JP5423295B2 - Ultrasonic transducer - Google Patents

Description

  The present invention relates to an ultrasonic transducer that transmits or receives ultrasonic waves by driving a piezoelectric body.

  As an ultrasonic transducer for aerial use, a piezoelectric element is joined to the bottom of a bottomed cylindrical case to form a diaphragm, and the piezoelectric element is spread and driven in vibration mode, causing the case bottom to bend and vibrate to generate ultrasonic waves. Is known (for example, see Patent Document 1). Such an ultrasonic transducer is manufactured by attaching a piezoelectric element to the bottom surface of a case with an adhesive. In this case, if the amount of adhesive or the bonding position varies, there is a problem that the transmission / reception accuracy of ultrasonic waves varies. In order to suppress variations in the adhesive, it is necessary to carry out the bonding process after precisely setting the pressing conditions using a dedicated pressing jig. At this time, if a foreign substance is caught in the adhesive, the piezoelectric element is cracked, so that it is necessary to manage the foreign substance and flatness of the component.

In addition, as an ultrasonic transducer for aerial use, the piezoelectric element, a cylindrical base provided with a recess for housing the piezoelectric element, and the outer surface of the piezoelectric element and the outer surface of the base are covered from the outside of the base. An ultrasonic sensor provided with an exterior material made of a resin is known. This ultrasonic transducer spreads a piezoelectric element and drives it in a vibration mode, thereby bending vibration of the exterior material and oscillating ultrasonic waves. (For example, refer to Patent Document 2).
FIG. 1A is a cross-sectional view for explaining an exterior material forming process in a conventional ultrasonic transducer, and FIG. 1B is a plan cross-sectional view. In the exterior material molding step, the ultrasonic transducer 101 in a state where the piezoelectric element 103, the base 104, the weight 102, and the sound absorbing material 105 are combined is placed in the mold 111. Then, resin is injected and cured in the gap in the mold 111 to form the exterior material 106, and the outside of the piezoelectric element 103 and the base 104 is molded with the exterior material 106. Thereafter, the ultrasonic transducer 101 is manufactured by extracting from the mold 111.

Japanese Utility Model Publication No. 09-284896 WO2007 / 102460 publication

In the ultrasonic transducer configured to cover the piezoelectric element 103 with the exterior material 106, the piezoelectric element 103 and the exterior material 106 can be joined with the resin used as the exterior material 106 without using an adhesive. Variation problems can be avoided. However, since the exterior material 106 is molded using the mold 111, a new problem arises.
For example, in order to create the exterior material 106, the mold 111 is separately required, and the process becomes complicated. In addition, the exterior material 106 is formed by filling a resin between the mold 111, but if the gap between the base 104 and the mold 111 is too narrow, the resin does not flow easily. There is a limit to reducing the thickness of the ultrasonic transducer, and there is a limit to miniaturization as an ultrasonic transducer.

  In the ultrasonic transducer, it is effective to cause the piezoelectric element 103 and the exterior material 106 to bend and vibrate at a desired resonance frequency. In order to adjust the frequency, the exterior material 106 is cut after the resin is cured. Sometimes. When the frequency is adjusted by cutting the exterior material 106, the frequency can be adjusted only in the direction in which the frequency decreases, and the adjustment to increase the frequency cannot be performed. Further, it takes a long time to remove the cutting time and cutting waste.

  In view of the above problems, the present application does not use an adhesive or the like for bonding the piezoelectric element to the vibration plate portion, and can be made smaller and less expensive than conventional ones, and can expand the degree of freedom of frequency adjustment. An object is to provide an ultrasonic transducer for use.

The ultrasonic transducer according to the present invention includes a diaphragm portion and a cylindrical support portion. The diaphragm vibrates along the principal surface normal direction. The cylindrical support portion has a hole axis along the main surface normal direction of the diaphragm portion. The vibration plate portion includes a piezoelectric element and a cured resin, and the piezoelectric element closes the inside of the cylindrical support portion at a position away from the end portion in the main surface normal direction of the cylindrical support portion, and in a spreading vibration mode. Driven. The cured resin is injected and cured in the cylinder in the main surface normal direction rather than the piezoelectric element in the cylindrical support portion.
In this configuration, the cured resin and the piezoelectric element form a diaphragm, and the piezoelectric element spreads and vibrates, whereby the entire diaphragm is vibrated. The cured resin is molded using the cylindrical support portion as a resin molding die, and a mold is unnecessary. Therefore, the manufacturing cost can be reduced and an ultrasonic transducer smaller than the conventional one can be obtained. In addition, by controlling the amount of resin injected during resin molding, adjustment for lowering the frequency of ultrasonic waves and adjustment for increasing the frequency can be realized, and the degree of freedom in frequency adjustment can be increased.

