JP2006088391A - Failure prediction system of inkjet recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure prediction system of an inkjet recording head capable of accurately predicting a critical time for compensation by a compensation means. <P>SOLUTION: A failure detection section 22 detects a failed nozzle whose discharge of ink drops becomes abnormal, outputs failure information concerning the failed nozzle such as failure time, a faulty position, a failure mode and the like to a failure information memory 30. A failure prediction data base section 34 stores failure prediction data base D. The failure prediction data base D stores data to make a judgment on a failure mode from a characteristics value detected by the failure detection section 22 and statistical data for every failure mode. The failure time prediction section 36 predicts a complete failure time when a paper width head 14 completely fails on the basis of information stored in the failure information memory 30, a manufacturing information section 32, and the failure prediction data base section 34. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inkjet recording head failure prediction system that predicts failure of an inkjet recording head that includes a plurality of ink ejection nozzles that eject ink droplets according to image information.

  Inkjet recording devices that eject ink droplets from fine ink ejection nozzles and record images on recording media are easier to reduce in size, cost, and color than other types of recording devices. It has features such as low noise, low power consumption and low running cost. On the other hand, since the ink jet recording apparatus is equipped with a large number of fine ink ejection nozzles, each of the nozzles is liable to fail and the reliability of the entire apparatus is low. Particularly, in recent years, as the recording speed of the ink jet recording apparatus is increased, the ink jet recording head has been provided with a larger number of ink ejection nozzles, and the probability of occurrence of a failure as the entire ink jet recording head has increased.

  The loss to the customer in the event of a failure is that the printer stops operating until the repair. For this reason, it is conceivable to issue a warning that recommends replacement before failure occurs and to prevent the inkjet recording apparatus from stopping by replacing the inkjet recording head before failure.

  Conventionally, an ink jet recording head replacement time warning has been made based on information on the number of printed dots. In other words, the manufacturer's guaranteed lifetime is calculated by adding the margin for the actual customer use environment and the margin for the safety factor to the result of the life evaluation test of the inkjet recording head obtained at the development stage of the inkjet recording head, A warning was issued based on the calculation result. Therefore, for the worst usage environment and safety factor, in the average usage state, a replacement time warning is displayed even though there is a considerable margin before failure occurs.

  By the way, as another method for reducing the non-operation period of the ink jet recording apparatus, there is a method of continuing printing while compensating for a failure even when a failed nozzle occurs, and many techniques have been proposed.

  For example, as one of the methods, a small spare head is provided, the small head is moved to the nozzle failure portion, and the failure portion is printed instead of the failure nozzle (see Patent Document 1). This method is a method in which a defective portion can be completely repaired by printing with a spare head, and image quality and printing speed are not reduced.

  As another method, when a failed nozzle occurs in an inkjet recording head that can modulate the dot diameter, printing is performed by ejecting ink droplets with a large dot diameter from the nozzles on both sides of the failed nozzle to print. There is a method of making the white muscles caused by the inconspicuous. According to this method, a spare nozzle is not required and the printing speed is not reduced.

  As another method, in an inkjet recording apparatus capable of color printing, when a failure occurs in a black inkjet recording head, there is a method in which the failed portion is compensated with process black that is printed with a color inkjet recording head. This method is effective only for black failures, but does not require a spare nozzle and does not cause a decrease in printing speed.

  In addition, as another method, there is a method of supplementing the failed nozzle portion by multi-scan. In this method, paper is fed in the sub-scanning direction, which is shorter than the width of the ink jet recording head, and the print of the portion missing by the failed nozzle is printed by another ink discharge nozzle. There are many printers that perform multi-scan for error diffusion in order to reduce the characteristic variation of each ink ejection nozzle even in the normal case where no failed nozzle is generated, and this method can be implemented simply by correcting the data for the failed nozzle It is.

In addition, even if the ink ejection nozzle does not reach complete non-ejection, the ink droplet ejection capability may deteriorate and the dot diameter may become smaller. In that case, it is possible to correct the dot diameter by increasing the input energy to the drive element. In a piezo-type ink jet recording head, the voltage amplitude of a vibration waveform applied to the piezo is increased. In the thermal type ink jet recording head, the time width of the pulse applied to the heater is increased.
Japanese Patent Laid-Open No. 02-276647

  However, no matter what compensation method is used to compensate for the failed nozzle, there will always be a time when the compensation range reaches its limit. That is, when the number of failed nozzles increases and exceeds the compensation limit, image quality defects are exposed.

  In the system having a small spare head, if the ink discharge nozzle of the main inkjet recording head fails at a position away from the width of the spare head, the spare head cannot compensate. Since there are many failure modes that occur in a concentrated manner, it is possible to compensate for the failure location as long as the failure occurs within the width of the spare head. The time for exceeding the cover area of the head is reached and the compensation limit is exceeded.

  In the dot diameter modulation method, the dots on both sides of the failed nozzle are enlarged to fill in the failed portion, so that compensation cannot be made if adjacent ink ejection nozzles fail together. Although it seems that the possibility of failure of adjacent nozzles in a head having a large number of nozzles is low, in reality, the cause of failure is highly location-dependent and the possibility of failure of adjacent nozzles is high. In addition, even if the adjacent nozzles do not fail, this compensation method cannot completely compensate for the failed nozzles. Therefore, when many nozzles fail, it reaches a time when image quality deterioration cannot be tolerated.

  The method of compensating for black failures with process black is not perfect, and black synthesized with process black is more blurred than single color black, and character image quality deteriorates. Therefore, the image quality degradation is not noticeable while the number of failed nozzles is small, but when the number of failed nozzles increases, it reaches a time when the image quality degradation becomes unacceptable.

  In the method of compensating by multi-scan, image quality deterioration occurs when the number of failed nozzles increases. Originally, an error is diffused by alternately printing a single line with different nozzles to improve the image quality, but the image quality deteriorates because the failed nozzles are continuously printed with the same nozzle. Further, if the failed nozzles are present at the same interval as the paper feed pitch in the sub-scanning direction, the failure cannot be compensated. Therefore, the image quality becomes unacceptable, or the nozzle has failed at the same interval as the paper feed pitch, so that the time when correction cannot be completed is reached.

  In the method of compensating with the drive waveform, the compensation width is limited. That is, the method of increasing the drive energy is generally a method of increasing the voltage or the pulse width, but both have an upper limit, and when the upper limit is reached, correction cannot be made.

  The present invention has been made in view of the above facts, and an object of the present invention is to provide an ink jet recording head failure prediction system capable of accurately predicting the limit time of compensation by a compensation means.

  In order to solve the above-described problem, an inkjet recording head failure prediction system according to claim 1 includes a plurality of ink discharge nozzles that discharge ink droplets according to image information, and a compensation unit that compensates for the failed failure nozzle. An ink jet recording head failure prediction system for predicting a failure of an ink jet recording head, the failure detecting means for detecting a failure relating to ejection of ink droplets from each ink ejection nozzle, and the failure detected by the failure detecting means Based on the failure information, a storage means for storing failure information and a time when a failure occurs in the ink discharge nozzles other than the failed ink discharge nozzle can be calculated. Based on the calculation result, compensation by the compensation means can be performed. Failure time predicting means for predicting the complete failure time to disappear.

