JP2005349595A - Liquid drop ejector, method and program for recovering liquid drop ejection performance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid drop ejector capable of reducing ink consumption while enhancing throughput, and to provide a method and a program for recovering liquid drop ejection performance. <P>SOLUTION: Liquid drop ejection abnormality is detected for each nozzle, driving of a means for sucking liquid from the nozzle is started based on detection of liquid drop ejection abnormality, recovery conditions of liquid drop ejection performance of the nozzle are judged under a state where liquid is sucked by the suction means, the judgment is repeated within a predetermined limit until the judgment results represent recovery of liquid drop ejection performance when the judgment results of recovery conditions do not represent recovery of liquid drop ejection performance, and the suction means is stopped when the judgment results in the recovery judgment step represent recovery of liquid drop ejection performance or when the judgment results do not represent recovery of liquid drop ejection performance within the predetermined limit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a droplet discharge device such as an ink jet printer, and more particularly to recovery of performance of discharging nozzle droplets.

  An ink jet printer, which is one of liquid droplet ejection devices, forms an image on a recording medium by ejecting ink droplets (liquid droplets) from a plurality of nozzles provided in a recording head. Ink jet printers may cause an abnormal discharge that does not properly eject ink droplets from nozzles due to an increase in ink viscosity, air bubbles, or dust or paper dust, resulting in a missing dot phenomenon in the image. There is.

  Therefore, the ink jet printer performs a process of sucking ink from the nozzles using a pump or the like and recovering the nozzles. The pump drive time, drive speed, etc. are such that in the nozzle recovery process, the amount of ink required for nozzle recovery can be sucked under the most severe use environment among the various assumed use environments. Is set. That is, under a normal use environment, ink more than the amount necessary for recovery of the nozzles is sucked, leading to waste of ink.

In order to eliminate such problems, a technique for detecting the ambient air pressure and temperature in the nozzle recovery process and controlling the ink suction so that the ink suction amount becomes a predetermined amount based on the detection result. (For example, refer to Patent Document 1).
JP 2000-108368 A

  However, in the prior art disclosed in Patent Document 1, it is not possible to reliably detect whether or not the nozzle has been recovered by the nozzle recovery process. Therefore, it is necessary to separately inspect the nozzle after the nozzle recovery process. Accordingly, there is an unsolved problem that it takes time to perform nozzle inspection and it is difficult to improve throughput. Further, depending on the result of the nozzle inspection after the recovery process, the recovery process of the nozzle may be required again, and there is an unsolved problem that it is difficult to reduce ink consumption.

  The present invention has been made in order to solve the above-described problems. A droplet discharge apparatus, a droplet discharge performance recovery method, and a droplet discharge that can improve throughput and reduce ink consumption. It aims to provide a performance recovery program.

  In order to solve the above-described problems, a first invention according to the present invention is a droplet discharge device that discharges a liquid as a droplet from a nozzle, the head unit having a plurality of the nozzles, and the liquid from the nozzle. A discharge abnormality detecting unit that detects, for each nozzle of the head unit, a droplet discharge abnormality in which a droplet is not properly discharged, and the discharge abnormality detecting unit detects the droplet discharge abnormality based on the detection of the droplet discharge abnormality. A discharge performance recovery means for recovering the droplet discharge performance for discharging the liquid droplets, and the discharge performance recovery means is a suction means for sucking the liquid from the nozzle, and a liquid suction state by the suction means, A recovery determination unit that determines a recovery status of the droplet discharge performance of the nozzle; and a suction control unit that controls the suction unit based on a determination result of the recovery determination unit. When the determination result of the recovery status is that the droplet discharge performance has not recovered, the determination means determines the recovery status until the determination result is that the droplet discharge performance has recovered. Provided is a droplet discharge device that repeats within a predetermined limit.

According to the above configuration, the recovery determination unit determines whether or not the droplet discharge performance of the nozzle in which the droplet discharge abnormality is detected is recovered in a state where the suction unit is sucking the liquid from the nozzle. This determination is repeated within a predetermined limit until the droplet discharge performance is recovered.
As described above, the discharge performance recovery means can monitor the recovery status of the droplet discharge performance of the nozzle in a state where the liquid is sucked by the suction means, and can control the suction means based on the monitoring result. .

According to a second aspect of the present invention, there is provided the liquid droplet ejection apparatus according to the first aspect, wherein the predetermined limit is set by the number of times the recovery determination means repeats the determination of the recovery status. .
As described above, it is possible to set a predetermined limit by setting the number of times the recovery determination unit repeats the determination of the recovery status.

According to a third aspect of the invention, in the first aspect of the invention, the predetermined limit is set according to an elapsed time since the suction by the suction means is started. .
As described above, by setting the elapsed time since the suction by the suction means is started, it is possible to set a limit at which the recovery determination means repeats the determination of the recovery state.

  According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the suction control unit is configured such that the determination result of the recovery determination unit is a recovery of the droplet discharge performance, and the predetermined The suction by the suction means is stopped when the determination result of the recovery state is within the limit of when the droplet discharge performance is not recovered. A dispensing device is provided.

According to the above configuration, when the droplet discharge performance of the nozzle is recovered, the suction control unit stops the suction of the liquid when the determination result is obtained, and the droplet discharge of the nozzle is within a predetermined limit. If the performance does not recover, the liquid suction is stopped when a predetermined limit is reached.
As described above, when the droplet discharge performance of the nozzle recovers within a predetermined limit, the suction of the liquid is stopped when the determination result is obtained, so the liquid is discharged after the droplet discharge performance of the nozzle is recovered. It is possible to suppress wasteful consumption. In addition, when the droplet discharge performance of the nozzle reaches a predetermined limit without being recovered, the suction of the liquid is stopped, so that it is possible to suppress the liquid consumption thereafter.

  According to a fifth invention, in any one of the first to fourth inventions, the discharge performance recovery means further includes a wiping means for wiping a nozzle surface on which the nozzles are arranged with a wiper. There is provided a droplet discharge apparatus configured to select either the suction unit or the wiping unit according to the mode of the droplet discharge abnormality detected by the abnormality detection unit.

As described above, in the recovery of the droplet discharge performance, when the wiping process using the wiper is appropriate, the wiping unit is selected, so that the liquid consumption by the suction unit can be suppressed.
According to a sixth invention, in any one of the first to fifth inventions, the head unit includes a diaphragm, an actuator for displacing the diaphragm, and a liquid filled therein. And a cavity for discharging the liquid as droplets from the nozzle by increasing or decreasing the internal pressure by the displacement, and the recovery determination means drives the actuator to discharge the droplets from the nozzle. Residual vibration detecting means for detecting residual vibration of the diaphragm when the diaphragm is displaced, and based on the mode of residual vibration detected by the residual vibration detecting means, Provided is a droplet discharge device configured to determine the recovery status.

As described above, the residual vibration of the diaphragm can be detected, and the recovery state of the droplet discharge performance can be determined from the detected residual vibration mode.
In addition, in a sixth aspect based on the sixth aspect, the recovery determining means determines whether or not the measured period is within a normal range and a period measuring means for measuring the period of the residual vibration. And a period determining means.

As described above, the recovery determination unit can measure the period of the residual vibration and determine the recovery status of the droplet discharge performance by determining whether or not the measured period is within the normal range. It becomes possible to do.
The eighth invention is a droplet discharge performance recovery method for recovering the droplet discharge performance of discharging a droplet of a nozzle that discharges the liquid as a droplet, wherein the droplet is appropriately discharged from the nozzle. A liquid discharge abnormality detecting step for detecting a liquid droplet discharge abnormality for each nozzle of the head unit having a plurality of nozzles, and the liquid is sucked from the nozzles based on the detection of the liquid droplet discharge abnormality The suction start step for starting the suction means and the liquid suction state by the suction means determine the recovery status of the droplet discharge performance of the nozzle, and the determination result of the recovery status restores the droplet discharge performance. A recovery determination step that repeats the determination within a predetermined limit until the determination result is that the droplet discharge performance has been recovered, and the recovery determination step. When the determination result at the top is a recovery of the droplet discharge performance and when the determination result is not the recovery of the droplet discharge performance within the predetermined limit And a suction stop step for stopping the driving of the suction means.

According to the above configuration, when the droplet discharge performance of the nozzle recovers within a predetermined limit, the suction of the liquid is stopped when the determination result is obtained, and the droplet discharge performance of the nozzle does not recover The suction of the liquid is stopped when a predetermined limit is exceeded.
As described above, it is possible to monitor the recovery state of the droplet discharge performance of the nozzle while the suction means is sucking the liquid, and stop the suction of the liquid based on the monitoring result.

