Liquid ejection device and determination method for determining ejection state

Abstract

Disclosed are a liquid ejecting apparatus and a determination method for determining an ejection state. A method for determining a state of liquid ejection from an ejection port in a liquid ejecting apparatus is provided. The liquid ejecting apparatus includes an ejection port configured to eject liquid, a substrate including an electro-thermal conversion element configured to generate heat for ejecting liquid from the ejection port, and a temperature detection unit configured to detect temperature information about the substrate. The method includes performing first comparison processing of comparing temperature information about the substrate detected by the temperature detection unit at a first timing with a first threshold value, and performing second comparison processing of comparing temperature information about the substrate detected by the temperature detection unit at a second timing with a second threshold value.

Description

Technical Field

[0001] The present disclosure relates to a liquid ejecting device configured to eject liquid and a determination method for determining an ejection state. Background Art

[0002] Inkjet recording devices (liquid ejection devices) record various information, such as images, on recording materials such as paper by ejecting ink (liquid) from small nozzles (ejection ports). Thermal inkjet is one of the recording methods used by inkjet recording devices. In thermal inkjet, film-boiling ink is ejected from the ejection ports using thermal energy generated by a heater (electrothermal conversion element).

[0003] In an inkjet recording apparatus, when an ink ejection failure occurs, an image formation problem occurs. In a full-line recording apparatus, a large number of nozzles are arranged on a row having a length corresponding to the entire width of the recording medium, which enables high-speed printing. The occurrence of an ejection failure may have an adverse effect on the image, so it is necessary to perform a recovery operation of the recording head. There are two types of recovery operations: wiping the nozzle surface during suction; and wiping the nozzle surface without suction. Both types result in downtime. When the recovery operation includes suction, ink waste occurs. For an inkjet recording apparatus, it is desirable to have as little downtime and ink waste as possible. Therefore, it is important to quickly identify which type of ejection failure is occurring in which of a large number of nozzles so that an appropriate recovery operation can be performed at an appropriate timing.

[0004] Ejection failures are generally categorized into two types: the first type, in which an ejection failure occurs when ink is present on the heater; and the second type, in which an ejection failure occurs when no ink is present on the heater. The first type of ejection failure in the first type is, for example, an external dust ejection failure, which occurs when ejection is obstructed by foreign matter, such as paper dust, attached to the nozzle surface. The second type of ejection failure in the first type is a wet ejection failure, which occurs when ink adheres to the nozzle surface due to satellite droplets or mist obstructing ejection. The third type of ejection failure in the first type is a thickened ink ejection failure, which is an ejection failure caused by thickening of the ink due to evaporation of water from the ejection port. The fourth type of ejection failure in the first type is an internal dust ejection failure, which occurs when foreign matter invades the interior of the nozzle and ejection is obstructed by the foreign matter. An example of an ejection failure in the second type is a bubble ejection failure, which occurs when bubbles invade the interior of the nozzle and ejection is obstructed by the bubbles. Which type of ejection failure is dominant depends on the head structure and nozzle structure.

[0005] Conventionally, in order to detect such ejection failure in a thermal inkjet recording apparatus, it is known to examine a change in temperature over time that occurs when a heater is driven to eject ink. An apparatus using a method of determining the type of ejection failure has been proposed.

[0006] Japanese Patent Laid-Open No. 2007-331354 discloses a method of identifying a state of an injection failure by measuring a temperature at a predetermined timing and comparing the measured temperature with a plurality of threshold values.

[0007] Although Japanese Patent Publication No. 2007-331354 discloses a technique for determining the state of an ejection failure by comparing a timing with multiple threshold values, the technique does not allow for a wide range of determination for each state determination because it requires comparison with multiple threshold values. Consequently, it may be difficult to maintain high determination reliability, including robustness against variations in ink and nozzles. Japanese Patent Publication No. 2007-331354 also describes a technique for performing determination by comparing a timing with a threshold value at each of multiple timings. However, in order to identify the ejection failure state, the determination process is performed three or more times, making it difficult to achieve high-speed determination.

[0008] In order to deal with the above situation, the present disclosure provides a method of determining the state of an injection failure with high determination reliability in a short time by comparing with a threshold value at each of two timings. Summary of the Invention

[0009] The present disclosure provides a method for determining a state of liquid ejection from an ejection port in a liquid ejection device, the liquid ejection device comprising: an ejection port configured to eject liquid; a substrate comprising an electrothermal conversion element configured to generate heat for ejecting liquid from the ejection port, and a temperature detection unit configured to detect temperature information about the substrate, the method comprising: performing a first comparison process of comparing the temperature information about the substrate detected by the temperature detection unit at a first timing with a first threshold value, and performing a second comparison process of comparing the temperature information about the substrate detected by the temperature detection unit at a second timing with a second threshold value.

[0010] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a perspective view of a full-line inkjet recording apparatus.

