Liquid ejection device, head control device and control method for liquid ejection device

Abstract

To sequentially read waveform information from a storage unit without using a large-scale memory access mechanism.SOLUTION: A head control device that generates voltage data for a drive voltage to be applied to an ejection head includes: an address counter that holds an address of an entry of a storage unit; a repetition counter and a voltage value holding unit that hold the number of repetitions of reading from the entry and an amount of change in voltage, respectively; and a data creating unit that creates new voltage data by adding the amount of change in voltage held in the voltage value holding unit, to voltage data corresponding to a current drive voltage. In a case where the new voltage data corresponding to the number of repetitions is created by the data creating unit, an operation of updating the address counter and storing the number of repetitions of reading from the subsequent entry and the amount of change in voltage into the repetitions counter and the voltage value holding unit, respectively, is repeated until the number of repetitions and the amount of change in voltage are read from all entries.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus, a head control device, and a method for controlling a liquid ejection apparatus. [Background technology]

[0002] Liquid ejection devices such as inkjet printers eject liquid by applying a drive signal to an ejection head equipped with a piezoelectric element or the like. This type of liquid ejection device has a CPU (Central Processing Unit) that controls the overall operation of the liquid ejection device, a storage unit that stores programs executed by the CPU, and a drive signal generation unit that generates the drive signal. The storage unit stores the voltage change value (increase, decrease, or maintenance) of the drive signal per unit time and the number of times the voltage change value is repeated.

[0003] The CPU outputs data stored in the memory unit to the drive signal generation unit based on a request from the drive signal generation unit, and outputs a change signal to the drive signal generation unit at a predetermined frequency based on the data stored in the memory unit. The drive signal generation unit generates a drive signal whose voltage value increases, decreases, or remains constant based on the data and change signal received from the CPU, and outputs the generated drive signal to the ejection head (see, for example, Patent Document 1).

[0004] Furthermore, for example, the liquid ejection device includes a print sequence control unit, an external memory, a DMAC (Direct Memory Access Controller), a drive waveform generation unit including multiple internal memories, and an ejection head that ejects liquid based on a drive signal output from the drive waveform generation unit. For example, the DMAC and the drive waveform generation unit are mounted on an ASIC (Application Specific Integrated Circuit).

[0005] The DMAC sequentially transfers the basic waveform data from the external memory to an internal memory that has already output the basic waveform data among the multiple internal memories based on a transfer request from the print sequence control unit. The drive waveform generation unit selects an internal memory that holds the basic waveform data that has not yet been output, and outputs the basic waveform data held in the selected internal memory to the ejection head (see, for example, Patent Document 2). Summary of the Invention [Problem to be solved by the invention]

[0006] However, when multiple voltage change values ​​of drive signals and the number of times the voltage change values ​​are repeated are stored in an internal memory, no method has been proposed for sequentially reading basic waveform data from the internal memory using waveform information contained in the basic waveform data stored in the internal memory without using a large-scale memory access mechanism such as a CPU or DMAC.

[0007] The disclosed technology has been made in consideration of the above-mentioned problems, and aims to sequentially read out waveform information from a storage unit without using a large-scale memory access mechanism. [Means for solving the problem]

[0008] In order to solve the above technical problems, one form of the present invention provides a liquid ejection device having an ejection head that ejects liquid in accordance with a drive voltage, and a head control device that generates voltage data for the drive voltage to be applied to the ejection head, wherein the head control device has a memory unit having a plurality of entries that hold the number of repetitions and the amount of voltage change used to generate the voltage data, an address counter that holds the addresses of the entries, a repetition counter and a voltage value holding unit that respectively hold the number of repetitions and the amount of voltage change read from the entry in accordance with the address held in the address counter, and a data generation unit that generates new voltage data by adding the amount of voltage change held in the voltage value holding unit to voltage data corresponding to the current drive voltage, and wherein when the new voltage data for the number of repetitions is generated by the data generation unit, the head control device updates the address counter and repeats the operation of storing the number of repetitions and the amount of voltage change read from the next entry indicated by the address of the updated address counter in the repetition counter and the voltage value holding unit, respectively, until the number of repetitions and the amount of voltage change are read from the plurality of entries. [Effects of the Invention]

[0009] Waveform information can be read out sequentially from the storage unit without using a large-scale memory access mechanism. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a first embodiment of a liquid ejection device of the present invention. [Figure 2] 2 is a plan view showing an example of the configuration of the liquid ejection unit of FIG. 1. FIG. [Figure 3] FIG. 2 is a plan view showing an example of the conveying drum of FIG. [Figure 4] FIG. 3 is a cross-sectional view showing an example of the structure of the inkjet head of FIG. 2. [Figure 5]3 is a block diagram showing an example of a hardware configuration of the inkjet head of FIG. 2 and a control board connected to the inkjet head. FIG. [Figure 6] 6 is a diagram showing an example of basic waveform data stored in a waveform information storage area of ​​the storage unit in FIG. 5. FIG. [Figure 7] 6 is a flowchart showing an example of a task executed by the CPU of FIG. 5 when the image forming apparatus of FIG. 1 is powered on. [Figure 8] 6 is a waveform diagram showing an example of a voltage waveform of a drive signal applied to an inkjet head based on the basic waveform data stored in the storage unit of FIG. 5. [Figure 9] 6 is a flowchart showing an example of the operation of a CPU that causes the FPGA of FIG. 5 to perform drive control of the inkjet head. [Figure 10] 10 is a flowchart showing an example of inkjet head drive control performed by the FPGA based on a print operation instruction from the CPU in step S21 of FIG. 9. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the embodiments will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

[0012] Here, a liquid ejection device, which is a device that ejects liquid, is a device that includes a liquid ejection head or a liquid ejection unit and ejects liquid by driving the liquid ejection head. Devices that eject liquid include not only devices that can eject liquid onto objects to which the liquid can adhere, but also devices that eject liquid into air or liquid. For example, devices that incorporate a liquid ejection device include an image forming device, a three-dimensional modeling device, a treatment liquid application device, or a spray granulation device. A treatment liquid application device may be incorporated into an electrode manufacturing device.

