JP2010120253A - Printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect a defective nozzle regardless of its position even if a printer uses an inexpensive light source or a long printing head. <P>SOLUTION: A detector (108) optically detects ink ejected from a nozzle and passed through a detecting luminous flux. For each of areas ((1) to (5)) into which a line of nozzles is divided, data obtained based on output from the detector in preliminary measurement, is stored for each data in a memory in advance. To detect a defective nozzle, ink is ejected from the plurality of nozzles, and the output from the detector and the correction data stored in the memory are used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technical field of detecting undischarge by directly detecting ink droplets ejected from nozzles in an ink jet printer.

  Inkjet printheads form a row with a plurality of nozzles for ejecting ink. Depending on how the print head is left for a long time or how it is handled, the nozzles may become clogged and some of the nozzles may fail to eject ink (hereinafter referred to as non-ejection). A nozzle that is clogged is called a defective nozzle. If printing is performed in this state, a horizontal streak enters a position corresponding to the defective nozzle in the print image, and print quality deteriorates.

In order to solve this problem, Patent Document 1 provides a detector including a light source and a light receiver, and scans a detected light beam between the light source and the light receiver in parallel with the arrangement direction of the ink nozzle rows, so that ink droplets A method for detecting whether or not the discharge is performed for each nozzle is disclosed.
JP-A-4-269549

  It is preferable to use a small and inexpensive light source such as an LED as the light source of the photodetector. However, it is difficult for an inexpensive light source to obtain perfect parallel light. In the case of a divergent light beam, the light intensity per unit area decreases as the distance from the light source increases, and the output of the light receiver when the ink droplet passes through the detection light beam varies depending on the detection position. The position dependency of the detection sensitivity becomes more prominent as the nozzle row is longer. According to the applicant's experiment, it was confirmed that the degree of modulation of light is highest when ink droplets are detected near the middle of the light source and the light receiver, and the degree of modulation decreases as the distance from the light source side to the light receiver side is approached.

  The present invention has been made based on recognition of the above problems. An object of the present invention is to provide a technique capable of accurately detecting a defective nozzle regardless of the position even when using an inexpensive light source or a long print head.

  A printer of the present invention that solves the above-described problems includes a carriage that has a print head in which a nozzle array is formed by a plurality of nozzles that eject ink, moves with respect to the medium, a light source, and a light receiver, and ejects from the nozzles. Then, a detector that optically detects ink passing through a detected light beam between the light source and the light receiver, and an output of the detector in a preliminary measurement for each region obtained by dividing the nozzle row into a plurality of regions. Originally obtained memory for storing correction data for each region in advance, ink is ejected from the plurality of nozzles, and defective nozzles are detected using the output of the detector and the correction data stored in the memory. And a control unit that controls to detect.

  According to the present invention, even if an inexpensive light source such as an LED is used or a long print head is used, a defective nozzle can be accurately detected regardless of the position. As a result, a highly reliable printer that eliminates the influence of defective nozzles can be realized.

  Exemplary embodiments of the present invention will be described below with reference to the drawings. However, the constituent elements described in this embodiment are merely examples, and are not intended to limit the scope of the present invention only to them.

  Hereinafter, an ink jet printer will be described as an example. However, the printer of the present invention can also be applied to a multifunction machine having a copying function and a scanning function, a so-called multi-function printer. As the inkjet method, various methods such as a method using a heating element, a method using a piezo element, a method using an electrostatic element, and a method using a MEMS element can be used.

(Embodiment 1)
FIG. 1 is a front view showing the configuration of the main part near the carriage in the ink jet printer of the present embodiment. A carriage 101 is detachably mounted with a print head 102, and ink of each color is individually supplied to the print head 102 from an ink tank (not shown). The carriage 101 is guided by a shaft 103 and reciprocated on the platen 106 in the main scanning direction (X direction) by a carriage conveyance belt 105 rotated by a carriage motor 104. The sheet-like medium 107 is conveyed on the platen 106 in a sub-scanning direction (Y direction) orthogonal to the main scanning direction by a conveyance roller (not shown).