[0012] Figure 2A 、 Figure 2B and Figure 2C Each is a schematic diagram of an inkjet recording head, wherein Figure 2Ais a top view and Figure 2B and Figure 2C Each is a cross-sectional view.

[0013] Figure 3 is a diagram showing control function blocks of the liquid ejecting device.

[0014] Figure 4 is a graph showing changes with time in the detected temperature that occurs when the electrothermal conversion element is driven.

[0015] Figure 5A 、 Figure 5B and Figure 5C Each illustrates a temporal change in the cross section of the ejection port that occurs when the electrothermal conversion element is driven.

[0016] Figure 6 is a flowchart showing the injection failure determination process.

[0017] Figure 7 is a graph illustrating changes in detected temperature over time according to one or more aspects of the present disclosure.

[0018] Figure 8 is a flowchart illustrating an injection failure determination process according to one or more aspects of the second embodiment of the present disclosure.

[0019] Figure 9 is a diagram showing time-related changes in temperature detected by a sensor that occur when a heater is driven in a second embodiment of the present disclosure when the nozzle is configured to have a nozzle size that allows it to eject all ink present on the heater in a normal ejection state, wherein the time-related changes in temperature are shown for each of the three ejection states.

[0020] Figure 10 is a diagram showing the first derivative of the time-related change in temperature detected by the sensor that occurs when the heater is driven when the nozzle is configured to have a nozzle size that allows it to eject all ink present on the heater in a normal ejection state in the second embodiment of the present disclosure, wherein the first derivative is plotted over the range of the temperature drop process for each of the three ejection states.

[0021] Figure 11A 、 Figure 11B and Figure 11C The diagram shows that when Figure 9 and Figure 10 ] shows time-dependent changes in the cross section of the nozzle portion that occur when the heater is driven in each ejection state.

[0022] Figure 12 It is a diagram showing that when Figure 5B1 is a diagram illustrating temporal changes in the cross section of the nozzle portion that occur when the heater is driven but the ejection port is partially blocked by foreign matter in a state similar to the state shown in . DETAILED DESCRIPTION

[0023] The following describes embodiments of the present disclosure in detail.

[0024] First embodiment

[0025] sensor

[0026] The configuration of an inkjet recording apparatus to which the present disclosure is applicable is described below.

[0027] Figure 1 7 is a schematic diagram illustrating the main components of a full-line inkjet recording device 700. A recording head 701 includes multiple nozzle rows, and multiple nozzles are arranged along each of the multiple nozzle rows. By ejecting ink droplets from the recording head including the nozzles, an image is recorded on a recording medium 703 transported by a transport unit 702.

[0028] Figure 2A is a schematic top view of the entire nozzle section provided in the recording head. Figure 2B It is along Figure 2A Schematic cross-sectional view taken along line IIB-IIB shown in FIG. Figure 2C It shows Figure 2B Schematic cross-sectional view of the membrane structure near the injection port is shown in FIG.

[0029] Figure 2A The top surface of the entire nozzle section of the recording head is schematically illustrated, in which the ejection ports 2 are arranged. By applying a drive signal to an electrothermal conversion element (hereinafter referred to as a heater 3) provided for each ejection port 2, the ink inside the ejection port 2 is heated, thereby ejecting the ink from the ejection port 2. Liquid supply ports 16 for supplying ink to the nozzles are formed on both sides of the nozzles.

[0030] Figure 2B is a schematic diagram showing the Figure 2A 1B-11B is a diagram showing a cross section of the nozzle structure taken along line IIB-IIB shown in FIG. A temperature detection element (hereinafter referred to as a temperature sensor 5 or a temperature detection unit) for detecting a temperature change (temperature information) of a substrate is formed just below each heater 3. Temperature information on the substrate is detected based on an output result from the temperature detection element. Figure 2B In the embodiment, the temperature sensor is arranged directly below the heater to detect the temperature change near the heater, but it can also be arranged directly above the heater as long as the temperature change near the heater can be detected. The ejection port forming portion 18 forming the ejection port 2 is supported by the flow path forming portion 17. Here, in order to express the nozzle size, as shown in FIG. Figure 2BAs shown in FIG, a nozzle height 19 and a flow path height 20 are defined.

