JP2013144371A - Droplet discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a droplet discharge device capable of detecting abnormal discharge without providing a special detection device by detecting abnormal discharge of a nozzle using a composition for adjusting discharge characteristics.SOLUTION: An inkjet printer 1 includes: a plurality of heaters 50 provided in a plurality of individual ink channels 27, respectively; a plurality of temperature sensors 51; a discharge characteristics adjusting part for adjusting discharge characteristics of the plurality of nozzles 16; and an abnormal discharge detection part for detecting abnormal discharges of the plurality of nozzles 16. The discharge characteristics adjusting part controls ink temperatures in the plurality of individual ink channels 27 using the heater 50 and the temperature sensors 51 so that variation in the discharge characteristics among the plurality of nozzles 16 is suppressed. The abnormal discharge detection part detects the abnormal discharges of the plurality of nozzles 16 based on the change in temperatures in the individual ink channels 27 when the droplets are discharged from the nozzles 16 while or after the ink in the individual ink channels 27 is heated by the heater 50.

Description

  The present invention relates to a droplet discharge device that discharges droplets.

  In the field of droplet discharge devices such as inkjet printers, in general, it is preferable that the discharge characteristics (amount of discharged droplets and droplet velocity) are uniform evenly between a plurality of nozzles. In practice, there are many cases in which ejection characteristics between a plurality of nozzles vary. Here, the variation in ejection characteristics means that there are slight differences among the nozzles for various factors that affect the ejection of droplets, so that the nozzle-specific ejection characteristics (e.g., ejection volume and This means that a difference occurs in the discharge speed. Typical factors that affect the ejection of droplets include the size and shape of the nozzles and the flow paths connected to the nozzles, or the characteristics of actuators that impart ejection energy to the liquid in each nozzle. And, in the field of inkjet printers, if the discharge amount and discharge speed are different among a plurality of nozzles, the size of the dots formed on the recording medium and the position of the dots (droplet landing position) are shifted. The print quality is adversely affected.

  In this regard, it can be considered that the viscosity of the liquid is individually changed by controlling the temperature of the liquid for each nozzle, thereby eliminating the variation in the ejection characteristics between the plurality of nozzles. For example, in the ink jet head of Patent Document 1, one heater is provided for each of a plurality of flow paths communicating with a plurality of nozzles. A preheat pulse and a main heat pulse, both of which are constant voltage pulses, are applied to each heater. The preheat pulse is a pulse for preheating the ink in the flow path before ejection. The main heat pulse is for giving ejection energy to the ink by heating the ink in the flow path to cause film boiling. In addition, Patent Document 1 describes that variation in the discharge amount of the nozzle is reduced by adjusting the waveform of the preheat pulse.

  By the way, apart from the above variations in discharge characteristics, abnormal discharge such as dust or bubbles entering the flow path including the nozzles while using the device, resulting in a low discharge amount or a state where no discharge is possible. Is known to occur. Regarding the detection of this ejection abnormality, for example, Patent Document 2 discloses a technique for detecting a nozzle ejection abnormality by a laser sensor. Further, in Patent Document 3, abnormal discharge of a nozzle is determined based on whether or not the vibration plate is deformed (that is, whether or not a liquid droplet has landed on the vibration plate) when a droplet is discharged from the nozzle toward the vibration plate. What detects is disclosed. In the above Patent Documents 2 and 3, when a discharge abnormality is detected in a certain nozzle, the discharge abnormality is eliminated by performing a recovery operation such as flushing or purging.

JP-A-9-281324 JP 2008-080724 A JP 2010-76361 A

  Japanese Patent Application Laid-Open No. 2004-151867 discloses that the variation in the discharge amount is reduced by controlling the temperature of the liquid for each flow path, but there is no disclosure about the configuration for detecting the discharge abnormality. However, providing a dedicated detection device as disclosed in Patent Documents 2 and 3 for detection of ejection abnormality increases the number of components and complicates the structure. In addition, since a separate installation space for the detection device is required, there is a problem that the overall size of the droplet discharge device is increased.

  An object of the present invention is to provide a droplet discharge device capable of detecting a discharge abnormality without providing a dedicated detection device by detecting a discharge abnormality of a nozzle by using a configuration for adjusting discharge characteristics. It is to be.

According to a first aspect of the present invention, there is provided a liquid droplet ejection apparatus including a liquid droplet ejection head having a plurality of liquid flow paths each including a nozzle for discharging liquid droplets, and a plurality of liquids individually heating the liquids in the plurality of liquid flow paths. Heating means, a plurality of temperature detecting means for detecting the temperature of the liquid in each of the plurality of liquid flow paths, and a discharge characteristic for adjusting the discharge characteristics of the plurality of nozzles using the heating means and the temperature detecting means Using the adjustment means, the heating means, and the temperature detection means, the discharge abnormality detection means for detecting the discharge abnormality of the plurality of nozzles,
The discharge characteristic adjusting means controls the liquid temperatures in the plurality of liquid flow paths using the heating means and the temperature detection means, respectively, so that variations in discharge characteristics among the plurality of nozzles are reduced. ,
The ejection abnormality detecting unit causes the droplet ejection head to eject droplets from the nozzles included in the liquid channel during or after heating of the liquid in one liquid channel by the heating unit. The nozzle discharge abnormality is detected based on a temperature change in the liquid flow path detected by the temperature detecting means.

  In the present invention, a plurality of heating means and a plurality of temperature detection means are provided for a plurality of nozzles (a plurality of liquid flow paths), respectively. The discharge characteristic adjusting means uses the heating means and the temperature detection means during the discharge operation of the droplet discharge head so that the variation in the discharge characteristics among the plurality of nozzles is reduced. The liquid temperature in each is controlled.

