JP2010221443A - Droplet delivering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a droplet delivering apparatus which circulates a liquid in a predetermined direction with a space saving and simple constitution. <P>SOLUTION: A first wall face 82A with a plurality of nozzles 80, a pressure room 84 corresponding to each of the nozzles 80 and filled with an ink liquid fed between the first wall face 82A and an opposing second wall face 82B, a feeding path 86 for feeding the ink liquid to each of the pressure rooms 84, and a discharging path 88 for discharging the ink liquid filled in each of the pressure rooms 84, are formed. By a plurality of actuators 92 for delivery provided at parts corresponding to each of the nozzles 80 of the second wall face 82B, a pressure is applied to the ink liquid filled in the pressure room 84 to deliver the ink liquid from the nozzle 80. By a plurality of actuators 98 for circulation provided in accordance with the feeding path 86 on the side provided with the actuators 92 for delivery on the second wall face 82B, a pressure is applied on the ink liquid filled in the feeding path 86, and the ink liquid filled in the feeding path 86 and the discharging path 88 is moved in a predetermined direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a droplet discharge device that discharges droplets from a nozzle.

  2. Description of the Related Art In recent years, liquid droplet ejection apparatuses that form dots on an image recording medium by ejecting liquid droplets from nozzles have become widespread.

  By the way, this type of liquid droplet ejection apparatus has a problem that liquid ejection failure may occur due to the circulated liquid remaining.

  In order to solve this problem, Patent Document 1 discloses an array having a nozzle plate that ejects ink and a first piezoelectric element that applies ejection pressure to the ink, and the stored ink to the array. An ink chamber to be supplied, an ink channel plate that communicates the ink chamber and the array, and an ink channel plate disposed on the ink channel plate and oscillating with the applied voltage to circulate the ink in the ink channel plate An ink jet printer including a second piezoelectric element is disclosed.

  Further, in Patent Document 2, an ink chamber in which a nozzle for ejecting ink is provided is divided into an ink ejection side and an ink suction side, and an inkjet in which a piezoelectric element for changing the volume in the ink chamber is attached. A head is disclosed.

  In Patent Document 3, two piezoelectric elements are arranged in series in the ink flow path in the ink ejecting system, and a rectifying element that distributes ink only in the ink discharge direction is provided at one position of the ink flow path between the piezoelectric elements. An inkjet head is disclosed.

  On the other hand, Patent Literature 4 and Patent Literature 5 disclose an ink jet head including a pump that sends ink in a predetermined direction in order to circulate ink ejected from a nozzle.

JP-A-6-126958 Japanese Patent Laid-Open No. 3-9845 JP-A-4-99646 JP-A-6-143602 JP 2008-254196 A

  However, in the technique described in Patent Document 1, the first piezoelectric element and the second piezoelectric element are arranged on different plates. In the technique described in Patent Document 2, the pressure chamber is divided into two parts. A piezoelectric element is provided in the ink chamber, and in the technique described in Patent Document 3, a rectifying element that circulates ink only in the ink discharge direction is provided in the ink flow path between the piezoelectric elements. There was a problem that the structure for distribution to the market was complicated. In addition, the techniques described in Patent Documents 4 and 5 have a problem that the pump for delivering the liquid is not downsized.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a droplet discharge device that can distribute liquid in a predetermined direction with a space-saving and simple configuration.

  In order to achieve the above object, a liquid droplet ejection apparatus according to claim 1 includes a first wall surface having a plurality of nozzles and a second wall surface facing the first wall surface, and the first wall surface and the second wall surface. A pressure chamber corresponding to each of the nozzles and filled with a supplied liquid, a head formed with a supply path for supplying the liquid to each of the pressure chambers, and the second wall surface A plurality of first pressure applying means provided at portions corresponding to each of the nozzles and applying pressure to the liquid filled in the pressure chamber to discharge the liquid from the nozzle; and the second wall surface A plurality of second pressure applying means provided corresponding to the supply path so as to apply pressure to the liquid filled by being driven on the side on which the first pressure applying means is provided; The liquid filled in the supply path moves in a predetermined direction. And a driving means for driving the second pressure applying means to.

  According to the droplet discharge device of claim 1, the first wall surface having a plurality of nozzles and the second wall surface facing the first wall surface are provided, and the nozzle is provided between the first wall surface and the second wall surface. And a head formed with a pressure chamber filled with the supplied liquid and a supply path for supplying the liquid to each of the pressure chambers, provided in a portion corresponding to each of the nozzles on the second wall surface. The plurality of first pressure applying means applies pressure to the liquid filled in the pressure chamber and discharges the liquid from the nozzle.

  Then, a pressure is applied to the liquid filled in the supply path by a plurality of second pressure application means provided corresponding to the supply path on the side of the second wall surface where the first pressure application means is provided. The second pressure applying means is driven by the driving means so that the liquid filled in the supply path moves in a predetermined direction.

  Thus, according to the droplet discharge device of the first aspect, the plurality of second pressures provided corresponding to the supply path on the side of the second wall surface on which the first pressure applying unit is provided. Since the applying unit is driven so that the liquid filled in the supply path moves in a predetermined direction, the liquid can be circulated in the predetermined direction with a space-saving and simple configuration.

  In order to achieve the above object, a droplet discharge device according to a second aspect includes a first wall surface having a plurality of nozzles and a second wall surface facing the first wall surface, the first wall surface and the first wall surface. A pressure chamber corresponding to each of the nozzles and filled with the supplied liquid, a supply path for supplying the liquid to each of the pressure chambers, and each of the pressure chambers are filled between two wall surfaces. The head is provided with a discharge path for discharging the liquid, and is provided in a portion corresponding to each of the nozzles of the second wall surface, and applies pressure to the liquid filled in the pressure chamber to discharge the liquid from the nozzle. The supply is performed so as to apply pressure to the liquid filled by being driven on the side of the second wall surface on which the first pressure applying means is provided and the plurality of first pressure applying means to be discharged. A path and at least one of the discharge paths A plurality of second pressure applying means provided, and a driving means for driving the second pressure applying means so that the liquid filled in the supply path and the discharge path moves in a predetermined direction. I have.

