JP4793916B2 - Ultrasonic flow meter sensor mounting structure - Google Patents

Description

  The present invention relates to a sensor mounting structure for an ultrasonic flowmeter.

  2. Description of the Related Art Conventionally, an ultrasonic flowmeter that measures flow velocity using ultrasonic waves is known as a flow measurement device that measures the flow rate of a fluid such as city gas or water. For example, in Patent Document 1, an ultrasonic wave is oscillated toward the upper or lower side in the fluid flow direction on the wall portion of the flow path for allowing the fluid to pass, and then arrives from the upper or lower side in the flow direction. An ultrasonic flowmeter having a pair of transmission / reception transducers (ultrasonic sensors) that receive ultrasonic waves is disclosed.

Japanese Patent No. 3334857

  In such an ultrasonic flowmeter, as shown in FIG. 9, a pair of transmission / reception transducers 123a and 123b (ultrasonic sensors) are respectively attached to the wall 121a of the flow path 121, and transmit and receive ultrasonic waves alternately. Thus, the flow rate is generally measured by measuring the delay time difference. Therefore, for example, when one transmission / reception vibrator 123 a oscillates (transmits) an ultrasonic wave, the vibration (vibration) of the vibration surface 123 c itself of the transmission / reception vibrator 123 a propagates through the wall 121 a of the flow path 121 (surface acoustic wave X ( In some cases, the vibration surface 123c of the other transmitting / receiving vibrator 123b is vibrated. When such a surface acoustic wave X is transmitted to the transmission / reception vibrator 123b earlier than the propagation time of the ultrasonic wave to be originally measured, it becomes impossible or difficult to distinguish from the output signal generated by the transmission / reception vibrator 123b. It may cause malfunction.

  Therefore, conventionally, the surface acoustic wave X is prevented from acting as a disturbance factor by inserting the transmission / reception vibrators 123a and 123b into the accommodation hole 122 through a buffer material 124 such as rubber or sponge. However, in the normally used buffer material 124, its isolation (blocking, insulation) effect varies greatly depending on its own hardness (or Young's modulus), contact state, and the like. For example, when the temperature becomes low, the cushioning material 124 becomes hard and the surface acoustic wave X easily propagates. Further, when the buffer material 124 is press-fitted into the accommodation hole 122 or tightened with screws or the like in order to improve the mounting accuracy, the buffer material 124 becomes hard and the surface acoustic wave X is easily propagated.

  Accordingly, an object of the present invention is to provide a sensor mounting structure for an ultrasonic flowmeter that is less likely to cause surface acoustic waves to act as a disturbance factor even when measurement conditions, mounting conditions, and the like change, and that can obtain stable measurement accuracy and mounting accuracy. Is to provide.

Means for Solving the Problems and Effects of the Invention

As a premise to solve the above problems, the sensor mounting structure of the ultrasonic flowmeter is
A pair of transmission / reception units that receive ultrasonic waves coming from the upper side or lower side in the flow direction after oscillating ultrasonic waves toward the upper or lower side in the fluid flow direction on the wall of the flow path for allowing the fluid to pass In the sensor mounting structure of the ultrasonic flowmeter to which the transducer is mounted,
Each of the transmission / reception vibrators has a vibration surface that is inserted directly into an accommodation hole formed through the wall portion of the flow path or indirectly through another member, and has a vibration surface that vibrates by receiving or oscillating ultrasonic waves. While being arranged on the front side in the insertion direction so as to face the flow path,
In a form in which a plurality of contact portions having minute contact areas such as dot-like, line-like, and dot-like are formed dispersed in the circumferential direction, the outer peripheral surface of the transmission / reception vibrator is formed of the accommodation hole or other member There is a case where the inner peripheral surface is contacted and held.

In addition, as a premise for solving the above problems, the sensor mounting structure of the ultrasonic flowmeter is specifically,
A pair of transmission / reception units that receive ultrasonic waves coming from the upper side or lower side in the flow direction after oscillating ultrasonic waves toward the upper or lower side in the fluid flow direction on the wall of the flow path for allowing the fluid to pass In the sensor mounting structure of the ultrasonic flowmeter to which the transducer is mounted,
Each of the transmission / reception transducers is accommodated in a cylindrical accommodation holder, inserted into an accommodation hole formed through the wall of the flow path through the accommodation holder, and oscillates or receives ultrasonic waves to vibrate. Is arranged on the front side in the insertion direction so that the vibrating surface to face the flow path,
In at least one of the space between the outer peripheral surface of the transmission / reception vibrator and the inner peripheral surface of the housing holder and between the outer peripheral surface of the housing holder and the inner peripheral surface of the housing hole, dot-like, linear, dot-like There are cases where the outer peripheral surface of the transmission / reception vibrator is in contact with and held by the inner peripheral surface of the housing holder in a form in which a plurality of contact portions having minute contact regions such as are formed dispersed in the circumferential direction. There is .

