JP4933073B2 - Droplet discharge device - Google Patents

Description

  The present invention includes a droplet discharge unit that discharges droplets from a plurality of nozzles, such as an inkjet recording apparatus that records an image by discharging ink droplets from a plurality of nozzles of a recording head to a recording medium. The present invention relates to a droplet discharge device.

  Ink jet recording devices cause non-ejection that does not eject ink droplets from the nozzles due to clogging of the nozzles of the recording head due to dust or thickened ink, or disconnection of the heater of the nozzle in the case of Bubble Jet (registered trademark). There is a case.

  In an ink jet recording apparatus, an image is recorded by ejecting ink droplets from a plurality of nozzles several thousand to several hundred thousand times per second. For this reason, if recording is continued, deterioration phenomena in the nozzle such as deterioration of the water-repellent state in the nozzle and burning of the heater occur, and energy efficiency for ejection deteriorates. As a result, the ejection speed (flying speed), size, flight interval, number of satellites, and ejection direction of the ejected ink droplets (main droplets and satellites that are minute ink droplets formed by splitting the main droplets) Physical characteristics such as change. For this reason, even when ejected, ink droplets do not land on the recording medium, substantial non-ejection, displacement of the landing position, and the size of the landing droplets that combine the main droplet and the satellite change (decrease). Discharge failure occurs such that initial discharge from the eyes until the number of discharges is repeated to some extent becomes defective (hereinafter referred to as a firing failure). When such ejection failure or non-ejection occurs, the recorded image is disturbed, and the recording quality is deteriorated.

  On the other hand, for example, as described in Patent Document 1 below, a configuration is adopted in which the discharge state of ink droplets from each nozzle of the recording head is detected by a photo interrupter method. In the photo interrupter method, a light emitting element and a light receiving element that constitute a photo interrupter are arranged to face each other, and an ink droplet ejected from each nozzle of a recording head passes through a light beam incident on the light receiving element from the light emitting element to shield it. I am doing so. Then, the ejection state is determined based on the change in the detection signal corresponding to the change (reduction) in the amount of light received by the light receiving element due to the amount of light shielding. Conventionally, ejection is performed when the amount of light shielding when the main droplet of the ejected ink droplet shields the light beam is greater than or equal to a certain value (a change in the detection signal is greater than or equal to a certain value). I was judging.

Before performing image recording, after performing the initial process, the ejection / non-ejection of each nozzle is detected as described above, and if there is no non-ejection nozzle, image recording is performed. Performs recovery control and error processing for sucking ink from all nozzles of the recording head to repair non-ejection nozzles, that is, to restore ejection.
JP-A-11-17985

  As described above, conventionally, when the discharge state is determined to be only two states of discharge / non-discharge based on the light shielding amount of only the main droplet of the discharged ink droplets, the ink from all the nozzles is detected when the non-discharge nozzle is detected. Suction and error handling were performed.

  However, the ejection state of the nozzle includes ejection failure due to the above-described deterioration phenomenon in the nozzle, in addition to non-ejection that does not completely eject. Such a defective ejection nozzle can be repaired on a nozzle-by-nozzle basis, for example, by preliminary ejection in which the nozzle is driven a plurality of times to eject ink droplets. For this reason, compared with the ink suction for repairing the non-ejection nozzle, it can be performed in a short time and the ink consumption is small.

  On the other hand, in the past, since ejection failure cannot be accurately determined separately from non-ejection, it may be judged that ejection failure is non-ejection and ink suction is performed, and it takes time to repair the nozzle, and repair There is a problem that the amount of ink used for the ink increases.

  On the other hand, physical characteristics such as the size of main droplets and satellites, ink ejection speed, flight interval, and number of satellites of ink droplets ejected normally are always constant. The characteristics change. Therefore, if the physical characteristics of the main droplet and satellite can be grasped in the detection of the discharge state, discharge failures can be accurately determined separately from non-discharge, and normal discharge, non-discharge, and discharge failure are accurately determined and detected. It is considered possible.

  Therefore, the problem of the present invention is not limited to the ink jet recording apparatus, but is a liquid droplet ejection apparatus including a liquid droplet ejection apparatus that ejects liquid droplets from a plurality of nozzles, and a control apparatus that controls the apparatus. In the system, when detecting the discharge state of the droplets from the plurality of nozzles, normal discharge, non-discharge, and discharge failure of each nozzle are determined based on the physical characteristics of the main droplet and satellite that change according to the discharge state of each nozzle. An object of the present invention is to provide a configuration that can be accurately determined and detected.

