JP2006327185A - Inkjet recorder and inkjet recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder which can surely detect poor delivery of ink even in the act of printing operation. <P>SOLUTION: A recording head 43 has a body and an electrode 100 (100-103). The body is equipped with a nozzle plate 98. The electrodes 100-103 are arranged on a surface of the nozzle plate 98. A current sensor is connected to the electrodes 100-103 via connecting terminals 51-54, measuring a current value flown in each of the electrodes 100-103. Each of the electrodes 100-103 corresponds to a color of ink delivered. Each of the electrodes 100-103 is isolated by 1-5 μm from the rim of a nozzle hole 48. The nozzle plate has a water-repellent film 120 formed on the surface. The electrodes 100-103 connect a plurality of the nozzle holes 48 in series to each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus including an ink jet recording head for ejecting ink droplets, and more particularly to the structure of the ink jet recording head.

  2. Description of the Related Art Conventionally, there has been provided an ink jet recording apparatus that records an image on a recording medium by ejecting ink droplets onto the recording medium. The ink droplets are ejected from an ink jet recording head provided in the ink jet recording apparatus. The ink jet recording head includes a plurality of nozzles from which ink droplets are ejected and an actuator such as a piezoelectric element, a strain electric element, or a heating element. The ink droplets are ejected from the nozzles due to the local boiling of the ink due to the deflection of the actuator and heat. This ink jet recording head is mounted on a scanning carriage that reciprocates in a direction perpendicular to the transport direction of the recording medium. The recording medium is transported in the transport direction for each predetermined line feed width, and the scanning carriage is moved for each line feed. As the scanning carriage moves, the ink jet recording head ejects ink droplets from the nozzles at a predetermined timing. Thereby, an image is recorded on the recording medium.

  In an ink jet recording apparatus, it is important that ink droplets are reliably discharged from all nozzles. This is because if one of the plurality of nozzles is clogged with foreign matter or air bubbles are mixed, ink droplet ejection failure occurs and the image quality deteriorates. In order to prevent clogging of nozzles and mixing of air bubbles, generally, an ink jet recording head performs a suction operation (purge) or an idle discharge operation (flushing). However, these operations do not directly detect nozzle clogging or bubble contamination. Therefore, conventionally, an ink jet recording apparatus that can positively detect nozzle clogging has been proposed (see Patent Document 1 and Patent Document 2).

JP 2003-191463 A JP-A-3-202354

  In the conventional ink jet recording apparatus, since the clogging of the nozzle is detected, the ink jet recording head must be moved to a predetermined detection position (typically a position where purge or flushing is performed) different from the normal printing area. did not become. That is, nozzle clogging is not detected during printing or immediately before printing, so there is a possibility that printing operation may be performed with the nozzle clogged, and as a result, nozzle clogging is reliably detected. There was no way for the user to check the image after printing.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ink jet recording head that can reliably detect ink ejection failure due to nozzle clogging or air bubbles even during a printing operation, and an ink jet recording apparatus equipped with the ink jet recording head. It is.

  (1) In order to achieve the above object, an ink jet recording head according to the present invention includes a recording head body having a nozzle plate in which a plurality of nozzle holes are arranged, and the nozzle plate adjacent to each other across the nozzle holes. Electrode.

  In order for ink droplets to be ejected satisfactorily from the ink jet recording head, it is necessary for the meniscus to follow the deformation (vibration) of the piezoelectric element or the like provided in the ink jet recording head, and the meniscus is normally formed in the nozzle hole. is there. Here, the “normal meniscus” refers to a state in which the ink liquid surface is formed in a curved shape that is concave inward from the outlet periphery of the nozzle hole in a cross-sectional view, and the ink liquid surface is the outlet periphery of the nozzle hole. It is located in In a state where a normal meniscus is formed, when ink is ejected from the nozzle hole as an ink droplet, the ink exhibits the following behavior. That is, when the piezoelectric element or the like is deformed, the normal meniscus is temporarily withdrawn to the inner side of the nozzle hole, and then the ink is transferred to the nozzle hole as the deformation of the piezoelectric element or the like is restored. It is pushed out as if bounced from.

  If air or the like has already entered the nozzle hole before ink droplets are ejected, the meniscus will escape to the inner part of the nozzle hole, and this ink will jump out of the nozzle hole. I can't. Also, if bubbles already exist in the flow channel upstream of the nozzle holes before the ink droplets are ejected, these bubbles can be used as a kind of cushioning material even if the piezoelectric element is deformed. It will work. That is, even if the meniscus is normally formed before the ink droplet is discharged, the pressure change of the ink due to the deformation of the piezoelectric element or the like deforms the bubble, and the ink in the nozzle hole jumps out of the nozzle hole. It is not possible. However, when a normal meniscus follows the deformation (vibration) of the piezoelectric element or the like, the ink temporarily retreats in the nozzle hole along with the deformation of the piezoelectric element, and then becomes a columnar shape. Projecting to the outside, a part of the columnar ink is detached and ejected as ink droplets.

  On the other hand, the column of ink after the ink droplet is detached is retreated to the nozzle hole side again. However, at that time, the end portion of the ink column expands in the radial direction by the reaction of the ink droplet detachment, and adheres around the periphery of the opening of the nozzle hole. However, since the inside of the nozzle hole is always under negative pressure (below atmospheric pressure), the ink column is retracted so as to be pulled into the nozzle hole. Accordingly, the ink attached around the periphery of the opening of the nozzle hole so as to be dragged by this is also retracted into the nozzle hole. The ink withdrawn in the nozzle hole again forms the normal meniscus.

  In the present invention, since the electrode is disposed adjacent to the nozzle hole, as described above, when a part of the ink adheres to the periphery of the opening of the nozzle hole after the ink droplet has ejected from the nozzle hole. The ink functions as a conductive material. Therefore, when a voltage is applied between the electrodes, a current flows between the electrodes due to adhesion of the ink. Therefore, if this amount of current is monitored, it can be determined whether or not the electrodes are in a conductive state, and based on this, it can be detected that ink droplets have been reliably ejected from the nozzle holes.

  (2) The electrode is preferably disposed on the surface of the nozzle plate. As described above, when the ink droplet is ejected from the nozzle hole, a part of the ink adheres around the periphery of the nozzle hole. Therefore, by arranging the electrode on the surface of the nozzle plate, the ink attached to the periphery of the opening of the nozzle hole functions reliably as a conductive material. It is definitely determined that

  The electrode is preferably separated from the peripheral edge of the nozzle hole by approximately 1 μm to 5 μm. As described above, when an ink droplet is ejected from a nozzle hole, a part of the ink adheres around the periphery of the opening of the nozzle hole. At this time, the ink is usually about 10 μm from the diameter of the nozzle hole. Expands into a large diameter circle. Therefore, since the ink adhered to the peripheral edge of the nozzle hole functions more reliably as a conductive material, it is more reliably determined that the electrodes are in a conductive state by monitoring the current amount.

  The nozzle plate preferably has a water repellent layer on the surface. By providing this water-repellent layer, the ink that has once spread on the surface of the nozzle plate can be quickly withdrawn into the nozzle hole, and the normal meniscus can be quickly re-formed.

  The electrode is preferably arranged so as to connect the plurality of nozzle holes in series. As a result, when ink is ejected from each nozzle hole, if ink does not become conductive between any one of the plurality of nozzle holes, the ink is ejected onto the surface of the nozzle plate after ink droplets are ejected. It can be detected that there is no adhesion. That is, it is detected that no ink droplet has been ejected from the nozzle hole.

