JP2013000917A - Liquid droplet ejection apparatus, and inkjet recorder having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid droplet ejection apparatus which can eject liquid droplets at high speed with high precision by stabilizing the ejection characteristics of liquid droplets.SOLUTION: The liquid droplet ejection apparatus comprises a pressure chamber 32 communicating with a nozzle 25, a diaphragm 37 provided across each pressure chamber 32, a pressure generation element 28 which drives the diaphragm 37, a pressure generation element drive unit 46, a recording sheet conveyance means, and a liquid droplet ejection control unit 40 which transmits a drive waveform in synchronism with the conveyance of the recording sheet for the pressure generation element drive unit 46. The liquid droplet ejection control unit 40 is provided with an intermediate potential correction amount calculation means 41 for calculating a correction amount of the intermediate potential of the drive waveform, and the drive voltage to be applied to the pressure generation element 28 is corrected by the correction amount of intermediate potentia calculated by the intermediate potential correction amount calculation means 41.

Description

  The present invention relates to a droplet discharge device used in, for example, an ink jet recording apparatus, and more particularly to a droplet discharge device that stabilizes droplet discharge characteristics and can discharge droplets at high speed and with high precision.

  2. Description of the Related Art Inkjet recording apparatuses are known as image forming apparatuses such as printers, facsimiles, copiers, and complex machines of these. This ink jet recording apparatus ejects ink droplets from an ink jet recording head onto a recording medium such as paper or OHP to form a desired image.

  A line-scan type ink jet recording apparatus uses a long ink jet recording head extending in the width direction of a recording paper (recording medium), and the recording head discharges a large number of ink droplets along the width direction of the recording paper. Nozzle holes are arranged. An image is formed on the recording paper by continuously moving the recording paper with the nozzle holes of the recording head facing the recording paper surface and simultaneously ejecting ink droplets from the nozzle holes.

  In order to stabilize the image quality, the line scanning type ink jet recording apparatus normally performs printing in a state where the paper is transported at a stable speed from the time when the recording paper is accelerated until before the deceleration is started. . However, particularly when printing on continuous paper, the recording paper passing through the recording head during acceleration or (and) acceleration / deceleration of the recording paper (hereinafter collectively referred to as acceleration / deceleration) is not printed but wasted paper (waste paper). It becomes.

  In order to solve this problem, there has been proposed an ink jet recording apparatus capable of performing printing even during acceleration / deceleration. However, conventional technology determines the ejection timing of ink droplets according to the transport speed of the recording paper, but if the transport speed is slower than when transporting at a constant speed such as during acceleration / deceleration, No particular consideration was given to the fact that the drive frequency was lowered.

  For this reason, the meniscus state at the ejection timing varies, and ink droplet ejection fluctuations may occur, which may lead to unstable ink droplet ejection characteristics. It was declining.

  Therefore, an ink jet recording apparatus that stabilizes the ejection characteristics of ink droplets even when the ejection driving frequency is not constant has already been proposed in Japanese Patent Application Laid-Open No. 2010-274637 (Patent Document 1).

  In this proposal, when the recording medium is being transported at a constant speed, the driving timing period calculated from the resolution and scanning speed of the ink jet recording apparatus is used as the specified speed, and n (n is an integer of 1 or more) is driven. It is characterized in that an additional timing is set a specified time before the (n + 1) th driving timing following the timing, and the pressure chamber is finely driven at the additional timing.

  In the above proposal, when the interval between the ejection of ink droplets is longer than the specified time, a new driving timing is provided between them. Therefore, it is necessary to make the drive cycle sufficiently longer than the cycle of the drive waveform, and the drive cycle cannot be shortened. Therefore, there is a problem that it is difficult to increase the printing speed and resolution.

  An object of the present invention is to provide a droplet discharge device capable of stabilizing droplet discharge characteristics and discharging droplets at high speed and with high precision, and an ink jet recording apparatus including the droplet discharge device.

