Ink jet recording device and control method of ink jet recording device

Abstract

To uniformly control an injection characteristic of each nozzle of a head.SOLUTION: An ink jet recording device 1 includes: a head having a plurality of nozzles for discharging ink to a recording medium; a drive waveform generation section 52 that generates a drive waveform for driving the nozzles; a reverberation waveform reception section 95 that acquires a reverberation waveform generated in the nozzle to be a measurement object according to the drive waveform; and a head control section 50 that generates a characteristic distribution of the acquired reverberation waveform and performs injection characteristic control processing for performing control so that the injection characteristics of the plurality of nozzles become uniform on the basis of the characteristic distribution.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an inkjet printing apparatus and a method for controlling the inkjet printing apparatus. [Background technology]

[0002] In an inkjet recording device, an inkjet head forms an image by ejecting ink droplets from multiple nozzles. To achieve high image quality, it is important to appropriately control the ejection characteristics, such as the nozzle ejection speed and the volume of ejected droplets. The nozzle ejection characteristics vary depending on the ink temperature near the nozzle. Therefore, the ink ejection characteristics can be maintained stable by maintaining a stable ink temperature. To maintain a constant temperature near the nozzle, the ink temperature is generally adjusted using a temperature sensor and heater installed in the inkjet head. A technique for adjusting the ink temperature inside an inkjet head is disclosed, for example, in Patent Document 1.

[0003] Patent Document 1 describes detecting residual vibrations of a diaphragm. It also describes a temperature detection means for detecting the temperature of the liquid in the cavity of the droplet ejection head based on the vibration pattern of the detected residual vibrations of the diaphragm. It also describes adjusting the temperature of the liquid in the cavity based on the ambient temperature of the droplet ejection head detected by a temperature sensor and the value detected by the temperature detection means. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-306529 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, a conventional technique (Patent Document 1) has been disclosed in which the temperature of the liquid in the cavity is adjusted based on the ambient temperature of the head detected by a temperature sensor and the temperature of the liquid in the cavity detected based on the residual vibration of the diaphragm. However, the ink temperature in the inkjet head varies due to a temperature difference distribution, and the ink temperature in the vicinity of each nozzle is different. The technique described in Patent Document 1 does not take into account the temperature difference distribution of the ink temperature in the inkjet head. However, in order to achieve higher image quality, it is necessary to adjust the ink temperature in the vicinity of each nozzle and uniformly control the ejection characteristics of each nozzle.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to uniformly control the ejection characteristics of each nozzle of a head. [Means for solving the problem]

[0007] In order to solve the above problems, the inkjet recording device of the present invention comprises a head having a plurality of nozzles that eject ink onto a recording medium, a drive waveform generation unit that generates a drive waveform for driving the nozzles, a reverberation waveform receiving unit that acquires a reverberation waveform generated in the nozzle that is the measurement target in accordance with the drive waveform, and a head control unit that generates a characteristic distribution of the acquired reverberation waveform and performs ejection characteristic control processing to control the ejection characteristics of the plurality of nozzles so that they are uniform based on the characteristic distribution. [Effects of the Invention]

[0008] According to the present invention having the above configuration, it is possible to uniformly control the ejection characteristics of each nozzle of the head. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating the overall configuration of an inkjet recording apparatus according to a first embodiment of the present invention. [Figure 2]2 is a block diagram showing an example of the functional configuration of a control system of the inkjet printing apparatus according to the first embodiment of the present invention. FIG. [Figure 3] 1 is a block diagram showing an example of the configuration of a control circuit in an inkjet printing apparatus according to a first embodiment of the present invention. [Figure 4] FIG. 2 is a block diagram showing an example of the configuration of a reverberation waveform measuring circuit in the inkjet recording apparatus according to the first embodiment of the present invention. [Figure 5] FIG. 10 is a diagram showing an example of a reverberation waveform acquired from a nozzle. [Figure 6] FIG. 10 is a diagram illustrating an example of an amplitude distribution of a reverberation waveform. [Figure 7] FIG. 3 is a diagram showing the procedure of an initialization process in the inkjet recording apparatus according to the first embodiment of the present invention. [Figure 8] FIG. 3 is a diagram showing a procedure of control processing during printing in the inkjet recording apparatus according to the first embodiment of the present invention. [Figure 9] 5 is a diagram showing the procedure of an ejection characteristic control process in the inkjet recording apparatus according to the first embodiment of the present invention. FIG. [Figure 10] FIG. 10 is a diagram showing an example of data in a drive voltage correction table in an inkjet printing apparatus according to a second embodiment of the present invention. [Figure 11] 10 is a diagram showing the procedure of ejection characteristic control processing by adjusting the drive voltage in an inkjet recording apparatus according to a second embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functions or configurations are designated by the same reference numerals, and redundant description will be omitted.

[0011] First Embodiment [Configuration of inkjet recording device] First, the configuration of an inkjet recording apparatus 1 according to a first embodiment of the present invention will be described. FIG. 1 is a diagram showing the overall configuration of the inkjet recording apparatus 1 according to this embodiment. As shown in FIG. 1, the inkjet recording apparatus 1 includes a medium supply unit 10, an image forming unit 20, a medium discharge unit 30, and an ink supply unit 40. The inkjet recording apparatus 1 transports a recording medium P stored in the medium supply unit 10 to the image forming unit 20 under the control of a control unit 60, which will be described later. The inkjet recording apparatus 1 also forms (prints) an image on the recording medium P in the image forming unit 20, and discharges the recording medium P with the printed image to the medium discharge unit 30.

