JP2006315335A - Liquid ejection head and cap means thereof, and image forming device equipped with them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid ejection head of a matrix structure adapted to refill a liquid in time even when much liquid is consumed. <P>SOLUTION: The liquid ejection head comprises a first liquid channel for supplying a liquid, a plurality of second liquid channels branched from the first liquid channel in a predetermined direction and aligned parallel to the same, a plurality of first pressure-generating units each having one ejection port, the plurality of first pressure-generating units communicating to each of the second liquid channels through a feed port, being disposed along the second liquid channels, and being arranged in a two dimensional matrix form, and a second pressure-generating unit having a plurality of ejection ports, the second pressure-generating unit being disposed near the first liquid channel opposite the first pressure-generating units arranged in a matrix form and communicating to the first liquid channel through a communicating conduit branched from the first liquid channel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid discharge head, its cap means, and an image forming apparatus equipped with these, and in particular, a plurality of liquid discharge ports are formed in one pressure generating unit for discharging liquid, and a large amount of liquid is discharged at a time. The present invention relates to a liquid discharge head having a pressure generating unit capable of discharging the liquid, a cap unit thereof, and an image forming apparatus including these.

  2. Description of the Related Art Conventionally, an image forming apparatus has an inkjet head (liquid ejection head) in which a large number of nozzles (liquid ejection ports) are arranged, and recording is performed from the nozzles while relatively moving the inkjet head and a recording medium. 2. Related Art Inkjet printers (inkjet recording apparatuses) that record images on a recording medium by ejecting ink (liquid) toward the medium are known.

  An ink jet head of such an ink jet printer is deformed by driving a piezoelectric element driven by an electric signal corresponding to image data, a pressure chamber to which ink is supplied from an ink tank through an ink supply path, and the piezoelectric element. There is a pressure generating unit that includes a diaphragm that forms part of the pressure chamber, and a nozzle that communicates with the pressure chamber through which ink in the pressure chamber is ejected as droplets by reducing the volume of the pressure chamber due to deformation of the diaphragm. is doing. In the ink jet printer, one image is formed on the recording medium by combining dots formed by the ink ejected from the nozzles of the pressure generating unit.

  In recent years, it has also been desired to form high-quality images comparable to photographic prints in inkjet printers. In order to achieve such high image quality, the nozzle diameter is reduced to reduce the ink droplets ejected from the nozzle, and the nozzles are arranged at high density to increase the number of pixels per image. Realization of high image quality is being considered. As a method for increasing the density of such a nozzle arrangement, it has been conventionally proposed to arrange the nozzles in a two-dimensional matrix.

  For example, FIG. 20 shows an enlarged view of a part of an inkjet head in which conventional nozzles are arranged in a two-dimensional matrix.

  As shown in FIG. 20, the inkjet head 950 includes, for example, a nozzle 951 along each of the tributaries 956 formed so as to span between the main streams 955 and 955 of the two ink supply channels that supply ink. Pressure chambers 952 are arranged.

  In the example shown in FIG. 20, the nozzles 951 are arranged so that 2400 nozzles 951 are aligned per inch in the longitudinal direction of the inkjet head 950 (the horizontal direction in the figure), that is, 2400 dpi (dots per inch). is there.

  In order to achieve such high density, nozzles 951 are arranged in a two-dimensional matrix as shown in the figure. For example, 48 nozzles 951-1 to 951-48 are arranged for each tributary 956. Is done. Here, the distance d between the nozzles 951 is d = 10.6 μm, and the distance D (that is, the pitch between the tributaries) with the nozzle 951-1 ′ formed in the adjacent tributary 956 is about 500 μm. . The nozzle pitch δ in the paper feed direction is about 500 μm. Further, pressure chambers 952-1 to 952-48 in which the nozzles 951-1 to 951-48 are formed are connected to a tributary 956 through ink supply ports 953-1 to 953-48, respectively. Ink is supplied.

  However, in such a matrix structure, since the ink is divided from the main flow into the tributary and further supplied to the pressure chambers arranged in the tributary, the distance that the ink flows becomes longer than in the conventional case where the matrix flow is not formed, and the entire ink flow path The flow path resistance increases. Further, in the matrix structure, if the nozzle density is increased, the width of the tributary can only be narrowed, and the flow resistance of the tributary is further increased.

  On the other hand, in a conventional inkjet head in which nozzles are arranged in a two-dimensional matrix, for example, even when a high-viscosity ink (for example, about 10 cP) is used, the branch flow height is increased so that the flow resistance is 800 Pa so that the refill is in time. There is known one in which the flow path resistance is designed to be within the range (for example, see Patent Document 1).

Further, for example, in an ink jet recording head in which nozzles are two-dimensionally arranged, the pressure generating chamber and the common channel are arranged so as to overlap each other, and the common channel has a constricted shape having a wide part and a narrow part. In order to reduce the flow path resistance, it is known (see, for example, Patent Document 2).
JP 2002-283585 A JP 2003-127363 A

  However, when a large amount of ink is consumed during image creation in an inkjet head having a matrix structure, the pressure loss in the ink flow path increases, and there is a problem that the ink supply (refill) to each pressure chamber cannot catch up. To do. For example, according to Patent Document 1, when the pressure loss in the ink flow path is 800 Pa or more, the refill cannot catch up and the ejection becomes unstable. Here, the pressure loss is proportional to the ink consumption. That is, there is a problem in that refilling is difficult because the pressure loss is maximum in the case of all ejections in which the ink consumption is maximum, such as solid printing.

  Moreover, in the thing of the said patent document 1, although the tributary height is raised and flow path resistance is lowered | hung, when using the ink (for example, 20 cP) whose viscosity is higher than 10 cP, or by the increase in the number of nozzles There is a problem that it cannot cope with a case where the ink consumption increases.

