WO2023233861A1 - Inkjet head - Google Patents

Abstract

This inkjet head comprises: multiple nozzles which are capable of ejecting ink to the outside; multiple pressure chambers which are respectively connected with the nozzles; a first common flow channel which is connected with the pressure chambers; a second common flow channel which is connected with the pressure chambers via a path different from the first flow channel; a first damper disposed in the first common flow channel; and a second damper disposed in the second common flow channel. The thickness of the first damper is thicker than that of the second damper.

Description

inkjet head

The present disclosure relates to an inkjet head.

Conventionally, as an example of an inkjet head, a drop-on-demand inkjet head (hereinafter referred to as "drop-on-demand" inkjet head) is capable of ejecting the required amount of ink droplets at the required timing onto a printing target with high precision using high frequency drive (for example, 50 kHz). , "DOD inkjet head") is known. A piezoelectric DOD inkjet head generally includes an ink flow path, a pressure chamber connected to the ink flow path and storing ink, a piezoelectric element (piezo element) that pressurizes the ink stored in the pressure chamber, and a pressure chamber connected to the ink flow path to store ink. It is equipped with communicating nozzles, etc. Ink droplets are ejected from the nozzle by energizing the piezoelectric element to pressurize the ink within the pressure chamber.

In the DOD inkjet head, residual vibration occurs at the Helmholtz resonance period after ink droplets are ejected. Therefore, when high-frequency ejection is performed in a DOD inkjet head, the ejection accuracy (variations in ejection angle and ejection speed) may deteriorate due to the influence of residual vibration after droplet ejection. In order to avoid such problems, it is important to suppress residual vibrations after droplet ejection at an early stage.

In order to quickly suppress residual vibrations, it is effective to provide a damper in the ink flow path. For example, Patent Document 1 discloses an inkjet head in which a plurality of dampers having different elastic coefficients are arranged in an ink flow path. Further, Patent Document 2 discloses that in a circulation type inkjet head, dampers having different cross-sectional areas are arranged in an ink supply channel and an ink discharge channel.

Patent No. 4493965 Japanese Patent Application Publication No. 2017-165051

An inkjet head according to one aspect of the present disclosure includes:
Multiple nozzles that can eject ink externally,
a plurality of pressure chambers communicating with each of the plurality of nozzles;
a first common flow path communicating with the plurality of pressure chambers;
a second common flow path communicating with the plurality of pressure chambers through a different path from the first common flow path;
a first damper disposed in the first common flow path;
a second damper disposed in the second common flow path,
The thickness of the first damper is greater than the thickness of the second damper.

An inkjet head according to another aspect of the present disclosure,
Multiple nozzles that can eject ink externally,
a plurality of pressure chambers communicating with each of the plurality of nozzles;
a first common flow path communicating with the plurality of pressure chambers;
a second common flow path communicating with the plurality of pressure chambers through a different path from the first common flow path;
a first damper disposed in the first common flow path;
a second damper disposed in the second common flow path,
The Young's modulus of the material forming the first damper is greater than the Young's modulus of the material forming the second damper.

FIG. 1 is an exploded perspective view showing the appearance of an inkjet head according to an embodiment. FIG. 2 is a cross-sectional view schematically showing an ink flow path of one nozzle in an inkjet head according to an embodiment. FIG. 3 is a plan view of the first laminate forming the channel plate. FIG. 4 is a plan view of the second laminate forming the channel plate. FIG. 5 is a plan view of the third laminate forming the channel plate. FIG. 6 is a plan view of the fourth laminate forming the channel plate. FIG. 7 is a plan view of the fifth laminate forming the channel plate. FIG. 8 is an explanatory diagram showing an example of vibration of an upstream damper and a downstream damper. FIG. 9 is an explanatory diagram showing an example of pressure waves generated by vibrations of an upstream damper and a downstream damper. FIG. 10 is a diagram for explaining vibration in the thickness direction parallel to the Z-axis direction in the upstream damper and the downstream damper. FIG. 11 is an explanatory diagram showing the volumes of the upstream common flow path and the downstream common flow path. FIG. 12 is an explanatory diagram showing an example of pressure waves caused by vibrations of the upstream damper and the downstream damper. FIG. 13 is an explanatory diagram showing an example of pressure waves caused by vibrations of the upstream damper and the downstream damper. FIG. 14 is a diagram showing the direction in which the upstream damper 121 and the downstream damper 122 push out ink. FIG. 15 is a cross-sectional view showing an example of nozzle arrangement. FIG. 16 is a cross-sectional view schematically showing an ink flow path of one nozzle in an inkjet head according to a modification. FIG. 17 is a cross-sectional view schematically showing an ink flow path of one nozzle in an inkjet head according to a modification.

In inkjet heads that require high ejection accuracy, in addition to residual vibrations in which the ink vibrates at the Helmholtz resonance period after ink ejection, pressure fluctuations caused by vibrations of the damper itself cannot be ignored as a factor that deteriorates ejection accuracy. If the amount of elastic deformation of the damper is increased in order to suppress the residual vibrations of the ink, a trade-off occurs in that pressure fluctuations caused by the vibrations of the damper itself become larger, and as a result, the residual vibrations of the ink increase.

In particular, in an ink circulation type inkjet head, when a damper is placed in the ink supply channel and the ink discharge channel, waves of pressure fluctuations due to the vibration of the damper itself overlap near the nozzle, which may have a large negative impact on ejection accuracy. be.

An object of the present disclosure is to provide an inkjet head that can suppress residual vibrations after ejecting ink and achieve high ejection accuracy.

Hereinafter, an inkjet head 1 according to an embodiment of the present disclosure will be described with reference to the drawings. The inkjet head 1 is, for example, an ink circulation type inkjet head. This disclosure will be described using a Cartesian coordinate system (X, Y, Z). The negative direction of the Z axis is the direction in which ink is ejected from the inkjet head 1 , the direction along the Y axis is the direction in which the nozzles 101 are arranged, and the direction along the X axis is the direction in which ink flows into the pressure chambers 103 . Hereinafter, directions along the X-axis, Y-axis, and Z-axis will be referred to as "X-axis direction," "Y-axis direction," and "Z-axis direction," respectively.

FIG. 1 is an exploded perspective view showing the appearance of an inkjet head 1 according to an embodiment.

As shown in FIG. 1, the inkjet head 1 includes a nozzle plate 10, a flow path plate 20, a vibration plate 30, a housing 40, and a pressure fluctuation section 50.

The nozzle plate 10 is arranged so that the plate surface of the nozzle plate 10 is perpendicular to the Z-axis. The nozzle plate 10 is formed of a stainless steel plate formed by etching or press working, for example. The thickness of the stainless steel plate is, for example, 100 μm. A plurality of nozzles 101 are bored in the nozzle plate 10 along the Y axis.

The channel plate 20 has a rectangular parallelepiped shape and is arranged on the positive side of the nozzle plate 10 in the Z-axis direction so that the plate surface of the channel plate 20 is orthogonal to the Z-axis. The flow path plate 20 is held between the vibration plate 30 and the nozzle plate 10. The channel plate 20 is, for example, a laminate of a plurality of stainless steel plates formed by etching or press working. The thickness of each stainless steel plate is, for example, 10 to 100 μm, and the number of laminated layers is, for example, 3 to 10 layers.

The vibrating plate 30 is arranged on the positive side of the channel plate 20 in the Z-axis direction so that the plate surface of the vibrating plate 30 is orthogonal to the Z-axis. The vibrating plate 30 is held between the housing 40 and the channel plate 20. The vibrating plate 30 is, for example, a thin film having a thickness of 5 to 50 μm, and is formed by electroplating, for example, a nickel alloy.

