JP2016198959A - Liquid discharging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the characteristic of liquid by making a nozzle face of a head and an electrode for detecting discharge conductive by liquid droplets when the droplets are lengthened to improve discharge detection accuracy.SOLUTION: A plurality of liquid droplets 700 (700a, 700b) are continuously discharged. The plurality of liquid droplets 700 discharged are linked from a nozzle face 40 on which a nozzle is formed up to the liquid droplet 700 closest to a landing surface of an electrode 101. A distance b from a tip of the liquid droplet 700 on the side close to the landing surface of the plurality of liquid droplets 700 linked to the nozzle face 40 is made shorter than an interval c between the nozzle face 40 and the landing surface.SELECTED DRAWING: Figure 16

Description

  The present invention relates to an apparatus for discharging a liquid.

  As a device that uses a liquid discharge head (droplet discharge head), discharge liquid droplets from the head toward the electrode (electrode member) and measure the electrical changes when the droplets land on the electrode. A device having a discharge detection device that detects non-discharge is known.

  Conventionally, it has a distance detecting means for detecting the distance between the recording head and the platen, and the droplet discharge amount used for the discharge state detection operation is adjusted according to the distance between the recording head and the platen detected by the distance detecting means. What was made to do is known (patent document 1).

Japanese Patent No. 4735120

  As described above, when ejection / non-ejection is detected from an electrical change when a droplet lands on the electrode, the longer the droplet, the greater the amount of charge and the more accurate detection can be performed.

  However, the distance from the nozzle surface of the ejected droplet to the tip of the droplet depends on the waveform and amplitude of the driving waveform for ejecting the droplet, the characteristics of the droplet (for example, viscosity, surface tension), etc. Change and do.

  For this reason, the nozzle surface of the head and the surface of the electrode for detecting discharge (electrode surface, landing surface) may be connected by droplets. When the nozzle surface (head) and the electrode are connected by the liquid droplet, a current flows from the electrode to the head, a voltage is applied to the liquid in the nozzle, and there is a problem that a liquid characteristic changes and an ejection failure occurs.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to enable highly accurate ejection detection while preventing conduction between a head and an electrode.

In order to solve the above problems, an apparatus for ejecting a liquid according to claim 1 of the present invention provides:
A liquid discharge head having a nozzle for discharging droplets;
A discharge detecting means for detecting presence or absence of discharge from an electrical change caused by landing of a droplet discharged from the liquid discharge head on a landing surface of a landing member;
Drive waveform generation means for generating a discharge detection drive waveform for discharging the droplets from the nozzle when detecting the presence or absence of the discharge,
The ejection detection drive waveform includes an ejection pulse for ejecting a plurality of droplets continuously,
The plurality of droplets ejected by the ejection pulse is connected from the nozzle surface on which the nozzle is formed to the droplet closest to the landing surface,
Of the plurality of connected droplets, the distance from the tip of the droplet on the side close to the landing surface to the nozzle surface is shorter than the interval between the nozzle surface and the landing surface. .

  According to the present invention, highly accurate ejection detection can be performed while preventing conduction between the head and the electrode.

It is plane explanatory drawing of the mechanism part of an example of the apparatus which discharges the liquid which concerns on this invention. It is explanatory drawing with which it uses for description of the head of the apparatus. FIG. 4 is a cross-sectional explanatory diagram along a liquid chamber longitudinal direction (a direction orthogonal to a nozzle arrangement direction) for explaining an example of a liquid discharge head. It is explanatory drawing of the liquid chamber longitudinal direction similarly used for description of the droplet discharge operation | movement of the head. It is block explanatory drawing with which the outline | summary of the control part of the apparatus is provided. FIG. 4 is a block explanatory diagram for explaining an example of a part related to head drive control in an image output control unit and a head driver. It is explanatory drawing with which it uses for description of the structure which concerns on the discharge detection in the same apparatus. It is explanatory drawing with which it uses for description of discharge detection operation. It is explanatory drawing of the state from the flight of a droplet when it discharges 1 drop to landing. It is explanatory drawing of the state from the flight of each droplet when it drops a plurality of droplets to landing. It is explanatory drawing of the state from the flight of a droplet to a landing when the several droplet used for description of the electric charge induced | guided | derived to the discharged droplet is discharged. It is explanatory drawing of the state from the flight of a droplet to landing when a plurality of droplets used for explanation of conduction of a head and an electrode by droplet are discharged. Explanation of the state from the flight to the landing of multiple droplets when multiple droplets are ejected when the viscosity of the droplet (liquid) is high to explain the variation in the viscosity of the liquid and the distance from the nozzle surface to the tip of the droplet FIG. Similarly, when the viscosity of the droplet is low, it is an explanatory diagram of a state from the flight of the droplet to the landing when a plurality of droplets are ejected. It is explanatory drawing explaining an example of the drive waveform for discharge detection in 1st Embodiment of this invention. It is explanatory drawing of the state from the flight of a droplet to a landing, when a plurality of droplets are discharged for similarly explaining the parameters (discharge cycle, amplitude) of the drive waveform for discharge detection. It is explanatory drawing of the state from the flight of a droplet to landing when a plurality of droplets are ejected using the standard ejection detection driving waveform for explaining the adjustment of the distance L from the nozzle surface to the tip of the droplet. It is explanatory drawing of the state from the flight of a droplet to landing when a plurality of droplets are ejected using the ejection detection drive waveform with changed amplitude. It is explanatory drawing of the state from the flight of a droplet to landing when a plurality of droplets are ejected using the ejection detection drive waveform in which the ejection cycle is changed. It is explanatory drawing of the state from flight of a droplet to landing when a plurality of droplets used for explanation of a 2nd embodiment of the present invention are discharged. It is explanatory drawing of the state from the flight of a droplet to a landing when the multiple droplet used for description of 3rd Embodiment of this invention is discharged. It is explanatory drawing with which it uses for description of the level of the electrical change of the distance from a nozzle surface to the front-end | tip part of a droplet, and an electrode member. It is a flowchart with which it uses for description of 4th Embodiment of this invention. It is explanatory drawing of an example of a temperature table similarly. It is explanatory drawing with which it uses for description of the amplification factor of the amplitude of the drive waveform for a maintenance with respect to temperature, and the drive waveform for discharge detection similarly. It is a flowchart with which it uses for description of 5th Embodiment of this invention. It is explanatory drawing of an example of a temperature table similarly. It is explanatory drawing of the state from the flight of a droplet to landing when a plurality of low-viscosity droplets are discharged using the standard discharge drive waveform. It is explanatory drawing of the state from the flight of a droplet to landing when a plurality of low viscosity droplets are discharged using the discharge drive waveform which changed the discharge cycle similarly. It is a flowchart with which it uses for description of 6th Embodiment of this invention. d It is explanatory drawing of an example of a temperature table similarly.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an apparatus for discharging a liquid according to the present invention will be described with reference to FIG. FIG. 1 is an explanatory plan view of a mechanism portion of the apparatus.

  This apparatus is a serial type apparatus, and a carriage 3 is movably held by a guide member 1 or the like that is bridged between left and right side plates. Then, the carriage 3 reciprocates in the main scanning direction (carriage moving direction) by the main scanning motor 5 via the timing belt 8 spanned between the driving pulley 6 and the driven pulley 7.

  On the carriage 3, liquid discharge heads 4a and 4b (referred to as “head 4” when not distinguished) are mounted. The head 4 ejects, for example, yellow (Y), cyan (C), magenta (M), and black (K) ink droplets. The head 4 is mounted with a nozzle row 4n composed of a plurality of nozzles arranged in the sub-scanning direction orthogonal to the main scanning direction and with the droplet discharge direction facing downward.