[0012] (1) Media supply section The medium supply unit 10 has a supply tray 11 that stores the recording medium P, and a transport unit 12 that transports the recording medium P from the supply tray 11 to the image forming unit 20. Note that the recording medium P may be any of various media that can be curved and held on the outer peripheral surface of the image forming drum 21, which will be described later. Examples of the recording medium P that can be used include printing paper (paper), cellulosic, film, and fabric. Hereinafter, the recording medium P may also be referred to as "paper."

[0013] The supply tray 11 is a plate-like member that can hold multiple recording media P. The supply tray 11 is configured to move up and down depending on the amount of recording media P placed on the supply tray 11. The supply tray 11 holds the topmost recording media P in the vertical movement direction at a position where it can be transported by the transport unit 12.

[0014] The conveying unit 12 has multiple rollers, for example, rollers 121 and 122, and a belt 123. The conveying unit 12 also has a conveying mechanism (not shown) and a supplying unit (not shown). The circular belt 123 is a circular belt stretched by rollers 121 and 122. The conveying mechanism drives the belt 123 to convey the recording medium P on the belt 123. The supplying unit delivers the uppermost recording medium P placed on the supply tray 11 onto the belt 123. The conveying unit 12 delivers the recording medium P delivered onto the belt 123 by the supplying unit in a direction from roller 121 toward roller 122.

[0015] (2) Image forming section The image forming section 20 includes an image forming drum 21, a delivery unit 22, a medium heating section 23, a plurality of head units 24, an irradiation section 25, and a delivery section 26.

[0016] The image forming drum 21 is composed of a cylindrical member and rotates counterclockwise in the drawing by a drive motor (not shown). The image forming drum 21 holds the recording medium P along its cylindrical outer surface and transports the recording medium P as it rotates. A medium heating section 23, multiple head units 24, and an irradiation section 25 are installed on the transport surface of the image forming drum 21. The medium heating section 23, the head unit 24, and the irradiation section 25 perform an image formation process on the recording medium P transported by the image forming drum 21.

[0017] 1, the delivery unit 22 is provided between the transport unit 12 of the medium supply unit 10 and the image forming drum 21. The delivery unit 22 has a claw portion 221 that holds one end of the recording medium P transported by the transport unit 12. The delivery unit 22 also has a cylindrical delivery drum 222 that guides the recording medium P held by the claw portion 221 to the image forming drum 21. The claw portion 221 picks up the recording medium P and guides it along the outer circumferential surface of the delivery drum 222 to deliver the recording medium P to the image forming drum 21.

[0018] The medium heating section 23 has, for example, an electric heating wire or the like, and generates heat in response to the passage of electricity. The medium heating section 23 is provided near the outer peripheral surface of the image forming drum 21, and at a position upstream of the head unit 24 in the transport direction of the recording medium P. The medium heating section 23 heats the recording medium P, which is held by the image forming drum 21 and passes near the medium heating section 23, to a predetermined temperature.

[0019] The head unit 24 has a plurality of inkjet heads (not shown). Each inkjet head has a plurality of nozzles that eject ink onto the recording medium P. The head unit 24 ejects ink droplets from the nozzles onto the recording surface of the recording medium P at appropriate timing, forming an image on the recording surface of the recording medium P. Hereinafter, the inkjet heads will be abbreviated as "heads."

[0020] The irradiation unit 25 irradiates the recording medium P with energy rays to cure the ink. The irradiation unit 25 has, for example, a fluorescent tube such as a low-pressure mercury lamp, and causes the fluorescent tube to emit light to radiate energy rays such as ultraviolet rays. The irradiation unit 25 is provided near the outer circumferential surface of the image forming drum 21, at a position downstream of the head unit 24 in the transport direction of the recording medium P.

[0021] The delivery unit 26 transports the recording medium P irradiated with energy rays by the irradiation unit 25 from the image forming drum 21 to the medium discharge unit 30. The delivery unit 26 has a plurality of rollers, for example, rollers 261 and 262, and a belt 263. The delivery unit 26 also has a transport mechanism (not shown) and a transfer drum 264. The belt 263 is a circular belt stretched by the rollers 261 and 262. The transport mechanism drives the belt 263 to transport the recording medium P on the belt 263. The transfer drum 264 is a cylindrical drum that transfers the recording medium P from the image forming drum 21 to the transport mechanism. The delivery unit 26 transports the recording medium P, which has been transferred to the belt 263 by the transfer drum 264, using the belt 263 to send it to the medium discharge unit 30.

[0022] (3) Media discharge section The medium discharge unit 30 stores the recording medium P sent out from the image forming unit 20 by the delivery unit 26. The medium discharge unit 30 has a plate-shaped discharge tray 31 and the like, on which the recording medium P after image formation is placed.

[0023] (4) Ink supply unit The ink supply unit 40 stores ink of each color used to record an image and supplies the ink to the corresponding head unit 24 of the image forming unit 20. The ink supply unit 40 may be installed in any manner. For example, the ink supply unit 40 may be placed on a dedicated rack or the like and connected to the image forming unit 20 via tubing or other tubing. The ink supplied to each head unit 24 of the image forming unit 20 is ejected from the nozzles of the head.

[0024] Fig. 2 is a block diagram showing an example of the functional configuration of a control system of the inkjet recording apparatus 1 according to this embodiment. In addition to the various components described in Fig. 1, the inkjet recording apparatus 1 also includes a head control unit 50, a control unit 60, and a communication unit 70, as shown in Fig. 2. The components are connected via a bus B so as to be able to send and receive information data to and from each other.

