JP2010162827A - Driving signal setting method for liquid ejection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving signal setting method for a liquid ejection device, capable of stably ejecting liquid without reducing a driving frequency. <P>SOLUTION: In the constitution where ink is ejected from a nozzle 28 with a first ejection pulse, thereafter, ink is ejected with a second ejection pulse, regarding a recording head having a natural vibration period where the position of residual vibration of meniscus with the first ejection pulse at a point of time equivalent to a timing Dt to start the ink ejecting operation with the second ejection pulse is located closer to an ejection side than that of a reference recording head, the intermediate potential is set so that a potential difference of a damping element p5 becomes higher than the reference one. On the other hand, regarding the recording head having a natural vibration period where the position of residual vibration of meniscus with the first ejection pulse at the point of time equivalent to the timing to start the ink ejecting operation with the second ejection pulse is located closer to a pressure generation chamber side than that of the reference recording head, the intermediate potential is set so that the potential difference of the damping element p5 becomes lower than the reference one. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a drive signal setting method for a liquid discharge apparatus such as an ink jet printer, and in particular, a liquid discharge apparatus capable of controlling liquid discharge by applying a discharge pulse included in the drive signal to a pressure generating element. This relates to a driving signal setting method.

  For example, a liquid ejection apparatus is an apparatus that includes a liquid ejection head capable of ejecting liquid from a nozzle 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 this image recording apparatus but also to various manufacturing apparatuses such as a manufacturing apparatus for a color filter such as a liquid crystal display.

  Here, taking the above ink jet printer (hereinafter simply abbreviated as a printer) as an example, this printer is a series of ink flow paths from a common ink chamber (reservoir) to a nozzle through a pressure generating chamber, and pressure generation. Mounted with a recording head having a pressure generating element (for example, a piezoelectric element) for changing the volume of the chamber, and a driving signal generating circuit (driving signal generating means) for generating a driving signal to be supplied to the pressure generating element I have. The discharge pulse included in the drive signal from the drive signal generation circuit is applied to the piezoelectric element to cause pressure fluctuation in the ink in the pressure generating chamber, and the ink is ejected from the nozzle using this pressure fluctuation. Has been. Along with this pressure fluctuation, the ink in the pressure generating chamber is excited by a pressure vibration having a Helmholtz frequency that behaves as if the pressure generating chamber is an acoustic tube. Hereinafter, the vibration period of the pressure vibration is expressed as a natural vibration period Tc.

  By the way, after ink discharge, residual vibration of ink (particularly meniscus) in the pressure generating chamber becomes a problem. That is, this residual vibration may adversely affect the next ink ejection operation. In particular, when a very small (for example, several pl) ink is continuously ejected as the recording speed increases and the resolution of the recorded image increases, it is desirable to suppress the residual vibration as much as possible. It is. For this reason, in the ejection pulse, a damping element is generated after the waveform element for ejecting ink (a damping process), and a counter vibration having a phase different from the residual vibration is generated by the damping element. Thus, residual vibration is reduced (for example, see Patent Document 1).

JP 2008-114502 A

  The natural vibration period Tc is individually determined according to the size of the ink flow path in the head including the pressure generation chamber. Even among the same type of recording heads, the natural vibration period Tc differs due to a dimensional error or the like. Therefore, if the drive signal is set uniformly for all the recording heads, the ejection characteristics may differ from head to head. For example, when an ejection pulse designed based on a predetermined natural vibration period Tc (reference value) is used, after ejecting ink with a front ejection pulse, and subsequently ejecting ink with a rear ejection pulse, If the actual natural vibration period deviates from the reference value, the state of the meniscus at the time of ejection will be different, the ink flying speed will vary, the landing position will become unstable, and the weight of the ejected ink will vary There is a problem that the discharge is not stable, such as.