[0031] Figure 2C is a diagram showing a multilayer structure forming a heater and a temperature sensor. Both the heater 3 and the temperature sensor 5 are formed in a multilayer structure on a substrate using the same film formation process. On a Si substrate 21, a heat storage layer 22 made of a thermal oxide film SiO2 or the like is formed, and an independent wiring 23 made of Al or the like for interconnecting the temperature sensor 5 is formed, as well as Al wiring connecting the control circuit formed on the Si substrate 21 and the heater 3. The temperature sensor 5 is formed from a thin film resistor whose resistance value changes depending on the temperature. Examples of materials for thin film resistors include Al, Pt, Ti, TiN, TiSi, Ta, TaN, TaSiN, TaCr, Cr, CrSi, CrSiN, W, WSi2, WN, polycrystalline silicon, α-Si, Mo, MoSi, Nb, and Ru. Furthermore, on the Si substrate 21, a passivation film 25 made of SiN or the like, and an anti-cavitation film 26 are formed in a high-density multilayer structure using a semiconductor process via an interlayer insulating film 24. The anti-cavitation film 26 is a film used to enhance the cavitation resistance of the heater 3. For example, a Ta film is used as the anti-cavitation film 26. A temperature sensor 5 is provided separately and independently for each heater 3 so that the temperature sensor 5 is disposed directly below the corresponding heater 3. An independent wiring 23 connected to a corresponding one of the temperature sensors 5 is formed as a part of a detection circuit that detects information related to the temperature detection element. According to this embodiment, the structure of the recording head is formed by patterning each element using a conventional process for producing an inkjet recording head. Therefore, the recording head can be produced without changing the structure of the recording head relative to the conventional structure of the recording head, which is a great advantage from the perspective of industrial production.

[0032] Figure 3 This is a block diagram of the control circuit of the recording device. Figure 3 As shown in , the control circuit includes an image input unit 403 , an image signal processing unit 404 , and a CPU 400 , which are configured such that they are allowed to access a main bus 405 .

[0033] The CPU 400 includes a ROM 401 and a RAM 402, and controls the recording head 412 so that appropriate recording conditions are applied to input information and the recording head 412 is driven to record the input information in accordance with the recording conditions. A program for executing a recovery process for recovering the recording head is pre-stored in the RAM 402, and the recovery conditions, such as preliminary ejection conditions, are supplied to the recovery process control circuit 407, the recording head, and the like.

[0034] The recovery processing motor 408 drives the recording head, a blade (cleaning blade) 409 provided facing the recording head, a cap 410 , and a suction pump 411 .

[0035] The recording head drive control circuit 414 drives the heater 3 as the electrothermal conversion element of the recording head 412 according to the drive conditions given by the CPU 400, and causes the recording head to perform preliminary ejection and recording ink ejection.

[0036] Determination based on temperature changes over time

[0037] Figure 4 : is a graph showing the change in temperature over time that occurs when a driving voltage pulse is applied to the heater to eject ink (temperature change waveform). Figure 4 As shown in , the temperature profile detected by the temperature sensor changes depending on the difference in the state a, b or c of the nozzle. Figure 5A 、 Figure 5B and Figure 5C The diagram shows Figure 4 The cross-section of the nozzle portion in each state a, b and c shown in FIG changes with time. Figure 5A 、 Figure 5B and Figure 5C In FIG. 1 , a0 to a10 , b0 to b10 , and c0 to c10 indicate time 0 μs to 10 μs from the time of the initial state, which is intercepted at intervals of 1 μs.

[0038] exist Figure 4 In , a represents a temperature change that occurs when ink is ejected normally without an ejection failure (hereinafter, this type of ejection will be referred to as normal ejection). Figure 4 In FIG, b represents a temperature change that occurs when an ejection failure occurs in a state where ink is present on the electrothermal conversion element (hereinafter, this type of ejection failure will be referred to as an ejection failure with ink present). Figure 4 In FIG. 1 , c represents a temperature change that occurs when an ejection failure occurs in a state where no ink exists on the electrothermal conversion element (hereinafter, this type of ejection failure will be referred to as an ejection failure without ink). Figure 4 As shown in FIG, in nozzle states a and b, the temperature rises in response to the application of the drive voltage pulse, and after reaching the maximum temperature, the temperature drops. During the temperature drop, a characteristic point where a sudden temperature drop occurs appears in the change in the detected temperature over time. Note that the characteristic point appears at different times depending on whether the nozzle is in state a or b. On the other hand, as Figure 4 As shown in FIG, in the case of nozzle state c, the temperature drops without the occurrence of a characteristic point.

[0039] refer to Figure 5A 、 Figure 5B and Figure 5C, describing why Figure 4 The reason why characteristic points appear in the temperature variation at different times in cases a and b shown in FIG. Figure 4 The reason why no feature points appear in case c is shown in FIG.

[0040] exist Figure 5A In the figure, a0 represents the initial state immediately before the drive voltage pulse is applied. When the drive voltage pulse is applied and the heater is heated, a bubble 33 appears at a1. As the temperature increases toward the maximum temperature, the bubble grows over the time periods a2 and a3, causing the ink to be squeezed out of the ejection port. At time a5, the interface on the ejection port side is pulled in, causing the bubble to disappear. As the bubble disappears, the bubble on the heater is replaced by ink. In other words, the gas covering the heater is replaced by liquid, and the heater is covered by liquid.

[0041] There is a large difference in thermal conductivity between the gas and the liquid, so rapid cooling occurs as the gas is displaced by the liquid. Figure 4 In the nozzle state a, the temperature rises in response to the application of the driving voltage pulse, and the temperature drops after reaching the maximum temperature. Figure 5A At the time corresponding to a5 in FIG, a characteristic point appears in the change of the detected temperature over time, and a sudden temperature drop occurs.

