LIQUID EJECTION DEVICE AND METHOD FOR DETERMINING EJECTION STATE - Patent application

Abstract

To provide a method for determining a state of discharge failure in a short time while maintaining determination accuracy.SOLUTION: A determination method for determining a liquid discharge state from a discharge port in a liquid discharge device having a substrate 21 having a discharge port 2 for discharging a liquid and an electro-thermal conversion element 3 for generating heat for discharging a liquid from the discharge port, and temperature detection means for detecting temperature information of the substrate includes: a first comparison step of comparing the temperature information of the substrate detected by the temperature detection means with a first threshold, at a first timing; and a second comparison step of comparing the temperature information of the substrate detected by the temperature detection means with a second threshold, at a second timing.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection device that ejects liquid and a method for determining an ejection state. [Background technology]

[0002] An inkjet recording device (liquid ejection device) records various types of information, such as images, on a recording material such as paper by ejecting ink (liquid) from minute nozzles (ejection ports). One of the recording methods used in inkjet recording devices is the thermal inkjet method, in which the ink is ejected from the ejection ports by film boiling the ink using thermal energy generated in a heater (electrothermal conversion element).

[0003] Inkjet recording devices suffer from image degradation when ink is not ejected properly. Full-line recording devices, which have a huge number of nozzles arranged in a line corresponding to the entire width of the recording medium, are capable of high-speed printing. However, ejection defects are likely to have an adverse effect on the image, and therefore must be reflected in the recovery operation of the recording head. Recovery operations include wiping the nozzle surface while suction is being applied, and wiping the nozzle surface without suction. Both types of recovery operations result in downtime, and those that involve suction also result in the waste of ink. It is desirable for inkjet recording devices to minimize downtime and waste ink. Therefore, it is important to quickly identify which nozzles among the large number of nozzles are experiencing ejection defects and what type of ejection defects they are experiencing, as this will enable appropriate recovery operations to be performed at the appropriate time.

[0004] Here, ejection failures are broadly divided into those that occur when there is ink on the heater, and those that occur when there is no ink on the heater. The former include external dust ejection failures, where foreign matter such as paper dust adheres to the nozzle surface and inhibits ejection, and wet ejection failures, where satellites or mist adhere to the nozzle surface and inhibits ejection. The former also includes ink thickening failures, where ejection is inhibited due to increased ink viscosity caused by evaporation of water from the ejection port, and internal dust ejection failures, where ejection is inhibited due to foreign matter entering the nozzle. On the other hand, the latter includes bubble ejection failures caused by air bubbles that have become trapped inside the nozzle. When ejection failures occur, which type of ejection failure is dominant varies depending on the configuration of the head and the configuration of the nozzle.

[0005] Conventionally, in a thermal inkjet system, a heater is heated as the ink is driven, and whether or not there is a discharge defect has been determined by noting the change in temperature over time. Devices that apply this method of determining the state of the discharge defect have been proposed.

[0006] Patent Document 1 proposes a method of measuring the temperature at predetermined timing and identifying the state of defective ejection by comparing the measured temperature with a plurality of threshold values. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-331354 Summary of the Invention [Problem to be solved by the invention]

[0008] However, Patent Document 1 describes determining the state of defective ejection by comparing with multiple thresholds at a single timing, but because multiple thresholds are used, it is not possible to set a wide range for determining each state. As a result, it may be difficult to maintain determination accuracy when robustness against variations in ink and nozzles is taken into account. Furthermore, while Patent Document 1 describes determining the state of defective ejection based on a single threshold at multiple timings, the process determination must be performed three or more times to identify the state of defective ejection, posing a challenge in speeding up the process determination.

