Liquid ejecting apparatus

Abstract

The present disclosure provides a liquid ejecting apparatus including: an ejecting head; a plurality of removal units for removing foreign matter; and a control unit. The ejection head is configured from a circuit substrate and a channel forming member that are joined, a chamber is provided in the joining portion, a liquid supply port is provided on the circuit substrate, a nozzle for ejecting liquid inside the chamber is provided in the channel forming member, and a plurality of driving elements and a plurality of temperature sensors are provided on the circuit substrate. The control unit selects the removal unit by analyzing a waveform of a signal from the temperature sensor, the protective film is disposed between the driving element and the chamber, and the removal unit removes fouling deposits as foreign matter by applying a voltage to the protective film and thereby elutes the protective film.

Description

Technical Field

[0001] The present invention relates to liquid ejection devices. Background Art

[0002] Liquid ejection devices that eject liquid through a nozzle are known. The liquid ejection device can be applied to an inkjet recording type liquid ejection device (recording device) that ejects ink (liquid) and allows the ink to adhere to a recording medium (e.g., paper). An example of a liquid ejection device is a thermal type inkjet device that ejects ink through a nozzle using thermal energy generated by a heater. For such a liquid ejection device, higher image quality and faster speed are always required.

[0003] Generally, a thermal inkjet recording device generates bubbles in a nozzle by locally heating a liquid such as ink using a micro heater, and ejects ink through the nozzle through these bubbles to allow the ink to adhere to a printing target. In the case of such a thermal liquid ejection device (recording head), a heating resistor element for heating the ink is integrated on a semiconductor substrate together with a logic circuit for driving the heating resistor element. Thus, the above-mentioned requirements for high image quality and faster speed are met, while the heating resistor elements can be arranged at a high density and high-speed driving can be achieved.

[0004] Japanese patent application with publication number 2018-094878 discloses a thermal inkjet recording device. The inkjet recording device includes a plurality of temperature sensors corresponding to a plurality of heating resistor elements in a liquid ejection head. It is proposed that a device for determining the ejection state of a nozzle based on the waveform of a temperature sensor and outputting the result is provided in a recording element substrate so as to determine the normality / fault of the ejection. Summary of the invention

[0005] In the case of detecting an abnormal ink ejection, the malfunctioning nozzle can usually be restored to a normal state by performing maintenance such as cleaning the ejection head. For example, if a poorly soluble substance such as a scale deposit adheres to the heater, the deposit on the heater must be cleaned or removed. For example, if the viscosity of the liquid near the nozzle increases due to drying, such liquid is replaced by normal liquid through suction or circulating flow. Therefore, most of the causes of ejection failures are foreign matter in the liquid chamber including the surface of the heater or foreign matter around the nozzle corresponding to the liquid chamber, and the ejection can be normalized by properly removing the foreign matter. On the other hand, cleaning involves physical contact and chemical changes, and the ejection head may be damaged depending on the foreign matter removal method, and cumulative damage like this may shorten the life of the liquid ejection head.

[0006] However, in Japanese Patent Application Publication No. 2018-094878, only the normality / failure of the ejection is determined, and the cause of the failure is not clearly identified, so the optimal cleaning means may not be selected. In addition, since the slight changes in the droplet velocity and droplet amount within the normal ejection range cannot be identified, the problematic ejection head can be used until it actually fails, and cleaning in this case may cause more damage.

[0007] In view of the above circumstances, an object of the present invention is to provide a liquid ejecting apparatus capable of appropriately selecting a cleaning means for a liquid ejecting head.

[0008] The present invention provides a liquid injection device, comprising:

[0009] a liquid ejection head configured to eject liquid;

[0010] a plurality of removing units configured to remove foreign matter inside the liquid ejecting head; and

[0011] control unit, wherein

[0012] The liquid ejecting head is formed by bonding a circuit substrate and a flow channel forming member,

[0013] a liquid chamber filled with liquid therein provided in a portion where the circuit substrate and the flow path forming member are joined,

[0014] A liquid supply port for supplying liquid to the liquid chamber is disposed on the circuit substrate,

[0015] A nozzle for ejecting liquid inside the liquid chamber is provided in the flow passage forming member,

[0016] A plurality of drive elements configured to be heated by application of voltage and eject liquid and a plurality of temperature sensors are provided on the circuit substrate,

[0017] the control unit is configured to select a removing unit for removing foreign matter from among the plurality of removing units based on an analysis result of a waveform of a signal output from the temperature sensor,

[0018] The protective film is arranged between the driving element and the liquid chamber on the circuit substrate,

[0019] The foreign matter is scaling deposits attached to the protective film, and

[0020] The removal unit is a unit for removing scaling deposits by applying a voltage to the protective membrane and thereby eluting the protective membrane.