The cylindrical support part of this invention is equipped with the resin support member and the space formation member . The resin support member is injected and cured with a cured resin. The space forming member forms a vibration space of the diaphragm portion. In this configuration, since the resin support member and the space forming member are provided separately, each molding is easy and the manufacturing cost can be reduced.

The space forming member of the present invention is made of a material having a specific gravity heavier than that of the cured resin and the resin support member . In this configuration, since the periphery of the resin support member is held by the space forming member having a higher specific gravity than that, unnecessary vibration is hardly transmitted to the space forming member, and reverberation can be suppressed.

  It is preferable that the cylindrical support portion of the present invention includes a thin portion in the vicinity of the connection position with the piezoelectric element. If the cylindrical support portion firmly fixes the piezoelectric element, the amplitude of the vibration portion may be reduced. However, by providing a thin portion, the amplitude of the vibration plate portion can be increased.

  According to the present invention, in the ultrasonic transducer in which the entire vibration plate portion bends and vibrates, the cured resin can be molded using the cylindrical support portion as a resin molding die without using an adhesive or a mold. Therefore, since no adhesive or the like is used for joining the piezoelectric element to the diaphragm portion, it is possible to suppress variations in transmission / reception accuracy caused by variations in the application of the adhesive. In addition, since a mold is not used, the manufacturing process is facilitated and a small ultrasonic transducer can be easily created.

  Furthermore, the frequency of the ultrasonic wave can be controlled by the amount of resin filled in the cylindrical support part, and not only the adjustment for lowering the frequency but also the adjustment for raising the frequency can be performed, which increases the degree of freedom of frequency adjustment. It becomes possible.

It is a figure explaining the manufacturing process of the ultrasonic transducer of a prior art example. It is a figure explaining an example of composition of an ultrasonic transducer concerning a 1st embodiment of the present invention. It is a figure which illustrates the manufacturing process of the ultrasonic transducer of FIG. It is a figure explaining the frequency adjustment example of an ultrasonic wave. It is a figure explaining the example of composition of the ultrasonic transducer concerning other embodiments of the present invention.

  Hereinafter, an ultrasonic transducer according to an embodiment of the present invention will be described.

FIG. 2A is a schematic cross-sectional view of the ultrasonic transducer 1 according to this embodiment, and FIG. 2B is a schematic plan view of the ultrasonic transducer 1.
The ultrasonic transducer 1 is used for automobile back sonar, corner sonar, parking spot, etc., and is used as a transmitter for transmitting ultrasonic waves to a target or a receiver for detecting reflected waves from a target. Used for devices.

  The ultrasonic transducer 1 includes an element base 2, a piezoelectric element 3, a cured resin 4, a weight 5, a mounting base 6, a sound absorbing material 7, driving terminals 8A and 8B, and mounting terminals 9A and 9B. The element base 2 as a resin support portion has a shape in which an opening is partially provided in a bottomed cylindrical bottom portion. The piezoelectric element 3 has a disk shape whose polarization direction is the normal direction of the main surface, and is provided at a position that closes the bottom opening in the cylinder of the element base 2. The cured resin 4 is filled in the cylinder of the element base 2. The piezoelectric element 3 and the cured resin 4 function as a diaphragm, and bend and vibrate in the normal direction of the principal surface by driving the piezoelectric element 3 in a spreading mode. The weight 5 as a space forming member has a bottomed cylindrical shape, and supports the element base 2 by securing a vibration space of the vibration plate portion on the side opposite to the main surface normal direction of the piezoelectric element 3. The weight 5 is made of a material such as a metal having a higher specific gravity than the element base 2 and the cured resin 4, and can prevent unnecessary vibrations from being transmitted through the space forming member, thereby suppressing reverberation. The mounting base 6 has a cylindrical shape made of an easily processable material, and supports the weight 5. The element base 2, the weight 5, and the mounting base 6 have a bottomed cylindrical shape as a whole, and constitute the cylindrical support portion of the present invention. The sound absorbing material 7 is disposed in the vibration space and suppresses reverberation in the vibration space. The drive terminal 8A is soldered to an external electrode (not shown) provided on the upper surface of the piezoelectric element 3. The drive terminal 8B is soldered to an external electrode (not shown) provided on the lower surface of the piezoelectric element 3. The mounting terminal 9A protrudes from the side surface of the mounting base 6 so as to be flush with the bottom surface of the mounting base 6, and is connected to the drive terminal 8A. The mounting terminal 9B protrudes from the side surface of the mounting base 6 so as to be flush with the bottom surface of the mounting base 6, and is connected to the drive terminal 8B.