  Further, the discharge abnormality detection means detects the nozzle discharge abnormality using the heating means and the temperature detection means. First, droplets are ejected from the nozzles during or after the heating of the liquid in the liquid channel. When liquid droplets are normally discharged from the nozzle, new liquid is supplied from the upstream side. However, when discharge abnormality occurs in the nozzle, almost no liquid is supplied from the upstream side. Therefore, the temperature change of the ink in the liquid channel differs depending on whether the nozzle is normal or abnormal. Therefore, it is possible to detect an abnormal discharge of the nozzle from the temperature change in the liquid channel when the droplet is discharged.

  As described above, in the present invention, the ejection abnormality of a plurality of nozzles is detected using the heating means and the temperature detection means used for adjusting the ejection characteristics of the nozzles. That is, it is possible to detect ejection abnormality without providing a dedicated device.

  In the liquid droplet ejection apparatus according to a second aspect, in the first aspect, the ejection abnormality detection unit heats the liquid in the liquid flow path to a predetermined initial temperature by the heating unit, and heats the liquid by the heating unit. When the temperature drop from the initial temperature in the liquid channel when the droplet discharge head discharges a droplet from the nozzle after the end is less than a predetermined threshold, the liquid channel It is determined that a discharge abnormality has occurred in the nozzle.

  By heating the liquid in the liquid flow path to a predetermined initial temperature, it becomes easier to grasp the temperature change in the liquid flow path after the liquid droplets are discharged from the nozzle, and it becomes easy to determine the discharge abnormality.

  According to a third aspect of the present invention, in the second invention, the ejection abnormality detection means is configured to set the initial temperature to a predetermined first temperature, and to set the initial temperature to the first temperature. One of the second detection modes set to a predetermined second temperature lower than the temperature is selected and executed.

  If the liquid in the liquid flow path is considerably higher than the temperature of the supplied liquid at the time of discharge abnormality inspection, the temperature change in the liquid flow path when the liquid droplets are normally discharged from the nozzle increases. Therefore, the detection accuracy of the ejection abnormality is increased. However, if the liquid temperature is too high, temperature control for adjusting discharge characteristics in the subsequent discharge operation is hindered. In addition, it is not preferable in terms of energy consumption to make the initial temperature too high when it is not necessary to perform detection with high accuracy, such as when there is a low possibility of occurrence of ejection abnormality. In the present invention, it is possible to detect discharge abnormality by selecting an appropriate one according to the situation from two types of initial temperatures (detection modes).

  According to a fourth aspect of the present invention, in the third aspect of the invention, the liquid droplet ejection head determines whether or not the liquid droplet ejection head performs the ejection operation after the ejection abnormality detection unit finishes detecting the ejection abnormality. And a first determination unit, and when the first determination unit determines that the droplet discharge head is in a standby state where no discharge operation is scheduled after the detection of the discharge abnormality, the discharge abnormality detection unit Executes the first detection mode, and when the first determination unit determines that the droplet discharge head performs a discharge operation after detecting the discharge abnormality, the discharge abnormality is detected. The detection means executes the second detection mode.

  First, the first determination means determines whether the droplet discharge head is in a standby state or a state immediately before discharge. In the standby state, since the discharge operation is not performed after the detection of the discharge abnormality is completed, the first detection mode having a high initial temperature is selected and detection with high accuracy is performed. On the other hand, in the state immediately before the discharge, since the discharge operation with the temperature control is scheduled immediately after the detection of the discharge abnormality, the second detection mode with a low initial temperature is selected.

  In the liquid droplet ejection device according to a fifth aspect of the present invention, in the third aspect, when it is detected by the ejection abnormality detection means that ejection abnormality has occurred in at least some of the plurality of nozzles, A purge unit that recovers the discharge performance of the nozzles by discharging liquid from the plurality of nozzles, and whether or not an elapsed time from the recovery operation by the purge unit to a current time is a predetermined time or more is determined. A second determination unit, and when the second determination unit determines that the elapsed time is equal to or longer than the predetermined time, the ejection abnormality detection unit selects the first detection mode, and the second determination unit selects the first detection mode. 2 When the determination unit determines that the elapsed time is less than the predetermined time, the discharge abnormality detection unit selects the second detection mode.

  If a long time has passed since the recovery operation by the purging means, it is highly possible that the nozzle has an abnormal discharge. Therefore, the first detection mode with a high initial temperature is selected to perform highly accurate detection. Do. On the other hand, if the time has not passed since the recovery operation, there is a low possibility that a discharge abnormality has occurred in the nozzle, so there is no problem even if the discharge abnormality is detected with coarse accuracy. Therefore, in such a case, the second detection mode having a low initial temperature is selected.

  According to a sixth aspect of the present invention, in any one of the second to fifth aspects, the liquid droplet discharge unit is connected to the liquid droplet discharge head and stores liquid supplied to the liquid droplet discharge head. Supply temperature detection means for detecting the temperature of the liquid supplied from the liquid reservoir to the droplet discharge head, and the discharge abnormality detection means is configured to detect the temperature of the liquid according to the temperature detected by the supply temperature detection means. The initial temperature is set.

  When the temperature of the liquid supplied from the liquid storage unit is high, there is not much difference between the supplied liquid temperature and the initial temperature at the start of the discharge inspection, and it becomes difficult to detect discharge abnormality. Therefore, it is preferable to change the initial temperature according to the temperature of the supplied liquid.

  According to a seventh aspect of the present invention, in any one of the second to sixth aspects, the discharge abnormality detecting means is configured such that the temperature drop from the initial temperature in a liquid flow path is not less than a first threshold value. In some cases, it is determined that the nozzle of the liquid flow path is normal, and when the temperature drop is less than the first threshold and not less than a second threshold lower than the first threshold, When the nozzle determines that the droplet is ejected but is in a defective ejection state where the ejection amount is small compared to the normal state, and the temperature drop is less than the second threshold, the nozzle It is determined that a non-ejection state in which no droplet is ejected.

  According to the present invention, it is possible to discriminate and distinguish the abnormal discharge state between a discharge failure state where the discharge amount is small and a non-discharge state where no droplets are discharged.

  In the present invention, since the nozzle discharge abnormality is detected using the heating means and the temperature detection means used for adjusting the discharge characteristics of the plurality of nozzles, the discharge abnormality can be detected without providing a dedicated device.

