JP2883057B2 - Ultrasonic transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transducer, and more particularly, to an ultrasonic transducer used in an ultrasonic flowmeter and an ultrasonic level meter, which transmits ultrasonic waves propagating through a pipe. The present invention relates to a structure of an ultrasonic transmitter / receiver that reduces the acoustic damping force of the ultrasonic transmitter / receiver and shortens a connection time of a transmitted / received signal.

[0002]

2. Description of the Related Art An ultrasonic flowmeter is an estimating type flowmeter which transmits and receives ultrasonic waves alternately in a forward direction and a reverse direction with respect to the flow direction of a fluid to be measured, and obtains a flow rate in proportion to a propagation time difference of the ultrasonic waves. It is.

FIG. 4 is a diagram for explaining a conventional ultrasonic flow meter based on the ultrasonic propagation time difference method. FIG.
FIG. 4B is a partial cross-sectional view in the flow direction of the fluid to be measured.
FIG. 4A is a cross-sectional view perpendicular to FIG.
It is a partial sectional view of the conventional ultrasonic transducer used for the ultrasonic flowmeters of (A) and (B), wherein 10 is an ultrasonic flowmeter main body, 11 is a measurement tube, and 12, 13 are A support tube integral with the measuring tube 11 that supports the ultrasonic transducer, 14 and 15 are ultrasonic transducers, 16 is a piezoelectric element, 17 is an impedance matching layer, 18 is a casing, and 19 is an elastic body (mold material). It is.

The ultrasonic flow meter shown in FIG. 4 has an angle β with respect to a tube axis OO of the measuring tube 11 through which the fluid to be measured flows, and passes through the tube axis OO. Support tubes 12 and 13 having a tube axis on the line are provided to face each other, and an ultrasonic transducer 14 is attached to the support tube 12 and an ultrasonic transducer 15 is fixed to the support tube 13 so as to face the same axis. Have been. Predetermined time from the ultrasonic transducer 15, and firing the flow and forward of an ultrasonic by arrow U _A is received at the ultrasonic transducer 14. After receiving the ultrasonic wave, the ultrasonic transducer 14 receives the arrow U _B
The ultrasonic waves are emitted toward the ultrasonic transducer 15 in the direction opposite to the flow indicated by. The ultrasonic transducers 14 and 15 have the same structure and alternately repeat transmission and reception. Ultrasonic transceivers 14 and 1
In 5 the section of the propagation time of the ultrasonic wave of the arrow U _A direction, the time difference indicated by the arrow U _B direction of propagation time, a time difference proportional to the arrow F direction of the flow velocity of the fluid to be measured. The ultrasonic flow meter obtains a flow rate obtained by performing the Reynolds number correction on the flow pattern of the fluid to be measured with respect to the time difference, and obtains the flow rate by multiplying the flow rate by the cross-sectional area of the measurement tube 11.

An ultrasonic level meter emits ultrasonic waves from one ultrasonic transducer toward a liquid surface of a liquid stored in a tank, for example, and transmits and receives ultrasonic waves reflected from the liquid surface. The level is determined as the distance between the ultrasonic transducer and the liquid surface, with half the distance obtained by multiplying the rise time of the transmitted / received signal by the sound velocity at the temperature and pressure of the atmosphere in the tank. Things.

[0006]

In the above-mentioned conventional ultrasonic flowmeter, the ultrasonic signal transmitted from one of the pair of ultrasonic transducers is received by the other ultrasonic transducer. For example, measure the flow and forward propagation time, then
Transmit the ultrasonic wave from the other ultrasonic transducer to the one ultrasonic transducer to measure the propagation time in the opposite direction to the flow, and to calculate the flow velocity from the propagation time difference in the forward and reverse directions. I have. However, as shown in FIG. 4 (B), U _A propagates like some measuring tube 11, through the support tube 12, 13 N _A, likewise, U _B, as part N _B Propagate. These N _A and N _B may affect correct propagation time measurement. In the ultrasonic level meter, the ultrasonic wave transmitted from one ultrasonic transducer is received, the ultrasonic wave reflected from the liquid surface is received, the propagation time is multiplied by the sound speed, and the liquid surface level is measured. I have. However, conventional ultrasonic transducers have a long oscillation duration after ultrasonic transmission, so ultrasonic flowmeters have a long repetition time of forward and reverse ultrasonic emission, and ultrasonic level meters have the same problem. There is a point, and it becomes impossible to measure the flow rate with a large fluctuation in the flow velocity, and the responsiveness of the detection of the liquid level is lowered.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a constricted portion provided at an intermediate portion of an elastic body surrounding an ultrasonic oscillation element of an ultrasonic transducer to reduce ultrasonic waves propagating in a pipe. It is another object of the present invention to provide an ultrasonic transducer capable of shortening the duration of ultrasonic oscillation and capable of measuring a flow rate or a liquid level with excellent responsiveness.