[0013] The liquid ejection device may 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.

[0014] For example, devices that can be equipped with a liquid ejection device include an image forming device that ejects ink to form an image on paper, and a three-dimensional modeling device (three-dimensional modeling device) that ejects modeling liquid onto a powder layer formed by layering powder in order to create a three-dimensional object (a three-dimensional model).

[0015] Furthermore, the liquid ejection device is not limited to a device that visualizes meaningful images such as letters and figures by ejecting liquid. For example, the liquid ejection device may be a device that forms meaningless patterns or the like, or a device that forms a three-dimensional image.

[0016] 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.

[0017] 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.

[0018] The "liquid" may be any liquid having a viscosity and surface tension that allows it to be ejected from a head. While not particularly limited, the "liquid" preferably has a viscosity of 30 mPa·s or less at room temperature and pressure, or upon heating or cooling. More specifically, the "liquid" may be a solution, suspension, emulsion, or the like containing a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a polymerizable compound, a resin, a surfactant, or the like, a biocompatible material such as DNA, amino acids, proteins, or calcium, or an edible material such as a natural dye. These liquids can be used, for example, in inkjet inks, surface treatment solutions, liquids for forming components of electronic devices or light-emitting elements, liquids for forming electronic circuit resist patterns, and liquid materials for 3D modeling.

[0019] Furthermore, the liquid ejection device may be a device in which the liquid ejection head and an object onto which the liquid can be attached move relatively, but is not limited to this. Specific examples of the liquid ejection device include a serial type device in which the liquid ejection head moves, and a line type device in which the liquid ejection head does not move.

[0020] In addition to the above, other liquid ejection devices include a treatment liquid application device that ejects a treatment liquid onto paper to apply the treatment liquid to the surface of the paper for purposes such as modifying the surface of the paper, and an injection granulation device that sprays a composition liquid in which raw materials are dispersed through a nozzle to granulate fine particles of the raw materials.

[0021] Hereinafter, an embodiment will be described taking as an example a case where the "object onto which liquid can be attached" is a sheet material and the liquid ejection device is mounted on a line-scan inkjet type image forming apparatus.

[0022] (One embodiment of a liquid ejection device) Fig. 1 is a block diagram showing one embodiment of a liquid ejection device of the present invention. The liquid ejection device 1 shown in Fig. 1 is, for example, an image forming device such as an inkjet printer, and has an input section 10, an image forming section 20, a drying section 30, and an output section 40. Hereinafter, the liquid ejection device 1 will also be referred to as the image forming device 1.

[0023] The image forming apparatus 1 applies liquid to sheet material P, which is a sheet-like member, transported from the transport section 10 in the image forming section 20 to form the required image, dries the liquid adhering to the sheet material P in the drying section 30, and then discharges the sheet material P to the transport section 40.

[0024] The carry-in section 10 includes an input tray 11 on which a plurality of sheet materials P are stacked, a feeding device 12 that separates and sends out the sheet materials P one by one from the input tray 11, and a pair of registration rollers 13 that sends the sheet materials P to the image forming section 20.

[0025] A device using rollers or a device using air suction can be used as the feeding device 12. After the leading edge of the sheet material P fed from the input tray 11 by the feeding device 12 reaches the pair of registration rollers 13, the pair of registration rollers 13 is driven at a predetermined timing, whereby the sheet material P is fed to the image forming unit 20.

[0026] The image forming unit 20 includes a conveying drum 21, which is an example of a rotating member that serves as a conveying unit that carries and conveys the sheet material P on its outer surface, and a liquid ejection mechanism 22 that ejects liquid toward the sheet material P carried on the conveying drum 21.

[0027] The image forming section 20 also includes a transfer drum 24 that receives the fed sheet material P and passes it to the conveying drum 21, and a transfer drum 25 that passes the sheet material P conveyed by the conveying drum 21 to the drying section 30.

[0028] The sheet material P conveyed from the carry-in section 10 to the image forming section 20 has its leading edge gripped by a sheet gripper provided on the surface of the transfer drum 24, and is conveyed as the transfer drum 24 rotates. The sheet material P conveyed by the transfer drum 24 is delivered to the conveying drum 21 at a position opposite the conveying drum 21.

[0029] A sheet gripper is also provided on the surface of the transport drum 21, and the leading edge of the sheet material P is gripped by the sheet gripper. A plurality of suction holes are formed and dispersed on the surface of the transport drum 21. An adsorption device 26, which is an adsorption unit, generates a suction airflow that flows inward from the suction holes of the transport drum 21.

[0030] Then, the sheet material P transferred from the transfer drum 24 to the conveying drum 21 has its leading edge grasped by the sheet gripper and is adsorbed onto the conveying drum 21 by the suction airflow of the adsorption device 26, and is conveyed as the conveying drum 21 rotates.

[0031] The liquid ejection mechanism 22 includes a plurality of liquid ejection units 23 (23A to 23F). For example, liquid ejection unit 23A ejects cyan (C) liquid, liquid ejection unit 23B ejects magenta (M) liquid, liquid ejection unit 23C ejects yellow (Y) liquid, and liquid ejection unit 23D ejects black (K) liquid. Liquid ejection units 23E and 23F are used to eject any of YMCK, or special liquids such as white, gold, or silver. Furthermore, the liquid ejection mechanism 22 can also be provided with an ejection unit that ejects a treatment liquid such as a surface coating liquid.

[0032] The ejection operation of each liquid ejection unit 23 is controlled by a drive signal corresponding to print information. When the sheet material P carried on the transport drum 21 passes through an area facing the liquid ejection mechanism 22, liquid of each color is ejected from the liquid ejection unit 23, and an image corresponding to the image data is formed on the sheet material P.

[0033] The drying section 30 has a drying mechanism section 31 for drying the liquid adhering to the sheet material P in the image forming section 20, and a suction conveying mechanism section 32 for conveying the sheet material P conveyed from the image forming section 20 in a suctioned state.

