JP2012179796A - Ejection detection device, liquid ejection device, and cleaning method - Google Patents

Abstract

Disclosed is a discharge detection device capable of performing a cleaning process without requiring a complicated structure for generating negative pressure, a liquid discharge device including the discharge detection device, and a cleaning method therefor.
According to one embodiment, a discharge detection device includes a detector and an electric field generation mechanism. The detector is provided so as to be opposed to a head that discharges the liquid, and detects a discharge state of the liquid. The electric field generating mechanism is provided in the detector and applies an electrostatic force to the liquid in the head.
[Selection] Figure 8

Description

  The present technology relates to a liquid ejection apparatus that ejects liquid from a head, an ejection detection apparatus that detects a liquid ejection state from the head, and a head cleaning method.

  In an ink jet printer, the viscosity of ink may increase due to drying, and dust or the like may adhere to the nozzles (ejection holes) of the head. As a result, there are cases in which ejection abnormalities occur, such as a decrease in ink ejection speed, deflection of the ejection direction, and further inability to eject. Such ejection abnormality causes deterioration in print image quality.

  In order to solve such a problem of ejection abnormality, the ink jet recording apparatus described in Patent Document 1 detects ejection of ink droplets using an entire cap including a light emitting element and a light receiving element. Specifically, the entire cap is attached to the ink ejection element. Within the entire cap, the light emitted from the light emitting element is intercepted by flying so that the ink droplet crosses. If it does so, the light quantity which reaches a light receiving element will fall, and by this, it will be detected whether the discharge failure of the ink has generate | occur | produced for every discharge port. And the cap part of a partial cap is located in the vicinity of the discharge outlet where the discharge defect occurred. The discharge port is covered with the cap, and the ink is sucked by the negative pressure in the cap generated by driving the pump, and bubbles and dust mixed in the ink liquid path are removed (for example, Patent Documents) (Refer to FIG. 5 and FIG. 6).

  The ink jet recording apparatus described in Patent Document 2 includes a recording head and a head cap. The head cap is placed on the recording head, and a nozzle cleaning process is performed by suction with a negative pressure (see, for example, paragraph [0023] of FIG. 4 of Patent Document 2).

Japanese Patent No. 2718724 Japanese Patent No. 3514235

  However, in the apparatuses of Patent Documents 1 and 2, since the cleaning process is performed by a negative pressure, a pump and a pipe for generating the negative pressure are required, and the structure of the apparatus is complicated.

  In view of the circumstances as described above, an object of the present technology is to provide a discharge detection device capable of performing a cleaning process without requiring a complicated structure for generating negative pressure, a liquid discharge device including the discharge detection device, and a cleaning method therefor Is to provide.

In order to achieve the above object, an ejection detection device according to one embodiment includes a detector and an electric field generation mechanism.
The detector is provided so as to be opposed to a head that discharges the liquid, and detects a discharge state of the liquid.
The electric field generating mechanism is provided in the detector and applies an electrostatic force to the liquid in the head.

  An electrostatic force is generated in the liquid by the electric field generating mechanism provided in the detector, and the liquid can be sucked from the head. Thereby, impurities mixed in the liquid in the head can be removed without requiring a complicated structure for generating negative pressure.

  Hereinafter, the process of removing impurities mixed in the liquid in the head is referred to as an electrostatic suction cleaning process.

  For example, the detector may include a receiving member that receives the liquid ejected from the head, and the electric field generation mechanism may include a conductor disposed on the receiving member.

  The head may include a plurality of nozzles that discharge the liquid. In that case, the detector has a first region and a second region. The first region is a region provided between the head and the receiving member, and a detection target droplet that is a detection target of an ejection state among the liquid ejected from the plurality of nozzles passes through the first region. It is an area. The second region is a region provided between the head and the receiving member, and non-detection target droplets other than the detection target of the ejection state among the liquid ejected from the plurality of nozzles. It is a passing area. The conductor forms an electric field between the conductor and the head, and is disposed at a position where an electric field is formed in a region including the second region and no electric field is formed in the first region. Has been. Thereby, the electrostatic suction cleaning process can be executed while detecting the ejection state of the first droplet by the detector. An electrostatic suction cleaning process can be performed.

  Alternatively, the conductor is disposed at a position where an electric field is formed in both the first and second regions. As a result, an electric field can be generated in a wide area, and the processing time of electrostatic suction cleaning can be shortened.

  The head may include a plurality of nozzles that discharge the liquid and are arranged in a predetermined direction. In this case, the discharge detection device further includes a moving mechanism that moves the detector in the arrangement direction of the plurality of nozzles. As a result, the discharge state detection process and the electrostatic suction cleaning process can be performed while moving the detector, so that an efficient process can be performed.

  A liquid ejection device according to one aspect includes a head and the ejection detection device described above.

  The liquid ejection device may further include a wiping member, a support base, and a moving mechanism. The wiping member performs cleaning by contacting the head. The support base integrally supports the discharge detection device and the wiping member. The moving mechanism moves the support base. The head can be cleaned by the wiping member supported by the support base being moved by the moving mechanism. Further, since the discharge detection device and the support base are integrally supported by the support base, the liquid discharge device becomes compact.

The cleaning method which concerns on one form includes detecting the discharge state of the said liquid with the detector provided so that it could be arrange | positioned facing the head which discharges a liquid.
An electrostatic force is applied to the liquid in the head by an electric field generating mechanism provided in the detector.

  The head may include a plurality of nozzles that discharge the liquid and are arranged in a predetermined direction. In that case, an electrostatic force is applied to the liquid by the electric field generating mechanism while moving the detector in the arrangement direction of the nozzles. As a result, the discharge state detection process and the electrostatic suction cleaning process can be performed while moving the detector, so that an efficient process can be performed.