  In a ninth aspect based on the eighth aspect, in the recovery determination step, an actuator for displacing a diaphragm included in the head unit is driven a predetermined number of times so that the droplets are ejected from the nozzle. Provided is a droplet discharge performance recovery method that detects residual vibration of the diaphragm and determines whether or not the droplet discharge performance has been recovered based on the detected period of the residual vibration. .

Based on the above, it is possible to measure the residual vibration detection timing based on the number of times the actuator is driven to discharge, and grasp whether the droplet discharge performance has been recovered based on the detected period of the residual vibration. Is possible.
The tenth aspect of the invention is a droplet discharge performance recovery program for causing a computer to execute a droplet discharge performance recovery process for recovering the droplet discharge performance of discharging a droplet of a nozzle that discharges a liquid as a droplet. A discharge abnormality detecting step for detecting, for each nozzle of the head unit having a plurality of nozzles, a droplet discharge abnormality in which the droplets are not properly discharged from the nozzle, and the droplet discharge abnormality is detected. Based on the suction start step of starting the suction means for sucking the liquid from the nozzle, and the recovery status of the droplet discharge performance of the nozzle is determined in the liquid suction state by the suction means, and the recovery When the determination result of the situation is that the droplet discharge performance is not recovered, the determination is performed until the determination result is the recovery of the droplet discharge performance. A recovery determination step that repeats within a limit, and when the determination result in the recovery determination step is a recovery of the droplet discharge performance, and the determination result is within the predetermined limit, the droplet discharge performance And a suction stop step for stopping the suction means when the suction means is not recovered, and causing the electronic computer to execute a droplet discharge performance recovery program. .

As described above, it is possible to cause the electronic computer to monitor the recovery state of the droplet discharge performance of the nozzle while the suction unit is sucking the liquid, and to stop the suction of the liquid based on the monitoring result.
In an eleventh aspect based on the tenth aspect, in the recovery determination step, an actuator for displacing a diaphragm included in the head unit is driven a predetermined number of times so that the droplets are ejected from the nozzle. Provided is a droplet discharge performance recovery program that detects residual vibration of the diaphragm and determines whether or not the droplet discharge performance has been recovered based on the detected period of the residual vibration. .

  Based on the above, it becomes possible to measure the timing for detecting the residual vibration depending on the number of times the actuator is driven to discharge, and based on the detected period of the residual vibration, whether or not the droplet discharge performance has been restored to the electronic computer. It is possible to make a determination.

A first embodiment of the present invention will be described with reference to the drawings, taking as an example an ink jet printer which is a kind of droplet discharge device.
As shown in FIG. 1, the ink jet printer 1 according to the first embodiment includes a carriage 4 on which a head unit 2 and an ink cartridge 3 are mounted. The carriage 4 is guided by a set of carriage shafts 5 in the main scanning direction. Can be moved to. A part of the carriage 4 is fixed to a toothed belt 9, and the toothed belt 9 is stretched between a driving pulley 7 and a driven pulley 8 fixed to a rotating shaft of the motor 6.

Furthermore, an encoder 10 is attached to the carriage 4, and a linear scale 11 is provided along the moving direction of the carriage 4. The position of the head unit 2 on the carriage 4 is detected by the encoder 10.
In FIG. 1, reference numeral 12 denotes a cable for electrically connecting the head unit 2 to a system controller described later. Reference numeral 13 denotes a wiper for cleaning the surface of the head, which will be described later. Reference numeral 14 denotes a cap for capping a nozzle substrate of a head to be described later.

In the inkjet printer 1 having such a configuration, when the detection signal of the encoder 10 is input to a motor control circuit (not shown), the rotation operation of the motor 6 is controlled by the motor control circuit as follows. That is, acceleration, constant speed, deceleration, inversion, acceleration, constant speed, deceleration, inversion, and so on are controlled.
Along with the operation of the motor 6, the carriage 4 repeats reciprocating movement in the main scanning direction, and on the recording paper a from the nozzles of the head unit 2 mounted on the carriage 4 in a constant speed section corresponding to the printing area. Ink droplets are ejected onto the surface. As a result, predetermined characters and images are recorded on the recording paper a by the ink droplets.

The configuration of the head unit 2 shown in FIG. 1 will be described in detail.
As shown in FIG. 2, the head unit 2 includes a large number of heads 20, and each head 20 uses an electrostatic actuator.
As shown in FIG. 2, the head 20 includes a vibration plate 21, an electrostatic actuator 22 that includes the vibration plate 21 and displaces the vibration plate 21, and is filled with ink that is a liquid. A cavity (pressure chamber) 23 in which the internal pressure is increased and decreased, and a nozzle 24 that communicates with the cavity 23 and ejects ink as droplets by increasing and decreasing the pressure in the cavity 23 are provided.

  More specifically, the head unit 2 has a three-layer structure in which a silicon nozzle substrate 26 is stacked on the upper side and a glass substrate 27 is stacked on the lower side with a central silicon substrate 25 interposed therebetween. A cavity 23 and a reservoir 28 communicating therewith are defined between the central silicon substrate 25 and the upper nozzle substrate 26. The reservoir 28 communicates with an ink intake port 29 provided on the glass substrate 27.

Further, a gap 31 is formed between the diaphragm 21 formed by the central silicon substrate 25 and functioning as the bottom plate of the cavity 23 and the individual electrode 30 provided on the glass substrate 27. The diaphragm 21 is connected to the common electrode 32.
Accordingly, the main part of the electrostatic actuator 22 is formed by the diaphragm 21, the individual electrode 30, and the gap 31 formed therebetween, and is applied between the individual electrode 30 and the common electrode 32. It is driven by a drive signal.

  Further, the nozzles 24 for each head 20 formed on the nozzle substrate 26 shown in FIG. 2 are arranged as shown in FIG. 3, for example. In the example of FIG. 3, the arrangement pattern of the nozzles 24 when applied to four colors of ink (yellow Y, magenta M, cyan C, black K) is shown. Further, in FIG. 3, in order to show the nozzles 24 in an easy-to-understand manner, the size of the nozzles 24 is exaggerated and the number is reduced.

  In the ink jet printer 1 having such a head 20, an ink droplet ejection abnormality in which ink droplets are not properly ejected from the nozzles 24 due to causes such as running out of ink, generation of bubbles, clogging (drying), paper dust adhesion, and the like. , So-called dot dropout phenomenon may occur. The paper dust is likely to be generated when the recording paper a made of wood pulp as a raw material comes into frictional contact with a paper feed roller or the like, and is composed of a part of the recording paper a or a fibrous or aggregate thereof. .

Of the causes of ink droplet ejection abnormalities (hereinafter referred to as ejection abnormalities), the wiping process is an effective recovery process when dust or paper dust adheres to the vicinity of the nozzle 24. The wiping process refers to a process of wiping the nozzle surface NP, which is the surface on which the nozzles 24 of the head unit 2 are formed, with the wiper 13 as shown in FIG.
The wiper 13 is lifted from the standby position (FIG. 4A) where the tip of the blade BL made of a flexible rubber member or the like is below the nozzle surface NP, and the blade BL Is disposed so as to be movable between a wiping position (FIG. 4B) in which the tip of the projection protrudes upward from the nozzle surface NP.

  In the operation of the wiping process, as shown in FIG. 4B, first, the wiper 13 is moved upward by a driving device (not shown) from the standby position to the wiping position. Next, as shown in FIG. 4 (c), when the motor 6 is driven and the head unit 2 is moved in the direction of the arrow in FIG. 4 (c), the nozzle BL is moved by the tip of the blade BL which is relatively moved while being bent. Dust, paper dust, etc. adhering to the surface NP are removed.

When the cause of the ejection abnormality is an increase in the viscosity of the ink in the nozzle 24 or the inclusion of bubbles in the nozzle 24, the flushing process or the pump suction process is an effective recovery process.
Here, the flushing process refers to a process in which the head unit 2 is driven to eject ink droplets from the nozzles 24 regardless of the formation of characters and images.
As shown in FIG. 5, the pump suction process covers the nozzle surface NP with a cap 14, drives the tube pump TP, and creates a negative pressure in the cap 14 through the tube PI connected to the cap 14. The process of sucking ink from the nozzles 24. In this pump suction process, the flushing process described above is performed along with the suction by the tube pump TP.