  According to these sensor mounting structures, a plurality of contact portions having minute contact areas such as dots, lines, dots (polka dots), etc. are formed in a distributed manner along the circumferential direction, and are transmitted and received. The outer peripheral surface of the child is brought into contact with and held on the inner peripheral surface of the storage hole or the storage holder. Accordingly, since the pair of transmission / reception vibrators are respectively held in the point contact (or minute contact similar to the state) in the accommodation hole or the accommodation holder, the vibration of the transmission / reception vibrator is not easily transmitted to the accommodation hole or the accommodation holder. The surface acoustic wave hardly propagates to the other transmitting / receiving transducer (it hardly acts as a disturbance factor). In addition, according to such an attachment structure, even if the measurement conditions and the attachment conditions change, the isolation effect of the surface acoustic wave does not vary so much, so that stable measurement accuracy and attachment accuracy can be easily obtained. . As a result, an ultrasonic flowmeter having a high surface acoustic wave isolation effect and an excellent S / N ratio can be realized.

  In addition, when the transmitting / receiving transducer is inserted into the accommodation hole via the accommodation holder, for example, the accommodation holder is injection-molded integrally with resin, and the contact portion is easily formed with a certain accuracy. Variations in measurement accuracy among individuals can be suppressed.

  In order to form a contact portion using such an accommodation holder, for example, the inner protrusion of the accommodation holder that contacts the outer circumferential surface of the transmission / reception vibrator is dispersed and bulged along the circumferential direction on the inner circumferential surface of the accommodation holder. The outer peripheral surface of the receiving holder can be fixed to the inner peripheral surface of the receiving hole in a state where the inner protruding portion is in contact with and held on the outer peripheral surface of the transmitting / receiving transducer to form the contact portion.

  In addition, outer protrusions that come into contact with the inner peripheral surface of the storage hole are formed on the outer peripheral surface of the storage holder so as to disperse and bulge along the circumferential direction, and the outer protrusion contacts the inner peripheral surface of the storage hole. It is also possible to fix the inner peripheral surface of the housing holder to the outer peripheral surface of the transmission / reception vibrator in the state of holding and forming the contact portion.

  Furthermore, the inner peripheral surface of the storage holder is formed with inner protrusions that come into contact with the outer peripheral surface of the transmission / reception vibrator in a distributed manner and bulge along the circumferential direction. The outer protrusions that contact the inner peripheral surface are dispersed and bulged along the circumferential direction, and the inner protrusions contact and hold the outer peripheral surface of the transmission / reception vibrator to form a contact portion, while the outer protrusions The contact portion can also be formed by contacting and holding the inner peripheral surface of the accommodation hole.

  In this way, depending on the measurement conditions and mounting conditions, the inner protruding portion like a claw shape is bulged, the outer protruding portion like a claw shape is bulged, or the inner protrusion like a claw shape is formed. Since the portion and the outer protruding portion can be bulged, the degree of freedom in design can be increased. Further, in any case, it is possible to contact between the outer peripheral surface of the transmitting / receiving vibrator and the inner peripheral surface of the receiving hole only by bulging and forming a plurality of protrusions on the inner peripheral surface and / or outer peripheral surface of the receiving holder. Since the portion is formed, a contact form in the minute contact region can be realized at low cost and with high accuracy.

On the other hand, in order to solve the above problems, the sensor mounting structure of the ultrasonic flowmeter according to the present invention is:
A pair of transmission / reception units that receive ultrasonic waves coming from the upper side or lower side in the flow direction after oscillating ultrasonic waves toward the upper or lower side in the fluid flow direction on the wall of the flow path for allowing the fluid to pass In the sensor mounting structure of the ultrasonic flowmeter to which the transducer is mounted,
Each of the transmission / reception vibrators is directly or indirectly inserted into an accommodation hole formed through the wall of the flow path through a cylindrical accommodation holder , and vibrates by oscillating or receiving ultrasonic waves. While the surface is disposed on the front side in the insertion direction so as to face the flow path,
A lid that closes from the rear side in the insertion direction is fixed to the accommodation hole or the accommodation holder in a state where a predetermined gap is formed between the rear end surface of the transmission / reception vibrator,
The lid has a minute contact area such as a dot shape, a line shape, or a dot shape, and a forward projecting portion that contacts the rear end surface of the transmission / reception vibrator is dispersed along the circumferential direction in the gap. When the lid is fixed to the accommodation hole or the accommodation holder, the rear end surface of the transmission / reception vibrator is brought into contact with and held by the front projecting portion of the lid .

