JP4763331B2 - Waveform generation method of inkjet head drive signal and inkjet recording apparatus - Google Patents

Description

The present invention relates to a method for creating a waveform of a drive signal for an inkjet head that varies the volume of a pressure chamber in accordance with the drive signal.

  2. Description of the Related Art Piezoelectric ink jet heads that discharge ink by changing the volume of a pressure chamber filled with ink by deformation of a piezoelectric actuator are widely used in ink jet recording apparatuses. As an example of such a piezoelectric inkjet head, there is a shear mode type disclosed in Patent Document 1. In order to discharge desired ink from the piezoelectric ink jet head, a drive signal having a waveform suitable for the ink jet head is applied to the piezoelectric actuator. Various attempts have been proposed for causing desired ink ejection by a drive signal and further controlling vibration of ink after ink ejection. The main purpose of the proposed drive signal is to enable gradation printing that varies the ink ejection volume while obtaining the required ink ejection speed, or to suppress residual pressure oscillations associated with ink ejection. is there. Furthermore, the purpose is to suppress the natural vibration of the actuator and the crosstalk. However, the waveform of the conventional drive signal is a combination of relatively simple waveform elements such as a rectangular wave, a linear waveform having a gradient, and a sine wave. A drive signal based on such a combination of simple waveform elements cannot sufficiently satisfy the above-described purpose.

In Patent Document 2, the frequency characteristic of the response displacement of the wall surface of the pressure chamber (liquid chamber) with respect to the drive signal is measured, and a predetermined response displacement waveform is generated on the wall surface of the pressure chamber (liquid chamber) based on the measured frequency characteristic. There is shown a driving method in which a drive signal having a waveform as obtained can be generated, and an actuator (pressurizing means) is driven using the drive signal to stably perform clean printing. This method can be regarded as a driving method for the purpose of suppressing the natural vibration of the actuator.
JP-A-63-252750 JP-A-9-267474

  The method for obtaining the drive signal based on the response characteristics of the wall surface of the pressure chamber to the drive signal described in Patent Document 2 has the following problems.

  First, since it is difficult to measure the response characteristic of the wall of the pressure chamber in a state where ink is filled, the response characteristic of the wall of the pressure chamber must be measured in a state where ink is not filled. Therefore, changes in the frequency characteristics of the actuator due to the interaction between the ink and the actuator in the pressure chamber are ignored, and there is a possibility that the natural vibration of the actuator cannot be sufficiently suppressed when the ink jet head actually ejects ink.

  Next, since the fluid response characteristics of the ink in the pressure chamber and the nozzle are not taken into account, there are effects such as suppression of residual pressure vibration, control of meniscus position in gradation printing, and suppression of crosstalk via ink. Absent.

  Furthermore, when this method is applied to a shear mode type ink jet head, it is difficult to measure the response characteristics of the wall surface of the pressure chamber unless the ink jet head is destroyed. Therefore, it is difficult to set drive signals for individual ink jet heads according to variations in the manufacture of ink jet heads.

  Therefore, the method for obtaining the drive signal described in Patent Document 2 has these technical problems, and as a result, the ink droplet ejection volume cannot be changed sufficiently in gradation printing, and sufficient print quality is obtained. It is not obtained or the speed and volume of the ink droplets ejected from the ink jet head vary, and the print quality is impaired.

  The present invention solves the above-described problems in addition to the suppression of the natural vibration of the actuator.

The present invention includes a nozzle that ejects ink, a pressure chamber that communicates with the nozzle, an ink supply unit that supplies ink to the pressure chamber, and an actuator that varies the volume of the pressure chamber according to a drive signal. In the method of creating the waveform of the drive signal of the inkjet head that discharges ink from the nozzle according to the measurement, the response characteristic of the meniscus flow velocity in the nozzle with respect to the drive signal of the inkjet head is measured, the meniscus flow velocity vibration is U, When the Fourier transform result is FU and the response characteristic of the meniscus flow velocity in the nozzle with respect to the drive signal of the inkjet head is R, the waveform is obtained by performing inverse Fourier transform on FV with FV = R ⁻¹ FU . .

  As described above, the present invention calculates the drive signal using the response characteristic of the ink meniscus vibration in the nozzle with respect to the drive signal, so that not only the response of the actuator to the drive signal but also the ink in the nozzle from the vibration of the actuator. It is characterized in that a drive signal is obtained in consideration of fluid response characteristics leading to meniscus vibration.

  According to the present invention, a virtual meniscus vibration that changes an ink discharge volume while obtaining a necessary ink discharge speed is defined in advance, and a drive signal that can obtain the meniscus vibration is calculated based on a response characteristic of the meniscus vibration to the drive signal. Seeking by Therefore, by driving the inkjet head with the drive signal obtained in this way, the ejection volume of ink droplets can be sufficiently changed in gradation printing, and sufficient print quality can be obtained.

  Further, according to the present invention, in addition to the above, a virtual meniscus vibration that does not have residual pressure vibration, crosstalk, or actuator natural vibration is defined in advance, and the drive signal from which the meniscus vibration is obtained is expressed as a response characteristic of the meniscus vibration to the drive signal. Based on the calculation. Therefore, by driving the ink jet head with the drive signal obtained in this way, residual pressure vibration, crosstalk, and actuator natural vibration can be suppressed as a result, and the speed of ink droplets ejected from the ink jet head can be reduced. The problem that the volume varies and the print quality is impaired can be solved.

  Furthermore, since the present invention can be easily implemented by observing the vibration of the ink meniscus in the nozzle, it is easy to set the drive signal according to individual characteristic variations even when the inkjet head is mass-produced. . Therefore, it is possible to solve the problem that the printing quality is impaired due to manufacturing variations.

  A first embodiment of the present invention will be described with reference to the drawings. The same numbered components in the drawings indicate the same components in other drawings unless otherwise specified.

  The structure of the inkjet head will be described. 1 and 2 are cross-sectional views showing the configuration of a shear mode type inkjet head 101 in which an actuator is shared between adjacent pressure chambers. The inkjet head 101 includes a low dielectric constant substrate 1, piezoelectric members 2 and 3, a top plate frame 4, a top plate lid 5, a nozzle plate 11, and a cable 16 connected to a drive circuit.

  Piezoelectric members 2 and 3 are embedded in the tip portion of the low dielectric constant substrate 1 so that the polarization directions are opposite to each other inward with respect to the plate thickness direction. In the piezoelectric members 2 and 3 and the portion of the substrate 1 behind the piezoelectric members 2, a plurality of long grooves 6 are formed in parallel to each other at a constant interval by cutting using a diamond cutter. An ink supply path 14 is formed by adhering the top plate frame 4 and the top plate cover 5 having the ink supply port 15 to the upper part of the substrate 1. A plurality of pressure chambers 7 are formed by the long grooves 6 and the top frame 4. Each piezoelectric member 2 and 3 is an actuator 13 (13a to 13k) that deforms the pressure chamber 7 by applying a voltage. A nozzle plate 11 on which nozzles 10 for ejecting ink droplets are formed at the tips of the piezoelectric members 2 and 3 is fixed with an adhesive. The nozzle 10 is located at the tip of each pressure chamber 7 and is formed with an inner diameter of a predetermined size. Electrodes 8 that are electrically independent of the other long grooves 6 are formed by electroless plating on the side and bottom surfaces of the respective long grooves 6 forming the pressure chamber 7. The electrode 8 extends from the rear end of the pressure chamber 7 to the upper surface of the substrate 1 and is connected to a drive circuit described later. In addition to the electroless plating, the electrode 8 may be formed in a predetermined pattern by etching after forming an electrode material by sputtering or vacuum deposition.

