JP2010188561A - Method for manufacturing liquid delivering apparatus, and liquid delivering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a liquid delivering apparatus in which variation in delivering characteristics such as a flying speed or a weight of liquid caused by a difference of an inherent oscillation period Tc can be reduced and delivering of the liquid can be stabilized, and to provide a liquid delivering apparatus. <P>SOLUTION: A delivery driving pulse is constituted by including at least an expansion element p1 which expands a pressure generating chamber, an expansion maintaining element p2 which maintains an expansion state for a fixed time, and a contraction element p3 which contracts the expanded pressure generating chamber to deliver the liquid. In the method for manufacturing the liquid delivering apparatus, setting of the delivery driving pulse includes: a Tc measuring process for measuring the inherent oscillation period Tc of the ink in the pressure generating chamber; and an expansion maintaining element setting process for setting a time width Pwh1 of the expansion maintaining element to satisfy TcD×Pwh1=Tc×Pwh1D on the basis of Tc measured in the inherent oscillation period measuring process, a reference TcA as a design reference inherent oscillation period, and a reference time width Pwh1D of the expansion maintaining element set on the basis of the reference TcA. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a liquid discharge apparatus such as an ink jet printer, and a liquid discharge apparatus manufactured by this method, and in particular, applies a discharge drive pulse included in a drive signal to a pressure generating element. The present invention relates to a method for manufacturing a liquid ejection device capable of controlling the ejection of liquid and the liquid ejection device.

  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.

  The printer applies a discharge drive pulse to a pressure generating element (for example, a piezoelectric element or a heating element) and drives it to apply a pressure change to the liquid in the pressure generating chamber, and the pressure change is used to generate a pressure. Some are configured to discharge liquid from a nozzle communicating with the generation chamber. This discharge drive pulse is an expansion element that preliminarily expands the pressure generation chamber (pressure generation chamber expansion process), an expansion maintenance element that maintains this expansion state (expansion maintenance process), and the pressure generation chamber rapidly contracts from the expansion state. Thus, it is configured to include a contraction element (pressure generation chamber contraction step) for discharging ink by increasing the internal pressure of the pressure generation chamber.

  In order to make the amount (weight / volume) of ink ejected from the nozzles constant in each recording head, generally, the amount of ink ejected by changing the magnitude of the voltage applied to the pressure generating element. The drive signal (ejection drive pulse) is adjusted for each head so that is constant. Specifically, ink droplets are ejected with at least two ejection drive pulses adjusted to different voltages, the weight of each ejected ink is measured, and the change amount of the ink weight is proportional to the change amount of the voltage. As a matter of course, the drive voltage of the ejection drive pulse is adjusted so that the ink weight is appropriate.

  Here, when the pressure generating chamber is expanded by the expansion element and the meniscus is drawn to the pressure generating chamber side, pressure vibration is generated in the ink in the pressure generating chamber. For this reason, if only the magnitude of the drive voltage is adjusted, there is a possibility that the ejection characteristics may vary depending on the phase of pressure vibration when the pressure generating chamber is contracted by the pressure generating contraction element. That is, even if the ink weight is made constant by adjusting the drive voltage, the flying speed of the ink may vary from head to head. The vibration period Tc of the ink in the pressure generation chamber can be expressed by the following equation (A) as disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-11352.

Tc = 2π√ [[(Mn × Ms) / (Mn + Ms)] × Cc] (A)
In the formula (A), Mn represents inertance at the nozzle, Ms represents inertance at the ink supply port leading from the reservoir to the pressure generating chamber, and Cc represents compliance of the pressure generating chamber (volume change per unit pressure, degree of softness). .) In the above formula (A), inertance M indicates the ease of movement of ink 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 perpendicular 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 (B). it can.
Inertance M = (density ρ × length L) / cross-sectional area S (B)
Tc is not limited to the above formula (A), but may be any vibration cycle that the pressure generation chamber has.

