JP2012125998A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured such that image density does not change even if an environmental temperature changes.SOLUTION: A drive waveform generation section in accordance with a detection temperature is configured to generate and output a drive waveform Pv2 when low temperature is detected, generate and output a drive waveform PvO when normal temperature is detected, and generate and output a drive waveform Pv1 when high temperature is detected. A voltage of a plurality of drive pulses P1 to P7 of the drive waveform Pv1 is lower than a voltage of a plurality of drive pulses P1 to P7 of the drive waveform Pv0. A rate-of-change of the drive pulse P4 of the drive waveform Pv1 with respect to the drive pulses P1 to P7 of the drive waveform PvO is different from that of other drive pulses P1 to P3 and P5 to P7 of the drive waveform Pv1, and the droplet volume of large liquid droplets ejected with the drive pulses P1 to P7 including the drive pulse P4 of the drive waveform Pv1 is made smaller than that of the liquid droplets ejected with the drive waveform PvO.

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus provided with a recording head for discharging droplets.

  As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a plotter, and a complex machine of these, for example, an ink jet recording apparatus is known as an image forming apparatus of a liquid discharge recording method using a recording head for discharging ink droplets. . This liquid discharge recording type image forming apparatus ejects ink droplets from a recording head onto a conveyed paper to form an image (recording, printing, printing, and printing are also used synonymously). Serial type image forming device that forms an image by ejecting droplets while the recording head moves in the main scanning direction, and a line type that forms images by ejecting droplets without the recording head moving There is a line type image forming apparatus using a head.

  In the present application, “image forming apparatus” means an apparatus for forming an image by landing ink on a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. "Image formation" is not only the application of images with meanings such as characters and figures to the medium, but also the addition of images with no meaning such as patterns to the medium (simply applying droplets to the medium) Also means landing). The term “ink” is not limited to what is referred to as ink, but is used as a general term for all liquids that can perform image formation, such as recording liquid, fixing processing liquid, liquid, and resin. . The term “paper” is not limited to paper, but includes the above-described OHP sheet, cloth, and the like, and means that ink droplets adhere to the recording medium, recording medium, recording paper, recording It is used as a general term for what includes what is called paper. 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.

  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, a plurality of droplets are ejected by selecting two or more driving pulses, and a plurality of droplets are combined and landed during flight, thereby forming a plurality of droplet size dots. It is known that a non-ejection pulse for driving the head without droplet ejection is included in the common driving waveform, and that stable ejection is performed by fine driving by selecting the non-ejection pulse in the same manner. ing.

  In the liquid ejection head, the viscosity of the liquid changes with temperature in different environments, and the droplet landing position on the paper is shifted due to the drop velocity Vj becoming faster or slower, or the drop volume Mj. As the value increases or decreases, the shade of the image quality changes or the image quality changes. In addition, when the droplet velocity Vj is increased or decreased, an injection bend may occur or an injection down may occur accordingly.

  Therefore, conventionally, the first waveform element P1 that expands the volume of the pressurizing chamber, the second waveform element P2 that holds the expanded state of the pressurizing chamber, and the volume of the pressurizing chamber is contracted from the expanded state. A drive waveform Pv including a third waveform element P3 for ejecting ink droplets is output, and a potential difference between the first waveform element P1 and the second waveform element P2 at the start of expansion of the volume of the pressurizing chamber is calculated. If the potential difference between the third waveform element P3 and the second waveform element P2 at the end of contraction of the volume of the pressurizing chamber is the second potential difference ΔV2, the first potential difference ΔV1 is 1 when the detected temperature is high. Is known that outputs a drive waveform Pv that reduces the difference between the first potential difference ΔV1 and the second potential difference ΔV2 and increases the difference between the first potential difference ΔV1 and the second potential difference ΔV2 at low temperatures (patent). Reference 1).

JP 2004-42576 A

  Including the configuration disclosed in Patent Document 1 described above, conventionally, when the drive waveform is changed according to the environmental temperature, the drive waveform is changed so that the droplet volume (discharge amount) remains the same even if the environmental temperature changes. (Adjustment) This is because even if the environmental temperature changes, it is considered that images having the same image density can be obtained by making the droplet volumes the same.