In order to achieve the above object, the present invention provides:
A number of pressure chambers for storing liquid to be discharged in communication with a number of nozzles;
A diaphragm disposed over each pressure chamber to form an elastic wall of each pressure chamber;
A pressure generating element, such as a piezo element, disposed so as to face the pressure chamber via the diaphragm;
A pressure generating element driving section for driving the pressure generating element;
An adherend transporting means for transporting an adherend such as recording paper to the nozzle;
The present invention is intended for a droplet discharge device including a droplet discharge control unit that transmits a drive waveform to the pressure generating element driving unit in synchronization with the transfer of the adherend by the adherend transfer unit. is there.

  The droplet discharge controller is provided with an intermediate potential correction amount calculating means for calculating an intermediate potential correction amount of the drive waveform, and the pressure generation is performed with the intermediate potential correction amount calculated by the intermediate potential correction amount calculating means. The drive voltage applied to the element is corrected.

  The present invention is configured as described above, and provides a droplet discharge device capable of stabilizing droplet discharge characteristics and discharging droplets at high speed and with high precision, and an ink jet recording apparatus including the droplet discharge device. it can.

1 is a schematic configuration diagram illustrating an overall configuration of a line scanning ink jet recording apparatus according to an embodiment of the present invention. It is a top view which shows arrangement | positioning of the head module of the inkjet recording device. It is an enlarged bottom view of the head module. It is an expanded sectional view of the head module. It is a figure for demonstrating the change of the conveyance speed of the recording paper in an inkjet recording device. It is a figure for demonstrating the ink droplet discharge control at the time of the acceleration of the conventional inkjet recording device. It is a figure for demonstrating the ink droplet discharge control at the time of acceleration in the inkjet recording device which concerns on a present Example. It is an enlarged view for demonstrating the voltage correction of the drive waveform to a pressure generating element (piezo element) in the Example of this invention. It is a block diagram of an ink droplet ejection control unit according to an embodiment of the present invention. 4 is a flowchart for explaining an ink droplet ejection control method according to an embodiment of the present invention.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing the overall configuration of a line scanning ink jet recording apparatus according to an embodiment of the present invention.

  The ink jet recording apparatus includes an unwinding device 3 that supplies the recording paper 1 wound in a roll shape to the printing device 2, and a winding device 4 that winds up the printing paper 1 printed by the printing device 2. The printing apparatus 2 is configured to print the recording paper 1 made of continuous paper connected in a strip shape from the unwinding device 3 to the winding device 4.

The printing apparatus 2 drives three roller pairs of an infeed roller 5, a heat roller 6, and an outfeed roller 7 to convey the recording paper 1 in a predetermined direction.
The recording paper 1 supplied from the unwinding device 3 is first conveyed by the infeed roller 5. The infeed roller 5 includes a driving roller 5a and a driven roller 5b. The recording paper 1 is sandwiched between the rollers 5a and 5b, and an infeed motor 8 that drives the driving roller 5a is rotated to rotate the recording paper 1. Is conveyed in the downstream direction (arrow direction). Reference numeral 9 in the figure denotes a drive control unit for the infeed motor 8, and reference numeral 10 denotes a pulse encoder that detects the rotational speed of the infeed motor 8.

The infeed tension detector 11 is disposed between the infeed roller 5 and the heat roller 6 on the conveyance path of the recording paper 1 and measures the tension of the recording paper 1 during this time. For example, the infeed tension detector 11 is configured to measure the pressure received by the roller due to the tension of the recording paper 1 using a pressure sensor such as a strain gauge. The in-feed tension detector 11 is connected to the control unit 12, converts the pressure (tension) of the recording paper 1 into an electrical signal and outputs it to the control unit 12.
The recording head 13 prints on the recording paper 1 by an ink jet method, and forms an image on the recording paper 1 by ejecting ink droplets based on print data from the host device 14.

