Liquid ejection head

Abstract

This invention relates to a liquid ejector head capable of removing air bubbles through a simple structure. The liquid ejector head of one embodiment includes a common liquid chamber, a common pressure chamber, an actuator, a base plate, a nozzle plate, a buffer, and a bypass flow path. The common liquid chamber has an opening. A common pressure chamber is connected to the common liquid chamber. The actuator has multiple pressure chambers connected to the common pressure chamber. The base plate is provided with the actuator and forms the common pressure chamber together with the actuator. The nozzle plate has multiple nozzles respectively disposed in the multiple pressure chambers. The buffer covers the opening of the common liquid chamber. The bypass flow path connects the common liquid chamber and the common pressure chamber.

Description

Technical Field

[0001] Embodiments of the present invention relate to liquid ejection heads. Background Technology

[0002] As an example of a liquid ejection head used in a liquid ejection device, an inkjet head for ejecting ink is known. Furthermore, an inkjet head having a buffer to maintain a constant negative pressure in a common pressure chamber during ink ejection is also known. The inkjet head needs to remove internal air bubbles during ink filling. However, such inkjet heads suffer from the problem of a relatively large number of air bubbles remaining locally in the buffer. Furthermore, a technique is known in which ribs are provided in the buffer chamber of the inkjet head to flush away air bubbles through the same path as the ink flow. Such inkjet heads require a path for expelling air bubbles and communicating with external gas, resulting in a larger inkjet head size. Summary of the Invention

[0003] The problem to be solved by the present invention is to provide a liquid nozzle that can remove air bubbles through a simple structure.

[0004] The liquid ejector head of this embodiment includes a common liquid chamber, a common pressure chamber, an actuator, a base plate, a nozzle plate, a buffer, and a bypass flow path. The common liquid chamber has an opening. A common pressure chamber is connected to the common liquid chamber. The actuator has multiple pressure chambers connected to the common pressure chamber. The base plate is provided with the actuator and forms the common pressure chamber together with the actuator. The nozzle plate has multiple nozzles respectively disposed in the multiple pressure chambers. The buffer covers the opening of the common liquid chamber. The bypass flow path connects the common liquid chamber and the common pressure chamber. Attached Figure Description

[0005] Figure 1 This is a perspective view showing the structure of the liquid ejector head according to the embodiment.

[0006] Figure 2 This is a perspective view showing the structure of the head body and manifold unit of the liquid ejector head according to the embodiment.

[0007] Figure 3 This is a top view showing the structure of the head body in the embodiment.

[0008] Figure 4 This is a top view showing the structure of the manifold unit according to the embodiment.

[0009] Figure 5 Through Figure 4 The VV-line section shows a cross-sectional view of the head body and manifold unit structure of the embodiment.

[0010] Figure 6 This is a cross-sectional view showing the structure of the head body and manifold unit of the embodiment.

[0011] Figure 7 This is a perspective view showing a portion of the flow path structure of the head body and manifold unit in an embodiment.

[0012] Figure 8 This is a top view showing a portion of the flow path structure of the head body and manifold unit in an embodiment.

[0013] Figure 9 This is a side view showing a portion of the flow path structure of the head body and manifold unit in an embodiment.

[0014] Figure 10 This is a side view showing a portion of the flow path structure of the head body and manifold unit in an embodiment.

[0015] Figure 11 This is an explanatory diagram showing the pressure changes in the shared pressure chamber.

[0016] Figure 12 This is an explanatory diagram showing the pressure changes in the shared pressure chamber.

[0017] Figure 13 This is an explanatory diagram showing the pressure changes in the shared pressure chamber.

[0018] Figure 14 This is an explanatory diagram showing the pressure changes in the shared pressure chamber.

[0019] Figure 15 This is an explanatory diagram showing the pressure changes in the shared pressure chamber.

[0020] Figure 16 This is an explanatory diagram showing the pressure changes in the shared pressure chamber.

[0021] Figure 17 This is an explanatory diagram showing the relationship between the width of the buffer and the strain area.

[0022] Figure 18 This is an explanatory diagram showing the relationship between the width of the buffer and the strain area.

[0023] Figure 19 This is an explanatory diagram showing the structure of the liquid ejection device according to an embodiment.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1: Liquid ejector head; 2: Liquid ejection device (inkjet recording device); 11: Head body; 12: Manifold unit; 13: Circuit board; 14: Cover; 111: Board; 112: Frame; 113: Actuator; 114: Nozzle plate; 116: Common pressure chamber; 121: Manifold; 122: Top plate; 123: Ink supply pipe; 124: Ink discharge pipe; 125: Temperature regulating water supply pipe; 127: Buffer; 128: Bypass flow path; 1111: Supply port; 1112: Discharge port; 1131: Pressure chamber; 1133: Wall; 1141: Nozzle; 1161: First common pressure chamber; 1162: Second common pressure chamber; 1163: Third common pressure chamber; 1211: Common liquid chamber; 1212: Discharge flow path; 1213: Temperature regulating flow path ; 1221: Opening; 2001: Conveying channel; 2111: Housing; 2112: Media supply unit; 2113: Image forming unit; 2114: Media discharge unit; 2115: Conveying device; 2116: Temperature regulating device; 2117: Maintenance device; 2118: Control unit; 2120: Support unit; 2130: Head unit; 2132: Supply tank; 2134: Pump; 2135: Connecting flow path; 12111: Top plate; 21121: Paper supply box; 21141: Paper discharge tray; 21161: Temperature regulating water tank; 21162: Temperature regulating circuit; 21201: Conveyor belt; 21202: Support plate; 21203: Belt roller; 21211~21218 guide plate pair; 21221~21228: Conveying roller; P: Paper. Detailed Implementation

[0026] The following is for reference Figures 1 to 19 The liquid nozzle 1 of the embodiment and the liquid ejection device 2 using the liquid nozzle 1 will be described. Figure 1 This is a perspective view showing the structure of the liquid ejector head 1 according to the embodiment. Figure 2 This is a perspective view showing the structure of the head body 11 of the liquid ejector head 1 and the manifold unit 12. Figure 3 This is a top view showing the structure of the head body 11 with the nozzle plate 114 omitted. Figure 4 This is a top view showing the structure of the manifold unit 12.