1 is a schematic plan view of an ink jet printer according to an embodiment. It is a top view of an inkjet head. (A) is the A section enlarged view of FIG. 3, (b) is the BB sectional drawing of (a). FIG. 2 is a block diagram schematically illustrating an electrical configuration of a printer. It is a flowchart of abnormal discharge detection.

  Next, an embodiment of the present invention will be described. FIG. 1 is a schematic plan view of an inkjet printer 1 according to the present embodiment. First, a schematic configuration of the inkjet printer 1 will be described with reference to FIG. In the following, the front side in FIG. 1 is defined as the upper side, and the other side of the page is defined as the lower side, and the explanation will be made using direction words “up” and “down” as appropriate. As shown in FIG. 1, the inkjet printer 1 includes a platen 2, a carriage 3, an inkjet head 4, a transport mechanism 5, a purge mechanism 6, a control device 8, and the like.

  On the upper surface of the platen 2, a recording sheet 100 as a recording medium is placed. In addition, above the platen 2, two guide rails 10 and 11 extending in parallel with the horizontal direction (scanning direction) in FIG. 1 are provided. The carriage 3 is configured to reciprocate in the scanning direction along the two guide rails 10 and 11 in a region facing the platen 2. In addition, an endless belt 14 wound between two pulleys 12 and 13 is connected to the carriage 3. When the endless belt 14 is driven by the carriage drive motor 15, the carriage 3 is connected to the endless belt 14. 14 moves in the scanning direction.

  The inkjet head 4 is attached to the carriage 3 and moves in the scanning direction together with the carriage 3. The lower surface of the inkjet head 4 (the surface on the opposite side of the paper surface in FIG. 1) is a droplet ejection surface on which a plurality of nozzles 16 are formed. Further, as shown in FIG. 1, a holder 9 is provided in the printer main body 1 a of the printer 1. The holder 9 is loaded with four ink cartridges 17 (liquid storage portions) each storing four colors of ink (black, yellow, cyan, magenta). Although not shown, the inkjet head 4 mounted on the carriage 3 and the holder 9 are connected by four tubes (not shown). The four color inks of the four ink cartridges 17 are respectively supplied to the inkjet head 4 through four tubes. The inkjet head 4 ejects four colors of ink from a plurality of nozzles 16 onto the recording paper 100 placed on the platen 2.

  The transport mechanism 5 includes two transport rollers 18 and 19 disposed so as to sandwich the platen 2 in the transport direction, and the two transport rollers 18 and 19 transport the recording paper 100 placed on the platen 2. Transport in the direction. Further, the transport mechanism 5 includes a motor for rotating the transport rollers 18 and 19.

  The ink jet printer 1 causes ink to be ejected from the ink jet head 4 that reciprocates in the scanning direction (left and right direction in FIG. 1) together with the carriage 3 with respect to the recording paper 100 placed on the platen 2. At the same time, the recording paper 100 is transported in the transport direction (downward in FIG. 1) by the two transport rollers 18 and 19. Through the above operation, images, characters, and the like are recorded on the recording paper 100.

  The purge mechanism 6 recovers the ejection performance of the nozzles 16 by discharging ink from the plurality of nozzles 16 when ejection abnormality occurs in the nozzles 16 of the inkjet head 4. The purge mechanism 6 is disposed at a position outside the area facing the recording paper 100 (on the right side in FIG. 1) in the movement range of the carriage 3 in the scanning direction. The purge mechanism 6 includes a cap 40, a suction pump 41 connected to the cap 40, and a cap drive motor 42 (see FIG. 4) for moving the cap 40 in the vertical direction. The cap 40 is driven in the up-down direction (perpendicular to the plane of FIG. 1) by a cap drive motor 42. With the carriage 3 facing the cap 40, the cap 40 moves upward so that the plurality of nozzles 16 on the lower surface of the inkjet head 4 are covered with the cap 40. In the following description, a state in which the plurality of nozzles 16 are covered with the cap 40 is referred to as a capping state.

  In the above-mentioned capping state, the suction pump 41 is operated to decompress the inside of the cap 40, whereby the suction purge in which ink is sucked from the plurality of nozzles 16 is performed. By this suction purge, the dust and bubbles in the inkjet head 4 or the ink thickened by drying is discharged from the plurality of nozzles 16, thereby recovering the discharge performance of the nozzles 16 in which the discharge abnormality has occurred.

  Next, the inkjet head 4 will be described. FIG. 2 is a plan view of the inkjet head 4. 3A is an enlarged view of a portion A in FIG. 2, and FIG. 3B is a sectional view taken along line BB in FIG. As shown in FIGS. 2 and 3, the inkjet head 4 includes a flow path unit 20 in which a plurality of nozzles 16 and a plurality of pressure chambers 24 are formed, and a piezoelectric actuator 21 disposed on the upper surface of the flow path unit 20. I have.

  As shown in FIG. 3B, the flow path unit 20 has a structure in which four plates are stacked. Four manifolds 25 each extending in the transport direction are formed. The four manifolds 25 are connected to four ink supply holes 26 formed on the upper surface of the flow path unit 20. The four ink supply holes 26 are supplied with four colors (black, yellow, cyan, magenta) of ink from the four ink cartridges 17, respectively.

  Further, the flow path unit 20 is formed with a plurality of nozzles 16 opened on the lower surface thereof and a plurality of pressure chambers 24 communicating with the plurality of nozzles 16, respectively. As shown in FIG. 2, the plurality of nozzles 16 and the plurality of pressure chambers 24 are arranged in four rows corresponding to the four color manifolds 25 in plan view. Each pressure chamber 24 communicates with a corresponding manifold 25. As a result, a plurality of individual ink flow paths 27 (liquid flow paths of the present invention) are formed in the flow path unit 20 and branch from the manifold 25 and include the pressure chambers 24 and the nozzles 16, respectively.