  According to the droplet discharge device of claim 1, the first wall surface having a plurality of nozzles and the second wall surface facing the first wall surface are provided, and the nozzle is provided between the first wall surface and the second wall surface. A head formed with a pressure chamber corresponding to each of the pressure chambers, a supply path for supplying the liquid to each of the pressure chambers, and a discharge path for discharging the liquid filled in each of the pressure chambers. The pressure is applied to the liquid filled in the pressure chamber by a plurality of first pressure applying means provided at portions corresponding to each of the nozzles of the second wall surface, and the liquid is discharged from the nozzle.

  Then, on the side of the second wall surface on which the first pressure applying means is provided, a plurality of second pressure applying means provided corresponding to at least one of the supply path and the discharge path is provided to the supply path or the discharge path. Pressure is applied to the filled liquid, and the second pressure applying means is driven by the driving means so that the liquid filled in the supply path and the discharge path moves in a predetermined direction.

  Thus, according to the droplet discharge device of the second aspect, the second wall surface is provided on the side on which the first pressure applying unit is provided, corresponding to at least one of the supply path and the discharge path. Since the plurality of second pressure applying units are driven so that the liquid filled in the supply path and the discharge path moves in a predetermined direction, the liquid can be circulated in the predetermined direction with a space-saving and simple configuration. .

  The liquid droplet ejection device according to claim 1 or 2, wherein the first pressure application unit and the second pressure application unit are piezoelectric elements as in the invention according to claim 3. Good. Thereby, a 1st pressure application means and a 2nd pressure application means can be made into a simple structure.

  Further, in the droplet discharge device according to any one of claims 1 to 3, the volume of the liquid that moves when the driving unit applies pressure as in the invention according to claim 4. A plurality of the second pressure applying means may be driven so as to be constant. Thereby, pressure increase / decrease and pulsation of the liquid due to the driving of the second pressure applying means can be suppressed, and it is possible to prevent the liquid from overflowing from the nozzle and air from being mixed into the liquid.

  In addition, the liquid droplet ejection device according to any one of claims 1 to 4 is a liquid droplet ejection device filled with a liquid corresponding to the second pressure applying unit, as in the invention according to claim 5. By making the length and cross-sectional area of the first region different from the length and cross-sectional area of the second region filled with the liquid not corresponding to the second pressure applying means, The ratio between the impedance of the region and the impedance of the second region may be varied according to the speed at which the second pressure applying unit is driven. Thereby, a flow can be generated in the filled liquid by changing the speed at which the plurality of second pressure applying means are driven.

  According to a fifth aspect of the present invention, in the liquid droplet ejection device according to the sixth aspect of the invention, the second pressure located in the left direction when the driving means moves the liquid in the left direction. A state in which the applying unit is changed from a state in which pressure is applied to the liquid to a state in which no pressure is applied to the liquid, and the second pressure applying unit positioned in the right direction is applied to the liquid from a state in which no pressure is applied to the liquid The first drive for driving at the first speed so that the second pressure applying means located in the left direction is changed from the state in which no pressure is applied to the liquid to the state in which the pressure is applied to the liquid, and the right direction The second pressure applying means positioned at a second speed at which the ratio is smaller than the ratio at the first speed so that the pressure is not applied to the liquid from a state where the pressure is applied to the liquid. Alternate second drive to drive Ri may be returned. As a result, a leftward flow can be easily generated in the filled liquid.

  Further, according to a fifth aspect of the present invention, in the droplet discharge device according to the seventh aspect, when the driving unit moves the liquid in the right direction, the second pressure positioned in the right direction is used. A state in which the applying unit is changed from a state in which pressure is applied to the liquid to a state in which no pressure is applied to the liquid, and the second pressure applying unit located in the left direction is applied to the liquid from a state in which no pressure is applied to the liquid The first drive for driving at the first speed so that the second pressure applying means located in the right direction is changed from the state in which no pressure is applied to the liquid to the state in which the pressure is applied to the liquid, and the left direction The second pressure applying means positioned at a second speed at which the ratio is smaller than the ratio at the first speed so that the pressure is not applied to the liquid from a state where the pressure is applied to the liquid. Alternate second drive to drive Ri may be returned. As a result, a rightward flow can be generated in the filled liquid.

  As described above, according to the present invention, there is an excellent effect that the liquid can be circulated in a predetermined direction with a space-saving and simple configuration.

1 is a side view illustrating a configuration of an image forming apparatus according to an embodiment. It is a figure which shows the structural example of the inkjet line head which concerns on embodiment. 1 is a block diagram illustrating a configuration of a main part of an electric system of an image forming apparatus according to an embodiment. It is a schematic diagram which shows the drive state of the actuator for circulation which concerns on embodiment. In the image forming apparatus according to the embodiment, it is a schematic diagram showing a flow path through which the ink liquid circulates. It is a graph which shows the change of the impedance of a flow path to the drive frequency of the actuator for circulation concerning an embodiment. FIG. 6 is a diagram illustrating the magnitude of a drive voltage applied to a circulation actuator when high-speed driving and low-speed driving are alternately repeated in the image forming apparatus according to the embodiment. FIG. 4 is a diagram illustrating the magnitude of a drive voltage applied to a circulation actuator from the start to the end of ink liquid circulation in the image forming apparatus according to the embodiment. It is a figure which shows the structural example of the inkjet line head which concerns on another form. It is a figure which shows the structural example of the inkjet line head which concerns on another form.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, the liquid droplet ejection apparatus according to the present invention is applied to an image forming apparatus.

