TW202404823A - 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

This disclosure relates to an inkjet head.

Conventionally, a drop-on-demand inkjet head (hereinafter referred to as "DOD inkjet head") has been known as an example of an inkjet head, which can print on a printing object. A necessary amount of ink droplets are ejected with high precision at a necessary time and driven at a high frequency (for example, 50 kHz). Generally speaking, a piezoelectric DOD inkjet head has the following components: an ink flow path; a pressure chamber that is connected to the ink flow path and stores ink; and a piezoelectric element (piezoelectric element) that reacts to the ink stored in the pressure chamber. pressurizing; and a nozzle connected to the pressure chamber. By energizing the piezoelectric element to pressurize the ink in the pressure chamber, ink droplets can be ejected from the nozzle.

In a DOD inkjet head, after ink droplets are ejected, residual vibration is generated in the cycle of Helmholtz resonance. Therefore, when high-frequency discharge is performed in a DOD inkjet head, the discharge accuracy (variation in discharge angle or discharge speed) may deteriorate due to the influence of residual vibration after discharge of droplets. In order to avoid the above problems, it is important to early suppress the residual vibration after the droplets are discharged.

In order to suppress residual vibration early, it is effective to install 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. Furthermore, Patent Document 2 discloses that in a circulation-type inkjet head, dampers having different cross-sectional areas are arranged in the ink supply flow path and the ink discharge flow path. Prior technical literature

patent documents Patent Document 1: Japanese Patent No. 4493965 Patent Document 2: Japanese Patent Application Publication No. 2017-165051

An inkjet head in one aspect of this disclosure has: Multiple nozzles can spit out ink to the outside; A plurality of pressure chambers connected to each of the aforementioned plurality of nozzles; The first common flow path is connected to the plurality of pressure chambers mentioned above; The second common flow path communicates with the plurality of pressure chambers via a path different from that of the first common flow path; The first damper is arranged in the aforementioned first common flow path; and The second damper is arranged in the aforementioned second common flow path, The first damper is thicker than the second damper. Other forms of inkjet heads disclosed in this disclosure include: Multiple nozzles can spit out ink to the outside; A plurality of pressure chambers connected to each of the aforementioned plurality of nozzles; The first common flow path is connected to the plurality of pressure chambers mentioned above; The second common flow path communicates with the plurality of pressure chambers via a path different from that of the first common flow path; The first damper is arranged in the aforementioned first common flow path; and The second damper is arranged in the aforementioned 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.

Form used to implement the invention In an inkjet head that requires high discharge accuracy, different from the residual vibration that causes the ink to vibrate in the cycle of Helmholtz resonance after the ink is discharged, the pressure fluctuation caused by the vibration of the damper itself also deteriorates the discharge accuracy. main reasons that cannot be ignored. When the elastic deformation amount of the damper is increased in order to suppress the residual vibration of the ink, the pressure fluctuation caused by the vibration of the damper itself becomes larger. As a result, there is a trade-off of increasing the residual vibration of the ink (trade- off).

In particular, in an ink circulation type inkjet head, when dampers are provided in the ink supply flow path and the ink discharge flow path, there is a risk that waves of pressure fluctuations caused by the vibration of the damper itself will overlap near the nozzle. , which may have a greater adverse impact on the discharge accuracy.

An object of this disclosure is to provide an inkjet head that can suppress residual vibration after ink is discharged and achieve high discharge accuracy.

Hereinafter, the inkjet head 1 according to the 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. In this disclosure, an orthogonal coordinate system (X, Y, Z) is used for explanation. The negative direction of the Z-axis is the direction in which ink is discharged from the inkjet head 1 , the direction along the Y-axis is the arrangement direction of the nozzles 101 , and the direction along the X-axis is the flow direction of the ink to the pressure chamber 103 . In the following, the directions along the X-axis, the Y-axis and the Z-axis are respectively referred to as the "X-axis direction", "Y-axis direction" and "Z-axis direction".

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

As shown in FIG. 1 , the inkjet head 1 is composed of a nozzle plate 10 , a flow path plate 20 , a vibration plate 30 , a housing 40 , and a pressure varying portion 50 .

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

The flow path plate 20 has a rectangular parallelepiped shape and is arranged on the front side of the nozzle plate 10 in the Z-axis direction so that the plate surface of the flow path 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 flow path plate 20 is a laminated body of a plurality of stainless steel plates molded by, for example, etching or press processing. The thickness of each stainless steel plate is, for example, 10 to 100 µm, and the number of layers is, for example, 3 to 10 layers.

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

Furthermore, the diaphragm 30 has a pressure receiving portion 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 diaphragm 30 , the portion where the pressure receiving portion 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 diaphragm 30 in the Z-axis direction. The thickness of the housing 40 in the Z-axis direction is, for example, 1 cm. The housing 40 is formed by cutting alloy steel such as stainless steel, for example.

The pressure varying unit 50 is disposed in a pressure varying unit accommodating chamber (symbol omitted) of the casing 40 and pressurizes the ink stored in the pressure chamber 103 to generate pressure variation. The pressure varying unit 50 includes a base 51, a control substrate 52, and a piezoelectric element 108 (see FIG. 2). The base 51 holds the control substrate 52 and the piezoelectric element 108 . The control board 52 is, for example, a flexible printed circuit board on which a control IC or the like is mounted. The control IC controls the applied voltages to the plurality of piezoelectric elements 108 individually.

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 fluctuating part 50 are each connected by an adhesive. fixed. As an adhesive, for example, an epoxy-based adhesive having thermosetting properties can be used. In addition, the adhesives that adhere each component may be the same adhesive or different adhesives. For example, a rubber-based adhesive agent and an epoxy-based adhesive agent may be used in combination.

Each element of the inkjet head 1 is formed inside the nozzle plate 10 , the flow path plate 20 , the diaphragm 30 , the casing 40 and the pressure varying unit 50 , or is formed by combining these components. .

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 reservoir 102 , a pressure chamber 103 , an upstream individual channel 104 , a downstream individual channel 105 , an upstream common channel 106 , a downstream common channel 107 , and a piezoelectric element 108 , ink supply path 109 and ink discharge path 110. Furthermore, the inkjet head 1 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 pressurize the ink stored in the pressure chamber 103 to eject the ink droplets from the nozzle 101 . The nozzles 101 may be arranged in one row along the Y-axis or in multiple rows. In FIG. 1 , the nozzles 101 are arranged in two rows along the Y-axis.

