JP2006231602A - Recording device and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording device and a recording method which can easily restrain irregular density. <P>SOLUTION: The recording device 10 has a recording head 20 where a plurality of droplet ejectors to discharge ink droplets are arranged, and a reaction liquid head 30 to discharge a reactive liquid to harden ink droplets discharged by the recording head 20 and is provided with a density sensor 40 to detect recording density as a physical quantity having a correlation with the temperature of the recording head 20, controls the discharge quantity of the reactive liquid discharged from the reaction liquid head 30 so as to restrain a density change caused by a temperature change of the recording head 20 in accordance with density detected by the density sensor 40. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a recording apparatus and a recording method for performing recording with a recording head including a droplet ejector that ejects droplets.

  Currently, a recording head having a plurality of droplet ejectors each provided with a drive element is arranged, and a pressure generation chamber of the droplet ejector is deformed by applying a drive signal having a predetermined waveform to the drive element. An ink jet recording apparatus that changes the volume of the ink and discharges ink droplets in the pressure generating chamber has become widespread.

  When recording with a high duty (high density) is performed with such a recording apparatus, heat is generated by flexural vibration of the drive elements, and switching ICs that control driving of the individual drive elements generate heat. When the ink of the recording head is warmed due to this heat generation and the viscosity of the ink decreases, the amount of droplets at the time of ink ejection increases, and the diameter of the dots formed on the recording paper tends to be larger than when the ink is not warmed. There is.

  Furthermore, recent recording heads have been made to have multiple nozzles and lengths. For example, a recording head in which a plurality of head units composed of a plurality of droplet ejectors are arranged to have a length substantially equal to the width of the recording paper. In other words, a so-called FWA (Full Width Array) type ink jet recording apparatus has been developed that performs recording while transporting only the recording paper while the recording head is fixed. In such a long recording head, when images having a duty difference among the nozzles of the recording head are continuously recorded, temperature irregularities are generated in the recording head, thereby causing an image to be recorded by the recording head. In some cases, uneven density may occur.

  This will be specifically described with reference to FIG. As shown in FIG. 11, by a recording head 80 in which a plurality of head units 82a to 82f having a plurality of droplet ejectors (not shown) are arranged and elongated to a width substantially equal to the width of the recording paper, When recording only a recording sheet while transporting it in the A direction, if a high density image B is recorded locally, the portion of the recording head on which the image B is recorded (head unit 82d) is heated up compared to the surroundings. To do. Thus, when the image C having a uniform density is recorded over a wide range after the image B is recorded, only the portion recorded by the droplet ejector (head unit 82d) that recorded the image B has a high density (D in FIG. 11). Uneven density occurs.

As a recording apparatus corresponding to a change in the temperature of the recording head, a recording apparatus that detects the temperature distribution of the recording head and controls the recording speed by changing the ejection frequency according to the detected temperature distribution has been proposed ( For example, see Patent Document 1.) There has also been proposed an ink jet printing apparatus in which an ink supply path is provided in a recording head and the recording head heated by recording is cooled at the same time as ink is supplied in the middle of recording (for example, see Patent Document 2).
Japanese Patent Laid-Open No. 04-219247 JP 2000-255048 A

  However, the technique described in Patent Document 1 has a problem that when the recording frequency is lowered, the recording speed is also reduced. The technique described in Patent Document 2 requires a mechanism for cooling the recording head. Furthermore, this technique does not take into account any countermeasure when the recording head is locally heated. Further, when trying to cope with local temperature rise using the technique of Patent Document 2, a means for controlling cooling is required for each head unit, which complicates the apparatus configuration.

  Conventionally, there is also a method of suppressing the density change by changing the droplet diameter and the droplet speed of the ejected ink droplet by correcting the drive waveform supplied to the droplet ejector with respect to the local temperature change of the recording head. Are known. However, in this method, it is necessary to calculate the voltage value of the drive waveform of each droplet ejector in consideration of the temperature rise of the recording head and the meniscus reverberation correction at that time. In addition, there is a problem that the cost of the arithmetic element is increased.

  Furthermore, there are various factors other than the temperature change of the print head in the occurrence of density fluctuation and density unevenness. For example, the change in the water head pressure caused by the variation in the remaining amount of ink in the ink tank provided for each head unit, Also, unevenness in density may occur due to variations in ejection characteristics of each droplet ejector of the recording head.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a recording apparatus and a recording method that can easily suppress density fluctuations and density unevenness.

  In order to achieve the above object, a recording apparatus according to the present invention includes a first head in which a plurality of first droplet ejectors that discharge a first droplet are arranged, and a first head that reacts with the first droplet. A second head in which a plurality of second droplet ejectors for ejecting two droplets are arranged, and ejection from the second droplet ejector in accordance with variation or variation in ejection characteristics of the first droplet ejector And a control means for controlling the amount of the second droplet.

  The recording density of the first droplet also changes depending on the degree of reaction between the first droplet and the amount of the second droplet. Therefore, by controlling the amount of the second droplet, it is possible to easily suppress density variation and density unevenness caused by variation or variation in the ejection characteristics of the first droplet ejector.

  The discharge characteristics of the first droplet ejector may be the discharge characteristics of each of the first droplet ejectors, or when the plurality of arranged first droplet ejectors are divided into a plurality of groups. It may be an average discharge characteristic for each group.

  The ejection characteristics include at least one of an ejection amount, a droplet diameter, a droplet speed, and a natural period of the first droplet ejector ejected from the first droplet ejector. Can do.

  When the discharge amount, droplet diameter, droplet speed, natural period of the first droplet ejector, etc. of the first droplet ejected from the first droplet ejector fluctuate or vary, the first droplet Droplet ejector The recording density of the first droplet varies or varies. Therefore, by controlling the amount of droplets ejected from the second droplet ejector according to such variation and variation in ejection characteristics, it is possible to suppress density variation and density unevenness.

