JP5359678B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which performs stable image forming without lowering throughput even if a plurality of image data are continuously inputted while making printing by interrupt processing by reducing wasteful ink consumption to prevent the nozzle-down of a non-printing nozzle. <P>SOLUTION: In one embodiment, the disclosed image forming apparatus is equipped with: a recording head in which a plurality of nozzles discharging droplets to a recording medium; a means for performing fine drive to vibrate ink meniscuses of the nozzles without making the nozzles discharge droplets to the recording head; and a means for making control so that the non-discharge nozzles positioned in the recording area of the recording medium are subjected to the fine drive when an image is recorded on the recording medium out of non-discharge nozzles made not to discharge the droplets while those positioned outside the recording area are not subjected to the fine drive. The apparatus performs control so that the fine drive is not performed when the image is not recorded on the recording medium. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a technique of an image forming apparatus.

  As an image forming apparatus such as a printer, a facsimile, a copying apparatus, a plotter, and a multi-function machine of these, for example, an ink jet recording apparatus which is a liquid discharge recording type image forming apparatus using a recording head for discharging ink droplets is known. . In this liquid discharge recording type image forming apparatus, ink droplets are transported from the recording head (not limited to paper, including OHP (Overhead Projector) sheets, etc.), and ink droplets and other liquids adhere to it. Meaning that it is possible, and it is ejected to the recording medium or recording medium, recording paper, recording paper, etc.) and image formation (recording, printing, printing, printing is also used synonymously) .). The liquid ejection recording type image forming apparatus includes a serial type image forming apparatus that forms an image by ejecting liquid droplets while the recording head moves in the main scanning direction, and a liquid droplet recording liquid without moving the recording head. There is a line-type image forming apparatus that uses a line-type head that discharges to form an image.

  In a line-type image forming apparatus, nozzles that do not discharge droplets that contribute to image formation during printing time (referred to as “non-ejection nozzles” or “non-printing”) depending on the recording area (image formation area) and image data of the paper. Nozzle ") occurs. Therefore, as described above, the ink meniscus is always exposed to the atmosphere, and the water in the ink near the nozzle opening volatilizes, thereby increasing the viscosity and causing clogging. In order to prevent this, so-called fine drive control is performed to apply a slight vibration that does not cause ink to be ejected to the non-ejection nozzles, thereby diffusing the ink near the nozzle openings and reducing the viscosity increase of the ink near the nozzle openings. Done.

  However, when fine drive control is performed for a non-ejection nozzle for a short time, an effect of reducing ink thickening near the nozzle opening can be expected. However, if fine drive is performed for a long time, ink increase in the entire liquid chamber is increased. On the contrary, viscosity is promoted. As a result, a phenomenon occurs in which the non-discharge nozzles cannot be continuously used without temporarily stopping the operation of the apparatus (without performing a maintenance operation on the non-discharge nozzles).

  This is due to the fact that, by performing fine driving for a long time, the thickened ink diffuses throughout the liquid chamber of the head, thereby promoting the increase in the ink viscosity of the entire liquid chamber. In particular, as described above, in the line-type image forming apparatus, the time during which the non-ejecting nozzle does not eject droplets tends to be relatively longer than that of the serial-type image forming apparatus. Becomes apparent.

  As a result, for example, when a plurality of consecutive different image data is input by an interrupt process during a printing operation, when it is necessary to form an image using a nozzle that has been a non-discharge nozzle until then, the non-discharge nozzle As a result, the nozzles are clogged and high quality recording cannot be performed.

  In view of the above-described problems, the present invention reduces nozzles of non-printing nozzles by reducing wasteful ink consumption without reducing throughput even when a plurality of image data is continuously input during printing by interruption processing. An object of the present invention is to provide an image forming apparatus that prevents image formation and performs stable image formation.

  According to one embodiment of the disclosed image forming apparatus, a recording head in which a plurality of nozzles that discharge droplets to a recording medium are arranged, and the nozzles of the nozzles are not discharged from the nozzles to the recording head. Means for finely oscillating an ink meniscus, and non-ejection nozzles located in a recording area of the recording medium among non-ejection nozzles that do not eject droplets when recording an image on the recording medium And a means for controlling the non-ejection nozzles located outside the recording area of the recording medium so as not to perform the fine driving, when the image is not recorded on the recording medium. Control is performed without driving.

  The disclosed image forming apparatus prevents a non-printing nozzle from being down without reducing the throughput even if a plurality of image data is continuously input during printing by interrupt processing and reducing wasteful ink consumption. Stable image formation can be performed.

1 is a schematic configuration diagram illustrating an overall configuration of an example of an image forming apparatus according to an exemplary embodiment. 1 is a schematic plan view illustrating an overall configuration of an example of an image forming apparatus according to an embodiment. It is a schematic explanatory view showing an example of a recording head according to the present embodiment. It is a typical explanatory view explaining an example of a head concerning this embodiment. FIG. 5 is a cross-sectional explanatory diagram in a direction orthogonal to a nozzle arrangement direction showing an example of a liquid discharge head constituting the head according to the present embodiment. FIG. 5 is an explanatory cross-sectional view in a direction along a nozzle arrangement direction showing an example of a liquid discharge head constituting the head according to the present embodiment. It is block explanatory drawing explaining the outline | summary of the control part which concerns on this Embodiment. It is block explanatory drawing explaining an example of the head drive control part of the control part which concerns on this Embodiment. FIG. 3 is a schematic plan view for explaining the flow of image formation for explaining the first embodiment. FIG. 5 is a schematic plan view for explaining fine drive control for explaining the first embodiment. It is a typical plane explanatory view used for description of fine drive control used for description of a 2nd embodiment. It is a typical plane explanatory view used for explanation of fine drive control used for explanation of a 3rd embodiment. It is a typical plane explanatory view used for description of fine drive control used for description of a 4th embodiment. It is a typical plane explanatory view used for description of fine drive control used for description of a 5th embodiment. It is typical plane explanatory drawing with which it uses for description of the fine drive control used for description of 6th Embodiment. It is typical plane explanatory drawing with which it uses for description of the fine drive control used for description of 7th Embodiment. It is explanatory drawing with which it uses for description of the drive waveform containing the drive signal which performs the fine drive which concerns on this Embodiment. It is explanatory drawing with which it uses for description of the relationship between the presence or absence of the fine drive which concerns on this Embodiment, and the time to nozzle down. It is explanatory drawing with which it uses for description of the relationship between the discharge amount per predetermined time in the discharge nozzle which concerns on this Embodiment, and the landing delay of the discharge droplet to the recording medium. It is a flowchart which shows the flow of the process which concerns on the idle discharge control which concerns on this Embodiment.