Further, the vibrating plate 30 has a pressure receiving part 31 (see FIG. 2) that receives pressure from the piezoelectric element 108. The pressure receiving portion 31 is provided corresponding to each of the plurality of pressure chambers 103 (see FIG. 2), and is formed to protrude toward the positive side in the Z-axis direction, for example. In the vibrating plate 30, the portion where the pressure receiving part 31 is formed forms the upper wall of the pressure chamber 103 (the wall on the positive side in the Z-axis direction).

The housing 40 has a rectangular parallelepiped shape and is arranged on the positive side of the vibration plate 30 in the Z-axis direction. The housing 40 has a thickness of 1 cm in the Z-axis direction, for example. The housing 40 is formed, for example, by cutting alloy steel such as stainless steel.

The pressure fluctuation unit 50 is disposed in a pressure fluctuation unit storage chamber (not shown) of the housing 40, and pressurizes the ink stored in the pressure chamber 103 to generate pressure fluctuation. The pressure variation unit 50 includes a base 51, a control board 52, and a piezoelectric element 108 (see FIG. 2). The base 51 holds the control board 52 and the piezoelectric element 108 . The control board 52 is, for example, a flexible printed circuit board on which a control IC and the like are mounted. The control IC individually controls voltages applied to the plurality of piezoelectric elements 108.

The nozzle plate 10 and the flow path plate 20, the flow path plate 20 and the vibration plate 30, the vibration plate 30 and the housing 40, and the vibration plate 30 and the pressure fluctuation part 50 are each bonded with adhesive. Fixed. As the adhesive, for example, an epoxy adhesive having thermosetting properties is used. Note that the adhesives used to bond the respective constituent elements may be the same adhesive or different adhesives. For example, a combination of a rubber adhesive and an epoxy adhesive may be used.

Each element of the inkjet head 1 is formed inside the nozzle plate 10, flow path plate 20, vibration plate 30, housing 40, and pressure variation section 50, or by combining these.

FIG. 2 is a cross-sectional view schematically showing the ink flow path of one nozzle 101 in the inkjet head 1.

As shown in FIG. 2, the inkjet head 1 includes a nozzle 101, a silo section 102, a pressure chamber 103, an upstream individual flow path 104, a downstream individual flow path 105, an upstream common flow path 106, a downstream common flow path 107, and a piezoelectric element 108. , an ink supply path 109 and an ink discharge path 110. The inkjet head 1 also includes an upstream damper 121, a downstream damper 122, a first space 123, and a second space 124.

The inkjet head 1 causes the piezoelectric element 108 to apply pressure to the ink stored in the pressure chamber 103, thereby ejecting ink droplets from the nozzle 101. The nozzles 101 may be arranged in one row or in multiple rows along the Y axis. In FIG. 1, the nozzles 101 are arranged in two rows along the Y-axis.

Note that when the nozzles 101 are arranged in multiple rows, the pressure chambers 103, the upstream individual channels 104, and the downstream individual channels 105 are also formed in multiple rows corresponding to the nozzles 101. The upstream common flow path 106 and the downstream common flow path 107 may be provided for each row of nozzles 101, or may be shared by multiple rows of nozzles 101. Furthermore, the flow direction of ink to the pressure chambers 103 belonging to different rows may be the same or may be opposite. In the following, a case will be described in which the flow direction of ink with respect to the pressure chamber 103 is the negative direction of the X-axis. That is, the positive side of the X axis will be described as upstream in the flow direction of ink, and the negative side will be described as downstream in the flow direction.

The nozzle 101 is a hole that penetrates the nozzle plate 10 in the Z-axis direction. The diameter of the nozzle 101 is, for example, 3 to 100 μm. Ink droplets are ejected to the outside through the nozzle 101 .

The pressure chamber 103 and the silo part 102 are provided one-to-one for each of the plurality of nozzles 101. The pressure chamber 103 communicates with the nozzle 101 via the silo part 102.

The pressure chamber 103 is an ink storage space formed by the flow path plate 20 and the vibration plate 30. In this embodiment, the pressure chamber 103 is formed by closing the upper surface (positive side surface in the Z-axis direction) of the recess formed in the flow path plate 20 with the vibration plate 30 . The pressure chamber 103 has, for example, a rectangular parallelepiped shape extending along the X axis. Note that a step may be formed on the inner surface of the pressure chamber 103.

The silo portion 102 is formed along the Z-axis and communicates the pressure chamber 103 and the nozzle 101. The silo portion 102 and the pressure chamber 103 form an ink storage space. The silo portion 102 may have a cylindrical shape or a quadrangular prism shape, for example.

The upstream individual flow path 104 is an ink flow path that communicates the pressure chamber 103 and the upstream common flow path 106. The upstream individual flow path 104 is arranged upstream of the pressure chamber 103 in the ink flow direction. The upstream individual flow paths 104 are provided one-to-one for each of the plurality of pressure chambers 103.

The downstream individual flow path 105 is an ink flow path that communicates the pressure chamber 103 and the downstream common flow path 107. The downstream individual flow path 105 is arranged downstream of the pressure chamber 103 in the ink flow direction. The downstream individual flow paths 105 are provided one-to-one for each of the plurality of pressure chambers 103.

The upstream common flow path 106 is an ink flow path arranged upstream of the upstream individual flow path 104 in the ink flow direction (on the positive side of the upstream individual flow path 104 in the X-axis direction). The upstream common flow path 106 is provided in common for the plurality of upstream individual flow paths 104. The upstream common flow path 106 has a first upstream common flow path 106a formed in the flow path plate 20 and a second upstream common flow path 106b formed in the housing 40. The first upstream common flow path 106a and the second upstream common flow path 106b communicate with each other via the filter section 106c. It can be said that the filter section 106c forms a part of the upstream common flow path 106.

The filter portion 106c is a portion of the vibrating plate 30 that corresponds to the first upstream common flow path 106a and the second upstream common flow path 106b, and has through holes arranged vertically and horizontally. The diameter of the through hole is set so that ink can pass therethrough, but particles that should be prevented from flowing into the nozzle 101 cannot pass therethrough. The diameter of the through hole is, for example, 5 to 30 μm.

The downstream common flow path 107 is an ink flow path arranged downstream of the downstream individual flow path 105 in the ink flow direction. The downstream common flow path 107 is provided in common to the plurality of downstream individual flow paths 105. The downstream common flow path 107 includes a first downstream common flow path 107a formed in the flow path plate 20 and a second downstream common flow path 107b formed in the housing 40. The first downstream common flow path 107a and the second downstream common flow path 107b communicate with each other via an opening 107c formed in the vibration plate 30. It can be said that the opening 107c forms a part of the downstream common flow path 107.

A plurality of piezoelectric elements 108 are arranged on the bottom surface of the base 51 and are pressure sources that pressurize the ink contained in the pressure chamber 103. The piezoelectric element 108 is provided corresponding to the plurality of pressure chambers 103 and comes into contact with the pressure receiving part 31 of the vibrating plate 30. The piezoelectric element 108 deforms, for example, by expanding and contracting in the Z-axis direction, by applying a voltage. For example, a D33 mode stacked piezo actuator is applied to the piezoelectric element 108.

In the inkjet head 1 , ink is supplied from an external ink supply tank (not shown) via an ink supply path 109 to an upstream common flow path 106 , an upstream individual flow path 104 , a pressure chamber 103 , a downstream individual flow path 105 , and The ink is discharged from the ink discharge path 110 via the downstream common flow path 107 . The discharged ink is circulated to the ink supply tank by, for example, a circulation pump (not shown). By circulating the ink without allowing it to stagnate, it is possible to prevent the ink from stagnation in the pressure chamber 103 or the nozzle 101 and clogging the nozzle.

