Liquid discharge apparatus and liquid discharge head

Abstract

To provide a liquid discharge device capable of suppressing excessive circulation of liquid.SOLUTION: A first energy generating element that is provided at a position corresponding to the pressure chamber of the flow path forming portion and generates energy for ejecting the liquid from the ejection orifice, a second energy generating element that is provided at a position corresponding to the individual flow path of the flow path forming portion and generates energy for causing the liquid to flow through the individual flow path, a temperature detection unit that is disposed at a position corresponding to the first energy generating element or the second energy generating element and detects a temperature, and a control unit that controls driving of the second energy generating element based on a detection result of the temperature detection unit.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus and a liquid ejection head provided in the liquid ejection apparatus. [Background technology]

[0002] In a liquid ejection head that ejects liquid such as ink, evaporation of volatile components in the liquid can cause the liquid near the ejection orifice to thicken. This thickening of the liquid can affect the ejection speed and landing accuracy of the ejected droplets. One known measure to suppress the thickening of the liquid is to perform a circulation drive operation that generates a minute circulating flow in individual flow paths including the ejection orifices.

[0003] Patent Document 1 discloses a configuration in which a fluid circulation element is provided and a circulation drive sequence for intermittently driving the fluid in circulation can be performed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016-068988 Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration described above, if the conditions and number of times for the circulation drive are set to reliably eliminate thickening while taking into consideration variations, etc., an excessive circulation amount may be set in some cases. Excessive circulation of liquid in the liquid ejection head may lead to heat generation and concentration of the liquid due to the circulation drive.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a liquid ejection device that can suppress excessive circulation of liquid. [Means for solving the problem]

[0007] In order to achieve the above object, a liquid ejection device of the present invention comprises: a flow path forming portion having a discharge port through which a liquid is discharged and a circulation flow path that is in communication with the discharge port and is configured to allow the liquid to circulate therethrough; a first energy generating element provided at a position corresponding to the ejection port of the flow path forming portion, the first energy generating element generating energy for ejecting liquid from the ejection port; a second energy generating element provided in the flow path forming portion and configured to generate energy for circulating the liquid through the circulation flow path; a temperature detection unit that is disposed at a position corresponding to the first energy generating element or the second energy generating element and detects a temperature; a control unit that controls driving of the second energy generating element based on a detection result of the temperature detection unit; The present invention is characterized by comprising: [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a liquid ejection device that can suppress excessive circulation of liquid. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a schematic configuration of a liquid ejection device according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing a control system of the liquid ejection device according to the first embodiment. [Figure 3] FIG. 1 is an explanatory diagram of a liquid ejection head according to a first embodiment. [Figure 4] 1 is a schematic diagram illustrating a main part of a liquid ejection head according to a first embodiment. [Figure 5] 4 is a flowchart of circulation amount control according to the first embodiment. [Figure 6] FIG. 2 is an explanatory diagram of a drive sequence according to the first embodiment. [Figure 7] 10 is a schematic diagram illustrating a main part of a liquid ejection head according to a second embodiment. FIG. [Figure 8] 10 is a flowchart of a circulation amount control according to the second embodiment. [Figure 9]FIG. 10 is a diagram illustrating a driving sequence according to the second embodiment. [Figure 10] FIG. 10 is a schematic diagram illustrating a main part of a liquid ejection head according to a third embodiment. [Figure 11] 10 is a schematic diagram illustrating a main part of a liquid ejection head according to a fourth embodiment. FIG. [Figure 12] 10 is a schematic diagram illustrating a main part of a liquid ejection head according to a fifth embodiment. FIG. [Figure 13] 10 is a schematic diagram illustrating a main part of a liquid ejection head according to a sixth embodiment. FIG. [Figure 14] 13 is a flowchart of a circulation amount control according to a seventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes in detail exemplary embodiments of the present invention with reference to the drawings. The dimensions, materials, shapes, and relative positions of the components described in the embodiments may be changed as appropriate depending on the configuration and various conditions of the device to which the invention is applied. In other words, the scope of the present invention is not limited to the following embodiments.

[0011] The present invention relates to a recording element unit provided in a liquid ejection head that performs recording by ejecting liquid onto a recording medium. The present invention is preferably applicable to, for example, a recording element unit of an inkjet head provided in an inkjet printer that uses an inkjet recording method to perform recording by foaming a liquid such as ink using thermal energy. However, the recording element unit of the present invention is not limited to this, and can be applied to recording element units of various liquid ejection heads that eject liquid using thermal energy.

[0012] Hereinafter, a liquid ejection head and a liquid ejection device including the liquid ejection head according to an embodiment of the present invention will be described with reference to the drawings. In each of the following embodiments, a specific configuration of a liquid ejection head that ejects ink will be described, but the present invention is not limited thereto. The liquid ejection head of the present invention can be applied to devices such as printers, copiers, facsimiles with communication systems, and word processors with printer units, as well as industrial recording devices combined with various processing devices. For example, it can also be used in applications such as biochip production and electronic circuit printing.

[0013] Example 1 A liquid ejection apparatus 50 according to a first embodiment of the present invention will be described below. The liquid ejection apparatus 50 is an inkjet recording apparatus that uses an inkjet recording method, and includes a liquid ejection head 1 that can eject ink as a liquid.

[0014] (Liquid discharge device) The following describes the schematic configuration of a liquid ejection device 50 according to Example 1. Figures 1(a) and 1(b) are perspective views showing an example of the configuration of a recording unit of the liquid ejection device 50. The liquid ejection device 50 is a serial type liquid ejection device that records an image by ejecting liquid onto a recording medium P using a liquid ejection head 1 that scans in a direction intersecting the transport direction of the recording medium P.

[0015] The present invention is not limited to serial-type liquid ejection devices, but can also be applied to page-wide liquid ejection devices that use a line head (page-wide head) that is long in the page width direction of the recording medium to eject liquid onto a recording medium transported in the transport direction to record an image.

[0016] The liquid ejection head 1 is capable of ejecting four types of ink: black (K), cyan (C), magenta (M), and yellow (Y), and is capable of recording full-color images using these inks. The inks that can be ejected from the liquid ejection head are not limited to the above four types of ink. The present disclosure is also applicable to liquid ejection heads for ejecting other types of ink. In other words, there are no limitations on the types and number of inks that can be ejected from the liquid ejection head.

[0017] In the following explanation, the scanning direction (movement direction) of the liquid ejection head 1 is referred to as the X direction, the transport direction of the recording medium P in the recording unit as the Y direction, and the vertical direction as the Z direction. The X direction, Y direction, and Z direction intersect with each other (in this example, they are perpendicular). Furthermore, the scanning direction (movement direction) of the liquid ejection head 1 may be referred to as the main scanning direction, and the transport direction of the recording medium P as the sub-scanning direction.

[0018] In a serial type liquid ejection device 50, the liquid ejection head 1 is mounted on a carriage 60. The carriage 60 moves back and forth in the main scanning direction (X direction) along a guide shaft 51. The recording medium P is transported in the sub-scanning direction (Y direction) that intersects (in this example, is perpendicular to) the main scanning direction by transport rollers 55, 56, 57, and 58 that constitute a transport unit (transport means).

[0019] Fig. 1(a) is a perspective view showing an example of a configuration in which a main ink tank 2 serving as a liquid storage unit is provided in the device body (outside the liquid ejection head 1) of a liquid ejection device 50, and a sub-ink tank 54 is provided in the liquid ejection head 1. The liquid (ink) stored in the ink tank 2 is supplied to the sub-ink tank 54 on the liquid ejection head 1 side via an ink supply tube (liquid communication path) 59 or the like by the driving force of an external pump 21. In other words, in the example shown in Fig. 1(a), the device body of the liquid ejection device 50 and the liquid ejection head 1 are each provided with a liquid storage unit for storing ink.

[0020] Fig. 1(b) is a perspective view showing an example of a configuration in which there is no main ink tank 2, and an ink tank 54 is provided directly above the liquid ejection head 1. In this case, the liquid ejection head 1 may be provided integrally with the ink tank 54 and configured to be removable and attachable to the carriage 60. Alternatively, the liquid ejection head 1 may be provided integrally with the carriage 60, and only the ink tank 54 may be removable and attachable. The following description will be given using the configuration in Fig. 1(a) as a representative example.