  As described above, since the natural vibration period Tc may be different for each recording head, the parameters of the ejection driving pulse are set so that desired characteristics can be obtained with respect to both the ink weight and the ink flying speed at the time of manufacturing the printer. ing. For example, in Patent Document 1, in a recording head having a large Tc (Tc = 8.0 μs), the time width (duration) Twd1 of the expansion element (expansion signal) is adjusted to 6.0 μs, which is 3/4 of Tc. In a recording head having a small Tc (Tc = 7.0 μs), a configuration is proposed in which Twd1 is adjusted to 7.0 μs, which is equal to Tc. That is, the time width of the expansion element is set in the range of 3/4 Tc to Tc according to the size of Tc. As a result, the ink flying speed is high in the recording head with Tc = 8.0 μs, and the ink flying speed is low in the recording head with Tc = 7.0 μs.

JP 11-058729 A

However, the configuration of Patent Document 1 described above can be applied only to a recording head having a specific range of Tc, and it is difficult to apply to a recording head having a Tc exceeding the specific range.
Further, by changing the time width of the expansion element, the magnitude of the pressure generated in the pressure generation chamber is changed by applying the expansion element to the pressure generating element, so that the residual vibration after ink ejection also changes. As a result, when ink is ejected continuously, the residual vibration generated in the front ejection operation has an adverse effect on the rear ejection operation, and as a result, there is a problem that ink ejection is not stable.

  The present invention has been made in view of such circumstances, and an object thereof is to reduce variations in ejection characteristics such as liquid flight speed and weight due to differences in the natural vibration period Tc, and to stably eject liquid. It is an object of the present invention to provide a method of manufacturing a liquid ejection device capable of performing the above and a liquid ejection device.

The present invention has been proposed in order to achieve the above object. By applying a discharge driving pulse to a pressure generating element, a pressure fluctuation is generated in the pressure generating chamber, and the liquid is discharged from the nozzle by the pressure fluctuation. A liquid discharge apparatus comprising: a liquid discharge head to be driven; and a drive signal generation circuit that generates a drive signal including the discharge drive pulse.
The ejection drive pulse has at least an expansion element that expands the pressure generation chamber, an expansion maintenance element that maintains the expanded state for a certain period of time, and a contraction element that contracts the expanded pressure generation chamber to discharge liquid.
A natural vibration period measuring step of measuring the natural vibration period Tc generated in the liquid in the pressure generating chamber for each liquid ejection head;
Based on the Tc measured in the natural vibration period measurement step, the reference TcD that is a natural vibration period that is a design reference, and the reference time width Pwh1D of the expansion maintaining element that is set based on the reference TcD, the following expression An expansion maintaining element setting step of setting a time width Pwh1 of the expansion maintaining element so as to satisfy (1).
TcD × Pwh1 = Tc × Pwh1D (1)

  According to the present invention, the natural vibration period Tc of the liquid in the pressure generation chamber is measured, and the expansion is maintained so as to satisfy TcD × Pwh1 = Tc × Pwh1D based on the measured Tc, the reference TcD, and the reference time width Pwh1D. Since the element time width Pwh1 is set, it is possible to reduce variations in ejection characteristics such as the liquid flying speed and weight between the liquid ejection heads regardless of the difference in the natural vibration period Tc. In addition, since variation in ejection characteristics can be reduced, the setting range of the appropriate value of the drive voltage of the ejection drive pulse can be reduced. Furthermore, since the variation in the magnitude of the residual vibration after the liquid ejection can be suppressed, it is possible to ensure the ejection stability when the liquid is ejected continuously.

  In the above configuration, it is desirable to employ a configuration in which a drive voltage setting step of setting the drive voltage of the discharge drive pulse is performed after the expansion maintaining element setting step so that the amount of liquid to be discharged becomes a design value.

