WO2004076182A1

WO2004076182A1 - Liquid drop ejector

Info

Publication number: WO2004076182A1
Application number: PCT/JP2004/002401
Authority: WO
Inventors: Yusuke Sakagami; 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 capable of detecting a missing dot (loss of a pixel) actually in a formed image. The liquid drop ejector comprises a plurality of liquid ejection heads for ejecting liquid, in the form of a liquid drop, from a nozzle communicating with a cavity filled with the liquid by driving an actuator through a drive circuit thereby varying the pressure in the cavity to eject a liquid drop toward a liquid drop receiving material from the nozzle while moving the liquid ejection head relatively thereto. The liquid drop ejector further comprises means (10) for detecting abnormal ejection of a liquid drop from the nozzle, wherein each means (10) detects abnormal ejecting operation of each liquid drop being ejected from the nozzle while the liquid ejection head is ejecting a liquid drop toward the liquid drop receiving material.

Description

Description Droplet ejection device Technical field

The present invention relates to a night drop ejection device. Background art

2. Description of the Related 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. The print head (ink-jet head) of an ink-jet printer has a large number of nozzles. May be clogged and ink drops cannot be ejected. If the nozzles are clogged, missing dots will occur in the printed image, which may cause a deterioration in image quality.

Conventionally, as a method of detecting such an ink droplet ejection abnormality (hereinafter also referred to as “missing dot”), a state in which an ink droplet is not ejected from the nozzle of the ink jet head (ink droplet ejection abnormal state) is used. A method of optically detecting each nozzle of the head has been devised (for example, Japanese Patent Application Laid-Open No. 8-30963). With this method, it is possible to identify the nozzle that has a missing dot (abnormal ejection). However, in the above-described optical dot missing (droplet ejection abnormality) detection method, a detector including a light source and an optical sensor is attached to a droplet ejection device (for example, an ink jet printer). In this detection method, generally, a light source and a light source are arranged so that a droplet ejected from a nozzle of a droplet ejection head (ink jet head) passes between the light source and the optical sensor and blocks light between the light source and the optical sensor. There is a problem that the optical sensor must be set (installed) with high precision (high accuracy). Further, such a detector is usually expensive, and there is a problem that the manufacturing cost of the ink jet printer is increased. In addition, light is generated by ink mist from the nozzles and paper dust such as printing paper. The output section of the source and the detection section of the optical sensor may become dirty, and the reliability of the detector may become an issue.

In addition, the droplet discharge apparatus that performs the above-described optical dot missing detection method detects missing dots of a nozzle (abnormal droplet ejection) during non-recording, and records the droplet on a droplet receiver such as printing paper. Since it cannot be detected during (printing), there is a problem that it is not possible to know (detect) whether a missing dot (pixel loss) has actually occurred in a printed image or the like. Disclosure of the invention

An object of the present invention is to provide a droplet discharge device capable of detecting whether or not a dot missing (pixel loss) actually exists in a formed image.

In order to solve the above-mentioned problems, a droplet discharge device according to the present invention is configured such that a drive circuit drives an actuator to change a pressure in a cavity filled with a liquid, so that the nozzle communicates with the cavity. A plurality of droplet discharge heads for discharging the liquid as droplets, wherein the droplets are discharged from the nozzles while scanning (moving) the droplet discharge head relative to a droplet receiver. A droplet discharge device for landing on a droplet receiver,

A discharge abnormality detecting unit that detects a discharge abnormality of the droplet from the nozzle; when the droplet discharge head is discharging a droplet to the droplet receiver, the droplet should be discharged from the nozzle; An ejection abnormality is detected by the ejection abnormality detection means for the ejection operation of each droplet.

In this way, when a droplet is ejected from each nozzle toward the droplet receiver, it is performed while detecting whether or not each droplet to be ejected has been normally ejected, so that a dot is actually missing in the formed image. (Pixel loss) can be accurately detected.

Further, it is preferable that the droplet discharge device of the present invention further includes a counting unit that counts the number of ejection abnormalities detected by the ejection abnormality detection unit.

Thereby, while forming an image by discharging a droplet to the droplet receiver, The number of ejection abnormalities that have occurred with respect to the droplet receiver can be counted. Therefore, the image quality of the formed image can be detected (determined) based on the number of missing dots (pixel loss) generated in the image formed on the droplet receiver.

Further, the droplet discharge device of the present invention further comprises a notifying unit,

If the number of ejection abnormalities for the droplet receiver counted by the counting means during ejection of the droplet to the droplet receiver exceeds a preset reference value, this fact is notified. Preferably, the notification is performed by the notification unit.

As a result, when an abnormal discharge occurred in an image formed on the droplet receiver exceeds a reference value, it is determined that the image does not satisfy the image quality standard based on the reference value. Person).

Further, the droplet discharge device of the present invention further includes a droplet receptor conveying means for discharging and supplying the droplet receptor,

If the number of abnormal discharges for the droplet receiver counted by the counting means while discharging the droplet to the droplet receiver exceeds a preset reference value, the droplet The discharge of the droplets to the receptor is stopped, the droplet receiver is discharged by operating the droplet receptor transport means, and the next droplet receptor is supplied, and the supplied droplet receptor is supplied. It is preferable to newly discharge droplets in the same manner.

As a result, the image forming operation is re-executed on a new droplet receiver until a droplet receiver having an image satisfying the image quality standard based on the reference value is obtained. ) Can surely obtain the desired image quality.

Further, in this case, the droplet discharge head further includes a recovery unit that performs recovery processing for eliminating a cause of the abnormal discharge of the droplet, and the same applies to the newly supplied droplet receiver. It is preferable to perform a recovery process by the recovery unit before discharging the droplets.

This makes it possible to more reliably prevent the discharge abnormality from occurring again when the droplet receiver having the discharge abnormality is discharged and the droplet is discharged again to a new droplet receiver.

In this case, preferably, the recovery unit is configured such that nozzles of the droplet discharge head are arranged. A wiping unit for wiping a nozzle surface with a wiper, a flushing unit for performing a flushing process for driving the actuator and preliminary discharging the droplet from the nozzle, Bombing means for performing a pump suction process by a pump connected to a cap covering the nozzle surface.

Further, in the droplet discharge device of the present invention, it is preferable that the reference value can be changed, and it is more preferable that the droplet discharge device has a plurality of operation modes in which the reference value is different, and that the operation mode can be selected. .

In this way, droplets can be ejected in accordance with the image quality desired by the operator (user) of the droplet ejection device so as to obtain an image of sufficient and sufficient image quality. An image forming operation can be performed.

Here, in the droplet discharge device of the present invention, the droplet discharge head has a diaphragm that is displaced by driving of the work piece,

The discharge abnormality detection means is configured to detect residual vibration of the diaphragm, and to detect abnormality of discharge of the droplet based on the detected vibration pattern of the residual vibration of the diaphragm. Is also good. In this case, it is preferable that the discharge abnormality detecting means determines whether or not there is a discharge abnormality of the droplets of the droplet discharge head based on a vibration pattern of residual vibration of the diaphragm, and When it is determined that there is a discharge abnormality of the head droplet, a determination means for determining a cause of the discharge abnormality is included. Here, the residual vibration of the vibrating plate means that the actuator performs a droplet ejection operation by a drive signal (voltage signal) of the drive circuit, and then receives a next drive signal and receives a droplet again. A state in which the diaphragm continues to vibrate while being attenuated by the droplet discharging operation before the discharging operation is performed.

Preferably, the vibration pattern of the residual vibration of the diaphragm may include a period of the residual vibration. In this case, preferably, the determination unit may determine that the period of the residual vibration of the diaphragm is a predetermined period. If the period is shorter than the range, it is determined that air bubbles are mixed in the capty.If the period of the residual vibration of the diaphragm is longer than a predetermined threshold, the liquid in the vicinity of the nozzle is thickened by drying. When the cycle of the residual vibration of the diaphragm is longer than the cycle of the predetermined range and shorter than the predetermined threshold, It is determined that paper dust has adhered to the vicinity of the outlet of the nozzle. As a result, it is possible to determine the cause of a droplet ejection abnormality that cannot be determined by a conventional droplet ejection device such as an optical detection device that can detect missing dots. An appropriate recovery process for the cause can be selected and executed as described above.

In one embodiment of the present invention, 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. It may be configured. In this case, it is preferable that 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. As described above, the droplet discharge device of the present invention detects the residual vibration waveform of the diaphragm as a time-series minute change (change in oscillation cycle) of the capacitance component of the actuator. When a piezoelectric element is used in the evening, the residual vibration waveform of the diaphragm can be accurately detected without depending on the magnitude of the electromotive force.

Here, it is preferable that the oscillation frequency of the oscillation circuit is set to be higher than the oscillation frequency of the residual vibration of the diaphragm by about one digit or more. In this way, by setting the oscillation frequency of the oscillation circuit to about several tens of times the oscillation frequency of the residual vibration of the diaphragm, the residual vibration of the diaphragm can be detected more accurately. As a result, it is possible to more accurately detect a droplet ejection abnormality.

Preferably, the discharge abnormality detection means generates a voltage waveform of residual vibration of the diaphragm using a predetermined signal group generated based on a change in oscillation frequency in an output signal of the oscillation circuit. Includes / V conversion circuit. As described above, by generating the voltage waveform using the FZV conversion circuit, the detection sensitivity can be set to be large when detecting the residual vibration waveform without affecting the driving of the actuator. In addition, preferably, the discharge abnormality detection means may include 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.

Here, preferably, the waveform shaping circuit includes a DC component removing unit configured to remove a DC component from a voltage waveform of a residual vibration of the diaphragm generated by the FZV conversion circuit. 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, wherein the comparator generates and outputs a square wave based on the voltage comparison May be configured. In this case, more preferably, the discharge abnormality detecting means includes a measuring means for measuring a period of the residual vibration of the diaphragm from the rectangular wave generated by the waveform shaping circuit. Preferably, the measuring means has a counter, and the counter counts a pulse of the reference signal, thereby detecting a time between rising edges of the rectangular wave or between rising edges and falling edges. The period of the residual vibration may be measured by measuring the interval. By measuring the period of the rectangular wave using the counter in this way, the period of the residual vibration of the diaphragm can be detected more easily and more accurately.

In addition, the droplet discharge device of the present invention is preferably configured such that after the droplet ejection operation by driving the actuator, switching means for switching a connection with the actuator from the drive circuit to the discharge abnormality detecting means. Is further provided. Preferably, the droplet discharge device of the present invention includes a plurality of the discharge abnormality detection means and the switching means, and the switching means corresponding to the droplet discharge head that has performed the droplet discharge operation is the liquid ejection apparatus. The connection with the actuator is switched from the driving circuit to the corresponding ejection abnormality detection means, and the switched ejection abnormality detection means is configured to detect an abnormality in ejection of the droplet. Good.

Further, the actuation may be an electrostatic actuation or a piezoelectric actuation utilizing a piezo effect of a piezoelectric element. Preferably, the droplet discharge device of the present invention may further include a storage unit that stores a cause of the droplet discharge abnormality detected by the discharge abnormality detection unit in association with a nozzle to be detected. In addition, preferably, the droplet discharge device includes an ink jet printer. 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 shows the configuration of an ink jet printing apparatus, which is one type of the droplet discharge device of the present invention. FIG.

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 a head unit (ink jet head) in the ink jet printing apparatus shown in FIG.

FIG. 4 is an exploded perspective view showing the configuration of the head unit of FIG.

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

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

FIG. 8 is a graph showing the relationship between the experimental value and the calculated value of the residual vibration in the case of normal ejection of the diaphragm 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 residual vibration in a state where ink droplets are not ejected due to air bubbles entering the cavity.

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

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

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

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

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

FIG. 16 is a schematic block diagram of the discharge abnormality detecting means.

Fig. 17 is a conceptual diagram when the electrostatic factory of Fig. 3 is a parallel plate capacitor. It is.

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

FIG. 19 is a 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.

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 the switching means for switching between the drive circuit and the detection circuit. FIG. 24 is a flowchart showing a discharge abnormality detection / determination process.

FIG. 25 is a flowchart showing the residual vibration detection processing.

FIG. 26 is a flowchart showing the discharge abnormality determination process.

FIG. 27 shows an example of the timing of detecting the ejection abnormality of a plurality of inkjet heads (when there is one ejection abnormality detection unit).

FIG. 28 shows an example of the timing of detecting ejection failures of a plurality of inkjet heads (when the number of ejection failure detection means is the same as the number of ink jet heads).

Fig. 29 shows an example of the timing of detecting abnormal ejection of multiple ink jet heads (when the number of ejection abnormality detecting means is the same as the number of ink jet heads and the abnormal ejection is detected when there is print data). It is.

FIG. 30 shows an example of the timing of detecting the ejection failure of a plurality of inkjet heads (when the number of ejection failure detection means is the same as the number of ink jet heads and the ejection failure detection is performed by circulating through each ink jet head). ).

FIG. 31 is a flowchart showing the timing of detecting a discharge abnormality during the flushing operation of the ink jet printing shown in FIG.

FIG. 32 is a flowchart showing the timing of detecting a discharge abnormality during the flushing operation of the ink jet printing shown in FIGS. 28 and 29.

FIG. 33 is a flowchart showing the timing of detecting an ejection failure during the flushing operation of the ink jet printer shown in FIG. FIG. 34 is a flowchart showing the timing of detecting a discharge abnormality during the printing operation of the ink jet printer shown in FIGS. 28 and 29.

FIG. 35 is a flowchart showing the timing of detecting an ejection failure during the printing operation of the ink jet printer shown in FIG.

FIG. 36 shows a schematic structure (partially omitted) of the ink jet pudding shown in FIG. 1 as viewed from above.

FIG. 037 is a diagram showing the positional relationship between the wiper and the head unit shown in FIG. FIG. 38 is a diagram showing a relationship between the head unit, the cap, and the pump during the pump suction process.

FIG. 39 is a schematic diagram showing the configuration of the tube pump shown in FIG.

FIG. 40 is a flowchart showing an ejection failure recovery process in the ink jet printer of the present invention. FIG. 41 is a flowchart showing an example of processing when an ejection failure is detected during image formation.

FIG. 42 is a flowchart showing another example of the processing when an ejection failure is detected during image formation.

FIG. 43 is a flowchart showing still another example of the processing when an ejection failure is detected during image formation. FIG. 44 is a cross-sectional view schematically showing another example of the configuration of the ink jet head according to the present invention.

FIG. 45 is a cross-sectional view schematically showing another configuration example of the ink jet head according to the present invention.

FIG. 46 is a cross-sectional view schematically showing another configuration example of the ink jet head according to the present invention.

FIG. 47 is a cross-sectional view schematically showing another example of the configuration of the ink jet head according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a preferred embodiment of the droplet discharge device of the present invention will be described in detail with reference to FIGS. Note that 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, as an example of the liquid droplet discharging apparatus of the present invention, an ink jet printer that discharges ink (liquid material) and prints an image on a recording paper (droplet receptor) will be described. I do.

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

An ink jet printer 1 shown in FIG. 1 includes an apparatus main body 2, a tray 21 for placing recording paper P at the upper rear, a discharge roller 22 for discharging the recording paper P to a 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 (see FIG. (Not shown). The display section of the operation panel 7 functions as a notification unit.

Further, inside the apparatus main body 2, a printing apparatus (printing means) 4 including a reciprocating printing means (moving body) 3 and a paper feeding apparatus for supplying and discharging recording paper P to the printing apparatus 4 are mainly provided. And a control unit (control means) 6 for controlling the printing device 4 and the paper feeding device 5.

Under the control of the control unit 6, the paper feeding device 5 intermittently feeds the recording paper P one by one. This recording paper P passes near the lower part of the printing means 3. At this time, the printing means 3 reciprocates in a direction substantially orthogonal to the feed direction of the recording paper P, and printing on the recording paper P is performed. That is, the reciprocating movement of the printing means 3 and the intermittent feeding of the recording paper P become main scanning and sub-scanning in printing, and ink jet printing is performed.

The printer 4 moves the printing means 3 and the printing means 3 in the main scanning direction (reciprocating movement). A carriage motor 41 as a drive source and a reciprocating mechanism 42 for reciprocating the printing means 3 in response to the rotation of the carriage motor 41 are provided.

