JP5838663B2 - Image forming apparatus, program, and liquid ejection head driving method - Google Patents

Description

  The present invention relates to an image forming apparatus, a program, and a liquid ejection head driving method.

  As an image forming apparatus such as a printer, a facsimile machine, a copying machine, a plotter, and a complex machine of these, for example, an ink jet recording apparatus is known as a liquid discharge recording type image forming apparatus using a liquid discharge head for discharging droplets as a recording head. It has been.

  In such an image forming apparatus, for example, a plurality of driving pulses (ejection pulses) for ejecting droplets within one driving cycle are generated in time series and output as a common driving waveform. When forming two or more drive pulses, a plurality of droplets are ejected, and a plurality of droplets are combined and landed during flight, thereby forming dots of a plurality of sizes. It is known that the drive waveform includes a non-ejection pulse that drives the head without droplet ejection, and similarly, by performing fine driving by selecting the non-ejection pulse, stable droplet ejection is performed. Yes.

  With regard to non-ejection pulse application control, there are those that are applied to all nozzles that do not perform droplet ejection in each drive cycle. It is known that this state is applied to a nozzle that has continued for a predetermined number of times (Patent Documents 1 and 2).

JP 2001-315332 A JP 11-314360 A

  However, even if the nozzles that supply non-ejection pulses are limited, it is still insufficient to reduce power consumption. For example, in a general text (character) document, about 5% to 10% of the total area of the paper is a print area, and the rest are often blank. When such an image is printed, when attention is paid to a certain nozzle, there is an ink jet that does not eject droplets at all.

  Therefore, for example, as described in Patent Document 1, the fine driving depends on only the discharge state of the nozzles before the current cycle (reference signal), that is, on the condition that the droplet discharge is not performed for a predetermined time or a predetermined driving cycle. In the configuration in which the pulse is applied, in the case described above, even if the number of times is reduced, the fine driving pulse is applied, and power is wasted.

  The present invention has been made in view of the above problems, and an object thereof is to reduce power consumption while maintaining ejection stability.

In order to solve the above problems, an image forming apparatus according to claim 1 of the present invention provides:
A recording head having nozzles for discharging droplets;
Drive waveform generation means for generating and outputting a drive waveform including a plurality of first pulses for ejecting droplets and a second pulse for causing the liquid in the liquid chamber to flow without ejecting the droplets for each drive cycle; ,
When ejecting droplets from the recording head, a first droplet ejection pulse including the first pulse and the second pulse, or a second droplet ejection pulse including the first pulse and not including the second pulse is used. Means for generating data to select,
The means for generating the data includes:
The sum of the application ratio per unit time of the first droplet ejection pulse with respect to all driving times and the application ratio per unit time of the second droplet ejection pulse with respect to all driving times, calculated from the input image data, When the ratio is below a predetermined ratio,
The second pulse is randomly applied to the driving times to which the first droplet ejection pulse and the second droplet ejection pulse are not applied, and the data is generated so as to reach the predetermined ratio. /> Configuration.

  According to the present invention, it is possible to further reduce power consumption while maintaining ejection stability.

1 is a schematic side view illustrating an overall configuration of a mechanism unit of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the mechanism part. FIG. 4 is a cross-sectional explanatory view in the longitudinal direction of the liquid chamber showing an example of a liquid discharge head constituting the recording head of the image forming apparatus. FIG. 6 is a cross-sectional explanatory view of the liquid discharge head in the lateral direction of the liquid chamber. FIG. 2 is a block explanatory diagram illustrating an overview of a control unit of the image forming apparatus. FIG. 3 is a block diagram illustrating an example of a print control unit and a head driver of the control unit. It is explanatory drawing with which it uses for description of a drive waveform and a pulse of each droplet size. It is explanatory drawing with which it uses for description of the application pattern of the non-ejection pulse in 1st Embodiment of this invention. It is explanatory drawing with which it uses for description of the application example of an ejection pulse similarly. FIG. 10 is also an explanatory diagram for explaining a case where a non-ejection pulse is applied to the application example of FIG. 9 according to the application pattern of FIG. 8. It is explanatory drawing with which it uses for description of the example of application of the ejection pulse and non-ejection pulse in 2nd Embodiment of this invention. FIG. 12 is also an explanatory diagram for explaining a case where a non-ejection pulse is applied to the application example of FIG. 11 according to the application pattern of FIG. 8. It is explanatory drawing with which it uses for description of the example which allocated the non-ejection pulse to the example of ejection pulse application in 3rd Embodiment of this invention. FIG. 14 is an explanatory diagram for explaining a case where a non-ejection pulse is further applied according to an application pattern of FIG. 8 with respect to the ejection pulse application example of FIG. 13 and the non-ejection pulse allocation. It is explanatory drawing with which it uses for description of the example which allocated the non-ejection pulse to the example of ejection pulse application in 4th Embodiment of this invention. FIG. 16 is also an explanatory diagram for explaining a case where non-ejection pulses are further applied according to the application pattern of FIG. 8 for the ejection pulse application example of FIG. 15 and the non-ejection pulse allocation.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory side view for explaining the overall configuration of the image forming apparatus, and FIG. 2 is an explanatory plan view of a main part of the apparatus.
This image forming apparatus is a serial type ink jet recording apparatus, and a carriage 33 is slidable in a main scanning direction by main and sub guide rods 31 and 32 which are guide members horizontally mounted on the left and right side plates 21A and 21B of the apparatus main body 1. It is held and moved and scanned in the direction indicated by the arrow (carriage main scanning direction) in FIG. 2 via a timing belt by a main scanning motor (not shown).