As shown in FIG. 5A, the cap 14 has a capping position in which the tip portion made of a material such as rubber is in close contact with the nozzle surface NP, and the tip portion touches the nozzle surface NP on the lower side in the figure from the capping position. It is arranged to be movable between a standby position (not shown) that does not contact.
In addition, an ink absorber CT that absorbs ink discharged from the nozzles 24 by flushing processing or pump suction processing is disposed inside the cap 14.

In the operation of the pump suction process, first, the cap 14 is moved upward from a standby position to a capping position by a driving device (not shown) (FIG. 5A). Next, suction is performed by rotating the tube pump TP shown in FIG. 5B in the direction R1 in FIG.
In general, in an inkjet printer, head cleaning by the above-described wiping process or pump suction process is performed regularly or irregularly regardless of the occurrence of ejection abnormality. An example of this regular or irregular head cleaning will be described below.
(B) Manual cleaning Manual cleaning is performed by the user arbitrarily instructing head cleaning.
(B) Timer cleaning Timer cleaning is performed by instructing head cleaning when the non-printing state of the inkjet printer continues for a predetermined time.
(C) Initial cleaning after ink cartridge replacement The ink from the replaced ink cartridge is guided to the nozzle through the ink flow path in the head, and the ink jet printer is put into a state suitable for printing.
(D) Cleaning when power is turned on When the power is turned on, it is performed to bring the ink jet printer into a state suitable for printing.
(E) Pass cleaning based on the number of head scans In order to maintain good print quality of the ink jet printer, the cleaning is performed based on the number of head scans (for example, every line of printing, every page, etc.).

As described above, there has been devised to maintain good print quality of the ink jet printer by performing regular or irregular head cleaning.
Here, the details of the ejection abnormality detection principle will be described.
When a driving signal is supplied to the electrostatic actuator 22 shown in FIG. 2 from a driving circuit, which will be described later, the diaphragm 21 is attracted to the individual electrode 30 side by electrostatic attraction force, elastic energy is accumulated, and driving signal is supplied. When is stopped, elastic energy is released. At this time, the diaphragm 21 is returned to the side opposite to the individual electrode 30 side, and the pressure in the cavity 23 increases and further decreases. As a result, a part of the ink filling the cavity 23 is ejected as an ink droplet from the nozzle 24 communicating with the cavity 23.

By a series of operations of the vibration plate 21, it is determined by the acoustic resistance r due to the viscosity of the nozzle 24, the ink intake port 29, or the ink, the inertance m due to the ink weight in the ink flow path, and the compliance c of the vibration plate 21. The diaphragm 21 generates free vibration at the natural vibration frequency. Hereinafter, the free vibration of the diaphragm 21 is referred to as residual vibration.
FIG. 6 shows a calculation model of simple vibration assuming residual vibration of the diaphragm 21. When the step response when the sound pressure P is applied to this calculation model is calculated for the volume velocity u, the following equation can be obtained.

  Here, if ink droplets are normally ejected from the nozzle 24 and there is no change in the acoustic resistance r, inertance m, and compliance c, the residual vibration of the diaphragm 21 always has a constant waveform. FIG. 7 shows the result of the residual vibration waveform obtained when the ink droplets are ejected normally.

However, when the ink droplets are not ejected normally and ejection abnormality occurs, the waveform of the residual vibration of the diaphragm 21 is different from that at the normal time. FIG. 8 shows an example of the experimental result of the residual vibration detection waveform. From the results of this experiment and the calculation model of simple vibrations, we found the following.
(I) When air bubbles are clogged in the ink flow path or the tip of the nozzle 24, the ink weight is reduced by the amount of air bubbles mixed in, the inertance m is reduced, and this is equivalent to a state where the nozzle diameter is increased by the air bubbles. Thus, it can be detected as a characteristic residual vibration waveform in which the acoustic resistance r decreases and the frequency increases (see FIG. 8A).
(II) When ink is dried and ink droplets are no longer ejected from the nozzle 24, the viscosity of the ink near the nozzle increases due to the drying, and the acoustic resistance r increases, resulting in overdamping. It can be detected as a residual vibration waveform (see FIG. 8B).
(III) When dust or paper dust adheres to the nozzle surface NP, the ink oozes out from the nozzle by the paper dust, thereby increasing the ink weight viewed from the vibration plate 21 and increasing the inertance m. Further, the acoustic resistance r is increased by the paper dust fibers adhering to the nozzle 24, and this can be detected as a characteristic residual vibration waveform in which the period becomes larger (the frequency becomes lower) than the period of normal ejection ( (Refer FIG.8 (c)).
(IV) When a residual vibration waveform is detected during the pump suction process, the cycle is larger than the cycle of normal ejection (frequency is low) and smaller than the cycle when dust or paper dust adheres (frequency is high). Features are seen (see FIG. 9). The reason why the period is longer than the normal discharge cycle is that the ink is forcibly discharged from the nozzle 24 by the pump suction, so that the ink adheres to the vicinity of the nozzle 24 and the inertance m increases. This is because the force has an influence on the diaphragm 21. Also, the smaller period than when dust or paper dust adheres is that the increase in inertance m or the degree of influence by the suction force acting on the diaphragm 21 depends on the inertance m and sound when dust or paper dust adheres. This is because the degree of influence is lower than the increase in resistance r.

From the above results, the ejection abnormality of the head 20 can be detected by the mode of residual vibration of the diaphragm 21, and the cause of the ejection abnormality can be specified.
Here, the principle of residual vibration detection will be described.
As shown in FIG. 10, the electrostatic actuator 22 is considered as a capacitor composed of an individual electrode 30 and a diaphragm 21 that have a gap (gap) and face each other. The capacitance C (x) of this capacitor is expressed by the following equation (4).

  Immediately after disconnecting the electrostatic actuator 22 and a drive circuit described later, the charge Q remains in the capacitor. For this reason, the charging voltage Vc of the capacitor is expressed by the following equation (5). The charging voltage Vc changes according to the change in the capacitance C of the capacitor, and the mechanical residual vibration of the diaphragm 21 can be detected as the voltage change.

  Here, S is the facing area of the diaphragm 21 and the individual electrode 30, g is the distance between them (initial gap), ε is the dielectric constant of the gap 31, and x is the diaphragm 21 generated by residual vibration of the diaphragm 21. The amount of displacement from the reference position.

A circuit configuration for detecting an ejection abnormality using the residual vibration detection principle and identifying the cause will be described.
As shown in FIG. 11, the inkjet printer 1 determines whether there is a discharge abnormality and determines whether there is a discharge abnormality, a system controller SC, a drive circuit HD that drives the head 20, a residual vibration detection circuit ZD that detects residual vibration. And a discharge abnormality determination circuit JD for identifying the cause.

  Then, a drive instruction signal for instructing driving of the head 20 is output from the system controller SC to the drive circuit HD. Based on the drive instruction signal from the system controller SC, the drive circuit HD outputs a drive signal for driving the head 20 to the head 20 via the residual vibration detection circuit ZD. Then, after the output of the drive signal, a pause signal that is a Hi level signal is output to a detection timing generation unit TM described later of the residual vibration detection circuit ZD for a predetermined time.

The detection timing generator TM connects the head 20 to the drive circuit HD based on the pause signal from the drive circuit HD and the detection timing setting value stored in the system controller SC, and the vibration waveform described later from the head 20. It manages switching to connection to the detection circuit WD.
When the head 20 and the vibration waveform detection circuit WD are connected, a SW switching signal described later is output to the system controller SC, and a residual vibration pulse described later is output to the discharge abnormality determination unit SP of the discharge abnormality determination circuit JD. To do.

The discharge abnormality determination unit SP determines whether or not there is a discharge abnormality based on the residual vibration pulse from the residual vibration detection circuit ZD, specifies the cause, and outputs a discharge abnormality determination result to the system controller SC.
Further, the determination criterion selection unit CH of the ejection abnormality determination circuit JD performs pump suction processing based on a pump suction execution signal from the system controller SC in a determination reference value for determining the length of the residual vibration cycle. It governs the selection of different reference values depending on whether or not it is implemented.

Here, the specific configuration of each circuit will be described in detail.
As shown in FIG. 12, the residual vibration detection circuit ZD includes a connection changeover switch SW, a detection timing generation unit TM, a vibration waveform detection circuit WD, and a waveform shaping circuit ST.
The connection changeover switch SW switches the connection between the drive circuit HD and the head 20 and the connection between the head 20 and the vibration waveform detection circuit WD. The connection switching by the connection switch SW is performed based on a SW switching signal from a detection timing generation unit TM described later. The connection changeover switch SW connects the head 20 and the vibration waveform detection circuit WD when the SW changeover signal becomes Hi level, and connects the head 20 and the drive circuit HD when the SW changeover signal becomes Lo level.

