JP2010032328A - Ultrasonic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic sensor which suppresses vibration of a housing section where a piezoelectric element for performing only reception of an ultrasonic wave is housed, stabilizes the directivity of the ultrasonic wave more, and improves a reverberation characteristics. <P>SOLUTION: A piezoelectric element 26a is a type of element which transmits an ultrasonic wave whose center frequency is 72 kHz, and the height of a vibration case and a uniting section 23 are set so that the ratio of the height of the vibration case 20 and the thickness of the uniting section 23 becomes 2:1 when the frequency is set. As a result, the vibration of the housing section 21b is suppressed, the directivity of the ultrasonic wave is more stabilized, and the reverberation characteristics are improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic sensor used in a vehicle obstacle detection device and the like.

  In recent years, an ultrasonic sensor is supported on a front or rear bumper of a vehicle, and a predetermined ultrasonic pulse signal is transmitted from the ultrasonic sensor, and a reflected wave from an object is received, thereby existing in front or rear. A vehicle obstacle detection device that detects an obstacle is known. As an ultrasonic sensor used in such a vehicle obstacle detection device, for example, there is one having a structure as disclosed in Patent Document 1.

As shown in FIG. 9, the ultrasonic sensor 40 of Patent Literature 1 has two bottomed cylindrical accommodating portions 51 a and 51 b that are spaced apart and recessed in one metal vibration case 50. The two accommodating portions 51 a and 51 b are connected by a connecting portion (flat plate portion) 52. In the ultrasonic sensor 40 of Patent Document 1, the thickness of the connecting portion 52 is much shorter than the height of the vibrating case 50 (for example, the height of the vibrating case 50: the thickness of the connecting portion 52 = 10). : 1). The accommodating portions 51a and 51b accommodate piezoelectric elements 53a and 53b that transmit and receive ultrasonic waves, respectively. The piezoelectric elements 53a transmit and receive ultrasonic waves, while the piezoelectric elements 53b transmit and receive ultrasonic waves. Only receive the wave. The direction and position where the obstacle exists can be detected from the difference between the time until the piezoelectric element 53a receives the ultrasonic wave and the time until the piezoelectric element 53b receives the ultrasonic wave. It has become.
JP 2004-253911 A

  In recent years, it has been considered to reduce the size of an ultrasonic sensor due to the design and appearance problems. Therefore, the ultrasonic sensor 40 of Patent Document 1 may be miniaturized using the ratio relationship in the thickness of the connecting portion 52, the height of the vibration case 50, and the like, while maintaining the same ratio relationship. Conceivable. However, if the ultrasonic sensor 40 of Patent Document 1 is downsized as it is, there is a possibility that the directivity of the ultrasonic wave and the length of the reverberation wave may change before and after the downsizing.

  And in the ultrasonic sensor, the characteristic that the directivity shape of the ultrasonic wave is reflected in the detection area as it is, or if the reverberation wave becomes long, the reflected wave overlaps with the reverberation wave. It is difficult to detect obstacles. These phenomena are caused by the vibration of the accommodating portion 51a that accommodates the piezoelectric element 53a being propagated to the accommodating portion 51b that accommodates the piezoelectric element 53b. However, regardless of the size or shape of the ultrasonic sensor, it is necessary to stabilize the directivity of the ultrasonic wave and to prevent the reverberant wave from becoming long.

  The present invention has been made in view of such circumstances, and its purpose is to suppress vibration of the housing portion in which the piezoelectric element that receives only the ultrasonic waves is housed, and to further improve the directivity of the ultrasonic waves. An object of the present invention is to provide an ultrasonic sensor that can stabilize and improve reverberation characteristics.

  In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a plurality of accommodating portions having an incident / exit surface on which an ultrasonic wave is emitted and incident and a bottom surface on the opposite side of the incident / exit surface are arranged. And a plurality of piezoelectric elements disposed on a bottom surface of the housing portion, wherein at least one of the piezoelectric elements is super In the ultrasonic sensor, which is a piezoelectric element for wave transmission used for transmitting a sound wave, and at least two of the piezoelectric elements are piezoelectric elements for wave reception used for receiving an ultrasonic wave, The piezoelectric element has a center frequency of ultrasonic waves to be transmitted of 72 kHz type, and the ratio between the height of the vibration case and the thickness of the connecting portion when the frequency is set is 2: 1. The gist is that it is set in a range of ˜3: 1.

