JP2006111000A - Liquid ejection head and image forming apparatus having it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a further increase in density so that high-frequency driving, particularly, ejection of high-viscous ink can be performed even when the density of nozzles is increased. <P>SOLUTION: The above described problem is solved by providing a liquid ejection head. The liquid ejection head has a plurality of ejection outlets for ejecting the liquid, a plurality of pressure chambers respectively communicating with the plurality of ejection outlets, a plurality of liquid supplying channels for respectively supplying the liquid to the plurality of pressure chambers, a common liquid chamber for supplying the liquid to the plurality of liquid supplying channels, piezoelectric elements for respectively deforming the plurality of pressure chambers, and piezoelectric element wiring for supplying drive signals to the pizoelectric elements. The piezoelectric element wiring is provided to penetrate through the common liquid chamber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid discharge head and an image forming apparatus including the liquid discharge head, and more particularly to a liquid discharge head capable of increasing the density of discharge ports for discharging a liquid and discharging a high-viscosity liquid. The present invention relates to an image forming apparatus.

  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 (ejection ports) are arranged, and the inkjet head and the recording medium are moved relative to each other while the inkjet head and the recording medium are moved relative to each other. Inkjet printers (inkjet recording apparatuses) are known that record an image on a recording medium by ejecting ink toward the recording medium.

  Such an ink jet printer supplies ink to a pressure chamber from an ink tank via an ink supply path, applies an electrical signal corresponding to image data to the piezoelectric element, and drives the piezoelectric element, thereby The diaphragm constituting the portion is deformed to reduce the volume of the pressure chamber, and the ink in the pressure chamber is ejected as droplets from the nozzle.

  Thus, in an inkjet printer, one image is formed on a recording medium by combining dots formed by ink ejected from nozzles. In recent years, it has been desired to form high-quality images that are comparable to photographic prints in inkjet printers. On the other hand, it is possible to achieve high image quality by reducing the nozzle diameter to reduce the ink droplets ejected from the nozzle and increasing the number of pixels per image by arranging the nozzles at high density. It is 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, a plurality of nozzles are arranged in a grid formed by a plurality of rows inclined at a certain angle with respect to the head main scanning direction and a plurality of columns orthogonal to the head main scanning direction, and provided corresponding to each nozzle. It is known that the planar shape of the vibration plate forming one surface of the pressure chamber is approximately square or rhombus, thereby improving the discharge efficiency of the pressure chamber and arranging the nozzles at high density. (For example, refer patent document 1 etc.).

In addition, a pressure chamber provided in the cavity plate is formed in a substantially rhombus shape, an ink supply port is formed in one acute angle portion of the pressure chamber, and an ink ejection nozzle is formed in the other acute angle portion. It is known that a large number of ink pressure chambers corresponding to multiple nozzles are arranged without increasing the size of the tee plate so as to increase the density of the nozzles (for example, Patent Document 2). reference).
JP 2001-334661 A JP 2002-166543 A

  However, if the nozzle density is increased with the configuration of the ink jet head described in the above-mentioned patent documents, the problem described below occurs. It is difficult to increase the density and increase the efficiency of ink ejection.

That is, in the configuration for ejecting ink from one nozzle of the ink jet head disclosed in the above-mentioned patent document, the common flow path and supply of ink with a diaphragm forming one wall surface of the pressure chamber as a boundary. The passage, the pressure chamber, and the nozzle are arranged on the same side, and the piezoelectric actuator is arranged on the opposite side.

  For example, as the density increases in such a configuration, the size of the common flow path decreases as the density increases. The ink supply cannot be caught up. Therefore, when the common flow path size is increased in order to make the ink supply smooth, the distance from the pressure chamber to the nozzle becomes longer, so that the discharge itself becomes difficult. After all, there is a problem that the discharge frequency cannot be increased due to the restriction on the arrangement of the common flow path size.

  In addition, in the case of an ink having a low viscosity, the ink that has landed on the recording medium immediately penetrates into the recording medium and causes bleeding, thereby causing deterioration of the image quality. Use of high viscosity ink is desired. However, when the high-viscosity ink is to be used for the head having a high-density nozzle as described above, the ink supply to the pressure chamber is further delayed and the discharge frequency is further increased. There is a problem of lowering.

  The present invention has been made in view of such circumstances. Even when the density of the liquid discharge ports is increased, the high-frequency drive, in particular, the discharge of a highly viscous liquid can be performed, and further electrode wiring and liquid discharge ports can be provided. It is an object of the present invention to provide a liquid discharge head that achieves high density and an image forming apparatus including the same.

  In order to achieve the object, the invention according to claim 1 includes a plurality of discharge ports for discharging a liquid, a plurality of pressure chambers communicating with each of the plurality of discharge ports, and each of the plurality of pressure chambers. A plurality of liquid supply channels for supplying liquid to the liquid, a common liquid chamber for supplying liquid to the plurality of liquid supply channels, a pressure generating means for deforming each of the plurality of pressure chambers, and the pressure generating means. There is provided a liquid discharge head including an electric wiring for supplying a driving signal, and the electric wiring is disposed so as to penetrate the common liquid chamber.

  Thereby, since the wiring of the pressure generating means is arranged so as to penetrate the common liquid chamber (rises substantially vertically), the space held by the wiring in the common liquid chamber can be minimized. In addition, it is possible to increase the density of the discharge ports and reduce the flow resistance of the common liquid chamber.

  According to a second aspect of the present invention, the pressure generating means is a piezoelectric element.

