WO2004076187A1

WO2004076187A1 - Liquid drop ejector and method for detecting abnormal ejection of liquid drop ejection head

Info

Publication number: WO2004076187A1
Application number: PCT/JP2004/002443
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 in which abnormal ejection of a liquid drop ejection head can be detected by counting the number of reference pulses generated during a specified interval after liquid drop ejecting operation, and a method for detecting abnormal ejection of the liquid drop ejection head. The liquid drop ejector comprises a plurality of liquid drop ejection heads each consisting of a diaphragm and an actuator for displacing the diaphragm, a circuit for driving the actuator, a means for generating a reference pulse, a subtraction counter (45) for counting the reference pulses being generated during a specified interval, and a means for detecting abnormal ejection of liquid drop based on the count of the counter during the specified interval.

Description

Description Droplet discharge device and method of detecting abnormal discharge of droplet discharge head

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

Background art

An ink jet printer, which is one of the droplet discharge devices, forms an image on a predetermined sheet by discharging ink droplets (droplets) from a plurality of nozzles. Ink jet printing The printing head (inkjet head) has a large number of nozzles. However, the number of nozzles depends on factors such as the increase in ink viscosity, the inclusion of air bubbles, and the attachment of dust and paper dust. Some of the nozzles may be clogged and cannot eject ink droplets. If the nozzles are clogged, dots will be missing in the printed image, causing a deterioration in image quality.

Conventionally, as a method of detecting such an ink droplet ejection abnormality (hereinafter also referred to as “dot missing”), a state in which ink droplets are not ejected from the nozzles of an inkjet head (ink droplet ejection abnormal state) is used. A method for optically detecting each nozzle has been devised (for example, Japanese Patent Application Laid-Open No. Hei 8-30963). With this method, it is possible to identify the 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 droplet discharged from a nozzle of a droplet discharge head (inkjet head) passes between a light source and an optical sensor, and blocks light between the light source and the optical sensor. There is a problem that the light source and the optical sensor must be set (installed) with high precision (high precision). Also, such detectors are usually expensive and require There is also a problem that the manufacturing cost of the printer increases. In addition, the ink mist from the nozzle and paper dust of printing paper may stain the output part of the light source and the detection part of the optical sensor, which may cause a problem in the reliability of the detector. In addition, the above-described optical dot missing detection method can detect missing dots of nozzles, that is, abnormal ejection (non-ejection) of ink droplets.However, dot missing (ejection) is performed based on the detection result. There is also a problem in that the cause of the abnormality cannot be specified (determined), and it is impossible to select and execute an appropriate recovery process corresponding to the cause of the dropout. Therefore, for example, although ink can be recovered by the wiping process, the ink is discharged from the ink jet by pump suction, etc., thereby increasing the amount of waste ink (wasteful ink). By performing a plurality of recovery processes because they are not performed, the throughput of the ink jet printer (droplet discharge device) is reduced or worsened. Disclosure of the invention

SUMMARY OF THE INVENTION It is an object of the present invention to provide a droplet discharge device and a droplet discharge device capable of detecting an abnormal discharge of a droplet discharge head by counting reference pulses generated during a predetermined period after a droplet discharge operation. The present invention provides a method for detecting a head discharge abnormality.

In order to solve the above-mentioned problems, in one embodiment of the present invention, the droplet discharge device of the present invention

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

A drive circuit for driving the actuator;

Pulse generation means for generating a reference pulse;

Based on a count value for counting the reference pulse generated within a predetermined period and a count value of the count value within the predetermined period, a droplet ejection abnormality is determined. Discharge abnormality detecting means for detecting,

It is characterized by having.

According to the droplet discharge device of the present invention, a pulse generated within a predetermined period when an operation of discharging a liquid as a liquid droplet is performed by driving the actuator is counted, and based on the count value. It detects whether the droplet was ejected normally or not (abnormal ejection).

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

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

Further, preferably, the predetermined period may be a period until the diaphragm displaced by the actuation unit when a droplet is normally ejected generates residual vibration, and Or a period of the first cycle of the residual vibration. Preferably, the ejection abnormality detection means includes: a normal counting range of a reference pulse when a droplet is normally ejected by driving the actuator; and a counting time of the counting pulse within the predetermined period. The discharge abnormality is detected by comparing with the value.

Here, preferably, when the count value is smaller than the normal count range, the discharge abnormality detection means detects that air bubbles have entered the cavity, and the count value is smaller than the normal count range. If it is larger, it is detected that the liquid near the nozzle has thickened due to drying or that paper dust has adhered near the nozzle outlet. Preferably, the counter subtracts the number of reference pulses counted in the predetermined period from a predetermined reference value, and the discharge abnormality detection means detects the discharge abnormality based on the result of the subtraction. I do. In this case, preferably, when the subtraction result is smaller than a first threshold value, the discharge abnormality detecting means detects that the bubble force is mixed in the cavity as a cause of the discharge abnormality, and the subtraction result Is larger than the second threshold, it is detected that the liquid in the vicinity of the nozzle is thickened by drying as a cause of the discharge abnormality, and the subtraction result is smaller than the second threshold and smaller than the third threshold. If it is larger, it is detected that paper dust has adhered to the vicinity of the nozzle outlet as the cause of the discharge abnormality. In the present invention, the term “paper dust” is not limited to paper dust generated 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 dust floating in air. Anything that adheres to the vicinity of the nozzle and hinders droplet ejection.

More preferably, the droplet discharge device of the present invention may further include a storage unit that stores a detection result detected by the discharge abnormality detection unit. In addition, the droplet discharge device of the present invention preferably further includes a switching unit that switches the actuator from the drive circuit to the discharge abnormality detection unit after the droplet discharge operation by the drive of the actuator. Prepare.

Here, preferably, the discharge abnormality detecting means includes an oscillating circuit, and the oscillating circuit oscillates based on a capacitance component of the actuator that changes due to residual vibration of the vibrating plate. It may be configured. Here, preferably, the oscillation circuit constitutes a CR oscillation circuit including a capacitance component of the actuator and a resistance component of a resistance element connected to the actuator. Further, the discharge abnormality detection means includes an F / V conversion circuit that generates a voltage waveform of residual vibration of the diaphragm by a predetermined signal group generated based on a change in oscillation frequency in an output signal of the oscillation circuit. May be included. More preferably, the discharge abnormality detecting means includes a waveform shaping circuit for shaping a voltage waveform of the residual vibration of the diaphragm generated by the F / V conversion circuit into a predetermined waveform. In this case, preferably, the waveform shaping circuit is generated by the FZV conversion circuit. DC component removing means for removing a DC component from the voltage waveform of the residual vibration of the vibration plate, and a comparator for comparing the voltage waveform from which the DC component has been removed by the DC component removing means with a predetermined voltage value. The comparator generates and outputs a rectangular wave based on the voltage comparison.

Incidentally, the actuation may be an electrostatic actuation or a piezoelectric actuation utilizing a piezoelectric effect of a piezoelectric element. Since the droplet discharge device of the present invention can use not only the electrostatic actuating device including the above-described capacitors but also the piezoelectric actuating device, the present invention is applied to most existing droplet discharging devices. can do. Further, preferably, the droplet discharge device of the present invention includes an ink jet printer.

In another embodiment of the present invention, a droplet discharge device of the present invention

A cavity filled with a liquid, a nozzle communicating with the cavity, and a piezoelectric actuator for changing a pressure of the liquid filled in the cavity, and discharging the liquid as droplets from the nozzle by the pressure fluctuation. A plurality of droplet ejection heads having

A drive circuit for driving the piezoelectric actuator,

Pulse generation means for generating a reference pulse;

A counter that counts the reference pulse generated within a predetermined period; a discharge abnormality detection unit that detects a droplet discharge abnormality based on a count value of the counter within the predetermined period;

It is characterized by having.

As described above, the droplet discharge device of the present invention can employ the same configuration as described above by utilizing the piezoelectric actuator and the electromotive voltage. Preferably, the predetermined period is a period until a residual vibration of a voltage due to an electromotive voltage of the piezoelectric actuator after the droplet is normally discharged is generated. Preferably, the droplet discharge device of the present invention includes an ink jet printer. In another aspect of the present invention, a method for detecting a discharge abnormality of a droplet discharge head according to the present invention comprises the steps of: driving an actuator and vibrating a diaphragm to convert liquid in a cavity into droplets; After performing the operation of discharging from the nozzle, the reference pulse , A predetermined period is measured, a reference pulse generated within the measured predetermined period is counted, and a drop ejection abnormality is detected based on the count value. .

Here, preferably, the number of reference pulses counted in the predetermined period is subtracted from a predetermined reference value, and the discharge abnormality is detected based on a result of the subtraction.

In another embodiment of the present invention, a method for detecting an abnormal discharge of a droplet discharge head includes the steps of: generating a reference pulse after driving a piezoelectric actuator to perform a droplet discharge operation; The present invention is characterized in that a predetermined period is measured, a reference pulse generated within the measured predetermined period is counted, and a discharge abnormality of the droplet is detected based on the count value. As a result, it is possible to detect a discharge abnormality similarly in the residual vibration based on the electromotive voltage of the piezoelectric actuator.

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 diagram showing a configuration of an ink jet printer 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 cross-sectional view of the ink jet head shown in FIG. FIG. 4 is an exploded perspective view showing the configuration of the head unit corresponding to the one-color ink shown in FIG.

FIG. 5 is an example of a nozzle arrangement pattern of the nozzle plate of the head unit 1 using a four-color ink.

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

FIG. 8 is a graph showing the relationship between the experimental value and the calculated value of the residual vibration of the diaphragm shown in FIG.

FIG. 9 is a conceptual diagram of the vicinity of the nozzle when bubbles are mixed in the cavity of FIG.

FIG. 10 is a graph showing calculated values and experimental values 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 a calculated value and an experimental value of the 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 to the vicinity of the nozzle outlet of FIG.

FIG. 14 is a graph showing calculated values and experimental values of the residual vibration in a state where the 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 schematic block diagram of the discharge abnormality detecting means shown in FIG. 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 oscillation circuit including a capacitor composed of the electrostatic actuator shown in FIG.

FIG. 19 is a circuit diagram of the FZV conversion circuit of the ejection abnormality detecting means shown in FIG.

FIG. 20 is a timing chart showing the timing of the output signal of each unit based on the oscillation frequency output from the oscillation circuit of the present invention.

FIG. 21 is a diagram for explaining a method of setting the fixed times tr and t1. FIG. 22 is a circuit diagram showing a circuit configuration of the waveform shaping circuit of FIG. FIG. 23 is a block diagram schematically showing switching means for switching between the drive circuit and the detection circuit.

FIG. 24 is a block diagram showing an example of the measuring means of the present invention.

FIG. 25 is a timing chart of the subtraction processing of the subtraction count shown in FIG.