[0042] exist Figure 5B In the example, b0 represents the initial state immediately before the drive voltage pulse is applied. Note that Figure 5B The figure shows a case where an external dust ejection failure occurs as one of the ejection failures in which ink is present. More specifically, in this external dust ejection failure, it is assumed that foreign matter 31 such as paper dust adheres to the outside of the nozzle surface and ejection is blocked by the foreign matter 31. When a driving voltage pulse is applied and the heater is heated, a bubble 33 appears at b1. So far, the behavior of the bubble in the nozzle is similar to Figure 5A However, with Figure 5A In contrast, the bubbles are larger in the period up to b4. Figure 5A The growth is slow, and the bubbles are larger than those in the period up to b9. Figure 5A It disappears slowly. Figure 4 In addition, in the nozzle state b, the temperature rises in response to the application of the driving voltage pulse, and after reaching the maximum temperature, the temperature drops, and in the process of temperature drop, Figure 5B At the time corresponding to b9 in the figure, a characteristic point appears in the change of the detected temperature over time, and a sudden temperature drop occurs. Figure 5AThe reason why the growth of bubbles is slow is that if there is no foreign matter on the nozzle surface, the growth of bubbles does not cause the ink to be pushed outward to the ejection port with small flow resistance, so the growth of bubbles is reduced. Figure 5A The reason why the bubbles disappear slowly is that the bubbles are not filled back with ink from the ejection port side during the bubble disappearance process.

[0043] During an external dust ejection failure, the bubble disappears over a longer period of time than during normal ejection. Furthermore, the heater temperature gradually decreases over time, reducing the temperature difference between the heater and the ink. Consequently, the temperature change during an external dust ejection failure is smaller than during normal ejection.

[0044] The above reference Figure 5B The temporal change in the cross section of the nozzle section that occurs in the external dust ejection failure state as one of the ink ejection failure states has been described. For example, other types of ink ejection failures may also occur in the following cases:

[0045] Wet jetting failures occur when ink adheres to the nozzle surface due to satellite droplets or mist, hindering ejection. Thickened ink jetting failures occur when the viscosity of the ink increases (thickens) due to evaporation of water from the ejection port, hindering ejection. Internal dust jetting failures occur when foreign matter invades the interior of the nozzle, hindering ejection. In these types of jetting failures involving the presence of ink, characteristic points appear later than in normal jetting conditions. However, the degree of delay in the appearance of characteristic points varies slightly depending on the type and severity of the jetting failure.

[0046] This is because the flow resistance on the ejection port side and the flow resistance on the ink supply flow path side in the nozzle portion vary depending on the type and degree of the ejection failure, and therefore, a difference occurs in the process of growth and disappearance.

[0047] exist Figure 5C In the example, c0 represents the initial state immediately before the drive voltage pulse is applied. Note that Figure 5C This figure shows a case where a bubble ejection failure, one type of ejection failure caused by the presence of ink, occurs. More specifically, in this bubble ejection failure, it is assumed that a bubble 32 intrudes into the nozzle interior, obstructing ejection. When a drive voltage pulse is applied, the heater is heated, but because there is no ink on the heater, no bubbles are generated during the period C1 and thereafter. Therefore, the bubbles do not disappear, and no gas-to-liquid substitution occurs on the heater surface, resulting in a simple, gradual temperature drop. Consequently, no characteristic point appears.

[0048] In this specific example, the nozzle has a nozzle height h1 = 26 μm and a flow path height h2 = 20 μm. Under the conditions of this embodiment, in the normal ejection state, the characteristic point appears 5 μs after the drive voltage is applied, and in the external dust ejection failure state, one of the ink ejection failure states, the characteristic point appears 9 μs after the drive voltage is applied. In these cases, the characteristic point is based on the bubble disappearance time. The time when the characteristic point appears in the normal ejection state is determined by various factors, including drive conditions such as the drive voltage pulse conditions, nozzle dimensions such as the ejection port shape and nozzle height, and physical ink properties such as ink viscosity and temperature. On the other hand, in the ink ejection failure state, because the flow resistance in the nozzle section is higher than in normal ejection, the characteristic point always appears later than in the normal ejection state. Regardless of the specifics of the conditions, the fact that the characteristic point appears in both the normal ejection state and the ink ejection failure state, and that the characteristic point appears later in the ink ejection failure state than in the normal ejection state, always holds true. Therefore, it is always possible to determine whether the ejection is normal or not.

[0049] Figure 6 : is a flowchart showing the nozzle ejection failure determination process according to the present embodiment. Figure 4 and Figure 6 , the flow of the injection failure determination process according to the present embodiment will be described below.

[0050] First, in step S1, the head driving conditions applied to the heater 3 are referred to, and the first detection timing 34 and the second detection timing 35 are pre-set so that the first detection timing 34 appears between the characteristic point in the normal ejection state and the characteristic point in the ejection failure state where ink exists, and the second detection timing 35 appears after the characteristic point in the ejection failure state where ink exists.