[0009] In order to solve the above problem, an object of the present invention is to provide a method for determining a discharge defect state in a short time while maintaining determination accuracy by comparing with a threshold value at two different times. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a liquid ejection device having ejection ports for ejecting liquid, a substrate provided with electrothermal conversion elements that generate heat for ejecting liquid from the ejection ports, and temperature detection means for detecting temperature information of the substrate, in a method for determining a state of ejection of liquid from the ejection ports, the method comprising: a first determination step of determining whether ejection of liquid from the ejection ports is normal or abnormal by comparing, at a first timing, temperature information of the substrate detected by the temperature detection means with a first threshold value; and a second determination step of determining, when ejection of liquid from the ejection ports is abnormal, the type of abnormality by comparing, at a second timing, temperature information of the substrate detected by the temperature detection means with a second threshold value. The temperature information is a first-order differential of the waveform of the temperature change of the substrate. It is characterized by: [Effects of the Invention]

[0011] According to the present invention, whether ink is being ejected normally and what the state of the ejection defect is can be determined by performing two processing judgments using a single threshold value for each, which has the effect of enabling faster and more accurate detection. This makes it possible to determine whether the state of the ejection defect is a state where there is ink on the heater, as typified by external dust ejection or wet ejection, or a state where there is no ink on the heater, as typified by bubble ejection. Depending on the state of the ejection defect that has been determined, appropriate recovery operations or other processing can be implemented. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a full-line inkjet recording apparatus. [Figure 2] 1A and 1B are a schematic top view and a cross-sectional view of an inkjet recording head. [Figure 3] FIG. 2 is a block diagram showing a control configuration of the liquid ejection device. [Figure 4] FIG. 10 is a diagram showing the change over time in detected temperature when an electrothermal converting element is driven. [Figure 5] 10A and 10B are diagrams showing changes over time in a cross section of a discharge port when an electrothermal converting element is driven. [Figure 6] FIG. 10 is a flowchart showing a discharge abnormality determination process. [Figure 7] FIG. 10 is a diagram showing the change over time of the detected temperature in the second embodiment. [Figure 8] FIG. 10 is a flowchart showing an ejection abnormality determination process according to the second embodiment. [Figure 9] 10 is a diagram showing, for each ejection state, the change over time in temperature detected by a sensor when a heater is driven in a nozzle dimension that allows all ink on the heater to be ejected during normal ejection, in relation to Example 2 of the present invention. FIG. [Figure 10] FIG. 10 is a diagram showing, for each ejection state, the change in temperature detected by the sensor over time when a heater having nozzle dimensions that allow all ink on the heater to be ejected during normal ejection, which is first-order differentiated during the temperature drop process, in relation to Example 2 of the present invention. [Figure 11]11 is a diagram showing the change over time in the cross section of the nozzle when the heater is driven in each of the ejection states shown in the diagrams of FIGS. 9 and 10. FIG. [Figure 12] 6 is a diagram showing the change over time in the cross section of the nozzle when the heater is driven in a state in which a foreign object is partially blocking the ejection port, in relation to FIG. 5. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail.

[0014] (First embodiment) (Sensor explanation) The configuration of an inkjet recording apparatus to which the present invention can be applied will be described.

[0015] 1 is a schematic diagram showing the configuration of the main parts of a full-line inkjet recording apparatus 700. A recording head 701 has a plurality of nozzle rows, each of which has a plurality of nozzles arranged therein. This device records an image on a recording medium 703 transported by a transport means 702 by ejecting ink droplets from the recording head having the nozzles.

[0016] Fig. 2(a) is a schematic top view of the entire nozzle portion provided in the recording head, Fig. 2(b) is a schematic cross-sectional view of Fig. 2(a) taken along plane AB, and Fig. 2(c) is a schematic cross-sectional view showing the film configuration near the ejection port in Fig. 2(b).

[0017] 2(a) is a diagram showing a schematic view of the top surface of the entire nozzle section of the print head in which ejection ports 2 are arranged. By applying a drive signal to an electrothermal conversion element (hereinafter referred to as heater 3) provided for each ejection port 2, the ink inside the ejection port 2 is heated and the ink is ejected from the ejection port 2. Liquid supply ports 16 are formed on both sides of the nozzle to supply ink to the nozzle.

[0018] Figure 2(b) is a schematic diagram of the AB cross section in Figure 2(a) to explain the nozzle configuration of one nozzle. A temperature detection element (hereinafter referred to as a temperature sensor 5 or temperature detection means) is formed directly below each heater 3 to detect temperature changes (temperature information) on the substrate. The substrate temperature information is detected based on the output results from the temperature detection element. In Figure 2(b), the temperature sensor is located directly below the heater, but since its purpose is to detect temperature changes near the heater, it may also be located directly above it. The outlet-forming member 18 that forms the outlet 2 is supported by the flow path-forming member 17. Here, the nozzle height 19 and flow path height 20 are defined as names representing the nozzle dimensions, as shown in the figure.