In addition, when the nozzles 101 are arranged in a plurality of rows, the pressure chamber 103, the upstream individual flow path 104, and the downstream individual flow path 105 are also formed in a plurality of 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 a plurality of rows of nozzles 101 . In addition, the flow direction of the ink to the pressure chambers 103 belonging to different rows may be the same or opposite directions. In the following, a case will be described in which the flow direction of the ink into the pressure chamber 103 is the negative direction of the X-axis. That is, the description will be made with the positive side of the X-axis being the upstream side in the flow direction of the ink, and the negative side being the downstream side in the flow direction.

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

The pressure chamber 103 and the storage portion 102 are provided one-to-one for each of the plurality of nozzles 101 . The pressure chamber 103 communicates with the nozzle 101 through the storage portion 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 upper surface (the surface on the positive side in the Z-axis direction) of the recess formed in the flow path plate 20 is closed by the vibration plate 30 , thereby forming the pressure chamber 103 . The pressure chamber 103 has, for example, a rectangular parallelepiped shape extending along the X-axis. In addition, a step may be formed on the inner surface of the pressure chamber 103 .

The storage chamber 102 is formed along the Z-axis and communicates with the pressure chamber 103 and the nozzle 101 . The storage part 102 forms an ink storage space together with the pressure chamber 103 . The storage part 102 may have a cylindrical shape or a square prism shape, for example.

The upstream individual flow path 104 is an ink flow path that connects 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 on a one-to-one basis for each of the plurality of pressure chambers 103 .

The downstream individual flow path 105 is an ink flow path that connects 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 on a one-to-one basis 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 front side of the upstream individual flow path 104 in the X-axis direction). The upstream common flow path 106 is provided commonly for the plurality of upstream individual flow paths 104 . The upstream common flow path 106 includes a first upstream common flow path 106 a formed in the flow path plate 20 and a second upstream common flow path 106 b formed in the casing 40 . The first upstream common flow path 106a and the second upstream common flow path 106b are connected through the filter unit 106c. The filter part 106c can be said to form part of the upstream common flow path 106.

The filter portion 106c is a portion of the diaphragm 30 corresponding 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 through it, and it is intended to prevent particles flowing into the nozzle 101 from being unable to pass through. 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 commonly for the plurality of downstream individual flow paths 105 . The downstream common flow path 107 includes a first downstream common flow path 107 a formed in the flow path plate 20 and a second downstream common flow path 107 b formed in the casing 40 . The first downstream common flow path 107 a and the second downstream common flow path 107 b are connected through the opening 107 c formed in the diaphragm 30 . The opening 107c can be said to form 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 accommodated in the pressure chamber 103 . The piezoelectric element 108 is provided corresponding to the plurality of pressure chambers 103 and is in contact with the pressure receiving portion 31 of the vibration plate 30 . The piezoelectric element 108 is deformed to expand and contract in the Z-axis direction by applying a voltage, for example. The piezoelectric element 108 may be a multilayer piezoelectric actuator of the D33 mode, for example.

In the inkjet head 1 , ink is supplied from an external ink supply tank (not shown) through the ink supply path 109 through the upstream common flow path 106 , the upstream individual flow path 104 , the pressure chamber 103 , and the downstream individual flow path. 105 and the downstream share the flow path 107, and are discharged from the ink discharge path 110. The discharged ink is circulated to the ink supply tank by a circulation pump (not shown), for example. By circulating the ink instead of retaining it, it is possible to prevent the ink from retaining in the pressure chamber 103 or the nozzle 101 and causing the nozzle to be clogged.

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 . high. For example, the pressure difference can be controlled by making the positions of the ink supply groove and the ink discharge groove in the Z-axis direction (height based on the pressure chamber 103) different. For another example, a regulator may be used to individually control the internal pressures of the ink supply tank and the ink discharge tank.

In the pressure varying portion 50 , when a voltage is applied to the piezoelectric element 108 , the piezoelectric element 108 deforms, for example, to expand in the Z-axis direction, so that the pressure-receiving portion 31 of the diaphragm 30 faces downward (the negative side in the Z-axis direction). Push. As a result, the upper wall of the pressure chamber 103 deforms, causing a pressure change in the ink stored in the pressure chamber 103 . This pressure change is propagated toward the nozzle 101 through the storage portion 102 , thereby ejecting ink droplets from the nozzle 101 .

In addition, 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 (the first upstream common flow path 106 a ) is formed with the upstream damper 121 . The upstream damper 121 is formed using, for example, one layer of the laminate constituting the flow path plate 20 . The thickness of the upstream damper 121 is, for example, 2 to 30 μm.

A first space portion 123 that allows deformation of the upstream damper 121 is provided on the opposite side of the liquid contact surface of the upstream damper 121 . The thickness of the first space portion 123 only needs to allow the elastic deformation of the upstream damper 121, and is, for example, 10 to 200 μm.

The upstream damper 121 has a film shape that can be elastically deformed in response 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 discharged, the pressure fluctuation of the ink propagates to the upstream common flow path 106 via the pressure chamber 103 , is reflected in the upstream common flow path 106 , and propagates to the pressure chamber 103 . Since the upstream damper 121 deforms toward the first space portion 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 vibration of the ink after the ink is discharged can be suppressed.

In addition, 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 diaphragm 30 . In the diaphragm 30 , the portion 122 where the liquid contact surface of the downstream common flow path 107 is formed functions as a downstream damper (hereinafter referred to as “downstream damper 122 ”). The thickness of the downstream damper 122 is equal to or lower than the vibration plate 30 , for example, 2~30 μm.

A second space 124 that allows deformation of the downstream damper 122 is provided on the opposite side of the liquid contact surface of the downstream damper 122 . The thickness of the second space portion 124 only needs to be able to allow the elastic deformation of the downstream damper 122 , and is, for example, 10 to 200 μm.

In addition, in the diaphragm 30 , the portion functioning as the downstream damper 122 may be formed with a concave portion or the like and may be processed to be thin in order to easily elastically deform. In addition, when the diaphragm 30 can be deformed sufficiently to suppress the pressure fluctuation, the thickness of the portion functioning as the downstream damper 122 does not need to be made thin.