[0021] According to the present invention, it is possible to provide a liquid ejecting apparatus capable of appropriately selecting a cleaning means for a liquid ejecting head.

[0022] 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

[0023] Figure 1 is a conceptual perspective view of a recording element substrate for a liquid ejection head;

[0024] Figure 2 is a plan view showing a sensor arrangement according to Embodiment 1;

[0025] Figure 3 is a cross-sectional view showing the structure of a sensor according to Embodiment 1;

[0026] Figure 4 is a block diagram according to Embodiment 1;

[0027] Figure 5 is a flow chart according to Example 1;

[0028] Fig. 6A and Figure 6B is a graph showing a waveform based on temperature change according to Example 1;

[0029] Figure 7 is a graph showing a signal output from the state classification circuit according to Embodiment 1;

[0030] Fig. 8A and Figure 8B is an example of output that associates a classification and classification number with each nozzle;

[0031] Fig. 9 is a schematic diagram of a liquid ejecting device to which the substrate of the present invention can be applied; and

[0032] Fig.10 This is a schematic diagram of a liquid ejecting head to which the substrate of the present invention can be applied. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, unless otherwise stated, the size, material, shape, relative position, etc. of the components described in the embodiments should not be construed as limiting the scope of the present invention. Unless otherwise stated, the materials, shapes, etc. of the components described below are also applicable to the subsequent description. For configurations and steps that are not specifically illustrated or described, known techniques or conventional techniques in the art can be used. Repeated descriptions can be omitted.

[0034] 1. Example 1

[0035] 1.1. Configuration of component substrate

[0036] Figure 1 1 is a partially cut-away conceptual perspective view showing a recording element substrate for a liquid ejection head of Example 1. The substrate (recording element substrate) 1 for the liquid ejection head of Example 1 is formed by a flow channel forming member 120 joined to a circuit substrate 100 for providing heat energy to a liquid. The flow channel forming member 120 is composed of a plurality of nozzles 121 for ejecting liquid, and the plurality of nozzles 121 are arranged at a position facing a driving element 101, which is a heat acting portion for heating the liquid. A liquid chamber 122 connected to the nozzle 121 is formed from a liquid supply port 102 penetrating the circuit substrate 100 via an area on the driving element 101. The circuit substrate 100 also includes an opposing electrode 103, to which a voltage needs to be applied in order to electrochemically elute the protective film.

[0037] Figure 2 1 is a schematic plan view showing the arrangement of the driving element 101 and the sensor 130 corresponding to the nozzle 121 . Figure 2 It is a plan view observed from the top surface of the substrate, and is a perspective view so that the pattern of the underlying layer can be seen through each component. The protective film is formed on the entire surface, so Figure 2 One or more driving elements 101 are provided on the circuit substrate 100, and the driving elements 101 generate heat by the flow of current. Figure 1 As shown, the liquid chamber 122 is provided at a portion where the circuit substrate 100 and the flow channel forming member 120 are joined, and ink is filled into the liquid chamber 122 from the liquid supply port 102 which is a part of the liquid flow channel.

[0038] Heat is generated by supplying current from the power supply section to the driving element 101, and the liquid receives the thermal energy generated by the heat to bubble, thereby ejecting the liquid. Figure 2 A driving element 101 having a rectangular shape in plan view is used in FIG. 1 , but the shape of the driving element 101 is not limited thereto.

[0039] The sensor 130 is disposed on the lower layer of the driving element 101 to detect temperature changes through changes in resistance or capacitance. Figure 2In the embodiment, nine sensors 130 are provided in the area corresponding to one driving element 101, but the position and number of the sensors 130 are not limited thereto. The shape of the driving element 101 is not limited to a rectangle, and is preferably designed to be suitable for the temperature change to be detected. With regard to the position of the sensor 130, it is preferred that at least a portion of the sensor 130 is provided at a position overlapping with the liquid chamber 122 in a plan view, so as to detect the size of the foaming and the defoaming position. However, the present invention is not limited thereto, and the sensor 130 may be provided at a position not overlapping with the liquid chamber 122 according to the design, because the change of environmental information (such as temperature) can still be detected. In order to detect a sharp temperature change, it is preferred that the sensor 130 is provided at a position close to the liquid. For example, if the sensor 130 is provided on the driving element 101, or provided on the surface of the flow channel forming member 120 or inside the flow channel forming member 120, the temperature change can be sensitively detected. The sensor 130 may be provided on the same layer as the driving element 101. However, the sensor 130 may be provided below the driving element 101, as long as the desired detection performance can be obtained.