  The discharge state of the first nozzle may be detected by the detector by discharging the liquid from the first nozzle among the plurality of nozzles. In this case, the electric field generating mechanism applies an electrostatic force to the liquid while detecting the discharge state of the liquid by the first nozzle by the detector, so that the first nozzle among the plurality of nozzles is The liquid is discharged from a different second nozzle. Then, while moving the detector, the discharge of the first droplet from the first nozzle and the discharge of the second droplet from the second nozzle are performed for the plurality of nozzles. Repeated in order. Accordingly, the discharge state detection process and the electrostatic suction cleaning process are sequentially performed on the plurality of nozzles while the detector is moved, so that an efficient process can be performed.

  After the liquid discharge state is detected by the detector, an electrostatic force may be applied to the liquid by the electric field generation mechanism.

  Alternatively, after the electrostatic force is applied to the liquid by the electric field generation mechanism, the discharge state of the liquid may be detected by the detector. After the discharge state of the liquid is detected by the detector, when it is determined that the discharge state is abnormal, an electrostatic force may be applied to the liquid again by the electric field generation mechanism.

  As described above, according to the present technology, the cleaning process can be performed without requiring a complicated structure for generating the negative pressure.

FIG. 1 is a schematic side view illustrating a configuration of a liquid ejection apparatus according to an embodiment of the present technology. FIG. 2 is a schematic front view of the configuration of the liquid ejection head and its peripheral part in the liquid ejection apparatus. FIG. 3 is a plan view showing a part of the liquid ejection head on the side where the nozzles (ink ejection holes) are arranged. FIG. 4 is a perspective view showing the liquid detection unit. FIG. 5 is a perspective view showing the detection block. FIG. 6 is a perspective view showing an arrangement relationship of the optical sensor, the aperture plate, and the like. FIG. 7 is a cross-sectional view of the detection block viewed in the X-axis direction. 8 is a cross-sectional view taken along line AA in FIG. FIG. 9 is a perspective view showing a moving mechanism that moves the liquid detection unit along the longitudinal direction (X-axis direction) of the line-type liquid ejection head. FIG. 10 is a diagram for explaining a detection processing area in the detection block and other non-detection areas. FIG. 11 is a perspective view for explaining a non-detection region where the preceding ejection is performed. FIG. 12 is a diagram for explaining an example of the preceding ejection process. FIG. 13 is a diagram for explaining an example of the preceding ejection process. FIG. 14 is a diagram for explaining an example of the detection process. FIG. 15 is a cross-sectional view showing another embodiment of the detection block. FIG. 16 is a block diagram showing an electrical configuration for realizing the detection process and the electrostatic suction cleaning process.

  Hereinafter, embodiments of the present technology will be described with reference to the drawings.

  [Configuration of liquid ejection device]

  FIG. 1 is a schematic side view illustrating a configuration of a liquid ejection apparatus according to an embodiment of the present technology. FIG. 2 is a schematic front view of the configuration of the liquid ejection head and its peripheral part in the liquid ejection apparatus.

  The liquid discharge apparatus 1 includes a paper feed unit 100, a liquid discharge unit 200, a platen 300, a suction unit 400, and a liquid detection unit 500 (see FIG. 2) as a discharge detection apparatus.

  The paper supply unit 100 supplies cut paper and roll paper used as the recording sheet 1000. The paper feed unit 100 includes a paper feed tray 11 on which roll paper is loaded among the recording sheets 1000 and a manual feed tray 12 on which cut paper is loaded among the recording sheets 1000.

  The liquid discharge unit 200 has a function of recording an image on a recording sheet 1000 that is fed and conveyed.

  The liquid discharge unit 200 includes a liquid discharge head 21 as a head capable of discharging liquid. The liquid discharge head 21 has a long shape extending along the X-axis direction, that is, a line type head.

  FIG. 3 is a plan view showing a part of the liquid ejection head 21 on the side where the nozzles (ink ejection holes) are arranged.

  The liquid discharge head 21 includes module heads 22, 22,... That discharge liquids (inks) having different colors, respectively. One module head 22 has a long shape extending along the X axis. These module heads 22, 22,... Are arranged along the X and Y axis directions.

  The lower surfaces of the module heads 22, 22,... Are formed as liquid ejection surfaces 22a, 22a,. A plurality of head chips 23, 23,... Are arranged in a zigzag manner on one liquid discharge surface 22a (the lower surface of one module head 22). One head chip 23 is provided with a plurality of nozzles (not shown) that eject ink. These nozzles in one head chip 23 are arranged in a straight line along the X-axis direction.

  The liquid discharge head 21 is provided with a plurality of electrothermal conversion elements (not shown). The electrothermal conversion element is selectively driven based on the image information, and the ink is ejected from the hole of each nozzle by the film boiling pressure generated in the ink due to the heat generated by the electrothermal conversion element.

  The liquid discharge head 21 is held by a head frame 24 formed in a frame shape while being covered from the outer peripheral side.

  As shown in FIG. 1, between the paper feed unit 100 and the liquid discharge unit 200, from the paper feed unit 100 side, the paper feed roller 13 and the paper feed pinch roller 14 opposed thereto, the transport roller 16 and the same are opposed. A pinch roller 17 is disposed. An edge sensor 15 is disposed between the paper feed pinch roller 14 and the pinch roller 17. The paper feed roller 13 and the transport roller 16 are each driven by a drive motor (not shown).

  An encoder and an encoder sensor (not shown) are attached to the transport roller 16. The conveyance speed of the recording sheet 1000 is detected by the encoder and the encoder sensor, and based on the detected conveyance speed, the discharge timing of the ink discharged from the liquid discharge head 21 is controlled so as to be synchronized with the conveyance speed.

  A set of the transport roller 18 and the pinch roller 19 is disposed on the opposite side of the set of the transport roller 16 and the pinch roller 17 with the liquid discharge unit 200 interposed therebetween. The transport roller 18 is driven by a drive motor (not shown).

