JP5454016B2 - Inkjet head - Google Patents

Description

  The present invention relates to an ink jet head, and more particularly, to an ink jet head capable of maintaining ink ejection performance and suppressing adverse effects on ejection performance due to bubble intrusion into a pressure chamber.

  As one form of an ink jet printer, an ink jet head in which a large number of nozzles are arranged so as to correspond to the entire width of the recording medium is scanned only once in a direction perpendicular to the width direction of the recording medium (sub-scanning direction). By so doing, a so-called single-pass type capable of printing on the entire recording medium is known. The single-pass method can print at a higher speed than the so-called serial method in which the ink-jet head is reciprocated in the width direction (main scanning direction) of the recording medium, but the relative relationship between the ink-jet head and the recording medium. Since the movement is only once, in order to improve the recording quality, it is necessary to arrange the nozzles arranged in the inkjet head at a high density.

  2. Description of the Related Art As an ink jet head that is suitably used for a single-pass printer, there is known an ink jet head in which a set of nozzles and pressure chambers communicating with the nozzles is two-dimensionally arranged. By arranging a set of nozzles and pressure chambers two-dimensionally, the head can be reduced in size, and as a result, the nozzles can be densified. In such an ink jet head, nozzles, pressure chambers, and other ink supply paths are divided into a plurality of substrates (layers), and the plurality of substrates are sequentially stacked, so that the pressure that leads to the nozzles in the stacked body A chamber and other ink supply paths are formed.

  In order to effectively utilize the merit that the head can be miniaturized, an ink jet head configured by laminating a plurality of substrates in this way has a common flow path for supplying ink to a plurality of pressure chambers in common. Further, it is known that the pressure chambers can be arranged at a high density by being provided in a layer different from the pressure chambers (Patent Documents 1 to 4).

  FIG. 9 shows a schematic configuration of the inkjet head disclosed in Patent Document 1. In the ink jet head 100, a nozzle 101 formed so as to extend in a vertical direction for discharging droplets and a pressure chamber 102 disposed on the nozzle 101 and having a substantially square shape in plan view are formed. . A vibration plate 103 is provided on the wall surface of the pressure chamber 102 opposite to the nozzle 101, and a pressure generating means 104 including a piezoelectric element such as a piezoelectric element is provided outside the vibration plate 103. A set of the nozzle 101 and the pressure chamber 102 having the pressure generating means 104 is two-dimensionally arranged on the inkjet head 100 in plan view.

  The common flow path 105 is disposed below the pressure chamber 102 so as to partially overlap the pressure chamber 102 in plan view. The common flow path 105 is formed for each of the plurality of pressure chambers 102 so as to supply ink in common to the plurality of pressure chambers 102, and the ink supply path 106 that extends vertically between the pressure chambers 102. Communicated by

  Note that “upper and lower” refers to a positional relationship in an ink jet head with the nozzle surface facing downward. The term “vertical” and “horizontal” refers to the vertical direction in the inkjet head with the nozzle surface facing downward, and “horizontal” refers to the horizontal direction.

  On the other hand, from the viewpoint of increasing the accuracy, speeding up, and stabilizing the discharge performance in recent years, the ink supply path may be reduced in cross-sectional area or provided with a throttle portion. For example, in Patent Document 2, as shown in FIG. 10, an ink supply path 204 between the pressure chamber 202 and the common flow path 203 extends in the lateral direction, and an internal flow path is provided in the ink supply path 204. It is described that an aperture 205 to be squeezed is formed and the flow of ink is restricted by this aperture 205 to provide an appropriate flow path resistance and to stabilize ink ejection. In the figure, 201 is a nozzle.

  Further, in Patent Document 3, as shown in FIG. 11, the ink supply path 304 between the pressure chamber 302 and the common flow path 303 is a vertical flow path, and the common flow path 303 in the ink supply path 304 is formed. It describes that it forms so that the flow path of the side may be restrict | squeezed. In the figure, reference numeral 301 denotes a nozzle.

  Further, in Patent Document 4, as shown in FIG. 12, an auxiliary guide hole 404 is formed in the upper part of the common flow path 403, and a passage 405 that extends laterally from the upper side of the auxiliary guide hole 404. It is described that the ink supply path is constituted by the auxiliary guide hole 404 and the passage 405 by communicating with the pressure chamber 402 by the above. The channel of the passage 405 is narrower than the auxiliary guide hole 404. In the figure, 401 is a nozzle.

  Each of these inkjet heads has a structure in which the ink in the common flow path flows through the ink supply path into a pressure chamber disposed above the common flow path.

JP 2001-334661 A JP 2003-31957 A JP-A-6-234218 Japanese National Patent Publication No. 10-508808

  One problem with inkjet heads is the problem of bubble inflow into the pressure chamber. When bubbles (air) mixed in the ink are supplied to the pressure chamber from the common flow path together with the ink and adhere to the diaphragm facing the pressure chamber, the bubbles should be added to the ink by the vibration of the diaphragm due to the compression action of the bubbles. The pressure is buffered and the generation of pressure necessary to normally discharge the droplets is hindered, the droplets are not discharged normally, causing variations in the discharge, or in some cases non-discharge There is a risk that. For this reason, the ink is sufficiently degassed, and air bubbles are carefully avoided during the supply process to the ink jet head, but the air bubbles in the ink supplied to the ink jet head are completely mixed. It is difficult to prevent.