The present invention also provides a liquid discharge head that causes a pressure fluctuation in the pressure generating chamber by applying a discharge driving pulse to the pressure generating element, and discharges liquid from the nozzle by the pressure fluctuation.
A drive signal generation circuit for generating a drive signal including the ejection drive pulse;
A liquid ejection device comprising:
The ejection drive pulse has at least an expansion element that expands the pressure generation chamber, an expansion maintenance element that maintains the expanded state for a certain period of time, and a contraction element that contracts the expanded pressure generation chamber to discharge liquid.
The expansion maintenance based on the natural vibration period Tc generated in the liquid in the pressure generation chamber, the reference TcD which is a natural vibration period used as a design reference, and the reference time width Pwh1D of the expansion maintenance element set based on the reference TcD The element time width Pwh1 is set so as to satisfy the following expression (1).
TcD × Pwh1 = Tc × Pwh1D (1)

FIG. 2 is a block diagram illustrating an electrical configuration of an ink jet printer. 2 is a cross-sectional view of a recording head. It is a wave form diagram explaining the structure of a drive signal. It is a wave form diagram explaining the structure of an ejection drive pulse. It is a flowchart explaining the flow of an ejection drive pulse setting process. It is a graph which shows the example of the Pwh1-Vm characteristic of three recording heads from which the natural vibration period Tc differs. It is a graph which shows a speed difference. It is a graph which shows the difference of an appropriate drive voltage. It is the graph which expanded and showed a part of FIG. It is a graph which shows the speed difference after discharge drive pulse setting. It is a graph which shows the difference of the appropriate drive voltage after an ejection drive pulse setting.

  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 and receives data to and 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 a program 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 a status signal such as a busy signal or 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 (or channel) 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. Then, pixel data (dot pattern data) SI used for ejection control of the recording head 8 is generated through a dot pattern development process or the like arranged in a predetermined arrangement for each ink type (for each nozzle array) 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 (slight 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. 3 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 in the present embodiment is a series of signals having one fine vibration pulse and four ejection drive 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 driving pulse P11 is generated in the period t1, the second ejection driving pulse P12 is generated in the period t2, the slight vibration pulse VP is generated in the period t3, and the third ejection driving pulse P13 is generated in the period t4. In the period t5, the fourth ejection driving 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.

  FIG. 2 is a cross-sectional view of an essential part for explaining the configuration of the recording head 8 (a kind of liquid ejection head). The recording head 8 includes a case 12, a vibrator unit 13 housed in the case 12, a flow path unit 14 joined to the bottom surface (tip surface) of the case 12, and the like. The case 12 is made of, for example, an epoxy resin, and a housing empty portion 15 for housing the vibrator unit 13 is formed therein. The vibrator unit 13 includes a piezoelectric vibrator 16 that functions as a kind of pressure generating element, a fixing plate 17 to which the piezoelectric vibrator 16 is joined, and a flexible cable 18 for supplying a drive signal and the like to the piezoelectric vibrator 16. And. The piezoelectric vibrator 16 is a laminated type produced by cutting a piezoelectric plate having alternately laminated piezoelectric layers and electrode layers into a comb shape, and can be expanded and contracted in a direction perpendicular to the lamination direction (electric field direction). This is a piezoelectric vibrator in a longitudinal vibration mode (field transverse effect type).

  The flow path unit 14 is configured by joining the nozzle plate 20 to one surface of the flow path forming substrate 19 and the diaphragm 21 to the other surface of the flow path forming substrate 19. The flow path unit 14 is provided with a reservoir 22 (common liquid chamber), an ink supply port 23, a pressure generation chamber 24, a nozzle communication port 25, and a nozzle 26. A series of ink flow paths from the ink supply port 23 to the nozzle 26 through the pressure generation chamber 24 and the nozzle communication port 25 are formed corresponding to each nozzle 26.

  The nozzle plate 20 is a thin plate made of metal such as stainless steel in which a plurality of nozzles 26 are formed in a row at a pitch (for example, 180 dpi) corresponding to the dot formation density. The nozzle plate 20 is provided with a plurality of nozzle rows (nozzle groups) by arranging nozzles 26, and one nozzle row is composed of, for example, 180 nozzles 26.

