JP2010179501A - Liquid discharging apparatus and control method of liquid discharging apparatus - Google Patents

Abstract

The present invention provides a liquid ejecting apparatus capable of preventing the separation of dots by suppressing the occurrence of mist and the like when ejecting a highly viscous liquid, and a method for controlling the liquid ejecting apparatus.
At a timing at which the meniscus reverses the movement from the discharge side to the pressure generating chamber side due to residual vibration after the ink is discharged by the first middle dot discharge drive pulse DPM1 which is the discharge drive pulse on the front side in terms of time. The first middle dot ejection drive that is the front side ejection drive pulse is temporally applied so that the first expansion element P11 of the second middle dot ejection drive pulse DPM2 that is the rear side ejection drive pulse is applied to the piezoelectric vibrator 17. The residual vibration when ink is ejected by the pulse DPM1 and the first expansion element P11 of the second middle dot ejection driving pulse DPM2 which is the ejection driving pulse on the rear side are applied to the piezoelectric vibrator 17 to thereby apply pressure in the pressure generating chamber. The interval t between the ejection drive pulses continuous in the front-rear direction is set so that the pressure vibration generated in the ink has the same phase.
[Selection] Figure 4

Description

  The present invention relates to a liquid ejection apparatus such as an ink jet printer and a method for controlling the liquid ejection apparatus, and in particular, it is possible to control liquid ejection by applying a driving pulse included in a driving signal to a pressure generating element. The present invention relates to a liquid ejecting apparatus and a method for controlling the liquid ejecting apparatus.

  The liquid ejection apparatus is an apparatus that includes a liquid ejection head capable of ejecting liquid and ejects various liquids from the liquid ejection head. As a representative example of this liquid ejection apparatus, for example, an ink jet recording head (hereinafter simply referred to as a recording head) as a liquid ejection head is provided, and liquid ink is ejected from the nozzle of this recording head to a recording medium such as recording paper. An image recording apparatus such as an ink jet printer (hereinafter simply referred to as a printer) that records an image or the like by discharging and landing on a (landing target) can be given. In recent years, liquid ejecting apparatuses have been applied not only to the image recording apparatus but also to various manufacturing apparatuses such as a manufacturing apparatus for a color filter such as a liquid crystal display.

  For example, the printer applies a discharge drive pulse to a pressure generating element (for example, a piezoelectric vibrator or a heating element) and drives it to apply a pressure change to the liquid in the pressure generating chamber, and use this pressure change. In some cases, liquid is ejected from a nozzle communicating with the pressure generating chamber. In such a printer, a phenomenon (tailing) occurs in which the rear end portion of the ejected ink extends like a tail. In particular, an attempt has been made to eject a liquid having a higher viscosity than an ink liquid of an ink jet printer conventionally used at home, such as a water-based dye ink (hereinafter also referred to as a high viscosity liquid). Viscous liquids tend to have longer tails. Then, there is a possibility that the tail portion separates from the droplet main body and flies and does not land on the regular position (desired position) on the landing target. For example, an ink jet printer has a problem in that the tail part becomes a mist and is displaced from a normal position and landed to separate dots, thereby causing deterioration in image quality. In particular, in a high-viscosity liquid, the tail part is separated into several parts, and these separated parts (satellite ink droplets or mist) cause a significant deterioration in image quality.

  In order to suppress the occurrence of the mist and the like, in the configuration of Patent Document 1, the ejection pulse is properly used according to the distance from the nozzle of the recording head to the recording surface of the recording paper. For example, when the above distance is long For this, an ejection driving pulse is used so that the flying speed of the ejected liquid is lowered.

JP 2006-212920 A

  However, if the flying speed of the ejected liquid is reduced, the occurrence of mist and the like can be reduced, while the flying accuracy is reduced due to disturbance before reaching the recording paper, and the landing accuracy is lowered. There was a fear.

  The present invention has been made in view of such circumstances, and the object thereof is a liquid ejection apparatus capable of preventing the separation of dots by suppressing the occurrence of mist and the like when ejecting a high viscosity liquid, And it is providing the control method of a liquid discharge apparatus.

The present invention has been proposed to achieve the above object, and includes a nozzle, a pressure generation chamber communicating with the nozzle, and a pressure generation element that causes a pressure fluctuation in the liquid in the pressure generation chamber. A liquid discharge head capable of discharging liquid from the nozzle by the operation of the pressure generating element;
Drive signal generating means for repeatedly generating a drive signal including a plurality of ejection drive pulses for driving the pressure generating element to eject liquid from the nozzle;
A liquid ejecting apparatus that forms a prescribed dot on an impact target by sequentially applying a plurality of ejection drive pulses included in the drive signal to the pressure generating element sequentially,
Each of the ejection drive pulses is a pulse waveform starting from a pressure generation chamber expansion element that expands the pressure generation chamber and draws a meniscus,
Residual vibration when liquid is discharged by the front discharge drive pulse, and pressure vibration generated in the liquid in the pressure generation chamber by applying the pressure generation chamber expansion element of the rear discharge drive pulse to the pressure generation element. , The interval between the ejection drive pulses that are continuous in the front and rear is set so as to have the same phase.
It should be noted that “in-phase” is used not only in a state where the phases are exactly the same, but also in a sense that allows vibrations to deviate within a range in which each other reinforces each other.

Furthermore, the present invention includes a nozzle, a pressure generation chamber communicating with the nozzle, and a pressure generation element that causes a pressure fluctuation in the liquid in the pressure generation chamber, and the liquid is discharged from the nozzle by the operation of the pressure generation element. An ejection drive pulse included in the drive signal, and a drive signal generation unit that repeatedly generates a drive signal including a plurality of ejection drive pulses for driving the pressure generating element to eject the liquid from the nozzle. A method for controlling a liquid ejection device to form a prescribed dot on a landing target by sequentially applying a plurality of pressures to the pressure generating element successively,
Each of the ejection drive pulses is a pulse waveform starting from a pressure generation chamber expansion element that expands the pressure generation chamber and draws a meniscus,
Residual vibration when liquid is discharged by the front discharge drive pulse, and pressure vibration generated in the liquid in the pressure generation chamber by applying the pressure generation chamber expansion element of the rear discharge drive pulse to the pressure generation element. The interval between the ejection drive pulses that are continuous in the front and back is set so that the phase is in the same phase.

