Filling Method for Liquid Jetting Device and Liquid Jetting Head

Abstract

The present invention provides a liquid ejection device and a filling method for a liquid ejection head that reduce the generation of bubbles on the downstream side of a filter of the liquid ejection device. The liquid ejection device includes: a liquid ejection unit that ejects ink; a liquid storage unit that stores ink; a filter chamber including an upstream chamber and a downstream chamber partitioned by a filter through which ink passes; a supply passage that allows ink to flow from the liquid storage unit to the upstream chamber; a discharge passage that allows ink to flow from the upstream chamber to the liquid storage unit; an on-off valve that opens and closes the discharge passage; and a pump that pressurizes the ink to cause the ink to flow from the liquid storage unit to the upstream chamber, and performs the following filling operation. That is, with the on-off valve open, after the upstream chamber is filled with ink by driving the pump in a manner that does not allow the ink to pass through the filter, the on-off valve is closed during the period when the ink flows from the liquid storage unit toward the supply passage, the upstream chamber, and the discharge passage by the driving.

Description

Technical Field

[0001] The present invention relates to a liquid ejection device and a method for filling a liquid ejection head, and more particularly to an inkjet recording device that ejects ink as a liquid and a method for filling an inkjet recording head. Background Art

[0002] A liquid ejection device represented by an inkjet recording device such as an inkjet printer or a plotter includes a liquid ejection head capable of ejecting a liquid such as ink stored in a cartridge, a tank, or the like as droplets. As the liquid ejection head, a filter chamber provided with a filter and a liquid ejection unit provided with nozzles for ejecting the liquid are provided. The ink supplied from a cartridge or the like passes through the filter in the filter chamber and is supplied to the liquid ejection unit.

[0003] For example, in the inkjet recording head disclosed in Patent Document 1, a filling operation of pumping ink from a cartridge, a tank, or the like to the inkjet recording head and filling the ink into the filter chamber is performed by a pressurizing mechanism such as a pump. In the filling operation, the ink is first filled on the upstream side of the filter. Then, when the pressure of the ink exceeds the bubble point of the filter, the ink passes through the filter, and the ink is filled on the downstream side of the filter.

[0004] When performing the above-described filling operation, it is possible that bubbles present on the upstream side of the filter in the filter chamber become smaller bubbles when passing through the filter and remain in the middle of the flow path from the filter chamber to the nozzles of the liquid ejection unit.

[0005] In addition, such a problem exists not only in inkjet recording devices but also in liquid ejection devices that eject liquids other than ink.

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-104495 Summary of the Invention

[0007] One aspect of a liquid ejection device according to a preferred embodiment of the present invention for solving the above problems is a liquid ejection device, characterized by comprising: a liquid ejection unit that ejects liquid; a liquid storage unit that stores liquid; a filter chamber including an upstream chamber and a downstream chamber divided by a filter through which liquid passes; a supply passage that allows liquid to flow from the liquid storage unit to the upstream chamber; a discharge passage that allows liquid to flow from the upstream chamber to the liquid storage unit; an opening / closing valve that opens and closes the discharge passage; a pressurizing mechanism that pressurizes the liquid to cause the liquid to flow from the liquid storage unit to the upstream chamber, and performs the following filling operation: in a state where the opening / closing valve is open, after filling the upstream chamber with liquid by driving the pressurizing mechanism in a manner that does not allow the liquid to pass through the filter, the opening / closing valve is closed during the period when the liquid flows from the liquid storage unit toward the supply passage, the upstream chamber, and the discharge passage by the driving.

[0008] One method of a filling method for a liquid ejection head according to a preferred embodiment of the present invention for solving the above problems is a filling method for a liquid ejection head, characterized in that the liquid ejection head comprises: a liquid ejection unit that ejects liquid; a liquid storage unit that stores liquid; a filter chamber including an upstream chamber and a downstream chamber divided by a filter through which liquid passes; a supply passage that allows liquid to flow from the liquid storage unit to the upstream chamber; a discharge passage that allows liquid to flow from the upstream chamber to the liquid storage unit; an opening / closing valve that opens and closes the discharge passage; a pressurizing mechanism that pressurizes the liquid to cause the liquid to flow from the liquid storage unit to the upstream chamber, and wherein the following filling operation is performed: in a state where the opening / closing valve is open, after filling the upstream chamber with liquid by driving the pressurizing mechanism in a manner that does not allow the liquid to pass through the filter, the opening / closing valve is closed during the period when the liquid flows from the liquid storage unit toward the supply passage, the upstream chamber, and the discharge passage by the driving. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A diagram showing the schematic configuration of an inkjet recording device according to Embodiment 1.

[0010] Figure 2 A schematic configuration diagram of the liquid supply unit and the recording head according to Embodiment 1.

[0011] Figure 3 A cross-sectional view of the recording head according to Embodiment 1.

[0012] Figure 4Cross-sectional view of the recording head during the filling operation according to Embodiment 1.

[0013] Figure 5 Cross-sectional view of the recording head during the filling operation according to Embodiment 1.

[0014] Figure 6 Cross-sectional view of the recording head during the filling operation according to Embodiment 1.

[0015] Figure 7 Cross-sectional view of the recording head during the filling operation according to Embodiment 1.

[0016] Figure 8 Flowchart of the filling operation according to Embodiment 1.

[0017] Figure 9 Graph showing the pressure change acting on the filter during the filling operation according to Embodiment 1.

[0018] Figure 10 Flowchart of the filling operation according to Embodiment 2.

[0019] Figure 11 Graph showing the pressure change acting on the filter during the filling operation according to Embodiment 2.

[0020] Figure 12 Cross-sectional view of the recording head according to Embodiment 3. Detailed Implementation Modes

[0021] Embodiment 1

[0022] Hereinafter, the present invention will be described in detail based on the embodiments. However, the following description represents one mode of the present invention, which can be arbitrarily changed within the scope of the present invention. Components denoted by the same reference numerals in the respective figures represent the same components, and the description will be appropriately omitted.

