um in Figur 2 ergeben. Stellvertretend wird in Figur 4 die Abhängigkeit des Schwingerspannungspegels Uw, der zur Einstellung der kürzesten Tropfenabrißentfernung und somit des satellitenfreien Bereichs repräsentativ ist, von der Tintenviskosität ηt dargestellt.An increase in the ink viscosity with unchanged system configuration (oscillator / nozzle) and with constant ink pressure would result in a family of curves with different values for the oscillation voltage levels U w , U o and Um in FIG. 2. The dependence of the oscillation voltage level Uw, which is representative of the setting of the shortest drop-off distance and thus of the satellite-free region, on the ink viscosity η t is shown as a representative in FIG.

Es ist klar ersichtlich, daß eine steigende Tintenviskosität ηt eine Erhöhung des Schwingerspannungspegels Uw erfordert, um eine optimale Tropfenabrißentfernung Sa zu erreichen. Dabei nimmt die Tropfenabrißenttemung sa, bezogen auf die Düsenplatte 1, ab.

  • Typische Werte für Uw min. bei ηtmin = 2,5 mPa x sec: 35 - 60 V.
  • Typische Werte für Uw max. bei llt max. = 5 mPa x sec: 80 - 120 V.
It is clearly evident that an increasing ink viscosity η t requires an increase in the oscillation voltage level Uw in order to achieve an optimal drop tear-off distance Sa. The droplet detachment s a decreases, based on the nozzle plate 1.
  • Typical values for Uw min. at η t min = 2.5 mPa x sec: 35 - 60 V.
  • Typical values for Uw max. at llt max. = 5 mPa x sec: 80 - 120 V.

Die Streuung der Grenzwerte für Uw min. und Uw max. liegen in den verschiedenen Schwingercharakteristiken begründet.The spread of the limit values for Uw min. and Uw max. are due to the different oscillator characteristics.

Figur 5 stellt in Abhängigkeit der Tintenviskosität den satellitenfreien Bereich dar, eingegrenzt durch die Schwingerspannungspegel Uo und Um. Dabei wird mit steigender Tintenviskosität dieser satellitenfreie Bereich kleiner. Der Verlauf des Schwingerspannungspegels Uw für eine optimale Tropfenabrißentfernung Sa ist gestrichelt gekennzeichnet. Eine optisch/manuelle Nachsteuerung dieses Pegels bei zunehmender Tintenviskosität ist nur sehr schwer möglich, da der Beobachter seine subjektive Meinung ausschließlich über den Satellitenzustand des Tintenstrahls bilden kann und nicht über die geeignete Tropfenabrißentfemung.FIG. 5 shows the satellite-free region as a function of the ink viscosity, limited by the oscillation voltage level U o and Um. This satellite-free area becomes smaller with increasing ink viscosity. The course of the oscillation voltage level U w for an optimal droplet removal distance S a is indicated by a broken line. An optical / manual readjustment of this level with increasing ink viscosity is very difficult, since the observer can only form his subjective opinion about the satellite state of the ink jet and not about the appropriate tear-off removal.

Eine Schaltung zur Durchführung des erfindungsgemäßen Verfahrens besteht nach Figur 6 aus drei Hauptblöcken: Einer Phasenregelung 20, einer Tropfenabrißregelung 40 und einer Viskositätsregelung 60. Phasenregelung 20 und Tropfenabrißregelung 40 sind über eine Systemtaktverbindung 15 miteinander gekoppelt, wobei einerseits ein Frequenzteiler 22, andererseits ein Frequenzteiler 43 angeregt wird, welche dieselbe Frequenz haben.According to FIG. 6, a circuit for carrying out the method according to the invention consists of three main blocks: a phase control 20, a drop break control 40 and a viscosity control 60 is excited which have the same frequency.

