JP2005289048A - Discharge detecting device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge detecting device which can precisely judge whether or not it is ready to bring about non discharge by detecting ink pressure of a pressure chamber or its vicinity to generated pressure of an actuator for discharge driving in a liquid droplet discharging apparatus, and to provide a discharge detection method. <P>SOLUTION: A pressure detector 72 utilizing a thin film 70 is set in the pressure chamber 52 or in a passage at the feeding side which leads to the pressure chamber 52. A volume change and a pressure change of a liquid are detected by the pressure detector 72. The presence or absence of the liquid and whether or not it is ready to cause non discharge are judged on the basis of the detected information. A pressure loss by a displacement of the thin film 70 is designed within a range not to affect discharge driving by the actuator 68 and refilling of the liquid. Thus the detection at the time when the actuator drives is enabled without the discharging function decreased. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a discharge detection apparatus and method, and more particularly, to a discharge detection apparatus suitable for detecting discharge failure in a discharge head having a large number of droplet discharge ports (nozzles) and a discharge detection method thereof.

  An ink jet recording apparatus forms an image on a recording medium by ejecting ink from the nozzles while relatively moving a print head having a plurality of nozzles and the recording medium. In this type of apparatus, ink is no longer ejected from the nozzles due to ink thickening or air bubble contamination, or the amount of ink ejected (dot size to be ejected onto the recording medium) or the position of ink ejection is inadequate. There may be a case where ejection failure such as appropriateness occurs. For this reason, techniques for detecting ejection / non-ejection of ink droplets from nozzles and recovering non-ejection have been proposed (see Patent Documents 1 and 2).

  The ink jet heads disclosed in Patent Documents 1 and 2 have a piezoelectric element for pressurization necessary for ink ejection, and detect non-ejection of ink from the response of the piezoelectric element after the ink ejection operation (after pressurization). It has become.

Patent Document 3 proposes an ink jet recording apparatus provided with an ink end detector that can accurately detect an ink end and use ink in a cartridge without waste. That is, the inkjet head disclosed in Patent Document 3 includes a plurality of nozzles, a discharge chamber that communicates with each nozzle, and a reservoir (common liquid chamber) that communicates with the discharge chamber, and generates pressure in the discharge chamber. Ink droplets are ejected from the nozzles. A diaphragm that can be deformed according to the pressure in the discharge chamber is formed in a part of the reservoir. A change in resistance value of a semiconductor diffusion resistance type pressure sensor provided in the diaphragm is detected by a detection circuit, and when a change in resistance value exceeding a predetermined value is detected, the ink end notification means notifies the user of the ink end. ing.
JP-A-5-131644 Japanese Patent Laid-Open No. 11-286124 JP 11-129472 A

  Many of the reasons why ink ejection cannot be performed normally are because bubbles exist in or near the pressure chamber (corresponding to “ejection chamber” in Patent Document 3), and the volume of the bubbles changes due to pressure. This occurs because the pressure generated by the ink discharge actuator cannot be used effectively for ink discharge. Therefore, it is possible to grasp the ejection state by detecting whether bubbles are present in or near the pressure chamber and whether the pressure generated by the actuator is transmitted to the ink as intended.

  In this regard, in Patent Documents 1 and 2, ejection / non-ejection detection is performed using the piezoelectric effect of a piezoelectric element (piezo element) for ejection and pressurization, and a detection signal after ejection driving (after pressurization) is detected. It is determined whether or not the discharge is normally performed. However, these documents do not disclose obtaining a detection signal during pressurization. If it is attempted to detect the state at the time of pressurization with the configuration as described in Patent Documents 1 and 2, it is considered that the circuit configuration becomes very complicated.

  On the other hand, Patent Document 3 is a technique for detecting ink shortage, and by providing a sensor in a reservoir near the ejection chamber, a change in back pressure at the time of ink shortage is accurately detected. However, it does not detect ink ejection failure.

  The present invention has been made in view of such circumstances, and is a state in which non-ejection occurs by detecting the ink pressure in the pressure chamber or the vicinity thereof with respect to the pressure generated by the actuator. It is an object of the present invention to provide a discharge detection device and a detection method suitable for accurately detecting whether or not a large number of nozzles in a long head or the like are detected efficiently.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a nozzle that discharges droplets, a pressure chamber that communicates with the nozzle and is filled with a liquid that is ejected from the nozzle, and communicates with the pressure chamber. A droplet discharge device comprising: a supply flow path for supplying a liquid to the chamber; and an actuator for deforming at least a part of the pressure chamber to change the pressure in the liquid in the pressure chamber and discharging the droplet from the nozzle A discharge detecting device for detecting a discharge state of the pressure sensor, comprising a membrane member that is disposed in the pressure chamber and forms a part of a surface forming the pressure chamber, and is displaceable in accordance with a pressure change of the liquid in the pressure chamber. A pressure detection unit that outputs a detection signal corresponding to the displacement of the membrane member, and a discharge state that determines a discharge state of the nozzle based on a detection signal obtained from the pressure detection unit in response to driving of the actuator Characterized in that it comprises a constant means.

  According to the present invention, the change in the pressure of the liquid is detected by the displacement of the membrane member arranged facing the pressure chamber, and the manner in which the generated pressure of the actuator is transmitted to the liquid is detected. Therefore, it is possible to determine not only the presence / absence of liquid from the detection information but also whether or not there is a bubble causing non-ejection due to pressure loss, and it is possible to judge whether or not there is a non-ejection state. In addition, since the displacement amount of the film member in the present invention does not affect the discharge of the liquid, the deterioration of the discharge performance due to the addition of the pressure detection means is minimized.

  The displacement of the membrane member includes a displacement due to the deformation of the membrane member, a displacement due to the movement of the membrane member, or a displacement due to a combination thereof.

  As one aspect of the present invention, it is preferable that the membrane member has a rigidity or a mechanism for returning to an initial state (shape or position) so that a liquid filling force is generated at the time of liquid filling after ejection.

  A second aspect of the present invention relates to the discharge detection apparatus according to the first aspect, wherein the film member can be displaced by a displacement amount within a range in which droplets can be discharged by driving the actuator. To do.

  A third aspect of the present invention relates to the discharge detection device according to the first or second aspect, wherein the film member is configured to return to an initial state when the pressure chamber is filled with liquid after the droplet discharge. It is characterized by being.

  A fourth aspect of the present invention relates to the discharge detection device according to the first, second, or third aspect, wherein the displacement amount of the film member is 1 in terms of a loss of pressure generated by the actuator for discharging a droplet. / 2 or less.

  When such a condition is satisfied, the displacement of the membrane member has little influence on the liquid discharge performance.

  A fifth aspect of the present invention relates to the discharge detection apparatus according to the first, second, or third aspect, wherein the displacement volume of the membrane member is ½ or less of the excluded volume of the pressure chamber by the actuator. And

  The “excluded volume” is a deformation volume when the actuator tries to push out the liquid. When such a condition is satisfied, the displacement of the membrane member has little influence on the liquid discharge performance.

