JP4288496B2 - Liquid ejecting apparatus and image forming apparatus provided with the same - Google Patents

Description

  The present invention relates to a liquid ejecting apparatus and an image forming apparatus including the same, and more particularly, a liquid ejecting apparatus that ejects a liquid such as ink from a discharge head toward a recording medium and forms an image, and an image forming apparatus including the liquid ejecting apparatus. Relates to the device.

  2. Description of the Related Art Conventionally, an image forming apparatus has an ink ejection head (printing head) in which a large number of nozzles are arranged, and recording is performed from the nozzles of the ink ejection head while relatively moving the ink ejection head and the recording medium. 2. Related Art An ink jet recording apparatus (ink jet printer) that forms an image on a recording medium by ejecting ink as droplets toward the medium is known.

  Conventionally, various methods are known as ink ejection methods in such an ink jet recording apparatus. For example, the diaphragm constituting a part of the pressure chamber (ink chamber) is deformed by deformation of the piezoelectric element (piezoelectric ceramic) to change the volume of the pressure chamber, and when the volume of the pressure chamber is increased, Ink is introduced into the pressure chamber, and when the volume of the pressure chamber is reduced, the ink is ejected as droplets from the nozzle, or the ink is heated to generate bubbles and the expansion energy when the bubbles grow. A thermal ink jet method for discharging is known.

  In an image forming apparatus having an ink discharge head such as an ink jet recording apparatus, ink is supplied from an ink tank for storing ink to an ink discharge head via an ink supply path, and the ink is discharged by the above various discharge methods. However, it is desirable that the ink used here is dried and fixed as soon as it is ejected onto the recording medium.

  On the other hand, the nozzles of the ink ejection head are always filled with ink so that printing is executed immediately when a printing instruction is given, and when the ink in the nozzles dries, ink ejection from the nozzles becomes unstable. Therefore, at the time of non-printing, the ink discharge head is sealed with a cap so that the ink in the nozzle is not dried.

  However, during printing, the ink in the nozzle is exposed to the air, so the ink in the nozzle that is not ejected for a long time dries out, the ink viscosity becomes high (thickening), or the nozzle is clogged. There is a risk that the ink in the nozzles may be exhausted and ejection may not be possible.

  Conventionally, a method has been conceived in which the head is humidified by applying steam or the like to the ink that has become harder in this way to soften the ink, thereby discharging the ink.

  For example, in order to maintain recording quality and perform stable discharge even in an environment where temperature and humidity change, a temperature detection unit and a humidity detection unit are provided near the discharge unit of the recording head, and the detection result depends on the detection result. In addition, there is known one in which the humidifying means is driven to evaporate the waste ink so as to humidify the discharge portion of the recording head (for example, see Patent Document 1).

Also, for example, a liquid is applied to the recording paper, and this is heated while moving to vaporize the applied liquid, and the vapor is guided to the nozzle surface where the nozzles of the print head are formed. Is known to maintain a predetermined value so as to prevent the occurrence of paper dust accompanying the running of the recording medium and to enable stable ejection in the recording head (see, for example, Patent Document 2). .
JP 2000-190528 A JP 2003-165203 A

  However, in the above conventional method of humidifying the head to prevent ink thickening, the entire head is humidified, so it takes time to obtain a sufficient effect, and only with a nozzle with thickened ink. At the same time, there is a problem that the normal nozzles are humidified and the ink characteristics (for example, density and viscosity) may be changed.

  In particular, since the waste ink is evaporated in the one described in Patent Document 1, there is a possibility that an ink “stone wall” or the like may occur, and the waste ink is evaporated between the head and the head. Since there is a distance, the humidifying effect of the head is insufficient, and there is also a problem of odor when ink is evaporated.

  Moreover, in the thing of the said patent document 2, since there exists a distance of a steam generation part and a head, there exists a problem that a humidification effect is inadequate. Further, these conventional humidifying means humidify the entire head, and there is a problem that it is not possible to selectively humidify only nozzles that may cause ejection failure due to ink thickening or the like.

  The present invention has been made in view of such circumstances, and selectively humidifies nozzles that are likely to have ejection failures, effectively recovering nozzles and preventing ejection failures, and stably ejecting. An object of the present invention is to provide a liquid ejection apparatus capable of performing the above and an image forming apparatus including the same.

In order to achieve the object, the invention according to claim 1 is characterized in that an ejection head having a plurality of nozzles for ejecting a liquid, nozzle selection means for selecting a predetermined nozzle from the plurality of nozzles, and the selected A humidifying mechanism that applies steam to a portion of the nozzle surface on which the nozzles of the discharge head are formed, in which several nozzles including predetermined nozzles are combined into one block, and the humidifying mechanism is disposed on the nozzle surface of the discharge head. And a moving mechanism that relatively moves in the longitudinal direction of the discharge head , wherein the humidifying mechanism has a plurality of vapor discharge ports for discharging vapor to the nozzle, and a shutter mechanism for opening and closing the vapor discharge port. a a plurality to correspond to the steam discharge port, selectively liquid discharge apparatus characterized in that as steaming for a plurality of nozzles of the ejection head To provide.

As described above, since the steam is selectively applied to the nozzles, it is possible to easily recover the nozzles that have failed to discharge while reducing the adverse effects of the steam on normal nozzles and It is also possible to prevent discharge and inappropriate discharge. Further, it is possible to selectively apply steam to the entire nozzle formed in the ejection head, and the adverse effect on normal nozzles can be suppressed as much as possible. Furthermore, the total time for applying steam to the nozzle can be shortened. Moreover, since the area | region to which a vapor | steam is applied can be changed easily without moving a humidification mechanism, space saving is possible. Furthermore, it is possible to selectively apply steam to nozzles that require humidification.