The printing means 3 includes a plurality of head units 35 and an ink cartridge (I / O 31) for supplying ink to each head unit 35. A carriage 3 2 on which each head unit 35 and the ink cartridge 31 is mounted. In the case of an ink-jet printer that consumes a large amount of ink, the ink cartridge 31 is installed in a different location without being mounted on the cartridge 32, and the ink cartridge 31 is connected to the head unit 35 with a tube. It may be configured to be connected and supplied with an ink (not shown).

By using an ink cartridge 31 filled with four color inks of yellow, cyan, magenta, and black (black), full color printing can be performed. In this case, the printing means 3 is provided with a head unit 35 corresponding to each color (this configuration will be described later in detail). Here, FIG. 1 shows four ink cartridges 31 corresponding to the four color inks, but the printing means 3 uses other colors, such as light cyan, light magenta, dark yellow, and special color ink. The ink cartridge 31 may be further provided. The reciprocating mechanism 42 has a carriage guide shaft 42 2 having both ends supported by a frame (not shown), and a timing belt 4 21 extending in parallel with the carriage guide shaft 4 22. are doing.

The carriage 32 is reciprocally supported by a carriage guide shaft 42 of the reciprocating mechanism 42 and is fixed to a part of the timing belt 421.

When the timing belt 4 21 is caused to travel forward and reverse via pulleys by the operation of the carriage motor 41, the printing means 3 is guided by the carriage guide shafts 4 22 and reciprocates. During this reciprocating movement, ink droplets are ejected from each ink jet head 100 of the head unit 35 appropriately in accordance with the image data (print data) to be printed. Printing is performed.

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

The paper feed rollers 52 face up and down with the recording paper P transport path (recording paper P) in between. The driving roller 52b is connected to a sheet feeding motor 51. The driven roller 52a includes a driven roller 52a and a driving roller 52b. As a result, the paper feed roller 52 feeds a large number of recording papers P set in the tray 21 one by one toward the printing device 4 or discharges one by one from the printing device 4. I have. Note that, instead of the tray 21, a configuration in which a paper cassette for storing the recording paper P can be detachably mounted may be used. Further, the paper feed motor 51 also feeds the recording paper P according to the resolution of the image in conjunction with the reciprocating operation of the printing means 3. The paper feeding operation and the paper feeding operation can be performed by different motors, respectively, or can be performed by the same motor by using a component that switches torque transmission such as an electromagnetic clutch.

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), thereby controlling the recording paper P. Print processing. The control unit 6 displays an error message or the like on the display unit of the operation panel 7 or turns on / flashes an LED lamp or the like, and responds to various switch press signals input from the operation unit. Based on this, the corresponding processing is executed by each unit. Further, the control unit 6 may transfer information such as an error message and a discharge abnormality to the host combination 8 as needed.

FIG. 2 is a block diagram schematically showing a main part of the ink jet printing of the present invention. In FIG. 2, the ink jet printer 1 of the present invention includes an interface unit (IF: Interface) 9 for receiving a print data input from a host computer 8, a control unit 6, and a printer. 4 1, Carriage motor driver 4 3 for driving and controlling Carriage mosquitoes 4 1, Paper feed motor 5 1, and Drive control for paper feed motor 5 1, Lined paper motor dryer 5 3, Head unit A head driver 33 for driving and controlling the head unit 35; a discharge abnormality detecting means 10; a recovery means 24; The details of the ejection abnormality detection means 10, the recovery means 24, and the head driver 33 will be described later.

In FIG. 2, the control unit 6 includes a CPU (Central Processing Unit) 61 for executing various processes such as a printing process and a discharge abnormality detection process, EEPR〇M (Electrically Erasable Programmable Read-Only Memory) (storage means) 62, which is a type of nonvolatile semiconductor memory that stores print data input via F9 in a data storage area (not shown), and discharge described later. Temporarily stores various data when executing abnormality detection processing, etc., or temporarily develops application programs for printing processing, etc. (RAM CRandom Access Memory) 63, and stores control programs for controlling each unit PROMO 64, which is a type of non-volatile semiconductor memory. The components of the control section 6 are electrically connected via a bus (not shown).

As described above, the printing unit 3 includes the plurality of headunits 35 corresponding to each color ink. In addition, each head unit 35 includes a plurality of nozzles 110 and an electrostatic actuator 120 corresponding to each of the nozzles 110. That is, the head unit 35 includes a plurality of ink jet heads 100 (droplet discharge heads) each having a set of nozzles 110 and an electrostatic actuator 120. It has become. 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 switching means 23. (See Figure 16). The configuration of the electrostatic actuator 120 will be described later.

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

When obtaining 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 process data and the input data from various sensors. Is output. When these drive signals are input via the respective drivers 33, 43, 53, a plurality of electrostatic actuators 120 of the head unit 35, the carriage motor 41 of the printing device 4, and the power supply Paper unit 5 is activated. Thus, the printing process is performed on the recording paper P. Next, the structure of each head unit 35 in the printing means 3 will be described. Figure 3 FIG. 4 is a schematic cross-sectional view of the head unit 35 (inkjet head 100) shown in FIG. 4, and FIG. 4 is an exploded perspective view showing a schematic configuration of the head unit 35 corresponding to one color ink; FIG. 5 is a plan view showing an example of the nozzle surface of the printing means 3 to which the head unit 35 shown in FIGS. 3 and 4 is applied. 3 and 4 are shown upside down from the state of normal use.

As shown in FIG. 3, the head unit 35 has an ink inlet 1 31 and a damper chamber.

It is connected to the ink cartridge 31 via 130 and the ink supply tube 311. Here, the damper chamber 130 is provided with a damper 132 made of rubber. The damper chamber 130 absorbs fluctuations in ink and ink pressure when the carriage 32 reciprocates, thereby stably supplying a predetermined amount of ink to the head unit 35. be able to.

In addition, the head unit 35 has a silicon nozzle 140 on the upper side with the silicon substrate 140 interposed therebetween, and a borosilicate glass substrate (glass substrate) on the lower side having a thermal expansion coefficient close to that of silicon. 16 have a three-layer structure in which they are stacked. The central silicon substrate 140 has a plurality of independent cavities (pressure chambers) 14 1 (seven cavities are shown in Fig. 4) and a single reservoir (common ink chamber) 144. Ink supply port (orifice) that connects the reservoir 1 4 3 to each cavity 1 4 1

Grooves each functioning as 14 2 are formed. 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 the cavities 144, the reservoirs 144, and the ink supply ports 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 vibration (displacement) of a diaphragm 121 described later. It is configured to eject ink (liquid material). 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, the portion of the glass substrate 160 where the reservoir 144 is located is connected to the reservoir 144. An ink inlet 1 3 1 through which the ink flows is formed. 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 inlet 1131. The ink supplied to the reservoirs 144 is supplied to the independent cavities 144 through the respective ink supply ports 142. Each cavity 144 is defined by a nozzle plate 150, a side wall (partition wall) 144, and a bottom wall 121.

Each of the independent cavities 1 4 1 has its bottom wall 1 2 1 formed thin, and its bottom wall 1 2 1 is elastically deformed in its out-of-plane direction (thickness direction), that is, in the vertical direction in FIG. It is configured to function as a diaphragm (diaphragm) capable of (elastic displacement). Therefore, the bottom wall 121 may be referred to as the diaphragm 121 for the sake of convenience in the following description (that is, hereinafter, both the “bottom wall” and the “diaphragm”). Use the symbol 1 2 1).

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

Here, the bottom wall (diaphragm) 1 2 1 of each cavity 1 4 1 is a common electrode 1 2 4 on the side of each cavity 1 4 1 for storing electric charge by the drive signal supplied from the head driver 3 3. Constitutes a part of. In other words, each of the diaphragms 121 of each of the cavities 14 1 also serves as one of the counter electrodes (the counter electrodes of the capacitors) 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, which is the electrode facing the common electrode 12 4, respectively, faces the bottom wall 12 1 of each captivity 14 1. 1 2 2 is formed. Further, as shown in FIG. 3, the surface of the bottom wall 121 of each cavity 141 is covered with an insulating layer 123 made of a silicon oxide film (Si ₂ ). Thus, each cavit The bottom wall 1 2 1 of 1 4 1, that is, the diaphragm 1 2 1 and the corresponding segment electrodes 1 2 2 are the lower surface in FIG. 3 of the bottom wall 1 2 1 of the cavity 1 4 1 A counter electrode (a counter electrode of the capacitor) is formed (configured) through the insulating layer 12 3 formed in the substrate and the gap in the recess 16 1. Therefore, the main part of the electrostatic actuator 120 is constituted by the diaphragm 122, the segment electrode 122, the insulating layer 123 and the gap therebetween.

As shown in FIG. 3, a head driver 33 including a drive circuit 18 for applying a drive voltage between these counter electrodes is provided according to a print signal (print data) input from the control unit 6. Charge and discharge between these opposed electrodes is performed. One output terminal of the head driver (voltage application 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 terminal 124a. Since the silicon substrate 140 has impurities implanted therein and has conductivity, the input terminal 124 a of the common electrode 124 and the common electrode 1 of the bottom wall 121 are formed. 24 can supply voltage. Further, for example, a thin film of a conductive material such as gold or copper may be formed on one surface of the silicon substrate 140. As a result, a voltage (charge) can be supplied to the common electrode 124 with 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, the silicon substrate 140 and the glass substrate 160 are bonded (joined) by anodic bonding, so that the conductive film used as an electrode in the anodic bonding is a silicon substrate 140. On the side of the flow path forming surface (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 having a plurality of nozzles 110 formed therein, a plurality of cavities 144, a plurality of ink supply ports 144, and one reservoir. It has a silicon substrate (ink chamber substrate) 140 on which a cover 144 is formed and an absolutely green layer 123, which are housed in a base 170 including a glass substrate 160. 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 nozzles 110 formed in the nozzle plate 150 are linearly arranged substantially in parallel with the reservoirs 144 for simplicity in FIG. 4, but the nozzle arrangement pattern is Not limited to the configuration, usually, for example, as shown in a nozzle arrangement pattern shown in FIG. Further, the pitch between the nozzles 110 can be appropriately set in accordance with the print resolution (dpi: dot per inch). FIG. 5 shows an arrangement pattern of the nozzles 110 when four color inks (ink cartridges 31) are applied.

FIG. 6 shows each state at the time of inputting the drive signal in the section taken along the line III-III of FIG. When a drive voltage is applied between the opposing electrodes from the head driver 33, a Coulomb force is generated between the opposing electrodes, and the bottom wall (diaphragm) 1 2 1 Then, the segment electrode 122 bends to the side, and the capacity of the cavity 141 increases (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 1 21 is restored upward in the figure by its elastic restoring force, and the diaphragm 1 2 in the initial state is restored. It moves to the top beyond the position of 1 and the volume of the cavity 141 contracts rapidly (Fig. 6 (c)). At this time, a part of the ink (liquid material) that satisfies the cavity 141 is discharged as an ink droplet from the nozzle 110 communicating with the cavity 141 due to the compression pressure generated in the cavity 141 at this time. You.

The diaphragm 1 2 1 of each cavity 1 4 1 receives the next drive signal (drive voltage) by this series of operations (ink discharge operation by the drive signal of the head driver 3 3) and discharges ink droplets again. Until then, it is damping. Hereinafter, this damped vibration is also referred to as residual vibration. The residual vibration of the diaphragm 1 2 1 includes the acoustic resistance r due to the shape of the nozzle 1 10 and the ink supply port 1 4 or the ink viscosity, the inertance m due to the ink weight in the flow path, and the diaphragm It is assumed that it has a natural vibration frequency determined by the compliance C m of 121.

A calculation model of the residual vibration of the 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. Thus, the calculation model of the residual vibration of the diaphragm 122 can be expressed by the sound pressure P, the above-mentioned inertia m, the compliance Cm, and the acoustic resistance r. Then, when the step response when sound pressure P is applied to the circuit of FIG. 7 is calculated for the volume velocity u, the following equation is obtained. '

[Equation 1]

P ■ OJI

u ■ e sm (1)

ω, m

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 ejection of the ink droplet performed separately. FIG. 8 is a graph showing the relationship between the experimental value and the calculated value of the residual vibration of diaphragm 121. As can be seen from the graph shown in Fig. 8, the two waveforms, the experimental value and the calculated value, generally agree.

By the way, in each of the inkjet heads 100 of the head unit 35, a phenomenon in which ink droplets are not normally ejected from the nozzles 110 despite the above-described ejection operation, that is, abnormal ejection of droplets. May occur. As described below, the causes of the discharge abnormality are as follows: (1) mixing of air bubbles into the cavity 141; (2) drying and thickening (fixation) of ink near the nozzle 110; 3) Adhesion of paper powder near the nozzle 110 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 a discharge abnormality, even if the droplet is discharged 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 land, it still appears as missing pixels. Therefore, in the following description, the ejection Sometimes the usual thing is simply called "missing dot".

In the following, based on the comparison results shown in FIG. 8, the dot missing (discharge abnormality) phenomenon (discharge failure) phenomenon (droplet non-discharge phenomenon) during the printing process that occurs in nozzle 110 of ink jet head 100 will be described. Adjust the acoustic resistance r and / or inertance m so that the calculated value of the residual vibration of the diaphragm 121 and the experimental value match (approximately match).

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

As described above, when the bubbles B are mixed into the cavity 141, it is considered that the total weight of the ink filling the cavity 141 decreases and the inertia m decreases. In addition, since the bubble B is attached to the wall surface of the cavity 141, it is considered that the diameter of the nozzle 110 increases as much as its diameter, and the acoustic resistance r decreases. .

Therefore, compared to the case of Fig. 8 in which ink was ejected normally, the acoustic resistance r and the inertance m were both set small and matched with the experimental values of the residual vibration when bubbles were mixed. A result (graph) like 0 was obtained. As can be seen from FIGS. 8 and 10, the characteristic residual vibration waveform having a higher frequency than in normal ejection is obtained when bubbles are mixed in the cavity 141. 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 ink drying (adhesion, thickening) near the nozzle 110, which is another cause of missing dots, will be examined. FIG. 11 is a conceptual diagram of the vicinity of the nozzle 110 when the ink near the nozzle 110 of FIG. 3 is fixed by drying. As shown in FIG. 11, when the ink near the nozzle 110 is dried and fixed, the ink in the cavity 141 is trapped in the cavity 141. Thus, when the ink near the nozzle 110 dries and thickens, the acoustic resistance r is considered to increase. Can be

Therefore, compared to the case of Fig. 8 where the ink was ejected normally, the acoustic resistance r was set to be large and matched with the experimental value of the residual vibration at the time of ink drying and sticking (thickening) near the nozzle 110. As a result, the result (graph) shown in Fig. 12 was obtained. The experimental values shown in Fig. 12 are based on the fact that the head unit 35 was left unattended for several days without a cap (not shown), and the ink near the nozzle 110 was dried and thickened, and the ink was ejected. This is a measurement of the residual vibration of the diaphragm 121 in a state where the ink cannot be applied (the ink is fixed). As can be seen from the graphs in Fig. 8 and Fig. 12, when the ink near nozzle 110 is fixed by drying, the frequency becomes extremely lower than during normal ejection, and the residual vibration is overdamped. A typical 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 1 This is because, when 21 moves upward in FIG. 3, there is no escape route for the ink in the cavity 141, so that the diaphragm 1 21 cannot vibrate suddenly (because of excessive attenuation).

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

Therefore, compared to the case of Fig. 8 in which ink was ejected normally, both the inertance m and the acoustic resistance r were set to be large, and the residual vibration when paper dust adhered near the outlet of the nozzle 110 was set. By matching with the experimental values, the result (graph) shown in Fig. 14 was obtained. Was. As can be seen from the graphs of Fig. 8 and Fig. 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. 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 dust 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 dust. 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, the case where the ink near the nozzle 110 dried and increased the viscosity and the case where paper dust adhered near the outlet of the nozzle 110 were both compared to the case where the ink droplet was normally ejected. The frequency of damped vibration is low. In order to identify the cause of these two missing dots (non-ejection of ink: abnormal ejection) from the waveform of the residual vibration of the diaphragm 121, for example, a predetermined threshold value is set for the frequency, period, and phase of the damped vibration. They can be compared with each other, or can be specified based on the residual vibration, the damping rate of the (damped vibration) period change, and the amplitude change. In this way, a change in the residual vibration of the diaphragm 121 when ink droplets are ejected from the nozzle 110 in each ink jet head 100, in particular, a change in the frequency causes a change in each ink jet head. It is possible to detect ejection failure of the nozzle 100. In addition, by comparing the frequency of the residual vibration in that case with the frequency of the residual vibration during normal ejection, it is possible to identify the cause of the ejection abnormality.

