Liquid discharge device and method for controlling the same

Abstract

To provide a liquid discharge device which removes scorch under an appropriate potential control condition even if a composition of ink changes.SOLUTION: A liquid discharge device has: a liquid discharge head having a discharge port for discharging a liquid, a liquid chamber communicating with the discharge port, a heating resistor which is provided in the liquid chamber and is configured to be able to discharge the liquid from the discharge port by generating heat, and a first electrode and a second electrode provided in the liquid chamber; and a control part for controlling potential application to the first electrode and the second electrode on the basis of a potential control condition according to the type of the liquid. When the liquid chamber is viewed from a direction in which the discharge port is provided, the first electrode is provided so as to overlap the position where the heating resistor is provided, and the second electrode is provided so as not to overlap the position where the first electrode is provided. The control part changes the potential control condition according to the change in the composition of the liquid.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a liquid ejection apparatus and a control method thereof. [Background technology]

[0002] In liquid ejection heads used in inkjet recording devices and the like, a method is often adopted in which the liquid inside a liquid chamber is heated by passing electricity through a heating resistor, and droplets are ejected from the ejection port by the bubbling energy generated when film boiling occurs in the liquid.

[0003] In such liquid ejection heads, the area above the heating resistor may be subjected to physical effects such as impacts caused by cavitation that occurs when the liquid foams, contracts, and disappears. In addition, when the liquid is ejected, the heating resistor is at a high temperature, so that the components of the liquid may thermally decompose and adhere to the area above the heating resistor, causing chemical effects such as adhesion and deposition. In order to protect the heating resistor from these physical and chemical effects on the heating resistor, a protective layer made of a metal material or the like that covers the heating resistor is disposed in the liquid ejection head.

[0004] When the liquid is heated to a high temperature, the coloring materials and additives contained in the liquid may be decomposed at the molecular level and may turn into poorly soluble substances. Such substances may then be physically adsorbed onto the heat application part, which is the part of the protective layer on the heating resistor that comes into contact with the liquid. This phenomenon is called "burning." When poorly soluble organic or inorganic substances are adsorbed onto the heat application part of the protective layer in this way, the heat conduction from the heat application part to the liquid becomes uneven, and the foaming becomes unstable.

[0005] As a measure against such kogation, Patent Document 1 discloses a method of removing kogation by dissolving the surface of a coating portion formed of iridium or ruthenium into a liquid through an electrochemical reaction. Specifically, the method discloses a kogation removal cleaning method in which a voltage is applied to the upper protective layer after starting the ink suction operation in order to dissolve the upper protective layer through an electrochemical reaction. This allows the bubbles generated by the electrochemical reaction to be discharged by ink suction without growing large, making it possible to remove kogation uniformly and reliably.

[0006] There are also some that utilize the fact that solid solutions in the ink are dispersed as colloids, as in Patent Document 2. This is a technology called potential control, which utilizes the fact that the colloid surface is electrically charged, and by applying a voltage to the upper protective layer, the presence rate of colloid particles directly above the electrode is reduced, thereby reducing the solid solutions that cause kogation. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2008-105364 A [Patent Document 2] JP 2009-051146 A Summary of the Invention [Problem to be solved by the invention]

[0008] On the other hand, the amount and polarity of the potential applied to the upper protective layer in conventional kogation removal and potential control varies depending on the type of ink. If an excessive potential is applied, not only the kogation but also the protective film underneath is excessively scraped off, shortening the life of the ejection head. In addition, depending on the polarity of the applied potential, the presence rate of colloidal particles on the electrode may increase, causing the kogation to change. Therefore, it is necessary to select potential control conditions that match the ink being used. Therefore, it is conceivable to record the kogation removal and potential control conditions for each ink in the storage device of the main body of the device, and select the conditions from there.

[0009] However, the composition of the ink changes slightly depending on the time between production and installation in the device and the environment in which the ink is placed. For example, if a long period of time passes between the production of the ink and its use, the solvent in the ink may volatilize and the composition may change. According to the applicant's investigation, the above-mentioned potential control has a significant effect on the ink ejection speed, so that if the composition changes, the ejection speed changes and the print quality is significantly affected. As a result, if the device is used under the conditions specified in the device as is, the print quality may change and the device may not function as intended.

[0010] The present invention has been made in view of the above problems, and has an object to perform kogation removal under appropriate potential control conditions in a liquid ejection device even when there is a change in the composition of the ink. [Means for solving the problem]

