JP4403438B2 - Inkjet head drive unit - Google Patents

Description

  The present invention relates to an inkjet head, and more specifically, in an inkjet head using a piezoelectric element as a drive source for an on-demand inkjet head recording apparatus, the shape of the joint surface of a base that supports and fixes the piezoelectric element and the piezoelectric element, It relates to the material of the base.

As one of drop-on-demand ink jet heads, there is a method using a laminated piezoelectric element as a drive source. The types of laminated piezoelectric elements are classified according to the direction of electric field such as longitudinal vibration and lateral vibration and the direction of displacement, and for example, d ₃₃ laminated piezoelectric elements and d ₃₁ laminated piezoelectric elements are generally used.

For ink-jet head using a piezoelectric element of d ₃₃ type in these drive source, after attaching a bulk piezoelectric element to the base of the gate-shaped, one end comb teeth-shaped so that the free ends vibrator (For example, see Patent Document 1).

Further, the ceramic plate electrode pattern is formed, stuck bulk-shaped piezoelectric element, there is what is cut into strips of laminated piezoelectric element ₃₃ type d using a dicing saw (e.g., Patent Document 2 reference). At that time, since the surface portion of the base is also cut at the same time, individual electrode patterns can be formed at the same time, and subsequent wiring becomes easy.

Japanese Examined Patent Publication No. 4-52213 JP-A-8-142325

  However, as a problem that occurs when dicing into strips, when cutting a piezoelectric element, cutting may not be successful depending on the material of the base that supports the piezoelectric element. For this reason, in the invention described in Patent Document 2, the material of the base is limited to ceramic because the blade is burdened. In metal dicing, since a dicing blade that easily wears is used, the dressing period is shortened and the efficiency is low. Furthermore, when a dicing is performed by joining a base that cannot be quenched, such as SUS430, which is an anti-vibration material, and a piezoelectric element, as shown in FIG. 15, a sag 37 occurs on the metal side that becomes the base 3, An external force is applied to the vibrator 2 that has been split. As a result, the separated vibrator 2 may be peeled off. If the nozzle pitch is small, the vibrator 2 may be blown off during dicing.

  On the other hand, when the base is limited to ceramic and the flow paths are all made of stainless steel or the like, the coefficient of thermal expansion is greatly different, so that high temperature cannot be applied to the drive section and the flow path section. Also, when the ink jet head is used, if the use temperature becomes high, both ends are displaced due to thermal expansion, resulting in a non-ejection state. Further, since the mass of ceramic is lower than that of metal, mutual interference (crosstalk) at the time of ink ejection becomes slightly large, and the ejection stability is poor.

  Further, when a bulk piezoelectric element is cut in a comb shape, it takes time and effort because an individual electrode pattern must be formed in advance according to the cutting pitch. In addition, since the electrode pattern of the piezoelectric element and the electrode pattern of the base must be matched, the number of man-hours increases compared to the strip shape.

The present invention constitutes an inkjet head drive unit having the following features, and effectively solves the above-described problems.
(1) A piezoelectric element that is divided so that one end is a free end and a base that holds the piezoelectric element. The base has a position that is divided in advance into a joint surface with the piezoelectric element. A groove is provided at the same position, and an individual electrode pattern and a common electrode pattern for transmitting an electric signal to the piezoelectric element are formed on the side surface.
(2) The groove is made by dicing or injection molding.
(3) The base is made of a metal material.

  By providing a groove on the joint surface of the base with the piezoelectric element, even when the base is made of stainless steel or the like having poor cutting properties, the twist generated when the piezoelectric element is diced does not reach the vibrator. Also, by dividing the base into two plates, one can be divided into one with good machinability, the second with the same thermal expansion coefficient as the flow path, one piece of piezoelectric element and base By cutting the eyes into strips, the expansion due to thermal expansion can be adjusted to the flow path while the bonding between the piezoelectric element and the base is strengthened.