  Therefore, in order to avoid ejection instability due to bubbles mixed in the ink, it is desirable that the inkjet head itself be provided with means for separating the bubbles from the ink and preventing them from flowing into the pressure chamber.

  However, the inkjet head 100 of Patent Document 1 shown in FIG. 9 does not have means for separating bubbles in the ink in the process from the common flow path 105 to the pressure chamber 102. In the inkjet head 100, the ink supply path 106 is opened at a position facing the vibration plate 103 in the pressure chamber 102, and the vibration plate 103 is disposed directly above the ink flowing from the ink supply path 106. Therefore, when the ink in the common flow path 105 flows into the pressure chamber 102 through the ink supply path 106, the air bubbles mixed in the ink together with the ink flow into the pressure chamber 102 without being separated. Resulting in. Bubbles that flow into the pressure chamber 102 rise by buoyancy and adhere to the vibration plate 103, causing unstable discharge.

  In the ink jet head shown in FIG. 10, the ink in the common flow path 203 rises from the common flow path 203 and flows into the ink supply path 204, and flows laterally in the ink supply path 204. The flow path is narrowed by the aperture 205 in the process of flowing in the lateral direction, but the ink supply path 204 is a means for separating bubbles in the ink and preventing them from flowing into the pressure chamber. Therefore, the bubbles flowing into the ink supply path 204 are supplied to the pressure chamber 202 together with the ink without being separated. In addition, the ink that has flowed laterally through the ink supply path 204 and reached the lower portion of the pressure chamber 202 is configured to flow upward and flow into the pressure chamber 202, so that the bubbles enter the pressure chamber 202 by buoyancy. The structure is easy to enter, and it is difficult to avoid the inflow of bubbles into the pressure chamber 202.

  Furthermore, in the ink jet head of Patent Document 3 shown in FIG. 11, the ink supply path 304 is configured to restrict the flow path, but the structure is merely to communicate the pressure chamber 302 and the common flow path 303 in the vertical direction. For this reason, the bubbles that have flowed into the ink supply path 304 together with the ink flow into the pressure chamber 302 as they are, and it is difficult to avoid the flow of bubbles into the pressure chamber 302.

  In the ink jet head of Patent Document 4 shown in FIG. 12, the passage 402 that connects the pressure chamber 402 and the auxiliary introduction hole 404 in the lateral direction has a structure that narrows the flow path more than the auxiliary guide hole 404. However, the ink flowing into the auxiliary guide hole 404 from the common flow path 403 has a slightly higher flow rate due to the auxiliary guide hole 404 smaller than the common flow path 403, and then the upper end side of the auxiliary guide hole 404. By flowing into the further smaller passage 405 that opens in the section, the flow velocity is further increased and the pressure chamber 402 is supplied to the pressure chamber 402. Therefore, the pressure chamber is passed through the auxiliary guide hole 404 and the passage 405 from the common flow path 403. In the process up to 402, there is no means (location and timing) that allows the bubbles to be separated from the ink, and the bubbles are not separated but are mixed in the pressure chamber without being separated. It will be carried up to 02. Accordingly, in this case as well, it is difficult to avoid the inflow of bubbles into the pressure chamber 402.

  In addition, in the case where an ink jet head is provided with some constituent parts for separating bubbles in the ink and preventing the ink from flowing into the pressure chamber, the constituent parts of the ink jet head are increased, and the ink jet head is configured. This leads to an increase in the number of stacked substrates. The increase in the number of stacked layers of substrates not only increases the cost of the substrate material, processing man-hours and assembly man-hours, but also increases the length to the nozzle outlet by increasing the thickness of the inkjet head. There is also a problem that energy loss for discharge increases and discharge efficiency deteriorates.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet head capable of maintaining desired discharge performance and suppressing adverse effects on discharge performance due to bubble penetration into a pressure chamber.

  Another object of the present invention is to provide an inkjet head capable of maintaining desired ejection performance and suppressing adverse effects on ejection performance due to bubble penetration into a pressure chamber without increasing the number of stacked substrates. That is.

  Still another subject of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

The invention described in claim 1 includes a plurality of pressure chambers provided with pressure generating means on one side via a diaphragm, a nozzle flow path provided corresponding to the pressure chamber, and discharging ink in the pressure chamber. A common flow path for supplying ink in common to the plurality of pressure chambers, and an ink supply path for communicating the common flow path and the pressure chamber, wherein the pressure chamber is higher than the common flow path. In an inkjet head arranged in
The ink supply path has at least a first flow path part, a second flow path part, and a third flow path part in order from the side close to the common flow path along the ink supply direction,
The first flow path portion is a vertical flow path for allowing ink supplied from the common flow path to flow upward into the second flow path portion,
The third flow path section is a horizontal flow path that causes the ink in the second flow path section to flow out sideways from the second flow path section,
When the cross-sectional area of the first flow path part is A1 and the cross-sectional area of the second flow path part is A2a, A2a> A1, and the vertical cross-sectional area of the second flow path part is A2b, when the longitudinal area of the third flow path part and A3, A2b> Ri A3 der,
The second flow channel portion has a cylindrical shape with a circular cross section, and the third flow channel portion opens in a slit shape on a side surface of the second flow channel portion,
The position of the upper inner wall surface of the second channel portion is between the upper inner wall surface of the second channel portion and the upper inner wall surface of the third channel portion. The ink jet head is characterized in that a level difference higher than the position of the upper inner wall surface is formed .