[0025] The head control unit 50 drives each nozzle of each head of the head unit 24 to properly eject ink from the nozzles. The head control unit 50 selects a pre-stored drive waveform pattern for printing based on a control signal from the control unit 60. The head control unit 50 also generates drive signals to drive the nozzles in accordance with the selected drive waveform pattern for printing. The head control unit 50 also switches whether or not to output drive signals to each nozzle, depending on the image data to be printed. Hereinafter, the drive signals will also be referred to as "drive waveforms."

[0026] The head control unit 50 also acquires the waveform of the residual vibration generated after each of the multiple nozzles in the head is driven. Hereinafter, the waveform of the residual vibration will be referred to as the "reverberation waveform." The reverberation waveform is acquired by measuring it using a residual vibration measurement circuit 100 shown in FIG. 4, which will be described later. The head control unit 50 generates a characteristic distribution of the acquired reverberation waveform and performs an ejection characteristic control process based on the characteristic distribution to control the ejection characteristics of the multiple nozzles so that they are uniform. Here, the characteristic distribution is, for example, the amplitude distribution of the reverberation waveform. The ejection characteristics include at least one of the nozzle ejection speed and the ejected droplet volume. The ejection characteristic control process will be described in detail with reference to FIGS. 10 and 11, which will be described later.

[0027] The control unit 60 controls the overall operation of the inkjet recording apparatus 1. The control unit 60 includes a CPU (Central Processing Unit) 61, a RAM (Random Access Memory), a ROM 63 (Read Only Memory), and a memory 64.

[0028] The CPU 61 performs image formation processing, ejection characteristic control processing, and the like in the inkjet recording apparatus 1 in accordance with the programs read from the ROM 63 .

[0029] The RAM 62 is configured by a storage medium such as a volatile memory, and temporarily stores information (data) necessary for each process performed by the CPU 61.

[0030] The ROM 63 is configured as a storage medium such as a nonvolatile memory, and stores programs and data executed and referenced by the CPU 61. The ROM 63 is used as an example of a computer-readable non-transitory storage medium that stores programs executed by the control unit 60. The memory 64 is an image memory that temporarily stores image data to be recorded.

[0031] The communication unit 70 is a communication interface that controls communication operations with external devices. Examples of communication interfaces include a LAN board, LAN card, and the like, which are compatible with various communication protocols. The communication unit 70 acquires image data to be recorded and setting data (print job) related to image recording from the external device under the control of the control unit 60.

[0032] Next, the configuration of the control circuit in the inkjet recording apparatus 1 will be described. Fig. 3 is a block diagram showing an example of the configuration of the control circuit in the inkjet recording apparatus 1 according to this embodiment. As shown in Fig. 3, the control circuit in the inkjet recording apparatus 1 is made up of a head 80 that the head unit 24 has, and a drive substrate 90. Only one head 80 is shown in Fig. 3. In reality, all of the multiple heads 80 that the head unit 24 has are connected to the drive substrate 90 as shown in Fig. 3.

[0033] 3, the head 80 has a plurality of nozzles (nozzles 81_1 to 81_N) and a driving IC (Integrated Circuit) 82. The head 80 also has a heater 83 and a temperature sensor 84. Each nozzle is connected to the driving IC 82. The heater 83, the temperature sensor 84, and the driving IC 82 are each connected to a driving substrate 90.

[0034] The drive IC 82 receives drive waveforms, image data, and waveform switching signals for driving the nozzles from the head control unit 50 installed on the drive board 90. The drive IC 82 also outputs drive waveforms to target nozzles in accordance with the image data and waveform switching signals, thereby driving the target nozzles. The heater 83 receives power from a heater power supply circuit 92 (described later) on the drive board 90, and heats the carriage (not shown) inside the head 80 to a predetermined temperature. This predetermined temperature can be set arbitrarily within the temperature range at which ink can be ejected. The temperature sensor 84 detects the temperature of the carriage and outputs the detected temperature to a temperature sensor receiving unit 93 (described later) on the drive board 90. The temperature sensor 84 is configured, for example, by a thermistor or the like.

[0035] 3, the drive board 90 has a heater control unit 91, a heater power supply circuit 92, and a temperature sensor receiving unit 93. The drive board 90 also has a head control unit 50, a drive circuit 94, and a reverberation waveform receiving unit 95.

[0036] The heater control unit 91 is composed of, for example, a CPU, and controls the operation of the heater power supply circuit 92 and the temperature sensor receiving unit 93. The heater power supply circuit 92 supplies power to the heater 83 in the head 80 under the control of the heater control unit 91. The temperature sensor receiving unit 93 receives the detected temperature from the temperature sensor 84 in the head 80 under the control of the heater control unit 91. The heater control unit 91 adjusts the output power of the heater power supply circuit 92 based on the detected temperature received by the temperature sensor receiving unit 93.

[0037] In this embodiment, the head control unit 50, drive circuit 94, reverberation waveform receiving unit 95, drive IC 82 of the head 80, and multiple nozzles shown in FIG. 3 constitute a residual vibration measuring circuit 100 (see FIG. 4).

[0038] 4 is a block diagram showing an example of the configuration of the residual vibration measuring circuit 100 in the inkjet recording apparatus 1 according to this embodiment. The head control unit 50 is configured with an FPGA (Field Programmable Gate Array) or the like. The head control unit 50 generates and outputs a drive waveform that drives a piezoelectric element (not shown) to properly eject ink from each nozzle of the head 80. As shown in FIG. 4, the head control unit 50 has a data output unit 51, a drive waveform generation unit 52, and a reverberation waveform detection unit 53 that is common to multiple nozzles.