[0051] Since a temperature difference occurs depending on whether a characteristic point appears, a temperature threshold value can be set in advance. In step S2, the threshold value at the first detection timing 34 is set to T(1_normal ejection). In step S3, the threshold value at the second detection timing 35 is set to T(2_ink ejection failure). Prior to shipment, the threshold value can be set in advance to a predicted value, or it can be set based on a normal ejection state and an ink ejection failure state experimentally generated by changing the conditions of the drive voltage pulse.

[0052] Then, in step S4, when performing drive control, the temperature is output from the temperature sensor at the first detection timing and the second detection timing. Then, in step S5, the temperature T(1) at the first detection timing (the first timing) 34 is obtained, and in step S6, the temperature T(2) at the second detection timing (the second timing) 35 is obtained.

[0053] In step S7, the detected temperature obtained in step S4 is compared with the threshold value set in step S2, and in step S9, the detected temperature obtained in step S5 is compared with the threshold value set in step S3. When it is determined in step S7 that T(1) ≥ T(1_normal injection), the process proceeds to step S8, where it is determined that the nozzle is in the normal injection state. On the other hand, when it is determined in step S7 that T(1) < T(1_normal injection), the process proceeds to step S9. That is, at the first timing 34, it can be determined whether the liquid is ejected from the ejection port normally or abnormally. When it is determined in step S9 that T(2) ≥ T(2_ink ejection failure), the process proceeds to step S10, where it is determined that the nozzle is in the ink ejection failure state. In this case, the process further proceeds to step S11, where a warning is displayed or a recovery operation is performed. When it is determined in step S9 that T(2) < T(2_ink ejection failure), the process proceeds to step S12, where it is determined that the nozzle is in the inkless ejection failure state. In this case, the process further proceeds to step S13, where a warning is displayed or a recovery operation is performed. That is, when it is determined that the liquid ejection from the ejection port is abnormal at the first timing 34, the type (cause) of the abnormality can be determined at the second timing 35. In the present embodiment, in steps S7 and S9, the detected temperatures detected at the first detection timing and the second detection timing are each compared with a corresponding one of the threshold values. This is important because each threshold value can be set within a large range, and thus a more reliable determination result can be achieved. That is, this makes it possible to enhance the robustness against manufacturing variations in nozzle size and changes in the physical properties of the ink due to changes over time.

[0054] According to the above first embodiment, two determinations are made as to whether a temperature drop related to the feature point occurs, such that one determination is made at one of the two detection timings based on the normal injection state, and one determination is made at the other of the two detection timings based on the ink ejection failure state. This makes it possible to determine whether the ejection failure is of the ink ejection failure type or the inkless ejection failure type.

[0055] In other words, the state of the liquid ejection from the ejection port can be determined.

[0056] Second embodiment

[0057] In the first embodiment described above, in the change of the sensor temperature over time, the state of the ejection failure is determined based on the detection at two detection timings based on the characteristic point. In the second embodiment described below, the fact that a sudden temperature drop occurs at the characteristic point is used to perform a first-order differential on the detected temperature over the entire range of the temperature drop process, thereby emphasizing the temperature change at the characteristic point. Changes in ink and nozzles usually appear as high-frequency noise, so by using a filter circuit, the influence of such changes on the result of the emphasis processing can be reduced. Therefore, from the perspective of detecting whether there are characteristic points, the second embodiment provides a better method than the first embodiment based on temperature changes described above. In this embodiment, the first-order differential is used in the emphasis processing, but the emphasis processing can be achieved using the second-order differential, frequency analysis, or other methods.

[0058] Figure 7 Shows the instructions when referring to the above reference Figure 4 The graph of the results obtained when the temperature change detected by the temperature sensor is first differentiated over the entire range of the temperature drop process for each of the states a, b, and c described above. In the case where there are characteristic points, performing first differentiation results in a peak appearing on the graph. In addition, in this case, as shown in FIG. Figure 7 It can be seen that, depending on whether the state is a or b, feature points appear in states a and b at different times, but for state c, no feature points appear.

[0059] Figure 8 : is a flowchart showing the nozzle ejection failure determination process according to the present embodiment. Figure 7 and Figure 8 , the flow of the injection failure determination process according to the present embodiment will be described below.

[0060] First, in step S21, the head driving conditions applied to the heater 3 are referred to, and the first detection timing 34 and the second detection timing 35 are pre-set so that the first detection timing 34 is located near the peak of the characteristic point based on the normal ejection state, and the second detection timing 35 is located near the peak of the characteristic point based on the ejection failure state in which ink exists.

[0061] Depending on whether a feature point exists, a peak appears and its value varies, so a threshold value may be set in advance.

[0062] In step S22, the threshold value at the first detection timing 34 is set to D(1_normal ejection). In step S23, the threshold value at the second detection timing 35 is set to D(2_ink ejection failure). In this case, the threshold value may be set in advance to a predicted value before shipment, or may be set based on a normal ejection state and an ink ejection failure state experimentally generated by changing the conditions of the drive voltage pulse.