According to a second aspect of the present invention, the upper inner wall surface of the third flow path portion is formed such that the height gradually decreases along the ink supply direction from the second flow path portion side. The inkjet head according to claim 1.

According to a third aspect of the present invention, there are provided a plurality of pressure chambers provided with pressure generating means on one side via a diaphragm, a nozzle channel provided corresponding to the pressure chamber, and discharging ink in the pressure chamber. A common flow path for supplying ink in common to the plurality of pressure chambers, and an ink supply path for communicating the common flow path and the pressure chamber, wherein the pressure chamber is higher than the common flow path. In an inkjet head arranged in
The ink supply path has at least a first flow path part, a second flow path part, and a third flow path part in order from the side close to the common flow path along the ink supply direction,
The first flow path portion is a vertical flow path for allowing ink supplied from the common flow path to flow upward into the second flow path portion,
The third flow path section is a horizontal flow path that causes the ink in the second flow path section to flow out sideways from the second flow path section,
When the cross-sectional area of the first flow path part is A1 and the cross-sectional area of the second flow path part is A2a, A2a> A1, and the vertical cross-sectional area of the second flow path part is A2b, When the vertical cross-sectional area of the third flow path portion is A3, A2b> A3,
The second flow channel portion has a cylindrical shape with a circular cross section, and the third flow channel portion opens in a slit shape on a side surface of the second flow channel portion,
The upper inner wall surface of the third flow path portion is formed so as to gradually decrease in height along the ink supply direction from the second flow path portion side. .

According to a fourth aspect of the present invention, the pressure chamber, the nozzle channel, the common channel, and the ink supply channel are formed with a first through hole for the nozzle channel and a recess for the common channel, respectively. A first through hole formed in the first substrate, a second through hole for the nozzle flow path communicating with the first through hole for the nozzle flow path, and a concave portion for the common flow path. A second substrate formed with a through hole for the first flow path portion communicating therewith, a recess for the pressure chamber, and a through hole for the first flow path portion formed in the second substrate A recess for the second channel portion communicating with the hole and a recess for the third channel portion communicating with the recess for the second channel portion and the recess for the pressure chamber are respectively formed. 4. The third substrate is formed by sequentially laminating at least three substrates. An ink jet head according to any one.

The invention according to claim 5 is the ink jet head according to any one of claims 1 to 4 , wherein the upper inner wall surface of the second flow path portion is roughened.

According to a sixth aspect of the present invention, the pressure chamber is disposed higher than the common flow path, and the pressure chamber and the common flow path are disposed so as to partially overlap each other in plan view. The inkjet head according to any one of claims 1 to 5 , wherein the inkjet head is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the inkjet head which can aim at the maintenance of desired discharge performance and the suppression of the bad influence on discharge performance by bubble permeation into a pressure chamber can be provided.

  In addition, according to the present invention, it is possible to provide an inkjet head capable of maintaining desired ejection performance and suppressing adverse effects on ejection performance due to bubble penetration into a pressure chamber without increasing the number of stacked substrates. it can.

1 is a longitudinal sectional view showing an example of an inkjet head according to the present invention. Sectional view along line (ii)-(ii) in FIG. 1 is an exploded perspective view of an inkjet head according to the present invention. The perspective view which shows only the part of an ink supply path The fragmentary sectional view which shows the other aspect of the connection part of a 2nd flow path part and a 3rd flow path The fragmentary sectional view which shows the other aspect of the connection part of a 2nd flow path part and a 3rd flow path The top view which shows the arrangement | sequence aspect of the separate flow path in the inkjet head which concerns on this invention Plan view showing other arrangement modes of individual flow paths Sectional drawing which shows schematic structure of the conventional inkjet head Sectional drawing which shows schematic structure of the conventional inkjet head Sectional drawing which shows schematic structure of the conventional inkjet head Sectional drawing which shows schematic structure of the conventional inkjet head

  An inkjet head according to the present invention includes a plurality of pressure chambers provided with pressure generating means on one side via a diaphragm, a nozzle flow path provided corresponding to the pressure chambers and discharging ink in the pressure chambers. A common flow path for supplying ink to a plurality of pressure chambers in common, and an ink supply path for communicating the common flow path with each pressure chamber, and the pressure chamber is disposed above the common flow path. The

  The diaphragm constitutes the upper wall surface of the pressure chamber, and pressure generating means made of a piezoelectric element such as a piezoelectric element is attached to the outer surface side of the diaphragm. By applying a predetermined voltage to this pressure generating means, the diaphragm is vibrated by the electromechanical conversion action of the piezoelectric element, the pressure required for ejection is applied to the ink in the pressure chamber, and the ink is discharged from the tip of the nozzle channel. It is ejected as fine droplets.