  However, it has been found that if the drive waveform is changed so that the drop volume (discharge amount) remains the same even when the environmental temperature changes, the image density decreases as the temperature decreases, and the image density increases as the temperature increases.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve image quality by preventing the image density from changing even when the environmental temperature changes.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head having nozzles for discharging droplets;
Drive waveform generating means for generating and outputting a drive waveform composed of a plurality of drive pulses for discharging droplets for each drive cycle;
Selection means for selecting one or more of the drive pulses according to the droplet size of the droplets discharged from the plurality of drive pulses;
Temperature detection means for detecting the environmental temperature;
Correction means for correcting voltages of the plurality of drive pulses of the drive waveform corresponding to a predetermined reference temperature according to the detected temperature detected by the temperature detection means,
The correction means corrects at least one drive pulse of the plurality of drive pulses with a change rate of the first correction, and the other drive pulse has a second correction different from the change rate of the first correction. Correct with the rate of change,
The change rate of the first correction with respect to the drive pulse of the drive waveform corresponding to the predetermined reference temperature is greater than the change rate of the second correction,
The droplet volume of droplets of a droplet size ejected by one or more drive pulses including the drive pulse corrected at the change rate of the first correction is configured to be smaller as the detection temperature is higher.

An image forming apparatus according to the present invention includes:
A recording head having nozzles for discharging droplets;
Drive waveform generating means for generating and outputting first and second drive waveforms composed of a plurality of drive pulses for discharging droplets in accordance with the environmental temperature for each drive cycle;
Selection means for selecting one or more of the drive pulses according to the droplet size of the droplets discharged from the plurality of drive pulses;
Temperature detecting means for detecting the environmental temperature,
The drive waveform generating means generates and outputs the first drive waveform at least when the detected temperature is low, and outputs the second drive waveform when the detected temperature is high, according to the detected temperature detected by the temperature detecting means. Generate and output the drive waveform of
The voltage of the plurality of drive pulses of the first drive waveform is greater than the voltage of the plurality of drive pulses of the second drive waveform,
At least one drive pulse of the plurality of drive pulses of the second drive waveform has a different rate of change from the other drive pulses with respect to the plurality of drive pulses of the first drive waveform,
The droplet volume of a droplet having a droplet size ejected by one or more drive pulses including one drive pulse having a different rate of change of the second drive waveform is the liquid ejected by the first drive waveform. It was set as the structure smaller than the droplet volume of a droplet.

An image forming apparatus according to the present invention includes:
A recording head having nozzles for discharging droplets;
Drive waveform generating means for generating and outputting first and second drive waveforms composed of a plurality of drive pulses for discharging droplets in accordance with the environmental temperature for each drive cycle;
Selection means for selecting one or more of the drive pulses according to the droplet size of the droplets discharged from the plurality of drive pulses;
Temperature detecting means for detecting the environmental temperature,
The drive waveform generating means is configured to generate and output a drive waveform in which the droplet volume of at least one droplet size droplet becomes smaller as the detected temperature detected by the temperature detecting means becomes higher.

  The image forming apparatus according to the present invention includes a correction unit that corrects voltages of a plurality of drive pulses having a drive waveform corresponding to a predetermined reference temperature in accordance with the detected temperature detected by the temperature detection unit. At least one of the plurality of drive pulses is corrected with the change rate of the first correction, and the other drive pulses are corrected with the change rate of the second correction different from the change rate of the first correction. The change rate of the first correction with respect to the drive pulse having the drive waveform corresponding to the predetermined reference temperature is larger than the change rate of the second correction, and includes the drive pulse corrected at the change rate of the first correction. Alternatively, since the droplet volume of droplets of a droplet size ejected by two or more drive pulses is configured to be smaller as the detection temperature is higher, the image density can be prevented from changing even if the environmental temperature is changed. Can improve image quality. That.