[0063] Then, in step S24, when the drive control is executed, the temperature sensed by the temperature sensor is first differentiated at the first detection timing and the second detection timing, and the resulting derivatives are output. In step S25, the derivative D(1) at the first detection timing 34 is acquired, and in step S26, the derivative D(2) at the second detection timing 35 is acquired.

[0064] In step S27, the derivative obtained in step S24 is compared with the threshold value set in step S22, and in step S29, the derivative obtained in step S25 is compared with the threshold value set in step S23. In the case where it is determined in step S27 that D(1) ≤ D(1_normal ejection), the process proceeds to step S28, in which it is determined that the nozzle is in a normal ejection state. On the other hand, in the case where it is determined in step S27 that D(1)> D(1_normal ejection), the process proceeds to step S29. In the case where it is determined in step S29 that D(2) ≤ D(2_ink ejection failure exists), the process proceeds to step S30, in which it is determined that the nozzle is in an ink ejection failure state. In this case, the process further proceeds to step S31, in which a warning is displayed or a recovery operation is performed. In the case where it is determined in step S29 that D(2)> D(2_ink ejection failure exists), the process proceeds to step S32, in which it is determined that the nozzle is in an ink ejection failure state. In this case, the process further proceeds to step S33 where a warning is displayed or a recovery operation is performed.

[0065] Although the first-order derivative allows for peaks to be used to identify characteristic points, slight shifts between detection timing and peaks due to variations in ink or nozzles can significantly affect the value. To address this, instead of setting the detection timing near the peak, it may be better to set a detection range with a time width near the peak and output its minimum value. This approach is particularly well-suited when using analog circuits, as they easily provide outputs in this manner.

[0066] In the second embodiment, as described above, two determinations are made as to whether a peak associated with a characteristic point appears in the first-order derivative during the temperature drop, so that one determination is made at the detection timing based on the normal ejection state, and one determination is made at the detection timing based on the ejection failure state in which ink is present. This makes it possible to determine whether the ejection failure type is an ejection failure in which ink is present or an ejection failure in which there is no ink. Therefore, it is possible to display an optimal warning and / or perform an optimal recovery operation depending on the type of ejection failure. In this second embodiment, as in the first embodiment, in each of the comparison steps S27 and S29 of the first detection timing and the second detection timing, a comparison with a threshold is made. This is important because each threshold can be set within a large range, and thus a more reliable determination result can be achieved. That is, this makes it possible to enhance the robustness against manufacturing variations in nozzle size and variations in the physical properties of the ink due to variations over time.

[0067] Applications where ink is supplied from one side

[0068] In the above example, ink is supplied to the nozzle from both sides. Assuming this nozzle configuration, the ejection failure state is determined based on the fact that a characteristic point appears due to the disappearance of bubbles in both the normal ejection state and the ejection failure state, and that the characteristic point appears later in the ejection failure state than in the normal ejection state. This characteristic also appears when the nozzle is configured so that ink is supplied from one side, so the determination process can be performed in a similar manner to the case of ink supply from both sides.

[0069] In the above description according to the present embodiment, it has been assumed that the bubbles generated in the nozzle disappear without being connected to the atmosphere. However, depending on the nozzle size, the bubbles generated may be connected to the atmosphere. In this case, the bubbles can behave as follows. The bubble pressure with negative pressure attempts to become equal to the atmospheric pressure, but the tail portion of the ejected droplet breaks due to the negative pressure of the bubble and collides downward to the heater surface (hereinafter, this will be referred to as the tail break collision). Such a nozzle can have a size of, for example, h1=22μm and h2=16μm. As a result of the tail break collision, the bubbles on the heater surface are replaced by ink, that is, the gas covering the heater surface is replaced by liquid, so rapid cooling occurs, which leads to the appearance of characteristic points. In addition, in this nozzle, in the normal ejection state, the re-contact of the ink with the heater surface leads to rapid cooling. Therefore, in this type of nozzle, as with the nozzle that is not connected to the atmosphere according to the first or second embodiment, the characteristic points appear later in the ejection failure state in which there is ink than in the normal ejection state. That is, the temperature changes with time in a manner similar to that in the previous embodiment, and an injection failure can be detected by performing the determination process in a similar manner.