  The heat roller 6 is for drying ink discharged on the recording paper 1 by heating. The heat roller 6 has a driving roller 6a and a driven roller 6b, and the recording paper 1 is formed by both rollers 6a and 6b. The recording paper 1 is conveyed in the downstream direction by rotating the heat roller motor 15 that drives the driving roller 6a. Reference numeral 16 in the figure denotes a drive control unit for the heat roller motor 15, and reference numeral 17 denotes a pulse encoder that detects the rotational speed of the heat roller motor 15.

  The outfeed tension detector 18 is disposed between the heat roller 6 and the outfeed roller 7 on the conveyance path of the recording paper 1 and measures the tension of the recording paper 1 during this time. The outfeed tension detector 18 is configured to measure the pressure received by the roller due to the tension of the recording paper 1 by a pressure sensor such as a strain gauge. The outfeed tension detector 18 is connected to the control unit 12, converts the pressure (tension) of the recording paper 1 into an electrical signal, and outputs it to the control unit 12.

  The outfeed roller 7 has a driving roller 7a and a driven roller 7b. The recording paper 1 is sandwiched between the rollers 7a and 5b, and the outfeed motor 19 for driving the driving roller 7a is rotated to rotate the recording paper 1. Is discharged to the winding device 4. Reference numeral 20 in the figure denotes a drive control unit for the outfeed motor 19, and reference numeral 21 denotes a pulse encoder that detects the rotational speed of the outfeed motor 19.

FIG. 2 is a plan view showing an example of the arrangement of head modules in the recording head 13.
In the recording head 13 according to the present embodiment, ten head modules 22 are used for one color, and 40 head modules 22 are mounted to print a full color image. As shown in the figure, a head module group 23 is configured by arranging ten head modules 22 in a staggered manner in the width direction of the recording paper 1.

  The head module group 23K ejects black ink droplets, the head module group 23C ejects cyan ink droplets, the head module group 23M ejects magenta ink droplets, and the head module group 23Y ejects yellow ink droplets. To do.

FIG. 3 is an enlarged bottom view of the head module 22.
As shown in this figure, a large number of nozzles 25 are formed in a row along the longitudinal direction of the head module 22 on the ink droplet discharge surface 24 corresponding to the bottom surface of the head module 22. In this embodiment, the number of nozzle rows is one, but a plurality of nozzle rows may be provided.

  The ink droplet ejection surface 24 of each head module 22 is arranged to face the recording paper 1 with a minute gap, and as shown in FIG. 2, ten head modules 22 of each color are arranged in a staggered manner. Thus, a recordable area is secured over the entire width of the recording paper 1.

FIG. 4 is an enlarged cross-sectional view of the head module 22.
The head module 22 mainly includes a flow path substrate 26, a high-rigidity plate 27, and a pressure generating element (piezo element) 28.

  The flow path substrate 26 also serves as the nozzle plate 29 in which a large number of nozzles 25 are formed as described above, the chamber plate 31 having the communication flow path 30 communicating with each nozzle 25, the pressure chamber 32, and the restrictor 33. It is composed of a laminate of a restrictor plate 35 having an opening hole 34 and a thin diaphragm plate 36 for sealing the pressure chamber 32 and the restrictor 33. The diaphragm plate 36 has a diaphragm 37. The diaphragm 37 is disposed over each pressure chamber 32 so as to form an elastic wall of each pressure chamber 32.

  The high-rigidity plate 27 holds the flow path substrate 26 and forms a common ink chamber 38 for introducing and storing ink from outside, and the flow path substrate 26 side of the common ink chamber 38 is for supplying ink. It is open. An ink groove 39 is formed next to the common ink chamber 38, and the pressure generating element (piezo element) 28 is inserted into the ink groove 39 so that the pressure generating element 28 faces the pressure chamber 32 through the vibration plate 37. Has been placed.

  FIG. 5 is a diagram for explaining a change in the conveyance speed of the recording paper. In the figure, the horizontal axis indicates the time from the start of conveyance of the recording paper, and the vertical axis indicates the conveyance speed of the recording paper.