[0040] It is preferable to match or approach the center of the nozzle 121 in a plan view to the center of the driving element 101. However, their center positions do not need to match as long as the liquid can be ejected by bubbling. In addition, the shape of the nozzle is not limited to a circle.

[0041] Figure 3 1 is a schematic cross-sectional view showing the positions of the driving element 101 and the sensor 130 corresponding to the nozzle 121. As shown here, the liquid chamber 122 formed at the joint of the flow channel forming member 120 and the circuit substrate 100 receives the liquid supplied from the liquid supply port 102 and communicates with the nozzle 121 so as to supply the liquid to the nozzle 121 when the liquid is ejected. The driving element 101 is covered by a lower protective film 141 and an upper protective film 142. Each of these protective films plays a corresponding role, specifically, the lower protective film insulates the driving element 101, and the upper protective film protects the driving element 101 from physical / chemical corrosion caused by liquid, etc. The number of layers of the protective film is not limited to 2 layers, as long as the driving element 101 is sufficiently protected.

[0042] The upper protective film 142 is in contact with the liquid in the liquid chamber 122. When power is supplied to the driving element 101 from the connected wiring 151 and heat is generated thereby, the temperature rises to several hundred degrees Celsius instantaneously and then drops within a few milliseconds. In some cases, a liquid that is foamed by boiling may produce tiny vacuum bubbles called "cavitations" when defoaming, and these bubbles exert a large impact pressure on the protective film when they burst. In order to properly protect the driving element 101 from such a harsh environment, it is preferred that at least a portion of the protective film contains a physically / chemically stable material, and a film containing platinum group elements such as palladium, iridium, and platinum is ideal. In Example 1, the upper protective film 142 is an iridium film with a film thickness of 100 nanometers, and the lower protective film 141 is a silicon nitride film with a film thickness of 100 nanometers.

[0043] The sensor 130 is arranged below the driving element 101. It is preferred to arrange the temperature sensor near the liquid chamber 122 and the liquid supply port 102 so that the temperature change caused by the movement of the liquid can be detected. In Embodiment 1, the sensor 130 is arranged below the driving element 101, but it can be arranged above the driving element 101, or arranged on the surface of the flow channel forming member 120 or inside the flow channel forming member 120. In addition, the same layer as the driving element 101 or the driving element 101 itself can be used as a temperature sensor. The temperature characteristics of each sensor are represented by a temperature coefficient of resistance (TCR), and it is preferred that the change in resistance value is large relative to the unit temperature change. Specifically, the sensor is preferably formed of a material containing at least one element of platinum, iridium, tungsten, zirconium, copper, nickel, zinc, titanium, silicon, aluminum, etc. In this example, an alloy film containing titanium is used.

[0044] 1.2. Examples of foreign matter and removal methods

[0045] "Foreign matter" in this specification generally refers to a substance that is in contact with the liquid and hinders normal foaming. Typical foreign matter is solid scaling deposits that are in contact with the membrane that protects the drive element 101. Other foreign matter is attachments and high-viscosity liquids from liquid that is retained at or attached to the nozzle 121, or retained at a position close to the nozzle 121 on the atmospheric side surface (the surface on the opposite side opposite to the liquid chamber side) of the flow channel forming member 120. Dirt, bubbles, etc. adhering to the liquid supply port 102 are also foreign matter. These foreign matter may affect the flow channel resistance during foaming and the hydrophilic / hydrophobic balance of the flow channel forming member 120, or may cause uneven foaming, which will lead to deterioration of the velocity, quantity, injection angle, etc. of the droplets.

[0046] The foreign matter described in Example 1 is removed by the following method. For example, foreign matter (e.g., attachments from liquid and high-viscosity liquid) on the surface of the atmosphere side of the flow channel forming member 120 can be wiped by a wiper formed of a highly flexible material. In addition, foreign matter around and inside the nozzle can be removed by sucking liquid from the nozzle 121 using air pressure by a suction device such as a straw. Wiping and suction can be performed simultaneously. However, in many cases where foreign matter is discharged in the direction of droplet ejection, such as in the case of wiping and suction, it is necessary to provide an additional mechanical device independent of the liquid ejection head. Therefore, the installation and disassembly of the device will increase downtime. In addition, costs will increase, and the demand for installation space for the device will increase the size of the liquid ejection device.