  The carriage 33 is provided with recording heads 34a and 34b composed of liquid ejection heads for ejecting ink droplets of yellow (Y), cyan (C), magenta (M), and black (K). The “recording head 34” is arranged in a sub-scanning direction orthogonal to the main scanning direction, and the ink droplet ejection direction is directed downward.

  Each of the recording heads 34 has two nozzle rows. One nozzle row of the recording head 34a has black (K) droplets, the other nozzle row has cyan (C) droplets, and the recording head 34b has one nozzle row. One nozzle row ejects magenta (M) droplets, and the other nozzle row ejects yellow (Y) droplets. As the recording head 34, a recording head having a nozzle row of each color in which a plurality of nozzles are arranged on one nozzle surface can be used.

  Further, the sub tanks 35a and 35b, which are sub tanks as the second ink supply unit for supplying ink of each color corresponding to the nozzle row of the recording head 34, are referred to as the “sub tank 35” when they are not distinguished. ) Is installed. In the sub tank 35, ink cartridges (main tanks) 10y, 10m, 10c, and 10k of various colors that are detachably attached to the cartridge loading unit 4 are supplied from the ink supply tubes 36 of the respective colors by the supply pump unit 24. The recording liquid is replenished and supplied.

  On the other hand, as a paper feeding unit for feeding the papers 42 stacked on the paper stacking unit (pressure plate) 41 of the paper feeding tray 2, a half-moon roller (feeding) that separates and feeds the papers 42 one by one from the paper stacking unit 41. A separation pad 44 made of a material having a large friction coefficient is provided facing the paper roller 43) and the paper feed roller 43, and the separation pad 44 is urged toward the paper feed roller 43 side.

  In order to feed the paper 42 fed from the paper feeding unit to the lower side of the recording head 34, a guide member 45 for guiding the paper 42, a counter roller 46, a transport guide member 47, and a tip pressure roller. And a holding belt 48 which is a conveying means for electrostatically attracting the fed paper 42 and conveying it at a position facing the recording head 34.

  The transport belt 51 is an endless belt, and is configured to wrap around the transport roller 52 and the tension roller 53 and circulate in the belt transport direction (sub-scanning direction). Further, a charging roller 56 that is a charging unit for charging the surface of the transport belt 51 is provided. The charging roller 56 is disposed so as to come into contact with the surface layer of the transport belt 51 and to rotate following the rotation of the transport belt 51. The transport belt 51 rotates in the belt transport direction of FIG. 2 when the transport roller 52 is rotationally driven through timing by a sub-scanning motor (not shown).

  Further, as a paper discharge unit for discharging the paper 42 recorded by the recording head 34, a separation claw 61 for separating the paper 42 from the conveying belt 51, a paper discharge roller 62, and a spur 63 that is a paper discharge roller. And a paper discharge tray 3 below the paper discharge roller 62.

  A duplex unit 71 is detachably mounted on the back surface of the apparatus body 1. The duplex unit 71 takes in the paper 42 returned by the reverse rotation of the conveyance belt 51, reverses it, and feeds it again between the counter roller 46 and the conveyance belt 51. The upper surface of the duplex unit 71 is a manual feed tray 72.

  Further, a maintenance / recovery mechanism 81 for maintaining and recovering the nozzle state of the recording head 34 is disposed in the non-printing area on one side of the carriage 33 in the scanning direction. The maintenance / recovery mechanism 81 includes cap members (hereinafter referred to as “caps”) 82a and 82b (hereinafter referred to as “caps 82” when not distinguished from each other) for capping the nozzle surfaces of the recording head 34, and nozzle surfaces. A wiper member (wiper blade) 83 for wiping the recording medium, an empty discharge receiver 84 for receiving liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge the thickened recording liquid, and a carriage And a carriage lock 87 for locking 33. A waste liquid tank 100 for storing waste liquid generated by the maintenance recovery operation is mounted on the lower side of the head maintenance recovery mechanism 81 in a replaceable manner with respect to the apparatus main body.

