JP2020032574A - Liquid discharge device and liquid discharge method of liquid discharge head - Google Patents

Abstract

To provide a liquid discharge device that supplies liquid to a plurality of recording heads through a branched supply part, which can suppress variation in pressure without converting pressure in the branch supply part to negative pressure.SOLUTION: The liquid discharge device according to one embodiment of a disclosed technique, which has a branched supply part that supplies liquid to each of a plurality of recording heads, comprises: a memorizing part that memorizes correction data for correcting variation in pressure inside the branched supply part when discharging the liquid, for each recording head; a pressurizing part that applies pressure to the liquid to be fed to the branched supply part; a correction data acquiring part that acquires the correction data by referring to the memorizing part, corresponding to the recording head specified as the recording head that discharges the liquid; and a pressurization control part that controls the pressurizing part on the basis of the correction data.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a liquid ejection apparatus and a drive control method for a liquid ejection head.

  In a liquid ejection apparatus using a plurality of recording heads such as a line head, the variation in the ejection of liquid by each recording head is detected by detecting and correcting pressure fluctuations in the liquid tank and keeping the pressure in the liquid tank constant. Suppression techniques are known.

  Further, there is known an apparatus that supplies liquid to a plurality of recording heads from a liquid tank via a branch supply unit (manifold) and discharges the liquid from the recording heads.

  In order to correct such pressure fluctuations in the branch supply unit, the amount of liquid ejected from the nozzles of the recording head is predicted, and the elasticity of the flexible film disposed between the liquid chamber and the gas chamber is predicted according to the predicted value. A device for controlling the rate is disclosed (for example, see Patent Document 1).

  However, in the device of Patent Literature 1, when the pressure is corrected, the pressure in the branch supply unit turns to a negative pressure, which may make it difficult to control the liquid ejection.

  The present invention has been made in view of the above points, and in a liquid ejection apparatus that supplies liquid to a plurality of recording heads via a branch supply unit, without changing the pressure in the branch supply unit to a negative pressure. Another object is to suppress pressure fluctuation.

  A liquid ejection device according to an aspect of the disclosed technology is a liquid ejection device that has a branch supply unit that supplies a liquid to each of a plurality of recording heads, and the ejection of the liquid is performed for each of the recording heads. A storage unit that stores correction data for correcting pressure fluctuations inside the branch supply unit, a pressure unit that applies pressure to the liquid that is sent to the branch supply unit, and a recording head that discharges the liquid are specified. A correction data acquisition unit configured to acquire the correction data by referring to the storage unit according to the recording head; and a pressure control unit configured to control the pressure unit based on the correction data.

  According to the embodiment of the present invention, in a liquid ejection apparatus that supplies liquid to a plurality of recording heads via a branch supply unit, it is possible to suppress pressure fluctuation without turning the pressure in the branch supply unit to a negative pressure. it can.

FIG. 1 is a diagram illustrating an example of a configuration of an image forming apparatus according to an embodiment. FIG. 2 is a diagram illustrating an example of a configuration of an image forming unit of the image forming apparatus according to the embodiment. FIG. 2 is a diagram illustrating an example of a configuration of a recording head unit according to the embodiment. FIG. 3 is a diagram illustrating an example of an internal structure of a recording head according to the embodiment. FIG. 2 is a block diagram illustrating an example of a hardware configuration of the image forming apparatus according to the embodiment. FIG. 2 is a block diagram illustrating an example of a configuration of a printhead control unit, a drive waveform generation circuit, and a printhead driver. FIG. 2 is a functional block diagram illustrating an example of a configuration of an image processing unit according to the embodiment. FIG. 3 is a diagram illustrating an example of a configuration of an ink supply unit according to the embodiment. FIG. 3 is a diagram illustrating, as functional blocks, an example of components of an ink supply control unit according to the first embodiment. 6 is a flowchart illustrating an example of a correction data acquisition process according to the embodiment. It is an image figure explaining an example of pressure change data acquired by the pressure acquisition part concerning an embodiment. FIG. 4 is an image diagram illustrating an example of correction data according to the embodiment. It is an image figure explaining an example of pressure change data acquired by the pressure acquisition part concerning an embodiment. FIG. 4 is an image diagram illustrating an example of correction data according to the embodiment. FIG. 5 is a diagram illustrating an example of correction data stored in a storage unit according to the first embodiment. 6 is a flowchart illustrating an example of a pressure fluctuation correction process according to the embodiment. It is a figure showing an example of the correction result of pressure change concerning an embodiment. It is a figure showing an example of the pressure fluctuation inside the branch supply part concerning an embodiment. It is a figure showing an example of the stable period of the pressure inside the branch supply part concerning an embodiment. FIG. 9 is a diagram illustrating, as functional blocks, an example of components of an ink supply control unit according to a second embodiment. FIG. 14 is a diagram illustrating an example of correction data stored in a storage unit according to the second embodiment. FIG. 13 is a diagram illustrating, as functional blocks, an example of components of an ink supply control unit according to a third embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicate description may be omitted.

  In the embodiment, an image forming apparatus that forms an image by ejecting ink onto recording paper by an inkjet method will be described as an example. The recording paper is, for example, a sheet cut into a certain size such as an A size or a B size. Note that the image forming apparatus is an example of a “liquid ejection apparatus”, the ink is an example of a “liquid”, and the recording paper is an example of a “recording medium”.

<Image forming apparatus>
FIG. 1 is a diagram illustrating an example of a configuration of an image forming apparatus according to an embodiment. As shown in FIG. 1, the image forming apparatus 10 includes a paper feed unit 11, an image forming unit 12, a drying unit 13, and a paper discharge unit 14.

  The paper feeding unit 11 stores the recording paper P and feeds the recording paper P in order from the top. The recording paper P is conveyed to the image forming unit 12 at a timing by the registration roller pair 110.

  The image forming unit 12 includes cylinders 122 and 123, a drum 121, and a recording head unit 120. Further, the recording head unit 120 includes a recording head unit 120K, a recording head unit 120C, a recording head unit 120M, and a recording head unit 120Y, facing the round surface of the drum 121. Incidentally, the subscripts of K, C, M and Y indicate the colors of K for black, C for cyan, M for magenta and Y for yellow.

  The recording paper P is transferred from the registration roller pair 110 to the drum 121 via the cylinder 122. The drum 121 rotates and conveys the recording paper P in the recording paper conveyance direction indicated by an arrow 124 in FIG. The recording head unit 120K discharges black ink and the recording head unit 120C discharges cyan ink on the recording paper P that is rotated and conveyed. Similarly, the recording head unit 120M discharges magenta ink, and the recording head unit 120Y discharges yellow ink. The image forming unit 12 is a recording head unit of a corresponding color based on image information, applies ink of each color to the recording paper P, and forms a visible image on the recording paper P.

  After the recording paper P is coated with ink, the recording paper P is supplied from the drum 121 to the transport belt 131 of the drying unit 13 via the cylinder 123 and is transported. The ink on the recording paper P is dried while passing through the drying unit 13. You. For example, the drying unit 13 is provided with a plurality of nozzles. The drying unit 13 blows the heated air (warm air) through the nozzles to the surface of the recording paper P on which the ink is applied, thereby drying the ink on the recording paper P in a non-contact manner.

  The recording paper P on which the ink has been dried is discharged to the outside of the image forming apparatus 10 by the paper discharge unit 14. Alternatively, the sheet is stored in a stacker provided in the sheet discharging unit 14.

