WO2015093571A1

WO2015093571A1 - Ultrasonic sensor

Info

Publication number: WO2015093571A1
Application number: PCT/JP2014/083579
Authority: WO
Inventors: 陽二東; 尚広堀田; 齊藤　直人; 亨羽田; 田中　正吉; 大矢　茂正; 伊藤　智彦; 鈴木　貴博; 繁雄小林
Original assignee: 日清紡ホールディングス株式会社; 日本無線株式会社; 上田日本無線株式会社
Priority date: 2013-12-18
Filing date: 2014-12-18
Publication date: 2015-06-25
Also published as: JPWO2015093571A1

Abstract

This ultrasonic sensor contains the following: an ultrasonic transducer, the underside of which is affixed to the surface of a flat plate-shaped base, that contains a piezoelectric transducer element, said piezoelectric transducer element consisting of a piezoelectric sintered-ceramic column with electrode layers provided on the top and bottom surfaces thereof, and may be provided with an acoustic-matching-material layer at the bottom of the piezoelectric transducer element; a transmission circuit and a reception circuit electrically connected to the respective electrode layers on the piezoelectric transducer element; computation circuits electrically connected to said transmission circuit and reception circuit, respectively; and a rigid tubular wall material that is affixed to the surface of the flat plate-shaped base and laid out so as to surround the ultrasonic transducer without contacting same and with a gap therebetween. Said ultrasonic sensor is easy to affix to the surface of a flat plate-shaped base such as a bumper on a vehicle without reducing the mechanical strength of said flat plate-shaped base, can stably transmit and receive ultrasonic signals to and from a space on the opposite side of the flat plate-shaped base through said flat plate-shaped base with a suitable degree of directionality, and can precisely measure the position of an object in the space on the side of the flat plate-shaped base opposite the ultrasonic sensor.

Description

Ultrasonic sensor

The present invention relates to an ultrasonic sensor fixed to the surface of a flat substrate such as an automobile bumper. The present invention also provides the position of an object existing in a space opposite to the ultrasonic sensor with respect to the flat substrate, which is configured by arranging and fixing an ultrasonic sensor on the surface of a flat substrate such as a bumper of an automobile. It also relates to a detection device for detection.

An ultrasonic sensor equipped with a piezoelectric vibrator is fixed to the bumper of the car in order to prevent contact between the car, which is likely to occur when the car is parked in a parking lot, and an object such as a person or an obstacle. The ultrasonic signal transmitted from the piezoelectric vibrator is used to check for the presence of various objects or to measure their positions, and to emit a warning sound when an automobile approaches the object beyond a predetermined limit. Development of a system to inform the driver is in progress.

As a typical method for attaching an ultrasonic sensor to a bumper of an automobile, there is a method of providing a through hole in the bumper and fixing the ultrasonic sensor to the through hole, and an inner surface of the bumper (the side facing the automobile body) And a method of fixing an ultrasonic sensor to the surface). The latter fixing method of fixing the ultrasonic sensor to the inner surface of the bumper makes it easier to install the ultrasonic sensor because the step of providing the through hole is not necessary compared to the method of providing the through hole in the bumper. Since the ultrasonic sensor is difficult to see from the outside, there is an advantage that the appearance of the automobile is not impaired. However, if the ultrasonic sensor is fixed to the inner surface of the bumper, that is, the piezoelectric vibrator of the ultrasonic sensor is fixed to the inner surface of the bumper, the directivity of the ultrasonic signal transmitted from the piezoelectric vibrator through the bumper becomes narrower. There is a problem that it becomes unstable and it becomes difficult to accurately measure the position of the object existing in the space outside the bumper with high reliability. Therefore, there is a demand for an ultrasonic sensor that can transmit and receive an ultrasonic signal to a space on the opposite side of the bumper with a wide and appropriate directivity and high reliability even when the bumper is fixed to the inner surface of the bumper.

In Patent Document 1, even when an ultrasonic sensor is accommodated in a housing and attached to the back surface of a vehicle bumper or a resin portion, ultrasonic waves are used as an ultrasonic sensor capable of ensuring good directivity. A piezoelectric vibrator (ultrasonic vibrator) for transmitting and receiving and housing the piezoelectric vibrator, the piezoelectric vibrator being in contact with the inner surface of the bottom surface portion and being fixed, and the outer surface of the bottom surface portion being A housing that contacts the inner surface of the vehicle bumper or the resin portion, and the housing is in contact with the vehicle bumper or the resin portion and the piezoelectric vibrator at a part of a bottom surface portion of the housing. And forming an ultrasonic transmission portion made of a material having an acoustic impedance intermediate between the acoustic impedance of the piezoelectric vibrator and the acoustic impedance of the vehicle bumper or resin portion. And the transmission and reception of ultrasonic waves, an ultrasonic sensor which is characterized in that through the ultrasonic transmission unit and said vehicle bumper or the resin portion is described.