In order to solve the above problems, the present invention provides a droplet discharge unit having a plurality of nozzles that discharge droplets, a light emitting unit that emits light, a light receiving unit that receives light emitted from the light emitting unit, A detection signal based on the amount of light received by the light receiving unit when the nozzle is driven at a position where a droplet discharged from the nozzle can block light emitted from the light emitting unit toward the light receiving unit. Determination means for determining the discharge state of the nozzles, suction means for performing a suction operation for sucking droplets from the plurality of nozzles, preliminary discharge means for causing the nozzles to perform preliminary discharge, the suction means, and the And a light emitting unit that emits light after the liquid droplets discharged from the nozzle are separated into main droplets and satellites. The determination means includes a predetermined normal ejection signal and a detection signal corresponding to a case where liquid is normally ejected from the nozzle for each of the plurality of nozzles. The first state in which droplets are ejected normally when substantially the same case, the second state in which droplets are not ejected when the waveform of the detection signal is substantially constant, and the waveform of the detection signal vary However, when the difference is different from the normal discharge signal, it is determined as a third state in which droplets are discharged but a discharge failure has occurred. When it is determined that at least one of the nozzles is in the second state, the suction unit performs the suction operation of the plurality of nozzles, and one of the plurality of nozzles is also in the second state. Judge that there is If non wherein the causing preliminary discharge of the nozzle it is determined that the third state by said determining means to the preliminary discharge means.

  According to the present invention, in the detection of a droplet discharge state from a plurality of nozzles of a droplet discharge unit, main droplets and satellites that change according to the discharge state together with the presence or absence of the main droplets and satellites discharged for each nozzle. Based on the physical characteristics (for example, main droplet and satellite size, discharge speed, flight interval, number of satellites, etc.), it is possible to accurately determine and detect normal discharge, non-discharge, and defective discharge of each nozzle. it can. And, based on the accurate detection result, the repair control of the non-ejection or defective ejection nozzle is optimally performed, the repair can be performed in a short time, and the excellent effect that the amount of liquid droplets used for the repair can also be saved. can get.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, an embodiment of a configuration for detecting the ejection state of ink droplets from a plurality of nozzles of a recording head in an ink jet recording apparatus configured as a printer will be described. The ink jet recording apparatus is of the bubble jet (registered trademark) type, and ejects ink droplets from the nozzles with the pressure of bubbles generated in the ink in the nozzles due to the heat generated by the heaters provided in the nozzles of the recording head. And

  FIGS. 1A and 1B show the configuration of the ink jet printer 101 according to the first embodiment, where FIG. 1A shows the front of the printer and FIG. 1B shows the side.

  1A and 1B, a carriage 102 is slidably attached to a guide shaft 103 and reciprocates in both directions of arrows A and A ′ by driving of a main scanning motor (see FIG. 10). On the carriage 102, a recording head 108 as a droplet discharge unit that discharges ink droplets from a plurality of nozzles is mounted downward. When the paper feed roller 105 is rotationally driven by a sub-scanning motor (see FIG. 10), a recording medium (paper) (not shown) is fed on the platen 104 in the direction of arrow B. Ink droplets are sequentially ejected from a plurality of nozzles (see FIGS. 2 and 3) provided on the front surface (lower surface in the drawing) of the recording head 108 and land on the recording medium, whereby an image is recorded on the recording medium. The

  A recovery unit 107 having a wiper 106 is provided at the home position at the right end in FIG. 1A of the movement range of the carriage 102, that is, the movement range of the recording head 108. As a preventive or repairing measure against the ejection failure of the nozzles of the recording head 108, wiping to remove dust attached to the front surface of the recording head 108 with a wiper, or an operation of sucking ink from the nozzles of the recording head 108 with the recovery unit 107 is performed. .

  Further, the ejection state detection sensor 109 is provided in the non-printing area at the left end in FIG. The sensor 109 detects the ejection state of ink droplets from each nozzle of the recording head 108 (normal ejection / non-ejection / ejection failure). The sensor 109 is configured as a photo interrupter having a light emitting element and a light receiving element. Ink droplets (main droplets and satellites) ejected from the nozzles of the recording head 108 pass through the light beam incident on the light receiving element from the light emitting element of the sensor 109 and shield it. The ejection state of each nozzle is determined and detected based on a detection signal generated from the output corresponding to the amount of light received by the light receiving element based on the amount of light blocked at that time. Hereinafter, the detection method will be described.

FIG. 2 shows an outline of discharge state detection using the discharge state detection sensor 109. As shown in FIG. 2, sensor 109 includes a light emitting element 202, light receiving element 203, an aperture 204 for emitting light device, and a like aperture 205 and the ink absorbing member 206, for receiving light elements. The light emitting element 202 and the light receiving element 203 are arranged so as to sandwich an area near the lower side of the front face of the recording head 108 at the ejection position detection position. Apertures 204 and 205 are provided in the vicinity of the front sides of both elements 202 and 203 in order to narrow the light beam 209 incident on the light receiving element 203 from the light emitting element 202 and improve the S / N ratio. Note that the size of the apertures 204 and 205 through which light passes is, for example, 2 mm × 2 mm. For the light emitting element 202, for example, a bullet-shaped diameter of 5 mm and a narrow directivity infrared LED are used, and light is emitted by applying a voltage of 5V. The light receiving element 203 reads the light amount of the light beam 209 incident on the light receiving element 203 from the light emitting element 202. A voltage is applied to the light emitting element 202 only when the ejection state of the nozzle is detected. For the light receiving element 203, for example, a photodiode having the highest spectral sensitivity characteristic in the infrared region is used. Of course, other elements such as a semiconductor laser may be used for the light emitting element 202, and other elements such as a phototransistor may be used for the light receiving element 203. Increasing the amount of light emitted from the light emitting element 202 can increase the discharge state detection signal and improve the S / N ratio.