  By adopting the above configuration, the residual vibration after the liquid is ejected by the front ejection drive pulse and the pressure generating chamber expansion element of the rear ejection drive pulse are applied to the pressure generating element, so that the pressure generating chamber Since the pressure vibration generated in the liquid of each other reinforces each other, when the meniscus is drawn to the pressure generating chamber side by the pressure generation expansion element of the rear discharge drive pulse, the meniscus becomes larger than in the case of the front discharge drive pulse. It can be pulled in and the amount of liquid ejected from the nozzle can be increased. Thereby, the inertial mass of the liquid droplet ejected later by the rear side ejection drive pulse can be made larger than the inertial mass of the liquid droplet ejected first by the front side ejection drive pulse. As a result, landing accuracy can be improved while preventing the generation of mist. That is, it is possible to fly stably by increasing the inertial mass, thereby improving the landing accuracy. Further, since the flying speed is slow, tailing of the liquid droplet is suppressed, and furthermore, the tail of the liquid droplet ejected earlier is absorbed by the liquid droplet ejected later, so that generation of mist can be prevented. .

FIG. 3 is a perspective view illustrating a configuration of a printer. FIG. 3 is a cross-sectional view of a main part of the recording head. 2 is a block diagram illustrating an electrical configuration of a printer. FIG. It is a figure explaining the structure of a drive signal. (A)-(d) is a wave form diagram explaining the structure of each drive pulse. It is a schematic diagram explaining the state by which ink is discharged from a nozzle. It is a schematic diagram explaining the state by which ink is discharged from a nozzle. It is a schematic diagram explaining the apparatus structure used in a pulse interval determination process.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments. In the following, an ink jet recording apparatus (hereinafter referred to as a printer) will be described as an example of the liquid ejection apparatus of the present invention.

  FIG. 1 is a perspective view showing the configuration of the printer 1. The printer 1 has a recording head 2 as a liquid ejection head and a carriage 4 to which an ink cartridge 3 is detachably attached, a platen 5 disposed below the recording head 2, and a carriage 4 (recording head 2). ) Is moved back and forth in the paper width direction of the recording paper 6 (a kind of landing object), that is, in the main scanning direction, and a paper feeding mechanism that transports the recording paper 6 in the sub-scanning direction orthogonal to the main scanning direction. 8 and is schematically configured.

  The carriage 4 is attached while being supported by a guide rod 9 installed in the main scanning direction, and is configured to move in the main scanning direction along the guide rod 9 by the operation of the carriage moving mechanism 7. ing. The position of the carriage 4 in the main scanning direction is detected by the linear encoder 10, and the detection signal, that is, the encoder pulse is transmitted to the control unit 41 (see FIG. 3) of the printer controller. Thereby, the control unit 41 can control the recording operation (ejection operation) by the recording head 2 while recognizing the scanning position of the carriage 4 (recording head 2) based on the encoder pulse from the linear encoder 10. .

  A home position serving as a scanning base point is set in an end area outside the recording area within the moving range of the carriage 4 (on the right front side in FIG. 1). A capping member 11 for sealing the nozzle forming surface (nozzle plate 21: see FIG. 2) of the recording head 2 and a wiper member 12 for wiping the nozzle forming surface are disposed at the home position in the present embodiment. Yes. The printer 1 moves forward when the carriage 4 (recording head 2) moves from the home position toward the opposite end, and when the carriage 4 returns from the opposite end to the home position. And so-called bidirectional recording in which characters, images, etc. are recorded on the recording paper 6 in both directions.

  FIG. 2 is a cross-sectional view of an essential part for explaining the configuration of the recording head 2. The recording head 2 includes a case 13, a vibrator unit 14 housed in the case 13, a flow path unit 15 joined to the bottom surface (tip surface) of the case 13, and the like. The case 13 is made of, for example, an epoxy resin, and a housing empty portion 16 for housing the vibrator unit 14 is formed therein. The vibrator unit 14 includes a piezoelectric vibrator 17 that functions as a kind of pressure generating element, a fixing plate 18 to which the piezoelectric vibrator 17 is joined, and a flexible cable 19 for supplying a drive signal and the like to the piezoelectric vibrator 17. And. The piezoelectric vibrator 17 is a laminated type produced by cutting a piezoelectric plate in which piezoelectric layers and electrode layers are alternately laminated into a comb-like shape, and is capable of expanding and contracting in a direction perpendicular to the laminating direction. This is a piezoelectric vibrator.

  The flow path unit 15 is configured by joining a nozzle plate 21 to one surface of the flow path forming substrate 20 and an elastic plate 22 to the other surface of the flow path forming substrate 20. The flow path unit 15 is provided with a reservoir 23, an ink supply port 24, a pressure generation chamber 25, a nozzle communication port 26, and a nozzle 27. A series of ink flow paths from the ink supply port 24 to the nozzle 27 via the pressure generation chamber 25 and the nozzle communication port 26 are formed corresponding to each nozzle 27.

  The nozzle plate 21 is a thin plate made of metal such as stainless steel in which a plurality of nozzles 27 are formed in a row at a pitch (for example, 180 dpi) corresponding to the dot formation density. The nozzle plate 21 is provided with a plurality of nozzles 27 (nozzle rows), and one nozzle row is composed of, for example, 180 nozzles 27. The recording head 2 in the present embodiment has different colors of ink (one type of liquid in the present invention), specifically cyan (C), magenta (M), yellow (Y), and black (K). Four ink cartridges 3 for storing ink of a total of four colors are configured to be mountable, and a total of four nozzle rows are formed on the nozzle plate 21 corresponding to these colors.

  The elastic plate 22 has a double structure in which an elastic film 29 is laminated on the surface of the support plate 28. In the present embodiment, the elastic plate 22 is manufactured using a composite plate material in which a stainless plate, which is a kind of metal plate, is used as the support plate 28 and a resin film is laminated on the surface of the support plate 28 as an elastic film 29. The elastic plate 22 is provided with a diaphragm portion 30 that changes the volume of the pressure generating chamber 25. The elastic plate 22 is provided with a compliance portion 31 that seals a part of the reservoir 23.

