Liquid ejecting head, liquid ejecting apparatus, and driving method for liquid ejecting head

Abstract

The present disclosure relates to a liquid ejecting head including a pressure chamber for ejecting a liquid, a first energy generating element for generating energy to eject the liquid, and circulation flow channels each provided with a second energy generating element and having a supply port through which the liquid supplied to the pressure chamber flows in and a discharge port through which the liquid is discharged from the pressure chamber. The liquid from the pressure chamber is discharged through the discharge port, and the pressure chamber is disposed between the supply port and the discharge port. The supply port is located on one side of the pressure chamber, the discharge port is located on the other side of the pressure chamber, and the supply port, the pressure chamber and the discharge port are sequentially arranged. The second energy generating element is provided on a side closer to the supply port than the pressure chamber, and drives the second energy generating element when the first energy generating element is stopped. The present disclosure also relates to a liquid ejecting apparatus and a method for driving a liquid ejecting head.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a liquid ejection head. BACKGROUND

[0002] In a liquid ejection head such as an inkjet recording head, one factor in the degradation of image quality is the concentration of ink (liquid). The progress of evaporation of ink from a nozzle at which ejection has not been performed for a long time causes an increase in the viscosity of the ink, which affects ejection. As a result, the ejection amount and the ejection direction change, resulting in streaks and unevenness in concentration in an image, thereby degrading the image quality.

[0003] In order to prevent the concentration of ink as described above, in recent years, mechanisms for circulating ink within a liquid ejection head have been proposed. By circulating the ink, concentrated ink near a nozzle can be flushed away and fresh ink can be supplied.

[0004] As one means of circulation, there is a method in which an electrothermal transducer is provided within a circulation flow passage. When ink is heated by the electrothermal transducer, a bubble grows due to film boiling of the ink, and during a subsequent contraction process, a flow is generated, urging the ink to circulate within the flow passage. In order to address the thickening of ink at a nozzle portion and to supply fresh ink, it is desirable to circulate the ink continuously. However, if the electrothermal transducer is continuously driven, there is a concern that local heating can hinder bubble generation, resulting in a decrease in flow rate.

[0005] Accordingly, WO 2016-068988 discloses a configuration in which, in a U-shaped circulation flow passage, one energy generating element for ejecting liquid and one electrothermal transducer for transporting liquid within a circulation flow passage including a pressure chamber are continuously arranged within the circulation flow passage, and the electrothermal transducer is intermittently driven to generate an intermittent circulation flow.

[0006] In WO 2016-068988, it is characterized that the electrothermal transducer is intermittently driven in the U-shaped circulation flow passage configuration. In the U-shaped circulation flow passage, since the liquid inflow portion and the outflow portion of the circulation flow passage are arranged close to each other, when intermittently driven, concentrated ink from the outflow portion side is recirculated to the inflow portion, thereby promoting concentration. Therefore, there is a risk that the ejection performance (also referred to as the launch characteristic) of the initial ejection in continuous ejection from a nozzle can deteriorate. SUMMARY

[0007] Accordingly, the present disclosure relates to providing a liquid ejection head capable of further improving the circulation efficiency by inhibiting recirculation concentration of the flow passage configuration and the driving method.

[0008] To address the above problem, the liquid ejection head according to the present disclosure includes:

[0009] a plurality of liquid ejection portions each having a nozzle for ejecting liquid, a pressure chamber, and a first energy generating element for generating energy to eject liquid from the nozzle;

[0010] a plurality of circulation flow channels provided corresponding to the plurality of liquid ejection portions, each having a supply port through which liquid supplied to the pressure chamber flows in, and a discharge port through which liquid collected from the pressure chamber is discharged, the pressure chamber being provided between the supply port and the discharge port; and

[0011] a second energy generating element provided in the circulation flow channel;

[0012] wherein the plurality of liquid ejection portions are arranged in a first direction,

[0013] wherein each of the plurality of circulation flow channels extends in a second direction intersecting the first direction, so that the supply port is located on one side of the pressure chamber in the second direction, the discharge port is located on the other side of the pressure chamber in the second direction, and the supply port, the pressure chamber, and the discharge port are arranged in the second direction in this order,

[0014] wherein the second energy generating element is provided in the circulation flow channel closer to the side of the supply port than to the pressure chamber,

[0015] wherein the second energy generating element is driven a plurality of times at a first time interval between a first timing at which the first energy generating element is driven and a second timing at which the first energy generating element is next driven after the first timing, and

[0016] wherein a third time interval between the first timing and a third timing at which the second energy generating element is next driven after the first timing includes a cycle generation operation that is greater than the first time interval.

[0017] Further, to solve the above-described problems, a liquid ejection apparatus according to the present disclosure includes:

[0018] a liquid ejection head according to the present disclosure; and

[0019] a control portion for controlling driving of the second energy generating element,

[0020] wherein the control portion drives the second energy generating element when driving of the first energy generating element is stopped.