  According to the image forming apparatus of the present invention, the drive waveform generating unit generates and outputs the first drive waveform at least when the detected temperature is low according to the detected temperature detected by the temperature detecting unit. The second drive waveform is generated and output when the voltage is high, and the voltages of the plurality of drive pulses of the first drive waveform are larger than the voltages of the plurality of drive pulses of the second drive waveform, and the plurality of second drive waveforms At least one of the drive pulses is different from the other drive pulses in the rate of change of the first drive waveform with respect to the plurality of drive pulses, and the rate of change in the second drive waveform is different. The droplet volume of a droplet of a droplet size ejected by one or more drive pulses including the droplet volume is configured to be smaller than the droplet volume of a droplet ejected by the first drive waveform, so that the environmental temperature changes. Even if the image density does not change It can be, it is possible to improve the image quality.

  According to the image forming apparatus of the present invention, the drive waveform generation unit generates and outputs a drive waveform in which the droplet volume of at least one droplet size droplet decreases as the detection temperature detected by the temperature detection unit increases. Since the configuration is adopted, the image density can be prevented from changing even when the environmental temperature changes, and the image quality can be improved.

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 explanatory 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 of the drive waveform with which it uses for description of embodiment of this invention. It is explanatory drawing with which it uses for description of the change of the image density with respect to environmental temperature when drop volume is made constant. It is explanatory drawing with which it uses for description of the change of the drop volume with respect to environmental temperature and image density in this invention.

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.

  The carriage 33 has head tanks 35a and 35b as second ink supply units for supplying ink of each color corresponding to the nozzle rows of the recording head 34 (referred to as “head tank 35” when not distinguished). It is equipped with. From the ink cartridges (main tanks) 10y, 10m, 10c, and 10k of the respective colors that are detachably attached to the cartridge loading unit 4 to the head tank 35, the respective colors are supplied by the supply pump unit 24 through the supply tubes 36 of the respective colors. The recording liquid is replenished.

  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 nozzle 104 that discharges droplets (ink droplets) communicates, 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 discharge 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 is lowered, and the volume of the liquid chamber 106 is reduced. By expanding, the ink flows into the liquid chamber 106, and then the voltage applied to the drive piezoelectric column 121A is increased to extend the drive piezoelectric column 121A in the stacking direction, and the diaphragm 102 is deformed in the nozzle 104 direction to form a liquid. By contracting the volume of the chamber 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 discharging the seven 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, and print control unit 508, motor control unit 510, 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 switch, and an analog switch 715 that is turned on / off (opened / closed) by an output of a decoder 713 provided via the level shifter 714.

  The analog switch 715 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, the analog switch 715 is turned on according to the result of decoding the serially transferred image data (gradation data) and the control signals M0 to M3 by the decoder 713, so that 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 drive waveform including ejection pulses for ejecting droplets of three types of droplet sizes (large droplets, medium droplets, and small droplets) and non-ejection pulses 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 seven drive pulses P1 to P7 are generated in time series in synchronization with a reference signal (not shown) within one print 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 P5 is a non-ejection pulse, and the drive pulses P1 to P4, P6, and P7 are ejection pulses.

  Then, the data transfer unit 702 outputs droplet control signals M0 to M3 shown in FIG. Here, as shown in FIG. 7C, the droplet control signal M0 selects the driving pulses P1 to P7 of the driving waveform to generate ejection pulses for large droplets. The droplet control signal M1 selects driving pulses P5 to P7 having a driving waveform and generates ejection pulses for medium droplets. The droplet control signal M2 selects a driving pulse P3 having a driving waveform to generate a droplet ejection pulse. The droplet control signal M3 selects the drive pulse P5 of the drive waveform and generates a non-ejection pulse for fine driving.

