WO2004076186A1

WO2004076186A1 - Liquid drop ejector and method for judging abnormal ejection of liquid drop ejection head

Info

Publication number: WO2004076186A1
Application number: PCT/JP2004/002437
Authority: WO
Inventors: Osamu Shinkawa
Original assignee: Seiko Epson Corporation
Priority date: 2003-02-28
Filing date: 2004-02-27
Publication date: 2004-09-10

Abstract

A liquid drop ejector and a method for judging abnormal ejection of a liquid drop ejection head in which a pulse oscillating through variation in the capacitance of an actuator after liquid drop ejecting operation is subtracted from a reference value and abnormal ejection of a liquid drop ejection head and its cause can be judged based on the subtraction results. The liquid drop ejector comprises a plurality of liquid drop ejection heads each consisting of a diaphragm (121) and an electrostatic actuator (120) for displacing the diaphragm (121), a circuit (18) for driving the electrostatic actuator (120), a circuit (11) oscillating based on the residual oscillation of the diaphragm (121) after the electrostatic actuator (120) is driven through the driving circuit (18), a counter (45) for subtracting the number of pulses during a specified interval of a signal oscillated by the oscillation circuit (11) from a specified reference value, and a means (20) for making a decision as to whether abnormal ejection is occurring in the liquid drop ejection head or not based on the subtraction results of the subtraction counter (45).

Description

TECHNICAL FIELD The present invention relates to a droplet discharge device and a method for determining a discharge abnormality of a droplet discharge head.

The present invention relates to a droplet discharge device and a method for determining a discharge abnormality of a droplet discharge head. Background art

Light

2. Description of the Related Art An ink jet printer, which is one of the droplet discharge devices, discharges an ink droplet (droplet) from a plurality of nozzles to form an image on a predetermined sheet. Inkjet printer print heads (inkjet heads) have a large number of nozzles. Some of the nozzles are used to increase the viscosity of the ink, mix air bubbles, and adhere to dust and paper dust. May be clogged and ink drops cannot be ejected. If the nozzles are clogged, missing dots will occur in the printed image, which may cause deterioration in image quality.

Conventionally, as a method of detecting such an ink droplet ejection abnormality (hereinafter also referred to as “missing dot”), a state in which an ink droplet is not ejected from the nozzle of the ink jet head (an abnormal ink droplet ejection state) is detected. A method of optically detecting each nozzle of the nozzle has been devised (for example, Japanese Patent Application Laid-Open No. Hei 8-30963). With this method, it is possible to identify a nozzle that has a missing dot (discharge abnormality).

However, in the above-described optical dot missing (droplet ejection abnormality) detection method, a detector including a light source and an optical sensor is attached to a droplet ejection device (for example, an ink jet printer). In this detection method, generally, a light source and a light source are arranged so that a droplet ejected from a nozzle of a droplet ejection head (ink jet head) passes between the light source and the optical sensor and blocks light between the light source and the optical sensor. There is a problem that the optical sensor must be set (installed) with high precision (high accuracy). Further, such a detector is usually expensive, and there is a problem that the manufacturing cost of the ink jet printer is increased. In addition, light is generated by ink mist from the nozzles and paper dust such as printing paper. The output section of the source and the detection section of the optical sensor may become dirty, and the reliability of the detector may become an issue.

In the above-described optical dot missing detection method, it is possible to detect missing dots of nozzles, that is, abnormal ejection (non-ejection) of ink droplets, but based on the detection result, missing dots (abnormal ejection). There is also a problem in that it is not possible to identify (determine) the cause of the error, and it is impossible to select and execute an appropriate recovery process corresponding to the cause of the missing dot. Therefore, for example, even though the ink can be recovered by the wiping process, the ink discharged from the inkjet head is suctioned by a pump, etc. By performing multiple recovery processes because the process is not performed, the throughput of an inkjet printer (droplet ejection device) is reduced or worsened. Disclosure of the invention

An object of the present invention is to subtract a pulse oscillating due to a change in capacitance over time after a droplet discharge operation from a reference value, and based on the subtraction result, determine whether a droplet discharge head has a discharge abnormality and its discharge abnormality. It is an object of the present invention to provide a droplet discharge device and a method for determining a discharge abnormality of a droplet discharge head that can determine the cause.

In order to solve the above problems, according to one embodiment of the present invention, a droplet discharge device according to the present invention includes a diaphragm, an actuator for displacing the diaphragm, and a liquid filled therein, and a displacement of the diaphragm. A plurality of droplet ejection heads having a cavity in which the pressure inside the cavity is increased and decreased, and a nozzle communicating with the cavity and ejecting the liquid as droplets by increasing and decreasing the pressure in the cavity.

A drive circuit for driving the actuator;

After the actuator is driven by the drive circuit, based on the residual vibration of the diaphragm displaced by the actuator, oscillating means oscillating; and in a predetermined period of a signal oscillated by the oscillating means, Subtraction means for subtracting the number of pulses from a predetermined reference value;

Based on the result of the subtraction by the subtraction means, an ejection failure occurs in the droplet ejection head. Determining means for determining whether or not

It is characterized by having.

ADVANTAGE OF THE INVENTION According to the droplet discharge apparatus of this invention, when the operation which discharges a liquid as a droplet by drive of an actuator is performed, it is based on the residual vibration of the diaphragm displaced by the actuator. The oscillation circuit oscillates and subtracts the oscillation pulse from a predetermined reference value (normal count value). Based on the result of the subtraction, it is determined whether the droplet has been ejected normally or not (abnormal ejection). To detect.

The droplet discharge device of the present invention does not require other components (for example, an optical detection device, etc.) as compared with a droplet discharge device provided with a conventional dot missing detection method. Abnormal droplet ejection can be detected without increasing the size of the device, and the manufacturing cost can be kept low. Further, in the droplet discharge head of the present invention, since the abnormal discharge of the droplet is detected using the residual vibration of the diaphragm after the droplet discharge operation, the abnormal discharge of the droplet is detected even during the printing operation. Can be detected.

Here, the residual vibration of the vibrating plate means that after the actuator performs a droplet discharge operation by a drive signal (voltage signal) of the drive circuit, the next drive signal is input and the droplet discharge operation is performed again. This means a state in which the diaphragm continues to vibrate while being attenuated by the droplet discharging operation until the step is performed.

Preferably, when the determination unit determines that the discharge abnormality has occurred, the determination unit determines a cause of the discharge abnormality. Preferably, the determining means determines that bubbles are mixed in the cavity when the subtraction result is smaller than a first threshold, and when the subtraction result is larger than a second threshold. When it is determined that the liquid in the vicinity of the nozzle has increased in viscosity due to drying, and when the subtraction result is smaller than the second threshold and larger than the third threshold, paper powder is attached near the outlet of the nozzle. Is determined. Preferably, the droplet discharge device of the present invention may further include a storage unit that stores a determination result determined by the determination unit. In the present invention, the term “paper dust” is not limited to paper dust generated simply from recording paper or the like, but may be, for example, a piece of rubber such as a paper feed roller (paper feed roller) or floating in the air. It refers to everything that adheres to the vicinity of the nozzle, including dust, and hinders droplet ejection.

Still preferably, in a droplet discharge device according to the present invention, the drive of the actuator The apparatus may further include a switching unit that switches the actuator from the driving circuit to the ejection abnormality detection unit after the droplet ejection operation. Further, the oscillating means may constitute a CR oscillating circuit using a capacitance component of the actuator and a resistance component of a resistance element connected to the actuator.

Here, preferably, the predetermined period is a period of one or a plurality of points in a residual vibration waveform of the diaphragm when a droplet is normally ejected from the droplet ejection head. The predetermined period may be a period until the residual vibration occurs, and a half period of the residual vibration of the diaphragm when the droplet is normally discharged from the droplet discharge head. The period up to may be used. Further, the predetermined period may be a period for every half cycle of the residual vibration of the diaphragm when a droplet is normally discharged from the droplet discharge head, and The period may be up to 1/4 cycle of the residual vibration of the diaphragm when the droplet is normally ejected from the nozzle, and when the droplet is normally ejected from the droplet ejection head. The residual vibration of the diaphragm may be a period of every 1 Z 4 periods.

Preferably, the predetermined reference value is the number of pulses oscillated by the oscillating means during the predetermined period when a droplet is normally ejected from the droplet ejection head. Here, the determination unit scans the plurality of droplet discharge heads and oscillates by the oscillating unit, and based on the subtraction result obtained by the subtraction unit, discharge abnormalities for each droplet discharge head. It may be configured to determine whether or not an error has occurred.

The actuator may be an electrostatic actuator or a piezoelectric actuator utilizing a piezoelectric effect of a piezoelectric element. Preferably, the droplet discharge device includes at least an inkjet printer.

Further, in another aspect of the present invention, a method for determining a discharge abnormality of a droplet discharge head according to the present invention includes:

By driving the actuator to vibrate the diaphragm, the liquid in the cavity is discharged from the nozzle as droplets, and then oscillated based on the residual vibration of the diaphragm. It is characterized in that the number of pulses in a predetermined period is subtracted from a predetermined reference value, and based on the subtraction result, it is determined whether or not an ejection abnormality has occurred. Preferably, when it is determined that the ejection abnormality has occurred, The cause of the discharge abnormality is determined. Thereby, the same effect as that of the above-described droplet discharge device can be obtained.

Here, preferably, when the subtraction result is smaller than a first threshold value, it is determined that air bubbles have entered the cavity, and when the subtraction result is larger than a second threshold value, the vicinity of the nozzle is determined. It is determined that the liquid has thickened due to drying, and when the subtraction result is smaller than the second threshold value and larger than the third threshold value, it is determined that paper dust has adhered near the outlet of the nozzle. Is also good. Preferably, the determination result determined in the determination is stored in the storage unit.

Preferably, after the discharge operation of the droplet by the driving of the actuator, the driving of the actuator may be switched from the driving circuit to the discharge abnormality detecting means. Here, the predetermined period is one or a plurality of periods in a residual vibration waveform of the diaphragm when a droplet is normally discharged from the droplet discharge head, and the liquid is discharged from the droplet discharge head. A period up to a half cycle of the residual vibration of the diaphragm when the droplet is normally ejected, every half cycle of the residual vibration of the diaphragm when the droplet is normally ejected from the droplet ejection head. During the period, the droplet is normally ejected from the droplet ejection head during a period of up to 1/4 cycle of the residual vibration of the diaphragm when the droplet is normally ejected from the droplet ejection head. This is one of the periods of 1/4 cycle of the residual vibration of the diaphragm when the vibration is applied.