[0023] In the respective figures, X, Y, and Z represent three mutually orthogonal spatial axes. In the present specification, the directions along these axes are defined as the X direction, the Y direction, and the Z direction. Further, an axis obtained by rotating the X axis by an angle θ around the Y axis is defined as the V axis, and an axis obtained by rotating the Z axis by an angle θ is defined as the W axis, and the directions along these axes are defined as the V direction and the W direction. The direction toward which the arrow mark in each figure points is defined as the positive (+) direction, and the direction opposite to the arrow mark is defined as the negative (-) direction for explanation. The Z direction represents the vertical direction, the +Z direction represents vertically downward, and the -Z direction represents vertically upward.

[0024] Figure 1A diagram showing a schematic structure of an inkjet recording apparatus 1, which is an example of the liquid ejection apparatus according to Embodiment 1 of the present invention.

[0025] As Figure 1 shown, the inkjet recording apparatus 1 is a printing apparatus that ejects / drops a kind of liquid, i.e., ink, as ink droplets onto a medium S such as printing paper, and performs printing of an image or the like by the arrangement of dots formed on the medium S.

[0026] The inkjet recording apparatus 1 includes a line head 2 constituted by an inkjet recording head 100 (hereinafter, also simply referred to as the recording head 100) that ejects ink, a liquid supply unit 10, a conveyance unit 4 that conveys the medium S in the conveyance direction, and a support table 5. The line head 2, the liquid supply unit 10, the conveyance unit 4, and the support table 5 are housed in a housing 3.

[0027] The line head 2 includes the recording head 100 and a holding unit 101 that holds the recording head 100. The number of recording heads 100 held by the holding unit 101 may be one or more. The holding unit 101 holds the recording head 100 such that a filter (described later) of the recording head 100 is inclined with respect to the XY plane as a horizontal plane.

[0028] The line head 2 holds the recording head 100 such that the ejection direction of the ink droplets becomes a +W direction in which the +Z direction (also known as the gravitational direction), which is the vertical direction, rotates around the Y axis and is inclined. In other words, the ejection direction of the ink droplets ejected from the nozzles becomes a +W direction that is inclined by -X direction with respect to the +Z direction. In addition, the inclination angle θ of the recording head 100 constituting the line head 2 with respect to the +Z direction, that is, the inclination angle θ of the W direction, which is the ejection direction of the ink droplets, with respect to the +Z direction, is set within a range of, for example, 0 < θ ≤ 180°. When θ exceeds 90°, the ejection direction of the ink droplets includes a component in the -Z direction.

[0029] In addition, although in the present embodiment, the recording head 100 of the line head 2 is held by the holding unit 101 in a state of always being inclined with respect to the horizontal plane, it is not necessary to be held in an inclined state all the time. For example, it may be a structure in which by providing an adjustment mechanism for adjusting the inclination of the line head 2 with respect to the horizontal plane, the recording head 100 is held in an inclined state only during maintenance operations such as suction cleaning or printing in which ink is ejected onto the medium S.

[0030] The medium S of the present embodiment is a type of medium composed of, for example, recording paper such as continuous paper, cloth, resin film, etc., and is held on the unwind reel 8 in a state of being wound into a roll shape. The medium S is conveyed by the conveying unit 4 onto a support table 5 such as an impression plate disposed at an interval from the nozzle surface of the recording head 100 where the nozzles are formed, and printing is performed on the support table 5 by the line head 2. The medium S on which printing has been performed by the recording head 100 on the support table 5 is configured to be wound onto the take-up reel 9 by the conveying unit 4.

[0031] The placement surface of the support table 5 for placing the medium S is configured to be inclined according to the inclination angle of the nozzle surface of the recording head 100. That is, the inclination angles θ of the nozzle surface and the support table 5 are set so that the distance between each nozzle of the nozzle surface and the medium S becomes fixed during the printing operation. In other words, the placement surface of the support table 5 is parallel to the VY plane defined by the V axis and the Y axis, and the angle with the XY plane becomes the inclination angle θ. The V direction is a direction orthogonal to the W direction and also orthogonal to the Y direction. The medium S is conveyed in the +V direction or the -V direction by the conveying unit 4 on the placement surface of the support table 5. Hereinafter, this +V direction or -V direction will also be referred to as the conveying direction.

[0032] The line head 2 equipped with the recording head 100 has the Y direction orthogonal to the conveying direction of the medium S as the long side direction, and is equipped with a plurality of nozzles arranged in such a manner that the printing range in the Y direction is larger than the printing range of the medium S in the Y direction. That is, the line head 2 of the present embodiment is fixed in such a manner that it does not move along the Y axis with respect to the frame 3 during the printing operation.

[0033] In addition, the medium S is not limited to a medium such as continuous paper, and various ejection media on which ink droplets ejected from the nozzles of the recording head 100 can fall can be used. For example, the present invention can also be applied to applications where ink droplets are ejected onto an ejection medium having a three-dimensional shape. In addition, the placement surface of the support table 5 for placing the medium S is not limited to a flat impression plate, and can also be a so-called impression cylinder such as a roller whose placement surface for placing the medium S is a curved surface. In addition, it can also be configured to support the back side of the medium S by a conveyor belt such as a seamless belt.

[0034] The conveying unit 4 includes a paper feed roller 6 and a conveying roller 7. The paper feed roller 6 is composed of a pair of upper and lower rollers that can rotate synchronously in opposite directions while clamping the medium S. The paper feed roller 6 is driven by the power of a motor (not shown) and supplies the medium S from the unwind reel 8 side to the support table 5 side. The conveying roller 7 is disposed on the opposite side of the support table 5 from the paper feed roller 6 and guides the printed medium S toward the take-up reel 9 side. In addition, the medium S does not necessarily have to be wound around the take-up reel 9. Furthermore, although in this embodiment, the conveying unit 4 is illustrated as including a paper feed roller 6 and a conveying roller 7, it is not particularly limited thereto, and the medium S may be conveyed by a belt or a roller.