  The diaphragm portion 30 is produced by partially removing the support plate 28 by etching or the like. That is, the diaphragm portion 30 includes an island portion 32 to which the tip surface of the piezoelectric vibrator 17 is joined and a thin elastic portion 33 that surrounds the island portion 32. The compliance part 31 is produced by removing the support plate 28 in the region facing the opening surface of the reservoir 23 by etching processing or the like in the same manner as the diaphragm part 30, and reduces the pressure fluctuation of the liquid stored in the reservoir 23. Functions as a damper to absorb.

  Since the tip end surface of the piezoelectric vibrator 17 is joined to the island portion 32, the volume of the pressure generating chamber 25 can be changed by expanding and contracting the free end portion of the piezoelectric vibrator 17. As the volume changes, pressure fluctuations occur in the ink in the pressure generating chamber 25. The recording head 2 ejects ink droplets from the nozzles 27 using this pressure fluctuation.

  FIG. 3 is a block diagram showing an electrical configuration of the printer 1. The printer 1 is schematically composed of a printer controller 35 and a print engine 36. The printer controller 35 includes an external interface (external I / F) 37 for inputting print data from an external device such as a host computer, a RAM 38 for storing various data, a control routine for various data processing, and the like. The stored ROM 39, a control unit 41 for controlling each unit, an oscillation circuit 42 for generating a clock signal, and a drive signal generation circuit 43 for generating a drive signal to be supplied to the recording head 2 (of the drive signal generating means in the present invention) And an internal interface (internal I / F) 45 for outputting pixel data, drive signals, and the like obtained by developing print data for each dot to the recording head 2.

  The control unit 41 outputs a head control signal for controlling the operation of the recording head 2 to the recording head 2 and outputs a control signal for generating the driving signal COM to the driving signal generating circuit 43. The head control signal is, for example, a transfer clock CLK, pixel data SI, a latch signal LAT, a first change signal CH1, and a second change signal CH2. These latch signals and change signals define the supply timing of each pulse constituting the drive signals COM1 and COM2.

  Further, the control unit 41 performs color conversion processing from the RGB color system to the CMY color system, halftone processing for reducing multi-gradation data to a predetermined gradation, and halftoned data based on the print data. The pixel data SI used for the ejection control of the recording head 2 is generated through a dot pattern development process in which the ink patterns (nozzle rows) are arranged in a predetermined arrangement and developed into dot pattern data. This pixel data SI is data relating to pixels of an image to be printed, and is a kind of ejection control information. Here, the pixel indicates a dot formation region that is virtually determined on a recording medium such as a recording paper that is a landing target. The pixel data SI according to the present invention includes gradation data relating to the presence / absence of dots formed on a recording medium (or presence / absence of ink ejection) and the size of dots (or the amount of ink ejected). In the present embodiment, the pixel data SI is composed of binary gradation data having a total of 2 bits. For 2-bit gradation values, [00] corresponding to non-recording (fine vibration) in which ink is not ejected, [01] corresponding to recording of small dots, and [10] corresponding to recording of medium dots. [11] corresponding to large dot recording. Therefore, the printer according to the present embodiment can record with four gradations.

  The drive signal generation circuit 43 is controlled by the control unit 41 and generates various drive signals. FIG. 4 is a diagram for explaining an example of the configuration of the drive signal COM generated by the drive signal generation circuit 43. The first drive signal COM1 is a series of signals having a plurality of middle dot ejection drive pulses DPM (a kind of ejection drive pulse in the present invention) within a unit recording period (ejection period) T, and is repeatedly generated every recording period T. Is done. In the present embodiment, one recording cycle T of the first drive signal COM1 is divided into two pulse generation periods T1 and T2. Then, the first middle dot ejection drive pulse DPM1 is generated in the period T1, and the second middle dot ejection drive pulse DPM2 is generated in the period T2. On the other hand, the second drive signal COM2 is a series of signals having a small ejection drive pulse DPS and a fine vibration pulse DPP within the recording period T. Similarly to the first drive signal COM1, one recording cycle T of the second drive signal COM2 is divided into two pulse generation periods T1 and T2, and the small ejection drive pulse DPS is generated in the period T1, and in the period T2. A fine vibration pulse DPP is generated. That is, the fine vibration pulse DPP (non-ejection drive pulse) is generated in a period corresponding to the generation period of the second middle dot ejection drive pulse DPM2 of the first drive signal COM1.

  Next, the configuration on the print engine 36 side will be described. The print engine 36 includes a recording head 2, a carriage moving mechanism 7, a paper feed mechanism 8, and a linear encoder 10. The recording head 2 includes a plurality of shift registers (SR) 48, latches 49, decoders 50, level shifters (LS) 51, switches 52, and piezoelectric vibrators 17 corresponding to the respective nozzle openings 27. Pixel data (SI) from the printer controller 35 is serially transmitted to the shift register 48 in synchronization with the clock signal (CK) from the oscillation circuit 42.

  A latch 49 is electrically connected to the shift register 48. When a latch signal (LAT) from the printer controller 35 is input to the latch 49, the pixel data of the shift register 48 is latched. The pixel data latched by the latch 49 is input to the decoder 50. The decoder 50 translates 2-bit pixel data to generate pulse selection data. The pulse selection data in this embodiment is generated for each drive signal COM1, COM2. That is, the first pulse selection data corresponding to the first drive signal COM1 is a total of 2 bits of data corresponding to the first middle dot ejection drive pulse DPM1 (period T1) and the second middle dot ejection drive pulse DPM2 (period T2). It is constituted by. The second pulse selection data corresponding to the second drive signal COM2 is composed of data of a total of 2 bits corresponding to the small dot discharge drive pulse DPS (period T1) and the minute vibration pulse DPP (period T2).

  Then, the decoder 50 outputs pulse selection data to the level shifter 51 when receiving the latch signal (LAT) or the channel signal (CH). In this case, the pulse selection data is input to the level shifter 51 in order from the upper bit. The level shifter 51 functions as a voltage amplifier. When the pulse selection data is “1”, the level shifter 51 outputs an electric signal boosted to a voltage capable of driving the switch 52, for example, a voltage of about several tens of volts. The pulse selection data “1” boosted by the level shifter 51 is supplied to the switch 52. Drive signals COM 1 and COM 2 from the drive signal generation circuit 43 are supplied to the input side of the switch 52, and the piezoelectric vibrator 17 is connected to the output side of the switch 52.