  The platen 300 is disposed to face the lower side of the liquid discharge unit 200 and has a function of holding the recording sheet 1000. The upper surface of the platen 300 is formed as a holding surface 31 that holds the conveyed recording sheet 1000 (see FIG. 2).

  The platen 300 is movable in a direction (Z-axis direction) in contact with and away from the liquid discharge surfaces 22a, 22a,... Of the liquid discharge unit 200 by a drive mechanism (not shown).

  The suction unit 400 has a function of generating a suction force for sucking the recording sheet 1000 on the platen 300. The suction unit 400 includes a suction fan 41 and an air suction path 42.

  When the suction fan 41 rotates, air is sucked from the platen 300 through the air suction path 42, and the recording sheet 1000 is sucked by the platen 300 and held by the holding surface 31. At this time, the recording sheet 1000 is attracted to the holding surface 31 of the platen 300 by a suction force that does not hinder its conveyance.

  The suction unit 400 can be moved in the Z-axis direction (vertical direction) integrally with the platen 300 by the drive mechanism (not shown).

  The liquid detection unit 500 mainly has a function of detecting the discharge state of the liquid discharged from the nozzles of the liquid discharge unit 200. Typically, droplets flying are detected by the liquid detection unit 500, and a discharge detection system (described later) electrically connected to the liquid detection unit 500 determines whether the liquid discharge is normal or abnormal. Is done.

  There are two cases when the liquid discharge abnormality occurs. One is a case where liquid ejection is hindered by impurities adhering to the periphery of the nozzle hole on the liquid ejection surfaces 22a, 22a,. The other is a case where liquid ejection is hindered when impurities are accumulated in the nozzles rather than on the liquid ejection surfaces 22a, 22a,. The impurity is a liquid material, dust, bubbles, or the like solidified by thickening.

  As shown in FIG. 2, the liquid detection unit 500 can be disposed at a position facing the liquid discharge surfaces 22 a and 22 a of the liquid discharge head 21. When the liquid ejection apparatus 1 prints on the recording sheet 1000, the liquid detection unit 500 stands by at a standby position that is not opposed to the liquid ejection surfaces 22a, 22a,... (See FIG. 2).

  FIG. 4 is a perspective view showing the liquid detection unit 500. The liquid detection unit 500 includes a detection block 52 that functions as a detector, a cleaning block 56, and a support base 51 that integrally supports them. FIG. 5 is a perspective view showing the detection block 52.

  The support base 51 includes a main body 51a and slide bearings 51b and 51b provided at one end of the main body 51a in the Y-axis direction. The slide bearings 51b and 51b are provided apart from each other in the X-axis direction that is the scanning direction of the liquid detection unit 500. The support base 51 is attached with a belt attachment portion 51c that protrudes outward below the slide bearing 51b. A slide roller 51d is rotatably provided at the other end of the main body 51a in the Y-axis direction. An encoder sensor 51e is disposed at a position near the slide roller 51d.

  As shown in FIG. 5, the detection block 52 has a support body 52a. The support 52a functions as a receiving member that receives the liquid discharged from the liquid discharge head 21. The support body 52a includes a base portion 52b extending along the Y-axis direction, and projecting portions 52c and 52c projecting upward from the base portion 52b at both ends in the Y-axis direction. The base portion 52 b functions as a tray for the liquid discharged from the liquid discharge head 21. The projections 52c and 52c are provided with two insertion through holes spaced apart in the X-axis direction. Two optical sensors 53 and 54 are inserted and disposed in these insertion through holes.

  Opening plates 52d and 52d are attached to the opposite sides of the protrusions 52c and 52c in the support 52a. Transmission holes 52e and 52e are formed in the opening plate 52d at positions facing the insertion through holes, respectively.

  FIG. 6 is a perspective view showing the positional relationship between the optical sensors 53 and 54, the aperture plates 52d and 52d, and the like. Antifouling plates 52f and 52f are attached to the side surfaces of the opening plates 52d and 52d facing each other. The antifouling plates 52f and 52f are made of a material that transmits infrared light. By providing the antifouling plates 52f and 52f, mist of ink droplets that may be generated when the liquid ejected from the liquid ejection head 21 is dropped adheres to the aperture plates 52d and 52d. It is prevented from becoming dirty.

  The optical sensors 53 and 54 are transmissive sensors. The optical sensor 53 includes a light emitter 531 and a light receiver 532. The optical sensor 54 includes a light emitter 541 and a light receiver 542. The light emitter 531 of the optical sensor 53 and the light receiver 542 of the optical sensor 54 are attached to one protrusion 52c. The light emitter 541 of the optical sensor 54 and the light receiver 532 of the optical sensor 53 are attached to the other protrusion 52c. That is, the traveling directions of the detection light emitted from the light emitters 531 and 541 are opposite to each other. Accordingly, the light receiver 532 can be prevented from receiving light from the light emitter 541, and the light receiver 542 can be prevented from receiving light from the light emitter 531.

  For example, LEDs (Light Emitting Diodes) are used as the light emitters 531 and 541 and the light receivers 532 and 542. An LD (Laser Diode) may be used instead of the LED. Although infrared light is used as detection light of the optical sensors 53 and 54, visible light or the like may be used.

  The liquid droplets ejected from the liquid ejection head 21 pass through the light beam of the detection light emitted from the light emitters 531 and 541, so that it is detected that the liquid droplets from the liquid ejection head 21 are flying.

  By providing the two optical sensors 53 and 54 in the X-axis direction, that is, the direction in which the liquid detection unit 500 moves (scans), it is possible to improve the detection processing speed of droplet flight.

  The width of the detection block 52 in the Y-axis direction is set to be substantially the same as or larger than the width of the liquid ejection head 21 in the Y-axis direction.