  According to a second aspect of the present invention, the humidifying mechanism generates steam on a side facing the nozzle, and applies the steam from the side facing the nozzle toward the nozzle. .

  Thereby, it is possible to effectively apply the vapor to the liquid having an increased viscosity in the nozzle.

  According to a third aspect of the present invention, the nozzle selection unit selects a nozzle whose liquid discharge frequency is lower than other nozzles based on data for discharging liquid from the nozzle. . Thereby, the prevention effect of non-ejection can be enhanced by applying steam only to nozzles that are likely to be non-ejection.

  According to a fourth aspect of the present invention, in the liquid ejection apparatus according to the first or second aspect, the liquid ejection device further includes a non-ejection detection unit that detects a liquid ejection state from the nozzle, and the nozzle selection unit Is characterized in that the nozzle is selected in accordance with the ejection status detected by the non-ejection detection means.

  Thus, by selecting a nozzle that has failed or improperly ejected and applying steam, it can be recovered almost by preliminary ejection, and the number of suctions that consume a large amount of ink can be reduced.

Moreover, as shown in Claim 5 , it is a liquid discharge apparatus of any one of Claims 1-4 , Comprising: The said humidification mechanism is the said nozzle surface by having apply | coated the vapor | steam with respect to the said nozzle. It has a blade for wiping off the adhering vapor.

Thereby, the excess water | moisture content by the vapor | steam adhering to the nozzle surface can be easily removed by applying a vapor | steam to a nozzle.

According to a sixth aspect of the present invention, in the liquid ejecting apparatus according to the fifth aspect , the blade is integrated with the humidifying mechanism and moves relative to the nozzle surface. .

This reduces the viscosity of the thickened ink by applying steam, softens the hardened ink, and then wipes off the vapor adhering to the nozzle surface with a blade, reducing the total humidification time and adding extra It is possible to prevent moisture from remaining on the nozzle surface.

  Similarly, in order to achieve the above object, the invention according to claim 9 provides an image forming apparatus comprising the liquid ejection device according to any one of claims 1 to 8. To do.

  This makes it possible to easily recover the nozzle that has failed to discharge, and to prevent non-discharge or inappropriate discharge and stably discharge liquid to form an image.

  As described above, according to the liquid ejection apparatus and the image forming apparatus including the liquid ejection apparatus according to the present invention, by selectively applying steam to the plurality of nozzles formed on the ejection head to perform humidification, Without adversely affecting the normal nozzle due to the steam, it is possible to effectively perform the recovery of the nozzle and the prevention of the discharge failure and perform the stable discharge.

  Hereinafter, a liquid ejection apparatus according to the present invention and an image forming apparatus including the same will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram showing an outline of an embodiment of an ink jet recording apparatus as an image forming apparatus according to the present invention.

  As shown in FIG. 1, the inkjet recording apparatus 10 includes a printing unit having a plurality of printing heads (inkjet recording heads) 12K, 12C, 12M, and 12Y provided for each ink color, and each printing head 12K, 12C, 12M, and 12Y, an ink storage / loading unit 14 that stores ink to be supplied, a paper feeding unit 18 that supplies recording paper 16, a decurling unit 20 that removes curling of the recording paper 16, and the printing The suction belt conveyance unit 22 that is arranged to face the nozzle surface (ink ejection surface) of the unit 12 and conveys the recording paper 16 while maintaining the flatness of the recording paper 16, and the print detection that reads the printing result by the printing unit 12 And a paper discharge unit 26 for discharging the printed recording paper (printed matter) to the outside.

  In FIG. 1, a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit 18, but a plurality of magazines having different paper widths, paper quality, and the like may be provided side by side. Further, instead of the roll paper magazine or in combination therewith, the paper may be supplied by a cassette in which cut papers are stacked and loaded.

  In the case of an apparatus configuration using roll paper, a cutter 28 is provided as shown in FIG. 1, and the roll paper is cut into a desired size by the cutter 28. The cutter 28 includes a fixed blade 28A having a length equal to or greater than the conveyance path width of the recording paper 16, and a round blade 28B that moves along the fixed blade 28A. The fixed blade 28A is provided on the back side of the print. The round blade 28B is arranged on the print surface side with the conveyance path interposed therebetween. Note that the cutter 28 is not necessary when cut paper is used.

  When multiple types of recording paper are used, an information recording body such as a barcode or wireless tag that records paper type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Therefore, it is preferable to automatically determine the type of paper to be used and perform ink ejection control so as to realize appropriate ink ejection according to the type of paper.

  The recording paper 16 delivered from the paper supply unit 18 retains curl due to having been loaded in the magazine. In order to remove this curl, heat is applied to the recording paper 16 by the heating drum 30 in the direction opposite to the curl direction of the magazine in the decurling unit 20. At this time, it is more preferable to control the heating temperature so that the printed surface is slightly curled outward.

  After the decurling process, the cut recording paper 16 is sent to the suction belt conveyance unit 22. The suction belt conveyance unit 22 has a structure in which an endless belt 33 is wound between rollers 31 and 32, and at least a portion facing the nozzle surface of the printing unit 12 and the sensor surface of the printing detection unit 24 is flat ( Flat surface).

  The belt 33 has a width that is wider than the width of the recording paper 16, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 1, an adsorption chamber 34 is provided at a position facing the nozzle surface of the print unit 12 and the sensor surface of the print detection unit 24 inside the belt 33 spanned between the rollers 31 and 32. Then, the suction chamber 34 is sucked by the fan 35 to be a negative pressure, whereby the recording paper 16 on the belt 33 is sucked and held.

