JP6897077B2 - Equipment and method for discharging liquid - Google Patents

Description

The present invention relates to a device and a method for discharging a liquid.

An inkjet recording method in which ink droplets are ejected from a nozzle onto a recording medium due to fluctuations in the pressure of the liquid chamber is adopted in an image forming apparatus such as a printer. The ink liquid surface exposed at the opening of the nozzle is displaced due to the deformation of the liquid chamber for ejecting ink droplets. The ejection speed and volume of the ink droplets ejected from the nozzle are affected by the residual vibration remaining on the ink liquid surface after the ink droplets are ejected before that. Due to the influence of this residual vibration, the position where the subsequent ink droplets land on the recording medium, the dot diameter of the ink droplets landing on the recording medium, and the like are varied, and density unevenness appears in the formed image.

Conventionally, in order to eliminate the density unevenness generated in this way, the density correction of the image is performed at each printing speed. In addition, there is a document that discloses a technique of aligning the phase of residual vibration by changing the start timing of the drive waveform for ejecting the second drop of ink when the transport speed of the continuous paper is changed. (See Patent Document 1).

When the printing speed is changed from the speed at the time of density correction to another speed, the phase at the time of ejection of each subsequent ink droplet in the residual vibration left by the previously ejected ink droplet is each at the printing speed at the time of correction. It shifts from the phase when the ink droplets are ejected. Therefore, the density correction performed does not match the printing speed after the change, and it is necessary to perform the density correction every time the printing speed is changed. Since the work of density correction imposes a heavy burden on the operator, it is a problem to carry out the density correction every time.

The present invention has been made in view of the above, and provides a device, a method, and a program for discharging a liquid, which adjusts to a printing speed corresponding to the density correction when the printing speed is changed after the density correction. The purpose is.

In order to solve the above-mentioned problems, the device for discharging the liquid according to the embodiment of the present invention includes a nozzle for discharging the liquid to the recording target, a pressure generating means for varying the pressure of the liquid chamber corresponding to the nozzle, and the above. The image density was corrected by the speed control means for controlling the relative speed between the nozzle and the recording target, the image density correction means for correcting the image density at the first relative speed of the relative speed, and the image density correction means. A discharge cycle calculating means for obtaining a second discharge cycle of the liquid based on the first discharge cycle of the liquid at the first relative velocity and the Helmholtz cycle corresponding to the nozzle, and the second discharge. It has an adjusting means for adjusting the relative speed to the second relative speed so as to have a period, and prints on the recording target at the second relative speed adjusted by the adjusting means.

According to the present invention, even if the printing speed is changed after the density correction, the printing speed can be adjusted to correspond to the density correction.

FIG. 1 is a diagram schematically showing an example of an inkjet recording device according to an embodiment. FIG. 2 is a plan view showing the internal structure of the recording head. FIG. 3 is a cross-sectional view of the recording head and the energy generation source at the positions indicated by the lines AA of the recording head of FIG. FIG. 4 is a cross-sectional view of the recording head and the energy generation source at the position indicated by the line BB of the recording head of FIG. FIG. 5 is a diagram showing an example of a configuration of a control board that controls an inkjet recording device. FIG. 6 is a diagram showing an example of the configuration of the print control circuit and the head driver. FIG. 7 is a diagram showing an example of the relationship between the waveform of the drive signal applied to the piezoelectric element (common drive waveform) and the meniscus displacement in the nozzle. FIG. 8 is a diagram showing an example of a functional block realized by the CPU. FIG. 9 is a diagram showing an example of the overall control flow of the inkjet recording device. FIG. 10 is a diagram showing an example of a processing flow of printing processing when the CPU executes a function of the printing processing unit. FIG. 11 is a diagram showing an example of a configuration of a functional block realized in the CPU according to the first modification. FIG. 12 is a diagram showing an example of a selection screen when the selection screen information is displayed on the operation panel. FIG. 13 is a diagram showing an example of a processing flow of the printing process. FIG. 14 is an explanatory diagram of a process for correcting the location where each nozzle strikes a dot on the image data according to the second modification.

Hereinafter, embodiments of a device, a method, and a program for discharging a liquid will be described in detail with reference to the accompanying drawings. In the present application, the "device for discharging a liquid" is a device including a liquid discharge head or a liquid discharge unit, which drives the liquid discharge head to discharge the liquid to a recording target. In the following, as an example of the “device for discharging a liquid”, an example of application of the image forming device to one inkjet recording device will be shown. In the following description of the inkjet recording apparatus, "ink (ink droplet)" is an example of the above "liquid", "recording head" is an example of the above "liquid ejection head", and "recording head unit" is an example of the above "liquid ejection". As an example of "unit", "continuous paper" is shown as an example of the above "recording target".

(Embodiment)
In the present embodiment, a line-type recording system in which a recording medium, which is an example of a recording target, is conveyed in one direction to a fixed-type recording head and ink is ejected is shown. The recording method shown in this embodiment is an example, and any other recording method may be adopted as long as it is a recording method in which the recording head and the paper are relatively moved for recording. For example, the recording head is moved in the main scanning direction and the sub-scanning direction for recording, the paper is moved in the main scanning direction and the sub-scanning direction for recording, and the recording head is moved in the main scanning direction for recording. Various recording methods may be appropriately adopted, such as those that move the paper in the sub-scanning direction.

Further, in the present embodiment, in order to make it easier to understand the principle, monochrome printing with one color ink (for example, K (Black)) will be described as an example, but the present invention is not limited to this. For example, color printing may be performed with inks of a plurality of colors such as CMYK. Further, the recording head may be provided with a plurality of rows of nozzles.

FIG. 1 is a diagram schematically showing an example of an inkjet recording device according to an embodiment. The inkjet recording device 1 shown in FIG. 1 includes a recording head unit 10, a paper transport mechanism 20, and a take-up device 30. The take-up device 30 is provided as an option because it is not an indispensable configuration.