A sixth aspect of the present invention relates to the discharge detection device according to the first, second, or third aspect, and the volume of the liquid returning from the pressure chamber to the supply flow path side when the droplet is discharged by driving the actuator, and the film A value obtained by adding the displacement volume of the member is ½ or less of the displacement volume of the pressure chamber by the actuator.
.

  Furthermore, it is assumed that the displacement volume of the membrane member is smaller than the volume of the liquid returning to the supply-side flow path, and more desirably, the displacement volume of the membrane member is 1/4 of the volume of the liquid returning to the supply-side flow path. It is configured to be smaller.

  A seventh aspect of the present invention relates to the discharge detection device according to the first, second, or third aspect, wherein the volume of the liquid flowing from the pressure chamber to the nozzle side when the droplet is discharged by driving the actuator, and the film member A value obtained by adding together the displacement volumes is less than or equal to ½ of the displacement volume of the pressure chamber by the actuator.

  Furthermore, the displacement volume of the membrane member is smaller than the volume of the liquid flowing to the nozzle side, and more preferably, the displacement volume of the membrane member is smaller than ¼ of the volume of the liquid flowing to the nozzle side. Constitute.

  According to an eighth aspect of the present invention, a nozzle that discharges droplets, a pressure chamber that communicates with the nozzle and is filled with a liquid that is ejected from the nozzle, and a supply that communicates with the pressure chamber and supplies the liquid to the pressure chamber Discharge for detecting a discharge state of a droplet discharge device including a flow path and an actuator that deforms at least a part of the pressure chamber to change the pressure in the liquid in the pressure chamber and discharge the droplet from the nozzle A membrane device which is a detection device and is arranged in the supply flow path connected to the pressure chamber and forms a part of a surface forming the supply flow path, and is displaceable in accordance with a change in pressure of the liquid in the flow path A pressure detection means for outputting a detection signal corresponding to the displacement of the membrane member, and a discharge state for determining a discharge state of the nozzle based on a detection signal obtained from the pressure detection means in response to driving of the actuator Judge Discharge detecting apparatus characterized in that it comprises, when.

  A ninth aspect of the present invention relates to the ejection detection device according to the eighth aspect, wherein the film member is displaceable by a displacement amount within a range in which droplets can be ejected by driving the actuator. To do.

  A tenth aspect of the present invention relates to the discharge detection apparatus according to the eighth or ninth aspect, wherein the film member is configured to return to an initial state when the pressure chamber is filled with liquid after the liquid droplet is discharged. It is characterized by being.

  An eleventh aspect of the present invention relates to the discharge detection device according to the eighth, ninth, or tenth aspect, wherein the displacement amount of the film member is 1 in terms of a loss of the pressure generated by the actuator for discharging a droplet. / 2 or less.

  A twelfth aspect of the present invention relates to the discharge detection device according to the eighth, ninth, or tenth aspect, wherein the displacement volume of the membrane member is ½ or less of the displacement volume of the pressure chamber by the actuator. And

  A thirteenth aspect of the present invention relates to the discharge detection device according to any one of the eighth to twelfth aspects, wherein the pressure detection means is a flow connected to n (where n is an integer of 2 or more) pressure chambers. One or more and less than n is provided on the liquid supply side of the passage.

  With a configuration in which the number of pressure detection means fewer than n is provided in a common supply-side flow path communicating with n pressure chambers, it is possible to detect the discharge state of n nozzles.

  A fourteenth aspect of the present invention relates to the discharge detection device according to any one of the eighth to thirteenth aspects, wherein the supply flow path has a shape in which the cross-sectional area of the flow path decreases toward the downstream. It is characterized by.

  With the configuration in which the flow path cross-sectional area is gradually reduced as it goes downstream in the liquid flow direction, the flow speed on the downstream side is increased, and the bubble elimination is enhanced. Further, the distance from the membrane member increases as it goes downstream, but by reducing the flow path cross-sectional area, the pressure wave attenuation can be reduced and the detection accuracy can be increased.

  A fifteenth aspect of the invention relates to the discharge detection device according to any one of the first to fourteenth aspects, wherein the pressure detection means includes a displacement amount limiting means for limiting a displacement amount of the film member. It is characterized by.

  The displacement amount limiting means may be configured to limit the displacement in both directions (the liquid side and the opposite side of the liquid) in the direction in which the membrane member is displaced, or may be configured to limit either one of the displacements.

  By adding such a displacement amount limiting means, it is possible to realize a non-linear response that the initial stage of the pressure change is displaced quickly, but no further displacement is obtained once the necessary displacement is obtained. High-precision pressure detection is possible with little influence.

  The invention according to claim 16 provides a method invention for achieving the object. That is, the discharge detection method according to claim 16 includes a nozzle that discharges droplets, a pressure chamber that is in communication with the nozzle and filled with a liquid that is discharged from the nozzle, and that is in communication with the pressure chamber. A discharge state of a droplet discharge device comprising: a supply flow path for supplying a liquid; and an actuator that deforms at least a part of the pressure chamber to change the pressure in the liquid in the pressure chamber and discharge the droplet from the nozzle. A discharge detection method for detecting the pressure chamber and the flow passage so that at least one of the pressure chamber and the supply flow passage forms part of a surface forming the pressure chamber or the supply flow passage. A film member that can be displaced according to a change in the pressure of the liquid is provided, a detection signal according to the displacement of the film member is obtained, and a discharge state of the nozzle based on the detection signal obtained according to driving of the actuator The Characterized in that it constant.

  In addition, the droplet discharge device provided with the discharge detection device of the present invention can be suitably used for an image forming apparatus such as an inkjet method. For example, an ejection head as one form of a droplet ejection apparatus is an inkjet recording head having a nozzle surface in which a plurality of nozzles for ejecting ink droplets are two-dimensionally arranged, and at least of the ejection head and the recording medium The image forming apparatus includes a conveying unit that conveys one of them and relatively moves the ejection head and the recording medium.

  In this case, the form of the ejection head is not particularly limited. For example, a nozzle array in which a plurality of nozzles that eject ink are arranged over a length corresponding to the entire width of the recording medium in a direction substantially orthogonal to the feeding direction of the recording medium. A full-line type recording head having

  The “full-line type recording head (discharge head)” is usually arranged along a direction perpendicular to the relative feeding direction of the recording medium, but with a certain predetermined angle with respect to the direction perpendicular to the feeding direction. There may also be a mode in which the recording head is arranged along an oblique direction with a gap. Furthermore, by combining a plurality of short recording head units having nozzle rows that are less than the length corresponding to the entire width of the recording medium, a nozzle row corresponding to the entire width of the recording medium may be configured as a whole of these units. .

  The “recording medium” is a medium (which can be called a printing medium, an image forming medium, a recording medium, an image receiving medium, or the like) that receives an image recorded by the action of the ejection head, and is a continuous sheet, a cut sheet, a seal sheet, It includes various media regardless of the material and shape, such as a resin sheet such as an OHP sheet, a film, a cloth, a printed board on which a wiring pattern or the like is formed by an inkjet recording apparatus. In this specification, the term “printing” represents the concept of forming an image in a broad sense including characters.

  The conveying means for relatively moving the recording medium and the ejection head is an aspect for conveying the recording medium to the stopped (fixed) ejection head, an aspect for moving the ejection head relative to the stopped recording medium, or Any of the modes in which both the ejection head and the recording medium are moved is included.