[0011] The present invention employs the following configuration. a liquid ejection head having an ejection port for ejecting a liquid, a liquid chamber communicating with the ejection port, a heating resistor provided within the liquid chamber and configured to be able to eject the liquid from the ejection port by generating heat, and a first electrode and a second electrode provided within the liquid chamber; Based on a potential control condition according to the type of the liquid, A control unit for controlling application of a potential; A liquid ejection device having when the liquid chamber is viewed from a direction in which the ejection port is provided, the first electrode is provided so as to overlap a position where the heating resistor is provided, and the second electrode is provided so as not to overlap a position where the first electrode is provided, The control unit changes the potential control condition in response to a change in the composition of the liquid. The liquid ejection device is characterized in that: The present invention also employs the following configuration. A control method for a liquid ejection device comprising: an ejection port for ejecting liquid, a liquid chamber communicating with the ejection port, a liquid ejection head having a heating resistor provided within the liquid chamber and configured to be able to eject the liquid from the ejection port by generating heat, and a first electrode and a second electrode provided within the liquid chamber; and a control unit, wherein, when the liquid chamber is viewed from a direction in which the ejection port is provided, the first electrode is provided so as to overlap a position where the heating resistor is provided, and the second electrode is provided so as not to overlap a position where the first electrode is provided; the control unit controls application of a potential to the first electrode and the second electrode based on a potential control condition according to a type of the liquid; The control unit changes the potential control condition in response to a change in the composition of the liquid. The liquid ejection device control method is characterized in that: Effect of the Invention

[0012] According to the present invention, in a liquid ejection device, even if there is a change in the composition of the ink, it is possible to perform kogation removal under appropriate potential control conditions. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a recording device. [Diagram 2] A perspective view of a liquid ejection head [Diagram 3] FIG. 13 is a perspective view of the liquid ejection head from another direction. [Figure 4] 1A and 1B are plan views of a recording element substrate. [Diagram 5] 1A and 1B are plan views of a recording element substrate. [Figure 6] FIG. 3 is a perspective view showing a cross section of a recording element substrate; [Figure 7] 1A and 1B are diagrams showing a recording element substrate. [Figure 8]A block diagram showing an example of the configuration of a controller for a recording device. [Figure 9] Flowchart showing the process of the first embodiment [Figure 10] Flowchart showing the process of the second embodiment [Figure 11] Flowchart showing the process of the third embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiments may be changed as appropriate depending on the configuration of the device to which the invention is applied and various conditions, and the scope of the present invention is not limited to the following embodiments.

[0015] [Embodiment 1] This embodiment is an inkjet recording apparatus in which liquid such as ink is circulated between a tank and a liquid ejection device. The present invention can also be understood as an inkjet recording apparatus (also called a "liquid recording apparatus" or a "recording device"), a liquid ejection device, or a control method thereof.

[0016] (Inkjet recording device) The schematic configuration of an inkjet recording apparatus 1 of this embodiment is shown in the block diagram of Fig. 1. The recording apparatus 1 generally includes a print mechanism section 3, a control section 4 that controls the entire apparatus, a transport mechanism section 30 that transports the recording material, an ink supply section 5 that supplies ink, a power supply section 6 that supplies power to the apparatus, an ink physical property measuring device 7 that measures the physical properties of the ink, and an ink ejection characteristic measuring device 8 that measures the ejection characteristics of the ink.

[0017] Next, the printing mechanism 3 will be described. The printing mechanism 3 includes a liquid ejection head 2 that ejects ink toward a recording material 9. In the figure, only one liquid ejection head 2 is shown, but there may be multiple liquid ejection heads. The recording material 9 is made of a material such as paper, plastic, or cloth, and is formed into a sheet shape. It is transported under the liquid ejection head by a transport mechanism 30.

[0018] The ink supply unit 5 is equipped with a memory element and has multiple removable ink supply tanks 10. Ink is supplied by a pressure-feeding device such as a pump from the ink supply unit 5 through an ink property measuring device 7 to a liquid ejection head 2 in the print mechanism unit 3. Multiple recording element substrates 11 are arranged inside this liquid ejection head 2. When ink is ejected from the recording element substrate 11, printing is performed on the recording material 9 directly below.

[0019] The ink property measuring device 7 is disposed in the ink flow path from the ink supply unit 5 to the print mechanism unit 3, and is a device that measures the ink properties and transmits an output signal to the control unit 4. The ink property measuring device 7 is typically a conductivity meter that measures the ink conductivity by arranging electrodes in the ink flow path. However, the ink property is not limited to conductivity, and may be, for example, resistivity measured by a resistivity meter, viscosity measured by a viscometer, flow velocity measured by a flow velocity meter, etc.

[0020] The ink ejection characteristic measuring device 8 is a device that measures the characteristics when the print mechanism unit 3 ejects ink and sends an output signal to the control unit 4. The ink ejection characteristic measuring device 8 is typically a speedometer consisting of a camera and an image analysis unit for measuring the ink ejection speed. However, the ink ejection characteristic is not limited to the speed, and may be, for example, the interval between droplets or the straightness of the droplets. These ejection characteristics other than the speed can also be measured by a device having a camera and an image analysis unit.

[0021] (Liquid ejection head) The configuration of the liquid ejection head 2 according to the embodiment will be described. 1 is a perspective view of the liquid ejection head 2 in a different direction according to the embodiment. The liquid ejection head 2 is a line-type liquid ejection head in which 16 recording element substrates 11 are arranged in a straight line (arranged in-line). One recording element substrate 11 is capable of ejecting ink of one color. When multiple liquid ejection heads 2 are provided for printing in multiple colors, the liquid ejection heads 2 that eject ink of each color have the same configuration.