  According to a third aspect of the present invention, the pressure generating means is provided on the opposite side of the pressure chamber from the discharge port, and the common liquid chamber is disposed on the opposite side of the pressure chamber with respect to the pressure generating means. It is characterized by that.

  As a result, the degree of freedom in designing the flow path for guiding the liquid from the common liquid chamber to the pressure chamber is increased, a space on the discharge port side from the pressure chamber can be secured, and the flow path from the pressure chamber to the discharge port side is shortened accordingly. Therefore, the liquid discharge efficiency can be increased, and high viscosity liquid can be discharged.

  According to a fourth aspect of the present invention, the liquid supply channel is formed substantially perpendicular to a surface including the pressure generating means.

  As a result, the common liquid chamber and the pressure chamber can be directly connected to each other fluidly, and even a high-viscosity liquid can be refilled quickly, and further, high-frequency driving can be performed.

According to a fifth aspect of the present invention, the electrical wiring is formed substantially perpendicular to a surface including the pressure generating means.

  As a result, the two-dimensional electrode can be taken out and the wiring density can be increased.

  According to a sixth aspect of the present invention, the plurality of pressure chambers are arranged in a two-dimensional matrix.

  Thereby, the density of the discharge ports can be further increased.

  According to a seventh aspect of the present invention, a wiring layer connected to the electric wiring is provided on the opposite side of the common liquid chamber from the pressure generating means.

  Thereby, the freedom degree of a wiring layer can be improved and it becomes possible to make a wiring high-density.

  Similarly, in order to achieve the object, an invention according to an eighth aspect provides an image forming apparatus comprising the liquid ejection head according to any one of the first to seventh aspects. To do.

  As a result, high-quality image formation can be performed by the liquid discharge head having a high density.

  As described above, according to the liquid ejection head and the image forming apparatus including the liquid ejection head according to the present invention, it is possible to secure a wiring space for supplying a drive signal to the pressure generating unit, and to increase the ejection port. Densification can be achieved.

  Further, when the common liquid chamber is arranged on the side opposite to the pressure chamber with respect to the pressure generating means, the size of the supply flow path can be increased, and the discharge ports can be densified and driven at high frequency. Further, when the wiring layer is arranged on the upper side of the common liquid chamber using the electric wiring, it can be integrated with the driver chip, and further high density can be achieved.

  In addition, by disposing the common liquid chamber on the opposite side of the pressure chamber with respect to the pressure generating means, the liquid supply section and the pressure chamber can be directly connected fluidly. And high-viscosity liquid can be easily discharged.

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

  FIG. 1 is an overall configuration diagram showing an outline of a first embodiment of an ink jet recording apparatus as an image forming apparatus having a liquid ejection 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.

  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. 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.
FIG. 3 shows a plan perspective view of the print head 50.

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

  The size of the nozzle arrangement on the print head 50 is not particularly limited. As an example, the nozzle 51 is arranged in 48 rows (21 mm) and 600 columns (305 mm) in length to achieve 2400 npi. .

  In the example shown in FIG. 3, when each pressure chamber 52 is viewed from above, the planar shape thereof is substantially square, but the planar shape of the pressure chamber 52 is not limited to such a square. Absent. 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 provided at the other end.

  FIG. 4 is a perspective plan view showing another structural example of the print head. As shown in FIG. 4, a plurality of short heads 50 'are arranged and connected in a two-dimensional staggered pattern so that the entire 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. 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.

  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 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.

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.

  Next, the liquid ejection head (printing head 50) that is capable of high-frequency driving and high-viscosity ink ejection even when the nozzle and ink supply system and the wiring for supplying the driving signal are increased in density is a feature of the present invention. explain.

  In the first embodiment, in order to realize such a high density print head, first, as shown in FIG. 3, for example, the pressure chambers 52 (nozzles 51) are arranged in a two-dimensional matrix to form the nozzles 51. The density is increased (for example, 2400 npi). Next, as will be described in detail below, in the present embodiment, a common liquid chamber that supplies ink to the pressure chamber 52 is disposed on the upper side of the vibration plate, and the pressure chamber is directly connected to the common liquid chamber in order to emphasize the refilling property of the ink. The ink supply system is highly integrated by eliminating the piping that provides the flow path resistance by supplying the ink to 52. Further, in the present embodiment, an electric wiring for supplying a drive signal to the electrode (individual electrode) of the pressure generating means that deforms the pressure chamber 52 is set up vertically from each individual electrode so as to penetrate the common liquid chamber. It is connected to the wiring of the upper flexible cable.

  FIG. 7 shows a simplified perspective view of a part of such a high-density print head 50.

  As shown in FIG. 7, in the print head 50 of the present embodiment, a diaphragm 56 that forms the upper surface of the pressure chamber 52 is disposed above the pressure chamber 52 having the nozzle 51 and the ink supply port 53, and the diaphragm A piezoelectric element 58 (piezoelectric actuator) as a pressure generating means composed of a piezoelectric body such as a piezo sandwiched between electrodes is disposed in a portion corresponding to each pressure chamber 52 on 56, and the piezoelectric element 58 is disposed on the upper surface thereof. Individual electrodes 57 are provided.

  An electrode pad 59 as an electrode connecting portion is formed to be extended from the end face of the individual electrode 57 to the outside, and the electric wiring 90 is substantially perpendicular to the surface including the piezoelectric element 58 (pressure generating means) on the electrode pad 59. Standing up and formed. A multilayer flexible cable 92 is disposed on the electrical wiring 90 that rises substantially perpendicular to the surface including the piezoelectric element 58, and a driving signal is transmitted from the head driver 84 to the piezoelectric element 58 via these wirings. It is supplied to the individual electrode 57.