  The power of a motor (not shown) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, so that the belt 33 is driven in the clockwise direction in FIG. The recording paper 16 is conveyed from left to right in FIG.

  Since ink adheres to the belt 33 when a borderless print or the like is printed, the belt cleaning unit 36 is provided at a predetermined position outside the belt 33 (an appropriate position other than the print area). Although details of the configuration of the belt cleaning unit 36 are not shown, for example, there are a method of niping a brush roll, a water absorbing roll, etc., an air blowing method of spraying clean air, or a combination thereof. In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

  Although a mode using a roller / nip transport mechanism instead of the suction belt transport unit 22 is also conceivable, when the print area is transported by a roller / nip, the roller comes into contact with the print surface of the paper immediately after printing, so that the image blurs. There is a problem that it is easy. Therefore, as in this example, suction belt conveyance that does not contact the image surface in the printing region is preferable.

  A heating fan 40 is provided on the upstream side of the printing unit 12 on the paper conveyance path formed by the suction belt conveyance unit 22. The heating fan 40 heats the recording paper 16 by blowing heated air onto the recording paper 16 before printing. Heating the recording paper 16 immediately before printing makes it easier for the ink to dry after landing.

  The printing unit 12 is a so-called full-line type head in which line-type heads having a length corresponding to the maximum paper width are arranged in a direction (main scanning direction) orthogonal to the paper transport direction (sub-scanning direction) ( (See FIG. 2). As shown in FIG. 2, each of the print heads 12K, 12C, 12M, and 12Y has a plurality of ink discharge ports (nozzles) over a length exceeding at least one side of the recording paper 16 of the maximum size targeted by the inkjet recording apparatus 10. It is composed of arranged line type heads.

  Printing corresponding to each color ink in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side (left side in FIG. 1) along the conveyance direction (paper conveyance direction) of the recording paper 16 Heads 12K, 12C, 12M, and 12Y are arranged. A color image can be formed on the recording paper 16 by discharging the color inks from the print heads 12K, 12C, 12M, and 12Y while the recording paper 16 is conveyed.

  Thus, according to the printing unit 12 in which the full line head that covers the entire width of the paper is provided for each ink color, the recording paper 16 and the printing unit 12 are relatively moved in the paper transport direction (sub-scanning direction). It is possible to record an image on the entire surface of the recording paper 16 by performing this operation only once (that is, by one sub-scan). Accordingly, high-speed printing is possible as compared with a shuttle type head in which the print head reciprocates in a direction (main scanning direction) orthogonal to the paper transport direction, and productivity can be improved.

  Here, the main scanning direction and the sub-scanning direction are used in the following meaning. That is, when driving the nozzles with a full line head having a nozzle row corresponding to the full width of the recording paper, (1) whether all the nozzles are driven simultaneously or (2) whether the nozzles are driven sequentially from one side to the other (3) The nozzles are divided into blocks, and each nozzle is driven sequentially from one side to the other for each block, and the width direction of the paper (perpendicular to the conveyance direction of the recording paper) Nozzle driving that prints one line (a line made up of a single row of dots or a line made up of a plurality of rows of dots) in the direction of scanning is defined as main scanning. A direction indicated by one line (longitudinal direction of the belt-like region) recorded by the main scanning is called a main scanning direction.

  On the other hand, by relatively moving the above-described full line head and the recording paper, printing of one line (a line formed by one line of dots or a line composed of a plurality of lines) formed by the above-described main scanning is repeatedly performed. Is defined as sub-scanning. A direction in which sub-scanning is performed is referred to as a sub-scanning direction. After all, the conveyance direction of the recording paper is the sub-scanning direction, and the direction orthogonal to it is the main scanning direction.

  Further, in this example, the configuration of KCMY standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink and dark ink are added as necessary. May be. For example, it is possible to add a print head that discharges light ink such as light cyan and light magenta.

  As shown in FIG. 1, the ink storage / loading unit 14 has tanks that store inks of colors corresponding to the print heads 12K, 12C, 12M, and 12Y, and each tank has a pipeline that is not shown. The print heads 12K, 12C, 12M, and 12Y communicate with each other. Further, the ink storage / loading unit 14 includes notifying means (display means, warning sound generating means, etc.) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. is doing.

  The print detection unit 24 includes an image sensor (line sensor or the like) for imaging the droplet ejection result of the print unit 12, and means for checking nozzle clogging and other ejection defects from the droplet ejection image read by the image sensor. It functions as (non-ejection detection means).

  The print detection unit 24 of this example is composed of a line sensor having a light receiving element array that is wider than at least the ink ejection width (image recording width) by the print heads 12K, 12C, 12M, and 12Y. The line sensor includes an R sensor row in which photoelectric conversion elements (pixels) provided with red (R) color filters are arranged in a line, a G sensor row provided with green (G) color filters, The color separation line CCD sensor includes a B sensor array provided with a blue (B) color filter. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used.

  The print detection unit 24 reads the test patterns printed by the print heads 12K, 12C, 12M, and 12Y for each color, and detects the ejection of each head. The ejection determination includes the presence / absence of ejection, measurement of dot size, measurement of dot landing position, and the like.

  A post-drying unit 42 is provided following the print detection unit 24. The post-drying unit 42 is means for drying the printed image surface, and for example, a heating fan is used. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

  When printing on porous paper with dye-based ink, the weather resistance of the image is improved by preventing contact with ozone or other things that cause dye molecules to break by blocking the paper holes by pressurization. There is an effect to.

