JP5857436B2 - Actuator unit, inkjet printer head, and image forming apparatus - Google Patents

Description

The present invention relates to an actuator unit of a liquid discharge head that discharges a liquid such as an ink droplet from a hole portion such as a nozzle hole, an ink jet printer head using the actuator unit , and an image forming apparatus .

  As an image forming apparatus, an ink jet printer that forms an image by ejecting ink droplets from nozzle holes and landing on a recording medium is widely used. Among them, only ink droplets for recording are selectively ejected. The so-called on-demand system has become the mainstream. This on-demand method is based on the principle of generation of kinetic energy discharged from the ink liquid, and the pressure in the ink liquid is determined by the volume displacement of the pressurized liquid chamber caused by the operation of a piezoelectric element (hereinafter also referred to as PZT) that is an electromechanical conversion element. The so-called piezo method that generates the kinetic energy of ink droplet discharge from this pressure, the electrostatic method that uses an electrostatic actuator as the electrical / mechanical conversion element, and the electrical / thermal conversion element generates bubbles in the ink liquid. This is classified into a so-called thermal system that obtains kinetic energy of ink droplet discharge by excluding ink by the expansion of the bubbles.

  As a liquid discharge head in the above-described piezo method, at least a part of wall surfaces of a plurality of liquid chambers arranged corresponding to a plurality of nozzles arranged in parallel to discharge ink droplets is formed by a vibration plate, and the vibration plate A piezoelectric head using a piezoelectric actuator that discharges ink droplets by changing the volume of a liquid chamber by deforming it with PZT is known, and a piezoelectric element member in which a plurality of piezoelectric element columns are formed as this piezoelectric head One having a piezoelectric actuator in which a plurality of the actuators are arranged side by side on a base member is known. In such a piezoelectric head, for example, a multilayer PZT is used, and an electrode of a flexible printed circuit board (hereinafter also referred to as an FPC) is joined to an external electrode in which the internal electrode is drawn to the end face, and an image is applied to each PZT. A drive signal corresponding to the signal is provided.

  In solder joining between the FPC connection electrode and the PZT external electrode, the FPC connection electrode is pressed against the PZT external electrode by the pressure of the air jet from the nozzle, and the FPC solder member is melted by heating with a laser. For example, “Patent Document 1” discloses a technique of soldering FPC and PZT by soldering. Further, for example, a technique for reducing the occurrence of poor bonding due to a step between PZT members by forming a cut in the FPC and correcting the undulation and curvature of the FPC dividing surface by forming a cut between the connection electrodes of the FPC is, for example, “ Patent Document 2 ”discloses.

  However, in the technique disclosed in “Patent Document 1”, the FPC is divided and used by the mold from the reel state. However, the undulation or curvature of the FPC is generated on the FPC dividing surface at the time of division. Since it cannot be suppressed by the pressure due to the jetting, there is a problem in that the connection electrode of the FPC and the external electrode of the PZT cannot be brought into close contact with each other at the time of solder bonding, resulting in poor solder bonding. Further, in the technique disclosed in “Patent Document 2”, the width and interval of the piezoelectric element columns have a very fine structure of several tens of μm, so that fine cuts are formed in the FPC at intervals of several tens of μm. In addition to the significant increase in cost, the FPC with the cut formed by the pressure of the air jet becomes unclear, so that the bonding position cannot be determined, and the FPC external electrode and the piezoelectric element column cannot be soldered. .

  The present invention solves the above-mentioned problems and corrects the undulation and curvature of the FPC split surface without cutting the FPC to improve the flatness of the solder joint surface. It is an object of the present invention to provide an actuator unit that can improve adhesion with an electrode and solder jointability to reduce solder joint failure.