  Moreover, in the thing of the said patent document 2, in order to reduce flow-path resistance, although the branch flow is made into the shape of a constriction, this certainly reduces flow-path resistance, but does not reduce significantly, There is a problem that it is not a fundamental solution when high-viscosity ink is used.

  The present invention has been made in view of such circumstances, and in a liquid discharge head having a matrix structure in which liquid discharge ports are two-dimensionally arranged, the liquid consumption is the same as when liquid is discharged from all liquid discharge units. It is an object of the present invention to provide a liquid discharge head, a cap unit thereof, and an image forming apparatus including the liquid discharge head in which liquid refilling is in time even when the amount is large.

  In order to achieve the object, the invention described in claim 1 is characterized in that a first liquid flow path for feeding a liquid and a plurality of second liquid lines branched in parallel from the first liquid flow path in a predetermined direction and arranged in parallel. The liquid flow channel communicates with each of the second liquid flow channels via the supply port, and is arranged along the second liquid flow channel and arranged in a two-dimensional matrix, each having one discharge port. A plurality of first pressure generating units, and the first pressure generating units arranged in a matrix and the first liquid flow channel disposed in the vicinity of the first liquid flow channel on the opposite side across the first liquid flow channel, There is provided a liquid discharge head comprising: a second pressure generation unit having a plurality of discharge ports that communicates with the first liquid flow path via a communication path branched from the one liquid flow path.

  This makes it possible to ensure refill performance even when the liquid discharge amount is large.

  In addition, according to a second aspect of the present invention, in the vicinity of the first liquid flow path where the second pressure generating unit is disposed, the distance from the first liquid flow path is equal to one first liquid flow path. It is the range below the half of the length of the said 2nd liquid flow path.

  Thereby, even when the liquid discharge amount is large, the liquid refill can be made in time.

  Moreover, as shown in claim 3, the branch position of the second liquid channel from the first liquid channel and the branch position of the communication channel from the first liquid channel are the first liquid. It is shifted in the liquid flow direction of the flow path.

  This makes it difficult for the pressure wave from the second pressure generating unit to be transmitted to the first pressure generating unit on the opposite side of the first liquid flow path, thereby preventing crosstalk.

  According to a fourth aspect of the present invention, the second pressure generating unit has a plurality of supply ports.

  Thereby, it is possible to recover when one of the supply ports is clogged, and to further improve the refill performance of the second pressure generating unit.

  Similarly, in order to achieve the object, the invention according to claim 5 includes the liquid discharge head according to any one of claims 1 to 4, and the liquid discharge head and the recording medium are relatively relative to each other. An image forming apparatus is characterized in that an image is formed by discharging liquid from the liquid discharge head toward the recording medium while being moved.

  Thereby, even when a high-viscosity liquid is used, it is possible to ensure liquid refill and form a high-quality image.

  According to a sixth aspect of the present invention, a plurality of the second pressure generating units are arranged at least one upstream or downstream in the relative movement direction of the recording medium.

  Thereby, landing deviation can be prevented.

  Similarly, in order to achieve the object, the invention according to claim 7 is the liquid ejection head cap means according to any one of claims 1 to 4, which is arranged in the two-dimensional matrix. By moving the discharge port of the first pressure generation unit and the discharge port of the second pressure generation unit parallel to the surface on which the discharge ports of the liquid discharge head are formed, A cap means for a liquid discharge head is provided, wherein the discharge port of the second pressure generating unit is switched between a sealed state and a non-sealed state.

  Thereby, the liquid can be selectively sucked from the discharge port of the second pressure generating unit by one cap means.

  As described above, according to the present invention, it is possible to ensure the refill performance even when the liquid discharge amount is large.

  Hereinafter, with reference to the accompanying drawings, a liquid discharge head according to the present invention, a cap unit thereof, and an image forming apparatus including these will be described in detail.

  FIG. 1 is an overall configuration diagram showing an outline of an embodiment of an ink jet recording apparatus as an image forming apparatus provided with a liquid discharge head (print head) according to the present invention.

  As shown in FIG. 1, the inkjet recording apparatus 10 includes a printing unit 12 having a plurality of printing heads (liquid ejection 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 that exceeds at least one side of the maximum size recording paper 16 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.

  As described above, according to the printing unit 12 in which the full line head covering the entire area of the paper width 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 the operation once (that is, by one sub-scanning). 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. Function as.

  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 pattern 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 arrangement of the nozzles (liquid ejection ports) of the print head (liquid ejection 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 according to the present embodiment has two types of pressure generating units. The first pressure generating unit includes a nozzle 51 that discharges ink as droplets, and ink that discharges ink. 3 is a pressure chamber unit 54 configured to include an ink supply port 53 that supplies ink to the pressure chamber 52 from a common flow path (not shown in FIG. 3). The pressure chamber units 54 are arranged in a zigzag two-dimensional matrix at the center in the width direction (short direction) of the print head 50 to increase the density of the nozzles 51.

  In addition, the second pressure generating unit of the print head 50 of the present embodiment is a perforated nozzle unit (perforated pressure chamber unit) 151 in which a plurality of nozzles 51 are formed in one pressure chamber 152, and the print head 50 is short. It is arranged on both sides in the hand direction.

  In FIG. 3, only a number smaller than the actual number of each pressure generating unit (pressure chamber unit 54, perforated nozzle unit 151) is displayed for easy understanding. In practice, more pressure generating units are arranged to achieve higher density. The size of the nozzle arrangement on the print head 50 is not particularly limited. For example, the nozzles 51 of the pressure chamber unit 54 are arranged in 48 horizontal (short direction) rows at 0.5 mm intervals and in the vertical (longitudinal) direction. (Direction) 2400 npi is achieved by arranging 600 rows at 0.5 mm intervals.