  As shown in FIG. 3, the piezoelectric actuator 21 includes a diaphragm 30 covering the plurality of pressure chambers 24, a piezoelectric layer 31 disposed on the upper surface of the diaphragm 30, and a plurality of individual corresponding to the plurality of pressure chambers 24. The electrode 32 is provided. The plurality of individual electrodes 32 are respectively connected to a driver IC 34 (see FIG. 4) that drives the piezoelectric actuator 21. The diaphragm 30 is made of a metal material and serves as a common electrode facing the plurality of individual electrodes 32 with the piezoelectric layer 31 interposed therebetween. The diaphragm 30 is connected to the ground wiring of the driver IC 34 and is always held at the ground potential. The portion of the piezoelectric layer 31 sandwiched between the diaphragm 30 and the individual electrode 32 is polarized in the thickness direction.

  The operation of the piezoelectric actuator 21 when ink is ejected from the nozzle 16 is as follows. When a drive signal is selectively applied to the plurality of individual electrodes 32 from the driver IC 34, the individual electrodes 32 on the upper side of the piezoelectric layer 31 and the diaphragm as a common electrode on the lower side of the piezoelectric layer 31 held at the ground potential. A potential difference is generated between the electrodes 30, and an electric field in the thickness direction is generated in a portion sandwiched between the individual electrode 32 and the diaphragm 30. At this time, since the polarization direction of the piezoelectric layer 31 coincides with the direction of the electric field, the piezoelectric layer 31 extends in the thickness direction as the polarization direction and contracts in the plane direction. Further, as the piezoelectric layer 31 contracts and deforms, the portion of the diaphragm 30 facing the pressure chamber 24 is bent so as to protrude toward the pressure chamber 24 (unimorph deformation). At this time, the volume of the pressure chamber 24 decreases, so that pressure is applied to the ink inside the pressure chamber 24, and ink droplets are ejected from the nozzle 16 communicating with the pressure chamber 24.

  As shown in FIG. 3B, a plurality of heaters 50 and a plurality of temperature sensors 51 are provided on the lower surface of the diaphragm 30 in contact with the plurality of pressure chambers 24, respectively. Each heater 50 is connected to a drive circuit 52 of the heater 50 that generates heat by passing a current through the heater 50 (see FIG. 4). The plurality of heaters 50 individually heat the ink in the plurality of pressure chambers 24. The plurality of temperature sensors 51 detect the temperatures in the plurality of pressure chambers 24, respectively. As will be described in detail later, the heater 50 and the temperature sensor 51 are used for the purpose of aligning the ejection characteristics of the plurality of nozzles 16 during recording of an image or the like. Used when performing control. Further, when an image or the like is not recorded, the heater 50 and the temperature sensor 51 are also used for detecting an ejection abnormality of each nozzle 16.

  Next, the electrical configuration of the printer 1 centering on the control device 8 will be described. FIG. 4 is a block diagram schematically showing the electrical configuration of the printer 1. A control device 8 of the printer 1 shown in FIG. 4 includes, for example, a central processing unit (CPU) and a ROM (Read Read) in which various programs and data for controlling the overall operation of the printer 1 are stored. Only memory), a microcomputer including a RAM (Random Access Memory) that temporarily stores data processed by the CPU, various arithmetic circuits for controlling each configuration of the printer 1, and various data A storage unit 63 composed of a storage medium such as a flash memory.

  When the CPU executes various programs stored in the ROM, the microcomputer and various arithmetic circuits operate as the recording control unit 60, the ejection abnormality detection unit 61, and the purge control unit 62. The storage unit 63 stores setting values used for various controls executed by the control device 8. The control device 8 is connected to an external device PC 70 and an operation panel 71 having a display, operation buttons, and the like. In addition, the control device 8 includes signals from a plurality of temperature sensors 51 provided in a plurality of individual ink flow paths 27 of the inkjet head 4 and an environment temperature detection sensor 53 that detects an ambient temperature around the inkjet head 4. A signal is also input.

  As described above, the control device 8 includes the recording control unit 60, the ejection abnormality detection unit 61, the microcomputer that operates as the purge control unit 62, and various arithmetic circuits. The recording control unit 60 controls the driver IC 34, the carriage drive motor 15, and the transport mechanism 5 of the inkjet head 4 based on data related to images and the like input from the PC 70.

  In addition, the recording control unit 60 includes a discharge characteristic adjustment unit 64 that adjusts the discharge characteristic of each nozzle 16. As will be described in detail later, the discharge characteristic adjusting unit 64 controls the heater 50 based on the temperature in the individual ink flow path 27 detected by the temperature sensor 51, and the ink in the individual ink flow path 27 is controlled. The temperature is controlled to a predetermined temperature set value.

  The discharge abnormality detection unit 61 detects whether or not a discharge abnormality has occurred for each of the plurality of nozzles 16. As will be described in detail later, the discharge abnormality detection unit 61 detects the discharge abnormality of each nozzle 16 by using the heater 50 and the temperature sensor 51 used for adjusting the discharge characteristics of the nozzle 16 described above. The purge control unit 62 controls the cap drive motor 42 and the suction pump 41 of the purge mechanism 6 to execute the suction purge of the inkjet head 4.

(Adjustment of nozzle discharge characteristics)
Next, the adjustment of the discharge characteristic of the nozzle 16 by the discharge characteristic adjusting unit 64 will be described. If drive signals having the same voltage and waveform are applied to the plurality of individual electrodes 32, the discharge characteristics (droplet amount and droplet velocity) should ideally be aligned by the plurality of nozzles 16. However, in practice, discharge characteristics vary among the plurality of nozzles 16 due to various factors as described below.

  The flow resistance of the individual ink flow path 27 and the rigidity of the piezoelectric actuator 21 have a great influence on the ejection characteristics of the nozzle 16. In this respect, if the individual ink flow paths 27 including the nozzles 16 and the pressure chambers 24 in the flow path unit 20 are slightly different in shape and size, there is a difference in flow resistance between the individual ink flow paths 27. . Further, if the thickness of the piezoelectric actuator (in particular, the thickness of the piezoelectric layer 31) is not uniform, a difference in the rigidity of the piezoelectric actuator 21 occurs between the plurality of pressure chambers 24.