  As shown in FIG. 2, the head 4 has two nozzle rows Na and Nb in which a plurality of nozzles 4n are arranged. One nozzle row Na of the head 4a discharges black (K) droplets, and the other nozzle row Nb discharges cyan (C) droplets. One nozzle row Na of the head 4b discharges magenta (M) droplets, and the other nozzle row Nb discharges yellow (Y) droplets.

  On the other hand, as a transport mechanism 51 for transporting the paper 10 facing the head 4, a transport belt 12 serving as transport means is provided. The transport belt 12 is an endless belt and is stretched between the transport roller 13 and the tension roller 14.

  The transport belt 12 rotates in the sub-scanning direction when the transport roller 13 is rotationally driven by the sub-scanning motor 16 via the timing belt 17 and the timing pulley 18.

  Further, a maintenance / recovery mechanism 20 that performs maintenance / recovery of the head 4 on the side of the conveyance belt 12 is disposed on one side of the carriage 3 in the main scanning direction, and an empty space from the head 4 to the side of the conveyance belt 12 is disposed on the other side. Empty discharge receptacles 21 for discharging are respectively disposed.

  The maintenance / recovery mechanism 20 includes, for example, a cap member 20a for capping the nozzle surface (surface on which the nozzle is formed) of the head 4 and a wiper member 20b for wiping the nozzle surface.

  In addition, a discharge detection unit 100 constituting discharge detection means for detecting the presence or absence of droplet discharge is disposed outside the recording area between the transport mechanism 51 and the maintenance / recovery mechanism 20 and capable of facing the head 4. Has been. On the other hand, the carriage 3 is provided with a wiping unit 200 for cleaning the electrode 101 of the discharge detection unit 100.

  Further, an encoder scale 23 having a predetermined pattern is stretched between both side plates along the main scanning direction of the carriage 3, and the encoder sensor 24 is formed of a transmission type photosensor that reads the pattern of the encoder scale 23 on the carriage 3. Is provided. These encoder scale 23 and encoder sensor 24 constitute a linear encoder (main scanning encoder) that detects the movement of the carriage 3.

  Further, a code wheel 25 is attached to the shaft of the transport roller 13 and an encoder sensor 26 including a transmission type photo sensor for detecting a pattern formed on the code wheel 25 is provided. These code wheel 25 and encoder sensor 26 constitute a rotary encoder (sub-scanning encoder) that detects the amount and position of movement of the conveyor belt 12.

  In the apparatus configured as described above, the paper 10 is fed from the paper feed tray onto the transport belt 12 and sucked, and the paper 10 is transported in the sub-scanning direction by the circular movement of the transport belt 12.

  Therefore, by driving the head 4 according to the image signal while moving the carriage 3 in the main scanning direction, ink droplets are ejected onto the stopped paper 10 to record one line. Then, after the sheet 10 is conveyed by a predetermined amount, the next line is recorded.

  Upon receiving a recording end signal or a signal that the trailing edge of the paper 10 has reached the recording area, the recording operation is finished and the paper 10 is discharged.

  Next, an example of the liquid discharge head will be described with reference to FIGS. 3 and 4 are cross-sectional explanatory views along the liquid chamber longitudinal direction (direction perpendicular to the nozzle arrangement direction) of the head.

  In the liquid discharge head, a flow path plate 401, a vibration plate member 402, and a nozzle plate 403 are joined. As a result, the individual liquid chamber 406 through which the nozzle 404 for discharging the droplet 700 communicates through the through hole 405, the fluid resistance portion 407 for supplying the liquid to the individual liquid chamber 406, and the liquid introduction portion 408 are formed.

  Then, the liquid is introduced from the common liquid chamber 410 formed in the frame member 417 to the liquid introduction unit 408 through the filter unit 409 formed in the diaphragm member 402, and individually from the liquid introduction unit 408 through the fluid resistance unit 407. Liquid is supplied to the liquid chamber 406. The “individual liquid chamber” is meant to include what is called a pressurizing chamber, a pressurized liquid chamber, a pressure chamber, an individual flow path, a pressure generating chamber, and the like.

  A columnar shape as actuator means (pressure generating means) for generating energy for pressurizing the liquid in the individual liquid chamber 406 to the surface of the vibration plate member 402 opposite to the individual liquid chamber 406 and discharging the droplet 700 from the nozzle 404. The laminated piezoelectric element 412 is joined. One end of the piezoelectric element 412 is joined to the base member 413, and an FPC 415 that transmits a drive waveform is connected to the piezoelectric element 412. These elements constitute a piezoelectric actuator 411.

  In this example, the piezoelectric element 412 is used in the d33 mode that expands and contracts in the stacking direction. However, the piezoelectric element 412 may be in a d31 mode that expands and contracts in a direction orthogonal to the stacking direction.

  In the liquid discharge head configured as described above, for example, as shown in FIG. 3, the piezoelectric element 412 is contracted and the diaphragm member 402 is deformed by lowering the voltage applied to the piezoelectric element 412 from the intermediate potential Ve. The volume of the individual liquid chamber 406 expands. As a result, the liquid flows into the individual liquid chamber 406.

  Thereafter, as shown in FIG. 4, the voltage applied to the piezoelectric element 412 is increased to extend the piezoelectric element 412 in the stacking direction, and the diaphragm member 402 is deformed in the nozzle 404 direction to contract the volume of the individual liquid chamber 406. . Thereby, the liquid in the individual liquid chamber 406 is pressurized, and the droplet 700 is ejected from the nozzle 404.

  Then, by returning the voltage applied to the piezoelectric element 412 to the intermediate potential Ve, the diaphragm member 402 is restored to the initial position, and the individual liquid chamber 406 expands to generate a negative pressure. At this time, the common liquid chamber 410 From this, the individual liquid chamber 406 is filled with liquid. Therefore, after the vibration of the meniscus surface of the nozzle 404 is attenuated and stabilized, the operation proceeds to the next discharge.

  Next, an outline of the control unit of this apparatus will be described with reference to FIG. FIG. 2 is a block diagram of the control unit.

  The control unit 500 includes a main control unit 500A including a CPU 501 that controls the entire apparatus, a ROM 502 that stores programs executed by the CPU 501 and other fixed data, and a RAM 503 that temporarily stores image data and the like. Yes.

  The control unit 500 also includes a host I / F 506 that controls data transfer with a host (information processing apparatus) 600 such as a PC, an image output control unit 511 that controls driving of the head 4, and an encoder analysis unit 512. I have. The encoder analysis unit 512 inputs and analyzes detection signals from the main scanning encoder sensor 24 and the sub-scanning encoder sensor 26.

The control unit 500 includes a main scanning motor driving unit 513 that drives the main scanning motor 5, a sub-scanning motor driving unit 514 that drives the sub-scanning motor 16, a temperature sensor 518, various sensors, and an actuator 517. I / O 516 is also provided.
It has.

  In addition, the control unit 500 includes a discharge detection unit 531 that measures (detects) an electrical change when a droplet reaches the electrode 101 of the discharge detection unit 100 to determine discharge / non-discharge. In addition, the control unit 500 includes a wiping unit driving unit 532 that drives the driving motor 203 of the wiping unit 200 that wipes the electrode 101 of the discharge detection unit 100.

  The image output control unit 511 includes a data generation unit that generates print data, a drive waveform generation unit that generates a drive waveform for driving and controlling the head 4, a head control signal that selects a required drive signal from the drive waveform, and Data transfer means for transferring print data is included.

  Then, the image output control unit 511 outputs a drive waveform, a head control signal, print data, and the like to the head driver 510 which is a head drive circuit for driving the head 4 mounted on the carriage 3 side. The droplets are ejected from the four nozzles according to the print data.