In the ink circulation type inkjet head 1, the pressure of the ink supply tank (not shown) connected to the ink supply path 109 is set to be higher than the pressure of the ink discharge tank (not shown) connected to the ink discharge path 110. is set to For example, the pressure difference can be controlled by varying the positions of the ink supply tank and the ink discharge tank in the Z-axis direction (heights with respect to the pressure chamber 103). Further, for example, the internal pressures of the ink supply tank and the ink discharge tank may be individually controlled by regulators.

In the pressure variation section 50, when a voltage is applied to the piezoelectric element 108, the piezoelectric element 108 deforms so as to expand in the Z-axis direction, causing the pressure-receiving section 31 of the vibrating plate 30 to move downward (negatively in the Z-axis direction). side). As a result, the upper wall of the pressure chamber 103 is deformed, and pressure fluctuations occur in the ink stored in the pressure chamber 103. As this pressure fluctuation propagates toward the nozzle 101 via the silo section 102, ink droplets are ejected from the nozzle 101.

Further, a part of the liquid contact surface of the upstream common flow path 106 that comes into contact with the ink is formed by a deformable upstream damper 121. Specifically, the bottom wall surface on the negative side in the Z-axis direction of the upstream common flow path 106 (first upstream common flow path 106a) is formed by the upstream damper 121. The upstream damper 121 is formed using, for example, one layer of the laminate forming the channel plate 20. The thickness of the upstream damper 121 is, for example, 2 to 30 μm.

A first space 123 that allows the upstream damper 121 to deform is provided on the opposite side of the liquid contact surface of the upstream damper 121. The thickness of the first space 123 may be 10 to 200 μm, as long as it can allow elastic deformation of the upstream damper 121.

The upstream damper 121 has a thin film shape that can be elastically deformed according to pressure fluctuations in the upstream common flow path 106, and suppresses pressure fluctuations in the upstream common flow path 106. Specifically, after the ink is ejected, the pressure fluctuation of the ink propagates to the upstream common channel 106 via the pressure chamber 103, is reflected at the upstream common channel 106, and propagates to the pressure chamber 103. Since the upstream damper 121 deforms toward the first space 123 in response to the pressure fluctuation propagated from the pressure chamber 103 to the upstream common flow path 106, the pressure fluctuation reflected and propagated to the pressure chamber 103 becomes smaller. Therefore, by providing the upstream damper 121 in the upstream common flow path 106, residual vibrations of ink after ink ejection are suppressed.

Further, a part of the liquid contact surface of the downstream common flow path 107 that comes into contact with the ink is formed by the vibrating plate 30. In the vibrating plate 30, a portion 122 forming the liquid contact surface of the downstream common flow path 107 functions as a downstream damper (hereinafter referred to as "downstream damper 122"). The thickness of the downstream damper 122 is equal to or less than that of the vibration plate 30, and is, for example, 2 to 30 μm.

A second space 124 that allows the downstream damper 122 to deform is provided on the opposite side of the liquid contact surface of the downstream damper 122. The thickness of the second space 124 may be 10 to 200 μm, as long as it can allow elastic deformation of the downstream damper 122.

In addition, in the vibrating plate 30, the portion functioning as the downstream damper 122 may be processed to be thin by forming a recessed portion, etc., in order to make it easier to elastically deform. Furthermore, if the vibrating plate 30 is sufficiently deformable to suppress pressure fluctuations, the thickness of the portion functioning as the downstream damper 122 does not need to be reduced.

The downstream damper 122 has a thin film shape that can be elastically deformed in response to pressure fluctuations in the downstream common flow path 107, and suppresses pressure fluctuations in the downstream common flow path 107. Specifically, after the ink is ejected, the pressure fluctuation of the ink propagates to the downstream common flow path 107 via the pressure chamber 103, is reflected at the downstream common flow path 107, and is propagated to the pressure chamber 103. Since the downstream damper 122 deforms toward the second space 124 in response to the pressure fluctuation propagated from the pressure chamber 103 to the downstream common flow path 107, the pressure fluctuation reflected and propagated to the pressure chamber 103 is reduced. Therefore, by providing the downstream damper 122 in the downstream common flow path 107, the residual vibration of the ink after ink discharge is suppressed.

An example of the laminated structure of the channel plate 20 will be described with reference to FIGS. 3 to 7. 3 to 7 are plan views of each laminate forming the laminate structure of the channel plate 20. FIG. 3 to 7, the structures of the first to fifth laminates 21 to 25 forming the flow path plate 20 are shown in plan view from the positive side in the Z-axis direction.

The flow path plate 20 is configured by stacking a first laminate 21, a second laminate 22, a third laminate 23, a fourth laminate 24, and a fifth laminate 25 in order from the negative side in the Z-axis direction. Ru. Openings are formed in the first to fifth stacked bodies 21 to 25 in the Z-axis direction.

As shown in FIG. 3, the first laminate 21 has an opening 21A forming the silo portion 102 and an opening 21B forming the first space 123. The thickness of the first laminate 21 is, for example, 80 μm. For example, the opening 21A has a circular shape when viewed in plan from the Z-axis direction, and a plurality of openings are formed along the Y-axis direction. The opening 21B has, for example, a rectangular shape extending in the Y-axis direction when viewed from the Z-axis direction, and is formed on the positive side of the opening 21A in the X-axis direction. Note that the opening 21B may be one opening as shown in FIG. 3, but may be divided into a plurality of openings in order to maintain strength. For example, in the Y-axis direction, the opening 21B may be divided every ten openings 21A, and one opening 21B may be provided for every ten openings 21A.

The second laminate 22 has an opening 22A that forms the silo part 102, as shown in FIG. The thickness of the second laminate 22 is, for example, 25 μm. The opening 22A corresponds to the opening 21A of the first stacked body 21. That is, the shape, size, and position of the opening 22A viewed from the Z-axis direction are the same as the opening 21A of the first stacked body 21. On the other hand, no opening is formed in the region 22B (the region surrounded by the broken line in FIG. 4) corresponding to the opening 21B in the first laminate 21 (hereinafter referred to as "solid region 22B").

As shown in FIG. 5, the third laminate 23 has an opening 23D forming the pressure chamber 103, an opening 23B forming the first upstream common flow path 106a, and an opening 23C forming the first downstream common flow path 107a. . The thickness of the third laminate 23 is, for example, 100 μm. For example, the opening 23D has a rectangular shape in a plan view from the Z-axis direction, and is formed one-to-one with the opening 22A of the second laminate 22. The opening 23B corresponds to the opening 21B of the first stacked body 21. That is, the shape, size, and position of the opening 23B viewed from the Z-axis direction are the same as the opening 21B of the first stacked body 21. Further, the opening 23C is formed symmetrically with the opening 23B with the opening 23D as a reference. Note that the opening 23B and the opening 23C may be one opening as shown in FIG. 5, but may be divided into a plurality of openings in order to maintain strength. For example, in the Y-axis direction, the openings 23B and 23C may be divided every time ten openings 23D are formed, and one opening 23B and one opening 23C may be provided for every ten openings 23D.

The fourth laminate 24 has an opening 24E that forms a pressure chamber 103, an upstream individual flow path 104, and a downstream individual flow path 105, as shown in FIG. The thickness of the fourth laminate 24 is, for example, 30 μm. The opening 24E is formed with a length that bridges the openings 23B and 23C of the third laminate 23 in the X-axis direction.