  Next to the platen 106, a detector 108 that optically detects ink droplets passing therethrough is provided. Details of this will be described later. Further, a recovery unit 109 is provided beside the detector 108. This includes a mechanism that covers the nozzles with a cap so that ink of the print head 102 does not dry when not in use, a recovery mechanism that eliminates clogging of defective nozzles by applying negative pressure from outside the nozzles, and the print head 102 A mechanism for filling ink therein is provided.

  FIG. 2 shows a nozzle arrangement on the nozzle surface of the print head 102. The nozzle surface is a surface facing the medium 107 during printing, and a plurality (six in this embodiment) of nozzle chips 201 are arranged along the main scanning direction (X direction). In each nozzle chip 201, 640 nozzles 202 form one row (nozzle row) at a density of 600 dpi along the sub-scanning direction (Y direction), and these are arranged in two rows. The two nozzle rows are shifted from each other by a half pitch in the sub-scanning direction, and a print resolution of 1200 dpi is obtained in the sub-scanning direction in one main scan. Each nozzle chip 201 is supplied with ink of a different color. In this embodiment, C (cyan), M (magenta), Y (yellow), LC (light cyan), LM (light magenta), K (black). 6 colors of ink are used. In other words, the print head 102 as a whole has 6 nozzle chips × 2 nozzle rows each, for a total of 12 nozzle rows.

  FIG. 3 is a cross-sectional view showing the configuration of the detector 108. The detector 108 includes an LED 301 as a light source, a photodiode 302 as a light receiver, an ink absorber 303, and a detection circuit 304. The LED 301 and the photodiode 302 face each other, and the optical axis 306 at the center of the detection light beam 305 generated from the LED 301 is parallel to the sub-scanning direction (Y direction), that is, the nozzle row forming direction on the nozzle surface of the print head 102. Further, the position of the detection light beam 305 in the Z direction of the optical axis 306 is substantially the same height as the print surface of the medium 107 placed on the platen 106. The interval between the LED 301 and the photodiode 302 is slightly larger than the length of the nozzle row of the print head 102 in the sub-scanning direction, and ink droplets can be detected for all nozzles included in the nozzle row. The ink ejected from each nozzle is absorbed by an ink absorber 303 such as a sponge. The LED 301 and the photodiode 302 are connected to the detection circuit 304.

  FIG. 4 shows an electrical block diagram of the control unit centered on the detector 108. A range surrounded by a dotted line in the figure is a circuit block of the detection circuit 304, and the CPU 402 and the memory 407 are controllers on the ink jet printer main body side. These integrally form a control unit for the entire apparatus.

  The LED 301 is driven by the LED drive circuit 401 based on a command from the CPU 402 to emit light. The light reception output of the photodiode 302 is converted into a voltage signal by the I / V conversion circuit 403. The LED drive circuit 401 monitors the signal of the I / V conversion circuit 403 and automatically adjusts the drive current of the LED 301 so that the voltage level becomes a desired constant value. As a result, even if the characteristic change of the LED 301 over time occurs, a constant output can always be maintained. The signal from the I / V conversion circuit 403 passes through the differentiation circuit 404 and amplifies the fluctuation component in the amplification circuit 405. The amplification circuit 405 can change the amplification factor step by step, and sets a desired amplification factor under the control of the CPU 402.

  The comparison circuit 406 compares the detection signal with a reference voltage. When an ink droplet passes through the detection light beam and crosses, the output fluctuation occurs in the detection signal, and the signal level from the amplifier circuit 405 is lowered. When this falls below the set reference voltage, the comparison circuit 406 outputs a signal indicating that an ink droplet has been detected. The CPU 402 receives this and stores it in the memory 407. The comparison circuit 406 does not output a signal unless the detection signal falls below the reference voltage. The CPU 402 sequentially drives each of the plurality of nozzles to discharge ink. If there is no signal from the comparison circuit 406 within a predetermined period from the discharge, the CPU 402 determines that the nozzle is a defective nozzle.

<Preliminary measurement: Correction data measurement method>
Next, the preliminary measurement method will be described with reference to the flowchart of FIG. In the preliminary measurement, a correction data table (correction data for each nozzle) for correcting the detection value of the detector 108 is acquired. The timing for performing the preliminary measurement is preferably at the initial setup of the printer or immediately after the print head 102 is replaced. Since there is a slight individual difference in the print head 102, each time the print head 102 is replaced, the correction data is measured to absorb the individual difference and maintain the accuracy of undischarge detection.

