JP2009214060A - Piezoelectric actuator unit and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric actuator unit molded integrally with a supporting frame, and also to provide a manufacturing method of the same. <P>SOLUTION: The piezoelectric actuator unit is assembled into a touch-panel type input device, transmitting vibration to a contact target. The unit includes a piezoelectric actuator 140 which vibrates in accordance with input by contact, a supporting frame 120 which is formed of thermoplastic resin and which supports the piezoelectric actuator 140 by a part of the actuator being imbedded in the frame through integrated molding, and a touch panel to which vibration is transmitted from the piezoelectric actuator. As a result, the integration reduces the number of man-hour and the piezoelectric actuator unit is manufactured that stably transmits vibration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piezoelectric actuator unit that is incorporated in a touch panel input device and transmits vibration to a contact target, and a method for manufacturing the same.

  Since the surface of the touch panel is flat and smooth, there is a situation in which it is difficult for the user to determine whether or not the user can operate correctly compared to a mechanical switch. For this reason, conventionally, a touch panel has been proposed in which vibration is given to the fingertip of the operating user to feed back the feeling of operation. As described above, the feedback method for applying vibration to the fingertip of the user who operates is called tactile feedback.

As a vibration generating means for tactile feedback, a bimorph type piezoelectric actuator that supports a touch panel is known, which is incorporated under the touch panel and transmits vibration to a contact target (see, for example, Patent Document 1). In the input / output device described in Patent Document 1, a piezoelectric actuator is fixed to a support frame or a touch panel with an adhesive. On the other hand, a piezoelectric vibrator formed by molding the entire metal diaphragm and a part of the connection terminal at the same time in the field of sound amplifying such as information terminal equipment is disclosed (for example, see Patent Document 2). .
JP 2004-094389 A JP 2004-188266 A

  As described above, in the touch panel type input device, the piezoelectric actuator is required to be stably supported and to transmit sufficient vibration to the touch panel. In consideration of such circumstances, the present inventor has conceived that the piezoelectric actuator is fixed to the resin support frame by integral molding.

  However, when the piezoelectric actuator is fixed to the resin by integral molding, it is often necessary to pour a resin having a temperature equal to or higher than the Curie point of the piezoelectric body at the time of integral molding, in which case the polarization of the piezoelectric body is depolarized. To do. When the polarization of the piezoelectric body disappears, the piezoelectric actuator loses its bending function, and the touch panel input device cannot generate vibration.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a piezoelectric actuator unit integrally formed with a support frame and a method for manufacturing the same.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the piezoelectric actuator unit of the present invention is a piezoelectric actuator unit that is incorporated in a touch panel type input device and transmits vibration to a contact target, and is formed of a piezoelectric actuator that vibrates in response to an input by contact, and a thermoplastic resin, The piezoelectric actuator includes a support frame that supports the piezoelectric actuator and a touch panel that transmits vibrations from the piezoelectric actuator by being partially embedded in the piezoelectric actuator.

  As described above, the piezoelectric actuator unit of the present invention is formed of a thermoplastic resin, and a part of the piezoelectric actuator is embedded in the support frame by integral molding (insert molding). Thereby, it is possible to produce a piezoelectric actuator unit that reduces man-hours by integration and transmits vibrations stably.

  (2) Further, in the piezoelectric actuator unit of the present invention, the support frame is formed of a thermoplastic resin having a glass transition temperature higher than a polarization temperature of a piezoelectric body constituting the piezoelectric actuator. Therefore, in order to manufacture a piezoelectric actuator unit in which a part of the piezoelectric actuator is embedded in the support frame by integral molding, it is necessary to perform polarization processing on the piezoelectric body of the piezoelectric actuator after the molding process in the manufacturing process. Even if the piezoelectric body is heated to a temperature equal to or higher than the depolarization temperature in the molding process, the polarization process is surely performed by the subsequent polarization process, and the piezoelectric actuator unit in which the piezoelectric actuator is integrally formed (insert molding) on the support frame can be manufactured. it can.

  Note that the polarization temperature is a temperature lower than the Curie temperature and the lowest temperature at which the piezoelectric body should be maintained during the polarization process. On the other hand, the depolarization temperature is a temperature at which the polarization characteristic of the piezoelectric body is reduced to the extent that the piezoelectric body does not function as an actuator when the piezoelectric body is heated to a temperature lower than the polarization temperature. For example, it has been confirmed that a PZT piezoelectric body having a Curie temperature of about 300 ° C. has a polarization temperature of about 180 ° C. and a depolarization temperature of about 100 ° C.