Next, driving waveforms in the present invention will be described with reference to FIG.
In the present embodiment, a plurality of drive waveforms, for example, three types of drive waveforms Pv are generated and output as the drive waveform Pv according to the environmental temperature. Here, a drive waveform Pv0 indicated by a solid line at an environmental temperature T0 (for example, 25 ° C .: this is a predetermined reference temperature), and a high temperature drive waveform Pv1 indicated by a broken line at an environmental temperature T1 (for example, 35 ° C.). When the ambient temperature is T2 (for example, 15 ° C.), a low-temperature drive waveform Pv2 indicated by an imaginary line is generated and output according to the detected temperature obtained from the temperature sensor as the ambient temperature detection means included in the sensor group 515.

  When the drive waveform Pv0 is used as a reference, the viscosity of the ink decreases at a high temperature. Therefore, the voltages of the drive pulses P1 to P7 of the high temperature drive waveform Pv1 (potential difference with respect to the reference potential Ve; the same applies hereinafter) of the drive waveform Pv0. The voltage is smaller than the voltage of each drive pulse P1 to P7. On the other hand, since the viscosity of the ink becomes high at low temperatures, the voltages of the drive pulses P1 to P7 of the drive waveform Pv2 for low temperature are set higher than the voltages of the drive pulses P1 to P7 of the drive waveform Pv0.

  Here, the rate of change of the voltage b2 of the drive pulse P4 of the drive pulse P4 for the high temperature drive waveform Pv0 with respect to the voltage a2 of the drive pulse P4 of the drive waveform Pv0 is the voltage of the other drive pulses P1 to P3, P5 to P7 of the drive waveform Pv1 for high temperature. The rate of change of the drive waveform Pv0 (illustrated by the voltage b1 of P3 in the figure) with respect to the voltages of the other drive pulses P1 to P3 and P5 to P7 (illustrated by the voltage a1 of P3 in the figure) is made larger. Specifically, the relationship is “(a1-b1) / a1 <(a2-b2) / a2”.

  That is, the voltages of the drive pulses P1 to P7 of the high-temperature drive waveform Pv1 are smaller than the voltages of the drive pulses P1 to P7 of the drive waveform Pv0, but the drive waveform P4 has other drive pulses P1 to P3. , The voltage is made smaller than P5 to P7.

  In this case, when the rate of change of the drive pulse P4 of the high temperature drive waveform Pv1 is the same as that of the other drive pulses P1 to P3 and P5 to P7, a large droplet ejected with the drive waveform Pv0 and a large droplet ejected with the drive waveform Pv1. The amount of drops is the same. That is, the drive pulses P1 to P3 and P5 to P7 of the high temperature drive waveform Pv1 change at a rate of change at which the drop volume (drop volume) of the large drops is the same.

  On the other hand, as described above, when the rate of change of the drive pulse P4 of the high temperature drive waveform Pv1 is larger than the rate of change of the other drive pulses P1 to P3 and P5 to P7, the voltage of the drive pulse P4 (falling potential). ) Becomes smaller, so that the change rate of the drive pulse P4 is ejected with the drive pulses P1 to P7 including the drive pulse P4 than when the change rate of the other drive pulses P1 to P3 and P5 to P7 is made the same. Drop volume of large droplets is reduced (drop volume is reduced).

  On the other hand, the rate of change of the voltage c2 of the drive pulse P4 of the drive waveform Pv2 for the low temperature with respect to the voltage a2 of the drive pulse P4 of the drive waveform Pv0 is the voltage of the other drive pulses P1 to P3 and P5 to P7 of the low temperature drive waveform Pv2. The rate of change of the drive waveform Pv0 of the drive waveform Pv0 (illustrated by the voltage b1 of P3 in the figure) with respect to the voltages of the other drive pulses P1 to P3 and P5 to P7 (illustrated by the voltage a1 of P3 in the figure) is made larger. Specifically, the relationship is “(c1-a1) / a1 <(c2-a2) / a2”.

  In other words, the voltages of the drive pulses P1 to P7 of the low temperature drive waveform Pv2 are larger than the voltages of the drive pulses P1 to P7 of the drive waveform Pv0, but the drive waveform P4 has other drive pulses P1 to P3. , The voltage is made larger than P5 to P7.