  When the ejection state of each nozzle 201 of the recording head 108 is detected, each nozzle 201 is sequentially driven (heater generates heat) in accordance with a ejection command from the host device, and the main droplet 207 of ink droplets is ejected from each nozzle 201 ( Fired). Immediately after the ejection, the main droplet 207 is torn and a satellite 208 is generated. The main droplet 207 and the satellite 208 pass (shield) the light beam 209 and land on the sponge-like ink absorber 206 to be absorbed.

  Here, the ink droplets ejected during normal ejection begin to separate into the main droplet 207 and the satellite 208 within a range of about 50 μm to 500 μm away from the front end of the ejection port of the nozzle 201. Therefore, unless the discharge port of the nozzle 201 in front of the recording head 108 is separated from the light beam 209, the main droplet 207 and the satellite 208 that have not yet been separated pass through the light beam 209 together, and thus cannot be distinguished. . For this reason, in this embodiment, the ejection opening of the nozzle 201 and the light beam 209 are separated by a predetermined distance Lz, and the distance Lz is at least the distance at which the ink droplets ejected between them are separated into the main droplet 207 and the satellite 208. Therefore, it is set to at least 0.1 mm, for example, about 3 mm. In this way, the main droplet 207 and the satellite 208 separately pass through the light beam 209 to be shielded.

  FIGS. 3A and 3B are a front view of the carriage 102 when the ejection state is detected, as viewed from the front, and a plan view as viewed from below. As shown in FIG. 3B, the plurality of nozzles 201 of the recording head 108 are arranged in four rows, and the arrangement direction of each row is a direction in which the light emitting element 202 and the light receiving element 203 face each other, and the sub-scanning is performed. Along the direction (the conveyance direction of the recording medium). The direction in which the nozzle rows are arranged at intervals is along the movement direction (main scanning direction) of the carriage 102.

  Here, for example, the upper three nozzle arrays are dye ink ejection nozzle arrays (cyan, magenta and yellow from the top), and the lowest nozzle array is a pigment black ink ejection nozzle array. Each nozzle in the nozzle row for pigment ink is intended for high-speed recording of a text document, and therefore the ejection port is one size larger than each nozzle in the nozzle row for dye.

  When the ejection state of the nozzle is detected and the ejection is normal, the main droplet 207 and the satellite 208 of the ink droplets ejected from the nozzle 201 are indicated by broken arrows in FIGS. 2 (a) and 3 (a). In this way, the light beam 209 is passed (light-shielded) and landed and absorbed by the absorber 206. At this time, a change in the amount of light incident on the light receiving element 203 is read by the light receiving element 203, and a signal obtained by current / voltage conversion of the output photocurrent becomes an ejection state detection signal for determining the ejection state of the nozzle 201.

  FIG. 4 shows how ink droplets ejected during normal ejection are separated into main droplets 207 and satellites 208. FIG. 4 shows the discharge state of one nozzle shown in FIG. The nozzle is formed by an ink flow path 401, a heater 402 provided on one side of the end portion, and an ejection port 403 provided on the opposite side. Ink is supplied from the tank (not shown) on the carriage to the ink flow path 401 of each nozzle and stored. A pulse is applied to the heater 402 at the start of ejection, and the heat generation generates bubbles 404 in the ink channel 401, and the ink in the channel 401 is ink droplets by the pressure of the bubbles 404 as shown in FIG. (Main droplet before separation) 207 is pushed out of the discharge port 403. Thereafter, the bubbles 404 are further enlarged, and the ink droplets 207 are ejected outside the ejection port 403 as shown in FIG. From here, the temperature of the heater 402 decreases, and the bubbles shrink. As shown in FIG. 4C, the tail portion of the ejected ink droplet 207 is torn off, and the main droplet 207 and the satellite 208 are divided into substantially the same size as shown in FIG. 4D. That is, at the time of normal ejection, the number of satellites 208 is one, and the size of the main droplets 207 and the satellites 208 is substantially the same and is almost constant. In addition, the discharge speed (flying speed) and the flying interval (time difference) between them are almost constant.

  FIG. 5 shows the waveform of the discharge state detection signal when the discharge state of the nozzle is normal discharge as shown in FIG. A drive signal 501 in FIG. 5 is a signal for starting ejection, and the level indicated by the arrow of the symbol Ch1 in the voltage on the vertical axis is 0V, and the broken line 1 枡 is indicated in units of 2V. The drive signal 501 is normally fixed at 3.3 V. However, when there is a discharge command, the drive signal 501 falls from 3.3 V, and discharge starts as a trigger. Here, a waveform when one nozzle is continuously ejected at the ejection frequency f = 1 KHz is shown. The time on the horizontal axis is indicated by a broken line of 1 枡 in units of 200 μs. The drive signal 501 falls at a period of 1 ms.