  A heating / pressurizing unit 44 is provided following the post-drying unit 42. The heating / pressurizing unit 44 is a means for controlling the glossiness of the image surface, and pressurizes with a pressure roller 45 having a predetermined uneven surface shape while heating the image surface to transfer the uneven shape to the image surface. To do.

  The printed matter generated in this manner is outputted from the paper output unit 26. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. The ink jet recording apparatus 10 is provided with a selecting means (not shown) for switching the paper discharge path in order to select the printed matter of the main image and the printed matter of the test print and send them to the respective discharge portions 26A and 26B. ing. Note that when the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter) 48. The cutter 48 is provided immediately before the paper discharge unit 26, and cuts the main image and the test print unit when the test print is performed on the image margin. The structure of the cutter 48 is the same as that of the first cutter 28 described above, and includes a fixed blade 48A and a round blade 48B.

  Although not shown, the paper output unit 26A for the target prints is provided with a sorter for collecting prints according to print orders.

  Next, the print head (droplet discharge head) will be described. Since the structures of the print heads 12K, 12C, 12M, and 12Y provided for each ink color are common, the print head is represented by the reference numeral 50 in the following, and the print head 50 is shown in FIG. The plane perspective view of is shown.

  As shown in FIG. 3, the print head 50 of the present embodiment includes a nozzle 51 that ejects ink as droplets, a pressure chamber 52 that applies pressure to the ink when ejecting ink, and a pressure chamber 52 from a common channel (not shown). The pressure chamber units 54 each including an ink supply port 53 for supplying ink are arranged in a staggered two-dimensional matrix so that the nozzles 51 have a high density.

  As shown in FIG. 3, each pressure chamber 52 has a substantially square shape when viewed from above. A nozzle 51 is formed at one end of the diagonal line, and an ink supply port 53 is provided at the other end. Yes.

  FIG. 4 is a cross-sectional view taken along line 4-4 in FIG.

  As shown in FIG. 4, the pressure chamber unit 54 is formed by a pressure chamber 52 that communicates with a nozzle 51 that discharges ink, and the pressure chamber 52 has a common flow channel 55 that supplies ink through a supply port 53. While communicating, one surface (the top surface in the figure) of the pressure chamber 52 is constituted by a diaphragm 56, and a piezoelectric element 58 for applying pressure to the diaphragm 56 to deform the diaphragm 56 is joined to the upper portion thereof. An individual electrode 57 is formed on the upper surface of the piezoelectric element 58. The diaphragm 56 also serves as a common electrode.

  The piezoelectric element 58 is sandwiched between a common electrode (diaphragm 56) and an individual electrode 57, and is deformed by applying a driving voltage to these two electrodes 56 and 57. The diaphragm 56 is pushed by the deformation of the piezoelectric element 58, the volume of the pressure chamber 52 is reduced, and ink is ejected from the nozzle 51. When the voltage application between the two electrodes 56 and 57 is released, the piezoelectric element 58 returns to the original state, the volume of the pressure chamber 52 is restored to the original size, and passes through the supply port 53 from the common channel 55. New ink is supplied to the pressure chamber 52.

  FIG. 5 is a perspective plan view showing another structural example of the print head. As shown in FIG. 5, a plurality of short heads 50 'are arranged in a two-dimensional zigzag pattern and connected so that the total length of the plurality of short heads 50' corresponds to the entire width of the print medium. One long full line head may be configured.

  FIG. 6 is a schematic diagram showing the configuration of the ink supply system in the inkjet recording apparatus 10. The ink tank 60 is a base tank for supplying ink to the print head 50, and is installed in the ink storage / loading unit 14 described with reference to FIG. In the form of the ink tank 60, there are a system that replenishes ink from a replenishing port (not shown) and a cartridge system that replaces the entire tank when the remaining amount of ink is low. When the ink type is changed according to the intended use, the cartridge system is suitable. In this case, it is preferable that the ink type information is identified by a barcode or the like, and ejection control is performed according to the ink type. The ink tank 60 in FIG. 6 is equivalent to the ink storage / loading unit 14 in FIG. 1 described above.

  As shown in FIG. 6, a filter 62 is provided in the middle of the conduit connecting the ink tank 60 and the print head 50 in order to remove foreign matter and bubbles. The filter mesh size is preferably equal to or smaller than the nozzle diameter of the print head 50 (generally, about 20 μm).

  Although not shown in FIG. 6, a configuration in which a sub tank is provided in the vicinity of the print head 50 or integrally with the print head 50 is also preferable. The sub-tank has a function of improving a damper effect and refill that prevents fluctuations in the internal pressure of the head.

  Further, the inkjet recording apparatus 10 includes a cap 64 as a means for preventing the nozzle from drying or preventing an increase in the ink viscosity near the nozzle, and the nozzle on the nozzle surface 50 </ b> A by selectively humidifying the nozzle to selectively humidify the nozzle. A humidifying mechanism 65 for recovering the above is provided. Further, as will be described in detail later, the humidifying mechanism 65 has a cleaning blade as a means for cleaning the nozzle surface 50A.

  The maintenance unit including the cap 64 and the humidifying mechanism 65 can be moved relative to the print head 50 by respective moving mechanisms (not shown), and maintenance can be performed below the print head 50 from a predetermined retraction position as necessary. Moved to position.

  The cap 64 is displaced up and down relatively with respect to the print head 50 by an elevator mechanism (not shown). The cap 64 is lifted to a predetermined raised position when the power is turned off or during printing standby, and is brought into close contact with the print head 50, thereby covering the nozzle area of the nozzle surface 50 </ b> A with the cap 64.