[0035] Utilize Figure 2 , to explain the liquid supply unit 10 and the recording head 100. Figure 2 FIG. is a schematic structural diagram of the liquid supply unit 10 and the recording head 100. In addition, in Figure 2 , for the line head 2, only the recording head 100 is illustrated, and the illustration of the holding unit 101 is omitted.

[0036] The liquid supply unit 10 is a mechanism for supplying ink to the recording head 100. In this embodiment, it includes a main tank 11, an intermediate tank 12, a supply passage 13, a discharge passage 14, an on-off valve 15, a pump 16, and an inter-tank supply passage 17.

[0037] The main tank 11 is a container for storing ink and supplies the ink to the intermediate tank 12. Specifically, the main tank 11 and the intermediate tank 12 are connected by the inter-tank supply passage 17. In addition, a pump (not shown) is provided in the middle of the inter-tank supply passage 17. According to such a structure, the ink is supplied from the main tank 11 to the intermediate tank 12 through the inter-tank supply passage 17 by the pump (not shown).

[0038] In addition, the timing of supplying the ink from the main tank 11 to the intermediate tank 12 is not particularly limited. For example, when the liquid level of the ink stored in the intermediate tank 12 is lower than a predetermined height, or when the amount of the ink is less than a predetermined amount, the ink is supplied from the main tank 11 to the intermediate tank 12.

[0039] The intermediate tank 12 is an example of a liquid storage portion for storing ink. The intermediate tank 12 stores the ink supplied from the main tank 11. The intermediate tank 12 and the recording head 100 are connected by the supply passage 13 and the discharge passage 14.

[0040] The supply passage 13 is a flow path for the ink to flow from the intermediate tank 12 to the upstream chamber 50A described later. The discharge passage 14 is a flow path for the ink to flow from the upstream chamber 50A described later to the intermediate tank 12. Although in the present embodiment, the supply passage 13 and the discharge passage 14 are each one, the number is not limited.

[0041] The on-off valve 15 is a device for opening and closing the discharge passage 14. The specific structure of the on-off valve 15 is not particularly limited, and valves such as electromagnetic type and pressure type can be used. In addition, the on-off valve 15 can be opened and closed by the control unit 18 described later.

[0042] The pump 16 is an example of a pressurizing mechanism for pressurizing the ink so that the ink stored in the intermediate tank 12 flows toward the recording head 100. Specifically, a tube pump, a diaphragm pump, etc. are provided as the pump 16 on the supply passage 13. In addition, the pump 16 can be operated or stopped by the control unit 18 described later.

[0043] In addition, the pressurizing mechanism is not limited to the pump 16. For example, it can also be a pressing unit that pressurizes the ink stored in the intermediate tank 12 by pressing the intermediate tank 12 from the outside. In addition, a device that uses the adjustment of the relative position in the vertical direction between the recording head 100 and the intermediate tank 12 to generate a water level pressure difference can also be used as the pressurizing mechanism. In addition, although a structure in which the pump 16 is provided in the middle of the supply passage 13 is illustrated, it is not limited thereto. For example, the pump 16 can also be provided in the intermediate tank 12.

[0044] The recording head 100 includes a filter member 20 and a liquid ejection unit 30.

[0045] The liquid ejection unit 30 has a nozzle surface 32 provided with nozzles 31 for ejecting ink. In the present embodiment, a nozzle row in which a plurality of nozzles 31 are arranged in parallel in the Y direction is formed on the nozzle surface 32. The number of nozzle rows is not particularly limited. In addition, although the recording head 100 is illustrated as having a structure with one liquid ejection unit 30, it is not limited thereto, and it can also have a plurality of liquid ejection units 30.

[0046] In addition, inside the liquid ejection unit 30 (not shown), there are provided a flow path communicating with the nozzle 31, a pressure generating unit that causes a pressure change in the ink within the flow path, and the like. As the pressure generating unit, for example, a unit that causes a volume change in the liquid flow path by the deformation of a piezoelectric actuator having a piezoelectric material with an electromechanical conversion function, thereby causing a pressure change in the ink within the liquid flow path and ejecting ink droplets from the nozzle 31; a unit that ejects ink droplets from the nozzle 31 by generating bubbles due to the heat generation of a heating element disposed within the flow path; or a so-called electrostatic actuator that generates static electricity between a diaphragm and an electrode and causes the diaphragm to deform by the static electricity, thereby ejecting ink droplets from the nozzle 31, etc. can be used.

[0047] Utilize Figure 3 , the filter component 20 according to the present embodiment will be described. Figure 3 Is a cross-sectional view of the recording head, and similar to Figure 1 , the recording head 100 is shown in a state where it is arranged such that the ink ejection direction is the +W direction.

[0048] The filter component 20 is laminated with a first filter component 21 and a second filter component 22, and has a filter chamber 50 inside. Specifically, the filter component 20 includes a first filter component 21 provided on the side of the holding portion 101 (not shown) Figure 3 The -W direction side shown) and a second filter component 22 provided on the liquid ejection unit 30 side of the first filter component 21 Figure 3 The +W direction side shown), and the first filter component 21 and the second filter component 22 are laminated. Although the first filter component 21 and the second filter component 22 can be formed of, for example, a resin material, the material is not particularly limited to the resin material.

[0049] In the first filter component 21, a first recess 51 is formed on the surface on the side closer to the second filter component 22 Figure 3 The +W direction side shown). On the side of the holding portion 101 (not shown) of the first filter component 21 Figure 3 The -W direction side shown), an inlet 54 and an outlet 59, which are through-holes penetrating in the W direction, are formed. The outlet 59 is located above the inlet 54 in the Z direction, which is the vertical direction.

