Ultrasonic Transmitter / Receiver

Abstract

To provide a supersonic echo sounder transducer capable of achieving waterproof with a simpler structure than the prior art and preventing dew condensation in a case.SOLUTION: In a supersonic echo sounder transducer 20, a connection chamber 22 N storing a connection part between a pair of terminal metal fittings 21 of a case 20A and first and second electrodes 32, 33 of a piezoelectric element 30 is filled with insulation fluid 60. This simple structure allows for waterproof and prevents dew condensation in the case 20A. As the piezoelectric elements of the supersonic echo sounder transducer are applied high-frequency voltage in order to generate supersonic, a waterproof potting material of the general circuit causes problems of short circuiting between the pair of electrodes of the piezoelectric element or a pair of conductive members. The insulation fluid filling the case of the disclosure has dielectric constant of 5 or less, so that the above short circuiting problems are solved. In addition, as the insulation fluid is not solidified as the general potting material, generation of supersonic is not prevented.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to an ultrasonic wave transmitter / receiver having a piezoelectric element. In a vessel Regarding. [Background technology]

[0002] Conventionally, as this type of ultrasonic transmitter / receiver, there is known one in which a piezoelectric element is housed in a waterproof case (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-270013 (paragraph

[0015] and figure 1) Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for the above-mentioned conventional ultrasonic transmitter / receiver to have a simpler structure and to have measures against condensation inside the case. [Means for solving the problem]

[0005] In order to solve the above problems, First aspect of the invention is an ultrasonic transmitter / receiver in which a pair of conductive members are connected to a pair of electrodes of a piezoelectric element within a case formed in part by a vibration plate to which the piezoelectric element is attached, and the connection parts within the case between the pair of electrodes of the piezoelectric element and the pair of conductive members are filled with an insulating fluid having a relative dielectric constant of 5 or less.

[0006] Second aspect of the invention The insulating fluid is silicone oil. First aspect 2 is an ultrasonic transmitter / receiver according to the first embodiment.

[0007] Third aspect of the inventionThe insulating fluid is a silicone grease or a silicone oil compound having a silicone oil as a base oil and a consistency of 200 or more. First aspect 2 is an ultrasonic transmitter / receiver according to the first embodiment.

[0008] Fourth aspect of the invention The pair of electrodes is disposed on the rear surface of the piezoelectric element opposite to the vibration plate, a fitting portion into which the piezoelectric element is fitted is provided in the case, the inside of the case is divided into front and rear portions by the piezoelectric element, and the insulating fluid is filled in a connection chamber in the case behind the piezoelectric element. First aspect from Third aspect Any one of Aspects 2 is an ultrasonic transmitter / receiver according to the first embodiment.

[0009] Fifth aspect of the invention The case includes a case body having the fitting portion at a front end, and a cap member that is fitted to the outside of the case body from the front side and has the diaphragm at the front end. Fourth aspect 2 is an ultrasonic transmitter / receiver according to the first embodiment.

[0010] Sixth aspect of the invention The case body is provided with a rear wall that faces the piezoelectric element with the connection chamber sandwiched therebetween, the pair of conductive members are a pair of terminal fittings that penetrate the rear wall and have elastic contact portions that contact the pair of electrodes of the piezoelectric element, and the rear wall is formed with an injection hole for injecting the insulating fluid into the connection chamber. Fifth aspect 2 is an ultrasonic transmitter / receiver according to the first embodiment.

[0011] Seventh aspect of the invention The rear wall is provided with a gas vent hole for releasing air from the connecting chamber when the insulating fluid is injected into the connecting chamber. Sixth aspect 2 is an ultrasonic transmitter / receiver according to the first embodiment.

[0012] Eighth aspect of the invention The opening end of the injection hole facing the connecting chamber faces one electrode of the piezoelectric element, and the opening end of the gas vent hole facing the connecting chamber faces the other electrode of the piezoelectric element. Seventh aspect 2 is an ultrasonic transmitter / receiver according to the first embodiment.

[0013] Ninth aspect of the invention The connection chamber is disposed above the piezoelectric element, and the case is filled with a sealant having a specific gravity smaller than that of the insulating fluid above the insulating fluid. Fourth aspect from Eighth aspect Any one of Aspects 2 is an ultrasonic transmitter / receiver according to the first embodiment.