Next, the discharge abnormality detecting means 10 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 includes a residual vibration detecting means 16 including an oscillation circuit 11, an F / V conversion circuit 12, and a waveform shaping circuit 15. A measuring means 17 for measuring a period, an amplitude, and the like from the residual vibration waveform data detected by the residual vibration detecting means 16, and an inkjet head 100 based on the period measured by the measuring means 17. And determination means 20 for determining whether or not there is a discharge abnormality. In the discharge abnormality detecting means 10, the residual vibration detecting means 16 oscillates the oscillating circuit 11 based on the residual vibration of the diaphragm 121 of the electrostatic actuator 120, and calculates the oscillation frequency from the oscillating frequency. The F / V conversion circuit 12 and the waveform shaping circuit 15 form and detect a vibration waveform. And the measuring means 17 detects Based on the measured vibration waveform, the cycle of the residual vibration is measured, and the judging means 20 determines, based on the measured cycle of the residual vibration, etc., each inkjet provided in each head unit 35 in the printing means 3. A discharge abnormality of the head 100 is detected and determined. Hereinafter, each component of the discharge abnormality detection means 10 will be described.

First, a method of using the oscillation circuit 11 to detect the frequency (frequency) of the residual vibration of the diaphragm 121 of the electrostatic actuator 120 will be described. Fig. 17 is a conceptual diagram when the electrostatic actuator 120 of Fig. 3 is a parallel plate capacitor, and Fig. 18 is a capacitor composed of the electrostatic actuator 120 of Fig. 3. FIG. 3 is a circuit diagram of an oscillation circuit 11 including the above. The oscillation circuit 11 shown in FIG. 18 is a CR oscillation circuit using the hysteresis characteristic of the 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 be configured to use, for example, an LC oscillation circuit. Further, in the present embodiment, an example using the Schmitt trigger is described. However, for example, a CR oscillation circuit using three stages of the inverter may be configured.

In the inkjet head 100 shown in FIG. 3, as described above, the diaphragm 121 and the segment electrodes 122 separated from each other by a very small space (gap) form an opposing electrode. 1 2 0 is constituted. This electrostatic actuator 120 can be considered as a parallel plate capacitor as shown in FIG. The capacitance of this capacitor is C, the surface area of each of the diaphragm 121 and the segment electrode 122 is S, the distance (gap length) between the two electrodes 121, 122 is g, and both electrodes are sandwiched. the dielectric constant of the space (gap) epsilon (dielectric constant of vacuum epsilon., when the relative dielectric constant of the space and _{_{ε r, ε = ε 0 ·}} ε r) when to the capacitor (electrostatic shown in FIG. 1 7 The capacitance C (X) of the electric device (120) is expressed by the following equation.

[Equation 2] S

C (x) = s _Q -e _r (4)

Note that x in Expression (4) indicates the amount of displacement of the diaphragm 121 from the reference position caused by 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) (if X is 0, gap length g). Note that, in the electrostatic factory 120 shown in FIG. 3, since the air gap is filled with air, the relative dielectric constant is = 1.

In general, as the resolution of a droplet discharge device (in the present embodiment, the ink jet printing device 1) increases, the size of the discharged ink droplets (ink dots) becomes smaller. Higher density and smaller size. As a result, the surface area S of the diaphragm 121 of the ink jet head 100 is reduced, and a small electrostatic actuator 120 is formed. Furthermore, the gap length g of the electrostatic actuator 120 that changes due to the residual vibration caused by ink droplet ejection is the initial gap g. Therefore, as can be seen from equation (4), the amount of change in the capacitance of the electrostatic actuator 120 is a very small value.

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, based on the capacitance of the electrostatic actuator 120. An oscillation circuit as shown in Fig. 18 is constructed, and the method of analyzing the frequency (period) of the residual vibration based on the oscillated signal is used. The oscillation circuit 11 shown in FIG. 18 includes a capacitor (C) composed of an electrostatic actuator 120, a Schmitt trigger inverter 111, and a resistance element (R) 112. When the output signal of the Schmitt trigger invertor 11 is at the Hig level, the capacitor C is charged through the resistor element 112. Charge voltage of capacitor C (diaphragm 12 1 and the potential difference between the segment electrode 1 2 2), shoe Mitsuto trigger inverter when Isseki reached 1 1 1 borrowing threshold voltage V _T tens, Schmitt trigger inverter evening 1 1 1 of the output signal is L ow level Flip to Then, when the output signal of the Schmitt trigger inverter 111 becomes low level, the electric charge charged in the capacitor C via the resistance element 112 is discharged. When this discharge causes the voltage of the capacitor C to reach the input threshold voltage ν _τ — of the Schmitt trigger inverter 111, the output signal of the Schmitt trigger inverter 111 is inverted again to the High 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, paper powder adhesion, and normal ejection), the oscillation frequency of the oscillation circuit 11 is The oscillation frequency must be set so that the frequency of the residual vibration, which is the highest when bubbles are mixed (see Fig. 10), can be detected. Therefore, the oscillation frequency of the oscillation circuit 11 must be, for example, several times to several tens times or more of the frequency of the residual vibration to be detected, that is, a frequency that is about one digit or more 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 because 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 oscillation waveform can be detected based on the minute change in the oscillation frequency.

In addition, for each period (pulse) of the oscillation frequency of the oscillation signal output from the oscillation circuit 11, the pulse is counted using a measurement count pulse (counter), 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 from the measured count amount, digital information of the residual oscillation waveform for each oscillation frequency can be obtained. By performing digital Z-analog (D./A) conversion based on these digital information, a rough residual vibration waveform can be generated. Although such a method may be used, a count pulse (counter) for measurement is used. Therefore, a high frequency (high resolution) that can measure a small change in the oscillation frequency is required. In order to increase the cost of such a count pulse (counter pulse), the discharge abnormality detection means 10 uses the FZV conversion circuit 12 shown in FIG.

FIG. 19 is a circuit diagram of the F / V 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 source that outputs a constant current Is. 13 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 such that a fixed time tr is set from the rising edge of the oscillation pulse of the oscillation circuit 11, and the charge signal is 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 is generated so as to fall 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 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 are output next to the output signal of the oscillation circuit 11. It is sufficient that one pulse is included before the rising edge of the signal, and the present invention is not limited to the rising edge and the falling edge as described above.

In order to obtain a clean residual vibration waveform (voltage waveform), a method of setting the fixed times tr and t1 will be described with reference to FIG. Fixed time tr is electrostatic Akuchiyue Ichita 12 0 is adjusted periodically or these oscillation pulse oscillated by an electrostatic capacitance C at the time of the initial gap length g _Q, charging range of the charging potential by the charging time t 1 is C 1 Is set to be around 1Z2 of Also, the gradient of the charging potential between the charging time t2 at the position where the gap length g is the maximum (Max) and the charging time t3 at the position where the gap length g is the minimum (Min) does not exceed the charging range of the capacitor C1. Is set. In other words, the charging potential Since the slope is determined by d VZd t == IsZC1, 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 the constant current source 13 as high as possible within the range, a minute change in the capacitance of the capacitor formed by the electrostatic actuator 120 can be detected with high sensitivity. It is possible to detect a minute change of 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 and V ref 2, an amplifier (op-amp) 151, and a comparator (comparator) 152. 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. . The output of the buffer 14 of the F / V conversion circuit 12 includes a capacitance component of the initial gap g _Q based on the DC component of the electrostatic Akuchiyue Isseki 120 (DC component). Since the DC component varies depending on each ink jet head 100, the capacitor C3 removes the DC component of the capacitance. Then, the capacitor C3 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 151.

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 151 is a single power supply circuit. The operational amplifier 151 constitutes an inverting amplifier composed of two resistance elements R2 and R3, and the input residual vibration (AC component) is amplified by one R3 / R2 times.

In addition, due to the single power supply operation of the operational amplifier 151, the amplified residual vibration waveform of the vibration plate 121, which oscillates around the potential set by the DC voltage source Vref1 connected to the non-inverting input terminal, is generated. Is output. Here, the DC voltage source Vref1 is The amplifier 151 is set to about 1/2 of the voltage range that can be operated with a single power supply. Further, the operational amplifier 151 forms a one-pass filter having a cutoff frequency of 1 / (27CXC4XR3) by the two capacitors C3 and C4. Then, the residual vibration waveform of the diaphragm 121 amplified after removing the DC component is, as shown in the evening chart of FIG. 20, another DC comparator 152 in the next stage. It is compared with the potential of the voltage source Vref2, and the comparison result is output from the waveform shaping circuit 15 as a rectangular wave. Note that the DC voltage source Vref2 may share another DC voltage source Vref1.

Next, operations of the F / V conversion circuit 12 and the waveform shaping circuit 15 of FIG. 19 will be described with reference to a 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 via the head driver 33, as shown in FIG. 6 (b), the electrostatic actuator 120 The diaphragm 121 is attracted to the segment electrode 122 side, and contracts rapidly upward in FIG. 6 in synchronization with the falling edge of the drive signal (see FIG. 6 (c)).

In synchronization with the falling edge of the drive signal, the drive / detection switch signal for switching between the drive circuit 18 and the ejection abnormality detection means 10 becomes High level. The drive / detection switching signal is held at the High level during the drive suspension of the corresponding ink jet head 100, and goes to the Low level before the next drive signal is input. While the drive / detection switching signal is at the High level, the oscillation circuit 11 in FIG. 18 oscillates while changing the oscillation frequency in response to the residual vibration of the diaphragm 121 of the electrostatic actuator 120.

As described above, a fixed preset value is set so that the waveform of the residual vibration does not exceed the range where the capacitor C1 can be charged from the falling edge of the drive signal, that is, the rising edge of the output signal of the oscillation circuit 11. Until the time t 1- elapses, the charging signal is held at the High level. Note that, while the charge signal is at the High level, the switch SW1 is off. When the fixed time tr elapses and the charging signal goes low, the switch SW1 is turned on in synchronization with the falling edge of the charging signal (see Figure 19). Then, the constant current source 13 and the capacitor C1 are connected, and the capacitor C1 is charged with the slope IssCl 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 reaches the IIigh level in synchronization with the rising edge of the next pulse of the output signal.

When the charge signal becomes High level, the switch SW1 is turned off (open), and the constant current source 13 and the capacitor C1 are disconnected. At this time, the capacitor C1 stores the potential charged during the low-level period t1 of the charge signal (ie, ideally, Isxt1 / C1 (V)). In this state, when the hold signal becomes High level, the switch SW2 is turned on (see FIG. 19), and the capacitor C1 and the capacitor 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 capacitors C1 and C2 are connected from capacitor C1 so that the potential difference between the two capacitors C1 and C2 is approximately equal. The charge moves to C2.

Here, the capacitance of the capacitor C2 is set to about 1/10 or less of the capacitance of the capacitor C1. Therefore, the amount of charge that moves (used) due to charge and discharge caused by the potential difference between the two capacitors C1 and C2 is less than 1/10 of the charge stored in the capacitor C1. 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 the F / V conversion circuit 12 shown in FIG. 19, when the capacitor C2 is charged, a resistance is set so that the charging potential does not jump up due to the inductance of the wiring of the F / V conversion circuit 12 or the like. The element R 1 and the capacitor C 2 form the primary mouth-to-pass fill.

After the charge potential of the capacitor C2 is substantially equal to the charge potential of the capacitor C1, the hold signal becomes low level, and the capacitor C1 is disconnected from the capacitor C2. Further, when the clear signal becomes the High level and the switch SW 3 is turned on, the capacitor C 1 is connected to the ground GND, and the capacitor C 1 The discharging operation is performed so that the electric charge stored in PT / JP2004 / 002401 becomes zero. After the discharge of capacitor C1, the clear signal goes to L0w level and switch SW3 turns off, causing the capacitor to clear. The upper electrode in Fig. 19 of Fig. 1 is disconnected from the ground GND, and waits until the next charging signal is input, that is, until the charging signal becomes Low level.

The potential held in the capacitor C 2 is updated at each rising timing of the charging signal, that is, every time the charging of the capacitor C 2 is completed, and the residual vibration of the diaphragm 1 2 1 is transmitted through the buffer 14. It is output as a waveform to the waveform shaping circuit 15 in FIG. Therefore, the capacitance of the electrostatic actuator 120 (in this case, the fluctuation width of the capacitance due to the residual vibration must be taken into consideration) and the resistance element 1 so that the oscillation frequency of the oscillation circuit 11 becomes higher. If the resistance value of 1 2 is set, each step (step) of the potential of capacitor C 2 (output of buffer 14) shown in the timing chart of Fig. 20 becomes more detailed, and the residual of diaphragm 1 2 1 It is possible to detect the change of the capacitance with time due to vibration in more detail.

Similarly, the charging signal repeats from low level to high level to low level... At the above-mentioned predetermined timing, the potential held in the capacitor C2 passes through the buffer 14 and the waveform shaping circuit 1 Output to 5. In the waveform shaping circuit 15, the DC component of the voltage signal (the potential of the capacitor C 2 in the timing chart of FIG. 20) input from the buffer 14 is removed by the capacitor C 3, and the operational amplifier is connected via the resistor R 2. 15 1 Input to the 1 inverted input terminal. The input AC (A C) 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. The comparator 15 2 compares the potential (reference voltage) preset by the 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 comparison circuit in chart).

Next, the timing of switching 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. What In FIG. 23, the drive circuit 18 in the head driver 33 shown in FIG. 16 will be described as a drive circuit for the inkjet head 100. As also shown in the timing chart of FIG. 20, the ejection abnormality detection process 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 from the drive circuit 18 to the diaphragm 122, the electrostatic actuator 120 is driven, and the diaphragm 122 is connected to the segment electrode. When the applied voltage is reduced to 0, it is suddenly displaced away from the segment electrode 122 and vibration (residual vibration) starts. At this time, ink droplets are ejected from the nozzle 110 of the ink jet 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 outputs the drive circuit 1 From 8 the discharge abnormality detection means (detection circuit) 10 is switched to the side, and the electrostatic work 120 (used as a capacitor of the oscillation circuit 11) is connected to the discharge abnormality detection means 10.

Then, the ejection abnormality detection means 10 executes the above-described ejection abnormality (missing dot) detection processing, and the residual of the diaphragm 12 1 output from the comparator 15 2 of the waveform shaping circuit 15 Vibration waveform data (rectangular wave data), are 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 period from the residual vibration waveform data, and outputs the measurement result (numerical value) to the judging means 20. Specifically, the measuring means 17 measures the time from the first rising edge of the waveform (rectangular wave) of the output signal of the comparator 152 to the next rising edge (period of the residual vibration). Using a counter (not shown), the pulses of the reference signal (predetermined frequency) are counted, and the period of the residual vibration (specific vibration period) is measured from the force point value. Note that the measuring means 17 measures the time from the first rising edge to the next falling edge, and outputs a time twice as long as the measured time to the determining means 20 as the cycle of the residual vibration. Good. Hereinafter, the cycle of the residual vibration obtained in this manner is referred to as Tw. You.

The determining means 20 determines whether there is a nozzle discharge abnormality, the cause of the discharge abnormality, the amount of comparison deviation, etc., based on the specific vibration period (measurement result) of the residual vibration waveform measured by the measuring means 17. 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 timing when the next drive signal from the drive circuit 18 is input, the drive Z detection switching signal is input again to the switching means 23, and the drive circuit 18 and the electrostatic actuator 120 are connected to each other. Connecting. 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.

In the present invention, the residual vibration waveform data is not limited to a rectangular waveform generated by the comparator 152. For example, the residual vibration amplitude data output from the operational amplifier 1551 is digitized as needed by the measuring means 17 that performs A / D conversion without performing comparison processing by the comparator 152, and the numerical value is obtained. The determination means 20 may determine whether or not there is a discharge abnormality based on the converted data, and the determination result may be stored in the storage means 62. .

