JP2023172719A - Recording device, and method for determining nozzle discharge state of the same - Google Patents

Abstract

To solve the problem that a drive condition and a discharge inspection determination condition that discharge inspection is optimally performed have a difference for each nozzle, and the discharge inspection is difficult to be highly accurately performed under an optimal condition for each of the nozzles.SOLUTION: A recording device includes a discharge data generation part 1 and a drive data generation part 1 for forming a print image, a drive data generation part 2 for specifying a drive method different from the drive data generation part 1, and a selection part for selecting drive data to be used from the drive data generation part 1 and the drive data generation part 2, wherein the drive data of the drive data generation part 2 includes a parameter for determining a discharge state detection condition, a printer performs discharge for discharge state detection by the drive data of the drive data generation part 2, the drive data generation part 2 generates drive data on a recording memory for adjusting a distance between nozzle rows using a previously held driving condition, and the discharge inspection part determines the discharge state using the data for determining the discharge state detection condition which is previously held on the recording memory for adjusting the distance between the nozzle rows.SELECTED DRAWING: Figure 13

Description

The present invention relates to a printing apparatus and a method for determining the nozzle ejection state thereof, and in particular, for example, to a printing apparatus that records an image by ejecting ink from a print head onto a print medium, and a method for determining the nozzle ejection state thereof.

2. Description of the Related Art Inkjet recording apparatuses that record an image on a recording medium by ejecting ink droplets from a recording head have been known. In a printing apparatus having such a configuration, a technique has been proposed that uses ink droplets ejected from the print head to inspect the ejection state of ink ejection nozzles (hereinafter referred to as nozzles) provided in the print head.

For example, when using a recording head equipped with multiple nozzles and a heater corresponding to each nozzle, the temperature change of each heater is monitored when a pulse is applied to each heater to drive it, and the inflection point of the temperature change is monitored. A technique has been disclosed for determining the ejection state of a nozzle based on the presence or absence of .

However, according to the inventor's study, the method of driving an element to eject ink and determining the ejection state does not allow testing by driving the element under the same driving conditions as the driving condition of the element when recording an image. It was found that sufficient accuracy may not be obtained if

Therefore, Patent Document 1 discloses a print head that includes a plurality of nozzles that eject ink, a plurality of sensors corresponding to each of the plurality of nozzles, and that detects the state of ink ejection from the nozzles, and a , the recording head is driven under a first driving condition, ink is ejected from the recording head to a first area to record an image, and a second driving condition different from the first driving condition is set based on the inspection data. a recording unit that drives the recording head under driving conditions to eject ink to a second area different from the first area; and a timing at which the recording unit drives the recording head under the second driving conditions. A configuration has been proposed that includes: a determination unit that determines the discharge state from each of the plurality of nozzles based on the output from each of the plurality of sensors.

Japanese Patent Application Publication No. 2020-142503

However, according to the inventor's study, sufficient accuracy cannot be obtained if the device is driven under the same driving conditions as those used when recording an image. It is known that the driving conditions vary from nozzle to nozzle.

Patent Document 1 has a recording unit that drives the recording head under a second drive condition different from the first drive condition and discharges ink to a second area different from the first area. It is difficult to individually designate specific drive conditions for specific nozzles whose states are to be determined.

An object of the present invention is to provide a recording device and a method for determining the nozzle ejection state thereof, which can perform an ejection test under the optimal drive conditions for each nozzle even if the drive conditions for optimally performing the ejection test are different for each nozzle. Our goal is to provide the following.

In order to achieve the above object, the present invention provides a recording apparatus that controls a recording head equipped with a sensor for detecting the state of ink discharge from a nozzle, and includes an discharge data generation section 1 for forming a print image. and a drive data generation section 1, a drive data generation section 2 that specifies a different drive method from the drive data generation section 1, and a selection section that selects drive data to be used from the drive data generation section 1 and the drive data generation section 2. , a printing apparatus characterized in that the drive data of the drive data generation section 2 includes a parameter for determining a discharge state detection condition, and the drive data of the drive data generation section 2 performs discharge for discharge state detection; In the method, the drive data generation section 2 generates drive data using drive conditions stored in advance on a recording memory for adjusting the distance between nozzle rows, and the ejection inspection section adjusts the distance between the nozzle rows. The present invention is characterized in that the ejection state is determined using data that is stored in advance in a recording memory for adjustment and that determines the previous ejection state detection conditions.

According to the present invention, since the ejection control for ejection state detection can be performed by referring to individual drive data for each nozzle for ejection detection, the drive conditions for optimally performing ejection inspection are different for each nozzle. Even if the discharge test is performed under optimal driving conditions for each nozzle, it is possible to perform the discharge test.

1 is a schematic diagram of a recording system that is a typical embodiment of the present invention. FIG. 3 is a diagram showing a connection configuration of parallelogram-shaped recording head chips. FIG. 2 is a perspective view showing the configuration of a recording head. 2 is a block diagram of the overall configuration of the recording system of FIG. 1. FIG. 2 is a block diagram of a control unit of the recording system of FIG. 1. FIG. This is an example of a table of ejection pulses for driving the thermal recording head of the present invention. FIG. 2 is a diagram showing a temperature waveform (sensor temperature: T) output from a temperature sensing element and a temperature change signal (dT/dt) of the waveform when a driving pulse is applied to a recording element. FIG. 2 is a diagram showing an area (print area) where an image is actually recorded on a recording medium and an inspection area used to inspect the ejection state of the nozzles of the recording head. FIG. 3 is a diagram showing the configuration of a drive pulse used to drive a heater of a recording head. It is a flowchart which shows inspection processing. FIG. 2 is a block diagram showing a conventional control configuration for printing operations. FIG. 2 is a diagram showing the arrangement of data in a memory for adjusting between nozzle rows during a conventional printing operation. FIG. 2 is a block diagram showing a control configuration for printing operations and inspection operations according to the present invention. 14 is a block diagram showing a detailed configuration of the drive control unit shown in FIG. 13 for controlling the thermal recording head during printing operation and ejection inspection operation. FIG. FIG. 7 is a diagram showing the arrangement of ejection test data, drive data, and test determination data in a memory for adjusting between nozzle rows during an ejection test when controlling a thermal recording head. FIG. 3 is a diagram showing an example of a drive waveform of a piezoelectric element type recording head. 14 is a block diagram showing a detailed configuration of the drive control section and ejection inspection control section shown in FIG. 13 for controlling the piezoelectric element type recording head during printing operation and ejection inspection operation. FIG. FIG. 7 is a diagram showing the arrangement of ejection test data, drive data, and test determination data in a memory for adjusting between nozzle rows during ejection test during piezoelectric head control.