  FIG. 2 is a diagram illustrating an example of a configuration of an image forming unit of the image forming apparatus according to the embodiment.

  As described above, the recording paper P is transferred from the registration roller pair 110 to the drum 121 via the cylinder 122. The cylinder 122 includes a gripper (not shown). The gripper grips the recording paper P to rotate and convey it, and delivers the recording paper P to the drum 121. The drum 121 can adsorb the recording paper P to the surface of the cylindrical surface of the drum 121 by flowing air from the outside to the inside of the drum 121.

  The drum 121 rotates and conveys the recording paper P in the conveyance direction indicated by the arrow 124 while the recording paper P is sucked by air. The recording head units 120K to 120Y discharge inks of respective colors on the surface of the recording paper P to be conveyed opposite to the suction surface.

  Each recording head unit of each color includes a plurality of recording heads arranged in a direction intersecting the transport direction of the recording paper P. The direction intersecting with the transport direction of the recording paper P is, for example, the axial direction of the drum 121. The configuration of the recording head unit will be separately described in detail with reference to FIG.

  The recording paper P coated with the ink is transferred from the drum 121 to the cylinder 123. The cylinder 123 also includes a gripper (not shown). The gripper grips the recording paper P to rotate and transport the recording paper P, and supplies the recording paper P to the transport belt 131 of the drying unit 13.

  The transport direction indicated by the arrow 124 in FIG. 1 or FIG. 2 is an example of a “predetermined transport direction”, and the axial direction of the drum 121 in FIG. 1 or FIG. "Is an example.

  In the embodiment, an image forming apparatus that ejects four color inks of black, cyan, magenta, and yellow is shown, but is not limited thereto. For example, a recording head unit that ejects green, red, light cyan, or other color inks may be further provided. Further, for example, a recording head unit for only black may be provided.

<Recording head unit>
FIG. 3 is a diagram illustrating an example of a configuration of the recording head unit according to the embodiment. FIG. 3A is a plan view illustrating an example of a configuration of the recording head unit according to the embodiment. FIG. 2A shows a full-line type recording head unit as an example.

  The recording head unit 120 arranges recording head units of respective colors in the order of black, cyan, magenta, and yellow from the upstream in the transport direction 124 of the recording paper P. The embodiment is not limited to black, cyan, magenta, and yellow, which are the order of arrangement in FIG. For example, yellow, magenta, cyan, black, and the like may be used.

  For example, the black recording head unit 120K includes a recording head 120K-1, a recording head 120K-2, a recording head 120K-3, a recording head 120K-4, and a recording head 120K-5. These are arranged in a staggered manner in a direction intersecting with the conveying direction 124 of the recording paper P as shown in the figure. The recording heads 120K-1 to 120-5 are connected to the ink supply unit 15K so that the ink can flow. The recording heads 120K-1 to K-5 are supplied with ink from the ink supply unit 15K, and can discharge the supplied ink with each recording head.

  Similarly, the recording head units 120K, 120C, 120M, and 120Y for each color also have five recording heads arranged in a staggered manner, and ink is supplied from an ink supply unit. The recording head unit 120 can perform image formation on the entire image forming area of the recording paper P in a direction intersecting with the transport direction 124 by using the recording head units of each color. The configuration and function of the ink supply unit will be described in detail with reference to FIGS. 8 to 10 and FIG.

  A recording head unit including a plurality of recording heads and capable of forming an image on the entire image forming area of the recording paper P in a direction intersecting with the transport direction 124 is referred to as a “line head”. Also, enabling image formation over the entire image forming area of the recording paper P in a direction intersecting with the transport direction 124 is referred to as “line-forming”.

  FIG. 3A shows an example in which a plurality of recording heads are arranged in a staggered manner to form a recording head unit in a line. However, a plurality of heads may be arranged in a straight line to form a line, or one head may be used. It may be a line. The color scheme is not limited to this.

  Since the black, cyan, magenta, and yellow recording heads all have the same configuration, the following describes the black recording heads 120K-1, 120K-2, 120K-3, 120K-4, and 120K-5 as examples. I do.

  FIG. 3B is a diagram illustrating one of the recording heads that is a main part of the recording head unit according to the embodiment. As shown in FIG. 3B, the recording head 120K-1 has a plurality of nozzles 40N formed on the nozzle plate 43. Each nozzle is a discharge port for discharging ink. The nozzles 40N are arranged in a direction intersecting with the transport direction 124 to form a nozzle row. Although FIG. 3B shows one nozzle row, the recording head 120K-1 may include a plurality of nozzle rows.

<Recording head>
Next, FIG. 4 is a diagram illustrating an example of the internal structure of the recording head according to the embodiment. FIG. 4A is a cross-sectional view of the recording head 120K-1 in the longitudinal direction of the liquid chamber, and FIG. 4B is a cross-sectional view of the transverse direction of the liquid chamber, which is a cross section of SC1 in FIG. .

  In FIG. 4A, the print head (eg, 120K-1) of the print head unit 120 includes a flow path plate 41 that forms a passage for ejecting ink, and a lower surface of the flow path plate 41 (inward of the print head). The vibration plate 42 includes a joined diaphragm 42, a nozzle plate 43 joined to the upper surface of the flow path plate 41 (outward of the recording head), and a frame member 44 that holds a peripheral portion of the diaphragm 42. The recording head has a pressure generating section (actuator section) 45 for deforming the diaphragm 42.

  The recording head according to the embodiment has a nozzle communication path 40R and a liquid chamber (pressure chamber) 40F which are flow paths communicating with the nozzles 40N by stacking the flow path plate 41, the vibration plate 42, and the nozzle plate 43. Is formed. In the recording head, by further laminating the frame member 44, an ink inlet 40S for supplying ink to the liquid chamber 40F, a common liquid chamber 40C for supplying ink to the liquid chamber 40F, and the like are formed.

  Further, in the embodiment, the frame member 44 has an accommodation portion for accommodating the pressure generating portion 45, a concave portion serving as the common liquid chamber 40C, and an ink supply port 40IN for supplying ink to the common liquid chamber 40C from outside the recording head. Are formed.

  In the embodiment, the pressure generation unit 45 includes a pressure generation element 45P that is an electromechanical conversion element, a base substrate 45B that joins and fixes the pressure generation element 45P, and a column that is disposed in a gap between the adjacent pressure generation elements 45P. It has. The pressure generating section 45 includes an FPC cable 45C for connecting the pressure generating element 45P to a drive circuit (drive IC).

  Here, as shown in FIG. 4B, a stacked pressure generating element (PZT; Piezoelectric Transducer) in which piezoelectric materials 45Pp and internal electrodes 45Pe are alternately stacked is used as the pressure generating element 45P. The internal electrode 45Pe has a plurality of individual electrodes 45Pei and a plurality of common electrodes 45Pec. In the embodiment, the internal electrodes 45Pe alternately connect the individual electrodes 45Pei or the common electrodes 45Pec to the end faces of the pressure generating elements 45P.

  Hereinafter, the operation of the recording head to eject ink from the nozzle 40N (pull-push operation) will be specifically described.

  In the recording head, first, the voltage applied to the pressure generating element 45P (pressure generating element) is reduced from the reference potential, and the pressure generating element 45P is reduced in the stacking direction. Further, the recording head bends and deforms the diaphragm 42 by reducing the size of the pressure generating element 45P. At this time, the recording head expands (expands) the volume (volume) of the liquid chamber 40F by the bending deformation of the diaphragm 42. By this operation, ink flows from the common liquid chamber 40C into the liquid chamber 40F in the recording head.