Further, the meniscus of the nozzle 110 (the surface where the ink in the nozzle 110 comes into contact with the atmosphere) vibrates in synchronization with the residual vibration of the diaphragm 121, so that the ink jet head 100 ejects ink droplets. After the operation, the apparatus waits for the residual vibration of the meniscus to attenuate in a time substantially determined by the acoustic resistance r (waits for a predetermined time), and then performs the next ejection operation. 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, it is possible to execute the discharge abnormality detection processing of the nozzle 110 of the ink jet head 100 without lowering the throughput of the ink jet printer 1 (droplet discharge device).

As described above, air bubbles are mixed in the cavities 1 41 of the ink jet head 100. In this case, since the frequency is higher than the residual vibration waveform of the diaphragm 122 during normal discharge, the period is shorter than the period of the residual vibration during normal discharge. 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 cycle 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 when the ink is dried. Since the period becomes higher, the period is longer than the period of the residual vibration during normal ejection and shorter than the period of the residual vibration during ink drying.

Therefore, a predetermined range T r is set 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 to distinguish the cycle of the residual vibration when the ink is dried, the cause of such an abnormal ejection of the inkjet head 100 is determined. be able to. The determination means 20 determines whether the cycle Tw of the residual vibration waveform detected by the above-described discharge abnormality detection processing is a cycle in a predetermined range, and is longer than a predetermined threshold. Then, the cause of the discharge abnormality is determined.

Next, the operation of the droplet discharge device of the present invention will be described based on the configuration of the above-described inkjet printer 1. First, the discharge abnormality detection process (including the drive / detection switching process) for the nozzle 110 of one inkjet head 100 will be described. FIG. 24 is a flowchart showing a discharge abnormality detection / determination process. When print data to be printed (discharge data in a flushing operation) is input from the host computer 8 to the control unit 6 via the interface (IF) 9, this discharge abnormality detection processing is executed at a predetermined timing. You. For convenience of explanation, the flowchart shown in FIG. 24 shows an ejection abnormality detection process corresponding to the ejection operation of one inkjet head 100, that is, one nozzle 110.

First, a driving signal corresponding to the printing data (ejection data) is input from the driving circuit 18 of the head driver 33, and as a result, as shown in the timing chart of FIG. A drive signal (voltage signal) is applied between both electrodes of the electrostatic actuator 120 based on the timing of the drive signal (step S 10 Do). Based on the switching signal, it is determined whether or not the ejected inkjet head 100 is in the driving suspension period (step S102), where the driving / detection switching signal is the driving signal of the driving signal. It goes to the High level in synchronization with the falling edge (see FIG. 20), and is input from the control unit 6 to the switching means 23.

When the drive / detection switching signal is input to the switching means 23, the switching means 23 disconnects the electrostatic actuator 120, that is, the capacitor constituting the oscillation circuit 11 from the drive circuit 18. The discharge abnormality detecting means 10 (detection circuit) is connected to the oscillation circuit 11 of the residual vibration detecting means 16 (step S103). Then, a residual vibration detection process described later is executed (step S104), and the measuring means 17 measures a predetermined numerical value from the residual vibration waveform data detected in the residual vibration detection process (step S104). 105). Here, as described above, the measuring means 17 measures the cycle of the residual vibration from the residual vibration waveform data.

Next, the determination means 20 executes a discharge abnormality determination process described later based on the measurement result of the measurement means (step S 106), and stores the determination result in the EEPR M (storage means) 6 of the control unit 6. 2. Save in the predetermined storage area. Then, in step S108, it is determined whether or not the inkjet head 100 is in the drive period. That is, it is determined whether or not the next drive signal has been input after the end of the drive suspension period, and the process stands by at step S108 until the next drive signal is input.

When the drive / detection switching signal goes low in synchronization with the rising edge of the drive signal at the timing when the pulse of the next drive signal is input ("yes" in step S108), the switching means 23 Then, the connection with the electrostatic actuator 120 is switched from the discharge abnormality detection means (detection circuit) 10 to the drive circuit 18 (step S109), and the discharge abnormality detection processing ends. '

The flowchart shown in FIG. 24 shows a case where the measuring means 17 measures the period from the residual vibration waveform detected by the residual vibration detection processing (residual vibration detecting means 16). It is not limited to such a case. For example, the measuring means 17 From the residual vibration waveform data detected in the residual vibration detection processing, measurement of the phase difference, amplitude, and the like of the residual vibration waveform may be performed.

Next, the residual vibration detection processing (subroutine) in step S104 of the flowchart shown in FIG. 24 will be described. Figure 25 is a flowchart showing the residual vibration detection process. As described above, when the electrostatic actuator 120 is connected to the oscillation circuit 11 by the switching means 23 (step S103 in FIG. 24), the oscillation circuit 11 Oscillates based on the change in the capacitance of the electrostatic actuator 120 (residual vibration of the diaphragm 121 of the electrostatic actuator 120) (step S201) .

As shown in the above timing chart and the like, a charge signal, a hold signal, and a clear signal are generated in the F / V conversion circuit 12 based on the output signal (pulse signal) of the oscillation circuit 11, and these signals are generated. The F / V converter circuit 12 performs an F / V conversion process of converting the frequency of the output signal of the oscillation circuit 11 into a voltage based on the F / V conversion circuit 12 (step S202). The residual vibration waveform of plate 1 2 1 is output. In the residual vibration waveform output from the F / V conversion circuit 12, the DC component (DC component) is removed by the capacitor C3 of the waveform shaping circuit 15 (step S203), and the operational amplifier 15 Due to 1, the residual vibration waveform (AC component) from which the DC component has been removed is amplified (step S204).

The post-amplification residual vibration waveform data is subjected to waveform shaping and pulsed by a predetermined process (step S205). That is, in the present embodiment, the comparator 152 compares the voltage value (predetermined voltage value) set by the DC voltage source Vref2 with the output voltage of the operational amplifier 151. The comparator 152 outputs a binarized waveform (rectangular wave) based on the comparison result. The output signal of the comparator 152 is the output signal of the residual vibration detection means 16 and is output to the measuring means 17 to perform the discharge abnormality determination processing, and the residual vibration detection processing ends. .

Next, the discharge abnormality determination process (subroutine) in step S106 of the flowchart shown in FIG. 24 will be described. FIG. 26 is a flowchart showing a discharge abnormality determination process executed by the control unit 6 and the determination unit 20. The judgment means 20 is Based on the measurement data (measurement result) such as the cycle measured by the above-mentioned measuring means 17, it is determined whether or not the ink droplet has been normally ejected from the corresponding ink jet head 100. If not, that is, if the discharge is abnormal, determine the cause.

First, the control unit 6 outputs the predetermined range Tr of the period of the residual vibration and the predetermined threshold T1 of the period of the residual vibration stored in the EEPROM 62 to the determination means 20. The predetermined range Tr of the cycle of the residual vibration is such that the residual vibration cycle at the time of normal ejection has an allowable range that can be determined to be normal. These data are stored in a memory (not shown) of the determination means 20, and the following processing is executed.

In step S105 of FIG. 24, the measurement result measured by the measuring means 17 is input to the judging means 20 (step S301). Here, in the present embodiment, the measurement result is the period Tw of the residual vibration of the diaphragm 122.

In step S302, the determination means 20 determines whether or not the residual vibration period Tw exists, that is, whether or not the discharge abnormality detection means 10 has not obtained residual vibration waveform data. When it is determined that the cycle of the residual vibration Tw does not exist, the determining means 20 determines that the nozzle 110 of the ink jet head 100 has not discharged an ink droplet in the discharge abnormality detection process. It is determined that the nozzle is a nozzle (step S306). When it is determined that the residual vibration waveform data exists, subsequently, in step S303, the determination means 20 determines that the cycle Tw is within a predetermined range Tr in which the cycle Tw is recognized as a normal ejection cycle. Is determined.

If it is determined that the period Tw of the residual vibration is within the predetermined range Tr, it means that the ink droplet has been normally ejected from the corresponding ink jet head 100, and the determination means 20 It is determined that the nozzle 110 of the ink jet head 100 has normally ejected an ink droplet (normal ejection) (step S307). When it is determined that the period Tw of the residual vibration is not within the predetermined range Tr, subsequently, in step S304, the determination unit 20 sets the period Tw of the residual vibration to the predetermined range Tr. It is determined whether it is shorter than the range Tr.

If it is determined that the cycle Tw of the residual vibration is shorter than the predetermined range Tr, This means that the frequency of the motion is high, and as described above, it is considered that air bubbles are mixed in the cavity 14 1 of the inkjet head 100, and the determination means 20 is connected to the ink jet head. It is determined that air bubbles are mixed in the cavity 1401 of the node 100 (bubble mixing) (step S308).

If it is determined that the period Tw of the residual vibration is longer than the predetermined range Tr, then the determining means 20 determines whether the period Tw of the residual vibration is longer than the predetermined threshold T1. It is determined whether or not it is (step S305). When it is determined that the cycle Tw of the residual vibration is longer than the predetermined threshold T1, it is considered that the residual vibration is excessively damped, and the determination means 20 determines whether the ink jet 1 0 0 It is determined that the ink in the vicinity of the nozzle 110 has thickened due to drying (dry) (step S309).

Then, in step S305, when it is determined that the cycle Tw of the residual vibration is shorter than the predetermined threshold T1, the cycle Tw of the residual vibration satisfies Tr <Tw <Tl As described above, it is considered that paper dust adheres to the vicinity of the outlet of the nozzle 110 having a higher frequency than that of drying, and the determination means 20 determines the ink jet head 100 It is determined that paper dust is attached near the nozzle 110 outlet (paper dust attached) (step S3110).

As described above, when the determination unit 20 determines the normal ejection or the cause of the ejection abnormality of the target inkjet head 100 (steps S306 to S310), the determination result is as follows. The output is output to the control unit 6, and the discharge abnormality determination processing ends. Next, assuming a plurality of inkjet heads (droplet ejection heads) 100, that is, an inkjet printer 1 having a plurality of nozzles 110, the ejection selection means (nozzle selector) 18 2 in the inkjet printer 1 The timing of the detection and determination of the ejection abnormality of each inkjet head 100 will be described.

In the following, in order to make the description easy to understand, one head unit 35 among a plurality of head units 35 provided in the printing means 3 will be described, and the head unit 35 will have five head units. Although it is assumed that the printing head 3 is provided with an ink jet head 100 a to 100 e (that is, five nozzles 110 are provided), in the present invention, the number of , Ink jets included in each head unit 35 The number of heads 100 (nozzles 110) can be any number. 27 to 30 are block diagrams showing some examples of ejection abnormality detection / determination timing in the ink jet printer 1 including the ejection selection means 182. Hereinafter, configuration examples of the respective drawings will be sequentially described.

FIG. 27 shows an example of the timing of detecting the ejection failure of a plurality (five) of the inkjet heads 100a to 100e (in the case of one ejection failure detection means 10). As shown in FIG. 27, the ink jet printer 1 having a plurality of ink jet heads 100 a to 100 e outputs a drive waveform generating means 181 for generating a drive waveform, and ejects ink droplets from any of the nozzles 110. And a plurality of ink jet heads 100a to 100e selected by the ejection selection means 182 and driven by the drive waveform generation means 181. I have. In the configuration of FIG. 27, the configuration other than the above is the same as that shown in FIG. 2, FIG. 16, and FIG.

In the present embodiment, the drive waveform generation unit 181 and the ejection selection unit 182 are described as being included in the drive circuit 18 of the head driver 33 (in FIG. 27, the drive waveform generation unit 181 and the ejection selection unit 182 are shown as two blocks via the switching unit 23). However, in general, both are configured in the head driver 33), but the present invention is not limited to this configuration. For example, the driving waveform generation unit 181 is configured as a configuration independent of the head driver 33. Is also good. As shown in FIG. 27, the ejection selection means 182 includes a shift register 182a, a latch circuit 182b, and a driver 182c. To the shift register 182a, print data (discharge data) output from the host computer 8 shown in FIG. 2 and subjected to predetermined processing by the control unit 6, and a clock signal (CLK) are sequentially input. The print data is sequentially shifted from the initial stage of the shift register 182a to the subsequent stage according to the input pulse of the clock signal (CLK) (each time the clock signal is input), and is input. The print data corresponding to e is output to the latch circuit 182b. In the ejection abnormality detection process described later, the ejection data at the time of flushing (preliminary ejection) is input instead of printing, but this ejection data is the printing data for all the ink jet heads 100a to 100e. De —It means evening. At the time of flushing, hardware processing may be performed so that all outputs of the latch circuit 18b are set to values at which ejection is performed.

After the latch circuit 18 2 b stores the print data corresponding to the number of nozzles 110 of the head unit 35, that is, the number of ink jet heads 100, in the shift register 18 a, Each output signal of the shift register is latched by the input latch signal. Here, when the CLEAR signal is input, the latched state is released, the output signal of the shift register 182a which has been latched becomes 0 (latch output is stopped), and the printing operation is stopped. When the CLEAR signal is not input, the print data of the latched shift register 18a is output to the driver 18c. After the print data output from the shift register 18 2 a is latched by the latch circuit 18 2 b, the next print data is input to the shift register 18 2 a, and the latch circuit 18 is synchronized with the print timing. The latch signal of 2b is updated sequentially.

The driver 18 c connects the drive waveform generating means 18 1 to the electrostatic actuator 120 of each ink jet head 100, and outputs from the latch circuit 18 b. 120 (Each of inkjet heads 100a to 100e or any of the electrostatic actuators 120) specified (specified) by the latch signal The output signal (drive signal) of the drive waveform generating means 18 1 is input to the controller, whereby the drive signal (voltage signal) is applied between both electrodes of the electrostatic actuator 120.

The ink jet printer 1 shown in FIG. 27 has one driving waveform generating means 18 1 for driving a plurality of ink jet heads 100 a to 100 e, and each of the ink jet heads 100 a to 100 e. A discharge abnormality detecting means 10 for detecting a discharge abnormality (ink droplet non-discharge) with respect to any one of the ink jet heads 100e of 0e, and a discharge abnormality obtained by the discharge abnormality detection means 10 It is provided with a storage means 62 for storing (storing) the determination result of the cause and the like, and one switching means 23 for switching between the drive waveform generating means 18 1 and the ejection abnormality detecting means 10. Accordingly, the ink jet printer 1 is configured such that the ink jets 100 a to 100 e selected by the driver 18 c on the basis of the drive signal input from the drive waveform generating means 18 1. One or more of After the drive and the drive / detection switching signal are input to the switching means 23 after the ejection driving operation, the switching means 23 is switched from the drive waveform generation means 18 1 to the ejection abnormality detection means 10 by an inkjet head. After switching the connection between the electrostatic head 120 and the electrostatic head 120 of the nozzle 100, the discharge abnormality detecting means 10 detects the ink jet head 100 based on the residual vibration waveform of the diaphragm 121. This is to detect a discharge abnormality (non-discharge of ink droplets) in the nozzle 110, and to determine the cause of the discharge abnormality in the case of discharge abnormality.

When the ink jet printer 1 detects and determines a discharge abnormality with respect to the nozzle 110 of one ink jet head 100, the ink jet printer 1 then determines a discharge abnormality based on the drive signal input from the drive waveform generating means 18 1. Then, a discharge abnormality is detected and determined for the nozzle 110 of the specified ink jet head 100, and thereafter, similarly, the ink jet head driven by the output signal of the drive waveform generating means 18 1 The ejection abnormality of the nozzle 110 of 100 is sequentially detected and determined. Then, as described above, when the residual vibration detecting means 16 detects the residual vibration waveform of the diaphragm 121, the measuring means 17 measures the period of the residual vibration waveform based on the waveform data and makes a determination. The means 20 determines whether the ejection is normal or abnormal based on the measurement result of the measuring means 17 and, in the case of an abnormal ejection (head abnormality), the cause of the abnormal ejection, and stores the result in the storage means 62. Output the judgment result. As described above, in the ink jet printer 1 shown in FIG. 27, in the ink droplet ejection driving operation of each of the nozzles 110 of the plurality of ink jet heads 100a to 100e, the ejection abnormality is sequentially detected. Since it is configured to detect and judge, it is only necessary to provide one ejection abnormality detection means 10 and one switching means 23, and the circuit configuration of the inkjet printer 1 that can detect and judge ejection abnormality can be scaled down. At the same time, an increase in the manufacturing cost can be prevented.