  For this reason, in order to solve the above problem, it is conceivable to change the timing of applying the damping element in accordance with the natural vibration period Tc of each recording head. In other words, the damping element is applied at the timing of canceling the residual vibration by adjusting the interval (damping hold element) from the end of the discharge element to the start of the damping element. However, for example, when the interval is increased, there is a problem in that the ejection cycle is increased as a whole, and the drive frequency is lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a drive signal setting method for a liquid discharge apparatus capable of stabilizing liquid discharge without reducing the drive frequency. There is.

The present invention has been proposed to achieve the above object, and a liquid discharge head capable of discharging liquid from the nozzle by driving a pressure generating element that varies the volume of a pressure generating chamber communicating with the nozzle. A drive signal setting method for a liquid ejection device, comprising: a drive signal generation unit that generates a drive signal including a discharge pulse for driving the pressure generating element to discharge liquid;
The discharge pulse changes from an intermediate potential to expand the pressure generating chamber, the discharge element that contracts the pressure generating chamber expanded by the expansion element and discharges the liquid, and returns the potential to the intermediate potential. And at least a damping element that suppresses residual vibration of the liquid after ejection,
The intermediate potential is determined based on the natural vibration period Tc of the liquid in the pressure generating chamber.

  In the above configuration, in the configuration in which the liquid is discharged by the second discharge pulse after the liquid is discharged from the nozzle by the first discharge pulse, the second time at the time corresponding to the liquid discharge operation start timing by the second discharge pulse. For a liquid discharge head having a natural vibration period in which the position of the residual vibration of the meniscus by one discharge pulse is on the discharge side compared to a liquid discharge head having a reference natural vibration period, the potential difference of the damping element is higher than the reference. While the intermediate potential is set to be high, the position of the residual vibration of the meniscus by the first ejection pulse at the time corresponding to the liquid ejection operation start timing by the second ejection pulse is the liquid ejection head having the reference natural vibration period. In comparison, the liquid discharge head having the natural vibration period on the pressure generation chamber side is based on the potential difference of the damping element. It is desirable to adopt a configuration for setting the intermediate potential to be lower than.

  According to the present invention, the intermediate potential is set in accordance with the natural vibration period of the liquid discharge head, so that the liquid is discharged by the second discharge pulse after the liquid is discharged from the nozzle by the first discharge pulse. The meniscus state at the liquid discharge operation start timing by the second discharge pulse can be made uniform regardless of the natural vibration period. This makes it possible to stabilize the liquid ejection without reducing the drive frequency.

FIG. 2 is a block diagram illustrating an electrical configuration of an ink jet printer. It is a wave form diagram explaining the structure of a drive signal. FIG. 3 is a cross-sectional view of a main part of the recording head. It is a schematic diagram explaining the residual vibration which arises in a pressure generation chamber when ink is ejected by an ejection pulse. It is a schematic diagram explaining the residual vibration after correcting the intermediate potential.

  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 block diagram illustrating the electrical configuration of the printer. The illustrated printer includes a printer controller 1 and a print engine 2. The printer controller 1 includes an external interface (external I / F) 3 that transmits / receives data to / from an external device such as a host computer (not shown), a RAM 4 that stores various data, and controls for various data processing. ROM 5 storing programs and the like, a control unit 6 including a CPU, an oscillation circuit 7 that generates a clock signal, a drive signal generation circuit 9 that generates a drive signal COM to be supplied to the recording head 8, pixel data SI and An internal interface 10 (internal I / F 10) for transmitting drive signals and the like to the print engine 2 is provided.

  The external I / F 3 receives print data such as image data from a host computer or the like. Further, the external I / F 3 outputs status signals such as a busy signal and an acknowledge signal to the external device. The RAM 4 is used as a reception buffer, an intermediate buffer, an output buffer, a work memory, and the like. The ROM 5 stores various control programs executed by the control unit 6, font data and graphic functions, various procedures, and the like. The print data includes various command data in addition to image data to be printed. The command data is data for instructing the printer to execute a specific operation. The command data includes, for example, command data for instructing paper feed, command data for indicating the carry amount, and command data for instructing paper discharge.

