JP2017217766A - Liquid discharge device and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress image quality deterioration of a formed image.SOLUTION: A liquid discharge device includes a plurality of nozzles, a pressure generating element, a detection part, a determination part, and an output part. The plurality of nozzles discharge a liquid. The pressure generating element is arranged for each of the plurality of nozzles, and the plurality of nozzles swing respective meniscus. The detection part detects non-discharge periods of the plurality of nozzles respectively during printing operation. The determination part determines meniscus swing periods indicating a period for swinging the meniscus of each of the plurality of nozzles based on the detected non-discharge period. The output part outputs a drive waveform for driving each of the pressure generating elements for swinging the meniscus of each object nozzle during the determined meniscus swing period.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a liquid ejection apparatus and a control method.

  2. Description of the Related Art Conventionally, as an image forming apparatus such as a printer, a facsimile, a copying apparatus, and a digital printing apparatus, for example, a liquid discharge recording type image forming apparatus using a recording head composed of a liquid discharge head (droplet discharge head) that discharges ink droplets. (For example, an inkjet recording apparatus) is known. An image forming apparatus of a liquid discharge recording system forms a desired image by discharging ink droplets from a recording head onto a recording medium such as paper.

  The recording head includes a nozzle that ejects ink droplets, an ink channel (pressure chamber) that communicates with the nozzle, and a pressure generation unit that pressurizes ink in the ink channel. As the recording head, a piezoelectric type, a thermal type, an electrostatic type and the like are generally known. Among these, the piezoelectric recording head uses a piezoelectric element such as a piezo element as a pressure generating unit, and causes a vibration plate that forms the wall surface of the ink flow path to vibrate with the piezoelectric element. The ink volume is ejected by changing the internal volume. A thermal recording head uses a heating resistor to discharge ink droplets with pressure generated by heating ink in an ink flow path to generate bubbles. The electrostatic recording head deforms the diaphragm that forms the wall surface of the ink flow path, thereby changing the volume in the ink flow path and ejecting ink droplets. Usually, a plurality of nozzles that eject ink droplets are formed in the recording head. Further, the ink flow path and the pressure generating means are provided for each nozzle.

  In such a recording head, there are nozzles in a non-ejection period (for example, between sheets) during printing standby and continuous printing, and nozzles that are not ejected depending on the printed image even during the printing period. Generally, a cap or the like for preventing evaporation of moisture is not attached to the nozzle. For this reason, in the nozzle in a non-ejection state, the water content of the ink evaporates and the ink is thickened. Due to the increased viscosity of the ink, subsequent ejection may result in ejection failure such as non-ejection, satellite or mist generation, and ejection speed and ejection droplet volume may be lower than desired. In some cases, it is difficult to land at a suitable position with a suitable drop amount, which may lead to a decrease in image quality. In order to suppress such a decrease in image quality, for example, the ink density in the nozzles is stirred by shaking the ink meniscus (bending of the liquid surface) to the extent that the ink is not ejected from the nozzles and stirring the ink in the nozzles. In order to prevent the ink viscosity from rising excessively.

  In addition, when the non-ejection period is longer than a certain period, the amount of thickened ink increases, and the above problem may not be solved even if the meniscus is swung. In such a case, a recovery process called forced ejection (or flushing) for forcibly discharging the thickened ink from the nozzles is performed. Normal printing cannot be performed while such a recovery process is being performed. For this reason, if the frequency of idle ejection increases, the productivity of printing decreases and the consumption of ink increases. Therefore, it is preferable that the frequency of idle ejection and the ejection amount of idle ejection are small. In general, the higher the water concentration of the ink in the vicinity of the meniscus (when the ink is not thickened), the faster the water evaporation rate from the nozzle. For this reason, as the meniscus is swung, the state in which the water concentration of the ink in the vicinity of the meniscus is high continues, so that drying is further promoted. That is, the total amount of water that evaporates increases (the amount of ink that thickens increases), and the amount of idle ejection for recovery and the processing frequency increase.

  Regarding the above-described meniscus oscillation, in Patent Document 1 (Japanese Patent No. 5079912), the meniscus oscillation timing is set to immediately before ejection, and the number of drive pulses for oscillation of the meniscus is determined based on non-ejection time and environmental conditions. A limiting technique is disclosed. Further, in Patent Document 2 (Japanese Patent No. 5362381), the image data to be printed is analyzed, and for the nozzles that are ejected for printing, the meniscus is swung between the paper before the printing area, and the nozzles that do not eject On the other hand, a technique for preventing the meniscus from swinging is disclosed. In Patent Document 3 (Japanese Patent Laid-Open No. 2013-240947), there is a line buffer for storing image data for printing N lines, and the N + 1th line is ejected, and all the previous N lines are not. A technique for swinging the meniscus during the N line in the case of discharge is disclosed.

  However, the conventional technique has a problem that the image quality of the formed image may be deteriorated. As described above, it is preferable that the vibration of the meniscus performed in order to suppress the increase in the viscosity of the ink in the nozzle is applied with a necessary amount of vibration immediately before the ejection. Moreover, it is preferable that the viscosity of the ink of each nozzle is maintained at a desired value so that the speed and the amount of ink droplets ejected from each nozzle become suitable values. In this regard, in the conventional technique, the meniscus is oscillated immediately before ejection for each nozzle. However, the prior art does not consider the non-ejection period before ejection between the nozzles with respect to the number of times the meniscus is swung. For this reason, according to the conventional technology, depending on the image data, the number of meniscus oscillations is insufficient or excessive, leading to ejection failure, or the ejection speed and the amount of ejected droplets being reduced, resulting in the image quality of the formed image being reduced. There is a possibility of deterioration.