  According to the present invention, at least one of the pressure chamber and the supply-side flow path connected to the pressure chamber is arranged with a pressure detection means using a membrane member, and the pressure detection means detects the pressure change of the liquid. Therefore, based on the detection information, it is possible to determine not only the presence / absence of liquid but also a state in which non-ejection occurs. In addition, according to one aspect of the present invention, the pressure loss due to the displacement of the membrane member is designed in a range that does not affect the ejection drive and refilling of the liquid by the actuator, so the actuator can be used without degrading the ejection function. Detection during driving is possible.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Overall configuration of inkjet recording apparatus]
FIG. 1 is an overall configuration diagram of an ink jet recording apparatus using an ejection detection apparatus according to an embodiment of the present invention. As shown in the figure, the inkjet recording apparatus 10 includes a print unit 12 having a plurality of print heads 12K, 12C, 12M, and 12Y provided for each ink color, and each print head 12K, 12C, 12M, An ink storage / loading unit 14 for storing ink to be supplied to 12Y, a paper feeding unit 18 for supplying recording paper 16, a decurling unit 20 for removing curling of the recording paper 16, and a nozzle of the printing unit 12 The suction belt transport unit 22 that transports the recording paper 16 while maintaining the flatness of the recording paper 16 and the recorded recording paper (printed material) are discharged to the outside. And a paper discharge unit 26.

  The ink storage / loading unit 14 has tanks (ink tanks) that store inks of colors corresponding to the print heads 12K, 12C, 12M, and 12Y, and each ink tank prints each print via a pipe line (not shown). The 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) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. ing.

  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.

  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.

  In the case of an apparatus configuration that uses roll paper, a cutter (first 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 disposed on the printing surface side with the conveyance path interposed therebetween. Note that the cutter 28 is not necessary when cut paper is used.

  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 forms a horizontal surface (flat surface). Has been.

  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, a suction chamber 34 is provided at a position facing the nozzle surface of the printing unit 12 inside the belt 33 spanned between the rollers 31 and 32, and the suction chamber 34 is connected to the fan 35. The recording paper 16 on the belt 33 is sucked and held by suctioning to negative pressure.

  When the power of a motor (not shown in FIG. 1, not shown in FIG. 8) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, the belt 33 rotates in the clockwise direction in FIG. , And the recording paper 16 held on the belt 33 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 blow method of blowing 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 conveyance mechanism instead of the suction belt conveyance unit 22 is also conceivable, if the roller / nip conveyance is performed in the print area, the image easily spreads because the roller contacts the printing surface of the sheet immediately after printing. There is a problem. Therefore, as in this example, suction belt conveyance that does not bring the image surface into contact with each other in the print 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 orthogonal to the paper feed direction (see FIG. 2). Although a detailed structural example will be described later, each of the print heads 12K, 12C, 12M, and 12Y has a length that exceeds at least one side of the maximum size recording paper 16 targeted by the inkjet recording apparatus 10, as shown in FIG. It is composed of a line-type head in which a plurality of nozzles are arranged.

  A print head 12K corresponding to each color ink in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 16 (hereinafter referred to as the paper transport direction). , 12C, 12M, and 12Y are arranged, and color images can be formed on the recording paper 16 by ejecting the color inks from the print heads 12K, 12C, 12M, and 12Y while conveying the recording paper 16, respectively.

  As described above, 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 feeding direction (sub-scanning direction). It is possible to record an image on the entire surface of the recording paper 16 with only one operation (that is, with one sub-scan). Thereby, it is possible to perform high-speed printing as compared with a shuttle type head in which the print head reciprocates in the main scanning direction, and productivity can be improved.

  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 may be added as necessary. Good. For example, it is possible to add a print head that discharges light ink such as light cyan and light magenta. Also, the arrangement order of the color heads is not particularly limited.

  As shown in FIG. 1, a post-drying unit 42 is provided after the printing unit 12. 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 surface uneven 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 sorting means (not shown) that switches the paper discharge path so as to select the print product of the main image and the print product of the test print and send them to the discharge units 26A and 26B. Yes.

  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 in FIG. 1, the paper output unit 26A for the target prints is provided with a sorter for collecting prints according to print orders.

[Print head structure]
Next, the structure of the print head will be described. Since the structures of the print heads 12K, 12C, 12M, and 12Y provided for the respective ink colors are common, the print heads are represented by reference numeral 50 in the following.

  FIG. 3 (a) is a plan perspective view showing an example of the structure of the print head 50, and FIG. 3 (b) is an enlarged view of a part thereof. FIG. 4 is a cross-sectional view showing a three-dimensional configuration of one droplet discharge element (an ink chamber unit corresponding to one nozzle 51).

  In order to increase the dot pitch printed on the recording paper surface, it is necessary to increase the nozzle pitch in the print head 50. As shown in FIGS. 3A and 3B, the print head 50 of this example includes a plurality of liquid droplets including nozzles 51 serving as ink droplet discharge ports, pressure chambers 52 corresponding to the nozzles 51, and the like. It has a structure in which the ejection elements 53 are arranged in a staggered matrix (two-dimensionally), thereby achieving a high density of the apparent nozzle pitch.

  That is, the print head 50 in this embodiment has one or more nozzle rows in which a plurality of nozzles 51 are arranged in a direction substantially orthogonal to the feeding direction of the recording paper 16 over a length corresponding to the entire width of the recording paper 16. doing.

  The pressure chamber 52 provided corresponding to each nozzle 51 has a substantially square planar shape, and has an outlet to the nozzle 51 and an ink inlet (supply path) on the supply side at both diagonal corners. Aperture) 54 is provided. The shape of the pressure chamber 52 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon and other polygons, a circle, and an ellipse.

  As shown in FIG. 4, a pressure chamber 52, a nozzle channel 56, a supply channel (common liquid chamber) 58 and the like are formed inside the print head 50. The nozzle plate 60 is provided with a nozzle 51 serving as a final throttle portion from which liquid is discharged, and the nozzle 51 communicates with the pressure chamber 52 via a nozzle channel 56. The pressure chamber 52 communicates with the supply flow path 58 via the supply path restrictor 54.

  The supply flow path 58 communicates with an ink tank (not shown in FIG. 4; indicated by reference numeral 80 in FIG. 7) serving as an ink supply source, and the ink supplied from the ink tank 80 passes through the supply flow path 58 in the head. The pressure chambers 52 are distributed and supplied.

  As shown in FIG. 4, an actuator 68 having an individual electrode 66 is joined to a vibration plate (pressure plate) 64 that constitutes a part of the pressure chamber 52 (the top surface in the figure). For the actuator 68, a piezoelectric body such as a piezoelectric element is preferably used. By applying a driving voltage to the individual electrode 66 corresponding to the pressure chamber 52, the actuator 68 is deformed to change the volume of the pressure chamber 52, and ink is ejected from the nozzle 51 due to the pressure change accompanying this. After ink ejection, new pressure ink is refilled into the pressure chamber 52 from the supply channel 58 through the supply channel throttle 54.

  Although not shown in FIG. 4, there is a common electrode (film) at the boundary between the diaphragm 64 and the actuator 68.