FIG. 26 is a flowchart showing a discharge abnormality detection process according to an embodiment of the present invention.

FIG. 27 is a flowchart showing the residual vibration detection processing of the present invention.

FIG. 28 shows an example of the result of determining the cause of the discharge abnormality in the discharge abnormality detection process of the present invention.

FIG. 29 is a block diagram showing another example of the measuring means of the present invention.

FIG. 30 is a diagram showing residual vibration waveforms in a case where an ejection failure has occurred in the ink jet head and a case where normal ejection has occurred.

FIG. 31 is a timing chart (every half cycle) of the subtraction processing of the subtraction count shown in FIG. 29.

FIG. 32 is a flowchart 11 showing a discharge abnormality detection process according to another embodiment of the present invention.

Fig. 33 is a table showing the relationship between the time until the occurrence of residual vibration, the half cycle of residual vibration, and the cause of discharge abnormality.

FIG. 34 is a cross-sectional view schematically showing another configuration example of the inkjet head according to the present invention.

FIG. 35 is a cross-sectional view schematically showing another configuration example of the ink jet head according to the present invention.

FIG. 36 is a cross-sectional view schematically showing another configuration example of the ink jet head according to the present invention.

111 37 is a sectional view schematically showing another configuration example of the ink jet head in the present invention.

FIG. 38 is a block diagram showing an outline of a means for switching between a drive circuit and a detection circuit when a piezoelectric actuator is used. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the droplet discharge device and the droplet discharge head discharge abnormality detection method of the present invention will be described in detail with reference to FIGS. 1 to 38. This embodiment is given as an example, and the content of the present invention should not be interpreted in a limited manner. Hereinafter, in the present embodiment, an ink jet printer that discharges ink (liquid material) and prints an image on recording paper will be described 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 inkjet 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 the recording paper P is placed at the upper rear, a paper discharge roller 22 for discharging the recording paper P at the lower front, and an upper surface. An operation panel 7 is provided.

The operation panel 7 includes, for example, a liquid crystal display, an organic EL display, an LED lamp, and the like. A display unit (not shown) for displaying an error message and the like, and an operation unit (not shown) including various switches and the like. ). In addition, a printing device (printing device) 4 having a reciprocating printing means (moving body) 3 and a recording paper P are supplied to and discharged from the printing device 4 one by one inside the apparatus body 2. It has a paper feeding device (paper feeding means) 5 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 feeding 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 main scanning and sub-scanning in printing, and the ink jet method is used. The printing of the formula is performed.

The printing device 4 includes a printing unit 3, a carriage motor 41 serving as a drive source for moving the printing unit 3 in the main scanning direction, and a reciprocating movement that reciprocates the printing unit 3 in response to rotation of the carriage motor 41. Mechanism 42.

The printing means 3 has 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 / C) for supplying ink to each head unit 35 at its lower part. ) 31 and a carriage 32 equipped with each head unit 35 and an ink cartridge 31. As will be described later with reference to FIG. 3, each of the head units 35 includes one nozzle 110, a diaphragm 121, an electrostatic actuator 120, and a cavity 141, respectively. A large number of ink jet recording heads (ink-jet heads or droplet discharge heads) 100 each including an ink supply port 144 are provided. Although the head unit 35 includes 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. Accordingly, in the following, apart from the printing means 3, one nozzle 110, a diaphragm 121, an electrostatic actuator 120, a cavity 144, and an ink supply port are respectively provided. A unit provided with a plurality of ink jet heads 100 constituted by 14 2 and the like is referred to as a head unit 35.

In addition, full color printing can be performed by using an ink cartridge 31 filled with ink of four colors, yellow, cyan, magenta, and black (black). In this case, the printing means 3 is provided with a head unit 35 corresponding to each color. Here, FIG. 1 shows four ink force cartridges 31 corresponding to four color inks, but the printing means 3 uses other colors, such as light cyan, light magenta, and dark yellow ink. It may be configured to further include the cartridge 31. The reciprocating mechanism 42 includes a carriage guide shaft 42 supported at both ends by a frame (not shown), and a timer extending in parallel with the carriage guide shaft 42. Belt 4 4 1.

The carriage 32 is reciprocally supported by a carriage guide shaft 42 of the reciprocating mechanism 42 and is fixed to a part of the timing belt 42.

When the timing belt 4 21 is caused to travel forward and reverse via the pulley by the operation of the carriage motor 41, the printing means 3 is reciprocated by being guided by the carriage guide shaft 4 22. During this reciprocation, a plurality of ink jets in the head units 1 and 35 eject ink from the nozzles 110 of the heads 100 in accordance with the image data (print data) to be printed. Then, printing on recording paper P is performed.

The paper feeding device 5 has a paper feeding motor 51 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 across the feed path (recording paper P) of the recording paper P, and the drive roller 52b is a paper feed motor. 5 Connected to 1. Thus, the paper feeder 52 can feed a large number of recording papers P set in the tray 21 one by one toward the printing device 4. Note that, instead of the tray 21, a configuration may be adopted in which a paper cassette that stores the recording paper P can be detachably mounted. The control unit 6 controls the printing device 4 and the paper feeding device 5 on the basis of print data input from a host computer 8 such as a personal computer (PC) or a digital camera (DC). Print processing is performed on P. In addition, the control unit 6 displays an error message or the like on the display unit of the operation panel 7 or turns on or blinks an LED lamp or the like, and responds based on push signals of various switches input from the operation unit. Is performed by each unit.

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) 9 for receiving print data and the like input from a host computer 8, a control unit 6, Carriage motor 41 and A carriage motor driver 43 for driving and controlling the carriage motor 41, a paper supply motor 51, a paper supply driver 53 for driving and controlling the paper supply motor 51, a head unit 35, and a head unit. A head driver 33 for controlling the drive of the motor 35 and a discharge abnormality detecting means 10 are provided. The details of the ejection abnormality detecting means 10 and the head driver 33 will be described later.

In FIG. 2, the control unit 6 includes a CPU (Central Processing Unit) 61 that executes various processes such as a printing process and a discharge abnormality detection process, and print data input from the host computer 8 via the IF 9. (Electrically Erasable Programmable Read-Only Memory) (storage means) 62, which is a type of nonvolatile semiconductor memory that stores data in a data storage area (not shown). A type of RAM (Random Access Memory) 63 that temporarily stores various data or temporarily develops application programs such as print processing, and a type of non-volatile semiconductor memory that stores control programs that control each unit. There is a PROM64. The components of the control unit 6 are electrically connected via a bus (not shown).

As described above, the printing means 3 is composed of a plurality of head units 35 corresponding to the respective color inks, and each head unit 35 corresponds to the plurality of nozzles 110 and the respective nozzles 110. Equipped with an electrostatic actuator 120 and (a plurality of inkjet heads 100). 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 includes a drive circuit 18 that drives the electrostatic actuator 120 of each inkjet head 100 to control the ink ejection timing, and a switching unit 23 ( See Figure 16). The configuration of the ink jet head 100 and the electrostatic actuator 120 will be described later.

Although not shown, the control unit 6 can detect, for example, the amount of ink remaining in the ink cartridge 31, the position of the printing unit 3, the printing environment such as the temperature and humidity, and the like. The seed sensors are each electrically connected.

When the control unit 6 receives the print data from the host computer 8 via the IF 9, the control unit 6 stores the print data in the EEPROM 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, 53, the electrostatic actuators corresponding to the plurality of inkjet heads 100 of the head unit 35, respectively, 1 2 0, the carriage motor 41 of the printing device 4 and the paper feeding device 5 operate. As a result, the printing process is performed on the recording paper P.

Next, the structure of each inkjet head 100 in each head unit 35 will be described. FIG. 3 is a schematic sectional view of one ink jet head 100 in the head unit 35 shown in FIG. 2 (including common parts such as the ink cartridge 31), and FIG. FIG. 5 is an exploded perspective view showing a schematic configuration of a head unit 35 corresponding to one color ink, and FIG. 5 is a nozzle of a head unit 35 to which a plurality of the inkjet heads 100 shown in FIG. 3 are applied. It is a top view showing an example of a surface. 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. .

As shown in FIG. 3, the head unit 35 is connected to the ink cartridge 31 via the ink inlet 131, the damper chamber 130 and the ink supply tube 311. . Here, the damper chamber 130 is provided with a damper 132 made of rubber. This damper chamber 130 absorbs the fluctuation of the ink and the fluctuation of the ink pressure when the carriage 32 reciprocates, whereby the ink jet heads of the head unit 35 can be absorbed. , A predetermined amount of ink can be supplied stably.

The head unit 35 has a silicon nozzle plate 150 on the upper side of the silicon substrate 140 and a borosilicate glass substrate (glass substrate) 1 on the lower side having a thermal expansion coefficient close to that of silicon. 3-layer structure in which 60 and each are stacked Has made. The central silicon substrate 140 has a plurality of independent cavities (pressure chambers) 14 1 (seven cavities are shown in FIG. 4), and one reservoir (common ink chamber) 144 Grooves are formed to function as ink supply ports (orifices) 142 that connect the reservoirs 144 to 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, the silicon substrate 140, and the glass substrate 160 are joined in this order, and each cavity 144, reservoir 144, and each ink supply port 144 are partitioned and formed. ing.

Each of these cavities 14 1 is formed in a strip shape (a rectangular parallelepiped shape), and its volume is variable by the vibration (displacement) of a diaphragm 121 described later. It is configured to eject ink (liquid material) from 110. In the nozzle plate 150, nozzles 110 are formed at positions corresponding to the front end portions of the cavities 141, and these are communicated with the cavities 141, respectively. In addition, an ink intake port 131, which communicates with the reservoir 134, is formed in a portion of the glass substrate 160 where the reservoir 144 is located. The ink is supplied from the ink cartridge 31 through the ink supply tube 311 and the damper chamber 130 to the reservoir 144 through the ink intake port 131. The ink supplied to the reservoir 144 is supplied to each of 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. (Elastic displacement) It is configured to function as a vibrating plate (diaphragm). 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 silicon substrate 140 side, the silicon substrate 14 A shallow concave portion 16 1 is formed at a position corresponding to each of the cavities 1 4 1 of 0. 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 concave portion 161 can be formed by, for example, etching.