  The present invention has been made in view of the above, and an object of the present invention is to suppress image quality deterioration of a formed image.

  In order to solve the above-described problems and achieve the object, a liquid ejection device according to the present invention is provided for each of a plurality of nozzles that eject liquid and each of the plurality of nozzles, and the meniscus of each of the plurality of nozzles is oscillated. A pressure generating element, a detection unit that detects a non-ejection period of each of the plurality of nozzles during a printing operation, and a period in which the meniscus of each of the plurality of nozzles is swung based on the detected non-ejection period. A determination unit that determines a meniscus swing period; and an output unit that outputs a drive waveform for driving each of the pressure generating elements that swing the meniscus of each target nozzle during the determined meniscus swing period.

  According to one aspect of the present invention, there is an effect that image quality deterioration of an image to be formed can be suppressed.

FIG. 1 is a diagram illustrating a schematic configuration example of an image forming apparatus according to the first embodiment. FIG. 2 is a diagram illustrating an example of a recording head according to the first embodiment. FIG. 3A is a diagram illustrating an internal structure example of the recording head according to the first embodiment. FIG. 3B is a diagram illustrating an internal structure example of the recording head according to the first embodiment. FIG. 4 is a diagram illustrating a schematic configuration example of the image forming apparatus according to the first embodiment. FIG. 5 is a diagram illustrating a configuration example of the liquid ejection apparatus according to the first embodiment. FIG. 6 is a diagram for explaining a generation example of the drive waveform selection signal according to the first embodiment. FIG. 7 is a diagram illustrating a detailed configuration example of the swing instruction unit according to the first embodiment. FIG. 8 is a diagram for explaining a setting example of a combination of the threshold value and the number of peristaltic pulses according to the first embodiment. FIG. 9 is a block diagram illustrating a hardware configuration example of the controller according to the first embodiment. FIG. 10 is a diagram illustrating an example of the switching element according to the second embodiment. FIG. 11 is a diagram for explaining an example of resetting the counter according to the second embodiment.

  Embodiments of a liquid ejection apparatus and a control method according to the present invention will be described below with reference to the accompanying drawings. In addition, this invention is not limited by the following embodiment.

(Embodiment 1)
[Schematic Configuration 1 of Image Forming Apparatus]
A schematic configuration of the image forming apparatus 100 according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a schematic configuration example of an image forming apparatus 100 according to the first embodiment.

  An image forming apparatus 100 shown in FIG. 1 is configured as a line scanning ink jet recording apparatus, and includes a recording unit 2 that forms an image on a recording medium 1 such as paper. In FIG. 1, a state of looking down in a direction perpendicular to the recording surface of the recording medium 1 is shown. The recording medium 1 may have any shape of roll paper (continuous paper) and cut paper, or may be a medium other than paper. The recording medium 1 is conveyed in a predetermined direction indicated by an arrow in FIG.

  The recording unit 2 is supported so as to face the recording surface of the recording medium 1 while maintaining a predetermined distance. The recording unit 2 includes a plurality of recording units 2K, a recording unit 2C, a recording unit 2M, and a recording unit provided corresponding to each ink of black (K), cyan (C), magenta (M), and yellow (Y). 2Y. The recording unit 2 ejects ink droplets in synchronization with the conveyance speed of the recording medium 1. As a result, a color image is formed on the recording medium 1. As a matter of course, the image forming apparatus 100 is provided with a mechanism for controlling the conveyance of the recording medium 1 so that the recording medium 1 passes through a predetermined position with respect to the recording unit 2 at a predetermined speed. . The illustration and detailed description of parts not directly related to the gist of the present embodiment, including such a transport control mechanism, are omitted.

  Each of the recording unit 2K, the recording unit 2C, the recording unit 2M, and the recording unit 2Y includes a plurality of recording heads 3 arranged in a direction orthogonal to the conveyance direction of the recording medium 1. The plurality of recording heads 3 may be arranged in a line in a direction orthogonal to the conveyance direction of the recording medium 1 or may be arranged in a staggered manner as shown in FIG. In the image forming apparatus 100, a wide print area width is secured by arraying the plurality of recording heads 3.

[Recording head]
Next, the recording head 3 according to the first embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating an example of the recording head 3 according to the first embodiment. FIG. 2 is a plan view when the recording head 3 is viewed from the ink ejection surface side.

  As shown in FIG. 2, the recording head 3 includes a plurality of nozzles 104 arranged at a predetermined pitch p in a direction orthogonal to the conveyance direction of the recording medium 1 (hereinafter sometimes referred to as “nozzle row direction”). Have Two nozzle rows are provided in the recording head 3 shown in FIG. Further, one nozzle row is formed such that each nozzle 104 is arranged at a position shifted by approximately ½ · p in the nozzle row direction with respect to the other nozzle row. As a result, high resolution recording can be performed in the nozzle row direction.

[Internal structure of recording head]
Next, the internal structure of the recording head 3 according to Embodiment 1 will be described with reference to FIGS. 3A and 3B. 3A and 3B are diagrams illustrating an example of the internal structure of the recording head 3 according to Embodiment 1. FIG. 3A and 3B are cross-sectional views along the longitudinal direction of the liquid chamber of the recording head 3 (direction perpendicular to the nozzle row direction).