[0008]

According to a first aspect of the present invention, there is provided an ultrasonic transducer for use in an ultrasonic flowmeter and an ultrasonic level meter, wherein the ultrasonic transducer is arranged in a direction perpendicular to a transmitting and receiving plane. A plate-shaped piezoelectric element having an ultrasonic wave transmitting / receiving surface vibrating in a direction; an elastic body surrounding one end of the piezoelectric element by exposing the ultrasonic wave transmitting / receiving surface of the piezoelectric element at one end side and a fixed end surface; A cylindrical housing that is fixed only on the fixed end side, and a small-diameter constricted portion is provided at an intermediate position between the fixed end side of the elastic body and the other end including the piezoelectric element. And a space between the housing and the housing communicates with a space for transmitting and receiving ultrasonic waves.

According to a second aspect of the present invention, in the ultrasonic transducer according to the first aspect, the elastic body is configured such that an outer diameter of the one end side defined by the constricted portion is larger than an outer diameter of the other end side. The outer peripheral surface at one end is fixed to the inner wall surface of the housing, and the outer peripheral surface at the other end has three or more point-like projections. It is designed to make point contact with the wall surface.

According to a third aspect of the present invention, in the ultrasonic transducer according to the first aspect, the elastic body is configured such that an outer diameter of the one end side defined by the constricted portion is larger than an outer diameter of the other end side. An outer peripheral surface on one end side is fixed to the inner wall surface of the housing, and the outer peripheral surface on the other end side has three or more linear projections extending in a longitudinal direction; The portion is in line contact with the inner wall surface of the housing.

According to a fourth aspect of the present invention, in the ultrasonic transducer according to the first aspect, the ultrasonic transducer is fixed to a fixed member at an end face on one end side defined by the constricted portion. It is.

According to a fifth aspect of the present invention, there is provided the ultrasonic transducer according to any one of the first to fourth aspects, wherein an ultrasonic wave transmitting / receiving surface of the piezoelectric element and an external medium for transmitting / receiving an ultrasonic wave are provided.
An impedance matching layer for matching acoustic impedance is provided.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

(Inventions of Claims 1, 2 and 5) FIG.
FIG. 1A is a diagram for explaining an embodiment of the present invention.
FIG. 1 is a partial cross-sectional view taken along line AA of FIG.
1 (B) is a view taken along the line BB of FIG. 1 (A), where 1 is an ultrasonic transducer, 2 is a piezoelectric element, 3 is an impedance matching layer, 4 is an elastic body, 5 is a space, Reference numeral 6 denotes a casing, and 7 denotes a fixing resin member.

[0014] Ultrasonic transducer 1 shown in FIG. 1, for example, a cylindrical casing 6 of stainless steel, a piezoelectric element of the piezoelectric constant d ₃₃ in the bottom end surface center interview engaged a disc shape at the position 2 and the impedance matching layer 3 are provided such that the impedance matching layer 3 is exposed at the lower part. The piezoelectric element 2 and the impedance matching layer 3 serve as an ultrasonic wave transmitting / receiving element, and an elastic body 4 is interposed between the ultrasonic wave transmitting / receiving element and the casing 6. A narrow portion 4c having a small diameter is provided at a central portion of the elastic body 4, and an outer peripheral surface of an upper end portion 4a at an upper portion vertically divided by the constricted portion 4c is fixed to an inner wall surface of the casing 6, and furthermore, an upper end surface is formed. It is joined to the resin member 7. The lower end 4b at the lower portion has a smaller diameter than the upper end 4a and has a gap between the lower end 4b and the casing 6, and is suspended by the constricted portion 4c. The ultrasonic wave transmitting / receiving element is coaxial with the lower end 4b, and a lead wire (not shown) of the piezoelectric element 3 penetrates through the elastic body 4 and the resin part 7 and extends to the outside.