  In the example shown in FIG. 3, when each pressure chamber 52 is viewed from above, the planar shape is a parallelogram, but the planar shape of the pressure chamber 52 is limited to such a parallelogram. It is not a thing. In the pressure chamber 52, as shown in FIG. 3, a nozzle 51 is formed at one end of the diagonal line, and an ink supply port 53 is connected to the other end.

  In addition, the multi-hole nozzle unit 151 has a large number of nozzles 51 formed in one pressure chamber 152. In particular, each nozzle 51 of the multi-hole nozzle unit 151 has a corresponding normal arrangement arranged at the center of the print head 50. The nozzle 51 of the (first pressure generating unit) is formed so as to coincide with the position when projected so as to be aligned in the longitudinal direction.

  Although not shown, a plurality of short heads in which pressure chamber units similar to those in FIG. 3 are arranged in a two-dimensional matrix are connected in a two-dimensional staggered manner, and the plurality of short heads are connected. One long full line head may be configured to have a length corresponding to the entire width of the print medium as a whole.

  4 is a cross-sectional view of the pressure chamber unit 54 taken along line 4-4 in FIG.

  As shown in FIG. 4, the pressure chamber unit (first pressure generating unit) 54 has a pressure chamber 52 that communicates with a nozzle 51 that ejects ink, and a tributary 155 is connected to the pressure chamber 52 via a supply port 53. Ink is supplied from. The configuration of the ink supply channel and the like will be described later.

  Further, one surface (the top surface in the figure) of the pressure chamber 52 is constituted by a diaphragm 56, and a piezoelectric body 58 that applies pressure to the diaphragm 56 and deforms the diaphragm 56 is joined to the upper portion of the diaphragm 56. Individual electrodes 57 are formed on the upper surface of 58. The diaphragm 56 also serves as a common electrode.

  The piezoelectric body 58 is sandwiched between the common electrode (the diaphragm 56) and the individual electrode 57 to form a piezoelectric element, and is deformed by applying a driving voltage to the two electrodes 56 and 57. The diaphragm 56 is pushed by deformation of the piezoelectric body 58 (piezoelectric element), 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 body 58 returns to its original state, the volume of the pressure chamber 52 is restored to its original size, and new ink passes from the tributary 155 through the supply port 53. Is supplied (refilled) to the pressure chamber 52.

  When the piezoelectric body 58 is driven in the flexural vibration mode (d31 mode), it is preferable to provide a gap 59 around the top of the piezoelectric body 58 so that the piezoelectric body 58 can be driven freely.

  FIG. 5 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. There are two types of the ink tank 60: a method of replenishing ink from a replenishing port (not shown) and a cartridge method of replacing the entire tank when the remaining amount of ink is low. When the ink type is changed according to the usage, the cartridge method 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. 5 is equivalent to the ink storage / loading unit 14 in FIG. 1 described above.

  As shown in FIG. 5, a filter 62 is provided in the middle of the conduit connecting the ink tank 60 and the print head 50 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. 5, 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 is provided with a cap 64 as a means for preventing the nozzle from drying or preventing an increase in ink viscosity near the nozzle, and a cleaning blade 66 as a means for cleaning the nozzle surface 50A.

  The maintenance unit including the cap 64 and the cleaning blade 66 can be moved relative to the print head 50 by a moving mechanism (not shown), and moves from a predetermined retracted position to a maintenance position below the print head 50 as necessary. Is done.

  The cap 64 is displaced up and down relatively with respect to the print head 50 by an elevator mechanism (not shown). The lifting mechanism is configured to cover the nozzle region of the nozzle surface 50 </ b> A with the cap 64 by raising the cap 64 to a predetermined raised position when the power is turned off or waiting for printing, and bringing the cap 64 into close contact with the print head 50.

  Note that the cap (cap means) 64 of the present embodiment is configured such that the nozzle 51 of the pressure chamber unit 54 and the nozzle 51 of the perforated nozzle unit 151 can be sucked separately, which will be described later.

  The cleaning blade 66 is made of an elastic member such as rubber, and can slide on the ink ejection surface (nozzle surface 50A) of the print head 50 by a blade moving mechanism (not shown). When ink droplets or foreign matters adhere to the nozzle surface 50A, the nozzle surface 50A is wiped by sliding the cleaning blade 66 on the nozzle surface 50A to clean the nozzle surface 50A.

  During printing or standby, when a specific nozzle 51 is used less frequently and the ink viscosity in the vicinity of the nozzle 51 is increased, preliminary ejection toward the cap 64 is performed to discharge the ink that has deteriorated due to the increased viscosity. Is done.

  In addition, when bubbles are mixed in the ink in the print head 50 (ink in the pressure chamber 52), the cap 64 is applied to the print head 50, and the ink in the pressure chamber 52 (ink in which bubbles are mixed) is applied by the suction pump 67. The ink removed by suction is sent to the collection tank 68. This suction operation is also performed when the initial ink is loaded into the head or when the ink is used after being stopped for a long time, and the deteriorated ink solidified by increasing the viscosity is sucked and removed.

  That is, 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, resulting in pressure generation means for ejection driving (not shown, described later). ) Does not discharge ink from the nozzle 51. Therefore, before this state is reached (within the viscosity range in which ink can be ejected by the operation of the pressure generating means), the pressure generating means is operated toward the ink receiver, and the ink in the vicinity of the nozzle whose viscosity has increased is removed. “Preliminary discharge” is performed. Further, after the dirt on the nozzle surface 50A is cleaned by a wiper such as a cleaning blade 66 provided as a cleaning means for the nozzle surface 50A, the foreign matter is prevented from being mixed into the nozzle 51 by this wiper rubbing operation. Also, preliminary discharge is performed. Note that the preliminary discharge may be referred to as “empty discharge”, “purge”, “spitting”, or the like.

  In addition, if bubbles are mixed in the nozzle 51 or the pressure chamber 52 or if the viscosity of the ink in the nozzle 51 exceeds a certain level, ink cannot be ejected by the preliminary ejection. Do.

