JP2008055855A - Ink-jet recording device and its discharge control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the generation of a defective discharge of nozzles without performing preliminary discharge on paper. <P>SOLUTION: From image data of a recording object, a change of a recording image from a no-image region to an image-including region caused along with movement of a record head with respect to a recording medium is detected. When an image is recorded, the power driving the record head is temporarily set higher than normal power upon the change from the detected region to the image-including region. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that records an image on a recording medium by ejecting ink from nozzles formed on a recording head.

  2. Description of the Related Art As an output device of an information processing apparatus such as a computer, an ink jet recording apparatus that records an image on a recording medium such as recording paper by discharging ink is known. Such an ink jet recording apparatus usually includes a recording head in which a nozzle array for ejecting ink is formed, a carriage on which the recording head is mounted and reciprocated in a predetermined direction, and a direction (recording medium) orthogonal to the predetermined direction. And a recording medium conveying device that conveys the recording medium in the conveying direction).

  When recording an image on the recording paper, the recording paper being transported by the recording medium transport device is temporarily stopped, and the carriage is reciprocated in the predetermined direction from the nozzle based on the image signal carrying the image information. Ink is ejected, and an image for one band is recorded in a region on the recording paper facing the nozzle outlet (ink ejection port).

  Thereafter, the recording paper is transported by the width of one band and stopped, and again, the ink is ejected from the nozzles based on the image signal while moving the carriage back and forth in the predetermined direction, and the next one band on the recording paper. Record the image in the corresponding part. By repeating such an operation, an image for one page is recorded on the recording paper.

  Further, the ink jet recording apparatus can achieve full color relatively easily by using a plurality of heads that eject inks of different ink colors. In recent years, two-way printing that ejects ink in both reciprocating scans for higher speed has been performed, and the ink droplets have been made smaller to improve image quality, and individual ink droplets on the image cannot be seen. The measures such as doing so are taken.

  By the way, as a process peculiar to the ink jet recording apparatus, in order to prevent the occurrence of ink discharge defects due to drying of ink in the nozzles, adhesion of dust, etc., ink that does not contribute to image recording in the non-recording area between scans. Discharging is performed. Such ink ejection is called “preliminary ejection”.

  Along with the recent miniaturization of ink droplets due to the miniaturization of nozzles, the need for preliminary ejection has become higher than in conventional ink jet recording apparatuses having larger ink droplets. In addition, miniaturization of ink droplets increases the resolution, but also increases the amount of data transferred from the information processing device. With a printer cable with a slow transfer speed, the transfer time cannot be met, and waiting for transfer between scans. You may have to do that.

Conventionally, with respect to such a problem, as described in Patent Document 1, preliminary ejection is performed by providing preliminary ejection holes on both sides of the recording scanning range, thereby preventing ink ejection failure of the nozzle due to ink drying. Yes.
JP 2000-158673 A JP-A-55-139269 Japanese Utility Model Publication No. 3-45814 JP-A-6-40042 JP 2004-25627 A

  Due to the recent miniaturization of ink droplets and the like, especially in recording devices that handle large format recording paper, nozzle drying occurs even when non-image areas continue in one scan. Drying cannot be prevented, and ink ejection may become unstable even if non-ejection does not occur.

  As a technique for preventing these, Patent Documents 2 to 5 disclose a technique for performing preliminary ejection on a recording medium. Such preliminary discharge is called paper preliminary discharge. However, if preliminary ejection is performed on a recording medium, it may be recorded as an image, so that a preferable result may not be obtained.

  The present invention has been made in such a background, and an object thereof is to provide an ink jet recording apparatus capable of preventing the occurrence of defective nozzle ejection without performing preliminary ejection on a paper surface, and an ejection control method therefor. It is in.

  An ink jet recording apparatus according to the present invention is an ink jet recording apparatus having a recording head having a nozzle for ejecting ink, and based on image data to be recorded, a non-image of a recorded image accompanying the movement of the recording head and the recording medium Means for detecting a change from the area to the imaged area, and when recording an image, a power for driving the recording head at the time of the change from the detected area to the imaged area is temporarily set higher than a normal power And a control means for performing the above.