  Further, in the non-printing area on the other side of the carriage 33 in the scanning direction, there is an empty space for receiving liquid droplets when performing empty discharge for discharging liquid droplets that do not contribute to recording in order to discharge the recording liquid thickened during recording or the like. A discharge receiver 88 is disposed, and the idle discharge receiver 88 includes an opening 89 along the nozzle row direction of the recording head 34.

  In this image forming apparatus configured as described above, the sheets 42 are separated and fed one by one from the sheet feed tray 2, and the sheet 42 fed substantially vertically upward is guided by the guide 45, and includes the transport belt 51 and the counter. It is sandwiched between the rollers 46 and conveyed, and the leading end is guided by the conveying guide 37 and pressed against the conveying belt 51 by the leading end pressing roller 49, and the conveying direction is changed by approximately 90 °.

  At this time, a voltage is applied to the charging roller 56 so that a positive output and a negative output are alternately repeated, and the conveying belt 51 is charged with an alternating charging voltage pattern, and the sheet 42 is placed on the charged conveying belt 51. When fed, the paper 42 is attracted to the transport belt 51, and the paper 42 is transported in the sub-scanning direction by the circular movement of the transport belt 51.

  Therefore, by driving the recording head 34 according to the image signal while moving the carriage 33, ink droplets are ejected onto the stopped paper 42 to record one line, and after the paper 42 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 42 has reached the recording area, the recording operation is finished and the paper 42 is discharged onto the paper discharge tray 3.

  When performing the maintenance and recovery of the nozzles of the recording head 34, the nozzle 33 performs the suction from the nozzles by moving the carriage 33 to a position facing the maintenance and recovery mechanism 81 which is the home position and performing capping by the cap member 82. By performing a maintenance and recovery operation such as an empty discharge operation for discharging droplets that do not contribute to image formation, it is possible to perform image formation by stable droplet discharge.

  Next, an example of the liquid discharge head constituting the recording head 34 will be described with reference to FIGS. 3 is a cross-sectional explanatory diagram along the longitudinal direction of the liquid chamber of the head, and FIG. 4 is a cross-sectional explanatory diagram of the head along the lateral direction of the liquid chamber (nozzle arrangement direction).

  The liquid discharge head is formed by bonding and laminating a flow path plate 101, a vibration plate 102 bonded to the lower surface of the flow path plate 101, and a nozzle plate 103 bonded to the upper surface of the flow path plate 101. Ink is supplied to the nozzle communication path 105, which is a flow path through which the nozzles 104 that discharge droplets (ink drops) communicate, the pressurized liquid chamber 106, which is a pressure generation chamber, and the liquid chamber 106 through a fluid resistance portion (supply path) 107. For example, an ink supply port 109 communicating with the common liquid chamber 108 is formed.

  Also, two (as shown in FIG. 3, only one row) stacked piezoelectric elements as electromechanical conversion elements that are pressure generating means (actuator means) for deforming the diaphragm 102 to pressurize the ink in the liquid chamber 106. A member 121 and a base substrate 122 to which the piezoelectric member 121 is bonded and fixed are provided. A plurality of piezoelectric columns 121A and 121B are formed on the piezoelectric member 121 by forming grooves by slit processing that is not divided. In this example, the piezoelectric column 121A is a driving piezoelectric column that applies a driving waveform, and the piezoelectric column 121B is a non-driving piezoelectric column that does not apply a driving waveform. Further, an FPC cable 126 equipped with a drive circuit (drive IC) (not shown) is connected to the drive piezoelectric column 121A of the piezoelectric member 121.

  The peripheral edge of the diaphragm 102 is joined to the frame member 130, and the frame member 130 serves as a through-hole 131 and a common liquid chamber 108 that house an actuator unit composed of the piezoelectric member 121 and the base substrate 122. A recess and an ink supply hole 132 which is a liquid supply port for supplying ink from the outside to the common liquid chamber 108 are formed.

  Here, the flow path plate 101 is formed by, for example, subjecting the single crystal silicon substrate having a crystal plane orientation (110) to anisotropic etching using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH), so that the nozzle communication path 105, Although a recess or a hole serving as the liquid chamber 106 is formed, the invention is not limited to a single crystal silicon substrate, and other stainless steel substrates, photosensitive resins, and the like can also be used.

  The vibration plate 102 is formed from a nickel metal plate, and is manufactured by, for example, an electroforming method (electroforming method). Alternatively, a metal plate or a joining member between a metal and a resin plate may be used. it can. Piezoelectric columns 121A and 121B of the piezoelectric member 121 are bonded to the diaphragm 102 with an adhesive, and a frame member 130 is bonded with an adhesive.

