JPH0548497U - Electro-acoustic transducer - Google Patents

Abstract

(57) [Summary] [Object] To provide an electroacoustic transducer which can be easily assembled, can maintain reliable electrical connection and good sound pressure characteristics, and can be miniaturized. In an electroacoustic transducer, a piezoelectric element 1 is arranged between a conductor layer 7 extending from an outer peripheral portion of a metal diaphragm 4 onto an electrode 5a of a piezoelectric ceramic 5 and between the conductor layer 7 and the electrode 5a. And an insulating layer 6. A conductive coating film 19 of silver, solder or the like is formed between the conductor layer 7 and the outer peripheral portion of the metal diaphragm 4.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an electroacoustic transducer, particularly an electroacoustic transducer using a piezoelectric ceramic.

[0002]

[Prior art]

 In a piezoelectric acoustic transducer having a structure in which a piezoelectric element to which a piezoelectric ceramic and a metal diaphragm are bonded is housed and held in a case, a pair of silver-plated silver plating is used as a structure in which electrodes of the piezoelectric ceramic are connected to an external drive circuit. A structure is adopted in which the spring terminals with the are attached to the case. (Actual exploitation No. 64-54498, No. 2-103997). In this case, the base portion of the spring terminal penetrates the case and is led out to the outside, and the lead-out portion is connected to the external drive circuit.

The tip portion of one spring terminal is electrically connected by elastically contacting the exposed electrode of the piezoelectric ceramic. The other spring terminal is electrically connected to the other electrode of the piezoelectric ceramic through the metal diaphragm by elastically pressing the tip of the spring terminal against the metal diaphragm such as 42 alloy.

In order to reduce the size of the piezoelectric sounding body, the applicant first formed a conductor layer of carbon or the like extending from the outer peripheral portion on the metal diaphragm side to the electrode of the piezoelectric ceramic, and We have proposed an electroacoustic transducer in which the tip of the other spring terminal is pressed against the conductor layer.

[0005]

[Problems to be solved by the device]

 However, in the above-described electroacoustic transducer, in particular, the electrical adhesion of the conductor layer that is in pressure contact with the tip of one spring terminal is not sufficient, causing variations in characteristics.

In order to form the conductor layer extending to the electrode of the piezoelectric ceramic, it is formed after the piezoelectric ceramic having the electrode is adhered on the metal vibration plate, and therefore it is required to be processed at a high temperature. I can't. For this reason, the insulating layer for ensuring the insulation between the electrodes of the piezoelectric ceramic and the conductor layer and the conductor layer have been formed by a relatively low temperature treatment of less than 150 ° C. For this reason, in particular, the adhesiveness at the portion connected to the metal vibration plate was lacking, and the above-mentioned characteristic scatter occurred.

The inventor of the present invention connects three electroacoustic transducers, in which lead wires are soldered to the electrodes and conductor layers of the piezoelectric ceramic, instead of the spring terminals, and further connects the resistors R in series to connect all of them. A voltage of 1 V was applied to the body, and the voltage of both terminals of the electroacoustic transducer part in which three elements were connected in series was examined by leaving it in a wet condition. As a result, it was confirmed that the terminal voltage suddenly increased after 1 hour and stable characteristics could not be obtained.

The object of the present invention was devised in view of the above-mentioned problems, and an object thereof is to provide an electroacoustic transducer capable of maintaining stable characteristics with respect to environmental changes. is there.

[0009]

[Means for Solving the Problems]

 An electro-acoustic transducer according to the present invention comprises a piezoelectric ceramic having first and second electrodes on both main surfaces, and a metal vibration plate attached to the piezoelectric ceramic so as to be electrically connected to the first electrode. A piezoelectric element having a conductor layer extending from the outer peripheral portion of the metal diaphragm to the second electrode of the piezoelectric ceramic as an underlying layer of an insulating layer, and the tip end elastically pressure-contacting the second electrode. An electroacoustic transducer comprising a first spring terminal electrically connected and a second spring terminal electrically connected by elastically pressure contacting a tip portion of the conductor layer with the conductor layer. And a surface of the metal diaphragm, a conductive coating film made of silver, solder, or a metal containing them as a main component is formed.

[0010]

[Action]

 In the electro-acoustic transducer according to the present invention, a conductive coating film made of a kind of silver or solder is provided between the conductor film extending from the outer periphery of the metal diaphragm to the electrodes of the piezoelectric ceramic and the outer periphery of the metal diaphragm. Are formed. In particular, since a conductive coating film made of a kind of silver, solder or the like can be formed on the outer peripheral surface of the metal diaphragm before bonding the piezoelectric ceramic, a method that is not restricted by temperature or other conditions, such as plating, The conductive coating film can be formed by baking. Therefore, the conductive coating film and the metal diaphragm can be firmly adhered to each other, and the conductive coating film can be made rougher than the surface of the 42 alloy metal diaphragm. Even if the conductor layer formed on the roughened conductive coating film is formed at a relatively low temperature, the adhesion is improved. As a result, a stable electrical connection state can be achieved, and an electroacoustic transducer with stable characteristics and less variation in characteristics can be achieved.