  In general, ink discharge nozzles and pressure generating parts constituting an ink jet recording head are manufactured collectively on a single substrate and a single film, or manufactured by being bonded together. Therefore, it is considered that there is little individual variation due to manufacturing for individual ink discharge nozzles and pressure generation units in the same ink jet recording head. Therefore, in the present invention, a failure relating to the ejection of ink droplets from each ink ejection nozzle is detected by the failure detection means. The failure information relating to the detected failure is stored in the storage means, and the failure time predicting means calculates the time when the failure occurs in the ink ejection nozzles other than the failed ink ejection nozzle based on the failure information.

  In the failure prediction derived from the result of a general life evaluation test, failure prediction is performed without considering manufacturing variation, but in comparison with this, in the present invention, failure prediction is based on an actually occurring failure. Therefore, it is possible to predict failure taking into account individual variations due to manufacturing. Therefore, it is possible to accurately predict the occurrence of the next failed nozzle.

  In the ink jet recording head described above, the failure nozzle is compensated by the compensation means, but the failure time prediction means predicts the complete failure time at which compensation by the compensation means cannot be performed. This prediction is performed based on the above calculation result. Therefore, it is possible to accurately predict the replacement time of the ink jet recording head.

  The failure information of the ink jet recording head failure prediction system according to the present invention may include a failure time and a failure mode related to the type of failure.

  Examples of the failure mode include failure types such as peeling of the joint portion, occurrence of cracks in the constituent members, and alteration of the constituent members.

  As described above, by calculating the failure occurrence timing of the next ink discharge nozzle according to the failure timing and the failure mode, it is possible to perform prediction with higher accuracy.

  According to a third aspect of the present invention, the ink jet recording head failure prediction system outputs information relating to the replacement timing of the ink jet recording head in accordance with the complete failure time predicted by the complete failure time prediction means. It is also possible to further include replacement time information output means.

  As described above, by outputting information related to the replacement timing of the inkjet recording head, it is possible to appropriately notify the user of the replacement timing of the inkjet recording head.

  According to a fourth aspect of the present invention, the storage means stores a failure prediction database stratified for each of a plurality of types of failure modes, and the failure time prediction means. However, the failure mode of the failure information detected by the failure detection means is compared with the failure prediction database, and the time when the failure occurs in the ink ejection nozzles other than the failure ink ejection nozzle can be calculated. .

  The failure time prediction means predicts the failure time of the next ink discharge nozzle based on the detected failure information, and the failure time of the next ink discharge nozzle varies depending on the failure mode. Therefore, a failure prediction database stratified for each of the plurality of types of failure modes is stored in the storage means, and the failure modes of the failure information detected by the failure detection means are checked against the failure prediction database, and ink other than the failure ink ejection nozzles is stored. The time when a failure occurs in the discharge nozzle is calculated.

  According to the above invention, it is possible to calculate the time when a failure occurs in the ink ejection nozzles other than the malfunctioning ink ejection nozzle with higher accuracy according to the failure mode.

  In addition, the inkjet recording head failure prediction system according to the present invention includes, as described in claim 5, the temperature of the inkjet recording head, the humidity around the inkjet recording head, the driving conditions of the inkjet recording head, the number of prints at the ink ejection nozzle, And failure acceleration information detecting means for detecting failure acceleration information including at least one of ink types, and the failure prediction database includes failure acceleration data corresponding to the failure acceleration information for each failure mode. And the failure time prediction means calculates a time when a failure occurs in the ink discharge nozzles other than the failure ink discharge nozzles in light of the detected failure acceleration information against the failure prediction database. You can also

  The failure time of the next ink discharge nozzle also varies depending on the temperature of the ink jet recording head, the humidity around the ink jet recording head, the driving conditions of the ink jet recording head, the number of prints at the ink discharge nozzle, and the type of ink. Therefore, data on such conditions is stored in advance in the failure prediction database as failure acceleration data. Then, the corresponding failure acceleration information is detected by the failure acceleration information detection means, and the failure acceleration information is compared with the failure prediction database to calculate the time when the failure occurs in the ink ejection nozzles other than the failure ink ejection nozzle. Accordingly, it is possible to calculate the time when a failure occurs in the ink discharge nozzles other than the failed ink discharge nozzle with higher accuracy.

  In the ink jet recording head failure prediction system according to the present invention, as described in claim 6, the failure time predicting means includes a manufacturing lot of an ink jet recording head, and an address on a wafer of a head chip constituting the ink jet recording head. In addition, it is possible to calculate the time when a failure occurs in the ink discharge nozzles other than the failed ink discharge nozzle in consideration of manufacturing information including at least one of the above.

  The individual variation due to the manufacture can be predicted to some extent by the manufacturing lot of the ink jet recording head and the address of the head chip constituting the ink jet recording head on the wafer. That is, the inkjet recording heads manufactured in the same process have a common failure occurrence tendency, and have a predetermined failure occurrence tendency depending on the address on the wafer. Therefore, as described above, it is possible to calculate with higher accuracy by calculating the time when the failure occurs in the ink discharge nozzles other than the failed ink discharge nozzle in consideration of the manufacturing information.

  The ink jet recording head failure prediction system according to the present invention, as claimed in claim 7, transmits the failure information to a manufacturer, receives the transmitted failure information, and collects and manages the failure information. And a management device that further includes a management device.

  In this way, by collecting and managing the failure information in the manufacturer, the failure tendency of the ink ejection nozzle can be analyzed, which can be used for future development and update of the failure prediction database.

  In the ink jet recording head failure prediction system according to the present invention, as described in claim 8, the ink jet recording head is a paper width head, and the compensation means arranges an auxiliary head having a width smaller than the paper width at the position of the trouble nozzle. In the case of a compensation method that ejects ink droplets instead of the failed nozzle, the ink ejection nozzle of the portion where the auxiliary head is not arranged out of the ink ejection nozzles of the ink jet recording head fails at the complete failure time. It can also be characterized by time.

  When the above compensation method is used, if the distance between one faulty nozzle and another faulty nozzle is larger than the width of the auxiliary head, it cannot be compensated. Therefore, the complete failure time in the complete failure time predicting means is a time when the ink discharge nozzles of the ink discharge nozzles of the ink jet recording head where the auxiliary head is not disposed fail.

  Further, according to the ink jet recording head failure prediction system of the present invention, as described in claim 9, when the compensation unit is a compensation method for printing the failed nozzle portion with another ink discharge nozzle by divided printing, The complete failure time may be a time when a plurality of ink ejection nozzles fail at the same pitch as the head feed pitch of divided printing.

  When the above compensation method is used, when the ink discharge nozzle that prints the failed nozzle portion fails, it cannot be compensated. That is, if a plurality of ink ejection nozzles fail at the same pitch as the head feed pitch for divided printing, the failed nozzle portion cannot be printed and cannot be compensated. Therefore, the complete failure time in the complete failure time predicting means is set as a time when a plurality of ink ejection nozzles fail at the same pitch as the head feed pitch for divided printing.

