WO2017061422A1

WO2017061422A1 - Ultrasonic transducer

Info

Publication number: WO2017061422A1
Application number: PCT/JP2016/079483
Authority: WO
Inventors: 悠河野
Original assignee: 株式会社村田製作所
Priority date: 2015-10-09
Filing date: 2016-10-04
Publication date: 2017-04-13

Abstract

An ultrasonic transducer (10) is provided with: a tubular bottomed case (20) having a hollow portion (20S) formed therein; and a piezoelectric vibration element (30) that is contained in the hollow portion and is arranged on the inner surface of a case bottom (22) positioned at the bottom surface of the hollow portion. In a cross section parallel with the case bottom, the hollow portion has a shape which is relatively long in one direction and is relatively short in another direction. The bottom (22) is provided with a thick portion (23) and a pair of thin portions (24, 25) positioned at both outer sides, in the relatively long one direction, of the thick portion (23). The piezoelectric vibration element is disposed on the thick portion (23). Of the case (20), a circumferential wall portion (28) of a recessed portion (26) formed by providing the thin portion (24) to the bottom (22) includes, at ends in the relatively short other direction, flat portions (28F1, 28F2) each having a flat planar shape. Accordingly, impact resistance can be improved, and anisotropy of directivity characteristics can also be improved.

Description

Ultrasonic transducer

The present invention relates to an ultrasonic transducer that performs sensing using ultrasonic waves.

As disclosed in Japanese Unexamined Patent Publication No. 2000-032594 (Patent Document 1), an ultrasonic transducer detects an object (obstacle) like various sensors such as a back sonar and a corner sonar of an automobile. It is used as a means for The ultrasonic transducer is attached to, for example, a bumper of an automobile, and the ultrasonic transducer is positioned in the ultrasonic radiation direction so that the bottom of the case is substantially perpendicular to the road surface. In such an ultrasonic transducer, if the ultrasonic transmission / reception range in the horizontal direction is too narrow, a blind spot occurs in the detection range, and if the ultrasonic transmission / reception range in the vertical direction is too wide, reflected waves from the ground are generated. It becomes noise.

In the ultrasonic transducer disclosed in Japanese Patent Application Laid-Open No. 2000-032594 (Patent Document 1), the hollow portion provided in the case has a relatively long difference in one direction and a difference in another direction. Has a relatively short shape, and a thick part and a thin part are provided at the bottom of the case. According to Patent Document 1, according to such an ultrasonic transducer, it is possible to narrow the directivity characteristics of the ultrasonic transducer in a relatively long direction without using an ultrasonic horn, and in a relatively long direction. It states that the anisotropy between the directional characteristic and the directional characteristic in a relatively short direction can be made higher (made more prominent).

Furthermore, in the ultrasonic transducer disclosed in Patent Document 1, the piezoelectric vibration element is fixed to the thick part instead of the thin part of the case. Even when an impact is applied from the outside, the piezoelectric vibration element is prevented from being broken (that is, chipping) due to the presence of the thick portion, and the impact resistance of the ultrasonic transducer is improved. And in patent document 1, since the intensity | strength of a case bottom face can be hold | maintained by a thick part, it is possible to make the thickness of a thin part thinner, and directing by making the thickness of a thin part thinner. It is said that characteristic anisotropy can be made more remarkable.

JP 2000-032594 A

As described above, in the ultrasonic transducer disclosed in Japanese Patent Laid-Open No. 2000-032594 (Patent Document 1), the strength of the bottom surface of the case is maintained by the thick portion, so the thickness of the thin portion is reduced. Thus, the anisotropy of directivity can be made more remarkable. Certainly, by reducing the thickness of the thin part or reducing the thickness of the entire case bottom, the resonance frequency of the vibration system including the case bottom is lowered, and the anisotropy of directivity is made more remarkable. There are cases where it is possible. However, reducing the thickness of the thin wall portion or the entire case bottom may cause a reduction in impact resistance (chipping resistance) of the case bottom.

An object of the present invention is to provide an ultrasonic transducer having a configuration capable of improving impact resistance and improving the anisotropy of directivity characteristics.

An ultrasonic transducer according to the present invention is provided on a bottomed cylindrical case provided with a hollow portion, and on the inner surface of the bottom portion of the case which is housed in the hollow portion and located on the bottom surface of the hollow portion. The hollow portion has a shape that is relatively long in one direction and relatively short in another direction in a cross section parallel to the bottom portion of the case, and the bottom portion has a thick wall. And a pair of thin portions positioned on both outer sides in the one direction that are relatively long with respect to the thick portion, and the piezoelectric vibration element is disposed on the thick portion, Of the case, the peripheral wall portion of the concave portion formed by providing the thin portion at the bottom portion has a flat portion having a flat planar shape at a relatively short end portion in the different direction.