According to the present invention, it is possible to suppress the vibration of the housing portion in which the piezoelectric element that only receives ultrasonic waves is housed, to further stabilize the directivity of the ultrasonic waves, and to improve the reverberation characteristics.
The invention according to claim 2 is the ultrasonic sensor according to claim 1, wherein the connecting portion is formed of resin.

The gist of the invention described in claim 3 is the ultrasonic sensor according to claim 1, wherein the connecting portion is formed of a rubber material.
According to the invention according to claim 2 and claim 3, since the two vibration cases can be connected by a relatively inexpensive member such as a resin or a rubber material, only by arranging the two vibration cases. The cost for manufacturing the ultrasonic sensor can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the vibration of the accommodating part in which the piezoelectric element which receives only an ultrasonic wave was accommodated can be suppressed, the directivity of an ultrasonic wave can be stabilized more, and a reverberation characteristic can be improved.

A first embodiment in which the present invention is embodied in an ultrasonic sensor used in an obstacle detection device for a vehicle will be described below with reference to FIGS.
As shown in FIGS. 1 and 2, the housing 11 constituting the ultrasonic sensor 10 of the present embodiment is substantially elliptical in cross-sectional view in the horizontal direction (see FIG. 2). In the housing 11, a metal vibration case 20 in which a plurality (two in this embodiment) of receiving portions 21 a and 21 b for receiving the piezoelectric elements 26 a and 26 b are arranged in the longitudinal direction and recessed is provided on the housing 11. It is inserted from the opening side.

  The vibration case 20 is formed with a partition recess 22 that opens in the same direction as the housing portions 21a and 21b so as to partition the housing portion 21a and the housing portion 21b. The depth of the partition recess 22 is shallower than the depths of the accommodating portions 21a and 21b, and is formed to a depth corresponding to half the height of the vibration case 20 in the present embodiment. In the vibration case 20, a portion corresponding to the bottom surface of the partition recess 22 is a connecting portion 23 that connects the accommodating portions 21 a and 21 b. In the present embodiment, the thickness of the connecting portion 23 is the same as the depth of the partition recess 22, and is formed with a thickness corresponding to half the height of the vibration case 20. Moreover, the connection part 23 is connected with the remaining parts 23a and 23b formed in the bottom side rather than the accommodating parts 21a and 21b by the recessed provision of the accommodating parts 21a and 21b. The vibration case 20 in the present embodiment is not formed by connecting two vibration cases in which one housing portion is formed, but two housing portions 21 a and 21 b are provided in one vibration case 20. It is configured by being recessed. In addition, the thickness of the connection part 23 is about half of the height of the vibration case 20, and the ratio between the height of the vibration case 20 and the thickness of the connection part 23 is 2: 1.

  In addition, two cylindrical portions 24 that are spaced apart in the longitudinal direction of the vibration case 20 are formed on the back surfaces of the connecting portion 23 and the remaining portions 23a and 23b. The portions sandwiched between the cylindrical portions 24 are the partition recesses 22 as well as the accommodating portions 21a and 21b.