Preferably, the predetermined reference value is the number of pulses oscillated in the predetermined period when a droplet is normally ejected from the droplet ejection head. BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other objects, features and advantages of the invention will be more readily apparent from the following detailed description of a preferred embodiment of the invention which proceeds with reference to the accompanying drawings. FIG. 1 is a schematic view showing a configuration of an ink jet printing apparatus which is a kind of the droplet discharge device of the present invention.

FIG. 2 is a block diagram schematically showing a main part of the ink jet printer of the present invention.

FIG. 3 is a schematic sectional view of the ink jet head shown in FIG.

FIG. 4 is a diagram showing the configuration of the head unit 35 corresponding to the single color ink shown in FIG. It is an exploded perspective view.

FIG. 5 is an example of a nozzle arrangement pattern of a nozzle plate of a head unit using four-color ink.

FIG. 6 is a state diagram showing each state at the time of inputting a drive signal on the section 111-111 in FIG. FIG. 7 is a circuit diagram showing a simple vibration calculation model assuming residual vibration of the diaphragm shown in FIG.

FIG. 8 is a graph showing the relationship between the experimental value and the calculated value of the residual vibration of the diaphragm in FIG. 3. FIG. 9 is a conceptual diagram of the vicinity of the nozzle when bubbles are mixed in the cavity in FIG. 10 is a graph showing a calculated value and an experimental value of the residual vibration in a state where the ink droplets are not ejected due to air bubbles entering the cavity.

FIG. 11 is a conceptual diagram of the vicinity of the nozzle when the ink near the nozzle of FIG. 3 is fixed by drying.

FIG. 12 is a graph showing calculated values and experimental values of residual vibration in a state where the ink near the nozzle is in a dry and thickened state.

FIG. 13 is a conceptual diagram of the vicinity of the nozzle when paper dust adheres near the nozzle outlet of FIG.

FIG. 14 is a graph showing calculated values and experimental values of the residual vibration in a state where paper dust adheres to the nozzle outlet.

FIG. 15 is a photograph showing the state of the nozzle before and after the paper dust adheres to the vicinity of the nozzle.

FIG. 16 is a block diagram schematically showing the discharge abnormality detection means shown in FIG. 2 and showing a switching operation between an oscillation circuit (oscillation means) and a drive circuit.

FIG. 17 is a conceptual diagram in the case where the electrostatic factor of FIG. 3 is a parallel plate capacitor.

FIG. 18 is a circuit diagram of an oscillator circuit including a capacitor composed of the electrostatic function shown in FIG.

FIG. 19 is a timing chart of the subtraction processing of the subtraction count shown in FIG. FIG. 20 is a diagram showing a residual vibration waveform in each state of the ink jet head.

FIG. 21 is a diagram illustrating an example of a subtraction result of the subtraction counter and a determination result of the determination unit based on the subtraction result.

FIG. 22 is a diagram showing the relationship between the cause of the discharge abnormality and the output of each reference value.

FIG. 23 is a flowchart showing a discharge abnormality detection process according to an embodiment of the present invention.

FIG. 24 is a schematic block diagram of the discharge abnormality detecting means shown in FIG. 2 according to another embodiment of the present invention.

FIG. 25 shows a residual vibration waveform when the count period is a half cycle of the residual vibration during normal ejection.

FIG. 26 shows a residual vibration waveform when the count period is 1/4 cycle of the residual vibration during normal ejection.

FIG. 27 is a timing chart (every half cycle) of the subtraction processing of the subtraction counter shown in FIG.

FIG. 28 is a diagram illustrating an example of a subtraction result of the subtraction counter and a determination result of the determination unit based on the result (every half cycle and every 1Z4 cycle).

FIG. 29 is a diagram showing the relationship between the cause of the discharge abnormality and the output of each reference value (every half cycle and every 1Z4 cycle).

FIG. 30 is a flowchart showing a discharge abnormality detection process according to another embodiment of the present invention.

FIG. 31 is a cross-sectional view schematically showing another configuration example of the inkjet head according to the present invention.

FIG. 32 is a cross-sectional view schematically showing another configuration example of the ink jet head according to the present invention.

FIG. 33 is a cross-sectional view schematically showing another configuration example of the ink jet head according to the present invention.

FIG. 34 is a cross-sectional view schematically showing another configuration example of the ink jet head according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment of a droplet discharge device and a method for determining a discharge abnormality of a droplet discharge head according to the present invention will be described in detail with reference to FIGS. This embodiment is given as an example, and the content of the present invention should not be limited to this. Hereinafter, the present embodiment will be described using an ink jet printer that discharges ink (liquid material) and prints an image on a recording sheet as an example of the droplet discharge device of the present invention. <First embodiment>

FIG. 1 is a schematic diagram showing a configuration of an ink jet printer 1 which is a kind of a droplet discharge device according to a first embodiment of the present invention. In the following description, the upper side in FIG. 1 is referred to as “upper”, and the lower side is referred to as “lower”. First, the configuration of the ink jet printer 1 will be described.

The ink jet printer 1 shown in FIG. 1 includes an apparatus main body 2, a tray 21 on which recording paper P is placed at the upper rear, and a paper discharge roller 22 for discharging the recording paper P at the lower front, and An operation panel 7 is provided on the upper surface.

The operation panel 7 includes, for example, a liquid crystal display, an organic EL display, an LED lamp, and the like, and includes a display unit (not shown) for displaying an error message and the like, and an operation unit (not shown) including various switches. Zu).

Also, inside the main body 2, a printing device (printing device) 4 having a printing means (moving body) 3 which reciprocates and a recording paper P are supplied to and discharged from the printing device 4 one by one. And a control unit (control means) 6 for controlling the printing device 4 and the paper feeding device 5.

Under the control of the control unit 6, the paper feeding device 5 intermittently feeds the recording paper P one by one. This recording paper P passes near the lower part of the printing means 3. At this time, the printing means 3 reciprocates in a direction substantially orthogonal to the feed direction of the recording paper P, and printing on the recording paper P is performed. That is, the reciprocating movement of the printing means 3 and the intermittent feeding of the recording paper P become the main scanning and the sub-scanning in the printing, and the ink jet printing is performed. The printing device 4 receives the rotation of the printing means 3, the carriage motor 41 as a drive source for moving the printing means 3 in the main scanning direction, and the carriage motor 41, and reciprocates the printing means 3 in response to the rotation of the carriage means 4. Moving mechanism 42.

Under the printing means 3, a plurality of head units 35 corresponding to the type of ink having a large number of nozzles 110, and a plurality of ink cartridges (I) for supplying ink to each head unit 35 are provided. / C) 31 and a carriage 32 on which each head unit 35 and an ink cartridge 31 are mounted.

As will be described later with reference to FIG. 3, each of the head units 35 includes one nozzle 110, a vibration plate 121, an electrostatic actuator 120, a cavity 144, and ink. It has a large number of ink jet recording heads (ink-jet heads or droplet discharge heads) 100 constituted by supply ports 144 and the like. Although the head unit 35 has a configuration including the ink cartridge 31 in FIG. 1, it is not limited to such a configuration. For example, the ink cartridge 31 may be separately fixed and supplied to the head unit 35 by a tube or the like. Therefore, in the following, apart from the printing means 3, one nozzle 110, one diaphragm 121, one electrostatic capacitor 120, one cavity 1401, and one ink supply are provided respectively. A head provided with a plurality of ink jet heads 100 constituted by the mouths 142 and the like is referred to as a head unit 35.

By using the ink cartridge '31 filled with ink of four colors of yellow, cyan, magenta, and black (black), full color printing can be performed. In this case, the printing unit 3 is provided with a head unit 35 corresponding to each color. Here, in FIG. 1, four ink cartridges 31 corresponding to four color inks are shown, but the printing means 3 includes ink cartridges of other colors, such as light cyan, light magenta, and dark yellow. 31 may be further provided.

The reciprocating mechanism 42 has a carriage guide shaft 42 2 having both ends supported by a frame (not shown), and a timing belt 4 21 extending in parallel with the carriage guide shaft 4 22. are doing.

The carriage 32 can reciprocate on the carriage guide shaft 42 of the reciprocating mechanism 42. It is supported and fixed to a part of the timing belt 4 21.

When the timing belt 421 runs forward and backward through the pulleys by the operation of the carriage motor 41, the printing means 3 is reciprocated by being guided by the carriage guide shaft 422. During this reciprocating movement, ink is ejected from the nozzles 110 of the plurality of inkjet heads 100 in the head unit 35 in accordance with the image data (print data) to be printed, and recording is performed. Printing on paper P is performed.

The paper feeding device 5 has a paper feeding motor 51 serving as a driving source thereof, and a paper feeding roller 52 rotated by the operation of the paper feeding motor 51.

The paper feed roller 52 is composed of a driven roller 52a and a drive roller 52b, which are vertically opposed to each other with a feed path (recording paper P) of the recording paper P therebetween. Mo It is connected to 51 overnight. As a result, the lined paper rollers 52 can feed a large number of recording papers P set in the tray 21 one by one toward the printing device 4. Instead of the tray 21, a configuration in which a paper cassette for storing the recording paper P can be detachably mounted may be used.

The control unit 6 controls the printing device 4 and the paper feeding device 5 based on a print data input from a host computer 8 such as a personal computer (PC) or a digital camera (DC) to record. Print processing is performed on paper P. In addition, the control unit 6 displays an error message or the like on the display unit of the operation panel 7 or lights / blinks an LED lamp or the like, and based on various switch press signals input from the operation unit. This causes each unit to execute a corresponding process.

FIG. 2 is a block diagram schematically showing a main part of the ink jet printer of the present invention. In FIG. 2, the inkjet printer 1 of the present invention includes an interface unit (IF: Interface) 9 for receiving print data and the like input from the host computer 8, a control unit 6, a carriage motor 41, A carriage motor driver 43 that drives and controls the carriage motor 41, a paper feed motor 51, a paper feed dryer 53 that drives and controls the paper feed motor 51, a head unit 35, and a head unit. A head driver 33 for controlling the driving of the head 35 and a discharge abnormality detecting means 10 are provided. The ejection abnormality detecting means 10 will be described later in detail.

In FIG. 2, the control unit 6 performs various processes such as a printing process and a discharge abnormality detection process. EE PROM (Electrically Erasable), a type of non-volatile semiconductor memory that stores print data input via a CPU (Central Processing Unit) 61 and IF 9 from a host computer 8 via an IF 9 in a data storage area (not shown) (Programmable Read-Only Memory) 62 (storing means), and temporarily store various data when executing ejection abnormality detection processing, which will be described later, or temporarily deploy application programs such as printing processing. A RAM (Random Access Memory) 63 and a PROM 64 which is a type of nonvolatile semiconductor memory for storing a control program for controlling each unit and the like are provided. The components of the control section 6 are electrically connected via a bus (not shown).