FIG. 28 shows an example of the timing of detecting abnormal ejection of the plurality of ink jet heads 100 (when the number of abnormal ejection detecting means 100 is the same as the number of inkjet heads 100). The ink jet printer 1 shown in FIG. 28 has one ejection selection means 18 2, five ejection abnormality detection means 10 a to 10 e, five switching means 23 a to 23 e, and 5 One drive waveform generating unit 181 common to one inkjet head 100a to 100e and one storage unit 62 are provided. Each component is described in the explanation of Fig. 27. Since the description has already been given above, the description thereof will be omitted, and these connections will be described. .

As in the case shown in FIG. 27, the ejection selection means 182 corresponds to each ink jet head 100a to 100e based on the print data (ejection data) input from the host computer 8 and the clock signal CLK. The print data is latched by the latch circuit 182, and according to the drive signal (voltage signal) input from the drive waveform generation means 181 to the driver 182c, the static inkjet heads 100a to 100e corresponding to the print data are output. Driving the drive 120. The drive Z detection switching signal is input to the switching units 23a to 23e corresponding to all the ink jet heads 100a to 100e, respectively.The switching units 23a to 23e output the corresponding print data (ejection Regardless of the presence or absence of data), after a drive signal is input to the electrostatic actuator 120 of the ink jet head 100 based on the drive Z detection switching signal, the ejection abnormality detection means 10a to Switch the connection with the inkjet head 100 to l0e.

After detecting and judging the ejection abnormality of each of the inkjet heads 100a to 100e by all the ejection abnormality detection means 10a to 10e, all the ink jet heads 100a obtained in the detection processing are determined. The determination result of ~ 100e is output to the storage means 62, and the storage means 62 stores the presence or absence of the ejection abnormality of each ink jet head 100a ~ 100e and the cause of the ejection abnormality in a predetermined storage area. .

As described above, in the ink jet printer 1 shown in FIG. 28, a plurality of ejection abnormality detecting means 10a to 10e are provided corresponding to each nozzle 110 of the plurality of ink jet heads 100a to 100e, and The switching operation is performed by the plurality of switching units 23a to 23e, and the discharge abnormality detection and the cause determination are performed. Therefore, the discharge abnormality detection and the cause determination are performed for all the nozzles 110 at once in a short time. be able to.

Fig. 29 shows an example of the timing of detecting abnormal ejection of a plurality of ink jet heads 100 (when the number of ejection error detecting means 10 is the same as the number of ink jet heads 100 and there is print data, When performing detection). The inset shown in Figure 29 The jet printer 1 is obtained by adding (adding) switching control means 19 to the configuration of the ink jet printer 1 shown in FIG. In the present embodiment, the switching control means 19 is composed of a plurality of AND circuits (AND circuits) ANDa to ANDe, and is input to each of the ink jet heads 100a to 100e. When the print data and the drive / detection switching signal are input, a high-level output signal is output to the corresponding switching means 23a to 23e. The switching control means 19 is not limited to an AND circuit (logical product circuit), and the switching means 23 that matches the output of the latch circuit 18 2 b from which the inkjet head 100 to be driven is selected is selected. What is necessary is just to be comprised so that it may be performed.

Each of the switching means 23a to 23e is provided with a corresponding discharge abnormality detecting means from the drive waveform generating means 181, based on the output signal of the corresponding AND circuit ANDa to ANDe of the switching control means 19. The connection between the corresponding inkjet heads 100a to 100e and the electrostatic actuators 120 to 100e to 100e is switched. Specifically, when the output signals of the corresponding AND circuits ANDa to ANDe are at the high level, that is, when the drive / detection switching signal is at the high level, the corresponding inkjet head 100a to If the print data input to 100 e is output from the latch circuit 18 2 b to the driver 18 2 c, the switching means 23 a to 23 e corresponding to the AND circuit is The connection to the corresponding inkjet heads 100a to 100e is switched from the drive waveform generating means 181 to the discharge abnormality detecting means 10a to 10e.

The ejection failure detection means 10a to 10e corresponding to the ink jet head 100 to which the print data was input determines whether or not each inkjet head 100 has an ejection failure and, if there is a discharge failure, After detecting the cause, the discharge abnormality detection means 10 outputs the determination result obtained in the detection processing to the storage means 62. The storage means 62 stores one or a plurality of determination results input (obtained) in this way in a predetermined storage area. Thus, in the ink jet printer 1 shown in FIG. 29, a plurality of ejection abnormality detecting means 10a correspond to the nozzles 110 of the plurality of ink jet heads 100a to 100e, respectively. 110e, and when print data corresponding to each of the ink jet heads 100a e100e is input from the host computer 8 to the ejection selection means 182 via the control unit 6. , The switching means 2 3 a specified by the switching control means 19 Since only 23 to e perform a predetermined switching operation to detect the ejection failure of the inkjet head 100 and determine the cause thereof, this detection is performed for the inkjet head 100 that is not performing the ejection driving operation. · Does not perform judgment processing. Therefore, the inkjet printer 1 can avoid unnecessary detection and determination processing. FIG. 30 shows an example of the timing of detecting the ejection failure of the plurality of inkjet heads 100 (the number of ejection failure detection means 100 is the same as the number of ink jet heads 100; This is the case where the discharge abnormality is detected by circulating through 0). In the ink jet printer 1 shown in FIG. 30, in the configuration of the ink jet printer 1 shown in FIG. 29, one ejection abnormality detecting means 10 is used, and the drive Z detection switching signal is scanned (detection (Ink jet heads 100 for executing the determination process are specified one by one.) The switching selecting means 19 a is added.

The switching selection means 19a is connected to the switching control means 19 shown in FIG. 29, and based on a scanning signal (selection signal) input from the control unit 6, a plurality of ink jet heads. This is a selector that scans (selects and switches) the input of the drive detection detection switching signal to the AND circuits ANDa to ANDe corresponding to the nodes 100a to 100e. The scanning (selection) order of the switching selection means 19a may be the order of the print data input to the shift register 18a, that is, the ejection order of a plurality of ink jet heads 100. However, the order of the plurality of inkjet heads 100a to 100e may be simply used.

If the scan order is the order of the print data input to the shift register 18 2a, if the print data is input to the shift register 18 2a of the ejection selection means 18 2, the print data will be The signal is latched by the latch circuit 18b and output to the driver 18c by the input of the latch signal. To identify the inkjet head 100 corresponding to the print data in synchronization with the input of the print data to the shift register 18a or the input of the latch signal to the latch circuit 18b. Is input to the switching selection means 19a, and the drive / detection switching signal is output to the corresponding AND circuit. The output terminal of the switching selection means 19a outputs a low level when not selected.

The corresponding AND circuit (switch control means 19) is input from the latch circuit 18b. By performing a logical AND operation on the print data thus obtained and the drive Z detection switching signal input from the switching selection means 19 a, a high-level output signal is output to the corresponding switching means 23. The switching means 23 to which the high-level output signal has been input from the switching control means 19 connects the corresponding inkjet head 100 to the electrostatic actuator 120 to generate a drive waveform. Switching from the means 18 1 to the discharge abnormality detecting means 10. The ejection failure detecting means 100 detects the ejection failure of the ink jet head 100 to which the print data has been input, determines the cause of the ejection failure if any, and stores the result of the determination. Output to 2. Then, the storage means 62 stores the judgment result thus input (obtained) in a predetermined storage area.

When the scan order is a simple ink jet head 100a to 100e, when print data is input to the shift register 182a of the ejection selecting means 1822, the printing is performed. The data is latched by the latch circuit 18b, and is output to the dry circuit, 18c by the input of the latch signal. Scan to specify the inkjet head 100 corresponding to the print data in synchronization with the input of print data to the shift register 18a or the input of the latch signal to the latch circuit 18b. (Selection) The signal is input to the switching selection means 19 a, and the drive Z detection switching signal is output to the corresponding AND circuit of the switching control means 19.

Here, when the print data for the inkjet head 100 determined by the scanning signal input to the switch selection means 19a is input to the shift register 18a, the corresponding AND signal is output. The output signal of the circuit (switching control means 19) becomes High level, and the switching means 23 sets the connection to the corresponding ink jet head 100 and discharges abnormalities from the drive waveform generating means 18 1 Switch to detection means 10. However, when the above-described print data is not input to the shift register 18 a, the output signal of the AND circuit is at the low level, and the corresponding switching means 23 does not execute a predetermined switching operation. Therefore, based on the logical product of the selection result of the switching selection means 19a and the result specified by the switching control means 19, the ejection abnormality detection processing of the ink jet 100 is performed.

When the switching operation is performed by the switching means 23, similarly to the above, the discharge abnormality detection is performed. The output unit 100 detects an ejection failure of the inkjet head 100 to which the print data has been input, determines the cause of the ejection failure if any, and stores the determination result.

6 Output to 2. Then, the storage means 62 stores the judgment result thus input (obtained) in a predetermined storage area.

When there is no print data for the ink jet head 100 specified by the switching selecting means 19a, as described above, the corresponding switching means 23 does not execute the switching operation, and therefore, the discharge abnormality detecting means It is not necessary to execute the ejection abnormality detection process by 10, but such a process may be executed. If the ejection failure detection processing is executed without performing the switching operation, the determination means 20 of the ejection failure detection means 10 will determine the nozzle of the corresponding inkjet head 100 as shown in the flowchart of FIG. It is determined that 110 is a non-ejection nozzle (step S306), and the determination result is stored in a predetermined storage area of the storage means 62.

Thus, in the ink jet printer 1 shown in FIG. 30, unlike the ink jet printer 1 shown in FIG. 28 or FIG. 29, each of a plurality of ink jet heads 100 a to 100 e is provided. Only one ejection abnormality detecting means 10 is provided for the nozzle 110, and print data corresponding to each of the inkjet heads 100a to 100e is sent from the host computer 8 via the control unit 6 Only the switching means 23 corresponding to the ink jet head 100 which is input to the ejection selection means 18 2, is simultaneously specified by the scanning (selection) signal, and performs the ejection driving operation according to the print data. Performs a switching operation to detect a discharge abnormality of the corresponding ink jet head 100 and determine the cause thereof, so that a large amount of detection results are not processed at once and the CPU 61 of the control unit 6 is not processed. Can reduce the burden on . In addition, since the ejection abnormality detection means 10 circulates the nozzle state separately from the ejection operation, it is possible to grasp the ejection abnormality for each nozzle even during driving printing, and the head unit 35 The state of 10 can be known. This makes it possible to reduce the number of steps for detecting an abnormal discharge for each nozzle during printing stoppage, for example, because the abnormal discharge is periodically detected. As described above, it is possible to efficiently detect the discharge abnormality of the ink jet head 100 and determine the cause thereof. Also, unlike the ink jet printer 1 shown in FIG. 28 or FIG. 29, the ink jet printer 1 shown in FIG. 30 only needs to be provided with one ejection abnormality detection means 10. Compared with the inkjet printer 1 shown in FIGS. 28 and 29, the circuit configuration of the inkjet printer 1 can be scaled down, and an increase in the manufacturing cost can be prevented.

Next, an operation of the printer 1 shown in FIGS. 27 to 30, that is, an ejection failure detection process (mainly, detection timing) in the ink jet printer 1 including the plurality of ink jet heads 100 will be described. Discharge abnormality detection / judgment processing (processing for multiple nozzles) consists of the vibration plate 1 2 1 when the ink droplet ejection operation of each ink jet 1 0 The residual vibration is detected, and based on the period of the residual vibration, whether or not an abnormal ejection (dot missing, ink droplet non-ejection) has occurred for the corresponding ink jet head 100, and whether or not the dot missing (ink drop) has occurred. If a non-discharge occurs, the cause is determined. As described above, according to the present invention, these detection / determination processes can be performed if an ink droplet (droplet) ejection operation is performed by the ink jet head 100. The ink droplets are ejected not only when actually printing (printing) on the recording paper P, but also during a flashing operation (preliminary ejection or preliminary ejection). Hereinafter, the discharge abnormality detection / judgment process (multiple nozzles) will be described for these two cases.

Here, the flushing (preliminary discharge) processing is performed when a cap (not shown in FIG. 1) is attached or at a place where ink droplets (droplets) do not fall on the recording paper P (media). This is a head cleaning operation for ejecting ink droplets from all or target nozzles 110. This flushing process (flushing operation) is performed, for example, when periodically discharging the ink in the cavity 141 to maintain the ink viscosity in the nozzle 110 within a proper range, or It is also performed as a recovery operation when the ink thickens. Further, the flushing process is also performed when the ink is initially filled into each cavity 141 after the ink cartridge 31 is mounted on the printing means 3.

Wiping to clean the nozzle plate (nozzle surface) 150 In some cases, processing (a treatment to wipe off deposits (paper dust, dust, etc.) adhering to the head surface of the printing means 3 with a wiper not shown in FIG. 1) may be performed. There is a possibility that the inside will become negative pressure and draw ink of another color (other types of droplets). Therefore, after the wiping process, the flushing process is also performed to discharge a fixed amount of ink droplets from all the nozzles 110 of the head unit 35. Further, the flushing process can be performed in a timely manner in order to maintain the state of the meniscus of the nozzle 110 normally and to ensure good printing.

First, the discharge abnormality detection / judgment process in the flushing process will be described with reference to the flowcharts shown in FIGS. These flowcharts will be described with reference to the block diagrams of FIGS. 27 to 30 (the same applies to the printing operation). FIG. 31 is a flowchart showing the timing of detecting an abnormal discharge during the flushing operation of the ink jet printer 1 shown in FIG. 27.

At a predetermined timing, when the flushing process of the ink jet printer 1 is executed, the ejection abnormality detection / determination process shown in FIG. 31 is executed. The controller 6 inputs the discharge data for one nozzle to the shift register 18 a of the discharge selection means 18 2 (step S 401), and the latch signal is input to the latch circuit 18 b. (Step S402), and this discharge data is latched. At this time, the switching means 23 connects the electrostatic actuator 120 of the inkjet head 100, which is the object of the ejection data, to the drive waveform generating means 18 1 (step S40) 3).

Then, the ejection abnormality detection / determination processing shown in the flowchart of FIG. 24 is performed on the ink jet head 100 that has performed the ink ejection operation by the ejection abnormality detection means 10 (step S404). In step S405, the control unit 6 performs the ink jetting shown in FIG. 27 based on the ejection data output to the ejection selecting unit 1832. It is determined whether or not the ejection abnormality detection / determination process has been completed for all the nozzle heads 100 a to 100 e of the printer 1. When it is determined that these processes have not been completed for all nozzles 110, the control unit 6 stores the next inkjet head 100 of the next inkjet head 100 into the shift register 182a. Input the discharge data corresponding to (Step S 406), and proceed to Step S 402 to Is repeated.

If it is determined in step S405 that the above-described ejection abnormality detection and determination processing has been completed for all nozzles 110, the control unit 6 sends a CLEAR signal to the latch circuit 18b. Then, the latch state of the latch circuit 18 2 b is released, and the discharge abnormality detection / determination process in the ink jet printer 1 shown in FIG. 27 ends.

As described above, in the ejection abnormality detection / determination process in the printer 1 shown in FIG. 27, the detection circuit is composed of one ejection abnormality detection unit 10 and one switching unit 23. The ejection abnormality detection processing and the determination processing are repeated by the number of the ink jets 100, but the circuit constituting the ejection abnormality detection means 100 has an effect that it is not so large.

Next, FIG. 32 is a flowchart showing the timing of detecting an ejection abnormality during the flushing operation of the ink jet printer 1 shown in FIGS. 28 and 29. Although the ink jet printer 1 shown in FIG. 28 and the ink jet printer 1 shown in FIG. 29 have slightly different circuit configurations, the number of the ejection abnormality detecting means 10 and the switching means 23 is different from that of the ink jet head 100. Match at (corresponding to) the number of. Therefore, the ejection abnormality detection / judgment process at the time of the flushing operation includes the same steps.

At a predetermined timing, when the flushing process of the ink jet printing 1 is executed, the control unit 6 inputs the ejection data of all nozzles to the shift register 18 2 a of the ejection selecting means 18 2. Then (step S501), the latch signal is input to the latch circuit 18b (step S502), and the ejection data is latched. At that time, the switching means 23a to 23e connect all the ink heads 100a to 100e to the drive waveform generating means 181, respectively (step S503). .

