JP2013052616A - Nozzle state detection method, cleaning method, inkjet recording method, and inkjet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nozzle state detection method for reliably detecting a nozzle state, a cleaning method according to the nozzle state, an inkjet recording method according to the nozzle state, and an long life inkjet recording apparatus without outputting a defective image for a long time.SOLUTION: The nozzle state detection method includes: a liquid chamber communicated with a respective plurality of nozzles provided in a head; a drive means for ejecting liquid from the nozzles by applying a first driving voltage to an actuator provided corresponding to the liquid chamber; and an ejection direction detection means for detecting an ejection direction of a liquid droplet. The drive means ejects a second liquid droplet by applying a second driving voltage to the actuator while a meniscus formed at the nozzles is protruded after the first driving voltage is applied to the actuator and the first liquid droplet is ejected. The ejection direction detection means detects the nozzle state from the direction in which the liquid droplet is ejected by detecting the direction in which the second liquid droplet is ejected.

Description

  The present invention relates to a nozzle state detection method, a cleaning method, an inkjet recording method, and an inkjet recording apparatus in an inkjet recording apparatus that forms an image by discharging droplets from nozzles.

  As an apparatus for forming an image on a recording medium such as recording paper, an inkjet recording apparatus is known. An ink jet recording apparatus performs recording by ejecting ink droplets from a recording head onto paper (image formation, printing, printing, printing, etc. are also synonymous), and records high-definition images at high speed. Can do. In addition, there are advantages such as low running cost, low noise, and easy recording of a color image using multicolor ink.

  In such an ink jet recording apparatus, a head for ejecting liquid droplets from a nozzle is mounted, and in many cases, a water repellent layer is formed on the nozzle surface in order to reduce sticking of ink to the nozzle surface of the head. Yes. Further, as a mechanism for cleaning ink adhering to the nozzle surface, a mechanism for mechanically rubbing the nozzle surface using a wiper is provided.

  When wiping is repeated to clean the nozzle surface, damage is accumulated in the water-repellent layer on the nozzle surface, the water-repellent layer peels off, and the dried ink adheres to the nozzle edge, causing droplets to be ejected from the nozzle. In some cases, the injection bend may occur.

  In particular, in recent years, pigment ink has become the mainstream for forming high-quality images on plain paper, but pigment ink is more damaging to the nozzle surface during wiping due to the presence of pigment particles than dye ink. It is getting bigger.

  In addition, by using quick-drying ink in order to achieve high speed, the ink attached to the nozzle surface and the wiper can be easily dried, and the dried ink is easily fixed to the nozzle edge.

  As described above, peeling of the water-repellent layer by wiping and jet bending due to sticking of dried ink to the nozzle edge are major issues, and the jet is ejected despite the fact that the actuator has not reached the end of its service life. The life of the head is often determined by the occurrence of bending.

  In recent years, there has been an increasing need for recording devices that perform a large amount of printing for office and industrial applications because of the advantages such as the above-mentioned high speed, high image quality, and low running cost. ) Is desired.

  The state of the nozzle varies greatly depending on the usage situation, and if the life is set in a range where no trouble occurs for all users, many users will set the life shorter than necessary. Therefore, in order to effectively use the apparatus, it is necessary to individually detect the state of the nozzle in real time and individually set the lifetime in each apparatus.

  Therefore, as a method of detecting the state of the nozzle in real time, a method of directly observing the nozzle as needed with a microscope or a CCD camera is known. Further, for example, in Patent Document 1, driving means for outputting a driving signal to an actuator provided corresponding to a pressure chamber communicating with a nozzle and ejecting ink droplets from the nozzle expands the volume of the pressure chamber to the driving signal. A phase in which the natural vibration of the pressure chamber in the ink-filled state generated in the first stage is reversed, and a first stage in which ink is drawn in and a second stage in which the volume of the pressure chamber is reduced and ink droplets are ejected are provided. A head driving device that sets the second stage according to the above is disclosed.

  According to the head drive device according to Patent Document 1, it is possible to secure residual vibration after driving the piezoelectric actuator of the ink jet printer and to estimate the state of the nozzle flow path, pressure chamber, and the like in the nozzle head.

  However, when directly observing the nozzle with a microscope, a CCD camera, or the like, it is necessary to incorporate such observation means in the apparatus, resulting in an increase in cost and size of the apparatus.

  Further, in the head driving device according to Patent Document 1, the state of the nozzle flow path and the pressure chamber in the nozzle head is estimated and image quality deterioration such as missing dots due to so-called nozzle clogging is detected. Therefore, there is a case where the state of the nozzle cannot be reliably detected.

  Therefore, an object of the present invention is to provide a nozzle state detection method that can accurately detect the state of a nozzle. It is another object of the present invention to provide a nozzle surface cleaning method and an ink jet recording method according to the state of the nozzle, and an ink jet recording apparatus that does not output a defective image for a long period of time and has a long life.