  In addition, disk-like piezoelectric elements 26a and 26b for transmitting and receiving ultrasonic waves are respectively disposed on the bottom surfaces 25 of the accommodating portions 21a and 21b. Specifically, the piezoelectric element 26a is disposed in the housing portion 21a, and the piezoelectric element 26b is disposed in the housing portion 21b. One of the electrodes of the piezoelectric elements 26a and 26b comes into contact with the bottom surface 25 of each of the accommodating portions 21a and 21b and is drawn out through the vibration case 20 and the lead wire R, and the other electrode is connected through the lead wire R. Are connected to external circuits for analyzing the outputs of the piezoelectric elements 26a and 26b, respectively, and used for receiving ultrasonic waves. One piezoelectric element 26a is also connected to a drive circuit for generating ultrasonic waves, and is used for transmitting ultrasonic waves. That is, each of the piezoelectric elements 26a and 26b is a receiving piezoelectric element used for receiving an ultrasonic wave, and the piezoelectric element 26a connected to the drive circuit further transmits an ultrasonic wave. It also serves as a piezoelectric element for transmission used in the above. The ultrasonic waves transmitted and received by the piezoelectric elements 26a and 26b are incident and output on the incident / exit surface 27 located on the opposite side of the bottom surface 25 formed in the remaining portions 23a and 23b. Furthermore, each accommodating part 21a, 21b is each filled with the buffer filler 28 for suppressing reverberation.

  The vibration case 20 is accommodated in the housing 11 such that the incident / exit surface 27 is exposed from the opening of the housing 11. On the other hand, the opening side of the vibration case 20 is accommodated in the housing 11 so as to face the bottom surface of the housing 11.

  In addition, between the housing 11 and the vibration case 20, a holding body 30 made of an elastic material (for example, synthetic rubber) whose sound absorption coefficient with respect to the ultrasonic wave transmitted by the piezoelectric element 26 a is higher than the material of the vibration case 20. Is provided. The holding body 30 has two holding recesses 31 arranged in parallel in the longitudinal direction. The dimension of the outer periphery of the holding body 30 is formed to be approximately the same as the inner periphery of the housing 11, and the dimension of the inner periphery of the holding recess 31 is formed to be approximately the same as the dimension of the outer periphery of the cylindrical portion 24 of the vibration case 20. . Each cylindrical portion 24 of the vibration case 20 is press-fitted into the holding recess 31, and the holding body 30 is press-fitted into the housing 11, whereby the vibration case 20 is held in the housing 11. Therefore, in the ultrasonic sensor 10 according to this embodiment, as shown in FIG. 2, the housing 11, the holding body 30, the vibration case 20, the buffer filler 28, and the piezoelectric element 26a (piezoelectric element 26b) are arranged in this order from the outside. Has been.

Next, an obstacle detection method using the ultrasonic sensor 10 will be described with reference to FIG.
The ultrasonic sensor 10 of this embodiment detects the presence of an obstacle by transmitting an ultrasonic wave to a detection range and receiving a reflected wave reflected by the obstacle. The direction of the obstacle can be detected by comparing the outputs of the two piezoelectric elements 26a and 26b that receive the reflected wave. Specifically, the piezoelectric element 26a intermittently transmits ultrasonic pulses toward the detection range, and the piezoelectric elements 26a and 26b receive the reflected waves reflected by the obstacle P existing in the detection range. The relative distance L to the obstacle P can be detected based on the time from when the ultrasonic wave is transmitted until the reflected wave is received. A straight line along the direction in which the piezoelectric elements 26a and 26b are arranged is a normal line from the difference between the time until the piezoelectric element 26a receives the ultrasonic wave and the time until the piezoelectric element 26b receives the ultrasonic wave. An angle θ formed by a straight line F connecting the ultrasonic sensor 10 and the obstacle P to the plane H can be detected. Then, the direction of the obstacle P can be detected based on the angle θ.

Then, according to the ultrasonic sensor 10 in which the ratio between the height of the vibration case 20 and the thickness of the connecting portion 23 is 2: 1, the test results as shown in FIGS. 4 to 7 can be obtained. .
FIG. 4 shows a waveform of a wave received by the ultrasonic sensor 10 in the present embodiment. In FIG. 4, the output signal waveform in the piezoelectric element 26 a is indicated as “transmission / reception side”, and the output signal waveform in the piezoelectric element 26 b is indicated as “reception side”.