  The fluctuation or variation in the discharge characteristics of the first droplet ejector is caused by the temperature of the first droplet ejector and the liquid in the droplet tank that stores the first droplet supplied to the first droplet ejector. It can be a variation or variation caused by at least one of the remaining amount of droplets, a change with time of the first droplet ejector, and a manufacturing variation of the first droplet ejector.

  For example, the first droplet ejector may increase in temperature when the discharge amount of the first droplet increases. When the temperature of the first droplet ejector increases, the viscosity of the internal droplets decreases, and the discharge amount of the first droplets increases. That is, density changes and density irregularities occur due to changes in the temperature of the first droplet ejector.

  Further, it is known that when the remaining amount of droplets in the droplet tank varies, the water head pressure changes. Due to the change in the water head pressure, the droplet diameter and the droplet speed of the droplets ejected from the first droplet ejector may fluctuate, and the concentration may change.

  In addition, the ejection characteristics of the first droplet ejector change depending on the use state. As the first droplet ejector changes with time, the discharge amount of the first droplet may fluctuate and density unevenness may occur.

  Further, due to the members constituting the first droplet ejector and manufacturing variations, ejection such as the diameter and speed of the ink ejected from the first droplet ejector or the natural period of the first droplet ejector Characteristics may vary. When the ejection characteristics vary in this way, the ejection amount of the first droplet to be ejected varies, resulting in density unevenness.

  The control means can suppress density fluctuations and density irregularities caused by fluctuations and variations in the ejection characteristics as described above by controlling the ejection amount of the second droplet.

  Further, a detecting means for detecting a variation or variation in the discharge characteristics of the first droplet ejector is further provided, and the control means discharges from the second droplet ejector according to the detection result of the detecting means. The amount of the second droplet may be controlled.

  By providing the detection means, even when the ejection characteristics of the first droplet ejector fluctuate in real time, density fluctuations and density unevenness due to fluctuations in the ejection characteristics of the first droplet ejector can be performed with higher accuracy. Can be suppressed.

  For example, the droplet speed indicating the ejection characteristics of the first droplet ejector may be detected, or the temperature of the first droplet ejector or the first as a physical quantity correlated with variation or variation in ejection characteristics. The remaining amount of droplets in the droplet tank that stores the droplets may be detected. Further, as a physical quantity having a correlation with temperature, a recording density, a discharge amount, a droplet speed, or the like may be detected.

  The control means is configured to discharge the second droplet discharged from the second droplet ejector per unit time or discharge per second discharge of the second droplet discharged from the second droplet ejector. By controlling the amount, the amount of the second droplet ejected from the second droplet ejector can be controlled. Further, when the control means controls the discharge amount per discharge of the second droplet discharged from the second droplet ejector, the waveform of the drive signal for driving the second droplet ejector By controlling the discharge amount, the discharge amount can be controlled.

  For example, when the second droplet ejector includes a pressure chamber to which the second droplet is supplied and a driving element that varies the pressure in the pressure chamber, the second droplet ejector is driven by a driving waveform applied to the driving element. The liquid diameter and liquid speed can be controlled. Therefore, the discharge amount of the reaction liquid per discharge can be controlled by controlling the waveform of the drive signal.

  Note that the waveform of the drive signal can be adjusted by changing the wave height, the rising and falling timings, and the like.

  The first head may have a length equal to or greater than a full width of a recording medium on which an image is recorded by the first head.

  A plurality of the first heads may be provided, and the second head may be provided for each of the plurality of first heads.

  With such a configuration, even when there are a plurality of first heads, density fluctuations and density unevenness caused by fluctuations and variations in the ejection characteristics of the first droplet ejector can be easily suppressed.

  According to the recording method of the present invention, a first head in which a plurality of first droplet ejectors that discharge a first droplet are arranged, and a second droplet that reacts with the first droplet are discharged. A recording method of a recording apparatus including a second head in which a plurality of two droplet ejectors are arranged, wherein the second droplet is in accordance with a variation or variation in ejection characteristics of the first droplet ejector. The amount of the second droplet discharged from the ejector is controlled.

  Since the recording method of the present invention also operates in the same manner as the recording apparatus of the present invention, density fluctuations and density unevenness can be easily suppressed.

  As described above, according to the present invention, a first head in which a plurality of first droplet ejectors that eject a first droplet are arranged, and a second droplet that reacts with the first droplet are ejected. And a second head in which a plurality of second droplet ejectors are arranged, and a second droplet ejector that ejects from the second droplet ejector in accordance with a variation or variation in ejection characteristics of the first droplet ejector. Since the amount of the second droplet is controlled, it is possible to easily suppress the density fluctuation and density unevenness caused by the fluctuation or variation of the ejection characteristics of the first liquid droplet ejector.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of an ink jet recording apparatus 10 according to the present embodiment. The recording apparatus 10 includes a CPU 12, a ROM 14, and a RAM 16, which are connected by a bus 50. The CPU 12 controls the operation of each component of the recording apparatus 10. The ROM 14 stores programs for various processing routines, and the CPU 12 performs various controls by executing the programs. In addition, the ROM 14 stores a correction table that stores the recording density and the correction value of the discharge amount of a reaction liquid (described later) in association with each other. This table is used for controlling the discharge amount of the reaction liquid described later.

  Further, the recording apparatus 10 includes a recording head 20 that ejects ink droplets, a recording head drive circuit 18 that drives the recording head 20, and a reaction liquid that ejects a reaction liquid for solidifying the ink droplets ejected from the recording head 20. Head 30, reaction liquid head drive circuit 28 for driving reaction liquid head 30, density sensor 40 for detecting recording density, paper feed motor 44 for transporting paper during recording, and paper feed drive circuit for driving the paper feed motor 42 is provided.