[0050] In the second filter component 22, a second recess 52 is formed on the surface on the side closer to the first filter component 21 Figure 3 The -W direction side shown). On the liquid ejection unit 30 side of the second filter component 22 Figure 3On the +W direction side (as shown), an outflow port 56 is formed as a through-hole penetrating in the W direction. The outflow port 56 is connected to a flow path (not shown) provided inside the liquid ejection unit 30.

[0051] The filter chamber 50 includes an upstream chamber 50A and a downstream chamber 50B divided by a filter 57 through which ink passes. In the present embodiment, the filter chamber 50 constituted by the first recess 51 and the second recess 52 is formed by laminating the first filter member 21 and the second filter member 22. And the filter 57 is provided so as to cover the opening of the second recess 52. Through such a filter 57, the filter chamber 50 is divided into the upstream chamber 50A and the downstream chamber 50B.

[0052] The upstream chamber 50A is the space on the upstream side of the filter chamber 50 compared to the filter 57, and the downstream chamber 50B is the space on the downstream side compared to the filter 57. The space on the upstream side compared to the filter 57 is referred to as the one of the two spaces divided by the filter 57 of the filter chamber 50 that is relatively farther from the nozzle 31 that ejects ink, and the downstream space is referred to as the one of the two spaces that is relatively closer to the nozzle 31.

[0053] The filter 57 is a component that captures foreign matters, air bubbles, etc. contained in the ink, and in the present embodiment, it is fixed to the second filter member 22 by hot melt bonding, an adhesive, or the like. In addition, examples of the filter 57 include a component formed by weaving fine metal wires diagonally, a component having a plurality of holes provided in a flat plate member made of SUS, a non-woven fabric, and the like.

[0054] In addition, the flow path resistance of the filter 57 is greater than the flow path resistance of the entire discharge channel 14. The flow path resistance of the discharge channel 14 referred to herein means the flow path resistance from the discharge port 59 of the upstream chamber 50A to the intermediate tank 12.

[0055] In the filter member 20 configured in this way, a supply channel 13 is connected to the inlet 54, a discharge channel 14 is connected to the discharge port 59, and the ink flows as follows. The ink is supplied from the intermediate tank 12 to the upstream chamber 50A of the filter chamber 50 via the supply channel 13 and the inlet 54. In addition, the ink that has not passed through the filter 57 is discharged from the upstream chamber 50A of the filter chamber 50 to the intermediate tank 12 via the discharge port 59 and the discharge channel 14. In addition, the ink that has passed through the filter 57 from the upstream chamber 50A and is supplied to the downstream chamber 50B is supplied to the liquid ejection unit 30 via the outflow port 56.

[0056] In addition, although the above-described inkjet recording apparatus 1 is configured such that one liquid supply unit 10 including a main tank 11, an inter-tank supply passage 17, an intermediate tank 12, a supply passage 13, a discharge passage 14, an on-off valve 15, and a pump 16 is provided for one recording head 100, the structure is not limited thereto. It may also be configured to supply ink to one recording head 100 from a plurality of liquid supply units 10. For example, the inkjet recording apparatus 1 is configured to include a plurality of liquid supply units 10 that respectively supply a plurality of inks having different colors. Further, it is configured such that a plurality of filter chambers 50 are provided in the recording head 100, and ink is supplied from each liquid supply unit 10 to each filter chamber 50.

[0057] In addition, although the above-described inkjet recording apparatus 1 is configured to include a line head 2 having one recording head 100, the structure is not limited thereto, and it may also have a plurality of recording heads 100. In this case, it is only necessary to be configured to distribute ink from one liquid supply unit 10 to each recording head 100 or to distribute ink from a plurality of liquid supply units 10 to each recording head 100, respectively.

[0058] For example, a flow path is provided in a holding unit 101 that holds a plurality of recording heads 100, and the flow path branches at the middle in the number corresponding to the number of recording heads 100. Further, it is configured such that ink supplied from the liquid supply unit 10 is supplied to the upstream chamber 50A of each recording head 100 via the flow path provided in the holding unit 101. In addition, it may also be configured such that the intermediate tank 12 and each recording head 100 are connected through a supply passage 13 and a discharge passage 14, respectively, and ink is distributed from the intermediate tank 12 to each recording head 100.

[0059] In addition, although the above-described inkjet recording apparatus 1 is configured such that one liquid ejection unit 30 is provided in one recording head 100, the configuration is not limited thereto, and the number of liquid ejection units 30 may also be two or more. In this case, for example, a branch flow path that communicates with the flow outlet 56 and branches at the middle in the number corresponding to the number of liquid ejection units 30 can also be used, so that ink is supplied from the downstream chamber 50B to each liquid ejection unit 30 via the branch flow path.

[0060] The inkjet recording apparatus 1 of the present embodiment includes a control unit 18. The control unit 18 is configured to include, for example, a control device such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array) and a storage device such as a semiconductor memory. The control unit 18 uniformly controls the conveyance unit 4, the liquid supply unit 10, the recording head 100, etc. of the inkjet recording apparatus 1 by executing a program stored in the storage device by the control device.

[0061] The control unit 18 performs an ink filling operation by controlling the opening / closing valve 15 and the pump 16. The filling operation refers to an operation of filling ink starting from a state where ink is not filled in the ink flow paths of the filter chamber 50 and the recording head 100. The filling operation is performed, for example, when the inkjet recording apparatus 1 is used for the first time. In addition, the filling operation is performed after all the ink in the ink flow paths of the filter chamber 50 and the recording head 100 has been discharged due to maintenance, cleaning, etc. of the inkjet recording apparatus 1 and the recording head 100.

[0062] Using Figures 4 to 9 , the filling operation performed by the control unit and the filling method of the recording head 100 will be described in detail. Figures 4 to 7 FIG. is a cross-sectional view of the recording head during the filling operation, and is arranged in the same manner as Figure 3 such that the ink ejection direction is the +W direction. In addition, Figure 8 FIG. is a flowchart of the filling operation. In addition, in Figures 4 to 7 , the white opening / closing valve 15 indicates an open state, and the blackened opening / closing valve 15 indicates a closed state.