In Patent Document 2, an ultrasonic sensor provided with an ultrasonic element is used as an ultrasonic sensor mounting structure capable of improving design and ensuring predetermined directivity. For example, an ultrasonic sensor mounting structure that is mounted on the inner surface of a bumper and uses the wall member as a vibration transmission path, and the inner surface of the wall member is adjacent to the mounting portion of the ultrasonic sensor. An annular groove is provided so as to surround the attachment site, and the relationship between the width W1 and depth D1 of the groove and the thickness T1 of the wall member is (D1 / T1) / (W1 / T1) ^{1 / An} ultrasonic sensor mounting structure that satisfies the formula ² ≦ 1 is described.
In this document, in the above-described ultrasonic sensor mounting structure, a groove is provided adjacent to the ultrasonic sensor mounting portion in the bumper, so that the rigidity of the groove forming portion in the bumper is the other portion of the bumper. It is described that it is possible to suppress the propagation of vibration to the outside of the groove portion because the groove portion forming portion of the bumper and the sensor mounting portion surrounded by the portion are likely to vibrate.

JP 2007-142967 A JP 2010-14496 A

When the inventor of the present invention advances development research on an ultrasonic sensor fixed to the surface of a flat substrate such as a bumper of an automobile, the structure of the ultrasonic sensor disclosed in each of the above patent documents and the ultrasonic wave thereof are disclosed. The performance as a sensor was examined. As a result, when the ultrasonic sensor disclosed in each patent document is used while being fixed to the surface of a flat substrate such as a bumper of an automobile, it has been found that there are the following problems. .

In the ultrasonic sensor described in Patent Document 1, the piezoelectric vibrator built in the ultrasonic sensor is fixed in contact with a vehicle bumper or a casing that contacts the inner surface of the resin portion. According to the study of the present inventor, it was confirmed that in the piezoelectric vibrator built in the ultrasonic sensor with such a structure, the ultrasonic vibration generated from the piezoelectric vibrator directly propagates to the housing. . That is, propagation of the ultrasonic vibration generated from the piezoelectric vibrator to the bumper is not performed only through the ultrasonic transmission unit but also through the housing. Then, the ultrasonic vibration propagated through the casing then propagates to the bumper. The ultrasonic vibration propagated to the bumper through these two paths causes a complicated vibration to be generated in the bumper including the mutual interference. Therefore, the ultrasonic vibration generated from the piezoelectric vibrator passes through the bumper and is influenced by the complicated vibration of the bumper when transmitted to the opposite side. For this reason, an ultrasonic signal pattern of a desired shape is transmitted to the space opposite to the ultrasonic sensor of the bumper, having a main lobe excellent in directivity and not accompanied by a noticeable side lobe. It becomes difficult.

In the method of fixing the ultrasonic sensor described in Patent Document 2, that is, the method of providing an annular groove on the bumper so as to surround the attachment site of the ultrasonic sensor, the step of providing the groove on the bumper when the ultrasonic sensor is attached includes Since this is necessary, the installation work of the ultrasonic sensor becomes complicated. Further, the portion provided with the groove portion of the bumper has a problem that it is easily damaged because it is thin and has low mechanical strength. Further, the bumper processed in the thickness direction in this way tends to generate an unpredictable vibration due to the ultrasonic vibration applied from the ultrasonic sensor. Therefore, the ultrasonic vibration generated by the piezoelectric vibrator is When propagating to the opposite space, there is a tendency to become an ultrasonic signal with an abnormal pattern. Furthermore, in the ultrasonic sensor mounting structure described in Patent Document 2, the ultrasonic sensor is fixed to the bumper through the bottom of a housing made of a conductive member such as aluminum. For this reason, the ultrasonic wave generated from the piezoelectric vibrator of the ultrasonic sensor propagates not only to the bumper but also to the surrounding housing, and the propagation efficiency of the ultrasonic vibration tends to decrease.