  In the present invention, the ink supply path includes the first flow path section, the second flow path section, and the first flow path section in order from the side closer to the common flow path along the ink supply direction from the common flow path to each pressure chamber. 3 flow paths. The first channel portion, the second channel portion, and the third channel portion constitute a continuous channel in the ink supply path.

  The first flow path unit, the second flow path unit, and the third flow path unit may be present in the ink supply path from the common flow path to the pressure chamber. Is directly connected to the common flow path and the third flow path portion is directly connected to the pressure chamber, the ink supply path is simplified and the ink jet head structure is simplified.

  The first flow path portion is a vertical flow path that allows ink supplied from the common flow path to flow upward into the second flow path portion, and the third flow path portion is ink in the second flow path portion. Is a lateral flow channel that causes the second flow channel portion to flow out laterally. In other words, the ink flowing in the ink supply path flows upward in the first flow path portion and flows into the second flow path portion, and then this time, the second flow path portion enters the third flow path portion. It flows sideways.

  Here, the vertical and horizontal arrangement relations are defined. The arrangement relationship of the inkjet head configuration in the present invention is based on the attitude of the inkjet head with the nozzle surface facing downward. Accordingly, the term “upper and lower” in the present invention refers to the positional relationship in the ink jet head with the nozzle surface facing downward. Also, the term “vertical” and “horizontal” refers to the vertical direction as the vertical direction and the horizontal direction as the horizontal direction in the inkjet head with the nozzle surface facing downward.

  In the present invention, means for preventing the bubbles in the ink from being separated and supplied to the pressure chamber are constituted by the first flow path portion, the second flow path portion, and the third flow path portion. The For this reason, the first flow path part, the second flow path part, and the third flow path part have a cross-sectional area of the first flow path part A1 and a cross-sectional area of the second flow path part A2a. When A2a> A1, and when the vertical cross-sectional area of the second flow path portion is A2b and the vertical cross-sectional area of the third flow path portion is A3, A2b> A3 is satisfied. That is, according to the present invention, when the cross section of the ink supply path (the cross section orthogonal to the ink supply direction) reaches the second flow path section from the first flow path section, the second flow path is once expanded. When it reaches the third flow path part from the part, it shrinks again.

  Each of these cross-sectional areas is the maximum value in each flow path portion.

  With this configuration, the ink flowing from the first flow path portion to the second flow path portion flows into the large flow path from the narrow flow path, and the flow velocity is reduced at a stroke. Stagnant. Therefore, the bubbles mixed in the ink flowing into the second flow path portion are easily separated from the ink. In addition, the ink flows upward into the second flow path portion, and then the path is bent laterally and flows out toward the third flow path portion, so that the inside of the second flow path portion is caused by its buoyancy. It quickly rises and is efficiently separated from the ink, and adheres to the upper inner wall surface in the second flow path portion. In some cases, the bubbles accumulated on the upper inner wall surface gather to form larger bubbles.

  In the present invention, the ink is intended for an ink having a viscosity of 10 mPa · s or less at the temperature when the ink jet head is used.

  In order to make the separation of the bubbles more effective, the cross-sectional area A2a of the second flow path part is preferably 1.2 to 8 times the cross-sectional area A1 of the first flow path part.

  Further, from the same viewpoint, the second flow path section has a length (height) in the vertical direction in order to increase the residence time of the ink inside and to more effectively perform the separation of bubbles in the ink. ) Is preferably at least twice the maximum horizontal diameter of the second flow path portion.

  The ink in the second flow path portion further flows out to the third flow path portion, but since the third flow path portion has a small vertical cross-sectional area, the ink in the third flow path portion is reduced. The flow rate rises again. At this time, the bubbles adhering to the upper inner wall surface of the second flow path section are less likely to enter the third flow path section where the opening is throttled and the flow velocity becomes larger than the ink itself. It stays on the inner wall surface of the upper part in the passage part, and it is difficult for it to flow out to the third flow path part, and the entry of bubbles into the pressure chamber is suppressed.

  That is, the present invention includes a configuration that makes it easy to separate bubbles from the ink in the second flow path portion and a configuration that makes it difficult for the bubbles to flow out to the third flow path portion side. It effectively prevents the intrusion of bubbles. In addition, since the ink supply path is narrowed in the third flow path portion, the desired ejection performance can be maintained by this portion.

  In general, when a discharge failure occurs due to the accumulation of bubbles in the ink jet head or the like, as a maintenance operation, suction is performed from the nozzle surface of the ink jet head, and the internal bubbles are discharged from the nozzle. Even in the present invention, the air bubbles accumulated in the second flow path portion are discharged from the nozzle by the suction operation at the time of maintenance, but the flow of air bubbles into the pressure chamber during the normal operation is greatly suppressed, Discharge failure is less likely to occur. Therefore, the maintenance frequency can be reduced as compared with the conventional case.