  During printing or standby, when the frequency of use of a specific nozzle 51 is reduced and the ink viscosity in the vicinity of the nozzle is increased, preliminary ejection for forcibly discharging the deteriorated ink toward the cap 64 is performed. Note that the preliminary discharge may be referred to as “empty discharge”, “purge”, “spitting”, or the like.

  Further, when air bubbles are mixed into the ink in the print head 50 (in the pressure chamber 52) and the ink cannot be ejected, the cap 64 is applied to the print head 50 and the suction chamber 67 uses the suction pump 67. A suction operation is performed in which the ink in which bubbles are mixed is removed by suction, and the sucked and removed ink is fed to the collection tank 68. This suction operation is performed when an initial ink is loaded into the head (at the time of first loading). Further, when the ink viscosity is increased and solidified at the start of use after a long stop, the deteriorated ink is sucked out.

  As described above, if the print head 50 is not ejected for a certain period of time, the ink solvent near the nozzles evaporates and the viscosity of the ink near the nozzles increases, and the ejection driving actuator 58 operates. Ink is no longer ejected from the nozzle 51, so that before this state is reached (within the viscosity range in which ink can be ejected by the operation of the actuator 58), the actuator 58 is operated toward the ink receiver. “Preliminary ejection” is performed to eject ink in the vicinity of the raised nozzle.

  If air bubbles are mixed in the nozzle 51 or the pressure chamber 52, or if the ink viscosity in the nozzle 51 exceeds a certain level and ink cannot be ejected by the preliminary ejection, the nozzle surface of the print head 50 An operation in which the cap 64 is applied to 50A and the ink or the thickened ink mixed with bubbles in the pressure chamber 52 is sucked by the pump 67 is performed.

  The cap 64 described with reference to FIG. 6 functions as a suction unit and can also function as a preliminary discharge ink receiver. Preferably, the inside of the cap 64 is divided into a plurality of areas corresponding to the nozzle rows by a partition wall, and each of the partitioned areas can be selectively sucked by a selector or the like.

  However, since the above suction operation is performed on the entire ink in the pressure chamber 52, the ink consumption is large. Therefore, when the increase in viscosity is small, it is preferable that the nozzle can be recovered by preliminary discharge rather than by suction operation as much as possible.

  FIG. 7 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 70, a system controller 72, an image memory 74, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, a head driver 84, and the like.

  The communication interface 70 is an interface unit that receives image data sent from the host computer 86. As the communication interface 70, a serial interface such as USB, IEEE 1394, Ethernet, and wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. Image data sent from the host computer 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the image memory 74. The image memory 74 is a storage unit that temporarily stores an image input via the communication interface 70, and data is read and written through the system controller 72. The image memory 74 is not limited to a memory composed of semiconductor elements, and a magnetic medium such as a hard disk may be used.

  The system controller 72 is a control unit that controls each unit such as the communication interface 70, the image memory 74, the motor driver 76, and the heater driver 78. The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and performs communication control with the host computer 86, read / write control of the image memory 74, and the like, as well as a transport system motor 88 and heater 89. A control signal for controlling is generated.

  The motor driver 76 is a driver (drive circuit) that drives the motor 88 in accordance with an instruction from the system controller 72. The heater driver 78 is a driver that drives the heater 89 such as the post-drying unit 42 in accordance with an instruction from the system controller 72.

  The print control unit 80 has a signal processing function for performing various processing and correction processing for generating a print control signal from the image data in the image memory 74 according to the control of the system controller 72, and the generated print A control unit that supplies a control signal (print data) to the head driver 84. Necessary signal processing is performed in the print controller 80, and the ejection amount and ejection timing of the ink droplets of the print head 50 are controlled via the head driver 84 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 80 includes an image buffer memory 82, and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the print control unit 80. In FIG. 7, the image buffer memory 82 is shown in a mode associated with the print control unit 80, but it can also be used as the image memory 74. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with one processor.

  The head driver 84 drives the actuator 58 of the print head 50 of each color based on the print data given from the print control unit 80. The head driver 84 may include a feedback control system for keeping the head driving conditions constant.

  As described with reference to FIG. 1, the print detection unit 24 is a block including a line sensor (not shown). The print detection unit 24 reads an image printed on the recording paper 16 and performs necessary signal processing and the like to perform a print status (discharge state). Presence / absence, variation in droplet ejection, etc.) and the detection result is provided to the print controller 80.

  The print control unit 80 performs various corrections on the print head 50 based on information obtained from the print detection unit 24 as necessary. Further, the print control unit 80 selects a nozzle 51 that does not discharge for a certain period of time based on the print data, or a nozzle 51 that is less frequently used than other nozzles, or causes the print detection unit 24 to perform no discharge. Is selected, and the humidifying mechanism 65 is controlled so as to humidify the selected nozzle 51 by applying steam. That is, the print control unit 80 also functions as a nozzle selection unit that selects the nozzle 51 to which steam is applied.

  FIG. 8 is a schematic configuration diagram including a partial cross-sectional view showing the humidifying mechanism 65 according to the present embodiment.

  As shown in FIG. 8, the humidifying mechanism 65 of this embodiment includes a steam liquid supply unit 90, a steam generation unit 92, and a nozzle surface cleaning unit 94, which are integrated on a support base 98 that moves on a shaft 96. Is formed.

  The vapor liquid supply unit 90 includes a vapor liquid supply pipe 102 that supplies the vapor liquid 100 from an evaporation liquid supply unit (not shown) to the vapor generation unit 92. The vapor liquid supply unit is a tank or the like in which the vapor liquid 100 is stored. When the ink used in the ink jet recording apparatus 10 is a water-based ink, it is preferable to use distilled water. Or you may make it shorten time to vapor | steam generation | occurrence | production by combining with a liquid with a low boiling point. In the case of oil-based ink, it is preferable to use a solvent that dissolves the ink and that is harmless when vaporized.