  The operation of the inkjet head will be described by taking as an example the case where ink is ejected from the pressure chamber 7c of FIG. The electrodes corresponding to the pressure chambers 7a to 7j are 8a to 8j, and the nozzles are nozzles 10a to 10j, respectively. The ink 12 supplied into the inkjet head from the ink supply port 15 is filled into the pressure chamber 7 through the ink supply path 14. When a potential difference is generated between the electrode 8c and the electrode 8b and between the electrode 8c and the electrode 8d by a driving signal, which will be described later, the actuators 13c and 13d are shear-deformed to change the volume in the pressure chamber 7c, and the ink is discharged from the nozzle 10c. Discharge.

  Since the actuator 13 is shared between the pressure chambers 7 adjacent to the left and right, the ink jet head cannot eject ink independently from the two pressure chambers 7 adjacent to each other. The inkjet head is time-division driven to discharge ink so that the pressure chambers 7 adjacent to each other are not driven simultaneously.

  Further, when the ink in the pressure chamber 7c is ejected, a potential difference is also generated between the electrodes 8a and 8b, so that the actuator 13b moves toward the pressure chamber 7a so that the pressure vibration generated in the pressure chamber 7b is dispersed in the pressure chamber 7a. It is deformed to. At the same time as the deformation of the actuator 13b, a potential difference is generated between the electrodes 8d and 8e, and the actuator 13e is deformed in the direction of the pressure chamber 7e so that the pressure vibration generated in the pressure chamber 7d is dispersed in the pressure chamber 7e. FIG. 2 shows a modified example of each of the actuators divided into five parts. As described above, when ink is ejected from a certain pressure chamber, the amplitude of the meniscus vibration in the non-ejection nozzle can be reduced by dispersing the pressure vibration generated in the adjacent pressure chamber to the other pressure chambers. . When the meniscus vibration in the non-ejection nozzle is reduced, the phenomenon of the meniscus rising from the nozzle surface is also reduced, and the variation in meniscus position is reduced when ink is ejected from the nozzle next time. By stabilizing the meniscus position, variations in ink droplet ejection speed and ejection volume are suppressed, and printing quality is improved.

  A block diagram of the drive circuit of the inkjet head will be described with reference to FIG. The drive circuit includes a drive waveform memory 21, a D / A converter 22, an amplifier 23, drive signal selection means 24, an image memory 25, and a decoder 26.

  The drive waveform memory 21 stores waveform information for generating a drive signal ACT applied to a pressure chamber that ejects ink and a drive signal INA applied to a pressure chamber that does not eject ink. The waveform information of these drive signals ACT and INA is converted into analog signals by the D / A converter 22 respectively. Further, these analog signals are amplified by the amplifier 23 and then input to the drive signal selection means 24.

  Based on the gradation information of each pixel of the image recorded in the image memory 25, the decoder 26 generates an ON / OFF signal 27 for controlling ejection / non-ejection of ink droplets. The ink jet head can selectively eject or not eject three types of ink droplets, each having a discharge volume of 6 pl, 12 pl, and 24 pl, per pixel. By combining the ink droplet volume in accordance with the gradation data, it is possible to perform gradation recording of up to eight values as shown in FIG.

  FIG. 5 shows a circuit diagram of the drive signal selection means 24. The decoder 26 has the number of ON / OFF signal outputs corresponding to the number of pressure chambers. 5 shows the ON / OFF signals 27a to 27j and the analog switches 30a to 30j corresponding to the electrodes of some of the heads shown in FIG. An ON / OFF signal 27 and an analog switch 30 are provided corresponding to the electrode 8. The drive signal selection means 24 includes analog switches 30a to 30j. When the ON / OFF signal outputs 27a to 27j are ON, the drive signal ACT is selected. When the ON / OFF signal outputs 27a to 27j are OFF, the drive signal INA is selected and the electrodes 8a to 8a are selected. Distribute to 8j. The drive signals ACT1 to ACT5 correspond to the first to fifth cycles in the time division drive, respectively.

  An example will be described in which ink is ejected from the pressure chamber 7c and ink is not ejected from the pressure chamber 7h at the same operation timing. The ON / OFF signal 27c corresponding to the pressure chamber 7c and two ON / OFF signals 27a, 27b, 27d, and 27e on both sides thereof are turned ON. At this time, the ON / OFF signal 27h corresponding to the pressure chamber 7h and the two ON / OFF signals 27f, 27g, 27i, and 27j on both sides thereof are turned OFF. By applying these ON / OFF signals, a pressure chamber 7c that discharges ink and two pressure chambers 7a, 7b, 7d, and 7e on both sides of the pressure chamber 7 are supplied with drive signals based on the ACT signal and do not discharge ink. A drive signal based on the INA signal is supplied to 7h and two pressure chambers 7f, 7g, 7i, and 7j on both sides thereof.

  The drive signals ACT1 to ACT5 and INA supplied to the drive signal selection unit will be described. FIG. 6 shows one printing cycle of the ink discharge drive signals ACT1 to ACT5 and the non-ink discharge drive signal INA. The drive signals ACT1 to ACT5 are composed of three types of drive signals W1, W2, and W3, and INA is composed of a drive signal of W4. The phases of the drive signals ACT1 to ACT5 are different from each other by the time-divided time. For example, when ink is ejected from the pressure chamber 7c, by turning ON the ON / OFF signals 27a to 27e in the third cycle, the drive signal of W3 is supplied to the pressure chambers 7a and 7e, and W2 is supplied to the pressure chambers 7b and 7d. Drive signal W1 is supplied to the pressure chamber 7c.

  The drive signals W1 to W4 will be described with reference to FIG. Each of W1 to W4 is W1a, W2a, W3a, W4a in a period for discharging a first drop with a volume of 6 pl, and W1b, W2b, W3b, W4b in a period for discharging a second drop with a volume of 12 pl , W1c, W2c, W3c, and W4c in a period for discharging the third drop having a volume of 24 pl.