The downstream damper 122 has a 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 discharged, the pressure fluctuation of the ink propagates to the downstream common flow path 107 via the pressure chamber 103 , is reflected in the downstream common flow path 107 , and propagates to the pressure chamber 103 . Since the downstream damper 122 deforms toward the second space portion 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 becomes smaller. Therefore, by providing the downstream damper 122 in the downstream common flow path 107, residual vibration of the ink after the ink is discharged can be suppressed.

An example of the laminated structure of the flow path plate 20 will be described with reference to FIGS. 3 to 7 . 3 to 7 are plan views of respective laminated bodies forming the laminated structure of the flow path plate 20 . In FIGS. 3 to 7 , the structures of the first to fifth laminated bodies 21 to 25 forming the flow path plate 20 are shown in a plan view viewed from the front side in the Z-axis direction.

The flow path plate 20 is composed of a first laminated body 21 , a second laminated body 22 , a third laminated body 23 , a fourth laminated body 24 , and a fifth laminated body 25 laminated in this order from the negative side in the Z-axis direction. Openings penetrating in the Z-axis direction are formed in the first to fifth laminated bodies 21 to 25 .

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

As shown in FIG. 4 , the second laminated body 22 has an opening 22A forming the storage portion 102 . The thickness of the second laminated body 22 is, for example, 25 μm. The opening 22A corresponds to the opening 21A of the first laminated 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 laminated body 21 . On the other hand, no opening is formed in the region 22B corresponding to the opening 21B in the first laminated body 21 (the region surrounded by a dotted line in FIG. 4 ) (hereinafter, referred to as “solid region 22B”).

As shown in FIG. 5 , the third laminated body 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 laminated body 23 is, for example, 100 μm. The opening 23D has a rectangular shape in a plan view viewed from the Z-axis direction, for example, and is formed one-to-one with the opening 22A of the second laminated body 22 . The opening 23B corresponds to the opening 21B of the first laminated 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 laminated body 21 . In addition, opening 23C is formed symmetrically with opening 23B based on opening 23D. In addition, the opening 23B and the opening 23C may be one opening as shown in FIG. 5 , but may also be divided into a plurality of openings in order to maintain strength. For example, in the Y-axis direction, the opening 23B and the opening 23C may be divided every time ten openings 23D are formed, and one opening 23B and one opening 23C may be provided for each of the ten openings 23D.

As shown in FIG. 6 , the fourth laminated body 24 has openings 24E forming the pressure chamber 103 , the upstream individual flow path 104 , and the downstream individual flow path 105 . The thickness of the fourth laminated body 24 is, for example, 30 μm. The opening 24E is formed by the length of the openings 23B and 23C of the cross-linked third laminated body 23 in the X-axis direction.

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

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

The storage part 102 is formed by laminating the 1st laminated body 21-3rd laminated body 23. By laminating the third to fifth laminated bodies 23 to 25, the first upstream common flow path 106a and the first downstream common flow path 107a are formed. The upstream individual flow path 104 and the downstream individual flow path 105 are formed by the opening 24E of the fourth laminated body 24 .

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

The vibration plate 30 is joined to the positive side of the flow path plate 20 in the Z-axis direction, and the openings 25D and 25F of the fifth laminated body 25 are closed by the vibration plate 30, thereby forming the pressure chamber 103 and the second space part 124. Moreover, the opening 25B of the fifth laminated body 25 is closed by the filter part 106c provided in the diaphragm 30.

In addition, by joining the case 40 to the positive side of the diaphragm 30 in the Z-axis direction, the portion of the diaphragm 30 sandwiched by the second downstream common flow path 107b and the second space portion 124 serves as the second damper. 122 and function.

In the inkjet head 1 having the above structure, after ink is ejected, pressure fluctuation occurs in a cycle of Helmholtz resonance, and the pressures of the upstream common flow path 106 and the downstream common flow path 107 increase. This pressure change will be attenuated due to the elastic deformation of the upstream damper 121 and the downstream damper 122 . Therefore, the pressure fluctuation reflected in the upstream common flow path 106 and the downstream common flow path 107 and propagated to the pressure chamber 103 becomes smaller, and residual vibration of the ink can be suppressed.

On the other hand, pressure changes will be propagated to the pressure chamber 103 due to vibrations caused by the elastic deformation of the upstream damper 121 and the downstream damper 122 themselves. When the phases of pressure fluctuation waves (hereinafter referred to as "pressure waves") are consistent, in the pressure chamber 103, the first pressure wave P1 propagating from the upstream and the second pressure wave P2 propagating from the downstream overlap. , causing the pressure variation in the pressure chamber 103 to increase. Although the amount of pressure change at this time is small compared with the amount of pressure change caused by Helmholtz resonance after the ink is discharged, it may cause unacceptable problems in an inkjet head that requires high-definition discharge accuracy. Risk of adverse effects.

That is, 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 have the same phase, compared with the first pressure wave P1 If the phase of the second pressure wave P2 is shifted, the pressure fluctuation generated in the pressure chamber 103 due to the first pressure wave P1 and the second pressure wave P2 will become larger, and the discharge speed or discharge volume of the ink may become unable to be achieved. Ignore the risk of changes in levels. In particular, when discharging is performed in a high frequency band, the dispersion speed or the discharging volume caused by the difference in discharging frequency becomes larger.

Therefore, in this embodiment, 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, so that the first pressure generated by the vibration of the upstream damper 121 is reduced. The phase of the wave P1 is shifted from the phase of the second pressure wave P2 generated by the vibration of the downstream damper 122 . In addition, in the embodiment, the thickness directions of the upstream damper 121 and the downstream damper 122 are parallel to the ink discharge direction, but they may not be parallel to the ink discharge direction. In the following, 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 . In FIG. 8 , a case is shown in which the time at which the pressure fluctuation generated in the pressure chamber 103 reaches the upstream damper 121 is the same as the time at which it reaches the downstream damper 122 . In addition, 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 plus (plus).

When the pressure in the upstream common flow path 106 and the downstream common flow path 107 rises due to the propagation of the pressure fluctuation generated in the pressure chamber 103, at the time point t1 in FIG. 8, the upstream damper 121 and the downstream damper 122 are moved. The ink is pushed and elastically deformed toward the negative side in the Z-axis direction.