  The best mode for carrying out the present invention will be described with reference to the drawings. First, an image forming apparatus according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram for explaining the overall configuration of the image forming apparatus, and FIG.

  This image forming apparatus is a line type image forming apparatus, and includes an apparatus main body 1, a paper feed tray 2 for stacking and feeding paper 10, a paper discharge tray 3 for discharging and stacking printed paper 10, and paper 10. An image forming unit 5 that includes a recording head 51 that discharges and prints droplets on a sheet 10 conveyed by the conveying unit 4, and Ink is applied to the cleaning device 6 that is a maintenance and recovery mechanism that performs maintenance and recovery of each recording head of the image forming unit 5 at a required timing, a conveyance guide portion 7 that opens and closes the cleaning device 6, and each recording head 51 of the image forming unit 5. Ink tank unit 8 for supplying ink, and main tank unit 9 for supplying ink to ink tank unit 8 are provided.

  The apparatus main body 1 includes front and rear side plates and stays (not shown), and the sheets 10 stacked on the sheet feed tray 2 are fed one by one to the transport unit 4 by a separation roller 21 and a sheet feed roller 22. Is done.

  The transport unit 4 includes a transport drive roller 41a, a transport driven roller 41b, and an endless transport belt 43 wound around these rollers 41a and 41b. A plurality of suction holes (not shown) are formed on the surface of the transport belt 43, and a suction fan 44 that sucks the paper 10 is disposed below the transport belt 43. Further, conveyance guide rollers 42a and 42b are respectively held on guides (not shown) on the conveyance driving roller 41a and conveyance driven roller 41b and are in contact with the belt 43 by their own weight.

  The conveyance belt 43 rotates around when the conveyance drive roller 41 a is rotated by a motor (not shown), and the paper 10 is sucked onto the conveyance belt 43 by the suction fan 44 and is conveyed by the rotation movement of the conveyance belt 43. The transport driven roller 41 b and the transport guide rollers 42 a and 42 b rotate following the transport belt 43.

  An image forming unit 5 including a plurality of recording heads 51 including a plurality of head units that discharge droplets to be printed on the paper 10 is disposed above the transport unit 4 so as to be movable in the arrow A direction. The image forming unit 5 is moved to above the cleaning device 6 during the maintenance / recovery operation (during cleaning).

  The image forming unit 5 has a plurality of recording heads 51y, 51m, 51c, and 51k (hereinafter, no distinction between colors) that discharges yellow (Y), magenta (M), cyan (C), and black (K) color inks. In some cases, a code without sub-codes y, m, c, and k is used (the same applies to other members and the like). As shown in FIG. 3, each recording head 51 has 10 heads (liquid ejection heads) 101 </ b> A to 101 </ b> J arranged in a staggered pattern on the head support member 100, and the nozzle arrangement direction intersects the paper transport direction. (In this case, the directions are orthogonal to each other, but can also be obliquely intersected.). As shown in FIG. 4, each head 101 has a nozzle surface 203 a in which nozzle rows in which a plurality of nozzles 204 that eject droplets are arranged side by side are arranged in two rows in a staggered manner. Note that the configuration of the recording head 51 is not limited to these examples.

  In this image forming unit 5, a distributor (branching member) 52 that is a branching section that supplies ink of a required color to the head 101 of each recording head 51 is disposed above each recording head 51. The liquid discharge heads 101 are connected by a supply tube 53. On the upstream side of the distributor 52, an ink tank 81 of the ink tank unit 8 (only one ink tank is provided with a sign for convenience of illustration) is supplied to the recording head 51 via a supply tube 82, A negative pressure is formed on the recording head 51 due to a water head difference between the ink tank 81 and the recording head 51. The ink tank unit 8 is arranged so as to be movable in the direction of arrow A together with the image forming unit 5.

  Further, the main tank unit 9 is disposed on the upstream side of the ink tank 81, and ink is supplied from the main tank 91 through the supply tube 92 to the ink tank 81.

  On the downstream side of the transport unit 4, a transport guide unit 7 that discharges the paper 10 to the paper discharge tray 3 is provided. The sheet 10 guided and conveyed by the conveyance guide unit 7 is discharged to the sheet discharge tray 3. The paper discharge tray 3 includes a pair of side fences 31 that regulate the width direction of the paper 10 and an end fence 32 that regulates the front end of the paper 10.

  The maintenance / recovery mechanism (cleaning device) 6 includes four rows of cleaning means 61 corresponding to each recording head 51 of the image forming unit 5, and one cleaning means 61 includes ten heads 101 of the recording head 51. 10 cap members 62 corresponding to, and a wiper member (not shown). Note that the cap member 62 can be moved up and down independently. Further, a suction pump 63 for sucking ink from the nozzles 204 of the head 101 while the nozzle surface 203 a of the head 101 is capped by the cap member 62 is disposed below the cleaning unit 61.