[0047] In other words, it is desirable to discharge foreign matter in the direction of the flow channel (e.g., the liquid supply port 102). For example, foreign matter around the nozzle 121 can be discharged in the direction of the flow channel by using one liquid supply port 102 as an inlet and using another liquid supply port as an outlet to pressurize and circulate liquid. In addition, by bubbling the liquid by the drive element 101, not only foreign matter around the nozzle 121 but also solid foreign matter contacting the film protecting the drive element 101 can be peeled off by utilizing the foaming pressure or defoaming pressure of the liquid. In this case, the drive element for peeling off foreign matter does not need to be the same as the drive element 101 for ejecting droplets used for printing, and the drive element and the flow channel can be designed separately so that the force for peeling off foreign matter can be appropriately applied.

[0048] If scaling deposits generated by liquid exposed to high temperatures accumulate, it becomes relatively difficult to remove them using any of the above methods. In this case, for example, foreign matter on the upper protective film 142 can be removed by electrochemical elution from the upper protective film 142. Specifically, the upper protective film 142 is formed as a conductive film containing platinum group elements such as palladium, iridium and platinum, and is used as an anode by applying a voltage, thereby eluting the film. The film material is not limited to platinum group elements, as long as the film can be eluted by applying a voltage. The potential to be applied is also not limited to a positive potential. The elution amount can be precisely controlled by controlling the current value. On the other hand, the film thickness that can be eluted is limited relative to the film thickness of the manufactured protective film, so the disadvantage of this method is that this deposit removal operation may shorten the life of the liquid injection head.

[0049] Figure 41 is a block diagram showing an example of a hardware / software configuration when a waveform acquired from the sensor 130 is fed back to the ejection head cleaning device. Modules related to sensor waveform processing are shown here, and some hardware / software modules are omitted. For example, an interface for inputting printing data to the liquid ejection device is omitted. Each function shown in the software configuration is implemented by an information processing device (e.g., a computer, a control circuit) including computing resources (e.g., a processor, a memory) operating in response to program instructions or user input. Figure 4 The following are shown: a recording element unit 501, which is installed in the liquid ejection head and includes the above-mentioned circuit substrate, etc.; a state classification unit 502, which determines the classification of foreign matter, etc.; and a device main unit 503, which is the main unit of the liquid ejection device (recording device). However, this does not necessarily mean a physical distinction. For example, the function of the state classification unit 502 can be performed by an information processing device included in the main unit of the liquid ejection device. In addition, various information processing can be performed by an external information processing device that can communicate with the liquid ejection device. In the present invention, these modules perform acquisition and analysis of the waveform output from the sensor 130, determination of foreign matter, selection of a removal device (removal unit), etc., and these modules as a whole can be regarded as a control unit.

[0050] Typically, according to the instruction of the application unit 451, the image to be printed, the driving conditions of the driving element, and other information are transmitted from the data transmission unit 441 to the data receiving unit 401 of the recording element unit 501 installed in the liquid ejection head. Based on the information, the driving element unit 402 of the recording element unit 501 selects the ejection nozzle and inputs the driving conditions. In addition, at the same time, as the driving element is driven, the temperature sensor unit 403 of the recording element unit 501 acquires the temperature waveform through the sensor 130. The temperature sensor unit 403 can be regarded as the sensor 130 itself, or can be regarded as a collection of the sensor 130 and a control module for processing the output of the sensor 130. The sensor waveform is acquired during printing or between printing steps independently of printing, so the information transmitted from the data transmission unit 441 can be dedicated data for acquiring the sensor waveform. The temperature waveform acquired by the temperature sensor unit 403 is transmitted to the waveform collection unit 411 of the state classification unit 502.

[0051] The waveform information received by the waveform collection unit 411 of the state classification unit 502 is used to extract waveform features in the feature extraction unit 412, and the state is determined and classified in the state determination unit 413. A plurality of nozzles 121 for ejecting liquid are usually provided, and a plurality of temperature sensors corresponding to the nozzles are provided in some cases. Therefore, in order to increase the printing speed, a plurality of waveforms must be processed at high speed. This means that it is preferred that at least a portion of the circuit constituting the state classification unit is configured to process a large number of sensor waveforms at high speed. It is more preferred that the circuit is arranged in the liquid ejection head. In addition, it is further preferred that the circuit is arranged on the same element substrate as the recording element unit installed in the liquid ejection head. It is also preferred that the information output from the state classification unit 502 is a digital signal that can be output at high speed. However, depending on the amount and frequency of the sensor waveform to be acquired, the state classification unit 502 can be integrated in the device main unit, and its installation position is not limited to the above description. Information about the results of classification and determination is output from the determination output unit 414 and transmitted to the determination recording unit 421 of the device main unit 503.