In the structure described above, the lower end surface 4b of the elastic body 4 is suspended by the constricted portion 4c with a gap between it and the casing 6, and three or more points provided on the outer peripheral surface of the lower end portion 4b. It is coaxially supported on the casing 6 by the projections 4d. Since the point-like projections 4d are provided, the space 5 near the constricted portion 4c communicates with the space for transmitting and receiving ultrasonic waves, and the elastic body 4 always keeps a stable state.

In the ultrasonic transducer 1 having the above structure, when the piezoelectric element 2 is driven by the fall of the driving pulse, the vibration system composed of the spring force of the elastic body 4 and the mass of the lower end 4b. A piezoelectric alternating strain that compresses and expands in the axial direction is generated, the acoustic impedance with the external medium that transmits and receives ultrasonic waves is matched via the impedance matching layer 3, and the ultrasonic waves are emitted more efficiently than the piezoelectric element 2 alone. I do. At the same time, the lower end 4b of the elastic body 4 also vibrates, and this vibration propagates to the constricted portion 4c at the center. However, this vibration is caused by the fact that the cross-sectional area of the constricted portion 4c is small and the internal friction is large.
Damping is effected by the damping action of the space 5, and the piezoelectric alternating distortion rapidly attenuates.

(Invention of Claim 3) FIG. 2 is a view for explaining an embodiment of the invention of claim 3, and FIG. 2 (A) is a portion taken along line AA of FIG. 2 (B). The cross-sectional view, FIG.
FIG. 3 is an arrow BB diagram of FIG. In the figure, reference numeral 4e denotes a linear projection provided in the longitudinal direction of the outer peripheral surface of the lower end portion 4b of the elastic body 4, and portions having the same operation as in FIG. 1 are denoted by the same reference numerals as in FIG. It is.

The linear projection 4e shown in FIG. 2 is a linear body provided with at least three (four in FIG. 2) dividing the outer periphery on the outer peripheral surface of the lower end 4b of the elastic body 4, and is parallel to the axis. Or
It has a shape inclined with respect to the axis or curved in the axial direction. Moreover, the space 5 outside the constricted portion 4c communicates with a space for transmitting and receiving ultrasonic waves.

By providing the linear projection 4e, the lower end portion 4b is more stably suspended on the constricted portion 4c.
The internal friction between the linear projection 4e and the casing 6 is larger than that of the point-like projection 4d, and the attenuation at the time of transmitting the ultrasonic wave is larger.

(Invention of Claim 4) FIG. 3 is a view for explaining an embodiment of the invention of claim 4, and FIG. 3 (A) is a portion taken along line AA of FIG. 3 (B). FIG. 3B is a sectional view.
3A is an arrow BB line in FIG. 3 (A), in which 4c 'is a constricted portion, and portions having the same function as in FIG.
The same reference numerals as in FIG. 1 are used.

The ultrasonic transducer shown in FIG. 3 has a structure in which the casing 6 is omitted and the elastic body 4 is joined to and supported by a fixing resin member 7. This is a portion that stably supports the lower end portion 4b including the piezoelectric element 2 and the impedance matching layer 3 of the elastic body 4 that is not supported by the elastic member 4, and requires a large strength. It is shown in the figure). Moreover, due to the elastic resistance of the constricted portion 4c ', there is a function of attenuating the ultrasonic waves, and since there is no casing 6, an inexpensive ultrasonic transducer can be obtained.

[0022]

【The invention's effect】

The elastic body 4 joined to the casing 6 and the resin member 7 for fixing is provided in the casing 6,
An ultrasonic wave transmitting / receiving element in which the piezoelectric element 2 and the impedance matching layer 3 are joined to each other is provided at a lower end portion 4b, and a constricted portion 4 is provided at an intermediate portion.
c, and the space 5 outside the constricted portion 4c and the space for transmitting and receiving ultrasonic waves are communicated and suspended in a stable state, so that the ultrasonic vibration when the ultrasonic transducer is pulse-driven is Attenuation increases. As a result, the ultrasonic wave propagating in the pipe is reduced, and the repetition period of the ultrasonic wave transmission and reception is shortened, so that it is suitably used for an ultrasonic flowmeter for measuring a flow rate with a large flow rate variation or a level meter with a large level variation. can do.