  The nozzle plate 103 forms a nozzle 104 having a diameter of 10 to 30 μm corresponding to each liquid chamber 106 and is bonded to the flow path plate 101 with an adhesive. The nozzle plate 103 is formed by forming a water repellent layer on the outermost surface of a nozzle forming member made of a metal member via a required layer.

  The piezoelectric member 121 is a stacked piezoelectric element (here, PZT) in which piezoelectric materials 151 and internal electrodes 152 are alternately stacked. An individual electrode 153 and a common electrode 154 are connected to each internal electrode 152 drawn out to different end faces of the piezoelectric member 121. In this embodiment, the ink in the liquid chamber 106 is pressurized using the displacement in the d33 direction as the piezoelectric direction of the piezoelectric member 121. However, the pressure in the d31 direction is used as the piezoelectric direction of the piezoelectric member 121. The ink in the liquid chamber 106 may be pressurized.

  In the liquid ejection head configured as described above, for example, the drive piezoelectric column 121A contracts by lowering the voltage applied to the drive piezoelectric column 121A from the reference potential Ve, the diaphragm 102 descends, and the volume of the liquid chamber 106 expands. As a result, the ink flows into the liquid chamber 106, and then the voltage applied to the driving piezoelectric column 121A is increased to extend the driving piezoelectric column 121A in the stacking direction, and the diaphragm 102 is deformed in the nozzle 104 direction to change the liquid chamber. By contracting the volume of the ink 106, the ink in the liquid chamber 106 is pressurized, and ink droplets are ejected (ejected) from the nozzle 104.

  Then, by returning the voltage applied to the drive piezoelectric column 121A to the reference potential, the diaphragm 102 is restored to the initial position, and the liquid chamber 106 expands to generate a negative pressure. The chamber 106 is filled with ink. Therefore, after the vibration of the meniscus surface of the nozzle 104 is attenuated and stabilized, the operation proceeds to the next droplet discharge.

  Note that the driving method of the head is not limited to the above example (drawing-pushing), and striking or pushing can be performed depending on the direction of the drive waveform.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. In addition, the figure is a block explanatory drawing of the control part.
The control unit 500 temporarily stores a CPU 511 that controls the entire apparatus, a ROM 502 that stores fixed data such as a program related to data generation executed by the CPU 511 and other programs, and other image data. In order to control the RAM 503, a rewritable nonvolatile memory 504 for holding data even while the apparatus is powered off, image processing for performing various signal processing and rearrangement on image data, and other overall apparatus. ASIC 505 for processing the input / output signals.

  Further, a print control unit 508 including a data transfer unit for driving and controlling the recording head 34 and a driving signal generating unit, a head driver (driver IC) 509 for driving the recording head 34 provided on the carriage 33 side, Motor drive for driving a main scanning motor 554 that moves and scans the carriage 33, a sub-scanning motor 555 that moves the conveyor belt 51 in a circular motion, and a maintenance and recovery motor 556 that moves the cap 82 and the wiper member 83 of the maintenance and recovery mechanism 81 A unit 510, an AC bias supply unit 511 for supplying an AC bias to the charging roller 56, and the like.

  The control unit 500 is connected to an operation panel 514 for inputting and displaying information necessary for the apparatus.

  The control unit 500 has an I / F 506 for transmitting and receiving data and signals to and from the host side, an information processing device such as a personal computer, an image reading device such as an image scanner, an imaging device such as a digital camera, and the like. From the host 600 side via the cable or network via the I / F 506.

  The CPU 501 of the control unit 500 reads and analyzes the print data in the reception buffer included in the I / F 506, performs necessary image processing, data rearrangement processing, and the like in the ASIC 505, and prints the image data. The data is transferred from the unit 508 to the head driver 509. It should be noted that generation of dot pattern data (generation of data or image data according to the present invention) for outputting an image can be performed by the printer driver 601 on the host 600 side or by the control unit 500.

  The print control unit 508 transfers the above-described image data as serial data, and outputs a transfer clock, a latch signal, a control signal, and the like necessary for transferring the image data and confirming the transfer to the head driver 509. Including a D / A converter for D / A converting D / A conversion of drive pulse pattern data stored in the ROM, a voltage signal amplifier, a current amplifier, and the like, and a drive signal or a plurality of drive pulses Is output to the head driver 509.

  The head driver 509 generates a discharge pulse by selecting a pulse constituting a drive waveform provided from the print control unit 508 based on image data corresponding to one line of the recording head 34 input serially, and generates a recording pulse. The recording head 34 is driven by applying it to a piezoelectric element as pressure generating means for generating energy for ejecting 34 droplets. At this time, by selecting part or all of the pulses constituting the drive waveform or all or part of the waveform elements forming the pulses, for example, dots of different sizes such as large drops, medium drops, and small drops Can be sorted out.