  When the ultrasonic transducer 1 is used as a wave transmitter, the mounting terminals 9A and 9B are connected to the driving electrodes of the set substrate and a driving signal is applied. As a result, an electric field is applied in the polarization direction (main axis direction) of the piezoelectric element 3, and spreading vibration is generated in which the piezoelectric element 3 expands and contracts in the radial direction. Then, the vibration plate portion formed by the piezoelectric element 3 and the cured resin 4 undergoes bending vibration, and ultrasonic waves are transmitted. When used as a wave receiver, the piezoelectric element 3 receives an ultrasonic wave and vibrates, so that a received signal is generated between the drive terminals 8A and 8B.

  In this configuration, the piezoelectric element 3 and the drive terminals 8A and 8B have a drip-proof structure that is covered by the element base 2 and the cured resin 4, and have high environmental resistance against water drops and moisture. In addition, the dimension of the piezoelectric element in the direction perpendicular to the main surface normal direction is mainly determined by the wall thickness of the weight 5, and this dimension can be changed according to the product.

  Next, the manufacturing process of the ultrasonic transducer 1 will be described.

FIG. 3 is a diagram for explaining a state in the manufacturing process of the ultrasonic transducer 1.
FIG. 3A is a state diagram in the mounting terminal equipment step. In this process, a mounting base 6 is prepared, and mounting terminals 9A and 9B are mounted in the mounting base 6 by insert molding. Following this process, the weight equipment process is performed.

  FIG. 3B is a state diagram in the weight mounting process. In this step, a weight 5 provided with a hole for inserting a rod-shaped wiring is prepared, and the weight 5 is mounted on the mounting base 6 from the principal surface normal direction while inserting the rod-shaped wiring into the hole of the weight 5. Following this process, a sound-absorbing material installation process is performed.

  FIG. 3C is a state diagram in the sound absorbing material installation process. In this step, the sound absorbing material 7 is prepared and adhered to a position in the vibration space of the weight 5 with an adhesive or the like. Subsequent to this process, an element base equipment process is performed.

  FIG. 3D is a state diagram in the element base installation process. In this step, the element base 2 is prepared, and the element base 2 is mounted on the weight 5 from the main surface normal direction. As shown in FIG. 2B, the inner shape of the element base 2 is a substantially cylindrical shape having inner grooves at two locations, and is mounted on the weight 5 while inserting a bar-like wiring into the inner groove. Following this process, a piezoelectric element mounting process is performed.

  FIG. 3E is a state diagram in the piezoelectric element mounting process. In this step, first, the drive terminals 8A and 8B are solder-connected to both surfaces of the piezoelectric element 3 to form a structure having a plan view shape on the right hand side in the drawing. Then, this structure is mounted on the element base 2 so that the rod-shaped wiring enters the holes provided in the drive terminals 8A and 8B. Then, the drive terminals 8A and 8B are each solder-connected to the rod-like wiring. Subsequent to this step, a resin filling and curing step is performed.

  FIG. 3F is a state diagram in the resin filling and curing step. In this step, a liquid resin is dropped into a dish-shaped space composed of the element base 2 and the piezoelectric element 3 and filled to the edge of the element base 2. Next, the liquid resin is heated and cured using a heating device to produce a cured resin 4.

  Potting equipment can be used in the resin filling and curing process, and the manufacturing cost can be reduced compared to using a mold and filling equipment. In addition, by controlling the amount of resin to be injected, adjustment that lowers the frequency of ultrasonic waves and adjustment that increases the frequency can be realized.

Next, an example of ultrasonic frequency adjustment will be described.
4A is a partial perspective view of the ultrasonic transducer 11, FIG. 4B is a cross-sectional view, and FIG. 4C is a graph showing an analysis result. Here, the analysis is performed by the ultrasonic transducer 11 having a configuration different from that of the above embodiment. In addition, the same code | symbol is attached | subjected to the structure equivalent to the ultrasonic transducer 1 shown in FIG. 2, and description is abbreviate | omitted.