Preferably, in the ultrasonic transducer, the flat portion extends in a direction parallel to the relatively long one direction.

Preferably, in the ultrasonic wave transmitter / receiver, when the case is viewed in plan along the axial direction, the flat portion provided on one thin portion side and the other thin portion side are provided. The plane portion is located on the same straight line.

Preferably, in the ultrasonic transducer, when the case is viewed in plan along the axial direction, the bottom portion of the case has a point-symmetric shape with respect to the center of the thick portion.

In the ultrasonic transducer, preferably, the ratio of the length of the planar portion in the relatively long one direction to the inner diameter of the case is 0.03 or more and 0.27 or less.

According to the above configuration, it is possible to provide an ultrasonic transducer having a configuration capable of improving impact resistance and improving the anisotropy of directivity characteristics.

It is sectional drawing which shows the ultrasonic transducer in embodiment. It is a top view which shows the case and piezoelectric vibration element with which the ultrasonic transducer in embodiment is equipped. FIG. 3 is a sectional view taken along line III-III in FIG. 2. FIG. 4 is a sectional view taken along line IV-IV in FIG. 2. FIG. 5 is a sectional perspective view taken along line VV in FIG. 3. It is a top view which expands and shows the area | region enclosed by VI line | wire in FIG. 6 is a plan view showing a case and a piezoelectric vibration element provided in an ultrasonic transducer in Comparative Example 1. FIG. It is a top view which shows the case for describing and contrasting embodiment and the comparative example 1. FIG. 10 is a plan view showing a case and a piezoelectric vibration element provided in an ultrasonic transducer in Comparative Example 2. FIG. It is a top view which shows the case for describing and contrasting embodiment and the comparative example 2. FIG. It is a top view which shows the case with which the ultrasonic transducer in the modification of embodiment is equipped, and a piezoelectric vibration element. 6 is a table showing conditions and results of experimental examples conducted in the embodiment (Examples 1 to 6) and Comparative Example 1. FIG. 6 is a plan view for explaining conditions of an experimental example conducted with respect to the embodiment (Examples 1 to 6) and Comparative Example 1. 6 is a graph showing results (relationship between L / D and resonance frequency) of experimental examples conducted with respect to the embodiments (Examples 1 to 6) and Comparative Example 1; 6 is a graph showing the results (relationship between L / D and horizontal directivity) of experimental examples conducted with respect to the embodiment (Examples 1 to 6) and Comparative Example 1;

Embodiments will be described below with reference to the drawings. The same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

(Ultrasonic transducer 10)
FIG. 1 is a cross-sectional view showing an ultrasonic transducer 10 according to an embodiment. As shown in FIG. 1, the ultrasonic transducer 10 includes a case 20, a piezoelectric vibration element 30, a lower layer silicone 31, a sound absorbing material 32, a filling silicone 33, an FPC 34, and a lead wire 35. FIG. 2 is a plan view showing the case 20 and the piezoelectric vibration element 30. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a sectional perspective view taken along line VV in FIG.

As shown in FIGS. 2 to 5, the case 20 is made of, for example, aluminum. The case 20 includes a cylindrical portion 21 having a cylindrical shape and a bottom portion 22 having a shape that closes an opening on one side of the cylindrical portion 21 and has a bottomed cylindrical shape as a whole. . A hollow portion 20 S is provided inside the case 20. The hollow portion 20S has a comparatively long passing length in one direction and a comparing length in another direction in a cross section parallel to the bottom portion 22 of the case 20 (cross section perpendicular to the cylindrical axis of the case 20). It has a short shape.

In the present embodiment, one direction is represented by an arrow X in the figure, and another direction is represented by an arrow Y. One direction (arrow X) and the other direction (arrow Y) have a perpendicular relationship with each other. The arrow Z is perpendicular to both the arrows X and Y, and is parallel to the cylinder axis of the case 20.