The recording head unit 10 mainly includes a recording head 11, an energy generation source 12, an ink tank (not shown), and the like.

The recording head 11 is a "line head" having a nozzle row 100 in a direction orthogonal to the conveying direction of the continuous paper 40 which is a recording medium. The nozzle row 100 is a row in which a large number of nozzles are arranged in one row or a plurality of rows (in this example, one row), and each nozzle is directed to the entire print width (depth side in FIG. 1) of the continuous paper 40. Is arranged. Each nozzle has an ejection port that ejects the ink replenished from the ink tank as ink droplets A onto the continuous paper 40.

The energy generation source 12 is, for example, a piezoelectric actuator (laminated piezoelectric element and thin film piezoelectric element) that contracts and expands a pressure generating chamber (liquid chamber) described later, which is configured in the recording head 11. The pressure fluctuates as the pressure generating chamber repeatedly contracts and expands due to the energy generation source 12, and ink droplets A are ejected from each nozzle in the nozzle row 100.

The paper transport mechanism 20 feeds the continuous paper 40 from the roll paper 41, transports the fed continuous paper 40 to the printing area E where the nozzle rows 100 face each other, and ejects the continuous paper 40 after printing. Send to the paper side.

The paper transport mechanism 20 of the present embodiment has a paper feed side transport roller pair 200, a paper discharge side transport roller pair 201, and a platen roller 202, and the continuous paper 40 is driven from the roll paper 41 to the paper discharge side by a motor drive. In the transport direction X of. The paper feed side transport roller pair 200 feeds the continuous paper 40 unwound from the roll paper 41 in the transport direction X while being sandwiched between the rollers 200a and the rollers 200b. The platen roller 202 is formed by arranging a plurality of rollers in parallel in the transport direction X, and feeds the continuous paper 40 in the transport direction X by sucking the continuous paper 40 from the back surface side. The paper discharge side transport roller pair 201 discharges the continuous paper 40 in the transport direction X while sandwiching the continuous paper 40 between the rollers 201a and the rollers 201b. In addition, it has a charging roller (not shown) for charging the continuous paper 40.

The take-up device 30 is a device that winds up the continuous paper 40 discharged by the paper ejection side transport roller pair 201.

2, FIG. 3 and FIG. 4 are structural explanatory views of the recording head 11 and the energy generation source 12. FIG. 2 is a plan view showing the internal structure of the recording head 11, and the main internal structure is shown from the forming surface side of the nozzle 100a in a perspective view. FIG. 3 is a cross-sectional view of the recording head 11 and the energy generation source 12 at the positions indicated by the lines AA of the recording head 11 of FIG. FIG. 4 is a cross-sectional view of the recording head 11 and the energy generation source 12 at the positions indicated by the lines BB of the recording head 11 of FIG. Note that both FIGS. 3 and 4 have a cross-sectional structure in which the recording head unit 10 of FIG. 1 is turned upside down. Hereinafter, with reference to FIGS. 2 to 4, the structure of the recording head 11 and the energy generation source 12 and the operating principle in which each nozzle of the nozzle row 100 ejects the ink droplet A will be described.

The recording head 11 shown as an example in FIG. 2 has nozzles 100a arranged in a row as the nozzle row 100. The pitch of each nozzle 100a is, for example, 150 dpi. Further, the recording head 11 has a pressure generating chamber 101, a fluid resistance portion 102, an ink inflow port 103, and the like for each nozzle 100a. These form an ink flow path that communicates with the nozzle 100a. Further, the recording head 11 has a common liquid chamber 104 for supplying ink to the ink flow path of each nozzle 100a, an ink supply port 105 from the ink tank, and the like. On one surface of each pressure generating chamber 101, a thin film diaphragm portion 112a that facilitates deformation of the pressure generating chamber 101 and an island-shaped convex portion (island portion) 112b that connects to the energy generation source 12 are provided.

Further, the structure of the recording head 11 and the energy generation source 12 will be described in detail using the cross-sectional structure of the recording head 11 of FIGS. 3 and 4.

The ink flow path is formed by a nozzle plate 110, a flow path plate 111 joined to the nozzle plate 110, a diaphragm 112 joined to the flow path plate 111, and a frame 113 joined to the diaphragm 112.

The nozzle plate 110 is formed of a metal material, for example, a Ni plating film produced by an electroforming method. The nozzle plate 110 is formed with a nozzle 100a having a fine ejection port for flying ink droplets A (see FIG. 1). The shape of the nozzle 100a is a horn shape (a substantially cylindrical shape, a substantially cylindrical shape, etc.), and the diameter of the ink droplet A of the nozzle 100a on the outlet side is about 20 to 35 μm. A water-repellent treatment layer (not shown) having a water-repellent surface treatment is provided on the surface of the nozzle plate 110 on the outlet side of the ink droplet A in order to stabilize the shape and flight characteristics of the ink droplet A.

The flow path plate 111 is obtained by patterning a communication port 100b communicating with a nozzle 100a, a pressure generating chamber 101, and a fluid resistance portion 102 by an etching method using a silicon single crystal substrate. In the present embodiment, a portion for narrowing the etching width is provided, and the portion is formed as the fluid resistance portion 102. The portion left by etching is a partition wall 101a forming each pressure generating chamber 101 of each nozzle 100a.