[0022] As shown in FIG. 2 and FIG. 3, the liquid ejection head 2 includes a recording element substrate 11, a flexible wiring substrate 40, and an electric wiring substrate 43 provided with a signal input terminal 41 and a power supply terminal 42. The signal input terminal 41 and the power supply terminal 42 are electrically connected to the control unit 4 of the recording device 1. The recording element substrate 11 is supplied with an ejection drive signal and power required for ejection via the signal input terminal 41 and the power supply terminal 42. By consolidating the wiring using the electric circuit of the electric wiring substrate 43, the number of the signal input terminals 41 and the power supply terminals 42 can be reduced compared to the number of the recording element substrates 11. In addition, by using the electric wiring substrate 43, the number of electrical connections that need to be removed when assembling the liquid ejection head 2 to the recording device 1 or when replacing the liquid ejection head can be reduced. The connection portions 44 provided at both ends of the liquid ejection head 2 are connected to the ink supply portion 5 of the recording device 1. Ink is supplied to the liquid ejection head 2 from the supply system of the recording device 1 via one connection part 44, and the ink that has passed through the liquid ejection head 2 is collected into the supply system of the recording device 1 via the other connection part 44. In this way, the liquid ejection head 2 is configured so that ink can circulate via the path of the recording device 1 and the path of the liquid ejection head 2.

[0023] (Recording element substrate) Fig. 4(a) is a schematic diagram of the surface of the recording element substrate 11 serving as a substrate for a liquid ejection head on which the ejection ports 13 are arranged. Fig. 4(b) is a schematic diagram showing the reverse side of the surface of Fig. 4(a). Fig. 5(a) is a schematic diagram showing the surface of the recording element substrate 11 when the cover member 22 provided on the reverse side of the recording element substrate 11 in Fig. 4(b) is removed. Fig. 5(b) is an enlarged view of the portion surrounded by the dashed line XD in Fig. 4(a). Fig. 6 is a perspective view showing a cross section of the recording element substrate 11.

[0024] The recording element substrate 11 includes a substrate 12 configured by laminating multiple layers on a silicon base, an ejection port forming member 14 formed from a photosensitive resin, and a cover member 22 bonded to the rear surface of the substrate 12. A plurality of ejection port arrays 15 are formed in the ejection port forming member 14 of the recording element substrate 11. Note that hereinafter, the direction in which the ejection port array 15, in which a plurality of ejection ports 13 are arranged, extends is referred to as the "ejection port array direction."

[0025] The substrate 12 has recording elements 16 formed thereon, and grooves that form a supply path 19 and a recovery path 20 extending along the ejection port array direction are formed on the back surface side. The recording elements 16 are elements that generate energy used to eject liquid. As shown in FIG. 5(a), the back surface of the recording element substrate 11 has supply paths 19 and recovery paths 20 extending along the ejection port array direction, and in the region corresponding to each ejection port array 15, the supply path 19 is provided on one side and the recovery path 20 is provided on the other side. The supply paths 19 and the recovery paths 20 are provided alternately in a direction that intersects with the ejection port array direction.

[0026] Also, as shown in FIG. 5(b), a plurality of supply ports 18a connected to a supply path 19 are arranged along the ejection port row direction to form a supply port row, and a plurality of recovery ports 18b connected to a recovery path 20 form a recovery port row.

[0027] As shown in Fig. 4(b) and Fig. 6, a sheet-like lid member 22 is laminated on the back surface of the substrate 12 opposite to the surface on which the ejection port forming member 14 is provided. The lid member 22 is provided with a plurality of openings 23 communicating with the supply path 19 and the recovery path 20. Ink is supplied from the ink supply unit 5 through the liquid ejection head 2 from each opening 23 of the lid member 22. The lid member 22 is a recording It functions as a lid that forms part of the wall of the supply path 19 and the recovery path 20 formed in the substrate 12 of the element substrate 11 .

[0028] As shown in FIG. 5(b), a recording element 16 is disposed at a position corresponding to each ejection port 13 as a heating resistor for foaming the ink with thermal energy. A pressure chamber 25 having the recording element 16 therein is partitioned by a partition wall 24 shown in FIG. 5(b) and FIG. 6. The recording element 16 is electrically connected to a terminal 41 in FIG. 3 by an electric wiring provided on the recording element substrate 11. The recording element 16 generates heat based on a pulse signal input from the control unit 4 of the recording device 1 via an electric wiring substrate 43 and a flexible wiring substrate 40, and boils the ink. The ink is ejected from the ejection port 13 by the force of foaming caused by this boiling. The recording element 16 is covered with a plurality of layers provided on the substrate 12 as described later, but in FIG. 5(b), the recording element 16 is illustrated diagrammatically on the surface of the substrate 12.