  Therefore, when the manufacture of the inkjet head 4 is completed, droplets are actually ejected from each of the plurality of nozzles 16 and the amount of ejected droplets and the droplet velocity are measured. Then, the basic discharge characteristics of each of the plurality of nozzles 16 are evaluated from the measured values of the droplet amount and the droplet velocity. This evaluation of the ejection characteristics requires that the amount of droplets ejected from each nozzle 16 and the velocity of the droplets be measured with high accuracy. Therefore, before being used by the user, that is, before shipping, the manufacturer side It is preferably performed by equipment. In addition, when actually used by the user (when an image or the like is recorded), the discharge characteristic adjusting unit 64 is configured so that the variation in the discharge characteristics of all the nozzles 16 becomes as small as possible. Adjust the discharge characteristics.

  The adjustment of the ejection characteristics is specifically performed by controlling the temperature of the ink. Generally, when the temperature of the ink is raised, the viscosity is lowered, so that the ink can easily flow. Therefore, with respect to the individual ink flow path 27 corresponding to the nozzle 16 having a low basic discharge characteristic (low discharge amount or low discharge speed), the discharge characteristic can be improved by increasing the ink temperature. . For all the nozzles 16, temperature setting values are determined in advance so that variations in the discharge characteristics among the nozzles 16 are reduced according to the basic evaluation of the discharge characteristics. These temperature set values are stored in the storage unit 63.

  Each time recording data is input from the PC 70 to the control device 8 and an image or the like is recorded on the recording paper 100, the ejection characteristic adjustment unit 64 reads the temperature setting value stored in the storage unit. The ejection characteristic adjustment unit 64 refers to the current ink temperature information detected by the temperature sensor 51 for each nozzle 16 so that the temperature of the ink in the individual ink flow path 27 becomes the temperature setting value. The drive circuit 52 of the heater 50 is controlled. Thereby, the dispersion | variation in the discharge characteristic between the some nozzles 16 is suppressed small.

(Detection of nozzle discharge abnormality)
Next, detection of ejection abnormality of the nozzle 16 by the ejection abnormality detection unit 61 will be described. Nozzle 16 may not be ejected normally due to dust or air bubbles flowing from the upstream ink cartridge 17 into the ink jet head 4 or ink drying progressing at the opening of the nozzle 16. is there. Specifically, the amount of ink ejected from the nozzles 16 is reduced and ejection failure occurs. In a more severe case, no ink is ejected from the nozzles 16 and non-ejection occurs. Accordingly, the discharge abnormality detection unit 61 detects whether or not a discharge abnormality such as the above-described discharge failure or non-discharge has occurred for each nozzle 16.

  The detection timing of the ejection abnormality is not particularly limited, and can be performed at an arbitrary timing. However, it is effective when it is considered that there is a high possibility that a discharge abnormality has occurred. For example, when the recording operation of the printer 1 that ejects ink from the inkjet head 4 has not been performed for a while, there is a high possibility that the bubbles are mixed in or the ink is dried. Therefore, the ejection abnormality may be detected when the printer 1 is turned on or when a predetermined time has elapsed since the previous recording operation. Alternatively, detection may be performed when a user inputs a command for detecting an ejection abnormality from the PC 70 or the operation panel 71.

  When detecting the ejection abnormality of the nozzles 16, the ink in all the individual ink flow paths 27 is heated to a predetermined initial temperature by the heater 50. Thereafter, droplets are discharged from all the nozzles 16. Here, with respect to the individual ink channel 27 in which the ejection of the nozzles 16 is normal, ink having a low temperature is supplied from the upstream manifold 25 into the individual ink channel 27 according to the ejection of the ink. Therefore, the temperature change (degree of temperature decrease) detected by the temperature sensor 51 increases. On the other hand, for the individual ink flow path in which the ejection abnormality occurs in the nozzle, the ink supply amount from the upstream side is also small because the ink ejection amount is small. Therefore, the temperature change detected by the temperature sensor 51 is also reduced. As described above, the ejection abnormality of the nozzle 16 can be detected from the temperature change of the ink in the individual ink flow path 27.

  As shown in FIG. 4, the ejection abnormality detection unit 61 includes a detection mode selection unit 65 that selects one from two detection modes having different initial temperatures. The ejection abnormality detection unit 61 executes the detection mode selected by the detection mode selection unit 65.

  The detection mode selection unit 65 (first determination unit) is a standby state in which the inkjet head 4 is in a standby state where it is not scheduled to perform a discharge operation after detection of a discharge abnormality to be performed, or a discharge operation that performs a discharge operation after detection of a discharge abnormality. The detection mode is selected depending on whether the state is immediately before. Note that whether the inkjet head 4 is in a standby state or a state immediately before ejection can be determined, for example, based on whether or not recording data is input from the PC 70 when ejection abnormality is detected.

  When the ejection abnormality is detected, the temperature difference from the upstream ink temperature (approximately equal to the environmental temperature) increases as the temperature of the ink in the individual ink flow path 27 (initial temperature) is increased by the heater 50. Become. Therefore, the temperature change in the individual ink flow path 27 when ink is normally ejected from the nozzles 16 is increased, and the detection accuracy of ejection abnormality is increased. However, if the inkjet head 4 is scheduled to perform the recording operation with the temperature control for adjusting the ejection characteristics described above after the detection of the ejection abnormality, the ink temperature is excessively increased in the detection of the ejection abnormality. This hinders subsequent temperature control. Therefore, the detection mode selection unit 65 selects the first detection mode having a high initial temperature when the inkjet head 4 is in a standby state. On the other hand, when the inkjet head 4 is in a state immediately before ejection, the second detection mode having an initial temperature lower than that in the first detection mode is selected.

  A series of operations of the control device 8 that detects ejection abnormality will be described in detail with reference to the flowchart of FIG. In FIG. 5, Si (i = 10, 11, 12,...) Represents each step.