  The encoder analysis unit 512 includes a direction detection unit 520 that detects the movement direction from the detection signal, and a counter unit 521 that detects the movement amount.

  The control unit 500 controls the movement of the carriage 3 by controlling the driving of the main scanning motor 5 via the main scanning motor driving unit 513 based on the analysis result from the encoder analyzing unit 512. Further, the feeding control of the paper 10 is performed by controlling the driving of the sub-scanning motor 16 via the sub-scanning motor driving unit 514.

  The main control unit 500 </ b> A of the control unit 500 also serves as a discharge control unit, and moves the head 4 to a position facing the discharge detection unit 100 when detecting the discharge of the head 4. Then, the main control unit 500 </ b> A performs droplet discharge from a required nozzle of the head 4 via the image output control unit 511, and determines the droplet discharge state (discharge / non-discharge) based on the detection signal from the discharge detection unit 531. Take control.

  Next, an example of a head drive control portion and an example of a head driver in the image output control unit will be described with reference to the block diagram of FIG.

  The image output control unit 511 includes a drive waveform generation unit 901, a data transfer unit 902, and a discharge detection drive waveform generation unit 903.

  The drive waveform generation unit 901 generates and outputs a common drive waveform Vcom composed of a plurality of ejection pulses within one printing cycle (one drive cycle) during image formation.

  The data transfer unit 902 outputs 2-bit image data (grayscale signals 0 and 1) corresponding to the print image, a clock signal, a latch signal (LAT), and selection signals 0 to 3 which are droplet control signals.

  The selection signals 0 to 3 are 2-bit signals that instruct the opening and closing of the analog switch 915 that is the switch means of the head driver 510 for each droplet. The selection signals 0 to 3 transition to the L level (“0”) when selected, and transition to the H level (“1”) when not selected.

  The discharge detection drive waveform generation unit 903 generates and outputs a discharge detection drive waveform Pv to be given to the piezoelectric element 412 of the head 4 when performing discharge detection.

  The head driver 510 includes a shift register 911 that inputs a transfer clock (shift clock) from the data transfer unit 902 and serial image data (gradation data: 2 bits / 1 channel (1 nozzle)). 510 includes a latch circuit 912 for latching each resist value of the shift register 911 by a latch signal, and a decoder 913 for decoding the gradation data selection signals 0 to 3 and outputting the result.

  Further, the head driver 510 is turned on / off (open / close) by a level shifter 914 that converts the logic level voltage signal of the decoder 913 to a level at which the analog switch 915 can operate, and an output of the decoder 913 provided through the level shifter 914. An analog switch 915 is provided.

  The analog switch 915 is connected to the selection electrode (individual electrode) of each piezoelectric element 412, and the common drive signal Vcom from the drive waveform generation unit 901 and the discharge detection drive waveform Pv from the discharge detection drive waveform generation unit 903 are received. Have been entered.

  Therefore, when image formation is performed, image data (gradation data) is serially transferred and selection signals 0 to 3 are transferred, so that the analog switch 915 is turned on according to the result decoded by the decoder 913. As a result, a required drive pulse (or waveform element) constituting the common drive signal Vcom passes (is selected) and applied to the piezoelectric element 412.

  When performing ejection detection, data for selecting a nozzle for ejecting a droplet for detection is transferred instead of image data, and a signal for selecting all drive waveforms (for example, selection signal 3) is transferred as a selection signal. Thus, the analog switch 915 corresponding to the selected nozzle is turned on. As a result, the ejection detection drive waveform Pv passes and is applied to the piezoelectric element 412, and the ejection detection droplets are ejected.

  Next, a configuration relating to ejection detection in this apparatus will be described with reference to FIG.

  A voltage is applied to the electrode 101 through the electrode 101 disposed at a position that can face the head 4, the detection waveform detection circuit 551 connected to the electrode 101 included in the ejection detection unit 531, and the detection waveform detection circuit 551 ( Voltage applying means 552. The surface of the electrode 101 (the surface on the side facing the head 4) is the landing surface 101a.

  Next, the discharge detection operation will be described with reference to FIG.

  When detecting the droplet discharge state of the head 4, as shown in FIG. 8A, for example, a voltage having a polarity that gives a positive charge to the electrode 101 is applied by the voltage applying unit 552.

  The electrode 101 is charged with a positive charge, a negative charge is induced on the electrode 101 side of the ejected droplet 700, and a positive charge is induced on the head 4 side of the droplet 700. That is, a charge having a polarity opposite to that of the electrode 101 is induced on the electrode 101 side of the droplet 700 in the vicinity of the nozzle.

  At this time, since the liquid in the head 4 is connected to GND, the positive charge on the head 4 side of the droplet 700 moves to GND until the droplet 700 and the head 4 are separated. When the droplet 700 ejected from the head 4 is away from the head 4, the positive charge on the head 4 side of the droplet 700 is ejected in a state where a part of the positive charge remains on the head 4 side of the droplet 700. That is, the charge of the ejected droplet 700 is more negative than the negative charge.

  In this state, when the droplet 700 is ejected and landed on the electrode 101, the positive charge of the electrode 101 and the negative charge of the droplet 700 cancel each other as shown in FIG. 8B. At this time, an electrical change of the electrode 101 appears as shown in FIG. By detecting this with the detection waveform detection circuit 551, ejection / non-ejection of droplets can be detected.

  Next, droplets ejected from the head will be described with reference to FIGS. FIG. 9 is an explanatory diagram of a state from the flight of a droplet to landing when one droplet is ejected, and FIG. 10 is an explanatory diagram of a state from the flight of each droplet to landing when a plurality of droplets are ejected.

  In FIGS. 9 and 10, it is assumed that time elapses from the left side to the right side in the drawings, and the nozzles that eject droplets are the same in the case of FIG. The same is true for the following explanation of the state from the flight of the droplet to the landing.

  Since the liquid droplet (droplet) 700 discharged from the head 4 is viscous, the discharged droplet 700 is stretched to some extent while being connected to the head 4, and then the head 4 and the rear end portion of the droplet 700 are separated. Land on the electrode 101.

  At this time, as shown in FIG. 9 or FIG. 10, the ejected droplet 700 is stretched to some extent, and then splits into the main droplet 701 and the other minute droplets 702 in flight.

  By the way, in the discharge detection operation, in order to increase detection accuracy, it is preferable to discharge a plurality of droplets 700 continuously.

  For example, as shown in FIG. 10, a plurality of droplets 700 (700a, 700b, 700c, etc.) are continuously ejected. At this time, by selecting a discharge cycle, a discharge amount, or a discharge speed, before the preceding droplet 700a of the continuous droplets 700a and 700b breaks into the main droplet 701 and the other minute droplets 702, the liquid While the rear end portion of the droplet 700b is connected to the head 4, it can be connected to the front end portion of the following droplet 700b.

  Note that, between the continuous droplets 700b and 700c, the droplet 700b is a leading droplet and the droplet 700c is a trailing droplet. However, in order to simplify the description, the continuous droplets 700a and 700b are the same. I will explain it. Also, three or more droplets 700 can be connected.

  Here, as shown in FIG. 9, the distance from the nozzle surface 40 to the tip of the droplet 700 when only one droplet is ejected (hereinafter referred to as “distance L from the nozzle surface to the tip of the droplet”). Is the distance a.

  Similarly, as shown in FIG. 10, in the case where a plurality of droplets are continuously ejected, the liquid is discharged from the nozzle surface when the trailing edge of the droplet 700a preceding the leading edge of the trailing droplet 700b is not connected. The distance L to the tip of the droplet is the distance a.