[0052] All judgment records of the liquid ejection heads used by the device are stored in the judgment record unit 421. In order to retain past information even if the recording head is replaced, the judgment record unit 421 is preferably included in the main unit of the liquid ejection device. The inference unit 422 uses the judgment records of each nozzle of the liquid ejection head, information about other liquid ejection devices, and the latest inference model based on the information as judgment materials to determine the optimal processing flow. Then, the selection of the cleaning method and the necessity of the selection are fed back to the application unit 451 from the means selection unit 423, and cleaning is performed. In this example, three types of cleaning means A, B and C (reference numerals 431 to 433) are provided, but this is not intended to limit the number of cleaning means of the present invention. Even if the same cleaning method is selected, the target range and intensity can be changed. The inference unit 422 also infers the optimal cleaning conditions. Thus, effective cleaning can be performed in the shortest downtime.

[0053] Figure 5 1 is a flowchart showing an example of a sensor waveform processing flow of a liquid ejecting device during printing. In step S601, a voltage is applied to a driving element 101 at a predetermined position based on image information, and ink droplets are ejected, whereby an image is recorded on a recording medium. In step S602, the sensor 130 that detects a temperature change caused by the image recording (printing) outputs a sensor waveform. The output and determination processing of the sensor waveform is not always performed. Considering the information processing cost, it is preferable to perform the processing when cleaning for removing foreign matter can be effectively performed. Figure 5The flow in is the case where the sensor waveform is output, and the case where the sensor waveform is not output is omitted. The determination process in step S603 is performed based on the output waveform, and the necessity of cleaning the liquid ejection head is determined according to the determination result. The appropriate timing for outputting the sensor waveform is usually when the device is started, when a predetermined number of images are recorded, at predetermined intervals, when device maintenance is performed, etc. However, the sensor waveform may always be output each time an image is recorded.

[0054] When it is determined in step S604 that cleaning is required, in many cases, printing is stopped in step S605. However, depending on the type of foreign matter and the specific circumstances of cleaning, some cleaning can be performed during printing. In such a case, it is not necessary to stop printing. For example, if there is a small amount of dirt in the liquid chamber, foaming is performed only for the nozzle 121 corresponding to the position of the dirt, thereby removing the dirt while printing is performed. In addition, if ink is slightly attached around the nozzle 121, such an attachment problem can be solved while printing is performed by applying a relatively strong pulse to the drive element 101 used as a heat action unit.

[0055] Since the sensor waveform is used to analyze how the foaming, ejection, and defoaming deviate from the normal state, and the position and state of the foreign matter causing the deviation are estimated, an effective cleaning means is selected in step S606. For example, cleaning means A to C can be selected, and if one of A to C is determined to be effective, the selected cleaning process is executed, and the process ends.

[0056] If it is determined that none of the provided cleaning means are effective (determined as "none" in S606), unnecessary cleaning is not performed, but the necessity of replacing the injection head is determined in step S607. The selection of cleaning means refers to selecting an effective means from multiple feasible means, and a combination of multiple means can be selected, or the same means can be performed multiple times. In the case where it is determined in step S604 that cleaning is not required, the processing also proceeds to step S607, and the necessity of replacing the injection head is determined. The situation in which the injection head needs to be replaced is, for example, the situation in which there are nozzles that cannot obtain normal injection characteristics (for example, injection speed, injection amount, injection angle) even after various cleanings are performed, and there are no nozzles with normal characteristics that can compensate for the faulty nozzles. The processing for measuring the injection characteristics can be performed after the cleaning process in order to determine the necessity of replacing the injection head.

[0057] If the jet head needs to be replaced, a replacement sequence is initiated. The replacement can be performed automatically, or can be performed manually after notifying the user that the jet head needs to be replaced. If the jet head does not need to be replaced, it is determined in step S608 whether the printing job has ended. If the printing job has not ended, printing is restarted.

[0058] In the configuration of this example, three types of cleaning means, A, B, and C, are provided, but this is not intended to limit the number of cleaning means of the present invention. The output of the sensor waveform corresponding to a certain nozzle can be performed in parallel with the droplet ejection of another nozzle, and the determination process in S603 can be determined based on multiple outputs of the sensor waveform as a whole. Through the above-mentioned processing, the optimal and effective removal means for foreign matter generated in the liquid ejection head can be selected based on feedback, and the downtime and damage to the ejection head can be minimized.