  The shape of the second channel portion is a cylindrical shape having a circular cross section, and the third channel portion is preferably opened in a slit shape on the side surface of the second channel portion. When the ink in the second flow path portion flows out toward the third flow path portion, the effect of making it difficult for air bubbles on the upper inner wall surface of the second flow path portion to be brought in can be exhibited significantly. In particular, since the opening of the third flow path portion is slit-shaped, it is possible to make it difficult for air bubbles gathered on the upper inner wall surface of the second flow path portion to enter the third flow path portion.

  In order to make it difficult for bubbles to enter the third flow path portion, more preferably, the lateral width of the opening portion of the third flow path portion that opens in a slit shape on the side surface of the second flow path portion is 20 to 40 μm. It is to be.

  In the present invention, in order to keep the bubbles separated from the ink more effectively in the second flow path portion, it is preferable that the upper inner wall surface of the second flow path portion is roughened. . By roughing the upper inner wall surface, it is possible to more effectively exert the effect of keeping bubbles attached and to further improve the effect of preventing outflow to the third flow path portion side. . The rough surface treatment is performed at a portion corresponding to the upper inner wall surface of the second flow path portion of the pressure chamber plate by a conventionally known appropriate method, for example, exposure or electron beam direct drawing, with a period of 100 to 400 nm and a height of 100 to 400 nm. It can be performed by patterning a fine uneven shape of 1000 nm, exposing and developing.

  Such rough surface treatment may also be performed on the upper inner wall surface of the third flow path portion.

  In the present invention, the pressure chamber, the nozzle, the common flow path, and the ink supply path are each processed in the form of a through hole or a recess (concave groove) on a plurality of substrates, and the pressure is obtained by stacking the plurality of substrates. It is preferable to form the chamber, the nozzle flow path, the common flow path, and the ink supply path. By simply forming a through-hole or a recess (concave groove) in each substrate, a space or a channel that becomes a pressure chamber, a nozzle channel, a common channel, and an ink supply channel can be easily formed in the laminated substrate.

  As the substrate, a silicon substrate or a glass substrate is preferably used. Processing on the silicon substrate can be performed by, for example, dry etching processing, and the precision manufacturing technology of the semiconductor integrated circuit can be used. Moreover, the process with respect to a glass substrate can be performed by the conventional sandblasting method etc. All of these can be processed with extremely high accuracy, and the bonding between the silicon substrate and the glass substrate can be integrally performed by anodic bonding, so that it is not necessary to use an adhesive.

  In such an ink jet head, the pressure chamber and the common flow path are separately arranged on different substrates (layers) so that the pressure chamber is higher than the common flow path among the plurality of stacked substrates. Is done. When the pressure chamber and the common flow path are separately arranged on different substrates, the positional relationship between the pressure chamber and the common flow path is such that both of them overlap with each other in plan view. The spread of the ink jet head in the horizontal direction between the pressure chamber and the common flow path is suppressed, and the pressure chambers can be arranged with high density. As a result, it is possible to increase the density of the nozzles. Further, a large volume of the common flow path can be secured, and the ink supply amount can be increased accordingly.

  The plurality of substrates include a first substrate in which a nozzle channel through hole and a common channel recess are respectively formed, a through hole communicating with the nozzle channel through hole, and the common channel A second substrate in which a through hole for the first flow path portion communicating with the concave portion is formed, a concave portion for the pressure chamber, and a concave portion for the second flow path portion communicating with the concave portion for the pressure chamber And a third substrate having at least three recesses for the third channel portion communicating with the recesses for the second channel portion, respectively, and sequentially stacking them. Thus, the pressure chamber, the nozzle channel, the common channel, and the ink supply channel can be formed in the laminated substrate.

  According to this, the structure of the ink jet head is a minimum of three substrates, and without increasing the number of stacked substrates, the desired discharge performance can be maintained and the adverse effect on the discharge performance due to bubble intrusion into the pressure chamber can be suppressed. Can be achieved.

  Next, specific embodiments of the inkjet head according to the present invention will be described with reference to the drawings. In addition, the dimension described below is an example and this invention is not limited to the following dimension.

  1 is a longitudinal sectional view showing an example of an inkjet head according to the present invention, FIG. 2 is a sectional view taken along line (ii)-(ii) in FIG. 1, and FIG. 3 is a schematic diagram of the inkjet head according to the present invention. It is a disassembled perspective view of a part.

  The inkjet head 1 is a laminate in which three substrates, a nozzle plate 2 as a first substrate, an intermediate plate 3 as a second substrate, and a pressure chamber plate 4 as a third substrate are laminated in order from the bottom. It is made up of.

  The nozzle plate 2 is a silicon substrate having a thickness of 300 μm, and the first through hole 21 for the nozzle flow path is formed through the dry etching process, and the recess 22 for the common flow path is the upper surface in the drawing. Is recessed in a groove shape.

  In the present embodiment, the first through hole 21 for the nozzle channel is formed in a cylindrical shape whose diameter decreases in three stages along the ink discharge direction from the top to the bottom in the drawing. A large-diameter portion 21a having a height of 100 μm (length along the ink ejection direction; the same applies hereinafter), a medium-diameter portion 21b having a diameter of 60 μm and a height of 80 μm, and a small-diameter portion 21c having a diameter of 20 μm and a height of 20 μm It is made up of. The recess 22 for the common flow path has a height of 280 μm and a width W of 650 μm.