  In addition, a space in which columnar electric wires 90 are arranged between the diaphragm 56 and the flexible cable 92 is connected to a common liquid chamber 55 for supplying ink to the pressure chambers 52 through the ink supply ports 53. It has become.

  The common liquid chamber 55 shown here is one large space formed over the entire region where the pressure chambers 52 are formed so as to supply ink to all the pressure chambers 52 shown in FIG. However, the common liquid chamber 55 is not limited to the one formed as a single space as described above, and may be divided into several regions and formed in a plurality.

  The electrical wiring 90 that rises like a pillar vertically on the electrode pad 59 provided by being drawn out from the individual electrode 57 for each pressure chamber 52 supports the flexible cable 92 from below, and creates a space for the common liquid chamber 55. Forming. The electrical wiring 90 that rises like this column is also called an electric column because of its shape. In other words, the electrical wiring 90 (electric column) is formed so as to penetrate the common liquid chamber 55.

In addition, although the electrical wiring 90 shown here is formed one by one for each piezoelectric element 58 (the individual electrode 57), the number of wirings (the number of electric columns) is reduced. Therefore, one electrical wiring 90 may correspond to a plurality of piezoelectric elements 58 so that wirings for several piezoelectric elements 58 are combined into one electrical wiring 90. Further, not only the individual electrode 57 but also the wiring for the common electrode (diaphragm 56) may be formed as the electric wiring 90.

  As shown in FIG. 7, the nozzle 51 is formed on the bottom surface, and the ink supply port 53 is provided on the upper surface side of the corner that forms a diagonal with the nozzle 51. The ink supply port 53 passes through the vibration plate 56, and the common liquid chamber 55 and the pressure chamber 52 thereabove communicate with each other through the ink supply port 53. Thereby, the common liquid chamber 55 and the pressure chamber 52 can be directly connected fluidically.

  The diaphragm 56 is common to the pressure chambers 52 and is formed of a single plate. In addition, piezoelectric elements 58 for deforming the pressure chambers 52 are arranged at portions corresponding to the pressure chambers 52 of the diaphragm 56. Electrodes (common electrode and individual electrode) for applying a voltage to the piezoelectric element 58 for driving are formed on the upper and lower surfaces so as to sandwich the piezoelectric element 58.

  For example, the diaphragm 56 may be formed of a conductive thin film such as SUS, and the diaphragm 56 may also serve as a common electrode. At this time, individual electrodes 57 for individually driving the piezoelectric elements 58 are formed on the upper surface of the piezoelectric elements 58.

  As described above, the electrode pad 59 is drawn out from the individual electrode 57, and the electric wiring 90 (electric column) that rises vertically on the electrode pad 59 and penetrates the common liquid chamber 55 is formed. A method for manufacturing the electrical wiring 90 (electric column) will be described later. In the manufacturing process, the electrical wiring 90 is formed in a tapered shape as shown in FIG.

  A multilayer flexible cable 92 is formed on the columnar electrical wiring 90. The electrical wiring 90 serves as a column to support the multilayer flexible cable 92, with the diaphragm 56 as a floor and the multilayer flexible cable 92 as a ceiling. A space as the liquid chamber 55 is secured. Although not shown, each electric wiring 90 is connected to an individual wiring and a driving signal is supplied to each individual electrode 57 to drive each piezoelectric element 58.

  Although not shown in FIG. 7, since the common liquid chamber 55 is filled with ink, the surfaces of the diaphragm 56, the individual electrode 57, the electric wiring 90, and the multilayer flexible cable 92 that are in contact with the ink as the common electrode are respectively shown. It is covered with an insulating protective film.

  Each size of the print head 50 as described above is not particularly limited, but as an example, the pressure chamber 52 has a substantially square shape with a plane shape of 300 μm × 300 μm (excludes the stagnation point of the ink flow). The corners are chamfered for the purpose.) The height is 150 μm, the diaphragm 56 and the piezoelectric element 58 are each 10 μm thick, and the electric wiring 90 (electric column) is 100 μm in diameter at the connection with the electrode pad 59. The height is 500 μm or the like.

  FIG. 8 shows a part of the pressure chamber 52 in an enlarged plan perspective view. As described above, each pressure chamber 52 has a substantially square shape, the nozzle 51 and the ink supply port 53 are formed at both corners of the diagonal line, the electrode pad 59 is drawn out to the nozzle 51 side, and electrical wiring ( An electric column 90 is formed.

  FIG. 9 shows a cross-sectional view taken along one-dot chain line and line 9-9 in FIG.

As shown in FIG. 9, the print head 50 of the first embodiment is formed by laminating a plurality of thin films and the like. First, a flow path plate 96 in which a pressure chamber 52, an ink supply port 53, a nozzle flow path 51a connecting the pressure chamber 52 and the nozzle 51, and the like are formed is laminated on the nozzle plate 94 in which the nozzle 51 is formed. In the figure, the flow path plate 96 is represented as a single plate, but actually, the flow path plate 96 may be formed by stacking a plurality of plates.