  As shown in FIGS. 3A and 3B, the recording head 3 includes a nozzle 104 that discharges droplets at a portion where a flow path plate 101, a vibration plate member 102, and a nozzle plate 103 are joined, and the nozzle 104 penetrates the recording head 3. An individual liquid chamber 106 (also referred to as a pressurizing chamber, a pressurized liquid chamber, a pressure chamber, an individual flow path, a pressure generating chamber, etc., which is referred to as a “liquid chamber” hereinafter), A fluid resistance portion 107 and a liquid introduction portion 108 for supplying a liquid to the liquid chamber 106 are formed. Further, a common liquid chamber 110 is formed in the frame member 117, and a liquid (for example, ink) is introduced from the common liquid chamber 110 into the liquid introduction unit 108 through the filter 109 formed in the diaphragm member 102, and the fluid Ink is supplied from the liquid introduction unit 108 to the liquid chamber 106 via the resistance unit 107.

  The flow path plate 101 is produced by laminating metal plates such as SUS and forming openings and grooves such as the through hole 105, the liquid chamber 106, the fluid resistance portion 107, and the liquid introduction portion 108, respectively. The flow path plate 101 is not limited to a metal plate such as SUS, but may be formed by anisotropic etching of a silicon substrate.

  The diaphragm member 102 is a wall surface member that forms the wall surface of each liquid chamber 106, the fluid resistance portion 107, the liquid introduction portion 108, and the like, and is a member that forms the filter 109. On the surface opposite to each liquid chamber 106 of the vibration plate member 102 is a columnar electromechanical conversion element as a drive element that generates energy to pressurize the ink in the liquid chamber 106 and eject liquid droplets from the nozzle 104. A laminated piezoelectric member 112 is joined. The other end of the piezoelectric member 112 opposite to the end that is joined to the diaphragm member 102 is joined to the base member 113. Further, an FPC board 115 that transmits a drive waveform to the piezoelectric member 112 is connected to the piezoelectric member 112. Thus, the piezoelectric actuator 111 is configured.

  In the example shown in FIGS. 3A and 3B, the piezoelectric member 112 is used in the d33 mode that expands and contracts in the stacking direction. However, the piezoelectric member 112 is used in the d31 mode that expands and contracts in the direction orthogonal to the stacking direction. It is also good.

  In the recording head 3 configured as described above, as shown in FIG. 3A, the piezoelectric member 112 contracts by lowering the voltage applied to the piezoelectric member 112 from the reference potential Ve, the diaphragm member 102 deforms, and the liquid chamber 106 is deformed. As the volume of the liquid expands, ink flows into the liquid chamber 106. 3B, the voltage applied to the piezoelectric member 112 is increased to extend the piezoelectric member 112 in the stacking direction, and the diaphragm member 102 is deformed in the direction of the nozzle 104 to contract the volume of the liquid chamber 106. Thus, the ink in the liquid chamber 106 is pressurized, and the droplet 301 is ejected from the nozzle 104.

  Then, by returning the voltage applied to the piezoelectric member 112 to the reference potential Ve, the diaphragm member 102 is restored to the initial position, and the liquid chamber 106 expands to generate a negative pressure. At this time, ink is filled from the common liquid chamber 110 into the liquid chamber 106. After the vibration of the meniscus surface of the nozzle 104 is attenuated and stabilized, the operation proceeds to the operation for discharging the next droplet.

  Incidentally, the droplet 301 ejected from the nozzle 104 lands on the recording medium 1 kept at a constant distance L after the flight time Tj. At this time, if the ejection speed of the droplet 301 is Vj, Tj = L / Vj. The ejection speed Vj may fluctuate due to ink thickening in the vicinity of the nozzles 104, and the flight time Tj differs between the nozzles 104 due to this fluctuation. Since the recording medium 1 is transported at a constant speed, the landing positions in the transport direction vary. In addition, the amount of ink droplets to be ejected also varies.

[Schematic Configuration 2 of Image Forming Apparatus]
Next, a schematic configuration of the image forming apparatus 100a according to the first embodiment will be described with reference to FIG. FIG. 4 is a diagram illustrating a schematic configuration example of the image forming apparatus 100a according to the first embodiment. In FIG. 4, a configuration different from the schematic configuration of the image forming apparatus 100 shown in FIG. 1 will be described.

  An image forming apparatus 100a shown in FIG. 4 is configured as a serial type ink jet recording apparatus. A recording medium is constituted by a master-slave guide rod 11 and a guide rod 12 which are guide members horizontally mounted on left and right side plates of the apparatus main body. 1 has a carriage 13 slidably held in a direction (main scanning direction) orthogonal to the one conveyance direction. The carriage 13 is given a driving force via a timing belt by a main scanning motor or the like (not shown), and moves and scans in the carriage scanning direction indicated by a bidirectional arrow in FIG. The carriage 13 is mounted with a recording head 14a and a recording head 14b for ejecting ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K). Hereinafter, when the recording head 14a and the recording head 14b are not distinguished, the recording head 14a and the recording head 14b are simply referred to as “recording head 14”. Nozzle rows are arranged on the recording head 14 so as to be orthogonal to the main scanning direction, and nozzles whose ink droplet ejection direction is directed downward (on the recording medium 1 side) are mounted.

  Each of the recording head 14a and the recording head 14b has two nozzle rows. One nozzle row of the recording head 14a discharges black (K) ink droplets, and the other nozzle row discharges cyan (C) ink droplets. Further, one nozzle row of the recording head 14b ejects magenta (M) ink droplets, and the other nozzle row ejects yellow (Y) ink droplets. The image forming apparatus 100 a drives the recording head 14 according to the image signal while moving the carriage 13, thereby ejecting ink droplets onto the stopped recording medium 1 to record one scan, thereby recording the recording medium 1. After the predetermined amount is conveyed, the next line is recorded.