  In the pressure chamber 52, a pressure detector 72 that converts the displacement of the thin film 70 into an electric signal and extracts it from the detection electrode (film displacement detection electrode) 71 as a detection signal is disposed. The thin film 70 forms part of the lower surface of the pressure chamber 52 (the surface facing the diaphragm 64 to which the actuator 68 is bonded), and the surface of the thin film 70 opposite to the ink contact surface has a limited volume. It faces the cavity 73 having

  The pressure detector 72 functions as means for detecting a change in ink volume and a change in ink pressure due to ink filling, and the thin film 70 is deformed according to the ink volume and the ink pressure in the pressure chamber 52. The deformation amount (that is, the displacement amount) of the thin film 70 is converted into an electrical signal and taken out, and a change in ink volume or a change in ink pressure is detected.

  The deformation / displacement amount of the thin film 70 is an amount that does not affect ink ejection, and the thin film 70 has a rigidity or a mechanism that returns to an initial shape so as to generate an ink filling force when ink is filled after ejection. . The thin film 70 may be naturally restored to its initial shape by the tension of the thin film 70 itself, or a means for applying a restoring force to the thin film 70 may be provided.

  As a means for applying the restoring force, it is conceivable to use an electrostatic force or a force generated by an electromagnetic force generated by a coil / magnet. These can all be realized by using a structure that functions as a sensor as an actuator, and a restoring force can be applied by switching to the actuator immediately after pressure detection.

  Although details of pressure detection by the thin film 70 will be described later, the ink pressure when the actuator 68 is driven is detected by the pressure detector 72, and whether or not non-discharge occurs based on the detection result (normally discharged). Is determined).

  As shown in FIG. 5, the droplet discharge elements 53 having such a structure are arranged in a fixed arrangement pattern along a row direction along the main scanning direction and an oblique column direction having a constant angle θ not orthogonal to the main scanning direction. The high-density nozzle head of this example is realized by arranging a large number in a lattice pattern.

  That is, by arranging a plurality of nozzles 51 at a constant pitch d along the direction of an angle θ with respect to the main scanning direction, the pitch P of the nozzles projected so as to be aligned in the main scanning direction becomes d × cos θ. With respect to the main scanning direction, each nozzle 51 can be handled equivalently as a linear array with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which the number of nozzle rows projected so as to be aligned in the main scanning direction is 2400 per inch (2400 npi; nozzle / inch).

  When the nozzles are driven by a full line head having a nozzle row having a length corresponding to the entire printable width, (1) all the nozzles are driven simultaneously, (2) the nozzles are sequentially driven from one side to the other. (3) The nozzle is divided into blocks, each block is sequentially driven from one side to the other, and the like, and one line (one row) in the paper width direction (direction perpendicular to the paper conveyance direction) (Nozzle line or a line composed of a plurality of rows of dots) is defined as main scanning.

  In particular, when driving the nozzles 51 arranged in a matrix as shown in FIG. 5, the main scanning as described in (3) above is preferable. That is, nozzles 51-11, 51-12, 51-13,... 51-16 are made into one block (other nozzles 51-21,... 51-26 are made into one block, nozzles 51-31,. 36), one line is printed in the width direction of the recording paper 16 by sequentially driving the nozzles 51-11, 51-12, ... 51-16 according to the conveyance speed of the recording paper 16.

  On the other hand, by relatively moving the above-mentioned full line head and the 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. This is defined as sub-scanning.

  The direction indicated by one line (or the longitudinal direction of the belt-like region) recorded by the main scanning is referred to as a main scanning direction, and the direction in which the sub scanning is performed is referred to as a sub scanning direction. In other words, in the present embodiment, the conveyance direction of the recording paper 16 is the sub-scanning direction, and the direction orthogonal to it is the main scanning direction.

  The structure of the print head 50 and the form of the nozzle arrangement are not limited to the examples described with reference to FIGS. For example, as shown in FIG. 6, a nozzle array having a length corresponding to the entire width of the recording paper 16 is formed by connecting short head units 50 ′ in which a plurality of nozzles 51 are two-dimensionally arranged in a staggered manner. You may comprise the full line head which has.

[Configuration of ink supply system]
FIG. 7 is a schematic diagram showing the configuration of the ink supply system in the inkjet recording apparatus 10. The ink tank 80 is a base tank that supplies ink to the print head 50 and is installed in the ink storage / loading unit 14 described with reference to FIG. In the form of the ink tank 80, there are a system that replenishes ink from a replenishment port (not shown) and a cartridge system that replaces the entire tank when the remaining amount of ink decreases. A cartridge system is suitable for changing the ink type according to the intended use. 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 80 in FIG. 7 is equivalent to the ink storage / loading unit 14 in FIG. 1 described above.

  As shown in FIG. 7, a filter 82 is provided between the ink tank 80 and the print head 50 in order to remove foreign substances and bubbles. The filter mesh size is preferably equal to or smaller than the nozzle diameter (generally about 20 μm).

  Although not shown in FIG. 7, 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 84 as a means for preventing the nozzle 51 from drying or preventing an increase in ink viscosity near the nozzle, and a cleaning blade 86 as a means for cleaning the nozzle surface 50A. .

  The maintenance unit (recovery device) including the cap 84 and the cleaning blade 86 can be moved relative to the print head 50 by a moving mechanism (not shown), and maintenance is performed below the print head 50 from a predetermined retraction position as necessary. Moved to position.

  The cap 84 is displaced up and down relatively with respect to the print head 50 by an elevator mechanism (not shown). The cap surface 84 </ b> A is covered with the cap 84 by raising the cap 84 to a predetermined raised position when the power is turned off or during printing standby, and bringing the cap 84 into close contact with the print head 50.

  The cleaning blade 86 is made of an elastic member such as rubber, and can slide on the nozzle surface 50A (the surface of the nozzle plate 60 shown in FIG. 4) of the print head 50 by a blade moving mechanism (not shown). When ink droplets or foreign matter adhere to the nozzle plate 60, the surface of the nozzle plate 60 is wiped by sliding the cleaning blade 86 shown in FIG.

  During printing or standby, when a specific nozzle is used less frequently and the ink viscosity in the vicinity of the nozzle increases, preliminary ejection is performed toward the cap 84 to discharge the deteriorated ink.

  Further, when air bubbles are mixed in the ink in the print head 50 (in the pressure chamber 52 or in the flow path in the vicinity thereof), the cap 84 is applied to the print head 50, and the ink in the pressure chamber (air bubbles are mixed in) by the suction pump 87. Ink) is removed by suction, and the ink removed by suction is sent to the collection tank 88. In this suction operation, the deteriorated ink with increased viscosity (solidified) is sucked out when the ink is initially loaded into the head or when the ink is used after being stopped for a long time.

  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. Ink will not be ejected. Therefore, before this state is reached (within the range of viscosity at which ink can be discharged by the operation of the actuator 68), the actuator 68 is operated toward the ink receiver to discharge ink in the vicinity of the nozzle whose viscosity has increased. “Preliminary discharge” is performed. Further, after the dirt on the surface of the nozzle plate 60 is cleaned by a wiper such as a cleaning blade 86 provided as a cleaning means for the nozzle surface 50A, 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 into the nozzle 51 or the pressure chamber 52 or if the viscosity increase of the ink in the nozzle 51 exceeds a certain level, ink cannot be ejected by the preliminary ejection, and the suction operation described below is performed.