  In particular, the plurality of nozzle holes are preferably arranged for each color of ink to be ejected. Thus, it is detected for each color that no ink droplet has been ejected from the nozzle hole. As described above, there are various reasons why ink droplets did not fly out of the nozzle holes, such as clogging of foreign matter or bubbles in the nozzles.As measures to solve this, suction or empty discharge is performed. Is done. In that case, it is not necessary to perform suction or empty ejection for all colors, and it is only necessary to take such a measure for the nozzle holes of the color from which ink droplets have not been ejected. Absent.

  (3) Further, it is preferable that the electrode is embedded in the nozzle plate in a state where it is exposed to the inner peripheral surface of the nozzle hole at a position that contacts only the meniscus formed normally in the nozzle hole. . As described above, in order for the ink droplet to jump out of the nozzle hole, the meniscus must be formed so as to be positioned at the opening periphery of the nozzle hole. That is, the normal meniscus must be formed.

  In the present invention, since the electrode contacts only the normally formed meniscus, if the normal meniscus is formed before the ink droplets are ejected from the nozzle holes, the electrodes are in a conductive state. That is, if an abnormal meniscus is formed due to the presence of bubbles or the like before the ink droplet jumps out of the nozzle hole, the electrodes are insulated.

  As described above, when the piezoelectric element or the like is deformed, the normal meniscus temporarily retracts further to the inner back side of the nozzle hole. Therefore, at this time, between the electrodes changes from a conductive state to an insulating state. Further, when the deformation of the piezoelectric element or the like is restored, the ink in the nozzle hole jumps out of the nozzle hole so as to be repelled. Accordingly, at this time, the electrodes change from the insulated state to the conductive state again. Further, after the ink droplets are ejected, the ink returns again into the nozzle holes and the normal meniscus is formed, so that this conduction state is maintained. Since the determination means determines that the conductive state is established based on the current flowing between the electrodes, the electrodes instantaneously change from the conductive state to the insulated state before and after the ejection of the ink droplet, and the conductive state is again established. It can be determined that the state has changed. That is, a meniscus capable of ejecting ink droplets is formed in the nozzle holes before and after ink droplet ejection, in other words, normal meniscus is ejected in the nozzle holes before and after ink droplet ejection. It can be detected that the droplet can be ejected (normal behavior).

  The nozzle plate has a water repellent layer provided on the surface and an insulating layer laminated on the water repellent layer, and the electrode is sandwiched between the insulating layer and the water repellent layer. Is preferred. In this case, if the normal meniscus is formed, the electrodes are reliably connected. Further, the ink is not conducted between the electrodes by the ink existing in the flow path upstream of the nozzle holes. Therefore, the malfunction of the determination means is surely prevented.

  The electrodes are preferably arranged so as to connect the plurality of nozzle holes in parallel. As a result, when the ink is pushed out from each nozzle hole, the normal meniscus can eject ink droplets if the electrodes are not insulated in any one of the plurality of nozzle holes. Can be determined not to indicate. That is, it is detected that ink droplets are not ready to eject from the nozzle holes.

  In particular, the plurality of nozzle holes are preferably arranged for each color of ink to be ejected. As a result, it is detected for each color that the normal meniscus does not exhibit a behavior capable of ejecting ink droplets. As described above, there are various reasons why a normal meniscus is not formed. As measures for solving this, suction or idle discharge is performed. In that case, it is not necessary to perform suction or empty ejection for all colors, and it is only necessary to take such a measure for the nozzle holes of the color from which ink droplets have not been ejected. Absent.

  (3) Further, a predetermined voltage is applied between the inkjet recording head and the electrodes, and a current detection unit that detects a current flowing between the electrodes, and a gap between the electrodes based on a detection result of the current detection unit. An ink jet recording apparatus may be configured that includes a determination unit that determines whether or not a conductive state is established. In this ink jet recording apparatus, it can be reliably detected whether or not the ink has been satisfactorily ejected from the ink jet recording head.

  According to the present invention, when printing, it is detected that ink droplets are reliably ejected or that ink droplets are reliably ejected before ink droplet ejection. When a droplet ejection failure occurs or when there is a high probability that an ink droplet ejection failure will occur, it is during printing (typically during a flushing operation at a line feed or during a flushing operation immediately before printing). This is reliably detected. In addition, in an ink jet recording apparatus, even during printing, clogging of an ink jet recording head and retention of bubbles are prevented by regular flushing or purging. Therefore, when a discharge failure or the like of the ink droplet is detected, the discharge failure can be corrected during periodic flushing or the like.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  <First Embodiment>

  FIG. 1 is an external perspective view of a multifunction machine 10 (inkjet recording apparatus) according to the first embodiment of the present invention.

  The multi-function device 10 is a multi-function device (MFD) having a printer unit 11 at the bottom and a scanner unit 12 at the top, and has a printer function, a scanner function, and a copy function. The printer unit 11 of the multifunction machine 10 corresponds to the ink jet recording apparatus according to the present invention. Functions other than the printer function may be omitted. Therefore, the present invention can be applied to a single-function printer that does not have the scanner unit 12 and does not have a scanner function or a copy function, and can also be applied to a printer that has a facsimile function including a communication unit.

  When the present invention is implemented as an inkjet recording apparatus that is a multifunction peripheral, the apparatus may be configured as a small apparatus such as the multifunction peripheral 10 according to the present embodiment, or may include a plurality of paper feed cassettes and automatic document feeders ( You may comprise as a large sized apparatus provided with ADF (Auto Document Feeder). However, the present invention is not only applied to the ink jet recording apparatus, but can be applied to general image recording apparatuses including a recording head that performs an image recording operation on a recording medium (typically, recording paper). The multifunction device 10 may be configured to be connected to a computer (not shown) and record an image or document on a recording sheet based on image data or document data transmitted from the computer. . Further, the multifunction machine 10 is connected to a digital camera, and records image data output from the digital camera on a recording sheet or loaded with various storage media, thereby storing the image data stored in the storage medium. Or the like may be recorded on a recording sheet.

  As shown in FIG. 1, the multifunction machine 10 has a generally wide and thin rectangular parallelepiped shape, and the width and depth dimensions of the multifunction machine 10 are set larger than the height. A printer unit 11 is provided in the lower part of the multifunction machine 10. The printer unit 11 has an opening 13 on the front. The paper feed tray 14 and the paper discharge tray 15 are provided in two upper and lower stages so as to be exposed to the opening 13. The paper feed tray 14 is for storing recording paper, and can accommodate recording papers of various sizes such as B5 size, postcard size and the like of A4 size or less. The paper feed tray 14 includes a slide tray 16. When the slide tray 16 is pulled out as necessary, the tray surface is enlarged. The recording paper stored in the paper feed tray 14 is fed into the printer unit 11 to record a predetermined image and is discharged to the paper discharge tray 15.

  A scanner unit 12 is provided in the upper part of the multifunction machine 10. The scanner unit 12 is configured as a so-called flat bed scanner. The multifunction machine 10 includes a document cover 17. The document cover 17 is provided so as to be openable and closable with respect to the multifunction device 10, and is configured as a top plate of the multifunction device 10. A platen glass and an image reading carriage (not shown) are provided below the document cover 17. The platen glass is for placing a document. The image reading carriage is provided below the platen glass and is slidable in the width direction of the multifunction machine 10. The image reading carriage scans the document by sliding in the width direction of the multifunction machine 10.

  An operation panel 18 is provided on the front upper portion of the multifunction machine 10. The operation panel 18 is a device for operating the printer unit 11 and the scanner unit 12. The operation panel 18 includes various operation buttons and a liquid crystal display unit. The multi-function device 10 operates according to an operation instruction from the operation panel 18 or according to an instruction transmitted from a computer via a printer driver. In addition, a slot portion 19 is provided in the upper left part of the front surface of the multifunction machine 10. Various small memory cards, which are storage media, are loaded in the slot 19. The image data stored in the small memory card is displayed on the liquid crystal display unit. Then, by operating the operation panel 18, an arbitrary image stored in the small memory card is recorded on the recording paper by the printer unit 11.