  The diaphragm 21 has a double structure in which an elastic film 28 is laminated on the surface of a support plate 27. In the present embodiment, the vibration plate 21 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 27 and a resin film is laminated on the surface of the support plate 27 as an elastic film 28. The diaphragm 21 is provided with a diaphragm portion 29 that changes the volume of the pressure generating chamber 24. The diaphragm 21 is provided with a compliance portion 30 that seals a part of the reservoir 22.

  The diaphragm portion 29 is produced by partially removing the support plate 27 by etching or the like. That is, the diaphragm portion 29 includes an island portion 31 to which the tip end surface of the free end portion of the piezoelectric vibrator 16 is joined, and a thin elastic portion 32 surrounding the island portion 31. The compliance part 30 is produced by removing the support plate 27 in the region facing the opening surface of the reservoir 22 by etching processing or the like in the same way as the diaphragm part 29, and the pressure fluctuation of the liquid stored in the reservoir 22 is reduced. Functions as a damper to absorb.

  Since the tip end surface of the piezoelectric vibrator 16 is joined to the island portion 31, the volume of the pressure generating chamber 24 can be changed by expanding and contracting the free end portion of the piezoelectric vibrator 16. As the volume changes, pressure fluctuations occur in the ink in the pressure generation chamber 24. The recording head 8 uses this pressure fluctuation to eject ink droplets from the nozzles 26.

  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 a piezoelectric vibrator 16. The shift registers 33 and 34, the latch circuits 35 and 36, the level shifter 39, the switch 41, and the piezoelectric vibrator 16 are provided in a number corresponding to each nozzle 26. 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 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 26, 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 receives 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. 3, the pulse selection data includes the first ejection drive pulse P11 (period t1), the second ejection drive pulse P12 (period t2), the micro-vibration pulse VP (period t3), the third The data is composed of data of a total of 5 bits corresponding to the ejection drive pulse P13 (period t4) and the fourth ejection drive 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. A piezoelectric vibrator 16 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 vibrator 16. The switch 41 that operates in this manner functions as a selection supply unit. The above 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 COM1 is supplied to the piezoelectric vibrator 16. 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 vibrator 16. In short, a pulse in a period in which [1] is set as pulse selection data is selectively supplied to the piezoelectric vibrator 16. By such switch control, the ejection drive pulse included in the drive signal COM can be applied to the piezoelectric vibrator 16. That is, a part of the drive signal COM can be selectively applied to the piezoelectric vibrator 16. In this example, at the boundary timing (change pulse timing of the change signal CH) between t1 and t5 after the start timing of the repetition cycle (recording cycle) T (the timing of the latch pulse of the latch signal LAT), the piezoelectric vibrator The pulse applied to 16 can be switched.

  As shown in FIG. 4, each of the ejection drive pulses 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, a vibration suppression hold element p4, It consists of damping element p5. The expansion element p1 is a waveform element that increases the potential with a relatively gentle constant gradient from the intermediate potential VB (reference potential) to the expansion potential VH corresponding to the steady volume of the pressure generating chamber 24 (the volume that serves as a reference for expansion or contraction). The expansion hold element p2 is a waveform element that is constant at the expansion potential VH. The contraction element p3 is a waveform element that drops the potential with a steep slope from the expansion potential VH to the contraction potential VL, and the vibration suppression hold element p4 is a waveform element that maintains the contraction potential VL for a predetermined period. The damping element p5 is a waveform element that increases the potential with a constant gradient from the contraction potential VL to the intermediate potential VB.