The diaphragm 112 has a thin film diaphragm portion 112a that facilitates deformation of the portion corresponding to the pressure generating chamber 101, an island portion 112b formed in the central portion of the diaphragm portion 112a, and the like. The diaphragm portion 112a has a thickness of 3 μm and a width of 35 μm (one side). Further, the diaphragm 112 has an opening region as an ink inflow port 103. In the present embodiment, two layers of Ni-plated films produced by the electroforming method are laminated to form a diaphragm portion 112a, an island portion 112b, an ink inflow port 103, and the like. The island portion 112b is formed in a portion where the piezoelectric element 120, the strut portion 121, and the frame 113 are located, and the adhesive layer 115 including the gap material is patterned and adhered to each of them. The piezoelectric element 120 is an example of a laminated piezoelectric element of an energy generation source 12. The frame 113 is formed of resin and has a common liquid chamber 104 and a cavity portion serving as an ink supply port 105.

The piezoelectric element 120 is composed of one layer of lead zirconate titanate (PZT) piezoelectric layer 120a and an internal electrode layer 120b made of silver and palladium (AgPd) alternately laminated. In the present embodiment, the above-mentioned piezoelectric element member is slit-processed by half-cut dicing, and the piezoelectric element member is divided into a comb-teeth shape. As a result, as shown in FIG. 4, the piezoelectric elements 120 and the support columns 121 are arranged alternately, and the support columns 121 are provided at positions corresponding to the partition walls 101a. The strut portion 121 has the same configuration as the piezoelectric element 120, but functions as a strut because no driving voltage is applied.

The piezoelectric element 120 has an individual electrode 120c in which the end face electrode of one end surface of the piezoelectric element member is divided by dicing processing by half cut, and the end face electrode on the other end surface is not divided and conducts with all the piezoelectric elements 120. It has a common electrode 120d. As shown in FIGS. 3 and 4, the piezoelectric element 120 alternately connects the internal electrode layers 120b to the individual electrodes 120c on the end faces and the common electrodes 120d. When a drive signal is applied to the piezoelectric element 120 and charging is performed, the piezoelectric element 120 expands, and when the charged charge is discharged to the piezoelectric element 120, the piezoelectric element 120 functions to contract. That is, the diaphragm portion 112a is deformed by the expansion and contraction of the piezoelectric element 120, and the pressure generating chamber 101 contracts and expands.

In order to give a drive signal to the individual electrodes 120c of the piezoelectric element 120, the FPC cable 120e is connected by solder bonding, ACF (anisotropic conductive film) bonding, wire bonding, or the like. A head driver 508 (see FIG. 5) for selectively applying a drive waveform to each piezoelectric element 120 is connected to the FPC cable 120e. Further, the common electrode 120d is connected to the ground (GND) electrode of the FPC cable 120e by providing an electrode layer at the end of the piezoelectric element 120 and turning it around.

As the nozzle plate 110, for example, a metal such as stainless steel or nickel, a combination of a metal and a resin such as a polyimide resin film, silicon, or a combination thereof can be used.

Further, the base material of the flow path plate 111 is not limited to the single crystal silicon substrate described above, and for example, a stainless steel substrate, a photosensitive resin, or the like can be used.

FIG. 5 is a diagram showing an example of the configuration of a control board that controls the inkjet recording device 1. The control board communicates with an external device (not shown) on the host side, such as an information processing device such as a personal computer, an image reading device such as an image scanner, and an imaging device such as a digital camera, and performs the entire inkjet recording device 1. Control.

The control board 500 of FIG. 5 includes a CPU (Central Processing Unit) 501, a ROM (Read Only Memory) 502, a RAM (Random Access Memory) 503, an NVRAM 504, an ASIC (Application Specific Integrated Circuit) 505, a host I / F506, and the like. It is connected.

The CPU 501 controls the entire inkjet recording device 1. The ROM 502 stores a control program, fixed data, and the like. The RAM 503 is used as a work area or the like when the CPU 501 executes a control program. The ASIC 505 performs signal processing on image data, image processing such as sorting, input / output signal processing, and the like. NVRAM 504 stores print settings and the like. The host I / F506 is a communication interface such as USB (Universal Serial Bus) or LAN (Local Area Network) for transmitting / receiving data or signals to / from the host side.

Further, the control board 500 has a print control circuit 507, a motor drive circuit 510, an AC (Alternating Current) bias supply circuit 512, an I / O 513, and the like as hardware for controlling the printing process of the inkjet recording device 1. These are connected to the CPU 501 or the like via a bus.

The print control circuit 507 outputs the drive waveform of the drive signal applied to the piezoelectric element 120 (see FIG. 4) and the control signal corresponding to the printed image to the head driver (driver IC) 508 based on the instruction from the CPU 501. To do.

The head driver 508 selectively drives the piezoelectric element 120 based on the control signal output by the print control circuit 507.

The motor drive circuit 510 rotates various rollers of the paper transport mechanism 20 by driving various motors at a rotation speed corresponding to various speed information such as a printing speed from the CPU 501.

The AC bias supply circuit 512 supplies the AC bias to the charging roller M according to the instruction from the CPU 501.

The I / O 513 inputs the output signal from the sensor group 514 provided in the inkjet recording device 1 to the CPU 501. The sensor group 514 included in the inkjet recording device 1 includes encoder sensors for various motors, a position sensor for detecting the transport position of the continuous paper 40, a temperature sensor for detecting the environmental temperature, and the like.

The inkjet recording device 1 also has an operation panel 515 and the like. The operation panel 515 includes an operation key for receiving an operation input from the operator of the inkjet recording device 1, an LCD (Liquid Crystal Display) for displaying output information, and the like. The operation panel 515 notifies the CPU 501 of the input information received from the operator via the bus. Further, the operation panel 515 displays the output information output from the CPU 501 via the bus on the LCD.

FIG. 6 is a diagram showing an example of the configuration of the print control circuit 507 and the head driver 508. As shown in FIG. 6, the print control circuit 507 includes a drive waveform generation circuit 701, a data transfer circuit 702, and the like. In addition, there is also an empty discharge drive waveform generation circuit (not shown) that generates a drive waveform for empty discharge, but the description thereof will be omitted here.