  When the obstacle P exists on the side close to the piezoelectric element 26b (see FIG. 3), as shown in FIG. 4, the piezoelectric element 26b receives the reflected wave earlier than the piezoelectric element 26a. That is, the piezoelectric element 26b receives the reflected wave C1 after the reception time t1 has elapsed from the transmission start time T0 when the ultrasonic wave is transmitted from the piezoelectric element 26a. The wave reception time t1 is a time from when an ultrasonic wave is transmitted from the piezoelectric element 26a until it is reflected by the obstacle P and enters the piezoelectric element 26b. The piezoelectric element 26a receives the reflected wave C2 after the reception time difference t2 has elapsed since the piezoelectric element 26b received the reflected wave C1. Note that the reverberant waves B1 and B2 are received by the piezoelectric element 26a and the piezoelectric element 26b simultaneously with the reflected wave. Then, the relative distance L to the obstacle P and the direction of the obstacle P can be detected by the times t1 and t2 from when the ultrasonic wave is transmitted until the reflected wave is received.

  In an ultrasonic sensor in which the ratio of the height of the vibration case to the thickness of the connecting portion is approximately 10: 1, the vibration of the housing portion that houses the piezoelectric element for transmitting and receiving the piezoelectric element for receiving the wave There is a possibility that the reverberant wave becomes longer due to propagation to the accommodated accommodating portion, and the reflected wave overlaps the reverberant wave.

  On the other hand, as is clear from the results of FIG. 4, in the ultrasonic sensor 10 of the present embodiment, the ratio of the height of the vibration case 20 and the thickness of the connecting portion 23 is set to 2: 1. The vibration is less likely to propagate to the accommodating portion 21b, and the reverberation wave can be shortened as compared with the ultrasonic sensor in which the ratio of the height of the vibration case to the thickness of the connecting portion is approximately 10: 1.

  That is, in the ultrasonic sensor 10 of the present embodiment, since the connecting portion 23 itself has a certain thickness, the vibration of the accommodating portion 21a is difficult to propagate to the accommodating portion 21b from the result of FIG. It can be seen that the reverberation waves B1 and B2 are also shortened. As a result, in the ultrasonic sensor 10 of the present embodiment, the reverberant wave is shortened (the reverberation characteristic is improved), so that the reverberant wave and the reflected wave are difficult to overlap, and an accurate detection range can be provided. it can.

  5A shows the directional beam shape of the ultrasonic wave transmitted by the ultrasonic sensor 10 of the present embodiment, while FIG. 5B shows the height of the vibration case and the thickness of the connecting portion. The directional beam shape of an ultrasonic wave transmitted by an ultrasonic sensor having a ratio of approximately 10: 1 is shown.

  As is clear from the result of FIG. 5B, in the ultrasonic sensor in which the ratio of the height of the vibration case to the thickness of the connecting portion is approximately 10: 1, the ultrasonic directional beam shape pulsates. As a result, the detection area of the ultrasonic sensor 10 is distorted.

  On the other hand, as is clear from the result of FIG. 5A, in the ultrasonic sensor 10 of the present embodiment, the ratio of the height of the vibration case 20 to the thickness of the connecting portion 23 is 2: 1. The vibration of the accommodating portion 21a is difficult to propagate to the accommodating portion 21b, and the pulsation of the ultrasonic directional beam shape is suppressed.

  Since the ultrasonic sensor has a characteristic that the directivity shape of the ultrasonic wave is reflected as it is in the detection area, the height of the vibration case 20 and the connection portion 23 are determined based on the results of FIGS. It can be seen that by setting the ratio to the thickness to 2: 1, the pulsation of the ultrasonic directional beam shape is suppressed, whereby the detection area of the ultrasonic sensor 10 can be stabilized. Moreover, it turns out that it becomes difficult to reduce the vibration energy required in order to transmit an ultrasonic wave because it becomes difficult to propagate the vibration of the accommodating part 21a to the accommodating part 21b. That is, by providing the connecting portion 23 with a thickness, the vibration energy that has been propagated to the accommodation portion 21b until now becomes difficult to propagate to the accommodation portion 21b, so that it is necessary to transmit ultrasonic waves. It will be added to the vibration energy. Moreover, it turns out that the sensitivity fall of the ultrasonic sensor 10 by reduction of the vibration amount of the accommodating part 21a can also be suppressed.