  In this case, when the rate of change of the driving pulse P4 of the low temperature driving waveform Pv2 is the same as that of the other driving pulses P1 to P3 and P5 to P7, large droplets ejected with the driving waveform Pv0 and large droplets ejected with the driving waveform Pv2. The amount of drops is the same. That is, the drive pulses P1 to P3 and P5 to P7 of the low temperature drive waveform Pv2 change at a change rate at which the drop volume (drop volume) of the large drops is the same.

  On the other hand, as described above, when the rate of change of the drive pulse P4 of the low temperature drive waveform Pv2 is larger than the rate of change of the other drive pulses P1 to P3 and P5 to P7, the voltage of the drive pulse P4 (falling potential). ) Becomes larger, the ejection rate is changed to drive pulses P1 to P7 including the drive pulse P4 than when the rate of change of the drive pulse P4 is the same as the rate of change of the other drive pulses P1 to P3 and P5 to P7. Large drop volume increases (drop volume increases).

  In this way, the drive waveform generation unit 701 outputs a drive waveform in which the volume of large droplets decreases as the environmental temperature increases.

Therefore, the relationship between the image density and the droplet amount (drop volume) will be described.
First, as shown in FIG. 9, when large drops having the same drop volume are ejected regardless of the temperature, the higher the temperature, the higher the image density, and the image quality changes depending on the temperature. Decreases.

  On the other hand, as shown in FIG. 10, when a large droplet having a smaller drop volume is ejected as the temperature increases as in the above embodiment, the image density becomes constant and the image quality is improved.

  The plural types of drive waveforms corresponding to the environmental temperature described above, for example, store and hold the data of the drive waveform Pv0 in a ROM or the like, and change the drive waveform Pv0 described above according to the detected temperature (change rate of correction). ) And can be generated and output. In this case, since the correction is performed, the above-described “change rate” is referred to as a correction change rate.

  That is, in the embodiment, the drive waveform generation unit 701 that generates and outputs the drive waveform Pv composed of the plurality of drive pulses P1 to P7 for ejecting droplets for each drive cycle, and the plurality of drive pulses P1. Or selection means (head driver 509) for selecting one or more drive pulses corresponding to the droplet size of the droplets discharged from P7, a temperature sensor (included in the sensor group 515) for detecting the environmental temperature, and detection And a correction means including a control unit 500 that corrects the voltages of the plurality of drive pulses P1 to P7 of the drive waveform Pv0 corresponding to a predetermined reference temperature according to the detected temperature, and includes a plurality of drive pulses P1 to P1. The drive pulse P4 of P7 is corrected by the change rate (change rate) of the first correction, and the other drive pulses P1 to P3 and P5 to P7 are changes of the first correction. The first correction change rate is larger than the second correction change rate, and the drive pulse includes the drive pulse P4 corrected at the first correction change rate. The droplet volume of the discharged large droplet is made smaller as the detection temperature is higher.

  Further, a plurality of types of drive waveform data, for example, drive waveform Pv0Pv1, Pv2 data is stored and held in a ROM or the like in advance, and required drive waveform data is selected and generated according to the detected temperature. Can do.

  That is, in the above embodiment, a drive waveform that generates and outputs drive waveforms Pv2, Pv0, and Pv1 composed of a plurality of drive pulses P1 to P7 that eject droplets in accordance with the environmental temperature in each drive cycle. A generation unit 701, selection means (head driver 509) for selecting one or more drive pulses according to the droplet size of the droplets ejected from the plurality of drive pulses P1 to P7, and a temperature sensor for detecting environmental temperature ( The drive waveform generation unit 701 generates and outputs a drive waveform Pv2 when the detected temperature is low, and generates and outputs a drive waveform Pv0 when the detected temperature is normal temperature, according to the detected temperature. The drive waveform Pv1 when the detected temperature is high is generated and output, and the voltages of the plurality of drive pulses P1 to P7 of the drive waveform Pv1 are the plurality of drive pulses of the drive waveform Pv0. The drive pulse P4 of the drive waveform Pv1 is smaller than the voltage of P1 to P7, and the rate of change with respect to the plurality of drive pulses P1 to P7 of the drive waveform Pv0 is different from the other drive pulses P1 to P3 and P5 to P7. The droplet volume of the large droplets ejected by the drive pulses P1 to P7 including the drive pulse P4 of the waveform Pv1 is made smaller than the droplet volume of the droplets ejected by the drive waveform Pv0.