  (3) Further, in the piezoelectric actuator unit of the present invention, the resin forming the support frame has a glass transition point of 200 ° C. or higher. As a result, when a piezoelectric actuator using a piezoelectric body having a Curie temperature of less than 200 ° C. is integrally formed with the support frame, it is necessary to perform polarization processing of the piezoelectric actuator after performing the molding process. The piezoelectric material satisfying such conditions includes a piezoelectric material suitable for a piezoelectric actuator such as PZT.

  (4) In the piezoelectric actuator unit of the present invention, the piezoelectric actuator is a bimorph type piezoelectric actuator. Since the bimorph type has a symmetrical shape, the piezoelectric actuator does not warp due to a difference in thermal expansion during cooling after integral molding.

  (5) A method of manufacturing a piezoelectric actuator unit according to the present invention is a method of manufacturing a piezoelectric actuator unit that is incorporated in a touch panel type input device and transmits vibration to a contact target. A molding step of integrally molding the piezoelectric actuator and a support frame that supports the piezoelectric actuator, and a polarization step of performing a polarization process on the piezoelectric body of the piezoelectric actuator after the molding step. It is characterized by having.

  Thus, in the manufacturing method of the piezoelectric actuator unit of the present invention, the polarization process is performed on the piezoelectric body of the piezoelectric actuator after the molding step. Therefore, even if the piezoelectric body is heated to a temperature equal to or higher than the depolarization temperature in the molding process, the polarization is reliably performed by the subsequent polarization process. As a result, it is possible to manufacture a piezoelectric actuator unit that reduces man-hours by integration and transmits vibrations stably.

  (6) Further, before the molding step of the manufacturing method of the piezoelectric actuator unit of the present invention, the driving terminal and the electrode of the piezoelectric actuator are connected and arranged in advance. Thereby, the trouble of connecting the terminal to the electrode of the piezoelectric body later can be saved.

  (7) Further, the molding step of the method for manufacturing a piezoelectric actuator unit of the present invention further includes a connection step of embedding a terminal in a support frame and connecting the terminal to the piezoelectric actuator after the polarization step. It is said. As described above, since the terminal is connected to the electrode of the piezoelectric actuator after the polarization process, the molding and polarization process can be easily performed without setting the wiring or the direction of the voltage during the polarization in advance.

  According to the present invention, it is possible to produce a piezoelectric actuator unit that reduces man-hours by integration and stably transmits vibration.

  Next, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and duplicate descriptions are omitted.

(First embodiment)
FIG. 1 is a schematic diagram illustrating a configuration of a touch panel input device 100. This touch panel type input device 100 has a tactile feedback function and an acoustic feedback function. The touch panel input device 100 includes a piezoelectric actuator unit 110, a touch panel circuit 170, a digital signal processor (DSP) 180, and a class D amplifier 190.

  The piezoelectric actuator unit 110 includes a support frame 120, a piezoelectric actuator 140, and a touch panel 160. The piezoelectric actuator unit 110 is incorporated in a touch panel type input device, and transmits vibration to a contact target as a tactile sense or acoustic feedback with respect to the touch on the touch panel. The touch panel 160 detects a contact at a position corresponding to a display position of an image displayed on a display device (not shown) and generates an input signal. The touch panel circuit 170 processes a signal obtained from the touch panel 160 to output a signal indicating a position where the user's fingertip contacts on the panel surface of the touch panel 160.

  The digital signal processor 180 receives a signal representing a contact position on the touch panel 160, and classifies a mixed signal obtained by mixing the acoustic signal and the tactile signal so as to generate predetermined sound and tactile vibration according to the position. Output to the amplifier 190. The digital signal processor 180 does not distinguish between an acoustic signal and a tactile signal and mixes and outputs them.