Then, the ejection abnormality detecting means 100a to 100e corresponding to each of the ink jet heads 100a to 100e provides all the ink jet heads for performing the ink ejection operation. For 100, the discharge abnormality detection / determination processing shown in the flowchart of FIG. 24 is executed in parallel (step S504). In this case, all ink jets The determination results corresponding to the heads 100a to 100e are stored in a predetermined storage area of the storage means 62 in association with the target inkjet head 100 to be processed (see FIG.

Step 24 of step S107).

Then, in order to clear the ejection data latched in the latch circuit 18b of the ejection selection means 18, the control section 6 inputs a CLEAR signal to the latch circuit 18b (step S). 505), the latch state of the latch circuit 18b is released, and the discharge abnormality detection processing and determination processing in the ink jet printer 1 shown in FIGS. 28 and 29 are terminated.

As described above, in the processing in the printer 1 shown in FIGS. 28 and 29, a plurality of (five in this embodiment) ejection abnormality detecting means corresponding to the inkjet heads 100a to 100e are provided. Since the detection and determination circuit is composed of 10 and the plurality of switching means 23, the discharge abnormality detection / determination processing can be executed in a short time for all the nozzles 110 at a time. Having.

Next, FIG. 33 is a flowchart showing the timing of detecting an ejection failure during the flushing operation of the ink jet printing apparatus 1 shown in FIG. Hereinafter, similarly, using the circuit configuration of the ink jet printer 1 shown in FIG. 30, the ejection abnormality detection processing and the cause determination processing during the flushing operation will be described.

When the flushing process of the ink jet printer 1 is executed at a predetermined timing, first, the control unit 6 outputs a scanning signal to the switching selection means (selector) 19a, and the switching selection means 19a and First switching means 2 by switching control means 1 9

3a and the ink jet 100a are set (specified) (step S601). Then, the ejection data for all nozzles is inputted to the shift register 18 a of the ejection selecting means 18 2 (step S602), and the latch signal is inputted to the latch circuit 18 b (step S602). At step S603), the ejection data is latched. At that time, the switching means 23a connects the electrostatic actuator 120 of the ink jet head 100a to the drive waveform generating means 181 (step S640).

The ejection abnormality detection / determination process shown in the flowchart of FIG. 24 is performed on the ink jet head 100a that has performed the ink ejection operation (step S600). Five ). In this case, in step S103 of FIG. 24, the drive / detection switching signal, which is the output signal of the switching selection means 19a, and the ejection data output from the latch circuit 182b are ANDed. a, and the output signal of the AND circuit AND a is at the high level, so that the switching means 23 a is connected to the inkjet head 100 a of the electrostatic actuator 120 a with the electrostatic actuator 120 a. The discharge abnormality detecting means 10 is connected. Then, the determination result of the discharge abnormality determination process performed in step S106 of FIG. 24 is associated with the inkjet head 100 (here, 100a) to be processed. The data is stored in a predetermined storage area of the storage means 62 (step S107 in FIG. 24).

In step S606, the control unit 6 determines whether or not the discharge abnormality detection / determination processing has been completed for all the nozzles. If it is determined that the ejection abnormality detection / determination process has not been completed for all the nozzles 110, the control unit 6 switches the scanning signal to the switching selection means (selector) 19a. The next switching means 23 b and the ink jet head 100 b are set (specified) by the switching selecting means 19 a and the switching control means 19 (step S 607), The process proceeds to step S603 and the same processing is repeated. Hereinafter, this loop is repeated until the ejection abnormality detection-determination process is completed for all the ink jet heads 100.

If it is determined in step S606 that the ejection abnormality detection process and the determination process have been completed for all nozzles 110, they are latched by the latch circuit 182b of the ejection selection unit 182. In order to clear the ejection data, the control unit 6 inputs a CLEAR signal to the latch circuit 18 2 b (step S 609), releases the latch state of the latch circuit 18 2 b, The ejection abnormality detection processing and the determination processing in the ink jet printer 1 shown in FIG. 30 are ended.

As described above, in the processing in the ink jet printer 1 shown in FIG. 30, a detection circuit is composed of a plurality of switching means 23 and one ejection abnormality detection means 10, and the scanning of the switching selection means (selector) 19a is performed. Only the switching means 23 corresponding to the ink head 100, which is specified by the signal and drives the ejection in accordance with the ejection data, performs the switching operation to detect the ejection abnormality of the corresponding ink jet head 100, Since the cause determination is performed, it is possible to more efficiently detect the discharge abnormality of the inkjet head 100 and determine the cause. It can be carried out.

In step S602 of this flowchart, the ejection data corresponding to all the nozzles 110 is input to the shift register 182a. However, as shown in the flowchart of FIG. In accordance with the scanning order of the ink jet 100 by the selecting means 19a, the ejection data to be input to the shift register 18a is input to the corresponding one inkjet head 100, and the one nozzle 1 10 The discharge abnormality detection / judgment process may be performed each time.

Next, with reference to the flowcharts shown in FIG. 34 and FIG. 35, a process of detecting and judging a discharge abnormality of the ink jet printer 1 during a printing operation will be described. The ink jet printer 1 shown in FIG. 27 is mainly suitable for the ejection abnormality detection processing and the judgment processing at the time of the flushing operation, so the flow chart at the time of the printing operation and the description of the operation are omitted. In ink jet printing 1 shown in FIG. 27, the ejection abnormality detection / determination process may be performed during the printing operation.

FIG. 34 is a flowchart showing the timing of detecting the ejection failure during the printing operation of the ink jet printer 1 shown in FIGS. 28 and 29. The process of this flowchart is executed (started) by a print (print) instruction from the host computer 8. When print data is input from the host computer 8 to the shift register 18 a of the ejection selection means 18 2 via the control unit 6 (step S701), a latch signal is input to the latch circuit 18 b. (Step S702), and the print data is latched. At this time, the switching means 23a to 23e connect all the ink heads 100a to 100e to the drive waveform generating means 181 (step S700). 3).

Then, the ejection abnormality detection means 10 corresponding to the ink jet head 100 that has performed the ink ejection operation executes the ejection abnormality detection / determination process shown in the flowchart of FIG. 24 (step S7). 0 4). In this case, each determination result corresponding to each inkjet head 100 is stored in a predetermined storage area of the storage unit 62 in association with the target inkjet head 100 to be processed. Is done.

Here, in the case of the ink jet printer 1 shown in FIG. 28, the switching means 23 a to 23 e are based on the drive Z detection switching signal output from the control unit 6, and The heads 100a to 100e are connected to the discharge abnormality detecting means 100a to 100e (step S103 in Fig. 24). Therefore, in the inkjet head 100 where print data does not exist, since the electrostatic actuator 120 is not driven, the residual vibration detecting means 16 of the ejection abnormality detecting means 10 is provided with the diaphragm 1 2 Does not detect 1 residual vibration waveform. On the other hand, in the case of the ink jet printer 1 shown in FIG. 29, the switching means 23 a to 23 e are provided by the drive / detection switching signal output from the control unit 6 and the latch circuit 18 2 b. Based on the output signal of the AND circuit to which the print data to be output is input, the inkjet head 100 with the print data is connected to the ejection abnormality detection means 10 (Step S in FIG. 24). 10 3).

In step S705, the control section 6 determines whether or not the printing operation of the ink jet printing 1 has been completed. When it is determined that the printing operation has not been completed, the control unit 6 proceeds to step S701, inputs the next printing data to the shift register 18a, and performs the same processing. repeat. When it is determined that the printing operation has been completed, the controller 6 clears the CLEAR signal to clear the ejection data latched by the latch circuit 18 2 b of the ejection selection means 18 2. 182b (step S706) to release the latched state of the latch circuit 182b and detect the discharge abnormality in the ink jet printer 1 shown in Figs. 28 and 29. And the judgment processing ends.

As described above, the ink jet printer 1 shown in FIGS. 28 and 29 includes a plurality of switching means 23 a to 23 e and a plurality of ejection abnormality detection means 10 a to 10 e. Since the ejection abnormality detection / determination process is performed for all the ink jet heads 100 at a time, these processes can be performed in a short time. The inkjet printer 1 shown in FIG. 29 further includes a switching control means 19, that is, AND circuits AND a to AND e for performing a logical product operation of the drive Z detection switching signal and the print data, and performs a printing operation. Since the switching operation by the switching means 23 is performed only for the ink jet head 100, the ejection abnormality detection processing and the determination processing can be performed without performing useless detection.

Next, FIG. 35 shows the print operation of the ink jet printer 1 shown in FIG. 5 is a flowchart showing the timing of detecting abnormal discharge. In response to a print instruction from the host computer 8, the processing of this flowchart is executed in the inkjet printer 1 shown in FIG. First, the switching selection unit 19a sets (specifies) the first switching unit 23a and the inkjet head 100a in advance (step S801).

When print data is input from the host computer 8 via the control unit 6 to the shift register 182a of the ejection selection means 182 (step S802), a latch signal is input to the latch circuit 182b (step S803). The print data is latched. At this stage, the switching means 23a to 23e connect all the ink jet heads 100a to 100e to the drive waveform generation means 181 (the driver 182c of the ejection selection means 182) at this stage ( Step S804).

Then, when there is print data in the ink jet head 100a, the control unit 6 connects the electrostatic actuator 120 after the discharge operation to the discharge abnormality detection means 10 by the switching selection means 19a (FIG. 24). In step S103), the discharge abnormality detection / determination process shown in the flowchart of FIG. 24 (FIG. 25) is executed (step S805). Then, the determination result of the ejection abnormality determination process executed in step S106 of FIG. 24 is associated with the inkjet head 100 (here, 100a) to be processed and stored in a predetermined storage area of the storage unit 62. It is saved (step S107 in Fig. 24). In step S806, the control unit 6 determines whether or not the above-described discharge abnormality detection / determination processing has been completed for all the nozzles 110 (all the inkjet heads 100). Then, when it is determined that the above processing has been completed for all the nozzles 110, the control unit 6 sets the switching means 23a corresponding to the first nozzle 110 based on the scanning signal (Step S). 808), if it is determined that the above processing has not been completed for all the nozzles 110, the switching means 23b corresponding to the next nozzle 110 is set (step S807).

In step S809, the control unit 6 determines whether or not the predetermined printing operation instructed from the host computer 8 has been completed. If it is determined that the printing operation has not been completed, the next print data is input to the shift register 182a. 802), the same processing is repeated. When it is determined that the printing operation has been completed, the control unit 6 latches the CLE AR signal in order to clear the ejection data latched in the latch circuit 18 2 b of the ejection selection unit 18 2. Input to the circuit 18 2 b (step S 8 10), release the latch state of the latch circuit 18 2 b, and end the discharge abnormality detection and judgment processing in the ink jet printer 1 shown in FIG. 30. I do.

As described above, the liquid droplet ejection apparatus (inkjet printer 1) of the present invention includes a diaphragm 121, an electrostatic actuator 120 that displaces the diaphragm 121, and a liquid filled therein. Then, the displacement of the diaphragm 12 1 causes the internal pressure to change (increase / decrease). The cavity 14 1 communicates with the cavity 14 1, and the pressure inside the cavity 14 1 changes (increases / decreases). A plurality of inkjet heads (droplet ejection heads) 100 having nozzles 110 for ejecting liquids as droplets, and drive waveforms for driving these electrostatic actuators 120 Detecting means 181, generating means 181, discharging selecting means 182 for selecting which one of the plurality of nozzles 110 discharges a droplet, and detecting residual vibration of diaphragm 1 21. Based on the detected residual vibration of the diaphragm 122, abnormality of droplet ejection is detected. After one or a plurality of ejection abnormality detection means 10 and a droplet discharge operation by the electrostatic actuating device 120, the driving is performed based on the drive Z detection switching signal, the print data, or the scanning signal. One or a plurality of switching means 23 for switching the electrical equipment 120 from the drive waveform generating means 18 1 to the discharge abnormality detecting means 10 0, and a plurality of nozzles at once (in parallel) or sequentially It was decided to detect a discharge abnormality of 110.

Therefore, according to the droplet ejection apparatus and the ejection failure detection / determination method of the droplet ejection head of the present invention, the ejection failure detection and the cause determination thereof can be performed in a short time. The circuit configuration of the detection circuit including the same can be scaled down, and an increase in the manufacturing cost of the droplet discharge device can be prevented. Also, after the electrostatic actuator 120 is driven, it is switched to the discharge abnormality detecting means 10 to perform the discharge abnormality detection and the cause determination, so that it does not affect the drive of the actuator. Therefore, the throughput of the droplet discharge device of the present invention is not reduced or deteriorated. In addition, existing droplet discharge devices (ink-jet printers) equipped with predetermined components In addition, it is also possible to equip the discharge abnormality detecting means 10.

Further, unlike the above configuration, the droplet discharge device of the present invention includes a plurality of switching means 23, a switching control means 19, and a plurality of ejection abnormality detections corresponding to one or the number of nozzles 110. Means 10 and a corresponding electrostatic actuator based on the drive Z detection switching signal and ejection data (print data) or the scanning signal, drive Z detection switching signal and ejection data (print data). Evening 120 was switched from the drive waveform generation means 18 1 or the ejection selection means 18 2 to the ejection abnormality detection means 10 to perform ejection abnormality detection and cause determination.

Therefore, according to the droplet discharge device of the present invention, the discharge means (printing data) is not input, that is, the switching means corresponding to the electrostatic actuator 120 which is not performing the discharge driving operation performs the switching operation. Since this is not performed, useless detection / judgment processing can be avoided. In addition, when the switching selection unit 19a is used, the droplet discharge device only needs to include one discharge abnormality detection unit 10, so the circuit configuration of the droplet discharge device must be scaled down. In addition to this, it is possible to prevent an increase in the manufacturing cost of the droplet discharge device.

Next, the ink jet head 100 (head unit 35) in the droplet discharge apparatus of the present invention is configured to execute a recovery process for eliminating the cause of the discharge abnormality (head abnormality) (recovery means). 24) will be described. FIG. 36 is a diagram showing a schematic structure (partially omitted) as viewed from above the ink jet printer 1 shown in FIG. In the ink jet printer 1 shown in FIG. 36, in addition to the configuration shown in the perspective view of FIG. 1, a wiper 300 and a cap 310 for performing a recovery process for ink droplet non-ejection (head abnormality) are provided. Prepare.

The recovery process performed by the recovery unit 24 includes a flushing process of preliminary discharging droplets from the nozzle 110 of each inkjet head 100 and a wiper 300 (described below) (see FIG. 37). This includes a wiping process and a boping process (pump suction process) by a tube pump 320 described later. That is, the recovery means 24 includes a tube pump 320 and a pulse motor for driving the same, a vertical drive mechanism for the wiper 300 and the wiper 300, and a vertical drive mechanism for the cap 310 (see FIG. (Not shown) In the flushing process, the power of the head driver 33 and the head unit 35 is used. In the wiping process, the carriage motor 41 and the like function as a part of the recovery means 24. Since the flushing process has been described above, the wiping process and the pumping process will be described below.

Here, the wiping process refers to a process of wiping foreign matter such as paper powder attached to the nozzle plate 150 (nozzle surface) of the head unit 35 with the wiper 300. The pumping process (pump suction process) is a process in which a tube pump 320 described later is driven to suck and discharge ink in the cavities 144 from the nozzles 110 of the head unit 35. Say. As described above, the wiping process is an appropriate process as a recovery process in a state where paper dust adheres, which is one of the causes of the abnormal ejection of the droplet of the ink jet 100 as described above. In addition, the pump suction process removes air bubbles in the cavity 141 that cannot be removed by the flushing process described above, or the ink in the vicinity of the nozzle 110 is dried or the ink in the cavity 141 deteriorates over time. This is an appropriate process as a recovery process to remove the thickened ink when the viscosity increases. If the viscosity is not so increased and the viscosity is not so large, the above-described recovery process by the flushing process may be performed. In this case, since the amount of ink to be discharged is small, appropriate recovery processing can be performed without reducing throughput / running cost.

The plurality of head units 35 are mounted on a carriage 32, guided by two carriage guide shafts 42, and driven by a carriage module 41 via a connecting portion 34 provided at the upper end in the figure. To move in connection with the timing belt 4 2 1. The head unit 35 mounted on the carriage 32 can be moved in the main scanning direction (in conjunction with the timing belt 421) via the timing belt 421 moved by the drive of the carriage motor 41. is there. The carriage 41 plays a role of a pulley for continuously rotating the timing belt 421, and a pulley 44 is similarly provided on the other end side.