  The recording head driving circuit 18 and the reaction liquid head driving circuit 28 drive the recording head 20 or the reaction liquid head 30 according to a control signal transmitted from the CPU 12.

  FIG. 2 is a view showing the appearance of the recording head peripheral portion of the recording apparatus 10 excluding the paper transport system. The recording apparatus 10 according to the present embodiment is a so-called FWA (Full Width Array) type recording apparatus that performs recording by conveying only the paper P while the recording head 20 is fixed. As shown in FIG. 2, the recording head 20 of the recording apparatus 10 is a long recording head having a width substantially equal to the width of the paper P, and a plurality of droplet ejectors 24 (see FIG. 2) for discharging ink droplets. 3 (see 3), a plurality of (here, 6) head units 22 are arranged in the paper width direction.

  Each head unit 22 is provided with an ink tank for storing ink to be supplied to each head unit 22 corresponding to each head unit 22. Each head unit 22 is supplied with ink from the respective ink tank, and the droplet ejector 24 constituting each head unit 22 can eject ink droplets by the supplied ink. Each ink tank is connected to a main ink tank (not shown), and ink drops are supplied from the main ink tank to each ink tank when the remaining amount of each ink tank becomes a predetermined amount or less. Such an ink tank can be comprised with a porous body, for example.

Hereinafter, specific examples of the composition of the ink used for recording will be described. Here, a dispersant-type black ink is exemplified as the ink used for recording. This ink can be prepared by a predetermined method using a pigment processed according to a pigment processing method described later.
<Composition>
Mogul L (manufactured by Cabot) (pigment / no surface functional group): 4 mass. Styrene-acrylic acid-sodium acrylate copolymer: 0.6 mass%
・ Diethylene glycol: 15% by mass
Diglycerin ethylene oxide adduct: 5% by mass
Polyoxyethylene-2-ethylhexyl ether: 0.75% by mass
-Ion-exchanged water: remainder The pH of this liquid is 8.2, the volume average particle diameter is 120 nm, the surface tension is 32 mN / m, and the viscosity is 3.3 mPa · s.

The pigment treatment method is as follows.
<Pigment treatment method>
In a predetermined amount of ion-exchanged water, 10% by mass of a pigment and 1.5% by mass of a dispersant are added and stirred. An ultrasonic homogenizer is applied to the mixed liquid to disperse the pigment. Further, the dispersion liquid is subjected to a centrifugal separation process (8000 rpm × 30 minutes), and the residue (20% with respect to the initial charged amount) is removed, whereby a pigment dispersion liquid can be obtained.

  FIG. 3 is a schematic cross-sectional view illustrating the configuration of the droplet ejector 24. The droplet ejector 24 includes a nozzle plate 3 in which a plurality of nozzles 2 are formed, a pressure generating chamber 4 provided corresponding to each nozzle 2 and filled with ink ejected from the nozzle 2, and pressure from an ink tank (not shown). An ink supply path 5 for supplying ink to the generation chamber 4 and an actuator 7 provided corresponding to each pressure generation chamber 4 are configured. By driving the actuator 7, the pressure generating chamber 4 expands or contracts. When the volume changes by a predetermined amount (pressure changes) due to the expansion and contraction, the ink filled inside is ejected from the nozzle 2. The actuator 7 is driven by applying a predetermined driving voltage waveform from the recording head driving circuit 18 described above.

  Each actuator 7 is provided with a switching IC (not shown) for turning ON / OFF the driving of each actuator 7, and a driving voltage waveform generated by the recording head driving circuit 18 by switching the switching IC ON / OFF. Can be selectively supplied. The switching control of the switching IC is performed by a control signal from the CPU 12. Thereby, the drive of each actuator 7 is controlled.

  Note that when recording with a high duty (high density) is performed with the recording head 20 constituted by such a droplet ejector 24, a switching IC that controls heat generation due to flexural vibration of the actuator 7 and driving of the individual actuators 7. Etc. generate heat. When the ink of the recording head is warmed by this heat generation and the viscosity of the ink is lowered, the amount of droplets at the time of ink ejection increases, and the diameter of the dots formed on the paper P increases (the recording density increases). That is, the recording density varies according to the temperature of the recording head 20. In particular, when an image with a high density is partially recorded as in the image B in FIG. 2 and no image is recorded at other portions, the droplet ejector portion on which the image B of the recording head is recorded. However, the temperature rises locally compared to the other surrounding parts. When the temperature rise of the recording head 20 locally occurs in this way, for example, even if an attempt is made to print a uniform halftone density pattern following the image B, density unevenness (D in FIG. 2) occurs for the above reason. End up. Therefore, in this recording apparatus 10, the reaction liquid is normally ejected at a predetermined ejection amount (ejection ratio) with respect to the ink droplets, but the temperature of the recording head 20 is determined according to the recording density detection result of the density sensor 40. The discharge amount of the reaction liquid head 30 is corrected (partially) so that the concentration change due to the change can be suppressed. Details of this correction will be described later.

  The reaction liquid head 30 of the recording apparatus 10 is provided on the downstream side of the recording head 20 with respect to the paper transport direction A. The reaction liquid head 30 also has a length similar to that of the recording head 20 described above, and includes a plurality of head units 32 (here, a plurality of head units 32 configured by a plurality of droplet ejectors 24 having the same structure as in FIG. 3 for discharging the reaction liquid. In the same manner as the recording head 20, the number of the recording heads is 6). The reaction liquid is uniformly applied to the entire width of the paper P. Each head unit 32 is connected to a common reaction liquid tank (not shown) for each head unit 32 that stores the reaction liquid supplied to each head unit 32.