The drive waveform generation circuit 701 generates a common drive waveform from the drive waveform pattern data stored in the ROM 502 and outputs it to the analog switch 805 of the head driver 508. Specifically, the drive waveform generation circuit 701 is composed of a D / A converter (Digital to Analog Converter), a voltage amplifier, a current amplifier, and the like. The D / A converter D / A-converts the drive waveform pattern data, and a voltage amplifier, a current amplifier, or the like amplifies the converted analog signal. Then, the amplified signal is output to the head driver 508. The common drive waveform is a drive waveform common in one print cycle, and is a waveform having a plurality of drive pulses generated based on the drive waveform pattern data.

The data transfer circuit 702 serially outputs image data to the head driver 508. Further, the data transfer circuit 702 outputs a transfer clock, a latch signal, and a drop control signal M0 to M3 to the head driver 508. Here, the drop control signals M0 to M3 are 2-bit signals indicating the size of the ink droplet A to be ejected. For example, the drop control signal M0 is a 2-bit signal "00" indicating no drop, the drop control signal M1 is a 2-bit signal "01" indicating a small drop, and the drop control signal M2 is a 2-bit signal "10" indicating a medium drop. The drop control signal M3 is indicated by a 2-bit signal "11" indicating a large drop.

The head driver 508 includes a shift register 801, a latch circuit 802, a decoder 803, a level shifter 804, and an analog switch 805.

The shift register 801 registers the serially transferred image data in synchronization with the transfer clock. The latch circuit 802 latches each resist value of the shift register 801 with a latch signal. The decoder 803 decodes the image data and the drop control signals M0 to M3. The level shifter 804 converts the logic level signal voltage of the decoder 803 into a level at which the analog switch 805 can operate.

The analog switch 805 has a switch for each piezoelectric element 120, and each switch is connected to an individual electrode 120c of the corresponding piezoelectric element 120 as a changeover switch. Each switch opens and closes based on the signal voltage that controls each from the decoder 803. Specifically, each switch closes when a signal voltage indicating ON is output from the decoder 803, and passes the common drive waveform from the drive waveform generation circuit 701. Further, each switch opens when a signal voltage indicating off is output from the decoder 803, and blocks the passage of the common drive waveform from the drive waveform generation circuit 701. The voltage of the common drive waveform that has passed through each switch is applied to the corresponding piezoelectric element 120, and the piezoelectric element 120 is driven.

The inkjet recording apparatus 1 of the present embodiment eliminates density unevenness by performing density correction so that the image density is within a predetermined range at the first printing speed, and further, the first printing speed is the second. It has a function (automatic adjustment function) of automatically adjusting so that the density correction performed at the first printing speed is suitable even when the printing speed is changed. The "printing speed" refers to the same as the "relative speed" between the continuous paper 40 and the recording head 11.

Here, as an example, the CPU 501 realizes the automatic adjustment function by reading the program of the ROM 502 into the RAM 503 and executing the program. The automatic adjustment function is not limited to this example, and may be realized by a hardware circuit such as an ASIC.

FIG. 8 is a diagram showing an example of a functional block realized in the CPU 501. As shown in FIG. 8, the print execution unit 900 is realized in the CPU 501. The print execution unit 900 includes a speed setting unit 901, an image density correction unit 902, a discharge cycle calculation unit 903, an adjustment unit 904, and the like.

The speed setting unit 901 is a functional unit that sets the printing speed of image data in the motor drive circuit 510. Specifically, the speed setting unit 901 reads the print setting of the print data from the receive buffer of the host I / F 506, and outputs the speed information (print speed information) indicating the print speed set in the print setting to the motor drive circuit 510. Set to. Further, the speed setting unit 901 sets the speed-adjusted print speed information in the motor drive circuit 510 when the adjustment unit 904 instructs the speed adjustment.

When the operator inputs a density correction operation from the operation panel 515, the image density correction unit 902 is in a direction (that is, a scanning direction) orthogonal to the nozzle row 100 of the image (formed image) formed on the continuous paper 40. This is a functional unit that performs correction processing such as making the image density uniform. As an example of the correction process, the image density correction unit 902 changes the shape of the common drive waveform generated by the drive waveform generation circuit 701 by correcting the drive waveform pattern data stored in the ROM 502. For example, the discharge cycle of the common drive waveform is changed to improve the density unevenness.

As an example of other correction processing, the image density correction unit 902 data transfers the ejection time interval of the ink droplet A ejected from the nozzle row 100 from the N (N is a natural number) ejection to the N + 1th ejection. This is performed by shifting the timing of the control signal of the circuit 702. That is, the time interval for opening and closing each switch of the analog switch 805 is corrected so as to change for each print sequence. With this correction, for example, the time interval can be extended in the region where the dot density is high in the formed image, and the ejection time interval can be shortened in the region where the dot density is low, and the dot density in the entire region of the formed image can be shortened. Can be made uniform. Here, the dot refers to a dot formed by the impact of the ink droplet A on the continuous paper 40.

Further, as an example of other correction processing, the image density correction unit 902 performs a processing on the image data to correct a place provided as a dot in the formed image (that is, a place where each nozzle 100a strikes a dot). For example, the image density correction unit 902 uses a predetermined algorithm to thin out the number of dots to be struck in the region where the dot density is high in the formed image, or to increase the number of dots to be struck in the region where the dot density is low. Perform for image data. As a result, the image density correction unit 902 makes the dot density of the entire region of the formed image uniform. A specific example of this is shown in Modification 2.