  In view of the above problems, the present invention applies a voltage to a plurality of nozzles provided in a head, a liquid chamber communicating with each of the nozzles, an actuator provided corresponding to the liquid chamber, and the actuator. A nozzle state detection method in an inkjet recording apparatus, comprising: a drive unit that discharges droplets from the nozzle; and a discharge direction detection unit that detects a discharge direction of the droplets from the nozzle, wherein the drive unit includes: Applying a first driving voltage to the actuator to discharge the first droplet; and after discharging the first droplet, the meniscus formed by the nozzle is opposite to the liquid chamber from the nozzle. A step in which the driving means applies a second driving voltage to the actuator to eject a second droplet in a state of projecting to the actuator; and the ejection direction detecting means And having the steps of: detecting a direction in which the second liquid droplets are ejected from the nozzle.

  According to the embodiment of the present invention, by detecting the ejection direction of the small droplets ejected from the nozzle, the state of the nozzle such as separation of the water repellent layer at the end of the nozzle or occurrence of ink sticking is detected, and the head has a lifetime. It becomes possible to make effective use until it reaches.

  Further, by performing cleaning of the nozzle surface and image formation based on the detection result of the nozzle state, it is possible to extend the life of the head including the nozzle and to prevent the image quality from being deteriorated. Furthermore, by accurately detecting the nozzle state, it is possible to provide an ink jet recording apparatus that has a good image quality over a long period of time and has a long service life.

Schematic cross-sectional view showing the overall configuration of an inkjet recording apparatus according to an embodiment The top view which shows the principal part of the inkjet recording device which concerns on embodiment Top view and side view of head according to embodiment Partial enlarged sectional view in the width direction of the head according to the embodiment Partial enlarged sectional view in the longitudinal direction of the head according to the embodiment Schematic configuration diagram of nozzle surface cleaning means according to an embodiment The figure which shows a mode that the water-repellent layer of the nozzle edge part which concerns on embodiment peels. The figure which shows the influence which the peeling part 73 of the nozzle 104 edge part which concerns on embodiment has on the discharge direction of an ink droplet The figure which shows the structural example of the discharge direction detection means of the droplet which concerns on embodiment. The figure which shows the example of the waveform of the drive voltage applied to the piezoelectric element which concerns on embodiment The figure which shows the change of the meniscus position after the 1st droplet discharge which concerns on embodiment The figure which shows the relationship between the time interval Td of the 1st drive voltage and 2nd drive voltage which concern on embodiment, and the ejection speed Vj of a 2nd ink drop. The figure which shows the example of the waveform of the drive voltage applied to the piezoelectric element which concerns on embodiment Enlarged view of the waveform of the second drive voltage according to the embodiment The figure which shows the example which changes image data based on the nozzle state detection result which concerns on embodiment The figure which shows the dot formation example when the ejection bending | flexion of an ink drop arises in embodiment. The figure which shows the example in which the peeling part of the water-repellent layer by wiping is formed in the edge part of the nozzle which concerns on embodiment

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings.
<Configuration of inkjet recording apparatus>
An ink jet recording apparatus 100 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic cross-sectional view illustrating the overall configuration of an inkjet recording apparatus 100 according to the present embodiment, and FIG. 2 is a plan view illustrating a main part of the inkjet recording apparatus 100 according to the present embodiment.

  In the ink jet recording apparatus 100 according to the present embodiment, a carriage 3 is held movably in the main scanning direction by a guide rod 1 which is a guide member horizontally mounted on left and right side plates (not shown) and a guide rail 2. The carriage 3 is connected to the main scanning motor 4 via a timing belt 5 and moves and scans in the direction of the arrow in FIG. 2 (main scanning direction).

  The carriage 3 includes, for example, four droplet ejection heads 107 that eject ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). It is attached towards. The head 107 uses a piezoelectric actuator such as a piezoelectric element.

  Further, in order to supply ink of each color to the head 107, the sub tank 8 corresponding to each color is mounted on the carriage 3. The sub tank 8 is supplemented with ink from a main tank (ink cartridge) via an ink supply tube (not shown).

  On the other hand, as a paper feeding unit for feeding the paper 112 stacked on the paper stacking unit 111 such as the paper feeding cassette 110, a half-moon roller (paper feeding roller) that separates and feeds the paper 112 one by one from the paper stacking unit 111. 113) and a separation pad 114 made of a material having a large friction coefficient.

  The paper feed unit that transports the paper 112 fed from the paper feed unit includes a transport belt 21 for electrostatically attracting and transporting the paper 112, and transports the paper 112 to the head 107.

  The conveyance belt 21 is an endless belt, is stretched between the conveyance roller 127 and the tension roller 128, and circulates in the belt conveyance direction (sub-scanning direction) shown in FIG. It is configured like this.