  First, the overall configuration of the image forming apparatus 10 according to the present embodiment will be described with reference to FIG.

  As shown in the figure, in the image forming apparatus 10 according to the present embodiment, a sheet feeding unit that feeds and conveys a sheet upstream of a sheet as a recording medium (hereinafter referred to as “sheet”) is conveyed. A transport unit 12 is provided. On the downstream side of the paper feeding / conveying unit 12, a processing liquid application unit 14 that applies a processing liquid to the recording surface of the paper along the paper conveyance direction, and an image formation that forms an image with ink liquid on the recording surface of the paper A unit 16, an ink drying unit 18 that dries the image formed on the recording surface, an image fixing unit 20 that fixes the dried image on a sheet, and a discharge unit 21 that discharges the sheet on which the image is fixed are provided.

  Hereinafter, each processing unit will be described.

  (Paper feed section)

  The sheet feeding / conveying unit 12 is provided with a stacking unit 22 on which sheets are stacked, and is downstream of the stacking unit 22 in the sheet conveying direction (hereinafter, “sheet conveying direction” may be omitted). Is provided with a paper feeding unit 24 that feeds the paper stacked on the stacking unit 22 one by one. The sheet fed by the sheet feeding section 24 is transported to the processing liquid coating section 14 via a transport section 28 composed of a plurality of pairs of rollers 26.

  (Processing liquid application part)

  In the treatment liquid application unit 14, a treatment liquid application drum 30 composed of a cylindrical member that conveys the paper by rotating the paper around the outer peripheral surface is rotatably disposed. The processing liquid coating drum 30 is provided with a holding member 32 that holds the paper by sandwiching the leading end of the paper, and the paper is held on the surface of the processing liquid coating drum 30 via the holding member 32. In this state, the paper is conveyed downstream by the rotation of the treatment liquid coating drum 30.

  Note that an intermediate conveyance drum 34, an image forming drum 36, an ink drying drum 38, and an image fixing drum 40, which will be described later, are configured in the same manner as the processing liquid coating drum 30 and are provided with a holding member 32. The holding member 32 transfers the paper from the upstream drum to the downstream drum.

  A processing liquid coating device 42 and a processing liquid drying device 44 are disposed above the processing liquid coating drum 30 along the circumferential direction of the processing liquid coating drum 30. The treatment liquid is applied to the surface, and the treatment liquid is dried by the treatment liquid drying device 44.

  Here, the treatment liquid reacts with the ink to aggregate the color material (pigment) and has an effect of promoting separation of the color material (pigment) and the solvent. The treatment liquid application device 42 is provided with a storage portion 46 for storing the treatment liquid, and a part of the gravure roller 48 is immersed in the treatment liquid.

  A rubber roller 50 is disposed in pressure contact with the gravure roller 48, and the rubber roller 50 comes into contact with the recording surface (front surface) side of the paper to apply the processing liquid. Further, a squeegee (not shown) is in contact with the gravure roller 48 to control the amount of treatment liquid applied to the recording surface of the paper.

  Ideally, the treatment liquid film thickness is sufficiently smaller than the droplets (ink droplets) of the head droplets. For example, when the droplet volume is 2 pl, the average diameter of the droplets of the head droplet is 15.6 μm, and when the treatment liquid film thickness is thick, the ink dots float in the treatment liquid without contacting the recording surface of the paper. To do. In order to obtain a landing dot diameter of 30 μm or more with a droplet ejection amount of 2 pl, it is preferable to make the treatment liquid film thickness 3 μm or less.

  On the other hand, in the treatment liquid drying device 44, a hot air nozzle 54 and an infrared heater 56 (hereinafter referred to as “IR heater 56”) are disposed close to the surface of the treatment liquid application drum 30. The hot air nozzle 54 and the IR heater 56 evaporate a solvent such as water in the processing liquid to form a solid or thin film processing liquid layer on the recording surface side of the paper. By thinning the treatment liquid in the treatment liquid drying step, the dots formed by the ink droplets in the image forming unit 16 come into contact with the paper surface to obtain a necessary dot diameter, and the thinned treatment liquid and It is easy to obtain an action of reacting and aggregating the coloring material and fixing to the paper surface.

  In this way, the paper on which the processing liquid has been applied and dried on the recording surface by the processing liquid application unit 14 is conveyed to an intermediate conveyance unit 58 provided between the processing liquid application unit 14 and the image forming unit 16.

  (Intermediate transport section)

  An intermediate transport drum 58 is rotatably provided in the intermediate transport unit 58, and a sheet is held on the surface of the intermediate transport drum 34 via a holding member 32 provided in the intermediate transport drum 34. The sheet is conveyed to the downstream side by the rotation of 34.

  (Image forming part)

  An image forming drum 36 is rotatably provided in the image forming unit 16, and a sheet is held on the surface of the image forming drum 36 via a holding member 32 provided on the image forming drum 36. The sheet is conveyed downstream by the rotation of 36.

  Above the image forming drum 36, a head unit 66 composed of a single-pass inkjet line head 64 is disposed adjacent to the surface of the image forming drum 36. In this head unit 66, at least the basic color YMCK inkjet line heads 64 are arranged along the circumferential direction of the image forming drum 36, and are formed on the processing liquid layer formed on the recording surface of the paper by the processing liquid coating unit 14. An image of each color is formed.

  The treatment liquid has the effect of aggregating the color material (pigment) and latex particles dispersed in the ink into the treatment liquid, and forms an aggregate that does not generate color material flow on the paper. As an example of the reaction between the ink liquid and the treatment liquid, an acid is contained in the treatment liquid, the pigment dispersion is destroyed by PH down, the color material bleeds using a mechanism of agglomeration, color mixing between inks of each color, and ink droplet landing liquid Avoid droplet ejection interference due to coalescence.