  For example, when the first drop is discharged from the pressure chamber 7c and the first drop is not discharged from the pressure chamber 7h, the ON / OFF signals 27a to 27e are turned ON during the first drop period of the third cycle, and the ON / OFF The signals 27f to 27j are turned off. By the ON / OFF signal, the drive signal W1a is applied to the electrode 8c, the drive signal W2a is applied to the electrodes 8b and 8d, the drive signal W3a is applied to the electrodes 8a and 8e, and the electrodes 8f to 8f are applied. A drive signal W4a is applied to 8j. As a result, the actuators 13c and 13d are greatly deformed by the potential difference between the drive signals W1a and W2a, and a 6 pl ink droplet is ejected from the pressure chamber 7c. The actuator 13b is deformed in a direction in which the pressure vibration generated in the pressure chamber 7b is dispersed in the pressure chamber 7a due to the potential difference between the drive signals W2a and W3a. Similarly, the actuator 13e is deformed in a direction in which the pressure vibration generated in the pressure chamber 7d is dispersed in the pressure chamber 7e. The deformation of the actuator 13e increases the pressure of the ink in the pressure chamber 7e and generates a force that deforms the actuator 13f in the direction of the pressure chamber 7f. The actuator 13f is opposite to the force due to the potential difference between the drive signals W3a and W4a. Directional force is generated and substantially no deformation occurs. Therefore, the phenomenon that the pressure vibration generated in the pressure chamber 7e when the discharge operation is performed in the pressure chamber 7c leaks to the pressure chamber 7f through the actuator 13f is cut off, and the crosstalk through the actuator is substantially reduced to zero. be able to. Since the same drive signal W4a is applied to the actuators 13g to 13j to the electrodes sandwiching the actuators, the actuators 13g to 13j are not deformed.

  A method for determining the drive signals W1 to W4 will be described. The drive signals W1 to W4 define a desired meniscus vibration from the viewpoint of suppressing residual pressure vibration, prevention of crosstalk, gradation control, suppression of natural vibration of the actuator, etc., and driving that generates this desirable vibration in the meniscus The signal is obtained by calculating back using the response characteristic of the meniscus flow velocity vibration with respect to the drive signal of the inkjet head. Hereinafter, the meniscus vibration defined to calculate the drive signal backward is referred to as virtual meniscus vibration. The meniscus flow velocity vibration is simply referred to as flow velocity vibration.

  Virtual meniscus vibration is based on meniscus vibration that occurs in the actual ejection operation of the inkjet head, meniscus advance due to ink ejection from the nozzle, meniscus retraction that occurs after ink is discharged from the nozzle, ink surface tension, etc. This is a meniscus vibration that is linear with respect to the drive signal, in which non-linear components such as meniscus advance due to the ink refilling action are removed. Such meniscus vibration can be considered to be an expansion of the amplitude of the meniscus vibration that occurs when a drive signal whose amplitude is reduced to the extent that ink is not ejected is applied to the inkjet head. FIG. 8 is used to show the difference between actual meniscus vibration and virtual meniscus vibration.

  Such virtual meniscus vibration is different from the meniscus vibration that occurs in the actual ejection operation of the inkjet head, but the ink ejection speed and volume, residual vibration after the ink ejection operation, crosstalk between nozzles, and intrinsic vibration of the actuator This reflects important characteristics for the ejection operation of the inkjet head, such as the slight vibration of the meniscus. In addition to the non-linear vibration, the actual meniscus vibration is affected by factors unrelated to the drive signal, such as an ink refill action, so there is a limit to controlling the actual meniscus vibration by the drive signal. However, since the virtual meniscus vibration is not affected by factors unrelated to the drive signal, the virtual meniscus vibration can be sufficiently controlled by the drive signal. Therefore, by defining the desired virtual meniscus vibration and giving the actuator a drive signal that generates it, the ink ejection speed and volume, residual vibration after ink ejection operation, crosstalk between nozzles, and actuator natural vibration Desirable characteristics can be obtained with respect to fine vibration of the meniscus.

A method for obtaining the response characteristic R of the flow velocity vibration with respect to the drive signal of the inkjet head, which is required in the process of calculating the drive signal waveform from the virtual meniscus vibration, will be described. The response characteristic R is obtained from the flow velocity vibration UT in the nozzle with respect to the test drive signal VT. Specifically, test drive signals VT _{1 to} VT ₁₀ are applied to the respective electrodes 8a to 8j. VT ₁ is a noise waveform having a low voltage period Tc shown in FIG. 9, and VT _{2 to} VT ₁₀ are set to 0V. It is desirable that Tc be sufficiently longer than the time of ink ejection operation. Further, the same VT ₁ as that of the electrode 8a is applied to the electrode 8k, and a drive pattern every 10 channels is applied to as many pressure chambers as possible. When driving the head in such a driving pattern, when the respective _UT 1 _{~UT 10} the flow velocity of the meniscus in the nozzle 10a-10j, vibrating flow velocities of the period Tc as shown in FIG. 10 is generated. This flow velocity vibration can be observed by using a commercially available laser Doppler vibrometer, for example, LV-1710 of Ono Sokki Co., Ltd., and irradiating the meniscus in the nozzle of the inkjet head with a measuring laser beam.

ここで、ｍは、レーザドップラ振動計で観測された時系列流速データのデータ数である。レーザドップラ振動計で観測された流速データのサンプリング時間をｄｔとすれば、ｍはＴｃ／ｄｔの値となる。添字のｉは、チャンネル番号を示す１から１０までの整数であり、この番号は電極８ａ〜８ｊまたはノズル１０ａ〜１０ｊに対応している。また、添字のｊは、時系列データにおいて先頭からｊ番目のデータを示す１〜ｍまでの整数である。ｊ番目のデータは、時刻ｊ×ｄｔのデータを示している。添字のｋは、周波数系列データにおいて先頭からｋ番目のデータを示す１〜ｍまでの整数である。ｋ番目のデータは、周波数（ｋ−１）／Ｔｃのデータを示している。Ｉは虚数単位である。ここで述べた添字の記法は以下の説明においても用いることとする。 The test drive signal VT and the flow velocity vibration UT are Fourier-transformed using the following Equation [Equation 1] and Equation [Equation 2] to convert them into a voltage spectrum FVT and a flow velocity spectrum FUT, respectively.

Here, m is the number of data of time-series flow velocity data observed with a laser Doppler vibrometer. If the sampling time of the flow velocity data observed by the laser Doppler vibrometer is dt, m is a value of Tc / dt. The subscript i is an integer from 1 to 10 indicating the channel number, and this number corresponds to the electrodes 8a to 8j or the nozzles 10a to 10j. The subscript j is an integer from 1 to m indicating the jth data from the top in the time series data. The j-th data indicates data at time j × dt. The subscript k is an integer from 1 to m indicating the kth data from the top in the frequency series data. The k-th data indicates data of frequency (k−1) / Tc. I is an imaginary unit. The notation of the subscript described here will be used in the following description.

The voltage spectrum FVT _{i, k} represents the voltage amplitude and phase at the frequency (k−1) / Tc of the drive signal VT _i in complex form. The flow velocity spectrum FUT _{i, k} represents the flow velocity amplitude and phase at the frequency (k−1) / Tc of the flow velocity vibration UT _i in the form of complex numbers.

Ｒ_ｉ，ｋは、テスト駆動信号ＶＴ_１に対するノズル内のメニスカス流速Ｕ_ｉの周波数（ｋ−１）／Ｔｃにおける振幅と位相の変化を複素数の形で示している。Ｒ_ｉをチャンネルｉの応答特性としたとき、Ｒ_１〜Ｒ_１０の絶対値と位相角を図１１に示す。以上、テスト駆動信号としてノイズ波形を用いた場合について説明したが、テスト駆動信号として周波数可変の正弦波や余弦波を用い、各周波数における流速振動の振幅と位相を測定することによって応答特性Ｒを求めことも可能である。 The response characteristic R is obtained from the voltage spectrum FVT and the flow velocity spectrum FUT by the following equation [Equation 3].