Embodiments of the present invention in a printer using an inkjet full-line recording head will be described below. The printer of this example is a high-speed full-line printer that uses continuous paper or cut paper wound into rolls. For example, it is suitable for the field of printing a large number of sheets in print labs and the like.

<Recording system>
FIG. 1 is a schematic diagram showing the internal configuration of a printer. The inside of the printer includes a paper supply section 101, a print section, and a discharge section 102. The paper supply unit 101 is a unit that stores and supplies continuous sheets wound into rolls and cut paper. The paper is conveyed in the X direction in FIG. The print unit is a unit that forms an image on the sheet being conveyed using recording heads 105, 106, 107, and 108. The print section also includes a plurality of conveyance rollers 103 and 104 that convey sheets. The recording head has a line type recording head in which an array of inkjet nozzles is formed in a range that covers the maximum width of a sheet expected to be used. Note that a plurality of recording heads are arranged in parallel along the transport direction. In this example, there are four recording heads corresponding to four colors: C (cyan), M (magenta), Y (yellow), and K (black). Note that the number of colors and the number of recording heads are not limited to four. In addition, the configuration of the recording head is such that one recording head has a configuration in which multiple chips having multiple nozzle rows perpendicular to the paper conveyance direction are arranged in a staggered manner, or a configuration in which multiple parallelogram chips are arranged in a configuration, allowing for long recording. It doesn't matter if it's the head.

As the inkjet method, a method using a heating element, a method using a piezo element, a method using an electrostatic element, a method using a MEMS element, etc. can be adopted. Ink of each color is supplied from ink tanks (not shown) to recording heads 105, 106, 107, and 108 via ink tubes, respectively. The output unit 102 transports sheets that have been cut by a cutter (not shown) in the case of continuous paper, or conveys sheets as they are in the case of cut paper, and, if necessary, delivers printed sheets in groups to an output tray (not shown). This is a unit that distributes and discharges to different trays. The print control section 110 is a unit that controls each section of the entire printer. The image inspection section 109 is a unit that reads and inspects the content printed by the recording head.

<Detailed configuration of recording head>
As shown in FIG. 3A, connection portions 111 provided at both ends of the recording head 30 are connected to an ink supply mechanism of the recording apparatus. Thereby, ink is supplied from the ink supply mechanism to the recording head 30, and ink that has passed through the recording head 30 is recovered to the ink supply mechanism. In this way, ink can be circulated through the path of the ink supply mechanism and the path of the recording head 30.

As shown in FIG. 3B, the recording head 30 includes a signal input terminal 91 and a power supply terminal 92 that are electrically connected via each element substrate 10, the flexible wiring board 40, and the electric wiring board 90. . The signal input terminal 91 and the power supply terminal 92 are electrically connected to the recording control section 15A of the recording apparatus, and supply drive signals and electric power necessary for ejection to the element substrate 10, respectively. By consolidating the wiring using the electrical circuit in the electrical wiring board 90, the number of signal input terminals 91 and power supply terminals 92 can be reduced compared to the number of element boards 10. This reduces the number of electrical connections that need to be removed when attaching the recording head 30 to the recording unit 120 (FIG. 1) or when replacing the recording head 30.

In this embodiment, an ink circulation type recording head is used, but a conventional ink consumption type recording head without an ink circulation mechanism may also be used.

Now, when arranging a plurality of head chips in a predetermined direction to configure a full-line recording head with a longer recording width while making the nozzle pitch uniform, seams occur between the head chips. In order to effectively use all the nozzles mounted on the head chip, this embodiment employs a head chip having a parallelogram shape like the element substrate 10 in FIG. 2.

<Control unit>
Next, the control unit of the recording system 1 will be explained. FIG. 4 is a block diagram of the overall configuration of the recording system, and FIG. 5 is a block diagram of the control unit 13 of the recording system 1. The control unit 13 is communicably connected to a host device (DFE) HC2, and the host device HC2 is communicably connected to a host device HC1.

The host device HC1 generates or stores document data that is the source of recorded images. The manuscript data here is generated in the form of an electronic file such as a document file or an image file, for example. This document data is transmitted to the host device HC2, and the host device HC2 converts the received document data into a data format that can be used by the control unit 13 (for example, RGB data that expresses an image in RGB). The converted data is transmitted as image data from the host device HC2 to the control unit 13, and the control unit 13 starts a recording operation based on the received image data.

In the case of this embodiment, the control unit 13 is roughly divided into a main controller 13A and an engine controller 13B. The main controller 13A includes a processing section 131, a storage section 132, an operation section 133, an image processing section 134, a communication I/F (interface) 135, a buffer 136, and a communication I/F 137.