Therefore, the object of the present invention is to fix the plate-like substrate easily on the surface of the flat substrate such as a bumper without lowering the mechanical strength of the flat substrate, and suitable for fixing to the flat substrate. Ultrasonic signals with a wide directivity and pattern can be transmitted and received, so the position of an object in the space opposite to the ultrasonic sensor with respect to the flat substrate can be accurately and accurately determined. It is to provide an ultrasonic sensor capable of measuring. The object of the present invention is also fixed to a flat substrate, and can accurately and accurately measure the position of an object existing in the space opposite to the ultrasonic sensor via the flat substrate. There is also providing a detection device.

The inventor fixes the bottom surface of the piezoelectric vibrator of the ultrasonic sensor or the bottom surface of the acoustic matching material layer to the surface of the flat substrate when the piezoelectric vibrator is provided with the acoustic matching material layer. When an ultrasonic signal is transmitted from the piezoelectric vibrator to the flat substrate by fixing and arranging a cylindrical rigid wall material around the lower part of the side surface of the ultrasonic vibrator via a gap, the ultrasonic wave The present inventors have found that side lobes are less likely to occur in the signal pattern and that the range of the main lobe is reasonably wide, and the present invention has been completed based on this new knowledge.

Therefore, the present invention includes a piezoelectric vibrator that is a columnar piezoelectric ceramic sintered body having an electrode layer on each of an upper surface and a lower surface, and may include an acoustic matching material layer below the piezoelectric vibrator. An ultrasonic vibrator fixed to the surface of the flat substrate, a transmission circuit and a reception circuit electrically connected to each of the electrode layers of the ultrasonic vibration body, and each of the transmission circuit and the reception circuit An arithmetic circuit that is electrically connected, and a cylinder that is disposed around the side surface of the ultrasonic vibrating body via a gap without being in contact with the ultrasonic vibrating body and is fixed to the surface of the flat substrate. An ultrasonic sensor including a rigid wall material.

Preferred embodiments of the ultrasonic sensor of the present invention are as follows.
(1) The cylindrical rigid wall material is formed from a resin material.
(2) The cylindrical rigid wall material has a base portion with a relatively large wall thickness and an extension portion with a relatively small wall thickness extending upward from the base portion.
(3) The upper surface of the cylindrical rigid wall material is opened, and the opening is covered with a lid.
(4) At least a part of the ultrasonic vibrating body is accommodated in a cylindrical housing in a state where the side surface is covered with a buffer material, and the cylindrical housing is disposed inside the cylindrical rigid wall material.
(5) The columnar piezoelectric ceramic sintered body is a porous columnar piezoelectric ceramic sintered body.
(6) The flat substrate is an automobile bumper.

The present invention also includes a plate-like substrate, and a piezoelectric vibrator that is a columnar piezoelectric ceramic sintered body having electrode layers on each of the upper and lower surfaces, and an acoustic matching material layer is provided below the piezoelectric vibrator. The ultrasonic vibration body fixed to the surface of the flat substrate at the bottom surface, the transmission circuit and the reception circuit electrically connected to each of the electrode layers of the ultrasonic vibration body, the transmission circuit and the reception Arithmetic circuits that are electrically connected to each of the circuits, and around the side surface of the ultrasonic vibration member, without being in contact with the ultrasonic vibration member, with a gap between them, on the surface of the flat substrate. There is also an apparatus for detecting the position of an object located in a space opposite to the ultrasonic sensor with respect to the flat substrate, including an ultrasonic sensor including a cylindrical rigid wall member to be fixed.

Preferred embodiments of the detection device of the present invention are as follows.
(1) The cylindrical rigid wall material is formed from a resin material.
(2) The cylindrical rigid wall material has a base portion with a relatively large wall thickness and an extension portion with a relatively small wall thickness extending upward from the base portion.
(3) The upper surface of the cylindrical rigid wall material is opened, and the opening is covered with a lid.
(4) At least a part of the ultrasonic vibrating body is accommodated in a cylindrical housing in a state where the side surface is covered with a buffer material, and the cylindrical housing is disposed inside the cylindrical rigid wall material.
(5) The columnar piezoelectric ceramic sintered body is a porous columnar piezoelectric ceramic sintered body.
(6) The flat substrate is an automobile bumper.