The time point t2 in FIG. 8 is the time when the displacement of the vibration V1 of the upstream damper 121 reaches the maximum value. The time point t3 is the time when the displacement of the vibration V2 of the downstream damper 122 reaches the maximum value. In the case where the vibration period of the upstream damper 121 is shorter than the vibration period of the downstream damper 122, the time point t2 becomes earlier than the time point t3.

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

Time point t4 in FIG. 9 is the time when the pressure waves P1 and P2 arrive at the pressure chamber 103, and is later than the time point t1 in FIG. 8 by the propagation time of the pressure waves P1 and P2. The time point t5 is the time when the pressure wave P1 reaches the maximum value, and the time point t6 is the time when the pressure wave P2 reaches the 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 that propagate to the pressure chamber 103 are also shifted accordingly. As a result, the pressure waves P1 and P2 can be prevented from overlapping, and therefore the pressure fluctuation occurring in the pressure chamber 103 can be 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 thickness difference between the upstream damper 121 and the downstream damper 122 is preferably 8 μm or more.

In addition, 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 . In this embodiment, the upstream damper 121 is made of stainless steel, and the downstream damper 122 is made of nickel alloy. The Young's modulus of stainless steel is about 200 GPa, and that of nickel alloy is about 160 GPa. In addition, 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. In order to simplify the explanation, as shown in FIG. 10 , a beam model in which a load m is added to the center of a simple beam having a length L, a width b, and a thickness h will be used for the explanation. The spring coefficient k of the upstream damper 121 and the downstream damper 122 can be calculated by the following equation (1) using the length L, width b, thickness h, and Young's modulus E of the forming material. In addition, the vibration period of the upstream damper 121 and the downstream damper 122 becomes shorter as the spring coefficient k increases. [Mathematical formula 1]

According to equation (1), the spring coefficient k can be adjusted by the thickness h of the upstream damper 121 and the downstream damper 122 to shift the phases of the vibrations of the upstream damper 121 and the downstream damper 122. In addition, although the spring coefficient k can also be adjusted by the length L or width b of the upstream damper 121 and the downstream damper 122, due to the limitation of the size of the inkjet head 1, the value of the length L or the width b must be adjusted. There are difficulties with larger staggers. Accordingly, the spring coefficient k should be adjusted by the thickness of the upstream damper 121 and the downstream damper 122 .

In addition, according to the formula (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 vibration of the upstream damper 121 and the vibration of the downstream damper 122 can be adjusted. Phase shift.

In the upstream damper 121 and the downstream damper 122, when the spring coefficient k is adjusted by both the thickness h and the Young's modulus E, the spring coefficient k can be adjusted more easily than when the spring coefficient k is adjusted by either one. Adjust the spring coefficient k.

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 the spring coefficient of the downstream damper 122 , the vibration period of the upstream damper 121 is shorter than the vibration period of the downstream damper 122 . That is, the vibration phases of the upstream damper 121 and the downstream damper 122 are shifted. Therefore, the pressure fluctuation that occurs 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 can be suppressed.

The volumes of the upstream common flow path 106 and the downstream common flow path 107 are preferably different. 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" refer to the volume of the same space portion where ink continuously exists.

The first downstream common flow path 107 a and the second downstream common flow path 107 b forming the downstream common flow path 107 are connected through the opening 107 c of the diaphragm 30 . Therefore, ink continuously exists between the first downstream common flow path 107a and the second downstream common flow path 107b. Therefore, the pressure fluctuation propagated from the pressure chamber 103 is similarly propagated to the first downstream common flow path 107a, the second downstream common flow path 107b, and the opening 107c of the diaphragm 30. That is, when examining the influence of the pressure fluctuation propagating between the pressure chamber 103 and the downstream common flow path 107 , all of the downstream common flow paths 107 are targeted. In summary, "the volume of the downstream common flow path 107" refers to 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 are connected through the filter portion 106c having a through hole. In the filter part 106c, the through holes allow ink to flow, but the ink is reflected in parts other than the through holes. Therefore, it can be thought that the pressure fluctuation propagated from the pressure chamber 103 does not propagate easily to the second upstream common flow path 106b and propagates only to the first upstream common flow path 106a. That is, when considering the influence of the pressure fluctuation 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 can be regarded as different spaces, and only the first upstream common flow path 106a can be regarded as different spaces. The common flow path 106a becomes the target. In short, "the volume of the upstream common flow path 106" means the volume of the first upstream common flow path 106a.

When the lengths of the upstream common flow path 106 and the downstream common flow path 107 along the Y-axis are the same, as shown in bold lines in FIG. 11 , the upstream common flow path 106 and the downstream common flow path 107 can be parallel The cross-sectional area on the XZ plane is used to control their respective volumes. In addition, when 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 size restrictions, etc., the cross-sectional areas can also be made the same and the upstream common flow path 106 and the downstream common flow path can be used. The length of the path 107 along the Y-axis controls the respective volume.

Since the upstream common flow path 106 can be disconnected by interposing the filter portion 106c between the first upstream common flow path 106a and the second upstream common flow path 106b, compared with the first upstream common flow path 106a and the second upstream common flow path 106b, 2. When the upstream common flow path 106b becomes the same space, the cross-sectional area of the upstream common flow path 106 parallel to the XZ plane becomes smaller. Therefore, compared with the case where the volume of the upstream common flow path 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 flow path 106a or the second upstream common flow path 106b. , the volume of the upstream common flow path 106 can be easily reduced.

Most of the pressure fluctuation components caused by the vibration of the upstream damper 121 are initially propagated to the entire same space including the upstream damper 121 , that is, the entire upstream common flow path 106 , and then propagated to the pressure chamber 103 . Similarly, most of the pressure fluctuation components caused by the vibration of the downstream damper 122 are initially propagated to the entire same space including the downstream damper 122, that is, the entire downstream common flow path 107, and then propagated to the pressure Room 103.

Therefore, as the volumes of the upstream common flow path 106 and the downstream common flow path 107 increase, the propagation time until the pressure waves P1 and P2 due to vibrations of the upstream damper 121 and the downstream damper 122 reach the pressure chamber 103 becomes later.