[0014] Tenth aspect of the invention The case has a cylindrical wall extending upward, and the inside of the cylindrical wall is filled with the sealing material. Ninth aspect 2 is an ultrasonic transmitter / receiver according to the first embodiment.

[0015] Eleventh aspect of the invention The piezoelectric element has a rear wall that is provided in the case and faces the piezoelectric element with the connection chamber therebetween, an injection hole that is formed in the rear wall for injecting the insulating fluid into the connection chamber, and a gas vent hole that is formed in the rear wall for releasing air from within the connection chamber when the insulating fluid is injected into the connection chamber, and the cylindrical wall protrudes from a rear surface of the rear wall and communicates with the injection hole and the gas vent hole. Tenth Aspect 2 is an ultrasonic transmitter / receiver according to the first embodiment.

[0016] Twelfth aspect of the invention The present invention relates to a housing having a measurement flow path therein, and a measuring device attached to the housing for transmitting and receiving ultrasonic waves through a liquid flowing in the measurement flow path. First aspect from Eleventh aspect Any one of Aspects and a pair of ultrasonic transmitter / receivers according to the present invention. Effect of the Invention

[0017] First aspect of the invention and Twelfth aspectIn the ultrasonic transmitter / receiver, the connection between the pair of electrodes of the piezoelectric element and the pair of conductive members in the case is filled with an insulating fluid, so that waterproofing is achieved with a simple structure and condensation in the case is also prevented. Here, when the case is filled with a filler, the capacitance between the pair of electrodes of the piezoelectric element and the capacitance between the pair of conductive members change due to the difference between the dielectric constant of the filler and the dielectric constant of air. And, since a high-frequency voltage is applied to the piezoelectric element of the ultrasonic transmitter / receiver to generate ultrasonic waves, a short circuit between the pair of electrodes of the piezoelectric element or between the pair of conductive members becomes a problem with a waterproof potting material for a general circuit. In contrast, the insulating fluid filled in the case in the present disclosure has a relative dielectric constant of 5 or less, so the above-mentioned short circuit problem is solved. Moreover, since it is an insulating fluid that does not solidify like a general potting material, it is unlikely to interfere with ultrasonic generation.

[0018] The insulating fluid is, for example, a liquid, gel, or paste-like substance that does not solidify except in the form of a gas, and is preferably silicone oil, or a silicone grease or silicone oil compound that uses silicone oil as a base oil and has a consistency of 200 or more ( Third aspect of the invention ).

[0019] In addition, a pair of electrodes of the piezoelectric element may be arranged on the rear surface opposite the vibration plate, as in the ultrasonic transmitter / receiver of claim 4, and the insulating fluid may be filled in the connection chamber behind the piezoelectric element inside the case.

[0020] Also, Fifth aspect of the invention In the ultrasonic transmitter / receiver, the case has a case body with a fitting portion at the front end for fitting the piezoelectric element, and a cap member that fits into the case body from the front end, and the cap member has a vibration plate at the front end, so that the piezoelectric element and the vibration plate can be easily assembled. Sixth aspect of the inventionIn the ultrasonic transmitter / receiver described above, if the case body is provided with a rear wall that holds a pair of terminal fittings as a pair of conductive members, a connection chamber is provided between the rear wall and the piezoelectric element, and an injection hole is provided in the rear wall for injecting insulating fluid into the connection chamber, then after the pair of conductive members and the piezoelectric element are connected to assemble the case, the insulating fluid can be easily filled into the case through the injection hole.

[0021] moreover, Seventh aspect of the invention As in the ultrasonic transducer of , the rear wall is provided with a gas vent hole, which allows air in the connecting chamber to escape when the insulating fluid is injected into the connecting chamber, making it easier to fill the connecting chamber with the insulating fluid. Eighth aspect of the invention As in the ultrasonic transmitter / receiver described above, by positioning the opening end of the injection hole facing the connection chamber so as to face one of the electrodes of the piezoelectric element, and positioning the opening end of the gas vent hole facing the connection chamber so as to face the other electrode of the piezoelectric element, insulating fluid can be injected through the injection hole and filled until the insulating fluid reaches the gas vent hole, thereby reliably covering the space between the pair of electrodes with insulating fluid.