  In step S <b> 501, the carriage 101 is moved so that one of the 12 nozzle arrays included in the print head 102 is positioned at the inspection position facing the detector 108.

  In step S502, an amplification factor that is an adjustment value of the detector 108 is set. Here, the amplification factor in the amplifier circuit 405 in the detection circuit 304 is set. The gain set initially is read out as a value stored in the memory 407 as a predetermined value.

  In step S503, a predetermined nozzle in the nozzle row of the nozzle chip 201 to be inspected is selected, and ink is ejected from the selected inspection nozzle. In the measurement of correction data, one nozzle row is divided into a plurality of regions (5 regions in the present embodiment). And in each area | region, it test | inspects using five nozzles near the area | region center. That is, instead of inspecting all the nozzles in one row, the measurement is typically performed using only five nozzles in five regions, that is, a total of 25 nozzles. Ink droplets are ejected for each of the 25 nozzles, and 10 ink droplets per nozzle are continuously ejected in one inspection. At the moment when the ink droplet crosses the detected light beam of the detector 108, the amount of light received by the photodiode 302 decreases. In order to capture this, the output signal of the photodiode 302 that has passed through the I / V conversion circuit 403, the differentiation circuit 404, and the amplification circuit 405 is compared with a reference voltage by the comparison circuit 406. Only when the output signal falls below the reference voltage (period), the comparison circuit 406 outputs a signal indicating that an ink droplet has been detected. The signal output from the comparison circuit 406 is received by the CPU 402, and the time from when the drive signal is supplied to the inspection nozzle until the detection signal is obtained is stored in the memory 407. Even when a detection signal is not obtained before the next nozzle drive, the fact that it was not obtained is stored in 407 in the memory. Similarly, detection is repeated for all the inspection target nozzles in each region.

  FIG. 6 is a relationship diagram of ink droplet ejection positions, amplified sensor output signals, and threshold values. FIG. 6A shows the positional relationship between the nozzle array divided into five regions (1) to (5) and the detection light beam of the detector 108. FIG. 6B is an example of a sensor signal amplified with a certain amplification factor for each of the regions (1) to (5), the vertical axis indicates the amplitude of the sensor output, and the horizontal line in the graph indicates the comparison circuit 406. This is the reference voltage set by. Looking at the figure, the amplitude of the signal (degree of light modulation) in the central region (3) is the largest. Compared to this, the closer the LED 301 and the photodiode 302 are, the smaller the amplitude is. In this way, the degree of modulation of light when detecting ink droplets in the vicinity of the middle between the light source and the light receiver is the highest, and the degree of modulation decreases as it approaches the light source side or the light receiver side. This is presumably because the output fluctuation of the light receiver becomes small due to the influence of diffraction, although the light intensity shielded by the ink droplet is large near the light source. On the contrary, since the light intensity is small in the vicinity of the light receiver, the output fluctuation of the light receiving section is also small.

  In step S504 in FIG. 5, when ink droplets are detected for all 25 inspection target nozzles as described above, it is determined whether or not the amplification factor used here is appropriate as a threshold value (correction data). Determine the threshold. The determination procedure is as follows.

  For each area, out of 5 selected nozzles, signals are obtained from 3 or more nozzles (amplified sensor output signal is below the reference voltage), “appropriate”, if less than 3 Judged as “inappropriate”. This determination is performed for all five regions.

  Since the threshold cannot be determined only once, a change in the amplification factor of the amplifier circuit 405 (whether to increase or decrease) is determined based on the first determination result, and the process returns to step S502 for the second time. The same inspection is performed. Specifically, when the first determination result of a certain region is appropriate, the amplification factor for the region is set one step lower than the amplification factor at the first time in the second inspection. On the contrary, if the first determination result is inappropriate, the area is set to an amplification factor that is one step higher than the amplification factor in the first inspection in the second inspection. Thus, the amplification factor is reset (step S502), and the second inspection is performed (step S503).