  In the ink jet recording head failure prediction system according to the present invention, as described in claim 10, the ink jet recording head is capable of dot diameter modulation, and the compensating means replaces the failed nozzle with ink on both sides of the failed nozzle. In the case of a compensation method for ejecting ink droplets larger than usual from the ejection nozzle, the complete failure time may be set as the time when the ink ejection nozzles on both sides are failed.

  When the above compensation method is used, if the ink discharge nozzles on both sides of the failed nozzle fail, printing cannot be performed so as to compensate for the failed nozzle portion, and compensation cannot be performed. Therefore, the complete failure time in the complete failure time predicting means is set as the time when the ink discharge nozzles on both sides of the failed nozzle fail.

  In the inkjet recording head failure prediction system of the present invention, as described in claim 11, the inkjet recording head is capable of ejecting at least black, cyan, magenta, and yellow ink droplets, and the compensating means In the case of a compensation method in which cyan, magenta and yellow inks are overprinted to form overprinted black when a nozzle of an ink ejection head that ejects black ink droplets fails, the complete failure time is set to black. The number of the failed nozzles may be a time when the predetermined number of images cannot be maintained due to an increase in overprinting black.

  In the above compensation method, overprinting black in which cyan, magenta, and yellow inks are mixed is used instead of black ink droplets. Overprinting black is sufficient as a substitute for black if the number of dots is small, but if the number of dots increases, the image quality cannot be maintained. Therefore, the complete failure time in the complete failure time prediction means is set to a time when the number of black failure nozzles reaches a predetermined number at which a predetermined image quality cannot be maintained due to an increase in overprint black.

  In addition, in the ink jet recording head failure prediction system according to the present invention, as described in claim 12, the failure mode is of a type in which the size of a dot is reduced, and the failure mode compensation means removes ink droplets. In the case of a compensation method that increases the energy input to the drive unit driven for discharging, the complete failure time is set to a time when the input energy to the drive unit reaches the upper limit energy of the energy supply means. It can also be characterized.

  In the above compensation method, the energy supplied to the drive unit is increased in order to make the dot that has become smaller the original dot. However, when energy exceeding the upper limit of the supply energy is required to obtain the original dot, the original size dot cannot be formed, which is a limit of compensation. Therefore, the complete failure time in the complete failure time prediction means is set as the time when the input energy to the drive unit reaches the upper limit energy of the energy supply means.

  Further, according to the ink jet recording head failure prediction system of the present invention, the failure time prediction unit applies the failure information detected by the failure detection unit to the Weibull distribution, It is also possible to obtain the characteristic life and predict the next nozzle failure time.

  As described above, it is possible to predict with high accuracy by predicting the next nozzle failure time based on the Weibull distribution.

  Since the present invention is configured as described above, it is possible to accurately predict the limit time of compensation by the compensation means in the ink jet recording head having the compensation means.

  First, the manufacturing process of the ink jet recording head to which the present invention is applied will be described. This manufacturing process causes a variation in reliability between ink jet recording heads, that is, a manufacturing difference.

  FIG. 1 shows a manufacturing process of a piezo ink jet recording head. As the piezo sheet 101, a thinly molded ceramic material is used. In the step of FIG. 1A, the piezo sheet 101 is formed by firing. At that time, variations between sheets or within the sheet occur due to subtle mixing ratio variations of raw materials, temperature unevenness of firing, and thickness unevenness. In general, the variation in the sheet has a distribution, and the difference between the close locations is generally smaller than the difference between the distant locations.

  In the step of FIG. 1B, the fired piezo sheet 101 is polished to improve the thickness uniformity. At that time, in a portion where a higher polishing pressure is applied, the grain boundary of the piezo is disturbed, and there is a high possibility that distortion occurs inside the material. This non-uniformity inside the material is one of the non-uniformities that affects the reliability.

  In the step of FIG. 1C, an electrode layer is formed on the polished piezo sheet 101. This process also generally includes heating and cooling and a coating process, and includes causes of temperature unevenness and coating thickness unevenness.

  The process of FIG. 1D is a process of cutting out the piezo sheet 101 on which electrodes are formed as individual piezo elements 101A. In the cutting-out process, the size of individual piezo elements varies.

  The process shown in FIG. 1E is a process in which the piezo element 101A and the ink flow path substrate 102 are pressed together through the adhesive sheet 103. The adhesion may be applied with a dispenser or transferred with a sheet. In any case, variations in the adhesive layer are likely to occur, and the thickness, concentration, etc. vary between heads or within heads.

  The cutout process (D) and the bonding process (E) may be reversed in order depending on the manufacturing method, but here, the cutout process (D) is taken as an example.

  The process of FIG. 1F is a process of connecting the wiring path 105 and the ink supply path 104 to a structure in which the flow path substrate 102 and the piezoelectric element 101A are bonded to each other.

  A single ink jet recording head is manufactured as described above.

  FIG. 2 shows a manufacturing process of a thermal type ink jet recording head. In the case of the thermal ink jet type, a method in which a heating element, a drive circuit, and wiring are formed on the same substrate by an LSI process is mainly used, and it is generally created by pasting a flow path substrate on the heating element substrate. .

  FIG. 2A shows a manufacturing process of the heating element substrate 201. A heating element, a drive circuit, wiring, and the like are formed on a silicon wafer by an LSI process. At that time, variations occur due to non-uniformity of amounts of various additives, temperature unevenness in the heating process, time management of the process, and the like. These variations also include variations between wafers and variations within a wafer, and a characteristic difference tends to be larger at a distant place than at a close place.

  FIG. 2B is a process for forming the nozzle substrate 202. Here, the nozzle is formed on the silicon wafer by etching. As a method for forming the nozzle, there are many other methods such as a method of making a hole in the resin film with a laser and a method of making a hole in the metal film by press working. The formation of the nozzle does not significantly affect the reliability of the ink jet recording head.

  FIG. 2C illustrates a bonding process in which the nozzle substrate 202 and the heating element substrate 201 are bonded to form the substrate pair 203. In general, an adhesive is used for the bonding, and the nozzle substrate 202 and the heating element substrate 201 are bonded via an adhesive layer by a method such as spin coating or transfer. Here, if unevenness in the thickness of the adhesive layer and unevenness in bonding strength occur, variations in reliability occur.

  FIG. 2D shows a process of cutting the substrate pair 203 composed of the bonded nozzle substrate 202 and the heating element substrate 201 to cut out individual head chips. Cutting can be performed by a dicing blade 204. FIG. 2E shows an ink jet recording head that has been cut and separated one by one. This cutting process has little impact on reliability. Depending on the method of manufacturing the ink jet recording head, the order of the joining step (C) and the cutting step (D) may be reversed. Yes.

  The ink jet recording head manufactured as described above is roughly classified into several failure modes. Hereinafter, the failure mode for each injection method will be described.