[0039] The data output unit 51 selects pre-registered image data and outputs it to a switch control unit 821 (described later) of the head 80. The data output unit 51 also outputs a waveform switching signal that indicates the output timing of the drive waveform to the switch control unit 821 (described later) of the head 80.

[0040] The drive waveform generation unit 52 selects a pre-registered drive waveform pattern, generates a drive waveform for driving the nozzles, and outputs it to the drive circuit 94 .

[0041] The reverberation waveform detection unit 53 is common to multiple nozzles and receives the reverberation waveform acquired by the reverberation waveform receiving unit 95. The reverberation waveform detection unit 53 also generates a characteristic distribution of the received reverberation waveform and determines whether a nozzle is missing based on the characteristic distribution. In this embodiment, the head control unit 50 excludes nozzles determined to be missing by the reverberation waveform detection unit 53 from the injection characteristic control process. The determination of a missing nozzle based on the characteristic distribution (amplitude distribution) will be explained later with reference to FIG. 6.

[0042] The drive circuit 94 receives the drive waveform generated by the drive waveform generator 52, and applies the drive waveform to each nozzle of the head 80 via a drive IC 82 (described later) to drive each nozzle.

[0043] The reverberation waveform receiving unit 95 is composed of an AD (Analog to Digital) converter, etc. The reverberation waveform receiving unit 95 acquires the reverberation waveform generated in the nozzle and converts it into a digital signal. The reverberation waveform receiving unit 95 also outputs the converted digital signal of the reverberation waveform to the reverberation waveform detection unit 53 of the head control unit 50.

[0044] The head 80 has a plurality of nozzles, for example, nozzle 81_1 to nozzle 81_N. The drive IC 82 has two-channel switches (switches 82_1 to 82_N) in the same number as the nozzles. The output side of each switch is connected to a respective nozzle. The ON-side input terminal of each switch is connected to the output side of a drive circuit 94 on the drive board 90. The OFF-side input terminal of each switch is connected to the input side of a reverberation waveform receiving unit 95 on the drive board 90. When each switch is set to the ON side, the nozzle connected to the switch is driven by the drive waveform. When each switch is set to the OFF side, the reverberation waveform generated in the nozzle connected to the switch is acquired by the reverberation waveform receiving unit 95.

[0045] The switch control unit 821 receives image data and a waveform switching signal from the data output unit 51 of the head control unit 50. The switch control unit 821 is also connected to each switch and controls the ON / OFF operation of each switch according to the image data and waveform switching signal. When a nozzle is driven, the switch connected to the nozzle to be driven is set to ON. When a reverberation waveform is acquired, the switch connected to the nozzle to be acquired is switched from ON to OFF. At this time, the switches connected to nozzles other than the one to be acquired are maintained OFF. The reverberation waveform receiving unit 95 acquires the reverberation waveform generated after the drive waveform of the nozzle to be measured is turned OFF, and outputs it to the reverberation waveform detection unit 53.

[0046] FIG. 5 shows an example of a reverberation waveform acquired from a nozzle. The horizontal axis of FIG. 5 represents time in units of, for example, microseconds (μs). The vertical axis of FIG. 5 represents the amplitude of the reverberation waveform in units of, for example, millivolts (mV). As shown in the figure, the reverberation waveform is composed of a sine wave. Here, the peak-to-peak value of the first wave of the reverberation waveform is the amplitude of the reverberation waveform. The amplitude of the reverberation waveform varies depending on the temperature of the nozzle from which the reverberation waveform was acquired. When the nozzle temperature is high, the amplitude of the reverberation waveform is large. When the nozzle temperature is low, the amplitude of the reverberation waveform is small. In other words, the amplitude distribution of the reverberation waveform of each nozzle has the same distribution as the temperature distribution near each nozzle. Uniformly controlling the amplitude of the reverberation waveform of each nozzle is equivalent to uniformly controlling the temperature near each nozzle. Therefore, uniformly controlling the amplitude of the reverberation waveform of each nozzle can uniformly control the injection characteristics of each nozzle.

[0047] In the head 80, there is a temperature distribution near the nozzles due to the installation position of the heater 83 and the operating conditions of the parts around the nozzles. This temperature distribution causes the temperature of each nozzle to differ. Here, the temperature distribution near the nozzles is assumed to be highest near the nozzle in the center position and lowest near the nozzles at both ends. The amplitude distribution of the reverberation waveform for each nozzle in this case is shown in Figure 6. Figure 6 is a diagram showing an example of the amplitude distribution of a reverberation waveform.

[0048] The horizontal axis of Fig. 6 represents the nozzle number indicating the position of each nozzle on the head 80. The vertical axis of Fig. 6 represents the amplitude of the reverberation waveform, for example, in millivolts (mV). Fig. 6 shows the amplitude distribution (characteristic distribution) of the reverberation waveform when the heating temperature of the heater 83 is set to 60°C, 70°C, and 80°C. As shown in the figure, the higher the heating temperature of the heater 83, the higher the overall level of the amplitude distribution of the reverberation waveform. Furthermore, the amplitude distribution of the reverberation waveform has the same characteristics as the temperature distribution near each nozzle, with the amplitude being highest at the center position and lowest at both end positions.