Here, the bottom wall (diaphragm) 1 2 1 of each of the cavities 1 4 1 is a common electrode 1 2 4 on the side of each of the cavities 1 4 1 for storing electric charges by a drive signal supplied from the head driver 3 3. Constitutes a part of. In other words, each of the diaphragms 121 of each of the cavities 14 1 also serves as one of the opposite electrodes (opposite electrodes of the capacitor) of the corresponding electrostatic actuator 120 described later. Then, on the surface of the concave portion 16 1 of the glass substrate 16 0, the segment electrode is an electrode facing the common electrode 12 4 so as to face the bottom wall 12 1 of each cavity 14 1. 1 2 2 is formed. Further, as shown in FIG. 3, the bottom wall 1 2 1 of the surface of each wire carrier Sensitivity 1 4 1 is covered with oxide film (S i 0 ₂₎ Tona Ru insulating layer 1 2 3 silicon. Thus, the bottom wall 1 2 1 of each cavity 1 4 1, that is, the diaphragm 1 2 1 and the corresponding segment electrodes 1 2 2 are represented by the bottom wall 1 2 1 of the cavity 1 4 1 in FIG. A counter electrode (counter electrode of the capacitor) is formed (configured) through the insulating layer 123 formed on the middle and lower surfaces and the gap in the recess 161. 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 in accordance with a print signal (print data) input from the control unit 6. The charge and discharge between these opposing 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 connected to the common electrode 124 formed on the silicon substrate 140. Connected to input terminal 1 2 4a. The silicon substrate 1 4 0 Is supplied with a voltage from the input terminal 124 a of the common electrode 124 to the common electrode 124 of the bottom wall 121 because the impurity itself is conductive. be able to. 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 a low electric resistance (efficiently). This thin film may be formed by, for example, vapor deposition or sputtering. Here, in the present embodiment, for example, since the silicon substrate 140 and the glass substrate 160 are bonded (joined) by anodic bonding, a conductive film used as an electrode in the anodic bonding is formed on the silicon substrate 14. 0 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 may be anodic bonding. Not limited. As shown in FIG. 4, the head unit 35 includes a nozzle plate 150 on which a plurality of nozzles 110 corresponding to a plurality of inkjet heads 100 are formed, a plurality of cavities 141, and a plurality of inks. A silicon substrate (ink chamber substrate) 140 on which a supply port 14 2 and one reservoir 14 3 are formed, and an insulating layer 12 3, each of which includes a substrate 1 7 0 including a glass substrate 16 0 It is stored in. The base 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 base 170.

The plurality of nozzles 110 formed in the nozzle plate 150 are linearly arranged substantially in parallel with the reservoirs 144 in FIG. 4 for simplicity in FIG. The arrangement pattern of 0 is not limited to this configuration, and is usually arranged in a staggered manner, for example, as 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). 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 input of the drive signal in the section III-III in FIG. When a drive voltage is applied from the head driver 33 to the opposing electrode, the cooling Force is generated, the bottom wall (diaphragm) 1 2 1 deflects toward the segment electrode 1 2 2 side from the initial state (Fig. 6 (a)), and the capacity of the cavity 1 4 1 expands (Fig. 6 (b)). In this state, when the electric charge between the opposing electrodes is suddenly discharged under the control of the head driver 33, the diaphragm 121 recovers upward in the figure by its elastic restoring force, and the vibration in the initial state The plate moves to the top beyond the position of the plate 121, and the volume of the cavity 141 contracts rapidly (Fig. 6 (c)). At this time, due to the compression pressure generated in the cavity 141, a part of the ink (liquid material) that fills the cavity 141 is dropped from the nozzle 110 communicating with the cavity 141. Is discharged.

The diaphragm 1 2 1 of each cavity 1 4 1 is driven by this series of operations (ink ejection operation by the drive signal of the head driver 33) until the next drive signal (drive voltage) is input and ink droplets are ejected again. During the period, it is damping. Hereinafter, this damped vibration is also referred to as residual vibration. The residual vibration of the diaphragm 1 21 includes the acoustic resistance r due to the shape of the nozzle 110 and the ink supply port 144 or the ink viscosity, the inertance due to the ink weight in the flow path, and the diaphragm 1 2 It is assumed that it has a natural vibration frequency determined by the compliance Cm of 1.

A calculation model of the residual vibration of diaphragm 122 based on the above assumption will be described. FIG. 7 is a circuit diagram showing a simple vibration calculation model assuming residual vibration of diaphragm 122. As described above, the calculation model of the residual vibration of the diaphragm 122 can be represented by the sound pressure P, the inertance m, the compliance Cm, and the acoustic resistance r described above. 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]

r

a (3)

2m The calculation result obtained from this equation is compared with the experimental result obtained in 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 122. As can be seen from the graph shown in Fig. 8, the two waveforms, the experimental value and the calculated value, generally match.

By the way, in each of the ink jet heads 100 of the head unit 35, the phenomenon that the ink droplets are not normally ejected from the nozzle 110 despite the above-described ejection operation, that is, the ejection abnormality of the droplets is caused. May occur. As described later, the causes of this discharge abnormality are: ① air bubbles entering the cavity 141, ② drying of the ink near the nozzle 110 'thickening (sticking), ③ nozzle 110 Adhesion of paper powder near the exit.

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 it does not arrive, it also appears as a missing pixel dot. For this reason, in the following description, the abnormal discharge of the droplet may be simply referred to as “missing dot”.

In the following, based on the comparison result shown in FIG. 8, based on the comparison result shown in FIG. Adjust the values of acoustic resistance r and Z or inertance m so that the calculated value of the residual vibration of diaphragm 121 matches the experimental value (substantially the same) for each cause of droplet non-ejection phenomenon). Here, three types of air bubbles, dry thickening, and paper dust adhesion are examined.

First, let us consider the mixing of air bubbles into the cavity 141, which is one of the causes of dropout. FIG. 9 is a conceptual diagram of the vicinity of the nozzle 110 when bubbles B are mixed into the cavity 141 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 14 1 (in FIG. 9, the bubble B Shows the case where it is attached near 10).

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 inertance m decreases. Also, since the bubble B is attached to the wall surface of the cavity 141, it is considered that the diameter of the nozzle 110 becomes larger by the size of the diameter, and the acoustic resistance r decreases. Can be

Therefore, the acoustic resistance r and the inertance m are both set small compared to the case of Fig. 8 in which ink is normally ejected, and matched with the experimental value of the residual vibration when bubbles are mixed. The following results (graphs) were 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 is also reduced due to a decrease in the acoustic resistance r, and it can be confirmed that the amplitude of the residual vibration is slowly reduced.

Next, the drying (inking and thickening) of the ink near the nozzle 110, which is another cause of dropout, is 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 becomes as if it were trapped in the cavity 141. In this way, the ink near the nozzle 110 dried and thickened In some cases, the acoustic resistance] is considered to increase.

Therefore, compared to the case of Fig. 8 where the ink was ejected normally, the acoustic resistance r was set to be large to match 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. The experimental values shown in Fig. 12 are shown in Fig. 12. For several days, the head unit 35 was left unattached without a cap (not shown), and the ink near the nozzle 110 in the captive 144 dried and thickened. This is a measurement of the residual vibration of the diaphragm 122 in a state where the ink cannot be discharged (the ink is fixed). As can be seen from the graphs in Fig. 8 and Fig. 12, when the ink near the nozzle 110 is fixed by drying, the frequency becomes extremely lower than in normal ejection, and the residual vibration is overdamped. A good 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 has flowed into the cavity 1 4 1 from the reservoir 1 4 3, the diaphragm 1 2 1 (3) When moving upward in the middle, there is no escape route for the ink in the cavities 14 1, so that the diaphragm 1 21 cannot vibrate suddenly (because it becomes excessively damped).

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 dust 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 the inside of cavity 141 via the paper dust, and ink from nozzle 110 also becomes ink. Cannot be discharged. As described above, when paper dust adheres to the vicinity of the outlet of the nozzle 110 and ink seeps out of the nozzle 110, the inside of the cavity 141 and the part of the seepage from the vibrating plate 121 appear. 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 in Fig. 8 where ink was ejected normally, the inertance 111 and the acoustic resistance r were both set to be large, and paper dust near the nozzle 110 exit was set. By matching with the experimental value of the residual vibration at the time of adhesion, the result (graph) as shown in Fig. 14 was obtained. As can be seen from the graphs of FIGS. 8 and 14, when paper dust adheres to the vicinity of the outlet of the nozzle 110, a characteristic residual vibration waveform whose frequency is lower than that during normal ejection is obtained. Here, it can also be seen from the graphs of FIGS. 12 and 14 that the frequency of the residual vibration is higher in the case of paper powder adhesion than in the case of ink drying.) 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, it can be seen from FIG. 15 (b) that the ink oozes along the paper dust.

Here, both when the ink near the nozzle 110 dries and thickens, and when paper dust adheres near the outlet of the nozzle 110, the ink droplets are normally ejected. The frequency of the damped vibration is lower than that. In order to identify the cause of these two missing dots (ink non-discharge: abnormal discharge) from the waveform of the residual vibration of the diaphragm 121, for example, it is necessary to specify the frequency, period, and phase of the damped vibration. It can be compared with a threshold value, 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 100, and particularly, a change in the frequency, causes a change in each ink jet. An abnormal discharge of the head 100 can be detected. Further, by comparing the frequency of the residual vibration in that case with the frequency of the residual vibration during normal discharge, the cause of the discharge abnormality can be specified.

Next, the discharge abnormality detecting means 10 of the present invention will be described. FIG. 16 is a schematic block diagram of the ejection abnormality detecting means 10 shown in FIG. As shown in FIG. 16, the discharge abnormality detecting means 10 of the present invention comprises a residual vibration detecting means 1 comprising an oscillation circuit 11, an FZV conversion circuit 12, and a waveform shaping circuit 15. 6, measuring means 17 for measuring the period and amplitude from the residual vibration waveform data detected by the residual vibration detecting means 16, and an ink jet based on the period and the like measured by the measuring means 17 Determining means 20 for determining the ejection abnormality of the head 100. Discharge abnormality detection means 10 The oscillation circuit 11 oscillates based on the residual vibration of the vibration plate 12 1 of the electrostatic actuator 120 and the F / V conversion circuit 12 and the waveform shaping circuit 1 based on the oscillation frequency. In step 5, a vibration waveform is formed and detected. The measuring means 17 measures the cycle of the residual vibration based on the detected vibration waveform, and the judging means 20 determines the cycle of the residual vibration based on the measured vibration pattern of the residual vibration. The ejection abnormality of the ink jet 100 in the head unit 35 is detected and determined. Hereinafter, each component of the discharge abnormality detection means 10 will be described. First, an oscillation circuit 1 is used to detect the frequency (frequency) of the residual vibration of the diaphragm 121 of the electrostatic actuator 120. The method using 1 will be described. FIG. 17 is a conceptual diagram in the case where the electrostatic actuator 120 of FIG. 3 is a parallel plate capacitor. FIG. 18 is a conceptual diagram of the capacitor constituted of the electrostatic actuator 120 of FIG. FIG. 3 is a circuit diagram of an oscillation circuit 11 including a capacitor. The oscillation circuit 11 shown in FIG. 18 is a CR oscillation circuit using the hysteresis characteristic of Schmitt trigger, but the present invention is not limited to such a CR oscillation circuit. Any oscillation circuit may be used as long as the oscillation circuit uses the capacitance component (capacitor C). The oscillation circuit 11 may have a configuration using, for example, an LC oscillation circuit. Further, in the present embodiment, an example using the Schmitt trigger inverter is described, but for example, a CR oscillation circuit using three stages of inverters may be configured.