[0021] The liquid ejection head 1 is configured to include individual ejection units, which will be described later. The specific configuration will be described later, but the individual ejection unit is a recording element unit in which ejection ports for ejecting liquid, pressure chambers communicating with the ejection ports, and individual flow paths communicating with the pressure chambers are formed. The individual ejection units also include first energy generating elements (ejection energy generating elements) that are provided at positions corresponding to the pressure chambers and generate energy for ejecting liquid from the ejection ports, and second energy generating elements (flow energy generating elements) that are provided at positions corresponding to the individual flow paths. The liquid ejection head 1 has a plurality of individual ejection units, and each individual ejection unit has a supply flow path for supplying liquid to the individual flow paths in the individual ejection unit.

[0022] When using the liquid ejection head 1, the evaporation of volatile components such as water at the ejection ports and the resulting concentration of solids near the ejection ports can cause the ejection of the liquid to become unstable, and various measures have been taken to prevent this. For example, the liquid ejection device 50 can be provided with a cap member (not shown) at a position offset in the X direction from the conveyance path of the recording medium P, which can cover the ejection port surface of the liquid ejection head 1 on which the ejection ports are formed. The cap member is used to cover the ejection port surface of the liquid ejection head 1 when the recording operation is not being performed, and to protect and prevent the ejection ports from drying out.

[0023] Furthermore, an ink suction mechanism (not shown) can be provided in the liquid ejection device 50. When an ink suction mechanism is provided, the cap member is used to suck ink from the ejection ports. By performing this ink suction operation, the ink near the ejection ports can be refreshed, and the quality of the resulting image can be maintained.

[0024] It is also possible to discard concentrated ink by performing a process known as preliminary ejection (preliminary ejection) when no printing operation is being performed. Furthermore, even during printing, it is possible to preliminarily eject an inconspicuous amount of ink onto a position on the printing medium that is not noticeable in terms of image quality (paper preliminary ejection / intra-page preliminary ejection). While these methods contribute greatly to improving image quality, they also waste some ink to refresh the ejection orifices, so it is necessary to reduce the amount of wasted ink as much as possible.

[0025] To address this issue, by providing a second energy generating element (flow energy generating element) in each individual flow path and circulating the ink within the flow path, it is possible to suppress the drying of the ejection ports and the concentration of ink near the ejection ports while reducing the amount of waste ink. More specifically, it is possible to minimize the number of preliminary ejections and suction recovery operations. Furthermore, reducing the number of preliminary ejections and other operations also leads to improvements in throughput and yield.

[0026] The second energy generating element (flow energy generating element) does not necessarily have to be provided in all of the individual discharge units of the liquid discharge head. If it is provided in some of the individual discharge units, the above-mentioned effects can be obtained compared to when no second energy generating element is provided.

[0027] Furthermore, the liquid ejection head 1 may be configured so that all of the locations corresponding to the four types of ink are provided with second energy generating elements, or so that only the locations corresponding to one type of ink are provided with second energy generating elements. In other words, the liquid ejection head may be configured so that only at least one type of ink is circulated, rather than all four types of ink.

[0028] 2 is a block diagram showing a control system of the liquid ejection device 50. The CPU 800 is a control unit that controls the operation of each unit of the liquid ejection device 50 based on programs such as processing procedures stored in the ROM 301. The RAM 302 is used as a work area when the CPU 800 executes processing. The CPU 800 receives image data from a host device 400 external to the liquid ejection device 50, and controls the head driver 1A based on the image data to control the driving of the ejection elements provided in the liquid ejection head 1.

[0029] The CPU 800 also controls drivers of various actuators provided in the liquid ejection device 50. For example, the CPU 800 controls a motor driver 303A of a carriage motor 303 for moving the carriage 60, a motor driver 304A of a conveyance motor 304 for conveying the recording medium P, a pump driver 21A of the external pump 21, etc. Note that while FIG. 2 shows a form in which processing is performed after receiving image data from the host device 400, processing may also be performed in the liquid ejection device 50 without relying on data from the host device 400.

[0030] (liquid ejection head) An example of the configuration of the liquid ejection head 1 will now be described. Figures 3(a) to 3(d) are explanatory diagrams of the liquid ejection head 1 according to Example 1. Figure 3(a) is an exploded perspective view of the liquid ejection head 1.

[0031] The liquid ejection head 1 includes four sub-ink tanks 54 for temporarily storing ink in the head, and a liquid ejection tip 3 for ejecting ink supplied from the sub-ink tanks 54 onto a recording medium P.

[0032] The liquid ejection head 1 further includes a first support member 4, a second support member 7, and an electric wiring member (electric wiring tape) 5. The liquid ejection chip 3 is connected to one surface of the first support member 4, and an ink tank 54 is connected to the other surface. A flow path is formed in the first support member 4, penetrating from one surface to the other, and the first support member 4 supports the liquid ejection chip 3 while sending ink supplied from the ink tank 54 to the liquid ejection chip 3.

[0033] The second support member 7 is connected to the connection surface of the first support member 4 that connects to the liquid ejection chip 3. The second support member 7 has an opening formed therein through which the liquid ejection chip 3 can be inserted, and is connected to the first support member 4 so that the liquid ejection chip 3 is positioned within the opening. The second support member 7 also supports the electrical wiring member 5.

[0034] The electrical wiring member 5 is electrically connected to the liquid ejection chip 3 and sends to the liquid ejection chip 3 an ejection signal for ejecting ink, which is sent from the main body of the liquid ejection device 50 or the like.

[0035] The liquid ejection head 1 in Example 1 is fixedly supported on a carriage 60 of the liquid ejection device 50 by positioning means and electrical contacts (not shown) provided on the carriage 60. The liquid ejection head 1 ejects ink while moving together with the carriage 60 in the main scanning direction (X direction) to perform recording on the recording medium P.

[0036] An ink supply tube 59 is provided to an external pump 21 connected to a main ink tank 2, which serves as an ink supply source. A liquid connector (not shown) is provided at the end of the ink supply tube 59. When the liquid ejection head 1 is mounted on the liquid ejection device 50, the liquid connector provided at the end of the ink supply tube 59 is liquid-tightly connected to a liquid connector insertion port, which is a liquid inlet port provided in a head housing of the liquid ejection head 1. This forms an ink supply path from the ink tank 2 via the external pump 21 to the liquid ejection head 1. In Example 1, four types of ink are used, so a total of four sets of ink tanks 2, external pumps 21, ink supply tubes 59, and sub-ink tanks 54 are provided, one for each ink. The liquid ejection device 50 is then formed with four independent ink supply paths, one for each ink.

[0037] In this way, the liquid ejection device 50 is provided with an ink supply system to which ink is supplied from the ink tank 2 provided outside the liquid ejection head 1. The liquid ejection device 50 is not provided with an ink recovery system to recover ink inside the liquid ejection head 1 to the ink tank 2. Therefore, the liquid ejection head 1 is provided with a liquid connector insertion port for connecting the ink supply tube 59 of the ink tank 2, but is not provided with a connector insertion port for connecting a tube for recovering ink from the liquid ejection head 1 to the ink tank 2. A liquid connector insertion port is provided for each ink.

[0038] Figures 3(b), (c), and (d) are diagrams showing examples of the configuration of the liquid ejection chips 3 that make up the liquid ejection head 1. Figure 3(b) shows an example of a configuration where one chip is used for four colors of ink. Figure 3(c) shows an example of a configuration where one chip is used for two colors of ink. Figure 3(d) shows an example of a configuration where one chip is used for one color of ink. Each liquid ejection chip is provided with an ejection port 11 and pads used for electrical mounting. Figure 3(a) shows the chip configuration of Figure 3(b).

[0039] FIG. 3(b) shows an example in which one liquid ejection chip 3 is provided for each of four ink colors, and the liquid ejection head 1 is provided with one liquid ejection chip 3. The four colors are, for example, black, cyan, magenta, and yellow. The liquid ejection chip 3 is provided with an ejection port array, each of which is configured with a plurality of ejection ports 11 aligned at equal intervals in the Y direction, corresponding to each color. In this example, two ejection port arrays, offset in the X direction, are provided for each color. Alternatively, instead of two rows of ejection openings for each color, only one row of ejection openings may be provided. Alternatively, two rows of ejection openings may be provided for black, for a total of five rows for four colors.

[0040] 3(c) shows an example in which one liquid ejection chip 3 is provided for each of two colors of ink, and the liquid ejection head 1 is equipped with two liquid ejection chips 3. When mounting two chips on the liquid ejection head 1, two chips may be mounted on one liquid ejection head 1, or two heads may be prepared, each with one chip mounted on one liquid ejection head 1.

[0041] Fig. 3(d) shows an example in which one liquid ejection chip 3 is provided for each color of ink, and the liquid ejection head 1 is provided with four liquid ejection chips 3. In this example, as in the example of Fig. 3(c), four chips may be mounted on one liquid ejection head, or four liquid ejection heads, each mounted with one chip, may be prepared.