The invention according to claim 1 is used in an ink jet head that ejects ink in a liquid chamber by driving a piezoelectric element to obtain a desired amount of displacement, and a plurality of piezoelectric elements provided in the piezoelectric element joined to a base member. In the actuator unit configured by soldering a plurality of connection electrodes provided on the flexible printed cable to the external electrodes, in the vicinity of the joint between the external electrodes and the connection electrodes, the flexible printed cable includes A bending portion having an axis line in the same direction as the direction in which the connection electrodes are arranged is provided, and the bending portion is provided over the entire width of the flexible printed cable and on the tip side of the connection electrodes, The bending direction of the bending portion is the joint portion side, each external electrode and each connection electrode Bonding position is characterized in that the determined by abutted against the bent portion of the flexible printed cable to the piezoelectric element.

According to a second aspect of the present invention, in the actuator unit according to the first aspect, the tip of the flexible printed cable does not protrude from the piezoelectric element .

The invention described in claim 3 is an ink jet printer head using the actuator unit described in claim 1 or 2 .

According to a fourth aspect of the present invention, there is provided an image forming apparatus using the actuator unit according to the first or second aspect.

  According to the present invention, by providing the bent portion 16 with respect to the flexible printed cable, the strength of the flexible printed cable in the bent portion 16 is increased and the flatness is improved, which is caused by the undulation and curvature of the flexible printed cable. Therefore, it is possible to prevent the occurrence of poor solder joints, and to provide a good actuator unit free from solder joint defects.

It is the schematic of the actuator unit which can apply one Embodiment of this invention. It is an exploded view of the actuator unit which can apply one Embodiment of this invention. It is the schematic of the actuator unit which can apply one Embodiment of this invention. It is the schematic explaining joining of PZT and FPC of the actuator unit which can apply one Embodiment of this invention. It is the schematic explaining joining of PZT and FPC of the actuator unit which can apply one Embodiment of this invention. It is the schematic explaining FPC used for the actuator unit which can apply one Embodiment of this invention. It is the schematic explaining the problem in the actuator unit which can apply one Embodiment of this invention. It is the schematic explaining the problem in the actuator unit which can apply one Embodiment of this invention. It is the schematic explaining the problem in the actuator unit which can apply one Embodiment of this invention. It is the schematic explaining FPC used for one Embodiment of this invention. It is the schematic explaining FPC used for one Embodiment of this invention. It is the schematic explaining FPC used for the other example of one Embodiment of this invention. It is the schematic explaining FPC used for one Embodiment of this invention. It is the schematic explaining FPC and PZT used for one Embodiment of this invention. It is the schematic explaining PZT used for the modification of one Embodiment of this invention. It is the schematic explaining FPC and PZT used for the modification of one Embodiment of this invention. It is the schematic explaining FPC used for one Embodiment of this invention. It is the schematic explaining FPC which is not used in one Embodiment of this invention. It is the schematic explaining FPC which can be used for one embodiment of the present invention. It is the schematic explaining FPC used for one Embodiment of this invention. It is the schematic explaining PZT used for the modification of one Embodiment of this invention. It is the schematic explaining FPC and PZT used for the modification of one Embodiment of this invention. It is the schematic explaining FPC and PZT used for the modification of one Embodiment of this invention. It is the schematic explaining FPC and PZT used for the modification of one Embodiment of this invention. It is the schematic explaining the problem of FPC which can be used for one Embodiment of this invention. It is the schematic explaining FPC used for one Embodiment of this invention. It is the schematic explaining joining of PZT and FPC of the actuator unit used for one Embodiment of this invention. It is the schematic of the actuator unit to which one Embodiment of this invention is applied. It is the schematic explaining FPC and PZT used for one Embodiment of this invention. It is a schematic perspective view of the actuator unit to which one embodiment of the present invention is applied. It is a schematic sectional drawing of the actuator unit to which one Embodiment of this invention is applied. It is the schematic explaining the problem in one Embodiment of this invention.