  An ejection state detection signal (hereinafter simply referred to as a detection signal) 502 represents the amount of light incident on and received by the light receiving element 203 as an electrical signal. The level of the arrow indicated by the symbol Ch2 is 0V, and the first broken line is 5V. Shown as a unit. Here, the detection signal 502 is configured such that the voltage decreases when the amount of light received by the light receiving element 203 becomes small (darker).

  In FIG. 5, the detection signal 502 decreases to about −7 V after about 300 μs after the drive signal 501 falls and discharge is started, then increases to about 0 V, then decreases to about −7 V, and then decreases to about −7 V. The voltage before discharge is restored. That is, the voltage changes twice in a valley shape for one discharge. The first valley-shaped change portion represents the main droplet 207, and the next change portion represents the light shielding of the light beam 209 by the satellite 208. Here, since the detection signal 502 represents the light shielding amount, the amplitudes of the valley-like changed portions of the detection signal 502 represent the sizes of the main droplet 207 and the satellite 208, and the change times t1 and t3 represent the ejection speed (flying speed). ) Will be shown.

  As shown in FIG. 4D, the main droplet 207 and the satellite 208 are approximately the same size during normal ejection with the nozzle of the apparatus of this embodiment. For this reason, the amplitudes of the two valley-like change portions of the detection signal 502 in FIG. 5 are substantially equal. When the discharge speed is calculated, the time t1 required for the main droplet 207 to pass through the aperture length of 2 mm is about 250 μs, and the time t3 required for the satellite 208 to pass through the aperture length of 2 mm is about 400 μs. About 8 m / s and the satellite speed are about 5 m / s. Further, the number of satellites can be detected from the number of valley-shaped changes. Here, since the valley-shaped change is two times, there is one satellite, but when the change is three times, there are two satellites. Furthermore, it is also possible to detect the flight interval (time difference) between the main droplet 207 and the satellite 208 by detecting the interval between the changed portions of the main droplet 207 and the satellite 208. In the case of FIG. 5, the flight interval t2 between the main droplet and the satellite is about 10 μs. In this way, by detecting the amplitude of the detection signal, the change time, the interval between the change portions, and the number of changes, the size of the main droplet 207 and the satellite 208, the discharge speed (flying speed), the flying interval, and the number of satellites can be detected. Can do.

  FIGS. 6A to 6E show states after a certain time has elapsed since the discharge in different discharge states. FIG. 6A shows the normal ejection. As described above, the main droplet and the satellite have substantially the same size during the normal ejection. FIG. 6B shows a non-ejection state. In this case, ink droplets are not ejected due to ink sticking to the nozzles, clogging of dust, or the occurrence of bubbles, that is, a failure of the heater.

  6C to 6E show a discharge failure state. In FIG. 6C, the main droplet 207 and the satellite 208 are smaller than in normal ejection, and the sizes are also different. This is because the transfer of ejection energy becomes worse due to deterioration of the nozzle, ink fixation, and change in ink viscosity. As the main droplet 207 becomes smaller, the satellite 208 also becomes smaller, and the size of the main droplet 207 and the satellite 208 becomes larger. It also varies. In FIG. 6 (d), the satellite 208 is split into two. This is because the firing efficiency is unstable due to nozzle deterioration and ink sticking. The number of satellites 208 may be 0 (not generated) or may be two or more.

  In FIG. 6E, the size of the main droplet 207 and the satellite 208 is substantially the same as that of normal ejection, but the ejection speed is slow and the flight interval between the main droplet 207 and the satellite 208 is short. This occurs when the heater burns due to deterioration or the viscosity of the ink increases. The ink viscosity changes when the outside air temperature or humidity changes, or when the ink temperature in the nozzle changes due to continuous ejection. In this way, it is possible to know the normal ejection / non-ejection / ejection failure state by detecting the size, ejection speed, number of satellites, and flight interval, as well as the presence / absence of main droplets and satellites.

  FIG. 7 shows a drive signal 501 and a detection signal 502 when a certain nozzle is driven at an ejection frequency of 10 kHz in the same format (time is 1５100 μs) as in FIG. When the drive signal 501 falls to near 0V, a voltage is applied to the heater of the nozzle, and if normal, ejection starts, but in FIG. 7, the detection signal 502 does not change even if the drive voltage 501 falls to near 0V. . That is, since the detection target nozzle is in a non-ejection state as shown in FIG. 6B, ink droplets are not ejected, and the amount of light shielding does not change, so the voltage of the detection signal 502 becomes substantially constant. When such a waveform is shown, it is determined that the detection target nozzle is not ejected. Note that a small change in the detection signal 502 is noise in the measurement system.

  FIG. 8 shows the change of the detection signal 502 when the ejection command by the drive signal 501 is performed 18 times for a certain nozzle in the same format (time is 1 枡 10 ms unit) as in FIG. The output voltage (maximum fluctuation value) of the detection signal 502 is less than 5 V until the fall of the drive signal 501 (discharge command) is about tenth, and the amplitude and change time of the satellite are longer than the main droplet. . That is, this indicates that the ejected ink droplet is smaller than the normal ejection, the satellite is larger than the main droplet, and the ejection speed is slow, as shown in FIG. 6C. Yes.