As described above, the printing means 3 includes a plurality of head units 35 corresponding to the respective color inks, and each head unit 35 includes a plurality of nozzles 110 and an electrostatic actuator corresponding to each of the nozzles 110. Equipped with 120 overnight (100 multiple ink jet heads). That is, the head unit 35 is configured to include a plurality of ink jet heads (droplet discharge heads) 100 each having a set of nozzles 110 and an electrostatic actuator 120. The head driver 33 is composed of a drive circuit 18 for driving the electrostatic function 120 of each ink jet head 100 to control the ink ejection timing, and the switching means 23 (see FIG. 16). See). The configuration of the ink jet head 100 and the electrostatic actuator 120 will be described later.

Although not shown, the control unit 6 is electrically connected to various sensors that can detect a printing environment such as a remaining amount of ink in the ink cartridge 31, a position of the printing unit 3, temperature, humidity, and the like. ing.

When obtaining the print data from the host computer 8 via the IF 9, the control unit 6 stores the print data in the EE PROM 62. Then, the CPU 61 executes a predetermined process on the print data, and outputs a drive signal to each of the drivers 33, 43, 53 based on the processed data and input data from various sensors. When these drive signals are input via the drivers 33, 43, and 53, the electrostatic actuator 120 corresponding to the plurality of ink heads 100 of the head unit 35, the carriage motor 41 of the printing device 4, and The paper feeder 5 operates. This allows The printing process is executed on the recording paper P.

Next, the structure of each ink jet head 100 in each head unit 35 will be described. FIG. 3 is a schematic cross-sectional view (including common parts such as the ink cartridge 31) of one inkjet head 100 in the head unit 35 shown in FIG. 2, and FIG. FIG. 5 is an exploded perspective view showing a schematic configuration of a head unit 35 corresponding to FIG. 5, and FIG. 5 is an example of a nozzle surface of a head unit 35 to which a plurality of the ink jet heads 100 shown in FIG. 3 are applied. FIG. 3 and 4 are shown upside down from the state of normal use, and FIG. 5 is a plan view of the inkjet head 100 shown in FIG. 3 when viewed from above in the figure. It is.

As shown in FIG. 3, the head unit 35 is connected to the ink cartridge 31 via an ink inlet 131, a damper chamber 130, and an ink supply tube 311. Here, the damper chamber 130 is provided with a damper 132 made of rubber. The damper chamber 130 absorbs the fluctuation of the ink and the fluctuation of the ink pressure when the carriage 32 reciprocates, thereby making it possible to absorb the ink heads 100 of the head unit 35. A predetermined amount of ink can be stably supplied. In addition, the head unit 35 has a silicon nozzle 140 on the upper side with the silicon substrate 140 interposed therebetween, and a borosilicate glass substrate (glass substrate) on the lower side having a thermal expansion coefficient close to that of silicon. 16 have a three-layer structure in which they are stacked. The central silicon substrate 140 has a plurality of independent cavities (pressure chambers) 141 (in Fig. 4, seven cavities are shown) and one reservoir (common ink chamber) 144. Grooves are formed to function as ink supply ports (orifices) 142 for communicating the reservoirs 144 with the cavities 144, respectively. Each groove can be formed, for example, by performing an etching process from the surface of the silicon substrate 140. The nozzle plate 150, silicon substrate 140, and glass substrate 160 are joined in this order, and each cavity 144, reservoir 144, and ink supply port 144 are partitioned. Is formed.

Each of these cavities 14 1 is formed in a rectangular shape (a rectangular parallelepiped shape), and its volume is variable by the vibration (displacement) of a diaphragm 121 described later, and the nozzle (ink nozzle) is changed by this volume change. Configured to eject ink (liquid material) from 110 Have been. In the nozzle plate 150, nozzles 110 are formed at positions corresponding to the distal end portions of the cavities 141, and these are communicated with the cavities 141, respectively. Further, an ink inlet 131, which communicates with the reservoir 144, is formed in a portion of the glass substrate 160 where the reservoir 144 is located. Ink is supplied from the ink cartridge 31 to the reservoir 144 via the ink supply tube 3111, the damper chamber 130 and the ink intake port 131. The ink supplied to the reservoirs 144 is supplied to the independent cavities 144 through the respective ink supply ports 142. Each cavity 144 is defined by a nozzle plate 150, side walls (partition walls) 144, and a bottom wall 121.

Each of the independent cavities 1 4 1 has its bottom wall 1 2 1 formed to be thin, and its bottom wall 1 2 1 is elastically deformed in its out-of-plane direction (thickness direction), that is, in the vertical direction in FIG. It is configured to function as a diaphragm (diaphragm) that can be shaped (elastically displaced). Therefore, this portion of the bottom wall 121 may be referred to as a diaphragm 122 for convenience of the following description (that is, in the following, both the “bottom wall” and the “diaphragm”) will be described. The sign 1 2 1 is used).

On the surface of the glass substrate 160 on the side of the silicon substrate 140, shallow concave portions 161 are formed at positions corresponding to the cavities 141 of the silicon substrate 140, respectively. Therefore, the bottom wall 121 of each cavity 141 faces the surface of the opposite wall 162 of the glass substrate 160 in which the concave portion 161 is formed, with a predetermined gap therebetween. That is, a gap having a predetermined thickness (for example, about 0.2 μm) exists between the bottom wall 121 of the cavity 144 and a segment electrode 122 described later. The recess 161 can be formed by, for example, etching.

Here, the bottom wall (diaphragm) 1 2 1 of each cavity 1 4 1 is a common electrode 1 2 4 on the side of each cavity 1 4 1 for storing electric charge by the drive signal supplied from the head driver 3 3. Constitutes a part of. That is, the diaphragms 121 of the cavities 141 also serve as one of the counter electrodes (counter electrodes of the capacitors) of the corresponding electrostatic actuators 120 described later. Then, on the surface of the concave portion 16 1 of the glass substrate 160, a segment electrode which is an electrode opposed to the common electrode 124 so as to face the bottom wall 121 of each cavity 141 is provided. 1 2 2 is formed. Also As shown in FIG. 3, the bottom wall 1 2 1 of the surface of each Kiyabiti 1 4 1 are covered with an insulating layer 1 2 3 made of an oxide film of silicon (S i 0 _2). Thus, the bottom wall 1 2 1 of each cavity 14 1, that is, the diaphragm 1 2 1 and the corresponding segment electrode 1 2 2 are formed by the bottom wall 1 2 1 of the cavity 1 4 1 A counter electrode (a counter electrode of a condenser) is formed (configured) through the insulating layer 123 formed on the lower surface in FIG. Therefore, the main part of the electrostatic actuator 120 is constituted by the diaphragm 121, the segment electrode 122, the insulating layer 123 and the gap therebetween.

As shown in FIG. 3, a head driver 33 including a drive circuit 18 for applying a drive voltage between these counter electrodes is provided according to a print signal (print data) input from the control unit 6. Charge and discharge between these opposed electrodes is performed. One output terminal of the head driver (voltage applying means) 33 is connected to each segment electrode 122, and the other output terminal is an input terminal of the common electrode 124 formed on the silicon substrate 140. Connected to 1 2 4a. Since the silicon substrate 140 has impurities implanted therein and has conductivity, the input terminal 124 a of the common electrode 124 is connected to the common electrode 122 of the bottom wall 122. 4 can supply voltage. Further, for example, a thin film of a conductive material such as gold or copper may be formed on one surface of the silicon substrate 140. As a result, a voltage (charge) can be supplied to the common electrode 124 with low electric resistance (efficiently). This thin film may be formed by, for example, vapor deposition or sputtering. Here, in the present embodiment, for example, the silicon substrate 140 and the glass substrate 160 are bonded (bonded) by positive electrode bonding, so that the conductive film used as an electrode in the anodic bonding is formed of the silicon substrate 140. It is formed on the flow channel forming surface side (the upper side of the silicon substrate 140 shown in FIG. 3). Then, this conductive film is used as it is as the input terminal 124 a of the common electrode 124. In the present invention, for example, the input terminal 124 a of the common electrode 124 may be omitted, and the bonding method between the silicon substrate 140 and the glass substrate 160 is limited to anodic bonding. Not done.

As shown in FIG. 4, the head unit 35 includes a nozzle plate 150 on which a plurality of nozzles 110 corresponding to the plurality of inkjet heads 100 are formed, a plurality of cavities 141, and a plurality of nozzles. Ink supply port 1 4 2 and one reservoir 1 4 3 It has a recon substrate (ink chamber substrate) 140 and an insulating layer 123, which are housed in a substrate 170 including a glass substrate 160. The substrate 170 is made of, for example, various resin materials, various metal materials, and the like, and the silicon substrate 140 is fixed and supported on the substrate 170.

The plurality of nozzles 110 formed in the nozzle plate 150 are linearly arranged substantially parallel to the reservoirs 144 in FIG. 4 for simplicity in FIG. The arrangement pattern is not limited to this configuration. Usually, for example, as shown in a nozzle arrangement pattern shown in FIG. Further, the pitch between the nozzles 110 can be appropriately set according to the printing resolution (dpi: dot per inch). FIG. 5 shows an arrangement pattern of the nozzles 110 when four color inks (ink cartridges 31) are applied.

FIG. 6 shows each state at the time of inputting the drive signal in the section Π—II I in FIG. When a driving voltage is applied between the opposing electrodes from the head driver 33, a Coulomb force is generated between the opposing electrodes, and the bottom wall (diaphragm) 1 2 1 is moved with respect to the initial state (FIG. 6 (a)). The segment electrode is bent to the side of 122 and the capacity of the capacity 141 is increased (FIG. 6 (b)). In this state, when the electric charge between the opposing electrodes is rapidly discharged under the control of the head driver 33, the diaphragm 122 is restored upward in the figure by its elastic restoring force, and the diaphragm in the initial state is restored. It moves to the top beyond the position of 1 2 1, and the volume of the cavity 14 1 rapidly contracts (Fig. 6 (c)). At this time, the compression pressure generated in the cavity 1 41 causes the cavity 1 4 1 A part of the ink (liquid material) that satisfies is discharged from the nozzle 110 communicating with the cavity 141 as ink droplets.

The diaphragm 1 2 1 of each cavity 1 4 1 receives the next drive signal (drive voltage) and discharges ink droplets again by this series of operations (ink discharge operation by the drive signal of the head dryer 33). Until then, it is damping. Hereinafter, this damped vibration is also referred to as residual vibration. The residual vibration of the diaphragm 1 2 1 includes the acoustic resistance r due to the shape of the nozzle 1 10 and the ink supply port 1 4 or the ink viscosity, the inertance m due to the ink weight in the flow path, and the diaphragm It is assumed that it has a natural vibration frequency determined by the compliance Cm of 121.