  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 can be ejected from the nozzle 51 even if the actuator 68 is operated. Disappear. In such a case, a suction means for sucking ink in the pressure chamber 52 with a pump or the like is brought into contact with the nozzle surface 50A of the print head 50, and an operation of sucking ink mixed with bubbles or thickened ink is performed.

  However, since the above suction operation is performed on the entire ink in the pressure chamber 52, the amount of ink consumption is large. Therefore, when the increase in viscosity is small, it is preferable to perform preliminary discharge as much as possible. Note that the cap 84 described with reference to FIG. 7 functions as a suction unit and can also function as a preliminary discharge ink receiver.

[Explanation of control system]
Next, the control system of the inkjet recording apparatus 10 will be described.

  FIG. 8 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 90, a system controller 92, an image memory 94, a motor driver 96, a heater driver 98, a print control unit 100, an image buffer memory 102, a head driver 104, a maintenance unit 106, an ejection detection control unit 108, and the like. It has.

  The communication interface 90 is an interface unit that receives image data sent from the host computer 110. As the communication interface 90, a serial interface such as USB, IEEE1394, 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 110 is taken into the inkjet recording apparatus 10 via the communication interface 90 and temporarily stored in the image memory 94. The image memory 94 is a storage unit that temporarily stores an image input via the communication interface 90, and data is read and written through the system controller 92. The image memory 94 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 92 is a control unit that controls the communication interface 90, the image memory 94, the motor driver 96, the heater driver 98, and the like. The system controller 92 includes a central processing unit (CPU) and its peripheral circuits, and performs communication control with the host computer 110, read / write control of the image memory 94, and the like, as well as a transport system motor 114 and heater 116. A control signal for controlling is generated.

  The motor driver 96 is a driver (drive circuit) that drives the motor 114 in accordance with an instruction from the system controller 92. The heater driver 98 is a driver that drives the heaters 116 of the post-drying unit 42 and other units in accordance with instructions from the system controller 92.

  The print control unit 100 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the image memory 94 under the control of the system controller 92, and the generated print A control unit that supplies a control signal (dot data) to the head driver 104. Necessary signal processing is performed in the print control unit 100, and the ejection amount and ejection timing of the ink droplets of the print head 50 are controlled via the head driver 104 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 100 includes an image buffer memory 102, and image data, parameters, and other data are temporarily stored in the image buffer memory 102 when image data is processed in the print control unit 100. In FIG. 8, the image buffer memory 102 is shown in a form associated with the print control unit 100, but it can also be used as the image memory 94. Also possible is an aspect in which the print control unit 100 and the system controller 92 are integrated to form a single processor.

  The head driver 104 drives the ejection drive actuator 68 of the print head 50 for each color based on the dot data given from the print control unit 100. The head driver 104 may include a feedback control system for keeping the head driving condition constant.

  Data of an image to be printed is input from the outside via the communication interface 90 and stored in the image memory 94. At this stage, for example, RGB image data is stored in the image memory 94. The image data stored in the image memory 94 is sent to the print control unit 100 via the system controller 92. The print control unit 100 converts the data into dot data for each ink color by a known dither method, error diffusion method, or the like. Converted.

  Thus, the print head 50 is driven and controlled based on the dot data generated by the print control unit 100, and ink is ejected from the print head 50. An image is formed on the recording paper 16 by controlling ink ejection from the print head 50 in synchronization with the conveyance speed of the recording paper 16.

  The discharge detection control unit 108 includes a signal processing circuit that processes a detection signal from the pressure detector 72 disposed in the print head 50, and print-controls the detection result obtained from the pressure detector 72. Part 100.

  The print control unit 100 and the system controller 92 determine ejection / non-ejection of the nozzle 51 based on the detection information obtained through the ejection detection control unit 108. If a non-ejection nozzle is detected, a predetermined recovery operation or Control to perform droplet ejection correction and the like is performed.

  The maintenance unit 106 is a block including the cap 84 and the cleaning blade 86 described with reference to FIG. 7, and performs a required recovery process in accordance with a command from the system controller 92.

[Discharge detection method]
Next, a discharge detection method in the inkjet recording apparatus 10 configured as described above will be described.

  FIG. 9 is a schematic diagram of a state where normal ejection is performed. As shown in the figure, when the actuator 68 is deformed by applying a driving voltage to the individual electrode 66, the diaphragm 64 is displaced, the pressure chamber 52 is deformed, and the ink in the pressure chamber 52 is pressurized. . Thus, the ink droplet 120 is ejected from the nozzle 51 by the pressure generated by the actuator 68, and at the same time, the thin film 70 of the pressure detector 72 in the pressure chamber 52 is also displaced.

  On the other hand, for example, as shown in FIG. 10, in the state where the bubbles 124 exist in the pressure chamber 52 and no ejection occurs, the pressure generated by the actuator 68 is absorbed by the contraction of the bubbles 124, and ink is not ejected. At the same time, the displacement of the thin film 70 of the pressure detector 72 is smaller than in the case of FIG.

  Information on the ink pressure is obtained by obtaining a detection signal corresponding to the amount of displacement of the thin film 70 from the detection electrode 71, and whether or not there is a bubble 124 that causes non-ejection based on the pressure information, That is, a determination is made as to whether or not normal ejection is possible.

  The thin film 70 that moves according to the ink pressure includes various metal materials such as SUS, gold, silver, platinum, and aluminum alloys, materials such as silicon and germanium used in semiconductor manufacturing, and resin materials such as polyimide, kevlar, polyester, and polysulfone. Etc. can be used.

  What kind of material is used, not only in terms of whether the required displacement can be obtained with respect to the generated pressure, but also in relation to ink, that is, compatibility related to durability such as corrosion, when filling ink It is comprehensively judged from the compatibility with ink leakage, the manufacturing method of other head parts, and compatibility with materials.

In the present embodiment, in order to perform good pressure detection without affecting ink ejection, the deformation / displacement amount of the thin film 70 is converted into a loss of pressure generated by the actuator 68 for ejecting ink. / 2 or less is desirable. That is, when the actuator 68 is displaced by a predetermined amount, the pressure increase value in the pressure chamber 52 when the thin film 70 of the present invention does not exist is δP ₁ , and the pressure increase value in the pressure chamber 52 when the thin film 70 exists is δP ₁ . _{If it is 2,} it will be the relationship of following Formula [Formula 1].
[Formula 1] δP ₂ / δP ₁ ≧ 1/2
Alternatively, the deformation / displacement volume of the thin film 70 is V ₂ , and the excluded volume of the pressure chamber 52 generated by driving the actuator 68 during ink ejection is V ₁ (deformation volume when the actuator 68 tries to push out the ink). When it does, it is preferable to satisfy | fill following Formula [Formula 2].
[Formula 2] V ₂ / V ₁ ≦ 1/2
Further, when the volume of ink returning from the pressure chamber 52 to the ink supply side flow path (supply flow path 58) during ink ejection is V ₄ , it is preferable to satisfy the following formula [Formula 3].
[Formula 3] (V ₂ + V ₄ ) / V ₁ ≦ 1/2
Furthermore, the following formula [Formula 4],
[Formula 4] V ₄ > V ₂
More preferably, the following formula [Formula 5],
[Formula 5] V ₄ × 0.25> V ₂
It shall satisfy the conditions of