In the ink jet head 100 shown in FIG. 3, as described above, the diaphragm 122 and the segment electrode 122 with a very small space (gap) form an opposing electrode. It is composed of one hundred and twenty one days. 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 and 122 is g, and both electrodes are sandwiched. Assuming that the permittivity of the enclosed space (void) is ε (the permittivity of the vacuum is ε 0, and the relative permittivity of the void is ε _r , ε = ε 0 · ε,.) The capacitance C (X) of the electrostatic actuator (120) is Is represented by

[Equation 2]

S

C (x) (4)

g-X

In Equation (4), χ indicates the displacement of the diaphragm 121 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) As the quantity X) increases, the capacitance C (X) decreases. Thus, the capacitance C (x) is inversely proportional to (.gap length g—displacement X) (gap length g if X is 0). In the electrostatic actuator 120 shown in Fig. 3, since the air gap is filled with air, the relative permittivity is set to 1

In general, a droplet discharge device (in the present embodiment, an ink jet printer

As the resolution of 1) is increased, the ink droplets (ink dots) to be ejected are miniaturized, so that the density of the electrostatic actuator 120 is increased and the size thereof is reduced. As a result, the surface area S of the diaphragm 121 of the ink jet head 100 becomes small, and a small electrostatic actuator 120 is formed. Furthermore, the gap length g of the electrostatic actuator 120, which changes due to the residual vibration caused by the ink droplet ejection, is the initial gap g. Therefore, as can be seen from Equation (4), the change in capacitance of the electrostatic factor 120 is very small.

In order to detect the amount of change in the capacitance of the electrostatic actuator 120 (depending on the vibration pattern of the residual vibration), the following method is used, that is, the electrostatic actuator 120 An oscillation circuit as shown in Fig. 18 is configured based on the capacitance, and a 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 an electrostatic actuator 120 It consists of a capacitor (C), a Schmitt trigger inverter, and a resistive element (R) 112.

When the output signal of the Schmitt trigger inverter is at a high level, the capacitor C is charged via the resistive element 112. Charging voltage of capacitor C (potential difference between diaphragm 1 2 1 and segment electrode 1 2 2) Force Schmitt trigger Inverter 1 1 1 When input threshold voltage V _T + is reached, Schmitt trigger invertor 1 1 1 Output signal is inverted to Low level. Then, when the output signal of Schmitt 1 and the trigger invertor 111 becomes low level, the electric charge charged in the capacitor C through the resistive element 112 is discharged. When the voltage of the capacitor C by the discharge reaches the borrowing threshold voltage V _T one shoe Mitsuto trigger inverter Isseki 1 1 1, the output signal of the Schmitt trigger inverter 1 1 1 is inverted again H IgH level. Thereafter, this oscillation operation is repeated.

Here, in order to detect the time change of the capacitance of the capacitor C in each of the above phenomena (bubble mixing, drying, adhesion of paper powder, and normal ejection), the oscillation frequency of the oscillation circuit 11 is The oscillation frequency must be set so that the frequency of the highest residual vibration can be detected when bubbles are mixed (see Fig. 10). Therefore, 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 one digit higher than the frequency when bubbles are mixed. . 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, since the frequency of the residual vibration at the time of air bubble mixing is higher than that at the time of normal ejection. Otherwise, the frequency of the residual vibration cannot be detected accurately for the phenomenon of abnormal discharge. Therefore, in the present embodiment, the time constant of CR of the oscillation circuit 11 is set according to the oscillation frequency. By setting the oscillation frequency of the oscillation circuit 11 high as described above, a more accurate residual vibration waveform can be detected based on the minute change in the oscillation frequency.

For each period (pulse) of the oscillation frequency of the oscillation signal output from the oscillation circuit 11, the pulse is counted using a count pulse (counter) for measurement. And the initial gap g. By subtracting the count value of the pulse of the oscillation frequency when oscillating with the capacitance of the capacitor C in the above from the measured count value, digital information of the residual vibration waveform for each oscillation frequency can be obtained. By performing digital / analog (D / A) conversion based on these digital information, a rough residual vibration waveform can be generated. Although such a method may be used, the count pulse (counter) for measurement needs to have a high frequency (high resolution) capable of measuring a small change in the oscillation frequency. In order to increase the cost of such a count pulse (counter pulse), the discharge abnormality detecting means 10 of the present invention uses the FZV conversion circuit 12 shown in FIG.

FIG. 19 is a circuit diagram of the FZV conversion circuit 12 of the ejection abnormality detecting means 10 shown in FIG. As shown in FIG. 19, the FZV conversion circuit 12 includes three switches SW1, SW2, and SW3, two capacitors C1 and C2, a resistance element R1, and a constant current It is composed of a constant current source 13 that outputs Is and a buffer 14. The operation of the FZV conversion circuit 12 will be described with reference to the timing chart of FIG. 20 and the graph of FIG.

First, a method of generating the charge signal, the hold signal, and the clear signal shown in the timing chart of FIG. 20 will be described. The charging signal is generated by setting a fixed time tr from the rising edge of the oscillation pulse of the oscillation circuit 11 and keeping the signal at the High level during the fixed time tr. The hold signal rises in synchronization with the rising edge of the charge signal, is held at the high level for a predetermined fixed time, and falls to the low level. The clear signal rises in synchronization with the falling edge of the hold signal, is held at the high level for a predetermined fixed time, and is generated so as to fall to the low level. As will be described later, the transfer of the charge from the capacitor C1 to the capacitor C2 and the discharge of the capacitor C1 are performed instantaneously, so that the pulses of the hold signal and the clear signal correspond to the output signal of the oscillator circuit 11. It is sufficient that one pulse is included before the next rising edge, and the pulse is not limited to the rising edge and the falling edge as described above. A method for setting the fixed times tr and t1 will be described with reference to Fig. 21 in order to obtain a clean residual vibration waveform (voltage waveform). The fixed time tr is 120, which is the initial gap length g. It is adjusted from the cycle of the oscillation pulse oscillated by the capacitance C at the time of, and the charging potential by the charging time t1 is set to be about 1 Z2 of the charging range of C1. In addition, charging is performed so that the gap length g does not exceed the charging range of the capacitor C1 between the charging time t2 at the position of the maximum (Max) and the charging time t3 at the position of the minimum (Min). The potential gradient is set. That is, since the slope of the charging potential is determined by d V, 'cl t = Is ZC1, the output constant current Is of the constant current source 13 may be set to an appropriate value. By setting the output constant current Is of this constant current source 13 as high as possible within the range, it is possible to detect, with high sensitivity, minute changes in the capacitance of the capacitor formed by the electrostatic actuator 120. This makes it possible to detect a minute change in the diaphragm 121 of the electrostatic actuator 120.

Next, the configuration of the waveform shaping circuit 15 shown in FIG. 16 will be described with reference to FIG. FIG. 22 is a circuit diagram showing a circuit configuration of the waveform shaping circuit 15 of FIG. The waveform shaping circuit 15 outputs the residual vibration waveform to the determination means 20 as a rectangular wave. As shown in FIG. 22, the waveform shaping circuit 15 includes two capacitors C 3 (DC component removing means) and C 4, two resistance elements R 2 and R 3, and two DC voltage sources V ref 1, V ref 2, amplifier (op amp) 15 1, and comparator (comparator) 15 2. In the waveform shaping process of the residual vibration waveform, the detected peak value may be output as it is to measure the amplitude of the residual vibration waveform.

F ZV output of the conversion circuit 1 2 buffer 1. 4 includes the capacitance component of the electrostatic Akuchiyue Isseki 1 2 0 initial gap g _Q based on DC components of the (direct current component). Since the DC component varies depending on each ink jet head 100, the capacitor C3 removes the DC component of the capacitance. The capacitor C 3 removes the DC component in the output signal of the buffer 14 and outputs only the AC component of the residual vibration to the inverting input terminal of the operational amplifier 15 1. Power.

The operational amplifier 151 inverts and amplifies the output signal of the buffer 14 of the FZV conversion circuit 12 from which the DC component has been removed, and constitutes a low-pass filter for removing a high band of the output signal. It is assumed that the operational amplifier 15 1 is a single power supply circuit. The operational amplifier 15 1 constitutes an inverting amplifier composed of two resistance elements R 2 and R 3, and the input residual vibration (AC component) is twice as large as R 3 ZR.

In addition, because of the single power supply operation of the operational amplifier 151, the amplified diaphragm 121 oscillating around the potential set by the DC voltage source Vref1 connected to its non-inverting input terminal A residual vibration waveform is output. Here, the DC voltage source Vref1 is set to about 1 Z2, which is a voltage range in which the operational amplifier 151 can operate with a single power supply. Further, the operational amplifier 15 1 forms a low-pass filter having a power-off frequency of 1 / (27TXC 4 XR 3) by the two capacitors C 3 and C 4. Then, as shown in the timing chart of FIG. 20, the residual vibration waveform of the diaphragm 121 amplified after the removal of the DC component is applied to another DC voltage source by the next-stage comparator 152. It is compared with the potential of Vref2, and the comparison result is output from the waveform shaping circuit 15 as a rectangular wave. It should be noted that the DC voltage source Vref1 may share another DC voltage source Vref1.

Next, the operation of the FZV conversion circuit 12 and the waveform shaping circuit 15 of FIG. 19 will be described with reference to the timing chart shown in FIG. The F / V conversion circuit 12 shown in FIG. 19 operates based on the charging signal, the clear signal, and the hold signal generated as described above. In the timing chart of FIG. 20, when the drive signal of the electrostatic actuator 120 is input to the ink jet head 100 of the head unit 35 via the head driver 33, as shown in FIG. Then, the diaphragm 121 of the electrostatic actuator 120 is attracted to the segment electrode 122 side, and rapidly contracts upward in FIG. 6 in synchronization with the falling edge of this drive signal ( (See Fig. 6 (c)).

In synchronization with the falling edge of this drive signal, drive circuit 18 The drive Z detection switching signal for switching the output means 10 is at the High level. This drive Z detection switching signal is held at the High level during the drive suspension period of the corresponding ink jet head 100, and goes to the Low level before the next drive signal is input. While this drive Z detection switching signal is at the Hig level, the oscillation circuit 11 of Fig. 18 oscillates while changing the oscillation frequency in response to the residual vibration of the diaphragm 1 21 of the electrostatic actuator 120. are doing.

As described above, from the falling edge of the drive signal, that is, the rising edge of the output signal of the oscillation circuit 11, a fixed time set in advance so that the waveform of the residual vibration does not exceed the range where the capacitor C1 can be charged. Until tr elapses, the charging signal is held at the High level. Note that the switch SW1 is off while the charging signal is at the High level.