  A maintenance / recovery mechanism 15 for the recording head 14 is provided in an area where the carriage 13 does not overlap the recording medium 1 in the scanning direction (right side in FIG. 4). The carriage 13 moves to the position of the maintenance / recovery mechanism 15 when waiting for printing. At this time, the maintenance / recovery mechanism 15 performs a maintenance / recovery operation for removing the nozzle surface of the recording head 14 and dirt on the nozzles. Also, when performing idle ejection, the carriage 13 is moved to the position of the maintenance / recovery mechanism 15 and the thickened ink is ejected. The internal structure of the recording head 14 is the same as the internal structure of the recording head 3 shown in FIGS. 3A and 3B. In addition, illustration and detailed description are abbreviate | omitted about the part which is not directly related to the summary of this Embodiment.

[Configuration of liquid ejection device]
Next, the configuration of the liquid ejection apparatus 200 according to Embodiment 1 will be described with reference to FIG. FIG. 5 is a diagram illustrating a configuration example of the liquid ejection apparatus 200 according to the first embodiment. The liquid ejection device 200 is included in the image forming apparatus 100 and the image forming apparatus 100a.

  As shown in FIG. 5, the liquid ejection device 200 includes a head drive unit 31, a drive waveform generation unit 32, a print signal control unit 33, a controller 34, and N piezoelectric elements 112 (112-1 to 112-). N). The piezoelectric element 112 corresponds to the piezoelectric member 112 described above. The head drive unit 31 drives the piezoelectric elements 112 for one nozzle row of the recording head 3 (or recording head 14). For example, in the case of the image forming apparatus 100 illustrated in FIG. 1, the head driving unit 31 is provided for each recording head and each nozzle row. The head drive unit 31 is composed of one or a plurality of integrated circuits, and at least a portion connected to the piezoelectric element 112 is installed on the FPC board 115.

  The piezoelectric element 112 is driven to eject droplets from N nozzles provided in the recording head 3 (or the recording head 14) according to control by the head driving unit 31. The piezoelectric element 112 is connected to a common potential (for example, ground) together with the other piezoelectric element 112 via the FPC board 115 that transmits a driving waveform, and the other electrode is connected to the head driving unit 31. The

  The print signal control unit 33 separates the image data to be printed into image data corresponding to each recording head and nozzle row, and transfers the image data to the head drive unit 31. Further, the print signal control unit 33 generates a line synchronization signal LS serving as a reference for printing. The N nozzles driven by one head driving unit 31 discharge in synchronization with the line synchronization signal LS, and may be referred to as one dot row on the recording medium 1 (hereinafter referred to as “line” as appropriate). ) Is formed.

  The cycle T of the line synchronization signal LS is determined by the relative speed of the recording medium 1 in the direction perpendicular to the nozzle row direction and the printing resolution (line resolution) in that direction. The relative speed is, for example, the conveyance speed of the recording medium 1 in the case of the image forming apparatus 100 shown in FIG. 1, and the carriage 13 is scanned during printing in the case of the image forming apparatus 100a shown in FIG. Speed. That is, one pixel dot is formed at the period T. The line synchronization signal LS is supplied to the drive waveform generation unit 32 and used as a start reference for drive waveform generation. The line synchronization signal LS is also used when image data is transferred to the head driving unit 31. The line synchronization signal LS is preferably generated for each corresponding head drive unit 31 and the timing is preferably adjusted so that the positions of the dots formed from each nozzle row are aligned.

  In the transfer of image data from the print signal control unit 33 to the head drive unit 31, the print data of N nozzles to be printed within one line cycle is synchronized with the transfer clock SCK using the line synchronization signal LS as a transfer start reference. And transferred serially.

  The drive waveform generator 32 generates a drive waveform Vp for driving the piezoelectric element 112. The drive waveform Vp is generated based on the line synchronization signal LS. In addition, the drive waveform Vp is partly or entirely selected by the head drive unit 31 (a drive waveform selection output unit 37 described later) and applied to each piezoelectric element 112. Details of the drive waveform Vp will be described later.

  The controller 34 is connected to an external device such as a host computer and receives a print request, a print image, and the like. Then, the controller 34 supplies a print image to the print signal control unit 33 based on the print request. The controller 34 has a function of setting drive waveform information generated by the drive waveform generator 32 and a function of setting information for controlling the head driver 31. The head drive unit 31 can be provided integrally with the recording head 3. Hereinafter, a detailed configuration of the head driving unit 31 will be described.

  The head drive unit 31 includes a shift register 35, a latch 36, a plurality of drive waveform selection output units 37 (37-1 to 37-N), and a plurality of swing instruction units 38 (38-1 to 38-N). A drive waveform selection signal generation unit 39 and a head control unit 40. N pieces of print data corresponding to data for one line of the recording head 3 are serially input from the print signal control unit 33 in synchronization with the transfer clock SCK. N pieces of print data input serially are sequentially held in the shift register 35. Assuming that ink droplets corresponding to dots having different quaternary sizes such as large droplets, medium droplets, small droplets, and no ejection are ejected from the nozzles of the recording head 3, one print data is a 2-bit data. It is data. In the present embodiment, the print data represents large droplet = 3, medium droplet = 2, small droplet = 1, and no discharge = 0.

  The latches 36 are N latches that hold the N pieces of print data once held in the shift register 35 by the input of the line synchronization signal LS, and hold 2 bits of data (D1 to DN) per one. Are supplied to the corresponding peristaltic instruction units 38.