The detection timing generator TM outputs a SW switching signal to the connection switch SW based on the pause signal from the drive circuit HD and the detection timing setting value stored in the system controller SC, and discharges a reset signal and a Load signal. Output to the abnormality determination circuit JD.
When connected to the head 20 by the connection changeover switch SW, the vibration waveform detection circuit WD outputs the above-described mechanical residual vibration of the diaphragm 21 as a voltage change to the waveform shaping circuit ST.

The waveform shaping circuit ST outputs the output voltage from the vibration waveform detection circuit WD as a residual vibration pulse that is a pulse waveform voltage based on the comparison result with the reference voltage.
Details of the detection timing generation unit TM will be described with reference to FIG.
As shown in FIG. 13, the detection timing generator TM includes a counter CT, a coincidence comparator CR, a latch circuit La1 composed of flip-flop circuits, an AND circuit AN1, an edge detector ED, and a delay circuit DL. And.

The counter CT counts the number of times the pause signal is output from the drive circuit HD, and outputs the result to the coincidence comparator CR.
The coincidence comparator CR outputs a Hi-level set signal to the latch circuit La1 based on the fact that the detection timing set value stored in the system controller SC matches the number of times the pause signal is output.

The latch circuit La1 receives the Hi level set signal from the coincidence comparator CR and outputs a Hi level signal to the AND circuit AN1.
The AND circuit AN1 outputs a Hi level SW switching signal to the connection changeover switch SW and the edge detector ED based on the Hi level output signal from the latch circuit La1 and the Hi level pause signal.

Here, when the pause signal becomes Lo level after the SW switching signal becomes Hi level, the SW switching signal becomes Lo level. Then, the edge detector ED detects the edge at which the SW switching signal has become Lo level, and sends the Load signal that is turned on for a relatively short predetermined time to the ejection abnormality determination circuit JD and the delay circuit DL shown in FIG. Output.
The delay circuit DL outputs a reset signal to the counter CT, the latch circuit La1, and the ejection abnormality determination circuit JD after a predetermined time has elapsed from the input of the Load signal.

Based on this reset signal, the counter CT and the latch circuit La1 are reset.
As shown in FIG. 14, the discharge abnormality determination circuit JD includes a determination criterion selection unit CH and a discharge abnormality determination unit SP. The determination criterion selection unit CH selects either the normal discharge upper limit (T1 + h value) or the recovery reference value (T2 + j value) based on the pump suction execution signal input from the system controller SC, and the selected value Tc Is provided to the comparator CP1. The selector SL selects the normal discharge upper limit value when the pump suction process is not performed, and selects the recovery reference value when the pump suction process is performed.

Here, the normal discharge upper limit value is an upper limit value for determining whether or not the period of residual vibration is normal. This normal discharge upper limit value is determined by adding the allowable value h to the period T1 of the residual vibration obtained in the normal discharge shown in FIG.
The recovery reference value is an upper limit value for determining whether or not the residual vibration period obtained in the state where the pump suction process is being performed is normal, and is allowed for the residual vibration period T2 shown in FIG. It is determined by adding the value j.

The ejection abnormality determination unit SP includes a cycle counter PC, comparators CP1 and CP2, inverters IV1 and IV2, AND circuits AN2 to AN4, and latch circuits La2 to La3.
The period counter PC measures the residual vibration period from the residual vibration pulse signal, and outputs the residual vibration period T to the comparators CP1 and CP2 and the system controller SC as a period count value.

The comparator CP1 compares the residual vibration period T with the selection value Tc of the normal discharge upper limit value and the recovery reference value. When T> Tc, the comparator CP1 outputs a Hi level signal, and when T ≦ Tc. , Lo level signals are output to the inverter IV1 and the AND circuit AN4.
The comparator CP2 compares the residual vibration period T with the input normal discharge lower limit value (T1-h). If T <(T1-h), the Hi level signal T ≧ (T1 -H), the Lo level signal is output to the inverter IV2 and the AND circuit AN3.

The inverters IV1 and IV2 invert the input signals Hi and Lo and output the inverted signals to the AND circuit AN2.
The AND circuits AN2 to AN4 output Hi level signals to the latch circuits La2, La3, and La4 when the signals input to the AND circuits AN2 to AN4 are all at the Hi level.
The latch circuits La2, La3, La4 output the Hi level signals output from the AND circuits AN2, AN3, AN4 to the system controller SC until they are reset by the reset signal input from the detection timing generator TM. To do.

The period counter PC is also reset based on the reset signal.
Here, the flow of signals in the ejection abnormality determination unit SP will be described for each detected mode of residual vibration.
(I) In the case of normal ejection When ink droplets are ejected normally from the nozzle 24, the residual vibration period T in the period counter PC is T1 shown in FIG.

Each of the comparators CP1 and CP2 outputs a Lo level signal because the relationship of T> (T1 + h) and T <(T1-h) is not established.
The AND circuit AN2 receives a Hi level signal inverted from the Lo level by the inverters IV1 and IV2, and outputs a Hi level signal to the latch circuit La2 based on the Hi level Load signal.

The AND circuits AN3 and AN4 receive the Lo level signal from the comparators CP1 and CP2, so that even when the Hi level Load signal is received, the Lo level signal is output to the latch circuits La3 and La4.
Accordingly, only the latch circuit La2 outputs a Hi level signal among the latch circuits La2 to La4. When a Hi level signal is output from the latch circuit La2, this indicates that no ejection abnormality has occurred.

The Hi level signal output from the latch circuit La2 indicates the normal determination result when the normal discharge upper limit (T1 + h value) is selected as the determination reference value by the selector SL, and is used as the determination reference value. When the recovery reference value (T2 + j value) is selected, a nozzle recovery determination result indicating that the performance of ejecting ink droplets from the nozzle 24 has been recovered is shown.
(Ii) When bubbles are mixed When bubbles are mixed from the nozzle 24 and ink droplets are not ejected normally, the residual vibration cycle T in the cycle counter PC is TB (TB <(T1-h) shown in FIG. )).

In this case, the comparator CP1 outputs a Lo level signal, and the comparator CP2 outputs a Hi level signal. Thereafter, the same path as (i) is followed, the latch circuit La2 outputs a Lo level signal, the latch circuit La3 outputs a Hi level signal, and the latch circuit La4 outputs a Lo level signal.
That is, only the latch circuit La3 outputs a Hi level signal. When a Lo level signal is output from the latch circuit La2, this indicates that a discharge abnormality has occurred. When a Hi level signal is output from the latch circuit La3, the cause of the discharge abnormality is the inclusion of bubbles. It shows that.
(Iii) Ink drying or paper dust adhesion When ink droplets are not normally ejected from the nozzle 24 due to ink drying or paper dust adhesion, the residual vibration period T in the period counter PC is shown in FIG. TK and TS shown in (b) and (c).

In this case, the comparator CP1 outputs a Hi level signal, and the comparator CP2 outputs a Lo level signal. Thereafter, the same path as (i) and (ii) is followed. The latch circuit La2 outputs a Lo level signal, the latch circuit La3 outputs a Lo level signal, and the latch circuit La4 outputs a Hi level signal.
That is, only the latch circuit La4 outputs a Hi level signal, indicating that the cause of the ejection abnormality is ink drying or paper dust adhesion.

Here, the flow of the nozzle recovery process will be described.
When the inkjet printer 1 finishes the head cleaning operation described above, the system controller SC executes the nozzle recovery process shown in FIG.
In the nozzle recovery process, first, in step S1, a nozzle is specified and a drive instruction signal is output to the drive circuit HD to drive the head 20, to detect residual vibrations, and to determine a discharge abnormality, and then to step S2. Migrate to

In this step S2, it is determined whether or not a discharge abnormality determination result has been input. If it is determined that it has been input (YES), the process proceeds to step S3, and if it has been determined that it has not been input (NO), Wait for input.
In step S3, the ejection abnormality determination result is stored, and the process proceeds to step S4.
In this step S4, it is determined whether or not a discharge abnormality determination result has been obtained for all the nozzles 24. If it is determined that it has come out (YES), the process proceeds to step S5, and it is determined that it has not come out (NO). Then, the process proceeds to step S1.