  Next, the recording head increases the voltage applied to the pressure generating element 45P to extend the pressure generating element 45P in the stacking direction. Further, the recording head deforms the vibration plate 42 in the direction of the nozzle 40N by the extension of the pressure generating element 45P. At this time, the recording head reduces (shrinks) the volume (volume) of the liquid chamber 40F due to the deformation of the diaphragm 42. With this operation, the recording head applies pressure to the ink in the liquid chamber 40F. In addition, the recording head discharges (ejects) ink from the nozzles 40N by pressurizing the ink.

  Thereafter, the recording head returns the voltage applied to the pressure generating element 45P to the reference potential, and returns (restores) the diaphragm 42 to the initial position. At this time, the recording head decompresses the inside of the liquid chamber 40F by expanding the liquid chamber 40F, and fills (replenishes) the ink from the common liquid chamber 40C into the liquid chamber 40F. Next, after the vibration of the meniscus surface of the nozzle 40N is attenuated (stable), the recording head shifts to an operation for discharging the next ink, and repeats the above operation.

  Thus, the recording head deforms (bends) the diaphragm 42 by using the pressure generating unit 45. Accordingly, the recording head changes the volume (volume) of the liquid chamber 40F, and changes the pressure acting on the ink in the liquid chamber 40F. As a result, the recording head ejects ink from the nozzles 40N.

  Note that the method of driving the recording head to which the embodiment is applicable is not limited to the above example (pull-push). For example, in the method of driving the recording head, pulling or pushing may be performed by controlling the voltage (driving waveform) applied to the pressure generating element 45P. Further, the pressure generating section 45 is of a thermal type in which ink in the liquid chamber 40F is heated by using a heating resistor to generate bubbles, or a diaphragm and an electrode are arranged opposite to the wall surface of the liquid chamber 40F, An electrostatic type in which the diaphragm is deformed by the electrostatic force generated between the electrode and the electrode may be used.

  As described above, the recording head unit 120 of the image forming apparatus 10 according to the embodiment includes the recording head units for each color, and each recording head unit includes a plurality of recording heads. For example, the recording head unit 120K includes the recording heads 120K-1, 120K-2, 120K-3, 120K-4, and 120K-5. The image forming apparatus 10 forms a black-and-white or full-color image over the entire area of the image forming area by one conveyance operation of the recording medium by using such a recording head unit 120.

<Description of control>
FIG. 5 is a block diagram illustrating an example of a hardware configuration of the image forming apparatus 10 according to the embodiment. The image forming apparatus 10 includes a main control board 100, a head relay board 200, and an image processing board 300.

  The main control board 100 includes a CPU (Central Processing Unit) 101, an FPGA (Field-Programmable Gate Array) 102, a RAM (Random Access Memory) 103, a ROM (Read Only Memory) 104, and an NVRAM (Non-Volatile Random Access Memory). 105, a motor driver 106, a drive waveform generation circuit 107, and the like are mounted.

  The CPU 101 controls the entire operation of the image forming apparatus 10. For example, using the RAM 103 as a work area, the CPU 101 executes various control programs stored in the ROM 104 and outputs control commands for controlling various operations in the image forming apparatus 10. At this time, the CPU 101 controls various operations in the image forming apparatus 10 in cooperation with the FPGA 102 while communicating with the FPGA 102.

  The CPU 101 is electrically connected to the ink supply control unit 400 via the transmission unit 117, and can transmit a control command or a signal indicating data or the like to the ink supply control unit 400. The ink supply control unit 400 will be described in detail with reference to FIG.

  The FPGA 102 includes a CPU control unit 111, a memory control unit 112, an I2C control unit 113, a sensor processing unit 114, a motor control unit 115, and a printhead control unit 116.

  The CPU control unit 111 has a function of communicating with the CPU 101. The memory control unit 112 has a function of accessing the RAM 103 and the ROM 104. The I2C control unit 113 has a function of communicating with the NVRAM 105.

  The sensor processing unit 114 processes the sensor signals of the various sensors 130. The various sensors 130 are generic names of sensors that detect various states in the image forming apparatus 10. The various sensors 130 include, in addition to the encoder sensor described above, a recording paper sensor that detects passage of the recording paper P, a cover sensor that detects opening of the cover member 2a, a temperature and humidity sensor that detects environmental temperature and humidity, and a recording paper P. The recording paper fixing lever sensor for detecting the operation state of the lever for fixing the ink cartridge, the remaining amount detecting sensor for detecting the remaining amount of ink in the ink cartridge, and the like are included. Note that an analog sensor signal output from a temperature / humidity sensor or the like is converted into a digital signal by an AD converter mounted on, for example, the main control board 100 and input to the FPGA 102.

  The motor control unit 115 controls various motors 140. The various motors 140 are generic names of motors provided in the image forming apparatus 10. The various motors 140 include a sub-scanning motor for conveying the recording paper P in the sub-scanning direction, a paper feeding motor for feeding the recording paper P, a maintenance motor for operating a maintenance mechanism, and the like.

  Here, a specific example of control by cooperation between the CPU 101 and the motor control unit 115 of the FPGA 102 will be described using the operation control of the sub-scanning motor as an example. First, the CPU 101 notifies the motor control unit 115 of an operation start instruction of the sub-scanning motor and a moving speed and a moving distance of the recording paper P.

  Upon receiving this instruction, the motor control unit 115 generates a drive profile based on the information on the movement speed and the movement instruction notified from the CPU 101, and generates an encoder value (sensor signal of the encoder sensor) supplied from the sensor processing unit 114. The PWM command value is calculated and output to the motor driver 106 while comparing with the value obtained by the processing.

  Upon ending the predetermined operation, the motor control unit 115 notifies the CPU 101 of the end of the operation. Although an example in which the motor control unit 115 generates a drive profile has been described here, a configuration in which the CPU 101 generates a drive profile and instructs the motor control unit 115 may be used. The CPU 101 also counts the number of printed sheets.

  The recording head control unit 116 passes the head drive data, the ejection synchronization signal LINE, and the ejection timing signal CHANGE stored in the ROM 104 to the drive waveform generation circuit 107, and causes the drive waveform generation circuit 107 to generate a common drive waveform signal Vcom. The common drive waveform signal Vcom generated by the drive waveform generation circuit 107 is input to a recording head driver 210 described later mounted on the head relay board 200.

  FIG. 6 is a block diagram illustrating an example of a configuration of the printhead control unit 116, the drive waveform generation circuit 107, and the printhead driver 210.

  Upon receiving the trigger signal Trig that triggers the timing of ejection, the printhead control unit outputs to the drive waveform generation circuit 107 an ejection synchronization signal LINE that triggers generation of a drive waveform. Further, an ejection timing signal CHANGE corresponding to a delay amount from the ejection synchronization signal LINE is output to the drive waveform generation circuit 107. The drive waveform generation circuit 107 generates a common drive waveform Vcom at a timing based on the ejection synchronization signal LINE and the ejection timing signal CHANGE.

  Further, the recording head control unit 116 receives the image data SD ′ after the image processing from the image processing unit 310 described later provided on the image processing substrate 300, and based on the image data SD ′, the recording head 120K-1. A mask control signal MN for selecting a predetermined waveform of the common drive waveform signal Vcom in accordance with the size of the ink droplet ejected from each nozzle. The mask control signal MN is a signal having a timing synchronized with the ejection timing signal CHANGE. Then, the printhead control unit 116 transfers the image data SD ′, the synchronous clock signal SCK, the latch signal LT for instructing the latch of the image data, and the generated mask control signal MN to the printhead driver 210.