[0027] Figure 5 Through Figure 4 The VV-line section shows a cross-sectional view of the structure of the head body 11 and the manifold unit 12. Figure 6 This is a cross-sectional view showing the structure of the head body 11 and the manifold unit 12. Figure 7 This is a perspective view showing a portion of the flow path structure of the head body 11 and the manifold unit 12. Figure 8 This is a top view showing a portion of the flow path structure of the head body 11 and the manifold unit 12. Figure 9 as well as Figure 10 This is a side view showing a portion of the flow path structure of the head body 11 and the manifold unit 12. Figure 9 as well as Figure 10 Shown from different directions. Figures 11 to 16 This is an explanatory diagram showing the pressure change in the common pressure chamber caused by the shape difference of the buffer 127. Figure 17 as well as Figure 18 This is an explanatory diagram showing the relationship between the shape of the buffer 127 and the strain area. Figure 19 This is an explanatory diagram showing the structure of the liquid ejection device 2. Furthermore, in each figure, the structure is shown in an enlarged, reduced, or omitted manner for illustrative purposes.

[0028] Liquid ejector head 1 is, for example, set in Figure 19 The inkjet head of the liquid ejection device 2, such as the inkjet recording device, is shown. The liquid ejection head 1 is provided in the head unit 2130, which includes a supply tank 2132, which serves as a liquid receiving part, provided in the liquid ejection device 2.

[0029] The liquid nozzle 1 is supplied with liquid ink stored in the supply tank 2132. The liquid nozzle 1 can be a non-circulating type that does not circulate the ink, or it can be a circulating type that circulates the ink. In this embodiment, a non-circulating type nozzle is used as an example to illustrate the liquid nozzle 1. Furthermore, the liquid nozzle 1 is connected to a temperature control device 2116 provided in the liquid dispensing device 2 and is supplied with a temperature-regulating liquid (temperature-regulating water) for controlling the temperature of the ink.

[0030] like Figures 1 to 5 As shown, the liquid ejector head 1 includes a head body 11, a manifold unit 12, a circuit board 13, and a cover 14. For example, the liquid ejector head 1 is a side shooter type four-row integrated head with two sets of head bodies 11, wherein each head body 11 has a pair of actuators 113.

[0031] The head body 11 ejects liquid. For example... Figure 3 , Figure 5 as well as Figure 6 As shown, the head body 11 includes a base plate 111, a frame 112, an actuator 113, and a nozzle plate 114. Furthermore, the head body 11 has a common pressure chamber 116. In this embodiment, an example using one head body 11 with two actuators 113 will be described.

[0032] The substrate 111 is formed into a rectangular plate shape, for example, using a ceramic material. The substrate 111 is formed into a rectangle that is longer in one direction. The substrate 111 has one or more supply ports 1111 and one or more discharge ports 1112. A pair of actuators 113 are disposed on the substrate 111, and wiring patterns for driving the actuators 113 are formed. The supply ports 1111 and discharge ports 1112 are through holes passing through the two main surfaces of the substrate 111.

[0033] For example, a single supply port 1111 is provided at a position opposite to the first common pressure chamber 1161 (described later), which is the common pressure chamber 116. The supply port 1111 is, for example, an elongated hole that is longer in one direction along the long side of the first common pressure chamber 1161.

[0034] For example, two outlets 1112 are provided at a position opposite to one of the two third common pressure chambers 1163 described later as common pressure chamber 116. In addition, for example, an outlet 1112 is provided on a substrate 111 adjacent to one end of a pair of actuators 113 along the long side direction.

[0035] The frame 112 is fixed to the main surface of one side of the substrate 111 by an adhesive or the like. The frame 112 surrounds the supply port 1111, multiple discharge ports 1112 and actuator 113 provided on the substrate 111.

[0036] For example, the frame 112 is formed as a rectangular frame, thereby forming an opening that is longer in one direction along the long side of the frame 112. A pair of actuators 113, a supply port 1111, and two discharge ports 1112 are arranged at the opening of the frame 112.

[0037] A pair of actuators 113 are bonded to the mounting surface of the substrate 111. The pair of actuators 113 are arranged in two rows on the substrate 111, separated by a supply port 1111. Each actuator 113 is formed as a plate that is longer in one direction. The actuators 113 are disposed within an opening in the frame 112 and bonded to the main surface of the substrate 111. Specifically, the actuator 113 is formed by bonding two rectangular plates of piezoelectric material that are longer in one direction to each other, with their polarization directions facing opposite directions. Here, the piezoelectric material is, for example, PZT (lead zirconate titanate). The actuators 113 are bonded to the mounting surface of the substrate 111, for example, using a thermosetting epoxy adhesive.

[0038] The actuator 113, for example, has a plurality of pressure chambers 1131 arranged at equal intervals along its long side. On the main surface side of the actuator 113 opposite to the substrate 111 side, a plurality of grooves are formed along the long side of the actuator 113, through which pressure chambers 1131 are formed. In other words, the actuator 113 has a plurality of walls arranged at equal intervals along its long side, with grooves formed between them. The plurality of walls 1133 form a plurality of pressure chambers 1131 between adjacent walls. The walls 1133 are piezoelectric elements that change the volume of the pressure chambers 1131 by applying a driving voltage.