In step S5, it is determined based on the discharge abnormality determination result whether or not there is an abnormal discharge nozzle whose determination result is abnormal. If it is determined (YES), the process proceeds to step S6, and there is no (NO). If it is determined, the nozzle recovery process is terminated.
In step S6, one of the ejection abnormality nozzles is selected, it is determined whether or not the stored ejection abnormality determination result is ink drying or paper dust adhesion, and ink drying or paper powder adhesion is determined. If it is determined (YES), the process proceeds to step S7, and if it is determined that the ink is not dried or paper dust is adhered (NO), the process proceeds to step S11.

In step S7, a non-use time TU that is a time when the ink jet printer 1 is not used is read, and the process proceeds to step S8.
In step S8, it is determined whether or not the non-use time TU is less than the predetermined time FT, thereby determining whether the cause of the ejection abnormality is paper dust adhesion or ink drying. If it is determined that the cause of the ejection abnormality is paper dust adhesion (paper dust (YES)), the process proceeds to step S9, and if it is determined that ink is dried (dry (NO)), The process proceeds to S11.

  Here, the reason why it is determined whether or not the non-use time TU is less than the predetermined time FT is to specify whether the cause of the ejection abnormality is ink drying or paper dust adhesion. That is, in the case of ink drying and paper dust adhesion, it is difficult to specify which is the residual vibration period TK and TS shown in FIGS. 8B and 8C. Therefore, it is determined whether the non-use time TU of the inkjet printer 1 is less than the predetermined time FT or more than the FT, and when the non-use time TU is less than the predetermined time FT, the cause of the ejection abnormality is paper dust adhesion. It is determined that the ink is dry when the non-use time TU is equal to or longer than the predetermined time FT.

When the determination result in step S8 is paper dust, the wiping process is performed in step S9, and then the process proceeds to step S10.
In step S11, the pump suction execution signal for the tube pump TP is set to Hi level to start pump suction, and the process proceeds to step S12.
In step S12, after performing recovery determination processing described later, the process proceeds to step S13. In step S13, the pump suction execution signal is set to Lo level to stop pump suction, and the process proceeds to step S10.

In step S10, it is determined whether or not the nozzle recovery process has been completed for all ejection abnormal nozzles. If it is determined that the nozzle recovery process has ended (YES), the nozzle recovery process is ended, and it is determined that the nozzle recovery process has not ended (NO). Then, the process proceeds to step S14.
In step S14, the next abnormal discharge nozzle is selected and the process proceeds to step S6.
In the recovery determination process in step S12, as shown in FIG. 16, first, in step S31, the drive instruction signal is output to drive the head 20, and then the process proceeds to step S32.

  In this step S32, it is determined whether or not the SW switching signal input from the detection timing generation unit TM has become Hi level. If it is determined that it is (YES), the process proceeds to step S34 (not) ( If NO, it is determined in step S33 whether or not a predetermined time has elapsed. If the predetermined time has not elapsed, the process waits until the predetermined time has elapsed, and if the predetermined time has elapsed, the process proceeds to step S31.

In step S34, it is determined whether or not a recovery determination result has been obtained for the abnormal ejection nozzle. If it is determined that the nozzle has been discharged (YES), the process proceeds to step S35, and if it is determined that it has not been discharged (NO), the determination Wait for the result.
In step S35, it is determined whether or not the recovery determination result has been recovered. If it is determined that the recovery has been recovered (YES), the process proceeds to step S39, and the result that the ejection abnormal nozzle has recovered is determined. After saving, the process exits the recovery determination process (return), and if it is determined that it has not recovered (NO), the process proceeds to step S36.

In this step S36, by adding 1 to the variable L, the number of times L determined as NO in step S35 is counted, and the process proceeds to step S37.
In this step S37, it is determined whether or not the value assigned to the variable L matches the upper limit number Ls of the number of times of performing recovery determination for one ejection abnormal nozzle, and it is determined that they match (YES). Then, the process proceeds to step S38, and if it is determined that they do not match (NO), the process proceeds to step S31.

In step S38, after substituting 0 for the variable L, the process proceeds to step S39. In step S39, even if the number L of recovery determinations reaches the upper limit number Ls, the discharge abnormal nozzle has not recovered. After saving, exit the recovery judgment process (return).
Next, in order to simplify the description of the operation of the above-described embodiment based on the timing chart shown in FIG. 17, taking the case of bubble mixing as an example, in the example, one nozzle is abnormally discharged due to bubble mixing. A case will be described.

  When the head cleaning operation described above is completed, the system controller SC executes a nozzle recovery process shown in FIG. 15 and outputs a drive instruction signal to a predetermined circuit 24 to the drive circuit HD. Then, the drive circuit HD outputs the drive signal (A) shown in FIG. 17 to the residual vibration detection circuit ZD, and sets the detection timing set value to 1, which is used as the coincidence comparator CR of the detection timing generation unit TM. Output to. At this time, the connection changeover switch SW shown in FIG. 12 connects the drive circuit HD and the head 20, and the electrostatic actuator 22 of the head 20 is driven by the drive signal.

  Further, after outputting the drive signal (A), the drive circuit HD switches the pause signal (B) shown in FIG. 17 to the Hi level for a predetermined time. When the number of times that the pause signal (B) has reached the Hi level reaches the detection timing set value, the SW switching signal (C) shown in FIG. 17 output from the detection timing generator TM is switched to the Hi level, and the connection changeover switch SW Thus, the head 20 and the vibration waveform detection circuit WD are connected.

While the SW switching signal (C) is at the Hi level, the residual vibration waveform (D) shown in FIG. 17 is detected by the vibration waveform detection circuit WD, and this residual vibration waveform (D) is detected by the waveform shaping circuit ST. The waveform is shaped into a residual vibration pulse (E).
Based on the residual vibration pulse (E), the residual vibration period T from the rise of the first residual vibration pulse P1 to the rise of the next residual vibration pulse P2 is counted by the period counter PC, for example, a clock pulse of a predetermined period. Is measured as the cycle count value (F), and this is determined by the comparators CP1 and CP2 based on the normal discharge upper and lower limit values (T1 ± h value). In this case, assuming that bubbles are mixed, when the residual vibration period T is less than the normal discharge lower limit (T1-h value) as shown in FIG. A level comparison signal is output to the AND circuit AN3.

On the other hand, when the pause signal (B) output from the drive circuit HD is switched to the Lo level, the detection timing generation unit TM switches the SW switching signal (C) to the Lo level, and the ejection abnormality determination unit SP and The Load signal (H) output to the delay circuit DL is switched to the Hi level for a predetermined time.
Since this Load signal (H) is supplied to the AND circuit AN3, the output of the AND circuit AN3 becomes Hi level, which is supplied to the latch circuit La3 and latched, and the Hi level output signal of the latch circuit La3 is bubbled. Is output to the system controller SC as a cause identification signal (I) representing the contamination of the system.

  The delay circuit DL to which the Load signal (H) is input is delayed for a predetermined time after the Load signal (H) is switched to the Hi level, and is output to the counter CT, the period counter PC, and the latch circuits La1 to La4. The reset signal (G) is switched to the Hi level. Based on the reset signal (G) becoming Hi level, the counter CT, the cycle counter PC, and the latch circuits La1 to La4 are reset, and the cause identification signal (I) becomes Lo level.

  Since the cause of the ejection abnormality is air bubble mixing, the system controller SC switches the pump suction execution signal (J) output to the pump drive unit (not shown) and the determination criterion selection unit CH to the Hi level and starts the pump suction process. Then, the criterion for determining the residual vibration period T is switched to the recovery reference value (T2 + j value). The pump suction process is performed while the pump suction execution signal (J) is at the Hi level.

When the pump suction execution signal (J) is switched to the Hi level, the process proceeds to the recovery determination process described above, and the system controller SC outputs a drive instruction signal to the drive circuit HD and sets the detection timing set value to 2. This is output to the coincidence comparator CR of the detection timing generator TM.
The drive circuit HD outputs the drive signal (A) to drive the electrostatic actuator 22 of the head 20 and switches the pause signal (B) to the Hi level for a predetermined time, as described above. The number of times that the pause signal (B) becomes Hi level is counted by the counter CT, and when the counted number reaches the detection timing set value, the SW switching signal (C) becomes Hi level as described above. Thus, the residual vibration waveform (D) is detected, and the residual vibration period T is measured based on the residual vibration pulse (E).