  FIG. 6 shows the vibration distribution in the ultrasonic sensor 10 of the present invention and the vibration distribution in the ultrasonic sensor in which the ratio of the height of the vibration case to the thickness of the connecting portion is approximately 10: 1. 6 indicates the position of the vibration case 20, and the vertical axis indicates the amount of vibration. The value “0” on the horizontal axis indicates the center of the vibration case 20, and the right side of the graph across the center line indicates the vibration in the accommodating portion 21a (transmission / reception wave), while the left side of the graph. Shows the vibration in the accommodating portion 21b (received wave).

  From the result of FIG. 6, in the ultrasonic sensor in which the ratio of the height of the vibration case to the thickness of the connecting portion is approximately 10: 1, the vibration of the receiving portion for transmitting and receiving waves easily propagates to the receiving portion for receiving waves. As a result, it can be seen that vibration is also generated in the receiving portion for receiving waves. On the other hand, in the ultrasonic sensor 10 of the present embodiment in which the ratio of the height of the vibration case 20 and the thickness of the connecting portion 23 is 2: 1, vibration in the housing portion 21b is suppressed, and vibration in the housing portion 21a is It can be seen that the ratio between the height of the vibration case and the thickness of the connecting portion is greater than the vibration in the ultrasonic sensor of approximately 10: 1.

  From the result of FIG. 6, by setting the ratio of the height of the vibration case 20 and the thickness of the connecting portion 23 to 2: 1, vibration in the housing portion 21b can be suppressed and vibration necessary for transmitting ultrasonic waves. It turns out that the decrease in energy can be suppressed. Moreover, it turns out that it can suppress that the sensitivity of the ultrasonic sensor 10 by the reduction of the vibration amount of the accommodating part 21a falls.

  FIG. 7 shows a correlation between the ratio between the height of the vibration case 20 and the thickness of the connecting portion 23 and the vibration amount of the housing portion 21b. In addition, the horizontal axis shown in FIG. 7 has shown ratio of the height of the vibration case 20, and the thickness of the connection part 23, and the vertical axis | shaft has shown the vibration amount (micrometer). In the ultrasonic sensor 10 of the present embodiment, the frequency band of the piezoelectric element 26a is 60 to 80 kHz, specifically 67 to 77 kHz is preferable, and a more optimal value is 72 kHz.

  As is apparent from the result of FIG. 7, when the ratio of the height of the vibration case 20 to the thickness of the connecting portion 23 is larger than 3: 1, that is, the height of the vibrating case 20 is much larger than the thickness of the connecting portion 23. In the case of long, the vibration amount of the connecting portion 23 tends to be larger than 0.05 (μm). However, within the range of the height of the vibration case 20: the thickness of the connecting portion 23 = 2: 1 to 3: 1, the connecting portion 23 hardly vibrates. Further, when the ratio of the height of the vibration case 20 to the thickness of the connecting portion 23 is smaller than 2: 1, that is, the height of the vibration case 20 is substantially the same as the thickness of the connecting portion 23 or the vibration case 20. Even when the thickness of the connecting portion 23 is longer than the height of the connecting portion 23, the connecting portion 23 hardly vibrates.

  On the other hand, in the accommodating portion 21b, when the ratio of the height of the vibration case 20 and the thickness of the connecting portion 23 is larger than 3: 1, that is, when the height of the vibrating case 20 is much longer than the thickness of the connecting portion 23. In addition, the vibration amount of the housing portion 21b is larger than 0.05 (μm). And the vibration amount of the accommodating part 21b will be 0.05 (micrometer) or less in the range of the height of the vibration case 20: the thickness of the connection part 23 = 2: 1-3: 1. In addition, when the height of the vibration case 20: the thickness of the connecting portion 23 <2: 1, that is, when the difference between the height of the vibration case 20 and the thickness of the connecting portion 23 disappears, the vibration of the housing portion 21b is gradually increased. The amount increases. The height of the vibration case 20: the thickness of the connecting portion 23 <2: 1, and when approaching a certain ratio, the vibration amount of the housing portion 21b gradually decreases, but 0.05 (μm). It will never be

  That is, from the result of FIG. 7, in the ultrasonic sensor 10 of this embodiment in which the center frequency of the ultrasonic wave transmitted by the piezoelectric element 26 a is of the 72 kHz type, the height of the vibration case 20: the thickness of the connecting portion 23 = It was found that in the range of 2: 1 to 3: 1, the amplitude amount of the connecting portion 23 and the accommodating portion 21b could be suppressed to 0.05 (μm) or less, and extremely good results were shown.