  FIG. 2 is a schematic diagram illustrating the structure of the printer unit 11 of the multifunction machine 10. In the figure, the direction perpendicular to the paper surface is the width direction of the multifunction machine 10 and the main scanning direction of the recording head 43 described later.

  A paper feed tray 14 is provided at the bottom of the multifunction machine 10. On the back side (right side in the figure) of the paper feed tray 14, a separation inclined plate 21 is provided for separating and guiding the recording paper loaded on the paper feed tray 14 upward. A conveying path 22 is formed upward from the separation inclined plate 21. The conveyance path 22 extends upward, then curves to the left, and extends from the back side to the front side of the multifunction machine 10 (from the right side to the left side in the drawing). Further, the transport path 22 passes through the image recording unit 23 and leads to the paper discharge tray 15. Accordingly, the recording paper stored in the paper feed tray 14 is guided by the conveyance path 22 so as to make a U-turn from the lower side to the upper side, and reaches the image recording unit 23. After the image recording unit 23 records an image on the recording paper, the recording paper is discharged to the paper discharge tray 15. The direction along the conveyance path 22 is the conveyance direction of the recording paper. The transport direction and the main scanning direction are orthogonal to each other.

  A paper feed roller 25 is provided above the paper feed tray 14. The paper feed roller 25 separates the recording paper stacked on the paper feed tray 14 one by one and supplies it to the conveyance path 22. The structure of the paper feed roller 25 is known. For example, the paper feed roller 25 is pivotally supported at the tip of a paper feed arm 26 that moves up and down so as to come into contact with and separate from the paper feed tray 14. The paper feed roller 25 is connected to a motor via a drive transmission mechanism. The drive transmission mechanism can be configured by meshing a plurality of gears. When the motor operates, the driving force is transmitted to the paper feed roller 25, so that the paper feed roller 25 rotates.

  The paper feed arm 26 is provided so as to be rotatable around a base end shaft 27. As a result, the paper feed arm 26 can swing up and down about the base end shaft 27 as a swing center. In the standby state, the paper feed arm 26 is flipped up by a paper feed clutch or a spring (not shown), and swings downward when supplying the recording paper. As the paper feed arm 26 swings downward, the paper feed roller 25 pivotally supported at the tip thereof presses against the surface of the recording paper on the paper feed tray 14. In this state, the paper feed roller 25 rotates. The frictional force generated between the roller surface of the paper feed roller 25 and the recording paper feeds the uppermost recording paper to the separation inclined plate 21. The leading edge of the recording sheet comes into contact with the separation inclined plate 21 and is guided upward, and is fed into the conveyance path 22. Note that when the uppermost recording sheet is sent out by the paper feed roller 25, the recording sheet immediately below the recording sheet may be sent out together due to friction or static electricity. However, the recording sheet is stopped by contacting the separating inclined plate 21.

  The conveyance path 22 is defined by an outer guide surface and an inner guide surface that are opposed to each other at a predetermined interval, except for a place where the image recording unit 23 and the like are disposed. In this multifunction device 10, the outer guide surface is configured by the inner wall surface of the frame of the multifunction device 10, and the inner guide surface is configured by the surface of the guide member provided in the frame of the multifunction device 10. In particular, a conveyance roller may be provided at a location where the conveyance path 22 is bent. Although the conveyance roller is not shown in the figure, the conveyance roller may be provided so as to be rotatable with the width direction of the conveyance path 22 (direction perpendicular to the paper surface in the figure) as the rotation center axis direction. The transport roller is attached such that the roller surface is exposed to the outer guide surface or the inner guide surface. By providing the transport roller, the recording paper is smoothly transported in contact with the guide surface even at a portion where the transport path 22 is bent.

  As described above, the image recording unit 23 is provided on the downstream side after the conveyance path 22 makes a U-turn from below to above. FIG. 3 is a perspective view schematically illustrating the configuration of the image recording unit 23, and FIG. 4 is a block diagram schematically illustrating the configuration of the image recording unit 23.

  As shown in FIGS. 2 and 3, a driving roller 60 and a pressing roller 61 are provided on the upstream side of the image recording unit 23. The driving roller 60 and the pressing roller 61 sandwich the recording sheet 47 conveyed through the conveyance path 22 and send it onto the platen 41. On the other hand, a paper discharge roller 62 and a pressing roller 63 are provided on the downstream side of the image recording unit 23. The paper discharge roller 62 and the pressing roller 63 nipped and transport the recorded recording paper 47. The drive roller 60 is rotationally driven by a motor 64, and the paper discharge roller 62 is also rotationally driven by a similar motor. As a result, the recording paper 47 is intermittently sent with a predetermined line feed width.

  The pressing roller 61 is elastically biased against the driving roller 60 so as to press the driving roller 60 with a predetermined pressing force. Therefore, when the recording paper 47 enters between the driving roller 60 and the pressing roller 61, the pressing roller 61 records in cooperation with the driving roller 60 while elastically retracting by the thickness of the recording paper 47. The paper 47 is pinched. For this reason, the rotational force of the driving roller 60 is reliably transmitted to the recording paper 47. The pressing roller 63 is similarly provided with respect to the paper discharge roller 62. However, since the pressing roller 63 is in pressure contact with the recorded recording paper 47, the roller surface is preferably formed in a spur shape so as not to deteriorate the image recorded on the recording paper 47.

  By controlling the rotation of the motor 64, the recording paper 47 held between the driving roller 60 and the pressing roller 61 is intermittently conveyed on the platen 41 with a predetermined line feed width. A recording head 43 (ink jet recording head), which will be described later, is slid in the main scanning direction for each line feed of the recording paper 47 and records an image from the leading end side of the recording paper 47. The recording sheet 47 on which image recording has been performed is held between the discharge roller 62 and the pressing roller 63 from the leading end side. In other words, the recording sheet 47 is intermittently conveyed with a predetermined line feed width with the leading end side sandwiched between the paper discharge roller 62 and the pressing roller 63 and the trailing end side sandwiched between the driving roller 60 and the pressing roller 61. The recording head 43 records an image on the recording paper 47. Further, when the recording paper 47 is conveyed, the rear end of the recording paper 47 passes through the driving roller 60 and the pressing roller 61. As a result, the recording paper 47 is released from the driving roller 60 and the pressing roller 61 and is intermittently conveyed by the paper discharge roller 62 and the pressing roller 63 with a predetermined line feed width. Also in this case, the recording head 43 records an image on the recording paper 47. After the image is recorded in a predetermined area of the recording paper 47, the paper discharge roller 62 is continuously driven to rotate, and the recording paper 47 held between the paper discharge roller 62 and the pressing roller 63 is transferred to the paper discharge tray 15. Discharged.

  As shown in FIG. 2 to FIG. 4, the image recording unit 23 includes a head unit 28, a platen 41 disposed to face the head unit 28, cartridge-type ink tanks 37 to 40 in which ink is stored in advance, And a pump 130 (see FIG. 10) for supplying ink from the ink tanks 37 to 40 to the head unit 28 side. The pump 130 will be described later. In addition, the multifunction device 10 includes a control device 69 (see FIG. 9) that controls the operations of the printer unit 11, the scanner unit 12, and other components of the multifunction device 10 independently of the printer unit 11 and the scanner unit 12. I have. The configuration of the control device 69 will also be described in detail later.

  The ink tanks 37 to 40 do not have to be cartridge types, and may be anything that can store ink. In this embodiment, four ink tanks 37 to 40 are provided, and inks of four colors (black (Bk), magenta (M), cyan (C), and yellow (Y)) are stored in advance. The image recording unit 23 records an image on a recording sheet 47 conveyed on the platen 41. That is, the head unit 28 is slid in the main scanning direction while ejecting each color ink of black (Bk), magenta (M), cyan (C), and yellow (Y) supplied from the ink tanks 37 to 40. As a result, an image is recorded on the recording paper 47.