[0039] The side of the actuator 113 opposite to the substrate 111 is bonded to the nozzle plate 114. In addition, the actuator 113 is formed with wiring patterns for driving a plurality of pressure chambers 1131.

[0040] The pressure chamber 1131 is used to eject ink from the nozzle 1141 during printing or other operations of the liquid ejector head 1. In this embodiment, an example with multiple pressure chambers 1131 in the actuator 113 has been described, but a structure with air chambers alternately arranged with multiple pressure chambers 1131 is also possible. In the case of air chambers adjacent to the pressure chambers 1131, nozzles 1141 are arranged in the portion of the nozzle plate 114 opposite the pressure chambers 1131, while no nozzles 1141 are arranged in the portion opposite the air chambers. That is, ink is not ejected from the air chambers. The air chambers are, for example, blocked at both ends of the slot of the actuator 113 using walls formed of photosensitive resin. An air chamber is formed by blocking the slot of the actuator 113 using the substrate 111, the nozzle plate 114, and the walls at both ends.

[0041] The nozzle plate 114 is formed in a plate shape. The nozzle plate 114 is fixed to the main surface of the frame 112 opposite to the base plate 111 by an adhesive or the like. The nozzle plate 114 has a plurality of nozzles 1141 formed at positions opposite to the plurality of pressure chambers 1131. In this embodiment, the nozzle plate 114 has two rows of nozzles 1141 arranged in one direction.

[0042] The multiple nozzles 1141 opposite to the multiple pressure chambers 1131 are holes for spraying ink during printing or other actions of the liquid ejector head 1.

[0043] A common pressure chamber 116 is connected to a supply port 1111. The common pressure chamber 116 is disposed around a pair of actuators 113. Specifically, the common pressure chamber 116 is connected to the primary and secondary sides of the plurality of pressure chambers 1131 of each actuator 113. In addition, the common pressure chamber 116 is connected to a discharge port 1112.

[0044] As a specific example, the common pressure chamber 116 includes: a first common pressure chamber 1161, which is longer in one direction; two second common pressure chambers 1162, which are longer in one direction; and a third common pressure chamber 1163, such that the two ends of the first common pressure chamber 1161 are continuous with the two ends of the two second common pressure chambers 1162. Furthermore, the common pressure chamber 116 connects the primary side of the supply port 1111 and the plurality of pressure chambers 1131 of the actuator 113 through the first common pressure chamber 1161, and connects the secondary side of the third common pressure chamber 1163 and the plurality of pressure chambers 1131 through the second common pressure chambers 1162.

[0045] The primary side of pressure chamber 1131 is the upstream side of pressure chamber 1131 in the direction of liquid flow, and in this embodiment, it is the first common pressure chamber 1161 side of pressure chamber 1131. The secondary side of pressure chamber 1131 is the downstream side of pressure chamber 1131 in the direction of liquid flow, but in this embodiment, it is the second common pressure chamber 1162 side of pressure chamber 1131.

[0046] A first common pressure chamber 1161 is formed between a pair of actuators 113. The first common pressure chamber 1161 forms an ink flow path from the supply port 1111 to the primary side of the plurality of pressure chambers 1131 of each actuator 113. In addition, the first common pressure chamber 1161 forms an ink flow path from the supply port 1111 to the two third common pressure chambers 1163 at both ends in the long side direction of the first common pressure chamber 1161 (actuator 113).

[0047] The second common pressure chamber 1162 is formed between each actuator 113 and the frame 112. The second common pressure chamber 1162 forms an ink flow path with an opening from the third common pressure chamber 1163 to the secondary side of the plurality of pressure chambers 1131.

[0048] The third common pressure chamber 1163 is adjacent to both ends of the actuator 113 along its long side. The third common pressure chamber 1163 connects to the first common pressure chamber 1161 and the second common pressure chamber 1162 at both ends of the pair of actuators 113 along their long sides. The third common pressure chamber 1163 forms a portion of the ink flow path that does not pass from the first common pressure chamber 1161 through the multiple pressure chambers 1131 of each actuator 113, but reaches the second common pressure chamber 1162. Furthermore, the third common pressure chamber 1163 forms an ink path from the first common pressure chamber 1161 and the two second common pressure chambers 1162 to the discharge port 1112.

[0049] like Figure 1 , Figure 2 , Figures 4 to 6As shown, the manifold unit 12 includes a manifold 121, a top plate 122, an ink supply pipe 123, an ink discharge pipe 124, a pair of temperature regulating pipes, namely a temperature regulating water supply pipe 125 and a temperature regulating water discharge pipe, a buffer 127, and a bypass flow path 128. Furthermore, the number of ink supply pipes 123, ink discharge pipes 124, temperature regulating water supply pipes 125, and temperature regulating water discharge pipes can be appropriately set.

[0050] Manifold 121 is formed in a plate-like or block-like shape. For example... Figures 6 to 9 As shown, the manifold 121 includes: a common liquid chamber 1211, which is continuous with the supply port 1111 of the substrate 111 to form a liquid supply flow path; a discharge flow path 1212, which is continuous with the discharge port 1112 of the substrate 111 to form a liquid discharge flow path; and a temperature regulating flow path 1213, which forms a flow path for fluid used for temperature regulation. Additionally, Figures 7 to 10 This is a diagram showing the structure of the flow path formed by the head body 11 and the manifold unit 12.

[0051] One side of the manifold 121 is fixed to the main surface of the substrate 111. In addition, a top plate 122 is fixed to the main surface of the manifold 121 opposite to the main surface on which the substrate 111 is fixed. Furthermore, an ink supply pipe 123, an ink discharge pipe 124, a temperature-regulating water supply pipe 125, and a temperature-regulating water discharge pipe are fixed to the manifold 121, for example, through the top plate 122.