[0011]

【Example】

 1 and 2 show a piezoelectric acoustic transducer as an embodiment of the present invention. In the figure, this piezoelectric acoustic transducer is mainly composed of a piezoelectric element 1 and a front case 2 and a rear case 3 that house the piezoelectric element.

The piezoelectric element 1 has a metal diaphragm 4 and a piezoelectric ceramic 5 attached to the back surface of the metal diaphragm 4. The metal vibrating plate 4 is made of 42 alloy, for example, and is formed in a disc shape having a thickness of 100 μm and a diameter of 32 mm. The piezoelectric ceramic 5 has electrodes formed on both sides thereof of a thick conductor film made of a material mainly composed of silver, and the first electrode (not shown) is electrically connected to the metal diaphragm 4 by adhesion. ing.

As shown in FIG. 3, on the surface of the piezoelectric element 1, an insulating layer 6 and a conductor layer 7 are arranged in a laminated state. The conductor layer 7 is electrically connected at its outer peripheral side to the metal diaphragm 4, and extends from that part to the second electrode 5a of the piezoelectric ceramic 5 (surface side electrode shown in the figure: hereinafter simply referred to as electrode) 5a. ing. Further, the insulating layer 6 is interposed between the conductor layer 7 and the piezoelectric ceramic 5, whereby the conductor layer 7 and the electrode 5a are electrically insulated. The insulating layer 6 is made of, for example, an epoxy resin or an acrylic resin, and an ultraviolet curable resin is advantageous in manufacturing. The conductor layer 7 is made of, for example, a mixture of silver, graphite, carbon and the like in a phenol resin or an epoxy resin. Both layers 6 and 7 are formed by screen printing, for example, and the film thickness is preferably 10 to 20 μm.

The front case 2 is made of aluminum, and is formed in a cap shape that opens toward the rear case 3 side as shown in FIG. The outer peripheral edge of the surface case 2 is a caulking portion, and the caulking portion 8 integrally fixes the piezoelectric ceramic 1 and the two cases 2 and 3. The piezoelectric ceramic 1 is fixed by sandwiching only the outer peripheral portion between the caulking portion 8 of the front case 2 and the rear case 3.

The back case 3 is made of resin and is formed into a substantially disc shape. The back case 3 has a recess 9 that opens toward the front case 2, and a sound leakage hole 10 is formed in the bottom surface of the recess 9. The sound leak hole 10 is covered with an acoustic resistance cloth 11 made of Teflon mesh or nylon mesh attached to the bottom surface of the recess 9.

The base portion 16 of the first and second spring terminals 12 and 13 is fixed to the bottom surface of the back case 3. Through holes 14 are formed in the back case 3 at positions corresponding to the base portions 16 of the spring terminals 12 and 13, and the lead-out portions 15 of the spring terminals 12 and 13 pass through the through holes 14. The lead-out portion 15 is fixed in the through hole 14 with an adhesive or the like, and its tip extends outward so that it can be connected to an external drive circuit (not shown).

The spring terminals 12 and 13 each have a tip portion 17 extending from the base portion 16 in a slightly curved state, and the tip of the tip portion 17 has a contact 18. As shown in FIG. 3, both spring terminals 12 and 13 extend to the conductor layer 7 side. The contact 18 of the first spring terminal 12 is in contact with the electrode 5a, and the contact 18 of the second spring terminal 13 is in contact with the conductor layer 7. The spring properties of the tips 17 of the spring terminals 12 and 13 are maintained.

Here, as shown in FIG. 4, the present invention is characterized in that, on the surface of the metal vibrating plate 4, silver, solder, or one of silver or solder is formed at a portion where the conductor layer 7 is formed. That is, an alloy as a main component such as Ag-Pd or a laminated body including them, for example, a conductive coating film 19 including a copper layer as a base and a solder layer on the surface is formed.

The conductive coating film 19 is formed by a plating method or a baking method by applying and baking a conductive paste. The conductive coating film 19 may be at least 1 μm or more.

The material of the above-mentioned conductive coating film 19 is formed of silver, graphite, carbon or the like because the conductive layer 7 is formed of a conductive resin paste. Solder or the like is selected.

When assembling the above electroacoustic transducer, first, the conductive coating film 19 is formed on the outer peripheral portion or the entire surface of the metal diaphragm 4 by the above method.

Next, the piezoelectric ceramic 5 and the metal vibrating plate 4 are bonded together, and the insulating layer 6 and the conductor layer 7 are formed by screen printing or the like to form the piezoelectric element 1. In particular, since the conductor layer 7 is formed after the piezoelectric ceramic 5 and the metal diaphragm 4 are bonded to each other, the high temperature treatment cannot be performed due to the bonding reliability between the piezoelectric ceramic 5 and the metal diaphragm 4 and other restrictions. It is dried and cured at a relatively low temperature of 130 to 150 ° C. using a conductive resin paste.