  The control unit 6 outputs a head control signal for controlling the operation of the recording head 8 to the recording head 8 and outputs a control signal for generating the driving signal COM to the driving signal generation circuit 9. The head control signal is, for example, a transfer clock CLK, pixel data SI, a latch signal LAT, and a change signal CH. These latch signals and change signals define the supply timing of each drive pulse constituting the drive signal COM. The control signal for generating the drive signal COM is, for example, a DAC (Digital to Analog Converter) value. This DAC value is information for instructing the voltage to be output from the drive signal generation circuit 9, and is updated every extremely short update cycle.

  Further, the control unit 6 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. Pixel data (dot pattern data) SI used to control the ejection of the recording head 8 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 in the print data includes data (tone values) relating to the presence / absence of dots formed on the paper (or presence / absence of ink ejection) and the size of the dots (or the amount of ink ejected). . In the present embodiment, the pixel data SI is composed of 2-bit gradation values. That is, the pixel data SI includes data [00] corresponding to no dot (fine vibration), data [01] corresponding to small dots, data [10] corresponding to formation of medium dots, and large dots. There is data [11] corresponding to. Therefore, this printer in this embodiment can form dots with four gradations.

  FIG. 2 is a diagram for explaining an example of the configuration of the drive signal COM generated by the drive signal generation circuit 9. The drive signal COM is a series of signals having one fine vibration pulse and four ejection pulses within a predetermined generation period (recording period) T, and is repeatedly generated at the recording period T. In the present embodiment, one recording cycle T of the drive signal COM is divided into five periods (pulse generation periods) t1 to t5. Then, the first ejection pulse P11 is generated in the period t1, the second ejection pulse P12 is generated in the period t2, the micro-vibration pulse VP is generated in the period t3, the third ejection pulse P13 is generated in the period t4, and the period At t5, the fourth ejection pulse P14 is generated.

  Next, the print engine 2 will be described. As shown in FIG. 1, the print engine 2 includes a recording head 8, a carriage moving mechanism 44, a paper feeding mechanism 45, a linear encoder 46, and the like. The carriage moving mechanism 44 includes a carriage to which a recording head 8 that is a kind of liquid ejection head is attached, a drive motor (for example, a DC motor) that travels the carriage via a timing belt or the like (both shown in the figure). The recording head 8 mounted on the carriage is moved in the main scanning direction. The paper feed mechanism 45 includes a paper feed motor, a paper feed roller, and the like, and sequentially feeds recording paper (one type of recording medium and one type of landing target) onto the platen to perform sub-scanning. The linear encoder 46 outputs an encoder pulse corresponding to the scanning position of the recording head 8 mounted on the carriage to the control unit 6 through the internal I / F 10 as position information in the main scanning direction. The control unit 6 can grasp the scanning position (current position) of the recording head 8 based on the encoder pulse received from the linear encoder 46 side.

  As shown in FIG. 3, the recording head 8 is composed of a pressure generating unit 15 and a flow path unit 16, which are integrated in a superposed state. The pressure generation unit 15 includes a pressure generation chamber plate 18 for partitioning the pressure generation chamber 17, a communication port plate 19 having a supply side communication port 22 and a first communication port 24a, and a diaphragm on which the piezoelectric element 20 is mounted. 21 are laminated and integrated by firing or the like. The flow path unit 16 includes a supply port plate 25 having a supply port 23 and a second communication port 24b, a reservoir plate 27 having a reservoir 26 and a third communication port 24c, and a nozzle plate having a nozzle 28 formed therein. It is comprised by adhere | attaching the plate member which consists of 29 in a laminated state.