[0059] 1.3. Analysis of sensor waveforms

[0060] Fig. 6A A portion of the analog waveform of the signal (voltage) acquired by the temperature sensor (sensor 130). The horizontal axis represents time [s], and the vertical axis represents the sensor output voltage [V]. The output is obtained by supplying a constant current to the sensor 130 and reading the change in voltage value when the temperature changes. Fig. 6A In the case of an alloy film containing titanium, TCR has a negative value, so if the temperature rises, the resistance value decreases. In other words, the voltage value decreases as the temperature rises. This means Fig. 6A The minimum peak (1) of the middle waveform is considered to be the point with the highest temperature. Inside the liquid chamber 122, movement, phase change, etc. occur in a short time due to the thermal energy from the driving element 101. The liquid is boiled by the thermal energy and high-pressure bubbles are generated. At this time, the fluid in contact with the upper protective film 142 changes from liquid to gas. After the bubbling starts, the volume of the bubble increases, but the pressure in the bubble drops instantly and becomes negative pressure, so the volume of the bubble increases by inertial force. After the volume of the bubble reaches the maximum value, the bubble begins to shrink, and the liquid attracted by the negative pressure reaches the protective film on the driving element 101. During this period, depending on the size of the liquid chamber 122 and the size of the bubble, the liquid film around the bubble may rupture, and the room temperature atmosphere may flow into the bubble.

[0061] The waveform of the sensor 130 includes complex information such as the phase state and temperature change of the fluid inside the liquid chamber 122. When the fluid inside the liquid chamber moves and causes a phase change, a temperature change will always occur through the contact between substances with different thermal conductivities. If it is determined based on the sensor waveform whether this temperature change has occurred, the movement of the fluid can be detected. It is also important to analyze the time of the temperature change. For example, analyzing the time from the moment of foaming to the moment of defoaming makes it easier to estimate the movement of the fluid, and analyzing the timing and duration of the change point in addition to the position of the sensor and the temperature change amount can more accurately estimate the movement of the fluid. This means that the generation and state of foreign matter can be accurately determined. On the other hand, in the case of a sharp change, such as when the fluid in contact with the protective film changes from liquid to gas, as long as the time-based temperature curve is roughly known, the timing of the change point can be measured by the temperature change amount. Therefore, it is not always necessary to include a circuit that directly analyzes the timing.

[0062] An effective means for detecting the change point as a signal on a circuit is to convert the change point of temperature into a peak value. Figure 6B is a waveform processed so that the change point to be acquired becomes a peak value. The horizontal axis represents time [s], and the vertical axis represents voltage change [dV / dt]. At the moment of bubbling, the fluid contacting the protective film changes from liquid to gas, so the heat dissipation from the circuit substrate 100 to the liquid is weakened. Fig. 6A There is a moment when the voltage drop from the waveform starting point to the negative extreme value accelerates, and this change point is caused by bubbling. Figure 6B is to use a bandpass filter from Fig. 6A The waveform generated by the waveform in order to convert the change point into a peak value. Figure 6B In this example, a method of converting a change point into a peak value using a bandpass filter is described, but a method such as differential processing or frequency analysis may be used as long as the change point can be emphasized and output.

[0063] An example of this method for converting the time information of the waveform into the ejection velocity information of the droplet will be described. Figure 6B As shown in the waveform conversion in, the bubbling moment (first moment) indicated by (2) can be converted into the moment of the minimum value, and the moment (second moment) when the liquid contacts the protective film on the driving element again indicated by (3) can be converted into the moment of the maximum value accordingly. Then, by outputting the moments indicating the maximum and minimum values ​​or the interval between these two moments from the circuit, the interval from the bubbling moment to the moment of contacting the liquid again can be calculated. Figure 6BIn , the interval time is expressed as the time from (1) to (2). This time is related to the droplet ejection velocity, which depends on the design of the nozzle and the liquid chamber, and can be obtained Figure 7 The characteristics shown. Figure 7 In FIG. 1 , the abscissa represents the speed [m / s], and the ordinate represents the interval [μs].

[0064] Therefore, as long as you get Figure 7 By comparing the inherent characteristics of the nozzle / flow channel design shown, and the interval obtained from the sensor waveform, the velocity of the droplet can be obtained based on the time information of the waveform. For example, a 4.0μs interval can be converted to a jet velocity of 6.8m / s. In some cases, due to temporary changes, the characteristics may have shifted, so the jet velocity range can be determined in the conversion that takes into account the characteristic shift. Figure 7 In the case of , the original conversion coefficient is represented by a solid line, and the conversion coefficient after a predetermined time is represented by a dotted line. Therefore, when the interval time is 4.0μs, the estimated range of the injection speed is 6.8 to 7.1m / s. In this example, the timing of bubble generation and the timing of contacting the liquid again are focused on, but other timings of the change points affected by the injection speed include the timing of releasing the bubble pressure when connected to the atmosphere, the timing of refilling the liquid along the flow channel direction, etc. Focusing on these timings, it can also be converted into the injection speed or injection amount.