  The ink jet line head 64 performs droplet ejection in synchronization with an encoder (not shown) that detects the rotational speed disposed on the image forming drum 36, thereby determining the landing position with high accuracy and at the same time. Irregular droplet ejection can be reduced without depending on the shake, the accuracy of the rotary shaft 68, and the drum surface speed.

  (Ink drying section)

  An ink drying drum 38 is rotatably provided in the ink drying unit 18 shown in FIG. 1. A hot air nozzle 72 and an IR heater are disposed above the ink drying drum 38 in the vicinity of the surface of the ink drying unit 18. A plurality of 74 are arranged. By the hot air from the hot air nozzle 72 and the IR heater 74, the solvent separated by the color material aggregating action is dried in the image forming area of the paper to form a thin image layer.

  The hot air is usually set to 50 ° C. to 70 ° C., although it varies depending on the sheet conveyance speed. The evaporated solvent is discharged together with air to the outside of the image forming apparatus 10, but the air is recovered. This air may be cooled by a cooler / radiator or the like and recovered as an ink liquid.

  The sheet on which the image on the recording surface is dried is conveyed to an intermediate conveyance unit 76 provided between the ink drying unit 18 and the image fixing unit 20 by the rotation of the ink drying drum 38. Since the configuration is substantially the same as that of the intermediate conveyance unit 58, description thereof is omitted.

  (Image fixing part)

  An image fixing drum 40 is rotatably provided in the image fixing unit 20. In the image fixing unit 20, latex particles in a thin image layer formed on the ink drying drum 38 are heated / pressurized. And has a function of fixing and fixing on the paper.

  A heating roller 78 is disposed above the image fixing drum 40 in the vicinity of the surface of the image fixing drum 40. The heating roller 78 has a halogen lamp incorporated in a metal pipe made of aluminum or the like having good thermal conductivity, and the heating roller 78 applies thermal energy equal to or higher than the Tg temperature of the latex. As a result, the latex particles are melted and pressed into the irregularities on the paper for fixing, and the irregularities on the image surface are leveled to obtain glossiness.

  A fixing roller 79 is provided on the downstream side of the heating roller 78. The fixing roller 79 is disposed in pressure contact with the surface of the image fixing drum 40 so as to obtain a nip force with the image fixing drum 40. I have to. For this reason, at least one of the fixing roller 79 and the image fixing drum 40 has an elastic layer on the surface and a uniform nip width with respect to the sheet.

  The sheet on which the image on the recording surface is fixed by the above-described process is conveyed to the discharge unit 21 side provided on the downstream side of the image fixing unit 20 by the rotation of the image fixing drum 40.

  FIG. 2 shows a structural example of the inkjet line head 64. 2A is a longitudinal sectional view of the inkjet line head 64, and FIG. 2B is a transverse sectional view of the inkjet line head 64. As shown in FIG.

  As shown in FIGS. 2A and 2B, the inkjet line head 64 according to the present embodiment includes a first wall surface 82A having a plurality of nozzles 80 and a second wall surface facing the first wall surface 82A. 82B, and the ink liquid is supplied to each of the pressure chamber 84 and the pressure chamber 84 filled with the supplied ink liquid corresponding to each of the nozzles 80 between the first wall surface 82A and the second wall surface 82B. A supply path 86 for discharging the ink and a discharge path 88 for discharging the ink liquid filled in each of the pressure chambers 84 are formed.

  The supply path 86 and the discharge path 88 communicate with an ink tank (not shown) as an ink supply source. The supply path 86 supplies ink liquid from the ink tank to the pressure chamber 84 via the branch path 90A. The discharge path 88 circulates the ink liquid flowing in from the pressure chamber 84 through the branch path 90B to the ink tank.

  The second wall surface 82 </ b> B is provided at a portion corresponding to each of the nozzles 80 and applies a pressure to the ink liquid filled in the pressure chamber 84 to discharge the ink liquid from the nozzle 80. 92 is provided. The discharge actuator 92 is preferably a piezoelectric element using a piezoelectric material such as lead zirconate titanate or barium titanate, and the portion provided with the discharge actuator 92 is also used as a common electrode. A diaphragm 94 is provided, and an individual electrode 96 is provided on the surface of the discharge actuator 92 opposite to the surface in contact with the diaphragm 94.

  The ejection actuator 92 is deformed by applying a drive voltage between the individual electrode 96 and the common electrode, so that the volume of the pressure chamber 84 is changed, and the ink liquid is ejected from the nozzle 80 due to the pressure change accompanying this. . Further, when the displacement of the ejection actuator 92 returns to its original state after the ejection of the ink liquid, new ink is refilled into the pressure chamber 84 from the supply path 86 through the branch path 90A.

  The image forming apparatus 10 according to the present embodiment causes the ink liquid to be ejected from the nozzles 80 by controlling the driving of the ejection actuators 92 corresponding to the respective nozzles 80 according to the dot arrangement data generated from the image information. . Then, a process of forming an image indicated by image information on the paper (hereinafter referred to as the image information) by controlling the ink ejection timing of each nozzle 80 in accordance with the transport speed while transporting the paper in the sub-scanning direction at a constant speed And “image forming process”).

  Further, the image forming apparatus 10 according to the present embodiment supplies the supply path so as to apply pressure to the ink liquid filled by being driven on the side on which the ejection actuator 92 of the second wall surface 82B is provided. Circulating actuators 98 </ b> A and 98 </ b> B provided corresponding to 86 are provided. In the image forming apparatus 10 according to the present embodiment, two of the circulating actuators 98A and 98B are driven as a set. 2B shows only one set of circulating actuators 98A and 98B, a plurality of sets of circulating actuators 98A and 98B are supplied to the image forming apparatus 10 according to the present embodiment. Corresponding to the path 86 is provided. In addition, when it is necessary to distinguish between A and B for the circulating actuators 98A and 98B, either A or B is added after the code, and when it is not necessary to distinguish between A and B, A and B are added. Omitted.