The processing unit 131 is a processor such as a CPU, executes a program stored in the storage unit 132, and controls the entire main controller 13A. The storage unit 132 is a storage device such as a RAM, ROM, hard disk, or SSD, and stores programs and data executed by the CPU 131, and also provides a work area for the processing unit 131. The operation unit 133 is, for example, an input device such as a touch panel, a keyboard, or a mouse, and receives instructions from a user.

The image processing unit 134 is, for example, an electronic circuit having an image processing processor. The buffer 136 is, for example, a RAM, a hard disk, or an SSD. Communication I/F 135 communicates with host device HC2, and communication I/F 137 communicates with engine controller 13B. In FIG. 4, broken line arrows illustrate the flow of image data processing. Image data received from the host device HC2 via the communication IF 135 is accumulated in the buffer 136. The image processing unit 134 reads image data from the buffer 136, performs predetermined image processing on the read image data, and stores the image data in the buffer 136 again. The image data after image processing stored in the buffer 136 is transmitted from the communication I/F 137 to the engine controller 13B as recording data used by the print engine.

As shown in FIG. 5, the engine controller 13B includes a control unit 14 and 15A to 15E, and performs acquisition of detection results and drive control of the sensor group and actuator group 16 included in the recording system 1. Each of these control units includes a processor such as a CPU, a storage device such as a RAM or ROM, and an interface with an external device. Note that the division of control units is just an example, and some controls may be executed by multiple subdivided control units, or conversely, multiple control units may be integrated and their control contents may be executed in one place. It may be configured to be performed by one control unit.

The engine control section 14 performs overall control of the engine controller 13B. The recording control unit 15A converts the recording data received from the main controller 13A into a data format suitable for driving the recording head 30, such as raster data. The recording control unit 15A controls ejection of each recording head 30.

The reliability control unit 15C also controls a drive mechanism that moves the recording unit 120 (FIG. 1) between the ejection position and the recovery position.

The conveyance control section 15D controls the paper supply section 101 and the paper discharge section 102. The inspection control section 15E controls the image inspection section 109.

Of the sensor group and actuator group 16, the sensor group includes a sensor that detects the position and speed of a movable part, a sensor that detects temperature, an image sensor, and the like. The actuator group includes motors, electromagnetic solenoids, electromagnetic valves, and the like.

<Method of determining the nozzle ejection state of the thermal recording head>
FIG. 7 shows the temperature waveform (sensor temperature: T) output from the temperature detection element and the temperature change signal (dT/dt) of the waveform when a drive pulse is applied to the recording element of the element substrate 10 of the thermal recording head. FIG.

Although the temperature waveform (sensor temperature: T) is shown in temperature (°C) in Figure 7, in reality, a constant current is supplied to the temperature sensing element, and the voltage (V) between the terminals of the temperature sensing element is detected. be done. Since this detected voltage has temperature dependence, the detected voltage is converted into temperature and is expressed as temperature in FIG. Further, the temperature change signal (dT/dt) is expressed as a time change in detection voltage (mV/sec).

As shown in FIG. 7, when ink is normally ejected when a drive pulse 211 is applied to the recording element (normal ejection), the output waveform of the temperature sensing element becomes a waveform 201. In the process of decreasing the temperature detected by the temperature detection element 306 indicated by the waveform 201, this phenomenon is characterized by the fact that the trail (satellite) of the ink droplet ejected on the interface of the recording element during normal ejection falls and the interface is cooled. A point 209 appears. Then, after the feature point 209, the temperature decreasing rate of the waveform 201 increases rapidly. On the other hand, in the case of a discharge failure, the output waveform of the temperature detection element 306 becomes like the waveform 202, and the characteristic point 209 does not appear like the waveform 201 during normal discharge, and the temperature decrease rate gradually decreases during the temperature decrease process. I will do it.

The bottom of FIG. 7 shows the temperature change signal (dT/dt), and the waveforms 203 and 204 are obtained by processing the output waveforms 201 and 202 of the temperature sensing element into the temperature change signal (dT/dt). shall be. The method of converting the temperature change signal at this time is appropriately selected depending on the system. The temperature change signal (dT/dt) in this embodiment is a waveform output after passing the temperature waveform through a filter circuit (one time differentiation in this configuration) and an inverting amplifier.

Now, in the waveform 203, a peak 210 resulting from the maximum temperature decreasing rate after the characteristic point 209 of the waveform 201 appears. The waveform (dT/dt) 203 is compared with the ejection test threshold voltage (TH) set in advance in a comparator mounted on the element substrate 10, and the waveform (dT/dt) 203 is compared with the ejection test threshold voltage (TH) set in advance in a comparator mounted on the element substrate 10, and is detected in the range (dT/dt≧TH) exceeding the ejection test threshold voltage (TH). A pulse indicating normal ejection appears in the determination signal (CMP) 213.

On the other hand, since the characteristic point 209 does not appear in the waveform 202, the temperature decreasing rate is also low, and the peak appearing in the waveform 204 is lower than the ejection test threshold voltage (TH). The waveform (dT/dt) 202 is also compared with a discharge test threshold voltage (TH) set in advance in a comparator mounted on the element substrate 10. Then, in a section below the ejection test threshold voltage (TH) (dT/dt<TH), no pulse appears in the determination signal 213.

Therefore, by acquiring this determination signal (CMP), it is possible to grasp the ejection state of each nozzle. This determination signal (CMP) becomes the determination result signal TKOUT described above.

<Drive pulse table for thermal recording head>
FIG. 6 shows an example of a table of drive pulses, in which 16 types are used during printing, 15 types are used during preliminary ejection operation, and one type is used during ejection test operation, which is different from the preliminary ejection operation both during printing and during printing. Data of a drive pulse selected from among a plurality of types of drive pulses is transmitted to the printhead, and is restored to a drive pulse within the printhead to drive the printhead. The restored drive pulse is 211 in FIG.