  As described above, a plurality of nozzles arranged in a row, a plurality of pressure chambers corresponding to each of the nozzles and communicating with the nozzles, and a diaphragm forming a part of the pressure chambers A fixing plate having a hole for fixing the ink flow path portion so as to surround the pressure chamber row is bonded to the ink flow path portion, and one end of the piezoelectric element bonded to one surface of the base becomes a free end. In addition, a drive unit composed of a group of vibrators divided by a length reaching the base together with the pressure chambers is joined to the ink flow path unit to thereby displace the piezoelectric element. In the ink jet head that conveys to the pressure chamber through the nozzle and ejects ink from the nozzle, a groove is provided on the joint surface of the base with the piezoelectric element at a position that is substantially the same as the position where the teeth are split. Base and pressure made of poorly workable material The element at the time of tooth split prevents damage to the vibrator caused by curling occurs can allow the production of stable driving unit. At the same time, since a fillet is formed between the groove and the vibrator, the bonding strength is high.

  By setting the depth of the groove to such a depth that the blade that splits the teeth does not touch, it is possible to prevent wrinkling itself.

  By producing the groove by dicing or injection molding, it is possible to easily obtain the groove shape from various materials such as ceramic, metal and resin.

  In addition, after joining the first base made of a material with good machinability to the second base made of the same material as the flow path forming member, the piezoelectric element and the first base are joined, and one end of the piezoelectric element is free. When the head is heated and used by forming a plurality of vibrators by cutting the piezoelectric element and the first base into a strip shape in accordance with the shape of the pressure chamber so as to be at the end, the second base Since the base is made of the same material as the flow path forming member, it is possible to prevent the occurrence of misalignment due to thermal expansion.

  Since the first base is made of ceramic or hardened stainless steel, it can be cut with a blade in the same manner as the piezoelectric element, so that the processing becomes easy.

  A non-conductive material is used for the first base, and a material on which electrodes are deposited other than the contact surface of the piezoelectric element and the opposite surface is used. Since the first base is individually divided by using a material having a property, it is used as an individual electrode, and the second base is joined and connected to one end side of the first base, so it is used as a common electrode. And wiring of the electrodes is easy.

  FIG. 1 is an exploded perspective view showing a structure of an ink jet head as a first example according to the present invention, FIG. 2 is a side view in an assembled state, and FIG. 3 is a cross-sectional view of FIG.

  This head is roughly divided into two, a drive unit and a flow path unit.

  The drive unit includes a piezoelectric element 1 that is a displacement generation source, a base 3 that holds the piezoelectric element 1, a ShortFPC4 that is attached to the base 3 to form an individual electric path and a common electric path, and a control unit for the ShortFPC4 and the electric signal It consists of LongFPC5 to connect with.

The piezoelectric element 1 is produced by alternately laminating electrodes and piezoelectric bodies, and is produced as an elongated plate-like bulk material. The laminated piezoelectric element 1 has a d ₃₁ type and a d ₃₃ type depending on the polarization direction, and any of them may be used. In this embodiment uses a _33-inch d.

  The base 3 has a role of bonding and fixing one end of the piezoelectric element with an adhesive or the like, and the outer peripheral portion of the plate, which is a bonding surface, is processed with high flatness. In addition, since the surface opposite to the contact surface 6 of the piezoelectric element 1 is used as a pressure surface 7 as a reference surface for pressing the drive unit during assembly, the parallelism is also very high. The material of the base 3 is required to have a high strength for firmly fixing the piezoelectric element 1 and to prevent vibrations from being propagated elsewhere. Here, SUS430 is used. Since SUS430 is conductive, it is necessary to devise a way to connect individual electric signal lines from the piezoelectric element while maintaining insulation from the base 3.

  The assembly method of the drive unit will be described step by step. First, the four sides of the base of SUS430 are processed with high flatness, and the bonding surface 6 and the pressure surface 7 of the piezoelectric element 1 are processed with high parallelism, and then groove processing is performed. Dicing was performed as a process for forming the groove 8. FIG. 4 shows a state of the base 3 on which grooves 8 are formed by dicing. When dicing, the surface is wrinkled, so finish polishing is performed after processing.

  Another method for producing the groove 8 is metal injection. In this case, since the shape is almost ready at the stage of injection molding, the base 3 satisfying the target specification can be produced by performing only some post-processing.