  The I / O unit 513 acquires information from various sensor groups 515 mounted on the apparatus, extracts information necessary for controlling the printer, a print control unit 508, a motor drive unit 510, and an AC bias supply unit. Used to control 511. The sensor group 515 includes an optical sensor for detecting the position of the paper, a thermistor for monitoring the temperature in the machine, a sensor for monitoring the voltage of the charging belt, an interlock switch for detecting opening and closing of the cover, and the like. The I / O unit 513 can process various sensor information.

Next, an example of the print control unit 508 and the head driver 509 will be described with reference to FIG.
The print control unit 508 generates a drive waveform (common drive waveform) composed of a plurality of pulses (drive signals) within one print cycle (one drive cycle) during image formation, and outputs a drive waveform generation unit 701. A data transfer unit 702 that outputs 2-bit image data (gradation signals 0 and 1) corresponding to a print image, a clock signal, a latch signal (LAT), and droplet control signals M0 to M3 is provided.

  The droplet control signal is a 2-bit signal that instructs each droplet to open and close an analog switch 715, which will be described later, of the head driver 209. A pulse or waveform to be selected in accordance with the printing cycle of the common drive waveform. The element makes a state transition to the H level (ON), and when not selected, makes a state transition to the L level (OFF).

  The head driver 509 receives a transfer clock (shift clock) from the data transfer unit 702 and serial image data (gradation data: 2 bits / 1 channel (1 nozzle)), and register values of the shift register 711. Is latched by a latch signal, a decoder 713 that decodes gradation data and control signals M0 to M3 and outputs the result, and a logic level voltage signal of the decoder 713 is a level at which the analog switch 715 can operate. A level shifter 714 that performs level conversion to an analog output, and an analog switch 716 that is turned on / off (opened / closed) by an output of a decoder 713 provided via the level shifter 714.

  The analog switch 716 is connected to the selection electrode (individual electrode) 154 of each drive piezoelectric column 121A, and the common drive waveform from the drive waveform generation unit 701 is input thereto. Therefore, when the analog switch 715 is turned on in accordance with the result of decoding the serially transferred image data (gradation data) and the control signals MN0 to MN3 by the decoder 713, a required pulse (or a common drive waveform) (or Waveform element) is passed (selected) and applied to the drive piezoelectric column 121A.

  Next, drive waveforms will be described with reference to FIG. The drive pulse is a term indicating a pulse as an element constituting a drive waveform, the discharge pulse is a term indicating a pulse applied to the pressure generating means and ejecting a droplet, and the non-discharge pulse is a pressure generating means. Is used as a term indicating a pulse that is applied to the nozzle but does not eject a droplet (flows ink in the nozzle).

  This embodiment is an example of a driving waveform including ejection pulses for ejecting three types of droplets (large droplets, medium droplets, and small droplets) and a non-ejection pulse for performing fine driving. A drive waveform (common drive waveform) Pv as shown in FIG. 7A is output from the drive waveform generation unit 701. This drive waveform Pv is a waveform in which drive pulses P1 to P4 are generated in time series in synchronization with the reference signal within one printing cycle (one drive cycle). The reference signal is a signal output corresponding to the position of the carriage 33 in the main scanning direction according to the density of the image to be formed. The drive pulse P1 is a non-ejection pulse (second pulse), and the drive pulses P2 to P4 are ejection pulses (first pulse).

  Then, the data transfer unit 702 outputs droplet control signals M0 to M3 shown in FIG. The droplet control signal M0 selects the driving pulses P1 to P4 of the driving waveform to generate the large droplet ejection pulses shown in FIG. The droplet control signal M1 selects the driving pulses P2 and P4 of the driving waveform and generates the ejection pulse for the middle droplet shown in FIG. The droplet control signal M2 selects a driving pulse P3 having a driving waveform and generates a droplet ejection pulse shown in FIG. The droplet control signal M3 selects a driving pulse P1 having a driving waveform and generates a non-ejection pulse for fine driving shown in FIG.

  That is, in this example, the large droplet ejection pulse is the first droplet ejection pulse including the drive pulses P2 to P4 that are the first pulse and the non-ejection pulse P1 that is the second pulse. The ejection pulse for use is a second droplet ejection pulse that includes the drive pulses P2 and P4 or P3, which are the first pulses, and does not include the non-ejection pulse P1, which is the second pulse. The interval between the drive pulse P1 and the drive pulse P2 described above is substantially the same as the natural period determined by the pressure chamber, the nozzle, and the ejected ink, or substantially the same as an integer multiple of the natural period. It becomes possible to increase the amount of large droplets efficiently.

  Therefore, the control unit 500 generates data for selecting the non-ejection pulse together with the ejection pulse, and supplies the data to the data transfer unit 702. By selecting the required pulse at each driving time according to the droplet control signal, the control unit 500 selects the desired nozzle. An ejection pulse can be applied.