  A double-sided paper feeding unit 161 is detachably attached to the back of the inkjet recording apparatus 100. The double-sided paper feeding unit 161 takes in and reverses the paper 112 returned by the reverse rotation of the transport belt 21 and feeds the paper 112 again between the counter roller 22 and the transport belt 21.

  In the inkjet recording apparatus 100 according to the present embodiment configured as described above, the sheets 112 are separated and fed one by one from the sheet feeding unit, and conveyed in the sub-scanning direction while being electrostatically attracted to the conveyance belt 21. .

  When the paper 112 reaches below the head 107, the head 107 is driven according to the image signal while moving the carriage 3, thereby ejecting ink droplets onto the stopped paper 112 to record one line. After the paper 112 is conveyed by a predetermined amount, the next line is recorded.

  By receiving a recording end signal or a signal that the trailing edge of the paper 112 reaches the recording area, the recording operation is finished and the paper 112 is discharged to the paper discharge tray 54.

In the case of duplex printing, at the end of recording on the front surface (surface to be printed first), the conveyance belt 21 is reversely rotated to feed the paper 112 into the double-sided paper feed unit 161, and the paper 112 is reversed and conveyed again. After being transported by the belt 21 and recording on the back surface, it is discharged to the paper discharge tray 54.
<Configuration and operation of the head>
FIG. 3 shows a top view and a side view of the head 107 according to the present embodiment. FIG. 3A is a top view of the head 107 viewed from the nozzle surface, and FIG. 3B is a side view of the head 107. In the following drawings, the X direction indicates the width direction of the head 107, the Y direction indicates the longitudinal direction, and the Z direction indicates the height direction.

  In the head 107, a nozzle plate 103 in which a plurality of nozzles 104 are formed is joined to a frame member 130. The head 107 includes a liquid chamber for supplying ink therein, a piezoelectric element that applies pressure to the liquid chamber, a vibration plate, and the like, and can eject ink droplets from the nozzle 104. The number of nozzles 104 can be designed as appropriate according to the printing speed and the number of pixels.

  FIG. 4 shows a partially enlarged sectional view in the width direction of the head 107 according to the present embodiment, and FIG. 5 shows a partially enlarged sectional view in the longitudinal direction of the head 107 according to the present embodiment.

  The head 107 includes, for example, a channel plate 101 formed by anisotropic etching of a single crystal silicon substrate, a diaphragm 102 formed by nickel electroforming bonded to the lower surface of the channel plate 101, and the channel plate 101. And a nozzle plate 103 bonded to the upper surface of the substrate.

  The flow path plate 101 communicates with a nozzle communication path 105, which is a flow path through which a nozzle 104 that discharges droplets (ink droplets) communicates, a liquid chamber 106, and a common liquid chamber 108 for supplying ink to the liquid chamber 106. An ink supply port 109 and the like are formed.

  In addition, a laminated piezoelectric element 121 as an actuator, which is a pressure generating unit for deforming the diaphragm 102 to pressurize the ink in the liquid chamber 106, and a base substrate 122 for bonding and fixing the piezoelectric element 121 are provided. Yes. A column portion 123 is provided between the piezoelectric elements 121. The column portion 123 is a portion formed simultaneously with the piezoelectric element 121 by dividing and processing the piezoelectric element member. However, since the drive voltage is not applied, the column portion 123 is a simple column. The piezoelectric element 121 is connected to the FPC 12 equipped with a drive circuit (drive means) for applying a voltage to the piezoelectric element 121.

  The diaphragm 102 is joined to the frame member 130 at the periphery. In the frame member 130, an ink supply for supplying ink from the outside to the common liquid chamber 108, a through-hole 131 that accommodates an actuator unit composed of the piezoelectric element 121, the base substrate 122, and the like, a recess serving as the common liquid chamber 108, and the like. A mouth 132 is formed. The frame member 130 is formed by injection molding with a thermoplastic resin such as an epoxy resin or polyphenylene sulfite, for example.

  Here, the channel plate 101 is formed by, for example, subjecting a single crystal silicon substrate having a crystal plane orientation (110) to an anisotropic etching using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH), so that the nozzle communication path 105, A recess or a hole to be the liquid chamber 106 is formed. Moreover, it is not restricted to a single crystal silicon substrate, It can also comprise using another stainless steel substrate, photosensitive resin, etc.

  The diaphragm 102 is formed by, for example, an electroforming method (electroforming method) using a nickel metal plate, but a metal plate, a joining member of a metal and a resin, or the like can also be used. In the diaphragm 102, the piezoelectric element 121 and the support portion 123 are bonded with an adhesive, and the frame member 130 is further bonded with an adhesive.

  In the nozzle plate 103, nozzles 104 having a diameter of, for example, 10 to 30 μm are formed corresponding to the liquid chambers 106, and are joined to the flow path plate 101 with an adhesive. In the nozzle plate 103, a water repellent layer 34 is formed on the outermost surface of the nozzle forming member via a required layer. The nozzle plate 103 may be formed by, for example, Ni electroforming, a SUS plate press processed, a resin laser processed, or a photosensitive resin patterned.