  The intermediate plate 3 is a glass substrate having a thickness of 200 μm, and the second through hole 31 for the nozzle flow path communicating with the first through hole 21 for the nozzle flow path formed in the nozzle plate 2 by the sandblast method. And a through hole for the first flow path portion constituting a part of the ink supply path at a position corresponding to the upper part of the recess 22 for the common flow path formed in the nozzle plate 2. 32 is formed through.

  Here, each of the second through hole 31 for the nozzle flow path and the through hole 32 for the first flow path portion has a cylindrical shape with a diameter of 100 μm.

  The pressure chamber plate 4 is a silicon substrate having a thickness of 300 μm, and a recess 41 for the pressure chamber is formed from the lower surface in the drawing by dry etching so as to communicate with the recess 41 for the pressure chamber. In addition, a recess 42 for the second flow path portion and a recess 43 for the third flow path portion constituting the remaining part of the ink supply path are similarly provided from the lower surface in the drawing. Although only one pressure chamber recess 41 is shown here, a plurality of pressure chamber recesses 41 are provided for one pressure chamber plate 4.

  As shown in FIG. 2, the pressure chamber recess 41 has a substantially square shape with one side having a radius of curvature of 150 μm at the corner and a side of 450 μm in plan view. The height is 280 μm, and the remaining 20 μm becomes the upper wall portion, and the upper wall portion constitutes the diaphragm 41a. A piezoelectric element 5 having a size of 400 μm × 400 μm × thickness 50 μm is fixed to the outer side surface (the upper surface side in FIGS. 1 and 3) of the vibration plate 41a.

  The second through hole 31 for the nozzle flow path formed in the intermediate plate 3 is located 70 μm inside from both side walls of one corner of the recess 41 for the pressure chamber, and the inside of the recess 41 for the pressure chamber It is arranged to communicate with.

  The concave portion 42 for the second flow path portion is formed in a cylindrical shape having a diameter of 120 μm and a height of 280 μm, and corresponds to the first through hole 32 for the flow path portion formed in the intermediate plate 3. And it is arrange | positioned just above it and is connected with the through-hole 32 for this 1st flow path part in a lower end.

  The concave portion 43 for the third flow passage portion is formed in a groove shape that allows communication between the concave portion 42 for the second flow passage portion and the concave portion 41 for the pressure chamber, and has a height of 280 μm and a length (recess portion). (Length from 42 to the recess 41) is 300 μm, and is recessed in an elongated shape having a width of 30 μm orthogonal to the length direction. For this reason, the communicating part between the one end of the recess 43 for the third flow path and the recess 42 for the second flow path is a narrow slit.

  As shown in FIG. 2, the communication portion between the other end of the third flow path recess 43 and the pressure chamber recess 41 is formed in a substantially square pressure chamber recess 41 in a plan view. The corner portion 41b is located diagonally to the communication site with the second through hole 31 for the flow path. The concave portion 43 for the third flow path portion extends in a direction along the diagonal line from the corner portion 41b to the concave portion 41 for the pressure chamber, and communicates with the concave portion 42 for the second flow path portion.

  After the relative positions of the three substrates 2, 3, 4 are aligned with each other, the formation surface side of the recess 22 for the common flow path of the nozzle plate 2 faces the intermediate plate 3, and the pressure chamber plate 4 are formed so that the formation surface side of each of the concave portions 41, 42, 43 faces the intermediate plate 3, and then anodic bonded. In anodic bonding, silicon and glass at each bonding surface are heated at 200 to 500 ° C. to soften the glass side, and at the same time, a high voltage is applied by using the silicon side as an anode and the glass side as a cathode. And the bonding interface is tightly bonded by electrostatic attraction. According to anodic bonding, since no adhesive is used, highly reliable bonding can be performed on the bonding surface, which is a contact surface with ink, without the possibility of dissolution of the bonded portion by the solvent in the ink.

  The first through hole 21 for nozzle flow path formed in the nozzle plate 2 and the second through hole for nozzle flow path formed in the intermediate plate 3 by bonding the substrates 2, 3, 4. No. 31 communicates with the nozzle passage, and the lower surface side of the pressure chamber recess 41 formed in the pressure chamber plate 4 is closed by the intermediate plate 3 to form a pressure chamber. The nozzle channel and the pressure chamber communicate with each other when the second through hole 31 for the nozzle channel and the recess 41 for the pressure chamber communicate with each other.

  Further, the upper surface side of the common channel recess 22 formed in the nozzle plate 2 is closed by the intermediate plate 3 to become a common channel, and the first channel through-hole 32 and the second channel channel The recess 42 and the third channel recess 43 are a first channel unit, a second channel unit, and a third channel unit, respectively. Further, the first flow path part 32, the second flow path part 42, and the third flow path part 43 serve as an ink supply path that communicates between the common flow path 22 and the pressure chamber 41.