  In addition, as shown in FIG. 10, a plurality of droplets 700 connected from the nozzle surface 40 when a plurality of droplets are continuously discharged and the trailing edge of the preceding droplet 700a and the trailing droplet 700 are connected. When the distance from the nozzle surface to the tip of the droplet is the distance L to the tip of the droplet 700 (droplet 700a in FIG. 10) closest to the electrode 101, the distance L is the distance b. .

  At this time, the distance b when a plurality of drops are connected is naturally longer than the distance a when there is one drop or when a plurality of drops are not connected.

  Hereinafter, the “distance L from the nozzle surface to the tip of the droplet” refers to the distance from the nozzle surface 40 to the tip of the droplet 700 closest to the electrode 101 that is connected to the nozzle surface 40. Use as meaning.

  For example, when only one droplet is ejected, the distance to the tip of the droplet 700 (distance a in FIG. 9). In the case where a plurality of droplets are ejected and the preceding droplet is not connected to the following droplet, the distance a is the distance a to the tip of the droplet 700 that is connected to the nozzle surface 40. When a plurality of droplets are ejected and the trailing edge of the preceding droplet is connected to the trailing droplet, the distance from the nozzle surface 40 to the leading edge of the leading droplet 700 (for example, FIG. A distance b) of ten. Further, when a plurality of states occur (for example, when there is a distance a and a distance b as shown in FIG. 10), the maximum distance is defined as “distance L from the nozzle surface to the tip of the droplet”.

  Next, the charge induced in the discharged droplet will be described with reference to FIG. FIG. 11 is an explanatory view of a state from the flight of a droplet to the landing when a plurality of droplets are discharged for the same explanation.

  When ejection / non-ejection is detected by measuring an electrical change when a droplet reaches the electrode 101, the narrower the distance between the head 4 and the electrode 101 is induced in the droplet 700 ejected from the head 4. It is known that the amount of charge increases.

  At this time, as described above, the droplet 700 ejected from the head 4 is moved with respect to the head 4 while being connected to the head 4. Therefore, the droplet 700 ejected from the head 4 can be electrically considered as a part of the head 4 in a state where it is connected to the head 4.

  Accordingly, the longer the distance from the nozzle surface 40 to the tip of the droplet 700, the shorter the distance between the tip of the droplet 700 and the electrode 101, that is, the shorter the distance between the head 4 and the electrode 101. Is considered the same. Accordingly, when the distance L from the nozzle surface to the tip of the droplet is longer, the amount of charge induced in the droplet is larger than when the distance L is shorter.

  In this case, as shown in FIG. 11, after the discharged droplet 700 (700a, 700b) is separated from the nozzle surface 40, no charge is induced in the droplet 700. However, since the preceding droplet 700b is connected to the head 4 by connecting the preceding droplet 700a to the preceding droplet 700a, the following droplet 700b and the preceding droplet 700a connected to the head 4 are connected. While being connected, charge is again induced in the preceding droplet 700a.

  That is, a plurality of droplets 700 are ejected to generate a drive waveform that generates ejection in which the plurality of droplets 700 are connected, so that the closest to the electrode 101 among the plurality of droplets 700 connected from the nozzle surface 40. The distance L to the tip of the droplet 700 becomes longer, and the charge induced in the leading droplet 700 increases.

  This increases the detection accuracy when detecting ejection / non-ejection by measuring the electrical change when the droplet 700 lands on the electrode 101.

  Next, the conduction between the head and the electrode by the liquid droplet will be described with reference to FIG. FIG. 12 is an explanatory diagram of a state from the droplet flying to the landing when a plurality of droplets are discharged for the same explanation.

  First, since the droplet 700 ejected from the head 4 has a very small volume, in order to induce a charge necessary for detecting ejection / non-ejection of the droplet 700, the distance between the head 4 and the electrode 101 is extremely small. It is necessary to support at a close distance and with high accuracy. For example, the distance between the electrode 101 and the nozzle surface 40 of the head 4 is set to 5 mm or less.

  On the other hand, as described above, the distance L from the nozzle surface to the tip of the droplet is such that a plurality of droplets 700 (for example, 700a and 700b) are connected to increase the charge amount from the nozzle surface 40. It is preferable to increase the distance to the tip of the droplet 700.

  Therefore, as shown in FIG. 12, when a plurality of droplets 700a and 700b are connected, the distance from the nozzle surface 40 to the tip of the droplet 700a is longer than the distance between the nozzle surface 40 of the head 4 and the electrode 101. May be.

  At this time, as shown in FIG. 12, the head 4 and the electrode 101 are electrically connected by the connected droplet 700 (700a, 700b), a current flows through the droplet 700 connected from the electrode 101 to the head 4, and the liquid in the nozzle When a voltage is applied to the liquid, there is a case where the characteristics of the liquid change and ejection failure occurs.

  Therefore, in the present invention, the distance L from the nozzle surface to the tip of the droplet is made shorter than the interval (distance) between the nozzle surface of the head and the surface (landing surface) of the electrode while connecting a plurality of droplets. Thus, the occurrence of defective discharge due to the connection between the head and the electrode via the droplet is suppressed.

  Next, changes in the viscosity of the liquid and the distance from the nozzle surface to the tip of the droplet will be described with reference to FIGS. FIG. 13 is an explanatory diagram of a state from the flight to landing of a droplet when a plurality of droplets are ejected for explanation when the viscosity of the droplet (liquid) is high, and FIG. 14 is an explanation when the viscosity of the droplet is low. It is explanatory drawing of the state from the flight of a droplet when it discharges the multiple droplet to provide to landing.

  The distance L from the nozzle surface to the tip of the droplet is a value such as a waveform element or amplitude of an ejection detection drive waveform for ejecting the droplet 700, or a characteristic value (for example, viscosity or surface tension) of the droplet. It depends on.

  For example, the viscosity of the liquid becomes high in a low temperature environment, and the viscosity and surface tension of the ejected droplet 700 are relatively increased as compared to the high temperature environment. It becomes difficult to leave.

  On the other hand, since the viscosity of the liquid is low in a high temperature environment and the viscosity and surface tension of the droplet 700 are relatively decreased as compared with the low temperature environment, the rear end portion of the droplet 700 is separated from the nozzle surface 40 of the head 4. It becomes easy.

  For example, in a low temperature environment, a liquid droplet that leaves the nozzle surface 40 of the head 4 in 23 μs from the start of ejection comes away from the nozzle surface 40 of the head 4 in 17 μs from the start of ejection in a high temperature environment.

  That is, when the droplet 700 is continuously ejected in the low temperature environment as compared with the high temperature environment, the subsequent droplet 700b is ejected after the trailing end of the preceding droplet 700a is separated from the nozzle surface 40. Since the time interval until it is shortened, the distance between the trailing edge of the preceding droplet 700a and the following droplet 700b is shortened.

  As a result, in the low temperature environment, as shown in FIG. 13, the trailing edge of the preceding droplet 700a and the trailing droplet 700b are easily connected, and the distance L from the nozzle surface to the leading edge of the droplet is increased. It tends to be easy (becomes distance b). On the other hand, in a high temperature environment, as shown in FIG. 14, the trailing droplet 700b is difficult to connect to the trailing end of the preceding droplet 700a, and the distance L from the nozzle surface to the leading end of the droplet tends to be short. It tends to be (distance a).

  Thus, the distance L from the nozzle surface to the tip of the droplet varies depending on the environmental temperature, the droplet discharge state, the droplet characteristics (for example, viscosity and surface tension), and the like.

  Here, when the distance L from the nozzle surface to the tip of the droplet becomes long, as described above, ejection failure may occur due to conduction between the head 4 and the electrode 101 by the droplet. On the other hand, when the distance L from the nozzle surface to the tip of the droplet is shortened, the amount of charge induced in the droplet is reduced, and in order to detect a normal ejection state, many droplets must be ejected. It may not be.