  Further, in this image forming apparatus, after the printing is finished, when ink is sucked from the nozzle 102 in a state where the head 101 that discharges droplets is capped by the cleaning unit 61, or ink adhered to the nozzle surface 203 a of the head 101. Is cleaned by the cleaning means 61, after the printing is stopped, the entire transport unit 4 rotates in the direction of arrow B with the transport driven roller 41b as a fulcrum, and the space between the image forming unit 5 is larger than that at the time of image formation. Thus, a space for moving the image forming unit 5 is secured. At this time, the guide plate 71 of the conveyance guide portion 7 disposed on the upper portion of the cleaning device 6 is also rotated upward in the direction of the arrow C at the fulcrum 72, and the upper portion of the cleaning device 6 is opened.

  Then, after the transport unit 4 and the transport guide portion 7 are released (released), the image forming unit 5 moves in the paper passing direction (in the direction of arrow A), stops above the cleaning device 6, and the cleaning unit 61. Rise to shift to the cleaning operation (maintenance recovery operation) of the head 101 of each recording head 51.

  Next, with reference to FIGS. 3 and 4, an example of a liquid discharge head constituting the head 101 as one of the recording heads 51 will be described. 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).

  This liquid discharge head includes, for example, a flow path plate 201 formed by anisotropic etching of a single crystal silicon substrate, a vibration plate 202 formed by, for example, nickel electroforming bonded to the lower surface of the flow path plate 201, and a flow path A nozzle plate 203 bonded to the upper surface of the plate 201 is bonded and stacked, and a nozzle communication passage 205 that is a flow path through which a nozzle 204 that discharges droplets (ink droplets) communicates therewith and a liquid chamber that is a pressure generation chamber. 206, an ink supply opening 209 communicating with the common liquid chamber 208 for supplying ink to the liquid chamber 206 through the fluid resistance portion (supply path) 207, and the like are formed.

  Further, two rows of driving piezoelectric elements (only one row is shown in FIG. 5) as electromechanical conversion elements which are pressure generating means (actuator means) for deforming the diaphragm 202 to pressurize the ink in the liquid chamber 206 A laminated piezoelectric element member 221 having a column 221a and a base substrate 222 to which the piezoelectric element member 221 is bonded and fixed are provided. The laminated piezoelectric element member 221 is provided with a non-driving piezoelectric element column 221b serving as a supporting column between the driving piezoelectric element columns 221a. These piezoelectric element columns 221a and 221b are formed by slitting the piezoelectric element member 221 while leaving a part thereof. Further, an FPC cable 226 equipped with a drive circuit (drive IC) (not shown) is connected to the drive piezoelectric element column 221a of the piezoelectric element member 221.

  The periphery of the diaphragm 202 is joined to the frame member 230. The frame member 230 includes a through-portion 231 and a common liquid chamber 208 that house an actuator unit composed of the piezoelectric element member 121, the base substrate 222, and the like. An ink supply hole 232 for supplying ink to the common liquid chamber 208 from the outside is formed.

  Here, the flow path plate 201 is formed by, for example, subjecting the single crystal silicon substrate having a crystal plane orientation (110) to an anisotropic etching using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH), so that the nozzle communication path 205, Although a recess or a hole serving as the liquid chamber 206 is formed, it is not limited to a single crystal silicon substrate, and other stainless steel substrates, photosensitive resins, and the like can also be used.

  The diaphragm 202 is formed from a nickel metal plate, and is manufactured by, for example, an electroforming method (electroforming method). In addition, a metal plate or a joining member between a metal and a resin plate may be used. it can. A driving piezoelectric element column 221a and a non-driving piezoelectric element column 221b serving as a supporting column are bonded to the diaphragm 202 with an adhesive, and a frame member 230 is bonded with an adhesive.

  The nozzle plate 203 forms a nozzle 204 having a diameter of 10 to 30 μm corresponding to each liquid chamber 206 and is bonded to the flow path plate 201 with an adhesive. The nozzle plate 203 has a water repellent layer formed on the outermost surface of a nozzle forming member made of a metal member with a required layer interposed therebetween.

  The piezoelectric element member 221 is a stacked piezoelectric element (here, PZT) in which piezoelectric materials 251 and internal electrodes 252 are alternately stacked. An individual electrode 253 and a common electrode 254 are connected to each internal electrode 252 drawn to different end faces of the driving piezoelectric element column 221a of the piezoelectric element member 221. In this embodiment, the ink in the liquid chamber 206 is pressurized using the displacement in the d33 direction as the piezoelectric direction of the piezoelectric element member 221, but the displacement in the d31 direction is used as the piezoelectric direction of the piezoelectric element member 221. A configuration may be adopted in which the ink in the pressurized liquid chamber 206 is pressurized. Alternatively, a structure in which one row of driving piezoelectric element columns 221a is provided on one substrate 222 may be employed.

  In the liquid discharge head configured as described above, for example, the voltage applied to the drive piezoelectric element column 221a is lowered from the reference potential, so that the drive piezoelectric element column 221a contracts, and the vibration plate 202 descends to reduce the volume of the liquid chamber 206. When the ink expands, the ink flows into the liquid chamber 206, and then the voltage applied to the drive piezoelectric element column 221a is increased to extend the drive piezoelectric element column 221a in the stacking direction, and the diaphragm 202 is deformed in the nozzle 204 direction. By contracting the volume / volume of the liquid chamber 206, the ink in the liquid chamber 206 is pressurized, and ink droplets are ejected (jetted) from the nozzle 204.