  As shown in FIGS. 4 and 5, the absorber 52g is inserted and held in the base 52b of the support 52a. When the ink ejected from the liquid ejection head 21 is dropped, the absorber 52g absorbs the ink before the ink becomes mist. By providing the absorber 52g, occurrence of erroneous detection in the detection block 52 due to the presence of mist can be prevented, and contamination of the internal structure of the liquid ejection apparatus 1 due to mist can be prevented.

  As shown in FIG. 4, the cleaning block 56 includes a cleaner 56c (wiping member) and a cleaner holder 56b that rotatably holds the cleaner 56c. The cleaner 56c is in contact with the liquid ejection surfaces 22a, 22a,... Of the liquid ejection head 21, and has a function of removing dust and the like attached to the liquid ejection surfaces 22a, 22a,. As will be described later, when the liquid detection unit 500 moves between the liquid discharge unit 200 and the platen 300, the cleaner 56c contacts the liquid discharge surfaces 22a, 22a,.

  At the time of cleaning by the cleaner 56c, the cleaner 56c does not rotate, and a surface of a certain region of the surface of the cleaner 56c contacts the liquid discharge surfaces 22a, 22a,. Then, the liquid detection unit 500 is moved by wiping by the moving mechanism 57 (see FIG. 9) to be described later in a state where the surface of the fixed area of the cleaner 56c is in contact with the liquid discharge surfaces 22a, 22a,. A cleaning process is performed.

  Then, the cleaner 56c rotates until the next cleaning, so that the surface of another fixed region comes into contact with the liquid discharge surfaces 22a, 22a,.

  FIG. 7 is a cross-sectional view of the detection block 52 viewed in the X-axis direction. 8 is a cross-sectional view taken along line AA in FIG.

  A detection circuit board 58 electrically connected to the optical sensors 53 and 54 is disposed below the support body 52a. The detection circuit board 58 includes an LED driver that drives the optical sensors 53 and 54 and the like.

  An absorber 52g is disposed in the recess 52j of the support 52a, and electrodes 52h and 52h, which are conductors, are provided on the bottom surface in the recess 52j. An absorber 52g is disposed on the electrodes 52h and 52h.

  The electrodes 52h and 52h are connected to the DC power source 60 via, for example, an FPC (Flexible Printed Circuit) or FFC (Flexible Flat Cable) (not shown). Further, the conductive portion of the liquid discharge head 21 is set to a common potential or a ground potential. The electrodes 52h and 52h are designed to be physically conductive outside the recess 52j of the support 52a and to have the same potential. With such a configuration, a DC electric field is formed between the electrodes 52 h and 52 h and the liquid ejection head 21.

  When a DC voltage is applied to the electrodes 52h and 52h, for example, negative charges are charged in the electrodes 52h and 52h. The liquid (ink) in the nozzles in the liquid discharge head 21 has conductivity. Therefore, a positive charge is charged to the liquid in the liquid discharge head 21 by electrostatic induction. As a result, an electrostatic force is applied to the liquid, and the action of sucking the liquid (droplet) P from the nozzle occurs. In this case, at least the electrodes 52h and 52h function as an electric field generating mechanism that generates an electric field with the liquid P. The voltage applied to the electrodes 52h and 52h is −100 V to −2000 V, but is not limited to this range.

  An insulating sheet (not shown) is attached to the surfaces of the electrodes 52h and 52h. Thereby, electric leakage from the electrodes 52h and 52h to the liquid absorbed by the absorber 52g is prevented.

  FIG. 9 is a perspective view showing a moving mechanism that moves the liquid detection unit 500 along the longitudinal direction (X-axis direction) of the line-type liquid discharge head 21.

  The moving mechanism 57 has a drive part 57a including a motor. An endless belt 57b is connected to the drive part 57a. The liquid detection unit 500 is connected to the endless belt 57b via the belt attachment portion 51c described above. A guide shaft 57c is inserted into the slide bearings 51b and 51b of the liquid detection unit 500. The liquid detection unit 500 is slidably connected to the guide rail 57d. The drive unit 57a drives the endless belt 57b, so that the liquid detection unit 500 can move along the guide shaft 57c and the guide rail 57d.

  The moving mechanism is not limited to such a belt driving mechanism, and may be a ball screw driving mechanism, a linear motor driving mechanism, a rack and pinion driving mechanism, or the like.

  A scale (not shown) extending along the X-axis direction is provided at the lower part of the support base 51 (see FIG. 4). When the encoder sensor 51e reads this scale, the system that controls the moving mechanism 57 recognizes an arbitrary position of the liquid detection unit 500 in the X-axis direction. The moving mechanism 57 is configured to move the liquid detection unit 500 by a distance that is substantially the same as or longer than the width of the liquid ejection head 21 in the X-axis direction. Therefore, the discharge detection system to be described later can recognize the discharge state of droplets from all the nozzles of the liquid discharge head 21.

  10A and 10B are diagrams for explaining the detection processing area in the detection block 52 and the other non-detection areas.

  Here, typically, among the head chips 23, 23,... Arranged in a zigzag in one module head 22, as shown in FIG. , 23,... Are discharged by one optical sensor 53. Further, among the head chips 23, 23,... Arranged in a zigzag in the one module head 22, the liquid ejection of the head chips 23, 23,. Another optical sensor 54 is used to detect the state. As described above, since the head chips 23, 23,... To be detected are different depending on the optical sensors 53, 54, FIG. 10A and FIG. 10B are separated. This can be easily understood with reference to FIG.

  As will be described later, it is not essential to use two optical sensors 53 and 54 in the present technology. It is not the essence of the present technology that the two electrodes 52h and 52h are divided into two when the two optical sensors 53 and 54 are provided.

  As shown in FIGS. 10A and 10B, the optical sensors 54 and 53 detect the discharge state of the droplets P that are the detection targets of the discharge state. That is, the detection block 52 is an area provided between the head chip 23 and the support 52a, and a detection area (first area) through which the droplet P (detection target liquid droplet) to be detected passes. A1. In addition, the detection block 52 is an area provided between the head chip 23 and the support 52a, and a non-detection area (first detection area) through which droplets Pc (non-detection target liquid droplets) other than the detection target of the ejection state pass. 2 region) A2.