A piezo-type inkjet recording head mainly has the following three failure modes. (A) piezo peeling, (B) piezo cracking, (C) piezo alteration.
(A) Piezo peeling occurs mainly due to non-uniformity in the bonding step (see FIG. 1E) for bonding a piezo sheet to a flow path substrate. FIG. 3 shows an example of the distribution of the occurrence status. Indicate the position and timing (unit: number of drive pulses) at which a peel-type failure occurred in an inkjet recording head in which 20 (A to T) × 33 (01 to 33) piezo elements were cut out from one piezo sheet. (A blank location has not failed.) As can be seen from FIG. 3, failures frequently occur in the periphery of the ink jet recording head. The influence of non-uniformity in manufacturing, such as uneven temperature or pressure conditions during bonding, and accumulation of thermal stress in the peripheral area during use are considered to be factors that frequently cause peeling in the peripheral area.

  (B) Piezo cracks are caused by temperature in the firing process of the piezo, unevenness in the material, and stress in the polishing process. It is thought that it occurs when micro cracks grow. FIG. 4 shows an example of the situation of occurrence. The generation situation differs for each piezo sheet, and the piezo sheet generated even with one nozzle tends to occur one after another.

  (C) Degeneration of the piezo is one in which the piezo composition is denatured by repeated deformation, generated temperature, moisture absorption, hydrogen adsorption, etc., and the original performance cannot be exhibited. The deterioration of the piezo progresses gradually and the injection force decreases. Such a progressive failure is called a wear-type failure, and is known to follow the Weibull distribution. FIG. 5 shows an example in which the increasing tendency of piezo alteration-type failures is wiped-plotted. The plot was almost linear on the graph and was confirmed to follow the Weibull distribution. Therefore, by following the Weibull distribution, it is possible to predict an increase in failure rate as the number of drives increases.

  The thermal ink jet head mainly has the following three failure modes. (D) Heater destruction (cavitation-type failure), (E) Nozzle substrate peeling, (F) Koge deposition.

  (D) The destruction of the heater is caused by the destruction of the heater protective film due to cavitation, and depends on variations in the strength and thickness of the protective film. Also, the cavitation pressure may vary depending on the ink used. It is known that the strength of the protective film depends on the production lot. FIG. 6 shows an example in which a nozzle having a cavitation type failure is detected by a current value in a thermal ink jet head in which nozzles are linearly arranged. It can be seen that the location where the current value is reduced is the failure location, and the failure occurrence rate is high at both ends of the ink jet recording head. This is considered to be due to the fact that a portion having a weak protective film was also used because the end of the wafer was used to cut out a long head.

  FIG. 7 shows the failure rate for each number of drive pulses for the cavitation type failure. It was confirmed that this failure is also a wear-type failure and follows the Weibull distribution. As shown in FIG. 7, the slope of the straight line stands, and it can be seen that the failure progresses one after another when one failure occurs. Therefore, the failure rate for each number of drive pulses can be predicted according to the Weibull distribution.

  (E) The peeling of the nozzle substrate is a phenomenon in which the adhesive surface between the heater substrate and the nozzle substrate is peeled off. Depending on the quality of the bonding process, inkjet recording heads cut out from the same wafer often cause similar peeling failures, and those cut out from close areas within the same wafer are much more similar. Causes a peeling failure. FIG. 8 shows, on a map showing addresses in a wafer, those in which a peeling-type failure has occurred in an ink jet recording head cut out from one wafer. It can be confirmed that the one with the cross mark is the one where the peeling type failure has occurred and is concentrated in a part of the region (upper left).

  (F) Kogation is a phenomenon in which, in the thermal method, the surface temperature of the heater reaches a high temperature, so that the components in the ink burn and accumulate on the heater surface. When kogation accumulates, the thermal conductivity from the heater to the ink is hindered, the jetting energy becomes weak, and the volume of the ejected droplets becomes small. FIG. 9 shows the relationship between the drop amount and the number of drive pulses. It is known that the drop amount drop curve almost follows an exponential function. The variation in the temperature of the heater surface related to kogation deposition depends on the variation in the thickness of the protective film, the variation in the resistance value of the heater, the variation in the wiring resistance, and the like. In addition, if printing is performed in a concentrated manner, the temperature of the ink jet recording head in that region rises, and there is a phenomenon that kogation is accelerated.

  It is also known that these failures are accelerated by the use environment and the ink used. If the energy applied to the piezo and the heater is high, the change with time is accelerated and the driving stress increases, and the failure occurs early. Further, the change of the material with time has the property of proceeding faster as the temperature increases according to the Arrhenius law.

  Next, a failure detection method will be described. Various methods have been devised for detecting failures. There are roughly two methods, one that measures the output from the inkjet recording head, such as the dot on the image and the flying state of the ink, and the other that measures the electrical characteristics of the piezo and heater.

  In the method of detecting from dots on an image, a test pattern is printed on a recording medium and read by a scanner to detect missing dots or a decrease in density. What detects the flying state of the ink is a method in which the flying speed and size of the ink droplet are detected and read by an optical sensor, or the momentum is read by colliding the ink droplet with an impact sensor. Since the ink ejected directly from the ink jet recording head is detected, the determination criteria are clear and there are few erroneous determinations. On the other hand, since the inkjet droplet is very fine and has a large number of ink ejection nozzles, a detection device capable of high-speed detection with high sensitivity is required.

  Many methods have been proposed for measuring the electrical characteristics of piezos and heaters because the measurement system is simple and high-speed detection is possible. For a piezoelectric element, resonance frequency, capacitance, and dielectric loss are typical electrical characteristics that are often used. In the case of a peeling or cracking failure, the resonance frequency changes, and when piezo alteration occurs, the capacitance decreases and the dielectric loss increases. FIG. 10 shows how the characteristics change for each failure mode measured by capacitance. In the peeling type failure, since the electrical connection cannot be obtained due to the peeling, the capacitance suddenly drops to almost 0 (pF) (or suddenly increases to infinity). The crack type failure depends on the area of the remaining portion of the crack, but suddenly changes to the capacitance value obtained in the remaining area. Unlike other failure modes, the characteristics of the piezo-altered failure gradually deteriorate. This is because the internal alteration gradually proceeds according to the driving. The normal one shows a certain value.

  In addition, FIG. 11 shows how the characteristics change for each failure mode measured by dielectric loss. As for dielectric loss, exfoliation type faults cannot be measured, crack type faults do not change, and degradation type faults tend to increase loss.

  In addition, FIG. 12 shows how the characteristics change for each failure mode measured at the resonance frequency. Regarding the resonance frequency, the peeling type and the crack type cannot be measured, and the degradation type tends to increase the resonance frequency.

  By measuring the physical quantity as described above, it is possible to determine not only the presence / absence of a failure but also a failure mode.

  As for the electrical characteristics of a thermal ink jet heater, a change in resistance value is generally detected. When the heater breaks down, the insulating layer is broken at the moment of occurrence, and a large current flows instantaneously, but then the entire heater burns out and the resistance becomes infinite. FIG. 6 shows the state of failure of the heater destruction type measured by the current value. If the heater is destroyed, no current can flow, that is, the resistance becomes infinite, and detection is possible by the current value or resistance value. A failure due to peeling or burning is difficult to detect by a change in resistance value, and the above-described method of detecting printing or ink droplets is common.