[0021] The features of the present disclosure will become apparent from the following description of the embodiments with reference to the accompanying drawings. The following description of embodiments is given by way of example only. BRIEF DESCRIPTION OF DRAWINGS

[0022] FIG. 1A is a perspective view showing a configuration of the first embodiment of the liquid ejecting apparatus in which the main ink tank is provided in the apparatus body and the sub-ink tank is provided in the liquid ejecting head.

[0023] FIG. 1B is a perspective view showing a configuration example in which the main ink tank is not provided and the ink tank is provided right above the liquid ejecting head.

[0024] FIG. 2 is a block diagram showing a control system of the first embodiment of the liquid ejecting apparatus.

[0025] FIG. 3 is a perspective view of an inkjet recording head.

[0026] FIG. 4 is a view showing a recording element substrate in a comparative example as seen from a side facing nozzles.

[0027] FIG. 5 is a view showing a recording element substrate in the first embodiment as seen from a side facing nozzles.

[0028] FIG. 6A is a cross-sectional view of the recording element substrate in the first embodiment in which a supply-side through-flow passage and a discharge-side through-flow passage are formed in a second substrate laminated on a second surface of a first substrate, and both communicate with a common flow passage extending in a nozzle row direction.

[0029] FIG. 6B is a cross-sectional view showing a configuration in which a thickness of the first substrate is increased and a passage between the supply-side through-flow passage and the discharge-side through-flow passage via the common flow passage is lengthened.

[0030] FIG. 6C is a cross-sectional view showing a configuration in which the supply-side common flow passage communicates with the circulation flow passage via the supply-side through-flow passage, and the discharge-side common flow passage communicates with the circulation flow passage via the discharge-side through-flow passage.

[0031] FIG. 7A is a schematic view of a drive signal for a electrothermal transducer when the electrothermal transducer is repeatedly and uniformly driven by supplying a drive pulse to the element every other optimum drive pulse pause period within a jetting pulse pause period in the first embodiment.

[0032] FIG. 7Bis a timing chart of a drive signal for an electrothermal transducer in which, in a first embodiment, a time interval until an element drive pulse is supplied just after a first timing before a second timing at which an energy generating element is driven, is different from a predetermined time interval, and a time interval between a timing at which a subsequent element drive pulse is supplied just after the first timing and a timing next to the first timing at which a next element drive pulse is supplied is different from the predetermined time interval, when the electrothermal transducer is thus driven.

[0033] FIG. 7C is a timing chart of a drive signal for an electrothermal transducer in which, in a first embodiment, a time interval until an element drive pulse is supplied just after a first timing before a second timing at which an energy generating element is driven, is different from a predetermined time interval, and a time interval between a timing at which a subsequent element drive pulse is supplied just after the first timing and a timing next to the first timing at which a next element drive pulse is supplied is different from the predetermined time interval, when the electrothermal transducer is thus driven.

[0034] FIG. 7D is a timing chart of a drive signal for an electrothermal transducer in which, in a first embodiment, a pause period from a first timing at which an energy generating element is driven to a timing at which the electrothermal transducer is driven is shorter than a predetermined time interval, and a pause period between a timing at which an element drive pulse is supplied just after a first timing next to the first timing and a second timing before which the element drive pulse is supplied is different from the predetermined time interval, when the electrothermal transducer is thus driven.

[0035] FIG. 8A is a timing chart of a drive signal for an electrothermal transducer in which, in a second embodiment, when an element drive pulse is supplied every optimal drive pulse pause period to uniformly drive the electrothermal transducer, and an element drive pulse is also supplied just after a first timing before a second timing at which an energy generating element is driven, when the electrothermal transducer is thus driven.

[0036] FIG. 8B is a timing chart of a drive signal for an electrothermal transducer in which, in a second embodiment, for the first several times from a first timing, an element drive pulse is supplied at a uniform drive pulse pause period to drive the electrothermal transducer, and a time interval between a timing at which an element drive pulse is supplied just after a first timing next to the first timing and a timing at which a previous element drive pulse is supplied is shorter than a predetermined time interval, when the electrothermal transducer is thus driven. DETAILED DESCRIPTION

[0037] Embodiments of the present disclosure will now be described in detail based on examples with reference to the accompanying drawings. However, the size, material, shape, relative arrangement, and the like of the components described in the embodiments can be changed as appropriate in accordance with the configuration of the device to which the present disclosure is applied and various conditions. Also, not all combinations of the features described in the embodiments are essential to the solution of the present invention. The constituent elements described in the embodiments are merely examples, and the scope of the present disclosure should not be limited to this alone.

[0038] First Embodiment

[0039] An explanation will be given of a liquid ejecting apparatus 50 according to a first embodiment of the present disclosure. The liquid ejecting apparatus 50 is an inkjet recording apparatus using an inkjet recording method, and includes a liquid ejecting head 1 capable of ejecting ink as a liquid.