  The print head driver 210 includes a shift register 211, a latch circuit 212, a gradation decoder 213, a level shifter 214, and an analog switch 215.

  The shift register 211 receives the image data SD ′ and the synchronous clock signal SCK transferred from the recording head controller 116. The latch circuit 212 latches each resist value of the shift register 211 by a latch signal LT transferred from the recording head control unit 116.

  The gradation decoder 213 decodes the value (image data SD ′) latched by the latch circuit 212 and the mask control signal MN and outputs the result. The level shifter 214 converts the logic level voltage signal of the gradation decoder 213 to a level at which the analog switch 215 can operate.

  The analog switch 215 is a switch that is turned on / off by an output of the gradation decoder 213 provided via the level shifter 214. The analog switch 215 is provided for each pressure generating element (piezoelectric element) 45P associated with the above-described nozzle included in the recording head 120K-1, and is connected to the individual electrode 83 of the pressure generating element 45P corresponding to each nozzle. ing. The analog switch 215 receives the common drive waveform signal Vcom from the drive waveform generation circuit 107. Further, as described above, the timing of the mask control signal MN is synchronized with the timing of the common drive waveform Vcom.

  Therefore, by turning on / off the analog switch 215 at an appropriate timing in accordance with the output of the gradation decoder 213 given via the level shifter 214, each nozzle is selected from the drive waveforms constituting the common drive waveform signal Vcom. The waveform applied to the pressure generating element 45P corresponding to is selected. As a result, the size of the ink droplet ejected from the nozzle is controlled.

<Image processing unit>
FIG. 7 is a functional block diagram illustrating an example of the configuration of the image processing unit 310 according to the embodiment. The image processing unit 310 and the recording head control unit 116 function as a control unit of the image forming apparatus 10.

  The image processing unit 310 performs gradation processing, image conversion processing, and the like on the received image data, and converts the received image data into image data in a format that can be processed by the recording head control unit 116. Then, the image processing unit 310 outputs the converted image data to the recording head control unit 116.

  Specifically, the image processing unit 310 includes an interface 311, a gradation processing unit 312, a gradation data storage unit 313, a preceding data reading unit 314, a fine drive determination unit 315, and a fine drive instruction signal generation unit 316. And an image conversion unit 317.

  The interface 311 is an input unit for image data, and is a communication interface with a host device that transmits image data, the CPU 101, and the FPGA 102.

  The gradation processing unit 312 performs gradation processing on the received multi-valued image data, and converts the multi-valued image data into small-valued image data. The small-value image data is image data (original image data) having the same number of gradations as the types of droplets (large droplets, medium droplets, and small droplets) ejected by the recording head 120K-1. The gradation processing unit 312 is configured by, for example, a RAM, and stores the converted image data in the gradation data storage unit 313 for one or more bands.

  It is assumed that the image data Dn for one band includes, for example, at least data of the preceding data (for example, 10 dots ahead) for reading the preceding data.

  The destination data reading unit 314 is a counting unit, and counts a dot non-forming period from a predetermined position in the input original image data to a dot forming pixel (print pattern) which is a pixel where ink is to be ejected next. . More specifically, the preceding data reading unit 314 takes out the data every predetermined period, and performs the dot non-forming period from the position immediately before the start of each predetermined period to the next dot forming pixel, and the dot from the dot forming pixel to the dot forming pixel in the predetermined period. The non-forming period and the dot non-forming period from the dot forming pixel in the predetermined period to the end position of the predetermined period are counted. At this time, a line synchronization signal LS serving as a printing reference is used as a reference. With this operation, the pattern ahead of the print dot by several lines is pre-read.

  The fine drive determination unit 315 inputs a fine drive waveform for oscillating the meniscus of the nozzle or a strong / fine drive waveform having a larger swing amount than the fine drive waveform to the pressure generating element 45P based on the number of pixels counted by the preceding data reading unit. Decide if you want to.

  Fine drive instruction signal generation section 316 instructs image conversion section 317 to execute fine drive or strong fine drive.

  The image conversion unit 317 converts the image data for one band in the gradation data storage unit 313 into image data SD of large droplets, medium droplets, and small droplets in units of image to be output by fine driving and strong driving data. To convert to image data SD ′.

  The image conversion unit 317 outputs the converted image data SD ′ to the FPGA 102 of the main control board 100 via the interface 311.

  The function of the image processing unit 310 may be executed as a hardware function such as an FPGA or an ASIC, or may be executed by an image processing program stored in a storage device inside the image processing unit 310.

  The function of the image processing unit 310 may be performed by software installed in a computer instead of inside the image forming apparatus.

<Ink supply unit>
Next, FIG. 8 is a diagram illustrating an example of a configuration of an ink supply unit according to the embodiment. FIG. 5 illustrates an example of a black ink supply unit 15K that supplies black ink to the recording head unit 120K.

  As shown in FIG. 5, the ink supply unit 15K has a main tank 151K, a pump 153K, a sub tank 155K, a pressurization unit 157K, a branch supply unit 158K, and a decompression unit 160K.

  The main tank 151K and the pump 153K are connected by a tube 152K, the pump 153K and the sub tank 155K are connected by a tube 154K, and the sub tank 155K and the pressurizing unit 157K are connected by a tube 156aK so that ink can flow therethrough. The pressurizing section 157K and the branch supply section 158K are connected by a tube 156bK, the branch supply section 158K and the decompression section 160K are connected by a tube 156cK, and the decompression section 160K and the sub tank 155K are connected by a tube 156dK so that ink can flow.

  The recording head 120K-1 is connected to the branch supply unit 158K via the tube 159aK, the recording head 120K-2 via the tube 159bK, and the recording head 120K-3 via the tube 159cK. The recording head 120K-4 is connected to the branch supply unit 158K via a tube 159dK, and the recording head 120K-5 is connected to the branch supply unit 158K via a tube 159eK.

  The tube connecting each part is, for example, a plastic tube. By flowing the ink in the tube, the ink can be circulated between the respective parts.

  The main tank 151K stores black ink. The pump 153K sends the ink stored in the main tank 151K toward the recording head unit 120K. The ink sent from the pump 153K reaches the branch supply unit 158K via the sub tank 155K and the pressurizing unit 157K.

  The branch supply unit 158K has a function of branching the ink to be fed and supplying it to each of the recording heads 120K-1 to 120K-5. The branch supply unit 158K is, for example, a manifold having a structure in which a plurality of pipes branch from one pipe.

  For example, the ink sent to the branch supply unit 158K via the pressurizing unit 157K is partially distributed to each of the recording heads 120K-1 to 120K-5 while passing through the branch supply unit 158K, and supplied. . On the other hand, the ink that has passed through the branch supply unit 158K reaches the sub tank 155K via the pressure reduction unit 160K.

  The branch supply unit 158K includes a pressure sensor 161K inside. The pressure sensor 161K detects the pressure of the ink inside the branch supply unit 158K, and outputs an electric signal indicating the detected value to the ink supply control unit 400. The pressure sensor 161K is a device that detects the pressure of ink with a pressure-sensitive element via a diaphragm made of, for example, stainless steel or silicon, converts the pressure into an electric signal, and outputs the electric signal. The pressure sensor 161K is an example of a “pressure measurement unit”.