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, compared with the second pressure wave P2 based on the vibration of the downstream damper 122 with a longer vibration period , the first pressure wave P1 based on the vibration of the upstream damper 121 with a shorter vibration period shows a maximum value earlier (refer to Figure 9), and reaches the pressure chamber 103 earlier, which is earlier than the propagation time difference Δt (refer to Figure 12 ). That is, as shown in FIG. 12 , the phase difference between the two pressure waves P1 and P2 (the time between time points t5 and t6 ) becomes larger than the phase difference in the case shown in FIG. 9 . Therefore, the pressure fluctuation that occurs 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 can be reliably suppressed.

On the other hand, when the volume of the upstream common flow path 106 is set larger than the volume of the downstream common flow path 107, compared with the pressure wave P2 based on the vibration of the downstream damper 122 with a longer vibration period, the pressure wave P2 based on the vibration is Although the pressure wave P1 of the vibration of the upstream damper 121 with a shorter period shows a maximum value earlier (refer to FIG. 9 ), it reaches the pressure chamber 103 later by the propagation time difference Δt (refer to FIG. 13 ). In this case, as shown in FIG. 13 , the two pressure waves P1 and P2 are in phase and have their maximum values overlap, and there is a risk that the suppression effect of the pressure fluctuation occurring in the pressure chamber 103 cannot be obtained.

Therefore, when the volumes of the upstream common flow path 106 and the downstream common flow path 107 are different, it is preferable to set the volume of the upstream common flow path 106 where the upstream damper 121 with a shorter vibration period is disposed to be larger than the volume of the upstream common flow path 106 where the upstream damper 121 is disposed with a shorter vibration period. The volume of the downstream common flow path 107 of the longer downstream damper 122 is smaller.

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 liquid contact surface with the ink in the positive direction of the Z-axis (vertical upward), that is, the pushing direction D1. The upstream connection portion 111 connecting the upstream common flow path 106 and the upstream individual flow path 104 is located on the positive side in the Z-axis direction relative to 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 connecting portion 111 is the same as the pushing direction D1. This structure is called "direct reflection structure". In the direct reflection structure, the first pressure wave P1 caused by the vibration of the upstream damper 121 mainly propagates directly to the pressure chamber 103 .

The downstream damper 122 pushes out the ink from the liquid contact surface with the ink in the positive direction of the Z-axis (vertical upward), that is, the pushing direction D2. The downstream connection portion 112 connecting the downstream common flow path 107 and the downstream individual flow path 105 is located on the negative side in the Z-axis direction relative to 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 connecting portion 112 is opposite to the pushing direction D2. This composition is called "indirect reflection composition". In the indirect reflection structure, the second pressure wave P2 caused by the vibration of the downstream damper 122 mainly propagates to the pressure chamber through reflection from the wall surface of the downstream common flow path 107 facing the downstream damper 122 in the pushing direction D2. 103.

In the direct reflection structure in the upstream common flow path 106, the upstream individual flow path 104 exists in the pushing direction D1 of the upstream damper 121. In contrast, in the indirect reflection structure in the downstream common flow path 107, the downstream damping There is no downstream individual flow path 105 in the pushing direction D2 of the device 122 . Therefore, in the indirect reflection structure, the pressure fluctuation component that propagates directly from the downstream damper 122 to the downstream individual flow path 105 becomes smaller compared to the direct reflection structure. That is, the second pressure wave P2 caused by the vibration of the downstream damper 122 reaches the pressure chamber 103 later than the first pressure wave P1 caused by 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 can be said to be set so that the first propagation time is shorter than the second propagation time. The time it takes for the first pressure wave P1 generated by the vibration of the first damper 121 to reach the pressure chamber 103. The aforementioned second propagation time is the time it takes for the second pressure wave P2 generated due to the vibration of the second damper 122 to reach the pressure chamber 103. .

By making the upstream common flow path 106 in which the upstream damper 121 with a shorter vibration period is disposed is a direct reflection structure, and the downstream common flow path 107 in which the downstream damper 122 with a longer vibration period is disposed is an indirect reflection structure. , the phase shift of the two pressure waves P1 and P2 propagating toward the pressure chamber 103 will increase. Therefore, the pressure fluctuation 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 can be suppressed more reliably.

In addition, the pressure wave P1 propagating from the upstream common flow path 106 to the pressure chamber 103 proceeds in the same direction as the circulation direction of the ink. In contrast, the pressure wave P2 propagating from the downstream common flow path 107 to the pressure chamber 103 proceeds in the same direction as the ink circulation direction. The circulation direction of the ink is reversed. That is, for the pressure wave P2 caused by the vibration of the downstream damper 122, since the circulation of the ink acts as a resistance, 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 of 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 in the pressure chamber 103. As shown in FIG.

After the ink is ejected from the nozzle 101, the pressure fluctuation propagated from the pressure chamber 103 is absorbed by the upstream damper 121 and the downstream damper 122, but part of the pressure fluctuation component will be in the upstream common flow path 106 and the downstream common flow path. 107 is reflected by the wall surface and returns to the pressure chamber 103 without being absorbed by the upstream damper 121 and downstream damper 122 . In the indirect reflection structure in the downstream common flow path 107, compared with the direct reflection structure in the upstream common flow path 106, since the path length from the pressure chamber 103 to the downstream damper 122 is longer, it is not affected by the downstream damper 122. The pressure fluctuation component absorbed and returned to the pressure chamber 103 becomes larger. Therefore, in the indirect reflection structure, the effect of suppressing the residual vibration that vibrates with a period close to the Helmholtz resonance after the ink is discharged from the nozzle 101 is smaller than in the direct reflection structure.

Therefore, in this embodiment, the residual vibration generated after the ink is ejected and vibrating with a period close to the Helmholtz resonance propagates to the direct reflection structure in a greater amount than to the downstream common flow path 107 of the indirect reflection structure. The upstream common flow path 106. Specifically, as shown in FIG. 15 , the nozzle 101 is disposed away from the center of the pressure chamber 103 so as to be close to the downstream common flow path 107 in the flow direction of the ink. When the flow path lengths of the upstream individual flow path 104 and the downstream individual flow path 105 are the same, it can also be said that the first path length from the upstream common flow path 106 to the nozzle 101 is longer than the first path length from the downstream common flow path 107 to the nozzle 101 . 2 path length is longer.