  According to such a sensor mounting structure, a plurality of contact portions having minute contact areas such as dot-like, line-like, and dot (polka dot pattern) shapes are distributed and formed along the circumferential direction. The rear end surface of the vibrator is contacted and held by a lid that closes the housing holder from the rear side in the insertion direction. Therefore, the pair of transmission / reception vibrators are held in a point contact (or close contact with the lid) that closes the housing holder from the rear side in the insertion direction, so that the vibrations of the transmission / reception vibrators are not easily transmitted to the lid. As a result, the surface acoustic wave generated on the back side of the transmission / reception vibrator is less likely to propagate to the other transmission / reception vibrator. Accordingly, as in the case of the surface acoustic wave generated on the front end side of the transmission / reception vibrator, the surface acoustic wave is less likely to act as a disturbance factor. In addition, according to such an attachment structure, even if the measurement conditions and the attachment conditions change, the isolation effect of the surface acoustic wave does not vary so much, so that stable measurement accuracy and attachment accuracy can be easily obtained. .

  In this case, a front protrusion (for example, a claw shape) that contacts the rear end surface of the transmission / reception vibrator is formed on the lid in a distributed manner along the circumferential direction, and the front protrusion contacts the rear end surface of the transmission / reception vibrator. The lid can be fixed to the housing holder in a state where a contact portion is formed by holding and a predetermined gap is formed between the lid and the transmission / reception vibrator. By simply forming a plurality of front protrusions on the lid, a contact part and a gap are formed between the rear end face of the transmitting and receiving vibrator, so that it is possible to realize a contact form in a minute contact area at low cost and with high accuracy. . In addition, when using the same or the same kind of synthetic resin for the lid and the accommodation holder, various fixing methods can be employed. For example, a polyacetal (POM) resin may be fixed by a snap-in method or a screwing method, and an ABS resin or an ASA resin may be fixed by using an adhesive or a solvent such as acetone.

  Then, on the rear side in the insertion direction of the lid body, a pressing member that is attached and fixed to the wall portion of the flow path in order to insert the lid body and the housing holder and close the housing hole, and the front end surface of the pressing member and the lid An elastic member disposed between the rear end surface of the body and the elastic member elastically deforms by receiving a pressing action from the front end surface of the pressing member, thereby pressing the lid body and the storage holder forward in the insertion direction. Thus, it can be inserted and fixed in the accommodation hole.

  In this way, the lid body and the housing holder, and thus the transmission / reception vibrator can be fixed with high mounting accuracy by pressing the lid body and the housing holder forward using the elastic member and inserting and fixing them in the housing hole. Therefore, the accuracy of flow rate measurement is also improved.

  In that case, it is desirable that the thickness of the elastic member is larger than the set interval between the front end surface of the pressing member and the rear end surface of the lid. Accordingly, the elastic force (elastic force) of the elastic member can be reliably applied to the lid (and the housing holder), and the transmission / reception vibrator can be maintained in a more stable state.

  When the elastic member disposed between the front end surface of the pressing member and the rear end surface of the lid is made of a polymer material foam-molded so as to have a closed cell structure, the surface acoustic wave isolator is It is possible to easily obtain a mounting structure that is excellent in both the vibration effect (propagation suppression) and the cushion effect (the impact pressure of the lid and the housing holder).

  Here, the foamed polymer material includes foamed plastic and foamed elastomer. In general, "plastic" refers to a polymer substance that exhibits plasticity (a property that causes distortion without applying external force and deforms without breaking and does not return to its original state even when external force is removed) Also referred to as “plastomer”. The term “elastomer” refers to a high molecular weight material that exhibits rubber-like elasticity (deforms when an external force is applied but returns to its original shape when the external force is removed) at around room temperature. However, some foamed plastics, such as polyurethane foam, exhibit elasticity against an external force within a predetermined range at room temperature due to expansion and contraction of the internal bubbles (voids). Usually, a foamed synthetic resin (for example, closed foamed polyethylene (PE type)) is classified as a foamed plastic (plastomer), and a foamed synthetic rubber (for example, a closed foamed acrylonitrile-butadiene rubber sponge (NBR type)) is classified as a foamed elastomer.

  Further, in the polymer material having the closed cell structure, Young's modulus E ≦ 0.07 GPa is preferable in order to obtain the isolation effect and the cushion effect. Similarly, SRIS0101 hardness (C type) ≦ 50 is preferable. When these upper limit values (threshold values) are exceeded, the elastic member becomes hard and its elasticity is lost, so that the isolation effect and the cushion effect are reduced. Note that SRIS0101 is a hardness measurement standard defined by the Japan Rubber Association standard.