  Next, a first embodiment of the present invention will be described with reference to FIGS. 8 to 10 are explanatory views schematically showing the waveform application state in the embodiment.

  Here, as shown in each drawing, an example in which a pattern of 100 pixels is drawn with 10 nozzles (nozzles No. 1 to 10) × 10 driving times (driving times 1 to 10) will be described. In each figure, the vertical direction indicates the nozzle number (nozzle No.), and the horizontal direction indicates the number of times of driving.

  First, as shown in FIG. 8, based on a random number table, a nozzle and a driving time for applying a non-ejection pulse (“1”) and a nozzle and a driving time for which a non-ejection pulse is not applied (“0”) are randomly selected. (This is referred to as a “non-ejection pulse application pattern”). In this example, since the ratio of “1” and “0” is the same, even if the ejection pulse is not applied for all the nozzles for all the driving times, the non-ejection pulse is 50%. It will be applied at a rate. That is, in this example, the predetermined ratio is 50%.

  An example in which a large droplet, a medium droplet, and a small droplet are selectively applied to each nozzle in synchronization with the reference pulse based on the input image data with respect to the region of FIG. It is shown in FIG. In this example, image data in which a drive waveform (ejection pulse) is applied to 20 pixels is input to 100 pixels.

  That is, in this example, the sum of the application rate per unit time of the first droplet ejection pulse for all driving times and the application rate per unit time of the second droplet ejection pulse for all driving times is 20%.

  Specifically, the nozzle No. In the actuator corresponding to the 9 nozzles (hereinafter referred to as “nozzle 9”), the medium droplet ejection pulse is applied to the nozzle 2, 3, 5, and 7 in the driving operation 2, and Nozzles 2 and 7 have small droplet ejection pulses, nozzle 3 has medium droplet ejection pulses, drive time 4 has nozzles 2, 3, 5, and 7 have large droplet ejection pulses, and drive time 6 has nozzles 3, 5, 7, and so on. Reference numeral 10 denotes image data for applying a large droplet ejection pulse to the nozzle 5, 7 for the driving time 7, and a small droplet ejection pulse to the nozzle 2, 7 for the driving time 9. In the drive times 5, 8, and 10, no ejection pulse is applied to any nozzle.

  Therefore, as shown in FIG. 10, a non-ejection pulse (fine drive) is applied to a pixel that is “1” (non-ejection pulse application) in FIG. 8 and to which no ejection waveform (any ejection pulse) is applied. Waveform) is generated.

  Thus, with respect to 100 pixels, ejection pulses and fine driving waveforms (non-ejection pulses) for ejecting liquid droplets are necessarily applied to pixels of 50 pixels or more corresponding to 50%, which is a predetermined ratio that is determined in advance. Any one of these will be applied at random.

  By adopting such a configuration, the ejection waveform or the fine drive waveform is applied uniformly to the assumed pixels.

  In the present embodiment, it is assumed that if printing or fine driving is applied with a duty of 50% or more from the liquid discharge head and the ink to be used, there is no problem due to drying of the ink near the nozzle.

  This duty may be changed according to the system used (head configuration and ink type). For example, if the system uses ink that is easy to dry, the duty needs to be increased. Conversely, if the ink is difficult to dry, the duty may be decreased.

  Further, the duty can be changed according to the environment in which the image forming apparatus is used. That is, in an environment where the temperature is high and the humidity is low, drying of the ink is promoted, so that it is required to set the duty high. On the contrary, in an environment where the temperature is low and the humidity is high, stable discharge can be secured even if the duty is set low.

  As described above, in the present embodiment, the application ratio per unit time of the first droplet ejection pulse with respect to all the driving times calculated from the input image data and the unit time of the second droplet ejection pulse with respect to all the driving times. When the sum of the application ratios is equal to or less than a predetermined ratio, data is generated so that the second pulse is applied randomly and the predetermined ratio is reached.

  In this way, the fine drive waveform necessary for stable ejection can be applied as little as possible, and it is possible to achieve both reduction in power consumption and stable ejection.

  Next, a second embodiment of the present invention will be described with reference to FIGS. 11 and 12 show an example of a driving waveform applied to the liquid discharge head and its application diagram.

  First, FIG. 11 is an example in which image data to which the ejection waveform shown in FIG. 9 is applied is input, and a fine driving waveform (non-null) is applied to a pixel to which no waveform is applied in the driving time immediately before the ejection waveform. This is an example of applying a discharge pulse. In this case, the non-ejection pulses are arranged (applied) regardless of the non-ejection pulse application patterns “1” and “0” in FIG.

  FIG. 12 shows a pixel in which no waveform is applied and a pixel which is “1” by using the non-ejection application pattern of FIG. A fine drive waveform (non-ejection pulse) is applied.