The pulse selection data controls the operation of the switch 52, that is, the supply of the ejection pulse in the drive signal to the piezoelectric vibrator 17. For example, during a period in which the pulse selection data input to the switch 52 is “1”, the switch 52 is in a connected state, and the corresponding ejection pulse is supplied to the piezoelectric vibrator 17 and follows the waveform of the ejection pulse. Thus, the potential level of the piezoelectric vibrator 17 changes. On the other hand, during the period when the pulse selection data is “0”, the level shifter 51 does not output an electrical signal for operating the switch 52. For this reason, the switch 52 is disconnected and no ejection pulse is supplied to the piezoelectric vibrator 17.
That is, a part of the first drive signal COM1 and the second drive signal COM2 can be selectively applied to the piezoelectric vibrator 17. In this example, the drive signal COM applied to the piezoelectric vibrator 17 at the start timing of the repetition cycle (recording cycle) T (the latch pulse timing of the latch signal LAT) is changed from the first drive signal COM1 to the second drive signal COM2. Or you can switch to the reverse. Similarly, the timing of the boundary between T1 and T2 in the first drive signal COM1, or the timing of the boundary between T1 and T2 in the second drive signal COM2 (change pulse timing of the first change signal CH1, the second change signal The pulse applied to the piezoelectric vibrator 17 can be switched at the timing of the CH2 change pulse).

Here, each drive pulse included in each drive signal COM1, COM2 generated by the drive signal generation circuit 43 will be described.
First, the middle dot ejection drive pulse DPM1 generated in the period T1 in the first drive signal COM1 will be described. As shown in FIG. 5A, the first middle dot ejection drive pulse DPM1 includes a first expansion element P11 (pressure generation chamber expansion element), a first expansion hold element P12 (expansion maintenance element), and a first contraction. It consists of element P13 (discharge element). The first expansion element P11 is a waveform element that increases the potential with a constant gradient from the reference potential VHB to the first expansion potential VH1, and the first expansion hold element P12 is a waveform element that is constant at the first expansion potential VH1. The first contraction element P13 is a waveform element that lowers the potential with a steep slope from the first expansion potential VH1 to the reference potential VHB.

  When the first middle dot ejection drive pulse DPM1 is supplied to the piezoelectric vibrator 17, first, the piezoelectric vibrator 17 contracts in the longitudinal direction of the element by the first expansion element P11, and the pressure generating chamber 25 is set to the reference potential VHB. It expands from the corresponding reference volume to the expansion volume corresponding to the first expansion potential VH1. 6A and 6B, the ink surface (meniscus) exposed to the nozzle 27 is drawn to the pressure generation chamber 25 side, and the pressure generation chamber 25 has a reservoir 23 side. Ink is supplied through the ink supply port 24. And the expansion state of this pressure generation chamber 25 is maintained over the supply period of the 1st expansion hold element P12. Thereafter, the first contraction element P13 is supplied and the piezoelectric vibrator 17 expands. Due to the expansion of the piezoelectric vibrator 17, the pressure generating chamber 25 is rapidly contracted from the expansion volume to the reference volume corresponding to the reference potential VHB. The ink in the pressure generating chamber 25 is pressurized by the rapid contraction of the pressure generating chamber 25, and the central portion of the meniscus is pushed out to the discharge side as shown in FIG. It is ejected from the nozzle 27 as an ink droplet corresponding to the middle dot.

  Further, as shown in FIG. 5B, the second middle dot ejection drive pulse DPM2 generated in the period T2 in the first drive signal COM1 includes the first expansion element P11, the first expansion hold element P12, The basic configuration is common to the first middle dot ejection drive pulse DPM1, but the generation time (time width) Pw3 of the first contraction element P13 is the first middle dot ejection drive. The difference is that it is set larger than the generation time Pw3 of the first contraction element P13 of the pulse DPM1. Thus, when the second middle dot ejection drive pulse DPM2 is supplied to the piezoelectric vibrator 17, the gradient of the first contraction element P13 becomes gentler than that in the case of the first middle dot ejection drive pulse DPM1, so that the ejection is performed. The flying speed of the ink is reduced.

  Next, the small dot discharge drive pulse DPS generated in the period T1 in the second drive signal COM2 will be described. As shown in FIG. 5C, the small dot discharge driving pulse DPS includes the second expansion element P21, the second expansion hold element P22, the second contraction element P23, the contraction hold element P24, and the third expansion element. P25, 3rd expansion hold element P26, and 3rd contraction element P27 are comprised. The second expansion element P21 is a waveform element that increases the potential from the reference potential VHB to the third expansion potential VH3, and the second expansion hold element P22 is a waveform element that is constant at the third expansion potential VH3. The second contraction element P23 is a waveform element that suddenly decreases the potential from the third expansion potential VH3 to the first intermediate potential VM1, the contraction hold element P24 is a waveform element that is constant at the first intermediate potential VM1, and the third expansion element P25. Is a waveform element that increases the potential from the first intermediate potential VM1 to the second intermediate potential VM2, and the third expansion hold element P26 is a waveform element that is constant at the second intermediate potential VM2. The third contraction element P27 is a waveform element that returns the potential with a constant gradient from the second intermediate potential VM2 to the reference potential VHB.

  When the small dot discharge drive pulse DPS configured in this way is supplied to the piezoelectric vibrator 17, first, the piezoelectric vibrator 17 is rapidly contracted in the longitudinal direction of the element by the second expansion element P21. 32 is displaced away from the pressure generating chamber 25. Due to the displacement of the island portion 32, the pressure generating chamber 25 rapidly expands from the reference volume to the expansion volume corresponding to the third expansion potential VH3. Due to the expansion of the pressure generation chamber 25, a relatively strong negative pressure is generated in the pressure generation chamber 25, the meniscus is drawn into the pressure generation chamber 25 side, and ink is supplied from the reservoir 23 side to the pressure generation chamber 25. The And the expansion state of this pressure generation chamber 25 is maintained over the supply period of the 2nd expansion hold element P22.

