Liquid ejection device and liquid ejection method

Abstract

To enable a head to discharge liquid stably.SOLUTION: A liquid discharge device according to one embodiment of the present invention comprises: a head that discharges liquid; an output part that outputs, to the head, driving waveform data including data on discharging / driving waveforms for discharging the liquid and data on vibrating / driving waveforms for vibrating the liquid in the head without discharging the liquid; and a changing part that makes second frequencies at which the vibrating / driving waveforms are outputted to the head different from first frequencies, in accordance with the first frequencies at which the driving waveforms are outputted to the head.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus and a liquid ejection method. [Background technology]

[0002] 2. Description of the Related Art Conventionally, among liquid ejection devices having a head for ejecting liquid, there is known one that vibrates the liquid inside the head during periods when ejection is not being performed.

[0003] As such a liquid ejection device, a technology has been disclosed that controls the timing of vibration of the liquid filled in the head during periods when ejection is not occurring in order to stabilize the liquid ejection from the head (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration of Patent Document 1, the first frequency at which a drive waveform that causes the head to eject liquid is output to the head is equal to the second frequency at which a vibration drive waveform that causes the liquid in the head to vibrate without causing the head to eject liquid is output to the head. As a result, there is a concern that the vibration of the liquid cannot be controlled at an appropriate frequency, making it difficult to stabilize the liquid ejection from the head.

[0005] An object of the present invention is to stabilize the ejection of liquid from a head. [Means for solving the problem]

[0006] A liquid ejection device according to one aspect of the present invention includes a head that ejects liquid, and drive waveform data including data on an ejection drive waveform that ejects the liquid and data on a vibration drive waveform that vibrates the liquid in the head without ejecting the liquid. a first frequency for ejecting the liquid during a period in which the liquid can be ejected; an output section that outputs the drive waveform to the head; The aforementioned a change unit that changes a second frequency at which the vibration drive waveform is output to the head in accordance with a first frequency, with respect to the first frequency; When the first frequency is within a predetermined frequency range, the change unit does not change the second frequency and makes the second frequency equal to the first frequency; when the first frequency is not within the predetermined frequency range and the first frequency is lower than a lower limit frequency in the predetermined frequency range, the change unit makes the second frequency higher than the first frequency; and when the first frequency is not within the predetermined frequency range and the first frequency is higher than an upper limit frequency in the predetermined frequency range, the change unit makes the second frequency lower than the first frequency by thinning out the number of times the vibration drive waveform is output. . [Effects of the Invention]

[0007] According to the present invention, it is possible to stabilize the ejection of liquid from the head. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of a printing system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of an image forming unit according to the embodiment. [Figure 3] FIG. 2 is an enlarged view showing nozzles in a head according to an embodiment. [Figure 4] FIG. 2 is a cross-sectional view taken along the nozzle arrangement direction of the head according to the embodiment. [Figure 5] FIG. 2 is a cross-sectional view taken along a direction orthogonal to the nozzle arrangement direction of the head according to the embodiment. [Figure 6] FIG. 2 is a block diagram illustrating an example of a hardware configuration of an image forming apparatus according to an embodiment. [Figure 7] FIG. 2 is a block diagram showing an example of the configuration of a head driver according to the embodiment. [Figure 8] FIG. 2 is a block diagram illustrating an example of a functional configuration of an image processing unit according to the embodiment. [Figure 9] 10A and 10B are diagrams illustrating an example of changes in the transport speed of roll paper. [Figure 10] FIG. 2 is a diagram illustrating vibration driving in a head. [Figure 11] FIG. 4 is a diagram illustrating head drive waveform data. [Figure 12] 10 is a flowchart of an example of processing by an image processing unit according to the embodiment. [Figure 13] 10A and 10B are diagrams illustrating an example of modification of mask control signal data by a modifying unit. [Figure 14] FIG. 10 is a diagram showing a first example of a vibration drive waveform before a second frequency change. [Figure 15] FIG. 10 is a diagram showing a first example of a vibration drive waveform after a second frequency change. [Figure 16] FIG. 10 is a diagram showing a second example of a vibration drive waveform before a second frequency change. [Figure 17] FIG. 10 is a diagram showing a second example of a vibration drive waveform after a second frequency change. [Figure 18] FIG. 10 is a diagram illustrating an example of transition of a second frequency according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. In the drawings, the same components are designated by the same reference numerals, and redundant explanations will be omitted where appropriate.

[0010] <Example of overall configuration of printing system 1> 1 is a diagram showing an example of the overall configuration of a printing system 1 according to a first embodiment. The printing system 1 includes an inkjet image forming apparatus 2, which is an example of a liquid ejection apparatus. The ink ejected by the image forming apparatus 2 is an example of a liquid.

[0011] 1, the printing system 1 has an input unit 10 that inputs roll paper Md, a pre-processing unit 20 that pre-processes the input roll paper Md, and a drying unit 30 that dries the pre-processed roll paper Md by heating it. The printing system 1 also has an image forming unit 40 that forms an image on the surface of the roll paper Md, a post-processing unit 50 that post-processes the roll paper Md on which the image has been formed, an output unit 60 that outputs the post-processed roll paper Md, and maintenance recovery units 90A and 90B.

[0012] Roll paper Md is an example of a recording medium. Roll paper Md is, for example, continuous paper with tearable perforations formed at predetermined intervals, or continuous paper such as continuous forms wound into a roll. The pages of roll paper are, for example, the areas sandwiched between the perforations at predetermined intervals.

[0013] In the printing system 1, the roll paper Md is carried in by the carrying-in unit 10, and the surface of the roll paper Md is pre-processed and dried by the pre-processing unit 20 and the drying unit 30.

[0014] In the printing system 1, an image is formed on the surface of the roll paper Md after it has been pre-processed and dried using the image forming unit 40 in the image forming device 2. In the printing system 1, the roll paper Md on which the image has been formed is post-processed using the post-processing unit 50. Thereafter, in the printing system 1, the roll paper Md is wound up by the discharge unit 60 and then discharged.

[0015] The carry-in unit 10 is a means for transporting the roll paper Md to the pre-processing unit 20 and the like. The carry-in unit 10 has a paper feed unit 11 and a plurality of transport rollers 12. The carry-in unit 10 uses the transport rollers 12 and the like to carry in and move the roll paper Md that is wound around and held on the paper feed roll of the paper feed unit 11, and transports it to the pre-processing unit 20 (platen) and the like.

[0016] The pre-treatment unit 20 is a unit for treating the roll paper Md before an image is formed on it. The pre-treatment unit 20 pre-treats the surface of the roll paper Md that has been carried in by the carry-in unit 10 with a pre-treatment liquid. The pre-treatment is, for example, a process of uniformly applying a pre-treatment liquid that has the function of aggregating ink to the surface of the roll paper Md. The pre-treatment liquid is, for example, a treatment liquid containing a water-soluble aliphatic organic acid. A treatment liquid containing a water-soluble aliphatic organic acid is a treatment liquid that has the property of aggregating water-dispersible colorants. Furthermore, aggregating refers to the adsorption and aggregation of water-dispersible colorant particles together.