A calculation model of the residual vibration of the diaphragm 122 based on the above assumption will be described. Fig. 7 FIG. 4 is a circuit diagram showing a simple vibration calculation model assuming residual vibration of diaphragm 122; Thus, the calculation model of the residual vibration of the diaphragm 122 can be expressed by the sound pressure P, the above-mentioned inertia m, the compliance Cm, and the acoustic resistance r. Then, when the step response when the sound pressure P is applied to the circuit in FIG. 7 is calculated for the volume velocity u, the following equation is obtained.

[Equation 1] p

u = e— ^ft '' sm cot (ΐ)

ω * m o = ^ cr (2)

_M

2m The calculation result obtained from this equation is compared with the experimental result of the experiment on the residual vibration of the diaphragm 121 after the ink droplet is ejected separately. FIG. 8 is a graph showing the relationship between the experimental value and the calculated value of the residual vibration of diaphragm 121. As can be seen from the graph shown in Fig. 8, the two waveforms, the experimental value and the calculated value, generally agree.

By the way, in each of the inkjet heads 100 of the head unit 35, a phenomenon in which ink droplets are not normally ejected from the nozzles 110 despite the above-described ejection operation, that is, abnormal ejection of droplets. May occur. As described later, the causes of this discharge abnormality are: ① air bubbles in the cavity 144, ② drying and thickening (sticking) of ink near the nozzle 110, and ③ nozzle 110 Paper dust near the exit, etc.

When this discharge abnormality occurs, as a result, typically, a droplet is not discharged from the nozzle 110, that is, a non-discharge phenomenon of the droplet appears. In this case, printing (drawing) is performed on the recording paper P. A dot dropout of a pixel in an image occurs. In addition, in the case of abnormal ejection, even if the droplet is ejected from the nozzle 110, the amount of the droplet is too small or the flight direction (trajectory) of the droplet is deviated. Since they do not land, they appear as missing pixels. For this reason, in the following description, droplet ejection Abnormalities are sometimes simply referred to as "missing dots."

In the following, based on the comparison result shown in FIG. 8, the dot missing (discharge abnormality) phenomenon (abnormal discharge phenomenon) during the printing process that occurs in the nozzle 110 of the ink jet head 100 is classified according to the cause. Adjust the acoustic resistance r and / or the inertance m so that the calculated value of the residual vibration of the diaphragm 1 21 and the experimental value match (approximately match). Here, three types of air bubbles, dry thickening, and paper dust adhesion are examined.

First, let us consider the inclusion of bubbles in the cavity 141, which is one of the causes of missing dots. FIG. 9 is a conceptual diagram of the vicinity of the nozzle 110 when bubbles B are mixed in the cavity 14 1 of FIG. As shown in FIG. 9, it is assumed that the generated bubble B is generated and adhered to the wall surface of the cavity 144. (In FIG. 9, the bubble B This shows the case where it is attached near the nozzle 110).

As described above, when the bubbles B are mixed in the cavity 141, it is considered that the total weight of the ink filling the cavity 141 decreases, and the inertia m decreases. In addition, since the bubble B is attached to the wall of the cavity 141, it is thought that the diameter of the nozzle 110 becomes larger by the size of the diameter, and the acoustic resistance r decreases. Can be

Therefore, compared to the case of Fig. 8 where ink was ejected normally, the acoustic resistance r and the inertia m were both set to be small and matched with the experimental values of the residual vibration when bubbles were mixed. The result (graph) like 10 was obtained. As can be seen from the graphs of FIG. 8 and FIG. 10, when bubbles are mixed in the cavity 141, a characteristic residual vibration waveform having a higher frequency than in normal ejection is obtained. It should be noted that the attenuation of the amplitude of the residual vibration decreases due to the decrease in the acoustic resistance r, and it can be confirmed that the amplitude of the residual vibration is reduced slowly.

Next, the drying (fixing, thickening) of the ink near the nozzle 110, which is another cause of missing dots, will be examined. FIG. 11 is a conceptual diagram of the vicinity of the nozzle 110 when the ink near the nozzle 110 of FIG. 3 is fixed by drying. As shown in FIG. 11, when the ink near the nozzle 110 is dried and fixed, the ink in the cavity 141 is in a state where it is trapped in the cavity 141. Thus, when the ink near the nozzle 110 dries and thickens, the acoustic resistance r increases. Conceivable.

Therefore, compared to the case of Fig. 8 where the ink was ejected normally, the acoustic resistance r was set to be large and matched with the experimental value of the residual vibration at the time of ink drying and sticking (thickening) near the nozzle 110. As a result, the result (graph) shown in Fig. 12 was obtained. In the experimental values shown in Fig. 12, the head unit 35 was left unattended for several days without a cap (not shown), and the ink near the nozzle 110 in the cavity 141 dried and thickened. This is a measurement of the residual vibration of the diaphragm 122 in a state where the ink can no longer be ejected (the ink is fixed). As can be seen from the graphs in Fig. 8 and Fig. 12, when the ink near the nozzle 110 adheres due to drying, the frequency becomes extremely lower than during normal ejection, and the residual vibration is overdamped. An appropriate residual vibration waveform is obtained. This is because the diaphragm 1 2 1 is drawn downward in FIG. 3 to eject ink droplets, and after the ink flows from the reservoir 1 4 3 into the cavity 1 41, the diaphragm 1 2 When 1 moves upward in FIG. 3, there is no escape route for the ink in the cavity 14 1, so that the diaphragm 1 2 1 cannot vibrate suddenly (because of excessive attenuation). .

Next, the paper dust adhering to the vicinity of the nozzle 110 outlet, which is still another cause of missing dots, will be examined. FIG. 13 is a conceptual diagram of the vicinity of the nozzle 110 when paper powder adheres to the vicinity of the nozzle 110 exit of FIG. As shown in Fig. 13, if paper dust adheres to the vicinity of the outlet of nozzle 110, ink exudes from inside cavity 141 via the paper dust, and ink is discharged from nozzle 110. Discharge becomes impossible. In this way, when paper dust adheres to the vicinity of the outlet of the nozzle 110 and ink is seeping out from the nozzle 110, the inside of the cavity 144 and the amount of seeping out are seen from the diaphragm 121. It is considered that the ink m increases from the normal state, and the inertance m increases. In addition, it is considered that the acoustic resistance r increases due to the fibers of the paper powder attached near the outlet of the nozzle 110.

Therefore, compared to the case of Fig. 8 in which ink was ejected normally, both the inertance m and the acoustic resistance r were set to be large, and an experiment on residual vibration when paper dust adhered near the exit of nozzle 110 was performed. By matching the values, the result (graph) shown in Fig. 14 was obtained. As can be seen from the graphs in Fig. 8 and Fig. 14, paper dust was found near the exit of nozzle 110. When the ink adheres, a characteristic residual vibration waveform whose frequency is lower than that during normal ejection is obtained. (Here, the frequency of the residual vibration is higher in the case of paper dust adhesion than in the case of ink drying.) This can also be seen from the graphs in FIGS. 12 and 14.) FIG. 15 is a photograph showing the state of the nozzle 110 before and after the adhesion of the paper powder. When paper dust adheres to the vicinity of the outlet of the nozzle 110, the state in which ink oozes along the paper dust can be seen from FIG. 15 (b).

Here, the case where the ink near the nozzle 110 dried and increased the viscosity and the case where paper dust adhered near the outlet of the nozzle 110 were both compared to the case where the ink droplet was normally ejected. Therefore, the frequency of the damped vibration is low. In order to identify the cause of these two missing dots (non-ejection of ink: abnormal ejection) from the waveform of the residual vibration of the diaphragm 121, for example, a predetermined threshold value is set in the frequency, cycle, and phase of the damped vibration. They can be compared with each other or can be specified from the decay rate of the period change or amplitude change of the residual vibration (damped vibration). In this manner, a change in the residual vibration of the diaphragm 121 when an ink droplet is ejected from the nozzle 110 in each ink jet head 100, in particular, a change in its frequency causes a change in each ink jet head 1. It is possible to detect a discharge abnormality of 00. In addition, by comparing the frequency of the residual vibration in that case with the frequency of the residual vibration during normal ejection, the cause of the ejection abnormality can be specified.

Next, the discharge abnormality detecting means 10 according to one embodiment of the present invention will be described. Here, a case will be described in which a discharge abnormality is detected based on a period until a damped vibration of the diaphragm 121 occurs during normal discharge. FIG. 16 schematically shows the discharge abnormality detecting means 10 shown in FIG. 2 according to an embodiment of the present invention, and shows a switching operation between an oscillation circuit (oscillation means) 11 and a drive circuit 18. It is a block diagram. As shown in FIG. 16, the discharge abnormality detecting means 10 of the present invention includes an oscillating means 11, a subtraction counter 45, a normal count value memory 46, a comparison reference value memory 47, 20. The determination result of the determination unit 20 is stored in the storage unit 62 at a predetermined timing (timing of input of the Ls signal). Hereinafter, each component shown in FIG. 16 will be described.

Oscillation means (oscillation circuit) 11 is an oscillation circuit that oscillates based on the residual vibration of the diaphragm 121 of the electrostatic actuator 120, and subtracts the oscillation signal (pulse signal). It is output at 45. First, the operation of the oscillating means 11 will be described. Fig. 17 is a conceptual diagram when the electrostatic actuator 120 of Fig. 3 is a parallel plate capacitor, and Fig. 18 includes the capacitor composed of the electrostatic actuator 120 of Fig. 3. FIG. 3 is a circuit diagram of an oscillation circuit 11; The oscillation circuit 11 shown in FIG. 18 is a CR oscillation circuit that uses the hysteresis characteristic of the shunt trigger. However, the present invention is not limited to such a CR oscillation circuit. Any oscillation circuit may be used as long as it uses the capacitance component (capacitor C). The oscillation circuit 11 may be configured to use, for example, an LC oscillation circuit. Further, in the present embodiment, an example using the Schmitt trigger invertor 111 has been described. However, for example, a CR oscillation circuit using three stages of invertors may be configured.

In the ink jet head 100 shown in FIG. 3, as described above, the diaphragm 121 and the segment electrode 122 separated by a very small space (gap) form an opposing electrode. 1 2 0 is constituted. This electrostatic actuator 120 can be considered as a parallel plate capacitor as shown in FIG. The capacitance of this capacitor is C, the surface area of each of the diaphragm 121 and the segment electrode 122 is S, the distance (gap length) between the two electrodes 121, 122 is g, and both electrodes are sandwiched. If the dielectric constant of the space (void) is ε (the dielectric constant of vacuum is ε. The relative dielectric constant of the void is ε = ε. • ε _r ), the capacitor (electrostatic capacitor) shown in Fig. 17 is obtained. The capacitance C (X) at 120) is expressed by the following equation.