[0063] As Figure 4 shown, the control unit 18 opens the opening / closing valve 15 ( Figure 8 step S1), and drives the pump 16 in a state where the opening / closing valve 15 is open so that ink does not pass through the filter 57 ( Figure 8 step S2).

[0064] As a result of opening the opening / closing valve 15 and driving the pump 16, ink is supplied from an intermediate tank 12 (not shown) to the upstream chamber 50A. Since the pressure of the ink in this state does not exceed the bubble point of the filter 57, the ink does not pass through the filter 57.

[0065] As Figure 5 shown, the control unit 18 drives the pump 16 to fill the upstream chamber 50A with ink ( Figure 8 step S3). Strictly speaking, the space from the upstream chamber 50A to the opening / closing valve 15 of the discharge passage 14 is filled with ink.

[0066] Specifically, the control unit 18 determines that the upstream chamber 50A is filled with ink if a predetermined time has elapsed after driving the pump 16. As such a predetermined time, it is sufficient to obtain a time that is enough to fill the upstream chamber 50A with ink after driving the pump 16 through actual measurement or simulation.

[0067] As another method, the pressure applied to the on-off valve 15 or the pressure pressurized by the pump 16 when the upstream chamber 50A is filled with ink after driving the pump 16 is obtained in advance by measurement, and this is set as the reference pressure. And the control unit 18 measures in advance the pressure applied to the on-off valve 15 or the pressure pressurized by the pump 16, and if these pressures reach the reference pressure, it is regarded that the upstream chamber 50A is filled with ink.

[0068] In addition, as another method, a sensor for detecting the situation where the ink reaches the on-off valve 15 can be provided, and if the sensor detects the ink, the control unit 18 regards that the upstream chamber 50A is filled with ink. For this sensor, a liquid level sensor such as a capacitance type or an ultrasonic type can be used, etc., but the type of the sensor is not particularly limited as long as it can detect the situation where the ink has reached the on-off valve 15.

[0069] After the upstream chamber 50A is filled with ink by the control unit 18, the pump 16 is still driven, and the on-off valve 15 is in an open state. In addition, as described above, the flow path resistance of the filter 57 is greater than the overall flow path resistance of the discharge passage 14. Therefore, the ink does not pass through the filter 57 but flows from the discharge port 59 to the discharge passage 14. That is, by driving the pump 16, the ink flows from the intermediate tank 12 toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14.

[0070] As Figure 6 shown, the control unit 18 closes the on-off valve 15 during the period when the ink flows from the intermediate tank 12 toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14 by driving the pump 16 ( Figure 8 step S4). The timing of closing the on-off valve 15 can be any timing after the upstream chamber 50A is filled with ink.

[0071] By closing the on-off valve 15 by the control unit 18 while the ink is in a flowing state, a relatively high pressure is generated in the upstream chamber 50A due to the inertia of the ink flowing from the upstream chamber 50A toward the on-off valve 15. By this water hammer action, the pressure of the ink flowing in the upstream chamber 50A instantaneously rises and exceeds the bubble point of the filter 57. Therefore, the ink passes through the filter 57 and flows into the downstream chamber 50B. Then, as Figure 7 shown, the downstream chamber 50B is also filled with ink, and the ink is supplied to the liquid ejection unit 30 via the outflow port 56.

[0072] Further, although not particularly illustrated, after the entire filter chamber 50 has been filled with ink and the ink flow path up to the nozzles 31 of the recording head 100 has been filled with ink, the control unit 18 stops the pump 16 and ends the filling operation. For example, when a predetermined time has elapsed after driving the pump 16 or when it is detected that ink has been ejected from the nozzles 31 after driving the pump 16, it is determined that the ink flow path up to the filter chamber 50 and the nozzles 31 of the recording head 100 has been filled with ink, and the pump 16 is stopped.

[0073] Use Figure 9 to illustrate the change in the pressure acting on the filter 57 due to the ink. Figure 9 It is a diagram showing the change in the pressure acting on the filter during the filling operation. The vertical axis is the pressure P acting on the filter 57 due to the ink, and the horizontal axis is the time T. The solid line α represents the change in the pressure acting on the filter 57 during the filling operation of the inkjet recording apparatus 1 described above. The dashed line β represents the change in the pressure acting on the filter during the filling operation as a comparative example different from the filling operation of the present invention.

[0074] As shown by the solid line α, at the time T1 corresponding to Figure 8 step S2 of the flowchart, the control unit 18 drives the pump 16. Since the ink gradually increases in the upstream chamber 50A, the pressure P increases compared to the pressure P0 before driving the pump 16.

[0075] At the time T2 corresponding to Figure 8 step S3 of the flowchart, the upstream chamber 50A is filled with ink by the control unit 18. In this state, since the ink flows from the intermediate tank 12 toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14 due to the driving of the pump 16, the pressure P is fixed until the time T3.

[0076] At the time T3 corresponding to Figure 8 step S4 of the flowchart, the control unit 18 closes the on-off valve 15. As described above, since the on-off valve 15 is closed while the ink is flowing toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14, the pressure P generated by the ink acting on the filter 57 due to the water hammer effect instantaneously rises and reaches the bubble point Pb.

[0077] After the time T3, since the ink passes through the filter 57 and flows into the downstream chamber 50B, the pressure P decreases and then is maintained substantially fixed.

[0078] As shown by the dashed line β, in the filling operation of the comparative example, from the drive of the pump at time T1 to the time when the upstream chamber 50A is filled with ink at time T2, it is the same as the solid line α. In the filling operation of the comparative example, the pump is stopped at time T10 after time T2. Therefore, the flow of ink from the intermediate tank 12 toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14 gradually stops. As the flow of this ink stops, the pressure P of the ink acting on the filter 57 slowly decreases and becomes the pressure P0 before driving the pump 16.