The cap 310 is used for cabling the nozzle plate 150 of the head unit 35 (see FIG. 5). Cap 310 has its bottom side A hole is formed in the tube, and a flexible tube 321, which is a component of the tube pump 320, is connected to the tube, as described later. The tube pump 320 will be described later with reference to FIG.

During the recording (printing) operation, the recording paper P is moved in the sub-scanning direction, while the predetermined ink jet head 100 G is driven by the electrostatic actuator 120 of the night drop discharge head. That is, the ink jet printer (droplet ejection device) 1 moves downward in FIG. 36, and the printing means 3 moves in the main scanning direction, that is, right and left in FIG. Prints (records) a specified image on recording paper P based on the print data (print data) input from.

FIG. 37 is a diagram showing a positional relationship between the wiper 300 shown at 036 and the printing means 3 (head unit 35). In FIG. 37, the printing means 3 (head unit 35) and the wiper 300 are part of a side view of the ink jet printer 1 shown in FIG. Shown. As shown in FIG. 37 (a), the wiper 300 is vertically movable so as to be able to contact the nozzle surface of the printing means 3, that is, the nozzle plate 150 of the head unit 35. You.

Here, the wiping process which is a recovery process using the wiper 300 will be described. When performing the wiping process, as shown in FIG. 37 (a), the wiper 300 is driven by a drive unit (not shown) so that the tip of the wiper 300 is located above the nozzle surface (nozzle plate 150). 0 0 is moved upward. In this case, when the carriage unit 41 is driven to move the printing unit 3 to the left (in the direction of the arrow) in the figure, the wiping member 301 comes in contact with the nozzle plate 150 (nozzle surface). Will be. Since the wiping member 301 is made of a flexible rubber member or the like, as shown in FIG. 37 (b), the tip of the wiping member 301 that comes into contact with the nozzle plate 150 is The surface of the nozzle plate 150 (nozzle surface) is cleaned (wiped) by the bending and the tip. This makes it possible to remove foreign matter such as paper dust attached to the nozzle plate 150 (nozzle surface) (for example, paper dust, dust floating in the air, scraps of rubber, etc.). Also, according to the state of such foreign matter adhered (when a large amount of foreign matter is adhered), the wiper 300 is attached to the printing means 3 (head unit 35). By reciprocating upward, the wiping process can be performed multiple times.

FIG. 38 is a diagram showing a relationship between the head unit 35, the cap 310, and the pump 320 during the pump suction process. The tube 321 forms an ink discharge path in a bombing process (pump suction process), and one end thereof is connected to the bottom of the cap 310 as described above, and the other end is a tube pump. It is connected to the waste ink cartridge 340 via 320.

An ink absorber 330 is arranged on the inner bottom surface of the cap 310. The ink absorber 330 absorbs the ink discharged from the nozzle 110 of the ink jet head 100 during the pump suction process and the flushing process, and temporarily stores the ink. The ink absorber 330 can prevent the ejected droplets from splashing back and fouling the nozzle plate 150 during the flushing operation into the cap 310.

FIG. 39 is a schematic diagram showing the configuration of the tube pump 320 shown in FIG. As shown in Fig. 39 (B), the tube pump 320 is a rotary pump, and includes a rotating body 322 and four rollers 3 arranged around the circumference of the rotating body 322. 23 and a guide member 350. The roller 3 23 is supported by a rotating body 3 22, and a flexible tube 3 21 placed in an arc along the guide 3 51 of the guide member 350 is applied. To press.

The tube pump 320 is rotated by rotating the rotating body 322 in the direction of the arrow X shown in FIG. 39 around the shaft 32a so that one or two of the tubes 3221 are in contact with the tube 3221. While rotating in the Y direction, the two rollers 3 2 3 sequentially press the tubes 3 2 1 placed on the arcuate guide 3 5 1 of the guide member 3 50. As a result, the tube 3 2 1 is deformed, and the negative pressure generated in the tube 3 2 1 causes the ink (liquid material) in the cavity 14 1 of each ink jet head 1 0 to move the cap 3 10. Unnecessary ink that was sucked through, mixed with air bubbles, or thickened by drying was discharged to the ink absorber 330 through the nozzle 110, and was absorbed by the ink absorber 330. The discharged ink is supplied to the discharged ink cartridge 3400 via the tube pump 320 (see Fig. 38). ).

The tube pump 320 is driven by a motor such as a pulse motor (not shown). The pulse motor is controlled by the control unit 6. Drive information for the rotation control of the tube pump 320, for example, a look-up table in which the rotation speed and the number of rotations are described, a control program in which the sequence control is described, and the like, are stored in the PROM 6.4 of the control unit 6, etc. The CPU 61 of the control unit 6 controls the tube pump 320 based on the drive information.

Next, the operation of the recovery means 24 (discharge abnormality recovery processing) will be described. FIG. 40 is a front view showing the ejection failure recovery process in the ink jet printer 1 (droplet ejection device) of the present invention. In the above-described discharge abnormality detection / determination process (see the flowchart in FIG. 24), the nozzle 110 having a discharge abnormality is detected, and if the cause is determined, a predetermined operation that does not perform a printing operation (print operation) is performed. At the timing, the printing unit 3 covers the nozzle plate 150 of the printing unit 3 (head unit 35 in FIG. 36) with the cap 310, or the wiper 300 (A position where the wiping process can be performed by the), and the ejection failure recovery process is executed. First, the control unit 6 determines the determination result corresponding to each nozzle 110 stored in the EEPROM 62 of the control unit 6 in step S107 in FIG. 24 (where the determination result is The determination result is not limited to 110, but is determined for each inkjet head 100. Therefore, in the following, the nozzle 110 having an abnormal discharge is referred to as an inkjet head 1 having an abnormal discharge. 0 is also read.) (Step S910). In step S902, the control unit 6 determines whether or not the readout determination result includes a nozzle 110 having an ejection failure. Then, when it is determined that there is no ejection failure nozzle 110, that is, when the droplets are normally ejected from all the nozzles 110, the ejection abnormality recovery processing is terminated as it is.

On the other hand, when it is determined that any of the nozzles 110 has a discharge abnormality, in step S903, the control unit 6 determines that the nozzle 110 that has been determined to have the discharge abnormality It is determined whether or not it is adhesion. If it is determined that paper dust has not adhered to the vicinity of the outlet of the nozzle 110, the process proceeds to step S905, where paper dust adheres. If it is determined that the nozzle plate 150 is present, the wiping process for the nozzle plate 150 by the wiper 300 described above is executed (step S904).

In step S905, the control unit 6 subsequently determines whether or not the nozzle 110 determined to have the above-described discharge abnormality is a bubble. If it is determined that air bubbles are mixed, the control unit 6 executes a pump suction process by the tube pump 320 for all the nozzles 110 (step S 906), This discharge abnormality recovery process ends. On the other hand, when it is determined that there is no air bubble, the control unit 6 determines whether the pump by the tube pump 320 is based on the length of the period of the residual vibration of the diaphragm 121 measured by the measuring unit 17. The flushing process is performed on only the nozzle 110 or all the nozzles 110 determined to be the suction process or the discharge abnormality (step S <b> 907), and the discharge abnormality recovery process ends.

In the inkjet printer 1 of the present invention as described above, each inkjet head 100 of the head unit 35 ejects an ink droplet (droplet) to the recording paper P (droplet receptor). In this case, a discharge abnormality is detected by the discharge abnormality detecting means 10 for the discharge operation of each ink droplet to be discharged from each of the nozzles 110. That is, when forming an image on the recording paper P, the inkjet printer 1 performs the operation while detecting whether all the ink droplets to be ejected from each of the nozzles 110 have been ejected normally. As a result, the inkjet printer 1 can detect whether or not there is any dot missing (pixel loss) in the formed image, so it is possible to actually detect whether or not there is any defect in the formed image. can do.

As described above, since the ink jet printer 1 detects the presence or absence of a discharge abnormality for each of the ink droplets to be discharged from each nozzle 110, the discharge abnormality detection for the plurality of nozzles 110 is performed in parallel. In order to enable this, it is preferable to have the configuration as shown in FIG. 28 or FIG. 29 described above. However, the present invention may have a configuration as shown in FIG. 27 or FIG. 30 described above. In the configuration shown in FIG. 27 or FIG. 30, when forming an image on the recording paper P, instead of ejecting ink droplets from each nozzle 110 at the same time, timing from each nozzle 110 is used. By shifting the ink droplets sequentially to eject ink droplets, the ejection Presence or absence can be detected.

In addition, in the inkjet printer 1 of the present embodiment, the control unit 6 includes an abnormal counter (counting unit) that counts the number of ejection abnormalities detected by the ejection abnormality detecting unit 10. As a result, the inkjet printer 1 forms an image by ejecting ink droplets onto the recording paper P, and the number of ejection abnormalities occurring on the recording paper P, ie, the image formed on the recording paper P. It is possible to count the number of missing dots (pixel loss) that occurred inside. Therefore, the inkjet printer 1 can also detect (determine) the image quality of the image formed on the recording paper P based on the number of missing dots. This abnormality counter (counting means) may be configured as software as a part of the control program of the control unit 6, or may be configured as a circuit as a hardware.

Next, in such an ink jet printer 1 of the present invention, a process when an abnormal ejection is detected during image formation on the recording paper P (during ejection of ink droplets to the recording paper P) (error processing) Will be described.

FIG. 41 is a flowchart showing a process when an ejection failure is detected during image formation. Hereinafter, an example of an error process when an ejection failure is detected during image formation in the inkjet printer 1 will be described with reference to FIG.

When printing is started, the ink jet printer 1 first checks whether or not the head unit 35 is in a normal state (step S1001). In this initial confirmation, the ejection abnormality is detected by the ejection abnormality detection means 10 for each nozzle 110 while performing the flushing operation, and it is confirmed that the head unit 35 is in a normal state. When an abnormal discharge is detected, the recovery process is performed by the recovery unit 24 to recover. When receiving the print data from the host computer 8 (step S1002), the control section 6 operates the paper feeder 5 to supply the recording paper P (step S1003). Further, at the start of new printing, the control section 6 returns the number N of ejection abnormalities counted by the abnormal force control to N = 0 (step S1004). Further, the control unit 6 sets a reference value (allowable value) Z of the number of missing dots allowed in an image formed on the recording paper P (step S1005). In the present embodiment, the reference value Z is set to 5. The reference value Z may be a fixed value, or may be changed by operating the host computer 8 or the operation panel 7 and inputting an arbitrary numerical value. Further, the reference value Z may be determined (calculated) from an allowable ratio of missing dots with respect to the total number of pixels of an image to be formed. In this case, the allowable ratio may be a fixed value or may be changed by operating the host computer 8 or the operation panel 7 and inputting an arbitrary numerical value.

Next, based on the input print data, the control unit 6 drives each of the inkjet heads 100 to perform an ejection operation, and ejects ink droplets from each of the nozzles 110, whereby the inkjet printer 1 Then, a recording operation is performed on the recording paper P (step S106). In this recording operation, the ejection abnormality detecting means 10 detects the ejection abnormality by the ejection abnormality detecting means 10 for the ejection operation of each ink droplet to be ejected from each nozzle 110 (step S100). 7).

The abnormal count is detected (step S1008) every time one discharge abnormality is detected (step S1008), by setting the number of discharge abnormalities N to N = N + 1 (step S1009). Count the total number of discharge abnormalities that occurred.

The control unit 6 determines whether or not the number N of ejection abnormalities counted by the abnormal force counter has exceeded the reference value Z (step S11010). If the number N of ejection errors has not reached the reference value Z, it is determined whether printing based on the print data has been completed (step S 101). Returning to step S106, the recording operation is continued.

If the printing based on the print data is completed without the number of ejection failures N reaching the reference value Z, the inkjet printer 1 ends the printing. In this case, the image formed on the printed recording paper P satisfies the image quality standard based on the standard value Z.

On the other hand, when the control unit 6 determines that the number N of abnormal discharges exceeds the reference value Z in step S11010 during printing, the control unit 6 displays the fact on the display unit of the operation panel 7. (Step S 1 0 1 2). As a result, the operator of the ink jet printer 1 confirms that the image formed on the recording paper P does not satisfy the image quality standard based on the standard value Z. (User).

In this case, the display on the operation panel 7 may display, for example, the number of occurrences N of discharge abnormalities and the reference value Z, or only display that the image quality has not reached the reference. Further, in the present invention, the notifying means (notifying method) is not limited to the display on the display unit, and may be, for example, a sound, an alarm sound, a lighting of a lamp, or a host computer 8 via the interface 9. Or any device that transmits ejection abnormality information to a print server or the like via a network. If the controller 6 determines in step S1010 that the number N of ejection failures has exceeded the reference value Z, the controller 6 stops printing. Alternatively, printing may be completed to the end without stopping printing.

FIG. 42 is a flowchart showing another example of the process when an ejection failure is detected during image formation. Hereinafter, another example of the error processing when an ejection error is detected during image formation in the inkjet printer 1 will be described with reference to FIG. 42. The difference from the error processing shown in FIG. 41 will be mainly described. And similar items simplify the description. When printing starts, the inkjet printer 1 first performs an initial check (Step S1101), and the control unit 6 receives print data from the host computer 8 (Step S1102). Further, the control unit 6 sets the reference value (image defect allowable value) Z of the number of missing dots allowed in the image formed on the recording paper P in the same manner as described above (step S1103). In the present embodiment, the reference value Z == 5 is set.

Then, the control unit 6 operates the paper feeder 5 to supply the recording paper P (Step S1104), and returns the number N of ejection errors counted by the abnormal counter to N = 0 (Step S1105). ). .

Next, the ink jet printer 1 performs a recording operation on the recording paper P (step S1106). In this recording operation, the discharge abnormality detecting means 10 detects the discharge abnormality by the discharge abnormality detection means 10 for the discharge operation of each ink droplet to be discharged from each nozzle 110 (step S1107).

The abnormality counter detects (occurs) each time one ejection abnormality is detected (step S1108) by setting the number N of ejection errors to N = N + 1 (step S1109). The total number of ejection abnormalities counted is counted.

The control unit 6 determines whether or not the counted number N of discharge abnormalities exceeds the reference value Z (step S111). If the number N of ejection errors has not reached the reference value Z, it is determined whether printing based on the print data has been completed (step S111). Returning to step S1106, the recording operation is continued. If the printing based on the print data is completed without the number of ejection failures N reaching the reference value Z, the inkjet printer 1 ends the printing. In this case, the image formed on the printed recording paper p satisfies the image quality standard based on the standard value τ.

On the other hand, if the control unit 6 determines that the number of abnormal discharge occurrences Ζ exceeds the reference value において in step S11110 during printing, the control unit 6 prints (ink droplets) on the recording paper Ρ. Is stopped, and the flow returns to step S1104 to operate the paper feeder 5 to discharge the recording paper Ρ and supply the next recording paper 、, and perform steps S1105 and below. .

In other words, in the error processing of FIG. 42, when the number of discharge abnormalities Ν counted during printing exceeds the reference value Ζ, the recording paper Ρ is discharged and a new recording paper Ρ is replaced. Feeds paper and operates to perform the same printing (ejection of ink droplets) newly on this recording paper 新た (redo). As a result, printing is continued (re-started) until recording paper Ρ on which an image that satisfies the image quality standard based on the reference value 上がる is formed (re-starting). Even if a discharge abnormality occurs in the ink, a desired image quality can be obtained.

If the number of discharge abnormalities Ζ exceeds the reference value で during printing and printing is to be performed again on new recording paper Ρ, the recovery means 24 must first reset the ink jet head 100 (head unit 35). Recovery processing may be performed. As a result, the cause of the ejection failure of the ink jet head 100 (head unit 35) is reliably eliminated, so that the ejection failure can be prevented from occurring again in the reprinting of new recording paper Ρ. can do.

FIG. 43 is a flowchart showing still another example of the processing performed when an ejection failure is detected during image formation. It is a low chart. Hereinafter, another example of the error processing when an ejection failure is detected during image formation in the inkjet printer 1 will be described with reference to FIG. 43, but the difference from the error processing shown in FIG. 42 will be described. The explanation is focused on the points, and the explanation of the same items is omitted.