  Ink is not ejected from the nozzles of the head in the non-image area of the recorded image, so that ink is dried and thickened. Therefore, when actually recording an image, ink droplets are ejected more strongly from the nozzles by temporarily setting the power to drive the recording head higher than the normal power when the non-image area changes to the imaged area. As a result, the nozzle discharge port is maintained in a good state for ink discharge. In addition, since the ejection is originally performed on the pixels that eject ink, the pixels different from the original recorded image are not recorded unlike the preliminary ejection on the paper.

 The non-image area and the imaged area can be determined based on a dot density that is the number of ejection dots in a predetermined unit area. Control is facilitated by counting the ejection dots collectively for each unit region in this way. Further, instead of determining that there is no image area when the number of ejection dots in the unit area is 0, the number of ejection dots in the unit area may be a predetermined value that is non-zero. Even for the same recorded image, the greater the non-zero predetermined value is, the higher the possibility that it is determined as a non-image area. Therefore, the frequency of increasing the drive power of the recording head according to the present invention increases.

  The power may be increased when a predetermined number of unit regions having a dot density equal to or lower than a predetermined dot density continue and then change to a dot density higher than a predetermined dot density. As a result, it is possible to prevent the power from being increased more than necessary for an image that changes to an image area only once a unit area having a predetermined dot density or less is generated.

  Furthermore, a head temperature sensor that detects the temperature of the recording head and a data table that defines the regular power corresponding to the output of the head temperature sensor may be provided. Thereby, the control means can determine the regular power corresponding to the head temperature.

  Preferably, the control means is a power determined by the data table based on an output of the head temperature sensor detected after that, with a power set temporarily high when changing from a non-image area to an image area. Return to. This is because it is considered that the waste of continuing the power increase state is superior to the advantage of continuing the power increase state. At this time, when the power is returned, the control means returns only one index of the data table at a time, so that the discharge density is prevented from changing greatly due to a sudden change in power.

  The present invention can also be grasped as a discharge control method of an ink jet recording apparatus.

  According to the ink jet recording apparatus and the ejection control method of the present invention, it is possible to prevent the occurrence of nozzle ejection defects without performing preliminary ejection on the paper surface.

  First, embodiments of the present invention will be described in detail with reference to the drawings. Here, a printer will be described as an example of an ink jet recording apparatus. However, the ink jet recording apparatus according to the present invention is not limited to a printer, and can be applied to any recording apparatus that employs an ink jet recording method, such as a copying machine, a facsimile machine, a multifunction peripheral, or a plotter.

  The schematic operation of the ink jet printer according to this embodiment will be described below. FIG. 1 is a perspective view of the ink jet printer.

  This printer includes a platen 14 on which recording paper 12 as a recording medium conveyed in the direction of arrow A is placed. Two scanning rails (not shown) are spanned above the platen 14 in parallel with the platen 14. A carriage 20 that reciprocates in the directions of arrows B and C (directions orthogonal to the direction of arrow A) by a motor 16 and a belt 18 is attached to the scanning rail via a slide bearing (not shown).

  A linear scale 21 is arranged along the movement path of the carriage 20. The linear scale 21 is provided with regular slits for detecting the position of the carriage 20 and determining ink ejection timing. In order to read the slit of the linear scale 21, an optical linear scale sensor (described later) is mounted on the carriage 20. By counting the pulses output from the optical linear scale sensor, the position of the carriage 20 in the directions of arrows B and C is determined. The pulse count is initialized by moving the carriage 20 to the position of a home position (HP) sensor (not shown) at the end of the scanning rail when the power is turned on.

  Further, a reflection type optical sensor 114 is mounted on the carriage 20, thereby detecting the edge of the recording paper as will be described later.