In the ultrasonic sensor and the detection device of the present invention, an ultrasonic signal having a pattern in which the range of the main lobe is moderately wide and the occurrence of side lobes is suppressed with respect to the space on the opposite side of the planar substrate such as a bumper. The following three points can be considered as reasons for propagation.
First, a piezoelectric vibrator or a composite of a piezoelectric vibrator and an acoustic matching material layer (collectively referred to as an ultrasonic vibrator in this specification) directly contacts the surface of a planar substrate such as a bumper. Since the ultrasonic vibration generated from the piezoelectric vibrator propagates to a planar substrate such as a bumper directly or through an acoustic matching material layer, the propagation efficiency of the ultrasonic vibration is good. Further, it is possible to avoid complication of ultrasonic vibration due to the influence of peripheral members that cause other resonance.
Second, a cylindrical rigid wall material fixed to a flat substrate such as a bumper around the ultrasonic vibration member without contacting the ultrasonic vibration member, along the surface of the flat substrate. Propagation of a transverse wave, generally called a lamb wave, that propagates in the flat substrate beyond the fixing position of the cylindrical rigid wall material can be suppressed.
Thirdly, by fixing the cylindrical rigid wall material on the surface of the flat substrate, the rigidity of the flat substrate in the area around the ultrasonic vibrator is increased. It is difficult to generate an ultrasonic signal having a complicated pattern due to the vibration of the flat substrate.

The ultrasonic sensor according to the present invention is suitable for a side lobe hardly generated in the space on the opposite side through the flat substrate, even when fixed to the surface of the flat substrate such as a bumper, and the range of the main lobe is suitably wide. Since an ultrasonic signal having a simple pattern is propagated, it is possible to transmit and receive the ultrasonic signal with high reliability with moderately wide directivity. Therefore, by using the detection device in which the ultrasonic sensor of the present invention is fixed to the surface of the flat substrate, the position of an object existing in a wide range of the space opposite to the ultrasonic sensor with respect to the flat substrate is accurately determined. It becomes possible to measure.

FIG. 3 is a cross-sectional view of an example of a detection device in which an ultrasonic sensor according to the present invention is fixed to the surface of a bumper, and a diagram schematically showing a connection state of an electric signal system (control device). It is a chart figure which shows the directivity of the ultrasonic signal with the suitable breadth transmitted from the detection apparatus shown in FIG. (A) is sectional drawing which shows the example of another structure of the detection apparatus which fixed the ultrasonic sensor according to this invention to the surface of a bumper (however, illustration of an electric signal system is abbreviate | omitted), (b) These are chart figures which show the directivity of the ultrasonic signal transmitted from the detection apparatus of (a). (A) is sectional drawing of an example of the detection apparatus which fixed the ultrasonic sensor which does not contain a cylindrical rigid wall material to the surface of a bumper, (b) is an ultrasonic wave transmitted from the detection apparatus of (a). It is a chart figure which shows the directivity (a side lobe is large) of a signal.

The ultrasonic sensor of the present invention may include a piezoelectric vibrator which is a columnar piezoelectric ceramic sintered body having electrode layers on each of an upper surface and a lower surface, and may include an acoustic matching material layer below the piezoelectric vibrator. , An ultrasonic vibrator fixed to the surface of the flat substrate at the bottom, a transmission circuit and a reception circuit electrically connected to each of the electrode layers of the ultrasonic vibration body, and a transmission circuit and a reception circuit, respectively Arranged around the side surface of the above-described ultrasonic vibration body and the electrically connected arithmetic circuit through the gap without being in contact with the ultrasonic vibration body, and fixed to the surface of the flat substrate. Includes cylindrical rigid wall material.

The columnar piezoelectric ceramic sintered body is preferably a columnar shape or a polygonal columnar shape with a bottom surface of a square or more, and particularly preferably a columnar shape or a rectangular columnar shape with a bottom surface being a rectangle. When the columnar piezoelectric ceramic sintered body is cylindrical, the thickness (height) may be smaller than the diameter of the lower surface, but the thickness (height) is preferably larger than the diameter of the lower surface, It is particularly preferable that the thickness ratio is in the range of 1.5 to 5 when the diameter of the lower surface is 1. The columnar piezoelectric ceramic sintered body preferably has a height in the range of 10 to 30 mm.

Examples of the material of the columnar piezoelectric ceramic sintered body include lead zirconate titanate (PZT), lead titanate, lead zirconate and barium titanate. The columnar piezoelectric ceramic sintered body may be porous or non-porous, but is preferably porous. In the porous columnar piezoelectric ceramic sintered body, pores having an average diameter in the range of 1 to 100 μm are dispersed, and the porosity is preferably in the range of 5 to 50% by volume. The porous columnar piezoelectric ceramic sintered body is formed into a columnar shape by mixing a mixture containing piezoelectric ceramic powder, a binder, and a pore forming material into a columnar shape, and then the columnar molded body is heated to a temperature equal to or higher than the thermal decomposition temperature of the pore forming material. It can be produced by heating to temperature to decompose and remove the pore-forming material and to sinter the piezoelectric ceramic powder. An example of the binder is polyvinyl alcohol. The pore forming material is preferably a spherical resin material. Examples of the spherical resin material include polymethyl methacrylate and foamed polystyrene. The columnar piezoelectric ceramic sintered body is preferably a piezoelectric vibrator polarized in the thickness direction. Examples of the material for the electrode layer include gold and silver.