  The droplet Pc passing through the region A2 is a droplet ejected by “preceding ejection” described later. In this embodiment, electrostatic suction cleaning processing is performed by applying a voltage to the electrodes 52h and 52h during the preceding discharge. In the present embodiment, the electrodes 52h and 52h are arranged at the position of the support 52a so as not to form an electric field in the region A1.

  [Detection of discharge state by detection block of liquid detection unit and preceding discharge]

  Next, an example of ejection state detection processing by the detection block 52 will be described. The detection process is performed when the detection block 52 moves from the detection start end at which detection starts to the detection end end at which detection ends. The movement of the detection block 52 here may be either continuous (smooth) movement or step feed movement.

  In the detection process, the preceding discharge is performed prior to the liquid discharge operation from the nozzle to be detected. The pre-discharge is a liquid discharge operation from a nozzle that exists in a fixed region at a fixed distance on the detection end end side from the detection position.

  By performing the preceding discharge, it is possible to recover the state of the nozzle in an abnormal discharge state or to prevent the liquid in the nozzle from drying (thickening).

  Further, the preceding discharge is sequentially performed at a predetermined timing by nozzles in a certain region along the moving direction (X-axis direction) of the liquid detection unit 500. For example, the liquid is ejected substantially simultaneously from a certain number of adjacent nozzles so that the ejection is sequentially performed by the plurality of nozzles.

  Further, at the time of preceding ejection, an electric field is formed between the nozzles 52h and 52h and the electrodes 52h and 52h by the electrodes 52h and 52h for the nozzles that are the targets of the preceding ejection. Thereby, at the time of preceding ejection, an electrostatic force is applied to the liquid in the nozzle that performs the preceding ejection, and the liquid is forcibly ejected.

  FIG. 11 is a perspective view for explaining the non-detection area A2 where the preceding ejection is performed. As described above, the non-detection region A2 is outside the detection range of the droplet P to be detected. For example, the position between the optical paths S and S of the detection light and the optical path S of the detection light by the optical sensor 53 This is the position ahead in the movement direction X1. The distance between the nozzle that ejects the droplet P to be detected and the nozzle that ejects the droplet Pc to be the preceding ejection can be set as appropriate.

  12-14 is a figure for demonstrating an example of a preceding discharge process and a detection process. In the following, as an example, a detection process when four module heads 22, 22,... (Heads A to D) are arranged is shown. The heads A to D are heads that discharge different color inks.

  Each module head 22 has head chips 23, 23,... Arranged in a zigzag manner. The head chips 23, 23,... Are distinguished into odd-numbered chips (odd chips) and even-numbered chips (even chips) in order from the detection start end side. As described above, for example, the optical sensor 53 detects the liquid discharge state relating to the nozzles present in the even chips, and the optical sensor 54 detects the liquid discharge state relating to the nozzles present in the odd chips.

  However, without distinguishing between even-numbered chips and odd-numbered chips, even if the liquid discharge state relating to the nozzles present in each head chip 23, 23,... Good.

  In FIG. 13, numbers 1, 2,..., N1, n1, n2,... M + n,. In the description of FIG. 13, an example in which the ejection state is detected by one of the optical sensors 53 (or 54) will be described for the sake of simplicity. The same applies to FIG.

  Before the start of movement of the optical sensor 53 in the X1 direction, the optical sensor 53 is positioned n pitches away from the nozzle 1 at the detection start end (see FIG. 13A). At the start of the movement of the optical sensor 53, the preceding ejection is simultaneously performed at the nozzles existing between m pitches from the nozzles 1 to m.

  When the optical sensor 53 moves to a position immediately below the nozzle 1, the liquid is discharged from the nozzle 1, and the discharge state of the nozzle 1 by the optical sensor 53 is detected (see FIG. 13B). When the discharge state of the nozzle 1 is detected, the preceding discharge is performed from the nozzles existing between m pitches on the detection end end side from the nozzle n.

  Subsequently, the optical sensor 53 moves by one pitch from near the nozzle 1 and is positioned near the nozzle 2. Then, ink is ejected from the nozzle 2, and the ejection state of the nozzle 2 is detected by the optical sensor 53 (see FIG. 13C). When the discharge state of the nozzle 2 is detected, the preceding discharge is performed from the nozzles existing between m pitches on the detection end end side from the nozzle n1.

  Thereafter, as described above, the detection of the liquid discharge state by the optical sensor 53 and the preceding discharge (and the electrostatic suction cleaning process associated therewith) are repeated in order for each nozzle (see FIGS. 13D and E). Immediately before the end of detection, the number of outputs present on the detection end end side is reduced with reference to a nozzle separated by n pitches from the nozzle to be detected. Therefore, the preceding ejection is performed only from the nozzles existing on the detection end end side with reference to the nozzles separated by n pitches from the nozzles to be detected.

  The discharge state of the nozzle located closest to the detection end end is detected by the optical sensor 53, and the detection process of the discharge state of the nozzle ends when the optical sensor 53 moves to the detection end end.

  The above-described nozzle detection processing and preceding ejection processing of the module head for one row are performed for the nozzles for a plurality of rows.

  FIG. 14 shows an example in which liquid is alternately ejected from the nozzles of the heads A and B in the X1 direction, and the ejected liquid is detected by one optical sensor 53. Here, an example in which liquid is not discharged from the nozzle 4 of the head A and the nozzle 5 of the head B is shown. Here, when no liquid is ejected, there is no liquid in the light beam of the detection light of the optical sensor 53, so the output voltage at the time of detection increases. When the threshold voltage Q is set in advance and an output voltage higher than the threshold voltage Q is measured, a nozzle ejection abnormality is detected.