  N peristaltic instruction units 38 are provided corresponding to the piezoelectric elements 112 to be driven. The peristaltic instruction unit 38 includes a buffer 41, a conversion unit 42, a peristaltic period generation unit 43, and a non-ejection period detection unit 44. Among these, the buffer 41 is, for example, a FIFO (First In First Out) type buffer constituted by an Nb stage shift register or the like. The buffer 41 stores print data for a plurality of lines Nb. Each time the line synchronization signal LS is input to the buffer 41, the print data Dn (n is a nozzle number) that is output from the latch 36 is input, and the stored oldest print data is output.

  The non-ejection period detection unit 44 detects how long the print data Dn is (number of lines) and non-ejection continues. The peristaltic period generating unit 43 sets the meniscus peristaltic pulse number Nshk immediately before the ejection so that the ejection following the non-ejection period becomes a desired ejection according to the non-ejection period detected by the non-ejection period detection unit 44. decide. The peristaltic period generation unit 43 monitors the output from the last stage of the buffer 41 to Nshk + 1 stage before, and when the output is print data indicating ejection, the peristaltic pulse number Nshk line period, peristaltic instruction signal Shk. Enable (active) and output.

  The conversion unit 42 converts the print data input from the buffer 41 into data indicating the meniscus swing and outputs it when the ejection data is not discharged while the swing instruction signal Shk is valid. On the other hand, the conversion unit 42 outputs the data without conversion when the print data input from the buffer 41 is other than no discharge. In this manner, the peristaltic instruction unit 38 converts the print data so as to perform a predetermined number of peristaltic movements of the meniscus immediately before ejection in accordance with the non-ejection period of the corresponding nozzle, and supplies it to the corresponding drive waveform selection output unit 37. To do.

  The drive waveform selection signal generation unit 39 generates a drive waveform selection signal indicating which part of the drive waveform Vp is selected and supplied to the piezoelectric element 112. The drive waveform selection signal is generated in synchronization with the drive waveform Vp using the line synchronization signal LS as a generation start reference. For example, the drive waveform selection signal generator 39 generates a drive waveform selection signal corresponding to each of a large droplet (M3), a medium droplet (M2), a small droplet (M1), no discharge (M0), and a meniscus swing (M4). Is generated.

  A plurality of drive waveform selection output units 37 (37-1 to 37-N) are provided corresponding to the piezoelectric elements 112 to be driven. The drive waveform selection output unit 37 includes a switch 45 and a selection unit 46. Among these, the selection unit 46 selects one of the drive waveform selection signals M0 to M4 according to the image data supplied from the peristaltic instruction unit 38. The switch 45 switches the drive waveform Vp on and off according to the drive waveform selection signal selected by the selection unit 46. As a result, a drive waveform corresponding to the image data is partially selected and output to the piezoelectric element 112.

  The head control unit 40 performs overall control of the head drive unit 31. Further, the head controller 40 communicates with the controller 34 to set or update information in each block. In FIG. 5, in order not to be complicated, the arrow indicating the output from the head controller 40 is not connected to each block, and the head controller 40 is actually connected to each block.

[Generation of drive waveform selection signal]
Next, generation of a drive waveform selection signal according to the first embodiment will be described with reference to FIG. FIG. 6 is a diagram for explaining a generation example of the drive waveform selection signal according to the first embodiment.

  The drive waveform (drive waveform signal) Vp (FIG. 6B) and the drive waveform selection signals M0 to M4 (FIG. 6 (c-0) to FIG. 6 (c-4)) shown in FIG. Generation is started in synchronization with the LS (FIG. 6A). A drive waveform Vp shown in FIG. 6B is a voltage waveform applied to the piezoelectric element 112, and is generated within one cycle T, for example, as the illustrated waveform. Here, Ve represents a reference potential.

  The drive waveform selection signal shown in FIGS. 6C-0 to 6C-4 is a signal for switching on / off the drive waveform Vp. For example, when the drive waveform selection signal is High, the drive waveform Vp is applied to the piezoelectric element 112 by turning on the switch. On the other hand, during the period when the drive waveform selection signal is low, the switch is turned off to hold the potential just before that. The applied waveform varies depending on which portion of the drive waveform Vp is selectively output, and this causes the nozzle to change the amount of ink droplets when ejected or not.

  The drive waveform selection signal M0 in FIG. 6C-0 is a signal corresponding to the case of “no discharge”, and is kept at the reference potential Ve. If the switch 45 is turned off for a long period of time and no signal is applied to the piezoelectric element 112, the potential drops due to natural discharge, so that the potential is high so that it is applied during the period when the potential is the reference potential Ve. Yes.

  The drive waveform selection signal M1 in FIG. 6C-1 is a signal corresponding to the case of “small droplet discharge”. The drive waveform selection signal M1 is High so as to be applied during the period of FIG. 6 (iv).

  The drive waveform selection signal M2 in FIG. 6C-2 is a signal corresponding to the case of “medium droplet ejection”. The drive waveform selection signal M2 is High so as to be applied during the periods of FIGS. 6 (ii) and 6 (iv).

  The drive waveform selection signal M3 in FIG. 6C-3 is a signal corresponding to the case of “large droplet discharge”. The drive waveform selection signal M3 is High so as to be applied during the periods of FIGS. 6 (ii), 6 (iii), and 6 (iv). That is, within the printing cycle T, large droplets are formed by continuously ejecting ink droplets while changing the droplet velocity using a driving waveform composed of a plurality of pulse trains and coalescing as one droplet during flight. .

  The drive waveform selection signal M4 in FIG. 6C-4 is a signal corresponding to the case of “meniscus oscillation”. The drive waveform selection signal M4 is High so as to be applied during the period of FIG. That is, the vibration of the pulse during the period of FIG. 6 (i) is such that it does not eject from the nozzle, thereby realizing only the oscillation of the meniscus.