[0042] Also, when the chip is divided into multiple parts, as shown in Figure 3(c) and (d), not all of them need to be the same chip length. Also, various combinations of other colors for the chip are possible, and the same applies when the total number of colors is more than four.

[0043] (liquid ejection chip) The configuration of the liquid ejection chip 3 will be described in more detail. Figures 4(a) to 4(c) are explanatory diagrams of the flow path configuration of the liquid ejection chip 3 according to Example 1. Figure 4(a) is an explanatory diagram of the configuration in the vicinity of the ejection port 11 of the liquid ejection chip 3, and is a schematic diagram showing the positional relationship of the main components when the liquid ejection chip 3 is viewed in the Z direction. The Z direction is approximately parallel to the direction in which liquid is ejected from the ejection port 11. Figure 4(b) is a cross-sectional view taken along the line AA in Figure 4(a). Figure 4(c) is a schematic enlarged view of the individual flow path section in Figure 4(a).

[0044] The liquid ejection chip 3 has a substrate 18 in which ejection ports 11 are formed, and an orifice plate 19 connected to the substrate 18 and having a flow path formed therein, and is a flow path forming portion in which a flow path through which ink flows is formed. In FIG. 4(a), in order to show the positional relationship of the main components, the first energy generating element 14 and the second energy generating element 24 are shown with hatching similar to that in FIG. 4(b), and the ejection port 11 is shown with a solid line. Ink supplied from an ink tank 54 passes through a flow path formed in the substrate 18 and is ejected from the ejection port 11.

[0045] The liquid ejection chip 3 is formed with ejection ports 11, pressure chambers 13 communicating with the ejection ports 11, and individual flow channels 23 communicating with the pressure chambers 13. The orifice plate 19 is a plate member in which a plurality of ejection ports 11 are formed, and is connected to a substrate 18. The pressure chambers 13 and individual flow channels 23 are formed corresponding to each ejection port 11, and the orifice plate 19 and the substrate 18 form part of their inner walls. The individual flow channels 23 communicate with both sides of the pressure chambers 13 in the X direction. In other words, the pressure chambers 13 can also be considered part of the individual flow channels 23. The individual flow channels 23 in Example 1 are U-shaped when viewed in the Z direction, as shown in FIG. 4(c). Hereinafter, this type of flow channel shape will be referred to as a U-shape.

[0046] When viewed in the Z direction, a first energy generating element 14 is formed at a position that overlaps with the ejection port 11 and the pressure chamber 13 of the substrate 18. The first energy generating element 14 is an element that generates energy for ejecting liquid from the ejection port 11, and for example, an electrothermal conversion element or the like can be used.

[0047] Further, second energy generating elements 24 are formed on the substrate 18 at positions corresponding to the individual flow paths 23, specifically at positions different from the first energy generating elements 14 and overlapping with the individual flow paths 23 when viewed in the Z direction. The second energy generating elements 24 are elements that generate energy for causing ink to flow through the individual flow paths 23, and are similar to the first energy generating elements 14. In the first embodiment, the first energy generating element 14 and the second energy generating element 24 are arranged adjacent to each other in the Y direction with the partition wall sandwiched therebetween. That is, the first energy generating element 14 is provided corresponding to one straight portion forming the U-shape of the individual flow path 23, and the second energy generating element 24 is provided corresponding to the other straight portion.

[0048] The substrate 18 is formed with a common flow path 15 communicating with the plurality of individual flow paths 23 and a supply groove 12 communicating with the common flow path 15 as flow paths for the flow of ink. Ink is supplied to the individual flow paths 23 from the supply groove 12 formed in the substrate 18 via the common flow path 15. Energy generated by the second energy generating elements 24 causes the ink to circulate within the individual flow paths 23 in a direction from the second energy generating elements 24 toward the first energy generating elements 14. In FIGS. 4(a) to 4(c), arrows indicate a circulation flow 27, which is a flow of ink circulating within the individual flow paths 23. In other words, the individual flow paths 23 are circulation flow paths configured to allow the ink to circulate, and the second energy generating elements 24 generate energy for circulating the ink through the individual flow paths 23.

[0049] In the first embodiment, two rows of ejection ports are formed, each row consisting of a plurality of ejection ports 11 aligned in the Y direction. The supply groove 12 is formed between the two rows of ejection ports in the X direction. The supply groove 12 is a groove that is long in the Y direction, and is a flow path for supplying ink, which is supplied from the ink tank 54 via the first support member 4, to the individual flow paths 23.

[0050] Furthermore, a common liquid chamber 29 that communicates with the supply groove 12 is formed in the substrate 18. Ink supplied from an ink tank 54 flows into the common liquid chamber 29. That is, the ink supplied from the ink tank 54 passes through the common liquid chamber 29 and the supply groove 12 in this order and flows into the individual flow paths 23.

[0051] The circulation system will be described using Figure 4(c). Of the two ends of the individual flow path 23, one end into which ink flows when a circulation flow 27 is formed is called the inlet 25, and the other end from which ink flows out is called the outlet 26. The pressure chamber 13 and the first energy generating element 14 are located on the side closer to the outlet 26, and the second energy generating element 24 is located on the side closer to the inlet 25. In a U-shaped individual flow path 23, the outlet 26 and the inlet 25 are adjacent to each other in the Y direction. In the following description of the flow of ink (liquid) and circulation amount control, the pressure chamber 13 will be considered as part of the individual flow path 23.

[0052] As the water (volatile components) evaporates in the ejection port 11, the ink thickens and becomes concentrated ink. At this time, the second energy generating element 24 forms a circulating flow 27, causing the concentrated ink to flow out of the outlet 26. This replaces the concentrated ink in the ejection port 11, thereby achieving the effect of eliminating the concentration.

[0053] However, as the ink circulates, it flows out of the individual flow paths 23 from the outlet 26 and into the individual flow paths 23 from the inlet 25 at the same time. Therefore, when the outlet 26 and the inlet 25 are close to each other, as in the case of a U-shaped individual flow path 23, concentrated ink whose water has evaporated at the discharge port may re-flow into the individual flow paths 23. Therefore, if excessive circulation is performed, a new issue arises: the progression of concentration in each individual flow path 23. Therefore, in order to suppress the progression of concentration in each individual flow path 23 due to minute circulation, it is important to control the circulation amount so as not to circulate more than necessary.

[0054] In the first embodiment, electrothermal converting elements are used as the first energy generating element 14 and the second energy generating element 24. Note that the second energy generating element 24 may be another element such as a piezoelectric element.

[0055] The substrate 18 is provided with a temperature detection element 34 as a temperature detection unit (temperature detection means) that detects the temperature of at least one of the individual flow paths 23 and the pressure chambers 13. In Example 1, the temperature detection element 34 is disposed at a position corresponding to the pressure chambers 13, specifically at a position overlapping the ejection ports 11 and the first energy generating elements 14 when viewed in the Z direction. As shown in FIG. 4(b), the temperature detection element 34 is disposed directly below the first energy generating elements 14, that is, on the side farther away from the individual flow paths 23 and the ejection ports 11 than the first energy generating elements 14.

[0056] In the first energy generating element 14, the temperature rises in response to the application of a driving voltage pulse, reaches a maximum temperature, and then drops. During this temperature drop, a characteristic point occurs in the detected temperature over time, where the temperature drops suddenly. This characteristic point occurs due to a large change in thermal conductivity caused by the gas at the position corresponding to the first energy generating element 14 being replaced by liquid as the liquid bubbles due to the rise in temperature of the first energy generating element 14 and then disappears.

[0057] When the ink viscosity increases due to the thickening effect in each individual flow path 23, the viscous resistance increases, so the time until the bubbles disappear becomes longer, and accordingly the time when the characteristic points appear also becomes delayed. By utilizing such a difference in the disappearance time due to differences in ink viscosity, the first energy generating element 14 is driven to detect concentration, and it becomes possible to detect the viscosity in the individual flow path 23.

[0058] Furthermore, in this concentration detection drive, if viscosity detection is performed using drive pulses used for normal ejection, ink will be ejected, landing on the paper surface or the like and affecting the output image. Therefore, unlike normal drive pulses for normal ejection, it is preferable to apply low-energy drive pulses that generate bubbles but do not eject ink, or that generate bubbles and eject ink but do not land on the printed material. This makes it possible to detect viscosity information within the individual flow paths 23 without affecting the printed material and while suppressing ink consumption.