R _{i, k} indicates the change in amplitude and phase in frequency (k−1) / Tc of the meniscus flow velocity U _i in the nozzle with respect to the test drive signal VT _{1 in} the form of complex numbers. When R _i is the response characteristic of channel i, the absolute values and phase angles of R _{1 to} R ₁₀ are shown in FIG. As described above, the case where the noise waveform is used as the test drive signal has been described. However, the response characteristic R is obtained by measuring the amplitude and phase of the flow rate vibration at each frequency using a variable frequency sine wave or cosine wave as the test drive signal. It can also be sought.

A method of determining a drive signal from virtual meniscus vibration using the response characteristic R will be described. FIG. 12 shows the displacement X of the virtual meniscus vibration of this example. For example, by discharging the first to third drop from the pressure chamber 7c, if not ejecting ink from the pressure chambers 7h, displacement of hypothetical meniscus vibration in nozzle 10a~10j each becomes _X 1 _{to X 10.} The displacement of the peak on the + side of the displacement of the virtual meniscus vibration multiplied by the nozzle opening diameter corresponds to the ink ejection volume of each drop.

  The displacement of the virtual meniscus vibration is that the start point and the end point are substantially continuous for the calculation described below, the result of differentiation from the start point to the end point is continuous, and the start point and end point of the differentiated result are also substantially It is said to be continuous.

上記数式〔数４〕により求められた仮想メニスカス振動の流速Ｕ_１〜Ｕ_１０を、図１３に示す。 The flow velocity of the virtual meniscus vibration corresponding to the displacement X of the virtual meniscus vibration is obtained. The flow velocity U of the virtual meniscus vibration is obtained by the following equation [Equation 4].

FIG. 13 shows the flow rates U _{1 to} U ₁₀ of the virtual meniscus vibration obtained by the above mathematical formula [Equation 4].

  The flow velocity U of the virtual meniscus vibration is time series data that is substantially continuous from the start point to the end point, and the start point and the end point are also substantially continuous. Instead of calculating the flow velocity of the virtual meniscus vibration from the displacement of the virtual meniscus vibration, the flow velocity of the virtual meniscus vibration may be defined from the beginning.

流速スペクトルＦＵ_ｉ，ｋは、仮想メニスカス振動の流速Ｕ_ｉの周波数（ｋ−１）／Ｔｃにおける流速振幅と位相を複素数の形で表している。このようにして得られた流速スペクトルＦＵのうち、ＦＵ_３の絶対値を図１４に示す。ここで、ｆｍａｘは、その周波数以下に大部分の周波数成分が含まれる周波数であり、後述するように、駆動信号ＶＡの周波数成分の上限を定めるために用いられる。 Fourier transform of the flow velocity U of the virtual meniscus vibration is performed using the following formula [Equation 5] to obtain a flow velocity spectrum FU of the flow velocity U of the virtual meniscus vibration.

The flow velocity spectrum FU _{i, k} represents the flow velocity amplitude and phase at the frequency (k−1) / Tc of the flow velocity U _i of the virtual meniscus vibration in complex form. Of the flow velocity spectrum FU thus obtained, the absolute value of FU ₃ is shown in FIG. Here, fmax is a frequency in which most of the frequency components are included below that frequency, and is used to determine the upper limit of the frequency components of the drive signal VA, as will be described later.

上記の数式〔数７〕および数式〔数９〕で得られた電圧スペクトルＦＶＡ_ｉ，ｋは、仮想メニスカス振動の流速Ｕ_ｉを発生させる駆動信号ＶＡ_ｉの、周波数（ｋ−１）／Ｔｃにおける電圧振幅と位相を複素数の形で表している。また、上記数式〔数６〕で得られる［Ｒ］_ｋのａ行ｂ列目の要素は、ｂ番目のチャンネルの周波数（ｋ−１）／Ｔｃの電圧振動に対するａ番目のノズル内のメニスカス流速振動の振幅と位相の変化を複素数の形で表している。［Ｒ］_ｋ ^−１は［Ｒ］_ｋの逆行列である。逆行列の演算は、ＷＯＬＦＲＡＭ ＲＥＳＥＡＲＣＨ社のＭＡＴＨＥＭＡＴＩＣＡ（登録商標）などの数式解析ソフトウエアにより行うことができる。 Next, the voltage spectrum FVA of the drive signal is obtained from the response characteristic R of the inkjet head and the flow velocity spectrum FU of the virtual meniscus vibration. When the response characteristic matrix [R] _k is expressed by the following equation (6), the voltage vector {FVA} _k is expressed by the following equation (7), and the flow velocity vector {FU} _k of the virtual meniscus vibration is expressed by the following equation (8): 9], the voltage vector FVA _{k at the} frequency (k-1) / Tc is obtained.

The voltage spectrum FVA _{i, k} obtained by the above equations [Equation 7] and [Equation 9] is the frequency (k−1) / Tc of the drive signal VA _i that generates the flow velocity U _i of the virtual meniscus vibration. The voltage amplitude and phase are represented in complex form. Further, the element in the a row and the b column of [R] _k obtained by the above formula [Equation 6] is the meniscus flow velocity in the a-th nozzle with respect to the voltage oscillation of the frequency (k-1) / Tc of the b-th channel. The change in amplitude and phase of the vibration is represented in the form of a complex number. [R] _k ⁻¹ is an inverse matrix of [R] _k . The inverse matrix can be calculated by mathematical analysis software such as MATEMATICA (registered trademark) of WOLFRAM RESEARCH.

ここで、Ｒｅ［ｚ］は、複素数ｚ＝ａ＋ｂＩの実数部ａを得る関数である。ＶＡ_ｉ，ｊは、仮想メニスカス振動の流速Ｕを発生させる駆動信号ＶＡの、ｉ番目のチャンネルの時刻ｊ×ｄｔにおける電圧値である。
このように得られた駆動信号ＶＡ_ｉ、すなわちＶＡ_１〜ＶＡ_１０は、各々電極８ａ〜８ｊに印加された場合、ノズル１０ａ〜１０ｊ内のメニスカスに仮想メニスカス振動の変位Ｘ_１〜Ｘ_１０を生じさせる駆動信号になる。
また、ｍ’は、次の数式〔数１１〕のとおりとなる最も大きい整数である。

このように逆フーリエ変換の周波数の上限をｆｍａｘとすることにより、駆動信号ＶＡの周波数成分の上限値がｆｍａｘに定められる。仮想メニスカス振動が実際のインクジェットヘッドがほとんど応答しない周波数成分を有している場合に、ｆｍａｘを定めることによって、駆動信号ＶＡの電圧振幅が異常に大きくなる事態を防止できる。ｆｍａｘはＦＵの周波数成分の大部分がｆｍａｘ以内に含まれることが望ましい。駆動信号ＶＡの電圧変動が現れる期間や電圧振幅は、圧力室の長さＬに応じて変化する。圧力室の長さＬは、電圧変動が現れる期間が最小限になる範囲内で、電圧振幅が最も小さくなる値に定められることが望ましい。以上のようにして得られた駆動信号ＶＡ（ＶＡ_１〜ＶＡ_１０）を、図１５に示す。 The drive signal VA is obtained by performing an inverse Fourier transform on the voltage spectrum FVA using the following equation [Equation 10].