[0029] FIG. 7(a) is a plan view showing a schematic enlargement of the vicinity of the heat application part on the surface of the recording element substrate 11 on which the heat application part is provided. FIG. 7(a) shows the pressure chamber 25 (liquid chamber) viewed from the direction in which the ejection port 13 is provided with the ejection port forming member 14 removed. FIG. 7(b) is a schematic cross-sectional view taken along line AA' in FIG. 7(a), and in FIG. 7(b), an arrow M indicates the direction in which the pressure chamber 25 is viewed from the direction in which the ejection port 13 is provided. Note that the second adhesive layer 122 shown in FIG. 7(b) is omitted in FIG. 7(a). Note that the heat application part is a part that comes into contact with the ink to foam the ink and applies heat to the ink.

[0030] The substrate 12 included in the recording element substrate 11 is formed by stacking a plurality of layers on a silicon substrate. In this embodiment, a heat storage layer formed of a thermal oxide film, a SiO film, a SiN film, or the like is disposed on the silicon substrate. In addition, a heating resistor 126 as the recording element 16 is disposed on the heat storage layer. An electrode wiring layer as wiring formed of a metal material such as Al, Al-Si, or Al-Cu is connected to the heating resistor 126 via a plug 128 formed of tungsten or the like. The plug 128 is disposed in a pair with the heating resistor 126, and a portion of the heating resistor 126 through which a current flows via the plug 128 functions as a heat generating portion for ejecting ink. The plug 128 and the electrode wiring layer are formed inside the heat storage layer. An insulating protective layer 127 is disposed on the heating resistor 126 so as to cover the heating resistor 126. The insulating protective layer 127 is formed of, for example, a SiO film, a SiN film, or the like.

[0031] A first protective layer 125 and a second protective layer 124 are disposed on the insulating protective layer 127. These protective layers serve to protect the surface of the heating resistor 126 from chemical and physical shocks that accompany the heat generation of the heating resistor 126. For example, the first protective layer 125 is made of tantalum (Ta), and the second protective layer 124 is made of iridium (Ir). In addition, the protective layers made of these materials are conductive.

[0032] In addition, a first adhesive layer 123 and a second adhesive layer 122 are disposed on the second protective layer 124. The first adhesive layer 123 has a role of improving the adhesiveness between the second protective layer 124 and other layers, and is formed of, for example, tantalum (Ta). The second adhesive layer 122 has a role of protecting the other layers from ink and a role of improving the adhesiveness between the other layers and the ejection port forming member 14, and is formed of, for example, SiC or SiCN.

[0033] The ejection port forming member 14 is bonded to the surface of the substrate 12 on the side of the second adhesive layer 122, and forms an ink flow path including a pressure chamber 25 between it and the substrate 12. The flow path includes a supply port 18a and a recovery port 18b, and is an area surrounded by the ejection port forming member 14 and the substrate 12. The ejection port forming member 14 also has a partition wall 26 provided between adjacent heat application portions, and the partition wall 26 defines pressure chambers 25. The pressure chambers 25 are liquid chambers capable of containing liquid ink. It is a room.

[0034] As shown in FIG. 7(b), the heat application portion 124a as the first electrode is provided so as to overlap the position where the heating resistor 126 is provided when viewed from the direction in which the ejection port 13 is provided. When ejecting ink, the temperature of the ink rises instantaneously on the heat application portion 124a of the second protective layer 124 that covers the heating resistor 126 and contacts the ink, and the ink foams and defoams, causing cavitation. Therefore, the second protective layer 124 including the heat application portion 124a is formed of iridium, which has high corrosion resistance and high cavitation resistance. The heat application portion 124a of the second protective layer 124 is disposed between the supply port 18a and the recovery port 18b. Note that "disposed between the supply port 18a and the recovery port 18b" means that at least a part of the heat application portion 124a (second protective layer) is disposed between the supply port 18a and the recovery port 18b.

[0035] In addition, an electrode 129 used for the kogation suppression process and potential control described later is disposed downstream of the heat application portion 124a of the second protective layer 124 in the ink flow direction (arrow C in FIG. 6) from the supply port 18a to the recovery port 18b in the pressure chamber 25. As shown in FIG. 7(b), the electrode 129 as the second electrode is disposed so as not to overlap with the position where the heat application portion 124a is disposed when viewed from the direction in which the ejection port 13 is disposed. In other words, the electrode 129 is disposed on the recovery port 18b side, not on the supply port 18a side, as viewed from the heat application portion 124a. In addition, as shown in FIG. 5(b), when the supply port 18a is disposed on one side in the arrangement direction of the multiple heat application portions 124a and the recovery port 18b is disposed on the other side, the electrode 129 is disposed on the recovery port 18b side with respect to the row of the heat application portions 124a. In order to reduce the load of the manufacturing process, the electrode layer constituting the electrode 129 is preferably made of the same material (iridium) as the second protective layer .

[0036] (Method of removing burnt metal and controlling electric potential) Next, the method of kogation removal and potential control will be described. The second protective layer 124 is conductive, and the heat application part 124a and the electrode 129 sandwich the ink to form a pair of electrodes (first and second electrodes). Kogation removal is achieved when the control unit 4 applies a potential to the heat application part 124a and the electrode 129 so that the second protective layer 124 in the heat application part 124a part dissolves into the ink by electrochemical reaction. Furthermore, potential control for preventing kogation is achieved when the control unit 4 applies a potential to the heat application part 124a and the electrode 129 so as to reduce the presence rate of colloidal particles in the ink on the heat application part 124a.