  Accordingly, it is necessary to generate a discharge detection drive waveform for discharging a droplet with the distance L from the nozzle surface to the tip of the droplet adjusted.

  Here, the adjustment of the drive waveform according to the conventional temperature will be described.

  Conventionally, for example, because the viscosity and surface tension of droplets are higher in a low temperature environment than in a high temperature environment, the amplitude of the drive waveform increases as the temperature decreases, and the amplitude of the drive waveform decreases as the temperature increases. It has a temperature table that sets the rate. Then, the discharge volume is adjusted by adjusting the droplet volume and flight speed by increasing / decreasing the amplitude of the drive waveform at the rate of increase / decrease mounted in the temperature table according to the temperature detection result detected by the temperature detection means mounted inside the device. It is known to generate a drive waveform for performing the above.

  In this driving waveform adjustment method, the distance from the nozzle surface to the tip of the droplet further varies. That is, in a low temperature environment, the trailing edge of the droplet is difficult to separate from the nozzle surface of the head due to an increase in the viscosity and surface tension of the droplet. In addition, since the increase / decrease rate of the amplitude of the driving waveform of the head is set large in order to eject the droplet having the same volume as the high temperature environment, the droplet is ejected more strongly. As a result, the distance from the nozzle surface to the tip of the droplet tends to be longer. That is, the head and the electrode are easily connected by the liquid droplet, and the possibility of occurrence of ejection failure due to conduction is further increased.

  On the other hand, in a high temperature environment, the trailing edge of the droplet is easily separated from the nozzle surface of the head due to a decrease in the viscosity or surface tension of the droplet. In addition, since the rate of increase / decrease in the amplitude of the drive waveform of the recording head is set to be small in order to eject droplets of the same volume as the low temperature environment, the force to eject the droplets becomes weak, and the tip of the droplet from the nozzle surface The distance to the part tends to be further shortened. That is, since the amount of charge induced in the droplet is reduced, it is necessary to increase the discharge amount of the detection droplet in order to perform a normal discharge state detection operation.

  Therefore, in the adjustment of the drive waveform for the purpose of adjusting the volume and flying speed of the conventional droplet, the discharge / non-discharge is detected by measuring the electrical change when the droplet lands on the charged electrode. Is not preferred.

  Next, a first embodiment of the present invention will be described with reference to FIGS. 15 and 16. FIG. 15 is an explanatory diagram for explaining an example of the ejection detection driving waveform in the embodiment, and FIG. 16 is a droplet when a plurality of droplets are ejected for explaining the parameters (ejection period, amplitude) of the ejection detection driving waveform. It is explanatory drawing of the state from flight to landing.

  As described above, the distance L from the nozzle surface per droplet to the tip of the droplet is a distance a, the distance L from the nozzle surface to the tip of the droplet when a plurality of droplets are connected is the distance b, and the head 4 A distance between the nozzle surface 40 and the electrode 101 is a distance c.

  As shown in FIG. 15, the ejection detection drive waveform Pv in this embodiment is composed of ejection pulses P for ejecting droplets.

  The ejection pulse P includes, for example, a falling waveform element af that falls from the intermediate potential Ve, a holding waveform element bh that holds the falling potential, and a rising waveform element cr that rises from the holding potential to the intermediate potential Ve. .

  Here, the potential difference between the intermediate potential Ve and the holding potential is defined as an amplitude (drive voltage) Va. By changing the amplitude Va, the length of the droplet (distance L from the nozzle surface to the tip of the droplet) can be changed as shown in FIG.

  This ejection pulse P is repeatedly generated and output at a period (ejection period) Ta for ejecting droplets. By changing the ejection cycle Ta, the interval between the continuously ejected droplets 700 (for example, the droplets 700a, 700b, and 700c) shown in FIG. 16 can be changed.

  In the present embodiment, as shown in FIG. 16, when the plurality of droplets 700 (700a, 700b, 700c, etc.) are continuously ejected, the ejection detection drive waveform Pv is generated on the nozzle surface. 40 is connected to the droplet 700 closest to the landing surface of the electrode 101, and the distance b from the tip of the droplet 700 close to the landing surface of the electrode 101 to the nozzle surface 40 among the plurality of connected droplets 700 is b. Is a driving waveform for discharging a plurality of droplets 700 so as to be shorter than the distance (distance) c between the nozzle surface 40 and the landing surface of the electrode 101.

  In this way, the plurality of droplets 700 are connected from the nozzle surface 40 to the tip of the droplet 700 closest to the electrode 101, so that the amount of charge induced in the droplet 700 increases and the discharge detection accuracy can be improved. it can.

  The distance b from the tip of the droplet 700 close to the landing surface of the electrode 101 to the nozzle surface 40 among the plurality of connected droplets 700 is the distance between the nozzle surface 40 and the landing surface of the electrode 101 ( By being shorter than the distance (c), it is possible to prevent ejection failure due to the connection between the head 4 and the electrode 101 by the droplet 700.

  Next, adjustment of the distance L from the nozzle surface to the tip of the droplet will be described with reference to FIGS. FIG. 17 is an explanatory diagram of a state from droplet flying to landing when a plurality of droplets are ejected using the standard ejection detection driving waveform. FIG. 18 is an explanatory diagram of a state from droplet flight to landing when a plurality of droplets are ejected using the ejection detection drive waveform with the amplitude changed. FIG. 19 is an explanatory diagram of a state from droplet flight to landing when a plurality of droplets are ejected using the ejection detection drive waveform in which the ejection cycle is changed.

  First, as shown in FIG. 17A, the ejection detection drive waveform in which the ejection pulse P having the amplitude Va0 is repeated at the ejection cycle Ta0 is defined as a standard ejection detection drive waveform Pv0. As shown in FIG. 16, the standard discharge detection drive waveform Pv0 indicates that when a plurality of droplets 700 are continuously discharged under a predetermined condition (for example, a predetermined temperature range), the plurality of droplets 700 are The nozzle surface 40 is connected to the droplet 700 closest to the landing surface of the electrode 101, and the tip of the droplet 700 on the side close to the landing surface of the electrode 101 among the plurality of connected droplets 700 is connected to the nozzle surface 40. A plurality of droplets 700 having a distance b shorter than an interval (distance) c between the nozzle surface 40 and the landing surface of the electrode 101 are discharged.

  However, when a plurality of droplets 700 are continuously ejected with this standard ejection detection driving waveform Pv0, 3 consecutive from the nozzle surface 40 as shown in FIG. Assume that two droplets 700c, 700b, and 700a are connected, and the distance L (L = b) from the nozzle surface to the tip of the droplet is the distance (distance) c between the nozzle surface 40 and the electrode 101.

  Therefore, in the first example shown in FIG. 18, as shown in FIG. 18 (a), a discharge detection drive waveform Pv1 that repeats the discharge pulse P with the amplitude Va1 (Va1 <Va0) at the discharge cycle Ta0 is generated and output. A droplet is discharged.

  By reducing the amplitude Va of the ejection pulse P (Va1 <Va0), the flying speed and volume of the droplet 700 ejected from the head 4 can be reduced. As a result, as shown in FIG. 18B, the liquid column portion is broken in the air before the tip of the droplet 700 reaches the electrode 101, and the head 4 and the electrode 101 are connected by the connected droplet 700. It is possible to prevent conduction.

  In the second example shown in FIG. 19, as shown in FIG. 19A, a discharge detection drive waveform Pv2 that repeats the discharge pulse P with an amplitude Va0 at a discharge cycle Ta2 (Ta2> Ta0) is generated and output. Let the drops be ejected.