  The pressurizing unit 157K presses (pushes out) the ink sent from the sub tank 155K, and causes the ink to flow in the direction indicated by the solid arrow in FIG. The pressure unit 157K is, for example, a pressure pump. The pressure reducing unit 160K reduces the pressure of the ink fed from the branch supply unit 158K (pulls in the ink), and causes the ink to flow in the direction indicated by the dashed arrow in FIG. The pressure reducing unit 160K is, for example, a pressure reducing pump.

  The ink that has reached the sub-tank 155K via the pressure reducing unit 160K by the action of the pressure unit 157K and the pressure reducing unit 160K is sent again to the pressure unit 157K. Such circulation of the ink is repeated, and the ink circulates in the above-described path. The path having the tubes 156ak, 156bk, 156ck and 156dk is an example of a “circulation path”.

  The flow rate and flow rate of the circulating ink can be controlled by changing the pressure applied to the ink by at least one of the pressurizing unit 157K and the depressurizing unit 160K.

  On the other hand, the sub tank 155K has a function of storing ink. By circulating the ink through the sub-tank 155K, the pressure of the ink in the sub-tank 155K can be adjusted, and thereby the generation of bubbles in the tube can be suppressed.

  The image forming apparatus 10 includes an ink supply unit 15C for supplying cyan ink to the recording head unit 120C in addition to the ink supply unit 15K. Further, the image forming apparatus 10 includes a magenta ink supply unit 15M that supplies magenta ink to the recording head unit 120M, and a yellow ink supply unit 15Y that supplies yellow ink to the recording head unit 120Y. The functions of the ink supply unit 15C, the ink supply unit 15M, and the ink supply unit 15Y are the same as those of the ink supply unit 15K.

  The pressurizing units 157 of the ink supply units 15 for each color are electrically connected to the ink supply control unit 400, respectively, and the pressurization by the pressurization units 157 is controlled by the ink supply control unit 400.

  In the following, the ink supply unit 15K, the ink supply unit 15C, the ink supply unit 15M, and the ink supply unit 15Y may be collectively referred to as the ink supply unit 15. In addition, in each component of the ink supply unit 15 </ b> K illustrated in FIG. 8, a component number excluding “K” indicating black may be collectively referred to as a component including other colors.

[First Embodiment]
<Ink supply controller>
Here, when each recording head of the recording head unit discharges ink, the ink inside the branch supply unit 158 decreases by the discharge amount, and that amount of ink is supplied from the main tank 151K to the branch supply unit 158. You. Along with such ink ejection and supply, pressure fluctuation may occur inside the branch supply unit 158. The pressure fluctuation inside the branch supply unit 158 causes variations in the ink ejection characteristics of each recording head.

  In the embodiment, by controlling the pressurization by the pressurization unit 157 using the correction data, the pressure fluctuation inside the branch supply unit 158 is corrected, and the variation in the ink ejection characteristics of each recording head is suppressed.

  In the print head unit, the positions where the print heads are arranged are different from each other. Accordingly, the state in which ink is supplied by the branch supply unit 158 and the pressure fluctuation inside the branch supply unit 158 are changed in accordance with this. It differs from head to head. Therefore, in the embodiment, the correction data is provided for each of the plurality of print heads included in the print head unit.

  FIG. 9 is a diagram illustrating, as functional blocks, an example of components of the ink supply control unit according to the present embodiment. Note that each functional block of the ink supply control unit shown in FIG. 9 is conceptual and does not necessarily need to be physically configured as shown in the figure. All or a part of each functional block can be configured to be functionally or physically dispersed and combined in an arbitrary unit. All or any part of each processing function performed by each functional block can be realized by a program executed by a CPU, or can be realized as hardware by wired logic.

  The ink supply control unit 400 includes a reception unit 401, a storage unit 402, a correction data acquisition unit 403, a pressure control unit 404, a pressure acquisition unit 405, and a correction data calculation unit 406. The receiving unit 401 is electrically connected to the main control board 100. The receiving unit 401 receives, from the main control board 100, a signal that specifies a recording head that ejects ink among the plurality of recording heads, and outputs the signal to the correction data acquisition unit 403.

  The storage unit 402 stores, for each print head, correction data for correcting a pressure fluctuation inside the branch supply unit when ink is ejected. The correction data acquisition unit 403 acquires correction data with reference to the storage unit 402 based on a signal that specifies a recording head that ejects ink, and outputs the acquired correction data to the pressure control unit 404. The pressurizing control unit 404 controls pressurization by the pressurizing unit 157 according to the input correction data.

  The pressure acquisition unit 405 receives the pressure data of the ink inside the branch supply unit 158 detected by the pressure sensor 161 according to the control command input from the main control board 100 via the reception unit 401 and updating the correction data. And temporarily store it. After acquiring pressure data for a predetermined period as pressure fluctuation data, the pressure acquisition unit 405 outputs the pressure fluctuation data to the correction data calculation unit 406. The correction data calculation unit 406 calculates correction data based on the input pressure fluctuation data, and outputs the correction data to the storage unit 402 for storage. Note that such correction data will be described in detail with reference to FIGS.

  In the embodiment, an example is shown in which the ink supply control unit 400 is provided separately from the main control board 100. However, a part or all of the functions of the ink supply control unit 400 are realized by the main control board 100. Is also good. The function of the correction data calculation unit 406 may be provided in an external device such as a PC (Personal Computer). For example, pressure data by the pressure acquisition unit 405 is output to a PC, and the PC calculates correction data. The PC may output the calculated correction data to the storage unit 402 and store it. By such a function allocation, the calculation load of each hardware can be optimized.

<Correction of pressure fluctuation>
FIG. 10 is a flowchart illustrating an example of a correction data acquisition process according to the embodiment. The recording head unit 120K that discharges black ink will be described as an example. Further, it is assumed that the acquisition process of the correction data is executed under the control of the CPU 101 of the main control board 100.

  First, the printhead control unit 116 controls the printhead driver 210 to drive the pressure generating element 45P, and selects one of the printheads 120K-1 to 120K-5 for which correction data is to be acquired. One drop of ink is ejected (step S101). At this time, the pressurizing unit 157K applies a predetermined pressure R set for circulating the ink to the ink.

  The recording head from which the correction data is acquired is, for example, the recording head 120K-1 or the like, and is hereinafter referred to as a target recording head for simplification of description.

  The pressure sensor 161K detects a pressure fluctuation inside the branch supply unit 158K during a period from a timing when the target recording head starts discharging one drop of ink to a timing when the discharge ends. The pressure acquisition unit 405 inputs the value detected by the pressure sensor 161K, and acquires pressure fluctuation data during this period (Step S102).

  The ejection start timing is, for example, the start timing of a drive waveform for one cycle, which is input to the pressure generating element 45P to eject ink. The timing of the end of the ejection is also the timing of the end of the drive waveform for one cycle.

  The pressure acquisition unit 405 outputs the stored pressure fluctuation data of the target recording head to the correction data calculation unit 406. The correction data calculation unit 406 calculates correction data for a period from the discharge start timing to the discharge end timing based on the input pressure fluctuation data (Step S103).

  Here, FIG. 11 is an image diagram illustrating an example of the pressure fluctuation data acquired by the pressure acquisition unit 405. FIG. 11 shows the pressure fluctuation when one droplet of ink is ejected from the target recording head.