  A diaphragm 56 that forms the top surface of the pressure chamber 52 is stacked on the flow path plate 96. It is preferable that the diaphragm 56 also serves as a common electrode for driving a piezoelectric element 58 described later together with the individual electrode 57. The diaphragm 56 is provided with an opening corresponding to the ink supply port 53 of the pressure chamber 52, whereby the pressure chamber 52 and the common liquid chamber 55 formed on the upper side of the diaphragm 56 communicate directly.

  A piezoelectric body 58a is formed on a portion corresponding to substantially the entire upper surface of the pressure chamber 52 on the diaphragm 56 (common electrode), and an individual electrode 57 is formed on the upper surface of the piezoelectric body 58a. Thus, the piezoelectric body 58a sandwiched between the common electrode (the diaphragm 56) and the individual electrode 57 is deformed when a voltage is applied between the common electrode 56 and the individual electrode 57, and the volume of the pressure chamber 52 is increased. A piezoelectric element 58 (piezoelectric actuator) that discharges ink from the nozzle 51 is configured.

  The end of the individual electrode 57 on the nozzle 51 side is drawn outward to form an electrode pad 59 as an electrode connection portion. A columnar electric wiring 90 (electric column) is vertically formed on the electrode pad 59 so as to penetrate the common liquid chamber 55.

  A multilayer flexible cable 92 is formed above the electrical wiring 90, and each wiring (not shown) formed on the multilayer flexible cable 92 is connected to each electrical wiring 90 by an electrode pad 90a to drive each piezoelectric element 58. A driving signal for supplying the signal is supplied through each electric wiring 90.

  The space where the columnar electric wiring 90 (electric column) between the diaphragm 56 and the multilayer flexible cable 92 stands is a common liquid chamber 55 for pooling ink to be supplied to the pressure chamber 52. Ink is filled with ink, so that an insulating / protective film 98 is formed on the surface of the diaphragm 56, the individual electrode 57, the piezoelectric body 58 a and the electrical wiring 90, and the surface of the multilayer flexible cable 92 that contacts the ink.

  As described above, in the present embodiment, the common liquid chamber that has conventionally been on the same side as the pressure chamber with respect to the diaphragm is brought to the upper side of the diaphragm, and arranged on the side opposite to the pressure chamber. Piping for guiding ink from the common liquid chamber to the pressure chamber, which was necessary in the past, is no longer necessary, and the size of the common liquid chamber can be increased, so that the ink can be supplied properly and the nozzle density is increased. Can be achieved, and high-frequency driving is possible even when the density is increased.

  In addition, since the wiring to the individual electrode of each piezoelectric element is set up vertically from the electrode pad of the individual electrode so as to penetrate the common liquid chamber, the wiring for supplying the drive signal to each piezoelectric element must be densified. Became possible.

  In addition, since the common liquid chamber is arranged on the upper side of the diaphragm so that the common liquid chamber and the pressure chamber are connected by a straight ink supply port, the common liquid chamber and the pressure chamber can be directly connected fluidically. Furthermore, since the common liquid chamber is disposed on the upper side of the diaphragm, the length of the nozzle channel 51a from the pressure chamber 52 to the nozzle 51 can be made shorter than before, and even when the density is increased, Viscosity ink (for example, about 20 cp to 50 cp) can be discharged, and a flow path structure capable of quick refilling after discharge can be obtained.

  Next, a method for manufacturing such a print head 50 will be described.

  10A to 10D show a manufacturing process of the print head 50 as described above.

  First, as shown in FIG. 10A, the pressure chamber 52 is formed. The method for forming the pressure chamber 52 is not particularly limited. For example, the pressure chamber 52 may be formed by etching a SUS plate to form a SUS plate having a space to be the pressure chamber 52 or by etching Si. A method of forming the flow path plate 96 having a space to be the chamber 52 is mentioned.

  Next, a nozzle plate 94 having nozzles 51 made of polyimide, for example, is bonded to the flow path plate 96 in which a space to be the pressure chamber 52 is formed.

  Next, in FIG. 10B, the vibration plate 56 is pasted on the flow path plate 96 in which the space to be the pressure chamber 52 is formed. The diaphragm 56 also serves as a common electrode. The diaphragm 56 is provided with an opening at a position corresponding to the ink supply port 53 to the pressure chamber 52. Further, a thin film piezoelectric body 58a is formed in a portion corresponding to the pressure chamber 52 on the upper side of the diaphragm 56 by an AD method (aerosol method) or a sputtering method. Alternatively, it may be formed by polishing a bulk piezoelectric body. The thickness of the diaphragm 56 and the piezoelectric body 58a is, for example, about 10 μm.

  Next, as shown in FIG. 10C, a common liquid chamber 55 is formed.

  That is, first, the individual electrode 57 is formed on the piezoelectric body 58a formed on the vibration plate 56, and a part thereof, for example, an end portion on the nozzle 51 side is drawn out to form an electrode pad 59 for wiring connection. .

  On the other hand, the wiring plate 91 in which the electric wiring 90 (electric column) is erected substantially vertically on the plate is bonded so that the tip of the electric wiring 90 is connected to the electrode pad 59. Thus, the common liquid chamber 55 is formed with the electric wiring 90 (electric column) as a column, the diaphragm 56 as a floor, and the wiring plate 91 as a ceiling.

  Here, the tip of the electrical wiring 90 and the electrode pad 59 are connected by solder 90 a provided at the tip of the electrical wiring 90. A method for manufacturing the electrical wiring 90 (electric column) will be described later.