Based on the viewpoint of widening the transmission / reception range of ultrasonic waves in the horizontal direction and narrowing the transmission / reception range of ultrasonic waves in the vertical direction, the ultrasonic transducer 10 has a relatively long one direction in the vertical installation direction. In addition, it is arranged so that another direction which is relatively short coincides with the horizontal installation direction. That is, the arrow X direction (one relatively long direction) is the vertical installation direction, and the arrow Y direction (a relatively short alternate direction) is the horizontal installation direction. Ultrasonic wave transmission / reception with the bottom portion 22 of the case 20 facing the detection direction so that the long width direction of the hollow portion 20S is substantially perpendicular to the road surface and the short width direction of the hollow portion 20S is substantially parallel to the road surface. The vessel 10 is attached to a vehicle or the like.

The disc-shaped piezoelectric vibration element 30 is accommodated in the hollow portion 20S. The piezoelectric vibration element 30 is disposed on the inner surface of the bottom portion 22 of the case 20 located on the bottom surface of the hollow portion 20S of the case 20, and is bonded to the inner surface. As shown in FIG. 1, one end of the FPC 34 is connected to the piezoelectric vibration element 30, and the other end of the FPC 34 and the lead wire 35 are drawn out to the outside. The lower layer silicone 31, the sound absorbing material 32, and the filling silicone 33 are provided in this order in the case 20 so as to seal the piezoelectric vibration element 30 in the case 20.

(Detailed structure of the bottom 22 of the case 20)
As shown in FIGS. 2 to 5, the bottom portion 22 of the case 20 has a thick portion 23 and a pair of outer portions located on both outer sides in one direction (arrow X direction) that is relatively long with respect to the thick portion 23.

Thin portions

24 and 25 are provided. The piezoelectric vibration element 30 is disposed on the inner surface of the thick portion 23 at the center of the bottom portion 22. In the state where the ultrasonic transducer 10 is mounted on a vehicle or the like, the thick portion 23 having a substantially circular shape is located in the center portion of the bottom portion 22 in the vertical installation direction, and substantially crescent-shaped on both sides in the same direction. The thin-

walled portions

24 and 25 that have been subjected to are positioned.

Accordingly, in the cross section in the vertical installation direction, as shown in FIG. 3, the

thin portions

24 and 25 are respectively located on both sides of the thick portion 23 on which the piezoelectric vibration element 30 is mounted, and the horizontal portion passing through the center of the case 20. In the cross section in the installation direction, the entire bottom portion 22 is a thick portion 23 as shown in FIG. In the present embodiment, the thickness of the thick portion 23 is thicker than the minimum thickness of the cylindrical portion 21 of the case 20, and the thickness of the

thin portions

24 and 25 is the minimum thickness of the cylindrical portion 21 of the case 20. It is thinner than.

Here, the

recesses

26 and 27 are formed by providing the pair of

thin portions

24 and 25 on the bottom portion 22 of the case 20. The

recesses

26 and 27 are located on both outer sides in one direction (arrow X direction) that is relatively long with respect to the thick portion 23. The recess 26 has a bottom surface and a peripheral wall portion 28 (FIGS. 2, 3, and 5). The bottom surface of the recess 26 corresponds to the inner surface of the thin portion 24 in the case 20. Similarly, the recess 27 has a bottom surface and a peripheral wall portion 29 (FIGS. 2, 3, and 5), and the bottom surface of the recess 27 corresponds to the inner surface of the thin portion 25 in the case 20.

(The peripheral wall portion 28 of the recess 26)
FIG. 6 is an enlarged plan view showing a region surrounded by the line VI in FIG. Referring to FIGS. 2, 5 and 6, peripheral wall portion 28 of recess 26 includes an inner curved surface portion 28N, an outer curved surface portion 28G, and a pair of flat surface portions 28F1, 28F2. The inner curved surface portion 28N is a portion located on the inner side in the radial direction in the peripheral wall portion 28, and has a curved surface shape that is entirely curved. The outer curved surface portion 28G is a portion of the peripheral wall portion 28 that is located on the outer side in the radial direction, and has a curved surface shape that is entirely curved.

The flat portion 28F1 is located at one end of the peripheral wall portion 28 in a relatively short different direction (arrow Y direction) and has a flat planar shape. The flat surface portion 28F1 of the present embodiment has an end portion located on one side of the inner curved surface portion 28N and an end portion located on one side of the outer curved surface portion 28G in another relatively short direction (arrow Y direction). It is provided in between and has a rectangular shape consisting of a plane parallel to the XZ plane.