[0065] Choice of cleaning method

[0066] An example of a method for selecting a cleaning means based on the ejection speed as a characteristic of a droplet will be described. Figure 7 As shown, by obtaining certain information about the ejection velocity of the droplets and detecting the time change, the cleaning means can be effectively selected. For example, if a slight decrease in velocity is temporarily detected, it is likely that insoluble substances (such as scaling deposits) are attached to the protective membrane. In such a case, the ejection velocity can be effectively restored by applying voltage to the protective membrane with the scaling deposits attached and chemically washing away the scaling deposits.

[0067] In the case where a significant drop and recovery of the ejection speed occurs intermittently and repeatedly, the proper filling and circulation of the liquid is likely to be interrupted due to a reason such as clogging of a foreign object in the flow channel. In such a case, the ejection speed can be effectively restored by peeling off the foreign object along the flow channel direction using a liquid feeding pump, a filter, etc., or by sucking the foreign object in the liquid chamber out of the ejection head using a vacuum pump, etc.

[0068] By detecting various change points and their time changes in this way, the position and state of the foreign matter can be appropriately determined. The conversion process described in Example 1 is only an example, and other methods can be used as long as the state of the foreign matter can be appropriately determined. For example, by using Fig. 6A Part or all of the analog output waveform in is used as input data for deep learning to determine the position and state of the foreign matter, and in this case, a dedicated processing circuit is integrated in the feature extraction unit 412, the state determination unit 413, the inference unit 422, etc.

[0069] Will refer to Fig. 8A and Figure 8B The described example outputs a classification example based on the number output from the state classification unit 502 and the classification number associated with each nozzle of each column. Here, the injection amount accuracy and the injection angle can be calculated by applying the obtained waveform to a learning model, and the learning model represents the relationship between the pre-created waveform, the injection amount accuracy and the injection angle. The injection speed and the injection amount are obtained as numerical values ​​(scalars), and the index combining the injection speed and the injection amount can be referred to as "injection amount accuracy". Here, the accuracy of the injection speed and the injection amount is divided into 4 levels in descending order: "S", "A", "B" and "ND (Abnormal)". In other words, "S" is a case where there is no problem with both the injection speed and the injection amount. "A" is a case where one of them has changed, and "B" is a case where both of them have changed. In addition, the size of the injection angle (ejection angle) is divided into 3 levels: small, medium, and large. Then, as Fig. 8A As shown, a classification number is assigned to each position of the matrix. When the accuracy is "ND", a classification number (9) is assigned regardless of the injection angle.

[0070] Based on these classification numbers, some or all of the nozzles are classified using waveforms, and the results are output as digital signals. Figure 8B : is a table showing a classification example. It is assumed that each of the plurality of nozzle columns (column 1, column 2) includes 500 nozzles 121 (1 to 500). In the table, one of the above-mentioned classification numbers 0 to 9 is recorded for each nozzle 121. The device main unit 503 that records the classification performs selection of an appropriate foreign matter removal means and cleaning of the recording element unit 501 based on the distribution of the classification numbers and the information on the time change.

[0071] In Embodiment 1, the classification number is set based on the droplet ejection state, but the present invention is not limited to this. For example, the information output from the state classification unit 502 may directly indicate the type or condition of the removal method. In addition, information indicating the state and position of the foreign matter may be output, and in this case, the optimal removal method is also considered by the inference unit 422.

[0072] Device Configuration

[0073] Fig. 9 and Fig.10 1 is a schematic diagram showing the configuration of a main part of an inkjet liquid ejecting apparatus (recording apparatus) to which the present invention can be applied. Fig. 9 is an overall view of the liquid ejecting device 150 showing the overall configuration. Fig.10 1 is a perspective view showing a liquid ejection head 110 which is a constituent element of a liquid ejection device. Here, the liquid ejection head 110 records an image on a recording medium 125 by ejecting ink droplets from ejection ports corresponding to nozzles. The liquid ejection head 110 includes a recording element substrate 135 including a plurality of nozzle arrays on which a plurality of nozzles are arranged.