Therefore, in order to solve the above problems, the sensor mounting structure of the ultrasonic flowmeter according to the present invention is:
A pair of transmission / reception units that receive ultrasonic waves coming from the upper side or lower side in the flow direction after oscillating ultrasonic waves toward the upper or lower side in the fluid flow direction on the wall of the flow path for allowing the fluid to pass In the sensor mounting structure of the ultrasonic flowmeter to which the transducer is mounted,
Each of the transmission / reception transducers is accommodated in a cylindrical accommodation holder, inserted into an accommodation hole formed through the wall of the flow path through the accommodation holder, and oscillates or receives ultrasonic waves to vibrate. Is arranged on the front side in the insertion direction so that the vibrating surface to face the flow path,
A lid that is closed from the rear side in the insertion direction is fixed to the housing holder in a state where a predetermined gap is formed between the rear end surface of the transmission / reception vibrator,
The inner peripheral surface of the housing holder has a minute contact area such as a dot shape, a line shape, or a dot shape, and inner protrusions that contact the outer peripheral surface of the transmission / reception vibrator are dispersed along the circumferential direction. When the transmitting and receiving vibrator is housed in the housing holder, the outer peripheral surface of the transmitting and receiving vibrator is contacted and held by the inner projecting portion of the housing holder.
The lid has a minute contact area such as a dot shape, a line shape, or a dot shape, and a forward projecting portion that contacts the rear end surface of the transmission / reception vibrator is dispersed along the circumferential direction in the gap. When the lid is fixed to the housing holder, the rear end surface of the transmission / reception vibrator is contacted / held by the front protrusion of the lid .

  According to such a sensor mounting structure, a plurality of contact portions having minute contact areas such as dot-like, line-like, and dot (polka dot pattern) shapes are distributed and formed along the circumferential direction. The outer peripheral surface of the vibrator is in contact with and held by the inner peripheral surface of the housing holder, and the rear end surface of the transmission / reception vibrator is in contact with and held by a lid that closes the housing holder from the rear side in the insertion direction. Therefore, the surface acoustic wave generated on the outer peripheral surface side of the transmission / reception vibrator and the surface acoustic wave generated on the rear side of the transmission / reception vibrator can be reduced to further enhance the isolation effect.

(Example)
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an overall perspective view of an embodiment of an ultrasonic flow meter used as a general residential gas meter or the like. The ultrasonic flowmeter 100 includes a main body unit 10, an intermediate flow path forming unit 20, and a shut-off valve 30, and the main body unit 10 includes a main body portion 11 and a lid portion 17.

  FIG. 2 is a front sectional view of the ultrasonic flowmeter 100, and the AA sectional view of FIG. 2 is shown in FIG. As shown in FIG. 2, the main body 11 has a rectangular parallelepiped shape as a whole, and an inlet 12 connected to the upstream gas pipe and an outlet 13 connected to the downstream gas pipe are formed on the upper surface thereof. Each is open. In addition, a main body flow path 14 for allowing a gas (fluid) to pass between the inflow port 12 and the outflow port 13 is formed therein. A main body flow path cutting portion 15 is formed in the lower part of the main body portion 11 from the back side in FIG. 2 toward the front side (fitting direction). The main body flow path cutting portion 15 is provided with a packing 17a (seal material). It is covered from the outside by the cover 17. A pair of window holes 16, 16 (see FIG. 1) communicating with the main body flow path cutting portion 15 are opened on the outer surface of the main body portion 11 on the front side in the fitting direction (front side in FIG. 2).

  As shown in FIG. 3, when the intermediate flow path forming unit 20 is fitted into the main body flow path cutting section 15 of the main body section 11 from a direction (fitting direction) perpendicular to the gas flow direction, An intermediate flow path 21 connected to the path 14 is formed through. The intermediate channel 21 is connected to the inlet-side connecting channel 21b and the outlet-side connecting channel 21c that are smoothly connected to the main channel 14 and to both the connecting channels 21b and 21c at both ends. It is comprised from the linear intermediate | middle flow path 21a arrange | positioned along the lower surface of the main-body part 11 with the orthogonal form (refer FIG. 2). Further, the intermediate flow path forming unit 20 is integrally formed with a pair of projecting portions 22 and 22 on the front side in the fitting direction corresponding to the pair of window holes 16 and 16 opened in the main body portion 11. Further, the pair of projecting portions 22 and 22 of the intermediate flow path forming unit 20 has a pair of transmission / reception vibrators 23a and 23b of the ultrasonic sensor 23 in order to measure the flow rate of the gas passing through the linear intermediate flow path 21a. Are detachably attached. The axial orthogonal cross-sectional area of the straight intermediate flow path 21a is made smaller (throttle) than the axial orthogonal cross-sectional area of the main body flow path 14, and the flow rate of the ultrasonic sensor 23 is increased by increasing the flow velocity of the gas flowing through the linear intermediate flow path 21a. The measurement accuracy of (flow velocity) is increased. The main body flow path 14 between the inlet 12 and the intermediate flow path 21 is provided with a shut-off valve 30 that blocks the gas flow in the main body flow path 14 (see FIG. 2).

  Therefore, in FIG. 3, when the intermediate flow path forming unit 20 is fitted to the main body flow path cutting portion 15 of the main body portion 11 so that the intermediate flow path 21 communicates with the main body flow path 14, the protrusions 22, 22 become the main body. Projecting from the window holes 16 and 16 of the portion 11 to the outside. And each protrusion part 22 and 22 seals each window hole 16 and 16 via packing 16a (sealing material), respectively. Furthermore, the transmission / reception transducers 23a and 23b of the ultrasonic sensor 23 are inserted from the outside into the receiving holes 22a and 22b of the protrusions 22 and 22, respectively, and are attached with mounting screws 27a and 27a (mounting members) and a pressing plate 27 (pressing). (See FIG. 4). The mounting structure of the ultrasonic sensor 23 will be described in detail with reference to FIG.