  That is, when bubbles are mixed in the ink in the nozzle 51 or the pressure chamber 52, or when the ink viscosity in the nozzle 51 rises to a certain level or more, the ink is ejected from the nozzle 51 even if the pressure generating means is operated. become unable. In such a case, an operation in which the cap 67 is applied to the nozzle surface 50 </ b> A of the print head 50 and the ink or the thickened ink in which bubbles in the pressure chamber 52 are mixed is sucked by the pump 67.

  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 to perform preliminary discharge as much as possible. The cap 64 described in FIG. 5 functions as a suction unit and can also function as a preliminary discharge ink receiver.

  Preferably, the inner side 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.

  FIG. 6 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 made 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. 6, the image buffer memory 82 is shown in a form 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 pressure generating means of the print head 50 for 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.

  Hereinafter, the print head (liquid discharge head) 50 having the multi-hole nozzle unit 151 which is a feature of the present invention will be described in detail.

  FIG. 7 is an enlarged perspective view of the porous nozzle unit 151 of the present embodiment.

  As shown in FIG. 7A, the multi-hole nozzle unit (second pressure generating unit) 151 has a plurality of nozzles 51 (eight nozzles in the example shown in the figure) formed in one pressure chamber 152. Ink is supplied to the pressure chamber 152 from an unillustrated branch through the ink supply port 153. Further, on the upper surface of the pressure chamber 152, a vibration plate 156 that also serves as a common electrode, a piezoelectric body 158, and an individual electrode 157 are formed in the same manner as a normal pressure chamber unit (first pressure generating unit) 54. The piezoelectric body 158 is driven by applying a driving voltage between the common electrode (the diaphragm 156) and the individual electrode 157, the diaphragm 156 is deformed, the volume of the pressure chamber 152 is reduced, and each nozzle 51 Ink droplets 51a are ejected all at once.

  In addition, although the discharge method of the porous nozzle unit 151 shown in FIG. 7 is a piezoelectric method, a discharge method is not limited to this, For example, a thermal method may be used. Although not particularly illustrated, the wiring for supplying a drive signal to the individual electrode 157 may be drawn out in a direction parallel to the plane on which the piezoelectric body 158 is formed, or the piezoelectric body 158 is formed. A method of pulling out in a columnar shape in a direction perpendicular to the flat surface.

  In the example shown in the figure, the eight nozzles 51 are arranged in a line, but the arrangement of the nozzles 51 is not limited to the arrangement in a line in this way. For example, the nozzles 51 may be arranged in a staggered pattern. Alternatively, they may be arranged in an n × m two-dimensional matrix (n and m are positive integers).

  Further, since the multi-hole nozzle unit 151 has a plurality of nozzles 51 in one pressure chamber 152 and ejects a large amount of ink at a time, it is necessary to always supply sufficient ink to meet the requirement. Therefore, as shown in FIG. 7B, two ink supply ports 153 and 153 may be provided in the pressure chamber 152 to supply ink from two directions.

  FIG. 8 shows the arrangement of the porous nozzles in the print head 50 according to the first embodiment of the present invention. In this embodiment, 2 pl (picoliter) can be discharged from each nozzle in the multi-hole nozzle unit.

  As shown in FIG. 8, the main flow 55, 55 (first liquid flow channel) of two ink flow paths is arranged in the print head 50 in parallel with the longitudinal direction, and the main flows 55, 55 are spanned. A tributary 155 (second liquid flow path) is formed. 48 nozzles 51-1 to 51-48 are arranged in a two-dimensional matrix along a tributary 155 between the main streams 55 and 55. Further, a portion close to the main flow of the tributary 155 on the opposite side of the main flow 55 with respect to the nozzles 51-1 to 51-48 arranged in a two-dimensional matrix, that is, on a portion outside the main flow 55, 55. Are connected to the main flow 55 through this, and the porous nozzle units (second pressure generating units) 151A, 151C and 151B, 151D are respectively arranged. Each multi-hole nozzle unit 151A, 151B, 151C, 151D is supplied with ink from a branch 155 (communication path) outside the main stream 55 via an ink supply port 153.

  Each multi-hole nozzle unit 151A, 151B, 151C, 151D has 12 nozzles 51, each of 48 nozzles 51-1, arranged along the tributary 155 between the main streams 55, 55,. 51 to 48 are assigned to 12 nozzles so as to correspond to the nozzles of the multi-hole nozzle units 151A, 151B, 151C, and 151D.

  FIG. 9 shows the distribution of the 48 nozzles arranged along the tributary 155 between the main streams 55 and 55 to the perforated nozzle units 151A, 151B, 151C, and 151D, and the nozzle numbers of the nozzles arranged along the tributary 155. It shows using. Here, the nozzle number refers to branch numbers 1 and 2 such as reference numerals 51-1 and 51-2 attached to each nozzle.

  As shown in FIG. 9, for example, the 12 nozzles formed in the multi-hole nozzle unit 151A have nozzle numbers 1, 5, 9, 13, 17, 21, 25, 29, arranged along the tributary 155, respectively. This corresponds to nozzles 33, 37, 41 and 45. The same applies to the other multi-hole nozzle units 151B, 151C, 151D. For example, the nozzles of the multi-hole nozzle unit 151 </ b> B correspond to nozzles 6, 10, 14,.

  Specifically, as shown in FIG. 8, the nozzle 51-1 ′ of the multi-hole nozzle unit 151A corresponds to the nozzle 51-1 arranged along the tributary 155, and the nozzle 51-5 ′ is the nozzle 51-. Corresponds to 5. The nozzle 51-2 'of the multi-hole nozzle unit 151B corresponds to the nozzle 51-2 arranged along the tributary 155, and the nozzle 51-6' corresponds to the nozzle 51-6. The same applies to other cases.