[0059] In the first embodiment, the liquid ejection device 50 is configured to be able to control the amount of ink circulation based on viscosity information (temperature information) in the individual flow paths 23. The circulation amount control will now be described with reference to Fig. 5. Fig. 5 is a flowchart of the circulation amount control according to the first embodiment.

[0060] First, in step (hereinafter referred to as S) 101, the concentration detection drive conditions to be applied to the first energy generating element 14 are referenced, and the detection timing is set in advance to a characteristic point when the viscosity inside the flow path is normal. In other words, the detection timing is the timing when the temperature of the individual flow path 23 drops suddenly in response to the drive of the first energy generating element 14 when the viscosity of the ink inside the individual flow path 23 is normal. However, the detection timing is not limited to this, and may be set appropriately within the range in which the temperature of the individual flow path 23 drops.

[0061] Next, in S102, since a temperature difference occurs depending on the characteristic point, a temperature threshold value T0 at the detection timing is set in advance. Note that the threshold value T0 may be set by predicting it in advance, for example, before shipping, or may be set by creating a state where the viscosity in the flow path is normal, such as immediately after suction recovery during operation after shipping.

[0062] Next, in S103, the second energy generating elements 24 are driven to perform circulation driving. The driving of the second energy generating elements 24 is controlled by the CPU 800, which is the control unit. By driving the second energy generating elements 24, a circulation flow 27 is formed in the individual flow path 23, and the ink circulates.

[0063] Next, in S104, the first energy generating element 14 is driven to perform concentration detection driving. The driving of the first energy generating element 14 is controlled by the CPU 800 in the same manner as the second energy generating element 24.

[0064] Next, in S105, the temperature detection element 34 is driven, and the temperature detection element 34 detects the temperature T1. After that, in S106, the CPU 800 acquires the temperature T1 at the detection timing detected by the temperature detection element 34.

[0065] Next, in S107, the CPU 800 compares the threshold value T0 set in S102 with the temperature T1 acquired in S106, and determines whether the viscosity in the flow path is normal based on the comparison result. Specifically, in S107, it is determined whether T1≦T0. If T1≦T0 in S107, that is, the determination result is YES, the process proceeds to S108, where it is determined that the viscosity in the flow path is normal and circulation amount control is terminated. On the other hand, if T1>T0 in S107, that is, the determination result is NO, the process proceeds to S109, where it is determined that the viscosity in the flow path has increased.

[0066] If it is determined in S109 that there is thickening in the flow path, it is determined that the circulation amount to eliminate concentration in the individual flow path 23 is still insufficient, and in S110, the second energy generating element 24 is driven to perform additional circulation drive. After the additional circulation drive is performed, the process returns to S104, and concentration detection drive is performed again. Note that when circulation is performed with the second energy generating element 24, a small amount of circulation occurs with each drive, and the circulation amount increases proportionally depending on the number of drives, so it is preferable to perform additional drives a certain number of times before returning to S104.

[0067] In the first embodiment, in S107, the acquired temperature T1 is compared with a single threshold value T0 at the detection timing. This is important from the perspective of judgment accuracy because it allows a wider range of threshold values ​​to be set. This is because it improves robustness against variations in the nozzle dimensions during manufacture and variations in the ink properties due to changes in the ink over time.

[0068] In the first embodiment, an individual flow path 23 is formed corresponding to each ejection port 11, and a first energy generating element 14, a second energy generating element 24, and a temperature detecting element 34 are provided, so that the circulation amount can be controlled for each ejection port 11. The concentration state of ink in the individual flow path 23 varies depending on the frequency of use of the ejection port 11 (ink ejection frequency), etc. However, according to the configuration of the first embodiment, circulation drive is performed appropriately for each ejection port 11, and it is possible to suppress the progress of concentration due to an excessive circulation amount in each individual flow path 23.

[0069] In the first embodiment, the temperature information detected by the temperature detection element 34 is directly compared with the threshold value at the detection timing, but the present invention is not limited to this configuration. Since a feature point where a sudden temperature change occurs is used, the feature point may be emphasized by, for example, first-order or second-order differentiation of the temperature change over time, before being compared with the threshold value T0.

[0070] Furthermore, in Example 1, the determination was made by comparing the detection timing with a threshold value. On the other hand, whether the viscosity in the flow path is normal or has increased may be determined by utilizing the fact that the time at which a characteristic point appears differs depending on whether the viscosity in the flow path is normal or has increased. Specifically, the time at which a characteristic point appears (for example, the time from the start of circulation drive) may be detected, and whether the viscosity in the flow path is normal or has increased may be determined from the time difference from the time at which the characteristic point appears in the normal case. In this case, if there is no time difference or the time difference is less than a predetermined threshold, it can be determined that the viscosity in the flow path is normal, and if there is a time difference or the time difference is equal to or greater than a predetermined threshold, it can be determined that the viscosity in the flow path has increased.

[0071] Alternatively, it may be possible to determine whether the viscosity in the flow path is normal or has increased by utilizing the transition from the elimination of concentration (viscosity decrease) to the increase in viscosity (viscosity increase) as the concentration is circulated. Specifically, the time when the characteristic point occurs during the latest concentration detection drive and the time when the characteristic point occurs during the previous concentration detection drive may be determined. Alternatively, the time difference between the time when the concentration is reduced and the time when the viscosity is increased may be used. In this case, if there is no time difference or the time difference is less than a predetermined threshold, it is determined that the deconcentration in the flow path has been completed and the viscosity in the flow path is normal, and if there is a time difference or the time difference is equal to or greater than a predetermined threshold, it is determined that the concentration is being reduced and the viscosity in the flow path has increased. In this way, the determination of whether the viscosity in the flow path is normal or has increased can be made based on the detection result of the temperature detection element 34, and it is not necessarily necessary to use the detection result (temperature information) as is.

[0072] 6(a) to 6(f) are explanatory diagrams of a drive sequence including ejection drive and circulation drive. In FIGS. 6(a) to 6(f), the horizontal axis represents time, and the drive timings of the ejection drive and circulation drive are indicated by vertical lines (solid lines) on the axis. Also, the timing of performing the concentration detection drive is indicated by vertical lines (dotted lines) on the ejection drive axis. In other words, the timing of driving the first energy generating element 14 is indicated on the ejection drive axis, and the timing of driving the second energy generating element 24 is indicated on the circulation drive axis.

[0073] 6(a) and 6(b) are drive sequence diagrams according to a comparative example, and FIGS. 6(c), 6(d), 6(e), and 6(f) are drive sequence diagrams according to the first embodiment.

[0074] Fig. 6(a) shows a drive sequence of circulatory drive (hereafter referred to as back-end drive) in which circulatory operation is performed a specific number of times at a specific frequency just before the end of a pause in ejection drive. Fig. 6(b) shows a drive sequence of circulatory drive (hereafter referred to as intermittent drive) in which circulatory operation is performed a specific number of times at a specific frequency intermittently at regular intervals while ejection drive is paused.

[0075] In the methods of these comparative examples, it is necessary to determine the drive timing, the number of drives, etc. in advance, and therefore it is necessary to set the circulation amount including an excess amount that takes into account the ejection history of each nozzle and variations in the circulation amount. When the circulation amount is set in this way, there is a risk that the circulation amount will be excessive, exceeding the circulation amount necessary to eliminate concentration. As a result, the excessive circulation amount, which is specific to microcirculation, may cause concentration to progress in the individual flow paths.

[0076] On the other hand, according to the configuration of the first embodiment, the concentration detection drive is performed, and the drive timing and the number of drives of the circulation drive can be determined based on the detection result and the determination result. Below, an exemplary drive sequence in which the concentration detection drive is performed and the circulation drive is performed based on the result will be described.

[0077] FIG. 6(c) shows an example of performing concentration detection drive in the drive sequence for rear-loading drive. In this example, after performing circulation drive a certain number of times, concentration detection drive is performed, and the determination result is fed back to the circulation drive. If it is determined that concentration has been resolved, the circulation drive is terminated and control can be performed to prevent unnecessary circulation drive. On the other hand, if it is determined that concentration has not been sufficiently resolved, additional circulation drive is performed to increase the circulation amount and resolve the concentration of ink in the flow path. FIG. 6(c) shows an example in which it is determined that concentration has not been sufficiently resolved in the first concentration detection drive, additional circulation drive is performed multiple times, and it is determined that concentration has been resolved in the second concentration detection drive. The circulation amount control parameter can be adjusted by reducing the number of times the second energy generating element 24 is driven.