From another viewpoint, when the volume of ink flowing from the pressure chamber 52 to the ejection nozzle side (in the direction of the nozzle flow path 56 and the nozzle 51) is V _{3 when} ink is ejected, it is preferable to satisfy the following formula [Formula 6].
[Formula 6] (V ₂ + V ₃ ) / V ₁ ≦ 1/2
Furthermore, the following formula [Formula 7]
[Formula 7] V ₃ > V ₂
More preferably, the following formula [Formula 8],
[Formula 8] V ₃ × 0.25> V ₂
It shall satisfy the conditions of

  In the design of an inkjet head using a normal piezo drive system, the ink volume flowing to the ink ejection nozzle side and the ink volume returning to the ink supply path side are set to be approximately the same with respect to the excluded volume by the actuator. This is to refill the ink quickly while obtaining a discharge amount or a discharge speed as much as possible.

  The conditions shown in the above [Equations 2 to 5] are set for the purpose of obtaining the same discharge amount and discharge speed as those without the detection function even when the pressure detection function is added. In this case, the landing accuracy and the droplet size are more important than the driving frequency of the head.

  On the other hand, the conditions shown in the above [Formulas 6 to 8] are set for the purpose of obtaining the same ink refilling performance as that without the detection function even when the pressure detection function is added. . In this case, emphasis is placed on the use of high-viscosity ink that is difficult to refill or on driving the head at a high frequency.

  In addition, “× 0.25” in [Equation 5] and [Equation 8] can be ignored if the influence of pressure detection is less than this, based on the actual value of variation in flow path manufacturing accuracy and variation in discharge phenomenon. Is a value determined as If the loss of about 12.5% of the excluded volume is finally negligible, the discharge / refill is not affected if such a condition is satisfied.

  For the purpose of detecting pressure with high sensitivity, the thin film 70 is required to be easily displaced. However, if the thin film 70 is displaced more than necessary, the loss of discharge pressure increases, which is not desirable. Conversely, if the rigidity of the thin film 70 is increased too much to suppress the loss of the discharge pressure, the detection sensitivity decreases. Therefore, it is preferable to provide a stopper mechanism that appropriately limits the displacement of the thin film 70.

  FIG. 11 shows a first example of a stopper mechanism for limiting the displacement of the thin film. In the example of FIG. 11, the thin film 70 side has a flat plate shape, and a cylindrical protrusion 130 is provided on a surface (upper surface of the detection electrode 71 in FIG. 11) facing the thin film 70 with a necessary interval for detection. It has been. When the thin film 70 is displaced from the state shown in FIG. 11A and the thin film 70 contacts the upper surface of the protrusion 130 as shown in FIG. 11B, the thin film 70 is not displaced further. .

  Note that the shape of the protrusion 130 is not limited to a cylindrical shape, and may be a shape in which the contact portion is convexly rounded, or may be a depression that follows the deformation of the film. Furthermore, it is also possible to set the distance between the surfaces facing the film to the necessary distance. However, if a gas is present between the surfaces facing the membrane, the compressibility of the gas acts as a spring and hinders the displacement of the membrane, so it is desirable to provide a hole for releasing the gas in a portion other than the membrane. .

  FIG. 12 is a graph showing the relationship between pressure and membrane displacement. Graph [1] is an example having the stopper mechanism described in FIG. Graph [2] in FIG. 12 is an example that does not have a stopper mechanism. As shown in graph [1], in the case of a structure with a stopper mechanism, the displacement of the membrane with respect to the pressure change is displaced with high sensitivity up to the pressure necessary and sufficient for abnormality detection, and thereafter the displacement at the pressure reached at normal time. Can be suppressed. That is, there is an effect of reducing a pressure loss necessary for discharge. On the other hand, if the film is made to be highly rigid and difficult to displace without using a stopper mechanism, the loss during discharge is small as shown in graph [2], but the displacement under abnormal conditions is also small. Cannot detect with high sensitivity.

  Therefore, by using the stopper mechanism to realize the detection characteristics as shown in graph [1], better detection is possible.

  FIG. 13 shows a second example of a stopper mechanism for limiting the displacement of the thin film. That is, FIG. 13 shows an example in which the stopper protrusion 140 is provided on the thin film 70 side. A protrusion 140 is bonded to the back surface side of the thin film 70, and the lower surface of the protrusion 140 abuts against the detection electrode due to the displacement of the thin film 70, thereby preventing further displacement.

  14A and 14B show a third example of a stopper mechanism for limiting the displacement of the thin film, where FIG. 14A is a plan view and FIG. 14B is a cross-sectional view taken along line 14b-14b in FIG. The configuration shown in FIG. 14 is an example in which stopper members 150 and 152 are provided on both surfaces of the thin film 70 so that the displacement of the thin film 70 can be restricted in both cases of positive pressure and negative pressure. In FIG. 14, the stopper member 152 that limits the amount of upward displacement of the thin film 70 is constructed in a substantially arch shape above the effective movable region 70 </ b> A of the thin film 70, and faces the stopper member 150 below with the thin film 70 interposed therebetween. A protrusion 152A that is a contact portion with the thin film 70 is formed at the position. With such a configuration, pressure loss can be reduced not only when ink is ejected but also when ink is filled.

  FIG. 15 shows a fourth example of a stopper mechanism for limiting the displacement of the thin film. FIG. 15 shows an example in which the displacement is limited by devising the cross-sectional shape of the film, not the protruding stopper. In this example, a narrow groove 171 is formed so that the peripheral portion of the effective movable region 170A of the thin film 170 is thin, and a concave portion 173 is formed so that the central portion of the thin film 170 is easily displaced, so that the thin portion is thin. ing. Other parts are made of a relatively thick plate and are not easily deformed (see FIG. 15A).

  In such a configuration, when a pressure is applied to the thin film 70, as shown in FIG. 15B, the peripheral groove 171 portion is displaced to contact the side wall 177, and further displacement can be prevented. Further, when the structure as shown in FIG. 15 is provided symmetrically with respect to the film surface, the film displacement can be limited in both cases of positive pressure and negative pressure.

  For pressure detection, a method in which a capacitor is formed between the thin film 70 and a surface facing the thin film 70 and detection is performed by a change in capacitance, a strain gauge is formed in the thin film, and detection is performed based on the strain of the film, or As shown in FIGS. 11, 13, and 14, in the case where the protrusions facing the thin film 70 are in contact with each other, a method of using the contact portion as a switch is also conceivable.

  For example, the thin film 70 includes a dielectric, and there is a mode in which deformation and displacement of the film are detected by capacitance. There is also a mode in which deformation and displacement of the thin film 70 are detected by electric resistance. Furthermore, the thin film 70 is made of a piezoelectric material, and there is a mode in which a pressure change is detected by generating a voltage by pressure. In addition, it is also possible to detect the displacement of the thin film 70 based on the reflected sound return time of the ultrasonic wave or to detect it using a laser displacement meter.