  FIG. 1 shows an actuator unit to which an embodiment of the present invention can be applied. In the figure, an actuator unit 1 is configured by joining a flexible printed cable (also referred to as FPC) 4 to a piezoelectric element (also referred to as PZT) 3 fixed to a base member 2, and this actuator unit 1 is used. Accordingly, an ink jet printer head and an image forming apparatus can be configured in the same manner as the technique disclosed in Japanese Patent Application Laid-Open No. 2010-34127.

  FIG. 2 shows a detailed view of the actuator unit 1. The PZT 3 has an internal electrode 5, an external electrode 6, and a piezoelectric material layer 7. The FPC 4 is composed of a tape member 8, a connection electrode 9, a solder member 10 coated on the connection electrode 9, a wiring pattern 11, and the like. In addition, the PZT 3 and the FPC 4 are joined by melting and joining the solder member 10 in a state where the external electrode 6 and the connection electrode 9 are in close contact with each other.

  FIG. 3 shows the actuator unit 1 viewed from the FPC 4 side. As shown in the figure, the PZT 3 is constituted by a set of piezoelectric element columns 12. Solder bonding between the external electrode 6 and the connection electrode 9 is performed in a state where the bonding position between the piezoelectric element column 12 and the connection electrode 9 is adjusted so that the connection electrode 9 is accommodated in the piezoelectric element column 12.

  Next, solder joint between PZT 3 and FPC 4 will be described. For pressing the connection electrode 9 of the FPC 4 against the external electrode 6 of the PZT 3, the pressure of air injection is used as shown in FIG. After the alignment of the piezoelectric element column 12 and the external electrode 6, air is sprayed from above the FPC 4, the external electrode 6 and the connection electrode 9 are brought into contact with this pressure, and heat is applied to the solder member 10 in this state to perform soldering. Join.

  FIG. 5 shows a state of solder bonding. In FIG. 5, the connection electrode 9 of the FPC 4 is pressed against the external electrode 6 of the PZT 3 by air injection from the air nozzle 13, and the solder member 10 is melted by the laser irradiated from the irradiation port 15 through the lens 14. By doing so, the solder bonding between the connection electrode 9 and the external electrode 6 is performed.

  Next, problems of the prior art will be described. As shown in FIG. 6, the FPC 4 is formed so that a plurality of FPCs 4 are in a single roll shape, and are used by being individually divided by a mold. Since the FPC 4 is thus divided by the mold, undulation and curvature are generated in the FPC 4 as shown in the cross-sectional view of FIG. 7, and undulation and curvature are similarly generated on the divided surface of the connection electrode 9. FIG. 7 is a view seen from the FPC 4 side when the connection electrode 9 and the piezoelectric element column 12 are aligned before solder bonding. As shown in the cross-sectional view of FIG. 7, the piezoelectric element column 12 is in a state before air injection. However, there is a portion where the connection electrode 9 is not in contact (a portion where a gap is generated). Accordingly, the connection electrode 9 is brought into contact with the external electrode 6 by injecting air. As shown in FIG. 8, the undulation and curvature at a large pitch with respect to the entire longitudinal direction of the PZT 3 can be suppressed by the air ejection. As shown in the enlarged view, undulation and bending at a very narrow pitch cannot be suppressed, and the external electrode 6 and the connection electrode 9 are separated from each other at the time of soldering, resulting in poor bonding. On the other hand, there is a possibility that the adhesion between the external electrode 6 and the connection electrode 9 can be improved by increasing the pressure of the ejected air, thereby suppressing the occurrence of poor solder joints. However, if the air pressure is increased, As shown in FIG. 9, the tip including the connection electrode 9 of the FPC 4 flutters and the connection electrode 9 is separated from the external electrode 6, resulting in poor bonding. I can't let you.