Next, the acoustic resistance cloth 11 is attached to the sound leakage hole 10 of the back case 3. Further, the spring terminals 12 and 13 whose surfaces are silver-plated or solder-plated are fixed to the back case 3 with an adhesive or the like. Then, the piezoelectric element 1 and the back surface case 3 are inserted into the front surface case 2, and the caulking portion 8 is caulked to be integrated.

In this case, it is not necessary to connect the spring terminals 12 and 13 to the piezoelectric element 1 by soldering or the like, and the contact of the spring terminals 12 and 13 with the electrode 5a and the conductor layer 7 is surely maintained. It Therefore, according to this embodiment, the assembling is easy, and the reliable electrical connection which is not easily influenced by the environment can be maintained.

Further, in this case, the conductor layer 7 extends from the outer peripheral portion of the metal diaphragm 4 onto the electrode 5 a, and the second spring terminal 13 is connected to the metal diaphragm 4 via the conductor layer 7. It As a result, it is not necessary to provide a large gap between the piezoelectric ceramic 5 and the back case 3 to bring the second spring terminal 13 into contact with the metal vibrating plate 4. Therefore, according to this embodiment, the diameters of the piezoelectric ceramic 5 and the metal vibrating plate 4 and the cases 2 and 3 can be reduced, and the electroacoustic transducer as a whole can be downsized while maintaining the sound pressure characteristics. Can be achieved. In particular, since the conductor layer 7 in pressure contact with the contact 18 of the second spring terminal 12 is formed by disposing the insulating layer 6 as a base layer, no short circuit with the electrode 5a of the piezoelectric ceramic 5 occurs. Further, a conductive coating film 19 is formed as a base layer between the conductor layer 7 and the metal diaphragm 4.

Therefore, the metal diaphragm 4, the conductive coating film 19 and the conductor layer 7 can maintain a stable contact state with each other, whereby the contact reliability is greatly improved and the characteristics can be stabilized.

The inventor of the present invention compares the electroacoustic converter in which the conductor layer 7 is directly formed on the metal diaphragm 4 with a conventional product, as shown in FIG. 5A. Each of the electroacoustic transducers was connected in series with a resistor R, and a constant voltage, for example, 1 V was applied between them. Then, the change in the terminal voltage of the three-element electroacoustic transducer when left in the humidity (90% humidity, 60 ° C temperature) was measured.

The results are shown in FIG. 5 (b). The line A in the figure shows the characteristics of the product of the present invention, and the line B shows the characteristics of the conventional product.

With the electro-acoustic transducer of the present invention, the initial voltage of 0. 3v can be stably maintained, whereas in the conventional product, it is less than 0. The voltage value suddenly changes to 38v, and the voltage value is not stable thereafter, and a large variation occurs.

As shown in FIG. 6, the insulating layer 6 and the conductor layer 7 of the piezoelectric element 1 may be formed in an annular shape. In this case, the directionality of the piezoelectric element 1 is lost, so that automatic assembly becomes easier. In this case, the first spring terminal is configured to be shorter than the second spring terminal 13 so that the contact 18 of the first spring terminal 12 is arranged on the inner peripheral side of the insulating layer 6.

[0031]

[Effect of the device]

 As described above, since the conductive coating film made of silver, solder, or the like is formed between the conductor layer with which one spring terminal is in pressure contact and the metal diaphragm, each of the metal diaphragm, the conductive coating film, and the conductor layer is formed. The contact resistance between the layers is lowered, a stable contact state is obtained, and moreover, it can be stably maintained against environmental changes, so the contact reliability is improved. Therefore, according to the present invention, it is possible to realize an electroacoustic transducer that can be easily assembled, can maintain a reliable electrical connection, and can be downsized.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an electroacoustic transducer as one embodiment of the present invention.

FIG. 2 is a vertical sectional view thereof.

FIG. 3 is a bottom view of the piezoelectric element.

FIG. 4 is a partially enlarged sectional view of a piezoelectric element.

5A is a measurement circuit diagram for a contact reliability test, and FIG. 5B is a characteristic diagram showing the measurement result.

FIG. 6 is a diagram corresponding to FIG. 3 of another embodiment.

[Explanation of symbols]

 1 ... Piezoelectric element 2 ... Front case 3 ... Back case 4 ... Metal vibrating plate 5 ... Piezoelectric ceramics 5a ... Electrode 6 ... ... Insulating layer 7 ... Conductor layer 12 ... First spring terminal 13 ... Second spring terminal 18 ... Contact 19 ... Conductive coating film

Claims (1)

[Scope of utility model registration request] 1. A metal vibrating plate is attached with a piezoelectric ceramic having electrodes formed on both main surfaces, and the metal vibrating plate and a part of the piezoelectric ceramic are insulated from the surface side electrode of the piezoelectric ceramic. A piezoelectric element in which a conductor layer is formed so as to straddle, a first spring terminal whose tip portion elastically presses against the surface electrode, and a second spring terminal whose tip portion elastically presses against the conductor layer. In the electro-acoustic transducer, the electro-acoustic film is characterized in that a conductive coating film made of silver, solder, or a metal containing them as a main component is formed between the conductor layer and the surface of the metal diaphragm. converter.