[0019] FIG. 2(c) shows the layered structure forming the heater and temperature sensor. Both the heater 3 and the temperature sensor 5 are formed on a substrate by layering them using the same film formation process. On a Si substrate 21, individual wiring 23 made of Al or the like for connecting the temperature sensor 5 and Al wiring for connecting the heater 3 to the control circuit formed on the Si substrate 21 are formed via a heat storage layer 22 made of a thermal oxide film such as SiO2. The temperature sensor 5 is formed using a thin-film resistor whose resistance changes with temperature. Examples of materials for the thin-film resistor include Al, Pt, Ti, TiN, TiSi, Ta, TaN, TaSiN, TaCr, Cr, CrSi, CrSiN, W, WSi2, WN, Poly-Si, α-Si, Mo, MoSi, Nb, and Ru. On the Si substrate 21, a heater 3, a passivation film 25 made of SiN or the like, and a cavitation-resistant film 26 are densely layered via an interlayer insulating film 24 using a semiconductor process. The cavitation-resistant film 26 is a film, such as a Ta film, that enhances the cavitation resistance of the heaters 3. The temperature sensors 5 are disposed directly below each of the heaters 3, separately and independently for each heater 3. The individual wiring 23 connected to each temperature sensor 5 is configured as part of a detection circuit that detects information from the temperature detection element. According to the configuration of the print head described in this embodiment, each element is patterned using the manufacturing process of a conventional inkjet print head, which offers great advantages in terms of industrial production without changing the conventional print head structure.

[0020] 3 is a block diagram of the control circuit of the recording device. As shown in Fig. 3, the control circuit is configured so that the image input unit 403, the image signal processing unit 404, and the CPU 400 each have access to the main bus 405.

[0021] The CPU 400 has a ROM 401 and a RAM 402, and executes control to provide appropriate printing conditions for input information and drive a print head 412 to perform printing. A program for executing a print head recovery procedure is also stored in the RAM 402 in advance, and provides recovery conditions such as preliminary ejection conditions to a recovery processing control circuit 407, the print head, etc., as necessary. A recovery processing motor 408 drives the print head and the blade (cleaning) 409, cap 410, and suction pump 411 that are provided opposite the print head.

[0022] The printhead drive control circuit 414 drives the heater 3, which is an electrothermal change element of the printhead 412, in accordance with the drive conditions given by the CPU 400, and causes the printhead to perform preliminary ejection and ejection of ink for printing.

[0023] (Determined from temperature change over time) Figure 4 is a curve diagram (temperature change waveform) showing the change in temperature over time when a drive voltage pulse is applied to the heater to eject ink. Figure 4 shows that the temperature curve detected by the temperature sensor differs depending on the nozzle state (a), (b), or (c). Figures 5(a), (b), and (c) show the change in the cross section of the nozzle over time in each of the states shown in Figures 4(a), (b), and (c). A0 to A10 indicate the change in time in 1 μs increments from 0 μs, which is the initial state, to 10 μs.

[0024] Figure 4(a) shows the temperature change when ink is ejected normally without any ejection failure (hereinafter referred to as normal ejection). Figure 4(b) shows the temperature change when ejection is not successful when there is ink on the electrothermal conversion element (hereinafter referred to as non-ejection with ink). Figure 4(c) shows the temperature change when ejection is not successful when there is no ink on the electrothermal conversion element (hereinafter referred to as non-ejection without ink). In Figures 4(a) and 4(b), the temperature rises with the application of a drive voltage pulse, reaches a maximum temperature, and then drops. During this temperature drop, a characteristic point in the time change of the detected temperature, where the temperature drops suddenly, occurs at different times. In Figure 4(c), on the other hand, this characteristic point does not occur and the temperature drops.

[0025] The reason why characteristic points in the temperature change over time appear and occur at different times as shown in Figures 4(a) and (b), or why characteristic points do not appear as shown in Figure 4(c), will be explained using Figure 5.