  In the present embodiment, since the pressure chamber 41 and the common flow path 22 are disposed so as to partially overlap each other in a plan view, the ink supply path (the first flow path portion 32 and the second flow path portion). 42 and the third flow path portion 43), a pressure chamber 41, and a nozzle flow path (first and second through holes 21 and 31 for the nozzle flow path) (hereinafter referred to as individual flow paths 10). ) Can be brought closer to the common flow path 22 side in a plan view, the overall width of the individual flow path 10 and the common flow path 22 can be suppressed, and the individual flow paths 10 can be arranged with high density.

  The configuration of the ink supply path will be further described with reference to FIG. FIG. 4 is a perspective view showing only the ink supply path.

  In the ink supply path, the first flow path portion 32 becomes a vertical flow path in which ink flows upward from the common flow path 22, and is connected to the second flow path portion 42 at the upper end of the first flow path portion 32. Ink flows upward into the second flow path portion 42. The ink that has flowed into the second flow path portion 42 is then bent in the horizontal direction and flows out to the third flow path portion 43 that opens in a slit shape on the side surface of the second flow path portion 42. The third flow path portion 43 becomes a horizontal flow path from which the ink flows laterally from the second flow path portion 42, and the ink flows into the pressure chamber 41 through the third flow path portion 43. Therefore, the first flow path portion 32 connected to the common flow path 22 and the pressure chamber 41 do not overlap in a plan view, and the bubbles in the ink in the common flow path 22 rise upward as they are. Therefore, it does not flow directly into the pressure chamber 41.

  Since the first flow path portion 32 is a flow path having a diameter of 100 μm and the second flow path portion 42 has a cylindrical shape having a diameter of 120 μm, the second flow path is larger than the cross-sectional area A1 of the first flow path portion 32. The cross-sectional area A2a of the road part 42 is larger. For this reason, compared with the flow velocity of the ink flowing through the first flow passage portion 32, the flow velocity of the ink flowing into the second flow passage portion 42 decreases at a stretch and stays in the second flow passage portion 42. During this time, separation of bubbles in the ink is promoted, and the separated bubbles rise by buoyancy and adhere to the upper inner wall surface 42a.

Next, since the third flow path portion 43 has a height of 280 μm and a width of 30 μm, its vertical cross-sectional area (8400 μm ² ) is the maximum vertical cross-sectional area of the second flow path portion 42 (diameter 120 μm × height 280 μm). = 33600 μm ² ). As a result, the flow rate of the ink in the third flow path portion 43 increases again. At this time, only the ink flows out from the second flow path section 42 to the third flow path section 43, and the bubbles separated from the ink and attached to the upper inner wall surface 42a are transferred to the third flow path with a high flow velocity. It is difficult to flow into the opening 42 b at the connection portion with the passage 43, and the supply of bubbles to the pressure chamber 41 is suppressed.

  Further, in order to further enhance the effect of preventing the outflow of bubbles from the second flow path part 42 to the third flow path part 43 side, as shown in FIG. 5, the upper inner wall surface of the second flow path part 42 The position of the upper inner wall surface 42a of the second flow path part 42 is located between the position of the upper inner wall surface 43a of the third flow path part 43 and the position between the upper inner wall surface 43a of the third flow path part 43. It is also preferable to form the upper step 42c. By this step 42c, a chamber in which bubbles are accumulated can be formed in the upper part of the second flow path part 42, and the bubbles adhering to the upper inner wall surface 42a are less likely to flow out to the third flow path part 43 side. can do.

  The height of the step 42c is preferably 5 to 15 μm. Such a step 42 c is formed by forming the recessed depth of the second flow path portion 42 deeper than the recessed depth of the third flow path portion 43 by the height, or It can be formed by making the recessed depth of the flow path portion 43 shallower than the recessed depth of the second flow path portion 42 by the height.

  The step 42 c may be partially formed only in the vicinity of a portion where the third flow path portion 43 communicates with the second flow path portion 42.

  Further, for the same purpose, as shown in FIG. 6, the height of the upper inner wall surface 43a of the third flow path portion 43 gradually decreases from the second flow path portion 42 side along the ink supply direction. It is also preferable to form the above. In FIG. 6A, the upper inner wall surface 43a is an inclined surface whose height continuously decreases. The inclined surface may be formed over the entire length of the third flow path portion 43, or may be formed only on a part of the second flow path portion 42 side. Moreover, in FIG.6 (b), the upper inner wall surface 43a is formed in the staircase shape in which height becomes low in steps. This stepped portion may also be formed over the entire length of the third flow path portion 43, or may be formed only on a part on the second flow path portion 42 side.

  FIG. 7 is a plan view showing an arrangement mode of the individual flow paths 10 in the inkjet head 1.

  Here, four common channels (common channel tributaries) 22 are arranged in parallel, and both ends of each common channel 22 are connected to one common channel main stream 23, respectively. This common flow path main flow 23 is also recessed on the same surface as the common flow path 22 of the nozzle plate 2. At both ends of each common flow path main stream 23, connection ports 24 that connect the ink jet head 1 to an ink tank or an ink cartridge (not shown) face each other.