  In FIG. 8, the output voltage of the detection signal 502 increases as the number of ejections increases, and the fall of the drive signal 501 becomes substantially constant (stable) at about the 15th time. In this way, the detection voltage increases according to the number of ejection commands. The initial ejection failure is poor and the ejection state is poor and almost no ejection is performed. However, as the number of times of driving is increased, the ejection failure is improved and ejection droplets gradually. It shows that the normal discharge was achieved at about the 15th time. When the waveform as shown in FIG. 8 is shown, it is determined that there is a discharge failure (a discharge failure) until the 14th discharge command. Here, the discharge frequency f is set to 200 Hz in order to see the change state of the firing failure for a long time.

  FIG. 9 shows the change of the detection signal 502 when the ejection command is performed nine times for a certain nozzle in the same format (time is 1 枡 5 ms unit) as in FIG. From FIG. 9, it can be seen that the output voltage of the detection signal 502 is small for both the main droplet and the satellite from the first to the fifth time of the ejection command, the satellite is larger than the main droplet, and the ejection speed of the satellite is slower. In addition, at the fourth discharge command, it can be seen that the satellite is split into two as shown in FIG. When such a waveform of the detection signal 502 is shown, it is determined that there is a discharge failure (discharge unstable) until the fifth discharge command.

  As described above, by reading the physical characteristics such as the size of the main drop and satellite, the discharge speed, the flight interval, and the number of satellites, which change depending on the discharge state, from the detection signal 502, the presence or absence of the main drop and the satellite, It can be seen that the normal ejection / non-ejection / ejection failure state can be accurately determined and detected.

  FIG. 10 shows the configuration of the control system of the ink jet printer 101 of this embodiment. In the figure, a recording head control circuit 1002 electrically controls the recording head 108 in accordance with an instruction from a CPU 1005 and ejects ink droplets according to image data.

  The detection signal generation circuit 1004 generates detection signals as shown in FIGS. 5 and 7 to 9 by, for example, amplifying the photocurrent output from the light receiving element 203 of the ejection state detection sensor 109 by current / voltage conversion. To do. Further, the detection signal is further processed and converted into a discharge state information signal for each nozzle, specifically, a time-series data signal of the voltage value of the detection signal that changes due to light shielding of the main droplet and the satellite.

  The main scanning motor 1006 is a drive source for moving the carriage 102 in the directions of arrows A and A ′ in FIG. The sub-scanning motor 1007 is a drive source for transporting the recording medium in the B direction in FIG. A recovery operation motor 1008 and a recovery operation actuator 1009 operate the recovery unit 107 to perform recovery operations such as ink suction operation from the nozzles of the recording head 108 and wiping that wipes the front of the recording head 108 with the wiper 106. It is a driving source. The recovery operation sensor 1010 is a plurality of sensors for detecting the operation state of the recovery unit 107. The mechanism control circuit 1011 controls or manages the motors 1006 to 1008, the actuator 1009, and the sensor 1010.

  The CPU 1005 controls the operation of each unit of the inkjet printer as a whole in accordance with a control program stored in the ROM 1012. The control program stored in the ROM 1012 includes an ink droplet discharge state detection program for detecting the discharge state of ink droplets from each nozzle of the recording head in the processing procedure shown in FIG. The RAM 1013 is used to temporarily store data such as various parameters necessary for the process executed by the CPU 1005 according to the control program, and temporarily store image data. A non-volatile memory 1014 such as an EEPROM is used for storing necessary data such as the detection result of the ejection state of each nozzle of the recording head even when the apparatus power is turned off.

  The operation / display unit 1015 displays various switches for the user to perform necessary operations, such as power-on of the inkjet printer and online / offline settings with the host device 1017, and the status of the device, and notifies the user. It has a display to do.

  The host device 1017 supplies image data to the ink jet printer, and is, for example, a computer that creates and processes data such as images related to printing. In addition, a reader unit for image reading or a digital camera may be used as the host device 1017. Image data, other commands, status signals, and the like are transmitted / received to / from the host device 1017 via the interface 1016.

  In the above configuration, when detecting the ejection state of each nozzle 201 of the recording head 108, first, the main scanning motor 1006 is driven, and one column of the nozzle array of the recording head 108 is true of the luminous flux 209 as shown in FIG. The carriage 102 is moved to the upper position. Next, a signal is sent from the recording head control circuit 1002 to the recording head 108, and the ink ejection operation from each nozzle in the one row is sequentially performed for each nozzle. At the same time, the detection signal generation circuit 1004 generates a detection signal from the photocurrent output from the light receiving element 203, and the detection signal is based on the ink discharge timing signal from the recording head control circuit 1002 and the discharge state for each nozzle. It is converted into information (time series data of the voltage value of the detection signal). The ejection state information is temporarily stored in the RAM 1013.