Here, Re [z] is a function for obtaining the real part a of the complex number z = a + bI. VA _{i, j} is a voltage value at the time j × dt of the i-th channel of the drive signal VA for generating the flow velocity U of the virtual meniscus vibration.
When the drive signals VA _i thus obtained, that is, VA _{1 to} VA ₁₀ are respectively applied to the electrodes 8a to 8j, virtual meniscus vibration displacements X _{1 to} X ₁₀ are generated in the meniscus in the nozzles 10a to 10j. Drive signal to be generated.
Further, m ′ is the largest integer that is represented by the following equation [Equation 11].

Thus, by setting the upper limit of the frequency of the inverse Fourier transform to fmax, the upper limit value of the frequency component of the drive signal VA is set to fmax. When the virtual meniscus vibration has a frequency component that the actual ink jet head hardly responds to, the situation in which the voltage amplitude of the drive signal VA becomes abnormally large can be prevented by determining fmax. As for fmax, most of the frequency components of FU are desirably included within fmax. The period and voltage amplitude in which the voltage variation of the drive signal VA appears changes according to the length L of the pressure chamber. The length L of the pressure chamber is desirably set to a value at which the voltage amplitude is minimized within a range in which the period in which the voltage fluctuation appears is minimized. The drive signals VA (VA _{1 to} VA ₁₀ ) obtained as described above are shown in FIG.

The drive signal VA obtained as described above can be used as it is as a drive signal for the inkjet head, but the reference voltage waveform VREF (VREF _{1 to} VREF ₁₀ ) as shown by the dotted line in FIG. 15 from the drive signal VA. ) To obtain the drive signals VB (VB _{1 to} VB ₁₀ ) shown in FIG. 16, the drive signal length can be shortened. As a result, the drive cycle of the inkjet head can be shortened, and the printing speed can be improved.

ここで、ＭＩＮ［ＶＢ_１，ｊ，ＶＢ_２，ｊ，．．．］は、［ ］内の値のうち最小値を示す関数である。 The drive signal VB obtained as described above can be used as it is as a drive signal for the ink jet head. However, by obtaining the drive signal VD represented by the following equation [Equation 12], The voltage amplitude can be reduced. As a result, the cost of the drive circuit can be reduced, and an inexpensive ink jet recording apparatus can be provided. FIG. 17 shows drive signals VD _{1 to} VD ₁₀ .

Here, MIN [VB _{1, j} , VB _{2, j} ,. . . ] Is a function indicating the minimum value among the values in [].

The drive signal VD ₃ obtained by the above calculation becomes the drive signal W1, the drive signal VD ₂ or VD ₄ becomes the drive signal W2, the drive signal VD ₁ or VD ₅ becomes the drive signal W3, and the drive signals VD ₆ to VD ₆ . One of the VDs ₁₀ becomes the drive signal W4.

  If the inkjet head is not of the shear mode type and can control the pressure chambers independently, or if the crosstalk between the pressure chambers can be ignored even if it is a shear mode type structure, it is driven according to the following procedure. The signal waveform can be calculated.

この例において、インクを吐出する圧力室７ｃを駆動するアクチュエータ１３ｃ、１３ｄに印加される駆動信号ＶＥは「ＶＥ＝ＶＤ_３−ＶＤ_２」により算出され、図１８に示す駆動信号となる。 In the same manner as in the present embodiment, the response characteristic R is obtained for only one channel, the flow velocity U of the virtual meniscus vibration is defined for only one channel, and the flow velocity spectrum FU of the flow velocity of the virtual meniscus vibration is obtained. Then, the voltage spectrum FV of the drive signal is obtained by the following equation [Equation 13], and finally, the drive signal V is obtained by performing inverse Fourier transform on the voltage spectrum FV by the same method as in this embodiment.

In this example, the drive signal VE applied to the actuators 13c and 13d that drive the pressure chamber 7c that ejects ink is calculated by “VE = VD ₃ −VD ₂ ” and becomes the drive signal shown in FIG.

  An ink jet recording apparatus including an ink jet head that operates according to a drive signal obtained by using the waveform information generation method described above will be described.

  FIG. 19 shows the configuration of the ink jet recording apparatus. The sheet 104 is conveyed in the direction of the arrow by the endless conveyance belt 103. The same four inkjet heads 101 are mounted on the substrate 102 so that the ink ejection direction is directed to the paper surface. A desired image is formed by ejecting ink on the transported paper in accordance with the image data. In this ink jet recording apparatus, four ink jet heads are arranged in a row and recording is performed with a print width corresponding to the paper width, so that high speed printing is possible.

  When generating a drive signal for operating the inkjet head 101, as described above, an appropriate test waveform such as a noise waveform or a sine wave is used first, and the response characteristic R of the meniscus to the drive signal of the manufactured inkjet head is set. taking measurement. Next, based on the measured response characteristic and a predetermined virtual meniscus vibration, the waveform of the drive signal is created by calculation using the above-described equations [Equation 4] to [Equation 10]. The waveform of the obtained drive signal is stored in the drive waveform memory of the ink jet recording apparatus. The data stored in this memory corresponds to waveform information for generating a drive signal.

  As shown in FIG. 20, the measured response characteristic R and virtual meniscus vibration can be stored in the ink jet recording apparatus, and the waveform of the drive signal can be calculated in the ink jet recording apparatus by the method described above. In that case, the frequency component of the waveform of the drive signal VA equal to or greater than fmax is cut by the computing means 27, or the virtual meniscus vibration stored in the virtual meniscus vibration memory 28 or the response characteristic fmax stored in the response characteristic memory 29 in advance. It is desirable to cut the frequency component of.

  In the conventional ink jet recording apparatus, the timing of the drive signal and the voltage amplitude are adjusted at the time of manufacture according to the variation in the characteristics of the ink jet head, but the ink ejection is accompanied by the variation in the main acoustic resonance frequency of the ink jet head. Since the time changes, there is a problem in that the ink ejection speed and volume vary. However, in the present invention, since the drive signal is set so as to reproduce the predetermined meniscus vibration, the problem that the ink ejection speed and volume vary even if the main acoustic resonance frequency of the inkjet head head varies can be solved. Further, when the inkjet recording apparatus of the present invention is manufactured, the adjustment of the timing of the drive signal and the adjustment of the voltage amplitude can be omitted, so that an inexpensive inkjet recording apparatus can be provided.

このため、各ドロップの吐出体積に応じて吐出時間ｓｔを可変している。また、各ドロップの仮想メニスカス振動の変位の終端に、変位が０でありかつ変位の時間微分で表される流速が０となる条件を設定することにより、各ドロップの吐出動作終了後の残留振動を実質的に０にしている。その結果、例えば第２ドロップを吐出させる場合、第１ドロップを吐出させたか否かによるインク吐出速度の変動を防止でき、各ドロップの吐出速度を均一化できる。 The virtual meniscus vibration in the case where a plurality of ink drops having different ejection volumes are selectively ejected to form one pixel will be described in detail with reference to FIG. When the ink ejection speeds differ greatly between ink drops having different ejection volumes, ink droplets with too low ejection speeds have poor landing position accuracy, and when the ink ejection speeds are too large, the ink ejection operation becomes unstable. When the ink ejection time is st and the meniscus displacement at the time of ink ejection is a, the ink ejection speed is approximately a / st. In this embodiment, the displacement X ₃ of hypothetical meniscus vibrations in nozzles for ejecting ink, first drop, second drop, a third drop discharge each ejection time during st1, and st2, st3, virtual during ink ejection Assuming that the displacement of the meniscus vibration is a1, a2, and a3, the virtual meniscus vibration is defined so that the discharge speed of each drop is substantially constant as shown in the following formula [Formula 14].