[0052] The common liquid chamber 1211 is formed in the flow path of the manifold 121 through holes and grooves. The common liquid chamber 1211 fluidly connects the ink supply pipe 123 and the supply port 1111 of the substrate 111.

[0053] For example, such as Figures 6 to 9 As shown, the common liquid chamber 1211 is a cuboid flow path extending along the long side of the actuator 113 and the long side of the supply port 1111. The supply port 1111 is continuous with the lower part of the common liquid chamber 1211, and a buffer 127 is provided above the common liquid chamber 1211, i.e., the top plate portion 12111.

[0054] For example, the width of the long side of the common liquid chamber 1211 on the substrate 111 side is larger than the width of the long side of the supply port 1111, and the width of the top plate portion 12111 on the long side is smaller than the width of the long side of the substrate 111 side. Furthermore, for example, in the short side direction orthogonal to the long side of the common liquid chamber 1211, the width of the upper top plate portion 12111 is larger than the width of other portions (substrate 111 side). For example, the manifold 121 is formed by integrally assembling two separate components, with the substrate 111 side formed by the lower component and the top plate portion 12111 formed by the upper component.

[0055] The discharge path 1212 is a flow path formed in the manifold 121 through holes and grooves. The discharge path 1212, for example, fluidly connects the ink discharge pipe 124 and the two discharge ports 1112 of the substrate 111.

[0056] The temperature regulating flow path 1213 is a flow path formed in the manifold 121 through holes and grooves. The temperature regulating flow path 1213 fluidly connects the temperature regulating water supply pipe 125 and the temperature regulating water discharge pipe.

[0057] The two ends of the temperature regulating flow path 1213 are openings that connect to the temperature regulating water supply pipe 125 and the temperature regulating water discharge pipe provided on one side of the main surface of the manifold 121. In addition, the temperature regulating flow path 1213 is configured to exchange heat with the substrate 111 fixed to the manifold 121.

[0058] The top plate 122 is disposed on the side opposite to the surface of the base plate 111 on which the manifold 121 is disposed. The top plate 122 seals the common liquid chamber 1211, the discharge flow path 1212, and the temperature regulation flow path 1213 by covering the manifold 121.

[0059] In addition, the top plate 122 connects to each pipe 123, 124, 125 and has openings that connect each pipe 123, 124, 125 and each flow path 1211, 1212, 1213.

[0060] The ink supply pipe 123 is connected to the common liquid chamber 1211. The ink discharge pipe 124 is connected to the discharge flow path 1212. The temperature regulating water supply pipe 125 and the temperature regulating water discharge pipe are connected to the primary and secondary sides of the temperature regulating flow path 1213.

[0061] In this embodiment, an ink supply pipe 123 is disposed at one end along the long side of the manifold 121, and an ink discharge pipe 124 is disposed at the other end along the long side of the manifold 121. Furthermore, one of a temperature-regulating water supply pipe 125 and a temperature-regulating water discharge pipe is disposed at one end along the long side of the manifold 121, and the other of the temperature-regulating water supply pipe 125 and the temperature-regulating water discharge pipe are disposed at the other end along the long side of the manifold 121.

[0062] The buffer 127 is formed as an elastically deformable film or sheet. The buffer 127 covers the opening 12112 of the top plate portion 12111 of the common liquid chamber 1211. Here, the opening 12112 of the top plate portion 12111 is an opening formed on the side of the top plate 122 on which the manifold 121 is disposed. The buffer 127 elastically deforms according to pressure changes in the common liquid chamber 1211. The buffer 127 is fixed around the opening 12112 of the top plate portion 12111 of the manifold 121. Furthermore, for example, the buffer 127 is held between the manifold 121 and the top plate 122. The lower surface of the buffer 127 faces the common liquid chamber 1211, and the upper surface faces the opening of the top plate 122.

[0063] As a specific example, the buffer 127 is formed of a polyimide membrane. The buffer 127 is formed in a rectangular shape, which is longer in the same direction as the long side of the opening 12112 of the top plate portion 12111 of the common liquid chamber 1211, which is longer in one direction.

[0064] As a preferred example, the width of the buffer 127 in the short side direction is 4 mm or more. The width of the buffer 127 in the short side direction is a width that can be ensured when used in the head body 11. Here, the width of the buffer 127 in the short side direction is the width of the opening 12112 of the top plate portion 12111 of the common liquid chamber 1211 in the short side direction. Furthermore, the thickness of the buffer 127 is 25 μm or less. The lower limit of the thickness of the buffer 127 is set according to the characteristics of the buffer 127, based on the pressure of the common liquid chamber 1211, at which the buffer 127 will not undergo plastic deformation. Furthermore, for example, the buffer 127 is formed using a polyimide film with a Young's modulus of 3.4 GPa.

[0065] The following is based on Figures 11 to 18 The relationship between the width, thickness, and Young's modulus of the short side of the buffer 127 and the function of the buffer 127 is explained.

[0066] Figures 11 to 14 This illustrates the pressure variation when the width of the short side of the buffer 127 is changed. Figures 11 to 14 Pressure was measured and graphically represented at the inlet of the common liquid chamber 1211, which serves as the end of the long side of the common pressure chamber 116, the center of the long side of the common pressure chamber 116, and the inlet of the ink supply channel. Furthermore, Figure 11 This is an example where the width W of the buffer 127 in the short side direction (the width W of the opening 12112 of the top plate portion 12111 of the common liquid chamber 1211 in the short side direction) is set to 1.2 mm. Figure 12 This is an example where the width W of the buffer 127 in the short side direction (the width W of the opening 12112 of the top plate portion 12111 of the common liquid chamber 1211 in the short side direction) is set to 2.0 mm. Figure 13 This is an example where the width W of the buffer 127 in the short side direction (the width W of the opening 12112 of the top plate portion 12111 of the common liquid chamber 1211 in the short side direction) is set to 3.0 mm. Figure 14 This is an example where the width W of the short side of the buffer 127 (the width of the short side of the opening 12112 of the top plate portion 12111 of the common liquid chamber 1211) is set to 4.0 mm.