  FIG. 2 shows a schematic block diagram of a control hardware configuration in the printer 10 of FIG.

  The printer 10 includes a central processing unit (CPU) 110 for program-controlling the operation of the entire apparatus, a carriage motor 111 for driving a carriage, a medium transport motor 112 for transporting recording paper, and various user operation instructions. An operation panel 113 for receiving information, displaying information to the user, and transmitting various information to the user, a reflective optical sensor 114, a rotary encoder 115 associated with the transport motor 17, an optical linear scale sensor 116, ROM 117 for storing programs and data executed by the CPU 110, RAM 118 for providing a work area and temporary holding area for program processing, a non-volatile memory 119 for storing various data such as parameters and drive conditions unique to the printer 10, Imagecon A communication interface (I / F) 120 for communicating various information between the roller 200.

  The operation panel 113 can be composed of a display such as a liquid crystal panel that displays a message or the like, or a lamp such as an LED that functions as an indicator and various keys for sending instructions.

  As the nonvolatile memory 119, any rewritable nonvolatile storage device such as a flash memory, a battery backup memory, and an EEPROM can be used.

  These hardware portions are called an engine controller 100 and mainly play a role of driving / controlling hardware such as a motor and a head.

  The image controller 200 is a part responsible for image processing such as image data, protocol processing for connecting to a network, communication processing with an information processing apparatus, and the like. Command data and the like are operated by communicating with the engine controller via the communication I / F 120. The image controller 200 has an independent CPU different from the CPU 110 and is configured to operate in parallel with the engine controller 100 to improve the overall throughput.

  Before recording an image, the size of the recording paper 12 such as roll paper is measured, and the recording paper 12 is set on the platen 14 in order to detect a recordable range. Next, while the recording paper 12 is sandwiched between the conveyance roller 24 that exposes a part of the outer peripheral surface from the opening formed in the platen 14 and the pinch roller 26 that presses the recording paper 12 from above, the medium conveyance motor 112 The conveying roller 24 is rotated and conveyed until the leading edge of the recording paper 12 is discharged from the platen 14. Further, the carriage 20 is moved from the recording medium placement reference position 27 in the direction of arrow B by a distance shorter than the minimum recording medium size (ISO A4 210 mm × 297 mm) (here, 30 mm).

  Next, the conveyance roller 24 is reversed, and the recording paper 12 is conveyed in the direction opposite to the arrow A until the platen 14 is detected by the reflective optical sensor 114 provided in the carriage 20. Since the position where the platen 14 is detected is the leading end position of the recording paper 12, this position is stored.

  Next, the recording paper is conveyed in the direction of arrow A by a predetermined distance (here, 100 mm), the carriage 20 is moved to a position deviated from the recording medium placement reference position 27 in the direction of arrow C, and then the carriage 20 is moved in the direction of arrow B. Move in the direction at a constant speed. Since the position at the time when the reflective optical sensor 114 detects the amount of light reflected from the recording paper while moving is the side edge of the recording paper in the arrow direction C direction, this position is stored. Further, since the position when the carriage 20 continues to be detected and the platen 14 is detected is the side edge of the recording paper in the arrow B direction, this position is also stored.

  Through the above processing, the leading end position and both side end portions (horizontal width) of the recording paper 12 placed on the platen 14 are determined and image recording is possible. This operation is called load processing, and is always performed when a new recording medium is loaded in the printer.

  When recording an image on the recording paper 12, the recording paper 12 is placed on the platen 14, the carriage 20 is reciprocated in the directions of arrows B and C above the recording paper 12, and the raster sent from the image controller 200. A predetermined amount of data is stored in the RAM 118, and when the predetermined amount is stored, the raster data in the RAM 118 is converted in the direction of the head nozzle array, and the converted data is sequentially synchronized with the count pulse of the linear scale sensor 116 in the head controller (FIG. (Not shown).

  Based on an image signal including image information transmitted from the head control unit to the recording head 22, ink is ejected from the nozzles, and a band-shaped image is recorded in an area corresponding to the recording head 22 on the recording paper 12. .