The determination is made again based on the result of the second inspection. Specifically, if it is appropriate in the first inspection but inappropriate in the second inspection, the amplification factor in the first inspection is determined as a threshold value in the region. On the contrary, when it is inappropriate in the first inspection but appropriate in the second inspection, the amplification factor in the second inspection is determined as a threshold value in the region. If both the first time and the second time are appropriate, an amplification factor that is one step lower is set and the third inspection is performed. If both the first time and the second time become unsuitable, the amplification is further increased by one step and the third inspection is performed. In this way, for each region constituting one column, the amplification factor is changed and inspected until the determination result is inverted with respect to the previous inspection result, and the processing is repeated until the threshold values are determined for all the regions. (Step S504)
In step S505, it is determined whether the determination of the threshold value for each region has been completed for all nozzle rows (12 rows) of the print head. If NO, the process returns to step S510, another nozzle row is moved to the inspection position, and the inspection is repeated in the same procedure. If YES, the process moves to step S506.

  In step S506, all threshold values obtained for each nozzle row and each region are stored in the memory 407 as a correction data table. As shown in FIG. 6B, the detection sensitivity of the detector 108 varies depending on the detection position. The threshold value determined by the above-described procedure is a value for correcting the influence of the sensitivity fluctuation by reflecting the sensitivity fluctuation depending on the detection position. That is, this is a threshold value for setting a low amplification factor in a region with high detection sensitivity and a high amplification factor in a region with low detection sensitivity, whereby uniform detection is performed as a whole when a defective nozzle is detected. be able to.

  The graph of FIG. 6C is a plot of threshold values determined corresponding to each region. The threshold value is low in the central region (3) where the detection sensitivity is high, and the threshold value increases as the distance from the periphery increases. The threshold values obtained for each region in this way are stored in the memory 407 as a correction data table. This is used to correct the output of the detector in the actual defective nozzle detection described below.

<Defective nozzle detection method>
A procedure for detecting a defective nozzle using the correction data table obtained by the above preliminary measurement will be described with reference to the flowchart of FIG. The timing at which discharge failure is detected is immediately after the print head 102 is replaced, after a certain number of prints are performed, or when the user instructs a cleaning operation.

  In step S <b> 701, the carriage 101 is moved so that the nozzle row that performs non-discharge detection comes to the inspection position on the detector 108.

  In step S702, with reference to the correction data table stored in the memory 407 in the above-described procedure, the correction data corresponding to the first ejection region (one of the five divided regions) in the nozzle row is read out. A corresponding amplification factor is set in the amplifier circuit 405. What is stored as correction data is a threshold value. The amplification factor that is actually set is a value that is several counts higher than the threshold value. If the change amount of the amplification factor is linear with respect to the input value, it can be considered that the change amount of the amplitude level of the sensor signal by increasing the amplification factor by the same number of counts from the threshold value is almost uniform. Therefore, the sensor signal level obtained by increasing the amplification factor by several counts with respect to the threshold value is the same in any region in the nozzle array, and is a level sufficient for the threshold value for detecting ink droplets.

  In step S <b> 703, ink droplets are ejected in order of one nozzle for each region. In the nozzle discharge failure detection, the nozzle discharge drive is performed at the same discharge frequency and heating conditions as in actual printing. 10 ink droplets are continuously ejected per nozzle. At the moment when the ink droplet crosses the detected light beam of the detector 108, the amount of light received by the photodiode 302 decreases. The comparison circuit 406 outputs a signal indicating that an ink droplet has been detected only when the sensor output after amplification at the set amplification rate falls below the reference voltage (period). When the nozzle is driven but no ejection is performed, the sensor output remains higher than the reference voltage, and no signal is output from the comparison circuit 406. If no signal is output from the comparison circuit 406 within a predetermined period (from the time the next nozzle is driven) after the ejection signal is given to the nozzle, it is understood that the nozzle is a defective nozzle. The CPU 402 stores in the memory 407 the time from when the drive signal is given to the inspection nozzle until the detection signal is obtained. Even when the detection signal is not obtained, the fact that it was not obtained is stored in the memory 407. Ejection and detection are performed in the same manner for all nozzles in one divided area.

  In step S704, it is determined whether all the nozzles in one row have been completed. If NO, the process returns to step S702, the gain is set again to be suitable for the next region, and the same processing is repeated. If YES, the process moves to step S705.