  As described above, in the print head 50 having the two-dimensional matrix structure, the multi-hole nozzle units 151 </ b> A to 151 </ b> D are arranged so as to be close to the main stream 55. In the example shown in FIG. 8, four perforated nozzle units 151A, 151B, 151C, and 151D are arranged. However, one or a plurality of perforated nozzle units may be arranged. Further, the number of nozzles formed in the porous nozzle unit may be one or plural.

  By driving the multi-hole nozzle units 151A, 151B, 151C, and 151D arranged as described above, it is possible to perform solid printing with the largest ink consumption. When such multi-hole nozzle units 151A, 151B, 151C, 151D do not exist, all the pressure chambers 52 arranged along the tributary 155 must be driven in order to make a solid strike. In this case, it is possible to perform solid printing using only the nozzles near the main stream 155 (perforated nozzle units 151A, 151B, 151C, 151D).

  In this case, since a large amount of ink can be ejected from the vicinity of the main stream, the pressure loss in the tributary 155 is greatly reduced, and the pressure loss can be greatly reduced when viewed from the entire print head 50.

  As described above, by using the multi-hole nozzle units 151 </ b> A to 151 </ b> D as the solid nozzles, a large number of nozzles can be arranged at a position close to the main stream 55. In spite of adding redundant nozzles, such as a multi-hole nozzle unit, to the print head 50, the head width increase in the paper feed direction (short direction of the print head 50) is about several mm, and the nozzle arrangement efficiency is high. .

  In order to reduce the tributary pressure loss, a method of increasing the number of main streams can be considered, but according to the present embodiment, the pressure loss can be reduced without increasing the number of main streams, so it is not increased in the paper feed direction. The head width can be shortened by the width of the main stream.

  As described above, the porous nozzle units (151A to 151D) that are partially arranged for each tributary 155 and can be used for solid printing are partially solid even when the entire printing medium is not solid. The need to do is high and the frequency of use is high.

  Further, by using the image processing technique to drive the porous nozzle unit as much as possible, it is possible to perform more efficient printing.

  FIG. 10A shows a simple perspective view of the multi-hole nozzle unit 151A shown in FIG. As shown in FIG. 10 (a), the multi-hole nozzle unit 151A includes twelve nozzles 51-1 ′, 51-5 ′, 51-9 ′, 51-13 ′, 51-17 ′, and 51-21 ′. , 51-25 ′, 51-29 ′, 51-33 ′, 51-37 ′, 51-41 ′, 51-45 ′, and 2 pl of ink 51a is ejected from each nozzle.

  FIG. 10B shows a bottom view of a part of the multi-hole nozzle unit 151A. In the present embodiment, 48 nozzles for one row along the tributary 155 when the nozzle density is 2400 dpi is divided into four perforated nozzle units, and each nozzle 51 is arranged in a line at equal intervals. The diameter d1 of each nozzle 51 is 20 μm, and the nozzle interval D1 is 22.4 μm.

  Moreover, the width of the tributary 155 shown in FIG. 8 is 300 μm and the height is 500 μm. The ink viscosity is assumed to be 20 cP. Considering the length of the tributary 155 for one main stream 55, 48 nozzles are arranged in one tributary 155, but now there are two main streams 55 as shown in FIG. The number of nozzles for one main stream 55 is considered to be 24, which is half. That is, the length of the tributary 155 per main stream 55 is 12 mm when calculated as 500 μm × 24 using a nozzle pitch of 500 μm in the sub-scanning direction.

  At this time, as conditions for considering the volume velocity of the ink flowing through the branch flow 155 of 12 mm in length, the number of nozzles N = 24, the ejection frequency f = 40 kHz, and the ejection droplet volume V = 2 pl.

  By the way, the channel resistance R of the tributary 155 is calculated by the following equation (1).

R = ² kμl (S ² / A ³ ) (1)
Here, k = 1.5 / (1 + ε) ² [1- (192 / π ⁵ ) ε {tanh (π / 2ε) + (1/3 ⁵ ) tanh (π / 2ε) +. Where ε is the aspect ratio (ε <1), k is a constant determined from the aspect ratio, μ is the viscosity, l is the flow path length, S is the entire circumference of the pipe, and A is the cross-sectional area of the pipe.

For comparison with the present embodiment, when the flow path resistance R (conventional) in the conventional case shown in FIG. 20 is calculated, R (conventional) = 6.8 × 10 ¹¹ Ns / m ⁵ and the volume velocity. U = N × f × V = 24 × 40 × 10 ³ × 2 × 10 ⁻¹⁵ = 1.9 × 10 ⁻⁹ m ³ / s.

  Further, the tributary pressure loss is calculated by the product of the channel resistance and the volume velocity, such that (branch pressure loss) = (channel resistance) × (volume velocity). Thus, when the conventional tributary pressure loss P (conventional) is calculated, P (conventional) = R (conventional) × U ÷ 2 = 646 Pa. Here, the last divided by 2 was calculated with the tributary length of 12 mm as described above, but since all the ink does not flow to the tip of the tributary, on average, it is half the distance of the tributary. This is because the ink is considered to flow by 6 mm, so the actual pressure loss is halved.

  According to Patent Document 1 described above, when the pressure loss of the entire ink flow path system is 800 Pa or more, the refill cannot catch up and the ejection becomes unstable.

  As a result of calculating the pressure loss of each part in the ink flow path system assumed by the present inventor, it was found that the pressure loss in the tributary region accounts for about 50% of the total pressure loss. That is, in the ink flow path system targeted by the present invention, it is necessary to suppress the tributary pressure loss within 400 Pa. However, as calculated above, the conventional tributary pressure loss P (conventional) is 646 Pa, which exceeds 400 Pa, so that the discharge is not stable as it is.