  An electrical wiring 90 (electric column) is formed on the plate on which the piezoelectric element 58 formed of the piezoelectric body 58 a sandwiched between the diaphragm 56 (common electrode) and the individual electrode 57 is formed on the pressure chamber 52. After forming the common liquid chamber 55 by pasting the wiring plate 91, an insulating / protective film is formed on the surface of the common liquid chamber 55 in contact with the ink, although illustration is omitted.

  Finally, in FIG. 10D, a multilayer flexible cable 92 is attached to the upper side of the wiring plate 91 to form the print head 50. The electrical wiring 90 and the multilayer flexible cable 92 are connected by solder 90 a provided at one end of the electrical wiring 90. The multilayer flexible cable 92 has at least four layers.

  Next, a method for manufacturing the electrical wiring 90 (electric column) will be described.

  11A to 11E show a manufacturing process of the electric wiring 90. FIG.

First, as shown in FIG. 11A, a copper layer 93 having a thickness of about 500 μm is formed on an insulating substrate to be a wiring plate 91 on which an electric wiring 90 (electric column) is formed. Next, in FIG. 11B, the copper layer 93 having a thickness of about 500 μm is shaved by etching or the like to form columnar electrical wiring 90 (electric column).

  At this time, the size of each electric wiring 90 (electric column) is, for example, the diameter d1 of the tip portion (the portion to be connected to the electrode pad 59 later) is about 100 μm, and the height d2 is the thickness of the copper layer 93. It is formed to be equal to about 500 μm.

  Next, as shown in FIG. 11C, an insulating / protective film 98 is coated on the columnar side surfaces of the electric wiring 90. As described above, this is because the electric wiring 90 penetrates through the common liquid chamber 55 and is always in contact with the ink, so that the electric wiring 90 is protected therefrom.

  Next, in FIG. 11D, the wiring plate 91 is processed from the lower side, and a hole 91a for connection with the multilayer flexible cable 92 is opened in a portion where the electrical wiring 90 is present. This may be previously opened on the wiring plate 91 before the copper layer 93 is formed on the wiring plate 91.

  Finally, as shown in FIG. 11 (e), the solder 90 a is poured into the upper and lower ends of the electric wiring 90 to form the electric wiring 90 on the wiring plate 91. The print head 50 is formed as shown in FIG. 10 by turning it upside down and attaching it to the flow path plate 96 in which the pressure chambers 52 and the like are formed.

  The wiring plate 91 on which the electrical wiring 90 is formed in this way is not turned upside down and bonded to the flow path plate 96, but the electrical wiring 90 is separated from the wiring plate 91 one by one. You may make it join with respect to the electrode pad 59 of the flow-path plate 96. FIG. When attaching the electric wiring 90 one by one, it takes time, but there is no need to consider the positional accuracy when the electric wiring 90 is formed on the wiring plate 91.

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

  FIG. 12 is a sectional view showing a print head according to a second embodiment of the present invention. FIG. 12 is a cross-sectional view similar to FIG. The print head of this embodiment also has a common liquid chamber formed on the side opposite to the pressure chamber with respect to the diaphragm.

  That is, as shown in FIG. 12, in the print head 150 of this embodiment, a flow path plate 196 in which a pressure chamber 152 and the like are formed is disposed on a nozzle plate 194 in which a nozzle 151 is formed, and a vibration plate is disposed thereon. 156 is arranged.

  On the vibration plate 156, a piezoelectric element 158 including a vibration plate 156 as a common electrode, a piezoelectric body 158a, and an individual electrode 157 is formed, and upward from an electrode pad 159 formed by being drawn out from the individual electrode 157. Thus, the electrical wiring 190 (electric column) is formed substantially vertically.

  A multilayer flexible cable 192 is formed on the electrical wiring 190, and a space between the diaphragm 156 and the multilayer flexible cable 192 is a common liquid chamber 155, and the electrical wiring 190 is a common liquid chamber 155. It has a shape that penetrates the inside.

  As described above, the print head 150 of the present embodiment has substantially the same configuration as the print head 50 of the first embodiment described above. The difference between the print head 150 of the present embodiment and the print head 50 of the first embodiment is that an upper portion of the piezoelectric element 158 (piezoelectric actuator) including the vibration plate 156 (common electrode), the piezoelectric body 158a, and the individual electrode 157 A gap 158b for operating the actuator is provided.

  The gap 158b is formed by providing a housing 158c for each piezoelectric element 158 so as to completely cover the piezoelectric body 158a and the individual electrode 157 formed thereon. In addition, an insulating / protective film 198 is formed on the surface of the housing 158c. Note that the casing 158c may be formed of only the insulating / protective film 198.

  As described above, by providing the gap 158b on the piezoelectric element 158, the resistance when the piezoelectric element 158 is driven is reduced, so that the piezoelectric element 158 is easily operated and the driving efficiency of the piezoelectric element 158 is improved.

  Other parts in the present embodiment are exactly the same as those in the first embodiment described above, and detailed description thereof is omitted by making the last two digits of the respective symbols the same.

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

  FIG. 13 is a cross-sectional view similar to FIG. 12 showing a print head according to a third embodiment of the present invention.

  As shown in FIG. 13, the print head 250 of the present embodiment has a configuration substantially similar to the print head 150 of the second embodiment of the present invention shown in FIG.

  That is, the print head 250 according to the present embodiment also has the common liquid chamber 255 arranged above the vibration plate 256 and is erected vertically so as to penetrate the common liquid chamber 255, similarly to the print head 150 according to the second embodiment. The electrical wiring 290 is provided, and a gap 258b for facilitating the operation of the piezoelectric body 258 is provided.