  The CPU 1005 detects the size, discharge speed, flight interval, and number of satellites together with the presence or absence of discharged main droplets and satellites based on the discharge state information for each nozzle. Based on the results, normal discharge / non-discharge / Judge ejection failure. Then, the determination result is stored in the nonvolatile memory 1014. Details of the determination method will be described later with reference to FIG.

  In this way, the discharge state of each nozzle in the row is sequentially detected, and when the discharge detection processing for all the nozzles in the row is completed, the carriage 102 is moved to a position where the next nozzle row is directly above the light beam 209. And discharge detection processing for each nozzle in the nozzle row is performed.

  In this way, after performing ejection detection processing for all nozzles in all nozzle rows, if there is a non-ejection nozzle based on information stored in the nonvolatile memory 1014, ink suction operation from all nozzles of the recording head 108 is performed. Do. In this case, the main scanning motor 1006 is driven to move the carriage 102 to the position of the recovery unit 107, and the recovery operation motor 1008 and the recovery operation actuator 1009 are driven while monitoring the output of the recovery operation sensor 1010. Ink suction operation from all nozzles. If there is a defective discharge nozzle, a discharge command is sent only to the defective discharge nozzle to cause preliminary discharge. Thereby, it is possible to repair a temporary non-ejection or ejection failure of each nozzle of the recording head.

  Further, referring to the history of the non-volatile memory 1014, if there is a nozzle whose failure state does not completely recover even after several repair controls, the host device 1017 displays an error display and a message display prompting head replacement.

  In the above description, the discharge state information based on the detection signal is acquired for each nozzle, and the discharge state of the nozzle is determined based on the information. However, the discharge state information for all the nozzles is acquired for each nozzle and stored in the RAM 103. After storing, the discharge state may be determined for each nozzle based on the discharge state information.

  FIG. 11 shows a configuration relating to generation and processing of a detection signal. In the figure, reference numeral 1101 denotes a light emitting unit including the light emitting element 202 and the aperture 204 of the ejection state detection sensor 109, and 1104 denotes a light receiving unit including the light receiving element 203 and the aperture 205. The components from the IV converter 1105 to the A / D converter 1108 are included in the configuration of the detection signal generation circuit 1004.

  Necessary power supply is supplied from the power supply 1103 to the control unit 1102. The control unit 1102 removes noise from the supplied power and supplies voltage and current power suitable for the light emitting element of the light emitting unit 1101. Accordingly, the light emitting element emits light, and the light flux is received by the light receiving element of the light receiving unit 1104. When detecting the ejection state of the nozzle, the main droplet and satellite of the ink droplets ejected from the nozzle pass through the light flux to block the light, the amount of light received by the light receiving element changes, and the photocurrent output by the light receiving element changes. . After the photoelectric current is converted into a voltage by the IV converter 1105, only the component of the band necessary for detection is taken out by the filter circuit 1106, and it is amplified by the AMP circuit 1107 to generate a discharge state detection signal. Further, the A / D converter 1108 performs A / D conversion on the detection signal, and outputs time-series data of the voltage value (digital value; hereinafter also referred to as detection value) of the detection signal. The detected value data is divided and output as ejection state information data for each nozzle based on the ink ejection timing signal from the recording head control circuit 1002, and is temporarily stored in the RAM 1013. The CPU 1005 determines the size, discharge speed, as well as the presence / absence of main droplets and satellites discharged for each nozzle, depending on the presence / absence of the detection value as the stored discharge state information for each nozzle, the magnitude of the change, and the change time. The flight interval and the number of satellites are detected, and normal discharge / non-discharge / discharge failure is determined for each nozzle based on the detection result.

  FIG. 12 is a flowchart illustrating a control procedure of the CPU 1005 for detecting the discharge state of the nozzle and performing a repair operation. A discharge state detection program corresponding to this control procedure is stored in the ROM 1012. When the CPU 1005 executes this program, nozzle discharge state detection and repair operations are performed under control according to the program. Note that the discharge state detection and repair operation may be performed under the control of a control program such as a printer driver for the host device 1017 such as a PC to control the inkjet printer 101.

  In the control procedure of FIG. 12, first, when starting the detection of the discharge state of the nozzle, the normal discharge values of the physical characteristics related to the discharge state of the main droplet and the satellite for determining the normal discharge are used as the normal discharge values of the main droplet and the satellite discharge droplets. The size, discharge speed, flight interval, and number of satellites are set (step S1). These normal discharge values are set to values having a width in consideration of variations. In addition, the size, ejection speed, flight interval, and number of satellites of the ejected droplets vary depending on the type of ink to be ejected (dye / pigment or color) and the nozzle diameter. Depending on the type of ink and the nozzle diameter, it is set separately. These values are determined in advance and stored in the ROM 1012, and are selected and set according to the nozzle row to be detected.

  Next, the nozzle ejection conditions, that is, the number of ejection commands for each nozzle and the ejection frequency are determined (step S2).

  Next, the carriage 102 is moved, and one nozzle row to be detected by the recording head 108 is moved immediately above the light flux 209 of the ejection state detection sensor 109 (step S3).