[0074] By applying the present invention to the liquid ejection head 110 and the liquid ejection device 150, it is possible to select an optimum cleaning method and thereby reduce the occurrence of ejection failures. As a result, it is possible to perform good image recording with image failure suppressed.

[0075] As described above, according to the present invention, a liquid ejection device including a liquid ejection head (recording head) can be provided, which can effectively maintain high printing quality. Therefore, downtime due to cleaning and replacement can be reduced, and running costs can be minimized by maximizing the life of the liquid ejection head.

[0076] 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 liquid injection device, comprising: a liquid ejection head configured to eject liquid; a plurality of removing units configured to remove foreign matter inside the liquid ejecting head; as well as control unit, wherein The liquid ejecting head is formed by bonding a circuit substrate and a flow channel forming member, a liquid chamber filled with liquid therein provided in a portion where the circuit substrate and the flow path forming member are joined, A liquid supply port for supplying liquid to the liquid chamber is disposed on the circuit substrate, A nozzle for ejecting liquid inside the liquid chamber is provided in the flow passage forming member, A plurality of drive elements configured to be heated by application of voltage and eject liquid and a plurality of temperature sensors are provided on the circuit substrate, the control unit is configured to select a removing unit for removing foreign matter from among the plurality of removing units based on an analysis result of a waveform of a signal output from the temperature sensor, A protective film is provided on the circuit substrate between the driving element and the liquid chamber, The foreign matter is scaling deposits attached to the protective film, and The removal unit is a unit for removing the scaling deposits by applying a voltage to the protective film and thereby eluting the protective film.

2. The liquid ejecting device according to claim 1, wherein The control unit analyzes the waveform and thereby determines the type of the foreign matter, and selects the removing unit according to the type of the foreign matter.

3. The liquid ejecting device according to claim 1, wherein The control unit determines a position of the foreign matter based on a waveform of each of the plurality of temperature sensors, and selects the removing unit according to the position of the foreign matter.

4. The liquid ejecting device according to claim 1, wherein At least a portion of the plurality of temperature sensors is disposed at a position overlapping the liquid chamber in a plan view of the liquid ejection head.

5. The liquid ejecting device according to claim 1, wherein The protective film is a conductive film containing a platinum group element.

6. The liquid ejecting device according to claim 1, wherein The foreign matter is an attachment originating from the liquid or a high-viscosity liquid.

7. The liquid ejecting device according to claim 6, wherein The foreign matter is a substance attached to a surface of the flow path forming member on the opposite side from the liquid chamber, and The removing unit is a wiper configured to wipe the surface of the opposite side.

8. The liquid ejecting device according to claim 6, wherein The removing unit is a unit for discharging the foreign matter by pressurizing and circulating the liquid in the liquid chamber.

9. The liquid ejecting device according to claim 6, wherein The removal unit is a unit for discharging the foreign matter by applying a voltage to the driving element and thereby bubbling the liquid inside the liquid chamber.

10. The liquid ejecting device according to claim 6, wherein The foreign matter is matter attached to or retained inside the nozzle.

11. The liquid ejecting device according to claim 10, wherein The removing unit is a unit for sucking the foreign matter from a surface of the flow-path forming member on the opposite side opposite to the liquid chamber.

12. The liquid ejecting device according to claim 1, wherein The control unit determines the state of the foreign matter by analyzing a phase state and a temperature change of the liquid inside the liquid chamber based on a waveform of a signal output from the temperature sensor.

13. The liquid ejecting device according to claim 12, wherein The protective film is formed on the circuit substrate between the driving element and the liquid chamber, and The control unit calculates the first moment when the liquid bubbles due to the heating of the driving element and the second moment when the liquid contacts the protective film again based on the waveform of the signal, calculates the injection speed of the liquid based on the interval from the first moment to the second moment, and thereby determines the state of the foreign matter.

14. The liquid ejecting device according to claim 13, wherein The control unit determines that the foreign matter is scaling deposits attached to the protection film when the injection speed is temporarily reduced.

15. The liquid ejecting device according to claim 13, wherein The control unit determines that the foreign matter blocks the flow passage in a case where the ejection speed is repeatedly decreased and restored.

16. The liquid ejecting device according to any one of claims 1 to 15, wherein The temperature sensor is formed of a material including at least one element of platinum, iridium, tungsten, zirconium, copper, nickel, zinc, titanium, silicon, and aluminum.

17. The liquid ejecting device according to any one of claims 1 to 15, wherein The control unit determines necessity of replacing the liquid ejection head based on a waveform of a signal output from the temperature sensor.

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