  The ink tanks 37 to 40 are connected to connecting pipes 94 to 97 made of flexible tubes, respectively. As will be described later, the head portion 28 is slid in the left-right direction in FIG. The connecting pipes 94 to 97 are flexible and set to a sufficient length. Therefore, the connecting pipes 94 to 97 can be deformed so as to smoothly follow the slide of the head portion 28.

  As shown in FIG. 3, the head unit 28 includes the recording head 43, a scanning carriage 42, and sub tanks 29, 32, 34, and 36. Each sub tank 29, 32, 34, 36 is held by this scanning carriage 42. Each sub tank 29, 32, 34, 36 is for temporarily storing ink supplied from the tank tanks 37-40. The recording head 43 is also held by the scanning carriage 42. The recording head 43 is disposed so as to be exposed on the lower surface of the scanning carriage 42. The ink temporarily stored in the sub tanks 29, 32, 34, 36 is supplied to the recording head 43 and is ejected as ink droplets from the recording head 43. The scanning carriage 42 is supported by a guide shaft 44 and can slide along the guide shaft 44. An endless belt 45 is attached to the scanning carriage 42. A belt drive motor 46 is connected to the endless belt 45 via a pulley, and when the belt drive motor 46 operates, the head portion 28 slides in the main scanning direction.

  Although not shown in the figure, a position sensor (typically, an encoder 67 (see FIG. 9)) is provided on the frame of the multifunction machine 10. The encoder 67 detects the position of the scanning carriage 42 on the platen 41 and transmits the position data (voltage value) to the control device 69. As will be described later, the CPU 121 (see FIG. 9) of the control device 69 calculates the position of the scanning carriage 42 on the platen 41 based on the position data. Therefore, when the scanning carriage 42 slides, the relative position of the recording head 43 with respect to the recording paper 47 is grasped by the control device 69.

  FIG. 5 is an enlarged bottom view of the recording head 43. FIG. 6 is an enlarged cross-sectional view of the recording head 43. These drawings schematically show the structure of the recording head 43 in detail. 7 is an enlarged cross-sectional view of a main part in FIG. 6, and FIG. 8 is an enlarged view of the main part in FIG.

  As shown in FIGS. 5 and 6, the recording head 43 includes a main body 99 (recording head main body) including a nozzle plate 98 and electrodes 100 to 103 provided on the nozzle plate 98. A current sensor 68 (current detection means) for measuring a current value flowing through each of the electrodes 100 to 103 is provided in the multifunction machine 10, and includes a plurality of connection terminals 51 to 58 on the scanning carriage 42, and a connection terminal 51. Are connected to the respective electrodes 100 to 103 via .about.58. As this current sensor 68, a known one can be adopted. For example, the current sensor 68 has a built-in power source for applying a predetermined voltage to the electrodes 100 to 103 and detects a current flowing through the electrodes 100 to 103. Based on the current value detected by the current sensor 68, it is determined whether or not the electrodes 100 to 103 are in a conductive state. In the present embodiment, the control device 69 functions as a determination unit that determines whether or not the electrodes 100 to 103 are in a conductive state.

  The main body 99 includes a manifold 104, a cavity 105, and a descender 106 in addition to the nozzle plate 98. The nozzle plate 98 is provided with a plurality of nozzle holes 48. The manifold 104, the cavity 105, and the descender 106 are integrally formed as an ink flow path. The descender 106 and the cavity 105 are provided for each nozzle hole 48. The manifold 104 distributes the ink guided from the sub tanks 29, 32, 34, 36 to the nozzle holes 48. The manifold 104 is connected to the sub tanks 29, 32, 34, and 36. A plurality of cavities 105 corresponding to the nozzle holes 48 are provided on the downstream side of the manifold 104. Each cavity 105 can be easily elastically deformed, and a piezoelectric element 118 as a piezoelectric element is provided on the upper surface thereof. As the piezoelectric element 118 is deformed, the cavity 105 is deformed, and the ink in the cavity 105 is sent to the descender 106 side. The descender 106 is attached to the nozzle plate 98. The ink sent from the cavity 105 is pushed out through the nozzle hole 48. The ink is temporarily stored in the sub tanks 29, 32, 34, and 36, thereby removing bubbles generated in the ink and preventing the bubbles from entering from the manifold 104 to the downstream side.

  As shown in FIG. 5, in the present embodiment, a plurality of nozzle holes 48 are arranged. In addition, a plurality of nozzle holes 48 are arranged in four rows in the vertical direction for each ink color. In the figure, the “vertical direction” is the conveyance direction of the recording paper 47. In the drawing, the nozzle hole 48 positioned at the right end corresponds to black ink (Bk), and black ink (Bk ink) is ejected from the nozzle hole 48. Three rows of nozzle holes 48 are provided in order so as to be adjacent to the nozzle holes 48 for Bk ink. The nozzle holes 48 in each row correspond to yellow ink (Y ink), magenta ink (M ink), and cyan ink (C ink), respectively, and from each nozzle hole 48, Y ink, M ink, and C ink. Each ink is ejected. That is, the recording head 43 can eject four colors of ink. For simplification of description, only one row of the plurality of nozzle holes 48 arranged in the vertical direction is shown in FIG. However, actually, the plurality of nozzle holes 48 arranged in the vertical direction are arranged in four rows in the left-right direction in the drawing.

  As shown in FIG. 5, the scanning carriage 42 includes a media sensor 115. The media sensor 115 is for detecting the presence of the recording paper 47 conveyed along the conveyance path 22 and the end position thereof. The media sensor 115 includes a light source 116 and a light receiving element 117. The light source 116 can emit light downward. The light emitted from the light source 116 is applied to the surface of the recording paper 47 conveyed to the head unit 28 side. When the recording sheet 47 is not conveyed up to the platen 41, the light is applied to the platen 41. The light applied to the recording paper 47 or the platen 41 is reflected. The light receiving element 117 receives the reflected light and outputs it according to the amount of light received. This output value is represented by a so-called AD value (voltage value). As described above, when the scanning carriage 42 is slid, the media sensor 115 scans the platen 41. Then, according to the change in the AD value, the presence of the recording paper 47 on the platen 41 and the position of the end thereof are detected.

  Each of the sub tanks 29, 32, 34, and 36 corresponding to the respective color inks (Bk, Y, M, and C) (see FIG. 3) has a fitting portion (not shown). One end of each of the connecting pipes 94 to 97 is connected to the fitting portion. The other ends of the connecting pipes 94 to 97 are connected to ink tanks 37 to 40, respectively, as shown in FIG. A connection part 66 to which the other ends of the connection pipes 94 to 97 are connected is provided below the ink tanks 37 to 40, and the other ends of the connection pipes 94 to 97 are connected to the connection parts 66. Has been. That is, the ink tank 37 and the sub tank 29 are connected by the connecting pipe 94, the ink tank 38 and the sub tank 32 are connected by the connecting pipe 95, the ink tank 39 and the sub tank 34 are connected by the connecting pipe 96, and the ink tank 40 is connected. And the sub tank 36 are connected by a connecting pipe 97. The ink tanks 37 to 40 are held by the holder 65. As described above, the ink tanks 37 to 40 store Bk ink, M ink, C ink, and Y ink, respectively. When the above-described pump 130 (see FIG. 10) is operated, Y ink is drawn from the ink tank 40 and sent to the sub tank 36 via the connection pipe 97. Similarly, C ink is supplied from the ink tank 39 to the sub tank 34, M ink is supplied from the ink tank 38 to the sub tank 32, and Bk ink is supplied from the ink tank 37 to the sub tank 29. As described above, each ink temporarily stored in each sub-tank 29, 32, 34, 36 flows to the manifold 104, the cavity 105, and the descender 106, and each ink is transferred to the nozzle hole 48 by deformation of the piezoelectric element 118. Are ejected as ink droplets.