According to the above embodiment, the following effects can be obtained.
(1) The center frequency of the ultrasonic wave transmitted by the piezoelectric element 26a is of the 72 kHz type, and the ratio between the height of the vibration case 20 and the thickness of the connecting portion 23 when the frequency is set is 2: The height of the vibration case 20 and the thickness of the connecting portion 23 are set so as to be 1. As a result, the vibration of the accommodating portion 21b can be suppressed, the directivity of the ultrasonic wave can be further stabilized, and the reverberation characteristics can be improved.

  (2) Further, since the connecting portion 23 itself has a certain thickness, the connecting portion 23 becomes difficult to vibrate, the ultrasonic directional beam shape pulsates, and the detection area of the ultrasonic sensor 10 is distorted. Can be suppressed.

  (3) Further, by making it difficult for the vibration of the housing portion 21a to propagate to the housing portion 21b, it is possible to suppress a reduction in vibration energy necessary for ultrasonic transmission, and to reduce the vibration amount of the housing portion 21a. It can also be suppressed that the sensitivity of the ultrasonic sensor 10 is reduced.

  (4) Since the vibration of the accommodating portion 21a is less likely to propagate to the accommodating portion 21b and the reverberant wave is shortened, the reverberant wave and the reflected wave are less likely to overlap, thereby providing an accurate detection range.

  (5) By simply setting the height of the vibrating case 20 and the thickness of the connecting portion 23 so that the ratio of the height of the vibrating case 20 and the thickness of the connecting portion 23 is 2: 1, the vibration of the housing portion 21b can be reduced. The vibration of the accommodating part 21b can be suppressed without newly providing another member (for example, rubber material) for suppressing between the accommodating part 21a and the accommodating part 21b.

  (6) In the vibration case 20, the partition recess 22 is provided between the accommodating portion 21a accommodating the piezoelectric element 26a and the accommodating portion 21b accommodating the piezoelectric element 26b. As a result, the appearance is improved and the number of parts is reduced as compared with the case where a plurality of vibration cases each provided with one accommodating portion are used, and the cost can be reduced.

(Second Embodiment)
Next, a second embodiment in which the present invention is embodied in an ultrasonic sensor used in a vehicle obstacle detection device will be described with reference to FIG. In the embodiments described below, the same reference numerals are given to the same configurations as those in the already described embodiments, and the overlapping description is omitted or simplified.

  In the present embodiment, the two accommodating portions are not provided to be separated and recessed in one vibrating case, but a bottomed cylindrical vibrating case 20 in which only one accommodating portion 21a or one accommodating portion 21b is formed. Two are arranged in parallel in the horizontal direction. On the bottom surface of the accommodating portion 21 (21a, 21b) in each vibration case 20, a piezoelectric element 26a that transmits and receives ultrasonic waves and a piezoelectric element 26b that only receives ultrasonic waves are disposed. Yes. The two vibration cases arranged in parallel in the horizontal direction are connected by a connecting portion 23 formed of resin.

  Also in this embodiment, the ratio of the height of the vibration case 20 to the thickness of the connecting portion 23 is 2: 1, and the ultrasonic sensor 10 of this embodiment is also as shown in FIGS. Experimental results are obtained.

According to this embodiment, in addition to the effects (1) to (6) described in the first embodiment, the following effects can be obtained.
(7) Since the connecting portion 23 is formed of resin, the two vibrating cases 20 can be connected to each other by a relatively inexpensive member such as resin simply by arranging the two vibrating cases 20 in the horizontal direction. Therefore, the cost for manufacturing the ultrasonic sensor 10 can be reduced.