  Further, preliminary discharge is performed to the preliminary discharge port 30 before the carriage 20 moves to the image recording point, thereby preventing undischarge at the start of writing due to drying of the nozzle surface of the recording head 22. This preliminary ejection before image recording is configured to be performed before recording a belt-like image at a predetermined timing.

  By sequentially recording such a belt-like image while sequentially moving the recording paper by a predetermined amount, an image of one page is completed. When the image of one page is recorded, a cutter (not shown) mounted on the carriage 20 is projected to a predetermined position in the cutter guide 25, and the recording paper 12 is cut into a predetermined size by moving the carriage 20. To do.

  After cutting the recording paper 12, the carriage 20 moves the recording head 22 to the end of the scanning rail and covers the nozzles of the recording head 22 with a cap 31 to protect it from drying.

  The above is the description of the schematic operation of the ink jet printer according to the present embodiment. Next, details of the present embodiment will be described with reference to FIGS.

  FIG. 3 is a block diagram showing various functions of the inkjet printer 10. The ink jet printer 10 includes a recording control unit 300 and a recording head (also simply referred to as a head) 320 as part of the engine controller 100. The recording controller 300 is connected to a linear scale sensor 116, a main scanning motor 321, and a sub-scanning motor (not shown), which is a power source for conveying recording paper, and various sensors.

  The recording control unit 300 includes a memory 301, a main scanning motor control unit 302, a recording trigger generation unit 303, a head control signal generation unit 304, a linear scale count unit 305, a zero data detection unit 306, a memory control unit 307, an image memory 308, The data mask unit 309, the mask memory unit 310, the CPU 110, and the like are included. Among them, the CPU 110 performs an interface with the image controller 200 to which image data is transferred, and controls the operation of the entire recording control unit 300 such as the memory 301 and the I / O.

  When recording an image, the recording control unit 300 records an image image on a recording sheet using the head 320 based on the image data transferred from the image controller 200. Specifically, the recording control unit 300 generates signals necessary for this purpose. That is, when raster data (IN_DATA) is transferred from the image controller 200, raster data (IN_DATA) is fetched by the zero data detection unit 306 according to a command from the CPU 110, and rasters for several bands are sent via the memory control unit 307. Data is temporarily stored in the image memory 308.

  In the present embodiment, image data is transferred from the image controller 200 by 32-bit bus in units of 32 lines (in this embodiment, six colors of black, cyan, magenta, yellow, light cyan, and light magenta are used). The 32-line image data is once taken into the internal buffer in the zero data detection unit 306.

  In this zero data detection unit 306, HV conversion (Horizontal / Vertical: vertical / horizontal conversion) for converting the image data in the raster direction into the data in the direction in which the nozzles of the head are arranged is a block of 32 dots in the horizontal direction and 32 lines in the vertical direction. This is done in units of data. The data after the HV conversion is written (written) to the image memory 308 via the memory control unit 307. After writing the data for 32 lines to the image memory 308, the operation of transferring the next 32 lines from the image controller 200 is repeated. This HV conversion is a process for facilitating memory access for obtaining data to be given to the head 320 when data is read from the image memory 308, and this process itself is known.

  When performing the HV conversion, the zero data detection unit 306 simultaneously performs a process of counting the number of data “1” in a unit area of 32 dots in the horizontal direction and 32 dots in the vertical direction (referred to as dot count process), When image data is written to the image memory 308, a process of writing the number of pixels (dot count data) in units of 32 × 32 dots to another area of the image memory 308 is performed.

  By storing the image data for at least one band in the image memory 308 by the data processing as described above, recording scan is started, and reading of the image data from the image memory 308 is sequentially started. At this time, the memory control unit 307 performs a bus selection process of the image memory 308 for performing time-division input of image data from the image controller 200 and reading of image data to the head 320.

