JP5414427B2 - Ultrasonic transceiver - Google Patents

Description

The present invention relates to an ultrasonic transmitter / receiver capable of generating ultrasonic waves by vibration of a vibrating surface of a bottomed cylindrical case and receiving ultrasonic waves from the outside on the same surface.

2. Description of the Related Art Conventionally, ultrasonic transmitters / receivers that can generate ultrasonic waves by vibration of a vibration surface and can receive ultrasonic waves from the outside on the same surface have been widely used. 2. Description of the Related Art In recent years, ultrasonic transmitters / receivers made of a structure in which a piezoelectric element is attached to the bottom of a bottomed case made of metal have been produced in large quantities for back sonar of automobiles (vehicles). Since these ultrasonic transmitters / receivers generate ultrasonic waves in the air by the vibration of the ultrasonic transmitter / receiver, when attaching them, the ultrasonic transmitter / receiver is held with a soft material that does not interfere with the vibration of the ultrasonic transmitter / receiver. There is a need. Moreover, in order to prevent the noise which generate | occur | produces when the vibration of an ultrasonic transmitter / receiver is transmitted to the target object which attaches an ultrasonic transmitter / receiver, it is necessary to hold | maintain an ultrasonic transmitter / receiver with a material with high vibration insulation. In order to hold the ultrasonic transceiver, a cushion made of a low hardness silicone material is widely used. The cushion is often made of a material that cannot be painted, resulting in a problem of poor design.

Ultrasonic transceivers that do not require a cushion are being developed. For example, in the ultrasonic transmitter / receiver described in Patent Document 1, the side vibration of the ultrasonic transmitter / receiver is suppressed by forming a groove on the side surface of the bottomed cylindrical case to be configured. In the ultrasonic transmitter / receiver described in Patent Document 2, an ultrasonic transmitter / receiver with less vibration transmission to the outside is realized by attaching a vibration insulator made of resin outside the ultrasonic transmitter / receiver. The vibration insulator has, for example, double side walls and a bottom surface, and a space between the double side walls is filled with low-hardness silicone. An ultrasonic transmitter / receiver that does not require a cushion is realized by molding the vibration insulator with a resin material that can be painted such as PBT and has excellent durability.
Japanese Patent Publication No. 2004-343660 Patent application 2009-109783 Tanikoshi Shinji “Ultrasound and how to use it – Ultrasonic Transceiver / Ultrasonic Motor”, Nikkan Kogyo Shimbun

However, even if a vibration insulator is attached, vibration transmission to the outside may not be sufficiently suppressed. When the mounting portion is small and the vibration insulator cannot be designed to have a sufficiently effective dimension, reflection noise from the mounting portion is generated. Reflection noise from the mounting portion is particularly problematic when used for the purpose of detecting an object at a long distance. In order to satisfy the required acoustic characteristics within the limited dimensions, an ultrasonic transmitter / receiver installed inside is required to have a structure with less vibration transmission to the outside.

Accordingly, an object of the present invention is to realize an ultrasonic transmitter / receiver with improved vibration insulation by improving the ultrasonic transmitter / receiver to a structure with less vibration transmission to the outside.

According to the first aspect of the present invention, there are provided two bottom vibration modes comprising a double bottom cylindrical case having a space inside the bottom surface made of metal or resin, and a piezoelectric element bonded to the bottom surface of the double bottom cylindrical case. An ultrasonic transmitter / receiver characterized by having a vibration absorber composed of two or more multiple tubes arranged concentrically, the tube having the smallest inner diameter among the multiple tubes;
Ultrasonic wave transmission / reception with improved vibration insulation by attaching a vibration absorber made of a resin material characterized in that at least one end of the tube having the largest inner diameter among the multiple tubes is closed and has a bottom surface. Realize the vessel.

In the invention according to claim 2, two bottom vibrations comprising a double bottom cylindrical case having a space inside the bottom made of metal or resin, and a piezoelectric element bonded to the bottom surface of the double bottom cylindrical case. An ultrasonic transmitter / receiver with improved vibration insulation is realized by attaching a bottomed cylindrical tube made of resin with a larger inner diameter than the ultrasonic transmitter / receiver to an ultrasonic transmitter / receiver characterized by having a mode Do

In the invention described in claim 3, the inside of the vibration absorber described in claim 1 is filled with at least one of felt, a sound absorbing material composed of at least one of silicone and urethane, and at least one of silicone and urethane. In this way, it is possible to prevent the ultrasonic waves generated inside the vibration absorber. Realize ultrasonic transmitter / receiver with less noise.

According to a fourth aspect of the present invention, at least one tube constituting the vibration absorber according to the third aspect is integrated with a housing that houses a circuit related to processing of a received signal of the ultrasonic transceiver. It is characterized by things. By integrating the housing and the vibration absorber, the number of parts can be reduced.