  As shown in FIG. 3, the linear intermediate flow path 21a is a rectangular with the long side L (see FIG. 3) as the fitting direction to the main body flow path cutting section 15 and the short side S (see FIG. 2) as the vertical direction. It is formed into a shape. The ultrasonic sensor 23 is configured in the following reflective V-shaped arrangement. That is, a pair of transmission / reception vibrators 23a and 23b are separated from each other by a predetermined distance W in the flow direction on a wall surface (attachment surface) 21d that forms a short side on the front side in the fitting direction in the cross section orthogonal to the flow direction of the straight intermediate flow path 21a. The wall surface that is attached and forms the short side on the rear side in the fitting direction is defined as a reflecting surface 21e.

  Returning to FIG. 1, the output signals obtained by the transmission / reception transducers 23 a and 23 b (sensor elements) of the ultrasonic sensor 23 are transmitted to the flow rate calculation processing circuit 24 via the lead wires 25 and 25 to calculate the gas flow rate. The notification is made using a flow rate display unit (not shown) or the like. The transmission / reception vibrators 23a and 23b, the flow rate calculation processing circuit 24, the lead wires 25 and 25, the flow rate display unit, and the like constitute a flow rate measurement unit M. Since the lead wires 25 and 25 are drawn out from the ultrasonic sensor 23 (transmission / reception transducers 23a and 23b) provided to project outside from the window holes 16 and 16, the measurement gas leaks to the outside through the core wire portion and is airtight. Therefore, there is no insufficiency and measurement accuracy is not lowered. Thus, the airtightness of the three parts of the main body part 11, the lid part 17, and the intermediate flow path forming unit 20 is ensured, and the lead wires 25 and 25 are located outside the flow path. There will be no fire caused by sparks. Reference numeral 26 denotes a rectifying member that is provided between the inlet-side connecting flow path 21b and the linear intermediate flow path 21a, and suppresses the disturbance of the measurement gas flow in the flow path to equalize the velocity distribution ( (See FIG. 2).

  Next, FIG. 4 shows the main part of the sensor mounting structure in an exploded perspective view, and FIG. 5 shows it in an assembled state. The following description is mainly given for the transmission / reception vibrator 23b, but the same applies to the transmission / reception vibrator 23a. The straight intermediate flow path 21a is simply referred to as a flow path.

  4 and 5, the transmission / reception vibrator 23b is housed in a cylindrical housing holder 31 that opens in the front-rear direction, and the housing holder 31 is formed in a housing hole 22b that is formed through the wall portion (projecting portion 22) of the channel 21a. Has been inserted. Further, a vibration surface 23c that vibrates when the transmission / reception vibrator 23b oscillates or receives an ultrasonic wave is disposed on the front side in the insertion direction so as to face the flow path 21a obliquely. A plurality of (for example, four) claw-shaped (plate-shaped) inner protrusions 31b are formed on the inner peripheral surface 31a of the housing holder 31 so as to bulge in a distributed manner at regular intervals (for example, 90 ° intervals) in the circumferential direction. ing. Each of these inner protrusions 31b contacts (contacts) the outer peripheral surface 23d of the transmission / reception vibrator 23b to form a plurality of first contact portions (contact portions) having, for example, a linear minute contact region. Further, the outer peripheral surface 31c of the storage holder 31 is inserted and fixed to the inner peripheral surface of the storage hole 22b.

  On the other hand, a plurality of (for example, eight) claw-shaped (plate-shaped) front protrusions 32a that contact the rear end surface 23f of the transmission / reception vibrator 23b are arranged on the lid 32 at regular intervals (for example, 45 ° intervals). It is formed in a dispersed form. Each of these front protrusions 32a is in contact with the rear end face 23f of the transmitting / receiving vibrator 23b to form a second contact portion (contact portion). Further, the lid body 32 is bonded and fixed to the housing holder 31 in a state where a predetermined gap K is formed between the lid body 32 and the transmission / reception vibrator 23 b. The lid 32 is made of the same synthetic resin as the lid 32 (for example, ABS resin).

  Further, on the rear side in the insertion direction of the lid body 32, a plurality of (for example, four) mounting screws 27a are provided for the pressing plate 27 (pressing member) in order to insert the lid body 32 and the housing holder 31 and close the housing hole 22b. It is attached and fixed to the wall portion of the flow path 21a by (attachment member). A disc-shaped elastic plate 33 (elastic member) is disposed between the front end surface 27 b of the pressing plate 27 and the rear end surface 32 b of the lid 32. The elastic plate 33 is made of closed-foamed acrylonitrile-butadiene rubber sponge (NBR type) or closed-foamed polyethylene (PE type) that is foam-molded to have a closed cell structure. The thickness of the elastic plate 33 is larger than the set interval C (see FIG. 5B) between the front end surface 27b of the pressing plate 27 and the rear end surface 32b of the lid body 32. Accordingly, the elastic plate 33 is elastically deformed by receiving a pressing action from the front end surface 27b of the pressing plate 27, the lid body 32 and the storage holder 31 are pressed forward in the insertion direction, and the storage holder 31 abuts the storage hole 22b. It is inserted and fixed until it comes into contact with the surface 22d.