[0034] The sheet material P conveyed from the image forming unit 20 is received by the suction conveying mechanism 32, then conveyed to pass through the drying mechanism 31 and delivered to the discharge unit 40. When passing through the drying mechanism 31, the liquid on the sheet material P is dried. This causes the water content and other liquid components in the liquid to evaporate, the colorant contained in the liquid to be fixed on the sheet material P, and curling of the sheet material P is suppressed.

[0035] The discharge section 40 includes a discharge tray 41 on which a plurality of sheet materials P are stacked. The sheet materials P conveyed from the drying section 30 are sequentially stacked and held on the discharge tray 41. Note that the image forming apparatus 1 may have a pre-processing section disposed upstream of the image forming section 20 to perform pre-processing on the sheet materials P, or may have a post-processing section disposed between the drying section 30 and the discharge section 40 to perform post-processing on the sheet materials P.

[0036] For example, the pre-treatment section may perform a pre-coating process in which a treatment liquid that reacts with the liquid to suppress bleeding is applied to the sheet material P. The post-treatment section may perform a sheet reversing and conveying process in which a sheet printed in the image forming section 20 is reversed and sent to the image forming section 20 in order to print on both sides of the sheet material P, or a process in which multiple sheets are bound.

[0037] Fig. 2 is a plan view showing an example of the configuration of the liquid ejection unit 23 of Fig. 1. The liquid ejection unit 23 is, for example, a full-line type head in which a plurality of inkjet heads 100, each having a nozzle row 100a in which a plurality of nozzles are arranged, are arranged on a base member 52. It should be noted that the configuration of the liquid ejection unit 23 is not limited to that shown in Fig. 2. The inkjet head 100 is an example of an ejection head.

[0038] Fig. 3 is a plan view showing an example of the transport drum 21 of Fig. 1. Note that, for ease of understanding, Fig. 3 shows only one liquid discharge unit 23, and the width of the liquid discharge unit 23 in the transport direction is enlarged.

[0039] An encoder wheel 202 is provided on the rotation shaft 21a of the conveying drum 21, and an encoder sensor 203 that reads the encoder wheel 202 is disposed on the outer periphery of the encoder wheel 202. The encoder wheel 202 and the encoder sensor 203 form a first encoder 201. The first encoder 201 is a rotary encoder that outputs a first signal (output pulse) corresponding to the amount of rotation (amount of rotational drive) of the conveying drum 21.

[0040] An encoder scale 212 is attached to the circumferential surface of the conveying drum 21, and an encoder sensor 213 that reads the encoder scale 212 is disposed in a position facing the encoder scale 212. The encoder scale 212 and the encoder sensor 213 form a second encoder 211. The second encoder 211 is a linear encoder that outputs a second signal (output pulse) corresponding to the amount of movement of the circumferential surface of the conveying drum 21. The second signal includes information that correlates with the amount of movement of the sheet material P on the circumferential surface of the conveying drum 21.

[0041] The encoder sensor 213 included in the second encoder 211 is disposed near each of the plurality of liquid discharging units 23. In the example shown in Fig. 3, it is attached to the base member 52 on which the liquid discharging units 23 are disposed. Therefore, the encoder sensor 213 attached to the base member 52 of each liquid discharging unit 23 and the encoder scale 212 attached to the conveying drum 21 constitute the second encoder 211 for each liquid discharging unit 23.

[0042] Fig. 4 is a cross-sectional view showing an example of the structure of the inkjet head 100 of Fig. 2. Fig. 4 shows an example of the structure of a discharge block 120 in the inkjet head 100, which corresponds to one nozzle in the nozzle row 100a of Fig. 2.

[0043] The ejection block 120 has a pressurized liquid chamber 122 into which ink 121 flows, and a nozzle 123 and a vibration plate 124 provided at positions facing each other across the pressurized liquid chamber 122. The vibration plate 124 is in contact with the wall surface of the pressurized liquid chamber 122. The ejection block 120 also has a piezoelectric element 130 in contact with the vibration plate 124, and an input terminal 132 electrically connected to the piezoelectric element 130.

[0044] The piezoelectric element 130 deforms in response to the voltage of the drive signal received at the input terminal 132, and changes the volume of the pressurized liquid chamber 122 via the vibration plate 124, thereby changing the pressure of the ink 121 in the pressurized liquid chamber 122. When the ink 121 in the pressurized liquid chamber 122 is pressurized, the pressurized ink 121 is ejected as liquid from the nozzle 123. The amount of liquid ejected can be adjusted by the pressure applied to the ink 121 in response to the drive voltage.

[0045] Fig. 5 is a block diagram showing an example of the hardware configuration of the inkjet head 100 of Fig. 2 and the control board 200 connected to the inkjet head 100. That is, Fig. 5 shows an example of the main part of the liquid ejection mechanism 22 of Fig. 1.

[0046] The inkjet head 100 has a heater 102, a thermistor 104, and a piezoelectric element 130. The control board 200 has a CPU 210, a ROM (Read Only Memory) 220, a fan control unit 230, a fan 240, a heater control unit 250, a temperature monitoring unit 260, an FPGA (Field-Programmable Gate Array) 270, a DAC (Digital-to-Analog Converter) 280, and an amplifier unit 290.

[0047] The FPGA 270 has a CPU interface (I / F) 271, a register group 272, a memory unit 273, an address counter 274, a repetition counter 275, a voltage value holding unit 276, and a data generation unit 277. For example, the FPGA 270 operates in synchronization with a free-running clock signal generated using a crystal oscillator or the like (not shown). Note that while Fig. 5 shows one DAC 280, one amplifier unit 290, and one piezoelectric element 130, if the inkjet head 100 has a nozzle array 100a (Fig. 3) in which a plurality of nozzles are arranged, the liquid ejection mechanism 22 may have a plurality of DACs 280, a plurality of amplifier units 290, and a plurality of piezoelectric elements 130.