  In this way, the fine drive waveform is applied immediately before the drive time for applying the discharge waveform, that is, the first drop discharge pulse and the first drop pulse are applied to the drive time immediately before the first drop discharge pulse and the second drop discharge pulse are applied. When neither of the two-drop ejection pulses is applied, the ejection stability can be further improved by applying the second pulse to the immediately preceding driving time.

  Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 13 and FIG. 14 are explanatory diagrams for explaining the embodiment.

  In the present embodiment, as shown in FIG. 13, “1” and “0” are randomly assigned to pixels in which the pixels to which the ejection waveform is applied are excluded in advance. Here, “1” is a pixel to which fine driving is applied, and the sum of the number of pixels having “1” and the number of pixels to which a driving waveform is applied is 50 for all the pixels 100.

  Then, as shown in FIG. 14, the fine drive waveform is applied to the pixel whose non-ejection pulse application pattern is “1”. Pixels to which neither the ejection waveform nor the fine drive waveform is applied are held at an intermediate potential.

  In the present embodiment, it is assumed that if printing or fine driving is applied with a duty of 50% or more from the liquid discharge head and the ink to be used, there is no problem due to drying of the ink near the nozzle.

  In this configuration, that is, the second pulse is randomly applied to the driving times to which the first droplet ejection pulse and the second droplet ejection pulse are not applied, and data is obtained so as to reach a predetermined ratio. By generating, the sum of the pixels to which the ejection waveform is applied and the pixels to which the fine drive waveform is applied can be made equal to the minimum reduction duty necessary for stable ejection, compared to the above embodiment, The power consumption can be further reduced.

  In this example as well, the duty required for stable ejection may be changed according to the system used. It can also be changed according to the use environment.

  Next, a fourth embodiment of the present invention will be described with reference to FIGS. 15 and 16. 15 and 16 are explanatory diagrams for explaining the embodiment.

  In the present embodiment, as shown in FIG. 15, “1” for applying the fine driving waveform is assigned to the pixel to which no waveform is applied in the driving time immediately before the ejection waveform is applied. This is arranged irrespective of the non-ejection pulse application patterns of “1” and “0” in the pattern of FIG.

  Then, as shown in FIG. 16, the fine drive waveform is applied to the pixel to which no waveform is applied and the non-ejection pulse application pattern is “1”.

  In this way, fine driving is applied immediately before the ejection waveform, that is, either the first droplet ejection pulse or the second droplet ejection pulse is applied to the driving time immediately before application of the first droplet ejection pulse and the second droplet ejection pulse. Is not applied, the second pulse is applied to the previous driving time, and the second pulse is randomly applied to the driving time when the first droplet discharging pulse, the second droplet discharging pulse, and the second pulse are not applied. By generating data so as to reach a predetermined ratio, it is possible to further improve the ejection stability.

  Next, a fifth embodiment of the present invention will be described. In the first embodiment, for all nozzles, the sum of the application rate per unit time of the first droplet ejection pulse for all driving times and the application rate per unit time of the second droplet ejection pulse for all driving times. However, when the ratio is equal to or less than a predetermined ratio, the second pulse is applied at random and data is generated so as to reach the predetermined ratio, but this can be set for each nozzle.

  That is, the application rate per unit time of the first droplet ejection pulse for all the driving times for each nozzle, calculated from the input image data, and the unit time of the second droplet ejection pulse for each nozzle. When the sum of the application ratios is equal to or lower than a predetermined ratio, data can be generated by applying the second pulse at random and reaching the predetermined ratio.

  In this way, for example, even when image data that has never been ejected from a specific nozzle continues, ink thickening near the nozzle can be prevented, and preparation for the next ejection is possible. Thus, the image quality can be improved.

  Generation of data for inserting non-ejection pulses in the above embodiment can be performed by a computer by a program stored in a ROM or the like, and this program can be provided by being stored in a storage medium, or It can be provided by downloading through a network such as the Internet. In addition, when generating image data to be transferred to the image forming apparatus side by the printer driver (program) of the host (information processing apparatus), data for inserting a non-ejection pulse is added and transferred to the image forming apparatus side. You can also.

  In the present application, the “paper” is not limited to paper, but includes OHP, cloth, glass, a substrate, etc., and means a material to which ink droplets or other liquids can be attached. , Recording media, recording paper, recording paper, and the like. In addition, image formation, recording, printing, printing, and printing are all synonymous.

  The “image forming apparatus” means an apparatus that forms an image by discharging liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. “Formation” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium (simply causing a droplet to land on the medium). ) Also means.

  The “ink” is not limited to an ink unless otherwise specified, but includes any liquid that can form an image, such as a recording liquid, a fixing processing liquid, or a liquid. Used generically, for example, includes DNA samples, resists, pattern materials, resins, and the like.