  By increasing the ejection cycle Ta of the ejection pulse P (Ta2> Ta0), the distance between the trailing edge of the preceding droplet 700 and the leading edge of the trailing droplet 700 can be increased. Accordingly, as shown in FIG. 19B, the trailing end of the trailing droplet 700 can be separated from the head 4 at the moment when the leading end of the preceding droplet 700 lands on the electrode 101. It is possible to prevent the head 4 and the electrode 101 from being electrically connected by the connected droplet 700.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 20 is an explanatory diagram of a state from the droplet flying to the landing when a plurality of droplets are discharged for explanation of the embodiment.

  In the present embodiment, the interval between the nozzle surface 40 and the landing surface is the interval between the nozzle surface 40 and the surface of the deposit 800 deposited on the surface of the electrode 101. That is, a liquid deposit 800 is generated on the surface of the electrode 101 by detecting discharge. The height of the deposit 800 is defined as a height d.

  Therefore, the distance b from the nozzle surface 40 to the tips of the plurality of droplets 700 is a distance (cd) obtained by subtracting the deposition height d of the deposit 800 from the distance c from the nozzle surface 40 to the electrode 101. A plurality of droplets 700 are ejected so as to be shorter.

  That is, by repeatedly performing the discharge detection operation, the landed droplet 700 is deposited as a deposit 800 on the electrode 101. For example, when 100 droplets 700 are discharged by the discharge detection operation, the height d of the deposit 800 deposited on the electrode 101 is about 0.05 to 0.2 mm.

  Then, in order to prevent the head 4 and the electrode 101 from being connected by the connected droplet 700, the distance c between the head 4 and the electrode 101 is set such that the deposition height d of the deposit 800 adhering to the electrode 101 and the nozzle surface. It is necessary that the distance “b” from 40 to the tip of the connected droplet 700 is longer than the total distance.

  Thereby, the conduction between the head 4 and the electrode 101 due to the connected droplet 700 does not occur reliably, and the occurrence of defective discharge can be prevented.

  Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 21 is an explanatory diagram of a state from the flight of a droplet to landing when a plurality of droplets are discharged for explanation of the embodiment, and FIG. 22 is also the distance from the nozzle surface to the tip of the droplet and the electricity of the electrode member. It is explanatory drawing with which it uses for description of the level of an automatic change.

  Again, the distance L from the nozzle surface per droplet to the tip of the droplet is a distance a, the distance L from the nozzle surface to the tip of the droplet when a plurality of droplets are connected is the distance b, and the nozzle surface of the head 4 The distance between the electrode 40 and the electrode 101 is a distance c, and the height of the deposit on the electrode is a deposition height d.

  In FIG. 22, the level f indicates the level of electrical change of the electrode 101 necessary for determining normal ejection / non-ejection.

  In FIG. 22, the droplets A to C have different electrical characteristics (for example, electrical conductivity) of the ejected droplets, and have higher electrical characteristics in the order of droplet C <droplet B <droplet A. And The thresholds A1 to C1 indicate the distances from the nozzle surface 40 to the tip of the droplet 700 necessary for determining normal ejection / non-ejection in each of the droplets A to C. The length relationship between the thresholds A1 to C1 is threshold A1 <threshold B1 <threshold C1.

  In the present embodiment, the discharge detection unit 531 normally discharges the droplet 700 if the level of the electrical change of the electrode 101 when the droplet 700 discharged from the head 4 reaches the electrode 101 is a certain level or more. If it is less than a certain level, it is determined that no discharge has occurred.

  The ejection detection drive waveform generation unit 903 ejects the droplet 700 in which the distance from the nozzle surface 40 to the tip of the droplet 700 is longer than one tenth of the distance between the head 4 and the electrode 101. The drive waveform Pv is generated and output.

  That is, when the distance from the nozzle surface 40 to the tip of the droplet 700 is short, the amount of charge induced in the droplet 700 decreases, and the amount of charge that cancels out when the droplet 700 lands on the charged electrode 101. decrease. Therefore, the level of the electrical change of the electrode 101 becomes small, and it becomes difficult to separate the electrical change of the electrode 101 and the noise. That is, it is not possible to determine whether normal ejection / non-ejection.

  Therefore, it is necessary to generate a discharge detection drive waveform Pv that discharges a droplet longer than the distance from the nozzle surface 40 that can be determined to be discharged to the tip of the droplet 700 when the nozzle is in a normal state (discharge state).

  Here, the electrical characteristics of the droplets vary with temperature. In particular, since the electrical characteristics of the droplet increase as the temperature rises, the amount of charge induced in the droplet 700 tends to increase as the temperature rises when the distance L from the nozzle surface to the tip of the droplet is the same. have.

  Therefore, the distance L from the nozzle surface to the tip of the droplet by the droplet 700 to be discharged in order to obtain the level of electrical change of the electrode 101 necessary for determining normal ejection / non-ejection is high. As it gets shorter, it becomes shorter.

  This point will be described with reference to FIG. FIG. 22 shows that the higher the electrical characteristics of the droplet, the more the droplets are ejected from the nozzle surface by the droplet 700 ejected in order to obtain the level of electrical change of the electrode 101 necessary for determining normal ejection / non-ejection. It shows that the distance L (threshold value) to the tip end is short.

  That is, the electrical characteristics of the droplets A to C are higher in the order of droplet C <droplet B <droplet A. At this time, since the electrical characteristics of the droplets become higher as the temperature becomes higher, the droplets A to C can be considered as electrical characteristics for each temperature of the same droplet. Specifically, the droplet A can be considered as a high temperature, the droplet B as a normal temperature, and the droplet C as a low temperature.

  As the temperature of the droplet rises and the electrical characteristics increase, the liquid from the nozzle surface 40 of the droplet 700 that is ejected in order to obtain the level of electrical change of the electrode 101 necessary to determine normal ejection / non-ejection is increased. The distance to the tip of the droplet 700 can be short.

  Accordingly, it may be possible to determine normal ejection / non-ejection even for a short ejection in which droplets other than the ejection detection drive waveform in which a plurality of droplets are coupled are not coupled.

  At this time, in a droplet having general electrical characteristics (for example, aqueous pigment ink), the distance from the nozzle surface 40 at which normal ejection / non-ejection can be determined to the tip of the droplet 700 is the largest. As a result of experiments, it was found that the condition is that the distance between the head 4 and the electrode 101 is longer than one-tenth in a high temperature environment in which electrical characteristics are enhanced.

  For example, when the distance c between the nozzle surface 40 of the head 4 and the electrode 101 is 5.0 mm, ejection detection is performed to eject a droplet 700 whose distance a from the nozzle surface 40 to the tip of the droplet 700 is 0.5 mm or more. A drive waveform for generation may be generated.

  In this way, by generating a drive waveform that ejects a droplet in which the distance from the nozzle surface to the tip of the droplet is longer than one-tenth of the distance between the head and the electrode, normal ejection / non-ejection is achieved. The level of electrode electrical change required to make the determination can be obtained.

  In addition, even when a plurality of droplets are not connected, it is possible to perform normal ejection / non-ejection determination, thereby preventing ejection failure due to conduction between the head and the electrode via the droplets.

  Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 23 is a flowchart for explaining the embodiment, FIG. 24 is also an explanatory diagram of an example of a temperature table, and FIG. 25 is also for explaining the amplification factor of the amplitude of the maintenance drive waveform and the discharge detection drive waveform with respect to temperature. It is explanatory drawing.

  In this embodiment, as shown in FIG. 24, the temperature table storing the relationship between the temperature and the amplitude magnification multiplied by the standard ejection detection drive waveform Pv0 is held in the ROM 502 of the control unit 500 or the like.