As shown in FIG. 6, when the case 20 is viewed in plan along the axial direction (direction perpendicular to the bottom portion 22 of the case 20), one end of the plane portion 28 F 1 is represented by a point S, The other end portion of the plane portion 28F1 is represented by a point E. As shown in FIG. 6, when the case 20 is viewed in plan along the axial direction, in the ultrasonic transducer 10 of the present embodiment, the plane portion 28 F 1 provided between the point S and the point E is Appears in a straight line. The peripheral wall portion 28 of the recess 26 in the present embodiment includes at least a flat portion 28F1 having such a shape.

2, 5, and 6 again, on the other hand, the flat surface portion 28 F 2 is located at the other end of the peripheral wall portion 28 in another relatively short direction (arrow Y direction) and is flat. It has a flat shape. The flat surface portion 28F2 of the present embodiment has an end portion located on the other side of the inner curved surface portion 28N and an end portion located on the other side of the outer curved surface portion 28G in another relatively short direction (arrow Y direction). It is provided in between. The plane portion 28F2 also has a rectangular shape composed of a plane parallel to the XZ plane, as in the case of the plane portion 28F1.

(The peripheral wall portion 29 of the recess 27)
The peripheral wall portion 29 of the recess 27 includes an inner curved surface portion 29N, an outer curved surface portion 29G, and a pair of flat surface portions 29F1, 29F2. The inner curved surface portion 29N is a portion located on the inner side in the radial direction in the peripheral wall portion 29, and has a curved surface shape that is entirely curved. The outer curved surface portion 29G is a portion located on the outer side in the radial direction in the peripheral wall portion 29, and has a curved surface shape that is entirely curved.

The flat portion 29F1 is located at one end of the peripheral wall portion 29 in another relatively short direction (arrow Y direction), and has a flat planar shape. The flat surface portion 29F1 of the present embodiment has an end portion located on one side of the inner curved surface portion 29N and an end portion located on one side of the outer curved surface portion 29G in another relatively short direction (arrow Y direction). It is provided in between and has a rectangular shape consisting of a plane parallel to the XZ plane.

The flat portion 29F2 is located at the other end of the peripheral wall portion 29 in the relatively short different direction (arrow Y direction), and has a flat planar shape. The flat surface portion 29F2 of the present embodiment has an end portion located on the other side of the inner curved surface portion 29N and an end portion located on the other side of the outer curved surface portion 29G in another relatively short direction (arrow Y direction). It is provided in between and has a rectangular shape consisting of a plane parallel to the XZ plane.

As shown in FIG. 2, the flat portions 28F1, 28F2, 29F1, and 29F2 in the present embodiment all extend in a direction parallel to a relatively long one direction (arrow X direction).

As shown in FIG. 2, when the case 20 is viewed in plan along the axial direction, a flat portion 28F1 provided on one thin portion 24 side and a flat portion 29F1 provided on the other thin portion 25 side. Is located on the same straight line. In the present embodiment, the flat portion 28F2 provided on the one thin portion 24 side and the flat portion 29F2 provided on the other thin portion 25 side are located on the same straight line.

The peripheral wall portion 28 of the recess 26 has a symmetrical shape with respect to a straight line located at the center of the peripheral wall portion 28 in another direction (arrow Y direction) that is relatively short. The peripheral wall portion 29 of the concave portion 27 also has a symmetrical shape with respect to a straight line located at the center of the peripheral wall portion 29 in a relatively short other direction (arrow Y direction).

Furthermore, in the present embodiment, when the case 20 is viewed in plan along the axial direction, the configuration of the bottom portion 22 of the case 20 (thick portion 23,

thin portions

24 and 25,

concave portions

26 and 27, and peripheral wall portion 28). , 29) has a point-symmetric shape with respect to the center of the thick portion 23.

(Function and effect)
In the ultrasonic transducer 10 as described above, for example, one direction in which the width of the hollow portion 20S is relatively long is substantially perpendicular to the road surface, and the direction in which the width of the hollow portion 20S is relatively short is approximately the road surface. The case 20 is attached to a vehicle or the like with the bottom 22 of the case 20 facing the detection direction so as to be parallel. According to this configuration, the transmission / reception range in the vertical installation direction (the direction in which the width of the hollow portion 20S is long) can be narrowed. In particular, even when the ultrasonic transducer 10 is downsized, the transmission / reception range in the vertical installation direction is not easily widened, and a small transmission / reception range can be maintained in the vertical installation direction. As a result, the difference between the transmission / reception range in the horizontal installation direction and the transmission / reception range in the vertical installation direction can be increased, and the anisotropy of the directivity is increased even in the case of the small ultrasonic transducer 10. Can do.