For this reason, the discharge time st is varied according to the discharge volume of each drop. Further, by setting a condition that the displacement is zero and the flow velocity represented by the time derivative of the displacement is zero at the end of the displacement of the virtual meniscus vibration of each drop, the residual vibration after the end of the discharge operation of each drop Is substantially zero. As a result, for example, when the second drop is ejected, fluctuations in the ink ejection speed depending on whether or not the first drop is ejected can be prevented, and the ejection speed of each drop can be made uniform.

  The virtual meniscus vibration as described above has different discharge volumes, the discharge speed is substantially constant, and the residual vibration is substantially zero. Therefore, the ink droplets are excellent in gradation printing performance and discharged by the residual pressure vibration. Thus, it can be said that the ink ejection operation with excellent printing quality and small variations in the speed and volume is possible.

  In FIG. 13, the flow velocity vibrations U2 and U4 of the nozzles 10b and 10d adjacent to the discharge nozzle 10c are -1/4 of the flow velocity vibration U3 of the nozzle 10c. In such a configuration, when ink is simultaneously ejected from the nozzles 10c and 10h, the flow velocity vibration of the non-ejection nozzles 10d to 10g is -1/4 of the ejection nozzles 10c and 10h. That is, the flow velocity vibrations of the non-ejection nozzles 10d and 10g accompanying the ejection of the ink from the ejection nozzles 10c and 10h are dispersed with respect to the non-ejection nozzles 10e and 10f, so that the amplitude of the flow velocity vibration generated in the nozzles 10d to 10g is uniform. To do. This is because the amplitude of the flow velocity vibration is proportional to the amplitude of the pressure vibration, so that the pressure vibration of the pressure chambers 7d and 7g not ejecting ink accompanying the ink ejection operation of the pressure chambers 7c and 7h for ejecting ink is ejected from the ink. It may be expressed that the amplitude of the pressure vibration generated in the pressure chambers 7d to 7g is made uniform by dispersing the pressure chambers 7e and 7f that are not allowed to be distributed. In the non-ejection nozzle, the force that causes the meniscus to rise is approximately proportional to the square of the flow velocity of each nozzle. Obviously, in order to minimize the force that causes the meniscus to rise as a whole non-ejection nozzle, it is only necessary to uniformly disperse the flow velocity vibration associated with the ink ejection operation to the non-ejection nozzle. By uniformly distributing the flow velocity vibration, the phenomenon that the meniscus swells from the nozzle surface can be suppressed, variation in meniscus position during ink ejection is reduced, and variation in ink droplet ejection speed is suppressed, resulting in print quality. Will improve.

A second embodiment of the present invention will be described. In this embodiment, the virtual meniscus vibration X is as shown in FIG. Hypothetical meniscus vibration X ₃ of the meniscus displacement a and the discharge time st is a generally constant in each drop, the prior ink ejection meniscus retraction amount b (b1, b2, b3) by varying the respective drop ejecting ink The volume is variable. Since the meniscus displacement a and the discharge time st are generally constant for each drop, the discharge speed of each drop is generally constant. Further, by setting a condition that the displacement is zero and the flow velocity that is the time derivative of the displacement is zero at the end of the virtual meniscus vibration of each drop, the residual vibration after the discharge operation of each drop is substantially reduced. It is set to 0. Thus, for example, when discharging the second drop, it is possible to prevent fluctuations in the discharge speed caused by whether or not the first drop is discharged, and to uniformize the discharge speed of each drop.

Also in this embodiment, the method of creating the drive waveform is the same as that in the first embodiment. FIG. 22 shows the flow velocity vibration U of this embodiment, FIG. 23 shows the flow velocity spectrum FU ₃ of the flow velocity vibration U, FIG. 24 shows the drive signal VA, FIG. 25 shows the drive signal VB, and FIG. Show.

In the second embodiment, the drive signal VE applied to the actuators 13c and 13d for driving the pressure chamber 7c for ejecting ink is calculated by VE = VD ₃ −VD ₂ and becomes the drive signal shown in FIG. The drive signals for discharging the first drop, the second drop, and the third drop are VEa, VEb, and VEc, respectively. Here, the + side indicates that the volume of the pressure chamber is enlarged, and the − side indicates that the volume of the pressure chamber is contracted. The drive signals VEa, VEb, and VEc each have two cycles of voltage oscillation, and the voltage amplitude on the side that expands the volume of the pressure chamber and the voltage amplitude on the side that contracts the volume of the pressure chamber differ depending on each drop. ing. Further, the difference between the maximum value and the minimum value of the voltages of the drive signals VEa, VEb, and VEc is substantially the same. The drive signals VEa, VEb, and VEc are calculated in reverse from the virtual meniscus vibration in which the discharge volumes are different, the discharge speed is substantially constant, and the residual vibration is substantially zero. The signals VEa to VEc are excellent gradation printing performance, and can be said to be drive signals having excellent printing quality without variations in the speed and volume of ink droplets discharged due to residual pressure vibration.

  When this drive waveform is applied to the actuators 13c and 13d, the pressure chamber 7c performs the ink ejection operation described below. First, the volume of the pressure chamber is expanded, then the volume is contracted, the volume is expanded again, the volume is contracted again, and then the ink droplet is ejected by returning to the volume before the ink ejection operation. The ink discharge volume is varied by making the expansion amount and the contraction amount different. The difference between the maximum value and the minimum value of the volume of the pressure chamber in each discharge operation is substantially the same.

  The inkjet head driving method having the above characteristics is different in each discharge volume, has a constant output speed, and has substantially no residual vibration, so that it has excellent gradation printing performance and discharge by residual pressure vibration. It can be said that this is a driving method with excellent printing quality without variations in the speed and volume of ink droplets.

  A third embodiment of the present invention will be described. This embodiment is divided into four, and the virtual meniscus vibration in the nozzles that eject ink is the same as that of the first embodiment. In the 4-division drive, the drive signal selection means 24 is different from the 5-division drive.

FIG. 28 shows a circuit diagram of the drive signal selection means 24. In the drive signal selection means 24, the ACT signal is selected by the analog switches 30a to 30j when the ON / OFF signals 27a to 27j are ON according to the decoder output, and the analog switch 30a when the ON / OFF signals 27a to 27j are OFF. The INA signal is selected by ˜30j, and the drive signals ACT1 to ACT4 and INA1 to INA4 are applied to the electrode 8. ACT1 to ACT4 correspond to the first to fourth cycles in time-division driving, respectively. As an example, an operation when ink is ejected from the pressure chamber 7c at a certain timing and ink is not ejected from the pressure chamber 7g at the same operation timing will be described. In order to eject ink from the pressure chamber 7c, the ON / OFF signals 27a, 27b, 27c, and 27d are turned ON. These ON / OFF signals correspond to the pressure chamber 7c, two on one side (pressure chambers 7a and 7b), and one on the opposite side (pressure chamber 7d). In order not to eject ink from the pressure chamber 7g, the ON / OFF signals 27e, 27f, 27g, and 27h are turned OFF. These ON / OFF signals correspond to the pressure chamber 7g, two on one side (pressure chambers 7e and 7f), and one on the opposite side (pressure chamber 7h). By applying these ON / OFF signals, an ACT signal is supplied to the pressure chamber 7c that discharges ink and one pressure chamber 7a, 7b, and 7d on the opposite side of the pressure chamber 7c, and the pressure chamber 7g that does not discharge ink. The INA signal is supplied to the pressure chambers 7e, 7f, and 7h on the opposite side and the one on the opposite side.