As described above, the piezoelectric vibrator (also referred to as an ultrasonic vibrator) included in the ultrasonic sensor of the present invention may be directly fixed to the surface of the flat substrate at the bottom thereof, or the piezoelectric vibrator An acoustic matching material layer may be interposed between the substrate and the flat substrate. Examples of the material of the acoustic matching material layer include a synthetic resin (eg, epoxy resin, urethane resin) and rubber (eg, hard rubber).

The side surface and top surface of the piezoelectric vibrator may be covered with a buffer material. Examples of the buffer material include cork, bake material, resin (eg, epoxy resin) and rubber (eg, hard rubber). The buffer material may disperse a substance that absorbs or reflects ultrasonic waves. The piezoelectric vibrator may be accommodated in the cylindrical housing. Examples of the material of the cylindrical housing include metal (aluminum) and synthetic resin (eg, epoxy resin).

In the ultrasonic sensor according to the present invention, the cylindrical rigid wall material is arranged around the side surface of the ultrasonic vibration body (particularly, around the lower portion of the side surface) without being in direct contact with the ultrasonic vibration body. And fixed to the surface of the flat substrate. This cylindrical rigid wall material absorbs Lamb waves generated in a flat substrate such as a bumper by ultrasonic vibration transmitted from a piezoelectric vibrator, and has the effect of confining it inside the cylindrical rigid wall material. It is considered that the ultrasonic vibration transmitted from the vibrator appears as an ultrasonic signal having a preferable pattern having a main lobe with a small side lobe and a suitable width in a space on the opposite side of the flat substrate.

The material of the cylindrical rigid wall material is preferably the same material as that of the flat substrate or a material having higher rigidity than the material of the flat substrate. Examples of the material of the cylindrical rigid wall material include metals (eg, aluminum, stainless steel) and synthetic resins (eg, olefin resin). When the material of the cylindrical rigid wall material is the same material as the material of the flat substrate, the height of the cylindrical rigid wall material is preferably at least twice that of the flat substrate and is in the range of 2 to 50 times. It is particularly preferred. The gap between the lower portion of the side surface of the ultrasonic vibrator and the cylindrical rigid wall material is generally 2 mm or less, preferably in the range of 0.01 to 2 mm, particularly preferably in the range of 0.1 to 1 mm.

The diameter (longest diameter) of the region of the flat substrate surrounded by the cylindrical rigid wall material may be ½ or less of the wavelength λ of the vertical ultrasonic wave signal propagating through the flat substrate. For example, when the ultrasonic wave propagation speed in the flat substrate is 2000 m / sec and the frequency of the ultrasonic signal is 60 kHz, the diameter (longest diameter) of the region of the flat substrate surrounded by the cylindrical rigid wall material Is 16.5 mm or less (= (2000 × 1000) / (60 × 1000) × 1/2).

Next, the ultrasonic sensor of the present invention and the detection device in which the ultrasonic sensor is fixed to the surface of the flat substrate will be described with reference to the accompanying drawings, taking as an example the case where the flat substrate is a bumper for an automobile.

FIG. 1 shows a cross-sectional view of an example of a detection device in which an ultrasonic sensor according to the present invention is fixed to the surface of a bumper. In FIG. 1, the detection device includes a bumper 40 and an ultrasonic sensor 10 fixed to the surface of the bumper. The ultrasonic sensor 10 includes a piezoelectric vibrator (also referred to as an ultrasonic vibrator) 14 that is a columnar piezoelectric ceramic sintered body 12 provided with

electrode layers

13a and 13b on each of an upper surface and a lower surface, and a folded electrode layer 13c. . In the ultrasonic sensor of FIG. 1, an acoustic matching material layer 19 is provided below the piezoelectric vibrator 14, thereby constituting an ultrasonic vibrator, and the ultrasonic vibrator is formed of the acoustic matching material layer 19. It is fixed to the surface of the bumper 40 at the bottom. A transmission circuit 28 and a reception circuit 29 are electrically connected to each of the electrode layers of the piezoelectric vibrator 14, and an arithmetic circuit 30 is electrically connected to each of the transmission circuit 28 and the reception circuit 29 via a lead wire 15. ing. The electrical connection may be a wired connection via a lead wire, or may be a wireless connection. In FIG. 1, an ultrasonic vibrator (comprised of a piezoelectric vibrator 14 and an acoustic matching material layer 19) is in contact with the periphery of the side surface of the acoustic matching material layer 19 provided at the lower part of the ultrasonic vibrator. Instead, the cylindrical rigid wall member 21 is disposed through the gap 25 and is fixed to the surface of the bumper 40.