According to the second aspect of the present invention, three or more point-like projections 4d are provided on the outer periphery of the lower end 4b of the constricted portion 4c of the elastic body 4 and are supported by the casing 6, so that a superposition having a stable support position is provided. An acoustic transducer is obtained.

According to the third aspect, since the linear projections 4e in the longitudinal direction are provided on the outer peripheral surface of the lower end portion 4b of the elastic body 4, the support with higher stability is provided.

Effect corresponding to claim 4: Since the casing 6 is omitted, the structure becomes simpler and an inexpensive ultrasonic transducer can be obtained.

According to the fifth aspect, it is more efficient to transmit and receive ultrasonic waves to and from the piezoelectric element 2 via the impedance matching layer 3 as compared with the case where the ultrasonic wave transmitting and receiving element is the piezoelectric element 2. Ultrasonic transmission / reception is possible.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the first, second, and fifth aspects of the present invention;

FIG. 2 is a view for explaining an embodiment of the invention of claim 3;

FIG. 3 is a diagram for explaining an embodiment of the invention of claim 4;

FIG. 4 is a view for explaining a conventional ultrasonic flowmeter based on the ultrasonic propagation time difference method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic wave transmitter / receiver, 2 ... Piezoelectric element, 3 ... Impedance matching layer, 4 ... Elastic body, 5 ... Space, 6 ... Casing, 7
... Resin member for fixing.

Continued on the front page (72) Osamu Ono 3-10-8 Kamiochiai, Shinjuku-ku, Tokyo Inside the oval company (72) Inventor Tetsuya Kawada 3-10-8, Kamiochiai, Shinjuku-ku, Tokyo Inside the oval company (72) Inventor Hiroaki Nakazawa 3-10-8 Kamiochiai, Shinjuku-ku, Tokyo Inside Oval Co., Ltd. (56) References JP-A-51-13275 (JP, A) JP-A-52-16261 (JP, A) 60-148727 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01F 1/66

Claims (5)

(57) [Claims] In the structure of an ultrasonic transducer used for an ultrasonic flowmeter and an ultrasonic level meter, the ultrasonic transducer has a plate-like shape having an ultrasonic transmitting and receiving surface vibrating in a direction perpendicular to a transmitting and receiving surface. A piezoelectric element, one end of which is a fixed end face, and the other end of which is an elastic body that exposes the ultrasonic wave transmitting / receiving surface of the piezoelectric element and surrounds the periphery of the piezoelectric element, and a cylindrical shape that fixes the elastic body only on the fixed end side. A small-diameter constricted portion is provided at an intermediate position between the fixed end side of the elastic body and the other end including the piezoelectric element, and a space between the constricted portion and the housing transmits and receives ultrasonic waves. An ultrasonic transducer that is in communication with a wave-generating space. 2. The elastic body has an outer diameter on one end side defined by the constricted portion larger than an outer diameter on the other end side,
The outer peripheral surface on one end side is fixed to the inner wall surface of the housing, and the outer peripheral surface on the other end side has three or more point-like projections, and the point-like projections make point contact with the inner wall surface of the housing. The ultrasonic transducer according to claim 1, wherein: 3. The elastic body has an outer diameter on one end side defined by the constricted portion larger than an outer diameter on the other end side,
The outer peripheral surface at one end side is fixed to the inner wall surface of the housing, and the outer peripheral surface at the other end side has three or more linear projections extending in a longitudinal direction, and the housing is formed by the linear projections. The ultrasonic transducer according to claim 1, wherein the ultrasonic transducer is in line contact with the inner wall surface. 4. The ultrasonic transducer according to claim 1, wherein the ultrasonic transducer is fixed to a fixing member at an end face on one end side defined by the constricted portion. 5. An impedance matching layer for matching acoustic impedance is provided between an ultrasonic wave transmitting / receiving surface of the piezoelectric element and an external medium for transmitting / receiving ultrasonic waves. The ultrasonic transducer according to any one of the above.