[0040] Liquid ejecting apparatus

[0041] FIG. 1A and FIG. 1B is a perspective view showing a configuration of the liquid ejecting apparatus 50 according to Example 1. FIG. 1A and FIG. 1B The liquid ejecting apparatus 50 shown in FIG. 1 is a liquid ejecting apparatus of a serial type (serial type liquid ejecting apparatus) in which image recording is performed by ejecting a liquid onto a recording medium P using a liquid ejecting head 1 that scans in a direction intersecting a conveyance direction of the recording medium P. The present disclosure is not limited to the serial type liquid ejecting apparatus, and can also be applied to a page wide type liquid ejecting apparatus in which image recording is performed by ejecting a liquid onto a recording medium conveyed in a conveyance direction using a line head (page wide type head) longer in a page width direction of the recording medium. The liquid ejecting head 1 according to the present embodiment can eject four types of ink including black (K), cyan (C), magenta (M), and yellow (Y), and records a full color image using such inks. The ink that can be ejected from the liquid ejecting head 1 is not limited to the above-described four types of ink. The present disclosure can also be applied to a liquid ejecting head capable of ejecting other types of ink, and the type and number of inks ejected from the liquid ejecting head are not particularly limited.

[0042] In the following description, a scanning direction (moving direction) of the liquid ejecting head 1 is an X direction, a conveyance direction of the recording medium P in a recording section is a Y direction, and a vertical direction is a Z direction. The X direction, the Y direction, and the Z direction intersect each other (in the present example, these directions are perpendicular to each other). In some cases, the scanning direction (moving direction) of the liquid ejecting head 1 can be referred to as a main scanning direction, and the conveyance direction of the recording medium P can be referred to as a sub scanning direction.

[0043] In the serial type liquid ejecting apparatus 50, the liquid ejecting head 1 is mounted on a carriage 60. The carriage 60 is moved reciprocally along a guide shaft 51 in the main scanning direction (X direction). The recording medium P is conveyed in the sub scanning direction (Y direction) intersecting the main scanning direction (in the present example, perpendicular to the main scanning direction) by conveyance rollers 55, 56, 57, and 58 constituting a conveyance section (conveyance unit).

[0044] FIG. 1Ais a perspective view showing an example configuration in which the main ink tank 200, which is a liquid storage portion (outside the liquid ejection head 1), is provided to the main body of the liquid ejection apparatus 50, and the sub ink tank 54 is provided to the liquid ejection head 1. The liquid (ink) stored in the ink tank 200 is supplied to the sub ink tank 54 inside the liquid ejection head 1 by the driving force of the external pump 210 through, for example, an ink supply tube (liquid passage) 59. In other words, in FIG. 1A In the example shown, the liquid storage portion that stores ink is provided to each of the main body of the liquid ejection apparatus 50 and the liquid ejection head 1.

[0045] FIG. 1B is a perspective view showing an example configuration in which the main ink tank 200 is not provided, and the ink tank 54 is provided directly above the liquid ejection head 1. The liquid ejection head 1 can be integrated with the ink tank 54, and configured to be removable from the carriage 60. Alternatively, the liquid ejection head 1 can be integrated with the carriage 60, and only the ink tank 54 is configured to be removable. FIG. 1A The configuration shown will be used as a representative example in the following description.

[0046] The liquid ejection head 1 includes individual ejection units, which will be described later. The individual ejection units, the specific configuration of which will be described later, are recording element units that include a nozzle (ejects liquid through the nozzle), a pressure chamber that communicates with the nozzle, and an individual circulation flow passage that communicates with the pressure chamber. The individual ejection units include a first energy generating element (ejection energy generating element) that is provided at a position corresponding to the pressure chamber and generates energy for causing the nozzle to eject liquid, and a second energy generating element (electrothermal transducer) that is provided at a position corresponding to the individual circulation flow passage. The liquid ejection head 1 includes a plurality of individual ejection units, and has a supply flow passage for supplying liquid to the individual circulation flow passages in the individual ejection units.

[0047] When the liquid ejection head 1 is used, the ejection of liquid can become unstable due to evaporation of a volatile component (e.g., water) at the nozzle and concentration of a solid component in the vicinity of the nozzle resulting therefrom. Therefore, various measures have been taken to prevent the ejection from becoming unstable. For example, the liquid ejection apparatus 50 can be provided with a cap member (not shown) at a position away from the conveyance passage of the recording medium P in the X direction. The cap member is capable of covering a nozzle surface on which the nozzles of the liquid ejection head 1 are formed. The cap member functions to prevent the nozzles from drying, and to protect the nozzles by covering the nozzle surface of the liquid ejection head 1 when a recording operation is not performed.

[0048] An ink suction mechanism (not shown) can also be provided to the liquid ejecting apparatus 50. In a case where such an ink suction mechanism is provided, a cap member is used, for example, in an operation of sucking ink from the nozzle. By performing this ink suction operation, the ink in the vicinity of the nozzle can be renewed and the image quality of the obtained image can be maintained.