  Further, a steam liquid supply unit such as a tank for steam liquid is fixedly installed outside the support base 98, and a part of the steam liquid supply pipe 102 is formed by a deformable tube or the like. 100 may be guided to the steam generation unit 92, or the steam liquid supply unit itself may be installed on the support base 98.

  The steam generation unit 92 includes a heater 104 that generates steam by heating the supplied steam liquid 100, and a steam guide pipe 108 that guides the generated steam 106 to the meniscus surface 51 a in the nozzle 51. The steam guide pipe 108 is configured to apply steam from directly below the nozzle 51 on the nozzle surface 50 </ b> A toward the inside of the nozzle 51.

  A sliding shutter 110 is installed in an opening (steam discharge port) 108 a facing the nozzle surface 50 </ b> A of the steam guide pipe 108, and the steam discharge port 108 a can be opened and closed by the shutter 110. When the shutter 110 covers the vapor discharge port 108a, the vapor 106 does not hit the meniscus surface 51a of the nozzle 51, and only when the shutter 110 is opened and the vapor discharge port 108a is opened. Corresponds to the meniscus surface 51 a of the nozzle 51. Other than the shutter, the vaporization guide line may be sealed. For example, the vapor guide line may be sealed with a pinch roller.

  The nozzle surface cleaning section 94 includes a blade (cleaning blade) 66 that scrapes off dirt such as ink adhering to the nozzle surface 50A and water droplets (generated by the vapor 106), and a fixing member 112 that fixes the blade 66 to the support base 98. Consists of An absorbing member that absorbs ink, water droplets, and the like scraped off by the blade 66 is disposed in the fixing member 112 so as to contact the blade 66. These materials are not particularly limited. For example, the blade 66 is required to be in close contact with the nozzle surface 50A so that no gap is formed when the nozzle surface 50A is slidably contacted, and the nozzle surface 50A should not be damaged, such as rubber. It is preferable that the absorbing member is composed of an elastic member, and the absorbing member is preferably composed of a sponge or the like so as to absorb moisture well.

  The support base 98 on which the liquid supply unit 90 for steam, the steam generation unit 92, and the nozzle surface cleaning unit 94 are installed is shown by an arrow F in FIG. The shaft 96 is movably installed along the longitudinal direction of the print head 50.

  That is, while moving the support base 98 on the shaft 96 as shown by the arrow F, when the steam discharge port 108a comes to the position of the nozzle 51 that needs to be humidified, the shutter 110 is shifted to open the steam discharge port 108a. Steam 106 is applied to the meniscus surface 51 a of the nozzle 51. Then, after the viscosity of the thickened ink is lowered by the vapor 106 and the hardened ink is softened, the vapor adhering to the nozzle surface 50 </ b> A is continuously wiped by the blade 66.

  FIG. 9 is a bottom view showing the positions of the steam outlet, the shutter, and the blade in a simplified manner when the humidifying mechanism 65 is viewed from below in FIG.

  As shown in FIG. 9, the support base 98 of the humidifying mechanism 65 covers the width (short side) direction of the print head 50, and one end is supported by the shaft 96 in the longitudinal direction of the print head 50 (right side of FIG. 9). To the left).

  The blade 66 disposed on the support table 98 covers the width direction of the nozzle surface 50A from end to end so that the entire nozzle surface 50A of the print head 50 can be wiped as the support table 98 moves. ing.

  The steam discharge ports 108a are provided at a plurality of locations (two locations in FIG. 9) on the support base 98, each including a part of the nozzles 51 arranged in a two-dimensional matrix on the nozzle surface 50A. The print head 50 is arranged so as to cover the width (short side) direction and cover all the nozzles 51 as the support base 98 moves.

  In the example illustrated in FIG. 9, the vapor discharge ports 108 a are respectively provided in a part of the nozzle row arranged in the width (short) direction of the print head 50, for example, a position including the nozzle 51-1 and a position including the nozzle 51-2. The steam discharge port 108a is disposed on the support table 98 in such a positional relationship.

  Note that the shutter 110 of the steam outlet 108a at the position including the nozzle 51-1 slides sideways as indicated by an arrow in FIG. 9 to open the steam outlet 108a and apply steam to the nozzle 51-1. It has become. Further, the shutter 110 of the steam discharge port 108a at the position including the nozzle 51-2 is in a closed state so that the nozzle 51-2 is not exposed to steam.

  As described above, by opening and closing the shutter 110 provided in the vapor discharge port 108a, the viscosity of the nozzles 51 two-dimensionally arranged on the nozzle surface 50A increases due to some reason such as long-time non-discharge. Steam is selectively applied to the nozzles 51 that need to be humidified, such as the nozzles 51 that appear to be.

  Note that the number and arrangement of the steam discharge ports 108a are not limited to the example shown here, and it is possible to humidify all the nozzles 51 formed on the nozzle surface 50A as the support base 98 moves. Good. In addition, a plurality of shutters 110 may be provided in one vapor discharge port 108a that covers the entire nozzles 51 in the width direction of the print head 50 so that the vapor can be partially discharged.

  The selection of the nozzles 51 that need to be humidified is made based on the print data in addition to selecting the nozzles 51 with defective discharge by the print control unit 80 judging from the discharge status of each nozzle 51 by the print detection unit 24 as described above. The operating status of each nozzle 51 is judged, the discharge intervals from each nozzle 51 are integrated, and the nozzle 51 that does not discharge for a long time is selected.