  The class D amplifier 190 drives the piezoelectric actuator 140 based on the mixed signal input from the digital signal processor 180. The class D amplifier 190 is an amplifier that converts an input analog signal into a PWM (Pulse Wide Modulation) signal and outputs an analog signal amplified in terms of power by passing the PWM signal that has passed through the switching circuit through an LC filter. is there. Since the piezoelectric element has capacitance, it is possible to eliminate the LC filter capacitor required for the class D amplifier. In addition, when a piezoelectric element (piezoelectric actuator), which is a capacitive load, is driven by a general analog amplifier, the current phase is shifted by 90 degrees from the voltage, so that heat generation is large, whereas the class D amplifier 190 is amplified by switching. Since heat generation is small and a heat sink for diffusing heat is not required, it is advantageous for miniaturization. In this way, the piezoelectric actuator 140 vibrates when detecting contact with the touch panel 160, thereby enabling acoustic or tactile feedback.

  2A and 2B are a plan view and a front view showing a schematic configuration of the piezoelectric actuator unit 110, respectively. The piezoelectric actuator unit 110 transmits vibration to a contact target when the touch panel type input device 100 detects contact with the touch panel 160. The support frame 120 forms a frame of the screen of the touch panel input device 100, and supports the piezoelectric actuator 140 installed thereon. A touch panel 160 is installed on the piezoelectric actuator 140.

  The support frame 120 is made of resin, and is formed in a rectangular frame shape in which the screen display portion of the touch panel is a hollow 121. The resin forming the support frame 120 is preferably one having excellent moldability, and examples thereof include liquid crystal polymer, ABS, polycarbonate, PPS (polyphenylene sulfide), and PEEK (polyether ether ketone).

  The resin forming the support frame 120 is a thermoplastic resin having a glass transition temperature higher than the polarization temperature of the piezoelectric body. The glass transition temperature is preferably higher than the polarization temperature in order to maintain the shape of the resin during the polarization treatment. Specifically, the temperature is preferably 100 ° C. or higher, and more preferably 200 ° C. or higher in consideration of a piezoelectric material such as PZT. In particular, the liquid crystal polymer is preferable as a material for the support frame 120 because it can maintain its shape even if it is thin due to its crystallinity and has excellent heat resistance. The support frame 120 has four rectangular slots 122 for installing the piezoelectric actuator 140. The slot portion 122 has a space that can accommodate the piezoelectric actuator 140. Note that the polarization temperature is a temperature lower than the Curie temperature and the lowest temperature at which the piezoelectric body should be maintained during the polarization process.

  The piezoelectric actuator 140 is a bending type actuator and is formed in a rectangular shape with a size that can be accommodated in the slot 122. Support fixing portions 151 are provided at both longitudinal ends of the main surface of the piezoelectric actuator 140 on the support frame 120 side, and the piezoelectric actuator 140 is fixed to the support frame 120 by the support fixing portions 151. In addition, a driving fixing portion 152 is provided at the longitudinal center of the main surface of the piezoelectric actuator 140 on the touch panel 160 side, and the touch panel 160 is fixed to the piezoelectric actuator 140 by the driving fixing portion 152. Thereby, the vibration of the piezoelectric actuator 140 is transmitted to the touch panel 160, and an acoustic or haptic feedback signal can be transmitted to the user.

  The supporting fixing portion 151 and the driving fixing portion 152 are formed in a sheet shape or a plate shape by elastic rubber such as silicon rubber, and are applied to the piezoelectric actuator 140, the support frame 120, or the touch panel 160 by applying an adhesive or applying a double-sided tape. It is fixed. The touch panel 160 is a transparent film such as polyester or a resin plate, and is supported by a driving fixing portion 152 of the piezoelectric actuator 140. Further, the peripheral edge of the touch panel 160 is fixed by a frame outside the touch panel input device 100 (not shown).

  FIG. 3 is a plan view showing the configuration of the support frame 120 in which the piezoelectric actuator is installed, including terminal connections. 4A to 4C are a plan view, a front view, and a cross-sectional view showing, in an enlarged manner, one of the slot portions 122 of the support frame 120. FIG. 4C is a view of the cross section 4c shown in FIG. 4A viewed from the direction of the arrow. Since the four slots 122 are equivalent, the slot 122 shown in the lower left in FIG. 3 will be mainly described.

  As shown in FIGS. 3 and 4, terminals 125 a to 127 d are embedded in the support frame 120. The terminals 125a to 127d are preferably made of an elastic metal and are embedded by insert molding when the support frame 120 is molded. For the production of the support frame 120, insert molding including the terminals 125a to 127d is performed. At that time, the terminals 125a to 127d are set in the mold, and the resin plasticized by heating is injected.