  The drive signals ACT1 to ACT4 and INA1 to INA4 supplied to the drive signal selection unit will be described. FIG. 29 shows one print cycle of the ink ejection drive signals ACT1 to ACT4 and the non-ink ejection drive signals INA1 to INA4. ACT1 to ACT4 are composed of three drive signals W1, W2 and W3, and INA1 to INA4 are composed of three drive signals W3, W4 and W5. The phases of ACT1 to ACT4 are different from each other by the time divided. For example, when ink is ejected from the pressure chamber 7c, the ON / OFF signals 27a to 27d are turned ON in the third cycle, so that the pressure chamber 7a has W3, the pressure chambers 7b and 7d have W2, and the pressure chamber 7c has Is supplied with a drive signal W1.

  The drive signals W1 to W5 will be described with reference to FIG. W1 to W5 are W1a, W2a, W3a, W4a, W5a in the period for discharging the first drop having a volume of 6 pl, and W1b, W2b, W3b, W4b in the period for discharging the second drop having a volume of 12 pl. , W5b, and W1c, W2c, W3c, W4c, W5c in a period for discharging the third drop having a volume of 24 pl.

  A case where the first drop is discharged from the pressure chamber 7c and the first drop is not discharged from the pressure chamber 7g is illustrated. Ink is ejected in order from the pressure chambers 7a, 7b, 7c, and 7d in the order from the first cycle to the fourth cycle. In order to eject ink from the pressure chamber 7c, the ON / OFF signals 27a to 27d are turned ON and the ON / OFF signals 27e to 27h are turned OFF during the first drop period of the third cycle. By applying this ON / OFF signal, W1a is applied to the electrode 8c, W2a is applied to the electrodes 8b and 8d, W3a is applied to the electrodes 8a and 8e, W4a is applied to the electrodes 8f and 8h, and W5a is applied to the electrode 8g. Is done. As a result, as shown in FIG. 31, the actuators 13c and 13d are greatly deformed by the potential difference between the drive signals W1a and W2a, and 6 pl ink droplets are ejected from the pressure chamber 8c. The actuators 13b and 13e are deformed in a direction in which the pressure vibration generated in the pressure chambers 7b and 7d is dispersed in the pressure chambers 7a and 7e due to the potential difference between the drive signals W2a and W3a. The actuator 13f is deformed in the same manner as when the first drop is discharged from the pressure chamber 8g due to the potential difference between the drive signals W3a and W4a. Therefore, the pressure vibration generated in the pressure chamber 7e when the discharge operation is performed in the pressure chamber 7c is the same as that in the case where the discharge operation of the pressure chamber 7g is performed, and the crosstalk can be substantially reduced to zero. . The actuators 13g and 13h are deformed so as to disperse the pressure vibration generated in the pressure chamber 7f by the potential difference between the drive signals W4a and W5a. By doing so, the pressure vibration generated in the pressure chambers 7f to 7h becomes minute, and the phenomenon that the meniscus in the non-ejection nozzles 10f to 10i swells can be suppressed, so that the adverse effect on the print quality can be reduced.

Also in this embodiment, the method of creating the drive signal is the same as that in the first embodiment. FIG. 32 shows the displacement X of the virtual meniscus vibration. For example, by discharging the first to third drop from the pressure chamber 7c, if not ejecting ink from the pressure chamber 7 g, displacement of hypothetical meniscus vibration in nozzle 10a~10h each becomes _X 1 to X _8. FIG. 33 shows the flow velocity vibration U corresponding to the displacement of the virtual meniscus vibration, FIG. 34 shows the drive signal VA, FIG. 35 shows the drive signal VB, and FIG. 36 shows the drive signal VD.

In FIG. 33, the flow velocity vibrations U ₂ and U ₄ of the nozzles 10b and 10d adjacent to the discharge nozzle 10c are −1/3 of the flow velocity vibration U ₃ of the nozzle 10c. In such a configuration, when ink is simultaneously ejected from the nozzles 10c and 10g, the flow velocity vibration of the non-ejection nozzles 10d to 10f is −１ of that of the ejection nozzles 10c and 10g. That is, the flow velocity vibration of the non-ejection nozzles 10d and 10f accompanying the ejection of the ink from the ejection nozzles 10c and 10g is uniformly distributed to the non-ejection nozzles 10d to 10f.

  Since the amplitude of the flow velocity vibration is proportional to the amplitude of the pressure vibration, the pressure vibration of the pressure chambers 7d and 7f that do not eject ink accompanying the ink ejection operation of the pressure chambers 7c and 7g that eject ink is applied to the ink. It may be expressed that the pressure chambers 7d to 7f that are not discharged are uniformly dispersed. In the non-ejection nozzle, the force that causes the meniscus to rise is approximately proportional to the square of the flow velocity of each nozzle. For this reason, it is obvious that the flow velocity vibration accompanying the ink ejection operation should be uniformly distributed to the non-ejection nozzles in order to minimize the force that causes the meniscus to rise as a whole non-ejection nozzle. By uniformly dispersing the flow velocity vibration, the phenomenon that the meniscus swells from the nozzle surface can be suppressed, and variations in meniscus position during ink ejection are reduced. Therefore, variation in ink droplet ejection speed is suppressed, and print quality is improved.

  Numerical analysis simulation was performed on the meniscus displacement of the nozzles 10c to 10f when ink was simultaneously ejected from the pressure chambers 7c and 7g, and then ink was ejected simultaneously from the pressure chambers 7d and 7h, 7e and 7i, and 7f and 7j. The results are shown in FIG. The solid line shows the case where the flow velocity vibration accompanying the ink ejection operation is uniformly dispersed in the non-ejection nozzles. On the other hand, a broken line is a case where the flow velocity vibration accompanying the ink ejection operation is non-uniformly distributed in the non-ejection nozzles. In the case of non-uniform dispersion, ink is simultaneously ejected from the pressure chambers 7c and 7g, and the pressure ratios of the pressure chambers 7d, 7e, and 7f are calculated as 1/4: 1/4: 1/2, respectively. ing. Arrows indicate the timing at which ink ejection is started at each nozzle. The climax of the meniscus when unevenly distributed at each discharge start timing is greatest at the second discharge timing of the nozzle 10c, and the climax of the meniscus when uniformly distributed is at any discharge start timing. Below this.