When the fixed time tr elapses and the charging signal goes to the Low level, the switch SW1 is turned on in synchronization with the falling edge of the charging signal (see Fig. 19). Then, the constant current source 13 is connected to the capacitor C1, and the capacitor C1 is charged with the gradient Is s / C1 as described above. The capacitor C1 is charged while the charge signal is at the Low level, that is, until the output signal of the oscillation circuit 11 goes to the High level in synchronization with the rising edge of the next pulse.

When the charge signal becomes High level, switch SW1 is turned off (open), and constant current source 13 and capacitor C1 are disconnected. At this time, the capacitor C1 stores the potential charged during the low-level period t1 of the charging signal (ie, ideally, Isxt1ZC1 (V)). In this state, when the hold signal becomes High level, the switch SW2 is turned on (see FIG. 19), and the capacitors C1 and C2 are connected via the resistance element R1. After the connection of switch SW2, charging and discharging are performed by the charging potential difference between the two capacitors C1 and C2, and from capacitor C1 so that the potential difference between the two capacitors C1 and C2 becomes approximately equal. Charge moves to capacitor C2.

Here, the capacitance of the capacitor C 2 is the capacitance of the capacitor C 1 , About 1 Z 10 or less. Therefore, the amount of charge (used) that moves by charging / discharging generated by the potential difference between the two capacitors C 1 and C 2 is less than 1/10 of the charge charged in the capacitor C 1. Therefore, even after the electric charge is transferred from the capacitor C1 to the capacitor C2, the potential difference of the capacitor C1 does not change much (it does not decrease so much). In addition, in the FZV conversion circuit 12 of FIG. 19, when the capacitor C2 is charged, in order to prevent the charging potential from jumping rapidly due to the inductance of the wiring of the FZV conversion circuit 12, etc. The primary low-pass filter is composed of the resistor R1 and the capacitor C2.

After the charged potential of the capacitor C2 is substantially equal to the charged potential of the capacitor C1, the hold signal becomes the low level, and the capacitor C1 is disconnected from the capacitor C2. In addition, when the clear signal becomes High level and switch SW3 is turned on, capacitor C1 is connected to ground GND, and discharging operation is performed so that the charge stored in capacitor C1 becomes 0. . After the discharge of the capacitor C1, the clear signal goes to the low level, and when the switch SW3 is turned off, the upper electrode of the capacitor C1 in FIG. 19 is disconnected from the ground GND, and the next charge signal is input. , That is, wait until the charging signal becomes Low level.

The potential held in the capacitor C2 is updated at the time of the rising edge of the charge signal, that is, each time the charging of the capacitor C2 is completed. This is output to the waveform shaping circuit 15 in FIG. 22 as a vibration waveform. Therefore, the capacitance of the electrostatic actuator 120 (in this case, the fluctuation width of the capacitance due to residual vibration must be taken into consideration) and the resistance element so that the oscillation frequency of the oscillation circuit 11 increases. By setting the resistance value of 112, each step (step) of the potential of capacitor C2 (output of buffer 14) shown in the timing chart of Fig. 20 becomes more detailed. It is possible to detect in more detail the time-dependent change in the capacitance due to the residual vibration of.

Similarly, the charging signal is changed from the low level to the high level to the low level. The potential held in the capacitor C2 is output to the waveform shaping circuit 15 via the buffer 14 at the above predetermined timing. In the waveform shaping circuit 15, the DC component of the voltage signal (potential of the capacitor C2 in the timing chart of FIG. 20) input from the buffer 14 is removed by the capacitor C3, and the resistance element R Input to the inverting input terminal of the operational amplifier 15 1 via 2. The input alternating current (AC) component of the residual vibration is inverted and amplified by the operational amplifier 151, and is output to one input terminal of the comparator 152. Comparator 15 2 compares the potential (reference voltage) preset by DC voltage source V ref 2 with the potential of the residual vibration waveform (AC component), and outputs a square wave (see the timing in FIG. 20). Output of the comparison circuit in the chart). Next, the switching timing between the ink droplet ejection operation (drive) of the inkjet head 100 and the ejection abnormality detection operation (drive suspension) will be described. FIG. 23 is a block diagram schematically showing the switching means 23 for switching between the drive circuit 18 and the discharge abnormality detection means 10. In FIG. 23, the drive circuit 18 in the head driver 33 shown in FIG. 16 will be described as a drive circuit of the inkjet head 100. As also shown in the timing chart of FIG. 20, the discharge abnormality detection processing of the present invention is executed between the drive signals of the inkjet head 100, that is, during the drive suspension period.

In FIG. 23, the switching means 23 is initially connected to the drive circuit 18 in order to drive 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 actuating unit 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 to vibrate (residual vibration). At this time, ink droplets are ejected from the nozzle 110 of the inkjet head 100.

When the drive signal pulse falls, a drive / detection switching signal (see the timing chart in FIG. 20) is input to the switching means 23 in synchronization with the falling edge, and the switching means 23 is driven by the drive circuit 18 Is switched to the discharge abnormality detection means (detection circuit) 10 side, and the electrostatic actuating circuit 1 2 0 (condensation of oscillation circuit 11) Is connected to the discharge abnormality detecting means 10.

Then, the discharge abnormality detection means 10 executes the above-described discharge abnormality (missing dot) detection processing, and outputs the residual vibration of the diaphragm 12 1 output from the comparator 15 2 of the waveform shaping circuit 15. The waveform data (rectangular wave data) is digitized by the measuring means 17 into the period and amplitude of the residual vibration waveform. In the present embodiment, the measuring means 17 measures a specific vibration cycle from the residual vibration waveform data, and outputs the measurement result (numerical value) to the judging means 20. The measuring means 17 determines not only the period of the residual vibration but also a predetermined period of the residual vibration waveform, for example, from the fall of the drive signal (or the rise of the drive Z detection switching signal) to the occurrence of the residual vibration. , The first half cycle after the occurrence of the residual vibration (or every half cycle), the first one cycle after the occurrence of the residual vibration (or every one cycle), or the like may be measured. The measuring means 17 measures the time from the first rising edge to the next falling edge, and determines the time twice as long as the measured time (ie, half cycle) as the cycle of the residual vibration. 20 may be output.

FIG. 24 is a block diagram showing an example of the measuring means 17. The measuring means 17 measures the period from the first rising edge of the waveform (rectangular wave) of the output signal of the comparator 152 and the time from the first rising edge to the next rising edge (residual oscillation period). To do this, the reference pulse is subtracted and counted using a subtraction counter 45, and a predetermined period of the residual vibration is measured from the result of the subtraction. In FIG. 24, the measuring means 17 comprises an AND circuit AND, a subtraction counter 45, and a normal count value memory 46. Note that the reference pulse is generated by pulse generation means (not shown).

As shown in FIG. 24, the AND circuit AND outputs the logical product of the drive / detection switching signal and the reference pulse to the subtraction counter 45. That is, when the drive Z detection switching signal is at the high level, the reference pulse is 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. Then, when the reference pulse is input, the subtraction counter 45 subtracts the number of reference pulses from the predetermined count value for a predetermined time. The predetermined time is, for example, an inkjet head. Time until the residual vibration of diaphragm 121 occurs when ink droplets are ejected normally from 100, half a cycle of residual vibration during normal ejection, and one cycle of residual vibration during normal ejection And so on. Further, the predetermined count value stored in the normal count value memory 46 is the number of pulses counted by the reference pulse during the above-described predetermined time during normal ejection.

As shown in the timing chart of FIG. 25, the decrement counter 45 acquires a predetermined count value (normal count value) from the normal count value memory 46 at the timing of the input of the Load signal, and outputs a drive / detection switching signal. During the High level, open the gate and receive the reference pulse and subtract it from the normal count value. Then, the subtraction counter 45 outputs the result of the subtraction to the determination means 20. The timing generation means 36 generates an Ls signal based on the residual vibration waveform input from the residual vibration detection means 16, and outputs the Ls signal to the storage means 62. Note that the Ls signal corresponding to each inkjet head 100 is synchronized with the rising edge or falling edge of the residual vibration waveform detected as needed after the ejection drive of the electrostatic actuator 120. An arbitrary period of this edge may be counted using a reference pulse, and the determination result may be stored as the timing of the Ls signal.

The judging 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 input timing of the L s signal at the high level (timing at which the L s signal becomes the high level), the determination result of the determination means 20 is held, and the determination result is output to the storage means 62. You. It should be noted that several reference values (thresholds) are provided as the predetermined reference values, and by comparing the determination result with each of these reference values, the above-described discharge abnormality (bubble mixing, paper dust adhesion 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. In addition, such a subtraction counting process is performed by the electrostatic printer of the inkjet printer. 0 is performed during a drive suspension period during which no drive is performed. This makes it possible to detect an ejection failure without lowering the throughput of the ink jet printer 1.

The determination means 20 determines the presence or absence of a nozzle discharge abnormality, the cause of the discharge abnormality, the amount of comparison deviation, and the like, based on a specific vibration cycle of the residual vibration waveform measured by the measurement means 17 (measurement result). Then, the determination result is output to the control unit 6. The control unit 6 saves the determination result in a predetermined storage area of the EEPROM (storage means) 62. Then, at the time when the next drive signal from the drive circuit 18 is input, the drive Z detection switch signal is input again to the switching means 23, and the drive circuit 18 and the electrostatic actuator 120 are connected to each other. Connect. The drive circuit 18 maintains the ground (GND) level once the drive voltage is applied, so that the above-described switching is performed by the switching means 23 (see the timing chart of FIG. 20). As a result, the residual vibration waveform of the diaphragm 121 of the electrostatic actuator 120 can be accurately detected without being affected by disturbance from the drive circuit 18 or the like.

Note that, in the present invention, the residual vibration waveform data is not limited to the rectangular waveform generated by the comparator 152. As in the configuration in Fig. 24 above, the residual vibration amplitude data output from the operational amplifier 15 1 is digitized as needed by the measurement unit 17 that performs AZD conversion without performing comparison processing by the comparator 15 2. Then, based on the quantified data, the determination means 20 may determine whether or not there is a discharge abnormality, and the determination result may be stored in the storage means 62. In addition, the meniscus of the nozzle 110 (the surface where the ink inside the nozzle 110 contacts the atmosphere) vibrates in synchronization with the residual vibration of the diaphragm 121, so that the inkjet head 100 ejects ink droplets. After the operation, after waiting for the residual vibration of the meniscus to attenuate in a time substantially determined by the acoustic resistance r (waiting for a predetermined time), the next ejection operation is performed. In the present invention, since the residual vibration of the diaphragm 121 is detected by effectively utilizing the standby time, it is possible to detect a discharge abnormality that does not affect the driving of the ink jet head 100. That is, the throughput of the inkjet printer 1 (droplet ejection device) is reduced. In addition, it is possible to execute the ejection abnormality detection processing of the nozzle 110 of the ink jet head 100.