[0017] The pretreatment unit 20 adds an ionic substance, such as a water-soluble aliphatic organic acid, to the pretreatment solution to adsorb ions onto the surface of the water-dispersible colorant. This neutralizes the surface charge of the water-dispersible colorant. The pretreatment unit 20 also enhances the agglomeration action due to intermolecular forces, further agglomerating the water-dispersible colorant.

[0018] The pretreatment unit 20 can apply the pretreatment liquid using methods such as blade coating, gravure coating, gravure offset coating, bar coating, roll coating, knife coating, air knife coating, comma coating, U-comma coating, AKKU coating, smoothing coating, microgravure coating, reverse roll coating, four- or five-roll coating, dip coating, curtain coating, slide coating, and die coating.

[0019] The drying unit 30 is a means for drying the roll paper Md by heating, etc. The drying unit 30 includes a pre-processing drying unit 31 that dries the roll paper Md that has been pre-processed by the pre-processing unit 20, and a post-processing drying unit 32 that dries the roll paper Md that has been post-processed by the post-processing unit 50.

[0020] The pre-treatment drying section 31 has, for example, a heat roller. The pre-treatment drying section 31 heats the heat roller, for example, to 50 to 100°C, and brings the surface of the roll paper Md, on which the pre-treatment liquid has been applied, into contact with the heat roller. The pre-treatment drying section 31 heats the surface of the roll paper Md, on which the pre-treatment liquid has been applied, with the heat roller, evaporating the water content of the pre-treatment liquid and drying the roll paper Md. The post-treatment drying section 32 has the same configuration as the pre-treatment drying section 31.

[0021] The image forming unit 40 is a unit that forms an image on the roll paper Md. The image forming unit 40 ejects ink onto the roll paper Md that has been dried by the drying unit 30, thereby forming an image on the surface of the roll paper Md.

[0022] The post-processing unit 50 is a unit that processes the roll paper Md after an image has been formed on it. The post-processing unit 50 performs post-processing by applying a post-processing liquid to the surface of the roll paper Md on which an image has been formed by the image forming unit 40. The post-processing is a process in which the post-processing liquid is ejected and applied in a spotted form onto the roll paper Md.

[0023] Maintenance and recovery units 90A and 90B are provided near the image forming unit 40 and the post-processing unit 50. The maintenance and recovery units 90A and 90B perform cleaning or maintenance, which are maintenance and recovery operations for the nozzles and nozzle surfaces of the heads included in the image forming unit 40 and the post-processing unit 50.

[0024] The image forming section 40, the post-processing section 50, and the maintenance and recovery sections 90A and 90B are arranged on a housing 74. The housing 74 includes a transport unit 80.

[0025] <Configuration example of image forming unit 40> 2 is a diagram showing an example of the configuration of the image forming unit 40, and is a diagram of the image forming unit 40 facing the roll paper Md as viewed from the side of the roll paper Md. The image forming unit 40 is a full-line type head unit.

[0026] The image forming unit 40 is equipped with head modules 40K, 40Ca, 40M, and 40Y for each color, in the order of black (K), cyan (C), magenta (M), and yellow (Y), from upstream in the transport direction Xm of the roll paper Md. However, the arrangement order of the heads in the image forming unit 40 is not limited to the above order and can be changed as appropriate. Furthermore, the color combination is not limited to the above four colors and may be just black (K), or may be three colors: green (G), red (R), and light cyan (LC).

[0027] The black (K) head module 40K has four heads, heads 40K-1, 40K-2, 40K-3, and 40K-4, arranged in a staggered pattern along the width direction, which is approximately perpendicular to the transport direction Xm of the roll paper Md. By arranging the four heads across the entire width, the image forming unit 40 can form an image across the entire width of the roll paper Md without moving the heads in the width direction. Furthermore, by arranging the four heads in a staggered pattern, the image forming unit 40 can form an image across the entire width of the roll paper Md without any missing parts. Note that the heads for black (K), cyan (C), magenta (M), and yellow (Y) are similar, so the following explanation will use black (K) head 40K-1 as an example.

[0028] The post-processing unit 50 also has four treatment liquid ejection heads arranged in a staggered pattern in the head module 50H, allowing the post-processing liquid to be ejected across the entire width direction. While Fig. 2 illustrates a configuration in which multiple heads are arranged in a staggered pattern, the present invention is not limited to this configuration. The image forming unit 40 may eject ink across the entire width direction using multiple heads arranged in a straight line or a single elongated head along the width direction.

[0029] 3 is a diagram illustrating the nozzles in the head 40K-1. The head 40K-1 has a plurality of nozzles 40N. The nozzles 40N are arranged in a width direction perpendicular to the transport direction Xm, and form a nozzle row. The head 40K-1 may also have a plurality of nozzle rows aligned along the transport direction Xm.

[0030] <Example of the internal structure of head 40K-1> The internal structure of head 40K-1 will be described with reference to Figures 4 and 5. Figure 4 is a cross-sectional view of head 40K-1 taken along the nozzle arrangement direction. Figure 5 is a cross-sectional view of head 40K-1 taken along a direction perpendicular to the nozzle arrangement direction. In this embodiment, head 40K-1 is installed so that the nozzle arrangement direction is perpendicular to the transport direction Xm. This also applies to each head other than head 40K-1 included in image forming unit 40.

[0031] 4, head 40K-1 includes a flow path plate 41 that forms a path for ejected ink, a vibration plate 42 bonded to the lower surface of flow path plate 41 (facing the inside of head 40K-1), a nozzle plate 43 bonded to the upper surface of flow path plate 41 (facing the outside of head 40K-1), and a frame member 44 that holds the peripheral edge of vibration plate 42. Head 40K-1 also includes a pressure generating unit 45 that deforms vibration plate 42.

[0032] The head 40K-1 forms nozzle communication paths 40R, which are flow paths communicating with the nozzles 40N, and liquid chambers 40F, by laminating a flow path plate 41, a vibration plate 42, and a nozzle plate 43. The head 40K-1 also forms an ink inlet 40S for supplying ink to the liquid chambers 40F, a common liquid chamber 40C for supplying ink to the liquid chambers 40F, and the like, by further laminating a frame member 44.

[0033] The frame member 44 is formed with a housing portion that houses the pressure generating portion 45, a recess that becomes the common liquid chamber 40C, and an ink supply port 40IN for supplying ink from outside the head 40K-1 to the common liquid chamber 40C.

[0034] The pressure generating unit 45 is a piezoelectric actuator including pressure generating elements 45P (piezoelectric elements) that are electromechanical conversion elements, a base substrate 45B to which the pressure generating elements 45P are bonded and fixed, and support parts arranged in the gaps between adjacent pressure generating elements 45P. The pressure generating unit 45 also includes an FPC cable 45C and the like for connecting the pressure generating elements 45P to a drive circuit.

[0035] 5, the pressure generating element 45P is a laminated piezoelectric element (PZT) in which piezoelectric materials 45Pp and internal electrodes 45Pe are alternately laminated. The internal electrodes 45Pe have a plurality of individual electrodes 45Pei and a plurality of common electrodes 45Pec. The internal electrodes 45Pe are alternately connected to the end faces of the piezoelectric material 45Pp with the individual electrodes 45Pei or the common electrodes 45Pec.

[0036] Here, the operation (pull-push ejection operation) of the head 40K-1 to eject ink from the nozzles 40N will be described.