  A feature of the present invention that solves the above-described problems will be described. The present invention improves the flatness of the connection electrode 9 by correcting the waviness and curvature generated by the division of the FPC 4 by providing a bent portion near the position where the connection electrode 9 of the FPC 4 is disposed. This suppresses the occurrence of poor solder joints between the connection electrode 9 and the external electrode 6. The width of the connection electrodes 9 of the FPC 4 is several tens of μm, and the pitch between the connection electrodes 9 is several hundreds of μm. The present invention improves the flatness of the surface at a very narrow pitch. As the bent portion, there are a bent portion 16 having a fold as shown in FIG. 10A and a bent portion 17 which is curved without a fold as shown in FIG. 10B. The bending portion 16 employs the bending portion 16 in the present embodiment because the bending portion 16 has higher strength than the bending portion 17 and the flatness is further improved.

  FIG. 11 shows the FPC 4 having the bent portion 16. In the example shown in FIG. 11, the distal end side that is closer to the PZT 3 than the connection electrode 9 of the FPC 4 is bent, but even if the base member 2 side is bent from the connection electrode 9, the flatness can be improved. FIG. 12 shows the FPC 4 having the bent portion 16 on the base member 2 side with respect to the connection electrode 9, and in this example, the wiring pattern 11 is disposed at the forming portion of the bent portion 16. In the configuration shown in FIG. 12, since the wiring pattern 11 is also bent, there is a risk of disconnection in the wiring pattern. Therefore, in this embodiment, a configuration having a bent portion 16 on the PZT 3 side as shown in FIG. 11 is adopted. Yes.

  Next, the bending direction of the FPC 4 in the bent portion 16 is as shown in FIG. 13A, and is bent to the side opposite to the solder member 10, that is, the side opposite to the joint with the external electrode 6, As shown in FIG. 13B, there is a method of bending to the solder member 10 side, that is, to the joint portion side with the external electrode 6. However, when it is bent toward the joint as shown in FIG. 13B, there is a possibility that the tip of the FPC 4 and the external electrode 6 come into contact as shown in FIG. Processed PZT3A is used. The PZT 3A is formed by cutting a part of the piezoelectric material layer 7 that does not affect the capacitance and does not have the internal electrode 5. When this PZT 3A and the FPC 4 shown in FIG. 13B are joined, the configuration shown in FIG. 16 is obtained. With this configuration, PZT 3A and FPC 4 can be satisfactorily joined without affecting the drive characteristics of PZT 3A and without interference with bending portion 16 of FPC 4.

  As shown in FIG. 13A, in the case of the FPC 4 in which the bending portion 16 is bent on the side opposite to the joint portion with the external electrode 6, the bending angle is 90 degrees or less as shown in FIG. . As shown in FIG. 18A, when the bending angle is 90 degrees or more as shown in FIG. 18A, the laser irradiated from the irradiation port 15 when soldering as shown in FIG. This is because the tip of the bent portion 16 interferes with the laser and adversely affects the solder joint. However, this is a case of solder bonding using a laser. When solder bonding is performed by other than laser irradiation such as a reflow furnace, the bending angle of the bending portion 16 is 90 degrees or more as shown in FIG. However, there is no problem, and the connection electrode 9 and the external electrode 6 can be joined.

  As shown in FIG. 13B, in the case of the FPC 4 in which the bent portion 16 is bent on the joint portion side with the external electrode 6, the bending angle is set to −90 degrees or more and 0 degrees or less as shown in FIG. Yes. When the FPC 4 is bent further than -90 degrees, it is possible to use PZT 3B having an oblique notch at the tip as shown in FIG. In this configuration, since the PZT 3B has an inclination at the tip, the tip of the FPC 4 is caught by the PZT 3B, so that the joining position can be easily determined as shown in FIG. Also, as shown in FIG. 24, two bent portions 16 are formed in the FPC 4 as shown in FIG. 23A, and PZT3C corresponding to the shape of the FPC 4 is used as shown in FIG. Bonding is also possible.

  By providing the bending portion 16 with respect to the FPC 4 with the above-described configuration, the strength of the FPC 4 in the bending portion 16 is increased and the flatness is improved, and the occurrence of solder joint failure due to the undulation and curvature of the FPC 4 is caused. It is possible to provide a good actuator unit 1 that can be prevented and that has no solder joint failure. In addition, by providing the bent portion 16 over the entire width of the FPC 4, it is possible to prevent the occurrence of poor solder joints at all joint portions between the external electrodes 6 and the connection electrodes 9 in the actuator unit 1.