  First, the detection mode selection unit 65 determines whether the inkjet head 4 is in a standby state or a state immediately before ejection (S10). When it is determined that the state is the standby state (S10: Yes), the detection mode selection unit 65 selects the first detection mode (S11). On the other hand, when it is determined that the state is immediately before discharge (S10: No), the detection mode selection unit 65 selects the second detection mode (S31).

(First detection mode)
When the first detection mode is selected, the ejection abnormality detection unit 61 sets the initial temperature of the individual ink flow path 27 to T1 (S11), and starts detecting the ejection abnormality of the nozzles 16. First, all the individual ink flow paths 27 are heated to the initial temperature T1 by the heater 50 by controlling the drive circuit 52 (see FIG. 5) of the heater 50 while referring to the temperature information from the temperature sensor 51 (S12). . When the temperature of the ink in all the individual ink flow paths 27 reaches the initial temperature T1, heating by the heater 50 is stopped. Next, the driver IC 34 (see FIGS. 3B and 4) is controlled to eject ink droplets from all the nozzles 16 (S13). Then, the temperature change ΔT of the ink in the plurality of individual ink flow paths 27 is measured by the plurality of temperature sensors 51 (S14).

  At that time, it is necessary to eject a certain amount or more of ink from each nozzle 16 so that low temperature ink is supplied from the manifold 25 into the pressure chamber 24 in accordance with the ejection of the ink. For this purpose, ink is continuously ejected from each nozzle 16 many times. In addition, for so-called gradation printing, a plurality of types of droplets (large balls, medium balls, small balls, etc.) having different droplet volumes from one nozzle 16 are obtained by varying the drive signal from the driver IC 34 to the piezoelectric actuator 21. Can be ejected selectively, a droplet (large ball) having the largest volume is ejected.

  Next, it is individually determined whether or not a discharge abnormality has occurred for all the nozzles 16 (S15). That is, for a certain nozzle 16, if the temperature change ΔT in the individual ink flow path 27 is equal to or greater than the threshold A (S16: Yes), it is determined that this nozzle 16 is normal (S17). On the other hand, when the temperature change is less than the threshold value A (S16: No), the ejection abnormality detection unit 61 determines that an ejection abnormality has occurred in the nozzle 16 (S18).

  Further, if it is determined that there is a discharge abnormality (S18), whether the discharge abnormality is a discharge failure state in which droplets are discharged from the nozzle 16 but the discharge amount is small compared to the normal state, or Then, it is determined by distinguishing whether or not the liquid droplets are not ejected at all. In the case of ejection failure, since a small amount of ink is ejected, the temperature of the individual ink flow path 27 is slightly smaller than that in the normal state, but slightly changes. However, in the non-ejection state, the temperature of the individual ink flow path 27 hardly changes.

  Therefore, when the temperature change ΔT of the individual ink flow path 27 is smaller than the threshold value A (first threshold value) used for determining whether or not it is normal and is equal to or larger than the threshold value B (second threshold value) (S19: Yes). The discharge abnormality detection unit 61 determines that the nozzle 16 is in a discharge failure state with a small discharge amount (S20). On the other hand, when the temperature change ΔT is further smaller than the threshold value B (S19: No), the ejection abnormality detection unit 61 determines that the nozzle 16 is in a non-ejection state (S21).

  In the first detection mode, since the initial temperature T1 is higher than that in the second detection mode described later, the temperature change ΔT when the discharge of the nozzle 16 is normal increases. Therefore, the threshold value A (first threshold value) for determining whether ejection is normal can be set to a relatively large value. For this reason, when a threshold value B (second threshold value) smaller than the threshold value A is set separately, the difference between the threshold value A and the threshold value B can be increased. Therefore, it is possible to accurately detect the three states of normal, defective discharge, and non-discharge.

  When the ejection abnormality determination for one nozzle 16 is completed, the determination steps S16 to S21 are performed for another nozzle 16. When the determination is finished for all the nozzles 16 (S22: Yes), the detection of the ejection abnormality is finished.

  As described above, when the first detection mode is selected, a discharge abnormality of the nozzle 16 is detected by distinguishing between a discharge failure state where the discharge amount is small and a non-discharge state where no discharge is performed. Therefore, when a discharge abnormality is detected in a certain nozzle 16, the method for recovering the discharge performance can be varied depending on the type (degree) of the discharge abnormality. For example, in the case of an ejection failure state, it is considered that the degree of mixing of bubbles and ink thickening that cause ejection abnormality is lighter than in the non-ejection state. Therefore, when it is determined that the discharge is in a defective state, flushing is performed on the nozzle 16, while when it is determined that the nozzle is in a non-discharge state, suction purge with a strong recovery force by the purge mechanism 6 may be executed. Alternatively, when all of the nozzles 16 that are abnormally discharged are in a defective discharge state, a suction purge with a lower suction force may be performed as compared to the case where there are non-discharged nozzles 16. Thereby, the amount of ink (waste liquid) consumed by the recovery operation can be minimized.

(Second detection mode)
When the second detection mode is selected, the ejection abnormality detection unit 61 sets the initial temperature of the individual ink flow path 27 to a temperature T2 that is lower than the initial temperature T1 of the first detection mode (S31). Then, the detection of the ejection abnormality of all the nozzles 16 is started in the same manner as in the first detection mode. That is, the heater 50 heats all the individual ink flow paths 27 to the initial temperature T2 (S32). Next, after stopping the heating, droplets are discharged from all the nozzles 16 (S33). Furthermore, the temperature change ΔT of all the individual ink flow paths 27 is measured by the temperature sensor 51 (S34). Then, the presence / absence of ejection abnormality is individually determined for all nozzles 16 (S35). That is, if the temperature change ΔT of the ink in the individual ink flow path 27 is equal to or greater than the predetermined threshold C (S36: Yes), the ejection abnormality detection unit 61 determines that the nozzle 16 is normal (S37). On the other hand, when the temperature change ΔT is less than the threshold C (S36: No), the ejection abnormality detection unit 61 determines that ejection abnormality has occurred in the nozzle 16 (S38).