  Thereafter, the second contraction element P23 is supplied and the piezoelectric vibrator 17 expands. Due to the extension of the piezoelectric vibrator 17, the island portion 32 is suddenly displaced in the direction approaching the pressure generating chamber 25. Due to the displacement of the island portion 32, the pressure generating chamber 25 is rapidly contracted from the expansion volume to the discharge volume corresponding to the first intermediate potential VM1. The ink in the pressure generation chamber 25 is pressurized by the rapid contraction of the pressure generation chamber 25, and the central portion of the meniscus is pushed out to the ejection side. Subsequently, the contraction hold element P24 is supplied and the discharge volume is maintained for a short time. Subsequently, when the piezoelectric vibrator 17 is contracted by the third expansion element P25, the volume of the pressure generation chamber 25 is slightly expanded again, and after passing through the third expansion hold element P26, the third contraction element P27 causes the piezoelectric vibrator 17 to expand. Elongates, and the volume of the pressure generating chamber 25 rapidly contracts again. During the supply period of the contraction hold element P24 to the third contraction element P27, the central portion of the meniscus is broken halfway, and this part is ejected as an amount of ink corresponding to the small dot.

  FIG. 5D shows the waveform of the minute vibration pulse DPP generated in the period T2 in the second drive signal COM2. The fine vibration pulse DPP includes a fourth expansion element P31, a fourth expansion hold element P32, and a fourth contraction element P33. The fourth expansion element P31 is a waveform element that increases the potential with a relatively gentle constant gradient from the reference potential VHB to the fourth expansion potential VH4, and the fourth expansion hold element P32 has a waveform that is constant at the fourth expansion potential VH4. Is an element. The fourth contraction element P33 is a waveform element that lowers the potential with a relatively gentle constant gradient from the fourth expansion potential VH4 to the reference potential VHB.

  When the micro-vibration pulse DPP configured in this way is supplied to the piezoelectric vibrator 17, first, the piezoelectric vibrator 17 contracts in the longitudinal direction of the element by the fourth expansion element P31, and the pressure generating chamber 25 is set to the reference potential VHB. It expands from the corresponding reference volume to the expansion volume corresponding to the fourth expansion potential VH4. By this expansion, the meniscus is drawn to the pressure generation chamber 25 side. And the expansion state of this pressure generation chamber 25 is maintained over the supply period of the 4th expansion hold element P32. Thereafter, the fourth contraction element P33 is supplied and the piezoelectric vibrator 17 expands. By the expansion of the piezoelectric vibrator 17, the pressure generating chamber 25 is contracted from the expansion volume to the reference volume corresponding to the reference potential VHB. Here, the potential difference from the reference potential VHB to the fourth expansion potential VH4, that is, the driving voltage of the micro-vibration pulse DPP is set to a value sufficiently lower than the driving voltages of the small dot ejection driving pulse DPS and the middle dot ejection driving pulse DPM. Has been. For this reason, when this fine vibration pulse DPP is supplied to the piezoelectric vibrator 17, pressure vibration is generated in the pressure generating chamber 25 to such an extent that ink is not ejected from the nozzle 27.

  Here, as in the case of recording a large dot in the present embodiment, a plurality of ejection driving pulses are sequentially applied to the pressure generating element in one recording period to continuously eject a plurality of droplets from the nozzle. In the case where dots of a predetermined size are formed on a landing object such as recording paper by droplets of pressure, pressure vibration is generated in the pressure generating chamber every time each ejection driving pulse is applied. When the droplet is ejected by the ejection driving pulse, the ejection characteristic varies. For example, when a large dot is formed by applying middle dot ejection drive pulses DPM1 and DPM2 to the piezoelectric vibrator 17 and ejecting ink twice from the nozzle 27 twice to form a large dot, the middle dot ejection drive pulse DPM1 is ejected by the first middle dot ejection drive pulse DPM1. In some cases, the amount of ink droplets to be ejected is different from the appropriate amount of ink ejected second. The amount of the second ink droplet changes according to the interval between these ejection drive pulses.

  In the printer according to the present invention, the first middle dot discharge is performed by setting the interval t between the first middle dot discharge drive pulse DPM1 and the second middle dot discharge drive pulse DPM2 shown in FIG. The weight of the ink droplets ejected by the second middle dot ejection drive pulse DPM2 is made larger than the weight of the ink droplets ejected by the drive pulse DPM1. More specifically, the meniscus moves from the discharge side to the pressure generation chamber 25 side due to residual vibration after ink is discharged by the first middle dot discharge drive pulse DPM1 which is the discharge drive pulse on the front side in terms of time. At the time (FIG. 7A), the first expansion element P11 of the second middle dot ejection drive pulse DPM2 which is the rear ejection drive pulse is continuously applied before and after these so as to be applied to the piezoelectric vibrator 17. An interval t between the ejection drive pulses DPM1 and DPM2 is set. That is, the residual vibration after the ink is ejected by the first middle dot ejection drive pulse DPM1 and the first expansion element P11 of the second middle dot ejection drive pulse DPM2 are applied to the piezoelectric vibrator 17, thereby The interval t is set so that the pressure vibration generated in the ink of the ink has the same phase. More specifically, it is desirable to set t to an integral multiple of Tc / 2 (or a value close thereto), where Tc is the natural period of pressure vibration generated in the pressure generation chamber 25.

  As a result, as shown in FIG. 7B, the amount of meniscus pull-in when the first contraction element P13 is applied to the piezoelectric vibrator 17 is made larger than that in the case of the first middle dot ejection drive pulse DPM1. be able to. When the pressure generating chamber 25 is contracted by the first contraction element P13 in a state where the meniscus is largely drawn in this way, as shown in FIG. 7C, more ink can be pushed out using the reaction. As a result, as shown in FIG. 7D, the amount of the ink droplet (D2) ejected from the nozzle 27 is larger than the amount of the ink droplet (D1) ejected by the first middle dot ejection driving pulse DPM1. It becomes possible to make it. The reason why the amount of ink droplets ejected by the second middle dot ejection drive pulse DPM2 is made larger than the amount of ink droplets ejected by the first middle dot ejection drive pulse DPM1 will be described later. Although it is most desirable that the vibrations have the same phase, as a result, the amount of meniscus pull-in when the first contraction element P13 is applied to the piezoelectric vibrator 17 is the first middle dot ejection drive pulse. It may be larger than in the case of DPM1, and a slight shift in phase (application timing of the first expansion element P11 of the second middle dot ejection drive pulse DPM2) is allowed. That is, it is allowed that the phase shifts within a range in which vibrations strengthen each other.