[0037] (Control system configuration) Fig. 8 is a block diagram showing an example of the configuration of a control system in the recording device 1 configured as above. In Fig. 8, the host device 1000 is an external device to the recording device 1, and may take any suitable form such as a computer, a digital camera, or a scanner. The interface 1700 receives recording signals including commands and image data sent from the host device 1000. In addition, the interface 1700 sends status information of the recording device to the host device 1000 as necessary.

[0038] The control unit 4 includes an MPU 1701, a ROM 1702, a DRAM 1703, a gate array 1704 (GA), an energy table 1725, a non-volatile memory 1726 such as an EEPROM, and a potential control table 1727. The MPU 1701 controls each part of the recording device 1 according to a control program and required data corresponding to a cleaning process and an energy setting process procedure, which are stored in the ROM 1702 and will be described later. The data stored in the ROM 1702 includes steady driving conditions of the liquid ejection head 2, such as the shape and application time of a driving pulse applied to the heating resistor 126, as well as voltages applied to the heat application unit 124a and the electrode 129. The data can also include conditions for conveying the recording medium, and further the carriage speed.

[0039] The DRAM 1703 stores various data (such as the above-mentioned print signals and print data supplied to the head). The DRAM 1703 can also be provided with an area for flags used in the control process described below. The gate array 1704 controls the supply of print data to the liquid ejection head 2, and also controls data transfer between the interface 1700, the MPU 1701, and the DRAM 1703. The energy table 1725 stores data that determines the energy required for ink ejection, such as the pulse width of the ejection signal. The potential control table 1727 stores the contents of a memory element 1728, such as a ROM in an ink supply tank. When an ink tank is replaced, information is automatically written to the potential control table 1727, and when the ink tank is removed, the information in the potential control table 1727 is erased.

[0040] The ink supply tank has a memory element 1728 that stores ink manufacturing information such as information indicating the type of ink and information indicating the timing of ink manufacture. The memory element 1728 also stores the above-mentioned heat application unit 124a and the conditions for removing burnt ink and controlling the potential to be applied to the electrode 129. The memory element 1728 also stores a table or a calculation method (calculation formula) for determining the conditions for removing burnt ink and controlling the potential from the stored ink information, the ink characteristics measured in the present invention, and the ink discharge characteristics in a flow chart described later. The non-volatile memory 1726 stores necessary data even when the recording device is turned off. Examples of the ink manufacturing information include the product name, manufacturing lot number, model number, serial number, and manufacturing timing. The manufacturing timing is typically the date of manufacture. However, it is not limited to this, and may be approximate information such as the month, quarter, and year. Alternatively, the control unit may search an external database based on the serial number to obtain the manufacturing timing information.

[0041] The head driver 1705 drives the liquid ejection head 2 and performs cleaning operations and ejection energy setting operations. The measurement device 1706 detects the ink conductivity, ink ejection characteristics, etc., using an ink property measuring device 7 and an ink ejection characteristic measuring device 8 as shown in Fig. 1. The recording device 1 also has various motors 1708 and motor drivers 1707 for printing, which are controlled by the control unit 4 (two are shown in the figure).

[0042] Example 1 Fig. 9 is a flow chart of the kogation removal and potential control condition determination performed by the recording apparatus in the embodiment 1. An actual control procedure will be described with reference to Fig. 9. As the embodiment 1, a case where the potential control conditions are not changed will be described.

[0043] This flow starts when the ink supply tank 10 is attached to the ink supply unit 5 and an instruction to read the information in the memory element 1728 is issued from the host device 1000.

[0044] In step S101, the control unit 4 stores the contents of the memory element 1728 in the potential control table 1727. Next, in step S102, the control unit 4 starts discharging ink under the discharge conditions in the energy table 1725 and the standard potential control conditions in the potential control table 1727. Next, in step S103, the control unit 4 causes the measuring device 1706 to measure the ink discharge speed using the ink discharge characteristic measuring device 8, and then determines whether the value of the discharge speed satisfies a predetermined condition. Note that in S103, the discharge speed may be compared with a predetermined value, and if it is equal to or less than the predetermined value, the process may proceed to an aging process described below. Also, if the discharge speed is faster than the predetermined value, the process may proceed to an aging process. Also, if the discharge speed is within a predetermined range, the process may proceed to an aging process.

[0045] If the discharge speed satisfies the predetermined condition for the discharge speed in the potential control table 1727 (S103=Y), the process proceeds to potential control condition determination (step S104), and the determined potential control condition is written to the non-volatile memory 1726. The potential control conditions determined in this step differ depending on the type of ink and the situation. Typically, as the viscosity of the ink increases (i.e., the ratio of pigment increases), control is performed in the direction of strengthening the potential (increasing the potential difference between the electrode 129 and the heat application portion 124a). Here, strengthening the potential increases the effect of moving the pigment of the ink away from the heater surface, but there is a possibility that it will shorten the life of the protective film. Therefore, when determining the potential control conditions, it is preferable to appropriately correct the default conditions according to the elapsed time. Typically, as the viscosity of the ink increases over time, correction is performed in the direction of increasing the potential difference from the default value.