[0026] In Figure 5(a), a0 indicates the initial state immediately before the application of the drive voltage pulse. The heater heats up with the application of the drive voltage pulse, and a bubble 33 forms at a1. The bubble grows to a3 at its highest temperature, pushing ink out of the nozzle, and then collapses at a5 by drawing in the nozzle interface. As the bubble collapses, the heater is replaced by ink. That is, the material covering the heater is replaced by liquid. Because the thermal conductivity of gas and liquid differs significantly, rapid cooling occurs as the gas is replaced by liquid. During this collapse, as shown in Figure 4(a), the temperature rises with the application of the drive voltage pulse, reaches its peak temperature, and then begins to drop. During this cooling process, a characteristic point in the detected temperature over time occurs, corresponding to a5, where the temperature suddenly drops.

[0027] In Figure 5(b), b0 represents the initial state immediately before the drive voltage pulse is applied. This example illustrates the external dust ejection failure, where foreign matter 31, such as paper dust, adheres to the outside of the nozzle surface, impeding ejection. The application of the drive voltage pulse heats the heater, resulting in the formation of a bubble 33 at b1. This process is similar to Figure 5(a). However, the bubble grows more slowly toward b4 than in Figure 5(a), and then disappears more slowly toward b9 than in Figure 5(a). This disappearance of the bubble also leads to a characteristic point in the time change of the detected temperature, where the temperature suddenly drops at b9, during the temperature decrease process in Figure 4(b) after the application of the drive voltage pulse. The bubble grows more slowly than in Figure 5(a) because the ink cannot be pushed toward the nozzle, where the flow resistance is lower, during the bubble growth process, resulting in a delay. Furthermore, the bubble disappears more slowly than in Figure 5(a) because the volume of ink displaced by the bubble cannot be retracted from the nozzle side during the bubble disappearance process.

[0028] When external dust is not ejected, the time it takes for bubbles to disappear is slower than during normal ejection, and the heater temperature drops over time, so the temperature difference between the heater and the ink becomes smaller. Therefore, the temperature change when external dust is not ejected is smaller than during normal ejection.

[0029] Figure 5(b) shows the change over time in the cross section of the nozzle section in the case of external dust non-discharge, but there are other ink non-discharges, such as the following. For example, there is wet non-discharge, which occurs when satellites or mist adhere to the nozzle surface and inhibits discharge; thickened ink non-discharge, which occurs when water evaporates from the discharge port and inhibits discharge due to increased ink viscosity; and internal dust non-discharge, which occurs when foreign matter gets inside the nozzle and inhibits discharge. In these cases, too, the characteristic point appears later than during normal discharge. However, the delay in the characteristic point varies slightly depending on the type and severity of each non-discharge. This is because the flow resistance on the discharge port side of the nozzle and on the ink supply flow path side differs depending on the type and severity of the non-discharge, resulting in different processes from bubble growth to defoaming.

[0030] In Figure 5(c), c0 indicates the initial state immediately before the drive voltage pulse is applied. Here, the case where no ink is ejected is shown, where bubble ejection is inhibited by an air bubble 32 that has entered the nozzle. The heater is heated when the drive voltage pulse is applied, but from c1 onwards, no ink is present on the heater, so no bubble is generated. Therefore, the heater surface does not change from gas to liquid as the bubble disappears, and the temperature only gradually drops. Therefore, no feature points are generated.

[0031] In this example, a nozzle with a nozzle height h1 of 26 μm and a flow path height h2 of 20 μm was used. Under the conditions of this example, a characteristic point appears approximately 5 μsec after the application of the drive voltage during normal ejection, and approximately 9 μsec after the application of the drive voltage during ink-existence and ink-existence and dust-free ejection. Both of these characteristic points are based on the time it takes for bubbles to disappear. The time at which a characteristic point appears during normal ejection is determined by conditions such as the drive voltage pulse, nozzle dimensions such as the ejection port shape and nozzle height, and ink physical properties such as the ink viscosity and temperature. Meanwhile, the time at which a characteristic point appears during ink-existence and ink-existence is always delayed because the flow resistance in the nozzle is higher than during normal ejection. The occurrence of characteristic points during normal ejection and ink-existence and the timing relationship between the occurrence of these characteristic points do not change depending on the conditions. Therefore, normal ejection and ink-existence and ink-existence can be consistently determined.