[0078] FIG. 6(d) shows an example of performing concentration detection drive in an intermittent drive drive sequence. In this example, after repeating circulatory drives intermittently, concentration detection drive is performed, and the judgment result is fed back to the circulatory drive. Even in such a case, it is possible to determine whether or not to perform subsequent circulatory drives and the number of drives based on the judgment result. In this case, parameters that can be used to control the amount of circulation include the number of drives of the second energy generating element 24, the time interval between circulatory drives, and whether or not to perform the next circulatory drive in intermittent circulatory drives. FIG. 6(d) shows the first concentration detection drive in a drive sequence in which circulatory drives are performed intermittently four times. An example is shown in which the number of drives is reduced to two based on the determination results after the drive.

[0079] 6(e) shows an example of a drive sequence for rear-loading drive in which concentration detection drive is performed before circulation drive. When such a sequence is selected, the concentrated state before circulation is detected, circulation drive is performed according to the result of the concentrated state, and the state in which the concentration is being eliminated is detected and the circulation amount can be controlled.

[0080] 6(f) shows an example of an intermittent drive sequence in which the concentration detection drive is performed before the first circulation drive. Even in this case, the concentration state of the ink in the flow path can be detected and the circulation amount can be controlled according to that concentration state.

[0081] As described above, according to the configuration of the first embodiment, the concentrated state of ink in the flow path can be detected by determining whether a temperature drop based on the characteristic point has occurred at a detection timing based on when the viscosity in the flow path is normal during the temperature drop process, based on the detection result of the temperature detection element 34. Then, by feeding back the detection result to the circulation drive, the drive of the second energy generating element 24 can be controlled to prevent the circulation amount from becoming excessive, thereby performing the circulation drive. This makes it possible to suppress the circulation amount at each ejection port 11 (nozzle), and to suppress the progression of concentration in the individual flow path 23 due to an excessive circulation amount. Furthermore, since the time during which the effects of concentration are suppressed can be maximized, the maintenance time and amount of waste ink required for suction recovery operations to eliminate the effects of concentration can be reduced.

[0082] Furthermore, in the configuration of Example 1, the temperature detection element 34 is provided directly below the first energy generating element 14, so it is also possible to perform ejection detection, which detects whether ink has been ejected normally, using the temperature detection element 34. This utilizes the fact that the time it takes for characteristic points associated with defoaming and the like to appear differs between normal ejection and ejection failure due to ejection defects. Therefore, ejection detection and circulation amount control can be performed using the same temperature detection element.

[0083] In the first embodiment, the temperature detection element 34 is provided directly below the first energy generating element 14, but the configuration is not limited to this. The temperature detection element 34 is installed for the purpose of detecting temperature changes in the vicinity when the first energy generating element 14 is driven for concentration detection, and therefore may be disposed in a position corresponding to the first energy generating element 14, such as directly above or in close proximity to the first energy generating element 14. Furthermore, instead of providing the temperature detection element 34 independently, an element having both the energy generation function of the first energy generating element 14 and the temperature detection function of the temperature detection element 34 may be disposed.

[0084] <Example 2> Next, a second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in the position of the temperature detection element 34. Only the differences between the configuration of the second embodiment and the configuration of the first embodiment will be described below. The same reference numerals will be used to designate the same components in the second embodiment as those in the first embodiment, and descriptions thereof will be omitted.

[0085] 7 is an explanatory diagram of the configuration in the vicinity of the ejection port 11 of the liquid ejection chip 3 according to Example 2, and is a cross-sectional view taken along the line AA in FIG. 4(a). The plan view of the liquid ejection chip 3 according to Example 2 when viewed in the Z direction and the enlarged schematic diagram of the individual flow path portion are the same as those in FIGS. 4(a) and 4(c) of Example 1.

[0086] In the first embodiment, electrothermal converting elements are used as the first energy generating elements 14 and the second energy generating elements 24. Note that the first energy generating elements 14 may be other elements such as piezoelectric elements.

[0087] In Example 2, the temperature detection element 34 is disposed at a position overlapping the second energy generating element 24 when viewed in the Z direction. As shown in Fig. 7 , the temperature detection element 34 is disposed directly below the second energy generating element 24, that is, on the side farther away from the second energy generating element 24 with respect to the individual flow paths 23. Note that the temperature detection element 34 does not necessarily have to be disposed directly below the second energy generating element 24, and may be disposed at a position corresponding to the second energy generating element 24.

[0088] 8 is a flowchart showing circulation amount control according to Example 2. The circulation amount control according to Example 2 has many points in common with the circulation amount control according to Example 1, so the following description will focus on the differences from Example 1.

[0089] First, in step 101, the concentration detection drive conditions to be applied to the second energy generating element 24 are referenced, and the detection timing is set in advance to a characteristic point when the viscosity inside the flow path is normal. In other words, the detection timing is the timing when the temperature of the individual flow path 23 drops sharply due to the drive of the second energy generating element 24 when the viscosity of the ink inside the individual flow path 23 is normal. However, the detection timing is not limited to this, and may be set appropriately within the range in which the temperature of the individual flow path 23 drops.

[0090] 8, in the second embodiment, the concentration detection drive in S104 in the first embodiment is omitted. This is because the second energy generating element 24 is driven and the concentration detection drive is also performed by performing the circulation drive in S103. Therefore, after the circulation drive and the concentration detection drive are performed in S103, the process proceeds to S105, where the temperature is output from the temperature detection element 34.

[0091] Furthermore, in Example 2, the sequence of additionally performing circulation drive in S110 after determining in S109 that there is an increase in viscosity in the flow path is omitted. This is because circulation drive is also performed when concentration detection drive is performed in S103. Therefore, after determining in S109 that there is an increase in viscosity in the flow path, the process returns to S103, and circulation drive and concentration detection drive are performed simultaneously.

[0092] 9(a) and 9(b) are explanatory diagrams of a drive sequence including a discharge drive and a circulation drive according to Example 2. In Figures 9(a) and 9(b), the horizontal axis represents time, and the drive timings of the discharge drive and the circulation drive are indicated by vertical lines (solid lines) on the axis. In Example 2, the drive timing of the circulation drive is synonymous with the drive timing of the concentration detection drive.

[0093] FIG. 9(a) shows an example in which concentration detection drive is performed in the drive sequence of rear-filling drive. In this example, circulation drive is performed immediately before discharge drive. In Example 2, concentration detection drive is performed together with circulation drive. Then, based on the determination result of concentration detection drive, the number of subsequent circulation drives and concentration detection drives can be determined, and the circulation amount can be adjusted.

[0094] 9(b) shows an example of performing concentration detection drive in an intermittent drive drive sequence. In this example, circulation drive is performed intermittently multiple times or once. FIG. 9(b) shows an example in which the number of circulation drive drives gradually decreases from four times to two times, and then from two times to one time.

[0095] In the configuration of Example 2, as in Example 1, concentration detection drive can be performed to control the circulation amount. Therefore, the concentration state of the ink in the flow path is detected based on the detection result of the temperature detection element 34, and the detection result is fed back to the circulation drive, thereby controlling the drive of the second energy generation element 24 to perform the circulation drive so that the circulation amount does not become excessive. This makes it possible to suppress the circulation amount in each nozzle, and to suppress the progression of concentration in the individual flow paths 23 due to an excessive circulation amount.

[0096] Furthermore, by placing the temperature detection element 34 at a position corresponding to the second energy generating element 24, the following advantages are obtained. First, by driving the second energy generating element 24, it is possible to simultaneously perform concentration detection drive and circulation drive. This makes it possible to detect concentration for each circulation drive, enabling fine control of the circulation amount. Furthermore, because the circulation drive does not result in ink ejection, it is possible to detect viscosity by applying drive pulses used for normal circulation, improving detection sensitivity.

[0097] Example 3 Next, a third embodiment of the present invention will be described. The third embodiment differs from the first embodiment in the shape of the individual flow paths 23. Only the differences between the configuration of the third embodiment and the configuration of the first embodiment will be described below. The same reference numerals will be used to designate the same components in the third embodiment as those in the first embodiment, and the description thereof will be omitted.

[0098] 10(a) to 10(c) are explanatory diagrams of the flow path configuration of the liquid ejection chip 3 according to Example 3. FIG. 10(a) is an explanatory diagram of the configuration in the vicinity of the ejection orifice 11 of the liquid ejection chip 3, and is a schematic diagram showing the positional relationship of the main components when the liquid ejection chip 3 is viewed in the Z direction. FIG. 10(a) shows only one ejection orifice row in which a plurality of ejection orifices 11 are aligned in the Y direction. FIG. 10(b) is a BB cross-sectional view of FIG. 10(a). FIG. 10(c) is a schematic diagram showing an enlarged view of the individual flow path section in FIG. 10(a). In FIG. 10(a), in order to show the positional relationship of the main components, the first energy generating element 14 and the second energy generating element 24 are shown with hatching similar to that in FIG. 10(b), and the ejection orifice 11 is shown with a solid line.