[0046] Next, in step S108, the control unit 4 calculates the elapsed time from the manufacturing date of the ink recorded in the potential control table 1727. Then, the control unit 4 refers to the potential control table 1727, reads out and determines the kogation removal conditions derived from the elapsed time.

[0047] Here, the reason why the burnt removal conditions are determined based on the elapsed time since the ink was manufactured will be explained. Burnt removal is a process in which an electric potential is applied to the electrode, the electrode material is electrochemically dissolved in the ink, and the burnt part on the electrode is removed. Burnt removal has the role of cleaning the electrode, and is performed multiple times at intervals. The upper limit number of times that burnt removal can be performed is determined by the film thickness of the electrode. Note that the conductivity of the ink has a large effect on the amount of electrode dissolution, and when the conductivity is high, the electrode dissolves more than when the conductivity is low, and the electrode disappears earlier than expected. In addition, the solvent volatilizes according to the elapsed time since the ink was manufactured, so the conductivity of the ink changes with time. Therefore, in this embodiment, the conductivity of the ink is predicted based on the elapsed time since the ink was manufactured, and the burnt removal conditions according to the conductivity are selected. Finally, in step S109, the control unit 4 writes the selected burnt removal conditions into the non-volatile memory 1726 and completes preparations for printing.

[0048] Next, a case where the discharge speed in step S103 in Fig. 9 does not satisfy the predetermined condition (S103=N) will be described. In this case, it is necessary to change the potential control condition. Specifically, the voltage of the heat application part 124a and the electrode 129 is changed.

[0049] Here, when a potential of the same polarity as the potential to which the colloids in the ink are charged is applied to the heat application unit 124a, the presence of colloids on the heat application unit 124a decreases. For example, if there are many negatively charged colloids, the voltage applied to the heat application unit 124a is also made negative. On the other hand, when the probability of the presence of colloids on the electrode decreases, the mass of the ink to be ejected changes, and the ejection speed changes compared to when the potential control is not performed. Normally, the potential control conditions are determined taking these factors into consideration, but depending on the storage condition of the ink and the number of days since manufacture, the ink solvent evaporates, the viscosity of the ink increases, and the mass of the ink at the time of ejection changes from the expected value. This is the cause of the change in the ejection speed.

[0050] Therefore, the above phenomenon is corrected by the following procedure. In step S105, the control unit 4 reads out data recorded in the potential control table 1727 based on the measured ejection speed, and changes the potential control conditions. Next, in step S106, the control unit 4 performs an aging process in which ink is ejected for a certain period of time under the conditions determined in step S5. The aging process here is a warm-up process for stabilizing the operation of the heater equipped with the heating resistor 126. That is, in this flow, if the ink ejection speed is not within a predetermined range even though ink is ejected under control conditions derived from experimental data during product development, it is determined that the heater is not stable, and the aging process is performed.

[0051] Next, in step S107, the control unit 4 measures the discharge speed again. If the discharge speed satisfies a predetermined condition in the discharge speed potential control table 1727 (S107=Y), the step The process proceeds to step S4, where the potential control conditions are determined. The processes in steps S104 to S109 are the same as those in the first embodiment. On the other hand, if the discharge speed does not satisfy the predetermined conditions (S107=N), the process returns to step S105 again, and the potential control conditions are changed.

[0052] It should be noted that a specified upper limit may be set for the number of times to return from step S107 to step S105. In this case, if the number of times to return exceeds the specified number of times, a warning may be issued to the user via the host device 1000, and the user may be prompted to change to manual removal of burnt food.

[0053] Example 2 Next, as a second embodiment, the determination of kogation removal and potential control conditions when using an ink property measuring device 7 will be described with reference to the flowchart of Fig. 10. The same parts as those in the first and second embodiments are given the same reference numerals and the description thereof will be omitted.

[0054] The processes in steps S101 to S104 are performed in the same manner as in Fig. 9. Moreover, the processes in steps S105 to S107 in the case where the ejection speed is outside the predetermined range are also the same as in Fig. 9.

[0055] In this embodiment, after the potential control conditions are determined in step S104, in step S201, the control unit 4 causes the measurement device 1706 to measure the conductivity of the ink using the ink physical property measuring device 7. That is, in step S108 of Fig. 9, the kogation removal conditions were determined from the elapsed manufacturing time, but in this embodiment, the ink conductivity is measured directly. Next, in step S202, the control unit 4 refers to the potential control table 1727, reads out the kogation removal conditions derived from the measured conductivity, and determines them as the conditions at the time of execution. In step S109, the determined conditions are written to the non-volatile memory 1726, and printing preparation is completed.

[0056] In Examples 1 and 2, the ink ejection speed was measured as the ink ejection characteristics, and the ink conductivity was measured as the ink physical properties. However, the ink ejection characteristics and ink physical properties are not limited to these, and other measured values ​​may be used.

