JPH0574098U - Ultrasonic transducer - Google Patents

Abstract

(57) [Summary] [Purpose] In the ultrasonic transducer, its mounting base and
The object is to isolate the vibration between the piezoelectric elements and to improve the transmission sound pressure and the reception sensitivity. [Structure] The weight M ₁ of the base portion A and the weight M ₁ of the base portion A are optimally applied to the frequency region vibrating in the forced vibration mode.
The weight ratio f of the case portion B to the weight M ₂ was set to 2 or more to optimize the transmission sound pressure and the reception sensitivity of the transducer. On the other hand, at the position of the node in the forced vibration mode, the base is supported by the mounting portion C from its periphery, and the vibration between the mounting portion C and the transducer is insulated and used as a transmitter. In this case, the vibration leakage to the mounting portion C and the decrease in the S / N ratio due to the vibration propagation from the mounting portion C when used as a wave receiver are prevented. Therefore, it is possible to provide a transducer having excellent characteristics such that the transmission sound pressure and the reception sensitivity are good and the S / N ratio is high.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention is a wave receiver that receives a sound wave generated outdoors such as by a piezoelectric element provided inside a metal case and extracts it as an output signal. The present invention relates to an ultrasonic wave transmitter / receiver which is used as a wave transmitter for generation and can be applied to, for example, a rear detection device of an automobile.

[0002]

[Prior Art]

 This type of ultrasonic wave transmitter / receiver is known as disclosed in, for example, Japanese Patent Laid-Open No. 57-56099.

[0003]

[Problems to be solved by the device]

 By the way, when the ultrasonic transmitter / receiver is supported on the mounting part, if it is used as a transmitter, if vibration leaks from its base to the mounting part, the output will decrease or the mounting part will vibrate. Occurs, which causes various inconveniences such as noise. When it is used as a wave receiver, the vibration from the mounting part propagates to the piezoelectric element through the base, causing noise in the output signal and reducing various S / N ratios. It

It is an object of the present invention to isolate the vibration between the mounting base and the piezoelectric element as much as possible, and to improve the transmission sound pressure and the reception sensitivity of the piezoelectric element.

[0005]

[Means for Solving the Problems]

According to the present invention, a base formed by supporting two rod-shaped input / output terminals on a base is hermetically attached to a case formed by joining a piezoelectric element to an inner surface of a metal case. In an ultrasonic transducer which is formed by electrically connecting electrodes on the front and back surfaces of a piezoelectric element and the input / output terminals, and which is applied to a frequency range in which vibration occurs in a forced vibration mode, the weight M _{1 of the} base portion and , If the ratio f (= M ₁ / M ₂ ) to the weight M ₂ of the case is 2 or more and the diameter of the base is D, the force vibration mode of 0.40D to 0.45D from the center of the base is It is the one that is supported around the attachment part at the node position.

[0006]

[Action]

 As will be apparent from experiments described later, in the forced vibration mode, the transmitted sound pressure becomes 84 dB at f = 1 and rises sharply at f = 2. Also, by providing the mounting portion at a position of 0.40D to 0.45D (D; diameter of the base 1) from the center of the base, the mounting portion becomes a node of the forced vibration mode, and the vibration mode It can be optimally applied to the frequency domain that vibrates.

[0007]

【Example】

 The configuration will be described in more detail. There are two types of vibration modes of the base part, a forced vibration mode and a free vibration mode. The former remarkably occurs at a frequency of 40 KHz or less, and the latter remarkably occurs at a frequency of 40 KHz or more. In the former case, when the diameter of the base is d, bending vibration occurs in a vibration mode with a node at a position of 0.40d to 0.45d from the center, theoretically at a position of 0.417d. The latter oscillates at a position 0.30d to 0.35d from the center of the base, theoretically at a position 0.33d.

By the way, in the forced vibration mode, the weight ratio f (= M ₁ / M ₂ ) of the weight M ₁ of the base portion and the weight M ₂ of the case portion, the transmission sound pressure and the reception sensitivity thereof are The relationship was measured.

The ultrasonic transmitter / receiver used for the measurement has the configuration shown in FIG.

That is, 1 is a disk-shaped metal base, and is provided with insertion through holes 2 which are slightly deviated from the center thereof and which face upward and downward. On the outer surface of the base 1, a rod-shaped terminal 4 serving as a ground terminal is provided so as to project at a position symmetrical with respect to the through hole 2.

A rod-shaped terminal 5 is inserted into the through hole 2 and is electrically insulated from the base 1 and held by a glass seal 6 injected into the through hole 2. The base portion A is configured by the above-described configurations.