<Discharge detection inspection area>
FIG. 8 is a diagram showing an area (print area) where an image is actually recorded on a recording medium and an inspection area used to inspect the ejection state of the nozzles of the recording head. FIG. 8(a) shows a case where a part of a cut sheet is used as an inspection area, and FIG. 8(b) shows a case where one cut sheet is used as an inspection area. FIG. 8C shows a case where a part of the inspection area is provided in the printing area of the roll paper.

The recording control unit 15A described above sets a print area L1 and an inspection area L2 on the recording medium based on the information on the paper size and image size set by the user. The recording control unit 15A also operates the heater to inspect the ejection state of the nozzles of the recording head 30 using the drive pulse used to drive the heater to record an image in the print area L1 and the inspection area L2. Switch between the drive pulses used for driving. That is, the recording control unit 15A starts the counter operation from the head of the recording medium in the conveying direction of the recording medium during the recording operation, and calculates the number of lines corresponding to the printing areas L1 and L2 based on the information of the printing areas L1 and L2. The drive pulses are switched according to the timing after recording.

<Shape of ejection test pulse of thermal recording head>
FIG. 9 is a diagram showing the configuration of a drive pulse used to drive the heater of a thermal recording head.

In FIG. 9, PLS0 is a drive pulse used when the recording head 30 performs recording on the printing area L1 (recording mode), and PLS1 and PLS2 are drive pulses that the recording head 30 uses to check the nozzle ejection state using the inspection area L2. This is the drive pulse used when performing the test (inspection mode). The recording control unit 15A switches between the recording mode and the inspection mode during the recording operation by switching the drive pulse table (FIG. 6) that is data indicating drive pulses, that is, switches the drive pulses to control each of the recording heads 30. Drives the nozzle heater.

As shown in FIG. 9, as the drive pulse used in the inspection mode, a drive pulse whose ejection speed is slower than the recording speed in the print area is selected. For example, a drive pulse PLS0 having a double-pulse configuration is used for recording in the printing area L1, and a drive pulse PLS1 having a pulse width having a single-pulse configuration is used for recording in the inspection area L2, and the ejection speed is reduced.

When recording a print area, it is advantageous to shorten the time during which the droplets are suspended, as this allows the droplets to adhere to the targeted positions with high precision. Therefore, a driving pulse is applied to increase the kinetic energy of the ink. On the other hand, in the inspection mode, since the principle that the trail of ink droplets falls and the interface of the recording element 309 is cooled is utilized, the kinetic energy of the ink is lowered so that the trail falls to the interface of the recording element 309. Make it easier. The characteristic of the pulse is that by applying a single pulse in PLS1 for a time approximately equal to (t1-t0) + (t3-t2), which is the time applied in PLS0, the speed can be suppressed while maintaining the energy. I can do it. In fact, in order to further reduce the speed, a single pulse that is slightly shorter than (t1-t0)+(t3-t2) may be used.

Further, the drive pulse PLS2 used for recording on the inspection area L2 can also be used. Drive pulse PLS2, like drive pulse PLS1, generates bubbles the moment the current of the single pulse portion (T1) flows into the heater, but it heats up by passing a small pulse of current through the heater with an even more microscopic time difference (t5-t4). By doing so, inspection accuracy can be improved.

Furthermore, in practice, response speed is an issue, but for example, the drive voltage applied to the heater may be changed, or, for example, if heater heat retention control is being performed, the heater heat retention temperature may be lowered to the lower side. You may change it to

As described above, in this embodiment, after recording an image in the printing area L1, the operation mode of the recording head is switched to the inspection mode, and the ink ejection operation is executed in the inspection area L2 using a drive pulse exclusively for inspection. The discharge state of each nozzle can be inspected. Note that the drive pulse is one of the drive conditions for driving the recording head 30, but the drive conditions also include drive voltage, head adjustment temperature, and the like.

<Conventional recording head drive control unit configuration>
FIG. 11 is a block diagram showing a conventional printing operation, inspection operation, and control configuration. Here, with reference to FIG. 11, the flow of control of printing operations and inspection operations will be described.

The input image data is converted from RGB data to ink color data by an ink color conversion unit 501 that is a part of the image processing unit 134. The data converted into ink colors is quantized into recording data by a quantization unit 502, which is also a part of the image processing unit 134. The quantized print data is assigned to each nozzle by the ejection data generation unit 503 of the print control unit 15A. Ink is ejected from the recording head 30 according to nozzle data assigned to each nozzle.

Since the nozzles in the head are arranged two-dimensionally shifted from each other, the landing of the original nozzle data on the paper surface is adjusted by shifting the timing of transmitting the nozzle data to the head.

In order to shift the timing of transmitting nozzle data to the print head, it is necessary to hold the nozzle data in a memory capacity that is equal to or greater than the distance between the most upstream nozzle and the most downstream nozzle of paper transport. For this purpose, a memory 504 for adjusting between nozzle rows is provided.

The nozzle row distance adjustment section 505 shifts the nozzle data once held in the nozzle row adjustment memory 504 in accordance with the actual nozzle arrangement, and transmits it to the drive control section 507 and the ejection detection control section 508.

The drive timing control unit 506 controls the actual timing and cycle of ejection, and generates drive timing using encoder synchronized signals that are synchronized with paper conveyance, so that recording can be performed in response to changes in conveyance speed. Control is performed to follow the drive cycle of the head.

The drive control unit 507 receives nozzle data in which the distance between nozzle rows has been adjusted, adds drive data, and transmits the data to the print head 509 . At this time, in the thermal recording head, an appropriate one is selected from several originally prepared drive pulses based on, for example, the number of nozzles ejecting at the same time in distributed drive and the temperature.