  Referring to FIG. 23, when starting the discharge detection, the control unit 500 acquires a current temperature such as an environmental temperature (or liquid temperature, head temperature) detected by the temperature sensor 518.

  Thereafter, the amplitude magnification corresponding to the current temperature is read from the temperature table. Then, the discharge pulse P of the standard discharge detection drive waveform Pv0 is multiplied by the amplitude magnification to generate and output a discharge detection drive waveform Pv including the discharge pulse P having the amplitude Va corresponding to the current temperature, which is given to the head 4. That is, the amplitude of the standard ejection detection drive waveform Pv0 is corrected according to the temperature (environment temperature). The standard ejection detection drive waveform Pv0 is a waveform that obtains the distance from the nozzle surface to the tip of the droplet that satisfies the conditions described in each embodiment, for example, at normal temperature (predetermined temperature range).

  Here, the amplitude magnification is a magnification at which the distance a or the distance b from the nozzle surface to the tip of the droplet of each embodiment described above can be obtained even when the temperature changes.

  That is, in the temperature table of this embodiment, as shown in FIG. 24, the amplitude magnification is set so that the amplitude of the ejection detection drive waveform becomes smaller as the temperature becomes higher.

  As described above, the characteristic values such as the viscosity and surface tension of the droplet change depending on the temperature. Therefore, the temperature of the liquid or the head or the environmental temperature is detected, and the amplitude of the ejection detection drive waveform is changed in accordance with the temperature.

  As a result, it is possible to generate a discharge detection drive waveform that discharges a droplet with suppressed variation in the distance from the nozzle surface of the head to the tip of the droplet due to a temperature change in the characteristic value of the droplet. The distance from the head to the tip of the droplet can be made the same.

  That is, it is possible to suppress variation in the distance from the nozzle surface of the head to the tip of the droplet due to the variation in the characteristic value of the droplet accompanying a temperature change.

  As a result, it is possible to improve the detection accuracy of the discharge state in the discharge state detection operation and to suppress the occurrence of discharge failure due to the connection between the head and the electrode by the droplet. Furthermore, by suppressing the variation in the distance from the nozzle surface of the head to the tip of the droplet, the distance between the head and the electrode can be reduced, so that the number of droplets ejected for detection can be reduced and wasted liquid. Consumption can be suppressed.

  In FIG. 25, the amplification factor of the maintenance drive waveform is shown together with the amplification factor of the ejection detection drive waveform. The maintenance drive waveform is a drive waveform used for a maintenance operation for maintaining and recovering the state of the head 4 (such as an empty discharge operation which is a discharge operation other than the main purpose). The amplification factor of the ejection detection drive waveform is set to a value smaller than the amplification factor of the maintenance drive waveform.

  Next, a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 26 is a flowchart for explaining the embodiment, and FIG. 27 is an explanatory diagram of an example of a temperature table. FIG. 28 is an explanatory diagram of a state from droplet flight to landing when a plurality of low-viscosity droplets are discharged using the standard discharge drive waveform, and FIG. 29 similarly uses a discharge drive waveform in which the discharge cycle is changed. FIG. 5 is an explanatory diagram of a state from droplet flight to landing when a plurality of low-viscosity droplets are discharged.

  In this embodiment, as shown in FIG. 27, a temperature table storing the relationship between the temperature, the amplitude magnification multiplied by the standard ejection detection drive waveform Pv0, and the ejection cycle of the ejection pulse is held. The discharge cycle Ta is set shorter (higher discharge frequency) as the temperature becomes higher.

  Then, referring to FIG. 26, when starting the discharge detection, the control unit 500 acquires the current temperature such as the environmental temperature (or liquid temperature, head temperature) detected by the temperature sensor 518.

  Thereafter, the amplitude magnification and the discharge cycle corresponding to the current temperature are read from the temperature table. Then, the ejection pulse P of the standard ejection detection drive waveform Pv0 is multiplied by the amplitude magnification, and the ejection cycle Ta of the ejection pulse P having the amplitude Va corresponding to the temperature is set to the ejection cycle corresponding to the temperature. Pv is generated and output and given to the head 4. That is, the amplitude and the discharge cycle of the standard discharge detection drive waveform Pv0 are corrected according to the temperature (environment temperature).

  That is, as described in the first embodiment, the characteristic values such as the viscosity and the surface tension of the droplet change depending on the temperature. For example, in a low temperature environment, the viscosity and surface tension of the droplets increase, so that the rear end portion of the droplet 700 is difficult to separate from the nozzle surface 40 of the head 4. For example, the droplet 700 that leaves the nozzle surface 40 of the head 4 in a room temperature environment is separated from the nozzle surface 40 of the head 4 in a low temperature environment by 23 μs.

  In other words, in the low temperature environment, the viscosity and surface tension of the droplets increase, so that the rear end portion of the droplet 700 is difficult to separate from the nozzle surface 40 of the head 4. The distance to the part tends to be short, and the droplets tend to be connected easily. Accordingly, ejection failure due to the connection between the head 4 and the electrode 101 by the droplet 700 is likely to occur.

  Therefore, in the low temperature environment, for example, as described with reference to FIG. 19, a discharge detection drive waveform in which the discharge cycle Ta of the discharge pulse P is increased is generated and output. Therefore, the discharge cycle Ta in the discharge detection drive waveform is set for each temperature in the temperature table, and the longer discharge cycle Ta is set at lower temperatures.

  As a result, the discharge interval between the preceding droplet 700a and the following droplet 700b is increased, and the interval between the trailing edge of the preceding droplet 700a and the following droplet 700b is widened. Therefore, at the moment when the leading end of the preceding droplet 700a reaches the electrode 101, the trailing end of the trailing droplet 700b can be separated from the head 4, and the droplet 4 makes the head 4 and the electrode 101 conductive. Can be prevented.

  On the other hand, in a high temperature environment, the viscosity and surface tension of the droplets are reduced, so that the rear end portion of the droplet 700 is easily separated from the head 4. For example, a droplet 700 that leaves the head 4 in 20 μs in a normal temperature environment is separated from the head 4 in 17 μs in a high temperature environment.

  Then, when ejection is performed with the standard ejection detection drive waveform Pv0 shown in FIG. 28A, as shown in FIG. 28B, when the subsequent droplet 700b is ejected, the preceding droplet 700a is The interval is so wide that the following droplet 700b is not connected to the preceding droplet 700a. That is, in a high-temperature environment, the distance from the nozzle surface 40 of the head 4 to the tip of the droplet 700 tends to be short, and the distance e at which the level of electrical change necessary for normally determining ejection / non-ejection is reached. It becomes difficult to get.

  Therefore, the discharge cycle Ta in the discharge detection drive waveform is set for each temperature in the temperature table, and the shorter discharge cycle Ta is set for higher temperatures.

  For example, in a high temperature environment, as shown in FIG. 29A, the discharge cycle Ta is shortened (discharge cycle Ta3: Ta3 <Ta0), and the discharge detection drive waveform Pv3 is generated and output, so that FIG. As shown, the following droplet 700b can be connected to the preceding droplet 700a.

  As a result, the distance from the nozzle surface 40 to the tip of the droplet 700 is increased, and the amount of charge induced in the droplet 700a is increased. / A level of electrical change necessary to determine non-ejection can be obtained.

  In this way, it is possible to suppress variations in the distance from the nozzle surface 40 to the tip of the droplet 700 due to the variation in the characteristic value of the droplet accompanying a temperature change.