Based on the change in the printing speed, the ejection cycle calculation unit 903 performs the ejection cycle (second) so that the conditions such as the ejection speed and the ejection amount (ejection volume) of the ink droplet A in one printing cycle are the same as those before the speed change. It is a functional unit that calculates the discharge cycle). For example, the ejection cycle calculation unit 903 uses the printing speed when the image density correction processing is performed by the image density correction unit 902 as a reference, and ejects ink droplets A at that time (first ejection). The second discharge cycle is calculated using the cycle) and the Helmholtz cycle for each nozzle 100a. The Helmholtz period is a natural vibration period based on resonance, mainly according to the shape of the ink flow path such as the pressure generating chamber 101. The following equations (1) and (2) are examples of calculation equations for calculating the second discharge cycle.

V (k) = 1 / R × 1 / T (k) ・ ・ ・ (1)
T (2) = T (1) + Tc × n ... (2)
Here, "R" is the resolution in the scanning direction, "V" is the printing speed, "T" is the ejection cycle, "Tc" is the Helmholtz cycle, "k" is a natural number, and "n" is an integer.

Equation (1) is an equation for mutually converting the printing speed (V) and the ejection period (T). Equation (2) is an equation obtained by adding an integral multiple of Helmholtz period Tc to the second discharge cycle (T (2)).

The ejection cycle calculation unit 903 formulates the printing speed V (1) (printing speed V (1) = first printing speed) when the image density correction processing is performed by the image density correction unit 902 in the equation (1). Substituting into the variable V (k), the value of the discharge cycle T (1) at that time (discharge cycle T (1) = first discharge cycle T (1)) is obtained. Further, the discharge cycle calculation unit 903 obtains the second discharge cycle T (2) from the equation (2) using the obtained discharge cycle T (1). Then, the discharge cycle calculation unit 903 substitutes the second discharge cycle T (2) into the variable T (k) of the equation (1), and the value of the printing speed V (2) (printing speed V (2) = first. The printing speed V (2)) of 2 is obtained. The relationship of equation (2) will be described later with reference to FIG.

The adjusting unit 904 is a functional unit that instructs the speed setting unit 901 to adjust the printing speed of the image data to the second printing speed V (2) obtained by the ejection cycle calculating unit 903.

(Phase adjustment)
Here, the second printing speed V (2) obtained by the ejection cycle calculation unit 903 will be described.
FIG. 7 is a diagram showing an example of the relationship between the waveform of the drive signal applied to the piezoelectric element 120 (common drive waveform) and the meniscus displacement in the nozzle 100a. In FIG. 7, when the horizontal axis is the elapsed time (t) and the vertical axis is the meniscus displacement, the drive signal waveform (drive signal waveform) f1 and the residual meniscus that is displaced following the drive signal waveform f1. The relationship with vibration (meniscus residual vibration) f2 is shown. The drive signal waveform f1 is an example of a pulse waveform in which ink droplets A are ejected by pulling.

When the signal of the drive signal waveform f1 of FIG. 7 is applied to the piezoelectric element 120, the piezoelectric element 120 contracts at the falling edge of the pulse waveform P, the volume of the pressure generating chamber 101 expands, and the inside of the pressure generating chamber 101 becomes negative. It becomes pressure. In this state, the pressure generating chamber 101 is filled with ink from the ink tank. Subsequently, the piezoelectric element 120 expands at the rise of the pulse waveform P, the volume of the pressure generating chamber 101 contracts, and the inside of the pressure generating chamber 101 is pressurized. In this state, the ink in the pressure generating chamber 101 is pushed out from the nozzle 100a, and one drop of ink A is separated from the ink and flies to the outside.

The displacement of the meniscus of the nozzle 100a due to the flight of the ink droplet A based on the drive signal waveform f1 is as shown in the meniscus residual vibration f2 of FIG. That is, the reference plane of the meniscus is displaced so as to swing in the internal direction (minus side) and then in the external direction (plus side) by the pulling operation based on the drive signal waveform f1, and the ink droplet A is displaced by the displacement. Vibration remains even after ejection. Due to this residual vibration, the meniscus residual vibration f2 affects the size and ejection speed of the ink droplet A when ejecting the subsequent ink droplet A (mainly the second ink droplet A). This causes uneven density, which can be improved by correcting the density.

The residual vibration mainly vibrates at the Helmholtz period Tc, and the period of the meniscus residual vibration f2 can be considered as the Helmholtz period Tc (constant). Since this period does not depend on the printing speed, the printing speed changes. However, the Helmholtz period Tc remains, and the residual vibration vibrates in the period of the meniscus residual vibration f2 shown in FIG. Therefore, when the ink droplet A is ejected with the first ejection cycle at the original printing speed (first printing speed) in the state where the printing speed is changed, the meniscus when the second ink droplet A is ejected. The displacement phase deviates from the phase at the first printing speed. For example, suppose that the phase at the first printing speed is 0 ° (position at time T0) and the phase at the second printing speed is 180 ° (position at time Ti). In this case, since the directions of mutation of the ink droplet A are opposite between the first printing speed and the second printing speed, the ejection speed and the ejection amount are significantly different from each other.

Therefore, even at the second printing speed, the printing speed is obtained so that the second ink droplet A is ejected in the same phase as at the first printing speed, and the printing speed is adjusted to that printing speed.

In FIG. 7, the first discharge cycle T (1) is from the start time of the first cycle of the drive signal waveform to the start time of the second cycle (for example, time T0). The Helmholtz period Tc multiplied by an integer is added to the first discharge cycle T (1) to obtain a second discharge cycle T (2). The start time of the second cycle of the drive signal waveform is shown as time T0 as an example, but the start of the second cycle is in the middle of pulling in, such as between time T0 and time Ti, or between time Ti and time Ta. It may be in the middle of extruding. Also in the second printing speed, if the start of the second cycle is between time T0 and time Ti or between time Ti and time Ta at the first printing speed, the phase of the meniscus displacement is matched. Set the start time of the second cycle to.