  The print head 250 of the present embodiment is different from the print head 150 of the second embodiment in that the ink backflow is prevented by reducing the diameter of a part of the ink supply port 253 that supplies ink from the common liquid chamber 255 to the pressure chamber 252. This is to provide a diaphragm 253a for use.

  The method of forming the diaphragm 253a is not particularly limited, but in the example shown in the figure, the opening corresponding to the ink supply port 253 of the diaphragm 256 is narrowed to form the diaphragm 253a.

  In the case where such an aperture is not provided as in the first embodiment or the second embodiment described above, it is possible to shorten the refill time after discharging particularly high viscosity ink as described above. Become. On the other hand, when the diaphragm 253a is provided as in the present embodiment, it is possible to improve the ejection efficiency when using low-viscosity ink, to reduce the power consumption of the piezoelectric element, and to reduce the size of the pressure chamber. It becomes.

  Hereinafter, an effect obtained by providing the diaphragm 253a in the present embodiment will be described.

  FIG. 14 is a graph showing the refill characteristics when there is no aperture and when there is an aperture when 2 pl of ink having a viscosity of 20 cP is ejected. A specific method for analyzing the refill characteristics will be described later.

  In FIG. 14, a graph A shows a case without an aperture and a graph B shows a case with an aperture. The horizontal axis represents time (μsec), and the vertical axis represents meniscus volume (pl). Here, when the meniscus volume becomes zero, the refill is completed. When the meniscus volume is positive (> 0), it indicates that the meniscus surface is out of the initial position.

  As shown in the graph B of FIG. 14, the refill time is 60 μsec when there is a stop. On the other hand, as shown in graph A, the refill time is 30 μsec when there is no aperture, and is halved compared with the case where there is an aperture.

  FIG. 15 is a graph showing the ejection characteristics when there is no aperture and when there is an aperture when 2 pl of ink having a viscosity of 20 cP is ejected. A specific method for analyzing the ejection characteristics will be described later.

  In FIG. 15, graph A shows a case without an aperture and graph B shows a case with an aperture. The horizontal axis is time (μsec), and the vertical axis is nozzle particle velocity (m / sec). Important parameters for ejection characteristics are ejection droplet velocity and ejection droplet volume. The velocity is proportional to the nozzle particle velocity, and the volume is proportional to the area enclosed by the graph and (value on the vertical axis) = 0. Therefore, as can be seen from FIG. 15, both the graph A and the graph B show substantially the same characteristics. In other words, the ejection characteristics at the ink viscosity of 20 cP do not change greatly with or without the diaphragm.

  This can be explained as follows. That is, at the time of ejection, the ink flows in the ejection direction toward the nozzle side and flows in the reverse direction toward the supply side. At this time, the ratio of the ink movement volume from the nozzle side to the supply side, (nozzle side) / (supply side + nozzle side) is (nozzle side) / (supply side + nozzle side) = In the case of no diaphragm, (nozzle side) / (supply side + nozzle side) = 0.28. Therefore, the efficiency with the aperture is twice as good as that without the aperture. On the other hand, the attenuation factor is 1.32 when there is a diaphragm, and 1.79 when there is no diaphragm, and the attenuation factor is 1.4 times greater when there is a diaphragm. For this reason, it is considered that the two cancel each other, and there is no large difference in the ejection characteristics with and without the restriction.

  From the above, high-viscosity ink having a viscosity of 20 cP enables high-frequency ejection by shortening the refill time without significantly affecting the ejection characteristics even when there is no restriction.

  Similarly, FIG. 16 shows a graph representing the refill characteristics when there is no aperture and when there is an aperture when 2 pl of ink having a viscosity of 2 cP is ejected, and FIG. 17 shows a graph representing the ejection characteristics.

  As shown in FIG. 16, in this case, the meniscus surface vibrates greatly regardless of whether or not there is a diaphragm. Therefore, in order to shorten the refill time, it is important to suppress the vibration of the meniscus surface regardless of whether there is a diaphragm.

  On the other hand, as shown in FIG. 17, the discharge characteristics change with and without the restriction at the viscosity of 2 cP. This is because the attenuation rate hardly changes without the diaphragm, but when the ratio of the ink movement volume between the nozzle side and the supply side is the nozzle, (nozzle side) / (supply side + nozzle). Side) = 0.53, but when there is no aperture, (nozzle side) / (supply side + nozzle side) = 0.31, the efficiency with the aperture is 1.7 times. Because it is good.

  From the above, in the low-viscosity ink having a viscosity of 2 cP, when there is a restriction, the restriction does not dominate the refill time, and the discharge characteristics can be made efficient.

  Next, a specific analysis method of the refill characteristic and the discharge characteristic, which shows only the result above, will be described.

For the analysis of the refill characteristic, an equivalent circuit model as shown in FIG. 18 was applied. In FIG. 18, R is a combined resistance of the nozzle and the supply throttle, M is a combined inertance of the nozzle and the supply throttle, and C is a value that varies depending on the meniscus shape (refill state) according to the compliance of the nozzle meniscus. When the distance to the bottom is y, the nozzle radius is r _n , and the ink surface tension is σ, C is expressed by the following equation (1).