As the reaction solution, for example, a polyvalent metal type reaction solution can be used. Specific examples of the composition are shown below.
<Composition>
・ Diethylene glycol: 30% by mass
Calcium nitrate tetrahydrate: 6 parts by weight Acetylene glycol ethylene oxide adduct: 1% by mass
-Ion exchange water: remainder The pH of this liquid is 6.1, the surface tension is 30 mN / m, and the viscosity is 2.7 mPa · s.

  When the reaction liquid and the ink come in contact with each other on the paper, the dispersed state of the ink component such as a pigment can be destroyed, and the pigment can be agglomerated to form an aggregate on the paper. Fixing to P, that is, solidification can be promoted. For this reason, in this reaction liquid, if the discharge amount of the reaction liquid discharged onto the paper P is large, it is easy to agglomerate the pigment and fix the ink on the paper P. It can be seen that the recording density can be lowered if the liquid discharge amount is small.

  Although the reaction liquid also has a characteristic that the viscosity changes depending on the temperature, the reaction liquid head 30 always applies the reaction liquid to the entire width of the paper P regardless of the recorded image. Even if the discharge amount of the reaction liquid is locally changed, the reaction liquid is discharged from other parts of the reaction liquid head 30 (although the discharge amount is different). Therefore, the temperature difference generated in the reaction liquid head 30 is negligible compared to the temperature difference of the recording head 20 caused by the presence or absence of recording as shown in FIG. As a result, the discharge amount unevenness due to the temperature difference hardly occurs in the reaction liquid head 30.

  The density sensor 40 is provided on the downstream side of the recording head 20 and the upstream side of the reaction liquid head 30 with respect to the paper transport direction A. The density sensor 40 detects the recording density of the image formed by the ink droplets ejected from the recording head 20. The density sensor 40 includes a plurality of optical sensors such as CCDs. The light receiving surfaces of the optical sensors are arranged in the paper width direction. As a result, the density distribution in the paper width direction of the image recorded on the paper can be detected.

  Next, the recording operation controlled by the CPU 12 will be described in detail.

  FIG. 4 is a flowchart of a processing routine that is started when a recording start command is input.

  In step 100, recording by the recording head 20 is started based on a recording start command input from the outside. Specifically, the CPU 12 generates recording data to be recorded by the recording head 20 from the image data input together with the recording start command, and outputs the recording data to the recording head drive circuit 18. The recording head drive circuit 18 generates a drive voltage waveform for driving the actuator 7 and switches ON / OFF of the switching IC corresponding to each actuator 7 based on the input recording data, and selectively generates the waveform for the actuator 7. The drive voltage waveform is supplied. Ink droplets are ejected from the nozzle 2 of the droplet ejector 24 provided with the actuator 7 to which the drive voltage waveform is supplied. Further, the CPU 12 sends a control signal to the paper feed drive circuit 42 to control the paper P to be conveyed in a direction indicated by an arrow A in FIG. 2 at a predetermined speed.

  In step 102, the recording density (density distribution) of the image recorded as described above is detected by the density sensor 40.

  In step 104, the discharge amount of the reaction liquid is determined from the detected concentration distribution. Specifically, first, it is determined whether or not there is a portion recorded at a high density exceeding a predetermined value from the detected density distribution. Here, when it is determined that there is no portion recorded at the high density, it is determined that the temperature change of the recording head 20 is within a predetermined range and density unevenness does not occur, and the preset value is left as it is. It is determined as the discharge amount of the reaction liquid discharged from the all droplet ejector 24 of the reaction liquid head 30.

  If it is determined from the detected density distribution that there is a portion recorded at a high density exceeding a predetermined value, it is determined whether or not the recording of the high density portion has continued for a predetermined period. If it is determined that the recording head 20 has continued for a predetermined period, it is determined that the recording head 20 is heated and uneven density occurs, and the correction amount corresponding to the high density density value is read from the correction table stored in the ROM 14. The ejection amount value set in advance is corrected with the read correction amount. This corrected value is determined as the reaction liquid discharge amount of the droplet ejector 24 of the reaction liquid head 30 corresponding to the droplet ejector 24 of the recording head 20 that has recorded a locally high concentration portion.

  FIG. 5 is a diagram showing the relationship between the recording density and the ejection ratio (ejection amount) of the reaction liquid to the ink droplets. As is clear from FIG. 5, when high density recording continues, ejection of the reaction liquid from the droplet ejector 24 of the reaction liquid head 30 corresponding to the droplet ejector 24 of the recording head 20 that performed the high density recording. Control to reduce the amount. As described above, by reducing the ejection amount of the reaction liquid, the recording density of the ejected ink droplets can be reduced, and density unevenness can be suppressed. The correction of the ejection amount is continuously performed for a period calculated by a predetermined arithmetic expression according to the detected density. As a result, the reaction liquid is discharged with the discharge amount corrected by the correction value until the temperature difference of the recording head 20 falls within the predetermined range.

  For the remaining droplet ejector 24 of the reaction liquid head 30, a preset value is determined as the discharge amount.

  In step 106, a control signal is output to the reaction liquid head drive circuit 28 so that the reaction liquid is discharged from each droplet ejector 24 of the reaction liquid head 30 with the determined discharge amount.

  For example, as shown in FIG. 2, a case where an image B having a high density is recorded and a halftone image C having a uniform density over a wide range is recorded immediately after the image B is taken as an example. When the image B is recorded, the temperature of the recording head locally rises, and as shown in FIG. 2D, the density change occurs and density unevenness occurs. However, the discharge amount of the reaction liquid is controlled as described above. As a result, as shown in FIG. 2E, it is possible to suppress the concentration change due to the temperature rise and to prevent the concentration unevenness.