[0037] First, the head 40K-1 reduces the voltage applied to the pressure-generating element 45P from the reference potential, thereby causing the pressure-generating element 45P to shrink in the stacking direction. The head 40K-1 also flexes and deforms the vibration plate 42 due to the shrinkage of the pressure-generating element 45P. At this time, the head 40K-1 expands the volume of the liquid chamber 40F due to the flexure and deformation of the vibration plate 42. This action causes ink to flow from the common liquid chamber 40C into the liquid chamber 40F.

[0038] Next, the head 40K-1 increases the voltage applied to the pressure-generating element 45P, causing the pressure-generating element 45P to expand along the stacking direction. The expansion of the pressure-generating element 45P also causes the head 40K-1 to deform the diaphragm 42 toward the nozzle 40N. At this time, the head 40K-1 reduces the volume of the liquid chamber 40F by deforming the diaphragm 42. This action causes the head 40K-1 to apply pressure to the ink in the liquid chamber 40F, causing the ink to be ejected (squirted) from the nozzle 40N.

[0039] Thereafter, the head 40K-1 returns the voltage applied to the pressure generating element 45P to the reference potential, and restores the diaphragm 42 to its initial position. At this time, the head 40K-1 reduces the pressure inside the liquid chamber 40F by expanding the liquid chamber 40F, and draws ink from the common liquid chamber 40C into the liquid chamber 40F to replenish it. Next, after the vibration of the meniscus surface of the nozzle 40N has attenuated and stabilized, the head 40K-1 moves on to the operation for ejecting the next ink, and repeats the above operation.

[0040] In this way, the head 40K-1 changes the volume of the liquid chamber 40F and the pressure acting on the ink in the liquid chamber 40F by deforming the vibration plate 42 using the pressure generating unit 45. As a result, the head 40K-1 can eject ink from the nozzle 40N.

[0041] The driving method of the head 40K-1 is not limited to the pull-push driving method. For example, the driving method of the head 40K-1 may be a pull-push driving method or a push-push driving method by controlling the voltage (driving waveform) applied to the pressure generating element 45P.

[0042] In the image forming unit 40, head modules 40K, 40Ca, 40M and 40Y of each color, each equipped with multiple heads 40-1, 40-2, 40-3 and 40-4, are used to form a monochrome or full-color image across the entire area of ​​the roll paper Md along the width direction with a single transport operation of the roll paper Md.

[0043] Here, the printing system 1 may be configured to not include one or more of the pre-processing unit 20, drying unit 30, or post-processing unit 50, depending on the type of recording medium on which an image is formed. The recording medium is not limited to roll paper Md and may be, for example, cut paper. The recording medium may be any medium on which recording can be performed. For example, the recording medium may be plain paper, high-quality paper, thin paper, cardboard, recording paper, OHP (Overhead Projector) sheet, synthetic resin film, thin metal film, etc.

[0044] The image forming unit 40 is not limited to one equipped with head modules of four colors, black (K), cyan (C), magenta (M), and yellow (Y). For example, the image forming unit 40 may be equipped with heads that eject ink of other colors, such as green (G), red (R), and light cyan (LC). The image forming unit 40 may also be one that ejects a single color ink, such as black (K).

[0045] Furthermore, the liquid ejection device according to the embodiment is not limited to the form of an image forming device, and may be, for example, a device that ejects droplets of ink or the like from a head in a printer, scanner, copier, plotter, facsimile, or the like.

[0046] <Example of hardware configuration of image forming device 2> 6 is a block diagram showing an example of the hardware configuration of the image forming apparatus 2. The image forming apparatus 2 has a main control board 100, a head relay board 200, and an image processing board 300. The main control board 100 and the image processing board 300 form a control unit 400.

[0047] The main control board 100 has 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, an NVRAM (Non-Volatile Random Access Memory) 105, a motor driver 106, and a drive waveform generation circuit 107.

[0048] The CPU 101 is responsible for overall control of the image forming apparatus 2. For example, the CPU 101 uses the RAM 103 as a work area to execute various control programs stored in the ROM 104 and outputs control commands for controlling various operations in the image forming apparatus 2. In this case, the CPU 101 communicates with the FPGA 102 and controls various operations in the image forming apparatus 2 in cooperation with the FPGA 102.

[0049] 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 , a head control unit 116 , and a maintenance recovery control unit 117 .

[0050] The CPU control unit 111 communicates with the CPU 101. The memory control unit 112 accesses the RAM 103 and ROM 104. The I2C control unit 113 communicates with the NVRAM 105. The sensor processing unit 114 processes sensor signals from various sensors 130. The various sensors 130 is a general term for sensors that detect various conditions in the image forming apparatus 2. The various sensors 130 include a paper position sensor that detects the position of the widthwise edge of the roll paper Md, a temperature and humidity sensor that detects the ambient temperature and humidity, a remaining ink amount detection sensor that detects the remaining amount of ink in the ink cartridge, and a position sensor that detects the position during maintenance and recovery. Analog sensor signals output from the temperature and humidity sensor and the like are converted into digital signals by an AD (Analog / Digital) converter mounted on, for example, the main control board 100, and then input to the FPGA 102.

[0051] The motor control unit 115 controls various motors 140. The various motors 140 is a general term for the motors provided in the image forming apparatus 2. The various motors 140 include a sub-scanning motor for transporting the roll paper Md, a motor for raising and lowering the image forming unit 40 and post-processing unit 50, a maintenance motor for operating the maintenance recovery units 90A and 90B, and the like.

[0052] The motor control unit 115 generates a drive file. Alternatively, the CPU 101 may generate a drive profile and instruct the motor control unit 115. The CPU 101 also counts the number of sheets on which images have been formed.

[0053] The 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, causing 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 head driver 210 mounted on the head relay board 200.

[0054] The maintenance recovery control unit 117 controls the maintenance motor for operating the maintenance recovery units 90A and 90B, and also communicates the idle time count value with the image processing unit 310.

[0055] Image processing board 300 receives image data Im from an external device such as a PC (Personal Computer), and also receives transport speed information Ve for roll paper Md in printing system 1. Image processing board 300 executes predetermined processing based on this information. The functions of image processing board 300 will be described in detail separately using FIG. 8.

[0056] The head relay board 200 drives the pressure generating elements 45P based on a plurality of signals input from the main control board 100. The configuration of the head relay board 200 will be described below with reference to FIG.

[0057] 7 is a block diagram showing an example of the configuration of the head driver 210. When the head control unit 116 receives a trigger signal Trig, which triggers the timing of ejection, it outputs an ejection synchronization signal LINE, which triggers the generation of a drive waveform, to the drive waveform generation circuit 107. Furthermore, the head control unit 116 outputs an ejection timing signal CHANGE, which corresponds to the amount of delay from the ejection synchronization signal LINE, to the drive waveform generation circuit 107. The drive waveform generation circuit 107 generates a common drive waveform signal Vcom at a timing based on the ejection synchronization signal LINE and the ejection timing signal CHANGE. The drive waveform generation circuit 107 also acquires waveform data from the ROM 104 at a specified address.