[0048] In the inkjet head 100, the heater 102 heats the inkjet head 100 based on a control signal from the heater control unit 250 of the control board 200. The thermistor 104 detects the temperature of the inkjet head 100 and notifies the temperature monitoring unit 260 of the control board 200 of temperature information indicating the detected temperature.

[0049] The piezoelectric element 130 is driven based on the voltage of the drive signal DRV received from the control board 200 via the input terminal 132, and ejects an amount of liquid according to the voltage waveform of the drive signal DRV. Note that the voltage waveform of the drive signal DRV (i.e., the amount of liquid ejected from the piezoelectric element 130) differs depending on the image data.

[0050] In the control board 200, the CPU 210 executes a control program to control the operation of the control board 200 and the inkjet head 100. The CPU 210 performs initial settings for the control board 200 when the image forming apparatus 1 in FIG. 1 is turned on, and then receives a print instruction from the upper device 300 and causes the FPGA 270 to perform a print operation.

[0051] The CPU 210 reads basic waveform data for generating a drive waveform from the ROM 220, which stores the basic waveform data in advance, every time the image forming apparatus 1 or the liquid ejection mechanism 22 is powered on or reset (FIG. 5(a)). The CPU 210 writes the read basic waveform data to the storage unit 273 via the CPU interface 271 of the FPGA 270 (FIG. 5(b)). An example of the basic waveform data is shown in FIG. 6.

[0052] The waveform data written to the storage unit 273 is used to generate the voltage waveform of the drive signal DRV to be applied to the piezoelectric element 130 of the inkjet head 100. Hereinafter, data for generating the drive waveform will also be referred to as waveform data. The FPGA 270 can access the storage unit 273 at a higher speed than a RAM (Random Access Memory) (not shown) mounted on the control board 200 or the like.

[0053] The fan control unit 230 controls the operation of the fan 240 based on instructions from the CPU 210. The heater control unit 250 outputs a control signal to the heater 102 of the inkjet head 100 to control the heater 102 based on instructions from the CPU 210. The temperature monitoring unit 260 notifies the CPU 210 of temperature information output from the thermistor 104 of the inkjet head 100.

[0054] When the temperature detected by a thermistor (not shown) mounted on the control board 200 exceeds a preset temperature, the CPU 210 outputs an instruction to the fan control unit 230 to rotate the fan 240. When the temperature information from the temperature monitoring unit 260 is lower than the preset temperature, the CPU 210 outputs an instruction to the heater control unit 250 to turn on the heater 102. When the temperature information from the temperature monitoring unit 260 is higher than the preset temperature, the CPU 210 outputs an instruction to the heater control unit 250 to turn off the heater 102.

[0055] In the FPGA 270, a CPU interface 271 inputs and outputs data and information to and from the CPU 210. A register group 272 has a plurality of registers REG. Each register REG stores data such as various initial values ​​used to control the inkjet head 100.

[0056] The storage unit 273 has a waveform information storage area including multiple entries each holding multiple pieces of waveform information used to generate the voltage waveform (drive waveform) of the drive signal DRV. For example, the storage unit 273 may be an SRAM, a register, or a latch unit including multiple latches. Each entry can be identified by an address. The waveform information held in each entry includes the number of repetitions and the amount of change in voltage value. An example of waveform data is shown in FIG. 6.

[0057] The memory unit 273 mounted on the FPGA 270 can be accessed faster than an external memory unit that can be mounted on the control board 200. If an external RAM is used instead of the memory unit 273, it is necessary to consider whether it can be changed to an alternative if production of the external RAM is discontinued. On the other hand, if the memory unit 273 mounted on the FPGA 270 is used, it is not necessary to consider changing to an alternative.

[0058] An address used when reading waveform information from the storage unit 273 is set in the address counter 274, and the address is updated (for example, incremented) every time waveform information is read from the storage unit 273. If the storage unit 273 is a register or a latch unit, a number identifying multiple entries assigned to the register or multiple entries assigned to the latch unit is used as the address.

[0059] The repetition count counter 275 is set with the repetition count read from the entry of the storage unit 273 indicated by the address output by the address counter 274. For example, the repetition count counter 275 decrements the set repetition count at predetermined cycles (e.g., 10 ns), and increments the address counter 274 when the repetition count reaches "1." This allows the entry from which the repetition count and the amount of change in voltage value are read to be updated to the next entry every time the voltage value holding unit 276 outputs voltage values ​​corresponding to the repetition count to the data generating unit 277. Hereinafter, the predetermined cycle in which the repetition count is decremented will be referred to as the control cycle.

[0060] The voltage value holding unit 276 holds the amount of change in the voltage value read from the entry of the storage unit 273 indicated by the address output by the address counter 274 , and outputs the amount of change in the held voltage value to the data generation unit 277 .

[0061] The data generation unit 277 generates voltage data, which is digital data for generating the drive signal DRV, using digital data obtained by adding the amount of change in the voltage value output from the voltage value holding unit 276 to the current voltage value for each control cycle and data indicating the amount of liquid ejected from each nozzle of the inkjet head 100. The data generation unit 277 outputs the generated voltage data to the DAC 280. For example, the data generation unit 277 has an adder that adds the amount of change in the voltage value output from the voltage value holding unit 276 to the current voltage value.

[0062] The amount of liquid ejected from each nozzle is set by the FPGA 270 based on the pixel value (density) and color information of the image data (data to be printed) transferred from the host device 300. Although not particularly limited, the image data transferred from the host device 300 is stored in a memory (not shown) provided in the FPGA 270. The image data may also be stored in a storage unit 273.

[0063] The data generating unit 277 may recognize the update interval of the number of repetitions held by the repetition counter 275 as the control period. If the amount of change in the voltage value is a positive value, the digital data value increases with each control period. If the amount of change in the voltage value is a negative value, the digital data value decreases with each control period. If the amount of change in the voltage value is 0, the digital data value is maintained before and after the control period.