[0022] Here, the insulating fluid is Ninth aspect of the invention As in the ultrasonic transducer of the above, the connection chamber may be disposed above the piezoelectric element, and the insulating fluid filled in the case may be sealed with a sealant having a smaller specific gravity than the insulating fluid. The sealant may be, for example, configured to be filled inside a cylindrical wall that is provided in the case, extends upward, and communicates with the injection hole and the gas vent hole ( Tenth and eleventh aspects of the invention A lid member may be disposed at the interface between the insulating fluid and the sealant. The sealant may be a liquid, gel, or paste-like substance that does not solidify, or may be hardened and fixed inside the cylindrical portion. [Brief description of the drawings]

[0023] [Figure 1] 1 is a cross-sectional view of an ultrasonic flow meter according to an embodiment of the present disclosure; [Diagram 2] Cross-sectional view of the branch pipe taken along the line AA in Fig. 1 [Diagram 3] Side cross-sectional view of ultrasonic transducer [Figure 4] (A) Side cross-sectional view and (B) rear view of the piezoelectric element [Diagram 5] (A) is a cross-sectional view of the ultrasonic transducer taken along the line B-B in FIG. 3, and (B) is a front view seen from the rear side. [Figure 6] (A) Rear view and (B) side cross-sectional view of a cap equipped with a piezoelectric element [Figure 7] Graph showing the results of the confirmation experiment [Figure 8] 13A and 13B are a rear view and a side cross-sectional view, respectively, of a cap provided with a piezoelectric element according to another embodiment of the present invention; [Figure 9] FIG. 4 is a cross-sectional view of an ultrasonic transmitter / receiver according to another embodiment taken along line B-B of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of an ultrasonic flowmeter 10 of the present disclosure will be described with reference to Fig. 1 to Fig. 6. As shown in Fig. 1, the ultrasonic flowmeter 10 of this embodiment includes a housing 10A having a measurement sleeve 11 and a branch pipe 13 that diagonally intersects with the measurement sleeve 11, and includes a pair of ultrasonic transmitters and receivers 20 at both ends of the branch pipe 13. The measurement sleeve 11 is attached, for example, midway through a pipe, and liquid flows in an inner measurement flow path 12.

[0025] The branch pipe 13 is cylindrical and communicates with the measurement flow path 12, and both ends thereof are bent vertically upward to form a pair of receivers 14 having upper end openings, as shown in Fig. 2. An ultrasonic transmitter / receiver 20 is fitted into the upper end opening of each receiver 14, with the transmitting / receiving surface facing downward. The branch pipe 13 is also provided with a reflector 80 below each ultrasonic transmitter / receiver 20, which is held at an angle of 45 degrees to the horizontal direction, and when ultrasonic waves are transmitted and received between the pair of ultrasonic transmitter / receivers 20, 20 by a signal processing circuit (not shown), the ultrasonic waves transmitted from one ultrasonic transmitter / receiver 20 are reflected by each reflector 80 and reach the other ultrasonic transmitter / receiver 20. Then, as with known ultrasonic flowmeters, the flow rate of the liquid flowing through the measurement flow path 12 is measured based on the propagation time of the ultrasonic waves from one ultrasonic transmitter / receiver 20 to the other ultrasonic transmitter / receiver 20, and the propagation time of the ultrasonic waves from the other ultrasonic transmitter / receiver 20 to the one ultrasonic transmitter / receiver 20.

[0026] As shown in Fig. 3, the ultrasonic transmitter / receiver 20 is entirely covered by a case 20A having a case body 22 and a cap member 40 that closes the front end of the case body 22. The case body 22 holds a pair of terminal fittings 21 (only one of the terminal fittings 21 is shown in Fig. 3), and a piezoelectric element 30 attached to the cap member 40 is fixed to the front end of the case body 22. Hereinafter, the direction in which the terminal fittings 21 extend is referred to as the front-rear direction, and the side on which the piezoelectric element 30 is disposed relative to the terminal fittings 21 is referred to as the front side. The ultrasonic transmitter / receiver 20 is disposed with its front end facing downward at the upper end opening of the receiving portion 14 described above.