The piezoelectric element 121 is a stacked piezoelectric element in which piezoelectric materials 151 made of PZT (Pb (Zr, Ti) O ₃ ) and internal electrodes 152 made of AgPd or the like are alternately stacked.

  An individual electrode 153 and a common electrode 154 are connected to each internal electrode 152 drawn to alternately different end faces of the piezoelectric element 121. Although not shown, the common electrode 154 is drawn to the individual electrode 153 side, and the individual electrode 153 and the common electrode 154 are connected to the FPC 12 on the same surface.

  In the present embodiment, the ink is pressurized in the liquid chamber 106 using the displacement in the d33 direction as the piezoelectric direction of the piezoelectric element 121. However, the liquid chamber 106 is configured using the displacement in the d31 direction as the piezoelectric direction of the piezoelectric element 121. It is also possible to employ a configuration in which the inner ink is pressurized.

The material used as the piezoelectric element is not limited to this example, and an electromechanical transducer such as a ferroelectric material such as BaTiO ₃ , PbTiO ₃ , (NaK) NbO ₃ or the like generally used as a piezoelectric element material is used. It can also be used.

  In the present embodiment, the piezoelectric element is a laminated type, but a single-plate piezoelectric element can also be used. The single-plate piezoelectric element may be a machined one, a thick film obtained by screen printing and sintering, or a thin film formed by sputtering, vapor deposition, or sol-gel method. The configuration shown in this embodiment It is not limited to. Further, the piezoelectric elements 121 provided on one substrate 122 can be provided in a plurality of rows.

  In the head 107 having the above-described configuration, for example, the piezoelectric element 121 is contracted by lowering the voltage applied to the piezoelectric element 121 from the reference potential, and the diaphragm 102 is lowered. As the vibration plate 102 descends, the volume of the liquid chamber 106 expands and ink flows into the liquid chamber 106. Thereafter, the voltage applied to the piezoelectric element 121 is increased to expand the piezoelectric element 121 in the stacking direction, and the diaphragm 102 is deformed in the nozzle 104 direction to contract the volume and volume of the liquid chamber 106. By performing such an operation, the liquid in the liquid chamber 106 is pressurized, and droplets are ejected (jetted) from the nozzle 104.

  After the liquid droplets are ejected from the nozzle 104, the voltage applied to the piezoelectric element 121 is returned to the reference potential, whereby the diaphragm 102 returns to the initial position, and the liquid chamber 106 expands to generate a negative pressure. At this time, the liquid is filled into the liquid chamber 106 from the common liquid chamber 108.

Note that the driving method of the head 107 is not limited to the above example (pulling-pushing), and striking, punching, and the like can be appropriately selected depending on the method of applying the driving voltage.
<Cleaning the nozzle surface>
FIG. 6 is a schematic configuration diagram of a nozzle surface cleaning unit according to the present embodiment.

  In the non-printing area on one side in the scanning direction of the carriage 3 on which the head 107 of the ink jet recording apparatus 100 is mounted, a cleaning mechanism 71 for maintaining and recovering the state of the nozzle 104 of the head 107 is disposed.

  The cleaning mechanism 71 includes a wiper 72 that is a rubber blade member for wiping the nozzle surface, and is provided to be movable in the X direction in the figure in a state where the wiper 72 is pressed against the nozzle surface of the head 107. The cleaning mechanism 71 can move in both directions in the width direction of the head 107 and removes ink droplets 70 attached to the nozzle surface.

  A plurality of wipers 72 may be provided, and a sheet-like wiper that does not generate dust, such as a nonwoven fabric, may be used.

  In the present embodiment, the cleaning mechanism 71 is disposed so as to be movable in the width direction of the head 107, but may be disposed so as to be movable in the longitudinal direction of the head 107. Alternatively, the cleaning mechanism 71 may be fixed, and the nozzle surface of the head 107 may be configured to perform cleaning by moving the nozzle surface in contact with the wiper 72.

  Here, when the cleaning of the nozzle surface using the wiper 72 is repeatedly performed, the water repellent layer 34 may be peeled off from the end portion of the nozzle 104.

  FIG. 7 shows a state where the water repellent layer 34 at the end of the nozzle 104 is peeled off. 7A to 7C show a state in which the water-repellent layer 34 at the end of the nozzle 104 progresses by the wiper 72 of the cleaning mechanism 71 wiping the nozzle surface in one direction in the X direction in the drawing. Is shown.

  In order to eject ink droplets straight from the nozzle 104 in a direction perpendicular to the nozzle surface, the meniscus of the ink formed by the nozzle 104 needs to be formed symmetrically. Therefore, the nozzle 104 is formed so as to have high symmetry, and the water repellent layer 34 is formed uniformly at the edge of the nozzle 104 so as not to destroy the target property.