  A plurality of piezoelectric elements 20 are disposed on the outer surface of the diaphragm 21 on the side opposite to the pressure generation chambers 17 in a state corresponding to the pressure generation chambers 17. The illustrated piezoelectric element 20 is a vibrator in a flexural vibration mode, and is configured with a piezoelectric body 20c sandwiched between a drive electrode 20a and a common electrode 20b. When a drive signal (drive pulse) is applied to the drive electrode of the piezoelectric element 20, an electric field corresponding to the potential difference is generated between the drive electrode 20a and the common electrode 20b. This electric field is applied to the piezoelectric body 20c, and deforms according to the strength of the electric field applied with the piezoelectric body 20c. That is, as the potential of the drive electrode 20a is increased, the piezoelectric layer 20c contracts in a direction orthogonal to the electric field, and the diaphragm 21 is deformed so that the volume of the pressure generating chamber 17 is reduced.

  Next, the electrical configuration of the recording head 8 will be described. As shown in FIG. 1, the recording head 8 includes a shift register (SR) circuit including a first shift register 33 and a second shift register 34, and a latch circuit including a first latch circuit 35 and a second latch circuit 36. A decoder 37, a control logic 38, a level shifter 39, a switch 41, and the piezoelectric element 20. Each shift register 33, 34, each latch circuit 35, 36, level shifter 39, switch 41, and piezoelectric element 20 are provided in a number corresponding to each nozzle 28. In FIG. 2, only the configuration for one nozzle is shown, and the configuration for the other nozzles is omitted.

  The recording head 8 performs ink ejection control based on the pixel data SI sent from the printer controller 1. In this embodiment, since the upper bit group of the pixel data SI composed of 2 bits and the lower bit group of the pixel data SI are sent in order to the recording head 8 in synchronization with the clock signal CLK, first, the pixel data SI Are set in the second shift register 34. When the upper bit group of the pixel data SI is set in the second shift register 34 for all the nozzles 28, the upper bit group is then shifted to the first shift register 33. At the same time, the lower bit group of the pixel data SI is set in the second shift register 34.

  A first latch circuit 35 is connected to the subsequent stage of the first shift register 33, and a second latch circuit 36 is connected to the subsequent stage of the second shift register 34. When a latch pulse from the printer controller 1 side is input to the latch circuits 35 and 36, the first latch circuit 35 latches the upper bit group of the pixel data SI, and the second latch circuit 36 stores the pixel data SI. Latch the lower bit group. The pixel data SI (upper bit group, lower bit group) latched by the latch circuits 35 and 36 is output to the decoder 37, respectively. The decoder 37 generates pulse selection data for selecting each pulse constituting the drive signal COM based on the upper bit group and the lower bit group of the pixel data SI. For example, in the case of the drive signal COM in FIG. 2, the pulse selection data includes the first ejection pulse P11 (period t1), the second ejection pulse P12 (period t2), the micro-vibration pulse VP (period t3), and the third ejection pulse. It is composed of data of a total of 5 bits corresponding to P13 (period t4) and the fourth ejection pulse P14 (period t5).

  A timing signal from the control logic 38 is also input to the decoder 37. The control logic 38 generates a timing signal in synchronization with the input of a latch signal or a channel signal. Each pulse selection data generated by the decoder 37 is sequentially input to the level shifter 39 from the upper bit side at the timing defined by the timing signal. The level shifter 39 functions as a voltage amplifier. When the pulse selection data is [1], the level shifter 39 outputs an electric signal boosted to a voltage capable of driving the switch 41, for example, a voltage of about several tens of volts.

  A drive signal COM from the drive signal generation circuit 9 is supplied to the input side of the switch 41. The piezoelectric element 20 is connected to the output side of the switch 41. That is, the switch 41 is configured to switch between supply and non-supply of the drive signal COM to the piezoelectric element 20. The switch 41 that operates in this manner functions as a selection supply unit. The pulse selection data controls the operation of the switch 41. That is, during the period when the pulse selection data input to the switch 41 is [1], the switch 41 is in a conductive state, and the drive signal COM is supplied to the piezoelectric element 20. On the other hand, while the pulse selection data input to the switch 41 is [0], the switch 41 is in a disconnected state, and no drive signal is supplied to the piezoelectric element 20. In short, a pulse in a period in which [1] is set as pulse selection data is selectively supplied to the piezoelectric element 20. By such switch control, the ejection pulse included in the drive signal COM can be applied to the piezoelectric element 20. That is, a part of the drive signal COM can be selectively applied to the piezoelectric element 20. In this example, the piezoelectric element 20 is at the boundary timing (change pulse timing of the change signal CH) between t1 and t5 after the start timing (latching pulse timing of the latch signal LAT) of the repetition cycle (recording cycle) T. The pulse to be applied to can be switched.