  As described above, the selection unit 46 selects one of the drive waveform selection signals M0 to M4 in accordance with the image data indicating ejection or no ejection and the amount of ejected ink droplets, and controls the on / off of the switch 45. Will be.

[Details of automatic instruction section]
Next, a detailed configuration of the peristaltic instruction unit 38 according to the first embodiment will be described with reference to FIG. FIG. 7 is a diagram illustrating a detailed configuration example of the swing instruction unit 38 according to the first embodiment. In FIG. 7, the same reference numerals are assigned to the same blocks as those in the configuration illustrated in FIG. 5, and detailed descriptions of the same functions may be omitted.

  As shown in FIG. 7, the peristaltic instruction unit 38 includes a buffer 41, a conversion unit 42, a peristaltic period generation unit 43, and a non-ejection period detection unit 44. In addition, the peristaltic period generation unit 43 includes a selection unit 51, a peristaltic instruction signal generation unit 52, and a peristaltic period determination unit 55. The non-ejection period detection unit 44 includes a counter control unit 53 and a non-ejection period counter 54.

  The print data Dn input from the latch 36 is output as print data Dn ′ by the buffer 41 with a delay of the buffer stage number Nb lines. The buffer stage number Nb will be described later. Also, some print data in the middle of the data held in the buffer 41 is referred to by the peristaltic period generation unit 43.

  The non-ejection period counter 54 counts the number of lines where the print data Dn is “no ejection” with reference to the line synchronization signal LS, and outputs a count number Cnt. The non-ejection period counter 54 determines whether to count according to the enable signal EN supplied from the counter control unit 53 and resets the counter according to the counter reset signal RST supplied from the counter control unit 53.

  The counter control unit 53 includes an enable signal EN indicating that the non-ejection period counter 54 is enabled (counts) or disabled (not counted), and a counter reset signal RST indicating that the counter is reset. Is output. The enable signal EN is always valid during the printing operation. When data other than “no discharge” is input as the print data Dn, a counter reset signal RST for resetting the counter (reset to “0”) is output.

  Among the data held in the buffer 41, some print data on the way is input to the peristaltic period generation unit 43. Accordingly, the selection unit 51 selects one of the input print data according to the number of peristaltic pulses Nshk. When the output from the selection unit 51 is print data indicating ejection, the peristaltic instruction signal generation unit 52 validates and outputs the peristaltic instruction signal Shk for the period of the peristaltic pulse number Nshk lines.

  When the count number Cnt of the non-ejection period supplied from the non-ejection period counter 54 is equal to or greater than a preset threshold value Th, the peristaltic period determination unit 55 causes the ejection following the non-ejection period to be a desired ejection. In addition, the number of peristaltic pulses Nshk for peristaltic meniscus performed just before discharge is output. In order to add the optimum number of peristaltic pulses Nshk according to the non-ejection period, it is preferable that a plurality of combinations of the threshold Th and the number of peristaltic pulses Nshk are set.

  FIG. 8 is a diagram illustrating a setting example of a combination of the threshold Th and the number of peristaltic pulses Nshk according to the first embodiment. In FIG. 8, four sets of setting values are shown as an example. However, the set values and the number of combinations are not limited to those illustrated. In addition, the optimum number of peristaltic pulses Nshk for each non-ejection period differs depending on the ink characteristics, head structure, ambient environment (especially humidity), and the like. Are preferably updated. Since the non-ejection period is counted by the number of lines, the non-ejection period is set in terms of a value obtained by dividing the non-ejection time Ti [seconds] by the line period T. In the present embodiment, an example is given as a line cycle T = 25 [us] (discharge frequency 40 kHz).

  Further, the peristaltic pulse number Nshk is held until the peristaltic instruction signal Shk becomes valid even if the non-ejection period count number Cnt is reset to zero. If the count number Cnt is greater than or equal to the larger threshold Th, the corresponding number of peristaltic pulses Nshk is changed. The buffer stage number Nb of the buffer 41 is a value obtained by adding “+1” to the maximum value of the set number of peristaltic pulses Nshk. In the example shown in FIG. 8, the number of buffer stages Nb = 101. The maximum value of the assumed number of peristaltic pulses Nshk may be set with some allowance, but if it is too large, a delay time occurs from the input of print data to the start of printing, so the balance is set.

  The print data input from the buffer 41 to the selection unit 51 is print data Nshk + 1 before the last stage. Since the peristaltic period is changed according to the non-ejection period, a plurality of print data corresponding to Nshk that can be employed is input to the selection unit 51. In the example shown in FIG. 8, print data before 6, 11, 51, and 101 steps are input to the selection unit 51, respectively. For example, if Nshk = 5, the print data before the 6th stage is selected, and if the non-ejection time continues and Nshk = 10, the print data is switched to the print data before the 11th stage and output.

  The peristaltic instruction signal generation unit 52 monitors the print data selected and output by the selection unit 51, and when the print data indicates "discharge", the peristaltic instruction signal Shk for the period of the peristaltic pulse number Nshk line. Enable and output. The conversion unit 42 converts the data Dn ″ converted into data indicating that the meniscus is to be moved when the print data Dn ′ input from the buffer 41 indicates “no discharge” when the swing instruction signal Shk is valid. On the other hand, when the print data Dn ′ input from the buffer 41 indicates other than “no discharge”, the conversion unit 42 outputs the data without conversion. In the present embodiment, 1 bit of print data is added, and the meniscus swing = 4.