Ein erstes Steuersignal 10 = "Startregelung" gilt der Tropfenabrißregelung 40. Mit ihm 10a wird ein DAC-Zähler 41 (DAC = DigitaVAnalog-Converter) so angeregt, daß er sich mit einem DAC-Anfangswert 42 auflädt. Dieser Anfangswert soll so sein, daß am Ausgang eines Verstärkers 45 nach einem Impulssetzer 44 beispielsweise eine Sinusspannung von 20 Vpp mit einer Frequenz von beispielsweise 64 kHz anliegt, generiert von dem Frequenzteilerschwinger 43. Der Ausgang des Verstärkers 45 versorgt den Schwinger 5 und ist die Stellgröße der gesamten Tropfenabrißregelung 40. Gewünschte Spannungsänderungen für den Schwinger 5 werden dem Verstärker 45 über einen Digital/Analog-Wandler 54 über 55 eingegeben, welcher mit dem DAC-Zähler 41 in Verbindung steht.A drop control 40 applies a first control signal 10 = "start control". With it 10a a DAC counter 41 (DAC = digital analog converter) is excited in such a way that it is charged with a DAC initial value 42. This initial value should be such that a sinusoidal voltage of 20 Vpp with a frequency of, for example, 64 kHz is present at the output of an amplifier 45 after a pulse set 44, generated by the frequency divider oscillator 43. The output of the amplifier 45 supplies the oscillator 5 and is the manipulated variable of the entire drop separation control 40. Desired voltage changes for the oscillator 5 are input to the amplifier 45 via a digital / analog converter 54 via 55, which is connected to the DAC counter 41.

Mit einem zweiten Steuersignal 11 = "Start Synchronisation" wird die Phasenregelung 20 eingeleitet. Dabei wird ein lmpulszähler 21 über 11 a gestartet und für 8 Taktperioden der 64 kHz des Frequenzteilers 22, welcher wie der Frequenzteilerschwinger 43 mit dem Systemtakt 15 in Verbindung steht, Ladespannungen abwechselnd von 8 V und 0 V über einen Ladeimpulsgenerator 23 und gegebenenfalls einen Verstärker 24 an die Ladeelektrode 25 angelegt und die Tintentröpfchen aufgeladen. Mit dem Steuersignal 11 b wird gleichzeitig ein Flugzeitzähler 46 gestartet, der synchron zum Systemtakt 15 inkrementiert wird. Der Flugzeitzähler 46 kann vom Ausgang 16 eines Pulsbreitecomparators 26 gestoppt werden, vorausgesetzt die Tropfen 7 sind mit einer Ladung geladen worden. Andernfalls erreicht der Flugzeitzähler 46 einen maximalen Zählerstand und bewirkt, daß die Ladeimpulsfrequenz einen Phasensprung 17 von ca. +12° gegenüber der Schwingerfrequenz erfährt. Dieser Phasensprung wird dadurch erreicht, daß der Teilerfaktor des Frequenzteilers 22 vor dem Ladeimpulsgenerator 23 für eine Taktperiode geändert wird.Phase control 20 is initiated with a second control signal 11 = "start synchronization". A pulse counter 21 is started via 11 a and, for 8 clock periods of the 64 kHz of the frequency divider 22, which, like the frequency divider oscillator 43, is connected to the system clock 15, charging voltages alternating between 8 V and 0 V via a charging pulse generator 23 and optionally an amplifier 24 applied to the charging electrode 25 and charged the ink droplets. With the control signal 11 b, a flight time counter 46 is started, which is incremented synchronously with the system clock 15. The flight time counter 46 can be stopped by the output 16 of a pulse width comparator 26, provided the drops 7 have been loaded with a charge. Otherwise, the flight time counter 46 reaches a maximum counter reading and causes the charging pulse frequency to experience a phase jump 17 of approximately +12 ° with respect to the oscillator frequency. This phase jump is achieved in that the divider factor of the frequency divider 22 is changed before the charge pulse generator 23 for one clock period.

Die Phasenregelung wird solange wiederholt, bis Tropfen mit Ladungen von dem Ladungsdetektor 27 detektiert werden und diese Werte über einen Ladungsverstärker 28 gegebenenfalls mit Pulsaufbereitung am Eingang des Pulsbreitecomparators 26 als ein Rechteckimpuls anleigen. Der Pulsbreitecomparator 26 vergleicht dann die aktuelle Pulsbreite des Signals mit der letzten maximalen Pulsbreite aus einem Pulsbreitespeicher 29, welche ursprünglich vom Pulsbreitecomparator 26 dem Pulsbreitespeicher 29 über 30 eingegeben worden war. Gleichzeitig wird der Flugzeitzähler 46 über den Ausgang 16 gestoppt und ein Meßwertzähler 47 über 16a dekrementiert. Ist die aktuelle Pulsbreite größer, wird der alte Wert mit dem neuen im Speicher 29 über 30 überschrieben und die Phase des Ladeimpulsgenerators 23 richtungsgleich zum letzten Meßvorgang um 6° gegenüber der Schwingerfrequenz verschoben. Ist die aktuelle Pulsbreite kleiner, so wird die Phase um +6°, und sind beide Werte gleich um -6° verschoben. Für diese Phasensprünge sind die Verbindungen 18, 19 zwischen Pulsbreitecomparator 26 und Frequenzteiler 22 gedacht.The phase control is repeated until drops with charges are detected by the charge detector 27 and these values are applied as a rectangular pulse via a charge amplifier 28, optionally with pulse processing, at the input of the pulse width comparator 26. The pulse width comparator 26 then compares the current pulse width of the signal with the last maximum pulse width from a pulse width memory 29, which was originally input to the pulse width memory 29 via 30 by the pulse width comparator 26. At the same time, the flight time counter 46 is stopped via the output 16 and a measured value counter 47 is decremented via 16a. If the current pulse width is larger, the old value is overwritten with the new one in the memory 29 via 30 and the phase of the charging pulse generator 23 is shifted in the same direction as the last measurement process by 6 ° with respect to the oscillator frequency. If the current pulse width is smaller, the phase is shifted by +6 ° and both values are shifted by -6 ° . The connections 18, 19 between pulse width comparator 26 and frequency divider 22 are intended for these phase jumps.