このとき、Ｕ_１〜Ｕ_５は、圧力分散により下記の数式〔数１６〕のとおりとなる。

したがって、上記数式〔数１５〕および〔数１６〕より、次の数式〔数１７〕に示すとおりとなる。

ゆえに、メニスカス盛り上がりの力が流速の２乗に比例することを考慮すれば、下記の数式〔数１８〕のとおりであるのが最適なのは、明らかである。

In this embodiment, in order to make the ink ejection operation of the pressure chamber 7c constant regardless of whether or not ink is ejected from the pressure chamber 7g, the actuator 13f is deformed even when ink is not ejected from the pressure chamber 7g. The pressure vibration generated in the pressure chamber 7e when ink is ejected from the pressure chamber 7g is the same as the pressure vibration generated in the pressure chamber 7e when ink is not ejected from the pressure chamber 7g. In this case, the vibrating flow velocity _U 6 ~U ₈ nozzles 10F～10h, by the 1/9 of the vibrating flow velocity _{U 3} of the nozzle 10c, thereby minimizing the meniscus swelling of the non-discharge nozzle 10F～10h. This is derived using the shared wall head property that the sum of U _{1 to} U ₈ at any time is substantially zero. That is, U _{1 to} U ₈ are as shown in the following formula [Formula 15].

At this time, U _{1 to} U ₅ are represented by the following formula [Equation 16] due to pressure dispersion.

Therefore, from the above equations [Equation 15] and [Equation 16], the following equation [Equation 17] is obtained.

Therefore, considering that the meniscus rising force is proportional to the square of the flow velocity, it is clear that the following equation [Equation 18] is optimal.

1 is a longitudinal sectional view showing a configuration of an ink jet head according to an embodiment of the present invention. The figure which shows operation | movement of the actuator of a 1st Example. FIG. 3 is a block diagram showing a configuration of a drive circuit that drives the inkjet head according to the embodiment. The figure which shows the gradation control method of a 1st Example. The circuit diagram which shows the drive signal selection means of a 1st Example. The figure which shows an example of the drive signal of a 1st Example. The figure which shows the detail of the drive signal of a 1st Example. The figure which shows an actual meniscus vibration and a virtual meniscus vibration. FIG. 6 is a diagram illustrating a drive signal for measuring head response characteristics according to the first embodiment. The figure which shows the flow velocity vibration with respect to the drive signal for head response characteristic measurement of a 1st Example. FIG. 6 is a diagram showing head response characteristics of the first embodiment. The figure which shows the displacement of the virtual meniscus vibration of a 1st Example. The figure which shows the flow velocity of the virtual meniscus vibration of a 1st Example. The figure which shows the frequency component of the flow velocity of the virtual meniscus vibration of a 1st Example. The figure which shows the waveform of the drive signal calculated from the flow velocity and head response characteristic of the virtual meniscus vibration of 1st Example. The figure which shows the drive signal which correct | amended the drive signal of FIG. The figure which shows the drive signal which deform | transformed the drive signal of FIG. The figure which shows the drive signal applied to the actuator which drives the pressure chamber which discharges the ink of a 1st Example. 1 is a diagram showing an ink jet recording apparatus of the present invention. FIG. 3 is a block diagram showing a configuration of a drive circuit that drives the inkjet head according to the embodiment. The figure which shows the displacement of the virtual meniscus vibration of a 2nd Example. The figure which shows the flow velocity of the virtual meniscus vibration of a 2nd Example. The figure which shows the frequency component of the flow velocity of the virtual meniscus vibration of a 2nd Example. The figure which shows the waveform of the drive signal calculated from the flow velocity and head response characteristic of the virtual meniscus vibration of 2nd Example. The figure which shows the drive signal which correct | amended the drive signal of FIG. The figure which shows the drive signal which deform | transformed the drive signal of FIG. The figure which shows the drive signal applied to the actuator which drives the pressure chamber which discharges the ink of a 2nd Example. The circuit diagram which shows the drive signal selection means of a 3rd Example. The figure which shows an example of the drive signal of a 3rd Example. The figure which shows the detail of the drive signal of a 3rd Example. The figure which shows operation | movement of the actuator of a 3rd Example. The figure which shows the displacement of the virtual meniscus vibration of a 3rd Example. The figure which shows the flow velocity of the virtual meniscus vibration of a 3rd Example. The figure which shows the waveform of the drive signal calculated from the flow velocity and head response characteristic of the virtual meniscus vibration of 3rd Example. The figure which shows the drive signal which correct | amended the drive signal of FIG. The figure which shows the drive signal which deform | transformed the drive signal of FIG. The figure which shows the meniscus displacement at the time of discharge operation of a 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Inkjet head 1 Substrate 2, 3 Piezoelectric member 4 Top plate frame 5 Top plate lid 7 Pressure chamber 8 Electrode 11 Nozzle plate 13 Actuator 14 Ink supply path 15 Ink supply port

Claims (6)

A nozzle that ejects ink; a pressure chamber that communicates with the nozzle; an ink supply unit that supplies ink to the pressure chamber; and an actuator that varies a volume of the pressure chamber in accordance with a drive signal. In the method of creating the waveform of the drive signal of the inkjet head that ejects ink from the nozzle according to
The response characteristic of the meniscus flow velocity in the nozzle to the inkjet head drive signal is measured, the meniscus flow velocity vibration is U, the U Fourier transform result is FU, and the meniscus flow velocity response in the nozzle to the inkjet head drive signal is measured. A method of creating a waveform of a drive signal for an inkjet head , wherein the waveform is obtained by performing inverse Fourier transform on FV, assuming that the characteristic is R, and FV = R ^-1 FU .   In the meniscus flow velocity vibration, the displacement at the end of one ink discharge stroke is substantially the same as the displacement before the ink discharge stroke, and the flow velocity at the end of one ink discharge stroke is substantially zero. 2. The method of generating a waveform of a drive signal for an inkjet head according to claim 1, wherein the waveform is generated.   2. The method of creating a waveform of a drive signal for an inkjet head according to claim 1, wherein the calculation includes a step of cutting a frequency component having a predetermined frequency or higher. A nozzle that ejects ink; a pressure chamber that communicates with the nozzle; an ink supply unit that supplies ink to the pressure chamber; and an actuator that varies a volume of the pressure chamber in accordance with a drive signal. An ink jet head that ejects ink from the nozzles in response, a storage unit that stores waveform information of the drive signal, and a drive signal that is generated based on the waveform information stored in the storage unit. In an inkjet recording apparatus having a driving means for driving,
The waveform information is based on response characteristics obtained by measuring the meniscus flow velocity in the nozzle with respect to the drive signal of the inkjet head, U is the meniscus flow velocity vibration, FU is the Fourier transform result of U, and the inkjet head drive An ink jet recording apparatus, wherein the response characteristic of the meniscus flow velocity in the nozzle with respect to a signal is R, and FV = R ^-1 FU, and the FV is obtained by inverse Fourier transform . In the meniscus flow velocity vibration, the displacement at the end of one ink discharge stroke is substantially the same as the displacement before the ink discharge stroke, and the flow velocity at the end of one ink discharge stroke is substantially zero. The inkjet recording apparatus according to claim 4 , wherein the inkjet recording apparatus is provided. 5. The ink jet recording apparatus according to claim 4, wherein the calculation includes a process of cutting a frequency component having a predetermined frequency or higher.

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