1, the piezoelectric vibrator 14 is housed in a cylindrical housing 17 whose side surface and upper surface are covered with a buffer material 16 and whose upper part is closed and whose lower part is open. The lower opening of the cylindrical housing 17 is closed by a bottom plate 18.

The cylindrical rigid wall member 21 disposed around the ultrasonic vibrator (piezoelectric vibrator 14 + acoustic matching material layer 19) with a gap is provided with an outer extension 22 and an inner extension 23 at the lower part. Yes. The cylindrical rigid wall material 21 may be fixed to the surface of the bumper 40 by a method such as adhesion, or the cylindrical rigid wall material 21 may be formed integrally with the bumper 40.

In FIG. 1, the bottom surface of the cylindrical housing 17 that accommodates the piezoelectric vibrator 14 and the buffer material 16 is supported by the inner extension 23 of the cylindrical rigid wall material 21 via the bottom plate 18 and the annular flat metal material 24. ing. The upper surface of the cylindrical housing 17 is fixed by a screw lid 26 that is detachably fixed to the upper portion of the cylindrical rigid wall member 21. That is, the cylindrical housing 17 that houses the piezoelectric vibrator 14 and the buffer material 16 is fixed in a state of being sandwiched between the inner extension 23 of the cylindrical rigid wall member 21 and the screw lid 26. The reason why the annular flat metal member 24 is interposed between the inner extension 23 and the cylindrical housing 17 is to reinforce the rigidity of the inner extension 23. That is, when the acoustic matching material layer 19 is interposed, in order to suppress attenuation of the ultrasonic signal in the acoustic matching material layer 19, the thickness of the acoustic matching material layer 19 is reduced, that is, the inner extension 23. It is preferable to reduce the thickness of the material (reducing the height). However, if the thickness of the inner extension 23 is reduced, the rigidity is lowered and the effect as a cylindrical rigid wall material is reduced. For this reason, the rigidity of the inner extension 23 is reinforced by interposing the annular flat metal member 24.

The control device 27 is electrically connected to each of the transmission circuit 28 and the reception circuit 29 that are electrically connected to each of the electrode layers 13 a and 13 c of the piezoelectric vibrator 14, and each of the transmission circuit 28 and the reception circuit 29. The arithmetic circuit 30 is included. The transmission circuit 28, the reception circuit 29, and the arithmetic circuit 30 are each electrically connected to a power source 31.

In the detection apparatus of FIG. 1, the position of an object such as a person or an obstacle present in the space opposite to the ultrasonic sensor 10 with respect to the bumper 40 can be measured as follows.
First, when the arithmetic circuit 30 counts the time T ₀ , the transmission circuit 28 transmits pulsed electric energy to the piezoelectric vibrator 14 of the ultrasonic vibrator. The piezoelectric vibrator 14 converts electrical energy into an ultrasonic signal. The ultrasonic wave generated by the piezoelectric vibrator 14 passes through the bumper 40 and is radiated to the outer surface of the bumper 40 as an ultrasonic signal. The emitted ultrasonic signal is reflected by the surface of the object existing in the outer space. The reflected ultrasonic signal propagates again through the bumper 40 and reaches the piezoelectric vibrator 14. The reflected ultrasonic signal is converted into electric energy by the piezoelectric vibrator 14. The electric energy converted by the piezoelectric vibrator is then sent to the receiving circuit 29. The receiving circuit 29 removes noise of the electric energy, and only the electric energy generated due to the ultrasonic signal reflected on the surface of the object. Is sent to the arithmetic circuit 30. The arithmetic circuit 30 counts the time T ₁ when the electric energy is received, and obtains the distance (m) between the bumper 40 and the object from the following equation (I).

Distance between bumper and object (m) = {Propagation speed of ultrasonic wave in air (m / second) × (T ₁ −T ₀ )} / 2 (1)

FIG. 2 is a chart showing the directivity of the ultrasonic signal transmitted from the detection apparatus shown in FIG. In addition, the material and size of each part of a detection apparatus are as follows. Note that the solid line in FIG. 2 represents the pattern of the ultrasonic signal based on the actual measurement value, and the broken line represents the pattern of the ultrasonic signal based on the calculated value obtained by the simulation.