[0099] The individual flow paths 23 in Example 3 are formed in a straight line as shown in Fig. 10(c). Hereinafter, this type of flow path shape will be referred to as a straight type. The straight type individual flow paths 23 are formed in a straight line so as to extend in the X direction from the inlet 25 to the outlet 26. That is, the inlet 25 is located at one end of the individual flow path 23 in the X direction, and the outlet 26 is located at the other end of the individual flow path 23 in the X direction.

[0100] The first energy generating element 14 is disposed at a position overlapping with the ejection port 11 and the individual flow path 23 (pressure chamber 13) when viewed in the Z direction, and on the side closer to the outlet 26 in the X direction. The second energy generating element 24 is disposed at a position overlapping with the individual flow path 23 when viewed in the Z direction, and on the side closer to the inlet 25 in the X direction. In addition, the temperature detecting element 34 is disposed at a position overlapping with the first energy generating element 14 when viewed in the Z direction. When the second energy generating element 24 is driven, a circulating flow 27 of ink is formed in the individual flow path 23 in a direction from the inlet 25 toward the outlet 26 (to the right in FIG. 10(a)), and the ink in the individual flow path 23 circulates.

[0101] The substrate 18 has a supply opening 22 formed upstream in the direction of liquid circulation in the individual flow channels 23, and a recovery opening 28 formed downstream. The supply opening 22 and the recovery opening 28 are each connected to the common flow channel 15. The substrate 18 also has a common liquid chamber 29 formed therein that is connected to the supply opening 22 and the recovery opening 28 and into which ink supplied from the ink tank 54 flows. Therefore, by driving the second energy generating element 24, the ink can be circulated so that it passes through the common liquid chamber 29, supply opening 22, common flow channel 15, individual flow channels 23, common flow channel 15, recovery opening 28, and common liquid chamber 29 in that order. Circulating the ink in this manner can achieve the effect of eliminating ink concentration, as in Examples 1 and 2.

[0102] In the straight type, the outlet 26 and the inlet 25 of the individual flow path 23 are spaced apart, so compared to the U-shape type, the concentrated ink evaporated at the ejection port is less likely to re-flow into the individual flow path 23. However, even in the configuration of Example 3, the concentrated ink evaporated at the ejection port is less likely to re-flow into the individual flow path 23. The fact remains that the liquid remains in the common liquid chamber 29 connected to the individual flow paths 23. Therefore, if excessive circulation is performed, the progress of concentration in the entire flow path including the individual flow paths 23 and the common liquid chamber 29 remains an issue. Therefore, in order to suppress the progress of concentration in the flow path due to circulation, it is preferable to control the circulation amount so as not to circulate more than necessary.

[0103] In the configuration of Example 3, too, concentration detection drive can be performed and circulation amount control can be performed in the same manner as in Example 1. Therefore, the concentration state of the ink in the flow path is detected based on the detection result of the temperature detection element 34, and the detection result is fed back to the circulation drive, thereby controlling the drive of the second energy generation element 24 to prevent the circulation amount from becoming excessive, thereby performing circulation drive. This makes it possible to suppress the circulation amount in each nozzle, and to suppress the progression of concentration in the individual flow paths 23 due to an excessive circulation amount.

[0104] An advantage of making the individual flow paths 23 straight is that, because the circulation inlet 25 and outlet 26 are located apart, concentrated ink that has evaporated at the ejection port is less likely to re-flow into the individual flow paths 23. This makes it possible to focus solely on eliminating concentration in the common liquid chamber 29 due to excessive circulation.

[0105] Example 4 Next, a fourth embodiment of the present invention will be described. The fourth embodiment differs from the third embodiment in the position of the temperature detection element 34. Only the differences between the configuration of the fourth embodiment and the configuration of the third embodiment will be described below. The same reference numerals will be used to designate the same components in the fourth embodiment as those in the third embodiment, and descriptions thereof will be omitted.

[0106] 11 is an explanatory diagram of the configuration in the vicinity of the ejection port 11 of the liquid ejection chip 3 according to Example 4, and is a cross-sectional view taken along the line BB in FIG. 10(a). The plan view of the liquid ejection chip 3 according to Example 4 when viewed in the Z direction and the enlarged schematic diagram of the individual flow path portion are the same as those in FIGS. 10(a) and 10(c) of Example 3.

[0107] In Example 4, the temperature detection element 34 is disposed at a position overlapping the second energy generating element 24 when viewed in the Z direction. As shown in Fig. 11 , the temperature detection element 34 is disposed directly below the second energy generating element 24, that is, on the side farther from the second energy generating element 24 with respect to the individual flow paths 23. Note that the temperature detection element 34 does not necessarily have to be disposed directly below the second energy generating element 24, and may be disposed at a position corresponding to the second energy generating element 24.

[0108] In the configuration of Example 4, concentration detection driving can be performed and circulation amount control can be performed in the same manner as in Example 2. Therefore, the concentration state of the ink in the flow path is detected based on the detection result of the temperature detection element 34, and the detection result is fed back to the circulation drive, thereby controlling the drive of the second energy generation element 24 so that the circulation amount does not become excessive, thereby performing circulation drive. This makes it possible to suppress the circulation amount in each nozzle, and to suppress the progression of concentration in the individual flow paths 23 due to excessive circulation amount. Furthermore, because the individual flow paths 23 are straight, the same advantages as in Example 3 can be obtained.

[0109] <Example 5> Next, a fifth embodiment of the present invention will be described. The fifth embodiment differs from the first and third embodiments in the shape of the individual flow paths 23. Only the differences between the configuration of the fifth embodiment and the configuration of the third embodiment will be described below. The same reference numerals will be used to designate the same components in the fifth embodiment as those in the third embodiment, and the description thereof will be omitted.

[0110] 12(a) and 12(b) are explanatory diagrams of the flow path configuration of the liquid ejection chip 3 according to the fifth embodiment. FIG. 12(a) is an explanatory diagram of the configuration near the ejection orifice 11 of the liquid ejection chip 3, and is a schematic diagram showing the positional relationship of the main components when the liquid ejection chip 3 is viewed in the Z direction. FIG. 12(a) shows only one ejection orifice row in which multiple ejection orifices 11 are lined up in the Y direction. FIG. 12(b) is a cross-sectional view taken along CC in FIG. 12(a). In FIG. 12(a), in order to show the positional relationship of the main components, the first energy generating element 14 and the second energy generating element 24 are shown with the same hatching as in FIG. 12(b), and the ejection orifice 11 is shown with a solid line.

[0111] The individual flow paths 23 in Example 5 are straight and are formed so as to branch into two on the way from the inlet 25 to the outlet 26. The individual flow path 23 has one inlet 25 located at one end side in the X direction and two outlets 26 located at the other end side in the X direction, and two pressure chambers 13 (discharge ports 11) are connected to one individual flow path 23. In addition, two first energy generating elements 14 and one second energy generating element 24 are provided on the substrate 18 for one individual flow path 23.

[0112] The first energy generating elements 14 are provided corresponding to each of the bifurcated flow paths, and are positioned so as to overlap the ejection ports 11 and the individual flow paths 23 (pressure chambers 13) when viewed in the Z direction, and are disposed on the side closer to the outlet 26 in the X direction. The second energy generating elements 24 are provided in a portion that is not bifurcated, and are positioned so as to overlap the individual flow paths 23 when viewed in the Z direction, and are disposed on the side closer to the inlet 25 in the X direction. When the second energy generating elements 24 are driven, a circulating flow 27 of ink is formed in the individual flow paths 23 in a direction from the inlet 25 toward the outlet 26 (to the right in FIG. 12(a)), and the ink in the individual flow paths 23 circulates.

[0113] Furthermore, in Example 5, one temperature detection element 34 is provided corresponding to one individual flow path 23. The temperature detection element 34 is disposed at a position overlapping one first energy generating element 14 when viewed in the Z direction. In other words, a temperature detection element 34 is not provided corresponding to every first energy generating element 14.