In the error processing shown in Fig. 43, the reference values of the number of dots 1 and the number of missing dots (image defect tolerance) that are allowed in the image formed on the recording Value) The steps are the same as steps S1101-S1102 and S1104-S1111 in FIG. Therefore, description will be made focusing on this step S122.

The ink jet printer 1 according to the present embodiment has three operation modes having different reference values of the number of allowable dropouts, that is, a high-quality mode, a medium-quality mode, and a low-quality mode. The control unit 6 has a control program corresponding to each of these operation modes, and the operator (user) of the inkjet printer 1 operates the host computer 8 or the operation panel 7 to operate any one of the operation modes. Mode can be selected.

The high quality mode is an operation mode for forming an image having no missing dots in all pixels. In contrast, the medium-quality mode is an operation mode that allows dots to be skipped up to 0.1% of the total number of pixels, and the low-quality mode is one in which dots are missing up to 1% of the total number of pixels. This is an operation mode that allows generation.

In step S123, the reference value Z of the allowable number of missing dots is set according to the allowable dot missing ratio in each of the operation modes described above. Here, a description will be given assuming that the print data received in step S122 prints an image mainly composed of characters in which the total number of pixels is 20000 pixels. In this case, when the high-quality mode is selected, even one missing dot is not allowed, so the reference value Z of the number of allowed missing dots is set to Z == 0. When the medium quality mode is selected, the reference value Z of the allowable dot missing number is 0.1% of 20000 pixels, so that Z = 20 is set. When the low-quality mode is selected, the reference value Z of the allowable number of missing dots is 1% of 2000 pixels, so that Z is set to 2000.

The high-quality mode, medium-quality mode, and low-quality mode use the reference value Z as described above. Is not limited to the ratio defined with respect to the total number of pixels, but may be defined as an absolute number. In addition, in the high-quality mode, the medium-quality mode, and the low-quality mode, not only the reference value Z is operated so as to be different, but also other control methods may be different. It may be different.

As described above, in step S123, the reference value Z of the number of missing dots is set in accordance with the selected operation mode. Therefore, when the high-quality mode is selected, if even one ejection error (missing dot) is detected, replace the recording paper P with a new one and reprint (reprint). . When the medium-quality mode is selected, printing is continued while allowing up to 20 detected ejection abnormalities (missing dots). Replace recording paper P with a new one and reprint. When the low-quality mode is selected, printing is continued while permitting up to 200 detected ejection abnormalities (missing dots). Replace the recording paper P with a new one and print again.

As described above, according to the present embodiment, the operator (user) of the ink jet printer 1 can perform printing so as to obtain a printed matter having an image quality that is not excessive or insufficient according to a desired image quality. Without) printing operation can be performed.

As described above, the droplet discharge device of the present embodiment requires other components (for example, an optical dot missing detection device, etc.) as compared with the conventional droplet discharge device capable of detecting a discharge abnormality. Because of this, it is possible to detect a droplet discharge abnormality without increasing the size of the droplet discharge head, and to manufacture a droplet discharge device capable of detecting a discharge abnormality (missing dot). Can be kept low. Further, since the abnormal discharge of the droplet is detected using the residual vibration of the diaphragm after the operation of discharging the droplet, the abnormal discharge of the droplet can be detected even during the recording operation.

In the present invention, the discharge abnormality detection means may not determine the cause of the generated discharge abnormality. The ejection failure detection means is not limited to the above-described embodiment as long as it can detect the ejection failure while performing the printing operation. Any method may be used. <Second embodiment>

Next, another configuration example of the inkjet head according to the present invention will be described. FIG. 44 to FIG. 47 are cross-sectional views each schematically showing another example of the configuration of the ink jet head (head unit). Hereinafter, 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. In the ink jet head 100A shown in FIG. 44, the vibration plate 212 vibrates by driving the piezoelectric element 200, and the ink (liquid) in the cavity 208 is ejected from the nozzle 203. Is what you do. A stainless steel nozzle plate 202 having a nozzle (hole) 203 formed thereon is joined with a stainless steel metal plate 204 via an adhesive film 205. A metal plate 204 made of the same stainless steel is joined on the upper side via an adhesive film 205. Then, a communication port forming plate 206 and a cavity plate 207 are sequentially joined thereon.

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

A vibrating plate 212 is provided at an opening on the upper surface of the cavity plate 207, and a piezoelectric element (piezoelectric element) 200 is provided on the vibrating plate 212 via a lower electrode 21. Joined. An upper electrode 214 is joined to the piezoelectric element 200 on the side opposite to the lower electrode 211. The head driver 33 includes a drive circuit for generating a drive voltage waveform, and applies (supplies) the drive voltage waveform between the upper electrode 214 and the lower electrode 213 to form the piezoelectric element 20. 0 vibrates, and the diaphragm 2 1 2 vibrates to it. Due to the vibration of the vibration plate 212, the volume of the cavity 208 (pressure in the cavity) changes, and the ink (liquid) filled in the cavity 208 is ejected from the nozzle 203 as droplets.

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

In the ink jet head 100B shown in FIG. 45, similarly to the above, the ink (liquid) in the captivity 21 is discharged from the nozzle by driving the piezoelectric element 200. This ink jet head 100 B has a pair of opposed substrates 220, and a plurality of piezoelectric elements 200 are intermittently arranged at predetermined intervals between the two substrates 220. I have. A cavity 2 21 is formed between adjacent piezoelectric elements 200. A plate (not shown) is installed at the front in FIG. 4 5 of the cavity 2 2 1, and a nozzle plate 2 2 2 is installed at the rear, and a position corresponding to each cavity 2 2 1 of the nozzle play h 2 2 A nozzle (hole) 222 is formed.

A pair of electrodes 224 is provided on one surface and the other surface of each piezoelectric element 200, respectively. That is, four electrodes 224 are connected to one piezoelectric element 200. By applying a predetermined drive voltage waveform between predetermined electrodes of these electrodes 222, the piezoelectric element 200 is deformed in shear mode and vibrates (indicated by an arrow in FIG. 45). The volume of the cavity 222 (pressure in the cavity) changes due to the vibration, and the ink (liquid) filled in the cavity 222 is discharged as droplets from the nozzle 222. That is, in the inkjet head 100B, the piezoelectric element 200 itself functions as a diaphragm.

The ink jet head 100C shown in FIG. 46 also discharges the ink (liquid) in the cavity 233 from the nozzle 231 by driving the piezoelectric element 200 in the same manner as described above. The ink jet head 100C includes a nozzle plate 230 on which the nozzles 231 are formed, a spacer 232, and a piezoelectric element 200. The piezoelectric element 200 is installed at a predetermined distance from the nozzle plate 230 via a spacer 232, and the nozzle plate 230, the piezoelectric element 200, and the spacer A cavity 2 33 is formed in a space surrounded by 32.

A plurality of electrodes are joined to the upper surface of the piezoelectric element 200 in FIG. That is, a first electrode 234 is joined to a substantially central portion of the piezoelectric element 200, and a second electrode 235 is joined to both sides thereof. 1st electrode 2 3 4 and 2nd electrode 2 3 5 By applying a predetermined drive voltage waveform during the period, the piezoelectric element 200 is deformed in the shear mode and vibrates (indicated by an arrow in FIG. 46), and this vibration causes the volume of the cavity 23 3 (in the cavity) The pressure changes, and the ink (liquid) filled in the cavity 2 33 is ejected from the nozzle 2 31 as droplets. 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. 47, the ink (liquid) in the cavity 245 is discharged from the nozzle 241 by driving the piezoelectric element 200 in the same manner as described above. This ink jet head 100D is composed of a nozzle plate 240 on which the nozzles 241 are formed, a cavity plate 242, a vibration plate 243, and a plurality of piezoelectric elements 200. And a multi-layer piezoelectric element 201.

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

The middle and lower ends of the laminated piezoelectric element 201 shown in FIG. 47 are connected to the diaphragm 243 via the intermediate layer 244. A plurality of external electrodes 248 and internal electrodes 249 are joined to the laminated piezoelectric element 201. That is, an external electrode 248 is bonded to the outer surface of the multilayer piezoelectric element 201, and is provided between the piezoelectric elements 200 constituting the multilayer piezoelectric element 201 (or inside each piezoelectric element). The internal electrode 249 is installed. In this case, the external electrodes 248 and a part of the internal electrodes 249 are alternately arranged so as to overlap in the thickness direction of the piezoelectric element 200.

Then, by applying a driving voltage waveform from the head driver 33 between the outer electrode 248 and the inner electrode 249, the multilayer piezoelectric element 201 is deformed as shown by the arrow in FIG. 47. Vibrating (expanding and contracting in the vertical direction in Fig. 47), and the vibration causes the diaphragm 243 to vibrate. Due to the vibration of the vibrating plate 243, the volume of the cavity 245 (the pressure in the cavity) changes, and the ink (liquid) filled in the cavity 245 is ejected from the nozzle 241 as droplets. The amount of the liquid reduced in the cavity 245 due to the ejection of the droplet is supplied by supplying the ink from the reservoir 246. Ink is supplied to the reservoir 246 from the ink cartridge 31 via the ink supply tube 311.

In the case of the ink jet 100 A to 100 D having the above-described piezoelectric element, a diaphragm or a vibrating plate can be formed in the same manner as the above-described capacitive ink jet head 100. 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 inkjet heads 100B and 100C, a diaphragm (a diaphragm for detecting residual vibration) as a sensor is provided at a position facing the cavity to detect residual vibration of the diaphragm. It can also be configured.

As described above, the droplet discharge device of the present invention has been described based on the illustrated embodiments. However, the present invention is not limited to this, and each part configuring the droplet discharge head or the droplet discharge device includes: Any configuration that can exhibit the same function can be substituted. Further, other arbitrary components may be added to the droplet discharge head or the droplet discharge device of the present invention.

The ejection target liquid (droplet) ejected from the droplet ejection head (the ink jet head 100 in the above-described embodiment) of the droplet ejection device of the present invention is not particularly limited. (Including dispersions such as suspensions and emulsions). That is, a filter material (ink) for a color filter, a light emitting material for forming an EL light emitting layer in an organic EL (Electro Luminescence) device, a fluorescent material for forming a phosphor on an electrode in an electron emission device, and a PDP. (Plasma Display Panel) Fluorescent material for forming a phosphor in the device, electrophoretic material for forming the electrophoretic material in the electrophoretic display device, bank material for forming a bank on the surface of the substrate W, various coating materials, electrodes Liquid electrode material to form a micro-lens, liquid material to form a spacer to form a minute cell gap between two substrates, liquid metal material to form metal wiring, and micro lens Lens materials, resist materials, light diffusion materials for forming light diffusers, DNA chips, biochips such as protein chips, etc. Der various test liquid material You.

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 nonwoven fabrics, glass substrates, silicon substrates, Work such as various substrates may be used.

Claims

The scope of the claims

1. A plurality of droplet discharge heads that discharge the liquid as liquid droplets from the nozzles communicating with the cavities by driving the actuators by the driving circuit to change the pressure in the cavities filled with the liquids. A droplet discharge device that discharges droplets from the nozzles and lands on the droplet receiver while scanning the droplet discharge head relative to the droplet receptor,

Discharge abnormality detection means for detecting a discharge abnormality of the droplet from the nozzle,

When the droplet discharge head is discharging droplets to the droplet receiver, a discharge abnormality is detected by the discharge abnormality detecting means for a discharge operation of each droplet to be discharged from the nozzle. A droplet discharging device for detecting.

2. The droplet discharge device according to claim 1, further comprising a counting means for counting the number of discharge abnormalities detected by the discharge abnormality detecting means.

3. It is equipped with a notification means,

If the number of ejection abnormalities for the droplet receiver counted by the counting means during ejection of the droplet to the droplet receiver exceeds a preset reference value, this fact is notified. 3. The droplet discharge device according to claim 2, wherein the notification is performed by the notification unit.

4. The apparatus further comprises a droplet receiver conveying means for discharging and supplying the droplet receiver,

If the number of abnormal discharges for the droplet receiver counted by the counting means while discharging the droplet to the droplet receiver exceeds a preset reference value, the droplet The discharge of the droplets to the receptor is stopped, the droplet receiver is discharged by operating the droplet receptor transport means, and the next droplet receptor is supplied, and the supplied droplet receptor is supplied. 3. The droplet discharge device according to claim 2, wherein the droplet is newly discharged in the same manner.

5. For the droplet discharge head, perform recovery processing to eliminate the cause of abnormal droplet discharge. 5. The liquid droplet according to claim 4, further comprising a recovery unit that performs recovery processing by the recovery unit before newly discharging a droplet to the supplied droplet receiver in the same manner. Discharge device.

6. The droplet discharge device according to claim 3, wherein the reference value can be changed.

7. The droplet discharge device according to claim 3, wherein the droplet discharge device has a plurality of operation modes in which the reference values are different. The operation mode can be selected.

8. The droplet discharge head has a diaphragm that is displaced by driving the actuator over time.

The liquid according to claim 1, wherein the discharge abnormality detection means detects residual vibration of the diaphragm, and detects discharge abnormality based on a vibration pattern of the detected residual vibration of the diaphragm. Drop ejection device.

9. The discharge abnormality detecting means determines the cause of the discharge abnormality when it is determined that the droplet discharge head has a discharge abnormality based on the vibration pattern of the residual vibration of the diaphragm. 9. The droplet discharge device according to claim 8, comprising a determination unit.

10. The droplet discharge device according to claim 9, wherein the vibration pattern of the residual vibration of the vibration plate includes a period of the residual vibration.

When the period of the residual vibration of the diaphragm is shorter than a period in a predetermined range, the determination unit determines that air bubbles are mixed in the cavity, and the period of the residual vibration of the diaphragm is determined. When it is longer than a predetermined threshold, it is determined that the liquid in the vicinity of the nozzle is thickened by drying, and the cycle of the residual vibration of the diaphragm is longer than the cycle of the predetermined range, and the predetermined threshold is set. 10. The droplet discharge device according to claim 10, wherein when the length is shorter than the length, it is determined that paper dust has adhered near the outlet of the nozzle.

12. The discharge abnormality detection 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. Item 6. A droplet discharge device according to Item 1.

13. The liquid according to claim 12, wherein 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 amplifier. Drop ejection device.

14. The discharge abnormality detection means includes an FZV 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. Item 13. The droplet discharge device according to Item 12.

15. The discharge abnormality detection means includes a waveform shaping circuit for shaping a voltage waveform of residual vibration of the vibration plate generated by the F / V conversion circuit into a predetermined waveform. Droplet ejection device.

16. The waveform shaping circuit includes a DC component removing unit that removes a DC component from a voltage waveform of the residual vibration of the diaphragm generated by the FZV conversion circuit, and a DC component that is removed by the DC component removing unit. 16. The droplet according to claim 15, further comprising: a comparator that compares the voltage waveform obtained with the predetermined voltage value, wherein the comparator generates and outputs a rectangular wave based on the voltage comparison. Discharge device.

17. The droplet discharge device according to claim 16, wherein the discharge abnormality detection unit includes a measurement unit that measures a cycle of a residual vibration of the diaphragm from the rectangular wave generated by the waveform shaping circuit. .

18. The measuring means has a counter, and the counter counts a pulse of the reference signal. The droplet discharge according to claim 17, wherein a time between a rising edge of the rectangular wave or a time between a rising edge and a falling edge is measured.

19. The method according to claim 1, further comprising: a switching unit that switches a connection between the actuator and the actuator from the driving circuit to the ejection abnormality detecting unit after the droplet is ejected by driving the actuator. The droplet discharge device according to the above.

20. The droplet discharge device includes a plurality of the discharge abnormality detection means and the switching means, respectively.

The switching means corresponding to the droplet discharge head that has performed the droplet discharge operation switches the connection with the actuator to the corresponding discharge abnormality detection means from the drive circuit, and the switched discharge abnormality 10. The droplet discharge device according to claim 19, wherein the detection unit detects the discharge abnormality of the droplet discharge head.

21. The droplet discharging apparatus according to claim 1, wherein the actuating unit is an electrostatic actuating unit.

22. The droplet discharging device according to claim 1, wherein the actuator is a piezoelectric actuator utilizing a piezo effect of a piezoelectric element.

23. The droplet discharge apparatus according to claim 1, further comprising storage means for storing a cause of the discharge abnormality of the droplet detected by the discharge abnormality detection means in association with a nozzle to be detected. .

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