  FIG. 13 shows the characteristics relating to the failure in each failure mode. Thus, each failure mode has a specific failure tendency.

  Next, a specific failure prediction system for the ink jet recording head will be described.

[First failure prediction system]
First, as a first failure prediction system, a failure prediction system for an ink jet recording head in which a large number of piezoelectric heads are connected to form a paper width head will be described.

  As shown in FIG. 14, the inkjet recording apparatus 10 includes an apparatus main body 12, and a paper width head 14 and an auxiliary head 16 are mounted on the apparatus main body 12. The paper width head 14 is an ink jet recording head having a width capable of printing over the width W of the recording medium P. As shown in FIG. 15, the wiring path 105 and the ink supply are provided to the one in which the flow path substrate 102 and the piezoelectric element 101A are bonded. The unit head 14A to which the path 104 is connected is connected. As shown in FIG. 16, a plurality of ink discharge nozzles 18 are formed in the unit head 14A. One piezo element 19 is provided for one ink discharge nozzle 18, and ink droplets are discharged by driving the piezo element 19.

  Each unit head 14A is produced in the same production lot, and its characteristics are substantially the same. Here, 512 ink ejection nozzles 18 are provided per unit head 14A. The paper width head 14 is configured by connecting 12 unit heads 14A. The paper width head 14 requires extremely high splicing accuracy. Therefore, even if a failure occurs, the user cannot replace the failed part. If a failure occurs, the entire paper width head 14 must be replaced. Don't be. Therefore, an auxiliary head 16 that can move in the paper width direction is provided as a compensation head. The auxiliary head 16 is composed of one unit head 14A.

  When an abnormality occurs in the ink droplet ejection from the ink ejection nozzle 18 of the paper width head 14 (hereinafter, the ink ejection nozzle in which the abnormality has occurred is referred to as a “failed nozzle”), the inkjet recording apparatus 10 uses the auxiliary head 16 at the malfunctioning location. A compensation method (hereinafter referred to as an “auxiliary head compensation method”) in which printing is performed by the auxiliary head 16 is adopted. In the case of the auxiliary head compensation method, if a failure occurs in the ink discharge nozzles at a location where printing cannot be performed at once by the auxiliary head 16, compensation is impossible, and a complete failure in which the paper width head 14 must be replaced occurs. Therefore, it is predicted that a failure will occur in the ink discharge nozzles at locations where printing cannot be performed at once by the auxiliary head 16.

  As shown in FIG. 17, the failure prediction system 20 includes a failure detection unit 22, a pixel counter 24, an environmental sensor 26, and a failure information memory 30.

  The failure detection unit 22 detects a failed nozzle that has an abnormality in ink droplet ejection, and outputs failure information about the failed nozzle, such as a failure time, a failure location, and a failure mode, to the failure information memory 30. As a failure detection method, there is a method of measuring the ink ejected from the ink ejection nozzle 18 with a dot diameter or a droplet speed. This method may be used, but here, the characteristics of the piezoelectric element 19 are electrically reduced. A method of measuring by capacitance is adopted.

  The pixel counter 24 counts the usage amount of each ink ejection nozzle 18 and outputs it to the failure information memory 30. Ideally, it is desirable to store the used amount of each ink discharge nozzle 18 in a memory, and this method can be used. However, since the capacity of the memory becomes enormous, the ink discharge is performed for each unit head 14A here. A method of maintaining an average value of the usage amount of the nozzle 18 is used.

  The environmental sensor 26 measures the temperature and humidity in the vicinity of the paper width head 14 inside the inkjet recording apparatus 10 and outputs the data to the failure information memory 30.

  The failure information memory 30 is connected to the failure detection unit 22, the pixel counter 24, and the environmental sensor 26, and stores information input from these units.

  Further, the failure prediction system 20 includes a manufacturing information unit 32 and a failure prediction database unit 34.

  In the manufacturing information section 32, the manufacturing lot of the paper width head 14 and the address in the wafer are stored.

  The failure prediction database unit 34 stores a failure prediction database D. In the failure prediction database D, data for determining a failure mode from the characteristic value detected by the failure detection unit 22 and data of statistical properties for each failure mode are stored. Specifically, as shown in FIG. 18, as data for determining a failure mode, a determination threshold (capacitance) is held for each failure mode (peeling, cracking, piezo alteration). The statistical property data for each failure mode includes a statistical model, a Weibull parameter (shape parameter), and an acceleration coefficient (drive voltage, temperature, humidity) for failure prediction. These values are obtained from many life tests and simulations at the development stage.

  Further, the failure prediction system 20 includes a failure nozzle compensation unit 28, a failure time prediction unit 36, and a display unit 38.

  The failed nozzle compensator 28 is connected to the auxiliary head 16 and drives the auxiliary head 16 so as to print the failed nozzle portion. The failure time prediction unit 36 predicts a complete failure time at which the paper width head 14 completely fails based on information stored in the failure information memory 30, the manufacturing information unit 32, and the failure prediction database unit 34. Here, the complete failure time means a time when the auxiliary nozzle 16 cannot compensate the failed nozzle, and here, it is a time when the ink discharge nozzle 18 of the second unit head 14A fails. The display unit 38 is connected to the failure time prediction unit 36 and displays a head replacement time warning obtained by the failure time prediction unit 36.

  Next, a specific example in which the failure prediction system 20 predicts the replacement time of the paper width head 14 will be described.

  The capacitance detected by the failure detection unit 22 is input to the failure time prediction unit 36. The failure time prediction unit 36 determines the failure mode with reference to the failure prediction database D based on the input capacitance value (FIG. 19, step S10). For example, if the input capacitance is 300 pF, it can be determined that the piezo-altering type failure has occurred. Thereby, failure prediction is performed with reference to the piezo-altered portion of the failure prediction database D.

  Now, assume that one ink ejection nozzle 18 has a piezo-altering-type failure when the number of counts in the pixel counter 24 is 3 billion pulses (3 billion printing). Due to this failure, the auxiliary head 16 moves to the location of the unit head 14A where the failed nozzle has occurred to compensate for the failed nozzle, and the inkjet recording apparatus 10 continues to operate as it is. The failure time prediction unit 36 calculates the failure time of the second unit head 14A by the following calculation according to the statistical model (step S12).

Since one of the twelve unit heads 14A has failed, the failure rate F (3 billion) = 0.083. Since it is a failure mode according to the Weibull distribution of m = 2.5,
0.083 = 1−Exp ((− 3 × 10 ⁹ / η) ^2.5 )
Is obtained, and η = 7.9 billion pulses. From there, the time at which the second unit head 14A fails, that is, t at which the failure rate F (t) = 0.166 is calculated,
0.166 = 1−Exp ((− t / 7.9 × 10 ⁹ ) ^2.5 )
Thus, t = 4 billion pulses.