As described above, when air bubbles are mixed into the cavity 14 1 of the ink jet head 100, the frequency becomes higher than the residual vibration waveform of the diaphragm 12 1 during normal ejection. On the contrary, the cycle is shorter than the cycle of the residual vibration during normal ejection. Also, if the ink near the nozzle 110 thickens and sticks due to drying, the residual vibration will be over-attenuated and the frequency will be considerably lower than the residual vibration waveform during normal ejection. Is much longer than the period of the residual vibration during normal ejection. When paper dust adheres to the vicinity of the outlet of the nozzle 110, the frequency of the residual vibration is lower than the frequency of the residual vibration during normal ejection, but is lower than the frequency of the residual vibration during drying of the ink. Therefore, the cycle is longer than the cycle of the residual vibration during normal ejection and shorter than the cycle of the residual vibration during ink drying.

Therefore, a predetermined range T r is provided as the period of the residual vibration during normal ejection, and the period of the residual vibration when paper dust adheres to the exit of the nozzle 110 and the ink near the exit of the nozzle 110 By setting a predetermined threshold value (predetermined threshold value) T1 in order to distinguish the period of the residual vibration when the ink is dried, the cause of such abnormal discharge of the ink jet 100 is set. Can be determined. The determining means 20 determines whether the cycle T w of the residual vibration waveform detected by the above-described discharge abnormality detection processing is a cycle in a predetermined range, and whether the cycle is longer than a predetermined threshold value. Thus, the cause of the discharge abnormality is determined.

Next, the operation of the ejection abnormality detection means 10 of the present invention will be described with reference to the timing chart of FIG. First, a method of generating the Load signal, the Ls signal, and the CLR signal shown in FIGS. 24 and 25 will be described. As shown in the evening timing chart of FIG. 25, the Load signal is a signal that has a High level 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 predetermined time (stored in the storage means 62) in synchronization with the falling edge of the drive / detection switching signal input to the switching means 23 and the AND circuit AND. This is a signal that goes to the High level. Although not shown in the timing chart of FIG. 25, the CLR signal is a signal for clearing the subtraction result held in the subtraction counter 45 by the subtraction processing. The signal is inputted to the subtraction counter 45 at a predetermined timing until the oad signal is inputted.

The ejection abnormality detection 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 18, the normal count value from the normal count value memory 46 is transferred to the subtraction counter 45 at that timing. Entered and retained. When the ejection drive operation (drive period) of the inkjet head 100 ends, a drive / detection switching signal is input to the switching means 23 and the AND circuit AND in synchronization with the falling edge of the drive signal. In response to this drive Z 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 (see FIG. 23).

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 / detection switching signal. (Note that the reference pulse is output by the AND circuit AND unless the driving / detection switching signal is at the High level. , The gate may be left open), while the drive Z detection switching signal is at the High level (during T s), the number of reference pulses is subtracted from the normal count value. This T s is the time required for the diaphragm 121 to start residual vibration during normal ejection (until the residual vibration is generated). This is the time it takes for the actuator 120 to return to the position of the diaphragm 121 when not driven.

In the timing chart of FIG. 25, the discharge abnormality is determined based on the normal count value during the period from when the drive circuit 18 and the discharge abnormality detection means 10 are switched to when the residual vibration of the diaphragm occurs. Is determined. Therefore, the timing at which residual vibration occurs (timing at which diaphragm 121 returns to the initial position) As a result, the drive / detection switching signal falls to the Low level, and the Ls signal is generated. Based on the subtraction result of the subtraction counter 45, the determination result obtained by the determination means 20 performing the predetermined determination is stored in the storage means. 6 Stored (saved) in 2. The reference values N 1-. N 2 and P 1 in FIG. 25 are predetermined thresholds, as shown in Table 1 of FIG. 28, and the difference between these thresholds and the subtraction result (subtraction count value) The cause of the discharge abnormality is determined based on the magnitude.

Next, a description will be given of 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. FIG. 26 is a flowchart showing a discharge abnormality detection process of a droplet discharge head according to an embodiment of the present invention. When print data to be printed (which may be ejection data in a flushing operation) is input from the host computer 8 to the control unit 6 via the interface (IF) 9, this ejection abnormality detection processing is executed at a predetermined timing. Is performed. For convenience of explanation, the flowchart shown in FIG. 24 shows a discharge abnormality detection process corresponding to the discharge operation of one ink jet head 100, that is, one nozzle 110.

First, the Load signal is input to the subtraction counter 45 at the timing immediately before the drive signal is input (this timing is not limited to this), and the normal count value is input (preset) from the normal count value memory 46 (step). S 101) Then, a drive signal corresponding to the print data (ejection data) is input from the drive circuit 18 of the head driver 33, and as a result, as shown in the timing chart of FIG. 20 or FIG. A drive signal (voltage signal) is applied between both electrodes of the electrostatic actuator 120 based on the timing of the appropriate drive signal (step S102). Then, the controller 6 determines whether or not the input of the drive signal (voltage signal) to the electrostatic actuator 120 has been completed (step S103), and when the input of the drive signal has been completed, The drive / 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 causes the electrostatic actuator 120, that is, the capacitor constituting the oscillation circuit 11 to be driven by the driving circuit 1 Disconnected from 8 and discharge abnormality detection means 1 0 (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, and the oscillation pulse is output from the oscillation circuit 11, whereby the residual vibration of the diaphragm 12 1 is detected. (Step S105). At the same time, a reference pulse is output (step S106) and input to the subtraction counter 45. The subtraction counter 45 subtracts the reference pulse from the comparison reference value input from the comparison reference value memory 47 (step S107).

Then, in step S108, the control section 6 determines whether or not the Ls signal has been generated by the timing generation means 36, that is, whether or not the time has elapsed by Ts. The subtraction counter 45 performs a subtraction process until an Ls signal is generated. When the Ls signal is generated, the subtraction result obtained by the subtraction process is output to the determination means 20. The determination means 20 determines whether the result of the subtraction is within the normal range (step S.109).

Then, when the subtraction result is within the normal range, the judging means 20 judges that the ink is ejected normally (step S110). Conversely, when the subtraction result is not within the normal range, the ink jet head 100 is determined. Is determined to be a discharge abnormality (defective nozzle 110) (step S111). The result of the determination by the determination means 20 is stored (held) in the storage means 62 (step S112), and the connection with the electrostatic actuator 120 is set to the oscillation circuit 1 based on the drive / detection switching signal. Switching from 1 to the drive circuit 18 stops the oscillation of the oscillation circuit 11 (step S113).

In step S114, it is determined whether or not the ejection drive processing by the ink jet head 100 has been completed. If it is determined that the discharge drive processing has not been completed, the process is continued until the next drive signal is input. Waiting in step S114. If it is determined that the discharge has been completed, the generated reference pulse is stopped (step S115), and the discharge abnormality detection processing ends.

As described above, in the ejection failure detection processing of the droplet ejection head according to the present invention, the reference pulse is subtracted from the comparison reference value, and the subtraction result is compared with the predetermined reference value. If there is a discharge abnormality and if there is a discharge abnormality Can be detected with a simple configuration.

Next, the residual vibration detection processing of the present invention will be described. FIG. 27 is a flowchart showing the residual vibration detection processing of the present invention. As described above, by the switching means 23. When the electrostatic actuator 120 and the oscillation circuit 111 are connected, the oscillation circuit 111 constitutes a CR oscillation circuit, and the electrostatic actuator 120 Oscillation is performed based on the change in the electrostatic capacity of the capacitor (residual vibration of the diaphragm 122 of the electrostatic actuator 120) (step S201).

As shown in the above timing chart (see FIG. 20 or FIG. 25), based on the output signal (pulse signal) of the oscillation circuit 11, the FZV conversion circuit 12 generates the charge signal, the hold signal, and the clear signal. Signals are generated, and based on these signals, the FZV conversion circuit 12 performs an F / V conversion process of converting the frequency of the output signal of the oscillation circuit 11 into a voltage (step S202), and the FZV conversion circuit 1 From 2, residual vibration waveform data of the diaphragm 121 is output. From the residual vibration waveform data output from the FZV conversion circuit 12, the DC component (DC component) is removed by the capacitor C 3 of the waveform shaping circuit 15 (step S 203), and the DC voltage is output by the operational amplifier 15 1. The residual vibration waveform (AC component) from which the component has been removed is amplified (step S204).

The residual vibration waveform data after the amplification is shaped into a pulse by a predetermined process and turned into a pulse (step S205). That is, in the present embodiment, the voltage value (predetermined voltage value) set by the DC voltage source Vref2 is compared with the output voltage of the operational amplifier 151 in the comparator 152. The comparator 152 outputs a binarized waveform (rectangular wave) based on the comparison result. The output signal of the comparator 152 is an output signal of the residual vibration detecting means 16 and is output to the measuring means 17 for performing predetermined discharge abnormality determination processing, and the residual vibration detecting processing ends. .

Next, the measuring means 17 according to another 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 of each half cycle during normal discharge. FIG. 29 is a block diagram showing another example of the measuring means 17. Note that only the configuration different from that in FIG. Components having the same functions as those in the lock diagram are denoted by the same reference numerals, and description thereof will be omitted.

The measuring means 17 includes an AND circuit AND, a subtraction counter 45, and a normal count value memory 46 having a plurality of normal count value memories 46a to 46n. In FIG. 29, a first selector 48a for switching the normal count value memory, a first comparison reference value memory 47a, a first determination means 20a, and a plurality of storage means 6 2a Also shown are a storage means 62 having 〜6 2 n, a second selector 48b for switching the storage means 62, a second comparison reference value memory 47b, and a second determination means 20b. ing.

The first selector 48a switches the normal count value input to the subtraction counter 45 based on a predetermined timing of the residual vibration during normal ejection. The first determination means 20a (having the same configuration as the determination means 20 in the above example) corresponding to the normal count value memories 46a to 46n selected by the first selector 48a. This is to switch the storage means 62 for storing the judgment result of the above.

The second determination means 20 b is based on the determination results stored (saved) in the plurality of storage means 62 a to 62 n as shown in Table 2 of FIG. This is to finally determine the presence or absence of a discharge abnormality of 0 and the cause of the discharge abnormality. Note that a sequence as shown in Table 2 of FIG. 33 is stored in the second comparison reference value memory 47b, and these are output to the second determination means 20b at a predetermined timing.