  Next, an ejection pulse is applied to one detection target nozzle (step S4). As a result, the one nozzle is driven, and a detection signal corresponding to the discharge state of the main droplet and satellite from the nozzle is generated, which is converted into time-series data of detection values as discharge state information of the nozzle. Is temporarily stored.

  Next, the presence / absence of the main droplet, that is, the presence / absence of the ejection of the main droplet is determined by checking the presence / absence of the change in the detection value due to the light shielding of the main droplet (step S5). If there is no change in the detected value, it is determined that there is no ejection of the main droplet and, of course, no satellite is ejected, and the nozzle to be detected is stored as a non-ejection nozzle in the nonvolatile memory 1014 (step S11). Proceed to step S8.

  On the other hand, if there is a change in the detected value, it is determined that at least the main droplet has been ejected, and the process proceeds to step S6. In step S6, the size, discharge speed, flight interval, and number of satellites of the main droplets and satellites ejected from the time-series data of the detected values are detected, and whether each value is the same as the normal value set in step S1 ( Judge whether it is within the range of normal value). If each value is the same, the target nozzle is stored as a normal ejection nozzle in the nonvolatile memory 1014 (step S7), and then the process proceeds to step S8.

  On the other hand, if one item is different from the normal value among the size, discharge speed, flight interval, and number of satellites (if it is out of the normal value range), the target nozzle is non-volatile as a defective discharge nozzle. Stored in the memory 1014 (step S12), and then the process proceeds to step S8.

  In step S8, it is checked whether detection of all nozzles in all nozzle rows is completed. If detection of all nozzles in one detection target nozzle row is not completed, the process returns to step S3, and the next detection target nozzle row is moved directly above the luminous flux 209. If detection of all nozzles in the detection target nozzle row has not been completed, the process returns to step S4 as indicated by the dashed arrow. Then, the detection operation for each nozzle is sequentially repeated by repeating the processing from step S4 onward.

  On the other hand, when the detection of all nozzles in all nozzle rows is completed, it is checked whether there is a non-ejection nozzle by looking at the data stored in the nonvolatile memory 1014 (step S9). Non-ejection repair control such as suction is performed (step S13).

  If there is no non-ejecting nozzle, it is checked whether there is a defective ejection nozzle (step S10). If there is, a defective ejection repair control such as preliminary ejection is performed on the nozzle (step S14).

  After performing the non-ejection or ejection defect repair control in steps S13 to S14, the process returns to step S3 to repeat the processes in and after step S3 to perform the ejection detection operation for all nozzles again. Then, repair control is performed. If all nozzles do not discharge normally even after repair control is performed several times, an error display such as prompting replacement of the print head is performed.

  On the other hand, if there are no non-ejection nozzles or defective ejection nozzles, all nozzles in all nozzle rows are normal ejection nozzles, so the processing in FIG. 12 is terminated, the ejection detection operation is terminated, and then recording is started. .

  The non-ejection or defective ejection nozzle repair process in steps S13 to S14 is not limited to ink suction or preliminary ejection, and other processes such as increasing the ejection power by changing the ejection pulse voltage may be performed. Good. Further, instead of the repair process, interpolation control may be performed by using other normal discharge nozzles instead of non-discharge or defective discharge nozzles.

  In addition, the above-described discharge state detection operation is performed when a printing pause for several minutes or more is performed. This is because the ink sticking to the nozzles may occur due to a printing pause for several minutes, resulting in a defective firing.

In addition, the time required for the above discharge state detection is
Detection time = (total number of nozzles / ejection frequency) × number of ejection times of one nozzle + carriage movement time. For example, if the total number of nozzles is 1000, the ejection frequency is 10 kHz, the number of ejection times of the nozzle is 5, and the carriage movement time is 0.5 s, the time required for detection is about 1 s. In the discharge state detection sensor 109, to increase the number of sets of light emission elements 202 and the light receiving element 203 (the number of light beams 109), increasing the discharge frequency, or by reducing the number of discharges one nozzle, the detection time It is possible to make it shorter. Thus, it is possible to detect the ejection state of the nozzle in a very short time.

The total amount of ink used for detection is
Total ink amount = total number of nozzles × number of ejection times of one nozzle × 1 amount of ejected droplets. For example, when the total number of nozzles is 1000, the number of ejection times of one nozzle is 10, and the amount of ejected droplets is 5 pl, the total ink amount is about 50 nl, and detection is possible with an extremely small ink amount.

  As described above, according to the present embodiment described above, based on the detection signal generated from the output of the ejection state detection sensor 109, the presence of the main droplet and satellite ejected from each nozzle, the droplet size, the ejection speed, and the flight Since the interval and the number of satellites are detected and the normal discharge / non-discharge / discharge failure for each nozzle is determined based on the detection result, the determination can be made accurately, and the discharge state can be detected accurately. . In particular, for each nozzle row, normal ejection values are set separately according to the ink type (dye / pigment, ink color) and the nozzle diameter, and detection is performed based on the normal ejection value. Detection can be performed accurately regardless of the difference in nozzle diameter. Based on the accurate detection result, the repair control of the non-ejection or ejection failure nozzle can be optimally performed according to the type and the diameter of the ejection ink of the nozzle.