[0049] In this embodiment, the reverberation waveform detection unit 53 determines whether a nozzle is missing based on the amplitude distribution of the reverberation waveform. For example, the reverberation waveform detection unit 53 determines whether a nozzle is missing based on the amplitude distribution of the reverberation waveform shown in Fig. 6. In this case, as shown in Fig. 6, a nozzle corresponding to a position (nozzle number) where no amplitude exists in the amplitude of the reverberation waveform is determined to be a missing nozzle.

[0050] Note that nozzle ejection characteristics such as ejection speed and ejected droplet volume change with temperature. In other words, if the temperature of each nozzle differs, the ejection characteristics of each nozzle differ, making it impossible to maintain uniformity in the ejection characteristics of each nozzle. Since uniformity in the ejection characteristics of each nozzle affects the quality of the printed image, it is important to maintain uniformity in the ejection characteristics of each nozzle in order to achieve high image quality. In the present invention, ejection characteristic control processing is performed based on the amplitude distribution of the reverberation waveform so that the ejection characteristics of each nozzle are uniform. The control processing in the inkjet recording device 1 is described below using Figures 7 to 11.

[0051] [Initialization procedure for inkjet recording device] First, we will explain the initialization process in the inkjet recording apparatus 1. Figure 7 is a diagram showing the procedure of the initialization process in the inkjet recording apparatus 1 according to this embodiment. The process explained below starts when the inkjet recording apparatus 1 is started.

[0052] First, the control unit 60 of the inkjet recording apparatus 1 starts temperature adjustment of the carriage (S100). The carriage is equipped with a head 80 and a drive substrate 90. In this process, the control unit 60 outputs an instruction to start temperature adjustment to the heater control unit 91 of the drive substrate 90. In accordance with the instruction from the control unit 60, the heater control unit 91 controls the output power of the heater power supply circuit 92 to adjust the temperature inside the head 80.

[0053] Next, the control unit 60 makes each component stand by until the temperature of each part of the carriage reaches the temperature setting value for printing operation (S101). In this process, the control unit 60 outputs a process start instruction to the head control unit 50 when the temperature of each part of the carriage reaches the temperature setting value.

[0054] Next, the head control unit 50 performs ejection characteristic control processing (S300). That is, the head control unit 50 performs the ejection characteristic control processing during initialization processing when the head control unit 50 starts up its own device. After processing S300, the initialization processing ends. The ejection characteristic control processing will be described in detail later with reference to FIG. 9.

[0055] [Procedure for control processing during printing in inkjet recording device] First, we will explain the control process during printing in the inkjet recording apparatus 1. Fig. 8 is a diagram showing the procedure of the control process during printing in the inkjet recording apparatus 1 according to this embodiment. The process described below starts when a print job is executed.

[0056] First, the head control unit 50 selects and sets a pre-stored driving waveform pattern for printing based on a control signal from the control unit 60 (S200).

[0057] Next, the control unit 60 controls the medium supply unit 10 to start paper transport (S201).

[0058] Next, the control unit 60 controls each component unit to execute image forming processing (S202).

[0059] Next, the control unit 60 determines whether printing of the final line of the paper being printed has been completed (S203). That is, the control unit 60 determines whether it is time to enter the inter-page time being printed.

[0060] When the control unit 60 determines that printing of the final line of the paper being printed has not been completed (NO in S203), the control unit 60 returns to S202 and repeatedly executes S202 to S203.

[0061] On the other hand, when the control unit 60 determines that printing of the final line on the paper being printed has been completed (YES in S203), it outputs an instruction to start the ejection characteristics control process to the head control unit 50 (S204).

[0062] Next, the head control unit 50 performs ejection characteristics control processing (S300). That is, the head control unit 50 performs ejection characteristics control processing during the time between pages included in the print job while the print job is being executed. The ejection characteristics control processing will be described in detail later with reference to FIG. 9.

[0063] Next, the control unit 60 determines whether printing of all pages included in the print job has been completed (S205).

[0064] If the control unit 60 determines that printing of all pages has not been completed (NO in S205), the control unit 60 returns to S202 and repeatedly executes S202 to S205.

[0065] On the other hand, if the control unit 60 determines that printing of all pages has been completed (YES in S205), the control process during printing ends.

[0066] In the above description, an example of operation in which the ejection characteristics control process is performed for each page during the time between pages has been described, but the present invention is not limited to this. For example, the ejection characteristics control process may be performed every few pages during the time between pages.

[0067] [Injection characteristic control process procedure] Next, the ejection characteristics control process in the inkjet recording apparatus 1 will be described. In the ejection characteristics control process, the head control unit 50 controls the amplitude distribution of the reverberation waveform of each nozzle so that it falls within a predetermined range. This control uniforms the ejection characteristics of the multiple nozzles in the head 80. In this embodiment, the head control unit 50 selects nozzles whose reverberation waveform amplitude falls outside the predetermined range as target nozzles for the ejection characteristics control process. The head control unit 50 performs at least one of a process of applying a fluctuation waveform and a predetermined image correction process on the target nozzles to uniformize the ejection characteristics of the multiple nozzles. Here, the predetermined range is a range for determining whether the amplitude distribution of the reverberation waveform is uniform. The predetermined range varies depending on the accuracy required for the uniformity of the nozzle ejection characteristics, the model of the head 80 used, the control temperature within the head 80, etc.

[0068] 9 is a diagram showing the procedure of the ejection characteristic control process in the inkjet recording apparatus 1 according to this embodiment. The process described below is called and executed as a subroutine in S300 shown in FIG. 7 and S300 shown in FIG.