  Next, the calculation result is corrected in consideration of an acceleration factor depending on the environment (step S14). For example, the average temperature when driving the first 3 billion pulses was 25 ° C, but if the average temperature subsequently reached 30 ° C, the deterioration of 5 x 4% = 20% is accelerated. It is corrected to 3.8 billion pulses.

  Then, the head replacement time is obtained by subtracting a margin considering consumer risk from the corrected number of pulses (step S16). The head replacement time is output to the display unit 38 (step S18), and a warning for head replacement is notified to the user.

  According to the failure prediction system 20 described above, since the complete failure time of the paper width head 14 is obtained based on the actual failure, compared with the case of obtaining the complete failure time simply based on general data obtained in development. The failure time can be predicted with high accuracy.

  If the failure prediction of the present invention is not used, a head replacement warning is issued based on the worst data obtained in development in order to avoid a failure during use by the customer. In general, failure data varies widely, and the replacement time is determined based on the worst data. This is very wasteful and most heads will show a replacement indication even though they can be used in a considerable amount by failure. In order to avoid this, the present invention is effective.

  Further, the failure information stored in the failure information memory 30 is sequentially output to the failure data management device 40 managed by the manufacturer via the network. The failure data management device 40 receives failure information and constructs a database related to failure information. Failure information relating to failures occurring in the actual market environment is valuable technical information for the manufacturer and is used for the next product development. It is also effective to update the failure prediction database D based on the accumulated failure information.

  In the above embodiment, the example in which the failure information is output to the failure data management device 40 managed by the manufacturer via the network has been described. However, the failure information stored in the failure information memory 30 is At the time of replacement, it may be collected by the manufacturer together with the paper width head 14, and the data may be input to the failure data management device 40.

[Second failure prediction system]
As a second failure prediction system, a case where the failure nozzle compensation method is a dot diameter modulation method will be described. This method is a compensation method in which large ink droplets are ejected from the nozzles on both sides of the failed nozzle to make the failed nozzle inconspicuous.

  As shown in FIG. 20, the inkjet recording apparatus 50 includes an apparatus main body 52, and a paper width head 54 having the same configuration as that of the above-described inkjet recording apparatus 10 is mounted on the apparatus main body 52. However, the auxiliary head 16 is not provided. The paper width head 54 is composed of twelve unit heads 54A. In the paper width head 54, as shown in FIG. 21, for example, when one ink discharge nozzle 56B fails, large ink droplets are ejected from the adjacent ink discharge nozzles 56A and 56C. For this reason, if the two ink ejection nozzles 56 adjacent to the failed nozzle fail, compensation cannot be performed, and this time is predicted as the complete failure time.

  As shown in FIG. 22, the failure prediction system 60 includes a failure detection unit 22, a pixel counter 24, an environmental sensor 26, a failure information memory 30, a failure nozzle compensation unit 28, a failure information memory 30, a manufacturing information unit 32, and a failure prediction. A database unit 34, a failure time prediction unit 36, and a display unit 38 are provided.

  The failed nozzle compensator 28 is connected to each unit head 54A and controls each ink ejection nozzle 18 so that large ink droplets are ejected from the ink ejection nozzles on both sides of the malfunctioning nozzle.

  The failure time prediction unit 36 predicts a complete failure time at which the paper width head 14 completely fails based on information stored in the failure information memory 30, the manufacturing information unit 32, and the failure prediction database unit 34. The complete failure time here refers to a time when the ink discharge nozzles 18 on both sides of the failure nozzle fail and the failure nozzle cannot be compensated. The number of failure nozzles increases, and two adjacent ink discharge nozzles 18 fail. The time when the set probability exceeds the set value.

  Next, a specific example in which the failure prediction system 60 predicts the replacement time of the inkjet recording head 54 will be described.

  When the compensation method is the dot modulation method, the two adjacent ink ejection nozzles need only be considered within the unit head 54A. Assume that a warning is issued when the 512 ink discharge nozzles 56 fail randomly, for example, when the probability of failure of adjacent ink discharge nozzles 56 exceeds 10%. The probability that m of the N nozzles fail and the next m + 1 failure is not adjacent is P (m) = (N−3m) / (N−m). This is because N-m in the denominator is the number of normal ink discharge nozzles, and N-3m in the numerator is because failure does not continue if the ink discharge nozzles other than 3 m including the failure nozzle and the ink discharge nozzles on both sides thereof are broken. . Strictly speaking, it is necessary to consider the nozzles at both ends, but this formula can be substituted if the number of ink ejection nozzles is sufficiently large. The number of failures in which a unit head having 512 ink discharge nozzles has a probability of failure of an adjacent ink discharge nozzle of 10% or less can be easily calculated, and up to 24 failures can be tolerated.

Next, similarly to the first failure prediction system, the failure time / failure mode of the actually failed nozzle and the failure prediction mode database are used to calculate the time when the 25th failure occurs. In this dot diameter modulation method, since it is possible to allow a large number of ink ejection nozzles to fail, it is more accurate to determine the shape parameter m of the Weibull distribution from the failure information detected by the failure detection unit 22. FIG. 23 shows an example in which 24 nozzles fail at 10 billion pulses in an ink jet recording head. FIG. 24 is a Weibull plot of the failure data, and m = 2.486 and η = 3.438 × 10 ¹⁰ are obtained. From this, the number of pulses at which the 25th ink ejection nozzle breaks is obtained as 1.031 × 10 ¹⁰ . Accordingly, if a head replacement warning is issued with 10.31 billion pulses, the probability of failure of two adjacent ink ejection nozzles is 10% or less, and the user can be prompted to replace the head.

  In this case as well, the failure information recorded in the failure information memory 30 may be output to the manufacturer's failure data management device 40 in the same manner as in the first failure prediction system.

[Third failure prediction system]
A third failure prediction system is applied to a compensation method for returning the dot diameter by increasing the input energy to the drive element when the ink jetting ability deteriorates and the dot diameter becomes small. State.

  The ink jet recording apparatus 60 is a thermal type printer and includes an apparatus main body 62 as shown in FIG. An ink jet recording head 64 that prints while moving in the width direction of the recording medium P is mounted on the apparatus main body 62.

  FIG. 26 shows an example of drop amount fluctuation in the case where the ink droplet drop amount is reduced depending on the number of drive pulses in the thermal ink jet recording head and is corrected by the drive pulse. The fluctuation of the drop amount is caused by the accumulation of kogation on the heater and hindering heat conduction. In order to compensate for the decrease in the drop amount, the amount of energy is increased by increasing the length of the drive pulse in the order of initial waveform → correction waveform 1 → correction waveform 2 to correct the drop amount. In FIG. 25, the waveform is corrected so that the drop amount of 10 (pl) to 8 (pl) is maintained, but the drive waveform cannot be made longer than the corrected waveform 2 due to circuit restrictions. . Therefore, the time when the correction waveform 2 falls below 8 (pl) is the limit of compensation, and a head replacement warning is issued.