  Similarly to the discharge actuator 92, the circulation actuator 98 is preferably a piezoelectric element using a piezoelectric material such as lead zirconate titanate or barium titanate, and the above-mentioned portion where the circulation actuator 98 is provided is The diaphragm 94 is also used as a common electrode, and an individual electrode 96 is provided on the surface of the circulating actuator 98 opposite to the surface in contact with the diaphragm 94.

  The circulation actuator 98 is deformed by applying a driving voltage between the individual electrode 96 and the common electrode, whereby the volume of the supply path 86 is changed, and the ink filled in the supply path 86 due to the pressure change accompanying this change. The liquid is moved. That is, the circulation actuator 98 functions as a pump for circulating the ink liquid.

  In the image forming apparatus 10 according to the present embodiment, the piezoelectric element used as the ejection actuator 92 and the piezoelectric element used as the circulation actuator 98 are formed by the same process. As a method of forming the piezoelectric element on the vibration plate 94, a method in which a piezoelectric element that has been thinned in advance is bonded on the vibration plate 94, and after bonding a thick plate of the piezoelectric element on the vibration plate 94, the bonded piezoelectric element is ground. There are a method of polishing, a method of forming a piezoelectric element on the diaphragm 94 by a sol-gel method, a sputtering method, or the like. In addition, as a method of partitioning the piezoelectric element, a method in which a rectangular section is bonded is used, or the piezoelectric element on the plate is temporarily bonded to the handle substrate, and then partitioned by wet etching, dry etching, or sand blasting. After that, there are a method of transferring them collectively onto the vibration plate 94 and a method of partitioning the piezoelectric elements on the vibration plate 94 by direct wet etching, dry etching or sand blasting.

  By the above method, the piezoelectric element used as the discharge actuator 92 on the vibration plate 94 corresponding to the pressure chamber 84 and the piezoelectric element used as the circulation actuator 98 on the vibration plate 94 corresponding to the supply path 86 are patterned. . Unless the piezoelectric elements are individually attached, the thickness of the piezoelectric element used as the ejection actuator 92 and the thickness of the piezoelectric element used as the circulation actuator 98 are the same.

  FIG. 3 shows the main configuration of the electrical system of the image forming apparatus 10 according to the present embodiment.

  The image forming apparatus 10 includes a CPU (Central Processing Unit) 150 that controls the operation of the entire image forming apparatus 10, a ROM (Read Only Memory) 152 in which various programs, various parameters, various table information, and the like are stored in advance. A RAM (Random Access Memory) 154 used as a work area at the time of program execution, and an HDD (Hard Disk Drive) 156 for storing various information such as image information received via an external interface 162 described later are provided. .

  The image forming apparatus 10 also includes an image forming control unit 158 that controls operations of the image forming unit 16 and the ink drying unit 18 when performing image forming processing, operation buttons and numeric keys for inputting various operation instructions, And an external interface 162 for transmitting and receiving various information such as image information to and from an external terminal device.

  The CPU 150, ROM 152, RAM 154, HDD 156, image formation control unit 158, operation unit 160, and external interface 162 are electrically connected to each other via a system bus 164. Therefore, the CPU 150 accesses the ROM 152, RAM 154, and HDD 156, transmits and receives various information to and from the terminal device via the external interface 162, the image forming unit 16 via the image forming control unit 158, the ink drying unit 18, and the like. It is possible to control the operation, grasp the operation state with respect to the operation unit 160, and display various messages by the operation unit 160.

  The image formation control unit 158 applies a drive voltage to the ejection actuator 92 so as to eject ink droplets from the nozzles 80 based on the image information, and drives the supply path when performing image formation processing. A driving voltage is applied to the circulating actuators 98A and 98B so that the ink liquid filled in the nozzle 86 moves in a predetermined direction.

  Next, the operation of the present invention of the image forming apparatus 10 according to the present embodiment will be described.

When the volume of the ink pushed out by the circulation actuator 98 _{(the n} number of circulating actuator 98) [Delta] V n and the image forming apparatus 10 according to this embodiment, as shown in the following equation (1) The total volume of the ink liquid pushed out by the circulation actuator 98 is made constant.

  As a result, even when the circulation actuator 98 is driven, the total amount of ink liquid flowing through the supply path 86 and the discharge path 88 is constant. As a result, it is possible to prevent the ink liquid from overflowing from the nozzle 80 and air from being mixed into the ink liquid.

  Next, driving of the circulating actuator 98 performed while satisfying the expression (1) will be described with reference to the schematic diagram of FIG. Note that the impedances at both ends of the flow path shown in FIG.

  Here, assuming that the circulating actuator 98B is not driven, when the circulating actuator 98A is driven, pressure is applied to the ink liquid filled in the flow path, and the pushed out ink liquid has left and right impedances. Since they are equal, they try to flow equally to the left and right. Therefore, when only the circulation actuator 98A is driven, the ink liquid does not flow in one direction.

  However, as shown in FIG. 4A, the circulating actuator 98B is previously pushed out of the ink liquid, and then the circulating actuator 98A applies pressure to the ink liquid as shown in FIG. 4B. In addition to being driven at a high speed so as to be in a state of being pushed out (pressing out the ink liquid), the circulating actuator 98B is driven at a low speed so as to be in a state where no pressure is applied to the ink liquid (no ink liquid is pushed out). That is, the flow path is sharply reduced by the circulation actuator 98A, and the flow path is sharply expanded by the circulation actuator 98B. As a result, a force for drawing the ink liquid is generated on the circulation actuator 98B side, the ink liquid flows more easily in the left direction than in the right direction in FIG. 4, and the ink liquid flows in the left direction in FIG. As in the inkjet line head 64 according to the present embodiment, a circulation path is formed by the supply path 86 and the discharge path 88, but compared to the impedance in the left direction in FIG. 4 for a fast flow. The impedance in the right direction is large (a state where inertia is large, that is, a state where there is no quick response), and a flow hardly occurs in the right direction in FIG.