  In the second detection mode, the initial temperature is lower than that in the first detection mode described above, and hence the detection accuracy of the ejection abnormality is also lowered. Therefore, when the second detection mode is selected, only a simple determination as to whether the discharge is normal or abnormal is made, and it is not performed until the discharge abnormality is determined as a discharge failure state or a non-discharge state.

  Even when the second detection mode is selected, when the determination of the ejection abnormality for one nozzle 16 is completed, the determination steps S36 to S38 are executed for another nozzle 16. When the determination is completed for all the nozzles 16 (S39: Yes), the detection of the ejection abnormality is terminated.

  In the printer of the present embodiment, a plurality of heaters 50 and a plurality of temperature sensors 51 are provided for the plurality of nozzles 16 (a plurality of individual ink flow paths 27), respectively. The ejection characteristic adjusting unit 64 uses the heater 50 and the temperature sensor 51 during the ejection operation of the inkjet head 4 to reduce the variation in the ejection characteristics between the plurality of nozzles 16. The ink temperature in the flow path 27 is controlled. Further, the discharge abnormality detection unit 61 detects the discharge abnormality of the nozzle 16 by using the heater 50 and the temperature sensor 51 used for adjusting the discharge characteristics. Therefore, it is possible to detect ejection abnormality for each nozzle 16 without providing a dedicated device.

  Further, when detecting an abnormal discharge, the ink in the individual ink flow path 27 is heated to a predetermined initial temperature, and a droplet is discharged from the nozzle 16 after the heating is completed. According to this, since it becomes easy to grasp the temperature change in the individual ink flow path 27, it is easy to determine the ejection abnormality of the nozzle 16.

  The ink jet printer 1 in the present embodiment described above corresponds to a “droplet discharge device” in the claims. The ink jet head 4 in this embodiment corresponds to a “droplet discharge head” in the claims. The purge mechanism 6 in the present embodiment corresponds to a “purge unit” in the claims. Note that the purge mechanism 6 may be configured to perform a so-called “pressure purge” in which the ink is pressurized in the ink flow path upstream of the nozzle 16 and forcibly discharged from the nozzle 16. Further, the heater 50 in the present embodiment corresponds to “heating means” in the claims. The temperature sensor 51 in this embodiment corresponds to “temperature detection means” in the claims.

  In the present embodiment, the control device 8 that adjusts the discharge characteristics of the nozzle 16 using the heater 50 and the temperature sensor 51 corresponds to “discharge characteristic adjusting means” in the claims. In the present embodiment, the control device 8 that performs the discharge abnormality detection in S10 to S39 in FIG. 5 using the heater 50 and the temperature sensor 51 corresponds to “discharge abnormality detection means” in the claims.

  Next, modified embodiments in which various modifications are made to the embodiment will be described. However, components having the same configuration as in the above embodiment are given the same reference numerals and description thereof is omitted as appropriate.

1] The selection conditions for the two detection modes having different initial temperatures by the detection mode selection unit 65 are not limited to those described in the above embodiment. For example, when the elapsed time from the end of the previous suction purge (recovery operation) by the purge mechanism 6 is long, there is a high possibility that the nozzle 16 has a discharge abnormality. On the other hand, when the elapsed time from the previous suction purge is short, it is unlikely that a discharge abnormality has occurred in the nozzle 16, and there is no problem even if the discharge abnormality is detected with a somewhat rough accuracy. In such a case, it is not preferable in view of energy consumption to make the initial temperature too high. Therefore, the detection mode selection unit 65 (second determination means) may select the detection mode according to the elapsed time from the previous suction purge.

  The elapsed time since the previous suction purge can be measured by a timer in the control device 8, for example. Then, the detection mode selection unit 65 (second determination unit) determines whether or not the elapsed time from the time when the suction purge is performed to the current time is a predetermined time or more. When the elapsed time is equal to or longer than the predetermined time, the first detection mode having a high initial temperature is selected to perform highly accurate detection. On the other hand, when the elapsed time is less than the predetermined time, the second detection mode having a low initial temperature is selected.

  In addition, a signal for selecting which detection mode of the two detection modes is to be executed may be directly input by the user.

2] In the above-described embodiment, the ejection abnormality detection unit selectively executes two detection modes having different initial temperatures. However, one type of detection mode may be used. Alternatively, three or more detection modes may be selectively executed.

3] When the temperature of the ink supplied from the ink cartridge 17 (liquid storage unit) to the inkjet head 4 is high, the initial temperature in the individual ink flow path 27 at the time of detecting the ejection abnormality and the ink supplied from the upstream side The difference from the temperature becomes small, and it becomes difficult to detect the ejection abnormality of the nozzle 16. Therefore, the initial temperature may be changed according to the temperature of the supplied ink.

  Here, since the temperature of the ink supplied from the ink cartridge 17 to the inkjet head 4 is substantially equal to the environmental temperature, the environmental temperature detection sensor 53 (see FIG. 5) is used as a means for detecting the temperature of the ink (supply temperature detection means). 4). Alternatively, a temperature sensor that detects the temperature of the ink may be attached to the ink supply path from the ink cartridge 17 to the inkjet head 4. Then, the ejection abnormality detection unit 61 increases the initial temperature (T1 and T2 in FIG. 5) as the temperature of the ink detected by the environmental temperature detection sensor 53 or the temperature sensor installed in the ink supply path is higher. Set to a higher value.

4] In the above embodiment, when the ejection abnormality of the nozzles 16 is detected, the ink in all the individual ink flow paths 27 is simultaneously heated to the initial temperature (S12, S32), and the ink is ejected from all the nozzles 16. (S13, S33), the temperature change ΔT was measured for all the individual ink flow paths 27 (S14, S34). However, the heating in the individual ink channel 27, the ejection from the nozzle 16, and the measurement of the temperature change ΔT may be performed individually for each nozzle 16 (individual ink channel 27).