As shown in FIG. 7, the fifth laminate 25 includes an opening 25D forming the pressure chamber 103, an opening 25B forming the first upstream common flow path 106a, an opening 25C forming the first downstream common flow path 107a, and It has an opening 25F that forms the second space 124. The thickness of the fifth laminate 25 is, for example, 80 μm. The openings 25D, 25B, and 25C correspond to the openings 23D, 23B, and 23C of the third stacked body 23, respectively. That is, the shape, size, and position of the openings 25D, 25B, and 25C as viewed from the Z-axis direction are the same as the openings 23D, 23B, and 23C of the third laminate 23. Note that the opening 25B, the opening 25C, and the opening 25F may be one opening as shown in FIG. 7, but may be divided into a plurality of openings in order to maintain strength. For example, in the Y-axis direction, the openings 25B, 25C, and 25F are divided every time 10 openings 25D are formed, and one opening 25B, one opening 25C, and one opening 25F are provided for each ten openings 25D. It's okay to be

The upstream damper 121 is formed by stacking the first to third stacked bodies 21 to 23. Specifically, the solid region 22B of the second laminate 22 is interposed between the opening 21B of the first laminate 21 and the opening 23B of the third laminate 23 in the Z-axis direction. Therefore, the portion of the second laminate 22 corresponding to the solid region 22B becomes the upstream damper 121.

The silo portion 102 is formed by stacking the first to third laminates 21 to 23. By stacking the third to fifth laminates 23 to 25, a first upstream common flow path 106a and a first downstream common flow path 107a are formed. The opening 24E of the fourth laminate 24 forms an upstream individual flow path 104 and a downstream individual flow path 105.

The nozzle plate 10 is joined to the negative side of the channel plate 20 in the Z-axis direction, and the opening 21B of the first stacked body 21 is closed by the nozzle plate 10, thereby forming the first space 123.

The vibration plate 30 is joined to the positive side of the channel plate 20 in the Z-axis direction, and the openings 25D and 25F of the fifth stacked body 25 are closed by the vibration plate 30, so that the pressure chamber 103 and the second space 124 are closed. It is formed. Further, the opening 25B of the fifth laminate 25 is closed by a filter portion 106c provided on the vibration plate 30.

Furthermore, by joining the housing 40 to the positive side of the vibration plate 30 in the Z-axis direction, the portion of the vibration plate 30 sandwiched between the second downstream common flow path 107b and the second space 124 is connected to the second damper. 122.

In the inkjet head 1 having the above-described configuration, after ink is ejected, pressure fluctuation occurs at the period of Helmholtz resonance, and the pressures in the upstream common channel 106 and the downstream common channel 107 increase. This pressure fluctuation is attenuated by elastic deformation of the upstream damper 121 and the downstream damper 122. Therefore, pressure fluctuations that are reflected at the upstream common flow path 106 and the downstream common flow path 107 and propagated to the pressure chamber 103 are reduced, and residual vibrations of the ink are suppressed.

On the other hand, pressure fluctuations are also propagated to the pressure chamber 103 due to vibrations caused by elastic deformation of the upstream damper 121 and downstream damper 122 themselves. When the phases of pressure fluctuation waves (hereinafter referred to as "pressure waves") match, in the pressure chamber 103, the first pressure wave P1 propagating from upstream and the second pressure wave P2 propagating from downstream overlap, Pressure fluctuations in pressure chamber 103 increase. Although the amount of pressure fluctuation at this time is small compared to the amount of pressure fluctuation caused by Helmholtz resonance after ink ejection, it may have an unacceptable adverse effect on inkjet heads that require high ejection accuracy. .

In other words, when the first pressure wave P1 generated by the vibration of the upstream damper 121 and the second pressure wave P2 generated by the vibration of the downstream damper 122 are in the same phase, the phases of the first pressure wave P1 and the second pressure wave P2 are Compared to the case where there is a deviation, the pressure fluctuation occurring in the pressure chamber 103 due to the first pressure wave P1 and the second pressure wave P2 becomes larger, and there is a risk that the ink ejection speed and ejection volume may fluctuate at a level that cannot be ignored. There is. In particular, when ejection is performed in a high frequency band, variations in ejection speed and ejection volume due to differences in ejection frequency become large.

Therefore, in this embodiment, the upstream damper 121 in the thickness direction is adjusted such that the phase of the first pressure wave P1 caused by the vibration of the upstream damper 121 and the phase of the second pressure wave P2 caused by the vibration of the downstream damper 122 are shifted. The vibration period is shorter than the vibration period of the downstream damper 122 in the thickness direction. In the embodiment, the thickness direction of the upstream damper 121 and the downstream damper 122 is parallel to the ink ejection direction, but it does not have to be parallel to the ink ejection direction. Further, hereinafter, the first pressure wave P1 and the second pressure wave P2 may be collectively referred to as "pressure waves P1, P2."

FIG. 8 is an explanatory diagram showing vibrations V1 and V2 of the upstream damper 121 and the downstream damper 122. FIG. 8 shows a case where the time for pressure fluctuations generated in the pressure chamber 103 to reach the upstream damper 121 and the time for the pressure fluctuation to reach the downstream damper 122 is the same. Further, in FIG. 8, the displacement in the direction in which the upstream damper 121 and the downstream damper 122 push back the ink, that is, the displacement on the positive side in the Z-axis direction is shown as positive.

When the pressure in the upstream common flow path 106 and the downstream common flow path 107 increases due to the propagation of pressure fluctuations generated in the pressure chamber 103, at timing t1 in FIG. 8, the upstream damper 121 and the downstream damper 122 are pushed by the ink. Elastic deformation begins toward the negative side in the Z-axis direction.

Timing t2 in FIG. 8 is the time when the displacement of the vibration V1 of the upstream damper 121 reaches its maximum value. Timing t3 is the time when the displacement of the vibration V2 of the downstream damper 122 reaches its maximum value. When the vibration period of the upstream damper 121 is shorter than the vibration period of the downstream damper 122, timing t2 is earlier than timing t3.

FIG. 9 is an explanatory diagram showing pressure waves P1 and P2 in the pressure chamber 103. Pressure wave P1 and pressure wave P2 shown in FIG. 9 are pressure waves generated by vibrations of upstream damper 121 and downstream damper 122, respectively. FIG. 9 shows a case where pressure waves P1 and P2 based on the vibrations V1 and V2 shown in FIG. 8 propagate to the pressure chamber 103 in the same propagation time.

Timing t4 in FIG. 9 is the time when the pressure waves P1 and P2 reach the pressure chamber 103, and is later than timing t1 in FIG. 8 by the propagation time of the pressure waves P1 and P2. Timing t5 is the time when the pressure wave P1 reaches its maximum value, and timing t6 is the time when the pressure wave P2 reaches its maximum value.

As shown in FIGS. 8 and 9, the waveforms of the pressure waves P1 and P2 are almost the same as the vibrations V1 and V2 of the upstream damper 121 and the downstream damper 122. That is, when the vibration periods of the upstream damper 121 and the downstream damper 122 are shifted, the phases of the maximum values of the pressure waves P1 and P2 propagated to the pressure chamber 103 are also shifted by that amount. As a result, since the pressure waves P1 and P2 can be prevented from overlapping, pressure fluctuations occurring in the pressure chamber 103 are suppressed.

Specifically, the thickness of the upstream damper 121 is set larger than the thickness of the downstream damper 122. In this embodiment, the thickness of the upstream damper 121 is set to 15 μm, and the thickness of the downstream damper 122 is set to 5 μm. The difference in thickness between the upstream damper 121 and the downstream damper 122 is preferably 8 μm or more.

Furthermore, the Young's modulus of the material forming the upstream damper 121 is greater than the Young's modulus of the material forming the downstream damper 122. In this embodiment, the upstream damper 121 is made of stainless steel, and the downstream damper 122 is made of a nickel alloy. The Young's modulus of stainless steel material is approximately 200 GPa, and the Young's modulus of nickel alloy is approximately 160 GPa. Note that the Young's modulus of these materials can be adjusted by the manufacturing method, composition ratio, etc.

FIG. 10 is a diagram for explaining vibration in the thickness direction parallel to the Z-axis direction in the upstream damper 121 and the downstream damper 122.