[0049] Furthermore, the thickened ink can also be discarded by performing so-called preliminary ejection (pre-ejection) when a recording operation is not performed. Such preliminary ejection (paper preliminary ejection / in-page preliminary ejection) can also be performed during a recording operation by ejecting a small amount of ink to the recording medium at a position that is not noticeable in terms of image quality. Although these methods contribute greatly to the improvement of image quality, there is still a need to reduce the amount of waste ink as much as possible, since some ink is always discarded when the nozzle is renewed.

[0050] To solve these problems, by providing an electrothermal transducer as a second energy generating element in the circulating flow channel and circulating the ink within the flow channel, it is possible to suppress the drying of the nozzle and the concentration of the ink in the vicinity of the nozzle while reducing the amount of waste ink. More specifically, it is possible to reduce the number of times of performing preliminary ejection or suction recovery as much as possible. Furthermore, by reducing the number of times of preliminary ejection operation and the like, it is possible to improve the yield and productivity thereof.

[0051] The second energy generating element (electrothermal transducer) does not necessarily have to be provided in all of the individual ejection units of the liquid ejecting head. The above-described effects can be achieved more efficiently in a case where the second energy generating element is provided in a part of the individual ejection units compared to a case where the second energy generating element is not provided.

[0052] The liquid ejecting head 1 can also have a configuration in which the second energy generating element is provided in all of the portions corresponding to the four kinds of ink, or a configuration in which the second energy generating element is provided in only a portion corresponding to one kind of ink. That is, the liquid ejecting head can be designed so as not to circulate all of the four types of ink, but to circulate only at least one type of ink.

[0053] FIG. 2 is a block diagram showing a control system of the liquid ejecting apparatus 50. The CPU 800 is a control portion for controlling the operation of each portion of the liquid ejecting apparatus 50 based on a program such as a processing procedure stored in the ROM 301. The RAM 302 serves as a work area or the like when the CPU 800 performs processing. The CPU 800 receives image data from the host apparatus 400 outside the liquid ejecting apparatus 50, and controls the driving of the elements provided to the liquid ejecting head 1 by controlling the head driver 1A based on the image data.

[0054] The CPU 800 also controls the drivers of various types of actuators installed in the liquid jetting device 50. For example, the CPU 800 controls the motor driver 303A of the carriage motor 303 for moving the carriage 60, the motor driver 304A of the transfer motor 304 for transferring the recording medium P, and the pump driver 21A of the external pump 210. Although FIG. 2 The configuration for receiving image data from the host device 400 is shown, but it is also possible to perform processing on the liquid jetting device 50 without using any data from the host device 400.

[0055] Header configuration description

[0056] FIG. 3 This is a perspective view of an inkjet recording head 1 (hereinafter referred to as the recording head) that can be used as a liquid ejector head of the present disclosure. The recording head 1 is configured such that a plurality of recording element substrates 4 are further arranged in the Y direction, each recording element substrate having a plurality of recording elements arranged in the Y direction. Here, the recording head 1 shown is a full-line recording head, wherein the recording element substrates 4 are arranged along the Y direction at a distance corresponding to the width of an A4 size paper.

[0057] Each recording element substrate 4 is connected to the same electrical wiring substrate 102 via a flexible wiring substrate 101. The electrical wiring substrate 102 is provided with a power supply terminal 103 for receiving power and a signal input terminal 104 for receiving ejection signals sent from the CPU 800. In addition, the ink supply unit 105 forms a circulating flow channel for supplying ink from the ink tank (not shown) to each recording element substrate 4 and for collecting ink that is not consumed during recording.

[0058] With the above configuration, each recording element arranged on the recording element substrate 4 ejects ink supplied from the ink supply unit 105 in the Z direction of the figure based on the ejection signal input from the signal input terminal 104 and the power supplied from the power supply terminal 103.

[0059] Description of recording elements

[0060] FIG. 5 yes FIG. 3 An enlarged view of a portion of the recording element substrate 4 of the recording head 1 shown illustrates the flow channel configuration near the nozzle in this embodiment when viewed from the nozzle-facing side (+Z direction) of the recording element substrate 4. FIG. 6A to FIG. 6C It shows along FIG. 5 The cross-sectional view taken in the direction AA.