[0064] The DAC 280 converts the digital voltage data from the FPGA 270 into analog data and outputs it to the amplifier 290. The amplifier 290 amplifies the analog data and generates a drive signal DRV to be applied to the piezoelectric element 130. Although not shown, a driver IC (Integrated Circuit) (not shown) is provided between the amplifier 290 and the piezoelectric element 130, and the drive signal DRV is output to the driver IC. The driver IC then drives the piezoelectric element 130 in accordance with the drive signal DRV.

[0065] Fig. 6 is a diagram showing an example of basic waveform data stored in the waveform information storage area of ​​storage unit 273 in Fig. 5. The basic waveform data includes multiple pieces of waveform information, each of which includes a number of repetitions and an amount of change in voltage value. Storage unit 273 is assigned multiple entries each having an area for storing waveform information including the number of repetitions (6 bits) and the amount of change in voltage value (10 bits).

[0066] Each entry is identified by an address and can be accessed using the address. For the sake of simplicity, in Fig. 6, it is assumed that the storage unit 273 has 11 entries assigned with 11 consecutive addresses 0-10, and stores 11 pieces of waveform information.

[0067] The "3F" (hexadecimal) stored in the field for the number of repetitions of the first entry indicates the start code, the value stored in the field for the amount of change in voltage value of the first entry indicates the first base voltage value, the "3E" (hexadecimal) stored in the field for the number of repetitions of the last entry indicates the end code, and the value stored in the field for the amount of change in voltage value of the last entry indicates the second base voltage value.

[0068] The number of repetitions held in entries other than the first and last indicates how many times the change in voltage value indicated by the amount of change is repeated for the current voltage. The number of repetitions indicates the number of control periods. The number of repetitions can be set from 1 to 62 (10 ns to 620 ns in 10 ns increments). The multiple waveform information held in entries after the start code to just before the end code is basic waveform data. Below, the amount of change in voltage value may be simply referred to as the amount of change.

[0069] When the 11 pieces of waveform information shown in FIG. 6 are stored in the storage unit 273, the FPGA 270 sets the initial voltage value of the drive signal DRV to 20V, then repeats a change amount of 0V six times and a change amount of −5V four times. Next, the FPGA 270 repeats a change amount of 0V two times and a change amount of 3.3V six times. Next, the FPGA 270 repeats a change amount of 0V two times and a change amount of 7.5V two times. Next, the FPGA 270 repeats a change amount of 0V six times and a change amount of −7.5V two times. Next, the FPGA 270 repeats a change amount of 0V four times, and then sets the final voltage value to 20V.

[0070] Fig. 7 is a flow diagram showing an example of a task performed by the CPU 210 of Fig. 5 when the image forming apparatus 1 of Fig. 1 is powered on. The flow shown in Fig. 7 may be performed by the CPU 210 when the liquid ejection mechanism 22 or the control board 200 is powered on (i.e., when starting up or restarting). The operation shown in Fig. 7 is realized by the CPU 210 executing a control program.

[0071] First, in step S11, the CPU 210 reads out basic waveform data for generating the drive signal DRV from the ROM 220. Next, in step S12, the CPU 210 writes the basic waveform data read out from the ROM 220 into the storage unit 273.

[0072] Next, in step S13, the CPU 210 writes various initial setting values ​​required for the operation of the liquid ejection mechanism 22 to a register REG of the register group 272. For example, the initial setting values ​​include a storage address of the image data, information indicating the correspondence between pixels included in the image data and the nozzles of the nozzle array 100a, or identification information for an LED (Light Emitting Diode) to be turned on when an error occurs. For example, although not shown in FIG. 5, the LED is mounted on the control board 200.

[0073] Thereafter, CPU 210 performs steps S14, S15, and S16. In step S14, CPU 210 starts a temperature check using temperature information from thermistor 104 acquired by temperature monitoring unit 260. In step S15, CPU 210 starts control of heater control unit 250 based on the temperature check result. In step S16, CPU 210 starts control of fan 240.

[0074] Then, the CPU 210 completes the initial settings for driving the inkjet head 100. Since the drive control of the inkjet head 100 thereafter is performed by the FPGA 270, the resources of the CPU 210 are not used for drive control of the inkjet head 100. In other words, the CPU 210 can perform overall control of the liquid ejection mechanism 22, such as temperature monitoring, heater control, and fan control, without performing drive control of the inkjet head 100, thereby reducing the load on the CPU 210 related to drive control of the inkjet head 100.

[0075] Fig. 8 is a waveform diagram showing an example of the voltage waveform of the drive signal DRV applied to the inkjet head 100 based on the basic waveform data stored in the storage unit 273 of Fig. 5. The voltage waveform shown in Fig. 8 is generated by the DAC 280 and the amplifier unit 290 based on digital driving data generated by the FPGA 270 using the basic waveform data stored in the storage unit 273. Note that the voltage of the actual drive signal DRV applied to the inkjet head 100 may differ for each nozzle depending on the pixel value (density) and color information, etc., but in Fig. 8, each pixel of the image data is assumed to be monochromatic and have the same density.

[0076] 8 shows the values ​​of address counter 274, repetition counter 275, values ​​held by voltage value holding unit 276, and voltage data values ​​generated by data generating unit 277. The shaded areas show the control periods in which address counter 274 changes and the control periods in which values ​​are written from memory unit 273 to repetition counter 275 and voltage value holding unit 276. Note that the initial value (3F) of repetition counter 275 does not indicate the value set in repetition counter 275, but indicates the start code read from memory unit 273.

[0077] The number of repetitions set in the repetition counter 275 is decremented every control period (10 ns). The address counter 274 is incremented when the number of repetitions held in the repetition counter 275 becomes "0". Note that a new number of repetitions is written to the repetition counter 275 in the control period in which the number of repetitions becomes "0", so the number of repetitions in the table does not include "0".

[0078] The data generation unit 277 adds the amount of change in voltage held by the voltage value holding unit 276 to the current digital data value every control period (10 ns) until the number of repetitions held in the repetition counter 275 becomes "0", and generates voltage data to be output to the DAC 280.