Durch diese Phasenregelung 20 wird eine optimale Synchronistation zwischen der Aufladung der Tropfen 7 mit einer bestimmten Ladung und deren Abriß bewirkt. Des weiteren werden die elektrischen Eigenschaften der Meßeinrichtung (Ladeelektrode 25, Ladungsdetektor 27 und -verstärker 28) durch das adaptive Verfahren der Pulsbreiteauswertung automatisch angepasst.This phase control 20 ensures an optimal synchronization between the charging of the drops 7 with a specific charge and their tearing off. Furthermore, the electrical properties of the measuring device (charging electrode 25, charge detector 27 and amplifier 28) are automatically adapted by the adaptive method of pulse width evaluation.

Die Phasenregelung 20 und Tropfenabrißregelung 40 sind unter anderem über den Pulsbreitecomparator 26 miteinander verknüpft. Dieser stoppt, wie oben ausgeführt, den Flugzeitzähler 46 und dekrementiert den Meßwertzähler 47 nur dann, wenn die maximale Pulsbreite von der Phasenregelung 20 detektiert wurde. Der Zählerstand am Ausgang des Flugzeitzählers 46 ist direkt proportional der Flugzeit der Tropfen 7 und zwar von ihrem Abriß 8 bis zu einem Ladungsdetektor 27, d.h. umgekehrt proportional der Tropfenabrißentfemung Sa zu der Düsenplatte 1. Der aktuelle Zählerstand wird dann zu einer Mittelwertbildung in einem Flugzeitaddierer 48 hinzuaddiert. Ist eine Anzahl der benötigten Meßwerte 56 erreicht, aktiviert ein Ausgang 33 des Meßwertzählers 47 einen Flugzeitcomparator 49, so daß der aktuelle Mittelwert der Tropfenflugzeit mit dem letzten Mittelwert aus einem Flugzeitspeicher 50 verglichen wird. Anschließend wird der letzte Mittelwert mit dem aktuellen Mittelwert im Flugzeitspeicher 50 über 34 überschrieben. Ist der aktuelle Mittelwert der Tropfenflugzeit größer als der letzte Mittelwert, d.h. die Tropfenabrißentfernung Sa bezogen auf die Düsenplatte 1 ist kleiner geworden, so wird der DAC-Zähler 41 über die Verbindung 35 inkrementiert und die Schwingerspannung um ca. 2 V erhöht. Dieser Regelvorgang wird solange wiederholt, bis der aktuelle Mittelwert der Tropfenflugzeit gleich oder kleiner als der letzte Mittelwert geworden ist und dadurch der Bereich der optimalen Tropfenentfernung erreicht wurde.The phase control 20 and drop break control 40 are interlinked via the pulse width comparator 26, among other things. As stated above, this stops the flight time counter 46 and decrements the measured value counter 47 only when the maximum pulse width has been detected by the phase control 20. The counter reading at the output of the flight time counter 46 is directly proportional to the flight time of the drops 7, namely from their demolition 8 to a charge detector 27, that is to say inversely proportional to the drop detachment distance S a to the nozzle plate 1. The current counter reading then becomes an average in a time-of-flight adder 48 added. When a number of the required measured values 56 has been reached, an output 33 of the measured value counter 47 activates a time-of-flight comparator 49, so that the current mean value of the drop flight time is compared with the last mean value from a time-of-flight memory 50. The last mean value is then overwritten with the current mean value in time-of-flight memory 50 through 34. If the current mean value of the drop flight time is greater than the last mean value, ie the drop tear-off distance Sa in relation to the nozzle plate 1 has become smaller, the DAC counter 41 is incremented via the connection 35 and the oscillating voltage is increased by approximately 2 V. This control process is repeated until the current mean value of the trop the flight time has become equal to or less than the last mean value and the range of optimal drop removal has been reached.