  Each discharge pulse P11 to P14 included in the drive signal COM includes an expansion element p1, an expansion hold element p2 (expansion maintaining element), a contraction element p3 (discharge element), a vibration suppression hold element p4, and a vibration suppression element p5. It consists of. The expansion element p1 has a relatively gentle constant gradient that does not cause ink to be ejected from the intermediate potential VB (reference potential) corresponding to the steady volume of the pressure generating chamber 17 (the volume serving as a reference for expansion or contraction) to the expansion potential VL. It is a waveform element that lowers the potential, and the expansion hold element p2 is a waveform element that is constant at the expansion potential VL. The contraction element p3 is a waveform element that increases the potential with a steep slope from the expansion potential VL to the contraction potential VH, and the vibration suppression hold element p4 is a waveform element that maintains the contraction potential VH for a predetermined period. The damping element p5 is a waveform element that restores the potential with a constant gradient that does not cause ink to be ejected from the contraction potential VH to the intermediate potential VB.

  When the ejection pulse configured in this way is supplied to the piezoelectric element 20, first, the piezoelectric element 20 is bent in a direction away from the pressure generating chamber 17 by the expansion element p1, thereby causing the pressure generating chamber 17 to reach the intermediate potential VB. It expands from the corresponding steady volume to the expansion volume corresponding to the expansion potential VL. Due to this expansion, the meniscus is largely drawn to the pressure generating chamber 17 side, and ink is supplied into the pressure generating chamber 17 from the reservoir 26 side through the supply port. And the expansion state of this pressure generation chamber 17 is maintained over the supply period of the expansion hold element p2. Thereafter, the piezoelectric element 20 is bent toward the pressure generation chamber 17 by applying the contraction element p3. Due to the displacement of the piezoelectric element 20, the pressure generating chamber 17 is rapidly contracted from the expansion volume to the contraction volume corresponding to the contraction potential VH. The ink in the pressure generating chamber 17 is pressurized by the rapid contraction of the pressure generating chamber 17, and a predetermined amount (for example, several ng to several tens of ng) of ink is ejected from the nozzle 28. The contraction state of the pressure generation chamber 17 is maintained over the supply period of the vibration suppression hold element p4. During this period, the ink pressure in the pressure generation chamber 17 that has decreased due to ink ejection rises again due to its natural vibration. The damping element p5 is adjusted so as to be supplied in accordance with the rising timing. By supplying the damping element p5, the pressure generation chamber 17 expands and returns to the steady volume, and ink pressure fluctuation (residual vibration) in the pressure generation chamber 17 is absorbed.

Here, in order to sufficiently exhibit the effect of suppressing the residual vibration by the damping element p5, a drive signal (ejection pulse) is considered in consideration of the pressure fluctuation of the natural vibration period Tc generated in the ink in the pressure generation chamber during ink ejection. It is important to set The natural vibration period Tc is individually determined by the recording head in accordance with the size of the ink flow path in the head including the pressure generating chamber 17. For this reason, the natural vibration periods Tc are different between the recording heads of the same type. Therefore, if the drive signal is set uniformly for all the recording heads, the ejection characteristics may differ from head to head.
The ink vibration period Tc in the pressure generation chamber 17 can be expressed by the following equation (1) as disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-11352.
Tc = 2π√ [[(Mn × Ms) / (Mn + Ms)] × Cc] (1)
In Equation (1), Mn represents inertance at the nozzle 28, Ms represents inertance at the ink supply port (22, 23), and Cc represents compliance of the pressure generating chamber 17 (volume change per unit pressure, degree of softness). .) In the above equation (1), inertance M indicates the ease of ink movement in the ink flow path, and is the mass of ink per unit cross-sectional area. Then, assuming that the density of the ink is ρ, the cross-sectional area of the surface orthogonal to the ink flow direction of the flow path is S, and the length of the flow path is L, the inertance M can be expressed by the following equation (2). it can.
Inertance M = (density ρ × length L) / cross-sectional area S (2)
Further, Tc is not limited to the above formula (1), but may be any vibration cycle that the pressure generating chamber 17 has.