Here, by making the ultrasonic transmission / reception range (that is, the directivity) in the horizontal direction wider, the blind spot in the detection range of the ultrasonic transducer becomes smaller. In order to further widen the directivity in the horizontal direction, a method of reducing the thickness of the

thin portions

24 and 25 or reducing the entire thickness of the bottom portion 22 of the case 20 can be considered. According to these methods, since the resonance frequency of the vibration system including the bottom 22 of the case 20 is lowered, it is possible to widen the transmission / reception range of ultrasonic waves in the horizontal direction.

However, reducing the thickness of the

thin portions

24 and 25 or the entire bottom portion 22 of the case 20 may cause a reduction in impact resistance (chipping resistance) of the bottom portion 22 of the case 20. The piezoelectric vibration element 30 is likely to receive an impact from the outside, and the piezoelectric vibration element 30 may be easily cracked by the external impact. For this reason, when the thickness of the

thin portions

24 and 25 or the entire bottom portion 22 of the case 20 is reduced, it is difficult to put into practical use a small ultrasonic transducer having large anisotropy. Alternatively, considering the shock resistance of the ultrasonic transducer 10, there is a limit to reducing the thickness of the

thin portions

24 and 25 or the entire bottom portion 22 of the case 20, and sufficient anisotropy is obtained. I can't.

On the other hand, in the ultrasonic transducer 10 in the embodiment, the

peripheral wall portions

28 and 29 of the

concave portions

26 and 27 formed by providing the

thin portions

24 and 25 on the bottom portion 22 are flat surfaces having a flat planar shape. Portions 28F1, 28F2, 29F1, and 29F2 are provided. These flat portions 28F1, 28F2, 29F1, and 29F2 are located at both ends of the

peripheral wall portions

28 and 29 in a relatively short different direction (arrow Y direction).

When the technical idea of providing the flat portions 28F1, 28F2, 29F1, 29F2 at the ends of the

peripheral wall portions

28, 29 in a relatively short other direction is adopted, the

thin portions

24, 25 of the bottom portion 22 are considered in product design. It becomes easier to increase the volume occupied. When the volume occupied by the thin-

walled portions

24 and 25 is increased, the proportion occupied by the thick-walled portion 23 is relatively reduced, and the resonance frequency of the vibration system including the bottom portion 22 of the case 20 is lowered. The wave range can be expanded. Therefore, the ultrasonic transducer 10 having high anisotropy in the horizontal installation direction and the vertical installation direction can be put into practical use.

Hereinafter, while comparing the embodiment with Comparative Examples 1 and 2, in the case of the embodiment, the volume occupied by the

thin portions

24 and 25 in the bottom portion 22 can be increased (the rigidity of the bottom portion 22 as a whole can be reduced). ) More specifically.

(Comparative Example 1)
FIG. 7 is a plan view showing the case 20Y and the piezoelectric vibration element 30 provided in the ultrasonic transducer in the first comparative example. In the case 20Y, the peripheral wall portion 28 of the recess 26 is composed of only the inner curved surface portion 28N and the outer curved surface portion 28G. The peripheral wall portion 29 of the recess 27 is also composed of only the inner curved surface portion 29N and the outer curved surface portion 29G. That is, in the case 20Y, the technical idea of providing a flat portion at the end portion of the

peripheral wall portions

28 and 29 in a relatively short different direction is not employed.

FIG. 8 is a plan view showing a case 20 for comparison between the embodiment and the comparative example 1. FIG. In FIG. 8, the peripheral wall portions 28 and 29 (those having a plane portion) of the

recesses

26 and 27 provided in the case based on the embodiment are indicated by solid lines, and the recesses provided in the case based on the comparative example 1 The peripheral wall portion (having no flat portion) is indicated by a broken line.

As shown in the figure, by providing flat portions 28F1, 28F2, 29F1, 29F2 at the ends of the

peripheral wall portions

28, 29 in a relatively short other direction, the

peripheral wall portions

28, 29 indicated by solid lines are indicated by broken lines. It is possible to lengthen the perimeter compared to the peripheral wall portion shown. The

peripheral wall portions

28 and 29 indicated by the solid lines are provided so as to extend toward the position of the point S as compared to the peripheral wall portions indicated by the broken lines. As described above, the position of the point S indicates the position of the end portion on one side (inner side) of the plane portions 28F1, 28F2, 29F1, and 29F2. That is, by adopting the technical idea of providing a flat portion at the ends of the

peripheral wall portions

28 and 29 in a relatively short direction, the volume occupied by the

thin portions

24 and 25 in the bottom portion 22 is further increased in product design. You can see that it is possible.