Since the upstream damper 121 and the downstream damper 122 have a thin film structure, vibration in the thickness direction can be considered using a beam model. To simplify the explanation, a beam model in which a load m is applied to the center of a simple beam having a length L, a width b, and a thickness h will be used as shown in FIG. 10. The spring coefficient k of the upstream damper 121 and the downstream damper 122 is determined by the following formula (1) using the length L, width b, thickness h, and Young's modulus E of the forming material. Moreover, the vibration period of the upstream damper 121 and the downstream damper 122 becomes shorter as the spring coefficient k becomes larger.

From equation (1), the spring coefficient k can be adjusted by the thickness h of the upstream damper 121 and the downstream damper 122, and the phases of the vibrations of the upstream damper 121 and the downstream damper 122 can be shifted. Note that the spring coefficient k can also be adjusted by the length L and width b of the upstream damper 121 and the downstream damper 122, but since the size of the inkjet head 1 is restricted, the values of the length L and width b cannot be adjusted. It is difficult to make a large shift. Therefore, it is preferable to adjust the spring coefficient k depending on the thickness of the upstream damper 121 and the downstream damper 122.

Further, from equation (1), the spring coefficient k can be adjusted by the Young's modulus E of the material forming the upstream damper 121 and the downstream damper 122, and the phases of the vibrations of the upstream damper 121 and the vibrations of the downstream damper 122 can be shifted.

When adjusting the spring coefficient k using both the thickness h and the Young's modulus E in the upstream damper 121 and the downstream damper 122, the spring coefficient k can be adjusted more easily than when adjusting the spring coefficient k using either one. can do.

In this embodiment, the thickness of the upstream damper 121 is greater than the thickness of the downstream damper 122, and the Young's modulus of the material forming the upstream damper 121 is greater than the Young's modulus of the material forming the downstream damper 122. Since the spring coefficient of the upstream damper 121 is larger than that of the downstream damper 122, the vibration period of the upstream damper 121 is shorter than the vibration period of the downstream damper 122. In other words, the phases of the vibrations of the upstream damper 121 and the downstream damper 122 are shifted. Therefore, pressure fluctuations occurring in the pressure chamber 103 due to the propagation of the two pressure waves P1 and P2 caused by the vibration of the damper itself are suppressed.

It is preferable that the upstream common flow path 106 and the downstream common flow path 107 have different volumes. In this embodiment, the volume of the upstream common flow path 106 is smaller than the volume of the downstream common flow path 107. "The volume of the upstream common flow path 106" and "the volume of the downstream common flow path 107" are the volumes of the same space where ink continuously exists.

A first downstream common flow path 107a and a second downstream common flow path 107b forming the downstream common flow path 107 communicate with each other via an opening 107c of the vibrating plate 30. Therefore, ink continuously exists between the first downstream common flow path 107a and the second downstream common flow path 107b. Therefore, pressure fluctuations propagating from the pressure chamber 103 propagate to the first downstream common flow path 107a, the second downstream common flow path 107b, and the opening 107c of the vibrating plate 30 in the same way. That is, when considering the influence of pressure fluctuations propagating between the pressure chamber 103 and the downstream common flow path 107, the entire downstream common flow path 107 is considered. In short, "the volume of the downstream common flow path 107" is the combined volume of the first downstream common flow path 107a and the second downstream common flow path 107b.

On the other hand, the first upstream common flow path 106a and the second upstream common flow path 106b forming the upstream common flow path 106 communicate with each other via a filter portion 106c having a through hole. In the filter portion 106c, the through holes allow ink to flow, but the ink is reflected in areas other than the through holes. Therefore, the pressure fluctuation propagating from the pressure chamber 103 is difficult to propagate to the second upstream common flow path 106b, and may be considered to propagate only to the first upstream common flow path 106a. In other words, when considering the influence of pressure fluctuations propagating between the pressure chamber 103 and the upstream common flow path 106, the first upstream common flow path 106a and the second upstream common flow path 106b are considered to be separate spaces, and the first Only the upstream common flow path 106a is targeted. In short, "the volume of the upstream common flow path 106" is the volume of the first upstream common flow path 106a.

When the upstream common flow path 106 and the downstream common flow path 107 have the same length along the Y axis, as shown by the thick line in FIG. Each volume can be controlled by the cross-sectional area. Note that if it is difficult to make the cross-sectional areas of the upstream common flow path 106 and the downstream common flow path 107 different due to dimensional constraints, etc., the Y of the upstream common flow path 106 and the downstream common flow path 107 is Each volume may be controlled by the length along the axis.

Since the upstream common flow path 106 is separated by interposing the filter part 106c between the first upstream common flow path 106a and the second upstream common flow path 106b, the first upstream common flow path 106a and the second upstream common flow path 106b are separated. The cross-sectional area of the upstream common flow path 106 parallel to the XZ plane is smaller than when the paths 106b are in the same space. Therefore, compared to the case where the volume of the upstream common channel 106 is reduced by the cross-sectional area parallel to the XZ plane or the length along the Y-axis direction of the first upstream common channel 106a or the second upstream common channel 106b, The volume of the upstream common flow path 106 can be easily reduced.

Most of the pressure fluctuation components generated by the vibration of the upstream damper 121 first propagate to the entire space including the upstream damper 121, that is, the entire upstream common flow path 106, and then to the pressure chamber 103. Similarly, most of the pressure fluctuation component caused by the vibration of the downstream damper 122 first propagates throughout the same space including the downstream damper 122, that is, the entire downstream common flow path 107, and then propagates to the pressure chamber 103. do.

Therefore, the larger the volumes of the upstream common flow path 106 and the downstream common flow path 107, the slower the propagation time for the pressure waves P1 and P2 based on the vibrations of the upstream damper 121 and the downstream damper 122 to reach the pressure chamber 103.

As in this embodiment, when the volume of the upstream common flow path 106 is set smaller than the volume of the downstream common flow path 107, the first pressure wave P1 based on the vibration of the upstream damper 121 with a short vibration period is Compared to the second pressure wave P2 based on the vibration of the downstream damper 122, which has a long vibration period, the maximum value appears earlier (see FIG. 9), and it reaches the pressure chamber 103 earlier by the difference Δt in propagation time (see FIG. 12). reference). That is, as shown in FIG. 12, the phase difference between the two pressure waves P1 and P2 (time between timings t5 and t6) is larger than the phase difference in the case shown in FIG. Therefore, pressure fluctuations occurring in the pressure chamber 103 due to the propagation of the two pressure waves P1 and P2 caused by vibrations of the damper itself are reliably suppressed.

On the other hand, if the volume of the upstream common flow path 106 is set larger than the volume of the downstream common flow path 107, the pressure wave P1 based on the vibration of the upstream damper 121 with a short vibration period will be generated by the pressure wave P1 based on the vibration of the upstream damper 122 with a long vibration period. Compared to the pressure wave P2 based on vibration, the maximum value appears earlier (see FIG. 9), but it reaches the pressure chamber 103 later by the difference Δt in propagation time (see FIG. 13). In this case, as shown in FIG. 13, the two pressure waves P1 and P2 are in phase and their maximum values overlap, and there is a possibility that the effect of suppressing pressure fluctuations occurring in the pressure chamber 103 may not be obtained.

Therefore, when the volumes of the upstream common flow path 106 and the downstream common flow path 107 are made to be different, the volume of the upstream common flow path 106 in which the upstream damper 121 with a short vibration period is arranged is different from that in which the downstream damper 122 with a long vibration period is arranged. It is preferable to set the volume smaller than the volume of the downstream common flow path 107.

FIG. 14 is a diagram showing the direction in which the upstream damper 121 and the downstream damper 122 push out ink.