  The appropriate value of the interval t between these ejection drive pulses DPM1 and DPM2 is determined at the manufacturing stage of the recording head 2, and the appropriate value is stored in the storage means of the recording head 2. Then, the drive signal generation circuit 43 reads an appropriate value stored in the storage means, and an interval t between the first middle dot ejection drive pulse DPM1 and the second middle dot ejection drive pulse DPM2 of the first drive signal COM1. Is set to the read appropriate value.

The pulse interval determination process will be described below with reference to FIG.
This figure illustrates the apparatus configuration used in the pulse interval determination process. The pulse interval determination process in the present embodiment is performed using the control device 51 and the ink weight sensor 52. The control device 51 stores an interface unit (I / F) 53 that inputs and outputs signals from the recording head 2 and the ink weight sensor 52, a drive signal generation circuit 54 that can generate a drive signal, and various data. A nonvolatile memory element 55 (for example, a flash memory), a ROM, a RAM, a CPU, and the like, and a main control unit 56 that controls each unit are included.

  The drive signal generation circuit 54 generates the first drive signal COM1 in FIG. 4 under the control of the main control unit 56 and supplies it to the recording head 2 through the I / F unit 53. The interval t between the first middle dot ejection drive pulse DPM1 and the second middle dot ejection drive pulse DPM2 generated by the drive signal generation circuit 54 can be changed within a predetermined range.

  The ink weight sensor 52 is electrically connected to the main control unit 56 via the I / F unit 53, acquires the weight of ink ejected from the nozzles 27 of the recording head 2, and is used as ejection amount information. It transmits to the control part 56. As the ink weight sensor 52, for example, a sensor that can accurately measure the weight in milligram units is used. A control signal from the main control unit 56 is input to the ink weight sensor 52, and the measured weight when the start signal indicating the start of measurement is received and the measured weight when the end signal indicating the end of measurement are received, respectively. Output to the main control unit 56. In the present embodiment, the ink weight sensor 52 is mounted with a petri dish (a tray) 52 'for collecting ink droplets ejected from the recording head 2, and the petri dish 52' has a collecting oil. Reserved. That is, the recording head 2 ejects ink droplets toward the collecting oil in the petri dish 52 '. The ink weight sensor 52 and the main control unit 56 function as an ejection amount measuring unit that measures the amount of ink droplets ejected from the recording head 2 (ejection amount).

  In the pulse interval determination step, first, the ejection amount of ink droplets (ink droplets corresponding to middle dots) when the first middle dot ejection driving pulse DPM1 is supplied alone to the piezoelectric vibrator 17 of the recording head 2 is measured. At this time, the main control unit 56 (control unit) transmits a start signal to the ink weight sensor 52 immediately before ink droplet ejection. In response to the reception of the start signal, the ink weight sensor 52 transmits the weight information (the weight of the petri dish or oil) at the time of signal reception to the main control unit 56 as the start time weight information. The main control unit 56 controls the drive signal generation circuit 54 and the electric drive system (not shown) of the recording head 2, and repeats only the first middle dot ejection drive pulse DPM1 in the first drive signal COM1 a predetermined number of times. It supplies to each piezoelectric vibrator 17 which comprises a row | line | column. As a result, ink droplets are ejected from each nozzle 27 toward the collecting oil in the petri dish 52 'by the number corresponding to the number of times of supply of the first middle dot ejection drive pulse DPM1. If the first measurement drive pulse DP <b> 1 is supplied a predetermined number of times, the main control unit 56 transmits an end signal to the ink weight sensor 52. Upon receiving this end signal, the ink weight sensor 52 transmits weight information at the time of signal reception to the main controller 56 as end-time weight information. The main control unit 56 calculates the ink droplet ejection amount from the difference between the end-time weight information and the start-time weight information and sets it as the first ejection amount Wt1.

If the discharge amount by the first middle dot discharge drive pulse DPM1 is measured, the main control unit 56 performs the same procedure in the first middle dot discharge drive pulse DPM1 and the second middle dot discharge drive pulse in the first drive signal COM1. By repeatedly applying both the DPM 2 and each piezoelectric vibrator 17, ink droplets corresponding to large dots are ejected from the nozzles 27 constituting the nozzle row, and the ejection amount is measured by the ink weight sensor 52. This is the second discharge amount Wt2.

  Subsequently, the main control unit 56 determines whether or not the measured second discharge amount Wt2 is a value larger than twice the first discharge amount Wt1. That is, it is determined whether or not the ink droplet amount Wt2 ejected by the second middle dot ejection drive pulse DPM2 is larger than the ink droplet amount Wt1 ejected by the first middle dot ejection drive pulse DPM1. For this determination, any predetermined threshold value can be used. When Wt2 is smaller than Wt1, after changing the interval t between the first middle dot ejection drive pulse DPM1 and the second middle dot ejection drive pulse DPM2, the process of obtaining the second ejection amount Wt2 is performed again. Note that the interval t is changed within a range in which there is no practical problem, and is gradually increased from the minimum value of the range. When Wt2 becomes larger than Wt1, the interval t between the first middle dot ejection drive pulse DPM1 and the second middle dot ejection drive pulse DPM2 at this time is adopted as an appropriate value. As an appropriate value of the interval t, a storage means of the recording head 2 as drive pulse setting information, for example, a storage element that electrically stores information such as a ROM, or a non-electric information storage medium such as a two-dimensional code is adopted. (Both not shown). This appropriate value may be determined for each nozzle row, or may be determined as a value common to a plurality of nozzle rows.

  Through such a process, an appropriate value of the interval t between the first middle dot ejection drive pulse DPM1 and the second middle dot ejection drive pulse DPM2 is set, and this appropriate value is stored in the recording head 2 as drive pulse setting information. In the printer in which the recording head 2 is stored, the interval t between the adjacent ejection drive pulses is set based on the drive pulse setting information stored in the storage means. A drive signal can be generated.