  The control system of the liquid ejecting apparatus 1 specifies a nozzle that is detected to be abnormal in ejection by using together whether or not an output voltage higher than the threshold voltage Q is measured and time (phase) measurement. be able to.

  By adopting such a method, the discharge state of each nozzle of the two module heads 22 and 22 is detected substantially simultaneously by one movement of the liquid detection unit 500 from the detection start end to the detection end end. Can do. Therefore, this method can be extended to detection of the discharge state of each nozzle of three or more module heads 22, 22,.

  In the above detection process, the discharge state is determined based on the threshold voltage Q as shown in FIG. 14, but the discharge state may be detected by the following method.

  For example, it is known that when the liquid is ejected but the ejection state is abnormal, the flying speed of the liquid is slower than the standard speed (the flying speed of the liquid when the ejection state is normal). When the flying speed of the liquid is slower than the standard speed, the time for the liquid to block the detection light becomes longer. Since this length appears as the width of the time axis of the signal of the output voltage, it is possible to detect whether the ejection state is normal or abnormal depending on whether the time length exceeds a preset threshold value.

  Alternatively, there is a method in which a plurality of droplets are continuously discharged from one nozzle that is a detection target of the discharge state so that the droplet of detection light includes a plurality of droplets at a time (simultaneously). In this case, a waveform in which individual pulses corresponding to successive droplets are synthesized is obtained as the output voltage of the optical sensor 53 (or 54). When the ejection state is abnormal, the level of the synthesized waveform, that is, the level (absolute value) of the output voltage increases as the speed of each droplet decreases. Accordingly, in this case as well, the discharge state can be detected by threshold determination.

  As described above, in the present embodiment, an electric field is formed between the electrodes 52h and 52h and the electrodes 52h and 52h by the electrodes 52h and 52h provided in the detection block 52. Thereby, the electrostatic suction cleaning process is executed. That is, electrostatic force is generated in the liquid in the nozzle that performs the preceding discharge, and the liquid can be sucked from the head. Thereby, impurities mixed in the liquid in the liquid discharge head 21 can be surely removed without requiring a complicated structure (see Patent Documents 1 and 2) for generating negative pressure.

  That is, this embodiment can remarkably improve the reliability of the recovery operation that eliminates the ejection abnormality, and can reliably perform the recovery process. In addition, the amount of ink consumed in the recovery operation can be minimized.

  In particular, the present technology does not employ a structure in which the cap member is adsorbed to the head in order to suck ink with a negative pressure as in the past, and the liquid ejection head 21 is not contacted and gives suction to the liquid. be able to. Thereby, it is possible to prevent the liquid discharge head 21 from being damaged.

  In addition, by providing the electrodes 52h and 52h in the detection block 52 that detects the discharge state, the liquid discharge device 1 becomes more compact than when the detection block 52 and the liquid suction mechanism are provided separately.

  In the present embodiment, the electrostatic suction cleaning process by the preceding discharge can be executed while detecting the liquid discharge state, and the processing time can be shortened.

  In the present embodiment, it is possible to perform an ejection state detection process and an electrostatic suction cleaning process while moving the liquid detection unit 500 by the moving mechanism 57, and thus an efficient process can be performed. On the other hand, in the conventional negative pressure suction method, since the cap member contacts the head, it is impossible to move the cap member while performing the cleaning process.

  Here, the liquid in the nozzle is discharged by the film boiling pressure when the electrothermal conversion element in the nozzle is activated. Therefore, typically, at the time of preceding discharge, the liquid is discharged by a force obtained by applying a suction force by electrostatic suction to the film boiling pressure. However, at the time of preceding ejection, the electrothermal conversion element does not operate and the film boiling pressure is not applied to the liquid, and the liquid may be ejected only by the electrostatic force due to the electric field of the electrodes 52h and 52h. Thereby, power consumption can be reduced.

  [Ejection state detection processing and electrostatic suction cleaning processing timing]

The order of the discharge state detection process and the electrostatic suction cleaning process basically has the following three patterns.
1. Electrostatic suction cleaning process → discharge state detection process (corresponding to the above embodiment)
2. 2. electrostatic suction cleaning process → discharge state detection process → electrostatic suction cleaning process Discharge state detection process → electrostatic suction cleaning process

  In the pattern 2, the second electrostatic suction cleaning process may be performed for the nozzles that are determined to have an abnormal discharge state. Further, in pattern 2, instead of the first electrostatic suction cleaning process, a flushing process, that is, ejection by driving a nozzle may be used.

  [Other Embodiments of Detection Block]

  FIG. 15 is a cross-sectional view showing another embodiment of the detection block. FIG. 16 is a block diagram showing an electrical configuration for realizing the detection process and the electrostatic suction cleaning process. In the following description, the same components and functions included in the liquid ejection device 1, the liquid detection unit 500, and the like according to the embodiment shown in FIGS. The explanation will be focused on.

  As shown in FIG. 15, the electrode 52k provided in the detection block 152 according to the present embodiment is arranged and large so as to form an electric field in both of the regions A1 and A2, regardless of the above-described regions A1 and A2. Etc. In this example, the electrode 52k is provided on substantially the entire bottom surface of the recess 52j of the support 52a.

  A switch 67 is connected between the electrode 52k and the DC power source 60. The switch 67 can be switched by the CPU 30. When the switch 67 is turned on by the CPU 30, a DC voltage is applied to the electrode 52k to form an electric field. Thereby, an electrostatic suction cleaning process is performed.

  When the liquid discharge state is detected, the switch 67 is turned off. During the electrostatic suction cleaning process, the switch 67 is turned on.

  For example, the discharge state of each nozzle is detected while the liquid detection unit 500 moves while the switch 67 is OFF. Thereafter, the switch 67 is turned on, and the electrostatic suction cleaning process is performed while the liquid detection unit 500 moves. The movement here may be either continuous (smooth) movement or step feed movement.