  The slot 122 is a penetrating rectangular hole, and the piezoelectric actuator 140 is fixed by the shim plate 148 being embedded in the support frame 120. In the vicinity of the slot 122 where the shim plate 148 is embedded, connection holes 128a to 130d are provided corresponding to the number of connections between the terminals 125a to 127d and the electrodes 145 to 147. The terminals 125a to 127d and the electrodes 145 to 147 are connected to each other by connecting portions 155 in the connection holes 128a to 130d. For the coupling portion 155, a material that can conduct electricity such as solder or conductive adhesive and can couple metal members together is used.

  The piezoelectric actuator 140 is a bimorph type piezoelectric actuator in which laminated flat plate piezoelectric elements are attached to both sides of a shim plate 148. As shown in FIGS. 3 and 4, when the piezoelectric actuator 140 is installed, the electrodes and the piezoelectric bodies are alternately arranged in the order of the electrode 145, the piezoelectric body 140a, the electrode 146, the piezoelectric body 140b, and the electrode 147 from the opening side of the slot portion 122. Are stacked. Note that the unimorph piezoelectric actuator 140 is not suitable because the contraction rate between the piezoelectric body and the metal is different and the unimorph piezoelectric actuator 140 warps during cooling after insert molding.

  As shown in FIG. 4, the electrodes 145 to 147 extend to the terminal side shim plate 148 and are embedded in the support frame 120 together with the shim plate 148 by integral molding, specifically, insert molding. ing. In order to insulate each electrode, an insulating material is used as the shim plate 148, or the shim plate 148 and the electrode are insulated. The electrode 145 is connected to a terminal 125 a embedded in the support frame 120 by a coupling portion 155 at a connection hole 128 a and is also connected to the electrode 147. Further, the electrodes 146 and 147 are connected to terminals 126 a and 127 a embedded in the support frame 120 by a coupling portion 155. Instead of embedding the shim plate 148 in which the electrodes 145 to 147 are extended as in the above example, the electrodes 145 to 147 may be embedded. In that case, a metal shim plate may be used as the electrode 146 as it is.

  Next, a method for manufacturing the piezoelectric actuator unit 110 will be described. FIG. 5 is a flowchart showing a method for manufacturing the piezoelectric actuator unit 110. First, the terminals 125a to 127d and the unpolarized piezoelectric actuator 140 are installed at predetermined positions, and the mold is set (step S1). The terminals 125a to 127d and the electrodes 145 to 147 are arranged in advance so as to be close to each other in the connection holes 128a to 130d. Next, the thermoplastic resin is heated to the glass transition point or higher (300 to 500 ° C.), and the resin is poured into the mold (step S2). If it cools as it is and it cools sufficiently, the support frame 120 is removed from the mold and removed (step S3). In this manner, insert molding of the piezoelectric actuator 140 into the support frame 120 is performed. Steps S1 to S3 are the molding process.

  In the extracted support frame 120, the terminals 125a to 127d and the piezoelectric electrodes 145 to 147 are not connected. In this state, in order to apply a voltage directly to the electrodes 145 to 147 of the piezoelectric actuator 140, the polarization terminals are connected to the piezoelectric electrodes 145 to 147 (step S4). Then, a polarization process is performed using a terminal for polarization as a polarization process (step S5).

  In the polarization treatment, the support frame 120 is heated at a temperature not lower than the Curie temperature of the piezoelectric bodies 140a and 140b and not higher than the glass transition point of the resin forming the support frame 120, and a DC voltage is applied. Thereby, piezoelectricity is expressed in the piezoelectric body insert-molded in the support frame 120. The heating temperature is preferably about 200 ° C. The direction of voltage application during polarization will be described later. When the polarization process is completed, the terminals for polarization are removed from the electrodes 145 to 147, and the driving terminals 125a to 127d are connected as a connection process (step S6). At this time, electrical wiring is performed through the connection holes 128 a to 130 d opened in the support frame 120.

  Finally, the piezoelectric actuator unit 110 can be manufactured by fixing the touch panel 160 to the driving fixing portion 152 of each piezoelectric actuator (step S7). Thus, the piezoelectric function is developed by insert-molding the unpolarized piezoelectric actuator 140 to form the support frame 120 and then performing the polarization process. Thereby, depolarization of the piezoelectric bodies 140a and 140b due to heating during molding can be prevented.