  On the other hand, in this embodiment, the length L ′ from the main stream 55 from the tributary 155 to the ink supply port 153 for supplying ink to the perforated nozzle unit 151A shown in FIG. 1/10 or less of L, which is half of the distance 2L, that is, L ′ ≦ L / 10.

  As a result, the length of the tributary 155 (corresponding to L ′) from the main flow 155 to the ink supply port 153 of the multi-hole nozzle unit 151A corresponds to the length (corresponding to L) of the tributary 155 from the main flow 55 to the center of the tributary 155. 1/10). For this reason, the pressure loss in the tributary 155 toward the multi-hole nozzle unit 151A can be reduced to 1/10. Therefore, the pressure loss in the tributary 155 is 1/10 of the conventional tributary pressure loss P (conventional) = 646 Pa, which is about 65 Pa.

  What has been described above is the case of solid printing. For refilling when not solid, 48 normal nozzles 51-1 to 51-48 other than the multi-hole nozzle units 151A to 151D are combined with the multi-hole nozzle units 151A to 151D, and similar to the human eye. By performing image processing so as to form an image so that it can be seen as an image, the pressure loss in the tributary 155 can be suppressed to within 400 Pa.

  As usage examples of the multi-hole nozzle units 151A to 151D, FIG. 11A shows the state of dots formed in the case of full discharge and FIG. 11B shows the case of half-discharge.

  In the case of full discharge, all four porous nozzle units 151A to 151D are used, and these porous nozzle units 151A, 151B, 151C, and 151D are driven in order, so that a solid image as shown in FIG. Is formed.

  Further, in the case of half-discharge, for example, by alternately discharging a set of perforated nozzle units 151A and 151C and a set of perforated nozzle units 151B and 151D, full discharge as shown in FIG. Compared to the case, an image ejected by exactly half is formed.

  Furthermore, it is possible to add gradation by combining the discharge of these multi-hole nozzle units 151A to 151D. In addition, since there is a margin for the pressure loss when viewed from the entire print head 50, there is a margin for refilling.

  In the example described above, 10 M ′ ≦ M is set for the tributary length M corresponding to one main stream and the tributary length M ′ on the porous nozzle unit (redundant nozzle) side. Instead, by disposing the perforated nozzle unit near the main stream, it becomes possible to continue discharging high-viscosity ink without delaying refilling.

  In the embodiment described above, the number of mainstreams has been described as two, but the number of mainstreams is not limited to two. The main stream may be one. For example, the main flow may have a structure in which one main stream is arranged in the center and has a tributary branching on both sides, and the porous nozzle unit is arranged in the vicinity of the main flow.

  Moreover, the perforated nozzle unit is not only used for solid printing, but can also be suitably used when, for example, a line such as a vertical line of characters is drawn.

  Next, a print head (liquid discharge head) according to a second embodiment of the invention will be described.

  In the present embodiment, the ink droplets ejected from each nozzle of the multi-hole nozzle unit are 16 pl (picoliter).

In this case, the ejection amount is 16 pl, which is 8 times the volume and 4 times the area of 2 pl of the first embodiment described above, and the diameter of the landed ink is twice that of 2 pl.
Therefore, the number of nozzles required for solid printing is 24, which is half of the 48 nozzles formed along each tributary between the main streams. Therefore, 24 nozzles necessary for the solid printing are distributed to the two perforated nozzle units, 12 each.

  FIG. 12 shows the nozzle and flow path arrangement in the print head of this embodiment.

  As shown in FIG. 12, also in this embodiment, 48 nozzles 51-1, each ejecting 2 pl of ink along a tributary 155 spanned between two parallel main streams 55, 55, To 51-48 are the same as in the first embodiment described above.

  In the present embodiment, on the other hand, perforated nozzle units 151E and 151F each having 12 nozzles for ejecting 16 pl of ink are arranged near the main stream 55 of the branch stream 155 outside the main streams 55 and 55, respectively. Is done.

  In the porous nozzle unit 151E, nozzles n1, n3, n5,..., N23 are formed, and in the porous nozzle unit 151F, nozzles n2, n4, n6,. Each of these nozzles corresponds to two adjacent nozzles of 48 nozzles 51-1 to 51-48 arranged along the tributary 155.

  FIG. 13 shows the correspondence of this nozzle. As shown in FIG. 13, the ink ejected from the nozzles 51-1 and 51-2 formed along the tributary 155 was ejected from the nozzle n1 of the porous nozzle unit 151E at an intermediate position. The nozzle n1 of the multi-hole nozzle unit 151E is arranged so that the ink lands. The same applies to other nozzles.

  Since the diameter of the ink droplets ejected from the nozzle n1 is twice the diameter of the ink droplets ejected from the nozzles 51-1 and 51-2, the arrangement as shown in FIG. Thus, the two ink droplets ejected from the nozzles 51-1 and 51-2 can be exactly covered with the ink droplets ejected from the nozzle n1.

  In the present embodiment, the proportion that is advantageous in the pressure loss of the tributary is the same as in the first embodiment in which 2 pl is discharged from each nozzle of the porous nozzle unit described above. Because, in this embodiment, only one perforated nozzle unit is disposed outside the main stream, the tributary length communicating with the perforated nozzle unit is half that of the first embodiment described above. The flow path resistance is halved. However, the ink discharge amount for filling the same print width on the recording medium is doubled. Eventually, the pressure loss is the same as in the first embodiment.

  As a modification of the present embodiment, the multi-hole nozzle units 151E and 151F may be collected on one side of the main stream 55 as shown in FIG. By doing so, since the multi-hole nozzle units 151E and 151F are close to each other, it is possible to prevent a landing position shift with respect to a paper feed shift.

  Next, a third embodiment of the present invention will be described.