  Next, the piezoelectric element 1 and the base 3 are joined. This joining is performed by an adhesive. FIG. 5 shows a state in which the piezoelectric element 1 and the base 3 are joined. A high-strength adhesive such as an epoxy-based adhesive is used as the adhesive and is applied to the piezoelectric element 1 side. As a coating method, a transfer method is used in which a uniform adhesive layer is produced on a film or the like and pressed against a member to be bonded. The adhesive used in this example is Araldite manufactured by Bantico, which is a room temperature curable adhesive. There is also a method in which an adhesive is applied to the groove 8 side to adjust the amount of the adhesive, and the groove 8 is filled with the adhesive. In this case, even if dicing is performed, only a soft adhesive is drawn, so that the bonding strength is improved and the workability is good.

  Since the piezoelectric element 1 has been previously polarized, warping has occurred. Therefore, pressurization is performed so as to follow the surfaces to be joined appropriately so as to force warpage during joining. As a joining position, it arrange | positions so that it may align with the side surface of the base 3 on the same plane.

  After joining, polishing is performed so that the pressing surface 7 at the base position and the free end side of the piezoelectric element 1 are the same surface. Here, the piezoelectric element was designed to protrude slightly from the pressure surface, so the piezoelectric element was polished. After polishing, as shown in FIG. 6, the Short FPC 4 is attached to the side surface of the base 3. ShortFPC4 consists of three layers of polyimide 9-copper wire 10-polyimide 9, and the copper wire 10 is patterned according to the nozzle pitch. Individual electrode patterns 11 are arranged in the center, and common electrode patterns 12 are formed at both ends thereof. The polyimide 9 is a cover of the copper wire 10, and the surface in contact with the base 3 is completely covered, and the other surface exposes the copper wire portion at both ends. As a result, the base 3 and the copper wire 10 are completely insulated, and the other surface facilitates connection to the piezoelectric element 1 and the LongFPC. ShortFPC4 and base are attached with adhesive. This is also performed by the transfer method in the same manner as the connection between the piezoelectric element 1 and the base 3, and here, the adhesive is transferred and connected to the ShortFPC4. Araldite is also used as the adhesive. However, if the Short FPC 4 protrudes from the base 3, the adhesive may be broken when the Short FPC 4 is rolled. Therefore, EP001 made by Cemedine, which is an elastic adhesive, may be used. EP001 is an adhesive that can withstand some elongation.

  The front end portion of the ShortFPC 4 is connected so as to be positioned closer to the piezoelectric element 1 than the joint between the piezoelectric element 1 and the base 3. This is to prevent the copper wire 10 from coming into contact with the base 3. Then, after the ShortFPC 4 is connected, the one external electrode 13a and the ShortFPC4 of the piezoelectric element 1 and the other external electrode 13b and the base 3 are coupled by the conductive adhesive 14, respectively. In addition, the outermost common electrode pattern 12 is electrically connected to the base 3 by the conductive adhesive 14, thereby achieving electrical connection to the other external electrode via the conductive base.

  Thereafter, as shown in FIG. 7, the piezoelectric element 1 is diced according to the nozzle pitch and divided into a plurality of vibrators 2. Here, the dicing depth was set so as not to contact the groove. Note that dummy vibrators 15 that do not contribute to ink ejection remain at both ends.

  8A and 8B are enlarged views of the dicing portion of the base 3 in which the groove 8 is formed by metal injection in (a), and the base 3 in which the groove 8 is formed by dicing in (b). In the case of metal injection, stable groove width and depth can be realized compared to dicing. In the case of dicing, the depth changes due to wear of the teeth.

  After dicing, as shown in FIG. 9, LongFPC5 is stuck on ShotFPC4. Affixing is performed with an anisotropic conductive sheet affixed to LongFPC5. The drive unit is formed by the above steps.

  Then, the manufacturing method of a flow path unit is demonstrated. As shown in FIG. 10, the flow path unit is formed of an ink flow path portion 29 including a nozzle plate 18, a chamber plate 20, and a diaphragm plate 24, and a fixing plate 30 (see FIG. 11) for fixing the ink flow path portion 29. Is done. Each plate is positioned by the flow path unit positioning holes 17 (a) to (c) provided in each plate.