  In FIG. 11, the horizontal axis represents time, and the vertical axis represents the pressure value of the ink detected by the pressure sensor 161K. However, pressure fluctuations immediately after the start of discharge are largely irregular, and are not shown. A thick solid line 501 indicates a target value (specification value) of the ink pressure, a timing 502 indicates a discharge start timing by the print head, and a timing 503 indicates a discharge end timing.

  A graph 601 indicated by a thin solid line is pressure fluctuation data inside the branch supply unit 158K when one drop of ink is ejected by the recording head 120K-1. A graph 602 shown by a broken line is pressure fluctuation data inside the branch supply unit 158K when one drop of ink is ejected by the recording head 120K-2. A graph 603 indicated by an alternate long and short dash line is pressure fluctuation data inside the branch supply unit 158K when one drop of ink is ejected by the recording head 120K-3. The pressure acquisition unit 405 acquires such pressure fluctuation data for each recording head.

  The correction data calculation unit 406 corrects the pressure at each timing based on the pressure fluctuation data acquired by the pressure acquisition unit 405 during the period from the discharge start timing to the discharge end timing so as to cancel the pressure fluctuation during this period. Calculate the data. For example, when the target value 501 is X (Pa) and the pressure at an arbitrary timing in the pressure fluctuation data is X-2 (Pa), the correction data calculation unit 406 determines that the difference value between the target value and the detected value is 2 (Pa) is calculated as correction data.

  Alternatively, the correction data calculation unit 406 may approximate the pressure fluctuation data in the period from the discharge start timing to the discharge end timing of the graph 601, for example, by a polynomial, and calculate the pressure correction data for each timing based on the approximate polynomial. . The order of the approximate polynomial may be set in advance according to the pressure fluctuation data. For example, in the case of a substantially linear variation as shown in a graph 601, the order may be set to the first order (linear approximation). Further, for example, in the case of a non-linear fluctuation as in the graph 603, the order may be increased so as to increase the approximation accuracy. By using the approximate polynomial, it is possible to suppress the influence of noise detected by the pressure sensor 161K.

  FIG. 12 is an image diagram illustrating an example of the calculated correction data. A graph 701 shows correction data for correcting the pressure fluctuation shown in the graph 601 in a period up to the timing 503 in FIG. The correction data shown in the graph 701 is calculated as a difference value between the target value in FIG. 11 and the detection value shown in the graph 601 except for the correction data in a predetermined period T before and after the timing of starting the ejection. I have.

  In the period T, immediately after the start of the ejection, the ink in the liquid chamber of the recording head 120K-1 is greatly reduced by the ejection, and the inside of the branch supply unit 158K is turned to a negative pressure in order to supply the reduced ink to the liquid chamber. It will be easier. If the inside of the branch supply unit 158K turns to a negative pressure, it becomes difficult to control the ink supply.

  Therefore, in the embodiment, correction data for adding the offset pressure B in the period T is used so that the inside of the branch supply unit 158K does not turn to a negative pressure immediately after the start of the discharge. As described above, the offset pressure B is corrected so as to be applied before the start of the discharge, so that the inside of the branch supply unit 158K can be prevented from turning to a negative pressure. The period T and the offset pressure B are determined in advance by experiments and simulations so as to prevent the inside of the branch supply unit 158K from turning into a negative pressure and the offset pressure.

  Note that the offset pressure B is an example of a “predetermined positive pressure”, and the period T is an example of a “predetermined period”.

  Returning to FIG. 10, in step S104, the pressurization control unit 404 corrects the pressure applied by the pressurization unit 157K at each timing using the calculated correction data. In other words, the pressurization control unit 404 controls the pressurizing unit 157K at each timing so as to pressurize at a pressure value obtained by adding the correction data to the predetermined pressure R. In this state, the printhead control unit 116 controls the printhead driver 210 to drive the pressure generating element 45P, and ejects one drop of ink from the target printhead (step S104).

  The pressure sensor 161K detects a pressure fluctuation inside the branch supply unit 158K during a predetermined period after the discharge of one drop of ink by the target recording head is completed. The pressure acquisition unit 405 acquires pressure fluctuation data during this period (Step S105).

  The above "predetermined period" is set in advance. For example, since the time from when one drop of ink is ejected to when the next one ink is ejected differs depending on the ejection frequency, an appropriate “predetermined time” may be set according to the ejection frequency. More specifically, the “predetermined period” is shortened when the ejection frequency is high, and the “predetermined period” is lengthened when the ejection frequency is low.

  The pressure acquisition unit 405 outputs the acquired pressure fluctuation data of the target recording head to the correction data calculation unit 406. The correction data calculation unit 406 calculates correction data for a predetermined period after the end of the ejection based on the input pressure fluctuation data (step S106).

  Here, FIG. 13 is an image diagram illustrating an example of the pressure fluctuation data acquired by the pressure acquiring unit 405. FIG. 13 shows the pressure fluctuation when one droplet of ink is discharged from the target recording head in a state where the pressure fluctuation during the period from the discharge start timing to the discharge end timing is corrected. In FIG. 13, a timing 504 is a timing when a predetermined period has elapsed after the end of the ejection.

  The pressure acquisition unit 405 acquires pressure fluctuation data as shown by the graph 601a, the graph 602a, or the graph 603a, and outputs the data to the correction data calculation unit 406. The correction data calculation unit 406 calculates the correction data as a difference value between the target value and the detection value shown in the graph 601a in a predetermined period after the end of the ejection (the period from timing 503 to timing 504 in FIG. 13). calculate.

  FIG. 14 is an image diagram illustrating an example of the calculated correction data. A graph 701a is obtained by adding correction data in a period from timing 503 to timing 504 to the correction data corresponding to the graph 701 shown in FIG.

  Returning to FIG. 10, the storage unit 402 links the correction data of the pressure fluctuation during the period from the discharge start timing to the discharge end timing and the correction data of the pressure fluctuation during a predetermined period after the end of the discharge to the target print head. It is stored (step S107). The target recording head is specified by a signal received from the main control board 100 via the receiving unit 401, and is linked to the correction data.

  The CPU 101 determines whether the correction data has been stored in all the print heads (step S108). If the correction data has been stored in all the print heads (step S108, Yes), the CPU 101 ends the correction data acquisition process. When the correction data is not stored in all the print heads (No at Step S108), the main control board 100 changes the target print head (for example, changes to the print head 120K-2) (Step S109). Thereafter, the process returns to step S101, and the processes after step S101 are executed again.

  FIG. 15 is a diagram illustrating an example of the correction data stored in the storage unit 402. The correction data D1 associated with the recording head 157K-1, the correction data D2 associated with the recording head 157K-2, and the correction data D3 associated with the recording head 157K-3 are stored. The correction data D4 is stored in association with the recording head 157K-4, and the correction data D5 is stored in association with the recording head 157K-5.

  As described above, the image forming apparatus 10 can acquire the correction data for correcting the pressure fluctuation inside the branch supply unit 158 when ejecting the ink for each recording head, and store the correction data in the storage unit 402. .

  Next, FIG. 16 is a flowchart illustrating an example of a pressure fluctuation correction process. The recording head unit 120K that discharges black ink will be described as an example.

  First, the receiving unit 401 receives, from the main control board 100, a signal that specifies a recording head that ejects ink from among a plurality of recording heads, and outputs the signal to the correction data acquisition unit 403 (Step S161).