The ejection inspection control unit 508 operates only during inspection operations, receives nozzle data in which the distance between nozzle rows has been adjusted, determines the nozzles to be inspected, driving conditions for inspection, and inspection conditions, and transmits the determined nozzles to the print head 509. .

<How to use conventional memory for adjusting between nozzle rows>
FIG. 12 shows an example of data arrangement inside the memory 504 for adjusting between nozzle rows. The nozzle arrangement 1202 of the print head is composed of rows A to D, and for ease of explanation, each row is composed of eight nozzles. Nozzles 0 in rows A to D are arranged offset in the Y direction. FIG. 12 shows an example in which the pitch between the nozzles in row A is 300 dpi in the Y direction, and rows A and B are arranged with a deviation of 1200 dpi in the Y direction. By using all rows A to D, a pseudo nozzle row with a pitch of 1200 dpi is formed in the Y direction. Furthermore, the rows A to D are physically shifted in the X direction, and the nozzles 0 to 7 of the rows A to D are arranged two-dimensionally apart from each other. This is to ensure an area for configuring elements, ink flow paths, circuits for ejecting ink, etc. to configure a mechanism for ejecting ink from the nozzle.

The ejection data generation unit 503 writes data into the ejection data storage area 1201 every time data is generated. For example, the next line written to line I is written to line I+1. The data written at this time is data for one column (data for 32 nozzles) when columns A to D are regarded as 1200 dpi in the Y direction. The ejection data storage area 1201 is configured as a part of the memory area of the memory 504 for adjustment between nozzle rows, and stores data within the memory area of a size determined in advance between the ejection data generation section 503 and the inter-nozzle row distance adjustment section 505. Possible configurations include a ring structure that can be used repeatedly.

The nozzle inter-row distance adjustment unit 505 starts the read operation when ejection data corresponding to at least the inter-row distances of rows A to D has been accumulated. As shown, the nozzle arrangement in row A has an inclination: nozzle 0 is J+25, nozzle 1 is J+24, nozzle 2 is J+23, nozzle 3 is J+22, nozzle 4 is J+21, nozzle 5 is J+20, nozzle 6 is J+19, Nozzle 7 needs to read data from another column, such as J+18.

Furthermore, since the nozzles are arranged at a certain distance between columns A to D, as shown in the figure, column A nozzle 7 is in row J+18, column B nozzle 7 is in row J+12, column C is in row J+6, and column D is in row J+18. Ejection data at a distant location on the memory, such as row J, is read out and handed over to subsequent processing.

Therefore, the nozzle row distance adjustment memory 504 needs to have a memory capacity greater than the physical distance between row A nozzle 0 to row D nozzle 7. Although this case does not limit the type of memory, in order to secure a certain amount of memory capacity, SRAM, DRAM, etc. that are connected to the outside of the ASIC/FPGA can be considered.

Further, during the printing operation, writing by the ejection data generation unit 503 and reading by the nozzle array distance adjustment unit 505 occur simultaneously in the memory for adjusting the distance between nozzle rows. The amount of data that can be accessed per unit time to memory is determined by the memory's operating frequency and data bus width, and in order to improve memory access performance, it is necessary to increase the memory's operating frequency and data bus width. Since these are factors that increase costs, it is common to adopt a bus width and operating frequency configuration that satisfies the minimum required memory performance based on the amount of memory access per unit time during printing operations. In other words, during printing operation, drive pulse data that determines drive conditions, judgment criteria parameters for ejection inspection, etc., other than ejection data, are once written into the memory for adjusting the distance between nozzle rows, and then read out and operated from the memory. Difficult in terms of access performance. Therefore, in the conventional example, SRAM and registers inside the ASIC/FPGA are prepared separately from the memory for adjusting the distance between nozzle rows, and a configuration is adopted in which the drive pulse data that determines the drive conditions and the criteria parameters for ejection inspection are held. Ta. However, since the SRAM and registers inside the ASIC/FPGA have a smaller capacity than the external memory, a configuration has been adopted in which only representative values are selected and held in a limited manner. For example, FIG. 6 shows an example of a table of ejection pulses, in which 16 types are used during printing, 15 types are used during preliminary ejection operation, and one type is used during ejection test operation, which is different from the preliminary ejection operation both during printing and during printing.

<Configuration of the recording head drive control section of this embodiment>
FIG. 13 is a block diagram showing the printing operation, inspection operation, and control configuration of a printing apparatus using the thermal recording head of the present invention. Here, with reference to FIG. 13(a), the flow of control of the printing operation and inspection operation will be described.

Regarding the ink color conversion unit 601, quantization unit 602, ejection data generation unit 603, nozzle array adjustment memory 604, and nozzle array distance adjustment unit 605, the ink color conversion unit 501, quantization unit 502, and ejection in FIG. The data generation unit 503, inter-nozzle array adjustment memory 504, and inter-nozzle array distance adjustment unit 505 operate in the same manner, and will therefore be omitted.

A switching control unit 611 controls switching between printing operation and inspection operation. When the printing operation is selected, the ejection data processed by the ink color conversion unit 601, quantization unit 602, and ejection data generation unit 603 and held in the inter-nozzle array distance adjustment unit 605 is adjusted to the nozzle array distance. The adjustment unit 605 reads out the data, and the data selection unit 612 selects and transmits the selected data to the drive control unit 607. At this time, since the printing operation is selected, the ejection inspection control section does not operate.

When selecting a discharge test operation, the test data generation unit 613 reads the test discharge data, test drive data, and test determination data stored in the nozzle array distance adjustment memory 604, and the data selection unit 612 generates the test data. The data output from the section 613 is selected and transmitted to the drive control section 607 and the discharge inspection control section 608. A drive control unit 607 controls the drive of the recording head using a drive method for ejection testing. The ejection test control unit 608 performs ejection test control using the data output from the test data generation unit 613, and receives determination result data transmitted from the print head 609.