[0079] An example of the operation of the address counter 274, the repetition counter 275, the voltage value holding unit 276, and the data generation unit 277 is described in FIG. 10. Note that in the table, the amount of change in the voltage value may include a decimal point, as shown in the column for the voltage value holding unit 276 when the address counter 274 is "4." Depending on the accuracy of the adder installed in the data generation unit 277, an error may occur in the addition used to generate the voltage data. However, as described in FIG. 6, the second base voltage value is held in the last entry. Therefore, the error can be eliminated in the final voltage data generated by the data generation unit 277.

[0080] The voltage value holding unit 276 holds the amount of change in the voltage value read from the storage unit 273 after the value of the repetition counter 275 is updated until it becomes "0." The data generation unit 277 adds the amount of change held by the voltage value holding unit 276 to the current voltage data during the period in which the repetition counter 275 is decremented, and outputs the result to the DAC 280.

[0081] 9 is a flow diagram showing an example of the operation of the CPU 210 that causes the FPGA 270 in FIG. 5 to perform drive control of the inkjet head 100. The flow shown in FIG. 9 starts when the CPU 210 receives a print instruction from the upper device 300.

[0082] First, in step S21, the CPU 210 instructs the FPGA 270 to start printing based on a print instruction received from the upper device 300. The FPGA 270 starts driving control of the inkjet head 100 based on the instruction from the CPU 210, thereby performing a print operation.

[0083] Next, in step S22, the CPU 210 instructs the FPGA 270 to stop the printing operation, and the operation shown in Fig. 9 is terminated. The FPGA 270 stops drive control of the inkjet head 100 based on the instruction from the CPU 210, and terminates the printing operation. After instructing the FPGA 270 to start the printing operation, the CPU 210 can perform operations other than drive control of the inkjet head 100 while the FPGA 270 is performing the printing operation. In other words, the resources of the CPU 210 are not used for drive control of the inkjet head 100.

[0084] Fig. 10 is a flow diagram showing an example of drive control of the inkjet head 100 performed by the FPGA 270 based on a print operation instruction from the CPU 210 in step S21 of Fig. 9. The flow shown in Fig. 10 shows the print operation of one line of the inkjet head 100.

[0085] 3, one line is printed by the nozzle arrays 100a of the liquid ejection units 23 aligned in a direction perpendicular to the transport direction. The FPGA 270 performs the process of FIG. 10 multiple times based on the instruction to start the print operation from the CPU 210 in step S21 of FIG. 9, thereby performing the print operation for one sheet of paper (multiple lines), for example.

[0086] First, in step S31, the FPGA 270 receives a print operation instruction from the CPU 210 and sets the address (="0") of the first entry in the waveform information storage area of ​​the storage unit 273 in the address counter 274. Next, in step S32, the FPGA 270 reads out waveform information from the entry indicated by the address set in step S31.

[0087] Next, in step S33, the FPGA 270 determines whether to start or end the print operation or generate the drive signal DRV based on the data ("3F", "3E", or other) of bits 15-10 of the waveform information read out in step S32. If bits 15-10 are "3F", the FPGA 270 performs the start process of step S34. If bits 15-10 are "3E", the FPGA 270 performs the end process of step S42. If bits 15-10 are other than "3F" or "3F", the FPGA 270 performs the generation process of the drive signal DRV in step S37.

[0088] In step S34, the FPGA 270 acquires the amount of change in the voltage value held in bits 9-0 of the entry in the memory unit 273 indicated by the address counter 274 as the first base voltage value at the start of the print operation, and stores the acquired first base voltage value in the voltage value holding unit 276. Next, in step S41, the FPGA 270 increments the address counter 274 and returns the process to step S32.

[0089] By storing the start code and the first base voltage value in the first entry of the memory unit 273, voltage data can be generated sequentially in the subsequent drive control of the inkjet head 100 using the first base voltage value and the waveform information of the second and subsequent entries.

[0090] When generating the drive signal DRV, in step S35, the FPGA 270 sets the number of repetitions acquired from the entry of the storage unit 273 indicated by the address counter 274 in the repetition counter 275. In addition, the FPGA 270 sets the amount of change in the voltage value acquired from the entry of the storage unit 273 indicated by the address counter 274 in the voltage value holding unit 276.

[0091] Next, in step S36, the data generation unit 277 calculates the voltage value of the drive signal DRV by adding the current voltage value to the amount of change in voltage acquired in step S35. Note that in the next control cycle after the start code is read, the data generation unit 277 adds the first base voltage value as the current voltage value to the amount of change in voltage acquired in step S35. Next, in step S37, the data generation unit 277 outputs digital data indicating the calculated voltage value of the drive signal DRV to the DAC 280.

[0092] Next, in step S38, the FPGA 270 decrements the repetition counter 275. Next, in step S39, the FPGA 270 determines whether the counter value of the repetition counter 275 is "0". The counter value "0" is an example of an initial value.

[0093] If the counter value of the repetition counter 275 is greater than 0, the FPGA 270 returns to step S36 because the voltage change for the number of repetitions has not been completed. Then, in step S36, the FPGA 270 calculates digital data to be output to the DAC 280 based on the current voltage value and the amount of voltage change held by the voltage value holding unit 276.

[0094] On the other hand, if the counter value of the repetition counter 275 is "0", the voltage change for the number of repetitions has been completed, and the FPGA 270 performs step S40. Then, in step S40, the FPGA 270 increments the address counter 274 to read waveform information from the next entry in the storage unit 273, and in step S32 reads waveform information from the next entry in the waveform information storage area of ​​the storage unit 273.

[0095] In this way, by using the counter value of the repetition counter 275 as a trigger for incrementing the address counter 274 and as a trigger for generating voltage data by the data generation unit 277, it is possible to read waveform information from the memory unit 273 and generate voltage data using a simple mechanism without using a large-scale mechanism such as a CPU or DMAC.