  Specifically, the discharge amount is controlled by the number of discharges per unit time of the reaction liquid discharged from the droplet ejector 24 of the reaction liquid head 30 or the reaction liquid discharged from the droplet ejector 24 of the reaction liquid head 30. This is done by controlling the discharge amount per discharge. When controlling the discharge amount per discharge, the discharge amount is controlled by adjusting the drive voltage waveform supplied to the droplet ejector 24. Specifically, for example, the waveform is adjusted by changing the wave height of the drive voltage waveform, the rising and falling timings, and the discharge amount is controlled.

  In step 108, it is determined whether or not the recording by the input recording start command has been completed. If it is determined that the recording has not ended, the process returns to step 100 and the recording operation by the recording head 20 is continued. If it is determined that the recording has been completed, this processing routine is terminated.

  As described above, the recording density is detected, and the ejection amount of the reaction liquid is controlled so as to suppress the density change caused by the temperature change of the recording head 20 based on the detection result. In particular, even when high density recording is performed, the occurrence of density unevenness can be suppressed.

  In this embodiment, the example in which the recording density is reduced and the density unevenness is suppressed by reducing the amount of the reaction liquid ejected for the high density recording has been described. However, the present invention is not limited to this. When the ink and the reaction liquid whose recording density is lowered by increasing the amount of the reaction liquid to be discharged are used according to the composition of the reaction liquid, the discharge amount of the reaction liquid can be controlled in the opposite direction to the above control. .

  In addition, the composition of the ink and the reaction liquid described in the present embodiment is an example, and the present invention is not limited to this.

  Further, in the present embodiment, control is performed using a table in which the recording density and the correction value of the ejection amount of the reaction liquid are stored in association with each other. However, the correction value of the recording density and the ejection ratio (with respect to the ink droplet) of the reaction liquid is set. A table stored in association with each other may be used.

  In the present embodiment, the example in which the ejection amount is corrected for each droplet ejector 24 of the reaction liquid head 30 has been described. However, the present invention is not limited to this. For example, the concentration is corrected for each head unit 22 constituting the recording head 20. And the discharge amount of the reaction liquid may be corrected for each head unit 32 of the reaction liquid head 30 corresponding to the head unit 22. This also suppresses the density change due to the temperature change of the recording head 20 (head unit 22) in the same manner as described above.

  Furthermore, in the present embodiment, an example of a recording apparatus and method for detecting a recording density and controlling a discharge amount of the reaction liquid according to the detected recording density to suppress a density change caused by a temperature change of the recording head 20 is taken as an example. As described above, by detecting the temperature of the recording head 20 instead of the recording density, the density change caused by the temperature change of the recording head 20 according to the temperature may be suppressed. In this case, in the recording apparatus 10 shown in FIGS. 1 and 2, the concentration sensor 40 is configured in place of the temperature sensor. The temperature sensor is provided in the recording head 20 at a predetermined interval. For example, the recording head 20 may be provided for each head unit 22. The temperature sensor may be a contact type temperature sensor or a non-contact type temperature sensor using infrared rays or the like.

  Further, a correction table in which the temperature and the correction value of the discharge amount (or discharge ratio) of the reaction liquid are stored in association with each other is stored in the ROM 14.

  Next, a recording operation when a temperature sensor is used will be described with reference to the flowchart of FIG. Here, a case where a temperature sensor is provided for each head unit 22 of the recording head 20 will be described as an example.

  In step 200, recording by the recording head 20 is started based on a recording start command input from the outside. Details are the same as the processing in step 100 described in the above embodiment, and thus the description thereof is omitted.

  In step 202, the temperature of the recording head 20 is detected by a temperature sensor. Temperature detection by the temperature sensor is performed at predetermined time intervals.

  In step 204, the discharge amount of the reaction liquid is determined based on the correction table. Since a correction value corresponding to the temperature is stored in the correction table, the correction value is read according to the detected temperature, and a value predetermined as the discharge amount of the reaction liquid is corrected by the correction value. . In the correction table, for example, a value of 0 is stored as a correction value when there is no temperature rise (normal temperature).

  This corrected value is determined as the reaction liquid discharge amount of the head unit 32 of the reaction liquid head 30 corresponding to each head unit 22.

  In step 206, control is performed so that the reaction liquid is discharged from the droplet ejector 24 of each head unit 32 of the reaction liquid head 30 with the determined discharge amount.

  In step 208, it is determined whether or not the recording according to the input recording start command has been completed. If it is determined that the recording has not ended, the process returns to step 200 and the recording operation by the recording head 20 is continued.

  Note that during the recording operation, the ejection amount is corrected by the correction table until it is determined that the temperature of the heated recording head 20 falls within a predetermined range. When the temperature of the recording head 20 falls within a predetermined range, the reaction liquid is discharged with a normal discharge amount.

  If it is determined in step 208 that the recording has been completed, this processing routine is terminated.

  In this manner, the discharge amount of the reaction liquid is controlled according to the temperature detected by the temperature sensor, and the concentration change caused by the temperature change of the recording head 20 can be suppressed.

  Further, the ejection amount of the reaction liquid can be controlled by estimating the temperature of the recording head 20 according to the ejection amount and the ejection distribution of the ink droplets. For example, the ink droplet ejection amount is provided with a counter for each droplet ejector 24 or the head unit 22 of the recording head 20 and is increased each time an ink droplet is ejected. The ejection amount is detected from the ejection number indicated by the count value of this counter. Further, the discharge distribution can also be detected from each counter. When ink droplets are continuously ejected from the recording head 20, the temperature of the ejection portion rises. Therefore, the temperature of the recording head 20 can be calculated and estimated from the discharge amount and the discharge distribution.