It is known that the decrease in the ink droplet amount follows an exponential function. Therefore, the failure time prediction unit 36 approximately applies the fluctuation of the ink drop amount measured periodically to an exponential function, and obtains the number of pulses at which the droplet amount decreases to 8 (pl) from the obtained formula. The portion H of the correction waveform 2 in FIG. 25 can approximately approximate the relationship between the drop amount (Vol) and the number of pulses (n) as Vol = 14.7 × Exp (−9 × 10 ⁻¹⁰ × n) The time when the drop amount decreases to 8 (pl) is obtained as 6.76 × 10 ⁸ pulses. Therefore, if a warning is issued with the number of pulses obtained by subtracting the margin from 6.76 × 10 ⁸ pulses, image quality deterioration due to a drop amount reduction can be prevented.

  In this case as well, the failure information recorded in the failure information memory 30 may be provided to the manufacturer in the same manner as in the first failure prediction system.

[Fourth failure prediction system]
As a fourth failure prediction system, a case will be described in which the compensation method prints the failed nozzle portion with another ink ejection nozzle by divided printing. In the divided printing, N nozzles arranged in the sub-scanning direction are divided, and one row of dots in the main scanning direction is constituted by dots ejected from different nozzles. In the example shown in FIG. 27, the N nozzles are divided into two, and the dots in the recording area G are scanned by the nozzles of the A group (first scan, indicated by white dots in the figure), and then the B group. The nozzle is scanned (second scan, indicated by black dots in the figure) and recorded. This divided printing is a technique for diffusing characteristic variations such as the ejection directionality of each nozzle in a dot row so that poor image quality is not noticeable.

  When divided printing is performed, if a failed nozzle occurs, the failed nozzle is detected, and the nozzle data that prints the same dot row as that nozzle, that is, the nozzle that is separated by the head feed pitch, the data of the failed nozzle also takes over. By doing so, it is possible to print without causing missing dots. For example, as shown in FIG. 28, when the fifth nozzle A5 in the A group and the second nozzle B2 in the B group fail, all the fifth main scanning lines L5 in the recording area G are in the second scan. The second main scanning line L2 of the recording area G is recorded by the second nozzle A2 of the A group in the first scan. When recording is performed in this manner, the effect of diffusing the above-described characteristic variation is lost, but if there are only a few nozzles among all the nozzles, the influence on the image quality is small and the overall image quality is allowed.

  However, if the failed nozzles are present at the same pitch as the head feed pitch, there will be no nozzles that compensate for the missing nozzles, resulting in missing images. For example, as shown in FIG. 29, if both nozzles A5 and B5 fail, there will be no nozzle that can record the scanning line L5, and this compensation cannot be compensated for by the compensation method using divided printing. It becomes.

  The failure prediction in the fourth failure prediction system in the case of such a compensation method can be performed as follows.

  For example, in the case of a printing system having 512 ink ejection nozzles and a head feed pitch of 256 nozzle width, a case where a warning is issued when the complete failure probability reaches 10% will be described. The probability that m out of N nozzles fail and the next m + 1 failure does not overlap with the already failed ink ejection nozzle at the head feed pitch is P (m) = (N−2m) / (Nm). N-m in the denominator is the number of normal ink discharge nozzles, and N-2m in the numerator is a failure if an ink discharge nozzle other than 2 m, which is a combination of the failed nozzle and the ink discharge nozzle shifted from the failed nozzle, is broken. This is because the nozzle can be supplemented. With a unit head having 512 ink discharge nozzles, the number of failures in which the probability of failure of an ink discharge nozzle with a head feed pitch deviation is 10% or less can be easily calculated, and up to 46 failures can be tolerated.

Next, similarly to the first failure prediction system, the time when the 47th failure occurs is calculated from the failure time / failure mode of the actually failed nozzle and the failure prediction mode database. If the failure distribution with m = 2.486 and η = 3.438 × 10 ¹⁰ obtained in FIG. 24 is followed, the number of pulses at which the 47th ink ejection nozzle breaks is 1.341 × 10 ^10. . Therefore, if a head replacement warning is issued with 134.1 billion pulses, the probability of failure of an ink discharge nozzle with a head feed pitch shift is 10% or less, and the user can be prompted to replace the head.

[Fifth failure prediction system]
As a fourth failure prediction system, a compensation method is a compensation method in which, when a nozzle of an ink ejection head that ejects black ink droplets fails, cyan, magenta, and yellow ink are overprinted to form overprinted black. The case will be described. In the case of this compensation method, a complete failure occurs when a predetermined image quality cannot be maintained due to an increase in overprinting black printing.

  According to the applicant's research, when 5% of all the black nozzles fail in the case of random failure, more than 10% of users are not satisfied with the image quality. Accordingly, it is appropriate to set the time when 5% of all nozzles have failed as the complete failure time. Further, the black head has a usage rate several times higher than that of the color head, and has a higher probability of failure than the color head. Therefore, there are many cases where this compensation method works effectively. In addition, a method in which a compensation method using an auxiliary head is applied only to a color head and black is compensated by overprinting black is also an effective method for reducing the overall cost.

A case will be described in which there are 512 ink discharge nozzles, and if 5% of the nozzles fail, a complete failure will occur. The allowable number of failures is 512 × 0.05 = 25.6, and up to 25 failures are allowed. If the failure distribution with m = 2.486 and η = 3.438 × 10 ¹⁰ obtained in FIG. 24 is followed, the number of pulses for breaking the 26th ink ejection nozzle is 1.048 × 10 ^10. . Therefore, if a head replacement warning is issued with 10.48 billion pulses, a user who is not satisfied with the image quality can issue a warning prompting the head replacement at a level of 10% or less.

  As described above, according to the failure prediction system of the present invention, because the ink discharge nozzle failure information is used to predict the complete failure time when the inkjet recording apparatus is actually operating under the customer, It is possible to obtain the time when the compensation means stops functioning with high accuracy. As a result, the non-operating time of the ink jet recording apparatus can be shortened, and the lifetime of the expensive head can be effectively used to the end without taking an extra margin. Furthermore, by collecting the failure data by the manufacturer, valuable failure data in the market can be collected, and the manufacturer can use it for the next development.