[0067] In addition, Figures 11 to 14 In any of the examples shown, the liquid ejector head 1 is driven under the same conditions, and the thickness t is set to 25 μm. A membrane made of polyimide with a Young's modulus E of 3.4 GPa is used to form the buffer 127.

[0068] like Figure 11 As shown, when the width W of the short side of the buffer 127 is 1.2 mm, the pressure variation at various locations is relatively large. Figures 11 to 14 As shown, as the width of the short side of the buffer 127 increases, the pressure variation at each location decreases, and when the width W of the short side of the buffer 127 is 4 mm, there is essentially no pressure variation at each location. As is evident from these pressure variation results, when the width W of the short side of the buffer 127 increases, both the peak pressure and the number of pressure variations per time interval decrease. As is also evident from these results, when the buffer 127 is installed, the effect of suppressing pressure variation can be achieved. Furthermore, by setting the width W of the short side of the buffer 127 to 4 mm or more, pressure variation can be appropriately suppressed.

[0069] Figure 15 as well as Figure 16 This relates to the pressure variation when the thickness t of the buffer 127 is set to 50 μm and 25 μm. Additionally, in Figure 15 as well as Figure 16 In the example shown, buffer 127 is formed of a polyimide film with a width W of 4.0 mm in the short side direction and a Young's modulus of 3.4 GPa. Furthermore, Figure 15 as well as Figure 16 The pressure at the inlet of the common liquid chamber 1211, which serves as the end of the common pressure chamber 116, the central part of the common pressure chamber 116, and the inlet of the ink supply channel, is graphically represented.

[0070] like Figure 15 as well as Figure 16As shown, the pressure fluctuation when using a buffer 127 with a thickness of 50 μm was greater than that when using a buffer 127 with a thickness of 25 μm. In particular, when the thickness t of the buffer 127 was set to 25 μm, virtually no pressure fluctuation occurred. As is evident from these results, the use of the buffer 127 effectively suppresses pressure fluctuations. Furthermore, by setting the thickness t of the buffer 127 to 25 μm or less, pressure fluctuations can be appropriately suppressed.

[0071] Figure 17 as well as Figure 18 The graph shows the relationship between the strain area ds and the width of the short side of the buffer 127 when the Young's modulus E of the polyimide film formed by the buffer 127 is set to 9.1 GPa and 3.4 GPa, respectively, with the thickness t of the buffer 127 being 10 μm, 20 μm, 30 μm, 40 μm and 50 μm.

[0072] Here, the strain area ds is calculated based on the following mathematical formulas of the thickness t (m) of the buffer 127 and the width W (m) of the short side direction (short side) of the buffer 127.

[0073]

Mathematical Formula 1

[0074]

[0075] Here, the coefficient k varies depending on the Young's modulus E of the buffer 127. For example, when the Young's modulus E of the buffer 127 is 9.1 GPa, the coefficient k is 2.066 × 10⁻⁶. -12 When the Young's modulus E of buffer 127 is 3.4 GPa, the coefficient k is 5.530 × 10⁻⁶. -12 .

[0076] like Figure 17 as well as Figure 18 As shown, at various thicknesses t, the strain area ds of the buffer 127 made of a polyimide film with a Young's modulus E of 3.4 GPa is larger than that of the buffer 127 made of a polyimide film with a Young's modulus E of 9.1 GPa.

[0077] For example, in order to increase the strain area ds, it is preferable to form the buffer 127 from a polyimide film with a Young's modulus E of 3.4 GPa. Therefore, for example, setting the width W of the buffer 127 in the short side direction to 4 mm or more, setting the thickness t of the buffer 127 to 25 μm or less, and setting the Young's modulus E of the polyimide film forming the buffer 127 to 3.4 GPa are preferred examples of the buffer 127.

[0078] Furthermore, the strain area ds is desired to be, for example, 3.18 × 10⁻⁶.-10 However, as long as the strain area ds can be made to the desired value, the thickness t, the width W in the short side direction, and the Young's modulus E of the buffer 127 can be set appropriately.

[0079] like Figure 2 , Figure 4 , Figures 6 to 9 As shown, the bypass flow path 128 connects the top plate portion 12111 of the common liquid chamber 1211 to the common pressure chamber 116 or the secondary side of the common pressure chamber 116. The bypass flow path 128 is connected, for example, to a position on the top plate portion 12111 of the common liquid chamber 1211 adjacent to the buffer 127. Furthermore, the common pressure chamber 116 or the secondary side of the common pressure chamber 116 connected to the bypass flow path 128 is, for example, the second common pressure chamber 1162 or the third common pressure chamber 1163 of the common pressure chamber 116, the discharge flow path 1212, or the ink discharge pipe 124. The fluid resistance of the bypass flow path 128 is greater than the fluid resistance of the common liquid chamber 1211 and the fluid resistance of the common pressure chamber 116.

[0080] The bypass flow path 128 bypasses the common liquid chamber 1211 and the common pressure chamber 116, thereby expelling air bubbles from the common liquid chamber 1211 during ink maintenance and filling. The cross-sectional shape of the bypass flow path 128 is rectangular or circular. The shape of the bypass flow path 128 may be, for example, straight or partially curved.