[Other Embodiments]
FIG. 16 is a cross-sectional view showing another embodiment of the present invention. In FIG. 16, members that are the same as or similar to those in FIG. 4 are given the same reference numerals, and descriptions thereof are omitted. Although the example in which the pressure detector 72 is provided in the pressure chamber 52 has been described in FIG. 4, an embodiment in which the pressure detector 72 is provided in the ink supply path 180 connected to the pressure chamber 52 as shown in FIG. 16 is also possible. is there.

  That is, the print head 50 shown in FIG. 16 includes a pressure detector 72 for detecting ink discharge, ink volume change due to ink filling, and ink pressure change in the ink supply path 180 communicating with the pressure chamber 52. I have. The pressure detector 72 is configured to detect a change in ink volume and a change in ink pressure by deformation and displacement of the thin film 70 facing the flow path of the ink supply path 180. Note that the structure of the pressure detector 72 can be the same as the structure described in FIGS. 4 and 11 to 15.

  In such a form, in order to perform good pressure detection without affecting the ink ejection, the deformation / displacement amount of the thin film 70 is converted into a loss of the generated pressure of the actuator 68 for ejecting ink. It is desirable to set it to 2 or less. Alternatively, it is desirable that the deformation / displacement amount of the thin film 70 is not more than ½ of the displacement volume by the actuator 68 in terms of the displacement volume.

  In addition, regarding the excluded volume generated by driving the actuator during ink ejection, the amount of ink returning from the pressure chamber 52 to the ink supply side channel, to which the volume change amount of the ink supply channel 180 due to the displacement of the thin film 70 is added, is 1 of the excluded volume. / 2 or less.

  FIG. 17 is an essential part enlarged view of a plan perspective view of the print head 50 as viewed from above. Reference numeral 182 in the figure is a basic flow channel of the common flow channel, and a plurality of tributaries (common flow channel tributaries) 184 are branched from the basic common flow channel 182. Each common flow path tributary 184 communicates with a plurality of (four in FIG. 17) pressure chambers 52 via individual supply paths 185.

  As described above, the pressure detector 72 is provided at the most upstream portion of the branch from the base end portion (main common channel 182) of the common channel branch 184 connected to the plurality of pressure chambers 52. The single pressure detector 72 detects the ink discharge state from the plurality of nozzles 51 existing downstream from the pressure detector 72. That is, at the time of detection, ink is ejected from each of the plurality of nozzles 51 in order. Or it discharges continuously, shifting the discharge timing of each nozzle. Based on a detection signal corresponding to such nozzle drive (discharge operation), it is possible to specify a nozzle related to discharge abnormality.

  FIG. 17 shows an example in which four pressure chambers 52 are connected to one common flow path tributary 184. However, the number of pressure chambers and the location of the pressure detector 72 are limited to the example in FIG. Not.

  When the example of FIG. 17 is generalized, one or more and less than n pressure detectors 72 are provided on the ink supply side of the flow path connected to n (where n is an integer of 2 or more) pressure chambers 52. By providing, it is possible to detect ink ejection from n nozzles.

  Further, as shown in FIG. 17, the common flow path tributary 184 connected to the plurality of pressure chambers 52 has a gradually reduced cross-sectional area as it goes to the downstream side of the ink flow.

  If the common flow path tributary 184 has a uniform thickness, the flow velocity decreases toward the downstream, so that when bubbles are generated in the common flow path tributary 184, it is difficult for the bubbles to escape. Therefore, as shown in FIG. 17, the flow path short area is narrowed toward the downstream side, and the ink flow rate is gradually increased toward the downstream side, thereby improving the bubble evacuation property. Further, since the pressure wave is attenuated as it is farther away from the pressure detector 72, a configuration in which the channel cross-sectional area is gradually narrowed toward the downstream side is preferable in order to prevent this.

  Similarly, the basic common flow path 182 is preferably configured such that the cross-sectional area of the flow path gradually decreases as it goes downstream of the ink flow. FIG. 17 shows a structure in which the cross-sectional area of the basic common channel 182 and the common channel tributary 184 is continuously narrowed as it goes downstream of the ink flow. Instead of the channel structure, a structure in which the channel cross-sectional area is narrowed in a step shape is also possible.

  Of course, in the structure as shown in FIG. 17, the distance from each pressure chamber 52 connected to the same common flow path tributary 184 to the pressure detector 72 at the base end of the common flow path tributary 184 is different. Even if the nozzles 51 corresponding to the above are simultaneously ejected, there is a time difference between the pressure waves being transmitted to the pressure detector 72, so that the ejection of each nozzle 51 can be detected even if simultaneous ejection is performed. However, as described above, it is possible to further increase the time difference by intentionally shifting the drive timing of each nozzle 51, and the pressure detection of the plurality of nozzles 51 can be performed more accurately with one pressure detector 72. Can be detected well.

  In consideration of the time difference depending on the distance from the pressure detector 72 to the pressure chamber 52, in the case of continuous discharge, it is preferable to drive (detect) in order from the pressure detector 72 in order.

  FIG. 18 is a schematic diagram illustrating another example of the structure of the pressure detector 72. The surface opposite to the ink 190 of the thin film 70 forming a part of the flow path through which the ink 190 passes is in contact with the cavity 192 (hereinafter referred to as “first cavity”), and is formed inside the first cavity 192. Is filled with gas or liquid (hereinafter referred to as “fluid 194”). The first cavity 192 communicates with another cavity 198 (hereinafter referred to as “second cavity”) through a small hole 196, and the fluid 194 inside the first and second cavities 192, 198 passes through the small hole 196. By moving, the deformation speed of the thin film 70 is controlled. Further, the second cavity 198 has a lower pressure than the first cavity 192, and brings about an action of returning the thin film to the initial position.

  According to such a structure, it is possible to suppress free vibration of the thin film 70 by the fluid 194 in the first and second cavities 192 and 198, and to suppress unnecessary vibration of the ink 190, thereby further stabilizing ejection. Can be made.

  Further, it is preferable that the thin film 70 of FIG. 18 is set to have a natural frequency and a damping characteristic so as to function as a damper that suppresses vibration of ink in the ink ejection operation.

  As a further modification, the surface opposite to the surface facing the pressure chamber 52 or the ink supply path 180 of the thin film 70 described in the above embodiments faces another ink supply path. A structure in which both are in contact with ink is also possible. That is, for example, a structure in which a portion corresponding to the first cavity 192 in FIG. 18 is used as an ink flow path and the deformation speed of the thin film 70 is controlled by the ink flowing through the ink flow path is also possible.

  In the above description, the inkjet recording apparatus 10 has been exemplified, but the scope of application of the present invention is not limited to this. For example, the droplet discharge device of the present invention can be applied to a photographic image forming apparatus provided with a discharge head that applies a developing solution or the like to a photographic paper in a non-contact manner. The scope of application of the present invention is not limited to an image forming apparatus, and the present invention can be applied to various apparatuses such as a coating apparatus that applies a treatment liquid or other liquid to a medium using an ejection head.