  In this analysis, the frequency of the ultrasonic wave was detected when the thickness (resin thickness T) in the principal surface normal direction of the vibration plate portion made of the cured resin 4 and the piezoelectric element 3 was changed. When the resin thickness T was 0.20 mm, 0.25 mm, 0.30 mm, 0.35 mm, and 0.40 mm, the ultrasonic frequencies changed to about 27 kHz, 30 kHz, 33 kHz, 37 kHz, and 41 kHz, respectively. From this, it can be said that the frequency of the ultrasonic number can be arbitrarily set by controlling the resin thickness T. Therefore, it is possible to adjust the frequency by increasing the resin thickness T and increasing the resin thickness T in the resin filling and curing process, and lowering the frequency by decreasing the resin thickness T and decreasing the resin thickness T. Adjustments can be made. For example, it is possible to adjust the frequency by filling the resin less than the amount of resin assumed in the resin filling and curing step, performing frequency measurement, and additionally filling the insufficient amount of resin.

  Next, another embodiment of the present invention will be described.

  FIG. 5A is a cross-sectional view of the ultrasonic transducer 21. The ultrasonic transducer 21 is configured to be integrated with the weight 25 without the mounting base 6 in the ultrasonic transducer 1 of the above-described embodiment.

  In this configuration, since the mounting terminals 9A and 9B are attached to the weight 25 made of a material such as a metal having a large specific gravity, additional processing is required for the weight 25, but the number of parts can be reduced.

FIG. 5B is a cross-sectional view of an ultrasonic transducer 31 presented as a reference example for understanding the present invention . The ultrasonic transducer 31 is configured to be integrated with the element base 32 by omitting the weight 25 in the ultrasonic transducer 21 of the above-described embodiment.

  In this configuration, the element base 32 is made of a material such as a metal having a large specific gravity, thereby realizing a function of reflecting ultrasonic waves due to the weight. However, in that case, in addition to the additional processing for attaching the mounting terminals 9A and 9B to the element base 32, it is necessary to perform additional processing for configuring the vibration space of the diaphragm portion. The score can be reduced.

FIG. 5C is also a cross-sectional view of the ultrasonic transducer 41 presented as a reference example for understanding the present invention . The ultrasonic transducer 41 includes an element base 42 in which a thin portion 40 is formed in the vicinity of the connection position with the piezoelectric element 3 instead of the element base 32 in the ultrasonic transducer 31 of the above-described embodiment. The thin portion 40 is provided around the outer periphery of the element base 42.

Even thus the piezoelectric element to the metal element based has been firmly fixed, weaken Thus the restraint in the thin portion, to increase the amplitude of the bending vibration of the cured resins and Contact piezoelectric element it can.

  FIG. 5D is a plan view illustrating a configuration example of the distance measuring device 51. The distance measuring device 51 uses ultrasonic transducers 52 and 53 having substantially the same shape as the ultrasonic transducer 1 described above as a transmitter and a receiver, and the ultrasonic transducers 52 and 53 have a common weight. 55 (and a common mounting base).

DESCRIPTION OF SYMBOLS 1,11,21 ... Ultrasonic transducer 2 ... Element base 3 ... Piezoelectric element 4 ... Hardened resin 5 ... Weight 6 ... Mounting base 7 ... Sound absorption material 8A, 8B ... Drive terminal 9A, 9B ... Mounting terminal

Claims (2)

An ultrasonic transducer comprising: a diaphragm portion that vibrates along a main surface normal direction; and a cylindrical support portion having a hole axis along the main surface normal direction,
The diaphragm portion closes the inside of the cylindrical support portion at a position away from an end portion in the principal surface normal direction of the cylindrical support portion, and the piezoelectric element driven in a spreading vibration mode; A cured resin injected and cured in the cylinder in the principal surface normal direction than the piezoelectric element in the cylindrical support portion , and
The cylindrical support portion includes a resin support member into which the curable resin is injected and cured, and a space forming member that is made of a material having a higher specific gravity than the resin support member and forms a vibration space of the diaphragm portion. Ultrasonic transducer. The ultrasonic transducer according to claim 1 , wherein the cylindrical support portion includes a thin portion in the vicinity of a connection position with the piezoelectric element.

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