Further, considering the time after the phase of the meniscus displacement has passed 360 ° or more such as time Ta and time Tb as the start time of the second cycle of the drive signal waveform, “n” can take a negative value. For example, it is assumed that the start time of the second cycle of the drive signal waveform is the time Tb at the first printing speed. In this case, the start time of the second cycle of the drive signal waveform at the second printing speed can further take the time Ta (n = -1) and the time T0 (n = -2), and is "n". Is not limited to positive numbers including 0, but can also take negative values.

Although the second drop of ink A has been described here, the same applies to the second and subsequent drops of ink A.

Further, even when the ink droplet A includes a medium droplet or a large droplet formed by combining a plurality of ink droplets A in the air, the same effect can be obtained by aligning the phases of the residual vibrations.

In the present embodiment, the control board 500 (mainly the print control circuit 507), the head driver 508, the piezoelectric element 120, and the like correspond to the “pressure generating means”. The speed setting unit 901, the motor drive circuit 510, the paper transport mechanism 20, and the like correspond to the "speed control means". The image density correction unit 902 and the like correspond to the "image density correction means". The discharge cycle calculation unit 903 and the like correspond to the “discharge cycle calculation means”. The adjusting unit 904 or the like corresponds to the "adjusting means".

(Control flow)
FIG. 9 is a diagram showing an example of the overall control flow of the inkjet recording device 1. As shown in FIG. 9, the inkjet recording device 1 is first activated by turning on the power button or the like, and is in a standby state for a print job (S1).

After that, when a print request is received from the external device, the print process of the print job is executed (S2). Specifically, the CPU 501 reads the print processing program of the ROM 502 into the RAM 503 and executes the function of the print execution unit 900.

Then, the inkjet recording device 1 shuts down when the power button is turned off (S3).

FIG. 10 is a diagram showing an example of a processing flow of printing processing (see step S2 in FIG. 9) when the CPU 501 executes the function of the printing execution unit 900. Here, an example of a processing flow for adjusting the printing speed is mainly shown.

First, the print execution unit 900 (speed setting unit 901) sets the print speed of the image data in the motor drive circuit 510 (S11). Specifically, the speed setting unit 901 reads the print setting of the print data from the reception buffer of the host I / F 506, and sets the print speed information set in the print setting in the motor drive circuit 510 as an initial value. The host I / F 506 receives print data from an external device on the host side and stores it in the reception buffer.

Subsequently, the print execution unit 900 (image density correction unit 902) accepts the density correction operation (S12). For example, the image density correction unit 902 receives the density correction operation signal performed by the operator from the operation panel 515 as the density correction operation.

Subsequently, the print execution unit 900 (image density correction unit 902) performs correction processing such as making the image density of the formed image uniform in the scanning direction (S13). Here, as an example of the correction process, the image density correction unit 902 corrects the drive waveform pattern data stored in the ROM 502 and outputs it to the drive waveform generation circuit 701. For example, the interval (ejection interval) before and after each pulse for ejecting the ink contained in the common drive waveform is reviewed and changed for each pulse.

In this flow, an example is shown in which the image density correction unit 902 performs density correction when the density correction operation is accepted, but the image density correction unit 902 performs inkjet recording regardless of the operation of the operator. The density correction may be automatically performed once after the device 1 is started.

Subsequently, the print execution unit 900 reads the print data from the receive buffer of the host I / F 506 (S14), and determines whether or not the print speed setting has been changed (S15).

In the first determination in step S15, the read print speed is the same as the print speed read in step S11, so a No determination is made. In the determination from the second time, which will be described later, a Yes determination is made when the printing speed is changed. In the case of Yes determination, the processes of steps S16 to S20, which will be described later, continue.

If No is determined in step S15, the print execution unit 900 skips the processes of steps S16 to S18 and executes the print process (S19). In the printing process, the print execution unit 900 outputs the image data included in the print data to the data transfer circuit 702, outputs the drive waveform pattern data to the drive waveform generation circuit 701, and drives the motor at a set speed. The drive circuit 510 is instructed, and the AC bias supply circuit 512 is instructed to supply the AC bias. Based on those outputs from the print execution unit 900, each mechanism unit of the inkjet recording device 1 is controlled, and an image of the image data is formed on the continuous paper 40.

Subsequently, the print execution unit 900 determines whether the end flag of the flag area provided in the RAM 503 is set (S20). When the end flag is set (Yes determination), the main printing process (printing process in step S2 of FIG. 9) is terminated. If the end flag is not set (No determination), the process returns to step S14 and the process is repeated from step S14. It is assumed that the end flag is set by the operator turning off the power button of the inkjet recording device 1.

Next, the processing of steps S16 to S20 following the case where step S15 is a Yes determination will be described. If the print speed is changed from the immediately preceding one in the print settings of the subsequent print data, step S15 is a Yes determination.

When step S15 is a Yes determination, the print execution unit 900 (discharge cycle calculation unit 903) calculates the second printing speed (S16). The ejection cycle calculation unit 903 calculates the second printing speed by using, for example, equations (1) and (2).

Subsequently, the print execution unit 900 (adjustment unit 904) instructs the speed setting unit 901 to update the image data so as to adjust the print speed to the second print speed (S17).

Then, the print execution unit 900 (speed setting unit 901) sets the speed-adjusted print speed information in the motor drive circuit 510 (S18).

When the print speed is changed from the immediately preceding one in the print setting of the subsequent print data, the print execution unit 900 performs the processes of steps S16 to S18 to automatically adjust the changed print speed. , The printing process of step S19 is performed under the adjusted printing speed.

The information included in the print data indicating the change in the print speed may be the print speed itself, the information in which the print speed can be calculated, or the change level of the print speed (... , -3, -2, -1, 0, +1, +2, +3, ...). Here, the change level "0" indicates that there is no change in the printing speed. Further, the change level "+1" indicates that the printing speed is increased by one step, and "-1" indicates that the printing speed is decreased by one step.