[0081] That is, the cross-sectional area, length, and shape of the bypass flow path 128 are set to prevent ink from flowing beyond the required area, length, and shape. Here, ink flowing beyond the required flow means that the flow of ink accompanied by air bubbles during maintenance or filling does not impede the flow of ink during maintenance or filling, and / or does not impede the function of the liquid ejector head 1.

[0082] A specific example of the bypass path 128 in this embodiment will be described. For example... Figures 7 to 9 As shown in the fluid structure, one end of the bypass flow path 128 is connected to the top plate portion 12111 of the common liquid chamber 1211 and directly below the buffer 127, and to the opposite side of the side connected to the ink supply pipe 123 in the long side direction of the common liquid chamber 1211. In other words, one end of the bypass flow path 128 is connected to the secondary side of the top plate portion 12111 of the common liquid chamber 1211 and directly below the buffer 127.

[0083] Furthermore, the other end of the bypass flow path 128 is connected to the ink discharge pipe 124 connected to the discharge flow path 1212. The bypass flow path 128 is, for example, rectangular in shape. The cross-sectional area of ​​the bypass flow path 128 is, for example, 1mm × 1mm. The length of the bypass flow path 128 is 10mm. Furthermore, the bypass flow path 128 is, for example, formed with three 90° bends.

[0084] One end of the circuit board 13 is connected to the wiring pattern of the actuator 113 via the wiring pattern of the substrate 111. The circuit board 13 includes, for example, a wiring film, a driver IC mounted on the wiring film, and a printed wiring substrate mounted on the wiring film.

[0085] The circuit board 13 applies a driving voltage to the wiring pattern of the actuator through the driver IC to drive the actuator, thereby increasing or decreasing the volume of the pressure chamber 1131 and causing the droplets to be ejected from the nozzle 1141.

[0086] For example, multiple wiring films are provided. The wiring film is, for example, a COF (Chip on Film) on which a driver IC is mounted. The driver IC is electrically connected to the wiring pattern formed in the pressure chamber 1131 via the wiring film. The printed wiring substrate is a PWA (Printing Wiring Assembly) on which various electronic components and connectors are mounted.

[0087] Cover 14 covers or contains a portion of head body 11, a portion of manifold unit 12, and circuit board 13.

[0088] The liquid ejector head 1 constructed in this way is, for example, set as... Figure 19 The example of the liquid ejection device 2 shown is an inkjet recording apparatus. Hereinafter, the liquid ejection device 2 will be described as an inkjet recording apparatus 2. The liquid ejection head 1 is connected to the supply tank 2132, which serves as the liquid reservoir, provided in the inkjet recording apparatus 2. The liquid ejection head 1 is either a circulation type head that circulates ink between itself and the supply tank 2132, or a non-circulation type head that supplies ink from the supply tank 2132 and discharges ink to the maintenance device 2117 during maintenance. The liquid ejection head 1 is configured with the nozzle 1141 of the nozzle plate 114 of the head body 11 facing downwards.

[0089] The following is for reference Figure 19 The inkjet recording device 2 having a liquid ejector head 1 will be described. The inkjet recording device 2 includes a housing 2111, a media supply unit 2112, an image forming unit 2113, a media discharge unit 2114, a transport device 2115 as a support device, a temperature control device 2116, a maintenance device 2117, and a control unit 2118.

[0090] The inkjet recording device 2 is an inkjet printer that performs image forming processing on the paper P by conveying the recording medium, such as paper P, along a predetermined transport channel 2001 from the media supply unit 2112 through the image forming unit 2113 to the media discharge unit 2114 while ejecting the paper P.

[0091] The media supply unit 2112 includes multiple paper feed trays 21121. The image forming unit 2113 includes a support unit 2120 for supporting paper and multiple head units 2130 disposed above the support unit 2120. The media discharge unit 2114 includes a paper discharge tray 21141.

[0092] The support portion 2120 includes: a conveyor belt 21201 arranged in a ring in a predetermined area for image formation; a support plate 21202 supporting the conveyor belt 21201 from the inside; and a plurality of belt rollers 21203 disposed on the inside of the conveyor belt 21201.

[0093] The head unit 2130 includes multiple inkjet heads, namely liquid ejector heads 1, multiple supply tanks 2132 mounted on each liquid ejector head 1 as liquid tanks, a pump 2134 for supplying ink, and a connection flow path 2135 connecting the liquid ejector head 1 and the supply tanks 2132.

[0094] In this embodiment, the liquid nozzle 1 includes four liquid nozzles: cyan, magenta, yellow, and black, and four supply tanks 2132 for each color of ink. The supply tanks 2132 are connected to the liquid nozzles 1 via a flow path 2135.

[0095] Pump 2134 is, for example, a liquid delivery pump composed of a piezoelectric pump. Pump 2134 is connected to control unit 2118 and is driven and controlled by control unit 2118.

[0096] The connecting flow path 2135 includes a supply flow path connected to the ink supply pipe 123 of the liquid nozzle 1. Furthermore, the connecting flow path 2135 includes a recovery flow path connected to the ink discharge pipe 124 of the liquid nozzle 1. For example, since the liquid nozzle 1 is non-circulating, the recovery flow path is connected to the maintenance device 2117. Alternatively, for example, in the case where the liquid nozzle 1 is circulating, the recovery flow path is connected to the supply tank 2132.

[0097] The conveying device 2115 conveys paper P along a conveying channel 2001 from the paper feed cassette 21121 of the media supply unit 2112 through the image forming unit 2113 to the paper discharge tray 21141 of the media discharge unit 2114. The conveying device 2115 includes multiple guide plates 21211-21218 and multiple conveying rollers 21221-21228 arranged along the conveying channel 2001. The conveying device 2115 supports the paper P so that it can move relative to the liquid ejector head 1.