  Then, the diaphragm 202 is restored to the initial position by returning the voltage applied to the driving piezoelectric element column 221a to the reference potential, and the liquid chamber 206 expands to generate a negative pressure. The liquid chamber 206 is filled with ink. Therefore, after the vibration of the meniscus surface of the nozzle 204 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 overview of the control unit of the image forming apparatus will be described with reference to a block diagram shown in FIG. The control unit 500 includes a CPU 501 also serving as a unit for controlling the idle ejection operation and fine driving according to the present invention, which controls the entire apparatus, a ROM 502 for storing programs executed by the CPU 501 and other fixed data, and an image. RAM 503 for temporarily storing data, rewritable non-volatile memory 504 for holding data even while the apparatus is powered off, image processing for performing various signal processing, rearrangement, etc. on image data, and others And an ASIC 505 for processing input / output signals for controlling the entire apparatus.

  In addition, a data transfer unit for driving and controlling the heads 101 constituting each recording head 51, a head drive control unit 508 including a drive signal generating unit, and a head driver (driver) for driving each head 101 of the recording head 51 IC) 509, an image forming unit moving motor driving unit 511 for driving the image forming unit moving motor 510 for moving the image forming unit 5, and a conveying belt moving motor driving unit 513 for driving the conveying belt moving motor 512. A suction motor driving unit 515 that drives a suction motor 514 for the suction fan 44, and an I / 516 that inputs information from various sensors.

  Here, in the I / O 514, as sensor information, an environmental sensor (not shown) for detecting environmental temperature and environmental humidity, a paper sensor 521 for detecting paper provided in the head module array 50, and an empty ejection position of the transport belt 43 are detected. Various detection signals are input from a phase sensor 522 or the like that detects phase information teaching means (not shown).

  The control unit 500 is connected to an operation panel 517 for inputting and displaying information necessary for the apparatus.

  Here, the control unit 500 prints data including image data from the host side such as an information processing device such as a personal computer (hereinafter referred to as a PC), an image reading device such as an image scanner, and an imaging device such as a digital camera. The data is received by the host I / F 506 via a cable or a net.

  The CPU 501 reads and analyzes the print data in the reception buffer included in the host I / F 506, performs data rearrangement processing and the like (some image processing in some cases) by the ASIC 505, and the head. The image data is transferred to the drive control unit 508. The conversion of the print data for image output into bitmap data (print raster data) is performed by developing the image data into bitmap data using a printer driver on the host side and converting the bitmap data (print raster data) of the print data. After the creation, the print raster data is transferred to this apparatus.

  At this time, the CPU 501 analyzes in parallel the discharge nozzles used at the time of printing based on the image data, and creates an empty discharge pattern corresponding to the nozzle use frequency. The idle ejection pattern when ejecting into the recording area is such that the drops do not concentrate in one place or form a specific line or texture so that it is difficult for human vision to recognize. It becomes. Further, when the idle discharge is performed to the idle discharge receptacle through the hole of the conveyance belt, the idle discharge pattern corresponding to the hole of the conveyance belt is formed. The created idle ejection pattern is combined with the image data and transferred to the head drive control unit 508 as print raster data.

  Upon receiving the print raster data, the head drive control unit 508 sends this dot pattern data (print raster data) as serial data to the head driver 509 in synchronization with the clock signal, and also outputs a latch signal at a predetermined timing. The data is sent to the head driver 509.

  The head drive control unit 508 includes a ROM (can also be configured by the ROM 502) that stores pattern data of drive waveforms (drive signals), and a D / A converter that D / A converts the drive waveform data read from the ROM. A waveform generation circuit including an A converter and a drive waveform generation circuit including an amplifier and the like are included.

  The head driver 509 receives a clock signal from the head drive control unit 508 and serial data as image data, and a latch circuit that latches the register value of the shift register using a latch signal from the head drive control unit 508. A level conversion circuit (level shifter) that changes the output value of the latch circuit, an analog switch array (switch means) that is controlled to be turned on / off by the level shifter, and the like, and controls on / off of the analog switch array. As a result, a required drive waveform included in the drive waveform is selectively applied to the actuator means of the head unit 51 to drive the head, and the image data is printed to form a dot pattern.

  Next, an example of the head drive control unit 508 will be described with reference to the block diagram of FIG. As described above, the head drive control unit 508 generates and outputs a drive waveform (common drive waveform) composed of a plurality of drive pulses (drive signals) within one printing cycle at the time of image formation. A drive waveform generation unit 701 that generates and outputs a drive waveform (common drive waveform) composed of a plurality of drive pulses (drive signals) within one idle ejection cycle, and 2-bit image data (floor) corresponding to the print image And a data transfer unit 702 that outputs a clock signal, a latch signal (LAT), and droplet control signals M0 to M3.

  The droplet control signal is a 2-bit signal that instructs each droplet to open and close the analog switch 715 that is a switch unit of the head driver 209. The droplet control signal is a waveform to be selected according to the printing cycle of the common drive waveform. State transition to ON), and state transition to L level (OFF) when not selected.

  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 for level conversion to an analog switch 716 and an analog switch 716 that is turned on / off (opened / closed) by the output of the decoder 713 provided via the level shifter 714 are provided.

  The analog switch 716 is connected to a selection electrode (individual electrode) 254 of each piezoelectric element 221 of each head 101, and a common drive waveform from the drive waveform generation unit 701 is input thereto. Accordingly, 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 drive signal constituting the common drive waveform is obtained. Passing (selected) is applied to the piezoelectric element 221.