FIG. 30 is a diagram showing residual vibration waveforms in a case where an ejection abnormality has occurred in the ink jet head 100 and a case where normal ejection is performed. As shown in Fig. 30, the period Ts until the occurrence of residual vibration in each state is shorter than that during normal ejection. Can be identified. Similar results are obtained when the first half cycle of the residual vibration is compared. In the present invention, in order to more accurately identify (detect) the cause of the discharge abnormality, the determination result in the cycle of the residual vibration may be prioritized over the determination result in the time T s until the occurrence of the residual vibration. . Next, the operation of the ejection failure detection means 10 of the present embodiment will be described with reference to the timing chart of FIG. FIG. 31 is a timing chart (every half cycle) of the subtraction processing of the subtraction counter 45 shown in FIG. When the count period instruction signal is 0, the first Load signal is input immediately before the drive signal, and the normal count value 1 is input to the subtraction count 45. The subtraction counter 45 opens the gate in synchronization with the falling edge of the drive signal and starts the subtraction process. When 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 linear signal and the oad 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 2 Ob receives the comparison reference value (see the table in FIG. 33) from the second comparison reference value 47 b and, based on the comparison reference value, determines the corresponding ink jet head 1. The presence / absence of a discharge abnormality of 00 and the cause of the discharge abnormality are finally determined.

Next, a description will be given of a discharge abnormality detection process in a case where a discharge abnormality is detected based on a period of each half cycle of the residual vibration during normal discharge. FIG. 32 is a flowchart showing a discharge abnormality detection process of a droplet discharge head according to another embodiment of the present invention. As in the flowchart of FIG. 26, the ejection failure detection process is executed at a predetermined timing such as when print data is input to the inkjet printer 1.

First, at the timing immediately before the input of the drive signal (not limited to this timing), the load signal is input to the load-counting arithmetic counter 45, and the normal count value is input (preset) from the normal count value memory 46 (step). S301). Then, a drive signal corresponding to the print data (ejection data) is input from the drive circuit 18 of the head driver 33, and 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 electrostatic actuator 120 (step S302). Then, the control unit 6 inputs the drive signal (voltage signal) to the electrostatic actuator 120 It is determined whether or not the driving is completed (step S303). When the input of the driving signal is completed, the driving / detection switching signal is input from the control unit 6 to the switching unit 23. When the drive / detection switching 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 driven by the driving circuit 18. It is disconnected and connected to the discharge abnormality detection means 10 (detection circuit) side, that is, the oscillation circuit 11 (step S 304). Based on the capacitance of the electrostatic actuator 120, the oscillation circuit 1 1 and the oscillation pulse is output from the oscillation circuit 11 1. The residual vibration of the diaphragm 12 1 is detected (step S 305), and at the same time, the reference pulse is output (step S 306). , Is entered into the subtraction count 45. The subtraction counter 45 counts down the oscillation pulse from the first normal count value 1 (step S307). In the case of a preset counting period, in this case, the subtraction counting process is performed until the period from when the switching is performed by the switching means 23 to when the damping vibration occurs is completed. When the counting period is completed, the Ls signal is output. Occurs (step S 308), the process proceeds to the determination process.

In step S309, the first determination means 20a determines whether or not the subtraction result of the subtraction counter 45 is within the range of the normal count number (that is, the reference value N1 to P1). If the count is within the normal count range, the first determination means 20a determines that the ink has been ejected normally (step S310). The head 100 determines that the ejection is abnormal (the defective nozzle is 110) (step S311). Then, the determination result by the first determination means 20a is stored (held) in the first storage means 62a (step S312), and the control unit 6 finishes the subtraction processing for all count periods. It is determined whether or not it is (step S313). Since the subtraction process for each half cycle of the residual vibration has not been executed yet, the flow shifts to step S314 to increment the count period instruction signal by one (see the evening timing chart in FIG. 31). The second storage means 62 b is selected by the second selector 48 b (step S 3 15), and the next normal count value memory 46 b is selected by the first selector 48 a, and the normal count value 2 is stored. Subtraction Preset to the counter 45 (step S 3 16). Then, the processing after step S307 is repeated.

If it is determined in step S313 that the subtraction processing (the first determination processing) has been completed for all the count periods, based on the drive Z detection switching signal, the electrostatic actuator 120 and Is switched from the oscillation circuit 11 to the drive circuit 18 to stop the oscillation of the oscillation circuit 11 (step S 3 17), and the second judgment means 20 b stores the plurality of storage means 6 2 a Based on the first determination result and the second comparison reference value stored in the corresponding .about.62n, a discharge abnormality determination process for the inkjet head 100 is executed (step S318). Then, in step S319, 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 generated reference pulse is stopped. Then (step S320), the discharge abnormality detection processing ends. If it is determined that the processing has not been completed yet, the flow shifts to step S301 to repeat the same processing.

As described above, in the ejection failure detection processing of the droplet ejection head of the present invention, the reference pulse is subtracted from the normal count value at a plurality of times, and the subtraction result is compared with the predetermined reference value. The droplet ejection apparatus and the droplet ejection head ejection detection process of the present invention can be performed with a simple configuration by determining whether or not there is an ejection abnormality of the ink jet head 100 and, if there is an ejection abnormality, with a simple configuration. Can be detected more accurately.

As described above, the droplet discharge device (inkjet printer 1) of the present invention includes a vibration plate 121, an electrostatic actuator 120 for displacing the vibration plate 121, and a liquid (ink) inside. Is filled, and the displacement of the diaphragm 1 2 1 causes the internal pressure to increase / decrease, and communicates with the cavities 1 4 1 and 1 4 1, and the liquid flows by increasing / decreasing the pressure inside the cavities 1 4 1 A plurality of droplet discharge heads (ink jet heads 100) having nozzles 110 discharging as droplets, a drive circuit 18 for driving the electrostatic actuator 120, and a reference A pulse generating means for generating a pulse, a counter (subtraction counter 45) for counting a reference pulse generated within a predetermined period, and a count value of the counter 45 within a predetermined period. And a discharge abnormality detecting means 10 for detecting a droplet discharge abnormality.

Therefore, the droplet discharge head and the droplet discharge device provided with the conventional dot missing detection method (for example, the optical detection method, etc.) by the droplet discharge device and the droplet discharge head discharge abnormality detection method of the present invention. In comparison with the above, no other components (such as an optical dot missing detection device) are required to detect an abnormal discharge, so that abnormal discharge of the droplet can be detected without increasing the size of the droplet discharge head. In addition to this, the manufacturing cost of a droplet discharge device capable of detecting discharge abnormalities (missing dots) 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 method for detecting a discharge abnormality of the droplet discharge head (discharge abnormality detection processing) of the present invention is performed during the printing operation, the throughput of the droplet discharge device does not decrease or deteriorate.

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 capable of detecting missing dots, such as an optical detection device. Then, if necessary, an appropriate recovery process for the cause can be selected and executed.

Furthermore, in the droplet discharge device of the present invention, the cause of the discharge abnormality is detected and specified based on the time until the occurrence of the residual vibration of the diaphragm and the cycle of the residual vibration. The cause can be identified with higher accuracy.

Next, another configuration example of the ink jet head according to the present invention will be described. FIGS. 34 to 37 are cross-sectional views each schematically showing another example of the configuration of the inkjet head 100. Hereinafter, the description will be made based on these drawings, but the description will be focused on the points different from the above-described embodiment, and the description of the same matters will be omitted.

The inkjet head 100A shown in FIG. 34 is used to drive the piezoelectric element 200. The vibrating plate 212 vibrates further, and the ink (liquid) in the cavity 208 is ejected from the nozzle 203. A stainless steel nozzle plate h202 formed with a nozzle (hole) 203 is connected to a stainless steel metal plate 204 via an adhesive film 205. A metal plate 204 made of the same stainless steel is joined via an adhesive film 205 on the upper side. The communication port forming plate 206 and the cavity plate 207 are sequentially bonded thereon.

The nozzle plate 200, the metal plate 204, the adhesive film 205, the communication port forming plate 206 and the cavity plate 207 each have a predetermined shape (shape such that a recess is formed). By molding and overlapping 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. In addition, the reservoir 209 communicates with the ink intake port 211.

A diaphragm 2 12 is installed in the upper opening of the cavity plate 2 07, and a piezoelectric element 200 is joined to the diaphragm 2 12 via a lower electrode 2 13. Have been. 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 that generates a drive voltage waveform, and applies (supplies) a 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 joined thereto vibrates. The volume of the cavity 208 (pressure in the cavity) changes due to the vibration of the diaphragm 210, and the ink (liquid) filled in the cavity 208 is ejected as droplets from the nozzle 203. . The amount of liquid reduced in the cavity 208 due to the ejection of the liquid droplets is supplied and supplied from the reservoir 209. In addition, ink is supplied to the reservoir 209 from the ink intake port 211.

Similarly, the ink jet 1 and the head 100B shown in FIG. 35 discharge ink (liquid) in the cavity 22 from the nozzles by driving the piezoelectric element 200. This ink jet head 100 has a pair of opposing substrates 220, and a plurality of piezoelectric elements 200 are arranged at a predetermined interval between the substrates 220. It is installed intermittently.

A cavity 2 21 is formed between adjacent piezoelectric elements 200. A plate (not shown) is installed at the front in FIG. 3 5 of the cavity 2 2 1, and a nozzle plate 2 2 2 is installed at the back, and a nozzle is installed at the position corresponding to each cavity 2 2 1 of the nozzle plate 2 2. (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 joined to one piezoelectric element 200. By applying a predetermined driving voltage waveform between predetermined electrodes of these electrodes 224, the piezoelectric element 200 undergoes shear mode deformation and vibrates (indicated by an arrow in FIG. 35). As a result, the volume of the cavity 222 (pressure in the cavity) changes, and the ink (liquid) filled in the cavity 222 is ejected from the nozzle 222 as droplets. That is, in the inkjet head 100B, the piezoelectric element 200 itself functions as a diaphragm.

In the same manner as described above, the ink jet head 100C shown in FIG. 36 discharges ink (liquid) in the cavity 2 33 from the nozzle 2 31 by driving the piezoelectric element 200. The inkjet head 100C includes a nozzle plate 230 on which the nozzles 23 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 via a spacer 230, and the nozzle plate 230, the piezoelectric element 200, and the spacer 210 are arranged. Cavity 2 3 3 is formed in the space surrounded by 3 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 second electrodes 235 are joined to both sides thereof. By applying a predetermined drive voltage waveform between the first electrode 234 and the second electrode 235, the piezoelectric element 200 deforms in the shear mode and vibrates (indicated by an arrow in FIG. 36). Due to this vibration, the volume of the cavity 23 3 (pressure in the cavity) changes, and the ink (liquid) filled in the cavity 2 33 becomes droplets from the nozzle 2 31. And discharge. That is, in the inkjet head 100 C, the piezoelectric element 200 itself functions as a diaphragm.

In the ink jet head 100D shown in FIG. 37 as well, the ink (liquid) in the cavity 240 is ejected from the nozzle 241 by driving the piezoelectric element 200 in the same manner as described above. This inkjet head 100D is formed by laminating a nozzle plate 240 on which a nozzle 24 is formed, a cavity plate 24, a vibration plate 24, and a plurality of piezoelectric elements 200. And a multi-layer piezoelectric element 201.