  As shown in this figure, during a period (acceleration region: time 0 to time t1) in which the recording sheet gradually accelerates from the start of conveyance of the recording sheet until it reaches the constant speed Vcs, the recording sheet gradually decelerates from the constant speed Vcs. During the period until the recording paper stops (deceleration region: time t2 to time t3), the paper conveyance speed is slower than the constant speed Vcs.

  That is, the period during which the recording paper moves by one pixel during acceleration and deceleration is different from the period during which the recording paper moves by one pixel in the constant speed region (time t1 to time t2) at a constant transport speed Vcs. The ink droplet ejection timing with respect to the target landing position of the recording paper is different during acceleration / deceleration and constant speed conveyance.

  FIG. 6 is a diagram for explaining ink droplet ejection control in a conventional inkjet recording apparatus.

  This figure shows changes and timings of the sheet conveyance speed a, drive timing b, drive waveform c, and resonance waveform d. The resonance waveform d is a resonance waveform between the meniscus vibration period and the pressure generation element (piezo element) vibration period.

  In an on-demand line scanning ink jet recording apparatus, when printing is performed while the recording paper is being accelerated or decelerated, the time interval of the driving timing b during acceleration or deceleration of the recording paper is the driving timing b at the constant speed Vcs. Long compared to the time interval. If this time interval does not match well with the meniscus state such as meniscus vibration, problems such as ink droplet non-ejection, variation in ink droplet amount, variation in ink droplet ejection speed may occur.

  As shown in FIG. 6, when printing is performed during acceleration, the drive timing b is determined regardless of the state of the meniscus. Therefore, the ink droplet cannot be ejected in a meniscus state that is optimal for ink droplet ejection. Problems such as non-ejection, fluctuations in ink droplet amount, fluctuations in ink droplet ejection speed occur. This problem occurs similarly during deceleration of the recording paper.

FIG. 7 is a diagram for explaining ink droplet ejection control during acceleration in the ink jet recording apparatus according to the present embodiment.
FIG. 7 also shows changes and timings of the sheet conveyance speed a, the drive timing b, the drive waveform c, and the resonance waveform d, as in FIG.

  When the time interval of the drive timing b becomes longer than that at the constant speed Vcs, such as during acceleration or deceleration of the recording paper, the resonance frequency is changed by appropriately correcting the intermediate potential of the drive waveform c, and the next ink It can be expected that the meniscus state at the droplet discharge timing is matched with a state where normal ink droplet discharge can be performed.

  The intermediate potential of the drive waveform c is a voltage applied to the piezoelectric element when not driven, and corresponds to a flat portion of the drive waveform c. If the driving interval is short and the driving is performed so that the voltage is reduced to 0V, the voltage change must be made abrupt, that is, the rising of the driving waveform must be made abrupt, and ink droplets may be accidentally ejected. Inconvenience occurs. For this reason, a voltage is applied to the piezoelectric element in advance at an intermediate potential to reduce voltage change during driving.

  For example, the lowest potential can be set to 3V, the intermediate potential can be set to 12V, and the driving potential can be set to 25V.

  The ink droplet ejection control during acceleration will be described with reference to FIG. For example, the voltage applied to the pressure generating element (piezo element) after the first ink droplet ejection is made lower than the voltage at the constant speed Vcs. Similarly, the voltage applied to the pressure generating element (piezo element) is adjusted in accordance with the time interval between the next discharges. As the paper transport speed increases, the ink droplet ejection time interval becomes shorter, and if the ejection speed becomes constant at a constant speed Vcs, correction (adjustment) of the applied voltage becomes unnecessary.

  Note that it is only necessary that the ejection cycle and the resonance frequency coincide with each other in an optimal manner with respect to ink droplet ejection. Therefore, it is not necessary to correct the applied voltage so that the resonance frequency becomes smaller when the time interval becomes longer. Good.

  In the example of FIG. 7, in order to clarify the present invention, description is made using only a single waveform. However, in the figure, a driving waveform capable of ejecting at least three types of ink droplets of large, medium, and small, or more is used, and in practice the size of the ink droplet can be distinguished. ing.