[0069] First, the drive waveform generation unit 52 of the head control unit 50 generates and sets a drive waveform for measuring a reverberation waveform (S301). The drive waveform generation unit 52 also outputs the set drive waveform to the drive circuit 94.

[0070] Next, the data output unit 51 outputs the image data for measuring the reverberation waveform to the switch control unit 821 of the driving IC 82 of the head 80 (S302).

[0071] Next, the switch control unit 821 of the driving IC 82 connects the nozzle to be measured to the driving circuit 94 in accordance with the image data, and drives the nozzle (S303).

[0072] Next, the switch control unit 821 of the driving IC 82 switches and connects the nozzle to be measured from the driving circuit 94 to the reverberation waveform receiving unit 95 (S304).

[0073] Next, the reverberation waveform receiving unit 95 of the head control unit 50 acquires the reverberation waveform of the nozzle to be measured (S305). The reverberation waveform receiving unit 95 also outputs the acquired reverberation waveform of the nozzle to be measured to the reverberation waveform detection unit 53.

[0074] Next, the reverberation waveform detection unit 53 of the head control unit 50 measures the amplitude from the reverberation waveform of the nozzle to be measured (S306).

[0075] Next, the reverberation waveform detection unit 53 determines whether or not the measurement of the amplitudes from the reverberation waveforms of all the nozzles to be measured has been completed (S307).

[0076] If the reverberation waveform detection unit 53 determines that the amplitudes of the reverberation waveforms of all the nozzles to be measured have not been measured (NO in S307), the reverberation waveform detection unit 53 returns to S303. In addition, the reverberation waveform detection unit 53 repeatedly executes S303 to S307.

[0077] On the other hand, if the reverberation waveform detection unit 53 determines that it has completed measuring the amplitudes from the reverberation waveforms of all the nozzles to be measured (YES in S307), it performs S308. In the processing of S308, the head control unit 50 generates an amplitude distribution of the measured reverberation waveforms of each nozzle.

[0078] Next, the head control unit 50 determines whether the amplitude distribution of the reverberation waveform is within a predetermined range (S309). For example, the predetermined range is ±5 mV, which is the amplitude fluctuation range of the reverberation waveform corresponding to a nozzle temperature change of about ±1°C. Here, -5 mV is the lower limit of the predetermined range, and +5 mV is the upper limit of the predetermined range. If the amplitude distribution of the reverberation waveform (the amplitude of the reverberation waveform for all nozzles) is within the range of ±5 mV, the amplitude distribution of the reverberation waveform is determined to be uniform. In other words, the ejection characteristics of each nozzle are determined to be uniform.

[0079] If the head control unit 50 determines that the amplitude distribution of the reverberation waveform is outside the predetermined range (NO in S309), it performs S310. In the processing of S310, the head control unit 50 applies a wobbling waveform to the target nozzle if the amplitude of the reverberation waveform of the target nozzle is smaller than the lower limit of the predetermined range. By applying the wobbling waveform, it is possible to control the amplitude of the reverberation waveform of the target nozzle so that it falls within the predetermined range. Here, the wobbling waveform is, for example, a waveform that has the same waveform as the reverberation waveform and a predetermined amplitude. Note that a nozzle whose reverberation waveform amplitude is smaller than the lower limit of the predetermined range is a nozzle whose temperature is lower than the desired temperature. When the wobbling waveform is applied, the temperature of the low-temperature nozzle rises. The head control unit 50 repeatedly applies the wobbling waveform until the amplitude of the reverberation waveform of the target nozzle falls within the predetermined range.

[0080] Furthermore, in the process of S310, if the amplitude of the reverberation waveform of the target nozzle is greater than the upper limit of the predetermined range, the head control unit 50 performs a predetermined image correction process on the target nozzle. Here, the predetermined image correction process includes at least one of a process of thinning the number of ejections from the target nozzle and a process of reducing the size of the droplets ejected from the target nozzle. Note that a nozzle whose reverberation waveform amplitude is greater than the lower limit of the predetermined range is a nozzle whose temperature is higher than the desired temperature. When the nozzle temperature is higher than the desired temperature, the density of the printed image at the position corresponding to the nozzle becomes darker. By performing the predetermined image correction process, the density of the printed image can be corrected to be lighter. Furthermore, by performing the predetermined image correction process, the number of ejections or the amount of droplets ejected from the target nozzle are reduced, thereby lowering the temperature of the target nozzle. The process of applying the oscillation waveform and the image correction process described above increase the temperature of the low-temperature nozzle and decrease the temperature of the high-temperature nozzle. As a result, the ejection characteristics of each nozzle in the head become uniform. After the process of S310, the head control unit 50 returns to S302 and repeatedly executes S302 to S309.

[0081] On the other hand, if the head control unit 50 determines that the amplitude distribution of the reverberation waveform is within the predetermined range (YES in S309), it performs the process of S311. In S311, the head control unit 50 selects and sets a pre-stored driving waveform pattern for printing based on a control signal from the control unit 60. After the process of S311, the ejection characteristic control process ends.

[0082] [effect] As described above, in the inkjet recording apparatus 1 according to this embodiment, the head control unit 50 acquires the reverberation waveform of each nozzle after it is driven. The head control unit 50 generates the amplitude distribution of the reverberation waveform of the nozzle from the acquired reverberation waveform of each nozzle. The head control unit 50 performs ejection characteristics control processing so that the amplitude distribution of the reverberation waveform of the nozzle falls within a predetermined range. By performing the ejection characteristics control processing, the amplitude of the reverberation waveform of each nozzle becomes uniform, and the ejection characteristics of each nozzle also become uniform. Therefore, the inkjet recording apparatus 1 according to this embodiment can uniformly control the ejection characteristics of each nozzle of the head.