[0057] Example 3 Next, a method for determining potential control conditions for removing kogation without using a measuring device will be described as Example 3. Fig. 11 is a flow chart showing the process of this example.

[0058] When the flow starts, in step S301, the control unit 4 stores the contents of the memory element 1728 in the potential control table 1727. Next, in step S302, the control unit 4 calculates the elapsed manufacturing time based on the difference between the ink manufacturing date recorded in the potential control table 1727 and the current time. Then, the control unit 4 refers to the potential control table 1727, reads out and determines the potential control conditions derived from the elapsed manufacturing time. Next, in step S303, the control unit 4 refers to the potential control table 1727, reads out and determines the kog removal conditions derived from the elapsed manufacturing time. Finally, in step S304, the control unit 4 writes each condition into the non-volatile memory 1726, and becomes ready to print.

[0059] In the above-mentioned Examples 1 to 3, the ink production elapsed time was used to select the kogation removal conditions and the potential control conditions, but the present invention is not limited to this, and any composition change information other than the ink production elapsed time may be used as long as it indicates a change in the composition of the ink. Also, any information that can select the conditions described in the potential control table may be used, such as the type of ink or the production lot number.

[0060] In addition, the above-mentioned first to third embodiments start immediately after the ink supply tank is replaced, but this is not limiting. For example, the above flow may be executed during the use of ink. For example, this flow may be performed during maintenance of the apparatus, or may be performed periodically according to the number of prints or the duration of use of the apparatus.

[0061] In each embodiment, information indicating the elapsed time since manufacture is acquired based on information stored in the storage element, but the present invention is not limited to this. For example, information may be acquired based on an input from a user. The control unit may determine the state of change in the composition of the ink based on information indicating the environment in which the ink is stored, instead of or together with the information indicating the elapsed time since manufacture, and change the potential control conditions. The storage element 1728 does not necessarily need to store all of the ink type, manufacturing information, and tables and calculation formulas for the potential control conditions. For example, the storage element 1728 may store only information indicating the ink type and manufacturing timing, and the control unit may search an external database based on this information to acquire the potential control conditions.

[0062] As described above, in the present invention, the state of change in the composition of the ink is determined based on the ink production information and the information on the potential control kogation removal conditions written in the memory element of the ink tank, and the potential is controlled under conditions according to the composition. The state of change in the composition of the ink can be determined based on the measurement results by an apparatus for measuring the characteristics of the ink provided in the inkjet recording apparatus. The ink characteristics include, for example, the physical properties (typically the ink conductivity) measured by an ink physical property measuring device and the ejection characteristics (typically the ink ejection speed) measured by an ink ejection characteristic measuring device. By setting the potential values ​​of the multiple electrodes that form an electrolysis in the liquid ejection head based on these measurement results, it is possible to adjust the change in the ink over time and the change due to the installation environment. This makes it possible to set the kogation removal and potential control conditions that are suitable for the state of the ink, and to achieve long-term stable ejection.

[0063] [Configuration 1] a liquid ejection head having an ejection port for ejecting a liquid, a liquid chamber communicating with the ejection port, a heating resistor provided within the liquid chamber and configured to be able to eject the liquid from the ejection port by generating heat, and a first electrode and a second electrode provided within the liquid chamber; a control unit that controls application of a potential to the first electrode and the second electrode based on a potential control condition according to the type of the liquid; A liquid ejection device having when the liquid chamber is viewed from a direction in which the ejection port is provided, the first electrode is provided so as to overlap a position where the heating resistor is provided, and the second electrode is provided so as not to overlap a position where the first electrode is provided, The control unit changes the potential control condition in response to a change in the composition of the liquid. A liquid ejection device comprising: [Configuration 2] the liquid ejection device is capable of mounting a tank that supplies the liquid to the liquid chamber; the tank has a memory element that stores the potential control condition according to the type of the liquid, The control unit applies a potential to the first electrode and the second electrode using the potential control condition obtained from the memory element when the tank is attached. 2. The liquid ejection device according to configuration 1, [Configuration 3] the memory element of the tank stores information indicating a production timing of the liquid, The control unit changes the potential control condition based on a production timing of the liquid. 3. The liquid ejection device according to configuration 2. [Configuration 4] The storage element of the tank stores the A table or a formula for changing the potential control conditions is stored, The control unit calculates the elapsed time based on the manufacturing timing, and changes the potential control condition using the table or the calculation formula. 4. The liquid ejection device according to configuration 3. [Configuration 5] Further comprising a discharge characteristic measuring means for measuring the discharge characteristic of the liquid, the storage element of the tank stores a table or a formula for changing the potential control condition in accordance with the ejection characteristics; The control unit changes the potential control condition by using the ejection characteristics measured by the ejection characteristics measuring unit and the table or the calculation formula. 5. The liquid ejection device according to any one of configurations 2 to 4. [Configuration 6] The ejection characteristic measuring means measures an ejection speed of the liquid as the ejection characteristic. 6. The liquid ejection device according to configuration 5. [Configuration 7] Further comprising a physical property measuring means for measuring a physical property of the liquid, the storage element of the tank stores a table or a formula for changing the potential control condition in accordance with the physical property; The control unit changes the potential control condition by using the property measured by the property measuring unit and the table or the calculation formula. 7. The liquid ejection device according to any one of configurations 2 to 6, [Configuration 8] The physical property measuring means measures the electrical conductivity of the liquid as the physical property. 8. The liquid ejection device according to configuration 7. [Configuration 9] The memory element of the tank stores information indicating the type of the liquid. 9. The liquid ejection device according to any one of configurations 2 to 8, [Configuration 10] A control method for a liquid ejection device comprising: an ejection port for ejecting liquid, a liquid chamber communicating with the ejection port, a liquid ejection head having a heating resistor provided within the liquid chamber and configured to be able to eject the liquid from the ejection port by generating heat, and a first electrode and a second electrode provided within the liquid chamber; and a control unit, wherein, when the liquid chamber is viewed from a direction in which the ejection port is provided, the first electrode is provided so as to overlap a position where the heating resistor is provided, and the second electrode is provided so as not to overlap a position where the first electrode is provided; the control unit controls application of a potential to the first electrode and the second electrode based on a potential control condition according to a type of the liquid; The control unit changes the potential control condition in response to a change in the composition of the liquid. A method for controlling a liquid ejection device comprising the steps of: [Explanation of symbols]