[Equation 2]

C (x) = s _Q - _Er ^ (F) (4)

g-X

Note that X in Expression (4) indicates the displacement amount of the diaphragm 122 from the reference position caused by the residual vibration of the diaphragm 121, as shown in FIG.

As can be seen from this equation (4), when the gap length g (gap length g—displacement X) decreases, the capacitance C (x) increases, and conversely, the gap length g (gap length g—displacement X) As the quantity X) increases, the capacitance C (X) decreases. Thus, the capacitance The quantity C (x) is inversely proportional to (gap length g-displacement x) (gap length g if X is 0). In addition, in the electrostatic actuator 120 shown in FIG. 3, since the void is filled with air, the relative dielectric constant is £ _r = 1.

In general, as the angle of image of a droplet discharge device (in the present embodiment, the ink jet printer 1) increases, the size of the ejected ink droplets (ink dots) becomes smaller. 120 can be made denser and smaller. As a result, the surface area S of the vibration plate 121 of the inkjet head 100 becomes small, and a small electrostatic actuator 120 is formed. Further, the gap length g of the electrostatic Akuchiyue Isseki 1 2 0 which varies Te cowpea the residual vibration caused by ink droplet ejection, since the approximately 10% of the initial gap g _Q, as can be seen from equation (4), static The change in the capacitance of the electrical equipment overnight is a very small value.

In order to detect the amount of change in the capacitance of the electrostatic actuator 120 (which differs depending on the vibration pattern of the residual vibration), the following method is used, that is, the static capacitance of the electrostatic actuator 120 is measured. An oscillation circuit as shown in Fig. 18 is configured based on the capacitance, and the method of analyzing the frequency (period) of the residual vibration based on the oscillated signal is used. The oscillation circuit 11 shown in Fig. 18 consists of a capacitor (C) composed of an electrostatic actuator 120, a Schmitt trigger inverter 111, and a resistance element (R) 112. Is done. When the output signal of Schmitt trigger inverter is at High level, capacitor C is charged via resistor element. Charging voltage of the capacitor C (a potential difference between the diaphragm 1 2 1 and the segment electrode 1 2 2) reaches the input mosquito threshold voltage V _T tens Gerhard Mitsuto trigger inverter Isseki 1 1 1, the Schmitt trigger inverter evening 1 1 1 Output signal is inverted to Low level. Then, when the output signal of the Schmitt trigger inverter 11 becomes the Low level, the electric charge that has been charged in the capacitor C via the resistive element 112 is discharged. When this discharge causes the voltage of the capacitor C to reach the input threshold voltage V _T — of the Schmitt trigger, the output signal of the Schmitt trigger returns to the High level again. Thereafter, this oscillation operation is repeated.

Here, in order to detect the time change of the capacitance of the capacitor C due to each of the above phenomena (bubble mixing, drying, adhesion of paper powder, and normal ejection), the oscillation circuit 11 1 The oscillation frequency must be set to an oscillation frequency that can detect the frequency when bubbles are mixed with the highest residual vibration frequency (see Fig. 10). For this reason, the oscillation frequency of the oscillation circuit .11 must be, for example, several times to several tens times or more the frequency of the residual vibration to be detected, that is, a frequency that is at least about one digit higher than the frequency when bubbles are mixed. No. In this case, it is preferable to set the oscillation frequency at which the residual vibration frequency at the time of air bubble mixing can be detected because the frequency of the residual vibration at the time of air bubble mixing is higher than that at the time of normal ejection. ^ "If it does not, it is not possible to accurately detect the frequency of the residual vibration for the phenomenon of abnormal discharge. Therefore, in the present embodiment, the time constant of the CR of the oscillation circuit 11 according to the oscillation frequency By setting the oscillation frequency of the oscillation circuit 11 high as described above, a more accurate residual oscillation waveform can be detected based on the minute change of the oscillation frequency.

The drive circuit 18 is a circuit that generates a drive waveform of the electrostatic actuator 120 as shown in a timing chart of FIG. 19 described later. Although not shown, the drive circuit 18 selects which of the plurality of ink jet heads 100 ejects ink droplets from the nozzles 110 of the ink jet head 100. Discharge selection means (selector) is provided.

The switching means 23 is a switch (switching circuit) for switching the connection with the electrostatic actuator 120 between the drive circuit 18 and the oscillation circuit 11. The switching means 23 is connected to the drive circuit 18 for driving the electrostatic actuator 120. As described above, when a drive signal (voltage signal) is input to the diaphragm 12 1 from the drive circuit 18, the electrostatic actuator 120 is driven, and the diaphragm 12 1 When the applied voltage becomes 0, it is suddenly displaced away from the segment electrode 122 and starts vibrating (residual vibration). At this time, ink droplets are ejected from the nozzles 110 of the inkjet head 100.

When the pulse of the drive signal falls, the drive Z detection switching signal (see the timing chart in FIG. 19) is input to the switching means 23 in synchronization with the falling edge, and the switching means 23 is driven by the drive circuit 1 The discharge abnormality detection means (detection circuit) 10 is switched to 10 from 8, and the electrostatic work 120 (used as a capacitor of the oscillation circuit 11) is connected to the discharge abnormality detection means 10. As a result, the oscillation circuit 11 oscillates and the oscillation signal Output to the subtraction counter 45.

When a predetermined count value is input from the normal count value memory 46, the subtraction counter 45 holds it. When an oscillation signal (pulse signal) is input from the oscillation circuit 11, the subtraction counter 45 subtracts the number of pulses from the predetermined count value for a predetermined period (predetermined time). Note that the predetermined period is, for example, the time until the residual vibration of the diaphragm 121 occurs when the ink droplet is normally ejected from the inkjet head 100, and the residual vibration during normal ejection. For example, half cycle, 1/4 cycle of residual vibration during normal ejection. The predetermined count value stored in the normal count value memory 46 is the number of pulses counted during the above-described predetermined time during normal ejection.

As shown in the timing chart of Fig. 19, the decrement counter 45 acquires a predetermined count value (normal count value) from the normal count value memory 46 at the load signal input timing, and switches between drive / detection. While the signal is at the high level, open the gate and receive the oscillation pulse, which is the output signal of the oscillation circuit 11, and subtract it from the normal count value. The judgment means 20 compares the subtraction result obtained by the subtraction processing of the subtraction counter 45 with a predetermined reference value input from the comparison reference value memory 47. Then, at the timing of input of the Ls signal, the determination result of the determination means 20 is held, and the determination result is output to the storage means 62. Note that several reference values (thresholds) are set as the predetermined reference values, and by comparing the judgment result with each of these several reference values, the above-mentioned discharge abnormality (bubble contamination, paper dust adhesion) can be obtained. And dry thickening) can be detected and determined. Details will be described later.

The normal count and memory 46 and the comparison reference value memory 47 may be provided in the inkjet printer 1 as separate memories, respectively, or may be shared with the EEPROM (storage means) 62 of the control unit 6. Good. Such a subtraction counting process is performed during a drive suspension period in which the electrostatic work 120 of the ink jet printer 1 is not driven. This makes it possible to detect a discharge abnormality without reducing the throughput of the inkjet printer 1.

Next, the operation of the ejection abnormality detecting means 10 of the present invention will be described with reference to the timing chart of FIG. First, the Load signal and Ls signal shown in Fig. 16 and Fig. 19 And a method of generating a CLR signal will be described. As shown in the timing chart of FIG. 19, the Load signal is a signal that becomes High level only for a short time immediately before the rising edge of the drive signal output from the drive circuit 18, and the Ls signal is A signal that is at a high level for a predetermined time (sufficient time to store the judgment result in the storage means 62) in synchronization with the falling edge of the drive Z detection switching signal input to the switching means 23. You. Although not shown in the timing chart of FIG. 19, the CLR signal is a signal for clearing the subtraction result held in the subtraction counter 45 by the subtraction processing. It is input to the subtraction counter 45 at a predetermined timing until the oad signal is input.

The ejection abnormality detecting means 10 operates based on the signal group generated in this manner. When the Load signal is input to the subtraction counter 45 immediately before the rising edge of the drive signal output from the drive circuit 1 &, the normal count value is input from the normal count value memory 46 at that timing, Will be retained. The input timing of the L ad signal is not limited to the above timing, and may be any timing after the input of the L s signal until the end of the driving period. When the ejection drive operation of the ink jet head 100 ends, a drive / detection switching signal is input to the switching means 23 in synchronization with the falling edge of the drive signal. In response to the drive / detection switching signal, the switching means 23 switches the connection with the electrostatic actuator 120 from the drive circuit 18 to the oscillation circuit 11.

The capacitance component (C) of the oscillation circuit 11 changes due to the residual vibration of the diaphragm 121, and the oscillation circuit 11 starts oscillating based on the change. The subtraction counter 45 opens the gate in synchronization with the rise of the drive Z detection switch signal, and subtracts the number of pulses from the normal count value while the drive Z detection switch signal is at the High level (during T s). This T s is the time required for the diaphragm 121 to start the residual vibration during normal ejection (until the residual vibration occurs). After the ink jet 100 ejects the ink droplet, Actuy — This is the time it takes to return to the position of diaphragm 1 21 when evening 120 is not driven.

In the timing chart of FIG. 19, after switching between the drive circuit 18 and the discharge abnormality detecting means 10, the timing chart is based on the normal count value until the residual vibration of the diaphragm occurs. To determine the discharge abnormality. Therefore, when the residual vibration occurs

(The timing at which the diaphragm 1 2 1 returns to the initial position) The drive Z detection switching signal falls to the Low level, the Ls signal is generated, and based on the subtraction result of the subtraction counter 45, The determination result obtained by the determination means 20 making a predetermined determination is held (saved) in the storage means 62. The reference values Nl, N2, P1, and P2 will be described later. FIG. 20 shows that, after the drive signal is applied, the electrostatic means 120 and the oscillation circuit 11 are connected by the switching means 23, and the change in the oscillation frequency output from the oscillation circuit 11 is plotted on the vertical axis. FIG. 5 is a diagram showing a time transition of the oscillation frequency by providing the elapsed time on the horizontal axis. The change in the oscillation frequency over time indicates a residual vibration waveform in each state of the inkjet head. As shown in FIG. 20, the period of the residual vibration is shorter when air bubbles are mixed, and the period of the residual vibration is longer when paper dust adheres or thickens as compared with the normal ejection. Here, after the application of the drive signal, the oscillation frequency of the oscillation circuit 11 changes depending on the state of each residual vibration. During normal discharge, the time until the diaphragm 121 returns to the position (initial position) of the diaphragm 121 when the electrostatic actuator 120 is not driven (initial state). Comparing the conditions up to T s, when bubbles are mixed, the residual vibration waveform rises until it reaches T s, and an oscillation pulse with an oscillation frequency of the oscillation circuit 11 higher than that during normal ejection is output. ing. On the other hand, in the case of drying (thickening), since the residual oscillation waveform does not rise until T s, the oscillation pulse of the oscillation circuit 11 is mainly output lower than that in normal ejection. Means that Therefore, since the number of oscillation pulses of the oscillation circuit 11 changes according to the difference in the period of the residual vibration, that is, the difference in the frequency of the residual vibration, based on the subtraction result of the subtraction counter 45, Discharge abnormality determination processing by the determination means 20 can be performed.