  Depending on the image, there are nozzles that do not perform ejection even when the non-ejection period significantly exceeds the maximum threshold (Th = 400000, Ti = 10). Since the number of peristaltic pulses greater than the number of stages Nb of the buffer 41 cannot be added, in such a case, the meniscus is perturbed even if it is not immediately before ejection, so that the viscosity of the nozzle portion does not increase excessively. Is preferred. In the example shown in FIG. 8, the peristaltic period determination unit 55 enables the compulsory peristaltic signal Son for forcibly perturbing the meniscus when the count number Cnt of the non-ejection period becomes equal to or greater than the threshold Th = 800,000. The peristaltic instruction signal generation unit 52 is notified. When the forced peristaltic signal Son is valid, the peristaltic instruction signal generation unit 52 enables peristaltic instruction signal Shk during the period of the peristaltic pulse number Nshk line regardless of the output from the selection unit 51.

[Hardware configuration of controller]
Next, the hardware configuration of the controller 34 according to the first embodiment will be described with reference to FIG. FIG. 9 is a block diagram illustrating a hardware configuration example of the controller 34 according to the first embodiment.

  As shown in FIG. 9, the controller 34 includes a CPU (Central Processing Unit) 80, a ROM (Read Only Memory) 81, a RAM (Random Access Memory) 82, a nonvolatile memory 83, an interface 84, and an IO. The interface 85 is connected via the memory bus 86. Note that the memory bus 86 may be separated into a plurality of buses.

  The CPU 80 controls the entire image forming apparatus 100. The ROM 81 stores various information, control programs, and the like. The RAM 82 is used as a work area when various processes are executed. The nonvolatile memory 83 stores device-specific information, updatable information, and the like. The interface 84 mediates exchange of information with an external device such as a host computer. The IO interface 85 mediates exchange of information with each unit in the apparatus. In addition to the head drive unit 31, the drive waveform generation unit 32, and the print signal control unit 33 shown in FIG. 5, an input / output device such as an operation panel, various sensors, and the like are connected to the IO interface 85. The various sensors are, for example, a home position sensor of the carriage 13, a paper position detection sensor that detects the position of the recording medium 1, and a sensor that detects an internal environment such as temperature and humidity. Note that the nonvolatile memory 83 may be configured to be insertable / removable.

[Effects of Embodiment 1]
As described above, in the liquid ejection device 200, the number of meniscus peristaltic pulses is determined for each nozzle according to the non-ejection period, and the meniscus is perturbed immediately before ejection. Even if the discharge periods are different, desired discharge characteristics can be obtained from each nozzle. As a result, the liquid ejection device 200 suppresses ejection failures such as non-ejection and reduces the decrease in ejection speed and ejection droplet volume, and therefore it is possible to inhibit image quality deterioration of the formed image.

  Further, since the liquid ejection device 200 does not cause the meniscus to swing more than necessary with respect to each nozzle, it is possible to suppress the acceleration of ink drying due to the meniscus swinging and to perform emptying for recovery of the ink viscosity. It is possible to reduce the ejection amount and the frequency of idle ejection, improve the productivity of printing, and reduce ink consumption.

(Embodiment 2)
The embodiments of the liquid ejection apparatus 200 according to the present invention have been described so far, but the present invention may be implemented in various different forms other than the above-described embodiments. Therefore, different embodiments for (1) configuration and (2) resetting the count number of the non-ejection period will be described.

(1) Configuration Information including processing procedures, control procedures, specific names, various data, parameters, and the like shown in the above documents and drawings can be arbitrarily changed unless otherwise specified. Each component of the illustrated apparatus is functionally conceptual and does not necessarily need to be physically configured as illustrated. That is, the specific form of the distribution or integration of the devices is not limited to the illustrated one, and all or a part of the distribution or integration is functionally or physically distributed or arbitrarily in any unit according to various burdens or usage conditions. Can be integrated.

  For example, the drive waveform selection signal generation unit 39 may be provided outside the head drive unit 31 and the drive waveform selection signals M0 to M4 may be supplied to the head drive unit 31. Further, a part of the drive waveform selection signals M0 to M4 may be generated by the head drive unit 31. For example, the drive waveform selection signal M4 for selecting a waveform that swings the meniscus is generated by a logical sum of M0 and an inverted signal of M3. As a result, the number of signal lines to be transferred can be reduced.

  Further, for example, the print signal control unit 33 may include a swing instruction unit 38, and the generated swing instruction signal Shk may be transferred together with the print data using serial transfer signal lines SDI and SCK. At this time, the peristaltic instruction signal Shk is sequentially stored in the shift register 35 similarly to the print data, the data for one line is held in the latch 36, and is supplied to the drive waveform selection output unit 37. Further, in the controller 34, the peristaltic instruction signal Shk may be generated corresponding to each pixel together with the processing of the image data.

  In the above embodiment, a plurality of drive waveform elements for ejecting a plurality of types of ink droplets are combined for the drive waveform Vp, and a necessary waveform portion is selectively applied to each piezoelectric element 112 by a switching element. Explained. With respect to the drive waveform Vp, a plurality of drive waveforms corresponding to each type of ejection are generated by the drive waveform generation unit 32, and the drive waveform selection output unit 37 uses an analog multiplexer or the like to select among these drive waveforms. One of these may be selectively output. Moreover, it is good also as a form which combined these.

  FIG. 10 is a diagram illustrating an example of the switching element according to the second embodiment. In FIG. 10, a drive waveform Vp1 is a drive waveform for ejecting large droplets, medium droplets, and small droplets by selective application. The drive waveform Vp2 is a dedicated waveform for swinging the meniscus. The selection unit 47a selectively outputs the drive waveform Vp1 or the drive waveform Vp2 in accordance with the peristaltic instruction signal Shk. The selection unit 46a functions in the same manner as the selection unit 46 described above, and the switch 45a functions in the same manner as the switch 45 described above.