  Each individual flow path 10 is arranged at a predetermined interval P along the length direction of the common flow path 22 so that a part of the pressure chamber 41 overlaps the common flow path 22 and is arranged in a row. Constitutes a column. Here, four nozzle rows are shown by the four common flow paths 22, but if the interval P is 677 μm (corresponding to 37.5 dpi), when 16 nozzle rows are provided, 37.5 dpi × 16 = The head has a recording resolution of 600 dpi.

  In addition, as shown in FIG. 8, a plurality of individual flow paths 10 can be arranged in two rows so that a part of the pressure chamber 41 overlaps the same common flow path 22. High density can be achieved.

1: Inkjet head 2: Nozzle plate 21: Through hole for nozzle flow path 22: Recess (common flow path)
23: Common flow path main flow 24: Connection port 3: Intermediate plate 31: Nozzle flow path through hole 32: Through hole (first flow path portion)
4: Pressure chamber plate 41: Recess (pressure chamber)
41a: Diaphragm 41b: Corner part 42: Concave part (second flow path part)
42a: Upper inner wall surface 42b: Opening 42c: Step 43: Recess (third flow path)
43a: Upper inner wall surface 5: Piezoelectric element 10: Individual flow path

Claims (6)

Common to a plurality of pressure chambers provided with pressure generating means on one side, a nozzle channel provided corresponding to the pressure chamber and discharging ink in the pressure chamber, and the pressure chambers In an inkjet head, comprising: a common flow path for supplying ink to the ink supply path; and an ink supply path for communicating the common flow path and the pressure chamber, wherein the pressure chamber is disposed above the common flow path ,
The ink supply path has at least a first flow path part, a second flow path part, and a third flow path part in order from the side close to the common flow path along the ink supply direction,
The first flow path portion is a vertical flow path for allowing ink supplied from the common flow path to flow upward into the second flow path portion,
The third flow path section is a horizontal flow path that causes the ink in the second flow path section to flow out sideways from the second flow path section,
When the cross-sectional area of the first flow path part is A1 and the cross-sectional area of the second flow path part is A2a, A2a> A1, and the vertical cross-sectional area of the second flow path part is A2b, when the longitudinal area of the third flow path part and A3, A2b> Ri A3 der,
The second flow channel portion has a cylindrical shape with a circular cross section, and the third flow channel portion opens in a slit shape on a side surface of the second flow channel portion,
The position of the upper inner wall surface of the second channel portion is between the upper inner wall surface of the second channel portion and the upper inner wall surface of the third channel portion. An ink jet head, characterized in that a step which is higher than the position of the upper inner wall surface is formed . Upper inner wall surface of the third channel section, according to claim 1, wherein the progressively height along the feed direction of the ink from the second flow path portion side is formed to be lower Inkjet head. Common to a plurality of pressure chambers provided with pressure generating means on one side, a nozzle channel provided corresponding to the pressure chamber and discharging ink in the pressure chamber, and the pressure chambers In an inkjet head, comprising: a common flow path for supplying ink to the ink supply path; and an ink supply path for communicating the common flow path and the pressure chamber, wherein the pressure chamber is disposed above the common flow path ,
The ink supply path has at least a first flow path part, a second flow path part, and a third flow path part in order from the side close to the common flow path along the ink supply direction,
The first flow path portion is a vertical flow path for allowing ink supplied from the common flow path to flow upward into the second flow path portion,
The third flow path section is a horizontal flow path that causes the ink in the second flow path section to flow out sideways from the second flow path section,
When the cross-sectional area of the first flow path part is A1 and the cross-sectional area of the second flow path part is A2a, A2a> A1, and the vertical cross-sectional area of the second flow path part is A2b, When the vertical cross-sectional area of the third flow path portion is A3, A2b> A3,
The second flow channel portion has a cylindrical shape with a circular cross section, and the third flow channel portion opens in a slit shape on a side surface of the second flow channel portion,
The upper inner wall surface of the third flow path portion is formed so as to gradually decrease in height along the ink supply direction from the second flow path portion side. The pressure chamber, the nozzle flow path, the common flow path, and the ink supply path include a first substrate having a first through hole for the nozzle flow path and a recess for the common flow path, respectively. The first flow path communicating with the second through hole for the nozzle flow path communicating with the first through hole for the nozzle flow path formed in the first substrate and the recess for the common flow path. A second substrate formed with a through hole for a portion, a recess for the pressure chamber, and the second passage communicating with the through hole for the first flow passage formed in the second substrate. At least 3 of the 3rd substrate in which the crevice for channel parts and the crevice for the 3rd channel parts which connect the crevice for the 2nd channel part and the crevice for the pressure chamber are formed, respectively. in according to any one of claims 1-3, characterized in that the substrates are formed by sequentially stacking Kudgett head. The upper inner wall surface of the second channel portion, the ink-jet head according to any one of claims 1 to 4, characterized in that it is roughened. The pressure chamber is disposed above the common flow path, and the pressure chamber and the common flow path are disposed so as to partially overlap each other in plan view. Item 6. The inkjet head according to any one of Items 1 to 5 .

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