  When the ejection drive pulse configured in this way is supplied to the piezoelectric vibrator 16, first, the piezoelectric vibrator 16 contracts by the expansion element p <b> 1, so that the island portion 31 of the diaphragm portion 29 is separated from the pressure generation chamber 24. As a result, the pressure generating chamber 24 expands from a steady volume corresponding to the intermediate potential VB to an expansion volume corresponding to the expansion potential VH. Due to this expansion, the meniscus is largely drawn to the pressure generation chamber 24 side, and ink is supplied into the pressure generation chamber 24 from the reservoir 22 side through the ink supply port 23. The expansion state of the pressure generation chamber 24 is maintained over the generation period (Pwh1) of the expansion hold element p2. Thereafter, when the contraction element p3 is applied, the piezoelectric vibrator 16 expands and the island portion 31 is displaced toward the pressure generating chamber 24 side. Thereby, the pressure generation chamber 24 is rapidly contracted from the expansion volume to the contraction volume corresponding to the contraction potential VL. The ink in the pressure generation chamber 24 is pressurized by the rapid contraction of the pressure generation chamber 24, and a predetermined amount (for example, several ng to several tens of ng) of ink is ejected from the nozzle 26. The contraction state of the pressure generation chamber 24 is maintained over the supply period of the vibration suppression hold element p4, and during this time, the ink pressure in the pressure generation chamber 24 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 24 expands and returns to the steady volume, and ink pressure fluctuation (residual vibration) in the pressure generation chamber 24 is absorbed.

  Here, when the printer is manufactured, the parameters of the ejection drive pulse are set so that desired ejection characteristics can be obtained. However, the natural vibration period Tc generated in the ink in the pressure generating chamber may be different even between the same type of recording heads. In a general printer, the drive voltage Vd of the ejection drive pulse (potential difference between the expansion potential VH, which is the lowest potential, and the contraction potential VL, which is the highest potential) can be adjusted so that the weight of the ejected ink is uniform between the recording heads. However, if the difference in ejection characteristics is large, the adjustment range of the drive voltage Vd is expanded correspondingly, and there is a concern that the upper limit value that can be set is exceeded.

  Therefore, the printer according to the present invention solves the above problem by setting the time width Pwh1 of the expansion hold element p2 of the ejection drive pulse based on the natural vibration period Tc for each recording head. That is, the natural vibration period Tc generated in the ink in the pressure generation chamber 24 in the manufacturing stage is measured for each recording head, the generation period Pwh1 of the expansion hold element p2 of the discharge drive pulse is set based on the measured Tc, and the discharge drive An ejection drive pulse setting process for setting the pulse drive voltage Vd is performed. Hereinafter, this point will be described.

  FIG. 5 is a flowchart for explaining the flow of the ejection drive pulse setting process. The ejection drive pulse setting process in the present embodiment includes three steps: a Tc measurement step S1, a Pwh1 setting step S2 (expansion maintaining element setting step), and a Vd setting step S3 (drive voltage setting step). In the Tc measurement step S1, Tc is measured by discharging ink from all nozzles for each recording head. As a measuring method of Tc, while changing the time width Pwh1 of the expansion hold element p2 within a predetermined range, the ink flying speed Vm and the ink weight Iw when the ink is ejected by the ejection driving pulse are measured, and the change Can be used, and existing techniques such as a method of acquiring the interval between adjacent maximum values or minimum values of the change curve as Tc can be used.

FIG. 6 is a graph showing an example of Pwh1-Vm characteristics of three recording heads having different natural vibration periods Tc. In the figure, a recording head (reference head) having a reference TcD which is a design target, a recording head having + 5% Tc + with respect to the reference TcD, and a recording having −5% Tc− with respect to the reference TcD. The case of a head is illustrated. If the natural vibration period Tc is different in this way, the ejection characteristics vary for each print head depending on the time width Pwh1 of the expansion maintaining element (expansion hold element p2).
For example, FIG. 7 is a graph showing the difference between the Pwh1-Vm characteristic of the recording head having Tc + and the Pwh1-Vm characteristic of the recording head having Tc−, and FIG. 8 is a graph showing the appropriate drive voltage Vd of both heads. It is the graph which took the difference for every Pwh1. The appropriate drive voltage Vd is an appropriate value of the drive voltage set for the ejection drive pulse in order to make the ejected ink weight constant (target value). As described above, the difference in ejection characteristics also periodically varies according to the time width Pwh1 of the expansion maintaining element. It is ideal to set Pwh1 at which the difference between these characteristics is 0, but it is necessary to use a value other than Pwh1 at which the characteristic difference is 0 depending on the discharge conditions.