  Next, a case where the pixel data SI is data [11] in the above configuration will be described. In this case, in this embodiment, the pulse selection data corresponding to the first drive signal COM1 is [11], and the pulse selection data corresponding to the second drive signal COM2 is [00]. Accordingly, as shown in FIG. 4, the first middle dot ejection drive pulse DPM1 of the first drive signal COM1 is piezoelectric in the period T1, and the second middle dot ejection drive pulse DPM2 of the first drive signal COM1 is piezoelectric in the period T2. It is applied to the vibrator 17 in this order. On the other hand, in this case, none of the drive pulses of the second drive signal COM2 is applied to the piezoelectric vibrator 17. As a result, in the recording cycle T, the amount of ink corresponding to the medium dots is continuously ejected twice from the nozzles 27, and these inks land on the pixel area on the landing target to form large dots. The

  Here, since the interval t between the first middle dot ejection drive pulse DPM1 and the second middle dot ejection drive pulse DPM2 is set through the above-described process, as shown in FIG. 7D, the first middle dot ejection drive pulse DPM1 is set. The weight (inertia mass) of the ink droplet D2 ejected later by the second middle dot ejection drive pulse DPM2 is larger than the weight (inertia mass) of the ink droplet D1 ejected earlier by the ejection drive pulse DPM1. . Further, the generation time (time width) Pw3 of the first contraction element P13 of the second middle dot ejection drive pulse DPM2 is set to be greater than the generation time Pw3 of the first contraction element P13 of the first middle dot ejection drive pulse DPM1. Therefore, the flying speed Vm2 of the ink droplet D2 is lower than the flying speed Vm1 of the ink droplet D1. If the flying speed is slow, the ink droplet D2 tends to be mist easily because it tends to be subject to air resistance and other disturbances before landing on a landing object such as recording paper. However, the ink droplet D2 is ejected first. Since the inertial mass is larger than the inertial mass of the ink droplet D1, the influence of the disturbance is less likely to occur, and the flight is stabilized, thereby improving the landing accuracy. In addition, since the flying speed is slow, it is possible to prevent the trailing end of the ink droplet D2 from extending like a tail (tailing), thereby preventing the occurrence of mist. The ink droplet D2 is landed on the pixel area on the landing target while absorbing the tail of the preceding ink droplet D1 by surface tension, and a large dot is formed by these ink droplets D1 and D2.

  When the pixel data SI is data [10], in this embodiment, the pulse selection data corresponding to the first drive signal COM1 is [10], and the pulse selection data corresponding to the second drive signal COM2 is [01]. Is done. As a result, as shown in FIG. 4, the first middle dot ejection drive pulse DPM1 of the first drive signal COM1 is applied to the piezoelectric vibrator 17 during the period T1, and the fine vibration pulse DPP of the second drive signal COM2 is applied to the piezoelectric vibrator 17 during the period T2. Sequentially applied. As a result, an amount of ink corresponding to the medium dot is ejected once from the nozzle 27 in the recording cycle T, and the medium dot is formed by landing on the pixel area on the landing target. Then, after the ink is ejected by the first middle dot ejection drive pulse DPM1, the meniscus of the nozzle 27 is quickly drawn to the pressure generating chamber 25 side by the fourth expansion element P31 of the minute vibration pulse DPP. Thereby, the trailing of the ink ejected by the first middle dot ejection drive pulse DPM1 is reduced.

  Next, when the pixel data SI is data [01], in this embodiment, the pulse selection data corresponding to the first drive signal COM1 is [00], and the pulse selection data corresponding to the second drive signal COM2 is [ 11]. As a result, as shown in FIG. 4, the small dot ejection drive pulse DPS of the second drive signal COM2 is sequentially applied to the piezoelectric vibrator 17 in the period T1, and the fine vibration pulse DPP of the second drive signal COM2 is sequentially applied to the piezoelectric vibrator 17 in the period T2. Is done. As a result, an amount of ink corresponding to the small dots is ejected once from the nozzles 27 in the recording cycle T, and land on the pixel area on the landing target to form small dots. Also in this case, after the ink is ejected by the small dot ejection driving pulse DPS, the meniscus of the nozzle 27 is quickly drawn to the pressure generating chamber 25 side by the fourth expansion element P31 of the minute vibration pulse DPP. Thereby, the tailing of the ink ejected by the small dot ejection driving pulse DPS is reduced.

  In the case of non-printing in which ink is not ejected from the nozzles 27, that is, when the pixel data SI is data [00], in this embodiment, the pulse selection data corresponding to the first drive signal COM1 is set to [00]. The pulse selection data corresponding to the second drive signal COM2 is set to [01]. As a result, as shown in FIG. 4, no pulse is applied to the piezoelectric vibrator 17 in the period T1, and the fine vibration pulse DPP of the second drive signal COM2 is applied to the piezoelectric vibrator 17 in the period T2. . As a result, pressure vibration is applied to the nozzle 27 so that no ink is ejected in the recording period T, and the ink in the vicinity of the nozzle 27 is agitated to prevent the ink from thickening.

As described above, by setting the interval t between the ejection drive pulses, a plurality of ejection drive pulses (middle dot ejection drive pulses DPM1, DPM2) for forming a prescribed dot (in this embodiment, a large dot). Among them, the residual vibration after ink is ejected by the first middle dot ejection drive pulse DPM1 which is temporally the front ejection drive pulse and the second middle dot ejection drive pulse DPM2 which is the rear ejection drive pulse. When the first expansion element P <b> 11 is applied to the piezoelectric vibrator 17, the pressure vibration generated in the ink in the pressure generating chamber strengthens each other, whereby the first contraction element P <b> 13 is applied to the piezoelectric vibrator 17. The amount of meniscus pulling in can be made larger than in the case of the first middle dot ejection drive pulse DPM1. Therefore, the weight (inertia mass) of the ink droplet D2 ejected later by the second middle dot ejection drive pulse DPM2 can be made larger than the weight (inertia mass) of the ink droplet D1 ejected earlier, Thereby, landing precision can be improved, preventing generation | occurrence | production of mist. As a result, it is possible to prevent deterioration of the image quality of the recorded image or the like. In particular, it is suitable for a configuration that discharges a high-viscosity liquid such as UV ink (ultraviolet curable ink) that tends to cause tailing.
Further, the weight of the ink droplet D2 ejected by the second middle dot ejection drive pulse DPM2 can be increased by utilizing the reaction of the residual vibration after the ink is ejected by the first middle dot ejection drive pulse DPM1. It is not necessary to increase the drive voltage of the second middle dot ejection drive pulse DPM2, which can contribute to power saving.