  Hereinafter, the operation of the present embodiment will be described.

  In operating the humidifying mechanism 65, first, the nozzle 51 to be humidified by applying steam is selected. Selection of the nozzle 51 to be humidified is performed by the print control unit 80 detecting non-ejection by the print detection unit 24 or detecting a nozzle 51 having a low operation rate that is not ejected for a predetermined time based on the print data. .

  That is, when the non-ejection nozzle 51 is detected from the detection result of the print detection unit 24 or the nozzle 51 with a low operating rate that does not discharge for a certain period of time is detected based on the print data in the print control unit 80. Then, the ink in the selected nozzle 51 is humidified by the humidifying mechanism 65 to lower the viscosity of the ink to be soft, and the nozzle is recovered by performing preliminary ejection.

  Here, when selecting the nozzle 51 having a low operating rate, the operating rate for each nozzle 51 may be compared to select a nozzle 51 having a lower operating rate than the other, or a predetermined threshold value may be set in advance. It may be set and the nozzle 51 may be selected when the non-ejection time exceeds this threshold.

  Therefore, when the non-ejection nozzle is detected by the print detection unit 24 or when the non-ejection nozzle 51 is detected by the print control unit 80 for a certain period of time, the heater 104 of the steam generation unit 92 of the humidifying mechanism 65 is first turned on. To. A steam liquid (for example, distilled water if the ink is water-based ink) is always supplied to the steam generation section 92 through the steam liquid supply pipe 102 of the steam liquid supply section 90 and immediately after the heater 104 is heated. Steam is generated.

  Next, the print head 50 is retracted to a predetermined retract position. For example, the print head 50 is lifted straight up at the same position and waits at the retracted position (position where the blade 66 does not contact). Then, the humidifying mechanism 65 is moved to a space formed by raising the print head 50. At this time, the shaft 96 is disposed substantially parallel along the longitudinal direction of the print head 50, and the humidification mechanism 65 enters the lower side of the print head 50 by moving the humidification mechanism 65 along the shaft 96, It moves along the longitudinal direction of the print head 50.

  The humidifying mechanism 65 is moved along the shaft 96 (substantially parallel to the longitudinal direction of the print head 50), and the steam outlet 108a of the humidifying mechanism 65 comes to a position directly below the nozzle 51 to be humidified selected above. Then, the humidification mechanism 65 is once stopped, the shutter 110 that has closed the vapor discharge port 108a is slid to open the vapor discharge port 108a, and the vapor 106 is applied from directly below the nozzle 51 to the inside. A predetermined time may be set in advance by a timer for the time for which the steam 106 is applied.

  When the predetermined time elapses, the heater 104 that generates the steam 106 is turned off and the shutter 110 is closed. The print head 50 is lowered to the wipe position and the blade 66 is brought into contact therewith. Thereafter, the humidifying mechanism 65 is moved along the shaft 96 (for example, in the direction indicated by the arrow F in FIG. 8), and the nozzle surface 50A after the vapor 106 is applied is wiped by the blade 66.

  By wiping with the blade 66, water droplets and the like attached to the nozzle surface 50 </ b> A are collected and absorbed by an absorbing member installed below the blade 66. After wiping, the print head 50 is raised to the head retracted position. The humidification mechanism 65 moves to the nozzle 51 that needs the next humidification. The humidifying mechanism 65 moves along the longitudinal direction of the print head 50.

  The humidifying mechanism 65 thus moves to the retracted position after covering the entire nozzle surface 50A of the print head 50.

  Thereafter, instead of the humidifying mechanism 65, the cap 64 is moved below the print head 50, the nozzle surface 50 </ b> A is covered with the cap 64, and preliminary discharge is performed toward the cap 64. At this time, since the viscosity of the ink is lowered by applying the vapor 106 by the humidifying mechanism 65, it is possible to eject ink that cannot be normally ejected by preliminary ejection. As a result, the nozzle 51 such as non-ejection is recovered.

  After the preliminary ejection, the print head 50 is returned to the original position and printing is resumed. At this time, if non-ejection is detected for the first time, before performing normal printing, a non-ejection detection pattern or the like is printed, and this is detected by the print detection unit 24 and the ejection check is performed again. It is preferable to resume normal printing after confirming that the nozzles 51 are completely recovered.

  Here, if non-ejection is detected, the humidification mechanism 65 again applies the steam 106 to the non-ejection nozzle 51 and then performs preliminary ejection again. Alternatively, the cap 64 may be immediately applied to the print head 50 to perform the suction operation.

  However, in the present embodiment, the preliminary discharge is performed after the vapor 106 is applied by the humidifying mechanism 65, so that even if the discharge is not performed originally, the nozzle 51 is almost pre-discharged without suction. Recovery is possible, and the number of suctions that consume a large amount of ink can be reduced.

  As described above, in the present embodiment, a means (humidification mechanism) for applying steam to the nozzle surface of the print head is provided, and steam can be selectively applied to the nozzles at that time. It is possible to prevent non-ejection and improper ejection by applying steam to a nozzle with a low operating rate.

  In addition, by applying steam to the nozzles detected by non-ejection detection and pre-ejection, the non-ejection nozzle can be recovered, the number of times of suction can be reduced, and the amount of wasted ink due to suction can be reduced. Can do.

  Furthermore, since steam can be selectively applied only to nozzles that need to be humidified, it is not necessary to apply steam to normal nozzles. For example, changes in ink characteristics such as density and viscosity can be suppressed. .