  However, when the wiper 72 repeatedly wipes the nozzle surface in the X direction, the water-repellent layer 34 peels from the end of the nozzle 104, and a peeled portion 73 is formed (FIG. 7B). Thereafter, when cleaning by wiping is repeated, the peeling portion 73 expands (FIG. 7C).

  As described above, when the peeling portion 73 of the water repellent layer 34 is formed at the end portion of the nozzle 104, the symmetry of the meniscus of the ink pushed out from the nozzle 104 cannot be maintained. In addition, since the ink cannot be repelled at the peeling portion 73, the ink is easily attached and fixed, which causes a failure in ink ejection.

  FIG. 8 shows the influence of the peeling portion 73 at the end of the nozzle 104 on the ink droplet ejection direction. FIGS. 8A to 8C correspond to FIGS. 7A to 7C, and show the state of the meniscus 74 and the ink droplet ejection direction in each case.

  As shown in FIG. 8A, when the water repellent layer 34 is not peeled off and the shape of the nozzle 104 is maintained, the symmetry of the meniscus 74 of the ink rising from the nozzle surface is maintained. Ink droplets can be ejected straight in the direction of the arrow Za perpendicular to the nozzle surface.

  However, when the peeling portion 73 is formed at the end of the nozzle 104 as shown in FIGS. 8B and 8C, the symmetry of the ink meniscus 74 rising from the nozzle surface is lost, and the ink droplet ejection direction Deviates from the direction orthogonal to the nozzle surface in the directions of arrows Zb and Zc, resulting in a large injection bend.

  In addition, when ink is fixed to the peeling portion 73, the ink meniscus 74 is similarly broken and the ink droplets are ejected and bent.

As described above, the peeling of the water-repellent layer 34 at the end of the nozzle 104 and the fixing of the ink greatly affect the ink droplet ejection direction. When such a jetting bend occurs, the positions of dots formed on the paper are shifted, and the image quality is degraded.
<Detection of ink droplet ejection direction>
FIG. 9 shows a configuration example of the droplet discharge direction detection unit 200 according to the present embodiment. FIG. 9A is a top view, and FIG. 9B is a side view.

  The droplet (ink droplet) ejection direction detection means 200 includes a light emitting element 201 such as an LD and an LED, and a light receiving element 204 such as a PD, and the ink droplet 206 is ejected from a change in the amount of light received by the light receiving element 204. Is detected.

  The optical beam 207 output from the light emitting element 201 is converted into parallel light by the beam collimating means 202 such as a collimator lens to become parallel light 208. The generated parallel light 208 becomes detection beam light 209 flattened in one plane by passing through an optical element 203 such as an aperture or a cylindrical convex lens, which is a beam converging means.

  When the detection beam light 209 intersects the ejection path of the ink droplet 206 ejected from the nozzles 104 arranged on the head 107, the detection light 205, which is scattered light (reflected light), is generated.

  The light receiving element 204 is preferably arranged at a position where it can deviate from the optical axis of the detection beam light 209 and can receive the detection light 205 which is scattered light generated when the detection beam light 209 and the ink droplet 206 intersect. . In addition, by disposing the light receiving element 204 at a position where the light intensity is high, it is possible to detect the ejection state of the ink droplet 206 according to the light intensity of the scattered light 205.

  Since the detection beam light 209 is flat in the vertical direction so that the longitudinal direction thereof is parallel to the ejection direction of the ink droplet 206, the ink droplet 206 and the detection beam light can be used as long as the ink droplet 206 is not jetted. The time at which 209 intersects is increased, and the generation time of the detection light 205 is also increased. Therefore, by measuring the length of the generation time of the detection light 205, it is possible to detect the occurrence of injection bending.

  Further, since the ejection bend of the ink droplet 206 is related to the wiping direction for cleaning the nozzle surface, the ejection direction detection unit 200 is configured to detect at least a change in the ejection direction of the ink droplet in the wiping direction.

  Since the nozzle surface of the head 107 according to the present embodiment is wiped in the X direction in the drawing and the ink droplet ejection curve is generated in the X direction, the detection beam light is shortened in the X direction and flattened in the Y direction. Thus, the injection bending in the X direction can be detected.

The ejection direction detection unit 200 is not limited to the above configuration as long as the ejection direction of the ink droplet 206 ejected from the head 107 can be detected. For example, the landing position of the ink droplet ejected on the paper is measured. It can also be set as the structure detected by doing.
<Detection of nozzle status>
FIG. 10 shows an example of the waveform of the drive voltage applied to the piezoelectric element 121 when detecting the nozzle state.

  In the illustrated example, first, a first ink droplet having the same size as that during normal printing is ejected from the nozzle 104 using a drive waveform including five pulses as the first drive voltage. Next, when the time Td has elapsed from the first drive voltage, the second ink droplet is ejected by applying the second drive voltage.