  4 and 5, a cylindrical (ring-shaped) sound absorbing ring 41 (enclosure member) is disposed so as to surround the front end 23e including the vibration surface 23c of the transmission / reception vibrator 23b. The sound absorbing ring 41 prevents the ultrasonic wave oscillated from the vibration surface 23c of the transmission / reception vibrator 23b and reflected by the stagnation portion 22c (see FIG. 5A) of the accommodation hole 22b from being received again by the vibration surface 23c as a disturbance factor. ing.

  Specifically, the sound absorbing ring 41 is bonded and fixed to the outer peripheral surface of the front end portion 23e of the transmission / reception vibrator 23b, and is reflected by the connection portion between the accommodation hole 22b that becomes the stagnation portion 22c of the flow channel 21a and the flow channel 21a. Absorbs or attenuates sound waves. In addition, the front edge of the sound absorbing ring 41 is positioned flush with the vibration surface 23c of the transmission / reception vibrator 23b (on the same plane or in a slightly rearward direction), and the outer peripheral surface of the front end 23e of the transmission / reception vibrator 23b is annular. Covering. The sound absorbing ring 41 is made of closed foamed acrylonitrile-butadiene rubber sponge (NBR type) or closed foamed polyethylene (PE type) which is foam-molded to have a closed cell structure.

  On the other hand, in the gap K formed between the lid 32 and the rear end face 23f of the transmission / reception vibrator 23b, a sound absorbing plate 42 (filling member) is disposed so as to fill the gap K. The sound absorbing plate 42 prevents the ultrasonic wave oscillated from the rear end face 23f of the transmitting / receiving vibrator 23b and reflected by the lid 32 from being received again by the rear end face 23f as a disturbance factor. Specifically, the sound absorbing plate 42 is sandwiched between the lid 32 and the rear end surface 23f of the transmission / reception vibrator 23b, and absorbs or attenuates the ultrasonic waves reflected by the lid 32. The sound absorbing plate 42 is made of closed foam acrylonitrile-butadiene rubber sponge (NBR type) or closed foam polyethylene (PE type) which is foam-molded to have a closed cell structure.

  In this manner, the outer peripheral surface 23d of the transmission / reception vibrator 23b is held by the inner peripheral surface 31a of the housing holder 31 in a form in which a plurality of contact portions (inner protrusions 31b) are formed dispersed along the circumferential direction. Yes. Therefore, the transmission / reception vibrator 23b is held in a point contact (or close contact with the accommodation holder 31) in a point contact state (or a minute contact similar thereto), so that the vibration of the transmission / reception vibrator 23b is not easily transmitted to the accommodation holder 31. Propagation to the other transmitting / receiving vibrator 23a is difficult (does not act as a disturbance factor). In addition, according to such an attachment structure, even if the measurement conditions and the attachment conditions change, the isolation effect of the surface acoustic wave does not vary so much, so that stable measurement accuracy and attachment accuracy can be easily obtained. . As a result, it is possible to realize the ultrasonic flowmeter 100 having a high surface acoustic wave isolation effect and an excellent S / N ratio.

  Similarly, a lid body 32 in which the rear end face 23f of the transmission / reception vibrator 23b closes the housing holder 31 from the rear side in the insertion direction in a form in which a plurality of contact portions (front protrusions 32a) are formed in a distributed manner along the circumferential direction. Retained. Therefore, since the transmission / reception vibrator 23b is held in a point contact (or a minute contact approximate thereto) state on the lid 32 that closes the receiving holder 31 from the rear side in the insertion direction, the vibration of the transmission / reception vibrator 23b is transmitted to the lid 32. As a result, the surface acoustic wave generated on the back side of the transmitting / receiving transducer 23b is difficult to propagate to the other transmitting / receiving transducer 23a. Therefore, as in the case of the surface acoustic wave generated on the front end side of the transmission / reception vibrator 23b, the surface acoustic wave is less likely to act as a disturbance factor. In addition, according to such an attachment structure, even if the measurement conditions and the attachment conditions change, the isolation effect of the surface acoustic wave does not vary so much, so that stable measurement accuracy and attachment accuracy can be easily obtained. .