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

In this case, when the pressure fluctuation generated in the pressure chamber 103 due to the operation of the piezoelectric element 108 is propagated to the downstream common flow path 107 through the downstream individual flow path 105, it will also pass through the reservoir connecting the nozzle 101 and the pressure chamber 103. 102 and propagates to the nozzle 101. That is, the pressure fluctuation component generated in the pressure chamber 103 is distributed to the downstream individual flow path 105 and the storage section 102 . On the other hand, when the pressure fluctuation generated in the pressure chamber 103 propagates to the upstream common flow passage 106 through the upstream individual flow passage 104, the pressure fluctuation components are not distributed. Therefore, the pressure fluctuation component propagated to the downstream common flow path 107 becomes smaller than the pressure fluctuation component propagated to the upstream common flow path 106 .

Therefore, in the downstream common flow path 107 formed by indirect reflection, although the effect of suppressing residual vibration after ink discharge becomes smaller, 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 and the like. Therefore, compared with arranging the nozzle 101 in the center of the pressure chamber 103 , In this case (see FIG. 2 ), there is a risk that pressure crosstalk may easily occur in the 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 also becomes longer, the flow path resistance increases, so the influence of pressure crosstalk can be suppressed.

Alternatively, the flow path length from the nozzle 101 to the upstream common flow path 106 may be lengthened 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 . 1 path length, which increases the flow path resistance.

As described above, the upstream damper 121 is precisely manufactured inside the flow path plate 20 by laminating the first to third laminated bodies 21 to 23 of the flow path plate 20 . Furthermore, by joining the flow path plate 20 , the diaphragm 30 and the housing 40 , a part of the diaphragm 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 components. Compared with the case where they are precisely manufactured inside a molded part, the upstream damper 121 and the downstream damper 122 can be easily formed with a thickness of several μm to tens of μm.

Here, when a thermosetting adhesive is used to join the flow path plate 20 and the vibration plate 30 , the flow path plate 20 and the vibration plate 30 may expand or contract due to thermal influence. Specifically, when the adhesive is hardened by heating, the flow path plate 20 and the diaphragm 30 each thermally expand and are bonded in a thermally expanded state. After the heating is completed, the flow path plate 20 and the diaphragm 30 are in a bonded state and shrink as an integrated part.

If the thermal expansion coefficients of the flow path plate 20 and the diaphragm 30 are different, thermal stress will be generated when they shrink. And, after the thermal stress is balanced, a stable bonding state is achieved. At this time, one of the flow path plate 20 and the vibration plate 30 expands more than before heating, and the other shrinks more than before heating. Therefore, the degree of tension will be different between the upstream damper 121 and the downstream damper 122, which may increase the variation in discharge speed or discharge volume. In particular, the degree of tension of the damper tends to vary depending on the position in the longitudinal direction (Y-axis direction).

Accordingly, the thermal expansion coefficients of the flow path plate 20 and the diaphragm 30 are preferably the same. Specifically, the difference in thermal expansion coefficients should be within 30%. Thereby, since the damper functions of the upstream damper 121 and the downstream damper 122 become uniform, variations in the discharge speed or the discharge volume can be suppressed. In this embodiment, the upstream damper 121 is made of stainless steel and has a thermal expansion coefficient of 18 ppm. On the other hand, the downstream damper 122 is made of nickel alloy and has a thermal expansion coefficient of 16 ppm. In this case, the difference in thermal expansion coefficient becomes approximately 12%.

In this way, the inkjet head 1 of the embodiment includes a plurality of nozzles 101 capable of ejecting ink to the outside; a plurality of pressure chambers 103 connected to each of the plurality of nozzles 101; and an upstream common flow path 106 (first common flow path). path), communicates with the plurality of pressure chambers 103; the downstream common flow path 107 (the second common flow path), communicates with the plurality of pressure chambers 103 through a path different from the upstream common flow path 106; the upstream damper 121 (the first common flow path) damper), arranged in the 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 , the elastic deformation of the upstream damper 121 and the downstream damper 122 can suppress the residual vibration that causes the ink to vibrate in the Helmholtz resonance cycle after the ink is ejected. In addition, since the phases of the pressure waves P1 and P2 generated by the vibration of the upstream damper 121 and the downstream damper 122 are shifted, 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 at high frequency and with high precision even if there are limitations in size or productivity. In addition, in the inkjet equipment equipped with the inkjet head 1 of the present disclosure, printing tact time and productivity can be improved.

Specifically, in the inkjet head 1 , the thickness of the upstream damper 121 (first damper) is larger than the thickness of the downstream damper 122 (second damper). Thereby, simply by adjusting the thickness of the upstream damper 121 and the downstream damper 122, the phases of the pressure waves P1 and P2 generated by the vibration of the upstream damper 121 and the downstream damper 122 can be easily shifted, thereby suppressing the causes. Pressure changes due to the propagation of pressure waves P1 and P2.

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 to form 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. Thereby, by adjusting the Young's modulus of the material forming the upstream damper 121 and the downstream damper 122, the phases of the pressure waves P1 and P2 generated due to the vibration of the upstream damper 121 and the downstream damper 122 can be easily adjusted. By staggering, pressure changes caused by the propagation of pressure waves P1 and P2 can be suppressed.

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

Furthermore, in the inkjet head 1 , the volume of the first upstream common flow path 106 a (first common flow path) is smaller than the volume of the downstream common flow path 107 (second common flow path). Thereby, the propagation time until the pressure wave P1 generated by the vibration of the upstream damper 121 reaches the pressure chamber 103 and the propagation time until the pressure wave P2 generated by the vibration of the upstream damper 121 reaches the pressure chamber 103 will also be different. . Therefore, the phase shift of the pressure waves P1 and P2 in the pressure chamber 103 will be increased, and the propagation of the two pressure waves P1 and P2 caused by the vibration of the damper itself can be suppressed more reliably in the pressure chamber 103 pressure changes.

Furthermore, in the inkjet head 1, at least part of the wall surface of the first upstream common flow path 106a (first common flow path) is formed by the filter portion 106c in which a plurality of openings are formed, and the filter portion 106c passes through the filter portion 106c. It communicates with the second upstream common flow path 106b (ink flow path in other spaces). Thereby, since the upstream common flow path 106 is disconnected into the first upstream common flow path 106a and the second upstream common flow path 106b, compared with the flow through the first upstream common flow path 106a or the second upstream common flow path 106b When the volume of the upstream common flow path 106 is reduced by the cross-sectional area parallel to the XZ plane or the length along the Y-axis direction, the volume of the upstream common flow path 106 can be easily reduced.