  In the third embodiment, as in the modification of the second embodiment described above shown in FIG. 14, two porous nozzle units each having 12 nozzles for 16 pl discharge are arranged on one side of the main stream. In particular, each tributary is preferably a main stream so that the tributary in which the normal nozzles between the main streams are arranged and the tributary in which the porous nozzle unit outside the main stream is arranged not to face each other across the main stream. The position to be connected to is shifted by ½ pitch of the interval between the tributaries.

  FIG. 15 shows a print head according to this embodiment.

  As shown in FIG. 15, in this embodiment, normal nozzles 1, 2, and the like are arranged, a tributary 155 a inside the main flow 55, and porous nozzle units 151 </ b> E and 151 </ b> F are arranged than the main flow 55. The positions where the respective tributaries 155a and 155b are connected to the main stream 55 are shifted so that the outer tributary 155b does not face the main stream 55 in a straight line.

  At this time, it is preferable that each of the tributaries is arranged so as to be shifted by 1/2 pitch of the interval with the adjacent tributary.

  As described above, the connection position of the tributary 155a in which the normal nozzles 1 and the like are arranged and the tributary 155b in which the multi-hole nozzle units 151E and 151F are arranged to the main flow 55 is shifted from each other. Since the pressure waves coming out from the ink supply ports 153 of the units 151 and 151F are not easily transmitted to the opposite side of the main flow 55, there is an effect of preventing crosstalk.

  As a modification of the present embodiment, as shown in FIG. 16, the connection position of the tributary 155a in which the normal nozzles 1 and the like are arranged and the tributary 155b in which the multi-hole nozzle units 151E and 151F are arranged are connected to the main stream 55. Two ink supply ports 153 for supplying ink to each of the porous nozzle units 151E and 151F may be provided.

  At this time, as shown in FIG. 16, it is preferable that the ink supply ports 153 and 153 formed in the multi-hole nozzle units 151E and 151F are respectively connected to separate tributaries 155b. In this way, even if one of the ink supply ports 153 is clogged with dust or bubbles and cannot supply ink, ink is supplied from the other ink supply port 153 to the porous nozzle units 151E and 151F. Can be supplied.

  In FIG. 16, the tributaries 155a and 155b sandwiching the main stream 55 are displayed so as to be shifted by 1/2 pitch of the tributary intervals, but the way of shifting the tributaries 155a and 155b is limited to 1/2 pitch. It is not something.

  Next, a fourth embodiment of the present invention will be described.

  In the fourth embodiment, the porous nozzle unit is directly connected to the main stream. In each of the embodiments described above, since the multi-hole nozzle unit is connected to a tributary near the main flow, there is a length of the tributary from the main flow to the tributary connection portion of the multi-hole nozzle unit, and there is a pressure loss of the tributary in that portion. However, in this embodiment, since the multi-nozzle unit is directly connected to the main stream, the length of the tributary is zero, so that the pressure loss of the tributary to the multi-nozzle unit can be zero.

  In FIG. 17, the connection structure to the main flow of the porous nozzle unit in this embodiment is shown with a perspective view.

  As shown in FIG. 17, the ink supply port 153 of the multi-hole nozzle unit 151 </ b> G is directly connected to the main stream 55. Also in this embodiment, each nozzle n1 of the multi-hole nozzle unit 151G discharges 16 pl ink droplets as in the second embodiment, and the multi-nozzle nozzle unit 151G has 12 nozzles n1,. , N23 are provided. In addition, a piezoelectric body 158 as pressure generating means is formed on the upper portion of the pressure chamber 152 of the multi-hole nozzle unit 151G.

  Further, a branch stream 155 for supplying ink from the main stream 55 to a normal nozzle (not shown) is connected to the main stream 55 on the opposite side to the ink supply port 153 of the perforated nozzle unit 151G.

  Thus, since the ink supply port 153 of the multi-hole nozzle unit 151G is directly connected to the main flow 55, the length of the tributary 155 with respect to the multi-hole nozzle unit 151G becomes 0, and the pressure loss of the tributary 155 with respect to the multi-hole nozzle unit 151G is reduced. Can be zero.

  Next, the structure of the cap, which is another feature of the present invention, will be described.

  FIG. 18A shows a plan view of the cap, and FIG. 18B shows a perspective view of the cap.

  As shown in FIG. 18A, the cap 64 has one beam 64b on the side close to the side in the longitudinal direction in a rectangular frame 64a having a size sufficient to cover the entire print head 50. The two openings 64c and 64d are formed in the frame 64a.

  As shown in FIG. 18B, the frame 64a and the beam 64b are formed of an elastic member such as rubber so that the frame 64a and the beam 64b can be in close contact with the print surface of the print head 50. It is made of resin or the like. At this time, the width H1 of the opening 64c is large enough to include the porous nozzle unit disposed outside the main stream. Further, the width H2 of the beam 64b has a size that can cover and close the porous nozzle unit. The width H3 of the opening 64d has a size that can include all the normal nozzles arranged along the tributary. The lower side of the frame 64a also has the same width H2 as the beam 64b so as to cover and close the porous nozzle unit.

  A hose 65 communicating with a pump (not shown) is connected to the bottom surface of the opening 64d. Although not shown, a hose communicating with the same pump is also connected to the bottom surface of the opening 64c.

  FIG. 19 is a plan view showing the state during ink suction.

  FIG. 19A shows a case where the porous nozzle unit is capped and ink is sucked from a normal nozzle. FIG. 19B shows that the porous nozzle unit can be sucked from the porous nozzle unit without capping. This shows the case.

  As shown in FIG. 19A, when the porous nozzle unit is capped, the cap 64 is applied to the print head 50 so that the lower sides of the beam 64b and the frame 64a cap the porous nozzle unit 151, respectively. To. Then, a pump (not shown) is driven to suck ink from each nozzle 51 existing in the opening 64d.