[0079] In the filling operation of the comparative example, at the subsequent time T11, the on-off valve 15 is closed, and the pump 16 is driven at time T12. By such an operation, the pressure P of the ink acting on the filter 57 increases and reaches the bubble point Pb at time T13. After time T13, since the ink passes through the filter 57 and flows into the downstream chamber 50B, the pressure P decreases and is then maintained substantially constant.

[0080] In addition, as shown by the solid line α, within the time from when the on-off valve 15 is closed at time T3 to the time T4 when the ink passes through the filter 57, the average time change rate of the pressure of the ink acting on the filter 57 is set as the slope A1. In addition, as shown by the dashed line β, within the time from when the on-off valve 15 is closed at time T11 to the time T13 when the ink passes through the filter 57, the average time change rate of the pressure of the ink acting on the filter 57 is set as the slope B. The slope A1 is greater than the slope B.

[0081] In the filling method of the inkjet recording apparatus 1 and the recording head 100 described above, as Figure 5 shown, by continuing to drive the pump 16 even after the upstream chamber 50A is filled with ink, the ink flows from the intermediate tank 12 to the supply passage 13, the upstream chamber 50A, and the discharge passage 14. Through such a flow of ink, the bubbles remaining in the upstream chamber 50A can be discharged to the discharge passage 14 together with the ink. And, as Figure 6 shown, by closing the on-off valve 15 while the ink is in a flowing state, the pressure of the ink acting on the filter 57 instantaneously rises due to the water hammer effect. Thereby, the bubbles existing in the filter 57 can flow from the downstream chamber 50B to the recording head 100 all at once together with the ink, and the possibility of small bubbles remaining between the filter 57 and the nozzle 31 can be reduced.

[0082] In addition, regarding Figure 9The solid line α is driven by the pump 16 to increase the pressure during the period from time T1 to time T2, and at time T3, the pressure of the ink reaches the bubble point Pb by closing the on-off valve 15. In other words, not only the driving of the pump 16 but also the water hammer effect is used to increase the pressure of the ink.

[0083] On the other hand, for the dotted line β as a comparative example, the pressure is increased by the pump 16 from time T1 to time T2. However, since the pump 16 is stopped at time T10, when the on-off valve 15 is closed at time T11, the pressure of the ink has returned to the original pressure P0. In this state, the pump 16 is driven at time T12, and during the period until the bubble point Pb is reached, the pressure of the ink is increased only by the driving of the pump 16.

[0084] Thus, compared with the filling operation of the comparative example that uses only the pump 16, the filling operation of the present embodiment uses not only the pump 16 but also the water hammer effect. Therefore, in order to set the pressure of the ink to the bubble point Pb, in the inkjet recording apparatus 1 of the present embodiment, a pump 16 with a maximum output less than the maximum output of the pump used in the filling operation of the comparative example can be used. As a result, the energy consumed by the pump 16 can be reduced, and in addition, the pump 16 can be miniaturized.

[0085] In addition, as Figure 9 shown, the slope A1 in the filling operation according to the present embodiment is greater than the slope B in the filling operation according to the comparative example. This means that, compared with the filling operation according to the comparative example, in the filling operation according to the present embodiment, after closing the on-off valve 15 at time T3, the pressure of the ink can be increased in a short time. Thus, since the pressure of the ink can be increased in a short time, the driving time of the pump 16 can be shortened. As a result, the life of the pump 16 can be extended, and in addition, the amount of ink discharged from the nozzle 31 during the filling operation can be reduced. In addition, since the amount of ink can be reduced, the intermediate tank 12 for storing the ink pressurized by the pump 16 can be miniaturized.

[0086] Embodiment 2

[0087] Using Figure 10 and Figure 11 , the inkjet recording apparatus 1 according to Embodiment 2 will be described. Figure 10 is a flowchart of the filling operation, Figure 11 is a diagram for explaining the change in the pressure acting on the filter 57. Figure 11 The solid line γ represents the change in the pressure acting on the filter 57 in the filling operation of the inkjet recording apparatus 1 according to the present embodiment. In addition, the same reference numerals are given to the same components as in Embodiment 1, and redundant descriptions are omitted.

[0088] First, the control unit 18 opens the on-off valve 15 ( Figure 10 step S11), and drives the pump 16 in a state where the on-off valve 15 is opened so that the ink does not pass through the filter 57 ( Figure 10 step S12). Then, the control unit 18 fills the upstream chamber 50A with the ink ( Figure 10 step S13). Since these steps S11 to S13 are the same as steps S1 to S3 of the first embodiment, detailed description thereof is omitted.

[0089] Next, the control unit 18 stops the pump 16 ( Figure 10 step S14). The timing for stopping the pump 16 is not particularly limited.

[0090] The on-off valve 15 is opened by the control unit 18. In addition, as described in the first embodiment, the flow path resistance of the filter 57 is greater than the overall flow path resistance of the discharge passage 14. Therefore, even if the control unit 18 stops the pump 16 after filling the upstream chamber 50A with the ink, the flow of the ink from the intermediate tank 12 toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14 will continue for a while.

[0091] Next, the control unit 18 closes the on-off valve 15 during the period when the ink flows from the intermediate tank 12 toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14 by driving the pump 16 ( Figure 10 step S15). In the present invention, the "period during which the ink flows by driving the pump 16" includes not only the case where the ink flows while the pump 16 is in the driving state as in the first embodiment, but also the state where the ink flows after driving the pump 16 and then stopping the pump 16 as in the second embodiment.

[0092] In addition, as Figure 11 shown by the solid line γ, the time T24 when the on-off valve 15 is closed is set when the pressure P of the ink is equal to or higher than the threshold pressure Pth. The pressure Pth is set so that the pressure P exceeds the bubble point Pb after the on-off valve 15 is closed.

[0093] By closing the on-off valve 15 by the control unit 18 while the ink is in a flowing state, similarly to the first embodiment, the pressure of the ink flowing in the upstream chamber 50A instantaneously rises due to the water hammer effect and exceeds the bubble point of the filter 57. Therefore, the ink passes through the filter 57 and flows into the downstream chamber 50B. Then, the downstream chamber 50B is also filled with the ink, and the ink is supplied to the liquid ejection unit 30 via the outlet 56.