[0058] The head control unit 116 receives image data SD' after image processing from the image processing unit 310 provided on the image processing board 300, and generates a mask control signal MN based on this image data SD' to select a predetermined waveform of the common drive waveform signal Vcom depending on the size of the ink droplets to be ejected from each nozzle of the head 40K-1. The mask control signal MN is a signal synchronized with the ejection timing signal CHANGE. The head control unit 116 transfers the image data SD', the synchronous clock signal SCK, a latch signal LT that commands the latching of the image data, and the generated mask control signal MN to the head driver 210. The head control unit 116 is an example of a latch generating unit that generates a latch signal with a higher frequency than the trigger signal.

[0059] The 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 .

[0060] The shift register 211 receives the image data SD′ and the synchronous clock signal SCK transferred from the head control unit 116. The latch circuit 212 latches each register value of the shift register 211 in response to a latch signal LT transferred from the head control unit 116.

[0061] 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.

[0062] The analog switch 215 is a switch that is turned on or off by the output of the gradation decoder 213 provided via the level shifter 214. An analog switch 215 is provided for each pressure generating element (piezoelectric element) 45P associated with the nozzles of the head 40K-1, and is connected to the individual electrodes 45Pei of the pressure generating elements 45P corresponding to each nozzle. A common drive waveform signal Vcom is input to the analog switch 215 from the drive waveform generating circuit 107. A mask control signal MN is synchronized with the common drive waveform signal Vcom.

[0063] The head driver 210 selects a waveform to be applied to the pressure generating element 45P corresponding to each nozzle from the drive waveforms constituting the common drive waveform signal Vcom by switching on or off an analog switch 215 at appropriate timing in accordance with the output of a gradation decoder 213 provided via a level shifter 214. As a result, the size of the ink droplets ejected from the nozzles is controlled.

[0064] <Example of functional configuration of image processing unit 310> 8 is a block diagram showing an example of the functional configuration of the image processing unit 310. The image processing unit 310 and the head control unit 116 function as a control unit of the image forming apparatus 2.

[0065] The image processing unit 310 performs gradation processing, image conversion processing, etc. on the received image data Im, and converts it into image data SD' in a format that can be processed by the head control unit 116. The image processing unit 310 outputs the converted image data SD' to the head control unit 116.

[0066] As shown in FIG. 8, the image processing unit 310 includes an input unit 311, a tone processing unit 312, a determination unit 313, a change unit 314, an image conversion unit 315, and an output unit 316.

[0067] The input unit 311 is an interface that inputs image data Im from an external device and communicates with the external device, the CPU 101, the FPGA 102, and the like.

[0068] The gradation processing unit 312 performs gradation processing on the input multi-value image data Im and converts it into low-value image data SD. The low-value image data SD is image data (original image data) with the same number of gradations as the types of droplets (large droplets, medium droplets, small droplets) ejected by the head 40K-1.

[0069] The determination unit 313 determines whether the first frequency is within a predetermined frequency range, based on the first frequency acquired based on transport speed information Ve for the roll paper Md in the printing system 1. In other words, the determination unit 313 determines whether the first frequency is higher than the upper limit frequency in the predetermined frequency range, or whether the first frequency is lower than the lower limit frequency in the predetermined frequency range. If the determination unit 313 determines that the first frequency is higher than the upper limit frequency, it determines whether the mask control signal data MN' that selects vibration drive is consecutive. The determination unit 313 outputs the determination result to the change unit 314. Here, the mask control signal data MN' is the data from which the mask control signal MN is generated.

[0070] The first frequency corresponds to the frequency at which a drive waveform is output to head 40K-1. The drive waveform is a waveform that includes an ejection drive waveform that causes head 40K-1 to eject ink, and a vibration drive waveform that causes head 40K-1 to vibrate the ink inside head 40K-1.

[0071] The second frequency corresponds to the frequency at which a vibration drive waveform is output to the head. When the vibration drive waveform is input, head 40K-1 does not eject ink, but vibrates the meniscus, which is the gas-liquid interface between the air and the ink in the nozzles of head 40K-1.

[0072] The transport speed information Ve is information indicating the transport speed of the roll paper Md by the transport unit 80, or information related to the transport speed of the roll paper Md. The determination unit 313 acquires the transport speed information Ve from the detection results of a detector such as a rotary encoder provided in the transport unit 80. The rotary encoder is provided in a transport roller or the like provided in the transport unit 80, and outputs rotation angle information of the transport roller as the detection result.

[0073] The determination unit 313 can also acquire the conveying speed information Ve via an operation unit that accepts operational input to the printing system 1 by a user of the printing system 1 (hereinafter simply referred to as the user). This point will be explained in more detail below. The user can use the printing system 1 in two ways: when image formation is performed while conveying the roll paper Md at a constant conveying speed, and when image formation is performed while appropriately changing the conveying speed of the roll paper Md.

[0074] When forming an image while appropriately changing the conveying speed of the roll paper Md, the conveying speed may be set relatively slow to form an image with high resolution, or the conveying speed may be set relatively fast to form a large amount of images quickly.

[0075] Here, Fig. 9 is a diagram illustrating an example of changes in the transport speed V of the roll paper Md. The horizontal axis of Fig. 9 represents the printing time, and the vertical axis represents the transport speed V of the roll paper Md. Fig. 9 shows changes in the transport speed V as a result of the user appropriately setting or changing the transport speed.

[0076] The period t1 is a period in which the conveying speed is made relatively slow in order to form images with high resolution, and the period t2 is a period in which the conveying speed is made relatively fast in order to form images quickly and in large quantities.

[0077] Meanwhile, the printing system 1 may need to reset the image formation conditions. In this case, if the printing system 1 is completely stopped, no signals are supplied to heads such as head 40K-1, and the ink stops moving, causing the ink in the heads to dry and thicken through nozzles that are open to the atmosphere. If the ink thickens, ejection failures or ejection defects may occur when the operation of the printing system 1 is resumed. Ejection defects are particularly likely to occur when ink that dries easily is used.

[0078] To return the ejection failure to its original normal state, it is necessary to perform a waste ejection (blank ejection) to discharge the thickened ink, or a suction operation to suck out the thickened ink, which takes time and also results in ink waste due to the increased amount of ink to be discarded. For this reason, in this embodiment, even when resetting the image formation conditions by the printing system 1, the printing system 1 is not completely stopped, and an image can be formed slowly while transporting the roll paper Md at an extremely slow transport speed that allows the user to perform the resetting work in parallel with image formation. Period t3 in Figure 9 corresponds to the period during which the image is formed slowly.

[0079] The user can set or change the conveying speed as shown in FIG. 9 as appropriate via an operation unit or the like, and the determination unit 313 can acquire the conveying speed information Ve that has been set or changed via the operation unit or the like.

[0080] The printing system 1 determines the first frequency in proportion to the transport speed of the roll paper Md. The determination unit 313 acquires first frequency information according to transport speed information Ve, and can determine whether the first frequency is within a predetermined frequency range.

[0081] Returning to FIG. 8, the functional configuration of the image processing unit 310 will be described further.

[0082] The change unit 314 performs processing to change the second frequency relative to the first frequency in accordance with the first frequency. Specifically, when the determination unit 313 determines that the first frequency is lower than the lower limit frequency in a predetermined frequency range, the change unit 314 adds vibration drive waveform data corresponding to the latch signal to the predetermined drive waveform data. As a result, the change unit 314 causes the head 40K-1 to vibrate the ink in the head 40K-1 in accordance with the latch signal LT. As a result, the second frequency becomes higher than the first frequency. The vibration drive waveform data is data of a vibration drive waveform that vibrates the ink in the head 40K-1 without ejecting ink. The drive waveform data is waveform data that includes data of an ejection drive waveform that ejects ink and vibration drive waveform data.