  In addition, it has moving means to move the humidification mechanism in the longitudinal direction (main scanning direction) of the print head so that steam is applied to a plurality of nozzles in blocks, and after applying the steam, it is attached to the nozzle surface. By attaching the blade to the humidification mechanism so as to wipe off excess vapor (water droplets), the total humidification time can be shortened and excess moisture can be prevented from remaining on the nozzle surface.

  In addition, by selecting a nozzle in the width direction (sub-scanning direction) of the print head to which the steam is applied by providing a shutter mechanism near the steam discharge port and changing the place where the steam is discharged by opening and closing the shutter. Can do.

  In addition, as described above, static electricity that affects the ink ejection direction by spraying steam over the entire nozzle surface while moving the humidifying mechanism in the longitudinal direction (main scanning direction) of the print head (scanning). In addition, it is possible to easily clean the nozzle surface by floating the dirt on the nozzle surface with steam.

  In addition, it is not necessary to install one humidification mechanism for each print head, and one humidification mechanism for spraying steam onto the nozzle surface. May share a single humidifying mechanism.

  The liquid ejection apparatus and the image forming apparatus including the liquid ejection apparatus according to the present invention have been described in detail above. However, the present invention is not limited to the above examples, and various improvements and modifications can be made without departing from the gist of the present invention. Of course, deformation may be performed.

1 is an overall configuration diagram showing an outline of an embodiment of an ink jet recording apparatus as an image forming apparatus according to the present invention. FIG. 2 is a plan view of a main part around a printing unit of the ink jet recording apparatus shown in FIG. 1. FIG. 3 is a plan perspective view illustrating a structural example of a print head. FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 3, showing an example of the structure of the pressure chamber. It is a top view which shows the other example of a print head. It is the schematic which showed the structure of the ink supply system in the inkjet recording device of this embodiment. It is a principal part block diagram which shows the system configuration | structure of the inkjet recording device of this embodiment. It is a schematic block diagram including the partial cross section figure which shows the humidification mechanism which concerns on this embodiment. It is a bottom view which simplifies and shows the position of a steam discharge port, a shutter, and a blade when the humidification mechanism is viewed from below.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12 ... Printing part, 14 ... Ink storage / loading part, 16 ... Recording paper, 18 ... Paper feeding part, 20 ... Decal processing part, 22 ... Adsorption belt conveyance part, 24 ... Print detection part, 26 DESCRIPTION OF REFERENCE SYMBOLS: Paper discharge part, 28 ... Cutter, 30 ... Heating drum, 31, 32 ... Roller, 33 ... Belt, 34 ... Adsorption chamber, 35 ... Fan, 36 ... Belt cleaning part, 40 ... Heating fan, 42 ... Post-drying part, 44 ... heating / pressurizing unit, 45 ... pressure roller, 48 ... cutter, 50 ... print head, 50A ... nozzle surface, 51 ... nozzle, 52 ... pressure chamber, 53 ... ink supply port, 54 ... pressure chamber unit, 55 ... Common flow path, 56 ... Diaphragm (common electrode), 57 ... Individual electrode, 58 ... Piezoelectric element, 60 ... Ink tank, 62 ... Filter, 64 ... Cap, 65 ... Humidification mechanism, 67 ... Suction pump, 68 ... times Tank, 70 ... Communication interface, 72 ... System controller, 74 ... Image memory, 76 ... Motor driver, 78 ... Heater driver, 80 ... Print controller, 82 ... Image buffer memory, 84 ... Head driver, 86 ... Host computer, 88 DESCRIPTION OF SYMBOLS Motor, 89 ... Heater, 90 ... Steam supply part, 92 ... Steam generation part, 94 ... Nozzle surface cleaning part, 96 ... Shaft, 98 ... Support base, 100 ... Steam liquid, 102 ... Steam supply pipe , 104 ... Heater, 106 ... Steam, 108 ... Steam induction pipe, 108a ... Steam outlet, 110 ... Shutter, 112 ... Fixed member

Claims (7)

An ejection head having a plurality of nozzles for ejecting liquid;
Nozzle selecting means for selecting a predetermined nozzle from the plurality of nozzles;
A humidifying mechanism that applies steam to a portion of the nozzle surface on which the nozzles of the ejection head are formed, in which several nozzles including the selected predetermined nozzle are combined into one block;
Moving means for relatively moving the humidifying mechanism in the longitudinal direction of the discharge head with respect to the nozzle surface of the discharge head ;
The humidifying mechanism has a plurality of steam discharge ports for discharging steam to the nozzle, and has a plurality of shutter mechanisms for opening and closing the steam discharge ports corresponding to the steam discharge ports, A liquid ejecting apparatus, wherein vapor is selectively applied to a plurality of nozzles.   The liquid ejecting apparatus according to claim 1, wherein the humidifying mechanism generates steam on a side facing the nozzle and applies the steam toward the nozzle from a side facing the nozzle.   3. The liquid ejection according to claim 1, wherein the nozzle selection unit selects a nozzle having a liquid ejection frequency lower than other nozzles based on data for ejecting the liquid from the nozzle. apparatus.   The liquid ejection apparatus according to claim 1, further comprising a non-ejection detection unit that detects a status of ejection of the liquid from the nozzle, wherein the nozzle selection unit is detected by the non-ejection detection unit. A liquid ejection apparatus, wherein a nozzle is selected according to an ejection situation. The humidifying mechanism, liquid discharge according to any one of claims 1-4, characterized in that it comprises a blade for wiping the steam adhering to the nozzle surface by which rely on vapor to the nozzle apparatus. 6. The liquid ejecting apparatus according to claim 5 , wherein the blade is moved integrally with the humidifying mechanism to move relative to the nozzle surface. An image forming apparatus comprising the liquid ejecting apparatus according to any one of claims 1-6.

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