[0094] Using Figure 11, the change in the pressure acting on the filter 57 through the ink is described. As shown by the solid line γ, at time T21, the control unit 18 drives the pump 16. Since the ink gradually increases in the upstream chamber 50A, the pressure P increases compared to the pressure P0 before driving the pump 16.

[0095] At time T22, the upstream chamber 50A is filled with ink by the control unit 18. In this state, since the ink flows from the intermediate tank 12 toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14 by driving the pump 16, the pressure P is fixed until time T23.

[0096] At time T23, the control unit 18 stops the pump 16. Since the pump 16 is stopped, although the flow of the ink continues, the pressure P gradually decreases.

[0097] At time T24, the control unit 18 closes the on-off valve 15. As described above, after the pump 16 stops, the ink still flows toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14. Therefore, as in the first embodiment, when the on-off valve 15 is closed while the ink is flowing, the pressure P generated by the ink acting on the filter 57 due to the water hammer effect instantaneously rises and reaches the bubble point Pb.

[0098] After time T25, since the ink passes through the filter 57 and flows into the downstream chamber 50B, the pressure P decreases and is then maintained substantially fixed.

[0099] In addition, as shown by the solid line γ, within the time from when the on-off valve 15 is closed at time T24 to the time T25 when the ink passes through the filter 57, the average time change rate of the pressure of the ink acting on the filter 57 is set as the slope A2. The slope A2 is greater than the slope B. Also, the slope A1 is greater than the slope A2.

[0100] In the filling method of the inkjet recording apparatus 1 and the recording head 100 described above, by continuously driving the pump 16 from time T22 when the upstream chamber 50A is filled with ink to time T23, the ink flows from the intermediate tank 12 toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14. Through such a flow of the ink, the bubbles remaining in the upstream chamber 50A can be discharged to the discharge passage 14 together with the ink.

[0101] At time T22, after the upstream chamber 50A is filled with ink, the pump 16 is stopped at time T23. Thus, with the pump 16 stopped, but while the flow of ink from the intermediate tank 12 toward the supply passage 13, the upstream chamber 50A, and the discharge passage 14 due to the drive of the pump 16 is continuing, the on-off valve 15 is closed. Thereby, the pressure of the ink acting on the filter 57 can be instantaneously increased by the water hammer effect. And, the air bubbles present in the filter 57 can flow from the downstream chamber 50B to the recording head 100 all at once together with the ink, so that the possibility of small air bubbles remaining between the filter 57 and the nozzle 31 can be reduced.

[0102] In addition, similarly to the first embodiment, in the filling operation of the present embodiment, the maximum output required for the pump 16 can be lower than that of the filling operation of the comparative example. Therefore, in the inkjet recording apparatus 1 of the present embodiment, even if the maximum output of the pump 16 is small, the filling operation can be performed, and thus the pump 16 can be miniaturized.

[0103] Further, the slope A2 in the filling operation according to the present embodiment is greater than the slope B in the filling operation according to the comparative example. Therefore, the same effects as those of the first embodiment are achieved. That is, since the pressure of the ink can be instantaneously increased, the driving time of the pump 16 can be shortened. Thereby, the life of the pump 16 can be extended, and in addition, the amount of ink discharged from the nozzle 31 during the filling operation can be reduced. Further, since the amount of ink can be reduced, the intermediate tank 12 for storing the ink pressurized by the pump 16 can be miniaturized.

[0104] Embodiment 3

[0105] Using Figure 12 , the inkjet recording apparatus 1 according to the third embodiment will be described. Figure 12 FIG. is a cross-sectional view of the recording head, and shows the recording head 100 in a state where it is arranged such that the ink ejection direction is the +W direction, similarly to Figure 1 . In addition, the same reference numerals as those of the components in the first embodiment are used, and redundant descriptions are omitted.

[0106] In the recording head 100 of the present embodiment, a filter lower discharge passage 58 is provided on the filter member 20. The filter lower discharge passage 58 is a flow path for returning the ink in the downstream chamber 50B on the downstream side of the filter 57 to the intermediate tank 12 via the liquid ejection portion 30. In the present embodiment, one opening of the filter lower discharge passage 58 is connected to the liquid ejection portion 30, and the other opening is connected to the intermediate tank 12 through a flow path (not shown).

[0107] In such a recording head 100, ink is supplied from the downstream chamber 50B to the liquid ejection section 30, and the ink that has not been ejected from the nozzles 31 returns from the liquid ejection section 30 to the intermediate tank 12 via the under-filter discharge passage 58.

[0108] In the inkjet recording apparatus 1 described above, the same filling operation as in the first embodiment is performed, and the same effects as in the first embodiment are achieved. Further, in such an inkjet recording apparatus 1, minute bubbles in the liquid ejection section 30 that cannot be completely removed from the liquid ejection section 30 by the filling operation can also be discharged from the under-filter discharge passage 58 through the flow path inside the liquid ejection section 30. Therefore, even when minute bubbles flow into and remain in the downstream chamber 50B due to the filling operation, it is possible to prevent the bubbles from reaching the nozzles 31, and thus ejection failure due to bubbles can be reduced. Additionally, the under-filter discharge passage 58 may be formed in a component different from the filter member 20.

[0109] Other embodiments

[0110] As described above, although one embodiment of the present invention has been described, the basic structure of the present invention is not limited to the above description.

[0111] Although the intermediate tank 12 is used as the liquid storage section in the above embodiment, the present invention is not limited thereto. For example, the main tank 11 may be used as the liquid storage section, and the main tank 11 and the upstream chamber 50A may be connected by a supply passage 13 and a discharge passage 14.