By adopting the technical idea of providing a flat portion at the ends of the

peripheral wall portions

28, 29 in a relatively short direction, the thickness of the

thin portions

24, 25 can be reduced, or the bottom portion 22 of the case 20 can be reduced. Without reducing the overall thickness, the rigidity of the bottom portion 22 as a whole can be lowered, so that the directional characteristics in the horizontal direction can be further widened, and thus the anisotropy of the directional characteristics can be improved. Further, by not adopting the configuration in which the thickness of the

thin portions

24 and 25 or the entire bottom portion 22 of the case 20 is reduced, there is no possibility that the impact resistance (chipping resistance) of the bottom portion 22 of the case 20 is reduced.

(Comparative Example 2)
FIG. 9 is a plan view showing the case 20Z and the piezoelectric vibration element 30 provided in the ultrasonic transducer in the second comparative example. In the case 20Z, the peripheral wall portion 28 of the recess 26 includes an inner curved surface portion 28N, an outer curved surface portion 28G, and a pair of flat surface portions 28F1 and 28F2. The peripheral wall portion 29 of the recess 27 also includes an inner curved surface portion 29N, an outer curved surface portion 29G, and a pair of flat surface portions 29F1 and 29F2. The case 20Z has substantially the same configuration as the case body disclosed in Japanese Patent Laid-Open No. 2000-032594 (Patent Document 1) described at the beginning.

Here, also in the case 20Z, as in the case of the case 20Y (Comparative Example 1 shown in FIG. 7), the technical feature that the flat portions are provided at the end portions R1 to R4 of the

peripheral wall portions

28 and 29 in the relatively short other direction. Thought is not adopted. Specifically, the end portions R1 and R2 in the relatively short other direction of the peripheral wall portion 28 are constituted by a part of the outer curved surface portion 28G and do not have a planar shape. Ends R1 and R2 in the relatively short other direction of the peripheral wall portion 28 have only a curved surface shape. Similarly, end portions R3 and R4 in a relatively short other direction of the peripheral wall portion 29 are configured by a part of the outer curved surface portion 29G and do not have a planar shape. Ends R3 and R4 in a relatively short other direction of the peripheral wall portion 29 also have only a curved surface shape.

FIG. 10 is a plan view showing a case 20 for explaining the embodiment and the comparative example 2 in comparison. In FIG. 10, the peripheral wall portions 28 and 29 (those having a plane portion) of the

recesses

26 and 27 provided in the case based on the embodiment are indicated by solid lines, and the recesses provided in the case based on the comparative example 2 The peripheral wall portion (having no flat portion) is indicated by a broken line.

peripheral wall portions

28, 29 in a relatively short other direction, the

peripheral wall portions

28 and 29 indicated by the solid lines are provided so as to extend toward the position of the point E as compared with the peripheral wall portions indicated by the broken lines. As described above, the position of the point E indicates the position of the end portion on the other side (outer side) of the plane portions 28F1, 28F2, 29F1, and 29F2. That is, by adopting the technical idea of providing a flat portion at the ends of the

peripheral wall portions

28 and 29 in a relatively short direction, the volume occupied by the

thin portions

By adopting the technical idea of providing a flat portion at the ends of the

peripheral wall portions

28, 29 in a relatively short direction, the thickness of the

thin portions

(Modification of the embodiment)
FIG. 11 is a plan view showing a case 20 A and a piezoelectric vibration element 30 provided in an ultrasonic transducer according to a modification of the embodiment. In this modification, the length L in the same direction of the plane portions 28F1 and 28F2 is longer than the minimum width W of the thin portion 24 (recessed portion 26) in the arrow X direction (one relatively long direction). Similarly, the length L of the flat portions 29F1 and 29F2 in the same direction is longer than the minimum width W of the thin portion 25 (concave portion 27) in the arrow X direction (one relatively long direction).

This configuration makes it easier to increase the volume occupied by the

thin portions

24 and 25 in the bottom portion 22 in product design than in the case of the embodiment. When the volume occupied by the

thin portions

24 and 25 is increased, the resonance frequency of the vibration system including the bottom portion 22 of the case 20 is lowered, so that the ultrasonic transmission / reception range in the horizontal direction can be further expanded. Therefore, an ultrasonic transducer having high anisotropy in the horizontal installation direction and the vertical installation direction can be put into practical use.