  In this case, as will be described later, the CPU 30 may specify a nozzle for which the ejection state is determined to be abnormal, and perform an electrostatic suction cleaning process on the specified nozzle.

  In the present embodiment, the electrode 52k can generate an electric field in a wide area, and the processing time of electrostatic suction cleaning can be shortened.

  As shown in FIG. 16, this circuit includes a head drive circuit 25, an LED driver 26, a current / voltage converter 27, an amplifier 28, a voltage comparator 65, a CPU 30 and the like.

  The head drive circuit 25 drives an ejection mechanism (not shown) (such as the electrothermal conversion element described above) by the liquid ejection head 21.

  The LED driver 26 drives the light emitters 531 and 541 to generate detection light in them.

  The CPU 30 outputs a control signal to the head driving circuit 25, the LED driver 26, the driving unit 57 a of the moving mechanism 57 described above, or other systems in the liquid ejection apparatus 1. In particular, the CPU 30 sends control signals for the liquid discharge state detection process and the electrostatic suction cleaning process to the head drive circuit 25 and the switch 67.

  The current / voltage converter 27 converts the current detected by the light receivers 532 and 542 into a voltage. The amplifier 28 amplifies the signal having this voltage.

  The voltage comparator 65 compares the voltage signal obtained by the amplifier 28 with the threshold voltage Q described above, and outputs a signal obtained by the comparison.

  A signal obtained by the voltage comparator 65 is input to the CPU 30. The CPU 30 controls the head drive circuit 25, for example, based on the signal. In this case, the CPU 30 identifies the nozzle whose discharge state is determined to be abnormal, and performs an electrostatic suction cleaning process or a flushing process on the identified nozzle. Alternatively, the CPU 30 may restrict future use of the nozzle determined to be abnormal.

  Note that the electrical configuration of the detection block 52 shown in FIGS. 7 and 8 can be substantially the same as the configuration shown in FIG.

  [Wiping with cleaning block]

  The timing of the wiping process using the cleaner 56c of the cleaning block 56 may be any time. Typically, wiping is performed before the detection process and the electrostatic suction cleaning process. There are the following two forms before the detection process and the electrostatic suction cleaning process.

  One is a mode in which, for example, after the wiping process by the movement of the liquid discharge head 21 by the length of at least one time of the liquid detection unit 500 is completed, the above-described detection process and electrostatic suction cleaning process are performed. .

  The other is a mode in which, for example, at least one movement of the liquid detection unit 500 is performed for the length of the liquid ejection head 21, and three processes of the wiping process, the detection process, and the electrostatic suction cleaning process are performed. It is. In this case, the cleaning block 56 moves at the head.

  [Other embodiments]

  The present technology is not limited to the embodiments described above, and other various embodiments are realized.

  The arrangement, shape, size, and the like of the electrodes 52 of the electric field generating mechanism can be changed as appropriate as long as the positions can realize the above-described embodiments. For example, the electrode may be disposed at a position where the support 52a is sandwiched between the electrode and the liquid ejection head 21, that is, on the lower surface side of the support 52a.

  In the embodiment shown in FIGS. 7 to 13, the mode in which the electrostatic suction cleaning process is performed at the time of preceding ejection has been described. However, this is not limited to the preceding discharge. That is, the detection process may not be performed subsequent to the electrostatic suction cleaning process, and the electrostatic suction cleaning process may be performed independently at an appropriate time other than printing.

  In the above embodiment, the detection block 52 and the cleaning block 56 are provided integrally. However, these may be separate.

In addition, this technique can also take the following structures.
(1) a detector that is disposed so as to be opposed to a head that discharges liquid and detects a discharge state of the liquid;
An ejection detection device comprising: an electric field generating mechanism that is provided in the detector and applies an electrostatic force to the liquid in the head.
(2) The discharge detection device according to (1),
The detector has a receiving member for receiving the liquid discharged from the head,
The electric field generation mechanism includes a conductor disposed on the receiving member.
(3) The discharge detection device according to (2),
The head has a plurality of nozzles that discharge the liquid,
The detector is
A first region that is provided between the head and the receiving member, and is a region through which a detection target liquid droplet that is a detection target of a discharge state of the liquid discharged from the plurality of nozzles passes. When,
A second region that is provided between the head and the receiving member, and is a region through which non-detection target droplets other than the detection target of the ejection state pass through the liquid ejected from the plurality of nozzles. And having an area
The conductor forms an electric field between the conductor and the head, and is disposed at a position where an electric field is formed in a region including the second region and no electric field is formed in the first region. A discharge detection device.
(4) The discharge detection device according to (2),
The head has a plurality of nozzles that discharge the liquid,
The detector is
A first region that is provided between the head and the receiving member, and is a region through which a detection target liquid droplet that is a detection target of a discharge state of the liquid discharged from the plurality of nozzles passes. When,
A second region that is provided between the head and the receiving member, and is a region through which non-detection target droplets other than the detection target of the ejection state pass through the liquid ejected from the plurality of nozzles. And having an area
The said conductor is arrange | positioned in the position which forms an electric field in both the said 1st and said 2nd area | region. Discharge detection apparatus.
(5) The discharge detection device according to (1) or (2),
The head has a plurality of nozzles arranged in a predetermined direction to discharge the liquid,
The discharge detection apparatus further includes a moving mechanism that moves the detector in an arrangement direction of the plurality of nozzles.
(6) a head for discharging liquid;
Discharge detection having a detector that can be disposed to face the head and that detects the discharge state of the liquid, and an electric field generation mechanism that is provided in the detector and applies electrostatic force to the liquid A liquid ejection device comprising:
(7) The liquid ejection device according to (6),
A wiping member for cleaning in contact with the head;
A support base that integrally supports the discharge detection device and the wiping member;
A liquid ejecting apparatus further comprising a moving mechanism for moving the support base.
(8) By detecting a liquid discharge state by a detector provided so as to be able to be disposed opposite to a liquid discharge head,
A cleaning method in which an electrostatic force is applied to the liquid in the head by an electric field generating mechanism provided in the detector.
(9) The cleaning method according to (8),
The head has a plurality of nozzles arranged in a predetermined direction to discharge the liquid,
A cleaning method in which an electrostatic force is applied to the liquid by the electric field generation mechanism while moving the detector in the arrangement direction of the nozzles.
(10) The cleaning method according to (9),
By detecting the discharge state of the first nozzle by the detector by discharging the liquid from the first nozzle among the plurality of nozzles,
The electric field generating mechanism applies an electrostatic force to the liquid while detecting the discharge state of the liquid by the first nozzle by the detector, and thereby a second different from the first nozzle among the plurality of nozzles. Discharging the liquid from the nozzle of
While moving the detector, the discharge of the first droplet from the first nozzle and the discharge of the second droplet from the second nozzle are sequentially repeated for the plurality of nozzles. Cleaning method.
(11) The cleaning method according to any one of (8) to (10),
A cleaning method in which an electrostatic force is applied to the liquid by the electric field generation mechanism after the discharge state of the liquid is detected by the detector.
(12) The cleaning method according to any one of (8) to (10),
A cleaning method in which an electrostatic force is applied to the liquid by the electric field generation mechanism, and then a discharge state of the liquid is detected by the detector.
(13) The cleaning method according to (12),
A cleaning method, in which, after the discharge state of the liquid is detected by the detector, if it is determined that the discharge state is abnormal, an electrostatic force is again applied to the liquid by the electric field generation mechanism.