[0112] Although the supply passage 13 and the discharge passage 14 are directly connected to the upstream chamber 50A of the filter member 20 in the above embodiment, the present invention is not limited thereto. For example, a flow path for supplying ink to the filter chamber 50 may be provided on the holding section 101, and the supply passage 13 and the discharge passage 14 may be connected to the upstream chamber 50A via this flow path. Further, instead of the holding section 101, a flow path member for supplying ink to the filter chamber 50 may be provided, and the supply passage 13 and the discharge passage 14 may be connected to the upstream chamber 50A via this flow path member.

[0113] Although in the above-described embodiments, as the inkjet recording apparatus 1, a line head 2 having a recording head 100 is exemplified, which is fixed to a holding portion 101 and printing is performed only by conveying a medium S, it is not particularly limited thereto. The present invention can also be applied to a so-called serial recording apparatus in which the recording head 100 is mounted on a carriage that moves in a direction intersecting the conveying direction of the medium S and the recording head 100 reciprocates in a direction intersecting the conveying direction while printing is performed. In the serial recording apparatus, the carriage holds the recording head 100 while tilting it so that the direction of ejecting ink is inclined with respect to the +Z direction. And, the reciprocating movement direction of the carriage is set as the Y direction. In such a serial recording apparatus, the same operational effects as those in Embodiments 1 to 3 are also achieved.

[0114] Moreover, the present invention is an invention that broadly targets all types of liquid ejection heads. For example, it can also be applied to various inkjet recording heads and the like used in image recording apparatuses such as printers, color material ejection heads used in the manufacture of color filters for liquid crystal displays, etc., electrode material ejection heads used in the formation of electrodes for organic EL displays, FED (field emission displays), etc., and biological organic matter ejection heads used in the manufacture of biochips. Of course, it is not particularly limited to the liquid ejection apparatus equipped with such a liquid ejection head.

[0115] Reference Signs

[0116] 1... Inkjet recording apparatus (liquid ejection apparatus); 10... Liquid supply unit; 11... Main tank; 12... Intermediate tank (liquid storage unit); 13... Supply passage; 14... Discharge passage; 15... On-off valve; 16... Pump (pressurizing mechanism); 18... Control unit; 20... Filter member; 30... Liquid ejection unit; 31... Nozzle; 50... Filter chamber; 50A... Upstream chamber; 50B... Downstream chamber; 57... Filter; 100... Inkjet recording head.

Claims

1. A liquid ejection device, characterized in that, Comprising: A liquid ejection unit that ejects liquid; A liquid storage unit that stores liquid; A filter chamber that includes an upstream chamber and a downstream chamber divided by a filter through which liquid passes; A supply passage that allows liquid to flow from the liquid storage unit to the upstream chamber; A discharge passage that allows liquid to flow from the upstream chamber to the liquid storage unit; An opening / closing valve that opens and closes the discharge passage; A pressurizing mechanism that pressurizes liquid to cause the liquid to flow from the liquid storage unit to the upstream chamber, The liquid ejection device performs a filling operation as follows. That is, with the opening / closing valve open, the pressurizing mechanism is driven in such a way that liquid does not pass through the filter and the downstream chamber, causing the liquid to flow from the liquid storage unit toward the supply passage, the upstream chamber, and the discharge passage. After the upstream chamber is filled with liquid, during the period when the liquid is caused to flow from the liquid storage unit toward the supply passage, the upstream chamber, and the discharge passage by the driving, the opening / closing valve is closed so that the liquid passes through the filter and the downstream chamber.

2. The liquid ejection device according to claim 1, wherein: In the filling operation, after the upstream chamber is filled with liquid, the opening / closing valve is closed while the pressurizing mechanism is being driven.

3. The liquid ejection device according to claim 1, wherein: In the filling operation, after the upstream chamber is filled with liquid, the opening / closing valve is closed after the pressurizing mechanism is stopped.

4. The liquid ejection device according to any one of claims 1 to 3, wherein: The average time change rate of the pressure of the liquid acting on the filter from when the opening / closing valve is closed in the filling operation until the liquid passes through the filter is greater than the average time change rate of the pressure of the liquid acting on the filter when the pressurizing mechanism is driven with the opening / closing valve closed until the liquid passes through the filter.

5. A method for filling a liquid ejection head, wherein: The liquid ejection head comprises: A liquid ejection unit that ejects liquid; A liquid storage unit that stores liquid; A filter chamber that includes an upstream chamber and a downstream chamber divided by a filter through which liquid passes; A supply passage that allows liquid to flow from the liquid storage unit to the upstream chamber; A discharge passage that allows liquid to flow from the upstream chamber to the liquid storage unit; An opening / closing valve that opens and closes the discharge passage; A pressurizing mechanism that pressurizes liquid to cause the liquid to flow from the liquid storage unit to the upstream chamber, In the method for filling the liquid ejection head, Perform the following filling operation, that is, in a state where the opening / closing valve is opened, drive the pressurizing mechanism in such a manner that liquid does not pass through the filter and the downstream chamber, so that liquid flows from the liquid reservoir portion toward the supply passage, the upstream chamber, and the discharge passage. After the upstream chamber is filled with liquid, close the opening / closing valve during the period when liquid flows from the liquid reservoir portion toward the supply passage, the upstream chamber, and the discharge passage by the drive, so that the liquid passes through the filter and the downstream chamber.

6. The filling method of the liquid ejector head according to claim 5, wherein: In the filling operation, after the upstream chamber is filled with liquid, close the opening / closing valve in a state where the pressurizing mechanism is being driven.

7. The filling method of the liquid ejector head according to claim 5, wherein: In the filling operation, after the upstream chamber is filled with liquid, close the opening / closing valve after stopping the pressurizing mechanism.

8. The filling method of the liquid ejector head according to any one of claims 5 to 7, wherein: The average time change rate of the pressure of the liquid acting on the filter from when the opening / closing valve is closed in the filling operation until the liquid passes through the filter is greater than the average time change rate of the pressure of the liquid acting on the filter from when the pressurizing mechanism is driven in a state where the opening / closing valve is closed until the liquid passes through the filter.

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