[0032] 6 is a flowchart showing the nozzle discharge defect determination process in this embodiment. In the following, the flow of the discharge defect determination process in this embodiment 1 will be described with reference to FIGS.

[0033] First, in step S1, the head drive conditions applied to the heater 3 are referenced, and a first detection timing 34 is set in advance between the characteristic point of normal ejection and the characteristic point of ink presence / non-ejection, and a second detection timing 35 is set in advance after the characteristic point of ink presence / non-ejection.

[0034] Since a temperature difference occurs depending on the presence or absence of feature points, a temperature threshold can be set in advance. In step S2, the threshold at the first detection timing 34 is set as T(1_normal ejection), and in step S3, the threshold at the second detection timing 35 is set as T(2_ink presence and non-ejection). Here, the threshold may be set, for example, by predicting in advance before shipment, or may be set by creating states of normal ejection and ink presence and non-ejection by changing the conditions of drive voltage pulses.

[0035] And in step S4, temperatures are output from the temperature sensor at the first and second detection timings along with drive control. Then, in step S5, the temperature T(1) at the first detection timing (the first timing) 34 is acquired, and in step S6, the temperature T(2) at the second detection timing (the second timing) 35 is acquired.

[0036] In steps S7 and S9, the thresholds set in steps S2 and S3 are respectively compared with the detected temperatures acquired in steps S4 and S5. If T(1)>T(1_normal ejection) in step S7, it proceeds to step S8 and is determined as normal ejection. On the other hand, if T(1)<T(1_normal ejection) in step S7, it proceeds to step S9. That is, at the first timing 34, it can be determined whether the liquid ejection from the discharge port is normal or abnormal. If T(2)>T(2_ink presence and non-ejection) in step S9, it proceeds to step S10 and is determined as ink presence and non-ejection. In that case, subsequently, it proceeds to step S11 and warning display or recovery operation is performed. Also, if T(2)<T(2_ink presence and non-ejection) in step S9, it proceeds to step S12 and is determined as ink absence and non-ejection. In that case, subsequently, it proceeds to step S13 and warning display or recovery operation is performed. That is, at the first timing 35, when the liquid ejection from the discharge port is abnormal, the type (cause) of the abnormality can be determined. In this embodiment, in steps S7 and S9, one threshold is compared with each of the first and second detection timings. This is important from the viewpoint of determination accuracy because the range for setting the threshold can be widened. This is because the robustness is enhanced against manufacturing variations in nozzle dimensions and variations in ink physical properties due to changes in ink over time.

[0037] According to the first embodiment described above, by determining whether or not a temperature drop based on the characteristic point has occurred at each of two detection timings based on normal ejection and ink presence / absence during the temperature drop process, it is possible to determine whether the ejection defect is ink presence / absence or ink absence / absence. In other words, it is possible to determine the ejection state of the liquid from the ejection port.

[0038] (Second embodiment) In the first embodiment, the ejection defect state was determined from two detection timings based on a feature point in the time change of the sensor temperature. In this embodiment, however, the feature point is a sudden change in the temperature drop rate, and the determination is made by performing emphasis processing by first-order differentiation over the entire temperature drop process. Ink and nozzle variations are often high-frequency noise, and by using a filter circuit, this effect can be reduced while performing emphasis processing. Therefore, in terms of detecting the presence or absence of a feature point, this is preferable to the time change of temperature used in Example 1. Note that in this embodiment, first-order differentiation is used for emphasis processing, but emphasis processing methods such as second-order differentiation or frequency analysis may also be used.

[0039] The graph shown in Figure 7 is the result of first-order differentiation of the temperature change detected by the temperature sensor in each of the states (a), (b), and (c) described in Figure 4 over the entire temperature drop process. By performing first-order differentiation, a peak appears in the graph if there is a characteristic point. Here again, it can be seen that the characteristic points occur at different times in (a) and (b), but no characteristic point occurs in (c).

[0040] 8 is a flowchart showing the nozzle discharge defect determination process in this embodiment. In the following, the flow of the discharge defect determination process in this embodiment 2 will be described with reference to FIGS.