  Further, in the conventional method of determining only ejection / non-ejection, even if ejection is defective, it is judged as non-ejection, and ink is sucked in all nozzles by repair control. Therefore, the amount of ink used in repair control is large. On the other hand, in the present embodiment, it is possible to accurately determine the ejection failure separately from the non-ejection, and to perform repair control such as preliminary ejection and voltage change of the ejection pulse only for the ejection failure nozzle. Therefore, the amount of ink used for the repair process can be saved, and the repair process can be performed in a short time.

  In the above, the embodiment in the bubble jet (registered trademark) type ink jet recording apparatus (printer) has been described. However, the technique of the present invention can be applied to other types of ink jet recording apparatuses such as a method using a piezoelectric element. Of course. The present invention can also be applied to a recording system including the inkjet recording apparatus and a control device such as a PC that controls the inkjet recording apparatus. Furthermore, the present invention is not limited to ink droplets, and can also be applied to droplet ejection devices that eject droplets of other liquids, such as reaction liquids, chemicals, or liquids that become conductors when dried. The present invention can also be applied to a droplet discharge system including the control device.

  In the embodiment, the ejection state detection sensor 109 is configured as a photo interrupter that is an optical sensor. Instead, the ejection state detection sensor 109 is configured by, for example, an element such as a piezoelectric element that converts mechanical force into electricity. A sensor may be used.

1A and 1B are a front view and a side view showing a schematic configuration of an ink jet printer according to an embodiment of the present invention. It is explanatory drawing which shows a structure and arrangement | positioning etc. of the discharge state detection sensor of the printer. It is the front view (a) of the carriage peripheral part which shows the mode of discharge state detection, and the top view (b) seen from the bottom. It is explanatory drawing which shows a mode until an ink droplet is normally discharged from a nozzle and it separates into a main droplet and a satellite. It is a signal waveform diagram showing a waveform of a detection signal of a discharge state at the time of normal discharge. It is explanatory drawing which shows the discharge state of the main droplet and a satellite in each at the time of normal discharge, non-discharge, and the time of a different discharge defect. It is a signal waveform diagram which shows the waveform of the detection signal at the time of non-ejection. It is a signal waveform diagram which shows the waveform of the detection signal at the time of a defective firing. It is a signal waveform diagram showing a waveform of a detection signal when ejection is unstable. FIG. 3 is a block diagram illustrating a configuration of a control system of the printer according to the embodiment. It is a block diagram which shows the structure of the principal part of the light emission part and light-receiving part of a discharge state detection sensor, and a detection signal generation circuit. It is a flowchart figure which shows the control procedure in connection with the discharge state detection and nozzle repair in the printer of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Inkjet printer 102 Carriage 105 Paper feed roller 106 Wiper 107 Recovery unit 108 Recording head 109 Discharge state detection sensor 201 Nozzle 202 Light emitting element 203 Light receiving element 207 Main droplet 208 Satellite 209 Light flux 502 Detection signal 1002 Recording head control circuit 1004 Detection signal generation circuit 1005 CPU
1012 ROM
1013 RAM
1017 Host device 1101 Light emitting unit 1104 Light receiving unit 1105 I-V converter 1106 Filter circuit 1107 AMP circuit 1108 A / D converter

Claims (2)

A droplet discharge unit having a plurality of nozzles for discharging droplets, a light emitting unit that emits light, a light receiving unit that receives light emitted from the light emitting unit, and light emitted from the light emitting unit toward the light receiving unit Determining means for determining the discharge state of the nozzle by using a detection signal based on the amount of light received by the light receiving unit when the nozzle is driven at a position where the liquid droplets discharged from the nozzle can be blocked. A suction unit that performs a suction operation of sucking droplets from the plurality of nozzles, a preliminary discharge unit that causes the nozzle to perform preliminary discharge, and a control unit that controls the suction unit and the preliminary discharge unit. In the droplet discharge device,
The light-emitting unit and the light-receiving unit are arranged at positions that block light emitted from the light-emitting unit after the liquid droplets ejected from the nozzle are separated into main droplets and satellites,
The determination means determines whether the predetermined normal ejection signal corresponding to the case where the liquid is normally ejected from the nozzle and the detection signal are substantially the same for each of the plurality of nozzles. In the first state where the discharge signal is discharged, when the change in the waveform of the detection signal is almost constant, the second state where the droplet is not discharged, the waveform of the detection signal is changed, but is different from the normal discharge signal The case is judged to be a third state in which droplets are ejected but ejection failure has occurred,
The control unit causes the suction unit to perform the suction operation of the plurality of nozzles when the determination unit determines that at least one of the plurality of nozzles is in the second state. When it is not determined that one of the nozzles is in the second state, the preliminary discharge unit causes the determination unit to perform preliminary discharge of the nozzle determined to be in the third state. A droplet discharge device.   The determination unit determines the discharge state of the nozzle based on at least one of the presence / absence, size, discharge speed, flight interval, and number of satellites of main droplets and satellites. The liquid droplet ejection apparatus described.

Images