The drive timing control unit 606 generates drive timing using an encoder synchronized signal that is synchronized with the conveyance of paper, thereby controlling the drive cycle of the recording head to follow changes in the conveyance speed.

<Thermal recording head drive control unit of this embodiment>
FIGS. 14A and 14B show the drive control structure of the drive control unit 607, particularly for controlling the thermal recording head. FIG. 14(a) shows the configuration of a drive control unit during printing operation for thermal recording head control, including a nozzle number counting unit 701 that counts the number of nozzles driven at one time based on ejection data, and It is composed of a drive pulse table 702 that stores a plurality of drive pulses corresponding to values, and a drive pulse generation unit 703 that generates drive pulses. As is well known, it is known that the thermal recording head drives the nozzle rows in a distributed manner over multiple times, and among the ejection data received from the inter-nozzle row distance adjustment section, the drive The number of nozzles is counted, and control is performed to transmit a drive pulse that matches that value. The signal output from the drive control unit 607 includes BLE representing a drive group unit for driving in a distributed manner, DATA representing nozzle data to be driven, HE representing a drive pulse, and the like. These signals are sent to the recording head 609 via a serial interface in synchronization with CLK, and stored in a flip-flop inside the recording head 609 by the LT signal. The CLK signal and the LT signal are output at the timing generated by the drive timing control section 606.

FIG. 14(b) shows the detailed configuration of the drive control unit 607 and the ejection detection control unit 608 during the ejection test operation for controlling the thermal recording head. The drive pulse generation section 801 receives the test ejection data and test drive data read by the data generation section 613, and the ejection test control section 608 receives the test ejection data and test parameters. The ejection detection control unit selects the number SELDATA of the nozzle to be tested for ejection, Dth (a parameter that determines the ejection test threshold voltage (TH) shown in FIG. ), are transmitted in synchronization with the drive timing signal, and after a certain period of time, the ejection normality/abnormality determination result signal Tkout returned from the recording head is received.

<How to use the memory for adjusting between nozzle rows of the thermal recording head of this embodiment>
FIG. 15 shows an example of memory arrangement during adjustment between nozzle rows. In FIG. 15A, test ejection data 1502, test drive data 1503 (BLE, HE), and test determination data 1504 (Dth) written in advance are written for K columns. The number of columns K may be set to a sufficiently large value depending on the length of the discharge test pattern. For example, if a part of a cut sheet is used as an inspection area, 1,000 columns may be held, and if one A3 size cut sheet is used as an inspection area, 10,000 columns may be held. Inspection drive data and inspection determination data can be set individually for each column.

The test data generation unit reads test ejection data 1502, test drive data 1503, and test determination data 1504, and performs test drive for columns A to D. The arrows in FIG. 15 represent the correspondence between the test ejection data, test drive data, and test determination data in the first column for the nozzles 7 in row A. In a thermal recording head, a plurality of nozzles in a column are driven in a distributed manner in a time-division manner, so FIG. 15 shows a case where one column is driven eight times.

As shown in FIG. 15, test drive data and test determination data corresponding to each nozzle of the test ejection data can be individually specified, so that the optimum test drive can be performed for each nozzle. The test determination data refers to, for example, the test result determination condition Dth for each nozzle (a parameter that determines the ejection test threshold voltage (TH) shown in FIG. 7).

If the conditions for determining whether discharge is normal or abnormal (discharge test threshold voltage (TH) shown in FIG. Accuracy can be improved. Test discharge data, test drive data, and test judgment data for K columns are stored in advance in a specific area in the memory for adjustment between nozzle rows, and recalled each time a discharge test operation is performed. It can be used repeatedly for each inspection operation.

<Piezoelectric element type recording head operation principle>
Next, the configuration of a printing apparatus using the piezoelectric element type recording head of the present invention will be described.

A piezoelectric element type recording head has an ejection port for ejecting liquid, a pressure chamber communicating with the ejection port, a liquid supply path for supplying liquid to the pressure chamber, and an energy generation device provided for each ejection port. It has an element. Some energy generating elements use a piezoelectric material such as PZT (lead zirconate titanate), and supply and discharge liquid by changing the volume of a pressure chamber. When the volume of the pressure chamber contracts, the liquid in the pressure chamber is discharged as droplets from the discharge port, and when the volume of the pressure chamber expands, the liquid is supplied from the liquid supply path to the pressure chamber.

In such a recording head, the volume and speed of the ejected liquid change depending on the drive waveform of the drive power applied to the piezoelectric element. FIG. 16 shows an example of a drive waveform of a piezoelectric element type recording head. FIG. 16A shows drive waveforms corresponding to large, medium, and small droplets to be ejected depending on the voltage amplitude and pulse width. Further, FIG. 16(b) shows an example of a drive waveform for selectively ejecting large, medium, and small droplets by time-sharing within the ejection cycle and using a combination of a plurality of waveforms. A recording head using a piezoelectric element makes it possible to print high-definition images while changing the size of droplets using drive waveforms as shown in FIGS. 16(a) and 16(b). Furthermore, as shown in FIG. 16(c), an inspection vibration waveform for checking the ejection state of the recording head and a minute vibration waveform for preventing impressions of the head nozzle surface are also used as appropriate.

In addition, particularly in piezoelectric recording heads, it is possible to check whether the ejection state of the nozzle is normal by applying a vibration waveform for testing as shown in FIG. 16(c) to the nozzle and observing the state of residual vibration from the nozzle. Sometimes a method is used to determine whether During the printing operation, the recording head is driven using a drive waveform that selectively ejects large, medium, and small droplets as shown in FIGS. 16(a) and (b), and during the ejection test, the test as shown in FIG. 16(c) is performed. It is known to perform inspections using vibration waveforms.