Ist dieser Zustand erreicht, so wird der DAC-Zähler 41 über die Verbindung 36 dekrementiert. Ein Flipflop 51, welches durch das Signal 10 "Startregelung" über 10b rückgesetzt wurde, wird wieder gesetzt, so daß ein DAC-Comparator 52 über 37 aktiviert und ein Ausgang 38 des DAC-Zählers 41 mit einem Ausgang 39 eines DAC-Referenzspeichers 53 für alle weiteren Regelvorgänge kontinuierlich verglichen wird.If this state is reached, the DAC counter 41 is decremented via the connection 36. A flip-flop 51, which was reset by the signal 10 "start control" via 10b, is set again, so that a DAC comparator 52 is activated via 37 and an output 38 of the DAC counter 41 with an output 39 of a DAC reference memory 53 for all other control processes are continuously compared.

Beim erstmaligen Einschalten (Inbetriebnahme) des Systems wird der Wert am Ausgang 38 des DAC-Zählers 41 mit dem Setzen des Flipflops 51 im DAC-Referenzspeicher 53 geladen, wie dies über Pfeil 12 angedeutet ist. Dieser Wert dient als Referenz der Schwingerspannung für optimale Tropfenabrißentfemung in Abhängigkeit des eingesetzten Schwingers 5 und der gültigen Betriebsviskosität der Tinte.When the system is switched on for the first time (commissioning), the value at the output 38 of the DAC counter 41 is loaded when the flip-flop 51 is set in the DAC reference memory 53, as indicated by arrow 12. This value serves as a reference of the vibrating voltage for optimal droplet detachment depending on the vibrator 5 used and the valid operating viscosity of the ink.

Zur Regelung der optimalen Tropfenabrißentfernung wird während der nächsten Regelvorgänge der DAC-Zähler 41 solange dekrementiert, solange sich die Tropfenabrißentfemung Sa rechts vom Wendepunkt Uw oder in dem Bereich 9 befindet (siehe Fig. 3), d.h. die aktuelle gemessene Tropfenflugzeit ist größer als die der letzten Meßung oder zumindest gleich.In order to control the optimal drop tear-off distance, the DAC counter 41 is decremented during the next control processes as long as the drop tear-off distance S a is to the right of the turning point U w or in the area 9 (see FIG. 3), ie the currently measured drop flight time is greater than that of the last measurement or at least the same.

Wird die aktuelle gemessene Tropfenflugzeit kleiner als die der letzten Meßung, so ist die Tropfenabrißentfemung Sa größer and liegt deshalb links vom Bereich des Wendepunktes Uw (siehe Fig. 3). Der DAC-Zähler 41 wird solange inkrementiert, bis sich die Tropfenabrißentfemung Sa wiederum rechts vom Bereich des Wendepunktes Uw befindet. Durch diese Regelung der Tropfenabrißentfernung können Tintendruckschwankungen in Hydrauliksystemen bereits allein schon ausgeglichen werden.If the currently measured droplet flight time becomes shorter than that of the last measurement, the droplet detachment distance S a is larger and is therefore to the left of the area of the inflection point Uw (see FIG. 3). The DAC counter 41 is incremented until the drop removal distance S a is again to the right of the area of the turning point Uw. This regulation of the tear-off removal can already compensate for ink pressure fluctuations in hydraulic systems alone.