  As shown in FIG. 7, the nozzle plate 98 is formed in a plate shape and has a two-layer structure. That is, the nozzle plate 98 includes an insulating material 119 disposed on the descender 106 side, and a water repellent film 120 (water repellent layer) disposed outside the insulating material 119 (insulating layer). The insulating material 119 is made of, for example, polyimide, and the water repellent film 120 is made of, for example, fluorine resin. 7 and 8, the electrode 100 is disposed on the surface of the nozzle plate 98, that is, outside the water-repellent film 120. Further, the electrode 100 is disposed adjacent to the nozzle hole 48.

  As shown in FIG. 8, the electrode 100 is separated from the peripheral edge of the nozzle hole 48 by a predetermined distance d. The predetermined distance d is set to 1 μm to 5 μm. However, the predetermined distance d is not limited to 1 μm to 5 μm, and may be set in a range of approximately 1 μm to 5 μm. Moreover, as FIG. 5 shows, the electrode 100 is arrange | positioned so that each nozzle hole 48 may be connected in series. The electrode 100 is disposed corresponding to the nozzle hole 48 from which Bk ink is ejected. However, the electrodes 101 to 103 are respectively ejected from the nozzle hole 48 from which Y ink is ejected and M ink. The nozzle holes 48 and the nozzle holes 48 from which the C ink is ejected are arranged, and like the electrodes 100, the nozzle holes 48 are arranged to be connected in series.

  FIG. 9 is a block diagram illustrating a configuration of a control device of the multifunction machine 10.

  As shown in the figure, the control device 69 includes a central processing unit 70. The central processing unit 70 includes a CPU (Central Processing Unit) 121, a ROM (Read Only Memory) 122, and a RAM (Random Access Memory) 123. The central processing unit 70 includes a printer unit 11 including various sensors (the media sensor 115, the electrodes 100 to 103, and the like), a scanner unit 12, and an operation panel via a bus 71 and an application specific integrated circuit (ASIC) 72. 18 etc. so that data can be transmitted and received. As described above, the control device 69 functions as the determination means together with the electrodes 100 to 103.

  The ROM 122 stores a computer program and the like for controlling various operations of the multifunction machine 10. The RAM 123 is used as a storage area or a work area for temporarily storing various data necessary for the CPU 121 to execute the program. The CPU 121 performs a predetermined calculation based on the information of the current sensor 68 in accordance with the computer program. Thereby, the conduction state between the electrodes 100 to 103 based on the current value detected by the current sensor 68 is determined. Further, the presence of the recording sheet 47 on the platen 41 is determined based on the information (AD value) transmitted from the media sensor 115. Further, the CPU 121 performs various calculations based on information of other various sensors. The ASIC 72 drives the motor 64 (LF motor), the belt drive motor 46 (CR motor), the pump 130 for drawing ink from the ink tanks 37 to 40, the head unit 28, and the like according to a command from the CPU 121. Thus, the operations of the printer unit 11 and the scanner unit 12 are comprehensively controlled.

  The multifunction machine 10 is connected to, for example, a personal computer (PC) 73 in addition to input from the operation panel 18, and records images and documents on the recording paper 47 based on image data and document data transmitted from the computer 73. You can also For this purpose, an interface (I / F) 78 for transmitting / receiving data to / from the personal computer 73 is also provided. It should be noted that the configuration of the control device 69 shown in the present embodiment is an example, and therefore other configurations may be adopted as long as the control device performs control described later.

  FIG. 10 schematically shows an ink supply path through which ink is sent from the ink tanks 37 to 40 to the recording head 43 via the sub-tanks 29, 32, 34, and 36 and the operating position of the recording head 43.

  The ink supplied from the ink tanks 37 to 40 is stored in the sub tanks 29, 32, 34, and 36 as described above, and air bubbles in the ink are captured. Further, as described above, this ink is ejected from the manifold 104 (see FIG. 6) as an ink droplet from the nozzle hole 48 via the cavity 105 and the descender 106. In this way, the image is recorded on the recording paper 47 conveyed under the recording head 43 by sliding the image recording range W1 while the recording head 43 ejects ink droplets.

  As shown in the drawing, a purge mechanism 74 and a waste ink tray 75 are disposed outside the image recording range W1 of the recording head 43 and at both ends of the scannable range W2. In the present embodiment, the purge mechanism 74 includes the pump 130. When the pump 130 is operated, bubbles and foreign matters are sucked and removed from the nozzle holes 48 of the recording head 43. When the recording head 43 slides to the right end (purge position) of the scannable range W2, the cap 76 of the purge mechanism 74 moves upward, and the cap 76 is in close contact with the lower surface of the recording head 43 so as to cover the nozzle hole 48. To do.

  Inside the cap 76, a black ink cap 131 that covers the nozzle holes 48 from which the Bk ink is discharged of the recording head 43, and a color ink cap 132 that covers the nozzle holes 48 from which the C ink, M ink, and Y ink are discharged. And are provided. Therefore, in a state where the cap 76 is in close contact with the lower surface of the recording head 43, the black ink cap 131 covers the nozzle hole 48 from which the Bk ink is discharged, and the color ink cap 132 includes the C, M, and Y inks. The nozzle hole 48 from which the water is discharged is covered. The pump 130 is selectively connected to the black ink cap 131 or the color ink cap 132. Therefore, the nozzle holes 48 from which Bk ink is ejected and the nozzle holes 48 from which C, M, and Y ink are ejected can be purged separately. However, the pump 130 can be connected to both the black ink cap 131 and the color ink cap 132 simultaneously.

  Further, when the pump 130 is operated, ink is sucked from the nozzle holes 48 of the recording head 43, Bk ink is drawn into the sub tank 29 from the ink tank 37 (Bk ink), and the ink tanks 38 to 40 are used. M ink, C ink, and Y ink are drawn into the sub tanks 32, 34, and 36, respectively. Furthermore, by operating the pump 130, foreign matters clogged in the nozzle holes 48, bubbles existing in the flow path upstream of the nozzle holes 48, and the like can be removed by suction. At this time, if the pump 130 is selectively connected to the black ink cap 131 or the color ink cap 132, the nozzle hole 48 corresponding to the Bk ink or the nozzle corresponding to the C, M, and Y inks. For the holes 48, the foreign substances and bubbles are removed separately. The control device 69 controls the belt drive motor 46 for sliding the recording head 43, the movement control of the cap 76, and the drive control of the pump 130.

  In the multifunction machine 10 according to this embodiment, the ink tanks 37 to 40 communicate with the outside, and the pressure in the ink tanks 37 to 40 is equal to the atmospheric pressure. The recording head 43 is disposed above the ink tanks 37 to 40. Therefore, a back pressure (negative pressure) is constantly acting in the sub tanks 29, 32, 34, 36, and this back pressure contributes to the formation of the meniscus in the nozzle hole 48. When the recording head 43 ejects ink droplets, the ink in the ink tanks 37 to 40 is continuously supplied to the recording head 43 via the connection pipes 94 to 97 (see FIGS. 3 and 4).

  The waste ink tray 75 is for receiving the idle ejection of ink from the recording head 43. Such idle ejection of ink is generally called flushing. At the time of flushing, the recording head 43 is moved to the left end (flushing position) of the scannable range W2, and each color ink is ejected toward the waste ink tray 75 at that position. By performing such idle discharge, foreign matter clogged in each nozzle hole 48, bubbles existing in the flow path on the upstream side of each nozzle hole 48, and the like can be removed by suction. The arrangement of the purge mechanism 74 and the waste ink tray 75 on the left and right is not particularly limited, and the purge mechanism 74 and the waste ink tray 75 may be arranged in the scannable range W2 opposite to the above or on the left or right. Good.