  Thereby, it is possible to improve the discharge state detection accuracy of the discharge state detection operation and to suppress the occurrence of discharge failure due to the connection between the head and the electrode by the liquid droplets. Furthermore, since the distance between the head and the electrode can be reduced by suppressing variation in the distance from the head to the tip of the droplet, it is possible to reduce the number of droplets ejected for detection and reduce wasteful liquid consumption.

  Next, a sixth embodiment of the present invention will be described with reference to FIGS. 30 and 31. FIG. FIG. 30 is a flowchart for explaining the embodiment, and FIG. 31 is an explanatory diagram of an example of a temperature table.

  In the present embodiment, as shown in FIG. 31, a temperature table storing the relationship between the temperature and the amplitude magnification multiplied by the standard ejection detection drive waveform Pv0, the ejection cycle of ejection pulses, and the number of ejection pulses (number of drops). keeping. The discharge cycle Ta is set shorter (higher discharge frequency) as the temperature becomes higher. Also, the number of drops is set to increase as the temperature increases.

  Referring to FIG. 30, when starting the discharge detection, the control unit 500 acquires a current temperature such as an environmental temperature (or liquid temperature, head temperature) detected by the temperature sensor 518.

  Thereafter, the amplitude magnification, the discharge cycle, and the number of drops corresponding to the current temperature are read from the temperature table. Then, the ejection pulse P of the standard ejection detection drive waveform Pv0 is multiplied by the amplitude magnification, and the ejection cycle Ta of the ejection pulse P having the amplitude Va corresponding to the temperature is set to the ejection cycle corresponding to the temperature. A discharge detection drive waveform Pv including the discharge pulse P is generated and output and applied to the head 4.

  That is, as described in the fifth embodiment, when the ejection cycle of the ejection pulse is changed according to the temperature, the ejection cycle is adjusted if the number of droplets ejected is the same regardless of the temperature. Depending on the minutes, the time required to discharge a plurality of droplets required for the discharge detection operation varies.

  Here, as described above, in the case of detecting discharge / non-discharge by measuring an electrical change when a droplet lands on the electrode, in order to increase the detection accuracy of the discharge state, the discharge is detected by the discharge state detection operation. It is preferable that a plurality of droplets be ejected.

  However, in the case of detecting discharge / non-discharge by measuring the electrical change when the droplet hits the electrode, the electrical change per minute time of the electrode is detected. When discharged, the level of electrical change decreases.

  That is, in order to obtain the level of electrical change necessary for normally determining ejection / non-ejection, it is necessary to adjust the droplet ejection time to be constant.

  Therefore, it is optimal by increasing or decreasing the number of droplets to be ejected according to the adjustment of the frequency (ejection cycle of ejection pulses) of the ejection detection drive waveform so that the time during which the droplets are ejected is substantially constant. The discharge time can be maintained, and the level of electrical change of the electrode can be maintained at a higher level.

  In each of the above embodiments, the landing member is an electrode (electrode member). However, the landing member is a resistor (resistance member), and a resistance value change between both ends due to droplet landing is detected. The present invention can be similarly applied to a device that detects discharge.

  In the present application, the “apparatus for discharging liquid” is an apparatus that includes a liquid discharge head or a liquid discharge unit and drives the liquid discharge head to discharge liquid. The apparatus for ejecting liquid includes not only an apparatus capable of ejecting liquid to an object to which liquid can adhere, but also an apparatus for ejecting liquid toward the air or liquid.

  This “apparatus for discharging liquid” may include means for feeding, transporting, and discharging a liquid to which liquid can adhere, as well as a pre-processing apparatus and a post-processing apparatus.

  For example, as a “liquid ejecting device”, an image forming device that forms an image on paper by ejecting ink, a powder is formed in layers to form a three-dimensional model (three-dimensional model) There is a three-dimensional modeling apparatus (three-dimensional modeling apparatus) that discharges a modeling liquid onto the powder layer.

  Further, the “apparatus for ejecting liquid” is not limited to an apparatus in which significant images such as characters and figures are visualized by the ejected liquid. For example, what forms a pattern etc. which does not have a meaning in itself, and what forms a three-dimensional image are also included.

  The above-mentioned “thing to which liquid can adhere” means that liquid can adhere even temporarily. The material to which “the liquid adheres” may be any material as long as the liquid can temporarily adhere, such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics.

  “Liquid” also includes ink, treatment liquid, DNA sample, resist, pattern material, binder, modeling liquid, and the like.

  Further, the “device for ejecting liquid” includes both a serial type device that moves the liquid ejection head and a line type device that does not move the liquid ejection head, unless otherwise specified.

  In addition to the “device for discharging liquid”, a processing liquid coating apparatus for discharging a processing liquid onto a sheet for applying a processing liquid to the surface of the sheet for the purpose of modifying the surface of the sheet, or a raw material There is an injection granulating apparatus for granulating raw material fine particles by spraying a composition liquid in which a solution is dispersed in a solution from a nozzle.

  The “liquid discharge head” is not limited to the pressure generating means to be used. For example, in addition to the piezoelectric actuator as described in the above embodiment (a multilayer piezoelectric element may be used), a thermal actuator using an electrothermal conversion element such as a heating resistor, a diaphragm and a counter electrode are included. An electrostatic actuator or the like may be used.

  In addition, the terms “image formation”, “recording”, “printing”, “printing”, “printing”, “modeling” and the like in the terms of the present application are all synonymous.

3 Carriage 4, 4a, 4b Liquid discharge head 40 Nozzle surface 100 Discharge detection unit 101 Electrode (electrode member, landing member)
903 Discharge detection drive waveform generator

Claims (7)

A liquid discharge head having a nozzle for discharging droplets;
A discharge detecting means for detecting presence or absence of discharge from an electrical change caused by landing of a droplet discharged from the liquid discharge head on a landing surface of a landing member;
Drive waveform generation means for generating a discharge detection drive waveform for discharging the droplets from the nozzle when detecting the presence or absence of the discharge,
The ejection detection drive waveform includes an ejection pulse for ejecting a plurality of droplets continuously,
The plurality of droplets ejected by the ejection pulse is connected from the nozzle surface on which the nozzle is formed to the droplet closest to the landing surface,
Of the plurality of connected droplets, the distance from the tip of the droplet on the side close to the landing surface to the nozzle surface is shorter than the interval between the nozzle surface and the landing surface. A device for ejecting liquid. The apparatus for ejecting liquid according to claim 1, wherein an interval between the nozzle surface and the landing surface is an interval between the nozzle surface and a surface of a deposit deposited on the landing surface. 3. The apparatus for ejecting liquid according to claim 1, further comprising means for correcting the ejection detection drive waveform in accordance with an environmental temperature. 4. The apparatus for ejecting liquid according to claim 3, wherein the amplitude of the ejection pulse is increased when the environmental temperature is low compared to when the environmental temperature is high. 5. The apparatus for ejecting liquid according to claim 3, wherein when the environmental temperature is high, the ejection cycle, which is a repetition cycle of the ejection pulse, is made shorter than when the environmental temperature is low. 6. The apparatus for ejecting liquid according to claim 5, wherein when the environmental temperature is high, the number of ejection pulses is increased by increasing the number of ejection pulses compared to when the environmental temperature is low. A liquid discharge head having a nozzle for discharging droplets;
A discharge detecting means for detecting presence or absence of discharge from an electrical change caused by landing of a droplet discharged from the liquid discharge head on a landing surface of a landing member;
Drive waveform generation means for generating a discharge detection drive waveform for discharging the droplets from the nozzle when detecting the presence or absence of the discharge,
The ejection detection drive waveform includes the droplets in which the length from the nozzle surface on which the nozzle is formed to the tip of the droplet is 1/10 or more of the interval between the nozzle surface and the landing surface. An apparatus for ejecting liquid, comprising ejection pulses to be ejected.

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