  In the present embodiment, the output of the image data OUT_DATA, the generation of the head drive signal, the generation of the carriage using the signals LINSCL_A / LINSCL_B output by the linear scale sensor 116 in synchronization with the scanning of the head 320 by 90 degrees. Recording control such as position management and main scanning motor speed control is synchronized.

  The carriage moving direction is detected from the phase relationship between the two-phase signals from the linear scale sensor 116. The linear scale count unit 305 counts the amount of carriage movement based on these two-phase signals, and generates a region for reading data from the image memory 308 and a head control signal based on the position information designated by the CPU 110. A signal (WINDOW) representing the area is generated.

  The recording trigger generation unit 303 generates a recording timing signal (HSYNC) from the two-phase signals output from the linear scale sensor 116 as in the linear scale counting unit 305. The memory control unit 307 and the head control signal generation unit 304 read image data from the image memory 308 and generate a head control signal at the timing when both the WINDOW signal and the HSYNC signal are enabled.

  Since a high-resolution linear scale is very expensive, in this embodiment, a low-resolution (for example, 300 dpi) linear scale is used, and the recording trigger generation unit 303 generates a high-resolution recording trigger (1200 dpi in the present invention). And a multiplier circuit (not shown).

  The head control signal is configured to control the head with drive power corresponding to the HEAT_PULSE parameter set from the CPU 110 to the head control signal generator. The drive power can be changed, for example, by changing the pulse width or pulse amplitude of the heat pulse applied to the head.

  The image data read from the image memory 308 is subjected to data mask processing for multi-pass printing by the data mask unit 309. For this purpose, before starting the page recording, the CPU 110 writes the mask pattern corresponding to the number of recording passes to the mask memory unit 310 via the data mask unit 309.

  After the recording starts, when the carriage is driven and the head 320 reaches the recording area, the image data is read from the image memory 308 in synchronization with the HSYNC signal, and the mask data is read from the mask memory unit 310 at the same time. The data mask unit 309 controls to output the data “1” to the head 320 only when both data are “1” data.

  Further, in the present invention, in order to detect a change in the imaged area from the non-image area, the change is detected by using the dot count data described above.

  FIG. 4 shows the relationship between the band data and the dot count value. The total number of nozzles per color of the head used in the present embodiment is 512 nozzles. Therefore, the band data 401 is divided into 512 × 32 dot slice data 402 and further subdivided into 32 × 32 dot small sections.

The dot count data in each subsection is stored in a separate area (404). That is, the dot density of the image in units of 32 × 32 dots is stored individually. Since the total number of nozzles per color of the head is 512 nozzles, when a 512 × 32 dot area is subdivided into small sections,
512/32 = 16
Thus, there are 16 dot count value storage areas for 32 × 32 dots in the head nozzle direction.

In this embodiment, the maximum recording medium size in the main scanning direction is 24 inches, and the size excluding the left and right margins of 5 mm is the maximum image size in the main scanning direction, so the maximum image size is 599.6 mm. Since the minimum resolution in the main scanning direction is 1200 dpi in the present embodiment, the total number of dot count value storage areas (404) written when performing one-band recording is as follows. It is obtained by the formula.
599.6 / (25.4 / 1200) / 32≈885
Considering the area for storing the portion that cannot be divided, a value 886 obtained by adding +1 to the calculated value is the number of necessary subsections.

  Since the dot count in each small section when the entire band is subdivided into 32 × 32 dot units is written, the dot density in 32 dot units can be calculated in the main scanning direction.

  FIG. 5 shows the relationship between the dot count value storage area and the image change point. Here, the total value of the dot count in the 32 × 32 dot unit in the head nozzle direction, that is, the total number of dot counts in the unit area of 512 × 32 dots, calculated at the time of HV conversion in one band recorded image is sliced dots. The count value 503 is stored in the memory 301. This is performed for one band, and the band recording preparation is completed.

  This means that no image is present in the unit area where the slice dot count value 503 is zero. If the slice dot count value 503 is other than 0, it can be determined that some image data (pixels that eject ink) exists in the unit area.