  On the other hand, when the circulation actuators 98A and 98B are slowly driven from the state shown in FIG. 4B to the state shown in FIG. 4A, the flow of the ink liquid is sufficiently slow. There is no difference in flow.

  As described above, the circulating actuators 98A and 98B are steeply driven from the state shown in FIG. 4A to the state shown in FIG. 4B, and the state shown in FIG. 4B is changed to FIG. 4A. By slowly driving to the state shown, it is possible to cause the ink liquid to flow in the left direction.

  Next, the flow in one direction of the ink liquid described above will be described using the impedance of the flow path through which the ink liquid flows.

FIG. 5 shows a schematic diagram of a flow path through which the ink liquid circulates as in the image forming apparatus 10 according to the present embodiment. The flow path Z shown in FIG. 5 is a first region filled with ink liquid corresponding to the circulation actuators 98A and 98B, that is, the supply path 86 corresponding to the circulation actuators 98A and 98B in this embodiment. Indicates the area. On the other hand, the flow path Z _circ, the second region circulating actuator 98A, the ink that does not correspond to 98B are filled, i.e., regions and the discharge passage 88 of the supply passage 86 excluding the flow path Z in this embodiment Indicates.

The time is T, when the flow velocity of the ink flowing through the channel Z, and U _1, circulating actuator 98A, the pressure difference P _A-B of the ink liquid flowing between 98B is expressed by the following equation (2), the flow When the flow velocity of the ink liquid flowing in the road _{Z circ} and _{U 2,} circulation actuator 98A, the pressure difference _{P a-B} of the ink liquid flowing between 98B is expressed by the following equation (3).

  The constant R indicates the magnitude of the resistance of the flow path. When the length of the flow path is L and the cross-sectional area S of the flow path is expressed by the following equation (4). The constant M indicates the magnitude of the inertia of the ink liquid flowing through the flow path. When the density of the ink liquid is D, it is expressed by the following equation (5).

Here, the ratio of the impedance of the impedance of the flow path Z and the channel _{Z circ} (hereinafter, referred to as "impedance ratio".) If the same is circulated actuator 98A, from the state shown in FIG. 4 (A) of 98B Figure In the driving to the state shown in FIG. 4 (B) and the driving from the state shown in FIG. 4 (B) to the state shown in FIG. 4 (A), the ratio between the flow velocity U ₁ and the flow velocity U ₂ is the same. Therefore, after the ink liquid moves to the left, it moves to the right by the same distance, no flow occurs in the ink liquid, and the ink liquid does not circulate. However, different impedance ratio, the repetition of the driving, it is also the ratio of the flow velocity U ₁ and velocity U ₂ different, flow occurs in the ink liquid, ink liquid is circulated.

6 shows the rate at which circulating actuator 98 is driven, i.e. circulating actuator 98A, with respect to the driving frequency of the 98B, the impedance of the channel Z, and a change in the impedance of the channel _{Z circ.} The intercept a indicating the change in impedance is determined by the reciprocal of the constant R (1 / R), and the break point b is determined by the value obtained by dividing the constant M by the constant R (M / R).

6 (A) is one of the lengths of the flow path Z _circ of the channel Z are different, the cross-sectional area indicates a change in the impedance of the same case. In this case, the frequency characteristic of the impedance of the flow path Z and the flow path Z _circ is in the vertical direction differ only in case of the driving frequency f ₁ and the driving frequency f greater driving frequency f ₂ than the _first circulation actuator 98 in a certain case, the impedance of the flow path Z and the flow path Z _circ ratio (hereinafter, referred to as "impedance ratio".) is the same. That is, even if the speed at which the circulation actuator 98 is driven is changed, the ink liquid does not flow.

On the other hand, FIG. 6 (B), when the length and cross-sectional area of the length and cross-sectional area and the flow path Z _circ of the channel Z are different, indicates a change in impedance. In this case, the impedance ratio differs depending on whether the driving frequency f ₁ of the circulating actuator 98 is the driving frequency f ₂ . This means that, when driven at a speed corresponding circulation actuator 98 to the drive frequency f _1, while the flow is made substantially equal in the flow path Z and the channel Z _circ, corresponding circulation actuator 98 to the driving frequency f ₂ When driving at a speed greater inertia against the ink liquid in the channel Z _circ, hardly flow occurs in the flow path Z _circ, ink flows between the channel Z. That is, by changing the speed at which the circulating actuator 98 is driven, the ink liquid flows.

From the above, in the image forming apparatus 10 according to the present embodiment, in order to circulate the ink liquid filled in the supply path 86 and the discharge path 88, the image forming control unit 158 causes the ink liquid to flow in the left direction in FIG. Is moved from the state where pressure is applied to the ink liquid (state where the ink liquid is pushed out) to the state where pressure is not applied to the ink liquid (state where the ink liquid is not pushed out). both high-speed drive, circulating actuator to drive at a speed corresponding to the drive frequency f ₂ to a state of applying a pressure to the ink liquid circulation actuator 98A positioned to the right from a state without applying pressure to the ink liquid 98B is changed from a state in which no pressure is applied to the ink liquid to a state in which the pressure is applied to the ink liquid, and the circulation actuator 98A is turned on. Click solution are alternately repeated low-speed drive for driving at a speed corresponding to the drive frequency f ₁ to a state of not applying pressure to the ink liquid from a state in which pressure is applied to the.