  Further, since the sound absorbing ring 41 is disposed so as to surround the front end portion 23e of the transmission / reception vibrator 23b, the abnormally reflected wave at the stagnation portion 22c can be absorbed (attenuated) by the sound absorbing ring 41. Similarly, the sound absorbing plate 42 is disposed in the gap K formed between the lid 32 and the rear end face 23f of the transmission / reception vibrator 23b so as to fill the gap K. The reflected wave can be absorbed (attenuated) by the sound absorbing plate 42.

(Modification)
6 to 8 show modifications of the accommodation holder 31. FIG. FIG. 6 shows a case where an inner protrusion 31b (first contact portion; contact portion) that contacts the outer peripheral surface 23d of the transmitting / receiving vibrator 23b is formed on the inner peripheral surface 31a of the housing holder 31. Among these, in FIG. 6A, four claw-like inner protrusions 31b are bulged and formed at intervals of 90 ° in the circumferential direction, and each inner protrusion 31b is bent into an L shape. The front end 23e of the transmission / reception vibrator 23b is easily received by the inner protrusion 31b. In FIG. 6 (b), a total of six claw-shaped inner protrusions 31b are formed to bulge in the circumferential direction, two of which (reference numeral 31b ′) are located on the front side in the insertion direction, Since the remaining four (reference numeral 31b ″) are located on the rear side in the insertion direction, occurrence of twisting in the circumferential direction can be suppressed.

  In FIG. 6C, the four claw-shaped inner protrusions 31b are bulged and formed at intervals of 90 ° in the circumferential direction, and the inner protrusions 31b are arranged in a spiral shape. Generation of twist in the circumferential direction can be further suppressed. In FIG. 6 (d), the four claw-like inner protrusions 31b are bulged and distributed at 90 ° intervals in the circumferential direction, and each inner protrusion 31b protrudes in an S shape. The holding force can be increased by the spring effect (without increasing the contact area).

  FIG. 7 shows a case where an outer protrusion 31 d (first contact portion; contact portion) that contacts the inner peripheral surface of the accommodation hole 22 b is formed on the outer peripheral surface 31 c of the accommodation holder 31. Of these, in FIG. 7A, four claw-shaped outer protrusions 31d are formed in a bulging form at intervals of 90 ° in the circumferential direction, and the deformation of the inner protrusion 31b shown in FIG. 4 and FIG. It corresponds to an example. 7 (b), four claw-shaped outer protrusions 31d are formed in a bulging manner in the circumferential direction at intervals of 90 °, and the inner protrusions 31b are spirally arranged. ). 7 (c), four claw-shaped outer protrusions 31d are formed to bulge in a distributed manner at 90 ° intervals in the circumferential direction, and the inner protrusion 31b protrudes in an S shape. ).

  FIG. 8 shows that an inner protrusion 31 b (first contact portion; contact portion) that contacts the outer peripheral surface 23 d of the transmission / reception vibrator 23 b is formed on the inner peripheral surface 31 a of the storage holder 31 and the outer peripheral surface 31 c of the storage holder 31. The case where the outer side protrusion part 31d (1st contact part; contact part) which contacts the inner peripheral surface of the accommodation hole 22b is formed is shown. Four claw-shaped inner protrusions 31b are bulged and formed at intervals of 90 ° in the circumferential direction, and four claw-shaped outer protrusions 31d are bulged and formed at intervals of 90 ° in the circumferential direction. Has been. Further, since the arrangement of the inner protrusions 31b and the outer protrusions 31d are shifted by 45 degrees, the holding force between the outer peripheral surface 23d of the transmitting / receiving vibrator 23b and the inner peripheral surface of the accommodation hole 22b is improved. .

  In the above description, the transmission / reception vibrators 23a and 23b have been described only when they are inserted into the accommodation holes 22a and 22b after being accommodated in the accommodation holder 31, but the transmission / reception vibrators 23a and 23b are directly accommodated in the accommodation holes 22a and 22b. May be inserted. Further, the housing holder 31 and the lid 32 may be integrally formed by injection or the like. Further, the sound absorbing ring 41 may be divided into a plurality of parts in the circumferential direction. In the embodiment, the sound absorbing plate 42 such as a rubber sponge is sandwiched between the gaps K as the filling member, but the gap K may be filled with glass wool or the like.

  In addition, although the main body unit 10 was demonstrated only about the case where it comprised from the main body part 11 which has the main body flow path 14 inside, and the cover part 17 which covers the main body part 11 from the outside, the main body unit 10 is as follows. It may be. In other words, the main body unit may be configured such that the first main body portion and the second main body portion each having a half-shaped main body flow path are combined. However, in this case, the window hole is provided in at least one of the first main body and the second main body, and the lid may or may not be provided.

1 is an overall perspective view of an embodiment of an ultrasonic flowmeter according to the present invention. FIG. 2 is a front sectional view of FIG. 1. AA sectional drawing of FIG. The disassembled perspective view which shows the principal part of a sensor attachment structure. The assembly perspective view and assembly sectional drawing of FIG. The perspective view which shows the modification of an accommodation holder. The perspective view which shows the other modification of an accommodation holder. The perspective view which shows the further another modification of an accommodation holder. Explanatory drawing which shows the conventional sensor mounting structure.