  All of these are examined before starting the recording of one band, and change points (image change points) between the non-image area and the image area are listed.

  In parallel with this, the CPU 110 prepares for heat pulse setting for driving the head.

  In the present embodiment, heat pulse data corresponding to the temperature read from the head temperature sensor 311 mounted in the head is selected and set in advance in the head control signal generation unit before heating is started. .

  Since it is necessary to configure it so that appropriate ejection characteristics can be obtained while dynamically changing the heat pulse data according to the head temperature even during the recording scan, the heat pulse data is usually stored in a table format and the head temperature Control is performed to keep the output image density constant by selecting / setting the heat pulse data corresponding to.

  Also in the present embodiment, the heat pulse data is prepared in a table format, and the heat pulse data is searched using the head temperature acquired value as an index.

  FIG. 6 shows a configuration for retrieving heat pulse data. The CPU 110 reads the head temperature from the head temperature sensor 311, selects heat pulse data corresponding to the current temperature from the heat pulse table 604, and sets the acquired heat pulse data in the head control signal generation unit 304, so that an appropriate heat pulse is generated. Is set. The heat pulse update is controlled by time, and the heat pulse is updated with reference to the head temperature every unit time (for example, 10 ms). In this embodiment, the lower the head temperature, the stronger the heat power (in other words, the ink ejection power) is set.

  Further, in this embodiment, even if the difference between the current head temperature and the previous head temperature is an index difference larger than “1” on the table index, only the “1” index is always changed. This is to prevent a change in density from occurring in the output image due to a drastic change in the discharge density due to a sudden heat pulse change.

  Here, during the recording scan, an interrupt controller is set so that the CPU 110 is interrupted every 32 dots in the main scanning direction (not shown), and at each interrupt, the image change point is referred to determine whether there is an image to be recorded. To do.

  If it is determined by this determination that the area is a non-image area, the heat pulse data is changed to pulse data (stronger power) at a temperature lower than the current head temperature, and then enters the image area to perform ejection driving. At this time, it becomes possible to perform discharge with higher heat power than the pulse data based on the actual head temperature. By increasing the heat power, the ink droplets are strongly ejected from the nozzles, and as a result, due to factors such as increased ink viscosity due to ink drying near the nozzle ejection port and adhesion of dust due to continuation of the non-ejection period, Even if clogging occurs or is about to occur, the nozzle discharge port is expected to return to the original good state.

  When entering the image area, the index at a temperature lower than the actual head temperature is referred to. However, since the index fluctuation is only one index, the heat pulse is the head temperature at that time after a certain time. It is possible to make a transition to a heat pulse suitable for the actual head temperature little by little without a sudden density change in the heat pulse setting according to the above.

  By eliminating the ejection failure due to the drying of the head in the non-image area by strong ejection driving as described above, density unevenness and ejection failure due to drying can be prevented in advance.

  FIG. 7 shows the transition of heat pulse selection during one-band recording. In the figure, reference numeral 701 represents a change in the presence / absence of an image in one-band recording, and reference numeral 702 represents a change in heat pulse power according to the present invention.

  In the one-band recording / writing portion 703, heat pulse data 705 along the head temperature is selected. Thereafter, the heat pulse index is dropped when entering the non-image area to select the heat pulse data 706 to increase the power of the heat pulse and prepare for the next image area.

  When the image area is actually entered, a stepwise approach to the target heat pulse data 707 is started. By performing such an operation, recording for one band is completed.

  The above procedure is repeatedly applied to the received image data to complete the recording of one page.

  FIG. 9 is a flowchart showing an example of the power data setting process executed prior to the recording process in the present embodiment. A program representing the execution procedure of the process of this flowchart is stored in the ROM 117, and this process is realized by the CPU 110 reading it, interpreting it and executing it. The same applies to the processing of FIGS. 10 and 11 described later.