That is, in high-speed driving, the circulating actuator 98 is driven at a speed corresponding to the driving frequency f ₂ from the state shown in FIG. 4A to the state shown in FIG. 4B, and in low-speed driving, FIG. The circulating actuator 98 is driven at a speed corresponding to the drive frequency f ₁ from the state shown in FIG. 4 to the state shown in FIG.

  7A and 7B show the magnitudes of the drive voltages applied to the circulating actuators 98A and 98B when high-speed driving and low-speed driving are alternately repeated. Regions A in FIGS. 7A and 7B show changes in driving voltage for changing the circulation actuator 98 from a state in which no pressure is applied to the ink liquid to a state in which the pressure is applied to the ink liquid. Shows the change in the driving voltage for changing the circulation actuator 98 from the state where the pressure is applied to the ink liquid to the state where the pressure is not applied to the ink liquid.

  FIG. 8 shows the magnitude of the drive voltage applied to the circulation actuator 98 from the start to the end of the ink liquid circulation. A region C in FIG. 8 is a state where the ink liquid is circulated by the high-speed driving and the low-speed driving of the circulation actuator 98.

  Before starting the circulation of the ink liquid, since the driving actuator 98 is not applied with the driving voltage, the driving voltage is gradually applied so that the ink actuator is driven at a speed that does not cause a change in pressure. A state where high speed driving and low speed driving are possible. After the circulation of the ink liquid, in order to set the drive voltage of the circulation actuator 98 to 0 V, the drive voltage is gradually changed so that the ink liquid is driven at a speed that does not cause a change in pressure. Then, the circulating actuator 98 is brought into a state where no pressure is applied to the ink liquid.

  As described above in detail, according to the image forming apparatus 10 that is the liquid droplet ejection apparatus according to the present embodiment, the first wall surface 82A having the plurality of nozzles 80 and the second wall surface facing the first wall surface 82A. 82B, and supply the ink liquid to each of the pressure chamber 84 and the pressure chamber 84 filled with the supplied ink liquid corresponding to each of the nozzles 80 between the first wall surface 82A and the second wall surface 82B. The discharge path 88 for discharging the ink liquid filled in each of the supply path 86 and the pressure chamber 84 is formed, and a plurality of discharge actuators 92 provided at portions corresponding to the respective nozzles 80 of the second wall surface 82B. Then, pressure is applied to the ink liquid filled in the pressure chamber 84 and the ink liquid is ejected from the nozzle 80. Then, pressure is applied to the ink liquid filled in the supply path 86 by a plurality of circulation actuators 98 provided in correspondence with the supply path 86 on the side where the discharge actuator 92 is provided on the second wall surface 82B. The circulation actuator 98 is driven by the image formation control unit 158 so that the ink liquid filled in the supply path 86 and the discharge path 88 moves in a predetermined direction, so that the ink liquid can be supplied in a space-saving and simple configuration. It can be distributed in a predetermined direction.

  Further, since the discharge actuator 92 and the circulation actuator 98 are piezoelectric elements, the discharge actuator 92 and the circulation actuator 98 can be configured simply.

  Further, since the image formation control unit 158 drives the plurality of circulation actuators 98 so that the volume of the ink liquid that moves by applying pressure is constant, the pressure increase / decrease of the ink liquid by driving the circulation actuator 98 is increased. And the pulsation can be suppressed, and the ink liquid can be prevented from overflowing from the nozzle 80 and air from being mixed into the ink liquid.

The length of the channel Z _circ ink liquid ink corresponding to circulate actuator 98 and the length and cross-sectional area of the flow path Z being filled, does not correspond to the circulation actuator 98 is filled and by varying the cross-sectional area, the ratio of the impedance of the impedance of the flow path Z and the flow path Z _circ, since circulation actuator 98 has a varied according to the speed (driving frequency) to be driven, a plurality of By changing the speed at which the circulating actuator 98 is driven, a flow can be generated in the filled liquid.

Further, when the image formation control unit 158 moves the ink liquid to the left, the circulation actuator 98 positioned in the left direction is changed from the state in which the pressure is applied to the ink liquid to the state in which the pressure is not applied to the ink liquid. The high-speed driving of the circulating actuator 98 positioned in the right direction at a first speed (speed corresponding to the drive frequency f ₂ ) so that the pressure is applied to the ink liquid from the state where the pressure is not applied to the ink liquid. Driving, the circulation actuator 98 positioned in the left direction is changed from a state in which no pressure is applied to the ink liquid to a state in which pressure is applied to the ink liquid, and the circulation actuator 98 positioned in the right direction is applied to the ink liquid. The second impedance ratio is smaller than the impedance ratio at the first speed so that no pressure is applied to the ink liquid from the state. Since the repeat speed slow drive for driving at (a speed corresponding to the drive frequency f ₁₎ are alternately, it is possible to easily produce a left direction of flow in the ink liquid is filled.

  As mentioned above, although this invention was demonstrated using the said embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various modifications or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which such modifications or improvements are added are also included in the technical scope of the present invention.

  The above embodiments do not limit the invention according to the claims (claims), and all the combinations of features described in the embodiments are essential for the solution of the invention. Not exclusively. The embodiments described above include inventions at various stages, and various inventions can be extracted by combinations of a plurality of disclosed constituent elements. Even if some constituent elements are deleted from all the constituent elements shown in the above embodiment, as long as an effect is obtained, a configuration in which these some constituent elements are deleted can be extracted as an invention.

  For example, in the above embodiment, the case where the circulation actuator 98 is provided corresponding to the supply path 86 has been described. However, the present invention is not limited to this, and the discharge path 88 is provided as shown in FIG. Correspondingly, a configuration in which a circulation actuator 98 is provided may be adopted. Alternatively, a circulation actuator 98 may be provided corresponding to each of the supply path 86 and the discharge path 88.