[0070] There is a possibility that, depending on the nozzle size, all the ink on the heater surface is ejected without the tail breaking off and colliding with the heater surface after the bubble is connected to the atmosphere. Such a nozzle may have dimensions of, for example, h1=9.5 μm and h2=5.0 μm. Such a nozzle may have dimensions of, for example, h1=9.5 μm and h2=5.0 μm. Figure 9 The temperature change over time is shown in . In this case, Figure 10 The first-order derivatives obtained for these time-dependent temperature changes are shown in . Figure 11 illustrates the changes in the cross-section of the nozzle section for each state. In such a nozzle, since bubble disappearance and tail breakup collision do not occur, there is no ink on the heater surface even at a10 in the normal ejection state. When the ink is refilled, the bubbles on the heater surface are replaced by ink at a20. As a result of refilling, the bubbles on the heater surface are replaced by ink, that is, the gas covering the heater surface is replaced by liquid, resulting in rapid cooling, which leads to the appearance of a characteristic point. On the other hand, in the ejection failure state with ink present, the bubbles disappear at b7, and a characteristic point appears. Therefore, determination can be performed by setting a first detection timing based on the characteristic point caused by the refilling of ink in the normal ejection state and a second detection timing based on the characteristic point in the ejection failure state with ink present. Note that the characteristic point appears earlier in the ejection failure state with ink present than in the normal ejection state. That is, the second detection timing appears later than the first detection timing, which is the opposite of the order of appearance in the previous example. Therefore, the order of steps S7 and S9 used for determination can be reversed.

[0071] Second detection timing

[0072] In this embodiment, the first and second detection timings corresponding to each characteristic point are fixed, based on the fact that characteristic points appear earlier in the presence of an ink ejection failure than in the normal ejection state. In the normal ejection state, characteristic points appear at fixed times when the ink and nozzle conditions are the same. On the other hand, in the presence of an ink ejection failure, characteristic points appear at different times depending on the details of the ejection failure, and even for the same type of ejection failure, characteristic points appear at different times depending on the severity of the ejection failure.

[0073] Examples of types of ejection failures in an ink ejection failure state include external dust ejection failure, wet ejection failure, thickened ink ejection failure, and internal dust ejection failure. The flow resistance of the nozzle portion on the ejection port side and the flow resistance on the ink supply flow path side vary depending on the type of ejection failure, so the characteristic point appears at different times depending on the type of ejection failure. Depending on the type of ejection failure, the higher the flow resistance, the later the characteristic point appears. Therefore, by appropriately setting the detection timing, the type of ejection failure in an ink ejection failure state can be detected.

[0074] In the case of an external dust ejection failure, for example, the extent of the ejection failure may be such that Figure 12 As shown in FIG, the external dust does not completely block the ejection port, but rather partially blocks the ejection port. Figure 5A and Figure 5B The bubble disappearance corresponding to the characteristic point occurs at d6, between the disappearance of the bubble at a5 in the normal ejection state and the disappearance of the bubble at c9 in the external dust ejection failure state shown in FIG. As described above, the characteristic point appears more delayed as the flow resistance increases, depending on the extent of the ejection failure. Therefore, by appropriately setting the detection timing, the extent of the ejection failure in the ink ejection failure state can be detected.

[0075] As can be seen from the above discussion, the essence of the present disclosure lies in presetting a first detection timing based on a characteristic point that occurs in a normal ejection state depending on the nozzle, and setting a second detection timing based on a characteristic point that occurs in a state of ejection failure. In other words, the second detection timing is not necessarily set to determine whether a nozzle has an ejection failure that results in the presence of ink, but rather to determine the type of ejection failure to be detected and the extent of the ejection failure.

[0076] According to the above embodiment, it is possible to determine whether a nozzle has an ejection failure, and to determine the type of ejection failure such as an ejection failure with ink present or an ejection failure without ink. Determination is performed at two timings based on characteristic points corresponding to a normal ejection state and an ejection failure state with ink present, so that the determination process is performed twice, wherein a comparison with a threshold value is performed in each determination process. Since only two determination processes are performed, determination can be performed at high speed. In addition, since only one threshold value is used for comparison in each determination process, the comparison range is allowed to be set large, which makes it possible to achieve high reliability when determining. In addition, depending on the position where the second detection timing is set, the state of the ejection failure and the degree of the ejection failure can be determined more finely.

[0077] If the determination result indicates a non-ink ejection failure, a bubble ejection failure is assumed, and a recovery operation is performed to wipe the nozzle surface while performing suction. A specific example of this recovery operation is vacuum wiping. If an ink ejection failure occurs, a wet ejection failure or external dust ejection failure is assumed, and a recovery operation is performed to wipe the nozzle surface without performing suction. A specific example of this recovery operation is scraper wiping.

[0078] One example of an ink-existing ejection failure is a thickened ink ejection failure, which occurs when the viscosity of the ink increases due to evaporation of water from the ejection port, and ejection is hindered by the increased viscosity. Another example is an internal dust ejection failure, which occurs when foreign matter intrudes into the interior of the nozzle, and ejection is hindered by the foreign matter. When this type of ejection failure occurs, a recovery operation may be required, such as wiping the nozzle surface while performing suction, as is the case with an ink-free ejection failure. However, in nozzles equipped with the ability to recirculate ink using pressure differentials, for example, there is no increase in ink viscosity, and thus no ejection failure caused by this increased viscosity. In most cases, an internal dust ejection failure is caused by foreign matter that intrudes during the manufacturing process, and such foreign matter is generally difficult to remove through a recovery operation. In such cases, it may be sufficient to simply identify, with high precision and speed, whether the ejection failure is an ink-existing or ink-free type. In such cases, optimal recovery operations can be performed based on the determination of whether the ejection failure is an ink-existing or ink-free type, thereby reducing downtime and the amount of waste ink. Therefore, depending on the position where the second detection timing is set, the injection failure state and the degree of the injection failure can be determined more finely as needed.