1 is an overall configuration diagram of an ink jet recording apparatus using an ejection detection apparatus according to an embodiment of the present invention. FIG. 1 is a plan view of a main part around a printing unit of the ink jet recording apparatus shown in FIG. Plane perspective view showing structural example of print head Sectional drawing which shows the three-dimensional structure of one discharge element in a print head FIG. 3 is an enlarged view showing the nozzle arrangement of the print head shown in FIG. Plane perspective view showing another configuration example of the print head Schematic diagram showing the configuration of an ink supply system in an ink jet recording apparatus Main block diagram showing the system configuration of the inkjet recording apparatus of this example Sectional view showing the deformation state of the thin film during discharge Cross-sectional view showing the state of non-ejection due to the presence of bubbles in the pressure chamber FIG. 11A is a cross-sectional view showing an embodiment provided with a stopper for limiting the amount of displacement of the thin film, and FIG. 11B is a cross-sectional view showing the action of the stopper. Graph showing the relationship between pressure and thin film displacement Sectional view showing an example of providing a stopper on the thin film side The figure which shows the example which provided the stopper in the both sides of the displacement direction of a thin film Sectional view showing an example of realizing the stopper function by the shape of the thin film Sectional drawing which shows the internal structure of the print head by other embodiment of this invention. Plane perspective view of the main part showing an example of the flow path configuration of the print head Schematic diagram showing another structural example of pressure detector

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device 12 ... Printing part, 12K, 12C, 12M, 12Y ... Print head, 14 ... Ink storage / loading part, 16 ... Recording paper, 22 ... Adsorption belt conveyance part, 50 ... Print head, 51 ... Nozzle , 52 ... Pressure chamber, 54 ... Supply passage restriction, 56 ... Nozzle passage, 64 ... Diaphragm, 66 ... Individual electrode, 68 ... Actuator, 70 ... Thin film, 71 ... Detection electrode, 72 ... Pressure detector, 73 ... Cavity , 92 ... System controller, 100 ... Print controller, 108 ... Ejection detection controller, 130, 140 ... Protrusion, 150, 152 ... Stopper member, 171 ... Groove, 173 ... Recess, 180 ... Ink supply path, 182 ... Basic Common channel, 184 ... Common channel tributary, 185 ... Individual supply channel, 190 ... Ink, 192 ... First cavity, 194 ... Fluid, 196 ... Small hole, 198 ... Second cavity Part

Claims (16)

A nozzle that ejects liquid droplets, a pressure chamber that communicates with the nozzle and is filled with a liquid that is ejected from the nozzle, a supply channel that communicates with the pressure chamber and supplies the liquid to the pressure chamber, and at least the pressure chamber A discharge detecting device for detecting a discharge state of a droplet discharge device, comprising: an actuator that deforms a part of the pressure chamber to change a pressure in a liquid in the pressure chamber and discharge a droplet from the nozzle;
A membrane member that is disposed in the pressure chamber and forms a part of the surface forming the pressure chamber and that is displaceable in accordance with a change in pressure of the liquid in the pressure chamber includes a detection signal corresponding to the displacement of the membrane member. Pressure detecting means for outputting;
A discharge state determination unit that determines a discharge state of the nozzle based on a detection signal obtained from the pressure detection unit in response to driving of the actuator;
A discharge detection device comprising:   The discharge detection apparatus according to claim 1, wherein the film member can be displaced by a displacement amount within a range in which droplets can be discharged by driving the actuator.   The discharge detection device according to claim 1, wherein the film member is configured to return to an initial state when liquid is filled in the pressure chamber after droplet discharge.   4. The discharge detection device according to claim 1, wherein the displacement amount of the film member is 1/2 or less in terms of a loss of pressure generated by the actuator for discharging a droplet. .   4. The discharge detection device according to claim 1, wherein the displacement volume of the membrane member is ½ or less of the excluded volume of the pressure chamber by the actuator.   A value obtained by adding the volume of the liquid returning from the pressure chamber to the supply flow path side when the droplet is discharged by driving the actuator and the displacement volume of the membrane member is 1 / of the excluded volume of the pressure chamber by the actuator. The discharge detection device according to claim 1, wherein the discharge detection device is 2 or less.   A value obtained by adding the volume of the liquid flowing from the pressure chamber to the nozzle side when the droplet is discharged by driving the actuator and the displacement volume of the membrane member is 1/2 of the displacement volume of the pressure chamber by the actuator. The discharge detection device according to claim 1, wherein the discharge detection device is the following. A nozzle that ejects liquid droplets, a pressure chamber that communicates with the nozzle and is filled with a liquid that is ejected from the nozzle, a supply channel that communicates with the pressure chamber and supplies the liquid to the pressure chamber, and at least the pressure chamber A discharge detecting device for detecting a discharge state of a droplet discharge device, comprising: an actuator that deforms a part of the pressure chamber to change a pressure in a liquid in the pressure chamber and discharge a droplet from the nozzle;
A membrane member which is disposed in the supply channel connected to the pressure chamber and forms a part of the surface forming the supply channel, and which is displaceable in accordance with a change in pressure of the liquid in the channel; Pressure detection means for outputting a detection signal corresponding to the displacement of
A discharge state determination unit that determines a discharge state of the nozzle based on a detection signal obtained from the pressure detection unit in response to driving of the actuator;
A discharge detection device comprising:   The discharge detection apparatus according to claim 8, wherein the film member is displaceable by a displacement amount within a range in which droplets can be discharged by driving the actuator.   10. The discharge detection apparatus according to claim 8, wherein the film member is configured to return to an initial state when the pressure chamber is filled with liquid after droplet discharge.   11. The discharge detection device according to claim 8, wherein the displacement amount of the film member is ½ or less in terms of a loss of pressure generated by the actuator for discharging a droplet.   11. The ejection detection device according to claim 8, wherein a displacement volume of the film member is equal to or less than ½ of an exclusion volume of the pressure chamber by the actuator.   The number of the pressure detection means is 1 or more and less than n on the liquid supply side of the flow path connected to n (where n is an integer of 2 or more) pressure chambers. 13. The discharge detection device according to any one of items 12 to 12.   The discharge detection device according to claim 8, wherein the supply channel has a shape in which a channel cross-sectional area decreases as it goes downstream.   The discharge detection device according to claim 1, wherein the pressure detection unit includes a displacement amount limiting unit that limits a displacement amount of the film member. A nozzle that ejects liquid droplets, a pressure chamber that communicates with the nozzle and is filled with a liquid that is ejected from the nozzle, a supply channel that communicates with the pressure chamber and supplies the liquid to the pressure chamber, and at least the pressure chamber A discharge detecting method for detecting a discharge state of a droplet discharge device comprising: an actuator that deforms a part of the pressure chamber to change a pressure in a liquid in the pressure chamber and discharge a droplet from the nozzle;
Displaceable in accordance with the pressure change of the liquid in the pressure chamber and the flow path so that at least one of the pressure chamber and the supply flow path forms part of the surface forming the pressure chamber or the supply flow path A suitable membrane member,
Obtain a detection signal according to the displacement of the membrane member,
A discharge detection method comprising: determining a discharge state of the nozzle based on the detection signal obtained according to driving of the actuator.

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