  Next, a first embodiment of the image forming apparatus will be described with reference to FIGS. FIG. 9 is a schematic explanatory view of the image forming apparatus, and FIG. 10 is an explanatory view for explaining the fine drive control of the embodiment.

  As shown in FIG. 9, in this image forming apparatus, the sheet 10 fed from the sheet feeding cassette 2 is detected by the sheet detection sensor while being conveyed by the conveyance belt 43, and then is detected from the head 101 of the recording head 51. At this timing, droplets are ejected according to the image data, whereby an image is formed on the paper 10 and discharged onto the paper discharge tray 3.

  Here, when an image is formed (recorded) using the entire control unit paper 10 as a recording area, droplets are not collected from non-ejection nozzles that do not eject droplets but are located in the sheet (recording medium). A fine drive is performed to vibrate the ink meniscus without discharging, and further, the fine drive is not performed until the next paper arrives after the paper has passed. On the other hand, the non-ejection nozzle located outside the paper is controlled not to be finely driven.

  For example, as illustrated in FIG. 10, the heads 101A, 101B, 101I, and 101J among the heads 101A to 101J constituting the recording head 51 form an image in the nozzle arrangement direction (direction intersecting with the paper conveyance direction). Located outside the paper 10, the heads 101C to 101H are located outside the paper 10 on which an image is to be formed.

  At this time, among the heads 101C to 101H located in the paper 10, the nozzles of the heads 101C and 101H are non-ejection nozzles because they do not eject droplets for recording the image 800. Therefore, the nozzles of the head 101C and the head 101H are finely driven to oscillate the ink meniscus without discharging droplets, and further finely driven until the next paper arrives after the paper 10 passes. Have no control. On the other hand, the nozzles of the heads 101A, 101B, 101I, and 101J located outside the paper 10 are non-ejection nozzles because they do not eject liquid droplets for recording the image 800, but these heads 101A, 101B, 101I, and 101J. The nozzles are controlled so as not to perform the fine driving.

  In other words, in this embodiment, among the plurality of heads (heads 101A to 101J) constituting the recording head 51, image formation is not actually performed (not contributing) among the heads located in the paper in the nozzle arrangement direction. ) The head is finely driven, and further, the fine drive is not performed until the next paper arrives after passing the paper, while the head located outside the paper is not finely driven. .

  As described above, when an image is recorded on a recording medium using a recording head in which a plurality of heads in which a plurality of nozzles for discharging droplets are arranged on the recording medium are arranged in the nozzle arrangement direction, Of the non-ejection nozzles that do not eject droplets, finely drive the non-ejection nozzles of the head in which all the nozzles are located in the recording medium, and further, after passing the recording medium until the next recording medium arrives As a result, the fine drive is not performed for the non-ejection nozzles of the head including the nozzles located outside the recording medium. It is possible to prevent the occurrence of ejection failure due to thickening of the ink, and stable image formation can be performed.

  For example, when forming an image larger than the image during the printing operation added by the interrupt process during the printing operation, even when using a non-ejection nozzle that has not been used until then, the ink in the liquid chamber by fine driving is used. Therefore, the interruption image can be formed without causing a discharge failure.

  Next, a second embodiment of the image forming apparatus will be described with reference to FIG. FIG. 11 is an explanatory diagram for explaining the fine drive control of the embodiment. Here, when forming (recording) an image using the entire sheet 10 as a recording area, when using the recording head 51 in which a plurality of heads are arranged, droplets of a head in which all nozzles are located in the sheet 10 are ejected. Including non-ejection nozzles that are not allowed to perform fine driving to vibrate the ink meniscus without ejecting droplets, and control that is not finely driven until the next paper arrives after passing through the paper, including nozzles located outside the paper Control is performed not to finely drive the non-ejection nozzles of the head.

  For example, as shown in FIG. 11, among the heads 101A to 101J constituting the recording head 51, the heads 101A and 101J are located outside the paper 10 on which an image is formed, and the heads 101B and 101I have some nozzles on the paper 10 Located in. Of the heads 101C to 101H located in the paper 10, all the nozzles of the heads 101C and 101H are used for forming the image 800, and the heads 101D and 101G have some nozzles used for forming the image 800. The remaining nozzles are not used to form the image 800, and the heads 101E and 101F have a positional relationship in which all nozzles are not used to form the image 800.

  At this time, all the nozzles of the heads 101E and 101F that are located in the paper 10 but are non-ejection nozzles, and the head 101D that is a non-ejection nozzle that is located in the paper 10 but not used for forming the image 800. The remaining nozzles of 101G are finely driven to vibrate the ink meniscus without discharging droplets, and are further controlled not to be finely driven until the next paper arrives after passing through the paper 10. On the other hand, the nozzles of the heads 101A and 101J, which are all non-ejection nozzles with all the nozzles positioned outside the paper 10, are not finely driven. In addition, the heads 101B and 101F, in which some nozzles are located outside the paper 10 and serve as non-ejection nozzles, are located outside the paper 10 and serve as non-ejection nozzles and within the paper 10, but the image 800 is formed. Therefore, the nozzles that are non-ejection nozzles are not finely driven.

  As described above, when an image is recorded on a recording medium using a recording head in which a plurality of heads in which a plurality of nozzles for discharging droplets are arranged on the recording medium are arranged in the nozzle arrangement direction, During non-ejection nozzles that do not eject droplets, finely drive the non-ejection nozzles of the head where all nozzles are located in the recording medium, and after the recording medium passes until the next recording medium arrives Control that does not finely drive, and control that does not finely drive the non-ejection nozzles of the head including nozzles located outside the recording medium. Will be able to do.