In addition, the inkjet head 1 is provided with: an upstream individual flow path 104 (first individual flow path) connecting the pressure chamber 103 and an upstream common flow path 106 (first common flow path); and a downstream individual flow path 105 (second individual flow path). path), connecting the pressure chamber 103 and the downstream common flow path 107 (second common flow path), the upstream common flow path 106 is connected to the upstream individual flow path 104 through the connecting part 111 (the first connecting part), and the downstream common flow path 107 is connected to the downstream individual flow path 105 by a connecting portion 112 (second connecting portion). The direction from the liquid contact surface of the upstream damper 121 (first damper) to the connecting portion 111 is opposite to the ink discharge direction. The direction in which the liquid contact surface of the downstream damper 122 faces the connection part 112 is the same as the discharge direction. Thereby, the upstream common flow path 106 where the upstream damper 121 with a shorter vibration period is disposed has a direct reflection structure, and the downstream common flow path 107 where the upstream damper 122 with a longer vibration period is disposed has an indirect reflection structure. Therefore, the phase shift of the two pressure waves P1 and P2 propagating to the pressure chamber 103 increases, and the pressure generated due to the propagation of the two pressure waves P1 and P2 caused by the vibration of the damper itself can be suppressed more reliably. The pressure of chamber 103 changes.

Furthermore, in the inkjet head 1 , the upstream common flow path 106 (first common flow path) is arranged upstream of the pressure chamber 103 , and the downstream common flow path 107 (second common flow path) is arranged downstream of the pressure chamber 103 . Thereby, the pressure wave P1 propagating from the upstream common flow path 106 to the pressure chamber 103 will advance in the same direction as the circulation direction of the ink. In contrast, the pressure wave P2 propagating from the downstream common flow path 107 to the pressure chamber 103 will advance in the same direction as the circulation direction of the ink. Goes against the direction of circulation of ink. Therefore, the phase shift of 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 to be shifted from the center of the pressure chamber 103 so as to be closer to the downstream common flow path 107 (second common flow path) in the ink flow direction. As a result, the residual vibration with a periodic vibration close to the Helmholtz resonance generated after the ink is ejected will propagate to the upstream common flow path 106 made of direct reflection more than the downstream common flow path 107 made of indirect reflection. . Therefore, in the downstream common flow path 107 formed by indirect reflection, although the effect of suppressing residual vibration after ink discharge becomes smaller, the propagated pressure fluctuation component also becomes smaller, so the residual vibration can be sufficiently suppressed.

Furthermore, in the inkjet head 1 , the first path length from the upstream common flow path 106 (first common flow path) to the nozzle 101 is longer than the second path length from the downstream common flow path 107 (second common flow path) to the nozzle 101 . The path length is longer. As a result, the path length from the upstream common flow path 106 to the nozzle 101 also becomes longer, and the flow path resistance increases. Therefore, even if the pressure fluctuation component propagates to the upstream common flow path 106, it becomes larger than that of the downstream common flow path 107. , the influence of pressure crosstalk on the nozzles 101 adjacent in the Y-axis direction can also be suppressed.

Furthermore, in the inkjet head 1 , the flow path plate 20 (first member) forming the upstream damper 121 (first damper) and the diaphragm 30 (second member) forming the downstream damper 122 (second damper) are included. ) are joined by a thermosetting adhesive, and the difference in thermal expansion coefficient between the flow path plate 20 and the diaphragm 30 is 30% or less. Thereby, even when the flow path plate 20 and the vibration plate 30 are joined with a thermosetting adhesive, the damper functions of the upstream damper 121 and the downstream damper 122 become uniform, so that the discharge speed or the Variations in spit volume.

As mentioned above, the invention made by the present inventors has been specifically described based on the embodiments. However, the invention is not limited to the above-described embodiments and can be modified within the scope that does not deviate from the gist of the invention.

For example, the upstream damper configuration may be opposite to the downstream damper configuration. 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 becomes shorter than the vibration period of the downstream damper 122 , however, the thickness of the upstream damper 121 and the downstream damper 122 and the Young's modulus of the forming material may also 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 also be thicker than that of the upstream damper 121 , and the Young's modulus of the material forming the downstream damper 122 may also be greater than the Young's modulus of the material forming the upstream damper 121 . Alternatively, the upstream damper 121 may be formed on the vibrating plate 30 , and the downstream damper 122 may be formed inside the flow path plate 20 .

As shown in the inkjet head 2 shown in FIG. 16 , the upstream damper 121 and the downstream damper 122 can also be formed inside the flow path plate 20 , and the first space portion 123 and the second space portion 124 can also be formed through the nozzle plate 10 It is formed by joining with the flow path plate 20 . In this case, the pressure wave generated by the vibration of the upstream damper 121 and the downstream damper 122 can also be reduced by making the thickness of the upstream damper 121 and the downstream damper 122 and the Young's modulus of the forming material different. The vibration periods of P1 and P2 are different. In addition, even if it is difficult to make the laminates constituting the flow path plate 20 from different materials, it is necessary to form the upstream damper 121 with one laminate and the downstream damper 122 with two laminates. The thickness of each is different but it is easy.

In addition, in the inkjet head 3 shown in FIG. 17 , the upstream damper 121 and the downstream damper 122 can also be formed by the vibration plate 30 , and the first space portion 123 and the second space portion 124 can also be formed by the flow path. The vibration plate 20 is formed by joining the vibration plate 30 . In this case, the vibration periods of the pressure waves P1 and P2 generated by the vibration of the upstream damper 121 and the downstream damper 122 can be made different by making the thicknesses of the upstream damper 121 and the downstream damper 123 different. This is effective when it is difficult to form a damper structure on the flow path plate 20 due to size restrictions or the like. In addition, when the upstream damper 121 is formed of the diaphragm 30, an opening is formed in a region corresponding to the filter portion 106c.

In addition, 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, since the rigidity of the flow path plate 20 forming the upstream common flow path 106 and the downstream common flow path 107 is increased, workability is improved, and the production yield can be improved.