また、吐出特性の解析には、図１９に示すような等価回路モデルを適用した。ここで図１９において、Ｃ_ｐはピエゾアクチュエータのコンプライアンス、Ｃ_ｃは圧力室のコンプライアンス、Ｒ_ｎはノズル抵抗、Ｒ_ｓは供給絞り抵抗、Ｍ_ｎはノズルイナータンス、Ｍ_ｓは供給絞りイナータンス、Ｖはピエゾアクチュエータ発生圧力を表す。

Further, an equivalent circuit model as shown in FIG. 19 was applied to the analysis of the discharge characteristics. Here, in FIG. 19, C _p is the compliance of the piezo actuator, C _c is the compliance of the pressure chamber, R _n is the nozzle resistance, R _s is the supply throttle resistance, M _n is the nozzle inertance, M _s is the supply throttle inertance, V Represents the pressure generated by the piezo actuator.

  In addition, FIG. 20 shows specific numerical values of each element when analyzing refill characteristics and ejection characteristics. In FIG. 20, the nozzle side includes a nozzle + communication path from the pressure chamber to the nozzle, and the supply side includes a supply throttle + communication path to the common liquid chamber.

  In the embodiment shown in FIG. 9 and FIG. 12, the ink supply ports 53 and 153 communicating the common liquid chambers 55 and 155 and the pressure chambers 52 and 152 have a uniform diameter. It is not done. In these examples, the backflow is suppressed by the mass of the ink itself in the portion between the common liquid chambers 55 and 155 of the ink supply ports 53 and 153 and the pressure chambers 52 and 152. This emphasizes reliable ink supply when driving at high frequency or using high viscosity ink. On the other hand, in the present embodiment, a narrow-diameter restrictor 253a is installed in order to make the backflow prevention effect more reliable.

  Further, the configuration other than the diaphragm 253a is the same as the configuration of the second embodiment described above, and the lower two-digit symbols are the same for those components, and detailed description thereof is omitted.

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

  In the fourth embodiment, unlike what has been described so far, the common liquid chamber is arranged on the same side as the pressure chamber with respect to the diaphragm, as in the prior art. However, also in the present embodiment, the electrical wiring for supplying a drive signal to the individual electrodes of the piezoelectric element is formed perpendicular to the nozzle surface and penetrates the common liquid chamber.

  FIG. 21 is a sectional view showing a print head according to a fourth embodiment of the present invention.

  21 is a cross-sectional view in which a portion corresponding to one pressure chamber unit 54 as shown in FIG. 3, for example, is cut so as to pass through a nozzle, an ink supply port, and electric wiring (electric column) on a plane perpendicular to the nozzle surface. It is.

  As shown in FIG. 21, in the print head 350 of the present embodiment, the top surface of the pressure chamber 352 is constituted by a diaphragm 356 that also serves as a common electrode, and a piezoelectric body 358a is joined on the diaphragm 356, An individual electrode 357 is formed on the upper surface, and a piezoelectric element 358 is configured by the common electrode (the diaphragm 356), the piezoelectric body 358a, and the individual electrode 357. The pressure chamber 352 communicates with the nozzle 351 through the nozzle flow path 351a and supplies ink to the common liquid chamber 355 provided on the same side as the pressure chamber 352 (lower side of the pressure chamber 352 in the drawing) with respect to the vibration plate 356. It communicates through the mouth 353.

  Further, as shown in FIG. 21, the electrode pad 359 as an electrode connecting portion is pulled out from the individual electrode 357 to the side, and the electric wiring 390 (electric column) is formed substantially perpendicular to the nozzle surface downward from the electrode pad 359. To do. The electrical wiring 390 passes through the plate in which the pressure chamber 352 is formed, passes through the common liquid chamber 355 as it is, and extends downward toward the nozzle plate side where the nozzle 351 is formed, and is provided below the common liquid chamber 355. Connected to the wiring portion 395. A portion of the electrical wiring 390 that penetrates the common liquid chamber 355 is in contact with the ink and is protected by an insulating / protective film 398.

  The wiring part 395 extends along the nozzle surface to the end of the print head 350, is connected to a flexible cable (not shown), and receives a drive signal.

  The electrical wirings in this embodiment are not all formed so as to penetrate the common liquid chamber in this way, but are formed directly on the upper portion of the diaphragm 356 from the individual electrodes 357 as in the prior art and connected to the flexible cable. There is also electrical wiring.

  Then, as shown in FIG. 21, an electric wiring 390 (electric column) penetrating through the common liquid chamber 355 is formed and wiring is performed so as to pass under the common liquid chamber 355, and a diaphragm 356 of the related art is used. By alternately forming the upper wirings, it is possible to secure a wiring space for the electrodes and to increase the wiring density. Further, by increasing the wiring density, the nozzle density can be further increased.

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

  In the embodiments described so far, the piezoelectric element (58 or the like) is used as the pressure generating means. However, the fifth embodiment is different from those described so far, and the pressure generating means. As an example, an electrostatic actuator that drives and controls the diaphragm by electrostatic action is used.

  The electrostatic actuator applies a pulse voltage to the electrode, attracts and deflects the diaphragm by the positive or negative charge on the electrode surface and the negative or positive charge on the corresponding diaphragm surface, and then turns the electrode off. In this case, the volume of the pressure chamber is reduced by the restoring action of the diaphragm surface, and the pressure in the pressure chamber is instantaneously increased to eject ink from the nozzles.

  FIG. 22 is a sectional view of the print head according to the fifth embodiment.

FIG. 22 is a cross-sectional view similar to FIG. As shown in FIG. 22, the print head 450 of the present embodiment is the same as that of the first embodiment shown in FIG. 9 except for the pressure generating means. In other words, the print head 450 has the common liquid chamber 455 disposed above the vibration plate 456 and has the electrical wiring 490 that is erected vertically so as to penetrate the common liquid chamber 455.