Reference numeral 10 denotes a frustoconical metal case whose bottom surface is open, and a plate-shaped piezoelectric element 11 made of a piezoelectric material such as PZT has an electrode 12a on one surface thereof on the inner surface of the frusto-conical portion serving as a sound wave transmitting / receiving portion. The electrodes 12b on the other surface are joined and fixed to face the inside of the case. Further, a joining flange 13 is formed on the lower end peripheral portion of the metal case 10 so as to project outward. The case portion B is configured by the above-described configurations.

In the base 1 and the metal case 10, the rod-shaped terminal 5 and the electrode 12 b of the piezoelectric element 11 are connected by a conductive wire 14, and then the joint flange 13 is provided on the upper peripheral surface of the base 1. After welding, the metal case 10 and the base 1 are watertightly closed inside. In this structure, the weight and the like are as follows.

"Case part B"

Weight: 2.3 g (metal case 2.2 g, piezoelectric element 0.1 g)

Material and shape of metal case; made of stainless steel, a = 18 mm, b = 11 mm, c = 6 mm, d = 1 mm

Material and shape of piezoelectric element: lead zirconate titanate, diameter = 9 mm, thickness = 0.3 mm

"Base A"

Weight: Sample A (2.3 g), Sample B (3.45 g), Sample C (4.6 g), Sample D (5.75 g), Sample E (6.9 g)

-Material and shape of the base: stainless steel, diameter = 18 mm, thickness is determined for each sample according to its set weight

· Rod-shaped input / output terminal; made of iron-nickel alloy, diameter 1 mm, e = 10 mm

“Results”

The samples a to e were combined with the case portion A to form a transducer having different weight ratios f, and the transmitted sound pressure was measured. The result is as shown in FIG. As shown in this result, in the forced vibration mode, the transmission sound pressure becomes 84 dB at f = 1, sharply rises to 108 dB at f = 2, 109 dB at f = 2.5, and 113 dB at f = 3. And thereafter gradually increases as the weight ratio f increases.

The relationship between the weight ratio f and its receiving sensitivity is as shown in FIG. As shown in this result, the forced vibration mode is f = 1 and the receiving sensitivity is −64 dB, and the f / 1.5 sharply increases to −55 dB, and at f = 2, −53.5 and f = 2. It becomes −52 dB at 5 and −53 dB at f = 3, and thereafter gradually increases as the weight ratio f increases.

[0025] In summary of these results, it has been shown that the performance of the transducer is improved when the weight ratio f = 2 or more is set. Therefore,

A) 0.40 d to 0.45 d from the center of the base 1 (d; diameter of the base 1) by the mounting portion C in order to have a configuration that can be optimally applied to the frequency region that vibrates in the forced vibration mode. At the position of, support from around the base.

B) In such a support mode, a ratio f (= M ₁ / M ₂₎ of the weight M _{1 of the} base portion and the weight M ₂ of the case portion is set so that the transmission sound pressure and the reception sensitivity are optimized. M ₂ ) is 2 or more.

Accordingly, the present invention is constructed based on the above conditions a and b.

[0029]

[Effect of the device]

In the present invention, as described above, the weight ratio f between the weight M ₁ of the base portion A and the weight M ₂ of the case portion B is adjusted so that it can be optimally applied to the frequency range in which the forced vibration mode is applied. The transmission sound pressure and the reception sensitivity of the transmitter / receiver were set to the optimum value of 2 or more. On the other hand, at the position of the node in the forced vibration mode, the base is supported by the mounting portion C from its periphery to isolate the vibration between the mounting portion C and the transducer, and The leakage of vibration to the mounting portion C when used and the reduction of the S / N ratio due to the vibration propagation from the mounting portion C when used as a wave receiver are prevented. Therefore, there is an excellent effect that it is possible to provide a transducer having excellent characteristics such as a high transmission sound pressure and a high reception sensitivity and a high S / N ratio.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an example of a transceiver according to the present invention.

FIG. 2 is a graph showing the relationship between the weight ratio f and the transmitted sound pressure.

FIG. 3 is a graph showing the relationship between the weight ratio f and the reception sensitivity.

[Explanation of symbols]

 A case part B base part C mounting part 1 base 4, 5 rod-shaped terminal 10 metal case 11 piezoelectric element 20 support seat 21 screw

Claims (1)

[Scope of utility model registration request] 1. A case portion formed by joining a piezoelectric element to an inner surface of a metal case is hermetically adhered to a base portion which supports two rod-shaped input / output terminals on a base, and the piezoelectric element is sealed. The electrodes on the front and back of the element are electrically connected to the input / output terminals,
In the ultrasonic wave transmitter / receiver applied to the frequency region vibrating in the forced vibration mode, the weight M _{1 of the} base portion,
Assuming that the ratio f (= M ₁ / M ₂ ) to the weight M ₂ of the case is 2 or more and the diameter of the base is D, it is 0 from the center of the base.
An ultrasonic transducer that is supported around the attachment part at the node position in the forced vibration mode of 40D to 0.45D.