  FIG. 9 is an enlarged view of a part of FIG. 6 and shows only the case of the recording head of the reference TcD and the recording head of Tc +. For example, when the time width Pwh1 of the expansion hold element p2 of the ejection drive pulse used for the reference head (TcD) is set to a value (reference time width) indicated by Pwh1D in FIG. 9, the expansion hold element p2 used for the Tc + recording head. Is set to the reference time width Pwh1D, the flying speed Vm2 when the ink is ejected by the Tc + recording head is increased with respect to the ink flying speed Vm1 when the ink is ejected by the reference head.

In order to prevent such a problem, in the Pwh1 setting step S2, the time width Pwh1 of the expansion maintaining element is set based on the natural vibration period Tc measured in the Tc measurement step S1. Specifically, Pwh1 is set so as to satisfy the following expression (1) based on Tc measured in the Tc measurement step S1, the reference TcD, and the reference time width Pwh1D.
TcD × Pwh1 = Tc × Pwh1D (1)
When this is modified, the following equation (2) is obtained.
Pwh1 = Pwh1D × Tc / TcD (2)
That is, it is only necessary to set Pwh1 so that the ratio of the natural vibration period Tc and the ratio of the time width P of the expansion maintaining element are equal to the reference head. In other words, the recording head having a shorter natural vibration period Tc than the reference TcD sets the time width Pwh1 of the expansion maintaining element of the ejection drive pulse to be shorter than the reference time width Pwh1D, and the natural vibration period Tc becomes the reference TcD. The longer the recording head, the longer the time width Pwh1 of the expansion maintaining element of the ejection drive pulse is set to be longer than the reference time width Pwh1D.

In the example of FIG. 9, the ink flying speed Vm1 in the reference head and the ink flying speed Vm2 in the Tc + recording head are expressed by the following equations (3) and (4). Note that ω1 = 1 / TcD and ω2 = 1 / Tc +.
^Vm1 = Ae− ^{γ · pwh1D} sin (ω1 · pwh1D + φ) + D (3)
^Vm2 = Ae− ^{γ · pwh1A} sin (ω2 · pwh1A + φ) + D (4)
When Pwh1A satisfying Vm1 = Vm2 is obtained, it is represented by the ratio of Tc to the reference time width Pwh1D, and as a result, the above formula (2) is obtained.

  If Pwh1 has been set, a Vd setting step S3 is subsequently performed. In this step, an appropriate value of the drive voltage Vd of the ejection drive pulse in which the time width Pwh1 of the expansion hold element p2 is set in the Pwh1 setting step S2 is set. Specifically, the driving voltage Vd is set such that the weight of ink when the piezoelectric vibrator 16 is driven by the ejection driving pulse and ink is ejected becomes a target value (design value). The method for setting the drive voltage Vd can be the same as the conventional method. The reason why the Vd setting step S3 is performed after the Pwh1 setting step S2 is that the weight of the ink may slightly vary depending on the time width Pwh1. When the drive voltage Vd is changed, the flying speed of the ink also changes, but the change amount is smaller than the change amount of the ink weight.

  In this way, by setting Pwh1 based on the measured Tc and using the set ejection drive pulse for the recording head corresponding to the Tc, each recording head can be used regardless of the difference in the natural vibration period Tc. The discharge characteristic can be brought close to the target value, and variations in the discharge characteristic can be reduced. In addition, since variation in the magnitude of residual vibration after ink ejection can be suppressed, it is possible to ensure ejection stability when ink is ejected continuously.

In the example of FIG. 9, by setting the value of Pwh1 to Pwh1A, the flying speed Vm2 of the ink ejected from the recording head can be made equal to the flying speed Vm1 of the ink ejected from the reference head.
FIG. 10 is a graph showing the difference in the ink flying speed between the Tc− recording head and the Tc + recording head after the ejection drive pulse is set, and FIG. 11 is a graph showing the difference in the appropriate drive voltage Vd between the two heads. As shown in FIG. 10, after the ejection drive pulse is set, the difference in ink flying speed between the recording heads can be made closer to 0 than in the case of FIG. Similarly, the difference between the appropriate drive voltages Vd of both heads can be reduced as compared with the case of FIG.