  FIG. 7 is a flowchart of a processing routine for correcting the ejection amount of the reaction liquid by predicting the temperature change of the recording head from the ejection amount and the ejection distribution of the ink droplets. Here, a case where the ink droplet ejection amount is detected for each head unit 22 of the recording head 20 will be described as an example.

  In step 300, recording by the recording head 20 is started based on a recording start command input from the outside. Details are the same as the processing in step 100 described in the above embodiment, and thus the description thereof is omitted.

  In step 302, the temperature of the recording head 20 is determined by a predetermined calculation from the discharge amount and discharge distribution detected by the counter.

  In step 304, the discharge amount of the reaction liquid is determined based on the correction table. Specifically, the discharge amount of the reaction liquid is determined from the temperature obtained by calculation in step 302 in the same manner as in step 204 described above.

  In step 306, control is performed so that the reaction liquid is discharged from the droplet ejector 24 of each head unit 32 of the reaction liquid head 30 with the determined discharge amount.

  In step 308, it is determined whether or not the recording by the input recording start command has been completed. If it is determined that the recording has not ended, the process returns to step 300 and the recording operation by the recording head 20 is continued.

  Note that during the recording operation, the ejection amount is corrected by the correction table until it is determined that the temperature of the heated recording head 20 falls within a predetermined range. When the temperature of the recording head 20 falls within a predetermined range, the reaction liquid is discharged with a normal discharge amount.

  If it is determined in step 308 that the recording has been completed, this processing routine is terminated.

  Thus, the discharge amount of the reaction liquid can be controlled from the temperature obtained from the discharge amount and the discharge distribution, and the change in density due to the temperature change of the recording head 20 can be suppressed as described above.

  Further, instead of detecting the ejection amount of the ink droplets, it is also possible to determine the temperature of the recording head by detecting the ink droplet ejection speed and control the ejection amount of the reaction liquid. As the temperature of the recording head 20 increases, the viscosity of the ink droplets decreases and the droplet speed increases, so the temperature of the recording head 20 can be determined from the droplet speed.

  The droplet speed can be detected by, for example, irradiating the ink droplets ejected from the droplet ejector 24 with laser light. If the temperature of the recording head 20 is obtained from the detected droplet velocity and the discharge amount of the reaction liquid is controlled in the same manner as the processing routine shown in FIG. 7, the change in density caused by the temperature change of the recording head 20 is suppressed. be able to.

  In the above example, the temperature, the discharge amount, and the droplet speed are individually treated. However, a combination of these physical amounts may be used. For example, density unevenness caused by variations in the ejection amount and droplet speed with respect to the paper conveyance speed may be predicted, and a corresponding correction table may be prepared and corrected with the reaction liquid.

[Second Embodiment]
In the first embodiment, the example of the recording apparatus that suppresses the density change caused by the temperature change of the recording head 20 by controlling the discharge amount of the reaction liquid has been described. However, in the present embodiment, the ink in the ink tank is used. An example of a recording apparatus that suppresses density changes caused by fluctuations in the remaining amount will be described.

  It is known that the water head pressure value changes according to the remaining amount of ink. Further, depending on the image to be recorded, the head unit 22 at the central portion of the recording head 20 in the paper width direction uses a large amount of ink, and the head unit 22 at both ends of the recording head in the paper width direction often reduces the amount of ink used. . As described above, when the ink usage amount of each head unit 22 varies, the remaining amount of ink in the ink tank of each head unit 22 also varies. If the ink remaining amount varies, a water head pressure difference may occur for each head unit 22, and the diameter and speed of the ejected ink may vary, resulting in uneven recording density.

  In the present embodiment, the discharge amount of the reaction liquid is controlled in accordance with the remaining amount of ink in each ink tank, and unevenness in recording density is suppressed.

  In the recording apparatus of the present embodiment, the density sensor 40 is omitted from the recording apparatus 10 described in the first embodiment, and the ink remaining amount of each ink tank connected to each head unit 22 of the recording head 20 is determined. It is assumed that a remaining ink sensor to be monitored is provided. The ROM 14 stores a correction table that stores the remaining amount of ink and the correction value of the discharge amount (or discharge ratio) of the reaction liquid in association with each other.

  The CPU 12 controls the discharge amount of the reaction liquid based on the ink remaining amount detected by each ink remaining amount sensor.

  FIG. 8 is a flowchart of a processing routine executed by the CPU 12 in the present embodiment.

  In step 400, recording by the recording head 20 is started based on a recording start command input from the outside. Details are the same as the processing in step 100 described in the above embodiment, and thus the description thereof is omitted.

  In step 402, the ink remaining amount in each ink tank is detected by the ink remaining amount sensor. The detection of the ink remaining amount by the ink remaining amount sensor is always performed at predetermined time intervals.

  In step 404, the discharge amount of the reaction liquid is determined based on the correction table. As described above, since the remaining amount of ink and the correction value are stored in the correction table in association with each other, the correction value corresponding to the detected remaining ink amount is read out and predetermined as the reaction liquid discharge amount. The obtained value is corrected with the correction value, and the discharge amount of the reaction liquid is determined for each head unit 32 of the reaction liquid head 30.

  In step 406, control is performed so that the reaction liquid is discharged from the droplet ejector 24 of each head unit 32 of the reaction liquid head 30 with the determined discharge amount. Note that the discharge amount of the reaction liquid is controlled by controlling the number of discharges per unit time and the discharge amount per discharge, as in the first embodiment.

  In step 408, it is determined whether or not the recording by the input recording start command has been completed. If it is determined that the recording has not ended, the process returns to step 400 and the recording operation by the recording head 20 is continued. If it is determined in step 408 that the recording has been completed, this processing routine is terminated.