  FIG. 4 is a schematic diagram for explaining residual vibration generated in the pressure generating chamber 17 when ink is ejected by the ejection pulse. In the figure, the horizontal axis indicates the elapsed time, and the vertical axis indicates the position of the liquid surface (meniscus) exposed by the nozzle 28. On the vertical axis, the position indicated by 0.0 is a steady position (the position of the meniscus when no vibration is generated), the state where the meniscus protrudes toward the discharge side toward the + side, and the meniscus is the pressure toward the − side. It is in a state of being drawn into the generation chamber side. Further, at the time point represented by Dt, a plurality of ejection pulses (for example, the first ejection pulse P11 and the second ejection pulse P12, or the third ejection pulse P13 and the fourth ejection pulse) are continuously applied to the piezoelectric element 20. The timing at which ink ejection is started by the ejection pulse on the rear side when ink is ejected by supply (timing for applying the contraction element p3) is shown. A is a residual vibration when ink is ejected by a recording head (hereinafter referred to as recording head A) having a reference natural vibration period (hereinafter referred to as reference Tca), which is a design target, and B is a natural vibration period longer than the reference Tca. A part of residual vibration of the recording head (recording head B) having Tcb, C indicates a part of residual vibration of the recording head (recording head C) having a natural vibration period Tcc shorter than the reference Tca.

  As described above, when the natural vibration period is different for each recording head, the state of residual vibration of the meniscus is different at the next ejection timing Dt. For example, in the recording head B, the next ink is discharged in a state where the meniscus is raised to the discharge side as compared with the case of the recording head A. On the other hand, in the recording head C, the next ink is discharged in a state where the meniscus is drawn to the pressure generating chamber side as compared with the case of the recording head A. As described above, if the natural vibration period is different for each recording head, the flying speed of the ink fluctuates and the landing position becomes unstable as compared with the recording head A, and the weight of the ejected ink fluctuates. There is. For this reason, conventionally, the timing of applying the damping element p5, that is, the length of the damping hold element p4 (the generation time of the damping hold element p4) is changed according to the natural vibration period of each recording head. Thus, the state of the meniscus at the time of ejection was made uniform for each recording head. However, for example, when the interval of the vibration suppression hold element p4 is increased, there is a problem in that the recording cycle is extended correspondingly and the drive frequency is lowered.

  Therefore, in the printer according to the present invention, by changing the intermediate potential VB of the drive signal based on the natural vibration period for each recording head, the above-described problems can be suppressed without changing the time length of the ejection pulse itself. I am doing so. Specifically, the ink is ejected by the second ejection pulse (for example, the second ejection pulse P12) after the ink is ejected from the nozzle 28 by the first ejection pulse (for example, the first ejection pulse P11). , The position of the residual vibration of the meniscus by the first ejection pulse at the time corresponding to the ink ejection operation start timing Dt by the second ejection pulse is on the ejection side compared to the recording head A of the reference Tca. In the case of a recording head having a vibration cycle (in the case of recording head B with respect to recording head A as a reference in FIG. 4), the potential difference of damping element p5 is the reference (damping element p5 in drive signal COM set to recording head A). The intermediate potential is set so as to be higher than the potential difference), while the ink ejection operation start timing by the second ejection pulse P12 is set. In the case of a recording head having a natural vibration period such that the position of the residual vibration of the meniscus by the first ejection pulse P11 at the time corresponding to the rotation Dt is on the pressure generating chamber side as compared with the recording head A of the reference Tca (FIG. 4), the intermediate potential is set so that the potential difference of the damping element p5 is lower than the reference.