It should be understood that the embodiments disclosed this time are merely examples in all respects and are not restrictive. The scope of the present invention is expressed not by the above description but by the claimed scope, and is intended to include all changes within the meaning and scope that are equal to the claimed scope.

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

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

1,2,3: Inkjet head 10:Nozzle plate 20:Flow plate 21: The first layered body 21A, 21B, 22A, 23B, 23C, 23D, 24E, 25B, 25C, 25D, 25F, 107c: opening 22:Second layered body 22B: Solid area 23: The third layered body 24:The 4th layered body 25: The fifth layered body 30:Vibration plate 31: Pressure part 40: Shell 50: Pressure change part 51:Pedestal 52:Control substrate 101:Nozzle 102: Warehouse Department 103:Pressure chamber 104: Upstream individual flow paths 105: Downstream individual flow paths 106: Upstream common flow path 106a: 1st upstream common flow path 106b: 2nd upstream common flow path 106c: Filter Department 107:Downstream common flow path 107a: 1st downstream common flow path 107b: 2nd downstream common flow path 108: Piezoelectric element 109:Ink supply path 110: Ink discharge path 111:Upstream connection department 112: Downstream connection part 121:Upstream damper 122:Downstream damper 123: 1st Space Division 124:Second Space Division b:width D1, D2: push direction h: Thickness L: length m: load P1, P2: pressure wave t1,t2,t3,t4,t5,t6: time points V1, V2: vibration X,Y,Z: axis Δt: difference

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

2 is a cross-sectional view schematically showing an ink flow path of one nozzle in the inkjet head according to the embodiment.

FIG. 3 is a plan view of the first laminated body forming the flow path plate.

FIG. 4 is a plan view of the second laminated body forming the flow path plate.

FIG. 5 is a plan view of the third laminated body forming the flow path plate.

FIG. 6 is a plan view of the fourth laminated body forming the flow path plate.

FIG. 7 is a plan view of the fifth laminated body forming the flow path plate.

FIG. 8 is an explanatory diagram showing an example of vibration of the upstream damper and the downstream damper.

FIG. 9 is an explanatory diagram showing an example of pressure waves generated by vibrations of the upstream damper and the 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 generated by vibrations of the upstream damper and the downstream damper.

FIG. 13 is an explanatory diagram showing an example of pressure waves generated 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.

16 is a cross-sectional view schematically showing an ink flow path of one nozzle in an inkjet head according to a modified example.

17 is a cross-sectional view schematically showing an ink flow path of one nozzle in an inkjet head according to a modified example.

1: Inkjet head

10:Nozzle plate

20:Flow plate

30:Vibration plate

31: Pressure part

40: Shell

50: Pressure change part

51:Pedestal

52:Control substrate

101:Nozzle

102: Warehouse Department

103:Pressure chamber

104: Upstream individual flow paths

105: Downstream individual flow paths

106: Upstream common flow path

106a: 1st upstream common flow path

106b: 2nd upstream common flow path

106c: Filter Department

107:Downstream common flow path

107a: 1st downstream common flow path

107b: 2nd downstream common flow path

107c:Open your mouth

108: Piezoelectric element

109:Ink supply path

110: Ink discharge path

121:Upstream damper

122:Downstream damper

123: 1st Space Division

124:Second Space Department

X,Y,Z: axis

Claims (11)

An inkjet head having: Multiple nozzles can spit out ink to the outside; A plurality of pressure chambers connected to each of the aforementioned plurality of nozzles; The first common flow path is connected to the plurality of pressure chambers mentioned above; The second common flow path communicates with the plurality of pressure chambers via a path different from that of the first common flow path; The first damper is arranged in the aforementioned first common flow path; and The second damper is arranged in the aforementioned second common flow path, The first damper is thicker than the second damper. An inkjet head having: Multiple nozzles can spit out ink to the outside; A plurality of pressure chambers connected to each of the aforementioned plurality of nozzles; The first common flow path is connected to the plurality of pressure chambers mentioned above; The second common flow path communicates with the plurality of pressure chambers via a path different from that of the first common flow path; The first damper is arranged in the aforementioned first common flow path; and The second damper is arranged in the aforementioned 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. The inkjet head of claim 1 or 2, wherein 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 3, wherein at least part of the wall surface of the first common flow path is formed by a filter portion formed with a plurality of openings, and is communicated with the ink flow paths in other spaces through the filter portion. . The inkjet head of claim 1 or 2, wherein the positional relationship between the first damper and the pressure chamber and the positional relationship between the second damper and the pressure chamber are set so that the first propagation time becomes larger than the second propagation time. Even shorter, the first propagation time is the time for the first pressure wave generated by the vibration of the first damper to reach the pressure chamber, and the aforementioned second propagation time is the second pressure generated by the vibration of the second damper. The time it takes for the wave to reach the aforementioned pressure chamber. The inkjet head of claim 5, wherein the first pressure wave propagates directly to the pressure chamber, The second pressure wave propagates to the pressure chamber through reflection. For example, the inkjet head of claim 6 has: The first individual flow path connects the aforementioned pressure chamber and the aforementioned first common flow path; and The second individual flow path connects the aforementioned pressure chamber and the aforementioned second common flow path, The first common flow path is connected to the first individual flow path through a first connection part, The aforementioned second common flow path is connected to the aforementioned second individual flow path through a second connection portion, The direction from the liquid contact surface of the first damper toward the first connecting portion is opposite to the discharge direction of the ink, The direction from the liquid contact surface of the second damper toward the second connecting portion is the same as the discharge direction. The inkjet head of claim 1 or 2, wherein the first common flow path is arranged upstream of the pressure chamber, The second common flow path is arranged downstream of the pressure chamber. The inkjet head according to claim 1 or 2, wherein the nozzle is disposed away from the center of the pressure chamber in a direction of flow of the ink so as to be close to the second common flow path. The inkjet head according to claim 1 or 2, wherein the first path length from the first common flow path to the nozzle is longer than the second path length from the second common flow path to the nozzle. The inkjet head according to claim 1 or 2, wherein the first member on which the first damper is formed and the second member on which the second damper is formed are joined by a thermosetting adhesive, The difference in thermal expansion coefficient between the first member and the second member is 30% or less.

Images