  In this way, by controlling the ejection amount of the reaction liquid based on the ink remaining amount detected by the ink remaining amount sensor, a change in density due to a decrease in the head pressure of the recording head 20 caused by a change in the ink remaining amount in the ink tank is suppressed. , Density unevenness can be suppressed.

[Third Embodiment]
In the present embodiment, an example of a recording apparatus that suppresses variation in density caused by variations in ejection characteristics that occur during manufacture of each head unit 22 of the recording head 20 or ejection characteristics that occur during manufacture of each droplet ejector 24 of the recording head 20 is described. Will be described.

  For example, due to the members constituting the droplet ejector 24 and manufacturing variations, the diameter and speed of ink droplets ejected from the droplet ejector, the natural period of the droplet ejector, and the like (hereinafter collectively referred to as ejection characteristics) May vary). When the ejection characteristics vary, the recording density varies. In the present embodiment, concentration variation is suppressed by controlling the discharge amount of the reaction liquid in accordance with the discharge characteristics of each droplet ejector. Here, the natural period refers to a natural period when each droplet ejector 24 (pressure generation chamber 4) of the recording head 20 is filled with ink.

  The plurality of droplet ejectors 24 constituting the recording head 20 are divided into a plurality of groups, and the average value of the ejection characteristics of the droplet ejectors 24 constituting each group is set to the ejection characteristics (average ejection) for each group. Characteristics), and density variations caused by variations in the average discharge characteristics can be suppressed by controlling the discharge amount of the reaction liquid. For example, an average discharge characteristic may be obtained for each head unit 22 of the recording head 20, and density variations caused by the average discharge characteristic variation may be suppressed. When the ejection characteristics of each droplet ejector 24 of the recording head 20 do not vary so much in the head unit 22, the efficiency is improved by controlling the ejection volume of the reaction liquid according to the average ejection characteristics of each head unit 22. Thus, the discharge amount of the reaction liquid can be controlled.

  Hereinafter, a case where the discharge amount of the reaction liquid is controlled according to the average discharge characteristic for each head unit 22 will be described as an example.

  The recording apparatus of the present embodiment has a configuration in which the density sensor 40 is omitted from the recording apparatus 10 described in the first embodiment. In the ROM 14, the rank when the discharge characteristic (or average discharge characteristic of the head unit) of the droplet ejector is digitized and ranked is associated with the correction value of the discharge amount (or discharge ratio) of the reaction liquid in association with each other. The corrected table is stored.

  The recording head 20 is provided with a storage unit (not shown), and the storage unit stores a numerical value of the average ejection characteristics of each head unit 22 constituting the recording head 20. The average ejection characteristics of each head unit 22 are collected in advance by experiments or the like when the recording head 20 is manufactured, and stored in the storage unit of the recording head 20. This average ejection characteristic can be appropriately read from the CPU 12 of the recording apparatus.

  FIG. 9 is a flowchart of a processing routine executed by the CPU 12 in the present embodiment.

  In step 500, when a recording start command is input from the outside, the average ejection characteristic for each head unit 22 is read from the storage unit of the recording head 20.

  In step 502, the discharge amount of each reaction solution is determined based on the average discharge characteristics read from the storage unit of the recording head 20 and the correction table stored in the ROM 14.

  Specifically, the correction value corresponding to the average ejection characteristic for each head unit 22 read from the storage unit of the recording head 20 is read from the correction table stored in the ROM 14. Then, the predetermined value of the discharge amount of the reaction liquid is corrected by the read correction value, and each of the corrected values is determined as the discharge amount of the reaction liquid of each head unit 22.

  In step 504, the reaction liquid is set to be discharged from each droplet ejector 24 of each head unit 32 of the reaction liquid head 30 with the determined discharge amount.

  In step 506, recording by the recording head 20 is started based on a recording start command input from the outside. Details are the same as the processing in step 100 described in the above embodiment, and thus the description thereof is omitted. The reaction liquid is also discharged by the reaction liquid head 30. The CPU 12 outputs a control signal to the reaction liquid head drive circuit 28 so that the reaction liquid is discharged with the set discharge amount. Thereby, the reaction liquid is discharged with the set discharge amount.

  In step 508, it is determined whether or not the recording according to the input recording start command has been completed. If it is determined that the recording has not ended, the process returns to step 506 and the recording operation by the recording head 20 is continued. If it is determined in step 508 that the recording has been completed, this processing routine is terminated.

  In this way, by controlling the discharge amount of the reaction liquid in accordance with the discharge characteristics of the droplet ejector or the average discharge characteristics of each head unit, concentration variations can be suppressed.

  In the third embodiment, the ejection characteristics (average ejection characteristics) are collected in advance, but may be detected in real time during the recording operation. For example, the droplet velocity can be detected in real time by irradiating the ejected ink droplet with laser light as described in the first embodiment.

  The correction of the discharge amount of the reaction liquid is more preferably performed in consideration of manufacturing variations in the discharge characteristics of the reaction liquid head 30 itself. The ejection characteristics of the reaction liquid head 30 can be stored in, for example, the storage unit of the reaction liquid head 30. By adjusting the drive waveform or the like according to the stored discharge characteristics, it is possible to suppress the density variation with higher accuracy regardless of the manufacturing variation of the discharge characteristics of the reaction liquid head 30.

  In the first to third embodiments, the recording apparatus provided with one recording head 20 and one reaction liquid head 30 has been described as an example. However, the number of the recording head 20 and the reaction liquid head 30 is described. Is not limited to one and may be two or more. For example, as shown in FIG. 10, in order to perform color recording, recording heads 20C, 20M, 20C corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (K) are used. 20K may be provided, and four reaction liquid heads 30C, 30M, 30C, and 30K corresponding to each recording head may be provided.