<Piezoelectric element type recording head drive control unit of this embodiment>
FIG. 17A shows the configuration of a print head using piezoelectric elements in the drive control section 607 and inspection control section 608 of the present invention. The printing waveform pattern holding unit 905 holds several patterns of drive waveforms corresponding to large, medium and small droplets as shown in FIGS. 16(a) and 16(b). During a printing operation, the waveform pattern selection section reads a predetermined waveform pattern from the printing waveform pattern holding section 905 and transmits it as a digital value to the drive waveform generation section 0 of 902-1 and the drive waveform generation section 1 of 902-2. . Drive waveform generators 0 and 1 output high voltage drive waveforms com based on the input digital values. The inside of the drive waveform generation unit 902 has a configuration as shown in FIG. 17(b), for example, and includes a DA conversion unit that converts a digital value to an analog value, an amplifier that amplifies the analog value, and a gate driver that drives the piezoelectric element. and FET.

The waveform selection unit 904 has a function of switching which drive waveform among a plurality of drive waveforms (com0/com1 in FIG. 17(a)) is assigned to each of the N piezoelectric elements. The drive waveforms Vout0 to VoutN-1 are output to each of the N piezoelectric elements. Selection data Data for selecting which drive waveform to output to the piezoelectric element is input via a serial interface in synchronization with Clk for each unit of the Lat signal that determines the drive cycle.

<How to use the memory for adjusting between nozzle rows of the piezoelectric recording head of this embodiment>
FIG. 18 shows test ejection data 1802, test drive data 1803 (test waveform pattern), and test determination data 1804 stored in the inter-column distance adjustment memory during the ejection test of a recording head using a piezoelectric element. . A recording head using a piezoelectric element does not perform distributed driving like a thermal recording head, but has a configuration in which the inspection discharge data, inspection drive data, and inspection parameters for all nozzles in one row of row A are held together. There is. Correspondences among test ejection data, test drive data, and test determination data for all nozzles in row A surrounded by dotted lines in FIG. 18 are indicated by arrows.

At the time of ejection inspection, the test vibration waveform is selected only for the nozzle to be inspected using the drive waveform output selection data Data, and other nozzles are not allowed to eject, or a minute vibration waveform is selected to prevent the nozzles from drying out. Enter. Only the residual vibration of the nozzle into which the test vibration waveform has been input is output from the test Vout, inputted to the detection circuit 905, where it undergoes predetermined signal processing, and then the judgment circuit 906 determines whether the ejection state is normal or not according to predetermined judgment conditions. An abnormality is determined. The signal processing at this time may be, for example, processing to amplify the signal or reduce noise. A simple example of the condition for determining whether the discharge state is normal or abnormal is the period of residual vibration of the nozzle to which the test vibration waveform is input. Even if the conditions for determining whether the discharge status is normal or abnormal differ for each nozzle, in this case, the inspection judgment data is read out individually for each nozzle along with the inspection discharge data and inspection drive data (inspection waveform pattern). Since it is used for inspection operations, it is possible to accurately determine whether the discharge state is normal or abnormal.

<Effects of this example>
In this way, the recording head of the present printing apparatus can have the configuration shown in FIG. 13 regardless of whether it is a thermal type or a piezoelectric element type. In the configuration shown in FIG. 13, during the printing operation, only the nozzle data is written to and read from the memory for adjusting the distance between nozzle rows, and during the ejection inspection operation, the inspection data stored in advance in the memory for adjusting the distance between the nozzle rows is Only read operations for ejection data, inspection drive data, and inspection judgment data are performed. Even if the amount of inspection drive data and inspection parameters read out in addition to ejection data increases, writing is not performed at the same time as reading, and only read operations are performed with performance equal to or lower than memory access performance during printing operations. , it becomes possible to perform inspection by specifying inspection drive data and inspection parameters in detail for each nozzle without increasing the specifications of the memory for adjusting the distance between nozzle rows.

<Flowchart of nozzle discharge state inspection process>
Finally, the nozzle discharge state inspection processing described above will be explained with reference to a flowchart. FIG. 10 is a flowchart showing a nozzle discharge state inspection process.

This inspection process is executed during a printing operation in which images are successively formed on a plurality of sheets of cut paper or a plurality of images are continuously formed on a long roll paper.

Before starting printing, in step S00, test ejection data, test drive data, and test parameters are held in a memory for adjusting between nozzle rows.

Thereafter, in step S10, ink is ejected from the recording head 30 onto the printing area of the recording medium to perform image recording. At this time, the recording control unit 15A counts the number of lines recorded from the beginning of the recording medium P during conveyance of the recording medium. Taking FIG. 8(a) as an example, in the next step S20, it is checked whether the counted number has reached the number of lines corresponding to the printing area L1. Here, if the counted number is less than the number of lines corresponding to the print area L1, the process returns to step S10 and continues image recording. On the other hand, if it is determined that the count number has reached the number of lines corresponding to the print area L1, the process proceeds to step S30.

In step S30, the nozzle array of the head substrate intersects with the conveyance direction of the recording medium, and the ejection operation from all nozzles is completed considering that the ejection timing from each nozzle is different in the conveyance direction. to switch the recording head operation mode. That is, the operation mode of the recording head 30 is switched from the recording mode to the inspection mode. Furthermore, in step S40, a drive pulse to be used in the inspection mode is selected.

In the case of a thermal recording head, the drive pulse PLS1 or the drive pulse PLS2 shown in FIG. 9 is selected as the drive pulse. Typically, the shape is the drive pulse PLS1 or the drive pulse PLS2, but since the drive pulse data can be stored individually for each nozzle in the memory for adjusting the distance between nozzle rows, the drive pulse data for each nozzle can be It is possible to inspect while optimally changing the width and shape.