[0027] 4(A), the piezoelectric element 30 has first and second electrodes 32, 33, and a piezoelectric portion 31 sandwiched between these electrodes 32, 33. The piezoelectric portion 31 is disk-shaped, expands and contracts in the direction of voltage application when a voltage is applied, and is made of, for example, barium titanate, lead zirconate titanate, or the like.

[0028] The first electrode 32 is disposed in the center of the rear surface 31B of the piezoelectric part 31, and has a shape in plan view with a concave portion 32E with a part of a circle cut out, as shown in Fig. 4(B). As shown in Fig. 4(A), the second electrode 33 has a front electrode portion 33A covering the entire front surface 31A of the piezoelectric part 31, a rear electrode portion 33C disposed on the outer edge of the rear surface 31B of the piezoelectric part 31, and a side electrode portion 33B disposed on the side of the piezoelectric part 31 and connecting the front electrode portion 33A and the rear electrode portion 33C. The surface of the rear electrode portion 33C facing the concave portion 32E of the first electrode 32 is an arc surface along the concave portion 32E, as shown in Fig. 4(B).

[0029] 3, the case body 22 is made of resin and has a fitting portion 23 at its front end into which the piezoelectric element 30 fits. The fitting portion 23 has a cylindrical shape concentric with the central axis J1 of the piezoelectric element 30, and has a stepped surface on its inner circumferential surface that narrows toward the front end, against which the rear surface of the piezoelectric element 30 abuts.

[0030] The case body 22 also has a rear wall 22A through which the pair of terminal fittings 21 penetrate, on the rear side of the piezoelectric element 30 fitted in the fitting portion 23. A connection chamber 22N is formed between the piezoelectric element 30 and the rear wall 22A. As shown in FIG. 5(A), the connection chamber 22N has a cross section in the front-rear direction that surrounds the outer edges of adjacent large and small circles, and a part of the first electrode 32 on the rear surface of the piezoelectric element 30 and a part of the rear electrode portion 33C of the second electrode 33 are exposed in the connection chamber 22N. The pair of terminal fittings 21 have elastic abutment portions (not shown) at their front ends, and abut against the first electrode 32 and the rear electrode portion 33C of the second electrode 33 in the connection chamber 22N. As shown in FIG. 3, the rear wall 22A also has a pair of through holes 27 and 28 that penetrate in the front-rear direction and whose front ends communicate with the connection chamber 22N. Of the pair of through holes, one through hole 27 is arranged to communicate with the small circular portion of the internal space 22N, and the other through hole 28 is arranged to communicate with the large circular portion of the internal space 22N.

[0031] The rear ends of the pair of terminal fittings 21 protrude from the rear surface of the rear wall 22A and are connected to the lead wire 21R. The lead wire 21R is covered on the outside with a coating material made of insulating resin (e.g., polyvinyl chloride) and extends rearward, passes through the inside of an extension sleeve 50 (described later), is drawn out to the outside, and is connected to the signal processing circuit described above.

[0032] A lateral projection 25 is provided at the rear end of the case body 22. A cylindrical rear projection 26 is provided on the rear surface of the lateral projection 25 and surrounds from the outside the pair of terminal fittings 21 projecting from the rear wall 22A.

[0033] The rear projection 26 communicates with a pair of through holes 27, 28 that communicate with the connection chamber 22N. In detail, as shown in FIG. 5B, the pair of through holes 27, 28 are disposed at the furthest positions in the direction intersecting the axial direction inside the rear projection 26. As a result, the pair of through holes 27, 28 are disposed at the furthest positions in the direction intersecting the axial direction from the connection chamber 22N. As shown in FIG. 5A, the front end opening of one of the pair of through holes 27, 28 faces the rear electrode portion 33C of the second electrode 33 of the piezoelectric element 30, and the front end opening of the other through hole 28 faces the first electrode 32 of the piezoelectric element 30. The portion of the rear surface of the rear wall 22A that overlaps with the inside of the rear projection 26 is disposed rearward of the rear surface of the lateral projection 25 (see FIG. 3).