As shown in FIG. 14, the upstream damper 121 pushes out the ink from the surface in contact with the ink in the extrusion direction D1, which is the positive direction of the Z axis (vertically upward). The upstream connection portion 111 that connects the upstream common flow path 106 and the upstream individual flow path 104 is located on the positive side in the Z-axis direction from the liquid contact surface of the upstream damper 121. That is, the direction from the liquid contact surface of the upstream damper 121 toward the upstream connection portion 111 is the same as the extrusion direction D1. This configuration is referred to as a "direct reflection configuration." In the direct reflection configuration, the first pressure wave P1 due to the vibration of the upstream damper 121 is mainly propagated directly to the pressure chamber 103.

The downstream damper 122 pushes out the ink from the surface in contact with the ink in the extrusion direction D2, which is the positive direction of the Z axis (vertically upward). The downstream connection part 112 that connects the downstream common flow path 107 and the downstream individual flow path 105 is located on the negative side in the Z-axis direction from the liquid contact surface of the downstream damper 122. That is, the direction from the liquid contact surface of the downstream damper 122 toward the downstream connection portion 112 is opposite to the extrusion direction D2. This configuration is referred to as an "indirect reflection configuration." In the indirect reflection configuration, the second pressure wave P2 due to the vibration of the downstream damper 122 is propagated to the pressure chamber 103 mainly through reflection on the wall surface of the downstream common channel 107 that faces the downstream damper 122 in the extrusion direction D2.

In the direct reflection configuration in the upstream common flow path 106, the upstream individual flow path 104 exists in the extrusion direction D1 of the upstream damper 121, whereas in the indirect reflection configuration in the downstream common flow path 107, the upstream individual flow path 104 exists in the extrusion direction D2 of the downstream damper 122. There is no downstream individual flow path 105 in this case. Therefore, in the indirect reflection configuration, the pressure fluctuation component directly propagating from the downstream damper 122 to the downstream individual flow path 105 is smaller than in the direct reflection configuration. That is, the second pressure wave P2 due to the vibration of the downstream damper 122 reaches the pressure chamber 103 later than the first pressure wave P1 due to the vibration of the upstream damper 121. The positional relationship between the first damper 121 and the pressure chamber 103 and the positional relationship between the second damper 122 and the pressure chamber 103 are such that the first pressure wave P1 generated by the vibration of the first damper 121 reaches the pressure chamber 103 during first propagation. It can be said that the time is set to be shorter than the second propagation time for the second pressure wave P2 generated by the vibration of the second damper 122 to reach the pressure chamber 103.

The upstream common flow path 106 in which the upstream damper 121 with a short vibration period is arranged has a direct reflection configuration, and the downstream common flow path 107 in which the downstream damper 122 with a long vibration period is arranged has an indirect reflection configuration. The phase shift between the two pressure waves P1 and P2 propagating to increases. Therefore, pressure fluctuations occurring in the pressure chamber 103 due to the propagation of the two pressure waves P1 and P2 caused by the vibration of the damper itself are suppressed more reliably.

Furthermore, the pressure wave P1 propagating from the upstream common flow path 106 to the pressure chamber 103 travels in the same direction as the ink circulation direction, whereas the pressure wave P2 propagating from the downstream common flow path 107 to the pressure chamber 103 travels in the same direction as the ink circulation direction. Go against the direction of ink circulation. In other words, the circulation of ink acts as a resistance to the pressure wave P2 caused by the vibration of the downstream damper 122, so that the pressure wave P2 is less likely to propagate to the pressure chamber 103 than the pressure wave P1 caused by the vibration of the upstream damper 121. Therefore, the phase shift between the two pressure waves P1 and P2 propagating to the pressure chamber 103 can be increased more effectively.

FIG. 15 is a diagram showing an example of the arrangement of the nozzles 101 within the pressure chamber 103.

The pressure fluctuation that propagates from the pressure chamber 103 after ink is ejected from the nozzle 101 is absorbed by the upstream damper 121 and the downstream damper 122, but part of the pressure fluctuation component is absorbed by the upstream common flow path 106 and the downstream common flow path 107. It is reflected on the wall surface of the 100 and returns to the pressure chamber 103 without being absorbed by the upstream damper 121 and the downstream damper 122. In the indirect reflection configuration in the downstream common flow path 107, the path length from the pressure chamber 103 to the downstream damper 122 is longer than in the direct reflection configuration in the upstream common flow path 106. The pressure fluctuation component returning to 103 becomes larger. Therefore, in the indirect reflection configuration, compared to the direct reflection configuration, the effect of suppressing residual vibrations that vibrate at a period close to the Helmholtz resonance after ink is ejected from the nozzle 101 is reduced.

Therefore, in the present embodiment, the residual vibration that occurs after ink ejection and which oscillates at a period close to the Helmholtz resonance is propagated more to the upstream common flow path 106 of the direct reflection configuration than to the downstream common flow path 107 of the indirect reflection configuration. It has become so. Specifically, as shown in FIG. 15, the nozzle 101 is arranged offset from the center of the pressure chamber 103 so as to be close to the downstream common flow path 107 in the ink flow direction. When the upstream individual flow path 104 and the downstream individual flow path 105 have the same flow path length, the first path length from the upstream common flow path 106 to the nozzle 101 is the same as the second path length from the downstream common flow path 107 to the nozzle 101. It can also be said that it is longer than long.

The first path length is, for example, expressed as the shortest distance from the nozzle 101 to the upstream common flow path 106 via the liquid contact surfaces of the silo section 102, pressure chamber 103, and upstream individual flow path 104. Similarly, the second path length is represented by, for example, the shortest distance from the nozzle 101 to the downstream common flow path 107 via the liquid contact surfaces of the silo portion 102, the pressure chamber 103, and the downstream individual flow path 105.

In this case, the pressure fluctuations generated in the pressure chamber 103 due to the operation of the piezoelectric element 108 propagate to the downstream common flow path 107 via the downstream individual flow path 105 , when the pressure fluctuation occurs in the silo section 102 that communicates the nozzle 101 and the pressure chamber 103 . It also propagates to the nozzle 101 via the air. That is, the pressure fluctuation component generated in the pressure chamber 103 is distributed to the downstream individual flow path 105 and the silo section 102. On the other hand, when the pressure fluctuation occurring in the pressure chamber 103 propagates to the upstream common flow path 106 via the upstream individual flow path 104, the pressure fluctuation component is not distributed. Therefore, the pressure fluctuation component propagating to the downstream common flow path 107 is smaller than the pressure fluctuation component propagating to the upstream common flow path 106.

Therefore, in the downstream common channel 107 with the indirect reflection configuration, the effect of suppressing residual vibration after ink ejection is reduced, but the propagated pressure fluctuation component is also small, so the residual vibration can be sufficiently suppressed.

When the nozzle 101 is arranged as shown in FIG. 15, the pressure fluctuation component propagating to the upstream common flow path 106 is not distributed to the nozzle 101 etc. Therefore, when the nozzle 101 is arranged at the center of the pressure chamber 103 (see FIG. 2) There is a possibility that pressure crosstalk is more likely to occur between nozzles 101 adjacent to each other in the Y-axis direction. However, since the path length from the upstream common flow path 106 to the nozzle 101 is also long, the flow path resistance increases, so the influence of pressure crosstalk is suppressed.

Note that by making the flow path length of the upstream individual flow path 104 longer than the flow path length of the downstream individual flow path 105, the first path length from the nozzle 101 to the upstream common flow path 106 is increased, and the flow path resistance is increased. It is also possible to adopt a configuration that increases the .

As described above, the upstream damper 121 is built inside the channel plate 20 by stacking the first to third stacked bodies 21 to 23 of the channel plate 20. Moreover, by joining the flow path plate 20, the vibration plate 30, and the housing 40, a part of the vibration plate 30 is formed as the downstream damper 122. That is, the upstream damper 121 and the downstream damper 122 are formed by joining a plurality of members. The upstream damper 121 and the downstream damper 122 having a thickness of several μm to several tens of μm can be formed more easily than in the case where they are formed inside one molded part.