  Further, when the multi-hole nozzle unit is not capped, as shown in FIG. 19B, the cap 64 is slightly shifted downward in the figure so that the beam 64b covers one main flow 55, and the inside of the opening 64c. One porous nozzle unit 151 is included in the aperture 64d, and the other porous nozzle unit 151 is included in the opening 64d. The ink in the porous nozzle unit 151 can be sucked by driving the pump and sucking in this way.

  By configuring the cap 64 in this way, it is possible to easily switch between the case where the porous nozzle unit 151 is capped and the case where the porous nozzle unit 151 is not capped by simply shifting the cap 64 as described above. Become. In addition, since one cap 64 can cope with both cases where the multi-hole nozzle unit 151 is capped, the number of members can be reduced, and the cost can be reduced.

  In the case where the nozzle is not discharged from the perforated nozzle unit, an image can be created by driving a normal nozzle. This is due to the fact that the multi-hole nozzle unit is a so-called redundant nozzle that overlaps the normal nozzle.

  In addition to the above-described image sensor, the porous nozzle unit has a plurality of nozzles, and the plurality of nozzles discharge at the same time. In order to specify which nozzle is not ejecting when the nozzles of the ink jet are not ejected, it is possible to detect ink droplets in flight.

  As described above, the liquid discharge head, the cap unit thereof, and the image forming apparatus including these have been described in detail. However, the present invention is not limited to the above examples, and the scope of the present invention is not deviated. Of course, various improvements and modifications may be made.

1 is an overall configuration diagram illustrating an outline of an embodiment of an ink jet recording apparatus including a liquid ejection head according to the present invention. FIG. 2 is a plan view of a main part around a printing unit of the inkjet 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 of FIG. 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. (A), (b) is a perspective view which shows the example of a porous nozzle unit. FIG. 3 is a plan view showing an arrangement of a porous nozzle unit and an ink supply path in the print head according to the first embodiment of the present invention. It is explanatory drawing which shows a response | compatibility with the porous nozzle unit and normal nozzle in 1st Embodiment. (A) is a perspective view which shows the porous nozzle unit in 1st Embodiment, (b) is the top view which expanded the part. It is explanatory drawing which shows the usage example of a porous nozzle unit, (a) shows the case of full discharge, (b) shows the case of half discharge. It is a top view which shows arrangement | positioning of the porous nozzle unit and ink supply path in the print head which concerns on 2nd Embodiment of this invention. It is explanatory drawing which shows the relationship between the normal nozzle and porous nozzle unit in 2nd Embodiment. It is a top view which shows the modification of 2nd Embodiment. It is a top view which shows arrangement | positioning of the porous nozzle unit and ink supply path in the print head which concerns on 3rd Embodiment of this invention. It is a top view which shows the modification of 3rd Embodiment. It is a perspective view which shows the porous nozzle unit in the print head which concerns on 4th Embodiment of this invention. It is explanatory drawing which shows the cap which concerns on this invention, (a) is a top view, (b) is a perspective view. It is explanatory drawing which shows the use condition of a cap, (a) shows the case where a porous nozzle unit is capped, (b) shows the case where a porous nozzle unit is not capped. It is a top view which shows arrangement | positioning of the nozzle of an inkjet head of the conventional two-dimensional matrix structure, and an ink supply path.

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 ... main flow, 56 ... vibrating plate (common electrode), 57 ... individual electrode, 58 ... piezoelectric material, 59 ... gap, 60 ... ink tank, 62 ... filter, 64 ... cap, 66 ... blade, 67 ... suction pump, 6 DESCRIPTION OF SYMBOLS ... Collection tank, 70 ... Communication interface, 72 ... System controller, 74 ... Image memory, 76 ... Motor driver, 78 ... Heater driver, 80 ... Print control part, 82 ... Image buffer memory, 84 ... Head driver, 86 ... Host computer , 88 ... motor, 89 ... heater, 151 ... perforated nozzle unit, 153 ... ink supply port (for perforated nozzle unit), 155 ... tributary

Claims (7)

A first liquid flow path for feeding a liquid;
A plurality of second liquid flow paths branched in a predetermined direction from the first liquid flow paths and arranged in parallel;
A plurality of first pressures that communicate with each of the second liquid flow paths through the supply ports, are arranged along the second liquid flow paths, and are arranged in a two-dimensional matrix, each having one discharge port. Generating unit;
The communication path branched from the first liquid flow path disposed in the vicinity of the first liquid flow path on the opposite side across the first liquid flow path with the first pressure generating units arranged in a matrix form A second pressure generating unit having a plurality of discharge ports communicating with the first liquid flow path via
A liquid discharge head comprising:   In the vicinity of the first liquid channel where the second pressure generating unit is disposed, the distance from the first liquid channel is the length of the second liquid channel per one first liquid channel. The liquid discharge head according to claim 1, wherein the liquid discharge head is in a range equal to or less than half of the range.   The branch position of the second liquid channel from the first liquid channel and the branch position of the communication channel from the first liquid channel are shifted in the liquid flow direction of the first liquid channel. The liquid discharge head according to claim 1, wherein the liquid discharge head is provided.   The liquid discharge head according to claim 1, wherein the second pressure generation unit has a plurality of supply ports.   An image comprising the liquid discharge head according to claim 1, wherein liquid is discharged from the liquid discharge head toward the recording medium while relatively moving the liquid discharge head and the recording medium. Forming an image forming apparatus.   The image forming apparatus according to claim 5, wherein a plurality of the second pressure generation units are arranged at least one upstream or downstream in the relative movement direction of the recording medium. It is a cap means of the liquid discharge head according to any one of claims 1 to 4,
The discharge ports of the first pressure generating units arranged in the two-dimensional matrix;
For the discharge port of the second pressure generating unit,
The state in which the discharge port of the second pressure generating unit is sealed and the state in which the second pressure generation unit is not sealed are switched by moving in parallel to the surface on which the discharge ports of the liquid discharge head are formed. A cap means for a liquid discharge head.

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