Eine zunehmende Tintenviskosität erfordert eine stetige Erhöhung der Schwingerspannung U, um im Regelbereich der optimalen Tropfenabrißentfernung Sa zu bleiben (siehe Fig. 4). In Fig. 6 wird ein einfaches Verfahren und eine Anordnung zur Viskositätregelung 60' gezeigt. Der DAC-Comparator 52 vergleicht kontinuierlich den Ausgang 38 des DAC-Zählers 41 mit dem Wert des Ausgangs 39 aus dem DAC-Referenzspeicher 53. Dieser Referenzwert ist stellvertretend für die Schwingerspannung U, die zur Erreichung der Optimalen Tropfenabrißentfemung Sa erforderlich ist. Ist bei einer gültigen Betriebsviskosität der Wert am Ausgang 38 des DAC-Zählers 41 kleiner oder gleich demjenigen aus dem Referenzspeicher 53, so aktiviert der Ausgang 61 vom DAC-Comparator 52 ein Ventil 62 eines Tintentanks 63, so daß ein Haupttank 64 bis zu einer maximalen Füllstandshöhe mit Tinte nachgefüllt wird. Ist dagegen der Wert am Ausgang 38 des DAC-Zählers 41 größer als der Referenzwert, wird vom Ausgang 61 des DAC-Comparators 52 ein Lösungsmittelventil 65 eines Lösungsmittelstanks 66 aktiviert und der Haupttank 64 bis zur maximalen Füllstandshöhe mit Lösungsmittel nachgefüllt. Damit nimmt die Tintenviskosität im Haupttank 64 wieder ab.An increasing ink viscosity requires a constant increase in the oscillation voltage U in order to remain in the control range of the optimal drop tear-off distance Sa (see FIG. 4). 6 shows a simple method and an arrangement for viscosity control 60 '. The DAC comparator 52 continuously compares the output 38 of the DAC counter 41 with the value of the output 39 from the DAC reference memory 53. This reference value is representative of the oscillating voltage U, which is required to achieve the optimum drop-off removal distance S a . If the value at the output 38 of the DAC counter 41 is less than or equal to that from the reference memory 53, the output 61 from the DAC comparator 52 activates a valve 62 of an ink tank 63, so that a main tank 64 up to a maximum Level is refilled with ink. If, on the other hand, the value at the output 38 of the DAC counter 41 is greater than the reference value, the output 61 of the DAC comparator 52 activates a solvent valve 65 of a solvent tank 66 and the main tank 64 is refilled with solvent up to the maximum fill level. The ink viscosity in the main tank 64 thus decreases again.

Weiterhin ist im Haupttank 64 ein Füllstandswächter 67 angeordnet, dessen Signale an eine Füllstandsüberwachung 68 gegeben werden. Füllstandsüberwachung 68, Ventile 62 und 65 sowie Ausgang 61 von 52 sind durch entsprechende geeignete Schaltelemente, wie UND-Gatter 69 und Verstärker 70, miteinander verbunden.Furthermore, a level monitor 67 is arranged in the main tank 64, the signals of which are sent to a level monitor 68. Level monitoring 68, valves 62 and 65 and output 61 of 52 are connected to one another by corresponding suitable switching elements, such as AND gate 69 and amplifier 70.

Claims (19)