  Then, by setting the time width Pwh1 of the expansion maintaining element to an appropriate value in the Pwh1 setting step S2, the weight of the ejected ink can be brought close to the target value, so that the adjustment range when the drive voltage Vd is set is set. It can be made smaller than before.

  The process of setting Pwh1 according to the natural vibration period Tc described in the above embodiment may be performed at the time of manufacturing the printer, may be performed at the time of using the printer after manufacturing, or may be performed again during maintenance of the printer. It may be performed as a setting.

  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 the ejection drive pulse is not limited to that exemplified in the above embodiment, and the present invention can be applied to ejection drive pulses having various configurations. The point is an ejection driving pulse having at least an expansion element that expands the pressure generation chamber, an expansion maintenance element that maintains the expanded state for a certain period of time, and a contraction element that contracts the expanded pressure generation chamber to discharge liquid. I just need it.

  Note that the present invention is not limited to a printer as long as it is a liquid ejection apparatus capable of controlling liquid ejection using a drive signal (ejection drive pulse), and various ink jet recording apparatuses such as a plotter, a facsimile machine, and a copier. It can also be applied to liquid ejection devices other than recording devices, such as display manufacturing devices, electrode manufacturing devices, chip manufacturing devices, and the like.

  DESCRIPTION OF SYMBOLS 1 ... Printer controller, 2 ... Print engine, 6 ... Control part, 8 ... Recording head, 9 ... Drive signal generation circuit, 16 ... Piezoelectric vibrator, 26 ... Nozzle

Claims (3)

By applying a discharge drive pulse to the pressure generating element, a pressure fluctuation is generated in the pressure generating chamber, and a liquid discharge head that discharges liquid from the nozzle by this pressure fluctuation, and a drive that generates a drive signal including the discharge drive pulse A method of manufacturing a liquid ejection device comprising a signal generation circuit,
The ejection drive pulse has at least an expansion element that expands the pressure generation chamber, an expansion maintenance element that maintains the expanded state for a certain period of time, and a contraction element that contracts the expanded pressure generation chamber to discharge liquid.
A natural vibration period measuring step of measuring the natural vibration period Tc generated in the liquid in the pressure generating chamber for each liquid discharge head;
Based on the Tc measured in the natural vibration period measurement step, the reference TcD that is a natural vibration period that is a design reference, and the reference time width Pwh1D of the expansion maintaining element that is set based on the reference TcD, the following expression And a expansion maintaining element setting step for setting a time width Pwh1 of the expansion maintaining element so as to satisfy (1).
TcD × Pwh1 = Tc × Pwh1D (1)   After the expansion maintaining element setting step, a method of manufacturing a liquid ejection apparatus, comprising performing a driving voltage setting step of setting a driving voltage of the ejection driving pulse so that an amount of ejected liquid becomes a design value. A liquid discharge head that causes a pressure fluctuation in the pressure generation chamber by applying a discharge driving pulse to the pressure generating element, and discharges liquid from the nozzle by the pressure fluctuation;
A drive signal generation circuit for generating a drive signal including the ejection drive pulse;
A liquid ejection device comprising:
The ejection drive pulse has at least an expansion element that expands the pressure generation chamber, an expansion maintenance element that maintains the expanded state for a certain period of time, and a contraction element that contracts the expanded pressure generation chamber to discharge liquid.
The expansion maintenance based on the natural vibration period Tc generated in the liquid in the pressure generation chamber, the reference TcD which is a natural vibration period used as a design reference, and the reference time width Pwh1D of the expansion maintenance element set based on the reference TcD A liquid ejection apparatus, wherein an element time width Pwh1 is set to satisfy the following expression (1).
TcD × Pwh1 = Tc × Pwh1D (1)

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