[0114] In the configuration of Example 5, concentration detection drive can be performed and circulation amount control can be carried out in the same manner as in Example 1. Therefore, the concentration state of the ink in the flow path is detected based on the detection result of the temperature detection element 34, and the detection result is fed back to the circulation drive, thereby controlling the drive of the second energy generation element 24 to perform circulation drive so that the circulation amount does not become excessive. This makes it possible to suppress the circulation amount in each nozzle, and to suppress the progression of concentration in the individual flow paths 23 due to an excessive circulation amount.

[0115] An advantage of associating two ejection ports 11 and two first energy generating elements 14 with one individual flow path 23 is that it is possible to detect ink concentration and control the circulation amount based on the detection result of one temperature detecting element 34 for the two ejection ports 11. It is also possible to reduce the number of second energy generating elements 24 and temperature detecting elements 34 for the first energy generating elements 14. However, even in this configuration, a temperature detecting element 34 may be provided corresponding to each first energy generating element 14.

[0116] Example 6 Next, a sixth embodiment of the present invention will be described. The sixth embodiment differs from the fifth embodiment in the position of the temperature detection element 34. Only the differences between the configuration of the sixth embodiment and the configuration of the fifth embodiment will be described below. The same reference numerals will be used to designate the same components in the sixth embodiment as those in the fifth embodiment, and the description thereof will be omitted.

[0117] FIG. 13 is an explanatory diagram of the configuration of the vicinity of the ejection port 11 of the liquid ejection chip 3 according to the sixth embodiment; 12(a) is a cross-sectional view taken along CC line in Fig. 12. The plan view of the liquid ejection chip 3 according to Example 6 when viewed in the Z direction and the enlarged schematic view of the individual flow path portion are the same as those in Figs. 12(a) and 12(c) of Example 5.

[0118] In Example 6, the temperature detection element 34 is disposed at a position overlapping the second energy generating element 24 when viewed in the Z direction. As shown in Fig. 13 , the temperature detection element 34 is disposed directly below the second energy generating element 24, that is, on the side farther away from the second energy generating element 24 with respect to the individual flow paths 23. Note that the temperature detection element 34 does not necessarily have to be disposed directly below the second energy generating element 24, and may be disposed at a position corresponding to the second energy generating element 24.

[0119] In other words, the configuration of Example 6 differs from the configuration of Example 4 in that, in one individual flow path 23, one second energy generating element 24 corresponds to (is connected to) two first energy generating elements 14.

[0120] In the configuration of Example 6, concentration detection driving can be performed and circulation amount control can be performed in the same manner as in Example 2. Therefore, the concentration state of ink in the flow path is detected based on the detection result of the temperature detection element 34, and the detection result is fed back to the circulation drive, thereby controlling the drive of the second energy generating element 24 so that the circulation amount does not become excessive, thereby performing circulation drive. This makes it possible to suppress the circulation amount in each nozzle, and to suppress the progression of concentration in the individual flow paths 23 that would be caused by an excessive circulation amount. Furthermore, since two ejection ports 11 and two first energy generating elements 14 can be associated with one individual flow path 23, the same advantages as in Example 5 can be obtained.

[0121] Example 7 Next, a seventh embodiment of the present invention will be described. The seventh embodiment differs from the first and second embodiments in the method of controlling the circulation amount. Only the differences between the configuration of the seventh embodiment and the configuration of the second embodiment will be described below. The same reference numerals will be used to designate the same components in the seventh embodiment as those in the second embodiment, and the description thereof will be omitted.

[0122] Example 7 differs from the above-described examples in that circulation volume control is completed within the liquid ejection head 1. In Example 7, the temperature detection element 34 is provided at a position corresponding to the second energy generation element 24, and a control unit constituted by a CPU or the like is provided in the liquid ejection head 1. In other words, the configuration of the liquid ejection chip 3 is the same as any of Examples 2, 4, and 6 described above.

[0123] In the seventh embodiment, the liquid ejection head 1 is configured to be able to control the amount of ink circulation based on viscosity information (temperature information) in the individual flow paths 23. Fig. 14 is a flowchart of the circulation amount control according to the seventh embodiment.

[0124] First, in S201, the second energy generating element 24 is driven to perform circulatory driving. Since the temperature detecting element 34 is arranged corresponding to the second energy generating element 24, when circulatory driving is performed, concentration detecting driving can also be performed at the same time.

[0125] Next, in S202, the temperature detection element is driven, and the temperature detection element detects the temperature T11. After that, in S203, the control unit of the liquid ejection head 1 acquires the temperature T11 at the detection timing detected by the temperature detection element .

[0126] Next, in S204, the second energy generating element 24 is driven, and the circulation drive and the concentration detection drive are performed again. Then, in S205, the temperature detecting element 34 is driven, and the temperature detecting element 34 detects the temperature Thereafter, in S206, the control unit of the liquid ejection head 1 acquires the temperature T12 at the detection timing detected by the temperature detection element .

[0127] Next, in S207, the control unit obtains the temperature T11 obtained in S203 and the temperature T12 obtained in S206, and determines whether T12≦T11. If T12≦T11 in S207, that is, the determination result is YES, it determines that the viscosity in the flow path is normal, and the circulation amount control ends. On the other hand, if T12>T11 in S207, that is, the determination result is NO, it determines that the viscosity in the flow path has increased, and proceeds to S208.

[0128] In S208, T11 is rewritten as T12, that is, the value of temperature T11 is rewritten as the value of temperature T12, and the process then proceeds to S204, where the circulation drive is performed again.

[0129] Thus, in the seventh embodiment, the detected temperature (temperature T11) during the circulatory drive in steps S201 to S203 is compared with the detected temperature (temperature T12) during the circulatory drive in steps S204 to S206 in step S207. Furthermore, if it is determined in step S207 that T12 is greater than T11, the detected temperature during the first circulatory drive in steps S204 to S206 is compared with the detected temperature during the second circulatory drive in steps S204 to S206 in step S207. In other words, in the seventh embodiment, the second energy generating element 24 is driven and circulatory drive is performed based on the detected temperatures detected by the temperature detecting element 34 before and after driving the second energy generating element 24. By comparing the detected temperatures before and after the circulation in this way, it is possible to determine whether to continue or end the circulation and control the circulation amount. Such temperature comparisons can be implemented by incorporating a comparison circuit into the liquid ejection head 1.

[0130] As described above, even in the configuration of Example 7, concentration detection drive can be performed and circulation amount control can be performed. Therefore, the concentration state of the ink in the flow path is detected based on the detection result of the temperature detection element 34, and the detection result is fed back to the circulation drive, thereby controlling the drive of the second energy generation element 24 to perform circulation drive so that the circulation amount does not become excessive. This makes it possible to suppress the circulation amount in each nozzle, and to suppress the progression of concentration in the individual flow paths 23 due to an excessive circulation amount.

[0131] The advantage of completing the circulation control within the liquid ejection head 1 is that the circulation amount can be controlled by the liquid ejection head 1 alone, without incurring the load associated with data exchange between the liquid ejection head 1 and the liquid ejection device 50.