When the information indicating the change in the printing speed is the printing speed itself, the adjusting unit 904 selects the printing speed closest to the printing speed from the calculated n second printing speeds.

When the information indicating the change in printing speed is the change level, the change level (..., -3, -2, -1, +1, +2) is changed to "n" in the formula (2) based on the immediately preceding print speed. , +3, ...), And the second printing speed at that time is obtained.

(Modification example 1)
An example of a modification in which n second printing speeds are displayed on the inkjet recording apparatus 1 and the operator selects the printing speed from the display speeds will be shown.

FIG. 11 is a diagram showing an example of the configuration of the functional block realized in the CPU 501 according to the modification 1. As shown in FIG. 11, the print execution unit 900 is further provided with a print speed display reception unit 905. In the ejection cycle calculation unit 903 shown in FIG. 11, n second printing speeds are calculated immediately after the image density correction is performed. The calculated n second print speed information is temporarily stored in a predetermined area of the RAM 503. Here, n is a number equal to or less than a predetermined upper limit.

The print speed display reception unit 905 sets n second print speed information stored in the RAM 503 as the selection screen information and outputs the information to the operation panel 515. The print speed display reception unit 905, the operation panel 515, and the like correspond to the "display means".

FIG. 12 is a diagram showing an example of the selection screen 1000 when the selection screen information is displayed on the operation panel 515. As shown in FIG. 12, n print speed selection buttons b1 to bn are arranged in the print speed selection area 1001. Each selection button b1 to bn accepts a selection by a button operation by an operator, and notifies the CPU 501 of identification information for identifying each selection button b1 to bn.

The print speed display reception unit 905 receives the identification information notified by selecting the selection buttons b1 to bn from the operation panel 515, and notifies the speed setting unit 901 of the printing speed corresponding to the received identification information. The print speed display reception unit 905, the selection screen 1000 of the operation panel 515, and the like correspond to the "reception means".

FIG. 13 is a diagram showing an example of the processing flow of the printing process according to the modified example 1. A change from the processing flow of FIG. 10 will be described with reference to FIG. In the processing flow of FIG. 13, after the correction processing in step S13, the ejection cycle calculation unit 903 performs a process of calculating n second printing speeds (S13-1).

Further, after reading the print data in step S14, the print speed display receiving unit 905 outputs selection screen information including n second print speed information to the operation panel 515, and further receives the second print speed information. Process (S14-1).

Further, the process of step S16 is omitted, and the process of step S15 and step S17 is performed by the print speed display reception unit 905.

(Modification 2)
Another example of the correction process is shown. As another example of the correction process, the image density correction unit 902 performs a process of correcting a place provided as a dot in the formed image (that is, a place where each nozzle 100a strikes a dot) on the image data. For example, the image density correction unit 902 thins out the number of dots to be struck in the region where the dot density is high in the formed image, or increases the number of dots to be struck in the region where the dot density is low, for the image data. .. As a result, the image density correction unit 902 makes the dot density of the entire region of the formed image uniform.

FIG. 14 is an explanatory diagram of a process of correcting the location where each nozzle 100a strikes a dot on the image data. FIG. 14A shows an example of the dot arrangement of the formed image before the correction process, and FIG. 14B shows an example of the dot arrangement of the formed image after the correction process.

In FIGS. 14 (a) and 14 (b), each cell corresponds to one dot, the cells indicated by diagonal lines indicate the cells on which an image is formed, and the other cells are cells on which an image is not formed. Shown. Further, each dot arrangement of FIGS. 14 (a) and 14 (b) shows only a part of the first half of the entire formed image, and the other parts are not shown. By transporting the continuous paper 40 in the transport direction X at the first printing speed and sequentially ejecting ink droplets A from the nozzle row 100 at a predetermined timing, the continuous paper is sequentially ejected one row at a time from the first row on the transport direction X side. An image shown by a diagonal line is formed at 40.

In the example shown in FIG. 14A, the fourth ink droplet A ejected from the nozzle row 100 is different from the phase of the meniscus displacement when the second droplet is ejected by nearly 180 °. In this example, the ejection interval of the third and fourth drops A shown in the range m1 is narrowed from the ejection interval of the first and second drops A, and the ejection amount of the ink droplet A is also increased. In addition, the image is formed even in the cells where the image is not formed. Therefore, the dot density in the range m1 is higher than the other dot densities.

Such a region where the dot density is high appears repeatedly and causes density unevenness in the formed image. Therefore, the dots struck in such a region having a high dot density are corrected on the image data to make the dot density of the entire formed image uniform. For example, the dot pattern in the region with high dot density is compared with the pattern of the image data in that region, and the pattern is corrected so as to approach the pattern of the image data. Specifically, corrections are made such as changing the presence or absence of dots to reduce the number of dots originally struck, and changing the arrangement pattern of the discharged liquid to indicate whether or not the dots are struck.

FIG. 14B shows an example of the dot arrangement of the formed image after the correction process. The image of the range m2 shown in FIG. 14B is formed by the third and fourth ink droplets A forming the image of the range m1 shown in FIG. 14A. As shown in FIG. 14B, the correction adds a region in which no image is formed to the region of the range m2, and the density unevenness is improved.

As described above, in the present embodiment and each modification, even if the printing speed is changed after the density correction, the printing speed can be automatically adjusted to correspond to the density correction. Therefore, it is not necessary to manually perform the density correction every time the printing speed is changed, and the work load on the operator is reduced.

In the present embodiment and each modification, the "device for discharging the liquid" may include means for feeding, transporting, and discharging paper to which the liquid can adhere, and also includes a pretreatment device, a posttreatment device, and the like. it can.