  First, the received image data is analyzed, and the imaged area and the non-image area are checked as described above (S11). Therefore, power data at a change point from a predetermined non-image area to an image area is determined (S12). A method of determining the value of the power data as an absolute value and a method of determining it as a relative value as an increase with respect to the value of the power data determined according to the head temperature can be considered. The determined power data is stored in the RAM 118 corresponding to the non-image area (change point) (S13). Until the image data is completed (S14), the process returns to step S11 and the above processing is repeated.

  FIG. 10 is a flowchart showing an example of band recording processing in the present embodiment.

  When the storage process is started, if there is a non-image area at the current recording position as the carriage scans (S21, Yes), the power data stored corresponding to the non-image area stored in the RAM 118 is stored. To update the heat power (S22). However, at this time, the head is not yet driven. If so, the process proceeds to step S25.

  When the head reaches the image area by scanning the carriage (S23, Yes), the head is driven with the set heat power and ink is ejected from a predetermined nozzle to record an image and every unit time. The head temperature is confirmed and the heat power is updated (S24). Normally, the heat power set in step S22 is larger than the heat power determined for the head temperature in step S24, and the heat power decreases by one index per unit time until it matches the heat power determined for the head temperature. I will do it.

  Until one band is completed (S25), the process returns to step S21 and the above processing is repeated. For the recording of the next band, the processing of FIG. 10 is executed again.

<First Modification>
FIG. 11 is a flowchart showing another example of the band recording process in the present embodiment. In the process of FIG. 10, a relatively large fixed value heat power is set in the non-image area. However, in the process of FIG. 11, the head temperature is checked immediately before reaching the image area, and the corresponding heat power is set. The initial head drive of the imaged area is performed with a heat power that is larger by a predetermined relative value based on this.

  When the storage process is started, if there is a non-image area at the current recording position as the carriage scans (S31, Yes), wait for a certain time before the imaged area (S32, Yes). The head temperature is confirmed (S33). Next, referring to the heat pulse table 604, the heat power corresponding to the head temperature is obtained (S34). Therefore, the heat power is increased by a predetermined amount (S35). When the image area is reached (S36, Yes), the head is driven with the increased heat power, ink is ejected from a predetermined nozzle to record an image, and the head temperature is checked every unit time. The heat power is updated (S37). Normally, the heat power set at the time of shifting to step S37 is larger than the heat power determined for the head temperature, and the heat power is one index per unit time until it matches the heat power determined for the normal head temperature. It decreases gradually.

  Until the end of one band (S38), the process returns to step S31 and the above processing is repeated. For the recording of the next band, the process of FIG. 11 is executed again.

  In the above description, only control related to one ink color has been described, but in the embodiment, similar control can be applied to all six colors.

<Second Modification>
In the above processing, the heat pulse is changed simply by generating one non-image area. However, in that case, there is a possibility that a density change may occur when switching between non-image / present image in a very short section. The occurrence of such a problem can be prevented by the second modification.

The second modified example has the same configuration as that of the above-described embodiment, and when an image change point as shown in FIG. 8 is obtained, a non-image in which the number of non-image unit areas is less than a predetermined number (here, 4). In the region 801, the heat pulse is not changed to a stronger power, and the heat pulse is changed when a region 802 in which a predetermined number of non-image unit regions continue is detected. The distance between the four unit area non-image areas is obtained by the following equation.
32 × 4 × (25.4 / 1200) ≒ 2.7mm

  Therefore, the heat pulse change operates only when the non-image area of 2.7 mm or more continues.

<Third Modification>
The third modified example has the same configuration as that of the above embodiment, and does not determine the image change point based on a threshold value of no image and existence image (that is, the number of pixels is 0 or 1 or more). The image change point is determined by a fixed number of pixels. In the above embodiment, it is determined that there is an image only when one pixel is output within the 512 × 32 dot region. In this case, ink is ejected from many other nozzles. Considering that this is not done, it is conceivable that the threshold for determining whether there is no image or image is greater than zero.