(2) Reset of count number in non-ejection period In the above embodiment, when data other than “no ejection” is input as print data Dn, a counter reset signal RST for resetting the counter is output. Explained. The generation of the counter reset signal RST can be changed as follows according to the count number Cnt. For example, even when the non-ejection period is less than the minimum threshold (for example, Th = 4000, Ti = 0.1) for adding the peristaltic pulse, the viscosity of the ink is increased if the ejection frequency is low. However, it proceeds in the same manner as when the non-ejection period continues. Therefore, even if the non-ejection period is less than the minimum threshold for adding the peristaltic pulse, the counter is reset if the conditions described below are satisfied.

  FIG. 11 is a diagram for explaining an example of resetting the counter according to the second embodiment. For example, as shown in FIG. 11, when one pixel is ejected at intervals of 0.06 seconds, the meniscus is not oscillated if the counter is reset for each ejection. Therefore, when the count number Cnt of the non-ejection period exceeds a predetermined value Thr (for example, Th = 2000, Ti = 0.05) and does not reach the minimum value (4000) of the threshold Th, the ejection is within the predetermined period Trst. The counter is reset when an ink droplet (for example, three pixels) of a predetermined amount Mrst is ejected (value less than Thr).

  In FIG. 11, at the time of discharge of (A), since only 0.06 seconds have passed since the previous discharge, the previous swing is not performed. In addition, at the time of ejection of (B), although only 0.06 seconds have passed since the previous ejection (ejection of A), since the ejection amount in (A) is small, all the thickened ink has been ejected. The thickening of the ink has progressed, and it is better to perform the previous shaking. If the counter of the non-ejection period is not reset during the ejection of (A), the value of the counter of the non-ejection period exceeds 0.1 seconds during the ejection of (B). The meniscus will be perturbed. Note that, as shown in (C), if the thickened ink amount is ejected within a predetermined period, the counter for the non-ejection period is reset.

  Each parameter described above is determined and set in advance through experiments or the like. The predetermined amount Mrst of the ink droplet to be reset may correspond to the volume of the nozzle portion and may be determined according to the ink droplet amount. For example, a large droplet can be discharged once, and a small droplet can be discharged five times. Even if the non-ejection period is equal to or greater than the threshold Th, similarly, a prescribed number of ejections are performed within a predetermined period (Trst may be the same as above or may be set separately) from the ejection after the non-ejection period. If not, the non-ejection period may not be reset and may be moved immediately before the next ejection.

31 Head Drive Unit 32 Drive Waveform Generation Unit 33 Print Signal Control Unit 34 Controller 35 Shift Register 36 Latch 37 Drive Waveform Selection Output Unit 38 Percussion Instruction Unit 39 Drive Waveform Selection Signal Generation Unit 40 Head Control Unit 41 Buffer 42 Conversion Unit 43 Peristaltic Period Generation unit 44 Non-ejection period detection unit 45 Switch 46 Selection unit 112 Piezoelectric member, piezoelectric element 200 Liquid ejection device

Japanese Patent No. 5079912 Japanese Patent No. 5362381 JP2013-240947A

Claims (7)

A plurality of nozzles for discharging liquid;
A pressure generating element that is provided for each of the plurality of nozzles and that swings the meniscus of each of the plurality of nozzles;
A detecting unit for detecting a non-ejection period of each of the plurality of nozzles during a printing operation;
A determination unit that determines a meniscus peristaltic period representing a period during which the meniscus of each of the plurality of nozzles is perturbed based on the detected non-ejection period;
An output unit that outputs a drive waveform for driving each of the pressure generating elements that swing the meniscus of each of the target nozzles during the determined meniscus swing period.   The determination unit is configured to determine the meniscus swing period for the detected non-discharge period based on a set value of a plurality of combinations of a preset non-discharge period and a meniscus swing period. The liquid discharge apparatus according to 1.   The determining unit determines the meniscus peristaltic period when the detected non-ejection period is equal to or greater than a forced peristaltic threshold that is greater than a maximum threshold that is a maximum value of the condition for peristating the meniscus. The liquid ejection device according to claim 1 or 2.   In the situation where the non-ejection period is less than the minimum threshold value that is the minimum value of the condition for swinging the meniscus, the detection unit is an ejection amount that is equal to or greater than a predetermined value that is smaller than the minimum threshold and within a predetermined period from ejection. 4. The liquid ejection apparatus according to claim 1, wherein the count value of the non-ejection period is reset when the value reaches a predetermined amount. 5.   The set value of the non-ejection period and the meniscus swing period is updated according to at least one of an internal environment of the liquid ejection apparatus and a surrounding environment of the liquid ejection apparatus. Item 3. The liquid ejection device according to Item 2. A storage unit for storing a plurality of print data;
A conversion unit that converts the print data that is not a discharge target into print data that includes information indicating that the meniscus is swung when the meniscus swing period;
The output unit outputs the drive waveform for driving the pressure generating element that swings the meniscus of the target nozzle when the print data includes information indicating that the meniscus is swung. The liquid ejection device according to claim 1. A control method executed by a liquid ejection device,
The liquid ejection device includes:
A plurality of nozzles for discharging liquid;
A pressure generating element that is provided for each of the plurality of nozzles and that swings the meniscus of each of the plurality of nozzles;
Detecting a non-ejection period of each of the plurality of nozzles during a printing operation;
Determining a meniscus peristaltic period representing a period during which the meniscus of each of the plurality of nozzles is perturbed based on the detected non-ejection period;
And outputting a driving waveform for driving each of the pressure generating elements that swing the meniscus of each of the target nozzles during the determined meniscus swing period.

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