[0034] A metallic extension sleeve 50 is fitted from the outside to the rear projection 26. The extension sleeve 50 extends rearward from the rear projection 26, and the rear side through which the lead wire 21R is passed is smaller in diameter than the front side. A metallic flange portion 51 is brazed, welded or bonded to the front end of the extension sleeve 50. The flange portion 51 protrudes laterally from the front end of the extension sleeve 50 and covers the entire rear surface of the lateral protrusion portion 25. The outer edge of the flange portion 51 is brazed, welded or bonded to the rear end of the cap portion 40, which will be described later. The rear projection 26 and the extension sleeve 50 in this embodiment correspond to the "tube wall" in the claims.

[0035] The cap member 40 is formed of a conductive material, for example, a metal such as iron, stainless steel, copper, aluminum, etc. The cap member 40 includes a cylindrical ring portion 41 that is fitted to the outer surface of the case body 22, and a diaphragm 47 that closes the front end of the ring portion 41, as shown in FIG.

[0036] 6(A), the diaphragm 47 is in the form of a circular thin plate, and the piezoelectric element 30 is fixed to its rear surface. Specifically, the diaphragm 47 is placed on the front electrode portion 33A of the second electrode 33 of the piezoelectric element 30 (see FIG. 3). The diaphragm 47 is circular and larger than the piezoelectric element 30.

[0037] As shown in Fig. 6(B), the inner surface of the ring portion 41 is formed with a first fitting portion 42, a second fitting portion 43, and a third fitting portion 44 in this order from the front end side by a plurality of stepped surfaces that expand in diameter in a stepped manner toward the rear end side. As shown in Fig. 3, the first fitting portion 42 is fitted into the outer surface of the fitting portion 23, and the third fitting portion 44 is fitted into the outer surface of the lateral projection 25. The second fitting portion 43 is fitted into the outer surface between the fitting portion 23 and the lateral projection 25 of the outer surface of the case main body 22.

[0038] Further, a rib 42R is formed protruding in the circumferential direction at a position near the front end of the first fitting portion 42, and the peripheral edge portion of the rear surface of the vibration plate 47 is overlapped on the front surface of the rib 42R. The inner surface of the rib 42R surrounds the outer circumferential surface of the piezoelectric element 30. In this embodiment, the vibration plate 47 is fixed to the front surface of the rib 42R by welding, but it may be fixed by brazing or adhesive. Also, the vibration plate 47 and the ring plate 41 may be formed integrally.

[0039] A second step surface 45D and a third step surface 46D are formed on the outer surface of the ring portion 41, which are arranged in this order from the front end to the rear end, and each step surface 45D and the rear end of the ring portion 41 are formed in this order from the front end to the rear end of the ring portion 41. An O-ring 92 is fitted on the second step surface 45D and its outer surface in front of it, and is fitted on the inner surface of the receiving portion 14 of the branch pipe 13, as shown in Fig. 2. The ring portion 41 is fitted on the rear end side of the third step surface 46D to the upper opening edge of the receiving portion 14 of the branch pipe 13.

[0040] In this embodiment, the connection chamber 22N of the case body 22 is filled with an insulating fluid 60. The insulating fluid 60 is, for example, a liquid, gel, or paste-like substance that does not solidify except in the form of gas, and is preferably silicone oil, silicone oil compound, silicone grease, etc. In the case of silicone oil, the viscosity is preferably 1000 [mPa s] or less, and in the case of silicone oil compound and silicone grease, the consistency is preferably 200 or more.

[0041] In this embodiment, one of the through holes 27 is used as an injection hole, and the insulating fluid 60 is filled into the connection chamber 22N from its rear end opening. The other through hole 28 is used as a gas vent hole that releases air from the connection chamber 22N when the insulating fluid 60 is injected. In this embodiment, the insulating fluid 60 is filled not only into the connection chamber 22N, but also up to the rear end openings of the pair of through holes 27, 28. Note that the insulating fluid 60 may be filled into the connection chamber 22N by using the other through hole 28 as an injection hole and using the one through hole 27 as a gas vent hole.