At this time, when the residual vibration period T measured as the period count value (F) is not less than the normal discharge lower limit value (T1-h value) and not more than the recovery reference value (T2 + j value), the ejection abnormal nozzle is recovered. The nozzle recovery signal (K) indicating this is switched to the Hi level. The nozzle recovery signal (K) is output from the latch circuit La2 of the ejection abnormality determination unit SP.
Then, the nozzle recovery signal (K) is switched to the Lo level based on the Hi level reset signal (G). Thereafter, the pump suction execution signal (J) becomes Lo level, the pump suction is stopped, and the criterion of the residual vibration period T is switched to the normal discharge upper limit value (T1 + h value).

  In the example shown in FIG. 17, a case is shown in which the determination result in the first recovery determination after the pump suction is started is that the ejection abnormal nozzle has recovered, but the determination result in the first recovery determination is recovered. If the residual vibration cycle T is less than the normal discharge lower limit (T1-h value), the Hi-level output signal from the latch circuit La3 is used as the cause identification signal (I) representing the mixing of bubbles. Are output to the system controller SC.

Then, the system controller SC counts the number L of times when it is determined that the ejection abnormal nozzle has not recovered, and repeats the recovery determination process until the number L reaches the upper limit number Ls.
Even if the number L of times when it is determined that the ejection abnormal nozzle has not recovered reaches the upper limit number Ls, if the determination result of the recovery determination does not result in the recovery of the ejection abnormal nozzle, the recovery determination process ends.

  If the cause of the ejection abnormality is ink drying, the residual vibration period T measured as the period count value (F) exceeds the normal ejection upper limit (T1 + h value), and the comparator CP1 outputs a high level comparison signal. Is output to the AND circuit AN4. The output of the AND circuit AN4 becomes Hi level based on the Hi level Load signal (H), which is supplied to the latch circuit La4, and the reason why the Hi level output signal of the latch circuit La4 indicates ink drying. The specific signal (I) is output to the system controller SC. Thereafter, similarly to the above-described content, the pump suction process is started and the process proceeds to the recovery determination process.

  Further, when the discharge abnormality does not occur and is normal, the residual vibration cycle T measured as the cycle count value (F) is within the range of the normal discharge upper and lower limit values (T1 ± h value), and the comparator CP1 and The Lo level comparison signal output from CP2 is converted to Hi level by inverters IV1 and IV2, and input to AND circuit AN2. The output of the AND circuit AN2 becomes Hi level based on the Hi level Load signal (H), which is supplied to the latch circuit La2. The Hi-level output signal of the latch circuit La2 is output to the system controller SC as a normal determination result signal indicating that the nozzle 24 is normal. Thereafter, the nozzle recovery process is terminated without proceeding to the recovery determination process.

  In the first embodiment, the discharge abnormality determination circuit JD corresponds to the discharge abnormality detection means and the recovery determination means, the wiper 13 corresponds to the wiping means as the discharge performance recovery means, the cap 14, the tube PI, and the tube pump. TP corresponds to suction means as discharge performance recovery means, system controller SC corresponds to suction control means, residual vibration detection circuit ZD corresponds to residual vibration detection means, period counter PC corresponds to period measurement means, Comparators CP1 and CP2 correspond to the period determining means.

As described above, when a discharge abnormality is detected by the discharge abnormality determination circuit JD and the pump suction process by the tube pump TP is started, the recovery of the discharge abnormality nozzle is monitored while the ink is being sucked, and this monitoring is performed. The pump suction process can be stopped based on the result.
Therefore, it is possible to omit the time required for the nozzle inspection conventionally performed after the pump suction processing, and it is possible to eliminate the situation where the pump suction processing is required again by this nozzle inspection.

In addition, it is possible to grasp at an early stage that the abnormal ejection nozzle has recovered, and it is possible to keep the amount of ink sucked unnecessarily after the recovery extremely low, and there is a possibility that the abnormal ejection nozzle will recover due to a failure or the like. If not, the pump suction process is stopped at a predetermined limit, so that it is possible to suppress the wasteful consumption of ink thereafter.
Also, if the pump suction process is performed in the case of abnormal discharge due to the adhesion of paper dust, the ink consumption is increased and the effect of nozzle recovery is low, which is not appropriate. Therefore, in this embodiment, in the case of an ejection abnormality due to adhesion of paper dust, the wiping process by the wiper 13 is performed, and wasteful consumption of ink is suppressed.

In addition, the ejection abnormality determination circuit JD includes a determination reference selection unit CH, and can select different determination reference values depending on whether the pump suction processing is performed or not. ing. Accordingly, it is possible to perform the two processes of detecting the ejection abnormality and determining the recovery of the droplet ejection performance by one ejection abnormality determination circuit JD.
In the first embodiment, the repetition limit of the recovery determination performed for one ejection abnormal nozzle is the number of repetitions of the recovery determination for the ejection abnormal nozzle, but the elapsed time since the start of the pump suction process It can also be.

  In this case, the elapsed time from the start of the pump suction process is measured by a timer, and the recovery determination is not repeated after a predetermined time or more has elapsed. Specifically, as shown in FIG. 18, the recovery determination process includes step S41 for starting timer Tm0, step S42 for determining whether or not the time measured by timer Tm0 is equal to or longer than a predetermined time, and timer Step S43 for resetting Tm0.

The recovery determination process shown in FIG. 18 is the same as the recovery determination process shown in FIG. 16, except that steps S36 to S38 are omitted and steps S41 to S43 are included. Steps corresponding to those in FIG. 16 are denoted by the same reference numerals and description thereof is omitted.
As shown in FIG. 18, in the recovery determination process, first, in step S41, the timer Tm0 is activated and the process proceeds to step S31. Then, as described above, the process proceeds to step S42 through the processes of steps S31 to S35.

In this step S42, it is determined whether or not the time measured by the timer Tm0 is equal to or longer than the predetermined time. If it is determined that the time is equal to or longer than the predetermined time (YES), the process proceeds to step S43 and is less than the predetermined time. If it is determined as (NO), the process proceeds to step S31.
In step S43, the timer Tm0 is reset, and then the process proceeds to step S39. In step S39, the result that the ejection abnormal nozzle has not recovered even after a predetermined time has been saved is stored, and the recovery determination process is exited. (return).

  In the first embodiment, the SW switching signal is output from the detection timing generation unit TM to the system controller SC in the circuit configuration shown in FIG. 11, but this can be omitted. In this case, step S32 of the recovery determination process shown in FIGS. 16 and 18 includes a step of counting the number of times of outputting the drive instruction signal and a step of determining whether or not the counted number of times has reached a predetermined number. replace. If the counted number reaches the predetermined number, the process proceeds to step S34, and if not, the process proceeds to step S33.

A second embodiment of the present invention will be described with reference to FIGS.
In the ink jet printer 1 according to the second embodiment, in the circuit configuration shown in FIG. 11, the above-described system controller SC, detection timing generation unit TM, and ejection abnormality determination circuit JD are omitted, and arithmetic processing is performed instead. The configuration is the same as that of the first embodiment except that the unit CPU is provided, and the same reference numerals are given to the corresponding parts to those in FIGS. 11 and 12, and the description thereof is omitted.

As shown in FIG. 19, the arithmetic processing unit CPU outputs a pump suction execution signal, a drive instruction signal, and a SW switch signal to the motor drive circuit MD, the drive circuit HD, and the connection switch SW, respectively.
The motor drive circuit MD drives the pump drive motor PM that drives the tube pump TP based on the pump suction execution signal.

In addition, the arithmetic processing unit CPU receives the residual vibration pulse from the waveform shaping circuit ST and performs the nozzle recovery process.
In the inkjet printer 1 according to the second embodiment, when the above-described head cleaning operation is completed, the arithmetic processing unit CPU executes a nozzle recovery process shown in FIG.
First, in step S51, the nozzle 24 for determining whether or not there is a discharge abnormality is selected, and the process proceeds to step S52.

In this step S52, the residual vibration detection process mentioned later is implemented and it transfers to step S53.
In this step S53, it is determined whether or not the cause of the discharge abnormality is the mixing of bubbles by determining whether or not the residual vibration period T is less than the normal discharge lower limit (T1-h), and the bubbles are bubbles. If it is determined (YES), the process proceeds to step S57 and the result that the cause is a bubble is stored. Then, the process proceeds to step S58, and if it is determined that the bubble is not (NO), the process proceeds to step S54. .

  In step S54, it is determined whether or not the cause of the ejection abnormality is adhesion of paper dust or ink drying by determining whether or not the residual vibration period T exceeds the normal ejection upper limit (T1 + h). If it is determined that it is powder or dry (YES), the process proceeds to step S55, and if it is determined that it is not paper powder or dry (NO), the process proceeds to step S57, and an abnormal discharge occurs in the nozzle 24. If the result of normality is saved, the process proceeds to step S58.