Next, an example of the result of the subtraction count 45 will be shown. Fig. 21 is a graph showing an example of the result of the subtraction of the subtraction counter 45 and the result of the determination by the determining means 20 based on the result. As described above, the cycle of the residual vibration is shorter when air bubbles are mixed and longer when dry thickening or paper dust adheres, as compared with the case of normal ejection. Therefore, by setting at least two reference values as the reference values stored in the comparison reference value memory 47, it is possible to distinguish between normal ejection and abnormal ejection (in this case, the reference Only the values N 1 and P 1 Configuration) . However, more preferably, three or four reference values are provided, and the state of the above three types of discharge abnormalities is determined based on whether the subtraction result obtained by the subtraction processing is larger than these reference values. it can.

In the graph of FIG. 21, four reference values P2, Pl, Nl, and N2 are set as reference values for the subtraction result. The reference value N1 and the reference value N2 are set as the first threshold, and the judging means 20 judges that the cause of the ejection abnormality is air bubble mixing when the subtraction result is smaller than the first threshold. I do. If the subtraction result is less than the reference value N1 and more than the reference value N2, it is determined that minute air bubbles are mixed.If it is smaller than the reference value N2, a large amount of It can be determined that air bubbles are mixed. In this case, an appropriate recovery process can be executed by changing the pump suction time or the pump suction pressure, for example, based on the size of the air bubbles. If such a judgment is not particularly necessary, it may be possible to judge whether or not air bubbles are mixed based only on the reference value N1. The reference value P2 is set as the second threshold value, and the determination means 20 determines that the cause of the discharge abnormality is dry thickening when the subtraction result is larger than the second threshold value. In addition, the reference value P1 is set as the third threshold value, and the determination means 20 determines the cause of the discharge abnormality if the subtraction result is larger than the third threshold value and smaller than the second threshold value. Judge as paper dust adhesion. Note that, in FIG. 21, P 1 = + 3, P 2 = + 10, N 1 = 13, and P 2 = −10 in FIG. 21 as these reference values. As the judgment result output from the judging means 20, "1" is output when the absolute value of the subtraction result exceeds each reference value. Figure 22 shows the relationship between the cause of the discharge abnormality and the output of each reference value. The determining means 20 can determine the presence or absence of the discharge abnormality and the cause thereof based on the value of each reference value.

It is better to obtain these reference values in advance by experiments. This is because the period of the residual vibration of the diaphragm 121 when an ink droplet is ejected from the ink head 100 is based on the structure of the ink head 100, that is, the structure of the cavity 141. This is because it is determined by the above.

Next, a discharge abnormality detection process in the case of detecting a discharge abnormality based on a period until the damping vibration of the diaphragm 122 occurs will be described. FIG. 23 is a flowchart showing a discharge abnormality detection process according to an embodiment of the present invention. The print data to be printed (or the discharge data during the flushing operation) may be input from the host computer 8. When input to the control unit 6 via the interface (IF) 9, this discharge abnormality detection processing is executed at a predetermined timing. For convenience of explanation, the flowchart shown in FIG. 24 shows an ejection failure detection process corresponding to the ejection operation of one inkjet head 100, that is, one nozzle 110.

First, the Load signal is input to the subtraction force counter 45 at a timing immediately before the drive signal is input (this timing is not limited to this), and the normal force count value is input (preset) from the normal force value memory 46 ( Step S101). Then, a drive signal corresponding to the print data (discharge data) is input from the drive circuit 18 of the head dryer 33, and based on the drive signal timing as shown in the timing chart of FIG. A drive signal (voltage signal) is applied between both electrodes of the electrostatic actuator 120 (step S102). Then, the control unit 6 determines whether or not the input of the drive signal (voltage signal) to the electrostatic actuator 120 has been completed (step S103). The Z detection switching signal is input from the control unit 6 to the switching unit 23.

When the drive Z detection switching signal is input to the switching means 23, the switching means 23 disconnects the electrostatic actuator 120, that is, the capacitor forming the oscillation circuit 11 from the driving circuit 18, and discharge abnormality detection means 10 (Detection circuit) side, that is, connected to the oscillation circuit 11 (step S104). The oscillation circuit 11 is configured based on the capacitance of the electrostatic actuator 120 (step S105), and an oscillation pulse is output from the oscillation circuit 11 (step S106). This oscillation pulse is input to the subtraction counter 45, and the subtraction counter 45 counts down the oscillation pulse from the normal count value (step S107). In the preset counting period, in this case, the subtraction counting process is executed until the period from when the switching is performed by the switching means 23 to when the damping vibration occurs is completed, and when the counting period is completed (step S108), the determination is made. Move on to processing.

In step S109, the determination means 20 determines whether or not the number of oscillation pulses is within the range of the normal count number (that is, the reference values N1 to P1) based on the subtraction result of the subtraction counter 45. If it is within the range of the normal count number, the determination means 20 determines that the ink is discharged normally (step S110), and conversely, the range is within the range of the normal count number. If not, it is determined that the ink jet head 100 has a discharge abnormality (a defective nozzle 110) (step S111).

Then, the determination result by the determination means 20 is stored (held) in the storage means 62 (step S112), and the connection with the electrostatic actuator 120 is made based on the drive / detection switching signal. Is switched from the oscillation circuit 11 to the drive circuit 18, and the oscillation of the oscillation circuit 11 is stopped (step S113). In step S114, it is determined whether or not the ejection driving process by the inkjet head 100 has been completed. If it is determined that the ejection driving process has been completed, the ejection abnormality detection process ends. If it is determined that the processing has not been completed, the flow shifts to step S101, and the same processing is repeated.

As described above, in the ejection abnormality detection process of the present invention, the oscillation pulse is subtracted from the normal count value, and the result of the subtraction is compared with a predetermined reference value.

The presence / absence of a discharge abnormality of 100 and the presence of a discharge abnormality can be detected with a simple configuration.

Next, a description will be given of a discharge abnormality detection unit 10 according to another embodiment of the present invention. Here, a case will be described in which a discharge abnormality is detected based on a period of a half cycle or a quarter cycle during normal discharge. FIG. 24 is a schematic block diagram of the discharge abnormality detecting means 10 shown in FIG. 2 according to another embodiment of the present invention. Only the configuration different from that in FIG. 16 will be described, and the components having the same functions as those in the block diagram in FIG. 16 will be denoted by the same reference numerals, and description thereof will be omitted.

The discharge abnormality detecting means 10 switches between the oscillation circuit 11, the subtraction counter 45, the normal value memory 46 having a plurality of normal value memories 46a to 46n, and the normal value memory. A first selector 48a, a first comparison reference value memory 47a, a first determination means 20a, a storage means 62 having a plurality of storage means 62 to 62n, and a storage means It is composed of a second selector 48b for switching between 6 and 2, a second comparison reference value memory 47b, and a second determination means 20'b.

The first selector 48 a switches the normal count value input to the subtraction counter 45 based on a predetermined timing of the residual vibration during normal ejection, and the second selector 48 b According to the normal count value memories 46a to 46n selected by the first selector 48a, the first determination means 20a (the same structure as the determination means 20 in the above example) is used. The storage means 62 for storing the result of the determination is switched.

The second determination means 200b is configured to discharge the ink jet head 100 based on the determination results stored (saved) in the plurality of storage means 62a to 62n as shown in the graph of FIG. The presence or absence of an abnormality and the cause of the ejection abnormality are finally determined. Note that a sequence as shown in the table of FIG. 29 is stored in the second comparison reference value memory 47b.

Fig. 25 shows the residual vibration waveform when the count period is half the period of the residual vibration during normal discharge. Fig. 26 shows the residual vibration waveform when the count period is one-fourth of the residual vibration during the normal discharge. Is shown. In this embodiment, the subtraction counter 45 performs a subtraction process in the first half cycle or 1Z4 cycle of the residual vibration during normal ejection, or every half cycle or every 1 to 4 cycles, and performs a plurality of subtractions. Abnormal discharge is detected and judged based on the results.

Next, with reference to the timing chart of FIG. 27, the operation of the discharge abnormality detecting means 10 of the present embodiment will be described. FIG. 27 is an evening timing chart (every half cycle) of the subtraction process of the subtraction counter 45 shown in FIG. The first Load signal is input immediately before the drive signal, and the normal count value 1 is input to the subtraction counter 45. The subtraction counter 45 opens the gate in synchronization with the falling edge of the drive signal, and starts the subtraction process. When a residual vibration occurs (that is, when the diaphragm 121 returns to the steady position for the first time), the Ls signal is input to the storage means 62, and the subtraction result up to that time is stored in the storage means 62a. At the same time, the CLR signal and the Load signal are input to the subtraction counter 45, and the result of the previous subtraction is cleared, and the next normal count value 2 is input.

Hereinafter, similarly, the subtraction processing is repeated, and the subtraction result from each normal count value is stored in the storage means 62. The second determination means 20 b receives the comparison reference value (see the table in FIG. 29) from the second comparison reference value 47 b, and based on the comparison reference value, the corresponding inkjet head 10 0. The presence / absence of a discharge abnormality of 0 and the cause of the discharge abnormality are finally determined.

FIG. 28 is a diagram showing an example of the subtraction result of the subtraction count and the determination result of the determination means based thereon ((A) for each half cycle and (B) for each quarter cycle). FIG. 29 is a diagram showing the relationship between the cause of the discharge abnormality and the output of each reference value (each half cycle is shown in (A), and every 1 Z 4 cycles is shown in (B)). Thus, the subtraction result of the period of multiple places By using this, it is possible to execute more accurate discharge abnormality determination processing.

Next, a description will be given of a discharge abnormality detection process in the case where a discharge abnormality is detected based on a period of every half cycle or every 14 cycles of the residual vibration during normal discharge. FIG. 30 is a flowchart showing a discharge abnormality detection process according to another embodiment of the present invention. As in the front chart of FIG. 23, the ejection abnormality detection process is executed at a predetermined timing such as when print data is input to the ink jet printer 1.