In addition, you may change the said embodiment as follows.
In the second embodiment, the connecting portion 23 may be made of a rubber material such as synthetic rubber or natural rubber, or an elastic material such as a coil spring.

  In each embodiment, the height of the vibrating case 20 and the thickness of the connecting portion 23 may be set so that the ratio of the height of the vibrating case 20 to the thickness of the connecting portion 23 is 3: 1. Moreover, even if the height of the vibration case 20 and the thickness of the connection part 23 are set so that the ratio of the height of the vibration case 20 and the thickness of the connection part 23 is in the range of 2: 1 to 3: 1. good.

  In each embodiment, the accommodating portions 21a and 21b are formed by recessing the vibration case 20, but the accommodating portions 21a and 21b are formed so as to penetrate the vibration case 20, and the bottom surface 25 is formed as a separate member. Then, it may be installed so as to be covered with the bottom surface 25.

  In each embodiment, three or more accommodating portions may be formed in the vibration case 20 and a piezoelectric element may be accommodated in each accommodating portion. That is, the number of piezoelectric elements included in the ultrasonic sensor may be three or more.

Next, a technical idea that can be grasped from the above embodiment and another example will be added below.
(A) On the opposite surface of the vibration case from the incident / exit surface, there is provided a partition recess for partitioning between the accommodating portion for accommodating the transmitting piezoelectric element and the accommodating portion for accommodating the receiving piezoelectric element. The ultrasonic wave according to claim 1, wherein the connecting portion is provided between the incident / exit surface and a bottom surface of the partition recess. Sensor.

The sectional view to the horizontal direction in the type of use which shows the ultrasonic sensor in a 1st embodiment. The AA sectional view showing the ultrasonic sensor in a 1st embodiment. The schematic diagram which shows the principle in which an ultrasonic sensor detects an obstruction. The schematic diagram which shows the received waveform of the ultrasonic sensor in 1st Embodiment. (A) is a graph showing the directional beam shape of the ultrasonic wave in the ultrasonic sensor of the first embodiment, and (b) is an ultra-high ratio of the vibration case height to the connecting portion thickness of about 10: 1. The graph which shows the directional beam shape of the ultrasonic wave in a sound wave sensor. The graph which shows the distribution of the vibration in the ultrasonic sensor in 1st Embodiment, and the distribution of the vibration in the ultrasonic sensor whose ratio of the height of a vibration case and the thickness of a connection part is about 10: 1. The graph which shows the correlation with the ratio of the height of a vibration case and the thickness of a connection part, and the vibration amount of the accommodating part for receiving waves. Sectional drawing which shows the ultrasonic sensor by which the connection part was resin-formed as a modification. Sectional drawing which shows the conventional ultrasonic sensor.

Explanation of symbols

  B1, B2 ... reverberation wave, C1, C2 ... reflected wave, 10 ... ultrasonic sensor, 20 ... vibration case, 21a, 21b ... housing part, 23 ... coupling part, 25 ... bottom face (housing part), 26a, 26b ... piezoelectric Element, 27... Entrance / exit surface.

Claims (3)

A vibration case having an incident / exit surface on which ultrasonic waves are emitted and incident, and a plurality of accommodating portions having a bottom surface on the opposite side of the incident / exit surface;
A connecting portion for connecting the plurality of accommodating portions;
A plurality of piezoelectric elements disposed on the bottom surface of the housing portion,
At least one of the piezoelectric elements is a piezoelectric element used for transmitting an ultrasonic wave, and at least two of the piezoelectric elements are used for receiving an ultrasonic wave. In the ultrasonic sensor that is a piezoelectric element of
The piezoelectric element has a center frequency of ultrasonic waves to be transmitted of 72 kHz type, and the ratio between the height of the vibration case and the thickness of the connecting portion when the frequency is set is 2: 1. An ultrasonic sensor characterized by being set in a range of ˜3: 1.   The ultrasonic sensor according to claim 1, wherein the connecting portion is formed of a resin.   The ultrasonic sensor according to claim 1, wherein the connecting portion is formed of a rubber material.

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