  In the present embodiment, when the scanning carriage 42 is disposed at the flushing position (left end in FIG. 10), the encoder 67 is set to an initial value (origin). However, the encoder 67 may be set to the origin when the scanning carriage 42 is disposed at the purge position (the right end in FIG. 10). In short, when the scanning carriage 42 is at the purge position or the flushing position, the reference position of the scanning carriage 42 is set. The holder 65 (see FIG. 3) holding the ink tanks 37 to 40 can be installed at the right end of the scannable range W2, for example. Of course, the holder 65 may be disposed at the left end of the scannable range W2 or in the dead space of the frame of the multifunction machine 10.

  11 and 12 are enlarged cross-sectional views of the main part of the recording head 43. FIG. FIG. 11 shows a state where the ink forms a normal meniscus in the nozzle hole 48 before the ink droplet is ejected from the recording head 43. FIG. 12 illustrates a state at the moment when ink droplets are ejected from the head unit 43. 13 is a view taken in the direction of arrows XIII-XIII in FIG.

  In order for ink droplets to be ejected from the recording head 43 when the image is recorded, a meniscus is normally formed in the nozzle hole 48 and the piezoelectric element 118 provided in the recording head 43 is deformed. The meniscus must follow (vibration). Here, the “normal meniscus” refers to a state in which the ink liquid surface 124 (meniscus) is formed in a curved shape that is concave inward from the outlet peripheral edge 125 of the nozzle hole 48, as shown in FIG. This means that the edge portion of the ink liquid surface 124 is located at the outlet peripheral edge 125 of the nozzle hole 48. In a state where the normal meniscus 124 is formed, when ink is ejected from the nozzle hole 48 as an ink droplet, the ink exhibits the following behavior. That is, when the piezo element 118 is deformed, the normal meniscus 124 is temporarily retracted further inside the nozzle hole 48 as indicated by a two-dot chain line in FIG. As the deformation is restored, the ink is pushed out from the nozzle holes 48 so as to be repelled.

  If air or the like has already entered the nozzle hole 48 before ink droplets are ejected, the ink liquid level (meniscus) is retracted to the inner part of the nozzle hole 48. In this way, if the meniscus has already retracted to the inside of the nozzle hole 48 before the ink droplet is ejected, the ink cannot jump out from the nozzle hole 48 as an ink droplet. If air bubbles exist in the flow channel upstream of the nozzle holes 48 before the ink droplets are ejected, the air bubbles are a kind of buffer when the piezoelectric element 118 is deformed. Functions as a material. Specifically, the ink pressure fluctuates with the deformation of the piezo element 118, and the ink level (meniscus) is temporarily retracted in the nozzle hole 48. However, due to the presence of the bubbles, the pressure fluctuation of the ink only deforms the bubbles, and the meniscus cannot be retracted inside the nozzle hole 48. Therefore, even if a normal meniscus 124 is formed before the ink droplet is ejected, this ink cannot be ejected from the nozzle hole 48 as an ink droplet if the bubbles are present.

  However, when the normal meniscus 124 is formed in the nozzle hole 48 before the ink droplet is discharged and the meniscus 124 follows the deformation (vibration) of the piezo element 118, the ink is as follows. Show good behavior. That is, first, with the deformation of the piezo element 118, the meniscus 124 is retracted inside the nozzle hole 48. Thereafter, when the deformation of the piezo element 118 is restored, the ink becomes a columnar shape and protrudes to the outside of the nozzle hole 48, and a part of the columnar ink is detached to form an ink droplet 126 to become a nozzle hole. Jump out of 48.

  However, after a part of the columnar ink is detached as the ink droplet 126, the columnar ink spreads in the radial direction by the reaction of the separation of the ink droplet 126 and adheres to the periphery of the opening peripheral edge 127 of the nozzle hole 48. To do. As described above, since the back pressure (negative pressure) is applied to the sub tanks 29, 32, 34, and 36, the columnar ink after the ink droplet 126 is released again returns to the nozzle hole 48 side. It will be evacuated. That is, since the inside of the nozzle hole 48 is always at a negative pressure (below atmospheric pressure), the columnar ink is retracted so as to be pulled into the nozzle hole 48. Then, ink attached to the periphery of the opening peripheral edge 127 of the nozzle hole 48 is also retracted into the nozzle hole 48 by being dragged by this. The ink retracted into the nozzle hole 48 forms the normal meniscus again.

  As described above, after the ink droplet 126 jumps out of the nozzle hole 48, the columnar ink end 128 adheres to the periphery of the opening peripheral edge 127 of the nozzle hole 48. As shown in FIG. 13, since the electrodes 100 are arranged adjacent to each other with the nozzle holes 48 interposed therebetween, the end portions 128 of the columnar ink function as conductive materials that connect the electrodes 100. Accordingly, when the ink end portion 128 adheres so as to be spanned between the electrodes 100, a current flows between the electrodes 100. The same applies to the other electrodes 101 to 103. When the current flows between the electrodes 100 in this way, the current sensor 68 detects the current, and the control device 69 determines that the electrodes 100 are in a conductive state. That is, it is detected that the ink droplet 126 has been reliably ejected from the nozzle hole 48. In addition, after the ink droplet 126 is ejected from the nozzle hole 48, the ink again forms a normal meniscus in the nozzle hole 48 as described above. Therefore, after the current is detected, the ink is insulated again. Will be detected.

  As described above, in the multifunction machine 10 according to the present embodiment, it is detected that the ink droplet 126 has been reliably ejected during image recording. Therefore, when an ejection failure of the ink droplet has occurred for some reason. This is surely detected even during printing. Accordingly, even during printing, ink droplet ejection defects can be corrected.

  More specifically, in the multifunction machine 10 according to the present embodiment, as described above, generally, the flushing operation and the purge operation are periodically performed to prevent the recording head 43 from being clogged. Typically, the flushing operation is performed immediately before the printing operation, and during the printing, the flushing operation is performed during the line feed operation. Therefore, when the flushing operation is performed immediately before printing, and the ejection failure of the ink droplets or the risk thereof is detected immediately before printing, the ejection failure or the risk may be caused by performing a temporary purge operation or the like. Can be corrected. Further, by performing a flushing operation periodically for each line feed (or for every predetermined number of line breaks) during the printing operation, it is possible to detect the ejection failure of the ink droplets during printing or the possibility thereof. Even in such a case, the ejection failure or the possibility of correcting the ejection failure can be corrected by performing a temporary purge operation or the like.

  In particular, in the present embodiment, as shown in FIGS. 11 and 12, the electrode 100 is disposed on the surface of the nozzle plate 98. As described above, when the ink droplet 126 is ejected from the nozzle hole 48, a part of the ink adheres around the opening peripheral edge 127 of the nozzle hole 48. Therefore, by arranging the electrode 100 on the surface of the nozzle plate 98, the ink attached to the opening peripheral edge 127 of the nozzle hole 48 functions reliably as a conductive material, and the electrodes 100 are in a conductive state. There is an advantage that it can be reliably judged.

  Further, as shown in FIG. 8, the electrode 100 is separated from the peripheral edge of the nozzle hole 48 by 1 μm to 5 μm. For this reason, the malfunction of the current sensor 68 due to the electrode 100 coming into contact with a normal meniscus before ink droplet ejection is prevented. More specifically, as shown in FIG. 11, since the end of the normal meniscus 124 is located at the periphery of the nozzle hole 48, if the electrode 100 extends to the periphery of the nozzle hole 48. The end of the meniscus 124 may come into contact with the electrode 100 and the current sensor 68 may malfunction. However, since the electrode 100 is separated from the peripheral edge of the nozzle hole 48 by 1 μm to 5 μm, 68 malfunctions are prevented. Further, as described above, when the ink droplet 126 is ejected from the nozzle hole 48, a part of the ink adheres to the periphery of the opening peripheral edge 127 of the nozzle hole 48. It spreads in a circle with a diameter that is about 10 μm larger than the diameter of 48. Therefore, it is more reliably determined that the ink attached to the opening peripheral edge 127 of the nozzle hole 48 functions more reliably as a conductive material, and the electrode 100 is in a conductive state.