First, at the timing immediately before the drive signal input (not limited to this timing), the Load signal is input to the subtraction power unit 45, and the normal power value is input from the normal power value memory 46 (preset). (Step S201). Then, a drive signal corresponding to the print data (ejection data) is input from the drive circuit 18 of the head driver 33, and thereby, based on the timing of the drive signal as shown in the timing chart of FIG. A drive signal (voltage signal) is applied between both electrodes of the electrical equipment 120 (step S202). Then, the control section 6 determines whether or not the input of the drive signal (voltage signal) to the electrostatic actuator 120 has been completed (step S203), and the input of the drive signal has been completed. Then, a drive / detection switching signal is input from the control unit 6 to the switching unit 23.

When the drive detection switch signal is input to the switching means 23, the switching means 23 causes the electrostatic actuator 120, that is, the capacitor constituting the oscillation circuit 11 to be disconnected from the drive circuit 18. The discharge abnormality detecting means 10 (detection circuit) is connected to the oscillation circuit 11 (step S204). Then, based on the capacitance of the electrostatic actuator 120, the oscillation circuit 11 is configured (step S205), and an oscillation pulse is output from the oscillation circuit 11 (step S206). ). This oscillation pulse is input to the subtraction counter 45, and the subtraction counter 45 counts down the oscillation pulse from the first normal count value 1 (step S207). A preset counting period, in this case, a subtraction counting process is performed until the period from the time when the switching is performed by the switching means 23 to the time when the damping oscillation occurs is completed, and when the counting period is completed (step S 208) Then, the processing shifts to the judgment processing.

In step S209, the first determination means 20a sets the subtraction counter 45 Based on the result, it is determined whether or not the number of oscillation pulses is within the range of the normal count number (that is, the reference value Nl to PI). If the number is within the range of the normal count, the first determination means 20a determines that the ink has been discharged normally (step S210), and conversely, if the number is not within the range of the normal count. Determines that the inkjet head 100 has a discharge abnormality (is a defective nozzle 110) (step S211).

Then, the determination result by the first determination means 20a is stored (held) in the first storage means 62a (step S2122), and the control unit 6 performs the subtraction processing for all count periods. It is determined whether or not the processing has been completed (step S213). Since the subtraction process for every half cycle or quarter cycle of the residual vibration has not been executed yet, the process proceeds to step S2114, and the count period instruction signal is incremented by one (see the timing chart in FIG. 27). The next selector means 48 b selects the next storage means 6 2 b (step S 2 15), and the first selector 48 a selects the next normal count value memory 46 b, The normal count value 2 is preset in the subtraction counter 45 (step S2 16). Then, the processing from step S207 is repeated.

If it is determined in step S213 that the subtraction processing (first determination processing) has been completed for all count periods, the electrostatic actuator 120 and the electrostatic actuator 120 are determined based on the drive Z detection switching signal. Is switched from the oscillation circuit 11 to the drive circuit 18 to stop the oscillation of the oscillation circuit 11 (step S 2 17), and the second determination means 2 Ob uses a plurality of storage means 6 2 a Based on the first determination result and the second comparison reference value stored in 62n, a determination process of the ejection abnormality of the inkjet head 100 is executed (step S218). Then, in step S219, it is determined whether or not the ejection driving process by the inkjet head 100 has been completed. If it is determined that the ejection driving process has been completed, the ejection abnormality detection process ends. I do. If it is determined that the processing has not been completed, the flow shifts to step S201 to repeat the same processing.

As described above, in the ejection failure detection processing of the present invention, the oscillation pulse is subtracted from the normal force value at a plurality of timings, and the result of the subtraction is compared with a predetermined reference value. It is possible to more accurately detect the presence / absence of a discharge abnormality and the cause of the discharge abnormality with a simple configuration.

As described above, the droplet discharge device (inkjet printer 1) and the discharge device In the output abnormality determination method, when the operation of discharging the liquid as droplets from the inkjet head 100 is performed by driving the electrostatic actuator 120, the electrostatic actuator 120 The oscillation circuit 11 oscillates based on the change in the capacitance, and the subtraction counter 45 subtracts this oscillation pulse from the normal force count value, which is the power count value during normal ejection, based on the result of the subtraction. The determination means 20 determines whether the droplet has been discharged normally or not (discharge failure), and in the case of a discharge failure, what is the cause thereof.

Therefore, according to the droplet discharge device and the droplet discharge head discharge abnormality determination method of the present invention, a conventional dot missing detection method (for example, an optical detection method or the like) is provided. Compared with the droplet ejection device, other components (for example, optical dot missing detection device) are not required, so it is possible to accurately detect abnormal droplet ejection without increasing the size of the droplet ejection head. In addition, since the circuit configuration is not complicated, the manufacturing cost of a droplet discharge device capable of detecting a discharge abnormality (missing dot) can be reduced. Further, in the droplet discharge device of the present invention, since the abnormal discharge of the droplet is detected using the residual vibration of the diaphragm after the droplet discharge operation, the abnormal discharge of the droplet is detected even during the printing operation. be able to. Therefore, even if the ejection abnormality determination method of the present invention is executed during the printing operation, the throughput of the droplet ejection device is not reduced or deteriorated.

Further, the droplet discharge device of the present invention can determine the cause of a droplet discharge abnormality that cannot be determined by a conventional device that can detect missing dots, such as an optical detection device. Therefore, if necessary, an appropriate recovery process for the cause can be selected and executed.

Next, another configuration example of the inkjet head according to the present invention will be described. FIG. 31 to FIG. 34 are cross-sectional views each schematically showing another example of the configuration of the ink jet head 100. Hereinafter, description will be made based on these drawings, but description will be made focusing on differences from the above-described embodiment, and description of the same matters will be omitted.

The ink jet head 100A shown in FIG. 31 is vibrated by driving the piezoelectric element 200. The moving plate 212 vibrates, and the ink (liquid) in the cavity 208 is ejected from the nozzle 203. The stainless steel nozzle plate 202 with the nozzle (hole) 203 formed thereon is joined with a stainless steel metal plate 204 via an adhesive film 205. A metal plate 204 made of the same stainless steel is joined on the upper side via an adhesive film 205. Then, a communication port forming plate 206 and a cavity plate 207 are sequentially joined thereon.

The nozzle plate 202, the metal plate 204, the adhesive film 205, the communication port forming plate 206 and the cavity plate 200 each have a predetermined shape (shape such that a concave portion is formed). By molding and stacking these, a cavity 208 and a reservoir 209 are formed. The cavity 208 and the reservoir 209 communicate with each other via an ink supply port 210. Further, the reservoir 209 communicates with the ink intake port 211.

A vibrating plate 212 is provided at an opening on the upper surface of the cavity plate 207, and a piezoelectric element (piezoelectric element) 200 is provided on the vibrating plate 212 via a lower electrode 21. Joined. An upper electrode 214 is joined to the piezoelectric element 200 on the side opposite to the lower electrode 211. The head driver 210 includes a drive circuit for generating a drive voltage waveform, and applies (supplies) the drive voltage waveform between the upper electrode 214 and the lower electrode 213 to thereby generate the piezoelectric element 200. Vibrates, and the diaphragm 2 1 2 bonded thereto vibrates. The vibration of the diaphragm 212 changes the volume of the cavity 208 (pressure inside the cavity), and the ink (liquid) filled in the cavity 208 is ejected from the nozzle 203 as a liquid droplet. I do.

The amount of liquid reduced in the cavity 208 due to the ejection of the liquid droplets is supplied from the reservoir 209 by supplying ink. Further, ink is supplied to the reservoir 209 from the ink intake port 211.

Similarly to the above, the ink-jet head 100B shown in FIG. 32 discharges ink (liquid) in the cavity 22 from the nozzle by driving the piezoelectric element 200. This ink jet head 100B has a pair of opposed substrates 220, and a plurality of piezoelectric elements 200 are intermittently arranged at a predetermined interval between the two substrates 220. A cavity 2 21 is formed between adjacent piezoelectric elements 200. A plate (not shown) is installed at the front in FIG. 3 2 of the cavity 2 22, and a nozzle plate 222 is installed at the rear, and a position corresponding to each cavity 2 21 of the nozzle plate 222 is provided at the position. A nozzle (hole) 222 is formed.

A pair of electrodes 224 is provided on one surface and the other surface of each piezoelectric element 200, respectively. That is, four electrodes 224 are connected to one piezoelectric element 200. By applying a predetermined drive voltage waveform between predetermined electrodes of these electrodes 222, the piezoelectric element 200 is deformed in shear mode and vibrates (indicated by an arrow in FIG. 32). The vibration changes the volume of the cavity 222 (pressure inside the cavity), and the ink (liquid) filled in the cavity 222 is ejected from the nozzle 222 as a droplet. That is, in the ink jet head 100 B, the piezoelectric element 200 itself functions as a diaphragm.

The ink jet head 100C shown in FIG. 33 also discharges the ink (liquid) in the cavity 233 from the nozzle 231 by driving the piezoelectric element 200 in the same manner as described above. The ink jet head 100C includes a nozzle plate 230 on which the nozzles 231 are formed, a spacer 232, and a piezoelectric element 200. The piezoelectric element 200 is installed at a predetermined distance from the nozzle plate 230 through a spacer 23, and the nozzle plate 230, the piezoelectric element 200, and the spacer 23 A cavity 2 3 3 is formed in the space surrounded by 2.

A plurality of electrodes are joined to the upper surface of the piezoelectric element 200 in FIG. That is, a first electrode 234 is joined to a substantially central portion of the piezoelectric element 200, and a second electrode 235 is joined to both sides thereof. When a predetermined drive voltage waveform is applied between the first electrode 234 and the second electrode 235, the piezoelectric element 200 deforms in a shear mode and vibrates (indicated by an arrow in FIG. 33). However, the volume of the cavity 23 3 (pressure in the cavity) changes due to this vibration, and the ink (liquid) filled in the cavity 23 3 is ejected from the nozzle 23 1 as droplets. That is, in the inkjet head 100 C, the piezoelectric element 200 itself functions as a diaphragm.

In the same manner as described above, the ink jet head 100D shown in FIG. 34 discharges ink (liquid) in the cavity 245 from the nozzle 241 by driving the piezoelectric element 200. It is. This inkjet head 100D is formed by laminating a nozzle plate 240 on which the nozzles 24 are formed, a cavity plate 24, a diaphragm 24, and a plurality of piezoelectric elements 200. And a multi-layer piezoelectric element 201.