[0083] Second Embodiment In the first embodiment, the ejection characteristic control process includes a process for applying a fluctuating waveform and a predetermined image correction process. However, the present invention is not limited to this. The ejection characteristic control process may be a process for adjusting the drive voltage of a target nozzle so that the amplitude of the reverberation waveform of the target nozzle falls within a predetermined range. In the second embodiment, a control process in the inkjet recording apparatus 1 when the ejection characteristic control process is a process for adjusting the drive voltage is described. Note that the configuration of the inkjet recording apparatus 1 according to the second embodiment is the same as the configuration of the inkjet recording apparatus 1 according to the first embodiment (see FIGS. 1 to 4), and therefore a duplicated description will be omitted. Furthermore, the procedures of the initialization control process and the control process during printing in the second embodiment (see FIGS. 7 and 8) are the same as the procedures of each process in the first embodiment, and therefore a duplicated description will be omitted.

[0084] FIG. 10 shows an example of data in the drive voltage correction table T10 in the inkjet recording apparatus 1 according to this embodiment. The drive voltage correction table T10 is used to adjust the drive voltage of the nozzle in the ejection characteristic control process according to this embodiment. The drive voltage correction table T10 defines the correction value of the drive voltage applied to the nozzle corresponding to the amplitude correction value of the reverberation waveform of the nozzle. As shown in FIG. 10, the drive voltage correction table T10 has an amplitude correction value column T11 and a drive voltage correction value column T12. The amplitude correction value column T11 stores a correction value, for example, in mV, for correcting the amplitude of the reverberation waveform of the nozzle within a predetermined range. The drive voltage correction value column T12 stores a drive voltage correction value, for example, in mV, when correcting the amplitude of the reverberation waveform with the amplitude correction value. For example, if the amplitude correction value is "0," i.e., if no correction is performed, the drive voltage correction value is also "0." For example, when the amplitude correction value is "1," that is, when the amplitude of the current reverberation waveform is corrected to be 1 mV higher, the drive voltage correction value is "50 (mV)." Note that the data example of the drive voltage correction table T10 shown in FIG. 10 is arbitrarily created for the convenience of explanation. However, the drive voltage correction table T10 that is actually used must be obtained by prior measurement and registered in the inkjet recording apparatus 1.

[0085] 11 is a diagram showing the procedure of the ejection characteristic control process in the inkjet recording apparatus 1 according to this embodiment. The head control unit 50 corrects the drive voltage applied to the target nozzles based on the drive voltage correction table T10, thereby controlling the amplitude distribution to fall within a predetermined range. The process described below is called and executed as a subroutine in S300 shown in FIG. 7 and S300 shown in FIG. 8. Furthermore, duplicated explanations of the processes (S301 to S308) shown in FIG. 10 that are the same as those in FIG. 7 will be omitted.

[0086] In the process of S401, the head control unit 50 calculates the difference between the amplitude of the reverberation waveform of each nozzle and a predetermined reference value based on the amplitude distribution of the reverberation waveform. Here, the predetermined reference value differs depending on the accuracy required for the uniformity of the nozzle ejection characteristics, the model of the head 80 used, the controlled temperature inside the head 80, etc. The predetermined reference value is registered in advance in the inkjet recording apparatus 1.

[0087] Next, the head control unit 50 calculates an amplitude correction value corresponding to each nozzle for the difference between the amplitude of the reverberation waveform of each nozzle and a predetermined reference value (S402). For example, the head control unit 50 rounds off the difference between the amplitude of the reverberation waveform of each nozzle and the predetermined reference value, and sets the result as the amplitude correction value.

[0088] Next, the head control unit 50 determines the drive voltage correction value for each nozzle based on the amplitude correction value corresponding to each nozzle and the drive voltage correction table T10 (S403).

[0089] Next, the head control unit 50 adjusts the drive voltage for each nozzle based on the drive voltage correction value for each nozzle (S404). Also, in this process, the head control unit 50 instructs the drive circuit 94 on the value of the drive voltage after correction. Thereafter, the head control unit 50 executes the process of S311.

[0090] [effect] As described above, in the inkjet recording apparatus 1 according to this embodiment, the head control unit 50 adjusts the drive voltage applied to each nozzle so that the amplitude of the reverberation waveform of each nozzle becomes a predetermined reference value. Therefore, the inkjet recording apparatus 1 according to this embodiment can also uniformly control the ejection characteristics of each nozzle of the head.

[0091] The present invention is not limited to the above-described embodiments, and various other applications and modifications are possible without departing from the spirit of the present invention as set forth in the claims. In the above-described embodiments, the configuration of an inkjet recording apparatus is described in detail and specifically in order to clearly explain the present invention. However, the present invention is not necessarily limited to having all of the configurations described. In addition, it is possible to replace part of the configuration of the embodiments described here with the configuration of other embodiments. Furthermore, it is also possible to add the configuration of one embodiment to the configuration of another embodiment. Furthermore, it is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations. In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and do not necessarily show all the control lines and information lines in the product. In reality, it can be assumed that almost all components are interconnected.

[0092] In the above embodiments, examples have been described in which the amplitude of the reverberation waveform is acquired for each nozzle to be measured and the amplitude distribution of the reverberation waveform is generated, but the present invention is not limited to this. For example, for each predetermined number of adjacent nozzles, the amplitude of the reverberation waveform may be acquired from one of the adjacent nozzles to generate the amplitude distribution of the reverberation waveform.