[0096] As a result, as shown in the table at the bottom of FIG. 8, the waveform of the drive signal DRV shown at the top of FIG. 8 is generated by repeating the decrement of the repetition counter 275, the output of digital data from the data generation unit 277, and the increment of the address counter 274.

[0097] On the other hand, if bits 15-10 of the waveform information are "3E" in step S33, the FPGA 270 performs step S41. In step S41, the FPGA 270 acquires the amount of change in the voltage value stored in bits 9-0 of the last entry in the waveform information storage area of ​​the storage unit 273 as the second base voltage value at the end of the printing operation. Next, in step S42, the data generation unit 277 of the FPGA 270 outputs digital data corresponding to the acquired second base voltage value to the DAC 280, and the operation shown in FIG. 10 ends.

[0098] As described above, in this embodiment, the FPGA 270 updates the address counter 274 when the data generator 277 generates voltage data for the number of repetitions, and reads the number of repetitions and the amount of voltage change from the entry indicated by the updated address. The FPGA 270 then repeats the operation of generating voltage data for the new number of repetitions until the number of repetitions and the amount of voltage change have been read from all entries. This makes it possible to sequentially read basic waveform data from the storage unit 273 and sequentially generate voltage data for generating the drive signal DRV without using a large-scale memory access mechanism such as a CPU or DMAC.

[0099] By using the counter value of the repetition counter 275 as a trigger for incrementing the address counter 274 and as a trigger for generating voltage data by the data generation unit 277, it is possible to read waveform information from the memory unit 273 and generate voltage data using a simple mechanism without using a large-scale mechanism such as a CPU or DMAC.

[0100] By storing the start code and the first base voltage value in the first entry of the storage unit 273, voltage data can be generated sequentially using the first base voltage value and waveform information in the second and subsequent entries.

[0101] By storing an end code and the second base voltage value in the last entry of the storage unit 273 and outputting the second base voltage value when the generation of the waveform data is completed, even if the amount of change in the voltage value includes a decimal and an error occurs in the addition used to generate the voltage data, the error can be eliminated in the final voltage data generated by the data generation unit 277. This makes it possible to reduce the circuit size of the adder mounted in the data generation unit 277 and suppress an increase in the circuit size of the FPGA.

[0102] Drive control of the inkjet head 100 is performed by the FPGA 270, not the CPU 210. The CPU 210 only needs to transfer basic waveform data for generating a drive waveform from the ROM 220 to the storage unit 273 when starting up the image forming apparatus 1 or the liquid ejection mechanism 22 (control board 200). This reduces the load on the CPU 210 related to drive control of the inkjet head 100.

[0103] For example, aspects of the present invention are as follows. <1> A liquid ejection device having an ejection head that ejects liquid in response to a drive voltage, and a head control device that generates voltage data for the drive voltage to be applied to the ejection head, The head control device includes: a storage unit having a plurality of entries for storing the number of repetitions and the amount of change in voltage used to generate the voltage data; an address counter that holds the address of the entry; a repetition counter and voltage value storage unit that stores the repetition count and the voltage change amount read from the entry in accordance with the address stored in the address counter; a data generating unit that generates new voltage data by adding the amount of change in the voltage held in the voltage value holding unit to voltage data corresponding to a current drive voltage, the head control device repeats an operation of updating the address counter when the new voltage data for the number of repetitions is generated by the data generation unit, and storing the number of repetitions and the amount of change in voltage read from the entry indicated by the address of the updated address counter in the repetition counter and the voltage value holding unit, respectively, until the number of repetitions and the amount of change in voltage are read from the plurality of entries; A liquid ejection device characterized by: <2> the head control device decrements the repetition counter every time new voltage data is generated, and updates the address counter when the repetition counter returns to an initial value; The data generating unit generates new voltage data every time the repetition counter is decremented until the repetition counter returns to an initial value. Characterized by <1> The liquid ejection device according to claim 1. <3> The first entry of the storage unit stores a start code and a first base voltage value instead of the number of repetitions and the amount of change in the voltage, when the start code and the first base voltage value are read from the storage unit, the data generation unit adds the first base voltage value to the amount of change in the voltage read from the next entry to generate the new voltage data. Characterized by <1> or <2> The liquid ejection device according to claim 1. <4> an end code and a second base voltage value are stored in the last entry of the storage unit instead of the number of repetitions and the amount of change in the voltage; when the end code and the second base voltage value are read from the storage unit, the data generation unit generates voltage data corresponding to the second base voltage value as the new voltage data. Characterized by <1> Or <3> 10. The liquid ejection device according to claim 1, wherein: <5> a control board on which the head control device, a processor that instructs the head control device to operate, and one or more control units that are controlled by the processor are mounted; The processor writes the number of repetitions and the amount of change in voltage to each of the plurality of entries in the storage unit when the control board is started up, and starts control of the control unit after the control board is started up. Characterized by <1> Or <4> 10. The liquid ejection device according to claim 1, wherein: <6> A head control device that generates voltage data for a drive voltage to be applied to an ejection head that ejects liquid in accordance with a drive voltage, a storage unit having a plurality of entries for storing the number of repetitions and the amount of change in voltage used to generate the voltage data; an address counter that holds the address of the entry; a repetition counter and voltage value storage unit that stores the repetition count and the voltage change amount read from the entry in accordance with the address stored in the address counter; a data generating unit that generates new voltage data by adding the amount of change in the voltage held in the voltage value holding unit to voltage data corresponding to a current drive voltage, when the new voltage data for the number of repetitions is generated by the data generation unit, updating the address counter, and storing the number of repetitions and the amount of change in voltage read from the entry indicated by the address of the updated address counter in the repetition counter and the voltage value holding unit, respectively, repeating this operation until the number of repetitions and the amount of change in voltage are read from the plurality of entries; A head control device comprising: <7> A method for controlling a liquid ejection device comprising: an ejection head that ejects liquid in accordance with a drive voltage; and a head control device that generates voltage data for a drive voltage to be applied to the ejection head, wherein the head control device comprises: a storage unit having a plurality of entries that hold the number of repetitions and the amount of change in voltage used to generate the voltage data; an address counter that holds the addresses of the entries; a repetition counter and voltage value holding unit that respectively hold the number of repetitions and the amount of change in voltage read from the entries in accordance with the addresses held in the address counter; and a data generating unit, the data generating unit generates new voltage data by adding the amount of change in the voltage held in the voltage value holding unit to voltage data corresponding to the current drive voltage; The head control device When the new voltage data is generated by the data generating unit for the number of repetitions, the address counter is updated; repeating an operation of storing the number of repetitions and the amount of change in voltage read from the entry indicated by the updated address of the address counter in the repetition counter and the voltage value holding unit, respectively, until the number of repetitions and the amount of change in voltage are read from the plurality of entries; A method for controlling a liquid ejection device, comprising:

[0104] Although the present invention has been described above based on the embodiments, the present invention is not limited to the requirements shown in the above embodiments. These requirements can be changed without departing from the spirit of the present invention, and can be appropriately determined depending on the application form. [Explanation of symbols]

[0105] 1 Liquid ejection device (image forming device) 10 Loading area 20 Image forming unit 21 Transport drum 22 Liquid discharge mechanism 23 (23A to 23F) Liquid discharge unit 30 Drying section 40 Unloading section 100 Inkjet head 100a nozzle row 102 Heating heater 104 Thermistor 130 Piezoelectric element 132 input terminal 200 control board 210 CPU 220 ROM 230 Fan control unit 240 Fan 250 Heater control unit 260 Temperature monitoring section 270 FPGA 271 CPU interface 272 Registers 273 Memory section 274 Address Counter 275 Repeat Counter 276 Voltage value holding unit 277 Data Generation Unit 280 DAC 290 Amplification Unit REG register [Prior art documents] [Patent documents]

[0106] [Patent Document 1] Patent No. 5760771 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-264273

Claims

1. A liquid ejection device having an ejection head that ejects liquid in response to a drive voltage, and a head control device that generates voltage data for the drive voltage to be applied to the ejection head, The head control device includes: a storage unit having a plurality of entries for storing the number of repetitions and the amount of change in voltage used to generate the voltage data; an address counter that holds the address of the entry; a repetition counter and voltage value storage unit that stores the repetition count and the voltage change amount read from the entry in accordance with the address stored in the address counter; a data generating unit that generates new voltage data by adding the amount of change in the voltage held in the voltage value holding unit to voltage data corresponding to a current drive voltage, the head control device repeats an operation of updating the address counter when the new voltage data for the number of repetitions is generated by the data generation unit, and storing the number of repetitions and the amount of change in voltage read from the entry indicated by the address of the updated address counter in the repetition counter and the voltage value holding unit, respectively, until the number of repetitions and the amount of change in voltage are read from the plurality of entries; A liquid ejection device characterized by:

2. the head control device decrements the repetition counter every time new voltage data is generated, and updates the address counter when the repetition counter returns to an initial value; The data generating unit generates new voltage data every time the repetition counter is decremented until the repetition counter returns to an initial value. The liquid ejection device according to claim 1 ,

3. a start code and a first base voltage value are stored in the first entry of the storage unit instead of the number of repetitions and the amount of change in the voltage; when the start code and the first base voltage value are read from the storage unit, the data generation unit adds the first base voltage value to the amount of change in the voltage read from the next entry to generate the new voltage data.

3. The liquid ejection device according to claim 1, wherein:

4. an end code and a second base voltage value are stored in the last entry of the storage unit instead of the number of repetitions and the amount of change in the voltage; the data generating unit generates voltage data corresponding to the second base voltage value as the new voltage data when the end code and the second base voltage value are read from the storage unit.

3. The liquid ejection device according to claim 1, wherein:

5. a control board on which the head control device, a processor that instructs the head control device to operate, and one or more control units that are controlled by the processor are mounted; The processor writes the number of repetitions and the amount of change in voltage to each of the plurality of entries in the storage unit when the control board is started up, and starts control of the control unit after the control board is started up.

3. The liquid ejection device according to claim 1, wherein:

6. A head control device that generates voltage data for a drive voltage to be applied to an ejection head that ejects liquid in accordance with a drive voltage, a storage unit having a plurality of entries for storing the number of repetitions and the amount of change in voltage used to generate the voltage data; an address counter that holds the address of the entry; a repetition counter and voltage value storage unit that stores the repetition count and the voltage change amount read from the entry in accordance with the address stored in the address counter; a data generating unit that generates new voltage data by adding the amount of change in the voltage held in the voltage value holding unit to voltage data corresponding to a current drive voltage, when the new voltage data for the number of repetitions is generated by the data generation unit, updating the address counter, and storing the number of repetitions and the amount of change in voltage read from the entry indicated by the address of the updated address counter in the repetition counter and the voltage value holding unit, respectively, repeating this operation until the number of repetitions and the amount of change in voltage are read from the plurality of entries; A head control device comprising:

7. A method for controlling a liquid ejection device comprising: an ejection head that ejects liquid in accordance with a drive voltage; and a head control device that generates voltage data for a drive voltage to be applied to the ejection head, wherein the head control device comprises: a storage unit having a plurality of entries that hold the number of repetitions and the amount of change in voltage used to generate the voltage data; an address counter that holds the addresses of the entries; a repetition counter and voltage value holding unit that respectively hold the number of repetitions and the amount of change in voltage read from the entries in accordance with the addresses held in the address counter; and a data generating unit, the data generating unit generates new voltage data by adding the amount of change in the voltage held in the voltage value holding unit to voltage data corresponding to the current drive voltage; The head control device When the new voltage data is generated by the data generating unit for the number of repetitions, the address counter is updated; repeating an operation of storing the number of repetitions and the amount of change in voltage read from the entry indicated by the updated address of the address counter in the repetition counter and the voltage value holding unit, respectively, until the number of repetitions and the amount of change in voltage are read from the plurality of entries; A method for controlling a liquid ejection device, comprising:

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