  Further, the nozzle plate 98 has a water repellent film 120 formed on the surface thereof. By providing the water repellent film 120, the ink that has once spread on the surface of the nozzle plate 98 is quickly put into the nozzle hole 48 by the back pressure in the sub tanks 29, 32, 34, and 36 and the surface tension of the ink. Evacuate to. Therefore, there is an advantage that a normal meniscus can be quickly formed again after the ink droplet 126 is ejected.

  In the present embodiment, as shown in FIG. 5, the electrode 100 is disposed so as to connect the plurality of nozzle holes 48 in series. As a result, when ink is ejected from each nozzle hole 48, if any one of the plurality of nozzle holes 48 does not conduct between the electrodes 100, the ink is ejected after the ink droplets are ejected. It can be detected that it is not attached to the surface. That is, it is detected that the ink droplet 126 has not normally ejected from all the nozzle holes 48. Thereby, there is an advantage that printing defects are reliably prevented. In this case, “connected in series” is not limited to the case where all the nozzle holes 48 in the 48 nozzle nozzle rows from which Bk ink is ejected are connected in series. That is, “connected in series” includes a case where a plurality of nozzle holes 48 that may eject ink droplets at the same time are connected in series. For example, when printing is performed on the end of the recording paper 47 conveyed on the platen 41, ink droplets are not ejected from all the nozzle holes 48 at the same time, but are arranged at positions corresponding to the end. Ink droplets are discharged only from the predetermined number of nozzle holes 48. The case where the predetermined number of nozzle holes 48 are connected in series by the electrode 100 also corresponds to the case of “connected in series”.

  In addition, in the present embodiment, the plurality of nozzle holes 48 are arranged for each color of ejected ink, as shown in FIG. Accordingly, it is detected for each color that the ink droplet 126 has not been ejected from the nozzle hole 48. There are various reasons why ink droplets did not jump out of the nozzle holes, but as a measure for solving this, the above-described purging, flushing or the like is performed. In that case, it is not necessary to perform purging or flushing for all colors at the same time. What is necessary is just to take measures, such as purging. This also has the advantage that the ink is not wasted.

<Second Embodiment>

  Next, a second embodiment of the present invention will be described. FIG. 14 is an enlarged cross-sectional view of a main part of a recording head 129 according to the second embodiment of the present invention. FIG. 15 is a wiring diagram of electrodes disposed in the recording head 129.

  The recording head 129 according to the present embodiment differs from the recording head 43 according to the first embodiment in that the electrodes 100 to 103 are arranged on the surface of the nozzle plate 98 in the recording head 43. In the recording head 129 according to the present embodiment, the point embedded in the nozzle plate 98, and in the first embodiment, the electrodes 100 to 103 are disposed so as to connect the nozzle holes 48 in series. In contrast, the electrodes 100 to 103 according to the present embodiment are arranged to connect the nozzle holes 48 in parallel. Other configurations are the same as those of the multifunction machine 10 according to the first embodiment.

  As shown in FIG. 14, the electrode 100 is sandwiched between the insulating material 119 and the water repellent film 120, and its end is exposed on the inner peripheral surface of the nozzle hole 48. Specifically, the electrode 100 is disposed at a distance a from the surface of the nozzle plate 98 to the inner back side, and the distance a can be set to 1 μm to 100 μm, for example. The same applies to the electrodes 101-103.

  As described above, in order for the ink droplet 126 to jump out of the nozzle hole 48, the meniscus 124 must be formed so as to be positioned at the opening peripheral edge 127 of the nozzle hole 48 (see FIG. 12). That is, the normal meniscus 124 must be formed. In the present embodiment, since the electrode 100 is arranged at the position of the distance a, the electrode 100 comes into contact only with the normally formed meniscus 124, and before the ink droplet 126 jumps out of the nozzle hole 48. If the normal meniscus 124 is formed, the electrodes 100 become conductive. The same applies to the electrodes 101-103. That is, if an abnormal meniscus is formed before the ink droplet 126 jumps out of the nozzle hole 48 due to the presence of bubbles or the like, the electrodes 100 to 103 are insulated.

  As described above, when the piezo element 118 is deformed, the normal meniscus 124 temporarily retracts to the inner back side of the nozzle hole 48 (see FIG. 11). Therefore, at this time, the electrodes 100 to 103 change from a conductive state to an insulating state. Further, when the deformation of the piezoelectric element 118 is restored, the ink in the nozzle hole 48 is ejected from the nozzle hole 48 so as to be repelled. Therefore, at this time, the electrodes 100 to 103 change from an insulating state to a conductive state. In addition, after the ink droplet 126 is ejected, the ink returns to the nozzle hole 48 again, so that this conduction state is maintained. When the current flows between the electrodes 100 to 103 in this way, the current sensor 68 detects the current, and the control device 69 instantaneously changes between the electrodes 100 to 103 from the conductive state to the insulated state. Judging. That is, it can be detected that a meniscus 124 (normal meniscus) capable of ejecting ink droplets is formed in the nozzle hole 48 before and after ejection of the ink droplets 126.

  As shown in FIG. 15, the nozzle holes 48 are connected in parallel by electrodes 103, and the electrodes 103 are connected to the current sensor 68. In the present embodiment, the current sensor 68 has an internal circuit configured to detect conduction between the electrodes 103 arranged for each nozzle hole 48. For this reason, the current sensor 68 includes a plurality of connection terminals 81 to 90, and the electrodes 103 corresponding to the nozzle holes 48 are connected to the connection terminals 81 to 90. In addition, in the drawing, only the electrode 103 is shown for the sake of simplification, but actually, as in the first embodiment, an electrode is provided for each nozzle hole 48 corresponding to the color of each ink. 100 to 103 are arranged, and the plurality of nozzle holes 48 corresponding to the respective inks are connected in parallel by the respective electrodes 100 to 103. The meaning of “connected in parallel” is the same as that in the first embodiment. That is, “connected in parallel” is not limited to the case where all the nozzle holes 48 of the nozzle hole 48 row from which ink of each color is ejected is connected in parallel. This includes a case where a plurality of nozzle holes 48 that may eject ink droplets are connected in parallel. For example, when printing is performed on the end of the recording paper 47 conveyed on the platen 41, ink droplets are not ejected from all the nozzle holes 48 at the same time, but are arranged at positions corresponding to the end. Ink droplets are discharged only from the predetermined number of nozzle holes 48. The case where the predetermined number of nozzle holes 48 are connected in parallel by the electrodes 100 to 103 also corresponds to the case of “connected in parallel”.

  In the present embodiment, it can be detected that the normal meniscus 124 (ink liquid level on which ink droplets can be ejected) is formed in the nozzle hole 48 before and after the ejection of the ink droplet 126. That is, a normal meniscus is formed before the ink droplet 126 is discharged, and the meniscus is normally retracted in the nozzle hole 48 immediately before the ink droplet 126 is discharged (normal behavior of the normal meniscus). Detected. Accordingly, since it is detected that the ink droplet 126 can be reliably ejected during image recording, if there is a possibility that ink droplet ejection failure may occur due to any cause, printing is in progress. This is reliably detected. Therefore, even during printing, if there is a possibility of ink droplet ejection failure, this can be corrected. Specifically, as in the first embodiment, the possibility of the ejection failure is eliminated by performing flushing or the like for periodic flushing or forcibly, and thereafter The ejection failure that may actually occur is prevented in advance.