[0079] According to the present disclosure, by performing two determination processes using comparison with a threshold value in each determination process, it is possible to determine whether ink is ejected normally and to determine the state of an ejection failure. This makes it possible to increase detection speed and enhance detection reliability. Thus, it is possible to determine the state of an ejection failure, and more specifically, to determine whether an ejection failure occurs in a state where ink is present on the heater, as typified by an external dust ejection failure or a wet ejection failure, or in a state where no ink is present on the heater, as typified by a bubble ejection failure. Based on the determined state of the ejection failure, appropriate processing, such as a recovery operation, can be performed.

[0080] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A method for determining a state of liquid ejected from an ejection port in a liquid ejecting device, The liquid injection device includes an injection port configured to inject a liquid, a substrate including an electrothermal conversion element configured to generate heat for ejecting liquid from an ejection port, and a temperature detection unit configured to detect a temperature of the substrate, The method comprises: performing a first comparison process of comparing the temperature of the substrate detected by the temperature detection unit at a first timing with a first threshold value, wherein, at the first timing, it is determined whether the liquid is normally ejected or abnormally ejected from the ejection port based on a result of a first comparison of the detected temperature with respect to a first threshold value; and performing a second comparison process of comparing the temperature of the substrate detected by the temperature detection unit at the second timing with a second threshold value, Wherein, at the second timing, when liquid is abnormally ejected from the ejection port, the type of abnormality is determined to be an ejection failure state with ink or an ejection failure state without ink based on a result of a second comparison of the detected temperature relative to the second threshold value.

2. The determination method according to claim 1, wherein: at a first timing, when the detected temperature is greater than or equal to a first threshold, determining that the liquid is normally ejected from the ejection port, and when the detected temperature is less than the first threshold, determining that the liquid is abnormally ejected from the ejection port; and Among them, at the second timing, when the detected temperature is greater than or equal to the second threshold, the type of abnormality is determined to be an ink ejection failure state, and when the detected temperature is less than the second threshold, the type of abnormality is determined to be an ink ejection failure state.

3. The determination method according to claim 1, wherein: At the second timing, it is determined whether abnormality in ejection of liquid from the ejection port occurs in a state where liquid exists on the electrothermal conversion element, or whether abnormality in ejection of liquid from the ejection port occurs in a state where liquid does not exist on the electrothermal conversion element.

4. The determination method according to claim 1, wherein: The first timing is based on a timing at which the liquid comes into contact with the electrothermal conversion element after the electrothermal conversion element is driven in a normal state of liquid ejection from the ejection port, and The second timing is based on a timing at which the liquid comes into contact with the electrothermal conversion element after the electrothermal conversion element is driven in an abnormal state of liquid ejection from the ejection port.

5. The determination method according to claim 1, wherein: In a state where liquid is ejected normally from the ejection port, when the bubble generated by the electrothermal conversion element is not connected to the atmosphere, or when the bubble is connected to the atmosphere and the tail portion of the liquid droplet ejected from the ejection port collides with the electrothermal conversion element, the first timing is earlier than the second timing. The determination method according to claim 1 , wherein: In a state where liquid is normally ejected from the ejection port, the first timing is later than the second timing when bubbles generated by the electrothermal conversion element communicate with the atmosphere and the tail portion of the liquid droplet ejected from the ejection port does not collide with the electrothermal conversion element.

7. The determination method according to claim 1, wherein: A temperature detection element for detecting the temperature of the substrate is formed just below or just above the electrothermal conversion element, and The temperature detection unit detects the temperature of the substrate based on a result output by the temperature detection element.

8. The determination method according to claim 1, wherein: In the case where it is determined at the first timing that the ejection of the liquid from the ejection port is abnormal, a recovery operation for the ejection port is performed.

9. A liquid ejection device comprising: an injection port configured to inject a liquid; a substrate including an electrothermal conversion element configured to generate heat for ejecting liquid from the ejection port; as well as a temperature detection unit configured to detect a temperature of the substrate, in, The temperature of the substrate detected by the temperature detection unit at a first timing is compared with a first threshold value, wherein at the first timing, whether the liquid is normally ejected or abnormally ejected from the ejection port is determined based on a result of the comparison of the detected temperature with respect to the first threshold value, and The temperature of the substrate detected by the temperature detection unit at the second timing is compared with a second threshold value, wherein, at the second timing, in the case where liquid is abnormally ejected from the ejection port, the type of abnormality is determined to be an ejection failure state with ink present or an ejection failure state without ink based on the result of the comparison of the detected temperature relative to the second threshold value.

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