  FIG. 8 is an enlarged view for explaining voltage correction of the drive waveform c to the pressure generating element (piezo element) in the embodiment of the present invention. FIG. 8 shows the second to fourth ejection drive waveforms c of FIG. 7, that is, the ejection drive waveforms c that move from the acceleration region to the constant speed region.

  As shown in this figure, since the second and third drive intervals ΔT ′ of the ejection drive waveform c are longer than the third and fourth drive intervals ΔT, the intermediate potential of the ejection drive waveform c is corrected, The voltage of the second driving waveform is lowered from Vc to Vc ′. The correction is continued from point x to point y in FIG. 8 so that the potential difference in the drive waveform does not change. As a result, the resonance frequency can be varied to make the meniscus state constant at the ink droplet ejection timing, which makes it possible to stably eject ink droplets.

FIG. 9 is a block diagram of the ink droplet ejection control unit according to the embodiment of the present invention.
As shown in this figure, the ink droplet ejection control unit 40 includes a sheet conveyance synchronization control unit 42 including an intermediate potential correction amount calculation unit 41, a drive waveform generation unit 43, a drive waveform selection signal generation unit 44, and a drive waveform. The selection part 45 is comprised, and each part has the connection relation as shown in a figure. The ink droplet ejection control unit 40 is provided in the control unit 12 and connected to the recording head 13 as shown in FIG.

  As shown in this figure, a sheet conveyance profile g, a sheet conveyance synchronization signal h, and image data i are input to the sheet conveyance synchronization control unit 42, respectively. The sheet conveyance profile g is specifically a table of sheet conveyance speed data corresponding to FIG. The sheet conveying device (infeed roller 5, heat roller 6, outfeed roller 7, etc.) shown in FIG. 1 is rotationally driven so as to follow this sheet conveying profile g.

  The paper transport synchronization control unit 42 generates a head drive signal j synchronized with the paper transport based on the input paper transport synchronization signal h, and transmits it to the drive waveform generation unit 43. Further, the paper conveyance synchronization control unit 42 transmits the input image data i and the head drive signal j to the drive waveform selection signal generation unit 44.

  As described above, the intermediate potential correction amount calculation unit 41 is provided in the paper transport synchronization control unit 42. The intermediate potential correction amount calculation unit 41 predicts the driving timing of the pressure generating element (piezo element) from the paper transport profile g and the paper transport synchronization signal h, and calculates and determines the correction amount k of the intermediate potential. When the driving cycle of the pressure generating element (piezo element) is shortened, the correction amount k is set such that the intermediate voltage is increased so as to shorten the resonance frequency. The correction amount k determined in this way is transmitted to the drive waveform generator 43.

  The drive waveform generation unit 43 generates a drive waveform e based on the input head drive signal j and the intermediate potential correction amount k, and transmits the drive waveform e to the drive waveform selection unit 45. As a circuit for realizing the drive waveform, for example, a D / A converter is used, and the intermediate potential can be set to an arbitrary intermediate potential by setting digital data.

  The drive waveform selection signal generation unit 44 generates a drive waveform selection signal f based on the input head drive signal j and image data i, and transmits it to the drive waveform selection unit 45.

  The drive waveform selection unit 45 generates a drive waveform c from the drive waveform e and the drive waveform selection signal f, transmits it to the piezoelectric element drive unit 46, drives the pressure generating element (piezo element) 28, and the nozzle 25. (Both see FIG. 4), ink droplets are ejected at a predetermined timing.

FIG. 10 is a flowchart for explaining the ink droplet ejection control method according to the embodiment of the present invention.
S1: Predict the next and next drive timing (for example, the second and third ink droplet ejection timings shown in FIG. 8) based on the input sheet conveyance profile g.

  The correction amount determined at a certain prediction timing can be reflected from the next drive timing (here, n-th time) and the intermediate potential between the (n + 1) th time, and the nth and n + 1th intermediate potentials are Since the calculation is based on the n-th and (n + 1) -th driving intervals, it is necessary to predict the driving timing up to the next two times.