  In step S705, it is determined whether or not the inspection has been completed for all the nozzle rows to be inspected. If NO, the process returns to step S701, another nozzle row is aligned with the inspection position, and the same processing is repeated. If YES, the process moves to step S706.

  In step S706, the detection information stored in the memory 407 is analyzed to determine whether there is a defective nozzle. As described above, a nozzle for which no detection signal is obtained is determined as a defective nozzle. Also, check whether there is any deviation from the average time of other neighboring nozzles until the detection signal is obtained after the discharge signal is given. to decide. The case where the time is remarkably shifted is considered to be due to the fact that the ejection direction of the ink droplet is deviated from the original direction, or that there is a foreign matter near the nozzle and the ejection amount is small. When printing is performed using this nozzle, there is a high possibility that the image quality will be lowered as a result. Therefore, such a nozzle is also determined as a defective nozzle.

  If it is determined in step S706 that there is no defective nozzle (YES), the process ends. If it is determined that there is a defective nozzle (NO), the process proceeds to step S707 to determine whether a recovery operation is necessary. The judgment method is as follows.

  In step S707, the number of times the recovery operation has been performed is referred to. If it is equal to or less than the predetermined number of times (N times), the process proceeds to step S708 to execute the recovery operation. On the other hand, if the recovery operation is already performed more than the predetermined number of times (N times), it is determined that there is no possibility of recovery or that there is some abnormality in the detector 108, and an error is displayed to display the device. Interrupt the operation.

  In the recovery operation of step S708, the drive is controlled so that the nozzle determined to be a defective nozzle is not used in actual printing. That is, the area to be printed with defective nozzles is complemented by other normal nozzles for printing. As another recovery operation, the print head 102 may be moved to the recovery unit 109 to perform a cleaning process for removing nozzle clogging. The cleaning process includes, for example, a method of driving the print head so as to eject a large amount of ink, a method of removing clogging by forcibly sucking ink by applying negative pressure from the outside of the nozzle, and from the ink tank side. There is a method of forcibly pushing out ink by pressurizing ink.

  In the above description, the correction data measurement and the subsequent non-discharge detection have the same number of nozzle row divisions. However, if the number of non-discharge detection divisions is increased, correction data measurement can be performed. It is possible to shorten the time required. In this case, the data of the area in between is determined from the measured correction data by interpolation calculation.

  According to the present embodiment described above, a defective nozzle can be detected with high accuracy regardless of the position even if an inexpensive light source is used. Also, the longer the print head, the greater the effect.

(Embodiment 2)
In the first embodiment, the amplification factor in the amplifier circuit 405 is changed to adjust the sensitivity of the detector 108. In this embodiment, the reference voltage in the comparison circuit 406 is changed. Since the overall configuration and operation of the apparatus are similar to those of the first embodiment, the description will focus on different points.

  FIG. 8 is an electrical block diagram of the present embodiment. The D / A converter 801 converts the instruction value from the CPU 402 into an analog signal, and inputs this to the comparison circuit 406 as a reference voltage. The amplification factor of the amplifier circuit 405 is fixed.

  When measuring the correction data, a plurality of inspections are performed as in the first embodiment. For each area, the reference voltage is changed and inspected until the determination result is inverted with respect to the previous inspection result, and the process is repeated until threshold values are determined for all areas. Specifically, when a certain area is determined to be “appropriate”, a reference voltage that is one step higher is set in the next inspection. On the other hand, if it is determined as “inappropriate”, the reference voltage is set to be one step lower in the next inspection.

  In this way, by changing the reference voltage of the comparison circuit 406 instead of the amplification factor for sensitivity adjustment of the detector 108, it is possible to obtain uniform detection sensitivity as in the first embodiment. Thereby, it is possible to detect a defective nozzle with high accuracy regardless of the position even if an inexpensive light source is used.

(Embodiment 3)
In this embodiment, the sensor signal is A / D converted and the CPU 402 analyzes the signal to detect a defective nozzle. In the electric block diagram of FIG. 9, the A / D conversion circuit 901 converts the sensor signal amplified by the amplification circuit 405 into digital and inputs it to the CPU 402.