[0083] Furthermore, when the determination unit 313 determines that the first frequency is higher than the upper limit frequency in the predetermined frequency range and that the mask control signal selecting the vibration drive is continuous, the modification unit 314 modifies the mask control signal data MN' for the image conversion unit 315 to select the vibration drive waveform, thereby thinning out the number of times the vibration drive waveform data is output. As a result, the second frequency becomes lower than the first frequency. When the first frequency is within the predetermined frequency range, the modification unit 314 does not modify the second frequency. As a result, the second frequency becomes equal to the first frequency.

[0084] The image conversion unit 315 adds vibration drive information including information on the second frequency changed by the change unit 314 to the image data SD of large, medium, and small droplets, and converts the image data SD into image data SD'. This conversion is performed in accordance with information such as the image formation sequence obtained from the image data Im via the input unit 311, and in accordance with the configuration of the head 40K-1.

[0085] The image conversion unit 315 is an example of a selection unit that selects at least one of the ejection drive waveform data and the vibration drive waveform data. The image conversion unit 315 can select at least one of the ejection drive waveform and the vibration drive waveform by adding the mask control signal data MN' to the image data SD'.

[0086] The image conversion unit 315 outputs the converted image data SD' to the FPGA 102 of the main control board 100 via the output unit 316. In other words, the output unit 316 can output drive waveform data including ejection drive waveform data and vibration drive waveform data to the head 40K-1 via the main control board 100.

[0087] The functions of image processing unit 310 may be executed as hardware functions such as FPGA or ASIC, or may be implemented by an image processing program stored in a storage device inside image processing unit 310. Furthermore, the functions of image processing unit 310 may be realized by software installed on a computer, rather than inside image forming apparatus 2.

[0088] <Example of vibration drive> Fig. 10 is a diagram illustrating an example of vibration driving in head 40K-1. Fig. 10 is a cross-sectional view of the periphery of nozzle 40N in head 40K-1, as viewed from a direction perpendicular to ink ejection direction 81. Fig. 10 also shows nine states, from state 91 to state 99, of nozzle 40N.

[0089] 10, ink 90 filled inside head 40K-1 is open to the atmosphere through nozzle 40N. Meniscus 90a is the gas-liquid interface between the ink 90 and the atmosphere. When negative pressure acting in the direction opposite to the ink ejection direction 81 is applied to the ink 90 inside head 40K-1, the meniscus 90a is formed in a state where it is recessed in the direction opposite to the ink ejection direction 81.

[0090] When head 40K-1 is stopped without ejection from state 91 to state 93, the water content of ink 90 evaporates through nozzle 40N, which is open to the atmosphere, and the viscosity of ink 90 near meniscus 90a increases (thickens) over time. The increased viscosity of ink 90 increases the fluid resistance near meniscus 90a, which may prevent the intended ejection.

[0091] As shown in states 94 to 96, the image forming apparatus 2 applies pressure to the ink 90 in the head 40K-1 to a degree that does not cause the ink 90 to be ejected, and performs vibration driving to vibrate the ink 90 in the head 40K-1. Arrows 90b in Figure 10 represent the flow of ink 90 agitated by the vibration driving of the ink 90 in the head 40K-1. The image forming apparatus 2 can prevent ejection defects by moving the thickened ink 90 near the meniscus 90a to the head 40K-1 through agitation caused by the vibration driving.

[0092] However, if the frequency at which the ink 90 is vibrated (the number of times the ink is vibrated per unit time) is too high, the amount of thickened ink 90 flowing inside the head 40K-1 increases, and the entire ink 90 inside the head 40K-1 becomes thicker, making it difficult to fully suppress ejection defects.Furthermore, if the frequency at which the ink 90 is vibrated is too low, the stirring effect becomes insufficient, making it difficult to fully suppress ejection defects.

[0093] <Example of driving waveform> 11 is a diagram illustrating an example of drive waveform data for driving head 40K-1. Drive waveform data Da is digital data representing a voltage waveform. The drive waveform data Da is supplied to head driver 210, converted into an analog voltage signal, and then applied to pressure generating element 45P as a drive waveform. Pressure generating element 45P applies pressure to ink 90 in head 40K-1 in accordance with the drive waveform, causing ink 90 to be ejected from nozzle 40N.

[0094] The drive waveform data Da includes waveform data for four sections: sections 111a, 111b, 111c, and 111d. The mask control signal data MN0', MN1', MN2', and MN3' are signals for invalidating the waveform data for each section in the drive waveform data Da. When there is no need to distinguish between the mask control signal data MN0', MN1', MN2', and MN3', they are collectively referred to as mask control signal data MN'.

[0095] The masked control signal data MN0' enables the waveform data of only section 111b of the drive waveform data Da and disables the other sections 111a, 111c, and 111d, thereby selecting vibration drive as the drive for head 410K-1. The drive waveform data Da to which the masked control signal data MN0' has been applied drives head 40K-1 to vibrate.

[0096] The mask control signal data MN1' enables the waveform data of only section 111d of the drive waveform data Da and disables the other sections 111a, 111b, and 111c, thereby selecting the ejection of small droplets as the drive by head 410K-1. The drive waveform data Da to which the mask control signal data MN1' is applied causes head 40K-1 to eject small droplets.

[0097] The mask control signal data MN2' enables the waveform data of sections 111c and 111d of the drive waveform data Da and disables the other sections 111a and 111b, thereby selecting the ejection of medium droplets as the drive by head 410K-1. The drive waveform data Da to which the mask control signal data MN2' has been applied causes head 40K-1 to eject medium droplets.

[0098] The mask control signal data MN3' enables the waveform data of all sections 111a, 111b, 111c, and 111d of the drive waveform data Da, thereby selecting the ejection of large droplets as the drive of head 410K-1. The drive waveform data Da to which the mask control signal data MN3' is applied causes head 40K-1 to eject large droplets.

[0099] The image processing unit 310 can supply image data SD′ including drive waveform data Da and mask control signal data MN′ to the head driver 210 via the head control unit 116.

[0100] Drive waveform data based on drive waveform data Da in which only section 111b is valid corresponds to vibration drive waveform data. Drive waveform data based on drive waveform data Da in which sections other than section 111b are valid corresponds to ejection drive waveform data. The output unit 316 can output drive waveform data including ejection drive waveform data and vibration drive waveform data to head 40K-1.

[0101] <Example of processing by image processing unit 310> 12 is a flowchart showing an example of processing by the image processing unit 310. When the image data Im is input from an external device via the input unit 311, the image processing unit 310 starts the processing of FIG.

[0102] First, in step S121, the image processing unit 310 performs gradation processing on the multi-value image data Im input via the input unit 311 using the gradation processing unit 312, converts it into low-value image data SD, and outputs the image data SD to the image conversion unit 315.

[0103] Next, in step S122, the image processing unit 310 causes the determination unit 313 to acquire information about the first frequency from the transport speed information Ve of the roll paper Md.