  Next, a third embodiment of the image forming apparatus will be described with reference to FIG. FIG. 12 is an explanatory diagram for explaining the fine drive control of the embodiment. Here, when forming (recording) an image using the entire sheet 10 as a recording area, when using a recording head 51 in which a plurality of heads are arranged, a non-ejection nozzle that does not eject droplets of a head located in the sheet 10 Is finely driven to vibrate the ink meniscus without discharging droplets, and is located in the paper 10 among the nozzles of the head located outside the paper 10 and a part of the head located in the paper 10. A non-ejection nozzle that does not eject droplets is finely driven, and after the recording medium passes until the next recording medium arrives, control is performed so that the fine driving is not performed. The non-ejection nozzle that does not eject the nozzle is controlled not to be finely driven.

  For example, as shown in FIG. 12, among the heads 101A to 101J constituting the recording head 51, the heads 101A and 101J are located outside the paper 10 on which an image is formed, and the heads 101B and 101I have some nozzles on the paper 10 Located in. Of the heads 101C to 101H located in the paper 10, all the nozzles of the heads 101C and 101H are used for forming the image 800, and the heads 101D and 101G have some nozzles used for forming the image 800. The remaining nozzles are not used to form the image 800, and the heads 101E and 101F have a positional relationship in which all nozzles are not used to form the image 800.

  At this time, all the nozzles of the heads 101E and 101F that are located in the paper 10 but are non-ejection nozzles, and the head 101D that is a non-ejection nozzle that is located in the paper 10 but not used for forming the image 800. The remaining nozzles of 101G are finely driven to vibrate the ink meniscus without discharging droplets, and are controlled not to be finely driven until the next recording medium arrives after passing through the recording medium. On the other hand, the nozzles of the heads 101A and 101J, which are all non-ejection nozzles with all the nozzles positioned outside the paper 10, are not finely driven. Further, the heads 101B and 101F in which some nozzles are located outside the paper 10 finely drive the nozzles which are located in the paper 10 but are not used for forming the image 800, so that they become non-ejection nozzles. Control is performed not to finely drive after the passage until the next recording medium arrives. No fine driving is performed for the nozzles located outside the paper 10 and serving as non-ejection nozzles.

  As described above, when an image is recorded on a recording medium using a recording head in which a plurality of heads in which a plurality of nozzles for discharging droplets are arranged on the recording medium are arranged in the nozzle arrangement direction, Of the non-ejection nozzles that do not eject droplets, fine driving is performed for the non-ejection nozzles of the head in which all nozzles are located in the recording medium and the non-ejection nozzles of the head in which some nozzles are located in the recording medium. Further, control is performed such that the fine drive is not performed until the next recording medium arrives after passing through the recording medium. Further, fine driving is performed for the non-ejection nozzles of the head where all the nozzles are located outside the recording medium and the non-ejection nozzles located outside the recording medium of the head where some nozzles are located within the recording medium. Therefore, the ejection failure due to the fine drive control can be eliminated and stable image formation can be performed.

  That is, in this embodiment, the presence or absence of fine driving is controlled in units of nozzles, and the non-ejection nozzles outside the paper 10 are not finely driven, and the non-ejection nozzles in the paper 10 are finely driven. The fine driving is not performed until the next recording medium arrives after passing through the recording medium.

  Next, a fourth embodiment of the image forming apparatus will be described with reference to FIG. FIG. 13 is an explanatory diagram for explaining the fine drive control of the embodiment. Here, each of the above embodiments is an example in which the entire width of the paper 10 in the nozzle arrangement direction is the recording area, whereas an area narrower than the width of the paper 10 in the nozzle arrangement direction is the recording area (maximum image forming area). It is set as 801. In the first embodiment, the non-ejection nozzles of the heads 101A to 101J differ in the presence or absence of fine driving inside and outside the paper 10, whereas in the fourth embodiment, the fine driving is performed inside and outside the recording area 801. Existence is different. Other configurations and operations are the same as those in the first embodiment.

  Next, a fifth embodiment of the image forming apparatus will be described with reference to FIG. FIG. 14 is an explanatory diagram for explaining the fine drive control of the embodiment. In this embodiment, the second embodiment is applied to a case where an area narrower than the width of the paper 10 in the nozzle arrangement direction is set as a recording area (maximum image forming area) 801. The operation is the same as in the second embodiment.

  Next, a sixth embodiment of the image forming apparatus will be described with reference to FIG. FIG. 15 is an explanatory diagram for explaining the fine drive control of the embodiment. In the sixth embodiment, the third embodiment is applied to a case where an area narrower than the width in the nozzle arrangement direction of the paper 10 is set as a recording area (maximum image forming area) 801. The configuration and operation of are the same as in the third embodiment.

  Next, a seventh embodiment of the image forming apparatus will be described with reference to FIG. FIG. 16 is an explanatory diagram for explaining the fine drive control of the embodiment. Here, as the recording head 151, a full-line type head in which nozzles are arranged over the entire width of the usable paper size is used, and the non-ejection nozzles located in the paper 10 are applied by applying the first embodiment. The non-ejection nozzles that are finely driven and are located outside the paper 10 are configured not to be finely driven. Note that the second to fifth embodiments can be similarly applied when a full-line head is used.

  Next, with reference to FIG. 17, an example of a configuration when performing fine driving in units of nozzles and performing head driving control without performing fine driving in the third embodiment will be described. The drive waveform generation unit (common drive waveform generation unit) 701 described above generates a common drive waveform Vcom1.

  More specifically, the common drive waveform Vcom1 is a non-ejection drive signal that finely drives a nozzle meniscus that does not eject droplets in time series within one drive cycle (one printing cycle) determined by the pixel density and the paper conveyance speed. P0 and a plurality of first ejection driving signals (driving pulses) P1 to P3 for ejecting droplets of an ejection amount used for image formation.