  S2: The time interval between the next and the next drive timing is calculated from the predicted drive timing, and the correction amount of the drive voltage applied to the pressure generating element (piezo element) so as to obtain the optimum resonance frequency for the time interval ( Bias value) is calculated and determined.

  S3: At the driving timing described above, the pressure generating element (piezo element) is driven to eject ink droplets from the nozzles.

  S4: Based on the correction amount (bias value) of the driving voltage determined in S2, the driving voltage applied to the pressure generating element (piezo element) is corrected to drive the pressure generating element (piezo element) and Ink droplets are ejected.

  S5: It is determined whether or not printing is completed. If printing is in progress, the process returns to S1, and the operations of S1 to S5 are repeated until printing is completed.

  When correcting the intermediate potential of the drive waveform in this embodiment, the optimum intermediate potential is measured in advance for each drive frequency, and the value is tabulated as a correction value, and the drive timing of S1 described with reference to FIG. If the correction value is obtained from the table and voltage correction (S4) is performed in accordance with the prediction, the intermediate potential can be corrected easily and appropriately.

  In the above-described embodiment, an example of an ink droplet ejection device (inkjet recording device) has been described as the droplet ejection device. However, the present invention is not limited to this, and other examples such as a three-dimensional modeling device to which an inkjet method is applied. The present invention can also be applied to a droplet discharge device.

  DESCRIPTION OF SYMBOLS 1 ... Printing paper, 2 ... Printing apparatus, 12 ... Control part, 13 ... Inkjet recording head, 22 ... Head module, 23 ... Head module group, 25 ... Nozzle 28 ... Pressure generating element, 32 ... Pressure chamber, 37 ... Diaphragm, 40 ... Ink droplet ejection control unit, 41 ... Intermediate potential correction amount calculation unit, 42 ... Paper transport Synchronous control unit, 43... Drive waveform generation unit, 44... Drive waveform selection signal generation unit, 45... Drive waveform selection unit, 46. Speed, b: Pressure generating element driving timing, c: Pressure generating element driving waveform, d: Resonant waveform, g: Paper transport profile, h: Paper transport synchronization signal, i · ..Image data, j ... head drive signal, k ... intermediate voltage compensation Amount.

JP 2010-274637 A

Claims (4)

A number of pressure chambers for storing liquid to be discharged in communication with a number of nozzles;
A diaphragm disposed over each pressure chamber to form an elastic wall of each pressure chamber;
A pressure generating element disposed to face the pressure chamber via the diaphragm;
A pressure generating element driving section for driving the pressure generating element;
An adherend transporting means for transporting the adherend to the nozzle;
In the droplet discharge device provided with a droplet discharge control unit that transmits a drive waveform in synchronization with the transfer of the adherend by the adherend transfer means with respect to the pressure generating element drive unit,
The droplet discharge controller is provided with an intermediate potential correction amount calculating means for calculating an intermediate potential correction amount of the drive waveform, and the pressure generating element is applied with the intermediate potential correction amount calculated by the intermediate potential correction amount calculating means. A droplet discharge device characterized by correcting a drive voltage to be applied. The droplet discharge device according to claim 1,
The droplet discharge device is configured to land droplets on the adherend during acceleration or (and) deceleration of the adherend,
The drive voltage is corrected based on the intermediate potential correction amount calculation means during acceleration or (and / or) deceleration of the landing body, and driven based on the intermediate potential correction amount calculation means during constant speed conveyance of the landing body. A droplet discharge apparatus characterized by not correcting a voltage. The ink droplet ejection device according to claim 2,
A driving voltage applied to the pressure generating element during acceleration or (and) deceleration of the landing body is lower than a driving voltage applied to the pressure generating element during constant speed conveyance of the landing body. The liquid droplet ejection apparatus, wherein the drive voltage is corrected based on the intermediate potential correction amount calculation means.   An ink jet recording apparatus comprising the liquid droplet ejection apparatus according to claim 1.

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