[0132] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) a flow path forming portion having an ejection port from which a liquid is ejected, a pressure chamber communicating with the ejection port, and an individual flow path communicating with the pressure chamber; a first energy generating element provided at a position corresponding to the pressure chamber of the flow path forming portion, the first energy generating element generating energy for ejecting liquid from the ejection port; a second energy generating element provided at a position corresponding to the individual flow path of the flow path forming portion, the second energy generating element generating energy for causing liquid to flow through the individual flow path; a temperature detection unit that detects the temperature of at least one of the individual flow paths and the pressure chambers; a control unit that controls driving of the second energy generating element based on a detection result of the temperature detection unit; A liquid ejection device comprising: (Configuration 2) The liquid ejection device described in configuration 1, characterized in that the control unit controls the driving of the second energy generating element based on the comparison result between the detected temperature detected by the temperature detection unit and a predetermined threshold value. (Configuration 3) The liquid ejection device according to configuration 1, wherein the control unit controls the driving of the second energy generating element based on the time during which the temperature detected by the temperature detection unit changes suddenly. (Configuration 4) The liquid ejection device described in configuration 1, characterized in that the control unit controls the driving of the second energy generating element based on the respective detected temperatures detected by the temperature detection unit before and after driving the second energy generating element. (Configuration 5) the first energy generating element is disposed at a position overlapping the ejection port in a first direction, 5. The liquid ejection device according to any one of configurations 1 to 4, wherein the temperature detection unit is disposed at a position overlapping the first energy generating element in the first direction. (Configuration 6) The liquid ejection device described in configuration 5 is characterized in that the control unit is configured to be able to perform a concentration detection drive that drives the first energy generating element to detect concentration of liquid in the individual flow path, and controls the drive of the first energy generating element so that the amount of energy generated by the first energy generating element during the concentration detection drive is smaller than during the ejection drive that ejects liquid from the ejection port. (Configuration 7) The liquid ejection device described in configuration 5, characterized in that the temperature detection unit detects the temperature of the individual flow path at the timing when the temperature of the individual flow path suddenly drops due to the driving of the first energy generating element when the viscosity of the liquid inside the individual flow path is normal. (Configuration 8) the first energy generating element is disposed at a position overlapping the ejection port in a first direction, 5. The liquid ejection device according to any one of configurations 1 to 4, wherein the temperature detection unit is disposed at a position overlapping the second energy generating element in the first direction. (Configuration 9) The liquid ejection device described in configuration 8, characterized in that the temperature detection unit detects the temperature of the individual flow path at the timing when the temperature of the individual flow path suddenly drops due to the driving of the second energy generating element when the viscosity of the liquid inside the individual flow path is normal. (Configuration 10) the first energy generating element and the second energy generating element are provided at positions corresponding to the individual flow paths, A liquid ejection device described in any one of configurations 1 to 9, characterized in that the individual flow path is formed in a U-shape from a position corresponding to the second energy generating element to a position corresponding to the first energy generating element. (Configuration 11) the first energy generating element and the second energy generating element are disposed at positions overlapping the individual flow paths in a first direction, 11. The liquid ejection device according to configuration 10, wherein the inlet and outlet of the individual flow path are adjacent to each other in a second direction that intersects with the first direction. (Configuration 12) the first energy generating element and the second energy generating element are provided at positions corresponding to the individual flow paths, A liquid ejection device described in any one of configurations 1 to 9, characterized in that the individual flow path is formed in a straight line from a position corresponding to the second energy generating element to a position corresponding to the first energy generating element. (Configuration 13) the first energy generating element and the second energy generating element are provided at positions corresponding to the individual flow paths, A liquid ejection device described in any one of configurations 1 to 9, characterized in that the individual flow path is formed by branching into two from a position corresponding to the second energy generating element to a position corresponding to the first energy generating element. (Configuration 14) The liquid ejection device according to any one of configurations 1 to 13, wherein the flow path forming portion includes a plate member in which the ejection port is formed and which constitutes a part of the inner wall of the individual flow path, and a substrate connected to the plate member and which constitutes a part of the inner wall of the individual flow path. (Configuration 15) a liquid ejection head having the flow path forming portion and provided with the first energy generating element, the second energy generating element, and the temperature detecting portion; a conveying unit that conveys a recording medium at a position facing the ejection opening; 15. The liquid ejection device according to any one of configurations 1 to 14, further comprising: (Configuration 16) 16. The liquid ejection device according to any one of configurations 1 to 15, wherein at least one of the first energy generating element and the second energy generating element is an electrothermal converting element. (Configuration 17) a flow path forming portion having an ejection port from which a liquid is ejected, a pressure chamber communicating with the ejection port, and an individual flow path communicating with the pressure chamber; a first energy generating element provided at a position corresponding to the pressure chamber of the flow path forming portion, the first energy generating element generating energy for ejecting liquid from the ejection port; a second energy generating element provided at a position corresponding to the individual flow path of the flow path forming portion, the second energy generating element generating energy for causing liquid to flow through the individual flow path; a temperature detection unit that detects the temperature of at least one of the individual flow paths and the pressure chambers; a control unit that controls driving of the second energy generating element based on a detection result of the temperature detection unit; A liquid ejection head comprising: [Explanation of symbols]

[0133] 3...liquid ejection chip (flow path forming portion), 11...ejection port, 13...pressure chamber, 14...first energy generating element, 23...individual flow path (circulation flow path), 24...second energy generating element, 34...temperature detecting element (temperature detecting portion), 50...liquid ejection device, 800...CPU (control portion)

Claims

1. a flow path forming portion having an ejection port from which a liquid is ejected, a pressure chamber communicating with the ejection port, and an individual flow path communicating with the pressure chamber; a first energy generating element provided at a position corresponding to the pressure chamber of the flow path forming portion, the first energy generating element generating energy for ejecting liquid from the ejection port; a second energy generating element provided at a position corresponding to the individual flow path of the flow path forming portion, the second energy generating element generating energy for causing liquid to flow through the individual flow path; a temperature detection unit that is disposed at a position corresponding to the first energy generating element or the second energy generating element and detects a temperature; a control unit that controls driving of the second energy generating element based on a detection result of the temperature detection unit; A liquid ejection device comprising:

2. The liquid ejection device according to claim 1 , wherein the control unit controls the driving of the second energy generating element based on a comparison result between the detected temperature detected by the temperature detection unit and a predetermined threshold value.

3. The liquid ejection device according to claim 1 , wherein the control unit controls the driving of the second energy generating elements based on the time period during which the temperature detected by the temperature detection unit changes suddenly.

4. The liquid ejection device according to claim 1, wherein the control unit controls the driving of the second energy generating element based on the respective detected temperatures detected by the temperature detection unit before and after driving the second energy generating element.

5. the first energy generating element is disposed at a position overlapping the ejection port in a first direction, The liquid ejection device according to claim 1 , wherein the temperature detection unit is disposed at a position overlapping the first energy generating element in the first direction.

6. The liquid ejection device described in claim 5, characterized in that the control unit is configured to perform a concentration detection drive that drives the first energy generating element to detect concentration of liquid in the individual flow path, and controls the drive of the first energy generating element so that the amount of energy generated by the first energy generating element during the concentration detection drive is smaller than during the ejection drive that ejects liquid from the ejection port.

7. The liquid ejection device described in claim 5, characterized in that the temperature detection unit detects the temperature of the individual flow path at the timing when the temperature of the individual flow path suddenly drops due to the driving of the first energy generating element when the viscosity of the liquid inside the individual flow path is normal.

8. the first energy generating element is disposed at a position overlapping the ejection port in a first direction, The liquid ejection device according to claim 1 , wherein the temperature detection unit is disposed at a position overlapping the second energy generating element in the first direction.

9. The liquid ejection device described in claim 8, characterized in that the temperature detection unit detects the temperature of the individual flow path at the timing when the temperature of the individual flow path suddenly drops due to the driving of the second energy generating element when the viscosity of the liquid inside the individual flow path is normal.

10. the first energy generating element and the second energy generating element are provided at positions corresponding to the individual flow paths, The liquid ejection device according to claim 1 , wherein the individual flow paths are formed in a U-shape from a position corresponding to the second energy generating element to a position corresponding to the first energy generating element.

11. the first energy generating element and the second energy generating element are disposed at positions overlapping the individual flow paths in a first direction, The liquid ejection device according to claim 10 , wherein the inlet and the outlet of the individual flow path are adjacent to each other in a second direction intersecting the first direction.

12. the first energy generating element and the second energy generating element are provided at positions corresponding to the individual flow paths, The liquid ejection device according to claim 1 , wherein the individual flow paths are formed linearly from a position corresponding to the second energy generating element to a position corresponding to the first energy generating element.

13. the first energy generating element and the second energy generating element are provided at positions corresponding to the individual flow paths, The liquid ejection device according to claim 1 , wherein the individual flow paths are bifurcated from a position corresponding to the second energy generating element to a position corresponding to the first energy generating element.

14. The liquid ejection device according to claim 1, characterized in that the flow path forming portion includes a plate member in which the ejection port is formed and which constitutes a part of the inner wall of the individual flow path, and a substrate connected to the plate member and which constitutes a part of the inner wall of the individual flow path.

15. a liquid ejection head having the flow path forming portion and provided with the first energy generating element, the second energy generating element, and the temperature detecting portion; a conveying unit that conveys a recording medium at a position facing the ejection opening; The liquid ejection device according to claim 1 , further comprising:

16. 2. The liquid ejection device according to claim 1, wherein at least one of the first energy generating element and the second energy generating element is an electrothermal conversion element.

17. a flow path forming portion having an ejection port from which a liquid is ejected, a pressure chamber communicating with the ejection port, and an individual flow path communicating with the pressure chamber; a first energy generating element provided at a position corresponding to the pressure chamber of the flow path forming portion, the first energy generating element generating energy for ejecting liquid from the ejection port; a second energy generating element provided at a position corresponding to the individual flow path of the flow path forming portion, the second energy generating element generating energy for causing liquid to flow through the individual flow path; a temperature detection unit that is disposed at a position corresponding to the first energy generating element or the second energy generating element and detects a temperature; a control unit that controls driving of the second energy generating element based on a detection result of the temperature detection unit; A liquid ejection head comprising:

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