1. A method of controlling and improving the printing quality of a printer, in particular an ink jet printer, wherein at least one ink jet (6) is produced by means of the voltage and frequency applied to an oscillator (5) through at least one nozzle (2) of a perforated plate (1) and, after a certain distance from the perforated plate (1), charged droplets (7) are released from the ink jet (6), the droplet break-away distance (Sa) from the perforated plate (1) being optimally adjusted by regulation of the oscillator voltage, and the flight time of a droplet (7) from the droplet break-away point (8) to a charge detector (27) is measured, characterised in that the viscosity of the ink is regulated by observing the oscillator voltage and the droplet break-away distance (Sa).
2. A method according to claim 1, characterised in that, for regulating the optimum droplet break-away distance, the oscillator voltage values are continuously compared with reference values from a memory (53) which serve as a reference for the oscillator voltage for an optimum droplet break-away distance (Sa) as a function of the oscillator (5) used and a valid operating viscosity of the ink.
3. A method according to claim 1 or 2, characterised in that, if the charge detector (27) finds that the droplets (7) are not charged, the charging pulse frequency experiences a phase leap until a charge is detected by the charge detector (27).
4. A method according to claim 3, characterised in that the pulse width of the detected signal is compared with the pulse width of a stored signal.
5. A method according to claim 4, characterised in that, if the current pulse width deviates from the stored pulse width, the charging phases of the charging pulse are shifted relative to the oscillator frequency.
6. A method according to claim 5, characterised in that the new pulse width is stored as the current pulse width after the phase shift.
7. A device for controlling and improving the printing quality of a printer, in particular an ink jet printer, with an oscillator (5) for producing at least one ink jet (6) through at least one nozzle (2) of a perforated plate (1), wherein charging electrodes (25) are allocated to the ink jet (6) and, after a certain distance from the perforated plate (1), droplets (7) are released from the ink jet (6) and this droplet break-away distance (Sa) from the perforated plate (1) can be adjusted by regulating the oscillator voltage and a droplet break-away regulating means (40) which co-operates with a phase regulating means (20) is provided, characterised in that a viscosity regulating means (60) for the ink is connected to the droplet break-away regulating means (40).
8. A device according to claim 7, characterised in that a start signal (10) can excite a DAC counter (41) which is connected to a DAC initial value memory (42) and by means of which a certain sinusoidal voltage with a certain frequency, generated by a frequency divider (43), is applied to the oscillator (5) at the output of an amplifier (45).
9. A device according to claim 8, characterised in that switching elements for synchronising the charging voltage or a charging pulse can be connected via a second start signal (11) to the droplet break-away and consist of a pulse counter (21), a frequency divider (22) and a pulse width comparator (26) by means of which the charging pulse frequencies delivered from the frequency divider (22) via a charging pulse generator (23) to the charging electrode (25) can be phase shifted, the pulse width comparator (26) also being connected to the charge detector (27) and controlling the flight timer (46).
10. A device according to claim 9, characterised in that a pulse width memory (29) is allocated to the pulse width comparator (26) and contains altered values for comparing the current values of the pulse width comparator (26).
11. A device according to claim 9 or 10, characterised in that the frequency divider (22) is connected via a system clock (15) to the frequency divider (43) of the oscillator (5) and a flight timer (46).
12. A device according to claim 11, characterised in that the flight timer (46) is followed by a flight time comparator (49) which compares the flight time values with optionally variable values from a flight time memory (50) and controls the DAC counter (41).
13. A device according to claim 12, characterised in that the flight timer (46) is connected with a measured value counter (47) and optionally with a regulating arrangement (56) for a number of the measured values, a flight time adder (48) for forming a mean value being arranged between the flight timer (46) and flight time comparator (49).
14. A device according to claim 13, characterised in that the flight time comparator (49) is also connected via a flip flop (51) controlled by the start signal (10) to a DAC comparator (52) in which the values of the DAC counter (41) can be compared with values from a DAC reference memory (53).
15. A device according to claim 14, characterised in that this reference value is the oscillator voltage for an optimum droplet break-away distance (Sa) as a function of the oscillator (5) used and a valid operating viscosity of the ink.
16. A device according to one of claims 13 to 15, characterised in that the DAC comparator (52) is connected to the arrangement (60) for regulating the viscosity of the ink.
17. A device according to claim 16, characterised in that the arrangement (60) consists of a main tank (64) for the ink which is connected to an ink tank (63) and a solvent tank (66).
18. A device according to claim 17, characterised in that the filling in the main tank (64) is monitored.
19. A device according to claim 17 or 18, characterised in that valves (62, 65) for controlling the supply are arranged on the ink tank (63) and on the solvent tank (66).
EP86102874A 1985-03-05 1986-03-05 Operating method to improve the printing quality of a printer Expired - Lifetime EP0197300B1 (en)

Priority Applications (1)

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AT86102874T ATE53340T1 (en) 1985-03-05 1986-03-05 METHOD OF CONTROLLING AND IMPROVING THE PRINT QUALITY OF A PRINTER.

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DE3507670 1985-03-05
DE19853507670 DE3507670A1 (en) 1985-03-05 1985-03-05 METHOD FOR CONTROLLING AND IMPROVING THE WRITTEN QUALITY OF A PRINTER

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EP0197300B1 true EP0197300B1 (en) 1990-06-06

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WO2005087495A1 (en) * 2004-03-17 2005-09-22 Kodak Graphic Communications Canada Company Method and apparatus for controlling charging of droplets
US8807714B2 (en) 2009-06-24 2014-08-19 Hitachi Industrial Equipment Systems Co., Ltd. Ink-jet recording apparatus

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US3787882A (en) * 1972-09-25 1974-01-22 Ibm Servo control of ink jet pump
US4310846A (en) * 1978-12-28 1982-01-12 Ricoh Company, Ltd. Deflection compensated ink ejection printing apparatus
CA1156710A (en) * 1980-05-09 1983-11-08 Gary L. Fillmore Break-off uniformity maintenance
JPS597055A (en) * 1982-07-05 1984-01-14 Ricoh Co Ltd Ink jet recorder
DE3331587A1 (en) * 1982-09-01 1984-03-01 Ricoh Co., Ltd., Tokyo Ink jet printer with deflection control
US4496954A (en) * 1982-12-16 1985-01-29 International Business Machines Corporation Reservo interval determination in an ink jet system

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EP0197300A1 (en) 1986-10-15
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ATE53340T1 (en) 1990-06-15

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