Explanation of symbols

21a Linear intermediate flow path (flow path)
22 Protruding part 22a, 22b Accommodating hole 22c Rubbing part 22d Abutting surface 23 Ultrasonic sensor 23a, 23b Transmission / reception transducer (sensor element)
23c Vibrating surface 23d Outer peripheral surface 23e Front end portion 23f Rear end surface 27 Pressing plate (pressing member)
27b Front end surface 31 Housing holder 31a Inner peripheral surface 31b Inner protrusion (first contact portion; contact portion)
31c Outer peripheral surface 31d Outer protrusion (first contact portion; contact portion)
32 Lid 32a Front protrusion (second contact part; contact part)
32b Rear end face 33 Elastic plate (elastic member)
41 Sound absorbing ring (enclosure member)
42 Sound absorbing plate (filling member)
100 Ultrasonic flow meter

Claims (5)

A pair of transmission / reception units that receive ultrasonic waves coming from the upper side or lower side in the flow direction after oscillating ultrasonic waves toward the upper or lower side in the fluid flow direction on the wall of the flow path for allowing the fluid to pass In the sensor mounting structure of the ultrasonic flowmeter to which the transducer is mounted,
Each of the transmission / reception vibrators is directly or indirectly inserted into an accommodation hole formed through the wall of the flow path through a cylindrical accommodation holder , and vibrates by oscillating or receiving ultrasonic waves. While the surface is disposed on the front side in the insertion direction so as to face the flow path,
A lid that closes from the rear side in the insertion direction is fixed to the accommodation hole or the accommodation holder in a state where a predetermined gap is formed between the rear end surface of the transmission / reception vibrator,
The lid has a minute contact area such as a dot shape, a line shape, or a dot shape, and a forward projecting portion that contacts the rear end surface of the transmission / reception vibrator is dispersed along the circumferential direction in the gap. The ultrasonic flow rate is characterized in that when the lid is fixed to the accommodation hole or the accommodation holder, the rear end surface of the transmission / reception vibrator is in contact with and held by the front protrusion of the lid. Total sensor mounting structure. A pair of transmission / reception units that receive ultrasonic waves coming from the upper side or lower side in the flow direction after oscillating ultrasonic waves toward the upper or lower side in the fluid flow direction on the wall of the flow path for allowing the fluid to pass In the sensor mounting structure of the ultrasonic flowmeter to which the transducer is mounted,
Each of the transmission / reception transducers is accommodated in a cylindrical accommodation holder, inserted into an accommodation hole formed through the wall of the flow path through the accommodation holder, and oscillates or receives ultrasonic waves to vibrate. Is arranged on the front side in the insertion direction so that the vibrating surface to face the flow path,
A lid that is closed from the rear side in the insertion direction is fixed to the housing holder in a state where a predetermined gap is formed between the rear end surface of the transmission / reception vibrator,
The inner peripheral surface of the housing holder has a minute contact area such as a dot shape, a line shape, or a dot shape, and inner protrusions that contact the outer peripheral surface of the transmission / reception vibrator are dispersed along the circumferential direction. When the transmitting and receiving vibrator is housed in the housing holder, the outer peripheral surface of the transmitting and receiving vibrator is contacted and held by the inner projecting portion of the housing holder.
The lid has a minute contact area such as a dot shape, a line shape, or a dot shape, and a forward projecting portion that contacts the rear end surface of the transmission / reception vibrator is dispersed along the circumferential direction in the gap. The ultrasonic flowmeter sensor mounting is characterized in that when the lid is fixed to the housing holder, a rear end surface of the transmission / reception vibrator is in contact with and held by a forward projecting portion of the lid. Construction. The outer peripheral surface of the storage holder has a minute contact area such as a dot shape, a line shape, or a dot shape, and outer protrusions that contact the inner peripheral surface of the storage hole are dispersed and expanded along the circumferential direction. The sensor of the ultrasonic flowmeter according to claim 2 , wherein when the housing holder is inserted and inserted into the housing hole, an outer protruding portion of the housing holder is in contact with and held on an inner peripheral surface of the housing hole. Mounting structure. On the rear side in the insertion direction of the lid body, a pressing member that is attached and fixed to the wall portion of the flow path in order to insert the lid body and close the accommodation hole, a front end surface of the pressing member, and the lid An elastic member disposed between the rear end surface of the body,
The said elastic member receives the press action from the front-end surface of the said press member, and is elastically deformed, The said cover body is pressed to the insertion direction front side, and is inserted and fixed to the said accommodation hole . A sensor mounting structure for an ultrasonic flowmeter according to any one of the preceding claims. The elastic member is made of a polymer material foam-molded to have a closed cell structure,
The ultrasonic flowmeter sensor mounting structure according to claim 4 , wherein the elastic member has a thickness larger than a set interval between a front end surface of the pressing member and a rear end surface of the lid .

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