In step S55, the unused time TU is read, and the process proceeds to step S56.
In step S56, it is determined whether or not the non-use time TU is less than the predetermined time FT, thereby determining whether the cause of the ejection abnormality is paper dust adhesion or ink drying. Then, if it is determined that the cause of the ejection abnormality is adhesion of paper dust (paper dust (YES)), the process proceeds to step S57, where the result that the cause is paper dust is stored, and the ink is dried ( If it is determined that the process is dry (NO), the process proceeds to step S57, the result that the cause is dry is stored, and the process proceeds to step S58.

In step S58, it is determined whether or not the ejection abnormality determination has been completed for all the nozzles. If it is determined that the ejection abnormality has been completed (YES), the process proceeds to step S60, and if it has been determined that it has not been completed (NO). Control goes to step S59.
In step S59, the next determination nozzle is selected and the process proceeds to step S52.
In step S60, the discharge abnormality determination result is read, and the process proceeds to step S61.

In this step S61, it is determined whether or not there is an abnormal ejection nozzle. If it is determined (YES), the process proceeds to step S62, and if it is determined that there is not (NO), the nozzle recovery process is terminated.
In step S62, an abnormal discharge nozzle is designated and the process proceeds to step S63.
In this step S63, it is determined whether or not the discharge abnormality determination result is paper dust. If it is determined that the paper is dust (YES), the process proceeds to step S72 to perform the wiping process and then to step S70. If it is determined that it is not paper dust (NO), the process proceeds to step S64.

In step S64, the pump suction execution signal is set to Hi level to start pump suction, and the process proceeds to step S65.
In step S65, the timer Tm2 is activated and the process proceeds to step S66.
In step S66, it is determined whether or not the time measured by the timer Tm2 has reached a predetermined time. If it is determined that the time has reached (YES), the process proceeds to step S67, and it is determined that the time has not been reached (NO). Then, it waits until a predetermined time is reached.

Here, the reason why the timer Tm2 is activated in step S65 and the time is determined in step S66 is to perform the pump suction process for a predetermined time.
In step S67, the timer Tm2 is reset and the process proceeds to step S68.
In this step S68, after performing the recovery determination process described later, the process proceeds to step S69, the pump suction execution signal is set to Lo level, the pump suction is stopped, and the process proceeds to step S70.

In step S70, it is determined whether or not the nozzle recovery process has been completed for all ejection abnormal nozzles. If it is determined that the nozzle recovery process has ended (YES), the nozzle recovery process is ended, and it is determined that the nozzle recovery process has not ended (NO). If it does, it will transfer to step S71, and after selecting the next abnormal discharge nozzle, it will transfer to step S64.
In the residual vibration detection process in step S52, as shown in FIG. 21, first, in step S91, the detection timing setting value is read, and the process proceeds to step S92.

In step S92, the drive instruction signal is output to the drive circuit HD, and the electrostatic actuator 22 is driven so that the ink droplets are ejected from the nozzles 24. Then, the process proceeds to step S93.
In step S93, 1 is added to the variable N to count the number of times step S92 is performed, and the process proceeds to step S94.

In step S94, it is determined whether or not the value assigned to the variable N matches the detection timing set value Ns. If it is determined that the value matches (YES), the process proceeds to step S95, and does not match. If it is determined as (NO), the process proceeds to step S92.
In step S95, 0 is substituted into the variable N and the process proceeds to step S96.
In step S96, the SW switching signal is set to the Hi level, and the connection switching switch SW is switched to the connection between the head 20 and the vibration waveform detection circuit WD, and the process proceeds to step S97.

In step S97, the timer Tm1 is activated and the process proceeds to step S98.
In this step S98, it is determined whether or not the rising edge of the first residual vibration pulse P1 has occurred, and if it is determined (YES), the process proceeds to step S99 and is determined not (NO). Then, it waits until it turns on.
In step S99, the timer Tm3 is activated and the process proceeds to step S100.

In this step S100, it is determined whether or not the rising edge of the next residual vibration pulse P2 has occurred. If it is determined that it is (YES), the process proceeds to step S102, and it is determined that it is not (NO). Then, the process proceeds to step S101.
In step S101, it is determined whether or not the time measured by the timer Tm1 has reached a predetermined time. If it is determined that the time has reached (YES), the process proceeds to step S102, and it is determined that the time has not been reached (NO). Then, the process proceeds to step S100.

In step S102, the timer Tm3 is stopped, and then the process proceeds to step S103. The count value of the timer Tm3 is stored as the residual vibration period T, and the process proceeds to step S104.
Here, the timer Tm1 is started in step S97, and when the time of the timer Tm1 reaches a predetermined time in step S101, the timer Tm3 is stopped because the residual vibration is shown in FIGS. 8B and 8C. This is to cope with the fact that the rising edge of the next residual vibration pulse P2 does not occur and the period T cannot be clearly detected.

In step S104, the SW switching signal is set to Lo level to switch the connection switching switch SW to the connection between the head 20 and the drive circuit HD, and the process proceeds to step S105.
In step S105, the timers Tm1 and Tm3 are reset, and the residual vibration detection process is exited (return).
In the recovery determination process in step S68 shown in FIG. 20, as shown in FIG. 22, first, in step S111, the residual vibration detection process shown in FIG. 21 is performed, and the process proceeds to step S112.

In this step S112, it is determined whether or not the residual vibration period T is less than the normal discharge lower limit (T1-h). If it is determined that the residual vibration period T is less than the normal discharge lower limit (YES), the process proceeds to step S114. If it is determined that the value is equal to or higher than the normal discharge lower limit (NO), the process proceeds to step S113.
In this step S113, it is determined whether or not the residual vibration period T exceeds the recovery reference value (T2 + j). If it is determined that the residual vibration period T has exceeded the recovery reference value (YES), the process proceeds to step S114 and is less than or equal to the recovery reference value. If it is determined as (NO), the process proceeds to step S117 to save the result that the ejection abnormal nozzle has recovered, and then exits the recovery determination process (return).

In step S114, by adding 1 to the variable L, the number of times L determined as YES in step S112 or the number of times L determined as YES in step S113 is counted, and the process proceeds to step S115.
In this step S115, it is determined whether or not the value assigned to the variable L matches the upper limit number Ls of the number of times of performing the recovery determination for one ejection abnormal nozzle, and it is determined that they match (YES). Then, the process proceeds to step S116, and if it is determined that they do not match (NO), the process proceeds to step S111.

In step S116, after substituting 0 for the variable L, the process proceeds to step S117. In step S117, even if the number of times L for performing the recovery determination reaches the upper limit number Ls, the discharge abnormal nozzle has not recovered. After saving, exit the recovery judgment process (return).
In the second embodiment, the arithmetic processing unit CPU corresponds to the discharge abnormality detection means, the recovery determination means, and the suction control means as an electronic computer. The connection changeover switch SW, the vibration waveform detection circuit WD, and the waveform shaping circuit ST include It corresponds to the residual vibration detection means.

In FIG. 20, the processes in steps S53 to S56 correspond to the ejection abnormality detection step, the process in step S64 corresponds to the suction start step, and the process in step S69 corresponds to the suction stop step.
In FIG. 22, the processes in steps S112 to S115 correspond to a recovery determination step.

Further, the process of the discharge abnormality detection step corresponds to the discharge abnormality detection means, the process of the suction start step and the suction stop step corresponds to the suction control means, and the process of the recovery determination step corresponds to the recovery determination means.
As described above, the same effects as those of the first embodiment can be obtained, and the circuit configuration can be simplified as compared with the first embodiment.

In the second embodiment, the repetition limit of the recovery determination performed for one ejection abnormal nozzle is the number of repetitions of the recovery determination for that ejection abnormal nozzle, but the elapsed time since the start of the pump suction process It can also be.
In this case, the elapsed time from the start of the pump suction process is measured by a timer, and the recovery determination is not repeated after a predetermined time or more has elapsed. Specifically, as shown in FIG. 23, the recovery determination process includes a step S121 for starting the timer Tm4, a step S122 for determining whether or not the time measured by the timer Tm4 is a predetermined time or more, and a timer Step S123 for resetting Tm4.

The recovery determination process shown in FIG. 23 is the same as the recovery determination process shown in FIG. 22, except that steps S114 to S116 are omitted and steps S121 to S123 are included. Steps corresponding to those in FIG. 22 are denoted by the same reference numerals and description thereof is omitted.
As shown in FIG. 23, in the recovery determination process, first, in step S121, the timer Tm4 is activated and the process proceeds to step S111. Then, as described above, the process proceeds to step S122 through the processes of steps S111 to S113.