P, Pc ... droplet A1 ... detection area A2 ... non-detection area 21 ... liquid ejection head 22 ... module head 51 ... support base 52, 152 ... detection block 52a ... support body 52h, 52k ... electrodes 53, 54 ... optical sensor 56 ... Cleaning block 56c ... Cleaner 57 ... Moving mechanism 500 ... Liquid detection unit

Claims (13)

A detector that is disposed so as to be opposed to a head that discharges the liquid and that detects a discharge state of the liquid;
An ejection detection device comprising: an electric field generating mechanism that is provided in the detector and applies an electrostatic force to the liquid in the head. The discharge detection device according to claim 1,
The detector has a receiving member for receiving the liquid discharged from the head,
The electric field generation mechanism includes a conductor disposed on the receiving member. The discharge detection device according to claim 2,
The head has a plurality of nozzles that discharge the liquid,
The detector is
A first region that is provided between the head and the receiving member, and is a region through which a detection target liquid droplet that is a detection target of a discharge state of the liquid discharged from the plurality of nozzles passes. When,
A second region that is provided between the head and the receiving member, and is a region through which non-detection target droplets other than the detection target of the ejection state pass through the liquid ejected from the plurality of nozzles. And having an area
The conductor forms an electric field between the conductor and the head, and is disposed at a position where an electric field is formed in a region including the second region and no electric field is formed in the first region. A discharge detection device. The discharge detection device according to claim 2,
The head has a plurality of nozzles that discharge the liquid,
The detector is
A first region that is provided between the head and the receiving member, and is a region through which a detection target liquid droplet that is a detection target of a discharge state of the liquid discharged from the plurality of nozzles passes. When,
A second region that is provided between the head and the receiving member, and is a region through which non-detection target droplets other than the detection target of the ejection state pass through the liquid ejected from the plurality of nozzles. And having an area
The said conductor is arrange | positioned in the position which forms an electric field in both the said 1st and said 2nd area | region. Discharge detection apparatus. The discharge detection device according to claim 1,
The head has a plurality of nozzles arranged in a predetermined direction to discharge the liquid,
The discharge detection apparatus further includes a moving mechanism that moves the detector in an arrangement direction of the plurality of nozzles. A head for discharging liquid;
Discharge detection having a detector that can be disposed to face the head and that detects the discharge state of the liquid, and an electric field generation mechanism that is provided in the detector and applies electrostatic force to the liquid A liquid ejection device comprising: The liquid ejection device according to claim 6,
A wiping member for cleaning in contact with the head;
A support base that integrally supports the discharge detection device and the wiping member;
A liquid ejecting apparatus further comprising a moving mechanism for moving the support base. By detecting a liquid discharge state by a detector provided so as to be disposed to face a head for discharging the liquid,
A cleaning method in which an electrostatic force is applied to the liquid in the head by an electric field generating mechanism provided in the detector. The cleaning method according to claim 8, comprising:
The head has a plurality of nozzles arranged in a predetermined direction to discharge the liquid,
A cleaning method in which an electrostatic force is applied to the liquid by the electric field generation mechanism while moving the detector in the arrangement direction of the nozzles. The cleaning method according to claim 9,
By detecting the discharge state of the first nozzle by the detector by discharging the liquid from the first nozzle among the plurality of nozzles,
The electric field generating mechanism applies an electrostatic force to the liquid while detecting the discharge state of the liquid by the first nozzle by the detector, and thereby a second different from the first nozzle among the plurality of nozzles. Discharging the liquid from the nozzle of
While moving the detector, the discharge of the first droplet from the first nozzle and the discharge of the second droplet from the second nozzle are sequentially repeated for the plurality of nozzles. Cleaning method. The cleaning method according to claim 8, comprising:
A cleaning method in which an electrostatic force is applied to the liquid by the electric field generation mechanism after the discharge state of the liquid is detected by the detector. The cleaning method according to claim 8, comprising:
A cleaning method in which an electrostatic force is applied to the liquid by the electric field generation mechanism, and then a discharge state of the liquid is detected by the detector. The cleaning method according to claim 12, comprising:
A cleaning method, in which, after the discharge state of the liquid is detected by the detector, if it is determined that the discharge state is abnormal, an electrostatic force is again applied to the liquid by the electric field generation mechanism.

Images