The cavity plate 242 is formed in a predetermined shape (shape that forms a concave portion), and thereby, the cavity 245 and the reservoir 246 are formed. The cavities 245 and the reservoirs 246 communicate with each other via the ink supply ports 247. The reservoir 246 communicates with the ink cartridge 31 via the ink supply tube 311.

The middle and lower ends of the multilayer piezoelectric element 201 shown in FIG. 34 are connected to the diaphragm 243 via the intermediate layer 244. A plurality of external electrodes 248 and internal electrodes 249 are joined to the laminated piezoelectric element 201. That is, an external electrode 248 is bonded to the outer surface of the multilayer piezoelectric element 201, and is provided between the piezoelectric elements 200 constituting the multilayer piezoelectric element 201 (or inside each piezoelectric element). The internal electrode 249 is installed. In this case, the external electrodes 248 and a part of the internal electrodes 249 are alternately arranged so as to overlap in the thickness direction of the piezoelectric element 200.

Then, by applying a drive voltage waveform from the head driver 33 between the external electrode 248 and the internal electrode 249, the multilayer piezoelectric element 201 is deformed as shown by the arrow in FIG. Vibrating (expanding and contracting in the vertical direction in Fig. 34), and this vibration causes the vibration plate 243 to vibrate. Due to the vibration of the vibrating plate 243, the volume of the cavity 245 (pressure in the cavity) changes, and the ink (liquid) filled in the cavity 245 is discharged as droplets from the nozzle 241.

The amount of liquid reduced in the cavity 245 due to the ejection of the liquid droplets is supplied from the reservoir 246 by supplying ink. In addition, ink is supplied from the ink cartridge 31 to the reservoir 246 via the ink supply tube 311.

The ink jet heads 100 A to 100 D having the above-described piezoelectric elements also function as diaphragms or diaphragms in the same manner as the above-described capacitive inkjet head 100. Based on the residual vibration of the piezoelectric element, it is possible to detect an abnormality in droplet ejection or to specify the cause of the abnormality. In the ink jet heads 100 B and 100 C, a diaphragm as a sensor is provided at a position facing the cavity. It is also possible to provide a (vibration plate for detecting residual vibration) and detect the residual vibration of this diaphragm.

As described above, the droplet discharge device and the method for determining a discharge abnormality of the droplet discharge head according to the present invention include a method of driving a liquid droplet from a droplet discharge head by driving an electrostatic actuator or a piezoelectric actuator. When the ejection operation is performed, the residual vibration of the diaphragm displaced by the actuator is detected, and based on the residual vibration of the diaphragm, the droplet is ejected normally or ejected. (Discharge abnormality) was detected.

Further, in the present invention, the cause of the abnormal discharge of the droplet thus obtained is determined based on the vibration pattern of the residual vibration of the diaphragm (for example, the cycle of the residual vibration waveform). .

Therefore, according to the present invention, other components (for example, an optical dot missing detection device, etc.) are not required as compared with a conventional droplet ejecting device equipped with a dot missing detecting method. Abnormal droplet ejection can be detected without increasing the size, and the manufacturing cost can be kept low. Further, in the droplet ejection head of the present invention, the abnormal ejection of the droplet is detected by using the residual vibration of the diaphragm after the droplet ejection operation. Can be detected. Further, according to the present invention, it is possible to determine the cause of a droplet ejection abnormality that cannot be determined by a conventional device capable of detecting missing dots, such as an optical detection device. An appropriate recovery process can be selected and executed for the cause.

As described above, the droplet discharge device and the method for determining the discharge abnormality of the droplet discharge head according to the present invention have been described based on the illustrated embodiments. However, the present invention is not limited thereto. Each component of the head or the droplet discharge device can be replaced with any component having the same function. Further, other arbitrary components may be added to the droplet discharge head or the droplet discharge device of the present invention.

The ejection target liquid (droplet) ejected from the droplet ejection head (the inkjet head 100 in the above embodiment) of the droplet ejection apparatus of the present invention is not particularly limited. Liquid containing various materials (suspension, emulsion, etc.) (Including a dispersion). That is, an ink containing a filter material of a color filter, a light emitting material for forming an EL light emitting layer in an organic EL (Electro Luminescence) device, and a fluorescent material for forming a phosphor on an electrode in an electron emission device. , A fluorescent material for forming a phosphor in a PDP (Plasma Display Panel) device, a material for forming a electrophoretic material in an electrophoretic display device, and a bank for forming a bank on the surface of a substrate W Materials, various coating materials, liquid electrode material for forming electrodes, particle material for forming a spacer for forming a small cell gap between two substrates, liquid metal for forming metal wiring Materials, lens materials for forming microlenses, resist materials, and light diffusion materials for forming light diffusers.

Further, in the present invention, the droplet acceptor from which droplets are to be ejected is not limited to paper such as recording paper, but may be other media such as films, woven fabrics and non-woven fabrics, glass substrates, silicon substrates and the like. Work such as various substrates may be used.

Claims

The scope of the claims

1. a diaphragm, an actuator for displacing the diaphragm, a cavity in which liquid is filled, and a displacement in which the internal pressure is increased or decreased by the displacement of the diaphragm, and a communication with the cavity, A plurality of droplet ejection heads having nozzles for ejecting the liquid as droplets by increasing or decreasing the pressure in the cavity;

A drive circuit for driving the actuator;

Determining means for determining whether or not an abnormal discharge has occurred in the droplet discharge head based on a subtraction result of the subtracting means;

A droplet discharge device comprising:

2. The droplet discharge device according to claim 1, wherein the determination unit determines a cause of the discharge abnormality when determining that the discharge abnormality has occurred.

3. The droplet discharge device according to claim 1, wherein the determination unit determines that bubbles have entered the cavity when the subtraction result is smaller than a first threshold value.

4. The liquid drop ejection device according to claim 1, wherein the determination unit determines that the liquid near the nozzle has increased in viscosity due to drying when the subtraction result is larger than a second threshold value.

5. The method according to claim 1, wherein the determining unit determines that paper dust has adhered near the outlet of the nozzle when the subtraction result is smaller than a second threshold value and larger than a third threshold value. The droplet discharge device according to the above.

6. The droplet discharge device according to claim 2, further comprising a storage unit configured to store a determination result determined by the determination unit.

7. The liquid according to claim 1, further comprising a switching means for switching the actuator from the drive circuit to the discharge abnormality detecting means after the discharge operation of the droplet by the driving of the actuator. Drop ejection device.

8. The droplet according to claim 1, wherein the oscillating means constitutes a CR oscillation circuit that includes a capacitance component of the actuator and a resistance component of a resistance element connected to the actuator. Discharge device.

9. The predetermined period is one or a plurality of periods in a residual vibration waveform of the diaphragm when a night drop is normally discharged from the droplet discharge head. 3. The droplet discharge device according to claim 1.

10. The droplet according to claim 9, wherein the predetermined period is a period from when the droplet is normally ejected from the droplet discharge head to when the residual vibration occurs. Discharge device

11. The droplet according to claim 9, wherein the predetermined period is a period up to a half cycle of residual vibration of the diaphragm when a droplet is normally ejected from the droplet ejection head. Discharge device.

12. The droplet according to claim 9, wherein the predetermined period is a period for every half cycle of the residual vibration of the diaphragm when the droplet is normally ejected from the droplet ejection head. Discharge device.

1 3. During the predetermined period, when a droplet is normally discharged from the droplet discharge head, 10. The liquid drop ejection device according to claim 9, wherein the period is up to 1/4 cycle of the residual vibration of the diaphragm.

14. The method according to claim 9, wherein the predetermined period is a period of every 1/4 cycle of residual vibration of the diaphragm when a droplet is normally ejected from the droplet ejection head. The droplet discharge device described in the above.

15. The predetermined reference value is the number of pulses oscillated by the oscillating means during the predetermined period when a droplet is normally ejected from the droplet ejection head. 5. The droplet discharge device according to 4.

16. The determination means scans the plurality of droplet discharge heads and causes the vibration means to oscillate, and based on the subtraction result obtained by the subtraction means, applies the respective droplet discharge heads to the plurality of droplet discharge heads. 2. The liquid droplet ejection device according to claim 1, wherein it is determined whether or not an ejection abnormality has occurred.

17. The droplet discharge device according to claim 1, wherein the actuating unit is an electrostatic actuating unit.

18. The droplet discharge device according to claim 1, wherein the actuator is a piezoelectric actuator using a piezo effect of a piezoelectric element.

19. The droplet discharge device according to claim 1, wherein the droplet discharge device includes an inkjet printer.

20. By driving the actuator and vibrating the diaphragm, the liquid in the cavity is ejected from the nozzle as liquid droplets, and then oscillated based on the residual vibration of the diaphragm. Subtracts the number of pulses of the obtained signal in a predetermined period from a predetermined reference value, and determines whether or not a discharge abnormality has occurred based on the result of the subtraction. A method for judging a discharge abnormality of a droplet discharge head.

21. The method according to claim 20, wherein when it is determined that the discharge abnormality has occurred, the cause of the discharge abnormality is determined.

22. When the subtraction result is smaller than the first threshold value, it is determined that bubbles are mixed in the cavity. When the subtraction result is larger than the second threshold value, the liquid near the nozzle is discharged. Claims wherein it is determined that viscosity has increased due to drying, and when the subtraction result is smaller than a second threshold value and larger than a third threshold value, it is determined that paper dust has adhered near the outlet of the nozzle. Item 21. The method for judging a discharge abnormality of a droplet discharge head according to Item 21.

23. The method according to claim 21, wherein the determination result is stored in a storage unit.

20. The droplet discharge head according to claim 20, wherein after the discharge operation of the droplet by the drive of the actuator, the actuator is switched from the drive circuit to the discharge abnormality detecting means. For determining abnormal discharge.

25. The predetermined period is one or more periods in the residual vibration waveform of the diaphragm when the droplet is normally discharged from the droplet discharge head, and the liquid is discharged from the droplet discharge head. A period up to a half cycle of the residual vibration of the diaphragm when the droplet is normally ejected, every half cycle of the residual vibration of the diaphragm when the droplet is normally ejected from the droplet ejection head. During the period, the droplets are normally ejected from the droplet ejection head during a period of up to 1 Z 4 cycles of the residual vibration of the diaphragm when the droplets are normally ejected from the droplet ejection head. 20. The method for judging an abnormal discharge of a droplet discharge head according to claim 20, wherein the residual vibration of the diaphragm at the time of being performed is any one of periods of every 1 Z 4 cycles.

26. The predetermined reference value is that a droplet is normally ejected from the droplet ejection head. 20. The method according to claim 20, wherein the number is the number of pulses oscillated in the predetermined period.