  Here, FIG. 11 shows a change in the meniscus position after the first droplet is discharged.

  The meniscus position is based on the position where the ink meniscus coincides with the nozzle surface, plus a state protruding from the nozzle surface to the opposite side of the liquid chamber 106, and a state drawn from the nozzle surface to the liquid chamber 106 side as negative. Represents.

  After the ink droplets are ejected, the meniscus position is once drawn from the nozzle surface to the liquid chamber 106 side, and then supplied (refilled) to protrude to the opposite side of the liquid chamber 106 and rise. After this, the meniscus position is stabilized by being balanced with the external pressure at a position where it coincides with the nozzle surface.

  Thus, the meniscus vibration period Tr from the state in which the meniscus position protrudes most to the time when the meniscus position returns to the nozzle surface and becomes stable is about 110 μsec. Note that the vibration of the period Tc that appears when the meniscus is raised from the nozzle surface is the natural vibration period of the liquid chamber 106.

  When image formation is performed, in order to control the size of the ink droplet, a drive voltage is applied to the piezoelectric element 121 in a stable state after at least the meniscus vibration period Tr has elapsed after the ink droplet is discharged, and the next ink droplet Is discharged.

  FIG. 12 shows the relationship between the time interval Td between the first drive voltage and the second drive voltage and the ejection speed Vj of the second ink droplet.

  After the first ink droplet is ejected, the meniscus position protrudes from the nozzle surface to the side opposite to the liquid chamber 106, and the ejection speed Vj of the second ink droplet decreases. Further, the rising of the meniscus is reduced, the meniscus position is lowered, and the ejection speed Vj of the second ink droplet is increased.

  Here, when the ejection speed Vj is high, the ink droplets are likely to be ejected normally in a direction orthogonal to the nozzle surface. However, when the ejection speed Vj is small, the peeling portion 73 formed at the end of the nozzle 104. Therefore, it is easy to cause injection bending.

  Therefore, the second driving voltage is set under the condition that the ejection speed Vj of the ink droplet is reduced, that is, in the state where the meniscus formed by the nozzle protrudes from the nozzle to the opposite side of the liquid chamber 106 after the ejection of the first ink droplet. To discharge the second ink droplet. By detecting the ejection direction of the ink droplets ejected under such conditions, it becomes possible to sensitively detect the nozzle state, such as whether or not the peeling portion 73 has occurred at the end of the nozzle 104.

  In the ink jet recording apparatus 100 according to the present embodiment, the ejection curve of the second ink droplet is detected when the time interval Td between the first and second drive voltages is 30 μsec after printing 100K sheets. In addition, after 200K sheets were printed, the time interval Td was 25 to 40 μsec, and after 300K sheets were printed, the time interval Td was 25 to 50 μsec.

  When the number of printed sheets increases and damage to the nozzle 104 continues to be applied, the peeled portion 73 of the water-repellent layer 34 expands, and the meniscus symmetry is greatly lost. Therefore, the time interval Td and the jet velocity Vj at which jet bending occurs. The range of becomes larger.

  As shown in FIGS. 11 and 12, the time interval Td between the first and second drive voltages is set to a range in which the meniscus position rises from the nozzle 104 after the first ink droplet is ejected, thereby changing the nozzle state. It can be accurately detected.

  Furthermore, by setting the time interval Td in the vicinity of the maximum meniscus position, it is possible to detect with high sensitivity the nozzle state such as the peeled portion 73 and ink sticking generated at the end of the nozzle 104. In the present embodiment, it is preferable to set the time interval Td to 25 μsec corresponding to approximately one quarter of the meniscus vibration period Tr.

  Also, as shown in FIG. 13, the first ink droplet is made larger by making the amplitude of the first drive voltage larger than the amplitude of the second drive voltage, thereby increasing the first ink droplet. The rise of the meniscus after ejection can be increased, and a margin of the time interval Td for detecting the injection bending can be increased.

  FIG. 14 shows an enlarged view of the waveform of the second drive voltage.

  The second drive voltage lowers the vibration plate 102 by temporarily lowering the voltage applied to the piezoelectric element from the reference potential, and after the meniscus is largely drawn from the nozzle surface to the liquid chamber 106 side, the voltage is increased stepwise. A waveform that pushes out ink droplets.

  By using such a waveform, it is possible to easily cause the ejection bend, and it becomes possible to detect the ejection bend caused by the peeling of the water-repellent layer 34 at the end of the nozzle 104 and the ink sticking with high sensitivity. .

In addition, when ink droplets are pushed out step by step, the second-stage extrusion timing is Tc, which is the natural vibration period of the liquid chamber, and the first-stage extrusion timing is Tc / 2. By using such a waveform, the operation is in reverse phase with respect to the meniscus vibration, and it is possible to eject small-sized ink droplets at high speed while suppressing the residual meniscus vibration due to the natural vibration of the liquid chamber thereafter. become.
<Control after nozzle status detection>
When the ink droplet ejection bend is detected by the method described above, the nozzle surface is cleaned by the cleaning mechanism 71, and the first and second ink droplets are discharged again to detect the state of the nozzle.