Here, when the flow path plate 20 and the vibration plate 30 are bonded using a thermosetting adhesive, expansion or contraction occurs in the flow path plate 20 and the vibration plate 30 due to the influence of heat. Specifically, when the adhesive is cured by heating, each of the channel plate 20 and the vibration plate 30 is thermally expanded and bonded in the thermally expanded state. After the heating is completed, the channel plate 20 and the vibration plate 30 are bonded to each other and contract as an integral part.

If the flow path plate 20 and the vibration plate 30 have different coefficients of thermal expansion, thermal stress will be generated in each when contracting. Then, when the thermal stresses are balanced, a stable bonding state is achieved. At this time, one of the channel plate 20 and the vibrating plate 30 has expanded more than before heating, and the other has contracted more than before heating. Therefore, the degree of tension will be different between the upstream damper 121 and the downstream damper 122, and there is a possibility that variations in discharge speed and discharge volume will increase. In particular, the degree of tension of the damper tends to vary depending on the position in the longitudinal direction (Y-axis direction).

Therefore, it is preferable that the flow path plate 20 and the vibration plate 30 have the same coefficient of thermal expansion. Specifically, the difference in thermal expansion coefficients is preferably within 30%. This makes the damper functions of the upstream damper 121 and the downstream damper 122 uniform, so that variations in discharge speed and discharge volume can be suppressed. In this embodiment, the upstream damper 121 is made of stainless steel and has a coefficient of thermal expansion of 18 ppm. On the other hand, the downstream damper 122 is made of a nickel alloy and has a coefficient of thermal expansion of 16 ppm. In this case, the difference in thermal expansion coefficients is approximately 12%.

As described above, the inkjet head 1 according to the embodiment includes a plurality of nozzles 101 capable of ejecting ink to the outside, a plurality of pressure chambers 103 communicating with each of the plurality of nozzles 101, and a plurality of pressure chambers 103 communicating with each other. an upstream common flow path 106 (first common flow path), a downstream common flow path 107 (second common flow path) that communicates with the plurality of pressure chambers 103 through a different path from the upstream common flow path 106, and an upstream common flow path 106 , and a downstream damper 122 (second damper) arranged in the downstream common flow path 107 . In the inkjet head 1, the vibration period of the upstream damper 121 in the thickness direction is shorter than the vibration period of the downstream damper 122 in the thickness direction.

According to the inkjet head 1, residual vibration in which the ink vibrates at the Helmholtz resonance period after ink ejection can be suppressed by elastic deformation of the upstream damper 121 and the downstream damper 122. Further, since the pressure waves P1 and P2 generated by the vibrations of the upstream damper 121 and the downstream damper 122 are out of phase, pressure fluctuations caused by the propagation of the pressure waves P1 and P2 can be suppressed. Therefore, the inkjet head 1 can maximize the damper effect and eject ink droplets with high frequency and high accuracy even under size and productivity constraints. Furthermore, in inkjet equipment equipped with the inkjet head 1 of the present disclosure, printing tact and productivity can be improved.

Specifically, in the inkjet head 1, the thickness of the upstream damper 121 (first damper) is greater than the thickness of the downstream damper 122 (second damper). As a result, the phases of the pressure waves P1 and P2 generated by the vibrations of the upstream damper 121 and the downstream damper 122 can be easily shifted by simply adjusting the thickness of the upstream damper 121 and the downstream damper 122, and the pressure waves P1 and P2 It is possible to suppress pressure fluctuations caused by the propagation of

Furthermore, in the inkjet head 1, the Young's modulus of the material forming the upstream damper 121 is larger than the Young's modulus of the material forming the downstream damper 122. For example, by using different materials for forming the upstream damper 121 and the downstream damper 122, the Young's modulus of the upstream damper 121 and the downstream damper 122 can be easily made different. As a result, the phases of the pressure waves P1 and P2 generated by the vibrations of the upstream damper 121 and the downstream damper 122 can be easily shifted by simply adjusting the Young's modulus of the material forming the upstream damper 121 and the downstream damper 122, and the pressure waves Pressure fluctuations caused by the propagation of P1 and P2 can be suppressed.

In particular, in the inkjet head 1, the thickness of the upstream damper 121 (first damper) is greater than the thickness of the downstream damper 122 (second damper), and the Young's modulus of the material forming the upstream damper 121 is greater than that of the downstream damper 122. is larger than the Young's modulus of the forming material. Thereby, pressure fluctuations caused by propagation of pressure waves P1 and P2 can be suppressed more effectively.

Furthermore, in the inkjet head 1, the volume of the first upstream common channel 106a (first common channel) is smaller than the volume of the downstream common channel 107 (second common channel). As a result, there is also a difference in the propagation time between the propagation time for the pressure wave P1 generated by the vibration of the upstream damper 121 to reach the pressure chamber 103 and the propagation time for the pressure wave P2 generated by the vibration of the upstream damper 121 to reach the pressure chamber 103. occurs. Therefore, the phase shift between the pressure waves P1 and P2 in the pressure chamber 103 increases, and the pressure fluctuations occurring in the pressure chamber 103 due to the propagation of the two pressure waves P1 and P2 caused by the vibration of the damper itself are suppressed more reliably. can do.

Further, in the inkjet head 1, at least a part of the wall surface of the first upstream common channel 106a (first common channel) is formed by a filter section 106c in which a plurality of openings are formed, and through the filter section 106c, It communicates with the second upstream common flow path 106b (an ink flow path in a separate space). As a result, the upstream common flow path 106 is divided into the first upstream common flow path 106a and the second upstream common flow path 106b, so that the Compared to the case where the volume of the upstream common flow path 106 is reduced by the parallel cross-sectional area or the length along the Y-axis direction, the volume of the upstream common flow path 106 can be easily reduced.

The inkjet head 1 also includes an upstream individual flow path 104 (first individual flow path) that connects the pressure chamber 103 and the upstream common flow path 106 (first common flow path), and an upstream individual flow path 104 (first individual flow path) that connects the pressure chamber 103 and the downstream common flow path 107 ( a downstream individual flow path 105 (second individual flow path) that connects the upstream common flow path 106 to the upstream individual flow path 104 at a connection portion 111 (first connection portion). The downstream common flow path 107 is connected to the downstream individual flow path 105 at a connection part 112 (second connection part), and the direction from the liquid contact surface of the upstream damper 121 (first damper) toward the connection part 111 is connected to the ink flow path 105. The direction from the liquid contact surface of the downstream damper 122 toward the connecting portion 112 is the same as the discharge direction. As a result, the upstream common channel 106 where the upstream damper 121 with a short vibration period is arranged has a direct reflection configuration, and the downstream common channel 107 where the upstream damper 122 with a long vibration period is arranged has an indirect reflection configuration. Therefore, the phase difference between the two pressure waves P1 and P2 propagating to the pressure chamber 103 increases, and the pressure fluctuations occurring in the pressure chamber 103 due to the propagation of the two pressure waves P1 and P2 caused by the vibration of the damper itself are more reliably suppressed. can be suppressed to

Further, in the inkjet head 1, the upstream common channel 106 (first common channel) is arranged upstream of the pressure chamber 103, and the downstream common channel 107 (second common channel) is arranged downstream of the pressure chamber 103. Placed. As a result, the pressure wave P1 propagating from the upstream common flow path 106 to the pressure chamber 103 travels in the same direction as the ink circulation direction, whereas the pressure wave P2 propagating from the downstream common flow path 107 to the pressure chamber 103 travels in the same direction as the ink circulation direction. , counter to the direction of ink circulation. Therefore, the phase shift between the two pressure waves P1 and P2 propagating to the pressure chamber 103 can be increased more effectively.