[0041] First, in step S1, the head drive conditions applied to the heater 3 are referenced, and a first detection timing 34 is preset near a peak value based on a characteristic point during normal ejection, and a second detection timing 35 is preset near a peak value based on a characteristic point during ink presence / absence.

[0042] Peaks occur depending on the presence or absence of feature points, and differences in values occur, so a threshold value can be set in advance. In step S2, the threshold value at the first detection timing 34 is set as D(1_normal ejection), and in step S3, the threshold value at the second detection timing 35 is set as D(2_ink presence and non-ejection). Here, the threshold value may also be set by predicting in advance, for example, before shipment, or by creating states of normal ejection and ink presence and non-ejection by changing the conditions of the drive voltage pulse.

[0043] Then, in step S4, the value obtained by differentiating the output of the temperature sensor at the first and second detection timings with respect to the drive control is output. Then, in step S5, the differential value D(1) at the first detection timing 34 is obtained, and in step S6, the differential value D(2) at the second detection timing 35 is obtained.

[0044] In steps S7 and S9, the threshold values set in steps S2 and S3 are compared with the detected temperatures obtained in steps S4 and S5, respectively. If D(1) < D(1_normal ejection) in step S7, proceed to step S8 and determine normal ejection. On the other hand, if D(1) > D(1_normal ejection) in step S7, proceed to step S9. If D(2) < D(2_ink presence and non-ejection) in step S9, proceed to step S10 and determine ink presence and non-ejection. In that case, subsequently proceed to step S11 and perform a warning display or a recovery operation. Also, if D(2) > D(2_ink presence and non-ejection) in step S9, proceed to step S12 and determine ink absence and non-ejection. In that case, subsequently proceed to step S13 and perform a warning display or a recovery operation.

[0045] While the first-order differentiation can represent the feature point as a peak, when the detection timing and peak value deviate slightly due to variations in ink or nozzles, it greatly affects the value. Therefore, instead of providing a detection timing near the peak value, it is preferable to provide a detection range with a time width near the peak value and output its minimum value. Especially when using an analog circuit, such an output method is easier and thus more preferable.

[0046] According to the second embodiment described above, whether or not a peak based on a feature point occurs in the first-order differential of the temperature drop process is determined twice at each of two detection timings based on normal ejection and ink presence / absence. This makes it possible to determine whether the ejection defect is ink presence / absence or ink absence / absence. This makes it possible to display an appropriate warning or take recovery action depending on the cause of the ejection defect. In this embodiment, as in the first embodiment, a comparison is made with a single threshold value at each of the first and second detection timings in steps S7 and S9. This is important from the perspective of determination accuracy because it allows a wide range of threshold values ​​to be set. This is because it improves robustness against variations in nozzle dimensions during manufacturing and variations in ink properties due to changes in ink over time.

[0047] (Applicable to one-sided supply) In this example, a nozzle that supplies ink from both sides was used, and the characteristic points of normal ejection and ink presence / absence were determined to be due to the disappearance of bubbles, and the time delay between ink presence and absence was used to determine the state of defective ejection. However, this relationship does not change even for nozzles that supply ink from one side, so the same determination process as for double-sided supply is possible.

[0048] The nozzle in this embodiment is shown as a nozzle in which the bubble does not communicate with the atmosphere and collapses. However, depending on the nozzle dimensions, there are nozzles in which, after the bubble communicates with the atmosphere and reaches atmospheric pressure, the negative pressure of the bubble just before communication causes the trailing end of the ejected droplet to break off and crash onto the heater surface (hereinafter referred to as "tail crash"). An example of such a nozzle is one with dimensions h1 = 22 μm and h2 = 16 μm. As the heater surface is replaced by ink due to the tail crash, the heater surface changes from gas to liquid, causing rapid cooling and creating a feature point. Even with such a nozzle, during normal ejection, the ink cools rapidly upon re-contact with the heater surface. Therefore, as with the nozzles not communicating with the atmosphere described in Examples 1 and 2, the feature point indicating whether ink is ejected or not occurs later than during normal ejection. Therefore, the temperature changes over time in the same way as in this embodiment, and ejection defects can be detected using the same determination process.