[0061] exist FIG. 6AIn this design, an energy generating element 35 (first energy generating element) is disposed on the surface of the first substrate 17. This energy generating element 35 is an electrothermal transducer that generates energy for ejecting ink from the pressure chamber. A nozzle 2 is formed on the perforated plate 16 at a position corresponding to the energy generating element 35. On the surface of the first substrate 17, an electrothermal transducer 5 (second energy generating element) is disposed adjacent to the energy generating element 35 along the X direction, which is a second direction perpendicular to the Y direction (i.e., the direction of the nozzle array). FIG. 5 In this structure, a partition wall 27 is provided between the nozzle 2 and the energy generating element 35 arranged along the Y direction in the pressure chamber 3. The partition wall 27 forming the pressure chamber 3 extends in the X direction, which is perpendicular to the Y direction of the nozzle array, thereby forming a liquid jet section including the pressure chamber 3, the nozzle 2, and the energy generating element 35, and a circulating flow channel 6 including the electrothermal transducer 5. That is, on the first surface side of the first substrate 17 where the energy generating element 35 is provided, a flow channel forming member (first flow channel forming member) including the partition wall 27 is provided between adjacent pressure chambers 3 and circulating flow channels 6 in the Y direction. An orifice plate 16 is stacked on the opposite side of the first substrate 17 opposite to the flow channel forming member. The pressure chamber 3 and the circulating flow channel 6 are defined by the first surface of the first substrate 17, the partition wall 27, and the orifice plate 16. The circulating flow channel 6 communicates with a supply flow channel 7 (supply port) provided on one side of the pressure chamber 3 and a discharge flow channel 8 (discharge port) provided on the other side. Specifically, in this embodiment, the supply flow channel 7 and the discharge flow channel 8 are arranged on corresponding sides of the pressure chamber 3 in the X direction, and the supply flow channel 7, the pressure chamber 3, and the discharge flow channel 8 are arranged in a specific order. FIG. 5 The sequential arrangement of flow channels shown is called a straight-line flow channel configuration. For example... FIG. 5 As shown, on the first surface side of the first substrate 17 of the recording head 1, which serves as one surface side, multiple liquid jet portions including a pressure chamber 3, a nozzle 2, and an energy generating element 35 are formed and aligned along the Y direction. Additionally, multiple circulating flow channels 6 communicating with the supply flow channel 7 and the discharge flow channel 8 are also formed along the Y direction. A supply-side through flow channel 21, communicating with the supply flow channel 7 from the outside, is formed to penetrate the first substrate 17 along the Z direction (i.e., a third direction intersecting both the X and Y directions) between the first surface and the second surface, which serves as the rear surface. Similarly, a discharge-side through flow channel 22, communicating with the discharge flow channel 8 from the outside, is formed to penetrate the first substrate 17 in the Z direction.

[0062] like FIG. 6AAs shown, the supply-side through flow channel 21 and the discharge-side through flow channel 22 are formed in the second substrate 18 (second flow channel forming member) stacked on the second surface of the first substrate 17, and both are connected to the common flow channel 23 extending along the nozzle array direction.

[0063] In this case, the Z-direction flow channel height h (corresponding to the thickness of the first substrate 17) of the supply-side through flow channel 21 and the discharge-side through flow channel 22 formed in the first substrate 17 is set to 50 μm to 200 μm, and the X-direction spacing W1 between the supply-side through flow channel 21 and the discharge-side through flow channel 22 is set to 50 μm to 300 μm. To ensure refilling of the nozzle 2, pressure loss needs to be minimized; therefore, the first substrate 17 can be relatively thin. However, to suppress the effects of recirculation concentration, such as... FIG. 6B As shown, the thickness of the first substrate 17 can also be increased in the range of 50 μm to 200 μm, and it can be configured to lengthen the channel between the supply-side through flow channel 21 and the discharge-side through flow channel 22 via the common flow channel 23.

[0064] In addition, such as FIG. 6C As shown, a supply-side common flow channel 24 and a discharge-side common flow channel 25 can also be formed in the second substrate 18. The supply-side common flow channel 24 extends in the nozzle array direction and communicates with the supply-side through flow channel 21, and the discharge-side common flow channel 25 extends in the nozzle array direction and communicates with the discharge-side through flow channel 22. Both the supply-side common flow channel and the discharge-side common flow channel communicate with a common flow channel outside the recording head (not shown). That is, the supply-side common flow channel 24 communicates with the circulation flow channel 6 via the supply-side through flow channel 21, and the discharge-side common flow channel 25 communicates with the circulation flow channel 6 via the discharge-side through flow channel 22. By separating the supply-side common flow channel 24 and the discharge-side common flow channel 25, a further effect of suppressing recirculation concentration can be expected. In addition, regarding the spacing W2 between the supply-side common flow channel 24 and the discharge-side common flow channel 25, when the first substrate 17 and the second substrate 18 are bonded together, an adhesion margin must be ensured, therefore W2 is set to at least 50 μm.

[0065] As described above, the flow channels can be formed by dividing the flow channels between the first substrate and the second substrate, or the supply-side flow channel 21 and the discharge-side flow channel 22 can be formed in a single substrate.

[0066] Description of drive signals

[0067] To address ink thickening in the flow channel and supply fresh ink to the nozzle, in this disclosure, the electrothermal transducer 5 is driven during periods when the drive of the energy generating element 35 is stopped between each timing interval for ink ejection from the nozzle 2. In this manner, a cyclic generation operation for generating a circulating flow in the flow channel is performed multiple times. The timing of the drive signal for driving the electrothermal transducer 5 is... FIG. 7A to FIG. 7D As shown in the diagram, a first timing for sending discharge pulses to eject liquid from nozzle 2 and driving energy generating element 35 is designated as 31a, and a second timing for driving energy generating element 35 after the first timing 31a is designated as 31b. When the discharge pulse pause period between the first timing 31a and the second timing 31b is defined as 32, CPU 800 sends multiple element driving pulses 33 at a first time interval 33a, and then sends multiple element driving pulses 33 at a constant interval 34a (drive pulse pause period) as the second time interval to repeatedly drive electrothermal transducer 5, thereby performing a cyclic generation operation to generate a circulating flow in the flow channel.