  Further, in the above embodiment, the ejection applied to the piezoelectric vibrator at the rearmost side of the ejection drive pulses (DPM1, DPM2) of the first drive signal COM1 for forming a medium dot, which is a kind of specified dot. The micro-vibration pulse DPP as the non-ejection drive pulse of the second drive signal COM2 is generated in the period T2 corresponding to the generation period of the second middle dot ejection drive pulse DPM2 that is the drive pulse. When forming a medium dot, tailing of the ink after ejection can be reduced by the fine vibration pulse DPP. When forming a large dot, an ink droplet having a large inertial mass is ejected by the second middle dot ejection drive pulse DPM2. The tailing can be reduced. For this reason, it is not necessary to use the fine vibration pulse DPP when forming a large dot, that is, since it is not necessary to include the fine vibration pulse DPP in the first drive signal COM1, the discharge cycle can be shortened accordingly. Thereby, a drive frequency can be raised.

  By the way, the present invention is not limited to the above-described embodiment, and various modifications can be made based on the description of the scope of claims.

The waveform configuration of each drive pulse of each drive signal COM1, COM2 is not limited to that exemplified in the above embodiment, and the present invention can use drive pulses having various waveforms.
In the above embodiment, the configuration using the two middle dot ejection drive pulses DPM1 and DPM2 of the first drive signal COM1 is illustrated when large dots are formed. However, the present invention is not limited to this. For example, three or more The present invention can also be applied to a configuration in which large dots are formed using middle dot ejection drive pulses. In this case, in particular, it is desirable to determine the interval between the ejection drive pulses so that the inertial mass of the ink droplet ejected by the middle dot ejection drive pulse applied to the piezoelectric vibrator 17 last is maximized.
Furthermore, not only when forming large dots, but also when forming medium dots and small dots, it is possible to adopt a configuration using a plurality of drive pulses. That is, for example, even in a configuration in which medium dots are formed by a plurality of small dot ejection drive pulses, the smaller dot ejection drive pulses applied to the piezoelectric vibrator 17 on the rear side are applied to the piezoelectric vibrator 17 on the front side. By setting the interval between the drive pulses so that the inertial mass of the ink droplet is larger than that of the small dot ejection drive pulse, it is possible to obtain the same effect as the above embodiment.

  Furthermore, in the above embodiment, as shown in FIG. 4, the interval between the first middle dot ejection drive pulse DPM1 and the second middle dot ejection drive pulse DPM2 is the interval between the respective start ends (start ends of the first expansion elements P11). Although an example of t is shown, the present invention is not limited to this. For example, as indicated by t ′ in FIG. 4, from the end of the first middle dot discharge drive pulse DPM1 (first contraction element P13) to the start of the second middle dot discharge drive pulse DPM2 (start of the first expansion element P11). May be set by the method described above.

  In each of the above-described embodiments, the so-called longitudinal vibration type piezoelectric vibrator 17 is exemplified as the pressure generating element. However, the pressure generation element is not limited thereto, and for example, a so-called flexural vibration type piezoelectric element can be employed. . In this case, the illustrated drive signal has a waveform in which the potential change direction, that is, the top and bottom are inverted.

  The present invention is not limited to a printer as long as it is a liquid ejection device that can perform ejection control using a plurality of drive signals, and other than various ink jet recording devices such as plotters, facsimile devices, copiers, and recording devices. The present invention can also be applied to a liquid ejecting apparatus such as a display manufacturing apparatus, an electrode manufacturing apparatus, and a chip manufacturing apparatus.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Recording head, 17 ... Piezoelectric vibrator, 25 ... Pressure generating chamber, 27 ... Nozzle, 41 ... Control part, 43 ... Drive signal generation circuit

Claims (2)

A liquid discharge head having a nozzle, a pressure generation chamber communicating with the nozzle, and a pressure generation element that causes a pressure variation in the liquid in the pressure generation chamber, and capable of discharging liquid from the nozzle by the operation of the pressure generation element; ,
Drive signal generating means for repeatedly generating a drive signal including a plurality of ejection drive pulses for driving the pressure generating element to eject liquid from the nozzle;
A liquid ejecting apparatus that forms a prescribed dot on an impact target by sequentially applying a plurality of ejection drive pulses included in the drive signal to the pressure generating element sequentially,
Each of the ejection drive pulses is a pulse waveform starting from a pressure generation chamber expansion element that expands the pressure generation chamber and draws a meniscus,
Residual vibration when liquid is discharged by the front discharge drive pulse, and pressure vibration generated in the liquid in the pressure generation chamber by applying the pressure generation chamber expansion element of the rear discharge drive pulse to the pressure generation element. A liquid ejection apparatus in which an interval between ejection drive pulses that are continuous in the front and rear is set so that the two have the same phase. A liquid discharge head having a nozzle, a pressure generation chamber communicating with the nozzle, and a pressure generation element that causes a pressure variation in the liquid in the pressure generation chamber, and capable of discharging liquid from the nozzle by the operation of the pressure generation element; Drive signal generating means for repeatedly generating a drive signal including a plurality of discharge drive pulses for driving the pressure generating element to discharge the liquid from the nozzle, and a plurality of discharge drive pulses included in the drive signal are continuously generated. A method for controlling a liquid ejection device that forms prescribed dots on an impact target by sequentially applying pressure generating elements,
Each of the ejection drive pulses is a pulse waveform starting from a pressure generation chamber expansion element that expands the pressure generation chamber and draws a meniscus,
Residual vibration when liquid is discharged by the front discharge drive pulse, and pressure vibration generated in the liquid in the pressure generation chamber by applying the pressure generation chamber expansion element of the rear discharge drive pulse to the pressure generation element. A method for controlling a liquid ejection apparatus, wherein an interval between ejection drive pulses that are continuous in the front and rear is set so that the two have the same phase.

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