Piezoelectric vibrator (14): resonance frequency 62.5 kHz
Columnar piezoelectric ceramic sintered body (12): Porous cylindrical zirconium titanate sintered body (porosity 27 volume%, average diameter of pores: 30 μm), diameter 6.4 mm, height 17 mm
Upper electrode layer (13a), lower electrode layer (13b), folded electrode layer (13c): made of baked silver, thickness 10 μm
Buffer material (16): made of cork, width 3.8 mm
Cylindrical housing (17): made of aluminum, thickness 1mm
Bottom plate (18): epoxy resin, thickness 0.6mm
Acoustic matching material layer (19): made of polyurethane, thickness 3.0 mm
Cylindrical rigid wall material (21): made of polypropylene, width (W ₁ ) 2.5 mm
Outer extension portion (22): height 6.6 mm, a width (W ₂₎ 4.9 mm
Inner extension (23): height 1.5 mm, width (W ₃ ) 5.8 mm
Annular flat metal material (24): Made of stainless steel, 1 mm thick
Gap (25) between the acoustic matching material layer 19 and the inner extension 23: 0.5 mm
Bumper (40): made of polypropylene, thickness 2.6 mm, ultrasonic wave propagation speed 2000 m / sec

From the chart of FIG. 2, the detection device according to the present invention is compared with the detection device in which the ultrasonic sensor not including the cylindrical rigid wall material shown in FIG. As a result, side lobes are less likely to occur, and the range of the main lobe is moderately widened.

In the detection apparatus of FIG. 1, the ultrasonic vibrator includes an acoustic matching material layer, and is fixed to the surface of the bumper 40 at the bottom surface of the acoustic matching material layer. (The ultrasonic transducer does not include an acoustic matching material layer), the piezoelectric transducer is fixed to the surface of the bumper 40 at the bottom surface. An example in which the bottom surface of the piezoelectric vibrator 14 is fixed to the surface of the bumper 40 is shown in FIG.

In the detection device of FIG. 3A, the piezoelectric vibrator 14 is directly fixed to the surface of the bumper 40 at the bottom surface, and around the ultrasonic vibrator, the buffer material 16 and the gap are interposed, A cylindrical rigid wall member 21 is fixedly arranged. In FIG. 3, the material and size of each part of the detection device are as follows.

Piezoelectric vibrator (14): same as the piezoelectric vibrator of the apparatus of FIG. 1 Buffer material (16): Same as the buffer material of the apparatus of FIG. 1 Cylindrical rigid wall material (21): made of polypropylene, width 7.78 mm, high 6.57mm
Gap between the buffer material (16) and the cylindrical rigid wall material (21): 0.366 mm
Bumper (40): Same as the bumper of the device of FIG.

(B) of FIG. 3 is a chart showing the directivity of the pattern of the ultrasonic signal transmitted from the detection device of (a). Note that the data in FIG. 3B is based on calculated values obtained by simulation. From this chart, even when the piezoelectric vibrator 14 is fixed to the surface of the bumper 40 at its bottom without interposing the acoustic matching material layer, the ultrasonic wave not including the cylindrical rigid wall material shown in FIG. It can be seen that side lobes are less likely to occur compared to a detection device in which the sensor is fixed to the surface of the bumper.

FIG. 4A is a cross-sectional view of an example of a detection device in which an ultrasonic sensor not including a cylindrical rigid wall material is fixed to the surface of a bumper. In the detection device of FIG. 4A, the piezoelectric vibrator 14 is directly fixed to the surface of the bumper 40 at the bottom surface, and a buffer material 16 is provided around the piezoelectric vibrator 14, but a cylindrical rigid wall is provided. No material is attached. The rest of the configuration is the same as the configuration of the detection device in FIG.

(B) of FIG. 4 is a chart showing the directivity of the pattern of the ultrasonic signal transmitted from the detection device of (a). Note that the data in FIG. 4B is based on calculated values obtained by simulation. From this chart, it can be seen that in an ultrasonic sensor that does not include a cylindrical rigid wall material, a large side lobe is generated in the pattern of the ultrasonic signal that appears on the opposite side of the bumper.

In the description so far, the ultrasonic sensor of the present invention and the detection device in which the ultrasonic sensor is fixed to the surface of the flat substrate are described by taking the case where the flat substrate is a bumper for an automobile as an example. The use of the ultrasonic sensor of the present invention is not limited to automobile bumpers. For example, the ultrasonic sensor of the present invention is fixed to the outside of the lid of the liquid tank, and the liquid level detection device of the liquid in the liquid tank, particularly corrosive gas (eg, hydrogen sulfide, sulfurous acid, nitrous acid, chlorine) is generated. It may be used as a liquid level detection device for liquid or liquid fuel such as gasoline. Further, the ultrasonic sensor of the present invention can be used as an intruder detection device by being fixed to the outer wall of a building or the inner surface of an indoor wall.