[0068] At this time, before driving the electrothermal transducer 5, a certain time interval is set after the discharge pulse is sent in the first timing 31a ( FIG. 7A The drive of the energy generating element 35 is paused at least until the second timing 31b (34a). The optimal length of the drive pulse pause period 34a and the timing of the drive pulse 33 of the transmitting element depend on the flow resistance in the circulating flow channel, the viscosity of the liquid, and the size of the electrothermal transducer, and are determined experimentally. FIG. 7A This illustrates the case where, during the discharge pulse pause period 32, element drive pulses 33 are sent every experimentally determined optimal drive pulse pause period 34a, and the electrothermal transducer 5 is driven repeatedly and uniformly.

[0069] On the other hand, the discharge pulse pause period 32 between the first timing 31a and the second timing 31b for driving the energy generating element 35 varies depending on factors such as the image to be recorded on the recording medium P, the type of liquid, and the viscosity of the liquid. Therefore, depending on the timing of the energy generating element 35, it may be impossible to set the drive pulse pause period 34a within the discharge pulse pause period 32 and to send the element drive pulses 33 at uniform intervals to drive the electrothermal transducer 5. In such cases, as... FIG. 7BAs shown, during the pulse pause period 32, after the first timing 31a, the next element drive pulse 33 is sent, and the timing for driving the electrothermal transducer 5 is set to a third timing. The time interval between the first timing 31a and the third timing is set to a third time interval 34b, different from 34a. Subsequent timings for sending the element drive pulse 33 are set at uniform intervals corresponding to the drive pulse pause period 34a, and the electrothermal transducer 5 can be driven repeatedly multiple times. Furthermore, as... FIG. 7C As shown, the time interval until the element drive pulse 33 is sent exactly before the second timing 31b can be set to 34c, which is different from 34a. Furthermore, as... FIG. 7D As shown, the pause period from the first timing 31a when the energy generating element 35 is driven to the third timing when the electrothermal transducer 5 is driven can be set to a third time interval 34b that is shorter than 34a. The timing for driving the electrothermal transducer 5 exactly before the second timing 31b, by sending the element drive pulse 33 exactly before the second timing 31b for driving the energy generating element 35, is defined as the fourth timing. The pause period between this fourth timing and the second timing 31b is set to a fourth time interval 34c that is different from the drive pulse pause period 34a. The remaining pause periods can be set such that the element drive pulse 33 is sent every optimal drive pulse pause period 34a, and the electrothermal transducer 5 is driven multiple times. Note that both the third time interval 34b and the fourth time interval 34c are set to be shorter than the drive pulse pause period 34a, but this is not limiting, as long as the time interval suppresses ink concentration in the flow channel and generates a circulating flow close to a steady state.

[0070] exist FIG. 7A to FIG. 7D In this process, the drive cycle of the electrothermal transducer 5 is set to three times; however, there are no particular restrictions on the drive cycle of the electrothermal transducer, as long as it can discharge the concentrated ink in the nozzle 2.

[0071] Effect

[0072] The circulating flow in the flow channel decays over time and stops after a certain period. Therefore, to generate a stable circulating flow, the electrothermal transducer needs to be driven repeatedly. However, there is a problem that localized heating caused by continuous foaming of the electrothermal transducer can lead to bubble formation failure and reduced flow rate. Therefore, it is ideal to drive the electrothermal transducer intermittently while simultaneously achieving near-steady flow operation.

[0073] Here, as a comparative example, in FIG. 4 The image shows a U-shaped circulating flow channel configuration. In, for example... FIG. 4In the U-shaped circulating flow channel configuration shown, the liquid inlet and outlet portions of the circulating flow channel are arranged very close together. Therefore, when the electrothermal transducer is intermittently driven to achieve near-steady flow operation, concentrated ink from the outlet side is recirculated into the inlet portion, thereby promoting concentration and potentially causing jetting failure.

[0074] In this embodiment, as described above, a linear flow channel configuration is adopted, wherein the supply flow channel 7 and the discharge flow channel 8 are respectively arranged on one side and the other side of the pressure chamber 3 along the X direction, thereby achieving a configuration in which the supply flow channel and the discharge flow channel of the circulating flow channel are separated. Therefore, it is possible to prevent the ink flow discharged from the discharge flow channel 8 from returning to the supply flow channel 7. As a result, the concentration of the circulating flow can be avoided. In addition, the electrothermal transducer 5 for circulating flow in the circulating flow channel is configured to be driven intermittently during the pulse pause period between the timings 31a and 31b of the drive energy generating element 35. This enables pump drive that is close to a stable flow. In other words, by adopting a flow channel configuration and drive method that suppresses recirculation concentration, fresh ink can be continuously supplied to the nozzle section where the nozzle 2 is provided, thereby suppressing ink thickening at the nozzle section.