It is a figure which shows the manufacturing process of a piezo-type inkjet recording head. It is a figure which shows the manufacturing process of a thermal type inkjet recording head. It is a figure which shows generation | occurrence | production distribution in the piezo sheet | seat of the piezo element which caused the peeling type failure. It is a table | surface which shows the generation | occurrence | production condition of the crack for every piezo sheet | seat. It is the graph which wiped-plotted the increase tendency of the piezo alteration type failure. 6 is a graph showing an example in which a nozzle having a cavitation type failure is detected by a current value in a thermal ink jet head in which nozzles are arranged in a straight line. . It is the graph which calculated | required the failure rate for every drive pulse number about a cavitation type failure. The ink jet recording head cut out from one wafer is shown on the map showing the address in the wafer when the peeling type failure occurs. It is a graph which shows the relationship between drop amount and the number of drive pulses. It is a graph which shows the mode of the characteristic change for every failure mode measured by the electrostatic capacitance. It is a graph which shows the mode of the characteristic change for every failure mode measured by dielectric loss. It is a graph which shows the mode of the characteristic change for every failure mode measured at the resonant frequency. It is a list of the characteristic regarding the failure for every failure mode. It is the schematic of the inkjet recording device with which a 1st failure prediction system is applied. It is the schematic of the inkjet recording head to which a 1st failure prediction system is applied. It is the schematic of the ink discharge nozzle and piezoelectric element to which the 1st failure prediction system is applied. It is a schematic block diagram of a 1st failure prediction system. It is an example of a failure prediction database. It is a figure which shows the procedure of the complete failure time prediction in a failure time prediction part. It is the schematic of the inkjet recording device with which a 2nd failure prediction system is applied. It is a figure which shows the positional relationship of the failure nozzle in the 2nd failure prediction system, and the ink discharge nozzle of the both sides. It is a schematic block diagram of a 2nd failure prediction system. 6 is a table showing an example in which 24 nozzles fail at 10 billion pulses in a certain inkjet recording head. FIG. 24 is a Weibull plot of failure data of 24 nozzles at 10 billion pulses in an ink jet recording head. It is the schematic of the inkjet recording device with which a 3rd failure prediction system is applied. 6 is a graph showing an example of fluctuations in drop amount when a drop amount of ink droplets is reduced depending on the number of drive pulses in a thermal type ink jet recording head and is corrected with the drive pulses. It is a figure which shows the relationship of the nozzle arrangement | sequence and recording dot about the division | segmentation printing of a 4th failure prediction system. It is a figure which shows the relationship between a failure nozzle and a recording dot about the division | segmentation printing of a 4th failure prediction system. It is a figure which shows the relationship between a failure nozzle and a recording dot at the time of the nozzle separated only by head feed pitch about the division | segmentation printing of a 4th failure prediction system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inkjet recording apparatus 14 Paper width head 14A Unit head 16 Auxiliary head 18 Ink discharge nozzle 19 Piezo element 20 Failure prediction system 22 Failure detection part 24 Pixel counter 26 Environmental sensor 28 Failure nozzle compensation part 30 Failure information memory 32 Manufacturing information part 34 Failure prediction Database unit 36 Failure time prediction unit 38 Display unit 40 Failure data management device 50 Inkjet recording device 54 Inkjet recording head 54 Paper width head 54A Unit head 60 Inkjet recording device 60 Failure prediction system 64 Inkjet recording head D Failure prediction database

Claims (13)

An inkjet recording head failure prediction system that predicts failure of an inkjet recording head comprising a plurality of ink ejection nozzles that eject ink droplets according to image information, and compensation means that compensates for a failed failure nozzle,
Failure detection means for detecting a failure related to ejection of ink droplets from each ink ejection nozzle;
Storage means for storing failure information relating to the failure detected by the failure detection means;
Based on the failure information, a time when a failure occurs in the ink discharge nozzles other than the failed ink discharge nozzle is calculated, and a failure time for predicting a complete failure time at which compensation by the compensation means cannot be performed based on the calculation result Prediction means;
An inkjet recording head failure prediction system comprising:   2. The ink jet recording head failure prediction system according to claim 1, wherein the failure information includes a failure time and a failure mode related to a failure type. In accordance with the complete failure time predicted by the failure time prediction means, replacement time information output means for outputting information relating to the replacement time of the inkjet recording head,
The inkjet recording head failure prediction system according to claim 1 or 2, further comprising: The storage means stores a failure prediction database stratified for each of a plurality of types of failure modes,
The failure time predicting means calculates a time when a failure occurs in ink ejection nozzles other than the failed ink ejection nozzles by comparing the failure mode of the failure information detected by the failure detection means with respect to the failure prediction database. The inkjet recording head failure prediction system according to claim 2 or 3. Fault acceleration information detection that detects fault acceleration information including at least one of the temperature of the inkjet recording head, the humidity around the inkjet recording head, the driving conditions of the inkjet recording head, the number of prints at the ink ejection nozzle, and the type of ink. Means,
In the failure prediction database, failure acceleration data corresponding to the failure acceleration information is stored for each failure mode,
The failure time predicting means calculates the time at which a failure occurs in an ink discharge nozzle other than the failed ink discharge nozzle by comparing the detected failure acceleration information with the failure prediction database;
The inkjet recording head failure prediction system according to claim 4.   The failure time predicting means includes an ink discharge nozzle other than the failed ink discharge nozzle in consideration of manufacturing information including at least one of a manufacturing lot of an ink jet recording head and an address on a wafer of a head chip constituting the ink jet recording head. 6. The ink jet recording head failure prediction system according to claim 1, wherein a time at which a failure occurs is calculated. Transmitting means for transmitting the failure information to the manufacturer;
A management device that receives the transmitted failure information and collects and manages the failure information;
An inkjet recording head failure prediction system further comprising: When the ink jet recording head is a paper width head, and the compensation means is a compensation method in which an auxiliary head having a width narrower than the paper width is disposed at the failed nozzle position and ejects ink droplets instead of the failed nozzle. The complete failure time is set as a time when an ink discharge nozzle of a portion where the auxiliary head is not arranged among the ink discharge nozzles of the ink jet recording head fails.
The ink jet recording head failure prediction system according to claim 1, wherein the ink jet recording head failure prediction system is characterized in that: When the compensation means is a compensation method in which the defective nozzle portion is printed by another ink discharge nozzle by divided printing, a plurality of ink discharge nozzles fail at the same failure time as the head feed pitch of the divided printing. It is time to
The ink jet recording head failure prediction system according to claim 1, wherein the ink jet recording head failure prediction system is characterized in that: If the ink jet recording head is capable of dot diameter modulation, and the compensation means is a compensation method for ejecting ink droplets larger than normal from the ink ejection nozzles on both sides of the malfunctioning nozzle instead of the malfunctioning nozzle, the complete malfunction The time is the time when the ink discharge nozzles on both sides break down,
The ink jet recording head failure prediction system according to claim 1, wherein the ink jet recording head failure prediction system is characterized in that: The inkjet recording head is capable of ejecting at least black, cyan, magenta, and yellow ink droplets, and the compensation means detects cyan, magenta, and yellow when the nozzle of the ink ejection head that ejects black ink droplets fails. In the case of a compensation method in which ink is overprinted to form overprinted black, the complete failure time is set to a predetermined number in which the number of black failed nozzles cannot maintain a predetermined image quality due to an increase in overprinted black. When it is reached,
The ink jet recording head failure prediction system according to claim 1, wherein the ink jet recording head failure prediction system is characterized in that: The failure mode is of a type in which the size of the dot is reduced, and the compensation means for the failure mode is a compensation method that increases the energy input to the drive unit that is driven to eject ink droplets. The complete failure time is a time when the input energy to the drive unit reaches the upper limit energy of the energy supply means.
The ink jet recording head failure prediction system according to claim 1, wherein the ink jet recording head failure prediction system is characterized in that: The failure time prediction means applies the failure information detected by the failure detection means to the Weibull distribution to determine the shape parameter and characteristic life of the failure distribution, and predicts the next nozzle failure time.
The inkjet recording head failure prediction system according to any one of claims 1 to 12, wherein

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