The "device that discharges liquid" includes not only a device that can discharge liquid to a device to which liquid can adhere (recording target), but also a device that directs the liquid to the air or liquid (recording target). A discharge device is also included. For example, an image forming apparatus, a three-dimensional modeling apparatus, a processing liquid coating apparatus, an injection granulation apparatus, and the like are applicable. For example, as a "device that ejects a liquid", an image forming apparatus that ejects ink droplets to form an image on paper, and a three-dimensional object (three-dimensional object) are formed by layering powder. There is a three-dimensional modeling device (three-dimensional modeling device) that discharges a modeling liquid into the formed powder layer.

Further, the "device for discharging a liquid" is not limited to a device in which a significant image such as characters and figures is visualized by the discharged liquid. For example, those that form patterns that have no meaning in themselves and those that form a three-dimensional image are also included.

In addition, as a "device for ejecting liquid", a treatment liquid coating device for ejecting a treatment liquid to the paper in order to apply the treatment liquid to the surface of the paper for the purpose of modifying the surface of the paper, raw materials. There is an injection granulation device that granulates fine particles of raw materials by injecting a composition liquid in which the above-mentioned material is dispersed in a solution through a nozzle.

The above-mentioned "material to which a liquid can adhere" means a material to which a liquid can adhere at least temporarily, such as one that adheres and adheres, and one that adheres and permeates. Specific examples include recording media such as paper, recording paper, recording paper, film, and cloth, electronic substrates, electronic components such as piezoelectric elements, powder layers (powder layers), organ models, and media such as inspection cells. , Unless otherwise specified, includes anything to which the liquid adheres.

The material of the above-mentioned "material to which liquid can be attached" may be paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics or the like as long as the liquid can be attached even temporarily.

The "liquid" may have a viscosity and surface tension that can be discharged from the head, and is not particularly limited, but has a viscosity of 30 mPa · s or less at room temperature, under normal pressure, or by heating or cooling. It is preferable to have. More specifically, solvents such as water and organic solvents, colorants such as dyes and pigments, polymerizable compounds, resins, functionalizing materials such as surfactants, biocompatible materials such as DNA, amino acids and proteins, and calcium. , Solvents, suspensions, emulsions, etc. containing edible materials such as natural pigments, etc., for example, inks for inkjets, surface treatment liquids, constituents of electronic elements and light emitting elements, and formation of electronic circuit resist patterns. It can be used for applications such as a liquid for use and a material liquid for three-dimensional modeling.

The program executed in the embodiment and each modification is provided by being incorporated in a memory unit such as a ROM in advance, but the present invention is not limited to this. The program executed in the embodiment and each modification may be recorded on a computer-readable recording medium and provided as a computer program product. For example, a file in an installable format or an executable format may be recorded and provided on a recording medium such as a flexible disc, a CD-R, a DVD (Digital Versatile Disk), a Blu-ray disc (registered trademark), or a semiconductor memory. Good.

Further, the program executed in the embodiment and each modification may be stored on a computer connected to a network such as the Internet and provided by downloading via the network. Further, the program executed in the embodiment and each modification may be provided or distributed via a network such as the Internet.

501 CPU
900 Print execution unit 901 Speed setting unit 902 Image density correction unit 903 Discharge cycle calculation unit 904 Adjustment unit

JP-A-2015-24555

Claims (7)

A nozzle that discharges liquid to the recording target and
A pressure generating means that fluctuates the pressure of the liquid chamber corresponding to the nozzle, and
A speed control means for controlling the relative speed between the nozzle and the recording target,
An image density correction means for correcting the image density at the first relative speed of the relative speed,
The second discharge cycle of the liquid is set based on the first discharge cycle of the liquid at the first relative velocity when the image density is corrected by the image density correction means and the Helmholtz cycle corresponding to the nozzle. The desired discharge cycle calculation means and
An adjusting means for adjusting the relative velocity to the second relative velocity so as to have the second discharge cycle, and
Have,
A device that ejects a liquid that prints on the recording target at the second relative speed adjusted by the adjusting means. The discharge cycle calculating means
(Relative velocity) = (1 / resolution) x (1 / discharge cycle)
(Second discharge cycle) = (First discharge cycle) + (Helmholtz cycle) x (integer)
Find the second discharge cycle to satisfy
The device for discharging the liquid according to claim 1. The discharge cycle calculating means obtains the second discharge cycle corresponding to the second relative velocity input from the outside.
The device for discharging the liquid according to claim 1 or 2. In the adjusting means, the relative speed corresponding to the second discharge cycle, which is the closest to the relative speed instructed to be changed, is set as the second relative speed, and the first relative speed is set as the second relative speed. Adjust,
The device for discharging the liquid according to any one of claims 1 to 3. A display means for displaying a plurality of second relative velocity information indicating the second relative velocity, and
A receiving means for receiving one second relative velocity information as the second relative velocity from the plurality of second relative velocity information.
Have,
The adjusting means adjusts the relative velocity so as to have the second discharge cycle received by the receiving means.
The device for discharging the liquid according to claim 1 or 2. The correction of the image density is performed by changing the presence / absence of discharge of the liquid or the arrangement pattern of the discharged liquid.
The device for discharging the liquid according to any one of claims 1 to 5. A method of controlling a device that discharges liquid.
The step of setting the first relative speed between the nozzle that discharges the liquid and the recording target,
The step of correcting the image density at the first relative speed and
When instructed to change the speed of the first relative speed, the first discharge cycle of the liquid at the first relative speed when the image density is corrected and the Helmholtz cycle corresponding to the nozzle. The step of obtaining the second discharge cycle of the liquid based on
The step of adjusting the relative speed to the second relative speed so as to have the second discharge cycle,
The step of performing the printing process on the recording target at the adjusted second relative speed, and
Method to have.

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