[0104] Next, in step S123, the image processing unit 310 causes the determining unit 313 to determine whether or not the first frequency is lower than the lower limit frequency.

[0105] If it is determined in step S123 that the first frequency is lower than the lower limit frequency (step S123, Yes), in step S124, the image processing unit 310 causes the change unit 314 to add vibration drive waveform data corresponding to the latch signal to the drive waveform data. This causes the head 40K-1 to vibrate the ink in the head 40K-1 in accordance with the latch signal LT. As a result, the second frequency becomes higher than the first frequency. After that, the image processing unit 310 proceeds to step S128.

[0106] On the other hand, if it is determined in step S123 that the first frequency is not lower than the lower limit frequency (step S123, No), in step S125, the image processing unit 310 determines, by the determination unit 313, whether or not the first frequency is higher than the upper limit frequency.

[0107] In step S125, if it is determined that the first frequency is not higher than the upper limit frequency (step S125, No), image processing unit 310 proceeds to the process of step S128.

[0108] On the other hand, if it is determined in step S125 that the first frequency is higher than the upper limit frequency (step S125, Yes), in step S126, the image processing unit 310 determines whether or not the mask control signal data MN' that selects vibration drive is consecutive using the determination unit 313.

[0109] In step S126, if it is determined that the mask control signal data MN' are not consecutive (step S126, No), the image processing unit 310 proceeds to step S128. On the other hand, if it is determined that the mask control signal data MN' are consecutive (step S126, Yes), in step S127, the image processing unit 310 changes the mask control signal data MN' used by the image conversion unit 315 to select a vibration drive waveform, thereby thinning out the number of times the vibration drive waveform is output. As a result, the second frequency becomes lower than the first frequency.

[0110] Next, in step S128, the image processing unit 310 adds vibration drive information including information on the second frequency to the image data SD of large, medium, and small droplets using the image conversion unit 315, and converts the image data SD into image data SD'.

[0111] Next, in step S129, the image processing unit 310 outputs the image data SD′ to the head control unit 116 via the output unit 316.

[0112] In this way, the image processing unit 310 can output the image data SD′ generated based on the image data Im to the head control unit 116.

[0113] <Example of modification of mask control signal data MN′ by modification unit 314> FIG. 13 is a diagram illustrating an example of modification of the mask control signal data MN' by the modification unit 314. FIG. 12 shows the mask control signal data MN" and MN', and the image data P(X), for the image forming apparatus 2 to eject ink 90 from one nozzle 40N included in the head 40K-1 onto roll paper Md transported in the transport direction Xm. Each of the multiple grids arranged along the transport direction Xm represents one pixel in the image data SD'. The mask control signal data MN" represents the mask control signal data before modification by the modification unit 314, and the mask control signal data MN' represents the mask control signal data after modification by the modification unit 314.

[0114] Of the mask control signal data MN", signal group 121 has two consecutive "0"s, which are mask control signal data MN" that select vibration drive. The change unit 314 changes one of the two consecutive "0"s to "-1", as in signal group 122 in mask control signal data MN'. With this change, a vibration drive waveform is no longer output at pixels where the mask control signal data MN' has become "-1", and so the number of times the vibration drive waveform is output is thinned out.

[0115] <Example of changing the second frequency> The operation of changing the second frequency by the change unit 314 will be described with reference to Fig. 14 to Fig. 17. Fig. 14 is a diagram showing a first example of a vibration drive waveform before changing the second frequency. Fig. 15 is a diagram showing a first example of a vibration drive waveform after changing the second frequency. Fig. 16 is a diagram showing a second example of a vibration drive waveform before changing the second frequency. Fig. 17 is a diagram showing a second example of a vibration drive waveform after changing the second frequency.

[0116] 14 to 17 are timing charts showing three signals: a trigger signal Trig, a latch signal LT, and a drive waveform Da'. In each diagram, the signal shown in the upper row is the trigger signal Trig, the signal shown in the middle row is the latch signal LT, and the signal shown in the lower row is the drive waveform Da'. The latch signal LT has a higher frequency than the trigger signal Trig. The drive waveform Da' is an analog signal based on the drive waveform data Da after the mask control signal data MN' has been applied. Periods t4, t5, and t6 each correspond to one cycle of the first frequency.

[0117] 14 and 15, a drive waveform Da' including only a vibration drive waveform is output in response to a trigger signal Trig. Compared to the drive waveform Da' before change shown in Fig. 14, the drive waveform Da' after change shown in Fig. 15 has the vibration drive waveform thinned out during period t5. By thinning out one of the two cycles of the vibration drive waveform, the second frequency becomes half the frequency of the first frequency.

[0118] 16 and 17, a drive waveform Da' including both an ejection drive waveform and a vibration drive waveform is displayed in response to the trigger signal Trig. Period t7 is a period during which the voltage of the drive waveform Da' is not applied because the period corresponding to the drive waveform Da' is shorter than one cycle corresponding to the first frequency.

[0119] While no voltage is applied during period t7 in FIG. 16, voltage 171 is applied during period t7 in FIG. 17. This voltage 171 is applied in response to latch signal LT and corresponds to the vibration drive waveform output during period t7. Voltage 171 is output after a predetermined time determined using the count number of latch signal LT has elapsed, within one period corresponding to the first frequency, after the period corresponding to drive waveform Da' has ended. Because the drive waveform Da' also contains a vibration drive waveform, application of voltage 171 corresponding to the vibration drive waveform results in two vibration drive waveforms being output within one period corresponding to the first frequency. As a result, the second frequency is twice the frequency of the first frequency.

[0120] <Example of second frequency transition> Fig. 18 is a diagram showing an example of a transition of the second frequency. The horizontal axis of Fig. 18 represents the printing time, and the vertical axis represents the frequency f. Fig. 18 shows how the first frequency f1 (solid line) and the second frequency f2 (dashed line) transition in accordance with a change in the conveying speed V, which is the result of the user appropriately setting or changing the conveying speed. Fig. 18 can be read in the same way as Fig. 9 described above, except that the vertical axis represents frequency.

[0121] In response to changes in the transport speed V, the first frequency f1 becomes relatively low in the period t1, relatively high in the period t2, and very low in the period t3.

[0122] On the other hand, the second frequency f2 is different from the first frequency f1 due to the change process by the change unit 314, and falls entirely within the predetermined frequency range fth. Specifically, during the period t1, the first frequency f1 is within the frequency range fth, so the change unit 314 does not change the second frequency f2. As a result, the second frequency f2 is equal to the first frequency f1.

[0123] During period t2, the first frequency f1 is higher than the upper limit frequency th1 of the frequency range fth, so the change unit 314 changes the second frequency f2 to be lower than the first frequency f1. As a result, the second frequency f2 becomes lower than the first frequency f1 and falls within the frequency range fth.

[0124] During period t3, the first frequency f1 is lower than the lower limit frequency th2 of the frequency range fth, so the change unit 314 changes the second frequency f2 to be higher than the first frequency f1. As a result, the second frequency f2 is higher than the first frequency f1 and falls within the frequency range fth.