(Other variations of the embodiment)
In the above-described embodiment, the flat portions 28F1, 28F2, 29F1, and 29F2 all extend in a direction perpendicular to the bottom portion 22. The operations and effects described in the above embodiment can be expected even when the flat portions 28F1, 28F2, 29F1, and 29F2 extend with an inclination with respect to the bottom portion 22. Even when the flat surface portion is inclined with respect to the bottom portion 22, when the technical idea of providing the flat surface portions 28F1, 28F2, 29F1, 29F2 at the relatively short ends of the

peripheral wall portions

28, 29 is adopted. This makes it easier to increase the volume occupied by the

thin portions

24 and 25 in the bottom portion 22 in product design. When the volume occupied by the

thin portions

24 and 25 is increased, the resonance frequency of the vibration system including the bottom portion 22 of the case 20 is lowered, so that it is possible to widen the ultrasonic wave transmission / reception range in the horizontal direction. Therefore, an ultrasonic transducer having high anisotropy in the horizontal installation direction and the vertical installation direction can be put into practical use.

In the above-described embodiment, the lower end portions of the flat portions 28F1, 28F2, 29F1, and 29F2 (portions connected to the bottom surfaces of the concave portions 26 and 27 (inner surfaces of the thin portions 24 and 25)) are formed at right angles. Yes. The lower end portions of the flat portions 28F1, 28F2, 29F1, and 29F2 may be connected to the bottom surfaces of the concave portions 26 and 27 (inner surfaces of the thin portions 24 and 25) through curved portions. Even in this configuration, when the technical idea of providing the flat portions 28F1, 28F2, 29F1, 29F2 at the ends of the

peripheral wall portions

28, 29 in a relatively short other direction is adopted, the thin wall at the bottom portion 22 in terms of product design. It becomes easy to enlarge the volume which the

parts

24 and 25 occupy. Therefore, an ultrasonic transducer having high anisotropy in the horizontal installation direction and the vertical installation direction can be put into practical use.

[Experimental example]
Hereinafter, the conditions and results of the experimental example performed with respect to the embodiment and the comparative example 1 will be described with reference to FIGS. As shown in FIG. 12, the experimental example includes Examples 1 to 6 based on the embodiment. In Examples 1 to 6 and Comparative Example 1, those having a case inner diameter D (see FIG. 2) of 12.8 mm were prepared. In the arrow Y direction (another relatively short direction), the interval between the plane portions 28F1 and 28F2 and the interval between the plane portions 29F1 and 29F2 were both 7.85 mm. The minimum width W (see FIG. 11) of the thin-walled portion 24 (recessed portion 26) was 2.4 mm. Examples 1 to 6 have different conditions from each other in that the lengths L (see FIG. 11) of the plane portions 28F1, 28F2, 29F1, and 29F2 are different. The comparative example 1 does not have a plane part (plane part length L = 0).

The flat portion 28F1 in the first embodiment is provided between the position indicated by the point S1 and the position indicated by the point E in FIG. In the first embodiment, the length L (see FIG. 11) of the plane portion 28F1 in one relatively long direction (arrow X direction) is 3.48 mm. The ratio (L / D) of the length L of the plane portion 28F1 in one relatively long direction to the case inner diameter D of the case 20 is 0.27. The configuration of the plane portion 28F1 is common to the configurations of the remaining three plane portions (not shown).

The flat portion 28F1 in the second embodiment is provided between the position indicated by the point S2 and the position indicated by the point E in FIG. In Example 2, the length L (see FIG. 11) of the plane portion 28F1 in one relatively long direction (arrow X direction) is 2.78 mm. The ratio (L / D) of the length L of the plane portion 28F1 in one relatively long direction to the case inner diameter D of the case 20 is 0.22. The configuration of the plane portion 28F1 is common to the configurations of the remaining three plane portions (not shown).

The flat portion 28F1 in the third embodiment is provided between the position indicated by the point S3 and the position indicated by the point E in FIG. In Example 3, the length L (see FIG. 11) of the plane portion 28F1 in one relatively long direction (arrow X direction) is 1.95 mm. The ratio (L / D) of the length L of the plane portion 28F1 in one relatively long direction to the case inner diameter D of the case 20 is 0.15. The configuration of the plane portion 28F1 is common to the configurations of the remaining three plane portions (not shown).