[0098] The temperature control device 2116 includes a temperature-controlled water tank 21161, a temperature-controlled circuit 21162 for supplying temperature-controlled water (such as piping and hoses), a pump for supplying temperature-controlled water, and a temperature controller for adjusting the temperature of the temperature-controlled water. The temperature control device 2116 supplies temperature-controlled water, adjusted to a specified temperature by the temperature controller, from the temperature-controlled water tank 21161 to the temperature-controlled water supply pipe 125 via the pump and the temperature-controlled circuit 21162. Furthermore, the temperature control device 2116 recovers water discharged from the temperature-controlled water discharge pipe through the manifold 121 back to the temperature-controlled water tank 21161 via the temperature-controlled circuit 21162. The temperature controller may be, for example, a heater or a cooler.

[0099] The maintenance device 2117, for example, draws in and recovers ink remaining on the outer surface of the nozzle plate 114 during maintenance. Furthermore, in the case where the liquid nozzle 1 is non-circulating, the maintenance device 2117 recovers ink from the nozzle 1141 within the head body 11 during maintenance. Such a maintenance device 2117 includes a tray, container, or the like for storing the recovered ink.

[0100] The control unit 2118 includes: a CPU 21181, which is an example of a processor; ROM (Read Only Memory) for storing various programs; RAM (Random Access Memory) and other memory for temporarily storing various variable data, image data, etc.; and an interface unit for inputting data from the outside and outputting data to the outside.

[0101] Next, the flow of liquid ink in the liquid ejector head 1 as configured in this way will be explained. First, when liquid ink is supplied to the ink supply pipe 123, the ink flows in the common liquid chamber 1211 of the manifold 121. Furthermore, the ink moves from the supply port 1111 of the substrate 111 opposite to the common liquid chamber 1211 to the first common pressure chamber 1161.

[0102] As in Figure 3 As indicated by the arrows, a portion of the ink that has moved to the first common pressure chamber 1161 moves to the plurality of pressure chambers 1131. Furthermore, as in... Figure 3 As indicated by the arrows, a portion of the ink that has moved to the first common pressure chamber 1161 moves to the third common pressure chamber 1163. The ink that has moved to the third common pressure chamber 1163 moves to the second common pressure chamber 1162. The ink that has moved to the second common pressure chamber 1162 moves to the plurality of pressure chambers 1131. That is, in this embodiment, ink is supplied from both the first common pressure chamber 1161 and the second common pressure chamber 1162 to the plurality of pressure chambers 1131. Furthermore, the pressure chambers 1131 are driven, and the ink within the driven pressure chambers 1131 is ejected from the nozzle 1141.

[0103] In this embodiment, since the liquid ejector head 1 is non-circulating, the ink in the second common pressure chamber 1162 moves to the plurality of pressure chambers 1131. Furthermore, during maintenance, ink filling, etc., when the secondary side of the ink discharge pipe 124 is opened, the ink in the second common pressure chamber 1162 moves to the ink discharge pipe 124 through the third common pressure chamber 1163, the discharge port 1112 of the substrate 111, and the discharge flow path 1212 of the manifold 121.

[0104] Furthermore, during maintenance or ink filling, the pressure chamber 1131 is driven, causing the ink in the pressure chamber 1131, for example, to be ejected from the nozzle 1141 along with air bubbles accumulated in the first common pressure chamber 1161, the second common pressure chamber 1162, and the third common pressure chamber 1163.

[0105] Furthermore, since the liquid nozzle 1 is positioned with the head body 11 below and the manifold unit 12 above in the direction of gravity, if air bubbles are present in the common liquid chamber 1211, the air bubbles in the common liquid chamber 1211 are located directly below the buffer 127. Therefore, during ink maintenance or refilling, the ink and air bubbles in the common liquid chamber 1211 move through the bypass flow path 128 to the common pressure chamber 116 or the secondary side of the common pressure chamber 116, and are discharged from the common liquid chamber 1211. Air bubbles that have passed through the bypass flow path 128 from the common liquid chamber 1211 are discharged from the nozzle 1141. In addition, air bubbles that have passed through the bypass flow path 128 from the common liquid chamber 1211 can also be discharged from the ink discharge pipe 124 to the maintenance device 2117.

[0106] Based on the liquid nozzle 1 configured as described above and the liquid ejection device 2 using the liquid nozzle 1, a buffer 127 is provided on the top plate portion 12111 of the common liquid chamber 1211, which is connected to the common pressure chamber 116. The buffer 127 comes into contact with the ink liquid in the common liquid chamber 1211 and deforms according to the pressure fluctuation of the ink. As a result, the buffer 127 can suppress pressure fluctuations, keeping the negative pressure of the common pressure chamber 116 connected to the common liquid chamber 1211 constant or keeping the negative pressure of the common pressure chamber 116 approximately constant.

[0107] Therefore, the liquid nozzle 1 can suppress pressure fluctuations in the flow path of the liquid nozzle 1, including the common liquid chamber 1211, the secondary side of the common liquid chamber 1211 (i.e., the common pressure chamber 116), and the actuator 113. By suppressing pressure fluctuations, the liquid nozzle 1 can achieve higher ejection stability.

[0108] Furthermore, the liquid ejector head 1 can better suppress pressure fluctuations by setting the buffer 127 to a preferred shape and material. Specifically, by setting the width W of the buffer 127 in the short side direction to 4 mm or more, such as... Figure 14 As shown, the liquid ejector head 1 can better suppress pressure fluctuations. This is achieved by setting the thickness of the buffer 127 to less than 25 μm, as... Figure 16 As shown, the liquid ejector head 1 can better suppress pressure fluctuations. Furthermore, as... Figure 18 As shown, since the Young's modulus E of the polyimide membrane forming the buffer 127 can be set to 3.4 GPa, the strain area ds can be increased further, thus suppressing pressure fluctuations more effectively.