  In addition, the “image” is not limited to a planar image, and includes an image given to a three-dimensionally formed image and an image formed by three-dimensionally modeling a solid itself.

  Further, the image forming apparatus includes both a serial type image forming apparatus and a line type image forming apparatus, unless otherwise limited.

33 Carriage 34, 34a, 34b Recording head (liquid ejection head)
500 Control Unit 508 Print Control Unit 701 Drive Waveform Generation Unit 702 Data Transfer Unit

Claims (6)

A recording head having nozzles for discharging droplets;
Drive waveform generation means for generating and outputting a drive waveform including a plurality of first pulses for ejecting droplets and a second pulse for causing the liquid in the liquid chamber to flow without ejecting the droplets for each drive cycle; ,
When ejecting droplets from the recording head, a first droplet ejection pulse including the first pulse and the second pulse, or a second droplet ejection pulse including the first pulse and not including the second pulse is used. Means for generating data to select,
The means for generating the data includes:
The sum of the application ratio per unit time of the first droplet ejection pulse with respect to all driving times and the application ratio per unit time of the second droplet ejection pulse with respect to all driving times, calculated from the input image data, When the ratio is below a predetermined ratio,
The second pulse is randomly applied to the driving times to which the first droplet ejection pulse and the second droplet ejection pulse are not applied, and the data is generated so as to reach the predetermined ratio. An image forming apparatus characterized by the above. When neither the first droplet ejection pulse nor the second droplet ejection pulse is applied to the driving cycle immediately before the application of the first droplet ejection pulse and the second droplet ejection pulse, the first droplet ejection pulse is applied to the immediately preceding driving cycle. Two pulses are applied, and the second pulse is randomly applied to the first drop discharge pulse, the second drop discharge pulse, and the driving times to which the second pulse is not applied, so as to reach the predetermined ratio. the image forming apparatus according to claim 1, characterized in that to generate the data to. A recording head having nozzles for discharging droplets;
Drive waveform generation means for generating and outputting a drive waveform including a plurality of first pulses for ejecting droplets and a second pulse for causing the liquid in the liquid chamber to flow without ejecting the droplets for each drive cycle; ,
When ejecting droplets from the recording head, a first droplet ejection pulse including the first pulse and the second pulse, or a second droplet ejection pulse including the first pulse and not including the second pulse is used. Means for generating data to select,
The means for generating the data includes:
The application rate per unit time of the first droplet ejection pulse for all the driving times for each nozzle, calculated from the input image data, and the second droplet ejection pulse for all the driving times for each nozzle. When the sum of the application ratios per unit time is equal to or less than a predetermined ratio,
The second pulse is randomly applied to the driving times to which the first droplet ejection pulse and the second droplet ejection pulse are not applied, and the data is generated so as to reach the predetermined ratio. An image forming apparatus characterized by the above. Means for detecting at least one of the ambient temperature and ambient humidity of the device;
The image forming apparatus according to any one of claims 1 to 3, characterized in that changing the predetermined ratio in accordance with a detection result of said means. A recording head having nozzles for discharging droplets;
Drive waveform generation means for generating and outputting a drive waveform including a plurality of first pulses for ejecting droplets and a second pulse for causing the liquid in the liquid chamber to flow without ejecting the droplets for each drive cycle; ,
When ejecting droplets from the recording head, a first droplet ejection pulse including the first pulse and the second pulse, or a second droplet ejection pulse including the first pulse and not including the second pulse is used. A program for causing a computer to perform processing for generating image data to be output by an image forming apparatus.
The sum of the application rate per unit time of the first droplet ejection pulse for all driving times calculated from the input image data and the application rate per unit time of the second droplet ejection pulse for all driving times is calculated in advance. When the ratio is below the specified percentage,
A process of generating the data so that the second pulse is randomly applied to the driving times to which the first droplet ejection pulse and the second droplet ejection pulse are not applied and reaches the predetermined ratio. A program that lets a computer do it. A plurality of first pulses for ejecting droplets and a second pulse for causing the liquid in the liquid chamber to flow without ejecting the droplets for each driving cycle of the liquid ejection head having a nozzle for ejecting droplets. Generate and output drive waveforms including
When ejecting droplets from the liquid ejection head, the first droplet ejection pulse including the first pulse and the second pulse, or the second droplet ejection pulse including the first pulse and not including the second pulse. Generate data to select,
When generating the data,
The sum of the application rate per unit time of the first droplet ejection pulse for all driving times calculated from the input image data and the application rate per unit time of the second droplet ejection pulse for all driving times is calculated in advance. When the ratio is below the specified percentage,
The second pulse is randomly applied to the driving times to which the first droplet ejection pulse and the second droplet ejection pulse are not applied, and the data is generated so as to reach the predetermined ratio. A method for driving a liquid discharge head, characterized in that:

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