  The nozzle plate 18 has a nozzle 19 that is an ink discharge port, and the ink discharge surface is subjected to ink repellent treatment. The material is preferably SUS303, and the individual nozzles 19 are produced by pressing.

  The chamber plate 20 is formed with a pressure chamber 21 communicating with the nozzle 19, a manifold 23 serving as an ink reservoir, and a restrictor 22 connecting the pressure chamber 21 and the manifold 23. Silicon is used as a material, and each part is formed by wet etching or dry etching.

  The diaphragm plate 24 includes a diaphragm 25 that forms one side wall of the pressure chamber 21, a dummy vibrator joint 26 that contacts the dummy vibrator 15, an ink introduction hole 27 that introduces ink into the manifold 23, and ink fluctuations in the manifold 23. The damper 28 which absorbs is formed. The diaphragm plate 24 is formed by bonding a metal and a resin, and SUS303 is used for the metal and a polyimide film is used for the resin. After the metal and the resin are bonded together, a predetermined portion of the metal surface is removed by etching to form the diaphragm 25 and the damper 28 surrounded by the metal frame.

  In assembling the ink flow path portion 29, the nozzle plate 18, the chamber plate 20, and the diaphragm plate 24 are joined together with a sheet-like adhesive. Each adhesive layer is about 2 to 3 μm.

  Subsequently, as shown in FIG. 11, after forming the ink flow path portion 29, the fixing plate 30 is joined. The fixed plate 30 has a through hole 32 through which the ink supply path 31 and the drive unit 15 penetrate, and a surface joined to the ink flow path portion 29 is subjected to high flatness processing. The material is SUS430, which is very thick compared to the ink flow path 29, and therefore has high rigidity. Therefore, the warp and undulation generated in the ink flow path 29 at the time of joining with the ink flow path 29 is corrected by the rigidity of the fixing plate 30. The size of the through hole 32 is such that the drive unit 16 does not contact. This is because when the drive unit 16 and the fixed plate 30 are contacted or joined, an inclination is generated, and the ink ejection characteristics are remarkably deteriorated. A flow path unit is formed by the above process.

  Since the drive unit and the flow path unit are assembled in separate steps, either one may be assembled first.

  Subsequently, each unit is joined. Joining is performed by a transfer method using an adhesive. Here, EP001, which is a high-strength elastic adhesive, is used as the adhesive. Here, the transfer of the adhesive is performed by applying the adhesive to a flat plate and abutting the vibrator.

  After the transfer, the drive unit 16 is joined to the flow path unit 33 as shown in FIG. Positioning is performed by image processing using a jig (not shown). After positioning, the drive unit 16 is inserted into the flow path unit 33 (step (a)), and after hitting, the pressure surface 7 is pressed and cured by heating (step (b)). Thus, the head is completed.

  By assembling the inkjet head in the above-described process, it is possible to prevent defects (falling or breaking due to twisting) that occur when the piezoelectric element 1 is split, and stable cutting can be performed even on a base with poor workability.

  Next, another example of the present invention will be described. In this example, the base 3 is formed of two types of members having different materials. Of these, the first base bonded to the piezoelectric element 1 can be prevented from wrinkling that occurs during dicing processing of the piezoelectric element by using a material having high cutting ability, and the second base is the high temperature of the head. There is an effect of preventing elongation due to thermal expansion during use.

  The base of the present invention is manufactured by fixing the piezoelectric element 1 to the first base 34 and further joining the first base 34 to the second base 35. FIG. 13 shows the state. The first base 34 is made of ceramic (alumina), and the second base 35 is made of SUS304, which is a metal. The point of selecting the material of the second base 35 is that it is selected from those having a thermal expansion coefficient substantially equal to that of the material used for the flow path unit.