[0042] The inside of the rear projection 26 and the extension sleeve 50 are filled with a sealant 61. The sealant 61 is a material having a smaller specific gravity than the insulating fluid 60. In this embodiment, the rear projection 26 and the extension sleeve 50 are disposed above the connection chamber 22N, so that the sealant 61 is filled directly on the insulating fluid 60 filled up to the rear end openings of the pair of through holes 27, 28, and seals the insulating fluid 60. The sealant 61 is injected into the inside of the rear projection 26 and the extension sleeve 50 in a liquid or paste state, and is hardened by heating or natural solidification. The hardening fixes the lead wire 21R. Examples of the sealant 61 include urethane resin and epoxy resin.

[0043] This concludes the description of the configuration of the ultrasonic flowmeter 10 of this embodiment. Next, the procedure for assembling the ultrasonic transmitter / receiver 20 and the ultrasonic flowmeter 10 will be described.

[0044] First, the piezoelectric element 30 is attached to the rear surface of the vibration plate 47 of the cap member 40 by an adhesive, and the front electrode portion 33A of the second electrode 33 of the piezoelectric element 30 is fixed to the vibration plate 47.

[0045] Then, the case body 22 holding the pair of terminal fittings 21 is inserted into the cap member 40 from the rear to engage with the ring portion 41, and the vibration plate 47 is fixed to the front surface of the case body 22. At this time, the front end opening of one through hole 27 faces the rear electrode portion 33C of the second electrode 33 of the piezoelectric element 30, and the front end opening of the other through hole 28 faces the first electrode 32 of the piezoelectric element 30.

[0046] Furthermore, the lead wires 21R are connected and soldered to the pair of terminal fittings 21. Next, the extension sleeve 50, which has a flange portion 51 attached to its front end by welding, is fitted from the outside onto the rear projection 26 of the terminal holder 22. Then, the outer edge of the flange portion 51 of the extension sleeve 50 is attached to the rear end of the cap portion 40 by welding.

[0047] Next, insulating fluid 60 is injected using a syringe or the like from the rear end opening of one of the through holes 27 in the rear wall 22A of the case body 22. At this time, the injected insulating fluid 60 is injected until it reaches the rear end opening of the other through hole 28.

[0048] Then, the lead wires 21R are connected to the pair of terminal fittings 21, and the sealing material 61 is injected into the rear projection 26 and the extension sleeve 50 using a syringe or the like, and then hardened. This completes the assembly of the ultrasonic transmitter / receiver 20.

[0049] Then, with an O-ring 92 attached to the second step surface 45D of the ring portion 41 and its front outer surface, the ring portion 41 is fitted into the receiving portion 14 of the branch pipe 13. This completes the assembly of the ultrasonic flowmeter 10.

[0050] Next, the effect of the ultrasonic flowmeter 10 will be described. In the ultrasonic transmitter / receiver 20 of this embodiment, the insulating fluid 60 is filled in the connection chamber 22N in which the connection portion between the pair of terminal fittings 21 and the first and second electrodes 32, 33 of the piezoelectric element 30 is disposed in the case 20A, so that waterproofing is achieved with a simple structure and condensation in the case 20A is also prevented. Here, when the case is filled with a filler, the capacitance between the pair of electrodes of the piezoelectric element and the capacitance between the pair of conductive members change due to the difference between the dielectric constant of the filler and the dielectric constant of air. And, since a high-frequency voltage is applied to the piezoelectric element of the ultrasonic transmitter / receiver to generate ultrasonic waves, a short circuit between the pair of electrodes of the piezoelectric element or between the pair of conductive members becomes a problem in a general circuit waterproof potting material. In contrast, the insulating fluid filled in the case in the present disclosure has a relative dielectric constant of 5 or less, so the above-mentioned short circuit problem is solved. Moreover, since it is an insulating fluid that does not solidify like typical potting materials, it is less likely to interfere with the generation of ultrasonic waves.