  Here, each of the drive signals P0 to P3 includes a waveform element that falls from the reference potential Ve, a waveform element that rises from the state after the fall, and the like. The waveform element in which the potential V of the drive signal falls from the reference potential Ve is a pull-in waveform element in which the piezoelectric element 221 contracts and the volume of the pressurized liquid chamber 206 expands. The waveform element that rises from the state after the fall is a pressurization waveform element that causes the piezoelectric element 221 to expand and the volume of the pressurized liquid chamber 206 to contract.

  That is, the drive signal P0 included in the drive waveform is a fine drive signal that applies meniscus vibration without ejecting droplets, and the drive signals P1 to P3 expand the liquid chamber 206 with which the nozzle 204 of the liquid ejection head 101 communicates. After that, the drive waveform is such that the droplet is discharged by contracting.

  Then, for example, when fine driving is performed by the droplet control signals M0 to M3 as shown in FIG. 17 from the data transfer unit 702, the drive signal P0 is selected by the droplet control signal M0 (selected at the L level). When forming a small droplet (small dot), the drive signal P1 is selected by the droplet control signal M1, and when forming a large droplet (large dot), the drive signals P1 to P3 are selected by the droplet control signal M2, and fine driving is performed. If not, the droplet control signal M3 is selected and applied to the piezoelectric element 221 of the recording head. In addition, although it is set as two types of sizes, a small droplet and a large droplet here, the medium droplet of the magnitude | size between both can also be discharged, for example.

  Therefore, for each nozzle 204 of each head 101 of the recording head 51, a droplet control signal M0 is selected for a non-ejection nozzle that performs fine driving, and a droplet control signal M3 is selected for a non-ejection nozzle that does not perform fine driving. .

  Next, the relationship between the presence or absence of fine driving and the idle ejection operation will be described. In general, nozzles 204 that are used infrequently or are not used may cause the ink in the nozzles 204 to thicken and cause ejection failure. As one of the measures to prevent ejection failure, The discharge of droplets unrelated to image formation from the nozzle 204 that is not frequently used or is not used at other locations (for example, on the conveyor belt or openings provided in the conveyor belt). An idle discharge operation for performing preliminary discharge) is performed.

  In FIG. 18, among the nozzles that are non-ejection nozzles that are not finely driven, the nozzles are down when printing is performed with nozzles that are not adjacent to the ejection nozzles (discharging is impossible: the nozzles are completely clogged. An example of a measurement result of the occurrence time of a state in which droplets cannot be discharged is shown.

  From the result of FIG. 18, when the non-ejection nozzle adjacent to the ejection nozzle among the non-ejection nozzles without fine driving is left unattended, nozzle down occurs after time βt [s], and non-ejection without fine driving is performed. Among the nozzles, when a non-ejection nozzle that is not adjacent to the ejection nozzle is left unattended, nozzle down occurs after αt [s].

  According to this experiment, the time αt [s] is about several times the time βt [s]. Accordingly, when the printing time T of the recording medium T> βt [s], the non-ejection nozzles in the recording medium need to perform idle ejection at least once within βt [s] at the longest. On the other hand, the non-ejection nozzles outside the recording medium may perform idle ejection at least once within the time αt [s] at the longest.

  Accordingly, the number of idle ejections (idle ejection frequency) in a predetermined elapsed time is the non-ejection nozzle that is adjacent to the ejection nozzle, and is the non-ejection nozzle that is not adjacent to the ejection nozzle among the non-ejection nozzles that are not finely driven. This can be less than the empty discharge frequency of the empty discharge nozzle.

  Next, with reference to FIG. 19, the relationship between the discharge amount per predetermined time at the discharge nozzle and the landing delay of the discharged droplets on the paper will be described. If the discharge amount from the discharge nozzle does not discharge more than a certain amount per predetermined time, the ink in the vicinity of the meniscus is thickened by fine driving, and the droplet speed to be discharged decreases, so that the paper is transported from the desired landing position. This will cause a delay in landing at the rear of the direction, bending of discharge, and non-discharge.

  Therefore, by performing control that does not finely drive until the next recording medium arrives after passing through the recording medium, it is possible to suppress ink thickening due to fine driving. Further, with respect to the discharge nozzles whose discharge amount per predetermined time is equal to or less than the predetermined amount, an ink discharge operation is performed by discharging a droplet that does not contribute to image formation at the timing when the recording area of the recording medium passes. It becomes possible to prevent stickiness.

  As shown in FIG. 19, this idle ejection control is performed by reading the print data in the recording area (paper in the above example), and the ejection amount of the ejection nozzle for each nozzle is equal to or less than a preset value (set droplet amount) L. In the case where the amount is equal to or less than the set droplet amount, the idle ejection operation is performed, and when the ejection amount is larger than the set value, the idle ejection is not performed. FIG. 20 shows the flow of processing related to this idle discharge control. By performing such control, it is possible to reduce the amount of ink that is wasted in idle ejection.

  Here, the criteria for starting and ending fine drive control in each of the above embodiments will be described. In the following description, the paper sensor is attached to the upstream side in the transport direction from the head (nozzle). The presence or absence of fine driving is controlled after a predetermined time from the detection of the leading or trailing edge of the paper.

  First, the start of fine drive control will be described. For detection of paper, a paper sensor 521 is provided upstream of the head array in the paper transport direction, and detects the leading edge and the trailing edge of the paper. The leading edge of the sheet is detected by the sheet sensor, and fine driving is started after a predetermined time. Here, the predetermined time is a time shorter than the time when the recording area of the paper reaches the head (nozzle) after the paper sensor detects the leading edge of the paper. The paper recording area is obtained from the margin amount set on the operation panel or the like, and the set paper size (or the paper size on the paper feed tray). Although all heads may start fine driving at the same time, it is desirable to start fine driving sequentially for each line or each nozzle row of the head according to the distance from the paper sensor to each head.