  In the present invention, as shown in FIG. 13, only the tape material 8 on the tip side of the connection electrode 9 of the FPC 4 is bent to form the bent portion 16, but when bent from the connection electrode 9 as shown in FIG. There is a possibility that the connection electrode 9 and the solder member 10 break during bending. Further, when a crack occurs, an electrode piece, a solder member piece or the like is generated from the cracked place, which may become a foreign substance and adversely affect the ejection characteristics of the head. For this reason, in this invention, the structure which bends only the tape material 8 is employ | adopted.

  26A and 26B are perspective views of the FPC 4 provided with the bending portion 16. By bending the tape member 8 on the distal end side of the connection electrode 9 to form a bent portion 16, the flatness of the FPC 4 provided with the connection electrode 9 is improved to correct the undulation and curvature. . By using the FPC 4 and soldering the connection electrode 9 and the external electrode 6 as shown in FIG. 27, it is possible to reduce the occurrence of solder joint failure due to the undulation and curvature of the FPC 4. By this joining, the actuator unit 1 shown in FIG. 28A or FIG. 28B is completed.

  As shown in FIG. 29, in this embodiment, the tape member 8 at the tip of the bent portion 16 of the FPC 4 is configured not to protrude from the tip of the PZT 3. Even if the tape member 8 protrudes from the tip of the PZT 3, it does not affect the solderability of the connection electrode 9 and the external electrode 6. After joining the PZT 3 and the FPC 4 to complete the actuator unit 1, the diaphragm 18 is joined to the PZT 3 as shown in FIG. 30. FIG. 31 is a cross-sectional view at this time. At this time, if the tape member 8 at the tip of the bent portion 16 protrudes from the PTZ 3, the tape member 8 and the diaphragm 18 may come into contact with each other as shown in FIG. 32, which may affect the ejection characteristics of the head. is there. Therefore, in this invention, as shown in FIG. 29, it is comprised so that the tape member 8 at the front-end | tip of the bending process part 16 may not protrude from PTZ3. However, this configuration corresponds to the d33 mode that expands and contracts in the direction perpendicular to the surface of the internal electrode 5 of PZT3. Since the joining position of the diaphragm 18 joined to the actuator unit 1 using the d31 mode PZT 3 extending and contracting in the direction along the surface of the internal electrode 5 of the PZT 3 is different from the above, in this case, the bending portion 16 of the FPC 4 There is no restriction on the length of the tip.

1 Actuator unit 2 Base member 3 Piezoelectric element (PZT)
4 Flexible printed cable (FPC)
6 External electrode 9 Connection electrode 16 Bending part

JP 2008-218963 A JP 2010-34127 A

Claims (4)

Used in an inkjet head that ejects ink in a liquid chamber by driving a piezoelectric element to obtain a desired amount of displacement, and provided on a flexible printed cable on a plurality of external electrodes provided on the piezoelectric element joined to a base member In the actuator unit configured by soldering each of the plurality of connection electrodes formed,
In the vicinity of the joint between each external electrode and each connection electrode, the flexible printed cable is provided with a bent portion having an axis in the same direction as the direction in which the connection electrodes are arranged,
The bending portion is provided over the entire width of the flexible printed cable and on the tip side of the connection electrodes,
The bending direction of the bending portion is the joint portion side,
The actuator unit according to claim 1, wherein a joining position between each external electrode and each connection electrode is determined by abutting the bending portion of the flexible printed cable against the piezoelectric element. The actuator unit according to claim 1, wherein
An actuator unit, wherein a tip portion of the flexible printed cable does not protrude from the piezoelectric element.   An ink jet printer head using the actuator unit according to claim 1.   An image forming apparatus using the actuator unit according to claim 1.

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