<Fourth Modification>
The fourth modification is different from the first modification in that the image change point is not determined based on a threshold value of no image and existence image (that is, the number of pixels is 0 or 1 or more), but is set to a certain number of pixels other than 0. Thus, the image change point is determined.

  The preferred embodiments of the present invention have been described above, but various modifications and changes other than those mentioned above can be made. For example, the order of colors, the number of colors, the image division size, and the like shown in the above embodiment are merely examples and do not limit the present invention.

1 is a perspective view of an inkjet printer according to an embodiment of the present invention. FIG. 2 is a schematic block diagram of a control hardware configuration in the printer of FIG. 1. FIG. 2 is a block diagram showing various functions of the ink jet printer shown in FIG. 1. It is a figure which shows the relationship between the band data and dot count value in embodiment of this invention. It is a figure which shows the relationship between the dot count value storage area | region and image change point in embodiment of this invention. It is a figure which shows the structure for the search of the heat pulse data in embodiment of this invention. It is a figure which shows transition of the heat pulse selection in 1 band recording in embodiment of this invention. It is a figure for demonstrating the example of the image change point in the 2nd Embodiment of this invention. 5 is a flowchart illustrating an example of power data setting processing executed prior to recording processing in the embodiment of the present invention. It is a flowchart which shows an example of the band recording process in embodiment of this invention. It is a flowchart which shows another example of the band recording process in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Inkjet printer 100 ... Engine controller 111 ... Carriage motor 112 ... Medium conveyance motor 113 ... Operation panel 114 ... Reflection type optical sensor 115 ... Rotary encoder 116 ... Linear scale sensor 119 ... Non-volatile memory 200 ... Image controller 300 ... Recording control part 301 ... Memory 302 ... Main scanning motor control unit 303 ... Recording trigger generation unit 304 ... Head control signal generation unit 305 ... Linear scale count unit 306 ... Zero data detection unit 307 ... Memory control unit 308 ... Image memory 311 ... Head temperature sensor 320 ... Head 321 ... Main scanning motor 401,501 ... Band data 402 ... Slice data 503 ... Slice dot count value 604 ... Heat pulse table 703 ... Recording of one band Tooth portions 707 ... target heat pulse 801 ... non-image area 802 ... area 805 ... heat pulse data

Claims (7)

In an inkjet recording apparatus provided with a recording head having a nozzle for discharging ink,
Means for detecting a change from a non-image area of a recorded image to an imaged area associated with movement of the recording head and the recording medium based on image data to be recorded;
Control means for temporarily setting a power for driving the recording head higher than a normal power when the image is recorded to change to the imaged area from the detected area. apparatus.   The inkjet recording apparatus according to claim 1, wherein the control unit determines the non-image area and the imaged area based on a dot density that is the number of ejection dots in a predetermined unit area.   3. The control unit according to claim 2, wherein the control unit increases the power when a predetermined number of unit areas having a dot density equal to or lower than a predetermined dot density continue and then changes to a dot density higher than a predetermined dot density. Inkjet recording device.   The ink jet recording apparatus according to claim 1, further comprising: a head temperature sensor that detects a temperature of the recording head; and a data table that defines the regular power corresponding to an output of the head temperature sensor.   The control means returns the power temporarily set high when changing from the non-image area to the imaged area to the power determined by the data table based on the output of the head temperature sensor detected thereafter. Item 5. The ink jet recording apparatus according to Item 4.   6. The ink jet recording apparatus according to claim 5, wherein when the power is returned, the control means returns only one index of the data table at a time. An ejection control method for an ink jet recording apparatus including a recording head having a nozzle for ejecting ink,
The recording head detects a change in the recorded image from the non-image area to the imaged area accompanying the movement of the recording head and the recording medium, and records the image at the time of the change from the detected area to the imaged area. A discharge control method for an ink jet recording apparatus, wherein the power for driving the ink jet is temporarily set higher than the normal power.

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