  Specifically, first, a solid electrode 36 is vapor-deposited in advance on the joint surface of the first base 34 with the second base 35 and the opposite surface. Next, the first base and the second base are fixed with an adhesive. Thereafter, the piezoelectric element 1 and the first base 34 are joined. A room-temperature curable adhesive was used for these adhesions. Next, both the external electrode surfaces of the piezoelectric element are electrically connected to both the electrode surface surfaces of the first base 34 by the conductive adhesive 14. Similarly, the electrodes on the joint surface side of the second base 35 and the second base 34 of the first base are electrically connected. The surfaces that conduct electricity are the surface opposite to the fixed surface of the piezoelectric element, and both side surfaces thereof. Thereby, since the second base is conductive, conduction between the second base and the piezoelectric element on one surface of the external electrode can be established.

  After joining the piezoelectric element 1 and the bases 34 and 35 and establishing conduction between the respective components, the piezoelectric element 1 is separated. In this case, the piezoelectric element 1 and the first base 34 are cut to a strip-like depth. After cutting in this way, the LongFPC5 is pasted to complete the drive unit as shown in FIG.

  The ink jet head to which the drive unit manufactured by the above manufacturing method is applied is effective when heated and used. That is, when the inkjet head is heated and used, if the flow path components are disjoint, the thermal expansion causes warpage and undulation in the flow path, and in the worst case breaks. It needs to be assembled. However, in a drive unit manufactured without considering the coefficient of thermal expansion of the material, the base may generate accumulated warpage and deflection, and in the worst case, there is a high possibility of non-ejection at both ends. On the other hand, in the configuration of this example, a difference in thermal expansion occurs for each nozzle, but since there is almost no influence on the accumulation, it is effective for manufacturing a long drive unit.

FIG. 2 is an exploded view of an inkjet head as an example of the present invention. 1 is a front sectional view of an ink jet head of the present invention. FIG. 3 is a side cross-sectional view of the inkjet head of the present invention. The perspective view which shows the state of the base which performed the dicing and formed the groove | channel. The perspective view and sectional drawing which show the state which joined the piezoelectric element and the base. The perspective view and sectional drawing which show the state which attached ShortFPC to the base side. The perspective view which shows the state which diced the piezoelectric element according to the predetermined pitch. The enlarged view of a dicing process part. The perspective view of the drive unit of this invention. FIG. 3 is an exploded perspective view and a perspective view of an ink flow path portion of the present invention. The perspective view of the channel unit of the present invention Sectional drawing which shows a mode that a drive unit and a flow-path unit are assembled. The perspective view and sectional drawing which show the state which joined the piezoelectric element and base which become other examples of this invention. The perspective view which shows the state which diced the piezoelectric element according to the predetermined pitch in the other example of this invention. Explanatory drawing which shows the problem of joining of the conventional piezoelectric element and a base.

Explanation of symbols

1 is a piezoelectric element, 2 is a vibrator, 3 is a base, 4 is a ShortFPC, 5 is a LongFPC, 6 is a contact surface, 7 is a pressure surface, 8 is a groove, 9 is a polyimide, 10 is a copper wire, and 11 is an individual Electrode pattern, 12 is a common electrode pattern, 13 is an external electrode, 14 is a conductive adhesive, 15 is a dummy vibrator, 16 is a drive unit, 17 is a channel unit positioning hole, 18 is a nozzle plate, 19 is a nozzle, 20 Is a chamber plate, 21 is a pressure chamber, 22 is a restrictor, 23 is a manifold, 24 is a diaphragm plate, 25 is a diaphragm, 26 is a base joint, 27 is an ink inlet, 28 is a damper, 29 is an ink flow path , 30 is a reinforcing plate, 31 is an ink supply path, 32 is a through hole, 33 is a flow path unit, 34 is a first base, 35 is a second base, 36 is a solid electrode, and 37 is a flange.

Claims (3)

A piezoelectric element having one end divided so that the free end, the kinematic unit driving a composed inkjet head from the base to hold the piezoelectric element, wherein the base in advance on the bonding surface of said piezoelectric element A drive unit for an ink-jet head , wherein grooves are provided at substantially the same positions as the positions to be divided, and individual electrode patterns and common electrode patterns for transmitting electrical signals to the piezoelectric elements are formed on side surfaces. 2. The ink jet head drive unit according to claim 1, wherein the groove is formed by dicing or injection molding. 2. The ink jet head drive unit according to claim 1, wherein the base is made of a metal material.

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