Practical example 1

An embodiment of the present invention as set forth in claim 1 is shown in FIG. For example, the bottom of the aluminum case 1 made of an aluminum material having a height of 9 mm with a circle of φ14 as the design surface 1a is bonded to the bottom surface 1b of the aluminum case 1 by using an adhesive. A cylindrical case 13 is created. A circular piezoelectric element 2 made of lead zirconate titanate (PZT) is bonded to the top surface of the small case 3. The space between the aluminum case 1 and the small case 3 is filled with a sound insulator 11 formed by molding a silicone or urethane foam. The sound insulator 11 can be inserted when bonding the two cases. It is known that an ultrasonic transmitter / receiver in which a piezoelectric element is bonded to a bottom surface portion of a double bottom cylindrical case has two different bottom surface vibration modes. At this time, the dimensions of the double bottom cylindrical case 13 and the piezoelectric element 2 are designed so that the resonance frequency of the bottom vibration mode at a low frequency is 50 kHz and the resonance frequency of the bottom vibration mode at a high frequency is 68 kHz. Yes. The double bottom cylindrical case refers to a case having a structure having two vibration surfaces on the bottom surface.

One of the silver electrodes 2a provided on the piezoelectric element 2 and the double bottom cylindrical case 13 are electrically coupled. The lead wire 12 is attached to one electrode of the piezoelectric element 2 by soldering, and the lead wire 12 is soldered to the double bottom cylindrical case 13 by aluminum solder. One end of the lead wire 12 is soldered to the wire harness 14. The piezoelectric element 2 is covered with a sound absorbing material 10 formed by molding a foam of silicone or urethane. The inside of the aluminum case 1 is filled with a sealant 9 made of silicone or urethane. (In the top view of FIG. 1, the sound absorbing material 10, the lead wire 12, the sealant 9, and the wire harness 14 are omitted. In the top views of FIGS. 2, 6, and 7, the sound absorbing material 10 and the lead wire 12 are omitted. (The sealing agent 9 and the wire harness 14 are omitted.)

The vibration absorber 4 is attached to the outside of the double bottom cylindrical case 13. The vibration absorber 4 consists of two concentric cylinders, and the thickness of the outer cylinder 4a and the inner cylinder 4b is 0.3 mm. The outer cylinder 4a and the inner cylinder 4b are completely connected by a bottom surface 4c serving as a design surface having a thickness of 0.3 mm. The vibration absorber 4 can be formed by molding a resin material having a soft elastic modulus equivalent to ABS in order to enhance vibration insulation. A space between the outer cylinder 4 a and the inner cylinder 4 b of the vibration absorber 4 is filled with silicone 5 having a hardness of about 40. In addition to silicone, vibration transmission can also be suppressed by filling a sound insulating body formed of urethane, low-hardness elastomer, rubber, or a foam made of them. The side surfaces of the double bottom cylindrical case 13 and the vibration absorber 4 are bonded with an adhesive so that there is no step between the design surface 1a of the double bottom cylindrical case 13 and the design surface 4c of the vibration absorber 4. Yes.

For comparison, FIG. 2 shows a state of an ultrasonic transmission / reception apparatus assembled with a conventional vibration insulator. The piezoelectric element 2 is bonded to the bottom surface 6b of the bottomed cylindrical case 6 made of an Al material. The bottomed cylindrical case 6 is dimensioned so that the resonance frequency in the bottom vibration mode is 68 KHz. The other parts have the same structure as in FIG.

FIG. 3 shows the reflection sensitivity and reverberation waveforms observed when the ultrasonic transceiver is driven at 68 kHz. The reflected waveform from a pole installed 60 cm in front of the ultrasonic transceiver can be seen. The measurement was performed by installing the ultrasonic transmitter / receiver of the present invention shown in FIG. 1 and the conventional ultrasonic transmitter / receiver shown in FIG. 2 on a jig provided with an opening. 3a shows the case of the practical example of the present invention shown in FIG. 1, and FIG. 3b shows the case of the conventional embodiment shown in FIG. In the case of the present invention, noise due to external reflection is hardly observed. On the other hand, in the conventional case, many reflection noises due to vibration transmission to the outside (housing, bumper cover, etc.) are observed. When the outer diameter of the vibration insulator and the outer diameter of the internal ultrasonic transmitter / receiver are limited, vibration transmission to the outside may not be suppressed only by the vibration insulator. By adopting the structure of the present invention, high vibration insulation can be realized.

FIG. 4 shows the amount of displacement of the bottom surface of the ultrasonic transceiver. The amount of displacement between an ultrasonic transceiver using a double bottom cylindrical case and an ultrasonic transceiver using a conventional bottomed cylindrical case was compared. The measurement was performed with a laser displacement meter. It can be seen that the ultrasonic transmitter / receiver using the double bottom cylindrical case has a large decrease in displacement at the bottom edge (7 mm position) as compared with the ultrasonic transmitter / receiver having the conventional structure. By utilizing this feature of the double bottom cylindrical case, a great effect (a significant reduction in reflection noise during installation) that cannot be obtained with an ultrasonic transmitter / receiver having a conventional structure is obtained.