[0049] On the other hand, depending on the nozzle dimensions, there are nozzles in which all the ink on the heater surface is ejected after the bubble is released into the atmosphere, resulting in no ink trailing off the heater surface. An example of such a nozzle is one with dimensions h1 = 9.5 μm and h2 = 5.0 μm. Figure 9 shows the temperature change over time, Figure 10 shows the first-order derivative of the temperature change over time, and Figure 11 shows a cross-sectional view of the nozzle in each state. Since no defoaming or ink trailing off occurs in such a nozzle, no ink is present on the heater surface at a10 during normal ejection. As ink refills, the heater surface is replaced by ink around a20. This refilling process replaces the heater surface with ink, causing the heater surface to change from gas to liquid, resulting in rapid cooling and a characteristic point. On the other hand, when ink is present or absent, defoaming occurs around b7 and a characteristic point appears. This allows for similar determinations to be made by providing a first detection timing based on the characteristic point associated with ink refilling during normal ejection and a second detection timing based on the characteristic point associated with ink presence or absence. However, here, the characteristic points when ink is present or not appear earlier than the characteristic points when ink is normally ejected. In other words, the first detection timing is later than the second detection timing, and the time relationship is reversed. Therefore, the order of steps S7 and S9 may be reversed.

[0050] (Regarding the second detection timing) In this embodiment, the first and second detection timings are fixed and set according to each feature point, taking advantage of the fact that the feature points when ink is present but not ejected are delayed compared to the feature points when ink is ejected normally. The feature points when ink is ejected normally appear at a fixed position if the ink and nozzle conditions are the same. On the other hand, the feature points when ink is present but not ejected differ depending on the type of ejection failure, and even if the type is the same, the degree of the failure.

[0051] Types of ejection defects with or without ink include external dust ejection, wet ink ejection, thickened ink ejection, and internal dust ejection. The flow resistance on the ejection port side of the nozzle unit and on the ink supply flow path side differs depending on the type of ejection defect, and the timing at which the characteristic point occurs also differs. Therefore, the higher the flow resistance depending on the type of ejection defect, the later the timing of the characteristic point. Therefore, by appropriately setting the detection timing, it is possible to distinguish between types of ejection defects with or without ink ejection.

[0052] Furthermore, for example, in the case of external dust not ejecting, the degree of ejection failure can also be such that the external dust does not completely block the ejection orifice, but rather blocks only part of it, as shown in Figure 12. In this case, the bubble deactivation corresponding to the characteristic point is d6, which is between the bubble deactivation a5 for normal ejection and the bubble deactivation c9 for external dust not ejecting, as shown in Figures 5(a) and (b). Therefore, since the timing of the characteristic point becomes later the higher the flow resistance, even depending on the degree of ejection failure, it is also possible to distinguish between ejection failure states with and without ink ejection by appropriately setting the detection timing.

[0053] From the above, the essence of the present invention is that the first detection timing is set in advance based on characteristic points corresponding to the type of ejection that the nozzle performs during normal ejection, and the second detection timing is set based on characteristic points corresponding to the state of the ejection defect. In other words, the second detection timing does not necessarily determine whether ink is present or not, but rather can determine the type of ejection defect that is most desired to be detected and the extent of that ejection defect.

[0054] According to the embodiment described above, it is possible to determine whether there is a discharge defect, and the state of the discharge defect, such as whether the discharge defect is due to the presence or absence of ink. This determination is made at two timings based on the characteristic points of normal discharge and the presence or absence of ink, allowing for two processing determinations with a single threshold value for each. Because the processing determination is made twice, it is possible to make a high-speed determination, and because each determination is made using a single threshold value, a wide range can be set, allowing for a high-precision determination. Furthermore, by setting the second detection timing, it is possible to make a more detailed determination of the state of the discharge defect and its severity.

[0055] Based on the determination result, if there is no ink ejection, a recovery operation is performed by wiping the nozzle surface while suctioning, assuming no bubble ejection. For example, vacuum wiping is one such recovery operation. If there is ink ejection but no ink ejection, a recovery operation is performed by wiping the nozzle surface without suction, assuming no wet ejection or no external dust ejection. For example, blade wiping is one such recovery operation.