The flat portion 28F1 in the fourth embodiment is provided between the position indicated by the point S4 and the position indicated by the point E in FIG. In Example 4, the length L (see FIG. 11) of the plane portion 28F1 in one relatively long direction (arrow X direction) is 1.34 mm. The ratio (L / D) of the length L of the planar portion 28F1 in one relatively long direction to the case inner diameter D of the case 20 is 0.10. The configuration of the plane portion 28F1 is common to the configurations of the remaining three plane portions (not shown).

The flat portion 28F1 in the fifth embodiment is provided between the position indicated by the point S5 and the position indicated by the point E in FIG. In Example 5, the length L (see FIG. 11) of the plane portion 28F1 in one relatively long direction (arrow X direction) is 0.84 mm. The ratio (L / D) of the length L of the plane portion 28F1 in one relatively long direction to the case inner diameter D of the case 20 is 0.07. The configuration of the plane portion 28F1 is common to the configurations of the remaining three plane portions (not shown).

The flat portion 28F1 in Example 6 is provided between the position indicated by the point S6 and the position indicated by the point E in FIG. In Example 6, the length L (see FIG. 11) of the plane portion 28F1 in one relatively long direction (arrow X direction) is 0.40 mm. The ratio (L / D) of the length L of the plane portion 28F1 in one relatively long direction to the case inner diameter D of the case 20 is 0.03. The configuration of the plane portion 28F1 is common to the configurations of the remaining three plane portions (not shown).

Under the experimental conditions as described above, the horizontal directivity (directivity in the horizontal direction) and the resonance frequency were calculated by simulation for Examples 1 to 6 and Comparative Example 1. FIG. 14 shows the relationship between the ratio (L / D) of the length L of the planar portion 28F1 to the case inner diameter D of the case 20 and the resonance frequency. FIG. 15 shows the relationship between the ratio (L / D) of the length L of the flat portion 28F1 to the case inner diameter D of the case 20 and the horizontal directivity.

As shown in FIG. 14, with respect to the resonance frequency, if at least the ratio (L / D) of the length L of the planar portion 28F1 to the case inner diameter D of the case 20 is 0.03 or more and 0.27 or less, a comparative example It can be seen that an improvement is seen compared to the case of. Further, regarding the horizontal directivity, at least the ratio (L / D) of the length L of the flat portion 28F1 to the case inner diameter D of the case 20 is 0.03 or more and 0.27 or less, compared with the comparative example. It can be seen that improvement is seen.

Although the embodiments and examples have been described above, the above disclosure is illustrative in all respects and not restrictive. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

10 Ultrasonic transducer, 20, 20A, 20Y, 20Z case, 20S hollow part, 21 cylindrical part, 22 bottom part, 23 thick part, 24, 25 thin part, 26, 27 concave part, 28, 29 peripheral wall part, 28F1, 28F2, 29F1, 29F2 Planar part, 28G, 29G outer curved surface part, 28N, 29N inner curved surface part, 30 piezoelectric vibration element, 31 lower layer silicone, 32 sound absorbing material, 33 filled silicone, 35 lead wire, D case inner diameter, E , S, S1, S2, S3, S4, S5, S6, L length (plane portion length), R1, R2, R3, R4 end, W minimum width, X, Y, Z arrows.

Claims

A bottomed cylindrical case provided with a hollow portion;
A piezoelectric vibration element placed in the hollow portion and disposed on the inner surface of the bottom portion of the case located on the bottom surface of the hollow portion, and
The hollow portion has a shape that is relatively long in one direction and relatively short in another direction in a cross section parallel to the bottom portion of the case.
The bottom portion is provided with a thick portion and a pair of thin portions positioned on both outer sides in the one direction that are relatively long with respect to the thick portion,
The piezoelectric vibration element is disposed on the thick part,
Of the case, the peripheral wall portion of the recess formed by providing the thin portion at the bottom has a flat portion having a flat planar shape at an end portion in the relatively short other direction. Sonic transducer.
The plane portion extends in a direction parallel to the relatively long one direction.
The ultrasonic transducer according to claim 1.
When the case is viewed in plan along the axial direction, the plane portion provided on one thin portion side and the plane portion provided on the other thin portion side are on the same straight line. positioned,
The ultrasonic transducer according to claim 1 or 2.
When the case is viewed in plan along the axial direction, the bottom of the case has a point-symmetric shape with respect to the center of the thick part,
The ultrasonic transducer according to any one of claims 1 to 3.
The ratio of the length of the planar portion in the relatively long one direction to the inner diameter of the case is 0.03 or more and 0.27 or less.
The ultrasonic transducer according to any one of claims 2 to 4.