[0125] The ease with which the ink in the head 40K-1 thickens varies depending on factors such as the type of ink, the type of roll paper Md, or the method used to heat the ink applied to the roll paper Md. Methods for heating the ink include using a heater or blowing hot air. In this embodiment, the frequency range fth is predetermined according to at least one of the type of ink, the type of roll paper Md, or the method used to heat the ink applied to the roll paper Md. This makes it possible to further optimize the frequency of the vibration drive according to the ease with which the ink in the head 40K-1 thickens.

[0126] <Functions and Effects of Image Forming Apparatus 2> Next, the effects of the image forming apparatus 2 will be described.

[0127] In a liquid ejection type image forming apparatus, a technique is known in which the ink in the head is vibrated to prevent the ink in the head from drying and becoming thicker during periods when ink is not being ejected from the head.

[0128] When vibrating the ink in the head, for example, the image forming device provides vibration drive waveform data that vibrates the ink within the drive waveform data that causes the head to eject ink, and vibrates the ink by outputting drive waveform data to the head in which only the vibration drive waveform data is enabled during periods when ink is not being ejected from the head.

[0129] On the other hand, liquid ejection image forming devices may change the first frequency at which a drive waveform is output to the head in response to factors such as the transport speed of the recording medium. In this case, because the vibration drive waveform is included in the drive waveform, the second frequency at which the vibration drive waveform is output changes equally in response to changes in the first frequency. The second frequency has an optimum frequency range; if it is higher than this range, excessive vibration may occur, which may actually promote thickening of the ink in the head, while if it is lower than this range, the effect of suppressing ink thickening may be reduced, resulting in unstable ink ejection from the head.

[0130] The image forming apparatus 2 according to this embodiment includes a head 40K-1 that ejects ink (liquid), and an output unit 316 that outputs drive waveform data to the head 40K-1, the drive waveform data including data for an ejection drive waveform that ejects ink and data for a vibration drive waveform that vibrates the ink in the head 40K-1 without ejecting ink. The image forming apparatus 2 also includes a change unit 314 that changes a second frequency f2 at which a vibration drive waveform is output to the head 40K-1 relative to the first frequency f1, in accordance with a first frequency f1 at which a drive waveform is output to the head 40K-1.

[0131] For example, when the first frequency f1 is higher than the upper limit frequency th1 in the frequency range fth, the change unit 314 sets the second frequency f2 lower than the first frequency f1, and when the first frequency f1 is lower than the lower limit frequency th2 in the frequency range fth, the change unit 314 sets the second frequency f2 higher than the first frequency f1. This allows the second frequency f2 to fall within the frequency range fth, so that the image forming device 2 can appropriately suppress ink thickening due to vibration driving and stabilize liquid ejection from the head 40K-1.

[0132] Furthermore, the image forming device 2 applies ink to the roll paper Md by ejecting the ink, and the frequency range fth is predetermined according to at least one of the type of ink, the type of roll paper Md, or the method for heating the ink applied to the roll paper Md. This makes it possible to further optimize the frequency of the vibration drive according to the tendency for the ink in the head 40K-1 to thicken.

[0133] The image forming device 2 also has an image conversion unit 315 (selection unit) that selects at least one of ejection drive waveform data and vibration drive waveform data from the drive waveform data Da, and the change unit 314 changes the first frequency f1 so that the number of times the vibration drive waveform is output is thinned out when the first frequency f1 is higher than the upper limit frequency th1 in the frequency range fth. This allows the image forming device 2 to make the second frequency f2 lower than the first frequency f1.

[0134] The image forming device 2 also has a head control unit 116 (latch generating unit) that generates a latch signal LT with a higher frequency than the trigger signal Trig that vibrates the ink in the head 40K-1. When the first frequency f1 is lower than the lower limit frequency th2 of the frequency range fth, the change unit 314 changes the head 40K-1 to vibrate the ink in the head 40K-1 in accordance with the latch signal LT. This allows the image forming device 2 to make the second frequency f2 higher than the first frequency f1.

[0135] In this embodiment, the head 40K-1 has been described as an example, but the other heads included in the image forming unit 40 can also be operated in the same manner as the head 40K-1.

[0136] Changes in the transport speed V of the roll paper Md include both intentional changes due to user instructions and unintentional changes due to errors in the components that make up the transport unit 80. In either case, the image forming device 2 can change the second frequency f2 in accordance with the first frequency f1.

[0137] [Other Preferred Embodiments] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0138] For example, in the above embodiment, an image forming apparatus equipped with a recording head according to the present invention has been described, but the liquid ejection head according to the present invention and its control can be widely applied to devices that eject liquid, including image forming apparatuses.

[0139] For example, in this example, the head is described as head 40K-1 included in an image forming means that ejects ink, but the embodiment can also be applied to heads included in the pre-processing unit 20 or post-processing unit 50 shown in Figure 1.

[0140] Furthermore, in the above example, an example of applying the embodiment to a line-type liquid ejection device in which the head does not move in the width direction was described, but the embodiment can also be applied to a serial-type liquid ejection device in which the head moves in the width direction via a carriage.

[0141] In the embodiments, a "liquid ejecting device" is a device that includes a liquid ejection head or a liquid ejection unit and ejects liquid by driving the liquid ejection head. The liquid ejecting device includes not only a device that can eject liquid onto an object onto which the liquid can adhere, but also a device that ejects liquid into air or liquid.

[0142] This "liquid ejecting device" can also include means for feeding, transporting, and discharging items onto which liquid can be attached, as well as pre-processing devices and post-processing devices.

[0143] For example, examples of "liquid ejecting devices" include image forming devices that eject ink to form images on paper, and three-dimensional modeling devices (three-dimensional modeling devices) that eject modeling liquid onto a powder layer formed from layers of powder in order to create a three-dimensional object (a three-dimensional model).

[0144] Furthermore, the term "liquid ejection device" is not limited to devices that use ejected liquid to visualize meaningful images such as letters and figures. For example, it also includes devices that form patterns that have no meaning in themselves, and devices that create three-dimensional images.

[0145] The above-mentioned "object onto which a liquid can adhere" means an object onto which a liquid can adhere at least temporarily, an object onto which the liquid can adhere and stick, an object onto which the liquid can penetrate, etc. Specific examples include media such as paper, recording paper, film, and cloth, electronic circuit boards, electronic components such as piezoelectric elements, powder layers, organ models, and test cells, and unless otherwise specified, includes all objects onto which a liquid can adhere.

[0146] The material of the "substance to which a liquid can adhere" may be any material to which a liquid can adhere, even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, or ceramics.

[0147] Furthermore, the pressure generating element used in the "liquid ejection head" is not limited. For example, a piezoelectric actuator (including a laminated piezoelectric element), a thermal actuator using an electrothermal conversion element such as a heating resistor, an electrostatic actuator consisting of a vibration plate and an opposing electrode, etc. can be used.

[0148] In the embodiments, the terms image formation, recording, printing, copying, printing, modeling, etc. are all synonymous.

[0149] The embodiments also include a liquid ejection method. For example, the liquid ejection method is a liquid ejection method using a liquid ejection device, in which a head ejects liquid, an output unit outputs drive waveform data to the head, including data on an ejection drive waveform that ejects the liquid and data on a vibration drive waveform that vibrates the liquid in the head without ejecting the liquid, and a change unit changes a second frequency at which the vibration drive waveform is output to the head from the first frequency, depending on the first frequency at which the drive waveform is output to the head. This liquid ejection method can achieve the same effects as the image forming apparatus 2 described above.