  The pressure generating means of the present embodiment is of an electrostatic actuator type, the electrode 401 is disposed on the vibration plate 456, the insulating film 498 is formed on the electrode 401, and the electrode 401 and the vibration plate 456 are further formed. A gap 402 is provided between the two.

  An electrode pad 459 is drawn from the electrode 401 and is connected to an electric wiring 490 that rises vertically on the electrode pad 459. The electrical wiring 490 is connected to the multilayer flexible cable 492 at the upper portion by the electrode pad 490a. A pulse voltage is applied to the electrode 401 through the electric wiring 490.

  Since the remaining configuration is the same as that of the first embodiment described above, the last two digits are the same, and detailed description thereof is omitted.

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

  When a predetermined pulse voltage is applied to the electrode 401 through the electric wiring 490, when the surface of the electrode 401 is charged to a positive potential, the lower surface of the corresponding diaphragm 456 is charged to a negative potential. As a result, the diaphragm 456 bends upward in the figure by electrostatic attraction. When the vibration plate 456 is bent upward, the volume of the pressure chamber 452 increases, and ink is filled into the pressure chamber 452 from the common liquid chamber 455 through the ink supply port 453.

  Next, when the electrode 401 is turned OFF, the diaphragm 456 is restored, so that the volume of the pressure chamber 452 decreases. As a result, the pressure in the pressure chamber 452 rapidly increases and ink is ejected from the nozzles 451.

  Thus, the pressure generating means is not limited to the piezoelectric element, but may be an electrostatic actuator.

  The liquid ejection head of the present invention and the image forming apparatus including the liquid ejection head 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 spirit 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 inkjet recording apparatus shown in FIG. 1. FIG. 3 is a plan perspective view illustrating a structural example of a print head. 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 perspective perspective view which expands and shows a part of print head of this embodiment. It is a plane perspective view which expands and shows a part of pressure chamber. FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. (A)-(d) is explanatory drawing which shows the manufacturing process of the print head which concerns on 1st Embodiment. (A)-(e) is explanatory drawing which shows the manufacturing process of electrical wiring (electric column). It is sectional drawing which shows the print head of 2nd Embodiment of this invention. It is sectional drawing which shows the print head of 3rd Embodiment of this invention. It is a graph which compares and shows the refill characteristic in the case of an ink with a viscosity of 20 cP when there is no aperture and with an aperture. 7 is a graph showing a comparison of ejection characteristics between ink having a viscosity of 20 cP and those without a diaphragm and with a diaphragm. It is a graph which compares and shows the refill characteristic in the case of without an aperture and with an aperture for the ink of viscosity 2cP. 6 is a graph showing a comparison of ejection characteristics between ink without a restriction and with a restriction for ink having a viscosity of 2 cP. It is a circuit diagram which shows the equivalent circuit model applied to the analysis of a refill characteristic. It is a circuit diagram which shows the equivalent circuit model applied to the analysis of a discharge characteristic. It is explanatory drawing which shows the numerical value of each element used for the analysis of a refill characteristic and discharge characteristic. It is sectional drawing which shows the print head of 4th Embodiment of this invention. It is sectional drawing which shows the print head of 5th Embodiment of this invention.

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, 51a ... nozzle flow path, 52 ... pressure chamber, 53 ... ink supply port, 54 ... pressure chamber unit, 55 ... common liquid chamber, 56 ... diaphragm (common electrode), 57 ... individual electrode, 58a ... piezoelectric body, 58 ... piezoelectric element, 59 ... electrode pad, 60 ... ink tank, 62 ... filter, 64 Cap, 66 ... Blade, 67 ... Suction pump, 68 ... Collection 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 ... motor, 89 ... heater, 90 ... electric wiring (electric column), 91 ... wiring plate, 92 ... multilayer flexible cable, 94 ... nozzle plate, 96 ... flow path Plate, 98 ... Insulation / protection film

Claims (8)

A plurality of outlets for discharging liquid;
A plurality of pressure chambers communicating with each of the plurality of discharge ports;
A plurality of liquid supply passages for supplying a liquid to each of the plurality of pressure chambers;
A common liquid chamber for supplying a liquid to the plurality of liquid supply channels;
Pressure generating means for deforming each of the plurality of pressure chambers;
Electric wiring for supplying a driving signal to the pressure generating means,
A liquid discharge head, wherein the electric wiring is disposed so as to penetrate the common liquid chamber.   The liquid discharge head according to claim 1, wherein the pressure generating means is a piezoelectric element.   2. The pressure generating means is provided on the opposite side of the pressure chamber to the discharge port, and the common liquid chamber is disposed on the opposite side of the pressure chamber with respect to the pressure generating means. Or the liquid discharge head of 2.   The liquid discharge head according to claim 3, wherein the liquid supply channel is formed substantially perpendicular to a surface including the pressure generating unit.   5. The liquid discharge head according to claim 1, wherein the electrical wiring is formed substantially perpendicular to a surface including the pressure generating unit.   The liquid ejection head according to claim 1, wherein the plurality of pressure chambers are arranged in a two-dimensional matrix.   The liquid ejection head according to claim 1, wherein a wiring layer connected to the electric wiring is provided on the opposite side of the common liquid chamber from the pressure generating unit.   An image forming apparatus comprising the liquid discharge head according to claim 1.

Images