In the case of a piezoelectric element recording head, a test vibration waveform as shown in FIG. 16(c) is selected as the drive pulse. The inspection vibration waveform pattern can be stored individually for each nozzle in the memory for adjusting the distance between nozzle rows, so it is possible to inspect while optimally changing the width, voltage, and shape of the drive pulse for each nozzle. It is.

Next, in step S50, the recording head 30 is driven using the selected drive pulse to selectively drive the nozzles based on the test ejection data. Then, in step S60, in the case of a thermal recording head, the temperature change of each nozzle is monitored, and the ejection state of each nozzle is determined from the temperature change. Even if the criterion for this judgment changes for each nozzle, with this configuration, the inspection judgment data can be stored individually for each nozzle in the memory for adjusting the distance between nozzle rows, so the criterion for judging the ejection state can be changed for each nozzle. Inspections can be performed while changing the

In the case of a piezoelectric element type recording head, the residual vibration waveform of the nozzle driven is obtained for inspection, and the ejection state of each nozzle is determined from the shape of the waveform. For example, the criterion for determining the discharge state may be based on the period of the residual vibration waveform, but if the periodic characteristics of the residual vibration waveform differ from nozzle to nozzle, the criterion for determining the discharge state may be changed for each nozzle. Inspections can be performed while Note that since the method of determining the discharge state itself is well known, the explanation thereof will be omitted. Furthermore, in step S70, the determination result is stored in a storage unit (not shown).

In step S80, it is determined whether or not to continue recording. If it is determined that recording has ended, the process ends, but if it is determined to continue recording, the process proceeds to step S90. In step S90, the operation mode of the recording head 30 is switched from the inspection mode to the recording mode again. Furthermore, in step S100, a drive pulse to be used in the recording mode is selected. As a result, the drive pulse for image recording is selected again as the drive pulse. After that, the process returns to step S10 to continue recording the image.

Note that if the inspected nozzle is determined to be a defective nozzle as a result of the inspection process explained above, and if there is a good nozzle near the defective nozzle, it is recommended to eject ink from the neighboring nozzle and perform complementary recording. . However, if the number of nozzles determined to be defective is too large and it is difficult to continue high-quality recording, the operation of the recording device is stopped and a message is sent to the user prompting the user to replace the recording head or perform maintenance. indicate.

Therefore, according to the embodiment described above, it is possible to inspect the nozzle ejection state of the print head while continuing image printing. In particular, in this inspection, drive conditions such as drive pulses exclusively for inspection are used for each nozzle, and inspection criteria can also be set individually for each nozzle, allowing for highly accurate inspection. It is possible.

<Other configuration>
In the embodiment described above, the recording unit 130 (FIG. 1) has a plurality of recording heads 30, but it may have one recording head 30. The recording head 30 does not need to be a full-line head, and may be a serial type in which an ink image is formed while scanning the recording head 30 in the Y direction.

The recording medium conveyance mechanism is configured to convey a recording medium that has been cut into a predetermined paper size as a recording medium, but a roll sheet may also be used, and a recorded matter is manufactured by cutting the roll sheet after recording. It's okay.

Furthermore, although the recording system of the above embodiment employs a method of forming an image by directly ejecting ink from a recording head onto a recording medium, the present invention is not limited thereto. For example, the present invention is also applicable to a recording apparatus that employs a method of forming an image on a transfer body and transferring the image to a recording medium.

10 Element substrate 30 Recording head 40 Flexible wiring board 101 Paper supply section 102 Discharge section 103, 104 Conveyance rollers 105, 106, 107, 108 Recording head 109 Image inspection section 110 Print control section 120 Recording unit

Claims (4)

A recording device that controls a recording head equipped with a sensor for detecting the state of ink ejection from a nozzle,
A discharge data generation section 1 and a drive data generation section 1 for forming a print image,
a drive data generation unit 2 that specifies a drive method different from that of the drive data generation unit 1;
a selection section that selects drive data to be used from the drive data generation section 1 and the drive data generation section 2; an ejection inspection section that performs an ejection test using parameters that determine ejection state detection conditions;
Performs ejection for ejection state detection based on the drive data of the drive data generation unit 2,
The drive data generation unit 2 generates drive data using drive conditions stored in advance on a recording memory for adjusting the distance between nozzle rows,
The recording device is characterized in that the discharge inspection unit determines the discharge state using data that is stored in advance in a recording memory for adjusting the distance between nozzle rows and that determines the previous discharge state detection condition. . The drive data generated by the drive data generation section is
Data for controlling a thermal recording head, which is either a heat pulse for ejection, a block drive order, or a circuit selection signal for ejection inspection,
The discharge inspection unit performs the discharge inspection using inspection criteria for determining the discharge state determination conditions of the temperature sensor for determining the discharge state, which are stored in advance in a recording memory for adjusting the distance between nozzle rows. The recording device according to claim 1, characterized in that: The drive data generated by the drive data generation section 2 is as follows:
Data for controlling a piezoelectric element recording head,
Drive waveform pattern for ejection, test ejection data, circuit selection signal for ejection test,
The ejection inspection unit performs an ejection inspection using inspection judgment conditions for determining ejection state judgment conditions of residual vibration waveforms for ejection state judgment, which are stored in advance in a recording memory for adjusting the distance between nozzle rows. The recording device according to claim 1, characterized in that: The memory of the drive data generation unit 2 is a memory that satisfies the total bandwidth for reading and writing the ejection data for forming the print image, and the image data for ejection inspection is stored so that the bandwidth is equal to or less than the bandwidth for printing the previous image. 2. The recording apparatus according to claim 1, further comprising a memory band for reading out drive data for ejection testing, and ejection test determination condition data.

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