  Even when the jetting bend is detected once, the fixed ink or foreign matter may be removed by cleaning the nozzle surface, and the jetting bend may be corrected. If jetting of ink droplets is not detected after cleaning, printing can be performed as usual.

  The nozzle surface may be cleaned only once, but the fixed ink and foreign matter can be more reliably removed by performing the cleaning several times.

  In addition, when ejection bend occurs due to the peeling of the water repellent layer 34 at the end of the nozzle 104 or the influence of ink fixation, the image data can be changed and printed to prevent degradation of the image quality of the output image. it can.

  FIG. 15 shows an example of changing the image data based on the detection result of the nozzle state. In the figure, the intersection of the alternate long and short dash line is a position where an ink droplet is ejected according to image data to form a dot.

  The carriage 3 forms an image by ejecting ink droplets from the head 107 while moving in the main scanning direction (X direction in the figure). In addition, wiping by the cleaning mechanism 71 is also performed in the X direction in the drawing, and ink droplet jetting bending due to the formation of the peeling portion 73 at the end of the nozzle 104 also occurs in the X direction in the drawing. Further, the ejection bend of ink droplets is likely to occur when a small size ink droplet is ejected continuously after a normal size ink droplet is ejected.

  Therefore, when it is necessary to eject small droplets in the image data, the image data is changed so that ink droplets are not ejected to dots adjacent in the main scanning direction of the carriage 3. As shown in FIG. 15, when forming a dot with a small droplet in the center, the image data is changed so that no dot is formed at a point adjacent in the X direction.

  By changing the image data in this way, small-sized ink droplets are no longer ejected when the meniscus after ink droplet ejection is raised, and image quality can be maintained by preventing the occurrence of jet bending. .

  In addition, when ink droplet ejection bending occurs, image quality can be prevented from being lowered by controlling the driving frequency for applying a voltage to the piezoelectric element 121 while maintaining the image data as it is.

  By increasing the time interval for applying a voltage to the piezoelectric element 121, the printing speed is reduced, but the ink droplet is not ejected in a state where the meniscus position after the ink droplet ejection protrudes from the nozzle surface. Can be suppressed.

  Therefore, even when the nozzle 104 is in a deteriorated state such as the water-repellent layer 34 around the nozzle 104 is peeled off, it is possible to continue printing while maintaining the image quality.

  Next, FIG. 16 shows an example of dot formation in the case where an ink droplet ejection curve occurs. The intersection of the alternate long and short dash line in the figure is a target position for forming dots by ejecting ink droplets, and shows an example of dot formation in a pattern in which two small droplets are continuous.

  The carriage 3 moves in the X direction, and high-speed printing is realized by performing printing in both the forward path and the backward path. Further, the wiping by the cleaning mechanism 71 is also performed in the X direction in the figure, and the injection bend occurs in the X direction. When the ejection bend occurs, the landing position of the ink droplet deviates from the target, and the dot positions formed in the forward path and the return path of the carriage 3 are greatly different.

  FIG. 16A shows a state in which the state of the nozzle 104 is normal and dots are formed at the target position. In FIGS. 16B and 16C, ink droplets are ejected and bent, and ink droplets are ejected according to the carriage 3 moving in the direction of the arrow in the figure, and dots B1 and C1 are formed first, and thereafter The state where dots B2 and C2 are formed is shown.

  As shown in FIGS. 16B and 16C, the first ink droplet lands on the target position, and the dots B1 and C1 are formed at the normal position. However, the landing positions of the second ink droplets that continue thereafter are ejected and bent due to the rise of the meniscus after the first ink droplets are discharged, and the dots B2 and C2 are located at positions different from the target positions. It has been formed.

  If the dot interval is wide as shown in FIG. 16C, for example, a beard appears in the outline of the character, and the image quality is greatly reduced. However, when the dot interval is narrowed as shown in FIG. 16B, the image quality is not greatly reduced to the extent that the sharpness of the outline of the character is reduced.

  Therefore, when a jet bend occurs in a printer or the like that places particular emphasis on the image quality of characters for business use etc., printing is performed only in the direction in which the continuous dot interval in the scanning direction of the carriage 3 is narrowed, thereby improving the image quality. Can be suppressed. That is, control is performed so that printing is performed only when the carriage 3 is scanned in the direction opposite to the direction in which the peeling portion 73 is formed on the nozzle 104 by wiping.

  Further, the life of the head 107 can be extended by controlling the wiping direction of the cleaning mechanism 71 based on the detection result of the nozzle state.

  FIG. 17 shows an example in which a peeling portion 73 of the water repellent layer 34 is formed at the end of the nozzle 104 by wiping.