5] In the above embodiment, the ink in the individual ink flow path 27 is first heated to a predetermined temperature, and the liquid droplets are ejected from the nozzles 16 after the heating is finished. However, the ink in the individual ink flow path 27 is heated. A droplet may be ejected from the nozzle 16 inside. As described above, when ink is ejected from the nozzle 16 while heating, the ink is supplied from the upstream side when the ejection of the nozzle 16 is normal, so even if the ink in the individual ink flow path 27 continues to be heated. The temperature rise is not so great. However, if ejection abnormality occurs in the nozzle 16, since the ink supply from the upstream side is small, the temperature rise of the ink in the individual ink flow path 27 becomes large. Therefore, even when the ink is ejected from the nozzle 16 while the ink is heated by the heater 50, the ejection abnormality of the nozzle 16 can be detected from the temperature change of the ink.

6] In the above-described embodiment, the temperature setting value for adjusting the discharge characteristic is a fixed value that is not changed after being set before shipment of the printer 1, but after the printer 1 is used for the user. The temperature set value may be changeable.

  For example, the ejection characteristics of the nozzle 16 are affected by the piezoelectric characteristics of the piezoelectric actuator 21. This piezoelectric characteristic (specifically, the piezoelectric constant d33) gradually decreases as the printer 1 is used due to factors such as polarization deterioration, crack generation, and migration of the piezoelectric layer 31. Therefore, for example, the printer 1 may be configured to include a device that periodically inspects the ejection characteristics of all the nozzles 16 and corrects the temperature setting value according to the inspection result.

  The above-described embodiments and modifications thereof are examples in which the present invention is applied to an inkjet printer that is a kind of droplet discharge device, but the application target of the present invention is not limited to an inkjet printer. For example, the present invention can also be applied to a droplet discharge device used in other fields such as a device that forms various conductive patterns by discharging a liquid conductive material onto a substrate.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 4 Inkjet head 6 Purge mechanism 8 Control apparatus 16 Nozzle 17 Ink cartridge 27 Individual ink flow path 50 Heater 51 Temperature sensor 53 Environmental temperature detection sensor 61 Discharge abnormality detection part 64 Discharge characteristic adjustment part 65 Detection mode selection part

Claims (7)

A droplet discharge head having a plurality of liquid flow paths each including a nozzle for discharging droplets;
A plurality of heating means for individually heating the liquids in the plurality of liquid flow paths;
A plurality of temperature detection means for detecting the temperature of the liquid in each of the plurality of liquid flow paths;
Discharge characteristic adjusting means for adjusting discharge characteristics of the plurality of nozzles using the heating means and the temperature detecting means;
Using the heating means and the temperature detection means, and a discharge abnormality detection means for detecting discharge abnormality of the plurality of nozzles,
The discharge characteristic adjusting means includes
Using the heating means and the temperature detection means to control the liquid temperatures in the plurality of liquid flow paths, respectively, so as to reduce the variation in discharge characteristics between the plurality of nozzles,
The ejection abnormality detection means includes
The temperature detection means when the liquid droplet ejection head ejects liquid droplets from the nozzles included in the liquid flow path during or after heating of the liquid in one liquid flow path by the heating means A liquid droplet ejection apparatus, wherein an abnormality in ejection of the nozzle is detected based on a temperature change in the liquid flow path detected by the step. The ejection abnormality detection means includes
Heating the liquid in the liquid channel to a predetermined initial temperature by the heating means;
When the temperature drop from the initial temperature in the liquid flow path is less than a predetermined threshold when the liquid droplet discharge head discharges liquid droplets from the nozzle after the heating by the heating means is completed, The droplet discharge device according to claim 1, wherein it is determined that a discharge abnormality has occurred in the nozzle of the liquid flow path. The ejection abnormality detection means includes
Detection of either the first detection mode in which the initial temperature is set to a predetermined first temperature or the second detection mode in which the initial temperature is set to a predetermined second temperature lower than the first temperature The droplet discharge apparatus according to claim 2, wherein the mode is selected and executed. A first determination unit that determines whether or not the droplet discharge head performs a discharge operation after the detection of the discharge abnormality by the discharge abnormality detection unit;
When it is determined by the first determination means that the droplet discharge head is in a standby state where the discharge operation is not scheduled after detection of the discharge abnormality, the discharge abnormality detection means sets the first detection mode. Run,
When it is determined by the first determination means that the droplet discharge head performs a discharge operation after detecting the discharge abnormality, the discharge abnormality detection means executes the second detection mode. The droplet discharge device according to claim 3, wherein: When the discharge abnormality detecting means detects that discharge abnormality has occurred in at least some of the plurality of nozzles, the discharge performance of the nozzles is recovered by discharging liquid from the plurality of nozzles. Purge means;
A second judging means for judging whether or not an elapsed time from the recovery operation by the purge means to a current time is a predetermined time or more,
When the second determination means determines that the elapsed time is equal to or longer than the predetermined time, the ejection abnormality detection means selects the first detection mode, and the second determination means determines the elapsed time to be the predetermined time. 4. The droplet discharge device according to claim 3, wherein when it is determined that the value is less than the value, the discharge abnormality detection unit selects the second detection mode. 5. A liquid storage unit that is connected to the droplet discharge head and stores liquid supplied to the droplet discharge head, and a supply temperature detection unit that detects the temperature of the liquid supplied from the liquid storage unit to the droplet discharge head With
The droplet ejection apparatus according to claim 2, wherein the ejection abnormality detection unit sets the initial temperature according to the temperature of the liquid detected by the supply temperature detection unit. The ejection abnormality detection means includes
If the temperature drop from the initial temperature in a liquid channel is equal to or greater than the first threshold, determine that the nozzle of the liquid channel is normal,
When the temperature drop is less than the first threshold and not less than a second threshold that is lower than the first threshold, the nozzle is ejecting droplets, but the ejection amount is smaller than that in a normal state. It is determined that there are few ejection failures,
7. The droplet discharge according to claim 2, wherein when the temperature decrease is less than the second threshold, the nozzle determines that the nozzle is in a non-discharge state in which no droplet is discharged. apparatus.

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