  Further, in the above example, the terminals 125a to 127d and the electrodes 145 to 147 are connected after the polarization treatment. However, the terminals 125a to 127d and the electrodes are formed by insert molding after being previously connected before the molding process. 145 to 147 may be embedded in the support frame 120.

  Next, the direction of voltage application during polarization processing and driving will be described. FIG. 6A is a schematic diagram illustrating the piezoelectric actuator 140 and applied voltage during polarization, and FIGS. 6B and 6C are schematic diagrams illustrating the piezoelectric actuator 140 and applied voltage during driving. As shown in FIG. 6A, during the polarization process, a DC voltage is applied in the same direction to any of the piezoelectric bodies 140a and 140b arranged on both surfaces of the shim plate 148. As a result, the polarization direction of the piezoelectric body 140a and the polarization direction of the piezoelectric body 140b are the same.

  When the piezoelectric actuator 140 is driven after the polarization processing, as shown in FIGS. 6B and 6C, a voltage is applied to the piezoelectric body 140a in the same direction (or reverse direction) as that during polarization. In addition, a voltage is applied to the piezoelectric body 140b in the opposite direction (or the same direction) as that during polarization. Such a voltage application direction may be adjusted when wiring the terminals 125a to 127d and the electrodes 145 to 147 connected in advance to a predetermined power source, or the voltage is applied as such on the power source side. The wiring may be adjusted as described above.

It is the schematic which shows the structure of the touchscreen type input device which concerns on this invention. (A), (b) It is the top view and front view which show schematic structure of the piezoelectric actuator unit which concerns on this invention. It is a top view which shows the structure of the support frame in which the piezoelectric actuator which concerns on this invention was installed including a terminal connection. (A)-(c) It is the top view, front view, and sectional drawing which expanded and showed one of the slot parts of the support frame which concerns on this invention. It is a flowchart which shows the manufacturing method of the piezoelectric actuator unit which concerns on this invention. (A) Schematic diagram showing piezoelectric actuator and applied voltage during polarization, (b) (c) Schematic diagram showing piezoelectric actuator and applied voltage during driving.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Touch panel type input device 110 Piezoelectric actuator unit 120 Support frame 122 Groove hole part 125a-127d Terminal 128a-130d Connection hole part 140 Piezoelectric actuator 140a, 140b Piezoelectric body 145-147 Electrode 148 Shim plate 151 Support fixing part 152 For drive Fixed part 155 Coupling part 160 Touch panel 170 Touch panel circuit 180 Digital signal processor 190 Class D amplifier

Claims (7)

A piezoelectric actuator unit that is incorporated in a touch panel type input device and transmits vibration to a contact object,
A piezoelectric actuator that vibrates in response to input by contact;
A support frame that is formed of a thermoplastic resin and supports the piezoelectric actuator by embedding a part of the piezoelectric actuator by integral molding;
A piezoelectric actuator unit comprising: a touch panel to which vibration is transmitted from the piezoelectric actuator.   2. The piezoelectric actuator unit according to claim 1, wherein the support frame is formed of a thermoplastic resin having a glass transition temperature higher than a polarization temperature of a piezoelectric body constituting the piezoelectric actuator.   The piezoelectric actuator unit according to claim 1, wherein the resin forming the support frame has a glass transition point of 200 ° C. or higher.   4. The piezoelectric actuator unit according to claim 1, wherein the piezoelectric actuator is a bimorph type piezoelectric actuator. 5. A method of manufacturing a piezoelectric actuator unit that is incorporated in a touch panel type input device and transmits vibration to a contact object,
A molding step of integrally molding the piezoelectric actuator and a support frame that supports the piezoelectric actuator so as to embed a part of the piezoelectric actuator in a resin;
A method of manufacturing a piezoelectric actuator unit, comprising: a polarization step of performing polarization processing on the piezoelectric body of the piezoelectric actuator after the molding step.   6. The method of manufacturing a piezoelectric actuator unit according to claim 5, wherein the driving terminal and the electrode of the piezoelectric actuator are connected and arranged in advance before the molding step. In the molding process, the terminal is embedded in the support frame,
6. The method of manufacturing a piezoelectric actuator unit according to claim 5, further comprising a connecting step of connecting the terminal to the piezoelectric actuator after the polarization step.

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