  In this case, the mutual relationship between the drive waveforms Pv0, Pv1, and Pv2 is such that when the “first drive waveform” in the present invention is the drive waveform Pv2, the “second drive waveform” is the drive waveforms Pv0 and Pv1. When the “first drive waveform” is the drive waveform Pv0, the “second drive waveform” is the drive waveform Pv1.

  In the above embodiment, the drive pulse P4 used only for large droplet formation among the drive pulses P1 to P7 has been described as an example of a change rate different from that of the other drive pulses. However, for example, the drive pulses P1 and P2 Since these are driving pulses used only for large droplet formation, the rate of change of these can be made different from those of other driving pulses. Further, depending on the change in image density, the driving pulse P6 for forming large droplets and medium droplets can have a different rate of change from other driving pulses.

  The image forming apparatus according to the present invention is not limited to a serial type image forming apparatus, but can be applied to a line type image forming apparatus.

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 (3)

A recording head having nozzles for discharging droplets;
Drive waveform generating means for generating and outputting a drive waveform composed of a plurality of drive pulses for discharging droplets for each drive cycle;
Selection means for selecting one or more of the drive pulses according to the droplet size of the droplets discharged from the plurality of drive pulses;
Temperature detection means for detecting the environmental temperature;
Correction means for correcting voltages of the plurality of drive pulses of the drive waveform corresponding to a predetermined reference temperature according to the detected temperature detected by the temperature detection means,
The correction means corrects at least one drive pulse of the plurality of drive pulses with a change rate of the first correction, and the other drive pulse has a second correction different from the change rate of the first correction. Correct with the rate of change,
The change rate of the first correction with respect to the drive pulse of the drive waveform corresponding to the predetermined reference temperature is greater than the change rate of the second correction,
An image characterized in that a drop volume of a droplet having a droplet size discharged by one or more drive pulses including a drive pulse corrected at the change rate of the first correction is smaller as the detection temperature is higher. Forming equipment. A recording head having nozzles for discharging droplets;
Drive waveform generating means for generating and outputting first and second drive waveforms composed of a plurality of drive pulses for discharging droplets in accordance with the environmental temperature for each drive cycle;
Selection means for selecting one or more of the drive pulses according to the droplet size of the droplets discharged from the plurality of drive pulses;
Temperature detecting means for detecting the environmental temperature,
The drive waveform generating means generates and outputs the first drive waveform at least when the detected temperature is low, and outputs the second drive waveform when the detected temperature is high, according to the detected temperature detected by the temperature detecting means. Generate and output the drive waveform of
The voltage of the plurality of drive pulses of the first drive waveform is greater than the voltage of the plurality of drive pulses of the second drive waveform,
At least one drive pulse of the plurality of drive pulses of the second drive waveform has a different rate of change from the other drive pulses with respect to the plurality of drive pulses of the first drive waveform,
The droplet volume of a droplet having a droplet size ejected by one or more drive pulses including one drive pulse having a different rate of change of the second drive waveform is the liquid ejected by the first drive waveform. An image forming apparatus characterized by being smaller than a droplet volume. A recording head having nozzles for discharging droplets;
Drive waveform generating means for generating and outputting first and second drive waveforms composed of a plurality of drive pulses for discharging droplets in accordance with the environmental temperature for each drive cycle;
Selection means for selecting one or more of the drive pulses according to the droplet size of the droplets discharged from the plurality of drive pulses;
Temperature detecting means for detecting the environmental temperature,
The image forming apparatus characterized in that the drive waveform generating means generates and outputs a drive waveform in which the drop volume of at least one droplet size of the droplet becomes smaller as the detected temperature detected by the temperature detecting means becomes higher.

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