Furthermore, in the inkjet head 1, the nozzles 101 are arranged so as to be closer to the downstream common flow path 107 (second common flow path) with respect to the center of the pressure chamber 103 in the ink flow direction. As a result, residual vibrations generated after ink ejection that vibrate at a frequency close to Helmholtz resonance are propagated more to the upstream common flow path 106 of the direct reflection configuration than to the downstream common flow path 107 of the indirect reflection configuration. Therefore, in the downstream common channel 107 having the indirect reflection configuration, the effect of suppressing residual vibration after ink ejection is reduced, but the propagated pressure fluctuation component is also reduced, so that residual vibration can be sufficiently suppressed.

In the inkjet head 1, the first path length from the upstream common channel 106 (first common channel) to the nozzle 101 is the same as the length of the second path from the downstream common channel 107 (second common channel) to the nozzle 101. longer than long. As a result, the path length from the upstream common flow path 106 to the nozzle 101 becomes longer, and the flow path resistance increases, so the pressure fluctuation component propagating to the upstream common flow path 106 increases more than the downstream common flow path 107. Even in this case, the influence of pressure crosstalk on the nozzles 101 adjacent in the Y-axis direction can be suppressed.

In addition, in the inkjet head 1, the flow path plate 20 (first member) forming the upstream damper 121 (first damper) and the vibration plate 30 (second member) forming the downstream damper 122 (second damper) are heated. The channel plate 20 and the vibration plate 30 are bonded together using a curable adhesive, and the difference in thermal expansion coefficient is 30% or less. As a result, even when the flow path plate 20 and the vibration plate 30 are bonded using a thermosetting adhesive, the damper functions of the upstream damper 121 and the downstream damper 122 are made uniform, so variations in discharge speed and volume can be suppressed.

Although the invention made by the present inventor has been specifically explained based on the embodiments above, the present invention is not limited to the above embodiments, and can be modified without departing from the gist thereof.

For example, the upstream damper structure and the downstream damper structure may be reversed. That is, in the embodiment, the thickness of the upstream damper 121 and the downstream damper 122 and the Young's modulus of the forming material are set so that the vibration period of the upstream damper 121 is shorter than the vibration period of the downstream damper 122. The thickness of the upstream damper 121 and the downstream damper 122 and the Young's modulus of the forming material may be set so that the vibration period of the upstream damper 121 is longer than the vibration period of the downstream damper 122. That is, the thickness of the downstream damper 122 may be thicker than the thickness of the upstream damper 121, and the Young's modulus of the material forming the downstream damper 122 may be greater than the Young's modulus of the material forming the upstream damper 121. Alternatively, the upstream damper 121 may be formed by the vibrating plate 30, and the downstream damper 122 may be formed inside the channel plate 20.

As in the inkjet head 2 shown in FIG. 16, an upstream damper 121 and a downstream damper 122 are formed inside the channel plate 20, and a first space 123 and a second space 124 are formed between the nozzle plate 10 and the channel plate 20. It may also be formed by bonding. In this case as well, by varying the thickness of the upstream damper 121 and the downstream damper 122 and the Young's modulus of the forming material, the vibration cycles of the pressure waves P1 and P2 generated by the vibrations of the upstream damper 121 and the downstream damper 122 can be varied. can. Note that even if it is difficult to use different materials for forming the laminates that constitute the channel plate 20, it is possible to configure the upstream damper 121 with a single layer laminate and the downstream damper 122 with a two layer laminate, etc. Therefore, it is easy to make each thickness different.

Furthermore, as in the inkjet head 3 shown in FIG. It may be formed by In this case, by making the thicknesses of the upstream damper 121 and the downstream damper 123 different, the vibration cycles of the pressure waves P1 and P2 generated by the vibrations of the upstream damper 121 and the downstream damper 122 can be made different. This is effective when it is difficult to form a damper structure on the channel plate 20 due to dimensional restrictions or the like. Note that when the upstream damper 121 is formed of the vibration plate 30, an opening is formed in a region corresponding to the filter portion 106c.

Furthermore, the upstream common flow path 106 and the downstream common flow path 107 may have a structure divided in the Y-axis direction. In this case, the rigidity of the flow path plate 20 forming the upstream common flow path 106 and the downstream common flow path 107 is increased, so that workability is improved and production yield can be increased.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.

According to the present disclosure, residual vibration after ink ejection is suppressed, and high ejection accuracy can be achieved.

The present disclosure can be widely used in inkjet heads and printing equipment equipped with inkjet heads.

1 to 3 Inkjet head 10 Nozzle plate 20 Flow path plate 30 Vibration plate 40 Housing 50 Pressure fluctuation section 101 Nozzle 102 Silo section 103 Pressure chamber 104 Upstream individual flow path 105 Downstream individual flow path 106 Upstream common flow path 107 Downstream common flow path 108 Piezoelectric element 121 Upstream damper 122 Downstream damper

Claims (11)

Multiple nozzles that can eject ink externally,
a plurality of pressure chambers communicating with each of the plurality of nozzles;
a first common flow path communicating with the plurality of pressure chambers;
a second common flow path communicating with the plurality of pressure chambers through a different path from the first common flow path;
a first damper disposed in the first common flow path;
a second damper disposed in the second common flow path,
The thickness of the first damper is greater than the thickness of the second damper.
inkjet head. Multiple nozzles that can eject ink externally,
a plurality of pressure chambers communicating with each of the plurality of nozzles;
a first common flow path communicating with the plurality of pressure chambers;
a second common flow path communicating with the plurality of pressure chambers through a different path from the first common flow path;
a first damper disposed in the first common flow path;
a second damper disposed in the second common flow path,
The Young's modulus of the material forming the first damper is greater than the Young's modulus of the material forming the second damper.
inkjet head. The volume of the first common flow path is smaller than the volume of the second common flow path.
The inkjet head according to claim 1 or 2. The inkjet according to claim 3, wherein at least a part of the wall surface of the first common channel is formed by a filter section having a plurality of openings, and communicates with an ink channel in a separate space via the filter section. head. The positional relationship between the first damper and the pressure chamber and the positional relationship between the second damper and the pressure chamber are determined by a first propagation time during which a first pressure wave generated by vibration of the first damper reaches the pressure chamber. The second pressure wave generated by the vibration of the second damper is set to be shorter than the second propagation time to reach the pressure chamber.
The inkjet head according to claim 1 or 2. the first pressure wave is directly propagated to the pressure chamber;
The second pressure wave is propagated to the pressure chamber via reflection.
The inkjet head according to claim 5. a first individual flow path connecting the pressure chamber and the first common flow path;
a second individual flow path connecting the pressure chamber and the second common flow path;
The first common flow path is connected to the first individual flow path at a first connection part,
The second common flow path is connected to the second individual flow path at a second connection part,
The direction from the liquid contact surface of the first damper toward the first connection portion is opposite to the ink ejection direction,
A direction from the liquid contact surface of the second damper toward the second connection portion is the same as the discharge direction.
The inkjet head according to claim 6. the first common flow path is arranged upstream of the pressure chamber,
the second common flow path is located downstream of the pressure chamber;
The inkjet head according to claim 1 or 2. The nozzle is arranged offset from the center of the pressure chamber so as to be close to the second common flow path in the flow direction of the ink.
The inkjet head according to claim 1 or 2. A first path length from the first common flow path to the nozzle is longer than a second path length from the second common flow path to the nozzle.
The inkjet head according to claim 1 or 2. A first member on which the first damper is formed and a second member on which the second damper is formed are joined by a thermosetting adhesive,
The first member and the second member have a difference in thermal expansion coefficient of 30% or less,
The inkjet head according to claim 1 or 2.

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