[0109] Furthermore, the liquid nozzle 1 has a structure in which a buffer 127 is provided on the top plate portion 12111 of the common liquid chamber 1211, which is opposite the supply port 1111 of the substrate 111 continuous with the common pressure chamber 116. That is, the liquid nozzle 1 has a simple structure in which an opening forming the common liquid chamber 1211 is provided in the manifold 121, and the buffer 127 is fixed to the manifold 121 in a manner that covers the opening. Therefore, the liquid nozzle 1 can be easily manufactured. In addition, since the buffer 127 is formed in the common liquid chamber 1211 formed by the manifold 121, the buffer 127 can ensure a sufficiently large area of ​​contact with the liquid in the common liquid chamber 1211. As such, the liquid nozzle 1 with the buffer 127 can have a buffer with sufficient performance at low cost, and its manufacture is also easy.

[0110] Furthermore, the liquid ejector head 1 is connected to the common liquid chamber 1211 and the common pressure chamber 116 or the secondary side of the common pressure chamber 116 via a bypass flow path 128. This allows for easy removal of air bubbles from the common liquid chamber 1211 during maintenance and ink filling. Consequently, the liquid ejector head 1 can be easily maintained, including ink filling and cleaning of its flow path.

[0111] Furthermore, the liquid ejector head 1 connects the bypass flow path 128 to the top plate portion 12111 of the common liquid chamber 1211 and directly below the buffer 127. This allows the liquid ejector head 1 to effectively expel air bubbles accumulated directly below the buffer 127. Moreover, by reducing the fluid resistance of the bypass flow path 128, for example by setting the flow path cross-section to 1mm × 1mm and the length to 10mm or more, the liquid ejector head 1 can prevent ink from flowing excessively within the bypass flow path 128.

[0112] With the liquid ejector head 1 and liquid ejection device 2 configured in this way, air bubbles in the common liquid chamber 1211 can be removed by a simple structure with a buffer 127 and a bypass flow path 128.

[0113] Furthermore, the embodiments of the present invention are not limited to the structures described above. For example, in the above examples, a non-circulating head body 11 was described, but it could also be a circulating type. In addition, it could be configured without the third common pressure chamber 1163. For example, as another example, in the case where the liquid ejector head 1 is non-circulating or circulating, it could also be a structure without the third common pressure chamber 1163 but with an outlet 1112 provided in the second common pressure chamber 1162.

[0114] Furthermore, in the above example, the example of the bypass flow path 128 connecting the secondary side of the common liquid chamber 1211 to the flow path of the common pressure chamber 116 or the secondary side of the common pressure chamber 116 has been described, but it is not limited to this. For example, the bypass flow path 128 may also be a structure that connects the primary side of the common liquid chamber 1211 to the flow path of the common pressure chamber 116 or the secondary side of the common pressure chamber 116. In addition, it is also possible to configure multiple bypass flow paths 128. For example, the liquid nozzle 1 may also be configured to have two bypass flow paths 128. The liquid nozzle 1 with such a structure only needs to connect the bypass flow paths 128 such that one bypass flow path 128 connects the secondary side of the common liquid chamber 1211 to the flow path of the common pressure chamber 116 or the secondary side of the common pressure chamber 116, and the other bypass flow path 128 connects the primary side of the common liquid chamber 1211 to the flow path of the common pressure chamber 116 or the secondary side of the common pressure chamber 116.

[0115] Furthermore, while the above embodiments illustrate the use of the liquid ejector head 1 and the liquid ejection device 2 in a recording device that ejects ink as a liquid, the invention is not limited thereto. That is, the liquid ejector head 1 and the liquid ejection device 2 can also be used in applications such as 3D printers, industrial manufacturing equipment, and medical applications.

[0116] According to at least one embodiment described above, air bubbles in the common liquid chamber can be removed by a simple structure that includes a buffer and a bypass flow path.

[0117] Several embodiments of the present invention have been described, but these embodiments are merely illustrative and not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are also included within the scope of the invention as described in the claims and their equivalents.

Claims

1. A liquid ejector head, comprising: Shared liquid chamber with an opening; A shared pressure chamber is connected to the shared liquid chamber; The actuator has multiple pressure chambers connected to the common pressure chamber; A substrate is provided with the actuator, and together with the actuator, forms the common pressure chamber; The nozzle plate has a plurality of nozzles respectively arranged opposite to the plurality of pressure chambers; A buffer that covers the opening of the common liquid chamber; as well as A bypass flow path connects the common liquid chamber and the common pressure chamber. The buffer is a polyimide film with a thickness of less than 25 μm. The opening of the common liquid chamber covered by the buffer is elongated in one direction, and the width of the buffer in the short side direction is 4 mm or more. The width of the buffer in the short side direction is a width that can be ensured when used in the head body of the liquid ejection head. The Young's modulus of the buffer is 3.4 GPa.

2. The liquid ejector head according to claim 1, wherein, The fluid resistance of the bypass flow path is smaller than that of the common liquid chamber and the common pressure chamber.

3. The liquid ejector head according to claim 2, wherein, The bypass flow path has a rectangular cross-section with a width of 1 mm. The length of the bypass flow path is 10 mm or more.

4. The liquid ejector head according to claim 1, wherein, The bypass flow path is formed in a shape that bends at 90° in three places.

5. The liquid ejector head according to claim 2, wherein, The bypass flow path is formed in a shape that bends at 90° in three places.

6. The liquid ejector head according to claim 3, wherein, The bypass flow path is formed in a shape that bends at 90° in three places.

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