[0150] The ordinal numbers, quantities, and other figures used in the description of the embodiments are all provided as examples to specifically explain the technology of the present invention, and the present invention is not limited to the illustrated figures. Furthermore, the connection relationships between the components are provided as examples to specifically explain the technology of the present invention, and do not limit the connection relationships that realize the functions of the present invention.

[0151] Each function of the embodiments can be realized by one or more processing circuits. Here, the term "processing circuit" in this specification includes a processor programmed to perform each function by software, such as a processor implemented by an electronic circuit, as well as devices such as an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), and conventional circuit modules designed to perform each function described above. [Explanation of symbols]

[0152] 1 Printing System 2 Image forming device (liquid ejection device) 40 Image forming unit 40K, 40Ca, 40M, 40Y head modules 40K-1, 40K-2, 40K-3, 40K-4 head 40N nozzle 45P pressure generating element 100 Main control board 116 Head control unit (an example of a latch generating unit) 200 Head relay board 210 Head Driver 300 Image processing board 310 Image Processing Unit 311 Input section 312 Gradation Processing Unit 313 Judgment section 314 Changes 315 Image conversion unit 316 Output section Da Drive waveform data Da' drive waveform f1 First frequency f2 Second frequency fth frequency range th1 upper limit frequency th2 lower limit frequency Trig Trigger signal LT Latch signal MN Mask control signal MN' Mask control signal data Im, SD, SD' image data V Conveying speed Ve conveying speed information Md roll paper (recording medium) Xm conveying direction t1, t2, t3, t4, t5, t6, t7 period [Prior art documents] [Patent documents]

[0153] [Patent Document 1] Japanese Patent Application Publication No. 2019-166829

Claims

1. a head that ejects liquid; an output unit that outputs drive waveform data, including ejection drive waveform data that ejects the liquid and vibration drive waveform data that vibrates the liquid in the head without ejecting the liquid, to the head at a first frequency that ejects the liquid during a period in which the liquid can be ejected; a change unit that changes a second frequency at which the vibration drive waveform is output to the head relative to the first frequency in accordance with the first frequency at which the drive waveform is output to the head, The change unit If the first frequency is within a predetermined frequency range, the second frequency is not changed and the second frequency is made equal to the first frequency; When the first frequency is not within the predetermined frequency range and is lower than a lower limit frequency of the predetermined frequency range, the second frequency is set to be higher than the first frequency; When the first frequency is not within the specified frequency range and is higher than the upper limit frequency in the specified frequency range, the liquid ejection device reduces the number of times the vibration drive waveform is output per unit time, thereby making the second frequency lower than the first frequency.

2. A head that ejects liquid; an output unit that outputs drive waveform data, including ejection drive waveform data that ejects the liquid and vibration drive waveform data that vibrates the liquid in the head without ejecting the liquid, to the head at a first frequency that ejects the liquid during a period in which the liquid can be ejected; a change unit that changes a second frequency at which the vibration drive waveform is output to the head relative to a first frequency in accordance with a first frequency at which the drive waveform is output to the head, The change unit If the first frequency is within a predetermined frequency range, the second frequency is not changed and the second frequency is made equal to the first frequency; When the first frequency is not within the predetermined frequency range and is higher than an upper limit frequency of the predetermined frequency range, the second frequency is set lower than the first frequency; A liquid ejection device that, when the first frequency is not within the specified frequency range and is lower than a lower limit frequency in the specified frequency range, makes the second frequency higher than the first frequency by adding the number of times the vibration drive waveform is output per unit time.

3. the head applies the liquid to a recording medium by ejecting the liquid; The liquid ejection device according to claim 1 or 2, wherein the frequency range is predetermined according to at least one of the type of the liquid, the type of the recording medium, and a method of heating the liquid applied to the recording medium.

4. a head that ejects liquid; an output unit that outputs drive waveform data, including ejection drive waveform data that ejects the liquid and vibration drive waveform data that vibrates the liquid in the head without ejecting the liquid, to the head at a first frequency that ejects the liquid during a period in which the liquid can be ejected; a change unit that changes a second frequency at which the vibration drive waveform is output to the head relative to the first frequency in accordance with the first frequency at which the drive waveform is output to the head; a selection unit that selects at least one of the ejection drive waveform data and the vibration drive waveform data from the drive waveform data, The change unit If the first frequency is within a predetermined frequency range, the second frequency is not changed and the second frequency is made equal to the first frequency; When the first frequency is not within the predetermined frequency range and is lower than a lower limit frequency of the predetermined frequency range, the second frequency is set to be higher than the first frequency; A liquid ejection device that, when the first frequency is not within the specified frequency range and is higher than an upper limit frequency in the specified frequency range, makes the second frequency lower than the first frequency by thinning out the number of times the vibration drive waveform is output.

5. a head that ejects liquid; an output unit that outputs drive waveform data, including ejection drive waveform data that ejects the liquid and vibration drive waveform data that vibrates the liquid in the head without ejecting the liquid, to the head at a first frequency that ejects the liquid during a period in which the liquid can be ejected; a change unit that changes a second frequency at which the vibration drive waveform is output to the head relative to the first frequency in accordance with the first frequency at which the drive waveform is output to the head, The change unit If the first frequency is within a predetermined frequency range, the second frequency is not changed and the second frequency is made equal to the first frequency; When the first frequency is not within the predetermined frequency range and is lower than a lower limit frequency of the predetermined frequency range, the second frequency is set to be higher than the first frequency; A liquid ejection device that, when the first frequency is not within the specified frequency range and is higher than an upper limit frequency in the specified frequency range, makes the second frequency lower than the first frequency by thinning out the number of times the vibration drive waveform is output.

6. a selection unit that selects at least one of the ejection drive waveform data and the vibration drive waveform data from the drive waveform data, The liquid ejection device according to claim 2 , wherein the change unit changes the number of times the vibration drive waveform is output so as to be thinned out when the first frequency is higher than an upper limit frequency in the frequency range.

7. a latch generating unit that generates a latch signal having a frequency higher than a predetermined trigger signal that vibrates the liquid in the head; The liquid ejection device according to claim 2 , wherein the change unit changes the head so that the liquid inside the head vibrates in response to the latch signal when the first frequency is lower than a lower limit frequency in the frequency range.

8. A liquid ejection method using a liquid ejection device, The head ejects the liquid, an output unit outputs drive waveform data, including ejection drive waveform data for ejecting the liquid and vibration drive waveform data for vibrating the liquid in the head without ejecting the liquid, to the head at a first frequency for ejecting the liquid during a period in which the liquid can be ejected; a change unit that changes a second frequency at which the vibration drive waveform is output to the head relative to the first frequency in accordance with the first frequency at which the drive waveform is output to the head; The change unit If the first frequency is within a predetermined frequency range, the second frequency is not changed and the second frequency is made equal to the first frequency; When the first frequency is not within the predetermined frequency range and is lower than a lower limit frequency of the predetermined frequency range, the second frequency is set to be higher than the first frequency; A liquid ejection method in which, when the first frequency is not within the specified frequency range and is higher than an upper limit frequency in the specified frequency range, the second frequency is made lower than the first frequency by thinning out the number of times the vibration drive waveform is output.

Images