  FIG. 10 is a flowchart showing a procedure for measuring correction data. In step S <b> 1001, the carriage 101 is moved so that one of the nozzle rows is positioned at an inspection position facing the detector 108. In step S1002, ink droplets are ejected for each nozzle. At the moment when the ink droplet crosses the detected light beam of the detector 108, the amount of light received by the photodiode 302 decreases. The output signal of the photodiode 302 is amplified by the amplifier circuit 405 through the I / V conversion circuit 403 and the differentiation circuit 404. The amplified output signal is converted into a digital value by the A / D conversion circuit 901, and the CPU 402 samples it at a constant cycle. Sampling data is stored in the memory 407.

  In step S1003, the minimum value in the region is extracted for the sampling data corresponding to one nozzle among the five nozzles representing one region. Similarly, the minimum value is extracted from the sampling data obtained with the remaining nozzles, and the average minimum value of five nozzles in the same region is obtained. The minimum value of each region corresponds to the minimum value of each of the regions (1) to (5) in FIG. In step S1004, the same processing is repeated for all nozzle rows. In step S1005, the average minimum value for each region obtained by the above-described procedure is stored in the memory 407 as correction data. In the present embodiment, since the ejection in the correction data measurement may be performed once per nozzle, there is an advantage that the measurement time is further shortened.

  After the above initial operation, the defective nozzle is detected. When an ink droplet is ejected from a certain nozzle to detect a defective nozzle, the CPU 402 samples the digital value from the A / D conversion circuit 901 to obtain measurement data (a plurality of sampling data corresponding to each nozzle). The CPU 402 reads out correction data (average minimum value) of the area corresponding to the nozzle from the memory 407, and uses the median value of the correction data and the signal level when ink is not ejected as a threshold value. The CPU 402 compares the measurement data with the threshold value, and determines that the nozzle is a non-ejection nozzle if all corresponding sampling data does not fall below the threshold value. If there is data that falls below the threshold value, normality / defectiveness is determined by the above-described method from the time lag from the start of ink droplet ejection until the signal falls below the threshold value.

(Embodiment 4)
In the first and second embodiments, when defective nozzle detection is performed using correction data, inspection is performed while sequentially adjusting the amplification factor and reference voltage of the circuit. However, in order to perform stable measurement by changing the amplification factor and the reference voltage, it is desirable to have a waiting time required for the circuit to stabilize. Although this waiting time is short, if the nozzle row is divided into a plurality of areas and the waiting time is inserted at each changeover, the total of all the nozzle rows leads to a relatively large delay. Therefore, in this embodiment, in order to minimize the delay, the order of ejection is changed in ascending order or descending order in accordance with the amplification factor and the reference voltage in units of regions.

  The table of FIG. 11 shows the amplification factor and the discharge order for the divided areas in one nozzle row. Note that. When applied to the form of the second embodiment (FIG. 8), the amplification factor column may be replaced with a reference voltage. The method for obtaining the amplification factor and the reference voltage in each region is as described in the first and second embodiments.

  The order of the areas where the discharge failure is detected is determined by comparing the magnitudes of the amplification factors in the respective areas, and from the smallest one to the largest one. Conversely, the order from large to small may be used. Alternatively, a plurality of regions having the same amplification factor may be collectively put in order, and the other regions may be placed either before or after that.

  In the example of FIG. 11, since the region (3) has the smallest amplification factor (amplification factor 2), this is examined first. The CPU 402 sets an amplification factor of 2 in the amplifier circuit 405 (FIG. 4), and then performs an ejection failure test for the nozzles included in the region (3) one by one. Next, the regions with the same gain (5) and regions (2) and (4) have the smallest gain. The CPU 402 changes the amplification circuit 405 to an amplification factor of 5. Since the amplification factor is changed, a waiting time (wait) is added for the time necessary for the circuit to stabilize. Thereafter, the region (2) is discharged and inspected, and then the region (4) is discharged and inspected. There is no waiting time between these areas (2) and (4). This is because they have the same amplification factor and no change, so no waiting time until stabilization is required. Subsequently, ejection and inspection are performed in the order of the region (5) and the region (6).

  In this way, the inspection order of the divided areas is set according to the magnitude of the amplification factor and the reference voltage, and the areas of the same value are collectively detected in order, so the amplification factor and the reference voltage at the switching of the areas The number of changes, that is, the number of insertions of waiting time can be minimized. Therefore, the total inspection time can be further shortened.