[0051] Furthermore, in this embodiment, the case 20A has the case body 22 having at its front end the fitting portion 23 for fitting the piezoelectric element 30, and the cap member 40 that fits into the front end of the case body 22, and the cap member 40 has a vibration plate 47 at its front end, so that the piezoelectric element 30 and the vibration plate 47 can be easily assembled. The case body 22 has a rear wall 22A that holds the pair of terminal fittings 21, a connection chamber 22N between the rear wall 22A and the piezoelectric element 30, and a through hole 27 in the rear wall 22A for injecting the insulating fluid 60 into the connection chamber 22N, so that after the pair of terminal fittings 21 and the piezoelectric element 30 are connected to assemble the case 20A, the insulating fluid 60 can be easily filled into the case 20A through the through hole 27.

[0052] In addition, the rear wall 22A is also provided with a through hole 28 that serves as a gas vent hole, so that air in the connection chamber 22N can be released when the insulating fluid 60 is injected into the connection chamber 22N. This makes it easier to fill the connection chamber 22N with the insulating fluid 60. Furthermore, since the pair of through holes 27, 28 are disposed substantially at opposite ends of the connection chamber 22N, if the insulating fluid 60 injected from the through hole 27 is filled until it reaches the rear end opening of the through hole 28, it is possible to consider the connection chamber 22N to be sufficiently filled even if the inside of the case 20A cannot be seen. Furthermore, of the pair of through holes 27, 28, one through hole 27 is positioned to face the side electrode portion 33C of the second electrode 33 of the piezoelectric element 30, and the other through hole 28 is positioned to face the first electrode 32 of the piezoelectric element 30. Therefore, by filling the through hole 28 with insulating fluid 60 until it reaches the rear end opening, the area between the first and second electrodes 32, 33 can be reliably covered with insulating fluid 60.

[0053] In this embodiment, the rear projection 60 and the extension sleeve 50 are disposed above the connection chamber 22N, and the rear projection 60 and the extension sleeve 50 are filled with a sealant 61 having a lower specific gravity than the insulating fluid 60. In this embodiment, by filling the sealant 61 having a lower specific gravity than the insulating fluid 60, it is possible to directly overlap the upper surface of the insulating fluid 60, and the insulating fluid 60 can be easily sealed without the need to block the insulating fluid 60 with a lid member or the like.

[0054] It is known that the frequency-impedance characteristics of the ultrasonic transmitter / receiver 20 have a resonant frequency fr at which the impedance has the smallest peak value, and the smaller this peak value, the better the transmission / reception sensitivity. The experiment described below confirms that the peak value of the resonant frequency fr can be sufficiently low even if the connection chamber 22N is filled with insulating fluid 60.

[0055] [Confirmation experiment] The change in transmission and reception sensitivity was confirmed by an experiment using two materials with different dielectric constants as the insulating fluid filled in the connection chamber 22N of the ultrasonic transmitter / receiver 20 of the above embodiment. In this experiment, a test sample S1 in which the connection chamber 22N was filled with silicone grease with a dielectric constant of 2.8, a test sample S2 in which the connection chamber 22N was filled with ethanol with a dielectric constant of 24, and a test sample S3 before filling (no filling material was filled in the connection chamber 22N) as a comparative sample were prepared, and the impedance characteristics at 25[℃] were measured using an impedance analyzer (HIOKI IM3570).

[0056] 7 shows the frequency-impedance characteristics in each experimental example. The horizontal axis represents frequency in the range of 800 to 1200 [kHz], and the vertical axis represents logarithm of impedance in the range of 10 to 10000 [kΩ].

[0057] In the test sample S3, the impedance curve shows a very low peak value of the resonance frequency fr, whereas in the impedance curve of the test sample S2 filled with ethanol having a large relative dielectric constant, the peak of the resonance frequency fr is significantly blunted. On the other hand, in the impedance curve of the test sample S1 filled with silicone grease having a small relative dielectric constant, the peak of the resonance frequency fr is slightly blunted compared to the test sample S3, but a sufficiently low value (100 [Ω] or less) was obtained to obtain the necessary transmission and reception sensitivity of the ultrasonic transmitter / receiver 20.