  That is, in the recording head B according to the present embodiment, as shown in FIG. 2, the intermediate potential is set to VB ′ lower than the intermediate potential VB of the drive signal COM set to the recording head A, thereby suppressing vibration. The potential difference (VH−VB ′) of the element p5 is set higher than the reference (VH−VB). As a result, the damping action (counter vibration) against the pressure vibration generated at the time of ejection becomes stronger, and as shown in FIG. 5, the first ejection at the time corresponding to the ink ejection operation start timing Dt by the second ejection pulse. The amplitude of the residual vibration caused by the pulse is made smaller. In the recording head C, the potential difference of the damping element p5 is made lower than the reference by setting the intermediate potential to a value higher than VB. As a result, the damping action against the pressure vibration generated at the time of ejection is reduced, and as shown in FIG. 5, the residual vibration due to the first ejection pulse at the time corresponding to the ink ejection operation start timing Dt by the second ejection pulse. The amplitude is increased.

Thus, by setting the intermediate potential according to the natural vibration period Tcb of the recording head B without changing the length of the ejection pulse itself, the state of the meniscus at the timing Dt can be made uniform for each recording head. Thereby, it is possible to make the ejection characteristics uniform among the recording heads without reducing the driving frequency.
The process for setting the intermediate potential according to the natural vibration period Tc of the recording head described in the above embodiment may be performed when the printer is manufactured, or may be performed when the printer is used after manufacturing. It may be performed as a reset during maintenance.

  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.

  For example, the waveform configuration of each drive signal COM is not limited to that exemplified in the above embodiment, and the present invention can be applied to drive signals having various configurations.

  Note that 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 drive signal, and various ink jet recording devices such as plotters, facsimile devices, and copiers, and liquids other than recording devices. The present invention can also be applied to a discharge device such as a display manufacturing device, an electrode manufacturing device, and a chip manufacturing device.

  DESCRIPTION OF SYMBOLS 1 ... Printer controller, 2 ... Print engine, 6 ... Control part, 8 ... Recording head, 9 ... Drive signal generation circuit, 20 ... Piezoelectric element

Claims (2)

A liquid discharge head capable of discharging a liquid from the nozzle by driving a pressure generating element that varies a volume of a pressure generating chamber communicating with the nozzle, and an ejection pulse for driving the pressure generating element to discharge the liquid. A drive signal generation method for generating a drive signal including a drive signal at a constant cycle, and a drive signal setting method for a liquid ejection apparatus,
The discharge pulse changes from an intermediate potential to expand the pressure generating chamber, the discharge element that contracts the pressure generating chamber expanded by the expansion element and discharges the liquid, and returns the potential to the intermediate potential. And at least a damping element that suppresses residual vibration of the liquid after ejection,
A drive signal setting method for a liquid ejection apparatus, wherein the intermediate potential is determined based on a natural vibration period Tc of the liquid in the pressure generating chamber. In the configuration in which the liquid is discharged by the second discharge pulse after the liquid is discharged from the nozzle by the first discharge pulse, the first discharge pulse at the time corresponding to the liquid discharge operation start timing by the second discharge pulse. For liquid discharge heads with a natural vibration period where the position of the residual vibration of the meniscus is on the discharge side compared to the liquid discharge head with the reference natural vibration period, the potential difference of the damping element is higher than the reference While the intermediate potential is set, the position of the residual meniscus vibration by the first ejection pulse at the time corresponding to the liquid ejection operation start timing by the second ejection pulse is compared with the liquid ejection head having the reference natural vibration period. For liquid ejection heads with a natural oscillation period on the generation chamber side, the potential difference of the damping element will be lower than the reference. Drive signal setting method for a liquid ejecting apparatus according to claim 1, characterized in that setting the intermediate potential.

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