[0064] 1: recording device, 2: liquid ejection head, 4: control unit, 25: pressure chamber, 124a: heat application unit, 126: heating resistor, 129: electrode

Claims

1. a liquid ejection head having an ejection port for ejecting a liquid, a liquid chamber communicating with the ejection port, a heating resistor provided in the liquid chamber and configured to be able to eject the liquid from the ejection port by generating heat, and a first electrode and a second electrode provided in the liquid chamber; a control unit that controls application of a potential to the first electrode and the second electrode based on a potential control condition according to the type of the liquid; A liquid ejection device having when the liquid chamber is viewed from a direction in which the ejection port is provided, the first electrode is provided so as to overlap a position where the heating resistor is provided, and the second electrode is provided so as not to overlap a position where the first electrode is provided, the control unit changes the potential control condition in response to a change in the composition of the liquid, the liquid ejection device is capable of mounting a tank that supplies the liquid to the liquid chamber; the tank has a memory element that stores the potential control condition according to the type of the liquid, The control unit applies a potential to the first electrode and the second electrode using the potential control condition acquired from the memory element when the tank is attached. A liquid ejection device characterized by:

2. the storage element of the tank stores information indicating a production timing of the liquid, The control unit changes the potential control condition based on a production timing of the liquid. The liquid ejection device according to claim 1 .

3. the storage element of the tank stores a table or a formula for changing the potential control condition in accordance with the elapsed time from the production timing of the liquid, The control unit calculates the elapsed time based on the manufacturing timing, and changes the potential control condition using the table or the calculation formula.

3. The liquid ejection device according to claim 2.

4. further comprising a discharge characteristic measuring means for measuring the discharge characteristic of the liquid; the storage element of the tank stores a table or a formula for changing the potential control condition in accordance with the ejection characteristics; The control unit changes the potential control conditions using the ejection characteristics measured by the ejection characteristics measurement unit and the table or the calculation formula. The liquid ejection device according to claim 1 .

5. The ejection characteristic measuring means measures the ejection speed of the liquid as the ejection characteristic.

5. The liquid ejection device according to claim 4.

6. further comprising a physical property measuring means for measuring the physical properties of the liquid; the storage element of the tank stores a table or a formula for changing the potential control condition in accordance with the physical property; The control unit changes the potential control conditions using the physical property measured by the physical property measuring unit and the table or the calculation formula. The liquid ejection device according to claim 1 .

7. The physical property measuring means measures the electrical conductivity of the liquid as the physical property.

7. The liquid ejection device according to claim 6.

8. The storage element of the tank stores information indicating the type of the liquid. The liquid ejection device according to claim 1 .

9. a liquid ejection head having an ejection port for ejecting liquid, a liquid chamber communicating with the ejection port, a heating resistor provided in the liquid chamber and configured to be able to eject the liquid from the ejection port by generating heat, and a first electrode and a second electrode provided in the liquid chamber; and a control unit, wherein, when the liquid chamber is viewed from a direction in which the ejection port is provided, the first electrode is provided so as to overlap a position where the heating resistor is provided, and the second electrode is provided so as not to overlap a position where the first electrode is provided; the control unit controls application of a potential to the first electrode and the second electrode based on a potential control condition according to the type of the liquid; the control unit changes the potential control condition in response to a change in the composition of the liquid, the liquid ejection device is capable of mounting a tank that supplies the liquid to the liquid chamber; the tank has a memory element that stores the potential control condition according to the type of the liquid, In the controlling step, the control unit applies a potential to the first electrode and the second electrode using the potential control condition acquired from the memory element when the tank is attached. A method for controlling a liquid ejection device.

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