[0058] [Other embodiments] 8(A) and 8(B), a positioning recess 41M that opens to the outside may be provided at one location on the outer periphery of the rear end of the ring portion 41V of the cap member 40V. In this case, for example, if the rear electrode portion 33C of the second electrode 33 of the piezoelectric element 30 is disposed on the positioning recess 41M side, in the step of fitting the piezoelectric element 30 to the front end of the case body 22 when assembling the ultrasonic transmitter / receiver 20, the assembly work can be smoothly performed so that the front end opening of one through hole 27 faces the rear electrode portion 33C of the second electrode 33 of the piezoelectric element 30 and the front end opening of the other through hole 28 faces the first electrode 32 of the piezoelectric element 30.

[0059] (2) In the ultrasonic transmitter / receiver 20 of the above embodiment, the insulating fluid 60 is filled up to the rear end openings of the pair of through holes 27, 28, but the insulating fluid 60 may be filled up to a midpoint in the front-rear direction of the pair of through holes 27, 28, or may be filled up to the inside of the rear protrusion 26, which is above the rear end openings of the pair of through holes 27, 28. In this case as well, the sealant 61 may be filled directly on the upper surface of the insulating fluid 60.

[0060] (3) In the ultrasonic transmitter / receiver 20 of the above embodiment, the sealant 61 is directly placed on the upper surface of the insulating fluid 60 . However, a lid member may be disposed at the interface between the insulating fluid 60 and the sealant 61 .

[0061] (4) In the ultrasonic transmitter / receiver 20 of the above embodiment, the sealant 61 is hardened after being injected into the inside of the rear projection 26 and the extension sleeve 50, but a liquid, gel or paste substance that does not harden may be filled in. In this case, the rear end of the extension sleeve 50 may be closed with a cover member or the like.

[0062] (5) In the ultrasonic transmitter / receiver 20 of the above embodiment, a pair of through holes 27, 28 is provided, but three or more through holes may be provided.

[0063] (6) In the ultrasonic transmitter / receiver 20 of the above embodiment, the cross-sectional shape of the connection chamber 22N was a shape that surrounded the outer edges of adjacent large and small circles, but it may have any shape that communicates with a pair of through holes 27, 28 and exposes a portion of the first electrode 32 on the rear surface of the piezoelectric element 30 and a portion of the rear electrode portion 33C of the second electrode 33, and may have an irregular shape as shown in Figure 9.

[0064] In addition, although this specification and drawings disclose specific examples of the technology included in the scope of the claims, the technology described in the claims is not limited to these specific examples, but includes various modifications and variations of the specific examples, as well as parts of the specific examples taken alone. [Explanation of symbols]

[0065] 10 Ultrasonic flowmeter 10A Housing 12 Measurement flow path 20 Ultrasonic Transmitter / Receiver 20A Case 21 Terminal fittings (conductive parts) 22 Case body 22A Rear wall 22N Connecting room 23 Fitting part 26 Rear protrusion (cylindrical wall) 27 Through hole (injection hole) 28 Through hole (gas vent hole) 30 Piezoelectric element 32 First electrode 33 Second electrode 40 Cap member 47 Diaphragm 50 Extension sleeve (cylinder wall) 60 Insulating fluid 61 Encapsulating materials 92 O-ring

Claims

1. A part of the case that houses the piezoelectric element is made up of a diaphragm, The front surface of the piezoelectric element is adhered to the vibration plate, In the ultrasonic transmitter / receiver, a connection chamber in the case behind the piezoelectric element accommodates a connection portion between a pair of electrodes on a rear surface of the piezoelectric element and a pair of conductive members and is filled with an insulating fluid having a relative dielectric constant of 5 or less, In the case, a rear wall facing the piezoelectric element with the connection chamber therebetween; an injection hole penetrating the rear wall for injecting the insulating fluid into the connection chamber; a gas vent hole penetrating the rear wall for allowing air in the connection chamber to escape when the insulating fluid is injected into the connection chamber; the injection hole faces one electrode of the piezoelectric element, The gas vent hole faces the other electrode of the piezoelectric element.

2. In the case, a fitting portion into which the piezoelectric element is fitted; a case body having the fitting portion at a front end; a cap member that is fitted to the outside of the case body from the front side and has the diaphragm at a front end; Includes:

2. The ultrasonic transmitter / receiver according to claim 1, wherein the pair of conductive members are a pair of terminal fittings that pass through the rear wall and have elastic contact portions that contact the pair of electrodes of the piezoelectric element.

Images