(Embodiment 5)
When acquiring correction data in the preliminary measurement, there is a possibility that defective nozzles are included in the nozzles selected as representatives of the respective regions. If preliminary measurement is performed in such a state, correct correction data cannot be obtained. Therefore, in this embodiment, it is determined whether the representative nozzle is normal, and if there is a defective nozzle, it is changed to another nozzle.

  FIG. 12 is a flowchart showing a procedure for measuring correction data. Steps S1201 to S1203 are the same as steps S501 to S503 described in FIG. In step S1204, it is determined whether or not the detection results of five nozzles representing a certain region all match. If the same output fluctuation set by all five nozzles is obtained, all are determined to be normal nozzles, and the process proceeds to the next step S1205. If all five do not match (for example, if 4 nozzles are detected and 1 nozzle is not detected), the process proceeds to step S1208, and whether or not one undetected nozzle is defective is normal. Judgment is made.

  In step S1208, determination is performed as follows. Since the detection sensitivity of each nozzle in a certain area is substantially the same, an error in the amplification factor for one step is allowed in consideration of the influence of noise. In this case, even if the amplification factor is changed by two steps, the nozzle that has not been detected is likely to be an abnormal nozzle. Therefore, the discharge and the inspection are performed twice again while increasing the amplification factor step by step. As a result, if the five nozzles do not match, it is determined that the non-detected nozzle is defective. In step S1209, the representative nozzle is changed to another nozzle and replaced. The nozzle to be replaced is assumed to be close to the defective nozzle. Thereafter, returning to step 1203, the ejection is inspected again, and the same is repeated until the process returns to step S1205. The procedure from step S1205 is the same as that described with reference to FIG.

Front view showing the configuration of the main part near the carriage Diagram showing the nozzle arrangement on the nozzle surface Sectional view showing the configuration of the detector Electrical block diagram centering on the detector Flowchart diagram showing correction data measurement procedure Relationship diagram of ink droplet ejection position, sensor signal, and threshold Head undischarge detection flowchart Electrical block diagram in another embodiment Electrical block diagram in another embodiment Flowchart diagram showing correction data measurement procedure Table showing amplification factor setting value and discharge order Flowchart diagram showing the procedure for measuring correction data

Explanation of symbols

101 Carriage 102 Printhead 103 Shaft 104 Carriage Conveyance Motor 105 Conveyor Belt 106 Platen 107 Media 108 Detector 109 Recovery Unit 301 LED
302 Photodiode 303 Ink absorber 304 Detection circuit

Claims (8)

A carriage mounted with a print head in which a nozzle row is formed by a plurality of nozzles that eject ink, and a carriage that moves relative to the medium;
A detector comprising a light source and a light receiver, and optically detecting ink ejected from the nozzle and passing through a detected light beam between the light source and the light receiver;
For each region obtained by dividing the nozzle row into a plurality of regions, a memory that stores in advance correction data for each region obtained based on the output of the detector in a preliminary measurement;
A printer comprising: a control unit configured to discharge ink from the plurality of nozzles and to detect a defective nozzle using an output of the detector and correction data stored in the memory.   The printer according to claim 1, wherein the preliminary measurement is performed using a nozzle representing each of the divided areas.   3. The preliminary measurement is performed by determining whether or not a defective nozzle is included in the representative nozzle, and performing a preliminary measurement by changing to another nozzle if there is a defective nozzle. Printer.   The printer according to claim 1, wherein the correction data is a value for correcting an amplification factor of an amplifier circuit of the detector.   The printer according to claim 1, wherein the correction data is a value for correcting a reference voltage in a comparison circuit of the detector.   4. The printer according to claim 1, wherein the correction data is a value for correcting a threshold value to be compared with measurement data obtained by digitally converting the output of the detector.   5. The control unit detects a defective nozzle for each area, and sets the order of areas to be detected according to the magnitude of correction data for each area. Or the printer of 5.   8. The printer according to claim 1, wherein when a defective nozzle is detected, printing is performed without using the detected defective nozzle, or a cleaning process is performed to remove nozzle clogging.

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