  The correction data obtaining unit 403 obtains correction data by referring to the storage unit 402 based on a signal that specifies a recording head that discharges ink, and outputs the correction data to the pressure control unit 404 (step S162). The pressurizing control unit 404 controls the pressure applied by the pressurizing unit 157 to the ink to be sent according to the input correction data (step 163).

  In this manner, the ink supply control section 400 can correct the pressure fluctuation inside the branch supply section 158 when ejecting ink.

  FIG. 17 is a diagram illustrating an example of a pressure fluctuation correction result according to the embodiment. In FIG. 17, a graph 601b, a graph 602b, or a graph 603b shows the corrected pressure fluctuation data. As shown in FIG. 17, the time variation of the pressure inside the branch supply unit 158 is suppressed. In the period before and after the discharge start timing 502 and the period before and after the discharge end timing 503, a pressure difference from the target value is observed. In these periods, the reproducibility of the pressure fluctuation is compared with other periods. Therefore, it is a correction error caused by this.

  Although the processing shown in FIGS. 10 and 16 has been described using the recording head unit 120K that discharges black ink as an example, the same applies to a recording head unit that discharges other color inks.

<Effect>
Next, effects according to the embodiment will be described with reference to FIGS.

  FIG. 18 is a diagram illustrating an example of a pressure fluctuation inside the branch supply unit 158. FIG. 18 shows pressure fluctuation data inside the branch supply unit 158 when one drop of ink is ejected from an arbitrary print head.

  A graph 701 shown by a solid line shows the pressure after correction by the ink supply control according to the embodiment, and a graph 702 shown by a broken line shows the pressure after correction by PID (Proportional Integral Differential) control as a comparative example. Is shown. In this PID control, the pressure sensor 161 detects the pressure inside the branch supply unit 158 and outputs it to the ink supply control unit 400, and the ink supply control unit 400 presses the pressure unit 157 so that the pressure approaches the target value. Is assumed to be corrected by so-called feedback control.

  Before and after the timing of the start of the ejection, a period 505 is a period during which the pressure fluctuation deviates from the target value in the ink supply control according to the embodiment, and a period 506 is the PID control according to the comparative example, in which the pressure fluctuation is from the target value. This shows a period during which the time has shifted.

  Before and after the timing of the end of the ejection, a period 507 indicates a period in which the pressure fluctuation deviates from the target value by the control according to the embodiment, and a period 508 indicates the PID control according to the comparative example, in which the pressure fluctuation deviates from the target value. Shows the period of time.

  As shown in FIG. 18, the period 505 is shorter than the period 506, and the period 507 is also shorter than the period 508. In the PID control, since the actually measured pressure is fed back to the ink supply control unit 400 one by one and the pressure applied by the pressurizing unit 157 is controlled, it takes time to converge to the target value. In the embodiment, the pressure is corrected without turning the feedback loop by using the correction data measured in advance, so that the pressure fluctuation inside the branch supply unit 158 is brought close to the target value in a short time with respect to the PID control, and the pressure is stabilized. Can be changed.

  Also, as shown in FIG. 18, in the PID control, a period occurs in which the pressure of the correction result becomes a negative pressure. However, in the ink supply control according to the embodiment, a period in which the pressure of the correction result becomes a negative pressure. Has not occurred. In the embodiment, since the actually measured pressure is not used, the pressure by the pressurizing unit 157 can be controlled before the timing of starting the discharge. In the embodiment, by applying the above-described offset pressure B before the timing of starting the discharge, it is possible to correct the pressure fluctuation without making the pressure inside the branch supply unit 158 a negative pressure. According to the embodiment, in a liquid ejection apparatus that supplies liquid to a plurality of recording heads via a branch supply unit, it is possible to suppress pressure fluctuations without turning the pressure in the branch supply unit to a negative pressure.

  FIG. 19 is a diagram illustrating an example of a stable period of the pressure inside the branch supply unit 158. Periods 509, 510, and 511 indicate stable periods of the pressure inside the branch supply unit 158 according to the embodiment. Periods 512, 513, and 514 show the stable period of the pressure inside the branch supply unit 158 by the PID control as a comparative example. As shown in FIG. 19, in the embodiment, since the pressure fluctuation inside the branch supply unit 158 can approach the target value in a short time, the stable period can be lengthened as compared with the PID control. it can.

[Second embodiment]
Next, an example of the image forming apparatus according to the second embodiment will be described. The description of the same components as those of the above-described embodiment will be omitted.

  2. Description of the Related Art In an ink-jet type image forming apparatus, an image may be formed using a plurality of droplet types in which a droplet size of ink ejected from a recording head is changed. Examples of the droplet type include a large droplet having a large droplet size, a small droplet having a small droplet size, and a medium droplet having a droplet size intermediate between a large droplet and a small droplet.

  If the droplet type is different, the amount of ink to be ejected changes, and accordingly, the supply amount of ink changes for each droplet type, and the pressure fluctuation of the ink inside the branch supply unit 158 changes. Therefore, in the image forming apparatus 10a according to the present embodiment, correction data is provided for each droplet type, and the pressure fluctuation inside the branch supply unit 158 is corrected according to the droplet type.

  FIG. 20 is a diagram illustrating an example of components of the ink supply control unit in functional blocks. The ink supply control unit 400a includes a reception unit 401a, a storage unit 402a, and a correction data acquisition unit 403a.

  The receiving unit 401a receives, from the main control board 100, a signal that specifies a recording head that discharges ink and a signal that specifies the type of droplet to be discharged, and outputs the signal to the correction data acquisition unit 403a. The storage unit 402a stores pressure fluctuation correction data for each recording head and each droplet type.

  The correction data acquisition unit 403a acquires pressure fluctuation correction data with reference to the storage unit 402a in accordance with a signal that specifies a recording head that discharges ink and a signal that specifies a type of droplet to be discharged. The pressurization control unit 404 controls pressurization by the pressurizing unit 157 according to the correction data input from the correction data acquisition unit 403a.

  FIG. 21 is a diagram illustrating an example of the correction data stored in the storage unit 402a. The correction data D1a is stored in association with the large droplet of the recording head 157K-1, the correction data D1b is stored in association with the medium droplet of the recording head 157K-1, and the correction data D1c is associated with the small droplet of the recording head 157K-1. Is stored. Similarly, for each of the recording heads 157K-2 to 157K-5, correction data is stored in association with a large drop, a medium drop, and a small drop.

  As described above, the image forming apparatus 10a can correct the pressure fluctuation inside the branch supply unit 158 when ejecting ink by using the correction data for each recording head and each droplet type.

  The other effects are the same as those described in the first embodiment.

[Third Embodiment]
Next, an example of the image forming apparatus according to the third embodiment will be described. The description of the same components as those of the above-described embodiment will be omitted.

  In an ink-jet type image forming apparatus, two or more recording heads of a plurality of recording heads may eject ink at the same time. In this case, the branch supply unit 158 supplies an amount of ink corresponding to the sum of the amounts of ink ejected from the respective recording heads to the two or more ejected recording heads. The pressure fluctuation inside the branch supply unit 158 occurs as the sum of the pressure fluctuations of each of the two or more ejected recording heads.

  In the present embodiment, when two or more recording heads among a plurality of recording heads simultaneously eject ink, the sum of the correction data of the two or more ejected recording heads is used as the correction data, and the branch supply unit 158 Compensate for internal pressure fluctuations.