  For example, as shown in FIG. 17A, the peeling portion 73 of the water-repellent layer 34 is formed at the end of the nozzle 104 by wiping in the X direction in the drawing, and an ink droplet jetting curve occurs, but the output image Control is performed so that the wiping direction is changed in the reverse direction by 180 ° at a stage where there is no influence on the wiping.

  By changing the wiping direction, peeling of the water repellent layer 34 proceeds at the opposite end of the nozzle 104 as shown in FIG. Therefore, it is possible to prevent the occurrence of ink droplet ejection bends that affect the output image and extend the life of the head 107.

When it is determined from the ink droplet ejection direction that the nozzle has reached the end of its life due to peeling of the water-repellent layer 34 on the nozzle surface, ink sticking that cannot be removed by cleaning, or foreign matter adhesion, the head 107 is replaced. It can be displayed. By appropriately detecting the state of the nozzle 104, the head 107 can be effectively utilized to the maximum extent until it actually becomes unusable.
<Summary>
As described above, according to the embodiment of the present invention, the second droplet is ejected while the meniscus after the first droplet ejection is raised, and the ejection direction of the second droplet is detected. The nozzle status can be detected with high sensitivity, and the head can be utilized to the maximum extent until the end of its life. Further, by performing image formation by controlling the scanning direction of the carriage based on the detection result of the nozzle state, it is possible to suppress a decrease in image quality. Furthermore, it is possible to control the wiping direction of the nozzle surface based on the detection result of the nozzle state, thereby preventing the exfoliation part formed at the end of the nozzle from being enlarged and extending the head life.

  In addition, by accurately detecting the nozzle state, it is possible to provide an ink jet recording apparatus that has good image quality over a long period of time and has a long service life.

  It should be noted that the present invention is not limited to the configuration shown here, such as a combination with other elements in the configuration described in the above embodiment. These points can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form.

3 Carriage 71 Cleaning mechanism (cleaning means)
72 Wiper (cleaning means)
74 Meniscus 100 Inkjet recording device 104 Nozzle 106 Liquid chamber 107 Head 121 Piezoelectric element (actuator)
200 Discharge direction detection means

2006-218727

Claims (9)

A plurality of nozzles provided in the head;
Liquid chambers respectively communicating with the nozzles;
An actuator provided corresponding to the liquid chamber;
Driving means for applying a voltage to the actuator to eject droplets from the nozzle;
A discharge direction detecting means for detecting a discharge direction of the droplet from the nozzle;
A nozzle state detection method in an inkjet recording apparatus comprising:
The driving means applying a first driving voltage to the actuator to eject a first droplet;
After the discharge of the first droplet, the drive means applies a second drive voltage to the actuator in a state where the meniscus formed by the nozzle protrudes from the nozzle to the opposite side of the liquid chamber. Discharging the second liquid droplets;
And a step of detecting the direction in which the second liquid droplet is discharged from the nozzle by the discharge direction detecting means. 2. The nozzle state detection method according to claim 1, wherein the second driving voltage changes in a stepwise manner when the droplet is ejected from the nozzle. 3. The nozzle state detection method according to claim 1 or 2, wherein the amplitude of the first drive voltage is larger than the amplitude of the second drive voltage. The image forming apparatus includes a cleaning unit that cleans the nozzle surface of the head.
After the cleaning means cleans the nozzle surface,
4. The nozzle state detection method according to claim 1, wherein the first and second droplets are ejected and the ejection direction of the second droplet is detected. 5. The cleaning means is a wiper for wiping the nozzle surface;
The nozzle state detection method according to claim 4, wherein the ejection direction detection unit detects a change in the ejection direction of the droplet in a wiping direction of the wiper. Based on the detection result by the nozzle state detection method according to claim 5,
A method for cleaning a nozzle, comprising controlling a wiping direction of the wiper. 6. An ink jet recording method according to claim 1, wherein the driving means controls a driving frequency at which a voltage is applied to the actuator based on a detection result obtained by the nozzle state detecting method according to any one of claims 1 to 5. 6. An ink jet recording method, wherein, based on a detection result obtained by the nozzle state detection method according to claim 1, the scanning direction at the time of image formation of a carriage on which the head is mounted is set to one direction. . A plurality of nozzles provided in the head;
Liquid chambers respectively communicating with the nozzles;
An actuator provided corresponding to the liquid chamber;
Driving means for applying a voltage to the actuator to eject droplets from the nozzle;
A discharge direction detecting means for detecting a discharge direction of the droplet from the nozzle;
An ink jet recording apparatus comprising:
After the driving means applies a first driving voltage to the actuator to discharge the first droplet, the liquid meniscus protrudes from the nozzle to the opposite side of the liquid chamber, and Driving means applies a second driving voltage to the actuator to discharge the second droplet;
The ink jet recording apparatus, wherein the discharge direction detection unit detects a deterioration state of the nozzle by detecting a direction in which the second droplet is discharged from the nozzle.

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