[0075] In the above description, an electrothermal transducer is used as the first energy generating element. By driving the first energy generating element to generate heat and causing the ink in the pressure chamber 3 to generate bubbles, ink can be ejected from the nozzle 2 using foaming energy. The first energy generating element is not limited to an electrothermal transducer, and piezoelectric elements, etc., can also be used.

[0076] Although the example of using the electrothermal transducer 5 as a second energy generating element has been illustrated in the description given above, a piezoelectric element can also be used as a second energy generating element. In the case of a piezoelectric element, depending on its driving method, the direction of the circulating flow can be opposite to the direction of the circulating flow as described above.

[0077] Second Embodiment

[0078] The differences between the loop configuration of the second embodiment and the first embodiment will only be described.

[0079] Explanation of drive signals

[0080] To suppress the attenuation of the circulating flow in the circulating flow channel while simultaneously enabling ink ejection from the nozzle 2, this embodiment is characterized by sending an element drive pulse 33 to drive the electrothermal transducer 5 precisely before the timing of the energy generating element 35 being driven. In this embodiment, the timing of the drive signals for the electrothermal transducer 5 and the energy generating element 35 is as follows: FIG. 8A and FIG. 8BAs shown in the diagram, a first timing for sending a discharge pulse to eject liquid from nozzle 2 and driving energy generating element 35 is designated 31a, and a second timing for driving energy generating element 35 after the first timing 31a is designated 31b. A discharge pulse pause period between the first timing 31a and the second timing 31b is defined as 32. During this discharge pulse pause period 32, element driving pulses 33 for driving the electrothermal transducer 5 are sent at constant intervals (drive pulse pause period 34a), thereby intermittently driving the electrothermal transducer 5 multiple times.

[0081] At this time, during the discharge pulse pause period 32, the element drive pulse 33 for driving the electrothermal transducer 5 is controlled to be sent exactly before the second timing 31b. More specifically, the element drive pulse 33 is sent exactly before the second timing 31b to drive the electrothermal transducer 5 at a fourth timing, and the fourth time interval between this fourth timing and the second timing 31b for driving the energy generating element 35 is set to be equal to or less than the time interval 33b of the first time interval 33a. As in the first embodiment, the optimal length of the drive pulse pause period 34a and the timing of sending the element drive pulse 33 are determined experimentally, depending on the flow resistance in the circulating flow channel, the viscosity of the liquid, and the size of the electrothermal transducer. FIG. 8A This illustrates a situation in which, during the discharge pulse pause period 32, an element drive pulse 33 is sent every experimentally determined optimal drive pulse pause period 34a, and the electrothermal transducer 5 is driven uniformly, while a fourth time interval until the second timing 31b used to drive the energy generating element 35 is set to a time interval 33b that is equal to or less than the first time interval 33a.

[0082] On the other hand, when it is impossible to drive the electrothermal transducer 5 with uniform timing during the discharge pulse pause period 32, such as FIG. 8B As shown, for the first few times starting from the first timing 31a, the element drive pulse 33 is sent at uniform drive pulse pause intervals 34a during the discharge pulse pause interval 32 to drive the electrothermal transducer 5. Then, the electrothermal transducer 5 can be driven such that the time interval between the timing of sending the element drive pulse 33 just before the second timing 31b and the timing of sending the previous element drive pulse 33 becomes a time interval 34b that is shorter than the time interval 34a.

[0083] Effect

[0084] As in the first embodiment, if there is a pause during the discharge pulse pause period 32 during which the electrothermal transducer 5 is not driven just before the timing of the drive energy generating element 35, the problem is that the ink circulation efficiency just before the discharge pulse may decrease. Therefore, as in this embodiment, by driving the electrothermal transducer 5 just before sending the discharge pulse and driving the energy generating element 35, jetting can be performed while maintaining the circulation effect at the nozzle section.

[0085] In this case, the efficiency of the cycle can be further improved.

[0086] Although this disclosure has been described with reference to embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments. The scope of the appended claims should be accorded the broadest interpretation so as to cover all such variations and equivalent structures and functions.

Claims

1. A liquid ejection head comprising: a plurality of liquid ejection portions each having a nozzle for ejecting liquid, a pressure chamber, and a first energy generating element for generating energy to eject liquid from the nozzle; a plurality of circulation flow channels provided corresponding to the plurality of liquid ejection portions, each circulation flow channel having a supply port through which liquid supplied to the pressure chamber flows in and a discharge port through which liquid collected from the pressure chamber is discharged, the pressure chamber being provided between the supply port and the discharge port; and a second energy generating element provided in the circulation flow channel; wherein the plurality of liquid ejection portions are arranged in a first direction, wherein each of the plurality of circulation flow channels extends in a second direction intersecting the first direction so that the supply port is located on one side of the pressure chamber in the second direction, the discharge port is located on the other side of the pressure chamber in the second direction, and the supply port, the pressure chamber, and the discharge port are arranged in the second direction in this order, wherein the second energy generating element is provided in the circulation flow channel closer to the side of the supply port than the pressure chamber, wherein the second energy generating element is driven a plurality of times at a first time interval between a first timing at which the first energy generating element is driven and a second timing at which the first energy generating element is next driven after the first timing, and wherein a third time interval between the first timing and a third timing at which the second energy generating element is next driven after the first timing includes a cyclic generation operation that is greater than the first time interval.