The captive plate 2442 is formed into a predetermined shape (shape such that a concave portion is formed), thereby forming the capitol 245 and the reservoir 246. 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. 37 are joined 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 joined to the outer surface of the multilayer piezoelectric element 201, and between the piezoelectric elements 200 constituting the multilayer piezoelectric element 201 (or inside each piezoelectric element). Has an internal electrode 2 49. 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 between the external electrode 248 and the internal electrode 249 from the head driver 215, the multilayer piezoelectric element 201 is deformed as shown by the arrow in FIG. Then, it vibrates (expanding and contracting in the vertical direction in Fig. 37), and the vibration vibrates the diaphragm 243. Due to the vibration of the diaphragm 243, the volume of the cavity 245 (pressure in the cavity) changes, and the ink (liquid) charged in the cavity 245 is discharged as droplets from the nozzle 241. I do.

The liquid amount reduced in the cavity 245 due to the ejection of the liquid droplets is supplied and supplied from the lizano 246. Ink is supplied to the reservoir 2 46 from the ink cartridge 3 1 via the ink supply tube 3 1 1. In the ink jet heads 100 A to 100 D having the above-described piezoelectric elements, as in the case of the above-described capacitive ink jet head 100, as a diaphragm or a diaphragm, Based on the residual vibration of the functioning 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 100B and 100C, a diaphragm (a diaphragm for detecting residual vibration) is provided as a sensor at a position facing the capty, and the residual vibration of the diaphragm is detected. Such a configuration can also be adopted.

FIG. 38 is a block diagram schematically showing a switching means 23 for switching between a driving circuit 18 and a detection circuit 16 (here, a residual vibration detecting means) when a piezoelectric actuator (piezoelectric element 200) is used. FIG. With such a configuration, the electromotive voltage after the ejection driving operation of the piezoelectric element 200 of the piezoelectric actuator is input to the waveform shaping circuit 15 via the buffer 54, and the waveform shaping circuit 1 The square wave can be shaped by 5. Therefore, by using the electromotive voltage of the piezoelectric element 200, it is possible to execute the same detection processing as in the first embodiment. As described above, the droplet discharge device and the method for detecting a discharge abnormality of the droplet discharge head according to the present invention include the steps of: driving the electrostatic actuator or the piezoelectric actuator to discharge the liquid from the droplet discharge head; When performing the operation of discharging as droplets, the residual vibration of the diaphragm or the electromotive voltage of the piezoelectric element displaced by the actuator is detected, and based on the residual vibration of the diaphragm or the electromotive voltage of the piezoelectric element. Thus, it was determined whether the droplet was ejected normally or not (abnormal ejection).

Further, the present invention provides a method for detecting abnormal discharge of droplets obtained in this manner based on a vibration pattern (for example, a period of a residual vibration waveform) of the residual vibration (including a voltage pattern of an electromotive voltage) of the diaphragm. The cause was determined.

Therefore, according to the present invention, other components (for example, an optical dot missing detection device, etc.) are not required as compared with a droplet ejecting device provided with a conventional dot missing detecting method. Abnormal droplet ejection can be detected without increasing the size of the droplet, and manufacturing costs can be kept low. You. In addition, in the droplet discharge head of the present invention, the abnormal discharge of the droplet is detected using the residual vibration of the diaphragm after the droplet discharge operation, so that the abnormal discharge of the droplet is detected even during the printing operation. can do.

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. However, it is possible to select and execute an appropriate recovery process for the cause.

As described above, the droplet discharge device and the droplet discharge head discharge abnormality detection method of the present invention have been described based on the illustrated embodiments. The present invention is not limited to this. Each component constituting the droplet discharge 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 liquid to be discharged (droplets) discharged from the droplet discharge head (the ink jet head 100 in the above-described embodiment) of the droplet discharge device of the present invention is not particularly limited. (Including suspensions, dispersions of emulsions and the like). That is, an ink containing a color filter material, a light emitting material for forming an EL light emitting layer in an organic EL (Electro Luminescence) device, and a phosphor for forming a phosphor on an electrode in an electron emitting device. Fluorescent material for forming a fluorescent substance in a PDP (Plasma Dispray Panel) device, a migrating material for forming a migrating body in an electrophoretic display device, and a bank on the surface of the substrate W. Punk materials for forming, various coating materials, liquid electrode materials for forming electrodes, particle materials forming spacers for forming a small cell gap between two substrates, metal wiring A liquid metal material for forming microlenses, a lens material for forming microlenses, a resist material, and a light diffusion material for forming a light diffuser.

Further, in the present invention, the droplet receiver 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, or glass substrates. It may be a work such as a plate or various substrates such as a silicon substrate.

Claims

The scope of the claims

1. a diaphragm, an actuator for displacing the diaphragm, a cavity filled with a liquid, a cavity for increasing or decreasing the internal pressure by the displacement of the diaphragm, and a cavity communicating with the cavity. A plurality of droplet discharge heads each having a nozzle that discharges the liquid as droplets by increasing or decreasing the internal pressure, a driving circuit that drives the actuator, and

Pulse generation means for generating a reference pulse;

A counter for counting the reference pulse generated within a predetermined period, and a discharge abnormality detection unit for detecting a discharge abnormality of a droplet based on a count value of a counter within the predetermined period,

A droplet discharge device comprising:

2. The liquid according to claim 1, wherein the predetermined period is a period until the diaphragm displaced by the actuator generates a residual vibration when a droplet is normally ejected. Drop ejection device.

3. The droplet discharge device according to claim 1, wherein the predetermined period is a period of a first half cycle of the residual vibration.

4. The droplet discharge device according to claim 1, wherein the predetermined period is a period of a first cycle of the residual vibration.

5. The ejection abnormality detecting means compares the normal count range of the reference pulse when the droplet is ejected normally by the drive of the actuator with the count value of the counter within the predetermined period. 2. The droplet discharge device according to claim 1, wherein the discharge abnormality is detected.

6. The discharge abnormality detecting means sets the count value within the normal count range. 6. The droplet discharge device according to claim 5, wherein a request for detecting that air bubbles have entered the cavity when the diameter is smaller is provided.

7. When the count value is larger than the normal count range, the discharge abnormality detecting means may cause the liquid near the nozzle to thicken due to drying, or may cause paper dust to adhere near the nozzle outlet. 6. The droplet discharge device according to claim 5, wherein the droplet discharge device detects the droplet.

8. The counter subtracts the number of reference pulses counted in the predetermined period from a predetermined reference value, and the discharge abnormality detection means detects the discharge abnormality based on the result of the subtraction. 2. The droplet discharge device according to item 1, wherein

9. The discharge abnormality detecting means according to claim 8, wherein the discharge abnormality detection means detects that air bubbles have entered the cavity as a cause of the discharge abnormality when the subtraction result is smaller than a first threshold value. The droplet discharge device according to the above.

10. The discharge abnormality detecting means according to claim 8, wherein the discharge abnormality detection means detects that the liquid near the nozzle has increased in viscosity due to drying as a cause of the discharge abnormality when the subtraction result is larger than a second threshold value. 5. The droplet discharge device according to 4.

11. The discharge abnormality detecting means determines that paper dust has adhered to the vicinity of the outlet of the nozzle as a cause of the discharge abnormality when the subtraction result is smaller than a second threshold value and larger than a third threshold value. 9. The droplet discharge device according to claim 8, which detects.

12. The droplet discharge device according to claim 1, further comprising storage means for storing a detection result detected by the discharge abnormality detection means.

13. The switching device according to claim 1, further comprising: a switching unit configured to switch the actuator from the driving circuit to the ejection abnormality detecting unit after the droplet is ejected by driving the actuator. Droplet ejection device.

14. The method according to claim 1, wherein the discharge abnormality detecting means includes an oscillation circuit, and the oscillation circuit oscillates based on a capacitance component of the actuator that changes due to residual vibration of the diaphragm. The droplet discharge device according to the above.

15. The oscillation circuit according to claim 14, wherein the oscillation circuit forms a CR oscillation circuit including a capacitance component of the actuator and a resistance component of a resistance element connected to the actuator. The droplet discharge device according to the above.

1 6. The discharge abnormality detecting means includes an FZV conversion circuit that generates a voltage waveform of the residual vibration of the diaphragm by a predetermined signal group generated based on a change in the oscillation frequency of the output signal of the oscillation circuit. The droplet discharge device according to claim 14 or 15, further comprising:

17. The discharge abnormality detection unit according to claim 16, wherein the discharge abnormality detection unit includes a waveform shaping circuit that shapes a voltage waveform of the residual vibration of the diaphragm generated by the FZV conversion circuit into a predetermined waveform. Droplet ejection device.

1 8. The waveform shaping circuit removes a DC component from a voltage waveform of a residual vibration of the diaphragm generated by the F / V conversion circuit, and a DC component removing unit that removes a DC component by the DC component removing unit. The comparator according to claim 17, further comprising a comparator for comparing the obtained voltage waveform with a predetermined voltage value, wherein the comparator generates and outputs a rectangular wave based on the voltage comparison. Drop ejection device.

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

20. The droplet discharge apparatus according to claim 1, wherein the actuator is a piezoelectric actuator utilizing a piezo effect of a piezoelectric element.

21. The droplet discharge device according to claim 1, wherein the droplet discharge device includes an ink jet printer.

22. A cavity filled with a liquid, a nozzle communicating with the cavity, and a pressure that changes the pressure of the liquid filled in the cavity, and the pressure fluctuation causes the liquid to be ejected as droplets from the nozzle. A plurality of droplet ejection heads having an

A drive circuit for driving the piezoelectric actuator,

Pulse generation means for generating a reference pulse;

A counter that counts the reference pulse generated within a predetermined period; and a discharge abnormality detection unit that detects a discharge abnormality of the droplet based on a count value of the count within the predetermined period.

A droplet discharge device comprising:

23. The method according to claim 22, wherein the predetermined period is a period from a time when the droplet is normally ejected to a time when a residual vibration of a voltage due to an electromotive voltage of the piezoelectric actuator is generated. Droplet ejection device.

24. The droplet discharge device according to claim 22, wherein the droplet discharge device includes an inkjet printer.

25. By driving the actuator and vibrating the diaphragm, the liquid in the cavity is ejected from the nozzle as droplets, and then a reference pulse is generated and a predetermined period is measured. The reference pulse generated within the measured predetermined period is counted, and the droplet is discharged based on the counted value. A method for detecting an abnormal discharge of a droplet discharge head, comprising detecting an abnormality.

26. The droplet according to claim 25, wherein the number of reference pulses counted in the predetermined period is subtracted from a predetermined reference value, and the discharge abnormality is detected based on a result of the subtraction. Discharge head discharge abnormality detection method.

27. After performing the operation of driving the piezoelectric actuator to discharge liquid droplets, generate a reference pulse, measure a predetermined period, and generate a reference pulse within the measured predetermined period. Detecting abnormal discharge of a droplet based on the count value.