  Next, the end of the fine drive control will be described. When the trailing edge of the sheet is detected by the sheet sensor, the fine driving is finished at the timing when the trailing edge of the sheet passes under the head (nozzle). Specifically, the passage time is calculated from the distance from the sheet sensor to the head (nozzle) and the sheet conveyance speed, the trailing edge of the sheet is detected by the sheet sensor, and then the fine driving ends ( Process that does not finely drive). The fine driving may be terminated at the timing when the recording area of the sheet passes. Further, when fine driving is controlled in units of nozzles, it is desirable to end fine driving after the printing in the page of each nozzle is completed.

(Summary)
(1) In the disclosed image forming apparatus having a line head structure, since ejection failure due to fine drive control has been eliminated, even if a plurality of image data is continuously input during printing by interruption processing, throughput is not reduced and wasteful. It is possible to reduce the consumption of ink and prevent the nozzles of non-printing nozzles from going down, and perform stable image formation. Further, in the disclosed image forming apparatus, since the printing nozzles are not finely driven between the recording regions, the continuous fine driving time (number of times) can be reduced and the ink thickening can be suppressed. Image formation can be performed.
(2) The ink in the non-ejection nozzle adjacent to the ejection nozzle propagates the ejection vibration of the ejection nozzle, so that the ink in the nozzle tends to thicken compared to the non-ejection nozzle not adjacent to the ejection nozzle. Therefore, in the disclosed image forming apparatus, the idle discharge amount from the non-ejection nozzle that is not adjacent to the ejection nozzle is reduced as compared with the idle ejection amount of the adjacent non-ejection nozzle, so that the throughput is not reduced and wasteful. It is possible to reduce the consumption of ink and prevent the nozzles of non-printing nozzles from going down, and perform stable image formation.
(3) For a discharge nozzle that finely drives and discharges ink, when the discharge amount per page is equal to or less than a predetermined amount, the ink thickens compared to a nozzle that exceeds the predetermined amount. Therefore, in the disclosed image forming apparatus, by performing droplet discharge that does not contribute to image formation at the timing when the recording area passes, it is possible to suppress ink thickening even for discharge nozzles whose discharge amount is a predetermined amount or less. Can be prevented, and stable image formation can be performed.
Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications are possible within the scope of the gist of the present invention described in the claims.・ Change is possible.

4 Conveyance unit 5 Image forming units 51, 51Y, 51M, 51C, 51K Recording head 101 Head 204 Nozzle

JP 2008-001084 A

Claims (5)

A recording head in which a plurality of nozzles for discharging droplets to the recording medium are arranged;
Means for finely driving the recording head without causing droplets to be ejected from the nozzles and vibrating the ink meniscus of the nozzles;
When recording an image on the recording medium, the fine driving is performed on the non-ejection nozzles located in the recording area of the recording medium among the non-ejection nozzles that do not eject the droplets, and the recording medium Means for performing a fine drive for the non-ejection nozzles located outside the recording area, and
An image forming apparatus that performs control so as not to perform the fine driving when an image is not recorded on the recording medium. A recording head in which a plurality of nozzles for discharging droplets to the recording medium are arranged;
Means for finely driving the recording head without causing droplets to be ejected from the nozzles and vibrating the ink meniscus of the nozzles;
When recording an image on the recording medium, the fine driving is performed on the non-ejection nozzles located in the recording medium among the non-ejection nozzles that do not eject the liquid droplets, and are located outside the recording medium. Means for performing a fine drive for the non-ejection nozzle,
An image forming apparatus that performs control so as not to perform the fine driving when an image is not recorded on the recording medium. A recording head in which a plurality of heads in which a plurality of nozzles for discharging droplets are arranged on a recording medium are arranged in the nozzle arrangement direction; and
Means for finely driving the recording head without causing droplets to be ejected from the nozzles and vibrating the ink meniscus of the nozzles;
When recording an image on the recording medium, among the non-ejection nozzles that do not eject the liquid droplets, fine driving is performed on the non-ejection nozzles of the head in which all the nozzles are located in the recording medium, Means for performing a fine drive on the non-ejection nozzles of the head including the nozzles located outside the recording medium,
An image forming apparatus that performs control so as not to perform the fine driving when an image is not recorded on the recording medium. A recording head in which a plurality of heads in which a plurality of nozzles for discharging droplets are arranged on a recording medium are arranged in the nozzle arrangement direction; and
Means for finely driving the recording head without causing droplets to be ejected from the nozzles and vibrating the ink meniscus of the nozzles;
When recording an image on the recording medium, among the non-ejection nozzles that do not eject the droplets, the non-ejection nozzles of the head in which all the nozzles are located in the recording medium, and the recording medium The non-ejection nozzles of the head where some of the nozzles are located are finely driven, and the non-ejection nozzles of the head where all the nozzles are located outside the recording medium, and some of the non-ejection nozzles within the recording medium Means for controlling the fine ejection of the non-ejection nozzles located outside the recording medium of the head where the nozzles are located, and
An image forming apparatus that performs control so as not to perform the fine driving when an image is not recorded on the recording medium. A nozzle that is positioned in a recording area of the recording medium and is controlled to perform fine driving, and among the ejection nozzles that perform image formation, an ejection suitable amount per recording medium is equal to or less than a predetermined amount the nozzle, the image forming apparatus according to any one of claims 1 to 4, characterized in that the air discharge operation for discharging droplets not contributing to image formation.

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