[0056] Ink presence / absence failures include ink thickening failures, where ink thickening due to evaporation of water from the ejection ports inhibits ejection, and internal dust failures, where foreign matter has entered the nozzle interior and inhibits ejection. In these cases, a recovery operation, such as wiping the nozzle surface while suctioning, may be required, similar to ink non-ejection failures. However, ink thickening failures do not occur and are not a problem in nozzles equipped with nozzle circulation using differential pressure, etc. In addition, internal dust failures are often caused by foreign matter introduced during the manufacturing process, making recovery through recovery operations difficult in the first place. In such cases, it may be sufficient to simply quickly and accurately determine whether ink is present or absent. In such cases, downtime and the amount of wasted ink can be reduced by taking optimal recovery operations based on the determination of the ejection failure status, i.e., whether ink is present or absent. Therefore, depending on the setting of the second detection timing, more detailed determination of the ejection failure status and its severity is possible, but it is preferable to do so as needed. [Explanation of symbols]

[0057] 2 outlet 3. Electrothermal conversion element 21 PCB

Claims

1. a discharge port for discharging a liquid; a substrate provided with an electrothermal conversion element that generates heat for discharging liquid from the discharge port; a temperature detection means for detecting temperature information of the substrate; A method for determining a liquid ejection state from an ejection port in a liquid ejection device having the following: a first determination step of acquiring temperature information of the substrate at a first timing by the temperature detection means, and then determining whether ejection of liquid from the ejection port is normal or abnormal by comparing the temperature information at the first timing with a first threshold value; a second determination step of acquiring temperature information of the substrate at a second timing by the temperature detection means, and then determining the type of abnormality when the ejection of the liquid from the ejection port is abnormal by comparing the temperature information at the second timing with a second threshold value; and The determination method, wherein the temperature information is a first-order differential of a waveform of a temperature change of the substrate.

2. The determination method according to claim 1, wherein at the second timing, it is determined whether the ejection of liquid from the ejection port is abnormal when liquid is present on the electrothermal conversion element, or whether the ejection of liquid from the ejection port is abnormal when no liquid is present on the electrothermal conversion element.

3. the first timing is based on a timing at which the liquid comes into contact with the electrothermal converting element after the electrothermal converting element is driven in a case where the liquid is normally discharged from the discharge port; 3. The method according to claim 1, wherein the second timing is based on the timing at which the liquid comes into contact with the electrothermal converting element after the electrothermal converting element is driven in the event that the liquid is being abnormally discharged from the discharge port.

4. A determination method described in any one of claims 1 to 3, wherein when the liquid is normally ejected from the ejection port, the bubbling caused by the electrothermal conversion element does not communicate with the atmosphere, and when the bubbling communicates with the atmosphere and the rear end of the liquid droplet ejected from the ejection port falls onto the electrothermal conversion element, the first timing is earlier than the second timing.

5. A determination method described in any one of claims 1 to 3, wherein when the liquid is normally ejected from the ejection port, if bubbling caused by the electrothermal conversion element is connected to the atmosphere and the trailing end of the liquid droplet ejected from the ejection port does not fall onto the electrothermal conversion element, the first timing is later than the second timing.

6. a temperature detection element for detecting the temperature of the substrate is formed directly below or directly above the electrothermal conversion element; 6. The method according to claim 1, wherein the temperature detecting means detects the temperature information of the substrate based on the output result of the temperature detecting element.

7. 7. The method according to claim 1, further comprising the step of: performing a recovery operation for the ejection port when it is determined that the ejection of liquid from the ejection port is abnormal at the first timing.

8. a discharge port for discharging a liquid; a substrate provided with an electrothermal conversion element that generates heat for discharging liquid from the discharge port; a temperature detection means for detecting temperature information of the substrate; In a liquid ejection device having acquiring temperature information of the substrate at a first timing by the temperature detection means, and then comparing the temperature information at the first timing with a first threshold value to determine whether the ejection of liquid from the ejection port is normal or abnormal; acquiring temperature information of the substrate at a second timing by the temperature detection means, and then comparing the temperature information at the second timing with a second threshold value to determine the type of abnormality when the ejection of the liquid from the ejection port is abnormal; The liquid ejection apparatus is characterized in that the temperature information is a first-order differential of a waveform of a temperature change of the substrate.

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