[0093] Furthermore, in the above embodiments, examples have been described in which the ejection characteristics control process is performed in the time between pages, but the present invention is not limited to this. For example, the head control unit 50 may perform the ejection characteristics control process on the nozzles corresponding to the non-printing areas of each page included in the print job while the print job is being executed. Here, for example, if there are no image data for two or more consecutive lines (white dots) at a position corresponding to a nozzle, the area is treated as a non-printing area.

[0094] In addition, in each of the above embodiments, an example has been described in which the amplitude of the reverberation waveform of each nozzle is uniformly controlled by performing a process of applying a wobbling waveform, a predetermined image correction process, and a drive voltage adjustment process. However, the present invention is not limited to this. For example, multiple heaters may be installed at different positions within the head 80. In this case, the head control unit 50 may control the heating temperatures of the multiple heaters so that the reverberation waveform amplitude distribution falls within a predetermined range. [Explanation of symbols]

[0095] 1...inkjet recording apparatus, 10...medium supply unit, 20...image forming unit, 30...medium discharge unit, 40...ink supply unit, 50...head control unit, 51...data output unit, 52...driving waveform generation unit, 53...reverberation waveform detection unit, 60...control unit, 80...head, 81_1 to 81_N...nozzles, 82...driving IC, 821...switch control unit, 83...heater, 84...temperature sensor, 90...driving board, 91...heater control unit, 92...heater power supply circuit, 93...temperature sensor receiving unit, 94...driving circuit, 95...reverberation waveform receiving unit, 100...residual vibration measuring circuit,

Claims

1. a head having a plurality of nozzles that eject ink onto a recording medium; a drive waveform generation unit that generates a drive waveform for driving the nozzle; a reverberation waveform receiving unit that acquires a reverberation waveform generated in the nozzle that is the measurement target in response to the drive waveform; a head control unit that generates a characteristic distribution of the acquired reverberation waveform and performs an ejection characteristic control process to control the ejection characteristics of the plurality of nozzles so that they are uniform based on the characteristic distribution. Inkjet recording device.

2. The characteristic distribution is the amplitude distribution of the reverberation waveform. The inkjet recording apparatus according to claim 1 .

3. The ejection characteristics include at least one of an ejection speed of the nozzle and an ejected droplet volume. The inkjet recording apparatus according to claim 2 .

4. The head control unit controls the amplitude distribution to be within a predetermined range in the ejection characteristic control process, thereby controlling the ejection characteristics of the plurality of nozzles to be uniform. The inkjet recording apparatus according to claim 3 .

5. The head control unit determines the nozzles whose amplitude of the reverberation waveform is outside the predetermined range as target nozzles, and controls the target nozzles so that the ejection characteristics of the plurality of nozzles become uniform by performing at least one of a process of applying a fluctuation waveform, a predetermined image correction process, and a drive voltage correction process. The inkjet recording apparatus according to claim 4 .

6. the wobble waveform has the same waveform as the reverberation waveform and a predetermined amplitude; When the amplitude of the reverberation waveform of the target nozzle is smaller than a lower limit value of the predetermined range, the head control unit applies the fluctuation waveform to the target nozzle to control the amplitude of the reverberation waveform of the target nozzle to be within the predetermined range. The inkjet recording apparatus according to claim 5 .

7. When the amplitude of the reverberation waveform of the target nozzle is greater than an upper limit value of the predetermined range, the head control unit performs the predetermined image correction process on the target nozzle.

7. The inkjet recording apparatus according to claim 6.

8. The predetermined image correction process includes at least one of a process of thinning out the number of times the target nozzles eject, and a process of reducing the size of droplets ejected from the target nozzles. The inkjet recording apparatus according to claim 7 .

9. a drive voltage correction table is registered in advance, in which a correction value of a drive voltage to be applied to the nozzle corresponding to an amplitude correction value of the reverberation waveform of the nozzle is defined; The head control unit corrects the drive voltage applied to the target nozzle based on the drive voltage correction table, thereby controlling the amplitude distribution to be within the predetermined range. The inkjet recording apparatus according to claim 5 .

10. When multiple heaters are installed at different positions within the head, The head control unit controls the heating temperatures of the plurality of heaters so that the amplitude distribution falls within the predetermined range. The inkjet recording apparatus according to claim 4 .

11. The head control unit excludes the nozzle determined to be a missing nozzle from the ejection characteristic control process. The inkjet recording apparatus according to claim 4 .

12. The head control unit performs the ejection characteristic control process during initialization processing at the time of starting up the device. The inkjet recording apparatus according to claim 4 .

13. The head control unit performs the ejection characteristic control process during the time between pages included in the print job while the print job is being executed. The inkjet recording apparatus according to claim 4 .

14. The head control unit performs the ejection characteristics control process on the nozzles corresponding to non-printing areas of each page included in the print job during execution of the print job. The inkjet recording apparatus according to claim 4 .

15. 1. A control method for an inkjet recording apparatus equipped with a head having a plurality of nozzles that eject ink onto a recording medium, comprising: generating a drive waveform for driving the nozzle; acquiring a reverberation waveform generated in the nozzle to be measured in response to the drive waveform; generating a characteristic distribution of the acquired reverberation waveforms, and performing an injection characteristic control process to control the injection characteristics of the plurality of nozzles so that they are uniform based on the characteristic distribution. A control method for an inkjet recording apparatus.

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