  In the present embodiment, the electrodes 100 to 103 are sandwiched between the insulating material 119 and the water repellent film 120. Therefore, the ink existing in the flow path upstream of the nozzle hole 48 is not electrically connected between the electrodes 100 to 103. Further, as described above, the ink that has once spread on the surface of the nozzle plate 98 is quickly retracted into the nozzle hole 48 by the surface tension of the ink together with the back pressure in the sub tanks 29, 32, 34, 36. Therefore, if the normal meniscus exhibits the normal behavior, the electrodes 100 to 103 are surely changed to a conductive state, an insulating state, and a conductive state, and the current sensor 68 and the control device 69 malfunction. Is reliably prevented.

  In the present embodiment, the electrodes 100 to 103 are arranged so as to connect the plurality of nozzle holes 48 corresponding to the colors of the inks in parallel. If the electrodes 100 to 103 are not insulated in any one of the plurality of nozzle holes 48 when ejected, it is determined that the normal meniscus 124 does not exhibit normal behavior. That is, it is detected that the ink droplet 126 is not ready to eject from the nozzle hole 48. Thereby, there is an advantage that printing defects are reliably prevented.

  Further, also in the present embodiment, as described above, the plurality of nozzle holes 48 are arranged for each color of the ejected ink. Thereby, it is detected for each color that the normal meniscus 124 does not show a normal behavior, that is, the ink droplet 126 is not ready to eject from the nozzle hole 48. In this case, as in the first embodiment, purging or flushing is performed to eliminate the reason why a normal meniscus is not formed. When purging or flushing, it is not necessary to perform flushing or the like for all the colors, and it is only necessary to perform flushing or the like only for the nozzle hole 48 of the color where the ink droplet 126 did not jump out. Ink is never discarded.

  The present invention can be applied to an ink jet recording apparatus.

  <Third Embodiment>

  In the above-described embodiment, the current sensor is configured on the multifunction machine 10 side, and is configured to be connected to the electrode provided on the recording head via the connection terminal provided on the scanning carriage. A current sensor may be provided integrally. Other configurations are the same as those of the MFP 10 according to the above-described embodiment.

FIG. 1 is an external perspective view of a multifunction peripheral according to the first embodiment of the present invention. FIG. 2 is a schematic diagram showing the structure of the printer unit of the multifunction machine according to the first embodiment of the present invention. FIG. 3 is a perspective view schematically showing the configuration of the image recording unit of the multifunction peripheral according to the first embodiment of the present invention. FIG. 4 is a block diagram schematically showing the configuration of the image recording unit of the multifunction peripheral according to the first embodiment of the present invention. FIG. 5 is an enlarged bottom view of the recording head of the multifunction peripheral according to the first embodiment of the present invention. FIG. 6 is an enlarged cross-sectional view of the recording head of the multifunction peripheral according to the first embodiment of the present invention. FIG. 7 is an enlarged cross-sectional view of a main part in FIG. FIG. 8 is an enlarged view of a main part in FIG. FIG. 9 is a block diagram illustrating a configuration of the control device of the multifunction peripheral according to the first embodiment of the present invention. FIG. 10 is a diagram schematically illustrating the ink supply path and the operation position of the recording head in the multifunction peripheral according to the first embodiment of the present invention. FIG. 11 is an enlarged cross-sectional view of a main part of the recording head of the multifunction peripheral according to the first embodiment of the present invention, and shows a state in which the ink forms a normal meniscus. FIG. 12 is an enlarged cross-sectional view of a main part of the recording head of the multifunction peripheral according to the first embodiment of the present invention, and illustrates a state where ink droplets are ejected. 13 is a view taken in the direction of arrows XIII-XIII in FIG. FIG. 14 is an enlarged cross-sectional view of a main part of a recording head according to the second embodiment of the present invention. FIG. 15 is a wiring diagram of electrodes arranged in a recording head according to the second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Multifunction machine 11 ... Printer part 23 ... Image recording part 28 ... Head part 37-40 ... Ink tank 43 ... Recording head 48 ... Nozzle hole 68 ... Current Sensor 69 ... Control device 70 ... Central processing unit 74 ... Purge mechanism 98 ... Nozzle plate 99 ... Main body 100-103 ... Electrode 119 ... Insulating material 120 ... Water repellent Membrane 121 ... CPU
122 ... ROM
123 ... RAM
124 ... meniscus 125 ... peripheral edge of outlet 126 ... ink droplet 127 ... peripheral edge of opening 128 ... end of ink column 129 ... recording head

Claims (20)

A recording head body having a nozzle plate in which a plurality of nozzle holes are arranged;
Electrodes arranged adjacent to each other across the nozzle hole;
A current detector that applies a predetermined voltage between the electrodes and detects a current flowing between the electrodes;
An inkjet recording apparatus comprising: a determination unit that determines that the electrodes are in a conductive state based on a detection result of the current detection unit.   The inkjet recording apparatus according to claim 1, wherein the electrode is disposed on a surface of the nozzle plate.   The inkjet recording apparatus according to claim 2, wherein the electrode is separated from the peripheral edge of the nozzle hole by approximately 1 μm to 5 μm.   The inkjet recording apparatus according to claim 2, wherein the nozzle plate has a water repellent layer formed on a surface thereof.   5. The inkjet recording apparatus according to claim 2, wherein the electrode is disposed so as to connect the plurality of nozzle holes in series.   The inkjet recording apparatus according to claim 5, wherein the plurality of nozzle holes are arranged for each color of ejected ink.   2. The ink jet recording according to claim 1, wherein the electrode is embedded in the nozzle plate in a state where the electrode is exposed to an inner peripheral surface of the nozzle hole at a position in contact with only a meniscus normally formed in the nozzle hole. apparatus.   The nozzle plate has a water repellent layer provided on a surface and an insulating layer laminated on the water repellent layer, and the electrode is sandwiched between the insulating layer and the water repellent layer. Item 8. The ink jet recording apparatus according to Item 7.   The ink jet recording apparatus according to claim 7, wherein the electrode is disposed so as to connect the plurality of nozzle holes in parallel.   The inkjet recording apparatus according to claim 9, wherein the plurality of nozzle holes are arranged for each color of ejected ink. A recording head body having a nozzle plate in which a plurality of nozzle holes are arranged;
In the nozzle plate, an electrode disposed adjacent to the nozzle hole, and
An ink jet recording head comprising:   The inkjet recording head according to claim 11, wherein the electrode is disposed on a surface of the nozzle plate.   The ink jet recording head according to claim 12, wherein the electrode is separated from the peripheral edge of the nozzle hole by approximately 1 μm to 5 μm.   The inkjet recording head according to claim 12 or 13, wherein the nozzle plate has a water repellent layer formed on a surface thereof.   The inkjet recording head according to claim 12, wherein the electrode is disposed so as to connect the plurality of nozzle holes in series.   The inkjet recording head according to claim 15, wherein the plurality of nozzle holes are arranged for each color of ejected ink.   The inkjet recording according to claim 11, wherein the electrode is embedded in the nozzle plate in a state where the electrode is exposed to an inner peripheral surface of the nozzle hole at a position that contacts only a meniscus formed normally in the nozzle hole. head.   The nozzle plate has a water repellent layer provided on a surface and an insulating layer laminated on the water repellent layer, and the electrode is sandwiched between the insulating layer and the water repellent layer. Item 18. The ink jet recording head according to Item 17.   The ink jet recording head according to claim 17 or 18, wherein the electrode is disposed so as to connect the plurality of nozzle holes in parallel. The ink jet recording head according to claim 19, wherein the plurality of nozzle holes are arranged for each color of ejected ink.

Images