In this step S122, it is determined whether or not the time measured by the timer Tm4 is equal to or longer than the predetermined time. If it is determined that the time is equal to or longer than the predetermined time (YES), the process proceeds to step S123 and is less than the predetermined time. If it is determined as (NO), the process proceeds to step S111.
In step S123, the timer Tm4 is reset, and then the process proceeds to step S117. In step S117, the result that the ejection abnormal nozzle has not recovered even after a lapse of a predetermined time is stored, and then the recovery determination process is exited. (return).

In FIG. 23, the processes in steps S112, S113, and S122 correspond to the recovery determination step.
In the first and second embodiments, the head 20 that drives the electrostatic actuator 22 to apply pressure to the ink has been described as an example. However, the present invention is not limited to this, and a piezoelectric element such as a piezoelectric element is used. A head that applies pressure to the ink may be used.

As a head using this piezo element, there are a laminated actuator in which piezo elements are stacked, a unimorph actuator having a configuration in which a piezo element is sandwiched between upper and lower electrodes, and the like. In addition, as a driving mode of the piezo element, there is a shear mode actuator using shear mode deformation.
Since the piezoelectric element generates a voltage by being deformed, various heads using the above-described piezoelectric element can detect a voltage generated by the piezoelectric element and obtain a residual vibration waveform.

FIG. 2 is a plan view illustrating a schematic configuration of the ink jet printer according to the first embodiment. Sectional drawing explaining the structure of the head of an inkjet printer. The top view explaining the arrangement | sequence of the nozzle of a head unit. The figure explaining the structure of a wiper and a wiping process. The figure explaining the structure of a pump and a pump suction process. The circuit diagram which shows the calculation model of the simple vibration which assumed the residual vibration of the diaphragm. Residual vibration waveform when ink droplets are ejected normally. Residual vibration waveform when abnormal discharge occurs. Residual vibration waveform when nozzle recovers during pump suction process. The figure explaining the detection principle of the residual vibration of a diaphragm. FIG. 3 is a diagram illustrating a circuit configuration of the ink jet printer according to the first embodiment. The figure explaining the structure of a residual vibration detection circuit. The figure explaining the structure of a detection timing generation part. The figure explaining the structure of a discharge abnormality determination circuit. The figure which shows the flow of the nozzle recovery process in 1st Embodiment. The figure which shows the flow of the recovery determination process in 1st Embodiment. The timing chart which shows the example which discharge abnormality recovers by a pump suction process. The figure which shows the other example of the flow of the recovery determination process in 1st Embodiment. The figure explaining the circuit structure of the inkjet printer in 2nd Embodiment. The figure which shows the flow of the nozzle recovery process in 2nd Embodiment. The figure which shows the flow of a residual vibration detection process. The figure which shows the flow of the recovery determination process in 2nd Embodiment. The figure which shows the other example of the flow of the recovery determination process in 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inkjet printer, 2 ... Head unit, 13 ... Wiper, 14 ... Cap, 21 ... Diaphragm, 22 ... Electrostatic actuator, 23 ... Cavity, 24 ... Nozzle, PI ... Tube, TP ... Tube pump, ZD ... Residual Vibration detection circuit, JD: Discharge abnormality determination circuit, PC: Period counter, CP1, CP2 ... Comparator, CPU ... Arithmetic processing unit

Claims (11)

A droplet discharge device that discharges liquid as droplets from a nozzle,
A head unit having a plurality of the nozzles;
A discharge abnormality detecting means for detecting, for each nozzle of the head unit, a droplet discharge abnormality in which the droplets are not properly discharged from the nozzle;
A discharge performance recovery means for recovering the droplet discharge performance of discharging the droplets of the nozzle based on the detection of the droplet discharge abnormality by the discharge abnormality detection means;
The discharge performance recovery means includes a suction means for sucking the liquid from the nozzle, a recovery determination means for determining a recovery status of the droplet discharge performance of the nozzle in a liquid suction state by the suction means, and the recovery determination Suction control means for controlling the suction means based on the determination result of the means,
The recovery determination means determines the recovery status when the recovery status determination result indicates that the droplet discharge performance has not recovered, and the determination result indicates that the droplet discharge performance has recovered. The liquid droplet ejection apparatus is characterized in that it repeats within a predetermined limit.   The droplet discharge apparatus according to claim 1, wherein the predetermined limit is set by the number of times the recovery determination unit repeats the determination of the recovery status.   The droplet discharge apparatus according to claim 1, wherein the predetermined limit is set by an elapsed time since the suction by the suction unit is started.   The suction control unit determines that the determination result of the recovery determination unit indicates that the droplet discharge performance has recovered, and that the determination result of the recovery status is within the predetermined limit. 4. The droplet discharge device according to claim 2, wherein the suction by the suction unit is stopped when any of the cases is not recovered. 5. The discharge performance recovery means further comprises wiping means for wiping the nozzle surface on which the nozzles are arranged with a wiper,
5. The apparatus according to claim 1, wherein either the suction unit or the wiping unit is selected in accordance with a mode of the droplet discharge abnormality detected by the discharge abnormality detection unit. The droplet discharge device according to claim 1. The head unit includes a vibration plate, an actuator for displacing the vibration plate, and a liquid filled therein, and the displacement of the vibration plate increases or decreases the internal pressure to discharge the liquid as droplets from the nozzle. A cavity to be
The recovery determination means includes residual vibration detection means for detecting residual vibration of the diaphragm when the actuator is driven to eject the droplet from the nozzle and the diaphragm is displaced. 6. The apparatus according to claim 1, wherein the recovery state of the droplet discharge performance is determined based on a mode of the residual vibration detected by a vibration detection unit. The liquid droplet ejection apparatus described.   The recovery determination unit includes a cycle measurement unit that measures a cycle of the residual vibration, and a cycle determination unit that determines whether or not the measured cycle is within a normal range. 6. A droplet discharge device according to item 6. A droplet discharge performance recovery method for recovering the droplet discharge performance of discharging a droplet of a nozzle that discharges liquid as a droplet,
A discharge abnormality detecting step of detecting, for each nozzle of the head unit having a plurality of the nozzles, a droplet discharge abnormality in which the droplets are not properly discharged from the nozzle;
A suction start step for starting driving of a suction means for sucking the liquid from the nozzle based on detection of the droplet discharge abnormality;
In the liquid suction state by the suction means, the recovery status of the droplet discharge performance of the nozzle is determined, and when the determination result of the recovery status is that the droplet discharge performance has not recovered, the determination is A recovery determination step that repeats within a predetermined limit until the determination result is that the droplet discharge performance is recovered; and
When the determination result in the recovery determination step is a recovery of the droplet discharge performance, and the determination result is not the recovery of the droplet discharge performance within the predetermined limit And a suction stop step for stopping the driving of the suction means.   In the recovery determination step, the residual vibration of the diaphragm after the actuator that displaces the diaphragm included in the head unit is driven a predetermined number of times so as to eject the droplet from the nozzle is detected, and the detected 9. The droplet discharge performance recovery method according to claim 8, wherein whether or not the droplet discharge performance has been recovered is determined based on a period of residual vibration. A droplet discharge performance recovery program for causing a computer to execute a droplet discharge performance recovery process for recovering the droplet discharge performance of discharging the droplet of the nozzle that discharges the liquid as a droplet,
A discharge abnormality detecting step of detecting, for each nozzle of the head unit having a plurality of the nozzles, a droplet discharge abnormality in which the droplets are not properly discharged from the nozzle;
A suction start step for starting driving of a suction means for sucking the liquid from the nozzle based on detection of the droplet discharge abnormality;
In the liquid suction state by the suction means, the recovery status of the droplet discharge performance of the nozzle is determined, and when the determination result of the recovery status is that the droplet discharge performance has not recovered, the determination is A recovery determination step that repeats within a predetermined limit until the determination result is that the droplet discharge performance is recovered; and
When the determination result in the recovery determination step is a recovery of the droplet discharge performance, and the determination result is not the recovery of the droplet discharge performance within the predetermined limit And a suction stop step for stopping the driving of the suction means.   In the recovery determination step, the residual vibration of the diaphragm after the actuator that displaces the diaphragm included in the head unit is driven a predetermined number of times so as to eject the droplet from the nozzle is detected, and the detected 11. The droplet discharge performance recovery program according to claim 10, wherein it is determined whether or not the droplet discharge performance has been recovered based on a period of residual vibration.

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