FIG. 5 shows a modification of the ultrasonic transceiver having a double bottom cylindrical structure calculated by the finite element method. FIG. 5a shows the state of displacement in the bottom vibration mode at a low frequency (50 kHz in the embodiment). In the low frequency bottom vibration mode, the vibration surface 1 and the vibration surface 2 vibrate in the same phase. It can be seen that the bottom vibration vibrates throughout the case with the inner wall of the large case as a node. Similarly in the case of the conventional structure, the entire case vibrates with the inner wall of the case as a node. FIG. 5b shows the displacement in the bottom vibration mode at a high frequency (68 kHz in the embodiment). Contrary to the case of the low frequency, it can be seen that the vibrating surface 1 and the vibrating surface 2 vibrate in opposite phases. It can also be seen that the large case and the small case oscillate as a joint. From this result, in the bottom vibration mode on the higher frequency side, the vibration of the outer wall of the large case is small because the small case and part of the bottom surface of the large case vibrate somewhat independently, and therefore the vibration transmission to the outside Is also estimated to be small.

Practical example 2

Next, another embodiment is shown in FIG. The vibration absorber 4 in the previous embodiment is replaced with the vibration absorber 7 in which the innermost cylinder is provided with a thin bottom 7a. The thickness of the bottom surface 7a provided on the innermost cylinder is 0.3 mm. Other dimensions are the same as those in the first embodiment. The vibration absorber 7 is formed of a resin material having an elastic modulus equivalent to ABS. The top surface 1a of the double bottom cylindrical case is bonded to the vibration absorber 7 with an adhesive. The inside of the vibration absorber 7 is filled with silicone 5 having a hardness of about 40.

Practical example 3

Next, an embodiment of the invention of claim 2 is shown in FIG. The vibration absorber 4 in the previous implementation is replaced with a bottomed cylindrical vibration absorber 8 having an outer diameter φ16, an inner diameter φ15.4, and a height of 9 mm. The bottom surface of the vibration absorber 8 and the top surface 1a of the double bottom cylindrical case are bonded with an adhesive. The thickness of the bottom surface of the vibration absorber 8 is 0.3. The vibration absorber 8 is formed of a resin material having an elastic modulus equivalent to ABS. The inside of the vibration absorber 8 is filled with silicone 5 having a hardness of about 40.

An example of an ultrasonic transceiver embodying claim 1 Example of conventional ultrasonic transceiver Reflection sensitivity and reverberation waveform Comparison of measurement results by laser displacement meter Analysis result by finite element method An example of an ultrasonic transmitter / receiver embodying claim 2 An example of an ultrasonic transmitter / receiver embodying claim 3

1 Aluminum case 1a Aluminum case top 1b Aluminum case bottom 2 PZT
2a PZT both sides (silver electrode part)
3 Small case 4 Vibration absorber (Claim 1)
4a Outermost cylinder 4b Innermost cylinder 5 Silicone 6 Bottomed cylindrical case 6b Bottom part of bottomed cylindrical case 7 Vibration absorber having bottom (in case of claim 2)
7a Bottom surface of vibration absorber having bottom 8 Vibration absorber (Claim 3)
9 Sealant 10 Sound absorbing material 11 Sound insulator 12 Lead wire (electrode)
13 Double bottom cylindrical case 14 Wire harness

Claims (4)

It has two bottom vibration modes consisting of a double bottom cylindrical case having a space inside a bottom portion made of metal or resin, and a piezoelectric element bonded to the bottom surface of the double bottom cylindrical case. A vibration absorber composed of two or more multiple tubes arranged concentrically in an ultrasonic transceiver; a tube having the smallest inner diameter among the multiple tubes;
An ultrasonic transceiver characterized in that a vibration absorber made of a resin material characterized in that at least one end of a cylinder having the largest inner diameter among the multiple cylinders is closed and has a bottom surface. It has two bottom vibration modes consisting of a double bottom cylindrical case having a space inside the bottom surface made of metal or resin and a piezoelectric element bonded to the bottom surface of the double bottom cylindrical case. An ultrasonic transceiver characterized in that a bottomed cylindrical tube made of a resin having an inner diameter larger than that of the ultrasonic transceiver is attached to the ultrasonic transceiver. 2. The ultrasonic transmission / reception according to claim 1, wherein the inside of the vibration absorber is filled with felt, a sound absorbing material made of at least one of silicone and urethane, and at least one of silicone and urethane. vessel The at least one cylinder constituting the vibration collector is integrated with a housing made of resin containing a circuit related to processing of a reception signal of the ultrasonic transceiver. Ultrasonic transceiver

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