  Each of the reaction liquid heads 30C, 30M, 30C, and 30K is provided immediately after the corresponding recording head 20C, 20M, 20C, and 20K (on the downstream side in the sheet conveyance direction). Thereby, it is possible to suppress the concentration variation caused in each of the recording heads 20C, 20M, 20C, and 20K by controlling the discharge amount of the reaction liquid discharged from each of the reaction liquid heads 30C, 30M, 30C, and 30K. it can.

  Further, only one reaction liquid head 30 can be provided for the plurality of recording heads 20. The one reaction liquid head 30 is arranged downstream of the recording head 20 in the last stage in the sheet conveying direction, and the concentration unevenness generated in all the recording heads 20 is controlled to discharge the reaction liquid from the reaction liquid head 30. Can also be suppressed.

  In the above embodiment, the reaction liquid head is arranged on the downstream side of the recording head. However, in the case where feedback is not performed in real time as in the third embodiment or when the feedback is sufficiently in time, the reaction head is arranged. The liquid head may be arranged on the upstream side of the recording head.

  In the first to third embodiments, the long recording head 20 having a width substantially equal to the width of the paper P is provided, and only the paper P is conveyed while the recording head 20 is fixed to perform recording. A so-called FWA (Full Width Array) type recording apparatus has been described as an example. However, the present invention is not limited to this, and has a recording head having a width shorter than the width of the paper P, and the recording head in the main scanning direction. It may be a PWA (Partial Width Array) type recording apparatus that performs recording by conveying the paper P in the sub-scanning direction while moving.

  In such a recording apparatus, the same effect as described above can be obtained by providing a reaction liquid head and controlling the ink droplets discharged from the recording head to be discharged in a desired discharge amount. can get.

1 is a block diagram illustrating a schematic configuration of a recording apparatus according to a first embodiment. FIG. 3 is a diagram illustrating an external appearance of a recording head peripheral portion excluding a paper conveyance system of the recording apparatus. It is the cross-sectional schematic explaining the structure of a droplet ejector. It is a flowchart of the process routine started when the recording start command is input in 1st Embodiment. FIG. 6 is a diagram illustrating a relationship between a recording density and a discharge ratio (discharge amount) of a reaction liquid to an ink droplet. 10 is a flowchart of a processing routine in a case where the temperature of the recording head is detected to control the discharge amount of the reaction liquid. 10 is a flowchart of a processing routine in the case of correcting a discharge amount of a reaction liquid by predicting a temperature change of a recording head from a discharge amount and a discharge distribution. It is a flowchart of the processing routine which CPU performs in 2nd Embodiment. It is a flowchart of the processing routine which CPU performs in 3rd Embodiment. FIG. 6 is a diagram illustrating an arrangement example of each recording head and reaction liquid head when a plurality of recording heads and reaction liquid heads are provided. FIG. 6 is an explanatory diagram for explaining a state in which density unevenness occurs due to temperature rise of a recording head.

Explanation of symbols

2 Nozzle 4 Pressure generation chamber 5 Ink supply path 7 Actuator 10 Recording device 12 CPU
14 ROM
18 Recording head drive circuit 20, 20C, 20M, 20Y, 20K Recording head 22 Head unit 24 Droplet ejector 28 Reaction liquid head drive circuit 30, 30C, 30M, 30Y, 30K Reaction liquid head 32 Head unit 40 Concentration sensor

Claims (9)

A first head in which a plurality of first droplet ejectors for discharging the first droplet are arranged;
A second head in which a plurality of second droplet ejectors for ejecting second droplets that react with the first droplets are arranged;
Control means for controlling the amount of the second droplet ejected from the second droplet ejector in accordance with variation or variation in the ejection characteristics of the first droplet ejector;
Recording device including   The ejection characteristic includes at least one of an ejection amount, a droplet diameter, a droplet velocity, and a natural period of the first droplet ejector of the first droplet ejected from the first droplet ejector. Item 1. A recording apparatus according to Item 1.   The fluctuation or variation in the discharge characteristics of the first droplet ejector is caused by the temperature of the first droplet ejector and the liquid in the droplet tank that stores the first droplet supplied to the first droplet ejector. The recording apparatus according to claim 1, wherein the recording apparatus is a variation or variation caused by at least one of a remaining amount of droplet, a change with time of the first droplet ejector, and a manufacturing variation of the first droplet ejector. Detection means for detecting a variation or variation in discharge characteristics of the first droplet ejector;
4. The recording apparatus according to claim 1, wherein the control unit controls the amount of the second droplet ejected from the second droplet ejector in accordance with a detection result of the detection unit. 5. .   The control means is configured to discharge the second droplet discharged from the second droplet ejector per unit time or discharge per second discharge of the second droplet discharged from the second droplet ejector. The recording apparatus according to claim 1, wherein the amount of the second droplet ejected from the second droplet ejector is controlled by controlling the amount.   The control means controls the waveform of a drive signal for driving the second droplet ejector when controlling the ejection amount per ejection of the second droplet ejected from the second droplet ejector. The recording apparatus according to claim 5, wherein the discharge amount is controlled by performing the operation.   The recording apparatus according to claim 1, wherein the first head has a length equal to or greater than a full width of a recording medium on which an image is recorded by the first head.   The recording apparatus according to claim 1, wherein a plurality of the first heads are provided, and the second head is provided for each of the plurality of first heads. A first head in which a plurality of first droplet ejectors that eject the first droplet are arranged, and a plurality of second droplet ejectors that eject the second droplet that reacts with the first droplet. A recording method of a recording apparatus including the arranged second heads,
A recording method for controlling an amount of a second droplet ejected from the second droplet ejector according to a variation or variation in ejection characteristics of the first droplet ejector.

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