2. The liquid ejection head according to claim 1, further comprising: a substrate provided with the liquid ejection portions, the circulation flow channels, and the second energy generating element on a first surface side, wherein the substrate includes: a supply side through flow channel that penetrates the substrate in a third direction intersecting both the first direction and the second direction between a first surface of the substrate and a second surface that is a back surface of the first surface on an outer side of the supply port; and a discharge side through flow channel that penetrates the substrate in the third direction between the first surface and the second surface on an outer side of the discharge port, and wherein a common flow channel that communicates with the supply side through flow channel and the discharge side through flow channel is formed on a second surface side.

3. The liquid ejection head according to claim 2, further comprising: a flow channel forming member laminated on the first surface of the substrate, the flow channel forming member including a plurality of partition walls extending in the second direction between the plurality of first energy generating elements aligned in the first direction among the plurality of liquid ejection portions; and an orifice plate provided with the nozzles and laminated on an opposite side of the substrate with respect to the flow channel forming member, and wherein the pressure chamber and the circulation flow passage are defined by the first surface of the substrate, the partition wall, and the orifice plate.

4. The liquid ejecting head according to claim 3, wherein the flow passage forming member is a first flow passage forming member, the liquid ejecting head further comprising: a second flow passage forming member laminated on the second surface of the substrate, defining the common flow passage together with the second surface, and wherein the common flow passage communicates with each of the plurality of circulation flow passages via the supply side through flow passage and the discharge side through flow passage.

5. The liquid ejecting head according to claim 3, wherein the flow passage forming member is a first flow passage forming member, the liquid ejecting head further comprising: a second flow passage forming member laminated on the second surface of the substrate, defining the common flow passage together with the second surface, and wherein the common flow passage includes: a supply side common flow passage communicating with each of the plurality of circulation flow passages via the supply side through flow passage; and a discharge side common flow passage communicating with each of the plurality of circulation flow passages via the discharge side through flow passage.

6. The liquid ejecting head according to claim 1, wherein the second energy generating element is an electrothermal transducer.

7. A liquid ejecting apparatus comprising: the liquid ejecting head according to any one of claims 1 to 6; and a control portion for controlling driving of the second energy generating element, wherein the control portion drives the second energy generating element when driving of the first energy generating element is stopped.

8. The liquid ejecting apparatus according to claim 7, wherein the control portion controls the circulation generation operation so as to repeat the circulation generation operation a plurality of times at a second time interval longer than the first time interval when driving of the first energy generating element is stopped.

9. The liquid ejecting apparatus according to claim 8, wherein the third time interval between the first timing and the third timing is different from the second time interval.

10. The liquid ejecting apparatus according to claim 8, wherein wherein, in the circulation generation operation, in a case where the second energy generating element is driven at a fourth timing immediately before the second timing, a fourth time interval between the fourth timing and the second timing is different from the second time interval.

11. The liquid ejecting apparatus according to claim 10, wherein the fourth time interval is equal to or smaller than the first time interval.

12. A method for driving a liquid ejecting head, the liquid ejecting head including: a plurality of liquid ejecting portions aligned in a first direction, each liquid ejecting portion having a nozzle for ejecting liquid, a pressure chamber, and a first energy generating element for generating energy to eject liquid from the nozzle; a second energy generating element for generating energy to eject liquid from the nozzle; and a common flow passage communicating with each of the plurality of circulation flow passages via the supply side through flow passage and the discharge side through flow passage. a plurality of circulation flow channels each having a supply port through which liquid supplied to the pressure chamber flows in and a discharge port through which liquid collected from the pressure chamber is discharged, the pressure chamber being provided between the supply port and the discharge port, corresponding to the plurality of liquid ejection portions; and a second energy generating element provided in the circulation flow channel on a side closer to the supply port than the pressure chamber; the method comprising: driving the first energy generating element to eject liquid from the nozzle; performing a circulation generating operation in which the second energy generating element is driven to generate liquid flow in the circulation flow channel in the order of the supply port on a side of the pressure chamber in a second direction intersecting the first direction, the pressure chamber, and the discharge port on the other side of the pressure chamber in the second direction, wherein, in the circulation generating operation, the second energy generating element is driven a plurality of times at a first time interval between a first timing at which the first energy generating element is driven and a second timing at which the first energy generating element is next driven after the first timing, and a third time interval between the first timing and a third timing at which the second energy generating element is next driven after the first timing is greater than the first time interval.

13. The method for driving a liquid ejection head according to claim 12, wherein, the second energy generating element is intermittently driven to generate intermittent flow in the circulation flow channel.

Images