  FIG. 22 is a functional block diagram illustrating an example of components of the ink supply control unit according to the present embodiment. The ink supply control unit 400b has a correction data acquisition unit 403b. The correction data acquisition unit 403b receives a signal specifying two or more ejected print heads from the main control board 100 via the reception unit 401. The correction data acquisition unit 403b acquires correction data corresponding to each recording head with reference to the storage unit 402 according to a signal that specifies two or more ejected recording heads, calculates the sum of these, and Output to the pressurization control unit 404 as correction data. The pressurization control unit 404 controls pressurization by the pressurization unit 157 according to the correction data input from the correction data acquisition unit 403b.

  As described above, the image forming apparatus 10b can correct the pressure fluctuation inside the branch supply unit 158 even when two or more recording heads eject ink at the same time.

  The effects other than those described above are the same as those described in the first embodiment.

  The preferred embodiment has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various modifications and substitutions can be made to the above-described embodiment without departing from the scope described in the claims. Can be added.

  For example, in the above-described embodiment, the image forming apparatus including the recording head according to the embodiment has been described. However, the liquid ejection head according to the embodiment and the control thereof are widely applied to apparatuses that eject liquid including the image forming apparatus. Can be applied.

  In the present application, a “device that discharges liquid” is a device that includes a liquid discharge head or a liquid discharge unit and drives the liquid discharge head to discharge liquid. The device that discharges a liquid includes not only a device that can discharge a liquid to which a liquid can be attached, but also a device that discharges a liquid into the air or into the liquid.

  The “device for discharging liquid” may include a unit for feeding, transporting, and discharging paper to which liquid can be attached, as well as a pre-processing device and a post-processing device.

  For example, as a "device for ejecting liquid", an image forming apparatus which is an apparatus for ejecting ink to form an image on a recording paper, and forming a three-dimensional object (three-dimensional object) by forming powder in layers. There is a three-dimensional modeling device (three-dimensional modeling device) that discharges a modeling liquid to the formed powder layer.

  Further, the “device for discharging liquid” is not limited to a device in which a significant image such as a character or a graphic is visualized by the discharged liquid. For example, those that form a pattern or the like that has no meaning in itself and those that form a three-dimensional image are also included.

  The above-mentioned "thing to which a liquid can be attached" means a thing to which a liquid can be attached at least temporarily, such as a thing which is attached and fixed, a thing which is attached and penetrates, and the like. Specific examples include recording media such as paper, recording paper, recording paper, film, and cloth; electronic components such as electronic substrates and piezoelectric elements; powder layers (powder layers); organ models; and media such as inspection cells. Yes, unless otherwise specified, includes everything to which a liquid adheres.

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

  Further, the "liquid ejection head" is not limited to a pressure generating element to be used. For example, a piezoelectric actuator (a laminated piezoelectric element may be used), a thermal actuator using an electrothermal conversion element such as a heating resistor, or an electrostatic actuator including a diaphragm and a counter electrode can be used.

  Further, image forming, recording, printing, printing, printing, modeling, and the like in the terms of the present application are all synonymous.

  Further, the present embodiment also includes a liquid discharging method. For example, the liquid discharge method is a liquid discharge method using a liquid discharge device having a branch supply unit that supplies a liquid to each of a plurality of recording heads, wherein the branch supply when discharging the liquid is performed for each recording head. A step of storing correction data for correcting pressure fluctuations inside the unit, a step of obtaining the correction data by referring to the storage unit according to the recording head that discharges the liquid, and a step of storing the correction data based on the correction data. Changing the pressure applied to the liquid; and applying pressure to the liquid sent to the branch supply unit. According to such a liquid discharging method, the same effect as that of the above-described image forming apparatus can be obtained.

10 Image forming apparatus (an example of a liquid ejection apparatus)
DESCRIPTION OF SYMBOLS 11 Paper feed part 12 Image formation part 120 Recording head unit 121 Drum 122,123 cylinder 120K-1-120K-5 Recording head 13 Drying part 14 Paper discharge part 15 Ink supply part 151 Main tank 152, 154, 159 Tube 153 Pump 155 Subtank 156a to 156d Tube (example of circulation path)
157 Pressurization unit 158 Branch supply unit 160 Decompression unit 161 Pressure sensor (one example of pressure measurement unit)
45P pressure generating element 100 main control board 116 print head control unit 210 print head driver 400 ink supply control unit 401 reception unit 402, 402a storage unit 403, 403a, 403b correction data acquisition unit 404 pressure control unit 405 pressure acquisition unit 406 correction Data calculation unit P Recording paper R Predetermined pressure B Offset pressure (an example of predetermined positive pressure)
T period (an example of a period for applying a predetermined positive pressure)

JP 2009-241426 A

Claims (10)

A liquid ejection apparatus having a branch supply unit that supplies liquid to each of a plurality of recording heads,
For each recording head, a storage unit that stores correction data that corrects pressure fluctuations inside the branch supply unit when discharging the liquid,
A pressurizing unit that applies pressure to the liquid to be sent to the branch supply unit;
A correction data acquisition unit that acquires the correction data with reference to the storage unit, according to the recording head that is specified as the recording head that ejects the liquid;
And a pressurizing control unit that controls the pressurizing unit based on the correction data. The correction data is
The liquid ejecting apparatus according to claim 1, wherein the data is data indicating a pressure applied to the liquid at each timing, and includes a period in which a predetermined positive pressure is applied to the liquid before the recording head starts ejecting the liquid. The correction data is
Data indicating the pressure to be applied to the liquid during a period from when the predetermined positive pressure is started to when the ejection of the liquid by the recording head is completed,
The liquid ejection apparatus according to claim 2, further comprising: data indicating a pressure applied to the liquid within a predetermined period from when the ejection of the liquid by the recording head is completed. The liquid ejection device ejects the liquid onto a recording medium conveyed in a predetermined conveyance direction,
The liquid ejecting apparatus according to claim 1, wherein the plurality of recording heads are arranged in a direction intersecting a predetermined transport direction. A decompression unit that decompresses the liquid sent from the branch supply unit,
The liquid ejection device according to claim 1, further comprising: a circulation path configured to circulate the liquid between the pressurizing unit, the branch supply unit, and the pressure reducing unit. The liquid ejecting apparatus according to claim 1, further comprising a sub-tank provided in the circulation path and storing the liquid. The branch supply unit has a pressure measurement unit that measures the pressure of the liquid,
The liquid ejection apparatus according to claim 1, wherein the correction data is data based on the pressure measured by the pressure measurement unit when each of the plurality of recording heads is ejected. The plurality of recording heads respectively discharge droplets having different discharge amounts,
The storage unit stores the correction data for each discharge amount,
8. The liquid ejection apparatus according to claim 1, wherein the acquisition unit acquires the correction data according to the recording head that ejects the liquid and the ejection amount with reference to the storage unit. 9. 2. When simultaneously ejecting the liquid from two or more print heads of the plurality of print heads, the correction data is a sum of correction data of the two or more print heads that eject the liquid. 9. The liquid ejection apparatus according to any one of claims 1 to 8. A liquid discharge method by a liquid discharge device having a branch supply unit that supplies liquid to each of a plurality of recording heads,
For each recording head, a step of storing correction data for correcting a pressure fluctuation inside the branch supply unit when discharging the liquid,
Applying pressure to the liquid to be sent to the branch supply unit,
A step of obtaining the correction data by referring to the storage unit according to the recording head that discharges the liquid;
Controlling the pressure of the liquid to be sent to the branch supply unit based on the correction data.