  Moreover, although the said embodiment demonstrated the case where the supply path 86 and the discharge path 88 were provided, this invention is not limited to this, The form provided only with the supply path 86 as shown in FIG. It is good.

  In the above embodiment, the case where the ink liquid is moved in the left direction in FIG. 4 has been described. However, the present invention is not limited to this, and the ink liquid is moved in the right direction in FIG. Also good.

In this case, the image formation control unit 158 changes the circulation actuator 98 positioned in the right direction from the state in which the pressure is applied to the ink liquid to the state in which the pressure is not applied to the ink liquid, and the circulation actuator 98 is positioned in the left direction. speed driving to drive the actuator 98 at a first speed (speed corresponding to the drive frequency f ₂₎ to a state of applying a pressure to the ink liquid from a state that does not impart pressure to the ink liquid, circulation located in the right direction The actuator 98 is changed from a state where no pressure is applied to the ink liquid to a state where pressure is applied to the ink liquid, and the pressure is applied to the ink liquid from the state where the pressure is applied to the ink liquid by the circulating actuator 98 located in the left direction the second speed to a state which does not become smaller impedance ratio than the impedance ratio at the first speed (driving frequency f ₁ The low-speed drive for driving at a response speed of) to repeat alternately.

That is, in the high speed drive, the circulating actuator 98 is driven at a speed corresponding to the drive frequency f ₁ from the state shown in FIG. 4B to the state shown in FIG. 4A, and in the low speed drive, FIG. at a speed corresponding to FIG. 4 the driving frequency f ₂ to the state shown in (B) to drive the circulation actuator 98 from the state shown in.

  In the above-described embodiment, the case where the two circulation actuators 98 are driven in one set has been described. However, the present invention is not limited to this, and three or more circulation actuators 98 are combined in one set. It is good also as a form to drive.

10 Image forming device (droplet discharge device)
64 Inkjet line head (head)
80 Nozzle 82A First wall surface 82B Second wall surface 84 Pressure chamber 86 Supply path 88 Discharge path 96 Discharge actuator (first pressure applying means)
98 Circulating actuator (second pressure applying means)
158 Image formation control unit (drive means)

Claims (7)

A first wall surface having a plurality of nozzles and a second wall surface facing the first wall surface, and a liquid corresponding to and supplied to each of the nozzles is provided between the first wall surface and the second wall surface. A head formed with a pressure chamber to be filled, and a supply path for supplying the liquid to each of the pressure chambers;
A plurality of first pressure applying means provided at portions corresponding to each of the nozzles of the second wall surface, and applying pressure to the liquid filled in the pressure chamber to discharge the liquid from the nozzle;
A plurality of second walls provided in correspondence with the supply path so as to apply pressure to the liquid filled by being driven on the side of the second wall surface where the first pressure applying means is provided. Pressure applying means,
Driving means for driving the second pressure applying means so that the liquid filled in the supply path moves in a predetermined direction;
A droplet discharge device comprising: A first wall surface having a plurality of nozzles and a second wall surface facing the first wall surface, and a liquid corresponding to and supplied to each of the nozzles is provided between the first wall surface and the second wall surface. A head formed with a pressure chamber to be filled, a supply path for supplying the liquid to each of the pressure chambers, and a discharge path for discharging the liquid filled in each of the pressure chambers;
A plurality of first pressure applying means provided at portions corresponding to each of the nozzles of the second wall surface, and applying pressure to the liquid filled in the pressure chamber to discharge the liquid from the nozzle;
Corresponding to at least one of the supply path and the discharge path so as to apply pressure to the liquid filled by being driven on the side of the second wall surface on which the first pressure applying means is provided. A plurality of second pressure applying means provided;
Drive means for driving the second pressure applying means so that the liquid filled in the supply path and the discharge path moves in a predetermined direction;
A droplet discharge device comprising:   The droplet discharge apparatus according to claim 1, wherein the first pressure applying unit and the second pressure applying unit are piezoelectric elements.   4. The liquid droplet according to claim 1, wherein the driving unit drives the plurality of second pressure applying units so that the volume of the moving liquid is constant by applying the pressure. 5. Discharge device.   The length and cross-sectional area of the first area filled with the liquid corresponding to the second pressure applying means, and the second area filled with the liquid not corresponding to the second pressure applying means The ratio between the impedance of the first region and the impedance of the second region was made different according to the speed driven by the second pressure applying means. The droplet discharge device according to claim 1.   In the case of moving the liquid to the left, the driving unit changes the second pressure applying unit positioned in the left direction from a state in which pressure is applied to the liquid to a state in which no pressure is applied to the liquid, and in the right direction. A first drive for driving the second pressure applying means positioned at a first speed so as to change the pressure from the state in which no pressure is applied to the liquid to the state in which the pressure is applied to the liquid; The pressure applying means is changed from a state where pressure is not applied to the liquid to a state where pressure is applied to the liquid, and the second pressure applying means located in the right direction is not applied with pressure from the state where pressure is applied to the liquid. 6. The droplet discharge device according to claim 5, wherein the second drive for driving at a second speed having the ratio smaller than the ratio at the first speed is alternately repeated so as to be in a state.   In the case of moving the liquid in the right direction, the driving unit changes the second pressure applying unit located in the right direction from a state in which pressure is applied to the liquid to a state in which pressure is not applied to the liquid, and in the left direction. A first drive for driving the second pressure applying means located at a first speed so as to change a state in which no pressure is applied to the liquid from a state in which no pressure is applied to the liquid; The pressure applying means is changed from a state where pressure is not applied to the liquid to a state where pressure is applied to the liquid, and the second pressure applying means located in the left direction is not applied with pressure from the state where pressure is applied to the liquid. 6. The droplet discharge device according to claim 5, wherein the second drive for driving at a second speed having the ratio smaller than the ratio at the first speed is alternately repeated so as to be in a state.

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