DESCRIPTION OF SYMBOLS 10 Ultrasonic sensor 12 Columnar piezoelectric ceramic sintered body 13a Upper surface electrode layer 13b Lower surface electrode layer 13c Folding electrode layer 14 Piezoelectric vibrator (ultrasonic vibrator)
DESCRIPTION OF SYMBOLS 15 Lead wire 16 Buffer material 17 Cylindrical housing 18 Bottom plate 19 Acoustic matching material layer 20 Bottom surface 21 Cylindrical rigid wall material 22 Outer extension 23 Inner extension 24 Annular flat plate metal material 25 Gap 26 Screw lid 27 Control device 28 Transmission circuit 29 Receiving circuit 30 Arithmetic circuit 31 Power supply 40 Flat substrate (bumper)

Claims

A piezoelectric vibrator which is a columnar piezoelectric ceramic sintered body having electrode layers on each of the upper surface and the lower surface may be included, and an acoustic matching material layer may be provided below the piezoelectric vibrator. An ultrasonic vibrator fixed on the surface, a transmission circuit and a reception circuit electrically connected to each of the electrode layers of the piezoelectric vibrator, and an electric connection to each of the transmission circuit and the reception circuit An arithmetic circuit and a cylindrical rigid wall member that is disposed around the side surface of the ultrasonic vibrating body via a gap without being in contact with the ultrasonic vibrating body and fixed to the surface of the flat substrate. Ultrasonic sensor.
The ultrasonic sensor according to claim 1, wherein the cylindrical rigid wall material is formed of a resin material.
The ultrasonic sensor according to claim 1 or 2, wherein the cylindrical rigid wall member has a base portion having a relatively large wall thickness and an extension portion extending upward from the base portion and having a relatively small wall thickness.
The ultrasonic sensor according to any one of claims 1 to 3, wherein an upper surface of the cylindrical rigid wall member is opened, and the opening is covered with a lid.
The at least one part of the said ultrasonic vibrating body is accommodated in a cylindrical housing in the state which the side surface was covered with the buffer material, This cylindrical housing is arrange | positioned inside a cylindrical rigid wall material. 4. The ultrasonic sensor according to any one of 4 above.
The ultrasonic sensor according to any one of claims 1 to 5, wherein the columnar piezoelectric ceramic sintered body is a porous columnar piezoelectric ceramic sintered body.
The ultrasonic sensor according to any one of claims 1 to 6, wherein the flat substrate is an automobile bumper.
A flat substrate, and a piezoelectric vibrator that is fixed to the surface of the flat substrate and is a columnar piezoelectric ceramic sintered body with electrode layers on each of the upper surface and the lower surface, acoustically matched to the lower portion of the piezoelectric vibrator An ultrasonic vibration body that may be provided with a material layer, fixed to the surface of the flat substrate at the bottom, a transmission circuit and a reception circuit electrically connected to each of the electrode layers of the piezoelectric vibrator, An arithmetic circuit electrically connected to each of the transmission circuit and the reception circuit, and a flat plate disposed around the side surface of the ultrasonic vibration member via a gap without contacting the ultrasonic vibration member. An apparatus for detecting the position of an object located in a space opposite to an ultrasonic sensor with respect to a flat substrate, including an ultrasonic sensor including a cylindrical rigid wall member fixed to the surface of the substrate.
The detection device according to claim 8, wherein the cylindrical rigid wall material is formed of a resin material.
10. The detection device according to claim 8, wherein the cylindrical rigid wall member has a base portion having a relatively large wall thickness and an extension portion extending upward from the base portion and having a relatively small wall thickness.
The detection device according to any one of claims 8 to 10, wherein an upper surface of the cylindrical rigid wall member is opened, and the opening is covered with a lid.
The at least part of the ultrasonic vibrating body is accommodated in a cylindrical housing with its side surface covered with a cushioning material, and the cylindrical housing is disposed inside the cylindrical rigid wall material. The detection device according to any one of 11.
13. The detection device according to claim 8, wherein the columnar piezoelectric ceramic sintered body is a porous columnar piezoelectric ceramic sintered body.
The detection device according to claim 8, wherein the flat substrate is a bumper of an automobile.